HomeMy WebLinkAbout182402-Louisbourg-Wastewater-Pre-Design-Summary-Report-Final
182402.00 / 187116.00 ● Final Report ● March 2020
Environmental Risk Assessments & Preliminary
Design of Seven Future Wastewater Treatment
Systems in CBRM
Louisbourg Wastewater Interception & Treatment System
Summary Report
Prepared by:
Prepared for:
Louisbourg WW Interception &
Treatment System Summary Report May 28, 2020 Darrin McLean James Sheppard Darrin McLean
Issue or Revision Date Issued By: Reviewed By: Prepared By:
This document was prepared for the party indicated
herein. The material and information in the
document reflects HE’s opinion and best judgment
based on the information available at the time of
preparation. Any use of this document or reliance on
its content by third parties is the responsibility of the
third party. HE accepts no responsibility for any
damages suffered as a result of third party use of
this document.
March 27, 2020
164 Charlotte St.
PO Box 567
Sydney, NS
B1P 6H4
March 27, 2020
Matt Viva, P.Eng.
Manager Wastewater Operations
Cape Breton Regional Municipality (CBRM)
320 Esplanade,
Sydney, NS B1P 7B9
Dear Mr. Viva:
RE: Louisbourg Wastewater Interception & Treatment System - Summary Report
Please find enclosed for your files the final draft version of the Summary Report for the
Louisbourg Wastewater Interception & Treatment System.
This report presents a description of proposed wastewater interception and treatment
infrastructure upgrades for the Louisbourg Wastewater system, as well as an estimate of the
capital, operating costs and replacement costs for the proposed infrastructure. In addition,
estimated costs of upgrades and assessments related to the existing wastewater collection
system are provided. A desktop geotechnical review of the wastewater treatment facility site
is provided, along with an archaeological resources impact assessment review for all sites of
proposed wastewater infrastructure. Finally, an Implementation Timeline is provided, which
outlines a tentative schedule for implementation of the various proposed wastewater system
upgrades.
If you have any questions or require clarification on the content presented in the attached
report, please do not hesitate to contact us.
Yours very truly,
Harbour Engineering Joint Venture
Prepared by: Reviewed by:
Darrin McLean, MBA, FEC, P.Eng. James Sheppard, P.Eng.
Senior Municipal Engineer Civil Infrastructure Engineer
Direct: 902-539-1330 (Ext. 3138) Direct: 902-562-9880
E-Mail: dmclean@cbcl.ca E-Mail: jsheppard@dillon.ca
Project No: 182402.00 (CBCL)
187116.00 (Dillon)
HEJV Louisbourg Wastewater System Summary Report i
Contents
CHAPTER 1 Introduction & Background ......................................................................................... 1
1.1 Introduction ........................................................................................................................ 1
1.2 Background ......................................................................................................................... 1
1.3 Description of Existing Wastewater Collection System ...................................................... 1
1.4 Service Area Population ...................................................................................................... 2
CHAPTER 2 Wastewater Interceptor System .................................................................................. 3
2.1 Description of Proposed Wastewater Interceptor Infrastructure ...................................... 3
2.2 Interception Infrastructure Land/Easement Acquisition Requirements ............................ 3
2.2.1 Linear Infrastructure ............................................................................................... 3
CHAPTER 3 Existing Wastewater Collection System Upgrades / Assessments ................................ 5
3.1 Asset Condition Assessment Program ................................................................................ 5
3.2 Sewer Separation Measures ............................................................................................... 5
CHAPTER 4 Wastewater Treatment System ................................................................................... 6
4.1 Recommended Wastewater Treatment Facility ................................................................. 6
4.2 Wastewater Treatment Facility Land Acquisition Requirements ....................................... 7
4.3 Wastewater Treatment Facility Site Desktop Geotechnical Review .................................. 7
CHAPTER 5 Wastewater System Archaeological Resources Impact Assessment ............................. 8
5.1 Archaeological Resources Impact Assessment ................................................................... 8
CHAPTER 6 Wastewater Infrastructure Costs ............................................................................... 10
6.1 Wastewater Interception & Treatment Capital Costs ...................................................... 10
6.2 Wastewater Interception & Treatment Annual Operating Costs ..................................... 11
6.3 Annual Capital Replacement Fund Contribution Costs .................................................... 11
6.4 Existing Wastewater Collection System Upgrades / Assessment Costs ........................... 13
CHAPTER 7 Project Implementation Timeline .............................................................................. 14
7.1 Implementation Schedule ................................................................................................. 14
Appendices
A Louisbourg Collection System Pre‐Design Brief
B Louisbourg Wastewater Treatment System Pre‐Design Brief
C Louisbourg Environmental Risk Assessment Report
D Louisbourg Wastewater Treatment Facility Site Desktop Geotechnical Review
E Louisbourg Wastewater System Archaeological Resources Impact Assessment
HEJV Louisbourg Wastewater System Summary Report 1
CHAPTER 1 INTRODUCTION & BACKGROUND
1.1 Introduction
Harbour Engineering Joint Venture (HEJV) was retained by the Cape Breton Regional Municipality
(CBRM) to provide engineering services associated with the preliminary design of wastewater
interception and treatment infrastructure for the community of Louisbourg, Nova Scotia as part of
the greater Environmental Risk Assessment and Preliminary Design of 7 Future Wastewater Treatment
Systems in CBRM project. This report presents a description of that proposed infrastructure upgrades
for the Louisbourg Wastewater system, as well as an estimate of the capital, operating costs and
replacement costs for the proposed infrastructure. In addition, estimated costs of upgrades and
assessments related to the existing wastewater collection system are provided. A desktop
geotechnical review of the wastewater treatment facility site is provided, along with an archaeological
resources impact assessment review for all sites of proposed wastewater infrastructure. Finally, an
Implementation Timeline is provided, which outlines a tentative schedule for implementation of the
various proposed wastewater system upgrades.
1.2 Background
The wastewater collection system in the community of Louisbourg, as in many communities throughout
CBRM, currently discharges untreated wastewater to the Atlantic Ocean. The evolution of the existing
wastewater collection and disposal systems in CBRM included the creation of regions of a community
which were serviced by a common wastewater collection system tied to a local marine outfall. Such
design approaches have traditionally been the most cost‐effective manner of providing centralized
wastewater collection, and the marine environment has long been the preferred receiving water given
the available dilution. Due to a changing regulatory environment, CBRM is working toward intercepting
and treating the wastewater in these communities prior to discharge.
The Louisbourg system has been classified as low risk under the federal Wastewater System Effluent
Regulations under the Fisheries Act, requiring implementation of treatment systems by the year 2040.
1.3 Description of Existing Wastewater Collection System
The community of Louisbourg is serviced by a gravity sewer system, ranging in size from 200 to 750mm
in diameter. There are 5 wastewater sewersheds in the community of Louisbourg. Each sewershed
actively discharges raw sewage to Louisbourg Harbour. The outfalls for the sewersheds are located as
follows:
HEJV Louisbourg Wastewater System Summary Report 2
L#1 ‐ South of the Wolfe/Riverdale/Main Street intersection at the Barrachois;
L#2 ‐ South of the Centre and Commercial Street intersection;
L#3 ‐ Adjacent to the boardwalk, south of Harbourview Crescent;
L#4 ‐ Minto Street; and
L#5 – South of the Beatrice/Main Street intersection.
An additional unnamed outfall is located at the south end of Marvin Street, which has been denoted
as L#6 for the purposes of this preliminary design brief. This outfall receives discharge from one home.
This home would be best served in the future by a low pressure sewer system that would convey
discharge to the new interceptor sewer.
There are several commercial buildings on the Louisbourg Waterfront that appear to not be
connected to the existing sanitary sewer network. Each of these buildings may have their own outfalls
for sanitary and process sewer flows. These buildings would be best served in the future by a low
pressure sewer system that could convey sewer to the adjacent CBRM sewer network.
1.4 Service Area Population
For Louisbourg, the service area population was estimated to be 821 people in 391 residential units.
The population of the CBRM has been declining and this trend is expected to continue. Recent
population projection studies predict a 17.8% decrease in population in Cape Breton County between
2016 and 2036. For this reason, no allocation has been made for any future population growth.
For the purpose of preliminary design, wastewater infrastructure has been sized based on the current
population and measured flow data. While this may seem overly conservative, due to significant
amounts of inflow and infiltration (I&I) observed in sewer systems in the CBRM, a given population
decrease will not necessarily result in a proportional decrease in wastewater flow. Therefore, basing
the design on current conditions is considered the most reasonable approach.
HEJV Louisbourg Wastewater System Summary Report 3
CHAPTER 2 WASTEWATER INTERCEPTOR SYSTEM
2.1 Description of Proposed Wastewater Interceptor Infrastructure
The proposed wastewater interceptor system for the Louisbourg Wastewater System includes the
following major elements:
A 300mm diameter gravity sewer will intercept flow at L#1, with a connection at Riverdale
Street. The gravity interceptor will cross an existing box culvert at Main Street and convey
flow to Combined Sewer Overflow (CSO) #2.
CSO‐1 will be used to redirect flow and decrease pipe size from the existing 750mm diameter
L#5 outfall system to the new gravity interceptor.
A 250 mm diameter interceptor gravity sewer will convey the flow from CSO‐1 to the
Louisbourg Wastewater Treatment Plant (WWTP). The route will commence on Main Street
and flow to Commercial Street. L#3 will be intercepted on Harbourview Drive. L#4 will be
intercepted at Minto Street.
To intercept flow at Commercial Street, the interceptor sewer increases in size to 450mm
diameter at the intersection of Commercial and Aberdeen Street. The interceptor sewer will
connect to the existing sewer on Lower Warren, Alexandra and Strathcona Street.
The conveyed flow will then be intercepted by CSO‐2, to limit the flow into the proposed
WWTP.
In addition to the outlined pipe route, low pressure sewer systems would be provided for
buildings along the waterfront that are currently not connected to the CBRM sanitary sewer
system.
A detailed description of the proposed wastewater interceptor system, including preliminary layout
drawings is provided in Appendix A.
2.2 Interception Infrastructure Land/Easement Acquisition Requirements
2.2.1 Linear Infrastructure
Installation of linear infrastructure such as gravity sewer piping and manholes will require property
acquisitions or easements as shown in the table below.
HEJV Louisbourg Wastewater System Summary Report 4
Table 1 ‐ Linear Infrastructure Land Acquisition Requirements
PID# Property
Owner Assessed Value Description Size Required Purchase Entire
Lot (Y/N)
15458128
SNE Sea
Products
Incorporated
$34,500 Sewer
Easement 45mx10m N
15458243 3264937 Nova
Scotia Limited $307,900 Sewer
Easement 200mx10m N
HEJV Louisbourg Wastewater System Summary Report 5
CHAPTER 3 EXISTING WASTEWATER COLLECTION SYSTEM
UPGRADES / ASSESSMENTS
3.1 Asset Condition Assessment Program
To get a better sense of the condition of the existing Louisbourg sewage collection system, HEJV
recommends completing a sewage collection system asset condition assessment program in the
community. The program would carry out an investigation involving two components:
1. Visual inspection and assessment of all manholes in the collection system;
2. Video inspection of 20% of all sewers in the system
The program should be completed with the issuance of a Collection System Asset Condition
Assessment Report that would summarize the condition of the various assets inspected and include
opinions of probable costs for required upgrades.
3.2 Sewer Separation Measures
CBRM should consider completing further sewer separation investigation efforts in Louisbourg. The
program would review catch basins that are currently connected or possibly connected to existing
sanitary sewers. The program should also include the costing of the installation of new storm sewers
to disconnect catch basins from the existing sanitary sewer.
A sewer separation investigation could negate the requirement for CSO #1, should the existing system
allow for the reconfiguration to a smaller gravity sewer and a separate, larger storm sewer. The storm
sewer would still direct flow to L#5, whereas the reconfigured gravity sewer would convey directly to
the proposed interceptor sewer.
HEJV Louisbourg Wastewater System Summary Report 6
CHAPTER 4 WASTEWATER TREATMENT SYSTEM
4.1 Recommended Wastewater Treatment Facility
The recommended wastewater treatment facility for Louisbourg is the Sequencing Batch Reactor
(SBR) process, which is an aerobic suspended‐growth biological treatment process. The SBR process
is a batch process whereby secondary treatment, including nitrification, is achieved in one reactor. It
involves a “fill and draw” type reactor where aeration and clarification occur in the same reactor.
Settling is initiated after the aeration cycle and supernatant is withdrawn through a decanter
mechanism. The WWTP would provide the following general features:
1. A triplex sewage pumping station to lift sewage from the proposed interceptor sewer into the
WWTP;
2. Preliminary treatment involving raw wastewater screening and grit removal;
3. Secondary treatment involving two continuous‐flow SBR tanks;
4. Disinfection of the treated wastewater with the use of an ultraviolet (UV) disinfection unit;
5. Sludge management by means of an aerated sludge holding tank, sludge dewatering centrifuge
and associated bin room;
6. Odour control equipment;
7. Staff work spaces, including office space, laboratory space, control room, locker room, lunch
room, and washrooms.
8. Site access and parking, along with site fencing;
9. A new treated wastewater outfall.
The proposed site of the Louisbourg WWTP is located at the end of Strathcona Street. The design
loads for the proposed WWTP are as shown in the table below.
Table 2 ‐ WWTP Design Loading Summary
Parameter Average Day Peak Day
Design Population 821
Flow (m3/day) 590 2,360
CBOD Load (kg/day) 65.7 131
TSS Load (kg/day) 73.9 148
TKN Load (kg/day) 10.9 21.8
HEJV Louisbourg Wastewater System Summary Report 7
A detailed description of the proposed wastewater treatment system, including preliminary layout
drawings is provided in Appendix B.
The associated Environmental Risk Assessment Report, which outlines effluent criteria for the
proposed wastewater treatment facility for Louisbourg is provided in Appendix C.
4.2 Wastewater Treatment Facility Land Acquisition Requirements
Construction of the proposed wastewater treatment facility will require property acquisitions as
shown in the table below.
Table 3 ‐ WWTP Land Acquisition Requirements
PID# Property
Owner Assessed Value Description Size Required Purchase Entire
Lot (Y/N)
15458243
3264937 Nova
Scotia Limited $307,900 WWTP Site 100m x 100m N
4.3 Wastewater Treatment Facility Site Desktop Geotechnical Review
A review of the subsurface soil conditions at the proposed site for the Louisbourg Wastewater
Treatment Facility was carried out. In general, the review involved a field visit to the site to observe
the general conditions and a desktop review of available documents with the intent of commenting
on the following issues:
site topography;
geology (surficial ground cover, probable overburden soil and bedrock type);
geotechnical problems and parameters;
previous land use (review of aerial photographs);
underground/surface mining activities; and
proposed supplemental ground investigation methods (test pits and/or boreholes)
The following geotechnical issues were noted at the site:
1. The presence of old concrete foundation and uncontrolled and/or loose fills are suspected on
the site due to historical activities.
2. There is potential that a substantial volume of bedrock excavation may be required on the
site. Extraction and bedrock excavation will require drill and blast techniques to facilitate
removal of the bedrock.
3. There is a potential to find impacted soils (historical photographs depict above ground fuel
tanks, coal and fuel storage tanks) on the site. Soil samples should be analyzed to confirm the
presence or absence of contamination.
The review recommends an intrusive borehole program on the site to further define the subsurface
conditions.
A copy of the Louisbourg WWTP site geotechnical review report is provided in Appendix D.
HEJV Louisbourg Wastewater System Summary Report 8
CHAPTER 5 WASTEWATER SYSTEM ARCHAEOLOGICAL
RESOURCES IMPACT ASSESSMENT
5.1 Archaeological Resources Impact Assessment
In October 2018, Davis MacIntyre & Associates Limited conducted a phase I archaeological resource
impact assessment at sites of proposed new wastewater infrastructure for the Louisbourg
Wastewater System. The assessment included a historic background study and reconnaissance in
order to determine the potential for archaeological resources in the impact area and to provide
recommendations for further mitigation, if necessary.
The historic background study indicated that significant historic settlement occurred in the study area
in the 18th century, related to French fishing activity and occupation. After the second siege of
Louisbourg, there appears to have been little settlement in the study area itself until the mid‐19th
century. This occupation intensified in the late 19th and early 20th centuries with the construction of
railways. While there is little direct evidence of occupation by the Mi'kmaq and their ancestors, the
landscape features of the study area would have been conducive to First Nations and Mi'kmaq
occupation of the beach and adjacent areas.
Historic mapping and archival evidence also points to the potential for a chapel and possible human
burials in the area between Jerrett's Brook and Lorway Street, as well as under the lawn of the fish
plant. Human remains were found during the installation of a water line in 1902 and may have been
from an isolated burial or are evidence of burials associated with the chapel. Unfortunately, there is
little information available on the French chapel and there is confusion about whether the house in
the 1902 newspaper article was located on the south or north side of Main Street. An elevated
potential area buffer of 30 meters around the two possible houses, and extending a further 40 meters
west along the road, has been established.
Despite the presence of modern roads, buildings and utilities, which have created impact, the study
area has been assessed generally as moderate to high potential for archaeological resources related
to the 18th century French occupation and moderate potential for First Nations archaeological
resources. One area has also been identified as elevated potential for encountering burials or human
remains. A portion of the footprint for the WWTP has been evaluated as low to moderate potential
due to the presence of existing disturbance from the fish plant, as well as the area at Jerrett's Brook
HEJV Louisbourg Wastewater System Summary Report 9
and across Riverdale Street where previous disturbance related to road alignments and culverts is
located.
Due to existing roads, buildings, asphalt and packed gravel parking lots, and infilling, archaeological
testing is not easily conducted in most of the study area. However, a portion of the area designated
as elevated potential for human remains is currently a grass lawn. It is recommended that some level
of additional archaeological investigation be conducted in this area prior to construction. This
additional investigation may include a geophysical survey to search for burial anomalies, or stripping
of the sod within the impact area and an archaeological cleaning pass to attempt to identify potential
grave shafts. Some types of geophysical survey, such as ground penetrating radar, can be used over
paved or concrete surfaces and would allow the sidewalk and road to be investigated. However, the
results of geophysical surveys would still need to be confirmed with archaeological testing or
monitoring. The appropriate level of additional investigation should be determined in consultation
with the Department of Communities, Culture & Heritage.
In the remainder of the study area that was evaluated as moderate to high potential for archaeological
resources, it is recommended that archaeological monitoring be conducted, until the archaeologist
can make a determination that the area has been disturbed to the extent that intact archaeological
resources will not be expected to be encountered. Areas of low to moderate potential may require
only periodic check‐ins or for the archaeologist to be "on‐call" for construction crews to notify if they
encounter archaeological resources. Should intact archaeological resources be encountered during
monitoring, it is required that they are properly mitigated by a professional archaeologist.
It is also recommended that a contingency plan be developed to guide any discovery of human
remains in the west end of the study area. This plan should include a methodology for encountering
disturbed versus intact burials and should specify what level of recording of the skeletal material
would be required. The plan must also specify where any human remains will be kept during all phases
of the project (initial finding, recording and analysis, and re‐internment). This plan should be
developed in consultation with the Department of Communities, Culture & Heritage, as well as
Kwilmu’kw Maw‐klusuaqn (KMKNO). Parks Canada would also be a potential stakeholder to engage
due to the proximity of the Fortress of Louisbourg and their ongoing excavation of 18th century French
burials at Rochefort Point at the Fortress.
HEJV Louisbourg Wastewater System Summary Report 10
CHAPTER 6 WASTEWATER INFRASTRUCTURE COSTS
6.1 Wastewater Interception & Treatment Capital Costs
An opinion of probable capital cost for the recommended wastewater interception and treatment
system for Louisbourg is presented in the table below.
Table 4 ‐ Louisbourg Wastewater Interception & Treatment System Capital Costs
Project Component Capital Cost (Excluding
Taxes)
Wastewater Interception System $1,341,308
Wastewater Interception System Land Acquisition $25,000
Subtotal 1: $1,366,308
Construction Contingency (25%): $336,000
Engineering (10%): $135,000
Total Wastewater Interception: $1,837,308
Wastewater Treatment Facility $10,057,560
Wastewater Treatment Facility Land Acquisition $71,429
Subtotal 2: $10,128,989
Construction Contingency (25%): $2,514,400
Engineering (12%): $1,207,000
Total Wastewater Treatment: $13,850,389
Total Interception & Treatment System: $15,687,697
HEJV Louisbourg Wastewater System Summary Report 11
6.2 Wastewater Interception & Treatment Annual Operating Costs
An opinion of probable annual operating costs for the recommended wastewater interception and
treatment system for Louisbourg is presented in the table below.
Table 5 ‐ Louisbourg Wastewater Interception & Treatment System Operating Costs
Project Component Annual Operating Cost
(Excluding Taxes)
Wastewater Interception System
General Linear Maintenance Cost $1,000
Electrical Operational Cost $1,000
Total Wastewater Interception Annual Operating Costs: $2,000
Wastewater Treatment Facility
Staffing $175,000
Power $25,500
Maintenance Allowance $33,000
Total Wastewater Treatment Annual Operating Costs: $233,500
Total Interception & Treatment System Annual Operating Costs: $235,500
6.3 Annual Capital Replacement Fund Contribution Costs
The CBRM wishes to create a Capital Replacement Fund to which annual contributions would be made
to prepare for replacement of the wastewater assets at the end of their useful life. The calculation of
annual contributions to this fund involves consideration of such factors as the type of asset, the asset
value, the expected useful life of the asset, and the corresponding annual depreciation rate for the
asset. In consideration of these factors, the table below provides an estimate of the annual
contributions to a capital replacement fund for the proposed new wastewater interception and
treatment system infrastructure. This calculation also adds the same contingency factors used in the
calculation of the Opinion of Probable Capital Cost, to provide an allowance for changes during the
design and construction period. The actual Annual Capital Replacement Fund Contributions will be
calculated based on the final constructed asset value, the type of asset, the expected useful life of the
asset, and the corresponding annual depreciation rate for the asset type. Please note that costs shown
below do not account for annual inflation and do not include applicable taxes.
HEJV Louisbourg Wastewater System Summary Report 12
Table 6 ‐ Louisbourg Wastewater Interception & Treatment System Capital Replacement Fund
Costs
Description of Asset Asset Value
Asset Useful
Life
Expectancy
(Years)
Annual
Depreciation
Rate (%)
Annual Capital
Replacement
Fund
Contribution
Wastewater Interception System
Linear Assets (Piping, Manholes and
Other) $1,241,308 75 1.3% $16,137
Pump Station Structures (Concrete
Chambers, etc.) $55,000 50 2.0% $1,100
Pump Station Equipment (Mechanical
/ Electrical) $45,000 20 5.0% $2,250
Subtotal $1,341,308 ‐ ‐ $19,487
Construction Contingency (Subtotal x 25%): $4,872
Engineering (Subtotal x 10%): $1,949
Wastewater Interception System Annual Capital Replacement Fund Contribution
Costs: $26,307
Wastewater Treatment System
Treatment Linear Assets (Outfall and
Yard Piping, Manholes and Other) $2,341,682 75 1.3% $30,442
Treatment Structures (Concrete
Chambers, etc.) $2,333,623 50 2.0% $46,673
Treatment Equipment (Mechanical /
Electrical, etc.) $5,382,255 20 5.0% $269,113
Subtotal $10,057,560 ‐ ‐ $346,228
Construction Contingency (Subtotal x 25%): $86,557
Engineering (Subtotal x 12%): $41,547
Wastewater Treatment System Annual Capital Replacement Fund Contribution
Costs: $474,332
Total Wastewater Interception & Treatment Annual Capital Replacement Fund
Contribution Costs: $500,640
HEJV Louisbourg Wastewater System Summary Report 13
6.4 Existing Wastewater Collection System Upgrades / Assessment Costs
The estimated costs of upgrades and assessments related to the existing wastewater collection
system as described in Chapter 3 are shown in the table below.
Table 7 ‐ Existing Wastewater Collection System Upgrades / Assessment Costs
Item Cost
Collection System Asset Condition Assessment Program
Condition Assessment of Manholes based on 72MHs $40,000
Condition Assessment of Sewer Mains based on 2.1 kms of infrastructure $35,000
Total $75,000
Sewer Separation Measures
Separation based on 11.6 kms of sewer @ $45,000/km $522,000
Engineering (10%) $52,000
Contingency (25%) $131,000
Total $705,000
Total Estimated Existing Collection System Upgrade and Assessment Costs $780,000
HEJV Louisbourg Wastewater System Summary Report 14
CHAPTER 7 PROJECT IMPLEMENTATION TIMELINE
7.1 Implementation Schedule
Figure 1 provides a tentative schedule for implementation of wastewater system upgrades for
Louisbourg, including proposed wastewater interception and treatment infrastructure as well as
upgrades to and assessment of the existing collection system.
For the Low Risk systems such as Louisbourg, it is expected that implementation of proposed upgrades
will proceed on a staggered basis over the next 20 years as the availability of funding allows. As each
of these systems have the same target deadline, the prioritization will likely depend on not only the
availability of funding but also external factors. As the prioritization of the low risk systems is not
currently known, the project implementation schedule has been tentatively outlined on a generalized
basis (Year 1, Year 2, etc.) rather than with specified deadlines.
The schedule has been structured such that, in Year 1, asset condition assessments and investigations
to locate sources of extraneous water entering the system would be carried out. The two subsequent
years are allotted for design/construction of recommended upgrades, however, it is conceivable that
this could be completed in one year, depending on the scope of work required. It is proposed that,
during the following year, a follow‐up wastewater flow metering program would be carried out to
confirm design flows for new infrastructure and gauge the effect of upgrades to the existing collection
system. The subsequent four years after the follow‐up flow metering program have been allotted to
carry out design/construction of the new interception and treatment system. However, it is
conceivable that this work could be completed within three (3) years. This results in a tentative
implementation schedule that covers an eight (8) year timeline, which as noted above could be
compressed to six (6) years to align with typical funding programs for major infrastructure
It should be noted that, although the process of pursuing the acquisition of properties and easements
required to construct the proposed wastewater upgrades as outlined in previous sections is not shown
on the Project Implementation Schedule, it is recommended that the CBRM pursue these acquisitions
prior to the commencement of detailed design.
No. Project Component Period: Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Figure 1 ‐ Project Implementation Schedule Louisbourg Wastewater System
Year:1234
1 Carry out asset condition assessment of all manholes in the existing collection system
$40,000
2 Carry out video inspection and assessment of selected sanitary sewers in the existing collection system
$35,000
3 Carry out Sewer Separation Investigation Study to locate sources of extraneous water entering the
collection system $30,000
4 Carry out detailed design for recommended upgrades to the existing collection system based on
previous assessments $52,000
5 Carry out tendering, construction and commissioning for recommended upgrades to the existing
collection system $522,000
6 Carry out flow metering and wastewater testing in the existing collection system to confirm
wastewater flows and organic loading
7 Carry out detailed design for proposed wastewater interception infrastructure
8 Carry out tendering, construction, commissioning and initial systems operations for proposed
wastewater interception infrastructure
$20,000
$54,000
9 Carry out detailed design for proposed wastewater treatment infrastructure
10 Carry out tendering, construction, commissioning and initial systems operations for proposed
wastewater treatment infrastructure
No. Project Component Period: Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec Jan ‐ Mar Apr ‐ Jun Jul ‐ Sept Oct ‐ Dec
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Schedule:
Cash Flow:
Louisbourg Wastewater SystemFigure 1 ‐ Project Implementation Schedule
5678
1 Carry out asset condition assessment of all manholes in the existing collection system
2 Carry out video inspection and assessment of selected sanitary sewers in the existing collection system
3 Carry out Sewer Separation Investigation Study to locate sources of extraneous water entering the
collection system
Year:
4 Carry out detailed design for recommended upgrades to the existing collection system based on
previous assessments
5 Carry out tendering, construction and commissioning for recommended upgrades to the existing
collection system
6 Carry out flow metering and wastewater testing in the existing collection system to confirm
wastewater flows and organic loading
7 Carry out detailed design for proposed wastewater interception infrastructure
8 Carry out tendering, construction, commissioning and initial systems operations for proposed
wastewater interception infrastructure $1,783,308
$482,800
$13,367,589
9 Carry out detailed design for proposed wastewater treatment infrastructure
10 Carry out tendering, construction, commissioning and initial systems operations for proposed
wastewater treatment infrastructure
HEJV Louisbourg Wastewater System Summary Report Appendices
APPENDIX A
Louisbourg Collection System Pre‐Design
Brief
187116 ●Final Brief ●April 2020
Environmental Risk Assessments & Preliminary
Design of Seven Future Wastewater Treatment
Systems in CBRM
Louisbourg Collection System Pre-Design Brief
Prepared by: HEJVPrepared for: CBRM
March 2020
Re-Issued Louisbourg
Collection System Final Pre-
Design Brief
April 16, 2020 James Sheppard, P.Eng.Darrin McLean, MBA,
FEC., P.Eng.
Darrin McLean,
MBA, FEC., P.Eng.
Re-Issued Louisbourg
Collection System Final Pre-
Design Brief
May 9, 2019 James Sheppard, P.Eng.Darrin McLean, MBA,
FEC., P.Eng.
Darrin McLean,
MBA, FEC., P.Eng.
Louisbourg Collection System
Final Pre- Design Brief
March 21,
2019
James Sheppard, P.Eng. Darrin McLean, MBA,
FEC., P.Eng.
Darrin McLean,
MBA, FEC., P.Eng.
Louisbourg Collection System
Draft Pre- Design Brief
December 18,
2018
James Sheppard, P.Eng. Bob King, P.Eng.Darrin McLean,
MBA, FEC., P.Eng.
Issue or Revision Date Prepared By:Reviewed By:Issued By:
This document was prepared
for the party indicated herein.
The material and information in
the document reflects the
opinion and best judgment of
Harbour Engineering Joint
Venture (HEJV) based on the
information available at the
time of preparation. Any use of
this document or reliance on its
content by third parties is the
responsibility of the third party.
HEJV accepts no responsibility
for any damages suffered as a
result of third party use of this
document.
March 27, 2020
275 Charlotte Street
Sydney, Nova Scotia
Canada
B1P 1C6
Tel: 902-562-9880
Fax: 902-562-9890
_________________
LOUISBOURG COLLECTION SYSTEM PRE DESIGN BRIEF/ek
ED: 16/04/2020 13:32:00/PD: 16/04/2020 15:09:00
April 16, 2020
Matthew D. Viva, P.Eng.
Manager of Wastewater Operations
Cape Breton Regional Municipality
320 Esplanade, Sydney, NS B1P 7B9
Dear Mr. Viva:
RE: Environmental Risk Assessments & Preliminary Design of Seven Future
Wastewater Treatment Systems in CBRM – Louisbourg Collection System
Pre-Design Brief
Harbour Engineering Joint Venture (HEJV) is pleased to submit the following
Collection System Pre-Design Brief for your review and comment. This Brief
summarizes the interceptors and local sewers that will form the proposed
wastewater collection system for the community of Louisbourg. The collection
system will convey sewer to a future Wastewater Treatment Facility that has
been proposed to be located west of the intersection of Strahcona and
Commercial Streets, on the former fish plant site. The Brief also outlines the
design requirements and standards for the required collection system
infrastructure components.
We look forward to your comments on this document.
Yours very truly,
Harbour Engineering Joint Venture
Prepared by: Reviewed by:
James Sheppard, P.Eng. Darrin McLean, MBA, FEC, P.Eng.
Civil Infrastructure Engineer Senior Civil Engineer
Direct: 902-562-9880 Direct: 902-539-1330
E-Mail:jsheppard@dillon.ca E-Mail:dmclean@cbcl.ca
Project No: 187116 (Dillon) and 182402.00 (CBCL)
March 27, 2020
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief i
Contents
CHAPTER 1 Introduction & Background ........................................................................................... 1
1.1 Introduction ................................................................................................................... 1
1.2 System Background ........................................................................................................ 1
1.2.1 L#1...................................................................................................................... 2
1.2.2 L#2...................................................................................................................... 2
1.2.3 L#3...................................................................................................................... 2
1.2.4 L#4...................................................................................................................... 2
1.2.5 L#5...................................................................................................................... 2
CHAPTER 2 Design Parameters & Standards .................................................................................... 3
2.1 General Overview ........................................................................................................... 3
2.2 Design Standards ............................................................................................................ 3
CHAPTER 3 Wastewater Interceptor Pre- Design ............................................................................. 5
3.1 General Overview ........................................................................................................... 5
3.2 Design Flows .................................................................................................................. 5
3.2.1 Theoretical Flow ................................................................................................. 5
3.2.2 Observed Flow .................................................................................................... 6
3.2.3 Flow Conclusions & Recommendations ............................................................... 7
3.2.4 Wet Weather Conditions Assessment ................................................................. 8
3.3 Interceptor System ......................................................................................................... 8
3.3.1 WWTP Location Review ...................................................................................... 8
3.3.2 Interceptor System Breakdown ........................................................................... 9
3.4 Combined Sewer Overflows.......................................................................................... 10
3.4.1 CSO-1................................................................................................................ 10
3.4.2 CSO-2................................................................................................................ 11
3.5 Low Pressure Sewer System ......................................................................................... 11
CHAPTER 4 Existing Collection System Upgrades ........................................................................... 12
4.1 Asset Condition Assessment Program ........................................................................... 12
4.2 Sewer Separation Measures ......................................................................................... 12
CHAPTER 5 Pipe Material Selection and Design ............................................................................. 13
5.1 Pipe Material ................................................................................................................ 13
CHAPTER 6 Land and Easement Requirements .............................................................................. 14
6.1 WWTP Site ................................................................................................................... 14
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief ii
6.2 Linear Infrastructure and Access Road .......................................................................... 14
CHAPTER 7 Site Specific Constraints ............................................................................................... 15
7.1 Construction Constraints .............................................................................................. 15
7.2 Environmental Constraints ........................................................................................... 15
7.3 Access Requirements.................................................................................................... 16
CHAPTER 8 Opinion of Probable Costs ........................................................................................... 17
8.1 Opinion of Probable Construction Costs – New Wastewater Collection Infrastructure .. 17
8.2 Opinion of Operational Costs ........................................................................................ 17
8.3 Opinion of Existing Collection System Upgrades and Assessment Costs ........................ 18
8.4 Opinion of Annual Capital Replacement Fund Contributions ......................................... 18
CHAPTER 9 References ................................................................................................................... 20
Tables
Table 2-1 Sewer Design Criteria ............................................................................................... 3
Table 3-1 Theoretical Flow Summary for L#2 outfall ................................................................. 6
Table 3-2 Flow Monitoring Location Summary ......................................................................... 6
Table 3-3 Average Dry Weather and Design Flows Results ....................................................... 7
Table 3-4 Recommended Design Flows at each Outfall location ............................................... 7
Table 3-5 Observed Flows during Rainfall Events...................................................................... 8
Table 5-1 Comparison of Pipe Materials ................................................................................. 13
Table 6-1 WWTP Land Acquisition Details .............................................................................. 14
Table 6-2 Linear Infrastructure Land Acquisition Details ......................................................... 14
Table 8-1 Annual Operations and Maintenance Costs Breakdown .......................................... 17
Table 8-2 Estimated Existing Collection System Upgrade and Assessment Costs..................... 18
Table 8-3 Estimated Annual Capital Replacement Fund Contributions.................................... 19
Appendices
Appendix A –Drawings
Appendix B – Flow Master Reports
Appendix C – Opinion of Probable Design & Construction Costs
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 1
CHAPTER 1 INTRODUCTION &BACKGROUND
1.1 Introduction
Harbour Engineering Joint Venture (HEJV) has been engaged by the Cape Breton Regional
Municipality (CBRM) to carry out Environmental Risk Assessments (ERAs) and Preliminary Design of
seven future wastewater treatment Systems in the CBRM. The future wastewater collection and
treatment systems will serve the communities of Glace Bay, Port Morien, North Sydney & Sydney
Mines, New Waterford, New Victoria, Louisbourg and Donkin, which currently have no wastewater
treatment facilities.
The preliminary design of the wastewater interceptor systems are being completed as an addition to
the existing wastewater systems in each community. In general, the proposed interceptor sewers
will convey wastewater from the existing outfalls to the proposed Wastewater Treatment Plant
(WWTP) in each location. The complexity of each system is directly related to the number of
outfalls, geographic size and topography of each community. In general, the scope of work on the
interceptor system generally includes the following:
®Determination of design wastewater flows;
®Making recommendations on the best sites for proposed wastewater treatment facilities;
®Development of the most appropriate and cost-effective configurations for wastewater
interception; and,
®Estimation of capital and operations costs for recommended wastewater components.
This document relates to the interceptors and local gravity sewers that will form the wastewater
interceptor system for the proposed WWTP in the community of Louisbourg. This brief outlines the
design requirements and standards for the required infrastructure components. Information
regarding the preliminary design of the proposed wastewater treatment facility for Louisbourg will
be provided in a separate Design Brief.
1.2 System Background
The community of Louisbourg is serviced by a gravity sewer system, ranging in size from 200 to
750mm in diameter. There are 5 wastewater sewersheds in the community of Louisbourg. Each
sewershed actively discharges raw sewage to Louisbourg Harbour. The outfalls for the sewersheds
are located as follows:
®L#1 – South of the Wolfe/Riverdale/Main Street intersection at the Barrachois;
®L#2 - South of the Centre and Commercial Street intersection;
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 2
®L#3 – Adjacent to the boardwalk, south of Harbourview Crescent;
®L#4 – Minto Street; and,
®L#5 – South of the Beatrice/Main Street intersection.
An additional unnamed outfall is located at the south end of Marvin Street, which has been denoted
as L#6 for the purposes of this preliminary design brief. This outfall receives discharge from one
home. This home would be best served in the future by a low pressure sewer system that would
convey discharge to the new interceptor sewer.
There are several commercial buildings on the Louisbourg Waterfront that appear to not be
connected to the existing sanitary sewer network. Each of these buildings may have their own
outfalls for sanitary and process sewer flows. These buildings would be best served in the future by
a low pressure sewer system that could convey sewer to the adjacent CBRM sewer network.
1.2.1 L#1
The L#1 sewershed is made up of a gravity network that services Wolfe and Riverdale Streets. The
outfall is 450mm in diameter and conveys flow to the Barrachois, located south of the
Wolfe/Main/Riverdale Street.
1.2.2 L#2
The L#2 outfall receives approximately 40% of the sanitary sewer flow generated in the community
of Louisbourg. The outfall is 600mm in diameter. The outfall is located near the Louisbourg
Government Wharf, adjacent to the Centre/Commercial Street intersection.
1.2.3 L#3
Two buildings discharge to the L#3 outfall. The outfall is located near the boardwalk, adjacent to the
slipway, south of Harbourfront Crescent. The outfall is 100mm in diameter.
1.2.4 L#4
The L#4 outfall is located south east of Minto Street. The outfall is 100mm in diameter and services
one home.
1.2.5 L#5
A gravity network conveys to the L#5 outfall which receives approximately 40% of the sanitary
sewer flow generated in the community. The outfall is 750mm in diameter.
A drawing of the existing Louisbourg sewer system is located in Appendix A for reference.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 3
CHAPTER 2 DESIGN PARAMETERS &STANDARDS
2.1 General Overview
The development of a wastewater interceptor system for each of the communities is highly
dependent upon the selection of appropriate design parameters. HEJV has reviewed applicable
design standards and has developed the preliminary design of the interceptor sewer to meet and
exceed these industry standards.
2.2 Design Standards
The design of the interceptor system has been based on the following reference documents and
standards:
®Atlantic Canada Wastewater Guidelines Manual for Collection, Treatment, and Disposal
(ACWGM) (Environment Canada, 2006); and
®Water Environment Federation: Manual of Practice FD-4, Design of Wastewater and
Stormwater Pumping Stations.
The key design criteria that have been established for this project are presented in Table 2-1.
Table 2-1 Sewer Design Criteria
Description Unit Design Criteria Source Comments
Hydraulic Capacity l/s Location dependent HEJV
Flow has been set to minimize
overflow events in the interceptor
system prior to the WWTP. See
discussion Chapter 3.
Material of gravity pipe
PVC or Reinforced
concrete CBRM See discussion in Chapter 5
Hydraulic design gravity Manning’s Formula ACWGM n = 0.013
Maximum spacing
between manholes m
120 for pipes up to
and including 600 mm
and 150 for pipes over
600 mm
ACWGM
Gravity pipe minimum
design flow velocity m/s 0.6 ACWGM
Gravity pipe maximum
flow velocity m/s 4.5 ACWGM
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 4
Description Unit Design Criteria Source Comments
Pipe crossings separation mm 450 minimum
Minimum separation must also meet
Nova Scotia Environment (NSE)
requirements.
Horizontal pipe separation
gravity pipe to water main m 3.0 ACWGM Can be laid closer if the installation
meets the criteria in Section 2.8.3.1
Gravity pipe minimum
depth of cover m 1.5 HEJV Subject to Interferences
Gravity pipe maximum
depth of cover m 4.5 HEJV Subject to Interferences.Increased
depth may be considered where
warranted
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 5
CHAPTER 3 WASTEWATER INTERCEPTOR PRE-DESIGN
3.1 General Overview
A drawing of the existing Louisbourg collection system has been included in Appendix A. The
drawing was created using background data collected from various sources to depict the layout of
the existing gravity network.
The proposed wastewater interceptor system for Louisbourg will be a gravity sewer that will redirect
flow from the existing outfalls to the proposed Waste Water Treatment Plant (WWTP) site.
For this Pre-Design Brief, HEJV has compiled a preliminary plan and profile drawing of the proposed
linear infrastructure. The locations of the required linear infrastructure, Combined Sewer Overflow
(CSO) chambers and future WWTP have also been illustrated on the drawings and are included in
Appendix A.
3.2 Design Flows
HEJV completed a review of the theoretical and observed sanitary flows for the Louisbourg
sewersheds. The purpose of the assessment was to estimate average and design flows for the
environmental risk assessment (ERA) and the preliminary design of the future WWTP and
interception system.
3.2.1 Theoretical Flow
Theoretical flow was calculated based on design factors contained in the ACWGM. To estimate
population, the number of private dwellings were estimated then multiplied by an average
household size. An average value of 2.2 persons per household was used based on the average
household size found in the 2016 Statistics Canada information for Cape Breton. The number of
apartments, nursing homes, townhouses, and other residential buildings were estimated and
considered in the population estimate. Population estimates are shown in Table 3-1. The peak
design flow was calculated using the following equation (1):
ܳ(݀)=ܲݍܯ
86.4 +ܫܣ (1)
Where:
Q(d) = Peak domesƟc sewage flow (l/s)
P = PopulaƟon (in thousands)
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 6
q = Average daily per capita domesƟc flow (l/day per capita)
M = Peaking factor (Harman Method)
I = unit of extraneous flow (l/s)
A = Subcatchment area (hectares)
ACWGM recommends an average daily domestic sanitary flow of 340 l/day per person for private
residential dwellings. The unit of extraneous flow was assumed to be approximately 0.21 l/s/ha
based on typical ranges outlined in ACWGM. The contributing sewershed was estimated to be 52 ha.
The peaking factor used in Equation 1 was determined using the Harman Formula (2) shown below:
Harman Formula
ܯ =1+14
4+ܲ.ହ (2)
The estimated average dry weather flow (ADWF) and peak design flows were calculated for the flow
monitor location (L#2 outfall) based on the ACWGM methods discussed above are presented in
Table 3-1.
Table 3-1 Theoretical Flow Summary for L#2 outfall
Estimated Area (ha)Estimated Population1 ADWF2 (l/s)Peak Design Flow3 (l/s)
36 360 1.42 13.47
1 2016 Cape Breton Census from StaƟsƟcs Canada
2Based on average daily sewer flows of 340 L/day/person (ACWGM 2006)
3EsƟmated using ACWGM equaƟon for peak domesƟc sewage flows (including extraneous flows and peaking factor)
3.2.2 Observed Flow
One flow monitoring staƟon was installed in Louisbourg. The flow monitor was installed in the outlet
manhole for L#2, on Commercial Street.A summary of the flow meter locaƟon and monitoring
duraƟon is provided in Table 3- 2.
Table 3-2 Flow Monitoring Location Summary
Northing Easting Monitoring Start-End Dates Days of Data
5087630.112 4618444.369 February 26-April 11, 2018 45
Analysis for observed dry weather flows were completed using the United States Environmental
Protection Agency’s (EPA) Sanitary Sewer Overflow Analysis and Planning (SSOAP) toolbox. The
SSOAP toolbox is a suite of computer software tools used for capacity analysis and condition
assessments of sanitary sewer systems.
Flow and rainfall data were input into the SSOAP program, along with sewershed data. To determine
average dry weather flow (ADWF), days that were influenced by rainfall were deleted. This was done
in the SSOAP model by removing data from days that had any rain within the last 24 hours, more
than 5 mm in the previous 48 hours, and more than 5 mm per day additional in the subsequent days
(e.g. 10 mm in the last 3 days). Again, the subset of flow data without the three week period noted
in earlier in this section was used in the SSOAP program.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 7
The calculated ADWF estimates based on monitored flow data evaluated using the SSOAP program
is presented in Table 3-3, along with average, 4xADWF and peak flow from raw monitored data.
Please note that the value of 4xADWF was recommended by UMA Engineering Limited as the
minimum sewage flow rate that should be treated for Louisbourg in the report “Industrial Cape
Breton Wastewater Characterization Program – Phase II” prepared in 1994. HEJV compared the
4xADWF value with the other values compiled in Table 3-3.
Table 3-3 Average Dry Weather and Design Flows Results
ADWF From SSOAP Model
(l/s)
Average Daily Observed
Flow (l/s)4xADWF (l/s)Peak Flow
(l/s)
3.0 3.72 12.0 (l/s)12.23
3.2.3 Flow Conclusions & Recommendations
Based on the results presented in Tables 3-1 and 3-3,it is recommended that the peak theoretical
flow be used at this time to design the interceptor sewer because the peak flows being considered
only require a reasonably sized gravity interceptor sewer.Table 3-4 summarizes the peak design and
average dry weather flows that will be intercepted at each outfall. Due to the existing gravity sewer
configuration, a CSO has been proposed for the connection with L#5. Due to the size of the existing
sewer at L#5 and its overall contribution to the Louisbourg Interceptor Sewer, HEJV recommends
completing a flow monitoring program at this location during the detailed design of the project. The
flows developed by HEJV for L#5 based on the completed flow monitoring program fall well short of
requiring a 750mm diameter sewer. Methods of decreasing the size of the sanitary sewer in this
area could be looked at with further flow monitoring and system research. If there is an influence
from storm runoff, a sewer separation project could be completed in this area to reduce the size of
the sanitary sewer piping on Main Street and effectively delete the requirement for CSO-1. Please
see Section 3.4 for further discussion on the required CSO chambers.
Table 3-4 Recommended Design Flows at each Outfall location
Outfall Contributing Population ADWF2(L/s)Peak Flow3
(l/s)
L#1 113 0.94 5.30
L#21 360 2.98 13.50
L#3 4.6 0.04 0.40
L#4 2.3 0.02 0.20
L#5 327 2.71 13.00
L#6 14 0.11 0.50
1 Ouƞall at monitoring locaƟon
2 Based on observed values at OF#2
3 EsƟmated using ACWGM equaƟon for peak domesƟc sewage flows (including extraneous flows and peaking factor)
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 8
3.2.4 Wet Weather Conditions Assessment
To evaluate performance of the proposed interception system during wet weather conditions,
metered flows during rainfall events have also been considered. The results of the wet weather flow
assessment at the metered location is presented in Table 3-5. The calculated flows were compared
to the recommended design flow to determine if sewer overflow/surcharge conditions would be
anticipated.
Table 3-5 Observed Flows during Rainfall Events
Monitoring Station
Minor Rainfall Event
(10-25 mm Daily Rainfall)
# of Events Daily Average
Flow (l/s)
Expected Overflow1
(Y/N)
Louisbourg 6 4 to 7 N
1 Overflow expected when observed flow exceeds design flow
The results in Table 3-5 suggest that the interception system will be able to accommodate the wet
weather flows that were monitored during the flow gauging exercise.
3.3 Interceptor System
The proposed interceptor system for the Louisbourg WWTP is presented on the plan and profile
drawing attached in Appendix A. The proposed interceptor system is made up of various segments
of gravity sewer that extend across the community.
3.3.1 WWTP Location Review
The first step in laying out the interceptor sewer route was to determine the location of the future
WWTP that will serve the community. To accomplish this, the type of treatment process needed to
be considered, along with the availability of land.
An initial review for the Louisbourg WWTP site was completed. At that time, two locations were
reviewed. Initially a mechanical plant was contemplated for an undeveloped area at the northern
end of Elwood Street, while a stabilization pond was contemplated for an area north of Harbourview
Drive.
The undeveloped area north of Elwood Street was not selected as a feasible location due to the
proximity of neighboring residential properties. The design for the interceptor sewer would have
also required a pump station near the waterfront area and a forcemain to convey flows up-gradient
to the WWTP, and a gravity sewer back to the waterfront area for an outfall, increasing the costs of
the interceptor sewer. This same area was reviewed for a lagoon design. Due to the land
requirements and the proximity of existing dwellings, the inclusion of a lagoon at Elmwood Street
was determined not to be viable.
The location to the north of Harbourview Drive was remote and would have provided sufficient
room for the development of a stabilization pond. However, the portion of land required to
construct the WWTP is owned by Public Works Government Services Canada and is a portion of the
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 9
historical Fortress of Louisbourg property. Given the remoteness of the land, the infrastructure
required to convey discharge to the site, an unfavourable location for an outfall (inner portion of the
harbour) and property acquisition concerns, HEJV decided that this location was also not suitable.
Further review of the Louisbourg area took place with several promising locations being brought
forward. The site of the former SNE Sea Products Ltd. processing plant was reviewed. CBRM held
initial discussions with the property owner. It was concluded that the price to purchase the former
plant would be considerable. HEJV also reviewed two areas in front of the plant; however, a lift
station would be required near the harbourfront to convey flow to both sites, therefore increasing
the cost of the interceptor infrastructure. Another site was reviewed on the harbourfront, between
Alexandra Street and Strathcona Street, on the north side of Commercial Street. The location
provided sufficient room to develop the plant, but was too close to neighboring residential
properties.
The final location selected was adjacent to the previously mentioned former fish plant. The location
would be on the same parcel of land as the former plant, but located between the existing buildings
and Strathcona Street. This area is already commercially developed. Being on the waterfront, there
is easy access to permit the installation of a new outfall. Due to the topography of the area, gravity
flow to the WWTP site is achievable, but due to depth of the proposed linear infrastructure near the
proposed WWTP site, a lift station would be required. The forcemain to serve the lift station would
be of minimal length, as the station will only need to pump the sewage into the plant. The downfall
for the location is the proximity to residential development. The location does not meet the
ACWGM guidelines for setback distances from residential properties. As part of our pre-design
efforts, HEJV met with NSE to discuss locations for future treatment plants that do not meet the
ACWGM guidelines for setback distances but ultimately make the most sense for a community from
an economic stand point. NSE’s feedback to HEJV was that if the location of the WWTP did not meet
the ACWGM guidelines but ultimately made the most sense for a community, the detailed design of
the plant would need to include odour controls, to minimize the impact to neighbouring properties.
The proposed location of the WWTP has been shown on the existing sewer system drawing included
in Appendix A.
3.3.2 Interceptor System Breakdown
With the WWTP location selected, HEJV laid out the interceptor sewer. The interceptor sewer will
divert sewer from the six existing outfalls. HEJV determined that it was possible to convey discharge
to the proposed WWTP site by way of a gravity interceptor. The major elements of the interceptor
system include:
®A 300mm diameter gravity sewer will intercept flow at L#1, with a connection at Riverdale
Street. The gravity interceptor will cross an existing box culvert at Main Street and convey
flow to CSO-2.
®CSO-1 (see Sections 3.4 and 4.2 for further discussion on this CSO chamber) will be used to
redirect flow and decrease pipe size from the existing 750mm diameter L#5 outfall system
to the new gravity interceptor.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 10
®A 250 mm diameter interceptor gravity sewer will convey the flow from CSO-1 to the
Louisbourg WWTP. The route will commence on Main Street and meander to Commercial
Street.
®L#3 will be intercepted on Harbourview Drive.
®L#4 will be intercepted at Minto Street.
®To intercept flow at Commercial Street, the interceptor sewer increases in size to 450mm
diameter at the intersection of Commercial and Aberdeen Street.
®The interceptor sewer will connect to the existing sewer on Lower Warren, Alexandra and
Strathcona Street.
®The conveyed flow will then be intercepted by CSO-2, to limit the flow into the proposed
WWTP.
®In addition to the specified pipe route, low pressure sewer systems should be provided for
buildings along the water front that are currently not connected to the CBRM sanitary sewer
system. See Section 3.5 for further details.
Flow Master reports for the proposed linear infrastructure, illustrated on Sheet 1 in Appendix A,
have been included in Appendix B.
3.4 Combined Sewer Overflows
A Combined Sewer Overflow (CSO) should be utilized in the proposed interceptor system where
flows directed to the WWTP exceed the interception design rate defined in Section 3.2.3. The
proposed locations for the chambers have been illustrated on the plan and profile drawings included
in Appendix A.
In general, the interceptor system has been designed for peak flow. Each of the outfalls in
Louisbourg discharge raw sewage to the Atlantic Ocean on a continuous basis. By installing the
interceptor sewer, the amount of raw sewage being directed to the Atlantic Ocean will be greatly
reduced. Given the limited number of overflows anticipated, the CSOs for Louisbourg have been
proposed to be an unscreened chamber. The chambers will essentially act as a flow diversion
chambers. Each CSO chamber should be complete with a weir plate that will separate the chamber
into two sections, one for normal everyday flows and one for overflow events. Normal flows would
be directed to the interceptor system. As the flow increases above the interception design flow rate,
the level in the CSO chamber will rise, until it crests the weir plate. Flow that crests the weir plate
would be directed back to the original outfall.
The Louisbourg interceptor system will include 2 CSO chambers that will direct flow to various
components of the system.
3.4.1 CSO-1
The CSO-1 chamber has been shown as part of the connection with the L#5 outfall. The existing
gravity sewer leading to L#5 is 750mm in diameter. CSO-1 should be utilized to decrease the size of
the pipe being used in the interceptor system, as the intercepted flows identified in Section 3.2 do
not require a 750mm diameter gravity sewer. This flow chamber will allow the pipe size to be
decreased to 250mm, while providing overflow relief in case of a high flow event. The chamber
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 11
would be sized to allow the peak flow (13.0l/s) to be conveyed to the interceptor sewer. The peak
flow of 13.0l/s was selected so that cleansing velocity was provided in the interceptor sewer.
Additionally the flow rate is not such that would cause an upsizing of the pipe. The detailed design
of the interceptor should review the infrastructure in this area to confirm if the CSO is required or if
an alternative connection can be made to the existing sanitary sewer. Additionally a sewer
separation project could be undertaken in this area to permit the usage of a suitably sized sanitary
gravity sewer (i.e. +/- 250 diameter) to convey directly to the interceptor sewer, while diverting
storm runoff to L#5 directly, deleting the requirement for CSO-1. Existing information obtained by
HEJV suggests that sewer in the area should range between 200 – 300mm in diameter. The limited
manhole survey completed by HEJV for infrastructure in the immediate area (one manhole up and
downstream of the connection) connection conflicted with this data.
3.4.2 CSO-2
The second CSO chamber will be used to reduce the flow entering the WWTP. The flow rate will be
established during the preliminary design of the WWTP. As the interceptor sewer can accommodate
peak flows, without upsizing the linear infrastructure, a flow device is needed to restrict flow before
the plant. The preliminary design of the WWTP will review the requirements for CSO-2. It may be
possible to size the headworks to include additional flows such that they are screened and pass
through the UV system prior to discharge into the harbour.
3.5 Low Pressure Sewer System
There are a number of commercial buildings on the waterfront that currently do not appear to
connect to the existing CBRM sanitary sewer network. HEJV recommends low pressure sewer
systems to connect these buildings to adjacent sanitary sewer infrastructure for their inclusion in
the interceptor sewer. The connection at each of the buildings should only be completed for
domestic waste only. Process water should not be connected to the CBRM network and should be
conveyed as per their NSE Approvals to Operate.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 12
CHAPTER 4 EXISTING COLLECTION SYSTEM UPGRADES
4.1 Asset Condition Assessment Program
To get a better sense of the condition of the existing Louisbourg sewage collection system, HEJV
recommends completing a sewage collection system asset condition assessment program in the
community. The program would carry out an investigation involving two components:
®Visual inspection and assessment of all manholes in the collection system
®Video inspection of 20% of all sewers in the system
The program should be completed with the issuance of a Collection System Asset Condition
Assessment Report that would summarize the condition of the various assets inspected and include
opinions of probable costs for required upgrades.
4.2 Sewer Separation Measures
CBRM should consider completing a sewer separation investigation program for Louisbourg. The
program would review catch basins that are currently connected or possibly connected to existing
sanitary sewers. The program should also include the costing of the installation of new storm
sewers to disconnect catch basins from the existing sanitary sewer.
As discussed in Section 3.2.3, a sewer separation investigation could delete the requirement for CSO
#1, should the existing system allow for the reconfiguration to a smaller gravity sewer and a
separate, larger storm sewer. The storm sewer would still direct flow to L#5, whereas the re-
configured gravity sewer would convey directly to the proposed interceptor sewer.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 13
CHAPTER 5 PIPE MATERIAL SELECTION AND DESIGN
5.1 Pipe Material
Two pipe materials (PVC, and Reinforced Concrete) were considered for this project and were
evaluated against various factors. PVC and Reinforced Concrete were reviewed against each other
for a suitable gravity pipe material. A summary of the advantages and disadvantages of the different
materials is presented in Table 5-1.
Table 5-1 Comparison of Pipe Materials
Pipe Material Advantages Disadvantages
PVC
·CBRM standard
·Excellent corrosion resistance of
pipe
·Standard testing method
·Light weight
·High impact strength
·CBRM staff and contractors are
familiar with installation of PVC
forcemains
·Cost competitive
·Requires good bedding
·Must be handled carefully in
freezing conditions
·Fittings are susceptible to
corrosion
Reinforced Concrete
·High strength
·Standard testing method
·CBRM staff and contractors are
familiar with installation
·Heavy – harder to handle
·Susceptible to attached by H2S
and acids when not coated
·Requires careful installation to
avoid cracking
·Short laying lengths
Based on the above comparison, HEJV recommends that the material used for the gravity sewer
piping for the Louisbourg interceptor sewer be PVC.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 14
CHAPTER 6 LAND AND EASEMENT REQUIREMENTS
HEJV has reviewed the requirements for land acquisition and easements. While the majority of the
proposed infrastructure will be installed on CBRM property and public right of ways, a portion of the
proposed interceptor system and WWTP have been proposed to be constructed on privately owned
land parcels.
6.1 WWTP Site
As discussed in Section 3.3, the WWTP will be located on a parcel of land privately owned by
3264937 Nova Scotia Limited. HEJV understands that initial discussions have occurred between the
land owner and CBRM about purchasing the entire lot. Due to the cost to acquire the entire lot,
HEJV recommends purchasing a portion of the lot, located between the existing fish plant building
and the Lobster Kettle Restaurant. Exact dimensions and location of the required piece of land will
be confirmed in the WWTP Pre-Design Brief. Presented below in Table 6-1 are some of the pertinent
details of the parcel of land required to build the WWTP.
Table 6-1 WWTP Land Acquisition Details
PID Property Owner Assessed Value Description Purchase Entire Lot
(Y/N)
15458243 3264937 Nova
Scotia Limited $307,900 WWTP Site N
6.2 Linear Infrastructure and Access Road
The installation of the linear will require an easement on two parcels of privately owned by land.
The remaining linear infrastructure will be installed within CBRM owned land and public right of
ways. Details on the required easement area are as follows:
Table 6-2 Linear Infrastructure Land Acquisition Details
PID Property Owner Assessed
Value Description Size Required
Purchase
Entire Lot
(Y/N)
15458128 SNE Sea Products
Incorporated
$34,500 Sewer Easement 45mx10m N
15458243 3264937 Nova
Scotia Limited
$307,900 Sewer Easement 200mx10m N
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 15
CHAPTER 7 SITE SPECIFIC CONSTRAINTS
During the preliminary design of the interceptor system, HEJV has reviewed the pipe routing for
potential constraints. HEJV reviewed construction constraints, environmental constraints and access
requirements for the proposed interceptor infrastructure. The next sections of the Design Brief
briefly touch on items that were found during HEJV’s review.
7.1 Construction Constraints
HEJV has reviewed the preliminary design of the interceptor system from a construction constraints
perspective.
The proposed gravity interceptor sewer from Riverdale Street will be installed over an existing box
culvert that crosses below Main Street. HEJV had the top of the box culvert surveyed during the
preliminary design to ensure that the proposed alignment depicted on Sheet 2 in Appendix A would
be achievable. A maximum grade of 0.5% can be used between the existing manhole located on
Riverdale Street and the top of the existing box culvert. HEJV cautions that the resultant velocity for
a 300mm diameter pipe at 0.5% grade at peak design flow will be slightly less than the required
cleansing velocity of 0.6m/s. A resultant peak velocity of 0.57m/s, can be achieved.
The proposed gravity sewer will also traverse a piece of CBRM land that is destined to become part
of waterfront development project. CBRM owned PID 15659378 has already been part of a
preliminary design project for the Synergy Louisbourg Development Society. At this time, CBRM still
maintains ownership of this land parcel. A portion of the gravity interceptor has been shown to
cross this land parcel. Dillon Consulting Limited, completed a preliminary design of the site in 2016.
Utilizing the pre-design, the route of the proposed sewer was selected to provide minimal
disturbance to the site, i.e. the route was selected to traverse across the top of a proposed parking
lot.
The proposed gravity route will also need to cross CBRM owned PID 15659394. Construction across
this lot will be tight as the route is just south of the Louisbourg salt shed.
7.2 Environmental Constraints
The route for the proposed gravity outlet is in close proximity to a shoreline along Commercial
Street. Care will need to be exercised during construction to ensure appropriate erosion and
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 16
sedimentation control measures are put in place and properly maintained during construction. The
excavation in this area will also be deeper, so dewatering will be a major concern as well.
7.3 Access Requirements
Access to the WWTP site will be straight forward. Some thought will need to be given to the land
purchase involving a portion of PID 15458243. The lot segmented and purchased by CBRM will need
to leave a tract of land for an entrance to the remaining portion of PID 15458243 from
Commercial/Strahcona.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 17
CHAPTER 8 OPINION OF PROBABLE COSTS
8.1 Opinion of Probable Construction Costs – New Wastewater Collection
Infrastructure
An opinion of Probable Design and Construction Costs for new wastewater collection infrastructure
has been completed for the project. A detailed breakdown of the estimate has been provided in
Appendix C. The estimate is made up of the linear infrastructure design and construction costs and
associated land acquisition costs required to collect and convey the sanitary sewer in Louisbourg to
the proposed WWTP. For land acquisition costs, HEJV has used a ratio of the amount of land that is
affected by the required easement/property acquisition multiplied by the assessed value of the
entire lot. The Opinion of Probable Design & Construction Costs for the interceptor sewer for
Louisbourg is $1,837,308. This estimate is considered to be Class ‘C’, accurate within plus or minus
30%.
8.2 Opinion of Operational Costs
HEJV completed an Opinion of Operational Costs for the interceptor system. For annual costs, HEJV
considered the power consumption of the two CSO chambers based on typical Nova Scotia Power
rates and a linear maintenance cost based on similar sanitary sewer infrastructure. A breakdown of
costs has provided in Table 8-1.
Table 8-1 Annual Operations and Maintenance Costs Breakdown
The general linear maintenance cost for the interceptor system has been estimated to be $1,000 per
year in 2018 dollars. This includes flushing, inspection, and refurbishment of structures along the
linear portion of the collection system.
For the electrical operation cost, basic electrical loads for instrumentation were assumed.
Item Costs
General Linear Maintenance Cost $1,000/yr
Electrical Operational Cost $1,000/yr
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 18
8.3 Opinion of Existing Collection System Upgrades and Assessment Costs
An opinion of probable costs has been provided for the collection system asset condition
assessment program described in Chapter 4. These costs include the video inspection and flushing of
20% of the existing sanitary sewer network, visual inspection of manholes, traffic control and the
preparation of a collection system asset condition assessment report.
For sewer separation measures, budgetary pricing has been calculated by reviewing recent costs of
sewer separation measures in CBRM involving installation of new storm sewers to remove
extraneous flow from existing sanitary sewers. These costs have been translated into a cost per
lineal meter of sewer main. This unit rate was then applied to the overall collection system. The cost
also includes an allowance of 10% on the cost of construction for engineering and 25% for
contingency allowance. The estimated existing collection system upgrade and assessment costs are
provided in Table 8-2.
Estimates of costs for upgrades to and assessment of the existing collection system as outlines in
Table 8-2 are considered to be Class ‘D’, accurate to within plus or minus 45%.
Table 8-2 Estimated Existing Collection System Upgrade and Assessment Costs
8.4 Opinion of Annual Capital Replacement Fund Contributions
The CBRM wishes to create a Capital Replacement Fund to which annual contributions would be
made to prepare for replacement of the assets at the end of their useful life. The calculation of
annual contributions to this fund involves consideration of such factors as the type of asset, the
asset value, the expected useful life of the asset, and the corresponding annual depreciation rate for
the asset. In consideration of these factors,Table 8-3 provides an estimation of the annual
contributions to a capital replacement fund for the proposed new wastewater collection and
interception infrastructure.
Item Cost
Collection System Asset Condition Assessment Program
Condition Assessment of Manholes based on 72 MH’s $40,000
Condition Assessment of Sewer Mains based on 2.1km’s of infrastructure $35,000
Total $75,000
Sewer Separation Measures
Separation based on 11.6km’s of sewer @ $45,000/km $522,000
Engineering (10%)$52,000
Contingency (25%)$131,000
Total $705,000
Total Estimated Existing Collection System Upgrade and Assessment Costs $780,000
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 19
Table 8-3 Estimated Annual Capital Replacement Fund Contributions
Description of Asset Asset Value
Asset Useful
Life
Expectancy
(Years)
Annual
Depreciation
Rate (%)
Annual Capital
Replacement
Fund Contribution
Linear Assets (Piping, Manholes and Other) $1,241,308 75 1.3%$16,137
Pump Station Structures (Concrete
Chambers, etc.)$55,000 50 2.0%$1,100
Pump Station Equipment (Mechanical /
Electrical)$45,000 20 5.0%$2,250
Subtotal $1,341,308 --$19,487
Contingency Allowance (Subtotal x 25%):$4,872
Engineering (Subtotal x 10%):$1,949
Opinion of Probable Annual Capital Replacement Fund Contribution:$26,308
Note:
Annual contribuƟons do not account for annual inflaƟon.
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 20
CHAPTER 9 REFERENCES
Environment Canada (2006) –Atlantic Canada Wastewater Gidelines Manual for Collection,
Treatment and Disposal.
Harbour Engineering Inc. (2011).Cape Breton Regional Municipality Wastewater Strategy 2009.
Nova Scotia Environment (2018).Environment Act.
Nova Scotia Utility and Review Board (2013).Water Utility Accounting and Reporting Handbook.
UMA Engineering Ltd. (1994). Industrial Cape Breton Wastewater Characterization Programme –
Phase II.
Water Environment Federation (2009),Design of Wastewater and Stormwater Pumping Stations
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 21
APPENDIX A
Drawings
MAIN S
T
MI
N
T
O
S
T
PE
P
P
E
R
E
L
L
S
T
UP
P
E
R
W
A
R
R
E
N
S
T
LO
W
E
R
W
A
R
R
E
N
S
T
COMMERCIA
L
RI
V
E
R
D
A
L
E
S
T
HAV
E
N
S
I
D
E
R
D
MAIN ST
MAIN ST
MA
R
V
I
N
S
T
BE
A
T
R
I
C
E
S
T
WO
L
F
E
S
T
ST
R
A
T
H
C
O
N
A
S
T
EL
W
O
O
D
S
T
HARB
O
U
R
V
I
E
W
D
R
1
ENVIRONMENTAL RISK ASSESSMENTS
& PRELIMINARY DESIGN
JRS
JRS TAB
TAB 18-7116
1:3000
FEBRUARY 2018
HA
R
B
O
U
R
E
N
G
I
N
E
E
R
I
N
G
J
O
I
N
T
V
E
N
T
U
R
E
,
2
7
5
C
H
A
R
L
O
T
T
E
S
T
R
E
E
T
,
S
Y
D
N
E
Y
,
N
S
,
B
1
P
1
C
6
A
B
C
ISSUED FOR REVIEW
ISSUED FOR DRAFT DESIGN BRIEF
ISSUED FOR FINAL DESIGN BRIEF
02/27/18
11/12/18
03/11/19
JRS
JRS
JRS LOUISBOURG EXISTING COLLECTION SYSTEM
DATE
DESIGN
DRAWN
PROJECT NO.
SHEET NO.
No.DATE BYISSUED FOR
written permission from Dillon Consulting Limited.
than those intended at the time of its preparation without prior
Do not scale dimensions from drawing.
Report any discrepancies to Dillon Consulting Limited.
Verify elevations and/or dimensions on drawing prior to use.
Conditions of Use
REVIEWED BY
CHECKED BY
Do not modify drawing, re-use it, or use it for purposes other
SCALEj o i n t v e n t u r e
MAIN ST
L#1
MIN
T
O
S
T
PE
P
P
E
R
E
L
L
S
T
UP
P
E
R
W
A
R
R
E
N
S
T
LO
W
E
R
W
A
R
R
E
N
S
T
COMMERCIA
L
RIV
E
R
D
A
L
E
S
T
L#2
L#3
L#4
L#6
L#5
ELIZ
A
B
E
T
H
B
E
A
V
E
R
UPP
E
R
W
A
R
R
E
N
S
T
MAI
N
S
T
MAIN ST
MA
R
V
I
N
S
T
BE
A
T
R
I
C
E
S
T
WO
L
F
E
S
T
ST
R
A
T
H
C
O
N
A
S
T
OUTLINE OF PROPERTY
REQUIRING ACQUISITION
OUTLINE OF PROPERTY
REQUIRING AN EASEMENT
CS0-1CS0-2
300
Ø
3
0
0
Ø
450Ø
250Ø
250Ø
250Ø 25
0
Ø
15458243
(3264937 NOVA SCOTIA LIMITED)
15458128
(SNE SEA PRODUCTS
INCORPORATED
MAIN ST
MIN
T
O
S
T
PE
P
P
E
R
E
L
L
S
T
UP
P
E
R
W
A
R
R
E
N
S
T
LO
W
E
R
W
A
R
R
E
N
S
T
COMMERCIA
L
RIV
E
R
D
A
L
E
S
T
MAI
N
S
T
MAIN ST
MA
R
V
I
N
S
T
BE
A
T
R
I
C
E
S
T
WO
L
F
E
S
T
ST
R
A
T
H
C
O
N
A
S
T
EL
W
O
O
D
S
T
2
ENVIRONMENTAL RISK ASSESSMENTS & PRELIMINARY DESIGN
OF 7 FUTURE WASTEWATER TREATMENT SYSTEMS IN CBRM
TGB
TGB TAB
JRS 18-7116
1:2500
OCTOBER 2018
HA
R
B
O
U
R
E
N
G
I
N
E
E
R
I
N
G
J
O
I
N
T
V
E
N
T
U
R
E
,
2
7
5
C
H
A
R
L
O
T
T
E
S
T
R
E
E
T
,
S
Y
D
N
E
Y
,
N
S
,
B
1
P
1
C
6
A
B
ISSUED FOR REVIEW
ISSUED FOR FINAL DESIGN BRIEF
02/27/18
03/11/19
JRS
JRS
LOUISBOURG INTERCEPTOR
PLAN/PROFILE
DATE
DESIGN
DRAWN
PROJECT NO.
SHEET NO.
No.DATE BYISSUED FOR
written permission from Dillon Consulting Limited.
than those intended at the time of its preparation without prior
Do not scale dimensions from drawing.
Report any discrepancies to Dillon Consulting Limited.
Verify elevations and/or dimensions on drawing prior to use.
Conditions of Use
REVIEWED BY
CHECKED BY
Do not modify drawing, re-use it, or use it for purposes other
SCALEj o i n t v e n t u r e
PLAN
1:2500
PROFILE
1:2500 (HOR.) 1:500 (VERT.)
PROFILE
1:2500 (HOR.) 1:500 (VERT.)
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 22
APPENDIX B
Flow Master Reports
Harbour Engineering Joint Venture Louisbourg Collection System Pre-Design Brief 23
APPENDIX C
Opinion of Probable Design & Construction
Costs
OPINION OF PROBABLE
COST, CLASS 'C'
Preliminary
Collection and Project Manager:D. McLean
Interception Infrastructure Costs Only Est. by: J. Sheppard Checked by: D. McLean
Louisbourg, NS PROJECT No.:187116 (Dillon)
182402.00 (CBCL)
UPDATED:April 16, 2020
NUMBER UNIT
Linear Infrastructure $1,041,308.00
250 mm Diameter PVC gravity sewer 855 m $400.00 $342,000.00
300 mm Diameter PVC gravity sewer 462 m $425.00 $196,350.00
450 mm Diameter PVC gravity sewer 184 m $500.00 $92,000.00
450 mm Diameter PVC gravity sewer (deep installation)75 m $600.00 $45,000.00
Precast Manhole (1200mm dia.)19 each $5,500.00 $104,500.00
Connection to Existing Main (typ)10 each $8,000.00 $80,000.00
Closed Circuit Televsion Inspection 1,576 m $8.00 $12,608.00
Trench Excavation - Rock 2,250 m3 $60.00 $135,000.00
Trench Excavation - Unsuitable Material 1,125 m3 $10.00 $11,250.00
Replacement of Unsuitable with Site Material 565 m3 $10.00 $5,650.00
Replacement of Unsuitable with Pit Run Gravel 565 m3 $30.00 $16,950.00
Combined Sewer Overflow $200,000.00
Combined Sewer Overflow 2 L.S.$100,000.00 $200,000.00
Low Pressure Pump Systems $100,000.00
Low Pressure Pump Systems 10 L.S.$10,000.00 $100,000.00
SUBTOTAL (Construction Cost)$1,341,308.00
Contingency Allowance (Subtotal x 25 %)$336,000.00
Engineering (Subtotal x 10 %)$135,000.00
Land Acquisition $25,000.00
OPINION OF PROBABLE COST (Including Contingency)$1,837,308.00
THIS OPINION OF PROBABLE COSTS IS PRESENTED ON THE BASIS OF EXPERIENCE, QUALIFICATIONS, AND BEST JUDGEMENT. IT HAS BEEN PREPARED IN
ACCORDANCE WITH ACCEPTABLE PRINCIPLES AND PRACTICIES, MARKET TRENDS, NON-COMPETITIVE BIDDING SITUATIONS, UNFORSEEN LABOUR AND
MATERIAL ADJUSTMENTS AND THE LIKE ARE BEYOND THE CONTROL OF HEJV. AS SUCH WE CANNOT WARRANT OR GUARANTEE THAT ACTUAL COSTS WILL
NOT VARY FROM THE OPINION PROVIDED.
EXTENDED TOTALS QUANTITY TOTALUNIT COSTITEM DESCRIPTION
PREPARED FOR:
Cape Breton
Regional Municipality
March 27, 2020
HEJV Louisbourg Wastewater System Summary Report Appendices
APPENDIX B
Louisbourg Treatment System Pre‐Design
Brief
Prepared by: HEJVPrepared for: CBRM
187116 ●Final Brief ●April, 2020
Environmental Risk Assessments & Preliminary
Design of Seven Future Wastewater Treatment
Systems in CBRM
Louisbourg Wastewater Treatment Facility
Pre-Design Brief
March 2020
Louisbourg Wastewater
Treatment Facility Pre-
Design FINAL (2) Brief
April 13, 2020 David McKenna, P.Eng. Mike Abbott, P.Eng. DarrinMcLean,FEC,
P.Eng.
Louisbourg Wastewater
Treatment Facility Pre-
Design FINAL (1) Brief
Oct 10, 2019 David McKenna, P.Eng.Mike Abbott, P.Eng.Darrin McLean,FEC,
P.Eng.
Louisbourg Wastewater
Treatment Facility Pre-
Design DRAFT2 Brief
July 30, 2019 David McKenna, P.Eng.Mike Abbott, P.Eng.Darrin McLean,FEC,
P.Eng.
Louisbourg Wastewater
Treatment Facility Pre-
Design DRAFT1 Brief
May 20, 2019 Daniel Bennett, P.Eng. Mike Abbott, P.Eng.Darrin McLean,FEC,
P.Eng.
Issue or Revision Date Prepared By:Reviewed By:Issued By:
This document was prepared
for the party indicated herein.
The material and information
in the document reflects the
opinion and best judgment of
Harbour Engineering Joint
Venture (HEJV) based on the
information available at the
time of preparation. Any use
of this document or reliance
on its content by third parties
is the responsibility of the third
party. HEJV accepts no
responsibility for any damages
suffered as a result of third
party use of this document.
March 27, 2020
275 Charlotte
Street
Sydney, Nova
Scotia
Canada
B1P 1C6
Tel: 902-562-9880
Fax: 902-562-9890
_______________
__
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 3
April 13, 2020
Matthew D. Viva, P.Eng.
Manager of Wastewater Operations
Cape Breton Regional Municipality
320 Esplanade, Sydney, NS B1P 7B9
Dear Mr. Viva:
RE: Environmental Risk Assessments & Preliminary Design of Seven Future Wastewater
Treatment Systems in CBRM – Final Louisbourg Wastewater Treatment Plant Pre-Design
Brief
Harbour Engineering Joint Venture (HEJV) is pleased to submit the finalized Louisbourg
Wastewater Treatment Plant Preliminary Design Brief, which has been updated to reflect
additional CBRM comments on the draft report. The report summarizes an evaluation of
wastewater treatment options for the Community of Louisbourg, based on site specific
constraints.
Based on the preliminary design, HEJV is recommending that a new sequencing batch reactor
(SBR) mechanical wastewater treatment plant be constructed on the waterfront parcel of land
located at the former fish plant site on Strathcona Street. The treatment process will include
influent screening and grit removal, secondary treatment, and ultraviolet disinfection. The
facility will include a new building to house treatment equipment, and an odour control
system is included to minimize issues with neighboring land owners. A new outfall is included
in the design to discharge treated effluent further from the shoreline, to maximize dilution
and minimize the risk to recreational users.
We look forward to your comments on this document.
Yours truly,
Harbour Engineering Joint Venture
Prepared by:Reviewed by:
David McKenna, P.Eng.Mike Abbott, P.Eng.
Wastewater Treatment Engineer Wastewater Treatment Engineer
Phone: 506-633-5000 Direct: 902-423-3938
E-Mail:dmckenna@dillon.ca E-Mail:mikea@cbcl.ca
Project No: 187116 (Dillon) and 182402.00 (CBCL)
March 27, 2020
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief iv
Contents
CHAPTER 1 Introduction & Background ........................................................................................... 1
1.1 Introduction ................................................................................................................... 1
1.2 Louisbourg Background .................................................................................................. 2
1.3 Objectives ...................................................................................................................... 2
CHAPTER 2 Existing Conditions ........................................................................................................ 3
2.1 Description of Existing Infrastructure .............................................................................. 3
2.2 Population Projection ..................................................................................................... 3
2.3 Wastewater Flow Characterics ....................................................................................... 4
2.3.1 Observed Flows .................................................................................................. 4
2.3.2 Calculated Theorectical Flows ............................................................................. 5
2.4 Wastewater Quality Data ............................................................................................... 6
CHAPTER 3 Basis of design ............................................................................................................... 7
3.1 Service Area ................................................................................................................... 7
3.2 Design Flows .................................................................................................................. 7
3.3 Design Influent Loading .................................................................................................. 8
3.4 Design Effluent Requirements ........................................................................................ 9
CHAPTER 4 Treatment Process Alternatives ................................................................................... 11
4.1 Preliminary Treatment ................................................................................................. 11
4.1.1 Screening .......................................................................................................... 11
4.1.2 Grit Removal ..................................................................................................... 12
4.2 Secondary Treatment ................................................................................................... 14
4.2.1 Site Specific Suitability ...................................................................................... 16
4.2.2 Description of Candidate Processes for Secondary Treatment ........................... 17
4.3 Disinfection .................................................................................................................. 20
4.3.1 Chlorination ...................................................................................................... 20
4.3.2 UV Disinfection ................................................................................................. 21
4.3.3 Disinfection Recommendation .......................................................................... 21
4.3.4 SBR Disinfection ................................................................................................ 21
4.3.5 MBBR Disinfection ............................................................................................ 21
4.4 Sludge Management .................................................................................................... 22
4.5 Secondary Treatment Options Evaluation ..................................................................... 22
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief v
4.5.1 Opinion of Probable Capital Cost....................................................................... 22
4.5.2 Opinion of Probable Operating Costs ................................................................ 23
4.5.3 Life Cycle Cost Estimate .................................................................................... 23
4.5.4 Qualitative Evaluation Factors........................................................................... 24
4.5.5 Recommended Secondary Treatment Process .................................................. 25
CHAPTER 5 Preliminary Design ....................................................................................................... 26
5.1 General Overview ......................................................................................................... 26
5.2 Unit Process Description ............................................................................................... 26
5.2.1 Lift Station ........................................................................................................ 26
5.2.2 Preliminary Treatment ...................................................................................... 27
5.2.3 Secondary Treatment ....................................................................................... 28
5.2.4 Disinfection ...................................................................................................... 29
5.2.5 Sludge Management ......................................................................................... 30
5.2.6 Odour Control ................................................................................................... 31
5.3 Facility Description ....................................................................................................... 31
5.3.1 Civil and Site Works .......................................................................................... 32
5.3.2 Architectural ..................................................................................................... 32
5.3.3 Mechanical ....................................................................................................... 33
5.3.4 Electrical ........................................................................................................... 33
5.3.5 Lighting ............................................................................................................. 33
5.3.6 Instrumentation ................................................................................................ 34
5.3.7 Control System Overview .................................................................................. 34
5.3.8 Headworks........................................................................................................ 35
5.3.9 SBR ................................................................................................................... 35
5.3.10 Waste Activated Sludge .................................................................................. 35
5.3.11 Effluent Disinfection ....................................................................................... 35
CHAPTER 6 Project Costs ................................................................................................................ 36
6.1 Opinion of Probable Construction Costs ....................................................................... 36
6.2 Opinion of Annual Operating Costs ............................................................................... 36
6.3 Opinion of Annual Capital Replacement Fund Contributions ......................................... 37
CHAPTER 7 References ................................................................................................................... 38
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief vi
Tables
Table 2-1 Mira and East Population Projection ........................................................................................ 4
Table 2-2 Flow Monitoring Location Summary ......................................................................................... 4
Table 2-3 Average Dry Weather and Design Flows Results for L#2 Sewershed.......................................... 5
Table 2-4 Theoretical Flow Summary for L#2 outfall ................................................................................ 6
Table 2-5 HEJV Wastewater Sampling Results .......................................................................................... 6
Table 2-6 CBRM Wastewater Characterization Samples ........................................................................... 6
Table 3-1 Summary of Theoretical and Observed Flows for Outfall L#2 .................................................... 7
Table 3-2 Projected Flows at each Outfall location ................................................................................... 8
Table 3-3 Theoretical Wastewater Quality ............................................................................................... 9
Table 3-4 Design Effluent Requirements ................................................................................................ 10
Table 4-1 Secondary Treatment Processes ............................................................................................. 15
Table 4-2 Sequence Batch Reactor Process Design Criteria .................................................................... 19
Table 4-3 Moving Bed Bio-Reactor Process Design Criteria .................................................................... 20
Table 4-4 Secondary Process Capital Cost Comparison ........................................................................... 23
Table 4-5 Secondary Process Annual Operating Cost Comparison .......................................................... 23
Table 4-6 Secondary Process Life Cycle Cost Comparison ....................................................................... 24
Table 4-7 Secondary Process Life Cycle Cost Comparison – 73% Capital Funding ................................... 24
Table 4-8 Secondary Process Qualitative Evaluation Factors .................................................................. 24
Table 5-1 Preliminary Design Drawings .................................................................................................. 26
Table 5-2 Pump Station Summary .......................................................................................................... 27
Table 5-3 Fine Screening Design Summary ............................................................................................. 28
Table 5-4 Grit Removal Design Summary ............................................................................................... 28
Table 5-5 Secondary Treatment Design Summary .................................................................................. 29
Table 5-6 UV Disinfection Design Summary ........................................................................................... 30
Table 5-7 Sludge Tank Design Summary ................................................................................................. 30
Table 5-8 Sludge Dewatering Design Summary ...................................................................................... 31
Table 5-9 Classification of Building Areas ............................................................................................... 33
Table 6-1 - Annual Operating Costs Breakdown (2019 Dollars) ............................................................... 36
Table 6-2 - Estimated Annual Capital Replacement Fund Contributions ................................................. 37
Appendices
Appendix A –Drawings
Appendix B – SBR & MBBR Estimated Capital Cost Differential
Appendix C – Opinion of Probable Construction Costs
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 1
CHAPTER 1 INTRODUCTION &BACKGROUND
1.1 Introduction
Harbour Engineering Joint Venture (HEJV) has been engaged by the Cape Breton Regional Municipality
(CBRM) to carry out Environmental Risk Assessments (ERAs) and Preliminary Design of Seven Future
Wastewater Treatment Systems in the CBRM. The future wastewater collection and treatment systems
will serve the communities of Glace Bay, Port Morien, North Sydney & Sydney Mines, New Waterford,
New Victoria, Louisbourg, and Donkin, which currently have no wastewater treatment facilities. This
preliminary design brief summarizes the proposed wastewater treatment plant (WWTP) for the
Community of Louisbourg.
In general, the proposed WWTPs will treat wastewater to a standard set by the Nova Scotia Department
of Environment (NSE). The complexity of each system is directly related to incoming flow dynamics,
wastewater characteristics, available space, population attributes, and implementation strategy. The
objectives of this study can be summarized as follows:
®Using study outcomes from the ERAs, Population Growth Forecasts, Desktop Geotechnical
Reports, and in conjunction with the Collection System Preliminary Design Brief, accurately
assess existing conditions and determine design requirements for the new WWTP;
®Evaluate different wastewater treatment methods and make recommendations based on:
treatment efficiency, operational and maintenance requirements, site constraints, capital and
life cycle costing;
®Develop a clear implementation strategy that provides a plan and schedule for designing,
construction, commissioning, inspection, and occupy of the recommended WWTP option; and
®Present the findings for the preliminary design in a clear, concise manner containing project
information and recommendations developed throughout the preliminary design process.
The contents of this document relate solely to the proposed WWTP in the community of Louisbourg,
and have been produced in conjunction with the following documents:
®Louisbourg Environmental Risk Assessment;
®Louisbourg Collection System Preliminary Design Brief;
®Louisbourg Geotechnical Desktop Study; and
®Environmental Risk Assessments & Preliminary Design of Seven (7) Future Wastewater
Treatment Systems in CBRM - Base Information Summary Brief.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 2
1.2 Louisbourg Background
There is presently no WWTP in the Community of Louisbourg; wastewater is discharged untreated
directly into the Atlantic Ocean. As is the case in hundreds of coastline communities across Atlantic
Canada, the evolution of the existing wastewater collection and disposal systems in Cape Breton
included the creation of clusters / neighbourhoods / regions of a community, which were serviced by a
common wastewater collection system tied to a local marine outfall. Such design approaches have
traditionally been the most cost-effective manner of providing centralized wastewater service, and the
marine environment has long been the preferred receiving water given available dilution. Due to a
changing regulatory environment, CBRM is working toward intercepting and treating the wastewater in
these communities prior to discharge.
1.3 Objectives
The objectives of this report will be to:
®Review historic and recent data to establish design parameters for the new WWTP, including but
not limited to: population growth projections, sewer flows for both dry and wet weather
periods, and wastewater loading characteristics;
®Establish site-specific criteria for evaluating available wastewater treatment technologies;
®Screening and short-listing of potential wastewater treatment technologies that are viable for
the new Louisbourg WWTP;
®Evaluation of WWTP options based on the criteria herein, with a recommendation of the
optimal facility for Louisbourg; and
®The presentation of preliminary engineering design for the recommended option, along with
capital and operating cost estimates.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 3
CHAPTER 2 EXISTING CONDITIONS
2.1 Description of Existing Infrastructure
The Community of Louisbourg has six separate sewersheds, and is serviced by a gravity sewer system
ranging in size from 200 to 750mm in diameter. Each sewershed has a dedicated outfall that discharges
raw sewage to Louisbourg Harbour. The outfalls for the sewersheds are located as follows:
®L#1 – South of the Wolfe/Riverdale/Main Street intersection at the Barrachois;
®L#2 - South of the Centre and Commercial Street intersection;
®L#3 – Adjacent to the boardwalk, south of Harbourview Crescent;
®L#4 – Minto Street;
®L#5 – South of the Beatrice/Main Street intersection; and
®L#6 – Marvin Street.
In addition to these six named outfalls listed above, there are a number of commercial buildings on the
Louisbourg waterfront that do not appear to be connected to the existing sanitary sewer network. At
this moment in time it is unknown if wastewater from these buildings is connected to one of the above
listed outfalls or their own individual outfalls.
2.2 Population Projection
The population for the Louisbourg service area was calculated from the 2016 Census data contained in
CBRM’s GIS database using the following procedure: Each residential unit within the service area
boundary from CBRM’s structure database was multiplied by the average household size for the census
dissemination area that it falls within. For Louisbourg, the service area population was estimated to be
821 people in 391 residential units.
The population in Cape Breton County has been declining since the 1970s and a recent report by Turner
Drake & Partners Ltd predicts a 17.8% decrease in population in Cape Breton County between 2016 and
2036 (Turner Drake & Partners Ltd., February 2018). HEJV has trended population data and projected
areas of growth and decline as part of the Environmental Risk Assessments & Preliminary Design of
Seven Future Wastewater Treatment Systems in CBRM. The report divides the CBRM into five subsets
with the Community of Louisburg captured in the Mira and East data subset. This subset not only
includes the service area of the future Louisbourg wastewater plant, it also includes a significant amount
of unserved rural areas.Table 2-1 shows the actual and projected populations for the Mira and East
area, with actual populations denoted by red bold text.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 4
Table 2-1 Mira and East Population Projection
Year 1991 1996 2001 2006 2011 2016 2021
Population 7,850 7,840 7,320 6,525 5,770 5,080 4,430
The primary land use in the community of Louisbourg is residential single family dwellings with no
significant multi-unit dwellings or institutions/schools. There are a number of industrial and commercial
units in the community; however, it is suspected that these units are not connected to the existing
sanitary sewer and are serviced by their own private outfalls. The community is in close proximity to the
Fortress of Louisbourg which is a federal tourist attraction, and therefore it is expected to see a seasonal
increase in the number of visitors in the area.
2.3 Wastewater Flow Characterics
2.3.1 Observed Flows
HEJV conducted a sewer flow monitoring program to capture representative flow data from February 26
to April 11, 2018. The outlet of outfall L#2 was selected for the flow monitoring location as it receives
approximately 40% of the sanitary sewer flow generated by community. The summary of the flow meter
location data is shown in Table 2-2.
Table 2-2 Flow Monitoring Location Summary
Northing Easting Monitoring Start-End Dates Days of Data
5087630.112 4618444.369 February 26-April 11,45
Analysis for observed dry weather flows was completed using the United States Environmental
Protection Agency’s (EPA) Sanitary Sewer Overflow Analysis and Planning (SSOAP) toolbox. The SSOAP
toolbox is a suite of computer software tools used for capacity analysis and condition assessments of
sanitary sewer systems.
Flow and precipitation data were input into the SSOAP program, along with sewershed data. To
determine average dry weather flow (ADWF), days that may have been influenced by rainfall were
excluded. This was done in the SSOAP model by excluding data for days that had any rain within the last
24 hours, more than 5 mm in the previous 48 hours, and more than 5 mm per day additional in the
subsequent days (e.g. 10 mm in the last 3 days).
The ADWF calculated using monitored flow data and the SSOAP program is presented in Table 2-3.
Table 2-3 also shows the average and peak flows from flow monitoring data, which considers wet
weather flow events. The 4xADWF value is also shown, which was recommended in the report
“Industrial Cape Breton Wastewater Characterization Program – Phase II” prepared in 1994 by UMA
Engineering Limited as the minimum sewage flow that should be treated for the Community of
Louisbourg. HEJV compared the 4xADWF value with the other values compiled in Table 2-3.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 5
Table 2-3 Average Dry Weather and Design Flows Results for L#2 Sewershed
Outfall Estimated
Area (ha)
Estimated
Population1 m3/day L/p/d m3/ha/d
Observed ADWF
36 360
321 892 8.9
Observed Peak Flow 1057 2936 29.4
SSOAP Model ADWF 259 719 7.2
4 x ADWF2 1036 2878 28.7
1 2016 Cape Breton Census from StaƟsƟcs Canada
2 ADWF is from SSOAP model results
2.3.2 Calculated Theorectical Flows
Theoretical flows were calculated based on design factors contained in the Atlantic Canada Wastewater
Guidelines Manual (ACWGM). To estimate wastewater flow, total number of residents is multiplied by a
per capita wastewater rate.
Peak design flow was calculated using the following equation (1):
ܳ(݀)=ܲݍܯ
86.4 +ܫܣ +ܵܰ (1)
Where:
Q(d) = Peak domesƟc sewage flow (l/s)
P = PopulaƟon (in thousands)
q = Average daily per capita domesƟc flow (l/day per capita)
M = Peaking factor (Harman Method)
I = unit of extraneous flow (l/s/ha)
A = Subcatchment area (hectares)
S = Unit of Manhole inflow allowance for each manhole in sag locaƟon, in l/sec
N =Number of manholes in sag locaƟon
ACWGM recommends an average daily domestic sanitary flow of 340 l/day per person for private
residential dwellings, excluding extraneous flow. The unit of extraneous flow representing ingress and
infiltration was assumed to be 0.21 l/s/ha based on the midpoint of the range outlined in ACWGM. The
contributing sewershed was estimated to be 36 ha. The impact of inflow from manholes was excluded
based on the small size of the sewershed. The peaking factor used in Equation 1 was determined using
the Harman Formula (2) shown below:
Harman Formula
ܯ =1+14
4+ܲ.ହ (2)
The peaking factor, M, calculated for Louisbourg is 4.04.TheoreƟcal flows calculated for Ouƞall L2 are
shown in Table 2-4.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 6
Table 2-4 Theoretical Flow Summary for L#2 outfall
Estimated Area
(ha)
Estimated
Population1 m3/day L/p/d m3/ha/d
ADWF2
36 360 122.4 340 3.4
Peak Design Flow3 1148 3189 31.9
1 2016 Cape Breton Census from StaƟsƟcs Canada
2 Based on Average sewer flows of 340 L/day/person (ACWGM 2006)
3EsƟmated Using ACWGM equaƟon for peak domesƟc sewage flows (Includes extraneous flows and peaking factor)
2.4 Wastewater Quality Data
HEJV collected untreated wastewater samples from three of the six outfalls (L1, L2, and L5), and the
results are presented in Table 2-5. CBRM also conducted sampling at each of the outfalls from 2015
through 2017, summarized in Table 2-6. Note that only one sample was collected by CBRM at all outfalls
except L2; therefore, these results are not an average and only represent a single grab sample that
cannot be used with statistical confidence due to the limited dataset. Outfall L2 was sampled more than
13 times by CBRM and is more statistically significant.
Table 2-5 HEJV Wastewater Sampling Results
Parameter Units Outfall Location
L1 L2 L5
CBOD5 mg/L 110 61 41
Total Kjeldahl Nitrogen (TKN)mg/L 6.3 6.2 4.3
Nitrogen (Ammonia Nitrogen)as N mg/L 1.0 2.9 0.96
Unionized ammonia mg/L 0.0021 0.0069 0.0022
pH pH 6.89 6.94 6.92
Total Phosphorus mg/L 0.79 1.1 0.78
Total Suspended Solids mg/L 33 43 25
E.coli MPN/100mL 200000 820000 770000
Total Coliforms MPN/100mL >2400000 >2400000 2000000
Table 2-6 CBRM Wastewater Characterization Samples
Parameter Units
Outfall Location
L1 L2 L3 L4 L5
Avg No. of
Sample Avg No. of
Sample Avg No. of
Sample Avg No. of
Sample Avg No. of
Sample
CBOD5 mg/L 60 1 80.7 37 <5 1 <5 1 25 1
Nitrogen
(Ammonia
Nitrogen) as
N
mg/L 3.1 1 4.2 13 <0.05 1 <0.05 1 1.4 1
Unionized am
monia mg/L 0.0095 1 0.009 13 <0.0005 1 <0.0005 1 0.002
3 1
pH pH 7.1 1 6.8 13 7.4 1 7.13 1 6.8 1
Total
Suspended
Solids
mg/L 37 1 59.9 37 <2 1 <2 1 21 1
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 7
CHAPTER 3 BASIS OF DESIGN
3.1 Service Area
The primary method used to estimate future wastewater flows and loads is the projection of current per
capita flows and loads using estimates of future population. As discussed in Section 2.2, the population
of Louisbourg has been steadily declining for the previous forty years and is expected to continue to
decline for next twenty years.
The new WWTP will have a thirty year design life. Based on the declining Louisbourg population there is
potential for future industrial and commercial development in the community to be connected to the
sewer system. A conservative assumption for this report is that current wastewater flows will remain
relatively constant over the next thirty years, with population decline offset by industrial and
commercial growth.
The WSER has set the deadline of 2040 for the community of Louisbourg to meet the mandatory
national effluent quality standards. Consideration should be given to re-evaluating the population and
wastewater flows if a significant amount of time has passed between completion of the pre-design
study and the project moving to the detailed design stage.
3.2 Design Flows
The ACWGM, theoretical, and observed flows for Outfall L#2 are summarized in Section 2.2 and
displayed in Table 3-1. The Louisbourg collection system pre-design has recommended that the sewer
system be sized to accommodate ACWGM peak flows. Utilising data obtained from the flow monitoring
program, the SSOAP calculated ADWF value from Outfall L#2 was applied to the remaining outfalls by
pro-rating each based on population. The same approach was applied to calculate the theoretical peak
design flows for the other outfall catchments. The calculated ADWF and peak flows are shown in Table
3-2.
Table 3-1 Summary of Theoretical and Observed Flows for Outfall L#2
ADWF Peak Flow
m3/day L/p/day m3/day L/p/day
SSOAP 259 719 1036 2878
Theoretical 122 340 1148 3189
Observed 321 892 1057 2936
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 8
Table 3-2 Projected Flows at each Outfall location
Outfall Population ADWF2
(m3/day)
4x ADWF3
(m3/day)
Peak Flow4
(m3/day)
L#1 113 81.3 325 458
L#21 360 259 1036 1166
L#3 5 3.6 14 35
L#4 2 1.4 5 17
L#5 327 235 940 1123
L#6 14 10 40 43
Total 821 590 2360 2875
1Ouƞall at monitoring locaƟon
2 Pro-rated on populaƟon using SSOAP value at Ouƞall #2
3 Factor of 4 was applied to ADWF to account for inflow and infiltraƟon (Industrial Cape Breton Wastewater CharacterisaƟon Program – Phase
2, 1994)
4EsƟmated Using ACWGM equaƟon for peak domesƟc sewage flows (Includes extraneous flows and peaking factor)
HEJV is recommending that design flows for the new Louisbourg wastewater facility be based on the
following:
®Projected ADWF of 590 m3/day (719 L/p/d); and
®Projected Peak Design of 2360 m3/day (2875 L/p/d).
As stated in the Louisbourg Collection System Preliminary Design brief, the HEJV recommends that an
additional flow monitoring program that includes Outfall L#5 be considered prior to detailed design,
allowing for a greater confidence in the design flow parameters. As will be discussed in the following
section, the WWTP will be a mechanical plant, with an inlet lift station. Setting complementary design
flows for the lift station and process systems reduces the risk of not achieving wastewater treatment
objectives. The risk with not pursuing additional monitoring data therefore is related to the frequency
and volume of collection system overflows that could bypass the treatment facility, in the event that the
theoretical peak flow underestimates actual collection system peak flows during precipitation events.
3.3 Design Influent Loading
The theoretical per capita loading rates listed in the ACWGM are 0.08 kg BOD5/person/day and 0.09 kg
TSS/person/day. With a total service population of 821, this would result in a loading of 65.7 kg
BOD5/day and 73.9 kg TSS/day. Using the projected ADWF of 590 m3/day results in concentrations of
111 mg/L for BOD5 and 125 mg/L for TSS during dry weather conditions. HEJV is recommending that
peak loading use a factor of 2.0 relative to the ACWGM theoretical per capita loading, which results in
peak loading of 131 kg BOD5/day and 148 kg TSS/day, and concentrations of 55.7 mg/L for BOD5 and
62.6 mg/L for TSS based on the design peak flow of 2360 m3/d.
The loading rate for TKN is assumed to be 0.0133 kg TKN/person/day based on theoretical data from the
text:Wastewater Engineering: Treatment and Reuse (Metcalf & Eddy, Inc., 2003). The resulting ADWF
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 9
load for TKN is therefore 10.9 kg/d, and at peak flow 21.8 kg TKN /d. Corresponding TKN concentrations
are 18.5 and 9.3 mg/L at ADWF and peak flow, respectively.
The observed wastewater concentrations vary significantly between each outfall and between ACWGM
theoretical values. The smaller outfalls only had a single sampling event, and it’s possible that there was
a minimal sanitary component relative to I/I during the time of sampling. Other potential sources for the
difference in the data may be related to sampling procedures, or sampling during very wet periods.
Based on the largely residential population of Louisbourg, HEJV recommends that BOD5, TSS, and TKN
loading for design of the new wastewater treatment facility be based on the theoretical loadings stated
above.Table 3-3 summarises the design criteria to be used for the Louisbourg WWTP.
Table 3-3 Theoretical Wastewater Quality
Parameter ADWF Peak Day
Design Population 821
Flow (m3/day)590 2360
Strength
CBOD (mg/L)111 55.7
TSS (mg/L)125 62.6
TKN (mg/L)18.5 9.3
Loading
CBOD (kg/day)65.7 131
TSS (kg/day)73.9 148
TKN (kg/day)10.9 21.8
1 CBOD5 Loading Rate 0.08 kg BOD5/person/day
2 TSS Loading Rate 0.09 kg TSS/person/day
3 TKN Loading rate 0.0133 kg TKN/person/day
3.4 Design Effluent Requirements
HEJV has established effluent requirements based on the federal Wastewater System Effluent
Regulations (WSER) limits, and determined the effluent discharge objectives (EDOs) for parameters not
included in the WSER as part of the ERA.
The receiving water for the Louisbourg WWTP will be the Atlantic Ocean, adjacent to Louisbourg
Harbour. The ERA generally followed Technical Supplement 3 of the Canada-wide Strategy for the
Management of Municipal Wastewater Effluent – Standard Method and Contracting Provisions for the
Environmental Risk Assessment. Dilution modelling was conducted to determine the maximum 1 day
average effluent concentration with a mixing zone boundary of 100m for all parameters.
The WSER limits and calculated EDOs from the ERA are summarized in Table 3-4. As EDOs are calculated
values, they are not round whole numbers that are typical of permit requirements; therefore, we have
included both the EDOs and corresponding anticipated permit values in the table. The ERA values were
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 10
obtained based on the assumption of a single new outfall in Louisbourg Harbour. This assumption will be
revisited and EDOs confirmed after the final configuration of the outfall is determined.
Table 3-4 Design Effluent Requirements
Parameter Units EDO Effluent
Limit Required By
CBOD5 mg/L -25 WSER
TSS mg/L -25 WSER
Un-ionized Ammonia (as NH3-N)mg/L -1.25 WSER
Total Residual Chlorine (TRC)mg/L -0.02 WSER
E. coli (E. coli/ 100mL)34,522 200 ERA/NSE
Total Ammonia mg/L 710 700 ERA
TKN mg/L 212 210 ERA
Phosphorus mg/L 17 15 ERA
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 11
CHAPTER 4 TREATMENT PROCESS ALTERNATIVES
Current regulations (WSER) require that a municipal wastewater treatment process that includes
secondary treatment be installed at Louisbourg by December 31, 2040. Secondary treatment provides
treatment of dissolved organics and suspended solids, to a minimum performance level of 25 mg/L for
both CBOD5 and TSS. Secondary treatment for a mechanical WWTP normally includes aerobic
treatment, which requires aeration of the wastewater.
As will be identified in the following sections, the proposed WWTP for Louisbourg will be located on a
parcel of land that houses the former SNE Sea Products LTD facility. This design brief will focus on
packaged plant alternatives, but also specifically address preliminary treatment, disinfection, and solids
management technologies.
4.1 Preliminary Treatment
Municipal wastewater typically contains large solids and grit that if not removed can damage equipment
and interfere with the downstream treatment process. To eliminate this risk, these materials need to be
removed from the wastewater stream. The following sections discuss options for suspended solids and
grit removal.
4.1.1 Screening
Screens used in preliminary treatment applications are classified based on the size of openings as either
coarse or fine (6 mm openings or less). Selection of screen size and technology is dependent on multiple
factors, including wastewater flowrate, downstream processes, and odour management.
Coarse screens are used to remove larger objects that could damage or clog downstream equipment, so
they are typically the first unit operation in a wastewater treatment plant. They can include vertical bar
racks that are either manually or mechanically cleaned. There are a number of systems available,
including continuous chain driven rake, reciprocating rake, and continuous belt.
Fine screens provide increased solids capture compared to coarse screens, and several options are
available including band screens, drum screens, and step screens. For small WWTPs like Louisbourg,
there are packaged fine screen units available that include screening, solids washing and dewatering,
and bagging in a single package. The screen is a small drum, with collected solids removed by a screw
conveyor where the washing and dewatering occur. These units are available in multiple screen
openings, but for Louisbourg, a standard opening size of 6 mm is recommended.Figure 4-1 shows a
typical small facility packed drum screen unit.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 12
4.1.2 Grit Removal
Grit chambers are used to remove inert, non-biodegradable materials such as sand, gravel, cinders, or
other heavy solid material with specific gravities greater than those of organic solids in the wastewater.
The purpose of grit removal is to protect mechanical equipment from abrasion and wear, and to reduce
the formation of deposits in pipelines, channels, and tanks. Typical grit chamber configurations include
gravity settling, aerated channel, and vortex. Technology selection is typically based on grit load,
wastewater flow and dynamics, odour control, and footprint. For Louisbourg, grit treatment selection
will consider automated systems to reduce on-site manpower requirements and odour potential.
Gravity systems for grit removal are based on a horizontal grit chamber, where the flowrate was
controlled in order to settle solids based on Stokes Law. These systems were difficult to control with
variable flowrates, and were odorous. New gravity technologies rely on stacked parallel plates for a
more efficient and compact package that are able to operate over a wide flow range. An example is the
HeadCell® technology by Hydro International, shown in Figure 4-2.
Figure 4-1Typical Screening Conveyor
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 13
In aerated grit chambers, coarse bubble diffusers are installed along one side of each rectangular tank to
create a spiral flow pattern that is perpendicular to the flow through the chamber. This spiral pattern
causes the grit to settle in the tank and helps keep organic particles in suspension, so they can pass
through the tank to the downstream processes. The performance of an aerated grit chamber can be
controlled by adjusting the quantity of air that is supplied. If the spiral velocities are too low then
organics may settle in the chamber, causing excessive quantities of organics in the dried grit. If the spiral
velocities are too high, then grit may not settle in the chamber. The grit that settles in an aerated grit
chamber settles in a trough that spans the length of the chamber. There are a number of options
available for removing grit from the trough, including buckets, spiral conveyors, and grit pumps. A
typical aerated grit chamber is shown in the Figure 4-3.
Vortex-style grit chambers function by inducing a helical flow pattern in the tank, and the resulting
centrifugal force causes grit to settle into a bottom hopper. Grit is then removed from the hopper using
a grit pump. The vortex systems operate over a wide flow range, and have the advantage of no
submerged components that require maintenance. A typical vortex grit chamber is shown in the
Figure 4-4.
Figure 4-2 Headcell Grit Removal System
Figure 4-3 Typical Aerated Grit Chamber Figure 4-4 Typical Grit Vortex Chamber
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 14
Once grit is removed from the wastewater flow, it is typically cleaned in a classifier to remove organics
to reduce odour. Classifiers may be equipped with a hydrocyclone at the inlet to reduce slurry volumes
through centrifugal separation prior to discharging to the classifier. Grit that settles in the classifier is
removed by an auger or rake and discharged to a disposal bin until there are sufficient quantities for
disposal in a landfill.
For small WWTPs, there are package systems available for grit removal and washing that use the vortex
or gravity separation method. Both of these systems are suitable for Louisbourg, and have similar
footprint and performance. For the preliminary design, HEJV has based the grit removal on a vortex
system, with a conveyor to discharge clean grit to the screenings bin.
4.2 Secondary Treatment
There are many types of secondary treatment processes that can provide the required treatment to
meet the effluent requirements identified in Chapter 3. These processes can be classified as either
suspended growth or attached growth systems. Suspended growth systems use aeration and mixing to
keep a relatively high concentration of microorganisms (biomass) that consume organics in suspension
in an aeration basin. The biomass in the effluent from the aeration basin is normally separated from the
treated wastewater, with a portion returned to the inlet of the aeration basin, and a portion removed as
a waste stream for disposal. Attached growth systems use high surface area media on which a microbial
layer (biofilm) can grow; organics in wastewater are consumed when they contact the biofilm. Both
suspended and attached growth systems require aeration to provide oxygen for the bacteria, and
aeration also provides a means to remove excess biofilm from the attached growth media.
Additional secondary treatment systems that are commonly used by small communities include lagoon-
based treatment (stabilization basins and aeration lagoons), and treatment wetlands. These systems
have long hydraulic retention times, and are considered ‘land-based’ due to the large footprints
required. Stabilization basins and aerated lagoons typically develop algae growth in the warm season,
which increases suspended solids in the effluent, but also provides supplemental oxygen.
In stabilization basins, there is no mechanical aeration. Oxygen is supplied to the wastewater by algal
respiration and directly from the atmosphere; mechanical aeration is not used. Most of the oxygen from
algal respiration is produced near the surface because the algae require sunlight. Diffusion of oxygen
from the air and mixing from wind and waves are also highest near the surface. If a stabilization basin is
shallow enough, it can be aerobic throughout, but the most common type in this region is facultative. In
a facultative stabilization basin, the surface is aerobic, mid-depth has declining oxygen levels, and the
bottom layer is anaerobic allowing for sludge digestion. Gases produced from the anaerobic layer,
including methane and sulfide, are typically consumed or oxidized before they reach the water surface.
Stabilization basins are subject to turnover in the spring and fall because they are not mixed, resulting in
the release of intense odours, and therefore are normally located away from developed areas.
The facultative stabilization basin will be assessed for CBRM treatment facilities (subsequently referred
to in this report as “Stabilization Basin”). Stabilization basins are typically 1.5–1.8 m deep, and have
retention times in the range of 25 to 180 days, with 180 days being common in Atlantic Canada. Organic
loading rates for areas with an average winter air temperature of less than 0°C are typically in the range
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 15
of 11–22 kg/ha/d. They have at least two cells, while larger lagoons may have more cells to minimize
short circuiting. Effluent suspended solids can be seasonally high due to algae and turnover, and
stabilization basins may be followed by a constructed wetland for effluent polishing. The surface of
stabilization basins typically freeze in the winter, which impacts treatment performance due to lack of
aeration. Sludge residuals must be removed one or more times over the life of a stabilization basin.
In aerated lagoons, oxygen is supplied by mechanical aeration, and newer systems typically use
subsurface fine bubble aeration. They have average retention times ranging from 5 to 30 days, with 30
days being common in Atlantic Canada. They accept higher loading rates compared to stabilization
basins, are typically at least 3 m deep, require less land, and are typically less susceptible to odours.
Aerated lagoons also have higher operational costs related to power for aeration blowers.
Aerated lagoons can be either completely or partially mixed; completely-mixed aerated lagoons are
rarely cost effective in municipal applications because they use significantly more energy than partially-
mixed aerated lagoons and require additional solids separation infrastructure; therefore, only the
partially mixed aerated lagoon will be assessed for CBRM installations (subsequently referred to in this
report as “Aerated Lagoon”). In a partially mixed aerated lagoon, incoming organic and inorganic solids
and biosolids settle in the lagoon cells, where they are digested in the resultant sludge layer. The sludge
residuals must be removed one or more times over the life of the lagoon. These aerated lagoons
typically include a downstream quiescent zone (no aeration) as part of the main treatment cells, and
may be followed by a polishing pond or wetland to reduce suspended solids prior to discharge. Odour
generation has a lower risk compared to the stabilization basin; however, if aeration control is not
properly managed, septic conditions can still occur.
Constructed wetlands are normally only used for effluent polishing and nutrient removal in Canada due
to our cold winters. These wetlands rely on plant uptake and biofilm to provide treatment, and the
resultant wetland plants must be periodically harvested from the system. There are many examples in
Atlantic Canada where tertiary treatment of lagoon effluent is provided in a downstream constructed
wetland.
A listing of specific secondary treatment processes and the category to which they belong is presented
in Table 4-1.
Table 4-1 Secondary Treatment Processes
Process Category Specific Process
Suspended Growth Sequencing Batch Reactor (SBR)
Activated Sludge
Membrane Bio-Reactor (MBR)
Extended Aeration
Pure Oxygen Activated Sludge
Oxidation Ditch
Attached Growth Moving Bed Bio-Reactor (MBBR)
Rotating Biological Contactor (RBC)
Trickling Filter
Biological Activated Filter (BAF)
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 16
Process Category Specific Process
Land-Based Aerated Lagoon
Stabilization Basin
Constructed Wetlands
HEJV has worked on projects that have used the majority of the technologies listed in Table 4-1 so we
are able to use our practical experience to short-list the technologies that best satisfy the project
constraints at Louisbourg.
4.2.1 Site Specific Suitability
The main constraints at this site that will influence wastewater treatment technology for the Louisbourg
WWTP are:
®Effluent Requirements;
®Site Location;
®Odour Control;
®Capital Cost and Life Cycle Costing; and
®Ease of operation and maintenance.
Each of these criteria is discussed below.
4.2.1.1 EFFLUENT REQUIREMENTS
The effluent requirements summarized in Section 3.4 can be met by all of the listed technologies in
Table 4-1.
4.2.1.2 SITE CONDITIONS
As part of the Louisbourg Collection System Design, five locations were identified and evaluated as
potential WWTP locations. The collection system design brief concluded that the most appropriate
location for the WWTP is on the same parcel of land as the SNE Sea Products LTD, adjacent to the
existing structures and Strathcona Street. The reasons for this decision were: the land has previously
been commercially developed; proximity to the waterfront for outfall access; and ability to use gravity
sewers for the collection system (however a lift station will be required at the WWTP).
The proposed location of the WWTP does not meet the ACWGM guidelines for setback distances from
residential properties. HEJV has met with NSE to discuss locations for future treatment plants that do
not meet the ACWGM guidelines for setback distances but ultimately make the most sense for a
community from an economic stand point. NSE’s feedback to HEJV was that if the location of the WWTP
did not meet the ACWGM guidelines but ultimately made the most sense for a community, the detailed
design of the plant would need to include odour controls, to minimize the impact to neighbouring
properties.
The total area of available land at the proposed location is approximately 0.9 hectares, which does not
provide sufficient space to construct any of the Land Based treatments options (oxidation ditch,
stabilization basin, aerated lagoon, and wetlands) listed in Table 4-1. HEJV has eliminated processes
that are unable to provide sufficient treatment based on availability of land from further considerations.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 17
4.2.1.3 ODOUR CONTROL
Due to proximity to neighboring homes and commercial businesses, odour control must be included in
the design of the new Louisbourg WWTP. Ideally, the treatment process should have a small surface
area to minimize odour footprint, and be easily contained to optimize odour control. Technologies that
are difficult to contain and/or that have a high contact area between wastewater and the atmosphere
(oxidation ditch, trickling filter, rotating biological contactor) were eliminated.
4.2.1.4 COST
There are a number of technologies in Table 4-1 that can be eliminated based on their relatively high
cost. For example, pure-oxygen activated sludge is more costly to operate compared to conventional
activated sludge due to oxygen costs and the requirement for on-site storage and feed equipment for
liquid oxygen. As well, prior evaluations have identified that MBBR technology is more cost effective
than other fixed film options. Membrane bioreactors (MBR) are also not considered a cost effective
treatment process when the effluent discharge criteria does not necessitate their use.
4.2.1.5 EASE OF OPERATION
The remaining technologies typically require similar levels of operational expertise, which we would
classify as moderate. However, there is a potential operational benefit to utilizing an SBR process as the
CBRM WWTP operations staff have experience with this type of process. Based on this experience, SBR
is the preferred candidate suspended growth treatment process.
The MBBR treatment process is a simple process to operate, and does not require familiarity with
bulking sludge issues and biological control. It has also been demonstrated that the MBBR technology
can provide simultaneous nitrification (ammonia reduction). The MBBR technology typically uses
dissolved air flotation (DAF) for effluent clarification; while this technology is relatively simple to operate
and is widely used in municipal water and industrial water treatment, it is a relatively unknown process
for CBRM wastewater operators.
4.2.2 Description of Candidate Processes for Secondary Treatment
Based on the Louisbourg site-specific constraints above, and discussions with the CBRM, the SBR and
MBBR secondary treatment technologies were short-listed for additional evaluation by HEJV, largely due
to their compact footprint, similar technology used elsewhere by CBRM, operational complexity, and
relative ease of odour containment and treatment.
Each of these processes is described in more detail below. Both processes have similar solids
production, so the sludge handling processes will not be evaluated at this stage for comparative
evaluation. Similarly, the costs associated with common project elements, including site access, new
outfall, solids management, electrical service, etc. will not be evaluated as part of the secondary
treatment process comparison.
4.2.2.1 SEQUENCING BATCH REACTOR
The Sequencing Batch Reactor (SBR) process is a suspended growth system, where active treatment
occurs in a single tank. A conventional fill/draw SBR system requires at least 2 tanks. The SBR process
differs from other processes as it is a batch process and reactors operate on a “fill and draw” method.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 18
Flow is directed to an available reactor where aeration and clarification occur; once treatment is
achieved, settling occurs and treated effluent is withdrawn from the surface through a decanter
mechanism.
Alternatively, continuous flow SBR technology (ICEAS) does not follow a true fill/draw operation, but
instead uses continuous flow, with pre-react and react zones. With ICEAS, aeration in the react tank is
intermittently turned off to allow sludge settling and decanting or supernatant to occur. ICEAS can
therefore be configured as a single tank for small communities.
As indicated by the name, a conventional SBR operation is a sequence of stages, which are shown in
Figure 4-5. These stages can vary between manufacturers; however, the principal remains the same and
is summarized below:
1.Fill – Effluent from the preliminary treatment flows into an available reactor. Upon entering the
reactor, the wastewater is held in an anoxic state, as this condition encourages the creation of
microorganisms with good settling characteristics;
2.React – Once the reactor has been filled, aeration is turned on. The addition of oxygen degrades
organic matter and promotes nitrogen and phosphorous removal. The length of aeration period
determines the degree of BOD removal;
3.Settle – When the required BOD removal has been achieved, aeration and the mixing
equipment is turned off and the reactor acts as clarifier. Solids settle at the lower portion of the
reactor and form a sludge blanket, leaving a clear treated effluent above the blanket; and
4.Decant – The effluent valve is opened, and treated effluent is withdrawn from the upper portion
of the reactor using a floating decanter. During this stage, WAS pumps operate to remove solids
from the bottom of the reactor.
Figure 4-5 SBR Batch Operation Sequence (FRWA Whitepaper -Wastewater Treatment
recommendations for Small & Medium Sized Utilities, By Sterling L. Carroll, P.E., M.P.A., FRWA
State Engineer, FLORIDA RURAL WATER ASSOCIATION)
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 19
The process is generally implemented using a minimum of two (2) reactors in parallel. It can be
conducted as a batch process where one reactor is filling while the other is settling. The ICEAS SBR
receives influent during all phases of the treatment cycle and decants intermittently, so a single tank
configuration is possible. No RAS is required as the mixed liquor remains in the reactor at all times, with
WAS being withdrawn as necessary. The entire process is controlled using a programmable logic
controller (PLC).
SBRs are operated at extended solids and hydraulic retention times compared to conventional activated
sludge, resulting in larger reactor volume; however, the total number of tanks required is reduced,
which can result in more compact site layouts. Furthermore, since flow equalization is inherent in SBR
systems, the process is more resistant to peak hydraulic loadings compared to a conventional activated
sludge process, making it an attractive alternative for small to medium sized facilities. Due to the
degree of control required and the large volume of tankage required in each reactor, the capital costs
are often higher than more conventional activated sludge processes for larger plants. The discharge for
smaller systems is typically intermittent in nature, which can result in larger, more expensive
downstream UV disinfection systems.
A conceptual level cost estimate has been developed for the Louisbourg SBR option based on the design
flow, loads, and parameters listed in Table 4-2. A process similar to the Dominion Bridgeport WWTP
SBR process has been considered.
Table 4-2 Sequence Batch Reactor Process Design Criteria
Parameter Proposed Typical Design Standard
No. of Reactors 2 2 -3
Basin Length (m)11.4 -
Basin Width (m)5.7 -
Side Water Depth (m)4.5 -
Total Reactor Volume (m3)588 -
Design HRT (hr)24 15 –40
Cycles per Reactor per Day (average/ peak)4 -6 4 -6
React Time (min) (average/ peak)90 -60 120 -60
Settling Time (min) (average/ peak)45 -30 60 -30
Volumetric BOD5 Loading (kg BOD /m³·d)0.2 0.1 –0.3
MLSS (mg/L)3000 2000 -5000
F/M Ratio 0.07 0.04 –0.1
4.2.2.2 MOVING BED BIO-REACTOR (MBBR)
The MBBR is an attached growth, continuous flow system, which was developed by the Norwegian
company Kaldnes Miløteknologi (KMT). MBBRs are reaction vessels that are filled with plastic media
called “carriers” that have a high surface area to support biofilm growth. There is no need for sludge
recycle since the bacteria are attached to the media in the reaction vessel, and there is no need to
control biomass concentration or monitor F/M ratio. Since the biomass is fixed to the media and
retained in the reaction vessel, the MBBR is not subject to media washout at high flowrates, making it a
good option for communities with high peak flows due to I/I conditions.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 20
The specific gravity of the plastic media is just below the specific gravity of water, which allows diffused
aeration to maintain the media in suspension and completely mixed throughout the reactor. MBBR
aeration is typically coarse-bubble. The media carriers impact and abrade each other in the mixed
wastewater, which causes the growing biofilm to slough off to maintain an optimal biofilm thickness.
MBBR effluent, containing the excess biofilm, overflows to a clarifier for solids removal; however, the
MBBR media is retained in the reactor using screens. DAF has been the preferred process for
clarification of MBBR effluent; however, conventional secondary clarifiers have also been used.
The MBBR technology has been used for over 20 years, with a high degree of success. The plastic media
is very durable, with original media still in use with no deterioration. One reactor vessel has been
assumed for Louisbourg, although the reactor volume can be split into two trains to allow future
maintenance.
A conceptual level cost estimated has been developed for this option based on the projected design
flow, loads, and design parameters listed in Table 4-3.
Table 4-3 Moving Bed Bio-Reactor Process Design Criteria
Parameter Value
No. of Trains 1
No. of Stages 1
Total Reactor Volume (m3)100
Average / Peak HRT (hr)4 -1
Side Water Depth (m)4
BOD5 Loading (g/m2·d)6.1
Specific Surface Area (m2/m3)80
Secondary DAF Clarifier Average /Peak SOR (m/d)10 / 22
4.3 Disinfection
As established in the Louisbourg ERA, NSE has typically set treated wastewater effluent bacterial limits
to 200 E. coli/100mL, even though the EDO for E.Coli was established at 34,522/100mL. There are two
common forms of disinfection used for small municipal WWTPs: chlorination and ultra violet light (UV)
radiation. The WSER requires that Total Residual Chlorine in treated wastewater effluent be less than
0.02mg/L at discharge, so dechlorination must be provided with chlorination upstream of effluent
discharge. The following sections will look at each of these disinfection options in further detail.
4.3.1 Chlorination
Chlorine is a very effective wastewater disinfectant that oxidizes organic matter including bacteria and
viruses. Chlorine is available in different forms including chlorine gas, liquid sodium hypochlorite, and
solid calcium hypochlorite (calcium hypochlorite is typically dissolved prior to use). Chlorine is injected
as a gas or liquid upstream of a contact chamber that provides the necessary hydraulic retention time
for the chlorine to neutralize the bacteria. However, the wastewater leaving the chlorine contact
chamber normally has a free chlorine concentration that exceeds allowable discharge limits. To remove
the residual chlorine, contact with a dechlorination chemical such as sodium bisulfite is required.
The main advantage of chlorination is that it is a well-established and reliable technology; however,
chlorine itself is extremely toxic and needs to be transported, stored, and handled with great care.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 21
Operators need proper training, and safety equipment including emergency eye wash and showers must
be available. In addition, control of the chlorine and dechlorination chemical injection rates must be
closely monitored to ensure disinfection and discharge limits are achieved.
4.3.2 UV Disinfection
UV disinfection has become the most commonly used form of disinfection in Canada. UV disinfection
functions by exposing bacteria in the treated effluent to UV light, which damages the organisms’ DNA,
preventing reproduction. There are no chemicals added to the wastewater, which reduces the safety
risk for operators. The UV light is harmful to eyes, so operators must be trained on how to safely
operate the equipment, and proper use of eye protection.
UV systems are typically more user friendly than other disinfection systems, and do not require
downstream hydraulic retention time, reducing the overall footprint of the treatment area. UV
treatment requires the system to be designed for a specific UV transmittance, which is a measure of the
ability of the light to penetrate the wastewater stream. It is important to operate the upstream
secondary treatment process to maintain suspended solids below a target concentration, otherwise UV
disinfection performance is impacted. To maintain optimum operability the UV lamps should be cleaned
on a scheduled basis, to maintain lamp output and disinfection capacity. UV disinfection is flexible, and
additional lamps may be added for redundancy/contingency, or added in the future to increase
treatment capacity.
4.3.3 Disinfection Recommendation
HEJV recommends that a UV disinfection system be installed at the Louisbourg WWTP. The UV
equipment requires a smaller footprint to meet regulatory guidelines compared to chlorination. The
operation and preventative maintenance requirements for the UV system are less complex than
chlorination, and can be completed by CBRM Staff. Typical maintenance will include periodically
cleaning the UV lamps, and replacing lamps as they deteriorate.
4.3.4 SBR Disinfection
Flows from the SBR flow intermittently by gravity to the UV disinfection equipment during the decant
cycle which results in a larger UV system compared to the MBBR process (approximately 50 percent
higher design flow). Disinfection can take place in a single concrete or stainless steel channel located in
the new WWTP building. The SBR UV system will consist of a single bank of forty (40) low pressure UV
Lamps. The UV bank will arranged in ten (10) modules or racks, each containing four (4) lamps. The UV
channel will include a discharge weir to maintain optimal submergence of the UV lamps.
The UV system will include a monitoring system to monitor the UV dose, lamp failures, operating hours
for each lamp, and other diagnostic information. An automated lamp cleaning system has not been
included.
4.3.5 MBBR Disinfection
Unlike SBR Disinfection, discharge flow from the MBBR process to disinfection will be continuous, which
results in a smaller UV system compared to the SBR process. Disinfection can take place in a single
concrete or stainless steel channel located in the new WWTP building. The MBBR UV system will consist
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 22
of a single bank of thirty-two (32) low pressure UV Lamps. The UV bank will arranged in eight (8)
modules or racks, each containing four (4) lamps. The UV channel will include a discharge weir to
maintain optimal submergence of the UV lamps.
The UV system will include a monitoring system to monitor the UV dose, lamp failures, operating hours
for each lamp, and other diagnostic information. An automated lamp cleaning system has not been
included.
4.4 Sludge Management
Both the SBR and MBBR secondary treatment options will produce waste activated sludge which must
be removed from the treatment process on a regular basis and disposed of at an approved facility.
Regardless of which secondary treatment option is selected, sludge management at this facility will
likely involve an aerated sludge holding tank, with either onsite or centralized offsite sludge dewatering.
Onsite dewatering would involve a mechanical dewatering step, such as a rotary press or centrifuge.
After the recommended secondary treatment process has been selected, a preliminary design of the
solids management train will be provided in Chapter 5.
4.5 Secondary Treatment Options Evaluation
Capital and operating costs have been developed for the SBR and MBBR secondary treatment options
for the purposes of comparing the technology options. The estimated facility costs for the selected
option are presented in Section 4.5.1. At this stage, only the liquid treatment stream is evaluated. Solids
treatment train, site access, new lift station, new outfall, headworks, electrical service, site works, etc.
that are common to each option have not been included at this stage in the evaluation; therefore, the
cost estimates presented in this section do not represent the complete facility costs. Comprehensive
facility costs for the selected treatment option will be presented in Section 6.
A discussion has also been provided on qualitative factors associated with each of the secondary
treatment options.
4.5.1 Opinion of Probable Capital Cost
Option of probable capitals costs are provided in Table 4-4. These are comparative opinion of probable
costs for secondary process alternatives only and as previously discussed exclude preliminary treatment,
outfall upgrades, main lift station, and site works that would be common to all options.
HEJV contacted numerous technology suppliers for quotations for both SBR and MBBR package
treatment systems. These quotations were used to develop the opinion of probable capital costs for
each technology (excluding common items). Details related to the costs of each of the technologies are
shown in Appendix B.
Of the two technology options, the SBR process has the lowest capital cost, with the MBBR estimated
capital cost approximately 40% higher. The reasons for this difference were:
®Equipment Costs – The cost the MBBR equipment package is higher compared to the SBR
equipment package. For the purpose of this report HEJV obtained vendor costs for a continuous
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 23
flow SBR equipment package similar to the existing Dominion Bridgeport WWTP. An average
cost for the MBBR equipment package was calculated from several vendor quotations; and
®Probable Capital Costs – Although the MBBR process has a smaller tank volume compared to
SBR, MBBR requires effluent clarification, and a DAF process was assumed for this comparison.
The DAF is located indoors, and therefore the building footprint is larger compared to SBR.
Although the volume of concrete tankage is significantly less compared to SBR, the cost of
constructing an indoor process area outweighs potential cost savings in tankage.
Table 4-4 Secondary Process Capital Cost Comparison
Cost SBR MBBR
Vendor Package Cost $480,000 $825,000
Estimated Installed Capital Cost $2,580,000 $3,580,000
4.5.2 Opinion of Probable Operating Costs
The opinion of probable operating cost comparison is provided in Table 4-5. The SBR technology has the
lowest operating cost. The MBBR option includes operation of the DAF process, with associated
chemical consumption. Maintenance costs are based on a percentage (1%) of vendor package cost,
which may not accurately reflect actual costs. Labour costs for routine operation are assumed to be the
same, and have not been included in the comparison.
Table 4-5 Secondary Process Annual Operating Cost Comparison
Operation Annual Operation Cost (Secondary Process Only)
SBR MBBR
Power1 $5,690 $4,360
Chemicals2 - $12,220
Maintenance Allowances $4,800 $8,250
Total $10,490 $24,830
1 Power esƟmated based on secondary treatment equipment only
2 Allowance for polymer dosing for MBBR DAFs
3 Maintenance Allowance 1% of equipment cost
4.5.3 Life Cycle Cost Estimate
The Net Present Value of treatment plant options, which is a typical approach for comparing the relative
costs of different options, were calculated for each option using the following equation (1):
ܸܰܲ = ܥݏݐ ݅݊ ܲ݁ݎ݅݀ ݊
(1+ܴܽݐ݁) (1)
Where:
Cost in Period n = Net Cost in given year
n = Year from 1 to 30
Rate = Discount Rate at 8%
The effect of the NPV calculation is that costs which occur earlier in the project life are weighted more
heavily than costs which occur farther along the project timeline, based on the idea that a dollar today is
worth more than a dollar in the future. The discount rate used in these calculations is 8%, and the time
period over which it is calculated is 30 years. For the purpose of comparing the two options, year 1 was
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 24
assumed to be 2019. The net present value capital costs exclude taxes. These calculations do not
account for revenue streams from users.
The life-cycle comparison is presented in Table 4-6, based on total capital costs for installed secondary
treatment equipment.Table 4-7 shows the effect of the InvesƟng in Canada Plan where 73% of
investment is provided by the Provincial and Federal governments.Of the opƟons, the SBR process has
both the lowest operaƟng cost and life cycle cost. If the life cycle cost was adjusted to account for CBRM
paying 27% of the capital cost the SBR process would sƟll have the lowest life cycle cost.
Table 4-6 Secondary Process Life Cycle Cost Comparison
Cost SBR MBBR
Estimated Installed Secondary Capital Cost $2,580,000 $3,580,000
Estimated Annual operating cost, $/year $10,490 $24,830
NPV Major Capital Equipment Refurbishment (15th year, 3% Inflation)$118,000 $148,000
NPV Operating Cost (30 years, 8% discount rate)$118,100 $280,000
Life Cycle Cost $2,816,100 $4,008,000
Table 4-7 Secondary Process Life Cycle Cost Comparison – 73% Capital Funding
Cost SBR MBBR
Estimated Installed Secondary Capital Cost $696,600 $966,600
Estimated Annual operating cost, $/year $10,490 $24,830
Major Capital Equipment Refurbishment (15th year, 3% Inflation)$118,000 $148,000
NPV Operating Cost (30 years, 8% discount rate)$118,100 $280,000
Life Cycle Cost $932,700 $1,394,600
4.5.4 Qualitative Evaluation Factors
In addition to life-cycle cost, there are a number of other factors to consider when evaluating the
technology options that are less easily quantified. These factors are summarized in Table 4-8 Secondary
Process Qualitative Evaluation Factors, and additional discussion is provided below the table. Qualitative
factors have been rated 1 to 2 for each technology with 1 being the best and 2 being the worst.
Table 4-8 Secondary Process Qualitative Evaluation Factors
SBR MBBR
Local Experience with Process 1 2
Operational Simplicity 1 2
Sludge Production 2 1
Site Aesthetics 2 1
Odour Management 2 1
In terms of local experience with the treatment process, CBRM have experience with the SBR process at
the Dominion Bridgeport WWTP.
Both options are fairly straightforward to operate, however each option has their own benefits. The
entire SBR process is completed in a single tank; however, due to the batch process, multiple tanks are
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 25
required and the attention is required during elevated flows to ensure adequate sequencing. The MBBR
process is single flow stream throughout the plant and the operation does not change based on flows,
however, attention is needed during the secondary clarification stage at the DAF to ensure adequate
polymer dosing.
Each of the secondary treatment processes evaluated will produce sludge that will have to be removed
from the process. The longer HRT provided in the SBR process will result in a thinner sludge, while the
MBBR produces thicker sludge and therefore a smaller volume to handle before dewatering.
The majority of the MBBR process occurs indoors and can be hidden from view from the general public,
whereas the SBR process is completed in tanks which will be exposed to public view. The headworks and
sludge handling associated with each process has the potential for odours, but these operations will be
enclosed in a building for all technology options. The SBR process has more potential to generate odour
complaints in comparison to the MBBR process.
4.5.5 Recommended Secondary Treatment Process
From a life-cycle costing perspective, the SBR process offers the higher value, based on preliminary cost
estimates. However the MBBR is still a relatively new technology, and with the anticipated construction
date for the Louisbourg WWTP not being for another twenty years, the capital and life cycle costing
should be re-evaluated closer to the construction date. It is possible that the cost of the MBBR
technology will become more competitive as the technology is implemented at more facilities in North
America.
For the purpose of the preliminary design, the SBR technology has been selected as it is most cost
effective, and CBRM is experienced at operating SBR systems.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 26
CHAPTER 5 PRELIMINARY DESIGN
5.1 General Overview
This section will outline the specifics of the HEJV preliminary design for the Community of Louisbourg
WWTP. The recommended configuration includes a new pump station, preliminary treatment, SBR for
secondary treatment, followed by UV disinfection and new outfall pipe. An aerated sludge holding tank
is included for temporary sludge storage prior to additional treatment on-site, or transport to another
facility as part of a regional sludge management plan.
Preliminary layouts for the proposed treatment system and locations of individual unit processes are
shown in the “Preliminary Design” drawings, found in Appendix A. The processes depicted in these
drawings are consistent with those recommended in the previous chapter of this report. The drawings
contained in the appendix are listed in Table 5-1, below.
Table 5-1 Preliminary Design Drawings
Drawing Number Description
C01 Location Plan
C02 Process and Admin Building Layout
C03 Site Works Plan
P01 Process Flow Diagram
5.2 Unit Process Description
5.2.1 Lift Station
The WWTP will be fed via two new gravity interceptor sewers that will capture flow from the six existing
raw sewage outfalls. One new 300 mm diameter sewer will intercept flow from outfall L#1 and travel
along Main Street and follow the North West boundary of the SNE Sea Products property until it has
reached a new manhole adjacent to the WWTP. The second sewer, which transitions from 250 mm to
450 mm in diameter, will capture flow from the remaining five outfalls and travel down Commercial
Street to the proposed new manhole adjacent to the WWTP. Combined flow from the WWTP manhole
will be routed to the WWTP inlet lift station, located to the west of the proposed WWTP. Due to the
topography of the area and gravity flow of the influent sewers, a lift station will be required to feed the
WWTP. Wastewater will be pumped via a pipeline from the new lift station to the primary treatment
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 27
equipment located in the new WWTP process building. The lift station has been designed to operate as a
triplex station, with two duty pumps and one standby pump (3 x 50%).
The lift station design is based on alternating pump starts between available pumps while optimizing
retention time to avoid odours. The floor of the lift station wetwell will be benched to promote self-
cleansing and minimize any potential dead spots where solids can accumulate.
The lift station wetwell will be a common structure with the WWTP effluent chamber. The common wall
separating the inlet wetwell from the effluent chamber will have a fixed overflow weir at an elevation
higher than peak flow level, which will allow flows that exceed the design capacity of the WWTP to
overflow to the effluent chamber. This will bypass untreated wastewater to the outfall in this situation.
The overflow location should be revisited as part of the facility design, in the event that future
regulations dictate preliminary treatment of overflows.
The design parameters for the pumping station are summarized in Table 5-2.
Table 5-2 Pump Station Summary
Pumping Station Design Value
Duty Pumps 2
Standby Pumps 1
ADWF (L/s)6.8
Interception Design Flow (L/s)27.3
Minimum Pump Capacity 13.7
Forcemain Diameter (mm)150
TDH (m) at Maximum Design Flow 17.0
TDH (m) at Average Flow 16.0
Approximate power requirement (each pump) kW 7.5
5.2.2 Preliminary Treatment
Flow from the lift station will be pumped to the Grit and Screening Room, which is located at an
elevation to allow gravity flow of wastewater through the WWTP. Influent from the lift station will
discharge into an influent chamber and be directed to the screening equipment. The influent chamber
will contain an overflow/bypass in the event of a plugged screen, and a mud valve that drains to the lift
station wet well. The grit removal equipment is located downstream of the inlet screen.
Screening
Screening equipment can either be installed in a concrete channel or a self-contained stainless steel
tank, since the influent from the lift station is piped. The price difference between these two
alternatives is relatively small and the determining factor would be Owner preference. Wastewater will
flow through a shaftless spiral fine screen with 6mm diameter openings. Captured screenings will be
conveyed from the screen, dewatered and compacted in a single combined screw unit, and discharged
into a bin. The screenings are washed with spray water and dewatered in the tapered screw conveyor
section, with wash water returned to the influent channel.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 28
If the screen is installed directly in a concrete channel, the channel will need to have an approximate
width of 0.35m and depth of 1m. A bypass/overflow channel with bar rack is included in the event the
screen is off-line or screen basket plugged. The design parameters for the shaftless spiral fine screen are
summarized in Table 5-3.
Table 5-3 Fine Screening Design Summary
Parameter Design Value Design Value
No. of Units 1
Peak Flow (m3/d)2360
Screen Openings (mm)6.0
Dewatered Screenings Capacity (m3/d)Up to 18
Solids Content of Screenings (%)52
Concrete Channel Installation
Channel Width (m)0.35
Channel Depth (m)1
Grit Removal
The screened influent will pass through a vortex grit chamber. The vortex chamber hydraulics force
particles with a diameter larger than 0.2 mm to settle at the bottom of the chamber, from where it is
pumped to a grit classifier for washing and dewatering. Dewatered grit is discharged into the screenings
bin, and wash water flows via gravity back to inlet channel. A bypass/overflow channel can be provided
in the event the grit system is off-line or plugged. After grit removal, influent will flow to the SBR tanks
via gravity. Grit production is dependent on storm events, sewer flows, sewer infiltration, and seasonal
influences related to winter sand use on roads.
The design parameters for the grit vortex system are summarized in Table 5-4.
Table 5-4 Grit Removal Design Summary
Parameter Parameter Design Value
No. of Units 1
Peak Flow (m3/d)2360
Length (m)3.4
Diameter (m)2
Depth (m)3.3
Classified Grit Production (m3/d)<1.0
5.2.3 Secondary Treatment
Effluent from preliminary treatment will flow via gravity into a splitter channel, where flow will be
directed to the two ICEAS continuous flow SBR reactors, where the treatment steps outlined in Section
4.2.2.1 take place. Decanted effluent flows by gravity to the UV disinfection system. An air flow meter
and a dissolved oxygen (DO) probe will be provided for each SBR tank. A level transmitter and a level
float will also be provided for each tank. The design parameters for the ICEAS SBR system are
summarized in Table 5-5.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 29
Table 5-5 Secondary Treatment Design Summary
Parameter Design Value
Average Flow (m3/d)590
Peak Flow (m3/d)2360
No. of Tanks 2
Tank Dimensions (m)10 L x 4 W x 5.5 D (Plus 1 m freeboard)
Total Surface Area (m2)40
Total Volume (m3)440
Ave HRT (hr)24
Cycles per Reactor per Day (average/ peak)4 - 6
Preliminary Design Air Flow (m3/min)80
Air Flow per Blower (m3/hr)138
Volumetric BOD5 Loading (kg BOD /m³.d)0.16
MLSS (mg/L)3000
F/M Ratio 0.06
5.2.4 Disinfection
Effluent from the SBR will flow intermittently by gravity to the ultraviolet (UV) disinfection unit during
the SBR decant cycle. Disinfection equipment is located in the UV disinfection room, and similar to the
screening equipment, the disinfection equipment can either be installed in a concrete channel or self-
contained stainless steel channel. Unlike the screening equipment there is a significant difference in the
equipment cost between the two options; however, relative to the overall project cost, this difference is
small and ultimately Owner preference would determine equipment installation.
Disinfection will be conducted by a UV disinfection unit located in the new process building, and
connected to the upstream SBR by gravity flow piping. The UV disinfection unit will be approximately 4m
long, 1m wide and 2.4m deep. The lamps are oriented horizontal, parallel to flow and contain a single
module with a total of forty (40) low pressure lamps. In order for the decant flow from the SBRs to flow
by gravity through the UV system, the UV unit will be installed at an elevation lower than the decant
discharge. The specified power draw for the system is 33.7 kW.
The UV weir height will set the hydraulic grade line for the rest of the treatment process. The high water
elevation at large tide for Louisbourg is 2.1m (Geodetic) for 2018. The estimated extreme values for 100
years and 50 years periods for nearby outfalls was 0.4m and 0.3m, respectively. In addition, a sea level
rise of at least 1.0 m is likely to occur within the coming century, even if the timeline remains uncertain
(CBCL, 2018). Therefore, it is recommended that the UV weir height be set at a minimum elevation of
4.5m plus an allowance for head loss. The actual weir height can be higher than this elevation to
accommodate the WWTP process and site grade. The design parameters for the UV disinfection system
are summarized in the Table 5-6.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 30
Table 5-6 UV Disinfection Design Summary
Parameter Design Value Design Value
Average Flow (m3/d)590
Peak Flow Capacity (m3/d)2360
Number of Reactors (channels)1
Number of Banks per Reactor 1
Number of Lamp per Bank 40
Total Number of Lamps 40
Effluent TSS (mg/L)<20.0
Minimum UV Transmission (%UVT)65
Effluent Fecal Coliforms (MPN / 100 mL)200
5.2.5 Sludge Management
Sludge generated in the treatment stream must be removed and disposed of at an approved facility.
WAS from the SBR process will be pumped to an aerated sludge holding tank. The aeration will provide
mixing of the sludge, prevent septic conditions, as well as further VSS reduction. The sludge holding tank
will be sized such that it will provide a working volume equivalent to 10 days of WAS storage. The sludge
holding volume will be provided in a single tank. Supernatant from the aerated sludge tank can be
periodically decanted back to the SBRs to increase solids concentration. However, minimal thickening of
sludge is expected to occur in the sludge tanks.
An integrated solids management plan for the CBRM is being developed in a separate study by HEJV.
The sludge management concept is that dewatered sludge will be hauled from Louisbourg at regular
intervals to a centralized facility prior to transport to landfill. Sludge from the aerated sludge holding
tank will be dewatered using a centrifuge. Centrifuges deliver effective dewatering of WAS sludge while
reducing run hours and polymer use when compared to other available technologies. Final dewatering
design will need to consider Louisbourg WWTP solids production, and the feasibility of a small centrifuge
unit versus alternate technologies such as a rotary press.
Readers should refer to the separate Solids Management Plan report for final recommendations. Design
parameters for the Louisbourg WWTP sludge tank and centrifuge dewatering are provided below.
Table 5-7 Sludge Tank Design Summary
Parameter Design Value
No. of Sludge pumps 2
Daily Sludge Production (kg/d)60
Solids Content (%)1.0%
Daily Sludge Production (m3/d)6.0
Total Storage Volume (m3)45
No. of Tanks 1
Tank Dimensions (m)4.0 L x 3.5 W x 5.0 D
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 31
Table 5-8 Sludge Dewatering Design Summary
Parameter Design Value
Number of Centrifuge Units 1
Sludge Flow (m3/hr)1.5
Solids Loading Rate (kg/hr)15
Polymer Consumption (kg/dry tonne)12-15
Solids Capture (%)>95
Cake Solids (%)18-22
5.2.6 Odour Control
As discussed in Section 4.2.1.2,the location of the proposed WWTP does not meet the ACWGM
guidelines for setback distance from residential properties; however, discussions with NSE indicate that
they will accept the location of the WWTP if provisions for odour control are included in the design.
Odorous air generated at the WWTP will be captured through an air collection system for central
treatment. This includes outside tankage and the preliminary treatment area. The final odour treatment
system will be determined as part of the final design, but HEJV has assumed a biological filter system will
be used.
5.3 Facility Description
The WWTP will be housed in a single structure and will be divided into process and administrative areas.
The process area will include:
®Preliminary Treatment area with:
o Shaftless Spiral Fine Screen;
o Grit vortex chamber, grit pump and grit classifiers; and
o Screenings and grit bins;
®SBR Tanks (2);
®Process Room with:
o Blower Gallery; and
o Sludge Pumps;
®UV Disinfection Room
The administrative area with:
®Office space;
®Laboratory;
®Mechanical and electrical room; and,
®Washroom.
Facilities and infrastructure provided but housed outside the structure will include:
®Lift Station and effluent chamber structure;
®Site access and parking;
®Site fencing;
®Genset;
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 32
®Yard piping; and
®New outfall.
5.3.1 Civil and Site Works
Civil and site works will include site conditions, grading, draining, and site improvements.
The proposed site previously housed several interspersed structures containing fish processing
equipment and auxiliary equipment. The structures have long since undergone demolition, however the
concrete foundations remain and will need to be removed. The geotechnical desktop study has
indicated that the land has previously housed fuel storage tanks and although no evidence of petroleum
hydrocarbon contamination in the soil has been observed, a phase 1 ESA should be conducted to
confirm no contamination.
The geotechnical desktop study has indicated that the subsurface geology is a stony till plain and is
anticipated to be relatively thin at between 1 and 5 metres thick with under laying bedrock. Drilling and
blasting techniques and consideration for excavation dewatering will be required for the construction of
deep structures.
There are already two existing access roads through the proposed site, and one of these will need to be
removed and the other will need to be realigned and extended around the perimeter of the WWTP to
facilitate access.
The environmental risk assessment was completed on the assumption that the WWTP would discharge
through a new outfall pipe perpendicular to the shoreline in shallow water. At this stage it is unknown if
an existing outfall could function as the effluent outfall for the new facility, and this could add value by
utilising existing infrastructure. However, significant infrastructure with a new linear forcemain and
pumping would be required. For these reasons HEJV has based the facility design on a new outfall as
part of the WWTP project. The new outfall would likely include a new HDPE outfall pipe, manholes as
required, stone mattress, concrete pipe anchors, and reinstatement to the existing shoreline armour
stone protection. The approximate routing of the proposed outfall is shown on Drawing C03 – Site
Works Plan.
5.3.2 Architectural
HEJV has worked on numerous projects where neighboring properties are located in close proximity to
wastewater infrastructure such as pump stations. CBRM has expressed the need for the new building to
blend into the existing neighborhood, with process tankage partially obstructed as much as possible by
the building.
The inner walls of the new building will be reinforced concrete bearing block. The exterior wall veneer
will be vinyl or stained wood siding, to blend in with local neighbors. The new building will have a
conventional gable truss roof. The roofing material will be either asphalt shingles or pre-finished metal
panels, with aluminum low-maintenance fascia and soffits. Interior doors and frames will be stainless,
exterior doors, windows and louvers shall be aluminium, colour anodized to match existing features.
This approach will make the facility less conspicuous to the general public.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 33
All required site railings for tanks, walkways, and stairs will be welded aluminium with a clear anodized
finish.
Interior concrete walls of the buildings will be painted with an industrial epoxy coating. Interior metal
surfaces will be painted with epoxy coatings and exterior metal will be coated with an ultraviolet
resistant urethane finish. Process area ceilings and walls will be painted. Process area floors will be
concrete, coated with a durable industrial floor coating.
Alternative architectural designs and/or exterior colors can be re-evaluated by CBRM closer to the
planned construction timeline, to ensure that the final plant buildings are aesthetically pleasing to
neighbors, and fit into both current and future community architecture.
5.3.3 Mechanical
Mechanical systems will be designed in accordance with NFPA 820, 2016 edition, which describes the
hazard classification of specific areas and processes and prescribes ventilation criteria for those areas.
Table 5-9 summarizes the proposed classification for new facilities.
Table 5-9 Classification of Building Areas
Location Classification
Grit and Screening Platform Class 1 Zone 2
Bin Room Class 1 Zone 2
Process Room Unclassified
UV Disinfection Room Unclassified
Administration Area Unclassified
Process Areas will be heated by electric unit heaters and electric duct heaters in the air handling units,
and no provisions have been made for air conditioning. Provisions for air conditioning in non-process
areas (Office, Laboratory, Washrooms, and Electrical Room) have been made. Odorous air will be
contained and directed to the Odour Control Unit either by stainless steel or fibreglass ducting.
The facility will need to be serviced by domestic water, and sanitary drains from the facility will be
directed by gravity to the influent lift station.
5.3.4 Electrical
The previous building on the proposed site was serviced by 3-phase power, however this will need to be
extended to service the new WWTP. Existing power poles supporting electrical and communication
services will need to be re-routed as they will interfere with the new facility.
An emergency diesel generator housed in exterior enclosure along with fuel tanks will be located to the
west of the process building.
5.3.5 Lighting
Exterior lighting will consist of building mounted luminaires illuminating areas immediately adjacent to
the buildings, as well as pole mounted area lighting for access roadways and parking areas. Exterior
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 34
lights will be LED where available or to suit application. Exterior lighting fixtures shall be vandal resistant
and outdoor rated.
New pole mounted flood lights will be installed at the process tanks for maintenance purposes. The
interior lighting system will be designed for lighting performance and luminance levels in accordance
with the Illuminating Engineering Society (IESNA) Lighting Handbook, 10th Edition. Interior lights will be
fluorescent, LED, or metal halide to suit the application. Emergency and exit lights will be installed along
egress routing and around exit doors to meet the requirements of the National and Provincial Building
Codes.
5.3.6 Instrumentation
This section summarizes the functional requirements for the process control and instrumentation
system. It includes a narrative description of the instrumentation and control requirements.
Most unit processes in the treatment plant will be automated. There will be a main plant PLC that will
be used to control the unit processes. In addition to the main PLC, a local hand-off-auto (H-O-A) switch
will be required for most of the equipment. Some of the more complex unit processes will be provided
with their own individual PLCs including:
®UV disinfection system;
®SBRs; and
®Generator.
Each piece of equipment that is to be provided with a dedicated controller will be capable of operating
in either a manual or automatic mode (SCADA controlled) via an H-O-A switch.
5.3.7 Control System Overview
Unit operations at the treatment plant will be monitored and controlled using a system of instruments,
equipment motors and drives, PLCs, human machine interfaces (HMI), communications cable and
hardware that is integrated into a SCADA software program. The selection of Supervisory and Control
Software as well as the level and type of plant instrumentation will be made following the selection of a
system integrator and a review of options by the Owner and the engineers.
The system will also be configured to allow authorized staff to dial in and log on from a remote location
via laptop. This will permit the Supervisor or duty operator to check plant status, respond to after-hours
alarms, and to change equipment operation where appropriate.
In addition to the aforementioned monitoring and control terminals, there will be local control panels at
key locations using “soft panel” type HMIs (human/machine interface), which will permit the operator to
view process information and to take local control action. In some locations, where the only
requirement is to be able to stop a motor and to lock it out for maintenance, that capability will be
provided by hard-wired controls at the motor starter.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 35
The alarms integrated into the system will have audible and/or flashing light annunciation in the plant
during regular hours, and call-out by telephone and/or email after hours with a user-configurable
sequential call priority list.
5.3.8 Headworks
The Headworks consist of fine screening and a vortex grit system. All the equipment will be controlled
by the main PLC. Each piece of equipment will be monitored for status and faults in addition to the
alarms for high levels in the influent channels which will be registered on the central control computers
and monitors.
5.3.9 SBR
Effluent from preliminary treatment will be split between the SBR tanks via actuated gates.
The SBR and sludge tank blowers will be installed in the Process Building. The SBR blowers will discharge
to a common air header which will have a dedicated take off for each SBR. Blower operation will be
controlled by the SBR control system. The sludge tank blower will discharge to a common air header
which will be connected to diffusers in the tank.
The air headers will feed the fine bubble diffusers arranged along the bottom of the SBRs. A separate
header will feed the fine bubble diffusers arranged along the bottom of the aerated sludge holding
tanks. Dissolved oxygen will be monitored in the SBR tanks.
An air flow meter in the SBR supply header will indicate, totalize, and record the air flow. The dissolved
oxygen levels for each reactor will be indicated and recorded on the central SCADA system. Blower
operating status, header pressure, and inlet valve positions, as well as supply line pressure will be
indicated on the central computer system. The blowers will also be equipped with sensors and alarms
for surge, vibration, temperature, and general faults, which will register at the central control.
Treated effluent will be removed from the SBR tanks via a decanter mechanism. Flow into the decanter
will be automatically controlled via a valve by the SBR control system.
5.3.10 Waste Activated Sludge
The WAS will be pumped from the SBRs to the aerated sludge holding tanks automatically using WAS
pumps which will be controlled by the SBR control system. WAS flow will be measured by magnetic flow
meter.
5.3.11 Effluent Disinfection
Ultraviolet Disinfection will be used to achieve disinfection limits for fecal coliform prior to discharge.
The UV manufacturer will provide a PLC to control the UV system, which will be compatible with the
central station. UV dose will be controlled by plant flow and percent UVT. Monitoring and recording of
UV intensity, general alarms and low level, high levels alarms will be provided.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 36
CHAPTER 6 PROJECT COSTS
6.1 Opinion of Probable Construction Costs
An opinion of Probable Construction Costs has been completed for the project, and a detailed
breakdown of the estimate has been provided in Appendix C. The estimate is made up of the civil works,
structural works, equipment, mechanical and electrical installation, and associated land acquisition
costs. The opinion of probable construction costs for the WWTP for Louisbourg, as defined herein, is
$13,850,000.
6.2 Opinion of Annual Operating Costs
HEJV completed an opinion of probable operating costs for the Louisbourg WWTP using data provided
by CBRM for typical annual operating costs of existing infrastructure, typical employee salaries, Nova
Scotia Power rates, and experiences from similar installations for general maintenance. The opinion of
operation costs include equipment maintenance costs (lift station, preliminary treatment, SBR package,
and UV Equipment), employee operational costs, facility maintenance costs and electrical costs. The
probable opinion of annual operating costs is presented below in Table 6-1.
Table 6-1 - Annual Operating Costs Breakdown (2019 Dollars)
Items Costs
Operating and Maintenance Cost $33,000
Staffing Cost $175,000
Electrical Operational Cost $25,500
The maintenance costs include: pump repairs (impellers, bearings, seals), preliminary treatment
equipment (bearings, cleaning, greasing), SBR and Sludge Tank diffusers (cleaning), blowers (belts,
bearings, filters) and UV equipment (UV lamp, ballasts), minor building maintenance (painting, siding
repairs, roof repairs), electrical repairs, and instrumentation repairs and servicing.
For the electrical operation cost, HEJV assumed the building would require heat for 5 months of the
year. Basic electrical loads for instrumentation were assumed. Electrical demand for process equipment
was determined based on the yearly average flow of the plant.
The Points Classification System in the Atlantic Canadian Guidelines was used to determine staffing
requirements at the Louisbourg WWTP, and it has been determined that facility has 50 points based
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 37
upon interpretation. Since Class II plants are defined as having 31 – 56 points, the WWTP will be ranked
as at least a Class II treatment plant by the regulators.
According to ACWGM the guidelines, a Class II plant designed for an average flow of 588 m3/day will
require approximately 3,500 work-hours per year to operate, or about 2 fulltime employees. The
estimated burdened staff hourly rate is $50/hour.
6.3 Opinion of Annual Capital Replacement Fund Contributions
The CBRM wishes to create a Capital Replacement Fund to which annual contributions would be made
to prepare for replacement of the wastewater assets at the end of their useful life. The calculation of
annual contributions to this fund involves consideration of such factors as the type of asset, the asset
value, the expected useful life of the asset, and the corresponding annual depreciation rate for the asset
as per the accounting practices for asset depreciation and Depreciation Funds recommended in the
Water utility Accounting and Reporting Handbook (Nova Scotia Utility and Review Board, 2013). In
consideration of these factors,Table 6-2 provides an estimation of the annual contributions to a capital
replacement fund for the proposed new wastewater treatment system infrastructure. This calculation
also adds the same contingency factor used in the calculation of the Opinion of Probable Capital Cost.
The actual Annual Capital Replacement Fund Contributions will be calculated based on the final
constructed asset value, the type of asset, the expected useful life of the asset, and the corresponding
annual depreciation rate for the type of asset.
Table 6-2 - Estimated Annual Capital Replacement Fund Contributions
Description of Asset Asset Value
Asset Useful
Life
Expectancy
(Years)
Annual
Depreciation
Rate (%)
Annual
Capital
Replacement
Fund
Contribution
Treatment Linear Assets (Outfall and Yard
Piping, Manholes and Other)$2,341,682 75 1.30%$30,442
Treatment Structures (Concrete Chambers,
etc.)$2,333,623 50 2.00%$46,673
Treatment Equipment (Mechanical /
Electrical, etc.)$5,382,255 20 5.00%$269,113
Subtotal $10,057,560 --$346,228
Construction Contingency (Subtotal x 25%):$86,557
Engineering (Subtotal x 12%):$41,547
Opinion of Probable Annual Capital Replacement Fund Contribution:$474,332
Notes:
1.Annual contribuƟons do not account for annual inflaƟon.
2.Costs do not include applicable taxes
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief 38
CHAPTER 7 REFERENCES
ASA Consulting Ltd. (May 1994).Industrial Cape Breton Receiving Water Study, Phase II.
Environment Canada (2006) –Atlantic Canada Wastewater Gidelines Manual for Collection, Treatment
and Disposal.
Harbour Engineering Inc. (2011).Cape Breton Regional Municipality Wastewater Strategy 2009
Harbour Engineering Inc. (2018).Cape Breton Regional Municipality Environmental Risk Assessment
& Preliminary Design of Seven (7) Future Wastewater Treatment Systems in CBRM Base
Information 2018.
Nova Scotia Utility and Review Board (2013).Water Utility Accounting and Reporting Handbook.
Turner Drake & Partners Ltd. (February 2018).Population Projects Cape Breton, Nova Scotia.
UMA Engineering Ltd. (1994). Industrial Cape Breton Wastewater Characterization Programme – Phase
II.
Water Environment Federation (2009),Design of Wastewater and Stormwater Pumping Stations.
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief
APPENDIX A
Drawings
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief
APPENDIX B
SBR & MBBR Estimated Capital Cost
Differential
OPINION OF PROBABLE
COST, CLASS 'D'
SBR Cost Differential Evaluation
Project Manager:D. McLean
Louisbourg WWTP Est. by: D. Bennett Checked by: M. Abbot
PROJECT No.:187116 (Dillon)
182402.00 (CBCL)
UPDATED:July 19, 2019
NUMBER UNIT
1.0 General Conditions $233,711.80
Mobilization, Bonds, Insurance, P.C Mngmt 1 LS $100,000.00 $100,000.00
Contractor Overhead & Fees 10 %$133,711.80
2.0 Site Works $44,585.00
Site Preparation 233 m2 $5.00 $1,165.00
Mass Excavation 436 m3 $20.00 $8,720.00
Rock Excavation 145 m3 $60.00 $8,700.00
Gravel (Beneth slabs)117 m3 $40.00 $4,680.00
Fill - Import 44 m3 $30.00 $1,320.00
Site Reinstatement 1 LS $20,000.00 $20,000.00
3.0 Concrete $275,000.00
Baseslabs (Tank)122 m3 $1,000.00 $122,000.00
Tank Walls 30 m3 $1,600.00 $48,000.00
Suspended Slab 35 m3 $2,000.00 $70,000.00
Lean Concrete 10 m3 $1,000.00 $10,000.00
Misc. Concrete Items 10 %$25,000.00
4.0 Masonry $0.00
5.0 Metals & Roofing $0.00
6.0 Finishes/Doors/Windows $0.00
7.0 Process Equipment Supply $480,000.00
Process Equipment Package 1 Each $480,000.00 $480,000.00
8.0 Mechanicl $336,000.00
Process Mechanical 30 %$144,000.00
Process Installation 40 %$192,000.00
9.0 Electrical $222,853.00
Power Supply & Distribution 15 %$167,139.75
Instrumentation & Controls 5 %$55,713.25
TOTAL DIRECT & INDERECT COST (Excluding Contingencies and Allowances)$1,592,149.80
Design Development Contingency (Subtotal x 25 %)$398,100.00
Construction Contingency (Subtotal x 25 %)$398,100.00
Engineering (Subtotal x 12 %)$191,100.00
OPINION OF PROBABLE COST (Including Contingency)$2,579,449.80
PREPARED FOR:
Cape Breton
Regional Municipality
Louisbourg, NS
ITEM DESCRIPTION QUANTITY UNIT COST TOTAL EXTENDED TOTALS
OPINION OF PROBABLE
COST, CLASS 'D'
MBBR Cost Differential Evaluation
Project Manager:D. McLean
Louisbourg WWTP Est. by: D. Bennett Checked by: M. Abbot
PROJECT No.:187116 (Dillon)
182402.00 (CBCL)
UPDATED:July 19, 2019
NUMBER UNIT
1.0 General Conditions $289,827.48
Mobilization, Bonds, Insurance, P.C Mngmt 1 LS $100,000 $100,000
Contractor Overhead & Fees 10 %$189,827.48
2.0 Site Works $36,150.00
Site Preparation 132 m2 $5.00 $660.00
Mass Excavation 248 m3 $20.00 $4,960.00
Rock Excavation 83 m3 $60.00 $4,980.00
Gravel (Beneth slabs)120 m3 $40.00 $4,800.00
Fill - Import 25 m3 $30.00 $750.00
Site Reinstatement 1 LS $20,000.00 $20,000.00
3.0 Concrete $106,304.00
Baseslabs (Tank)20 m3 $1,000.00 $20,000.00
Baseslabs (Building)32 m3 $700.00 $22,400.00
Tank Walls 11 m3 $1,600.00 $17,600.00
Precast Roof Panels 80 m2 $208.00 $16,640.00
Suspended Slab 5 m3 $2,000.00 $10,000.00
Lean Concrete 10 m3 $1,000.00 $10,000.00
Misc. Concrete Items 10 %$9,664.00
4.0 Masonry $40,400.00
Exterior Masonry 101 m2 $400.00 $40,400.00
5.0 Metals & Roofing $0.00
6.0 Finishes/Doors/Windows $0.00
7.0 Process Equipment Supply $825,000.00
Process Equipment Package 1 Each $825,000.00 $825,000.00
8.0 Mechanical $577,500.00
Process Mechanical 30 %$247,500.00
Process Installation 40 %$330,000.00
9.0 Electrical $312,920.80
Power Supply & Distribution 15 %$234,690.60
Instrumentation & Controls 5 %$78,230.20
TOTAL DIRECT & INDERECT COST (Excluding Contingencies and Allowances)$2,188,102.28
Design Development Contingency (Subtotal x 25 %)$561,100.00
Construction Contingency (Subtotal x 25 %)$561,100.00
Engineering (Subtotal x 12 %)$269,400.00
OPINION OF PROBABLE COST (Including Contingency)$3,579,702.28
PREPARED FOR:
Cape Breton
Regional Municipality
Louisbourg, NS
ITEM DESCRIPTION QUANTITY UNIT COST TOTAL EXTENDED TOTALS
Harbour Engineering Joint Venture Louisbourg WWTP Pre-Design Brief
APPENDIX C
Opinion of Probable Construction Costs
OPINION OF PROBABLE
COST, CLASS 'C'
Preliminary Design
Louisbourg Wastewater Treatment Plant Project Manager:D. McLean
Louisbourg, NS Est. by: D. Bennett Checked by: M. Abbot
PROJECT No.:187116 (Dillon)
SBR Treatment Process 182402.00 (CBCL)
UPDATED:March 30, 2020
NUMBER UNIT
1.0 General Conditions $1,007,959.56
Mobilization, Bonds, Insurance, P.C Mngmt 1 LS $100,000.00 $100,000.00
Contractor Overhead & Fees 10 %$907,959.56
2.0 Site Works $1,929,574.00
Site Preparation 5,625 m2 $5.00 $28,125.00
Mass Excavation 1,077 m3 $20.00 $21,540.00
Rock Excavation 120 m3 $60.00 $7,200.00
Fill - Import 299 m3 $30.00 $8,970.00
Gravel (Beneath Slabs)641 m3 $40.00 $25,640.00
Asphalt 105 T $115.00 $12,075.00
Type 1 264 T $25.00 $6,600.00
Type 2 792 T $22.00 $17,424.00
Curb 350 m $100.00 $35,000.00
500 mm Diameter PVC gravity sewer (Deep install)100 m $750.00 $75,000.00
500 mm Diameter PVC Overflow (Deep install)100 m $750.00 $75,000.00
500 mm Diameter PVC Effluent (Deep install)100 m $750.00 $75,000.00
Manholes 4 ea $8,000.00 $32,000.00
Chainlink Fence and Gates 300 m $100.00 $30,000.00
Sediment Control 1 LS $10,000.00 $10,000.00
Dewatering 1 LS $50,000.00 $50,000.00
Reinstatement 1 LS $20,000.00 $20,000.00
Outfall Upgrade 1 LS $1,400,000.00 $1,400,000.00
3.0 Concrete $1,141,360.00
Baseslabs (Tank)150 m3 $1,000.00 $150,000.00
Baseslabs (Building)188 m3 $700.00 $131,600.00
Tank Walls 229 m3 $1,600.00 $366,400.00
Building Walls 67 m3 $1,500.00 $100,500.00
Suspended Slab 66 m3 $2,000.00 $132,000.00
Precast Roof Panels 450 m2 $208.00 $93,600.00
Precast Stairs 1 Ea $13,500.00 $13,500.00
Lean Concrete 50 m3 $1,000.00 $50,000.00
Misc. Concrete Items 10 %$103,760.00
4.0 Masonry $193,300.00
Interior Masonry 50 m2 170.00$$8,500.00
Exterior Masonry 462 m2 400.00$$184,800.00
5.0 Metals & Roofing $266,400.00
Metal Railings, Stairs, Grating, Hatches 641 m2 400.00$$256,400.00
Miscellaneous Metals Items 1 L.S 10,000.00$$10,000.00
6.0 Finishes/Doors/Windows $226,115.00
Membrane Roof 360 m2 150.00$$54,000.00
Carpentry, Assessories and Fixtures 360 m2 40.00$$14,400.00
Louvers 360 m2 65.00$$23,400.00
Painting 360 L.S 50.00$$18,000.00
Epoxy Painting 360 m2 54.00$$19,440.00
Floor Finishes (Lab, Office, Admin Area)140 m2 15.00$$2,100.00
Windows (Exterior - Single)10 ea 2,650.00$$26,500.00
Doors (Single Swing Steel)7 ea 1,100.00$$7,700.00
Doors (Double Swing Steel)5 ea 2,500.00$$12,500.00
Other Interior Finishes 641 m2 75.00$$48,075.00
Laboratory Specialities 1 LS 30,000.00$$30,000.00
7.0 Process Equipment Supply $1,968,303.00
Lift Station (Triplex Pump Station)1 Each $450,000.00 $450,000.00
Screening Equipment 1 Each $86,945.00 $86,945.00
Grit Removal 1 Each $186,100.00 $186,100.00
SBR Equipment 1 Each $480,000.00 $480,000.00
UV Disinfection System 1 Each $45,258.00 $45,258.00
Sludge Tank 1 Allow $120,000.00 $120,000.00
Centrifuge 1 Allow $300,000.00 $300,000.00
Odour Control 1 Allow $300,000.00 $300,000.00
8.0 Mechanical $1,826,512.10
HVAC and Plumbing 641 m2 $700.00 $448,700.00
Process Mechanical 30 %of Equipment $590,490.90
Process Installation 40 %of Equipment $787,321.20
9.0 Electrical $1,498,031.54
Power Supply & Distribution 15 %of Project Costs $1,123,359.62
Instrumentation & Controls 3 %of Project Costs $224,671.92
Generator 1 Allow $150,000.00 $150,000.00
TOTAL DIRECT & INDERECT COST (Excluding Contingencies and Allowances)$10,057,560
Contingency Allowance (Subtotal x 25 %)$2,514,400
Engineering (Subtotal x 12 %)$1,207,000
Land Purchase $71,429
OPINION OF PROBABLE COST (Including Contingency)$13,850,389
ITEM DESCRIPTION QUANTITY UNIT COST TOTAL EXTENDED TOTALS
PREPARED FOR:
Cape Breton
Regional Municipality
HEJV Louisbourg Wastewater System Summary Report Appendices
APPENDIX C
Louisbourg Environmental Risk Assessment
182402.00 ● Report ● May 2020
Louisbourg Wastewater Treatment Plant
Environmental Risk Assessment
Final Report
Prepared by:
Prepared for:
March 2020
Final May 21, 2020 Darrin McLean Karen March Holly Sampson
Draft for Review December 5, 2018 Darrin McLean Karen March Holly Sampson
Issue or Revision Date Issued By: Reviewed By: Prepared By:
This document was prepared for the party indicated
herein. The material and information in the
document reflects HE’s opinion and best judgment
based on the information available at the time of
preparation. Any use of this document or reliance
on its content by third parties is the responsibility of
the third party. HE accepts no responsibility for any
damages suffered as a result of third party use of
this document.
182402.00
March 27, 2020
275 Charlotte Street
Sydney, Nova Scotia
Canada
B1P 1C6
Tel: 902-562-9880
Fax: 902-562-9890
_________________
182402 RE 001 FINAL WWTP ERA LOUISBOURG.DOCX/klm
ED: 21/05/2020 11:08:00/PD: 21/05/2020 11:08:00
May 21, 2020
Matt Viva, P.Eng.
Manager Wastewater Operations
Cape Breton Regional Municipality (CBRM)
320 Esplanade,
Sydney, NS B1P 7B9
Dear Mr. Viva:
RE: Louisbourg Wastewater Treatment Plant ERA
Enclosed, please find a copy of the Environmental Risk Assessment (ERA) Report
for the Louisbourg Wastewater Treatment Plant (WWTP).
The report outlines Environmental Quality Objectives (EQOs) for all parameters
of potential concern listed in the Standard Method for a “small” facility.
Environmental Discharge Objectives (EDOs) were also calculated for all
parameters of potential concern.
If you have any questions or require clarification on the content presented in
the attached report, please do not hesitate to contact us.
Yours very truly,
Harbour Engineering
Prepared by: Reviewed by:
Holly Sampson, M.A.Sc., P.Eng. Karen March, M.Sc.
Intermediate Chemical Engineer Environmental Scientist
Direct: 902‐539‐1330 Phone: 902‐450‐4000
E‐Mail: hsampson@cbcl.ca E‐Mail: kmarch@dillon.ca
Project No: 182402.00 (CBCL)
187116.00 (Dillon)
March 27, 2020
Harbour Engineering Joint Venture Louisbourg WWTP ERA i
Contents
CHAPTER 1 Background and Objectives ................................................................................... 1
1.1 Introduction .................................................................................................................. 1
1.2 Background ................................................................................................................... 1
1.3 Facility Description ........................................................................................................ 2
CHAPTER 2 Initial Wastewater Characterization ...................................................................... 4
2.1 Substances of Potential Concern .................................................................................. 4
2.1.1 Whole Effluent Toxicity ..................................................................................... 5
2.2 Wastewater Characterization Results .......................................................................... 5
CHAPTER 3 Environmental Quality Objectives ......................................................................... 7
3.1 Water Uses .................................................................................................................... 7
3.2 Ambient Water Quality ................................................................................................. 8
3.3 Physical/ Chemical/ Pathogenic Approach ................................................................. 10
3.3.1 General Chemistry/ Nutrients ........................................................................ 10
3.3.2 Pathogens ....................................................................................................... 14
3.3.3 Summary ......................................................................................................... 14
CHAPTER 4 Mixing Zone Analysis ........................................................................................... 16
4.1 Methodology ............................................................................................................... 16
4.1.1 Definition of Mixing Zone ............................................................................... 16
4.1.2 Site Summary .................................................................................................. 18
4.1.3 Far‐Field Modeling Approach and Inputs ....................................................... 18
4.2 Modeled Effluent Dilution .......................................................................................... 21
CHAPTER 5 Effluent Discharge Objectives .............................................................................. 24
5.1 The Need for EDOs ...................................................................................................... 24
5.2 Physical/ Chemical/ Pathogenic EDOs ........................................................................ 24
5.3 Effluent Discharge Objectives ..................................................................................... 25
CHAPTER 6 Compliance Monitoring ....................................................................................... 27
CHAPTER 7 References .......................................................................................................... 28
Appendices
A Laboratory Certificates
Harbour Engineering Joint Venture Louisbourg WWTP ERA 1
CHAPTER 1 BACKGROUND AND OBJECTIVES
1.1 Introduction
Harbour Engineering (HE) was engaged by the Cape Breton Regional Municipality (CBRM) to complete
an Environmental Risk Assessment (ERA) for the proposed Louisbourg Wastewater Treatment Plant
(WWTP). As this is a proposed WWTP that has not yet been designed, this ERA was completed with the
objective that it serve as a tool to establish effluent criteria for the design of a new WWTP. For this
reason, the ERA was completed without the frequency of testing required by the Standard Method
outlined in Technical Supplement 3 of the Canada‐wide Strategy for the Management of Municipal
Wastewater Effluent (Standard Method) for initial effluent characterization. With the exception of the
initial effluent characterization sampling frequency, the ERA was otherwise completed in accordance
with the Standard Method.
1.2 Background
The Canada‐wide Strategy (CWS) for the Management of Municipal Wastewater Effluent was adopted
by the Canadian Council of Ministers of the Environment (CCME) in 2009. The Strategy is focused on
two main outcomes: Improved human health and environmental protection; and, improved clarity
about the way municipal wastewater effluent is managed and regulated. The Strategy requires that all
wastewater facilities discharging effluent to surface water meet the following National Performance
Standards (NPS) as a minimum:
Carbonaceous Biochemical Oxygen Demand for five days (CBOD5) – 25 mg/L;
Total Suspended Solids (TSS) – 25 mg/L; and
Total Residual Chlorine (TRC) – 0.02 mg/L.
The Wastewater Systems Effluent Regulations (WSER) came into effect in 2012 under the Fisheries Act.
The WSER include the above NPS as well as the following criteria:
Unionized ammonia – 1.25 mg/L, expressed as nitrogen (N), at 15°C ± 1°C.
The CWS requires that facilities develop site‐specific Effluent Discharge Objectives (EDOs) to address
substances not included in the NPS that are present in the effluent. EDOs are the substance
concentrations that can be discharged in the effluent and still provide adequate protection of human
health and the environment. They are established by conducting a site‐specific ERA. The ERA includes
characterization of the effluent to determine substances of concern, and characterization of the
Harbour Engineering Joint Venture Louisbourg WWTP ERA 2
receiving water to determine beneficial water uses, ambient water quality, assimilative capacity, and
available dilution. A compliance monitoring program is then developed and implemented to ensure
adherence to the established EDOs for the facility.
1.3 Facility Description
The proposed Louisbourg Wastewater Treatment Plant (WWTP) will be constructed north of
Commercial Street and west of Strathcona Street in the community of Louisbourg in CBRM, Nova
Scotia. Treated effluent will be discharged to Louisbourg Harbour in the Atlantic Ocean via an outfall
that will be constructed for the WWTP (Figure 1.2). The service population of Louisbourg is 796
people in 391 residential units.
Figure 1.1 Site Location
Harbour Engineering Joint Venture Louisbourg WWTP ERA 3
The theoretical domestic wastewater flow is an average of
271 m3/day with a peak of 1057 m3/day based on a per capita
flow of 340 L/person/day and a peaking factor of 3.9
calculated using the Harmon formula. The largest outfall in
the sewer system (L2) was flow metered from February 26 to
May 8, 2018. The service population upstream of this meter
was 360 people. The average dry weather flow was 259
m3/day (720 L/p/d). The average daily flow during the
metering period was 321 m3/day (893 L/p/d).
For the purposes of this ERA, the average daily design flow
was assumed to be 983 m3/day (1251 L/p/d) based on
analysis completed by HE. As the population in this area is
declining, accounting for a projected population increase
during the life of the plant was not necessary. The
preliminary design report was completed based on an
average design flow of 562 m3/day. However, it also
recommended that additional flow monitoring be completed
prior to detailed design of the WWTP. Therefore, the ERA will
not be revised at this time.
Figure 1.2 WWTP Location
Harbour Engineering Joint Venture Louisbourg WWTP ERA 4
CHAPTER 2 INITIAL WASTEWATER CHARACTERIZATION
2.1 Substances of Potential Concern
An initial characterization program covering a one‐year period is typically required by the Standard
Method to describe the effluent and identify substances of concern. As there is no existing WWTP
for this system, and the ERA is being conducted for the purpose of determining effluent objectives
for the design of a new WWTP, only one sample event was completed of the untreated wastewater.
Sample results of the untreated wastewater were also available for some of the parameters of
potential concern from three‐years of monthly sampling conducted by CBRM from 2015 through
2017. Substances of potential concern are listed in the Standard Method based on the size category
of the facility. The proposed design capacity of the new WWTP will be finalized during the pre‐
design study, but for the purposes of the ERA, an average annual design flow of 983 m3/day will be
used. Therefore, the WWTP is classified as a “small” facility based on an average daily flow rate that
is between 500 and 2,500 m3/day.
The substances of potential concern for a “small” facility, as per the Standard Method, are detailed in
Table 2.1. There were no additional substances of potential concern identified to be monitored as there
is no industrial input to the wastewater system that exceeds 5% of the total dry weather flow. It was
confirmed with CBRM that none of the fish processing plants in Louisbourg discharge to the sanitary
sewer system.
Table 2.1 Substances of Potential Concern for a Small Facility
Substance Group Substances
General Chemistry/ Nutrients
Total Suspended Solids (TSS)
Carbonaceous Biochemical Oxygen Demand (CBOD5)
Total Residual Chlorine (TRC) if chlorination is used
Total Ammonia Nitrogen
Total Kjeldahl Nitrogen (TKN)
Total Phosphorus (TP)
pH
Temperature
Pathogens E. coli
Harbour Engineering Joint Venture Louisbourg WWTP ERA 5
2.1.1 Whole Effluent Toxicity
Wastewater effluent potentially contains a variety of unknown or unidentified substances for which
guidelines do not exist. In order to adequately protect against these unknown substances, Whole
Effluent Toxicity (WET) tests are typically conducted to evaluate acute (short‐term) and chronic (long‐
term) effects.
The Standard Method requires the following toxicity tests be conducted quarterly:
Acute toxicity – Rainbow Trout and Daphnia Magna; and
Chronic Toxicity – Ceriodaphnia Dubia and Fathead Minnow.
A draft for discussion Mixing Zone Assessment and Report Template, dated July 6, 2016 that was
prepared by a committee of representatives of the environment departments in Atlantic Canada noted
that only Ceriodaphnia dubia testing is required for chronic toxicity. If the test does not pass, a fathead
minnow test is required.
As the wastewater in this system is currently untreated, and the purpose of the ERA is to determine
effluent discharge objectives for the design of a new WWTP, no WET tests were conducted at this time.
2.2 Wastewater Characterization Results
The results of the initial untreated wastewater characterization samples collected by Harbour
Engineering (HE) are provided in Table 2.2. A summary of the results of the untreated wastewater
characterization samples collected by CBRM from 2015 through 2017 are summarized in Table 2.3.
Table 2.2 Initial Wastewater Characterization Results
Parameter Units L1 L2 L5
CBOD5 mg/L 110 61 41
Total Kjeldahl Nitrogen (TKN) mg/L 6.3 6.2 4.3
Nitrogen (Ammonia Nitrogen) as N mg/L 1.0 2.9 0.96
Unionized ammonia(1) mg/L 0.0021 0.0069 0.0022
pH pH 6.89 6.94 6.92
Total Phosphorus mg/L 0.79 1.1 0.78
Total Suspended Solids mg/L 33 43 25
E. coli MPN/ 100mL 200000 820000 770000
Total Coliforms MPN/ 100mL >2400000 >2400000 2000000
Note: (1) The value of unionized ammonia was determined in accordance with the formula in the WSER, the
concentration of total ammonia in the sample, and the pH of the sample.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 6
Table 2.3 CBRM Wastewater Characterization Samples
Location Parameter Average Number of Samples
L1
TSS (mg/L) 37.0 1
CBOD5 (mg/L) 60.0 1
Total Ammonia (N) (mg/L) 3.1 1
pH 7.1 1
Unionized Ammonia (mg/L) 0.0095 1
L2
TSS (mg/L) 59.9 37
CBOD5 (mg/L) 80.7 37
Total Ammonia (N) (mg/L) 4.2 13
pH 6.8 13
Unionized Ammonia (mg/L) 0.009 13
L3
TSS (mg/L) <2 1
CBOD5 (mg/L) <5 1
Total Ammonia (N) (mg/L) <0.05 1
pH 7.440 1
Unionized Ammonia (mg/L) <0.0005 1
L4
TSS (mg/L) <2 1
CBOD5 (mg/L) <5 1
Total Ammonia (N) (mg/L) <0.05 1
pH 7.130 1
Unionized Ammonia (mg/L) <0.0005 1
L5
TSS (mg/L) 21.0 1
CBOD5 (mg/L) 25.0 1
Total Ammonia (N) (mg/L) 1.4 1
pH 6.8 1
Unionized Ammonia (mg/L) 0.0023 1
As mentioned previously, although the frequency of testing specified by the Standard Method was
not met, the ERA will be completed with the available data.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 7
CHAPTER 3 ENVIRONMENTAL QUALITY OBJECTIVES
Generic Environmental Quality Objectives (EQOs) are generated from established guidelines, typically
the Wastewater Systems Effluent Regulations (WSER), the Canadian Environmental Quality Guidelines
(CEQGs) and other guidelines specified by jurisdiction. Site‐specific EQOs are established by adjusting
the generic EQOs based on site‐specific factors, particularly ambient water quality. For example, if the
background concentration of a substance is greater than the guideline value (generic EQO), the
background concentration is used as the site‐specific EQO. However, substances where the EQO is
based on the WSER are not adjusted based on ambient water quality. Furthermore, there are some
guidelines that are dependent on characteristics of the receiving water like pH or temperature. Effluent
is required to be non‐acutely toxic at the end of pipe and non‐chronically toxic at the edge of the mixing
zone.
EQOs can be determined by three different approaches:
Physical/chemical/pathogenic – describes the substance levels that will protect water quality;
Whole Effluent Toxicity (WET) – describes the proportion of effluent that can enter the receiving
water without causing toxicological effects (both acute and chronic); and
Biological criteria (bio‐assessment) – describes the level of ecological integrity that must be
maintained.
This assessment follows the physical/chemical/pathogenic approach from the Standard Method
outlined in the CCME guidelines. The bio‐assessment is not included in the Standard Method as it is still
being developed (CCME, 2008).
3.1 Water Uses
EQOs are numerical values and narrative statements established to protect the receiving water – in this
case, Louisbourg Harbour in the Atlantic Ocean. The first step in determining EQOs is to define the
potential beneficial uses of the receiving water.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 8
The following beneficial water uses have been identified for Louisbourg Harbour in the Atlantic Ocean:
Primary contact recreational activities (scuba diving);
Secondary contact recreational activities like boating and fishing; and
Ecosystem health for fisheries and marine aquatic life.
There is no molluscan shellfish harvesting zone in the vicinity of the outfall. The outfall is situated in a
molluscan shellfish closure zone boundary extending from Lighthouse Point to Blackrock Point
(approximately 1.9km from the discharge). The closure zone boundary is shown on Figure 3.1.
Figure 3.1 Location of Outfall
3.2 Ambient Water Quality
Generic EQOs are first developed based on existing guidelines and then adjusted based on site‐
specific factors, particularly background water quality. Water quality data was obtained for two
locations in the Atlantic Ocean along the coast of Cape Breton. The locations were chosen in an
attempt to be representative of ambient water quality outside the influence of the existing
untreated wastewater discharges in CBRM. Samples were collected by HE on May 11, 2018, and the
sample locations are summarized as follows and presented in Figure 3.2:
BG‐1: Near Mira Gut Beach; and
BG‐2: Wadden’s Cove.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 9
Figure 3.2 Ambient Water Quality Sample Locations
A third sample was collected north of Port Morien but the results were not considered
representative of background conditions as sample results indicated the sample was impacted by
wastewater. Samples were collected as grab samples from near shore using a sampling rod. A
summary of the ambient water quality data is shown in Table 3.1.
Table 3.1 Ambient Water Quality Data
Parameter Units BG1 BG2 AVG
Carbonaceous BOD (CBOD) mg/L <5.0 <5.0 <5.0
Total Kjeldahl Nitrogen (TKN) mg/L 0.19 0.20 0.20
Nitrogen (Ammonia Nitrogen) mg/L <0.050 <0.050 <0.05
unionized ammonia mg/L <0.0007 <0.0007 <0.0007
pH pH 7.73 7.68 7.71
Total Phosphorus (TP) mg/L 0.037 0.032 0.035
TRC(1) mg/L NM NM NM
TSS mg/L 58 5.0 32
E. coli MPN/100mL 52 86 69
Total Coliforms MPN/100mL 16000 6900 11450
Note:
(1) NM = Parameter not measured.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 10
3.3 Physical/ Chemical/ Pathogenic Approach
The physical/chemical/pathogenic approach is intended to protect the receiving water by ensuring that
water quality guidelines for particular substances are being met. EQOs are established by specifying the
level of a particular substance that will protect water quality. Substance levels that will protect water
quality are taken from the CEQGs associated with the identified beneficial water uses. If more than one
guideline applies, the most stringent is used. Typically the Canadian Water Quality Guidelines (CWQGs)
for the Protection of Aquatic Life are the most stringent and have been used for this assessment. The
Guidelines for Canadian Recreational Water have also been used to provide limits for pathogens
(E. coli).
The guidelines for the Protection of Aquatic Life provide recommendations for both freshwater and
marine (including estuarine) environments. Since the receiving water for the proposed Louisbourg
WWTP is a marine environment, the marine guidelines were used, where available.
Site‐specific EQOs are derived in the following sections for each substance of potential concern.
3.3.1 General Chemistry/ Nutrients
The following general chemistry and nutrients parameters were identified as substances of potential
concern for a small facility: CBOD, un‐ionized ammonia, total ammonia, total nitrogen, total Kjeldahl
nitrogen (TKN), total suspended solids (TSS), total phosphorus, pH, and total residual chlorine (TRC).
EQOs for these substances are established in the following section for the ocean discharge option.
Oxygen Demand
Biochemical Oxygen Demand (BOD5) is a measure of the oxygen required to oxidize organic material
and certain inorganic materials over a given period of time (five days). It has two components:
carbonaceous oxygen demand and nitrogenous oxygen demand.
Carbonaceous Biochemical Oxygen Demand (CBOD5) measures the amount of biodegradable
carbonaceous material in the effluent that will require oxygen to break down over a given period of
time (five days). The CBOD5 discharged in wastewater effluent reduces the amount of dissolved
oxygen in the receiving water. Dissolved oxygen is an essential parameter for the protection of
aquatic life; and the higher the CBOD5 concentration, the less oxygen that is available for aquatic
life.
Traditionally performance standards have been set for BOD5; however, the WSER dictate a limit for
CBOD5. This is due to the variable effects of nitrogenous oxygen demand on the BOD5 test.
There are no CWQGs for the protection of aquatic life for CBOD5 in freshwater or in marine waters.
However, because CBOD5 affects the concentration of dissolved oxygen, the CWQG for dissolved
oxygen should be considered. The CWQG for freshwater aquatic life dictates that the dissolved
oxygen concentrations be greater than 9.5 mg/L for early life stages in cold water ecosystems. The
CWQG for marine aquatic life is a minimum of 8 mg/L.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 11
The background dissolved oxygen concentrations were not measured in the receiving water.
However, the concentration of CBOD5 discharged in accordance with the WSER criteria should not
cause the dissolved oxygen (DO) concentration to vary outside of the normal range. Based on an
average annual temperature of 6.9 °C (from Bedford Institute of Oceanography Area 4VN), the
solubility of oxygen in seawater is approximately 9.5 mg/L. Assuming the background concentration
of DO is saturated, there can be a drop of 1.5 mg/L for the DO to be a minimum concentration of 8
mg/L. The average annual temperature was used in this calculation as if the maximum annual
temperature was used, this results in the solubility of oxygen being less than the CWQG for marine
aquatic life. For an ocean discharge, the maximum DO deficit should occur at or near the point
source.
Assuming a deoxygenation rate of 0.3/day based on a depth of approximately 2.5m at the discharge
location, and assuming a reaeration coefficient of 0.49/day based on a depth of approximately 2.5m
and an average tidal velocity of 0.069 m/s. The maximum concentration of CBOD that would result
in a drop in DO of 1.5 mg/L can be calculated. The tidal dispersion coefficient has been assumed to
be 150 m2/s. The concentration of CBOD potentially affecting DO was calculated to be 13.6 mg/L.
Therefore, the WSER criteria of 25 mg/L CBOD at discharge should not cause the dissolved oxygen
(DO) concentration to vary outside of the normal range as initial dilution would result in a
concentration much lower than 13.6 mg/L CBOD. The background level of CBOD was less than the
detection limit of 5 mg/L.
Total Ammonia and Un‐ionized Ammonia
The CWQG for the protection of aquatic life for total ammonia in freshwater is presented as a table
based on pH and temperature. There is no CWQG for ammonia in marine water. Total ammonia is
comprised of un‐ionized ammonia (NH3) and ionized ammonia (NH4+, ammonium). Un‐ionized
ammonia is more toxic than ionized ammonia and the toxicity of total ammonia is related to the
concentration of un‐ionized ammonia present. The amount of un‐ionized ammonia is variable
depending on pH and temperature, which is why the total ammonia guideline is given by pH and
temperature. The USEPA saltwater guideline for total ammonia is 2.7 mg/L based on a temperature
of 17.7 °C, a pH of 7.7 and a salinity of 30 g/kg. The USEPA guideline of 2.7 mg/L will be used as the
EQO for total ammonia.
The WSER requires that un‐ionized ammonia concentrations be less than 1.25 mg/L at the discharge
point. For the purposes of this study, the EQO for un‐ionized ammonia was chosen based on the
WSER (1.25 mg/L at discharge).
Total Suspended Solids (TSS)
The WSER specifies a limit of 25 mg/L for TSS at the end of the pipe. The CWQG for the protection of
aquatic life in marine water for total suspended solids (TSS) is as follows:
During periods of clear flow, a maximum increase of 25 mg/L from background levels for any
short‐term exposure (e.g., 24‐h period). Maximum average increase of 5 mg/L from
background levels for longer term exposures (e.g., inputs lasting between 24 h and 30 d);
and
Harbour Engineering Joint Venture Louisbourg WWTP ERA 12
During periods of high flow, a maximum increase of 25 mg/L from background levels at any
time when background levels are between 25 and 250 mg/L. Should not increase more than
10% of background levels when background is ≥ 250 mg/L.
The background concentration of TSS was an average of 32 mg/L. A maximum average increase of
5mg/L from background levels would result in an EQO of 37 mg/L. As this is greater than the WSER
criteria, the WSER criteria of 25 mg/L at discharge will apply as the EDO. The background TSS
measurement is higher than would typically be expected in a marine environment, which may be
due to the near shore location of the samples. However, in a worst case scenario where the
background TSS concentration was 0 mg/L, application of the WSER criteria at the end of pipe would
be the more stringent criteria provided there is greater than five times dilution.
Total Phosphorus and TKN/TN
There are no CWQGs for the protection of aquatic life for phosphorus, Total Kjeldahl Nitrogen (TKN)
or total nitrogen (TN). However, in both freshwater and marine environments, adverse secondary
effects like eutrophication and oxygen depletion can occur. Guidance frameworks have been
established for freshwater systems and for marine systems to provide an approach for developing
site‐specific water quality guidelines. These approaches are based on determining a baseline
condition and evaluating various effects according to indicator variables. The approach is generally
very time and resource intensive, but can be completed on a more limited scale to establish interim
guidelines.
The Canadian Guidance Framework for the Management of Nutrients in Nearshore Marine Systems
Scientific Supporting Document (CCME, 2007) provides a framework as well as case studies for
establishing nutrient criteria for nearshore marine systems. This document provides a Trophic Index
for Marine Systems (TRIX), below.
Table 3.2 Criteria for evaluating trophic status of marine systems (CCME, 2007)
Trophic Status TN
(mg/m3)
TP
(mg/m3) Chlorophyll a (μg/L) Secchi Depth
(m)
Oligotrophic <260 <10 <1 >6
Mesotrophic ≥260‐350 ≥10‐30 ≥1‐3 3‐≤6
Eutrophic ≥350‐400 ≥30‐40 ≥3‐5 1.5‐≤3
Hypereutrophic >400 >40 >5 <1.5
The background concentrations of TKN and TP were measured as 0.2 mg/L and 0.035 mg/L,
respectively, which corresponds to a eutrophic status based on the phosphorus concentration. The
uppermost limit for this trophic status is a TN concentration of 0.4 mg/L and a TP concentration of
0.04 mg/L.
This document provides another index (NOAA) to determine the degree of eutrophication of the
marine system, below.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 13
Table 3.3 Trophic status classification based on nutrient and chlorophyll (CCME, 2007)
Degree of
Eutrophication
Total Dissolved N
(mg/L)
Total Dissolved P
(mg/L)
Chl a
(μg/L)
Low 0 ‐ ≤0.1 0 ‐ ≤0.01 0 ‐ ≤5
Medium >0.1 ‐ ≤1 >0.01 ‐ ≤0.1 >5 ‐ ≤20
High >1 >0.1 >20 ‐ ≤60
Hypereutrophic ‐ ‐ >60
However, the concentrations in Table 3.3 are based on dissolved nitrogen and phosphorus and the
background concentrations are for TKN and total phosphorus. For nitrogen, with a background
concentration of 0.2 mg/L for TKN, an assumption that the dissolved nitrogen background
concentration is anywhere between 50 and 100% of the TKN background concentration would result
in classification as “medium” based on Table 3.3. For phosphorus, with a background concentration
of 0.035 mg/L, an assumption that the dissolved background concentration is anywhere between 29
and 100% of the total background concentration would result in classification as “medium” based on
Table 3.3.
To maintain the same degree of eutrophication, the total dissolved nitrogen and total dissolved
phosphorus in the receiving water should not exceed the upper limit of the “medium” classification
which is 1 mg/L for Total Dissolved Nitrogen and 0.1 mg/L for Total Dissolved Phosphorus. In order
to determine the upper limit of the “medium” eutrophication range based on total phosphorus and
TN concentrations, an assumption must be made as to the percentage of the TN and phosphorus
that exists in the dissolved phase, both in the receiving water and in the effluent. As a measure of
conservatism, an assumption was made that 100% of the TN and phosphorus exist in a dissolved
phase. This allows for the upper limits of the “medium” classification to be used directly as the EQO
which results in an EQO of 1 mg/L for TN and 0.1 mg/L for total phosphorus.
The Canadian Guidance Framework for the Management of Nutrients in Nearshore Marine Systems
Scientific Supporting Document (CCME, 2007) presents both of the above criteria for assessing
trophic status and does not provide a recommendation for use of one rather than the other.
However, the framework presents a case study to establish nutrient criteria for the Atlantic
Shoreline of Nova Scotia, and the NOAA index is used. Therefore, that index will be used for the
purpose of this study.
pH
The CWQG for the protection for aquatic life for marine waters is 7.0 to 8.7. This pH range will be
applied as the EQO.
Total Residual Chlorine
The WSER requires that TRC concentrations be less than 0.02 mg/L. For the purposes of this study,
the EQO/EDO of 0.02 mg/L for TRC was chosen based on this regulation.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 14
3.3.2 Pathogens
Pathogens are not included in the CCME WQGs for the protection of aquatic life. The Health Canada
Guidelines for Canadian Recreational Water Quality specify a maximum E. coli concentration of
200 E. coli/100 mL for freshwater for primary contact recreation and 1000 E. coli/100 mL for
secondary contact recreation. The Health Canada guideline for Canadian Recreational Water Quality
for primary and secondary contact recreation in marine water is based on enterococci rather than E.
coli. However, historical Nova Scotia Environment has set discharge limits for E. coli rather than
enterococci for marine discharges. The background concentration of E. coli was 69 E. coli/100 mL.
An EQO of 200 E. coli/ 100mL based on the Canadian Recreational Water Quality guideline for
primary contact for freshwater will apply at the edge of the mixing zone.
There is currently a molluscan shellfish closure zone in the immediate vicinity of the outfall (MAR‐
SSN‐2014‐109 on Figure 3.1). However, consideration will have to be given to E. coli concentrations
outside of the closure zone. The CSSP requires that the median of the samples collected in an area
in one survey not exceed 14 E. coli/100 mL, and no more than 10% of the samples can exceed 43 E.
coli/100mL. However, the average measured background concentration for E. coli was 69 E.
coli/100 mL. These background samples were collected from shore and may not be representative
of the actual ambient concentration of E. coli in the area.
3.3.3 Summary
Table 3.4 below gives a summary of the generic and site‐specific EQOs determined for parameters of
concern. The source of the EQO has been included in the table as follows:
WSER – wastewater systems effluent regulations
CWQG Marine – CCME Canadian Water Quality Guidelines for the Protection of Aquatic Life
Marine;
USEPA Saltwater – United States Environmental Protection Agency National Recommended
Water Quality Criteria – Aquatic Life Criteria – Saltwater Criterion Continuous Concentration;
CGF, Marine – Canadian Guidance Framework for the Management of Nutrients in Nearshore
Marine Systems Scientific Supporting Document
CSSP – Canadian Shellfish Sanitation Program
HC Primary Contact – Health Canada Guidelines for Canadian Recreational Water Quality –
Primary Contact Recreation
HC Secondary Contact – Health Canada Guidelines for Canadian Recreational Water Quality –
Primary Contact Recreation
Harbour Engineering Joint Venture Louisbourg WWTP ERA 15
Table 3.4 EQO Summary
Parameter Generic EQO Background Selected EQO Source
CBOD5(1) (mg/L) 25 <5.0 25 WSER
TN (mg/L) 1 0.2 1 CGF, Marine
Nitrogen (Ammonia
Nitrogen) (mg/L)
2.7 <0.05 2.7(2) USEPA Saltwater
Unionized Ammonia (as N
at 15°C)(1) (mg/L)
1.25 <0.0007 1.25 WSER
pH 7.0 – 8.7 7.71 7.0 – 8.7 CWQG Marine
Total Phosphorus (mg/L) 0.1 0.035 0.1 CGF, Marine
TRC(1) (mg/L) 0.02 NM 0.02 WSER
TSS(1) (mg/L) 25 32 25 WSER
E. coli (molluscan
shellfish) (MPN/ 100mL)
14 69 14 CSSP
E. coli (Primary Contact)
(MPN/ 100mL)
200 69 200 HC Primary Contact
E. coli (Secondary Contact)
(MPN/ 100mL)
1000 69 1000 HC Secondary Contact
Notes:
Bold indicates EQO is a WSER requirement.
(1) EQO applies at the end of pipe.
(2) Although the EQO for ammonia has been calculated to be 2.7 mg/L, an EQO of 1 mg/L for total nitrogen would govern.
However, as the EQO for TN is based on eutrophication, EDOs will be developed for all parameters separately.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 16
CHAPTER 4 MIXING ZONE ANALYSIS
4.1 Methodology
4.1.1 Definition of Mixing Zone
A mixing zone is the portion of the receiving water where effluent dilution occurs. In general, the
receiving water as a whole will not be exposed to the immediate effluent concentration at the end‐
of‐pipe but to the effluent mixed and diluted with the receiving water. Effluent does not
instantaneously mix with the receiving water at the point of discharge. Depending on conditions
like ambient currents, wind speeds, tidal stage and wave action, mixing can take place over a large
area – up to the point where there is no measureable difference between the receiving water and
the effluent mixed with receiving water.
The mixing process can be characterized into two distinct phases: near‐field and far‐field. Near‐
field mixing occurs at the outfall and is influenced by the configuration of the outfall (e.g. pipe size,
diffusers, etc.). Far‐field mixing is influenced by receiving water characteristics like turbulence, wave
action, and stratification of the water column.
Within the mixing zone, EQOs may be exceeded but acutely toxic conditions are not permitted
unless it is determined that un‐ionized ammonia is the cause of toxicity. If the un‐ionized ammonia
concentration is the cause of toxicity, there may be an exception (under the WSER) if the
concentration of un‐ionized ammonia is less than or equal to 0.016 mg/L, expressed as N, at any
point that is 100 m from the discharge point. Outside of the mixing zone, EQOs must be achieved.
The effluent is also required to be non‐chronically toxic outside of the mixing zone. The allocation of
a mixing zone varies from one substance to another – degradable substances are allowed to mix in a
portion of the receiving water whereas toxic, persistent, and bio‐accumulative substances (such as
chlorinated dioxins and furans, PCBs, mercury and toxaphene) are not allowed a mixing zone.
A number of general criteria for allocating a mixing zone are recommended in the Strategy, including the
following:
Harbour Engineering Joint Venture Louisbourg WWTP ERA 17
The dimensions of a mixing zone should be restricted to avoid adverse effects on the designated
uses of the receiving water system (i.e., the mixing zone should be as small as possible);
Conditions outside of the mixing zone should be sufficient to support all of the designated uses
of the receiving water system;
A zone of passage for mobile aquatic organisms must be maintained;
Placement of mixing zones must not block migration into tributaries;
Changes to the nutrient status of the water body as a result of an effluent discharge should be
avoided; eutrophication or toxic blooms of algae are unacceptable impacts;
Mixing zones for adjacent wastewater discharges should not overlap; and
Adverse effects on the aesthetic qualities of the receiving water system (e.g. odour, colour,
scum, oil, floating debris) should be avoided (CCME, 1996).
The limits of the mixing zone may be defined for the following three categories of aquatic
environments based on their physical characteristics:
streams and rivers;
lakes, reservoirs and enclosed bays; and
estuarine and marine waters.
Where several limits are in place, the first one to be reached sets the maximum extent of the mixing
zone allowed for the dilution assessment. Nutrients and fecal coliforms are not allocated any
maximum dilution. For fecal coliforms, the location of the water use must be considered and
protected by the limits of the mixing zone.
Based on these general guidelines, mixing zone extents must be defined on a case‐by‐case basis that
account for local conditions. It may also be based on arbitrary mixing zone limits for open water
discharges, e.g. a 100 m (Environment Canada, 2006) or 250 m (NB DOE, 2012) radius from the
outfall and/or a dilution limit. A Draft for Discussion document “Mixing Zone Assessment and
Report Templates” dated July 7, 2016, prepared by a committee of representatives of the
environment departments in Atlantic Canada, provides guidance regarding mixing zones for ERAs in
the Atlantic Provinces. This document recommends that for ocean and estuary receiving waters a
maximum dilution limit of 1:1000 be applied for far‐field mixing.
Finally, the assessment shall be based on ‘critical conditions’. For example, in the case of a river
discharge ‘critical conditions’ can be defined as the seven‐day average low river flow for a given
return period. The Standard Method provides the following guidance on EDO development:
“…reasonable and realistic but yet protective scenarios should be used. The
objective is to simulate the critical conditions of the receiving water, where critical
conditions are where the risk that the effluent will have an effect on the receiving
environment is the highest – it does not mean using the highest effluent flow, the
lowest river flow and the highest background concentration simultaneously.”
Harbour Engineering Joint Venture Louisbourg WWTP ERA 18
As the critical low flow condition is used for the receiving water, the WWTP effluent will be
modelled based on an annual average flow, rather than a maximum daily or hourly flow, as applying
a critical high flow condition for the effluent simultaneously with a critical low flow condition in the
receiving water would result in overly conservative EDOs as this scenario doesn’t provide a
reasonable or realistic representation of actual conditions.
4.1.2 Site Summary
The WWTF is assumed to discharge through an outfall pipe perpendicular to the shoreline in shallow
water, extended to a depth estimated at ‐1.5 m below low tide. The low tide and ‐1.5 m depth
contours were estimated based on navigation charts. The total average effluent discharge is
modeled as a continuous point source of 983 m3/day.
The major coastal hydrodynamic features of the area are as follows:
Along‐shore currents along the open coastline are in phase with the tide, i.e. the current speed
peaks at high and low tide;
At the outfall site, breaking waves and associated longshore currents will contribute to effluent
dispersion during storms. For this assessment, we have assumed calm summer conditions (i.e.
no waves), when effluent dilution would be at a minimum.
4.1.3 Far‐Field Modeling Approach and Inputs
The local mixing zone is limited by the water depth at the outfall of approximately ‐1.5 m Chart
Datum and by the presence of the shoreline. Since the outfall is in very shallow water, the buoyant
plume will always reach the surface upon release from the outfall (Fisher et al., 1979). Far‐field
mixing will then be determined by ambient currents, which is best simulated with a hydrodynamic
and effluent dispersion model.
We implemented a full hydrodynamic model of the receiving coastal waters using the Danish
Hydraulic Institute’s MIKE21 model. MIKE21 is ideally suited to the study of outfall discharges in
shallow coastal areas where complex tidal and wind‐driven currents drive the dispersion process.
The model was developed using navigation charts, tidal elevations and wind observations for the
area. A similar model had been used by CBCL for CBRM in the past:
In 2005 for the assessment of the past wastewater contamination problem at Dominion
Beach, which led to the design of the WWTP at Dominion (CBCL, 2005).
In 2014 for ERAs at the Dominion and Battery Point WWTPs.
The hydrodynamic model was calibrated to the following bottom current meter data:
1992 current meters (4 locations) located in 10 m‐depth for the study by ASA (ASA, 1994) on
local oceanography and effluent dispersion;
2006 current meters (2 locations) off the Donkin peninsula for the CBCL study of mine
effluent dispersion.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 19
Calibration consisted of adjusting the following parameters:
Bottom friction; and
Model spatial resolution in the area of the current meters.
Numerical Model Domain with Locations of Current Meter Observations and Modeled Outfall
Location are shown in Figure 4.1. Inputs and calibrated outputs are shown in Figure 4.2. The
modelled current magnitudes at New Waterford, Glace Bay and Donkin are in relatively good
agreement with observations, which is satisfactory to assess the overall dilution patterns of effluent
from the outfall. The effect of waves was not included in the model, and therefore the modeled
effluent concentration near the outfall is expected to be conservatively high.
Figure 4.1 Numerical Model Domain with Locations of Current Meter Observations and
Modeled Outfall Location
Harbour Engineering Joint Venture Louisbourg WWTP ERA 20
Figure 4.2 Time‐series of Hydrodynamic Model Inputs and Calibration Outputs
Harbour Engineering Joint Venture Louisbourg WWTP ERA 21
4.2 Modeled Effluent Dilution
Snapshots of typical modeled effluent dispersion patterns are shown on Figure 4.3. Statistics on
effluent concentrations were performed over the 1‐month model run, and over a running 7‐day and
1‐day averaging period. Composite images of maximum and average effluent concentrations are
shown on Figure 4.4.
Effluent concentration peaks at any given location are short‐lived because the plume is changing
direction every few hours depending on tides and winds. Therefore, a representative dilution
criteria at the mixing zone limit is best calculated using an average value. We propose to use the
one‐day average effluent concentration criteria over the one‐month modeling simulation that
includes a representative combination of site‐specific tides and winds.
The diluted effluent plume reaches the shoreline directly north of the outfall and tends to remain
concentrated within the two piers surrounding it. Lower concentrations of effluent were observed
to reach the shoreline on the east and north ends of the basin. Maximum concentrations 100m
away from the outfall are observed both North‐West and South‐East of the outfall. The 100 m
distance from the outfall to the shoreline is within the brackets of mixing zone radiuses defined by
various guidelines. We propose that this distance be used as mixing zone limit.
The maximum 1‐day average effluent concentration 100 m away from the outfall over the
simulation period is 0.38%. Therefore we propose that a dilution factor of 263:1 be used for
calculating EDOs.
Table 4.1 Modelled Dilution Values 100 and 200 m away from the Outfall
Distance
away from
the outfall
Hourly maximum
effluent
concentration
Maximum 1‐day
average effluent
concentration
Maximum 7‐day
average effluent
concentration
1‐Month average
effluent
concentration
100 m 1.68 % (59.52:1
Dilution)
0.38 % (263.16:1
Dilution)
0.29 % (344.83:1
Dilution)
0.23 % (434.78:1
Dilution)
200 m 1.11 % (90.09:1
Dilution)
0.3 % (333.33:1
Dilution)
0.26 % (384.62:1
Dilution)
0.22 % (454.55:1
Dilution)
Harbour Engineering Joint Venture Louisbourg WWTP ERA 22
Figure 4.3 Snapshots of Typical Modeled Effluent Dispersion Patterns
Harbour Engineering Joint Venture Louisbourg WWTP ERA 23
Figure 4.4 Composite Images of Modeled Hourly Maximum (top) and Maximum 7‐Day
Average Effluent Concentrations (middle) with Concentration Time‐Series
(bottom)
Note: 100‐m radius (black) and 200‐m radius (grey) circle shown around outfall.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 24
CHAPTER 5 EFFLUENT DISCHARGE OBJECTIVES
5.1 The Need for EDOs
Effluent Discharge Objectives (EDOs) represent the effluent substance concentrations that will protect
the receiving environment and its designated water uses. They describe the effluent quality necessary
to allow the EQOs to be met at the edge of the mixing zone. The EQOs are established in Chapter 3; see
Table 3.4 for summary of results.
EDOs should be calculated where reasonable potential of exceeding the EQOs at the edge of the mixing
zone has been determined. Typically, substances with reasonable potential of exceeding the EQOs have
been selected according to the simplified approach: If a sample result measured in the effluent exceeds
the EQO, an EDO is determined. As there are a limited number of parameters considered as substances
of potential concern for very small and small facilities, EDOs will be developed for all substances of
potential concern.
5.2 Physical/ Chemical/ Pathogenic EDOs
For this assessment, EDOs were calculated using the dilution values obtained at the average
expected design flow of 983 m3/day. This resulted in a dilution of 263:1 at the edge of a 100 m
mixing zone.
Parameters for which there is a WSER criteria were not allowed any dilution and therefore the EDO
equals the WSER Criteria. The Standard Method does not allocate any maximum dilution for
nutrients and fecal coliforms. For nutrients, it recommends a case‐by‐case analysis. For fecal
coliforms, the location of the water use must be protected by the limits of the mixing zone.
The dilution values were used to obtain an EDO by back‐calculating from the EQOs. When the
background concentration of a substance was less than the detection limit, the background
concentration was not included in the calculation of the EDO.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 25
5.3 Effluent Discharge Objectives
Substances of concern for which an EDO was developed are listed in Table 5.1 below with the
associated EQO, maximum measured wastewater concentration, and the associated EDO. The
effluent must also be non‐acutely toxic at the end of pipe, and non‐chronically toxic at the edge of
the mixing zone.
Table 5.1 Effluent Discharge Objectives at Average Annual Flow
Parameter
Maximum
Wastewater
Concentration
Background Selected
EQO Source Dilution
Factor EDO
CBOD(1) (mg/L) 110 <5.0 25 WSER ‐ 25
TN (mg/L) 6.3 0.2 1 CGF,
Marine 263 212
Nitrogen
(Ammonia
Nitrogen) (mg/L)
6.1 <0.05 2.7 USEPA
Saltwater 263 710
Unionized
Ammonia(1) (mg/L) 0.019 <0.0007 1.25 WSER ‐ 1.25
Total Phosphorus
(mg/L) 1.1 0.035 0.1 CGF,
Marine 263 17
Total Residual
Chlorine(1) (mg/L) NM NM 0.02 WSER ‐ 0.02
Total Suspended
Solids(1) (mg/L) 290 32 25 WSER ‐ 25
E. coli (shellfish)(2)
(MPN/ 100mL) 820,000 69 14 CSSP 3333 See
Discussion
E. coli (Primary
Contact) (MPN/
100mL)
820,000 69 200
HC
Primary
Contact
263 34,522
E. coli (Secondary
Contact) (MPN/
100mL)
820,000 69 1000
HC
Secondary
Contact
263 244,922
Notes: (1) For parameters for which the EQO is based on the WSER, no dilution has been permitted.
(2) Dilution at closure zone boundary of 3333:1.
Based on the EDOs calculated above, sample results for the following parameters exceeded the EDO
in at least one wastewater sample:
CBOD5;
TSS; and
E. coli.
CBOD and TSS will meet the EDOs at the discharge of the new WWTP through treatment. E. Coli will
meet the EDO for primary and secondary contact recreation through treatment.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 26
In terms of an EDO for E. coli for the protection of molluscan shellfish, an EDO could not be
calculated because the measured background concentration was greater than the EQO. The
average measured background concentration for E. coli was 69 E. coli/100mL compared to an EQO
of 14 E. coli/100mL. These background samples were collected from shore and may not be
representative of the actual ambient concentration of E. coli in the area. Therefore, rather than
calculating an EDO using the EQO and background concentration, the concentration in the discharge
will be assumed to be equal to 200 E. coli/100 mL which is the typical design value for UV systems,
and the maximum background concentration that would result in a limit of 14 E. coli/100 mL at the
edge of the closure zone will be calculated. With a dilution of 3333:1, a concentration of 200 E.
coli/100 mL in the discharge, and an EQO of 14 E. coli/100 mL, the ambient background
concentration would have to be less than or equal to 13.9 E. coli/ 100mL.
It is possible that the existing shellfish closure zone boundaries may change after the proposed
WWTPs are constructed in CBRM. However, there will always be a closure zone surrounding each
outfall. The Canadian Shellfish Sanitation Program (CSSP) manual of operations indicates that
shellfish harvesting is prohibited in an area within a minimum 300m radius of the discharge from a
sanitary sewage system, and within the area around a sanitary discharge which does not achieve
adequate viral reduction through a combination of wastewater treatment and dilution in the
shellfish growing area.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 27
CHAPTER 6 COMPLIANCE MONITORING
The Standard Method utilizes the results of the ERA to recommend parameters for compliance
monitoring according to the following protocol:
The WSER requirements for TSS, CBOD and unionized ammonia must be monitored to
ensure they are continuously being achieved. Minimum monitoring frequencies are
specified in the guidelines based on the size of the facility. Monitoring of these
substances cannot be reduced or eliminated;
Nutrients, such as phosphorus and ammonia, and pathogens for which an EDO was
developed should be included in the monitoring program with the same sampling
frequency as TSS and CBOD5;
For additional substances, the guidelines require that all substances with average effluent
values over 80% of the EDO be monitored;
If monitoring results for the additional substances are consistently below 80% of the EDO,
the monitoring frequency can be reduced;
If average monitoring results subsequently exceed 80% of the EDO, monitoring frequency
must return to the initial monitoring frequency; and
If monitoring results are below 80% of the EDO for at least 20 consecutive samples spread
over a period of at least one‐year, monitoring for that substance can be eliminated.
Although the Standard Method results in recommending parameters for compliance monitoring, the
provincial regulator ultimately stipulates the compliance monitoring requirements as part of the
Approvals to Operate. In New Brunswick, the New Brunswick Department of Environment and Local
Government has been using the results of the ERA to update the compliance monitoring program
listed in the Approval to operate when the existing Approvals expire. At this time, it is premature to
use the results of this ERA to provide recommendations on parameters to monitor for compliance,
as the purpose of this ERA was to provide design criteria for design of a new WWTP.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 28
CHAPTER 7 REFERENCES
ASA Consulting Limited (1994). “Industrial Cape Breton Receiving Water Study, Phase II”. Prepared
for The Town of Glace Bay.
CBCL Limited (2005). Dominion Beach Sewer Study. Prepared for CBRM.
CCME (2008). Technical Supplement 3. Canada‐wide Strategy for the Management of Municipal
Wastewater Effluent. Standard Method and Contracting Provisions for the Environmental Risk
Assessment.
CCME (2007). Canadian Guidance Framework for the Management of Nutrients in Nearshore
Marine Systems Scientific Supporting Document.
CCME Canadian Environmental Quality Guidelines Summary Table. Water Quality Guidelines for the
Protection of Aquatic Life.
Environment Canada (2006). Atlantic Canada Wastewater Guidelines Manual for Collection,
Treatment, and Disposal
Environment Canada (Environment Canada). 1999. Canadian Environmental Protection Act Priority
Substances List II – Supporting document for Ammonia in the Aquatic Environment. DRAFT –August
31, 1999.
Fisheries Act. Wastewater Systems Effluent Regulations. SOR/2012‐139.
Fisher et al. (1979). Mixing in Inland and Coastal Waters. Academic Press, London.
Health Canada (2012). Guidelines for Canadian Recreational Water Quality. Retrieved from:
http://www.hc‐sc.gc.ca/ewh‐semt/pubs/water‐eau/guide_water‐2012‐guide_eau/index‐eng.php
NB Department of Environment & Local Government, (2012). Memo
Thomann, Robert V. and Mueller, John A. 1987. Principles of Surface Water Quality Modeling and
Control.
Harbour Engineering Joint Venture Louisbourg WWTP ERA 29
USEPA. National Recommended Water Quality Criteria for Saltwater. Retrieved from:
http://water.epa.gov/scitech/swguidance/standards/criteria/current/index.cfm
Prepared by: Reviewed by:
Holly Sampson, M.A.Sc., P.Eng. Karen March, M.Sc.
Intermediate Chemical Engineer Environmental Scientist
Harbour Engineering Joint Venture Appendices
APPENDIX A
Laboratory Certificates
HEJV Louisbourg Wastewater System Summary Report Appendices
APPENDIX D
Louisbourg Wastewater Treatment Facility
Site Desktop Geotechnical Review
301 Alexandra Street, Sydney, NS B1S 2E8
t: 902.562.2394 f: 902.564.5660 www.exp.com
October 29, 2018 SYD-00245234-A0/60.2
Mr. Terry Boutilier
Dillon Consulting Limited
275 Charlotte Street
Sydney, NS B1P 1C6
Re: Wastewater Treatment Plant Geotechnical Desktop Study
Louisbourg Site
Dear Mr. Boutilier:
It is the pleasure of EXP Services Inc. (EXP) to provide Dillon Consulting Limited (Dillon) with this letter
report summarizing the preliminary review completed by EXP on the potential site for the
construction of a wastewater treatment facility in Louisbourg, Nova Scotia.
Background
A geotechnical desktop study is an essential tool used by engineers to identify and gather as much
information as possible pertaining to the probable ground conditions at a proposed construction site
without commissioning an intrusive ground investigation. The information obtained from the desktop
study will identify potential problems, hazards and/or constraints associated with the probable ground
conditions in the proposed area of construction, as well as provide geotechnical recommendations for
new construction activities. When a walkover survey is completed in conjunction with the desktop
study it will allow engineers to refine and enhance their understanding of each of the sites in relation
to the topography, earth exposures, drainage conditions, etc. When completed together (the desktop
study and the walkover survey), the findings will provide invaluable information in the early stages of
the design at a negligible cost. It is the intent of the desktop study and walkover survey not only to look
at the site, but also at its surroundings. Noted below are the key findings to be reported in any desktop
study and walkover assessment:
• site topography;
• geology (surficial ground cover, probable overburden soil and bedrock type);
• geotechnical problems and parameters;
• previous land use (aerial photographs);
Dillon Consulting Limited
Wastewater Treatment Plant Geotechnical Desktop Study - Louisbourg Site
SYD-00245234-A0
October 29, 2018
2
\\trow.com\PROJECTS\SYD\SYD-00245234-A0\60 Project Execution\60.2 Reports\Louisbourg\Louisbourg_Site.docx
• underground/surface mining activities; and
• proposed supplemental ground investigation methods (test pits and/or boreholes).
Subject Site Description and Topography
The proposed site for the new wastewater treatment plant (WWTP) is located on a parcel of land
between the former fish processing plant and the Lobster Kettle Restaurant, off of Commercial Street
in Louisbourg, Nova Scotia, and is identified by Property Identification Number (PID) 15458243. The
subject property is relatively level, but slopes slightly and gently from the north toward the southeast.
The property then drops off rapidly along the Atlantic coastline. The property is bound by residential
dwellings to the north, the Atlantic coastline and Commercial Street to the south, Strathcona Street
and the Lobster Kettle Restaurant to the east and the former commercial fish processing plant to the
west.
Published Geological Mapping (Surficial and Bedrock)
Review of the surficial geological mapping of the study area indicated that the subsurface geology
consists of a Stony Till Plain. This type of till is generally comprised of a stony, sandy matrix material
with varying amounts of cobbles and boulders and can vary in thickness from 2 to 20 metres thick.
Typically, these materials were released from the base of ice sheets during the melting process of the
ice sheet.
A review of the existing bedrock mapping for the area indicates that the site is underlain by materials
from the neopoterozoic period, which are further identified from the Fourchu Group. These formations
are comprised of felsic, intermediate and mafic tuff, tholeiitic volcanic arc basalt, rhyolite, sandstone,
siltstone and chert.
A review of historical mapping and online reference documents indicated that no mining activities have
been carried out under the site.
Existing Ground Conditions
At the time of the investigation, the proposed site was primarily covered in low lying vegetation,
interspersed with several old concrete foundations and fish processing equipment. The eastern limit of
the property is enclosed by a chain link fence, complete with overhanging barb wire. A significant
portion of the site appears to have been levelled by fill placement. Infilling along the shore line with
armor stone was observed during the site visit.
The native overburden soil (glacial till) consists of coarse sand and gravel with a high fines content of
silt and sand with varying amounts of cobbles and boulders. The thickness of the native glacial till
material is anticipated to be relatively thin and is anticipated to be between 1 and 5 metres thick. The
native till material should provide satisfactory bearing stratum for the support of shallow foundations
with bearing capacities between 150 and 200 kPa. The underlying bedrock would provide a higher
Dillon Consulting Limited
Wastewater Treatment Plant Geotechnical Desktop Study - Louisbourg Site
SYD-00245234-A0
October 29, 2018
3
\\trow.com\PROJECTS\SYD\SYD-00245234-A0\60 Project Execution\60.2 Reports\Louisbourg\Louisbourg_Site.docx
capacity for allowable bearing. Should extraction in the bedrock be required on the site, it will require
drill and blast techniques.
An above ground fuel storage tank was observed during the site visit; however, no evidence of
petroleum hydrocarbon contamination in the soils was observed. A subsurface investigation would be
required to confirm no contamination exists at the locations investigated.
Geotechnical Problems and Parameters
Summarized below are the key geotechnical problems of the site.
• The presence of old concrete foundation and uncontrolled and/or loose fills are suspected on
the site due to historical activities.
• There is a potential that a substantial volume of bedrock excavation may be required on the
site. Extraction and bedrock excavation will require drill and blast techniques to facilitate
removal of the bedrock.
• There is a potential to find impacted soils (historical photographs depict above ground fuel
tanks, coal and fuel storage tanks) on the site. Soil samples should be analyzed to confirm the
presence or absence of contamination.
Previous Land Use
Aerial photographs from 1931 to 2009 have been reviewed and are summarized below.
• An aerial photograph taken in 1931 depicts the site void of any structures. A roadway from
Strathcona Street connects to Gerrards Head across the Barrachois. Residential and commercial
building are found to the north, east and west of the site. The site appears to be covered with
low lying vegetation.
• An aerial photograph taken in 1947 depicts the construction of a new wharf southwest of the
site.
• An aerial photograph taken in 1953 depicts the construction of several buildings (new fish
processing plant) and roadways across the site. The wharf has been expanded and the roadway
connecting Strathcona Street to Gerrards Head has been rerouted.
• An aerial photograph taken in 1961 depicts little to no discernable change to the site since the
1953 photograph was taken.
• An aerial photograph taken in 1970 depicts little to no change to the site since the 1961
photograph.
• An aerial photograph taken in 1985 depicts little to no change to the site since the 1970
photograph.
• An aerial photograph taken in 1987 depicts the parking lot expansion on the northern side of
the fish processing plant.
• An aerial photograph taken in 2009 depicts the construction of the Lobster Kettle Restaurant
to the east. The roadway and parking lots on the site are paved in asphalt.
Dillon Consulting Limited
Wastewater Treatment Plant Geotechnical Desktop Study - Louisbourg Site
SYD-00245234-A0
October 29, 2018
4
\\trow.com\PROJECTS\SYD\SYD-00245234-A0\60 Project Execution\60.2 Reports\Louisbourg\Louisbourg_Site.docx
Proposed Supplemental Ground Investigation Methods
It is also recommended that a preliminary geotechnical investigation (land based drilling) be completed
at the site to collect pertinent information pertaining to the subsurface conditions within the footprint
of the proposed new facility. This information will then be used to develop geotechnical
recommendations for use in the design and construction of the new facility.
Borehole locations should be selected based upon the location of buried infrastructure (sewer, water,
electrical and fiber optic lines) and to provide adequate coverage of the site. It is proposed that
representative soil samples be collected continually throughout the overburden material of each of the
five boreholes advanced at the site. Additionally, it is recommended that during the investigation
samples of the bedrock should be collected continuously to a depth of at least 15 metres, in two of the
five boreholes. The intent of the bedrock coring is to accurately characterize the bedrock for design.
It is recommended that the remaining three boreholes be terminated either at 12 metres depth below
ground surface or once refusal on assumed bedrock is encountered (whichever comes first).
A Geotechnical Engineer should oversee the advancement of each of the boreholes. A CME 55 track
mounted geotechnical drill rig (or equivalent), equipped with bedrock coring equipment and a two-
man crew (driller and helper), should be used to advance each of the boreholes. Representative soil
samples should be attained from a 50 mm diameter standard split spoon sampler during Standard
Penetrating Tests (SPT) conducted ahead of the casing and/or auger equipment. A preliminary
assessment of each recovered sample should be completed for particle size, density, moisture content
and color. The SPT should continue until refusal or contact with assumed bedrock. Bedrock should be
confirmed through coring of the material using coring equipment and drill casing. Each core sample
should be removed from the core barrel and placed into core boxes for identification.
Upon completion of the intrusive portion of the program, all boreholes are to be plugged (at various
depths within the borehole) using a bentonite plug and backfilled to grade using silica sand. Following
the installation and backfilling activities, the location and elevations are to be determined using Real
Time Kinematic (RTK) survey equipment in the AST 77 coordinate system.
This letter report is prepared for the Louisbourg site. Should you have any questions or concerns,
please contact John Buffett or Gary Landry at 902.562.2394.
Sincerely, Sincerely,
John Buffett, P.Eng., B.Sc., RSO Gary Landry, P.Eng., B.Sc.
Project Engineer Project Manager
EXP Services Inc.
HEJV Louisbourg Wastewater System Summary Report Appendices
APPENDIX E
Louisbourg Wastewater System
Archaeological Resources Impact
Assessment