Musquodoboit Harbour Follow Up Study Report Final Report
061034.01 Final Report May 2010
ISO 9001 Registered Company Prepared for: Prepared by:
23 May 2013
Marcus Garnet Senior Planner Regional and Community Planning Halifax Regional Municipality P.O. Box 1749 Halifax, NS B3J 3A5
Dear Mr. Garnet:
RE: FinalReportforHRMRFPNumber09 048 Musquodoboit Harbour Watershed / Servicing Study Follow up Analysis
Please find enclosed one (1) bound copy and one (1) copy on CD of our Final Report for this 1489 Hollis Street study. As agreed we have: PO Box 606 Made editorial changes to the Draft Report; and Halifax, Nova Scotia We have not updated the costs to 2013 dollars in this Final Report, they are still in 2009 Canada B3J 2R7 dollars.
We have also included a separate copy of Table 5.5.1 from the report. Costs in this version Telephone: 902 421 7241 were prorated from May 2009 to 2013 using the multipliers provided by Halifax Water in Fax: 902 423 3938 2011 when they evaluated the Water Only option (between the Medium and Low Growth
E-mail: [email protected] Scenarios) that was developed on your recommendation. www.cbcl.ca If you have any questions or comments, feel free to contact us.
Yours very truly,
CBCL Limited
ISO 9001 Mike DeLay, P.Eng. Registered Company Senior Water Resources Engineer Direct: (902) 492 6754 E Mail: [email protected]
Project No. 061034.01
061034 01-LE002 FINAL REPORT.DOC/VB ED: 5/23/2013 1:32:00 PM/PD: 5/23/2013 1:47:00 PM Contents
CHAPTER 1 Introduction...... 1 1.1 Background ...... 1 1.2 2007 Watershed Study ...... 1 1.3 Community Visioning...... 2 1.4 Study Scope and Objectives...... 2 1.5 Report Layout ...... 3 CHAPTER 2 Existing Conditions...... 4 2.1 Existing Population ...... 4 2.2 Existing Development Patterns...... 4 2.3 Wastewater Treatment ...... 4 2.3.1 Wastewater Treatment Facilities...... 4 2.3.2 Onsite Wastewater Treatment ...... 7 2.4 Stormwater ...... 8 2.5 Water Supply ...... 8 2.6 Receiving Water Quality ...... 8 CHAPTER 3 Growth in the Community...... 11 3.1 Design Population and Number of Services ...... 11 3.2 Density of Population ...... 11 3.3 Preferred Development Areas...... 13 CHAPTER 4 Constraints on Central Services ...... 14 4.1 Receiving Water Quality ...... 14 4.1.1 Potential Sources of Pollutants...... 14 4.1.2 Potential Reductions of Pollutants ...... 16 4.2 Source Water Supplies...... 17 4.2.1 River Aquifer Water Availability...... 17 4.2.2 River Aquifer Water Quality ...... 19 4.2.3 Potential Sources of Pollutants...... 21 CHAPTER 5 Central services ...... 25 5.1 Central Wastewater Collection and Treatment...... 25 5.1.1 Wastewater Collection ...... 25 5.1.2 Wastewater Treatment ...... 26 5.2 Stormwater Collection...... 29
CBCL Limited Contents i 5.3 Water Supply, Treatment and Distribution ...... 29 5.3.1 Water Demands...... 29 5.3.2 Well Field Development ...... 32 5.3.3 Water Quality Comparison and Treatment Objectives ...... 33 5.3.4 Water Treatment Plant Process Assessment...... 36 5.3.5 Water Distribution ...... 37 5.3.6 Central Water without other Services ...... 37 5.4 Phased Implementation...... 38 5.5 Estimated Costs of Servicing...... 39 5.5.1 Estimates of Probable Capital Costs ...... 39 5.5.2 Operating and Maintenance Costs ...... 39 5.5.3 Life Cycle Costing Analysis ...... 40 5.6 Sources of Funding...... 40 CHAPTER 6 Summary of Assessments...... 42 6.1 TOR Issues...... 42 6.2 Proposed Water and Wastewater Systems...... 44
List of Tables* Table 2.3.1.1: Twin Oaks Wastewater Treatment Facility Effluent Sampling Results Table2.6: HRM Summer 2009Sampling Results at PetpeswickInlet Beach Table 3.2: Areas Required for Development Based on Population Estimates Table 3.3: Musquodoboit Harbour Development Scenarios Table 4.2.1(a): Estimated River Flow Regime for the Musquodoboit and Little Rivers Table 4.2.1(b): Comparison of Water Demand to Potential River Water Supply Table5.1: DesignofCentralServicing Table 5.1.2: Wastewater Treatment Plant Design Flows Table 5.1.3(a): Average Daily Flow Expected with Existing Population and Under Three Growth Scenarios Table 5.3.1(b): Maximum Daily Flow Expected with Existing Population and Under Three Growth Scenarios Table 5.3.2: Production Wells Required to Satisfy Expected Water Demands Table 5.3.3: Comparison of Groundwater and Surface Water Quality Table 5.5.1: Capital Costs of Central Servicing Table 5.5.2: Operating and Maintenance Costs Table5.6: LifeCycle Costs for Various Funding Alternatives
CBCL Limited Contents ii List of Figures* Figure1.2: StudyArea Figure 2.3.1(a): Birches, Twin Oaks, Eastern Shore District High School Wastewater Treatment System Site Plan and General Arrangement Figure 2.3.1(b): Eastern Shore District Community Centre Wastewater Treatment System Site Plan Figure 2.4: Local Drainage and Receiving Water Sampling Locations Figure 3.2(a): Density Fact Sheet Suburban Development Figure 3.2(b): Density Fact Sheet Small Town, Neighborhood with Main Street Commercial Figure 3.2(c): Density Fact Sheet Traditional Urban Development Figure 3.2(d): Density Fact Sheet Urban Development Figure 3.2(e): Density Fact Sheet Urban Village Figure3.3: AreasforNewDevelopmentinCore Areas Figure 4.1: Hydrodynamic Model Domain of Petpeswick Inlet Figure 4.1.1: Modelled Contamination from Bacterial Loadings at the Head of Petpeswick Inlet Figure 5.1(a): Plan of Central Wastewater Collection, Secondary STP and Outfall Figure 5.1(b): Plan of Central Wastewater Collection, Tertiary STP and Outfall Figure 5.2: Planof Central Stormwater Collection Systems Figure 5.3: Plan of Central Water Supply, Treatment, Transmission and Distribution System Figure 5.3.1: Maximum Day Flow as a Function of the percentage of the Water Demand Represented by Resident Users
*Note: Table and Figures are numbered after the report section where they are first referenced.
Appendices
A WaterQualitySampleAnalysisData
CBCL Limited Contents iii CHAPTER 1 INTRODUCTION
1.1 Background In 2006 HRM completed a Regional Municipal Planning Strategy to ensure that development within the municipality proceeds in an effective and efficient manner. As part of the Regional Municipal Planning Strategy (MPS), watershed studies form the basis of community planning strategies and are required before any other secondary planning processes are advanced.
In 2006, CBCL Limited was commissioned to complete the first of these studies, in the Musquodoboit Harbour Watershed. Musquodoboit Harbour was identified as a Rural Commuter Centre in the MPS with an ultimate population in the order of 7050 people.
1.2 2007 Watershed Study The study assessed existing development and its impacts on the environment as well as investigated the potential for additional development. It looked at opportunities for additional development and constraints to potential development in the community.
Existing development is typically serviced by wells for water supply and on site wastewater treatment and dispersal systems. Development serviced by similar systems was investigated as well as various forms of central systems, including cluster systems. The study also identified where the community centre could be developed, with much denser development than is currently experienced as well as the incremental costs to provide central services to service HRMs objective population for the community. Constraints to development at population densities greater than can be achieved using onsite services were identified and included: Supply of water for a central system; and Impacts of wastewater treatment plant effluent and stormwater on receiving water quality, which is currently unsuitable for some desired uses.
Strategies were outlined to manage these constraints and allow the development to occur if desired: Supply of water for a central system could be provided by withdrawing water from wells located near the Musquodoboit River. Test wells would need to be constructed and tests completed to confirm the number and location required to supply 5050 additional people in the community; and
CBCL Limited Introduction 1 Impacts of wastewater treatment plant effluent and stormwater on receiving waters could be minimized by producing wastewater treatment plant effluent of high quality as well as including stormwater Best Management Practices (BMPs) to minimize increases in runoff peak flows and degradation of runoff quality.
Figure 5.1 from the 2007 study report is reproduced as Figure 1.2. It identifies the areas that should be considered for the centre of the community, where central services are considered suitable. Also identified in the report were the probable costs of: Central services; Services for cluster development; and Onsite services for individual properties.
Assessments of central services included costs to construct for each street in the community: Conventional wastewater collection and treatment systems; Small diameter gravity and pressure septic tank effluent collection systems; Central water supply, treatment and distributions systems; and Swales for surface runoff collection and attenuation of peak flows, constructed wetlands for stormwater treatment and small diameter storm sewers for collection of foundation drainage.
Because the existing community is serviced with onsite systems that require large lots, the existing community of approximately 2000 people is spread over a significant area. The costs to service all of the existing streets with central services and allow future development to occur as infilling were unfeasible and unappealing to HRM and existing property owners.
1.3 Community Visioning Following the study, HRM and the community embarked on a visioning program, to identify their image of how the community would eventually develop. However, the visioning process did not provide direction for the physical development of the community. There remained a need for a public workshop where the consultant would work with the community to get a sense of acceptable density. The community visioning process did lead to a number of specific issues, opportunities and concerns that HRM, Halifax Water and the community wished to address before proceeding. This study provided the means to assess each issue and evaluate opportunities for addressing them.
Terms of Reference for the study were received from HRM in late April, 2009. They outlined a number of specific tasks to be completed as part of the overall evaluation. The following sections outline the planning and engineering studies and analysis that were completed to address each issue.
1.4 Study Scope and Objectives The study area is shown on Figure 1.2. The existing community centre and surrounding areas with potential to be included in the community was provided in Figure 5.1 (a) of the 2007 Watershed Study.
CBCL Limited Introduction 2
In the study area the following assessments were completed as described in the TOR: 1. Determine the assimilative capacity that could be made available by reducing inputs from known or suspected defective or malfunctioning wastewater collection and treatment systems. 2. Define an optimum configuration for a small scale wastewater management system. 3. Determine the feasibility and cost of providing central water supply without other services. 4. Confirm the suitability of the Musquodoboit River and Little River as potential supplies of raw water for a central water system. 5. Determine the impacts of possible contaminant sources on water taken from potential wells adjacent the Musquodoboit River. 6. Estimate future achievable population growth, density and distribution over a 5 to 10 year horizon in the community with on site services, central water only or central water and wastewater services, accounting for projected commercial development. 7. Analyse existing water quality data for the Little River and assess potential sources.
The objective of the additional analysis is to optimize the general concepts and costs presented in the 2007 watershed study and select appropriate servicing schemes to allow development to proceed as the community envisions it. This project is not to provide a pre design; a concept is required that will feed into the Municipal Planning Strategy review.
1.5 Report Layout This report will address these issues and integrate the findings into a comprehensive plan for the long term development of the community. Development of servicing plans for the community is outlined in subsequent sections of this report as follows: Chapter 2 Existing Conditions is an assessment of existing development and servicing in the community; Chapter 3 Growth in the Community. Three growth scenarios were developed and presented in this chapter; Chapter 4 Constraints on Central Services describes the constraints development; Chapter 5 Central Services describes the development of central wastewater, stormwater and water systems to service a Core Area for future development; and Chapter 6 Summary of Assessments completed to address the specific issues in the terms of reference for this study are presented in this chapter.
CBCL Limited Introduction 3 CHAPTER 2 EXISTING CONDITIONS
2.1 Existing Population The existing population of Musquodoboit Harbour is estimated to be in the order of 2000 people.
2.2 Existing Development Patterns The minimum lot size to accommodate onsite wastewater systems has generally determined property sizes as the community has developed. Although many properties do not meet current minimum property size requirements, the lots are considered large. Most of the existing development is spread out in ribbon fashion along: Highway 7; Highway 357; The East Petpeswick Road; Clamshell Road; The West Petpeswick Road; and Several small side roads.
2.3 Wastewater Treatment Malfunctioning wastewater treatment plants were identified as potential sources of pollutants in the two main receiving waters in the community, Musquodoboit River Musquodoboit Harbour and Little River Petpeswick Inlet. There are two larger wastewater treatment systems in the community, one services the high school, the hospital and a seniors complex, and the second serves the community centre. Onsite wastewater treatment systems for individual properties service the remainder of the community.
2.3.1 Wastewater Treatment Facilities The two larger wastewater treatment systems in the community are the Twin Oaks Treatment Facility and the Community Center Treatment Facility. These are described as follows.
2.3.1.1 TWIN OAKS TREATMENT FACILITY This Rotating Biological Contactor (RBC) based treatment plant services the Twin Oaks Hospital; The Birches seniors complex and the Eastern Shore Regional High School. Figure 2.3.1(a) shows the
CBCL Limited Existing Conditions 4 collection system from each of the tributary systems, the location of the treatment plant, the treatment processes and the alignment of the outfall to the Little River just upstream of Petpeswick Inlet. It was suggested that this plant may be hydraulically overloaded and as a result not functioning properly, resulting in the discharge of excessive amounts of pollutants to Petpeswick inlet. These suggestions were investigated by completing the following reviews of: The treatment process with the operators. This review identified a problem with the siphon system that discharges to the outfall. This problem resulted in a continuous discharge of effluent to the receiving waters rather than less frequent discharges at higher flow rates to produce cleansing velocities in the outfall; Effluent water quality records for 2008.The operator of the Twin Oaks Wastewater Treatment Facility provided effluent sampling data for the year 2008, summarized in Table 2.3.1.1. The maximum Fecal coliform count observed was over 8,000 FC/100ml on one occasion. All other results were less than 500 FC/100ml, 75% being less than 10 FC/100ml.
Table 2.3.1.1: Twin Oaks Wastewater Treatment Facility Effluent Sampling Results Year 2008 FC/100ml Number of Samples 0 10 45 10 100 6 100 200 4 200 500 4 >500 1(at8,640/100ml) Total 60(5samples/month)
This information indicates that for most of the samples (91.7%), the treatment plant effluent meets the Fecal coliform objective of less than 200 counts per 100 mL for swimming and for 75% of the samples, the treatment plant effluent meets the Fecal coliform objective of less than 14 counts per 100 mL for consuming shellfish as set by the Fournier Task Force for Halifax Harbour 1990(1); Water use records for all contributing systems (Twin Oaks Hospital, the Eastern Shore District High School, The Birches seniors complex) for 2008. Daily water use data is currently being collected from these users and the most recent records were requested for review; The assessment of 2008 records indicates that water use totals approximately 25 cubic metres per day, 33% of the stated STP capacity of 77 cubic metres per day. Available capacity based on the water use records could potentially service approximately 60 additional people; Flow monitoring is not normally carried out at the sewage treatment plant (STP). A flow monitoring program at the STP was started to quantify actual wastewater flows through the treatment plant and define the level of extraneous flow in the existing systems. The initial location of the flow meter at the inlet to the plant proved ineffective. Flows were so low that the measuring device would not work properly. Plant operators indicate that the flows to the plant are typically low. A new location at the clarifier weir was selected and the meter was installed on Friday November 28th2009; and Daily flows from the wastewater treatment plant are compared to the daily water use records in the following figure. On both Thursdays during the flow monitoring period the flows were higher at the treatment plant. The operator was contacted and it was determined that there are operational procedures completed each Thursday that alter the flows.
CBCL Limited Existing Conditions 5 The average flows recorded during the gauging period were: Water used: 25 m3/day (5741 igd); and Wastewater generated: 18.4 m3/day (5041 igd).
CBCL Limited Existing Conditions 6 The effects of rain on the system were also investigated. This figure shows the wastewater flow record in red and the daily rainfall in blue. There appears to be a relation between the rainfall and daily flows, which would typically indicate extraneous flow in the wastewater collection system. However, there is inconsistency in that the large flows sometimes occur before a day with rain. Also noted in the data is that the large flow days are followed by very low flow days. The average flow during the gauging period was 18.4 cubic metres per day. Since the overall measured wastewater flow was less than the average annual water demand for the same customers (25 cubic metres per day) it does not appear that there is a significant problem with extraneous flows entering the wastewater collection system. It is more likely that the flow variations are due to operational procedures in the wastewater treatment plant. The system operators were contacted to assess this possibility; but a source has not yet been determined.
2.3.1.2 EASTERN SHORE COMMUNITY CENTER WASTEWATER TREATMENT FACILITY The system that services the Eastern Shore Community Center is presented in Figure 2.3.1(b). Assessment of this system included the following: A component review (septic tank, single pass sand filter, chlorine disinfection) was completed with the operator and it was found that the disinfection system was not operating; Dye testing of the system to locate the outfall discharge point; and Samples of effluent were collected from the wastewater treatment system on November 24th 2009. The effluent was not being chlorinated. Samples were analysed for Total Coliform/E. Coli, BOD, and suspended solids. Sample analysis results indicated that the treatment plant is producing acceptable effluent, even without disinfection.
Based on these assessments it was concluded that the two treatment plants produce effluent that is generally acceptable. Intermittent excursions in effluent quality might be expected to cause intermittent quality issues in the receiving waters.
2.3.2 Onsite Wastewater Treatment Other potential contributors of pollutants typically associated with sewage to the receiving waters are on site wastewater treatment systems associated with residences and other properties. Onsite wastewater treatment systems that are properly designed for site soils and depth to groundwater are able to treat wastewater generated in a residence or commercial building to an acceptable level then disperse the effluent to the groundwater. There should be no discharges to surface waters from a properly functioning onsite wastewater treatment and dispersal system.
However, the existing systems in Musquodoboit Harbour have been constructed over time. Not all systems have been designed and constructed to meet current standards. Some sites may be missing some or all of the components necessary to treat the wastewater under all conditions. As a result, there is potential for generation of the following pollutant sources in the receiving waters in the community: Untreated wastewater where there are no treatment facilities; Septic tank effluent where dispersal systems are being bypassed; and Partially treated septic tank effluent from poorly functioning dispersal systems.
A detailed study of each onsite system in the community is typically required to assess whether or not it is complete and functioning properly. The scope of this study didnt allow for such a detailed
CBCL Limited Existing Conditions 7 assessment, instead an assessment of signs of failing systems was completed in the small tributaries and roadside ditches that contribute flows to the main receiving waters. Signs of the presence of effluent, including lush plant growth and high concentrations of nutrients in sampled runoff were evident in these systems during the site visits. The impacts on receiving waters are discussed in Section 2.6.
2.4 Stormwater Stormwater drainage systems in the community currently include roadside ditches in developed areas. These discharge to natural systems including intermittent streams, the Little River, and the Musquodoboit River as well as the estuaries associated with these systems, as shown in Figure 2.4.
2.5 Water Supply Water supply in the community is currently by on site wells. The exceptions include: A central system that supplies treated water to the Twin Oaks Hospital and the Birches complex; and The Eastern Shore Regional High School that has water delivered by truck.
Typical water use was discussed in section 2.3.1.
2.6 Receiving Water Quality A water sampling program was completed to quantify existing water quality in the Little River and Musquodoboit River systems. Water samples were collected at 4 sites on the Little River (1 at the public beach at the west head of Petpeswick Inlet) and 3 sites on the Musquodoboit River on 2 occasions: Once following an extended period of dry weather; and Following Tropical Storm Bill, 24th of August 2009 and the heavy rain associated with that event (60 to 70 mm of rain).
Sample locations (shown on Figure 2.4) included: Little River: - Site 1: Upstream of the Highway 7 bridge to assess water quality in the Little River upstream of most development in Musquodoboit Harbour; - Sites 2 and 3: Upstream and downstream of the STP outfall to assess the direct impact of the Twin Oaks Wastewater Treatment Facility on Little River water quality; - Site 4: At the public beach near the outlet of the Little River; and - Twin Oaks Wastewater Treatment Plant effluent water quality records for August 2008 to August 2009 were also obtained from the plant operators and reviewed for input to the receiving water quality model. Musquodoboit River: - Site 5: Upstream of the new bridge to assess the water quality of river flows upstream of the community; - Site 6At the old railway bridge, part way through the community, to determine which section has a greater impact on water quality as the river flows pass through the community; and
CBCL Limited Existing Conditions 8
- Site 7: Downstream of the Highway 7 Bridge to assess the total impact imparted by sources in the community.
Sample analysis results at each sampling site for the two events are presented in Appendix A Table A.1. A summary of the findings follows: Dry Weather: - Fecal coliform while there is an increase in concentration in the Little River at the treatment plant outfall from 36 to 50 counts per 100 mL, the concentration in the river is much lower than the measured concentration at the public beach. In the Musquodoboit River the concentration increases through the community, the concentration doubles between the old railway bridge and Highway 7; and - Phosphorous in the Little River the concentration increased from 0.012 mg/L upstream of the treatment plant outfall to 0.015 mg/L downstream of the outfall but was 0.030 mg/L at the public beach. The concentration of phosphorous decreases through the community in the Musquodoboit River, most of the decrease occurs upstream of the old railway bridge. Wet Weather: - Fecal coliform A 30 percent increase in concentration in the Little River at the treatment plant outfall from 226 to 296 counts per 100 mL was observed. E coli concentrations increase in the Little River from Highway 7 to the outfall, but are in the order of 3.5 times the concentration at the public beach. In the Musquodoboit River the concentration increased from the new bridge to the old railway bridge but then fell back by half at Highway 7. E coli concentrations increased though the community; and - Phosphorous in the Little River the concentration decreased from 0.023 mg/L at Highway 7 to 0.0202 mg/L upstream of the treatment plant outfall to 0.016 mg/L downstream of the outfall but was 0.034 mg/L at the public beach. The concentration of phosphorous in the Musquodoboit River decreases upstream of the old railway bridge and then increases.
Beach Monitoring In addition to the samples collected for this study, data collected by HRM on E coli concentrations at the public beach was obtained and reviewed. The following Table 2.6 indicates that high counts of E coli are intermittent.
Table 2.6: HRM Summer 2009 Sampling Results at Petpeswick Inlet Beach E Coli #/100ml Number of Samples 0 10 6 10 100 1 100 200 2 200 400 1 Total 10
The sample dates and their results are provided on the following chart:
CBCL Limited Existing Conditions 9 This assessment of water quality indicates that: The Twin Oaks STP effluent has an effect on the Little River water quality but there are significant impacts from other sources, including from upstream of the community; and Conditions at the Petpeswick Inlet beach are influenced by water quality in the Little River but in order to reach the higher concentrations observed, there must be other significant factors that affect water quality at the public beach.
CBCL Limited Existing Conditions 10 CHAPTER 3 GROWTH IN THE COMMUNITY
3.1 Design Population and Number of Services In the Watershed Study Musquodoboit Harbour Final Report by CBCL Limited dated June 2007, a maximum population allocation of 7,050 people by the year 2026 was used. This information was received from the HRM Regional Plan and was confirmed by telephone conversations with Marcus Garnet of HRM Planning.
Based on further discussions with Mr. Garnet in August of 2009, it is understood that the Rural Express Bus Study estimated the population of the Musquodoboit Harbour area, adjusted to subtract Jeddore and the Petpeswicks, would be about 5,500 in 2026.
The Nova Scotia Community Counts website (www.gov.ns.ca/communitycounts) was also reviewed on 10 August 2009. Based on the 2006 Census, Community Counts indicates a total population of 2,136 for 2006 in Musquodoboit Harbour including the Petpeswicks, with a growth rate of 12.1% since 1996 (1.15% per year). Rounding down to 2,000 to more closely approximate Musquodoboit Harbour alone, and applying a rate of growth of 1.15% per year over the next twenty years, gives a straight line population estimate of about 2,500 by the year 2026.
Based on this information, a set of low, medium and high population growth scenarios was agreed. The low estimate is the straight line extrapolation of information from the Nova Scotia Community Counts website providing a population of approximately 2,500 by 2026. The high scenario uses the number from the 2007 CBCL Limited study of 7,050 people by the end of the plan period. The median estimate of 4,800, which splits the high and low estimates, is close to the estimate provided but the Rural Express Bus Study.
3.2 Density of Population Areas required for development for the three population growth scenarios were generated based on a range of average development densities from 4 to 40 people per hectare (1.6 to 16 people per acre) as outlined in the Municipal Planning Strategy (see Table 3.2).
CBCL Limited Growth in the Community 11 Table 3.2: Areas Required for Development Based on Population Estimates Population Estimate High Medium Low TotalPopulationin2026 7,050 4,800 2,500 ExistingPopulation 2,000 2,000 2,000 IncreaseinPopulation 5,050 2,800 500 GrowthDensity:People/Hectare 4 4 4 HectaresRequiredforNewDevelopment 1260 700 130 GrowthDensity:People/Hectare 40 40 40 HectaresRequiredforNewDevelopment 126 70 13
From community consultations undertaken as part of the Community Visioning process for Musquodoboit Harbour, it is understood that preservation of the village character of the community is important to residents. The wholesale infilling of individual lots across the existing community analysed in the 2007 Study Report would result in a significant change in community character.
Allowable development densities depend on the type of services provided. Nova Scotia Environment specifies the minimum lot size and dimensions for properties serviced by onsite wastewater systems, based on the type and depth of soils as well as the depth to groundwater. To achieve higher development densities requires some form of central services where wastewater is collected and treated at a central location. Generally, a density of 40 persons per hectare or higher is required to achieve the necessary construction and operational efficiencies to make the price for the installation of central services cost effective.
An average density of 40 people per hectare can be achieved while maintaining a desirable character for the community of Musquodoboit Harbour. The achievement of an average density of 40 people per hectare will allow variations in density where the creation of a higher density in one portion of the area will allow a lower density in another.
Figures 3.2 (a) to 3.2(e) illustrate densities of 25 to 62 people per hectare in other Nova Scotia communities. An average household size of 2.4 people per dwelling is used to determine the number of dwelling units per hectare. This household size was obtained from Version 7 of the new Dwellings and Population Worksheet of the HRM Regional Plan and confirmed by Marcus Garnet of HRM planning.
Some of these areas have densities more than double the required 40 people per hectare, but still provide extremely pleasant places to live with a character that could fit well within Musquodoboit Harbour. What creates the desirable characteristics of these areas are design related features, such as location of the building in relation to the street, variation in building sizes / massing, street width, the presence of mature vegetation in front of the houses, etc. Many of these features can be achieved through the use of form based zoning, which specifies requirements for site layout and building design including these types of features. The design of the new areas will also require consideration of innovation in servicing to allow alternative approaches to surface drainage and stormwater management, and installation of above ground services to allow the establishment of full size street front trees.
CBCL Limited Growth in the Community 12
Musquodoboit Harbour Wastewater and ServicingWastewaterHarbour and Musquodoboit - Study Follow-up #:061034.01 Project May Date: 2010
3.3 Preferred Development Areas Figure 3.3 presents a potential plan for locating future development in the community based on the population growth scenarios and estimates of areas required for these populations as outlined in Table 3.3. The plan is to select larger development parcels and develop them to the desired density. These areas were denoted as areas suitable for initial central servicing and infill development in Figure 5.1(a) in the Watershed Study Musquodoboit Harbour Final Report (CBCL Limited, 2007). Services would be developed to service the new development but could be extended to adjacent areas that may be experiencing water supply or wastewater disposal issues.
The potential development areas demarcated on Figure 3.3 have been adjusted to reflect property lines and to try to consist of larger undeveloped lots that could be suitable for subdivision. The potential development areas have also been located to create an area of relatively high density close to the intersection of Highways 7 and 357 which was suggested as the core area in the 2007 study. The areas are also close to the Arena, which was felt to be a good site for the development of a bus rapid transit terminal.
All three areas are required to accommodate the expected new development in the high growth scenario at 40 people per hectare. The low growth scenario would be accommodated in the area identified as Options 1 and 2. These areas are located to allow infill of areas close to Highway 7 and the potential transit terminal. Residential development could perhaps be set back from Highway 7 allowing for commercial development along the road. The commercial development would buffer the residential development from traffic and noise, and would benefit from a high visibility and, if appropriately designed, could contribute to the streetscape development of a village centre. Area Option 1 is ringed with existing roads providing good access, and would constitute infill development, which is encouraged under the Regional Plan.
If a medium growth scenario is attained, development can be directed to either Area Option2 and/or Area Option 3 (a or b), based on community preference. In order to achieve higher efficiencies and lower costs, it is recommended that only one of the areas be developed.
This approach of providing blocks of potential development areas allows flexibility so that different growth scenarios can be accommodated in a logical non disruptive manner. It allows efficient servicing, but also provides additional areas for growth, as required.
CBCL Limited Growth in the Community 13
Table 3.3 Musquodoboit Harbour Development Scenarios Development Scenario High Medium Low Population Estimate Total Population 7050 4800 2500 Existing Population 2000 2000 2000 Increase in Population 5050 2800 500
Estimate of Number of Services Total Number of Services 3052 2078 1082 Existing Number of Services 866 866 866 Increase in Number of Services 2186 1212 216
Estimate of Area Required for Growth Future Development Density (People/ hectare) 40 40 40 Area Required* (hectares) 126.3 70.0 12.5 Area Required* (acres) 312.0 173.0 30.9 * assuming all growth is directed to central area Notes: Future Residential Occupancy 2.31 People/Service Development density 16 People/Acre 40 People/Hectare Area conversion factor: 2.471 Acres/Hectare CHAPTER 4 CONSTRAINTS ON CENTRAL SERVICES
4.1 Receiving Water Quality The three dimensional hydrodynamic model developed for the initial study was revisited for the present assessment, with a higher resolution at the head of Petpeswick Inlet (Figure 4.1) to refine the assessment of potential pollutant source. No additional bathymetric surveying was conducted for the study, so the model bathymetry relies on approximate navigation charts and visual observations of the position of the shoreline over a tidal cycle. This level of detail is appropriate for order of magnitude estimates of assimilative capacity. The model is driven by tidal oscillations and salinity at the ocean boundary and freshwater flows and bacterial contamination from the Little River at the head of the inlet. The assumed Fecal coliform exponential decay rate was 1/day.
Following are findings of the updated assessments: Water quality at the Petpeswick Inlet beach is a function of water quality of the inflows, including the Little River, as well as high retention times due to low flushing rates in the Inlet; and Numerous sources around Petpeswick Inlet as well as along the Musquodoboit River are suspected.
4.1.1 Potential Sources of Pollutants Water quality sampling results described in earlier sections of the report indicate that: The bacterial contamination problem at the head of the inlet where the public beach is located appears intermittent in nature; and The worst contamination tends to occur during and after rainfall.
The model was used to better quantify the bacterial loadings necessary to produce the relatively high FC concentrations at the beach.
Hydrodynamic and effluent dispersion modelling results for a mean tidal range is presented in Figure 4.1.1. Modelling indicates that to get a bacterial concentration range of 200 400 FC/100ml at the beach, an estimated loading of 6x106 FC/sec is necessary at the head of the estuary. On 25 September 2006 these conditions were met due to high bacterial contamination in the Little River. However, during the additional sampling done in late August 2009, the measured bacterial concentrations in the Little River were not high enough to generate the concentrations measured at the beach. This finding points to the presence of other sources around the head of the inlet.
CBCL Limited Constraints on Central Services 14 Little River
Public Beach
Watershed/Servicing Study Follow-Up Analysis – Musquodoboit Harbour May 2010
Hydrodynamic Model Domain of Petpeswick Inlet Fig. 4.1 Modelled ebb tide dispersion patterns
Conditions measured on 25-9-2006 Potential benefits with bacterial loading into FC concentration = 2500 cfu/100ml in Little River the inlet reduced by a factor of 10 with assumed flow of 0.25 m^3/s to 0.6 million FC/second i.e. bac tillterial loa ding = 626.2 milli on FC/ secon d FC concentration [cfu/100ml] 3000 2000 1000 500 200 100 50 14 0
Public beach FC range = 200-400 cfu/100ml with tidal fluctuations
Watershed/Servicing Study Follow-Up Analysis – Musquodoboit Harbour May 2010 Modelled Contamination from Bacterial Loadings Fig. 4.1.1 at the Head of Petpeswick Inlet The Twin Oaks wastewater treatment plant has an average flow of 0.63 L/s (12,000 Igpd). Even at a Fecal coliform concentration of 15,000 counts/100mL (1.74 times the maximum measured effluent concentration see Table 2.3.1.1), the loading into the estuary is only about 95,000 FC/sec, which would produce a concentration of less than 6 FC/100mL at the beach, much less than what was observed on both sampling occasions. Therefore the STP loadings alone cannot account for the intermittent bacterial contamination observed at the head of Petpeswick Inlet.
In view of the above, the area was visited on November 24th 2009 to locate other potential sources of contamination. Following is a summary of findings and discussions related to sampling locations.
4.1.1.1 POTENTIAL CONTRIBUTORS 1. Location 1 Little River upstream of Highway 7: Homes on Brian Dickie Drive and Scott Pond Road are located within the drainage area. There are approximately seven homes. 2. Location 2 Little River upstream of STP outfall: The following developed areas are located with the drainage area: Rowling Drive; Little River Drive; Highway 7 from Rowlings Drive to Little River Drive; Willowdale Drive; Mill Pond Court; Willow Street/Spruce Court; and West Petpeswick Road (Highway 7 to the outfall). 3. Area tributary to the Head of the Inlet (sampling point 4): This area includes approximately 80 homes, 8 commercial uses, the Hospital, the Birches, and the High School; The area tributary to the Head of the Inlet would include the areas outlined above, plus the area along Clamshell Road, and along the West and East Petpeswick Roads; There are seven homes along the Clamshell Road, and approximately 68 homes along the East Petpeswick Road, including Fraser Island, up to the Yacht Club; On the West Petpeswick Road, there are approximately six homes adjacent to the Beach; and In addition, the commercial area along Highway 7 between The West Petpeswick Road and the East Petpeswick Road is within the tributary area of the Head of the Inlet (say approximately twelve commercial/homes). 4. Overall tributary area: The overall contributory area to the Head of the Inlet therefore includes approximately 188 homes/commercial uses.
4.1.1.2 POTENTIAL FOR CONTAMINATION Malfunctioning on site sewage disposal system can include the following: Straight pipe discharges; Seepage at the surface, with drainage to a ditch/ surface water; Direct seepage of effluent to a ditch/ surface water; Seepage to a ditch/ surface water by means of a foundation drainage system; Impacts by elevated water table; and Impacts by roof discharges.
CBCL Limited Constraints on Central Services 15 A cursory inspection of the contributory area indicated potential areas of contamination, as evidenced by areas of lush green grass where on site sewage disposal systems would be located and green grass in ditches. In addition, some lots are very small in area, and the systems would be placed very close to the drainage ditches (where lots slope to the front).
The assessment process for water table elevation would not have been as rigorous in the past at it is now, and therefore it is very likely that elevated water table is a concern.
Assessment of Potential Impacts During wet periods when the ground is saturated, sceptic field runoff would increase, which would contribute to the high concentrations observed during or immediately after heavy rainfall. Following are some estimates on the number of malfunctioning sceptic systems that would cause a FC loading at the head of the inlet of 6x106 FC/sec.
These are based on the following assumptions: Residential wastewater loading =109 FC/L (the range of values given by EPAi is 108 to 1010 FC/L) Septic system of design flow rate = 1000 L/day; and Leak rate of 1% to 10% of the design flow rate, i.e., 10 to 100 L/day.
The FC loading leaking into the environment from one malfunctioning septic system would be 105 to 106 FC/second. The required number of malfunctioning septic systems to cause the observed beach contamination would range from 6 to 60, which is a realistic range in light of the level of development around the head of the inlet.
It can therefore be concluded that malfunctioning septic systems on properties at the head of Petpeswick Inlet are a potential cause for the intermittent bacterial contamination observed at the beach.
4.1.1.3 OTHER POTENTIAL WASTEWATER SOURCES Animal waste can be a concern if residents kick the waste into the ditch instead of picking it up. Placing the waste in the ditch would result in the direct entry of the waste into the storm water system, and a direct pathway to the receiving body of water.
Wastes from ducks have been documented as being a problem when the ducks are fed at a swimming area. The duck population, however, does not appear to be a concern in the Inlet.
4.1.2 Potential Reductions of Pollutants To minimize the identified sources of contamination requires the following: Balancing of effluent discharges from the existing wastewater treatment plant to minimize the potential for large fluctuations in loads to the receiving waters. Based on the information collected on site, it appears that replacement of the old UV bulbs will greatly increase the effectiveness of the disinfection system. Modification of operations to decrease the flows typically discharged on Thursday during the monitoring period should be implemented;
CBCL Limited Constraints on Central Services 16 A sanitary survey of all properties that could potentially contribute flows to the inlet, identifying those that are potentially malfunctioning, then upgrading them with more reliable systems or replacing them with central wastewater collection and treatment. The issue of a Sanitary Survey being conducted in the past was discussed with citizen representatives on the Steering Committee. The representative indicated that past minutes of PIPOA, were reviewed but there was no reference to a sanitary survey being discussed or conducted. The study team checked with NSE, and determined that NSE did not conduct a survey, and they did not know of anyone else doing such. There is a possibility that a sanitary survey was conducted by a group like the Atlantic Coastal Action Program (ACAP) or another group funded by government. The steering committee representative checked with the residents who insisted that a survey was done in the past but was unable to locate any records; and Investigations completed in the 2007 Study indicated that it is much more costly to replace the existing systems with central services due to the extents of the collection systems required. Identification and upgrading of existing malfunctioning systems is the more cost effective solution.
4.2 Source Water Supplies The suitability of the Musquodoboit River and Little River as potential supplies of raw water for a central water system was investigated from the perspectives of water quantity and water quality.
4.2.1 River Aquifer Water Availability With respect to the quantity of water available, a comparison was made between expected water demands and minimum river flows. In order to be considered for water supply, a water source must be able to provide enough water to meet expected water supply demands, as well as any other potential demands, including the water required to maintain fish habitat. Expected water demands for the three growth scenarios presented in Table 3.2 are developed in section 5.3.1.
Low flows in the Musquodoboit River were estimated based on the flow record available at the river gauging station located upstream of the community and predictions of low flows for this station that were developed by Environment Canada (Inland Waters Directorate 1989). The flow estimates developed for the gauging station were prorated based on the ratio of tributary areas to the station and to the existing well field located between the new bridge and the bridge for the former railroad. Predicted low flows in the Musquodoboit River at the well field and in the Little River at Petpeswick Inlet are presented in Table 4.2.1(a) and a comparison of water demand to potential river water supply is presented in Table 4.2.1(b).
The numbers typically considered in this type of assessment include: The 1 day low flow for a system with no storage; A seven day low flow if there are seven days of storage available; and As a minimum, a 1 in 50 year recurrence period or 2% chance of occurrence to ensure that the flows are usually available.
These tables indicate that the demand generated by the high growth scenario for the entire community is in the order of 30% of the lowest 1 day flow expected 1 in 100 years on average for the Musquodoboit
CBCL Limited Constraints on Central Services 17 River so would typically be considered a suitable source water supply. The expected maximum water demands for existing development is greater than the 1 in 20 year one day low flow for the Little River. If the maximum day water demand occurs on the lowest flow day, all of the flow in the Little River would be used to satisfy the demand if no additional raw water supply was provided. Based on this assessment, the Musquodoboit River would be the best surface water supply from a water quantity perspective.
Table 4.2.1(a): Estimated River Flow Regime for the Musquodoboit and Little Rivers
Measured Calculated Study Area
Musquodoboit Musquodoboit Little River River at Flow River at at Crawford Falls Musquodoboit Petpeswick Gauging Station Harbour Inlet 01EK001 (m3/s) (m3/s/km2) (m3/s) (m3/s) DrainageArea(km2) 650 677 56
Daily Flows (1) DailyMaximum 351 0.5400 365.58 30.24 MonthlyMaximum 39.2 0.0603 40.83 3.38 MeanAnnualDischarge 20.1 0.0309 20.93 1.73 MonthlyMinimum 7.24 0.0111 7.54 0.62 DailyMinimum 0.15 0.0002 0.16 0.01
1 Day Low Flow Assessment (2) 1in2year 0.8 0.0012 0.833 0.069 1in5year 0.38 0.0006 0.396 0.033 1in20year 0.21 0.0003 0.219 0.018 1in50year 0.175 0.0003 0.182 0.015 1in100year 0.162 0.0002 0.169 0.014
7 Day Low Flow Assessment (2) 1in2year 0.91 0.0014 0.948 0.078 1in5year 0.44 0.0007 0.458 0.038 1in20year 0.25 0.0004 0.260 0.022 1in50year 0.21 0.0003 0.219 0.018 1in100year 0.19 0.0003 0.198 0.016 Source: (1) Environment Canada Historical Streamflow Summary to 1988 Source: (2) Environment Canada Low Flow Characteristics of Nova Scotia 1986 Note: 1 m3/s is equal to 1000 L/s and 86.4 million Litres per day
CBCL Limited Constraints on Central Services 18 Table 4.2.1(b): Comparison of Water Demand to Potential River Water Supply 0.00787 L/s/cap Halifax Water Maximum Day 680 L/day/cap Water Demand Assessment Growth Scenarios Estimated Water Demand High Medium Low Existing development plus Musquodoboit development of Core Area 55.5 37.8 19.7 River is a suitable (L/s) source, Little River (m3/day) 4794 3264 1700 is not DevelopmentoftheCoreArea(L/s) 39.7 22.0 3.9 Musquodoboit River is a suitable 3434 1904 340 source, Little River (m3/day) is not ExistingDevelopmentonly(L/s) 15.7 15.7 15.7 Musquodoboit River is a suitable source, Little River (m3/day) 1360 1360 1360 is not (1) Lowest day flow occurring in 50 or 100 years (2) Lowest 7 day flow occurring in 50 years
4.2.2 River Aquifer Water Quality Throughout this study the primary focus for a future centralized water supply has been groundwater, with secondary consideration being given to surface water from the Musquodoboit River. This section will describe the impacts on treatment as it relates to information available for both a surface water (river) and groundwater supply.
Surface Water Musquodoboit River Surface water sampling of the Musquodoboit River has been conducted at the location of the new river bridge upstream of the community and along the riverbank adjacent to the test well locations. The testing included analysis of common drinking water parameters for the preliminary determination of parameters of concern with respect to treatment. Sampling at the bridge coincided with sampling at other locations for bacteriological water quality testing completed during wet and dry weather periods in August, 2009. Sampling adjacent the test wells occurred during winter conditions
The Musquodoboit River and associated watershed(s) originate in central Nova Scotia and flow through several counties before emptying into Musquodoboit Harbour near the community. From a potable water perspective the water quality of the river is very typical of that found across Nova Scotia and the Atlantic Region. In general the water is described as very soft and neutral in pH. Organic matter concentrations are high to very high, with occasional spikes in turbidity associated with precipitation events. Only iron and manganese concentrations are above guidelines with respect to metals, which is also common in the region. Background bacteria levels are elevated, presumably due to agricultural practices and runoff in the area. No significant levels of nutrients were noted. The exact variations in parameters such as turbidity and bacteria may be different between seasons and the amount of runoff containing solids and/or nutrients
CBCL Limited Constraints on Central Services 19 would be similarly variable. Overall, the water quality data from the river indicates a source water which is challenging for treatment, but also similar to many other source waters in the province. This includes upstream locations along the river where other water treatment plants are located (i.e., Middle Musquodoboit). Primary treatment objectives would include the reduction of organic matter content (i.e., colour and Total Organic Carbon (TOC)), iron and manganese, and pathogen removal. It is expected that greater than 50 60% removal of TOC would have to be accomplished through treatment in order to control subsequent water quality parameters following treatment and disinfection. The water sampling event data is included in a table in Appendix A for the wet and dry sampling dates.
Any surface water source for municipal drinking water in Nova Scotia must be treated to meet Treatment Standards as published by NSE. These standards require specific engineered treatment steps to meet accepted practices for components such as disinfection. Utilizing the river as a source water would necessitate the construction of a full treatment plant to treat the Maximum Day flow for the community. Consideration could be given to more than one treatment plant, if the Little River were similarly considered for treatment.
One important consideration with respect to potential locations for treatment and extraction methods for water from the river relates to the possible use of riverbank or engineered filtration for water supply from the river. Water sources utilizing rivers generally have larger variations in water quality when compared with low velocity or low energy sources such as rivers and lakes. The velocity of river water particularly during precipitation, combined with runoff, creates more turbid and variable source water quality. This is undesirable for treatment. To ensure simplified design and operation, river water can be extracted using engineered intake systems which use the natural filtration capacity of the riverbank to attenuate peaks (i.e., degradation) in water quality variation. Riverbank intake systems can be made using drilled shallow wells, sections of riverbank with installed intake pipe, or intake pipes buried in the riverbed. Several variations on these systems are in use across Nova Scotia. Such a system in Musquodoboit River could simplify treatment of a surface water source in this case.
As part of any assessment of the rivers suitability as a long term water supply, data from the yield analysis (presented in Section 4.2) would be as part of an application for withdrawal of water from the river for municipal water supply.
Groundwater The identified preferred source of water for a future centralized water supply is groundwater from a series of new wells to be constructed in the area around the sports field and existing test wells. An investigation was completed to document potential sources of contamination which may affect groundwater in this area. Test wells, constructed 40+ years ago were identified for pumping and investigation of water quality. These wells were pumped under test conditions in January, 2010.
CBCL Limited Constraints on Central Services 20 The location of the test wells and potential future production wells is in close proximity to the Musquodoboit River. The use of groundwater as opposed to surface water offers the potential of improved quality as a result of using either a secure groundwater supply from a deep well, or attenuating degraded water quality from the river (i.e., turbidity, bacteria) as a result of flow through the geological formations between the river and the well location.
Conversely, groundwater supplies may be subject to contamination from external sources such as previous industrial activity, which is not present in surface water. Additionally, the geology in the area of the well locations may be such that it introduces concentrations of minerals or metals which are not present in surface water.
Based on the proposed location of new well supplies, the wells would be, by definition, under the influence of surface water (GUDI) as they are located in close proximity to surface water in the Musquodoboit River. In terms of treatment systems, GUDI supplies must undergo the same standard of treatment as surface water for the removal of pathogens by a combination of filtration and disinfection according to NSE standards. The use of a groundwater or surface water supply in this case does not alter the type of treatment required for disinfection.
There is however, the potential that future wells, once formally classified as GUDI, may qualify for a natural filtration credit for treatment due to measured differences between groundwater and surface water quality. This would not occur by default and would only be known after new wells are constructed. Considering this, the only difference in the required treatment resulting from using surface water or groundwater would be determined by the required removal of other parameters such as organics, minerals, and metals.
4.2.3 Potential Sources of Pollutants Potential sources of contamination to groundwater were identified in a watershed study of the Musquodoboit Harbour area (CBCL 2007). These sources have been evaluated in the context of groundwater flow paths connecting contaminant sources to nearby receptors. This preliminary analysis is in accordance with the framework described in the Nova Scotia Environment (NSE) document Developing a Municipal Sourcewater Protection Plan: Step 3 Identify Potential Contaminants and Assess Risk.
Potential contaminant sources were identified as agriculture (3 locations), light industry (a lumber yard and welding shop), a golf course, cemeteries (3 locations), abandoned mines (2 locations), gas stations (2 locations), a former landfill site, Twin Oaks Memorial Hospital, Eastern Shore District High School, and road salt spreading. Seawater intrusion and surface water were also noted to have the potential to affect well water quality in the study area.
These potential contaminant sources are listed in this section, together with a preliminary assessment of their connection to receptors along groundwater flow paths. A three dimensional conceptual model of groundwater flow was developed to assess the possible connections between contaminant sources and receptors. A more comprehensive study would be required to confirm and quantify routes of contaminant transport. The analysis focused on receptors located in the outwash valley aquifer which
CBCL Limited Constraints on Central Services 21 has the greatest potential to provide a central water supply source. Individual or cluster well receptors were also considered.
4.2.3.1 CONCEPTUAL MODEL OF GROUNDWATER FLOW Groundwater flow in and around the outwash valley aquifer was classified according to local and intermediate components of flow. Local flow paths originate as precipitation on or immediately adjacent to the outwash valley aquifer. Local flow is expected to predominate over the shallowest interval of the aquifer, with components of lateral flow toward the Musquodoboit River, and shallow flow along the valley axis to the southeast. Groundwater velocities in the outwash aquifer are expected to be on the order of hundreds of metres per year.
An intermediate flow regime is expected to originate on the valley ridges to the north of the outwash aquifer, following intermediate routes through quaternary and bedrock strata. Intermediate flow should generate deeper flow paths within the outwash aquifer, and would be oriented primarily to the southwest along the valley axis. Intermediate flow paths have the potential to transport contaminants over greater distances.
4.2.3.2 OUTWASH AQUIFER Former Landfill The former landfill site is located over the aquifer. A buried landfill is likely to contain household and industrial wastes releasing metals, polynuclear aromatic hydrocarbons (PAHs), chloride, sulfate, and elevated alkalinity to the aquifer. Depending on the source of waste materials, petroleum hydrocarbons and volatile organic compounds (VOCs) could also be present. Incoming precipitation has the potential to transport contaminants directly into the underlying aquifer, toward the Musquodoboit River, and to the southwest along the valley axis. A pumping well placed on the southwest side of the Musquodoboit River would have a high potential to intercept contaminants released by this landfill. Subsequent work should include an examination of the former landfill area to identify any affected creeks, seeps, odours or other physical evidence of landfill leachate. A sampling program could incorporate nearby private wells, or may require the installation of monitoring wells. The installation of monitoring wells could be coordinated with a future pumping test.
Abandoned Mine Existing research and anecdotal evidence suggests that there is an abandoned mine to the immediate west of the outwash aquifer. A former mine site would have the potential to release metals and/or to consume aquifer buffering capacity and generate acidic groundwater. Records from a mine several kilometers to the north suggest that ore or waste rock rich in minerals such as lead, copper, and zinc could impart elevated concentrations of these species to groundwater. Dissolved metals in mine water or water infiltrating through waste rock or tailings piles could affect groundwater quality in the area. Geological mapping indicates that the abandoned mine is located on the margin of the outwash aquifer. A pumping well in the outwash aquifer could induce gradients that would draw water affected by the mine into the outwash aquifer. An investigation of the former mine site could reveal further information on the potential for the generation of leachate. Monitoring wells may be required to rule out the possibility of mine water contamination of the aquifer. This activity would ideally be coordinated with a pumping test of the outwash aquifer.
CBCL Limited Constraints on Central Services 22 Agricultural Land Agricultural land located over the outwash aquifer and adjacent to the Musquodoboit River has a moderate to high potential to affect water quality. Fertilizers and pesticides released at this location would follow a direct pathway into the shallow aquifer. Nitrate is relatively persistent and is transported conservatively in groundwater environments. Ammonium and phosphates are less mobile, and tend to be broken down or adsorbed by organic matter, but if gradients and the rate of application were high enough, these species could also affect a central water supply. Pesticides, while not highly mobile in groundwater environments, can be persistent and pose serious health effects if consumed. An inventory of substances, and the rate and masses of these substances applied each year would be required. The application of fertilizers and pesticides would ultimately have to be limited or eliminated. Ideally, the land would by purchased by the municipality and designated as a well head protection area.
Road Salt Road salting in areas adjacent to the outwash aquifer would need to be limited or eliminated.
Summary and Recommendations Prior to or concurrent to installation and testing of a pumping well in the outwash aquifer, attention to the following action items is recommended: 1. Field Investigations: The former landfill, abandoned mine, and farm(s) should be visited to conduct physical inspections of the area and inventory any apparent contaminant sources. Rates of application should be determined for farms on the agricultural land on the northeast bank of the Musquodoboit River. 2. Monitoring Wells: The installation of monitoring wells would be required to confirm that contaminant sources are not present in the vicinity of the former landfill and abandoned mine. These monitoring wells would furthermore present an opportunity to monitor responses to pumping.
CBCL Limited Constraints on Central Services 23 ii EPA Design Manual Onsite Wastewater Treatment and Disposal Systems. 1980. EPA 625/1 80 012
CBCL Limited Constraints on Central Services 24 CHAPTER 5 CENTRAL SERVICES
Current policies that direct the types of applicable services include the following: The Municipal Planning Strategy suggests that areas serviced with central water also require central wastewater collection and treatment; and Areas serviced with central wastewater collection and treatment requires deep stormwater systems for drainage of each property by current Halifax Water policies.
Central services anticipated for the Core Area include sanitary sewers, and treatment, clearwater sewers with discharge to local waters, central water supply treatment and distribution. Each system is described in the following sections.
5.1 Central Wastewater Collection and Treatment A plan of the proposed central wastewater collection and treatment system to service the Core Area is presented in Figure 5.1(a). Design parameters for the systems considered are presented for the 3 growth scenarios in Table 5.1.
5.1.1 Wastewater Collection Figure 5.1(a) shows the components necessary to service some existing development in the community as well as allow development of the Core Area to proceed. It includes the trunk sewers, the treatment plant and the outfall. It does not include the wastewater collection systems that would be required on each street in the proposed development areas.
The assessment of alternative technologies in the 2007 Study identified a small diameter pressure sewer system as the most suitable alternative to conventional wastewater collection systems. It was determined that the maximum development density for economical use of this type of system is in the order of 20 people per hectare. Above this density the per service costs for conventional systems are lower. Conventional systems also easily allow for system extensions due to the requirements for use of a minimum pipe diameter and slope. Design of the alternative systems sizes pipes to more closely match the design number of services (This is where cost savings are typically generated, as well as no manholes and shallower burry). However, future extensions are not feasible unless they were originally included in the design. Because the proposed Core Area will have an average density of 40 people per
CBCL Limited Central Services 25
Diameter Forcemain PipeDia Flows Design Factor Harmon Peaking Area Serviced of Number Ultimate Services Design Serviced Population Diameter Forcemain PipeDia Flows Design Factor Harmon Peaking Area Serviced of Number Ultimate Services Design Serviced Population Diameter Forcemain PipeDia Flows Design Factor Harmon Peaking ihGot cnroMdu rwhSeai Low Growth Scenario Medium Growth Scenario High GrowthScenario Area Serviced of Number Ultimate Services (3) Design Serviced Population 0 5829 5 .0 8 2812 9 .0 0 8 2 4 .0 113 3.803 242 428 99 988 3.803 199 428 988 202 3.408 299 1423 3288 188 3.408 256 1423 3288 282 3.204 355 2397 5538 269 104 3.204 312 2397 5538 104 of Units Number Existing Services Adjacent Note: (1) HRM Policy suggests areasthat serviced withcentral wastewater collection and treatment shouldalso beserviced with centralstormwater drainage systems. Pipe Pressure Length of Stations Pumping m m H)(/)(m m)(a Ls m)(m H)(/)(m (mm) (mm) (L/s) (Ha) (mm) (mm) (L/s) (Ha) (mm) (mm) (L/s) (Ha) (m) (m) Pipe Length Note: Treatment Treatment Component hs b115#,# 4 96 61 .9 5 0 02 6428820106 61 .9 5 100 150 250 525 250 525 450 8 490 23 250 377 375 194 4.298 4.184 375 113 113 16 53 200 113 3.803 100 113 3.803 26 68 250 242 242 8 3.803 3.803 100 250 100 100 300 250 60 242 158 428 242 428 8 300 60 99 19 100 428 99 988 428 988 100 99 8 150 100 3.743 3.803 4.039 988 99 100 988 3.803 1 53 12 3.803 199 2 16 199 250 250 3.803 199 428 428 527 375 12 159 199 428 23 8 12 12 428 988 450 988 1217 428 367 428 988 12 450 525 4.184 4.298 988 202 525 988 428 450 988 53 202 490 16 200 202 100 3.408 377 428 26 988 194 68 3.408 375 202 68 3.408 26 299 250 988 299 428 250 60 299 3.408 158 375 988 158 1423 375 60 428 60 1423 299 988 19 1423 988 3288 188 988 150 188 26 988 3288 3.743 3288 100 100 1423 188 4.039 150 988 3.408 3.408 100 53 150 3288 26 16 256 188 3.408 256 375 150 250 527 250 256 150 26 1423 3.408 159 1423 39 23 450 1217 1 450 256 2 8 1423 3288 367 3288 39 282 4.184 3288 282 1423 1423 39 4.298 200 39 53 3288 3288 3.204 3.204 375 39 282 100 16 1423 355 355 68 250 282 525 3.204 3288 450 26 1423 250 450 525 2397 2397 1423 450 355 60 3.204 158 490 3288 26 269 68 19 5538 60 269 5538 3288 377 355 194 2397 1423 3.743 3.204 37 60 158 3.204 1423 4.039 48 5538 104 2397 3288 3288 53 269 19 312 3288 200 312 16 3288 500 5538 3288 44 1935 104 269 3.204 527 3288 2397 245 100 2397 200 100 159 312 #1,#2, #3 104 2,680 2,540 3.204 5538 1217 200 #4,#5 44 5538 725 367 312 2397 200 #6,#7 1,185 66 48 44 37 104 5538 2397 1,175 19 4,450 2 66 1,935 1 500 5538 104 66 2397 245 Collection 48 and Laterals 66 #2,#3 104 2,680 1,090 5,625 Phase 1 5538 #4,#5 37 725 19 Phase 2a 2397 #6,#7 Phase 2b 1,185 131 Total Collection 5538 2397 2397 500 Secondary 104 Outfall 3,000 5538 5538 131 Sub- totalSanitary 2397 68 26 2397 Collectionand Laterals 5538 131 131 1,890 3,500 Phase 1 158 5538 60 5538 Phase 2a 1,140 900 40 Phase 2b 5538 Total Collection 54 131 16 Tertiary 1420 21 Outfall 3,930 1935 1815 Sub- totalSanitary 585 1252 Clearwater Sewers and Laterals High Lift 131 Phase 1 Phase 2a Phase 2b 5072 Sub- 7007 totalStorm Wells Well Pumps Water Treatment Transmission Reservoir (4) Design basis forwatermains - Maximumvelocity at peak hourly flow: 1.5 m/s Distribution and Laterals Phase 1 (3) Design basis forforcemains - Maximum Phase 2a velocity at design flow: 2.5 m/s Phase 2b m3/ha/day 11 Phase 3 Total Distribution L/day/cap Sub- totalWater 330 L/cap/day 410 L/cap/day 680 L/cap/day 1025 Wastewater Generation Generation I/I Average Daily MaximumDaily MaximumHourly (1) (1) (2) Table5.1 Design ofCentral Servicing Sanitary Sanitary Storm (2)HRM RegionalPlan suggests thatareas serviced withcentral wastewatercollection and treatment shouldalso beserviced with central water Water Design Flow Criteria (1) Water Demands (2) hectare, the wastewater system considered has been a conventional system. Design of the system will meet current Halifax Water Design and Construction Specifications.
5.1.2 Wastewater Treatment The 2007 Study suggested that for a population of 7050, the most suitable wastewater treatment technology for the community of Musquodoboit Harbour would be a Sequencing Batch Reactor (SBR) system. This would provide secondary treatment of the wastewater, acceptable to the Nova Scotia Environment for discharge into Musquodoboit Harbour. Secondary treatment will also meet the minimum effluent requirements stated in the recent CCME Guidelines.
A sequencing batch reactor (SBR), sized to treat wastewater from the Core Area is shown on Figure 5.1(a). The development of the wastewater treatment plant to service the area is presented in two development phases: (i) service population of 4,800 people, and (ii) an ultimate design population of 7,050 people. A description of the treatment process follows.
Flow Estimates Wastewater flow estimates were developed based on existing and projected growth within the proposed Core Area. Some assumptions were made for the flow estimates including that a new wastewater collection system would result in lower inflow and infiltration rates and population projections developed in the original watershed study prepared by CBCL Limited.
Table 5.1.2: Wastewater Treatment Plant Design Flows
Average Daily Flow Peak Flow Development Scenario (cubic metres/day) (cubic metres/day) MediumGrowth 1960 5880 HighGrowth 2900 8700
Equalization SBR treatment plants operate in a batch mode with one tank being filled while the other is undergoing settling and decant operations. Flow equalization does not benefit this process and therefore is not proposed.
Preliminary Treatment Preliminary treatment requirements for SBR treatment systems typically include screening and grit removal. A hopper bottomed primary clarifier, is proposed. This tank will remove heavy materials such as grit and gravel. A grinder will be installed before the primary clarifier to eliminate the potential maintenance issues associated with screenings carrying through the primary tankage.
All influent will flow into the tank which will also be used as the wet well for the SBR influent pumps. Ground screenings and grit will settle in the hopper with the remainder of the flow pumped to the SBRs which will be controlled by the level in the tank. SBR feed pump suction lines will enter the tank approximately 3 meters below the operating water level to ensure the solids and grit is not pumped to the SBRs. The accumulation of screening and grit will require this tank to be cleaned out on a regular basis.
CBCL Limited Central Services 26 Sequencing Batch Reactor The main treatment components of the plant are the Sequencing Batch Reactors. The SBRs were designed based on the wastewater loading rates presented as well as the design parameters listed below:
Design Parameter HydraulicResidenceTime(HRT) =20hours SolidsResidenceTime(SRT) =13days MLSSatTWL =2,900mg/L F/M =0.11
The dimensions and water levels of each SBR tank are: Length = 13 m Width =13m HighWaterLevel(HWL) =5m Average Bottom Water Level (BWL) = 3.8 m
Control Strategy The SBR will be operated based on a 6.0 hour cycle during average flow. This will result in 8 batches per day of 245 m3 each. During periods of peak flow operating parameters will be altered to allow for a 3.0 hour cycle resulting in 16 batches per day of 735m3 each. Operation will be controlled by a PLC operating on timer control with a level override. Operation during average flow will contain fill, fill/react, react, settle, decant, and idle cycles. Operation during peak flows will contain fill, fill/react, react, settle, decant, and fill/decant cycles.
Floating Decanter The decanter is designed for the removal of 245 m3 of effluent over a 30 minute period. This results in an average decanter flow rate of 8.2 m3/min. The decanter will also be designed to exclude scum and solids. Scum that accumulates in the SBR tanks may be either sprayed down or physically skimmed off and placed in the aerobic solids holding tanks. Depending on the configuration of the decanter, peak decant rates may be considerably higher than the average rate.
Waste Activated Sludge Waste activated sludge will be removed on an automated cycle and pumped to the aerated solids holding tank. This tank will be sized for one month sludge production at the peak design flow rate with the decant overflowing and returning to the preliminary treatment tank by gravity.
Ultraviolet Disinfection Effluent will require disinfection to meet discharge criteria of 200 fecal coliform per 100 mL. Ultraviolet disinfection has been selected as the means to achieve this limit. Advantages of an UV disinfection system include eliminating safety concerns associated with chlorine gas and some handling problems with other types of chlorination such as dechlorination stock supply, storage and feed pumps.
CBCL Limited Central Services 27 During the decant cycle clarified effluent will flow by gravity to the UV disinfection unit. Disinfection will take place in a single concrete channel located in the first floor of the new control building. The UV system will consist of a single reactor containing two banks of low pressure, high intensity UV lamps. The lamps will be oriented horizontally and parallel to the direction of flow.
SCADA Operation of the treatment plant will be monitored by a supervisory control and data acquisition (SCADA) system designed to be monitored at the plant. This system will monitor all process equipment status as well as process variables such as dissolved oxygen, wastewater flow rates, and tank water levels.
Tertiary Treatment Option An option to the original wastewater collection and treatment scheme was considered. This scheme considered a treatment plant that removes more pollutants, by tertiary treatment, and discharges the effluent closer to the Core Area, in the lower reach of the Musquodoboit River. Treatment to a tertiary level is required by Nova Scotia Environment for discharges to freshwater receiving environments.
In this scheme, shown as an alternate on Figure 5.1(b), the treatment plant would be located in the vicinity of the intersection of Riverside Avenue and Anderson Road. An outfall would be constructed on Riverside Avenue to the river. The original series of pumping stations, forcemains and gravity sewers from Riverside Avenue to the original wastewater treatment plant site would not be constructed. The net benefit of this scheme is a reduced pollutant load to Musquodoboit Harbour (in the order of 25 percent of the load with secondary treatment) as a result of a higher level of wastewater treatment.
Tertiary treatment includes the removal of solids and nutrients to below secondary levels. The effluent hydraulics of the secondary plant will require a pump station to be installed to lift the flow through the proposed tertiary treatment processes. A description of each tertiary treatment option follows.
Sand filtration is typically utilized to remove TSS and subsequently BOD levels to less than 10 mg/L. Although a number of different configurations exist, the most common is a moving bed or continuous clean sand filter. This system would be enclosed within a small building.
Continuous clean filters provide a continuous supply of filtered water without the interruption of backwash cleaning cycles. In the upflow mode, influent enters the bottom of the filter and flows upward through the sand bed. Clean filtrate exits the sand bed and overflows a weir as it leaves the filter. Simultaneously, the sand bed, with the accumulated solids, is drawn downward into the suction of an airlift pipe positioned at the center of the filter. A small volume of compressed air is introduced into the bottom of the airlift causing a turbulent upward flow of sand, dirt, air, and water. This turbulence scours impurities from the sand. At the top of the airlift dirty slurry spills over into a central reject compartment. Sand returns to the bed through a gravity washer/separator and reject water is returned to the primary clarifiers.
Provided the secondary treatment process is efficient in removing soluble BOD, the required discharge levels can be met.
CBCL Limited Central Services 28
5.2 Stormwater Collection Current Halifax Water policies include a need for a deep storm drainage system to service any new development serviced by sanitary sewers. Halifax Water representatives have indicated that these may include: Conventional deep storm sewers, designed as per the current Halifax Water Design and Construction Specifications. These require that the storm sewers have capacity to convey peak flows from rainfall intensities with 1 in 5 year return periods, without surcharging during less frequent rainfall intensities; and Deep Clearwater sewers designed to convey only foundation drainage.
Clearwater sewers are proposed for the Core Area to convey basement drainage from all services. Those necessary to service existing properties in the area proposed as the Core Area are shown on Figure 5.2. General surface drainage will be conveyed by swales and ditches with integrated detention storage and infiltration capabilities. Additional retention and treatment of surface drainage in constructed wetlands was described and recommended in the 2007 Study report.
5.3 Water Supply, Treatment and Distribution Figure 5.3 shows the proposed extent of the water distribution system as well as the proposed location of the water supply wells and the water treatment plant.
5.3.1 WaterDemands Water Usage Rates in Nova Scotia In 2006, Environment Canada collected data from municipalities across the country to determine the amount of water being used by Canadians in different provinces. The findings were published as the Municipal Water and Wastewater Survey (MWWS) and are available online. As part of the study, a residential demand of 313 L/person/day was calculated for Nova Scotia based on responses from 473,858 people in 30 municipalities. This represented approximately 60% of the total per capita water demand for the province (532 L/person/day). The remainder of the total demand was made up by commercial (including institutional) and industrial users as well as system losses.
The future commercial and institutional profile of Musquodoboit Harbour is not known in detail, and is expected to change depending on the magnitude of the increase in population. Therefore, the sections below refer to a residential demand based on a per capita demand of 313 L/person/day as well as a total demand based on a per capita demand of 532 L/day. The actual water demand is expected to vary depending on the amount of commercial growth experienced by the community as it expands.
Water Usage in Musquodoboit Harbour Three different growth scenarios have been projected for Musquodoboit Harbour: low, medium and high representing populations of 2,500, 4,800 and 7,050 respectively. In lieu of actual water use data for the community these populations were multiplied by the per capita water usage numbers for Nova Scotia as provided by the MWWS (Environment Canada, 2006) to develop average water use estimates as shown in Table 5.3.1(a) below.
CBCL Limited Central Services 29
Table 5.3.1(a): Average Daily Flow (L/day) Expected with Existing Population and Under Three Growth Scenarios Average Total Water Usage High Medium Low Existing ResidentialOnly 626,000 626,000 626,000 Total 1,064,000 1,064,000 1,064,000 Anticipated ResidentialOnly 2,206,650 1,502,400 782,500 Total 3,750,600 2,553,600 1,330,000
The anticipated average water use per day varies linearly with population, ranging from 1.33 MLD in the low growth scenario to 3.75 MLD in the high growth scenario. Average water usage rates, however, do not take into account the variability in demand that occurs from day to day and from season to season. As a result, they should not be used to design treatment processes, as this would underestimate the amount of water required on high demand days.
Design standards require that water treatment systems be sized to be meet Maximum Day demand the largest total daily water demand experienced by a system in a given year. The Maximum Day factor is a multiplier which relates the Average Day demand to Maximum Day demand. It is used where Average Day demands are known or calculated, and predicts a theoretical Maximum Day demand. Maximum Day peaking factors are used to account for the normal expected variations in water demand. These factors were developed empirically over time and are dependent on the size of the community. Maximum day peaking factors of 2.25 and 2 are recommended by the Atlantic Canada Guidelines for the Supply, Treatment, Storage, Distribution and Operation of Water Supply Systems (CBCL, 2004) for communities of less than 3,000 residents and 3,000 to 10,000 residents respectively. Maximum day peaking factors have been shown to increase as communities become smaller because the day to day variability is more strongly impacted by the actions of individual users. The maximum water demand anticipated in each population growth scenario is shown in Table 5.3.1(b) below.
Table 5.3.1(b): Maximum Daily Flow (L/day) Expected with Existing Population and Under Three Population Growth Scenarios Maximum Total Water Usage High Medium Low Existing ResidentialOnly 1,408,500 1,408,500 1,408,500 Total 2,394,000 2,394,000 2,394,000 Anticipated ResidentialOnly 4,413,300 3,004,800 1,760,625 Total 7,501,200 5,107,200 2,992,500
5.3.1.1 DEVIATIONS FROM CALCULATED VALUES BASED ON COMMERCIAL AND INSTITUTIONAL DEVELOPMENT Residential users utilize water in different ways than commercial, industrial and institutional users. Thus, the total amount of water required for a community is not only dependent on the number of residents; the type and size of other major water users will also have an influence. According to the
CBCL Limited Central Services 30 MWWS (2006), Nova Scotia municipalities distribute approximately 60% of their treated water to residential users, 20% to commercial users, 5% to industrial users and list the remainder as water loss. Figure 5.3.1 below shows how the percentage of the demand caused by residential users affects the maximum daily flow that must be treated at the water treatment plant.
Figure5.3.1: Maximum Day Flow Expected as a Function off the Percentage of theWater Demand Represented By Residential Users
Figure 5.3.1 shows that as the percentage of the flow required for commercial and other non residential users increases, so does the anticipated maximum day flow. A situation where 100% of the water provided by the water treatment plant is used directly by residents is unlikkely as there will inevitably be water losses in the distribution system and within the treatment process itself. Given that a new distribution system is likely to have fewer losses than an aging onea minimum of 10% loss should be reasonable. Thus, the maximum amount of residential demandto be expected would be 90%.
The maximum daily flows calculated for each growth scenario previously assumed that 60% of the water demand is from residential users, with 20% from commerciall users and 5% from industrial users. The demand in Musquodoboit Harbour, however, will likely have a larger residential component. Initial calculations based on existing institutional flow rates (hospital, school, nursing home) and anticipated commercial projects (Lawtons, Sobeys) suggested that commercial users will make up between 2% and 19% of the total anticipated water demand depending upon the growth scenario and the textbook values used in the calculations. No information is yet availablle with regards to industrial users. Thus,itis
CBCL Limited Central Services 31 expected that the residential component of the water demand will make up between 71% and 88% if no further commercial or institutional users are added to the system.
In the absence of more detailed information about the commercial, institutional and industrial profile of the community of Musquodoboit Harbour, it is recommended that a conservative per capita flow rate of 532 L/person/day combined with the maximum day peaking factors listed in the Atlantic Canada Guidelines for the Supply, Treatment, Storage, Distribution and Operation and Drinking Water Supply Systems be used to calculate the anticipated maximum daily flow required under each growth scenario. This would result in a treatment plant sized to treat 3.0 MLD under the low growth scenario and 7.5 MLD under the high growth scenario.
The following describes the steps that would be required to develop a well field for Musquodoboit Harbour. The outline includes some assumptions about the work and the approximate costs involved. A more detailed work plan would be required if this work were to go ahead.
5.3.2 WellField Development Based on calculations provided in the Watershed Servicing Study Musquodoboit Harbour (CBCL, 2007), and from the Department of Mines pumping test report (Pinder, 1968), with multiple wells installed in the outwash aquifer, each well can be expected to sustainably produce approximately 13 L/s. A single operating well may be pumped at up to 27 L/s for shorter time frames to satisfy peak demands as listed in table 5.3.1(b). The sustainability of the suggested pumping rates remain to be evaluated as part of an updated pumping test of the proposed well field.
Assuming a conservative per capita flow rate of 532 L/person/day, and the assumptions listed for well pumping rates, the well configurations listed in Table 5.3.2 would be required to satisfy .
Table 5.3.2: Production Wells Required to Satisfy Total Expected Water Demands Population Demand (m3/d) Wells Required (with redundant well) 2500 1330 2.(3) 4800 2553 3.(4) 7050 3750 4(5)
The recommended locations for production wells are shown on Figure 5.3. The numbering of production well locations provides the recommended sequence of drilling as additional locations are added. The approximate cost to drill, case, and screen each well is $20,000. Production wells are assumed to have the following characteristics: Depth: 20metres StaticWaterLevel: 2metres CasingLength: 7metres ScreenLength: 13metres Diameter: 200mm PumpingRate: 13L/s
CBCL Limited Central Services 32 A pumping test would be required to assess the long term yield of the aquifer and potential interactions with surrounding features. The recommended test would be as follows: Initiate pumping at PW1; Initiate pumping at PW2 after 12 hours; Initiate pumping at PW3 after 24 hours; Initiate pumping at PW4 after 36 hours; Continue pumping for 72 hours; Monitor water levels in PW1, PW2, PW3, PW4, PW5, and TH 196 by hand and using data loggers; Sample each well 1 hour and 24 hours after the initiation of pumping; and Sample each well immediately before shut down of the pumps.
5.3.3 Water Quality Comparison and Treatment Objectives Summarized results of water quality sample analysis for common treatment parameters is presented in Table 5.3.3 below. Although each potential source was evaluated for a spectrum of additional parameters, only those presented are considered relevant for treatment. The only other parameter which exceeded the Guidelines for Canadian Drinking Water Quality during sampling was bromate, and was measured in TH 196. The guideline limit for bromate in drinking water is 0.01 mg/L and was measured at 0.04 mg/L. Bromate is not naturally occurring and is not normally found in water sources. It is typically formed as a byproduct of water disinfection where there was bromide present before disinfection (commonly ozonation processes). Although there are a number of cases where bromate contamination has been found in groundwater, there is no straightforward explanation for the concentration measured in this case, particularly since no other related parameters suggesting contamination were measured. Almost all past incidences of bromate in drinking water have been from disinfection processes during treatment. The initial response to this reading would be to investigate further and re sample the source since it appears unlikely that the bromate is naturally occurring or consistently present. If bromate is in fact found to be sustained, it would alter the assumed treatment process below. For the purposes of this study it has been assumed that bromate will not be a parameter included for removal during treatment and that the measured concentration is not consistent.
The complete analysis results for all parameters are included in Appendix A. Additional in situ water quality data collected as part of the sampling program are also provided in Appendix A. The in situ data show changes in the quality of water over time, with three stepped pumping intervals. Initially fine material in the well and filter pack imparted high turbidity to the pumped water and resulted in generally lower water quality. Toward the end of the test the filter pack of the well was redeveloped, resulting in improved water quality. In situ data indicated that water drawn from the well was distinct from the adjacent river water.
CBCL Limited Central Services 33 As there were stated concerns at the onset of the project regarding potential groundwater contamination the groundwater test wells were sampled for a range of hydrocarbons, pesticides and herbicides, aromatic compounds, and other synthetic organics. The complete analysis results showed no evidence of influence by any of the potential contaminant sources identified in the terms of reference for the study, but additional pathway and contaminant specific monitoring is recommended.
The complete analysis showed evidence of potential radionuclides in the shallow interval of the outwash aquifer. The gross alpha count was 0.11 Bq/L, exceeding the guideline concentration of 0.1 Bq/L. Although it exceeded the guideline concentration only marginally, the gross alpha count of water from the shallow aquifer is elevated; ideally a groundwater supply would show a gross alpha count below the detection limit (0.03 Bq/L). Further evaluation of the quality of groundwater from the outwash aquifer will require testing for radionuclides.
Table 5.3.3: Comparison of Groundwater and Surface Water Quality Average Maximum Parameter Unit RDL GCDWQ* SW GW SW GW Total CFU/100 2 0 1,238 1 2,407 1 Coliforms mL (MPN) E. Coli CFU/100 2 0 44 1 115 1 (MPN) mL TSS mg/L 5 2.5 40.0 2.5 40.0 pH1 7.17 6.20 7.30 6.20 Alkalinity mg/L 5 11.7 7.0 13.0 7.0 TrueColor TCU 5 <153 60.7 2.5 97.0 2.5 Turbidity NTU 0.1 0.1 1.60 7.70 1.80 7.70 Electrical Umho/cm 1 83 100 84 100 Conductivity Total mg/L 0.5 5.2 1.3 7.3 1.3 Organic Carbon Total mg/L 0.1 <2003 4.17 11.90 4.40 11.90 Sodium Calculated mg/L 1 45 51 46 51 TDS Hardness mg/L 27.4 11.4 27.7 11.4 Total ug/L 10 10 134 39 153 39 Aluminum2 Total ug/L 2 10 1 1 1 1 Arsenic TotalIron ug/L 50 3003 488 240 641 240 TotalLead ug/L 0.5 10 0.25 0.50 0.25 0.50
CBCL Limited Central Services 34 Average Maximum Parameter Unit RDL GCDWQ* SW GW SW GW Total ug/L 2 503 154 853 211 853 Manganese Total ug/L 0.1 20 0.07 0.05 0.10 0.05 Uranium
In general the water quality differences between the groundwater and surface water are mainly associated with metals and organics. Whereas the surface water is high in colour and TOC, the groundwater sample had very little. Conversely, the surface water exceeds the drinking water standard by an order of magnitude less than the groundwater.
The use of the groundwater data should be approached with caution. The wells used for sampling had not been developed or pumped for many years and were only pumped for three hours for the test samples collected. Therefore it is not expected that the water quality results are the same as would be the case if the wells were pumped for a longer duration to reach a true steady state. The test well depth is also much shallower than the proposed future production wells. Further, with new deeper wells being proposed for the long term the water quality from these remains a relative unknown, with only slight indications being provided by the data set in Table 5.3.3.
Despite the cautious approach to the groundwater data, some generalized objectives for treatment of both surface water and groundwater can be summarized. These are considered against both the existing and proposed upgrades to the NSE Treatment Standards for surface water and groundwater sources. The NSE standards describe in detail minimum amounts of treatment and are not fully summarized here. Rather, the objectives below are those considered most significant in terms of required capital impacts. Treatment to provide a minimum of 3 log giardia and cryptosporidium removal by a combination of engineered filtration and disinfection; Treatment to provide a minimum of 4 log virus removal by filtration and/or disinfection; Turbidity reduction to below 0.1 NTU; Removal of metals such as iron, manganese, and aluminium; Reduction of colour to below 15 TCU or that required to produce a THM and HAA formation potential below guidelines (100 and 80 µg/L respectively); Secondary disinfection; Instrumentation and monitoring; and Filtration redundancy.
Without a representative sample of groundwater which is reasonably confident to represent the future water quality, it will be assumed for the purposes of considering treatment design, based on the sampling completed, that the following conditions will apply to groundwater: The groundwater is direct or high GUDI due to close proximity to the river; There is significant levels of manganese and possibly iron; Breakthough of organic matter, to some extent, occurs from the river; pH is neutral; Hardness and alkalinity are below 300 mg/L;
CBCL Limited Central Services 35 Turbidity and solids are significantly lower than during pumping tests and turbidity is less than 10 NTU; and No other synthetic or organic contaminant (i.e., industrial source) is found in the groundwater.
Considering these conditions it becomes apparent that from a treatment perspective the goals for treatment of either groundwater or surface water are generally the same. Both require pathogen removal, organics removal, metals removal, and solids removal. The extent to which one source or the other requires treatment of a specific parameter is variable but treatment options will be examined to cover all parameters for either source, and can be adjusted in the future to account for the actual levels given the source selected.
5.3.4 Water Treatment Plant Process Assessment
5.3.4.1 POTENTIAL TREATMENT SYSTEMS In general, conventional water treatment systems used for organics removal will also achieve the requisite pathogen removal credits. Treatment processes specifically designed for the removal of metals such as manganese may or may not achieve these credits depending on the type of treatment used. The type(s) of treatment systems may include simultaneous organics reduction and metals removal, or each may be separated into different unit processes.
Treatment systems for organics and turbidity removal commonly employed in similar applications around Atlantic Canada include the use of coagulation, flocculation, and filtration in different configurations. These processes use chemical pretreatment to neutralize and precipitate organic matter into particles which may be filtered directly or clarified prior to filtration using a flotation, settling, or a solids contact basin. The extent to which coagulation and flocculation are required are a function of the amount of organics to be removed. Filtration methods commonly use a gravity multi media configuration or a membrane system. Where no organic matter removal is required but filtration credits are still necessary a multi media system without coagulation will not achieve filtration credits and an ultrafiltration or microfiltration membrane system is typically more appropriate. This is significant since the ultimate level of organic matter present in new wells is unknown and thus the treatment system requirements can vary.
Assuming some level of organic matter and turbidity reduction is required, the following list of processes is typical of those which would be considered, but is not exclusive or exhaustive: Coagulation, flocculation, sedimentation, filtration; Coagulation, flocculation, dissolved air flotation, filtration; Coagulation, flocculation, enhanced settling, filtration; Coagulation, filtration; and Filtration (no coagulation).
The levels of metals (particularly manganese based on sample results) to be removed is also not finalized but consideration of potential treatment methods can be included in preliminary process evaluations. Considered independently the treatment of metals commonly includes the addition of an oxidant to precipitate dissolved metals into a form which can be filtered. This may be combined with
CBCL Limited Central Services 36 methods of flocculation as with organics removal or dissolved metals may be removed biologically using specially design filtration media. This media generates layers of biofilm which will metabolize dissolved metals as water is passed through the media, thereby removing the metals from solution.
For manganese removal, processes using manganese greensand (i.e., zeolite media saturated in potassium permanganate), or a synthetic variation of greensand with adsorptive capacity, combined with chlorine oxidation, or oxidation with potassium permanganate are most common. Whereas iron removal can be achieved with oxidation using air, the oxidation of manganese requires a stronger oxidation potential and is commonly done at a higher pH (i.e., >8). For Musquodoboit Harbour a range of oxidation and removal processes are possible. Additionally, the oxidation and removal of manganese can be combined with the organic removal process either by the addition of a dedicated oxidation chamber prior to coagulation, and/or the inclusion of manganese absorptive media in the filtration process.
The general flow schematic of a water treatment system will include the pumping of water from wells or the river (through an engineered riverbank infiltration system) to a central treatment building. The treatment building will include processes described for turbidity, organics, and metals reduction, followed by disinfection using UV, chlorine, or alternate disinfectant as selected during design. Treated water may be stored onsite or an additional water storage tower may be constructed to provide pressure throughout the system. An elevated storage tower may be an option to provide gravity flow to the distribution system following treatment, disinfection, and pumping. The treatment plant will include all necessary instrumentation to monitor raw, intermediate, and treated water quality. The system will be automated and controlled centrally. Residuals handling will provide for either disposal to the municipal sewer system or a method of onsite residuals volume reduction and concentration. Additional capital can be invested initially to reduce the volume of residual waste and limit impacts on wastewater collection systems.
5.3.5 Water Distribution Water will be supplied to the Core Area by pumped flows from the treatment plant with excess demand supplied from the reservoir. Water from the treatment plant will be pumped to an elevated reservoir located on the high piece of land northwest of the treatment plant.
Water distribution mains considered in this assessment are shown in Figure 5.3. The distribution mains were sized to supply maximum demands without fire flows to minimize the size of the components. Design flows and component sizes are presented in Table 5.1. All criteria for the design of the distribution mains are based on Halifax Water Design and Construction Specifications.
5.3.6 Central Water without other Services A central water supply, treatment and distribution system on its own, without the other services discussed, is technically feasible and would be as discussed in sections 5.3.1 and 5.3.2. Although the number of services would remain as presented, the overall extent of the water distribution systems in the sub divisions could potentially be much greater, to provide services to much larger properties sized for on site wastewater systems.
CBCL Limited Central Services 37 The concern with supplying only water is with the impact it could have on the on site wastewater treatment facilities. Typically water consumption with on site water supply and wastewater treatment systems is lower than on centrally supplied systems. Onsite wastewater treatment systems for a single family home (4 residents) are typically designed to accept approximately 1000 liters of wastewater per day or 250 liters per person per day (L/person/day). Typical average water use estimated for the central supply, based on measurements for Nova Scotia) is in the order of 313 L/person/day, 25% higher than the capacity of the onsite treatment system if there are 4 people in the house. This can create problems for the onsite wastewater treatment systems designed to current standards and even greater problems for systems that may be sub standard due to insufficient property size. Failed systems do not provide required treatment of the septic tank effluent and it becomes a potential contaminant for receiving waters including surface waters such as the rivers as well as groundwater.
There are measures that can be taken to offset this effect. Properties that are serviced with central water but are on onsite wastewater treatment systems should be designed or retrofitted with devices designed to minimize water use including: Low volume flush toilets; Water saver shower heads; and Reduced water use clothes washers.
These measures may be used to reduce the water use to the design capacity of the onsite systems. Alternatively, the on site systems for new developments may be designed to accommodate the typical water use associated with central systems. This may result in even larger properties and larger distribution systems in the sub divisions. Individual developers would typically assess the advantages and disadvantages of the various scenarios to determine an optimum combination for their sub division.
5.4 Phased Implementation Construction of the central services may occur in multiple phases as budgets allow. However there are some general requirements as follows: Phase 1 of the wastewater treatment system must include: - The treatment plant and outfall; and - Phase 1 of the collection system which includes the trunk system to the treatment plant. Phase 1 of the water system must include: - The wells, water treatment plant and reservoir; and - Phase 1 of the distribution system which includes the watermains to the reservoir and system on Highway 357 to the water main on Highway 7. All services should be constructed on any street at the same time to minimize overall construction costs including reinstatement of disturbed surfaces.
CBCL Limited Central Services 38 5.5 Estimated Costs of Servicing Costs to provide the services discussed were estimated for each component and summed for each system. These estimates may be considered order of magnitude only for the purposes of project planning and are based on current and past market trends and rates. Construction costs typically increase 5 10% per year. Please note that this is not a guarantee of a price, tendered price, or actual costs. Market and bidding conditions may affect the accuracy of this budget. CBCL is not responsible for any variances from this amount.
5.5.1 Estimates of Probable Capital Costs Estimates of the probable capital costs for each component of each system were generated based on estimation of the quantities of typical components of each system and unit costs for components that are based on historical cost records. As these designs can be considered concept level, a contingency of 25 percent was added to account for items not considered in the estimate.
Estimates generated in this manner are presented in Table 5.5.1. Also shown in this table are the estimated costs on a per service basis for each system. These were generated by dividing the estimated capital costs by the number of services contributing. It is interesting to note the following: In the 2007 study, the central service systems considered servicing all existing development. All of the systems considered to service the proposed Core Area in this assessment are much less extensive than was considered in the original study so the overall costs as well as the per service costs are lower; Capital costs of the systems to service the high growth scenario are higher than the costs of the smaller systems; and The cost per service are smaller than the per service costs of the medium and low growth scenarios. The larger the number of services, typically the lower the per service costs.
5.5.2 Operating and Maintenance Costs Operating and maintenance costs for components of the systems are summarized as follows:
Table 5.5.2: Operating and Maintenance Costs Medium Development Scenario High Growth Low Growth Growth SecondaryWastewaterTreatment $ 135,000 $ 100,500 $ 92,500 Wastewater Collection 2nd $ 468,363 $ 249,115 $ 140,373 TertiaryWastewaterTreatment $ 152,000 $ 115,500 $ 104,500 Wastewater Collection 3rd $ 297,273 $ 169,104 $ 105,536
Stormwater $ 26,288 $ 26,288 $ 26,288
WaterSupply,Treatment&Transmission $ 538,462 $ 370,192 $ 222,115 WaterDistribution $ 35,565 $ 31,273 $ 27,579 Total with Secondary STP $ 1,203,678 $ 777,368 $ 508,856 Total with Tertiary STP $ 1,049,588 $ 712,357 $ 486,018
CBCL Limited Central Services 39 Service Cost/Ultimate $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ Service Cost/Existing 16,525 31,436 75,066 26,124 11,546 $ 2,433 48,854 $ $ $ 12,426 $ 5,184 $ 13,066 $ 23,667 14,043 940 $ 46,578 $ $ $ 4,584 $ $ 18,247 $ 32,016 9,451 $ 334 $ 446 $ 6,462 $ 2,563 495 $ 10,300 $ 1,582 $ $ 13,433 $ 11,144 $ 27,331 5,554 $ 15,854 $ 74,160 $ 71,883 $ $ $ $ $ (3) CapitalCost 147,271 58,058 103,081 107,459 35,577 7,496 150,532 $ $ $ $ 110,745 73,807 $ $ 109,366 97,352 $ 43,269 2,896 143,517 $ $ $ 40,851 $ 33,699 $ $ 43,965 38,876 $ $ 1,145 $ 1,527 22,137 $ 8,781 $ 1,697 35,287 $ $ 17,750 $ 16,999 $ 18,172 $ 27,331 19,028 $ 54,315 $ 243,722 $ 236,708 $ $ $ $ $ $ Ultimate Services Service 2 7,069,007 2,148,149 1,958,543 428 68 11,175,698 26 3,700,000 779,604 428 15,655,302 320 320 320 $ 5,315,764 $ 2,730,855 $ 2,077,945 $ 428 $ 527 10,124,564 159 4,500,000 $ 301,226 $ 428 14,925,791 320 320 320 $ 1,960,868 $ 1,246,876 835,328 $ $ 428 68 4,043,072 $ 26 $ $ 428 150,000 200,000 2,900,000 $ 449 1,150,262 $ 449 222,342 $ 449 4,622,604 $ 449 917,955 449 709,983 449 290,747 $ 573,958 $ 68 449 $ 26 2,492,643 $ 21 7,115,246 $ 26,813,621 $ 449 26,084,109 449 $ $ $ $ $ $ $ $ Cost/Ultimate Service 6,864 31,436 75,066 9,749 3,951 730 $ 15,225 $ $ $ 4,905 $ 5,059 $ 13,011 $ 8,231 4,863 252 $ 14,017 $ $ $ 1,378 $ 18,247 $ 32,016 $ 2,840 $ 121 $ 208 $ 2,492 $ 1,012 512 4,346 $ 562 $ $ 13,433 $ 11,144 $ 31,633 $ 1,859 6,205 $ $ 24,270 $ 23,062 $ $ $ $ $ Cost/Existing (3) 203,555 58,058 103,081 133,436 50,000 9,240 $ 192,675 $ $ $ 145,456 $ 72,026 $ 108,905 $ 112,654 61,538 3,190 $ 177,383 $ $ $ 40,851 $ 33,699 $ 43,965 $ 38,876 $ 1,336 $ 2,290 $ 27,481 $ 11,164 5,648 47,918 $ $ 20,311 $ 16,999 $ 18,172 $ 31,633 $ 20,500 68,418 $ $ 299,969 $ 284,676 $ $ $ $ $ CapitalCost Ultimate Services (5) Service Cost/Ultimate 82,148,149 9,770,637 1,958,543 68 1423 26 13,877,328 5,200,000 960,916 1423 1316 20,038,244 $ 1316 $ 1316 $ 6,981,895 2,664,953 $ 2,069,202 $ 1423 527 $ 159 11,716,051 $ 6,400,000 331,746 1423 1316 18,447,797 $ 1316 $ 1316 1,246,876 $ 835,328 1,960,868 $ 68 $ 1423 26 $ 4,043,072 $ 1423 175,000 $ 300,000 3,600,000$ $ 1444 1,462,469 1444 $ 739,842 1444 6,277,311 1444 917,955 1444 $ 812,443 1444 290,747 $ 664,296 68 $ 1444 26 $ 21 $ 2,685,442 8,962,753$ 33,044,069 1444 31,453,622 $ 1444 $ $ $ $ $ $ $ (4) Service 4,853 31,436 75,066 6,566 2,753 401 9,720 $ $ $ 3,514 $ $ 5,059 $ 13,011 5,489 $ 3,504 171 9,163 $ $ $ 818 $ $ 18,247 $ 32,016 $ 1,686 83 $ $ 165 $ 1,613 705 $ 515 3,081 $ 358 $ $ 13,433 $ 11,144 $ 33,855 $ 1,152 4,232 $ $ 15,639 $ 15,082 $ $ $ $ $ Cost/Existing (3) ihGot cnroMdu rwhSeai LowGrowth Scenario MediumGrowth Scenario HighGrowth Scenario 242,412 58,058 103,081 151,370 63,462 9,240 $ 224,071 $ $ $ 175,526 $ 72,026 $ 108,905 $ 126,533 80,769 3,932 $ 211,233 $ $ $ 40,851 $ 33,699 $ 43,965 $ 38,876 $ 1,527 $ 3,053 $ 29,771 $ 13,011 9,512 56,874 $ $ 21,634 $ 16,999 $ 18,172 $ 33,855 $ 21,260 78,134 $ $ 341,081 $ 328,243 $ $ $ $ $ CapitalCost Ultimate Services 0 376,600,000 2397 104 8,400,000 2397 104 Existing Services Component hs 829 11,635,799 2,148,149 1,958,543 2397 68 26 48 960,916 37 15,742,491 19 2397 2397 104 8,425,227 104 2,664,953 2397 2,069,202 527 48 159 408,900 23,303,407 Collectionand Laterals 37 13,159,382 Phase1 19 2397 2397 Phase2a 2397 Phase2b 104 104 1,960,868 TotalCollection 104 1,246,876 835,328 Treatment - Secondary 2397 Outfall 68 Sub- totalSanitary - Secondary 26 21,968,283 48 200,000 Collectionand Laterals 37 2397 4,043,072 Phase1 19 Phase2a 104 2418 2397 400,000 Phase2b TotalCollection 131 104 Treatment - Tertiary 2418 1,246,092 1,704,464 3,900,000 Outfall Sub- totalSanitary - Tertiary 865,355 131 2418 2418 917,955 2418 290,747 ClearwaterSewers and Laterals 710,948 131 131 2418 131 Phase1 68 Phase2a 26 40 Phase2b 21 7,450,556 Sub- totalStorm 54 16 2418 21 2,785,005 Wells 10,235,561 131 2418 WellPumps 2418 WaterTreatment 131 Transmission 131 Reservoir WaterSupply and Treatment Distribution andLaterals Phase1 Phase2a Phase2b Phase3 TotalDistribution Sub- totalWater (1) (2) Table5.5.1 Capital Costsof Central Servicing Sanitary Storm Water 37,582,040 36,246,916 TotalServicing Costs Secondary - STP TotalServicing Costs Tertiary - STP 5.5.3 Life Cycle Costing Analysis The available growth scenarios for Musquodoboit Harbour were subjected to a Life Cycle Cost Analysis (LCCA) using the program available from Service Nova Scotia and Municipal Relations web page dated October, 2007. Life Cycle Cost is the total discounted dollar cost of purchasing, owning, operating, and maintaining an asset over a period of time. Using the LCCA equation allows the breakdown of the proposed project into the following three variables: The pertinent costs of ownership; The period of time over which these costs are incurred; and The present value factor (PVF) that is applied to future costs to equate them with present day costs.
The program provides the interest rate to be used based on the available rate from the Municipal Finance Corporation as well as the inflation factor based on a five year running average. The length of time used for the analysis of the scenarios in Musquodoboit Harbour was selected at 75 years based on the recommended depreciation rate for major components from the NS Utility and Review Board Accounting and Reporting Handbook. The analysis included replacement of major electrical and pumping equipment at 25 years, water supply wells at 35 years and major structural improvements (25% of original cost) at 35 years for treatment plants and reservoirs. The estimated operating and maintenance costs were included in the analysis.
5.6 Sources of Funding Funding Sources for the Musquodoboit Harbour project were investigated from Canada Nova Scotia Infrastructure Secretariat (CNSIS) who administers the federal provincial agreements that provide funding to infrastructure projects in Nova Scotia. In 2007 the CNSIS administers the following programs: Building Canada Fund Communities Component; Building Canada Fund Communities Component Top Up; Building Canada Fund Major Infrastructure Component; Infrastructure Stimulus Fund; Municipal Rural Infrastructure Fund; Federal Gas Tax Fund; Federal Public Transit Fund; and Canada Nova Scotia Infrastructure Program.
Discussions with staff indicate that all programs are fully committed with the exception of Building Canada Fund Major Infrastructure Component and the Federal Gas Tax Fund. Based on discussions with staff it is understood that funds from the Major Infrastructure Component are primarily directed towards infrastructure that benefits the overall community. They noted that the proposed new Library in Halifax is being funded under this program. The Gas Tax funds are administered by the Municipalities and were intended for: Environmentally sustainable municipal infrastructure projects: community energy systems, public transit infrastructure, water infrastructure, wastewater infrastructure, solid waste, local roads and bridges, capacity building, and active transportation infrastructure; and
CBCL Limited Central Services 40 Public transit infrastructure projects: rapid transit infrastructure, rolling stock, intelligent transit systems, accessible transit, and related capital infrastructure
Funds under this program would have to be secured from HRM.
After all sources of funding have been secured the remaining capital costs can either be incorporated into the rate structure for the services provided or paid for separately by the users. The later is generally used as it does not place a burden on other users when the long term operation and maintenance is taken over by Halifax Water. The connection fee can be either a lump sum payment or it can be related to the frontage of the property. Both of these fee structures have been used by HRM in the past.
Based on the information assembled (2010) it appears that available funding from government is limited. However, this may change as the senior levels of government may initiate new programs in the future which could provide funding for Musquodoboit Harbour. Given this possibility and the level of funding available under previous programs three alternatives have been prepared for review as follows: Alternative 1 0 % funding from government (100% funding from those served by the systems); Alternative 2 66.7% % funding from government (33.3% funding from those served by the systems); and Alternative 3 80% % funding from government (20% funding from those served by the systems).
The summary of costs for each of the three Growth Scenarios with Secondary and Tertiary Wastewater Treatment options follows for each funding Alternative in Table 5.6.
CBCL Limited Central Services 41 Service NPV per per NPV $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ Net Present Present Net Value (NPV) Value 1,534 3,743 1,944 2,729 $ 248 $ 2,880 $ 281 $ 8,687 $ 8,083 $ $ 2,010 4,401 $ $ 2,494 3,436 $ 417 $ 3,589 $ 422 $ 10,839 $ 10,358 $ $ 5,233 10,350 $ $ 6,353 8,736 $ 1,388 $ 7,804 $ 1,223 $ 25,997 $ 25,503 $ $ $ $ ital ital Cost Total p Installed Estimated Ca 8,495,949 20,732,066 10,765,926 15,115,790 $ $ 1,371,376 $ 15,952,169 $ 1,557,844 $ 48,109,405 44,763,106 $ $ 6,609,047 $ 14,471,507 $ 8,200,026 11,299,318 $ $ 1,371,376 $ 11,802,078 $ 1,386,188 $ 35,640,196 34,058,986 $ $ $ 5,171,039 10,227,252 $ 6,277,710 8,632,449 $ $ 1,371,376 $ 7,711,638 $ 1,208,664 $ 25,689,969 25,201,836 $ $ $ $ Service NPV per per NPV 1,512,211 3,148,630 1,761,792 2,450,429 $ 808,717 $ 1,490,140 $ 557,068 $ 7,516,767 $ 7,068,146 $ $ 1,232,211 2,775,598 $ $ 1,346,359 2,181,757 $ 808,717 $ 1,255,489 $ 537,153 $ 6,609,167 $ 6,129,475 $ $ 895,943 2,235,255 $ $ 960,254 1,875,456 $ 808,717 $ 924,543 $ 498,587 $ 5,363,046 $ 5,067,558 $ $ $ $ Net Present Present Net Value (NPV) Value 1,725 4,141 2,167 3,039 350 $ $ 3,069 352 $ $ 9,637 $ 8,976 $ $ 2,272 4,992 $ $ 2,780 3,901 589 $ $ 3,857 536 $ $ 12,246 $ 11,663 $ $ 5,868 11,933 $ $ 7,033 10,064 $ 1,961 $ 8,459 $ 1,576 $ 29,796 $ 29,093 $ $ $ $ ital ital Cost Total p Installed Estimated Ca 9,554,497 22,936,107 11,999,180 16,831,090 $ $ 1,937,478 $ 16,995,267 $ 1,947,792 $ 53,371,141 49,710,808 $ $ 7,471,595 $ 16,414,426 $ 9,142,478 12,826,549 $ $ 1,937,478 $ 12,680,920 $ 1,762,195 $ 40,266,613 38,349,619 $ $ 5,798,200 $ 11,791,930 $ 6,949,887 9,945,268 $ $ 1,937,478 $ 8,358,818 $ 1,557,675 $ 29,444,101 28,749,127 $ $ $ $ Service NPV per per NPV 2,570,759 5,352,672 2,995,046 4,165,729 $ $ 1,374,819 2,533,237 $ 947,016 $ 12,778,503 $ 12,015,848 $ $ 2,094,759 4,718,516 $ $ 2,288,810 3,708,988 $ 1,374,819 $ 2,134,331 $ 913,159 $ 11,235,585 $ 10,420,107 $ $ 1,523,104 3,799,933 $ $ 1,632,432 3,188,276 $ 1,374,819 $ 1,571,723 $ 847,598 $ 9,117,177 $ 8,614,849 $ $ $ $ Net Present Present Net Value (NPV) Value 2,626 6,018 3,216 4,499 $ 832 $ 3,957 $ 684 $ 14,116 $ 13,188 $ $ 3,509 7,778 $ $ 4,132 6,090 $ 1,401 $ 5,117 $ 1,075 $ 18,879 $ 17,814 $ $ 8,859 19,397 $ $ 10,240 16,327 $ 4,661 $ 11,546 $ 3,241 $ 47,706 $ 46,016 $ $ $ $ %6%80% 66% 0% ital ital Cost Total p Installed Estimated Ca 14,544,794 33,326,587 17,813,094 24,917,504 $ $ 4,606,245 $ 21,912,728 $ 3,786,117 $ 78,176,471 73,035,688 $ $ 11,537,891 $ 25,573,899 $ 13,585,462 20,026,348 $ $ 4,606,245 $ 16,824,032 $ 3,534,798 $ 62,076,865 58,576,885 $ $ 8,754,813 $ 19,168,270 $ 10,118,726 16,134,274 $ $ 4,606,245 $ 11,409,810 $ 3,203,013 $ 47,142,151 45,472,068 $ $ $ $ Costs Annual Operating & Operating Maintenance 7,561,056 15,743,152 8,808,960 12,252,143 $ 4,043,586 $ 7,450,698 $ 2,785,341 $ 37,583,833 $ 35,340,728 $ $ 6,161,056 13,877,990 $ $ 6,731,795 10,908,787 $ 4,043,586 $ 6,277,443 $ 2,685,763 $ 33,045,837 $ 30,647,374 $ $ 4,479,717 11,176,273 $ $ 4,801,270 9,377,282 $ 4,043,586 $ 4,622,715 $ 2,492,936 $ 26,815,228 $ 25,337,790 $ $ $ $ Estimated Capital Cost Capital 135,000 468,363 152,000 297,273 26,288 $ $ 538,462 35,565 $ $ 1,203,678 $ 1,049,588 $ $ 100,500 249,115 $ $ 115,500 169,104 26,288 $ $ 370,192 31,273 $ $ 777,368 712,357 $ $ $ 92,500 140,373 $ $ 104,500 105,536 26,288 $ $ 222,115 27,579 $ $ 508,856 486,018 $ $ $ $ $ Total Installed Installed Total Cost Component Cost Table 5.6 Life Cycle Costs for Various Funding Alternatives Funding Various for Costs Cycle 5.6 Life Table 4,043,586 15,743,152 7,561,056 12,252,143 8,808,960 Funding External 2,785,341 Scenario Development Growth High Treatment Wastewater Secondary 2nd Collection Wastewater 37,583,833 35,340,728 Treatment Wastewater Tertiary 3rd Collection Wastewater 7,450,698 Stormwater Transmission & Treatment Supply, Water 4,043,586 13,877,990 Watermains Major 6,161,056 STP Secondary with Total 10,908,787 6,731,795 STP Tertiary with Total 2,685,763 Scenario Development Growth Medium Treatment Wastewater Secondary 2nd Collection Wastewater 33,045,837 30,647,374 Treatment Wastewater Tertiary 3rd Collection Wastewater 6,277,443 Stormwater Transmission & Treatment Supply, Water 4,043,586 11,176,273 Watermains Major 4,479,717 9,377,282 STP Secondary with Total 4,801,270 STP Tertiary with Total 2,492,936 Scenario Development Growth Low Treatment Wastewater Secondary 2nd Collection Wastewater 26,815,228 25,337,790 Treatment Wastewater Tertiary 3rd Collection Wastewater 4,622,715 Stormwater Transmission & Treatment Supply, Water Watermains Major STP Secondary with Total STP Tertiary with Total CHAPTER 6 SUMMARY OF ASSESSMENTS
6.1 TOR Issues The Terms of Reference for this study identified several issues that were to be addressed in the study. Investigations completed, their findings, assessment of the findings as well as recommendations to resolve each issue were presented in previous sections of the report. Following is a presentation and a brief description of recommended measures to address each issue, reference is made to the section where more detail can be obtained where appropriate.
Determine the assimilative capacity that could be made available by reducing inputs from known or suspected defective or malfunctioning wastewater collection and treatment systems: Existing water quality is such that there is little if any assimilative capacity in the receiving waters. Potential reductions in pollutant loads are defined by the level of pollutants generated by existing sources and sources that will exist in the proposed development as well the proposed level of treatment associated with the proposed development. Management of wastewater treatment and stormwater to a level that is higher than the minimum required will reduce potential pollutant loads to the receiving waters. These measures should reduce pollutant loads from existing development and reduce the loads typically generated from new development. This approach should improve existing water quality and make assimilative capacity available in the Musquodoboit River and Musquodoboit harbour as well as in the Little River and Petpeswick Inlet.
Define an optimum configuration for a small scale wastewater management system An optimum configuration for a small scale wastewater collection and treatment system is the one shown on Figure 5.1(b) and includes: A treatment plant located close to the Core Area with tertiary level of treatment and an outfall to the Musquodoboit River near Musquodoboit Harbour; and The conventional wastewater trunk sewers to collect wastewater from the proposed Core Area and adjacent areas considered for future development and discharge it to the treatment plant as the first phase. Future extensions to Phase 1 (Phases 2a, 2b and 3) would include servicing properties outside of the Core Area where there is a concern with malfunctioning on site wastewater treatment systems.
CBCL Limited Summary of Assessments 42 Determine the feasibility and cost of providing central water supply without other services As discussed in section 5.3.6, it is feasible to provide central water supply, treatment and transmission mains to a community serviced with on site wastewater treatment systems, provided: New developments are designed with low water use fixtures and appliances and existing properties are retrofitted in the same manner; and It is understood that the costs per service for distribution systems in the new sub divisions will be significantly larger than in areas serviced with central wastewater systems as a result of larger properties sizes required for on site wastewater treatment systems. Distribution system costs presented in the 2007 report were in the order of $27,000 per service to service the entire existing community with most properties smaller than currently required for on site wastewater treatment systems. The estimated probable costs of the water system components presented in Table 5.5.1 will generally be the same with or without the sanitary and storm systems shown in the table.
Confirm the suitability of the Musquodoboit River and Little River as potential supplies of raw water for a central water system Table 4.2.1(a) indicates that the 1 in 100 year 1 day low flow in the Musquodoboit River is less than 20 percent of the estimated maximum day demand for 7050 people, the population in the high growth scenario. The Musquodoboit River is considered able to supply the demand without input from the Little River. The Little River would not be able to satisfy the communitys water demands.
The treatment system presented in section 5.3.4 is able to treat the river water with the potential contaminants identified at the levels measured and produce potable water for the community.
Determine the impacts of possible contaminant sources on water taken from potential wells adjacent the Musquodoboit River Water from an existing well near the site where production wells to service the community would be located was removed and then samples taken and analysed for a range of possible contaminants typically generated from potential sources identified in the vicinity of the wells, as discussed in section 4.2.3. Concentrations of most of the potential contaminants were in ranges that are treatable, the exceptions were bromate and potential radionuclides.
Additional investigations of the potential outwash aquifer are recommended to confirm that measured raw water quality and quantity are sustainable as a supply for a central water treatment and distribution system. Additional investigations should be completed before proceeding with wells in the outwash aquifer.
Estimate future achievable population growth, density and distribution over a 5 to 10 year horizon in the community with on site services, central water only or central water and wastewater services, accounting for projected commercial development If development in Musquodoboit Harbor continues as it has in the past ten years the expected increase in population will be in the order of 240 additional people. As discussed in Section 3.1, a range of growth scenarios were considered where there might be 1100 to 1755 additional people.
CBCL Limited Summary of Assessments 43 To achieve a community centre with significant development within a 5to 10 minute walk to a central transit stop requires development within a radius of 500 to 1000 metres of the centre. Within this walking distance there would be 60 to 250 hectares of developable land. Potential areas were identified in Figure 3.3.
Minimum lot sizes for on site wastewater treatment systems define the largest lot size required. Table 3.2 indicates that with a development density of 4 persons/ hectare that might be achieved with on site wastewater treatment systems, the available area might accommodate the low growth scenario or 500 additional people in the community. A similar limitation is placed on development if only central water is provided as the lot size for on site wastewater treatment still dictates the achievable development density. A density of 40 people per hectare is required to achieve the high growth scenario of an additional 5050 people within a radius of 500 to 1000 metres of the centre of the community, all of the land identified as Options 1, 2, and 3a&b on Figure 3.3 would be required. To achieve a development density of 40 people per hectare, central wastewater, stormwater and water services are required.
Analyse existing water quality data for the Little River and assess potential pollutant sources As presented in section 4.1.1, the most likely sources of pollutants in the Little River and in the upper reaches of Petpeswick Inlets are: Effluent discharges from the Twin Oaks Wastewater treatment Facility, although it appears to meet its effluent discharge requirements. Effluent discharges are routinely monitored and the results are recorded; and Partially treated septic tank effluent from failing on site wastewater treatment systems, particularly during wet weather. The exact locations of the offending systems have not been determined; a sanitary survey would be required to identify these sources.
6.2 Proposed Water and Wastewater Systems There are two issues to consider with the provision of water and wastewater systems: Ultimate capacity, which growth scenario should be considered for the design of central services; and The initial capacity of the systems and the rate of growth that will provide for a reasonable level of development but does not require large capital expenditure in the initial stages of development.
Wastewater collection systems and water distribution systems are similar in size for the medium and high growth scenarios; it is recommended that these systems be designed to accommodate the high growth scenario, at a minimal cost premium. Mechanical components such as pumping stations should be sized to ultimately accommodate the high growth scenario but initially to accommodate the medium growth scenario.
Wastewater and water treatment systems should be designed in a modular fashion. Initially they should accommodate the medium growth scenario; ultimate capacity to service the high growth scenario may be provided by adding treatment units.
CBCL Limited Summary of Assessments 44 APPENDIX A Water Quality Sample Analysis Data
CBCL Limited Appendices Appendix A: Summary of Preliminary Water Quality Investigations 29 September 2009
Water quality samples were taken at seven sites throughout the community on Friday the 20th of August 2009, after an extended dry period, and on Monday the 24th of August 2009, the day after Hurricane Bill dumped between 60 and 70mm of rain on HRM. The objective was to better identify the probable location of potential water contaminations sources into Petpeswick Inlet and Musquodoboit River. Sampling results are shown in Table A.1.
Table 1: Water quality sampling results August 2009 Petpeswick Inlet watershed Musquodoboit River Site STP1234567
description UTM E 487491 486983 487627 487644 487674 487393 488166 489020 UTM N 4958807 4958934 4958520 4958488 4958183 4960595 4960062 4959600
20 Aug 2009 - Dry weather Time 09:00 09:55 09:15 09:20 11:45 10:10 11:00 11:30 Temperature deg C 25.1 25.7 24 Total Coliforms (MPN) CFU/100 mL 12997 >4838 >4838 >4838 NA 651 429 922 E. Coli (MPN) CFU/100 mL 10 24 30 22 131 13 17 46 Fecal Coliform CFU/100 mL 15100 14 36 50 480 18 26 50
Total Phosphorus mg/L 7.92 0.011 0.012 0.015 0.03 0.025 0.019 0.017
BOD mg/L 10 <2 <2 <2 <2 <2 <2 <2 TSS mg/L 9 <5 <5 <5 13 <5 <5 <5 pH 7.1 5.7 6 6 7.7 7.3 7.3 7.3 TKN as N mg/L 7.1 1.2 1.5 1.2 1.1 0.9 1 0.8 Ammonia as N mg/L 3.01 <0.05 <0.05 <0.05 <0.05 0.05 <0.05 <0.05 Nitrate + Nitrite as N mg/L 8.6 0.19 <0.05 <0.05 <0.05 <0.05 <0.05 0.23 Total Nitrogen mg/L 15.5 1.4 1.5 1.2 1.1 0.9 1 1
24 Aug 2009 - Wet weather, after Hurricane Bill Time 11:55 12:05 12:07 13:10 11:10 11:30 11:40 Temperature deg C 21.8 21 22.9 Total Coliforms (MPN) CFU/100 mL 922 >4838 >4838 NA 2407 4838 >4838 E. Coli (MPN) CFU/100 mL 35 102 96 345 115 131 150 Fecal Coliform CFU/100 mL 86 226 296 present 224 844 484
Total Phosphorus mg/L 0.023 0.02 0.016 0.034 0.021 0.016 0.024
BOD mg/L <2 <2 <2 <2 <2 <2 <2 TSS mg/L <5 <5 7 <5 <5 <5 <5 pH 5.7 6 6.2 7.3 7.1 7.1 7.2 TKN as N mg/L 1.3 1.2 1.2 1.2 0.9 0.9 1.4 Ammonia as N mg/L <0.05 0.08 <0.05 <0.05 0.05 <0.05 <0.05 Nitrate + Nitrite as N mg/L <0.05 0.19 <0.05 <0.05 0.21 <0.05 <0.05 Total Nitrogen mg/L 1.3 1.4 1.2 1.2 1.1 0.9 1.4 Petpeswick Inlet Watershed One of the main objectives of these preliminary analyses was to investigate whether effluent from the Twin Oaks Sewage Treatment Plant (STP) represents a contamination source for Little River and Petpeswick Inlet.
Past Data In 2006 during the initial study, FC counts of 2500 and 680 FC/100ml was detected in Little River approximately 20m upstream of the outfall, at site #2 listed in Table 1. The exact location of the outfall was pointed by Len VanTol of HRM on 20th August 2009. The contamination in Little River observed in September 2006 cannot have been from the STP.
Len VanTol also provided effluent sampling data for the year 2008. The maximum FC count observed was over 8,000 FC/100ml on one occasion. All other results were less than 500 FC/100ml, 75% being less than 10 FC/100ml (table 2).
Table A.2: STP Effluent Sampling Results Year 2008 FC/100ml Number of Samples 0 10 45 10 100 6 100 200 4 200 500 4 >500 1(at8,640/100ml) Total 60(5samples/month)
Additional bacterial sampling results for the summer of 2009 at the beach in Petpeswick Inlet were obtained from Marlo McKay of HRM. The peaks observed by HRM were consistent with the values from Table 1, the highest counts being observed at the end of August 2009. During most of July and the first half of August the E Coli counts were below 200/100ml. The bacterial contamination problem at the head of the inlet appears intermittent in nature.
Table A.3 HRM Summer 2009 Sampling Results at Petpeswick Inlet Beach E Coli #/100ml Number of Samples 0 10 6 10 100 1 100 200 2 200 400 1 Total 10
August 2009 Sampling Results On the dry day (24th August 2009) the FC count for the STP effluent was 15,000 FC/100ml, which happens to be higher than the 2008 maximum sampled. Yet there was no detectable effect in the water quality immediately downstream of the outfall (<50 FC/100ml in the river, most of it being detected upstream already). The most likely reason for the apparent discrepancy is that the STP discharges its effluent intermittently, so the river sample would have missed the discharge.
At the beach, on the dry day the bacterial count was 480 FC/100ml. On the wet day the E Coli count is 345 /100ml, and the FC count would have been much higher (the lab reported that the bacterial growth for that sample was too rapid to produce an accurate number). To better quantify the necessary bacterial loadings that would produce such values, the hydrodynamic model developed for the initial study was revisited for the present assessment, with a higher resolution at the head of Petpeswick Inlet. Modelling indicates that to get a concentration range of 200 400 FC/100ml at the beach, an estimated loading of 6M FC/sec is necessary at the head of the estuary.
With a STP average flow of 12,000 Igpd (0.63 L/s) even at a 15,000 FC/100ml concentration, the loading into the estuary is only about 95,000 FC/sec, which would produce a concentration of less than 6 FC/100ml at the beach, much less than what was observed on both occasions. The STP loadings alone cannot account for the intermittent bacterial contamination observed at the head of Petpeswick Inlet.
Therefore, there are other intermittent bacterial loading sources into Petpeswick Inlet that are likely more important than the STP. Some of the additional loadings are related to runoff, as evidenced by the higher counts in the Little River after the storm.
Musquodoboit River Watershed Bacterial counts were below 50 FC/100ml at the three sites on the dry weather sampling day, and peaked to over 800 at the trail bridge on the day following the storm. This indicates contamination related to runoff, which would probably also include sources upstream of the community (the count at the new bridge on 24 August was 224 FC/100ml).
Site 1: Little River Site 2: Little River Upstream of STP Outfall
Site 3: Little River Downstream of STP Outfall Site 4: Public Beach on Petpeswick Inlet
Site 5: Musquodoboit River New Bridge on Upstream of Community Site 6: Musquodoboit River Site 7 Musquodoboit River Downstream OldRailwayBridgeonPublicTrail ofHW7Bridge Table A.4: Reproduction of Table 3 Water Quality Sampling Results 2006 Study Musquodoboit Harbour Petpeswick Inlet site 1 1B 2 2B 3 3B 4 4B
description UTM E 492964 491382 488945 489639 486898 488030 487728 488271 UTM N 4951655 4945570 4959754 4959845 4950943 4954376 4958570 4957932
25 Sep 2006 - Dry weather, 25 km/h west winds. Time 15:10 15:40 15:55 16:05 16:30 16:50 17:20 17:05 Tide condition ebb ebb ebb ebb low low flood low Offshore tide level, m CD 0.55 0.45 0.41 0.39 0.35 0.34 0.37 0.35 Water depth at site, m 2 0.5 0.5 1 2 1.5 0.3 0.2 Salinity (surface), ppt 26.6 22.7 0.1 17.7 27.1 26.9 0 North 17.8 Salinity (bottom), ppt 27.4 22.7 0.1 21 27.3 27 0 South 21.4 Temperature, C 16.8 18.1 17.9 17.5 17 17.8 18.2 19.5 DO, mg/L 9.4 10.3 8.7 9.5 8.7 pH 5.8 6.1 6.2 6.3 BOD5, mg/L <5 <5 <5 <5 TP, mg/L 0.087 0.034 0.1 <0.004 TN, mg/L <0.5 0.24 <0.5 0.18 FC, MPN/100ml 170 610 30 2500 E-Coli, MPN/100ml 5 62 3 67
13 Oct 2006 - Following 44mm rainfall the day before. Calm conditions, no wind. Time 08:00 08:30 08:45 10:30 09:00 10:10 09:55 Tide condition low flood flood flood flood flood flood Offshore tide level, m CD 0.60 0.65 0.70 1.10 0.75 1.00 0.90 Water depth at site, m 2 0.5 0.5 1 2 0.3 0.2 Salinity (surface), ppt 26.5 26.3 0.1 4.4 27 0 26.3 Salinity (bottom), ppt 26.8 0 25 27.3 Temperature, C 14.1 13.8 14.2 14.4 14.6 DO, mg/L 6.04 6.59 5.55 6.05 pH 8.01 7.5 7.96 6.04 BOD5, mg/L <2 <2 <2 <2 TP, mg/L 0.017 <0.002 0.049 0.003 TN, mg/L 0.15 0.2 FC, MPN/100ml 310 120 7 680 E-Coli, MPN/100ml 190 61 6 510