Appendix D. Stormwater Pollution Prevention Plan

Transcription

1 Appendix D

2 Memorandum AECOM 3292 Production Way, Floor tel Burnaby, BC, Canada V5A 4R fax To Joan Liu, Metro Vancouver Page 1 CC Subject Conveyance for the NSWWTP From Michael Celli, AECOM Brent Start, AECOM Date April 12, 2017 Project Number Introduction Metro Vancouver is currently undertaking a program to upgrade wastewater treatment in the North Shore area by constructing a new secondary treatment plant, the North Shore Wastewater Treatment Plant (NSWWTP) and decomissiong the existing Lions Gate Wastewater Treatment Plant. As part of this program, the Conveyance for the NSWWTP project is in design to collect flow from the Hollyburn Interceptor (HI) and pump the flow to the new NSWWTP. As part of the project, conveyance of treated effluent will the NSWWTP to the existing outfall is also provided. Metro Vancouver has engaged AECOM Canada Ltd. (AECOM) to prepare the indicative design for the new NSWWTP Conveyance System including a pump station, Hollyburn Extension, forcemain and Effluent sewer. The intent is to procure the improvements through a design-build process. A portion of the project will be located on land under the Vancouver Fraser Port Authority jurisdiction including the pump station, Hollyburn Extension, Forcemain, and Effluent sewer. This draft Stormwater Pollution Prevention (SWPP) Plan has been prepared by AECOM for the port authority to satisfy the requirements of the proposed Project and Environmental Review Process, and the project specific submission requirements dated January 20, The draft SWPP plan is designed to provide guidance for appropriate stormwater management and pollution protection for the proposed project and for ongoing operations. The design-build contractor will be responsible for finalizing the SWPP Plan prior to construction once both the detailed design and the construction plan for the proposed project are finalized. 2. Overview 2.1 Background The Greater Vancouver Sewage and Drainage District is currently undertaking a project to design and construct a new treatment facility, the North Shore Wastewater Treatment Plant (NSWWTP), which will replace the existing Lions Gate Wastewater Treatment Plant. The existing Lions Gate

3 Page 2 Wastewater Plant will be decommissioned after the new NSWWTP is commissioned with the exception of the existing outfall system which will remain in service. The new NSWWTP will be located some 2000 m to the east of the existing plant at Philip Avenue and West 1st Street in the District of North Vancouver. Flow from the Hollyburn Interceptor currently flowing into the existing Lions Gate Wastewater Treatment Plant will be diverted to the new NSWWTP and treated effluent from the new NSWWTP will flow back to the existing outfall for discharge into Burrard Inlet. As such, the new 1200 mm Hollyburn Extension sewer, pump station, and 900 mm Forcemain are required to convey flow from the Hollyburn Interceptor at the existing treatment plant to the new NSWWTP. A new 2100 mm Effluent sewer will convey treated effluent from the new NSWWTP to the existing outfall. The Greater Vancouver Sewage and Drainage District has engaged AECOM Canada Ltd. to prepare indicative design for the conveyance system. The improvements will be procured through a design-build process. 2.2 Project Location The pump station and adjacent conveyance piping is proposed to be located underneath the Lions Gate Bridge, near the southern tip of the existing wastewater treatment plant. The proposed project location is illustrated in Figure 1 and Figure 2. Figure 1. Project Location Pump Station Site

4 Page 3 Figure 2. Project Location in Relation to VFPA Boundary 3. Site Inventory 3.1 Construction and Operations Activities Activities on the project site related to operations and maintenance and construction include: Operational Activities Operation of centrifugal pumps, VFDs, HVAC equipment, and odour control carbon scrubber. Operation of standby power genset during power outages. Periodic exercise of standby power genset once per month. Periodic visits to site by operations and maintenance staff once per week. Maintenance and replacement of equipment as needed. Construction Activities Underground piping installation by both trenched and trenchless methods Excavation shoring, likely by secant piling Deep excavation 13 m from finished grade Excavation dewatering

5 Page 4 Concrete formwork, rebar tying, and pouring Backfill and grading Construction of buildings Mechanical and electrical installation Landscaping 3.2 Identification of Materials Materials and potential pollutants associated with construction and operational activities include: Diesel and gasoline petroleum fuels from equipment re-fueling and storage Hydraulic and lubricating oils for mechanical equipment Particulates from dust, combustion, construction debris, and soil erosion Aggregate and fill material required for construction Wood and steel construction material Uncured concrete and concrete wash water Trash and solid waste Contaminated soils if present to be disposed off-site Groundwater with potential quality issues (e.g. salinity, contamination, etc.) Raw sewage Dust from activated carbon used as odour control media Treated effluent from the NSWWTP 3.3 Hydrologic Assessment Sub-catchment Areas The project site consists of three sub-catchment areas described as follows: Area A: Area B: Bridge Road extension from CN rail tracks to the pumping station site. The majority of this area is outside of the port authority property. The roadway will be constructed of gravel and cross sloped towards the land underneath the Lions Gate Bridge where runoff from the bridge is currently discharged. The land under the bridge is a mixture of gravel and some natural vegetation. Runoff from the roadway in Area A is of low volume and is expected to infiltrate in the area under the bridge with some flow running overland to the undeveloped area to the east. Project site, including pumping station building, roadway around the pumping station, and landscaped area. All stormwater will be collected on site and infiltrated to the ground.

6 Page 5 Area C: Roadway and turnaround for firetrucks. This roadway is also constructed of gravel. This area is crowned with runoff flowing off the roadway to its perimeter. The runoff will be discharged to the vegetated area around the roadway, where it will infiltrate with some flow running overland to the beach and riprap wall constructed around the bridge pier. These areas are illustrated in Figure Storm Drainage Event The storm drainage event chosen for the analysis of the project site is based on a design rainfall intensity with a 10-year return period. The analysis is based on an intensity-duration-frequency equation for the City of Vancouver (CoV 2014 IDF Curve - Dwg. No. S-4.1). Figure 4. IDF Curve Intensity - Duration - Frequency 100 Intensity (mm/hr) year (2014) Duration (hours)

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8 Page 6 Table 1: Sub-catchment Characteristics (10-year event) Catchment Area (Ha) Time of Concentration (min) Intensity (mm/hr) Runoff Coefficient Q 10 (2050) (m 3 /s) A B C Water Quality Event The Urban Stormwater Guidelines and Best Management Practices for Protection of Fish and Fish Habitat (DFO 2001) outlines criteria for meeting water quality objectives shown in Table 2 below. In the Metro Vancouver document Stormwater Source Control Design Guidelines 2012, the same criteria were used for the development of the design guidelines for stormwater management. Table 2: DFO Stormwater Guidelines Objective Volume Reduction Water Quality Detention or Rate Control Target Retain the 6-month/24-hour post-development volume from impervious areas on-site and infiltrate to ground. If infiltration is not possible, the rateof-discharge from volume reduction Best Management Practices (BMPs) will be equal to the calculated release rate of an infiltration system. Collect and treat the volume of the 24-hour precipitation event equalling 90% of the total rainfall from impervious areas with suitable BMPs. Reduce post-development flows (volume, shape and peak instantaneous rates) to pre-development levels for the 6-month/24-hour, 2-year/24-hour, and 5-year/24-hour precipitation events. Runoff from the roadways (areas A and C) will be infiltrated on site in the nearby greenspace and gravel areas. The roadways are also constructed of gravel and therefore will infiltrate some stormwater in place. Runoff from area B will be containted and infiltrated on site using semipermeable materials and swales. Therefore, any risk of off-site pollution from stormwater run-off caused by activities on site (e.g. re-fueling of the genset) is mitigated. As such, the guidelines described above are met in the project design. 4. Issues Identification and Risk Analysis 4.1 Applicable Standards, Acts and Regulations At a minimum, the DB Contractor is to comply with the legislation detailed in Table 3.

9 Page 7 Table 3: Applicable Legislation & Guidelines Legislation & Guidelines Authority Subject Fisheries Act Fisheries and Oceans Canada Requirements regarding release of harmful substances to fish bearing waters. Canada Shipping Act Transport Canada Requirements regarding release of pollutants to the marine environment. Canadian Environmental Protection Act Environment and Climate Change Canada Requirements regarding the management of harmful substances, including the Storage Tanks Systems Petroleum Products and Allied Petroleum Product Storage Tanks Regulations. Canadian Council of Ministers of the Environment (CCME) Water Quality Guidelines Ambient Water Quality Objectives for Burrard Inlet British Columbia Approved Water Quality Guidelines: Aquatic Life, Wildlife & Agriculture Metro Vancouver Design Standards CCME BC Ministry of Environment BC Ministry of Environment Metro Vancouver Guidelines regarding water quality for the protection of aquatic life and other uses. Requirements Pursuant to Section 2(e) of the BC Environmental Management Act to protect aquatic life, wildlife and primary-contact recreation. Generic guidelines regarding water quality for the protection of aquatic life and other uses. Design standards for civil infrastructure. Included in the legislation listed in Table 3 are guidelines and BMPs arising from the listed Acts and Regulations including, to the extent possible, the Federal DFO Urban Stormwater Guidelines and Best Management Practices for Protection of Fish and Fish Habitat, and the CCME Environmental Code of Practice for Aboveground and Underground Storage Tank Systems Containing Petroleum and Allied Petroleum Products. 4.2 Potential Pollutant Sources Potential pollutant sources associated with the activities that occur on the Site include: Leaking containers, fuel tanks, and refueling nozzles that can release diesel fuel Combustion of petroleum fuels by the genset, releasing Polycyclic Aromatic Hydrocarbons (PAHs) Carbon used for the odour control system Operation and maintenance of machinery that has the potential to release hydraulic and lubricating oils Dust, combustion particles, fine construction debris, carbon media dust, and soil erosion that will result in the accumulation of particulates on the Site Aggregate and fill stockpiles that could result in mobilization of particulates Collection, storage, and removal of solid waste, which could result in trash being spilled onto the ground Raw sewage spills from operational upsets. Leaking of raw sewage to the site when performing maintenance on equipment

10 Page 8 These potential pollutant sources have been taken into account in the development of this SWPP Plan. 4.3 Potential Sensitive Receptors The pump station is situated on the north shore of the Burrard Inlet underneath the Lions Gate Bridge. The site is adjacent to Squamish Nation (SN) approximately 500 m to the north of the project site. Sensitive receptors are labelled in Table 4. Table 4: Sensitive Receptors Receptor UTM E (m) UTM N (m) Distance from Project Site Nearest Residence (SFN) m Ambleside Park m Capilano Reserve Park m Park Royale Mall m Burrard Inlet is a marine environment that is considered to be a sensitive habitat area supporting marine birds, fish, and marine mammals. Recently, the entire near-shore marine waters of British Columbia, to a distance of 3 nautical miles from shore and including Burrard Inlet, have been designated under the Species at Risk Act (SARA) as potential critical habitat for transient killer whales (DFO 2016). It is currently unclear, however, whether the identified attributes related to critical biophysical features of killer whale habitat are present in Burrard Inlet, which means that specific designation of Burrard Inlet or the proposed Project area as critical habitat under SARA is uncertain. Design features in this project mitigate any risk of impacts to sensitive receptors described above. The design features, level of risk, and mitigative measures are described in the following subsections. 4.4 Identified Issues Table 5 outlines the risk matrix for potential stormwater effects as taken from the port authority guideline document. This table will act as a point of reference for quantifying risk related to stormwater events.

11 Page 9 Table 5: Risk Matrix of Potential Stormwater Effects Environmental Risk of Stormwater Effects Likelihood of Occurrence Risk Assessment Matrix: Certain (4) Likely (3) Unlikely (2) Negligible (1) Negligible (1) Low (2) Medium (3) High (4) Environmental Consequence 1 NEGLIGIBLE 2 to 4 LOW 6 to 9 MEDIUM 12 to 16 HIGH Notes: Negligible risks, if realized, potentially impact the environment over short durations, in a limited geographical area, and are fully reversible even with no remediation. Low and medium risks are intermediate along a gradation between negligible and high risk events. High risk events can impact the environment over wide geographic areas, are often irreversible even with remediation, and can accumulate over time. Stormwater has the potential to mobilize contaminants, resulting in pollution of nearby environments. Potential issues related to construction, operation and maintenance activities at the pump station site include the following: Hard surfaces required for parking areas, storage areas, and roadways will continually accumulate toxic substances over time, primarily from operation of vehicles. Pollutants include PAHs, metals, particulates, trash, fuel oil, and lubricating oil. The probability that these substances will be mobilized during precipitation events is certain: the highest pollutant concentrations will occur during the first flush of a precipitation event, particularly after a dry period, and will decline to relatively low levels as precipitation continues. The release of pollutants can be mitigated, but not eliminated, through good housekeeping measures. Runoff from the pump station will be containted and infiltrated on site using semi-permeable materials and swales. Runoff from roadways is directed to the vegetated areas for infiltration. The environmental risk is therefore low with mitigation (Table 5). Fuel storage areas have the potential to leak if not properly maintained. Further, fuel could be spilled during a refueling operation. If these materials were to enter Burrard Inlet, the environmental consequences could be high in the local environment including direct mortality to marine organisms from toxic materials and fouling of the environment from fuels and oils. Storage areas will be clearly marked and will include containment and best management measures consistent with applicable legislation and guidelines. All storage tanks are registered with Environment Canada and operations activity adheres to requirements of the Petroleum Products and Allied Petroleum Products Storage Tank Systems Regulations and the CCME Environmental Code of Practice for Aboveground and Underground Storage Tank Systems Containing Petroleum and Allied Petroleum Products. In the unlikely event of a spill, proper spill containment measures will be followed to mitigate off-site migration of fuel. Storage areas and structures will also be constructed to ensure that stored hazardous materials are not directly exposed to the weather, and that stormwater is directed away from storage structures and areas. The environmental risk is therefore assessed as low with mitigation (Table 5).

12 Page 10 Erosion of disturbed soils during excavation, and stockpiling of disturbed soils and aggregate fill during construction have the potential to release particulates. These have the potential to smother benthic organisms in areas close to the outfalls into Burrard Inlet. BMPs will protect soil and aggregate stockpiles and disturbed soils to ensure that to the extent possible, they do not release particulate materials. It is therefore unlikely that large quantities of particulate materials will be mobilized during precipitation events. Refer to the Construction Environmental Management Plan for more details on sediment control and mitigation during construction. The environmental risk is therefore assessed as low with mitigation (Table 5). Collection, storage, and removal of solid waste and construction debris have the potential to release trash and construction waste. Good housekeeping practices will largely eliminate release of these materials such that is will be unlikely that these materials will enter any off-site runoff. With proper management of the Site, it is anticipated that the environmental consequences of this source of pollution on the marine environment will be negligible. The environmental risk is therefore assessed as low with mitigation (Table 5). The pumping station receives domestic wastewater and pumps it to the NSWWTP. There is risk of sewage spill from this operation, which could lead to off-site release of raw sewage. The system includes a back-up genset that provides continuity of operation during power failure. There is a pumped bypass that discharges directly to the outfall in case the NSWWTP is unable to receive flow. Therefore, the environmental risk of contaminating off-site run-off with sewage from a pump station failure is low with mitigation through provision of redundancy (Table 5). Sewage handling equipment (pumps, valves, pipes, etc.) will be serviced at the pumping station in a water-tight building and taken off-site for service. There is risk that sewage could leak from equipment when it is being removed for service and transported. This could lead to small leaks of raw wastewater on the site. This risk is mitigated by cleaning the equipment on-site with potable water before removing the equipment. Therefore, the environmental risk of contaminating offsite run-off with sewage from maintenance activities is low with mitigation (Table 5). 4.5 Identified Pollutant Pathways The primary pathway for pollutants to move off-site is from the roadway (Area A) and the turn-around (Area C). These areas discharge run-off directly to the adjacent gravel and vegetated area for infiltration. Run-off from the pumping station site (Area B) infiltrates to the ground. Therefore, there is low risk for pollutants to impact nearby sensitive receptors Management Strategy Stormwater is not considered wastewater unless it becomes contaminated from interaction with pollutants. To avoid contamination of stormwater, a twofold stormwater pollution management strategy has been implemented for ongoing operations and will be implemented for construction: 1) Implement BMPs that target the sources of potential pollutants identified in Section 4, and 2) Design water management components to divert stormwater away from areas that could be potential sources of contamination.

13 Page 11 The objectives are to prevent accidental release of pollutants, contain any erosion or spills that do occur, and reduce the use of potential pollutants to the extent possible Construction Stormwater Management During construction, stormwater will be managed according to the measures listed below and all applicable legislation. An Erosion and Sediment Control Plan will be developed by the design-builder to control erosion and manage soil stockpiles on the Site. The Construction Environmental Management Plan (CEMP) will also include measures to manage stormwater and minimize the release of sediment laden water into Burrard Inlet. Mitigation and Management Measures The following BMPs will be applied. All drainage and stormwater flows in and around works sites will be managed to minimize contact of stormwater with pollutants. Physical barriers will be placed to prevent unrestricted passage of stormwater flows from the work sites to marine environments, including concrete walls, silt curtains, booms, and straw bales as appropriate. Flow-velocity controls will be instituted, such as sumps, baffles, and other containment measures. Stormwater flows from construction work sites will be regularly monitored to determine water quality and flow volumes. All fuel will be located inside the pump station above the FCL and secured such that it will not be impacted by flooding and spills would be maintained inside of the pump station. Spill containment measures will be followed in the unlikely event of a spill during a refueling operation. Carbon used for the odour control system will also be stored inside the pump station above the FCL and secured such that it will not be impacted by flooding. Plan Development and Further Measures During the final engineering design, and prior to construction, the design builder will finalize the Draft SWPP Plan, including undertaking the following: Inventory all areas and facilities likely to produce contaminated stormwater, and review measures to avoid or reduce transport of contaminants off Site Evaluate the need for settling ponds or settling screens to manage stormwater on the Site Evaluate the need for additional drains and sumps for stormwater capture and diversion Identify opportunities for stormwater diversion around construction areas to avoid stormwater contamination Identify opportunities to use clean stormwater on the Site, maximizing use during dry periods (e.g., dust suppression)

14 Page Implementation and Monitoring 6.1 Construction Phase The design-builder will identify an operational SWPP Plan Manager who will be responsible for the implementation of this plan. The SWPP Plan Manager will be a qualified professional and will possess the knowledge and skills to assess conditions and activities that could affect stormwater quality at the Site, and who can also evaluate the effectiveness of BMPs. Regular site inspections will be conducted to confirm that stormwater BMPs outlined in this plan are being implemented effectively. If required, stormwater will be sampled and analyzed to identify any possible concerns related to the quality of stormwater discharged to the marine environment. The SWPP Plan Manager will conduct regular inspections of all areas of the site where materials are stored or activities are conducted that have potential to contaminate stormwater, including: aggregate or soil storage areas, construction areas, chemical and fuel storage areas, areas where vehicle or equipment maintenance takes place, and waste disposal areas. During construction these inspections would be weekly, with monthly inspections during regular operations. The SWPP Plan Manager will monitor local weather reports for upcoming storm events and conduct inspections during a period when a stormwater discharge is occurring. The discharge water will be inspected for the presence of odor, foam, discoloration, sediment and/or an oily sheen. If stormwater is found to be affected, contaminant sources will be investigated and appropriate mitigating action will be undertaken. These efforts will ensure that stormwater is in compliance with regulatory requirements. Regular and storm event SWPP Plan inspections will be documented. Reports will include weather at the time of the inspection, the identification of all implemented BMPs, and stormwater characteristics. Also included will be the effectiveness of the management plan, a list of any required repairs and maintenance of existing infrastructure, any proposed new BMPs, a list of the personnel responsible for BMP maintenance or installation, and a timeline for completion of the prescribed maintenance or installation. All operational and construction Site staff will be trained on the SWPP Plan at orientation and annually. The training will clearly indicate that it is the responsibility of all staff to recognize potential adverse effects on stormwater, and to report to the SWPP Plan Manager. 6.2 Operation Phase Metro Vancouver operations and maintenance staff will regularly inspect the pumping station to ensure that equipment is functioning as designed. Metro Vancouver staff are expected to visit the pumping station once per week and review of the pump station condition is part of their normal activities on site. 7. References City of Vancouver, 2014 IDF Curve - Drawing. No. S-4.1, 2016