AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT PROJECT FILE EXECUTIVE SUMMARY

Transcription

1 AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT PROJECT FILE EXECUTIVE SUMMARY Prepared for: City of Toronto Prepared by: Stantec Consulting Ltd.

2 1.0 BACKGROUND, PURPOSE AND OBJECTIVES On August 19, 2005, the City received a record amount of rainfall that resulted in widespread surface and basement flooding. The majority of basement flooding occurred north of Highway 401, where over 4,200 basement flooding complaints were reported. As a result, the City approved a Basement Flooding Work Plan requiring a comprehensive engineering review be undertaken to address chronic basement flooding problems in over 30 separate study areas located across the City. The subject area in this study is identified as Area 19 in the Work Plan. The objectives of this study are to assess the existing major and minor stormwater systems as well as the sanitary system to identify the potential causes of basement and surface flooding, and to identify solutions that meet the elevated level of service criteria approved in the City s 2006 Work Plan to reduce the risk of future flooding. Based upon the Work Plan, the basement flooding protection level has been set to the equivalent of the May 12, 2000 storm event for the sanitary system, and the 100-year design storm, where feasible, for the storm minor and major systems. In addition, the study will address stormwater runoff quality and develop solutions to reduce the adverse effects of stormwater entering watercourses in the study area, in order to help meet long-term water quality objectives of the City s Wet Weather Flow Management Master Plan (WWFMP). 2.0 STUDY AREA CHARACTERISTICS Study Area 19 is located in the central portion of the City and covers part of Wards 15 and 16 completely within North York District. The area is bisected by Sheppard Avenue and Bathurst Street, and is roughly bounded by Highway 401 to the south, Finch Avenue to the north, Dufferin Street/Allen Road to the west, and the West Don River to the east, and covers an area of approximately 836 hectares (see Figure ES.1). There are approximately 7,056 properties representing a population of 26,110 within Study Area 19. The predominant land use in the study area is residential, comprising approximately 50% of the overall land coverage. There is also a significant institutional presence (~14%) and some limited commercial and industrial presence (~5%). Road right-of-ways file\30dayreview\rpt_a19_executivesummary_projectfile.docx 2.1

3 Figure ES-1 Study Area 19 file\30dayreview\rpt_a19_executivesummary_projectfile.docx 2.2

4 make up a large percentage of the overall area (>25%) due to the presence of the Highway 401, the Allen Road, and associated on-ramps in the southern portion of the Study Area. Development of the area occurred mainly in the 1950s and 1960s with no significant development having been implemented since Growth is projected in the Downsview Area Secondary Plan (DASP) along with intensification along the arterial roads of Sheppard Avenue, Wilson Avenue, Bathurst Street, and Wilson Heights Avenue. Similar to other areas in the former City of North York, a separate drainage system was constructed. The sanitary sewer network, with a total length of approximately 88 km, collects flows from several sub-trunks which discharge easterly to the West Don Trunk Sewer, which ultimately discharges to the Ashbridges Bay Wastewater Treatment Plant. Stormwater is collected from 22 separate sewersheds and flows into the storm sewer systems having a total length of over 116 km, with the majority discharging into the West Don River watercourse. The southwestern portion of the study area drains via Area 16 to the Black Creek watershed. 2.1 EXISTING CONDITIONS Since the development of the area, basement flooding has occurred periodically in response to extreme storms throughout the years, including the major events of August 1986, May 2000, July 2002, August 2005, and more recently in July Field investigation and inspection were conducted to identify the specific characteristics of the study area and its drainage systems. A review was also undertaken of the existing natural and socio-economic environments, as well as a review of available data sources and any previous studies. Hydrologic-hydraulic simulation models of the sanitary system and the storm major and minor systems were developed. The models were used as a tool to assess the hydraulic performance of the existing drainage systems, to identify their current performance level, determine probable causes of deficiencies, and to develop the potential remedial measures for the basement and surface flooding issues in the study area. Annual runoff water quality simulations were also performed for storm outfalls to gauge the pollutant reduction potential with implementation of source, conveyance and end-of-pipe control measures in the area (excluding the area tributary to the recently constructed Earl Bales Park file\30dayreview\rpt_a19_executivesummary_projectfile.docx 2.3

5 stormwater management pond facility that was evaluated in a separate 2006 EA). Based on the analysis completed, it was determined that the sanitary and storm drainage systems generally have the hydraulic capacity to convey peak flows resulting from everyday rainfall events (less than the 5-year event). 3.0 STUDY PROCESS AND CONSULTATION The study has complied with the requirements for a Schedule B project under the Municipal Class Environmental Assessment (Class EA) process. A Class EA applies to a group of projects that are permitted under the Environmental Assessment Act as long as they follow the approved planning process. The specific requirements depend on the type and complexity of the project as well as the significance of potential environmental impacts. Agreements made or commitments given the proponent to affected agencies or the public must be followed through and implemented. If an affected agency or the public has a concern that cannot be resolved by discussion and negotiation with the proponent, they can request a Part II Order which may elevate Schedule B and C projects to an Individual EA, or for Schedule B projects to become elevated to a Schedule C project. The residents of Area 19 have experienced surface and/or basement flooding during extreme wet weather conditions. The project assesses the major and minor storm drainage systems and the sanitary sewer system to identify the causes, mechanisms and impacts of surface and basement flooding and receiving water quality degradation. The result is the development of comprehensive flooding remediation plans that best meet the target level of service criteria of the City. It is anticipated that all of the sewer and surface drainage system remediation works will be constructed within the existing road allowance or on City property. Accordingly, this project follows a Schedule B process. This Project File document is intended as a summary report, documenting Phase1 and 2 of the Class EA for this Schedule B project. The Project File is presented for the 30-day public and agency review period. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 3.4

6 3.1 AGENCY AND PUBLIC CONSULTATION A comprehensive consultation program was conducted with the following components: A Notice of Study Commencement mailed to approximately 19,000 residents and business owners within the boundaries of three study areas (17, 18 and 19). A mailing list was created and maintained over the course of the study that included review agency contacts, local interest groups, ratepayer associations, and all members of the public who requested to be added to the list. Two Public Information Centre (PIC) events were held, consisting of a drop-in centre with display panels and provided an opportunity for the public to speak with City and consultant staff. The PICs were held on July 4/5, 2012 and PIC#2 on July 9, Councillor Briefings were held with staff to present and collect feedback on the proposed solutions. Throughout the duration of the study, staff from the TRCA and the City s internal divisions (Parks, Forestry and Recreation, Development Services, District Operations, Engineering and Construction Services) were consulted throughout the screening, development and evaluation of alternatives. The City maintained a project website with background information, meeting materials, project updates and staff contact information. 4.0 EVALUATION OF ALTERNATIVES 4.1 METHODOLOGY There are several possible remediation measures to control incidents of surface and basement flooding, and to mitigate impacts of stormwater runoff on receiving water quality. The methodology to develop and evaluate viable alternatives included a long-list screening of remedial measures, followed by development of an overall solution strategy comprising a combination of shortmp m:\active\ _swm_basement_flooding\preliminary\report\area 19\project file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.5

7 listed remedial measures. The evaluation was undertaken using a standard pairwise weighting process where each strategy is evaluated with respect to a number of environmental, social and economic criteria (developed with input from PIC#1) and assigned a rating. The ratings were subsequently multiplied by the criteria weightings and summed for each alternative to provide a total weighted score. Given the number of constraints associated with siting of locallevel solutions and the size and interconnectivity of the solution set, an additional evaluation of individual solutions was performed only where feasible alternative alignments existed. These locations were further evaluated in a similar manner to the strategies however with a risk-based approach to determine those with the least impact to the triple-bottom-line (environmental, social, and economic environments). 4.2 DEVELOPMENT AND EVALUATION OF ALTERNATIVES Solution Strategies Following the principles of the WWFMP, overall strategies were developed with the hierarchical approach of source, conveyance, and end-of-pipe controls. Within the strategies, high-level alternatives were derived to capture variables in the potential make-up of the solution sets. The strategies and their alternatives are discussed briefly as follows: Strategy 1: Aggressive Source Control Implementation. Through application of by-law creation/enforcement, target aggressive implementation of source controls to that of the WWFMP Enhanced levels in the immediate term. Strategy 2: Conveyance Controls. Implement conveyance infrastructure improvements alone to improve system capacity. One alternative is to consider implementation within the municipal road allowance alone while a secondary alternative would consider acquisition, either through easements or property purchase, for conveyance through private lands. Strategy 3: Storage Facilities. Implement storage infrastructure improvements alone to relieve and optimize existing system capacity. Four alternative considerations include application of in-line versus endof-pipe storage, on public versus public and private lands. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.6

8 Strategy 4: Integrated Water Quality Solutions with Source, Conveyance & EOP Controls. Incorporate Strategies 1 through 3 in various combinations. Alternative considerations include application of the creation of new outfalls as part of the solution, and implementation of dedicated interceptor sewers for diversion to centralized end-ofpipe water quality treatment facilities. Strategy 5: Do Nothing. Maintain the Status Quo in system performance/operation, with continued maintenance and asset renewal programs, but no specific flood/water quality solutions. The following is a synopsis of the evaluation: Implementation of source controls alone will not meet the objectives of flood control, and will greatly burden the public through reliance on private improvement measures. Implementation of conveyance controls alone will not meet water quality or no-net increase to sanitary trunk sewer objectives, and will result in larger social and environmental impacts due to the increased length requirements of solutions, and the larger flow contributions to the receiving watercourse. Implementation of storage controls alone will partially meet the overall objectives, at the expense of increased short and long-term maintenance costs, greater impact to open space/natural environment due to footprint requirements, and higher degree of technical difficulty to design/operate. An integrated strategy combining opportunistic implementation of source controls, conveyance controls, and end-of-pipe measures provides the most flexibility for meeting the water quality and flood control objectives, and optimizing the natural, social and economic impacts of required projects. A dedicated interceptor sewer for water quality treatment at centralized end-of-pipe treatment facilities causes too great an environmental and social impact at greater cost, given the sensitive natural environment within the West Don floodplain, and need for space not owned by the City. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.7

9 The Do Nothing alternative cannot meet the water quality and flood control objectives, and would serve to continue degradation of water quality in the receiving watercourses and the level of service experienced in the study area. Preference for implementation on municipally-owned property since this involves lower approval needs, less cost, and greater control of implementation scheduling; however, easement or land acquisition should be investigated where feasible Project-Level Alignments Sanitary System SAN-19-01/02: Garratt Boulevard & Wilson Avenue Two alternatives were reviewed to reduce the amount of surcharge occurring in the Wilson Avenue sewer. Alternative 1: providing in-line storage to reduce the amount of flow to Wilson Avenue and Alternative 2: replacing and upsizing the entire Wilson Avenue system to lower surcharge amounts. The extent of upgrades associated with Alt. 2 is much larger than the relatively local improvement works associated with two storage facilities, therefore is more expensive and has a greater social impact. Hence, Alt. 1 is preferred. SAN-19-03/04: Westgate Boulevard / Ravine To relieve the system surcharging to the surface down the Westgate Ravine through to the discharge point to the West Don Trunk, in-line underground storage (Alt. 1) and conveyance (Alt. 2) were reviewed. A large deep storage tank at the cul-de-sac/entrance pathway to the ravine would control peak flows to the trunk and reduce environmental impact to the ravine. While it does not eliminate an upgrade (twinning) of the existing sanitary after the confluence with the Timberlane sewer in the valley, it avoids the need to replace the recently constructed sanitary sewer bypass sewers associated with the Earl Bales Pond project. Alt. 2 increases flow to the trunk, has greater environmental disturbance downslope and in the valley, and does not avoid the EBP upgrades. Therefore, Alt. 2 is not preferred. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.8

10 SAN-19-06/13: Bathurst St./ Ellison Ave./ Timberlane Ravine Similar to SAN-19-03/04, this adjacent and connecting project is upstream of the Westgate Ravine and works in tandem with the solution. Alt. 1 comprises a combination of two in-line storage facilities: optimization of the existing Ellison Ave. super-pipe by way of orifice control, and through new pipe on Timberlane Avenue upstream of the ravine. Both serve to eliminate the need for major disturbance that conveyance would require through the wooded ravine. While more costly, the reduced impact to the downstream trunk and natural features deems Alt. 1 more preferred than the conveyance Alt. 2. SAN-19-09/10/15: Searle Ave./Hove St. Alt. 1 provides a combination of upstream diversion (Searle and Maxwell) and in-line passive storage on Hove St. to control the local hydraulic grade line on Searle and further upstream at Waterloo Ave. where a flow split east to Bathurst exists. The length of disturbance is much shorter than Alt. 2, which is conveyance upgrades on Searle Ave., Hove St., and Bathurst Street (resulting from higher HGL at flow split). In addition, the need for construction on Bathurst Street increases traffic / commuter impacts. Therefore, Alt. 1 is preferred. SAN-19-11: Overbrook Place The difference between Alt. 1 and 2 is minor. Alt. 1 provides a combination of local sewer upgrade along with in-line storage while Alt. 1 has additional conveyance instead of storage. The resulting cost is similar; however, there is additional traffic/access disruption and more conflicts requiring resolution for Alt. 2, therefore Alt. 1 is preferred Storm Drainage System STM-19-01: Bayhampton Court The small drainage area and sewer system at the north end of Area 19 has two potential alternatives to relieve the trapped overland flow. Alt. 1 upgrades the deficient storm sewers including through a short portion of wooded area while Alt. 2 has a dedicated major system pipe to an underground storage that avoids the wooded area. The reduced risk of less potential for tree loss is outweighed by the increased cost, long-term O&M burden, and greater disturbance to recreational space. Alternative 1 is preferred. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.9

11 STM-19-02: Purdon Drive Trapped overland low point on Purdon can be conveyed by pipe increase along its current alignment which traverses between two houses to an upgraded outfall (Alt. 1), or by a longer route that avoids construction between properties yet requires the construction of new outfall at Garthdale Park. The shorter route of Alt. 1 is less disruptive, especially with trenchless methods employed between the properties, at the expense of increased design/constructability. Both alternatives require some disturbance to the wooded area, however, Alt. 1 does not require construction of a new outfall. Both options can be coordinated with watercourse rehabilitation efforts to mitigate construction disturbances associated with the outfall. Should trenchless construction be suitable at the detailed design stage, then Alternative 1 is preferred, however Alt. 2 remains a feasible fall back. STM-19-03: Arlstan Dr. This project is in tandem with STM-19-02, whereby the trapped low point on Arlstan is either conveyed by short pipe upgrade along the existing route via easement between homes to an upgraded Purdon system (Alt. 1), or by a much longer route via Blue Forest Dr. to the new Garthdale Park storm outlet. Following the same logic as STM-19-02, the shorter and therefore cheaper and less disruptive approach via more involved construction is preferred; however, Alt. 2 remains a closely scored viable approach. STM-19-06/07/09/12: Overbrook Place/Maxwell St. Major system control can be provided by a single large storage facility (Alt. 1), or by two smaller and spatially separated storage facilities, plus associated reduction in connecting conveyance infrastructure. Alt. 1 is favoured due to being more economical (one tank is easier to maintain than two), and based on concerns from PF&R regarding high impact to recreational function of Irving W. Chapley Park. STM-19-44: Allen Rd. N. of Sheppard Ave. Trapped overland flow paths on Allen Rd. are controlled via major system storage with minor system upgrades (Alt. 1) or major system conveyance that extends almost double the distance along Allen to south of Sheppard Ave. W (Alt. 2). Costs are comparable, however the reduced traffic/environmental disturbance and inability to renew existing storm infrastructure favours Alt. 1. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.10

12 STM-19-46/47: Banting Ave./Reiner Rd. Trapped overland low points on Reiner and Banting are controlled in Alt. 1 by a combination of surface diversion to dry pond in Banting Park, along with underground storage in the south portion of Banting Park. Alt. 2 requires the extension of major system conveyance of both low points to the Wilson Heights Boulevard connection to the deep trunk. PF&R and the public identified some rehabilitation / bioretention efforts in Banting Park, however the footprint of the facilities remain small and can avoid disturbance. Greater social impacts for traffic and construction associated with the longer Alt. 2 favour the cheaper Alt. 1. STM-19-51: Cocksfield / Yeomans / Alexis Low Points Central trapped overland low points can be controlled by linear storage in Earl Bales Park, with conveyance by two alternatives. Alt. 1 conveys the subject low points via dedicated major system pipe from Cocksfield via Maxwell/Harlock/Alexis. Alt. 2 conveys the Cocksfield and Alexis/Harlock low point via Sheppard Avenue to the existing sewer new the outfall at the bridge crossing the West Don River, in addition to conveying the Alexis/Yeomans low point via Alexis to a smaller storage in Earl Bales Park. The length of disturbance to a major commuter/arterial road and the constructability challenges (trenchless / major conflicts) outweighs the increased cost associated with the shorter, therefore preferred Alt. 1. STM-19-40/67/68: Wilson Ave. E./Delhi Ave. To relieve the trapped overland flow that is overwhelming the existing storm trunk crossing Hwy. 401 at Bathurst St., two alternatives were developed. Alt. 1 creates a deep storm tunnel with alignment along Wilson Ave east to a new outfall to the West Don River. Alt. 2 uses several underground storage tanks located throughout the system to control flows to the existing storm trunk. Alt. 1 involves a high degree of constructability risks associated with tunneling, however the trenchless approach reduces the traffic disturbance. Impacts of a new outfall were discussed with TRCA, and it was demonstrated that flows to the flood-sensitive Hoggs Hollow area would not increase beyond those assumed by current floodplain hydrologic/hydraulic modeling, since no new drainage area is directed to the watercourse. Land availability for storage facilities is extremely limited in this area, and therefore the need for siting of tanks on institutional properties (Toronto Public file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.11

13 Library parking lot, Summit Heights Public School) was needed. These properties would require additional consultation for suitability, and initial feedback from the TDSB indicated a high level of uncertainty with property availability. This, in addition to the higher cost and impact to open space render Alt. 1 as preferred. Model and Faith Avenue Due to concerns of residents on Model and Faith Avenues in the aftermath of the July 8, 2013 flooding, additional analysis was conducted on the collection system including CCTV inspection and fog-testing. In addition, supplemental sanitary model calibration was undertaken to compare against the reported flood complaints observed from the extreme July 8 event. The CCTV inspection of the sanitary found no signs of blockage or structural issues, and the fog-testing revealed one flat roof contribution and potential foundation drain/rear patio drain connections to the sanitary on Model and Faith Ave. Testing of the storm system revealed no cross-connections. The updated hydraulic model runs demonstrated that the local contributions to the Faith and Model sanitary were not the cause of local flooding. Therefore, in addition to promoting home isolation measures on the private side, including foundation drain disconnection to sump pumps and properly connected backflow valves on the sanitary laterals, the downstream improvements to the sanitary system and proposed storm drainage improvements on Model/Wilson Heights Blvd. will help reduce flood risk as per the City s enhanced design criteria. Sanitary manhole lids at low points will also be sealed to reduce inflow to the sanitary sewer. 4.3 PREFERRED SOLUTION Based on the evaluation of the alternative strategies and project-level alignment/siting scoring, Alternative 4 was selected as the preferred approach. At the project-level, the preferred siting alignments have also been selected based on a risk-based evaluation, grouped as Alternative 1. To help achieve the target level of protection against surface and basement flooding, it has been determined that upgrades to the existing drainage systems are necessary. Figure ES.2 presents the recommended improvement works to help address the flooding problem in Study Area 19, and improve the runoff water quality to the West Don River. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.12

14 Figure ES-2 Recommended Solutions file\30dayreview\rpt_a19_executivesummary_projectfile.docx 4.13

15 5.0 CONCLUSIONS AND RECOMMENDED SOLUTIONS To help achieve the target level of protection against surface and basement flooding, it has been determined that upgrades to the existing drainage systems are necessary. The estimated 50-year life-cycle cost of these works is $237.7 million (2013 Canadian dollars), including engineering and contingencies but excluding taxes. The following conclusions can be drawn from the completion of this study: The historic flow monitoring program was useful in the calibration/verification of the hydrologic/ hydraulic simulation models for the sanitary and storm sewers; however, the storm events recorded were limited in severity and thus extrapolation of parameters to mimic extreme storm event response was required using best engineering judgment. Infiltration and inflow experienced in the monitored sanitary sewersheds is typical for the vintage of the infrastructure ( s) with a large degree of connected foundation drains. As part of the detailed design process, opportunities for pipe/manhole rehabilitation and/or private property disconnection measures should be further investigated. The main causes of basement and surface flooding include overloading of storm sewers, surcharge of sanitary sewers caused by excess inflow and infiltration and pipe bottlenecks, lack of a continuous major system, trapped overland flow paths causing surface flooding, pockets of high groundwater table, and blockage in sewers and street catchbasins. Source control measures alone will not significantly reduce basement/surface flooding (approximately 13% reduction in annual outflow volume), however, will contribute to the improvement of water quality of the receiving West Don River. The preferred remedial measures consist of a combination of source control measures, conveyance improvements, and storage elements in the storm and sanitary collection systems. With the implementation of the preferred sanitary remedial measures, the sanitary sewer system can safely convey the May 12, 2000 design storm event under 2031 anticipated population growth (including the file\30dayreview\rpt_a19_executivesummary_projectfile.docx 5.14

16 Downsview Area Secondary Plan), within City criteria with no net increase to peak flows received in the West Don Sanitary Trunk Sewer. With the implementation of the preferred storm remedial measures, the storm drainage system can convey both the major and minor systems during the 100-year design storm within City criteria. The storm capacity improvement measures including the new outfalls, will not alter the existing floodplain in the sensitive Hogs Hollow area, since the proposed storage measures act to decrease peak flow to the existing outfalls, and no additional flow from other drainage areas has been diverted to the river. In addition to the existing Earl Bales Park stormwater management water quality pond, there exists one additional opportunity for an end-of-pipe facility downslope of Maxwell Park. Further consultation with the City and TRCA is required to confirm feasibility of this location, as it has been recommended that the site remain undisturbed and in situ until the proposed impact is cleared of any further archaeological concerns. With the application of enhanced source controls, conveyance controls and the Maxwell end-of-pipe facility, the collective annual pollutant reduction from outfalls not discharging to Earl Bales Park in Area 19 is 26% TSS, 23% Total Phosphorus, 23% Copper, and 21% E. Coli. These measures along with the Earl Bales facility and implementation of the recommendations throughout the Don Watershed, will help meet the objectives of the WWFMP. The recommended improvement works to help address the flooding problem in Study Area 19 is estimated at a capital cost of $195.6 million (2013 Canadian dollars), including project delivery allowance and contingencies, excluding taxes. The recommended solutions within Parks and Open Spaces may affect potential archaeological sites, therefore a Stage 2 Assessment is required for these projects as outlined in the Conceptual Designs. All other projects within municipal right-of-ways do not require Stage 2 works. The Schedule B Class EA process has been fulfilled through public consultation including two PICs, agency consultation, and the submission of this project file document. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 5.15

17 The following recommendations are made with respect to this study: City to proceed with short-term local measures including sealing of sanitary maintenance hole covers at low points in the road, implementation of inlet control devices and overland diversions where sufficient major system conveyance exists, continued promotion of the residential roof downspout disconnection program, and continuation of the City s infiltration and inflow reduction and operations and maintenance programs. City to continue promoting the Basement Flooding Protection Subsidy Program and the Fat, Oils and Grease public education initiatives. Implementation of the measures included in this program will provide protection to most residences and will enhance the performance and level of protection provided by the remedial measures in the preferred alternative. City to proceed to detailed design of the preferred remediation measures and commence implementation as capital budget permits. Liaison with all review and approval agencies and the public to be conducted as part of the design process. Continued monitoring of rainfall-runoff response across the City, including review and analysis of new basement and/or surface flooding complaints. Investigate reconfiguration options of storm outfalls to reduce sediment build-up and blockage. The Maxwell Park siting opportunity for a stormwater management water quality facility should be investigated further with the TRCA to determine if the impact of the facility footprint can be cleared of any further archaeological concerns. file\30dayreview\rpt_a19_executivesummary_projectfile.docx 5.16