PROJECT FILE REPORT - Mississauga · The Project File Report represents the documentation of the...

PROJECT FILE REPORT

LAIRD ROAD STORMWATER MANAGEMENT FACILITY RETROFIT CITY OF MISSISSAUGA PROCUREMENT NO. FA.49.308-08

PREPARED FOR:

CITY OF MISSISSAUGA October 2009 08269

TABLE OF CONTENTS

PAGE

1.0 INTRODUCTION AND BACKGROUND .........................................................................................................1

1.1 PROJECT FILE REPORT....................................................................................................................1 1.2 PURPOSE OF THE PROJECT ...........................................................................................................1 1.3 BACKGROUND ...................................................................................................................................3 1.4 NEED AND JUSTIFICATION...............................................................................................................3

2.0 PROJECT APPROACH ..................................................................................................................................5

2.1 PROJECT STAGES AND ORGANIZATION........................................................................................5 2.2 EXTERNAL INVOLVEMENT AND PUBLIC CONSULTATION............................................................7

3.0 EXISTING CONDITIONS ................................................................................................................................8

3.1 NATURAL ENVIRONMENT WITHIN THE EXISTING SWM FACILITY BLOCK .................................8 3.2 GEOTECHNICAL ASSESSMENT .......................................................................................................8 3.3 GEOTECHNICAL INVESTIGATION....................................................................................................8 3.4 LAND USE AND SOCIO-ECONOMIC ENVIRONMENT .....................................................................9 3.5 SERVICING CONDITIONS AND UTILITIES .......................................................................................9

4.0 ALTERNATIVES AND EVALUATION ..........................................................................................................10

4.1 ALTERNATIVES................................................................................................................................10 4.2 EVALUATION OF ALTERNATIVES ..................................................................................................11

5.0 PUBLIC AND AGENCY INPUT.....................................................................................................................17 6.0 SELECTED DESIGN.....................................................................................................................................18

6.1 DESIGN AND APPROVAL REQUIREMENTS FOR SELECTED DESIGN .......................................18 6.2 POTENTIAL ENVIRONMENTAL IMPACTS AND MITIGATING MEASURES...................................18 6.3 CONSTRUCTION TIMING ................................................................................................................20 6.4 MONITORING AND COMMUNICATION...........................................................................................20

FIGURES FIGURE 1 LOCATION PLAN..............................................................................................................................2 FIGURE 2 DRAINAGE AREA PLAN...................................................................................................................4 FIGURE 3 MUNICIPAL CLASS EA PLANNING AND DESIGN PROCESS .......................................................6 FIGURE 4 DO NOTHING..................................................................................................................................12 FIGURE 5 OPTIMIZATION OF GARTHWOOD PARK .....................................................................................13 FIGURE 6 RETROFIT WITHIN EXISTING BLOCK..........................................................................................14 FIGURE 7 RETROFIT WITHIN EXPANDED BLOCK.......................................................................................15

TABLES TABLE 1 SUMMARY OF ENVIRONMENTAL IMPACTS ...............................................................................16 TABLE 2 POTENTIAL SHORT TERM CONSTRUCTION RELATED ENVIRONMENTAL IMPACTS............19 TABLE 3 LONG TERM ENVIRONMENTAL IMPACTS ..................................................................................19

TABLE OF CONTENTS

APPENDICES APPENDIX A “NEEDS AND JUSTIFICATION” EXERPT FROM 1997 MISSISSAUGA STORM WATER QUALITY

CONTROL STUDY APPENDIX B PUBLIC NOTICES AND ADVERTISEMENTS APPENDIX C PUBLIC INFORMATION; PUBLIC INFORMATION CENTRE REGISTRY APPENDIX D CREDIT VALLEY CONSERVATION CONSULTATION APPENDIX E TREE SURVEY/ARBORIST’S REPORT APPENDIX F GEOMORPHIC ASSESSMENT APPENDIX G GEOTECHNICAL INVESTIGATION APPENDIX H EXISTING INFRASTRUCTURE WITHIN POND BLOCK APPENDIX I PRELIMINARY DESIGN CONCEPT

Sernas Associates October 2009 Project File Report A Member of the Sernas Group Inc. 08269 Laird Road Stormwater Management Facility Retrofit 1 Municipal Class Environmental Assessment

1.0 INTRODUCTION AND BACKGROUND

1.1 PROJECT FILE REPORT

The Project File Report represents the documentation of the Municipal Class Environmental Assessment (Class EA) process undertaken for municipal infrastructure projects, including road improvements, water and wastewater projects. This study has been undertaken in accordance with the Municipal Class Environmental Assessment, October 2000, as amended in 2007 document, which identifies the approved planning process that municipalities must follow in order to satisfy the provincial Environmental Assessment Act. The Municipal Class EA approach allows for the evaluation of the environmental effects of alternatives to a project and alternative methods of carrying out a project. It includes mandatory requirements for public input and expedites the assessment of smaller recurring projects that have a predictable range of environmental effects and that are responsive to mitigating measures. The Laird Road Stormwater Management Facility Retrofit Environmental Assessment (EA) has been completed as a Schedule ‘B’ project. Schedule B projects generally include improvements and minor expansions to existing facilities and consider the potential for some adverse environmental impacts. Appendix 1 of the Municipal Class Environmental Assessment, October 2000, as amended in 2007 lists wastewater management projects which “(3) Enlarge stormwater retention/detention ponds/ tanks or sanitary or combined sewage detention tanks by addition or replacement, at substantially the same location” under Schedule B. The Municipality is required to undertake a screening process, involving two (2) mandatory contacts with directly affected public and relevant government agencies to ensure that they are aware of the project and that their concerns are addressed. If there are no outstanding concerns, then the proponent may proceed with final design and implementation (i.e. construction).

1.2 PURPOSE OF THE PROJECT

The City of Mississauga Transportation and Works Department is undertaking this Municipal Class EA to select the preferred retrofit solution for the Laird Road Stormwater Management facility, which is located at the northwest corner of Laird Road and Winston Churchill Blvd. The location of the existing Laird Road Stormwater Management Facility is illustrated on Figure 1. The Laird Road Stormwater Management Facility outlets to the Loyalist Creek which is within the jurisdiction of the Credit Valley Conservation (CVC). The existing stormwater management (SWM) quantity facility was identified as having high potential for retrofit to provide water quality control in the 1997 Mississauga Storm Water Quality Control Study (MSWQCS) prepared by Winter Associates and Gore and Storrie Ltd. in collaboration with the City of Mississauga and other Provincial and Municipal Authorities. The City of Mississauga is in the process of implementing the recommendations of the MSWQCS report. At this time, several SWM facility retrofits identified in the MSWQCS report have been completed. The primary purpose of this project, in keeping with the recommendations of the MSWQCS, is to retrofit the existing SWM facility to provide quality treatment of stormwater runoff within the Loyalist Creek watershed.


Figure 1 Laird Road Stormwater Management Facility Location Plan


1.3 BACKGROUND

The Laird Road facility is part of a two pond system on the south branch of the Loyalist Creek. An upstream flood detention area within Garthwood Park is used for quantity control between the 10-year and 100-year storms. All flows then continue downstream to the Laird Road SWM Facility where quantity control is provided for the 2-year to 100-year storms. The drainage area to the facility is wholly located within City of Mississauga municipal boundaries. The Laird Road SWM Facility was constructed in 1986 at the northwest corner of Laird Road and Winston Churchill Blvd. The Proctor and Redfern Group designed the facility, and the design brief for the facility is entitled “Erin Mills West Loyalist Creek Drainage Report” (Proctor and Redfern, 1985). The brief outlines the stormwater management plan and design options for the proposed facility. Stormwater management objectives for the drainage area were obtained from the “The Cadillac Fairview Corporation Limited Master Drainage Plan for Loyalist Creek” (Proctor and Redfern, 1982) and the “Loyalist Creek Watershed Study” (CBCL, 1980). The Laird Road SWM Facility has a tributary area of approximately 219 ha. The drainage area has been fully developed and includes a mix of single-family residential, high-density residential, schools, parks, commercial and industrial areas. The area is generally bounded to the north by Burnhamthorpe Rd E, to the east by the eastern edge of Garthwood Park, to the west by Hwy 403, and to the south by Dundas St E. The contributing watershed is shown on Figure 2. The facility was designed to be an erosion control facility and a quantity control facility, controlling the 2-year post development peak flow to 2 m3/s and the 100-year post development peak flow to 14 m3/s. Flows up to the 100-year event are to be conveyed through the facility and discharged through the culverts extending under Winston Churchill Blvd. Flows in excess of the 1:100 year event are to be conveyed via a spillway over Winston Churchill Blvd. Flows are then conveyed east within an engineered channel section of the Loyalist Creek. The existing facility is a “dry-pond” that does not contain a permanent pool portion for water quality improvement. The following information was reviewed during the completion of the study.

• Mississauga Stormwater Quality Control Study, prepared by Winter Associates & Gore & Storrie Limited, 1997.

• Erin Mills West Loyalist Creek Drainage Report, prepared by Proctor and Redfern Group, Febuary 1985.

• The Cadillac Fairview Corporation Limited Master Drainage Plan for Loyalist Creek, prepared by Proctor & Redfern Group, 1982.

• Loyalist Creek Watershed Study, prepared by CBCL, 1980. In accordance with the Municipal Class EA process, this report must consider the best-fit solution that suits the natural, social, cultural, built and economic environments. A preferred solution must be derived that will identify acceptable measures which will allow the project to be undertaken at reasonable cost, while at the same time protecting the environment against net negative impacts.

1.4 NEED AND JUSTIFICATION

The “need” and “justification” to retrofit the existing Laird Road SWM Facility has been clearly identified in the “Mississauga Stormwater Quality Control Study”, and discussed in Section 1.3 of this Project File Report. Attached in Appendix A is a copy of the retrofit screening sheet for the Laird Road SWM Facility from the MSWQCS.


2.0 PROJECT APPROACH

2.1 PROJECT STAGES AND ORGANIZATION

As previously documented, this project has been carried out in accordance with the Schedule ‘B’ process prescribed in the Municipal Class Environmental Assessment Document, October 2000, as amended in 2007. This approach identifies the problem or opportunity, evaluates the effects of various alternative solutions to the problem and the alternate design concepts for the preferred solution, and evaluates the impact on the existing environment, adjacent residents, businesses and land owners through public consultation and documentation of the decision making process. The Municipal Class EA tasks include information gathering, public review, evaluation of planning and design alternatives, selection of a preferred alternative and determination of environmental impacts and resultant mitigative measures. The main elements of the Class EA process are incorporated in five phases as shown on Figure 3. Phase 1 of the process identifies the problem or opportunity. Phase 2 identifies and evaluates alternative solutions, establishes the preferred solution, and solicits input from review agencies and the public. Phase 3 provides alternative design concepts for the preferred solution. Phase 4 documents all activities completed through Phases 1 through 3 in an Project File Report. Finally, Phase 5 is the implementation of the project, including completion of detailed drawings and construction. The City of Mississauga has fulfilled the Phase 1 component of the process in the preparation of the MSWQCS. Phase 2 of the process has been carried out by Sernas Associates on behalf of the City of Mississauga under the direction of the Transportation and Works department. As this project falls under a Schedule ‘B’, Phases 3 and 4 are not required to be completed. This Project File Report has been prepared to document the Phase 1 and 2 planning process in order to allow a Notice of Completion to be submitted to review agencies and the public. Upon completion of the proper 30 day review period this project will proceed to Phase 5, which allows the project to be completed based on the preferred solution. Specialist sub-consultants were retained through Sernas Associates to complete detailed inventories/ assessments/investigations to assist with the evaluation of alternatives, the selection of a preferred solution and possible constraints to be considered during detailed design and to provide guidance on mitigating measures to be considered and/or employed. The firm retained, the contact person and the type of work completed by each is summarized below:

Cosburn Giberson Landscape Architects. – Mr. Marc Willougby, Landscape Architect Geomorphic Solutions – Dr. Jeff Doucette, Geomorphologist Soil-Eng Ltd. – Mr. Frank Lee, P.Eng., Geotechnical Investigation A copy of the preliminary landscape concept and the geotechnical investigation from the respective sub-consultants are included in Appendix E, F and G respectively.


Figure 3

Municipal Class EA Planning and Design Process


2.2 EXTERNAL INVOLVEMENT AND PUBLIC CONSULTATION

Through out the Municipal Class EA process the public and stakeholder agencies have been consulted. A Public Information Centre (PIC) was held on March 3, 2008 to consult with the public on Phase I of the process and the background for the study. A Public Information Package (PIP) was made available to the public to consult during Phase II of the process in August, 2009. Copies of all public notices are included in Appendix B. Appendix C includes the public information presented at the PIC and in the PIP, a copy of the comment sheet provided at the PIC, and the PIC register. The PIC was held at the Erin Mills Twin Arena, 3205 Utility Drive, Mississauga. The notice for the PIC was advertised prior to the meeting in the Mississauga News, as well as hand delivered to property owners located adjacent to the existing facility. Staff from the City of Mississauga, and Sernas Associates were present at the PIC to provide information and to answer questions from those in attendance. A comment sheet was provided with the request to record comments or concerns for further consideration through the final stages of the Municipal Class EA process. The meeting register indicates that three (3) people were represented at the meeting including staff from Enersource Hydro Mississauga. It is noted that no letters or comment sheets were received at the PIC, during the established commenting period or thereafter. Two people present at the PIC, indicated on the register that they would like to be informed throughout the rest of the Municipal Class EA process. Subsequent public information was sent to these people directly via e-mail. A PIP was made available August 28, 2008. The package was hand delivered to property owners located adjacent to the existing facility and a copy of the package was posted on the City of Mississauga’s webpage. An advertisement was posted in the Mississauga News to let the public know how they could access the package. A comment sheet was included in the PIP. It is noted that no letters or comments sheets were received during the established commenting period or thereafter. Throughout the study process staff from Credit Valley Conservation (CVC) and Enersource Hydro Mississauga were consulted. Staff from the City of Mississauga and Sernas Associates met with CVC staff on January 21, 2009 and June 29, 2009 to discuss the project. Minutes and correspondence from these meeting are included in Appendix D.


3.0 EXISTING CONDITIONS

3.1 NATURAL ENVIRONMENT WITHIN THE EXISTING SWM FACILITY BLOCK

The existing SWM block contains a dry pond with a low flow channel for conveyance of minor storm flows. The vegetation found within the block consists of common grasses and other native species while the low flow channel is comprised primarily of reeds and cattails. A tree survey of the existing facility and a section of the downstream channel was completed in March, 2009. The Tree Survey/Arborist’s Report, prepared by Cosburn Giberson Landscape Architects, prioritized the existing trees for preservation based on the tree’s overall biological health and condition, maturity, history of disturbance and species type/value. The report is included in Appendix E. The existing SWM facility is not considered fish habitat however it is noted that the facility has the potential to impact fish habitat downstream if thermal impacts are not mitigated. This is discussed in further detail in Section 5 and 6 below. The receiving water course; the Loyalist Creek is discussed in Section 3.2 below. The SWM facility is bound by a retirement residence to the south, commercial properties to the east and west, and residential properties to the north across Laird Road. The facility is bordered by a chain link fence.

3.2 GEOMORPHIC ASSESSMENT

A geomorphic assessment of Loyalist Creek was completed downstream of the SWM facility. The Geomorphologically Based Erosion Threshold Assessment for Laird Road Pond Retrofit Memorandum, prepared by Geomorphic Solutions is included in Appendix F. Stream reaches were delineated and the stream corridor was characterized for a section of the Loyalist Creek extending approximately 1.3 km downstream from the facility. Reach R4 was identified as sensitive to changes in water flow and a detailed geomorphic assessment was completed. An erosion threshold, calculated to account for increases in water flow while limiting impacts on the channel and surrounding area, was calculated to be 0.21m3/s. The memorandum recommended that the pre- and post-development exceedance of the erosion threshold should be matched. Given that the first sensitive reach downstream of the existing SWM facility is reach R4 because all other reaches were structurally controlled and very resistant to erosion it was determined that a pre to post erosion threshold analysis for the proposed retrofit was not necessary. Reach R4 is grater than 1 km downstream from the facility and there are other significant flow inputs to the channel that impact the exceedance of the erosion threshold.

3.3 GEOTECHNICAL INVESTIGATION

A geotechnical report was completed for the subject site by Soil-Eng Limited, and is included as Appendix G. Five boreholes were advanced to a depth of 5 m. In the areas of the proposed retrofit, it was noted that underneath the fill surface, soils generally consist of silty clay, fine to medium sand, fine to coarse sand and gravelly sand. The silty clay deposits are of a low permeability, while the sandy deposits were found to be relatively pervious. The water level was found to be 0.91-1.54 m below the pond bottom


3.4 LAND USE AND SOCIO-ECONOMIC ENVIRONMENT The lands that the existing facility is located on are owned by the City of Mississauga. The existing SWM block is currently fenced and is not expected to be subject to any pedestrian, social or recreational access in the future. The facility does provide an aesthetic benefit to the community as a green space.

3.5 SERVICING CONDITIONS AND UTILITIES The SWM facility receives stormwater flows from three storm sewer inlets; from an inlet located at the northwest corner of the facility block, from an inlet located at the southwest corner of the facility and from and inlet located in the centre of the north edge of the facility. Flow from these inlets is conveyed along a channel within the facility. There are two 15 m wide Region of Peel sanitary sewers easements located within the SWM block; one oriented north-south through the centre of the facility, the other oriented east-west along the south edge of the SWM block. The existing channel within the facility passes over a 600 mm diameter sanitary sewer which runs north to south within the first easement. The sewer is concrete encased for a 20 m length below the invert of the channel. A 525 mm diameter sanitary sewer runs west to east within the second easement until it converges with the 600 mm sewer and is upgraded to a 750 mm diameter sanitary sewer. Reference drawings from Region of Peel illustrating the existing sewer infrastructure can be found in Appendix H.


4.0 ALTERNATIVES AND EVALUATION

The objective of Phase II of the Municipal Class EA process is to list alternatives that can be considered in finding a “best fit” solution to address the stated need to provide water quality control within the Laird Road SWM facility. Furthermore, the impacts of alternatives are to be considered with mitigating measures. Finally, a recommended solution must be derived for presentation to solicit input from the public and review agencies. Outlined below are alternatives considered to address the stated “problem” of the existing facility not providing any significant level of quality control and insufficient quantity control prior to discharge into the Loyalist Creek.

4.1 ALTERNATIVES The existing stormwater management facility provides a certain level of quantity control; however the existing facility does not provide any significant level of quality control prior to discharge into the Loyalist Creek. The objective of this task is to provide a retrofit design for the existing facility that incorporates a level of quality control and improves the level of quantity control. At the conceptual design stage, other alternatives should be considered along with the proposed solution to ensure the option with most appropriate benefit to cost (environmental, social, capital, maintenance) ratio is selected. The feasibility of implementing a wide range of alternative designs is hampered by the fully developed status of tributary lands. As such, strategies involving the design of lot level or conveyance controls are limited. However, there remain a number of alternative ways that the project can move forward.

1. Do Nothing – A “do nothing” solution would mean the stormwater management facility would remain in its present state. Typically a do nothing alternative is selected when the financial and environmental costs of all the other alternatives outweigh the benefits. Refer to Figure 4 - Do Nothing to see the existing facility.

2. Lot level and Conveyance Controls – This alternative could be combined with either of the above retrofit options or the do nothing alternative. The implementation would involve items such as: the installation of flow regulators to utilize storage capacity within the existing sewage system, or the improvement of street cleaning practices to remove sediments and pollutants at the source. The benefits provided by this type of control would be dependant upon the level at which they were implemented.

3. Optimization of Garthwood Park – This option involves re-grading of Garthwood Park to provide more upstream storage while maintaining space for the existing uses including two soccer fields and a baseball diamond. This option is constrained in terms of ability to alleviate quantity control issues because there is limited space within Garthwood Park however in combination with a retrofit of the existing facility it could improve quantity control. Refer to Figure 5 - Optimization of Garthwood Park.

4. Retrofit within Existing Block –The retrofit to this on-line facility in its most general terms will involve the re-grading (may range from aggressive 3:1 slopes to the preferred 7:1 & 4:1 slopes recommended by the MOE Stormwater Management Planning and Design Guidelines) of the facility to provide more storage for quality and quantity control, as well as the potential construction of a revised control structure. The benefits of this alternative include the provision of stormwater quality treatment, which is absent from the current facility. The retrofit facility would have a greater ability to provide attenuation of peak flows from infrequent storm events. The negative aspects of the retrofit are mainly financial, as thermal impacts to downstream habitat can be mitigated during detailed design. Refer to Figure 6 - Retrofit within Existing Block.


5. Retrofit with Expanded Block – This option would be carried out in the same way as a retrofit to the existing facility, however, additional land would be acquired to provide a greater level of quality and quantity control. The existing facility is bound to the north by Laird Road, to the east and west by existing commercial development and to the south by existing residential development. Enersource Hydro Mississauga presently owns the lands to the east of the facility. The site presently has a number of switching cubicles and it was once believed that there maybe an opportunity for the City to purchase these lands to enlarge the footprint of the stormwater management block by approximately 0.3ha. Refer to Figure 7 - Retrofit within Expanded Block. Through correspondence with Enersource Hydro Mississauga we have learnt that a substation is planned for this site, as such it is presently not feasible to purchase this land.

4.2 EVALUATION OF ALTERNATIVES

A “technical review” of alternatives was completed to confirm the feasibility of each in terms of potential impacts on the natural, social and economic environments. A summary of this evaluation is shown on Table 1.

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