UPPER CEDAR CREEK SCOPED SUBWATERSHED STUDY Prepared for: THE REGIONAL MUNICIPALITY OF WATERLOO AND GRAND RIVER CONSERVATION AUTHORITY Prepared by: MATRIX SOLUTIONS INC. WOOD ENVIRONMENT AND INFRASTRUCTURE SOLUTIONS NATURAL RESOURCE SOLUTIONS INC. SGL PLANNING & DESIGN Version 1.0 October 2019 Guelph, Ontario Unit 7B, 650 Woodlawn Rd. West Guelph, ON, Canada N1K 1B8 T 519.772.3777 F 226.314.1908 www.matrix-solutions.com UPPER CEDAR CREEK SCOPED SUBWATERSHED STUDY Prepared for the Regional Municipality of Waterloo and the Grand River Conservation Authority October 2019 reviewed by Amanda McKay, P.Eng. Sam Bellamy, P.Eng. Water Resources Engineer Principal Water Resources Engineer Matrix Solutions Inc. Matrix Solutions Inc. reviewed by Aaron Farrell, M.Eng., P.Eng., CPM Ron Scheckenberger, M.Eng., P.Eng. Associate Principal Consultant Wood Environment & Infrastructure Solutions Wood Environment & Infrastructure Solutions Contributors Wood Environment & Infrastructure Solutions Natural Resource Solutions Inc. SGL Planning & Design Paul Martin, Aqua Insight Inc DISCLAIMER We certify that this report is accurate and complete and accords with the information available during the site investigation. Information obtained during the site investigation or provided by third parties is believed to be accurate but is not guaranteed. We have exercised reasonable skill, care, and diligence in assessing the information obtained during the preparation of this report. This report was prepared for the Regional Municipality of Waterloo and Grand River Conservation Authority. The report may not be relied upon by any other person or entity without our written consent and that of the Regional Municipality of Waterloo and Grand River Conservation Authority. Any uses of this report by a third party, or any reliance on decisions made based on it, are the responsibility of that party. We are not responsible for damages or injuries incurred by any third party, as a result of decisions made or actions taken based on this report. 24812-528x SWS R 2019-10-03 final V1.0.docx ii Matrix Solutions Inc. Version Control Version Date Issue Type Filename Description V0.1 March 2019 Draft Phase 1 and Phase 2 Reports Issued to client for review V0.2 07-Aug-2019 Draft Revised 24812-528 SWS R 2019-08-07 draft V0.2.docx Compilation report; Issued to client for review V1.0 03-Oct-2019 Final 24812-528 SWS R 2019-10-03 final V1.0.docx Compilation report; Issued to client as final 24812-528x SWS R 2019-10-03 final V1.0.docx iii Matrix Solutions Inc. Executive Summary The Regional Municipality of Waterloo, partnered with the Grand River Conservation Authority (GRCA), has retained the consulting teams of Matrix Solutions Inc. (Matrix), Wood Environment and Infrastructure (Wood), Natural Resource Solutions Inc. (NRSI), and SGL Planning & Design (SGL Planning) to undertake the Upper Cedar Creek Scoped Subwatershed Study. The Project Study Area (PSA) lies almost entirely within the Township of North Dumfries, with a small section of the northwest headwaters of Cedar Creek extending to the outskirts of the City of Kitchener, within the Regional Municipality of Waterloo. The Project includes two levels of study – a subwatershed-scale analysis for the entirety of the 7,463 ha Cedar Creek Subwatershed (i.e., the PSA), and a detailed local-scale analysis for those lands within the Detailed Study Area (DSA). The DSA consists of Cedar Creek Subwatershed lands north of Cedar Creek Road and west of Dumfries Road within the City of Kitchener and the Township of North Dumfries. Subwatershed studies are an integral component of the land use planning process. They provide fundamental input on natural features, with a focus on water-based elements including watercourses, wetlands, recharge and discharge areas, and other natural systems to help determine appropriate land use designations. Based on a fully integrated examination of how the surface and subsurface water systems work in supporting natural system functionality, various levels of guidance are established through the Subwatershed Study process to protect, restore, manage, and monitor subwatershed resources through subsequent development approvals and other stewardship initiatives. The Scoped Cedar Creek Subwatershed Study was conducted in two (2) phases: a) Phase 1 – Subwatershed Characterization and Integration b) Phase 2 – Impact Assessment & Preliminary Management Strategy Phase 1 of the study is focussed on understanding and characterizing the hydrology, hydrogeology, fluvial geomorphology, and water quality, as well as aquatic and terrestrial ecology of the Upper Cedar Creek Subwatershed, specifically within the DSA. Phase 2 is focussed on assessing the impacts of potential development within the DSA (Southwest Kitchener Policy Area – SKPA, and Prime Industrial Strategic Reserve – PISR), specifically impacts to natural environment features, as well as adjacent municipal well fields. A preliminary management strategy to mitigate identified impacts is also included as part of Phase 2. The land use concepts developed as part of Phase 2 were completed in consultation with Regional planning staff and only represent one possible land development scenario. The land use concept has 24812-528x SWS R 2019-10-03 final V1.0.docx iv Matrix Solutions Inc. been established solely for the purpose of analytical assessments of potential impacts associated with surface and ground water, as well as the associated natural systems. The use of the land use concept for the subject purpose does not suggest any endorsement or support for potential future land uses. Both phases are documented within this consolidated Scoped Subwatershed Study (existing document). The Scoped Subwatershed Study is intended to guide and coordinate decision-making by the Region, area municipalities, the Grand River Conservation Authority, and others involved in development planning and subwatershed stewardship and restoration. Impacts and Management Strategies The impact assessment portion of the SWS identified a number of impacts that may occur, should the potential land use scenarios proceed in an unmitigated fashion. To be clear, it is not expected that any potential development would be permitted to advance without mitigation measures. However, for the purposes of the SWS, it can be useful to assess potential impacts without mitigation so as to understand the scale of mitigation measures required. The following sections describe potential impacts as well as recommended measures to mitigate the identified impacts. Water Budget/Groundwater Recharge Impact In terms of the water budget, the most significant change associated with potential land use scenarios is related to evapotranspiration. As lands are urbanized, and impervious cover increases, rainfall/snowmelt is unable to infiltrate into the upper soil layer. This reduces the amount of available soil moisture that sustains evapotranspiration through dry periods. Rather than infiltrating, this water runs off, becoming stormwater. This has a secondary impact of reducing groundwater recharge to the underlying aquifer. While the impact assessment analysis has shown that the Strasburg municipal wellfield would not be significantly affected by reductions in recharge within the DSA, a number of key environmental features (Roseville Swamp, headwater reaches of Cedar Creek) could be affected by this reduction in groundwater recharge. Mitigation To mitigate this impact, any potential development should be required, at a minimum, to maintain existing groundwater recharge rates. This could be achieved through a combination of infiltration of clean water (e.g., roof runoff) at source, as well as the collection of runoff from paved surfaces (typically carrying contaminants) to a centralized stormwater management facility for appreciate quality treatment and subsequent infiltration. 24812-528x SWS R 2019-10-03 final V1.0.docx v Matrix Solutions Inc. Flooding Impact As described above, with modifications in the water budget associated with potential development, there is a certainty of more stormwater being generated under the potential land use scenarios than under existing conditions. This increased stormwater would eventually discharge into Cedar Creek. Analysis has shown that the unmitigated release of this stormwater into Cedar Creek would increase peak flow rates between Roseville Road and Highway 401 by a range of 33 to 490% (depending on the return interval of the storm event). This is clearly an unacceptable impact and would increase both the 100-year as well as the Regional flood elevations along the length of Cedar Creek. In addition to riverine flooding, there is no defined natural outlet adjacent to the SKPA lands. As a result, unmitigated stormwater discharge would flow overland from the SKPA lands, through multiple land parcels in North Dumfries (largely through agricultural fields and forests), before entering Cedar Creek downstream of Rosevillle Road. This would have significant negative impacts to landowners by frequently inundating lands within the overland flow path. Mitigation To mitigate this impact, it is recommended that potential urban developments shall only discharge stormwater offsite at an approximately similar frequency, rate, and volume as is occurring under baseline conditions. Stormwater that is not discharged offsite should be infiltrated. As described in the Water Budget/Groundwater Recharge summary, the conversion of agricultural lands to urban lands generally results in decreased evapotranspiration