4. Environmental Impacts Assessment and Remediation Targets

Transcription

1 4. Environmental Impacts Assessment and Remediation Targets 4.1 Environmental Impacts Significant additional development in the Alder Creek watershed is not anticipated at this time; however, there are impacts from increased urbanization that must be considered in this study. Development is anticipated in the Upper Strasburg Creek subwatershed but it is primarily of a residential nature. Increased development results in additional water demand and generates additional wastewater. The increased demand would come from the Region s integrated well supply system in Kitchener and would not directly impact the Mannheim East well field since they are already pumped at capacity. Wastewater is conveyed out of the subwatershed to treatment facilities in Kitchener. Development does generate significant amounts of runoff from hard surfaces (such as roof tops and roadways) if the stormwater management systems are not designed to successfully meet the pre-existing conditions for runoff and infiltration in the watershed. Environmental impacts need to be mitigated to provide adequate protection of ground and surface water and important natural heritage features. Environmental impacts, as a result of increased urbanization, can be anticipated in the following areas: Increased runoff from development areas Increased pollutant loads from residential hard surfaces Increased pollutant loads from other types of developments such as golf courses Increased runoff volumes from hard surfaces (primarily roads and non-residential development) Increased erosion in streams Elevated temperatures in streams Degraded stream water quality Reduced groundwater infiltration affecting water supplies and any groundwater dependent natural heritage features Contamination of water supply from infiltration of urban runoff including pesticides, road salt, nutrients, and industrial contaminants Disruption of the hydrology of natural wetlands Loss of natural heritage features Impairment of natural features function Loss of natural hummocky terrain features Reduced groundwater infiltration affecting water supplies Increased runoff volumes Increased erosion in streams Elevated temperatures in streams Degraded stream water quality T111_W KWO 4-1

2 ALDER CREEK WATERSHED STUDY AND UPPER STRASBURG CREEK SUBWATERSHED PLAN -FINAL REPORT Road salt application Increased chloride contamination of surface waters and groundwater resources Development and rehabilitation of the gravel pits in the watersheds Decrease in the amount of groundwater recharge to water supply wells and the Mannheim ASR Potential changes in quality and quantity of water recharging the underlying aquifer systems of the Waterloo Moraine both during extraction and subsequent rehabilitation Specific to the Alder Creek watershed, there are also potential impacts from stream features such as Alder Lake. Alder Lake is an online pond feature in the watershed that can contribute to watershed impairment through a number of ways, including: Increased water temperatures in the lake and downstream which limits fisheries habitat viability Increase in contaminant loads downstream through the loss of nutrients accumulated in lake sediments Reduction in natural sediment loads to downstream section of the creek by acting as a sediment sink Limiting fish habitat connections by acting as a barrier to fish passage/migration It is the intent of this study to provide criteria, targets, and recommendations to mitigate the environmental impacts noted above. 4.2 Remediation Targets As stated in the introduction to this report, there are a number of objectives of the Alder Creek Watershed Study and the Upper Strasburg Creek Subwatershed Plan Update. Some of these objectives require specific targets that will provide benchmarks for measuring success against goals for the objectives. The potential impacts from urbanization also need to be addressed in these targets. The objectives are to: Provide BMP recommendations that will address groundwater and surface water management from a water quality and water quantity perspective Provide recommendations that will address aquatic systems protection from a water quality and water quantity perspective Provide land use management recommendations that will protect vulnerable groundwater areas and well head protection areas Provide guidance on management of natural heritage components in the watershed Specific to Alder Creek Identify opportunities for improving the water quality in Alder Lake Goals associated with each of these objectives need to be set to identify specific targets for urbanizing areas. This will result in significant environmental protection related to the environmental threats and the measurable success of the implementation strategy T111_W KWO

3 4. ENVIRONMENTAL IMPACTS ASSESSMENT AND REMEDIATION TARGETS Goals and targets for each objective are, as follows: 1) Provide BMP recommendations that will address groundwater and surface water management from a water quality and water quantity perspective: Goal is to maintain groundwater infiltration capacities in the watershed that will ensure sustainability of municipal groundwater supply. This applies to the Alder Creek watershed and adjacent Upper Strasburg Creek subwatershed. Target Maintain existing conditions or increase infiltration where it is beneficial to groundwater resources or stream baseflow maintenance. This is supported by the infiltration rate target response units illustrated in Figure 4-1 for the Alder watershed, and more specifically for the Upper Strasburg subwatershed in 4-2 and shown as target rates in Table 4.1 for the Alder watershed and Table 4.2 for the Upper Strasburg subwatershed. Target Maintain the form and function of the gravel pits in the watershed as it relates to maintenance of groundwater infiltration rates and location Goal is to maintain groundwater infiltration rates in the watershed that will ensure maintenance of the groundwater contribution of baseflow volumes in Alder Creek and Upper Strasburg Creek. Target Balanced water budget to maintain existing conditions of storage and infiltration in hummocky terrain or increase infiltration where it is beneficial to groundwater resources or stream baseflow maintenance. This is supported by the infiltration rate targets illustrated in Figure 4-1 for the Alder watershed and more specifically for the Upper Strasburg subwatershed in Figure 4-2 and shown in Table 4.1 for the Alder watershed and Table 4.2 for the Upper Strasburg subwatershed. Target Maintain the function of the hummocky terrain in the watershed as it relates to maintenance of groundwater infiltration rates Goal is to protect groundwater resources from contamination from industrial sources, agricultural sources, urban residential sources including contaminated runoff, chlorides from road salt application and communal wastewater treatment systems, and rural residential sources including private sewage systems. Target Maintain water quality of groundwater resources to current levels or improve where opportunities arise. In urban developing areas, ensure that chloride levels meet the RUC criteria 2) Provide recommendations that will address aquatic systems protection from a water quality and water quantity perspective: Goal is to maintain flow quantities in Alder Creek and tributaries and Upper Strasburg Creek. Target Maintain streamflow rates and frequencies at pre-development (existing) conditions. (It is assumed these targets address erosion thresholds.) Peak flow rates based on the Alder Creek hydrologic model are provided in Table 4.3. Peak unrouted flow rates based on the Upper Strasburg Creek hydrologic model are provided in Table 4.4. These flows are currently modified by the existing culvert as shown in Table 4.4. Target Maintain Alder Creek flood elevations at current levels to protect property from flood risk and maintain wetland habitats. Maintain Upper Strasburg Creek flood elevations below elevation 335 m to protect property from flood risk T111_W KWO 4-3

4 ALDER CREEK WATERSHED STUDY AND UPPER STRASBURG CREEK SUBWATERSHED PLAN -FINAL REPORT TABLE 4.1 ALDER CREEK WATERSHED FINAL CALIBRATED HYDRAULIC CONDUCTIVITY AND RECHARGE VALUES FOR RUS (LAYER 1) RU Hummocky/Nonhummocky Material/Description K (m/sec) Recharge (mm/year) 1 Non-hummocky Impervious and water bodies 5.0E Hummocky Impervious and water bodies 5.0E Non-hummocky Wetland 5.5E Hummocky Wetland 5.5E Non-hummocky Clay till (low vegetation) 1.0E Hummocky Clay till (low vegetation) 1.0E Non-hummocky Clay till (medium vegetation) 1.0E Hummocky Clay till (medium vegetation) 1.0E Non-hummocky Clay till (high vegetation) 1.8E Hummocky Clay till (high vegetation) 1.8E Non-hummocky Silt till (low) 4.2E Hummocky Silt till (low) 4.2E Non-hummocky Silt till (high) 4.2E Hummocky Silt till (high) 4.2E Non-hummocky Sand till (low) 5.0E Non-hummocky Sand and gravel (low) 3.7E Hummocky Sand and gravel (low) 3.7E Non-hummocky Sand and gravel (medium) 3.7E Hummocky Sand and gravel (medium) 3.7E Non-hummocky Sand and gravel (high) 5.0E Hummocky Sand and gravel (high) 5.0E T111_W KWO

5 ALDER CREEK WATERSHED STUDY Figure 4-1 Recharge Distribution and Response Units _W KWO

6 ALDER CREEK WATERSHED STUDY AND UPPER STRASBURG CREEK SUBWATERSHED PLAN -FINAL REPORT This page intentionally left blank T111_W KWO

7 UPPER STRASBURG CREEK SUBWATERSHED PLAN UPDATE PROJECT NO Figure 4-2 Upper Strasburg Recharge Distribution and Gawser Response Units _W KWO

8 ALDER CREEK WATERSHED STUDY AND UPPER STRASBURG CREEK SUBWATERSHED PLAN -FINAL REPORT TABLE 4.2 AVERAGE RECHARGE CALCULATIONS FOR UPPER STRASBURG/ALDER CREEK AREAS BASED ON MODFLOW MODEL OUTPUT Recharge Rate (mm/yr) Recharge Area (km 2 ) Recharge (m 3 )/yr AREA Total Total Avg. Recharge Rate (mm/yr) AREA Total Total Avg. Recharge Rate (mm/yr) AREA 3 a) AREA 3 Modelling Data b) AREA 3 No Modelling Data Total Total Avg. Recharge Rate (mm/yr) AREA 4 a) AREA 4 Modelling Data b) AREA 4 No Modelling Data Total Total Avg. Recharge Rate (mm/yr) T111_W KWO

9 4. ENVIRONMENTAL IMPACTS ASSESSMENT AND REMEDIATION TARGETS TABLE 4.3 GAWSER MODEL EXISTING PEAK FLOW RATE RESULTS FOR ALDER CREEK Location Railway Embankment Upstream of Petersburg GAWSER ID Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr Reg. # Snider Rd. at Petersburg # Hwy 7/8 West Branch # Alder East Branch # Confluence of West and East Branches # Bleams Road # Alder Creek upstream of trailer park tributary # Alder Creek downstream of trailer park tributary # Alder Creek at WSC gauge, Huron Road # Trout Tributary # Confluence of Trout Tributary and Alder Creek # Alder Lake # Alder Lake at New Dundee (in) # Alder Lake at New Dundee (out) # GRCA Town line Gauge # Outlet to Nith River # *Note: Refer to complete hydrologic output tables in Appendix B TABLE 4.4 PEAK FLOWS IN CURRENT UPPER STRASBURG CREEK WATERSHED (M 3 /S) Location Upper Portion of Subwatershed Area GAWSER ID Unrouted With Culvert 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr Reg. 100-Yr Reg West of Fischer-Hallman North of Bleams Road Fischer-Hallman Culvert To Sunfish Pond Total Above Development Area Development Area Total with Development Area Total at Huron Road *Note: Refer to complete hydrologic output tables in Appendix B T111_W KWO 4-9

10 ALDER CREEK WATERSHED STUDY AND UPPER STRASBURG CREEK SUBWATERSHED PLAN -FINAL REPORT Goal is to maintain water quality in Alder Creek and tributaries and Upper Strasburg Creek. Target Provide Enhanced or normal stormwater quality control in accordance with the Ministry of the Environment SWM criteria as recommended in Section 10.5 of this report Goal is to maintain or improve aquatic habitat in Alder Creek and tributaries and Upper Strasburg Creek. Target Maintain cold water fisheries habitats that currently exist (see Appendix C for stream conditions that must be maintained, Strasburg Creek Master Drainage Plan Study Report [Paragon Engineering and Ecologistics, 1991]) Target Improve warm water fisheries areas to cold water fisheries through improvements in groundwater recharge and protection of surface water resources from temperature increases 3) Provide land use management recommendations that will protect vulnerable groundwater areas and well head protection areas: Goal is to reduce the impact of existing land uses on groundwater resources and minimize the impact from new land uses Target Make land use decisions that would lead to an improvement in water quality Target Mitigate the impacts of any land use changes through appropriate SWM practices Target Apply and/or maintain existing well head protection areas in the watershed identified in the Region s Water Resources Protection Strategy and watershed based source water protection initiatives Target Maintain land use programs identified in this study, the Region s Water Resources Protection Strategy and watershed based source water protection initiatives Target Any new development must achieve Reasonable Use Criteria at property boundaries and cumulatively at the water supply in regard to the impacts of road salt applications to groundwater contamination Target Maintain the function of the hummocky terrain in the watershed as it relates to the distribution and maintenance of groundwater infiltration rates 4) Provide guidance on natural heritage components in the watershed Goal is to protect or enhance existing natural heritage features in the watershed Target Maintain existing wetland form and function as defined in this report Target Stabilize erosion areas in the watershed Target Improvement in extent and function of riparian cover in the watershed Target Maintain or enhance form and function of existing hectares of woodland area Target Maintain or improve the form and function of wildlife/greenspace linkages T111_W KWO

11 4. ENVIRONMENTAL IMPACTS ASSESSMENT AND REMEDIATION TARGETS 5) Look at opportunities for improving the water quality in Alder Lake and reducing the impact of Alder Lake on the downstream aquatic environment: Goal is to improve water quality in Alder Lake and in the downstream aquatic environment Target Reduce sediment load to Alder Lake Target Reduction in nutrient loading emanating from existing sediments in the lake Target Improve water quality to levels above PWQOs Target Improve water quality downstream of Alder Lake T111_W KWO 4-11