Hydrogeological Assessment Report

Transcription

1 Oakville Green Health Sciences and Technology District Oakville, Ontario Prepared For: Oakville Green Development Inc. (OGDI) November HG1

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3 Oakville Green Health Sciences and Technology District Oakville, Ontario Prepared For Oakville Green Development Inc. (OGDI) MMM Group Limited November HG1

4 EXECUTIVE SUMMARY MMM Group Limited (MMM), a subsidiary of WSP Global Inc., was retained by Joseph Dableh of Oakville Green Development Inc. (OGDI) to provide hydrogeological consulting services for the proposed (the Site ), located northwest of Dundas Street West and northeast of Third Line, in the Town of Oakville, Ontario. MMM s scope was to carry out additional field investigations and prepare reporting to update a previously submitted EIR/FSS (Stantec, 2010) which included the Site, with this report to be submitted in support of a Draft Plan submission to the Town of Oakville in Comments received from the Town of Oakville and Conservation Halton in October, 2016 for our second submission have been taken into account and incorporated into this resubmission. The Site will be fully serviced with municipal water and sewers. The proposed development will consist of a Health Sciences and Technology District adjacent to the newly constructed Oakville Trafalgar Memorial Hospital and the proposed development will include a total of 3 phases, which will include a mix of employment use, office use, residential use, commercial and retail use, luxury condominium use, hotel and conference centre uses, medical and assisted living uses, and a Technology Innovation Center. The proposed development will also include belowground parking situated underneath almost the entire Site (excluding the proposed OGDI SWMP Block and land next to the wetland buffer and the Sixteen Mile Creek valley lands at the north property line). In terms of underground and surface water management, the proposed development will include Low Impact Development (LID) measures such as green roofs and grey-water cisterns, as part of the overall stormwater management approach. The Site is approximately ha in area and is comprised of two components: the OGDI lands at ha in area and an existing stormwater management pond block of 3.74 ha area. The Site is bordered by the following existing land uses: The newly completed Oakville Trafalgar Memorial Hospital at the lands to the southwest (on the west side of 3 rd Line); Former agricultural lands to the northwest and north (lands are currently fallow) and designated as Conservation lands. A tributary to Sixteen Mile Creek is located within 50 m of the north boundary of the Site, along with a Provincially Significant Wetland (PSW) sited along the axis of this tributary. The main branch of Sixteen Mile Creek is found within 500 to 700 m of the Site boundary, to the north and northeast; Agricultural lands to the north and northeast that are designated for residential redevelopment (Mattamy Homes); Residential and commercial developments to the southeast, on the south side of Dundas Street West; and, An existing L-Shaped SWMP Block services the land contained within the revised Glen Oak Creek subwatershed, located within the Site, fronting onto Dundas Street West. This pond is identified as the Glen Oak Regional Detention Facility (RDF). It is proposed to reconfigure the SWMP by relocating and resizing it during the development of the Site. Up until recently the Site was comprised of agricultural lands. The lands have been regraded in conjunction with the construction of the new Oakville Hospital (site grading we understand commenced after July 2011) and in conjunction with the creation of the RDF, almost the entire Site has been covered with fill, likely obtained from the excavations for the RDF and the new hospital. The permanent pool elevation for the RDF is designed to be at about masl and with the base of the pond generally found at masl. The Site is flat with elevations November HG1 Page i

5 typically graded at about masl (+/- 0.5 m) with short slopes along the north, northeast and southeast property limits to match lower grades beyond the property. Other than the RDF, the remainder of the site is vacant, and is covered in grasses and weeds. The Site and surrounding area are situated in the South Slope physiographic region and the till plain on which the Site lies is comprised of reddish coloured Clay-Silt Halton Till which is locally derived from the underlying bedrock. The underlying bedrock in the area is Upper Ordovician red Shale and interbedded Limestone of the Queenston Formation. It is encountered at shallow depth and is reported locally at depths between 0 to 5.5 metres below ground surface (mbgs) at an average depth of 2.9 mbgs. The surficial fine-grained deposits of Halton Till found throughout the study area serves to limit infiltration to the groundwater system (87 mm/year) and as a result, the local stream systems receive about three-fifths of their total water from surface runoff (123 mm/year). Almost all of the groundwater base flow into the watercourses is predicted to occur over the period of November to May, when the entire shallow system would be saturated and contributing water to the streams. The watercourses were observed in a dry condition during the summer and fall months as predicted by the water balance and in a frozen state during the winter months. Flows were observed during the spring season (March and April 2016). As presently existing, the Site is almost entirely covered with Clayey Sandy Silt Fill (1.5 and 3.2 m thickness at MMM boreholes) and which is believed to have originated from the construction of the new hospital to the southwest of the Site. The native soils below the fill are logged as Clayey Sandy Silt Till overlying weathered to highly weathered Queenston Shale bedrock with a very gradual transition from till to bedrock. The top of the Shale was interpreted between and masl at the MMM boreholes. The fill and till soils at the Site are high in clay and silt content and permeability of these soils will be low and therefore not particularly favourable for use with infiltration based mitigation measures. Permeameter testing of the fill soils on the site indicated infiltration rates on the order of 0.8 and 1.9 mm/hour (2.2 to 5.3x10-7 m/sec) to as low as 0.1 mm/hour (1.9x10-8 m/sec). The weathered Shale bedrock is considered moderately permeable with hydraulic conductivity values at bedrock monitoring wells ranging from 1.5x10-5 m/sec to 1.1x10-8 m/sec, with a geometric mean calculated at about 1.2x10-6 m/sec. Groundwater at the Site is interpreted to flow from northwest to southeast (156.5 to masl) at a gradient of about There is a northwest to southeast oriented flow divide passing through the center of the Site with groundwater being directed towards both the Glen Oak Creek subwatershed to the south, and towards the Sixteen Mile Creek watershed to the east. Groundwater passing below the north corner of the Site also is interpreted to flow towards the PSW, and during the summer and fall seasons, the data indicates this groundwater would be flowing below the wetland, which has an elevation of about 157 masl. During the early spring, groundwater levels have been observed at the Site to have risen by between 0.4 to 1.5 m above levels observed in late August 2015, with static levels ranging between masl at the north end of the Site and masl along Dundas Street West. Groundwater discharge into the wetland during the spring season was identified through monitoring of mini-piezometers within the wetland. The potential for discharge was highest at the west end of the wetland where shallow groundwater levels were recorded above the surface water elevations. At minipiezometers located at the central and eastern portions of the PSW, the shallow groundwater levels, although above grades during March 2016, were lower than the corresponding surface water elevations which suggests recharge to the ground in those areas. There is limited opportunity across the Site in the post-development condition to construct measures to mitigate against the predicted reduction in infiltration. The post development November HG1 Page ii

6 imperviousness of the Site is calculated at 96.1% due to the extent of the 1.5-level underground parking garage and the proposed interior SWMP location that will be entirely surrounded by the parking structures. The development will include 3.51 ha of green roofing area that will help to reduce runoff from the Site through evapotranspiration. Excess runoff from green roofs and standard roofs will be used for additional LID measures, such as use in grey-water cisterns and infiltration trenching and runoff augmentation towards natural areas. After accounting for water directed towards infiltration trenches, approximately 24,000 m 3 /year of this roof water can be available for greywater cisterns or other LID uses. A length of 135 m of infiltration trenching is proposed along the perimeter of the wetland buffer plus an additional 165 m of trench immediately to the south ending just north of where the internal road leaves the Site. Despite the low infiltration capacity of the fill soils (1.4 mm/hour on average, 0.6 mm/hour used in the calculations), the post-development water balance calculations indicate that a balance in infiltration to the groundwater that is directed towards the wetland van be achieved, currently calculated at about an additional 1.1% over the predevelopment (2010) condition (1,202 m 3 /year vs. 1,188 m 3 /year). The total proposed length of infiltration trenches of 240 m however, cannot achieve an overall infiltration balance of the Site s contributions towards the tributary to Sixteen Mile Creek and a loss of 70% is predicted by the water balance (5,785 m 3 /year reduction). The feature-based water balance for the PSW indicates a small reduction in infiltration to the wetland on the order of 6.1% with mitigation measures employed at the OGDI Site (3,786 m 3 /year reduction). These losses are wholly originating on development lands northwest of the OGDI Site (the District Energy Lands and future 407 Transitway) as mitigation measures for these lands were not included in the water balance. However, approximately 600 m length of development lands border onto the watercourse (natural heritage system lands), and it was demonstrated that infiltration trenches along these boundaries, with similar design to those proposed at OGDI should be capable of providing enough water into the ground to achieve an overall balance to the PSW. The proposed 1.5 level underground parking garage structures with their footprints extending to the property lines or within 6 to 12 m of the PSW buffer, will, if uncontrolled, lead to a lowering of the water table at the Site boundary and in the lands surrounding the Site. The base of these structures is anticipated to be at about masl, or between about 0.5 and 3.0 m below the groundwater table as monitored in late August 2015, or to about a maximum of 4.0 m under spring conditions with the seasonally high water table. Based on the average horizontal hydraulic conductivity (1.2x10-6 m/sec) of the weathered Shale bedrock, the ZOI to the point where groundwater level declines are predicted to be less than 0.5 m, and therefore well within the range of natural groundwater level variability, is calculated at about 39 m from the edge of the buildings and underground parking structures. In order to limit the effects of this drawdown on lands within the natural environment to the north and northeast of the Site (the PSW and Sixteen Mile Creek tributary valley) and not negate the mitigation value of the proposed infiltration trenches, measures to limit this induced drawdown will need to be implemented. These include measures such as constructing the underground basements and parking structures as tanked structures or installing a slurry wall trench around the perimeter of the structures to retard groundwater flow towards the sub-drainage system. Dewatering of the extensive excavations that will extend below the water table within the Site limits is anticipated for the weathered Shale bedrock and an Environmental Activity Sector Registry (EASR) or a Permit to Take Water (PTTW) will likely need to be obtained from the November HG1 Page iii

7 MOECC for these activities. A long-term PTTW may also need to be obtained for the operation of the development s sub-drainage system. The following recommendations are provided: Collect clean runoff from the green roofs and the standard roofs and use this water for LID measures such as providing water to the infiltration trenches nearby to the PSW. The remainder of this water may be used to supply grey-water for non-potable uses in the multi-story buildings or for irrigation of landscaping features within the development limits; Construct an infiltration trench along the edges of the PSW buffer and along the Sixteen Mile Creek tributary valley edge and direct clean roof runoff into the trenches and permit it to infiltrate into the ground. These will consist of narrow swales filled with clear stone constructed at the of edge of the PSW buffer; Additional permeameter testing should be conducted along the proposed infiltration trench alignment during detailed design to confirm the infiltration rates of the surficial soils along the alignment of the proposed trenches, and this information used in refining the sizing of the trenches; Steps to minimize post-development reduction in the infiltrative capacity of the low permeability Fill soils should be implemented where feasible, including: o Scheduling site grading and heavy construction activities during the drier summer months to reduce the potential of lowering the permeability of these materials while they are in a wet state; o Designate the area where infiltration trenches are proposed as a no-traffic zone. In particular heavy construction equipment must be kept away from the crests of the slope by the valley lands along the PSW buffer boundary, where infiltration trenches are proposed; o Construction of the infiltration trenches should only be done in dry weather to avoid additional remoulding the soil and effectively lining the trench walls and trench base with an impervious smeared layer of soil; o Manual scraping and removal of smeared soils from the sidewalls and base of the trenches to remove any smeared zones and to expose what fracturing that may be present in the fill should be contemplated; Incorporate measures that will eliminate or greatly reduce the magnitude of any underground parking level induced groundwater drawdown in the direction of the PSW and Sixteen Mile Creek tributary, and that will not interfere with the benefits of the proposed Infiltration trenches. Two potential options have been examined: o o Construct the underground levels as tanked (waterproof) structures; or, Install slurry wall trenches between the building footprints and the property boundaries. This will necessitate a small reduction in the sizes of the building and underground parking level footprints to provide adequate space for the slurry wall, building sub-drainage systems (e.g., perimeter drains) and mitigation measures such as the infiltration trenches (which would need to be constructed between the slurry wall and the PSW buffer) Additional investigations carried out by a geotechnical engineer would be required during detailed design; At this time, the second option is anticipated to be the preferred option. Further examination of the options presented above and other potential methods not yet identified will take place during detailed design to confirm the preferred option; Anti-seepage collars should be installed at 50 m intervals along the proposed Glen Oak RDF storm sewer to prevent groundwater flow along the backfill to the south towards Dundas Street West; November HG1 Page iv

8 The underground parking structures will have a proposed base elevation of about masl and the SWMP will have a proposed bottom elevation, excluding liner thickness, at about masl. Where bedrock or sand seams within the native Till are encountered within the SWMP envelope, a clay liner will be required. Bedrock was encountered at the MMM boreholes on the Site between and masl; Construction dewatering of the underground parking structures and the SWMP should be anticipated and an Environmental Activity Sector Registry (EASR) or a Permit to Take Water (PTTW) from the Ministry of Environment and Climate Change will likely be required for dewatering. The particulars for the EASR or PTTW would be confirmed at detailed design as additional details become known (e.g., construction staging, final depths, layouts, availability of additional soils and groundwater information from geotechnical drilling, etc.). The application would include mitigation measures to address short-term drawdown effects at the PSW due to construction dewatering as well as contingency plans in the event that the impacts from dewatering are greater than had been anticipated; Long-term operations of the building sub-drainage system network, which will likely require pumping of the collected groundwater to the sewer network, may also be subject to issuance of a separate, long-term PTTW for the operation of the system; and, Over one year of baseline monitoring has been completed at the Site and the PSW. Baseline monitoring should be continued up to the spring of 2017 to obtain a second set of seasonal high groundwater level data at which time the active monitoring will be suspended unless a review of collected data suggests otherwise. Monitors presently constructed on the Site are recommended to remain in place for future monitoring in support of this development until such time as they are no longer needed, in which case they will also need to be decommissioned as per the requirements of O.Reg. 903 (as amended). November HG1 Page v

9 TABLE OF CONTENTS EXECUTIVE SUMMARY... I 1.0 INTRODUCTION Subwatersheds Work Program REGIONAL PHYSIOGRAPHY AND GEOLOGICAL SETTING Regional Geology and Hydrostratigraphy Topography and Drainage HYDROGEOLOGICAL EVALUATION On-Site and Off-Site Investigations Investigations by Others Site Geology Grain Size Analyses In-Situ Permeability Testing Groundwater Level Monitoring Groundwater Quality Surface Water Quality Local Hydrogeological Setting IMPACTS OF THE PROPOSED DEVELOPMENT Water Balance Methodology Climate and Water Surplus Inputs to Water Balance Pre-Development Condition (2010) and Existing Condition (2015) Post-Development Conditions Water Balance Pre-Development and Existing Condition Water Balances Post-Development Water Balances Post-Development Water Balance with No Mitigation Post-Development Water Balance with Mitigation Discussion of Water Balance Results Discussion of the Potential for Base Flow Reductions to Watercourses Dewatering Potential CONCLUSIONS AND RECOMMENDATIONS November HG1 Table of Contents

10 6.0 STANDARD LIMITATIONS REFERENCES LIST OF FIGURES Page Figure 1: Site Location... 3 Figure 2: Pre-Existing and Existing Subwatersheds... 4 Figure 3: Surficial Geology... 9 Figure 4: MOECC Water Well Records...10 Figure 5: Hydrogeologic Cross-Section A-A...11 Figure 6: Interpreted Groundwater Contours Summer Figure 7: Interpreted Groundwater Contours Fall Figure 8: Interpreted Groundwater Contours Spring Figure 9: Proposed Development Plan and Infiltration Measures...36 Figure 10: Groundwater and Surface Water Catchments for the PSW...48 Figure 11: Conceptual Infiltration Trench...57 November HG1 Table of Contents

11 LIST OF TABLES Page Table 1: Pre-Existing and Existing Subwatershed Areas at the Site... 5 Table 2: Pre-Existing and Existing Contributing Areas to the PSW... 6 Table 3: Hazen Estimates of Hydraulic Conductivity...16 Table 4: Tri-Linear Soil Classification...18 Table 5: In-Situ Permeability Testing Summary...19 Table 6: Permeameter Test Results...21 Table 7: Data Logger Locations...22 Table 8: Inputs Used in the OGDI Site Specific Water Balance...39 Table 9: Inputs Used in the PSW Feature Based Water Balance...40 Table 10: Comparison of LID Measures...44 Table 11: Areas of Site Contributing Infiltration and Runoff towards the PSW...47 Table 12: Pre-Development and Existing Condition (2015) Water Balance...50 Table 13: Pre and Post Development Water Balance No Mitigation...54 Table 14: Pre and Post Development Water Balance With Mitigation...58 Table 15: Predicted Zone of Influence...60 APPENDICES APPENDIX A MOECC Water Well Records APPENDIX B Borehole Logs APPENDIX C Soil Analysis Results APPENDIX D Hydraulic Conductivity Testing APPENDIX E Water Level Data APPENDIX F Groundwater Quality Data APPENDIX G Monthly Water Balance APPENDIX H Standard Conditions and Limitations November HG1 Table of Contents

12 1.0 INTRODUCTION MMM Group Limited (MMM), a subsidiary of WSP Global Inc., was retained by Joseph Dableh of Oakville Green Development Inc. (OGDI) to provide hydrogeological consulting services for the proposed (the Site ), located northwest of Dundas Street West and northeast of Third Line, in the Town of Oakville, Ontario (see Figure 1). MMM s scope was to carry out additional field investigations and prepare reporting to update a previously submitted EIR/FSS (Stantec, 2010) which included the Site, with this report to be submitted support of a Draft Plan submission to the Town of Oakville in Comments received from the Town of Oakville and Conservation Halton in October, 2016 for our second submission have been taken into account and incorporated into this resubmission. The Site is approximately ha in area and is comprised of two components: the OGDI lands at ha in area and an existing stormwater management pond (SWMP) block of 3.74 ha area. For the purposes of this report, these two parcels will be combined and referred to as the Site as the proponent is proposing to reconfigure and shift the location of the SWMP. The Site is bordered by the following existing land uses as illustrated on Figure 2: The newly completed Oakville Trafalgar Memorial Hospital at the lands to the southwest (on the west side of 3 rd Line); Former agricultural lands to the northwest and north (lands are currently fallow) and designated as Conservation lands. A tributary to Sixteen Mile Creek is located within 50 m of the north boundary of the Site, along with a Provincially Significant Wetland (PSW) sited along the axis of this tributary. The main branch of Sixteen Mile Creek is found within 500 to 700 m of the Site boundary, to the north and northeast; Agricultural lands to the north and northeast that are designated for residential redevelopment (Mattamy Homes); Residential and commercial developments to the southeast, on the south side of Dundas Street West; and, An existing L-Shaped SWMP Block services the land contained within the revised Glen Oak Creek subwatershed, located within the Site, fronting onto Dundas Street West. This pond is identified as the Glen Oak Regional Detention Facility (RDF). It is proposed to reconfigure the SWMP by relocating and resizing it during the development of the Site. The future development on the Site will be fully serviced with municipal water and sewers. The proposed development will consist of a Health Sciences and Technology District adjacent to the newly constructed Oakville Trafalgar Memorial Hospital. The proposed development will include a total of 3 phases, which will include a mix of employment use, office use, residential use, commercial and retail use, luxury condominium use, hotel and conference centre uses, medical and assisted living uses, and a Technology Innovation Center. The proposed development will also include below-ground parking situated underneath almost the entire Site (excluding the SWMP Block and the lands bordering the PSW buffer and Sixteen Mile Creek valley lands). In terms of underground and surface water management, the proposed development will include Low Impact Development (LID) measures, as part of the overall stormwater management approach. Up until 2011 the Site was comprised of agricultural lands. The lands have been regraded in conjunction with the construction of the new Oakville Hospital (site grading we understand November HG1 Page 1

13 commenced after July 2011) and in concert with the creation of the RDF, almost the entire Site has been covered with fill, likely obtained from the excavations for the RDF and the new hospital. The permanent pool elevation for the existing RDF is designed to be at about masl, with the base of the pond generally found at masl. The Site is flat with elevations typically graded at about masl (+/- 0.5 m) with short slopes along the north, northeast and southeast property limits to match lower grades beyond the property. Other than the RDF, the remainder of the site is vacant, and is covered in grasses and weeds. Prior to the site grading activities, three NOCSS 1 -identified subwatersheds traversed the Site, identified from west to east as GO1116 (Glen Oak Creek), SM1117a, and SM117 (the latter two subwatersheds fall into the Sixteen Mile Creek watershed system, see Figure 2). The site grading has resulted in almost all of the site draining into the RDF, with minor drainage along the Site periphery along Dundas Street West (southeast side of the property, draining to the Glen Oak Creek and Sixteen Mile Creek systems) and to the tributary to Sixteen Mile Creek along the north and northeast edges of the property. Treated water from the RDF is discharged into the Glen Oak Creek and Sixteen Mile Creek watershed systems with approximately 82% of the treated discharge directed into the Glen Oak watershed system, and the remainder (18%) being directed into the Sixteen Mile Creek watershed through a flow splitter. One stormwater management option was considered by WalterFedy in their Preliminary Glen Oak & Sixteen Mile Creek Stormwater Management Plan Report (WalterFedy, November 2016). This option proposes relocating the existing Glen Oak RDF onto the District Energy lands to the north of the Site. This facility will treat all storm water runoff from lands within the Glen Oak subwatershed that are north of William Halton Parkway. The treated runoff from the Glen Oak RDF will be directed primarily into the Sixteen Mile Creek watershed via a storm sewer to be located along the eastern property line of the Site, with some overflow draining to the Glen Oak subwatershed to expedite drain down times in the pond. Storm water runoff from the OGDI Site will be treated through a privately owned facility featuring 690 below-grade treatment and storage chambers. Treated runoff from the OGDI SWM chambers will be directed to the Glen Oak Creek outlet at Dundas Street West. A municipal pond is also proposed within the OGDI district. This pond will treat runoff from the Oakville Trafalgar Memorial Hospital (following decommissioning of the hospital s on-site facility), William Halton Parkway, and Third Line as well as provide the previously mentioned additional attenuation of outflow from the District Energy Pond. Discharge from this municipal pond will also be directed to the Glen Oak Creek outlet at Dundas Street West. This scoped hydrogeological evaluation of the Site was carried out by MMM based on the North Oakville Environmental Implementation Report and Functional Servicing Study Terms of Reference (Town of Oakville, 2013). The stated purpose of the EIR is to characterize and analyze the natural heritage features and functions, and to determine and address the potential impacts of a proposed development application, including servicing requirements on the natural heritage system. The hydrogeological evaluation included interpreting regional geology and site-specific geology and hydrogeology, based on fieldwork carried out by MMM at the Site between June 2015 and October A breakdown of the fieldwork activities carried out is provided in Section 1.2 with detailed descriptions of the activities provided in Section 3.1 and its sub-sections. 1 North Oakville Creeks Subwatershed Study November HG1 Page 2

14 . Milton Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Site Location Lake Ontario Legend ^_ Site Location Site Boundary Kilometers Glen Oak Regional Detention Facility (Town of Oakville Lands) Watercourses HWY 407 Sixteen Mile Creek Neyagawa B oulevard Municipal Boundary J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 1 Site Location.mxd 2016 Microsoft Corporation and its data suppliers Bronte Road Dundas Street West Third Line Oakville Client Prepared By Scale Date Oakville Green Development Inc. Scale as Shown November 2016 Queen's Printer for Ontario Kilometers Project No HG1 Figure: 1

15 . HWY 407. Pre-Existing Subwatersheds - Circa 2010 Existing Subwatersheds HWY 407 Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Pre-Existing and Existing Subwatersheds Legend Site Boundary Pre-Existing Subwatersheds - Circa 2010 GO1116 SM117 SM1117a Existing Subwatersheds Glen Oak Creek Sixteen Mile Sixteen Mile Sixteen Mile Creek J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 2 Pre-Existing and Existing Subwatersheds.mxd Dundas Street West 2016 Microsoft Corporation and its data suppliers Third Line Cr e e k Glen Oak Regional Detention Facility Dundas Street West 2016 Microsoft Corporation and its data suppliers Regional Municipality of Halton Third Line Cr e ek Glen Oak Regional Detention Facility Client Prepared By Scale Date Scale as Shown Oakville Green Development Inc. November 2016 Queen's Printer for Ontario Meters Project No HG1 Figure: 2

16 1.1 Subwatersheds The Site was originally located within three subwatershed catchments identified in the NOCSS prior to the placement of fill on the property and construction of the RDF. These subwatersheds were identified in the NOCSS as being in part of the Glen Oak Creek watershed (subwatershed GO1116), and within the Sixteen Mile Creek watershed (subwatersheds SM1117a and SM117), as shown on Figure 2. Site grading and the construction of a diversion channel to the northwest of the Site have thoroughly altered the drainage pattern such that the original subwatershed catchments no longer apply. The existing watershed boundaries are also presented on Figure 2. Almost all of the drainage from the Site (estimated at about 13.3 ha), as well as drainage from 3 rd Line, a small part of the hospital lands and from the currently fallowed lands to the north and northwest, are directed to the central SWMP (the RDF). Small portions of the Site drain directly towards the Sixteen Mile Creek tributary (about 1.6 ha) or towards the Glen Oak Creek system via Dundas Street West (approx. 0.5 ha). Treated water from the RDF is discharged into the Glen Oak Creek (82% of discharge) and Sixteen Mile Creek watershed systems (18% of total discharges) through a flow splitter. Table 1: Pre-Existing and Existing Subwatershed Areas at the Site Glen Oak Creek (GO1116) Sixteen Mile Trib. (SM1117a) Sixteen Mile Creek (SM117) Sixteen Mile Creek (combined) Pre-Existing Condition (2010) Total Area ha ha ha ha Portion within Site (% of subwatershed) 4.29 ha (9.5 %) 2.70 ha (19.2 %) 8.33 ha (9.0 %) ha (10.3 %) Glen Oak Creek Sixteen Mile Creek (combined) Existing Condition (2015) Total Area ha ha Portion within Site (% of subwatershed) ha (29.4 %) 1.62 ha (1.6 %) Note: Changes to the subwatersheds were made as a result of the development of the hospital lands to the southwest of the Site and these are reflected in the 2015 area calculations. A further note regarding the ha portion within the Site that is identified within the Glen Oak Creek subwatershed. Runoff from the Site and upgradient lands outside of the Site are directed to the RDF, and the RDF is designed with a flow splitter that directs 82% of the runoff to the Glen Oak Creek system, and the balance (18%) to the Sixteen Mile Creek system. As noted in the introduction, there is a PSW sited immediately north of the Site along the tributary to Sixteen Mile Creek. As requested by Conservation Halton, MMM carried out a water balance for the entirety of lands contributing water towards this PSW (see Section 4.0). Table 2 presents the contributing areas to the PSW for both surface water and groundwater inputs. November HG1 Page 5

17 Currently, the OGDI lands contribute less than 2% of the calculated surface runoff and groundwater inputs towards the wetland. Table 2: Pre-Existing and Existing Contributing Areas to the PSW Entire Catchment Area Groundwater Surface Water Pre-Existing Condition (2010) Total Area ha ha Portion within Site (% of catchment) 1.23 ha (1.7 %) 1.80 ha (2.3 %) Existing Condition (2015) Total Area ha ha Portion within Site (% of catchment) 1.23 ha (1.7 %) 1.05 ha (1.2 %) Note: Changes to the subwatersheds were made as a result of the development of the hospital lands to the southwest of the Site and these are reflected in the 2015 area calculations. 1.2 Work Program The work program for the hydrogeological investigation was designed to address the requirements outlined in the Terms of Reference (TOR), including: Review of background information pertinent to the subwatersheds, including areas beyond the Site limits; Field investigations, including: o Site visits, initial site inspection and quarterly monitoring visits; o Drilling boreholes and installing monitoring wells and a mini-piezometer nest; o Soil sampling and grain size analyses of selected samples; o Quarterly groundwater level monitoring, including continuous monitoring using data loggers at selected monitoring wells; o Groundwater and surface water sampling; and, o Single well hydraulic conductivity testing and shallow soil permeameter testing. Assessing site conditions, including: o Characterizing the local geologic and hydrogeologic conditions; o Identifying groundwater discharge areas and evaluating surface water base-flows; o Establishing surface water-groundwater interactions; o Preparing pre-development and post-development water balance analyses at the Site including a feature based water balance for the adjacent PSW; Assessing LID methodologies for suitability of use at the Site; Analyzing and assessing the potential impacts of the development; and, Providing recommendations for the mitigation of any potential impacts. November HG1 Page 6

18 2.0 REGIONAL PHYSIOGRAPHY AND GEOLOGICAL SETTING 2.1 Regional Geology and Hydrostratigraphy The Site and surrounding area are situated in the South Slope physiographic region identified by Chapman and Putnam (1984). The Trafalgar Moraine, a subtle topographic ridge that was formed during the retreat of the Lake Ontario ice lobe 12-13,000 years ago, extends from western Mississauga across the northern part of Oakville and is found to the northwest of the site marking the boundary between the South Slope and the Peel Plain physiographic region located further to the north. The till plain on which the Site lies is comprised of reddish coloured Clay-Silt Halton Till which is locally derived from the underlying bedrock. The surficial geology at the Site and the surrounding area is shown on Figure 3. The underlying bedrock in the area is Upper Ordovician red Shale and interbedded Limestone of the Queenston Formation. It is encountered at shallow depth and is reported in the MOECC water well records within a 500 m radius of the site as seen on Figure 4 (see Appendix A for the well records). The bedrock is identified as red shale with limestone, at depths between 0 to 5.5 metres below ground surface (mbgs) at an average depth of 2.9 mbgs. This is illustrated on Cross-Section A-A presented on Figure 5. The shale is exposed at surface along the steep valley walls of Sixteen Mile Creek to the northeast and east. On a regional basis the bedrock surface is interpreted to be dipping from the northwest to southeast, generally following the regionally topographic slope, mapped with a surface elevation of approximately 157 down to 152 masl in the vicinity of Site (Ontario Department of Mines, 1964). The Halton Till and the Queenston Shale are poor aquifers due to their fine-grained nature and low permeability and are capable of providing only limited quantities of groundwater to water wells. In terms of existing groundwater usage, within the jurisdiction of the Halton Region Conservation Authority, approximately 75% of all wells are completed into the bedrock, which indicates that the surficial overburden deposits of Halton Till are not a significant source of groundwater in the area (Singer et al, 2003). Most wells in the study area are completed into the bedrock. The bedrock in the area is also described as a poor aquifer due to poor pore space interconnections in the shale. The Queenston Formation shale does not fracture easily or dissolve, which limits its effective porosity. The upper 3 to 5 m of the bedrock is weathered, and is where most of the available yield is observed. The reported geometric mean averages of the specific capacity and Transmissivity for this formation are 1.5 litres/min/m and 2.7 m 2 /day, respectively (Singer et al, 2003). The bedrock is therefore considered a poor aquifer with yield capacities barely enough to satisfy individual domestic water needs. As reported in Singer et al (2003), 92% of all wells completed within the Queenston Shale (across Southern Ontario, not only Halton Region) are reported as providing fresh water. Salty water is reported at 5% of these wells and the remaining 3% of wells are reported with either mineralized or sulphurous water. Water quality from the shale is considered highly variable, ranging from good to poor. Water quality from 12 samples were presented in the Singer report, and indicated the water is hard (mean hardness of 472 mg/l), has high levels of sodium and chloride (averages of 88 and 123 mg/l respectively), and an average concentration for sulphate of 251 mg/l. Groundwater flow in the bedrock is shown on published mapping as flowing to the southeast below the Site (approx to masl) with a deflection towards the deep valley of Sixteen Mile Creek (Ostry, 1979). Figure 6 presents the interpreted bedrock groundwater November HG1 Page 7

19 contours at the Site based on the on-site borehole data collected in August On this figure, groundwater in the bedrock is seen to generally flow from northwest to southeast with deflections to the south and to the east towards the Sixteen Mile Creek tributary with horizontal flow gradients ranging from about at the northwest to between and at the south and east portions of the Site. Downward leakage from the RDF, which we understand was constructed without a liner, may be resulting in some groundwater mounding below the pond, and which may be leading to the prominent groundwater flow divide and the divergent flow paths being interpreted at the Site. The present day groundwater contour pattern, while similar to the generally easterly groundwater flow presented in the original EIR/FSS (Figure 3.8, Stantec, 2010), does differ in the pronouncement of the flow divide and in the observed groundwater elevations. Groundwater levels measured at the Site in 2015 were approximately 2 to 3 m lower than inferred by the original EIR/FSS interpretation. We note that the originally reported elevation of monitoring well MW which has survived is shown on the borehole log at masl, whereas the ground elevation at this well was surveyed by MMM s hydrogeological staff at masl; a difference of approximately 2.2 m lower than originally stated. 2 We suspect that the elevations of the Stantec monitoring wells were based on the regional topographic contours presented on Figure 3.2 of the original EIR/FSS report in Further discussion on groundwater levels is provided in Section Topography and Drainage The surrounding area has moderate relief (between 165 to 155 masl within 500 m of the Site), whereas the Site, after placement of fill materials and construction of the RDF, is almost flat. The slope of lands in the area of the Site generally falls from the west-northwest to eastsoutheast. The area is referred to as part of the South Slope physiographic region by Chapman and Putnam (1984). The Trafalgar Moraine, a subtle topographic ridge that extends from western Mississauga across the northern part of Oakville, lies to the northwest of the property. The local drainage network is generally oriented in a west-northwest to east-southeast direction. The local subwatersheds are located in what can be described as a bevelled till plain with local relief provided by the creek valleys, which are locally incised in the order of 5 m. Major watercourses, such as Sixteen Mile Creek to the northeast and east are incised deeply into the underlying bedrock (bedrock exposed), with steep side slopes and relief in the order of 30 m relative to the table lands. Drainage on the Site, following its alteration is almost exclusively directed to the RDF. From the RDF, the treated water is discharged to the Glen Oak Creek system (82% of flows) and the Sixteen Mile Creek system (18% of flows) through a flow splitter. 2 The elevations of the other Stantec wells could not be confirmed by MMM as these wells no longer exist or were located well beyond the Site boundaries and therefore not searched for. November HG1 Page 8

20 . Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Sixteen Mile Creek Surficial Geology Legend Site Boundary Glen Oak Regional Detention Facility (Town of Oakville Lands) Watercourses Topographic Contours (5m Interval) Surficial Geology Queenston Formation (Shale with Limestone) Halton Till Modern Alluvial Deposits Proudfoot Trail J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 3 Surficial Geology.mxd 2016 Microsoft Corporation and its data suppliers Dundas Street West Third Line Client Prepared By Scale Date Scale as Shown Oakville Green Development Inc. November 2016 Queen's Printer for Ontario Meters Project No HG1 Figure: 3

21 . Sixteen Mile Creek A' Oakville Green Health Sciences and Technology District - Hydrogeological Investigation MOECC Water Well Records Legend Site Boundary Dundas Street West Cross Section Watercourses Topographic Contours - 1m Interval Glen Oak Regional Detention Facility Provincially Significant Wetland (PSW) MOECC Water Well Records Water Well Geotechnical/Monitoring Well Geotechnical/Well Cluster Abandoned No Information J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 4 MOECC Water Wells.mxd 2016 Microsoft Corporation and its data suppliers A Third Line Proudfoot Trail Monitoring Locations Client!A Monitoring Well (MMM)!A Monitoring Well (Soil Eng)!= Monitoring Well (Stantec)!= Decommissioned Monitoring Well (Stantec)!? Decommissioned Mini-Piezometer (Stantec)!? Wetland Mini-Piezometers Prepared By Scale Date Scale as Shown Oakville Green Development Inc November 2016 Queen's Printer for Ontario Meters Project No HG1 Figure: 4

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23 3.0 HYDROGEOLOGICAL EVALUATION 3.1 On-Site and Off-Site Investigations MMM carried out hydrogeological field investigations across the Site between June 2015 and October MMM s initial hydrogeological site visit took place on June 19, During this visit, MMM hydrogeologists MMM staked out 6 on-site borehole locations (MMM15-01 to MMM15-06) across the Site. During this initial site visit, three pre-existing monitoring wells were identified at the south quadrant of the property. OGDI indicated that these monitoring wells had been installed as part of a Phase 2 ESA investigation carried out by Soil Engineers Ltd. (Soil Eng) earlier in These wells are identified in this report as SE-MW-101 to SE-MW-103. A total of 9 boreholes were drilled under MMM s supervision at 6 locations within the Site to depths of between 4.3 and 9.2 mbgs in July 2015 (MMM15-01 to MMM15-06). The borehole and monitoring well locations are presented on Figure 6 to Figure 8, which also includes the locations of the Soil Eng monitoring wells and of the monitoring wells from the original EIR/FSS study 3. Soil samples from the overburden and the weathered bedrock were collected using split spoon sampling techniques. At selected intervals, split spoon samples were obtained from the upper portion of the sample intervals. Water levels in the boreholes on the completion of drilling were recorded and monitoring wells were installed at each borehole. The monitoring wells were constructed with 51 mm diameter Schedule 40 PVC screen and riser, equipped with O-rings at the threaded joints. Screens were between 0.9 to 1.5 m in length and a sand pack was installed around the screen, extending 0.3 m above the top of the screen. A bentonite seal was placed from the top of the sand pack to about 0.3 m below grade. A protective lockable steel casing and 0.3 m of concrete at surface completed the installations. Three of the monitoring well locations (MMM15-01, MMM15-03 and MMM15-05) were constructed as nested wells with both a shallow and deeper monitoring well (constructed within adjacent boreholes) to ascertain vertical groundwater gradients. Per Conservation Halton s request on September 21, 2015 at the North Oakville Agency Review Meeting (NOARM meeting), MMM installed a nested mini-piezometer within the PSW once Permission to Enter the Glenorchy Conservation Area lands was received from Conservation Halton. The mini-piezometer nest, identified by MMM as MP15-01 Nest was installed on November 25, 2015 by MMM staff near the lower end of the wetland close by to what appeared to be the watercourse channel which was dry at the time of the installation. Two minipiezometers, comprised of 20 mm diameter stainless steel drive points housed in 38 mm diameter stainless steel shields, were driven into pre-augured shallow boreholes to depths of 1.24 mbgs (MP15-01D) and 0.52 mbgs (MP15-01S). The mini-piezometers included 21 cm long 50 mesh cylindrical filter-screens and a sand pack, consisting of No.2 silica sand, was placed around the screen, followed by a bentonite seal above the sand pack up to ground surface. Data loggers were installed within both mini-piezometers and at a surface water monitoring station completed as part of this monitoring location. During our initial entry into the PSW, and aided by the die-off in vegetation at that time of year, MMM staff was able to locate 6 additional, pre-existing, mini-piezometer stations within the 3 The locations shown on the figure of the monitors that had been decommissioned prior to filling of the Site are approximate (MW and MW108-08). November HG1 Page 12

24 wetland. Three of these mini-piezometers were identified as units installed by WalterFedy as part of the hospital construction monitoring program (SM-2 to SM-4 inclusive), and monitored by WalterFedy in 2013 and The other three mini-piezometers (one being nested) were of unknown origin with no identifying information and were arbitrarily identified by MMM as MP-A to MP-C inclusive (refer to Figure 6 for the locations for all these mini-piezometers). MMM has included all of these mini-piezometers in the monitoring program since November, None of 4 previously installed mini-piezometers located to the north of the Site from earlier EIR/FSS studies were found by MMM. A drive point piezometer (DP8-08) had been installed in the Sixteen Mile Creek tributary downstream of the PSW as part of the original EIR/FSS study on Mattamy owned lands and no attempt was made to look for that station. Borehole logs for all boreholes, including stratigraphic descriptions, sampling intervals and monitoring well details, are contained in Appendix B. Grain size analysis results from these boreholes are presented in Appendix C. Information pertaining to the mini-piezometers is found in Appendix E Investigations by Others Three previous investigations or monitoring programs are known to have been carried out at the Site or within the watercourse subcatchments previously associated with the Site. Copies of the available borehole logs and borehole location plan from the Stantec EIR/FSS report and Soil Engineers Phase 2 ESA are also included in Appendix B. Monitoring data from the PSW to the north of the Site is also available (WalterFedy, 2014) and is included in Appendix E. In addition to the three studies mentioned above, an EIR/FSS was submitted to the Town of Oakville on behalf of Mattamy Homes (lands located to the east and northeast of the Site) in October Taplow Creek, Glen Oak Creek, and 16 Mile Creek Environmental Implementation Report and Functional Servicing Study As part of the hydrogeological investigation activities for the EIR/FSS prepared for the Oakville General Hospital site, Stantec supervised the drilling of 8 boreholes in late November 2008 across the broader study area, each equipped with monitoring wells, screened in the shale bedrock. Of the well 8 locations, 1 monitoring well was located at the present Site but had been decommissioned prior to filling of the Site (MW104-08), and 2 monitoring wells had been installed to within about 50 to 100 m of the Site boundaries. These were wells MW to the northwest and still in existence, and MW108-08, to the west within the hospital building envelope and decommissioned. These monitoring well locations are shown on Figure 6 to Figure 8. In addition to the 8 monitoring wells, eight drive-point mini-piezometers were also installed across the EIR/FSS study area, with one such device (identified as DP8-08) installed into Sixteen Mile Creek to the north of the Site (this mini-piezometer could not be located by MMM staff and is presumed decommissioned). Additionally, as part of the EIR/FSS, a 12 borehole drilling program was carried out at the District Energy Site north of future Burnhamthorpe Road and the Site, by Terraprobe Limited. Those 12 borehole logs are missing from the 2010 EIR/FSS report appendices and therefore they were not considered in this current report. In addition to the above noted drilling program, Stantec s EIR/FSS field work program also included the following: Groundwater level monitoring at the 8 monitoring wells across the study area between December 2008 and January Data loggers were installed at each monitoring well. o As noted in Section 1.0, the reported borehole elevation at the one remaining surviving monitoring well, MW105-08, was reported as 2.2 m higher than the November HG1 Page 13

25 elevation surveyed by MMM field staff in 2015, and therefore the reported water level readings relative to sea level (i.e., masl) from the original EIR/FSS report should be considered as approximate; Bedrock groundwater samples were collected from each of the 8 monitoring wells and the water samples were analyzed for general chemistry and metals; and, In-situ permeability testing was carried out at 6 of the 8 wells, including monitors MW (on-site) and MW (immediately northwest of the Site) Phase 2 ESA A Phase 2 ESA at the Site was carried out by Soil Engineers, and three boreholes and six test pits were advanced by Soil Engineers as part of their investigation, with the boreholes located in the area of the south corner of Site and the test pits located across the site surrounding the RDF. MMM was provided copies of the borehole logs for three monitoring wells installed by Soil Engineers in February 2015 at the Site. The monitoring wells are identified in this report as SE- MW-101 to SE-MW-103. MMM has accessed these wells for the purposes of water level monitoring beginning in July Stormwater Monitoring Report, Halton Healthcare System New Oakville Hospital WalterFedy provided MMM with selected information from their 2014 stormwater monitoring report related to the new Oakville hospital located to the southwest of the Site. As part of their monitoring activities, a number of monitoring stations were sited within the tributary to Sixteen Mile Creek to the north and northeast, including 3 drive-point piezometer stations within the PSW (SM-2, SM-3, and SM-4). Monitoring data from 2013 and 2014 is available and includes manual measurements at each of the 3 stations and continuous data-logger readings from the upstream piezometer station (SM-4). WalterFedy recorded water levels from within the piezometers (shallow groundwater levels) and did not record the corresponding surface water levels at the stations, limiting the utility of their data in determining what groundwater-surface water interactions are occurring at the wetland. The data provided by WalterFedy is presented in Appendix E Environmental Implementation Report and Functional Servicing Study for the Mattamy-Owned Lands MMM obtained the EIR/DSS prepared for the Mattamy-owned lands located east of the Site (Stonybrook Consulting, et al, October 2015) from the Town of Oakville web-site in order to review borehole and groundwater monitoring data to assist in defining the groundwater catchment shed for the feature-based water balance of the PSW. The EIR/FSS report indicates there were 32 drilling locations across the Mattamy-owned lands, at 15 of these locations, 17 monitoring wells were installed (2 locations constructed as nests with shallow and deep wells). Mini-piezometers had been installed at 4 locations. Post-development site imperviousness for the Mattamy-owned lands was also reviewed and utilized in MMM s water balance calculations for the PSW. 3.2 Site Geology MMM s drilling program confirmed the surficial soils consist of recently placed fill materials overlying native deposits of clay-rich Halton Till, underlain by weathered Queenston Shale. The discussions below include information from MMM s boreholes as well as the 3 Soil Engineers November HG1 Page 14

26 boreholes and 2 of the Stantec boreholes from 2010 (MW (on-site) and MW (located immediately northwest of the Site)). Topsoil was identified at 3 of the 6 MMM boreholes ranging between 0.11 and 0.45 m thickness. Soil Engineers borehole logs indicated topsoil was 0.76 m thick at each of their 3 boreholes found at the south corner of the Site. Generally, the soils at ground surface and/or below the topsoil layer were classified as a brown to reddish brown firm to very stiff Clayey Sandy Silt Fill, with trace to some sand and gravel and often with broken shale bedrock fragments present within the matrix. The soil moisture was qualitatively assessed in the field as damp to moist. The fill thickness across the Site at the MMM and Soil Eng boreholes ranged between 1.5 and 3.2 m, except for MMM15-02, located at the north corner of the Site below the base of the fill slope, where only a 0.1 m thin veneer of fill was present 4. At MMM15-03D, 0.15 m of native topsoil was logged at the base of the fill, between 2.74 and 2.89 mbgs (approx to masl). The original surficial native soils are generally comprised of low hydraulic conductivity clay-rich soils. At the MMM boreholes, these soils were interpreted as Clayey Sandy Silt Till with trace to some gravel and with shale fragments whereas at MW the native soils were logged as a mixed sequence of Clayey Silt and Silty Clay Till. At the 3 Soil Eng boreholes, the deposit was logged as Silty Clay. The top of these native deposits at the boreholes range in elevation from masl at the west corner of the Site (MMM15-01) down to masl at the east corner of the Site (MMM15-04). The thickness of these deposits at the borehole locations ranged between 0.6 m (MMM15-02) and 6.0 m (MMM15-01), and was interpreted to be generally thinnest at the boreholes located closest to the Sixteen Mile Creek tributary valley along the southeast and north property lines. Mottling within the till was evident at most of the MMM boreholes, with fractures only logged at one borehole, MMM15-02, which was in a limited area that had little to no fill placed on the ground. Evidence of mottling or fracturing was not reported on the borehole logs prepared by the other consultants. The till deposits were logged to the underlying shale bedrock which was classified as weathered to highly weathered at the MMM and Stantec boreholes 5. On review of the samples from the MMM boreholes, the transition from Till to weathered shale was observed to be quite gradual and difficult to demarcate. Penetration of the split spoon sampler through the weathered shale bedrock at the MMM boreholes was also noted to be quite short, generally ranging between 5 and 23 cm of penetration before refusal, though occasionally managing between 45 and 60 cm of penetration at highly weathered zones, these areas were often encountered towards the top of the bedrock. The shale bedrock was identified as red Queenston Shale. The bedrock was classified as weathered to highly weathered throughout the depth of penetration at the MMM boreholes, with the weathered depth of the shale bedrock at the on-site boreholes generally extending beyond the lower completion depths of the boreholes. At the Site, the surface of the bedrock was noted to decline in elevation from roughly the north and dropping to the south and southwest. Bedrock along the north property line was 4 This borehole is located at a small part of the Site near the north corner that was essentially left at original grade. 5 Shale bedrock was not reported at any of the 3 boreholes drilled by Soil Engineers, nor was auger refusal noted on their logs. November HG1 Page 15

27 encountered at approximately 157 masl elevation. Along the southwest side and towards the south corner of the Site, the bedrock surface is interpreted to be at or below about 154 masl Grain Size Analyses Following installation of MMM15-01 to MMM15-06 monitoring wells, six soil samples were submitted to ALS Environmental Laboratories in Waterloo for a grain size analyses. The results of these grain size analyses were reviewed and used to provide estimates of hydraulic conductivity and soil classification for use in the water balance analysis. The grain size curves are found in Appendix C. Table 3: Hazen Estimates of Hydraulic Conductivity BH ID Sample ID Depth (mbgs) MMM15-01D SS MMM15-02 SS MMM15-03D SS Soil Description Sandy Gravel, trace silt, trace clay (FILL) Sandy Clayey Silt, trace gravel (TILL) Sandy Gravel, some silt, trace clay (FILL) d10 (mm) Hazen K ~0.01 x d10 2 (m/sec) x10-6 < <1.0x x10-7 MMM15-04 SS Clayey Sandy Silt, some gravel (TILL) < <1.0x10-8 MMM15-05D SS Sandy Clayey Silt, trace gravel (TILL) < <1.0x10-8 MMM15-06 SS Clayey Sandy Silt, trace gravel (TILL) < <1.0x10-8 Note: Hazen estimates were provided by the laboratory on the grain size curves found in Appendix C. Table 3 presents the location and depth of soil samples that were tested for grain size distribution and the estimated hydraulic conductivity. The estimates of hydraulic conductivity presented in Table 3 were obtained based on grain size results using the Hazen approximation: K = 0.01 x Cd 10 2 (m/sec) Where: K = bulk hydraulic conductivity (m/sec); d 10 = grain size at which point 10% of the soil passes the sieve (mm); and C = a constant generally set at 1 for these units. 6 Neither bedrock nor auger refusal is logged at the three Soil Engineer boreholes at the south end of the Site. These boreholes are completed to elevations of between and masl (based on MMM surveying). November HG1 Page 16

28 The Till / Fractured Shale deposits are estimated by the Hazen approximation 7 to have hydraulic conductivities of less than 1x10-8 m/sec. This is considered a reasonable estimate for the Till, in an unweathered state. In a typical situation, where the Till is found at surface and has been exposed to long-term weathering effects and fracturing, its bulk hydraulic conductivity in the shallow zone will be expected to be higher than these estimates would suggest, as the fracture planes would result in preferential pathways for the movement of water. With the placement of the fill at the Site, some of the natural fracturing in the upper portion of the Till deposit will have been squeezed shut and/or smeared leading to a reduction in the bulk hydraulic conductivity of the Till. From Table 3, the Fill deposits were estimated to have a geometric mean hydraulic conductivity of 5.3x10-7 m/sec (based on 2 samples only). This approximation is based on the d 10 for the submitted soil samples, but with the Fill samples, the soil description and d 10 are interpreted to be heavily influenced by pieces of broken shale that were present in the samples and which resulted in grain size curves that reportedly contain significant amounts gravel and sand sized particles. The hydraulic conductivity of the Fill would be controlled principally by the composition of the soil matrix (Clayey Sandy Silt) and we would expect that a more representative value for the hydraulic conductivity of the Fill would be an order of magnitude lower that estimated (e.g., 10-8 m/sec). Consequently, the hydraulic conductivity calculated using the Hazen approximation as shown above are believed to be higher than the actual hydraulic conductivity for this soil. The tri-linear soil classifications obtained through the grain size analyses were used to derive the soil classification for estimating infiltration input into the water balance analysis (along with published soils mapping of the site (see Section 4.3.1). The percentage composition of soils was categorized as percentages of sand, silt, and clay and compared against classifications in a tri-linear soil classification chart. The results are presented on Table 4, and the tri-linear plot is found in Appendix C. The predominant soils found at shallow depth, within the Fill, are Sandy Gravel, some silt, trace clay (and typically classified as Sandy Loam). It is believed that the broken pieces of shale found within the fill samples affected the soil classification as while there was gravel noted in the samples, the soil matrix was comprised of the native Clayey Silt Till found at the Site and surrounding lands. Based on grain size analyses, the Till was generally classified as Sandy Clayey Silt (typically classified as Medium Loam). The tri-linear soil classifications for the Till samples ranged between Medium Loam to Clay Loam. On average, Silty Loam was therefore considered representative of the soils found near surface for input into the water balance. 7 Hazen estimates of hydraulic conductivity were not used to classify the soil type for use in the water balance calculations. Data from the tri-linear soil classifications and published soils mapping were used in the water balance calculations (see Section ). November HG1 Page 17

29 Table 4: Tri-Linear Soil Classification Percent BH/SA Description Sand Silt Clay Soil Classification MMM15-01D/ SA 02 MMM15-02/ SA 01 MMM15-03D/ SA 02 MMM15-04/ SA 06 MMM15-05D/ SA 06 MMM15-06/ SA 04 Sandy Gravel, trace silt, trace clay (FILL) see notes Sandy Loam Sandy Clayey Silt, trace gravel (TILL) Medium Loam Sandy Gravel, some silt, trace clay (FILL) see notes Sandy Loam Clayey Sandy Silt, some gravel (TILL) Medium Loam Sandy Clayey Silt, trace gravel (TILL) Silty Loam Clayey Sandy Silt, trace gravel (TILL) Clay Loam Notes: The percentages expressed in the table above are based on the proportions of Clay, Silt and Sand sized particles only, excluding Gravel content. The presence of broken and crushed shale bedrock in the Fill leads to significant percentages of gravel and sand sized particles in the grain size analyses which skews these results towards a sandier soil classification than would be warranted based on the source of the soil matrix In-Situ Permeability Testing Hydraulic conductivity testing was carried out at five MMM monitoring well locations in July 8, August and September 2015 to provide estimates of the in situ hydraulic conductivity of the deposits across the Site. The monitoring well locations were selected on the basis of providing data from locations across the Site and in the vicinity of the PSW. Six hydraulic conductivity tests had been performed by Stantec in February 2009 at monitoring wells across the larger EIR/FSS study area (MW to MW inclusive). The results of the MMM tests and the Stantec tests are presented on Table 5. 8 The recovery of the groundwater at MMM15-03S after completion of drilling (July 2015) was captured by the data logger and this data was treated as a rising head test. November HG1 Page 18

30 Table 5: In-Situ Permeability Testing Summary Monitoring Well Screen Interval (mbgs) Description Method Hydraulic Conductivity (m/sec) Falling Head Rising Head MMM Weathered to Highly Weathered Shale Slug 9.4x x10-7 MMM15-03S Weathered Shale Slug 5.7x10-8 N/A MMM15-03D Highly Weathered Shale Slug 1.5x x10-7 MMM15-05S Clayey Silt Till over Fractured Shale Recovery N/A 9.9x10-10 MMM15-05D Highly Weathered Shale Slug 1.6x x10-6 Previously reported test results (Stantec, 2010) MW Weathered Shale Purge N/A 7.9x10-7 MW Weathered Shale Purge N/A 3.2x10-5 MW Shale Purge N/A 9.9x10-7 MW Weathered Shale Purge N/A 4.2x10-5 MW Weathered Shale Purge N/A 1.1x10-8 MW Weathered Shale Purge N/A 7.7x10-7 Notes: The calculated horizontal hydraulic conductivity may be underestimated due to effects such as smearing of the borehole wall during drilling. This can reduce the ability of water to be transmitted across the perimeter of the borehole and so may result an underestimate of the hydraulic conductivity. Three methods were employed for the in-situ permeability testing: Slug indicates that a slug of known volume was rapidly dropped into the well to displace the water in the well instantaneously and allowed for a falling head test to be recorded. Removing the slug rapidly then permitted a rising head test to be recorded. Purge means that water was actively removed from the well using methods such as tubing with foot-valves or bailers. It is not known how Stantec s purge tests were carried out as details were not provided in their EIR/FSS report. Finally Recovery means that groundwater recovery in the borehole after drilling was completed was recorded using a data logger that had been installed in the well after completion. The hydraulic conductivity testing at three monitoring wells (MMM15-02, MMM15-03S and MMM15-03D) was carried out by using a slug with a known volume to displace the water and a falling and rising head test was carried out 9. At MMM15-05S, a data logger had been installed in the monitoring well immediately after borehole drilling. The groundwater level recovery at this 9 Recovery was very slow at MMM15-03S (about 40% recovery) and only a falling head test was carried out. November HG1 Page 19

31 well was viewed as being equivalent to a rising head test. In all but one case, the recovery of the water levels in the well was measured over time until they had recovered to within approximately 80% of the original water level (MMM15-03S, refer to footnotes). MMM s recovery data was analysed with Aquifer Test Pro using the Bouwer and Rice (1976) approach and the results of the hydraulic conductivity testing are presented in Table These values are considered representative of horizontal hydraulic conductivity in the immediate vicinity of the well. It is anticipated that the vertical hydraulic conductivities will be an order of magnitude lower than these values. As may be noted from the information presented on Table 5, 10 wells were screened within the weathered shale bedrock, and the measured horizontal hydraulic conductivities of the data from these wells ranged across 3 orders of magnitude (1.5x10-5 m/sec to 1.1x10-8 m/sec) 11, with a geometric mean horizontal hydraulic conductivity of the weathered shale calculated at about 1.2x10-6 m/sec. The results from monitoring well MMM15-05S (9.9x10-10 m/sec) are significantly lower than the results from the remaining wells, and may be reflective of smearing of the inside of the borehole walls with clay particles that would reduce the ability of water to pass into or out of the native soil/rock to the well Permeameter Testing Three permeameter tests were performed at locations identified as PT-1 (MMM15-03), PT-2 (MMM15-05), and PT-3 (MMM15-04) on September 9, A fourth location was planned by MMM, next to MW15-02, however water placed in the hole to pre-soak the surrounding soil did not drain out of the hole during the day and so no testing was carried out at this location 12. The tests were all performed close by to existing monitoring wells as the stratigraphy was known from drilling and sampling of those boreholes. The permeameter tests were carried out using a Guelph Permeameter. The Guelph Permeameter is an in-hole constant head permeameter test. By measuring the steady-state rate of water recharge into soil from a cylindrical well hole, the permeameter employs the Marriot Principle to accurately determine soil hydraulic conductivity. The percolation test holes were 60 mm in diameter and were augured to a minimum depth of 0.38 m into the fill below the base of the overlying topsoil. Each hole was pre-soaked by filling it with water and allowing the water to infiltrate completely prior to the start of the test. If necessary following pre-soaking, silt and sediment were removed from the bottom and sides of the hole and the hole was cleaned to its original depth. A rough brush was used to remove any smear layer present on the walls of the augured well hole as per the equipment manufacturer s instructions. A desired water height was established by raising the air inlet tip within the permeameter reservoir to create a partial vacuum within the reservoir tube and allowing water to be released into the hole until the water head was a minimum of m above the base of the hole. Measurements of the water level were taken using the scale on the permeameter reservoir tube, and were recorded at consistent time intervals. The Single Head Method was used exclusively for all tests. The inner reservoir tube of the permeameter was used for test 10 MMM s Bouwer and Rice analyses are presented in Appendix D. The remaining six test results were obtained from Table H.1 in the original EIR/FSS report (Stantec, 2010). 11 MMM15-05S, screened in both Till and the upper weathered shale had a calculated hydraulic conductivity of 9.9x10-10 m/sec and these low values compared to the others may be due to smearing of the borehole walls during drilling. 12 This also indicates that a very low infiltration rate would have been obtained from any permeameter testing, either due to smearing of the test hole walls by auguring, or due to compaction of the native Till soil and closing up of fractures within it due to heavy construction equipment traffic. November HG1 Page 20

32 locations PT-1 and PT-3. At PT-2 testing was done using the inner reservoir tube only (PT-2a), followed by a test using both the inner and outer reservoir tubes (PT-2b). Table 6: Permeameter Test Results Permeameter Test Monitoring Well Location Saturated Conductivity (m/sec) Saturated Conductivity (mm/hr) Comments N/A MMM15-02 N/A N/A Water did not drain from hole into surrounding soils during pre-soak. Testing was not performed at this location. PT-1 MMM x PT-2a PT-2b MMM x x PT2a was performed using the inner reservoir tube PT2b was run using the inner and outer reservoir tubes PT-3 MMM x Results may be questionable see text Results were analyzed using the methods established by Reynolds and Elrick (1986) in the Guelph Permeameter Quick Calculator provided by the manufacturer of the equipment and are presented on Table 6 above. Printouts of the permeameter test results at PT-1, PT-2 and PT-3 are presented in Appendix D. The results of the permeameter testing at PT-3 (MMM15-04) may be suspect as the rate of water drop within the permeameter fluctuated erratically during most of the test 13, only stabilizing after about 95 minutes. The saturated soil hydraulic conductivities in the upper zone of the Fill at test locations PT-1 and PT-2 ranged in the order of 2x10-7 to 5.3x10-7 m/sec, alternatively expressed as rates of between 0.8 to 1.9 mm/hour (average of 1.4 mm/hour). These are not high values. At test location PT-3 the testing indicated a saturated hydraulic conductivity of 1.9x10-8 m/sec or 0.1 mm/hour, although the results at this location are considered suspect considering that the water level in the inner reservoir tube was observed to both rise and fall during most of the test (it should only fall). The saturated hydraulic conductivity of the Fill provided by the permeameter testing indicates that infiltration-based LID measures at the Site will be difficult to employ in consideration of these results Groundwater Level Monitoring Groundwater level measurements at the monitoring wells have been carried out on a quarterly schedule since July of 2015 (approximately in January, April, July, and October) and included monitoring of all on-site wells and nearby off-site mini-piezometers located within the PSW since the fall of MMM s monitoring wells were installed in early to mid-july 2015, and water levels were recorded multiple times during the July to September 2015 period, at times when other field activities took place, and at quarterly intervals thereafter. During such visits, manual water level readings were taken at each of the monitoring wells and mini-piezometers and data loggers were downloaded. The complete results of groundwater level monitoring at the Site are 13 The water level within the permeameter water column was observed to rise at times instead of falling consistently as expected. November HG1 Page 21

33 tabulated on Table SWL-1 (and Figures SWL-1 and SWL-2) found in Appendix E. Table SWL-1 also includes water levels from the previously installed Soil Eng monitors SE-MW-101 to SE- MW-103 inclusive, which are included in the MMM monitoring program. Groundwater levels were also continuously monitored at selected wells using pressure transducers (data loggers). MMM staff installed Schlumberger Mini-Diver DI501 data-loggers at three on-site monitoring wells in July Table 7 identifies the locations and date ranges over which time data loggers have been installed. A Schlumberger Mini Baro-Diver DI500 was also installed at the Site to provide barometric compensation of the data. The loggers were suspended from the tops of the monitors by steel cables and were set to record water level fluctuations at hourly intervals. Table 7: Data Logger Locations Monitoring Well Figure Reference Start Date End Date MMM15-01D SWL-3/3a December 15, 2015 March 28, 2016 MMM15-02 SWL-4/4a December 15, 2015 presently installed MMM15-03S SWL-5/5a July 16, 2015 December 15, 2015 MMM15-03D SWL-5/5a July 16, 2015 presently installed MMM15-04 SWL6/6a December 15, 2015 March 28, 2016 MMM15-05S SWL-7/7a July 16, 2015 presently installed MP15-01SW SWL-8/8a November 25, 2015 March 28, 2016 December 15, 2015 presently installed MP15-01S SWL-8/8a November 25, 2015 March 28, 2016 December 15, 2015 presently installed MP15-01D SWL-8/8a November 25, 2015 presently installed Note: The shallowly installed data loggers at the wetland mini-piezometer nest (MP15-01S (shallow) and MP15-01 SW (surface water)) were temporarily moved over the winter season to prevent damage to the units from freezing to monitoring wells MMM15-01D and MMM These loggers were returned to the mini-piezometer station in March, The data from each data logger and the baro-logger were downloaded during the quarterly monitoring visits. Figures SWL-3 to SWL-8 in Appendix E present plots of the continuous water level measurements at all locations with data loggers and include the spot water level measurements and generalized stratigraphy and well construction details at the boreholes (Plots SWL-3a and SWL-8a show the water level data with a 3 m vertical range to better express variations in the groundwater levels, and these plots also show daily precipitation events and depth of snow on ground (based on the Oakville Town Centre weather station data) to allow for comparison of rainfall events and snow melts with fluctuations in the groundwater levels). Data logger plots from the Stantec EIR/FSS are also included with this appendix. Groundwater monitoring data is available for a 15 month period from mid-july 2015 to mid- October Groundwater levels from about mid-july to late September 2015 across the site November HG1 Page 22

34 were seen to generally decline, from between about 0.1 to 0.5 m around the southeast boundary of the Site, and between roughly 0.7 and 1.0 m along the northwest boundary of the Site. Groundwater levels from late September 2015 to late March 2016 across the site were seen to generally rise between 0.5 to 1.3 m (average of about 1.0 m), with the increases observed to the north-northwest of the RDF generally seen as higher than those observed at wells downgradient of the pond. At wells upgradient of the pond, the change in groundwater level was recorded at between 0.7 and 1.3 m (1.0 m average) whereas downgradient of the pond, these changes were between 0.5 and 1.1 m (0.9 m average). During the period following the spring freshet to the late summer/early fall when groundwater levels are typically recorded at their seasonal lows, the observed change in groundwater elevations was greater than the increases seen between the fall of 2015 and spring of This was attributed to the dry conditions observed regionally during the spring and summer of Across the site these declines in the water tabled ranged from 0.6 m to 1.9 m (average decline of 1.3 m) and again the greatest changes were observed at monitoring wells upgradient of the existing SWMP (1.4 to 1.9 m, on average 1.6 m) while at the monitors downgradient of the SWMP, the absolute magnitude of the changes were approximately equivalent to those observed during the previous fall to spring period, with the water tale declines ranging between 0.6 and 1.1 m (0.9 m average). The groundwater levels and interpreted groundwater flow pattern at the site from late August 2015 are shown on Figure 6. Groundwater is interpreted to flow from northwest to southeast (156.5 to masl) at a gradient of about The groundwater flow pattern indicates that there is a northwest to southeast oriented flow divide passing through the center of the Site with groundwater being directed towards both the Glen Oak Creek subwatershed to the south, and towards the Sixteen Mile Creek watershed to the east. Groundwater under the north corner of the Site, is also interpreted to flow in the direction of the PSW, and this area is also shown on Figure 6. We note that we understand the perimeter elevation of the PSW is mapped at masl and that the interpreted groundwater contours at the north corner of the site in the late summer was below the masl elevation, ranging between and masl at the Site s north property line. Figure 7 illustrates the interpreted groundwater conditions under fall conditions (September 26, 2015) and includes groundwater data from the Mattamy monitoring wells (October 22, 2015). Groundwater levels at the south part of the Site are slightly lower than recorded in the summer, and slightly higher at the monitors located along the north boundary in the direction of the PSW. Also shown on this figure is the interpreted groundwater catchment for the PSW which will be used with the feature-based water balance for the wetland described later in this report. Figure 8 presents the interpreted groundwater contours at the site under the spring conditions (March 28, 2016). The general pattern of flow is similar to the summer condition, but with groundwater found between 0.4 and 1.5 m higher than the levels reported from August 24, 2015 (average rise of about 1.0 m). Static water levels at the Site under spring conditions ranged between approximately masl at the southeast alongside Dundas Street West, and about masl at the north property line. Notable is the rise in groundwater levels downgradient of the RDF ranged between 0.4 m and 1.0 m, whereas at monitors located upgradient of the RDF (to the north and west), the rise in groundwater was more pronounced, recorded between 1.0 and 1.5 m), being greatest along the Site boundary with the wetland. Groundwater elevations downgradient of the RDF may be elevated due to some leakage through the base of the pond, with the result that the spring to fall seasonal difference is not as significant as seen at the wells on the upgradient side of the RDF. The groundwater level patterns from the data-logger equipped wells showed that the declines during the summer months were generally steady, and did not show any variation that can be correlated to rainfall events during the summer November HG1 Page 23

35 monitoring period (the largest rainfall events were recorded at 28 mm on August 2 and 24.5 mm on August 10, 2015). A rise in groundwater levels in response to a 27.8 mm rain event on September 29, 2015 is visible in the data logger data at MMM15-03 (approx. 0.8 m) and MMM15-05 (approx. 0.2 m). Groundwater levels then declined slowly after that date until late December 2015 when groundwater at 5 data-logger equipped wells were seen to rise between approximately 0.4 and 0.8 m. Between January and April 2016, the groundwater slowly rose an additional 0.2 to 0.8 m at these 5 monitoring wells. Static water levels at the Site between spring and fall 2016 conditions ranged between approximately masl at the southeast alongside Dundas Street West, and about masl at the north property line, generally lower that what was previously observed in during the summer of The groundwater levels downgradient of the RDF showed a decline ranging between 0.6 m and 1.1 m between July and October 2016, whereas at monitoring wells located upgradient of the RDF (to the north and west) were recorded to differ between 1.4 and 1.9 m between the two seasons. The lesser range observed in the downgradient wells is potentially due to leakage effects through the base of the pond that may be elevating the groundwater levels downgradient of the pond during the year and minimizing the variation in the levels due to the presence of the pond. Fluctuations due to rainfall events and snowmelts in the groundwater elevations are clearly seen in the data logger traces, being more evident during the fall to spring months than in the late summer months when the soils are in moisture deficit (this relationship is observable on Figures SWL-3a to SWL-7a in found in Appendix E). An estimate of the seasonally variability in the groundwater table prior to any of the recent site works (filling, construction of the RDF, etc.) was made through review of the data logger data presented in the original EIR/FSS (Stantec, 2010). The differences between the maximum and minimum water levels recorded at each of the 8 Stantec monitoring wells was estimated from the data logger plots presented in the EIR/FSS (and also included with Appendix E of this report), and were estimated to range from between 0.85 to 1.25 m over the course of a year (about 1.15 m change on average). At the three original monitors located on or closest to the Site (MW104-08, MW105-08, and MW108-08), the range in year to year water levels were from 0.9 to 1.25 m, with an average of about 1.15 m. This is similar to the variations seen at on-site groundwater monitors located upgradient of the RDF, and generally higher than the variations observed at monitors downgradient of the RDF, which is possibly due to effects of leakage through the base of the pond. Vertical gradients are available from the three monitoring well nests (MMM15-01S/D, MMM15-03S/D, and MMM15-05S/D) (see Table SWL-1 in Appendix E). Downward groundwater gradients were identified at all three well nests. These downward gradients have been generally higher at location MMM15-01 at the northwest corner of the site, ranging between 0.09 and 0.15 and lowest at monitoring well nest location MMM15-03 where the vertical gradient has ranged between (downward) to (upward) 14. At location MMM15-05 the vertical gradients observed in 2015 ranged between 0.01 and 0.04 downward, while in 2016 the measured vertical gradient has been higher, between 0.08 and 0.31, with the higher values seen at the time of the spring freshet. These increases in vertical gradients are attributed to higher water levels in the upper elevations of the fill due to the spring melt. 14 Vertical gradients at MW15-03 have been observed to be typically slightly downward but on occasion weak upward gradients have also been noted, ranging between (downward) to (upward). November HG1 Page 24

36 These findings imply that minor groundwater recharge is occurring at the Site. The decrease in vertical gradient in the direction of the tributary to Sixteen Mile Creek at borehole nest location MMM15-03, that is located close to the top of the fill slope, may be reflective of the nearby slope to the monitoring well nest. The decrease in vertical gradient could also be taken as indicative of a change from a recharge environment to discharge environment at the watercourse and its associated PSW although the PSW and watercourse channel were observed by MMM staff to be in a dry condition from June 2015 through to December 2015 and from mid-may 2016 through to October 2016 and thus not interpreted to be receiving groundwater inputs during the summer and fall, and insignificant groundwater input during the early winter season (insufficient to result in significant flow as channels was frozen). Flows observed at the PSW in late March 2016 were interpreted to be from runoff, with some groundwater input. November HG1 Page 25

37 . Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Interpreted Groundwater Contours Summer 2015 Legend Site Boundary Monitoring Locations!A Monitoring Well (MMM)!A Monitoring Well (Soil Eng)!= Monitoring Well (Stantec)!= Decommissioned Monitoring Well (Stantec) Proudfoot Trail!? Wetland Mini-Piezometers Provincially Significant Wetlands (PSWs) J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 6 Interpreted Groundwater Contours_Summer 2015.mxd 2016 Microsoft Corporation and its data suppliers Third Line Dundas Street West Client Prepared By Scale Date November 2016 Scale as Shown Topographic Contours (1m Interval) Watercourses Interpreted Groundwater Contours Interpreted Groundwater Flow Direction Interpreted Groundwater Divide Approximate limit of site in which groundwater is projected to flow in the direction of the PSW Groundwater Contours - Stantec 2010 #* Surface Water Sampling Location Vertical Groundwater Flow Gradient and Direction 155.3/155.1 Static Water Levels of Shallow Well/ Deep Well Note: Static groundwater elevations (masl) were taken on August 24, Oakville Green Development Inc Queen's Printer for Ontario Meters Project No HG1 Figure: 6

38 . Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Interpreted Groundwater Contours Fall 2015 Legend Site Boundary Topographic Contours (1m Interval) Watercourses Sixteen Mile Creek Interpreted Groundwater Contours Interpreted Groundwater Catchment to PSW J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 7 Interpreted Groundwater Contours_Fall 2015.mxd Glen Oak Creek 2016 Microsoft Corporation and its data suppliers Client Prepared By November 2016 Scale as Shown Extrapolated Groundwater Catchment to PSW Provincially Significant Wetlands (PSWs) Post Development Watersheds Monitoring Locations!A Monitoring Well (MMM)!A Monitoring Well (Soil Eng)!= Monitoring Well (Stantec)!= Decommissioned Monitoring Well (Stantec) ½ Mini-Piezometers - Mattamy Lands!? Monitoring Wells - Mattamy Lands / Static Water Levels of Shallow Well / Deep Well Notes: 1. MMM groundwater elevations (masl) were taken on September 26, Mattamy Lands groundwater elevations (masl) were taken on October 22, Scale Date Oakville Green Development Inc Queen's Printer for Ontario Meters Project No HG1 Figure: 7

39 . Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Interpreted Groundwater Contours Spring 2016 Legend Site Boundary Monitoring Locations!A Monitoring Well (MMM)!A Monitoring Well (Soil Eng)!= Monitoring Well (Stantec)!= Decommissioned Monitoring Well (Stantec) Proudfoot Trail!? Wetland Mini-Piezometers Provincially Significant Wetlands (PSWs) J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 8 Interpreted Groundwater Contours_Spring 2016.mxd 2016 Microsoft Corporation and its data suppliers Third Line Dundas Street West Client Prepared By Scale Date November 2016 Scale as Shown Topographic Contours (1m Interval) Watercourses Interpreted Groundwater Contours Vertical Groundwater Flow Gradient and Direction Static Water Levels of Shallow Well/ / Deep Well Note: Static groundwater elevations (masl) were taken on March 28, Oakville Green Development Inc Queen's Printer for Ontario Meters Project No HG1 Figure: 8

40 Wetland Mini-Piezometer Monitoring MMM has monitored the mini-piezometers in the wetland along Sixteen Mile Creek on 7 occasions between November 25, 2015 and October 13, 2016 (data is presented in Table SWL- 2 found in Appendix E). Groundwater at all mini-piezometers was below ground surface on November and December 15, 2015, between 0.10 mbgs and 0.52 mbgs (average of 0.25 mbgs on both dates) and ground condition was reported dry at all locations except SM-2 on December 15. The data indicates downward gradients at all locations. By January 26, 2015, shallow groundwater levels had risen to on average depth of 0.09 mbgs 15, though the ground condition at each station was recorded as dry. On March 28, 2016, the groundwater levels at most of the mini-piezometers were seen to be above grade (one at 0.03 m below grade, the remainder between 0.04 m and 0.26 m above grade, average of 0.13 m above grade). However, when compared to the surface water table at each mini-piezometer, the surface water level was above the mini-piezometer level at 3 locations 16 at the southeastern half of the wetland (implying downward flow), equivalent with each other at 4 locations (implying no vertical flow) and lower than the mini-piezometer level at 3 locations 17 at the northwestern end of the wetland (implying upward flow or discharge). By April 20, 2016, mini-piezometer levels were seen to have declined during the month, with shallow groundwater levels above existing ground at 3 locations (MP-A, MP-B(D) and MP-C, between 0.04 m and 0.14 m above grade), and below grade at the remaining mini-piezometers (between 0.04 mbgs and 0.21 mbgs). Ground surface was reported as dry at mini-piezometers MP15-01 Nest, SM-2, SM-3, and SM-4 (and levels in the piezometers at these 4 locations were all found below ground), while ground conditions were reported as wet at MP-A, MP-B (Nest) and MP-C with water levels in the mini-piezometer generally above surface water at these locations, all located at the west end of the PSW along its periphery. The surface data logger located at MMM monitoring station SW15-01 indicated the wetland channel at that location was dry after the third week of May On July 14, 2016, the mini-piezometers were generally observed to be dry, with the exception of shallow groundwater levels below grade at one location (SM-3 at 1.72 mbgs, Ground surface was reported as dry at all mini-piezometer locations during the July monitoring event. During the October 13, 2016 monitoring event, the mini-piezometers were generally observed to be dry, with the exception of shallow groundwater levels below grade at three locations (SM-3, MP-B(D) and MP-C, between 0.81 and 1.36 mbgs). The channel bottom was reported as dry at all mini-piezometer locations during both the summer and fall monitoring events of Data logger information obtained at MMM mini-piezometer MP15-01 in November-December 2015 and March-April 2016 has indicated that surface water levels are generally always higher than the shallow groundwater level at the two piezometers, on average 1.3 cm higher than the shallow piezometer, and 1.4 cm higher than the deep piezometer (this is most clearly visible on Figure SWL-8a, located in Appendix E). The water level traces at the 2 piezometers also mirror the changes in surface water levels, which are seen to correlate very strongly with rainfall events and snow melts. This data indicates that water flows from the surface into the ground at this location. Data logger information obtained at MMM mini-piezometer MP15-01 in July and 15 This excludes readings for 3 mini-piezometers that were frozen (MP15-01D, MP-A and MP-B (S)) where the results would not be accurate due to expansion of ice upon freezing. 16 MP15-01 Nest, SM-2, and SM MP-A, MP-B (nest) and MP-C. November HG1 Page 29

41 October 2016 indicated all monitoring points were dry. Significant rain fall events after June 6, 2016 were not reflective in rises of the recorded water levels in the watercourse (the watercourse remained dry). This indicates that surface water runoff was not being carried into the watercourse during the summer and early fall seasons. Previously reported mini-piezometer data from older EIR reports is discussed below. DP8-08 was monitored 4 times by Stantec between April 2009 and January A downward gradient was noted on April 4, 2009 (surface water was 0.02 m higher than the shallow groundwater), followed by an upward gradient on April 27, 2009 (0.05 m head differential, with groundwater being higher than the surface water on this date). The surface water elevations were recorded as about 26 cm higher in early April than in late April and may have been higher in the earlier part of that month due to runoff or spring melt conditions. This station was reported as dry in September 2009 and frozen in mid-january A data logger had been installed at the mini-piezometer SM-4 between January 2013 and mid- November 2014 (removed between late-november 2013 and late-may 2014). Groundwater levels at this piezometer were generally recorded below ground level at the piezometer ( masl 18 ) during the year, except during the winter and spring seasons when groundwater levels would be close to and/or above ground surface 19. In 2013, the shallow groundwater levels recorded at piezometer SM-4 were generally observed to be at or above masl elevation (the mapped elevation of the perimeter of the PSW) between January and the end of May and also at the end of May in 2014 (in the short window of time immediately after the reinstallation of the data logger for the 2014 season). During the summer and fall periods, the groundwater at the piezometer location would decline below ground surface (Stream Base Flow Measurements There are no watercourses passing through the Site and therefore estimates of the stream flows were not completed. Subsequently, no comparison of actual streamflow data can be made against baseflows predicted by the water balance, one of the technical requirements identified in the Town of Oakville s Terms of Reference. The tributary to Sixteen Mile Creek north and northeast of the Site was observed to be in a dry state by MMM Ecologists at the time of field visits in June 2015 and by MMM Hydrogeologists on September 9, November 25, December 15, 2015, and on July 14 and October 13, 2016 at the watercourse channel immediately downstream of the PSW. The channel was observed to be in frozen condition in late January Information from the original EIR/FSS report identified this channel as wet in April of 2009, dry in September 2009 and frozen in January 2010 (which does not suggest significant groundwater input is discharging to the watercourse during the winter months). During monitoring events on March 28 and April 20, 2016, MMM Hydrogeologists observed moderate to slow flowing water conditions in the watercourse channel. At the time of both visits, MMM were not able to locate well-defined reaches within the channel to permit us to estimate a volumetric rate of stream baseflow. 18 MMM field staff surveyed the elevation of the ground at this mini-piezometer at masl in November Water levels at the piezometer correlated strongly with precipitation events, and short term rises above ground level recorded during the winter and spring seasons in 2013 and 2014 were associated with precipitation events. This is similar to the behaviour observed at MMM s MP November HG1 Page 30

42 3.2.4 Groundwater Quality Groundwater samples were collected by MMM staff at selected locations on August 25, 2015, for background general chemistry. The samples were obtained from two monitoring wells (MMM15-05D, MMM15-03S). One duplicate sample (DUP01) was collected from MMM15-05D, for quality assurance purposes. Dedicated low density polyethylene Waterra tubing and footvalves were used for the development of wells and purging of the groundwater on August 24, Due to high levels of sediment in the groundwater dedicated polyethylene bailers were used for the sampling of the groundwater into laboratory prepared sample bottles the day after purging. The samples were then placed in a cooler with ice and transported to the laboratory (ALS Environmental) under standard Chain of Custody procedures. Water quality sample results are provided in Table WQ-1 found in Appendix F. Water quality results were compared to the Ontario Drinking Water Standards (ODWS) and the Provincial Water Quality Objectives (PWQO) 20. The sample results from MMM15-03S represented water screened in the till/bedrock interface, while the groundwater quality results from MMM15-05D represent water quality in the Queenston Shale formation. As shown on Table WQ-1, several parameters exceed the ODWS, PWQO, or both comparative standards, from at least one location, including aluminum, boron, cobalt, copper, iron, manganese, uranium, total dissolved solids (TDS), and dissolved organic carbon (DOC). Due to sample matrix inferences the detection limit had to be raised for some parameter analysis. The detection limit was raised above the PWQO criteria value for copper and silver at MMM15-05D (DUP01). Water quality results from MMM15-05D were also compared to water quality results from MW as sampled on March 17, 2009 (Stantec, 2010). MW was located very close to the location of MMM15-05D and so MMM s monitoring well location was selected to allow for a comparison of results between 2009 and The water quality in the water samples was generally comparable. One notable difference was seen in the concentrations of chloride and sodium in the groundwater. The concentration of chloride reported at MW in 2009 was 44 mg/l, whereas chloride was reported at a concentration of 179 mg/l from the sample obtained at MMM15-05D in The concentration of sodium also increased in the groundwater sample from MMM15-05D (171 mg/l) when compared to the concentration reported in 2009 from MW (130 mg/l) but not as dramatically as that of chloride. Monitoring well MMM15-05 is located downgradient of the existing RDF, which is unlined, and the increase in chloride and sodium may be originating from the RDF or from salt application onto Dundas Street West. Overall, water quality results were generally indicative of rural land uses, with no widespread evidence of inorganic parameter impacts at the Site other than the increase in chloride, attributed to the RDF or Dundas Street West to the southeast. 20 ODWS are from Table 2 (Chemical Standards) and Table 4 (Chemical/Physical Objectives and Guidelines) of Technical Support Document for Ontario Drinking Water; Standards, Objectives and Guidelines (MOE), June 2003, revised June PWQO are from Table 2 (Table of PWQOs and Interim PWQOs) of Water Management, Policies, Guidelines, Provincial Water Quality Objectives (MOE), July 1994, and revised February November HG1 Page 31

43 3.2.5 Surface Water Quality Surface water samples were collected by MMM staff at the watercourse channel immediately downstream of the PSW on April 20, 2016, for background general chemistry. The sample location is shown on Figure 6. Samples were conveyed directly into laboratory supplied sample containers. The surface water sample was not filtered in the field. The samples were then placed in a cooler with ice and transported to the laboratory (ALS Environmental) under standard Chain of Custody procedures. Water quality sample results are provided in Table WQ-1 found in Appendix F. Water quality results were compared to the Provincial Water Quality Objectives (PWQO) 21. The sample results from SW15-01 represented water flowing through the watercourse channel. As shown on Table WQ-1, several parameters exceed the PWQO standards, including aluminum, copper, iron and phosphorous. The surface water sample was not filtered in the field, as a result, the exceedances in metals represent the total concentrations of the parameters in the sample (as opposed to dissolved concentrations reported with groundwater samples). Water quality results from the surface water sampling point (SW15-01) were compared to the water quality results from the diversion channel as sampled on September 21 and September 24, (WalterFedy, 2015). The total phosphorous observed by WalterFedy during the September 2014 sampling events were 0.30 mg/l and 0.14 mg/l, respectively. The total phosphorous was observed as mg/l during MMM s sampling event in April The more recent water quality results are noted to be generally lower when compared to the values recorded in Local Hydrogeological Setting The following discussion of the local hydrogeology is based on the information gathered during this investigation and from previous studies conducted on the property and elsewhere within the watersheds. The surficial fine-grained deposit of Halton Till found throughout the study area serves to limit infiltration to the groundwater system and as a result, the local stream systems receive about three-fifths of their total water from surface runoff. As will be demonstrated in the water balance discussion, average infiltration in this environment in the local area is approximately 87 mm/year, based on the pre-development (2010 condition) water balance calculations for the PSW (discussed in Section of this report). Almost 100% of this contribution occurs primarily in the period of November to May when the entire shallow system will be saturated and capable of contributing water to the watercourses. Most of the infiltrating groundwater would move laterally through the upper fractured and weathered zones of the Till towards the watercourse system, and drain after the spring freshet. This enhanced permeability allows infiltrating groundwater to travel somewhat quickly through the shallow zone towards the watercourses. Lateral groundwater flow through the upper weathered and fractured zone of the bedrock, immediately below the base of the Till would also be expected, though the data collected to date does not show the bedrock as becoming drained (i.e., the bedrock has remained saturated). 21 PWQO are from Table 2 (Table of PWQOs and Interim PWQOs) of Water Management, Policies, Guidelines, Provincial Water Quality Objectives (MOE), July 1994, and revised February November HG1 Page 32

44 However, the existing condition at the Site (2015) has been altered due to development activities, with the construction of the hospital on the lands abutting the southwest property line of the Site. Between about 1.5 and 3.2 m of fill materials have been placed across the site 22, comprised of Clayey Silt Till soils with broken shale bedrock, all believed to have originated from the excavations for the hospital. The placement of the fill on the Site has also resulted in flatter grades than found in the 2010 condition. In addition to the placement of fill, a large SWMP (the RDF) has been constructed on the central part of the Site. Groundwater flow in the region is identified on published mapping as flowing to the south and southeast with deflection towards the deep valley of Sixteen Mile Creek under lands to the north and northeast of the Site. Monitoring data from 2015 and 2016 confirms that the shallow groundwater flow is in the same general direction beneath the site, declining from approximately masl at the northwest down to about at the southeast under a horizontal gradient of about Minor recharge is anticipated at the site due to the presence of downward vertical gradients which have ranged through the study from about to 0.15 at the northwest corner of the site down to (upward) to along the edge of the fill by the northeast property line over the same period of time 24. Up to about 15 months of continuous water level data is available from on-site monitors constructed in 2015 and this data showed steady water level declines between July and late September 2015 with no discernible effects from precipitation events until late September. Groundwater levels then rose rapidly on a number of occasions between October 2015 and January 2016 in response to large precipitation events, and from January to April 2016 groundwater levels rose and additional 0.2 to 0.8 m. After the 2016 spring freshet groundwater levels were observed to decline early April to mid-may with occasional rises following rainfall events, and after mid-may groundwater declined steadily to approximately mid-august after which time they stabilized and remained roughly steady up to the most recent monitoring event in October Total declines between the spring and fall of 2016 ranged between about 0.6 and 1.9 m, with the largest declines observed at the 2 monitoring wells located closest to the PSW along the northeast property line (MMM15-02 and MMM15-03 Nest, with total declines between 1.8 and 1.9 m at these two locations). Continuous water level data collected by Stantec from late 2008 to early 2010 indicated that the seasonal variation in the groundwater table across their entire EIR/FSS study area was on average about 1.15 m per year, which is considered reasonable for Till soils. Data collected by MMM indicates that the seasonal variability of the groundwater across the entire Site from the fall of 2015 to the spring of 2016 ranged between 0.5 and 1.3 m (1.0 m average). At monitoring wells upgradient of the RDF, the variability ranged between 0.7 and 1.3 m (average of 1.0 m) is similar to the pre-filling condition reported by Stantec, while at groundwater monitors located downgradient of the RDF, the variation in water levels is less, between 0.5 and 1.1 m (0.9 m average). For the period between the spring and fall of 2016 (a period with very low rainfall), the variability of groundwater levels across the site ranged between 0.6 and 1.9 m (average of 22 As measured at the 6 MMM borehole locations. 23 Based on measurements obtained on August 24, Vertical gradients measured in March and April 2016 were higher as a result of the spring freshet, up to 0.21 to 0.31 at the southwest corner of the property, and along the edge of the fill by the northeast property line. An upward gradient was measured on one occasion at the MW15-03 Nest in September 2015, otherwise gradients at this location have always been downward. Gradients calculated for July 28, 2015 were not included as water levels at the wells may not have yet fully recovered after drilling. November HG1 Page 33

45 1.3 m), at monitors upgradient of the RDF, the range was measured between 1.4 and 1.9 m (1.6 m average), while for monitors downgradient of the RDF the range was observed between 0.6 and 1.1 m (average of 0.9 m). The lesser and more consistent level of variability in groundwater fluctuation seen at the downgradient wells is potentially due to leakage effects through the base of the pond that may be elevating the groundwater levels downgradient of the pond during the year and minimizing the variation in the levels due to the presence of the pond. It is anticipated that the PSW found to the north of the Site, along the tributary channel to Sixteen Mile Creek, receives minor groundwater inputs during the winter and spring seasons, particularly at its upstream (western) limits based on the data collected from November 2015 to April Furthermore, spring groundwater levels along the Site s northern property line next to the PSW were observed at between and masl on March 28, 2016 (and therefore at or above the base of the wetland), thereby resulting in the potential for groundwater to discharge to the PSW. Groundwater that passes below the PSW during the drier seasons would eventually discharge into the deep, main valley of Sixteen Mile Creek to the northeast. November HG1 Page 34

46 4.0 IMPACTS OF THE PROPOSED DEVELOPMENT The Site Plan developed by Gensler Architects (October 2016) was used in this EIR/FSS submission. The development proposal indicates that almost the entire Site (13.58 ha) will contain 1.5 levels of underground parking that will extend to the property boundaries and below the internal road network, with the exception of the proposed SWMP block (0.59 ha) and the 0.59 ha of lands located within and adjacent to the 30 m PSW buffer at the north and east sides of the Site (see Figure 9). The proposed SWMP is to be lined and is therefore also considered impervious is to be landlocked by the underground parking structures. Therefore, approximately ha of the total ha Site area will be impervious, resulting in an imperviousness ratio of 96.1%. The original EIR/FSS considered an overall site imperviousness of 74.2% (56.7 ha imperviousness within a total study area of 76.4 ha). Under the pre-development condition (2010) studied under the original EIR/FSS, existing conditions, three subwatersheds were originally present at the Site. Subwatersheds GO1116 (Glen Oak Creek) and SM1117a (part of the Sixteen Mile Creek system) were essentially farm fields that drained towards Dundas Street West, and were classified by NOCSS as lowconstraint streams. The SM117 subcatchment (tributary to Sixteen Mile Creek) was also originally found over the northern part of the Site, though the watercourse (high constraint feature per NOCSS) and the PSW are found to the north of the Site. Regrading of the Site has led to the existing condition (2015) which includes 1.5 to 3.2 m of fill over the Site, and with a Regional Detention Facility that discharges treated stormwater to both Glen Oak Creek (82%) and Sixteen Mile Creek (18%). As described in Section 1.0 of this report, it is proposed to relocate the existing Glen Oak RDF onto the District Energy lands to the north of the Site. This facility will treat all storm water runoff from lands within the Glen Oak subwatershed that are north of William Halton Parkway. The treated runoff from the Glen Oak RDF will be directed primarily into the Sixteen Mile Creek near the Dundas Street West crossing, with some overflow draining to the Glen Oak via the OGDI pond. Storm water runoff from the OGDI Site will be treated through a privately owned facility featuring 690 below-grade treatment and storage chambers. Treated runoff from the OGDI SWM chambers will be directed to the Glen Oak Creek outlet at Dundas Street West. A municipal pond is also proposed within the OGDI district and this pond will treat runoff from the Oakville Trafalgar Memorial Hospital (following decommissioning of the hospital s on-site facility), William Halton Parkway, and Third Line as well as provide the previously mentioned additional attenuation of outflow from the District Energy Pond. Discharge from this municipal pond will also be directed to the Glen Oak Creek outlet at Dundas Street West. The main focus of the following impact assessment will be on the effects of the proposed development on the water balance at the Site and within the contributing areas to the adjacent PSW, more specifically on changes to infiltration to the groundwater system. The water balance analysis will also be examining the potential impacts to the PSW from changes at the Site and elsewhere within the PSW s catchment areas, and will outline mitigation measures to counteract such potential impacts. The feature-based water balance for the PSW was carried out with assumptions regarding the areal extent of the groundwater contribution to the as there is no available off-site groundwater level data to define the overall extent of the area from which groundwater may be directed towards the PSW. Data from the EIR/FSS submitted on behalf of Mattamy Homes (Stonybrook, 2015) was used to provide some definition of the groundwatershed to the north and northeast of the wetland. However, in areas to the northwest (towards Highway 407) with no monitoring wells, the ground-watershed to the PSW was simply assumed to be defined by the original SM117 subwatershed boundary under all scenarios. November HG1 Page 35

47 . Oakville Green Health Sciences and Technology District - Hydrogeological Investigation Proposed Development Plan and Infiltration Measures Legend Site Boundary Private Roads Limits of Underground Parking Edge of Natural Heritage Buffer Infiltration Trench J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 9 Prop Development Plan and Infiltration Measures.mxd 2016 Microsoft Corporation and its data suppliers Dundas Street West Client Prepared By Scale Date November 2016 Scale as Shown Slurry Wall Towers Terrace SWMP Block Oakville Green Development Inc Queen's Printer for Ontario Meters Project No HG1 Figure: 9

48 4.1 Water Balance Methodology The MOE Stormwater Planning and Design Manual (2003) offers a method to estimate the infiltration on the site, based on a local infiltration factor i", which is applied to the available water surplus to determine the groundwater recharge for a given area with pervious cover. The methodology considers factors such as the soil type, topography, and vegetation to arrive at the infiltration factor that is then applied against the water surplus to provide an estimate of the amount of water infiltrating into the ground. The remaining water surplus is considered runoff. Under the post-development conditions the infiltration factor is recalculated to account for changes in soil types, vegetation and topography after development, and the infiltration and runoff at the pervious land areas are recalculated. As the land after development will have impervious surfaces that prevent infiltration, such as building footprints, roads and parking areas, the pervious area available for infiltration is reduced. Furthermore, there is limited opportunity for evapotranspiration (ETR) on these impervious surfaces, other than evaporative losses from wetting and ponding of water in shallow depressions (estimated at 10% of total precipitation), and so total precipitation is applied to these surfaces instead of the water surplus. 4.2 Climate and Water Surplus The inputs used for the water balance calculations are based on information provided by Environment Canada using climate data from the Oakville Gerard meteorological station (43 o 26 -N 79 o 42 -W), for the period 1990 to 2006, with mean annual precipitation of 819 mm. This climate station is considered to be more representative of climatic conditions at the Site than the Hamilton Royal Botanical Garden (HRBG) station used in the NOCSS and in the original EIR/FSS prepared by Stantec 25. The Oakville Gerard station is located approximately 5.5 km southeast of the Site, whereas HRBG is located about 22 km southwest from the Site, along the edge of Hamilton Harbour. Furthermore, the Oakville Gerard station is also not located immediately adjacent to the lake (as is the case of the HRBG) and therefore will experience less climatic lake effect potential. Environment Canada inputted their climate data into a computer model (Johnstone and Louie, 1983) to provide actual evapotranspiration and water surplus inputs for soils with different water holding capacities (WHCs). Under pre-development (2010) conditions, the Site and surrounding areas, assumed with moderately rooted crops in the fields and forest blocks, were analysed using WHC s of 200 mm and 400 mm. Under the existing condition (2015), with fill soils covering the Site and weedy growth, the WHC of the soils at the Site are estimated to be 125 mm (see Section 4.3.1). The Environment Canada data (including the Johnstone and Louie paper) is presented in Appendix G and is also found on Table WB-1 within this same Appendix. The Site is located in an area of temperate climate with a mean annual temperature of 9.0 C and a mean annual precipitation of 819 mm. The potential evapotranspiration estimate that was provided by Environment Canada based on the Thornthwaite approach is 656 mm per year. The mean actual evapotranspiration in the vicinity of the Site (pervious areas excluding existing imperviousness runoff contributions) is 607 mm per year and 644 mm/year respectively for soils with WHC s of 200 mm and 400 mm (pre-development, 2010 condition) and 559 mm per year 25 Stantec s water balance presented in the original EIR/FSS, indicated HRGB receives 769 mm/year of precipitation. This value is in fact the annual rainfall recorded at the station, and we note that the annual snowfall (124 cm = 124 mm rainfall equivalent) was omitted from the calculations. This would result in under-estimates of the water surplus and therefore of the calculated infiltration and runoff potential within the original EIR/FSS study area. November HG1 Page 37

49 for soils with a WHC of 125 mm (2015, existing condition, see below) reflecting periods of soil moisture deficiency. The pre-development and existing condition water surpluses, the water available for infiltration and runoff, is estimated to be between 166 and 210 mm per year and between 166 and 258 mm per year respectively under pre-development (2010) and existing (2015) conditions at the Site. 4.3 Inputs to Water Balance Site specific inputs used in the water balance analyses are summarized in Table 8 and Table 9, and the inputs under the post-development case are explained below. The rationale for the predevelopment and post-development inputs is discussed in Sections and November HG1 Page 38

50 Table 8: Inputs Used in the OGDI Site Specific Water Balance Infiltration Factors Based on Land Conditions Pre- Development Existing Condition Post- Development Topography Soils Vegetation Sum Water Holding Capacity of Soils (mm) Pre- Development Existing Condition Post- Development and 200 Site Areas for Use in Calculations (ha) OGDI Pre- Development Existing Condition Post- Development Pervious Impervious SWMP (Impervious) Total Area Notes: Post-development areas are based on the Draft Plan of Subdivision submitted to the Town of Oakville in May The pervious area within and next to the PSW buffer and Sixteen Mile Creek (0.59 ha) is the only portion of the Site with potential to provide infiltration in the post-development scenario, and currently has a steep slope (currently about 14% slope). Therefore the slope-based infiltration factor has been set at 0.10 for this area in the post-development scenario. Interior landscaping (e.g., trees) will be planted within isolated planters (bio-retention chambers) located above the underground parking structures (estimated at 0.53 ha total area), with no opportunity to provide infiltration into the ground, and are thus not included in the sub-totals presented in the table. Evapo-Transpiration (ETR) from these plantings is factored into the analyses. Approximately 3.51 ha of roof area will be utilized as green roof and this green roof total is also not included in the above table as they will also not contribute any water directly to infiltration but ETR from the green roofs is factored into the analyses. Water Holding Capacity of Soils is based values presented on Table 3 from the MOE Stormwater Management Manual (2003). November HG1 Page 39

51 Table 9: Inputs Used in the PSW Feature Based Water Balance Infiltration Factors Based on Land Conditions Pre- Development Existing Condition Post- Development Topography to to 0.20 Soils to to 0.15 Vegetation 0.10 to to to 0.20 Sum 0.41 to to to 0.51 Water Holding Capacity of Soils (mm) Pre- Development Existing Condition Post- Development 200 and , 200 and , 200 and 400 Areas for Use in Calculations (ha) for Groundwater to the PSW PSW Pre- Development Existing Condition Post- Development Pervious Impervious SWMP (Impervious) Total Area Areas for Use in Calculations (ha) for Surface Water to the PSW PSW Pre- Development Existing Condition Post- Development Pervious Impervious SWMP (Impervious) Total Area Notes: Changes in areas (notably surface water catchment) are the result of grading that revised the subwatersheds boundaries between 2010 and 2015 and for future development (OGDI and Mattamy lands). November HG1 Page 40

52 4.3.1 Pre-Development Condition (2010) and Existing Condition (2015) The surficial soils in the surrounding area and at the Site prior to construction of the neighbouring hospital and placement of fill on the Site, are generally comprised of Clayey Sandy Silt Till, underlain by Shale Bedrock. The site is currently covered with Clayey Sandy Silt Fill with broken shale bedrock fragments contained within the soil matrix. As described in Section 3.2.1, the surficial soils are best classified as Silty Loam on the basis of grain size analyses performed on soil samples collected from the Site. Soils mapping of the Site and the hospital lands to the west presented on Figure 4W.6.1 in the NOCSS (included in Appendix G) identifies most of the Site was originally comprised of soils classified as Chinguacousy Clay Loam and Jeddo Clay Loam (Hydrologic Soil Group C (i soil = 0.20)), while at the hospital site, about half of that property was covered with the above soil types, with the remainder covered by Oneida Clay Loam (Hydrologic Soil Group D (i soil = 0.10), ref. Table 4W.6.2 from NOCSS). The Site has been covered by fill materials presumed to be obtained from the construction of the hospital and the RDF and we have assumed that the fill placed at the Site is comprised evenly of soils that were classified in Hydrologic Soil Groups C and D. This results in a weighted average for the i soil of 0.15 at the Site under its current condition. The lands north and northwest of the Site within the PSW subcatchment are roughly evenly split between soils of Hydrologic Soil Groups C and D, resulting in an average i soil of 0.15 for these lands. Prior to any works being carried out at the Site, the vegetation would have been comprised of moderately rooted crops which in a Silty Loam would lead to a soil water holding capacity (WHC) of 200 mm as defined on Table 3 of the MOE Stormwater Planning and Design Manual (2003). The present vegetation at the Site is comprised of shallow rooted weeds and grasses and with these soil and vegetation conditions, a WHC of 125 mm was used in analysing the existing condition for the water balance. The pre-development infiltration factor for the Site, prior to any development activities (2010 condition), i, is calculated at 0.46 based on the following: Topography is classified per the MOE method as rolling land, i topo = 0.16 (average slopes across the Site and surrounding lands before any development of about 0.9%); Soils are considered to be a silt loam from grain size analysis, as Hydrologic Soil Group C, i soils = 0.20; and, Cover is predominantly comprised of moderately rooted crops, i cover = The infiltration factor for the Site, i, is calculated at 0.40 under the existing condition (2015) based on the following: Topography is flatter, but still classified per the MOE method as rolling land, i topo = 0.20 (average slope across the Site on the order of 0.4%); Soils are considered to be a silt loam from grain size analysis, as a 50:50 mixture of Hydrologic Soil Groups C and D, i soils = 0.15; and, Cover is predominantly comprised of grasses and weeds, i cover = The pervious surface area of the Site under existing conditions is approximately 13.4 ha, down from the 15.3 ha of permeable area in 2010, due to the 1.9 ha RDF currently located on the Site that is treated as impervious area. The infiltration factor for the limited pervious area to remain at the Site, i, is calculated at 0.35 under the future post-development condition and based on the following: November HG1 Page 41

53 Topography at the pervious area along and within the wetland buffer is steep (14% +/-) classified per the MOE method as hilly land, i topo = 0.10; Soils are considered to be a silt loam from grain size analysis, as a 50:50 mixture of Hydrologic Soil Groups C and D, i soils = 0.15; and, Cover is predominantly comprised of native vegetation, i cover = For the lands within the PSW subcatchments (but excluding the OGDI property described above), the infiltration factor for both the 2010 and 2015 conditions, i, is calculated at between 0.41 and 0.51 based on the following: Topography is classified per the MOE method as rolling land, i topo = 0.16 (average slopes across the Site and surrounding lands before any development of about 0.9%); Soils are considered to be a clay to silt loam based on review of soil mapping (Hydrologic Soil Groups CD and C), i soils = 0.15 and 0.20; and, Cover is predominantly comprised of moderately rooted crops with some woodlots, i cover = 0.10 and The post-development infiltration factor for the developed lands outside of OGDI (District Energy Lands, Mattamy), i, is calculated at 0.36 based on the following: Topography at the developed parcels (District Energy Lands, Mattamy) is assumed to remain roughly the same as present, classified per the MOE method as rolling land, with i topo = 0.16; Soils are considered to be a silt loam, as a 50:50 mixture of Hydrologic Soil Groups C and D, i soils = 0.15; and, Cover is predominantly comprised of grassed landscaping, i cover = Post-Development Conditions The future development of the Site will change the lands from a vacant (formerly agricultural) land use to a mixed land use (employment, residential, hotel, institutional). This will change the evapotranspiration, runoff and infiltration conditions of these lands by adding hard surfaces such as roads, sidewalks and roofs that are effectively impervious. With this particular development proposal, 1.5 levels of underground parking that will cover ha of the total site area is being proposed which in addition to the AK highlighted for the SWMP block, leaves about 0.59 ha of pervious land available for infiltration (this land being located within and next to the 30 m PSW buffer). For the purposes of the water balance analyses, the total area covered by impervious surfaces for this type of development is calculated at 96.1% of the total land area. The development application plans to include green roofs across the development lands and trees along the boulevards and open-area public spaces. Two post-development water balance conditions will be examined. In the first instance, a postdevelopment scenario where there is no attempt to mitigate runoff or infiltration will be considered. All runoff generated from hard surfaces in that scenario is assumed to be directed towards the SWMP facility as runoff. The second post-development water balance scenario will examine infiltration and runoff when attempts to mitigate these components are incorporated into the design. Runoff from all areas within the developed lands will eventually be directed to the stormwater management system. The exception would be the runoff from pervious areas abutting and draining to natural features or runoff conveyed to these features by means of mitigation such as LIDs. November HG1 Page 42

54 Evaluation of LID Measures An evaluation of infiltration-based LID measures was carried out at the request of the Town of Oakville. The development plans for the Site propose to construct a number of multi-storied towers with underground parking, in a ring about a centralized SWMP facility. The underground parking is proposed to extend down to 1.5 levels, and extend across the full area of the site, to the property lines excluding the 0.59 ha of land located within and immediately adjacent to the 30 m PSW buffer (along the northeast property line) and the Sixteen Mile Creek valley, and at the central SWMP (0.59 ha). Underground water and sewer services will be conveyed within the underground parking structures. This design, which results in the coverage of almost the entire Site with hard (impermeable) surfaces, limits the opportunities to apply infiltration-based LIDs at the site. Table 10 provides a comparison of potential LID strategies for the Site. Four LIDs methods were considered to be feasible at the Site, only one of which provides infiltration opportunity. These are: Rainwater Harvesting / Greywater Use leads to runoff reductions only; Green Roofs leads to increased evapotranspiration and runoff reduction; Infiltration Trenches reduces runoff and increases infiltration; and, Bio-Retention leads to increased evapotranspiration and runoff reduction. These will be proposed within the internal development blocks above the underground parking structures and therefore infiltration cannot be utilized. November HG1 Page 43

55 Table 10: Comparison of LID Measures LID Technique Water Balance Benefits Overall Benefits Disadvantages Maintenance/Upkeep Requirements Suitability for Site Rainwater Harvesting / Greywater Use Reduces run-off component, but no Infiltration benefit Green Roofs Downspout Disconnection Reduces run-off component through Evapotranspiration, but no Infiltration benefit Reduces overall runoff and directs water to ground Has an Infiltration benefit Infiltration Trenches / Soak-away Pits Has direct Infiltration benefit and reduces runoff Bio-retention Reduces run-off component through Evapotranspiration Can have an Infiltration benefit depending on design Reduces volume of runoff Reduces volume of treated City water used by the development If storage tanks are indoors, can be used year-round Reduces volume of runoff Can be designed as a landscape feature with public access If properly constructed may extend service life of roof Reduces volume of runoff Can reduce volume of City water used for irrigation when rain barrels are also used Reduces volume of runoff Increases infiltration Infiltration trenches are suitable along narrow pieces of land Reduces volume of runoff May increases infiltration Can be designed as a landscape feature Can accept roadway runoff Can be used with overflows in areas where infiltration is not possible Variability of rainfall requires backup connection to City water to ensure constant supply May be subject to algal growth in cisterns, serve as mosquito breeding grounds depending on design Weight of saturated soil media, plants will require increased structural support Potential for water leaks (leak detection system recommended) Requires pervious area for discharge. Could lead to standing water and ponding issues Best with permeable soils Requires seasonally high water table (and bedrock) be greater than 1 m below the base of the device Requires pre-treatment to prevent clogging of the granular material Heavy equipment must be kept clear of proposed area to prevent compaction of soils Requires seasonally high water table (and bedrock) be greater than 1 m below the base of the device Requires pre-treatment to prevent clogging of the soil media Heavy equipment must be kept clear of proposed area to prevent compaction of soils Should be inspected minimum every 6 months (spring/fall) for clean out of debris, repairs, etc. Minimum of twice per year. Maintenance includes weeding, replacement of dead plants, removal of debris and inspection of the overflow conveyance system to ensure that excess water will be removed Minimal. Ensure downspouts remain unblocked and that they direct water away from structures Should install monitoring wells within the trenches to permit assessment of system operation Clean out of pre-treatment chambers to remove debris, accumulated sediments should be carried out on an annual basis Requires routine maintenance and inspection similar to general landscaped areas. Quarterly inspection and monitoring of the bio-retention facility over first 2 years of use is recommended and after every storm event greater than 25 mm. Afterwards, inspections should be twice/year (spring/fall) and after major storm events Pre-treatment system to be inspected twice per year (spring/fall) for removal of accumulated sediments and debris Yes multi-storied office and residential buildings can be utilized for toilets and irrigation Yes green roofs are planned No this is more suitable for residential developments with smaller roofs and larger green areas to receive the water Yes Limited area is available at the Site though soil conditions are not optimal. Infiltration trenches are preferred over soak-away pits due to the linear configuration of the available space Yes Limited area with infiltration potential is available at the Site. Can be used within the development area as landscape features (Planters, boulevard trees) leading to evapotranspiration with reduction in total runoff but no infiltration benefit

56 Table 10: Comparison of LID Measures Vegetated Filter Strips Permeable Pavement Enhanced Grass Swales Bio Swales Perforated Pipe Systems Generally used as a pre-treatment system Can have minor Infiltration benefit Can provide Infiltration potential when underlain by soils. In cases where an impervious surface underlies the pavers, limited evaporation benefits only, and limited water quality improvements may be seen in runoff Reduces run-off component through Evapotranspiration Has an Infiltration benefit Reduces run-off component through Evapotranspiration Has an Infiltration benefit Provides Infiltration benefit Reduces runoff Pre-treats runoff and filters out sediments and contaminants Can be designed as a landscape feature Provides some Infiltration potential Can reduce runoff with increased infiltration where soil conditions allow Provides pre-treatment of stormwater, slows down runoff and provides some infiltration potential Provides infiltration benefit Reduces runoff through evapotranspiration Can be designed as a landscape feature Provides Infiltration benefit Reduces runoff with little to no footprint Requires sheet runoff flows and wide space requirements Should not be used where high pollution activities are expected Heavy equipment must be kept clear of proposed area to prevent compaction of soils Expensive Sand should not be spread over permeable pavement in the winter to prevent clogging, and use of deicers should be minimized Can introduce contaminants to groundwater system from spills of chemicals should not be used in areas where hazardous materials may be transported Requires seasonally high water table (and bedrock) be greater than 1 m below the base of the device Ponded water can be used as Mosquito breeding grounds if swales are designed poorly Requires wide space Heavy equipment must be kept clear of proposed area to prevent compaction of soils Requires seasonally high water table (and bedrock) be greater than 1 m below the base of the device Ponded water can be used as Mosquito breeding grounds if swales are designed poorly Requires wide space Heavy equipment must be kept clear of proposed area to prevent compaction of soils Requires pre-treatment of water entering the system to prevent clogging (e.g., oil-grit separators Should not receive runoff from high traffic areas or where pollution potential is great Quarterly inspection and monitoring of the filter strip over first 2 years of use is recommended and after every storm event greater than 25 mm. Afterwards, inspections should be twice/year (spring/fall) and after major storm events, confirming that vegetative cover is greater than 80% and repairing damage caused by foot traffic, etc. Annual inspections (spring) to confirm continued infiltration performance (not applicable at this site). Surface sweeping at least twice per year (spring/fall) Quarterly inspection and monitoring of the filter strip over first 2 years of use is recommended and after every storm event greater than 25 mm. Afterwards, inspections should be twice/year (spring/fall) and after major storm events, confirming that vegetative cover is greater than 80% and repairing damage caused by foot traffic, etc. Requires regular mowing Quarterly inspection and monitoring of the filter strip over first 2 years of use is recommended and after every storm event greater than 25 mm. Afterwards, inspections should be twice/year (spring/fall) and after major storm events, confirming that vegetative cover is greater than 80% and repairing damage caused by foot traffic, etc. Requires regular mowing Should install monitoring wells along the perforated piping alignments to permit assessment of system operation Clean out of pre-treatment chambers to remove debris, accumulated sediments should be carried out on an annual basis Not feasible Limited area is available for other infiltration based LIDs, and runoff from roof headers would not result in sheet flows which makes this method impractical at the Site No Provides no benefit with parking garages located below roadways and pedestrian venues Not feasible better infiltrationbased LID methods/opportunities are available at the Site Not feasible Width requirements make this impractical with the limited available space No Cannot be used at the Site due to underground parking structures

57 Proposed LID Measures For the post-development scenario with mitigation, rainwater harvesting/greywater use, green roofing and infiltration trenches will be the principal LID techniques used at the Site, with some internal bio-retention opportunities included. There is 3.51 ha area of proposed green roofing proposed for the Site. Roof areas designated for public access or HVAC mechanical services (not included in the 3.51 ha total) will be treated as impervious and while the 3.51 ha will be green. Precipitation falling on the green roof surfaces will be absorbed by the soil media (WHC treated as 100 mm), and a portion of this water will be used up from ETR of the plantings, with the balance treated as runoff. Runoff from both the green roofs and roofs of standard construction will be retained for use in LID techniques, such as being directed to infiltration trenches, with the balance being available for use in grey-water cisterns and irrigation. Approximately 135 m of infiltration trenching is proposed along the 0.59 ha green space next to the PSW at the north side of the site plus an additional 165 m of trench continuing south alongside the Sixteen Mile Creek valley up to the point where an internal road exits the Site (300 m length in total). The 165 m long section of infiltration trench would provide additional water towards the downstream reaches of the tributary to Sixteen Mile Creek. For the calculations, the trenches were assumed to be 1.3 m in width and 1.15 m deep, with an infiltration rate of 0.6 mm/hour 26 and they will receive their water from clean roof runoff. They are also assumed to generally remain in a permanent saturated condition so that infiltration occurs continuously. Under the post development condition, the soil composition is expected to remain classified as a Silt Loam in the 0.59 ha of green space at the north end of the site. We anticipate that natural plantings to support the PSW will be made in this area thus increasing the soil s WHC from 125 mm to 200 mm. There is a Town of Oakville requirement regarding the number of trees to be planted across proposed development blocks based on a formula provided by the Town. For the Oakville Green development, 159 trees are required within the development blocks to meet the Town s requirements. Because of the fact that almost the entire site will be covered with underground parking facilities, these trees will need to be planted in discrete planters with specified volumes of soil and minimum surface area coverage (calculated as 33.3 m 2 /tree). This leads to a total pervious surface area of 0.53 ha across the site. The planters are effectively bio-retention cells with an underdrain and impermeable liner, and as there is no possibility to infiltrate any water reaching these planters because of the underlying parking garages, only ETR and runoff is calculated for these trees in the water balance. The effects of these tree plantings are included in both post-development water balance scenarios. Additional bio-retention opportunities within the internal development blocks are possible through incorporation of additional landscape features such as large planter boxes incorporated along the boulevards and within public meeting spaces. 26 This infiltration rate incorporates a factor of safety of 2.5 (1.4 mm/hour / 2.5 = 0.6 mm/hour) as prescribed in the Low Impact Development Stormwater Management Planning and Design Guide (CVC, TRCA, 2010). Additional permeameter testing along the proposed trench alignment is recommended during detailed design. November HG1 Page 46

58 4.4 Water Balance Water balance analyses were performed for the entire Site area, and for the lands on the Site that have potential to contribute groundwater and surface water runoff to the PSW to the north of the Site. The detailed water balance prepared for the Site apportioned groundwater and surface water contributions from the Site towards the PSW 27 based on the calculated areas contributing runoff and infiltration on the Site. Thus if the area with infiltration potential towards the PSW was calculated to be 10% of the total Site area, then 10% of the calculated infiltration at the Site was considered to be directed towards the PSW (under 2010 and 2015 conditions only). A feature-based water balance for the PSW, including lands located beyond the limits of the Site was also carried out. With regard to the PSW, the areas beyond the Site limits that contribute groundwater infiltration and surface water potential were different, and furthermore the area contributing runoff potential was seen to change between scenarios (refer to Figure 10). The water balance analyses for the PSW therefore individually considered the portions of the Site and surrounding lands contributing runoff and infiltration towards the PSW as illustrated on Table 11. Table 11: Areas of Site Contributing Infiltration and Runoff towards the PSW Water Balance Scenario Pre-Development (2010) Existing Condition (2015) Post-Development No Mitigation Post-Development With Mitigation Contributing Areas to PSW OGDI Site Only Contributing Areas to PSW Overall Subwatershed (incl. OGDI) Infiltration Runoff Infiltration Runoff 1.23 ha 1.80 ha ha ha 1.23 ha 1.05 ha ha ha 0.38 ha 0.38 ha ha ha 0.38 ha 0.38 ha ha ha 27 Note that the term towards, as it relates to the groundwater, should not be taken as meaning all of this groundwater discharges into the PSW. Some of this groundwater is expected to pass below the base of the wetland based on observations and data collected at the Site during this study to date. November HG1 Page 47

59 .. Pre-Existing PSW Catchments (2010) Existing PSW Catchments (2015). Post Development PSW Catchments Oakville Green Life Sciences and Technology District - Hydrogeological Investigation Groundwater and Surface Water Catchments for the PSW Legend Site Boundary Provincially Significant Wetland (PSW) Subwatershed Catchments Groundwater Catchment Surface Water Catchment Groundwater Catchment (A=70.85 Ha) Groundwater Catchment (A=70.85 Ha) Groundwater Catchment (A=70.85 Ha) J:\1442 Projects by Job Number\2015\ HG1 Oakville Green\Mapping\MXD\Figure 10 GW and SW Catchments.mxd 2016 Microsoft Corporation and its data suppliers Surface Water Catchment (A=79.92 Ha) 2016 Microsoft Corporation and its data suppliers Regional Municipality of Halton Surface Water Catchment (A=86.58 Ha) Glen Oak Regional Detention Facility 2016 Microsoft Corporation and its data suppliers Regional Municipality of Halton Surface Water Catchment (A=86.05 Ha) Glen Oak Regional Detention Facility Client Prepared By Scale Date Scale as Shown Oakville Green Development Inc November 2016 Queen's Printer for Ontario Meters Project No HG1 Figure: 10