7.0 SURFACE WATER QUALITY AND QUANTITY 7.1 Background: Surface Water. 7.2 Current Baseline Conditions: Surface Water

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1 7.0 SURFACE WATER QUALITY AND QUANTITY 7.1 Background: Surface Water An Environmental Study Report (ESR) for the extension of Terry Fox Drive from Eagleson Road / Hope Side Road to March Road was completed in November 2000 (ESR dated October 2000). In 2007, Dillon completed an EA Addendum for revisions to the original ESR, and submitted supporting documents, including a Preliminary Design Report and a Draft Stormwater Management Report. In 2009, given the accelerated timelines for the project, the potential for integration of storm water management facilities with private land-development project adjacent to Terry Fox Drive is limited, as most of the developments are not yet at the detailed design stage. Therefore, the design approach to Terry Fox Drive has been to develop a stand-alone storm water management solution with the flexibility to accommodate, or integrate with, other solutions as they come on-line in the future. Dillon is currently completing the detailed design of Terry Fox Drive, and has prepared a Storm Water and Floodplain Management (SWFM) Report, which is included in Appendix B of this document. The SWFM document also provides an update of issues and key design decisions related to storm water management along Terry Fox Drive since the 2007 Preliminary Design. This document is intended to support the application to MOE for Certificate(s) of Approval as well as provide the City with the necessary documentation required for the project to proceed. This document is also in support of an application to the Mississippi Valley Conservation Authority (MVCA) for a permit under the Water Resources Act to fill in the floodplain of a fill-regulated area. A brief summary of the Storm Water and Floodplain Management Report is included in the following sub-sections. 7.2 Current Baseline Conditions: Surface Water The Storm Water and Floodplain Management Report provides a summary of surface water management targets and objectives, as well as the existing environment, including specific features of the Carp River Sub-Watershed and the Shirley s Brook Sub-Watershed. There are four small tributaries that cross the road alignment, two flowing into the Carp River and two tributaries to Shirley s Brook. Other than the main Carp River, which is about 3 m wide, all are small drainages, with each watercourse not more than 50 cm wide at any point. The numerous wetlands of the South March Highlands contain limited open water areas, with only a few straightened channels through the wetlands where drainage improvements in the past have opened up channels to aid farming. The location of the drainage areas for each Sub- Watershed adjacent to Terry Fox Drive is briefly summarized as follows: Shirley s Brook Watershed The Shirley s Brook sub-watershed covers an area of approximately 2,700 ha and has an average basin length and width of 6 km and 5 km respectively, with 39% covered by forest, wetland or exposed rock. The remainder has been cleared for agricultural purposes including pastureland, hay, mixed grain and corn, but many of these areas are now giving way to estate residential or small-scale commercial/retail development. Within the Shirley s Brook sub-watershed are several distinct natural areas including the South March Highlands Provincially Significant Wetlands Complex and Trillium Woods Park. Within the northern portion of the study area (Shirley s Brook sub-watershed), surface water runoff currently traverses the ROW of the proposed Terry Fox Drive alignment via wetlands, poorly defined channels and slow moving overland flow routes. From south of the Arnprior-Nepean Railroad (future Project No

2 Ottawa Transit Line) to the proposed termination point at March Road, a distance of approximately 3 km, the study area straddles two headwater sub catchments of the Shirley s Brook watershed. These wetlands drain generally westerly, descending to lower lands where they turn and flow easterly toward the main branch of Shirley s Brook at Goulbourn Forced Road. What is commonly referred to as the east branch of Shirley s Brook runs parallel with the Arnprior Nepean railway tracks through the study area and then turns south in a ditched channel through the KNL Lands. The west branch crosses the proposed alignment south of the rail crossing before flowing east to join the east branch in the centre of the KNL Development Ltd. lands. A small volume of surface drainage that originates within the undeveloped natural areas west of Second Line road is accommodated by a network of shallow depressions and intermittent tributaries. No clearly defined channels bisect this area. Local surface drainage is characterized by poorly defined intermittent tributaries associated with small groundwater seeps near the Second Line Road allowance junction with Terry Fox Drive. The small ephemeral flow is directed across Second Line Road via small diameter culverts and continues east over a distance of approximately 1 km, through undeveloped lands, where it outlets into the main branch of Shirley s Brook (Dillon Consulting, 1999). The combined watercourse meanders southeast for approximately 6.5 km at an average slope of m/m, through industrial/commercial business parks and residential areas within the former City of Kanata prior to combining with two additional tributaries from the north. From this point, the Shirley s Brook flows an additional 4.5 km at an average slope of m/m, through agricultural and Federal Department of National Defence lands prior to emptying to the Ottawa River at Shirley s Bay (Dillon Consulting, 1999). Local drainage through the proposed route is characterized by steep folded topography, associated with granite bedrock outcrops, sloughs, seasonal pools, forested swamps and deep wetland pockets. Surface runoff is conveyed generally westerly to concentrate in the east and west tributaries, which cross the Arnprior-Nepean Railroad Line via small diameter, low capacity culverts. A small ditch at the corner of (proposed) Second Line and Terry Fox drains groundwater seepage from one small area, but otherwise this area has no defined creeks or tributaries Kizel Drain/ Watts Creek Watershed Kizel Drain, a large tributary of the Watts Creek Watershed, maintains a drainage area of approximately 10 km2, and has an average basin length and width of 4 km and 2.5 km respectively. A small portion of the project study area, north of Richardson Side Road, is located within the western headwater area of Kizel Drain. The Kizel Drain Wetland Complex generally lies well outside the study area. Drainage from the south portion of the headwater area is conveyed through residential subdivisions via storm sewers and overland flow routes. Surface runoff from these upper reaches discharge into the Beaver Pond, a large on-line wet pond which serves as a water quality facility for adjacent urban development areas. Outflow from the pond enters the main branch of Kizel Drain and flows northeasterly for approximately 2 km at an average slope of m/m, crossing through the south end of the Kanata North Business Park. The Drain turns and continues south-easterly to its outlet into Watts Creek, approximately 1 km downstream of Carling Avenue (Dillon Consulting, 1999) Carp River Watershed The Carp River Watershed comprises a total drainage area of approximately 310 km2 and is oriented from southeast to northwest. The drainage basin maintains an average length and width of 30 km and 10 km respectively, with the main branch totalling approximately 40 km in length. Surface drainage is Project No

3 conveyed by a network of natural tributary watercourses and improved agricultural drains that outlet along the entire length of the River. The main channel originates east of Glen Cairn within the Stony Swamp Conservation Area, and extends north-westerly, parallel to the proposed routes. Previous channel modifications to the River, including localized straightening and protection works, have been carried out within the upper reach of the basin to facilitate urban growth along the western portion of the former City of Kanata. North of the City, the main branch flows north-westerly, at an average slope of m/m, through numerous communities, including Carp, Elm and Kilburn prior to emptying into the Ottawa River at it s mouth in Fitzroy Harbour. Land uses found within the watershed include agricultural and idle lands, forest and wetland areas and urban development associated with the City of Kanata and smaller towns and hamlets (Dillon Consulting, 2000). The local upstream external drainage areas adjacent to Terry Fox Drive represent a very small portion of the Carp River sub-watershed. These areas range in size from several hectares to over 50 hectares. The drainage patterns of the Carp River area are well defined, highly meandering where natural, yet periodically straightened, typical of low-lying, flat, drained agricultural floodplains adjacent to a watercourse. Within the southern portion of the study area, overland drainage currently traverses the ROW via poorly defined overland flow routes and small tributaries and swales along hedgerows, which drain westerly towards the Carp River. The Carp River runs parallel with the proposed alignment for about 1,500 m through the study area on the west side of Terry Fox Drive, flowing in a north-westerly direction. Overland drainage patterns are generally perpendicular to the proposed ROW through a low-lying, flat, floodplain adjacent to the Carp River. One small watercourse ( Carp Tributary 1) drains forested lands on the Carp Ridge, west of the un-built First Line road allowance, crossing the Terry Fox Drive alignment at Stn in an unclassified wetland on the Carp River floodplain. A second small tributary (Carp Tributary 2) crosses the alignment at Stn in an open swale along a hedgerow Roadway Proximity to Water Bodies The TFD alignment crosses or intersects watercourses at six locations. No bridges are required as all watercourses are quite small, less than two meters wide. The roadway will require four stream crossings and one significant creek realignment as noted. Several small depressions, wetlands and pools occur along the alignment, several of which contained fish and amphibians, which indirectly indicated which depressions were permanent, and which were ephemeral or seasonal. There are no large ponds, lakes or other open water bodies that occur within or near the Right of Way (ROW) of the roadway. The Carp River lies parallel to the ROW, with the closest approach approximately 85 metres to the grading easement at Stn and to within 30 metres to the grading easement at Stn Overall the Carp River parallels the road closely for about 1,400 m. The road alignment lies within the 100-year floodplain of the Carp River, as noted above, and will be subject to compensation of flood volume on a like-for-like basis as detailed in Chapter 7. There are no current or past navigational uses of the Shirley s Brook watercourses as they are much too small for navigation and are ephemeral in nature. The watersheds of Shirley s Brook in the study are less than that required to be fill regulated, so the potential impacts on property from flooding are considered negligible by the Mississippi Valley Conservation Authority. The study area watercourses carry water that is not potable nor of sufficient quality or quantity to use as a drinking source. The Carp River drains urban areas and agricultural lands east of the study area and is considered to be organically enriched and slightly polluted with runoff (Robinson Assoc, 2007), yet is Project No

4 used for livestock watering in some areas. The Shirley s Brook tributaries arise in wetlands from precipitation runoff, weak groundwater discharge and although relatively clean due to natural treatment processes, would not be of sufficient quality for regular human consumption. There are no commercial or recreational uses of the fishery in Shirley s Brook. The tributaries are too small and insignificant to be used as such. The small warm water fish species found here would not be of interest as a human food resource. There are few open water areas within the wetlands, affording lowoxygen concentration levels, which significantly limits the year round availability of fish habitat resources in the area. We can expect that there was no aboriginal use of Shirley s Brook as a fishery, with the abundant resource of the Ottawa River and Shirley s Bay so close nearby, but this question may be more definitively answered as part of the consultation with the aboriginal groups currently underway. The area may have been important for aboriginal hunting of mammals, birds and reptiles, however there is no current evidence of this and is speculation only. There are no significant watercourses or open water bodies to be crossed by the project. The Carp River lies adjacent to the Project, however there are no crossings of this river required for the TFD alignment. All water crossings shall use a hydraulically sized culvert, as there are no structural features (i.e. bridges) required. 7.3 Effects Assessment: Surface Water The Storm Water and Floodplain Management Report identifies potential impacts that may occur as a result of the proposed roadway, as follows: Potential Water Quantity Impacts Displaced flood storage; Reduced infiltration and increased run-off volume; Reduction in the time of concentration resulting in increased peak flow rates; Increased flow velocities; Reduction of base flow in streams due to reduced infiltration and flow diversion; An increase in the frequency of erosive run-off events that result from typical, highly frequent rain storms; Increased frequency of upstream flooding resulting from misdirection of overland drainage; and, Habitat disruption Potential Water Quality Impacts Sediment transport as a result of erosion during the construction phases; Inadvertent spills of fuels or materials during the construction activities; Contaminants transported from the roadway and external lands, to the receiving system during the operational phases; Reduction in receiver assimilative capacity for contaminants as a result of a decrease in base-flow and groundwater recharge rates; and, Project No

5 Increased run-off water temperature due to an increase in paved area and retention times within the storm water management facilities. In addition to the potential impacts of the project, the physical setting of the project provides a number of design considerations, which are described below Geophysical Considerations According to the recent geotechnical analysis, the clay deposit along the Carp River requires careful design. According to Golder Associates Ltd.: The rate of settlement is highly dependent on the rate of drainage and traditionally in this clay deposit it is anticipated that settlement will continue to occur for several years after the roadway embankment has been constructed, which is unacceptable for roadways containing [underground] services and paved surfaces. Therefore the majority of the settlement will need to be accelerated by methods of installing artificial drainage within the silty clay and placing temporary surcharge loads on the embankment to have the settlement occur during or prior to the construction period. (Golder Associates Ltd., 2009). Furthermore, where embankments overlie areas of soft or firm grey silty clay they will settle by an amount that is relative to the height of the embankment. (Golder, 2003). Therefore, the higher the embankment through this stretch of road the greater the amount of settlement can be expected, the more pre-loading required and the more stress placed on buried stormwater drainage systems. Any reduction in the embankment height will therefore reduce the problems associated with settlement after the pre-loading period is complete and the road is commissioned Natural Environment Considerations Terry Fox Drive traverses three wetlands, two of which are identified as Provincially Significant Wetlands providing important habitat to western chorus frog, wood frogs, spring peepers, birds, turtles and toads. It is therefore prudent that any form of roadway through this biologically unique area be constructed with an adequate number of crossings (dry and wet) to allow these creatures to move safely from one side of the road to the other. To allow the safe passage of animals across the proposed alignment, these crossings must also ensure that important biological linkages found in the soils and water is maintained and protected from developing urban lands on the easterly side of Terry Fox Drive and the natural lands on the westerly side of the alignment. The wetlands identified in the Shirley s Brook watershed have been identified as Provincially Significant by the Ministry of Natural Resources as noted above. The 2000 ESR identifies that Terry Fox Drive crosses two PSW s and identified a potential loss of 0.5 ha of wetland in the potential impacts of the project and that a detailed mitigation plan would be required as part of the final design. Based on updated mapping from the MNR, this impact has been more accurately defined as 0.69 ha (PSW#1) and 0.30 ha (PSW#2) during the detailed design as noted in Chapter 6. A priority for the design of the drainage associated with the road is therefore to minimize the impact on these natural features Urban Development Considerations The storm water management design in the ESR (Dillon Consulting, 2000) and subsequent PDR (Dillon Consulting, 2007) was based on the upstream lands outside the urban boundary remaining generally undeveloped. Therefore the clean storm water runoff from these upstream areas will be directed to the existing downstream receivers and the road runoff directed to treatment facilities. This necessitates a separate conveyance system for the roadway flow (i.e., sewer and / or ditches) and the upstream external flow (interceptor ditches and road crossing culverts). While this approach is still the preferred approach Project No

6 for the project, and the upstream land-use will remain undeveloped for the next 7-10 years, the land development plans in the urban area have advanced considerably since the 2007 EA Addendum, and where possible these plans have been considered in the design of the storm water measures for the Terry Fox Drive project. The management of the Carp River and Shirley s Brook sub-watersheds have different, distinct objectivebased criteria and therefore strategies for each have been developed to achieve the goals. A discussion of the constraints related to storm water drainage within each sub-watershed follows Carp River Watershed Drainage/SWM Design Considerations The locations previously set aside for SWM facilities 3A & 3B is within the Carp River floodplain below the 100 year flood level and within an unclassified wetland community; The clay soils of the floodplain require surcharging (pre-loading) of the road embankment, therefore a lower road profile is preferred; The clay soils limit the potential for infiltration Best Management Practices (BMPs) intended to recharge the water table; The new roadway is within the Carp River Floodplain and therefore lowering the vertical profile will reduce the floodplain storage volume displacement; The alignment is located within the regulatory floodplain, therefore an end-of-pipe stormwater facility, such as a pond, will displace additional floodplain storage; A floodplain embayment is located on the easterly/upstream side of Terry Fox Drive, which must remain connected to the main floodplain. The embayment contains a moderate sized nonsignificant wetland, with an ephemeral stream channel running through the wetland that together provides a migration corridor for wildlife eastwards to the Kizel Drain system; and, Normal-level runoff water quality control (i.e. 70% Total Suspended Solids (TSS) removal) is required according to the Carp River sub-watershed study (Robinson Consultants et al, 2004). The preferred solution for the stormwater management within the Carp River floodplain is a series of Vortechs TM oil & grit separators that discharge to enhanced swales integrated into the floodplain topography, that convey the treated runoff to the Carp River. The enhanced swales can be adjusted for integration into the future Carp River restoration plans or along a recreational trail as needed in the future Shirley s Brook Watershed Drainage/SWM Constraints The road alignment crosses a railroad track where planning for a future grade separation is required; The locations previously set aside for SWM facilities 4A & 4B are within two segments (PSW #1 & PSW#2) of the provincially significant wetland complex; The location of SWM Pond 4A is in an area (PSW#1) of important habitat for a Species at Risk (Blanding s turtle) and an important breeding area for amphibians (forested swamp); The underlying soils are silty clays which perch the causes the wetlands to occur where the groundwater table is at the surface. A small road footprint is most desirable here; A realignment of the east tributary of Shirley s Brook is necessary to offset the loss of 190 m of fish habitat; (Chapter 8); Clay-based organic soils are identified immediately adjacent to the west Shirley s Brook crossing Project No

7 point and limit the applicability of infiltration Best Management Practices; and, Enhanced treatment of runoff for water quality (i.e. 80% TSS removal) and pre-development runoff equal to post-development runoff for the 1:100-year even quantity control is required according to Shirley s Brook Subwatershed study (Dillon Consulting, 1999). The recommended storm water management concept for the Shirley s Brook watershed consists of oil-grit separators replacing SWM ponds 4A and 4B, used in conjunction with enhanced swales. The enhanced swales will be integrated into the roadway embankments, adjacent to the toe of slope, and will provide further quality treatment as well as mitigate for the minor increase in storm flows during the initial phase of the design storm events. Specifically fine particle sediments will be trapped in a matrix of gravel and limited nutrient treatments wil occur in a series of vegetated basins longitudinally arranged. Peak flow reduction will be achieved by providing storage of runoff within a wide flat-bottom ditch with minimal longitudinal grade. The low gradients of the Carp River clay floodplain will help to keep velocities low during frequent storm events. Velocity control and peak flow attenuation will help reduce the downstream erosion potential in Shirley s Brook. Quality and quantity management of roadway runoff will permit discharge to the sensitive Shirley s Brook watercourses in a manner that is integrated with the surrounding wetlands and with the intent of maintaining critical year-round base-flows and supporting habitat diversity. 7.4 Mitigation Strategy: Surface Water Quantity The Surface Water Quantity Mitigation Strategy comprises three main parts: Permanent overland flow/cross drainage features; Carp River Floodplain management; and the Shirley s Brook Realignment (Chapter 8). The mitigation strategy recommends a combination of drainage structures, drainage features, and floodplain compensation. Each of these features has been designed to meet or exceed Provincial performance targets. The Mitigation Strategy for maintaining Water Quality levels is provided in Section 7.5 below. Overland ditch design, and the location and sizing of cross culverts are based on the maintenance of existing major (overland) flow routes. These design features address the need to maintain macroscopic drainage patterns for the various drainage areas associated with Terry Fox Drive. Overland drainage cross culverts should be considered necessary if the construction of Terry Fox Drive progresses independently of the adjacent urban development. Associated issues pertaining to development and site servicing, including lot grading, storm sewers, stream realignment, and interceptor ditch configuration may dictate the need to update crossing locations as the detailed design progresses. The Storm Water and Floodplain Management Report describes the surface water management strategy for the two main watercourses found within the study area as well as the management of smaller natural drainage features and overland flow. East Shirley s Brook will be permanently realigned as part of the current construction works. The realignment will be a short piece, about 250 m, intended to maintain the flow dynamics to PSW#2 and downstream habitats. Additional details on the Shirley s Brook realignment strategy are found in Chapter Drainage Area Details and Road Crossing Culverts Currently most of the land surrounding the proposed Terry Fox Drive alignment is undeveloped, natural lands, with the exception of the south end of the alignment where agriculture has been long practiced and more recent residential land development is underway. Current development plans for properties adjacent to the road are being considered cumulative to this project, and part of this CEAA screening and as an update to the 2007 PDR, to coordinate drainage infrastructure where feasible. Project No

8 The major flow concept in the 2007 Preliminary Design Report will be used to manage flows from upstream of the Terry Fox Drive right-of way. Major flow from Terry Fox Drive will be managed as outlined in the 2007 Report except through the area of the Carp River Floodplain, which has been designed with a saw tooth (0.5%) profile. Appendix A of the Storm Water and Floodplain Management Report, provided in Appendix B of this report, summarizes the existing and proposed conditions within the drainage areas impacted by the extension of Terry Fox Drive. Details of the proposed road crossing culverts are provided in Appendix B of the SWFM Report Carp River Floodplain Water Quantity Due to the installation of the roadway along the alignment preferred through the Class EA process, there will be a significant amount of flood storage lost from the Carp River floodplain. The following discussion provides the analysis for determining the proper level of mitigation of floodplain loss Background - Floodplain Displacement and Compensation Options Floodplains play an important role in both the conveyance capacity and storage capacity of a natural watercourse system. As floodwaters rise in the watercourse, the size and shape of its floodplain allows the system to convey much greater volumes of water flow, based on the larger cross-sectional area seen by the river. In instances where other restrictions exist such as confined valleys with limited floodplain width or restrictive hydraulic structures (bridges, weirs, dams), floodplains provide storage of runoff, attenuating the peak flows and therefore limiting potential downstream adverse effects on public and private property and ensuring public safety. Floodplains also provide the ecological interface between land and water, conveying the flow of nutrient-rich silts from the watercourse back to the lands and providing habitat to many amphibians, reptiles, fish, small mammals and some birds. During the Preliminary Design exercise completed in July 2007, the encroachment on the floodplain resulting from the Terry Fox Drive project was calculated to be approximately 45,000 m 3. The removal of this much flood storage volume could have flooding implications, both upstream and downstream of the project. The volume calculation was based on the modeled flood water elevation provided by the Mississippi Valley Conservation Authority (MVCA). Based on HEC-RAS modeling using the Carp River stations (Figure 10), this encroachment raised water levels very marginally (i.e. by 1 cm) and at only two of the modeled cross-sections. Despite this minimal impact on flood levels, it was recognized that a displacement of flood storage can adversely affect design flow rates in downstream reaches of a system due to a reduction in flow attenuation capacity. Therefore, a compensation plan was developed at a conceptual level that compensated for lost storage volumes by cutting the surrounding terrain down at specific locations and at corresponding vertical elevations. The compensation plan proposed in the 2007 PDR consisted of a large cut just north of the project area on private property and was a viable solution to offsetting the floodplain impacts. Floodplain management guidance was provided by the MVCA during the preliminary design phase at which time they indicated the following general requirements for Terry Fox Drive within the floodplain: The road surface must be above the 100-year floodplain elevation to ensure appropriate flood proofing; The loss of floodplain storage due to the roadway footprint will be compared to the additional floodplain storage created from the construction of any stormwater management and any required fish habitat compensation works; Local grading that creates additional storage can be used to compensate for any residual loss of flood plain storage; and, Project No

9 The three cross culvert(s) near Stn must remain to allow water and biota access to the existing backwater floodplain storage upstream of the road and allow proper drainage. Consistent with the approach presented during the 2007 preliminary design, the method of impact assessment and compensation planning has been to assess the impacts and corresponding compensation on a volumetric basis. This approach was previously approved by the MVCA and is consistent with the approach taken on other projects within the Carp River watershed and elsewhere in the province of Ontario. The general approach to mitigate the impact of floodplain displacement of the volume displaced within certain elevation bands is to compensate for the loss within the same elevation range. For example, 1,000 m 3 of volume displaced between elevation and should be compensated for by the excavation of 1,000 m 3 of soil from within the same 0.25 m elevation band. There are several different methods used in this approach, the most direct method to provide floodplain compensation is to achieve the compensation at relatively the same cross-section of the river as the displacement occurs. The second method uses a similar approach, providing volumetric compensation at the appropriate elevation, except not at the same cross-section, but still within the same river reach as the displacement is caused. Both of these approaches have technical merit and have been considered in the options presented below. Error! Reference source not found. illustrates the location of Terry Fox Drive relative to the location of the Carp River and the 100yr flood-line, as well as the Carp River river-station IDs through the study area. Figure 11 schematically illustrates a typical cross section from the proposed Terry Fox Drive roadway embankment located within the Carp River floodplain. The typical section shows the elevation bands used to define the displaced floodplain volume as it relates to the 100 yr water surface elevation and the existing ground surface. Project No

10 Terry Fox Drive Terry Fox Drive Road Corridor Road Corridor Part B Figure Figure 10: Carp 14: Floodplain River Floodplain Compensation HEC-RAS Sections Restoration and Preloading Legend Grading Limit Footprint TFD Right of Way Road Centreline Railway Estimated Hydro Lines Carp River Floodplain Watercourse (93.5) HEC-RAS Restored Agriculture River Cross Section ID Restored Wetland Floodplain Cut Area ² Legend Preloaded Roadway Meters :8,800 NTS Projection: UTM NAD83, Zone 18 Infrastructure Canada & Fisheries and Oceans Canada Project Name: Terry Fox Fox Drive EA EA Map Map Created By: By: SFG BC Map Checked By: AZ Date Created: July July 14, 14, 2009 Date Modified: April n/a 1, 2010 File File Name: I:\GIS\ Terry Fox Fox Drive Final Design\Mapping\Figures -- Part Part B CEAA\Figure 11.cdr 14 Floodplain Compensation.mxd

11 Figure 11: Terry Fox Drive Typical Section within Floodplain Area (includes vertical exaggeration) Floodplain Displacement Compensation Options There are a variety of different sites in the general vicinity of the Terry Fox Drive extension project that have appropriate topographic relief suitable for providing volumetric floodplain compensation. It is most desirable to provide floodplain compensation as close to where the displacement of floodplain occurs. General practice dictates that compensation be located within the same river reach in order to replicate the hydrologic and hydraulic characteristics of the watercourse. The section of Terry Fox Drive that lies within the floodplain is within the river reach between Richardson Side Road and Huntmar Road. Throughout this river reach the Carp River is characterized as having similar low-flow channel and floodplain configurations, similar hydraulic gradient properties, and similar resultant floodwater elevations during the 100 year event. The entire length of the Carp River through this reach has been previously improved by straightening the meander curves and deepening the channel cross section. In addition, the bridges located at Huntmar Road and Richardson Side Road further influence water levels at these two locations, and act as hydraulic control points on the river along this reach. Based on the hydrologic and hydraulic uniformity of the subject reach, storage lost, but compensated for within the reach, should have fewer impacts on the hydraulic dynamics of the watercourse upstream and downstream of the study area. Three options for floodplain compensation have been developed to mitigate the impacts of lost floodplain storage caused by the construction of the Terry Fox Drive extension. The three compensation options include: Option 1 - All displaced storage compensated for on an elevation basis in one large area located west of Terry Fox Drive and east of the Carp River between river-station and Project No

12 Option 2 - High-level displaced storage compensated for on an elevation basis in one large area located west of Terry Fox Drive and east of the Carp River between river-station and plus some low-level displaced storage compensation on a cross-sectional basis along the west Terry Fox Drive toe-of-slope and the Carp River, between river-station and Option 3 - All displaced storage compensated for on a cross-sectional basis along the west side of the Carp River between river-station and Each of the options noted above has been hydraulically modeled and developed to a preliminary-design level of detail in order to verify its ability to provide the appropriate level of compensation within the impacted elevation ranges. Figure 12 illustrates the spatial extents of the floodplain compensation options. The limits shown for each option represent the physical grading limits required in order to achieve the required floodplain compensation volumes within given elevation ranges. The grading limits vary based on the existing topography and application of some basic grading design criteria, such as utilization of a minimum 0.5% transverse slope and a maximum 4:1 grading daylight slopes. Option 1 is shown hatched in cyan, Option 2 is shown in red and Option 3 is shown in magenta. Project No

13 Terry Fox Drive Terry Fox Drive Road Corridor Road Corridor Part B Figure 14: 12: Floodplain Flodplain Compensation Restoration Options and Preloading Legend Grading Limit Footprint TFD Right of Way Legend Road Centreline Floodplain Railway Compensation Option Hydro 1Lines Floodplain Watercourse Compensation Option 2 Restored Agriculture Floodplain Compensation Option Restored 3 Wetland Floodplain Displacement Cut Area ² HEC-RAS Preloaded River Roadway Cross Section ID Meters :8,800 NTS Projection: UTM NAD83, Zone 18 Infrastructure Canada & Fisheries and Oceans Canada Project Name: Terry Fox Fox Drive EA EA Map Created By: By: SFG BC Map Checked By: AZ Date Created: July July 14, 14, 2009 Date Modified: April n/a 1, 2010 File File Name: I:\GIS\ Terry Fox Fox Drive Final Design\Mapping\Figures -- Part Part B CEAA\Figure 12.cdr 14 Floodplain Compensation.mxd

14 Evaluation of Proposed Compensation Options Based on the information available to date, there is no significant difference between the 3 options presented with respect to existing fishery resources, surface water resources, groundwater resources or archaeology resources. From the perspective of terrestrial resources, Option 1 and 2 will have a slightly greater impact on trees and related terrestrial habitat. Currently-available geotechnical information for the area required for Option 1 and 2 indicates a combination of gneiss granite bedrock and clay soils are expected to be encountered. Although the geotechnical investigation work for the Option 3 area is not yet complete, it is expected to consist only of clay material to depths of up to 30 m deep. From a geotechnical perspective there is a possible advantage in using Option 1 or 2 in that the rock cut material may be used for rock fill in the Terry Fox Drive embankment in the floodplain area. Given the sensitivity of the floodplain-related issues for the Carp River, it is felt that the section by section compensation provided by Option 3 is preferred. Furthermore, the section by section approach to floodplain compensation is endorsed by the Third Party Review Report as the most technically appropriate. On this basis Option 3 is recommended Final Area and Volumetric Compensation Design Criteria The following data (Table 7-1 and Table 7-2) provide the volumetric displacement of floodplain volume, both in an incremental elevation basis and on a stream section basis. Table Summary of Displacement Volumes Elevation Range (m) Displacement volume (m3) Percent of Total Displaced Volume , % , % ,007 19% , % , % , % % Project No

15 Table Summary of Displacement Volumes between Cross-Sections Cross-Section Station Incremental Displacement Volume (m3) Percent of Total Displaced Volume % % ,099 3% ,831 9% ,674 27% ,841 14% ,857 7% ,858 7% ,894 7% ,570 6% ,832 4% % ,639 4% ,352 6% ,957 5% % % The following Table 7-3 outlines the design criteria and characteristics of the 3 compensation options. Table Summary of Compensation Option Details Design Detail Option 1 Option 2 Option 3 Location - River-station Range Elevation Range of Compensation Physical Area Impacted by Grading Compensation Volume Provided Excavation Volume above 100yr Floodwater Elevation to East Bank to East Bank to East Bank to West Bank 92.1 to 93.5 Part 2a Part 2b Ha Part 2a 10.4 Ha 18.2 Ha Part 2b 1.3 Ha 63,690 m3 Part 2a 56,624 m3 50,899.3 m3 Part 2b 6,467m3 Approx 140,000 m3 Approx 140,000 m3 Approx 25,726.2 m3 As the area of the floodplain compensation cut is excavated to the specified elevations, the area will require protection from erosion and sediment releases so the Carp River is not impacted by additional siltation. A site-specific sediment and erosion control plan will be developed during the detailed design of the cut area, and the contractor will be required to submit a stamped plan detailing how they will complete the work. Project No

16 Floodplain Cut Area Restoration The majority of the floodplain cut area will be restored to agricultural lands, where fields now exist. They cover approximately 10 ha of the proposed 18.2 ha cut, are currently in private ownership and are actively farmed. These areas will be stripped of topsoil, about 250 mm deep, the sub-soils removed to a specified elevation, and the topsoil replaced to meet the finished grades required in the floodplain compensation. This will be done as progressive operations, during the winter of 2010, preferably in time for spring planting, so there may be no loss of productivity (time-wise) for the agricultural production, but more likely, one year of production will be forfeited over the 10 ha area. This timing will depend on the receipt of approvals and when it makes the most sense to do the work to minimize impacts of sedimentation to the Carp River. There will be a change in the nature of the drainage patterns, so the operators may need to shift their crop rotations to account for the greater depth and duration of spring inundation and poorer drainage characteristics. The remaining floodplain compensation area, of approximately 8.2 ha will be forever inhibited from further land development, as it is within the 100 year flood line and close to the Carp River watercourse. Figure 13 shows the extents of the compensation works, the limits of the proposed agriculture and wetland areas as well as the area of preloading to be completed. As abandoned agricultural land along the river, it is frequently flooded and of marginal value for the production of crops. Therefore, the completed cut area in the riparian zone represents an opportunity to expand the availability of wildlife habitat resources in the area and compensate for the loss of wetlands on the project. Habitats for some species identified in the South March Highlands forested portion of the project, generally do not exist in the open grasslands of the riparian zone of the floodplain. The clay-based floodplain is imperfectly drained, where the highlands over bedrock are very well drained. Trees, stone outcrops and wet areas are nearly nonexistent, so the habitats and ecological processes are quite different. As part of the future plans to restore the Carp River to it s former natural state, it seems appropriate to begin the rebuilding early stages for that process in the floodplain compensation area through the Terry Fox Drive project. Impacts to reptile and amphibian habitat have been identified, primarily through the direct removal of 0.5 ha of wetlands as approved in the Class EA process (Dillon Consulting, 2000). Chapters 6 and 9 identifies the specific areas, the quantities of habitat removed or disturbed and better defines the potential impacts, particularly to Species at Risk such as Blanding s Turtle, Western Chorus Frog, Snapping Turtle, Eastern Musk Turtle and the unique habitats that support amphibians (frogs, toads and salamanders) on the road alignment. In addition to the wet habitats, ha of Provincially Significant ANSI, mostly forested areas, is to be directly removed by the roadway. The 8.2 ha area of cut will be restored as a constructed wetlands, targeting seasonal wetlands swamp habitat for turtles, amphibians and microscopic aquatic organisms with the surrounding area sheltering it with an area of shrub thicket, as preferred for nesting by song birds. These are the general target species for the restoration, with the Western Chorus frog the primary target species. Project No

17 PART B Terry Fox Dr Terry Fox Drive Road Corridor Part B Figure 13: Floodplain Compensation Restoration and Preloading Legend Grading Limit Footprint TFD Right of Way Road Centreline First Line Road Allowance Railway Hydro Lines Watercourse Restored Agriculture Restored Wetland Floodplain Cut Area Preloaded Roadway Future Land Development Richardson Side Rd Carp River ² Meters :8,800 Projection: UTM NAD83, Zone 18 $ Kanata Ave Area Hectare Agriculture Wetland 8.17 Total Infrastructure Canada Project Name: Terry Fox Drive EA Map Created By: BC Map Checked By: AZ/SFG Date Created: July 14, 2009 Date Modified: April 1, 2010 File Name: I:\GIS\ Terry Fox Drive Final Design\Mapping\Part B Figures - CEAA / Figure 13 Floodplain Compensation.mxd & Fisheries and Oceans Canada

18 Additional, relatively shallow excavations will be made at elevations that will allow for frequent flooding from the Carp to be captured and held. The wet basins will have no direct connection to the Carp River, so whatever water is captured, will remain in the basin in a relatively stagnant condition. The groundwater table is high in this area and the boreholes indicate a shallow seam of silty sand, which should liberate groundwater and so the basins should stay relatively wet year round. If the pools periodically dry out that is acceptable as well as it will allow the accumulated detritus to oxidize, stimulating photosynthetic growth and the nutrients to mineralize. The intent will be to contour the wet basins in a series of crescent shapes, looking like a series of oxbow cut-offs from the river, as several existing areas now appear, when viewed from above. The basins will be lined with a minimum of 400 mm of a mix of 60% topsoil and 40% organic soils or 250 mm of well rotted manure and municipal compost to provide a Carbon source of energy. Organic soils dredged from the unclassified wetland across the river between Stn and will be used, for it s carbon content, seed bank and wealth of beneficial microrganisms to inoculate the new wetlands. Water depths will vary from a few meters to a few centimetres to provide as many habitat niches as possible. The existing seed bank in the wetland soils will be the primary seed source to regenerate the area, with plant species readily adapted to the floodplain. This donor soil will also inoculate the new swamp wetlands with soil microbes, fungi, protozoan s, algal communities, insect larvae and the many micro-organisms common to a wetland environment. Sheltering each basin, a combination of shrubs, trees and herbaceous plants will be planted at the time of initial construction. Around the perimeter, as the land slopes up to match existing grades, and between the wet basins, willow and dogwood shrub cuttings and wet-tolerant native trees will be planted to generate the thicket preferred by some song birds. Butternut trees will not thrive here as they require well-drained soils. Some lowrising hillocks will be placed to diversify the habitat by adding vertical relief, edge and expanded cover. Exposed, sandy-gravel deposits will be left on the warm south-facing slopes as a site where turtles can successfully lay eggs. Extra logs and brush from the clearing activities can be used to provide cover, edge habitat and to make the swampy habitat more complex, interesting for the fauna and to protect them from their predators. The area will take more than 5 years to grow and begin to see results, but almost immediately it is created, the small toads and frogs will find this and colonize the habitats. Over a longer time period of years the swamp should become a dense thicket, with muddy sediments where frogs and turtles can over-winter in safety. Afforestation of 2 ha of native trees to offset the impacts to woodlands will also be planted along the Carp River face of the roadway. It is unlikely that Species at Risk like Blanding s turtle will utilize this habitat, at least within the first decade, as there is no upland forest associated with the proposed floodplain feature. Snapping turtle, also a species at risk in the area, are more likely to use this habitat along with common amphibians, field nesting birds and some small mammal species. The eastern musk turtle may find and use this habitat, although there is evidence that they may prefer a more secluded type of habitat. Fish may seasonally use the habitat, but these are incompatible with amphibian habitats as fish eat the developing tadpoles. Fortunately, the turtles will eat the fish. Channels connecting to the Carp River have not been included for this purpose. Although fish will find their way into the wetland basins, the preference is to support the amphibian species of which are under increasing pressure due to environmental chemicals such as Atrazine TM, and due to habitat loss. Overall this new constructed wetland is expected to be a significant enhancement to the habitats and ecology of the Carp River system along Terry Fox drive. Figure 14 is a preliminary concept drawing of the potential turtle and frog habitats that will be used to restore some of the ecosystem processes in the floodplain compensation area. Detailed drawings are available for review upon request. Project No

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20 7.5 Mitigation Strategy: Surface Water Quality Potential effects related to surface water quality degradation are associated with the potential for storminduced erosion of working surfaces and any associated contaminants that may enter watercourses downgradient of the project area during construction. This generally is restricted to potential impacts to downgradient Fish and Fish Habitat discussed in Chapter 8, as recreational or potable water use is not present or utilized as a resource in the study area. Potential effects include suspended sediment generated during construction activities; sediment and associated trace hydrocarbon or metals contaminants generated by operations or equipment/materials storage; sediment or salt associated with maintenance activities; and changes to surface water flow associated with roadway operations. During construction earthworks, such as root grubbing and stripping topsoil/overburden and the placement of excess material in stockpiles may lead to increased erosion and sedimentation of adjacent water bodies during and following rain events. Preloading of the roadbed will be required in some sections of the embankment within the Carp River floodplain. Wick drains will be installed to accelerate the consolidation of the clay materials. Granular or rock fill will be imported and overfilled on the roadbed footprint to squeeze water from the clay during an extended period of time, roughly six months. Excess granular B will be reused elsewhere on the project when the preloading is complete. Flooding from the Carp River is likely to occur while preloading is ongoing due to spring runoff, summer storms or fall hurricanes. With the fill being completed using rock fill, the potential for sediment and silt transfer is more likely from the exposed grade once the topsoil is removed (prior to rock fill being placed), or from stockpile topsoil. Depending on the timing and extent of the preloading, this risk can be minimized by stockpiling the topsoil offsite, and then reusing it in the spring on the project, prior to seeding or placing plantings. At the discretion of the MVCA, the floodplain compensation will be done either at the same time as the preloading or preferably, preceding the preloading so that there is always a net surplus of flood storage volume in the floodplain. The restoration construction on the surface can be done at any time following the cut. An Erosion and Sediment Control (ESC) Plan will be developed for the floodplain cut area as the area will be prone to flooding from the Carp River. However considering the negative slope grading on this area, it is likely to be an area of sediment deposition, removing silt and sediments from the Carp, rather than an area that would be expected to generate sediments into the river. Nonetheless, two options are being considered for sediment and erosion control of this compensation area. These are either a double walled silt fences (two silt fences squeezing straw bales) or a rock dyke, would be installed between the compensation area and river to reduce sediment transfer from the embankment area. Pipes with flap gates would allow flood waters into the excavated areas, yet retard the outflowing waters long enough to settle the silts and sediments from the water before returning to the River. The method used will be a function of the season of when approvals are received and the constructability of either system. Where surface water or ground water pumping (dewatering) is required to maintain dry excavations, there is also the potential to discharge silt-laden water to watercourses and wetlands. Dewatering is likely required to install the main culverts at Stn , and Dewatering may be required to install the stormwater drainage and treatment systems at these same low points of the road. Water pumped from these locations will be kept separate, designated as clean or dirty. Clean water from streams and wetlands will be pumped around the site into receiving watercourses, ensuring the discharge surface does not promote scour. Dirty water from excavations or access roadways will be pumped into purpose built settling basins, or mobile Envirotanks or Silt Sacks, for clarification before discharge. Project No