Appendix J West Brampton Watermain Geomorphology Desktop Study

Transcription

1 Appendix J West Brampton Watermain Geomorphology Desktop Study

2 Technical Report (Geomorphology) Desktop Analysis West Brampton Watermain EA Zone 5 Sub-Transmission Main June 2013

3 Table of contents 1. Introduction Background review Climate Geology Watershed characteristics Reach delineation Design considerations Fluvial geomorphology Redside Dace habitat considerations Next steps Historical assessment Field investigations Scour analysis Proposed mitigation plan References Table index Table 1 General reach characteristics... 6 Figure index Figure 1 Reach delineation map preferred watermain alignment GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA, 13212JobNumber i

4 1. Introduction In support of the Zone 5 Sub-Transmission Main Class Environmental Assessment (Class EA), GHD was retained to undertake a geomorphic assessment for those portions of watercourse located in vicinity of the preferred watermain route. The preferred alignment follows Williams Parkway West between Mississauga Road and Hurontario Street in the City of Brampton, Ontario (Figure 1). In fulfillment of the Class EA technical requirements, and in response to preliminary comments provided by review agencies, the following desktop tasks were completed Background review of relevant materials pertaining to Huttonville Creek, Springbrook Creek, Fletchers Creek, Etobicoke Creek and Spring Creek within the general study area; Delineation of reaches in vicinity of the preferred watermain alignment based on underlying geomorphic controls; and Preliminary evaluation of the preferred watermain alignment from a geomorphic perspective. It should be noted that the findings presented in this technical report reflect a desktop level of detail. It is suggested that a geomorphological field assessment and analyses would be undertaken at the detailed design phase to provide the details required to assess design approaches and meet the submission requirements of Toronto and Region Conservation Authority (TRCA), Credit Valley Conservation Authority (CVC) and the Ministry of Natural Resources (MNR). GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

5 Bovaird Drive West Mississa uga Roa d CN Ra il wa y Chinguac o usy SB-1 McLaughlin Road Nort h Road HC-1 Reach Break and ID Preferred Alignment of Watermain Watercourse Generic Regulation Limit Reach Break and ID GHD, 2013; Preferred Alignment of Watermain TMIG, 2013; Watercourse MNR, 2010, and GHD, 2013; Generic Regulation Limit Credit Valley Conservation Authority, 2013; Imagery Google Earth Pro, West Brampton Watermain EA Zone 5 Sub-Transmission Main Reach Map FIGURE 1 DATE JUNE 2013 ± EC-1 HC-1 Legend Main Stree t North FC-1 Williams Parkway West FCT-1 FC-2-1 8B SB-2 FCT-2 HC-2-2 EC 8B Metres 500 PROJECT DRAWN BY S.G., L.W.

6 2. Background review The following section provides an overview of relevant background information and reports relating to the West Brampton Watermain EA study area. 2.1 Climate Climate provides the driving energy for a fluvial system and directly influences basin hydrology and rates of channel erosion, particularly through precipitation. Precipitation records obtained from climate normals ( ) recorded at Toronto s Lester B. Pearson International Airport, located north of the study location, averaged 56 mm per month in winter (November through February), and 77 mm in summer (July and August; Environment Canada, 2013). This increase over the summer months is likely a result of convective thunderstorms. However, the highest sustained flows tend to occur in the spring as a result of snowmelt or rain-on-snow events. 2.2 Geology The planimetric form of a watercourse is fundamentally a product of the channel flow regime and the availability of sediments (i.e., surficial geology) within the stream corridor. The dynamic equilibrium of these inputs governs channel planform. These factors are influenced in smaller systems by physiography, riparian vegetation and land use Etobicoke Creek subwatershed Spring Creek The study area is situated within the Lake Iroquois Sand Plain formation, which is composed of sand, silt and clay (TRCA, 2010a). The surficial geology of the area is dominated by low permeability silt, clay and silt till, with some sands associated with the former Lake Iroquois shoreline (TRCA, 2010a). The study site falls within the South Slope physiographic region, a clay till plain characterized by gentle topography, sloping towards Lake Ontario (TCRA, 2010a). The bedrock geology of the Etobicoke Creek valley consists of the gray shale of the Georgian Bay Formation. Deposited materials can include up to 7.5 m of soils and glacial deposits consisting of well-drained Oneida clay loam formed within depositions of the Halton Till, within a partially beveled till plain Huttonville, Springbrook, Tributary 8b, Fletcher s Creeks subwatersheds The portions of these subwatersheds located along the watermain alignment are situated within the Peel Plain physiographic region. The shape of the bedrock surface as well as the occurrence of the overburden units, which make up the above region, is a result of the repeated glacial advances and retreats that have occurred in Southern Ontario. The most recent glacial advance and retreat formed much of the land surface and geology present in the area today (City of Brampton and CVC, 2004). In the subwatersheds, glacial till (Halton Till) consisting of a mixture of silt and clay materials, as well as sand, gravel and larger stones overlies the Queenston shale bedrock formation over the majority of the study area. The Peel Plain is relatively flat, generally sloping to the southeast through the study area. GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

7 2.3 Watershed characteristics Etobicoke Creek subwatershed Spring Creek Etobicoke Creek drains 21,164 ha and consists of four main branches Main Etobicoke Creek, Little Etobicoke Creek, Etobicoke Creek West Branch and Spring Creek (TRCA, 2010a). The Creek begins on the South Slope of the Oak Ridges Moraine and drains into Lake Ontario. The Etobicoke Creek watershed consists of three major land uses, including 63% urban, 22% rural and 15% natural land cover (TRCA, 2010a). Spring Creek flows into the Main Branch of Etobicoke Creek south of Courtney Park Drive East and East of Dixie Road. Percent impervious cover within the portion of the Etobicoke Creek watershed ranges between 26-65%, or highly impacted and has resulted in a flashy, altered, seasonal hydrology. Urbanized systems such as this offer little in the way of retention function and often exhibit evidence of adjustment in the form of erosion. In general, erosion management projects within the Etobicoke Creek watershed have focused on enhancing bank stability, improving substrate habitat conditions and implementing low impact stormwater design to enhance retention functions within the stream corridor (TRCA, 2010b) Huttonville, Springbrook, Tributary 8b, Fletcher s Creeks subwatersheds The subwatersheds (Huttonville Creek, Springbrook Creek and 8b) are tributaries to the Credit River and drain approximately 23 km 2 of land in west Brampton (City of Brampton and CVC, 2004). The total drainage area of Huttonville Creek is 1,260 ha, whereas the drainage area of Subwatershed 8a (Springbrook Creek) is 490 ha. Fletcher s Creek has a drainage area of 4,500 ha. Land use within the watersheds include agricultural, recreational (golf courses, parks), and residential. Tributary 8B flows in a generally north-south direction and enters the Credit River immediately west of Creditview Road, north of Steeles Avenue. Generally, the channel within the study area is poorly defined (swale), with a limited riparian zone. The existing riparian vegetation consists of meadow vegetation and actively cultivated agricultural fields. South of Queen Street West, the watercourse enters a confined valley where the channel has incised into the underlying shale (Queenston Formation) bedrock. 2.4 Reach delineation To facilitate a systematic evaluation of streams within the study area, the channels were segmented into reaches upstream and downstream of the stream crossings. Reaches are homogenous sections of channel with regards to form and function, with consideration to channel gradient, hydrology, surficial geology, land use, and vegetative controls (Montgomery and Buffington, 1997; Richards et al., 1997). Each reach is therefore expected to adjust in a generally uniform manner along its full length to changes in hydrology and sediment inputs, as well as other modifying factors. In support of the West Brampton Watermain EA, reaches were delineated for those portions of watercourse upstream and downstream of the preferred alignment based on available contour mapping, surficial geology map and recent aerial imagery. Results of the reach delineation process are illustrated in Figure 1. It is suggested that the identified reach extents be verified in the field through the detailed design phase. Length, gradient and sinuosity information for reach is provided in Table 1. 4 GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA, 13212

8 2.4.1 Huttonville Creek Reach HC-1 was delineated from Williams Parkway West downstream to a confluence with small tributary. The reach extends as a constructed corridor through residential development with a narrow width of riparian vegetation. Reach HC-2 extends from an upstream confluence, downstream to Williams Parkway West. The reach consists of a channelized feature through agricultural lands with a narrow riparian buffer. Existing infrastructure and channel planform were used in determining reach limits Springbrook Creek Reach SB-1 was defined from Williams Parkway West downstream to the wooded/wetland area east of Maybeck Drive. Determination of reach limits was based on existing infrastructure (road crossing) and channel planform. The entire reach has been reconstructed as a naturalized corridor through the recent residential development of the adjacent land. Upstream of Williams Parkway West, Reach SB-2 extends to the road crossing at Valleyway Drive. Upstream reach limits were delineated based on degree of alteration (channelization) and existing infrastructure Tributary 8b Reach 8B-1 extends from Williams Parkway West downstream to a break in the channelized planform. The entire reach is a reconstructed channelized corridor through residential development. The reach was delineated based on degree of alteration (channelization) and the existing road crossing. Reach 8B-2 was delineated from the railway crossing to Williams Parkway West based on existing infrastructure. It is a channelized corridor relocated for the residential development through which it runs Fletcher s Creek Reach FC-1 was defined from Williams Parkway West to the road crossing at McLaughlin Road North. Reach limits were determined based on the existing infrastructure (road crossings). The reach runs along an industrial development and McLaughlin Road North. Reach FC-2 extends from Williams Parkway West to an upstream confluence. The reach limits were based on the existing infrastructure and channel planform. Reach FCT-1 was defined from Williams Parkway West to the Vodden Street West crossing based on the existing infrastructure. The channel is a reconstructed corridor along Williams Parkway West through residential development. Reach FCT-2 extends from Williams Parkway West upstream to where it becomes a piped channel that runs beneath an existing trail system. Reach limits were delineated based on existing infrastructure, channel planform and degree of alteration Etobicoke Creek Reach EC-1 was delineated from Williams Parkway West to Vodden Street East. Upstream of Williams Parkway West, Reach EC-2 extends to the Etobicoke Creek Trail crossing. Both reaches are modified channel corridors through residential development. Reach limits were determined based on the existing infrastructure. GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

9 Table 1 General reach characteristics Reach Length (m) Gradient (%) Sinuosity HC HC < SB SB < B < B FC < FC < FCT FCT EC EC < GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA, 13212

10 3. Design considerations 3.1 Fluvial geomorphology The preferred watermain design solution proposes a directional drilling approach. The preferred route coincides with Williams Parkway alignment, and generally crosses each watercourse downstream of the existing road crossing structure. From a geomorphic perspective the directional drilling approach avoids the requirement for instream work and subsequent channel stabilization requirements. Erosion hazards and maintenance concerns associated with this type of design approach relate to long-term bed incision (scour) processes. As illustrated in drawings Sheets 3, 6, 8, 16, 18-19, 21 (as provided TMIG), the proposed watermain will be constructed to a depth ranging from m below the centerline inverts of Huttonville, Springbrook, Tributary 8b, Fletcher s Tributary and Etobicoke Creek watercourses. While it is anticipated that additional field observations and scour analyses would be undertaken through the detailed design stage, the following observations provide a level of confidence that the preferred design solution is both appropriate and conservative, given the local watercourse conditions Six (6) crossings are proposed under existing or proposed naturalized channel designs which have been designed to remain stable under a range of flow conditions; as such, substantial erosion of bed or banks is not anticipated; and Based on professional experience, a m depth of cover is typically recommended for municipal infrastructure projects being undertaken on large, dynamic river systems in the City of Toronto. The proposed design approach achieves a greater depth of cover on smaller scale watercourses. 3.2 Redside Dace habitat considerations Within Canada, Redside Dace occur solely in Ontario and are found in southern Ontario and St. Joseph Island. Populations have been experiencing declining numbers over the last 50 years (MNR, 2011). The main threats to Redside Dace are considered to be habitat degradation and loss associated with urbanization (MNR, 2011; Redside Dace Recovery Team - RDRT, 2010). According to the draft guidance document for development activities in Redside Dace protected habitat (MNR, 2011), the degree of impact associated with a development activity on the species increases as the amount and duration of total suspended solids to which the fish are exposed increases. Redside Dace are reported to most often reside in headwater streams, in areas of clear, cool, slowflowing water with riffle-pool sequences and overhanging vegetation (RDRT, 2010; Scott and Crossman, 1973; COSEWIC, 2007). Riffles are generally used for spawning and pools are used as resident habitat. Habitat temperatures are usually less than 24ºC and dissolved oxygen concentrations are at least 7 mg/l (RDRT, 2010). Bottom substrate most often includes boulders, gravel, rock, or sand with a shallow surface covering of detritus or silt (RDRT, 2010). Although they are typically found in clear water, they have been found to tolerate moderate levels of turbidity (COSEWIC, 2007). Redside Dace are considered sensitive to turbidity, as the bulk of their ingested food consists of terrestrial insects captured through a jumping-out-of-water feeding method; unclear waters hinder the vision and capture of insects (Scott and Crossman, 1973). Increased turbidity can cause stress and behavioural changes (MNR, 2011). GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

11 Important habitat elements include overhanging riparian vegetation (grasses and shrubs), undercut banks, and in-stream cover in the form of boulders and woody debris (COSEWIC, 2007). Unless spawning, they are reported to prefer residing in pools from 0.1 to 2.0 m in depth. Spawning occurs in shallow gravel riffles with ideal flow in the range of 0.05 to 0.30 m/s (COSEWIC, 2007). Redside Dace eggs are non-adhesive and therefore vulnerable to high flows; in-stream cover in the form of submerged branches and logs, aquatic vegetation, and rocks can control the velocities of flow which easily wash away eggs (Scott and Crossman, 1973). Redside Dace habitat is often found in open streams associated with wetland communities (COSEWIC, 2007). The following watercourses within the study area are known to have records of Redside Dace Huttonville Creek; Springbrook Creek; Tributary 8b; and Fletcher s Creek. It is important to note that, to the greatest extent possible, the preferred West Brampton Watermain design solution has taken steps to avoid potential impacts to the habitat of Redside Dace by avoiding the requirement for instream work. 8 GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA, 13212

12 4. Next steps To meet timelines associated with the project work plan, a desktop geomorphic assessment was completed based on relevant available information. It is recommended that the following next steps be undertaken to provide for a more informed understanding of the watercourse systems within the study area and to provide a design level of detail that will conform to regulatory requirements for geomorphic assessments. 4.1 Historical assessment An historic assessment of channel form and land use using available aerial photographs is recommended to provide insight into the scale of natural and human-induced changes within a watershed and document evidence of active erosion. 4.2 Field investigations Based on the preferred construction approach, rapid assessments and scoped field investigations are required to confirm that the proposed depth of cover for the watermain is sufficient to mitigate long-term risk to the structure due to erosion and scour processes. Field investigations at the proposed crossings located within Credit Valley Conservation Authority s jurisdiction (Redside Dace habitat Species at Risk status) will be coordinated with Savanta to ensure that existing habitat conditions were thoroughly and accurately documented. Three additional crossings, including a major crossing of Etobicoke Creek (west branch) will also be evaluated. Information regarding the age and dimension of the existing crossing structures will also be reviewed at this time. 4.3 Scour analysis Based on collected field data, scour analysis will be conducted based on scour depths, maximum pool depths, energy gradient, flow depth, and bank material strength. Empirical models, including, but not limited to Ministry of Transportation (MTO) Scour Calculator (MTO, 1997) and Depth of Activation model (Haschenburger, 1999) will be employed. The modelled scour depth will be compared to the depth of cover to determine whether scour represents a potential erosion hazard. 4.4 Proposed mitigation plan While the mitigation plan for the Class EA will be developed in close consultation with the MNR and based on recommendations provided in the Recovery Strategy for Redside Dace in Ontario (MNR, 2005) and Guidance for Development Activities in Redside Dace Protected Habitat (MNR, 2011) guidance documents, the following best management practices have been identified for incorporation into the design process. Construction activities within Redside Dace habitat will be undertaken using appropriate construction methods within the recommended construction timing window of July 1 to September 15. Site preparation will include appropriate erosion and sediment control measures and site supervision along occupied reaches. Once construction is completed, riparian habitat will be restored, as required, using native species. GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

13 Redside Dace erosion and sediment control BMPs can be addressed through the following recommendations Limiting disturbance to protected habitat through Construction phasing and grading plans; Minimizing nonessential clearing and grading; The use of trenchless technology for excavating under the channel, effectively avoiding potential disturbance of Redside Dace habitat; and Retaining existing vegetation to the greatest extent possible. Erosion will be minimized through the following measures Minimizing duration of exposure to erosion; and Appropriate stabilization measures for disturbed soils (i.e., erosion control blankets, geotextile rolls, seeding, planting, live stakes and wattles). Sediment from the construction area will be captured through measures including A multi-barrier approach to prevent sediment entering the stream; Methods to trap sediment (i.e., filter bag and straw bales, double row of sediment control fencing consisting of a non-woven material with straw bales staked in-between); and Monitoring and maintenance of sediment and erosion controls at all times to ensure they are effective. 10 GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA, 13212

14 5. References City of Brampton and Credit Valley Conservation Authority. January Credit Valley Subwatershed Study [Huttonville Creek (7), Springbrook Creek(8a), Churchville Tributary (8b)]. Downs, P.W. and Gregory, K.J., River Channel Management Towards Sustainable Catchment Hydrosystems. Oxford University Press Inc., New York, New York. Environment Canada Climate normals at Toronto Lester B. Pearson International Airport. http//climate.weatheroffice.ec.gc.ca/climate_normals. Galli, J Rapid Stream Assessment Technique (RSAT) Field Methods. Metropolitan Washington Council of Governments, Washington, D.C. Haschenburger, J.K., A probability model of scour and fill depths in gravel-bed channels. Water Resources Research 35(9) Ministry of the Environment Stormwater Management Planning and Design Manual. Document # 4329e. Queen s Printer for Ontario, Ontario, Canada. Ministry of Transportation MTO Drainage Management Manual. Chapter 5. P. 50. Montgomery, D.R and J.M. Buffington, Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin, 109 (5) Ontario Ministry of Natural Resources (MNR). February Guidance for Development Activities in Redside Dace Protected Habitat (Draft). Ontario Ministry of Natural Resources (MNR) DRAFT Guidance for Development Activities in Redside Dace Protected Habitat. Ontario Ministry of Natural Resources. Peterborough, Ontario. ii + 42 pp. Redside Dace Recovery Team Recovery Strategy for Redside Dace (Clinostomus elongates) in Ontario. Ontario Recovery Strategy Series. Prepared for the Ontario Ministry of Natural Resources, Peterborough, Ontario iv + 29 pp. Richards, C., R.J. Haro, L.B. Johnson, and G.E. Host Catchment and reach-scale properties as indicators of macroinvertebrate species traits. Freshwater Biology, Scott, W.B. and Crossman, E.J Freshwater Fishes of Canada. Fisheries Research Board of Canada Bulletin No Ottawa. Toronto and Region Conservation Authority (TRCA). 2010a. Etobicoke and Mimico Creeks Watersheds Technical Update Report- Geology. Toronto and Region Conservation Authority (TRCA). 2010b. Etobicoke and Mimico Creeks Watersheds Technical Update Report- Stormwater Management and Streamflow GHD Report for The Municipal Infrastructure Group Ltd. West Brampton Watermain EA,

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16 GHD 6705 Millcreek Drive Unit 1 Mississauga, ON L5N 5M4 T F E Shelley.Gorenc@ghd.com GHD 2013 This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited. Document Status Rev No. Author Reviewer Approved for Issue Name Signature Name Signature Date Shelley Gorenc

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