Caledon Villas Corp. c/o Mr. John Spina 55 Blue Willow Drive Woodbridge, ON L4L 9E8 May 14, 2013 Re: Floodplain Characteristics, Old Church Road This letter serves to confirm that I, Linda Sober, have attended the subject property proposed for residential development and stormwater management pond during production of a Natural Heritage Evaluation. The floodplain has been a part of my seasonal attendance and evaluation, and was discussed with the TRCA during a joint site inspection in 2012. The TRCA administers Ontario Regulation 166/06 which protects drainage, wetland, shoreland and valley landform through maintaining water and natural heritage functions of valley and stream corridors. Stream and valley corridors are also mandated under the TRCA VSCMP (Valley and Stream Corridor Management Plan, 1994). They can be critical features that function to recharge and discharge ground and shallow groundwater for aquatic wildlife including fisheries. We agree and observe close parallel with cultural and archaeological heritage when drainage paths parallel meander paths that humans have selected over time. Some of the flood plain and flood fringe areas however are dry lower elevation land that convey seasonal storm events and spring snow melt, also important but without the supported aquatic and semi-terrestrial wildlife use that would occur in an intermittent or year round stream. This can be particularly true in agrarian landscapes and is the case for the Old Church Road subject property. We confirm through seasonal inspections that the floodplain area delineated near Old Church Road is a low elevation point in a farmed tract of land. We observed conveyance but no supported longer drainage, aquatics or terrestrial wildlife because of active crop and no regular flow. 1
Character of Floodplain A cross culvert along Old Church Road is in place at this low point of lands. This is a gentle undulating dip in the landform as seen by the photo diary. Looking north at the Old Church Road culvert onto the site One can see there is no defined stream or valley corridor wall here, but there is a gentle undulating landscape conveying seasonal rain events and spring melt. 2
No seepage was evident along the floodplain during our 2012-2013 inspections which could have indicated it had once functioned as a larger drainage system. The lands are however part of a calculated floodplain using datum such as the 1:100 year storm event. They do convey storm events and snow melt. Looking south from Old Church Road off the site Fallow fields exist off site, and are generally still dominated by grasses and plants of farm catchments including Canada Blue-grass, Redtop, Thistles, Timothy, Red Clover, Wild Carrot, Dandelion, Cow Vetch, Heals-all. 3
I would expect some limited nesting of birds in the fallow fields off site, and this function would be maintained given no change in post development flows. I would not direct enhancement planting to the stormpond area since they could entice wildlife travel across the road, subjecting birds, butterflies, small mammals and herpetofauna to vehicular mortality. Conveyance Storm events are conveyed off site, under culverting of Old Church Road into a southerly adjacent lands grassy swale. We are agreed it is important to maintain pre and post construction flows moving through the subject property. Regulation 166/06 is partly in place to ensure no damage to the adjacent lands of the catchment area occurs as a result of development given the impact that development within floodplains can cause to adjacent lands. Potential impacts can arise when infill of these low catchment areas affects soil bank stabilization or is carried in erosional flow through the lower floodplain. Improper design, construction and maintenance of a stormwater pond can affect neighboring lands if it alters the existing shape and character of the floodplain. We have confirmed through liaison with the project engineers that the stormwater management pond proposed on the subject property, at the low point in the basin, is properly designed and will meet the unit flow rates established for this watershed For our natural heritage commenting, the farmed lands do not support native vegetation. Seasonal surveys on the lands confirmed the storm pond location and adjacent lands do not support support significant ecological features or functions. Therefore hydrological function is the paramount baseline to maintain given the crop use and absence of support wildlife function. 4
The stormwater management pond would replace the existing farm practices and regulate for storm events, providing a measure of protection for potential flood events that is not available on site today. Engineering support documents can confirm that essential best management practices to safeguard the floodplain have been met. Specifically, the storm pond will not result in damages to hydrological or ecological functions such as: Create an upstream or downstream impact on control of flooding as a result of changing flood storage and conveyance characteristics Impact watercourse erosion (there is no watercourse) Reduce or fragment wildlife habitat, food, water, shelter or living space or wildlife diversity and movement (currently crop) MTRCA VALLEY AND STREAM CORRIDOR MANAGEMENT PROGRAM October 28 1994 p. 21 alterations I welcome comments and am available via 519 538 2667. Best regards, L.L. Sõber, H.B.Sc. Senior Ecologist SAAR Environmental Limited LLS:eksw 5