In addition to the above, we found the pre-construction condition of the Healy Drain to be limited in terms of both depth and cross-section. The stormwater management ponds that were originally located on the Nemak property experienced frequent flooding according to Nemak personnel.
Given the above, we concluded that the maintenance of two separate drains through the study area would be impractical and unnecessary, having due regard for the following:
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the substantial reconfiguration of land ownership in the area, combined with the scope of the proposed bridge and plaza development; and,
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the lands that contained the original Nemak stormwater management ponds were acquired by Transport Canada, which necessitated the construction of new ponds and the establishment of a new outlet.
In consultation with the City of Windsor and Stantec, we confirmed that the most appropriate strategy would be to outlet the new ponds to an improved Broadway Drain. We consulted with both Stantec and D.C. McCloskey Engineering Ltd. (Nemak’s engineering consultant), regarding options and details for the new pond designs and the outlet design criteria.
As previously noted, Stantec Consulting had been retained by Transport Canada/WDBA to prepare a design for the PAR. Their work included the preparation of a computer model to simulate the runoff that would be generated from the entire tributary area - including the plaza and adjacent lands, which included: West Windsor Power, Hydro One, Nemak, Dainty Foods, ETR, as well as potential future development areas designated as E1, E2 and W1 in the SWM Report. Refer to Drawing No. 1 for an overall catchment plan which depicts the proposed plaza and its adjacent lands. Simulations were conducted to predict peak runoff from the site over a range of storm events - including the 5, 10, and 100-year return periods. The 1:100 year return period was selected as the design event for sizing of the Broadway Drain.
6.2 Habitat Considerations
In consultation with the City’s naturalist, it was determined that all reasonable efforts should be made to ensure that the drainage improvements do not alter the hydrologic characteristics of the south abutting lands. These lands currently exist as natural open area that has environmental significance. Due the characteristics of the surface soils and lack of significant drainage outlet, the area promotes the establishment of hydrophilic plants. A focus of the design was to avoid any intentional or unintentional improvement of drainage of the south abutting lands.
In addition, it was pointed out by the City that snakes may be hibernating in the crayfish burrows located within the existing Broadway Drain. It was recommended that consideration be given to creating features within the new drain corridor that may attract crayfish - as well as constructing hibernacula habitat features. Habitat enhancement features should also include basking habitat to discourage snakes from basking on the PAR pavements.