In 2020, the Town of Innisfil retained Tatham Engineering to look at drainage improvements in the vicinity of Goodfellow and Bonsecours beaches, at the downstream end of Leonard’s Creek.
Flooding during spring melt, and following high precipitation events, has been observed in the vicinity of Reid Street, Bonsecours Crescent, Goodfellow Avenue, Crystal Beach Road, Tall Tree Lane, and especially Buchanan Street, where flooding periodically leads to road closures.
Contributing factors to drainage issues in the area include climate change, leading to more intense and higher rainfall; low ground elevation and proximity to Lake Simcoe; development that has occurred on the flood plain; and increased upstream development, increasing the area covered by impermeable, paved surfaces and resulting in higher stream flows in Leonard’s Creek.
A Class Environmental Assessment is now underway. A virtual public presentation on the GetInvolvedInnisfil site provides both a summary of the options being considered, and an opportunity for public input on the proposed solutions to the “known drainage problems.”
Among the options under consideration:
. Replace the Crystal Beach Road culverts at Outlet 3 with two larger pipe arch culverts, create a low point in the roadway that would allow water to run across the road, and install a sediment barrier at the culvert end, made of boulders and Armour stone, to prevent blockage of the outlet by lake sediment.
. Improve Tall Tree Lane, where there is ponding in the existing ditches, and install a sediment barrier at Outlet 2.
. Carry out ditch improvements in the area, to improve both capacity and the grade.
. Replace the culvert at Crystal Beach Road and Hartley Road. The culvert is blocked, and has caved in.
. Upgrade Leonard’s Creek culvert crossings at Crystal Beach Road, Buchanan Street and Tall Tree Lane. Currently the culverts sit below the Lake Simcoe high water level, limiting their effectiveness.
. Implement the recommendations of the Alcona North Secondary Plan. The plan was developed in 2011, but never formally adopted, or implemented. The consultants suggest that the recommendations could reduce maximum flows in Leonard’s Creek by up to 25 percent.
. Carry out improvements on Reid Street. Reid has a right-of-way of only nine metres – less than half the standard – and was recently paved, increasing runoff. Reinstating minor drainage ditching on both sides of the road, with perforated subdrain installed in stone infiltration trenches, could reduce flooding.
. Rain Barrel program. While this would not have a significant impact on flooding, it would provide minor local improvement, and an opportunity for public education and engagement.
. Diversion of flow now going to Outlet 1, through the 9th Line Park. A ditch from Goodfellow Avenue to the existing drainage ditch in the park, and upsized culverts under Line 9, are proposed.
Among the proposals that were rejected:
. Do nothing – which does not address the problems.
. Acquire property along Leonard’s Creek, or at the outflow to create alternative retention and outflow options. The consultant described this as “very expensive, and not feasible in the short term.”
. Storm sewer diversion from Chappell Court and Sandy Trail. It was found that the Happy Vale Drive Storm Sewer does not have the capacity to accept the diversion – and that it would have little impact on downstream flows, anyway. The solution was not recommended.
. Upland wetland reconstruction, to create additional water storage upstream. The consultants note that town-owned properties in the area are not large enough to provide flood retention and storage; the option is also “not recommended.”
The public is invited to comment, either on a survey or comment sheet, by Wednesday, June 30 (click here). Comments received will be used in identifying the preferred alternative(s).
Once the study is completed, a report to council with the recommendations will be prepared, and posted.
