December 02, 2009

Deer Pit storm water headed for Credit

As published in The Erin Advocate

Work has started on a project to drain storm water from Erin's Deer Pit into the Credit River at the Tenth Line, solving a drainage problem that dates back to construction of the railroad.

Located north of Centre 2000 near the Elora-Cataract Trail, the Deer Pit is a low-lying area of Town-owned land. Surface water from a 451-acre zone, including Main Street storm sewers, the industrial subdivision and farmland well north of County Road 124, drains to the Deer Pit, but has nowhere to go.

The ability of the pit to absorb the water is declining, so a plan to flow it east to join the Credit River system was made ten years ago, with a price tag of $800,000. The expenditure was never approved, and now the cost will be $1.21 million.

The Town is proceeding with the help of infrastructure funding announced this year. The federal and provincial governments will each pay one-third of the cost, and Erin will use money held in reserves to pay its share, said Town Manager Lisa Hass.

Long-known for its dirt bike trails, the Deer Pit is actually an old quarry. A spur line of the Credit Valley Railroad (later Canadian Pacific) was completed in 1879, linking Cataract, Erin, Hillsburgh and Elora. A short siding had been built into the Deer Pit to haul out ballast – stone and gravel needed to build the rail bed further down the line.

Local historian Steve Revell said a second siding was built on the other side of the rail line, through what is now Centre 2000, for a small quarry near the current baseball diamond. (The area beyond the outfield is another prime candidate for improved drainage – it is now a stagnant pond, covered in algae and strewn with garbage.)

The federal government website on this project (Google: Deer Pit) says it will "help mitigate flooding in neighbouring residential developments and recreational areas".

Hass said that while moving the surface water could reduce the risk of basement flooding in the May Street area, there is no guarantee it will help. Flooding has been due to underground water, not directly from water in the Deer Pit, she said.

The new Deer Pit will still have a natural appearance. The western half will have an improved ditch, but large storms could still soak the whole area. The eastern half will be carved into a more formal "pool" area, with a layer of clay trucked in to reduce infiltration of water into the ground. Water will flow into a forebay next to the school's sewage treatment plant, then through a wetland and into a deep pool (five feet deep). There will be no fencing.

This will "treat" the water, by allowing dirt from the industrial area to settle out before it flows to the river. If the industrial park were being built now, it would be required to have its own storm water treatment facility, said Hass. The sewage plant does not discharge into the Deer Pit; the effluent goes to a tile field back on the south side of the trailway.

From the Deer Pit, a controlled flow of water will go into a pipe buried 3-10 feet directly under the trailway, over to the Tenth Line. It will go south a short distance under the road and discharge into a tributary of the West Credit River. The outlet will disperse the water flow, reducing impact on the stream, which joins the main branch of the river near the Woollen Mills Conservation Area.

An access road has been built from Erin Park Drive to bring in equipment and clay. Roads Superintendent Larry Van Wyck plans to start the pipe work late this winter, before the spring thaw, with most of the project done by early summer and final landscaping / cleanup by September.