Excavation is nearly complete at the Petun Conservation Area, but this dig is not for artefacts.
The crew on site – including heavy machine operators and biologists – has been looking for a riverbed.
Several decades ago, the land, located about halfway up Blue Mountain off Grey Road 19 was under private ownership and an earth dam was built over a coldwater stream (part of Black Ash Creek) to create a pond. The dam inevitably let water through and flooding and erosion led to water passing from upstream, into the pond, where it warmed up, and then down Blue Mountain into Black Ash Creek.
The result was a warm stream where a coldwater stream was meant to be, causing damage to fish habitat and impacting flood management.
This summer, Nottawasaga Valley Conservation Authority (NVCA), the current owner of the property, secured grants and funding to remove the dam and restore the stream.
Two months ago, the sunny spot was home to a rust brown, stagnant pond with a hill at one end where water was making its way around and into the stream below.
Today, a stream with high riverbeds runs nearly straight through the site. The pond is gone and the riverbanks are starting to grow small shrubs and green oats.
Fred Dobbs, manager of stewardship services for NVCA and Laura Wensink, fisheries biologist with NVCA, have been overseeing the reconstruction of the mountain stream.
The goal is to place vertical bumps to slow the water down just enough to allow fish passage and habitat, but not so much that it pools and warms up. The water should flow downhill like a mogul skier rather than a slalom skier.
By the end of the week, the stream that was below the dam for decades will once again connect to the stream above it.
During construction, the water has followed a bypass created by Dobbs and Wensink. A dam above the old pond site directs water to a 500-foot bypass pipe, which will be disconnected once the stream is ready for the water.
Dobbs said they will leave the bypass in place, ready to be connected again next season for any necessary upgrades or further work.
Along the bank, an operator skilled with his excavator bucket has planted dogwood trees scooped up from elsewhere on the property. Blankets of straw line the banks to help stop erosion, and oats grow from the restored riverbank.
Oats are considered a nurse crop, they help stabilize fresh soil.
Dogwood is also a stabilizer, and the leaves that drop are “well-integrated” into the food chain, said Dobbs.
He expects there will be an improvement in the temperature and water quality of the stream by next summer.
Ideally, Dobbs said, the NVCA could secure further funding for naturalization of the stream banks to increase vegetation and shade in the area.
You can read more about the dam decommissioning project here.
