Rock’s Mill dam decommissioning being studied

[Spiel]

Rock’s Mill dam decommissioning being studied

Plan no longer a source of contention

 

 

July 18, 2008

By Jeff Helsdon / tillsonburgnews.com

 

 

Rock’s Mill Dam is on the road to decommissioning.

 

Long Point Region Conservation Authority, which owns the dam, hosted a public meeting in Springford Monday night to explain its plans. About 15 people turned out for the meeting, which is about a third of the crowd that appeared when the authority first suggested decommissioning the dam in the late 1990s. What was a contentious topic then, didn’t meet any resistance Monday night.

 

Constructed in 1911, Rock’s Mill dam was originally built to provide power to the adjacent grist mill. LPRCA purchased the property in 1978 and rented it to the Noels brothers. The property was sold again, but the authority purchased it back earlier this year.

 

Paul Gagnon, the authority’s lands and waters supervisor, explained an engineer identified a number of structural problems in 2001. In addition, the reservoir created by the dam warms the water downstream below the dam. Gagnon pointed to research that shows there is a 2° to 3° Celsius difference in water temperature above and below the dam.

 

“When you warm that water up, you take away biodiversity, you take away habitat,” he said.

 

Water quality is further degraded by Canada geese that don’t migrate south and defecate in the system year-round. Carp that make a home in the reservoir uproot natural vegetation and stir up the water, further degrading water quality and warming the water.

 

Following meetings in 2002, the municipalities along the watershed decided not to put money into the maintenance of the dam.

 

A bottom draw in the dam was opened last fall to draw down the reservoir above the dam, and a fence to hold back the silt was installed downstream. With the water level down, further problems were uncovered. Tree roots had created holes in the dam berm and beavers had made multiple holes in it.

 

Gagnon explained the bottom draw has kept the reservoir down during low-flow times, but it builds back up after heavy rainfall and melting. The plan is to keep the bottom draw, which is on the side of the dam, open and to cut a notch in the centre of the dam to allow the water flow to continue while the water is high.

 

In more detail, the proposal is to remove 18.41 metres, or one-third, of the arch and 7.85 metres of the apron that is below the dam.

 

After the dam has been altered, the upstream banks will be planted with annual rye to prevent erosion. Next spring, trees will be planted along the bank.

 

Removal of the dam will not affect the water levels in wells of adjacent property owners. Irrigation from the creek, which was a big issue the last time removal of the dam was suggested, can still take place from deeper pools in the creek.

 

One of the benefits of removing the dam will be opening up the habitat above the stream to migratory trout.

 

Following the public meeting, a report will go to the conservation authority board. If decommissioning is approved, and it is to take place this year, it must be completed by Sept. 30 so it won’t negatively impact spawning trout.

[wildeye rainbow]

Super news. A few more impediments to go on that creek & it'll open her right up for bows, browns, etc. Need to look at the head difference at the railway trestle in Tillsonburg to get the fish past there to the decommissioned Rocks Mills, then Otterville. Boy, could things open up without those two obstructions. Fish on!

 

I'd like to see more dams decommissioned particularly if they're old and serve little purpose - might be a few more in the London area.

 

WR