GRCA sets aside plan to shore up Drimmie Dam: will monitor situation

The Grand River Conservation Authority has scrapped its plan to bolster the Drimmie dam in the Grand River near the Elora Mill.

The GRCA made some plans to protect the dam with fill earlier this year when it re­ceived a report stating that the dam is increasingly unstable.

However, the Ministry of Natural Resources has refused permission to use fill to support the structure.

So instead, the GRCA will monitoring the condition of the dam on a daily basis to watch for signs of deterioration. If signs of possible failure do develop, the GRCA will then shut down its tube renting operation in Elora Gorge Con­ser­vation Area and issue a safety warning to other river users.

That decision by the GRCA board, meeting in committee of the whole on June 15, followed the receipt of a letter from the ministry.

The ministry letter stated the likelihood of a sudden collapse of the dam in summer is low.

In March, the GRCA adop­ted a plan to place rock fill on either side of the dam to shore it up to protect the dam from a “sunny day failure.” That would be a sudden, unexpected collapse of the dam – in as short a time as 15 minutes – which would send a two-metre wave of water cascading downstream.

The GRCA adopted the plan as the result of a report from its own consulting engineer who said there was a risk of such a failure because of the extreme­ly poor condition of the Drim­mie dam.

To place the fill, the GRCA needs the ministry’s approval, which it did not get.

Drimmie Dam straddles the Grand River in downtown Elora, about 65 metres up­stream of the Elora Falls. It was built in the late 1800s to power mills. It was acquired by the GRCA in 1984 from the Elora Mill Inn and some remedial work was done at the time to allow the mill to operate a hydroelectric generator using water from the head pond created by the dam.

However, the dam has sig­ni­ficantly deteriorated in recent years, according to the report done by the GRCA’s consulting engineer, who was hired in late 2007 to do a dam safety as­sessment. The next step is an envi­ronmental assessment to exam­ine alternatives, ranging from complete removal of the dam to replacement.