District staff are taking a close look at the dam holding up one of Houston’s favourite swimming holes.
Built before 1947, the dam on Dunalter Lake, popularly known as Irrigation Lake, no longer complies with B.C.’s dam safety standards.
Speaking to Houston councillors last week, Chelton van Geloven, dam safety officer for the Skeena region, said the dam is unlikely to break. But it does need an upgrade soon or the province will have to pull it down.
“It seems like this dam was particularly well made,” van Geloven said. “There’s lots and lots of rock on it. Water has flown over the top and we haven’t seen very much erosion.”
“That said, enough water could cause it to erode and fail.”
If the dam did break, Dunalter Lake and whatever debris is picked up could spill into a house downstream.
In 2010, a wall of mud destroyed five homes and several orchards near Oliver, B.C. after an earthen dam built in the 1930s suddenly failed and released two-thirds of a nearby reservoir.
Soon after that, B.C.’s natural resources ministry ordered a review and annual reports on every dam in the province. Van Geloven said that’s when Dunalter was found to be non-compliant.
“We’ve definitely kept it safe since then,” he said, noting that he and a neighbouring landowner now monitor the dam’s floodgate.
But with no spillway and less than a metre between the lake and the top of the dam, van Geloven said someone has to take action.
Complicating matters is the fact no one owns Dunalter dam, although it does stand on former Crown land given to the District of Houston for a recreation site.
If no one steps up to take it over and the dam is dismantled, the water level will drop two metres, van Geloven said, noting that campers at the Rough Acres and Mountain View summer camps likely want the lake to stay at or near its current level. The lake is also a popular ice-fishing spot in winter.
If the District or another owner takes over, van Geloven said they have two options.
First, they could hire a professional engineer to upgrade the dam and install a spillway, allowing the lake to stay at its current height.
A less costly option is to simply build a spillway, which van Geloven estimated at less than $5,000, and allow the lake to drop by a metre.
Council voted to direct the issue to Engineering Services Director Michael Glavin, who will report back with more information on those options and related issues on June 19.