Exshaw lagoon still draining into Bow River
By: Rob Alexander
| Posted: Thursday, Jul 19, 2012 06:00 am
Partially treated sewage continues to flow from an emergency outflow into the Bow River from the Exshaw wastewater treatment lagoon, a result of above average water levels.
Bill Luka, director of operations for the MD of Bighorn, said Tuesday (July 17) the problem began on June 11 during spring flooding and recent heavy rains are contributing to the problem.
“(The rain) has contributed to it. The levels are still high, causing the release and we are monitoring it,” Luka said. “Last week it looked like the elevation was going down and we thought it was ending, but it has gone up a bit.”
Luka said the MD is looking at ways to control the outflow, including extending the weir in the emergency outfall trench.
The MD is conducting additional testing of the effluent every four hours, as required by Alberta Environment, at a cost of $7,000 per week.
MD Reeve Dene Cooper said the tests are indicating that the effluent is not raw sewage and it is within government standards.
“We’re not releasing something that is above standard to the Bow system. We’re releasing water that is within their standards,” Cooper said, adding this is the first time the Exshaw wastewater treatment lagoons have overflowed.
“We haven’t had this problem and part of it is because of the very high runoff volumes and we know we have some kind of infiltration problem.”
The one positive in the effluent discharge from the overflowing lagoons is that the MD was part-way through an Inflow and Infiltration study as the municipality was aware water was infiltrating into the wastewater system.
“If there ever was a silver lining in a dark cloud, we were actually studying (the infiltration) when it happened, and it will tell us more than we expected to get,” Cooper said. “There was no knowledge that this would happen, but it has happened at a time when we can best understand it.”
Luka said the sewage system has a design capacity of 345 cubic metres per day.
However, Cooper pointed out flooded basements in the hamlet have pushed the daily volume much higher.
“The more likely source is pumping basements into a sewer system never designed for that volume and if your basement was flooding, what decision would you make? I don’t want to sound like I’m blaming my citizens.”
Once water levels have subsided and the lagoons stop draining, Cooper said the MD would likely have to dredge the lagoons.
“I think if we had more volume into the upper cells we wouldn’t have a super release into the polishing cell,” he said.
“We’re always concerned when our technology is not functioning as designed.”