STERLING – The city is considering using sonar as a lower-cost way to locate leaks in overworked, aging portions of its stormwater and sewer systems.
The city has been using flow meters and rain gauges to track down cracked pipes and other sources of water inflow, but Scott Howard, superintendent of the wastewater treatment plant, told the City Council last week that using sonar could save the city money, though he didn’t know exactly how much.
The system has been plagued by aging pipes, a persistent winter and a wet spring.
“We had a screwy winter where things melted multiple times. Then in spring, it never stopped raining,” Howard said. “You spike the rain flow, you spike the flow coming down through the sewer.”
During the weekend of June 8, flow from the storm sewers into the sanitary sewer went from 1.2 million gallons to 12 million gallons.
“Water in the sanitary sewer is overworking the lift systems. There’s more cost. The electrical cost goes up. We’re also losing ground in the pond,” Howard said.
About two-thirds of the 37-acre pond, or wastewater treatment lagoon, is surrounded by the Elkhorn Creek.
“The pond is at a manageable level right now. We want to keep the creek water out of the pond and the pond water out of the creek,” Howard said.
Howard said the downtown area is the biggest problem.
“We took measurements [June 4]. … Wallace Street triples its flow with 3/4 of an inch of rain,” he said.
City staff began the first phase of a flow test study April 16 to find cracked pipes and other sources of inflow. Flow meters and rain gauges were placed throughout the city, and moved between locations to see how much rain affects inflow and infiltration in the sewers, Howard said.
The next phase would use a system called SmartCover, which hangs from a manhole cover and uses sonar to measure the amount of water flow.
City staff have already identified some leak sources. Howard told the council about a 36-inch sewer line along Lynn Boulevard that has leaky manholes.
“There’s a lot of really old barrels that need to be fixed. The barrel is a part that the manhole cover sits on. Some of those barrels are very old, even red brick. When it rains, it leaks like a sieve. It’s not going to the storm sewer, it’s going right into the sanitary sewer,” he said.
Leaky and cracked pipes and human error are other sources. Howard noted increased flow from floor drains in buildings and runoff from roof and parking lot drains.
“The city isn’t trying to point a finger. We’re simply trying to find where the problems are,” Howard said.
The Sterling City Council next meets at 6:30 p.m. Monday in the first-floor council chambers at City Hall, 212 Third Ave.
Go to sterling-il.gov or call City Hall at 815-632-6621 for an agenda or more information.