A leaking underground water reservoir has been drained but should not cause any disruptions in service, according to Al Towlerton, head of Public Utilities for the city of Billings.
The 6 million-gallon tank is built into the slope beneath the Rims at the north end of Stanford Drive, a block and a half northwest of Rimrock Road and 17th Street West. The underground reservoir is directly under the tall, red-and-white-checked water tower that sits on top of the Rims.
City workers discovered the leak three weeks ago. Towlerton said the reservoir was leaking 300,000 to 400,000 gallons a day through a leak barely wider than a knife blade, near the base of a wall. But that was with the reservoir empty. When the tank was full of water the pressure may have increased the size of the fracture, Towlerton said.
The tank is made of concrete and steel, is 31 feet deep and 188 feet in diameter. It was built in 1970 and should have had a lifespan of at least 50 to 60 years, Towlerton said.
City crews will try to determine in the next month what caused the leak. Towlerton said the ground may have settled under the reservoir or the wall itself might have moved. If it has to be rebuilt, he said, it could cost as much $10 million.
Towlerton also said there will be no disruption of service in the area served by the reservoir, which is most of the central part of Billings west of the downtown and running all the way south to ZooMontana.
If there were a major fire in the area, the Fire Department would be asked to notify Public Utilities, which could make changes in its pumping of water to ensure continued service to its customers.
“Other than that, there shouldn’t be any problems,” Towlerton said.
If the reservoir needs to be rebuilt, he said, it would probably take at least a couple of years. The city wouldn’t raise rates, he said, because a three-year rate increase for water and waster water was already approved in July 2008. He said the city would probably need to defer some other project or projects to pay for a new reservoir.
The reservoir sits within about 500 feet of two other water-storage facilities — a half-million-gallon above-ground tank slightly uphill and a little east of the reservoir, and a 3 million-gallon underground reservoir just east of the larger reservoir.
The reservoir that is leaking was originally built with two city tennis courts on top of it. Towlerton said those were removed five or six years ago, and they had been unusable for some years before that.