City strikes mother lode – locates massive water leak

Sean C. Morgan

City of Sweet Home workers last week found what may be the mother lode of leaks in the water distribution system, a rupture that is likely responsible for the majority of water lost from the system – almost a third of the city’s daily production of treated water.

For many years, the city has tried to find something similar in the sewer system, hoping to find a storm drain or something else draining into the sewer pipes during heavy rains and overloading the Wastewater Treatment Plant. That hope has come up empty.

Instead, the the city’s sewer system was actually suffering from a thousand cuts, deteriorating public and private sewer pipes across the city that have required wholesale repair and replacement of pipes.

The upcoming expansion of the Wastewater Treatment Plant is supposed to deal with the remaining inflow and infiltration, the water that leaks into the sewer system through cross connections with storm drainage or through deteriorating pipes.

Things have turned out far differently for the leakage problem in the water system. City staff members were elated last week to discover a water distribution line pouring nearly 350,000 gallons per day into the stream that crosses 9th Avenue north of Nandina Street entering Ames Creek to the west. The line had three different leaks in the area.

“It’s super exciting,” said City Manager Ray Towry. “It could be the silver bullet to that water loss.”

“We may have found the main one,” Public Works Director Greg Springman said. “This is a big one.”

Springman cautioned that it’s a rough estimate, but it explains a significant amount of the city’s water loss.

Utilities Manager Steve Haney said the average city water production for the seven days prior to closing the leak was 1.1 million gallons per day.

Production varies day to day, Springman said, because the Water Treatment Plant produces water until reservoirs are full, and then shuts down while reservoirs provide water to customers.

Of the water the city produces, roughly 40 percent never goes through a customer’s water meter and is lost.

The city measured flows in the stream using a weir prior to shutting down the leak, although the most accurate method to measure an open flow channel was not available, Springman said. Prior to fixing the leak, the stream had a flow of 475,000 gallons per day. Afterward, it had a flow of 127,000 gallons per day.

If the flow estimate for the leak holds true, then the 9th Avenue leak accounts for roughly 79 percent of the lost water in Sweet Home.

He cautioned that “we will never get away from leaks in this system,” noting that the city repaired 120 leaks last year.

The Public Works water distribution crew shut down the the leak Thursday morning, April 16.

Over the next year, the city will be able to verify that estimate based on metering at the Water Treatment Plant, Springman said.

The city will be able to make its most accurate early assessment based on a seven-day average following the repair, Haney said. Longer-term averages won’t be reliable because residents will soon begin watering their yards and gardens.

The three-day average for water production following the repair was .7 million gallons per day, a 36-percent reduction over the previous seven-day average.

The leak was among 68 located by a contractor in 2018, Springman said. It was the biggest among them and so loud it could be heard without equipment at the culvert on 9th Avenue and above ground. That sound masked the other two leaks in the area.

The city estimated it was leaking roughly 72,000 gallons per day, far less than it appears in reality, Springman said. Because the leak was in a complicated location, the city couldn’t move quickly to repair it.

The main leak was under the culvert, Springman said, and the city had to take time to plan for it.

The crew shifted homes in the area to a second water line in 9th Avenue that the city used to feed other areas of the city when the Water Treatment Plant was located at the north end of 9th Avenue.

Once those services were transferred, the crew closed off the line at the intersection of Nandina and 9th and closed a valve to the north of the leak. The city will close that end permanently later.

Springman said that if the leak were confirmed at 300,000 gallons per day, it would represent a 30-percent cost reduction in energy and chemicals used to treat water.

“I’m extremely proud,” Springman said. “It’s like we’re winning the playoffs.”