In the single-biggest expenditure of the city’s nearly two-year hunt for the source of the “mystery pipe” dumping E. coli into Mill Creek, a Salem company will line 700 feet of sewer main next week for $40,000.
Michael’s Pipe Service is expected to start the approximately three-day job on June 9, said Steve Byers, wastewater collections manager for The Dalles Public Works Department.
After it’s done, the city will again put dye in the sewer main. Hopefully, this time the dye won’t quickly flush out into Mill Creek via the mystery pipe as it did a few weeks ago.
The mystery pipe was discovered in August 2012 by the Wasco County Soil & Water Conservation District.
The clear water constantly pouring from it had such high levels of E. coli that testing equipment couldn’t measure it. E. coli is an indicator of fecal contamination in water.
Officials believe the mystery pipe is a drainpipe that is dewatering a natural springs, and somehow sewage is mingling with the natural spring water.
The upcoming slip lining project will put a hard plastic lining inside three sections of sewer main: two in Wright Street and one that goes from Wright Street and Wright Drive underneath a house toward Jordan Street.
After multiple efforts, including dye-testing over 15 homes in the area, the city finally thought it had found a house in the 2500 block of Wright Street that was the source of the E. coli.
But further testing found the house was not the culprit, but rather the sewer main was. When the main was studied with a camera, three cracks that went the circumference of the main were found.
The slip-lining project will be done through the manholes. The city has been busy getting ready for the project by identifying where each home connects to the sewer, since the new lining has to be cut to accommodate those sewer taps.
It costs about $200 to create each of those taps, so the city has also been identifying unused sewer lines connected to the main, to ensure they are not paying for taps to those lines. The city has found about 10 of those, Byers said.
The city is also doing prep work for the project by cleaning and putting a camera up each of the sewer connections to locate them all. The city is also getting “intruding taps” out of the way, Byers said. In those cases, a sewer connection tap was made into the main, and the pipe sticks into the main a little bit. Those will be trimmed back to the edge of the main.
City crews won’t have to be on hand for the actual slip lining, Byers said.
Rather, they will finally be able to turn their attention to other maintenance duties. The department has one project it hasn’t started but needs to finish this fiscal year, which ends June 30.
The city did not go out to bid on this job because it was an emergency situation and it was the low bidder for another slip lining job of about 450 feet, which was also done in search of the mystery pipe source.
Byers said he doesn’t know how much the city has spent – mostly in the form of man hours – in the hunt for the source of the mystery pipe.