The city is now certain the home it thought was the source of E. coli being dumped out of a “mystery pipe” into Mill Creek is not the culprit, but rather the city’s sewer main is.
Crews from The Dalles Public Works Department thought they hit paydirt two weeks ago when a dye test on a home in the 2500 block of Wright Street produced dye at the “mystery pipe,” several hundred feet away.
It was the first of more than 15 dye tests to get a result.
Crews replaced the four-inch connection from the sewer main to the home’s property line, about 35 feet of pipe, then blocked off the new connection from the sewer main and re-dyed the home, to test whether the home was leaching sewage to the to the creek. No dye appeared. They then turned to the circa 1950s sewer main itself. They cleaned it yesterday and put a camera up the pipe and found three cracks that went around the circumference of the 10-inch concrete pipe, and some in just the top of the pipe, said Steve Byers, wastewater collections manager for The Dalles Public Works Department.
He has contacted a company the city has worked with before to do an emergency slip-lining project on about 700 feet of sewer main along Wright and Jordan streets.
It involves putting a hard plastic and fiberglass liner in the sewer main, and cutting new connections to the 12 homes that connect to the main.
Byers estimated the project will cost $30,000 to $35,000, and he hopes work on it can begin next week.
Once the slip-lining project is finished, the city will re-dye the sewer main, and hopefully will not get dye in the creek. Byers plans to test it several times, with the expectation that residual E. coli may take some time to flush out.
While this concrete sewer main is 60 years old, it is “far from the oldest concrete pipe we have,” Byers said. It wasn’t really in that bad a shape, but it was not laid perfectly straight, so there could be some settling that occurred, leading to cracking, he said.
As for the mystery pipe itself, it follows the direction of the sewer line for at least 80 feet under Wright Street. The city was unable to follow the pipe’s path further than that.
The homeowner of the property in the 2500 block of Wright plans to replace the portion of her sewer line that is on her property, Byers said.
The city put a camera up the home connection, going some 53 feet, clear under the house, and the pipe was “not in very good shape, but we didn’t find a hole or anything, nothing stood out as a great big hole,” he said.
The city cleaned and visual inspected with remote cameras about 275 feet of the sewer main on Wednesday, and found the cracks in the pipe.
The mystery pipe was found in August 2012 and is believed to be a drainpipe to dewater natural springs in the area. It’s made of orangeberg, a tar-like 1950s era type of pipe that is prone to failure.
The pipe has a constant water flow — leading officials to believe its draining a natural springs. E. coli levels in the pipe are so high they cannot be measured by tests. Nearly two miles downstream, at the Second Street Bridge, the levels still exceed “acute” E. coli contamination standards.
E. coli is present in human and animal waste. Most strains of it are harmless, but some can cause serious illness in small children and older adults. Multiple agencies have maintained they lack jurisdiction over the creek. The city eventually posted signs along the creek warning people not to swim there, after a citizen complained to city council.
Officials were operating on the belief that someone’s sewage was leaching from a failed pipe and merging with the natural spring that is drained by the mystery pipe.