The city plans to dig a hole perhaps 14 feet deep in Wright Street today in hopes of tracing the origins of the “mystery pipe” dumping dangerous levels of E. coli into Mill Creek.
The Dalles Public Works Department has made numerous non-invasive attempts to trace the pipe from its outfall in the creek to its origins, but has consistently run into a blockage under Wright Street.
Workers sent a scope with a camera up the pipe, sent smoke up the pipe, and sent metal up the pipe and traced it aboveground with a metal detector. The scoping methods always ran into a blockage about five feet into Wright Street.
The city knows it will have to dig about 14 feet or so down because that’s how far they dug into a homeowner’s front yard in the 2400 block of Wright Street searching for the pipe. The pipe runs under that homeowner’s house and send outflow into the creek behind it in Ericksen’s Addition. In that case, they found the pipe and traced it from the hole in the front yard, but again ran into a blockade just a few feet away, under Wright Street.
The city initially didn’t want to tear up the street looking for the pipe, but has run out of other options, said Steve Byers, wastewater collections manager for the city of The Dalles.
The road was chip sealed just last year, he said.
The city has put dye down fixtures in over 15 homes in the area, and in all cases where the homes were connected to city sewer, the dye quickly appeared where it should: in the city’s sewer system.
Five homes some 400 to 500 yards away, outside city limits and on septic systems, were dye-tested in late April and no dye appeared at the pipe’s outfall.
The city has a theory that the pipe — which has constant, clear water coming from it — was installed in the 1950s to drain a natural spring in the area to stabilize the hillside for homebuilding. They believe perhaps a failed septic drainfield is contaminating the natural springs and the contaminants are ending up in the drain pipe.
Officials know it is from a domestic source because the water contains a brightener used in laundry detergent.
The levels of E. coli coming from the pipe are so high that they exceed the capabilities of testing equipment. The mystery pipe was discovered in August 2012 by the Wasco County Soil and Water Conservation District, which was testing Mill Creek waters for E. coli.
The city last week posted signs on Mill Creek warning swimmers to avoid the water due to the contamination. E. coli is a bacteria found in human and animal waste. Many strains of E. coli are harmless, but some can cause illness, especially in the very young and the elderly.