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THE DALLES, Ore. (AP) — For nearly two years, health and city officials in The Dalles have been working on a mystery: What's the source of the sewage that's flowing through a pipe that drains into a stream through the Columbia Gorge town?
More than two dozen tests of the water flowing into Mill Creek have contained levels of E. coli bacteria higher than the equipment measures, The Dalles Chronicle reported (http://bit.ly/1eFUKa3 ).
Authorities suspect the mystery pipe, 4 inches in diameter, is decades old and has been damaged, so wastewater from another source, such as a septic tank, is contaminating underground water that flows into the line.
Workers have pushed metal detectors up the pipe. They've blown smoke through it. They've used dye tests to trace the lines from some homes. They've used ground-penetrating radar to trace part of the line's route. They used a dowser to trace the pipe to one home, but no leaks were found.
They dug a 14-foot hole in a city lot to find the pipe — nothing.
They dug up the front yard of a home — and there was the pipe. But when a camera was sent in, a sharp bend or some other impediment blocked its progress under the street.
"And we don't want to cut up a perfectly good street in this effort," said Public Works Director Dave Anderson.
Because of the risk of liability, the city is not considering the drastic option of just plugging the pipe and seeing whether anybody's house gets the backflow.
Among the city's expenditures: A $2,400 power snake. As for the total costs of the investigation, Anderson said, "I don't even want to know."
The pipe was partially obscured by foliage when a worker taking samples for the Wasco County Soil and Water Conservation District found its end jutting from the bank behind a house nearly 2 miles upstream of the Columbia River.
A chronic level of E. coli bacteria, above the level of "acceptable human health risk," is 126 organisms per 100 milliliters, said Anna Buckley of conservation district.
Testing equipment can measure up to 2,419 organisms, and even in a dilution test, the sample in this case "was still orders of magnitude beyond the test," she said.
Agencies are still trying to figure out who's responsible for posting warnings on the creek.
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Information from: The Dalles Chronicle, http://www.thedalleschronicle.com
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