ASHLAND — Water used to clean filters at the city's water treatment plant gurgled Tuesday out of an underground sewer line and eventually into Ashland Creek, and now city officials are warning against water contact there until the creek can be tested.
City officials posted warning signs at the creek's popular swimming hole Tuesday afternoon following the spill of the so-called "filter backwash water," which totaled about 500 gallons, said Pieter Smeenk, the city's senior engineer.
The state Department of Environmental Quality ordered the city to take a water sample from Ashland Creek to check for E. coli.
Filter backwash water typically contains fine sediments and a water-cleaning agent called alum, and it was not expected to contain biological contaminants or be hazardous to people, Smeenk said.
"It's not likely to have anything, but we have to make sure," Smeenk said.
DEQ engineer Jon Gasik said the test typically takes about 24 hours to complete.
"If it's just backwash water, it's probably not hurting anything," Gasik said.
However, the water was flowing in a sewer line, where it could have picked up E. coli, Gasik said.
E. coli, a form of fecal coliform bacteria, is closely associated with human and animal waste. People who ingest E. coli-infected water can develop abdominal cramping, diarrhea and nausea. It is most dangerous to younger and older people, as well as those with poor immune systems.
Ashland Creek often has E. coli spikes that trigger volunteer advisories against water contact in the summer independent of spills like this, Gasik said.
"It's probably good to test it anyway," Gasik said.
The filtering process is the last step Ashland water goes through before chlorination and distribution citywide, Smeenk said. The backwash water is sent down an 8-inch pipe about three miles to the city's sewage treatment plant, he said.
The pipe clogged Tuesday, spewing water out of a manhole on a dirt road connecting the treatment plant with Granite Street, eventually reaching the creek above the swimming hole, Smeenk said.
The water is thought to have leaked out for at least a few hours before it was discovered about 2 p.m. by a plant operator driving by, Smeenk said.
That line contains manholes and is cleaned of sediment about every two years, Smeenk said. City crews will look into the cause of the clog, he said.
Reach reporter Mark Freeman at 541-776-4470 or firstname.lastname@example.org.