Below you will find a map of the affected area and instructions on treatment of water.
An order to boil water has been issued for households at the north edge of College Place.
Coliform bacteria, and possibly E. coli, were found during testing of water in the Green Tank Irrigation District, according to Barry Jenkins, director of environmental health for the Walla Walla County Health Department.
"They took a routine sample that was uncharacteristically contaminated. We have two tests that are run in our certified lab ... one is a positive for coliform bacteria in general, which is what this sample had. When we subsequently checked it, it had E. coli contamination as well," Jenkins said.
Subsequent samples included one positive result for coliform bacteria, but none for E. coli, he said.
"The fact that we had an E. coli hit on the original test is concerning, but it didn't show up on the second test. The state health department is working closely with the water system to try to determine why they got the contamination," Jenkins said.
No illnesses have been reported in connection with the contamination, the state Department of Health said Wednesday in a prepared statement.
The irrigation district is bordered by Northeast Rose Street and North College and Wallula avenues. State records showed the district had 193 connections, a county lab official said.
State and local officials are working to contact all water users in the district, and Jenkins stressed that the problems appear limited to the irrigation district.
"There's been no problems with water samples from College Place or Walla Walla or to my knowledge in other water systems in this time period," he said.
The state Office of Drinking Water is working with the system operator to pinpoint the source of contamination and fix the problem, according to a news release. The problem may be tied to pump failures that occurred last week, the release said.
Coliform bacteria in general and E. coli in particular can cause health problems if ingested.
Symptoms can include stomach cramping and diarrhea -- including bloody diarrhea -- fever and occasionally more serious problems such as kidney failure.
For more information, call the Green Tank Irrigation District at 509-525-4608, or the Walla Walla County Health Department at 509-524-2662.