The Environmental Protection Agency yesterday said a treatment plan must be developed to rid the Ebbetts Pass water system of byproducts.

The Calaveras County Water District has known about the presence of noncompliant levels of haloacetic acids in the water since February and has been working to lower those levels since that time, said Fred Burnett, district operations and maintenance manager. In fact, recent tests have shown the levels to be within the accepted range, he said.

Haloacetic acid is a byproduct chemical sometimes created when organic compounds in raw water react with chlorine, said John Merkle, a senior environmental scientist in the EPA's San Francisco drinking water office.

The acid has an increased chance of multiplying if the water is stored in tanks for long periods of time. An EPA report states that the drinking-water standard for haloacetic acids is 60 parts-per-billion and the Ebbetts Pass levels have ranged from 66 to 77 ppb.

The acid is not expected to affect human health, but is potentially harmful because it has been associated in lab studies with liver cancer in rats.

The EPA has spent the last few months documenting the problem and coming up with a reasonable compliance schedule, Merkle said. The water district has 30 days from the time it receives written notice from the EPA to submit a written plan for treating the problem, describing the steps to be followed to reach an acceptable level of haloacetic acid, Merkle said.

Merkle has been in touch with district officials and understands acceptable levels have been detected in recent weeks, he said, but to be sure the levels don't rise again, the EPA will monitor it throughout the next year.

"It's probably going to take a while, which is why we give them a long time to come into compliance," he said.

"We have already implemented many changes, and we feel confident that when we take our June samples we will be, once again, in compliance," Burnett said.