A Sept. 23 Metro article incorrectly said that the D.C. Water and Sewer Authority had increased disinfectant treatment of city water. The Army Corps of Engineers runs the two city water-treatment plants. (Published 9/25/04)

Preliminary tests this month of the District's water have registered some of the highest bacteria levels since summer 1996, when the city warned some people to boil tap water because of possible contamination, federal officials said yesterday.

The D.C. Water and Sewer Authority and the Environmental Protection Agency plan to hold a news conference this afternoon to announce the increase in bacteria levels in routine water tests and to explain what action will be taken if remaining tests confirm an overall bacteria problem.

"While this is preliminary data, we feel it's important to explain what it means so the public can be aware and informed," said EPA spokeswoman Cynthia Bergman. "At this time, we don't believe a boil-water advisory is necessary as there is no evidence of an acute health risk."

In recent weeks, WASA has increased its disinfection treatment and flushing of distribution pipes to ease the problem, WASA officials said.

WASA officials said that they surmise that the addition this summer of a new chemical to curb high lead levels is contributing to the peeling of bacteria film from pipe surfaces. That is natural and was expected, said WASA chief engineer John Dunn, but may be happening at a faster rate than predicted.

The EPA has primary responsibility for overseeing the city's drinking water quality. Dunn and Bergman cautioned in interviews yesterday that the partial results should not cause alarm. Complete tests are not in, so it's too early to say whether the authority will violate the federal safety standard for bacteria in drinking water, they said.

So far, 8.4 percent of the 143 tests the utility has analyzed have found positive readings of total coliform bacteria, common in soils, plants and animals. The agency must take at least 210 tests but could take more by the end of the month.

The EPA considers water to have potentially unsafe levels of bacteria when more than 5 percent of the monthly tests are positive.

Dunn said this situation is "a world of difference" from the boil-water times during summer 1996 because the utility has found no evidence of E. coli, a bacterium that is often harmless but sometimes toxic and a cause of foodborne and waterborne illness.

The news comes as WASA contends with continuing criticism about its failure to effectively warn the public about high levels of lead it found in the tap water of thousands of city homes last year.

Total coliform include a vast group of microorganisms that are generally found in all water systems and are not considered harmful as a rule. However, they are considered important indicators of the possible presence of germs that can cause intestinal ailments and headaches.

In July 1996, after a series of high results in June, District health officials advised all city residents older than 65 and patients with weak immune systems to boil city tap water before drinking it because it contained potentially unsafe levels of bacteria.

Another boil-water alert came in November 1995 but covered just one Southwest Washington neighborhood and lasted one day.

Also yesterday, Interim D.C. Inspector General Austin A. Andersen testified before a D.C. Council committee about the findings of his audit into the authority's handling of elevated lead levels in the drinking water. The review found what other investigations had concluded: WASA failed in some instances to provide regulators with all the required lead test results, to share information with the D.C. Department of Health and to communicate the urgency of the pervasive high lead readings to the public.