"Ample evidence" exists that water suppliers are falsifying monitoring reports on contamination of drinking water to avoid violating federal pollutant limits, congressional investigators said.

In a report that EPA Administrator William Reilly acknowledged Friday is "disturbing," investigators with the General Accounting Office said the extent of the falsification was unknown, but that state and Environmental Protection Agency officials knew it was happening."While most EPA and state official we interviewed did not believe data falsification is extensive, they all cited cases in which such practices had been detected or were strongly suspected," said the GAO, the investigative arm of Congress. "Ample evidence exists that these practices are occurring."

The GAO report said one case in Oklahoma involved a water system operator who admitted he was not testing his supplies for turbidity - or cloudiness - as required under law.

"He said his predecessor told him to take a water sample, `hold it up to the light, and if it looks pretty clear, give it (a passing score),"' the GAO said. "He was also told not to report, under any circumstances, (a violation of) the drinking water standard."

The GAO report was released at a House hearing where Democratic legislators charged the EPA's new regulations to reduce lead in drinking water were effectively unenforceable and an open invitation to the kind of abuses documented by the GAO.

The lawmakers said the EPA had abolished any legal limit on toxic lead levels in favor of a mushy "action level" that could not be readily enforced through court action if people found their water had excessive lead levels.

"We are talking about such a flabby regulation," complained Rep. Henry Waxman, D-Calif., chairman of a House subcommittee on environment and health.

Reilly defended the lead rules, insisting they would be tough and effective, but he agreed the GAO report revealed major problems in the overall enforcement of safe drinking water laws.

"Some of the findings are disturbing," said Reilly. "They are valid, realistic concerns."

The EPA chief maintained the administration had tightened its enforcement of drinking water rules, but he promised, "We will do a better job with this program."

The GAO said data falsification was just one of a host of problems undermining public assurance that drinking water is being properly tested to ensure its purity.

The GAO found states - the primary enforcers of safe drinking water laws - were:

-Underreporting violations to the EPA.

-Suspending monitoring requirements they deem impractical.

-Not enforcing requirements that water suppliers notify the public when contaminant limits are exceeded.

-Failing to crack down on "significant non-compliers." In many cases, the GAO said states reported reaching compliance agreements with water suppliers to correct problems, but the suppliers refused to sign them. The reason: They were concerned that "signing would legally obligate them to take the designated corrective actions."

And the report said the incentives for dodging drinking water laws were increasing as Congress and the EPA regulated more contaminants, placing ever greater monitoring and compliance requirements on water suppliers and already overburdened state enforcement officials.