Teams of inspectors and investigators descended beginning shortly after dawn yesterday on the District's Blue Plains Sewage Treatment Plant to oversee emergency repairs in the toxic chemical work area, while local and federal officials expressed outrage at what they called a blatant disregard for public safety there.

The actions came in response to a report in The Washington Post yesterday that detailed a series of shortcomings in the monitoring and alarm systems designed to prevent the release of liquid chlorine, a highly toxic chemical used to help sanitize wastewater. The plant typically stores at least 180 tons of chlorine in rail cars, one of the region's largest stockpiles of toxic chemicals.

Four of the plant's seven chlorine leak sensors were replaced yesterday, new emergency breathing equipment was installed, an audible alarm system was repaired, plant security was beefed up and nighttime supervisors were added. The D.C. Water and Sewer Authority hired an investigator to try to figure out who is to blame for the safety flaws, city officials said.

The U.S. Environmental Protection Agency, the Department of Labor and the Department of Transportation plan to join the D.C. director of emergency management early next week for a tour of the Southwest Washington plant to assess what else might be necessary to resolve the safety concerns.

New evidence surfaced yesterday that the D.C. agency assigned to ensure worker safety at Blue Plains had found a range of serious safety violations in the plant's chlorine facility in 1996--and never conducted a second inspection to determine whether the problems had been corrected.

District Mayor Anthony A. Williams (D) and water and sewer officials sought to assure residents across the region that Blue Plains poses no imminent public health threat, particularly after yesterday's emergency repairs.

But Williams reiterated that he was "deeply disturbed and troubled" by what he called unacceptable conditions at Blue Plains, which treats wastewater from the District and Montgomery, Prince George's, Fairfax and Loudoun counties. The mayor said the plant's administrators and staff members would be held accountable for the failures.

Liquid chlorine is so toxic that even if one rail car's load of the substance were released at Blue Plains--a highly unlikely event--it could kill plant workers and others who work or live in the area in seconds and create a poisonous plume more than 30 miles long. Even a small-scale leak could threaten workers.

"This is a serious situation; we take it seriously," Williams said during an afternoon news conference. ". . . It really erodes confidence. We are acting on it immediately."

Alexandria Mayor Kerry J. Donley (D), whose city is just across the Potomac River from Blue Plains, said he wants assurances from Williams that everything possible is being done to improve safety there.

"How can you have such a large amount of chlorine and store it there and have blatant disregard for safety?" Donley asked yesterday, adding that he intended to call Williams. "It is terrible. It is outrageous. It is not acceptable."

On Capitol Hill, Washington area Reps. James P. Moran Jr. (D-Va.), Thomas M. Davis III (R-Va.) and Steny H. Hoyer (D-Md.) sought urgent authority for the District to divert funds from the pending $4.7 billion D.C. appropriations bill to overhaul safety systems at the plant.

"Regardless of how remote the possibility of chlorine tanks rupturing at Blue Plains might be, the potential catastrophic consequences demand an immediate response," the congressmen wrote to House Appropriations Chairman C.W. Bill Young (R-Fla.) and David R. Obey (Wis.), the panel's ranking Democrat.

Democratic Sens. Charles S. Robb (Va.), Barbara A. Mikulski (Md.) and Paul S. Sarbanes (Md.) wrote a similar appeal to the Senate Appropriations subcommittee on the District, headed by Republican Kay Bailey Hutchison (Tex.) and Democrat Richard J. Durbin (Ill.).

The lawmakers hope to amend the D.C. budget to allow the city to tap economic development and infrastructure funds for the $18 million needed to convert the plant's chlorine operation to one that uses a much less toxic form of the disinfectant.

But Del. Eleanor Holmes Norton (D-D.C.) blasted the suburban lawmakers' proposals, saying any cleanup should be paid for by Water and Sewer Authority users--most of whom are suburban residents--rather than by raiding D.C. funds.

"This is not going to happen," Norton said. "Nobody could be more concerned about this than the residents [who live near the plant], or for that matter me. . . . This is a responsibility of Maryland, Virginia and the District. It's a responsibility of rate payers, not District taxpayers."

Williams has asked his director of emergency management, Peter G. LaPorte, for a report on safety problems at Blue Plains by tomorrow night. LaPorte, who arrived at the plant at 7:30 a.m. yesterday, said it was obvious to him after his initial tour that there were serious shortcomings in the plant's Chlorine Building I and in other facilities that handle toxic chemicals.

"It was plain as day," he said. "There are issues of concern here. We need to address them in a timely fashion. And we can never slip again."

Battalion Chief Damion Wilk, the D.C. fire department official who oversees hazardous materials incidents, joined LaPorte yesterday at Blue Plains, along with a full fire department hazardous materials team. They concluded that while many repairs were necessary to improve safety, the possibility of a large-scale chlorine release remains remote.

Ron M. Linton, chairman of the D.C. Water and Sewer Authority Board, offered an even stronger assessment during an afternoon news conference outside the plant.

"Let me make this clear: There is no danger and there has been no danger to the general public in the way chlorine or any other chemical substance is handled here," he said.

But Linton said the water board, in a hastily called session yesterday, had agreed to appoint a special counsel, lawyer James V. Dick, to investigate conflicting explanations by plant management and a safety consultant as to why the weaknesses in the chlorine leak prevention program were not eliminated. The investigation "will allow the determination of what management steps, if any, are needed to avoid any lapses in future contractor/management relationships," Linton said.

The water board also authorized the authority's management to accelerate its $18 million project to replace the liquid chlorine treatment system with a new, less dangerous chemical process. Under the old plan, that conversion was at least three years away.

Linton said repairs to Blue Plains have been planned for years and objected to any suggestion that they were inspired by The Post's article yesterday.

The D.C. Office of Occupational Safety and Health acknowledged that three years ago it had warned the Water and Sewer Authority about many of the same safety flaws reported yesterday.

During a November 1996 tour of the plant's two chlorine buildings--conducted in response to a chlorine leak the previous month--safety inspectors found alarm system flaws, malfunctioning or missing breathing equipment, pipes and valves that were leaking water, and staff members who were not trained on how to use safety equipment and lacked basic equipment such as goggles, gloves or proper shoes.

Many of those same conditions were evident during a reporter's tour of the plant Wednesday and were documented in city memorandums written in recent months. The Occupational Safety and Health office--a division of the D.C. Department of Employment Services--sent a detailed violation report to Larry King, then the Water and Sewer Authority's general manager.

But the safety inspectors have not returned to the plant since the 1996 visit.

John M. Cates, acting associate director of the Occupational Safety and Health office, said his department assumed that Water and Sewer Authority officials would take care of the matter. He added that because his office has only three inspectors, it had not had time to return to the plant.

"We figured that notifying them of the hazard would be sufficient to correct the hazards," he said. "Our resources are limited; we try to do the whole city."

Now that it is clear the repairs were not made--or made but not maintained--he said it is evident that the agency should have been more diligent.

"It would have been nice if we had [returned to the plant], looking back on it now," he said.

Williams, who appoints some members of the water and sewer board, said the trouble at Blue Plains is like many other problems in D.C. government he has faced since taking office in January.

"Look, you inherited a mess," Williams said. "You are going to have things show up before you can get to them. But as they show up, you swing around and you address them. That is what we are trying to do."

Staff writers Spencer S. Hsu and David Montgomery contributed to this report.