The city of Fredericksburg declared a local state of emergency yesterday as a 30-mile long kerosene slick on the Rappahannock River threatened to contaminate the area's shrinkage reserve of fresh drinking water.

City manager John Nolan, calling the situation "a real disaster," said officials had told businesses that use a high volume of water to close and urged residents to limit personal consumption to a bare minimum.

The city's 3,000-student public and parochial school systems will be closed today in an attempt to curtail water use, Nolan announced last night. "Such action is absolutely necessary," he said.

Nolan said the area's 55,000 residents, who normally use about 2.8 million gallons of water daily, have been forced to rely on about 800,000 gallons imported from neighboring Stafford County and the Quantico Marine Base, and another million gallons from Spotsylvania County.

The emergency action followed two ruptures last Thursday of a major underground oil pipeline that spilled a total of about 300,000 gallons of kerosene into the Rappahannock and the Occoquan River in southern Fairfax county.

With an 80,000-gallon pocket of kerosene threatening to overwhelm recovery efforts on Bull Run near the Occoquan, U.S. officials announced yesterday they were taking over clean-up operations there.

The Occoquan supplies drinking water for 660,000 Northern Virginians in southern Fairfax County.

The worsening situation in Fredericksburg was blamed on leaks in a lock on an intake canal that feeds water from the Rappahannock into the city's fresh water system. The lock was closed on Friday in a futile attempt to keep the foul-smelling kerosene from ruining water supplies.

Workers yesterday toiled feverishly to construct an earthen dam inside the lock to seal off the canal. They also drained the canal to a level below the leak, Nolan said. "It's now a question of how quickly the river can clean itself. This is a man-made disaster."

City officials earlier estimated they had about four days' supply of fresh water in a 10 million gallon storage pond. Yesterday they said they were unsure how much water the pond held, or whether it was safe.

""We're waiting for chemical tests," Nolan said. "If the pond is contaminated then we'll ask Gov. Dalton to declare a state of emergency for the area." Results of the tests were expected this morning.

Fredericksburg police reported "a rash" of residents who were attempting to buy distilled water and other liquids yesterday in preparation for an indefinite period of reduced water use.

Other Fredericksburg residents said they are conserving water by not washing dishes or cars or laundry.

City superintendent of public works Bill Hanson, standing on a bank overlooking the canal, said that if tests determine the water is contaminated, then the city is considering pumping out a three-mile section of the canal. He said that would enable the city to replace the contaminated water with pure water brought in from other jurisdictions.

Environmental Protection Agency officials set up a trailer near the river to oversee recovery operations, and brought in tank trucks from New Jersey, but had not yet decided to take over the operation, Nolan said. Virginia also has supplied 10 auxiliary pumps to help recovery efforts.

From the Manassas control center for the Bull Run-Occoquan River spill, EPA's on-scene coordinator Tom Massey made the decision to bring the federal government's "massive resources" to bear on the problem there at 2:15 p.m. yesterday.

"This is an official, federal response action," said EPA press spokesman Peter Acly, "that occurred in a meeting with state and federal officials. The Colonial Pipeline Co. (owner of the pipeline) had control over the operation until that point, but their resources are very limited. This shouldn't be seen as a punitive response against the company."

Additional floatation collars deflection booms, rubber bladders, tank trucks and skimmers (vacuum cleaners for the river), oil spill experts from the Navy, the Army and the Coast Guard, and a plethora of federal response teams were due to arrive at the Occoquan overnight and early today, Acly said.

"We're not saying that people should become alarmed," Acly said "But a surface sheen from the spill has gotten past Bull Run, and that's why they decided to give the feds control."

"The vast remainder of the spill has been contained," Massey said. "And meteorological conditions (Saturday) had caused breezes to blow the kerosene back upstream to an inlet where about 80,000 gallons had collected. But the slick moved two miles downstream last night."

"The potential still exists for a disruption of the (Occoquan) water system," Acly said. "And there is a potential for serious damage to wildlife and fish."

Representatives from the Interior Department's Fish and Wildlife Service have expressed concern for an "environmentally fragile" area just below Bull Run, an ecosystem that supports beavers, bird populations that include bald eagles, and major fish populations.

Environmentalists spent the day in two canoes yesterday assessing the damage to animal life and reported that fish were "near the surface and struggling" in some areas.

Meanwhile Colonial Pipeline spokesman James Sorrow said the break at Manassas has been repaired. A second break southeast of Culpeper that went undiscovered for almost 24 hours last week still is being worked on. Sorrow said the company hopes to have the entire Northern Virginia portion of the system operating again by Tuesday.