Raw sewage that disappeared this week after leaking from a broken sewer line in Frederick County, Md., turned up yesterday in the town water supply in Walkersville, prompting officials to truck in water and plan for an emergency pipeline to bring in more potable water.

Town officials began testing the water supply every six hours Monday after discovering that a construction accident had ruptured an 18-inch sewer line June 19. About 900,000 gallons of sewage had leaked by the time the break was discovered.

"The tests came back this morning showing an elevated level of bacteria, so we know the sewage has reached our water," Beth Pasierb, planning and zoning administrator for the town, said. "We have now ordered a boil-water advisory for all the residents of town."

Water for the town of 7,500 residents is drawn from wells about a mile from the broken sewer line. Hydrogeologists had warned that the town's unusual geology--porous limestone riddled with fissures and sinkholes--might allow the sewage to reach the wells.

Volunteer firefighters yesterday delivered notices of the contamination to residents and to homeowners with water from private wells, which also may be contaminated. Pasierb said the town will deliver water to anyone with special needs.

Tank trucks were being set up at four locations in town to supply water, and residents came with buckets and jugs to carry it home, Pasierb said.

Pasierb said she met with town and county officials yesterday to conceive a longer-term solution to the water crisis. Frederick County officials were preparing to lay a 1.3-mile temporary pipe to bring water in from Frederick. The Maryland State Highway Administration has agreed to help with construction of the pipe.

Michael G. Marschner, chief of Frederick County's water and sewer bureau, said the pipeline could be completed by early next week. He said the wells eventually will run clean again--probably within a few weeks--because organic contamination, unlike chemical contamination, eventually breaks down.

Another possibility may be a special filtering system at the town's water treatment plant. "It's very expensive, but we might consider that, if we could get approval from the Maryland Department of the Environment," Pasierb said.

Contaminated water was about the only topic of discussion in town yesterday, said Walkersville Market owner Barry Bloomquist.

"I'm not selling individual bottles anymore. It's going out by the case," Bloomquist said.