To residents of the leafy, bucolic neighborhoods surrounding the Dalecarlia Water Treatment Plant, the idea of a daily convoy of sludge-laden trucks rattling down their streets is downright alarming.

With the public comment period ending Monday, residents in adjacent Northwest D.C. and Montgomery County neighborhoods are scrambling to change an Army Corps of Engineers plan that would use trucks to haul waste materials from a proposed water treatment tower behind Sibley Memorial Hospital. The Concerned Neighbors, a coalition of residents from both sides of the District line, has raised tens of thousands of dollars to hire experts to examine the massive six-volume draft environmental impact statement recommending the plan.

Their actions have swayed local officials, but the ultimate decision is up to the Corps. It operates the Washington Aqueduct, which collects the water from the Potomac River and treats it for the District and several communities in Northern Virginia.

"A very substantial amount of people would be affected and care," said Stuart Ross, president of the 1,700-member Palisades Citizens Association (PCA). At the group's last board and membership meetings, residents voted unanimously to have PCA join Concerned Neighbors. "We appropriated funds from our organization, and some people wrote personal checks. I think the total was $4,000 or $5,000," Ross said.

At public hearings in the District and Montgomery County, residents' chief objections to the plan have been the noise and traffic they fear the trucks would generate, according to meeting participants. The impact statement projected eight to 66 round trips a day, depending on the size of truck (10 to 20 tons) and the amount of sediment involved.

Thomas Jacobus, chief of the Washington Aqueduct, said aqueduct officials would use the largest trucks possible because it would be to their advantage to pay for fewer trips. He also reasoned that the highest estimates would apply in only the most extreme conditions.

"What the neighbors need to have in their mind is that most days, 95 percent of the time they'd see around eight trucks. Twenty trucks would be extraordinary and would be to react to an unusual, short-term climatic situation," Jacobus said.

Del. Eleanor Holmes Norton (D-D.C.), Maryland Democratic Senators Paul S. Sarbanes and Barbara A. Mikulski and Rep. Chris Van Hollen (D-Md.) together signed a letter requesting more time for the community to study the plan. District Council member Carol Schwartz (R-At Large) also wrote a letter with a similar appeal. Resolutions asking for an extension and questioning the proposal have been passed by ANC 3D and the Montgomery County Planning Board.

What precipitated the controversy is the Washington Aqueduct's attempt to meet new Environmental Protection Agency standards forbidding the release of residuals into rivers. In short, the Aqueduct isn't allowed to dump them into the Potomac anymore. To comply with the EPA regulations, the Corps agreed to evaluate alternatives and implement the best one by 2009. The draft environmental impact statement, published April 14, determined that, of 160 screened alternatives, four were appropriate. The recommended course of action calls for constructing a dewatering tower, which would remove the unwanted matter, on Dalecarlia plant land bordering the hospital. The residuals would be hauled to an undetermined site by truck. The cost of that option would be $48 million.

Community residents say they cannot effectively counter the proposal without more time before the public comment period ends and the draft is finalized. Worse, some feel that the publication of the draft signaled an almost unchangeable course of action even before the public comment period began.

"From an activist perspective, once the report is written, you're pretty far down the road," said Rachel Thompson, an ANC 3D commissioner. "We're very disappointed that we didn't see an option in that report that we could live with and that was workable."