The commissioners first floated a debt-forgiveness proposal last year, drawing skepticism from lawmakers who said forgiving the debt would set a dangerous precedent in the state.
Even after the commissioners cut their request in half last week, several lawmakers said it seemed to be a longshot bid.
Banks said his agency, which administers water and sewer loans, cannot consider forgiving the debt.
"That pretty much verifies what we suspected," said Del. D. Bruce Poole, D-Washington.
Washington County Administrator Rodney M. Shoop said the county will continue its push to have the debt forgiven, despite the agency's stance.
"We don't see that as a roadblock," Shoop said.
He said there ways of getting the debt relieved other than through the state agency, most likely with the help the county's delegation in the General Assembly.
"We know who writes the law," Shoop said.
But some lawmakers believe the county's best answers might be at home. Poole suggested the county work on its marketing effort and other strategies to attract new water and sewer customers.
Del. Robert A. McKee, R-Washington, said continuing work between the county and the city of Hagerstown, which has its own water and sewer system, can only help the situation.
"That's one of the things I think the delegation wants to see - a general level of cooperation between the city and county," McKee said.