The Washington Surburban Sanitary Commission is expected to set rates for the next fiscal year at a meeting in June -- and to approve a plan to offset the costs of expanding water and sewer facilities by charging $1,560 for each new dwelling unit getting WSSC service.

The proposal, approved by the Montgomery and Prince George's county councils, has been denounced by suburban Maryland builders. At a recent press conference, Robert L. Mitchell -- a Montgomery County builder who heads the Suburban Maryland Home Builders Association -- contended that the fee increase has little to do with residential growth and expansion of WSSC service in Montgomery and Prince George's counties.

"There is unused capacity in the present system," Mitchell charged. He said the fees attached to new homes will be used to offset debt service and rising operating costs of the existing system.

"It would be fairer for everyone, including new residents, to pay the extra 11 cents that it would cost if everyone who will be using the existing system were to pay an equal share of the extra operating money needed by WSSC," he said.

A WSSC spokesman said that the proposed hook-up increase in cost for new homes is expected to be approved, taking the current charge from $750 to $1,560. He said that the money will be used for capital expenditures, not operating funds.

In another policy matter, the suburban builders also urged the Montgomery County Council to modify the moderately priced dwelling unit program that requires subdivisions of more than 50 units to provide 15 percent of the total as MPDUs at prices controlled by a government agency.

Mitchell rapped the entire concept as mandatory and without voluntary incentives to produce affordable housing. However, he also said that the present program would be more workable if the density bonus for builders is permitted to remain at 20 percent while decreasing the 15 percent requirement on lower price units to 10 percent of total density.