Montgomery County Executive Charles W. Gilchrist said yesterday he will go ahead with planning for a new $60 million sewage treatment plant in affluent Potomac as a long-range solution to a sewer crisis that threatens to halt development.

In a lengthy "plan of action," Gilchrist also reiterated the county's request for a share of the sewer capacity in existing Prince George's treatment plants as a temporary means of preventing a new moratorium on housing and commercial construction in Montgomery.

Gilchrist's action, coupled with a request from Prince George's County Executive Lawrence J. Hogan for a meeting of officials of the two counties on sewer matters, were the first signs in months that the so-called sewer feud or war between Montgomery and Prince George's may be abating. *tThe meeting has not yet been scheduled, but is expected to take place within two weeks, according to knowledgeable sources.

"If something isn't worked out by then -- some new (sewage) capacity for Montgomery -- there really will be a resumption of the sewer war," said David Scotton, a Montgomery commissioner on the bicounty Washington Suburban Sanitary Commission, which provides sewer and water service to Washington's Maryland suburbs.

Gilchrist warned that Montgomery will be "obligated" to sue Prince George's for a share of the treatment plant if the negotiations fail.

The latest developments in the longstanding dispute over allocation of sewage treatment capacity were prompted by the latest WSSC calculations that Montgomery has exhausted its share of capacity at the Blue Plains regional sewage plant in the District of Columbia'

The same calculations showed that Prince George's has enough unused treatment capacity to permit construction of 100,000 new homes even though the county's population is expected to grow by only 75,000 in the next 15 years.

Montgomery's and Prince George's share of the Blue Plains treatment capacity is determined by a bicounty agreement that could be altered at any time.

Prince George's, anxious for a share of the expensive housing construction that has tended to go to Montgomery, has been unwilling until now to renegotiate the agreement.

Yesterday, in a letter to the WSSC, Hogan urged the commission to "vigorously pursue" bicounty bargaining "with the aim being an acceptable amendment to the existing agreement." *tRobert Wilson, Montgomery's chief administrative officer, who is in charge of the county's bargaining, said he considered Hogan's statements encouraging.

Meanwhile, Gilchrist announced that his government will "aggressively" attempt to reclaim millions of gallons of treatment capacity committed to builders who have shown no intention of using it. He also will try to borrow Rockville's unused share of Blue Plains capacity, at least on a temporary basis, to head off a new construction moratorium.

Hogan said in his memo that a "must" in the longterm solution is the "phased construction of a sewage treatment plant in Montgomery County on a timetable acceptable to both counties."

By proceeding with preliminary plans for the plant at Brickyard and Persimmon Tree roads in Potomac, Gilchrist hs demonstrated a willingness to pursue that course. He also made it clear that "all solutions pursued would not necessarily need to be implemented."

"Experience dictates that several alternative solutions must be available to Montgomery County since the availability of sewerage service can change so rapidly," Gilchrist said.