Tough new interim regulations governing development along the environmentally sensitive Chesapeake Bay, its rivers and tributaries have developers in tidewater counties scurrying back to their drafting boards or withdrawing building proposals rather than complying, according to planning officials in several Maryland counties.

In Baltimore County, the Birchwood and the Beachwood, two planned mobile home communities adjacent to one of the area's major coastal rivers, were scaled back from their original proposals to conform to interim guidelines set by the 1984 Maryland General Assembly and the Chesapeake Bay Commission.

"One went from 126 to 100 units and the other from 300 to 200 before being granted approval," said Andrea Van Arsdale, critical areas specialist for Baltimore County's planning department. "Generally, we are seeing projects lose about one-third of their units before passing the environmental review."

Until final regulations are drafted during the 1986 legislative session, local planning and approving agencies are required to scrutinize all development plans within 1,000 feet of the shoreline and inland riverways -- the so-called Critical Areas -- and to minimize adverse effects on water quality, plant and wildlife habitats.

"Under the interim procedures, projects in the pipeline from March of 1984 became subject to the Critical Areas legislation, so we've been applying the environmental guidelines retroactively," Van Arsdale said.

Baltimore County has chosen to use "variable guidelines," which means there are no hard-and-fast rules and each development must be considered independently.

"We have a general 300-foot setback requirement from the shore or tidal wetlands -- although we have made that buffer more or less in individual cases. And each project must submit an environmental impact statement," Van Arsdale said.

In St. Mary's County, two projects along the water have been withdrawn "because the applicant didn't want to comply with the environmental restrictions," county planner Robin Guyther said.

One was a town-house development on the bay for 300 units, Guyther said. In the other, the developer of a community designed with single-family homes and town houses, called Eagle's Nest, said he planned to straddle a number of steep slopes and ravines but chose "not to pursue the project when he saw what would be necessary to gain approval."

In contrast, Guyther said the developer of Shannon Farms, a 750-unit mixed residential community proposed for a site just south of the Patuxent Naval Air Station, agreed to a 200-foot setback, left 50 percent of the land open and did a "very thorough wildlife inventory." The effort evidently has paid off, because the project now goes before the county commissioners for a final say, bolstered by a favorable recommendation from county planners.

Guyther said Patuxent River Farms, a 498-unit development with a hotel, conference center and marina, was approved before the Chesapeake legislation went into effect. But in more than two years the development has not proceeded beyond the site-plan stage because of opposition from local environmental groups. Earlier this year, the Maryland Court of Special Appeals upheld the St. Mary's zoning authority, and the "state's highest court hasn't decided whether to hear the case," Guyther said.

In Charles County, a massive waterfront community planned by U.S. Steel Corp. for 695 acres on Swan Point is back on the drawing board. A report from the county planning and zoning commission's technical staff recommended that the project be rejected unless developers could provide a detailed plan to protect sensitive wetlands and important fish and oyster breeding areas and create a minimum 100-foot shoreline buffer.

Local officials say the Swan Point development is "precedent-setting" for Charles County and the most important case to come before zoning authorities since the Critical Areas legislation was passed.

"We recognize that this area will be developed eventually and that this is phase two of a project, but many things just were not addressed," one planning and zoning commission worker said. "For us, this is a landmark case, and their analysis fell far short of what's necessary. It was an incomplete and rather inaccurate sort of analysis. . . . Basically, they've been sent back to the drawing board."

Despite the negative review, a U.S. Steel representative said the company remains "extremely enthusiastic" about the luxury waterfront project, which is modeled after Hilton Head Island and similar luxury developments in the Carolinas.

"We have no intention of throwing in the towel," said Gus Tremer, spokesman for U.S. Steel's realty division. "We want to do whatever is necessary to mitigate the environmental concerns." In fact, representatives for the developers sat down with planning and zoning officials just days after the unfavorable technical staff study came out to begin a point-by-point dissection of the report.

Impervious but highly erodable soils characterize much of the land slated for town houses, single-family homes, tennis courts, club houses and parking lots and are a major concern under the Critical Areas guidelines. The report says that runoff from construction and other erosion will silt and clog already sensitive areas of the Weir and Cuckold creeks that feed Potomac breeding areas for oysters, finfish and softshell crabs.

To reduce runoff, only 15 percent of the entire site should be located on impervious soils, the report says. It also suggests that U.S. Steel substantially reduce housing densities along the coast by clustering houses toward the center of the development, and it asks developers to submit a detailed storm-water management plan and a proposal to landscape -- and thus stabilize -- the shoreline if U.S. Steel wants zoning approval.

The development group also was asked to dedicate property for a school to the board of education to accommodate the estimated 1,567 children projected to arrive with the new luxury homes.

Another controversial Charles County development plan to put several 37-story high rises on 23 acres in the Town of Indian Head also falls under Critical Areas guidelines.

The county now has few buildings that exceed five stories. But "the central issue is whether that many units -- 790 -- is feasible for the proposed area," one county official said.

Planning officials in Anne Arundel and Calvert counties say they have not seen any rush by developers to "beat the clock" or sneak in under the wire before the Critical Areas regulations are finalized.

"We are experiencing a countywide building boom that has more to do with low interest rates than impending environmental regulations," said Florence Beck Kurdle, planning officer for Anne Arundel County.

In Anne Arundel, a county where there's a mile of waterfront property for every one of its 416 square miles, planners are getting one or two project proposals a week that come under provisions of the Critical Areas legislation. "We routinely give subdivision developers a checklist: They must tell us about slopes, plans for storm-water management and tell us their plans to ensure water quality, plants and wildlife," Kurdle said.

"Nearly everyone has to come back a second or third time with more information, and many subdivisions are having to reduce the number of units," she said.

"The five-acre zoning limits we have in most of Calvert fit in with the current Critical Areas criteria," said Frank A. Jaklitsch, director of planning and zoning for Calvert County. "Because of strict local controls, we've had very little trouble administering the environmental regulations, and they've not been much hindrance to local developers."

A Holiday Inn planned for Solomon's Island is the biggest project in Calvert to fall under the new regulations, and the hotel firm "did a very thorough environmental impact analysis of the site," Jaklitsch said.

But he worries that finalized regulations now in draft form before the Chesapeake Bay Critical Areas Commission may undo much of what the county has worked for.

"The new proposals would allow a 100 percent increase in intensely developed areas -- those less than one-quarter acre. If that goes through, we'll be under intense pressure to develop our waterfront," he said.