Members of the Montgomery County Planning Board, grappling with a staff proposal to severely limit Clarksburg area construction near a waterway that feeds the region’s drinking supply, said they are looking for ways to balance the right of landowners to develop with the need to protect the environment.

“I struggle with this,” said board member Casey Anderson, speaking at a Thursday night meeting. “How do you justify this when you intentionally created a market for density here? Property owners bought up additional development rights in reliance on this idea that this is where development is supposed to be.”

The Montgomery County Council last year asked the five-member planning board to take a new look at the 1994 master plan for development of Clarksburg, one of the last major undeveloped sections of the county, to see if they can protect fragile Ten Mile Creek but allow some development that has been on the books for years.

The council is trying to determine if there is a way to complete the walkable, urban community that planners had envisioned for Clarksburg Town Center in northern Montgomery and allow some nearby developments to be built, while controlling water pollution from runoff and storm water that could harm Ten Mile Creek.

A report in 2009 by county scientists, which examined sediment, runoff and the health of microscopic organisms in Ten Mile Creek, said more development could be harmful. Ten Mile Creek flows into Little Seneca Lake, a reservoir that is part of the region’s emergency water supply.

The planning board’s staff this month completed its own study, which recommended new limits on construction along Interstate 270 near Clarksburg Town Center, as well as scaling back some retail development.

The staff report, which the board began reviewing at Thursday’s session, urged the planning board and ultimately the County Council to amend the 1994 master plan for Clarksburg by restricting Pulte Homes’ plans to build 1,000 single-family houses on 538 acres west of I-270. The staff recommended allowing about 215 homes and turning much of the area into open space.

The planners proposed fewer changes to development on the east side of the highway, where Virginia-based Peterson Cos. wants to build 450,000 square feet of high-end retail, dining and housing on 100 acres. They are recommending a small reduction in the project’s footprint to limit the amount of impervious surface to help control storm-water runoff from the site. The board recently approved a mixed-use development with retail at nearby Cabin Branch.

An analysis released by Pulte a few hours before the board began its review of the Clarksburg master-plan revisions, said the down-zoning could cost Montgomery County about $13 million in lost retail spending by prospective homeowners.

“In a community like Clarksburg that is already desperate for successful retail services, it is hard to reconcile how planning staff justifies this outcome,” said Lewis Birnbaum, president of Pulte’s Mid-Atlantic division, in a statement. “There’s nothing in the staff report that addresses the realities of lost spending and lost jobs, which are absolutely essential to the vitality of Clarksburg. . . . And based on what we’ve heard from residents, there is widespread concern about making sure Clarksburg gets the chance it deserves to be the thriving community it was intended to be.”

Members of the Save Ten Mile Creek Coalition, which includes the Audubon Naturalist Society, held a rally Thursday morning at the planning board headquarters in Silver Spring to say the recommendations in the staff report don’t go far enough to protect the watershed . Environmental groups have pushed for several years for tighter restrictions in the area, where Montgomery County also had proposed a bus maintenance depot but has put those plans on hold.

Norman Dreyfuss, the only developer on the planning board, pressed the staff to provide more data about the impact of its proposed restrictions.

“To make me feel comfortable, say that there are these various things that we can do to protect Ten Mile Creek,” he said. “They can all be done, or different ones can be done, rather than saying they all have to be done. I don’t think we have enough information.”

A public hearing is scheduled for Sept. 10 at the planning board’s headquarters. The board is expected to make its recommendation to the council in October, and the council is then expected to take several months to make a decision. The board can amend the staff report or send it along as is to the County Council.

“I want to hear from the public,” said the board’s chair, Francoise Carrier, who rebuffed Dreyfuss’s efforts to revise the staff report ahead of the September hearing. “There are many people who know way more than I do about this. . . . If we water this down now, we get a different set of reactions.”