The Montgomery County Council tentatively agreed Tuesday to sharp new limits on construction in Clarksburg’s Ten Mile Creek watershed, ending a contentious chapter in the long debate over where and how the town at the county’s northern edge should grow.

The straw vote of 9 to 0, which will be followed by final action within the next three weeks, follows months of scientific briefings, closed-door meetings with attorneys, and intense lobbying by real estate firms and environmental groups. It effectively rebuffs two major developers’ long-standing plans.

The Peterson Companies envisioned a retail and hotel project on 100 acres east of Interstate 270, near the site of the planned Clarksburg Town Center. Pulte Homes sought approval for about 800 single-family houses and townhouses on 538 acres west of the interstate.

The council’s action, which amends Clarksburg’s 1994 long-term land-use plan, aligns members with environmental advocates who contended that polluted storm runoff from major new development imperiled the health of Ten Mile — one of the county’s last clean, biologically robust streams. It is one of several that empty into Little Seneca Reservoir, part of the region’s emergency water supply.

Council members said they were not attempting to pick economic winners and losers.

“We’re not taking sides here,” said council member Nancy Floreen (D-At Large), head of the council’s planning committee. “I think we were justified in what we did. The science was very clear about what we did.”

The council’s decision will not completely forbid construction, but it makes deep reductions in the amount of roads, parking lots and other impervious surfaces each project can produce. Pulte is limited to six percent imperviousness, about a 50 percent less than what was proposed. Depending on how homes are clustered, it would allow up to about 500 units of housing.

Peterson and the owner of an adjacent site had originally sought 35 percent for impervious surfaces but will be limited to 15 percent. County planners said the company can still build under the cap, using up to five acres for a hotel or other project. The rest of the land available for construction could accommodate a limited number of homes.

But Peterson officials said last week that unless the council lifted the impervious cap to at least 25 percent, they would likely walk away from the site.

Pulte, which has delivered several public threats to sue the county for limiting its ability to build on the land, expressed disappointment in Tuesday’s outcome.

“The council’s decision, obviously influenced by outside interests, is frustrating and very discouraging,” Pulte Mid-Atlantic President Lewis Birnbaum said in a statement. “It sends a confusing message to established businesses like ours that play by the rules and expect fair treatment in return.”

Many council members were swayed by three key pieces of scientific and economic analysis. A marketing study, commissioned by the Montgomery Planning Board late last year, concluded that there was room in the Clarksburg area for only one major shopping development. With zoning and other regulatory approvals in place for a major outlet center in the nearby Cabin Branch community, council members decided that allowing Peterson to go forward would create an unnecessary glut. It could also further inhibit the evolution of Clarksburg Town Center.

Matthew Baker, an environmental scientist at the University of Maryland, told the council on Feb. 11 that streams in excellent health, such as Ten Mile, are especially sensitive to even tiny environmental changes. By the same token, portions of the watershed already somewhat degraded by construction can more easily absorb more development.

Lowering imperviousness on the Pulte Homes site to six percent would enhance the protection of some of the watershed’s cleanest stream segments, Baker said. A higher cap of 15 percent on the Peterson site was permissible because it was near water already significantly polluted by construction.

The council also heard from hydrologists who refuted developers’ contentions that state-of-the-art environmental site protection could safeguard the watershed.

The one dissenting voice was that of Council President Craig Rice (D-Upcounty), whose district includes Clarksburg. Rice said that the council’s decision on the Peterson project sold short Clarksburg residents looking for more economic development in their community.

“How did their voices get lost in this whole discussion?” Rice asked. He also expressed resentment at being what he called “mischaracterized and demonized” as a tool of developers by opponents of new construction.

He joined the council’s unanimous vote, he said, because there were still “a lot of good things” in the amendments.

Tuesday’s action does not resolve all of the long-term questions surrounding Clarksburg. Now a town of 40,000, it was envisioned in its 1994 master plan as a shining exemplar of new urbanism. More than another generic exurban housing development, Clarksburg was supposed to be a town where residents lived side-by-side in city-style density.

Residents were to be able to walk to a Town Center that served as a community hub, with shopping, a library, a post office, open-air cafes and other amenities.

The density emerged, but much of the original vision still exists only on paper. Light-rail transit, a high-tech employment center, and improvements to Route 355 and other key roads have not come to pass. And for years, the town’s historic district has languished with failing septic systems.

In 2004, some residents discovered that houses and townhouses were built too high or too close to roads. The developer, Newland Communities, planned a retail core that looked more like an ordinary commercial strip, not the heart of an urban village.

A sour economy intervened, leaving the acreage set aside for Town Center vacant. After hearings, mediation, arbitration and lawsuits, Newland bailed in 2011, selling its interest to Elm Street Development of McLean for $1. The company is expected to unveil its plans for Town Center in the spring.