Montgomery County Council members spent roughly as much behind closed doors as they did in public Tuesday trying to sort out land-use issues surrounding Clarksburg and Ten Mile Creek.

But the three-hour joint session of the council’s planning and transportation committees ended without a vote on a proposal to cap at eight percent the amount of impervious surface that could be produced by new development. Members said there was simply too much left to discuss.

“We have hit our psychic limit,” said Council member Nancy Floreen (D-At-Large), the planning committee chair, indicating that the panels would convene again next week.

Earlier Tuesday, the full council did take a key vote on Clarksburg, approving plans for an outlet mall in the Cabin Branch neighborhood on 283 acres west of I-270 and Clarksburg Road. Last month, the council heard from retail consultants who said the project could meet the needs of Clarksburg residents without hindering the progress of Clarksburg Town Center.

The center was envisioned in the town’s 1994 master plan as the centerpiece of a walkable new urbanist community, with shops, cafes, and gathering places to promote civic life. A series of setbacks, including a sour economy and a lack of compliance by the town’s original developer, have left the site vacant.

The Cabin Branch project passed 8-to-0 with Council President Craig Rice (D-Upcounty) abstaining. Rice, who represents Clarksburg, unsuccessfully attempted to have the plan sent back to the county hearing examiner because of water quality issues.

The imperviousness measure, sponsored by Council members Roger Berliner (D-Potomac-Bethesda), Marc Elrich (D-At Large) and Hans Riemer (D-At Large) would roll back the size of two major projects proposed for land within the environmentally fragile northern Montgomery watershed: single-family homes and town homes west of I-270 near Clarksburg and a major retail development east of the highway.

Under the trio’s plan, just eight percent of developable land on either site could be impervious — meaning stormwater is not absorbed into the ground but runs off into the creek. Opponents of the projects are concerned that polluted runoff will further degrade the quality of a stream that flows into Little Seneca Reservoir , a part of the region’s emergency drinking water supply. Rice also raised questions Tuesday about the impact of the Cabin Branch development on the reservoir.

County officials have said that the available evidence suggests that any additional pollution generated by the proposed construction within the Ten Mile Creek watershed would not pose a threat to Little Seneca’s water quality. Officials said the possible impact of the proposed Cabin Branch development, which is in a different watershed, is not an issue they have studied.

The eight percent cap would raise imperviousness across the Ten Mile watershed from four percent to six percent, a level that experts view as “the upper end of the range of what the watershed may absorb without significant degradation,” Berliner, chairman of the transportation committee, said in a letter to council colleagues.

The proposal’s three sponsors represent a majority of the combined committees’ five members. Floreen also sits on the transportation committee. Council member George Leventhal (D-At Large) is a member of the planning committee

Berliner indicated Monday night that he expected the measure to be the recommendation of the joint panel. But instead of taking a vote, the committees retreated into closed session for 90 minutes, to consult with county attorneys about potential lawsuits that might result from their decisions.

Pulte Homes, which expected to construct up to 1,000 houses and town homes on its 538-acre site west of I-270, has placed the council on notice that it could face litigation. The company has asserted that proposals sharply limiting its ability to build violate the Constitution’s taking, due process and equal protection clauses.

Council members declined to discuss specifics of their private deliberations. But some indicated that they needed more time to study aspects of the trio’s proposal, which they received Monday evening.

“This is a monumentally consequential decision,” said Leventhal, explaining that he wasn’t yet prepared to say how he would vote. He added that he remained troubled by several aspects of the proposal, including the fate of a new Clarksburg fire station planned for a forested and undeveloped site within the Ten Mile Creek watershed. The station as designed would produce 37 percent imperviousness.

Berliner, Elrich and Riemer said it was important that the county “act as a model” and commit to the eight percent cap on its own property. That would mean finding another site for the fire station, a task complicated by protective land use regulations in Clarksburg. The current site took five years to secure, county officials told council members Monday.

The two developers with projects pending approval, Pulte and the Peterson Companies, both expressed disappointment Tuesday with the proposed eight percent cap.

“This is certainly not what we anticipated when we invested in Clarksburg years ago, believing in the master plan and the vision for this community, which may now never reach its potential,” said Pulte spokesman Charlie Maier.

Peterson’s proposal-- a major mixed-use project with retail, dining and possibly a hotel on a site east of I-270 near Clarksburg Town Center-- was already a difficult sell because of council members’ concerns that it would stunt the progress of nearby Clarksburg Town Center.

The company also expressed dismay with the proposed imperviousness cap. Last summer the Montgomery County Planning Board recommended that the development proceed with a 25 percent limit.

“Should the Council proceed with the proposed 8% cap, it will have significant ramifications on our ability to deliver the walkable community that was envisioned in the 1994 master plan,” Taylor Chess, Peterson’s retail division president, said in a statement.

Chess said the cap would make it impossible to bring sewer connection to relieve failing septic systems in Clarksburg’s historic district, or to help underwrite a bypass road that would take traffic from Rt. 355 around the district.