The Montgomery County Planning Board has rebuffed widely varying alternatives proposed for the Belward Farm in Gaithersburg, forging ahead under a blueprint that would allow up to 4.5 million square feet of buildings up to 143 feet high.

The 107-acre farm off Darnestown and Muddy Branch roads is the largest undeveloped parcel in and around the Shady Grove Life Sciences Center. It is a lynchpin in a widely hailed vision to turn the 900-acre area into a live-work research hub with 20 million square feet of laboratory, office and commercial space that will support 60,000 jobs over the next 30 and 40 years.

County planners must first draft the Gaithersburg West master plan to lay the groundwork for transit, density, roadways, congestion and other infrastructural needs.

The alternatives floated at Planning Board sessions on Gaithersburg West on Thursday and Monday — proposed by Johns Hopkins University, which owns Belward, and two civic groups created by residents living around the farm — differed by more than 4 million square feet.

Hopkins has been a leading catalyst behind talk of transforming the Life Sciences Center. As part of that plan, Hopkins wanted as much as 6.5 million square feet of development on Belward to create a research campus with enough "critical mass" to draw federal health and scientific research agencies.

The extra transit trips that much development would generate would make federal transit officials more likely to approve funding for the Corridor Cities Transitway, a proposed mass transit line that would form the backbone of Gaithersburg West, Hopkins officials said. And because federal agencies plan in broad, far-reaching time horizons, small projects will not make the cut, said David McDonough, senior director of development oversight in Hopkins's real estate division.

"It makes us more competitive. Size matters," he told planners Monday night. "… If you want to have their interest, then you need to have a plan that entices them."

But the Planning Board was unconvinced.

Multi-decade horizons are too murky, said Commissioner Jean Cryor, while the CCT argument is not the salient issue.

"It's going to come or it's not going to come. It's going to be a political decision, no matter what anyone wants to say," she said. "It's going to take the muscle that you have and everybody else has to make it happen. If [we] think it's just going to be on numbers, we're just kidding ourselves."

An alternative proposed by Residents for Reasonable Development, a civic group made up largely of residents from Belward's surrounding neighborhoods, called for no more than 2 million square feet of construction. They also want the CCT to go north up Great Seneca Highway, not across Belward to get to Muddy Branch Road.

The group suffered nearly as deflating a fate: Commissioners dismissed the notion of minimizing development at Belward by giving Hopkins "transferable development rights" to boost development at Hopkins's existing county campus, and picked apart the group's traffic projections.

"It makes little sense to have several transit stops in an area that isn't going to have the density to make the transit system cost-effective," said Planning Board Chairman Royce Hanson. "Certainly, we won't get any federal aid for that."

After parsing details for nearly six hours over the two sessions, the planners told staff to move forward with the 4.5 million square feet and 143-foot-tall buildings. Even that, several board members said, is not guarantee to work.

"The staff recommendation alone is going to be a struggle," said Commissioner John Robinson.

The Planning Board has had to resign itself to leave the realignment of the CCT through the Life Sciences Center unsettled in the master plan that it transmits to the County Executive this summer before County Council hearings and final OK by the end of the year.

State transit officials will not complete their study on the impact of realigning the CCT until late summer or early fall. Planning staff have not modeled a version of Gaithersburg West that does not realign the CCT. WHAT'S NEXT

The County Planning Board has two more work sessions scheduled for the Gaithersburg West master plan: May 28 and June 11, times to be announced. The board's headquarters are at 8787 Georgia Ave. in Silver Spring. The sessions can be seen live and in recording by following the links on www.montgomeryplanningboard.org.