The design of a future Purple Line station in Bethesda rests with a group of people who might never ride the proposed light-rail line: 40,000 pharmacists from across the United States.

Montgomery County planners are trying to persuade a reluctant American Society of Health-System Pharmacists to tear down and rebuild the trade group’s office building that sits atop the proposed station site near Wisconsin Avenue and Elm Street. A new building, local planners say, would allow for a more spacious station platform in a tunnel beneath it, as well as a separate tunnel that would let joggers and cyclists on the Capital Crescent Trail cross beneath busy Wisconsin Avenue. Elevators that would connect the street-level Purple Line with Metro’s underground Red Line also could be better located, planners say.

In fact, the building’s constraints on a Purple Line station are considered so critical to downtown Bethesda’s role as a transit hub and entertainment destination that county planners have recommended that the Montgomery County Council change the area’s zoning to attract redevelopment proposals. The zoning change would allow for a new building up to 250 feet — or 15 to 20 stories — high, about 10 stories taller than it is now.

“The improved station design would provide greater flexibility, a higher level of service and a better user experience,” planner Elza Hisel-McCoy said.

But a lawyer for the association, which represents pharmacists who work in hospitals and other health-care systems, says the group’s leaders aren’t in the development business and are happy with the building they have. Even so, the group has consulted with a half-dozen developers, said David Silver, a Holland & Knight lawyer.

Map of the proposed Purple Line

“They’d like to accommodate people,” Silver said, “but it has to make good sense for them.”

Silver said the group’s leaders are weighing the greater lease revenue that a bigger building would bring against the costs of moving, buying interim office space, terminating tenants’ long-term leases, demolishing the building and forgoing the lease income while it’s rebuilt. The Apex office building at 7272 Wisconsin Ave. also houses the Regal Bethesda 10 movie theater, the Food Wine & Co. restaurant and a For Eyes optical store.

Silver said the association thinks it’s unfair that under the current proposal the group would have to pay $25 million or more to build a “shell” to house a Purple Line station beneath a new building.

“We’ve been good corporate citizens, and we’re not bad guys,” Silver said. “We’re really just innocent bystanders who happen to own a building where they want to build the Purple Line.”

Hisel-McCoy said the association might require financial incentives beyond the high-density zoning. A consultant for the Montgomery planning department found that even with the financial benefits of a bigger building, the group would still need $5 million to $10 million to be made whole.

The Maryland Transit Administration, which hopes to begin construction on a $2.2 billion Purple Line in 2015, has asked the pharmacist group for a decision by the end of the year. The council is scheduled to consider the zoning change in January.

A 16-mile light-rail Purple Line would connect Montgomery and Prince George’s counties, with 21 stations between Bethesda and New Carrollton. The Bethesda station is projected to be one of the busiest. The station also would be a transfer point between the Purple and Red lines.

The Apex building was built above a rail tunnel about 25 years ago, officials said. However, the tunnel then carried a single-track freight rail line, with no need for a station.

The tunnel has always posed one of the biggest engineering challenges of a Purple Line, said Michael Madden, the state’s head of Purple Line planning. About a dozen large support columns from the building above would jut into the station platform, taking up room and impeding the flow of passengers.

The primary concern for county officials and many residents, however, has been finding a way to keep the trail within the tunnel to prevent joggers and cyclists from having to cross six-lane Wisconsin Avenue. The council rejected one $51 million plan as too expensive.

That left the current plan: a sidewalk 5 to 7 feet wide in the tunnel for pedestrians and the trail running outside it, along local streets.

In addition to keeping the trail in a tunnel, Madden said, a new Apex building would allow elevators between the Purple and Red line platforms to be more visible on Wisconsin, rather than on Elm. A ventilation system for the station also could be incorporated into a new building, rather than placed in a 90-foot-tall, townhouse-size tower in the Woodmont Avenue plaza, outside the Landmark Bethesda Row Cinema.

“It would be very nice if this happened,” Madden said. “We’re okay with the station if it does not happen, but we know we can get a better quality station if the Apex [building] is redeveloped.”

Madden said the tunnel land is owned by the county. The state won’t try to buy the building via its powers of eminent domain because it’s not necessary for the project and would be too expensive, Madden said. The station’s construction costs are expected to remain about the same, regardless of whether the Apex building is redeveloped, he said.

Council member Roger Berliner (D-Potomac-Bethesda) said the zoning proposal jibes with county growth policies to focus development around transit stations.

“If in the process of giving more density, you get a better [Purple Line] station, isn’t that a good thing?” Berliner said.

Council member Nancy Floreen (D-At Large) said the county should explore whether any other economic incentives the Apex building owners require would count toward the $110 million the county is expected to contribute toward a Purple Line’s construction.

“This could have huge benefits to a Purple Line if all these pieces fall into place,” Floreen said. “But we’re expecting a great deal from the private sector to make this happen.”