David Weinberg, vice president of Cadillac Fairview Inc., talks in millions: millions of square feet and millions of dollars. His Canadian development firm wants to build a massive commercial and residential complex in Fairfax County at Rte. 50 and the Capital Beltway, on one of the most valuable tracts of land in Fairfax.

Herbert A. Doyle Jr. is vice president of the Pine Spring Civic Association. He's worried that the proposed development, combined with a similar project by Costain Washington Inc. just north of Cadillac Fairfax's land, will turn Rte. 50 in front of his home into a 10-lane highway.

Weinberg and Doyle brought their hopes and concerns to the Fairfax County Planning Commission last week at a public hearing on rezoning applications for the area, known as the Chiles Tract. Facing Mobil Oil Corporation headquarters, the Chiles Tract encompasses 333 acres on the east side of the Beltway, with 155 acres north of Rte. 50 and 178 acres to the south. Developers have lusted after the open space for the past 15 years, but none of their ambitious proposals has made it through the planning process.

Last Thursday, the planning commission heard four hours of testimony on the proposals, but decided to defer a final recommendation until April 23. Following the planning commission recommendation, the proposal will then go to the county Board of Supervisors for a final decision.

Costain and Cadillac Fairview came to the planning hearing armed with multicolored viewgraph displays of their companion projects. They were met by savvy homeowners loaded with zoning lingo, slinging facts and figures at the developers and the planning commission.

"We have listened with an open mind to representatives of the two developers applying for the rezoning now before you," Doyle told the commission. "While there is much that we like, the overall size and resulting traffic situations lead us to ask that you deny the application."

Doyle and 14 other representatives of neighboring civic groups and the adjacent Melpar firm, a small research and development company just east of the Costain land, raised a litany of objections. They contended the twin projects would create traffic havoc, block the horizon with 15-story buildings, overcrowd their schools and promote flooding along the Holmes Run Stream that bisects both tracts.

In essence, the civic groups want the projects reduced in scale from the current combined 3.6 million square feet of commercial space, and they want firm assurances that construction would be halted if the developers did not achieve their promised goals of assuring smooth traffic flow and reducing adverse effects on the surrounding communities.

"What the citizens are really asking for is a checkpoint or phrased development so, at a certain point, development will cease if traffic strategies don't work or flooding becomes a problem," said Katherine Hanley, president of the Holmes Run Woods and Crossings Civic Association.

Officials from Cadillac Fairview and Costain have joined forces and insist they won't compromise further. They estimate the proposed development will create 6,000 new jobs, and the two firms have pooled their resources to finance an $18 million overhaul of the roads leading to the Chiles Tract, according to officials.

Those plans include construction of a Rte. 50 overpass and an in interchange of the Beltway and Rte. 50, both designed to provide access to the two sites, and the addition of at least two lanes each to the Beltway and Rte. 50 to ease traffic flow to and from the area. Those plans already have won preliminary approval from the Virginia Department of Highways, according to a letter released at the hearing.

"It's all over if we have to reduce the scale," Costain's attorney John T. Hazel said during a break in the hearing. "We've been reducing and reducing all along, and at the same time we've been reducing, transportation (road construction) costs have been increasing."

Cadillac Fairview is one of the largest real estate developers in North America. It built the Eaton Center in Toronto, the Bunker Hills development in Los Angeles and is in the midst of completing a $700 million office and commercial complex in Houston, according to Weinberg.

The firm's $300 million proposal for the southern part of the Chiles Tract, described by Cadillac attorney Martin D. Walsh as "the last prime undeveloped parcel in Fairfax County along the Beltway," would include a 1.9 million square foot office complex, a 500-room luxury hotel, a small retail center and approximately 250 town houses. Across Rte. 50 to the north, Costain is proposing 1.7 million square feet of office space, up to 50,000 squae feet of retail space and 400 residential units (town houses and condominiums), according to the zoning application.

Both developers have stressed that the high-rise office buildings and hotels would front on the main highways, that a swath of open space would be maintained along the Holmes Run Stream valley and the smaller, low-rise residential units would face existing homes that border the eastern and southern edges of the two sites.

As the hearing opened, Costain summarily rejected two requests for changes in its plans. Hazel said a request by the Fairfax County Park Authority for a donation of 10 acres for public use was "not possible in the development scheme." Then planning commissioner Rosemarie Annunziata asked Hazel if some residences could be set aside for low-and middle-income housing.

But Hazel said the costs of the proposed road improvements precluded any other concessions to the county.

"The cost of transportatio has gone so long we don't think we can specifically donate units for low-and middle-income housing," Hazel told the commission.

As the testimony from opposing civic groups progressed past midnight and the crowd thinned down the stalwarts, attention focused on the developers' plans to ensure that traffic plans could be carried out as planned. The builders' fundamental assumptions for reducing traffic flow is based on projections that car pooling and ride-sharing would slash expected trips by more than 50 percent. Opponents attacked that assumption.

"If the Pentagon can't enforce car pooling for 25 percent of its employes, who can?" asked Kevin Bell, president of the Raymondale Civic Association. "Your projection is based on voodoo analysis by a traffic consultant."

If the two proposals win approval from the planning commission and the county Board of Supervisors, the developers will have to return to the planning commission with final, detailed proposals. And citizens at last week's hearing predicted that their fight to oppose both developments is far from over.

"We could be at this for the next five years," said Hanley of the Holmes Run neighborhood. "It's hard being a citizen sometimes."