The first phase of a planning effort to extend the Aspen/Pitkin County Airport runway is likely to be wrapped up in August, when the Pitkin County commissioners will be asked to choose between lengthening the runway anywhere from 500 to 1,000 feet.

The next phase will include a formal environmental assessment of the proposed expansion by the Federal Aviation Administration, which will, among other things, compare and contrast the length options.

The runway expansion would widen the window for crowded commercial flights to take off on hot summer days from Aspen’s airport, as the combination of the plane’s weight, high temperatures, the mountainous altitude and current runway length frequently limits current airline operations. A longer runway would allow planes to take off on summer afternoons with more people and more fuel aboard, allowing airlines to schedule longer direct flights.

The extension would also increase the margin of safety for planes landing in Aspen.

On Tuesday, a group of consultants and Federal Aviation Administration officials helped airport director Jim Elwood brief the commissioners on the status of the expansion project. Paul Dunholter, an airport noise consultant with Bridgenet International, presented the results of a recently completed noise study.

If the runway is extended 1,000 feet toward Buttermilk Mountain, there will be an increase in the amount of noise heard at various locations just upvalley from the airport, and especially at the seasonal Burlingame housing project across Highway 82 from the upper end of the airport property.

Dunholter explained that, in general, it takes an increase of 3 decibels for humans to perceive an increase in a noise.

If the runway was lengthened by 1,000 feet, planes would begin their run down the runway closer to the seasonal Burlingame housing, closer to Buttermilk and closer to the homes in the West Buttermilk neighborhood.

The seasonal housing would likely see an increase of 4 to 6 decibels when it came to the CRJ-700 commercial jet now in service at the airport and an increase of 6 decibels when it came to the noisiest private planes now in use at the airport, Stage II aircraft. The noise level in several locations in the West Buttermilk neighborhood would increase by 2 to 4 decibels.

“Some people may notice it, some won’t,” Dunholter said of the increase.

Dunholter also pointed out that the number of noisy Stage II aircraft operations continue to diminish as older planes such as the Gulfstream II and III models are being phased out of corporate jet fleets. In 2004, Dunholter said there were 661 Gulfstream II and III flights out of Aspen. By 2007, the number had dropped to 360 and is expected to drop by half again in three years. One reason the planes are being phased out is that they are fuel inefficient.

With the runway extension, the noise level could actually drop in some locations around the airport, such as the North Forty neighborhood because the longer runway would allow planes to lift up off the ground sooner than they do today.

Landscape architect Shannon Murphy presented a series of drawings that showed how a variety of elements at the upper end of the runway would be affected by extending the runway by 500, 600, 800 or 1,000 feet. The longer the extension, the more impact there will be on wetlands, the Owl Creek bike path, the airport service road that wraps around the end of the runway, water wells in the area and a sage meadow.

On the other hand, Murphy said there is very little difference in how the end of the runway area would appear visually, although a 1,000-foot extension would place the end of the runway that much closer to Highway 82.

The county is not considering extending the runway past 1,000 feet because of the constraints of the state highway.

A citizen’s advisory committee that has been meeting periodically about the runway expansion is going to meet again in August and then the commissioners will be asked to decide the runway options for the environmental process to review, Elwood said.

FAA officials in Denver will be responsible for the environmental document and subsequent decision. The FAA recently approved a grant of $365,000 to help fund the runway extension environmental study and expects to fund most of the cost of the extension.

bgs@aspendailynews.com