Plans to study the environmental impact of the proposed Potomac Yard Metrorail station will cost more than initially expected.

The Environmental Impact Statement study project -- which was projected to cost the city of Alexandria $3 million -- passed through Metro's Finance and Administration Committee on Thursday with a budget of $4.6 million.

The leap in price will better allow officials to study the potential impact on both Alexandria and the George Washington Memorial Parkway property, while also permitting the "inclusion of the National Park Service as a cooperating agency"to the study, according to an Alexandria memorandum.

The environmental study of the Potomac Yard station, which is slated for construction along the existing Blue and Yellow Lines between the Ronald Reagan Washington National Airport and Braddock Road stations, aims to review impacts of the station on community facilities, traffic, air quality and protected species and habitats and other community aspects.

The $4.6 million proposal originally passed through the Alexandria City Council in April.

Richard Baier, director of the city's Department of Transportation and Environmental Services, said he expected it to be another 15 to 18 months before the study is completed.

City officials hope the proposed station will help them develop the area into a transit-oriented, mixed-use location and better serve the 3.1-mile gap between the Reagan National airport and Braddock Road stations.

The area, which the city expects to see a 30 percent population growth in the next 30 years, is already home to numerous residential communities and a 600,000-square-foot retail center which is planning further development.

Initial estimates put the project cost around $497 million, but possible difficulties about building the station around a set of existing CSX freight tracks that lie between the Metro tracks and the Potomac Yard development may drive the price up further.

Baier said the city has already hosted public hearings about the plan, and will continue to do so before a final decision about construction is made as early as 2014.

Early projections show the station is unlikely to open before 2016.