WASHINGTON (AP) — Preservationists say proposed upgrades to Washington’s Union Station could jeopardize its standing as an architectural icon.

Amtrak announced last month that it wants to spend $7 billion to double the number of trains the station can accommodate and turn it into a high-speed rail hub.

Union Station opened in 1907 and is the second-busiest train station in the country. Amtrak has not laid out how the project would be funded.

Rebecca Miller is executive director of the D.C. Preservation League, which has compiled a new report that warns about the possibility of damaging the station’s historic value. Miller tells The Washington Examiner  that Amtrak “remains vague on how exactly the proposed changes would impact the physical structure or visual appeal” of Union Station.

(Copyright 2012 by The Associated Press. All Rights Reserved.)