AIR FORCE ACADEMY, Colo. — The landmark Cadet Chapel at the Air Force Academy will close for up to four years starting next summer for major restoration work.

The academy said Wednesday the project includes replacing the 53-year-old chapel's aluminum skin, removing and cleaning 24,000 stained-glass tiles, stiffening the steel superstructure and adding a water barrier.

The restoration is expected to cost between $58 million and $68 million.

The academy says the chapel has leaked since it was built and previous repairs failed.

Officials say they will arrange alternative sites for all the faiths that use the chapel.

The chapel, a National Historic Landmark, is a striking, triangular-shaped structure that stands 150 feet tall.

The principal architect was Walter A. Netsch Jr. of Chicago. It cost $3.5 million to build.