By Lynne Adkins

PHILADELPHIA (CBS) - The 17-story U.S. Custom House in Philadelphia has been under construction for years, but the project is nearly complete.

The massive building at 2nd and Chestnut streets has been undergoing a major renovation since spring of 2010. The $30.8 million project should be complete by the end of this summer.

Gina Gilliam, spokeswoman for the U.S General Services Administration, says once the scaffolding comes down, the building will be more energy-efficient with upgraded lighting fixtures, high-efficiency boilers and 1,200 new windows.

“The project will also include the installation of a 4th floor green roof, the second largest green roof in the Philadelphia area.”

The Custom House which was built in the 1930′s takes up an entire city block and currently houses federal offices for the FDA, Passport and customs services.