SAVANNAH — The federal agency seeking to deepen the Savannah harbor sent letters to Vice President Joe Biden, House Speaker John Boehner and eight other Washington lawmakers saying the $652 million project should be allowed to bypass environmental review by South Carolina, which shares the Savannah River with Georgia.

The letters from the Army Corps of Engineers were disclosed in filings Thursday in U.S. District Court. The Corps wants to deepen more than 30 miles of the river from 42 feet to 47 feet to give supersized cargo ships room to reach the Port of Savannah.

The federal government gave final approval to the project in October and the Corps wants to begin construction in 2013. However, the federal Clean Water Act typically requires environmental permits from affected states.

Georgia granted one last year, but efforts to obtain approval in South Carolina are tied up in state and federal courts. In some cases, the law allows the Corps to bypass state permitting for projects specifically authorized by Congress that have undergone appropriate environmental studies.

Jo-Ellen Darcy, assistant Army secretary for civil works, said in the letters to 10 House and Senate leaders, including Biden in his capacity as the Senate’s presiding officer, that the Savannah harbor deepening qualifies for such an exemption because Congress conditionally authorized the project in 1999. Darcy said an exemption is needed “in order to prevent inappropriate delays to this project due to pending litigation.”

Her letters urged that Congress should consent to the exemption by going ahead and funding construction. A federal judge presiding over one of the South Carolina lawsuits had ordered the Corps to disclose the correspondence.

Opponents, meanwhile, are sending responses telling members of Congress the project, which would scoop 5 feet of sand and muck from more than 30 miles of the Savannah River, is too massive to allow the Corps to bypass state environmental agencies.

The Southern Environmental Law Center sent a letter Wednesday to Sen. Barbara Boxer, the California Democrat who chairs the Senate Committee on Environment and Public Works, and members of South Carolina’s congressional delegation. The center has filed a federal lawsuit in South Carolina on behalf of several conservation groups who say the dredging would cause irreparable environmental harm.

“Exempting projects from the Clean Water Act is a rare and extraordinary action,” law center attorney Blan Holman wrote, “and the Corps’ request is an affront to South Carolina.”

Holman said Wednesday he planned to forward copies to other lawmakers who got letters from the Corps. He argued the Corps failed to meet the Clean Water Act’s requirements for bypassing state permits.

Georgia has been seeking to deepen the waterway connecting the Atlantic Ocean to the Port of Savannah, the nation’s fourth busiest container port, since the 1990s. South Carolina operates a competing seaport in Charleston.