Portions of two major east metro highways will be closed for all or part of this weekend as Minnesota Department of Transportation crews work on the new Hwy. 61 bridge in Hastings and inspect the Lafayette Bridge in St. Paul.

Meanwhile, a portion of the Hiawatha light-rail line in downtown Minneapolis will be closed for maintenance and construction.

The northbound and southbound lanes of Hwy. 61 will be closed at the Mississippi River to allow crews to float the main span of the new $120 million four-lane bridge into place. The closure will last for 72 hours, beginning at 6 a.m. Saturday and reopening late Monday. The Mississippi River also will be closed to water traffic between the bridge and Lock and Dam No. 2 while the work is underway, MnDOT said.

Motorists will be detoured via Interstate 494 and Hwys. 52 and 55.

In St. Paul, the southbound lanes of Hwy. 52 from W. 7th Street and Interstate 94 to Concord Boulevard will be shut down from 7:30 a.m. to about 8 p.m. Saturday to allow crews to inspect the bridge. Northbound lanes will remain open, but the exit ramp to eastbound I-94, which is under construction, will remain closed until Oct. 8. The posted detour is via southbound Hwy. 61 to I-494, then north on 52 to Concord Boulevard, also known as Hwy. 156.

The ramp from E. 7th Street leading to southbound I-35E will close at 7 p.m. Friday to allow for reconstruction of bus shoulders. It is scheduled to reopen at 5 a.m. Monday, MnDOT said.

Light-rail trains will not run between Target Field and the Franklin Avenue stations starting at 6:30 p.m. Friday to allow crews to begin maintenance work and construction. The work is expected to be complete by 3:30 a.m. Sunday, well before the Vikings game against the San Francisco 49ers at the Metrodome, spokesman John Siqveland said. During the shutdown, buses will run between the stops. Trains will operate as normal along the rest of the 12-mile line.

In Bloomington, crews will begin putting down fresh asphalt on ramps to and from southbound I-35W and Cliff Road at 6 a.m. Saturday; they are expected to finish by 6 p.m. Cliff Road in both directions from Dupont Avenue and I-35, as well as access to three businesses, will be closed.

Tim Harlow • 651-925-5039 Twitter: @timstrib