The South Dakota Department of Transportation will be closing down a portion of Interstate 90 for approximately two hours beginning at 2 p.m. this afternoon.

Northwestern Public Service will be installing a new transmission power line over the interstate at approximately milepost 309 near Plankinton.

Traffic will be taken on and off the interstate at Exits 308 and 309 and routed through Plankinton.  Northwestern Public Service expects the installation could take up to two hours.