ASHLAND - Northern States Power Co.-Wisconsin has agreed to clean up the on-land portion of a contaminated site along the Lake Superior shore in Ashland.NSP-Wisconsin, the U.S. Department of Justice, the U.S. Environmental Protection Agency and the Wisconsin Department of Natural Resources announced the settlement Wednesday.Under the agreement, NSP-Wisconsin will fund the on-land cleanup, expected to cost $40 million. Work could begin later this year and is expected to take two to three years.The 40-acre lakefront site is on Chequamegon Bay. A predecessor company to NSP-Wisconsin operated a manufactured gas plant at the site between 1885 and 1947.Sawmills, railroads and a city wastewater treatment plant also have used the site over the past century.Cleanup of contaminated sediment still has to be determined.