Work aims to keep pollution out of Idaho, Washington water Posted: Feb 25, 2018 10:35 AM PSTUpdated: Feb 25, 2018 10:35 AM PST Jesse Tinsley / The Spokesman-Review SPOKANE, Wash. - Motorists traveling through northern Idaho's Silver Valley will see the signs of a $48 million federal project to keep heavy metals out of the Coeur d'Alene River's South Fork. The Spokesman-Review reports the work to trap and divert polluted groundwater to a wastewater treatment plant gets underway this spring and will continue through 2021. Ditches will be dug as contractors install an 8,000-foot-long underground clay barrier so the polluted water can be piped to the treatment plant. The work will at times leave large dirt piles next to the freeway. It's all part of an effort to get cleaner water in the South Fork and Lake Coeur d'Alene as well as the Spokane River in Washington state. Groundwater in the region becomes polluted as it percolates through historic mine waste in the Silver Valley, picking up lead, arsenic, cadmium and zinc.