Stimson-Bonner Mill PCB Site

April 2004 - Looking upstream on the Blackfoot River at the Bonner Mill, Bonner Dam, and Cooling Pond area. PCB originated from inside the old stud mill (yellow building).

March 2011 - Phase I construction, removal of the stud mill PCB source area and cooling pond area.

June 2014 - Reclaimed Blackfoot River and Bonner Mill area after the Bonner Dam removal and the Stimson Phase I, II, and III PCB removal actions were completed.

Please click on the tabs below for more information on the Stimson-Bonner Mill PCB Site.

The Bonner Mill Cooling Pond cleanup project is located in Bonner, Montana, along the Blackfoot River. In the early 1880s, the first logs were cut at the Bonner mill site and shipped to the mining operations in Butte. Over time, the Bonner mill site owners built and operated a “cooling pond,” which actually extended out into the Blackfoot River. In 2006, DEQ discovered contaminants (PCB) in the sediments of the cooling pond. The Department of Natural Resources & Conservation determined that because of the removal of the Bonner and Milltown dams immediately downstream from the cooling pond area, the berm of the cooling pond would fail during the next 100 year high flow flood, washing the PCBs downstream. Working with DEQ, Stimson Lumber entered into an Administrative Order of Consent in 2010 to remove the PCB contaminated areas threatening the Blackfoot River. Between September 2010 and April 2016, contaminated soils and debris was removed from the site and shipped to landills or an on-site repository; the river was restored and no-longer does a threat from PCBs exist from areas it once did. This webpage provides links to public fact sheets and updates throughout the life of the project.

August 2017- September 2017 Progress Report

July 2017- August 2017 Progress Report

June 2017- July 2017 Progress Report

May 2017- June 2017 Progress Report

March 2017- April 2017 Progress Report

February 2017- March 2017 Progress Report

January 2017- February 2017 Progress Report

December 2016- January 2017 Progress Report

October 2016- November 2016 Progress Report

September 2016- October 2016 Progress Report

August 2016-September 2016 Progress Report

July 2016-August 2016 Progress Report






Current Activities


Keith Large

Project Manager
P.O. Box 200901
Helena MT  59620-0901
(W) 406-444-6569 (C) 406-431-2253
1-800-246-8198 (in-state only)