2023 Simplot Slurry Spill in Caribou-Targhee National Forest
In 2023, the J.R. Simplot Company (Simplot) estimated 1000-1500 cubic yards of phosphate ore slurry (powdered ore mixed with water) leaked into Caribou-Targhee National Forest (CTNF) from a pipeline connecting the Smoky Canyon Mine (near the ID/WY border) to the Don Plant in Pocatello. Idaho government agencies kept it quiet.
In September 2023, while moving cattle within their CTNF grazing allotments, the Rassmussen Ranch-owner's son encountered a large quantity of dark substance in a dry creek bed. The Rasmussens reported their discovery only to learn that the U.S. Forest Service (USFS) was aware of the May 2023 spill as reported by Simplot. The Rasmussens expressed frustration with not being informed because they could have diverted their cattle away from the spill area.
On May 2, 2025, the Rasmussens filed a $280M lawsuit against: Simplot; the Idaho State Department of Agriculture (ISDA—which oversees the USFS/CTNF district); the Idaho Department of Environmental Quality (IDEQ); and the U.S. Environmental Protection Agency (EPA).
The now-closed lawsuit sought damages for alleged toxic contamination of Rasmussen cattle characterized in a 212-page complaint as “nothing short of an ecological disaster.”
On July 29, 2025, a legal “Notice of Voluntary Dismissal” was filed by both parties, quietly ending the entire case on July 30, 2025.
With the Rasmussen case closed, no judge or jury will decide the merits of all the evidence. We are left to simply trust that public interests were protected over conflicting interests. Unfortunately, the lawsuit raises many unanswered questions.
--Why was the slurry spill kept largely quiet from the public awareness? There was only one notice created by the USDA/USFS, dated October 2023, however the agency has responded through a public record request, they are unable to confirm it was posted on their public information page on their Caribou-Targhee webpage.
--Why did the regulatory agencies rely almost entirely upon Simplot to conduct its own investigation and report findings (including submissions with missing data)? What (if any) independent verification has taken place?
--Why did Idaho officials believe the initial Simplot 5-gallon leak estimate (later revised and significantly increased)? Simplot slurry is transported via a closely monitored pipeline requiring extreme pressure which cannot be shut down for long periods. The smallest of leak would produce a sizeable amount of material very quickly.
--Why did the USFS and/or IDEQ fail to calculate their own spill estimate using available inputs? [i.e., diameter of pipe (8-inch), PSI (1500 psi), the reported quarter sized hole, slurry density, etc.]?
--Did the USFS/CTNF investigate the pipe breach in May 2023? If not, why?
--Despite snowpack and remoteness, why did the USFS/CTNF fail to verify the quantity of the spill and take timely action to mitigate/slow the spread of the phosphate ore slurry, ultimately allowing material to spread approximately 2.4 miles across public forest land and into waterways?
The public deserves honest answers.