Guest Columnist Heather Disselkoen: Idaho Gov’t Agencies Stayed Quiet on 2023 Simplot Slurry Spill in Caribou-Targhee National Forest

The 2023-2025 events came to light through a $280M lawsuit filed by the Rasmussens, a ranching family, against: Simplot; the Idaho State Department of Agriculture (ISDA); Idaho Department of Environmental Quality (IDEQ); and the U.S. Environmental Protection Agency (EPA). This now-closed federal lawsuit (voluntarily dismissed by the parties) sought damages for alleged toxic contamination of Rasmussen cattle characterized in a 212-page complaint as “nothing short of an ecological disaster” in the Caribou-Targhee National Forest (CTNF). The following is information gathered from the 05/02/25 court complaint, exhibit documents, and related IDEQ public record documents. See Pocatello for the Accountable Government Entities’ webpage for the full court document and pictures at: http://www.pagefiles.org/spill.

In southeast Idaho, near the Wyoming border, Simplot operates the Smoky Canyon Mine (established in the mid-1980s). This mine refines phosphate ore, supplying approximately 1.7 million tons of phosphate ore slurry annually to the Pocatello Don Plant. The plant produces phosphate fertilizer, feed phosphates and industrial products. The slurry is transported 86 miles via an 8-inch underground pipeline, which crosses through the CTNF.

The historic Rasmussen Ranch has raised cattle and been in continuous operation in Idaho for over 154 years, spanning seven generations with one of the oldest brands recorded in Idaho (before Idaho statehood in 1890). It utilizes approximately 4,000 acres of CTNF on four grazing allotments plus the Rasmussens’ 700 private acres and 640 state-leased acres.

In May 2023, Simplot discovered an approximate “5-gallon” pipeline leak of phosphate ore slurry in the Caribou-Targhee National Forest and reported it to the U.S. Forest Service (USFS/CTNF). Later that summer, that spill volume was revised to an estimated 1,000 to 1,500 cubic yards.

A second leak occurred and was immediately repaired when Simplot workers accidentally breached the pipeline during excavation in July 2023 to replace 4,000 feet of pipe.

On 09/11/23, Rasmussen Ranch workers encountered a large quantity of dark substance in a dry creek bed while moving cattle. According to the court complaint, phosphate ore slurry had leaked and flowed 2.4 miles down the Hornet Canyon Creek drainage, aided by spring runoff, thereby contaminating both natural forage and water sources. The area of concern was in Unit 2 of the four (4) Rasmussen grazing allotments in the CTNF and is an area that “… includes a mountain stream ‘Hornet Creek’ which drops down a canyon from a high mountain ridge and feeds into a year-round waterway, Diamond Creek and its associated wetlands and riparian areas.” The Rasmussens reported their discovery only to learn that the U.S. Forest Service (USFS) had been aware of the May 2023 spill as reported by Simplot. An exhibit document indicates the Rasmussens expressed frustration with not being notified, since they asserted their cattle could have been redirected to avoid the leaked slurry.

Court filings indicate in October 2023, five months after the spill, Simplot and the USFS “…issued public notices about the slurry line leak with information about the incident as well as the current status of the ongoing issue.” Through a public record request I submitted, CTNF was unable to confirm the 10/04/23 USFS notice was posted on their website’s public information page. Public record requests to IDEQ, CTNF and the Governor’s Office for press releases about the slurry line leak yielded no records.

That same month, Simplot conducted cleanup and removal of slurry material on the lower half mile of Hornet Canyon and deployed sediment controls into Hornet Canyon Creek just above the confluence with Diamond Creek.”

From the information available, Simplot worked with the various Idaho agencies to try to clean up the spill to the extent possible. The spill ultimately resulted in two Notices of Non-Compliance (NONC) being issued to Simplot. One by CTNF dated 09/01/23 and the second by IDEQ, dated 03/26/24, for “illegal unpermitted discharge to waters of the US under the CWA section 301.” (Exhibit 26). Neither of these notices were publicly posted. And, when the U.S. Forest Service (USFS) issued a Facebook notice on 04/15/24 stating Simplot was approved to conduct replacement and maintenance operations to a slurry line within the forest, resulting in temporary road closures, the public notice made no mention of the spill contributing to this maintenance.

After two years of ongoing efforts to reach a resolution, the Rasmussens filed a formal $280M complaint/lawsuit on 05/02/25 against Simplot and the ISDA (which is over the CTNF), IDEQ and the federal EPA, seeking damages for alleged toxic contamination of their cattle caused by this major phosphate ore slurry spill. According to the court filing, “… virtually all the Rasmussen’s cattle exposed to the Slurry and the calves born to these cattle which were tested demonstrated high levels of metal contaminants particularly in the kidneys, as well as signs of distress from the effects of the toxicity.” It also highlights that these tests “conducted under the direction of ISDA’s animal health and safety division were provided to Simplot, the USFS, and the IDEQ, but were never referenced or included in any reports prepared and submitted in relation to the spill.” Plaintiffs included in their lawsuit their estimated 15-year revenue loss of $29.5M plus $250M in punitive damages from alleged willful disregard by Simplot in their response and management of a substantial toxic slurry leak.

Soon after, the plaintiffs filed a motion for emergency injunctive relief to order 740 cattle (alleged to be contaminated) to be condemned/disposed of by Simplot, but on 06/30/25, the judge denied the motion. The judge’s reasoning for the denial, in part, sought to preserve the cattle as evidence for potential retesting. The Rasmussens asserted they could not risk putting contaminated/affected cattle into the open market for consumption or breeding. The judge ruled that for the duration of the litigation, Simplot must (financially) maintain/care for the cattle.

Weeks later, on 07/29/25, a “Notice of Voluntary Dismissal” was filed by the plaintiffs, preceded by a defendant-filed “Stipulation of Dismissal with Prejudice”, quietly ending the entire case on 07/30/25.

The lawsuit raises legitimate questions.

-What happened with these alleged contaminated cattle?

-Why was the slurry spill kept largely quiet from public awareness by Idaho agencies? Why were there no press releases?

-Why did the regulatory agencies rely almost entirely upon Simplot to conduct its own investigation and report their findings? Isn’t independent verification the responsibility of regulatory agencies?

-Despite snowpack and remoteness of the canyon, upon notification of the slurry spill, did USFS/CTNF fail to verify the quantity of the spill using available inputs (i.e. diameter of pipe, 1500 psi, the quarter sized hole, slurry density, etc.) and to take timely action to mitigate/slow the spread of the phosphate ore slurry, ultimately allowing material to travel approximately 2.4 miles into public forest land and waterways?

The public is not served when information about public land/water is kept from them. We deserve honest, timely reports of incidents and answers to these questions.