On February 8, 1990, a tanker truck owned and operated by Thatcher Trucking Company of Salt Lake City, Utah, skidded off Highway 395 and rolled down an embankment into the North Fork of the John Day River in north-central Oregon. An estimated 3,500 gallons, or 33,500 pounds, of hydrochloric acid was discharged into the river and flowed downstream at an approximate rate of one mile per hour.

The spill drastically changed the pH of the river water resulting in extensive mortality and injury to fish resources. An estimated 98,000 to 145,000 fish were destroyed, including 4,000 anadromous fish, 300 bull trout, and 9,500 Pacific lamprey. Additionally, 50 percent of the chinook salmon alevins in the area impacted by the spill were estimated to have been killed. Aquatic mammals, waterfowl, and endangered species which utilize the John Day River Basin may also have been directly or indirectly impacted by the spill.