Montana authorities monitored downstream water supplies for contamination Tuesday after a truck crash spilled about 7,000 gallons of a chemical salt used to deice roads into a Yellowstone River tributary near the Wyoming border.
The estimated volume of magnesium chloride spilled was up 2,000 gallons from initial reports. The increase came as authorities gained a better grasp on the scope of the accident after crews pulled most of the wreckage from the Clarks Fork of the Yellowstone.
A semitrailer crashed into a bridge over the river Monday, sending two trailers into the river about 2 miles north of the Wyoming border. The river flows north, feeding into the Yellowstone about 45 miles from the spill site.
Carbon County emergency coordinator Darrel Krum said the spill appeared small enough that dilution with river water should minimize problems. Because of the season, irrigation dozens of irrigations ditches that feed off the river were closed, preventing pollution of agricultural areas.
Magnesium chloride can cause eye and lung irritation and vomiting. It is not considered highly hazardous.
State wildlife officials said there have been no further reports of fish kills since about two dozen dead fish were found just below the spill on Monday.
Crews will continue to monitor the site in coming days, said Bob Gibson, a spokesman for Montana Fish, Wildlife and Parks. He said some wreckage from the truck crash remained in the river and will have to be removed because it is a boating hazard.
Gibson said earlier fears that a concentrated plume would cause more damage as it flowed downstream have so far proven unfounded.
"They were able to find nothing to indicate there is a bigger problem," Gibson said.
Downstream past the Clarks Fork's confluence with the main branch of the Yellowstone River, water suppliers in the Billings area were on watch for contamination coming getting into their intakes.
Woody Woods, manager of the Lockwood Water and Sewer District, said no signs of the chemical had turned up by late Tuesday. He said workers will continue daily checks to monitor the water, but added that after Wednesday any potential threat likely will have passed.
The truck was operated by Lynch Trucking of Riverton, Wyo., according to the Montana Highway Patrol, which issued the driver a citation for reckless driving. The company could not be reached for comment.
Any potential water pollution violations will be investigated by the Montana Department of Environmental Quality.