A Pasco barge company has been fined $18,000 for spilling 40,000 gallons of liquid urea ammonium nitrate into the Snake and Columbia rivers.

An investigation by the state Department of Ecology found that two steel tank barges owned and operated by Tidewater Barge Lines, Inc. were not properly maintained, causing the liquid fertilizer to spill into the rivers during three separate incidents in April 2017.

This common fertilizer is corrosive to steel, according to the Department of Ecology.

The first spill occurred between April 11 and 21 during transfer and storing operations at the Tidewater Snake River Terminal in Pasco.

The Vancouver, Washington-based company’s operations span 465 miles on the Columbia and Snake river systems, extending from the Port of Astoria, Oregon, to the inland Port of Lewiston, Idaho, according to its website. Tidewater operates five terminals with key intermodal connections to railroads, highways and pipelines. The Pasco terminal operates a railcar storage facility.

State investigators determined that 16,639 gallons of urea ammonium nitrate were released by Barge No. 78 due to corrosion of the storage tank.

The second spill occurred between April 20 and 24 during a transfer operation as the barge transited and moored on the Columbia River near Vancouver. Investigators determined that 22,104 gallons of urea ammonium nitrate were released by Barge No. 74 due to corrosion of the storage tank.

The third spill was reported on April 28 and occurred in the preceding days during transporting operations on the Columbia River near Vancouver. Investigators determined that 950 gallons of urea ammonium nitrate were released by Barge No. 74 due to physical damage to the tank’s side shell.

“These spills were preventable through proper maintenance of the barges,” said Rich Doenges, Ecology’s water quality section manager, in a release. “While it dispersed rapidly in the Columbia and Snake rivers, urea ammonium nitrate fertilizer can stimulate plant and algae growth in water, which could impact fish and wildlife.”

Along with the fine, the company is required to take immediate action to prevent future urea ammonium nitrate releases and submit to Ecology an annual comprehensive corrosion management plan for its barges. Detailed cleaning and inspection processes will help ensure the integrity of the steel plates and welds within the barge tanks.

Tidewater Barge Lines Inc., has 30 days to pay the penalty or appeal it to the state’s Pollution Control Hearings Board.