The Washington Department of Ecology has fined Coleman Oil of Lewiston $189,000 for an oil spill at its Wenatchee facility, and total fines and damages related to the incident are expected to reach more than $1 million.

According to a news release from the agency, a corroded underground pipe at the company’s Wenatchee bulk oil plant was responsible for the spill. The fuel contaminated nearby soil and groundwater, and seeped into the Columbia River, creating a visible sheen that appeared off and on for more than a year. The property is now a toxic cleanup site, according to the news release.

The agency cited Coleman Oil for negligence and not monitoring levels in the 20,000-gallon, above-ground storage tank connected to the corroded pipe. Although Coleman Oil believed the underground pipe had been in place since 1935, the company did not follow its own inventory control procedures or industry guidance for buried piping, according to the release.

“This spill happened over a long period of time and impacted the health of the river system,” said Dale Jensen, who manages the Department of Ecology Spills Program. “It could easily have been prevented if the company had been properly monitoring the fuel level in that tank.”

Agency officials first responded to the site when the sheen was reported in March of last year. Its source remained a mystery until lab results identified the pollution as biodiesel. Responders then traced the product to the Coleman Oil facility.

The company was cooperative and has worked with the department on cleanup. Groundwater monitoring wells are in place and are being sampled regularly to determine how much, if any, contamination remains in the groundwater. If fuel is found in the wells, it will be pumped out to prevent it from reaching the river. The next phase of the investigation is to determine whether river sediments have been contaminated.

In addition to the fine, the company must reimburse the state $213,400 for its spill response costs. It is also faces a resource damage assessment, which may be an environmental restoration or enhancement project, or a payment into a fund that pays for such projects. The combination of the state’s penalty, cost reimbursement and damage assessment is expected to total more than $1 million.

Funds collected from the penalty will go into the state’s Coastal Protection Fund. The company also faces a potential resource damage assessment from tribes. The company can appeal the penalty to the state Pollution Control Hearings Board.