Cleaning up residual petroleum and gas from spills at Chevron Pipe Line Co.'s Pasco Bulk Fuel Terminal site may be left to nature.
The state Department of Ecology is accepting public comment through Wednesday about cleanup options from a two-year investigation and feasibility study completed by Chevron and Tidewater Terminal Co.
The report addresses spills that Chevron and Tidewater Terminal Co. were considered responsible for on the 33-acre property near Sacajawea State Park.
Fuel from the property owned by Northwest Terminalling Co. is transported through pipelines from Salt Lake City to Pasco and then is moved to other locations by truck, barge or pipelines. The property has been used to store fuel since 1950.
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In the mid-1980s, petroleum was discovered in ground water monitoring wells on the site, and a petroleum sheen was seen along the bank of the Snake River, said Jani Gilbert, Department of Ecology communications manager for Eastern Washington. A Chevron-owned pipe that transferred aviation fuel was leaking, and it, along with contaminated soil and fuel product, were removed.
Chevron added clean soil to the site and along the shoreline and monitoring increased, she said.
In 2000, workers discovered gasoline leaking from a hole in the Tidewater transfer pipe that moves fuel to Chevron, according to the state.
About 42,000 gallons were spilled, and almost all the gallons were recovered, Gilbert said.
Through the years, cleanup has included soil vapor extraction, in which contaminants in the soil are vacuumed out of the ground and then treated; and air sparging, in which air or steam is injected into ground water using blowers and injection wells, Gilbert said. With air sparging, the contamination transfers to the air bubbles and the resulting vapor is treated.
The Herald was not able to reach Chevron for comment.
Now, according to the study, the site is naturally correcting itself. Most wells tested meet state standards, and ground water quality is continuing to improve.
Chevron and Tidewater's preferred option is to allow the natural process to continue and maintain barriers to limit access and land use on the property. Other options also include using natural correction, but adding oxygen-releasing compounds into monitoring wells or using a blower system to provide more venting, both to enhance the natural process.
The state Model Toxics Control Act requires the companies to determine the most feasible option based on a formula, said Sam Pounds, Tidewater's director of environmental health safety and security. That determined natural attenuation was the most feasible option.
"We've been working really closely with the state and we are just about at the end," he said.
The company will be happy to get the site cleaned up to state standards, Pounds said.
Residents at the nearby Lakeview Mobile Home Park receive drinking water from the city of Pasco's system, which is not influenced by ground water at the terminal, Gilbert said. Contaminants from the site are not moving toward the mobile home park.
The ultimate cleanup option will not be decided until after the public comment period, Gilbert said. Natural attenuation is an acceptable, scientifically sound cleanup practice.
Monitoring still will occur while the contaminants are naturally cleaned up, she said.