Stillwater Holdings Chevron

Page updated April 18, 2025.

Stillwater Holdings has been cooperative and communitive and is working toward complying with the Enforcement Order. The first deliverable required from Stillwater Holdings is a comprehensive schedule and a remedial investigation work plan, which has not been submitted to us yet.

Ecology requested $3.5 million from the state capital budget to continue cleaning up the gasoline spill. We estimate this is the amount needed to complete the remedial investigation, feasibility study, cleanup action plan, implementing final cleanup, and long-term monitoring.

Ecology's contractor NWFF Environmental is now overseeing the vapor and water mitigation systems at the sites, taking over for the previous contractor Clean Harbors, to continue protecting the community. Mitigating potentially harmful vapors in the Marcus Whitman Hotel and 106 Building remains the highest priority.

New equipment installed

More efficient vapor removal systems and pumps for the water mitigation system have been installed and are fully operational at the Marcus Whitman and the 106 Building. The new systems discharge into the City of Walla Walla’s sewer after treatment, have a smaller footprint, and reduce the impact to the 106 Building.

During the installation of the new vapor and water mitigation system, the basement of the 106 Building flooded. Ecology's contractor Clean Harbors is working with a restoration company to comprehensively and quickly address and repair the damage.

Water mitigation system incident

On April 5, a 4,000-gallon water container used with the water mitigation system split and released untreated sump water that had been collected from the 106 Building. The holding tank, located on Stillwater Holdings property, failed and sent the water down the street and into storm drains on 2nd and Cherry streets.

NWFF and Ecology worked to set up a temporary system, keeping the mitigation system operational. NWFF hired a vacuum truck to clear out the storm drains. Ecology collected samples from the water container and storm drains to characterize the water, determine contaminant levels and inform next steps. NWFF has replaced the container tank with a hard-sided tank and reconfigured the system to manage water.

Sampling results 

GeoEngineers completed another round of groundwater sampling at Stillwater Chevron, 106 Building, and the Marcus Whitman Hotel properties during the last week of March 2025. Vapor intrusion sampling is tentatively scheduled for all three properties in April. We will post the results on this page as soon as they are available.

The sump water sample collected from the Marcus Whitman Hotel in November 2024 met state standards, while samples collected from the sump at the 106 Building had petroleum levels above standards. Groundwater samples from wells on and around the Chevron property were also above standards, although overall, levels are decreasing.

On September 5, 2024, Stillwater Holdings had five soil samples collected on their property while removing some old product lines and fuel pumps. Sample results showed contaminated soil near the southern fuel canopy at 300 milligrams per kilogram (mg/kg), and cleanup is required at 30 mg/kg. Stillwater Holdings’ consultant, Aspect, interpreted the contamination as highly weathered gasoline likely from the historical release.

Between August 16 and 21, 2024, Ecology sampled indoor air in the 106 Building, basement sumps in the 106 Building and the Marcus Whitman Hotel, and all site groundwater wells. The 106 Building sampling results showed initial indoor air was safe for adults working an 8-hour shift, but not for children or adults occupying the building for longer than a normal work shift. Groundwater sampling analysis showed results above state standards. 

Concerns regarding a broken sewer line were provided via a letter from the owner of the 106 Building on August 15, 2024. Based on these concerns, the City of Walla Walla completed a dye test August 20, to check if there was a break in the sewer line. The city found that water discharging from the sink is discharging to Rose Ave., not 2nd Ave., indicating the system is functioning as it should.

Local, state, and federal agencies, along with third-party contractors, have deemed the area safe for residents and visitors with protection measures and air quality monitoring in place. Testing of Walla Walla's municipal water and wastewater systems and nearby Mill Creek has shown no evidence of contamination.

We held a public comment period June 18 – August 16 for the Enforcement Order and Public Participation Plan. The order requires Stillwater Holdings to continue work to reduce harmful vapors and remove contaminated water from nearby buildings until a permanent treatment system is installed. You can learn more in the public notice we mailed to the surrounding community. We responded to comments from five people and thank them for their input. Based on concerns expressed about using state funding for cleanup, we amended the Enforcement Order to require a remedial investigation and feasibility study.

Ecology held a public comment period for the draft State Environmental Policy Act documents for the underground storage tank system replacement April 1–15, 2024. We responded to comments from four people, and we thank them for their input. The tank replacement was postponed because the leaking tank was emptied during the initial spill response and has not been put back into use.

On September 14, 2023, the Marcus Whitman Hotel was evacuated due to volatile organic vapors entering the building, also known as vapor intrusion. The Walla Walla Fire Department called in Ecology’s Spill Response Team to help assess the situation and identify the source.

Testing identified potentially harmful vapors and gasoline in the basement, and in two nearby buildings. The buildings were ventilated to eliminate the risk of an explosion, and the buildings’ drainage systems, also known as sumps, were pumped to reduce vapor concentrations.

An investigation found that gasoline pooling in the adjacent building sumps matched the fuel in Stillwater Holdings’ gasoline underground tank. Since the tank was taken out of service and emptied, product is no longer visible in the sumps, and petroleum contaminants continue to decrease in water samples from the sumps.