Big B Mini Mart

The Site is the location of a former gas station and convenience store. The Site began operating as a retail fueling station in the early 1970s. In December 1990, soil and groundwater contamination from diesel fuel was discovered when an underground storage tank was replaced. Additional investigation revealed that gasoline and other petroleum chemicals contaminated the soil and groundwater.

The Site was placed on Ecology’s Hazardous Sites List with a ranking of “3” in early 1999.  Sites on the Hazardous Sites List are a priority for Ecology and have completed a Site Hazard Assessment (SHA). A SHA provides information about the environmental risk of the Site. Risk is based on the amount of contaminants, how toxic they are, and how easily they can come in contact with people and the environment. Sites are ranked relative to each other on a scale of “1” to “5”; with a rank of “5” being the lowest.

After the discovery of the release, an independent remedial action was performed to remove petroleum-contaminated soil. Approximately 420 cubic yards of contaminated soil was removed and disposed of offsite.  Wells to monitor groundwater were also installed and sampled in 1990 and 1991. Groundwater sampling showed contamination above state cleanup levels were still present. 

In early 2014, the U.S. Environmental Protection Agency (EPA) recorded violations and issued a civil penalty for failing to monitor underground storage tanks (USTs).

Sampling in 2015 continued to show groundwater contamination above state cleanup levels. Additional investigations revealed petroleum contamination throughout the site and an Interim Action to recover the free product began in 2016 and ended in 2017. Free product is petroleum contamination, which is lighter than water, usually floats on top of groundwater. This work was performed and completed in December 2018 under an Agreed Order for Remedial Investigation and Feasibility Study (RI/FS). A Remedial Investigation (RI) uses data to see how far contamination has spread and a Feasibility Study (FS) looks at options to clean up contamination.

In 2019, the land treatment option of the proposed cleanup action identified in the FS as a cleanup alternative was performed on a portion of contaminated soil. Land treatment usually consists of isolating an area onsite and placing contaminated soil in the controlled space, turned over frequently and is done in the warmer months to aid in the breakdown of contaminants. The land treatment along with pumping oxygenated air into the soil are part of the proposed cleanup actions outlined in the Draft Cleanup Plan. 

From July 2019 to November 2019, an Interim Action was done that involved a pilot test called Landfarming to treat contaminated soil. Landfarming usually consists of preparing an isolated area, preferably onsite, is performed during warm months of the year with soil turned over periodically to allow air and the warmer temperatures to help degrade the contaminants. Natural sources of nitrogen and aerobic bacteria, such as liquid nitrogen and fertilizer granules, are often applied to aid in the biodegradation. The results of the pilot test Landfarming activities performed at this site produced some favorable results.

After the public comment period was held in late 2020 and no comments were received, the Agreed Order and Cleanup Action Plan became final and the PLPs are proceeding with the cleanup.

From 2021 to 2022, the following cleanup actions were performed:

• Excavation of contaminated soil (as shown in Figure 2.1 of the Remedial Action Completion Report)
• On-site landfarming of excavated soil
• Transportation and proper disposal of some petroleum-contaminated soil at a permitted landfill
• Installation of monitoring wells and groundwater monitoring
• Sub-slab vapor assessment at the station building