Unocal Coupeville Bulk Plant

The Site was developed as a bulk fuel plant in 1927 and renovated with new facilities in 1958. The improvements consisted of five aboveground storage tanks (ASTs), three underground storage tanks (USTs), aboveground distribution lines, a loading dock, warehouse, office, garage and drum storage area. The bulk fuel plant was closed in 1982 and by 1995, all tanks and related auxiliary equipment had been removed from the Property.

In December 2004, the Property was sold to DRM Properties LLC, which began redevelopment. At that time, the Property was subdivided into Parcels A and B. A single-story retail business and restaurant were built on Parcel A, the northern portion of the Property. Parcel A is where the former bulk fuel plant, aboveground fuel lines, loading rack and drum storage area were located. A single-family residence, garage and “mother-in- law” apartment were built on Parcel B, the southern portion of the Property. Parcel B formerly included the ASTs, USTs, and fuel lines.

The Site is defined by the nature and extent of contamination associated with the following releases:
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·         Petroleum hydrocarbons as total petroleum hydrocarbons (TPH) into the soil;

·         Petroleum hydrocarbons as gasoline (TPH-GRO) into the soil and groundwater;

·         Petroleum hydrocarbons as diesel (TPH-DRO) into the soil and groundwater;

·         Petroleum hydrocarbons as heavy-oil range (TPH-HRO) into the soil and groundwater;

Volatile organic hydrocarbons associated with gasoline called benzene, toluene, ethylbenzene, and xylenes (BTEX) in the soil; and benzene and toluene in groundwater

Prior to redevelopment of the Property in January 2005, the extent of residual petroleum-impacted soil was characterized and groundwater impacts were investigated. Approximately 589 tons of diesel-impacted soil were excavated and removed from the vicinity of the former loading rack and disposed of off-Site.  A cleanup method called air sparging was used to remediate the impacted groundwater at the base of the excavation, which was at a depth of 26 feet below ground surface (bgs).  Air sparging was continued in this area until 2007.

The cleanup activities included confirmation sampling for soil and groundwater. Model Toxics Control Act (MTCA) Method B cleanup levels were calculated and used for this Site. A Method B soil cleanup level for total Petroleum Hydrocarbons (TPH) was calculated at 2,829 mg/kg or parts per million (ppm). The groundwater cleanup level for TPH was calculated at 552 μg/l or parts per billion (ppb). 

The concentrations of petroleum hydrocarbons and BTEX at the Site now meet the MTCA cleanup levels at the points of compliance for soil and groundwater. Concentrations of petroleum hydrocarbons in soil from the surface down to 15 feet bgs are below the calculated Method B cleanup level of 2,829 mg/kg (ppm) for direct contact.  Concentrations of BTEX in soil meet the levels specified in Ecology’s CLARC database (MTCA Method A).  Concentrations of petroleum hydrocarbons dissolved in groundwater are below the Method B cleanup level of 552 µg/L (ppb) for four consecutive quarters, the State’s minimum requirements for compliance. Therefore this Site has achieved the MTCA requirements for site cleanup.

In 2000, a restrictive covenant was placed on the Property because groundwater contained gasoline and diesel hydrocarbons and associated BTEX compounds at concentrations exceeding MTCA Method A cleanup levels.  The restrictive covenant was removed in 2014 following issuance of the 2013 No Further Action (NFA) letter.

In 2010, Ecology added the Property to the Hazardous Sites List (HSL). A Site Hazard Assessment (SHA) was conducted and the Site was ranked a “1” under the Washington Ranking Method (WARM). WARM ranking uses a scale of 1 to 5, where “1” represents the highest risk and “5” represents the lowest risk compared to other sites ranked. This ranking estimates the potential threat to human health and the environment relative to other ranked sites in Washington State.  Following issuance of the NFA determination in 2013, the Site removed from the HSL.