Tank Farm Terminal

In 2014, Stratus Environmental, Inc. (Stratus) was retained by a confidential refiner to perform site assessment and remediation services at one of their refineries in southern California. The operator of the facility has been required to address petroleum hydrocarbon conditions by the Los Angeles Regional Water Quality Control Board (LARWQCB) under a Cleanup and Abatement Order.

The site is set within an 18-acre parcel with the refinery pass-through of approximately 30,000 barrels per day. Based on assessment work performed at the facility to date, there are a number of subsurface conditions at the facility which require treatment to reduce current impacts to groundwater and potential future impacts to off-site receptors. These conditions include high concentrations of petroleum hydrocarbon volatile organic compounds (VOCs) and light non-aqueous phase liquids (LNAPL) in shallow soil and groundwater (less than 25 feet below ground surface [bgs]) in the central part of the refinery and in the crude unit, and the presence of elevated concentrations of dissolved-phase petroleum hydrocarbons in deeper groundwater (greater than 25 feet bgs) below the southwestern portion of the refinery and beyond the property boundary to the southwest.

A network of 55 groundwater monitoring wells has been installed in the shallow aquifer generally delineating the extent of the on- and off-site dissolved-phase impacts and partially delineating the impacted soils and source areas.

Based on the nature and extent of the hydrocarbons and VOCs present in the subsurface, preliminary soil vapor extraction (SVE) test using cryogenic recovery technology and air-sparge (AS) pilot tests were executed. The SVE test demonstrated efficient recovery of high concentrations of vapor-phase hydrocarbons from the subsurface, a relatively high radius of influence, and should facilitate the recovery of volatile compounds. During SVE testing, approximately 12,600 gallons (79,000 pounds) of LNAPL was recovered and reprocessed through the refinery. The AS testing suggested a strong piezometric response and a limited dissolved oxygen (DO) and oxidation reduction potential (ORP) response.

While both the preliminary SVE and AS tests were successful, they were limited in time and to only a small portion of the total area known or suspected to have high in-situ soil and groundwater concentrations. As such, a larger network of vapor extraction wells was evaluated through a longer duration SVE test executed over a broader area to better evaluate the long-term remedial actions.

The longer term pilot test was successfully completed and provided sufficient extraction data to support both site wide remedial action and a remedial design effort while also closing several assessment gaps. Stratus is in the initial phases of the site-wide process design, equipment specifications and procurement, piping layout, utility coordination, and will likely initiate site-wide remedial efforts in 2015.