Following a series of investigations, it was determined that a portion of an active refinery located in a sensitive marine setting was affected by light non-aqueous phase liquid (LNAPL) and dissolved-phase petroleum hydrocarbons. A remedial action plan had previously been developed, which recommended installing a 1,900-foot groundwater interceptor trench to control shallow groundwater. The installation of four recovery wells was also recommended to control deeper groundwater.

Trihydro was asked to finalize the engineering design for the approved plan. During the review, Trihydro identified several important data gaps that reduced confidence in the ability of the chosen remedy to achieve the client’s goals for the site. It was also determined that the proposed remedy would likely interrupt operations and pose health and safety risks.

Based on these concerns, Trihydro proposed and gained approval to conduct additional field investigation and develop an updated conceptual site model (CSM) to reflect LNAPL distribution and mobility in the area. These additional, focused efforts led to the conclusion that the proposed remedy would not be an effective final solution. Trihydro developed an alternative remedy consisting of a linear series of groundwater extraction wells. A tidal study and aquifer testing were then performed and groundwater modeling, design, and installation of the 42-well extraction system were completed.