Corrective Action Planning
CATEGORY OF SERVICE, LOCATION:
Corrective Action Plan, Morro Bay, CA
TYPE OF CLIENT:
Major Oil Company
An active service station has a dissolved petroleum hydrocarbon plume consisting primarily of gasoline (TPHg) with low concentrations of BTEX compounds centered in the middle of the site near the underground storage tank (UST) complex. Concentrations of TPHg consistently above 100,000 parts per billion (ppb) persist in one well installed in the UST complex and two other wells downgradient of the USTs have concentrations above closure levels. The dissolved plume is limited to the site and has not migrated off-site.
CLIENT GOALS FOR PROJECT:
Per Central Coast Regional Water Quality Control Board directive, evaluate remedial alternatives for site cleanup per UST corrective active regulations and prepare a corrective action plan (CAP). Implement the selected remedial alternative in a timely manner following regulatory approval of the CAP.
Prepare a CAP which included detailed site background information including previous investigations and results of a receptor well survey. The CAP included assessment of impacts, an evaluation of fate, transport and persistence of contaminants of concern in the environment, an exposure pathways evaluation; a determination of applicable cleanup levels; remedial strategies discussion including feasibility studies, technology screening and remedial alternatives evaluations. The CAP also included a corrective action work plan and verification monitoring plan for the remedial alternative selected which was biostimulation using the iSOC® oxygen delivery system in existing and proposed wells.
RESULTS, RESOLUTION, NEXT STEPS:
- The iSOC® oxygen delivery system was permitted and installed at the service station in June 2006 and has been operating continuously in three on-site wells to the present. Two of the three iSOC® remediation wells have concentrations below or at closure action levels and the TPHg concentrations in the well located in the UST complex has been reduced to less then 60,000 ppb TPHg. Continued operation of the iSOC® oxygen delivery system is planned with optimization and possible expansion of the system in the UST complex area to deliver more dissolved oxygen in the oxygen-depleted source area.
- Semi-annual groundwater monitoring and reporting to evaluate system performance.