Tuesday, November 6, 2007 : 1:00 p.m.

Effective MTBE Treatment on Track for Site Closure Through the Use of ORC(r)

David Clexton, PG1, David Schultz2 and Michael Marello, PG2, (1)Regenesis, (2)Aqua Science Engineers Inc.

Extensive methyl tertiary-butyl ether (MTBE) and total petroleum hydrocarbons as gasoline (TPHg) contamination was discovered within the subsurface as a result of leaking underground storage tanks (USTs) at a former service station. Immediately after the removal of the leaking USTs, a total of 1,192 cubic yards of gasoline-contaminated soil in the source area was excavated and transported off-site for treatment. Monitoring following the excavation activities revealed residual source contamination found in the capillary fringe zone immediately downgradient, near wells MW-6 and MW-7. Concentrations of MTBE exceeded 7 parts per million (ppm) and TPHg concentrations were approximately 11 ppm. Efforts to further delineate the plume revealed petroleum contamination extending 1,700 feet downgradient from the source. Early efforts were made to remediate the downgradient plume utilizing an air sparging/vapor extraction system placed 800 feet downgradient from the site of the original release. This approach proved to be effective as MTBE and TPHg were reduced to non-detect levels downgradient from where it was installed. However, the source area continued to reveal MTBE and TPHg concentrations above the cleanup goals enforced by the California Regional Water Quality Board. To treat the source area and bring the site to closure, an enhanced bioremediation barrier (biobarrier) was designed and implemented using Oxygen Release Compound (ORC®).  The ORC biobarrier was injected less than 50 feet downgradient of the excavated source area using 950 pounds of ORC into 24 injection points. Complete reduction of MTBE and TPHg occurred in wells MW-6 and MW-7 with concentrations reaching non-detect within one year.

David Clexton, PG, Regenesis Mr. Clexton serves as the Southwest District Manager for Regenesis. He is a Registered Professional Geologist with 13 years of project experience at both Navy sites and commercial sites throughout California, including CERCLA, RCRA, and UST remediation sites. His project experience includes in-situ and ex-situ remediation, remedial investigations, remedial system construction and operation, and system optimization. He is experienced in the design, construction, operation, maintenance, and optimization of environmental remediation systems, including air sparging/ soil vapor extraction systems, multi-phase free-product recovery systems, and fluidized-bed reactor groundwater treatment systems. Mr. Clexton earned his B.S. in Geological Sciences from Old Dominion University.


Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation® Conference