Tuesday, November 6, 2007 : 11:10 a.m.
Rapid In Situ Benzene and MTBE Treatment Using the RegenOx(tm) Chemical Oxidation System in a Tight Clay Formation
Methyl tertiary-butyl ether (MTBE) and benzene contamination occurred in tight soils as a result of leaking underground storage tanks at an active service station in Texas . The contaminant plume had extended 320 feet downgradient from the release area. Further soil investigations revealed a silty-sand matrix with increasing clay content at a depth between 4.5 and 10 feet and silty-clay found below 10 feet. Remediation technologies were evaluated to determine an effective strategy to reduce petroleum contamination within the tight soils. In 2004, a dual-phase extraction system (DPE) was installed and removed a total of 9,964 pounds of petroleum hydrocarbons over a 6-month period. However, contaminant removal reached a level of diminishing returns due to the tight geologic conditions present at the site. A new, aggressive method of remediation was needed to reduce concentrations to lower levels. RegenOx™ Chemical Oxidation System was proposed and pilot tested as a replacement for the DPE system since it offered a more rapid and cost-effective contaminant destruction approach. The pilot test was designed around downgradient well DPRW-6 using 1,020 pounds of RegenOx. Prior to the injection, baseline samples from DPRW-6 revealed concentrations of benzene and MTBE at 36 parts per million (ppm) and 8 ppm, respectively. In August 2005, injection activities began using 11 injection points around well DPRW-6. Due to the tight soils and the proposed shallow treatment area, the total amount of RegenOx was reduced to 510 pounds to avoid loss of the product through surfacing. Within two weeks of the initial RegenOx injection, benzene declined to 20 ppm and MTBE concentrations reduced to below 5 ppm. A follow up application was performed using the remaining 510 pounds of RegenOx. Concentrations continued to decline over a 15 week period. Overall, a benzene reduction of 76% and a MTBE reduction of 85% were observed.
Todd Herrington, PE, Regenesis Mr. Herrington serves as the Rocky Mountain District Manager for Regenesis. He has over 11 years of environmental remediation experience and is a registered P.E. in Colorado. He was a research scientist at the U.S. EPA in Cincinnati where he developed oil-spill bioremediation technologies. He served as a project manager for a consulting firm where he specialized in in-situ remediation technologies. Mr. Herrington contributed to the detailed protocols published by AFCEE for assessing natural attenuation at contaminated sites. He earned his B.S. in Civil Engineering from Colorado State University and his M.S. in Environmental Engineering from the University of Cincinnati.