Injection Remediation

Former property and underground storage tank (UST) system owner for an active retail fueling station and convenience store.

Unleaded gasoline constituents at concentrations exceeding the applicable PADEP Used Aquifer Non-Residential Statewide Health Standards (UANRSHS) Medium-Specific Concentrations (MSC) were present within on-site soil and groundwater and off-site groundwater beneath and beyond a Pennsylvania State Route right-of-way.   The remedial strategy to attain the MSC for soil and groundwater utilized a coupled in-situ adsorption (ISAD) and enhanced (aerobic/anaerobic) bioremediation approach utilizing an application of BOS 200+^® to target recalcitrant petroleum hydrocarbons in soil and groundwater.

BOS 200+ is an in situ bioremediation technology specifically designed to degrade petroleum hydrocarbons, related solvents, and oils (Trap & Treat^® process https://astenvironmental.com/services/bos-200-plus/).  BOS 200+ is a complete system effecting accelerated biodegradation of various organic compounds on an activated carbon platform that includes micro and macro nutrients, time release terminal electron acceptors (TEAs), and a blend of facultative microorganisms designed to flourish within the aerobic to anaerobic conditions present in the pore structure of the activated carbon.  It has been demonstrated to be effective with light non-aqueous phase liquid (LNAPL), fuel oxygenates, alcohols, glycols, and cyclic ethers.

Remediation activities conducted on-site for several years involved short-term focused source remediation (FSR), which utilizes total phase extraction technology, combined with monitored natural attenuation (MNA).  These remedial efforts were successful in decreasing petroleum concentrations in soils and groundwater; however, recalcitrant impacts remained including benzene, ethylbenzene, methyl tertiary-butyl ether (MTBE), naphthalene, and 1,2,4-trimethylbenzene.  Therefore, an additional strategy involving direct push technology (DPT) injection was completed to accelerate the remediation process. During an approximate three-week timeframe, AST Environmental, Inc. installed BOS 200+ into the subsurface via a total of 138 injection points at the targeted injection intervals (which included smear and saturated zones).  The injection was completed in 2-foot vertical intervals from 8 to 30 feet below ground surface in selected treatment zones at the site.  During the injection event, injection rates and pressures were approximately 100 gallons per minute (gpm) and 120 pounds per square inch (psi). The entire proposed injection amount of BOS 200+ (21,750 pounds) and water solution was successfully injected and distributed into the subsurface at the site.

Based on the preliminary analytical results of five post-injection quarterly groundwater sampling events completed to date, all groundwater attainment monitoring results in all monitoring and recovery wells were below the MSC, with the exception of one parameter (MTBE) at one monitoring well.  A minimum of three additional quarterly events inclusive of all monitoring wells will be completed to demonstrate groundwater attainment.  Considering groundwater results to date, the injection program successfully improved groundwater quality, accelerated the time to site closure, and is expected to have improved soil quality (pending future soil attainment sampling results).