Pleasant Hill, CA 2008-2009 - GeoSierra Environmental Inc. installed a 480-linear foot zero valent iron (ZVI) permeable reactive barrier (PRB) in Pleasant Hill, CA. The PRB was installed within a local park and within the right-of-ways on a highly trafficked main road. Prior to mobilization and installation of the PRB, a complete design consisting of column treatability testing, custom hydroxypropyl guar and associated crosslinker and enzyme mixture testing, Monte-Carlo probabilistic design process and detailed design specifications was developed and approved by the California Regional Water Quality Control Board. Following completion of the design, forty (40) specialized fracture wells and twenty (20) customized subsurface receivers were installed to allow for the installation of a vertical hydraulically fractured PRB and monitoring system down to depths of 50 feet BGS. Injection and support systems consisting of two (2) 3,000 gallon stainless steel guar mix tanks, hydraulically controlled injection equipment including centrifugal mixing and transfer pumps, 300-HP diesel power unit, 2,500 psi piston pumps, iron mixing vapor control system, 3,000 lbs concrete hoppers and weight control systems, custom electronic QA/QC s and all supporting systems were mobilized to the site to install the patented vertical hydraulically fractured PRB from 15’ to 50’ BGS along the alignment.

San Antonio, TX - GeoSierra installed two Permeable Reactive Barriers (PRBs) within 26 feet of an active Union Pacific Railroad (UPRR) line near the former Kelly Air Force Base (AFB) in San Antonio, Texas. The PRB consisted of two segments totaling 1500 feet, and in length extending from 20 feet down to 40 feet in depth. The PRB varies in thickness from 3 to 4 ½ inches along the PRB length and nearly 500 tons of iron was injected to form the PRB. The work zone was located entirely within the UPRR right-of-way, resulting in an area of less than 25 feet in access width for all of the PRB construction equipment. The treatment zone consisted of a shallow, perched aquifer with a gravelly layer underlain by a silty clay aquitard (Navarro Formation). The objective of the PRB was to degrade volatile organic compounds (VOCs) in the perched groundwater into non-toxic end products and thus stop groundwater migration of those contaminants.

Oakley, CA - GeoSierra installed an extension in 2005 to the pilot PRB installed in 2001 at the Oakley, CA site. For the extension, two full-scale PRB’s were constructed. Groundwater at the chemical facility was contaminated with elevated levels of volatile organic compounds (VOCs), primarily carbon tetrachloride, FREON113®, FREON11®, and 1,2-dichloroethane. After installation of the first phase, completed in 2001, sampling of the downgradient monitoring wells verified that contaminant concentrations had decreased by 90%. The second phase PRB’s included: 1) an extension of the pilot PRB to its full-scale length of 485-feet, extending from 60-feet down to 115-feet 2) the installation of a shallow PRB, upgradient of the original pilot PRB, 485 feet long from a depth of 25 feet down to 50 feet in depth.

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Oklahoma City, OK - GeoSierra completed the installation of a 95-foot deep iron PRB at Tinker AFB in Oklahoma City, OK. The PRB was constructed using GeoSierra’s azimuth controlled vertical hydraulic fracturing technology. Thirty-four (34) six (6) inch boreholes were drilled every 15-feet along the alignment of the PRB. Fracture casings were then placed into the boreholes for injecting the iron filings.
The constructed PRB was 500 feet in length, with a treatment depth of extending 70 to 95 feet below ground surface (bgs) with an iron effective thickness of 4-½ inches in the central section of the PRB and 3 inches thick elsewhere. A total of 340 tons of iron filings was injected into the subsurface to complete the PRB.

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Montross, VA - An Iron PRB system was designed and built by GeoSierra for treatment of groundwater contaminated with VOCs and heavy metals. The PRB was approximately 1200 ft in length, extended in height from 17 ft bgs down to a total depth of 45 ft bgs. The soils consisted of sands and silts, with extremely loose flowing sands and silts encountered over a 15 ft depth interval. A strong iron stone stratum was located in the seasonally fluctuating water table. Although moderate in depth, the PRB was installed by GeoSierra’s trenchless construction technology because of the need to minimize spoil. The project was completed in June 2002.
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Oakley, CA - A pilot PRB was designed and installed by GeoSierra at a former chemical manufacturing facility in the Bay Area, California in 2001. The deep pilot PRB measured, - 110 feet long and ranged in depth from 45 to 110 feet in depth, at the site. The soils consisted of medium to fine silty sands changing with depth to coarse the fine silty sands with little to some fine gravel. The project was completed in January 2001. ENR Magazine (Engineering News Record) published an article about this particular project in their December 2, 2002 issue. You can learn more about this site at www.dupontoakley.com.
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Centerville, IA - An in situ iron PRB system was designed and built by GeoSierra in 2000 for treatment of groundwater contaminated with VOCs at a manufacturing facility. The PRB is 240 ft in length, extending in height from a depth of 25 ft bgs to a total depth of 75 ft bgs. The site soils consisted of fine lenticular sand lenses and medium river channel sands, overlain and underlain by stiff over consolidated glacial till. The PRB was completed in late October.
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Fairfield, NJ - GeoSierra designed and constructed a PRB in 2007 at the Caldwell Superfund Site in a highly geologically complex glacial environment to treat groundwater contaminated with TCE and other VOCs. The system consists of two parallel iron PRBs in the overburden soils, which consisted of an eskar deposit of sands, gravel, and boulders, overlain by clay till. The PRB was 360 ft long and extended in height from approximately 25 ft bgs down to a total depth of 65 ft bgs. The PRB was extended by an additional 90 feet in mid-1999. The installation of the PRB extension was constructed at record productivity and achieved clean breakdown of the iron-gel mixtures in 1-2 hours.
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