San Antonio, TX 2005 - GeoSierra is presently installing 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 consists of two segments totaling 1500 feet, in length extending from 20 feet down to 40 feet in depth. The PRB will vary in thickness from 3 to 4 ½ inches along the PRB length and, when completed, nearly 500 tons of iron will have been injected to form the PRB. The work zone is 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 consists of a shallow, perched aquifer consisting of a gravelly layer underlain by a silty clay aquitard (Navarro Formation). The objective of the PRB is 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 2005 - GeoSierra is currently installing an extension to the pilot PRB installed in 2001 at the Oakley, CA site. For the extension, two full-scale PRB’s are being 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 include: 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.

San Antonio, TX 2004 - In the 4th quarter of 2004, GeoSierra completed the installation of 3 PRB segments totaling over 2000 feet in length near the former Kelly Air Force Base (AFB) in San Antonio, Texas. Groundwater off-base was contaminated with VOCs in the shallow groundwater region, with tetrachloroethene (PCE) and trichloroethene (TCE) being of primary concern. Two of the PRBs were installed in a residential neighborhood on Commercial Street and Collingsworth Avenue. The project work site consisted of two-lane streets congested with a maze of underground and aboveground utilities. GeoSierra was able to navigate around the utilities by careful placement of 180 boreholes for frac casing installation without infrastructure damage. While these PRBs constructed in the roadway are relatively shallow (approximately 45-feet bgs), the site complexities and minimal intrusive/disruptive requirements eliminated trenching as an installation option.

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Oklahoma City, OK 2004 - GeoSierra recently 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 is 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 of the PRB.

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Gardena, CA 2003 - A pilot iron PRB was designed and constructed for treatment of groundwater contaminated with VOCs at this site. The PRB is designed to be approximately 800 ft in length, extending in height from 24 ft bgs to a total depth of 100 ft bgs. The soils consist of interstratified sands, silts, and clays that are predominantly fine-grained. With the exception of several thin (approx 5 ft thick) sand layers, soil layers are for the most part discontinuous and pinch-out laterally. Two stratigraphic units, each composed of silty sand, are continuous across the site. Groundwater monitoring results, since installation in late 2003, have demonstrated decreases in contaminant concentrations by 90% from original concentrations in groundwater prior to construction of the PRB.
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Montross, VA 2002 - An Iron PRB system was designed and built by GeoSierra for treatment of groundwater contaminated with VOCs and heavy metals. The PRB is approximately 1200 ft in length, extending in height from 17 ft bgs down to a total depth of 45 ft bgs. The soils consist of sands and silts, with extremely loose flowing sands and silts encountered over a 15 ft depth interval. A strong iron stone stratum is 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 2001 - 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, 110 feet long and from 45 to 110 feet in depth, at the site. The soils consist 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 the December 2, 2002 issue. You can learn more about this site at www.dupontoakley.com.
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Centerville, IA 2000 - An in situ iron PRB system was designed and built by GeoSierra in 1999 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 1999.
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Fairfield, NJ 1997 - GeoSierra designed and constructed a PRB 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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