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S ECOR - - �
<br /> 76(Former BP)Service Station No. 11193
<br /> SJCEHD
<br /> August 30,2007
<br /> Page 3
<br /> (CSMWS), there were no CSMWS water supply wells located within the 2,000-foot search
<br /> radius (Cambria, 1999).
<br /> On June 12 and 13, 2000, Cambria replaced destroyed well MWA and damaged well MW-2
<br /> with wells MW-1R and MW-2R, which were completed at depths of 31.5 and 30 ft bgs,
<br /> respectively. In addition, Cambria oversaw the installation of two additional groundwater
<br /> monitoring wells (MW-9 and MWA 0), each completed at a depth of 31.5 ft bgs. Groundwater
<br /> samples from the wells contained GRO, benzene, MtBE, and tertiary butyl alcohol(TBA) up to
<br /> maximum concentrations of 3,400 µg/L, 84 pg/L, 250,000 µg/L, and 17,000 µg/L (Cambria,
<br /> 2000).
<br /> In August 2000, GRI implemented an interim migration control plan to remove petroleum
<br /> hydrocarbons and MtBE from beneath the site, and to prevent further off-site migration of the
<br /> dissolved plume (GRI, 2000). The plan consisted of the periodic extraction of approximately
<br /> 5,000 gallons of groundwater from wells historically containing the highest concentrations of
<br /> petroleum hydrocarbons and MtBE(MW-1 R, MW-2R, and VW-1). Groundwater batch extraction
<br /> activities continued through June 2004, resulting in the removal of approximately 958,180
<br /> gallons of groundwater from beneath the site. Pumping occurred primarily from well MW-1 R.
<br /> In November 2001, SECOR conducted a five-day dual-phase extraction(DPE)test to evaluate
<br /> the feasibility of DPE as an applicable technology for remediation at the site. DPE tests were
<br /> performed on well MW-1 R for three hours, MW-2R for three hours, VW-1 for two hours, and
<br /> simultaneously on wells MW-1 R, MW-2R, and VW-1 for 92 hours. DPE was conducted at vapor
<br /> extraction flow rates ranging between 10.90 standard cubic ft per minute(scfm)to 42.86 scfm,
<br /> at vacuums ranging from 14 to 25 inches of mercury, and at groundwater extraction flow rates
<br /> ranging from 0.01 gpm to 6.2 gpm. During DPE testing, an estimated 8.11 pounds of GRO, ,
<br /> 0.17 pounds of benzene, and 5.26 pounds of MtBE were removed from beneath the site, and
<br /> approximately 26,210 gallons of groundwater were extracted and transported off-site for
<br /> disposal. The results of DPE testing indicated that this technology was ineffective based on the
<br /> low soil vapor extraction radius of influence(24 ft),the large quantity of extracted groundwater,
<br /> and low estimated mass removal quantities (SECOR, 2002).
<br /> To replace interim groundwater batch extraction at the site and to prevent further off-site
<br /> migration of MtBE and TBA, SECOR supervised the installation of 10 ozone sparge(OS)wells
<br /> in March and April 2004, and completed the installation of an OS system in April and May 2004.
<br /> The OS system consists of a KVA C-spargeT"' panel, a ten-point injection manifold,and buried
<br /> 318-inch diameter, high density polyethylene (HPDE) system lines contained in two to six-inch
<br /> diameter polyvinyl chloride (PVC) conduits. Each point on the injection manifold is equipped
<br /> with an electrical solenoid, which controls the flow of ozone/air mixture to the OS wells. The
<br /> sparge panel is equipped to with a compressor rated to deliver six scfm at ten pounds per
<br /> square inch (psi). The OS system was brought on-line on May 25, 2004 (SECOR, 2004).
<br /> IABP-ARCOW BP-CDP Sites1111931Work Plans111193 Vertical Delineation WP.doc
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