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<br /> S E C 0 R
<br /> 3ti
<br /> Ms Victoria L McCartney
<br /> . March 3, 2005 i
<br /> Page 4
<br /> On June 12 and 13, 2000, Cambria replaced destroyed Well MW-1 and damaged Well MW-
<br /> 2 with wells MW-1 R and MW-2R, which were completed at depths of 31 5 and 30 feet bgs,
<br /> respectively In addition, Cambria drilled and installed two additional groundwater
<br /> monitoring wells (MW-9 and MW-10) to a total depth of 31 5 feet bgs Laboratory analysis
<br /> of soil samples collected from the soil borings Indicated maximum concentrations of TPHg
<br /> at 0 82 mg/kg (MW8-12') and MtBE at 2 6 mg/kg (MW8-30) BTEX was not detected above
<br /> laboratory detection limits Laboratory analysis of groundwater samples collected from all
<br /> wells confirmed maximum concentrations of TPHg at 3,400 �tg/L (VW-1), benzene at 84
<br /> gg/L (VW-1), MtBE at 250,000 µg/L, and tert-butyl alcohol (TBA) at 17,000 84 Etg/L (MW-
<br /> 2R, Cambria, 2000)
<br /> In August 2000, GR implemented an Interim migration control plan at the site to reduce the
<br /> amount of petroleum hydrocarbons and MtBE beneath the site, and to prevent further off-
<br /> site migration of the dissolved plume (GR, 2000) The plan consisted of the periodic
<br /> extraction of approximately 5,000 gallons of groundwater from wells historically containing
<br /> the highest concentrations of petroleum hydrocarbons and MtBE (MW-1 R, MW-2R, and
<br /> VW-1) Groundwater batch extraction activities continued through June 2004, resulting in
<br /> the removal of approximately 958,180 gallons of groundwater from beneath the site
<br /> Pumping occurred primarily from well MWA R
<br /> In November 2001, SECOR conducted a five-day dual-phase extraction (DPE) test to
<br /> reduce the amount of petroleum hydrocarbons in soil and groundwater beneath the site,
<br /> and to determine the feasibility of DPE as an applicable technology for remediation at the
<br /> site DPE tests were performed on well MWA R for 3 hours, MW-2R for 3 hours, VW-1 for 2
<br /> hours, and simultaneously on wells MWA R, MW-2R, and VW-1 for 92 hours DPE was
<br /> conducted at vapor extraction flow rates ranging between 10 90 standard cubic feet per
<br /> minute (scfm) to 42 86 scfm, at vacuums ranging from 14 to 25 inches of mercury, and at
<br /> groundwater extraction flow rates ranging from 0 01 gpm to 6 2 gpm During DPE testing,
<br /> an estimated 8 11 pounds of TPHg, 0 17 pounds of benzene, and 5 26 pounds of MtBE
<br /> were removed from beneath the site, and approximately 26,210 gallons of groundwater
<br /> were extracted and transported off-site for disposal The results of DPE testing indicated
<br /> that this technology was ineffective based on the low soil vapor extraction radius of
<br /> influence (24 feet), the large quantity of extracted groundwater, and low estimated mass
<br /> 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)
<br /> wells in March and April 2004, and completed the installation of an OS system in April and
<br /> May 2004 The OS system consists of a KVA C-spargeTm panel, a ten-point injection
<br /> manifold, and buried 3/8-inch diameter, and high density polyethylene (HPDE) system lines
<br /> contained in 2 to 6-inch diameter PVC conduits Each point on the injection manifold is
<br /> equipped with an electrical solenoid, which controls the flow of ozone/air mixture to the OS
<br /> wells The solenoids are controlled by a timer, which Is programmed to sequentially inject
<br /> into each well for 7 minutes (70 minutes total for each cycle), 18 times a day (18 cycles per
<br /> day) The sparge panel is equipped to with a compressor rated to deliver 6 standard cubic
<br /> • feet per minute at 10 pounds per square inch (psi) The OS system was brought on-line on
<br /> May 25, 2004 (SECOR, 2004)
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<br /> 11C0nocoPhi1hps\Retajl sites1111931QMR14QMR04 Final doc
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