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<br /> ikl rJ T E C ® R
<br /> Ms Lori Duncan
<br /> February 9, 2004
<br /> Page 3
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<br /> supply wells were documented in the vicinity of the site These water supply wells were located in the
<br /> field, approximately '/� mile east of the site at the Stockton State Hospital, and approximately 2,000 ;
<br /> feet northwest of the site, at the Intersection of Wyandotte and Commerce Streets Results of the
<br /> well survey are Included in SECOR's report titled, Additional Site Assessment Report, dated
<br /> November 9, 2001
<br /> Also In 2001, SECOR performed a utility survey to evaluate whether nearby off-site utilities or otherT'
<br /> underground improvements may act as potential conduits for migration of petroleum hydrocarbons
<br /> Since depth to water at the site is approximately 27 feet bgs and no underground Improvements ory
<br /> utilities were identified near this depth, it is unlikely that any subsurface utilities or other unknown
<br /> underground improvements are preferential migration pathways for petroleum hydrocarbon-impacted
<br /> groundwater SECOR concluded that higher potential exists for vapor-phase contaminant migration
<br /> through these areas (SECOR,Additional Site Assessment Report, dated November 9, 2001)
<br /> As a result of the discovery of LPH in wells MW-4 and SVE-1 during the third quarter 2001 sampling
<br /> event on July 20, 2001, weekly interim groundwater remediation was initiated on October 29, 2001,
<br /> which consisted of the removal of LPH and petroleum hydrocarbon-impacted groundwater from the
<br /> wells with a bailer Interim GWE continued for approximately six weeks until measurable LPH was
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<br /> no longer present Between October 29, 2001 and December 17, 2001, approximately 10 to 15
<br /> gallons of LPH had been removed from the wells As a result of the continued presence of elevated
<br /> concentrations of petroleum hydrocarbons and MtBE in on-site wells, interim GWE was reinitiated on
<br /> March 18, 2002 utilizing a vacuum truck Between March 18 and August 2, 2002, approximately
<br /> 23,350 gallons of LPH and petroleum hydrocarbon-Impacted groundwater had been removed from
<br /> beneath the site ,
<br /> On March 14 and 15, 2002, West Hazmat Installed one deep groundwater monitoring well (DMW-1) "
<br /> and one GWE well (EW-1) DMW-1 and EW-1 were completed at 81 feet bgs and 44 feet bgs,
<br /> respectively Stabilized groundwater levels in wells DMW-1 and EW-1 were measured at 29 and 28 �
<br /> feet bgs, respectively TPHg was detected in four of the ten samples at a maximum concentration of fy
<br /> 780 mg/kg (EW-1, 27 5') Benzene was detected in six of the ten samples at a maximum
<br /> concentration of 5 1 mg/kg (EW-1, 27 5') MtBE was detected in eight of the ten samples at a ,
<br /> maximum concentration of 290 mg/kg (EW-1,27 5')
<br /> On April 2 through 4, 2002, a step drawdown pumping test, constant rate drawdown pumping test,
<br /> and aquifer test were completed Results were as follows
<br /> • Capture zones of approximately 31 feet and 48 feet were calculated in the downgradlent and f
<br /> cross-gradient directions, respectively The capture zone was calculated using the Javandel g,
<br /> and Tsang method
<br /> • A pumping rate 4 and 6 gallons per minute was used for the constant rate drawdown
<br /> pumping test
<br /> The well Installation and aquifer pumping test Is documented in SECOR's report titled, Site
<br /> Assessment and Aquifer Testing Results, dated June 7, 2002
<br /> On June 10 through 13, 2002, two monitoring wells (MW-10 and MW-11), two deep monitoring wells 'x
<br /> (DMW-2 and DMW-3), and one extraction well (EW-2) were installed at the site by West Hazmat
<br /> (Figure 2) Monitoring wells MW-10 and MW-11 were completed at 40 feet bgs, and were Installed
<br /> with a 2-inch PVC well casing screened from 20 to 40 feet bgs These wells are located off-site to
<br /> . the north, MW-10 is in an alley off EI Dorado Street and MWA 1 is on the corner of EI Dorado Street
<br /> and Sperry Avenue Deep monitoring wells (DMW-2 and DMW-3) were completed at 82 feet bgs,
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