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Site History
<br /> Boyett Petroleum(419 S.Main St., Manteca)
<br /> ' Page 2 of I l
<br /> intervals for soil classification and three soil samples were collected from each boring at depth intervals
<br /> of 16-16.5 feet, 20-21.5 feet, and 26-26.5 feet for laboratory analyses. Laboratory analytical results of the
<br /> twelve soil samples indicated petroleum hydrocarbons were not detected at or above the laboratory
<br /> reported detection limits in any of the samples.
<br />' On February 2, 2001, WHF, in conjunction with VBI In-Situ Testing of Sacramento,California, advanced
<br /> two CPT borings at the site. CPT-1 and CPT-2 were completed to depths of 76 and 76.4 feet bgs,
<br /> respectively. Both borings were terminated due to refusal. Beds of clay were encountered in CPT-] at
<br /> depths of 20 to 24.1 feet and 50.2 to 57.6 feet bgs. In CPT-2, beds of clay were encountered at depths of
<br /> 23.8 to 26.4 feet, 49.7 to 56.4 feet, and 62.7 to 66.9 feet bgs. WHF submitted a report of their findings of
<br /> the CPT borings in a letter dated February 7, 2001,to Mr. Jeffrey Wong of the SJCEHD.
<br />' On April 25, 2001, WHF, in conjunction with Frontier Drilling, completed a deep monitoring well, MW-
<br /> 9, to a depth of 50.5 feet bgs. The screened interval for the well was installed at approximately 40.5 to
<br />' 50.5 feet bgs. Groundwater depth was measured at approximately 17 feet bgs. Two soil samples were
<br /> collected from the borehole at depths of 43.5 feet and 50 feet for laboratory analyses.None of the analytes
<br /> of concern (BTEX, TPH-G, and MTBE) were detected in the soil samples collected from the borehole of
<br /> MW-9. Laboratory analytical results of a groundwater sample collected from MW-9 indicated that none
<br />' of the analytes of concern (BTEX,.TPH-G, and selected gasoline oxygenates/additives) were detected,
<br /> with the exception of MTBE, which was detected at a concentration of 14 µg/L. In the Final Report of
<br /> Findings —Lateral Extent of Groundwater Contamination dated June 29, 2001, WHF concluded that the
<br />' source of the petroleum hydrocarbon contamination had not been identified and recommended that
<br /> quarterly groundwater monitoring continue, one additional monitoring well be installed directly east of
<br /> the fuel island, and that no remedial action be taken at this site until the source was identified.
<br />' • On September 26, 2002, a representative of Condor was onsite to measure water levels and collect
<br /> groundwater samples at monitoring wells MW-1 through MW-9 for the third quarter 2002 groundwater
<br /> monitoring event. Monitoring wells MW-4, MW-5,and MW-6 were heavily silted, and MW-4 and MW-5
<br /> were dry. Mr. Jeffrey Wong of the SJCEHD was onsite to observe a portion of the field activities.
<br /> At the request of the SJCEHD, a Condor representative was onsite to redevelop monitoring wells MW-4,
<br /> MW-5, and MW-6 on September 27, 2002. The redevelopment procedure applied to MW-4 and MW-5
<br /> consisted of flushing the wells with potable water, and then bailing the water from the wells. The
<br /> sediment removed from the wells consisted of medium to coarse-grained, well-rounded, and well-sorted
<br />' sand. The redevelopment activities failed to significantly reduce the amount of sediment inside the well
<br /> casings; consequently, redevelopment of MW4 and MW-5 was not successful. Based on Condor's field
<br /> observations, it appeared the casings of these wells are damaged and allowing the annular sand pack to
<br /> infiltrate inside the casings. MW-6 was successfully redeveloped by removing a significant amount of the
<br /> sediment from inside the well casing. A groundwater sample was collected for laboratory analyses from
<br /> MW-6 on September 30, 2002. No floating product, sheen, or odors associated with petroleum
<br />' hydrocarbons were observed in any of the wells sampled during the third quarter 2002 quarterly
<br /> groundwater monitoring event. All of the groundwater monitoring wells sampled contained a significant
<br /> amount of suspended sediment. Laboratory analytical results for the groundwater samples collected at the
<br /> site on September 26 and 30, 2002, indicated that none of the analytes of concern (BTEX, TPH-G, and
<br /> selected gasoline oxygenates/additives) were detected at or above the laboratory reported detection limits
<br /> .in the groundwater samples collected from MW-3, MW-6, and MW-8. MTBE was detected in the
<br />_ groundwater samples collected from MW-1, MW-2. MW-7. and MW-9. TAMF. was detected in the
<br /> groundwater samples collected from MW-1 and MW-7. Static water level measurements collected on
<br /> September 26, 2002, generally indicated a groundwater flow direction to the south/southwest.
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