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Site History
<br /> Boyett Petroleum(419 S.Main St.,Manteca)
<br /> Page 6 of 9
<br /> . conducted on foot and residents were contacted by knocking on residential (houses, duplexes/triplexes,
<br /> and apartments) doors and inquiring of the owner/renter. The actual and potential locations of wells were
<br /> identified either by a caretaker or by a neighbor living within the SRS area. Three well locations were
<br /> identified within the study area. No DWR well records were available for two of the three wells. During
<br /> the 2002 sensitive receptor survey for the site vicinity, a well was thought to be located at 188 W. Oak
<br /> Street. When asked, the owner indicated there was no well. During the SRS reconnaissance, the resident
<br /> at 123 W. Stockton Street indicated that a well at this Oak Street location was used by its owner. A well
<br /> was located at 144 W. Wetmore Street during the 2003 SRS reconnaissance. Condor requested permission
<br /> from the property owner to sample the well at this location. Based on conversations with the resident at
<br /> 123 W. Stockton Street, there may be several improperly abandoned wells within the residential area.
<br /> These wells are potential vertical conduits for hydrocarbon contaminants in groundwater in the vicinity of
<br /> the site.
<br /> On July 15, 2003, a Condor representative was onsite to collect water level measurements and redevelop
<br /> monitor wells MW-1 through MW-3 and MW-6 through MW-9. Attempts were made to redevelop
<br /> monitor well MW-9 by surging and pumping the groundwater in the well with a surge block and pump.
<br /> This redevelopment procedure was ineffective due to large volumes of medium-grained, well-rounded,
<br /> and well-sorted sand infiltrating the well.The infiltration of sand resulted in a decrease of 0.10 feet in the
<br /> measured total depth of MW-9. The water purged from MW-9 was light brown in color and cleared
<br /> during redevelopment. Heavy amounts of sand periodically interfered with the pump equipment. Based
<br /> on the results of the redevelopment procedure applied to MW-9, the previous loss of MW-4 and MW-5 to
<br /> sand infiltration, and the historic high sediment content observed in all the site monitor wells, the decision
<br /> was made not to surge or pump the remaining monitor wells. In addition, it was determined even if
<br /> redevelopment was successful, the potential benefits would be limited as water level measurements
<br /> collected from the site monitor wells indicated the wells contained only two to three feet of water.
<br /> A provisional increase in the groundwater monitoring frequency was instituted in July 2003 in which
<br /> water levels in monitor wells MW-1 through MW-3 and MW-6 through MW-9 will be measured on a
<br /> monthly basis and groundwater samples will be collected for MTBE laboratory,analysis for a period of
<br /> six consecutive months. On July 22, 2003, a Condor representative was on site to measure water levels in
<br /> and collect groundwater samples from the specified monitor wells. Laboratory analytical results for the
<br /> groundwater samples collected at the site on July 22, 2003, indicated that MTBE was detected in the
<br /> groundwater samples collected from MW-1, MW-2, MW-7, and MW-9. Static water level measurements
<br /> collected on July 22, 2003, generally indicated a groundwater flow direction to the southwest, consistent
<br /> with that reported in the Second Quarter Monitoring Report June 2003, dated July 30, 2003. In addition,
<br /> the average groundwater elevation (14.32 feet) decreased with respect to the previous quarterly
<br /> monitoring event by 1.06 feet.
<br /> jOn August 6, 2003, Condor collected a water sample from the well located at 144 West Wetmore Street,
<br /> Manteca, California, Laboratory analytical results of the groundwater sample indicated that TPH-G,
<br /> BTEX, and gasoline oxygenates/additives were not detected at or above the laboratory reported detection
<br /> limits.
<br /> On August 19, 2003, a Condor representative was on site to measure water levels and collect groundwater
<br /> samples at monitor wells MW-1 through MW-9. Groundwater samples were not collected from MW-4
<br /> and MW-5 because they were dry. Laboratory analytical results for the groundwater samples collected at
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<br /> ... —ri ..,a .., ... ...... .. .. .. ... ...... ... ... b. ..,. ....... .,,.Y. .,. ...
<br /> from MW-1, MW-2, MW-7, and MW-9. Static water level measurements generally indicated a
<br /> ..e
<br /> . groundwater flow direction to the southwest, consistent with that calculated for the July 22, 2003,
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