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Site History
<br /> Boyett Petroleum(419 S.Main St.,Manteca)
<br /> Page 4 of 8
<br /> indicated that a groundwater sample collected from this well in September 2002 tested negative
<br /> for MTBE.
<br /> A detailed description of the SRS was presented in Condor's Groundwater Monitoring Report, Third
<br /> Quarter 2002, dated January 16, 2003.
<br /> In the Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003, Condor
<br /> recommended that quarterly monitoring of the site should continue. All of the monitoring wells contained
<br /> a high percentage of sediment and require redevelopment. In addition, Condor recommended that
<br /> damaged wells MW-4 and MW-5 be properly destroyed and MW-4 be replaced with a new monitoring
<br /> well. AIso, Condor recommended the installation of an additional well south of MW-9 in order to provide
<br /> data between the USTs and the northwestern portion of the site, which has historically contained elevated
<br /> levels of MTBE in groundwater samples collected from monitoring wells MW-1 and MW-7. Data from
<br /> this location should be useful in evaluating whether the UST area is the likely source of the elevated
<br /> levels of MTBE in groundwater in the northwestern portion of the site.
<br /> On December 27, 2002, a Condor representative was onsite to measure water levels and collect
<br /> groundwater samples at all nine monitoring wells for the fourth quarter 2002 groundwater monitoring
<br /> event. Monitoring well MW-5 was dry, and MW-4 contained significant sediment and was purged dry
<br /> during sampling and did not recharge; thus, groundwater samples were not collected from MW4 and
<br /> MW-5. No floating product, sheen, or odors associated with petroleum hydrocarbons were observed in
<br /> any of the wells sampled during the fourth quarter 2002 monitoring event. All of the groundwater
<br /> monitoring wells sampled contained a significant amount of suspended sediment. Laboratory analytical
<br /> results for the groundwater samples collected at the site on December 27, 2002, indicated that BTEX and
<br /> TPH-G were not detected at or above the laboratory reported detection limits in any of the groundwater
<br /> samples collected from the monitoring wells. Selected gasoline oxygenates/additives were not detected at
<br /> or above the laboratory reported detection limits in the groundwater sample collected from MW-6. MTBE
<br /> was detected in the groundwater samples collected from MW-I through MW-3 and MW-7 through MW-
<br /> 9. TAME was detected in the groundwater samples collected from MW-I and MW-7. TBA was detected
<br /> in the groundwater sample collected from MW-l. Static water level measurements collected on December
<br /> 1:
<br /> 27, 2002, generally indicated a groundwater flow direction to the north/northeast, a reversal from that
<br /> reported in the Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003.
<br /> In the Fourth Quarter Groundwater Monitoring Report, December 2002, Condor restated the
<br /> recommendations presented in the Groundwater Monitoring Report, Third Quarter 2002, dated January
<br /> 16, 2003, with the additional recommendation that the water levels in the site's monitoring wells be
<br /> measured and groundwater samples collected for MTBE laboratory analyses on a monthly basis, for a
<br /> consecutive six month period. The primary objective of this increase in monitoring frequency would be to
<br /> garner additional information pertaining to the site's historically highly variable groundwater gradient,
<br /> which may help explain the fluctuations in the MTBE levels recorded for MW-2 and MW-8 and the
<br /> historically elevated levels of MTBE in groundwater samples collected from MW-1 and MW-7.
<br /> On March 21, 2003, a Condor representative was onsite to measure water levels and collect groundwater
<br /> samples at all nine monitoring wells for the first quarter 2003 groundwater monitoring event. Monitoring
<br /> well MW-5 was dry, and MW-4 contained significant sediment and was purged dry during sampling and
<br /> did not recharge; thus, groundwater samples were not collected from MW4 and MW-5. Laboratory
<br /> analytical results for the groundwater samples collected at the site on March 21, 2003, indicated that
<br /> MTBEMTB was dee-..!--d in the 1-1 ncu+�ilw tar n.,mr1As. call-ecte 1 {- -- AXIA1 1 ll4111 7 .,.1 AXIAL n 'rA-NAT ....n
<br /> ...... ................ ... ..,.. b• .....,........a .,.. rwu vvawvwu i.., AA —,. a, —..-I, .0 i.i„-1. .1-1—
<br /> detected in the groundwater samples collected from MW-1 and MW-7. Static water level measurements
<br /> collected on March 21, 2003, generally indicated a groundwater flow direction to the west/southwest, a
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