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Boyett Petroleum, Manteca Third Quarter 2002 Groundwater Monitoring Report Page 8 Monitoringevent relative to the previous sampling event conducted in December 2001 indicate a decrease in p p g the concentration of MTBE detected in samples collected from MW-1 and MW-7, and an increase in the concentration of MTBE detected in MW-2. Monitoring wells MW-4 and MW-5 were dry on September 26, 2002. This represents the first time MW-4 and ' MW-5 have been dry since monitoring of these wells was initiated in September 1999 and December 2000, respectively, with the exception of September 10, 2001, when MW-5 was reported to have been dry. Static water level measurements collected from monitoring wells MW-1, MW-2, MW-3, MW-6, MW-7, and MW-8 on September 26, 2002 generally indicate a groundwater gradient direction to the south/southwest. 7.0 RECOMMENDATIONS ' Quarterly monitoring of the site should continue. All of the monitoring wells contain high percentage of sediment and require redevelopment. Condor recommends that damaged wells MW-4 and MW-5 be properly destroyed and MW-4 be replaced by a new monitoring well. Condor also recommends the installation of an additional well south of MW-9 as shown in Figure 4, Appendix A. Installation of a well south of MW-9 should provide data between the USTs and the northwestern portion of the site, which has historically contained elevated levels of MTBE in groundwater samples collected from monitoring wells MW-1 and MW-7. Data from this location should be useful in evaluating whether the UST area is the likely source of the elevated levels of MTBE in groundwater in the northwestern portion of the site. ' 8.0 LIMITATIONS AND SIGNATURE This report was prepared under the direct supervision of a Registered Geologist in the State of California. The standard of care for all services performed or furnished by Condor is commensurate with the care and skill ordinarily used by members of the environmental profession practicing under similar conditions at the same time in the same locality. Condor is not responsible for the accuracy and completeness of information collected ' and developed by others. This report was prepared for the sole use of Boyett Petroleum, and may not be used or relied upon by any other person(s) without the express written consent and authorization of Boyett Petroleum and Condor. If any changes are made or errors found in the information used for this report, the interpretations and conclusions contained herein shall not be considered valid unless the changes or errors are reviewed by Condor and either ' appropriately modified or re-approved in writing. Any questions regarding the content of this document should be addressed to Todd Hafiier at(209)234-0518. Respectfully submitted, CONDOR EARTH TECHNOLOGIES,INC. rRED GE�l p� aMicheline Doyle Kipf Todd C. Hafner David ood No. 6532 MW Staff Geologist Associate Geologist Californ'a egistered Geolagis iqrF GAl.1F�P P:\376 IP Boyett Manteca\QMRASeptember 200213QMR.doc OF 1 1 i s CONES.