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S EC ® R <br /> JAN 2 3 2006 <br /> • Mr Harlin Knoll ENVIRONMENT HEALTH <br /> January 23, 2006 <br /> Page 2 PERNIIT1SERVICES <br /> butyl ether (MtBE), and tertiary butyl alcohol (TBA) laboratory analytical data are presented <br /> below <br /> Number of Detections Minimum Detected Maximum Detected <br /> Constituents above the MDL of the 10 Concentration in pg1L(well ID) Concentration in pg/L(Well ID) <br /> Total Samples <br /> TPHg 4 <50 2,200(MW-4D) <br /> Benzene 2 <0 5 360(MW-4D) <br /> MtBE 3 <0 5 20(MW-3) <br /> TBA 4 <5 58(MW-3) <br /> Explanation <br /> MDL=Method detection limit <br /> ug/L= Micrograms per liter <br /> CONCLUSIONS <br /> Historical groundwater monitoring data Indicates that concentrations of tertiary amyl methyl <br /> • ether (TAME) have not been at or above the MDL since sampling began In 1998 in <br /> groundwater monitoring wells MW-1, MW-2, MW-4, MW-5, MW-5D, MW-6, MW-6D, and <br /> MW-7 TAME was detected in MW-3 at 2 6 Ng/L In February 2001 and In MW-4D during <br /> three consecutive monitoring events of May, June and October 2003 with concentrations of <br /> 11 Ng/L, 5 pg/L and 3 pg/L, respectively However, prior to and following these detections, <br /> TAME concentrations have been below the MDL Furthermore, there are no detections of <br /> ethanol, di-Isopropyl ether (DIPS), and ethyl tertiary butyl ether (EtBE) at or above their <br /> respective MDLs In any of the site monitoring wells since sampling began In 1998 <br /> RECOMMENDATIONS <br /> In light of the above observations, with the approval of the San Joaquin County <br /> Environmental Health Department (EHD), SECOR recommends removing the analytes <br /> ethanol, DIPE, EtBE, and TAME from the sampling protocol beginning in the first quarter <br /> 2006 SECOR would also like to meet with the EHD to discuss future activities at the site <br /> • <br /> N IFdeslProlectslChevron%Retaill#9-32321Periodic Monitonng1200514QMR0514QO5 QMR doc <br />