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Teichert-Stockton December 17, 2001 Page 2 • in any of the four soil samples analyzed. Table 1 from Stratus' Confirmation Boring and Site Closure Report has been updated to include TAME, ETBE, DIPE, and TBA, and is attached. Two single-walled, 20,000-gallon USTs and one double-walled, 12,000-gallon UST were removed by Town and Country on March 23, 1999. One double-walled, 1,000-gallon UST was removed by Savidge Construction on October 24, 2000. Figure 2 from Stratus' Confirmation Boring and Site Closure Report has been updated to show the locations of the former USTs. A copy of this revised Figure 2 is attached Copies from portions of previously prepared reports that include analysis for lead are attached (Appendix B). An October 6, 1988 letter from L.B.M.E. Corporation to PHS- EMD included results for lead analyses performed on two samples collected after removal of the last UST. Soil samples were collected from 17 feet bgs at the east end of the UST, and from 15 feet bgs at the west end of the UST. Lead was not detected in either of these samples. Soil samples collected at 35 feet, 45 feet, and 55 feet bgs in borings for wells MW-9, MW-10, and MW-11 were also analyzed for lead. Organic lead was not detected in any of these samples. If other samples from this site have been analyzed for lead, these data are not available for review at this time. Stratus sampled the three remaining groundwater monitoring wells (MW-13, MW-14, and AS-1) on October 3, 2001. Stratus' Sampling and Analysis Procedures are attached . (Appendix Q. The samples were submitted under chain-of-custody to Alpha Analytical, Inc. (Alpha), a California-licensed analytical laboratory. The samples were analyzed for TPHG, BTEX, MTBE, TBA, DIPE, ETBE, TAME, 1,2-dibromoethane (EDB), 1,2- dichloroethane (1,2-DCA) by EPA Method SW8260B, and for lead by EPA Method 200.8. TPHG was detected in all three wells at concentrations ranging from 0.19 to 6.1 milligrams/liter (mg/L). BTEX or MTBE were only detected in the sample from well MW-13. Benzene was detected at a concentration of 68 micrograms/liter (pg/L), and MTBE was detected at a concentration of 13 l.tg/L. TBA was detected in the samples from wells MW-13 (61 µg/L) and MW-14 (7.1 µg/L). 1,2-DCA was detected in the samples from wells MW-14 (1.8 µg/L) and AS-1 (9.7 pg/L). Lead was detected in the samples from wells MW-13 (0.035 mg/L) and AS-1 (0.03 mg/L). Analytical data are summarized in Table 2. A copy of the Alpha report and chain-of-custody documentation are attached (Appendix D). Wells MW-13, MW-14, and AS-1 are located in the core of the dissolved hydrocarbon plume. Historical groundwater analytical data summarized in Table 3 of Stratus' Final Closure Report suggests that the dissolved hydrocarbon plume has been delineated. The groundwater samples collected from these wells on October 3, 2001, contained TPHG, BTEX, and MTBE at concentrations that were similar to historical concentrations of these analytes when the wells were last sampled. These recent petroleum hydrocarbon concentrations fit the historical trends at the site, suggesting that the dissolved plume P:\Teichert\Stockton-103\Reports\Tiechert letter.doc