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y Mr.Harlin Knoll Y' San Joaquin County Environmental Health Department Page 2 of 3 Groundwater Sampling and Analytical Results i Groundwater monitoring wells MW-1 through MW-3 were sampled on July 13, 2005. The methods used to collect the samples are presented in Attachment A Samples from these wells were analyzed for total petroleum hydrocarbons in the gasoline range (TP g), benzene, toluene, ethylbenzene, xylenes (BTEX), methyl tertiary butyl ether (MTBE), tertiary am 1 methyl ether (TAME), tertiary butyl alcohol (TBA), di-isopropyl ether(DIPE), and ethyl tertiary butyl ther (ETBE) using EPA Test Method 8260B. Due to a sampling oversight, samples were not tested fortotal petroleum hydrocarbons as diesel (TPHd). Kiff Analytical Labs, Inc. (Kill Analytical) of Davis, California, a California state-certified laboratory, performed the chemical analyses. The analytical la oratory report, including chain-of-custody documentation, is included as Enclosure C. Laborator3 analyses results for the third quarter 2005 sampling event are presented in Table 1 and concentrations of MTBE, benzene, and TPHg are shown on Figure 4. Conclusions ■ Concentrations of TPHg remained below the laboratory reporting limit of 50 micrograms per liter (µg/L) in wells MW-1,MW-2 and MW-3. ■ Concentrations of MTBE in groundwater collected from MW-1 continue to decrease, despite a slight increase last quarter. ■ The groundwater flow direction trend is in a northwesterly direction (Figure 3), although the overall trend for the site has generally been in a southeasterly direction. Future Work The next groundwater monitoring event is scheduled f r October 2005. A down-gradient, off-site groundwater monitoring well has been proposed and will be installed if Delta is successful at obtaining a right-of-entry agreement with the owner of the adjacent shopping center,Mr. Daniel McNeer. Remarks The recommendations contained in this report representDelta's professional opinions based upon the currently available information and are arrived at in acco dance with currently acceptable professional standards. This report is based upon a specific scope ol work requested by the client. The contract between Delta and its client outlines the scope of work, and only those tasks specifically authorized by the contract or outlined in this report were performed. Thi report is intended only for the use of Delta's client and anyone else specifically listed on this reporl. Delta will not and cannot be liable for unauthorized reliance by any other third party. Other than as contained in this paragraph, Delta makes no express or limited warranty as to the contents of this report. rl I