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Mr.M. Scott Mansholt—CEMC Second Quarter 2007 Groundwater Monitoring and Sampling Report July 26,2007 US Can-Welty Road Page 4 of 6 QUALITY ASSURANCE/QUALITY CONTROL All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis2 procedures. Based on SAIC's evaluation, all analytical data are usable as qualified for the purpose of determining chemical concentrations in groundwater at the site. Qualified data with applicable reason codes are shown in Table B-1 of Attachment B. Unless noted otherwise,analytical data collected in support of this investigation are considered precise, accurate,representative, complete, and comparable, and they may be used for their intended purposes. CONCLUSIONS AND RECOMMENDATIONS The second quarter 2007 groundwater monitoring and sampling event was completed on April 30,2007. Groundwater elevation at the site varied between 71.48 and 71.94 feet above MSL with a flow gradient toward the east at 0.001 ft/ft. Historically,the groundwater flow direction has been east/southeast and the groundwater elevation at the site has ranged from 70.19 to 73.09 feet above MSL. The average groundwater elevation at the site is 71.48 feet above MSL. Wells MW-1 and MW-2 were not sampled during the second quarter 2007 due to the observation of a petroleum-hydrocarbon sheen during monitoring activities. Wells MW-3 and MW-4 were not sampled due to insufficient water volume to collect a sample. Groundwater samples were collected from MW-5 and WFSMW-1 and analyzed for TPHd and PAHs. TPHd were detected above the WQO and ESL in WFSMW-I at 630 gg/L and were non-detect(<50 gg/L) following silica-gel cleanup. Results of the fuel- fingerprint analysis conducted by ETC on this sample showed that hydrocarbons detected in the WFSMW-1 sample were predominantly in the gasoline range(C,-Clo at 78.4 percent). These results are also consistent with the first quarter 2007 fuel fingerprint-analysis results. This indicates that the petroleum-hydrocarbon detection in the WFSMW-1 sample analyzed by Lancaster and reported as TPHd likely represents the heavier hydrocarbons within the gasoline range that overlap with lighter-fraction hydrocarbons sometimes present within the diesel range, and are not representative of materials transported in the pipeline. Dissolved-phase hydrocarbons appear to be localized in the vicinity of off-site well WFSMW-1. Samples from well WFSMW-I have historically shown elevated levels of petroleum hydrocarbons reported as TPHd,with concentrations ranging from 66 gg/L to 970 gg/L. All samples with detectable concentrations of TPHd were silica-gel cleaned prior to reanalysis. Results have shown that TPHd were non-detect after silica-gel cleanup. Historically, TPHd have not been detected in MW-5 above the WQO or ESL. The oleophilic socks in wells MW-I and MW-2 were replaced during second quarter 2007 monitoring because they exhibited SPO staining. However,no measurable amounts of SPO were removed from either of these wells. SPO has been observed in wells MW-1 and MW-2 since 1999 with a total of 0.34 gallon of SPO removed from these wells to date. PAHs were not detected above ESLs or WQOs in any of the second quarter 2007 samples. Historically, PAHs have only been detected above ESLs or WQOs in wells MW-2 and MW-3,but not since 2005. 2. SAIL,2007. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. April(Update).