ARCHIVED REPORTS_ANNUAL 2010 GROUNDWATER MONITORING AND SAMPLING REPORT

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' Mr,Lee Higgins—CEMC Annual 2010 Groundwater Monitoring and Sampling Report April 19,2010 Alden Park Page 6 of 7 ASSURANCE/QUALITY E QUALITY Q C (QUALITY CONTROL All field procedures were conducted in accordance with SAIC's quality assurance/quality control procedures5. SAIC-Benham's evaluation concludes that all analytical data are usable as qualified for the purpose of determining chemical concentrations in groundwater at the site. Data reported in laboratory report 1177787 for this sampling event were qualified E for ' values that were estimated due to associated quality control results. Qualified data with applicable reason codes are provided in Table C-1 of Attachment C. Analytical data collected in support of this investigation are considered precise, accurate, ' representative, complete, and comparable, and may be used for the intended purposes unless noted otherwise. ' CONCLUSIONS AND RECOMMENDATIONS Groundwater samples were collected on January 5 and 6, 2010, from MW-4, MW-7 through MW-12, and MW-14; and SPO extraction was performed on MW-1, MW-3, 1 MW-5, MW-6, MW-15, MW-16, MW-18, MW-20, and MW-21. Approximately 122 gallons of SPO were removed during 2009, and approximately 40 gallons of SPO ' were removed during the first quarter of 2010. The calculated groundwater elevation and gradient were consistent with historical results. TPHd were present in concentrations above the ESL and WQO in MW-7, which is consistent with previous sampling events. The PAHs benzo(a)pyrene, ' benzo(b)fluoranthene, benzo(k)fluoranthene, dibenz(a,h)anthracene, and indeno(1,2,3- cd)pyrene were detected in MW-8 in concentrations that exceeded the respective WQOS ' and/or ESLs. Prior to 2009, PAHs were not detected or did not exceed screening levels in MW-8. The 2011 sampling event will provide data that can be used to determine if the PAHs detected in groundwater in MW-8 are an anomaly or representative of a trend. ' The SPO plume has shown little variation since 1995 and is considered stable. SAIC-Benham recommends the following: t • Continue annual groundwater monitoring and sampling of the wells that do not contain SPO; • Perform semi-annual SPO recovery from MW-5 and MW-21 via oleophilic socks; and + Perform quarterly extraction of SPO from the remaining wells via vacuum extraction. f1 ; ' 5. SAIC,2007. Quality Assurance and Quality Con trQl Sample Collection,Handling, and Analysis. April (Updated).