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Mr.M. Scott Mansholt—CEMC <br /> ' Annual 2009 Groundwater Monitoring and Sampling Report April 15,2o09 <br /> Page 6 of 6 <br /> Alden Park <br /> ' CONCLUSIONS AND RECOMMENDATIONS <br /> Groundwater samples were collected on January 15 and 16, 2009, from MW-4,MW-7 through <br /> MW-12, and MW-14, and SPO extraction was performed on MW-1,MW-3,MW-5, MW-6, <br /> jMW-15, MW-16, MW-18, MW-20, and MW-21. Approximately 142 gallons of SPO were <br /> removed during 2008, and approximately 41 gallons of SPO were removed during the first <br /> quarter of 2009. The calculated groundwater elevation and gradient were consistent with <br /> historical results. <br /> TPHd were present in concentrations above the ESL and WQO in MW-7, which is consistent <br /> with previous sampling events. The PAHs benzo(a) pyrene and dibenz(a,h)anthracene were <br /> detected in MW-8 in concentrations that exceeded their respective WQOs and/or ESLs. <br /> ' The SPO and dissolved petroleum hydrocarbons plume has shown little variation since 1995 and <br /> is considered stable. <br /> SAIC recommends the following: <br /> t • Continue annual groundwater monitoring and sampling of the wells that do not contain <br /> SPO; and <br /> ' • Perform semi-annual quarterly SPO recovery from MW-5 and MW-21 via oleophilic <br /> socks, and from the remaining wells containing SPO via vacuum extraction. <br /> • The decrease in SPO recovery frequency from quarterly to semi-annual events is <br /> recommended on the basis of the stability of the plume. <br /> CLOSING <br /> If you have any questions regarding this report, please call Caryl Sheehan at (916) 979-3836. <br /> ' Sincerely, <br /> SCIENCE APPLICATIONS INTERNATIONAL CORPORATION <br /> �, <br /> Sean Gehlke C ryl S han P.G. 6620 <br /> Project Geologist Princip' eologist �\pNP&G_ <br /> Enclosures: <br /> Qi �r <br /> Figure 1. Vicinity Map C SNEC AN <br /> o <br /> Figure 2. Site Map °� Na•� <br /> Figure 3. Potentiometric Surface Map �! <br /> Figure 4. Petroleum Distribution in Groundwater <br /> Table 1. Water-Level Elevation Data <br /> Table 2. Groundwater Analytical Results (TPH and BTEX) gr�oF CPQ%' <br /> Table 3. Groundwater Analytical Results (PAHs) <br /> Table 4. Summary of SPO Extracted <br /> Table 5. Summary of Groundwater Flow Directions and Gradients <br /> Table 6. Summary of Well Construction Details <br /> ' Attachment A.References for Previous Environmental Investigations <br /> Attachment B.Field Sheets <br /> Attachment C.Data Usability Summary and Laboratory Analytical Reports <br />