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 4 of 7 ' Depth to groundwater was measure p g d in MW-4, MW-7 through MW-12, and MW-14 on January 5, 2010. Cumulative depth-to-groundwater measurements and groundwater ' elevations are provided in Table 1. A potentiometric map showing groundwater elevation contours and flow direction is shown on Figure 3. Field data sheets are ' provided as Attachment B. • Site Wells in Program: MW-1, MW-3 through MW-12, MW-14 through MW-16, MW-18, MW-20, and MW-21. ' • Wells Containing SPO: MW-1, MW-3, MW-5, MW-6, MW-15, MW-16, MW- 18, MW-20, and MW-21 have historically contained SPO. MW-5 and MW-21 ' contain oil-absorbent(oleophilic) socks that are monitored on a semi-annual basis. Vacuum extraction of SPO from the remaining wells is performed on a quarterly basis. ' • Depth to Groundwater at the Site: Ranged from 11.42 feet below top of casing (btoc) in MW-8 to 14.18 feet btoc in MW-11. Depth-to-groundwater measurements collected to date from these wells indicate that the average depth to ' groundwater at the site is 11.23 feet btoc. • Calculated Groundwater Elevation: Ranged from 38.36 feet above mean sea ' level (MSL) in MW-7 to 41.33 feet above MSL in MW-12. Groundwater elevation measurements collected to date from these wells indicate that the average groundwater elevation at the site is 41.54 feet above MSL. ' • Approximate Groundwater Flow Direction/Gradient: Predominantly toward the north northwest at 0.003 ft/ft, which is consistent with historic groundwater flow-gradient site data. ' SAMPLING MW-4, MW-7, MW-8, MW-10, MW-11, and MW-12 were purged by the regulatory- approved, low-flow minimal drawdown method using a low-flow submersible pump with dedicated polyethylene tubing following depth-to-groundwater measurements. MW-9 and MW-14 were purged using the three-volume purge method because draw down ' exceeded 0.33 foot. Measurements of pH, specific conductance, temperature, oxygen- reduction potential, turbidity, and dissolved oxygen water-quality parameters were ' recorded during the purge process. Groundwater samples were collected after water- quality parameters stabilized (stabilization criteria are shown on the field data sheets). The groundwater samples were decanted into laboratory-provided bottles, which were I ' labeled, sealed, and placed immediately into an ice-cooled container for delivery to Lancaster Laboratories, Inc. (Lancaster)3, under SAIC chain-of-custody protocol. Samples were not collected from MW-1, MW-3, MW-5, MW-6, MW-15, MW-16, ' MW-18, and MW-20 due to the presence of SPO. A sample was not collected from MW-21 due to the presence of sheen. ' 3. Lancaster is a California-certified laboratory(FLAP#2116).