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URS Mr. Ross Atkinson Regional Water Quality Control Board—Central Valley Region May 20,2011 Page 3 of 10 to March 2007 (1Q07), were analyzed for general minerals for December 2006 (4Q06), and were analyzed for metals and TDS from December 2006 (4Q06)to March 2011 (1Q11). Groundwater samples were collected from the three monitoring wells using the following procedures: • The water level from each monitoring well was measured using an electronic water level sounder. • Prior to groundwater sample collection,each well was purged using a bailer. During purging, groundwater parameters(pH,temperature, and conductivity)were recorded on the Monitoring Well Sampling Data format least once per well casing volume. Purging was completed when the groundwater parameters had stabilized to within 10 percent. The purged water was placed in a sealed 55-gallon drum. Periodically,the 55-gallon drums of purged groundwater are transported to a permitted disposal facility by a licensed transporter. • A groundwater sample, collected with a bailer from each well,was placed into the analytical laboratory-prepared sample containers. • Groundwater samples were labeled and placed in an ice chest filled with ice. The ice chest was shipped to EMAX analytical laboratory in Torrance, California, under proper chain-of-custody procedures for analysis (i.e.,VOCs by United States Environmental Protection Agency(EPA) Method 8260B,TDS by EPA Method 160.1, and dissolved metals(CAM 17) by EPA Methods 6010/6020/7470). RESULTS Well Search A well search could not be completed at the State of California Department of Water Resources (DWR) offices because a letter from RWQCB was not received by URS. However, a well search was completed by URS on the following DWR website: llttp://www.water.ca.gov/waterdatalibrary/. Based on this well search,two wells were found to be within a mile of the site. One well (A002) is actively monitored and the other well (J001)was abandoned in 1974. The active well is located approximately 0.4 mile east-northeast of the site. Figure 3 shows the location of the wells found during the well search. Table 1 provides a summary of the wells located within a mile of the site. Hydrogeology An interpreted groundwater contour map was prepared for each quarter from June 2006 to March 2011. The groundwater flow direction was found to be to the east-northeast six times (4Q06, 1 Q07, 2Q07, 4Q07, 1 Q08, and 4Q 10),to the northeast seven times (2Q06, 4Q08, 1 Q09,2Q09, 1 Q10, 2Q 10, and 1Q11),to the northwest once (3Q07),to the west-northwest three times (3Q08,4Q09, and 3Q10),to the west twice(2Q08 and 3Q09), and to the southwest once(3Q06). During the period when the groundwater samples were collected for metals(4Q06 to 1Q11), the groundwater flow direction was typically found to be to the east-northeast or to northeast 67 percent of the time(12 of the 18 times). Table 2 summarizes the quarterly groundwater flow direction and gradient. H:AWprocess\25532\WorldEnterpriseAClosureA05201 I.doc