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Well Installation RMgq August 17,2001 ARCO Facility No. 5469 Stockton, California • Page 3 Delta contacted the District Manager of California Water Services, Mr. Paul Risso, to verify the location and use of water wells located in the DWR well search. Mr. Risso indicated that wells 1-09, 1-11, and- 1-13 (located at Wilson Way and Sonora Street) have been abandoned. Well 1- 16 (also located at Wilson Way and Sonora Street) is in the process of being abandoned. Wells 1-23, 1-24, and 1-25 are currently"standby wells" and have not been operated in the last 8 years. Mr. Risso indicated that wells 1-23, 1-24, and 1-25 are not likely to be operated in the near future. Well 34-01 (located at Sonora and Locust Streets) and well 40-01 (located at 1800 East Lafayette Street) are also inactive wells that have not been operated in the last 8 years. Well 39- 01, located near the outer limit of the 2,000-foot radius, is an active well. Mr. Risso did not know the pumping rate of this well. The only other known water supply well located within the 2,000-foot radius of the site is listed as being owned by the Richmond-Chase Company. The location of the well is listed at A Street and Weber Avenue. Contact has not been made to ascertain the status of this well. The Richmond-Chase Company well is located northeast of the site at the outer limit of the 2,000- foot radius. Monitoring Well Installation Prior to the initiation of field activities, well permits were obtained, the proposed well locations were marked, and Underground Service Alert and San Joaquin County PHS/EHD were notified of the work schedule. The initial 5 feet of the borings were advanced with a posthole digger and/or hand auger to reduce the possibility of damaging underground utilities. On May 30 and 31, 2001, a Delta representative, under the direction of a California Registered Geologist, was on site to oversee the drilling of four soil borings. The borings were subsequently converted to monitoring wells MW-7 through MW-10. The borings were drilled in two general locations, with each location containing two wells screened at two depth intervals. The wells were constructed using 4-inch diameter, 0.020-inch factory-slotted PVC casing installed to a depth of approximately 33 to 53 feet bgs (MW-7 and MW-8) and approximately 59 to 74 feet bgs (MW-9 and MW-10). Boring logs and well construction diagrams for the newly installed wells are presented in Appendix B. The wells were drilled using a truck-mounted drilling rig equipped with 10-inch diameter hollow-stem augers. All sampling equipment was cleaned using a LiquinoxTM solution and triple rinsed prior to, and between, each sampling event. Soil borings MW-9 and MW-10 were sampled at five-foot intervals. Soil boring MW-10 was continuously sampled from approximately 65 to 74 feet bgs. Given the proximity of monitoring wells MW-7 and MW-8 to wells MW-9 and MW-10, soil samples were not collected from soil borings MW-7 and MW-8. Soil samples were collected by driving a modified California-type split-spoon sampler, equipped C:1ARC0154691REP0RTS15469Well Installation 0601.doc