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I 2.0 FIELD METHODS The procedures and methods used during field activities are described in the following sections: 2.1 Drilling and Sampling -- Before drilling, a well installation permit was acquired from the SJCEHD, and an encroachment permit was acquired from the City of Lathrop. Copies of the permits are presented in Appendix A. On September 8, 1993, Borings MW-6 and MW-7 were drilled at the site to 20 feet below grade. Drilling was performed by Soils Exploration Services, Vacaville, California, using a CME 75 drilling rig equipped with 8-inch-diameter, hollow-stem augers. Drilling and soil sampling procedures are presented in Appendix B. Boring logs were prepared using the Unified Soils Classification System. They include a description of soil characteristics such as color, moisture, and consistency. The boring"logs are presented in Appendix C. 2.2 Monitoring Well Installation and Construction On September 8, 1993, Soil Borings MW-6 and MW-7 were converted into Monitoring Wells MW-6 and MW-7 in accordance with the field procedures for groundwater monitoring i well installation presented in Appendix B.' Monitoring Wells MW-6 and MW-7 were constructed using 2-inch-diameter, flush-threaded, Schedule 40, polyvinyl chloride blank casing and 0.020-inch slotted casing. The slotted casing was-installed from 7 to 20 feet below grade. Well construction details'are included. on the boring logs presented in Appendix C. 2.3 Monitoring Well Development and Sampling i Well development and sampling procedures were conducted in accordance with the guidelines of the SJCEHD and RWQCB. Field procedures for groundwater monitoring well development and sampling are presented in Appendix D. Wells were. developed on September 8, 1993, before installing the bentonite and neat cement seal, by removing at least 10 casing volumes or until groundwater was relatively free of sediment. Monitoring Wells MW-1 through MW-7 were sampled on September 15, 1993. To obtain groundwater samples that were representative of the shallow water-bearing zone, the wells were purged of at least 3 well casing volumes before sample collection and while monitoring Ph, specific conductivity, and temperature. The samples were then transported in an iced cooler to a state-certified laboratory following proper chain of custody procedures. Field observations during well development and sampling are presented in the sampling forms in Appendix E. 2.4 Groundwater Level Monitoring and Well Surveying The wells were surveyed to the top of each well casing in reference to a brass disk labeled "UV-34", on Manthey Road, approximately 45 feet north and 52 feet west of the centerline, with an elevation of 12.50 feet above mean sea level. On September 15, 1993, the depth to E:\0\1a-151\ss1:RPrt020494 3