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1 ERI 205503 R03 Tosco 7¢Serv=Station 5886—Stockton. California June 9 1914 under the guidance of a California Registered Geologist who observed collection of soil samples from the deepest borings during driling Soil samples were collected at approximately 5-foot intervals from the deep soil boring at each well cluster location (borings B11, B14, and B17) Soil samples were not ' collected from the shallow and intermediate soil borings at each well cluster location due to the proximity of the deep borings ERI's geologist described soil lithology from the soil samples collected from the borings using visual and manual classification methods The samples were classified using the Unified Soil Classification System (Attachment D) Descriptions of the materials encountered are presented in the Boring Logs (Attachment D) Soil cuttings generated during drilling were placed in 55-gallon drums, temporarily placed on site, and sampled for laboratory analyses,pending appropriate disposal by Tosco Monitoring-Well Construction= Development,_Samph".-and Surveying On April 8, 1999, immediately after the borings were drilled and sampled, off-site groundwater monitoring wells MW8S/IID through MWIOSII/D were constructed in borings BI I through B19 Groundwater monitoring well locations are shown on Plate 2 The groundwater monitoring wells at 1 each well cluster location were slotted at specific depth intervals to evaluate groundwater conditions at discrete depths Shallow well casings (MW8S through MW10S) were slotted from 5 to 15 feet bgs Intermediate well casings (MW81 through MW101) were slotted from 17 to 22 feet bgs Deep well casings (MWBD through MW10D) were slotted from 30 to 35 feet bgs Details of the monitoring well construction are shown on the Boring Logs (Attachment D) On April 12, 1999, Morrow Surveying of Sacramento, California surveyed the new well locations relative to a permanent datum and top of casing (TOC) elevations relative to mean sea level (msl) On April 14, 1999, ERI's representative developed the nine new wells using surging and pumping ' techniques On April 14 and 15, 1999, ERI's representative measured depth to water in wells MW1 through MW 10S1I/D and collected groundwater samples from newly installed wells MW8S/I/D through MW IOS/IID Purge water generated during well development and sampling was left on site pending ' removal by Tosco to the Tosco Refinery in Rodeo, California Analytical Methods- Groundwater SaMples ' Groundwater samples collected from off-site clustered wells MW8SIIID through MW l0S/I/D were submitted under Chain of Custody Protocol to Sequoia Analytical Laboratories([Sequoia] California Certification#1210) The laboratory analysis reports and Chain of Custody records are provided in Attachment E Groundwater samples were analyzed for TEPHd,TPPHg, BTEX, MTBE, methanol,and ethanol using the methods listed in Table 1 3