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'r u ERI 205503 R02 Tosco 76 Service Station 5886 Stockton,California March 2, 1999 Cone Penetrometer ti n ERI provided the proposed locations of five off-site CPT borings in the fourth quarter 1997, Quarterly Summary Report (ERI, dated January 28, 1998) The purpose of these CPT borings was to further evaluate the extent of dissolved MTBE detected in groundwater during ongoing quarterly groundwater monitoring and sampling activities The proposed CP locations are shown on PIate 2 PRESENT INVESTIGATION Based upon discussions with a representative of the City, and difficulties in obtaining access agreements with property owners near the site, Tosco and ERI selected to conduct this investigation within the City right-of-way ERI obtained an encroachment permit from the City to advance CPT borings within the March Lane right-of-way and drilling permits from the County to advance up to five off-site CPT borings and three on-site soil borings Copies of these permits are provided in Attachment D Due to the provisions of the encroachment permit, which limited work exclusively to sidewalk areas ,and the location of underground utilities, ERI was unable to drill near the southwest corner of the site or directly south of the site on the south side of March Lane ERI performed the work in accordance with ERI's Work Plan and Addendum to the Work Plan whenever possible, a Site Safety Plan (which was kept on site during field operations) and ERI'S field protocol (Attachment E) Any deviation from the work scope was discussed with Mr Ron Rowe of the County and was conducted with Mr Rowe's knowledge On February 18, 19, and 22, 1999, ERI observed the advancement of three CPT borings (CPT1 through CPT3) and three continuous core soil borings (B8 through B10) by Precision Soil Sampling, Inc (PSS) of San Rafael, California Drilling was performed under the guidance of a California Registered Geologist (registration #4412)/California Certified Engineering Geologist (certification #1675), who observed collection of soil samples from the borings during coring The approximate locations of the CPT soil borings are shown on Plate 2 CPT borings were advanced to refusal, at depths ranging from approximately 9 5 to 18 5 feet bgs Due to the relatively shallow depths of CPT refusal, ERI obtained authorization from Mr Rowe to continuously core at each of the CPT locations Continuous core borings were advanced to depths ranging from 28 to 40 feet bgs Soil samples were collected at approximately 5-foot intervals ERI's geologist described soil lithology from the continuous care soil samples collected from the borings using visual and manual classification methods The samples were classified using the Unified Sol] Classification System(Attachment F) Descriptions of the materials encountered are presented in the Boring Logs and CPT Logs (Attachment F) Based upon an evaluation of the continuous core samples, CPT data, and depth to water measurements, ERI's geologist identified the depth of first encountered groundwater and two saturated zones of increased permeability in each boring ERI observed PSS collect depth specific grab groundwater samples from each of these zones from soil borings B8 through B 10 utilizing Hydropunch®technology and/or a bailer Groundwater samples were collected from boring B8 at 7, 17, and 31 feet bgs, from boring B9 at 7, 18, and 30 feet bgs, and from boring 1310 at 11, 16, and 30 feet bgs • 4