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Additional Soil and GrouiRlwater Investigation Report California Central Traction Company, 1645 Cherokee Lane,Stockton,CA September 22, 2oo8 Page 3 June 14-15, 2005: Four groundwater monitoring wells (MW-1 through MW-4) were abandoned by over drilling in preparation for site excavation activities. June to December 2005: Approximately 10,400 tons of soil was excavated from the site. The maximum depth of the excavation was 8o fbg and the diameter of the excavation was approximately 200 feet (CLS Environmental Services, Inc. 2oo6). 5.o ADDITIONAL SITE ASSESSMENT ACTIVITIES TRC completed six (6) onsite soil borings to groundwater and converted three (3) of the soil borings to groundwater monitoring wells to provide additional, long-term groundwater monitoring data and to better define the current extent of the dissolved-phase groundwater plume. The newly installed onsite wells are located in the vicinity of the former diesel UST on the western side of the Site(Figure 2). 5.1 PRE-FIELD ACTIVITIES Prior to commencing soil boring activities, drilling permits were acquired from SJCEHD. Underground Service Alert(USA)was notified two days prior to field activities to mark underground utilities at the proposed boring locations and around the property boundaries. In addition, a private utility locator was contracted to confirm the absence of buried utilities at each proposed boring/well location. Prior to advancing each boring, a pilot hole was cleared with a hand auger to approximately 5 fbg to verify the absence of buried utilities. 5.2 SOIL AND GROUNDWATER SAMPLING TRC completed the additional soil and groundwater investigation from,June 12 through June 18, 2oo8. TRC completed six (6)soil borings using a Sonic drilling rig equipped with a 6-inch diameter outer drive casing. Soil borings were completed to total depths ranging from 68 feet below grade(fbg) to 85 fbg depending upon soil and groundwater conditions. Soil boring locations are shown on Figure 2. Soil samples were collected from the soil borings continuously using a 5-inch diameter core barrel installed within the 6-inch diameter drive casing. Samples were collected for soil description in accordance with the Unified Soil Classification System(ASTM D-2487). In addition,soil cores were field screened using a hand-held photo-ionization detector(PID). Two(2) soil samples from each boring were collected from directly above the water table and were submitted for chemical analysis. Soil and groundwater samples were submitted to Test America Inc., a California certified laboratory, for analysis. The samples were properly preserved and transported to the laboratory under appropriate chain-of-custody protocol. The soil and groundwater samples were analyzed for total purgeable petroleum hydrocarbons as diesel (TPH-d)by EPA Method 8o15B, and for total purgeable petroleum hydrocarbons as gasoline (TPH-g),benzene, toluene, ethylbenzene, and total xylenes (BTEX), and fuel oxygenates including MTBE and ethanol by EPA Method 826oB.The composite soil sample was additionally analyzed for lead by EPA Method 6olo.