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December 8, 1993 Working to Restore Nature <br /> ARCO Station No 760, Lodi, California <br /> According to SJCPHS-EHD the depth to groundwater beneath the site is approximately 80 <br /> feet bsg. Because residual hydrocarbons were detected in soil approximately 15 feet above <br /> groundwater beneath the site, an investigation of groundwater was requested by SJCPHS- <br /> EHD <br /> ADDENDUM TO WORK PLAN <br /> To investigate soil and groundwater, RESNA will conduct the following work <br /> o Obtain permits from the SJCPHS-EHD to drill three borings and install three <br /> groundwater monitoring wells onsite <br /> o Subcontract an underground locating service to mark underground utilities with <br /> respect to the proposed boring/well locations and contact Underground Service Alert <br /> at least 48 hours before drilling to delineate public utility lines at the site <br /> o Observe a licensed well driller drill three 10-inch-diameter borings one boring will <br /> be east of the station building, one boring between the underground storage tanks <br /> and the dispenser islands, and one boring near the southwest comer of the site The <br /> soil borings will be drilled with a hollow-stem auger drilling rig to approximately 80 <br /> feet below surface grade (bsg) or 10 feet below groundwater, or less if a 2- to 5-foot <br /> thick low permeability layer is encountered beneath the first encountered <br /> groundwater The well driller will install 4-inch-diameter monitoring wells in the <br /> borings,with slotted intervals from approximately 10 feet below the first encountered <br /> groundwater to 5 feet above Drill cuttings will be stockpiled on and covered with <br /> plastic and left at the site, pending characterization and disposal The proposed <br /> locations of the borings/wells are shown on Plate 2. <br /> o Collect relatively undisturbed soil samples at 5-foot intervals or sediment changes <br /> from the ground surface to the total depth of each boring, identify the samples using <br /> visual and manual methods, and classify soil samples according to the Unified Soil <br /> Classification System <br /> o Submit selected soil samples to a State-certified laboratory for analysis of total <br /> petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd) using <br /> Environmental Protection Agency (EPA) Methods 5030/8015, benzene, toluene, <br /> ethylbenzene, and total xylene isomers (BTEX) using EPA Method 8020, and total <br /> oil and grease using EPA Method 5520 <br />• 0913ccar <br /> 38018-10 y 2 <br />