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March 20, 1992 <br /> ARCO Station No 6100, Tracy, California <br /> o Installing a vapor-extraction well in a boring near boring B-14 to remediate gasoline <br /> hydrocarbons in soil from surface grade to 30 feet below grade <br /> o Deferring the Preliminary Investigation and Evaluation Report until the lateral extent <br /> of residual gasoline hydrocarbons in soil have been delineated <br /> ADDENDUM TO WORK PLAN <br /> At ARCO's request, RESNA will perform the following work after the appropriate permits <br /> have been obtained <br /> o Contract with a licensed drilling company to drill two borings offsite and four borings <br /> onsite at the locations shown on Plate 2 and collect soil samples for laboratory <br /> analyses <br /> o Construct 4-inch-diameter vapor-extraction wells in the four onsite borings to <br /> remediate soil affected by gasoline hydrocarbons In addition, if field conditions <br /> indicate that hydrocarbons are present, construct a vapor-extraction well in the <br />. borings offsite <br /> o Analyze soil samples from the borings for TPHg and BTEX in a laboratory certified <br /> by the State of California <br /> o Interpret the field and laboratory data to evaluate whether additional work is needed <br /> to delineate residual gasoline hydrocarbons in soil beneath the site and south of the <br /> site If residual gasoline hydrocarbons in the soil have not been delineated, a status <br /> report will be prepared describing findings and recommendations for additional work <br /> o Prepare a Preliminary Investigation and Evaluation Report after the lateral extent <br /> of residual gasoline hydrocarbons in soil have been delineated <br /> The work described in this addendum will be performed according to the methods and <br /> procedures described in RESNA's Work Plan No 30041-2W, dated August 5, 1991, and <br /> prepared using the Central Valley Regional Board Staff Recommendations for Initial <br /> Evaluation and Investigation of Underground_Tanks (Tri-Regional Recommendations), <br /> Appendix A of the Tri-Regional Recommendations, and the Leaking Underground Fuel <br /> Tank Manual (LUFT) as references The methods for installation and construction of <br /> vapor-extraction wells and performing a vapor-extraction test are described in the attached <br /> Field Procedures Remediation of soil will not be performed at the site during this phase <br /> 0129ccar <br /> 30041-2 6 <br />