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5.0 REMEDIAL ACTIONS 51 Soil Excavation I Following removal of USTs A, B, and C by Triangle, LBME excavated petroleum hydrocarbon impacted soil from the area north of the warehouse and lubrication station between September 15 and 18, 1987 The excavation measured approximately 47 feet in length by 25 feet in width at the ground surface The sides of the excavation were terraced, and the excavation narrowed with depth The deepest portion of the excavation was approximately 38 feet bgs Approximately 1,700 cubic yards of soil were excavated and aerated prior to disposal Overexcavation was also performed following removal of Tank D by Elder in 1988 Information regarding the volume of soil excavated was not available in the documents reviewed for this report Additional excavation was performed after Tanks T-5, T-6, and T-8, and the associated dispenser island, were removed by Town and Country in 1999 Approximately 560 to 700 cubic yards of soil were subsequently transported to the Teichert facility in Tracy for bio-remediation prior to disposal 52 Soil Vapor Extraction A subgrade SVE manifold was installed in the excavated area north of the lubrication station and warehouse EMCON utilized this manifold and well MW-13 to perform an SVE test in October 1992 BCR installed well MW-14 in December 1994, and initiated soil vapor extraction from well MW-14 at that time Anderson reconstructed well MW-13 for vapor extraction, and simultaneous extraction from wells MW-13 and MW-14 began in January 1995 EMCON installed air sparge well AS-I in May 1995 Concurrent air sparging and SVE was initiated in June 1995 Use of the SVE/air sparge system was discontinued in December 1995 Available information relating to the operation of the SVE system at the site is presented in Appendix I EMCON4 estimated that approximately 13,400 pounds of TPHG have been removed via excavation and SVE Stratus estimates that less than 50 pounds of TPHG remain ' beneath the site 53 Bioventing ' Bioventing activities were initiated on November 16, 2004 and are on-going An oil-less compressor is utilized to pump air into wells MW-13, MW-14, and AS-1 In wells MW-13 and MW-14, the air is delivered via drop tubes installed to approximately 1 foot above the bottom of ' the well In well AS-1, the air is applied directly to the well casing, as in conventional sparging Airflow from the compressor to the wells has ranged from 40 to 65 liters per hour, at pressures ranging from 24 to 30 pounds per square inch A table summarizing bioventing operations ' through the fourth quarter 2005 is included in Appendix I 4 Report dated August 15, 1996 ' s Final Closure Report, dated July 20, 2001 K ITeichertlStockton 1031Reports\scm 04 2006 doe Page 10 STRATUS