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01 June 1999 AGE-NC Project No 95-0137 Page 12 of 26 TPH-g-impacted soil on the subject site extends to depths of 20 feet bsg and more in the vicinity of former the USTs The lateral extent of impacted vadose zone soil in the vicinity of former the USTs is limited,making excavation a viable alternative Although impacted soil extends along the capillary fringe or smear zone from the former UST area westward under the shop building, and TPH-d- impacted soil extends vertically to 30 feet bsg, a mayor portion of the vadose impacted soil could be addressed by excavation AGE does not anticipate that special equipment would be required to excavate to the depth of ground water at the subject site, however, sand is present below a depth of approximately 15 feet bsg at the site and in soil below the water table, and shoring would be required for depths below 20 feet bsg, and may be required for excavation below the saturated zone at 17 feet bsg Impacted soil is also present in the smear zone and saturated zone near the former location of the USTs A primary disadvantage of excavation is the disruption of site use, the site is currently in use as a farm fertilizer storage and transport area Other potential disadvantages include air pollution control concerns, backfilling and compaction costs 5 2 3 Estimated Costs For Excavation At the site, AGE anticipates that impacted soil could be excavated with traditional equipment Approximately 600 cubic yards of soil would have to excavated from the former location of the USTs Very little"clean"overburden soil would likely need to be removed in the UST area, however considerable quantities of"clean" overburden would be moved to remediate the smear zones i Once excavated, the soil can then be treated on-site or transferred to an off-site disposal facility ' Replacement backfill material must be imported if off-site disposal is chosen Permitting would be required and space is not readily available for on-site treatment of excavated soil The cost for excavation, treatment/disposal and backfilling would probably be between $150 and $200 per cubic yard, depending upon hydrocarbon concentrations Total costs for excavation and treatment or disposal could therefore approach $90,000 to 120,000 5 3 IN-SITU SOIL BIOREMEDIATION Local acceptance of this treatment technology by the regulatory community has grown recently, due to documented success for remediation of petroleum hydrocarbon contaminants at a number of sites in California and elsewhere The CVRWQCB has been reluctant to issue discharge permits required to infect bacterial inoculum and/or nutrients into the subsurface Adianced GeoEn�iron mental,Inc I