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Mr. Dave Lewis October 13, 1986 Page 2 j ABATEMENT OPTIONS Option 1. Soil Excavation - The physical removal of the soils beneath the leak point would eliminate continued - contamination of the groundwater. The major area of soils which have been in direct contact with free phase gasoline can be approximated by assuming a 45 degree angle of spreading from the point of leakage to a barrier which impedes further vertical migration, in this case a shallow water table at a depth of about 30 feet. This conical shaped area equals a volume of approximately 1040 cubic yards of contaminated soil. To remove the contaminated ' soil, a minimum area of 60 by 60 feet to the depth of groundwater would have to be excavated : a volume of 4000 cubic yards (See Figure 1) . This excavation would require the removal of the underground product lines, tanks and dispensing pumps at the site in addition to extensive shoring of the excavation to reach the required depth. A 60 foot square by 30 foot deep braced exca- vation would be difficult to construct and would require some detailed engineering design studies. As shown on figure one, the excavation would also require temporary closure of portions of Thornton Road and Waldman Avenue. Once removed, the disposal or. sur£ace treatment of soils f would have to be addressed. Disposal to a Class II or Class I f landfill would be the least desireible method because of the high cost for disposal and limitedjlandfill space available. Additionally, this method does not provide for cleanup of the contamination but just transfers it to a location which poses less of a threat to public health and safety. Surface aeration and/or land farming of the contaminated soil would require more space than is available at the project site property. If permis- sion from a nearby property owner with vacant land could be obtained and variances secured from involved regulatory agencies, the aeration or land farming option could be considered. These methods provide for volatilizationand degradation of the gasoline components in the soils by venting and stimulation of hydrocarbon consuming bacteria through nutrient addition. Preli minary cost estimates for the two excavation options are provided below.