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j 6 l From the Beta work,indications are that groundwater is not encountered until approximately 43 feet. { Site investigation suggests contamination vertically stops at or above the confining clay layer at approximately 29 feet. Therefore we feel that groundwater is unaffected. { ,r a 5.0 Remediation 5.1 General �1 I� - There are two issues which present themselves as potential limiting factors to remediating the site. One is the location/proximity of a school, the other is the location of a building. �a 1. Remediation methods which could potentially ca lui significant air emissions, (such as soil aeration or vapor extraction), are undesirable due to the proximity of the school. i 2. Methods proposing traditional excavation would require shoring to protect the integrity of the sides of the excavation and the building foundation. There are two alternatives which avoid the aforementionedIconcerns: . It 3. In situ bioremediation. 3 � 4. Bucket auger excavation. ji I For the purposes of this report remediation methods which would potentially cause concern for air emissions will be abandon. Options 2, 3, and 4. will be discussed! 5.2 Traditional Excavation i. 5.2.1 Background f The lateral extent sod investigation suggests the contamination is localized directly under the location of the gasoline tank. One technique for 6mediation would be to conventionally excavate the soil directly beneath the tank location to a depth of 28 feet. Due to the proximity of the building the excavation would requu�e shoring. �I 5.2.2. General Procedure 1. Remove the concrete cap slab from the top of the original excavation. 2. Remove backfill materials, (pea gravel and Isoil),to a depth of 14 feet. 3. Install shoring. [It may be necessary to install shoring before completing excavation to 14 feet]. •1 4. Remove native soils to a depth of 28 feet. Page 5 I�