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Page GeologicalTeck�ciCs Inc. e 5 g Sinclair Trucking Feasibility Study Addendum Project No. 1030.3 April 26,2004 2.2.2 In Situ Related Costs GTI has obtained bids to perform in situ remediation at the site. The following is a list of ' approximate associated costs: Descri tion Estimated Costs ' Project Planning & Coordination $ 6,000 Install Injection Wells (install and modify 30 (may only need 20 wells)) 18,000 In Situ Oxidation Estimate 72,000 In Situ field work oversight 7,000 ' Background Data Collection 2,000 Background Data(Gen Min,TOC, metals, alkalinity, COD, BOD, etc) 2,000 Sampling During Injection Cycle (bi-weekly or 5 events) 10,000 ' Analyses During Injection Cycle (GW analyses) 6,000 Project Management& Supervision 5,000 Data Evaluation & Reporting 10,000 Abandon Injection Wells 6,000 $ 144,000 GTI would propose starting with 20 injection wells and only adding additional wells if the ' radius of influence warrants the additions. If 20 injection wells sufficiently cover the area the remediation costs would be proportionately reduced. The goal of in situ injection is a 90 to 95% destruction rate leaving 5 to 10% bound to soil and/or dissolved in groundwater. The enriched oxygen environment caused by the in situ process should enhance natural attenuation. Attenuation of this contamination will require ' additional monitoring and the costs associated with that work. Costs related to monitoring will depend on the length of monitoring required and may range in the tens of thousands. 2.3 Contaminated Soil Excavation Excavation simply involves the digging and removal of contaminated soil from the site. Excavations are simple and cost effective at sites that have heavy contamination in the vadose zone located in a spatially small area. The Sinclair site has several limiting factors to soil excavation. At the Sinclair site, most of the contamination is located at or above the depth of 14 to 15 ft ' bgs and is spread over a small area of approximately 60 x 60 ft. An excavation. would require the removal of approximately three feet of clean overburden so_that apprgmatel'Y_ U+^ I I-feet of contaminated soil could be excavated. An estimated 00 cubic yards would be n.�' ;/� excavated from this area, which would equate to approximately 2,000 yards would have to ' be disposed of(assuming a 30% fluff factor). 0" ' The site of the proposed excavation is easily accessible to large equipment. If excavation is ` used, this work must be performed during low stand of groundwater, which occurs during the fall or winter months of October through February. Low groundwater levels are approximately 12.1 to 12.7 feet bgs. Dewatering the excavation will be difficult and expensive. Sands will sluff into the pit from under the silt layer, destabilizing the outer edge of the excavation area, and it would complicate the excavation of the last two feet of contaminated soil. 1