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KLEINFELDER asbestos, the DTSC threshold for hazardous waste. Soils containing greater than or equal to 1% asbestos will be remediated. Those with trace levels below I% will be left undisturbed. Without regulatory cleanup levels at the state or federal levels, the proposed cleanup level of 1% is a reasonable vehicle to drive the remediation. A second issue related to soil remediation is the lateral limits of the remediation. As can be seen from Drawing 2, there are a number of isolated points (underlined sample numbers) where surface soil concentrations in excess of 1% were found but the surrounding sample concentrations were not similarly elevated. The question becomes what criteria are to be used to set the lateral limits for remediation of these isolated points. Instead of taking a number of additional samples (140 soil samples have already been collected and analyzed for asbestos) in an attempt to delineate the extent of the surface soil contamination at an isolated point, surface topography and other features will be used to estimate the lateral extent of remediation. For instance, if a- suspect sample location is intersected by a drainage Swale leading from the manufacturing area, it would be reasoned that the swale was responsible for contamination in the specific area. The surface soil in and around the swale would be considered to be contaminated and would be remediated. In a situation where there are no features or indicators that could be used to estimate the lateral extent of contamination, a radius of 20 feet around the sample point would be remediated. After remediation, a limited number of confirmation samples would be collected immediately outside the area of excavation. 6.1.2 Methods of Remediation Two methods of remediation have been selected for asbestos surface soil contamination. The first method will utilize capping of WMUs. At contaminated sample points failing within the footprint of one of the WMUs, the cap that will be placed over the WMU will also cover the surface soil contamination. The second method utilizes areas that fall outside of WMU footprints. In these areas, the contaminated soil will be excavated to a depth of one foot and then backfilled with clean soil. The lateral extent of the excavation will be established using the approach discussed in Section 6.1.1. After excavation the contaminated soil will be PP , transported to the surface impoundments for disposal. The surface impoundments will then be capped. CR14-92-12 Page 24 of 39 24-220109-1709 Copyright 1992 KLeinfetder, Inc.