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1 PROVEN TECHNOLOGIES AND REMEDIES GUIDANCE-REMEDIATION OF METALS IN SOIL 7.0 DESIGN AND IMPLEMENTATION OF EXCAVATION/DISPOSAL ALTERNATIVE This chapter describes the approach that will be used to complete the soil removal action and the disposal requirements for the excavated soil and restoration of the excavated site. The objective is to remove soil contaminated at levels exceeding site cleanup goals. The excavation and disposal alternatives discussed in subsequent sections can be applied to either an interim action (i.e., early measure to reduce the risk of releases of hazardous substances before the initiation of more complicated, comprehensive, and long-term cleanup remedies) or the final remedy at a site. 7.1 DATA NEEDED TO SUPPORT EXCAVATION DESIGN At a minimum, the following data is necessary to adequately address the excavation limits and design: • Vertical and horizontal distribution of contaminants (i.e., areal extent of impacted soils, depth of impact) and volume of soils to be excavated; • Identification of soil conditions that affect the selection of excavation equipment; • Average depth to groundwater; • Climatology/ seasonal variations; • Survey map of site features (e.g., topography, existing structures, utilities, wells, surface water control measures, property boundaries, areas to be shored), if applicable; • Geotechnical data for each soil type (i.e., USCS classification, Atterberg limits, moisture content, bulk density), if applicable; and • Structural contour map of the top of competent bedrock, if applicable. Ideally, these data will be collected during the characterization phase of the project (see Chapter 4) rather than requiring another field mobilization during the design phase. 7.2 EXCAVATION, DISPOSAL, AND RESTORATION PLAN A workplan identifying the logistical procedures and site activities associated with excavation, disposal and site restoration should be prepared. The actual title of this plan will depend on the cleanup process applied to the site. For example, DTSC's RAW process incorporates the required plan elements into the RAW. DTSC's RAP and corrective action processes often require preparation of a separate plan. However, additional streamlining under the PT&R approach could be achieved if the plan is included in another document (e.g., as an appendix to the RAP). For the purposes of this chapter, the workplan is referred to as the "excavation, disposal, and restoration plan". 29