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3.0 SOIL PARAMETERS If the soil gas data will be used in a health risk assessment, an estimation of the indoor air concentration should be performed using soil gas data with an Agency approved or modified predictable indoor air model. Default values of input parameters may be used in accordance with the approved indoor air modeling guidance and in consultation with Agency staff. If default values are not used, site- specific soil parameters should be obtained as discussed below. To assess health risk, indoor air quality, the threat of groundwater contamination from VOCs, or to evaluate the effectiveness of a proposed remedial technology, the following soil matrix parameters should be obtained from a minimum of three (3) sample locations (at depths' corresponding to or associated with the detected VOCs)for each soil type in association with the soil gas investigation: 3.1 Soil description performed and presented in accordance with the Unified Soil Classification System (USCS); 3.2 Density; 3.3 Organic carbon content of the soil** (by the Walkee Black Method); 3.4 Soil moisture; 3.5 Effective permeability***; 3.6 Porosity; and 3.7 Grain size distribution analysis(curve)and evaluation of fine-grained soil content(by wet sieve analysis and any supplementary methods as necessary)to determine the percent clay, silt and sand. (The grain size distribution analysis will be used to classify the soil in accordance with the U. S. Soil Conservation Service [SCS] soil type,which is the same as the U. S. Department of Agriculture soil type.) * Samples maybe collected from proposed depths at the continuously cored boring. This input parameter is required for soil matrix VOC samples only. This parameter sample should not be collected from an impacted area. "*As an alternative,the measurements of saturated hydraulic conductivity may be used to estimate vapor permeability. 4.0 REFERENCES Additional information may be found in the following documents: American Society for Testing and Materials (ASTM), "Standard Guide for Soil Gas Monitoring in the Vadose Zone,ASTM Standard D 5314-92;' January 1993; Reapproved 2001;website http://www.astm.org 01/28/2003 -21 -