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Response to Comments Table <br /> California Army National Guard <br /> Stockton, California <br /> (Page 7 of 7) <br /> Comment Comment from <br /> Number Central Valley Regional Water Quality Control Board Letter Response <br /> dated March 15, 1999 <br /> 9 Table 2 of the Work Plan indicated a majority of the proposed boring Comment noted. The sampling plan has been <br /> locations will include sampling for volatile organic contaminants revised to include soil gas sampling instead of <br /> (VOCs), Benzene Toluene, Xylene and Ethyl benzene (BTEX) and soil sampling and the method analyses have <br /> MTBE. All locations which include sampling for VOCs should been added to Table 2. <br /> include soil gas sampling instead of soil sampling. It has been our <br /> experience that collection and handling of soil samples inherently <br /> allows losses of contaminants to occur. Method analyses used in the <br /> soil gas surveys should include Environmental Protection Agency <br /> (EPA) methods TO-14 (for VOCs) and TO-3 (for BTEX). <br /> 10 Table 2 (or an additional table) should be revised to describe which Comment noted and Table 2 has been revised <br /> analytical methods will be used to evaluate the vadose zone at each to include the proposed laboratory method. <br /> boring location. We recommend that the soil gas sampling for The total depth of each soil boring will be <br /> VOCs and BTEX include discrete sample collection at lithologic approximately two to five feet below the <br /> changes or every 10 feet, until the water table is reached. estimated bottom of potential subsurface <br /> contamination. The presence of contamination <br /> will be evaluated in the field based on visual <br /> observation and field monitoring equipment <br /> measurements. <br /> 1527-99/3134-100/AUG 13'99 <br />