Laserfiche WebLink
4 SUMMARY OF RESULTS <br />A geophysical survey was conducted at a former waste disposal area at the California Army <br />National Guard facility in Stockton, California in May 2006. The purpose of this investigation <br />was to map, if possible, vertical extents of the waste pit area. Geophysical methods used durinc2.- <br />this investigation included the 2-D electrical resistivity imaging, multi-channel analysis of <br />surface waves, and seismic refraction methods. Fizure 1 illustrates the location of the <br />geophysical arrays. <br />2-D electrical resistivity imaging, along with shallow seismic techniques, were employed as non- <br />invasive means of determining the depth extent of the fill material within the bounds of the drum <br />disposal area. Electrical resistivity models (Figures 2-3) indicate the presence of a relatively <br />conductive unconsolidated fill material overlaying more resistive consolidated soils. Seismic <br />refraction and surface wave data (Figures 4 to 7) were modeled as having a low-velocity <br />unconsolidated soils unit overlaying a higher-velocity, more consolidated soils unit. Depth <br />estimates from the electrical resistivity survey were consistent with seismic surface waves and <br />refraction models within 10%. On average, thickness of the fill material is modeled as being 10- <br />14 ft thick in the central portion of the pit area, with thickness decreasing slightly at the edges. <br />6243 Versax 10 July 6, 2006