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Wastewater <br /> percolating through the washpad would be untreated. <br /> Contaminants floated out of the secondary clarifier would have been <br /> slightly treated. Contamination reaching the unlined collection <br /> pit would be of much lower concentration, however, due to upstream <br /> treatment. <br /> 3.0 SITE ASSESSMENT <br /> The AASF washpad system site assessment was conducted in accordance <br /> with the approved workplan. All field and laboratory procedures <br /> were in conformance with guidelines presented in State Water <br /> Quality Control Board Staff Recommendations for Initial Evaluation <br /> and Investigation of Underground Tanks (Revised November 9 , 1989 ) <br /> and the Tri-Regional Board Staff Recommendations for Preliminary <br /> Evaluation and Investigation of Underground Tank Sites (August 10, <br /> 1990 ) . As stated in the SWQCB guidelines, the goal of the site <br /> investigation is to determine the nature, horizontal and vertical <br /> extent, geologic and hydrogeologic controls and potential <br /> groundwater impact of the unauthorized release. <br /> In the following Sections of this report each element of the site <br /> assessment, including procedures and equipment for conducting sub- <br /> surface investigations, is described. Technical details are <br /> presented in the Appendices - <br /> 0 <br /> 3 . 1 Soils Barings <br /> Soil samples were collected in and around the two known and one <br /> suspected release point. Three soil borings were completed under <br /> the aircraft wash pad, three from the secondary clarifier vicinity, <br /> and two from the downstream discharge pit . Figure 5, Boring <br /> Locations, indicates the sampling locations . In the following <br /> sections a description of soils borings performed at each study <br /> area is presented. <br /> Borings were permitted in accordance with San Joaquin County, <br /> Public Health Services, Environmental Health Division requirements . <br /> Approved boring permit applications are presented in the appendix. <br /> 3.1 . 1 Washpad <br /> The washpad is bisected by 4 expansion joints and three maDor <br /> cracks. Four sampling locations were selected at joint/crack <br /> intersections . Two foot square sections of concrete were sawcut <br /> and removed at three of the locations . The fourth was sawcut, but <br /> not removed, in the event auger refusal was encountered in one of <br /> the other three locations. <br /> 10 <br />