SITE INFORMATION AND CORRESPONDENCE_CASE 2

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4. Prepare a written report to describe the investigation conducted, summarize the analytical results, and present professional opinions regarding the extent of soil contamination and the potential of groundwater impact of the study area. III. WORK PLAN PREPARATION AND PERMIT APPLICATION To conduct soil sampling through soil boreholes in San Joaquin County, a drilling permit must be obtained from the San Joaquin County Environmental Health Division (SJCEHD). In support of the permit application, AllWest prepared a work plan outlining the elements of a proposed subsurface investigation in December 1993. The permit application along with the work plan were submitted to SJCEHD on December 29, 1993. SJCEHD approved the permit application on January 21, 1994 and a copy of the permit is included as Appendix A. The SJCEHD case officer, Ms. Linda Trukatte, was notified of the starting date of the subsurface r investigation on February 2, 1994. IV. FIELD INVESTIGATION A. Soil Boring and Sampling Soil boring and sampling was performed on February 9 and 10, 1994. Becker Drills, a drilling contractor arranged by RMC Lonestar, performed the soil boring work under the direction of an AllWest engineer. The AllWest engineer was present to facilitate the locating of boring locations, to observe and record site soil conditions, to collect representative soil samples, to maintain soil sampling logs, and to provide technical assistance as required. Representatives from RMC Lonestar and the SJCEHD case officer were also present to observe the sampling process. Five soil borings were originally planned for this investigation. An additional three borings were added in the field based on site conditions revealed by the first five borings and the recommendations of the SJCEHD case officer. The approximate locations of the soil borings are indicated on Figure 3 of this report. Soil borings were advanced through the reverse air-circulation hammer-drill process. The process involved the driving of 8-foot sections of double-walled steel drill casing into the subsurface with a Link-Belt double-action diesel hammer. Air circulations between the inner and outer walls of the double-walled casing were maintained by a high capacity air compressor. The soils underneath the casing tip were loosened and displaced by the hammering effect to allow the advancement of drill casings into the subsurface. The loosened subsurface soils were brought to the surface by the reverse circulation of compressed air through the casing and discharged into sample buckets at the bottom of a cyclone hopper that was connected to the top of the casing through air hoses. Additional 3