FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Metals. The following constituents of concern (CDCs) were detected in groundwater: Chloroform (320 parts per billion - ppb), and TPH (430 ppb). The COCs were detected above their respective Regional Water Quality Control Board (RWQCB) Environmental Screening Levels (ESLs) of 70 ppb and 100 ppb, respectively. Additionally Advanced GeoEnvironmental Inc. performed a Preliminary Site Assessment in January and February 1998 and determined that no USTs were present onsite. However; in October 1998, the San Joaquin County Environmental Health Department (SJCEHD) responded to a complaint that a UST (volume not stated) had been removed from the subject property and was being stored on site. As a result, the SJCEHD required the property owner to obtain a tank identification number and complete state UST forms. In September 1999, the complaint log indicated that a UST was removed under permit. The incident, which originated in October 1998, was noted as "abated" in February 2000. No UST removal reports or confirmation soil/groundwater sample data was on file with the SJCEHD. Due to the fact that TPH and Chloroform were reported above ESLs in groundwater at the site and the lack of any documented samples collected from either of the UST removals, AEI issued a proposal to further investigate these issues. The proposal included the use of a geophysical survey which would be conducted to evaluate the presence of any remaining USTs and a subsurface investigation to investigate the potential presence of the CDCs which were previously identified at the site. The subsurface investigation included soil sampling from three (3) borings and groundwater sampling from one (1) boring. The borings were proposed in the area of the previous 'gas & oil" building footprint as noted on the Sanborn maps in the Phase I ESA and based on the results of the geophysical survey. 3.0 INVESTIGATIVE EFFORTS Drilling permits were obtained from San Joaquin County Environmental Health Department (SJCEHD) for this investigation (Appendix A). The public underground utility locating service Underground Service Alert was notified to identify public utilities in the work area. Private utility locating was conducted by Ground Penetrating Radar Systems, Inc. (GPRS) of Sacramento, California to identify underground utilities on the property. A site-specific health and safety plan was prepared, reviewed by onsite personnel, and kept onsite for the duration of the fieldwork. GEOPHYSICAL SURVEY On March 21, 2012, a geophysical survey was conducted by GPRS of Sacramento, California. The purpose of the survey was to assess whether any USTs remain in place or whether evidence of former UST cavity(s) are present. The survey was performed in the western portion of the northern parking lot area of the site in the area denoted by the Sanborn maps as being Aloil & gas" (Figure 2). The geophysical survey was conducted using ground penetrating radar, electromagnetic induction, and radio detection. A full description of the geophysical survey is included in the report dated March 22, 2012 by GPRS (Appendix B). The results from the geophysical survey revealed two (2) areas of subsurface disturbance. These areas may be related to the former presence of USTs onsite. No indication of current Project No. 305662 AE1 April 4, 2012 Page 2 of 6