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1 PAR-Eckert Cold Storage,Manteca,CA November 25,2002 I Page 3 groundwater gradient is predominantly towards the northwest at the site. The highly variable gradient at the site may be related to domestic/supply well pumping both on and off site. At times, the water table slope has been very flat; consequently, any slight variability in groundwater measurements and the tolerance for error for the water level measurement devices can result in apparent groundwater elevation contours that are not particularly coherent. Therefore, when the water table at the site is relatively flat, it may be more representative to depict the groundwater gradient with a three-point construction using groundwater elevation data from three site monitor wells that circumscribe the site, allowing triangulation of the contaminant plume, including the contaminant source area. At the direction of the SJCEHD, Condor prepared and submitted a Problem Assessment Work Plan (PAWP) for the site, dated May 31, 2002. Mr. Harlin Knoll of the SJCEHD approved the PAWP in a letter dated July 11, 2002. Condor subsequently prepared a UST Fund cost pre-approval request dated ' July 29, 2002, for the scope of work described by the PAWP. Condor performed quarterly monitoring at the site on June 26, 2002 and September 30, 2002. Results of the monitoring indicated concentrations of petroleum hydrocarbon constituents and a groundwater gradient that were consistent with historical data. ' Quarterly sampling of Total Petroleum Hydrocarbons quantified as Diesel (TPH-D) was discontinued during the third quarter 2002. Condor documented approval by the SJCEHD regarding discontinuation of TPH-D as a quarterly monitored analyte in a letter to Mr. Knoll dated September 26, 2002. SJCEHD approval was based on historical data indicating that the presence of TPH-D in site groundwater has been sporadic, very low in concentration, and likely the result of weathered gasoline rather than from the . possible presence of diesel in the source area. Condor has currently conducted three quarterly groundwater monitoring events using monitor wells MW-1, MW-3, MW-4, MW-5,MW-6, MW-7, MW- 8, and the on-site domestic well (DW). Detailed site background information and historical groundwater monitoring data are included as Appendix B to this report. 4.0 FIELD METHODS This section includes a description of the site preparation, drilling procedures, CPT and hydropunch ' groundwater sampling, and laboratory analyses. The results of this investigation are presented in Section 6.0. I4.1 SITE PREPARATION Prior to commencement of fieldwork, the required drilling permits were obtained from the SJCEHD. The I site was marked with white paint and Underground Service Alert (USA) was notified. Because companies contacted by USA will not identify utilities past private property lines and into the site, it was the responsibility of Eckert to identify any site utilities prior to commencement of fieldwork. All field activities were scheduled and coordinated through the property owner(Eckert). A tailgate safety meeting was held and a site-specific Heath and Safety Plan was discussed with, and presented to, all field personnel for their signatures. 1 4.2 DRILLING PROCEDURES On October 10 and 11, 2002, Condor conducted additional groundwater investigation at the site using ' direct push boring methods [Cone-Penetrometer (CPT) and Hydropunch]. Condor supervised the installation of ten hydropunch borings (HP-1 through HP-10) and two deep CPT boring pairs (CPT-1 and CPT-2) shown in Figure 2, Appendix A. The ten hydropunch borings were advanced to a depth sufficient to collect a groundwater grab sample to investigate the lateral extent of contamination in shallow ' ICONDOR