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UNDERGROUND STORAGE TANK DELINEATION SAMPLING USING CONE PENETRATION TESTING WITH AN ULTRA-VIOLET OPTICAL SCREENING TOOL REPORT City of Stockton,Redevelopment Department 216 N. California Street Stockton, San Joaquin County, California 1.0 INTRODUCTION This report was prepared by Condor Earth Technologies, Inc. (Condor) to describe soil and groundwater investigation activities at 216 N. California Street (Site) in Stockton, California (Figures 1 and 2, Appendix A). This report presents results of subsurface soil and groundwater sampling adjacent to the northwestern corner of the Site. The purpose of the work was to investigate the lateral and vertical extent of petroleum hydrocarbon contamination related to an underground storage tank (UST) formerly located at the Site. This report includes Site background information, a description of field activities, laboratory analyses, and conclusions. This location has been assigned to the San Joaquin County Environmental Health Department (SJCEHD) Local Oversight Program and given the site code 1687. The property is designated by Assessor Parcel Number (APN) 139-250-26. The Site is owned by the City of Stockton (Property Owner) and managed by the Redevelopment Department (Client). The work described in this .. report was performed with the oversight of SJCEHD and under San Joaquin County Well Permit # 55816. Condor prepared this report at the request of the Property Owner, Client, and as directed by the SJCEHD in their letter to the City of Stockton dated October 30, 2008. The work included advancing three Cone Penetration Test (CPT) borings to collect soil behavior data in conjunction with an Ultra-Violet Optical Screening Tool (UVOST) to delineate hydrocarbon impacted soil, and then collecting soil and groundwater samples for laboratory analyses. All work conducted by Condor was performed under the supervision of a Professional Geologist licensed in the State of California. This report includes project background information, a description of the field, and laboratory procedures, analytical results, and conclusions and recommendations. 1.1 PROJECT BACKGROUND On December 3, 2004, Thorpe Oil removed one UST at the Site. Soil staining and petroleum odors were noted in the excavation and excavated soil. Soil samples were collected from locations directed by the SJCEHD following removal of the UST. Based on our review of background information and correspondence provided to us by the Client, Condor understands that a UST was located and removed from the western portion of the Site. The UST had the following characteristics: 1,500-gallon capacity; single-wall steel construction; formerly contained heating oil; and located beneath the sidewalk on _ California Street. Upon removal, the UST was noted to have corrosion and adjacent dark, stained soil was present with indications of long-term leakage. The laboratory analytical results provided to Condor indicated that diesel-range hydrocarbons were detected in soil samples collected from the excavation during the UST removal activities. Samples were collected from the north and south ends of the UST excavation near the bottom of the excavation. The laboratory analytical results indicated that total extractable petroleum hydrocarbons .. quantified as diesel (TEPH-D) were detected at a concentration of 3,300 milligrams per kilogram(mg/kg) ia CONDOR