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LOT B UNDERGROUND STORAGE TANK am MONITORING WELL INSTALLATION AND ADDITIONAL DELINEATION SAMPLING WORKPLAN City of Stockton-Redevelopment Department 216 N. California Street Stockton,California 1.0 INTRODUCTION 6' This work plan was prepared by Condor Earth Technologies, Inc. (Condor)to describe proposed soil and groundwater investigation activities and monitoring well installation at 216 N. California Street (Site) in Stockton, California(Figures 1 and 2, Appendix A). The purpose of the work is to further investigate the 60 eastern lateral extent of petroleum hydrocarbon contamination related to an underground storage tank (UST) formerly located at the Site. This location has been assigned to the San Joaquin County Environmental Health Department (SJCEHD) Local Oversight Program and given the site code 1687. 60 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). Condor prepared this work plan at the request of the Property Owner and as directed by the SJCEHD in person during a meeting at SJCEHD offices on January 13,2010. The proposed work includes the installation of one monitoring well near the former location of the ` Underground Storage Tank (UST), then advancing Cone Penetration Test borings (CPT) to collect soil behavior data and soil and groundwater samples for laboratory analyses. Depending on the groundwater laboratory results of the first monitoring well, two additional monitoring wells may be substituted for the ` CPT borings. All work conducted by Condor will be performed under the supervision of a Professional Geologist licensed in the State of California. This work plan includes project background information, a description of the field, laboratory, and reporting procedures proposed to conduct the work, and a project Lschedule. 2.0 PROJECT BACKGROUND `. On December 3, 2004, Thorpe Oil removed one heating oil UST from the sidewalk along the northwestern Site boundary. 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. 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 stained soil was present,indicating long-term leakage. L The tank was removed and stained soil was overexcavated to a depth of 15 to 17 feet below ground surface(bgs),which was the maximum practical excavation depth. 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 petroleum hydrocarbons quantified as diesel (TPH-D) were detected at a concentration of 3,300 milligrams per kilogram (mg/kg) on the north Lend, and 6,300 mg/kg on the south end of the UST excavation. The UST removal activities were described by SJCEHD and Thorpe Oil in the notes made during the UST removal. L %�' �� CONDOR