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N Pi MONITORING WELL INSTALLATION WORK PLAN 630 N California Street Stockton, California ' 1 1.0 INTRODUCTION This work plan was prepared by Condor Earth Technologies, Inc. (Condor) to describe proposed monitoring well installation activities at 630 N. California Street (Site) in Stockton, California (Figures 1 , 2, and 3, Appendix A). The Site is owned by the County of San Joaquin (Client) and is used for records storage. A meeting was held on April 4, 2013 with Condor, the Client and San Joaquin County Environmental Health Department (SJCEHD) representatives. During the meeting Mr. Nuel Henderson with SHCEHD indicated that additional groundwater , investigation would be required at the Site. The purpose of the work is to investigate the potential presence of groundwater contamination beneath the Site. The proposed work includes installing one groundwater monitoring well and collecting groundwater 1 samples for laboratory analyses . All work conducted by Condor will be performed under the supervision of a State of California licensed Professional Geologist. This work plan includes project background information, a description of the field, laboratory, and reporting procedures proposed to conduct the work, and a project schedule. 2.0 PROJECT BACKGROUND JA vent pipe consistent with those typically found associated with historic USTs was located immediately south of the west doorway to the warehouse along the exterior wall, Figure 2, Appendix A. Condor j acquired historic Sanborn® Fire Insurance Maps and City Directories to ascertain the history of the Site. JPrior to 1917, the Site was the location of the Stockton Electric Railroad Company car house and blacksmith repair shop. The buildings (current County Records Center and adjoining warehouse) located at 630 N. California Street were originally constructed in 1917, occupied by the Stockton Transfer JI Company. By 1940, the Site buildings were occupied by the Stockton Transfer Company and H. S . Dawson Van and Storage, possibly one company or two companies sharing the buildings. The warehouse contained vans and automobiles according to the 1950 Sanborn® Map. From at least 1970 until 1984, the warehouse was used for parking, and the main building was occupied by Morris Brothers Office Supplies and Equipment. The County of San Joaquin appears to have purchased the Site in the late 1980s. 'I- The southern adjoining property is the location of Stallworth Auto Sales (602 N. California St.), a former retail fueling facility with documented soil and groundwater contamination. Groundwater gradient directions measured at this location have been historically northeasterly to easterly, and the depth to groundwater has varied between 26 and 35 feet below ground surface (bgs). Groundwater beneath the Site is likely impacted by petroleum hydrocarbons. Groundwater contaminants from Stallworth Auto Sales include: benzene, toluene, ethyl benzene, and total xylenes (BTEX); the fuel oxygenates 1 ,2- 1 drehloroethane (1 ,2-DCA) and tertiary-amyl methyl ether (TAME); total petroleum hydrocarbons quantified as gasoline (TPH-G); and total petroleum hydrocarbons quantified as diesel (TPH-D). On May 5 , 2011 , Condor conducted a subsurface investigation to evaluate potential soil contamination, and to determine whether a UST was present. At approximately 3 .4 feet below ground surface (bgs), a metal object was confirmed to be present near the vent pipe, measuring approximately four feet in diameter (based on magnetic response). Four continuous core borings were advanced in the vicinity of the UST to 30 feet bgs (Figure 2, Appendix A). Contaminated soil was observed in three of the four borings. Fifteen soil samples were collected for laboratory analysis and submitted under chain-of-custody procedures to Argon Laboratories in Ceres, California. The analytical results indicated that subsurface �s Ji /� CONDOR