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tCalifornia Department of Transportation Revised September 23, 1994 Project No. 102818A-01 INTRODUCTION AND SCOPE OF SERVICES ' In accordance with Caltrans Statewide Contract No 56SO67 and Work Order No. 10- 565067-06,Ninyo &Moore has conducted groundwater monitoring activities at the Caltrans Maintenance facility located at 1604 South B Street in Stockton, California (Figure 1). Our scope of services included the following tasks: 1) attendance of a prework site visit, 2) ' preparation of a work plan and site safety plan, 3) measurement of the depth to groundwater at selected wells, 4) collection and chemical analysis of three groundwater samples, 5) disposal of water generated from sampling activities, and 6) preparation of this report documenting our field activities and findings SITE BACKGROUND ' The property is owned by the California Department of Transportation and has been a state highway repair and maintenance yard since approximately the late 1940s Prior to its use ' as a repair and maintenance facility, it was reportedly undeveloped land The following information was obtained from the review of documents supplied by Caltrans and interviews with Caltrans personnel ' Two underground,storage tanks were removed from the facilityin December of 1989 The tanks had reported capacities of 5,000-gallons and 10,000-gallons and contained diesel fuel ' and gasoline, respectively Laboratory analysis of soil samples collect from the tank excavation indicated that soil contaminated with petroleum hydrocarbons was present. A ' preliminary investigation of the site was conducted in March of 1992 and two soil bonngs and three groundwater monitoring wells were installed in and near the former tank location ' Laboratory analysis of soil and groundwater samples collected indicted that soil and groundwater had been impacted by petroleum hydrocarbons Additional groundwater ' sampling and analysis was conducted in October of 1993 ' GROUNDWATER MONITORING WELL SAMPLING On May 24, 1994, a representative of Ninyo&Moore measured the depth to the static water rlevel in the three previously constructed groundwater monitoring wells at the site (Figure 2). The monitoring wells were first checked for the presence of immiscible layers using a 1 PVI99aT0 &4 ®MITTM