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Workplan for a Limited Subsurface Site Investigation Moore Petroleum, 5491 F Street,Banta,California Page 4 MONITORING WELL INSTALLATION The primary purpose of this task is to determine the vertical and lateral extent of soil and groundwater impacted by petroleum hydrocarbons at the site and to assess the extent the site is being impacted by upgradient off-site sources. A total of five groundwater monitoring wells will be installed at the locations identified on Figure 3. All field work will be performed according to Apex's Standard Operating Procedures (SOP) included in Appendix B. Monitoring well installation permits will be obtained from the SJCEHD prior to drilling. The Underground Service Alert (USA) network will be contacted at least 48 hours prior to drilling to identify the location of underground utilities at the site and adjacent public right-of-ways. The first five feet of each boring will be hand augured as a further precaution to avoid underground utilities. Apex will also obtain right of entry agreements from all offsite well locations. The groundwater level, based on the existing monitoring wells at the subject site, is at approximately 10 to 14 feet below ground surface (bgs). The groundwater monitoring wells are proposed to be completed to 20 feet bgs. The borings will be drilled using a hollow-stem auger rig. Each boring will be continuously cored below the 5 feet bgs for classification, field screening and for possible chemical analysis. Soil samples will be classified by the Unified Soil Classification System. Field screening will consist of soil headspace analysis using a portable photoionization detector. At a minimum, the wells will be constructed according to the standards found in the California Code of Regulations, Title 23, Section 2647 and 2648 and the California Department of Water Resources Bulletins 74-81 and 74-90. The monitoring wells will be constructed of two-inch diameter Schedule 40 PVC with a 0.020-inch slotted casing. The screened interval will extend approximately 5 feet above and 10 feet below the water table (5 feet to 20 feet bgs). The filter pack will be placed from one foot above the screen interval to the total depth of the well. A one- foot bentonite seal will be placed on top of the filter pack. A neat cement sanitary seal will be placed from the top of the bentonite seal to the surface. The wellheads will be secured with a locking, water-tight cap and a traffic-rated wellhead vault box. Construction specifications for a typical groundwater monitoring well are shown on Figure 4. The monitoring wells will be developed,purged, and sampled following installation according to Apex's SOP included in Appendix B. Groundwater from the monitoring wells will be collected at least 24 hours after completion of well development according to the included SOP. The wells will be surveyed to an established benchmark, if available, and to the other wells. Soil and groundwater samples will be submitted, under chain-of-custody documentation, for chemical analyses to a state-certified analytical laboratory. The samples will be analyzed for: