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program has been developed, and as part of this program, the soil samples initially will be analyzed as follows: Sample Depths (feet bgs) Selected for Analysis Constituents to be Analyzed 0.5 2 5 10 15 20 TPHg, TPHd, VOCs, SVOCs X X TPHo X X X Metals X X PCBs X X pH X X The indicated analysis for the PCOCs and COCs at the identified depths is a guideline and may be analyzed at other than their pre-selected depths to further characterize the PCOCs depending on the results of the initial laboratory analysis. Selection of additional analysis will be at the discretion of the Professional Geologist responsible for this project. 2.8.3 MONITORING WELL CONSTRUCTION Prior to mobilization, well permits will be obtained from the San Joaquin County Environmental Health Division (SJCEHD). The proposed new wells will be constructed similar to the other existing wells, both on- and off- site. The wells will be of 2-inch diameter construction and Schedule 40 polyvinyl chloride (PVC) casing/screen. The wells will be constructed and installed by a California State Water Well C57-licensed drilling contractor, using a hollow stem auger-drilling rig. The auger will be at least 8-inch outside diameter to allow for sufficient annular spacing around the well casing for proper filter pack placement. The total depth of the well will be determined in the field and represent a depth that is five (5) feet below the first encountered significant groundwater (water bearing zone). A generalized schematic well construction diagram is provided in Figure 6. The well casing will consist of ten (10) feet of 0.020-inch machine cut slots, set adjacent to the first water bearing zone encountered during drilling; the remaining casing to surface completion will be blank. The annular space surrounding the slotted well screen will be filled with a 2x12 sand filter pack that will extend two (2) feet above the top of the screen. During placement of the filter pack, mechanical surging using a "surge block" may be used to settle the filter sand to minimize the potential for filter pack bridging in the annular space. The surge block will be moved slowly in an up-and-down sweeping motion over five (5)-foot lengths, and care will be taken not to stress the surrounding strata. The depth to the top of the filter sand will be gauged periodically during surging process to monitor settlement; filter pack sand will be added as necessary to maintain the proper amount of sand above the well screen. Two (2) feet of 1/4-inch bentonite chips will be placed above the filter pack sand. The chips will be hydrated and allowed to swell for 15 minutes. The remaining annulus will be filled with neat cement to within two (2) feet of ground surface. The ground surface will be constructed with either a traffic-rated flush mount well box set in concrete or a stovepipe-type riser. In both cases the well casings will be fitted with a locking cap mechanism to deter tampering with the well. Each well will be identified as a monitoring well on the well lid or well riser. Golden State Environmental, Inc. - 23 - Los Angeles, San Diego and Houston Revised Work Plan — Soil and GW Characterization July 2006