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I Mr. Jeffrey M.Baker,P,E Baseline Assessment for Soil Boring and Monitoring Well nstallation April 30,2004 Page 3 Well Develo meat The wells were developed 72 hours after completion by su ging the well with a surge block followed by purging with a disposable bailer. Surging and purging were repeated until purge water was relatively sediment free. The water generated during development was containerized 3n site pending evaluation of disposal options. A licensed waste hauler was contracted to dispose of the purg water. Groundwater Elevation Measurements and Flow Diree 'on Depth to groundwater was measured in the three wells on December 12, 2003 and March 11, 2004. Depth to groundwater on December 12, 2003 ranged from 47.20 to 48.33 feet below the tops of casings (TOC) and on March 11, 2004, ranged from 46.04 to 47.14 feet below TOC. The groundwater table elevation data are presented in Table 1. Elevation contour maps of the groundwater table using measurements that were taken on December 12, 2003 and in March 11, 2004, are presented in Figure 3 and Figure 4. The elevation of a reference point on the monitoring well and adjacent ground surface was surveyed at each newly installed well by Morrow Surveying, a licensed land surveyor on January 14, 2004. The Surveyor used Global Positioning Satellite GPg, and Delta requested that they use the California State Coo dinates for all AB2886 locations in compliance with State regulations. The TOC elevations of the monitoring wells and ground surface elevations were surveyed relative to MSL within 0.01 foot. Groundwater beneath the site generally flowed towards the southeast at a gradient of approximately 0.002 (measured between MW-I and MW-3), on December 17, 2003. The gradient was also southeasterly at approximately 0.002 on March 11,2004. Well Sampling and Water Level Measurement Groundwater samples were collected from the newly instal ed monitoring wells on December 12, 2003. Prior to purging and sampling, the depth to the water table was me sured to within 0.01 foot relative to a reference point on each monitoring well. The wells were purged and ampled in accordance with the field methods and procedures described in Enclosure B. The groundwater s mples were submitted to Kiff for analysis of BTEX, TPH in the gasoline range, and oxygenates using EPA Mi thod 8260B and TPH in the diesel range using EPA Method 8015 modified. Laboratory chemical analyses results are presented in Table 2 and the laboratory report is presented in Enclosure D. Groundwater samples were collected again on March 11, 2004. Prior to sampling the wells were purged by using a 2-inch submergible pump and 9 to 12 gallons of groundwater removed. Clean disposable bailers were used to collect the samples. The wells were measured to within 0.01 feet relative point for each monitoring well. All wells were sampled in accordance with the field methods and procedures described in Enclosure B. The ground water samples were sent to Kiff for analysis of BTEX,TPH in the gasoline range, and oxygenates using EPA Method 8260B, and TPH in the diesel range using EPA Method 8015 modified. The laboratory report is presented in Enclosure D. Waste Disposal Soil cuttings were not generated by the Sonic drill rig. Rinse and development water generated during monitoring well installation, development, and sampling activities was placed into 55-gallon drums on site pending evaluation of disposal options. Based on the laboratory analytical results on groundwater samples, the water disposal was coordinated by InStrat, Inc. of Davis, California. Waste disposal documentation is presented in Enclosure E.