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1 Phase 11 Environmental Site Assessment 1645 Cherokee Lane,Stockton,CA ' Hydro-Environmental Technologies,Inc ' 3.0 GROUND WATER MONITORING AND SAMPLE METHODOLOGY ' Ground water monitoring was conducted in accordance with procedures required in CCR Title 23 procedures, and guidelines from the PHD/EHD Ground water monitoring wells were installed after completion of the initial soil boring investigation ' 3.1 Monitoring Well Installations ' Between August 28 and 29, 2000, Spectrum Exploration Inc (Spectrum) installed three ground water monitoring wells, using hollow stem auger, in the shallow unconfined saturated zone The upper 35-feet of the ground water monitoring well was 2-inch diameter schedule 40 PVC blank casing and the lower ' 15-feet was 2-mch schedule 40 PVC slotted screen The gravel pack consisted of number 2/16 sand with a 0 01-inch slot All monitoring wells were sealed with at least 10 0 feet of Portland cement, all monitoring wells were completed with a watertight locked cap and a traffic-rated bolt down well cover, flush mounted with the pavement Well construction diagram is included in Appendix B One monitoring well was installed up gradient from the removed USTs, one monitoring well was installed cross-gradient and one monitoring well was installed down gradient Completed ground water monitoring well elevations were surveyed in February 2001 by Dillon & Murphy Consulting Civil Engineers of Lodi, California, a California licensed land surveyor Monitoring wells were surveyed to the ' nearest 0 01-foot using the closest USGS bench mark or other appropriate survey mark 3.2 Ground Nater Investigation On August 31, 2000, Spectrum developed the ground water monitoring wells Monitoring wells were developed until silt-free ground water was observed or the well was dewatered ' 3.21 Ground Water Measurements and Sampling ' On September 1, 2000, HETI measured and sampled the subject site's ground water from the developed monitoring wells Ground water depths were measured to the nearest 0 01-foot using a Solmist "well ' sounder" or sirmlar measuring device Monitoring wells were measured and sampled in specific order from the least contaminated ground water to the most contaminated ground water to lower the possibility of cross contamination This was based on analyses obtained from the grab ground water monitoring ' event Prior to ground water sample collection, each monitoring well was purged of a minimum of three well casings volumes of water, or less if the well was dewatered Once temperature, pH, and conductivity, ' were stabilized within 10 percent, ground water samples were collected Monitoring wells were sampled using a pump All equipment was subsequently decontaminated between sample events in a detergent and tap-water wash followed by a tap-water rinse, and a final rinse with distilled water 4