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1 <br /> FOURS QUARTER, 2000 <br /> GROUNDWATER MONITORING REPORT <br /> USA STATION#110 - STOCKTON <br /> JANUARY 2001 <br /> 2.2 Monitoring Well Purging <br />' The monitoring wells were purged using a 2-inch diameter, submersible Rediflo groundwater <br /> pump or disposable bailer, until a minimum of three equivalent well volumes of water were <br /> removed from each well. Groundwater purged from the wells was placed into Department of <br /> ' Transportation approved 55-gallon drums and stored on-site prior to disposal by USA. <br /> To reduce the potential for cross contamination between the wells, all purging and sampling <br /> ' equipment was washed in a trisodium phosphate solution and rinsed in potable water, prior to <br /> each usage. During the groundwater purging operations, physical parameters such as pH, <br /> temperature and conductivity were monitored and recorded on field data sheets, which are <br /> included in Appendix A. Groundwater purging was discontinued when the physical parameters <br /> appeared to stabilize in the purged groundwater. <br /> The groundwater sample from monitoring well MW-5-P as collected without purging the well. <br /> This well has gravel in it from previous construction operations on-site all efforts made to remove <br /> ' the sediment have failed. The well is still used for monitoring purposes, but little water is <br /> available for sampling at this time. <br /> • 2.3 Groundwater Sampling <br /> Prior to sampling, the wells were allowed to recharge to a minimum of 80% of their initial static <br /> ' water levels. Groundwater samples were collected from MW-I-P through MW-6-P, MW-1 and <br /> MW-2 using new disposable bailers. The samples were placed into the appropriate laboratory <br /> 1 prepared containers, using proper sample handling and chain-of-custody (COC) protocol issued <br /> by the USEPA. The samples were labeled with the date, time, identifying well number, then <br /> stored in a cooler at 4° Centigrade or less, and transported to a California State certified <br /> ' laboratory under completed COC documentation. <br /> 2.4 Groundwater Analyses <br /> ' Groundwater samples were analyzed for TPH G, BTEX, 1,2-DCA, and the oxygenated fuel <br /> additives MTBE, DIPE, TAME, ETBE, and TBA using EPA Methods 8015M, 8020 and 8260B, <br /> ' respectively. The analyses were conducted by Sierra Laboratories (Sierra), a California State <br /> certified laboratory, in accordance with state guidelines and EPA protocol. <br /> ' 3.0 SUMMARY AND CONCLUSIONS <br /> The following sections discuss findings from the groundwater gauging and sampling activities <br /> conducted on October 31, 2000. <br /> ' 2 <br />