Laserfiche WebLink
1 <br /> THIRD QUARTER,1998 ' <br /> GROUNDWATER MONITORING REPORT <br /> USA STATION 9110-STOCKTON <br /> AUGUST, 1998 ' <br /> 2.2 Monitoring Well Purging <br /> The monitoring wells were purged using a 2-inch diameter, submersible Redifio 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 To <br /> reduce the potential for cross contamination beiween wells all purging and sampling equipment <br /> were washed in a tnsodium phosphate solution and rinsed in potable water, prior to each usage <br /> Dunng the groundwater purging operations, physical parameters such as pH, temperature and <br /> conductivity were monitored and recorded on field data sheets, which are included in Appendix <br /> A Groundwater purging was discontinued when the physical parameters appeared to stabilize in <br /> the purged groundwater <br /> 2.3 Groundwater Sampling ' <br /> Prior to sampling, the wells were allowed to recharge to a minimum of 80 percent of their initial ' <br /> static water levels Groundwater samples were collected from MW-1, MW-2, MW-1-P through <br /> MW-4-P, and MW-6-P using new disposable b�lers The samples were placed into the <br /> appropriate laboratory prepared containers, usmg proper sample handling and chain-of-custody .' <br /> {COC} protocol issued by the USEPA The samples were labeled with the date, time, identifying <br /> well number, then stored in a cooler at 4* Centigrade or less, and transported to a state certified <br /> laboratory under completed COC documentation ' <br /> 2.4 Groundwater Analyses <br /> Groundwater samples were analyzed for TPH G and BTEX using MethodsEPA ' <br /> 8015M and <br /> 8020, respectively The analyses were conductd by Sierra Laboratories (Sierra), a California <br /> State certified laboratory, in accordance with state guidelines and EPA protocol ' <br /> 3.0 SUMMARY AND CONCLUSIONS <br /> I <br /> _ The following sections discuss findings from the groundwater gauging and sampling activities - - - - - - <br /> conducted on July 17, 1998 <br /> 3.1 Groundwater Flow and Gradient <br /> Groundwater data collected at the site indicates that depths to groundwater ranged from 59 26 to ' <br /> 60 44-feet below ground surface (bgs) The groundwater elevations ranged from 34 40 to 34 83- <br /> feet below mean sea level ' <br /> 12 <br /> I I I <br /> I <br />