ARCHIVED REPORTS_XR0005202 - Laserfiche WebLink

Home Browse Search

FIRST QUARTER, 1997 GROUNDWATER MONITORING REPORT USA STATION #110 - STOCKTON MAY, 1997 MW-1 and MW-2 were not purged before sampling due to very low groundwater levels Groundwater purged from the wells was placed into Department of Transportation approved 55- gallon drums and stored on-site prior to disposal by USA To reduce the potential for cross contamination between wells, all purging and sampling equipment was washed in a trisodium phosphate solution and rinsed in potable water prior to each usage During the groundwater purging operations, physical parameters such as pH, temperature and conductivity were monitored and recorded on field data sheets, which are included in Appendix A Groundwater purging was discontinued when the physical parameters appeared to stabilize in the purged groundwater 2.3 Groundwater Sampling Prior to sampling, the wells were allowed to recharge to a minimum of 80 percent of their initial static water levels (SWLs) Groundwater samples were collected from MW-1, MW-2 and MW- 1-P through MW-6-P using a new disposable baler Samples were placed into the appropriate laboratory prepared containers, using proper sample handling and chain-of-custody (COC) protocol established under applicable SW-846 procedures issued by the USEPA The samples were labeled with the date, time, identifying well number, then stored in a cooler at 4° Centigrade or less, and transported to a state certified laboratory under completed COC documentation 2.4 Groundwater Analyses Groundwater samples were analyzed for TPH G and BTEX using EPA Methods 8015M and 8020, respectively The analyses were conducted by Sierra Laboratories, Inc (Sierra) a California State certified laboratory in accordance with state guidelines and EPA protocol 3.0 SUMMARY AND CONCLUSIONS 1 The following sections discuss findings from the groundwater gauging and sampling activities conducted on January 24, 1997 3.1 Groundwater Flow and Gradient Groundwater data collected at the site indicates that depths to groundwater ranged from 66 03 to 67 18-feet below ground surface (bgs) The groundwater elevations ranged from 41 57 to 40 82- feet below mean sea level Groundwater elevations have increased an average of 1 82-feet since the last sampling event 2