ARCHIVED REPORTS XR0000260 - Laserfiche WebLink

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California Department of Transportation July 7, 1994 Project No 102818A-01 level was then measured relative to the reference marking on the top of the well casing The water level measuring instrument was decontaminated after each use by washing the probe and lead line th tion of potable water and trisodium phosphate, followed by a Potable water rin e i r rinse Groundwater at the site is present at an approximate depth of 65 fee low ound surface (bgs) and flows to the north at an ' approximate gradient of 0 0013 feet per foot The groundwater elevation measurements are summarized in Table 1 A groundwater gradient map is presented as Figure 3 The threeg roundwaterwells,designated MW-A(MW-1),MW-B (MW-2),and MW-C(MW-3), ' were also sampled On June 1, 1994, the wells were purged using a 2-Inch diameter submersible pump The submersible pump and associated hoses were decontaminated after each use with a solution of potable water and trisodium phosphate, followed by a potable water rinse and a deionized water rinse The interior and exterior of the pump and hoses ' were washed by submersing the equipment in the solutions and drawing wash and rinse water through the pump system A mirumum of three casing volumes were purged from each of the monitoring wells prior to collection of a water sample Temperature, pH, and specific conductance measurements were made in the field for the purpose of establishing when a representative groundwater sample could be taken Purging continued to each well until pH, temperature, and conductivity did not vary by more than 10 percent The morutortng well purge water was placed in labelled 55-gallon, DOT-approved drums and left on site in the stewardship of Caltrans Field measurements and general observations for each well were recorded on the well sampling records presented in Appendix A After purging, the water in each well was allowed to recover to at least 80 percent of its original elevation Water samples were then collected using a disposable, Teflon, bottom- ' discharging bailer, transferred to an appropriate sample container, labelled, and placed in a cooler containing ice T amples were transported to Quality Assurance Laboratories for ichemical testing unde st y protocol a U 1