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URS <br /> • Ms Carol Oz, R E H S Page 3 <br /> LOP/Site Mitigation Unit <br /> ' San Joaquin County—Public Health Services <br /> Environmental Health Division <br /> ' December 7, 2000 <br /> Quarterly Groundwater Sampling <br /> ' Groundwater samples were collected by URS on October 31, 2000 from each of the three monitoring <br /> wells Groundwater levels, visual observations, and general water quality measurements collected <br /> ' during well purging were recorded in the sampling data sheets (Attachment I) Following depth to <br /> groundwater measurements, the wells were purged of three well casing volumes by hand bailing prior <br /> to collection of the groundwater samples General water quality parameters (pH, temperature, specific <br /> ' conductance, color, and odor)were measured and recorded at regular intervals throughout the purging <br /> and sampling procedure Purged groundwater from the wells was placed in 55-gallon drums and stored <br /> onsite pending analytical results <br /> 1 Groundwater samples were collected from each monitoring well using a new disposable Teflon®bailer <br /> with a bottom dispensing valve The samples were placed into the appropriate sample containers <br /> ' provided by the analytical laboratory, then sealed, labeled and placed on ice in a cooler A quality <br /> control/quality assurance (QA/QC)field duplicate sample was collected from monitoring well MW 1 and <br /> identified as sample "X-1" The samples were submitted under Chain-of-Custody procedures to Curtis <br /> &Tompkins, Lid , Analytical Laboratories, a California certified analytical laboratory All groundwater <br /> samples were analyzed for TPH-G using modified EPA Method 8015, and BTEX, MTBE,TBA,DIPE, <br /> ' ETBE, and TAME using EPA Method 8260B <br /> Groundwater Flow Direction and Gradient <br /> ' URS reviewed the field data for depth to groundwater measurements and calculated the groundwater <br /> elevations for October 31, 2000 using established top of well casing elevations To determine <br /> approximate groundwater flow direction and gradient, the relative groundwater elevations from three <br /> triangulated wells were calculated To establish relative groundwater elevation, the depth to <br /> groundwater was subtracted from the surveyed relative elevation of the well casing Based on these <br /> t measurements, the groundwater flow direction for October 31, 2000 is to the north-northeast and is <br /> presented in Figure 1 The calculated groundwater flow gradient is 0 004 feet per foot across the Site <br /> 1 <br /> • <br /> I <br /> i11SACDATAMHAREDIPHIUPROJECTSIRESDITRACY110_31 OOREPORTM DOC <br />