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San Joaquin County Public Health Services <br /> Environmental Health Division <br /> November 1, 1994 <br /> Page 8 <br /> Static Water Level Measurement <br /> The static water level will be measured in the wells using an electronic water level indicator <br /> Measurements will be recorded and repeated until at least two consecutive depth readings are within <br /> 0 01 feet Water level data will be recorded to the nearest 0 01-foot from a surveyed reference point <br /> marked on the top of the well casing Before and after each use, the measurement device will be <br /> rinsed with distilled water <br /> Well Purging <br /> The monitoring wells will be purged prior to sample collection to obtain samples which are <br /> representative of groundwater in the formation Prior to purging, the static water level will be <br /> measured from each monitoring well and compared to the total depth of the well to calculate the well <br /> casing volume Also prior to purging, a polyethylene bailer will be used to detect and sample any <br /> immiscible layers Monitoring wells will be purged until three to five casing volumes are moved <br /> from the well or the field measured pH, specific conductivity and temperature of the discharged <br /> water have substantially stabilized, whichever volume is greater Measurements of the pH, specific <br /> conductivity, and temperature will be taken at regular intervals during purging which will proceed <br /> until these parameters have stabilized Criteria used for stabilization will be three consecutive <br /> readings within 0 2 pH units, 10 percent fluctuation in specific conductivity, and 0.2 degree <br /> temperature difference A log will be kept documenting water level measurements, field measured <br /> parameters, and casing volumes removed prior to sampling Purge water shall be contained in DOT- <br /> approved 55 gallon drums and stored on-site The pump used for purging will be initially steam <br /> cleaned, then washed in a trisodium phosphate solution, rinsed with potable water, and given a final <br /> rinse with distilled water prior to each use <br /> Sample Collection <br /> Samples for groundwater (collected after purging) will be collected from monitoring wells <br /> using disposable polyethylene bailers These bailers are discarded after one use and do not require <br /> SAC 128 18 Page-8 DAMES & MooRE <br />