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1 ' 1 <br /> R604 :UPDATE 24 11-15-1993 <br /> METHODS AND QA/QC <br /> WELL SAMPLING AND ANALYTICAL TECHNIQUES <br /> Depth to ground water and ground water samples were obtained from <br /> all of the ground water monitoring wells on September 15, 1993 <br /> Vacuum and depth to water measurements were obtained from all of <br /> the wells on October 27, 1993 . Depth to top of fluid and ground <br /> water measurements were obtained using a clean product water <br /> interface probe. The probe, lowered into the well attached to a <br /> tape calibrated in 0 02 foot intervals, signals at the contact of <br /> floating product and at the top of ground water. The measurement <br /> is obtained from the calibrated tape reading ad3acent to a <br /> reference point on the casing The probe is cleaned with <br /> trisodium phosphate water followed by a distilled water rinse <br /> before measuring the next well Measurements are started at the <br /> historically cleanest wells and progress to the dirtiest wells <br /> All depth to ground water measurements were obtained before <br /> purging the wells for sampling. The depth to water is then <br /> subtracted from the elevation of the casing' s reference point for <br /> a corrected ground water elevation A computer generated <br /> gradient program was not utilized. The more interpretive <br /> gradient map was developed by calculating the gradient from each <br /> well to all surrounding wells (difference in ground water <br /> elevations/distance between wells) , "a e . " MW1 to MW2, MW to <br /> MW3 , MW1 to MW4, and MW1 to MW6 Depth to ground water data from <br /> MW5 is not used; this well was installed in a slant boring and <br /> produced an anomalous high when used. From these gradient lines, <br /> data points representing the contact for the proposed contours <br /> are plotted along each individual line . Once the data points <br /> have been plotted between all the wells, the data points <br /> representing a given gradient elevation ( -45 foot contour, for <br /> example) are connected with site specific factors, "i e . " <br /> incorporating conditions caused by local geology, hydrogeology, <br /> utility trenches, etc These are used to control the contour <br /> between data points This site is presently being influenced by <br /> vapor extraction at MW5, VS33 , VSB5, VSB9 and VSB11 . A vacuum at <br /> these wells and surrounding wells will influence the shape of the <br /> ground water surface and subsequent flow directions of the ground <br /> water To obtain representative measurements that show the <br /> influence by the vacuum extraction at this site, a vacuum <br /> measurement is obtained at the well head before removing the cap <br /> and the subsequent depth to water measurement is corrected for <br /> the negative vacuum head (potentiometric head) <br /> Vapor Recovery System and Monitoring- <br /> As stated in the Update Status Report #11, SB3 , SB5 , SB9 and SB11 <br /> were converted into vapor extraction wells on July 22 , 1992 <br /> (VSB3 , VSB5 , VSB9 and VSB11) Along with MW5, these wells are <br /> manifolded to a vapor extraction system with individual valved <br /> orifices for flow control and measurement from the individual <br /> wells . The individual wells are fitted with a PVC tee head with <br /> a locking air tight cap, for well access . The tee lateral (2 <br /> inch) is fatted with a 1/4 inch pipe to tubing fitting for <br /> obtaining vacuum/pressure and temperature readings . A pipe to <br /> hose 2 inch union is placed between the tee and the 2 inch PVC <br /> page 4 <br />