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<br />A-2.36 YAl~A ALLUVIUM TEST <br />• <br />A pump test was conducted on the alluvial aquifer at William Fork Company's <br />gravel pit to define the aquifer properties. A sump was dug with a backhoe in the <br />alluvium for the pump test. Two sand points were installed near the sump for <br />observing drawdowns from the sump pumping. The sump was approximately 20 feet in <br />diameter prior to pumping and was approximately 12 feet in diameter a[ the water <br />surface during most of the pump test. <br />The centrifugal pump in the sump was started on 9:38 a.m. on November 21, <br />1985. The pump test was conducted for approximately 24 hours. The average pumping <br />rate was 15 gpm. Barometric pressure was recorded during the pump teat and was <br />found to be insignificant in affecting water levels. Table A-43 presents the <br />pumping information for this pump test. <br />YAMPA ALLUVIUM OBSERVATION WELL A <br />A sand point with a two foot length of screen was installed 24 feet from the <br /> <br />center of the sump and called well A. The bottom of the sand point was installed 8.9 <br />feet below the top of the land surface. Table A-44 presents the drawdown data for <br />observation well A while Figures A-52 and A-53 show the plots of the drawdown data. <br />The drawdow data for both observation wells was corrected for aquifer thinning see <br />Section A-3.0 of Appendix A, Aquifer-Test Theory) because the alluvial aquifer ie an <br />unconfined aquifer. Slightly over one-half of a foot of drawdown was observed in <br />well A in 24 hours. <br />A-24 <br />REVISED FEB 13 '67 <br />