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1ie11 5014-]-H <br />:: • <br />Procedure: <br />Well SOM-1 was tested on September 9, 1982 using a slug measuring 5.5 feet <br />,long, by 2.36 inches diameter. A continuous water level recording device which <br />was operating in the well was removed from the well during testing and replaced <br />when testing was completed. The slug was rapidly dropped into the 4-inch PVC <br />well casing and falling head data were collected for 120 minutes. Because of <br />the relatively quick response of this well, the water level had equilibrated <br />after the falling head test allowing a recovery test to be conducted upon re- <br />moval of the slug from the well. Recovery data were collected for 30 minutes. <br />Interpretation: <br />r:= Falling head and recovery data agree closely and are plotted together for <br />analysis by the Cooper et. al. method. Avery good fit of the type curve yields <br />a transmissivity value of 600 gpd/ft. Separate plots of s vs. 1/t by the Ferris <br />and Knowles method give nearly identical T values of 246 and 247 gpd/ft. for <br />C~. falling. head and recovery data respectively. The range in T values obtained by <br />these two analysis methods is not great considering that permeabilities of natu- <br />ral geologic materials can range over 9 orders of magnitude. The factor of approxi- <br />mately 2.4 difference is attributable to the fact that the line source method (Fer- <br />ris F, Knowles, 1954) does not account for well storage. The higher value of 600 <br />gpd/ft. obtained by the Cooper et. al. method is therefore interpreted to be the <br />most valid estimate of aquifer transmissivity. <br />The well log of SOM-1 indicates that there is approximately 90 feet (88 ft.) <br />of gravel packed well screen and slotted casing within saturated sandstone, shale, <br />and coal of the Barren Member. Using the T of 600 gpd/ft divided by 90 ft. gives <br />an average formation permeability of K=6.67 gpd/ft2. Although in terms of useable <br />aquifers this is a low value of permeability, this is one of the highest observed <br />permeabilities of the rock units tested. Since this well is shallow (113 feet total <br />depth) and static water level is only 16.4 feet below ground surface, the higher <br />rock permeability here is probably due to possible weathering of the shallow bedrock. <br />::• <br />12 ESA Geotechnical Consultants <br />