Laserfiche WebLink
The slug testing method and apparatus proved satisfactory for wells at the <br />h1t. Gunnison.~l D1ine with the unusual situation of deep wells (up to 982 feet <br />to water) completed in very low permeability materials. Other well testing <br />::• methods involving setting pumps in the wells or using air-lift to remove water <br />from the wells would be unpractical in most of the wells tested due to extreme <br />,lift heights, small well diameters, and the need for steady, very low flow pro- <br />i.. duct ion rates. <br />B. Analysis of Slug Test Data <br />Two methods were used to calculate transmissivity from the water level <br />versus time data collected for each well. These are the Cooper et, al. (1967) <br />type curve method and the Ferris and Knowles (1954) method. A third method <br />which was mentioned in ESA's proposal is the Bouwer and Rice (1976) method. <br />The Bouwer and Rice method relies on drawing a straight line through very early <br />test data and knowledge of well construction and borehole geometry. Since early <br />data at close time intervals is difficult to obtain without the use of pressure <br />transducers, and well geometry was unknown for some wells, this method was not <br />used to evaluate the slug tests conducted in this study, <br />• The Cooper et. al. method involves plotting H/Ho against log t on semi-loga- <br />rithmic paper and matching the test data to a type curve. With the arithmetic <br />(H/Ho) axes coincident, the data is matched to a best fit with the type curves <br />(Figure III-2; in back cover pocket) and the time value from the test data which <br />overlie the point at which T t/r~ = 1.0 is used to calculate transmissivity by <br />the following equation: <br />1,0 r- <br />T - c <br />t <br />where <br />H =head above static water level; <br />Ho = initial head increase in the well (either calculated or assumed <br />based upon observations); <br />t =time since instantaneous injection; <br />r =radius of well casing in which water level fluctuates; <br />c <br />• T =transmissivity of aquifer. <br />7 ESA Geotechnical Consultants <br />