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?• H. KLEINFELDER &AS50CIATE5 <br /> The two most common methods for estimating transmi.ssivity from single--well <br /> slug tests are those of Hvorslev (1951) and :sooner, Bredehoeft and <br /> Papadopulos (1967). In each method, water is ewther suddenly added to or <br /> suddenly abstracted from the well casing and the water level in the casing <br /> is allowed to recover to its original position. Some £unction of the <br /> various water levels during recovery is plotted on the ordinate scale <br /> versus some function of the respective times for recovery on the <br /> abscissa. The actual form of the plot is Unique to the method chosen for <br /> transmissivity estimation. Both methods of slug test analysis have been J~ <br /> applied on tests conducted in well locations NW-4, MW-6, and RW-1 on 25 + <br /> June 1987. <br /> Y1 6.2.1 THE HVORSLEV METHOD <br /> i <br /> In the Hvorslev method, as described by Hvorslev (1951), Cedergren (1967), 3 <br /> and Freeze and Cherry (1979), the head ratio is defined as h(t)/ho <br /> where: <br /> 4 <br /> s <br /> ho = head in the well at the beginning of recovory period (L) <br /> k h(t) = head in the well at any time during recovery period (L) <br /> t = elapsed time since beginning of recovery <br /> The head ratio is plotted on vertical <br /> logarithmic scale and the recovery <br /> time corresponding to each value of head ratio is plotted on the <br /> arithmetic horizontal scale as shown in Figure 1. i <br /> f <br /> Hvorslev defines the basic time lag Tb as the time at which the head <br /> ratio equals 4.37 and this value is readily determined from the plot. The <br /> , <br /> hydraulic conductivity is then computed from: <br /> K =<r2 <br /> FTb <br /> where: . <br /> r radius of the piezometer screen or open hole (L) <br /> K � hydraulic_ conductivity (LT') <br /> ¢ F = shape <br /> factor which depends on the <br /> (L) shape and size of the <br /> Piezometer screen or intake area <br /> 53-87-443 14 <br />