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Appendix B - Packer Test Methods and Results <br />i _ 2;rLKH <br />Q R <br />In[-] <br />Yh <br />where: Q = volumetric flow [L3T-'] <br />L = packer interval [L] <br />K = hydraulic conductivity [LT-'] <br />H = water head above static [L] <br />R = radius of influence [L] <br />rh = radius of the drill hole [L] <br />8 <br />Under steady-state conditions (constant flow), the assumption can be made that R is approximately equal to <br />L. Accordingly: <br />2;rLKH <br />Q = <br />In[ L J <br />rh <br />Re-arranging: <br />L <br />Q In (-) <br />K = rh <br />2 rcL H <br />0 4.5 Falling Head (Slug Injection) Test Analysis (Hvorslev,1951) <br />Underground packer tests can be analyzed using methods similar to the classic single-well test methods <br />described by Hvorslev (1951). However, in the case of very low permeability rock, minor modifications to <br />the solution must be made to account for the compressibility of the system and the geometry of the test <br />situation. <br />The Hvorslev method involves injecting (or extracting) a slug of water into a (typically vertical) bore hole <br />and monitoring the pressure decay (or increase). The hydraulic conductivity is determined by: <br />2L h - tz <br />where: K = hydraulic conductivity [LT-'] <br />r = radius of the drill hole [L] <br />L = length of the packer test interval [L] <br />hi = measured head at a given time ti [L] <br />h2 = measured head at a given time t2 [L] <br />ti = measured time at head hi [T] <br />t2 = measured time at head h2 [T] <br />The solution is commonly simplified, using a log-linear plot (Fig _) which is useful for rapid analysis of <br />hydraulic conductivity tests in the field. At the time when the ratio of the head to the starting head (h/ho) is <br />equal to 0.37, the equation simplifies to: <br />K= <br />2•L•T. <br />4109B.071116 Whetstone Associates