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Red Creek Quarry Baseline Water Investigation Section 3 <br /> <br /> <br />3-7 <br />DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this docu ment. <br />3.4.2 Analysis Methods <br />The response data from the slug tests were analyzed using AQTESOLV (HydroSOLV 2019). The <br />method of analysis used for estimating hydraulic properties was selected for each well based on the <br />expected subsurface hydrogeologic conditions at each well and the actual water level response <br />observed during the slug test. The guidelines for analysis of slug tests provided by Butler (1998) <br />were used to select the most appropriate methods for each well and a method comparison and <br />sensitivity analysis was completed on a portion of the tests as described in the following section. <br />3.4.3 Slug Test Analysis Methods <br />A method comparison evaluation was performed on the slug test data to verify the best fit solutions <br />and characterize the variability in results from the best fitting methods. For each designated test, <br />18 total methods for confined, unconfined, and fractured aquifers were applied and the results <br />compared. From these 18 solutions, conceptual and visual analyses determined the best fit <br />solutions by considering various parameters including, but not limited to, aquifer type, wellbore skin, <br />partial penetration of the aquifer, and over-, under-, or critically damped responses. <br />Based on this comparison, one method was determined to best fit the observed data: Butler-Zhan <br />(2004) inertial test well method for confined aquifers. The use of the terms confined and unconfined <br />aquifers, as they relate to slug test analysis, refers to two conditions either included or excluded from <br />the method assumptions. One of these elements assumes the saturated thickness of the unit being <br />tested either does or does not change when the slug is introduced or removed. If the saturated <br />thickness is significantly altered in the process of inducing groundwater flow into or out of the well, <br />then the condition is generally considered unconfined. However, if no appreciable change in <br />saturated thickness results from the addition or removal of the slug, the well is typically considered <br />confined. The second characteristic of unconfined methods is the underlying assumption that <br />explicitly excludes elastic storage (specific storage) of the aquifer. In contrast, most confined <br />methods include elastic storage and can provide estimates of specific storage through analysis of <br />response data. These distinctions are relevant only to the degree the response data exhibit behavior <br />suggesting either the saturated thickness is being significantly impacted by the test, or elastic <br />storage is making a significant contribution to water movement in the test well. <br />Determination of the presence of either of these conditions relating to the analysis methods cannot <br />always be reliably made prior to evaluation of test response data. In addition, with respect to the <br />elastic storage related definition fractured rock can exhibit semi-confined or convertible (confined to <br />unconfined) conditions which is especially difficult to identify prior to testing. As a result, the <br />response data fit to solution type curves provides additional evidence for the storage conditions <br />acting at a given well. <br />Butler-Zhan is based on Hvorslev (1951) which does include the effects of elastic storage. This <br />preferred solution is designed to work with data for a single well system with no wellbore skin, the <br />option for partial penetration of the aquifer, and the option for underdamped responses (inertial <br />component). In order to evaluate the sensitivity of the estimated hydraulic conductivity values to <br />assumptions regarding confined vs unconfined conditions, results from the method comparison were <br />used to characterize the variation in estimated hydraulic conductivity. The comparison of test <br />response curves does not indicate any significant sensitivity to the confined versus unconfined <br />conditions assumption. Furthermore, based on the sample of two separate test locations used in the <br />method comparison the estimated hydraulic conductivity values do not vary significantly between <br />analysis of the same test data performed with Butler-Zhan. The Butler-Zhan method was then <br />applied to the remainder of the tests for all wells and the best curve fit for each test was then used <br />as estimated hydraulic conductivity for that test as described in the following section.