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There are four categories of aquifer property data presented in this TM, and each varies <br />in its reliability and level of supporting documentation. The four categories include data <br />derived from aquifer pumping tests, specific capacity tests, lab testing of aquifer <br />materials, and published contour data (for which no underlying point data are <br />available). The general reliability of aquifer property data decreases in order of aquifer <br />pumping tests, specific capacity tests, contoured data, and lab tests as discussed below. <br />The first category of aquifer property data consists of those derived from aquifer <br />pumping tests. Aquifer pumping tests, as defined in this TM, are generally performed <br />by collection of multiple water level measurements from one or more wells during <br />drawdown/recovery as a well is pumped and after cessation of pumping, respectively. <br />The pumping period may be on the order of hours to several days, resulting in a high- <br />resolution data set which may consist of hundreds of data points measured with <br />automated high-precision equipment. The longer a well pumps, the more extensive its <br />radius of influence becomes and thus the volume of aquifer tested becomes greater and <br />more representative of bulk aquifer conditions than a shorter duration test. <br />Additionally, potential bias due to well-bore storage will diminish with time. The <br />detailed data are then subjected to analysis during which any interference or potential <br />biases can be determined and accounted for during the interpretation. The data quantity, <br />collection and analysis methods provide the highest level of certainty relative to the <br />other types of data presented here. <br />Significant sources of published aquifer property data derived from aquifer testing and <br />used in this TM include Robson (1983), Hillier et al. (1978), Wilson (1965), Hill (1991), <br />and, the South Metro Water Supply Study (Mulhern MRE 2003). In Phase 2 Task 37, <br />previously unpublished aquifer test data and results from the aquifer testing field <br />program are additional sources of aquifer pumping test data used in this TM. During <br />Task 37 activities, 86 bedrock aquifer tests were received from cooperating entities, and <br />14 aquifer tests were performed by CDM at wells operated by cooperating entities (CDM <br />2005). <br />The second category of aquifer property data is derived from specific capacity tests. <br />This type of test is generally conducted after a well is completed to determine the <br />pumping rate a well can sustain, and consists of the pumping rate divided by the <br />drawdown in the pumped well. During a specific capacity test, water level <br />measurements are generally collected only at the beginning and end of a generally <br />shorter-duration test generally lasting on the order of several hours. Due to the <br />generally shorter test duration (often 1-4 hours) the volume of aquifer tested is typically <br />less than alonger-term aquifer pumping test. Specific capacity tests of longer duration <br />provide data representative of the surrounding aquifer rather than of the well bore <br />and/or filter pack and provide water levels more representative of equilibrium <br />conditions. The water level data set from a specific capacity test consists of two data <br />points (beginning and ending water level measurements) which may not be as precise as <br />measurements collected during an aquifer test due to manual data collection or use of <br />less precise equipment. During Phase 1 Task 43 (CDM 2004a), a total of 67 specific <br />capacity tests for bedrock aquifers were obtained from McConaghy et al. (1964). During <br />Phase 2, Task 37, a total of 1,341 specific capacity tests were obtained from DWR's well <br />SPDSS Phase 2 Task 43.2 TM -Final 6 <br />2/ 13/ 2006 <br />