Laserfiche WebLink
Removing specific capacity data derived from wells completed to depths of less than 100 <br />ft eliminated data that may be more representative of weathered bedrock or alluvial <br />material overlying the bedrock aquifer. <br />As described in Phase 1 of the SPDSS (a 2004), Robson (1983) provides one of the most <br />comprehensive data sets for the Denver Basin aquifers, accounting for a significant <br />amount of the aquifer test data and approximately 40 percent of the laboratory based <br />test results analyzed for the Denver Basin region. The Robson (1983) study, prepared <br />prior to development of the Denver Basin Rules (DWR 1985a), did not distinguish <br />between the upper and lower portions of the Dawson and Arapahoe Aquifers within <br />their respective divided zones. Rather than screen these points from the database <br />because they could not be assigned to an aquifer as defined by the Denver Basin Rules <br />(DWR 1985a), these points are defined as Arapahoe "undesignated" or Dawson <br />"undesignated." <br />For the purposes of the SPDSS study, the Robson (1983) data are posted on both the <br />Upper and Lower Dawson and the Upper and Lower Arapahoe Aquifer figures <br />presented in this TM. The Robson (1983) data from these aquifers are shown as a <br />separate data category to distinguish them from data known to be from one of the <br />divided aquifers. As presented in Section 3, the Robson (1983) data constitute a <br />significant portion of the data derived from aquifer tests and are generally similar to <br />other posted values from the upper and lower units of the aquifer in question. It is felt <br />the Robson (1983) data are a reasonable representation of the hydraulic conductivity <br />distributions for these aquifers. For the purpose of the SPDSS, all non laboratory data <br />obtained from Robson (1983) are considered as "aquifer test" data regardless of whether <br />the data were obtained from specific capacity or aquifer tests, since neither the method <br />nor the source of the data was identified in the original report. <br />In Phase 1, it was found that some of the same aquifer test and laboratory sample data <br />were being provided by more than one data source. To remove redundant data, GIS <br />spatial queries were performed between several source data sets that were considered to <br />have reported the same aquifer test data. If a data point was located within <br />approximately 500 feet of a data point from another source, it was screened. Data <br />screened as duplicates and other reasons are identified in Table 3. In several cases, <br />additional duplicate or redundant data were identified between K data obtained during <br />aquifer pumping tests conducted under Phase 2 Task 37 activities and K data that had <br />been obtained from well permits or other sources (Mulhern MRE 2003, Hi111991) during <br />Phase 1. In these instances, data from an aquifer pumping test performed as part of the <br />SPDSS under Task 37 took priority since it was well documented and usually included <br />an aquifer S value. <br />Table 3 summarizes aquifer property tests from the Denver Basin bedrock aquifers <br />removed or screened from further analysis and contouring, for the reasons discussed <br />above and defined in Table 3. The screening process is described in Appendix A and <br />resulted in removal of 106 data points. The data retained for further analysis and <br />mapping will be added to HydroBase as described in Section 3. <br />SPDSS Phase 2 Task 43.2 TM -Final 10 <br />2/ 13/ 2006 <br />