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4.0 WELL DATA BASE ANALYSIS <br />4.1 WELL RECORDS <br />The 1967 Beck Report states there were approximately 1,020 active wells registered <br />with the State Engineer's Office (SEO) by 1966. The records of the SEO were reviewed <br />and updated from the August 1999 list used in the 1999 Feasibility Study by MWE, with <br />the assistance of staff from the SEO. Based upon the updated records, there are <br />approximately 2,600 registered and permitted wells in the Basin as of May 2000. These <br />wells are shown on Map 1 and are separated into respective well types. Of this total, <br />approximately 1,300 wells are considered high-capacity wells (i.e., they are permitted to <br />produce water at rates greater than 50 gpm). The remaining 1,300 wells are considered <br />small capacity wells because they are permitted to produce less than 50 gpm. Few new <br />wells were drilled in the Basin and an additional tabulation of wells in the District was <br />beyond the scope of this study. The list of newly permitted wells is available from the <br />Colorado Division of Water Resources, and included herein as Appendix C. <br />4.2 WELL LOGS <br />The District is part of a basin that is hydrogeologically complex and poorly documented <br />by modern standards. As part of the Phase 1 Study, approximately 300 driller's logs <br />were evaluated in an attempt to define the geologic formations penetrated. Only 83 of <br />those logs contained information adequate to aid in describing the geology. About half <br />of the monitoring wells records had associated geologic information. Typical lithologic <br />descriptions (driller's logs) may only list footages associated with "topsoil" or "surface", <br />followed by a rock type tabulation such as 120 ft. of shale, 100 ft of sand, 20 ft of shale, <br />etc." In other words, the driller's logs are inadequate for geologic interpretation; the detail <br />is rarely adequate to define formations or Iithologic character. Fortunately, color <br />descriptions assist in distinguishing the formations, particularly the black shales of the <br />Graneros and Kiowa, and the "red beds" of the Dockum. The initial part of this Phase 2 <br />Study included copying logs associated with about 1500 of the 2,600 wells in the data <br />files at the Colorado SEO. MWE technicians pulled only the logs with the "best" or <br />,'most" information in each township. These logs were studied and correlated by MWE <br />staff geologists who were able to incorporate less than 200 additional descriptions. The <br />data gathered at the SEO was supplemented with USGS surface sections (McLaughlin, <br />1954) and descriptions available from various Kansas Geological Survey reports for <br />wells in adjacent Kansas. Appendix A contains a list of permitted wells and USGS <br />stratigraphic sections used in compiling the maps within this report. <br />IV -1 <br />99-028.003\Phase 2 Report\ SHP Well Data <br />