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61/31/2603 17:09 2799186 DOTY & ASSOCIATES PAGE 02 <br />Mr. Christopher C. LaRue <br />Page 2 <br />January 28, 2003 Doty & Associates <br />at the base of the dry mining slope. We calculate that the applicant proposes to <br />construct the slurry wall approximately 45 feet west of the Off Partnership property <br />line. <br />OFF PARTNERSHIP WELL <br />The Off Partnership owns three properly permitted wells that are located on its <br />property. One of these is a deep bedrock well producing water for household use. <br />This well is unlikely to be impacted by the proposed gravel mining operation. The <br />other two are alluvial Ishallow) wells in irrigation use. This letter describes the likely <br />impacts to the older of these wells (Permit No. 12992 with an appropriation date of <br />1905), although a similar demonstration could be made with regard to the second <br />alluvial well (Permit No, 12993 with an appropriation date of 1954). It should be clear <br />that these wells have very senior rights and, as a result, are valuable real property. <br />Well No. 12992, hereafter called the well, is located approximately 663 feet north of <br />the southwest corner of the parcel that is the subject of the application (the southwest <br />corner of Section 35, Township 1 South, Range 67 West, 6th Principal Meridian) and <br />139 feet west of the west property line of the same parcel. Used on the logic <br />presented earlier, the proposed slurry wall will be approximately 184 feet from the <br />well. The well is 20 feet deep. The upper portion of the well (to 8 feet below ground) <br />is 7.5 feet in diameter and is constructed of solld concrete. The lower portion (from <br />8 to 20 feet) is 4 feet in diameter and is perforated over the entire 12 foot length. The <br />static depth to water is approximately 12 feet below ground surface. Water is <br />produced from the well using a 6-inch centrifugal pump that appears capable of <br />delivering the full adjudicated 500 gallons per minute, <br />The hydraulic characteristics of the subsurface materials in the well vicinity have not <br />been developed through direct testing; however, the following information is available <br />in the literature. According to Robson (1989), the hydraulic conductivity of the South <br />Platte River alluvium near Denver averages 870 feet per day (0.31 centimeters per <br />second) and decreases in the downstream direction. Hurr et al. (1972) report a <br />transmissivity of 80,000 gallons per day per foot and a saturated thickness of 20 feet <br />for the area of the well, which corresponds to an hydraulic conductivity of 400 feet <br />per day or 0.14 centimeters per second. No direct information relative to an <br />appropriate storage coefficient was found, so the standard range of 0,1 to 0.3 for <br />unconfined aquifers is assumed. The total alluvial thickness is also not known; <br />however, it may be as much as 50 feet (based on the TH-4 boring log and assuming <br />a 15 foot elevation drop between the drilling location and the well). On the other <br />hand, Hurr et al. (1972) estimate that the saturated thickness at the well location is <br />20 feet, implying a total alluvial thickness of 32 feet.