2011-02-11_HYDROLOGY - M1984036 - Laserfiche WebLink

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Cheryl Signs, P.E. Page 2 Kurtz Pit, DBMS-1999-006 as another replacement source is obtained. A copy of the affidavit is attached to this letter. For the purposes of this SWSP, this affidavit will be accepted for the dedication of the shares; however, if the State Engineer determines that a different affidavit or dedication process is necessary to assure proper dedication of the shares, additional Information may be required prior to future SWSP approvals. Depletions The anticipated net depletions for this SWSP are 258.38 acre-feet per year. The currently exposed groundwater at the site totals 19 acres. However, the plan anticipates that a total of 173.1 acres of water surface will be exposed at the site if dewatering ceases. The evaporation calculations were based on the entire exposed surface area in the event that the dewatering ceased and this plan will cover replacements for depletions associated with the 173.1 acres. However for purposes of accounting, depletions will be based on the ground water surface area actually exposed at the site. You indicated that in addition to the dewatering pumps installed in the pit for dewatering, the Applicant intends to use well no. 74389-F (2489-FR canceled), for dewatering purposes at the site. This well was decreed by the Division 1 Water Court as Kurtz Well No. 11 in Case no. W-3873, for 1.84 cis and irrigation purposes of 50 acres in the NW1/4 of Section 28, Township 3 North, Range 67 West of the 61h P.M. The well is located on the Kurtz site DBMS permitted boundary and the well has not been used for irrigation since mining started at the Kurtz site. You have provided a monthly breakdown of the annual depletions made up of 235.42 acre-feet of net evaporative loss, 20.60 acre-feet of water lost with the mined product (which represents 700,000 tons of mined product), and 3.36 acre-feet of water used for dust control. A phreathophyte credit for the native salt grass has been applied to this plan which reduced the net evaporation depletions to 235.42 acre-feet. The credit given for the salt grass in this plan was based on the 3-feet depth to ground water, pending better site-specific information. The demand for the salt grass was calculated to be 22.78 inches using the modified Blaney-Criddle method with Longmont 2ESE weather station data. In the previous SWSP approval we indicated that no credit will be given for the phreathophyte in any subsequent renewals of this plan unless the Applicant provides site-specific information regarding the depth to the ground water table at this location and the Information is accepted by this office. You Indicated that the site is dewatered and no current information regarding the historical depth to ground water can be obtained in the field at this time. There Is some information on the depth to the ground water from wells located on or near the parcel. However you indicated that the wells were not drilled during the growing season and do not reflect the ground water condition during this season. There is a seepage ditch on the east side of the property that historically drained the parcel. The USGS map shows part of the parcels and lands as marsh/swamp land. Although the depth to the ground water table during the growing season cannot be determined at this time, you stated that the evidence of a seepage ditch necessary to drain the land and a marchlswamp points to a water table near the surface. Additionally the credit from the historical vegetation will not be implemented until the dewatering at the site ceases. For the currently exposed surface area the evaporation depletions shall be calculated based on the gross evaporation minus the effective precipitation. Information regarding the depth to the ground water table at this location must be provided to this office at the time that the dewatering at the site ceases. This information must be accepted by this office prior to claiming any credit for the native vegetation.