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I -PROJECT DESCRIPTION Asphalt Constructors, Inc. has a gravel pit mining operation located approximately one mile west of the Town of Fort Garland. The legal description of the location is the NE'/. Section 20, T. 30 S., R. 72 W., Costilla Estates Survey. The pit is locally known as the Lyle Smith nit. Although the pit was used previous to activities by the current operator, Asphalt Constructors, Inc. has held a permit for the pit since 1988. Figure 1 is a general vicinity map showing the location of the gravel pit mining operation and neazby topographic features. Amore detailed map of the pit azea is included in Appendix B. II -WATER DEPLETIONS The ground water table in the vicinity of the pit is quite deep, however there are imgation ditches located northwest and northeast of the pit that cause the ground water table to rise locally. The relative location of these ditches is shown on Figure 1. An expression of the ground water table in the pit was noted for the first time in during the summer of 1993. Minor amounts of water percolated into the northeast comer of the pit during the summer and then disappeared during eazly fall. Since this first experience, ground water has entered the northeast comer of the pit each summer in approximately July and disappeared during November. When the pit is in use, the water is pumped out of the pit where it flows in a southwesterly direction and seeps into the ground within a short distance. .An accurate estimate of the free water surface azea is difficult because it varies depending on the available water for ditch diversions and activity in the pit by the operator which often results in ?removal of the water fiom the pit. When the pit is in operation, the water seeping into the pit 'from the northeast is controlled by pumping so gravel is not removed below the ground water table. A liberal, but reasonable estimate can be derived by assuming a pond forms over the entire :bottom of the pit during the period July through November. The approximate area of the bottom of the pit lira[ may result in an exposed water surface using the present and proposed pennit is five acres. In accordance with the State Engineer's guidelines, the gross evaporation was estimated to be 43 inches annually based upon evaporation from shallow lakes (NOAA Technical Report NWS 33). A copy of a portion of the report showing the evaporation isopleths for Colorado is included in Appendix A. The net monthly evaporation was calculated as gross evaporation minus 70% of precipitation based on records from the Alamosa weather station. The monthly evaporation was estimated based on the following percentages of total evaporation: January - 2.9%, February - 3.2°./0, Mazch - 4.5%, Aprti - 6.7%, May - 9.0%, June - 13.4°.0,July - 15.9%, August - 15.2%, September - 12.1 %, October - 8.3%, November - 5.4%, December - 3.4%.