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002839 CESPK-CO-R Page 2 Public Notice Number 200375243 The LPWCD will work closely with the Colorado Omce of the State Engineer to manage releases from the reservoir for delivery of Compact water to New Mexico. Rel.;f'rvoir C:onstrllrtion Sandstone with interbedded siltstone and silty shale in the Cliff House Sandstone (Kch) appears to be present at relatively shallow depths at the proposed dam site, An earth embankment roller compacted concrete (RCC) dam is proposed for the reservoir. The dam will be about 115 feet high with a crest elevation of 6,320 feet mean sea level (msl). The reservoir would extend approximately 3.5 miles upstream when full. The outlet works would be tunneled in either the right or left abutment of the dam, An integrated, multi- level outlet works is being considered to prOVide water temperature control. The goal of the integrated, multi.level outlet is to provide a temperature profile comparable to natural existing conditions. Seepage paths through highly pernleable soil and rock are not present in the reservoir area and excessive reservoir seepage losses are not anticipated, T :'l 'Pht:'l R lvpr ('omp~rt Article II of the La Plata River Compact states, in part: a. (2)(a) Between December 1st and February 15th, each state shall have the unrestricted right to use all the waters within its boundaries on each day when the mean daily flow at the Interstate Station is 100 cubic feet per second (cfs), or more, b, (2)(b) On all other days, the state of Colorado shall deliver at the Interstate Station a quantity of water equivalent to one-half of the mean flow at the Hesperus Station for the preceding day, but not to exceed 100 cfs, The current delivery system for Compact water is via the La Plata River. Flows measured at Hesperus, Colorado, must travel approximately 31 river miles to the New Mexico-Colorado border (see Figure I)., However, during many years after spring rUlloffhas occurr~d, the stream flow at Hesperus declines substantially, and due to natural stream conditions, flows do no reach the state line, After this decline, Long Hollow !lows alorle are riot sufficient to satisfy one-half of the !low at Hesperus, This results jrl a partial delivery of Compact water to New Mexico. Partial delivery occurs because water at the Hesperus Gauge !lows downstream into a losirlg reach begilllling near Breen and ending at the confluence with Cherry Creek (see Figure I). The low flows at Hesperus and the losing nature of the La Plata River streambed can make the water rights call from New Mexico futile (i.e, water cannot physically be delivered) and often difficult to admirlister by the Water Commissioner and State Engineer. DUring other periods, there can be a surplus of Compact water. The purpose of the Long Hollow Reservoir facility is to provide Compact water to New Mexico, particularly during periods of low or no !low when partial delivery to New Mexico occurs. A storage facility near the state line would allow the State Engineer of Colorado to effectively administer Compact water and mcet Compact obligations. Long Hollow Creek and the La Plata River below the proposed reservoir to the state line typically are perelUlial, which allows for delivery of Compact water. According to the applicant, the proposed reservoir is the best alternative for satisfying Colorado's Compact requirements for several reasons: I. The inundated area is in a location tl1at would cause minimal adverse environmental impacts.