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Long Hollow Dam and Reservoir Phase I Summary Report <br /> • An evaluation of institutional issues that might constrain LHR development, such as <br /> water allocation, reservoir operations, payment issues, local agency consultations, and <br /> obtaining right-of-way, permitting, and financing. <br /> The Phase I study did not include any geotechnical or feasibility-level design work, including the <br /> hydrology work for calculating the probable maximum flood. If WWE is authorized by the <br /> CWCB to proceed, this additional work will be included in the Phase II LHR feasibility study. <br /> 1.2 Project Location and Description <br /> The proposed LHR is to be located in southwest La Plata County, approximately 22 miles <br /> southwest of Durango, Colorado in Sections 29, 32, and 33, T33N, R12W, NMPM. LHR is a <br /> proposed on-channel reservoir. The dam embankment would be located on Long Hollow <br /> approximately 0.5 miles upstream of the confluence of Long Hollow and the La Plata River, and <br /> 5 miles upstream of the Colorado-New Mexico border(see Figure 1). <br /> LHR would capture flows from the 43-square miles of the elongated Long Hollow watershed, <br /> including groundwater inflows resulting from irrigation return flows and surface water inflows <br /> derived from precipitation within the watershed (see Figure 2). The current land use within the <br /> watershed is predominantly agriculture with much of the land irrigated when a water supply is <br /> available. The northeast-southwest trending mesa that comprises most of the watershed slopes at <br /> a uniform grade of approximately 2 percent to the southwest from an elevation of 8,100 feet <br /> above sea level (ASL) to 6,200 feet ASL near the proposed LHR embankment. The Long <br /> Hollow channel and its tributaries are incised into the mesa. The average annual precipitation <br /> measured at the Fort Lewis station, located about 14 miles north of the LHR site, was 18.17 <br /> inches for the 32 years of measured record between water years (WY) 1949 through WY 1998. <br /> LHR would have an estimated maximum reservoir pool volume of 5,432 AF. The maximum <br /> pool elevation would be 6,310 feet ASL and would cover approximately 160 acres (see Figure 3). <br /> The average LHR fill volume for the period WY 1989 through 2002 projected by using the water <br /> allocation model described in Section 8.1 would be 3,540 AF/yr. Average LHR project <br /> depletions, as determined by the U.S. Bureau of Reclamation's (USBR) San Juan River model, <br /> 991-077.115 Wright Water Engineers, Inc. Page 2 <br /> July 2004 <br />