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<br />i <br /> <br />, <br /> <br />DATE: <br />SUBJECT: <br />PARTICIPANTS: <br /> <br />MEETING MINUTES <br /> <br />R.CEIVED <br />FER 25 1999 <br /> <br />~do W.. <br />4 February 1999 CoI\servaliOft8oanl <br />La Plata County FPMS Flood Plain Delineation Study <br />Butch Knowlton, La Plata County <br />Stan Powers, U.S. Bureau of RecIamation (USBR) <br />Tom Browning, Colorado Water Conservation Board (CWCB) <br />Gary Lopez, Corps of Engineers (COE), Albuquerque District <br />Bet Lotosky, Corps of Engineers, Albuquerque District <br /> <br />Representatives from La Plata County, the USBR, the CWCB, and the COE met <br />to discuss and agree upon the hydrologic methodology to be used for the Pine River <br />through La Plata County for the flood plain delineation study. The effective Flood <br />Insurance Study (FIS) for the town of Bayfield, dated March 1978, reports a 100-year <br />discharge of 6,000 cfs at Bayfield. Camp, Dresser, and McKee completed the analysis in <br />September 1977. The FIS reports that the discharges for the Pine River at Vallecito Dam <br />were based on the operational records of the dam from 1943 to 1973. Discharges for the <br />area downstream of the dam were determined by applying regional regression <br />relationships established for the upper San Juan River basin. FEMA also used the 6,000 <br />cfs discharge for the La Plata County FIS, effective June 1981. Based on local <br />knowledge, all parties agree that a 100-year discharge of 6,000 cfs seems low. <br />The USBR constructed Vallecito Dam in 1940 for water supply. The dam is <br />owned by the Pine River Irrigation District and operated by the USBR for both irrigation <br />and.emergency releases. The dam does not have a flood control allocation; however, the <br />dam can be used for flood control during the spring and fall when the. irrigation pool is <br />not completely full. The maximum recorded inflow to Vallecito Dam is 12,000 cfs. The <br />two drainage basins contributing to Vallecito Reservoir are the Pine River and Vallecito <br />Creek. Vallecito Creek, with a 100-square-mile watershed, has a flood of record of 7,000 <br />cfs that occurred 6 September 1970. The maximum recorded Vallecito Dam release of <br />13,000 cfs occurred in the 1950's when the spillway gates stuck during a test. We agreed <br />that the COE will consider the effect of Vallecito Reservoir in the flood plain analysis <br />and use a constant release of 3, I 00 cfs from the dam that represents the maximum outlet <br />discharge with the reservoir full to the top of the joint-use pool. No spillway discharge <br />will be considered. <br />Mr. Browning reported that Harris Water Engineering completed in June 1986 a <br />Pine River flood plain study for a site 8 miles north of Bayfield and 4 miles south of <br />Vallecito Dam for the Pine River Cattle Company. Harris reports 100-year discharges of <br />11,000 cfs for Vallecito Creek, 15,000 cfs for the 150-square-mile Pine River, and 2,400 <br />cfs for the 18-square-mile area below the dam. Combining these discharges with <br />concentration times factored in results in a 100-year discharge of 26,000 cfs at the study <br />site. Using the U.S. Forest Service report Region 2 Water Resource Analysis System, <br />Channel Geometry and Culvert Sizing (May 1984) developed for the San Juan National <br />Forest, Harris computed a 100-year discharge of 18,000 cfs. Harris determined that <br />18,000cfs is the more reasonable flow and used this discharge for the flood plain <br />analysis. <br />