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Meridian Village WW Reuse Dam, (DAMID 080457) July 19, 2017 <br /> Jurisdictional Status E. Hazard Classification Page 4 of 9 <br /> associated with the foundation seepage case, the breach parameters for the second analysis <br /> were based on the Froehlich (2008) empirical equations. Printouts of both cases are attached <br /> to this report. <br /> Hydraulic Model <br /> The reservoir was modeled as a storage area with initial water surface elevation of 5,947.7 ft, <br /> corresponding to the lowest point along the spillway crest. The area capacity data was based <br /> on the data provided by CDG and is presented in Figure 3. The downstream drainage was <br /> modeled as a 2D flow area with 40 ft by 40 ft grid cells and a global Manning's n-value of 0.06 <br /> was assigned. Breaklines with 10 ft by 10 ft grid cells were provided to improve resolution of <br /> the low-flow ditches. The culvert extending beneath Chambers Road was conservatively <br /> assumed to be plugged in both cases. The dam was modeled as a SA/2D Area Connection. <br /> Figure 3: Reservoir area-capacity data for Meridian Village WW Reuse Reservoir (CDG, 2013) <br /> Surface Area Surface Area Intake Intake Acre-Feet above <br /> Pond Elevation (sf) (ac) Pond Depth Press.(psi) Press. Pond Volume Acre-Feet permanent pool <br /> Gauge(psi) <br /> 5948 684080 15.70 22 8.7 8.5 8294960 190.43 181.51 <br /> 5947 669030 15.36 21 8.3 8.1 7618405 174.89 165.98 <br /> 5946 654370 15.02 20 7.8 7.6 6956705 159.70 150.79 <br /> 5945 639900 14.69 19 7.4 7.2 630957C 144.85 135.93 <br /> 5944 625430 14.36 18 7.0 6.8 5676905 130.32 121.41 <br /> 5943 611220 14.03 17 6.5 6.4 505858C 116.13 107.21 <br /> 5942 597120 13.71 16 6.1 5.9 445441 C 102.26 93.34 <br /> 5941.2 585920 13.45 15.2 5.7 5.6 3982314 91.42 82.50 <br /> 5941 583120 13.39 15 5.7 5.5 386429C 88.71 79.79 <br /> 594C 569250 13.07 14 5.2 5.1 3288105 75.48 66.57 <br /> 5939 555590 12.75 13 4.8 4.6 2725685 62.57 53.66 <br /> 5938 540160 12.40 12 4.4 4.2 217781 C 50.00 41.08 <br /> 5937 516180 11.85 11 3.9 3.8 164964C 37.87 28.95 <br /> 5936 469400 10.78 10 3.5 3.3 1156850 26.56 17.64 <br /> 5935 394660 9.06 9 3,: 2.9 724820 16.64 7.72 <br /> 5934 278040 6.38 8 388470 8.92 Permanent Pool <br /> 5933 138520 3.18 7 180190 4.14 <br /> 5932 53300 1.22 6 84280 1.93 <br /> 5931 29780 0.68 5 42740 0.98 <br /> 5930 17200 0.39 4 19250 0.44 <br /> 5929 6100 0.14 3 7600 0.17 <br /> 5928 3270 0.08 2 2915 0.07 <br /> 5927 1280 0.03 1 640 0.01 <br /> 5926 1 0 0.00 0 0 0.00 <br /> The breach routing was terminated where Newlin Gulch crosses East Mainstreet. This location <br /> was selected because the primary point of concern was the Chambers Road crossing. The <br /> 2017 FEMA Flood Insurance Study for Douglas County states that the 100-year peak flood flow <br /> at this location is 4,590cfs. The estimated peak breach flood flow calculated in the empirical <br /> equation spreadsheets was roughly 3,100cfs (less than 100-year peak flood flow rate), <br /> therefore Newlin Gulch downstream of Mainstreet is presumed to have sufficient capacity to <br /> safely route the dam breach flood. A screenshot of the hydraulic model geometry is <br /> presented as Figure 4. <br /> cpra <br /> 1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 www.water.state.co.us <br /> John W. Hickenlooper, Governor I Robert Randall, DNR Executive Director I Kevin Rein, Director/State Engineer *�� <br /> �`1876�` <br />