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<br />Rex Burns, PE and Bob Smith, P,E, <br />Final Report. Hydrologic Analysis of the Cooper Slough Within Larimer COUlIty, Colorado <br />Pa"oe 2 <br /> <br />A copy of the Boxelder Creek Uvlli1P Flood Insurance Study (F1S) report was obtained to <br />detennine the peak lOa-year overflow discharg,~ at the fc)llowing five locations along 1-25, <br /> <br />. Larimer-Weld Canal <br />. Vine Drive <br />. Low point 00-25 south ofVin" Street <br />. C&S Railroad <br />. State Highway 14 <br /> <br />Figure 1 shows the approximate location of these owrtopping amilS. <br /> <br />Only the lOa-year peak overtopping discharge values could be d\:t(=IDed from the FIS report, In <br />order to update the 1987 S\VMM model th(: p(:ak overtopping discharges and the runoff <br />hydrographs for each of these stann ('vents needed to be input into the S vVNTh! mod,,!.. <br /> <br />The peak overtopping discharges for 1he 10-, 50-, 100-, and 500'.yl;ar stonns were obtained from a <br />meeting with J\1r, Gerald Shultz of the USBR (Re[(:rence 3). MI'. Shultz prepared the Boxelder <br />Creek hydraulic analysis and detennined the overtopping dischargos, The following table lists the <br />peak overtopping discharges determined by Mr, Shultz, for each of the stonn reCUlTence intervals <br />at each of the overtopping locations. <br /> <br />TABLE I <br />PEAK OVERTOPPI.i~G DISCHARGES INTO <br />THE COOPJ!<:R SLOFGH BASIN (cf~) <br /> <br />Location lO-'>T SO~L. lOO-vf SOO-vr <br />Larimer-Weld Canal* 57 258 258 258 <br />Vine Street 191 930 1450 2430 <br />South of Vine Street 18 68 104 158 <br />C&S Railroad" 47 74 94 132 <br />State Highway 14** 275 530 726 1136 <br /> <br />*The canal and railroad flows go through underpasses under 1-25. <br />.""The flow to the 1-25 median has :not been su.btracted from these values (See Table 2, and <br />Appendix A). <br /> <br />OVERTOPPING ANALYSIS AT STATE HIGHWAY 14 <br /> <br />At each of the locations listed abov(" except at State ,Highway 14, the USBR detennined the <br />amount offlow that goes down the 1-25 median and subtracted that amount from the total flow 10 <br />detennine the amount of flow that crosses OV\:r the southbound lanes into the Cooper Slough <br />basin. At State Highway 14, the USBR detemlined the peak ovmflow that leaves the Boxelder <br />