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Fort Morgan Farms,LLC <br /> Delta Reservoir—West Cell Preliminary and East Cell Conceptual Design <br /> April 16,2021 <br /> and shear stress created by the constricted flows through the spillway. No concrete is <br /> needed for the interior embankment of the outflow spillway for the West Cell since there is no <br /> backflow through the spillway due to existence of fuse plug that prevents any flow entering <br /> the reservoir. Since it was determined based on the 2D modeling that the East Cell will be <br /> filled with flows from the CLPR during the 1-PAC flooding before the SPR peak arrives, it is <br /> recommended to protect minimum 10 vertical feet below the crest of the interior slope of the <br /> East Cell spillway. <br /> The preliminary design would require Type VL riprap with a median grain size (D50) of 6 <br /> inches and a thickness of(2xD50) 1 foot on the revetment along the outer embankment and <br /> spillway crests of the storage cells. Type VL riprap would be underlain by 4 inches of granular <br /> bedding to act as a filter layer to satisfy the design criteria in the USDCM. The design plans <br /> for the bank protection are presented in Figure 1 and Figure 2 in Appendix 1. <br /> Opinion of Probable Cost Estimate <br /> Costs were calculated for embankment fill and bank erosion protection only. Other costs for <br /> additional improvements and any mobilization, utility coordination/relocation, contingencies, <br /> legal fees and construction management costs were not included in the cost estimate <br /> provided in the following table. Embankment fill volume along with riprap and bedding <br /> quantities were calculated using Autodesk Civil3D for the preliminary/conceptual design. <br /> OPINION OF PROBABLE COST ESTIMATE (AVERAGE INSTALLATION) <br /> ITEM QUANTITY UNITS I UNIT COST TOTAL COST <br /> West&East Cells <br /> Bedding CDOT Type ll 1278.6 CY $84 $107,400 <br /> 6-in D50 Riprap,Type VL 5192.0 CY $65 $337,480 <br /> Reinforced Concrete 9993.9 CY $100* $999,390 <br /> Embankment Fill 47117.7 CY $14 $659,650 <br /> SUBTOTAL FOR IMPROVEMENT COSTS: $2,103,920 <br /> Unit cost obtained from Fort Morgan Farms, LLC <br /> The improvement costs were estimated by multiplying cost item quantities with their <br /> corresponding average unit costs in the above table, which was developed using the unit cost <br /> data from UDFCD UD-MP Cost Version 2.2 and CDOT Cost Data Books with adjustments, if <br /> necessary, per the CDOT 2019 3rd Quarter Construction Cost Index of 1.45 compared to <br /> 2012 1 st Quarter unit costs. <br /> Conclusions <br /> In the proposed design analysis, one-dimensional, steady flow hydraulic models of the CLPR <br /> and SPR were developed for the pre-project/existing condition using the hydrologic and <br /> hydraulic data from the 2017 CHAMP Study and the 2019 Risk MAP Study as baselines. <br /> Proposed design was subsequently developed from the hydraulic model of the existing <br /> condition. The CHAMP and Risk MAP model geometries within the storage areas were <br /> revised for the pre- and post-project conditions while the remaining hydraulic, hydrologic and <br /> topographic information were conserved. The proposed design was evaluated to meet the <br /> "no-rise" requirement by the Weld County and FEMA NFIP for the regulatory floodway. <br /> FM F_TechMemo-20210416.docx <br /> Galloway&Company, Inc. Page 6 of 7 <br />