2019-05-23_REVISION - M1987049 - Laserfiche WebLink

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No-Rise/No-Impact Certification September 11, 2018 <tjC Page 4 of 6 Effective Cross- EFFECTIVE EXISTING EX.vs. Section ID EFF. (Letter) BFE BFE BFE FHAD-XS-17.7 4994.71 4990.08 -4.63 FHAD-XS-17 4988.80 4988.80 0.00 FHAD-XS-16 4984.50 4983.40 -1.10 FHAD-XS-15 4982.40 4982.57 0.17 FHAD-XS-14 4981.98 4981.98 0.00 Table 2 compares the results of the duplicate model to the Duplicate Effective Model report. Exhibit C contains the cross sections generated for the Existing Conditions Model. The results indicate the base flood elevations and the regulatory floodway elevations for the effective hydraulic model revised to incorporate existing conditions at the proposed CRFT between E-470 and Ken Mitchell Park/Open Space. 4. Proposed Conditions Model The Existing Conditions Model was modified to reflect the proposed 10' wide concrete trail adjacent to the South Platte River between E-470 and Ken Mitchell Park/Open Space. The new cross sections were used while retaining the currently adopted regulatory floodplaih widths. The overbank roughness parameters used are the same as the Currently Effective Model. A comparison of the results indicates that the floodway elevations between the Existing Conditions Model and the Proposed Conditions Model are substantially the same. Deviation between the two model results are insignificant as outlined below: Effective Cross- EXISTING PROPOSED EX.vs. Section ID EFF. (Letter) BFE BFE BFE FHAD-XS-17.7 4990.08 4990.08 0.00 FHAD-XS-17 4988.80 4988.80 0.00 FHAD-XS-16 4983.40 4983.37 -0.03 FHAD-XS-15 4982.57 4982.57 0.00 FHAD-XS-14 4981.98 4981.98 0.00 A comparison of the Proposed Conditions Model results against the Existing Conditions Model is denoted in table 2. Exhibit D contains the cross sections generated for the Proposed Conditions Model.