Engineering Comments 11/16/17

Master Development Drainage Plan

  1. Resolved
  2. Provide all required checklist items (attached). The East Tributary flows (existing and future; reference new DBPS) and channel improvements need to be addressed. No channel design calculations or referenced flowrates for the East Tributary were received with the submittal. Provide complete preliminary design information, calculations and modeling for the improved condition. Note: the analysis and design of stormwater facilities must be on future development flow rates; therefore, FEMA flow rates shall not be used without written approval. Further comments will be provided when the information is provided with the next submittal. Unresolved; if the information in the Kiowa CLOMR/bridge/channel report will be used for this MDDP, that report needs to receive County approval and be included as an appendix of this MDDP referenced where appropriate in the MDDP and PDR.Partially resolved; include approved version of the Kiowa report when available.
  3. through 14 – Resolved
  1. See redlined report and plans for clarification of these comments and further minor comments. See updated redlines.Partially resolved; see updated redlines.
  2. Regarding the proposed ponds along the power line easement, completely address PDR comment #11. Per DCM Section 11.3.2: Discharges from emergency spillways shall be so directed that flows return to the downstream channel.Partially resolved; the calculations provided seem to show flow width resulting in less than 10 feet of drivable lanes on the ultimate Fontaine Blvd. cross-section. Provide the interim cross-section and address the same concerns. Address whether the eastern contributing area will need the road widened prior to development to provide the required capacity or the proposed initial grading and road section will result in conveyance meeting the depth and drivable lane requirements.
  3. Address, in general, maintenance access to bridges and the channel and show all conceptual maintenance access / recreation trails on the developed drainage plans.Unresolved; please add a statement to the effect that maintenance access will be provided to all channels and bridges in accordance with County criteria, exact locations to be addressed at the PDR/FDR stages.
  4. Regarding the discussion on potentially reimbursable facilities on page 3, the potential reimbursement for any of the facilities depends only on whether the facilities are included in the DBPS that would be adopted by the County (not the MTCP, which only reimburses for standard costs).
  5. The Emergency Overflow Conveyance section added contains flow values that do not match the Hydraflow model in the corresponding Appendix. Clarify which flows are pre-development. See redlines and revise as appropriate. If the flows are being split somehow, address how; also quantify the flows in both the eastbound and westbound lanes of Fontaine Blvd.
  6. Note: Cross-checking of values in calculations, on plans and report text was not completed to expedite sending these comments.