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HomeMy WebLinkAboutRIVER DISTRICT BLOCK ONE MIXED-USE (ENCOMPASS) - PDP - PDP120020 - CORRESPONDENCE - DRAINAGE REPORT (5)Marsha Hilmes-Robinson, CFM Floodplain Administrator City of Fort Collins Utilities P.O. Box 580 700 Wood Street Fort Collins. CO 80522-0580 Phone: (970) 224-6036 E-Mail: mhilmesrobinson(cDfatov.com Comments are also provided on the\ accompanying construction plans " River District Block One Mixed Use Bank Stabilization", December 2012. • Sheet 3 of 9 — o Label floodplain lines, Include 500-year floodplain boundary, include floodway boundary. o Show limits of existing bridge and outfall riprap. o Differentiate between limits of new and existing riprap. • Sheet 4 of 9 — o Show and label the 100-year FEMA floodway. o Revise the labeling for the floodplain line. This should be "Proposed 100-year floodplain and floodway boundary" not "WSEL". o New riprap rundown for water quality outlet to be buried. o Try to minimize or completely bury all exposed riprap for the project. o Add more detail/explanation regarding the incorporation of the existing bridge and Linden Street Outfall riprap into the project. It is unclear as to what riprap treatment practices are proposed in this area. o Also, bury the bridge riprap using the same bank treatment as that shown on the southern end of the project. o Differentiate between the new and existing riprap areas and the treatment of each area. o Show limits of existing riprap. o Bury riprap at water quality and Linden Street Outfall rundowns. o Note 4 - A single Floodplain Permit can be obtained for all of the work shown on the plans. Separate permits are not required. o Add Note 8 — Developer acknowledges risk associated with bank protections not extending along the entire length of the development. Areas of landscaping, parking, trails, etc. may be subject to erosion o Add Note 9 - to the plans regarding the tolerances of the proposed grading. Project grades shall be built to the elevations shown on the construction plans and in the project CLOMR. Also note that any deviation from the design grades that causes a rise in 100-year water surface elevations different than those shown in the CLOMR shall be corrected by the Developer. (You may wish to confer with Northern Engineering to see if there are any allowable vertical tolerances that will not cause a rise in water surface elevations). o Add Note 10—A LOMR is required to be submitted and approved by FEMA. • Sheet 8 of 9 — Pleas address how the willow cuttings will be inserted into the soil riprap. — as shown on sections such as Sta 11+25 and Detail 7/9 on Sheet 9 of 9 • Sheet 9 of 9 — Specify riprap color • Sheet 9 of 9 — add toe wall detail for storm water outfall pipe FESt Thank you again for your work on this project. If you would like the redline plans and report, please call one of us to arrange for pick-up. If you have any questions or would like to go over these comments, please feel free to give us a call and we would be happy to discuss these issues. Sincerely, Mark Kempton and Marsha Hilmes-Robinson Mark Kempton, P.E., CFM Stormwater Master Planning Manager City of Fort Collins Utilities P.O. Box 580, 700 Wood Street Fort Collins, CO 80522-0580 0: (970) 416-2233 -- C: (970) 682-4988 E-Mail: rnkempton@fcgov.com www.fcgov.com/stormwater 2 Ted Shepard From: Marsha Hilmes-Robinson Sent: Wednesday, January 16, 2013 9:58 AM To: Bill Schenderlein (bill@flywater.com); Randall Provencio; Aaron Cvar; Rich Shannon Cc: Ted Shepard; Lindsay Ex; Mark Kempton Subject: FW: Mark Kempton and Marsha Hilmes-Robinson Comments on Block One Stability Evaluation and Design Report and Construction Plans Bill, Randall, Aaron, and Rich, Thanks for your submittal for the Block 1 Development. The design you proposed will result in a much improved condition by reducing the risk to the future development. We appreciate your efforts in making this project a success and a showcase for bank stabilization in Fort Collins . The following are review comments for the report "Cache la Poudre River Bank Stability Evaluation and Design Report", Prepared by Flywater, Inc., December 2012 and the Bank Stabilization Plans. Although there are numerous comments, these are all considered tome minor in nature or clean-up documentation. We do not see any substantial items and we feel that Stormwater staff can recommend the project moving forward toward hearing. Comments on the CLOMR will come in a separate email. • Page 1—Add North arrow to Vicinity Map • Page 2- Section 3.0 — Please add text pertaining to the City's concerns regarding the stability of the bank during and after the construction of the proposed building • Page 2- Section 4.0 —A CLOMR is required before the preparation of the as -built based LOMR. Please revise the text to reflect the required CLOMR as well as the LOMR. Also, please reference the project CLOMR prepared by Northern Engineering. • Page 7 — 2"d paragraph — please include the explanation of the flows used in the bank analysis from the CLOMR in this paragraph. The CLOMR discharges are more detailed than those shown 2003 Ayres report. Also, please ensure that the discharges used in the bank revetment design align with those shown in the CLOMR. • Page 8 —Section 6.4 —Add a paragraph explaining the treatment and incorporation of the existing bridge riprap. Also, bury the bridge riprap using the same bank treatment as that shown on the southern end of the project. • Page 8 —Section 6.4— self launching riprap is included as a bank treatment. Please clarify if this is part of the proposed design. Self launching riprap was not indicated on the construction plans. • Page 8 —Section 6.4— please address the color of the riprap. Per the City's Stormwater Criteria Manual non- native riprap is not allowed within the City. • Page 10— Section 6.6 VRSS — Can the stability of the VRSS be analyzed using a specific return period flow event? All of the stability calculations pertain to the buried riprap. Can the stability of the fully vegetated VRSS and the MSE walls be quantified? Also, address the irrigation requirements, both temporary and permanent for the VRSS and vegetated bank areas. • Page 11— Section 6.7 — "Drainage see EEC section". Please explain this section or revise as necessary. • Page 11— Section 6.9 - Address the irrigation requirements, both temporary and permanent for the VRSS and vegetated bank areas. • Page 11—Section 6.10 — Please specify who is responsible for obtaining and maintaining the listed permits. Also address the necessary construction and permanent drainage easements. • Page 12 —Section 6.11— Discuss the timing and sequence of events involved in the bank construction and activities within the river. • Page 12 — Section 6.11— Discuss needing to stage and keep materials out of the 100-year floodplain and floodway during construction. • Page 13 — Section 7.0 — Include reference to the project CLOMR by Northern Engineering.