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HomeMy WebLinkAboutFDP202000008 Correspondence 2021-02-02608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com February 1, 2021 Benjamin Kaiser, PE, CFM LOMC Clearinghouse 3601 Eisenhower Avenue Suite 500 Alexandria, VA 22304 RE: Southwood — Case No. 21-03-0029P — Community: Unincorporated Areas of Albemarle County, Virginia — Community No. 510006 Comment Response Letter Dear Mr. Kaiser: We have reviewed all of your comments from December 31, 2020 and made the necessary revisions. Please find our responses to the comments below in bold lettering. 1. The submitted Form 1, entitled "Overview and Concurrence Form," did not include the signature of the community official from Albemarle County. Please submit a signed copy of Application/Certification Form 1, entitled "Overview and Concurrence Form," Section D. All forms and instructions are available for your information on the FEMA Web site at http://www.fema.gov/library/viewRecord.do?id=1493 . Response: Timmons has provided the revised report to Albemarle County for the community acknowledgement signature. 2. Our review of the submitted as -built plans for the modeled structure at Cross Section 3375.67 revealed that they are not certified by a registered Professional Engineer (PE), and do not reference a vertical datum. Please provide certified (sealed, signed, and dated) surveyed plans for the existing culvert and ensure that the vertical datum such as the North American Vertical Datum of 1988 (NAVD 88) is referenced on each plan. Please also include the high chord elevations on the plans. Additionally, our review revealed that the modeled span and width of the structure are 56.65 feet and 11.88 feet, respectively, while on the as -built plan these values are 55 feet and 12.5 feet, respectively. Please ensure that the modeled dimensions of the structure are consistent with the values shown on the as-builts. Response: The labels of the culvert dimensions were listed as approximate as the dimensions vary slightly from one end to the other. Additional dimensions have been added to the as - built plan and the model has been updated to match these added dimensions. Additionally, the high cord elevations of the top of wall for the crossing have been added to the as -built plan along with the vertical datum of NAVD 88. Lastly, the as -built has been sealed by a PE with the resubmission. ENGINEERING I DESIGN I TECHNOLOGY 3. Our review revealed that the encroached (floodway) profile is included with the multiple profile plan. Please create two separate plans; the multiple profile plan and the floodway plan. The floodway plan should only include the encroached (floodway) and unencroached (natural) base flood profiles. The unencroached profile for the existing conditions floodway plan should be exactly the same as the base flood profile in the existing conditions multiple profile plan. Response: Two separate plans have been provided with this resubmission to separate the floodway and base flood profile from the multiple profile plan as requested. The geometry file between the two plans are identical with the only difference being the profiles included in the flow files. 4. Our review revealed that the downstream section of the revision area is impacted by backwater effects from Biscuit Run. On the submitted topographic work map entitled "Unnamed Tributary to Biscuit Run Floodplain Work map Exhibit", prepared by Timmons Group and dated September 23, 2020, please use the backwater elevations of the 1- percent-annual-chance (base) and 0.2-percent-annual-chance floods from Biscuit Run and delineate these elevations upstream along the Unnamed Tributary to Biscuit Run until the backwater elevation intersects the modeled water surface elevation. Response: Reach boundary conditions have been updated to the know water surface elevations for each profile taken from profile 02P in the Albemarle County FIS. The impact of this tail water condition dissipates by cross section 656.54. The inundation boundaries of the 100yr and 500 yr events have been updated on the work maps. 5. Please provide an updated certified work map and updated annotated FIRM to reflect the changes requested above. Response: Work maps have been updated for changes from the above comments. 6. To assist our review and to expedite processing of this request, please provide digital Geographic Information System (GIS) or Computer -Aided Design (CAD) data that reflect the topographic work map. Please ensure the digital data are spatially referenced and cite what projection (coordinate system, example: Universal Transverse Mercator (UTM)/State Plan) was used, so that the data may be used for accurate mapping. The important data to show on the digital work map are the contour information, the stream centerline, the cross-section lines, the road crossing and hydraulic structures, the revised flood hazard delineations and the tie-in locations. Everything should be clearly labeled, and all information should be contained within the drawing and not externally referenced. Response: Digital files have been provided with this resubmission. 7. Please submit a copy of the newspaper notice distributed by Albemarle County stating its intent to revise the flood hazard information (i.e., revise or establish 1-percent- annual-chance flood elevations, the base flood floodplain and regulatory floodway) along the Unnamed Tributary to Biscuit Run. Alternatively, please submit documentation that individual legal notices were sent to all the property owners affected by any changes in the flood hazard information. Documentation of legal notice may take the form of a signed copy of the letter sent and either a mailing list or certified mailing receipts. Individual notices are not sent on community letterhead must also include certification from the community that all affected property owners have been notified of the floodway revision. The newspaper notice or the individual legal notices must include the extent of revision and contact information for any interested parties and must also mention the community's intent to revise the regulatory floodway. Please submit a draft copy of the notification for verification of content, prior to publication or distribution. One of the attached templates may be used to prepare the draft notification. Response: Timmons is working with Albemarle County on their preference of handling the notices. We have included PDF copies of the plans and calculations for your review. If you have any questions or comments, please feel free to give me a call at 434.295.5624 or email bryan.cichocki@timmons.com . Sincerely, Bryan Cichocki, PE Project Manager