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HomeMy WebLinkAboutFDP201900006 Correspondence 2021-07-16Frank Pohl From: Montague, Michael C. <montaguemc@cdmsmith.com> Sent: Friday, July 16, 2021 4:19 PM To: Scott Collins Cc: Khambhammettu, Uday; Kaliakin, Ian; Frank Pohl Subject: Follow up to AD01 Submittal - 21-03-0459R Attachments: Annotated_FIRM_Ex.pdf,, Workmap_Ex.pdf CAUTION: This message originated outside the County of Albemarle email system. DO NOT CLICK on links or open attachments unless you are sure the content is safe. Hello Scott, Here is a list of comments that were not completely addressed by the submittal dated July 6, 2021, in response to our additional data request on April 7, 2021. We will be suspending the case based on not receiving community concurrence requested in Comment 1. 1 am able to give you an extension to complete the remaining comments listed below by Friday, July 23'. If the remaining comments are completely and fully addressed by Friday, July 23', 1 will be able to get a fee transfer approved. The case and fee would then be transferred to a new case number once community concurrence is received. This is assuming all other comments on the additional data letter are addressed. If the comments are not addressed by Friday, July 23'' I will not be able to get a fee transfer approved, and the fee submitted with this CLOMR will be forfeited, and must be paid again when the new case number is opened. I have updated our meeting time on Tuesday as requested, and we can discuss what is expected in order to transfer the fee in more detail then. Comment 4: For a bridge, the proposed plans must show the upstream and downstream, high and low cord elevations which can be verified in the hydraulic model. The width, length, and any dimensions between piers should also be shown. Bridge plans must be on a separate plan and cannot be shown on the work map. Comment 5: A duplicate effective model for the effective LOMR case No.: 20-03-1553P was not submitted. This would be a copy of the model approved in the effective LOMR that was received from the FEMA engineering library, with no changes at all. The pre -project and proposed conditions models did not use the effective model approved with the above referenced LOMR as a base. There are several effective cross sections and structures missing in the pre -project and proposed modeling. The effective model approved in the LOMR 20-03-1553P should be used as a base for the pre - project and proposed conditions models, with no changes made outside of the proposed changes for this CLOMR. This includes but is not limited to, starting boundary conditions, cross section geometry, Manning's "n" values, bank stations, structure geometry, expansion and contraction coefficients, etc.. Cross sections and structures should not be removed outside of the proposed revision area. Comment 6(a): The proposed and effective base flood elevations do not tie-in to each other within 0.5 feet at the upstream most cross section. The BFE at proposed Cross Section 8110 is 785.01 and the effective BFE is 786.36. If the effective model is not revised upstream of your project area, the tie-in will likely converge within 0.5 feet before Cross Section 8110, which is where the revised mapping should tie-in to the effective mapping. Comment 6(b) Cross Section 7555 does not have cross section end points above the 0.2-percent-annual-chance water surface elevations. Comment 6(d) The Manning's "n" values were revised at every cross section to be the same, which does not appear to be indicative of natural conditions throughout the entire model extents. These values should also not be changed outside of the revised area. Comment 6(g) I agree that the contraction and expansion coefficients should remain at 0.1 and 0.3, respectively, near the proposed bridge. The bridge is a significant amount above the floodplain and does not restrict the floodplain. The coefficients should not have been revised at any other effective structures. Comment 6(h) The floodway and multiple profile plans do not compute identical water surface elevations for the 1- percent-annual-chance profile. Comment 6(i) The floodway delineation is not reasonable due to the inappropriately placed ineffective flow areas. Comment 7(a/b) The boundary delineations of the effective base floodplain, 0.2-percent-annual-chance floodplain, and regulatory floodway are not shown the same as the FIRM panel 51003CO29D and the effective LOMR 20-03-1533P. An example work map is attached. Comment 7(d) There are no effective delineations, so there is no tie-in to the effective delineations. Comment 9 The annotated FIRM should show the effective delineations on the FIRM panel 51003CO29D including the revised delineations for the LOMR 20-03-1553P effective June 23, 2021. The proposed delineations should be shown through your revised area and how they tie into the effective delineations. An example annotated FIRM is attached. Additional Comments: I will not hold you to these comments for the submission by Friday, July 23rd, however they will need to be addressed before the CLOMR is issued. - An ineffective flow area is defined as the area of a cross section that will contain water that is not actively being conveyed. It is used to describe portions of a cross section where the water will pond, but the velocity in the downstream direction is close to 0. Ineffective flow was placed near the bank station of most cross sections throughout the entire proposed and existing conditions, and does not appear to meet the above criteria. Please revise the ineffective flow areas so that they are only placed at locations and elevations which meet the above criteria. These areas should be identical between the floodway and multiple profile plans. - Please ensure the floodway plan and encroachment stations are revised appropriately as a result of the comment above. Please ensure the encroachments are placed within the flood fringe, the area between the limit of the base floodplain and the bank stations. Please ensure ineffective flow is not within the encroachment stations, excluding ineffective flow at structures. Please ensure the resulting surcharges are between 0.0 and 1.0 feet. Please ensure the floodway is hydraulically smooth, and free of sudden expansion and contraction. - Please show topography under the entire area proposed floodplain delineations are shown, including each overbank, and the upstream and downstream limits of the revision area. Contour information must be shown under all revised delineations so that the delineation can be verified. Please ensure enough proposed and existing conditions contours are labeled to verify the delineations. Please do not show line work under the proposed topography which obstructs the proposed topography. Please ensure existing conditions topography does not overlap the proposed topography and obstruct contours. Thank you, Michael Montague, CFM CDM Smith, a member of Compass PTS JV Email: montasuemc@cdmsmith.com Phone: (303) 383-2306 CONFIDENTIALITY NOTICE: The transmission of personally identifiable information (PII) such as an individual's social security number, date and place of birth, and other information that is linked or linkable to the individual is strictly prohibited. Such information should not be included, whether embedded or in an attachment, in any communication sent to this email address. 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