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Home My WebLink About20200546 Ver 1_Cover Letter_Final_2020.04.22_20200423fto WithersRavenel .. our People. Your Success. 04/22/2020 US Army Corps of Engineers Regulatory Field Office Ms. Amanda Jones 151 Patton Avenue Room 208 Asheville, North Carolina 28801 NC -Division of Water Resources 401 & Buffer Permitting Unit Mr. Paul Wojoski 1617 Mail Service Center Raleigh, North Carolina 27699 Re: Kenilworth Road - Culvert Replacement Asheville, Buncombe County, North Carolina NWP 3 PCN Submittal WR Project #08181125.00 Dear Ms. Jones and Mr. Wojoski, On behalf of the City of Asheville, we are requesting authorization from the USACE to use NWP 3 for 87 If of permanent stream impacts and 11 If of temporary stream impacts for the replacement of the existing culvert within Kenilworth Road. We are also requesting a 401 WQC from NCDWR for the above referenced impacts. The project is ±0.14 acres in size and is located at the intersection of Kenilworth Road and Rosefield Drive in Asheville, NC (Lat: 35.585263; Long:-82.536742). The project is located in the French Broad River basin and onsite waters drain to Ross Creek (Lake Kenilworth). The Water Quality Classification for Ross Creek (Lake Kenilworth) is B and the Stream Index Number is: 6- 78-23. The cataloging unit for the site is 06010105. Proposed Project The purpose of the proposed project is to replace the failing existing structure to alleviate flooding issues upstream. One of the existing 86-foot long 24" corrugated metal pipe culverts has collapsed, filled in with sediment. The stream has eroded under the culverts, and now actually flows below the culverts, rather than through them. The erosion by the stream has caused the second culvert to shift down as shown in the attached Culvert Installation Profile Detail in the Impact Maps and Photo Documentation. Since the stream flows beneath the culverts instead of through the culverts, the erosion and flooding has caused the existing concrete/stone headwall and endwall to collapse, and has compromised the structural integrity of the road itself. The proposed project consists of removal of the existing two 86-foot long 24" corrugated metal pipe (CMP) culverts and concrete/stone headwall and endwall. The existing culverts will be replaced with a 110-ft long 42" HDPE culvert and the concrete/stone headwall and endwall will be replaced with pre -cast concrete headwalls. The proposed 42" culvert will be installed a minimum of 9" below the existing stream bed, as noted in the Culvert Installation Profile Detail in the attached Impact Exhibits. The culvert is located within the extreme upper reach of Stream 1, which has intermittent flow. In order to allow for work "in the dry" the construction will occur during a window with no forecasted rainfall. If necessary during construction, flow will be diverted by constructing temporary coffer 219 Station Road I Suite 1011 Wilmington, NC 28405 t: 910.256.9277 www.withersravenel.com I License No. C-0832 Asheville I Cary Greensboro I Pittsboro I Raleigh I Wilmington Kenilworth Road - Culvert Replacement - NWP 3 PCN 4: WitherSRavenel Our People. Your Success. dams on the upstream and downstream ends of the pipe, and flow will be pumped around the construction area, and discharged through filter bag to remove sediment and prevent turbidity issues in downstream waters. Traditional open trench techniques and equipment will be used for the proposed project. It is anticipated that the overlying soil materials are backfill from the original installation, and will not include any rock excavation requiring percussive equipment to reach grade of the existing pipes. If removal of rock is required to install the culvert at the designed inverts, it will be completed using a pneumatic jackhammer. The proposed project primarily takes place within the existing ROW of Kenilworth Road. The limits of disturbance encroach into four adjacent privately owned parcels (PINs: 9648867771; 9648864658; 9648863651; 9648865743). The City of Asheville has obtained easements within all four parcels in order to complete the proposed culvert replacement. Project History Site reviews conducted by WR staff determined that there are no wetlands within the project area. The only jurisdictional feature is an intermittent stream (Stream 1). Please note that we are not requesting issuance of a Jurisdictional Determination, as the project consists of maintenance of an existing structure. Proposed Impacts The proposed impacts consist of 87 If of permanent stream impacts and 11 If of temporary stream impacts for replacement of the existing culvert. Due to the sinuosity of Stream 1, the alignment of the proposed culvert has been shifted slightly from the existing alignment, and the overall culvert length increased in order to provide more direct flow through the culvert to prevent erosion and undercutting of the headwall resulting from the stream flowing into the culvert at a sharp angle. A channel will be constructed on the upstream end of the culvert to convey flow directly into the culvert. The constructed channel will be constructed to mimic the width and depth of the natural channel. Impact #1 will occur from the installation of the proposed 42" HDPE culvert, the precast headwall and relocation of Stream 1 resulting in 35 If of permanent stream impacts. Impact #2 will occur from construction activities associated with the constructed channel, resulting in 6 If of temporary stream impacts. Impact #3 will occur from the installation of the prosed 42" HDPE culvert and precast endwall and riprap dissipator pad resulting in 52 If of permanent stream impacts. Impact #4 will occur from construction activities during installation of the riprap dissipator pad resulting in 5 If of temporary stream impacts. The rip -rap dissipator will be installed so that the rip -rap is embedded such that the top of the rip -rap matches the contours of the existing stream bed and banks in order to allow for aquatic life passage. Avoidance and Minimization The project consists of replacement of an existing culvert, and therefore impacts to streams could not be avoided. Page 2 of 4 Kenilworth Road - Culvert Replacement - NWP 3 PCN r: WithersRavenel Our People. Your Success. One culvert has collapsed/filled with sediment and the other culvert is undersized to handle the flow during storm events, which has resulted in flooding issues upstream. Conventional culvert cleaning or repair will not correct the erosion and flooding issues and culvert replacement is required. Permanent upstream impacts could not be avoided due to the sinuosity of Stream 1. In order to prevent erosion and failure of the proposed headwall, the culvert must be lengthened and realigned, with a new channel constructed in order to provide a more direct flow into the culvert. Permanent stream impacts have been minimized to the greatest extent practicable in order to construct a structurally sound culverted road crossing that will alleviate the flooding issues and require minimal maintenance in the future. The proposed riprap downstream of the culvert is required to reduce flow exiting the culvert to non -erosive rates. Additionally, the rip -rap dissipaters will be installed by burying the riprap such that the top of the riprap matches the pre -construction grades of the natural stream bed, allowing for the passage of aquatic life. The culvert is located within the extreme upper reach of Stream 1, which has intermittent flow. In order to allow for work "in the dry" the construction will occur during a window with no forecasted rainfall. If necessary during construction, flow will be diverted by constructing temporary coffer dams on the upstream and downstream ends of the pipe, and flow will be pumped around the construction area, and discharged through filter bag to remove sediment and prevent turbidity issues in downstream waters. Construction techniques used to avoid or minimize the proposed impacts include the installation of erosion and sedimentation control devices prior to construction. Additionally, access during construction will be from high ground. Mitigation The proposed permanent stream impacts are less than 150 If, and therefore the applicant does not propose mitigation. The current request is for 87 If of permanent stream impacts and 11 If of temporary stream impacts (see the attached maps and PCN for details). Please feel free to call if you have questions or require additional information. Sincerely, withersRavenel Troy Beasley Senior Environmental Scientist Page 3 of 4 Kenilworth Road - Culvert Replacement - NWP 3 PCN Attachments: • PCN Form • Agent Authorization • Aerial Exhibit • Wetland Delineation Exhibit • USGS Quad Exhibits • Buncombe County Soil Survey Exhibit • NCNHP Project Review Letter • Photo Documentation • Impact Exhibits r: WithersRavenel Our People. Your Success. Page 4 of 4