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Home My WebLink About20160012 Ver 1_More Info Received_20160209 Strickland, Bev From:Sean Martin <sean.martin@mcgillengineers.com> Sent:Tuesday, February 09, 2016 3:38 PM To:Price, Zan (George) Cc:lcarreiro@ashevillenc.gov; Leslie, Andrea J; William.A.Elliott@usace.army.mil; John Vilas; Mike Lewis Subject:Beetree Creek Bank Stabilization: DWR 2016-0012 - Buncombe County Attachments:DWR 2016-0012 Buncombe_Modification.pdf Zan, Please find attached our response to the request for an alternative stabilization method as originally proposed in the PCN application dated December 28, 2015. We are proposing a boulder toe design as a replacement to using gabion baskets. We appreciate the opportunity to work with you on an effective and appropriate design to mitigate the stream bank and slope erosion problem. Please contact me or John Vilas if you have any questions or concerns over the design. Sincerely, Sean Martin Environmental Specialist 468 New Market Blvd. Ste. B| Boone, NC 28607 Phone: 828.386.1920 | Fax: 828.386.1923 sean.martin@mcgillengineers.com | www.mcgillengineers.com 1 @McGill February 9, 2016 NCDEQ — Division of Water Resources Water Quality Regional Operations Section Asheville Regional Office 2090 US Hwy. 70 Swannanoa, NC 28778 Attn: Zan Price RE: City of Asheville Beetree Creek Bank Stabilization PCN Modification DWR 2016-0012 - Buncombe County Dear Mr. Price: The purpose of this letter is to inform you of a design change on the Beetree Creek Bank Stabilization project as a direct response to a request to revise the proposed stabilization method. Comments on January 29, 2016 regarding a concern for the long-term stability of the proposed gabion basket design initiated the change in project approach. The project will be using a boulder toe stabilization technique instead of gabion baskets. Please find enclosed a typical drawing for the boulder toe, as well as, a revised project Impact Map. We are confident the boulder toe design will meet the project's need for bank and slope stabilization, as well as, providing a natural and long-term solution to protecting the aquatic resource. Please contact me if you have any questions or comments at (828) 386-1920. Sincerely, McGill Associates, P.A. 9� Jo C. Vilas Program Services Manager- Environmental Enclosures: Cc. William Elliot - US Army Corps of Engineers Andrea Leslie—NC Wildlife Resources Commission Byron Hamstead — US Fish and wildlife Service Mike Lewis, PE — McGill Associates, P.A. McGill Associates, P.A. Project # 15.00109 Environmental a Planning 0 Finance McGillAssociates, P.A. • 468New Market Blvd. Ste. B. Boone, North Carolin a 28607 0/fice: (828) 386-1910 • Fax: (818) 386-1913 BEETREE CREEK JOB— 15.00109 BANK STABILIZATION D1EFEB20,6 DESICNEo BY CARD BY DESIGN REVIEW: BOULDER TOE CONNAREE IEw Plan ENM101615-9 PROTECTION DETAIL CONSTRUCTION NOTES 1. Excavate trench along toe of the stream bank to a depth slightly below the stream bed scour depth (see Dimension Table). 2. Install filter fabric along backside of trench; place fabric loosely and evenly on the prepared slope secured with staples 2' centers. Adjacent strips should overlap 12"; upslope filter fabric should overlap downslope fabric. 3. Boulders to be installed should be flat sided with size specifications according to designer (see Deimension Table). Install footer rocks to design embedment depth. 4. Coarse backfill placed behind footers. Make sure to fill voids between and behind boulders. 5. Install header boulders setback from footers and resting on coarse backfill. 6. Coarse backfill to be placed at a thickness equal to the height of the header rocks. 7. Soil backfill shall be placed above coarse backfill to transition between top of bank and boulder toe. Erosion control mat placed over soil backfill slope. MATERIAL SPECIFICATIONS 1. Boulders: Footer and header rocks must be large enough to achieve design height and resist movement during peak flow events. Boulders should be rectangular and uniform in shape and size with a typical dimension of 4'x3'x2'. 2. Filter fabric: 10-12 oz. non—woven geo—textile specific to aggregate separation. DIMENSIONS TABLE PLAN VIEW TOP OF SLOP EROSION CONTROL MAT BOULDER HEADER BOULDER HEADER 3—ft. BACKFILL STREA 2:1 SLOPE FLOW Toe Protection Height A EARTHEN 6—ft. BACKFILL NOR ALBASEFLOW DOTER TOE OULDER TOE PROTECTION WIDTH TOE OF BAN EMBEDMENT Not to Scale DEPTH BEETREE CREEK JOB— 15.00109 BANK STABILIZATION D1EFEB20,6 DESICNEo BY CARD BY DESIGN REVIEW: BOULDER TOE CONNAREE IEw Plan ENM101615-9 PROTECTION DETAIL CONSTRUCTION NOTES 1. Excavate trench along toe of the stream bank to a depth slightly below the stream bed scour depth (see Dimension Table). 2. Install filter fabric along backside of trench; place fabric loosely and evenly on the prepared slope secured with staples 2' centers. Adjacent strips should overlap 12"; upslope filter fabric should overlap downslope fabric. 3. Boulders to be installed should be flat sided with size specifications according to designer (see Deimension Table). Install footer rocks to design embedment depth. 4. Coarse backfill placed behind footers. Make sure to fill voids between and behind boulders. 5. Install header boulders setback from footers and resting on coarse backfill. 6. Coarse backfill to be placed at a thickness equal to the height of the header rocks. 7. Soil backfill shall be placed above coarse backfill to transition between top of bank and boulder toe. Erosion control mat placed over soil backfill slope. MATERIAL SPECIFICATIONS 1. Boulders: Footer and header rocks must be large enough to achieve design height and resist movement during peak flow events. Boulders should be rectangular and uniform in shape and size with a typical dimension of 4'x3'x2'. 2. Filter fabric: 10-12 oz. non—woven geo—textile specific to aggregate separation. DIMENSIONS TABLE CROSS-SECTION A -A' DESCRIPTION EROSION CONTROL MAT Boulder Length HEADER BOULDER EARTHEN 3—ft. BACKFILL 2—ft. 2:1 SLOPE 2—ft. Toe Protection Height 6—ft. FILTER FABRIC ------ ABRICNORMAL 6—ft. NOR ALBASEFLOW APPROX. STREAMBED TOE PROTECTION HEIGHT EMBEDMENT COARSE BACKFILL DEPTH TOE PROTECTION FOOTER BOULDER Not to Scale WIDTH BEETREE CREEK JOB— 15.00109 BANK STABILIZATION D1EFEB20,6 DESICNEo BY CARD BY DESIGN REVIEW: BOULDER TOE CONNAREE IEw Plan ENM101615-9 PROTECTION DETAIL CONSTRUCTION NOTES 1. Excavate trench along toe of the stream bank to a depth slightly below the stream bed scour depth (see Dimension Table). 2. Install filter fabric along backside of trench; place fabric loosely and evenly on the prepared slope secured with staples 2' centers. Adjacent strips should overlap 12"; upslope filter fabric should overlap downslope fabric. 3. Boulders to be installed should be flat sided with size specifications according to designer (see Deimension Table). Install footer rocks to design embedment depth. 4. Coarse backfill placed behind footers. Make sure to fill voids between and behind boulders. 5. Install header boulders setback from footers and resting on coarse backfill. 6. Coarse backfill to be placed at a thickness equal to the height of the header rocks. 7. Soil backfill shall be placed above coarse backfill to transition between top of bank and boulder toe. Erosion control mat placed over soil backfill slope. MATERIAL SPECIFICATIONS 1. Boulders: Footer and header rocks must be large enough to achieve design height and resist movement during peak flow events. Boulders should be rectangular and uniform in shape and size with a typical dimension of 4'x3'x2'. 2. Filter fabric: 10-12 oz. non—woven geo—textile specific to aggregate separation. DIMENSIONS TABLE DESCRIPTION DIMENSION Boulder Length — Boulder Width 3—ft. Boulder Thickness 2—ft. Embedment Depth 2—ft. Toe Protection Height 6—ft. Toe Protection Width 6—ft. 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