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Home My WebLink About20140041 Ver 1_Concept Plan_LPC III_94903_ Repair Phase 3_20210810 Conceptual Plan Little Pine Creek III Repair Alleghany County, North Carolina DMS Project ID 94903 USACE ACTION ID: SAW 2012-01299 DWR # 14-0041 Prepared by ECOSYSTEM PLANNING & EPR RESTORATION Ecosystem Planning & Restoration 204 Stone Ridge Boulevard Asheville, NC 28804 Prepared for NCDEQ Division of Mitigation Services 217 West Jones St., Suite 3000A Raleigh, N.C. 27603 (919)707-8976 August 9, 2021 PROJECT DESCRIPTION The North Carolina Division of Mitigation Services (DMS) has requested that Ecosystem Planning and Restoration (EPR)provide site evaluation, design, construction administration and oversight services for repairs at the Little Pine Creek III Mitigation Project in the New River Basin,in Alleghany County,NC. The repairs will occur on UT1,UT2, UT2A,UT2B, and Little Pine Creek. SITE ASSESSMENT EPR conducted an initial site assessment to investigate each repair area. This assessment included visual inspections, measurements,and photo documentation at each repair location. These assessments also included investigations into the likely causes of the instability on each reach and potential solutions. From these assessments,EPR has developed an adaptive management plan that provides a general description of the repair site,potential causes of the instability, and provides a conceptual approach for the proposed repairs. UT1 REPAIR AREA DMS Location#5: Existing conditions The UT1 Repair Area consists of a section of UT1 where a headcut has formed and active downcutting is occurring. This headcut has developed upstream of previous headcut repairs. The cause of this headcut is likely due to lack of grade control designed into the original restoration plans and not addressing during previous repairs. Unless stabilization activities occur,the headcut is likely to continue migrating upstream. Proposed approach EPR proposes to stabilize this headcut a by using instream structures to provide adequate grade control. Structures will be placed in a way that dissipates energy during storm events and provides grade control.The vertical banks that currently exist due to the migrating headcut and any other disturbed or unstable areas adjacent to the existing headcut will be graded to 3:1 slopes or flatter and seeded,mulched,matted,and live staked. Concept Plan Little Pine Creek III Stream Repair(DMS#94903) . ,. ... 1 - --wmuimpllIllr!'mw". .. ,. .r.,.,... ..1•.. ., .... ..,.. -Tre..4.-. .. .,..t.-7,..p; -- , • 1 , . . , , ' . , ... ir.414- . `1,`. , iiiiale, . ,_ ling it 1Vt. '1" ' , .'" - • ,-..",-, 1 ,. r . I-ingrAreri", ..•"'..r .( ', . -4. ..,..7 . „it . . ,. ,.. .., • I. , .1'.'•" 1 ,1,,,,,,,;., ...4.44. 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'' _, ---- -741 ',*.).'--, '.',. ..• 'I.,''Iv 0 i':t.V ,„.,..,...... , ..01:7. -----r ' , \. , ,• ..-.:.,' /1 ,i,-,1 4.:yhx,,,,,,,,), 401,,,,.„2,z7••• •••,',..1.-:•,1; , •!..t-''$ f.....,,::.,......061 ''',,, •,,, ' .•''' .T./.4 .-.- i, A-- . _......••--: 11‘ . t k<1.'' '7,"' ti..4,', - ..-;. 1 • A , - -. -/Na 1 . '.'../" ,Jr' ,...,,a,'4,,0 1.,11 ir. ,1.- . - . .. , ,..- ." 1 ,. .11v d i'y,•f.,,,,-;:,: , . .'. . "-'..,r••I,' . • - . .....L • / ' . ;II,, e. dr.. '. e ..i .1, -.. UT 1 Repair Area Little Pine Creek III Stream Repair(DMS#94903) Concept Plan UT2 Repair Area DMS Location#1 and Location #3 Existing conditions This repair area consists of existing culverts at stream crossings at locations #1 and #3. Both culverts appear to be undersized and are frequently inundated with sediment. The crossings have also been overtopped on several occasions. Proposed approach Based on hydraulic analysis of the culverts, both culverts are undersized for the 25-year storm. Replacement of the 30-inch culverts with 48-inch culverts will convey the 25-year discharge without overtopping the road. EPR will work with DMS to determine if installing a larger culvert or replacing the culvert crossing with a ford crossing is the best course of action. Bed and bank stabilization upstream and downstream of both crossings will be incorporated as needed and include grade control structures to step down the channel if required. Cross fencing will be repaired. Upstream of location #1 at approximate station 310+10 the streambed will be stabilized using in-stream structures and the banks will be graded,matted, seeded,mulched,and live staked. \!� ,,) 6° 1 1,\ �" .,;,„,41)1, ;. . , \ _ M , /4 ' . ..1.:., 1;:-...)<,":„-_. .L ' t Q 1 e -0 14 -4 - 01 °01 "ZIE.i .,, , A. 1 vs ilk , , s-. 1 7 Culvert at Location#3 Little Pine Creek III Stream Repair(DMS#94903) Concept Plan DMS Location#4 and Approximate Station 328+10 Existing conditions These repair areas consist of bed and bank instability. Banks are eroding and several existing grade control structures are piping. Proposed approach EPR proposes to stabilize the bed instability by repairing or replacing the existing grade control structures. Structures will be repaired by excavating upstream and installing new filter fabric and bankfull to prevent piping or by re- building structures utilizing existing materials as much as possible. Banks will be graded to slopes of 3:1 or flatter, seeded,mulched,matted and live staked. Y • ok '- .. - -' - - , x f i ,- ?s , -/ 'Iv ''....:!•'.' 1,- - - - '# '' ,,_:'.4 7 11,::..-.,if , #(4-- is& liCcir 7u0aAi _.-:'' --I --;-6,.'4'-,7,:., 1,'—;',.1..',".,...\..:„..'/,,_o.....4 o,. f �- r 1 ► k 'y. _,.,_ f...N. : ,'. '> .0 1 ` - / I ' , ,( — - e 1 Piping structure and bank instability Little Pine Creek III Stream Repair(DMS#94903) Concept Plan UT2A Repair Area: DMS Location#7 Existing conditions Bank scour is occurring below UT2A culvert. Proposed approach EPR proposes to stabilize stream banks utilizing bank grading,bio-engineering and potentially an in-stream structure to help protect the stream bank. ! - � • �''- 1(f , 'dray :� 7J"._ - ,. ,. - i , i , 0 M r( " of 1 ,Y r t, j L • - 4 .a a' P 1 i 1f ,,g, '__ , , _. _..,,„), , ;.--:\ . / - : 4,., .:1, . , .' , ,,,f 4.0..•--...- ' -, ' ' fl \ � �� F �,i� �,/ Bank erosion along UT2A Little Pine Creek III Stream Repair(DMS#94903) Concept Plan UT2B Repair Area: DMS Location#2 Existing conditions Headcut in early stages of development is observed at location#2. Due to proximity to the repair work at location#1 this minor headcut will be stabilized while other repair work is being performed. Proposed approach EPR proposes to install a grade control structure such as a step or constructed riffle that will repair the head cut and prevent future degradation. Stream banks will be graded, seeded,mulched,matted and live staked. Little Pine Creek Repair Area: DMS Locations#9 and#11 Existing conditions Locations#9 and#11 along Little Pine Creek are exhibiting bank slumping. Slumping is likely due to existing seeps and overland flow along with the lack of deep-rooted woody vegetation along banks. Proposed approach EPR proposes that areas suffering from bank erosion/slumping will be repaired and stabilized by a combination of grading and bioengineering with any seeps or overland flow being addressed with a stabilized outlet structure. k ,/� � �i /ems. q� ,..,, te , , M'1 F ` E . .,, � k � at , - . .), I' ar7. 1 " o--, y , a F +"jiff ,,�I -, . �I Y i, t 4:A.4..., ..-_,.. ., - .. , .,,,,.- ---•.,*, i , ,,,t-4- — li.--. .'s-- I 1 '7' _ Little Pine Creek III Stream Repair(DMS#94903) Concept Plan Bank slumping along Little Pine Creek Little Pine Creek Repair Area: DMS Locations#10 Existing conditions Bank erosion near the log step at approximate station 124+50 is occurring. This is likely due to the structure being placed perpendicular to the flow. Other areas adjacent to log steps in the lower section of Little Pine Creek are also exhibiting this problem. Proposed approach These banks will be repaired and stabilized utilizing a combination of large stone and bioengineering. Geolifts utilizing live cuttings with a stone toe will be constructed in combination with the placement of some larger stone where needed. 0 . yam.'. •� 0 -;''''.0..„.' ,'',:'.....?,)1,,ii: 4:,,,,,,, .—..,.. ,..,;t!., .1, . -,,,. .,r,4,,,,,,, iiir rr ,; ,',,p,- - _. 4s , M P * 3`c :ICt : +9 R'�D. s' k1. &3,,r 'f Y�c 7f ", ;3n a t e � o- 5h 15 e,'it '�div,-�t r/ , ir311d ,- tea' = t a z x,�; li a i i -� p x,,,, is. l -� - -,l - fir �y� ,L -y*: '1 v '0 :m et C �� ,- ,, kt •r Little Pine Creek III Stream Repair(DMS#94903) Concept Plan Bank erosion below log step structure on Little Pine Creek Little Pine Creek Repair Area: DMS Locations#12 Existing conditions Bank erosion near the log step is occurring. This is due to the structure being placed perpendicular to the flow and from consistent flow coming from an adjacent wetland seep. Proposed approach This seep will be stabilized utilizing boulder step structures. This will also provide bank protection and prevent further bank erosion caused by this structure in this location. `: N - .,, -, _, \ ki , - '', idF - • -.� \ _,� r -I. TAN c.L -;. ' .`-,..'.---, ',.r- '-'•\ --4' -..f-- --;-----'- ---..'--_,z,-.7. 4", . •-„z; N E, ' .�' \\I\ ) �\ '�$r,lkr# L '�[1 T +-.... )V 4,'s/ .ems"`, t":i 4 1 L.,', i,/41.,.-v,.,--.."' `t /.../tbr ""-, - a .. -' I.- -"-er,..- ,_ :.,-,,- - _- vol--- , -., , ,...„,.. „„:„.„,, f A fd ...hr. 4 1- + :"., , • ' '# - f --' 1 4 ,- �- s: -/ I! .• - y",� d3" " Ste. V. a4 .', ,ice VL i._F. . a$" I I - , Al yi ft IP o, L Af. t ' , ' ' \ 6 Bank erosion at log step on Little Pine Creek Little Pine Creek III Stream Repair(DMS#94903) Concept Plan Little Pine Creek Repair Area: DMS Locations#13 Existing conditions Existing streambanks from approximate station 131+00 down to the bridge are exhibiting significant bank erosion. Poor woody vegetation growth was noted along this section. It was also noted that this section did not have very good floodplain access which likely is increasing bank shear stresses during flood events. Proposed approach A combination of bank grading and bioengineering will be utilized to stabilize these streambanks. Live stakes will be replanted along both banks in areas that do not receive any additional bioengineering such as soil lifts. Mak . ;-,-- Grp ollii• 40141P .-‘•:„.:.t2ti r �� f j - r_._ 5 re - , iise.:;.. , , g \ ' ` N a+ - :rn:,a ' _ _ 1`l fI . _ - _ - .- y 1 1 t��'t a5^ K ,, 7 1 r w� �, E ; J • k 1,, , Little Pine Creek Repair Area: Bank erosion near station 131+00(Location#13) Little Pine Creek III Stream Repair(DMS#94903) Concept Plan Little Pine Creek Repair Area: Boulder J-Hook Structure at Approximate Station 120+50 Existing conditions This structure is beginning to fail. The structure is piping,boulders have shifted,and flow is beginning to cut around the structure. Proposed approach EPR proposes to re-build the hook of this structure utilizing the existing boulders,new filter fabric and stone backfill and additional boulders for a longer sill. This will prevent futurecutting around of this structure. � � - , ti,'' y 9,a --%' >-* 7`Q'� 1: ''1 � ; '''_. .. tar 4' , 4. _ �• �° i+. pia g,! —��\ !4i y` ,, ,- i. A \ } • Y w t _ - .,., %t 7 5 i- ,4 ‘,,, r b k i ,7 :1 Ik , .., ,fi r.'t-i . '�f ice✓ iftigii Failing J-hook structure along Little Pine Creek Little Pine Creek III Stream Repair(DMS#94903) Concept Plan Little Pine Creek Repair Area: Planting and General Repairs Existing conditions Supplemental planting along previous repair haul road is required. This is along Phase 2,Area C. Proposed approach EPR proposes to plant 1 gallon tree species in this area. Existing conditions "Lunker logs"presumably installed originally for habitat improvements are causing stability issues in several areas. Proposed approach These logs will be removed where issues are occurring. Any disturbed areas will be stabilized using seeding, mulching,matting and live staking. Existing conditions Fencing near the farm crossing at station 107+00 has been damaged by storms. Proposed approach EPR proposes to repair this fencing. Site Wide Notes: All areas including access paths, staging areas, etc. that have been disturbed from construction/repair activities will be repaired and stabilized using seeding and mulching. Any disturbed areas outside the conservation easement will utilize tall fescue seed and areas inside the conservation easement will utilize a native riparian seed mix. All disturbed streambanks will be seeded,mulched,matted, and live staked unless another bioengineered approach is used such as soil lifts with live cuttings.