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HomeMy WebLinkAbout19970330 Ver 1_Mitigation Plans_20010712 (2) DETAILED WETLAND MITIGATION PLAN '1:cc ` OFF[ RANDLEMAN RESERVOIR WATER SUPPLY JUL 12 2001 f EDGAR BRANCH MITIGATION SITE RANDOLPH COUNTY, NORTH CAROLINA x, I' Prepared for: PIEDMONT TRIAD REGIONAL WATER AUTHORITY I' P d b repare y: I' EcoScience EcoScience Corporation 1101 Haynes Street, Suite 101 Raleigh, North Carolina 27604 July 2001 I' a TABLE OF CONTENTS Paqe LIST OF FIGURES ................................................. iii LIST OF TABLES .................................................. iv ° 1.0 INTRODUCTION ................................ 1 1.1 ............... PURPOSE ........................ 1 1.2 OBJECTIVES OF WETLAND RESTORATION . . . . . . . . . . . . . . . 1 1.3 . . . . . . . PRIMARY METHODS FOR WETLAND RESTORATIO N ............... 3 ® 1.4 MITIGATION SITE SELECTION ................................ 4 2.0 METHODS .................. ............................... .8 ' 3.0 EXIS TING CONDITIONS ...................... 11 .................. 3.1 PHYSIOGRAPHY, TOPOGRAPHY, AND LAND USE ................ 11 ' 3.2 SOILS ................................... 14 3.3 ............. PLANT COMMUNITIES .................................... 17 3.4 HYDROLOGY ... 20 ' 3.5 WATER QUALITY ........... 2 ............................ 2 3.6 JURISDICTIONAL AREAS .................................. 23 ' 4.0 WETLAND RESTORATION STUDIES .......................... 26 4.1 ..... RESTORATION ALTERNATIVES ANALYSES 26 4.2 ..................... SURFACE WATER ANALYSES ............................... 28 4.3 GROUNDWATER MODELING ............... 33 4.4 ................. REFERENCE GREENTREE IMPOUNDMENTS .......... 36 i 4.5 ............ REFERENCE PLANT COMMUNITIES ........................... 41 5.0 WETLAND RESTORATION PLAN .................................. 5 1 I 47 . MPOUNDMENT / WEIR CONSTRUCTION ....................... 50 5.2 WOODY DEBRIS DEPOSITION ............................... 5.3 WETLAND COMMUNITY RESTORATION 50 . ? ....................... 50 6.0 MONITORING PLAN ....................... 56 ' 6.1 .................... HYDROLOGY .......................................... 56 6.2 HYDROLOGY SUCCESS CRITERIA ............................ 56 6.3 SOIL .................................... 56 6.4 ............. SOIL SUCCESS CRITERIA .................................. 59 6.5 VEGETATION .................... 59 ...................... i 11 6.6 VEGETATION SUCCESS CRITERIA ........................... 60 6.7 REPORT SUBMITTAL ..................................... 61 7.0 IMPLEMENTATION SCHEDULE ..................... . 8 0 MANAGEMENTPROGRAM . ...................................... 63 1 9.0 DISPENSATION OF PROPERTY ................................... 65 10.0 WETLAND FUNCTIONAL EVALUATIONS ............................ 66 ' 10.1 EXISTING CONDITIONS 10.2 PROJECTED, POST-RESTORATION CONDITIONS ................. 66 66 ' 11.0 REFERENCES ................................................ 67 I 11 ii I LIST OF FIGURES Fi ure 1: Miti ti Sit L ti R dl R i Paqe g ga on e oca ons: an eman eservo r ................ .... 2 Figure 2: Site Location: Edgar Branch Mitigation Site ................... .... 6 Figure 3: Fi ure 4 Aerial Photograph (1999) ............................... Ph i h T h d L d .... 9 g : ys ograp y, opograp y, an an Use .................... 12-13 Figure 5: Soil Map Units ....................................... 15-16 Figure 6: Fi ure 7: Plant Communities .................................... Jurisdi ti l W tl d 18-19 g c ona an e s ........................... ... 24-25 Figure 8: Flood Frequency Analysis ............................... 31-32 Figure 9: Site Location: Falls Lake Greentree Impoundment .............. ... 37 Fi ure 10: Site Location: Countr Li C k G I d g y ne ree reentree mpoun ment ........ ... 38 Figure 11: Site Location: Jordan Lake Greentree Impoundments ............ ... 39 Figure 12: Conceptual Impoundment Design ............................. 40 Figure 13: Reference Greentree Im oundm t p en ........................ ... 42 Figure 14: Reference Plan View and Cross-Section ........................ 43 Figure 15: Hydrology Restoration Plan .............................. 48-49 Figure 16: Plantin Plan 54 g ........................................ -55 Figure 17: Monitoring Plan / Mitigation Design Units .................... 57-58 iii is ?e is is is ?e is ?e ?e ?e is q ?e q LIST OF TABLES Paqe Table 1: Estimated Area of Mitigation Design Units Based on Preliminary Studies for 10 Potential Mitigation Sites Associated with the Randleman Reservoir ...................................... 5 Table 2: Water Surface Elevation Estimates for Various Flood Frequencies ...... 29 Table 3: Modeled Groundwater Discharge Zone of Influence on Wetland Hydroperiods: Congaree Soils ....................... 35 Table 4: Reference Forest Ecosystem Plot Summary ..................... 45 Table 5: Reference Forest Ecosystem Plot Summary ...................... 46 Table 6: Planting Plan ........................................... 53 iv is DETAILED WETLAND MITIGATION PLAN g RANDLEMAN RESERVOIR WATER SUPPLY EDGAR BRANCH MITIGATION SITE RANDOLPH COUNTY, NORTH CAROLINA 1.0 INTRODUCTION 1.1 PURPOSE The Piedmont Triad Regional Water Authority (PTRWA) proposes development of the Randleman Reservoir in Randolph and Guilford Counties, North Carolina (Figure 1). The purpose of this project is to develop a safe and dependable water supply source for North Carolina's Piedmont Triad region that will satisfy the projected water demand for a period of 50 years. The proposed 3000-acre reservoir will unavoidably impact approximately 121 acres of wetlands through impoundment and establishment of an open water system. These jurisdictional wetlands are subject to regulation under Section 404 of the Clean Water Act (CWA) (33 U.S.C. § 1344). ' For unavoidable wetland impacts, compensatory mitigation is required to facilitate no net loss of wetland functions in the region. Compensatory mitigation is typically performed to replace similar wetland types and wetland functions as those impacted (for example, forested, stream- side wetlands). Wetland restoration, creation, enhancement, and preservation are typical methods designed to offset wetland impacts. The North Carolina Division of Water Quality (DWQ) has instituted a policy that prefers a minimum of 1 acre of wetland be restored or created for every acre of wetland impacted. Subsequently, remaining wetland functional replacement needs may be off-set through wetland enhancement and/or preservation. ' The purpose of this study is to evaluate wetland restoration/creation potential at Edgar Branch, a proposed mitigation site located immediately contiguous with proposed reservoir pool elevations. The project boundary encompasses approximately 45.5 acres. Wetland mitigation is projected to involve approximately 36.1 acres of created/restored wetlands and open waters and approximately 0.9 acres of preserved/enhanced wetlands. Other sites will be evaluated in separate documents to address the 121-acre mitigation needs of Randleman Reservoir. ' 1.2 OBJECTIVES OF WETLAND RESTORATION The primary objectives for wetland restoration include the following. I' 1) Restore or create 121 acres of wetlands as required under regulatory guidance. 2) Assist in protecting the drinking water supply from pollutants discharged from the developing upstream watersheds. Excess nutrients, fecal coliform bacteria, sediments, and chemical contaminants (metals, etc.) represent the primary water quality concerns for the reservoir. 11 1 11 I a ao ?o ?o ?o ao ,e ?o ,s oe SELECTED POTENTIAL MITIGATION SITES ?5 1 / ?" ? f • , ,1?'' _,? •.. .. ? _ // ? _ - 1. RICHLAND CREEK ©ARCHDALE r o y - r ?t? /. _ EDDICKS CREEK MILE BRAN re CH HICKORY CREEK KERSEY VALLEY ti 1?' 'r_ 1 ?? • `^ \ ?.. j •?; ® MUDDY CREEK O BOB BRANCH EDGAR ?Q SOPHIA (?' • y (Upper Muddy Creek) o 17 l V<L f \, # 5 Y .? ( `?r ,?J{?'L(S i ?. .. ??,.....""`•'L .'fir !/? i ..?'"j ? .?, y` \, ? r 1 ? ii ?? r; ??! .., - _, / ••, ^ - '7a ,? ,./`' ' flN to In ? - S` +! ? ? ?;'• ,- ? _ / ? ;l ,. \?? •, r, ?jce .?%`J ,I^? rte, lam, ?? : ? `-? L\ t . tKv."T 1 IT. C'? f A ? S\ '?? ~`"+ V i'F??I..1•(``- ,q ` P 0 2m+. {. 1 v ?tj/? 1 c (j 1:63.360 ?. Source; USGS 1:100,000 Quadrangle (Chapel Hill, N.C.) a D EcoScience Corporation Raleigh, North Carolina Client: PIEDMONT TRIAD REGIONAL WATER AUTHORITY Greensboro, North Carolina Project RANDLEMAN RESERVOIR Guilford and Randolph Counties, North Carolina I Tide: MITIGATION SITE LOCATIONS Dwn By. Date: MAF JUL2001 Ckd By: Scale: ES As Shown ESC Project No.: 01-015 FIGURE i 1 r 3) Maximize benefits to water quality through establishment of functioning r wetlands above the reservoir pool. 4) Replace habitat for wetland-dependent wildlife displaced by establishment of open water. ! 5) Maximize the area of wetland restoration or creation achieved at the Edgar Branch mitigation site. ! Goals 1-4 will be accomplished at multiple sites, including Edgar Branch. ! Water quality benefits are maximized by reducing the capacity for sediment to reach open water within the reservoir pool. Entrenched streams in the region have abandoned adjacent floodplains and tend to discharge large quantities of sediment into water supply reservoirs ! (Simmons 1976). Within reservoir pools downstream of entrenched streams, sediment from the watershed is deposited directly into the water supply, in a permanently inundated, reducing environment. Without periodic oxidation processes, pollutants generally dissolve within the r 1 water column and consequently reduce drinking water quality. Therefore, wetland restoration for water quality should be designed to reduce entrenchment, ! erosion, and sediment transport within streams and to entrap sediment within vegetated wetland surfaces. Sediment would be deposited on floodplain surfaces that periodically dry r out in areas outside of the reservoir pool. Wetland vegetation would be established on the alluvial deposition to stabilize the sediment and provide for pollutant recycling through oxidation (drying) and reduction (wetting) processes. Wetland vegetation would serve to ! provide nutrient uptake and recycling functions within deposited sediment. Using this rationale, entrenched stream and terrace systems would be converted into alluvial wetland fans or greentree impoundments. A highly sinuous (E) to braided (D) stream system would be r developed within the alluvial deposition area (Rosgen 1996). 1.3 PRIMARY METHODS FOR WETLAND RESTORATION Two primary methods for wetland restoration have been proposed to extend the sediment wedge into design wetlands above the reservoir pool, restore 121 acres of riverine wetlands, ' and provide suitable habitat for wetland dependent wildlife. Primary methods include 1) in- stream structures designed to reduce sediment transport capacity, and 2) greentree impoundments designed to allow management of water levels and sediment deposition ' patterns. In-Stream Structures In-stream structures are proposed primarily along dredged or entrenched stream corridors on relatively low-slope valley floors (<0.009 rise/run) supporting forest vegetation and broad floodplains (greater than 500 feet in width). Adjacent floodplains have been abandoned by the incised stream and converted to elevated terraces not regularly exposed to overbank flooding or wetland hydrodynamics. Properly designed in-stream structures are expected to reduce the 3 r' io degree of channel incision, reduce the rate of groundwater discharge from the floodplain into the channel, increase overbank flooding from the channel onto the floodplain, reduce sediment ' transport capacity, and provide greater sediment deposition within vegetated wetlands. Greentree Impoundments Greentree impoundments are typically proposed on more steeply sloped, narrow floodplains and stream terraces (>0.008 rise/run) or where relatively severe stream channel degradation and steepening has occurred above the reservoir pool. Greentree impoundments have also been considered in instances where water levels may need to be controlled for wetland development in rapidly urbanizing areas. The greentree impoundment option is the preferred alternative for wetland restoration/creation at Edgar Branch. In general, a greentree impoundment consists of a floodplain levee and controllable outlet structure that is modified periodically to promote the development of forested wetlands. Functioning greentree impoundments above the lake reservoir are expected to provide for significant nutrient uptake, recycling, and management benefits, including increased habitat for wetland-dependent wildlife species. The elevation of the outlet is typically raised during winter months to promote ponding, sediment deposition, and waterfowl habitat. The elevation of the outlet is lowered in early spring to allow for vegetation growth, nutrient uptake, and seedling establishment. Regular monitoring and maintenance of the wetland system is critical, including periodic vegetation sampling, periodic replanting, structural repair, and precise hydrologic control on a semi-annual basis. 1.4 MITIGATION SITE SELECTION During the environmental impact assessment, project planners identified and evaluated a total of 25 potential mitigation sites within stream corridors extending above the reservoir pool. A description of mitigation potential for each of these sites was prepared in previous documents (ESC 1998a, ESC 1998b, ESC 1999). Of these 25 sites, 10 sites were determined to support wetland restoration / creation potential IN on up to 121 acres of floodplain. Table 1 and Figure 1 depict the location of each site and projected areas potentially available for wetland restoration use. IN This document details restoration and enhancement procedures for riverine wetland restoration and creation along Edgar Branch, one of the 10 mitigation sites (Figure 2). The Edgar Branch mitigation site (Site) consists of approximately 46 acres that encompass the stream and 10 adjacent floodplain. The stream drains a watershed of approximately 2.06 square miles (1320 acres). A series of greentree impoundments is proposed within the stream channel and no adjacent floodplain to reduce the rate of groundwater discharge from the floodplain into the 4 1-tJ 67, io IB io IN is In io la is IN IN is is ?B ?B ?e ?e ?e C O C «' to m Co d `- O m N U LT y C C N M- ?. u > co L1J L1) 'O > O > E C '- N C U Co C M ++ U W O > !n N S a? - CO (n 0 -J ' a G1 C C ' C C a ? m v G. = a U1 y O Q yr O -C O cn Y (o N Q ai r y . .1 C U Co O .U 5 0 F- m N _ y •N Q O N , -C C .0. o . C _ n c'0 C :: v O L? .O y + + m o v fo C LL LV G > r- y. ±+ O Q O a? (fl V r Q C H... Q) 'O d O co O O c > i a a L) E E O c co a) V) e- Q) J c O U) C O LM N Q) 7 U ?c E co O L. U) C L 3 O a N r O LO LO M r, d M r" N (D N N C o 0 a r. O V .O O O O •" N ?2 L N C N _ O O U O L 3 C33 ? v c > 3 c d o M M '- `- '- ^ M- N O r- 00 m o N > c0 > - D 7 d y ' ` N ? C O E a C) CL O N N > p7 N o O . C L > 9 N CO a n .- lO O 1 1 1 1 1 1 1 1 N O 3 H o C (,? c c W N d w o CL E O N O U N O ._ C m L1 LL C O > a c D E a o .c o m ° O 3 a O LO M 'Rd, O C = 0 M M ^ o E Lo o v r N r r LO 0 N r o p L N w E O- ? y C M d ? O U > a U a o o c ¢? O Y 41 cm L O N M Q? c0 V ? ? 0 0 0 0 0 0 ?? ? 0 0 o 0 ? > N m ., o > ? w c 0 n r O 0 LO (D Cr) L() . LO 0 c LO t`o N L C E o, E . C y a E v o m m y c0 N ? >. w L L ? C O ? O O p L 0 0 0 0 0 0 0 0 0 0 0 E N U) E E 0 0 0 0 0 0 O O O O M - •• L N y y '4 LO r N r M 00 (D 0A N 0 an d M M . N It M ?-- (D M N M >. N C c . a? c - d L W o d > L C N O C _ O M L > •CL L O- m N d U ` O _ Y ? Y o L E d O Q) M U c U C fo U Co > U C U m = J Q N O N L OR N O m co , 0 . . O O X ` o v a) -0 4 o 0 3 N CL o q -6 U Y CC f0 C m QI O y L w LL ~ N M LO / ' 99 I ? / Y=?• 7 i , ' J b ; Mitigation ? 193? Site Location W '' / ,-.\`_.,'+ ?l y'1 6`•' ... 7 ,/t `"! X14 ? 4'liCi? - ?a. Yt Randleman -- ' Reservoir r 1 r N?w arket ?j `) (r eCh ?[ - ' • u ? r 1 y 1 i fi - . ?? i ? ?? ((P!f til., ^i'(? ?.? L l?,n. b . _ 1 (i. r ?•?t?r .:,.)i / ., t t, t 1 ?•` . ? / (/ ? +, ? 1 l '?? ` d v IitOn s `- P r 4 ? 1 . , r 1 A ^I +, rl , 1 r;:" - / 1936 s >/ ll 2400 4300 n , , `'' / C)?'?? ?. '• /? 1:29,520 / ' Source: USGS 7 5 Minute To o M s . p ap (Glenola / Randleman, N.C.) I ' Idr 50 ,_* 1.. RANDLEMAN RESERVO IR MITIGATION PROJECT Dwn. by: MAF FIGURE RcoScience PHASE 11 Ckd by: ES Corporation EDGA R SITE Date: JUL 2001 Raleigh, North Carolina Randolph Coun ty, North Carolina project: 1 1 01-075 II if III 1 11 ' channel, increase overbank flooding from the channel onto the floodPlain and increase deposition of sediment on vegetated wetland surfaces above the Randleman Reservoir. I This document includes the following: 1) descriptions of existing conditions; 2) surface and ' groundwater hydraulic analyses; 3) reference greentree impoundment studies; and 4) reference soil and forest ecosystem investigations. Detailed plans are provided for wetland restoration/creation, vegetation planting, site monitoring, and success criteria. It Is Is 1e I (n -0 n m Z a < 0 0 T 34 m _ p m ?p D G) m ' Dpi n? n z cn w o rn c N G) Vr frl M Z=> ? o 29 r) 0' ? 1 CA 1 4 °o_ g I L--?- AEdgar\fAures\Fjq m z ? (D 03.dgn 07/02/01 03:40:36 PM n I Groundwater conditions were modeled using DRAINMOD, a computer model for simulating ' withdrawal rates for shallow soils with high water tables. The model was utilized to predict historic hydroperiods, the extent of wetland degradation due to channel entrenchment, and the potential for wetland restoration through stream modification. ri, y IN ]1 is Surface water analyses for the Site were completed using standard study methods of the U.S. Army Corps of Engineers (USACE) and NRCS. Flood events of a magnitude which are expected to be equaled or exceeded once on average every 5-, 10-, 25-, 50-, or 100-year period were selected for use. These analyses reflect either existing or proposed conditions at the Site. The projected frequency and extent of overbank flooding were used to determine potential for riverine wetland restoration in floodplain portions of the Site. In addition, potential for impacts to adjacent roads and bridges was evaluated for pre-project and projected, post- project conditions. This Site has been selected for wetland restoration use to promote a reduction in sediment, nutrients, and pollutants flowing into Randleman Reservoir. Mitigation activities are intended to provide sediment deposition, and pollutant recycling from surface waters within created and restored wetland areas. Recycling functions are designed to reduce elevated nitrogen and phosphorus loads from the watershed towards background (forest) levels, prior to discharge into the reservoir. 10 Is io In 3.0 EXISTING CONDITIONS 3.1 PHYSIOGRAPHY, TOPOGRAPHY, AND LAND USE The Site is located in the Piedmont Physiographic Province of North Carolina. Physiography is characterized by moderately hilly terrain with interstream divides intermixed with steeper slopes along well-defined drainage ways. The Site is situated in the Edgar Branch floodplain within the Cape Fear River Basin (Hydrologic Unit #03030003 [USGS 19741, DWQ Sub-Basin 03-06-08). The Site is located approximately 11 miles southeast of High Point and approximately 16 miles south of Greensboro. Annual precipitation in the region averages 42 inches per year with June and August representing the months that support the highest average rainfall (4.21 inches and 4.36 inches, respectively) (USDA 1977). The project boundary has been defined as the limit of the 5-year, post-project flood elevation. The Site contains an approximately 8550-foot reach of Edgar Branch (Figure 4). The on-site section of Edgar Branch supports a primary watershed of approximately 1.95 square miles and flows into Muddy Creek 0.7 miles downstream. Muddy Creek empties into the Deep River 3.0 miles downstream of its confluence with Edgar Branch. After construction of the Randleman Reservoir, the downstream portion of the Site will reside immediately upstream of the reservoir's conservation pool, at 682 feet above mean sea level. On-site floodplain elevations range from 683 feet to approximately 730 feet. The Site consists of agricultural and pasture land, as well as bottomland hardwood forest corridors along the stream channel and in a few larger patches. A few scattered residential and farm buildings are also present (Figure 3). Near the downstream end of the Site, an outbuilding on a residential property on Spencer Road is located approximately 9-10 feet above the floodplain (701-702 feet above sea level). A group of three buildings on a cul-de-sac off Banner Whitehead Road is situated approximately 10-15 feet above the floodplain (705 to 710 feet above sea level). Another residence and two outbuildings at the same cul-de-sac are 15- 20 feet above the floodplain. At the western (upstream) end of the study corridor, a building to the north is situated approximately 12-15 feet above the Edgar Branch floodplain. Approximately 925 feet upstream of the Site, US 311 crosses Edgar Branch. The road elevation at this crossing is 738, while the adjacent floodplain reaches 732 feet. The projected inundation level during the 100-year storm after construction of greentree impoundments is 730 feet, with the normal winter pool level at 726 feet. A soil road at the upstream end of the Site crosses Edgar Branch by means of a ford. This road would be inundated by approximately 4-6 feet of water during winter impoundment periods. Lower and upper stream terraces form two primary physiographic landscape areas for restoration planning purposes. Upper stream terraces will experience saturation due to the proximity of open water and elevated water tables. Lower stream terraces will be actively inundated. Stream levees, a feature often found in floodplains of dredged streams as well as 11 10 am cm L;ZL?-j UQJ m 00 OX :rte • ne -= <.. o - > I o N -i C() N Z p m Al ;u C: 0 m ° m Z v l l 1 Z REAP COMPILED DY PHOTOGRAMMETRIC METHODS. 1 111 - TJJ 'r 'l/?I' 11?'; ; _' ,\\i? ,11111 ?`I `111\\ ? _ - -nm ;;111! s z_-_ - "uz p I X; \ r. 1 1X?4 I jZ{' Jq> 1? f ?I,1 1,;11 1 k ' to •10 _ M, x1;1 10? 1, I\ 17 W 1, s O __- 1 \1\1`1\ ? 11 I'1 '?,1/Il?" '`- - ------------- -!'- 't//???'r \? '\ ?1\ l "?.. MJSI,+•11,11 1 1 UL j, } I ?? U) 0 Dn OM _qm _n (A C_ m 11 ,'fj/ ?? 17 --`t?` `,, ?'•11 ?,{//111 \'I =il ?1i?I1 /?\I?11`'?\?`II I``?; 11`?11,'1 ,;11`1. W - / •?? X111 ? 1 ? ' ?; 1' 111`1 '?A`1 ? I M I/ 1 , ? \ 1? 1'11 p ;,k 1 I 11v ?, A 1 ,1 ?11, rl? IVJ?1`'\\??? 1J 111`1 111 \ 11 , 1 ??I? 1`11 1\ `? ?t? i - ? ; ` ' 'i , ??1111?k ,, I i 11 ' ` ? 1?' li ' _ ?? ?,iif??.I t• •''?r. ?' : ? E 11 1111 o MATCHLINE SHEET 1 __ ' ° MATCHLINE SHEET 2 n ° o CD m N F .? c m n z m 5 O.< m 3 ? 0 0 >M O 1 ;0 g m o N .. .. ZDOO O =Z =m -+ZO 0 O m C/) c N o OOO Oy? nN =OrZ N IND > co ?5 Z O m O C ° C??? ?m 9 00 w`? 3, mow} ?. i r y fl) rO 14 o o m= m z z D- ?ma o `j (_n 0 MATCHLINE SHEET 1 N o MATCHLINE SHEET 2 kle , t'/" -c2.' 17 ??: ?`, r.?l\•?XS.,e'? _J/ /' lj,J _-, X11 ?'it. / ' , ?„? ,,; _ ft,ot t•\ '..' !?- _ °'/?` ..111 ? i ii?? I'1'r ' II''I. ?? --I z C)o ,x,? ; 4 IZY? a ??sss?rrr ' , r m f0 N ;u ;u rn Z z z (n -4 03 Ul Z Z co M m f= o -a O w ;, r h j o r Z i17 .I ;O o - D J ? f %VA m MAP COMPILED BY PHOTOGRAMMETRIC METHODS. It _- :??. = ?- - ':' _ ? ;/ .,, ? Jet f:? ? ' k'?'' / '??'•?,, .. ??'1 5. ''.?' QS? it ?_ _ '` c ? A ,` ' - \ ? `?' `'i ? `? ', 1 ?' ?, , \ ', L-??. '? 0 10 11 k n ° - o co V _ m z 0 1p n a ?i Z O- G1 =1 = 2 = m 4? ? N o v z C) 0 C) D G? cn O N m o o A CO?? fn ?mM o° 6 cn c: ?3 m Z-Z DO 14 00 ° m r-n mm 1 C7? CO O Ord m n My O n O m < i o O ? O se se I e I I in undisturbed drainages, are virtually absent at the Site. The primary variables utilized to segregate landscape units include land slope, overbank flood frequencies (Section 4.2), and the rate and direction of groundwater flow (Section 4.3). The lower stream terrace physiographic area encompasses approximately 40 acres located along both sides of the stream channel and open waters of Edgar Branch (Figure 4). This terrace historically supported frequent overbank flooding (estimated at an approximate, 1-year return interval for hydraulic models) and was periodically re-worked by alluvial processes and periodic, long term inundation/saturation. Dredging and incision along the stream has reduced the frequency of overbank flooding within the primary floodplain from an estimated 1-year return interval to a 5-year or more return interval, with some sections of the reach never overtopping their banks (Section 4.3). Therefore, associated riverine wetland functions (sediment retention, nutrient cycling, energy dissipation, etc.) have been effectively eliminated from the physiographic area by stream alterations. Accelerated drainage is evident throughout the stream terrace physiographic area due to dredging activities and secondary stream diversions. During dredging programs along Edgar Branch, portions of the stream terraces appear to have been converted for agricultural use. However, these agricultural tracts have been abandoned over the last several decades, allowing re-development of disturbance adapted, successional communities. Under historic conditions, natural communities are expected to include Piedmont bottomland hardwood forest and oval to linear pockets of riverine swamp forest in low-lying areas (Schafale and Weakley 1990). 3.2 SOILS Surficial soils have been mapped by NRCS (USDA, unpublished). Soils were verified in the spring of 2001 by licensed soil scientists to refine soil map units and locate inclusions and taxadjunct areas. Systematic transects were established and sampled to ensure proper coverage. Refined soil mapping is depicted in Figure 5. Primary soil types include the Chewacla series, Wehadkee series, Mecklenburg series, and Wynott-Enon complex. ?s Two nonhydric soil series occur on the steep, drier slopes of upper terraces, along the edges of the project boundary. Mecklenburg clay loam (U/tic Hpa/udaifs) consists of very deep, well drained, eroded soils that have developed in residuum from mafic rock. The soils have a loamy surface layer and a clayey subsoil with low permeability and high shrink-swell potential. The seasonal high water table is below 6 feet. Wynott-Enon complex map units consist of an intergrade of strongly sloping soils on uplands. Both Wynott (Typic Hap/uda/fs) and Enon (U/tic Hap/udaifs) soils are deep and well-drained. They formed on residuum from mafic rock, have slow permeability and a high shrink-swell potential. Depth to the seasonal high water table is greater than six feet. Mecklenburg and Wynott-Enon map units are not expected to have supported wetlands historically. 14 Q® O t L C D O A ? J v t A P ?r C4 m m / U o cn o 0 ? m z 1 w 0 o m 0 0 n ? a o G 0 0 G Cl) rri m m o O g z r ? ? Oz n M r ? C r- D ? IA m m m Cl) o X O N O p O n + y W wn f, i a? vz?_ ul MATCHLINE SHEET 1 MATCHLINE SHEET 2 O ? r X ? X X A Y, V) V) 0 o m m 0 0 n 0 -'{ ? W N Z W v C -4 --1 0 m r m c) Z M ° m ? Z v r 0 N m -< ?O j 1 \, v ? ' O 1 ? 4 N r,; n 6 ? O V A ^ ? m rri Z ? m (0O n -4Z in N A' Zo G) Z =z A cog C) m A J 5 0 ;u C- . -1 g 35,vu) 0 r- -, r c p. 6 v ?o -=i = n 2- N On ? o 0o m z Z D v r? CD t t Ul ?,. r ® ® i? O CA CA o 0 O m z m m m 0 L4 0 0 rn 0 O 0 0 n N A A O O O Ar o: E 0 O . : O :t..o ADZ 7 n Z r r? D v Om x? m r D C o M m D -i o o O C X Z ? O O O O fD It f t It t t c o \ l? MATCHLINE SHEET 1 V - o 7 r 7 X X X ? m ? ? o ? m m o o C) 0 n 0 --j Z M ca M --4 0 z o OC 0 -flZt F' I m 0 0 m cn 0 Z i i 1 1 Z m -? 94??I d? V c n a A _ v a n rn - I o m N m i .. N C O m ?o D .a C) z o? DG7o = m --I Z A 0 J ?/ ? Zr 0 z z C/) C o nN? 0 prz N O t7 o o r N V 'A o_y 0 ;o . C: 0 N h'? \V 0 cil o 0 0 o o m Z z Z m n 0 CAD M v' / 4 Chewacla Fluva ue c D ( q nti ystrochrepts) loams encompass 41.9 acres of the 45.5-acre Site. These soils occur on the flat historic floodplain of Edgar Branch. Chewacla soils are somewhat poorly drained, nonhydric soils which have been formed on floodplains primarily by fluvial activity. Chewacla soils generally exhibit broad, inter-layered variability in texture and permeability dependent upon energy dissipation and sediment deposition patterns associated with each stream overbank flood event. Soil texture generally ranges from coarse sandy loam to silt loam of moderate to moderately rapid infiltration. Hydric soils are defined as "soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper soil layer" (USDA 1987). Hydric soils comprise the Wehadkee series (Fluvaquentic Endoaquepts), located primarily within relict backwater sloughs, depressions, ephemeral channels, and swales which remain within the secondary floodplain. These soils are very deep and poorly to very poorly drained. Under existing conditions, the Wehadkee series comprises approximately 1.1 acres of the Site. Important factors in the formation and maintenance of wetland systems as hydric inclusions in the Chewacla map units include 1) microtopography and variability in fluvial deposition across the landscape, 2) groundwater and surface water movement from adjacent uplands along the outer edge of the floodplain, and 3) groundwater discharge rates from the interior floodplain into the stream channel. These soils are subject to frequent flooding. The seasonal high water table is within 0.5 to 1.5 feet. Stream dredging, incision, and conversion to agricultural lands has likely increased the extent of Chewacla (nonhydric) soils and concurrently decreased the extent of Wehadkee (hydric) map units in the Site. 3.3 PLANT COMMUNITIES Plant communities are influenced by logging, grazing, and past conversion to agricultural lands. Three primary communities have been identified for descriptive purposes, including 1) mesic mixed hardwood forest, 2) shrub/scrub assemblage, and 3) crop land / pasture (Figure 6). Mesic Mixed Hardwood Forest Mesic mixed hardwood forest accounts for approximately 16.4 acres of the Site. This forest assemblage occurs in a relatively continuous swath along the project corridor. The forest canopy includes sweet gum (Liriodendron tulipifera), red maple (Acer rubrum), sycamore (Platanus occidentalis), black walnut (Juglans nigra), green ash (Fraxinus pennsylvanica), tulip poplar (Liriodendron tulipifera), redbud (Celtis laevigata), American elm (Ulmus americana), black willow (Salix nigra), and hackberry (Celtis laevigata), and, in drier areas, eastern red cedar (Juniperus virginiana) and hickory (Carya sp.). Under-story and shrub layer species distribution is variable along hydrologic gradients and sunlight regimes, and includes horse sugar (Symplocos tinctoria), ironwood (Carpinus caroliniana), hop-hornbeam virginiana), elderberry (Sambucus canadensis), multiflora rose (Rosa multiflora), and Chinese privet (Ligustrum sinense). Vines include muscadine grape (Vitis rotundifolia) and Japanese r 17 ® ® ® ® ® elf a M- n _ Lzj ' O M M3 WA IM IM f ? m • rn m xm ? v ^ l x x 0 Y, C- 0- tn ? ° ° m U m t `?.`?i V / -4 cu (n z co v ;a C O ;u 0 C: m o o Z s m -c aJJ?, I r' 41 Y W X A S? I ? x ?4 ID CA -J z m N CA C4 O \ \ c2 Fn 0 k\ 41 z z? vN me -+ z n ? o D? m D ?? ,. E4 Ox m C) cn m c ^v m0 ;u m 0 C= Fn rt m m r + ?+ + + + y MATCHLINE SHEET 1 MATCHLINE SHEET 2 F ° v n n m m p m zo ?m n O n Al cog 0 z :5 c N ° CZ nom (an) 0 a Ch 1 m e Z -f m o 70 z >y ?p o 0 °o ° N m z Z D m D ,? CD 1 11 . 111 11 My ®4 ® ® !® Fri _: CII O MATCHLINE SHEET 1 wo MATCHLINE SHEET 2 0 o m R- 2 i m Y Y? w ?? ? N L (v ?//?/; O ? N Cy 0 x x ?, YF ti ;T )r ?. x r cn l p I r n ? .?cr r R1 / \ X x x x x -I -_I =-1 O J r kr,? ss rw O z Z Z 'D c W / G7 p p 0 0 C -4 O m ro m o0 Z r z ? Dv x Z O N m -? 1 n I\j N cam, H X r'? t? `? JUG l ?k k IC ? 14 1 _ s m v p m ?n m 30. v0 c z n ' \ r, m D o Jl Ox \ J S? ?,? O p t<? v my -n m m 9 o f f_ m m o m p ---OE D / .. i.+ o 00 m r? d 6 f?6? -00 I+ I+ I+ I+ 0 F ° ? - o n T m m n m z 0m ^ IM o CD G?D? 0N =DZ N o p z C) o w No m O=> Zo 4v? 00 o N m z Z D mD CD _ 11 11 :0 v _Jll q '' honeysuckle (Lonicera 'a onica which becomes invasive in sunnier areas. The herb layer ' includes speedwell (Veronica persica), common blue violet (Viola papi/ionacea) and jewelweed (Impatiens capensis). Other herbs are bedstraw (Galium sp.), chickweed (Stellaria media), dock (Rumex sp.), Indian strawberry (Duchesnea indica), bitter cress (Cardamine parviflora), and Christmas fern (Polystichum acrostichoides). This community intergrades into dry-mesic oak-hickory forest at higher elevations, outside of the project boundary. Shrub/Scrub Assemblage This plant community occurs as a distinct type only at the western end of the Site. In this 1.5-acre area, shrub/scrub assemblage lines the banks of Edgar Branch as it winds through a pasture. The thin, linear strips of this community contain both relict bottomland species and early-successional, opportunistic species. The canopy layer consists of a few isolated ' individuals of shagbark hickory (Carya ovata) and eastern red cedar. Among the shrub layer are winged elm (Ulmus alata), black willow, sassafras (Sassafras albidum), Chinese privet, tag alder (Alnus serrulata), and blackhaw (Viburnum prunifolium). The herb layer consists of 11 grasses and other species common to the surrounding pasture community, such as white clover (Trifolium repens), buttercup (Ranunculus sp.) and common blue violet. Crop Land / Pasture Land Approximately 16.3 acres of the Site remains as active crop land and maintained pasture land. ' Pasture land is dominated by a variety of grasses and herbs, including fescue (Festuca spp.). Other characteristic volunteer species occurring in fields and pastures include buttercup, goldenrod (Solidago sp.), dock (Rumex crispus), horse nettle (Solanum carolinense), wingstem ' (Verbesina occidentalis), common blue violet, milkweed (Asclepias sp.), burdock (Arctium minus), wild onion (Allium canadense), clovers (Trifolium spp.), thistles (Carduus spp.), and henbit (Lamium purpureum). 3.4 HYDROLOGY The Site is located within the Piedmont hydrophysiographic province, which encompasses the entire drainage basin for the East and West Forks of the Deep River. The region is characterized by moderately hilly terrain with interstream divides exhibiting dendritic drainage patterns and moderately steep slopes along valley floors (0.005-0.015 rise/run). The region is characterized b moderate rainfall. In Y Randolph County, precipitation averages ' 42 inches per year with precipitation evenly distributed throughout the year (USDA 1977). Large floods (20-100 year return interval) typically correspond to large thunderstorms and tropical events in the region. Bed-load material supplied by the region consists primarily of silts, sands, and weathered bedrock (very coarse sand and small gravel). Bedrock outcrops are common within incised streams in more steeply sloped valleys. Suspended load consists primarily of easily eroded clays and silts, which transport attached nutrients into downstream waters. Erosion and 20 11 suspended sediment loads have been linked to nutrification problems within the Piedmont hydrophysiographic province, including the Randleman Reservoir region (DWQ 2000). Surface Water The Site encompasses a 3930-foot reach of Edgar Branch supporting a drainage area of 1.93 square miles. The valley slope measures approximately 0.007 rise/run, suggesting the presence of a relatively flat valley floor relative to typical conditions in the Piedmont Province. The lower valley slope may be due to the presence of geologic controls and a change in valley orientation downstream from the Site. The floodplain ranges from 100 feet to 350 feet in width along the length of the Site. Surface water runoff within the stream terrace would be relatively sluggish in wooded areas. Surface detention and ponding on the rough soil surface, and interception by dense forest vegetation, would occur in this area immediately after significant rainfall events with delayed return flow into the main-stem channel. Cross-valley and down-valley flow would be more rapid from steep side slopes planted in pasture grasses or crops. Numerous upstream ponds may be partly responsible for incision of the stream channel. The 11 average existing bankfull depth of the channel is 3.6 feet, compared with 1.7 feet calculated from the regional curves based on drainage area. In addition, the average, existing cross- sectional area of the Edgar Branch channel measures approximately 89 square feet. According to regional curves, a stable Edgar Branch channel is projected to support cross-sections of approximately 27 square feet (assumes rural conditions) (Harman et a/. 1999, Rosgen 1996). The incised channel supports a sinuosity (channel length/valley length) of 1.14. Substrate within the channel is composed of unconsolidated sand, small gravel, and bedrock outcrops exposed by incision and localized bank erosion. The channel is classified as an E4c (gravel dominated channel) based on fluvial geomorphic features (Rosgen 1996). Stream discharge and flood elevations under existing and post-project conditions have been ' predicted based on hydraulic models. Section 4.2 provides model predictions for the 5- and 100-year storms, under existing conditions, and for the 5-year storm after construction of impoundments. Table 2 (Section 4.2) details flood elevations for the 5-, 10-, 25-, 50, and 100-year storm. The study suggests that overtopping of the streambanks occurs during the 5-year storm in most areas of the Site. However, entrenchment of the stream channel likely confines the 1- and 2-year flows within the eroding banks, effectively bypassing floodplain functions associated with pollutant removal and maintenance of wildlife habitat for overbank flood dependent species. Evidence of recent flooding outside of the stream banks was observed only in rare, isolated pockets during field surveys. The hydraulic model further suggests that the existing soil road at the western end of the Site is overtopped during the 5-year storm with the roadway inundated along a 125-foot to 150- foot reach. Post-construction flood elevations would extend the inundated roadway segment I 21 I Is 11 I? I? ?e is is ?e is is ?e is is is is is is is is to approximately 250 feet (Section 4.2). The existing crossing of Edgar Branch on this soil road simply consists of a ford, with no culvert or bridge construction in place. Stream flow across the road is shallow and braided. The crossing is undoubtedly a continuing source of sedimentation in Edgar Branch downstream. Groundwater Surface water hydrodynamics, such as periodic overbank floods, fluvial sediment deposition, and hydraulic energy dissipation, represent important attributes of floodplains and bottomland hardwood forest in the region. However, streams in the region typically function as groundwater withdrawal features throughout most of the year. Therefore, groundwater inputs from auxiliary watersheds and upland slopes abutting the floodplain represent the primary hydrologic input resulting in the development and maintenance of riverine wetlands at this Site. Groundwater gradients in May 2000 and after rainfall events in August 2000 indicate that the groundwater table typically resides from 1 foot to 6 feet below the land surface. The groundwater gradient typically remained more than 2 feet below the surface throughout the stream terrace with a relatively steep gradient induced by the incised stream channel. Based on observed groundwater gradients, the Site is expected to support limited groundwater storage potential typically associated with maintenance of wetland surfaces. Although adjacent escarpments supply riparian inflow of groundwater, this flow appears steeply inclined with relatively rapid discharge towards the stream channel. Entrenchment of Edgar Branch has accelerated groundwater discharge to depths of greater than 5 feet below the surface near the stream channel. Restoration of a shallower (less incised) stream network will generate a flatter groundwater gradient. However, groundwater models (Section 4.3) suggest that groundwater tables will continue to remain more than 1 foot below the surface. Therefore, restoration of wetlands within this Site may require establishment of backwater (surface water induced) wetlands behind a greentree impoundment. 3.5 WATER QUALITY Edgar Branch maintains a State best usage classification of WS-IV* (Stream Index No. 17-9-(1) (DWQ 2000). Class WS-IV waters are protected as water supplies which are in moderate to highly developed watersheds. Point source discharges are generally required to meet stringent pre-treatment standards, to maintain pre-treatment failure (spill prevention) plans, and to perform point source monitoring for toxic substances. Local programs to control nonpoint source and stormwater discharge of pollution are also required. The symbol * signifies waters that are within a designated Critical Supply watershed and are subject to a special management strategy specified in 15A NCAC 2B .0248. In this case, the watershed areas is within 0.5 mile of a water supply intake for the Randleman Reservoir. The Site consists primarily of existing and former agricultural land, second-growth forest, and scattered residential development. Fertilizers, pesticides, and nutrients associated with land 22 uses, including the golf course upstream of the Site, may currently influence water quality in the vicinity. Historically, the floodplain provided water quality benefits to the watershed associated with Edgar Branch. However, runoff from cleared land area effectively bypasses wetland floodplains and flows directly to the channel and through the Site. Restoration of wetland hydrology and diversion of watersheds onto restored wetland surfaces will provide for restoration of overbank flooding and associated water quality benefits above the Randleman Reservoir. Particulate retention, removal of elements and compounds, and nutrient cycling would be among these benefits. 3.6 JURISDICTIONAL AREAS ' Jurisdictional areas are defined using the criteria set forth in the U.S. Army Corps of Engineers Wetlands Delineation Manual (DOA 1987). Approximately 1.1 acres of jurisdictional wetlands and 1.3 acres of open waters (in-stream habitat) were delineated on the Site on May 3 by ECS, Ltd., and verified by the USACE. Figure 7 depicts the boundary locations of existing jurisdictional systems. Wetland extent was most likely more extensive prior to stream dredging and channel incision on the Site. •? .?.? ?M. i.Il® nor winnow ws?w INVINEWs fiiM® 66. A r`te' 6. J i. r:WJ t..a 3 1 um" C. F LTI 1'1 1) x s 'A X W ? ? A I , ln? ?6`l cR 1 m e --o x x L< D O 1 r (n z --4 Fn Uj --1 (n :1 - O m m v ;u n ° co m Z m -4 cu W Z z m o M ° z C: 0 ;u v D z (n : I7 0 + + H r` UAP COMPILED BY PHOTOGRAMMETRIC METHODS. Py ° ° m ? -P W V?IJ {' ? ?i? (A cn r ° A J Ik (7 ° W \ m `' A' ?j # "o CAT Z O m mr? m g rrg m?v .Azov Zcnr, z m 0mo O Z F)m Z )> 0 ;u m v o aw ° w ., ? c l 4??4 ; a ° r j 2)' Chi o MATCHLINE SHEET 1 v MATCHLINE SHEET 2 a C a M m Div ?J C) -1 Z N DNS '??Z ?m Cod 1*4 DF, z ?C a cn Z ° 0 f7 ^ o n t^ ?-1 MM 0 AAV 0 r -? IT1 if C: -1 ° o z CD 0 C/) 0 ;a o o Z m z_Z Do ?•f?D r7 cn 0 r p JIL ® = = Q MATCHLINE SHEET 1 w MATCHLINE SHEET 2 m ° yy2Y J ` /1\ j JF 3 rn LIP a ' o I r? n 4r chsx' ?L 4" 111YYY ? ??t 1 m m m ? v m C- e -u x x x r ? { r,cn z -4 ? o ° m \ -?, x DO Z Z Z M ?0 rn z ? o m ? c-4 z --4 0 c V) 0 Z, m 0 0 -A: 11 ? 1+ 1+ /?X ? I rte.. r) 1 1 ,O MAP COMPILED BY PHOTOGRAMMETRIC METHODS. 23 / Via'/f 2S' \es z ;ur- * m ???? ?0 \ \ kr?k 4DDZm r p fi +\ ++ (A rrl Zcnr > + ?j x rmn Z ?. k r 0 \ ?' k k D ? l I ?. Al" /\ / \ \ ro, N F ` .: n M .. 70 O •fl D °u ? D p O (? C Z N o > 25 > O z = D Z A o O o r yp W C:0 4 0 ° r m z z D rn > '? CD 11 4.0 WETLAND RESTORATION STUDIES This section summarizes studies performed to orient restoration design. Studies include the following: -? 1) Restoration Alternatives Analyses: Alternatives for wetland restoration relative to stream, floodplain, and reservoir functions were assessed. 2) Surface Water Analyses: Overbank flooding frequency and extent was evaluated for wetland restoration alternatives to assess potential for impacts to adjacent roads and structures. 3) Groundwater Modeling: The effect of drainage features on groundwater wetland hydroperiods was modeled. ' 4) Reference Plant Communities: Reference wetland communities were sampled to predict the target distribution of vegetation to be established in restoration areas. 5) Reference Physiography and Surface Topography: Reference wetland surfaces were measured within an existing greentree impoundment to characterize long- term, projected Site conditions. 4.1 RESTORATION ALTERNATIVES ANALYSES The objectives of this project include the following: 1) Assist in protecting the drinking water supply from pollutants discharged from ' the developing watersheds. Pollutants attached to sediment represent the primary water quality concern for this project. 2) Maximize benefits to water quality through establishment of functioning wetlands above the reservoir pool. 3) Replace habitat for wetland-dependent wildlife displaced by establishment of open water. 4) Maximize the area of wetland restoration achieved by the project. Restoration alternatives suggested by project participants are briefly described below. Stable Channel Construction Reconstruction of a potentially stable stream system was assessed as a replacement for the existing, dredged and incised channel. The new channel would be designed to mimic referenced, stable attributes including the geomorphic dimension, pattern, and profile needed to transport water and sediment produced by the watershed. The restored channel would reduce the rate of groundwater withdrawal from adjacent floodplains, potentially resulting in wetland hydrology restoration-in certain areas. J 26 oe Ig 10 In ?B 10 IB In In sa Stream restoration through natural channel design represents a viable option for this Site. If applied, approximately 4500 linear feet of channel may be relocated into a sinuous channel that reduces bank erosion and increases in-stream aquatic habitat. Based on groundwater models, this option is expected to provide for less than 1 acre of wetland restoration on the relatively narrow floodplain floor. Because the wetland restoration area is inadequate, the stable channel construction option was discarded. Alluvial Wetland Fan Development This option is designed to elevate water tables and reduce sediment transport within the floodplain and stream corridor. Alluvial fan development entails placement of fixed, in-stream weirs within the dredged channel. The in-stream modifications are expected to reduce the degree of channel incision, increase overbank flooding, reduce stream sediment transport capacity, and provide greater sediment deposition within vegetated wetlands. The system would progress toward an alluvial wetland fan where the channel actively migrates across fluvial material. During the interim period, in-stream structures will sustain significant energy during flood events; therefore, the potential exists for development of channel by-passes (shoot cut-offs) around the structures. As such, risk of wetland restoration failure exists. The structures must be designed to avoid short-circuiting and provide for sediment deposition in the incised channel. Over a relatively long period of time, the shallower channel would inevitably abandon the structures and begin to actively migrate across the restored floodplain. At this point, the system would need to be monitored for evidence of head-cutting from the downstream reach. A step-pool channel would need to be established due to the significant change in elevation immediately above and below the alluvial wetland fan. Because the potential for future head- cutting is considered significant, this option was discarded. Greentree Impoundments This alternative is similar to alluvial fan development described above. However, greentree impoundments include a floodplain levee and controllable outlet structure that is modified periodically throughout the year to induce backwater flooding and promote the development of forested, shrub-scrub, and emergent wetlands. Greentree impoundments have been constructed above other water supply reservoirs in the region for wetland, wildlife, and sediment retention functions. These structures can be controlled to regulate the depth and frequency of inundation based upon objectives of the system. In this case, the structures would be used to establish vegetated wetlands and limit transport of pollutants into the reservoir. In general, the levee system is constructed to provide for less than 2 to 3 feet of inundation during winter months, to prevent over-topping, and to allow for survival of tree seedlings. The winter depth is generally dependent upon the height of seedlings. The raising and lowering of outlet structures requires regular monitoring and maintenance by qualified personnel to 27 IN facilitate the growth of tree species. The actual date that the outlet is modified may vary annually and is dependent upon localized conditions within the watershed. Seedling mortality is tracked on an annual basis and the date of spring lowering is modified to maximize the rate of forest regeneration. Tree species selected for planting may also be modified based upon collected data. Greentree impoundments designed for forested wetland restoration have failed in the past, due primarily to lack of resources for long-term monitoring, management, and manipulation. Based on alternatives analyses, construction of a greentree impoundment across the Edgar Branch floodplain represents the preferred option for this Site. The capacity to manage, regulate flows, and regulate sediment transport/deposition rates at the Site outfall will reduce potential for head-cut migration into an alluvial wetland fan as described above. In addition, the structures would allow pro-active control of wetland development and function behind each impoundment. 4.2 SURFACE WATER ANALYSES Surface drainage on the Site and surrounding area was analyzed to predict the effects of diverting existing surface drainage into wetland restoration areas along the primary and secondary floodplains. Several alternatives were evaluated to determine surface water modifications that minimize potential for impacts to adjacent properties and maximize wetland ® area. Hydrologic and hydraulic analyses were completed using standard study methods of USACE and NRCS. Flood events of a magnitude which are expected to be equaled or exceeded once on average every 5-, 10-, 25-, 50-, or 100-year period were selected to characterize existing and proposed conditions at the Site. Hydrologic Analyses Hydrologic analyses were carried out using the USACE HEC-1 model to establish the peak in stream discharge for the 5-, 10-, 25-, 50-, or 100-year flood events. Input for the HEC-1 model consisted of synthetic storm precipitation data, drainage area, NRCS curve numbers, and drainage basin lag time. Table 2 summarizes the total, 24-hour precipitation event for each storm that was analyzed. Precipitation data was obtained from IN U.S. National Weather Service documents (NOAA TP-40 and Hydro-35). The drainage area was delineated on 7.5-minute USGS topographic maps and then subdivided into sub-basins based on land use or location of tributaries. The drainage area for each sub-basin was IN estimated using a planimeter. The NRCS curve numbers were estimated using methods described in NRCS TR-55. The sub-basin lag times were estimated using Snyder's method. 28 W 0 .L N W_ U Z w CI W tr LL O O J LL N O Q M O N LL -i III m H Q Q F- ? p N W Z O_ F- Q W J W W U Q LL CC D N x W a C C > X co O O O a*;-, .0 J (0 M - M r- N It LO N M M O M r M a-0 Co co ca N r, 00 00 00 M M M O O O o r- ,- ?- a o co (D (D co (D ca (D (D t` t` n r` r` r` t` Q o- LLwW N M L[) (D Lt7 rl M O (D CD 00 00 (D (D M r* U o 00 00 O N LO M .- d r, O N LO 00 '- 'tt r- ° M 0o a) M M M o o o ?- N N N co - (D 0 (D M (O CD r r r, r rl? N r r N r >- N N N O M r `- O C O t0 ?t N t` ?- O ?- 00 O r? (0 M d' w M , m M - m M '- 4 W CO M (n N CO CO 00 M M M 0 0 0 - - N N X M (D (D (D (0 CD (D r` r- r\ N r\ N r` r r w ?, t\ to M d M M ?} qt Nt It M (D It tt m It h 0 (D M O N M M 4 r O N L6 00 d r? 0 0 M M M M M M O o 0 ? ?- ?- r- N N N co w (D (D (O (0 M N r\ N N r` N N r N N O - N LO } co M (D M Lf) C y C N LO N .- Co LO M M M CO w t\ ao co r, M O C .. M M M M O (D M O 't r, '- M ?t r N (O > W co U r M M w m M M 0 0 0 r' r' N N lL (D (D M (D CD M (D r? t? t` t\ n t\ r? E a) O O N .- N N N M Cl) r- N N M -0 N to M O N m m , 4 N O N . rn CO r j a CO co M M M M 0 0 0 - r- r- - N N N O CO (2) CD (D O (D M O N r- N r N N N N N N = a? a> N 00 LO d' N ? N C N .- M 00 W N n W (D (O r- M d ?t d M M to ? +O CO M r- 00 O (D 00 O ?t r r- M It N N It m co y N M M M M M M 0 0 0 - - .- A N N > W w M M CO w (D M N N N N N N N N N Q) a i " W C C O O 't -,t 't q* M M [t lA (D O LO ct to 7 O O M N M ?- 't M O M M M ?t r- O M CD LL CL 00 00 CO M M M 0 0 0 0 N N ci: co O (D (D CD w M M N r- r- r, r r r r r? r Q a? M O N } 0 p ' N to LD C LO M ll? M M M M O ( M N Cn OR M M O M C- y r` N r\ o0 M W oO O 4 r O N M M N 4 X o 00 o M (0 00 M 00 o M o M (D 0 N 0 N 0 N N N - N - N N r, N N L11 M M M M M M M M M O O M M M M y O N M M O M r M N M M d (D M N LO 00 00 00 M M M M 0 0 0 e '- N N Q) r ?t 00 N d W LO C O O ?t CD o r` O O r- d tD M rl M ? r\ N r` CO M CD 00 M It r\ O N Cl) (D r- M L r\ 00 00 00 00 M M M O O N N X M M M O (D (D CD (D r, r, r` r\ r\ n r\ r\ W C O C N o CD O 0,2 a C ' C p C O 0 co c t> O C Co to tr O U V U ~ O E U p ?s o my E ?) ?>. C co ?L) C O .. c9 7 -0 co O y oo . =„ 0 CL W U a+ O a ` O C X U) d y E 0 N M LO (D Q= Q) Q N 0 p .- (ri O 7 M LL C a? U 'a a? 'D N N C 0 co a O C O C O CL E M N io J Ip se Because there were no on-site gage data, the HEC-1 computer models could not be calibrated. The models were validated by comparing the 100-year peak discharges estimated from the HEC-1 models with peak discharges estimated by regional formulas for the Piedmont region of North Carolina in the USGS Water-Resources Investigations Report 87-4096. NRCS curve numbers for the HEC-1 models were adjusted until the HEC-1 peak discharges were within 25 - 30 percent of the regional formula values. Table 2 summarizes peak discharges estimated by the validated HEC-1 model and the regional equations. Hydraulic Analyses Water-surface elevations of the 5-, 10-, 25-, 50-, or 100-year floods of Bob Branch were estimated using the USACE HEC-2 computer program. Channel cross sections for the hydraulic analyses were obtained from digital orthophoto maps prepared by Geodata Corporation with a contour interval of 1 foot. Aerial photography was taken in April 1999. Roughness coefficients (Manning's "n") in the channels and on the overbank areas were taken from FEMA studies previously conducted in the area and verified with field inspections of the sites. Roughness coefficients were 0.06 in the main channel and 0.12 for overbank areas. Starting water surface elevations and energy slope for existing conditions were estimated using data from the HEC-1 analysis and digital orthophoto maps. The slope-area option provided by the HEC-2 model was used to estimate the water surface elevation at the beginning cross-section. Model Results: Existing Conditions Table 2 summarizes the water surface elevations for existing conditions. Figure 8 depicts modeled flood elevations for the 5- and 100-year, 24-hour storm event. The model suggests that Bob Branch overtops its banks on an interval as small as five years. Frequent overbank flood events (1-year return interval) have likely been effectively eliminated along the entrenched channel under existing conditions. Model Results: Proiected Post Restoration Conditions Several restoration alternatives were evaluated in the hydraulic model to determine the change in flood elevations for various storm events. Modeled alternatives include in-stream weirs located at systematic intervals within the entrenched channel. Twelve structural arrangements were modeled, including cross-vane weirs spaced at up to 150-foot intervals within the channel. Channel cross-sectional areas were subsequently reduced along with profiles above 10 and below each structure. The structural arrangement was also modified to establish a pool to pool spacing characteristic of natural channel design. The selected alternative maximizes wetland restoration/creation area associated with the design. In summary, a series of greentree impoundments is proposed beginning at a channel elevation of 681 feet. The impoundment weirs will be designed to allow unrestricted channel flows during periods of increased probability for large (tropical) storms. The series of weirs Ip 30 10 _ ? AJ S Y o ? V N m W G 0 ° m MAP COMPILED BY PHOTOGRAMMETRIC METHODS. C C7 0 m CP z x ? x v x m m o W Ul r-'O 0 r? '09 X X e e ;u 0 0 0-< ox m z U) ( :j 0 O m °;u 0m D z O z O 0 m x Mtn 4 O7 U) Z 07 D -4 ?z D z ?o r- o m O c z C 00 z 00 z0 z 0 (n ;u o 0 z Z o Z N N x CPm? t? \?\ -4 1, t W 0 O rn 0 0 ?UI? WNW m K W s m z -I ?? m V V V V V V rrl < g W N N N O V OD CJI D7c _I om zz i M - 2 f m VVVVV? c NNN -+-: = V? D m 0)WO o z12 ?x \o ti ?¢ K / N ?m U (A a) z C' Z ? / ? ? CtD O . ?C 1'D I cn r w MATCHLINE SHEET 1 W ^ MATCHLINE SHEET 2 .'1 I co z 0 m N O o? c- cu ooc 4z -q o rs O.{ O v• m cn D? O z h2 E' m m v m -n n v? o 0? aoo o 00 - *? z N ZR1?=Z =m ?Z? A ? ` o r m Q m 0 C: cc ? m 0 'A n cn m 0( O r- -Z-I a o (7). m c m ? o ?0 C N CD 1' 0 o 0 N? m z z D• ?mD fD 14 Ul 0 - Ma Lip-i L= UM O D O D t C U N 0 O n it M Z m m m 0 L4 0 0 MATCHUNE SHEET 1 MATCHUNE SHEET 2 / ? n L00 0 I 1 I Q ? ? o 1 1 i ?? 0 -no -0 X x e ? r 0 O O-< O m Z N -i N -a o 0 m m o? v m ?1 Q r D N TI X I m r j c z co ?z z ?a o m a z 00 z o Z z 0 v O N 0 O z v 0 O z U) N MAP COMPILED BY PHOTOGRAMMETRIC METHODS. Z, / r cu w Cr A m Z 'z ?ZZ\- A- \ s? l x ?\ _ 1 X"?\ l ? N n m W 0 0 M z M -a m _ MCu rm- o? X ? ?1 i y) ? o cno J'1 vmci m\ m -n ;u o m c- a) I DD m0 f m /J ;u =v°m --4z AIL // l /? _J c-,p LA m M N z k_ 0 0 m & - w tO ODV W(T?A WNW m K y0 A m z m me rm jVVVV000 MM <? O O O 0 to W W Co N O D 7C V? ? ?O 0 0 M z z m - Z r V V V V a) Q1 Q? Q) Q1 Q) < ( j 0 0 0 0 1. c0 ip Dv 00 Du cornw0-4Ln Corn. ; o:E z? 2 'o -OZL? \\\\ m n o o 'f1 N ? ()0 Zmm r p?q ;u o r a O W a -?m0 m ° _1) Z O o w No -? UI O ° ?,b bf?n' Sips JJJ ° m m - o? D- 0 G) Dcc = m ? o m Zp 0 o? w M ? 0 O 0 r 0 ? ? m Z Z n 1 v ? 0 l .?1 n O O A m z J \ 1 o O z 1 ?•. O•n ? C'D were modeled with top elevations of 684 to 726 feet. The results oft he projected post- restoration model are depicted in Table 2 and Figure 8. Restoration me}ho ds are designed to reduce the channel from 5.5 feet in depth below the floodplain to saturated / inundated conditions at the floodplain surface during the winter and early portions of the growing season. The weir and associated water levels would be lowered during the remaining portions of the year. The model assumes that the weirs will be left in place during large storm events in the winter months. However, maintenance planning recommends that weirs be lowered prior to large storms, if possible, to prevent damage to the structures. 4.3 GROUNDWATER MODELING Groundwater modeling was performed to characterize water table elevations under historic (reference), existing, and post-restoration conditions. The groundwater modeling software selected for simulating shallow subsurface conditions and groundwater behavior at the Site is DRAINMOD. This model was developed by R.W. Skaggs, Ph.D., P.E., of North Carolina State University (NCSU), to simulate the performance of water table management systems. Model Description DRAINMOD was originally developed to simulate the performance of agricultural drainage networks on sites with shallow water table conditions. DRAINMOD predicts water balances in the soil-water regime at the midpoint between two drains of equal elevation. The model is capable of calculating hourly values for water table depth, surface runoff, subsurface drainage, infiltration, and actual evapotranspiration over long periods referenced to climatological data. The reliability of DRAINMOD has been tested for a wide range of soil, crop, and climatological conditions. Results of tests in North Carolina (Skaggs, 1982), Ohio (Skaggs et ai. 1981), ' Louisiana (Gayle et a/. 1985; Fouss et aL 1987), Florida (Rogers 1985), Michigan (Belcher and Merva 1987), and Belgium (Susanto et ai. 1987) indicate that the model can be used to reliably predict water table elevations and drain flow rates. DRAINMOD has also been used to evaluate wetland hydrology by Skaggs eta/. (1993). Methods for evaluating water balance equations and equation variables are discussed in detail in Skaggs et a/. (1993). DRAINMOD has been modified for application to wetland studies by adding a counter that accumulates the number of events wherein the water table rises above a specified depth and remains above that threshold depth for a given duration during the growing season. Wetland I? hydrology is defined as groundwater within 12 inches of the surface for 28 consecutive days (12.5 percent of the growing season), and 11 consecutive days (5 percent of the growing ' season). Wetland hydrology is achieved in the model if target hydroperiods are met for more than one-half of the number of years modeled (i.e., 16 out of 31). Groundwater drainage contours are established on available mapping for various durations of saturation within 1 foot of the soil surface (i.e. saturation contour for 0-5 percent, 5-12.5 percent, and 12.5-20 percent of the growing season). '? 33 I Model inputs for DRAINMOD simulations were obtained as follows: the United States Department of Agriculture (USDA) soil texture classification, number of days in the growing „ season (defined as March 26 - November 6), and hydraulic conductivity data were obtained from the NRCS soil survey for Randolph County and Guilford County (USDA unpublished, USDA 1977). Inputs for soil parameters such as the water table depth/volume, drained/upflux relationship, Green-Ampt parameters, and water content/matric suction relationship were obtained utilizing the MUUF computer software developed by NRCS. Precipitation and temperature files were obtained for the years 1930 through 1980 for Charlotte, North Carolina. DRAINMOD simulations were designed to predict the transition zone from Chewacla soils to Wehadkee soils based on groundwater drainage conditions within a relatively flat floodplain surface. Chewacla soils represent a non-hydric (non-wetland), somewhat poorly drained soil that is common on primary floodplains immediately adjacent to streams. The Wehadkee series comprises hydric (typically wetland), poorly drained soils that are typical in backwater floodplain areas situated further from drainageways. ® Forested conditions (evapotranspiration rates) and published hydraulic conductivity values were assumed for Chewacla soils. The simulations were run for six channel inverts (0, 1, 2, 4, 6, and 8 feet) and at various target hydroperiods during the growing season. Table 3 provides a depiction of the groundwater discharge zone of influence by invert depth (elevation below floodplain). For example, a stream channel invert 6 feet below the floodplain elevation is modeled as reducing surface hydroperiods below 5 percent of the growing season at a distance of 215 feet from the channel. A former floodplain surface 6 feet in elevation above the channel invert and greater than 215 feet from the channel is projected to support wetlands. The preliminary groundwater drainage model was interpreted based upon field verification of NRCS soil map units, channel depth (based on measured cross-sections), and floodplain elevation (based on topographic maps). Model parameters were set to predict the average annual duration in which groundwater remains within 1 foot of the soil surface at assigned elevations above a channel invert or in-stream structure. The floodplain elevations outside of the groundwater drainage contour and at the modeled channel depth were judged to have a hydroperiod greater than 5 percent. Post-Restoration Model Applications and Results For groundwater wetland restoration, the primary objectives of this project include 1) reduce channel incision along Edgar Branch and associated tributaries, 2) elevate the groundwater gradient into the rooting zone for developing vegetation, and 3) establish minimum wetland hydroperiods encompassing 5 percent of the growing season, which are typical for riverine wetlands in the Piedmont hydrophysiographic province. Therefore, the effective post-project depths of the Edgar Branch channel will be reduced from an average of 5.5 feet under existing conditions to gradients between 1 to 3 feet below the floodplain. 34 P ?e ?e ?s ?e ?B ?e ?e ?s ?e ?e ?e ?e ?e ?s ?a Table 3 Modeled Groundwater Discharge Zone of Influence on Wetland Hydroperiod Chewacla / Wehadkee Soil Floodplain Groundwater Number of Groundwater Number of Surface Discharge Zone Years Discharge Zone Years Elevation Above of Influence2,3 Wetland of Influence Wetland Channel Invert / (feet) Criteria (feet) Criteria Weir Height' (Surface Met (Surface Met Hydroperiods <5% Hydroperiods < (feet) of the growing 12.5% of the season) growing season )4 Forested Conditions (relatively high surface water storage and rooting functions) 0 ----- 29/31 ----- 27/31 1 253 20/31 145 16/31 2 85 16/31 225 16/31 3 125 16/32 275 17/31 4 160 16/31 315 16/31 6 215 16/31 380 16/31 8 245 16/31 405 16/31 1 : "Weir Height" is assumed to represent the effective depth (invert) of the drainage feature. 2: Soil hydraulic conductivities and drainage rates have been generalized based upon NRCS data and regional averages. 3: Discharge Zone of Influence is equal to %: of the modeled ditch spacing 4: Based on field observations, soil types projected to support wetland hydroperiods for greater than 5 percent to 12.5 percent of the growing season are expected to exhibit characteristics more indicative of the Wehadkee series, a poorly drained soil. Based on the model, these areas may occur on floodplains within 25 feet to 200 feet of streams potentially lacking significant effluent (groundwater withdrawal) character, such as very shallow channels. Conversely, the model suggests that the transition from Chewacla soils (somewhat poorly drained) to Wehadkee soils (poorly drained) may be achieved adjacent to larger (dredged) effluent channels at distances ranging from 300 feet to 400 feet from the drainage structure (assuming a relatively flat floodplain surface). 35 DRAINMOD simulations modeled the zone of influence of the post project channel on wetland hydroperiods within the primary floodplain. The maximum zone of influence may be used to predict the area of groundwater wetland hydrological influence that may result due the elevation of stream flow within the channel. In addition, the model provides an estimate of the area that may continue to be affected in perpetuity by the stream channel at a depth of 1 to 3 feet below the floodplain elevation. Based on these simulations, the post-restoration channel is expected to continue to effectively drain groundwater from the Chewacla soils within the map unit. Model simulations indicate that a series of in-stream weirs placed to within 1 foot of the adjacent floodplain elevation may not restore significant areas of wetlands in Chewacla soils. A channel invert 2 feet below the adjacent stream terrace continues to effectively drain an area 85 feet adjacent to the drainage feature. Gradual slopes in remaining portions of the outer floodplain are projected to continue draining towards the modified stream channel. Therefore, in-stream weirs do not provide a viable option for wetland restoration based on the groundwater model. To create wetlands, greentree impoundments will be required to elevate the groundwater surface above the floodplain elevation (immediately adjacent to the channel) periodically throughout the year. 4.4 REFERENCE GREENTREE IMPOUNDMENTS Established greentree impoundments within the Piedmont of North Carolina were visited to measure wetland attributes, review various structural designs, and to discern management strategies employed. Reference systems include the Rocky Branch impoundment above Falls Lake in Wake County, the Country Line Creek impoundments in Caswell County, the Beaver Creek greentree impoundment above Jordan Lake in Wake County, and the Little Creek impoundment to Jordan Lake in Durham County (Figures 9-11). These impoundments have typically been located above water supply reservoirs in the region to replace wetland habitat inundated by the reservoir, provide waterfowl habitat, and control sedimentation. Controllable weirs range from concrete dams and electronic sluice gates on larger tributaries to corrugated metal pipe using flash-board risers on smaller systems. The associated dams typically consist of an earthen causeway with rip-rapped emergency spillways and erosion control areas. Dams likely to be overtopped within watersheds greater than 10 square miles have often been reinforced with concrete materials placed on the earthen dam. IN Figure 12 provides a conceptual depiction of a typical weir and dam for greentree impoundments within watersheds ranging in size from 2 to 7 square miles. The weir consists of two 4-foot wide slots with wooden flash-board risers used to control the water surface elevation. For this application, the flash boards could be completely removed to provide for existing channel flows during summer months, planting periods, or for other management purposes. 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D --1 m o z - i i i i i i i i i i Oo mA -?i MU) ?z 0 x zz m r 0 m O U) m n 1 O Z W i i i i immA J ?5 .4 ;z i a '1 O y T n N n /? ca CD V ?o ' m 3 ?o ° z Duo ° O v M ° D c? mco n G7ar =Z =D0 G7 -I cn 9 ° Z EC D Or -? r o No zr m Z Z D ° ?1 1 0 ?O n O Cl) m n O Z D D i m;o ? v N .D r r f mm tnm (40 co 0 ;U(n COz 3;-4 ME! 'V-4 ;u r,z z C) ;up -Zi = o r J z c r z ZO Ko vm?o cz m--4 me o v 2 OMm I=m *m m-4 vi ?m op oz N o v r r -DC G O ?J M O O s .. . Z 1CD $s 0 o VARIFC MIN sn 9p to IN the weir used at the Edgar Branch Site may be modified during the engineering design phase to reduce flood potential, increase potential for stability, and/or other management concerns. A profile of the Country Line Creek impoundment in Caswell County was measured to evaluate wetland development relative to the dam height, typical winter weir height, summer weir height, and valley slope. Figure 13 provides a depiction of the reference greentree impoundment characteristics, including vegetation development patterns relative to water surface elevations. Within the reference greentree impoundments, stream channels have been obscured due to alluvial sediment deposition and vegetation development patterns. The stream channel has been altered to the extent that wetland characteristics typically occupy the entire impoundment land area, up to the water surface elevation established during winter months (Figure 14). 4.5 REFERENCE PLANT COMMUNITIES In order to establish a forested wetland system for mitigation purposes, a reference community must be established. According to Mitigation Site Classification (MiST) guidelines (EPA 1990), the area of proposed restoration should attempt to emulate a Reference Forest Ecosystem (RFE) in terms of soils, hydrology, and vegetation. In this case, the target RFEs were composed of steady-state woodlands in the region that have sustained loading of fluvial sediments on floodplains in the past. Forest canopies have developed on these reference sites which support soil, landform, and hydrological characteristics that restoration will attempt to emulate. IN All of the RFEs have been impacted by sediment deposition, selective cutting or high-grading, channel migration/disturbances, and relatively high energy flood events. Therefore, the species composition of these plots should be considered as a guide only. Reference forest data used IN in restoration was modified to emulate steady-state community structure as described in the Classification of the Natural Communities of North Carolina (Schafale and Weakley 1990). Two RFEs were selected within floodplains along the Rocky River in Cabarrus County, North Carolina. Floodplains associated with this river system have aggraded over the past century, inducing braided channel configurations and accelerated sediment deposition within reference feeder tributaries. Sixteen plots have been placed within relatively mature, bottomland hardwood/swamp forests that have developed on accreted sediment. IN 11 The reference vegetation samples are designed to characterize the plant communities proposed for restoration. Circular, 0.1-acre plot sampling was utilized to establish base-line vegetation composition and structure in reference areas. Species were recorded along with individual tree diameters, canopy class, and dominance. From collected field data, importance values (Brower et al. 1990) of dominant canopy and mid-story trees were calculated (Table 4 and Table 5). The composition of shrub/sapling and herb strata were recorded and identified to species. 41 mm gnu din cn z eLlC)D dm? 0 ° Mzz CL99 cn o 00 0, Co c 0 rz Z om n o Cn m m? Um-? 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T- -i__ " 1 1 1 1 1 I 1 1 1 I I 1 1 I I I 1 I 1 i 1 1 1 I I 1 1 1 1 1 1 1 I 1 I r 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 I 1 I I 1 I 1 1 1 1 I 1 I I I 1 1 1 I 1 1 1 1 1 I I 1 I 1 I I 1 1 1 1 I I 1 1 1 I 1 1 1 1 1 I I 1 1 1 1 I 1 1 1 I 1 1 1 I 1 I I L I 1 I 1 1 I 1 1 I I 1 I I 1 I 1 I I 1 1 1 I I I O N (jl -*1 cn r O r cn N G) O 0 X O N N N M N n Cn O z N Ln O V Cn V/ 0 N m 0 O z O Cn C7 Elevation in Feet ° 0 0 0 O O N ? 1 1 1 1 -r 1 I I 1 1 I I -t- -I- -I- -r -r -r -r 1 I I I I I I 1 7- ti- -1- -r r -r -r -r _ L I -1- 1 ti- I -r 1 -r 1 I -h - 1 -h 1 -r J_ J_ _I _L 1 1 1 i 1 I I 1 1 I I 1 I 1 ?- -I' -r -r -r -r -F J- J- -1_ -4 -4 -4 -4 r -I- -r -r I I -r -r -r I 1 1 1 1 I I 1 1 1 o i- r -I- -r -r - _ - r J_ J_ _I_ _L _L L -L 1 n- 1 1- I -1- 1 -r I 1 - r 1 -r I r I ?- 1 -1- 1 -r I r -r I -r 1 1 1 1 I I I ?- ?- -I- -r -r -r 1 I I 1 I 1 1 J_ J_ J I - _1_ i _L _L I I i r I r ti- r ti- yr -1- -r -r -r -r r -r r - -F -/- -1- -1- -L 4 - 4 1 ? 1 1 1 I 1 J_ J_ J_ _L _L L -4 1 I I I I 1 I J_ J_ J- -L _L L L _L r n- -1- -r -r r -r 1 1 1 1 1 I 1 r ?- -I- -r -r -r - -r 1 1 1 1 1 1 I 1 1 1 I ?- r -t1 - -r - r -r -r 1 r 1 -I- I ?- I 1 -r -r I -r 1 -r I I 1 I I I 1 I '1- ti- -1- -r -t -h -r -r J_ J_ J_ -1- ti- -I- -r -/ -h -r -h 1 I r I -1- 1 -r I -r I I -r -r 1 -r I -r J_ J_ J- _L _L L _L _4 I I 1 I I 1 I r ?- ?- -r -r - -r -r I ?- I r 1 -r 1 -r I -r - 1 -r 1 -r 1 I 1 I I i 1 I ti- -1- -1- -r -r -r -r -r I I 1 1 1 1 1 1 1 1 1 1 I 1 1 I J- 1 I- -1 J 1 I -1 I_ 1 ' 1 _L 1 _L 1 i' -r -r 1 - r - r r - r - r J_ J- -1- -1- -L L -4 -4 fi ll 1 r 1 ?- I -I- 1 -r 1 -r -r 1 -r 1 -r J- J_ J_ _L _L _L 4 _L r r r -1- -r I -r -r r -r I I 1 1 1 I 1 1 ?- ?- -I- -r -r -r r -r 1 1 1 I I 1 I I ?- -1- -1- -r -r -r -r -r I I 1 _L I _L _L 1 I I N m(° 0 0 0 N CO O N ? Ln z _ o =r rrn (D n 00 O 7 1 rn rr (D D? (D r. p 37 on ? "rl =i p (D n rr-r 7 O? 7 Elevation in Feet ° 0 0 0 O O N -P m Cp O N .0. I 1 1 I 1 1 I I I 1 Y 1 1 1 I -t- -I- -1 +M -r -r -r -r I 1 r 1 1 I 1 I ti- ti- -r -r -r -r -r 1 1 I 1 I I 1 ti- J_ -1- J_ -r -r _L -r _L -r _L -r _L 1 1 1 I 1 1 1 I I 1 1 1 1 1 1 I I ?- I -I- 1 -I- 1 r I -r I -r I -r I -r 1 1 I I I 1 1 I 1 1 1 1 1 1 1 I r ?- ?- -r -r -r -r -r I ?- 1 ?- 1 ? 1 -r 1 -r 1 -r I -r I -r I r -1- -r -r -r - r -r 1 ti- 1 ti- - I -I- I -r I -r I -r I -r I J_ J_ _L _L I I ' 1 I F 1 1 I I I I •?_ y_ - -I- -4 -4 - _r 1 1 I 1 I I J- J- - -L -L -L - -L I I 1 I I 1 1 I I 1 I I t 1 1 1 1 1 1 I 1 r 1 r 1 ? 1 -r 1 -r 1 -r I -r 1 I I 1 I I 1 I 1 1 1 1 I I I 1 1 1 I I 1 I ?- r -1 -r -r -r - -r 1 1 I I 1 1 y- -1- -1 -r -r -r -r I 1 1 1 I I ti- -1- -r I -r I -r _L -r _ L 1 1 I 1 I I 1 1 I -r 1 1 I I ?- -r I -I -r -r - -r 1 I I I I 1 1 1 1 I I 1 r r ? -r -r r - -r 1 1 I I 1 I I r r -r -r -r - -r 1 _L _L -L 1 -1- I r- I -r I -r 1 -r I I -r -r J- J_ J _I_ T. _L L _L _L 1 1 1 Y r _? _L _L r -1- r -r -r -r -r -?- ?- 1- -I- -L -4 -4 _4 1 4 - r ?- - -r -r 1 -r: - r -r J- J_ J _L _L _L -L _L r n- - -r -r -r -r -r 1 I r r - -r -r " -r -r -r I r I r ?- ? r -IL -r - I L -r _ I L -r _L -r 1 1 I I I I I (A O O Un O O) O v O CO O O = O N O j O N. O 7 n (D N _ O 7J (D u O r+ O Cn O (n O v O Cb O 8 O m n o 0 y ? n 0 CO m ° °70 o z 01 Colo) m gC) ?.? " o0 v??v G n? m 2 ?? A D r ? o m Z m " y w m z OZ ra- Z o F? ?0? fTi o c- n /1 v J Q v /11 O 22 z 1?'+1?. r W CD C: Fn Z o N O ? m z --1 0 Z0 14 0 . ? D ao s s O C? > N v m0 p Ul ? °o z Coll) C4 O 0 O Cu Cr) C o r r v O Cro O (O = O O 0 O N 0 p 7 N O o 0 X O -:t N O o 7 1 n U) (D m N _ C7 O 7 O z G( 0 O 41, O Ln O M O CA v n O m o° z O O _ W W C7 At Site 1 (Table 4), the forest canopy is dominated by green ash, (Importance value (IV) 28 IN percent), sweetgum (Liquidambarstyraciflua) (IV 19 percent), American elm (Ulmusamericana) (IV 11 percent), box elder (IV 8 percent) and red maple (IV 7 percent). Canopy species with lesser importance include black willow, slippery elm (Ulmus alata), river birch, tulip poplar, and water oak (Quercus nigra). Understory trees include flowering dogwood, ironwood, and sugarberry (Celtis laevigata). A developed shrub layer is not generally present. Herbs include Nepal microstegium, violets (Viola spp.), asters (Aster sp.), and river oats (Chasmanthium latifolium). At Site 2 (Table 5), the forest canopy is dominated by green ash, (IV 39 percent), box elder (IV 22 percent), American elm (IV 12 percent), and swamp chestnut oak (IV 6 percent). Portions of the canopy at RFE locations were also dominated by ironwood, overcup oak (Quercus lyrata), sugarberry, sweet gum, red maple, black willow, slippery elm, water oak, and river birch. The shrub/sapling layer is characterized by the non-native Chinese privet (Ligustrum chinensis), paw-paw (Asimina triloba), and shade tolerant canopy species. IN Herbaceous species include Japanese honeysuckle (Lonicera japonica), blackberry, muscadine, common greenbriar, sedges (Carex spp.), and poison ivy. Piedmont swamp forests are communities located in depressional areas, along toe slopes, and at the confluence of alluvial valleys, where lateral flow is restricted. These sites are hydrologically influenced by upland seeps and drainages, and by occasional riverine flooding. Overstory species are dominated by flood-tolerant bottomland elements such as sweetgum, American elm, willow oak (Quercus phellos), swamp chestnut oak, green ash, overcup oak, and swamp cottonwood (Populus heterophylla). Wetter sites may provide a broken to open canopy providing enough light for development of a dense herbaceous/shrub layer. Species found on these sites may include button-bush (Cephalanthus occidentalis), elderberry (Sambucus canadensis), silky dogwood, false nettle (Boehmeria cylindrica), sedges (Carex spp), rushes (Juncus spp.), and lizard's tail (Saururus cernuus). Giant cane (Arundinaria gigantea) is prevalent in scattered locations. is ?B ?e 44 b so 'o b b b ?o ?o sa so ea ao ae BD ?a TARI G A Reference Forest Ecosystem Plot Summary Bottomland Forest (Canopy Species) Tree Species Number of Individuals' Relative Density (%) Frequency' Relative Frequency 1 /o) Basal Area (ftZ/ acre) Rely Basa 1 Fraxinus pennsylvanica 41 31 6 17 38.8 Liquidambar styraciflua 32 24 5 14 20.7 Ulmus americana 18 14 4 11 9.0 Acer negundo 8 6 3 9 8.7 Acer rubrum 11 8 2 6 8.5 Salix nigra 6 5 2 6 7.3 Ulmus alata 4 3 3 9 1.3 Betula nigra 2 2 2 6 0.7 Liriodendron tulipifera 3 2 2 6 2.2 Quercus michauxii 1 1 1 3 2.6 Quercus nigra 1 1 1 3 1.5 Celtis laevigata 3 2 1 3 1.8 Cornus florida 1 1 1 3 0.2 Platanus occidentalis 1 1 1 3 0.4 Prunus serotina 1 1 1 3 0.4 TOTALS 133 100 35 100 104 1 Summary of six - 0.1-acre plots 45 10 90 IB 9p io la Lf) W J m Q O E N E .O M O O a > 0 E o CD c «. co ? U 0 O N W c N LL O C U. U O C .O. c a) m O tr a? U U ? C 0 .O`. o M M N N N r (D In to t!) N N ?- O r O 0 a E 0 0 > 7 m co LO L&O M O '- ?- O N O O O co am c m Q O `U Q M O 1" w .- ?- O M ?- M •- M ` O 1? I? O '- to r` '- O O O ?- H w LO r- ? ? 0 0 0 0 C3 > C co 7\ (D N M N M M 00 OJ lD M M M M O .- cr .r Q tr U- c U C ai 7 O r M M M N .- r- .- Q) co O' a) U. d c~o r- OR \ N It co N O r tD co r- O .- cc O y 0 :3 CN LO O) E > ' 0 v Z c ro U ` c ro ro c ;o co c a) 3 ro ro to C c % ro e o 12 c H d N O U V O ro ? co U D O ?p C h . C G) d j ro j j j . J co j J u? ,c c y ? .c c, .y c ti .c y Q O - x ro i U ? Q) o d ro U ' d a) U M ? J ? ?' O 1 ? Q N r-. 0 CL Q) U f9 r 0 c O c`9 E (D It 5.0 WETLAND RESTORATION PLAN This restoration plan has been designed to establish wetlands within watersheds situated immediately upstream of the Randleman Reservoir. A greentree impoundment is proposed to establish contiguous wetland presence within 37.0 acres of Edgar Branch floodplain at elevations ranging from 676 feet to 719 feet above mean sea level (Figure 15). The area of wetland restoration is a subset of the area within the project boundary, which is defined as the limits of the 5-year, post-project flood elevation. Wetland restoration or creation comprises approximately 30.7 acres of the total wetland presence. This area is composed of actively inundated land surfaces, and passively formed, saturated wetlands within 1.0 foot in elevation above the impounded water surface. Based 1 on reference studies, the one foot delineation of passively formed wetlands constitutes a conservative estimate of the extent of wetland formation expected. (See ESC 2000a and ESC 2000b for a description of the passive formation of wetlands). An additional 5.4 acres of the mitigation total is composed of open waters. The shorelines of these areas are expected to accrete as sediment deposition within the impoundments progresses. Submerged, emergent, and shrub/scrub aquatic vegetation is projected to colonize these areas. Finally, approximately 0.9 acres of the mitigation area is comprised of pre-existing wetlands. These areas will be preserved or enhanced during impoundment construction. Enhancement activities will include hydroperiod regulation and improvements in buffer vegetation. The green tree impoundment comprises an embankment (flood lain levee) and weir (controllable outlet structure). The elevation of the outlet is typically raised during the winter months, while trees are dormant, to promote ponding, sediment deposition, and wetland habitat. The elevation of the outlet is lowered in early spring to allow for vegetation growth, nutrient uptake, and seedling establishment. For this project, the outlet may only be raised during a brief portion (5 percent to 12.5 percent) of the growing season until wetland communities and associated habitat are successfully restored. Subsequently, the period that the outlet is raised may be incrementally increased during the winter months each year to increase inundated wetland habitat for water fowl and other species adapted to use of greentree impoundments during winter months. The long term objective of wetland restoration/creation by greentree impoundments is to maintain forested wetland communities to the maximum extent feasible. Therefore, long term management will be required. A management plan has been prepared (Section 8.0) for long term maintenance of the impoundment over the life of the Randleman Reservoir. Management techniques for greentree impoundments surrounding the reservoir will be managed according to constructs outlined in the Greentree Reservoir Management Handbook (Fredrickson and Batema 1996). 47 1--:J Lz? 0 r, ? O ] CJ ? ? O D ?] p O C G?- 00 \ Ile, s? W N 0 0 O M Z m m -I 0 .s N 'D n m w 0 o w < 0 o m 0 0 \ • ?U y3 ? Q V I t? 0 0 cl, i f ?2 = z? y? j :iA Ql? Sam/ VA ? - I ? 0 o v m K x X x e r r m -I w vn cn N m z r D Z =I ;u U) ° o c) o c- D ? -? m --4 0 O m ;u z 0 m O C v ° Z 0 z Z c i N z i m c 00 N n --I CA C) I 0 + IT w z MAP COMPILED BY PHOTOGRAMMETRIC METHODS. 'a Nm? TL ti w ' m m CA Al ;alp 1?'?? CO r 1 Wn MATCHLINE SHEET 1 MATCHLINE SHEET 2 m n n u CD o i _ m= m z ?m -4 v ' O? 2 D ?Dv m cog = Z SZ o = m o 7D nmm D 0 in m Or? it z -40 U) 9 0 r- %J N pG? Z O_D m z z z0 D7v D J? O 0 L m y M - m ?(TP W N? K m m z m me rm V V V V V V M < g _ _ CA P.3 K3 0 NJ m o zz z i m - N N N J J D m O? z r^ C) O O N o (/, • CD T s l? w? m L I ] L. J Imo- mj L J L 1U I __- - t' - O O = 0 I Q W O N O 0 M M M O U 0 0 I I 1 01 o ? CD . I o ° m r. X X v X r 0 a C) 0 0 Y, 4 co U) n o m ? X o z 0 m 0 o ;u z Z Z O N :U v i m c ? co w ?°, - + I t + y z MAP COMPILED QY PHOTOGRAMMETRIC METHODS. ?r0 J -0? MATCHLWE SHEET 1 MATCHUNE SHEET 2 ?w f w ti x E.S ? ?a x «? N 'fl o m 0 C 0 o m 0 ?x aj a y? AT, A + \?+1/11? w w w i K? J n n m m ?= m m z Qm a m ;a > CA m r Z?O N -4 mm 0 o0 W o _ ? o mG n? rAi ?. O n o O C/) F _ - I ? rD m K mm p c0 co V Om Ui -N (A D Z m z -4 P ? ? V V V V V M O)O)Q)Q1 m Gg OOpc0OcDt0 NO D7C V -P(1?N0 M 00 om zz z r .rVV-4mC" mrnrn OOOOcDtO?pOD0o0D mm D? oo rn c,, o v cn oo rn -??• ? o? z? ° u O Cll ? 1 I 10 Components of this plan have been established based on reference wetland studies described in Section 4.0. This effort will be performed by 1) installing a series of sixteen controllable weirs and dams, 2) woody debris deposition, and 3) planting of target wetland tree species 10 in the area. Monitoring of wetland development will be performed to track successional characteristics of the Site and to verify wetland restoration success. 5.1 IMPOUNDMENT / WEIR CONSTRUCTION A series of greentree impoundment structures consisting of 16 embankments will be constructed within the Site, as depicted in Figure 15. The impoundment series begins just within the conservation pool of Randleman Reservoir (682 feet). Construction of impoundment and weir structures may be subject to restrictions under the North Carolina Dam Safety Law of 1967 (GS 143-215.23). Detailed construction plans will be described in the design engineering phase of the project. Embankment The embankment series will be constructed with crest elevations ranging from 688 to 730 feet above mean sea level. The embankment elevation may be modified during the engineering design phase to provide increased capacity for transporting floodplain flows across or around the structure. As proposed, the embankment surface will reside up to four feet in elevation above the existing floodplain surface. Weir The weir (outlet structure) will be designed to allow for open channel flow at base levels of 710 feet or below. The weir design will allow raising of the water surface to 714 feet during impoundment periods. Figure 12 provides a conceptual depiction of the proposed impoundment structure including target elevations for the winter water surface and embankment height. The design or placement of these impoundments may be modified during the engineering design phase based on potential stability, constructability, cost, or other constraints. 5.2 WOODY DEBRIS DEPOSITION Woody debris, including downed trees, tip mounds, snags, and decomposing material represents important habitat elements for wetland dependent wildlife. Therefore, woody material generated from embankment construction or other Site activities will be distributed across future wetland surfaces to the extent feasible. The material may be lifted or pushed from adjacent windrows or forest areas as well. 5.3 WETLAND COMMUNITY RESTORATION Restoration of wetland forested communities provides habitat for area wildlife and allows for development and expansion of characteristic wetland-dependent species across the landscape. Ecotonal changes between communities contribute to diversity and provide secondary benefits 50 J jl In 0 such as enhanced feeding and nesting opportunities for mammals, birds, amphibians, and other wildlife. RFE data, on-site observations, and ecosystem classification has been used to develop the species associations promoted during community restoration activities. Target plant community associations include 1) bottomland hardwood / swamp forest, and 2) scrub-shrub / swamp forest. Scrub-shrub elements will be targeted toward areas immediately behind the impoundment within the construction limits and along the stream channel banks (Figure 17). Planting Plan The planting plan consists of 1) acquisition of available wetland species, 2) implementation of proposed surface topography improvements, and 3) planting of selected species on-site. A total of 36.4 acres of the Site will be planted in a random distribution, including the species listed below. Planted areas consist of restored/created wetlands and preserved/enhanced wetlands, and do not include open waters. Bottomland Hardwood / Swamp Forest 1. Cherrybark Oak (Quercus pagoda) 2. Overcup Oak (Quercus lyrata) 3. Willow Oak (Quercus phellos) 4. Swamp Chestnut Oak (Quercus mlchauxli) 5. Swamp Cottonwood (Populus heterophylla) 6. Shagbark Hickory (Carya ovata) 7. Bitternut Hickory (Carya cordiformis) 8. Green Ash (Fraxinus pennsylvanica) 9 American Elm (Ulmus americana) 10 Winged Elm (Ulmus alata) 11. Tulip Poplar (Liriodendron tulipifera) Scrub-Shrub / Swamp Forest 1. Possum-haw (flex decidua) 2. Carolina holly (flex ambigua) 3 River Birch (Betula nigra) 4. American Sycamore (Platanus occidentalis) 5. Green Ash (Fraxinus pennsylvanica) 6. American Elm (U/mus americana) 7. Swamp Cottonwood (Populus heterophylla) 8. Overcup Oak (Quercus lyrata) 9. Swamp Chestnut Oak (Quercus mlchauxli) 10. Silky Dogwood (Corpus amomum) 11. Button-bush (Cephalanthus occidentalis) 12. Elderberry (Sambucus canadensis) 51 17 10 Species selected for planting will be dependent upon availability of local seedling sources. Advanced notification to nurseries (1 year) may facilitate availability of various non-commercial species. In full planting areas (existing agricultural land), the soil surface will be scarified. go Disking or ripping may be employed to create a rough surface for the detention of runoff and sediment, and to provide a more hospitable planting bed for tree seedlings. Then, bare-root rl seedlings of selected species will be planted within specified areas at a density of 680 trees per acre (8-foot centers). In existing forested areas, a supplemental planting will consist of 170 stems per acre (16-foot centers). Supplemental plantings will retain existing Site canopy trees, while introducing a greater component of wetland-dependent species. The total number of stems and species distribution are depicted in Table 6. Planting will be performed between December 1 and March 15 to allow plants to stabilize during the dormant period and set root during the following spring season. Opportunistic species, which typically dominate early- to mid-successional forests have been excluded from initial plantings on interior floodplains. Opportunistic species such as sweetgum, red maple, and loblolly pine may become established naturally. However, to the degree that long-term species diversity is not jeopardized, these species should be considered important components of steady-state forest communities. Planting of opportunistic species such as black willow will be targeted as stabilization elements in erosion control areas immediately adjacent to the creek. The planting plan is the blueprint for community restoration (Figure 16). The anticipated 10 results stated in the regulatory success criteria (Section 6.0) may reflect vegetative conditions achieved after steady-state forests are established over many years. However, the natural progression through early successional stages of floodplain forest development will prevail regardless of human interventions over a 5-year monitoring period. In total, approximately 20000 seedlings will be planted during wetland community restoration efforts. so so 52 :z 10 In s0 Ip TABLE 6 Planting Plan Vegetation Association (Planting area) Shrub-Scrub/ Swamp Forest Bottomland Hardwood/ Swamp Forest (full planting) Bottomland Hardwood/ Swamp Forest (supplemental planting) TOTAL STEMS PLANTED Stem Target (trees/ac) 680 680 170 ----- Area (acres) 5.4 19.4 11.6 36.4 SPECIES # planted M total) # planted M total) # planted M total) # planted M total) River Birch 400(10) 400 Silky Dogwood 400(10) 400 Button-bush 400(10) 400 Elderberry 40000) 400 Black Willow 200(5) 200 Possum-haw 200(5) 200 Carolina Holly 200(5) 200 American Sycamore 200(5) 200 Swamp Cottonwood 400(10) 1400 (10) 20000) 2000 American Elm 200(5) 700(5) 100(5) 1000 Green Ash 400(10) 700(5) 100(5) 1200 Swamp Chestnut Oak 200(5) 1400 (10) 200(10) 1800 Overcup Oak 40000) 1400 (10) 20000) 2000 Cherrybark Oak 1400 (10) 200 (10) 1600 Willow Oak 1400 (10) 20000) 1600 Shagbark Hickory 1400 (10) 200 (10) 1600 Bitternut Hickory 1400 (10) 200 (10) 1600 Winged Elm 1400 (10) 200(10) 1600 Tulip Poplar 1400 (10) 20000) 1600 TOTAL 4000 14000 2000 20000 53 ® ® ® 0?l9 ® L. .1 1.? J L.Z;j J UMM E ;1wJ .° P 4A 14 'vl l 1 Z. W w N 0D t m z M M m G1 0 0 0 w 0 0 4 ?y •? f 0 rn o ? 0 17 / 0 0 ° m m O ? v C C N N r c c -1 m r 0 0 U m z Az v °N 1 -4 (n m ;u N Y, C ?W r -n m o C) m o Z v Orn V rn N n ZY) CO -4 0 + IN I MATCHLINE SHEET 1 MATCHLINE SHEET 2 ? V ? O I m x X O r D 0 m rri A z Z 0 G7 0 n -4 Z -4 z z m r c 0 v m c z z 0 N N M c 0 z J ti rL m A ,r 1 . ? Q ?Ig ° I m 0 r 6 ° 31 - T p •v A w a m m .. N m .. M m v 'O -i Z 2 m 0 DOmv ?? co m i O O o M 0 D GAD z Zen DO m z l If, ZI m 0?-I A I 2 m e c- ;; ?m Aco " ? °v cn 0 ° 2 m z v m a v CD 0 M ?l f !i'l cn r? ® ?1 ®1 !S? ? Gt?l ?? Illy ?:! L :,r:? LJ L_:.:;J i1 l',J ? e? MATCHLINE SHEET 1 N Wo MATCHLINE SHEET 2 f-? N f 0 m z ? m m m 003 W N L 0 ? C N C? r L O. y y?? < z " rn o cu w z Z? A- m rn m -0 ? N N o o r x X Z Z 0` G7 G1 0 -4 ° m x / O I / x z co z W w M m JI/ ; i --1 z 1 J:. ` 0 rv to O Z v xi \\ C r ? \ x 0 o W <_ _x x 1 I 0 C2 - \\ J x '\ O n? 0 r '? x I J C-)• I ?-- 0 -u m 'v m g o z oN 1 Z m n 0 We Sao -02 0/ ?/ + ?+ o -+ ;u rt ? 1 J?X LJ c (i1 .jL, I+ I+ I+ I+ I m m? m x / O ?? In x \ or'i (r/n) cu x < ) S .) Al -? 2;o ov o n n j o n M m z G) m \( LyJ N" Z -4 m C 0 3 ?. O O ?' 'vD D D Z =D0 o ?d O z U) 9 r- O-1 0 W ° N n z? .D z0 ?D7o N O (? O WO 00 Z Z D m D (J 14 cn O It is ie ?s ?s 11 It I? 6.0 MONITORING PLAN The Monitoring Plan will entail analysis of the restoration area according to jurisdictional wetland criteria (DOA 1987). Monitoring will include the observation and evaluation of three primary parameters including hydrology, soil, and vegetation. Monitoring of restoration efforts will be performed for 5 years or until success criteria are fulfilled. 6.1 HYDROLOGY After hydrological modifications are performed, surficial groundwater monitoring gauges will be designed and placed in accordance with specifications in USACE's Installing Monitoring We//s/Piezometers in Wet/ands (WRP Technical Note HY-IA-3.1, August 1993). Monitoring gauges will be set to a depth of up to 24 inches below the soil surface to track water surface elevations in the impoundment relative to the weir height. All screened portions of the gauge will be buried in a sand screen, filter fabric, and/or a bentonite cap to prevent siltation during floods. Recording devices (if used) will be placed 5 feet above the ground elevation. Placement of recording devices at this height should guard against over topping for a projected 50-year flood elevation. The gauge will be stabilized from flood shear by reinforcing steel bar (re-bar). Nine groundwater monitoring gauges will be installed in restoration areas to provide representative coverage throughout the Site. Approximate gauge locations are depicted in Figure 17. Hydrological sampling will be performed during the growing season (March 26 to November 6) at intervals necessary to satisfy the hydrologic success criteria. In general, the gauges will be sampled weekly through the spring and early summer and intermittently through the remainder of the growing season, if needed to verify success. 6.2 HYDROLOGY SUCCESS CRITERIA Target hydrological characteristics have been evaluated using regulatory wetland hydrology criteria. The regulatory wetland hydrology criterion requires saturation (free water) within one foot of the soil surface for 5 percent of the growing season under normal climatic conditions. Success Criteria Under normal climatic conditions, hydrology success criteria comprises saturation (free water) within 1 foot of the soil surface for a minimum of 5 percent of the growing season. This hydroperiod translates to saturation for a minimum, 11-day (5 percent) consecutive period during the growing season, which extends from March 26 through November 6 (USDA 1977). If wetland parameters are marginal as indicated by vegetation and hydrology monitoring, a jurisdictional determination will be performed in the questionable areas. 6.3 SOIL Mitigation activities are expected to increase the deposition and transport of stream sediments during overbank flood events. As a result, soils (F/uvaquents) are continuously reworked by fluvial processes. Because iron reduction rates (gleying) are not spatially or temporally uniform 56 ® ® ® l L h ,?/ A .` o O LAI W cn O 0 O P z m m m O k' I w jr? i X S' W I c\ x (r ? ? \x k y ?InX gam, W W O O (7) O O N 'Q 7 z 0 < o m O)U1? W N? m m z mm cu r DmD VVVVVV <z W "NNE. O V -p. z z Z m m -i VVV.iV < m NNN'4.1 ? OWOV? -+ D i - * 0 z r^ MATCHUNE SHEET 1 MATCHUNE SHEET 2 (r (r , cN \2 401 ; W J c o a o i ?O m K X L< M -u Z? ?Z ?? g Z ? ? 0 o Zzp ?? ?g az c 0 m-U ; a-M4 Om ; zm m ? m N ? z --1 m O o m Z (/) mi N z o --4i 0 m ? 9 m cc z o C) 0 < > r D N N (n g O z m z E7) ;u C ;A Z 0 p) O NA c i p + + + y Z m m 2 v LEAP COMPILED BY PHOTOGRAMMETRIC METHODS. J f?!d / y f m m ,( Fla) M -Zj ~'-- O l ? k N m ? ?" \ ?a (!j m n o T n 0 .2. N n 1 mg m ?p o C)m nm a m cn O D D c? a- D O n mma m o `n 4; C)Z C7 -1 Z =m --44Zg l N o zo?=? a ciao 0N =aZ o m o r CZm ?m? ?;u CDN z5z .? o=a Z° C= 1 ? 0 00 Z G7 m z Z D m y '0? n w cn 0 n ° I? M Z m m m --I 0 w O O rn O 0 o a o i \m n0 \m z O m ?s m ?5 r. 'u r Zr- xz Xrr- co z-i V) U) 0 m m go ?? ?o 02 0 0 G) m C) --1-1 O M K Z r) O m m m z z c N -4 --1 0 I -Zm m m cn O N 0 O :* r- F Z X P m O C7 z 0 -I < X m D N y ° a N - m z v Z n 0 0 w rn n o U '4 4. + co N Z MAP COMPILED BY PHOTOGRAMMETRIC METHODS. m r. m p0 CD V G) 0 tI wN? r- m z --1 m MK rm ?1 JIJ%J0M01 MM V mg y _ O O O co 10 c0 (0 OD N O 4 la -+ c0 0 N O OD K Om Z Z --1 m r - Z V V ?1?4 M0 01 M001 mm 00oOWca0MM00 D oDrnwovv+?aDrn?. ? X J/ 2 z? c? MATCHLINE SHEET 1 MATCHLINE SHEET 2 . r 0 m (n m n m (,7 m ao ) -q z o C)m 2 :0 0 © ? + + ° m 0 f- (7N nN m J n " L ° c: 1 r- z 0 C_I D m m N --gy 3 0 -? 00; T or 0 N ° ZO\Z G) N Z O- z m z c: 0 Z- ?DM D m> 1 0_ O m a ' t„ N O?n p co ,o 10 on recent alluvial deposits, soil color or other visual, hydric soil properties are not considered suitable for quantitative wetland soil monitoring/success criteria on active floodplains. Soil monitoring will entail measurement of sediment accretion/reduction (aggradation/ degradation) at the location of each monitoring gauge and other hydraulically active areas as identified by Site managers. Mitigation activities are designed to provide for flood and sediment storage from the watershed. Therefore, hydraulic and energy dissipation patterns should be distributed throughout as much of the Site as possible. However, an area of particularly accelerated sediment deposition may raise land surfaces above the elevation of the primary wetland floodplain over a relatively short period of time. Conversely, deep scour holes or head-cuts may form in locations where flow velocity or sediment deficits exceed a "normal distribution." Soil monitoring is designed to provide a cursory review to predict the need for additional site modifications if accelerated deposition or scour potentially jeopardizes wetland restoration efforts. The re-bar used to support monitoring gauges will be marked upon installation and in each monitoring year at the elevation of the existing ground surface. In addition, the height of silt lines will be recorded to predict the depth of inundation during the flood period. Additional re- bar will be placed and measured in high energy areas identified by Site managers, as needed. The change in elevation of the alluvial surface and deposition/scour patterns relative to flood elevations will be recorded and compared to previous years. 6.4 SOIL SUCCESS CRITERIA Success criteria require that the deposition/scour rate not exceed over 1 foot change in surface elevations in any given year. Any areas affected by this excessive deposition/scour will be mapped in the field. The area will be reviewed to determine modifications to drainage patterns that should be implemented, if any. Changes in surface elevations of less than 1 foot per year will meet regulatory success criteria; however, modifications to deposition / scour patterns may also be considered in certain circumstances. 6.5 VEGETATION Restoration monitoring procedures for vegetation are designed in accordance with EPA guidelines presented in MiST documentation (EPA 1990) and Compensatory Hardwood Mitigation Guidelines (DOA 1993). The following presents a general discussion of the monitoring program. Vegetation will receive cursory, visual evaluation during periodic reading of monitoring wells to ascertain the general conditions and degree of competition or overtopping of planted elements. Subsequently, quantitative sampling of vegetation will be performed once annually during the fall (September/November) for 5 years or until vegetation success criteria are achieved. Sampling dates may be modified to accommodate flood events and plot inundation, as needed. ?e sa 59 10 In IM 10 During the first sample event, a visual survey will be performed in the reference wetlands to identify all canopy tree species represented within target communities. These reference tree species will be utilized to define "character tree species" as termed in the success criteria. Permanent (on each gauge head) or nonpermanent, randomly placed plots will be established at representative locations in the restoration areas. Each plot will consist of two, 300-foot transects extending at a randomly selected compass bearing from a central origin. The plot width along the transect will extend 4 feet on each side of the tape, providing a 0.1 1-acre plot sample at the location (600 feet x 8 feet / 43,560 square feet/acre). Eight plots will be established to provide an 8 percent sample and a depiction of tree species available for current and future seed sources within the restoration area. In each plot, tree species and number of stems will be recorded and seedling/sapling/tree height measured. Tree data from all plots will be combined into one database to calculate an average density, by species, represented in restoration areas of the Site. In each plot, presence/absence of shrub and herbaceous species will be recorded. A wetland data form (DOA 1987) will be completed to document the classification and description of vegetation, soil, and hydrology. 6.6 VEGETATION SUCCESS CRITERIA Success criteria include the verification, per the wetland data form, that each plot supports a species composition sufficient for a jurisdictional determination. Additional success criteria are dependent upon density and growth of "Character Tree Species." "Character Tree Species" are identified through visual inventory of reference wetland communities used to orient the restoration project design. All canopy tree species identified in the reference wetland will be utilized to define "Character Tree Species" as termed in the success criteria (Character Tree Species are generally listed in Section 4.5 and Section 5.6). An average density of 320 stems per acre of Character Tree Species must be surviving in the first three monitoring years. Subsequently, 290 stems per acre of character tree species must be surviving in year 4, and 260 stems per acre of Character Tree Species in year 5. Each individual species is limited to representing up to 20 percent of the 320 stems per acre total. Additional stems of a particular species above the 20 percent threshold are discarded from the statistical analysis. In essence, a minimum of five different character tree species must be present with each species representing up to 20 percent of the 320 stems per acre total. If vegetation success criteria are not achieved based on average density calculations from combined plots over the entire restoration area, those individual plots that do not support the stem per acre requirement and the representative area will be identified. Supplemental planting will be performed in the identified area as needed until vegetation success criteria are achieved. 60 ao so 10 s? so so 10 ?o is ?o In In 10 io 10 0 ?o No quantitative sampling requirements are proposed for herb assemblages. Development of a forest canopy over several decades and restoration of wetland hydrology will dictate success in migration and establishment of desired wetland understory and groundcover populations. 6.7 REPORT SUBMITTAL An Annual Wetland Monitoring Report (AWMR) will be prepared at the end of each monitoring year (growing season). The AWMR will depict the sample plot and quadrant locations and include photographs which illustrate site conditions. Data compilations and analyses will be presented as described in Sections 6.1 through 6.6 including graphic and tabular format, where practicable. Raw data in paper or computer (EXCEL) file format will be prepared and submitted as an appendix or attachment to the AWMR. 61 In 10 7.0 IMPLEMENTATION SCHEDULE Project implementation will include performance of restoration work in four primary stages including 1) impoundment / weir construction, 2) tree and shrub planting, 3) monitoring plan implementation, and 4) management program implementation. This mitigation plan or implementation schedule may be modified based upon civil design specifications, permit conditions, or contractor limitations. Stage 1: Impoundment / Weir Construction Stage 2 will be performed concurrent with or subsequent to filling of the reservoir. The greentree impoundments will be installed at the designated locations. This work will be performed during late spring and/or early summer months to reduce erosion hazards associated with saturated soil or large August storms. Site preparation, including debris removal, woody debris deposition, and scarification (if needed) will be performed during the same summer period, prior to tree planting. Stage 2: Tree Planting Tree and shrub planting will be performed the first winter after Stage 2 is complete. The seedlings will be planted during the winter dormant period, prior to March 1. Stage 3: Monitoring Plan Implementation Groundwater monitoring gauges and permanent vegetation plots will be established immediately after construction and planting activities are completed (prior to March 26, the start of the growing season). The Site will be visited regularly to read monitoring gauges and to evaluate wetland development during the first growing season. Vegetation sampling and hydrology monitoring will be completed by November 6 (the end of the growing season). The first year of monitoring would be completed upon submittal of the Annual Wetland Monitoring Report and fulfillment of success criteria. The monitoring sequence will be repeated as described for four additional years or until success criteria are achieved. Stage 4: Management Program Implementation Green tree impoundments require active management throughout the life of the wetland facility and water supply reservoir. Therefore, long-term management programs will be required to ensure that wetland development is established and maintained. The management program will be implemented concurrent with the monitoring plan as described above. Constructs of the management program are described in the next Section. eo so 62 Iq IN 8.0 MANAGEMENT PROGRAM Greentree impoundments require modification of water surface elevations on a regular basis. Typically, the elevation of outlets is raised and lowered at variable times each year to provide for development of target wetland vegetation. Wetland vegetation is typically harvested and/or planted periodically to establish target vegetation patterns for waterfowl or other wetland dependent wildlife. Invasive species such as kudzu (Pueraria iobata) may require systematic removal as well. For this project, outlet controls and vegetation maintenance must also be manipulated to promote forested wetland development within the Site. Target hydrological goals include soil saturation or inundation for a minimum of 5 percent of the growing season (March 26 to November 6). The 5 percent criterion must be achieved in 50 percent of the years over the life of the Randleman Reservoir. 10 The Piedmont Triad Regional Water Authority (PTRWA) will provide the fiscal and administrative resources necessary to maintain and manage the greentree impoundments over the life of the water supply reservoir. PTRWA will make provisions for establishment of an 1 Environmental Compliance Officer (Officer) to serve as the primary administrator and authority over the greentree impoundments. The Officer will be under control of PTRWA while PTRWA continues to manage the property. If the property is deeded to a resource agency as described In in Section 9.0, the resource agency will provide resources necessary for establishment and maintenance of the Officer. 1 The Officer will be tasked to supervise, coordinate, monitor, and manipulate the greentree impoundments throughout the life of the water supply reservoir. The Officer will coordinate t and implement, in consultation with qualified wildlife biologists, the following greentree impoundment management components as described in the Greentree Reservoir Management Handbook (Fredrickson, L.H. and D.L. Batema 1996, Mitchell and Newling 1986). 1) The Officer will be responsible for raising and lowering the controllable weirs at a frequency and duration needed to establish wetland hydrology and maximize development of wetland vegetation. Target vegetation patterns include establishment of tree species to the maximum extent feasible. 2) The Officer will periodically visit the Site to visually assess waste debris dumping, erosion problems, debris jams on structures, vegetation patterns, and other aspects of wetland development. The Officer will repair identified problems to ensure continued functioning of the wetland. IN 3) The Officer will provide for periodic quantitative sampling of vegetation to ensure that target vegetation species are developing and being replaced within the impoundments. The results of vegetation samples will be used by the 1 Officer to adjust the frequency and/or duration that the controllable weirs are raised or lowered and to order and plant vegetation elements as needed. ?s 63 In 10 4) The Officer will submit an annual report to the responsible resource agency summarizing the dates of weir modification, the current vegetation sample, trends in vegetation patterns, and recommendations for weir modifications over the next monitoring weir. The report will also include recommendations for structural modifications or additional plantings, as needed. These reports will be prepared and submitted on annual basis over the life of the Randleman Reservoir Water Supply. Sp 'a 64 In Bp 9.0 DISPENSATION OF PROPERTY PTRWA will maintain ownership of the property until all mitigation activities are completed and the site is determined to be successful. Although no plan for dispensation of the Site has been developed, PTRWA may continue to manage the property or may deed the property to a resource agency (public or private) capable of managing the greentree impoundments over the life of the reservoir. The resource agency will be approved by the appropriate regulatory agencies. Covenants and/or restrictions on the deed will be included along with adequate fiscal resources to ensure adequate management and protection of the Site throughout the life of the reservoir. eo to es to eo eo 65 !p 1 0 10.0 WETLAND FUNCTIONAL EVALUATIONS Mitigation activities at the Edgar Branch Mitigation Site should be determined based on wetland functions generated and a comparison of restored functions to potentially impacted wetland resources. Therefore, an evaluation of mitigation wetlands by physiographic area is provided to evaluate site utility for mitigation in the region. 10.1 EXISTING CONDITIONS Under existing conditions, hydrodynamic functions have been degraded or effectively eliminated due to stream entrenchment, bed/bank erosion and removal of characteristic vegetation. Features which depict performance of hydrodynamic wetland functions such as surface microtopography, seasonal ponding, meandering stream channels, and characteristic wetland vegetation have been effectively eliminated on the abandoned floodplains. Reduction or elimination of wetland hydrology has also negated nutrient cycling and biological functions within the complex. These former wetlands do not support natural communities adapted to wetlands or the wetland dependent wildlife characteristic in the region. 10.2 PROJECTED, POST-RESTORATION CONDITIONS The Site will be used to establish wetland communities capable of providing wildlife habitat and water quality benefits. The greentree impoundment is projected to provide for restoration of regular overbank flood events and filling of the entrenched channel with sediment over time. As a result, the floodplain areas are expected to support an array of emergent, shrub-scrub, and forested wetland communities, providing replacement of habitat for wetland dependent species displaced by the reservoir. Water quality benefits are projected to include sediment retention and pollutant processing of waters generated by the 2.1-square mile, urbanizing watershed. Pro-active mitigation within the greentree impoundments is projected to provide approximately 30.7 acres of wetland restoration / creation and 5.4 acres of open waters with accreting shoreline. An additional 0.9 acres of wetland and upland buffer preservation will be included in the Site (37.0-acre total) (Figure 17). g0 66 18 Bp 11.0 REFERENCES a Baumer, 0. and J. Rice. 1988. Methods to predict soil input data for DRAINMOD ASAE Paper No. 88-2564. ASAE, St. Joseph, MI 49085. Beets, C.P. 1992. The relation between the area of open water in bog remnants and storage capacity with resulting guidelines for bog restoration. (in) Peatland Ecosystems and Man: An Impact Assessment. (ed.) 0. M. Bragg, P. D. Hulme, H. A. P. Ingram, and R.A. Robertson. International Peat Society. University of Dundee, Dundee, Scotland. Belcher, H.W. and G.E. Merva. 1987. Results of DRAINMOD verification study for Zeigenfuss soil and Michigan climate. ASAE Paper No. 87-2554. ASAE, St. Joseph, MI 49085. Brinson M.M., F.R. Hauer, L.C. Lee, W.L. Nutter, R.D. Smith, D. Whigham. 1995. Guidebook for Application of Hydrogeomorphic Assessments to Riverine Wetlands. U.S. Army Corps of Engineers Waterways Experiment Station. Vicksburg, MS. Brinson, M.M. 1993a. Changes in the functioning of wetlands along environmental gradients. Wetlands 13(2): 65-74, Special Issue, June 1993. The Society of Wetland Scientists. Brinson M.M. 1993b. A Hydrogeomorphic Classification for Wetlands. Wetlands Research Program Technical Report WRP-DE-4. U.S. Army Corps of Engineers Waterways Experiment Station. Vicksburg, MS. Brinson M., B. Swift, R. Plantico, J. Barclay. 1981. Riparian Ecosystems: Their ecology and status. U.S. Fish and Wildlife Service FWS/OBS 81/17. Brower, J.E., J.H. Zar, and C.N. von Ende. 1990. Field and Laboratory Methods for General Ecology. William C. Brown Publishers, Debuque, IA. Brown, Philip M., et a/. 1985. Geologic Map of North Carolina, North Carolina Department of Natural Resources and Community Development, 1-.500,000 scale. Chang, Howard H. 1988. Fluvial Processes in River Engineering. John Wiley & Sons. Department of the Army (DOA). 1993. Corps of Engineers Wilmington District. Compensatory Hardwood Mitigation Guidelines (12/8/93). Department of the Army (DOA). 1987. Corps of Engineers Wetlands Delineation Manual. Tech. Rpt. Y-87-1. U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. 67 mom Division of Water Quality (DWQ). 1998. Classifications and Water Quality Standards 11 Assigned to the Waters of the Cape Fear River Basin, N.C. Department of Environment and ra Natural Resources, Raleigh, N.C. Division of Water Quality (DWQ). 2000 (draft). Cape Fear River Basinwide Water Quality Plan. North Carolina Department of Environment and Natural Resources. Raleigh, N.C. Division of Water Quality (DWQ). 1996. 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