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HomeMy WebLinkAbout19970330 Ver 1_Complete File_20010209 r. U it [I 7 E j tic Op r. c, DoRESI,IL,.- 4f? P- DETAILED WETLAND MITIGATION PLAN' FEB 0 9 2001 I ! RANDLEMAN RESERVOIR WATER SUPPLY 1,f TERQG;:iw,?,"??;C?? } REDDICKS CREEK MITIGATION SITE GUILFORD COUNTY, NORTH CAROLINA Prepared for: PIEDMONT TRIAD REGIONAL WATER AUTHORITY Prepared by: E 0 EcoScience EcoScience Corporation 612 Wade Avenue, Suite 200 Raleigh, North Carolina 27605 0 E October 2000 l'+E1L'.`;'?a G ,OLD y d ?I 0 TABLE OF CONTENTS Page D LIST OF FIGURES ................................................ 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 Restoration ..................... 3 1.4 Mitigation Site Selection ................................. 4 2.0 METHODS ................................................ 8 3.0 EXISTING CONDITIONS ...................................... 11 3.1 Physiography, Topography, and Land Use ..................... 11 3.2 Soils ...............................................13 3.3 Plant Communities ..................................... 13 3.4 Hydrology ........................................... 16 3.5 Water Quality ......................................... 17 3.6 Jurisdictional Wetlands .................................. 19 4.0 WETLAND RESTORATION STUDIES .............................. 20 4.1 Restoration Alternatives Analyses ........................... 20 4.2 Reservoir Pool Level and Sedimentation Analysis ................. 22 4.3 Surface Water Analyses ................................. 27 4.4 Groundwater Modeling .................................. 31 4.5 Reference Greentree Impoundments ......................... 35 4.6 Reference Plant Communities .............................. 39 4.7 Reference Physiography and Surface Topography ................ 42 5.0 WETLAND RESTORATION PLAN ................................ 45 5.1 Passive Saturation / Inundation from the Reservoir Pool ........... 45 5.2 Impoundment / Weir Construction .......................... 46 5.3 Surface Scarification / Waste Debris Removal .................. 46 5.4 Woody Debris Deposition ................................ 48 5.5 Wetland Community Restoration ........................... 48 0 6.0 MONITORING PLAN ......................................... 53 6.1 Hydrology ...........................................53 6.2 Hydrology Success Criteria ............................... 53 6.3 Soil ................................................55 6.4 Soil Success Criteria .................................... 55 6.5 Vegetation ........................................... 55 6.6 Vegetation Success Criteria ............................... 56 6.7 Report Submittal ...................................... 57 7.0 IMPLEMENTATION SCHEDULE ................................. 58 8.0 MANAGEMENT PROGRAM .................................... 59 9.0 DISPENSATION OF PROPERTY ................................. 61 10.0 WETLAND FUNCTIONAL EVALUATION ........................... 62 10.1 Existing Conditions ..................................... 62 10.2 Projected Post-Restoration Conditions ........................ 62 11.0 REFERENCES ..............................................63 LIST OF FIGURES Page Figure 1: Site Location: Randleman Reservoir ......................... 2 Figure 2: Site Location: Reddicks Creek Mitigation Site ................... 7 Figure 3: Aerial Photograph (1999) ................................. 9 Figure 4: Physiography, Topography, and Land Use ..................... 12 Figure 5: Plant Communities ..................................... 14 Figure 6: Flood Frequency Analyses ................................ 18 Figure 7: Pool Level and Sedimentation: Reference Site 1 ................. 25 Figure 8: Pool Level and Sedimentation: Reference Site 2 ................. 26 Figure 9: Pool Level and Sedimentation: Randleman Reservoir .............. 28 Figure 10: Conceptual Impoundment Design ........................... 36 Figure 11: Reference Greentree Impoundment .......................... 37 Figure 12: Reference Lake Shoreline ................................. 38 Figure 13: Reference Site: Plan View and Cross-Sections .................. 44 Figure 14: Hydrology Restoration ................................... 47 Figure 15: Planting Plan ......................................... 49 Figure 16: Monitoring Plan / Mitigation Design Units ..................... 54 LIST OF TABLES Paqe Table 1: Estimated Acreage 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 ..... 30 Table 3: Modeled Groundwater Discharge Zone of Influence on Wetland Hydroperiods: Congaree Soils ..................... 32 Table 4: Reference Forest Ecosystem Plot Summary .................... 40 Table 5: Reference Forest Ecosystem Plot Summary .................... 41 Table 6: Planting Plan ......................................... 51 iv D A DETAILED WETLAND MITIGATION PLAN RANDLEMAN RESERVOIR WATER SUPPLY REDDICKS CREEK MITIGATION SITE GUILFORD 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 3,000-acre reservoir will unavoidably impact approximately 121 acres of wetlands through impoundment and establishment of an open water system. The"s '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 (ex: forested, stream-side wetlands). Wetland restoration, creation, enhancement, or preservation represent 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 then be off-set through wetland 91 enhancement and/or preservation. 1.2 OBJECTIVES OF WETLAND RESTORATION The primary objectives for wetland restoration include: 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 watersheds. Excess nutrients, fecal coliform, sediments, and chemical contaminants (metals, etc.) represent the primary water quality concerns for the reservoir. 3) Maximize benefits to water quality through establishment of functioning wetlands above the reservoir pool. 4) Replace habitat for wetland dependent wildlife displaced by establishment of open water. 5) Maximize the acreage of wetland restoration or creation achieved at the Reddicks Creek mitigation site. 1 ?..' G L7=> i • ) 1. f\\!``? r;?. . ,`.? ,?? ? 't ?. ri /• ?, J ?! (`?•\?' ,. °`• , x ,i'' •• ??'.'.??_ ? i? 1 _,. yr, ,. ??' '• '. ??• •.v?. 41, t 10 $ ?? j ?. tI i Sri r• t}•-` tL, i' I., ?:: ^.v :?? . s ?;? f .`? .. 0 0 0 0 0 .." --m _ + ?3 V t7 (D D 0 p p N M Fn 7 m m m °"` o x m m D m ; Z 0 (1) co x y . 5 Z .. X!' ?{ = W m m = a n co 3 a :U o G? 'D o A rn u p .?1 o a0 ;u> ;u a?o T tn7 n o D o U) ??°- NZ S cz? o v' 3 0 „ D-G) =•o Rim 8 El < ? 0 : irk, m gyp Qm? 3c0 ? OS' '?z? D 00 N Z a ?Z co N a? o E. 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 within water supply reservoirs (Section 4.2). Therefore, wetland restoration for water quality should be designed to reduce sediment transport capacity of streams immediately above the reservoir and to entrap sediment within vegetated wetland surfaces. As a result, sediment would be deposited on floodplain surfaces that periodically dry out in areas outside of the reservoir pool. 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 developed within the alluvial deposition area (Rosgen 1996). 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. Within reservoir pools immediately 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 water column and consequently reduce drinking water quality. Establishment of the reservoir will effectively stop sediment transport capacity within each tributary that flows into the lake. The primary objective of mitigation is to extend the sediment deposition wedge in the upstream direction of each valley, prior to confluence with the lake. The reservoir will passively develop wetlands within a certain area in each valley, immediately above the reservoir pool. This project is intended to assist that process through active measures, including extension of wetlands in the up-valley direction and establishment of wetland vegetation on active alluvial surfaces. 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 to 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. 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 degree of channel E incision, reduce the rate of groundwater discharge from the floodplain into the channel, 3 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 proposed on more steeply sloped floodplains and stream terraces (>0.008 rise/run) or pastured sites where relatively severe stream channel degradation and steepening has occurred above the reservoir pool. In general, a greentree impoundment comprises 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. The elevation of the outlet is typically raised during winter months to promote ponding, sediment deposition, and waterfowl habitat. Subsequently, the elevation of the outlet is lowered in early spring to allow for vegetation growth, nutrient uptake, and seedling establishment. Levee systems are typically 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 facilitate the growth and survival of tree species. The time for outlet adjustment may vary annually and is dependent upon localized conditions within the watershed. Seedling mortality is typically tracked on an annual basis, and the date of spring lowering of water levels is modified periodically to maximize the rate of forest regeneration. Tree or shrub species selected for planting will vary based on expected hydrologic regimes and other site-specific conditions. In general, sites lacking substantial forest vegetation and primarily used as pasture land were targeted for this mitigation option. 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 potential on floodplains encompassing up to 121 acres of restorable land area. Table 1 and Figure 1 depict the location of each site and projected acreages potentially available for wetland restoration use. 8 4 ?. 0 O O Cl) N ? O cs = E IN •? (D o`. c ca O O ++ N ? m y 3 r c O C 0 O y N oa = N O O c O O ? d L }? V a? 0 a° ?C G 0 rZ N W M C O C O 0 cm 2 c 0 0 Q) ? c U v ? c a) y .D C y CD ? U C =9 .y x w " E N Co N E 2 in a) y > E N J U a) a a) CU in U) c ° c co O Q C)) - U Co F- 0 L .? C CO -- 0. a) CD 'n a? o 0 0 a) LL a T O CO r > a) m E w C cp a) y J (n a) N c 0 rn 2 N (7 0 U p U) E O CD Lo c,) r, ct M n CY) I?t rl e- In It co O N Cl - LO ? ° 00 ccoo t? (00 cl N N - w O O O O O O N (o - N .- (`') M N ? M Y Y T Y U L U a) a) O ` U Q U co U > U L > m > o a) v aa)) ca Y - ? y Q U c C Y U = C G ? U) C 4) E C ' ? I O 0. E W a) C 0 a) (D N N N co N cV 0 - - e- N co N a) It n r- r 0 0 0 0 ; rn u') N i O O O O 0 co (0 a) N C) co m N ? Y 3 6) L O co Q C Q H - a Q v o O j U) F- 0 07 O d Q1 ? LU W o ? a) O) _ N > C t ca O a i co 3 3 a) 6 0) c " co m 0 ? U c > co N O L r 7 O O O s m M y m a L :3 p > U y ? N C CD LL) O C_ 'O O N O 'O v E c 00 °o E m LL y O CO c E O) C ? -O c m a 0 CL ?0a R « 0 E O a) U ?.0.. a) 'O L O « O 0 0 0 0. ca .0 o O y r 0 c>o ayi O O) > y O m O Q) '- 0 a) C U > O C '' O O CO CO .O 7 y 9 ? - O ? Q) Eon E ao v O O Q) «O y U ? ? v O Q) >` a7 N a) C C N R E°0fa NE c .0 N ai 'a > 0 c C r c c a0i E c .0 Q) y > a O N co L O y ? Q) C ? O „ O U Q) = O 0 N N w y x L a) _O 3 aci y p y o 3 0. 00 a) C y O . co a O c O U O O O Q) O °.) t a z LL OI- 0~ Lo 0 - N ° M 1 This document details restoration and enhancement procedures for riverine and lake shoreline wetland restoration and creation along Reddicks Creek, one of the 10 mitigation sites (Figure 2). The Reddicks Creek mitigation site (Site) includes 22.7 acres that encompass the stream and adjacent floodplain servicing a watershed of approximately 9.1 Square miles immediately above the reservoir. Greentree impoundments are proposed along the dredged and entrenched Reddicks Creek corridor to reduce the rate of groundwater discharge from the floodplain into the channel, increase overbank flooding from the channel onto the floodplain, and increase deposition of sediment on vegetated wetland surfaces above the reservoir pool. This summary document includes the following: 1) descriptions of existing conditions; 2) surface and groundwater hydraulic analyses; 3) reference lake shoreline and greentree impoundment studies; and 4) reference soil and forest ecosystem investigations. Subsequently, detailed plans are provided for in-stream structures, wetland restoration/creation, vegetation planting, site monitoring, and success criteria. Remaining mitigation sites that follow the format of this mitigation plan (utilizing greentree impoundments above the reservoir pool) will be attached as appendix documents to this summary mitigation plan. 0 L_ 0 6 L 1>, i 9 r ? ti , 'r ti },r•. r' s ??,'• "„i e ?» t? i- , ?? , 1 ?? Jjr ? . _ rJ•..\ X41 f l\ :. ?a !.- ?? \\ 1 < tom- ` J .????. !? ? ?' ?..,<<? ? `'a f' ;r 1 \? ? J J 0 51 '? ? ;?N J f/> / ? r^' . ``+ ?? C;' ? 8 ? t1W j , ? ?j ,rr(r"""? _ i; : ? , ?? ? ? '?? \ \l+ `13>_;..?? :.•'?i1 `? ???N(?' ? ? ? 1' Jr,-,y,? tel:-. %???y '.?-.: y ' :. I?.\? ~v/ ?>?? `,?\ i-h •?'? + ?U ?' /? 1? 1?,• /r i !'` ?` z'SS ?__. ,-?•....YI ',Yl ?ti? j'i '/' ? ,F' _ :•??.? I? ?.?(?x \?.C ?,\`?. ? y, +• '7?,.?',.?' l?.'. F? ,,?,?"` >? , • Mitigation ^? > ?? Y , ?I,???{'\ Site Location ' •r, ??iJ r ? ?r •`.i t ?1?_., ? r-._\? `C J???l t?)• '/ ''?4?% ?t y. /7pi ? ! "?v}\'_"i ~pt?--?. • _It ..?! 7 _ _' _ /v^?.=-1-... `1A17_?i f. • ,??^LC? r' 1?\\ Ali'` -/"• .?'. ? ?,. ?-F f \? ??? fit `\, lF'y?. 5?? ?k,_i A°••{'j~?`.=? }? /- ??- , ;fir' t .fit ?, •,, y?/_ t , ??,? '_`%!? .• t r- fir(,)`!. ?,,`??15/ ? «.t `?? .,?.?,? r?['? V... ,i ? ?'/?? ?. ,f ?7 `, Iry /1 J Ott 1? r ?i I'• ail .?.?^ / .. '? ry r?S .? '.a ' ?'+ 1 1 • ?i!,1 r , , ,1; . . fi lCi-?, .?'l./+' ?j l? -/ _ ray _ ??n "• •+? ? ?'• r-?• j' •?l. ,'r ''..?,,??-, ! 1 ; ? _< - , r 1.4 '? , f 1? ? r Randleman r,) .\I Reservoir ?:• ; ?_ii ?''?? . % Y h .? ' "? ?j ? ? -' r! 1 thy,,, ?? ?" ?? n. 1-4. W4 / lei ? • ?,, ? / n ? /: ? +4? ' / L ? ? ? r' ??t1*• j,i?iJ '° /' 1 /F ! !11 ; `?? .??f?'!•? ?ii J ?1 / - f° ,?e• f? 't'.t i ,rV • 3YJ!1i ?r ?.Y. , ?'?l /?t, r'te`` 7ti, ' ,-?? ? 0 2400 ft. 4800 ft t { `s, \!?/ * 1:29,520 / Y i / 1> • .. 3 ?BgIJ Source: USGS 7.5 Minute Topo Maps (Pleasant Garden, Hio Point East, N.C.) \v ,/ R• \ /+?t l f /j "? /i n. by: MAF FIGURE EcoScience RANDLEMAN RESERVOIR MITIGATION PROJECT Ckd by: JW N Corporation REDDICKS CREEK SITE Date: -"' Raleigh, North Carolina Guilford County, North Carolina f'roJect Oct 2000 00.010 2.0 METHODS Natural resource information for the Site was obtained from available sources, including U. S. Geological Survey (USGS) topographic mapping (USGS High Point East and High Point West 7.5 minute quadrangles), U. S. Fish and Wildlife Service (USFWS) National Wetlands Inventory (NWI) mapping, and Natural Resource Conservation Service (NRCS) soil survey (USDA 1977). These resources were utilized for base mapping and evaluation of existing landscape and soil information prior to on-site inspection. Current (1999) aerial photography was obtained and utilized to map relevant environmental features (Figure 3). Characteristic and target natural community patterns were classified according to constructs outlined in Schafale and Weakley's, Classification of the Natural Communities of North Carolina (1990). North Carolina Natural Heritage Program (NCNHP) data bases were evaluated for the presence of protected species and designated natural areas which may serve as reference (relatively undisturbed) wetlands for restoration design. On-site reference (relatively undisturbed) stream and wetland sites were selected to orient restoration design and to provide baseline information on target (post-restoration) wetland conditions. A regional vegetation reference data base and on-site inventory were used to characterize target, post-restoration species composition. Topographic maps of the basin floor were also prepared to show the gradation from permanently to semi-permanently inundated conditions throughout the lower half of the Site. A concurrent pool elevation and sedimentation study provided information on sedimentation and wetland development around the point of stream inflow and conservation pool levels. Topographic data were overlaid on wetland restoration areas to establish methods for construction and restoration of wetland communities within the Site. Detailed topographic mapping to 1-foot contour intervals was developed by ground survey paneling and aerial photogrametric methods. Additional land surveys were performed to establish channel cross-sections and measure reference wetland surface topography. Field investigations were performed in the Summer of 2000 including soil surveys, on-site resource mapping, land surveys, and landscape ecosystem classifications. Existing plant communities and jurisdictional wetlands were described and mapped according to landscape position, structure, composition, and groundwater analyses. Wetland boundaries were obtained from a delineation performed in 1998. NRCS soil map units were ground truthed by licenced soil scientists to verify units and to map inclusions and taxadjunct areas. The revised soils maps were used as additional evidence for predicting natural community patterns and wetland limits prior to human disturbances. J 8 E AA m ? 0 9 o -0 -n I' C- 3 3nM Ao y 00 IC ao° 3 po o p? 11 I'd i 8 ?Dr = o O;R Z Z s? 0 o oo D rig) c? O.p p o 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. Surface water analyses for the Reddicks Creek 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 1-, 2-, 5-, 10-, or 100-year period were selected for use. These flood events are commonly called the 2-, 5-, 10-, and 100-year floods. Floods with a return frequency of less than 2 years are usually not studied in engineering applications. 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. 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 and nutrient cycling 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. E fl H U C1 P-1 0 FJ 10 P M 9 3.0 EXISTING CONDITIONS 3.1 PHYSIOGRAPHY, TOPOGRAPHY, AND LAND USE The Site is located in the Piedmont Physiographic Province of North Carolina within the Cape Fear River Basin. 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 Reddicks Creek floodplain within the Cape Fear River Basin (Hydrologic Unit #03030003 [USGS 1974], DWQ Sub-Basin 03-06-08). The Site is located approximately 10 miles southwest of Greensboro and 7 miles southeast of High Point. 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 Site contains an approximately 3900-foot reach of Reddicks Creek (Figure 4). Reddicks Creek supports a primary watershed of approximately 9.1 square miles and flows into Hickory Creek 1.1 miles downstream. Hickory Creek continues to the southeast for approximately 0.6 miles before entering the Deep River. One auxiliary tributary flows into the Site from a pond located immediately west of the Site boundary. Otherwise, the gently sloping valley floor is enclosed by moderate to steeply sloped escarpments in adjacent uplands. The Reddicks Creek watershed supports a mixture of forest, agricultural, residential, commercial, and infrastructural uses. The headwater region extends into urban areas associated with the City of Greensboro, including the Interstate 85 (1-85) highway corridor. Lower portions of the watershed, south of 1-85, primarily support residential communities, pasture land, forest, and limited commercial development. Land use within the watershed surrounding the Site includes maintained grass lawns associated with a recently abandoned golf course and nearby residential homes. Several abandoned structures associated with the golf course reside immediately west, with concrete cart paths and bridges bisecting the Site at numerous locations (Figure 4). The Site encompasses one primary physiographic landscape area for restoration planning purposes; elevated stream terrace (Figure 4). The primary variables utilized to segregate wetland landscape units include land slope, overbank flood frequencies (Section 4.3), and the rate and direction of groundwater flow (Section 4.4). 11 cum %up= m am ma =I me ma IIMB Cm rg 0 o w O ?? '? ro w tc? o c c 6 fl1 --- q ? 11 Q 6 - GOLF FARVIAY ?-' - C 2` ? 1 • V - ?W U a tn 0 00 J CA 1. \ 1 / ? NSA` ,. / r b [ > -i Pi 4r 4 V I ?1 I o r. , Z N ? m ?<*1 ? CC.) o ?7 o m -? o n -1 cn v ca cn o m z ? p ° m c c z ° r fl1 o -p ? -o 0? a? o Gym n? Z .. 'vtn M S? o -jnm ? O? A A 8 O o ° zN o G?0? 0° m0 0m? o a' O c o" o o m -I m C1 o ao m (? it 0 0 o m ?S D 21 z a mg $? 0 0 °O C m 11 ?.* The stream terrace encompasses 22.7 acres along both sides of the stream channel. The channel averages approximately 25 feet in width and 7 feet in depth through the area. Removal of riparian vegetation during antecedent pasture use and recent golf course development induced a down-cut in the channel bed, effectively eliminating the presence of an active floodplain in adjacent areas. The existing stream terrace (abandoned floodplain) ranges from 50 feet to 275 feet in width and supports well drained, upland soils. Immediately outside of the terrace, valley escarpments impinge upon the stream terrace, including erodible slopes ranging from 0.05 to 0.15 (rise/run). Under historic conditions, the stream terrace is expected to have included active floodplains and a low stream terrace supporting natural communities such as Piedmont bottomland hardwood forest and mixed mesophytic hardwood forest (Schafale and Weakley 1990). Down-cutting in the stream has reduced the frequency of overbank flooding within the primary floodplain from an estimated 1-year return interval to a 5- to 10-year return interval under existing conditions. Due to colluvial and erosional forces, the terrace floor is also sloping towards the stream channel, inducing relatively rapid groundwater discharge along the reach. As a result, wetland functions (sediment retention, nutrient cycling, energy dissipation, etc.) have been effectively eliminated from the physiographic area by stream alterations and valley type. 3.2 SOILS Surficial soils have been mapped by NRCS (USDA 1977). Soils were verified in the summer of 1999 by licenced soil scientists to refine soil map units and locate inclusions and taxadjunct areas. Systematic transects were established and sampled to ensure proper coverage. ® The only soil series mapped within the Site is Congaree loam (Typic Udif/uvents). The ® map unit consists of nonhydric, well drained soils that have developed in loamy alluvium The soil is characteristic of long, narrow floodplains on more steeply sloped valleys with the seasonal high water table ranging from 2 to 4 feet below the surface. Congaree soil map units are not expected to have supported wetlands historically with the exception of minor inclusions of the Wehadkee series (Typic Fiuvaquents) in depressional sloughs. 3.3 PLANT COMMUNITIES Plant communities are influenced by logging, site conversion to pasture, and subsequent golf course development. Three communities have been identified for descriptive purposes, including: 1) open field (abandoned golf course); 2) riparian scrub forest; and 3) mesic hardwood forest (Figure 5). 13 u = ® m = E C W O 0 O W O O O O ! I m r -o x 0 z ; n z 0 o 0 -? z m -1 o r ;a C: o m c o -c ILI i ? Cv • ? N Jl r - q N ?G 9 9 ? u c v to CA 6'`\ G" v a r o z a m o- ?10 0 a v 2 ? o o 0 o N ? m rt O N O (Jt ,?,, N ?j + b3 + + (A + 'O O _2 m looo m i 0 n n ^ -1 T ED rn oz G) n it ;a ;a 0 r) c (? 0 •I0 G1mC 0? Z N ? 0 m o ; N .. ?? Z? OWN zo A? ?w$ O.0 it z U 1 1 r C L Li U rz Open Field Open field areas associated with the abandoned golf course, fairways, and recreational areas comprises approximately 10.8 acres of the 22.7-acre Site. The golf course was regularly maintained and has had less than 2 years to naturalize since abandonment. This community is dominated by grasses and herbs with a few canopy species randomly scattered throughout the area. This community is characterized by various lawn grasses typical of golf course settings including Bermuda grass (Cynodon dacty/on) and fescue (Festuca spp.). Invasive grasses and herbs are characterized by species habituated to unforested maintained environments and include: sheep-sorrel (Rumex acetosella), dog fennel (Eupatorium capillifolium), milkweed (Asclepias syriaca), lespedeza (Lespedeza virginica), wild onion (Allium canadense), goldenrod (Sofidago spp.), red clover (Trifolium pratense), white clover (Trifolium repens), dandelion (Taraxacum officinale), and plantain (Plantago sp.). Sapling species of eastern red cedar (Juniperus virginiana), box elder (Acer negundo), and red maple (Acer rubrum) are randomly interspersed throughout this community. Riparian Scrub Forest A narrow strip of Riparian Forest occurs adjacent to Reddicks Creek throughout its reach. The Riparian Forest is approximately 10 to 30 feet in width, encompassing 4.1 acres, and consists primarily of a successional, shrub-scrub community and intermittent hardwood forest stands. Characteristic tree species include river birch (Betula nigra), green ash (Fraxinus pennsylvanica), American elm (Ulmus americana), black cherry (Prunus serotina), sweetgum (Liquidambar styraciflua), swamp dogwood (Corpus foemina), tulip poplar (Liriodendron tulipifera), ironwood (Carpinus caroliniana), American sycamore (Platanus occidentalis), black willow (Salix nigra), box elder, and red maple. Sub-canopy species include saplings of canopy species as well as tag alder (Alnus serrulata). Understory species are characterized by common greenbrier (Smilax rotundifolia.), poison ivy (Toxicodendron radicans), Japanese honeysuckle (Lonicera japonica), blackberry (Rubus sp.), and common ragweed (Ambrosia artemisiifolia). These areas were not typically mowed by golf course superintendents; however, a canopy was not allowed to develop between fairways. Mesic Hardwood Forest A hardwood forest community is located in two areas within the Site and comprises approximately 5.5 acres of land area. This vegetative community extends from Reddicks Creek along two relatively steep ridges located in the central and southern sections of the Site. Species composition within this community is consistent with those identified in the riparian scrub forest with additional canopy species composed of short-leaf pine (Pious echinata), Virginia pine (Pinus virginiana), mockernut hickory (Carya tomentosa), dogwood (Corpus florida), rock chestnut oak (Quercus prinus), red mulberry (Morus rubra), white oak (Quercus alba), black walnut (Juglans nigra), sugar maple (Acer saccharum), and eastern red cedar. The limited sub canopy includes saplings of canopy species as well as American holly (Ilex opaca), and ironwood (Carpinus caroliniana). 15 ri 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 by moderate rainfall. In Guilford 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 consist primarily of silts, sands, and weathered bedrock (very coarse sand and small gravel). Bedrock outcrops are considered 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 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 relatively narrow stream terraces associated with a 3900-foot reach of Reddicks Creek. At site outfall, the system supports a watershed of approximately 9.1?:) square miles. The terrace ranges from approximately 50 to 275 feet in width, dependent upon confinement characteristics of the valley wall. Relative to the terrace elevation, the incised channel supports a bankfull width of 25 feet, and average depth of 7 feet. Due to passive or active down-cutting, cross-sectional area of Reddicks Creek is approximately 175 square feet. However, according to regional curves, a stable Reddicks Creek channel is projected to support cross-sections of approximately 100 square feet (Harman et a/. 1999, Rosgen 1996). The incised channel supports a sinuosity (channel length/valley length) of 1.1. 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 a G4 (gravel dominated gully) based on fluvial geomorphic features (Rosgen 1996). Topographic mapping and historic (1963) aerial photography indicate that Reddicks Creek has remained at the present location in surrounding pasture land for the last several decades. However, the channel has deepened and subsequently widened during the period. Riparian vegetation appears to have been cleared several times during the period. However, bank collapse and active erosion into the adjacent pastures was induced. As a result, land managers allowed limited riparian vegetation to recolonize the banks. Three small unnamed tributaries dissect the southern portion of the Site (Figure 4). These systems extend for a total of approximately 1000 linear feet and support watersheds less 16 i than 0.1 square miles. These tributaries represent ephemeral or marginally intermittent streams that receive drainage from the adjacent open field areas and a pond located at the southwestern edge of the site. Both systems have been diverted into canals that bypass the primary and secondary floodplains, providing direct connectivity to Reddicks Creek. Stream discharge and flood elevations under existing conditions have been predicted based on hydraulic models (Section 4.2). Figure 6 provides model predictions for the 1- (projected bankfull), 2-, 5-, and 100-year storm (Section 4.3). The study suggests that entrenchment has confined the 1- to 2-year flows within the eroding channel banks, effectively bypassing floodplain functions associated with pollutant removal and maintenance of wildlife habitat for overbank flood dependent species. 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 June 1998 and May 2000 indicate that the groundwater table typically resides from 2 to 7 feet below the land surface. The groundwater gradient appears relatively steep with runoff rates moderate to rapid. Therefore, 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 Reddicks Creek has further accelerated groundwater discharge to depths of greater than 6 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 4.4) suggest that groundwater tables will continue to remain more than 1 foot below the surface. Therefore, restoration of wetlands within the Site may require establishment of a backwater (surface water induced) wetland immediately above the reservoir. 3.5 WATER QUALITY 11 Reddicks Creek maintains a State best usage classification of WS-IV CA ((Stream Index No. 17-8) (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. `CA signifies a Critical Area designation for watershed areas within 0.5 miles of a water supply intake for the reservoir. 17 m 0 ow I O LU ° ° CROSS-SECTION 7900 ?s r? ?? \ N /1 • d r/ i / o _ W r now, I r1i d ;n z 0 0 0 131 En C 6 m c O N i Liz m v ?-c ?z w 0 0 0 X ? v ° z 0 c- ; o 0 0 z m 0 00. 0 v o z cn n g CL r ; M s °a 4 CL o :3 7 n 0 Z N M r? m < 0 > < 0 > < 0 > n N N N N + + 'T In r- 0 °v m Q m z 1 a r? O it G t 4700 1 TV G ?( C O A o m 'I1 zS o Om 0 n? c. .. Oz nm z? ;u DOV y a 0 h o z Ji O0 ZQr ?z N_.0D -if*1 S O B ?. 0 M 0 0 °z 0 9m o o 000 R1 0 ;u CD C o w No NA Nov zz z cn zap ?a w •N C The Site consists primarily of open land adjacent to the stream channel. Fertilizers, pesticides, and nutrients associated with golf course maintenance may have influenced water quality in the vicinity. Two intermittent channels as well as an overflow drain from an adjacent pond have direct connectivity with Reddicks Creek and may have deleterious effects on water quality. Restoration of wetland hydrology and diversion of area runoff onto restored wetland surfaces will provide local water quality benefits, including important functions such as particulate retention, removal of elements and compounds, and nutrient cycling. Historically, the floodplain provided water quality benefits to the 9.1 square mile watershed associated with Reddicks Creek. However, runoff from this land area effectively bypasses wetland floodplains as the entrenched channel transports flow directly 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. Because the Site is located at the elevation of the reservoir conservation pool, sediment transport capacity of the stream system will be generally stopped at elevations of 681 feet above MSL. A sediment wedge will develop within the reservoir pool and incrementally extend further into the open water area. Research suggests that up to 300,000 cubic feet (0.7 acre-feet) of sediment will be deposited annually within the reducing aquatic environment (Simmons 1976). Associated pollutants will not generally be degraded, assimilated, or recycled through periodic wetting (reduction) and drying (oxidation). Therefore, wetland restoration has been designed to reduce sediment transport capacity within the 3,900-foot reach of Reddicks Creek. As a result, the sediment wedge will be extended in the upstream direction outside of the reservoir pool (above elevation 682), ® where wetland functions will potentially provide for greater pollutant processing. 3.6 JURISDICTIONAL WETLANDS Jurisdictional areas are defined using the crhria set forth in the U.S. Army Corps of Engineers, Wetlands Delineation Manual (DOA 1987). Based on the assessment, functioning jurisdictional wetland systems were not identified on the Site. Jurisdictional systems are generally limited to open water within the banks of the entrenched stream channel. L 0 u 19 d- 0 4.0 WETLAND RESTORATION STUDIES This section summarizes studies performed to orient restoration design. Studies include: 1) Restoration Alternatives Analyses: Alternatives for wetland restoration relative to stream, floodplain, and reservoir functions were assessed. 2) Reservoir Pool Sedimentation and Wetland Vegetation Study: Sedimentation patterns and extent of wetlands were assessed on existing reservoirs in the region. 3) Surface Water Analyses: Overbank flooding frequency and extent was estimated based on the selected wetland restoration method. 4) Groundwater Modeling: The effect of drainage features on groundwater wetland hydroperiods was modeled. 5) Reference Plant Communities: Reference wetland communities were sampled to predict the target distribution of vegetation to be established in restoration areas. 6) Reference Physiography and Surface Topography: Reference wetland surfaces were measured within an existing greentree impoundment to characterize long term, projected conditions at the Site. 4.1 RESTORATION ALTERNATIVES ANALYSES The objectives of this project include: 1) Assist in protecting the drinking water supply from pollutants discharged from the developing watersheds. Pollutants attached to sediment represents 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. LJ 20 is This alternative would facilitate transport of sediment generated by the watershed into the Randleman Reservoir. Within the lower half of the Site, this capacity to transport sediment would be unavoidably stopped by the conservation pool associated with the reservoir. In addition, facilitating transport of sediment and pollutants into water supply waters is considered contrary to project objectives. Therefore, this option was discarded. Alluvial Wetland Fan Development This option is designed to elevate water tables and reduce sediment transport into the reservoir. 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 towards 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 invariably 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 immediately above the reservoir or migration back into the abandoned, dredged channel. Additional structural modifications may be required in the future, after the migrating stream abandons the existing dredged channel. Based on groundwater models (Section 4.4) passive development of an alluvial wetland fan immediately above the reservoir does not represent a viable option for this Site. Due to soil characteristics, across terrace slope, and down-valley slope, the groundwater model suggests that groundwater migration will continue into the low-lying channel corridor, with development of shoot cut-offs considered likely during storm events. In essence, the floodplain floor is not wide enough or flat enough to induce adequate groundwater retention or to provide adequate energy dissipation functions in the vicinity of the in- stream weirs. Therefore, this option was discarded in favor of greentree impoundments. -' Greentree Impoundments This alternative is similar to alluvial fan development described above. However, Greentree impoundments include a series of floodplain levees and controllable outlet structures that are 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. 21 u 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 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 greentree impoundments across the Reddicks Creek floodplain represents the preferred option for this project. Construction activities would occur within maintained grass areas associated with the former golf course. Impacts to existing forest stands will be limited. In addition, the structures would allow pro-active control of wetland development and function behind each impoundment. 4.2 RESERVOIR POOL LEVEL AND SEDIMENTATION ANALYSIS Reservoir sediment quality is an important environmental concern because sediment may act as both a sink and a source of water-quality constituents to the overlying water column and biota. Sedimentation rates are dependent on existing land use, land use modifications, soils, and basin topography. Alternatives for sediment reduction potentially include up-stream land management techniques, sluicing of sediment through the reservoir, or interception of the sediment prior to entry into the reservoir. Even with strict land management techniques in an urbanizing watershed, a certain amount of "background" sediment will continually be moved by erosion processes. In a stable river bed, erosion, sediment transport and deposition are in equilibrium. Dam construction disrupts this balance, raising the base level of streams above the reservoir, and encouraging the deposition through reduction of the gradient. As a result, the stream deposits sediment as a delta at the confluence with the conservation pool. The deposition process, otherwise known as warping or shoaling, advances at varying rates dependent on the site and rate of sediment supply. Slope angles and extension patterns on the delta are dependent on the particle size of the prevailing sediment deposited, with courser sediment associated with higher angle slopes. The Reddicks Creek wetland restoration project resides immediately above the normal pool elevation (i.e. conservation pool) for the Randleman reservoir (Elevation = 682 feet above MSL). Currently, the stream channel is incised to depths which induce a groundwater withdrawal gradient (rate) that does not allow for wetland presence on the adjacent primary floodplain. After the reservoir is constructed, sediment accretion is likely to occur within the Site, immediately upstream and downstream of the conservation pool. This accretion will form a "sediment wedge" within the floodplain, stream channel, and delta 22 r area inducing passive wetland conditions for an unknown distance (or elevation) in both the upstream and downstream direction. Objectives The objective of this study is to collect the following information on existing reservoirs in the region: 1) Determine the elevation range above the conservation pool that supports relatively contiguous wetlands apparently resulting from the conservation pool, groundwater mounding, and/or sediment accretion. The data reported will include the elevation of the conservation pool, the average period that the reservoir water surface resides at the conservation pool elevation, the elevation range for relatively contiguous, forested wetland formation, and elevation range for emergent wetland formation. 2) Determine the elevation range of the stream bed above the conservation pool that has sustained sediment accretion to the extent that the channel supports an average depth of 1 foot or less. 3) Determine the range of channel depths present in the wetland elevation range. 4) Prepare a profile and plan view that depicts typical conditions relative to the conservation pool. Methods Field reconnaissance of several reservoirs and impoundments in the central Piedmont was conducted in order to establish baseline information on sedimentation and wetland development around the point of stream inflow and conservation pool levels. Two sites were chosen that best exhibited long term (> 10 years) sedimentation processes for large and small watersheds. One site is located at the point of inflow of Little Briar Creek into . Crabtree Lake, Wake County. Little Briar Creek services a watershed of approximately 13.5 square miles. Land use for this sub-basin is predominantly forested, but is part of a rapidly developing part of Research Triangle Park, including the Raleigh-Durham International Airport. The second site is located at the inflow of an unnamed tributary of Horse Creek into Falls Lake, Wake County. The tributary services a watershed of approximately 0.3 square miles. Land use for this watershed is predominantly forested, though residential development is encroaching upon the upper reaches of the area. Topographic maps of the alluvial wetland fans were prepared to 0.5-foot contour intervals by laser level and Global Positioning System (GPS) measurements. Embankments, shorelines, and wetland boundaries were measured and surveyed relative to the reservoir water surface elevations. For Falls Lake, conservation pool and daily water surface elevations were obtained for a 16-year period from USACE (1984-1999). Pool elevation 23 a G for Crabtree Lake was obtained from the elevation of the low-flow spillway crest tied to a local USGS benchmark. Cross-sections and profiles were generated for the local stream reach and floodplain area. Sediment borings were sited at various points along the boundary of wetlands to determine depth of groundwater table relative to reservoir pool elevations. Results Figures 7 and 8 provide a plan view and cross section for the sites at Crabtree Lake and Falls Lake, including the groundwater elevations along the wetland fringe. Within the conservation pool, a majority of the sediment deposition area resides under approximately 0.5 feet of water. Sediment deposition is greatest below the pool elevation contour with inundated sediment bars generally extending into the lake over time. As the deposition wedge elevates within central reaches of the inundated floodplain, the channel tends to ® migrate towards the toe of adjacent slopes, incrementally filling the inundated valley floor. i? On average, emergent wetland vegetation is present on accreted sediment to within 1 foot below the normal pool. Forested and shrub-scrub wetland vegetation is typically present to 2 feet above the normal pool in the upstream direction. These wetlands appear be induced by an up-welling in the down-valley migration of groundwater, prior to inflow ® with the conservation pool. A review of lake level data for these reservoirs suggests that the water surface that induces these wetlands resides within 0.5 feet of the conservation pool elevation, on average, for 66% of the year. In Falls Lake, data indicate that the sediment wedge is generated by water surfaces within 2 feet of the conservation pool elevation for 82% of r the time over the 15-year monitoring period'. The study suggests that sediment deposition is concentrated within inundated areas at or just below the conservation pool elevation. As the sediment surface approaches the elevation of the conservation pool, the wedge begins to extend further into the reservoir. This accreting surface passively develops emergent wetland vegetation on surfaces within 1 foot of the conservation pool. This accreting wetland surface will continue to enlarge over the life of the reservoir. r 1 For Falls Lake, the conservation pool elevation has been held fixed at 250.1 feet above MSL over the 15-year monitoring period. r.: 24 C N O O ELEVATION N N N N N m v m D pp O O W O O O O N O O O N N N o 0 ' o 0 W 0 0 m O -' co 4 o a a L` O O O O N O O OI O O I I I 1 I m 0 z ELEVATION N N N N N %4 V m O O O O y yy N O R1 0 O P4 a ,r ' o 0 A N t7 - O O O O N N N N W O .? O O O 0 0 0 O 0 O m O O to O O O 0 O 0 O N O O W O O W J 46 O O ~ o z z 71 W n C, rTl o n O O N O O 0 cn .1. W N PQ CA *1 O O O O O O O O O O O O O n Cl) 1 n mm og 2 O ;u n m m zZ o 'g f/1 a v oo I>?C7 ?9;0 0 S y? -9`+ c n(A : a R p tTj A x o l ca r m 35 -1 o c n ? C m h o 3; 0 70 ?- z CD r r ? ? O 0•ry m Z - ?v -min - CZZ? I IZA U ELEVATION N N N ? W 0 O I t:. J m I I O i . I. O _I L . i . ?7 - N N I. m O .. l ? . ,. z ? a O m I A c 0 . m 1 in n O 4 • i. v 4% O D O N N m 0 0 z a N I ( I ; i I. I 1 1 1 1 I 0 z N O O O 0 n ? 0 j. O p N N -? O O z O O N o -i m m o m -+. O c ? 0 N O O n ° 0 f/! M O O z 9 m N C0 O rn 0 O O O O m O Qf 0 O N O 0 N 0 -P 0 0 O O O N O O m 0 m 0 N O O mss) ' GIN O 4 4 i ;0 O a N 1 1 ? n z ,c n ,c ?D i? :. r V . O 0 i1 0 0 000 ?. o m ? ? C; *U Q? z N is ^ ^ Y/ s '?a 00 46 En M Cy 1 f K300 -T C* p> < R7 I N? V Z ? 0 CM N z N N NO N ? Q N O OD rn {? N O O C13 N O O O O O O O O O O O O O O O I , i 00 . I. i I - -- ---- - - { -_ - ,. I MfI ' I i ` 1Ca ? , C* 00 tr I I I I 153, I I A i i , .:. ; I . 54 I I r s r . i I , I I i ! w I i ? i , • I i I I i I 1 I ' I ? I I I I I I • ? I I . ?3a t i I ' I i n m CD n ° ~ ° Z z m z .? rn O I? O CR = z ?? m 00 D?o O a -420 n? R x o ` a N mDr Z =o mo 1 w + ? m (A o m no r r -1 O Ar °b m ?, O m -i o z ?• lf ?' R ' cv O O > RI N r >N ? _ ? ?? C'D 0 g CD m m H." Based on the two reference sites studied, forested and shrub-scrub-wetlands typically develop passively on floodplain surfaces that reside up to 2 feet above the conservation pool. The area sustains sediment deposition in the active channel, including channel migration across the developing delta over time. Application For this application, the water surface within the filled, Randleman Reservoir is assumed to remain within 0.5 feet of the conservation pool (682 feet above MSL) for a minimum of 66% of the year and within 2.0 feet of the conservation pool for a minimum 82% of the time over a 15-year period. Figure 9 depicts mapping of resulting passive wetland development projected to occur on the Site as a result of the Randleman Reservoir. The Site includes approximately 3.0 acres of open water (below 681 elevation) that are projected to support future accretion and development of emergent wetlands. The 3.0- acre area includes backwater conditions from the reservoir that will extend up a majority ® of the on-site reach of the Reddicks Creek channel under existing conditions. Between elevations of 681 and 682 feet above MSL, emergent and submerged aquatic vegetation is projected to develop. This area will be semi-permanently saturated or inundated up to 1 foot in depth immediately after filling the reservoir. Based on reference studies, the area is expected to support 1.3 acres of wetlands upon project completion. In upper reaches of the lake effect area, shrub-scrub and forested wetland systems are expected to be passively restored, encompassing approximately 3.6 acres on lands from 682 to 684 feet above MSL. In total, approximately 4.9 acres are expected to support wetlands as a result of hydrological modifications associated with the reservoir. Active wetland restoration measures will include construction of green tree impoundments within the restoration area, preparation of pastured surfaces, and planting of wetland adapted vegetation, The pro-active measures are designed to laterally extend the sediment wedge and wetland extent in the up-valley direction. 4.3 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 maximize wetland acreage and water quality benefits, while providing for increased wetland habitat for dependent species. u_-_ 27 J °w F o 1 o k-rl I o o 01, ? ? f j i i b o _? 6 N ? l N.„ . m ? r • I? JA . " III ' I! o N o M o m? '? z z m` p m o c? ti 1_ r -4 0-4 r m to -? -4 o m ?, o 0 mo. 3z c -i z m m P m o c o _0 :u o (? m m $ m C Q 0 (n -Ai r Q -1 0 D w N r W 1 ?' 01 e M 1+ 1+ 1+ IT (n cla MAP COMPILED BY PHOTOGRAMMETRIC METHODS. w a 3 ? 70 'fl m O 0 os 0o amp In tTj =? C? ? A x O o 'S O o In p?In m r o N??o 4 =zp ??>' cnk o cn Z= 0 -q>m G o? O -i ? O 0 m ° ^" o. 1' c m -I m C7 Ah o w z C' [IL o ; o .. r, o? DAN Co N ` O?n 0 o No O r a Z 0 0 0 a Z ?o v 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 1-, 2-, 5-, 10-, 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 stream discharge for the 1-, 2-, 5-, 10-, and 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 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 subbasins based on land use or location of tributaries. The drainage area for each subbasin was estimated using a planimeter. The NRCS curve numbers were estimated using methods described in NRCS TR-55. The subbasin lag times were estimated using Snyder's method. Because there were no onsite 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% 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 1-, 2-, 5-, 10-, and 100-year floods of Reddicks Creek were estimated using the USACE HEC-2 computer program. Channel cross sections for the hydraulic analyses were obtained from the most currently available HEC-2 computer runs completed for Federal Emergency Management Agency (FEMA) Flood Insurance Studies (FIS). Additional cross-sections that were needed to model proposed structures were taken from digital orthophoto maps with a contour interval of 1 foot. D P.X-. 29 0 a; ?e W U W a a w N (? W E"+ W z Q d W a W w U d a w d 3 o ¢ o ' • °o w cs r- 00 00 0 ON ? `n O N 00 O\ M 00 N ?+ Ar 00 O% O M kn G1 cl 00 00 ON O\ O\ Ol N ~O cV t- M O • cn 00 O N M tn ' k .-. \?6 00 O? t!) O? w c-, C7, `n O O rl: N v'1 00 00 y ?+ N 00 O N V r- O N N C\ O CA O N C\ V \.O 00 0 0 0 0 en M 0 0 0 0 0 0 0 0 ON G W ? O O O Y p O M O N ?t • -? N 00 O N ?t r- .." N N O to > ? \J M 00 Q\ -+ { O U x O\ M ?O o cV [- o _ L=. cn O 00 00 C\ .-• N t--: C; M ?O 00 00 00 rn O, O. O ?10 ?o ?o \0 ? ? N N M C W ti O, O, N k Oo N Vf V, 14 v o ?? o o ?n v a 00 0 00 G' rn C\ % o O\ to rj ch N ? to y .-- DD O? N N r? C) en c) "T w r- 00 00 I ON Cl\ O C O ? O Cp '.... U n O co `? p e o u C-) V] O O `' En O 2 J to x w 0 O 0 0 0 t 0 . w O O n O O > y N (? M d V \J v n, is OVA L7r b U U 'CS CS U) O w Roughness coefficients (Manning's "n") in the channels and on the overbank areas were taken from the HEC-2 computer runs previously mentioned and verified with field inspections of the sites. Roughness coefficients in the main channel were 0.06 and 0.12 for overbank areas. Starting water surface elevations and energy slope for existing conditions were estimated from the published flood insurance studies for Guilford County. The slope-area option provided by the HEC-2 model was used to estimate the true value of the water surface elevation at the beginning cross-section. For future conditions, the starting water surface elevation at the first cross-section was 688.21 feet (100-year reservoir pool elevation) for the 100-year flood and 682 feet for the 1-, 2-, 5-, and 10-year floods (normal reservoir pool elevation). Tables 2 summarizes the water surface elevations for existing and proposed conditions. Figure 6 (Section 3.0) depicts modeled flood elevations for the 1-, 2-, 10- and 100-year, 24-hour storm event. The model indicates that overbank flooding has been effectively eliminated until the 2-year storm along the entrenched channel under existing conditions. Establishment of the greentree impoundments will elevate flood levels to elevations desired under the management program. Therefore, post-project conditions were modeled to evaluate the potential increase in flood levels if the controllable weirs were lowered to the maximum extent feasible. Water surface elevation are approximately 4.9 feet to 6.4 feet higher for proposed conditions in downstream reaches of the Site, due primary to the reservoir pool. As the cross-sections progress upstream away from the reservoir, the difference between proposed and existing conditions decreases with the 100-year flood elevation increasing by an average of approximately 1.8 feet (starting upstream of cross- section 4700). 4.4 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 Descriation 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 31 range of soil, crop, and climatological conditions. Results of tests in North Carolina (Skaggs, 1982), Ohio (Skaggs et a/. 1981), Louisiana (Gayle et al. 1985; Fouss et ai. 1987), Florida (Rogers 1985), Michigan (Belcher and Merva 1987), and Belgium (Susanto et a/. 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 et al. (1993). Methods for evaluating water balance equations and equation variables are discussed in detail in Skaggs et al. (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 hydrology is defined as groundwater within 12 inches of the surface for 28 consecutive days (12.5% of the growing season), and 11 consecutive days (5% 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%, 5-12.5%, and 12.5-20% of the growing season). 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 Guilford County (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 run for Congaree soils, the dominant series in the Site. Forested and maintained pasture conditions (evapotranspiration rates) were modeled. 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 4 feet below the forested floodplain elevation is modeled as reducing surface hydroperiods below 5% of the growing season at a distance of 145 feet from the channel in a Congaree soil. A forested floodplain surface 6 feet in elevation above the channel invert and greater than 195 feet from the channel is projected to support wetlands. ?f 32 t k TABLE 3 Modeled Groundwater Discharge Zone of Influence on Wetland Hydroperiod Congaree Soil Floodplain Groundwater Number of Groundwater Number of Elevation Above Discharge Zone of Years Discharge Zone of Years Channel Invert / Influence2 Wetland Influence Wetland Weir Height' (feet) Criteria Met (feet) Criteria Met (feet) (Surface (Surface Hydroperiods Hydroperiods < <5% of the 12.5% of the growing season) growing season) Forested Conditions (relatively high surface water storage and rooting functions) 0 ----- 27/31 ----- 19/31 1 55 16/31 UA3 14/31 2 90 17/31 UA 14/31 4 145 16/31 UA 14/31 6 195 16/31 UA 12/31 8 215 16/31 UA 12/31 Fallow Field/Pasture Conditions (relatively low surface water storage and rooting functions) 0 ----- 25/31 UA 6/31 1 120 16/31 ILIA 3/31 2 165 17/31 UA 3/31 4 240 16/31 UA 2/31 6 280 16/31 UA 2/31 8 305 16/31 UA 2/31 1: "Weir Height" is assumed to represent the effective depth (invert) of the drainage feature. 2: Discharge Zone of Influence is equal to '/: of the modeled drainage spacing 3: UA = wetland criteria unachievable ESC interpreted the groundwater drainage model based upon 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 be wetlands. Draft mapping of areas potentially supporting wetlands was prepared based on available topographic mapping. DRAINMOD simulations were designed to predict the transition zone from Congaree soils to Wehadkee soils based on groundwater drainage conditions within a relatively flat floodplain surface. Congaree soils represent a nonhydric (nonwetland), well drained soil that is common on stream terraces 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. Post-Restoration Model Applications and Results For groundwater wetland restoration, the primary objectives of this project include: 1) reduce channel incision along Reddicks Creek and associated tributaries; 2) elevate the groundwater gradient into the rooting zone for developing vegetation; and 3) establish minimum wetland hydroperiods encompassing 5% of the growing season, which are typical for riverine wetlands in the Piedmont hydrophysiographic province. Therefore, the effective post-project depths of the Reddicks Creek channel will be reduced from an average of 7 feet under existing conditions to gradients between 1 to 3 feet below the floodplain. 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 Congaree soil map unit which encompasses the entire Site. Model simulations indicate that a series of in-stream weirs placed to within 1 foot of the adjacent floodplain elevation will not restore significant areas of wetlands. Based on NRCS-MUUF parameters, Congaree soils exhibit relatively low vertical hydraulic conductivity and rapid lateral flow within the upper soil profile. A channel invert 1 foot below the adjacent stream terrace continues to effectively drain an area 120 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 ?x 34 C? Randleman Reservoir Mitigation Plan (Oct 24) This is an interesting concept, unfortuately I'm not qualified to review in detail. However, I am interested in the progress of this project. My opinions are as follows; • Wetland creation, as presented in this proposal, raise a lot of questions for me. I assume that the soils at the creation sites are not hydric enough to support a wetland fauna. How will this be addressed? How can these wetlands be constructed to account for sediment transport? EcoScience did discuss how pool elevation will change seasonally and that this will have to be monitored. Has the reference greentree reservoirs discussed in the plan worked? Has a DWQ person looked at them? • Has wetland creation like this been given mitigation credits for other projects? • 1 would suggest that water quality conditions of all of the tributaries be analyzed. It may be that these conditions could/would prevent wetland success. 0 1 would also suggest that a "wetland" person rather than a stream person look this over as well. weirs do not provide a viable option for wetland restoration use based on the groundwater model. To create wetlands in the valley, greentree impoundments will be required to elevate the groundwater surface above the floodplain elevation (immediately adjacent to the channel) periodically throughout the year. 4.5 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 Beaver Creek greentree impoundment above Jordan Lake in Wake and Chatham Counties, the Little Creek impoundment to Jordan Lake in Durham County, the Rocky Branch impoundment above Falls Lake in Wake County, and the Country Line Creek impoundments in Caswell County. These impoundments have typically been located above water supply reservoirs in the region primarily to replace wetland habitat inundated by the reservoir and to 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. Figure 10 provides a conceptual depiction of a typical weir and dam for greentree impoundments within watersheds ranging 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. Subsequently, the boards may be installed during the winter and/or early part of the growing season to establish wetland hydrology behind the impoundment. The type or size of the weir used at the Reddicks Creek Site may be modified during the engineering design phase based upon watershed size, projected discharge/velocities on the structure, potential for stability, cost, constructability, and/or 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. Figures 11 and 12 provide a depiction of the impoundment and lake shoreline reference 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. 35 m m m m m m m m m= m m m m m m r m m 5' MIN. g ?? ?- SIDE SLOPE a 113 ---? 10, I r ?N 00 m s m I Z < DIRECTION OF FLOW I N I y ->( a 10, a > I -t z I I I I ? i t I !i lit ,r,l ji % > W N L f W c i r all G) fi 30 1 0 o Z -? n m o cn z m 11 rn Fee - o m is • zEr ;1111I MA 5 15 z CA r r = m m= r r w == = == = r == m law rn z a0D > ? p .6m s CO' _ Mzz o = 00 CO) A) ? z It M z n im ?' ?i O Q 3 d O CD CD cn m - fJ rC ° r1i _ ? 'R tn?o r `O (D CI- - CO co co ? mD m n rn CO) p -I c CD CD N W ^? w m co zc -i ca p 9z T -4 _ C? cn C Zrn o ? DA ?-u m? -Zi 8 z i aw Wo O co m> _ m ?rn R). = a 0 _0 , Co CL ON CD ?erg ?_ me OM vm -z 00 Eii o ?m Cl) G) CL O o ?rn :mz z mm 0 -im o cQ $ 0 o = m -n - C7 * G) o ? 3 ? _v s C7 _ N O a m o O 0_ CD =m rn p C) p =. m N5 -p O. W CD cD cc m T p T 9 o ZC 0 w CD 1 _0 =3 p m 5' 0 m 0 0 :1 3a 0 ? 0 z m z m? _n ' M < O I _0 # Ali o CD - i 00 !! a i 4w m CO G) C =Dr ° Q cp 1. ? -5' c) ? (CD cr =T w ? o 0 ? D v Z9 =3. c ( I I ?2Dc? i o o =r,?! 3 p? 3 00 0z _n IR I O X CD I ' yM 1-0. fY uM• 3 c CL R?. mo co O N co N N ° N 4 O c i IK D 1 1 ' ? !fl n 0 ° a./ m I I ; 1 rn O? Dn i?O p 104 'D N O Z K D Z ;rn ' irn ;0) ;rn m (a U) - ' rn D Zo : rn I U i IM OD OD :00 OD r Cl) d O c z l l 00 W o v T ; D Z ? rn co O ' (D C 1 I I ' ; ; I ' I 1 CD I ' ' ' I CL D I ; I I 1 ; , > 0) D r* n m 2 °-u, 3 1 I 1 I 1 I ' 1 1 1 M ;u 0171 O "n rn (D - ; ' n c LT Cn - o rn (n _ G) -0M 7C r;0 n m :3 w,:?°. ? M n N :k ?? cQ co s O m z a m CID 0 oo m rn n+ ?: ?;, I Z m c M X? 0 ; I z K;K o I ' ?rn CO) G) (D m 0 o ?0 o Om z r (n Z 0 C D = co- =r mrn rn 3 C ? Q v ? ?a?°?ae m C3 ° o E a- ? ? D ° c °' (D (D W 3 Cf) 4VU1 0 C (D ; - I 1 I I I I (D Q Q 33 ° 3 03 T S U- ?• tV 0) > V/ O 0 d v O r+ -n m 0 O °1 3 -0 0 °- O co cD _ D \ o uo C r D U = T N 0 _s C) N C D 0 O ' N N °O 03 I S T 2 -? CO) lk fD X ? n = S N- j HI 4.6 REFERENCE PLANT COMMUNITIES In order to establish a forested wetland system for mitigation purposes, a reference community needs to 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. However, forest canopies have developed on these reference sites which support soil, landform, and hydrological characteristics that restoration will attempt to emulate. All of the RFE sites 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 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 regional reference sites 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. However, the 16 plots have been placed within relatively mature bottomland hardwood/swamp forests that have developed on accreted sediment. 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 1 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 a/. 1990) of dominant canopy and mid-story trees were calculated. The composition of shrub/sapling and herb strata were recorded and identified to species (Table 4 and Table 5). At Site 1 (Table 4), the forest canopy is dominated by green ash, (Importance value [IV] 28%), sweetgum (IV 19%), American elm (U/mus americana) (IV 11 %), box elder (IV 8%) and red maple (IV 7%). Canopy species with lesser importance include black willow, slippery elm (Uimus aiata), river birch, tulip poplar, and water oak (Quercus nigra). Understory trees include flowering dogwood, ironwood, and sugarberry (Ceitis iaevigata). A developed shrub layer is not generally present. Herbs include Nepal microstegium, violets (Viola spp.), asters (Aster sp.), and river oats (Chasmanthium /atifo/ium). 0 fl 39 d [l M 'J 0 It WI J m H co co CG y E 7 U m Cl) n o ? a C' CL ? E o = ro ?U N r 0 to W m «+ O N u. CD O C U. Co m E U O a? m m CC m m ? > R -- 00 m O n O ?t M M N N N ?- .- .- O t j \ N r- O O .? CL E ?= w r? o rn oo w n .- .- N M ? N o 0 0 0 an d M N O ? ?- . Ci Q O co n O r- U•) M M 1- N CD to co N It qt Q 00 O M co co r, ?- O N N .- .- O O O M N O U) N t N C,1 w m Q U > C ++ m o r- •- OA CD CD M CD Co Cl) M Cl) M M M O 10 ? \ r '- •-- Q LL v O CD LD 't M N N M N N r- '- t- .- .- In m m c m U. ?-' to o d ?t CD 00 to M N N .- N .-- - - O n C M N e- O p ... OC O N -0 'o -t M M Ea 7 m Z c U j Lo m czi c Q J m y (n ro ci c ro ro CO ro a ro N m N m c ro ro c ° t:,) a o 0 Z3 m ?o c o a? ?., ro m ro c c y c y ro I y c h rn J .C ro a ?, c c ? ? a? ? ? i y J C CO 5 Q C c v ro o o . n? o ro O LC Q Q J m -j d d U U F- 0 CL Q U O X .N 0 E Cn u i 0 0 LO LL,I J m H U E y N d a o N a ? a E O d c m ?U N O LO W d M O h U. d ? O C O U. co U O d m r- d (D U Co O N N CD LO LO LO N N .- O R M N O 0 ... E r- LO a) O d cD N O O O CO m to r r CD m ` a co ` co O n O '- ?- O O '- M •- Q r` ? O r- '- LO r` .- O O O M co LO e- .- r- ?N ? N N ? co m (D U > C CD M O M O O LO M M M M M o N N '- O r. O a: ED U. U U 7 r M CS C9 U. CU ?. m C o N N O It M M .- .- .- O N .- O CC) O to O N LO CD M "t CD e- M N Q) O ? 'L7 O d ?- E z .- 3 C z s cri co ti m k m to v co C Q) ;D C CCi • U h c O r V ° > 'cu ° c cn Q j C C Q) ? ' V co h J CO G i CV c m V 3 O y V H ? ? O :: m C v .C ? ? C C h H C Q C a m V Co J . k J a U y O a U CD O c O O E At Site 2 (Table 5), the forest canopy is dominated by green ash, (IV 39%), box elder (IV 22%), American elm (IV 12%), and swamp chestnut oak (IV 6%). Portions of the canopy M 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. Herbaceous species include Japanese honeysuckle (Lonicera japonica), blackberry, muscadine, common Fr,I 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 phe/%s), swamp chestnut oak, green ash, overcup oak, and swamp cottonwood (Popu/us 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 places. Q 4.7 REFERENCE PHYSIOGRAPHY AND SURFACE TOPOGRAPHY Surface features were mapped within reference Piedmont swamp/bottomland hardwood forest in order to establish base-line topographic conditions for restoration planning use. This community lies within a seasonally to semi-permanently inundated area that has supported sediment accretion in the past with inundation from stream flows occurring on a frequent basis. The channel is actively migrating across aggrading floodplain, similar to conditions that may be induced in a greentree impoundment over time. Topographic maps of the accretion area were prepared to 0.5-foot contour intervals by laser level and tape measure. Abandoned stream channels were mapped along with approximate jurisdictional wetland extent relative to the water surface within stream channels. A plan view, cross-sections, and profiles were generated for the channel and adjacent alluvial surface. The channel dimension, rate of channel migration, and slope of the floodplain floor represent the primary features extrapolated for use in restoration planning. The objective of restoration is to reduce the effective size of the Reddicks channel to induce sediment deposition, channel migration, braiding, ponding, and/or anastomosed stream types above the water supply reservoir. E 42 a Figure 13 depicts a plan view and cross-sections of the alluvial fan, including locations of abandoned channels that have developed over the last several years. The channel exhibits active migration across the valley floor as aggradation processes elevate isolated portions of the floodplain. The active channel is classified as an E5 (highly sinuous) stream type in upper reaches of the reference site. Subsequently, the channel transitions into an anastomosed (DA5-6) channel and subsequent braided (D6) channel immediately prior to the confluence with a near-permanently inundated section of the reference reach. This braided reach and near-permanently inundated area represents projected conditions within the transition zone into the reservoir conservation pool. The floodplain throughout this reference reach continues to support forest vegetation, including shrub-scrub dominated communities within the potentially inundated areas. I 0 43 m m = = = = m = = C;? = = = = = C= c3m = LI-1:1, F L' I r? F n n iJ I 1 J 7 C. 5.0 WETLAND RESTORATION PLAN This wetland restoration plan has been designed to convert the entrenched channel and adjacent abandoned terrace into a series of greentree impoundments immediately above the Randleman Reservoir conservation pool. A greentree impoundment is an alternative mitigation option which is expected to facilitate the establishment of emergent, shrub, and forested wetlands. In general, a green tree impoundment comprises a floodplain levee and controllable outlet structure. The elevation of the outlet is raised during winter months to promote ponding, sediment deposition, and wetland habitat. Subsequently, the elevation of the outlet is lowered in early spring to allow for vegetation growth, nutrient uptake, and seedling establishment. These impoundments should be constructed to provide for less than 3 feet of inundation during winter months to prevent over-topping and to allow for survival of planted tree seedlings. The winter depth is generally dependent upon the height of seedlings planted. The raising and lowering of outlet structures require regular monitoring and maintenance by qualified personnel to facilitate the growth and survival of tree species. The time for outlet adjustment may vary annually and is dependent upon localized conditions within the watershed. Seedling mortality should be tracked on an annual basis and the date of spring lowering of water levels should be modified to maximize the rate of forest regeneration. Tree or shrub species selected for planting will also vary based on expected hydrologic regimes and other site- specific conditions. Therefore, a management plan has also been prepared (Section 8.0) for long term maintenance of these systems over the life of the Randleman Reservoir. Components of this plan have been established based on reference wetland studies described in Section 4.0. This effort will be performed by: 1) passively saturating/inundating surfaces associated with the reservoir conservation pool; 2) installing controllable weirs and dams; 3) removing waste debris and scarifying pastured surfaces for reforestation; 4) distributing woody debris into formerly cleared and pastured areas; and 5) planting of target wetland tree species 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 PASSIVE SATURATION / INUNDATION FROM THE RESERVOIR POOL Based on reference studies within existing water supply reservoirs in the region, wetlands are projected to develop on surface elevations ranging from a minimum of 1 foot below, to 2 feet above the conservation pool (681-684 feet above MSL). As depicted in Figure 9, shrub/scrub and submerged aquatic vegetation is projected to develop on surfaces ranging between 681 and 682 feet above MSL, encompassing approximately 1.3 acres of land area. This land area is expected to expand into open water portions of the Site over time as sediment accretion occurs within the reservoir pool (below existing elevations of 45 P I F i 681 feet above MSL). However, restoration plans are designed to delay this accretion in favor of alluvial deposition within greentree impoundments. Based on reference studies, elevations between 682 and 684 feet above MSL will passively develop shrub-scrub, bottomland hardwood, and bottomland swamp forest wetlands. This area encompasses approximately 3.6 acres within central to lower portions of the Site (Figure 9). These areas will be planted with tree species likely to replace existing elements as wetland hydrology begins to dominate the area (Section 5.5). Active wetland restoration will be initiated immediately above wetlands passively restored by the conservation pool. Because restoration design is dependent upon initial establishment of backwater conditions in Reddicks Creek, construction activities associated with controllable weirs and dams should be performed concurrent with filling of the reservoir. 5.2 IMPOUNDMENT / WEIR CONSTRUCTION Four impoundments with in-stream weir structures will be constructed within the Site, at each 2-foot rise in the valley floor (Figure 14). The first impoundment has been placed on the valley floor at the 684-foot contour depicted on topographic mapping. A more accurate placement of this structure can be achieved by observing actual water surface elevations in the channel resulting from the established conservation pool. Subsequently, the weir would be accurately placed 2 feet above the conservation pool water surface. The remaining three impoundments have been placed in the valley at approximate floodplain elevations of 686, 688, and 690 feet above MSL. Figure 10 provides a conceptual depiction of the proposed impoundment structure including target elevations for the winter water surface and embankment height at each location. The design or placement of these impoundments may be modified during the engineering design phase based on potential stability, constructability, cost, or other constraints. 5.3 SURFACE SCARIFICATION / WASTE DEBRIS REMOVAL Before wetland community restoration is implemented, pasture lands will be scarified (Figure 14). The scarification will be performed as linear bands directed perpendicular to land slope (surface water flows). After scarification, the soil surface will exhibit complex microtopography ranging to 0.5 feet in vertical asymmetry across local reaches of the landscape. Restored microtopographic relief is considered critical to short term hydrology restoration efforts. Therefore, multiple passes along each band is recommended to ensure adequate surface roughing and surface water storage potential across the Site. Subsequently, community restoration will be initiated on scarified wetland surfaces. Prior to scarification, golf course debris will be removed from areas projected to be inundated by mitigation activities. Debris will include concrete cart pathways, sheds, and cart bridges. All existing cart bridges over Reddicks Creek are projected to reside at or under the projected, winter water surface elevation (Figure 4). 46 O M W m 0 I o Mlm rn O O 0 0 . w ro - OR 0 I O • m r 0 A \ \ Cep\'? ?? I Y 11 1 1 T A O C7 'T1 (? 17 r- o g ? _ ro Z Z ;u C') 3: o o c X z uzi m0 N o ??j z c xo zzz ? m r V D ?b A? \ 6 0 a A 0 A 0 A - •? -'- ??'?'0 011 !.) -'?'"????„J' ?? . - .?)'?11 En x ° 1 o n - o' a co m= OS m FR? O 23 o z ?i -v ?w 3? z cl) 2 a> M C) 0 _O m o° - i r- M3 Z-40 ?c O W N4 c w No C? > Zg fD - 0 Z 0 °o_ 0 11 ---111 -ill -Ljll 5.4 WOODY DEBRIS DEPOSITION Re-introduction of woody debris represents an important component of wetland restoration on pastoral lands. Woody debris, including downed trees, tip mounds, snags, and decomposing material represents important habitat elements for wetland dependent wildlife. However, the restoration areas on pasture land will not be capable of providing coarse, woody habitat elements for up to 50 years after re-planting. Therefore, woody material generated from embankment construction or other activities on the property 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. This effort will be supervised by a wildlife biologist to establish adequate material for wetland habitat restoration. 5.5 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 community types contribute to diversity and provide secondary benefits 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) Piedmont swamp/bottomland hardwood forest and 2) scrub-shrub/Piedmont swamp forest. Planting Plan Emphasis has been focused on developing a diverse plant assemblage. This is particularly vital due to the limited distribution of mast-producing bottomland hardwood tree species presently existing in the vicinity, as evidenced during the RFE search. Planting a variety of mast-producing species will provide a food source for wildlife and will facilitate habitat diversity on the Site. 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. Figure 15 depicts the locations targeted for planting, encompassing 22.7 acres of land area. Planted species names by community are listed below. F11 7 Q'I 48 Cl w M 0 1 0 hm o FW 0 0 A O --W j4? A 4 N n m w 0 0 4 n °o ® ® IO ,= fo m m - -?i o m ° UT -00 m n (On ic 0 -1 m e m -Zi -Zi co m o Z ;u ° o c o 0 -i o N ? m I Z ?! W a? m i` rfl V? b?\ \? a \? w `v M ti m x o ..) n " o z 0 0 0 0 0 0 _o u C m C. =10 SSob D € 4 00 Mc: O ^ z C/) D1 zg 0 0 A °m alb p A ,q ?•? ffi? O• n Piedmont Swamp/Bottomland Hardwood Forest 1. Cherrybark Oak (Quercus pagoda) 2. Overcup Oak (Quercus lyrata) 3. Willow Oak (Quercus phellos) 4. 5. Swamp Chestnut Oak (Quercus michauxii) Swamp Cottonwood (Popu/us heterophyllal 6. Shagbark Hickory (Carya ovata) 7. Bitternut Hickory (Carya cordiformis) 8. Green Ash (Fraxinus pennsylvanica) 9 American Elm (U/mus americana) 10 Winged Elm (U/mus alata) 11. Tulip Poplar (Liriodendron tulipifera) Scrub-Shrub/Piedmont Swamp Forest 1. Black Willow (Sa/ix nigra) 2. Possum-haw (ilex decidua) 3. Carolina holly (l/ex ambigua) 4. River Birch (Betula nigra) 5. American Sycamore (Platanus occidentalis) 6. Green Ash (Fraxinus pennsylvanica) 7. American Elm (U/mus americana) 8. Swamp Cottonwood (Populus heterophylla) 9. Overcup Oak (Quercus lyrata) 10. 11. Swamp Chestnut Oak (Quercus michauxii) Silky Dogwood (Corpus amomum) 12. Button-bush (Cephalanthus occidentalis) 13. Elderberry (Sambucus canadensis) 14. Tag Alder (A/pus serru/ata) 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. Bare-root seedlings of tree species will be planted within specified areas at a density of 680 stems per acre (8-foot centers). The total number of stems and species distribution within each planting association are depicted in Table 6. 0 50 I?l 0 0 9 TABLE 6 Planting Plan Vegetation Association (Planting area) Shrub-Scrub/ Swamp Forest Bottomland Hardwood/ Swamp Forest TOTAL STEMS PLANTED Stem Target (trees/ac) 680 680 Area (acres) 4.3 18.4 22.7 SPECIES # planted M total) # planted M total) # planted M total) River Birch 30000) 300 Silky Dogwood 300(10) 300 Button-bush 30000) 300 Elderberry 300(10) 300 Tag Alder 30000) 300 Black Willow 150(5) 150 Possum-haw 150(5) 150 Carolina Holly 150 (5) 150 American Sycamore 150(5) 150 Swamp Cottonwood 300(10) 1250 (10) 1550 American Elm 150(5) 650(5) 800 Green Ash 150(5) 650(5) 800 Swamp Chestnut Oak 150(5) 1250 (10) 1400 Overcup Oak 150(5) 125000) 1400 Cherrybark Oak 1250 (10) 1250 Willow Oak 1250 (10) 1250 Shagbark Hickory 1250 (10) 1250 Bitternut Hickory 1250 (10) 1250 Winged Elm 125000) 1250 Tulip Poplar 1250 (10) 1250 TOTAL 3000 12550 15550 1: Some non-commercial elements may not be locally available at the time of planting. The stem count for unavailable species should be distributed among other target elements based on the percent (%) distribution. One year of advance notice to forest nurseries will promote availability of some non-commercial elements. However, reproductive failure in the nursery may occur. 2: Scientific names for each species, required for nursery inventory, are listed in the mitigation plan. 1491 91 0 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. 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. The anticipated 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 15,550 seedlings will be planted during wetland community restoration efforts. 0 52 11 0 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 monitoring wells will be designed and placed in accordance with specifications in U.S. Corps of Engineers', Installing Monitoring Wells/Piezometers in Wetlands (WRP Technical Note HY-IA-3.1, August 1993). Monitoring wells will be set to a depth of up to 80 inches below the soil surface to track water surface elevations in the impoundment relative to the weir height. All screened portions of the well 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 five 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 well will be stabilized from flood shear by reinforcing steel bar (re-bar). Five monitoring wells will be installed in restoration areas to provide representative coverage throughout the Site. Approximate well locations are depicted in Figure 16. 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 wells 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% 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% of the growing season. This hydroperiod translates to saturation for a minimum, 11-day (5%) 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. 0 53 0 M M _ M =3 [ CD = ,> C:::l ME EM Wa w I o 6J%1 o o L.U Q 0 0 -0 p 0 Ja Lm N ` O At 9 IM 4 Ri" O ' r A A Cep\'L4 (N? C/ Uv?- b? t o ? i o I :* i c m m u o? zD z0 0 -I 0 tn? N z %p 0 o?. -i O o v :, 0 ;u m 0 ;u z z o N a r*i o z m ? r r 0 fi a N N ... j V V O n I+ I+ I+ m v 11? C r! O 0 A A coo m `r v y v /? n ED co m os ?:9 ? o 0 ZQH -It. m e m o 0 C? 000 m??? o w N Z??Z a fA $tg 0 0 0 0 -1 ,n 0 0 °o V1 J n IT u U C E C1 0 F?J 0 P U Gl 6.3 SOIL Mitigation activities are expected to increase the deposition and transport of stream sediments during overbank flood events. As a result, soils (Fluvaquents) are continuously reworked by fluvial processes. Because iron reduction rates (gleying) are not spatially or temporally uniform 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 well 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 wells 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. 55 ki 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. 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. well 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 0.11-acre plot sample at the location (600 feet x 8 feet / 43,560 square feet/acre). Ten plots will be established to provide a 5% 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 4.6 and Section 5.5). 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% of the 320 stem per 0 56 ° Q acre total. Additional stems of a particular species above the 20% 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% of the 320 stem 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. 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. 57 F417"i 7.0 IMPLEMENTATION SCHEDULE Project implementation will include performance of restoration work in three primary stages including: 1) impoundment / weir construction and site preparation; 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 and Site Preparation Stage 1 will be performed concurrent with or subsequent to filling of the reservoir. Greentree impoundment dams and weirs 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 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 1 is complete. The seedlings will be planted during the winter dormant period, prior to March 1. Stage 3: Monitoring Plan Implementation Monitoring wells 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 frequently to read monitoring wells 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. 0 58 Fj'? 0 8.0 MANAGEMENT PROGRAM Greentree impoundments require modification of water surface elevations on a regular 1.? 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 /obata) 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 22.7-acre Site. Target hydrological goals include soil saturation or inundation for a minimum of 5% of the growing season (March 26 to November 6). The 5% criterion must be achieved in 50% of the years over the life of the Randleman Reservoir. 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 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 Section 9.0, the resource agency will provide resources necessary for establishment and maintenance of the Officer. 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 and implement, in consultation with qualified wildlife biologists, the following greentree impoundment management components. 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. 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 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. 59 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. 0 60 M. 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. i 61 i 0 10.0 WETLAND FUNCTIONAL EVALUATIONS Mitigation activities at the Reddicks Creek 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, soil leveling/compaction in pasture areas, 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 by alternative land uses on the stream terrace. 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 Lake Effect Wetlands Wetland restoration objectives have been adapted for this project due to location of the Site relative to the Randleman Reservoir. The lower half of the Site will be directly influenced by the reservoir conservation pool, including sediment deposition within stream channels, development of accreting sediment bars, and establishment of wetlands on saturated/inundated surfaces. Based on reference studies, these lake effect wetlands are projected to support a mosaic of emergent, shrub-scrub, and forested wetland communities on land surfaces from 1 foot below to 2 feet above the conservation pool. This land area, comprising approximately 4.9 acres (Figure 9), will provide wetland functions such as increased habitat for wetland dependent wildlife, sediment retention above the water supply, and pollutant processing on vegetated wetland surfaces. Open water is also projected to encompass approximately 1.7 acres within the lake effect area that will provide for sediment storage and accreting wetland shorelines (Figure 16). Monitoring and management of these lake effect wetlands will assist in ensuring that land surfaces exposed to long-term sedimentation are not elevated above the water table, with capacity to support wetland functions subsequently reduced or diminished over time. In addition, efforts to maintain vegetation within rapid sedimentation or inundated areas will also be employed during the monitoring period. Greentree Impoundments I3 The upper half of the Site will be used to extend the sediment deposition wedge associated with the reservoir and to establish wetland communities capable of providing 0 62 L M wildlife habitat and water quality benefits. Greentree impoundments are 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 9.1-square mile, urbanizing watershed. Pro-active mitigation within the greentree impoundments is projected to provide approximately 16.1 acres )f wetland restoration / creation above the lake effect, wetland restoration / creation area (an additional 4.9 acres). Therefore, 21.0 acres of wetland restoration / creation and '1.7 acres of open water are potentially provided by the Site. i 63 L 0 11.0 REFERENCES 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. 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Memorandum of Agreement Between the EPA and the DOE Concerning the Determination of Mitigation Under the Clean Water Act, Section 404(b)(1) Guidelines. Washington, DC. Rohde, F. C., R. G. Arndt, D. G. Lindquist, and J. F. Parnell. 1994. Freshwater Fishes of the Carolinas, Virginia, Maryland, and Delaware. The University of North Carolina Press, Chapel Hill, NC. 222 pp. Rogers, J.S. 1985. Water management model evaluation for shallow sandy soils. Transactions of the ASAE 28 (3): 785-790. Rosgen, D. 1996. Applied River Morphology. Wildland Hydrology (Publisher). Pagosa Springs, Colorado. Schafale, M. P., A.S. Weakley. 1990. Classification of the Natural Communities of North Carolina: Third Approximation, NC Natural Heritage Program, Division of Parks and Recreation, NC DEM, Raleigh NC. Schouwenaars, J.M. 1995. The selection of internal and external water management options for bog restoration. (in) Restoration of Temperate Wetlands. (ed.) B. D. Wheeler, S. C. Shaw, W. J. Fojt, and R. A. Robertson. John Wiley & Sons, Ltd. West Sussex, England. L? 66 ji-a H1 Simmons, C.E. 1976. Sediment Characteristics of Streams in the Eastern Piedmont and Western Coastal Plain Regions of North Carolina. U.S. Geological Survey Water Supply Paper, W 1798-0,p. 01-032. Reston Va. Skaggs, R.W. 1982. Field Evaluation of a Water Management Simulation Model. Transactions of the ASAE 25 (3), pp 666-674. Skaggs, R.W., N.R. Fausey, B.H. Nolte. 1981. Water Management Evaluation for North Central Ohio. Transactions of the ASAE 24 (4), pp 922-928. Skaggs, R.W., J.W. Gilliam, R.O. Evans. 1991. A Computer Simulation Study of Pocosin Hydrology. Wetlands (11), pp 399-416. Skaggs, R.W., et al. 1993. Methods for Evaluating Wetland Hydrology. ASAE Meeting Presentation Paper No. 921590. 21 p. Smith, R.D., A. Ammann, C. Bartoldus, M.M. Brinson. 1995 (unpublished). An Approach for Assessing Wetland Functions Using Hydrogeomorphic Classification, Reference Wetlands, and Functional Indices. Wetlands Research Program Technical Report WRP DE- US Army Engineer Waterways Experiment Station, Vicksburg, MS Strahler, A.N. 1964. Geology. Part II. Quantitative geomorphology of drainage basins and channel networks. (in) Handbook of Applied Hydrology. (ed. V.T. Chow), pp. 4-39 to 4-76, McGraw Hill, New York. Susanto, R.H., J. Feyen, W. Dierickx, G. Wyseure. 1987. The Use of Simulation Models to Evaluate the Performance of Subsurface Drainage Systems. Proc. of the Third International Drainage Workshop, Ohio State University, OH. pp. A67 - A76. U.S. Department of Agriculture (USDA). 1987. Hydric Soils of the United States. In cooperation with the National Technical Committee for Hydric Soils, USDA Natural Resource Conservation Service. U.S. Department of Agriculture (USDA). 1977. Soil Survey of Guilford County, North Carolina. Natural Resource Conservation Service. U.S. Department of Agriculture (USDA). 1970. Soil Survey of Wake County, North Carolina. Natural Resource Conservation Service U.S. Fish and Wildlife Service. 1994. Schweinitz's Sunflower Recovery Plan. Atlanta, GA. 28 pp. 0 67 0 U.S. Fish and Wildlife Service (USFWS). 1988. Cape Fear Shiner Recovery Plan. U.S. Fish and Wildlife Service, Atlanta, GA. 18 pp. U.S. Geological Survey (USGS). 1974. Hydrologic Cataloging Unit Map for the State of North Carolina. U.S. Geological Survey (USGS). 1982. 7.5 minute, High Point East 1:24000 Quadrangle. Yoakum, J., W.P. Dasmann, H.R. Sanderson, C.M. Nixon, and H.S. Crawford. 1980. Habitat Improvement Techniques. Pp 329-403 in S.D. Schemnitz (Editor). Wildlife Management Techniques Manual, 4th ed., rev. The Wildlife Society, Washington, DC 686 pp. 0