20170537 Ver 1_DRAFT_Mitigation Plan_04.27.2017_20170517

DRAFT MITIGATION PLAN
Hannah Bridge Stream and Wetland Mitigation Site
Johnston County, North Carolina
Neuse River Basin
CU 03020201
Prepared by:
fires
Bank Sponsor: EBX-Neuse I, LLC,
302 Jefferson Street, Suite 110
Raleigh, NC 27605
919-209-1056
April 2017

1 *14 lu I\ 1
The Hannah Bridge Stream and Wetland Mitigation Site (the "Site") is located within a watershed
dominated by agricultural land use in Johnston County, North Carolina, approximately 5 miles south
of the town of Four Oaks. The project streams and wetlands have been significantly impacted by
channelization and cattle access. The project will involve the restoration and protection of streams in
the Neuse River watershed and the enhancement of adjacent riparian wetlands. The purpose of this
mitigation site is to restore and enhance a stream/wetland complex located within the Neuse River
Basin. The Site has been designed in concurrence with the Hannah Bridge Riparian Buffer and Nutrient
Offset Mitigation Bank.
The Site lies within USGS Hydrologic Unit Code (HUC) 03020201150020 (USGS, 2012) and within
the North Carolina Division of Water Resources (NCDWR) Neuse River Sub -basin 03-04-02
(NCDENR, 2005). The 2010 Neuse River Basin Plan (NRBP) identified the Hannah Creek watershed
(HUC 03020201150020) as a Targeted Local Watershed (TLW), a watershed that exhibits both the
need and opportunity for wetland, stream, and riparian buffer restoration. The Hannah Creek watershed
includes 34 square miles of watershed area, with forty-two percent of the 102 stream miles lacking
wooded buffers. Fifty-four percent of the watershed is used for agricultural purposes and seven percent
is currently developed.
The Site is located within the downstream end of HUC 03020201 and includes streams that directly
discharge into Hannah Creek. Many of the project design goals and objectives, including restoration of
riparian buffers to filter runoff from agricultural operations and improve terrestrial habitat, and
construction of in -stream structures to improve habitat diversity, will address the degraded water quality
and nutrient input from farming that were identified as major watershed stressors in the 2010 Neuse
RBRP. The project presents 6,687 linear feet of stream restoration and enhancement generating 5,209
Stream Mitigation Units (SMU) and 27.18 acres of wetland restoration, enhancement, and preservation
generating 11.73 Wetland Mitigation Units (WNW).
The site consists of agricultural fields, cattle pastures and wooded areas. The total easement area is 46.2
acres. The wooded areas along the easement corridor designated for restoration activities are classified
as mixed hardwoods. Invasive species are present throughout the wooded areas. Channels proposed for
restoration are degraded to a point where they no longer access their floodplain, lack riparian buffers,
allow livestock access, and aquatic life is not supported. Current stream conditions along the proposed
restoration reaches exhibit habitat degradation as a result of impacts from livestock and channelization
performed to promote agricultural activities. Additionally, the riparian buffer is in poor condition
throughout most of the project area where it is devoid of trees or shrubs and active pasture is present
up to the edge of the existing channel.
The objective for this mitigation site is to restore and design natural waterways through stream/wetland
complexes with appropriate cross-sectional dimension and slope that will provide function and meet
the appropriate success criteria for the existing streams. Accomplishing this objective entails the
restoration of natural stream characteristics, such as stable cross sections, planform, and in -stream
habitat. The floodplain areas will be hydrologically reconnected to the channels where feasible to
provide natural exchange and storage during flooding events. The design will be based on reference
conditions, USACE guidance (USACE, 2005), and criteria that are developed during this project to
achieve success. Additional site objectives, such as restoring the riparian buffer with native vegetation,
ensuring hydraulic stability, and eradicating invasive species, are listed in Section 1.
The stream design approach for the Site is to combine the analog method of natural channel design with
analytical methods to evaluate stream flows and hydraulic performance of the channel and floodplain.
Hannah Bridge Mitigation Plan ii April 2017

The analog method involves the use of a "template" stream adjacent to, nearby, or previously in the
same location as the design reach. The template parameters of the analog reach are replicated to create
the features of the design reach. The analog approach is useful when watershed and boundary conditions
are similar between the design and analog reaches (Skidmore et al., 2001). Hydraulic geometry was
developed using analytical methods in an effort to identify the design discharge.
The Site will include Priority I restoration, Enhancement Level ll, and Enhancement Level 111. Priority
I restoration reaches will incorporate the design of a single -thread meandering channel, with parameters
based on data taken from the reference site described above, published empirical relationships, NC
Coastal Plain Regional Curves, and hydrologic and hydraulic analyses.
The Site will include wetland restoration, enhancement, and preservation. Wetland restoration will
occur adjacent to Priority I stream restoration reaches. The restoration approach is to reconnect the
floodplain wetlands to the stream, fill existing ditches, rough the floodplain surface, and plant native
tree and shrub species commonly found in small stream swamp ecosystems. The wetland enhancement
treatment will primarily be excluding livestock from the pasture and currently grazed forested,
improving hydrology via pond removal and ditch plugging, and planting native tree and shrub species.
After completion of all construction and planting activities, the Site will be monitored on a regular basis
and a physical inspection of the Site will be conducted at a minimum of twice per year throughout the
seven-year post -construction monitoring period, or until performance standards are met. These site
inspections will identify site components and features that require routine maintenance. The measure
of stream restoration success will be documented by bankfull flows and no change in stream channel
classification. Sand bed channels are dynamic and minor adjustments to dimension and profile are
expected. The measure of vegetative success for the Site will be the survival of at least 210 seven-year
old planted trees per acre with an average height of 10 feet at the end of year seven of the monitoring
period.
Upon approval for closeout by the Interagency Review Team (IRT), the site will be transferred to the
North Carolina Wildlife Habitat Foundation (NCWHF). The NCWHF will be responsible for periodic
inspection of the Site to ensure that restrictions required in the Conservation Easement or the deed
restriction document(s) are upheld. Endowment funds required to uphold easement and deed
restrictions will be negotiated prior to site transfer to the responsible party.
Hannah Bridge Mitigation Plan iii April 2017

TABLE OF CONTENTS
1 PROJECT INTRODUCTION........................................................................................................ 7
1.1 Site Selection..........................................................................................................................
7
1.2 Project Components................................................................................................................
7
2 WATERSHED APPROACH.........................................................................................................
9
2.1.1 Historical Land Use and Development Trends...............................................................
9
2.2 Soil Survey.............................................................................................................................
9
2.3 Site Photographs..................................................................................................................
12
3 SITE PROTECTION INSTRUMENT.........................................................................................
15
3.1 Site Protection Instrument(s) Summary Information...........................................................
15
4 BASELINE INFORMATION......................................................................................................
16
4.1 Watershed Summary Information........................................................................................
16
4.1.1 Drainage Area...............................................................................................................16
4.1.2 Surface Water Classification........................................................................................16
4.2 Reach Summary Information...............................................................................................
16
4.2.1 Channel Classification..................................................................................................17
4.2.2 Discharge......................................................................................................................17
4.2.3 Channel Morphology....................................................................................................17
4.2.4 Channel Stability Assessment......................................................................................19
4.2.5 Bankfull Verification....................................................................................................20
4.2.6 Vegetation.....................................................................................................................20
4.3 Wetland Summary Information............................................................................................
21
4.3.1 Existing Wetlands.........................................................................................................21
4.3.2 Existing Hydric Soil.....................................................................................................
22
4.4 Regulatory Considerations and Potential Constraints..........................................................
23
4.4.1 Property Ownership, Boundary, and Utilities...............................................................
23
4.4.2 FEMA/ Hydrologic Trespass........................................................................................23
4.4.3 Environmental Screening and Documentation.............................................................
23
5 FUNCTIONAL UPLIFT POTENTIAL.......................................................................................
25
6 DETERMINATION OF CREDITS.............................................................................................
26
7 CREDIT RELEASE SCHEDULE...............................................................................................
27
7.1 Initial Allocation of Released Credits..................................................................................
27
7.2 Subsequent Credit Releases..................................................................................................
28
8 MITIGATION WORK PLAN.....................................................................................................
29
8.1 Reference Stream Studies.....................................................................................................
29
8.1.1 Target Reference Conditions........................................................................................
29
8.2 Design Parameters................................................................................................................
30
8.2.1 Stream Restoration Approach.......................................................................................
30
8.2.2 Wetland Restoration and Enhancement........................................................................
36
8.2.3 Natural Plant Community Restoration.........................................................................
36
8.2.4 Best Management Practices (BMPs)............................................................................
38
8.2.5 Soil Restoration............................................................................................................
38
8.3 Data Analysis.......................................................................................................................
38
8.3.1 Stream Data Analysis...................................................................................................
38
8.3.2 Mitigation Summary .....................................................................................................41
9 MAINTENANCE PLAN.............................................................................................................
43
10 PERFORMANCE STANDARDS................................................................................................
44
10.1 Stream and Wetland Restoration Success Criteria...............................................................
44
10.1.1 Bankfull Events............................................................................................................
44
10.1.2 Cross Sections..............................................................................................................44
Hannah Bridge Mitigation Plan iv April 2017

List of Tables
Table 1. Hannah Bridge Site Project Components — Stream Mitigation ................................................ 7
10.1.3 Digital Image Stations..................................................................................................
44
Table2. Mapped Soil Series.................................................................................................................
10.1.4 Wetland Hydrology Criteria.........................................................................................44
Table 4. Project Parcel and Landowner Information............................................................................15
10.2 Vegetation Success Criteria..................................................................................................
44
11
MONITORING REQUIREMENTS............................................................................................
45
20
11.1 As -Built Survey....................................................................................................................46
Table 9. Regulatory Considerations.....................................................................................................
11.2 Visual Monitoring................................................................................................................
46
25
11.3 Cross Sections......................................................................................................................
46
Table 12a. Stream Credit Release Schedule.........................................................................................27
11.4 Wetland Hydrology..............................................................................................................
46
28
11.5 Vegetation Monitoring.........................................................................................................
46
Table14. Peak Flow Comparison........................................................................................................
11.6 Scheduling/Reporting...........................................................................................................47
Table 15. Stable Channel Design Output.............................................................................................
40
11.7 Adaptive Management..........................................................................................................
47
12
LONG-TERM MANAGEMENT PLAN.....................................................................................
48
13
ADAPTIVE MANAGEMENT PLAN.........................................................................................
49
14
FINANCIAL ASSURANCES......................................................................................................
50
15
OTHER INFORMATION............................................................................................................
51
15.1 References............................................................................................................................
51
List of Tables
Table 1. Hannah Bridge Site Project Components — Stream Mitigation ................................................ 7
Table 2. Hannah Bridge Site Project Components — Wetland Mitigation ..............................................
8
Table2. Mapped Soil Series.................................................................................................................
11
Table 4. Project Parcel and Landowner Information............................................................................15
Table 5. Project Watershed Summary Information..............................................................................16
Table 6. Summary of Existing Channel Characteristics.......................................................................17
Table 7. Channel Stability Assessment Results....................................................................................
20
Table 8. Wetland Summary Information..............................................................................................22
Table 9. Regulatory Considerations.....................................................................................................
24
Table 10. Functional Benefits and Improvements................................................................................
25
Table 11. Mitigation Credits.................................................................................................................26
Table 12a. Stream Credit Release Schedule.........................................................................................27
Table 12b. Wetland Credit Release Schedule......................................................................................
28
Table13. Proposed Plant List...............................................................................................................
37
Table14. Peak Flow Comparison........................................................................................................
40
Table 15. Stable Channel Design Output.............................................................................................
40
Table 16. Comparison of Allowable and Proposed Shear Stresses......................................................41
Table 17. Comparison of Allowable and Proposed Velocities.............................................................
41
Table18. Maintenance Plan .................................................................................................................
43
Table 19. Monitoring Requirements.....................................................................................................
45
Hannah Bridge Mitigation Plan v April 2017

List of Figures
Figure 1- Vicinity Map
Figure 2- USGS Topographic Map
Figure 3- Historical Conditions Map
Figure 4- Soils Map
Figure 5- Landowner Map
Figure 6- Land -use Map
Figure 7- Existing Conditions Map
Figure 8- National Wetlands Inventory Map
Figure 9- FEMA Map
Figure 10- Conceptual Plan Map
Figure 11- Monitoring Plan
Appendices
Appendix A —Site Protection Instrument(s)
Appendix B — Baseline Information Data
Appendix C — Mitigation Work Plan Data and Analyses
Appendix D- Soils Report
Appendix E — Design Plan Sheets (11"x17")
Hannah Bridge Mitigation Plan vi April 2017

1 PROJECT INTRODUCTION
The Hannah Bridge Stream and Wetland Mitigation Site (the "Site") is located within a rural watershed
dominated by agricultural and low density residential land use in Johnston County, North Carolina. The
project streams and wetlands proposed for restoration and enhancement have been significantly
impacted by channelization and agricultural practices. Due to its location and proposed improvements,
the Site will provide numerous ecological and water quality benefits within the Neuse River Basin. The
Site has been designed in concurrence with the Hannah Bridge Riparian Buffer and Nutrient Offset
Mitigation Bank.
1.1 Site Selection
The Site is located in Johnston County approximately 5 miles south of the town of Four Oaks, North
Carolina (Figure 1). To access the Site head south on NC Hwy 96 and turn left onto Green Pasture
road. The Site is located in the Neuse River Basin within Cataloging Unit 03020201 (NCDWR sub -
basin 03-04-02), 14 -digit USGS Hydrologic Unit Code (HUC) 03020201150020 (USGS, 2012)
(Figure 2). The Site is located in the Rolling Coastal Plain (65m) ecoregion.
1.2 Project Components
The project area is comprised of two separate easement locations along multiple drainage features that
flow into Hannah Creek. The northern easement area captures a single tributary to Hannah Creek and
a portion of its headwaters. The southern easement area is separated from the northern area by an active
agricultural field, and is divided into three different areas due to a utility crossing and a culvert crossing.
The stream and wetland mitigation components are summarized in Tables 1 and 2, as well as Figure
10.
Table 1. Hannah Bridge Site Project Components — Stream Mitigation
Total 6,280 6,687 5,209
* SMU adjusted on HB 1 for a 30 ft crossing
t Restoration Credit
Hannah Bridge Mitigation Plan 7 April 2017
Existing
ProposedMitigation
Mitigation
Stationing
Reach
Length
Length
SMUs
Type
(Proposed)
Ratio
(LF)
(LF)
HBI
Restoration
0+15
to
14+45
1,484
1,430
1:1
1,400*
HB2
Enhancement II
14+45
to
18+37
392
392
2.5:1
157
HB3
Restoration
18+37
to
36+44
1,588
1,807
1:1
1,807
H134
Restoration
36+84
to
42+63
579
579
1:1
579
HB4
Enhancement III
42+63
to
44+91
228
228
5:1
46
HF1
Enhancement III
2+18
to
13+58
1,140
1,140
5:1
228
HF1
Restoration
13+58
to
16+04
0
246
1:1
246
HF2
Enhancement III
6+40
to
7+89
149
149
5:1
30
TH3
Enhancement II t
0+63
to
7+79
716
716
1:1
716
Total 6,280 6,687 5,209
* SMU adjusted on HB 1 for a 30 ft crossing
t Restoration Credit
Hannah Bridge Mitigation Plan 7 April 2017

Table 2. Hannah Bridge Site Project Components — Wetland Mitigation
Mitigation Type
Total Acres
MitigationWMUs
Ratio
Re-establishment
3.27
1:1
3.27
Enhancement - High
13.18
2:1
6.59
Enhancement - Low
3.46
3:1
1.15
Preservation
7.27
10:1
1.72
27.18
11.73
Hannah Bridge Mitigation Plan 8 April 2017

2 WATERSHED APPROACH
The 2010 Neuse River Basin Restoration Priorities (RBRP) identified several restoration needs for the
entire Neuse River Basin, as well as for HUC 03020201, specifically. The Hannah Creek watershed
(HUC 03020201150020) was identified as a Targeted Local Watershed (TLW), a watershed that
exhibits both the need and opportunity for wetland, stream, and riparian buffer restoration. The Hannah
Creek watershed includes 34 square miles of watershed area, with forty-two percent of the 102 stream
miles lacking wooded buffers. Fifty-four percent of the watershed is used for agricultural purposes and
seven percent is currently developed.
The Site was identified as a stream and buffer restoration opportunity to improve water quality, habitat,
and hydrology within the Neuse River Basin. The Site is located within the downstream end of HUC
03020201 and includes streams that directly discharge into Hannah Creek. Many of the project design
goals and objectives, including restoration of riparian buffers to filter runoff from agricultural
operations and improve terrestrial habitat, and construction of in -stream structures to improve habitat
diversity, will address the degraded water quality and nutrient input from farming that were identified
as major watershed stressors in the 2010 Neuse RBRP.
The project goals address stressors identified in the TLW and include the following:
• Nutrient removal,
• Sediment removal,
Invasive species treatment,
Filtration of runoff, and
• Improved aquatic and terrestrial habitat.
The project goals will be addressed through the following project objectives:
• Exclusion of livestock,
• Treatment and control of exotic invasive species,
• Restoration of forested riparian stream buffers,
• Stabilization of eroding stream banks due to lack of vegetation and livestock hoof shear,
• Addition of large woody debris, such as log vanes, log weirs, and root wads,
• Restoration, enhancement, and preservation of bottomland hardwood wetlands, and
• Restoration of appropriate pattern, dimension, and profile in stream channels.
2.1.1 Historical Land Use and Development Trends
Aerial imagery indicates that the subject Site has been used extensively for agricultural purposes, and
that the location of the streams has not changed in over 50 years (Figure 3). In the late 1980s, the
upstream most portion of Reach HB1, and the majority of Reach HB3 was cleared for pasture. Since
the early 1990s little has changed in the project area. The area remains in an agricultural community
with some neighboring property forested. Several watershed characteristics, such as groundwater,
vegetation, surface drainage, and potentially soil parameters have been modified. Soil structure and
surface texture have been altered from intensive agricultural operations.
2.2 Soil Survey
The Site is located in the Coastal Plain Physiographic Province. The soils within the Coastal Plain
region of Johnston County formed in sediments deposited several million years ago by the oceans and
streams. The flood plains along the Neuse River consist of relatively recent deposits of sediments that
Hannah Bridge Mitigation Plan 9 April 2017

are not as highly weathered as sediments in the Coastal Plain Region. Much of Johnston County is well
drained; however, several areas are poorly drained.
The Johnston County Soil Survey shows several mapping units across the site. Map units include seven
soil series (Figure 4). The soil series found on the Site are described below and summarized in Table
3.
Goldsboro sandy loam. This is a very deep, moderately drained soil found on uplands of the Coastal
Plain. Soils formed in fluviomarine deposits, and generally occur on slopes between 0-10%. Runoff is
negligible to medium and permeability is moderate. Major uses are cropland. Goldsboro sandy loams
occur along the stream near the middle of the proposed conservation easement.
Lynchburg sandy loam. This is a very deep, somewhat poorly drained soil that occurs on terraces and
flats of the Coastal Plain. They formed in fluviomarine deposits, and generally occur on slopes between
0-5%. Runoff is negligible and permeability is moderate. Major uses are cropland, pasture, and forest.
Lynchburg sandy loam occurs along the stream near the middle of the easement almost opposite of the
Goldsboro sandy loam.
Bibb sandy loam. This is a very deep, poorly drained soil found on flood plains of the Coastal Plain.
Slopes are generally less than 2%. Soils formed in stratified sandy alluvium and have very slow runoff
with moderate permeability. The water table is generally within 8 inches of the surface for six to eleven
months of the year. Bibb sandy loams occurs along the majority of the easement around the stream.
Gilead sandy loam. This is a very deep, moderate to well -drained soil that occurs on ridges and terraces
of the Coastal Plain. They formed in clayey marine deposits, and generally occur on slopes between 2-
8%. Runoff is medium and permeability is moderate. Major uses are cropland. Gilead sandy loam
occurs within the South most wetland and southern end of the tributary inside of the proposed
conservation easement.
Rains sandy loam. This is a very deep, poorly drained soil that occurs on crests of the Coastal Plain.
They formed in Loamy and sandy marine deposits, and generally occur on slopes between 2-6%.
Runoff is low and permeability is moderate. Major uses are cropland. Rains sandy loam occurs within
the North most wetland inside of the proposed conservation easement.
Uchee loamy course sand. This is a very deep, well -drained soil that occurs on flats and depressions
of the Coastal Plain. They formed in fluviomarine deposits, and generally occur on slopes between 0-
2%. Runoff is negligible and permeability is moderate. Major uses are forest and cropland. Uchee
loamy sand occurs within the south wetland inside of the proposed conservation easement.
Altavista fine sandy loam. This is a very deep, moderately to well -drained soil that occurs on stream
terraces of the Coastal Plain. They formed in old loamy alluvium derived from igneous and
metamorphic rock, and generally occur on slopes between 0-3%. Runoff is negligible and permeability
is moderate. Major uses are cropland. Altavista fine sandy loam occurs along the east boundary of the
proposed easement in wetland/stream area.
Hannah Bridge Mitigation Plan 10 April 2017

Table 2. Mapped Soil Series
Map
Unit
Map Unit Name
Percent
Drainage
Hydrologic
Landscape
Symbol
Hydric
Class
Soil Group
Setting
GoA
Goldsboro sandy
2°
�0
Moderately
B
Flats, marine
loam, 0-2% slopes
well
terraces
Ly
Lynchburg sandy loam
6%
Somewhat
C
Flats, marine
poorly
terraces
Bb
Bibb sandy loam,
90%
Poorly
D
Floodplains
frequently flooded
Ra
Rains sandy loam
90%
Poorly
B/D
Flats, arine terraces
Broad interstream
UcB
Uchee loamy coarse
0%
Well
C:
divides on marine
sand
terraces, ridges on
marine terraces
GeB
Gilead sandy loam
0%
Moderate/Well
C
Marine terraces
AaA
Altavista fine sandy
9%
Moderate/Well
C
Stream terraces
loam
Hannah Bridge Mitigation Plan 11 April 2017

2.3 Site Photographs
Upper end of Reach HB 1. 01/14/2016
Eroded banks and oversized channel dimensions
on Reach HB 1. 01 / 14/2016
Hoof shear along Reach HB 1. 05/10/2016
Reach HB2. 01/14/2016
Facing upstream on Reach HB3. 01/14/2016
Facing downstream on Reach H133. 01 /14/2016
Hannah Bridge Mitigation Plan 12 April 2017

Reach HB4. 01/14/2016
HB4 and Hannah Creek Confluence. 01/14/2016
HB4 and Hannah Creek Confluence. 05/10/2016
General conditions along Reach HF 1. 01/14/2016
General channel conditions along Reach HF2.
01/14/2016
Facing downstream on Reach C. 03/09/2015
Hannah Bridge Mitigation Plan 13 April 2017

Pond above Reach TH1. 05/10/2016
Reach TH2. 01/14/2016
Reach TH3. 01/14/2016
General conditions of Wetland Area 1 (WI).
05/10/2016
General conditions of Wetland Area 10 (W10).
05/10/2016
General conditions of Wetland Area 13 (W 13).
05/10/2016
Hannah Bridge Mitigation Plan 14 April 2017

3 SITE PROTECTION INSTRUMENT
3.1 Site Protection Instrument(s) Summary Information
The land required for the construction, management, and stewardship of this Site includes portions of
the following parcels (Table 4 & Figure 5). Once finalized, a copy of the land protection instrument(s)
will be included in Appendix A.
Table 4. Project Parcel and Landowner Information
The Wilmington District Conservation Easement model template was utilized to draft the site protection
instrument. Once finalized, a copy of the final recorded easement will be provided in Appendix A.
EBX-Neuse I, LLC, acting as the Bank Sponsor, will establish a Conservation Easement, and will
monitor the Site for a minimum of seven years. This Mitigation Plan provides detailed information
regarding bank operation, including long term management and annual monitoring activities, for review
and approval by the Interagency Review Team (IRT). Upon approval of the Site by the IRT, the Site
will be transferred to the NCWHF. The NCWHF will be responsible for periodic inspection of the Site
to ensure that restrictions required in the Conservation Easement or the deed restriction document(s)
are upheld. Endowment funds required to uphold easement and deed restrictions will be negotiated
prior to site transfer to the responsible party.
The Bank Sponsor will ensure that the Conservation Easement will allow for the implementation of an
initial monitoring phase, which will be developed during the design phase and conducted by the Bank
Sponsor. The Conservation Easement will allow for yearly monitoring and, if necessary, maintenance
of the Site during the initial monitoring phase. These activities will be conducted in accordance with
the terms and conditions of the approved Mitigation Plan for the Hannah Bridge Mitigation Site. The
Hannah Bridge Mitigation Site will be authorized under the Neu -Con Wetland and Stream Umbrella
Mitigation Bank made and entered into by EBX-Neuse I, LLC, US Army Corps of Engineers, and NC
Division of Water Resources.
Hannah Bridge Mitigation Plan 15 April 2017
Deed Book and
Landowner
Pin
County
Page Number
Parcel Acreage
J & M HOG FARM
INC
157900-32-5319
Johnston
01316-0140
25.555
THOMPSON,
RONALD GREY
157900-22-7731
Johnston
03633-0723
15.328
THOMPSON, C P
JR
157900-34-5414
Johnston
--
19.880
JOHNSON, EARL
BENTON JR
157900-43-3410
Johnston
01218-0278
20.729
THOMPSON, C P
JR
157900-34-8390
Johnston
01432-0212
9.965
THOMPSON,
RONALD GREY
157900-44-5315
Johnston
03633-0723
28.032
The Wilmington District Conservation Easement model template was utilized to draft the site protection
instrument. Once finalized, a copy of the final recorded easement will be provided in Appendix A.
EBX-Neuse I, LLC, acting as the Bank Sponsor, will establish a Conservation Easement, and will
monitor the Site for a minimum of seven years. This Mitigation Plan provides detailed information
regarding bank operation, including long term management and annual monitoring activities, for review
and approval by the Interagency Review Team (IRT). Upon approval of the Site by the IRT, the Site
will be transferred to the NCWHF. The NCWHF will be responsible for periodic inspection of the Site
to ensure that restrictions required in the Conservation Easement or the deed restriction document(s)
are upheld. Endowment funds required to uphold easement and deed restrictions will be negotiated
prior to site transfer to the responsible party.
The Bank Sponsor will ensure that the Conservation Easement will allow for the implementation of an
initial monitoring phase, which will be developed during the design phase and conducted by the Bank
Sponsor. The Conservation Easement will allow for yearly monitoring and, if necessary, maintenance
of the Site during the initial monitoring phase. These activities will be conducted in accordance with
the terms and conditions of the approved Mitigation Plan for the Hannah Bridge Mitigation Site. The
Hannah Bridge Mitigation Site will be authorized under the Neu -Con Wetland and Stream Umbrella
Mitigation Bank made and entered into by EBX-Neuse I, LLC, US Army Corps of Engineers, and NC
Division of Water Resources.
Hannah Bridge Mitigation Plan 15 April 2017

4 BASELINE INFORMATION
4.1 Watershed Summary Information
4.1.1 Drainage Area
The easement totals 46.2 acres and the project streams include multiple drainage features that flow into
Hannah Creek. The total drainage area at the downstream limits of the main project area is 894 acres
(1.39 mi2). The land use in the Site watershed is approximately 54% agricultural, 39% forested, and
5% low-density residential (Table 5 & Figure 6).
4.1.2 Surface Water Classification
The current State classification for the Site restoration reaches is undefined. Tributaries of the Site run
directly into Hannah Creek. Hannah Creek is defined as Class C; NSW (NCDWQ 2012a). Class C
waters are suitable for aquatic life, secondary recreation, and agricultural usage. The NSW is a
designation for nutrient sensitive waters — intended for waters needing additional nutrient management
due to being subject to excessive growth of microscopic or macroscopic vegetation.
Table 5. Project Watershed Summary Information
Level IV Ecoregion
65m - Rolling Coastal Plain
River Basin
Neuse
USGS Hydrologic Unit 8 -digit
03020201
USGS Hydrologic Unit 14 -digit
03020201150020
DWR Sub -basin
03-04-04
Project Drainage Area (acres)
894
Percent Impervious Area
2%
4.2 Reach Summary Information
The project area is comprised of two separate easement locations along multiple drainage features that
flow into Hannah Creek. The northern easement area captures a single tributary to Hannah Creek and
a portion of its headwaters. The southern easement area is separated from the northern area by an active
agricultural field, and is divided into three different areas due to a utility crossing and a culvert crossing.
The northern portion of the project contains Reach TH3, while the southern portion is comprised of
Reaches HB 1, HB2, HB3, H134, HF 1, and HF2.
The Hannah Bridge stream channels include unnamed tributaries that eventually flow into Hannah
Creek (Figure 7). Invasive treatment and stabilization will be performed in select segments of the
project. Stream Classification Forms were completed at representative locations throughout the project
area and stream determinations were confirmed by NCDWR staff (Appendix B). Results of the
preliminary data collection are presented in Figure 7 and Table 6. The Stream Morphology Table is
included in Appendix C.
In general, all or portions of HB 1, HB3, HB4, HF2, and TH3 do not function to their full potential.
Current conditions demonstrate significant habitat degradation as a result of impacts from livestock,
historic land uses, and water diversion. Having been channelized in the past and/or ditched to drain
nearby fields for agricultural activities, some of the streams do not access their floodplains as frequently
as they naturally would have prior to agricultural operations. In most cases, these streams are
hydraulically unstable and are devoid of bedform diversity. Habitat along the majority of the restoration
Hannah Bridge Mitigation Plan 16 April 2017

reaches is poor in that there is little woody debris or overhanging vegetation for fish cover or protection
for other aquatic species. Site photographs and morphological parameters are located in Appendix C.
Table 6. Summary of Existing Channel Characteristics
Reach
Drainage
Area (ac)
ABKF 1
(ft2)
Width
(ft)
Mean
Depth (ft)
Width:Depth
Ratio
Sinuosity
Slope (ft/ft)
HBI
667
12.2
12.1
1.0
12.1
1.2
0.008
HB2
752
15.2
11.5
1.3
8.7
1.2
0.003
HB3
816
14.9
14.8
1.0
15.0
1.0
0.002
HB4
894
19.4
23.8
0.8
29.3
1.1
0.001
HF1
78
3.5
7.2
0.5
15.0
1.1
0.003
HF2
73
1.5
4.5
0.3
13.4
1.1
0.008
TH3
24
1.8
3.7
0.6
9.7
1.0
0.009
'ABKF= cross-sectional area (measured at approximate bankfull stage as estimated using existing conditions
data and NC Regional Curve equations where field indicators were not present)
4.2.1 Channel Classification
The streams have been classified as intermittent and perennial streams using the NCDWR Stream
Identification Form version 4.11 (Appendix B) and are E- and G -stream types as classified using the
Rosgen stream classification system (Rosgen, 1994). The design reaches have been separated into seven
distinct sections that are described in Section 4.2.3. Channel characteristics are summarized in Table
6, and Appendix B. Stream determinations have been verified by NCDWR staff.
4.2.2 Discharge
Estimating flows (discharge) for the Hannah Bridge Site is difficult due to the channelization and
agricultural impacts of the existing streams. Several models, regression equations, and the Coastal Plain
regional curves were used to estimate existing bankfull discharges. Land use and slope were considered
when the discharge calculations were developed. All hydraulic and hydrologic analyses are discussed
in Section 8.3. Data and analysis of the hydrologic and hydraulic models are included as Appendix C.
4.2.3 Channel Morphology
4.2.3.1 Reach HBI
Reach HB 1 is a perennial, meandering channel within an active pasture located at the upstream section
of the project. The reach is approximately 1,097 linear feet and flows to the east to its confluence with
Reach HFI. The channel is located along the southern edge of the valley and is relatively stable
throughout. There are some areas of localized erosion and irregular banks due to cattle access. It has a
drainage area of 1.04 square miles (667 acres). Reach HB 1, an E -type channel, is typically 12 to 14 feet
wide with a mean depth of 1.0 feet and a max depth of 2.2 feet. The approximate bankfull cross sectional
area is 12.2 square feet. The existing slope of Reach HB 1 is 0.008 ft/ft, and the dominant bed material
is very fine gravel. The riparian buffer is comprised of pasture grasses with a narrow band of woody
vegetation located intermittently along the top of banks prior to entering a wooded area near the
downstream limits of the reach.
4.2.3.2 Reach HB2
Reach HB2 is a stable, perennial channel that flows in a northeasterly direction through a heavily
forested area with adjacent wetlands and ends just upstream of the treeline near the confluence with
reach TH2. The reach has a drainage area of 1.17 square miles (752 acres) and is approximately 1,233
Hannah Bridge Mitigation Plan 17 April 2017

linear feet. Reach HB2, a E -type channel, is typically 11.5 feet wide and 1.3 feet deep near bankfull,
with a max depth of 2.0 feet at top of bank. The approximate bankfull cross sectional area is 15.2 square
feet. The existing slope of Reach HB2 is 0.003 ft/ft, and the dominant bed material is fine gravel. The
riparian buffers are hardwood and pine trees with localized areas of invasive species, primarily privet.
4.2.3.3 Reach HB3
Reach HB3 is a channelized perennial ditch within an active pasture that begins upstream of the
confluence with TH2 and ends at an existing culvert (2-24 inch RCPs) crossing. Erosion and irregular
banks are common throughout resulting from frequent cattle access along the channel. HB3 has a
drainage area of 1.28 square miles (816 acres), is approximately 2,267 linear feet and flows in an
easterly direction. This reach is an E -type channel and has widths ranging from 8 to 18 feet. The
approximate bankfull cross sectional area is 14.9 square feet, and mean depths range from 0.9 to 1.2
feet. The existing slope of Reach HB3 is 0.002 ft/ft, and the dominant bed material is very coarse sand.
The riparian buffer consists primarily of pasture grasses with little to no woody vegetation located along
the channel banks.
4.2.3.4 Reach HB4
Reach HB4 is a straightened perennial ditch in an active pasture that begins on the downstream end of
an existing culvert on Reach HB3. The reach is approximately 807 linear feet, has a slope of 0.001 ft/ft,
and flows in a northeasterly direction to its confluence with Hannah Creek. It has a drainage area of
1.40 square miles (894 acres) and has an approximate bankfull cross sectional area of 19.4 square feet.
Reach HB4, a E -type channel, is typically 23 feet wide and has a mean depth of 0.8 feet and max depth
of 2 feet. The existing slope of Reach HB4 is 0.001 ft/ft, and the dominant bed material is coarse sand.
The downstream portion of the channel is multi -threaded and impacted by backwater from Hannah
Creek, a stream/wetland complex. The riparian buffer is comprised of active pasture along the left bank;
however, a narrow strip of woody vegetation with widths ranging from 5 to 20 feet is located along top
of bank. The buffer along the right bank is forested and is contiguous to the riparian corridor along
Hannah Creek.
4.2.3.5 Reach HF1
Reach HF 1 is a meandering, perennial channel that flows in a northerly direction through a wooded
corridor and terminates at the confluence with reach HB2. This reach has a drainage area of 0.12 square
miles (78 acres), an existing length of 1,140 linear feet, and is stable throughout the project area. HFI
is an E -type channel with an average cross-sectional area of 3.5 square feet. The channel has a coarse
sand bed and a slope of 0.0030 ft/ft. Channel widths range between 6 and 8 feet, and the average depth
is 0.5 feet.
4.2.3.6 Reach HF2
Reach HF2 begins downstream of an oversized, channelized ditch. The channel begins in a wooded
area just upstream of the confluence with HFI. Reach HF2 has a drainage area of 0.02 square miles
(13 acres) and has an existing length of 153 linear feet. The reach is a G -type channel, has an average
cross-sectional area of 1.5 square feet. The width and depth at bankfull are 4.5 feet and 0.3 feet. The
dominant bed material is silt/muck, and the overall channel slope is and a slope of 0.008 ft/ft.
4.2.3.7 Reach TH3
Reach TH3 is a straightened perennial ditch located in an active pasture with a drainage area of 0.04
square miles (24 acres). The reach is approximately 713 linear feet, and flows in an easterly direction
into Hannah Creek. Reach TH3, a G/F-type channel, is typically 5.3 feet wide and 0.6 feet deep near
bankfull, and 8.2 feet wide with a max depth of 1.5 feet at top of bank. The approximate bankfull cross
sectional area is 1.6 square feet. The existing slope of Reach TH3 is 0.009 ft/ft, and the dominant bed
material is medium sand.
Hannah Bridge Mitigation Plan 18 April 2017

4.2.4 Channel Stability Assessment
A modified version of the channel stability assessment method (CSA) provided in "Assessing Stream
Channel Stability at Bridges in Physiographic Regions" by Johnson (2006) was used to assess channel
stability for the Hannah Bridge existing channels. This method may be rapidly applied on a variety of
stream types in different physiographic regions having a range of bed and bank materials.
The original CSA method was designed to evaluate thirteen stability indicators in the field. These
parameters are: watershed characteristics, flow habit, channel pattern, entrenchment/channel
confinement, bed material, bar development, presence of obstructions/debris jams, bank soil texture
and coherence, average bank angle, bank vegetation/protection, bank cutting, mass wastingibank
failure, and upstream distance to bridge. As this method was initially developed to assess stability at
bridges, a few minor adjustments were made to remove indicators that contradict stability
characteristics of natural channels in favor of providing hydraulic efficiency at bridges. First, the
"channel pattern" indicator was altered such that naturally meandering channels scored low as opposed
to straightened/engineered channels that are favorable for stability near bridges. Secondly, the last
indicator, "upstream distance to bridge," was removed from the assessment as bridges are not a focus
of channel stability for this project. The twelve indicators were then scored in the field, and a rating of
excellent, good, fair, or poor was assigned to each project reach based on the total score. (See Appendix
B for the CSA field form.)
The CSA results (scores and ratings) for the Hannah Bridge Mitigation project and reference reaches
are provided in Table 7. Project Reaches HB1, HB3, HB4, HF2, and TH3 all received "Fair" ratings,
while reaches HB2 (used as a reference reach) and HFI received a "Good" rating. All channels
proposed for either Restoration or Enhancement have been channelized and/or heavily impacted by
livestock or agricultural activities. These characteristics are reflected in the fair to poor CSA scores for
channel pattern and bank vegetation/protection. All reaches scored fair to poor for watershed
characteristics since the surrounding land use is dominated by agriculture activities, residential
development, and lack of riparian buffers.
Hannah Bridge Mitigation Plan 19 April 2017

Table 7. Channel Stability Assessment Results
*Excellent (0 < Score <= 33), Good (33 < Score <= 66), Fair (66< Score <= 99), Poor (99 < Score <= 132)
4.2.5 Bankfull Verification
Bankfull is difficult and often times impossible to accurately identify on actively maintained channels
and agricultural ditches. The usual and preferred indicators rarely exist, and other factors may be taken
into consideration in order to approximate a bankfull stage. Other factors that may be used are wrack
lines, vegetation lines, scour lines, or top of a bankfull bench; however, complete confidence should
not be placed on these indicators. Along the proposed restoration reaches, the channel is generally
entrenched and actively maintained, which means bankfull indicators were very limited or non-existent.
Therefore, bankfull stage was estimated by using Coastal Plain Regional Curves and other hydrologic
analyses, existing cross-sections, and in-house spreadsheets to estimate bankfull area and bankfull
discharge.
4.2.6 Vegetation
Current land use in the vicinity of the project is primarily agriculture and forested. Vegetation along
the top of Reach HB 1 is active cattle pasture with pockets of common rush (Juncus effusus) throughout
the hydric areas. The left banks of 1-1133 and 1-1134 are also active cow pasture with common rush and
other disturbed herbaceous vegetation. There is no tree or sapling stratum in these areas. Reach TH3 is
also active pasture, but has sparse tree cover. Reaches H132 and HFI are best characterized as
bottomland hardwood forests, that vary from functional to disturbed based on the level of cattle access.
Cattle do not have access to the streams from the southern parcels, therefore the riparian buffer along
the right bank of H132 and the entirety of Reach HF 1 is in much better condition with a full tree canopy,
and a less disturbed shrub/sapling stratum. Common species include red maple (Acer rubrum), tulip
poplar (Liriodendron tulipifera), sweetgum (Liquidambar styraciflua), and swamp tupelo (Nyssa
biflora). Invasive species are widespread throughout the majority of the project area, most notably
Chinese privet (Ligustrum sinense) and multiflora rose (Rosa multiflora). The confluence of 1-1134 and
Hannah Bridge Mitigation Plan 20 April 2017
HBI
(ReR nce)
HB3
HB4
HFI
HF2
TH3
1
Watershed characteristics
9
8
9
9
5
8
8
2
Flow habit
2
2
2
2
3
3
3
3
Channel pattern
3
2
11
11
4
11
11
4
Entrenchment/channel
4
4
7
7
7
6
7
confinement
5
Bed material
4
4
5
6
5
10
6
6
Bar development
5
3
5
6
5
6
6
7
Obstructions/debris jams
4
4
3
3
4
2
2
Bank soil texture and
8
7
7
7
7
7
7
7
coherence
9
Average bank angle
8
5
8
6
4
7
8
10
Bank
7
4
11
8
3
9
11
vegetation/protection
11
Bank cutting
7
4
8
4
3
4
4
Mass wasting/bank
7
12
2
9
3
2
3
4
failure
13
Upstream distance to
NA
NA
NA
NA
NA
NA
NA
bridge
Score
67
49
85
72
5 2
76
77
Rating*
Fair
Good
Fair
Fair
Good
Fair
Fair
*Excellent (0 < Score <= 33), Good (33 < Score <= 66), Fair (66< Score <= 99), Poor (99 < Score <= 132)
4.2.5 Bankfull Verification
Bankfull is difficult and often times impossible to accurately identify on actively maintained channels
and agricultural ditches. The usual and preferred indicators rarely exist, and other factors may be taken
into consideration in order to approximate a bankfull stage. Other factors that may be used are wrack
lines, vegetation lines, scour lines, or top of a bankfull bench; however, complete confidence should
not be placed on these indicators. Along the proposed restoration reaches, the channel is generally
entrenched and actively maintained, which means bankfull indicators were very limited or non-existent.
Therefore, bankfull stage was estimated by using Coastal Plain Regional Curves and other hydrologic
analyses, existing cross-sections, and in-house spreadsheets to estimate bankfull area and bankfull
discharge.
4.2.6 Vegetation
Current land use in the vicinity of the project is primarily agriculture and forested. Vegetation along
the top of Reach HB 1 is active cattle pasture with pockets of common rush (Juncus effusus) throughout
the hydric areas. The left banks of 1-1133 and 1-1134 are also active cow pasture with common rush and
other disturbed herbaceous vegetation. There is no tree or sapling stratum in these areas. Reach TH3 is
also active pasture, but has sparse tree cover. Reaches H132 and HFI are best characterized as
bottomland hardwood forests, that vary from functional to disturbed based on the level of cattle access.
Cattle do not have access to the streams from the southern parcels, therefore the riparian buffer along
the right bank of H132 and the entirety of Reach HF 1 is in much better condition with a full tree canopy,
and a less disturbed shrub/sapling stratum. Common species include red maple (Acer rubrum), tulip
poplar (Liriodendron tulipifera), sweetgum (Liquidambar styraciflua), and swamp tupelo (Nyssa
biflora). Invasive species are widespread throughout the majority of the project area, most notably
Chinese privet (Ligustrum sinense) and multiflora rose (Rosa multiflora). The confluence of 1-1134 and
Hannah Bridge Mitigation Plan 20 April 2017

Hannah Creek at the downstream end of the project is a cypress -gum swamp community with a fully
developed canopy, but lower stem density than seen in the other wooded reaches of the project. This
area is dominated by swamp tupelo and bald cypress (Taxodium distichum). Japanese stiltgrass
(Microstegium vimineum) is very common throughout the understory. Detailed observations of
vegetation species, soils, and hydrology were recorded in each community type.
4.3 Wetland Summary Information
4.3.1 Existing Wetlands
The USFWS National Wetland Inventory Map (NWI) depicts two small wetland areas within the site
(Figure 8). A Freshwater Pond (PUBHh) is mapped within the the northcentral part of the easement
and the confluence of Reach H134 and Hannah Creek is mapped as a Freshwater Forested/Shrub
Wetland (PFO 1 Q.
A wetland delineation was performed in May 2016. Wetland boundaries were delineated using current
methodology outlined in the 1987 U.S. Army Corps of Engineers Wetland Delineation Manual (DOA
1987) and Regional Supplement to the U.S. Army Corps of Engineers Wetland Delineation Manual:
Atlantic and Gulf Coastal Plain Region (Version 2.0) (U.S. Army Corps of Engineers 2010). Soils were
characterized and classified using the Field Indicators of Hydric Soils in the United States, Version 7.0
(USDA-NRCS 2010). Wetland boundaries were marked with sequentially numbered wetland survey
tape (pink/black striped) (Figure 7; Table 10).
Jurisdictional wetlands are present in the enhancement and preservation areas throughout the site. The
wetlands are divided between heavily disturbed and functional. The disturbed wetlands are disturbed
from over twenty years of continued cattle access. The non -forested wetlands have been historically
cleared for pasture, have altered drainage patterns due to channelization, and lack a native vegetation
community. The forested -disturbed wetlands are grazed forested areas, while the forested -not disturbed
wetlands have cattle excluded. A notification of jurisdictional determination was received on USACE
on August 12, 2016. Documentation is included in Appendix B.
Hannah Bridge Mitigation Plan 21 April 2017

Table 8. Wetland Summary Information
Parameters
W1
W2
W3
W4
W5
W6
W7
Size of
Wetland
5.8
0.81
4.41
4.67
0.97
0.75
0.45
(Ac)
Mapped Soil
Gilead Sandy
Bibb Sandy Loam;
Gilead Sandy
Series
Bibb Sandy Loam
Loam
Bibb Sandy Loam
Lynchburg Sandy Loam
Loam
Bibb Sandy Loam
Bibb Sandy Loam
Drainage
Moderately Well
Poorly Drained;Moderately
Well
Poorly Drained
Poorly Drained
Somewhat Poorly
Poorly Drained
Poorly Drained
Class
Drained
Drained
Drained
Soil Hydric
Hydric
Not Hydric
Hydric
Hydric;
Not Hydric
Hydric
Hydric
Status
Not Hydric
Source of
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Hydrology
Overbank Flooding
Overbank
Overbank
Overbank Flooding
Overbank Flooding
Overbank Flooding
Overbank
Flooding
Flooding
Flooding
Hydrologic
Overgrazed;
Overgrazed;
None
Cattle
Overgrazed;
Overgrazed;
Overgrazed;
Impairment
Incised Channel
Incised Channel
Incised Channel
Incised Channel
Incised Channel
Vegetative
Pasture
Pasture
Bottomland
Pasture/Forest
Pasture
Pasture
Pasture
Community ni
Hardwood Forest
Percent
<5%
<5%
25%
<5%
<5%
<5%
Invasive
Parameters
W8
W9
W10
Wil
W13
Size of
0.11
1.61
1.36
0.65
tSandy
1.74
Wetland
Mapped Soil
Bibb Sandy Loam
Bibb Sandy Loam
Bibb Sandy Loam
Bibb Sandy loam
Rains Sandy Loam
Series
Drainage
Poorly Drained
Poorly Drained
Poorly Drained
Poorly Drained
Poorly Drained
Class
Soil Hydric
Hydric
Hydric
Hydric
Hydric
Hydric
Hydric
Status
Source of
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Groundwater;
Overbank Flooding
Overbank
Overbank
Overbank Flooding
Overbank Flooding
Groundwater
Flooding
Flooding
Hydrologic
Overgrazed;
Overgrazed;
Impairment
None
None
Incised Channel
None
Incised Channel
Cattle
Vegetative
Bottomland
Bottomland
Bottomland Hardwood
Pasture
Pasture
Pasture Forest
Community
Hardwood Forest
Hardwood Forest
Forest
Percent
25%
25%
<5%25%
< 5%
<5%
Invasive
4.3.2 Existing Hydric Soil
In addition to the jurisdictional wetland areas, one hydric soil area was located within the project
easement along Reach HB3. The area evaluated focused upon areas with high potential for containing
hydric soil. These areas have suitable landscape position and NRCS county soil mapping indicates the
presence of hydric soil. The NRCS Web Soil Survey has the poorly drained Bibb series mapped the
length of the project area with upland soils that extend into the project. The upland soils are a somewhat
poorly drained Lynchburg sandy loam and, a moderately well drained Goldsboro sandy loam. The Bibb
soil can have up to a 10 percent inclusion of Johnston soil, a deep mucky mineral soil.
The soils in this area lack hydrology for jurisdictional wetland primarily due to soil drainage from the
incised channel, ditching, and active livestock affecting soil compaction. Other changes to the site
include surface churning, loss of organic matter in the surface, and the loss of the normal reduction
cycle characteristic of wetlands. The construction of a farm pond has altered surface drainage and
provided spoil across the floodplain. Soil borings within the boundary exhibited hydric soil indicators
within 12 inches of the soil surface throughout the natural drainage way. Throughout most of the site
the surface has a sandy loam texture underlain by a black silt loam high in organic matter. Small
Hannah Bridge Mitigation Plan 22 April 2017

rounded gravel is found in some areas. Due to increased drainage, sandy textures, and surface
disturbance from the agricultural management, redoximorphic concentrations in the surface 6 inches
are weak or absent. The hydric soil indicators present at the Hannah Bridge site are the A11 -Thick Dark
Surface, F6 -Redox Dark Surface, and F7 -Depleted Dark Surface. These indicators depend on
accumulated organics in the soil. A water table was observed in some boring location below 20 inches.
Areas with fill or significant disturbance are located near the excavated pond and at an old farm
crossing. Hydric Soil Indicators are present within most areas of the floodplain. Hydric soils within
the proposed enhancement and restoration areas were verified through auger borings by a licensed soil
scientist (Appendix D)
4.4 Regulatory Considerations and Potential Constraints
4.4.1 Property Ownership, Boundary, and Utilities
There are no major constraints to construction of the Site. There is one utility crossing at the top of
Reach HB 1 and a culvert crossing above Reach HB4. There is also an existing farm crossing at the top
of Reach TH3; no additional crossings or easement breaks are proposed at this time.
4.4.2 FEMA/ Hydrologic Trespass
Reaches HB3 and HB4 are located within the FEMA 100 -year floodplain (Zone AE) of Hannah Creek,
and approximately 200 feet of the downstream end of Reach HB4 is located within the FEMA floodway
(Figure 9). However, no grading or construction activities are proposed along the portions of the
project located within the FEMA floodway. Therefore, it is not anticipated that a No -Rise or CLOMR
will be required for the project. Hydrologic trespass is a not a concern for this project. While designing
the Hannah Bridge project, appropriate measures were taken to eliminate hydrologic trespass of the
adjacent agricultural fields and animal operations. The adjacent land use will not be affected by the
proposed design, and no detrimental impacts are expected beyond the easement limits.
4.4.3 Environmental Screening and Documentation
4.4.3.1 Threatened and Endangered Species
The US Fish and Wildlife Service (USFWS) database lists four endangered species for Johnston
County, North Carolina: red -cockaded woodpecker (Picoides borealis), Tar River spinymussel (Eliptio
steinstansana), dwarf wedgemussel (Alasmidonta heterodon), and Michaux's sumac (Rhus michauxii).
No protected species or potential habitat for protected species was observed during preliminary site
evaluations. RES submitted a request to USFWS for review and comments on the proposed Hannah
Bridge Mitigation Project on April 8, 2016 in regards to any potential impacts to threatened and
endangered species. A response from the USFWS received on May 5, 2016 stated that "the proposed
project is not likely to adversely affect and federally -listed endangered or threatened species, their
formally designated critical habitat, or species currently proposed for listing under the Act."
Documentation is included in Appendix B.
4.4.3.1 Cultural Resources
A review of the North Carolina State Historic Preservation Office GIS Web Service database revealed
that there are National Registered listings within a one -mile radius of the proposed project area. No
architectural structures or archeological artifacts have been observed or noted during preliminary
surveys of the site for restoration purposes. RES submitted a request to the NC State Historic
Preservation Office (SHPO) to search records to determine the presence of any areas of architectural,
historic, or archaeological significance that may be affected by the Hannah Bridge Mitigation Site on
April 8, 2016. In a letter dated April 4, 2016 the SHPO stated that they had "conducted a review of the
Hannah Bridge Mitigation Plan 23 April 2017

project and are aware of no historic resources which would be affected by the project." Documentation
is included in Appendix B.
Table 9. Regulatory Considerations
Regulation
Applicable?
Resolved?
Supporting Documentation
Waters of the United States -
Yes
No
Appendix B
Section 404
Waters of the United States -
Yes
No
Appendix B
Section 401
Endangered Species Act
Yes
Yes
Section 4.4.3; Appendix B
Historic Preservation Act
Yes
Yes
Section 4.4.3; Appendix B
Coastal Zone Management Act
(CZMA)/Coastal Area
No
N/A
N/A
Management Act (LAMA)
FEMA Floodplain Compliance
N/A
N/A
N/A
Essential Fisheries Habitat
No
N/A
N/A
Hannah Bridge Mitigation Plan 24 April 2017

5 FUNCTIONAL UPLIFT POTENTIAL
The Stream Functions Pyramid Framework (Harman et. al. 2012) separates stream functions into five
categories, ordered into a hierarchy, which communicate the interrelations among functions and
illustrate the dependence of higher level functions (biology, physiochemical and geomorphology) on
lower level functions (hydrology and hydraulics). Anticipated functional benefits and improvements
within the project area, as based on the Function -Based Framework are outlined in Table 10.
Table 10. Functional Benefits and Improvements
Hannah Bridge Mitigation Plan 25 April 2017
Functional
Objective
Description
Level
- = L
(1-5)
Benefit will be achieved through cattle exclusion and direct removal of fecal
Nutrient removal
inputs, filtering of runoff through buffer areas, the conversion of active farm
3,4
fields to forested buffers, and improved denitrification and nutrient uptake
through buffer zones.
Benefit will be achieved through the stabilization of eroding stream banks
Sediment removal
through cattle exclusion (passive) and bioremediation, bed loss will be
3
arrested with grade control structures, and reduction of sediment loss from re-
forested pasture.
Benefit will be achieved through the restoration of buffer areas that will
Runoff filtration
receive and filter runoff, thereby reducing nutrients and sediment
3
concentrations reaching aquatic resources.
Benefit will be achieved through the enhancement of floodplain connectivity
Water storage
which will store more water during precipitation events than under current
1,2
drainage conditions.
Improved
Benefit will be achieved through the increased storage of precipitation in
groundwater
floodplain wetlands. Greater storage of water will lead to improved
2
recharge
infiltration and groundwater recharge.
Restoration of
Benefit will be achieved by restoring riparian buffer and wetland buffers to
habitats
hardwood ecosystems.
3
Improved substrate
Substrate will become coarser as a result of the stabilization of stream banks
and instream cover
and an overall decrease in the amount of fine materials deposited in the
3
stream.
Addition of large
Benefit will be achieved through the addition of wood structures as part of
woody debris
the restoration design. Such structures may include log vanes, root wads, log
3,4
weirs, and log toes.
Reduced water
temperature due to
Benefit will be achieved through the restoration of canopy tree species to the
4
shading
stream buffer areas.
Hannah Bridge Mitigation Plan 25 April 2017

6 DETERMINATION OF CREDITS
Mitigation credits presented in these tables are projections based upon site design (Figure 10). Upon
completion of site construction, the project components and credits data will be revised to be consistent
with the as -built condition.
Table 11. Mitigation Credits
Hannah Bridge Mitigation Plan 26 April 2017
The Hannah Bridge Site Mitigation Credits
Mitigation Credits
Stream
Riparian Wetland
Non -Riparian Wetland
Totals
5,209
11.73
N/A
STREAM
Existing
ProposedMitigation
Mitigation
Stationing
Base
Reach Type
(Proposed) Length
Length
Ratio
SMUs
LF
LF
HB1 Restoration
0+15 to
14+45 1,484
1,430
1:1
1,400
HB2 Enhancement 11
14+45 to
18+37 392
392
2.5:1
157
HB3 Restoration
18+37 to
36+44 1,588
1,807
1:1
1,807
HB4 Restoration
36+84 to
42+63 579
579
1:1
579
HB4 Enhancement I11
42+63 to
44+91 228
228
5:1
46
HF1 Enhancement 111
2+18 to
13+58 1,140
1,140
5:1
228
HFl Restoration
13+58 to
16+04 0
246
1:1
246
HF2 Enhancement 111
6+40 to
7+89 149
149
5:1
30
TH3 Enhancement 11
0+63 to
7+79 716
716
1:1
716
Total
6,280
6,687
5,209
WETLAND
Existing
Mitigation Type
Mitigation Ratio
WMUs
Acreage
Re-establishment
3.27
1:1
3.27
Enhancement High
13.18
2:1
6.59
Enhancement Low
3.46
3:1
1.15
Preservation
7.27
10:1
0.72
Total
27.18
11.73
Hannah Bridge Mitigation Plan 26 April 2017

7 CREDIT RELEASE SCHEDULE
All credit releases will be based on the total credit generated as reported by the as -built survey of the
mitigation site. Under no circumstances shall any mitigation project be debited until the necessary
Department of the Army (DA) authorization has been received for its construction or the District
Engineer (DE) has otherwise provided written approval for the project in the case where no DA
authorization is required for construction of the mitigation project. The DE, in consultation with the
IRT, will determine if performance standards have been satisfied sufficiently to meet the requirements
of the release schedules below. In cases where some performance standards have not been met, credits
may still be released depending on the specifics of the case. Monitoring may be required to be restarted
or be extended, depending on the extent to which the site fails to meet the specified performance
standard. The release of project credits will be subject to the criteria described as follows in Table 12a.
Table 12a. Stream Credit Release Schedule
Release
Credit Release Activity
Interim
Total Released
Milestone
Release
1
Site Establishment (includes all required criteria
15%
15%
stated above
2
Baseline Monitoring Report and As -built Survey
15%
30%
3
First year monitoring report demonstrates
10%
40%
performance standards are being met.
4
Second year monitoring report demonstrates
10%
50%
performance standards are being met.
(60%**)
5
Third year monitoring report demonstrates
10%
60%
performance standards are being met.
(70%**)
6
Fourth year monitoring report demonstrates
5%
65%
performance standards are being met.
(80%**)
7
Fifth year monitoring report demonstrates
o
10%
75%
erformance standards are beingmet.
85%**
g
Sixth year monitoring report demonstrates
5%
80%
performance standards are being met.
(90%**)
9
Seventh year monitoring report demonstrates
90%
performance standards are being met, and project
10%
(100%**)
has received close-out approval.
* *10% reserve of credits to be held back until the bankfull event performance standard has been met.
7.1 Initial Allocation of Released Credits
The initial allocation of released credits, as specified in the mitigation plan can be released by the IRT
with written approval of the DE upon satisfactory completion of the following activities:
a) Approval of the final Mitigation Plan
b) Recordation of the Conservation Easement, as well as a title opinion acceptable to the USACE
covering the property
c) Financial assurances.
d) 404 Permit Approval
Hannah Bridge Mitigation Plan 27 April 2017

Table 12b. Wetland Credit Release Schedule
Monitoring
Credit Release Activity
Interim
Total
Year
Release
Released
I
Site Establishment (includes all required criteria
15%
15%
stated above
2
Baseline Monitoring Report and As -built Survey
15%
30%
3
First year monitoring report demonstrates
10%
40%
performance standards are being met.
4
Second year monitoring report demonstrates
10%
50%
performance standards are being met.
5
Third year monitoring report demonstrates
10%
60%
performance standards are being met.
6*
Fourth year monitoring report demonstrates
10%
70%
performance standards are being met.
7
Fifth year monitoring report demonstrates
10%
80%
performance standards are being met.
8*
Sixth year monitoring report demonstrates
10%
90%
performance standards are being met.
Seventh year monitoring report demonstrates
9
performance standards are being met, and project
10%
100%
has received close-out approval.
*Please note that vegetation plot data may not be required with monitoring reports submitted during
these monitoring years unless otherwise stated by the Mitigation Plan or directed by the IRT.
7.2 Subsequent Credit Releases
The second credit release will occur after the completion of implementation of the Mitigation Plan and
submittal of the Baseline Monitoring Report and As -built Survey. All subsequent credit releases must
be approved by the DE, in consultation with the IRT, based on a determination that required
performance standards have been achieved. As projects approach milestones associated with credit
release, the Bank Sponsor will submit a request for credit release to the DE along with documentation
substantiating achievement of criteria required for release to occur. This documentation will be included
with the annual monitoring report.
Hannah Bridge Mitigation Plan 28 April 2017

8 MITIGATION WORK PLAN
8.1 Reference Stream Studies
8.1.1 Target Reference Conditions
The restoration portions of the Site are characterized by agricultural and livestock practices. Several
ditches exist in the watershed and contribute to the project site. Physical parameters of the site were
used, as well as other reference materials, to determine the target stream type. An iterative process was
used to develop the final information for the site design.
To develop the target reference conditions, physical site parameters were reviewed. This included the
drainage area, land use, soils mapping units from the Johnston County Soil Survey for the watershed
and Site, typical woody debris and habitat available for the area, as well as general topography. The
"Classification of the Natural Communities of North Carolina" was also used to narrow the potential
community types that would have existed at the Site (Schafale and Weakley, 2003).
Targeted reference conditions included the following:
• Located within the Physiographic Region — Inner Coastal Plain,
• Similar drainage area,
• Similar land use onsite and in the watershed,
• Similar watershed soil types,
• Similar site soil types,
• Ideal, undisturbed habitat — several types of woody debris present,
• Similar topography,
• Similar slope,
• Pattern common among coastal plain streams, and
• Minimal presence of invasive species.
8.1.1.1 Reference Site Search Methodology
All the parameters used in Section 4.1 were used to find appropriate reference stream sites. Obtaining
property owner information and owner authorization for access was another factor in locating suitable
reference sites for the project. For this project, there was no predetermined amount of reference sites
needed as long as the site was suitable and met the parameters. Several potential reference sites were
assessed, and their characteristics were noted. It is difficult to find reference sites in the Coastal Plain
because many have been disturbed by farming or urban development. Most streams tend to be modified
ditches and may have some of the characteristics that are sought in a reference, but too few to make it
an ideal reference for the project site. One reference stream site that proves to be ideal in both
geomorphology and habitat is Reach HB2 located on the project site just downstream of HB 1.
8.1.1.2 Reference Watershed Characterization
The reference stream, Reach H132, flows west to east and is near the upstream portion of the project
along an unnamed tributary that drains to Hannah Creek. The portion of HB2 that was surveyed and
analyzed is approximately 275 feet long. The drainage area for the H132 reach is 1.24 square miles (795
acres). The land use in the watershed is characterized by mostly agricultural (52%), mixed pines and
hardwoods (42%), residential (4%), and open water (2%). Site photographs of the reference stream are
located in Section 2.3.
8.1.1.3 Reference Discharge
Several hydrologic models/methods were used to develop a bankfull discharge for the reference
reaches. Existing drainage area, land use, slope, roughness, and cross-sectional area were all factors
Hannah Bridge Mitigation Plan 29 April 2017

considered when performing the calculations. Using a combination of Coastal Plain Regional Curves,
in-house spreadsheet tools, and a project specific regional flood frequency analysis, the existing
discharge was found to be around 29-31 cubic feet per second (ft3/s) for HB2. See Section 8.3 for a
more detailed description of the hydrologic analyses performed for this project.
8.1.1.4 Reference Channel Morphology
See Section 4.2.3 for a detailed description of the channel morphology for Reach HB2.
8.1.1.5 Reference Channel Stability Assessment
The reference reach was stable and showed no evidence of incision or erosion in the portion that was
surveyed and analyzed. The stream appeared to maintain its slope and had sufficient amounts of
vegetation to secure its banks. Riparian buffer widths exceeded fifty feet on each side. The CSA results
(scores and ratings) for H132 are provided above in Table 7 (Section 4.2). The reach received a "Good"
rating as the channel demonstrates a stable meandering pattern and a well vegetated riparian buffer.
8.1.1.6 Reference Bankfull Verification
Typical indicators of bankfull include vegetation at the bankfull elevation, scour lines, wrack lines,
vegetation lines, benches/inner berm, and point bars. Throughout the entire length of the reference
reach, bankfull is located at the top of bank elevation. The accuracy of this bankfull stage is verified by
the Coastal Plain Regional Curves and hydrologic analyses using existing cross sections to calculate
area and discharge. Evidence that can further support the location of bankfull is the lack of any bench
or berm features within the channel, and wrack lines present within the floodplain.
8.1.1.7 Reference Riparian Vegetation
The reference reach riparian community is characteristic of a Coastal Plain Small Stream Swamp
community. This community was determined to have had past disturbance altering the species
composition. It is anticipated that a local seed source for high dispersal species is present and will
disperse across much of the mitigation site. These species are often found in early successional
communities and quickly fill disturbance gaps. Because many of these high dispersal species often
become aggressive in these sites, they are not included in the Restoration Planting List (Section 8.2.2).
Hardwood species typical of the target community were observed in adjacent and nearby communities,
and were judged to be more appropriate for this site.
8.2 Design Parameters
8.2.1 Stream Restoration Approach
Stream restoration efforts along the tributaries at the Site will be accomplished through analyses of
geomorphic conditions and watershed characteristics. The design approach applies a combination of
analytical and reference reach based design methods that meet objectives commensurate with both
ecological and geomorphic improvements. Proposed treatment activities may range from minor bank
grading and planting to re-establishing stable planform and hydraulic geometry. For reaches requiring
full restoration, natural design concepts have been applied and verified through rigorous engineering
analyses and modeling. The objective of this approach is to design a geomorphically stable channel that
provides habitat improvements and ties into the existing landscape.
The Site will include Priority I restoration, Enhancement Level II, Enhancement Level III, and
headwater valley restoration. Priority I restoration reaches will incorporate the design of a single -thread
meandering channel, with parameters based on data taken from the reference site described above,
published empirical relationships, NC Coastal Plain Regional Curves, and hydrologic and hydraulic
Hannah Bridge Mitigation Plan 30 April 2017

analyses. As a result of the restoration of planform and dimension, frequent overbank flows and a
restored riparian buffer will provide the appropriate hydrology and sediment transport throughout this
Coastal Plain watershed. A conceptual plan view is provided in Figure 10.
Current stream conditions along the proposed restoration reaches exhibit habitat degradation as a result
of impacts from livestock and channelization performed to promote agricultural activities. Additionally,
the riparian buffer is in poor condition throughout most of the project area where much of the riparian
buffer is devoid of trees or shrubs and active pasture is present up to the edge of the existing channel.
The Site design approach began with a thorough study of existing conditions, including the onsite
streams, valleys, and watershed. Design parameters, including active channel, habitat and floodplain
features were developed from analyses performed on the reference site data. Analytical design
techniques were used to determine the design discharge and to verify the design as a whole.
Engineering analyses were performed using various hydrologic and hydraulic models to verify the
reference reach based design. A combination of methods (including Hydraflow Hydrographs, regional
curves and flood frequency analysis) were used to calculate flows received by the channel for bankfull
and other significant storm events. Through this hydrologic analysis, the design discharge (typically
referenced as bankfull or dominant discharge) was determined, and the subsequent design was based
on this calculated discharge. Design parameters developed through the analyses of reference reach data
and hydrologic and hydraulic modeling were confirmed using the Stable Channel Design function
components within HEC -RAS and through spreadsheet tools.
Engineering analyses were performed concurrently to geomorphic and habitat studies. While the stream
design was verified by simulations of hydrology and fluvial processes, analogs of desirable habitat
features were derived from reference sites and integrated into the project design. Both riparian habitat
features and in -stream structures such as log grade controls, brush toes, log vanes, log toes, log drops
were used throughout the project to act as grade control and for bank stabilization by dissipating and
redirecting the stream's energy. Bank stability will also be enhanced through the installation of live
stakes that include native species (e.g. black willow (Salix nigra) and silky dogwood (Cornus
arnornurn)).
Sections of abandoned stream channel will be backfilled to the elevation of the floodplain in areas
adjacent to the new channel with material excavated onsite and by installing channel plugs where
necessary. The floodplain will be planted with native species creating a vegetated buffer, which will
provide numerous water quality and ecological benefits. Stream banks will be stabilized using a
combination of grading, erosion control matting, bare -root plantings, native material revetment
techniques (i.e. bioengineering), structure placement, and sod transplants where possible. The stream
and adjacent riparian areas will be protected by a permanent conservation easement, which will be
fenced as needed to exclude livestock.
The Hannah Bridge Mitigation Site has been broken into the following design reaches:
• Reach HBI (STA 0+15 to STA 14+45) —Reach beginning at western limits of project totaling
1,430 linear feet of PriorityIl Restoration. Pasture and disturbed wetlands are located adjacent
to the reach.
• Reach HB2 (STA 14+45 to STA 18+37) —Reach begins at the end of HBI and flows northeast
to the confluence with Reach HB3 totaling 392 linear feet of Enhancement Level II.
Bottomland hardwood forest and riparian wetlands surround this reach.
Hannah Bridge Mitigation Plan 31 April 2017

• Reach HB3 (STA 18+37 to STA 36+44) — Reach immediately downstream of Reach 14132 and
flows east to an existing farm crossing totaling 1,807 linear feet of Priority I Restoration.
Pasture and small pockets of disturbed wetlands are located adjacent to the reach.
• Reach HB4 (STA 36+84 to STA 42+63; STA 42+63 to 44+91) — Reach beginning at farm
crossing just downstream of Reach H133 and flows north to its confluence with Hannah Creek.
The reach totals 579 linear feet of restoration and 228 linear feet of Enhancement III. Pasture
and disturbed wetlands are located along the west side of the reach, and bottomland hardwood
forest and riparian wetlands are located on the east.
• Reach HF1(STA 2+18 to STA 13+58; STA 13+58 to 16+04) — Reach beginning in a forested
area in the southern portion of the project and flows north until its confluence with Reach HB 1
totaling 1,140 linear feet of Enhancement III and 246 linear feet of restoration. Riparian
wetlands surround this reach.
• Reach HF2 (STA 6+40 to STA 7+89) — Reach beginning in agricultural field in the southern
portion of the project and flows north until its confluence with Reach HFI totaling 149 linear
feet of Enhancement III. Agricultural fields and disturbed wetlands are located adjacent to the
reach along the upstream segment, while the downstream section is bordered by woods.
• Reach TH3 (STA 0+63 to STA 7+79) —Reach begins just downstream of disturbed wetlands
and an existing farm crossing located at the top of the project. The reach flows to the east into
Hannah Creek totaling 716 linear feet of Enhancement Level II. Pasture and small pockets of
disturbed wetlands are located adjacent to this reach.
Reaches HB1, HB2, HB3, and 11B4
A combination of Priority I Restoration, Enhancement Level 1I, and Enhancement Level III is proposed
along the primary project channel (Reaches HBI through H134) to address existing impairments,
particularly channelization and impacts from continued cattle access. The watershed that drains to the
upper end of the project is approximately 667 acres, and land use is primarily agricultural and forested.
Priority I Restoration is proposed for Reach HB 1 which will include relocating the channel towards the
north, such that it meanders within the middle of the valley. An existing 24" reinforced concrete pipe
(RCP) culvert crossing near the upstream end will be removed, and all sections of the abandoned
channel will be backfilled to provide positive drainage towards the proposed channel. A minimum of a
100 -foot buffer will be established along the majority of Reach HBI and will be planted with native
riparian vegetation. Livestock will be excluded from the buffer with fencing installed along the
easement boundary. A 30 -foot easement break is proposed near the upstream end of the reach to
accommodate an existing overhead powerline.
Enhancement Level II is proposed for Reach H132, beginning approximately 200 feet downstream of
the confluence with HFI. The channel is stable throughout, except for a few minor areas of erosion,
and provides a variety of aquatic habitats. The riparian buffer is intact and consists primarily of mature
hardwoods; however, there are areas of invasive species located throughout the buffer. Minimal grading
and live stake planting will be required in the few areas that exhibit bank erosion. Invasive species will
be treated and removed during construction, and those areas will be replanted with native riparian
vegetation.
Priority I Restoration is proposed for Reach H133 to address historic straightening and irregular banks
resulting from cattle impacts. The design approach will include meandering the proposed channel
Hannah Bridge Mitigation Plan 32 April 2017

within the natural valley, and backfilling the existing stream. A minimum 50 -foot buffer will be
established and planted with native riparian vegetation. Because much of the buffer is devoid of
significant woody vegetation, woody debris and log grade control structures will be installed along the
bed to improve in -stream habitat and stability. Livestock will be excluded with fencing installed along
the easement boundary. There is an existing crossing located within the downstream section of the
project that will be removed.
A 40 -foot easement break is proposed at the existing farm crossing located at the reach break between
HB3 and HB4. The existing culverts will be removed and replaced with 30 linear feet of 42" and 24"
high-density polyethylene (HDPE) pipes. The 42" pipe will be buried one foot to allow for fish passage
and to convey baseflow, while the invert of the adjacent 24" pipe will be set two to three inches above
the channel bed elevation.
A combination of restoration and Enhancement III is proposed for Reach HB4 downstream of the
easement break. Restoration is proposed for over 500 feet beginning downstream of the easement break,
and buffer enhancement is proposed for the channel from the restoration section to the confluence with
Hannah Creek. The design approach will include installing log structures at various points along the
channel to raise the channel invert within the upper section. Because the channel was previously
channelized and relocated to the west side of the valley, the proposed structures will allow flows to
frequently inundate the valley floor and existing wetlands located to the east. A floodplain bench will
also be constructed along the left bank within the restoration section. A minimum of a 50 -foot buffer
will be established along Reach HB4, and the west side of the buffer will be planted with native riparian
vegetation.
Reach TH3
Enhancement Level II is proposed on Reach TH3. The design approach on this reach will focus on
improving the riparian buffer and in -stream habitat and floodplain benching. Proposed activities include
cutting a floodplain bench along the south side of the channel along the upper reach, and installing
grade control and woody debris structures throughout to improve vertical stability and aquatic habitat.
Livestock will be excluded with fencing installed along the easement boundary. All disturbed areas
within the proposed buffer will be planted with native riparian and wetland vegetation.
A 40 -foot easement break is proposed at the existing farm crossing located at the upstream end of the
reach. The existing culvert will be removed and replaced with 24 linear feet of 24" HDPE pipe. The
headwaters of the reach (wetland system) located just upstream of the crossing will also be placed under
a conservation easement. All existing ditches will be filled/plugged using adjacent spoil piles. All
disturbed areas within the easement will be planted with native wetland vegetation, and cattle will be
excluded from the area by installing fencing along the easement limits.
Reach HF1
A combination of Enhancement Level III and restoration is proposed for Reach HFI. The majority of
the channel is stable throughout the proposed easement and provides a variety of aquatic habitats. The
riparian buffer is intact, but invasive species (privet) are present throughout. All non -vegetated areas
within the proposed easement will be planted with native vegetation and any areas of invasive species
will be removed and/or treated. Restoration is proposed for approximately 246 feet along the
downstream end of the reach. Along this section, a new channel will be constructed such that it
meanders within the natural valley to reconnect the existing reach to the proposed channel associated
with Reach HB 1. Construction activities will include installing grade control structures, log toes and/or
brush toes for stability and to improve aquatic habitat.
Hannah Bridge Mitigation Plan 33 April 2017

Reach HF2
A combination of headwater valley restoration and Enhancement Level III is proposed for Reach HF2.
The existing channel will be backfilled to the extent possible, such that cut and fill is balanced along
the reach beginning at the upstream end of the reach and ending where the channel enters the existing
tree line. The proposed headwater valley design includes maintaining an approximate bottom width of
eight feet, very low side slopes, installing woody debris, and re -vegetating the corridor with native
riparian vegetation. Buffer enhancement activities are proposed along the downstream end of the reach
and include planting open areas of buffer with native riparian vegetation and invasive species treatment.
8.2.1.1 Design Discharge
Based upon the hydrologic analyses described below, design discharges were selected that fall between
model results for the 1.1 -year and 1.5 -year flood frequency analysis for each reach. The selected flows
for the restoration reaches are 30-32 ft3/s for Reaches HB1 and HB3. These discharges will provide
frequent inundation of the adjacent floodplain.
The design discharges were selected based on the following rationale:
• The calculated bankfull discharge for the analog/reference reach and existing reaches fall
between the results of the 1.1 -year and 1.5 -year flood frequency analysis,
• The results of the 1.1 -year flood frequency analysis are slightly higher than the NC regional
curve (Doll et al., 2003), and
• Selecting design discharges slightly higher than the 1.1 -year storm events allows frequent
inundation of the adjacent floodplain.
8.2.1.2 Design Methods
There are three primary methods that have demonstrated success in stream restoration: analog,
empirical, and analytical. All three methods have advantages and limitations, and it is often best to
utilize more than one method to address site-specific conditions or to verify the applicability of design
elements. This is particularly true in developed watersheds where existing conditions do not always
reflect current inputs and events, and sediment and hydrologic inputs may remain unstable for some
time. Combinations of analytical and analog methods were used to develop the stream designs for the
Site.
Analytical Approach
Analytical design is based on principles and processes considered universal to all streams, and can
entail many traditional engineering techniques. The analytical approach utilizes continuity, roughness
equations, hydrologic and hydraulic models, and sediment transport functions to derive equilibrium
conditions. Because the project is located within a rural watershed, restoration designs are based on
hydrologic and hydraulic analyses, including rainfall -runoff models to determine design discharges
coupled with reference reach techniques.
Analog Approach
The analog method of natural channel design involves the use of a "template" or reference stream
located near the design reach, and is particularly useful when watershed and boundary conditions are
similar between the design and analog reaches (Skidmore et al., 2001). In an analog approach, the
planform pattern, cross-sectional shape, longitudinal profile, and frequency and locations of woody
debris along the analog reaches are mimicked when developing the design parameters for the subject
stream.
1. The appropriate bankfull cross-sectional area (CSA) of each design reach was calculated using
the designer's (WK Dickson) in-house spreadsheet based on Manning's Equation. The input
Hannah Bridge Mitigation Plan 34 April 2017

parameters included the design discharge as determined by the hydrologic analysis described
above, and proposed slope based on site conditions and the sinuosity measured for the analog
reach.
2. The cross-sectional shape was adjusted within the spreadsheet to replicate the width -depth
ratios and side slopes surveyed along the analog reach, while also maintaining the CSA
necessary to convey the design discharge.
3. Pool cross-sectional areas were calculated using both typical reference reach techniques and
the analog approach. Design CSA areas were determined using the measured analog ratios of
shallow/riffle CSA to pool CSA as applied to the design CSAs. The pool cross-sectional shape
was adjusted within the in-house spreadsheet as described above in step 2.
8.2.1.3 Typical Design Sections
Typical cross sections for shallows and pools are shown on the design plan sheets in Appendix E. The
cross-section dimensions were developed for the three design reaches by using a WK Dickson in-house
spreadsheet described in Section 8.3 of this report. The cross-sections were altered slightly to facilitate
constructability; however, the cross-sectional area, width to depth ratio, and side slopes were preserved.
Typical pool sections include pools located on straight reaches and pools on meander bends.
8.2.1.4 Meander Pattern
The design plans showing the proposed channel alignment are provided in Appendix E. The meander
pattern was derived directly from the analog reach and was altered in some locations to provide
variability in pattern, to avoid onsite constraints, to follow the valley pattern, and to make the channel
more constructible. The morphologic parameters summarized in the Appendix C were applied
wherever these deviations occurred.
8.2.1.5 Longitudinal Profiles
The design profiles are presented in Appendix C. These profiles extend throughout the entire project
for the proposed channel alignment. The profiles were designed using the analog reach bed features
that were sized with the scaling factors. The bed slopes and bankfull energy gradients were determined
for each design reach based on the existing valley slope and the sinuosity of the design reach. Log
structures will be utilized in the design to control grade, divert flows, and provide additional habitat
diversity and stability.
8.2.1.6 In -Stream Structures
Structures will be incorporated into the channel design to provide additional stability and improve
aquatic habitat. Native materials and vegetation will be used for revetments and grade control structures
where applicable. Additionally, rock structures will be utilized intermittently along Reaches HB 1 and
1-1133 to provide increased stability and habitat. Typical rock structures that will protect the channel bed
and/or banks will include riffle grade controls and j -hooks.
Woody debris will be placed throughout the channel at locations and at a frequency that is similar to
those mapped in the analog reaches. The analog reach has woody debris throughout the length of the
channel, providing grade control for shallows and forcing scour pools. Woody habitat features installed
will include dead brush, woody debris bundles, root wads, brush toes, and log vanes. To provide
additional bank stability, sod mats harvested onsite will be installed along stream banks during
construction if and when feasible. Sod mats will only be harvested and used if comprised of appropriate
Hannah Bridge Mitigation Plan 35 April 2017

vegetation. The use of sod mats that include aggressive turf grasses will be avoided. Sod mats are
natural sections of vegetation taken from the banks when they were cut during construction, and are
about nine inches thick. Before installation, proposed banks are graded lower than specified to
accommodate the thickness of the mat. The mats are placed on top of the bank to act as a natural
stabilizer of native species, and they grow much faster than the combination of coir fiber matting and
seeding. Other bank stability measures include the installation of live stakes, log sills, log drop
structures, and log toes. Typical details for proposed in -stream structures and revetments are in
Appendix E.
8.2.2 Wetland Restoration and Enhancement
The Site offers a total ecosystem restoration opportunity. As such, the wetland restoration and
enhancement is closely tied to the stream restoration. The Site will provide 11.73 WNWs through a
combination of wetland restoration, enhancement, and preservation treatments.
Because of the soil characteristics and variations observed throughout the site, the primary wetland
restoration activities, at a 1:1 credit ratio, will be plugging the existing channel and constructing a
stream channel at a higher elevation that elevates shallow groundwater depths and more frequently
floods adjacent wetlands. Additional backfilling to create shallow depressions within the old channel
and removal of spoil from pond excavation along the floodplains will aid in the restoration of a natural
floodplain surface relative to the surrounding landscape. Surface roughening and creation of shallow
depressions throughout the restoration area will provide an appropriate landscape for diverse habitat.
Due to compaction and long term agricultural use, a shallow ripping of the surface to a depth of 6 to 8
inches is called for to allow adequate porosity for infiltration and storage and provide microtopographic
relief.
Proposed wetland enhancement is located along the floodplains of the stream restoration and
enhancement reaches within the jurisdictional wetland areas. The construction of a farm pond has
altered surface drainage and placed spoil across the floodplain. As part of the wetland enhancement,
this pond will be removed and hydrology will be redirected towards the forested and grazed wetlands.
The existing pasture areas on the Site will be treated with Wetland Enhancement at a credit ratio of 2:1.
A credit ratio of 3:1 is proposed for the grazed, forested wetland areas. The wetland mitigation treatment
will primarily be re -planting the disturbed pastures as forested wetlands and excluding livestock from
the pasture and currently grazed forested wetlands. Enhancement activities will include: reconnecting
low lying areas of hydric soil with the floodplain, farm pond removal, planting native tree and shrub
species commonly found in small stream swamp ecosystems, and surface roughening to increase
infiltration and storage. Combined with the proposed stream restoration, these actions will result in a
sufficiently high water table and flood frequency to support hydrophytic vegetation and wetland
hydrology, resulting in enhanced riparian wetlands.
8.2.3 Natural Plant Community Restoration
8.2.3.1 Plant Community Restoration
The restoration of the plant communities is an important aspect of the restoration project. The selection
of plant species is based on what was observed at the reference reach, species present in the forest
surrounding the restoration site, and what is typically native to the area. Several sources of information
were used to determine the most appropriate species for the restoration project. The reference stream is
located within a disturbed Coastal Plain Small Stream Swamp. Dominant species included sweetgum,
red maple, tulip poplar, swamp tupelo (Nyssa biflora), and various oak species (Quercus sp.) in the
canopy. Shrubs included sweetbay (Magnolia virginiana) and American holly (Ilex opaca). The
reference site was chosen due to the stability of the channel, the physical structure of the forest
Hannah Bridge Mitigation Plan 36 April 2017

community, and to evaluate stream habitat. The species present are indicative of early successional
species that have high dispersal rates. The mitigation site also supports many species typical of this
community type due to its past disturbance history. Typically, a Coastal Plain Small Stream Swamp
would occur along the stream banks and adjacent floodplain of the proposed restoration site.
Coastal Plain Small Stream Swamp will be the target community type and will be used for all areas
within the project, as well as for buffer around the site. The plant species list has been developed and
can be found in Table 13. Species with high dispersal rates are not included because of local occurrence,
adjacent seed sources, and the high potential for natural regeneration. The high dispersal species include
red maple, tulip poplar, and sweetgum.
The restoration of plant communities along the Site will provide stabilization and diversity. For rapid
stabilization of the stream banks (primarily outside meanders), silky dogwood, cottonwood (Populus
deltoides) buttonbush (Cephalanthus occidentalis), silky willow (Salix sericea), and black willow were
chosen for live stakes along the restored channel because of their rapid growth patterns and high success
rates. Willows grow at a faster rate than the species planted around them, and they stabilize the stream
banks. Willows will also be quicker to contribute organic matter to the channel. When the other species
are bigger, the black willows and silky willows will slowly stop growing or die out because the other
species would outgrow them and create shade that the willows do not tolerate. The live stake species
will be planted along the outside of the meander bends three feet from the top of bank, creating a three-
foot section along the top of bank. The live stakes will be spaced one per linear foot with alternate
spacing vertically. See Appendix E for a detailed planting plan.
After construction activities, the subsoil will be scarified and any compaction will be deep tilled/ripped
before the topsoil is placed back over the site. Any topsoil that is removed during construction will be
stockpiled and placed over the site during final soil preparation. This process should provide favorable
soil conditions for plant growth. Rapid establishment of vegetation will provide natural stabilization
for the site.
Table 13. Proposed Plant List
Tree Species- Floodplain and Wetland
Common Name Scientific Name Wetland Indicator* Growth Rate
Black Gum
Nyssa biflora
OBL
moderate
Bald cypress
Taxodium distichum
OBL
rapid
Overcup oak
Quercus lyrata
OBL
moderate
River birch
Betula nigra
FACW
rapid
Willow oak
Quercus phellos
FACW
rapid
Swamp chestnut oak
Quercus michauxii
FACW
moderate
American sycamore
Platanus occidentalis
FACW
rapid
Yellow Poplar
Liriodendron tulipifera
FACU
rapid
Live Staking and Live Cuttings Bundle Tree Species
Common Name
Scientific Name
Wetland Indicator*
Silky dogwood
Cornus amomum
FACW
rapid
Silky willow
Salix sericea
OBL
rapid
Black willow
Salix nigra
OBL
rapid
Cottonwood
Populus deltoides
FAC
rapid
Buttonbush
Cephalanthus occidentalis
OBL
rapid
*National Wetland Indicator Status from Draft Rating 2012 -Atlantic Gulf Coastal Plain.
8.2.3.2 On -Site Invasive Species Treatment
Treatment for invasive species will be required within all grading limits associated with stream
restoration. Invasive species will require different and multiple treatment methods, depending on plant
Hannah Bridge Mitigation Plan 37 April 2017

phenology and the location of the species being treated. All treatment will be conducted to maximize
its effectiveness and reduce chances of negative impacts to surrounding native vegetation. Treatment
methods will include mechanical control (cutting with loppers, clippers, or chain saw) and chemical
control (foliar spray, cut stump, and hack and squirt techniques). Plants containing mature, viable seeds
will be removed from the site and properly disposed. All herbicide applicators will be supervised by a
certified ground pesticide applicator with a North Carolina Department of Agriculture and Consumer
Services (NCDA&CS) license and adhere to all legal and safety requirements according to herbicide
labels and NC and Federal laws. Management records will be kept on the plant species treated, type of
treatment employed, type of herbicide used, application technique, and herbicide concentration and
quantities used. These records will be included in all reporting documents.
8.2.4 Best Management Practices (BMPs)
Diffuse flow structures will be applied at locations where ditches or other forms of concentrated flow
enter the conservation easement. All diffuse flow structures will be installed within the conservation
easement so that landowners will not have access to the structures. Failure or maintenance of the
structures is not anticipated as these structures will be installed in low -gradient areas, and the areas
proposed to diffuse flow will be well vegetated and matted.
Stormwater management issues resulting from future development of adjacent properties will be
governed by the applicable state and local ordinances and regulations. It is recommended that any future
stormwater entering the site maintain pre -development peak flow. Any future stormwater diverted into
the project should be done in a manner as to prevent erosion, adverse conditions, or degradation of the
project in any way.
8.2.5 Soil Restoration
After construction activities, the subsoil will be scarified and any compaction will be deep tilled before
the topsoil is placed back over the site. Any topsoil that is removed during construction will be
stockpiled and placed over the site during final soil preparation. This process should provide favorable
soil conditions for plant growth. Rapid establishment of vegetation will provide natural stabilization
for the site.
8.3 Data Analysis
8.3.1 Stream Data Analysis
8.3.1.1 Stream Hydrologic Analysis
Hydrologic evaluations were performed for the design reaches using multiple methods to determine
and validate the design bankfull discharge and channel geometry required to provide regular floodplain
inundation. The use of various methods allows for comparison of results and eliminates reliance on a
single model. Peak flows (Table 14) and corresponding channel cross-sectional areas were determined
for comparison to design parameters using the following methods:
• Regional Flood Frequency Analysis,
• AutoCAD's Hydraflow Hydrographs,
• NC and VA/MD Regional Curves for the Coastal Plain, and
• USGS regional regression equations for rural conditions in the Coastal Plain.
Regional Flood Frequence
A flood frequency analysis was completed for the study region using historic gauge data on all nearby
USGS gauges with drainage areas less than 6,400 acres (10 mit) which passed the Dalrymple
Hannah Bridge Mitigation Plan 38 April 2017

homogeneity test (Dalrymple, 1960). This is a subset of gauges used for USGS regression equations.
Regional flood frequency equations were developed for the 1.1-, 1.5-, and 2 -year peak discharges based
on the gauge data. Discharges were then computed for the design reach. These discharges were
compared to those predicted by the discharge regional curve and USGS regional regression 2 -year
discharge equations.
AutoCAD's Hydraflow Express
Hydraflow Express was used to simulate the rainfall -runoff process and establish peak flows for the
watersheds. This model was chosen over the U.S. Army Corps of Engineers model HEC -HMS because
it allows the user to adjust the peak shape factor for the Coastal Plain conditions. Rainfall data reflecting
both a 100 and 284 peak shape factor were used along with a standard Type Il distribution, and NRCS
hydrology (time of concentrations and runoff curve numbers), to simulate the rainfall -runoff process.
Calibration studies across the State of North Carolina have been developed by the National Resources
Conservation Service (NRCS) that show the standard 484 peak shape factor found in HEC -1 and HEC -
HMS are too conservative. The NRCS recommends using a value that ranges between 100 and 284 for
those areas on the eastern side of the state.
Reizional Curve Repression Equations
The North Carolina Coastal Plain regional curves by Doll et al. (2003) and Sweet and Geratz (2003)
and the Virginia/Maryland (Krstolic et al., 2007) Coastal Plain regional curves for discharge were used
to predict the bankfull discharge for the site. The NC regional curves predicted flows that are similar to
those predicted by the 1.1 -year flood frequency, while the VA/MD curves are comparable to flows
predicted by the 1.5 -year flood frequency equation. The regional curve equations for NC discharges by
Doll et al. (2003) (1) and Sweet and Geratz ( 2003) (2) and VA/MD (3) discharges are:
(1) Qbk=16.56*(DA)I32 (Doll et al., 2003)
(2) Qak>8.49*(DA)0_76 (Sweet and Geratz, 2003)
(3) Qbk1` 28.3076*(DA)0.51134 (Krstolic et al., 2007)
Where Qbkf=bankfull discharge (ft3/s) and DA=drainage area (mi2).
USGS Regional Regression Equations
USGS regression equations estimate the magnitude and frequency of flood -peak discharges (Gotvald,
et al., 2009). The regression equations were developed from gauge data in different physiographic
regions of the Southeastern United States. For this analysis, there was only concern for the 2 -year return
interval. The equation for the rural Coastal Plain (Hydrologic Region 4) is:
(4) Q2=60.3 *(DA)o.6a9
Hannah Bridge Mitigation Plan 39 April 2017

Table 14. Peak Flow Comparison
Reach
Drainage
Area
(Ac)
Hydratlow
Q�
FFQ
Qi'�
FFQ
Qi's
NC
Regional
Curve Q (1)
NC Regional
Curve Q (2)
VA/MD
Regional
Curve Q (3)
Regional
Regression
Eqns. Q2
Design/
Calculated
Q
H132
(Analog)
752
63
25
56
19
10
31
67
29-31
HBI
667
63
23
51
17
9
29
62
30-32
H133
816
82
27
59
20
11
33
71
30-32
HB4
894
82
29
62
21
11
35
75
30-32
HFI
78
---
3.7
12
4
1.8
8
15
4-5
HF2
13
1.2
0.8
4
1.0
0.4
3
5
1.54
TH3
24
---
1.4
6
1.6
0.7
4
7
2-6
8.3.1.2 Sediment Transport Analysis
An erosion and sedimentation analysis was performed to confirm that the restoration design creates a
stable sand bed channel that neither aggrades nor degrades over time. Typically, sediment transport is
assessed to determine a stream's ability to move a specific grain size at specified flows. Various
sediment transport equations may be easily applied when estimating entrainment for gravel bed
streams; however, these equations are not as effectively applied to sand bed channels where the entire
bed becomes mobile during geomorphically significant flows. Therefore, more sophisticated modeling
techniques were used to analyze the stream design for this project. The following methods and functions
were utilized during the sediment transport analysis:
• Stable Channel Design Function — Copeland Method (HEC -RAS),
• Shear Stress, and
• Velocity.
Stable Channel Design
Design cross-section dimensions as determined from the analog approach were evaluated using the
stable channel design functions within HEC -RAS. These functions are based upon the methods
presented in the SAM Hydraulic Design Package for Channels developed by the USACE Waterways
Experiment Station. The Copeland Method was developed specifically for sand bed channels (median
grain size restriction of 0.0625 mm to 2 mm) and was selected for application at the Site. The method
sizes stable dimensions as a function of slope, discharge, roughness, side slope, bed material gradation,
and the inflowing sediment discharge. Results are presented as a range of widths and slopes, and their
unique solution for depth, making it easy to adjust channel dimensions to achieve stable channel
configurations. The stable design output parameters are listed in Table 15. The results are acceptable
and match closely with the design reach parameters.
Table 15. Stable Channel Design Output
Reach Q (ft/s3) Bottom Depth (ft) Energy Composite Velocity Shear Stress
Width (ft) Slope (ft/ft) n value (ft/s) (lbs/ft )
HB1/HB3 30 7 1.5 0.0032 0.040 2.2 0.29
Hannah Bridge Mitigation Plan 40 April 2017

Shear Stress Approach
Shear stress is a commonly used tool for assessing channel stability. Allowable channel shear stresses
are a function of bed slope, channel shape, flows, bed material (shape, size, and gradation),
cohesiveness of bank materials, and vegetative cover. The shear stress approach compares calculated
shear stresses to those found in the literature. Shear stress is the force exerted on a boundary during the
resistance of motion as calculated using the following formula:
(1) r=yRS
i = shear stress (lb/ft)
y = specific gravity of water (62.4 lb/ft')
R = hydraulic radius (ft)
S = average channel slope (ft/ft)
Table 16. Comparison of Allowable and Proposed Shear Stresses
Proposed Shear Stress Allowable Shear Stress'
Reach at Bankfull Stage Critical Shear Stress
z (lbs/ft) Sand/Silt/Clay Gravel Vegetation
(lbs/ft) (lbs/ft') (lbs/ft2) (lbs/ft2)
HBI/HB3 0.24 >0.004 0.03 to 0.26 0.33 to 0.67 0.2 to 0.1.7
'(Fischenich,2001)
Review of the above table shows that the proposed shear stresses for the Site design reaches fall between
the critical shear stress (shear stress required to initiate motion) and the allowable limits. Therefore, the
proposed channel should remain stable.
Velocity Approach
Published data are readily available that provide entrainment velocities for different bed and bank
materials. A comparison of calculated velocities to these permissible velocities is a simple method to
aid in the verification of channel stability. Table 17 compares the proposed velocities calculated using
Manning's equation with the permissible velocities presented in the Stream Restoration Design
Handbook (NRCS, 2007).
Table 17. Comparison of Allowable and Proposed Velocities
Reach Manning's "n" Design Velocity (ft/s) Allowable Velocity' (ft/s)
value Fine Sand Coarse Sand Fine Gravel
HB1/1-1133 0.05 1.8 2.0 4.0 6.0
1(NRCS, 2007
8.3.2 Mitigation Summary
Natural channel design techniques have been used to develop the restoration designs described in this
document. The combination of the analog and analytical design methods was determined to be
appropriate for this project because the watershed is rural, the causes of disturbance are known and
have been abated, and there are minimal infrastructure constraints. The original design parameters were
developed from the measured analog/reference reach data and applied to the subject stream. The
parameters were then analyzed and adjusted through an iterative process using analytical tools and
numerical simulations of fluvial processes. The designs presented in this report provide for the
restoration of natural Coastal Plain sand -bed channel features and stream bed diversity to improve
Hannah Bridge Mitigation Plan 41 April 2017

benthic habitat. The proposed design will allow flows that exceed the design bankfull stage to spread
out over the floodplain, restoring a portion of the hydrology for the existing wetlands.
A large portion of the existing stream will be filled using material excavated from the restoration
channel. However, many segments will be left partially filled to provide habitat diversity and flood
storage. Native woody material will be installed throughout the restored reach to reduce bank stress,
provide grade control, and increase habitat diversity.
Forested riparian buffers of at least fifty feet on both sides of the channel will be established along the
project reach. An appropriate riparian plant community, a Coastal Plain Small Stream Swamp, will be
established to include a diverse mix of species. Replanting of native species will occur where the
existing buffer is impacted during construction.
The Hannah Bridge Stream Mitigation Site is being built in conjunction with the Hannah Bridge
Buffer/Nutrient Offset Site. Reductions in nutrients and other pollutants will be achieved with the buffer
restoration work, providing substantial benefits to the watershed.
Due to the nature of the project, complete avoidance of stream and wetland impacts is not possible.
Proposed stream impacts, including stream relocation and culverts, will be replaced on site. Wetland
impacts associated with restoration and enhancement efforts will only temporarily impact wetlands and
will provide an overall increase in wetland function with the addition of native trees and shrubs along
the stream banks, and restored hydrology. All stream and wetland impacts will be accounted for in the
Pre -Construction Notification (PCN) form.
Hannah Bridge Mitigation Plan 42 April 2017

9 MAINTENANCE PLAN
The site will be monitored on a regular basis and a physical inspection will be conducted a minimum
of once per year throughout the post construction monitoring period until performance standards are
met. These site inspections may identify site components and features that require routine maintenance.
Routine maintenance should be expected most often in the first two years following site construction
and may include the following:
Table 18. Maintenance Plan
Component/Feature
Maintenance through project close-out
Stream
Routine channel maintenance and repair activities may include chinking of
in -stream structures to prevent piping, securing of loose coir matting, and
supplemental installations of live stakes and other target vegetation along
the channel. Areas where stormwater and floodplain flows intercept the
channel may also require maintenance to prevent bank failures and head -
cutting. Stream maintenance activities will be documented and reported in
annual monitoring reports.
Wetland
Routine wetland maintenance and repair activities may include securing of
loose coir matting, channel plug maintenance, and supplemental
installations of live stakes and other target vegetation within the wetland.
Vegetation
Vegetation shall be maintained to ensure the health and vigor of the targeted
plant community. Routine vegetation maintenance and repair activities may
include supplemental planting, pruning, mulching, and fertilizing. Exotic
invasive plant species shall be controlled by mechanical and/or chemical
methods. Any vegetation control requiring herbicide application will be
performed in accordance with NC Department of Agriculture (NCDA) rules
and regulations. Vegetation maintenance activities will be documented and
reported in annual monitoring reports. Vegetation maintenance will
continue through the monitoring period.
Site Boundary
Site boundaries shall be identified in the field to ensure clear distinction
between the mitigation site and adjacent properties. Boundaries will be
marked with signs identifying the property as a mitigation site, and will
include the name of the long-term steward and a contact number.
Boundaries may be identified by fence, marker, bollard, post, tree -blazing,
or other means as allowed by site conditions and/or conservation easement.
Boundary markers disturbed, damaged, or destroyed will be repaired and/or
replaced on an as -needed basis. Easement monitoring and staking/signage
maintenance will continue in perpetuity as a stewardship activity.
Road Crossing
Road crossings within the Site may be maintained only as allowed by
conservation easement or existing easement, deed restrictions, rights of
way, or corridor agreements. Crossings in easement breaks are the
responsibility of the landowner to maintain.
Livestock Fencing
Livestock fencing is to be placed outside the easement limits. Maintenance
of fencing is the responsibility of the landowner.
Beaver
Routine site visits and monitoring will be used to determine if beaver
management is needed. If beaver activity poses a threat to project stability
or vegetative success, RES will trap beavers and remove impoundments as
needed. All beaver management activities will be documented and included
in annual monitoring reports. Beaver monitoring and management will
continue through the monitoring period.
Hannah Bridge Mitigation Plan 43 April 2017

10 PERFORMANCE STANDARDS
The success criteria for the Site will follow accepted and approved success criteria presented in the
USACE Stream Mitigation Guidelines and subsequent agency guidance. Specific success criteria
components are presented below.
10.1 Stream and Wetland Restoration Success Criteria
10.1.1 Bankfull Events
Four bankfull flow events must be documented within the seven-year monitoring period. The four
bankfull events must occur in separate years. Otherwise, the stream monitoring will continue until four
bankfull events have been documented in separate years.
10.1.2 Cross Sections
There should be little change in as -built cross-sections. If changes do take place, they should be
evaluated to determine if they represent a movement toward a less stable condition (for example down -
cutting or erosion), or are minor changes that represent an increase in stability (for example settling,
vegetative changes, deposition along the banks, or decrease in width/depth ratio). Cross-sections shall
be classified using the Rosgen stream classification method, and all monitored cross-sections should
fall within the quantitative parameters defined for channels of the design stream type.
10.1.3 Digital Image Stations
Digital images will be used to subjectively evaluate channel aggradation or degradation, bank erosion,
success of riparian vegetation, and effectiveness of erosion control measures. Longitudinal images
should not indicate the absence of developing bars within the channel or an excessive increase in
channel depth. Lateral images should not indicate excessive erosion or continuing degradation of the
banks over time. A series of images over time should indicate successional maturation of riparian
vegetation.
10.1.4 Wetland Hydrology Criteria
The Natural Resources Conservation Service (NRCS) has a current WETs table for Johnston County
upon which to base a normal rainfall amount and average growing season. The closest comparable data
station was determined to be the WETS station for Smithfield, NC. The growing season for Johnston
County is 233 days long, extending from March 18 to November 6, and is based on a daily minimum
temperature greater than 28 degrees Fahrenheit occurring in five of ten years.
Based upon field observation across the site, the NRCS mapping units show a good correlation to actual
site conditions in areas of the site. Mitigation guidance for soils in the Coastal Plain suggests a
hydroperiod for the Bibb soil of 12-16 percent of the growing season. The hydrology success criterion
for the Site is to restore the water table so that it will remain continuously within 12 inches of the soil
surface for at least 12 percent of the growing season (approximately 27 days) at each groundwater
gauge location. Based on the extensive management history of the Site and soil compaction, RES
proposes a target hydroperiod of nine percent for monitoring years 1 and 2, with the understanding that
12 percent will be the target hydroperiod for the remainder of the monitoring period.
10.2 Vegetation Success Criteria
Specific and measurable success criteria for plant density within the riparian buffers on the site will
follow IRT Guidance. Vegetation monitoring plots will be a minimum of 0.02 acres in size, and cover
a minimum of two percent of the planted area. Vegetation monitoring will occur annually between
July 15 and leaf drop. The interim measures of vegetative success for the site will be the survival of
Hannah Bridge Mitigation Plan 44 April 2017

at least 320 planted three-year old trees per acre at the end of Year 3, 260 five-year old trees at the
end of Year 5, and the final vegetative success criteria will be 210 trees per acre with an average
height of ten feet at the end of Year 7. Volunteer trees will be counted, identified to species, and
included in the yearly monitoring reports, but will not be counted towards the success criteria of total
planted stems.
11 MONITORING REQUIREMENTS
Annual monitoring data will be reported using the IRT monitoring template. A detailed monitoring plan
is provided in Figure 11. The monitoring report shall provide a project data chronology that will
facilitate an understanding of project status and trends, research purposes, and assist in decision making
regarding project close-out. The success criteria for Site will follow current accepted and approved
success criteria presented in the USACE Stream Mitigation Guidelines, and subsequent agency
guidance. Specific success criteria components are presented in Table 19. Monitoring reports will be
prepared annually and submitted to the IRT.
Table 19. Monitoring Requirements
Requi
red
Parameter
Quantity
Frequency
Notes
As per April 2016
Additional surveys will be performed
Pattern
USACE Wilmington
Baseline
if monitoring indicates instability or
District Stream
significant channel migration
Mitigation Guidelines
As per April 2016
Baseline,
Dimension
USACE Wilmington
Years
Surveyed cross sections and bank pins
District Stream
1,2,3,5,
Mitigation Guidelines
and 7
As per April 2016
Profile
USACE Wilmington
Baseline
Additional surveys will be performed
District Stream
if monitoring indicates instability
Mitigation Guidelines
As per April 2016
Crest gauges and/or pressure
Surface Water
USACE Wilmington
transducers will be installed on site;
Hydrology
District Stream
Quarterly
the devices will be inspected on a
Mitigation Guidelines
quarterly basis to document the
occurrence of bankfull events
Vegetation
2% of planted area
Semi-
Vegetation will be monitored per IRT
Annual
guidelines
Groundwater monitoring gauges with
Groundwater
4-6 groundwater wells
data recording devices will be installed
Hydrology
distributed throughout
Quarterly
on site; the data will be downloaded
the site
on a quarterly basis during the
growing season
Exotic and
Nuisance
Semi-
Locations of exotic and nuisance
Vegetation
Annual
vegetation will be mapped
Project
Semi-
Locations of fence damage, vegetation
Boundary
Annual
damage, boundary encroachments, etc.
will be mapped
Stream/Wetland
Semi -
Semi-annual visual assessments
Visual
Annual
Hannah Bridge Mitigation Plan 45 April 2017

11.1 As -Built Survey
An as -built survey will be conducted following construction to document channel size, condition, and
location. The survey will include a complete profile of thalweg, water surface, bankfull, and top of bank
to compare with future geomorphic data. Longitudinal profiles will not be required in annual
monitoring reports unless requested by USAGE. Stream channel stationing will be marked with stakes
placed near the top of bank every 200 feet.
11.2 Visual Monitoring
Visual monitoring of all mitigation areas will be conducted a minimum of twice per monitoring year
by qualified individuals. The visual assessments will include vegetation density, vigor, invasive species,
and easement encroachments. Visual assessments of stream stability will include a complete
streamwalk and structure inspection. Digital images will be taken at fixed representative locations to
record each monitoring event, as well as any noted problem areas or areas of concern. Results of visual
monitoring will be presented in a plan view exhibit with a brief description of problem areas and digital
images. Photographs will be used to subjectively evaluate channel aggradation or degradation, bank
erosion, success of riparian vegetation, and effectiveness of erosion control measures. Longitudinal
photos should indicate the absence of developing bars within the channel or an excessive increase in
channel depth. Lateral photos should not indicate excessive erosion or continuing degradation of the
banks over time. A series of photos over time should indicate successional maturation of riparian
vegetation.
11.3 Cross Sections
Permanent cross-sections will be installed at a minimum of one per 20 bankfull widths with half in
pools and half in shallows. All cross-section measurements will include bank height ratio and
entrenchment ratio. Cross-sections will be monitored annually. There should be little change in as -built
cross-sections. If changes do take place, they should be evaluated to determine if they represent
movement toward a less stable condition (for example down -cutting or erosion), or are minor changes
that represent an increase in stability (for example settling, vegetative changes, deposition along the
banks, or decrease in width/depth ratio). Bank height ratio shall not exceed 1.2, and the entrenchment
ratio shall be no less than 2.2 within restored reaches. Channel stability should be demonstrated through
a minimum of two bankfull events documented in the seven-year monitoring period.
11.4 Wetland Hydrology
Wetland hydrology will be monitored to document hydric conditions in the wetland restoration areas.
This will be accomplished with automatic recording pressure transducer gauges installed in
representative locations across the restoration areas and reference wetland. The gauges will be
downloaded quarterly and wetland hydroperiods will be calculated during the growing season. Gauge
installation will follow current NCIRT guidance. Visual observations of primary and secondary wetland
hydrology indicators will also be recorded during quarterly site visits.
11.5 Vegetation Monitoring
Vegetation monitoring plots will be a minimum of 0.02 acres in size, and cover a minimum of two
percent of the planted area. There will be 21 plots within the planted area (26.4 acres). Plots will be a
mixture of fixed and random plots, but random plots will make up no more than 50% of the total plots.
Planted area indicates all area in the easement that will be planted with trees. Existing wooded areas
(e.g. Reach HB2, HF 1, and right bank of Reach 1-1134) are not included in the planted area. The following
data will be recorded for all trees in the plots: species, height, planting date (or volunteer), and grid
location. Monitoring will occur each year during the monitoring period. Invasive and noxious species
Hannah Bridge Mitigation Plan 46 April 2017

will be monitored and controlled so that none become dominant or alter the desired community
structure of the site. If necessary, RES will develop a species-specific control plan.
11.6 Scheduling/Reporting
A mitigation plan and as -built drawings documenting stream restoration activities will be developed
within 60 days of the planting completion on the Site. The report will include all information required
by IRT mitigation plan guidelines, including elevations, photographs and sampling plot locations,
gauge locations, and a description of initial species composition by community type. The report will
also include a list of the species planted and the associated densities. Baseline vegetation monitoring
will include species, height, date of planting, and grid location of each stem. The baseline report will
follow USACE guidelines.
The monitoring program will be implemented to document system development and progress toward
achieving the success criteria. The restored stream morphology will be assessed to determine the
success of the mitigation. The monitoring program will be undertaken for seven years or until the final
success criteria are achieved, whichever is longer.
Monitoring reports will be prepared in the fall of each year of monitoring and submitted to the IRT.
The monitoring reports will include all information, and be in the format required by USACE.
11.7
11.8 Adaptive Management
In the event that the site, or a specific component of the site, fails to achieve the defined success criteria,
RES will develop necessary adaptive management plans and/or implement appropriate remedial actions
for the site in coordination with the IRT. Remedial action required will be designed to achieve the
success criteria specified previously, and will include identification of the causes of failure, remedial
design approach, work schedule, and monitoring criteria that will take into account physical and
climatic conditions. If tree mortality affects 40 percent or greater of the canopy in a stream restoration
area, then a remedial/supplemental planting plan will be developed and implemented for the affected
area(s). If beaver activity poses a threat to project stability or vegetative success, RES will trap beavers
and remove impoundments as needed. All beaver management activities will be documented and
included in annual monitoring reports
Hannah Bridge Mitigation Plan 47 April 2017

12 LONG-TERM MANAGEMENT PLAN
Upon approval of the Site by the IRT, the site will be transferred to the NCWHF:
North Carolina Wildlife Habitat Foundation
[phone]
PO Box 29187
Greensboro, NC 27429
www.ncwh£or
The NCWHF will be responsible for periodic inspection of the Site to ensure that restrictions required
in the Conservation Easement or the deed restriction document(s) are upheld. Easements held by the
NCWHF are stewarded in general accordance with the guidelines published by the National Land Trust
Alliance. These guidelines include annual monitoring visits to easements and related communication
with the landowner(s). During the visit a standard report is completed and pictures taken for the record.
If the Site is found to be in violation of the easement terms NCWHF works with the landowner to see
the problem rectified. When appropriate NCWHF pursues legal action to enforce the easement terms.
NCWHF typically requires the site developer to install standard NCWHF signage as part of the
easement transfer package. This includes well marked corners of the easement boundary, as well as
plastic or metal signs identifying the easement. The current sign standard is a 6"x6" aluminum sign
with contact information. Signs are refreshed on an as needed basis. Typically a sign will last 5-10
years before it is no longer legible due to sun fading. An overview of the NCWHF Easement
Stewardship program is included in Appendix A.
NCWHF requires and endowment for each easement it agrees to hold. All endowments are held
together in an investment fund. Endowments are sized so that the interest from the principal will pay
the expected monitoring costs for that easement. This assumes a seven year monitoring period for the
site during which NCWHF will not incur any expenses. It also assumes a 5% annual return. Currently
NCWHF employs a contractor to handle annual monitoring visits and basic easement stewardship. This
flat fee includes a property walkthrough, report, pictures, sign installation, etc. The endowment fee has
not yet been confirmed for the easement transfer of the Hannah Bridge Site, and it will be updated once
finalized.
Hannah Bridge Mitigation Plan 48 April 2017

13 ADAPTIVE MANAGEMENT PLAN
Upon completion of project construction, RES will implement the post -construction monitoring
protocols previously defined in this document. Project maintenance will be performed as described
previously in this document. If, during the course of annual monitoring, it is determined that the Site's
ability to achieve site performance standards are jeopardized, RES will notify the USACE of the need
to develop a Plan of Corrective Action. Once the Corrective Action Plan is prepared and finalized RES
will:
1. Notify the USACE as required by the Nationwide 27 permit general conditions.
2. Revise performance standards, maintenance requirements, and monitoring requirements as
necessary and/or required by the USACE.
3. Obtain other permits as necessary.
4. Implement the Corrective Action Plan.
5. Provide the USACE a Record Drawing of Corrective Actions. This document shall depict the
extent and nature of the work performed.
Hannah Bridge Mitigation Plan 49 April 2017

14 FINANCIAL ASSURANCES
CONFIDENTIAL
The Sponsor will provide financial assurances in the form of a $695,000 Construction Performance
Bond to the USACE to assure completion of mitigation construction and planting. Construction and
planting costs are estimated to be at or below $695,000 based on the Engineer's construction materials
estimate and recent bid tabulation unit costs for construction materials. Following completion of
construction and planting the Construction Performance Bond will be retired and a $262,000
Monitoring Performance Bond will be provided to assure completion of seven years of monitoring and
reporting, and any remedial work required during the monitoring period. The $262,000 amount includes
contingency and estimated monitoring costs from the Engineer. The Monitoring Performance Bond
will be reduced by $ 37,000 following approval of each annual monitoring report. The Monitoring
Performance Bond will be retired in total following official notice of site close-out from the IRT.
Financial assurances shall be payable to a standby trust or other designee at the direction of the obligee.
Financial assurances structured to provide funds to the USACE in the event of default by the Bank
Sponsor are not acceptable. A financial assurance must be in the form that ensures that the USACE
receives notification at least 120 days in advance of any termination or revocation. The Performance
Bonds will be provided by RLI Insurance Company. All Performance Bonds will be submitted to the
USACE in draft form for approval prior to execution. In the event of Sponsor default, the NCWHF has
agreed to receive the funds and ensure the work is successfully completed.
Construction Costs
General (e.g. mobilization, erosion control, etc)
$ 110,000
Sitework
$ 136,000
Structures (e.g. ditch plugs,logs, rocks, coir,
etc)
$ 292,000
Crossings
$ 15,000
Vegetation
$ 110,000
Miscellaneous
$ 32,000
Total
$ 695,000
Monitorin
Annual Monitoring and Reports
$ 154,500
Equipment (e.g. gauges, markers, etc)
$ 5,500
Miscellaneous
$ 5,000
Contingency (8%)
$ 97,000
Total
$ 262,000
Hannah Bridge Mitigation Plan 50 April 2017

15 OTHER INFORMATION
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Hannah Bridge Mitigation Plan 52 April 2017

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Hannah Bridge Mitigation Plan 53 April 2017