20140192 Ver 1_Corrective Action Plan_20150928

CORRECTIVE ACTION PLAN
FOR
Lower Big Hungry Mverc
Dam Removal bite
Henderson County, North Carolina
Prepared for
AGENCY REVIEW
September 2015
Prepared by:
AMo Gill

Big Hungry River — Corrective Action Plan 17- Sep -15
Henderson County, NC McGill Associates, P.A.
INTRODUCTION
The Big Hungry River is a tributary of the Green River in the Broad River Basin. There
are two historic dams in the lower reaches of the Big Hungry River (BHR), the lower of
these is about 3/4 miles above the confluence with the Green River and the upper dam is
about 3/4 miles above the lower. The Big Hungry River lower dam removal project is part
of a larger project involving removal of both upper and lower dams. Both dams occur
within the Green River Game Lands owned by the NC Wildlife Resources Commission.
The dam removal project was initiated to enhance recreational opportunities on the BHR,
remove aquatic migration barriers and eliminate hazards associated with both structures.
Clean Water Act Section 404 and 401 permits were issued for the removal of the lower
dam on May 7, 2014 and July 1, 2014 respectively. Construction commenced in February
of 2015. The final portions of the lower dam were removed in early March 2015. This
action resulted in a lowering of the base gradient of the river that caused an immediate
headcut through accumulated sediment in the channel above the old dam. The sediment
released from the project site as a result of this headcut led to the issuance of a
Notification of Noncompliance with Permit from the USACE (March 26, 2015) and a
Notice of Violation from NC DENR DWR (March 17, 2015).
The Correction Action Plan (CAP) provided herein and attached materials are in response
to the referenced notices issued to the NC Wildlife Resources Commission, Division of
Engineering and Lands Management (Owner /Applicant) and Graham County Land
Company, LLC (Contractor) in March 2015. McGill Associates, P.A. is the project
engineer and is providing this response on behalf of the Owner and Contractor.
Following the sediment release that occurred during an approximate 24 hour period
between mid -day March 3, 2015 and mid -day March 4, 2015, staff members from NC
DENR DWR and DEMLR conducted a site investigation of the Big Hungry River (BHR)
below the project area of the lower dam removal project. Substantial volumes of sediment
in the river, in excess of four feet in depth were observed. In response to the March 3 -4
event and subsequent communications with NCWRC, DWR, and other state and federal
agencies, the Project Engineer initiated survey and planning efforts aimed at assessing the
impacts and developing remedial action plans.
This Corrective Action Plan (CAP) is submitted to the USACE and NC -DWR to describe
how proposed remedial and restorative actions will bring the Big Hungry River, lower
dam site, into compliance with Clean Water Act 404/401 permit conditions and to
address the various other issues raised in the NOV's and Notification of Permit
Noncompliance. Specific focus will be given to the following items:
• Details to remove the unauthorized fill material
• Short-term and long -term streambank and stream bed stabilization measures
upstream of the dam to minimize further sediment destabilization
• Stream restoration/enhancement activities downstream of the dam
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• Location of sediment disposal areas and details of how this sediment will be
handled and stabilized
• Proposed schedule to perform the corrective action tasks
• Preparation of the final document detailing the performance of the remedial
actions with supporting as -built drawings and photos
A. REMOVAL OF UNAUTHORIZED FILL MATERIAL
Following the sediment release that occurred during an approximate 24 hour period
between mid -day March 3, 2015 and mid -day March 4, 2015, staff members from NC
DENR DWR and DEMLR conducted a site investigation of the Big Hungry River
(BHR) below the project area of the lower dam removal project. Substantial volumes
of sediment in the river, in excess of four feet in depth were observed. The observed
sediment deposition contributed to the issuance of a Notice of Violation to the project
Applicant and Contractor that requires, among other things, the development of a
Sediment Removal Plan and a Stabilization Plan for all involved areas of the BHR.
In response to the March 3 -4 event and subsequent communications with NCWRC,
DWR, and other state and federal agencies, the Project Engineer initiated survey and
planning efforts aimed at assessing the impacts and developing remedial action plans.
The results from the sediment impact analysis performed by McGill Associates are
summarized below followed by an analysis of downstream sediment removal options:
1. Impact Analysis
On -site Impacts: On -site impacts are those direct 404/401 impacts within the
immediate area of the old lower dam and extending upstream for approximately
125 feet. These are temporary impacts associated with the access ramp
constructed out of demolition rubble and soil, the temporary dam constructed out
of Jersey Barriers, rubble and rock, and bank sloughing along the lower portion of
the headcut channel.
Off -Site Impacts: Off -site impacts were determined through a stream sediment
study conducted March 20, 2015. The study involved an assessment of the BHR
downstream of the lower dam site for approximately 2850 linear feet as well as
approximately 1850 linear feet upstream of the old impoundment limits above the
lower dam. The assessment was conducted using 4 -foot and 7 -foot long sediment
probes to measure depth and estimate average depth of depositional areas. The
surface area of each depositional area was measured or estimated as well.
Generally, pool areas consisted of one large sediment plume but riffle areas
consisted of multiple smaller pockets of deposition in micro -pools or eddies
within the riffle; the multiple smaller depositional areas within the riffles were
aggregated into a single quantity for most riffles. GPS points were taken at the
approximate center of each area evaluated. The locations are shown on figures
(U1 -U2 and D1 -D2). Results of the evaluation are recorded in the attached table
(T -1).
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McGill Associates, P.A.
Downstream Impacts: The downstream sediment evaluation area begins at the
base of the waterfall below the old dam (station 0 +00) extending downstream
about 2,850 linear feet (station 28 +50). The average slope of this reach is roughly
1.8 %. Every pool evaluated downstream of the lower dam contained large
deposits of sediment. The composition of the sediment was predominantly
medium to coarse sand mixed with a small amount of organic material. Along
channel margins and backwater areas, particle size decreased and the sand was
mixed with small amounts of silt and clay. Water clarity was high throughout the
assessment area even in areas of high velocity. Most riffle sections contained
multiple smaller sediment deposits as described above. There was sediment on the
lower banks in places, but this was not measured. Within the 2,850 linear foot
reach evaluated for sediment impact, 29 depositional areas were measured, 20
pools and 9 riffle /run areas, the total length of the measured areas was 1,047
linear feet. The total volume of sediment measured was 2,533 cubic yards. The
volume of sediment measured per 1,000 feet of reach evaluated is about 889 cubic
yards. The volume of sediment measured per 1,000 feet of reach measured is
about 2,419 cubic yards. See below (Impact Assessment Analvsis) for a
description of the difference between the length of reach measured and the length
of reach evaluated.
Upstream Impacts: The upstream evaluation area begins roughly 1,120 linear feet
above the old dam (station 11 +20) and extends upstream for about 1850 linear
feet (station 29 +50). The average slope of this reach is roughly 2.05 %. Every pool
evaluated upstream of the backwater limits of the lower dam was filled with
sediment of roughly the same composition as described for the downstream reach.
Water clarity was high throughout this reach, no apparent difference from the
downstream reach. Riffle sections contained scattered pockets of sediment but the
frequency and size was somewhat reduced when compared to the downstream
reach. Within the 1,790 linear foot reach evaluated, 13 depositional areas were
measured, 9 pools and 4 riffle /run areas, the total length of the measured areas
was 530 linear feet. The total volume of sediment measured was 1,138 cubic
yards. The volume of sediment measured per 1,000 feet of reach evaluated is
about 636 cubic yards. The volume of sediment measured per 1,000 feet of reach
measured is about 2,147 cubic yards. See below (Impact Assessment Analvsis)
for a description of the difference between the length of reach measured and the
length of reach evaluated.
Impact Assessment Analvsis: The sediment assessment performed by McGill
Associates clearly shows that the BHR below the lower dam site is severely
impacted by sediment deposition. The assessment also shows that the BHR is
severely impacted by sediment above the limits of backwater behind the old lower
dam. The degree to which pools are filled with sediment and the distribution of
sediment in riffles and runs appears similar in the two reaches. The following
method was used to compare the relative degree that the BHR is impacted by
sediment between the upstream and downstream reaches. Estimated sediment
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volume per 1,000 feet of reach evaluated was determined by dividing the total
volume of sediment measured by the length evaluated (2,533 yds. /2,850 lin.ft. for
downstream and 1,137 yds. /1,790 lin.ft. for upstream). Estimated sediment
volume Der 1,000 feet of reach measured was determined by dividing the total
volume of sediment measured by the combined total length of the depositional
areas measured (2,533 yds. /1,047 lin.ft. for downstream and 1,137 yds. /530 lin.ft.
for upstream). This comparison shows a nearly 40% increase in sediment per
linear foot of reach evaluated downstream vs. upstream. However, when
considering that the upstream reach has a steeper average gradient (2.05%
upstream to 1.8% downstream) and correspondingly fewer depositional areas per
unit length (more riffles and shallow bedrock sections) than the downstream
reach, a direct comparison of the amount of sediment trapped in depositional
areas may be more appropriate. Such a comparison shows only a 13% increase in
sediment per linear foot of measured depositional area downstream vs. upstream.
Therefore, we believe the actual difference in the relative abundance of sediment
between the two reaches to be closer to 13% than 40 %.
The results of the instream sediment assessment seem to indicate that the entire
section of the BHR from above the upper dam to at least 3,000 linear feet below
the lower dam site is severely impacted by sediment and has been for some time.
Direct evidence to support this is limited to two observations:
1. In a couple of the downstream pools there was a clearly visible organic
layer with approximately 6 to 8 inches of sediment on top. This could
indicate that the sediment below this organic layer may have existed prior
to the March 3 -4 sediment release.
2. All along the downstream reach there was extensive sediment deposition
along the banks and inner -berm features at elevations above the water
surface elevation at the time of the evaluation. Between the March 3 -4
sediment release and the March 20 sediment assessment there were not
any precipitation events greater than 0.40 inches in 24 hours. This would
appear to indicate that previous events delivered heavy sediment loads to
the reach.
2. Sediment Removal Analysis
Sediment Impact Assessment and Removal Plan Options: Following review and
analysis of the instream sediment assessment performed both upstream and
downstream of the lower BHR dam, it has become apparent that the BHR from
the upper reaches of the old lake above the upper dam, downstream to the
confluence with the Green River is a severely sediment stressed system. The
sediment analysis did not extend upstream above the sediment wedge collected at
the upper dam but it is likely that area will be sediment stressed as well. High
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sediment loads have been documented in the BHR and are well documented for
the entire Green River watershed above Lake Adger.
The NOV requires that a Sediment Removal Plan must be proposed but also
requires that this plan should not be implemented until the entire area, including
the area above the dam, is stabilized. We agree with this mandated sequence of
events. Clearly it would not make sense to expend substantial resources and incur
the environmental impacts associated with removing sediment below the lower
dam when a single storm event could refill every pool in a short period of time.
We have identified four substantial sources of sediment upstream of the impacted
reach:
1. The BHR channel through the old lake bed immediately above the lower
dam site, this reach is approximately 900 linear feet.
2. The large volumes of measured sediment in pools, riffles and runs above
the old lower dam lake bed and below the upper dam.
3. The estimated 50,000 cubic yards of sediment currently held behind the
upper dam, but apparently being released on a regular basis.
4. The high sediment load delivered from the 19 square mile watershed
above the upper dam. A watershed with predominantly sandy loam soils,
steep topography and a substantial amount of agricultural land use.
A second issue with any sediment removal plan for the impact reach will be the
environmental impacts necessary, simply to gain sufficient access to the sediment
deposits with the equipment needed to implement the plan. Options considered for
sediment removal include mechanical removal and hydraulic removal.
Mechanical: Given the volume of sediment in this area and the need to minimize
instream work (equipment in flowing water) it would be necessary to use fairly
large tracked equipment to dig out the sediment. Additionally, off -road trucks
would need to access each removal area to facilitate removal of sediment to a
suitable disposal site. This operation would require the construction of a road
down to the riparian area and then all along the riparian area. This would
significantly disturb and alter the riparian zone along the right bank of the BHR
for over 1,000 linear feet. In many areas isolating the sediment removal work area
from flowing water would be extremely difficult without a much larger
mobilization involving multiple cycles of coffer dam installation and removal,
and this would be far from a perfect solution. Needless to say, the cost/benefit
reality of such an operation would be hard to justify.
Hvdraulic: This approach would offer some clear benefits over mechanical
sediment removal, most notably it would eliminate the need to mechanically
excavate a large portion of the impact reach. This approach would, however, also
require the construction of an access road to and along the riparian zone. The
hydraulically dredged or pumped sediment would have to be dewatered in the
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riparian zone and be loaded into trucks for removal offsite. The limiting factors
for these operations include vertical lift and horizontal distance so the dewatering,
stockpiling and loading operations would have to move down along the river with
the dredging operation causing a substantial amount of disturbance.
Focus Resources on Source Control: It is important to consider that the root cause
of the sediment release is the fact that there are extremely large quantities of
unconsolidated, highly erodible sediments behind both the lower and upper BHR
dams. The watershed above the upper dam will also continue to produce large
sediment loads well into the future. The best solution for the long term health of
the BHR will be to remove or permanently stabilize in place the sediment behind
both dams and restore a channel with appropriate dimension, pattern, and profile
to move the high sediment loads that will emanate from the watershed. It may be
appropriate to focus, in the near term, on stabilizing the area behind both dams
and monitor the sediment deposition areas until all other work is complete. A
reassessment of sediment removal options could be made at that time.
Off -Site Sediment Mitigation: A fourth option would be to investigate potential
off -site stabilization or sediment removal opportunities. The upper reaches of the
BHR watershed contain numerous areas of intense agricultural activities in areas
of highly erodible soils, while we are not aware of any specific sites at this time, it
is understood that there are numerous areas in need of enhancement or
stabilization efforts.
Given the stated circumstances we propose the following to address the issues
stated in the NOV and Notice of Noncompliance:
A. Stabilize BHR channel upstream of the lower dam site for approximately
500 linear feet or an amount sufficient to prevent any future head cuts and
to stabilize any unconsolidated sediment along the banks and active flood
prone areas.
B. Proceed with planning efforts for the removal of the upper BHR dam,
removal of excess impounded sediment above the upper dam and
stabilization of the BHR channel above the upper dam.
C. Commence an investigation into various sediment removal /mitigation
options, coordinate the findings with DWR and develop a plan for the
most appropriate course of action.
D. Monitor sediment levels in the BHR below and above the lower dam
removal project area.
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McGill Associates, P.A.
B. SHORT AND LONG TERM MEASURES TO STABILIZE THE STREAM
BED AND BANKS UPSTREAM OF THE LOWER DAM
1. Project Purpose & Description
The purpose of this project is to reconstruct and stabilize eroded and unstable stream
banks along the Big Hungry River (BHR) upstream of the recently removed lower
dam structure. The severely eroded stream banks consist of exposed sediment
deposits that were trapped behind the old dam and have eroded as the river has
headcut above the old dam location. The proposed design is intended to reconstruct a
stable channel for approximately 500 linear feet upstream of the old dam. The
channel design is based on relevant upstream reference data and regional curve data.
The project will involve the removal of instream sediment and stabilization of newly
established streambanks using bioengineering and natural channel design approaches
and techniques.
The work described in this Corrective Action Plan (CAP) is urgent and necessary to
prevent further sediment loss from the project area. The North Carolina Wildlife
Resources Commission is the sponsor and responsible party for the project. Work on
the site consists of repair and stabilization effort only, and is not considered natural
channel restoration or enhancement work. However, some methods and approaches
utilized in the proposed repairs are routinely applied in natural channel design efforts
due to their ability to protect channel banks from shear stresses and the resultant
erosion.
All work in or near surface waters will be supervised by trained personnel from
McGill Associates.
2. Site Description
The project site consists of the area disturbed during the removal of the old lower
dam, and a reach of the BHR extending approximately 500 linear feet upstream. The
site also includes an access road from the end of Gallimore Road, approximately
1,500 feet to the old dam site and a graded ramp from the end of the access road
down to the channel edge at the lower end of the project reach. A portion of the cul-
de -sac at the end of Gallimore Rd. will be used for equipment and material staging as
will an area at the lower end of the access road.
The area immediately above the old dam contains large sediment deposits primarily
along the left bank and further upstream sediment deposits are evident along the right
bank. The channel bed also contains large quantities of sand with depths of greater
than 7 feet in pools. A temporary dam was installed in the channel at the approximate
location of the old dam following removal of the dam in early March of 2015. The
purpose of the dam was to halt a rapid headcut through unconsolidated depositional

Big Hungry River — Corrective Action Plan
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McGill Associates, P.A.
material. The temporary dam consists of several jersey barriers and concrete rubble
from the dam demolition. The river has backed up by approximately 6 feet behind the
temporary dam and this area is effectively trapping sediment.
3. Technical Approach
Stabilization of the site and area above the dam will be accomplished as outlined
in the attached plans. The area to be stabilized extends from the old dam site
upstream for approximately 500 linear feet. This area consists of the construction
access ramp at the old dam site and the temporary dam installed to abate the
headcut and sediment loss on March 4, 2015. Above the access ramp, the BHR
currently flows in a channel that has formed through deep sediment deposits. The
depth of sediment in and adjacent to the existing channel tapers in an upstream
direction. The primary goal of the design is to establish a stable, appropriately
sized channel through the area of accumulated sediment, establish vertical grade
control, and stable vegetated streambanks. The final plans are based on the
following design objectives:
• Locate and utilize existing natural channel Grade control to the extent
practically feasible: The preferred design for this reach is one that allows
the BHR to flow through the valley in a manner similar to the pre -dam
condition of the early 1900's. The BHR both upstream and downstream of
this reach is characterized by frequent bedrock control and deep pools,
based on our analysis of the channel substrate below the sediment
deposition, it appears this characteristic is present in this reach as well.
The length of the project reach was determined based on natural grade
control points identified at approximately 500 linear feet above the old
dams location. The grade control at this location is covered by less than
one foot of sediment, minimizing the risk of additional head cuts above
this location.
• Locate and utilize existing stable natural features to incorporate into
design: Features such as vertical bank rock, vegetated natural ground, and
large existing trees are incorporated into the design to anchor proposed
cross sections to the extent practically feasible.
• Avoid or minimize anv required cut in natural ground: There is a large
amount of unconsolidated sediment adjacent to the existing channel that is
masking the depth and shape of the underlying natural ground. Our
objective is to locate and leave intact these previously existing natural
features. This will involve field adjustments to the design where
conditions are uncovered that don't fit with the current design.
• Minimize the volume of sediment that will have to be moved: The final
design for this reach incorporates a balance between practical feasibility
and the ideal natural channel design. Perhaps the most significant cost will
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McGill Associates, P.A.
be associated with the moving and stabilization of the large volumes of
sediment throughout the reach.
• Locate areas on -site to be used for sediment disposal: There are two
existing benches along this reach that are above the bankfull elevation, the
feasibility of permanently disposing of excess sediment in these areas was
investigated by a geotechnical engineer and the final design incorporates
the engineers recommendations. Beyond these areas, sediment disposal
will occur at an approved off -site disposal site.
• Maintain low instream turbidity during various construction activities:
Various approaches are incorporated into the final plan to be used
individually and in concert to achieve this objective. These include a
temporary crossing to facilitate access to the left bank of the BHR at the
lower end and leaving the temporary dam constructed on March 4, 2015 in
place until the final stage of construction, to facilitate settling and trapping
of what sediment does get into the river. Accumulated sediment behind the
temporary dam will be periodically removed and disposed of at a suitable
upland location.
4. Design Summary
The BHR at the project site has a drainage area of approximately 20 square miles that
is predominantly forested with scattered pockets of low density residential and larger
areas of agricultural use, particularly in the upper reaches of the watershed. The
average water surface slope through the project reach is about 2 %. The bankfull width
will range between 45 and 55 feet, bankfull cross sectional area will range from 145
to 165 square feet, and average depth will be approximately 3 feet. The design stream
type will be a B -3 (using Rosgen terminology).
The attached Final Plan provides details of our approach for design of the roughly
500 foot -long reach above the lower dam site. Given uncertainties regarding the
location of buried bedrock grade control features and the precise location of the
natural ground/unconsolidated sediment interface, we have built in limited
alternatives and contingency measures into the design. As discussed during the April
8, 2015 meeting, these added design elements will allow for some on- the - ground
adjustments to the stream design based on new information encountered during the
construction phase. Every reasonable effort has been made to minimize uncertainty
prior to construction, but these elements will allow the project to proceed with
maximum efficiency.
Typical channel dimensions shown in the plans are derived from regional curve data
and refined using appropriate reference data from above the project reach. The plan
view shows our intention to generally follow the existing flow path with minor
variations to soften a couple of sharp bends and utilize existing bedrock outcroppings
in the banks to the extent practicable. The plan view also shows locations for a
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McGill Associates, P.A.
temporary crossing, temporary dam and onsite locations for disposal of excess
sediment.
A longitudinal profile is provided that shows only an approximate average grade line
for the proposed channel. The current profile is based on identified, assumed shallow
bedrock ledges in the existing streambed. All bed features in the project reach are
obscured by sediment and can only be identified using a probe rod. Consequently, we
anticipate numerous minor adjustments to the plan will be necessary as we acquire
more information about existing bed features during the construction phase. The plan
is to minimize or avoid altogether the use of constructed grade control. A boulder
cross vane grade control detail is included in the plans if field conditions indicate one
is required.
Typical and design cross sections are provided to illustrate the general concept of this
design. The primary challenge will be to stabilize and provide for permanent
vegetation establishment on the extensive sediment deposits to be left along the reach.
The design is to stabilize the streambanks adjacent to the sediment deposit with
naturally vegetated, reinforced soil lifts. The base of the soil lifts will be rock or
concrete rubble. If field conditions require additional toe armoring, a detail for
boulder toe stabilization, with or without soil lifts above may be used. Existing
bedrock has been identified in the stream banks throughout the reach. The design
cross section ties to the existing bedrock in all locations where possible on outside
meander bends.
The plan includes a revegetation plan for all disturbed areas including the riparian
corridor, sediment disposal areas, access road, and staging areas. The streambanks
will be stabilized using live stakes along graded low banks (3 -feet c -c), live cuttings
or bare -root whips in between soil lifts (continuous), and bare -root whips in the upper
banks and sediment disposal areas (approximate 2 -feet c -c). All disturbed areas will
be seeded with a native seed mix and temporary erosion control mix (see plans for
mix and rate). Graded slopes above bankfull will be stabilized with a natural fiber,
fully biodegradable erosion control mat, and areas along the access road may be
hydroseeded.
5. Proposed Sequence of Construction
The proposed Repair Plan is described in the attached construction plans and
specifications. The general sequence of construction is explained here:
1. The contractor will mobilize onsite and install any additional erosion control
measures or safety fence needed to properly protect the work area and
surrounding areas from unintended erosion, sedimentation or disturbance.
2. The contractor will regrade water bars on access road to allow for sediment
trapping and filtration of runoff prior to mixing with flow from upslope seeps
and/or before discharge below the access road.
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3. The contractor will remove sediment from the area behind the temporary dam
upstream to the area of the temporary crossing. Sediment removed will be
placed in a temporary containment area with adequate filtration to remove all
visible sediment from any return water. Once the sediment is dewatered it will
be removed to a stable disposal area and permanently stabilized.
4. The Contractor will install the temporary crossing at the approximate location
specified on the plans. The crossing will consist of non - erodible material to
provide a suitable crossing for construction equipment and allow passage of
anticipated flows. Final design to be approved by Engineer based on site
conditions at the time of construction.
5. The Contractor will prepare the sediment disposal area to accept excess
material from the upstream channel grading.
6. The contractor will proceed to shape the design channel from the upstream
end of the project area. Installation of all toe protection, grade control
structures, and bank stabilization measures will be installed before proceeding
downstream.
7. Contractor and Engineer will develop a plan to divert flow away from work
area in the lower 100 linear feet of the project reach. Engineer will coordinate
plan with Agencies.
8. All graded banks will be seeded and matted within 24 hours of finished
grading. Finished grade is to be determined by the engineer.
9. The Contractor will continue working downstream until the limit of backwater
from the temporary dam prevents work from proceeding further.
10. Contractor will install erosion control measures and confinement per the
Drawings in the cul -de -sac of Gallimore road for temporary storage of excess
sediment to be disposed of offsite.
11. Contractor will implement flow diversion plan and proceed to grade and
stabilize the left bank to the lower end of the project reach.
12. Contractor will complete grading activities in sediment disposal area and
stabilize all slopes and commence installation of all woody plant material.
13. Contractor will remove temporary stream crossing and clean out sediment
storage area above temporary dam.
14. Contractor will remove temporary dam and complete grading and stabilization
measures on the right bank at the lower end of the project reach.
15. Contractor will remove all excess sediment and debris from the riparian zone
and haul to an approved offsite disposal area.
16. Contractor will complete installation of all woody plant material and complete
all stabilization activities in the riparian corridor.
17. Contractor will remove all construction debris and stabilize the staging at the
lower end of the access road.
18. Contractor will stabilize the access road and slopes above and below the road,
all disturbed areas will be seeded and mulched according to the plans.
19. Contractor will monitor access road for stabilization and remove all silt fence
and metal posts once road is permanently stabilized.
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6. Construction Monitoring
Construction observation and monitoring will be provided by McGill Associates
(Engineer) throughout the construction phase of the project. Personnel trained in
stream restoration and natural channel design concepts will be onsite during critical
phases of the construction and will be on -call during other times. The Engineer will
produce work logs and progress reports on a regular basis. The Contractor will inform
the Engineer when activities requiring the Engineer's approval are anticipated so that
work can proceed without interruption. The Engineer will contact the permitting
agencies if field conditions are encountered that require deviations from the plans
beyond the scope described in this CAP and the Plans and Specifications.
C. STREAM RESTORATION /ENHANCEMENT ACTIVITIES DOWNSTREAM
OF THE LOWER DAM
At the present time there are no planned restoration or enhancement activities for the
BHR below the lower dam site. Based on observations over the past 6 months, the
BHR below the lower dam site is generally stable despite the fact that large sediment
accumulations remain within most pools along the reach. Section A (above)
describes the sediment impacts and existing condition of the BHR above and below
the lower dam project area. From the analysis performed and opinions expressed in
the NOV, it is understood that remedial action downstream of the lower dam site is
not advised until after both the lower and upper dam removal projects are concluded.
It is also understood that restoration /enhancement activities downstream of the lower
dam site involving construction equipment may do more harm than good to the
ecosystem. Such activities would require access roads and staging areas in the
riparian zone and on steep wooded slopes. The effectiveness of sediment removal
activities is also in question and there would be a large short-term impact to instream
habitat during any such operation. Given the stated issues, it is our recommendation
that planning for any downstream restoration/enhancement activities be delayed until
after completion of both upper and lower dam removal projects, at which time the
need for such activities should be reassessed.
D. SEDIMENT DISPOSAL PLAN
The stream stabilization plan described under section B (above) outlines the current
plan to remove and /or stabilize accumulated sediment behind the old lower dam. The
construction phase for this plan is scheduled to commence in October 2015 and will
involve grading and shaping in and adjacent to the existing channel above the lower
dam to establish an appropriate bankfull channel and stabilize the graded streambanks
in areas where bedrock is not present in the lower banks. Excess sediment removed
from the channel and riparian areas will be relocated to an existing high bench on the
left side of the BHR that extends approximately 300 linear feet upstream of the old
dam location. A geotechnical study was conducted to determine the volume of
13

Big Hungry River — Corrective Action Plan
Henderson County, NC
17- Sep -15
McGill Associates, P.A.
additional sediment that could be supported on the existing bench and the appropriate
method of stabilization. The attached construction plans detail the proposed grading
and stabilization for this area. Additional excess sediment that cannot be disposed of
on -site will be hauled off -site to an approved, permitted waste area. The contractor
has indicated that the excess material will be hauled to the Henderson County landfill.
E. SCHEDULE FOR PROPOSED ACTIVITIES
The construction phase for the stabilization of the BHR above the lower dam site is
scheduled to begin as soon as approvals are obtained from the USACE and NC DWR
on the proposed plan. Also required prior to construction is approval of a contract
change order from the State Construction Office. All approvals are anticipated by the
end of September of 2015.
Anticipated Project Timeline:
10 -5 -2015 — begin mobilization
10 -8 -2015 — begin river stabilization activities
11 -13 -2015 — complete river stabilization activities
11 -25 -2015 — complete final site stabilization activates including access road and
staging areas
11 -30 -2015 — begin post construction monitoring for both river stability and site
stabilization
F. POST CONSTRUCTION AS -BUILT AND MONITORING
Following construction activities, an as -built survey will be conducted for the project
reach. The survey will consist of two representative cross sections at locations agreed
upon by the agencies. Cross section locations will be marked in the field. Numerous
photo points will be established with GPS points and angle of shot. WRC will
develop plans for annual monitoring of the stabilized reach in connection with the
ongoing upper dam removal project.
14

Graphic Scale (Feet)
0 25 50 100
SCALE IS APPROXIMATE
CONTOUR INTERVAL: 20'
SEDIMENT ASSESSMENT SITES
UPSTREAM ANALYSIS
SHEET U -1
MARCH 24, 201.5
Channel Shift to
Right Bank
+00
{
F +00
5 +00
3 +00
11 +00
Limits of Backwa
from Lower Dam
0400
3 +00
8+
Lower Dam - Removed
BIG HUNGRY RIVER LOWER DAM
SEDIMENT ASSESSMENT
HENDERSON COUNTY
NORTH CAROLINA
0
DATA SOURCES: 2010 AERIAL
IMAGERY ACQUIRED THROUGH
NC ONEMAP GEOSPATIAL PORTAL;
LIDAR TOPOGRAPHY ACQUIRED ,
THROUGH NCDOT; SEDIMENT
ASSESSMENT AREAS FIELD
LOCATED USING HANDHELD GPS.
I 1IMcG
•
A S S O C I A T E S
ENVIRONMENTAL SERVICES
468 NEW MARKET BLVD. STE B BOONE, NC 28607 PH. (828) 386 -1920

°
°
°
°
S
S
Em
Graphic Scale (Feet)
8�»
0 25 50 100
SCALE IS APPROXIMATE
CONTOUR INTERVAL: 20'
SEDIMENT ASSESSMENT SITES
UPSTREAM ANALYSIS
SHEET U -2
MARCH 24, 2015
ao.
1
ry
1
�O.
BIG HUNGRY RIVER LOWER DAM
SEDIMENT ASSESSMENT
HENDERSON COUNTY
NORTH CAROLINA
'T
DATA SOURCES: 2010 AERIAL
o IMAGERY ACQUIRED THROUGH
° NC ONEMAP GEOSPATIAL PORTAL;
.'' LIDAR TOPOGRAPHY ACQUIRED
±'� THROUGHNCDOT; SEDIMENT
Y;y j ASSESSMENT AREAS FIELD
+ LOCATED USING HANDHELD GPS.
—AU °
A S S O C I A T E S McGill
ENVIRONMENTAL SERVICES
468 NEWMARKET BLVD. STE B BOONS, NC 28607 PH. (828) 386 -1920

00
Graphic Scale (Feet)
0 25 50 100
SCALE IS APPROXIMATE
CONTOUR INTERVAL: 20'
SEDIMENT ASSESSMENT SITES
DOWNSTREAM ANALYSIS
SHEET D -1
MARCH 24, 2015
BIG HUNGRY RIVER LOWER DAM
SEDIMENT ASSESSMENT
HENDERSON COUNTY
NORTH CAROLINA
.{
J
O
O
k00
a
DATA SOURCES: 2010 AERIAL
IMAGERY ACQUIRED THROUGH
NC ONEMAP GEOSPATIAL PORTAL;
LIDAR TOPOGRAPHY ACQUIRED
THROUGH NCDOT; SEDIMENT
ASSESSMENT AREAS FIELD
LOCATED USING HANDIIELD GPS.
A S S O C I A T E S I jMcG
ENVIRONMENTAL SERVICES
468 NEWMARKET BLVD. STE B BOONE, NC 28607 PH. (828) 386 -1920

Graphic Scale (Feet)
0 25 50 100
SCALE IS APPROXIMATE
CONTOUR INTERVAL: 20'
SEDIMENT ASSESSMENT SITES
DOWNSTREAM ANALYSIS
SHEET D -2
MARCH 24, 2015
BIG HUNGRY RIVER LOWER DAM
SEDIMENT ASSESSMENT
HENDERSON COUNTY
NORTH CAROLINA
DATA SOURCES: 2010 AERIAL
IMAGERY ACQUIRED THROUGH
NC ONEMAP GEOSPATIAL PORTAL;
LIDAR TOPOGRAPHY ACQUIRED
THROUGH NCDOT; SEDIMENT
ASSESSMENT AREAS FIELD
LOCATED USING HANDHELD GPS.
JMcG•
A S S O C I A T E S
ENVIRONMENTAL SERVICES
468 NEWMARKET BLVD. STE B BOONE, NC 28607 PH. (828) 386 -1920

STREAM SEDIMENT STUDY -MARCH 20, 2015
Table T -1
Location relative to
Evaluated
Measured
Area
Lower Dam
Length
Length
Width
Depth
Cu. Ft.
Cu. Yds.
Max Depth
Notes
1
Downstream
20
20
20
3.5
1400
51.9
7
Pool beneath large falls - old dam to right side of channel.
2
Downstream
20
12
20
1.5
360
13.3
4.5
Pool beneath large falls -old dam to left side of channel.
3
Downstream
70
70
10
1.5
1050
38.9
Run section bordered by boulder outcropping.
4
Downstream
190
100
23
3
6900
255.6
Long pool.
5A
Downstream
310
25
45
3
3375
125.0
6
Deep chute along left side of channel.
Wide boulder garden: shallow sediment (-1 ") in high velocity zones;
5B
Downstream
350
45
35
1.5
2363
87.5
deeper sediment deposition (^3') in eddies of rocks.
Section with vegetated bars and chutes: deeper sediment
6A
Downstream
440
40
30
0.75
900
33.3
3
deposition in eddies and shallow sediments in high velocity zones.
6B
Downstream
515
10
10
2
200
7.4
Pool along right side of channel.
7
Downstream
610
15
5
1
75
2.8
Right side of channel area of deposition.
8
Downstream
680
18
10
1.5
270
10.0
Right side of channel area of deposition.
9
Downstream
745
12
25
1.7
510
18.9
Center of channel area of deposition (run).
10
Downstream
880
100
35
2.5
8750
324.1
Long pool.
11
Downstream
1100
35
10
1
350
13.0
Pool
12
Downstream
1140
10
20
1
200
7.4
Shallow pool.
13
Downstream
1170
25
15
1.5
562.5
20.8
Deposition in center of channel in run section.
14
Downstream
1210
18
12
1.5
324
12.0
Shallow pool.
15
Downstream
1275
40
12
1.2
576
21.3
Boulder garden section with intermittent pockets of sediment.
16A
Downstream
1450
30
10
1
300
11.1
Pool above falls.
16B
Downstream
1500
12
10
1.5
180
6.7
Pool below falls.
17
Downstream
1580
50
30
2.5
3750
138.9
Long pool.
18
Downstream
1660
12
8
1
96
3.6
Pool
19
Downstream
1760
40
12
2.5
1200
44.4
Pool
20
Downstream
1860
18
25
2.5
1125
41.7
5
Pool in gorge section.
21
Downstream
1935
60
30
5
9000
333.3
8
Pool below gorge section.
22
Downstream
2070
30
20
1.5
900
33.3
3
Pool
23
Downstream
2180
65
40
5
13000
481.5
7+
Long pool.
24
Downstream
2445
40
20
1.5
1200
44.4
Intermittent pockets of sediment in bouldery section.
25
Downstream
2565
30
15
3
1350
50.0
5
Pool
26
Downstream
2850
65
25
5
8125
300.9
7+
Long pool.
DOWNSREAM TOTAL
2850
1047
68391
2533.0
PAGE 1

volume of sediment per foot of reach evaluated =1138 yards / 1790 lin.ft. = 0.64 yards /ft evaluated
volume of sediment per foot of reach measured =1138 yards / 530 lin.ft. = 2.15 yards /ft evaluated
Percent Difference Downstream vs Upstream
Evaluated: 0.89 yards /ft - 0.64 yards /ft = 0.25 yards /ft / .064 yards /ft = 39% increase
Measured: 2.42 yards /ft - 2.15 yards /ft = 0.27 yards /ft / 2.15 yards /ft = 13% increase
PAGE 2
Location Relative to
Evaluated
Measured
Area
Lower Dam
Length
Length
Width
Depth
Cu. Ft.
Max Depth
Notes
A
Upstream
1120
12
20
1.5
360
13.3
3
Pool
B
Upstream
1220
8
10
1
80
3.0
Pool
C
Upstream
1350
10
10
1
100
3.7
Run
D
Upstream
1610
30
20
1.5
900
33.3
Pool
E
Upstream
1760
110
30
2.5
8250
305.6
7+
Long pool.
F
Upstream
1900
85
25
2.7
5738
212.5
7+
Long pool.
G
Upstream
2240
30
15
1.3
585
21.7
Pool
Two areas of deposition in channel between riffles and boulder
H
Upstream
2310
10
10
1.5
150
5.6
sections.
I
Upstream
2360
20
8
1.5
240
8.9
small pool
J
Upstream
2400
80
35
3
8400
311.1
7+
Long pool.
K
Upstream
2540
40
40
2.5
4000
148.1
6
Pool
L
Upstream
2820
15
8
1
120
4.4
Run
M
Upstream
2910
80
15
1.5
1800
66.7
2.5
Run
UPSTREAM TOTAL
1790
530
30723
1137.9
ANALYSIS
Downstream
volume of sediment per foot of reach evaluated
= 2533 yards / 2850 lin.ft.
= 0.89 yards /ft evaluated
volume of sediment per foot of reach
measured
= 2533 yards / 1047 lin.ft.
= 2.42 yards /ft evaluated
volume of sediment per foot of reach evaluated =1138 yards / 1790 lin.ft. = 0.64 yards /ft evaluated
volume of sediment per foot of reach measured =1138 yards / 530 lin.ft. = 2.15 yards /ft evaluated
Percent Difference Downstream vs Upstream
Evaluated: 0.89 yards /ft - 0.64 yards /ft = 0.25 yards /ft / .064 yards /ft = 39% increase
Measured: 2.42 yards /ft - 2.15 yards /ft = 0.27 yards /ft / 2.15 yards /ft = 13% increase
PAGE 2