HomeMy WebLinkAbout20240486 Ver 1_USACE Permit_20240611DEPARTMENT OF THE ARMY
U.S. ARMY CORPS OF ENGINEERS, WILMINGTON DISTRICT
ASHEVILLE REGULATORY FIELD OFFICE
151 PATTON AVENUE SUITE 208
ASHEVILLE NC 28801
June 11, 2024
Regulatory Division
2024-00641
John & Andromeda Williams
8954 Winged Bourne Road
Charlotte, NC 28210
Dear Mr. and Mrs. Williams:
This letter is in response to the Pre -Construction Notification (PCN) you submitted to
the Wilmington District, Asheville Regulatory Field Office on March 27, 2024, for a
Department of the Army Nationwide permit (NWP) verification. This project has been
assigned the file number 2024-00641 and is known as the Pigeon Roost Pond
Modification. This file number should be referenced in all correspondence concerning
this project.
A review of the information provided indicates that the proposed work would include
the installation of culverts, excavation and placement of fill associated with upgrades to
a single-family residence with an existing on-line impoundment. See the attached table
below for permitted impacts. The project area is illustrated on the enclosed site
plans/maps and located at Latitude 36.170799 and Longitude-81.821523, at 1776
Pigeon Roost Road, near Banner Elk, Watauga County, North Carolina.
Impact
Reason
Impact
Open
Wetland
Stream
#
Type/NWP
Water
Impact
Impact (If)
Impact
(acre)
(acre)
W1
Driveway Improvements
P/NWP29
0.059
W2
Spoils from Pond Dredging
P/NWP29
0.011
S1
Bank
P/NWP29
147
Stabilization/Enhancement
S2
Extension of pond outflow
P/NWP03
10
S3
Culvert crossing
P/NWP29
30
01
Sediment Removal/Dam
T/NWP03
0.21
maintenance
Total
0.21
0.07 acre
187 If
acre
(0.039
acre)
*T = temporary and P= permanent
We have determined that the proposed work is authorized by Nationwide #29 and
Nationwide Permit #3 pursuant to authorities under Section 404 of the Clean Water Act
(33 U.S.0 § 1344). The proposed work must be accomplished in strict accordance with
the general permit conditions, any regional conditions, the application materials, and the
enclosed plans. If the extent of the project area and/or nature of the authorized impacts
to waters are modified, a revised PCN must be submitted to this office for written
approval before work is initiated. Any violation of permit conditions or deviation from
your submitted plans may subject the permittee to enforcement action. Below are
Special Permit Conditions for this authorization:
No in-stream/impoundment work between January 1 and April 15 to minimize
impacts to trout resources. Enclosed is the letter from the North Carolina Wildlife
Resource Commission which includes additional recommendations for your
consideration and conditioned below.
2) Installation of cold -water release should be adjusted to continuously allow
downstream flows (see below).
3) Downstream flows during and post pond maintenance activities must be
maintained to at least 50% of incoming flows.
This verification is valid until March 14, 2026, unless prior to this date the subject
NWP(s) is suspended, revoked, or is modified such that the activity no longer complies
with the terms and conditions of this NWP. If you commence or are under contract to
commence this activity before the date that the relevant NWP is modified or revoked,
you will have 12 months from the date of the modification or revocation of the NWP to
complete the activity under the present terms and conditions of this NWP.
This NWP verification does not preclude the necessity to obtain any other Federal,
State, or local permits, licenses, and/or certifications, which may be required.
If you have any questions related to this verification or have issues accessing
documents referenced in this letter, please contact Amanda Fuemmeler, Project
Manager of the Asheville Regulatory Field Office at (828)271-7980 x4225, by mail at the
above address, or by email at amanda.jones@usace.army. mi1. Please take a moment
to complete our customer satisfaction survey located at
https://regulatory.ops.usace.army.miI/customer-service-survey/.
Sincerely,
Amanda Jones Fuemmeler
Project Manager
Copies Furnished:
Brushy Fork Environmental Consulting, Attn: David Pedersen (via email)
Compliance Certification Form
File Number: 2024-00641 County: Watauga
Permittee: John & Andromeda Williams
Project Name: Pigeon Roost Pond Modification
Date Verification Issued: 6/11/2024
Project Manager: Amanda Fuemmeler
Upon completion of the activity authorized by this permit and any mitigation required by
the permit, sign this certification and return it to the following address:
AshevilleNCREG@usace.army.mil
Please note that your permitted activity is subject to a compliance inspection by a U. S.
Army Corps of Engineers representative. Failure to comply with any terms or conditions
of this authorization may result in the Corps suspending, modifying or revoking the
authorization and/or issuing a Class I administrative penalty, or initiating other
appropriate legal action.
hereby certify that the work, and mitigation (if applicable), authorized by the above
referenced permit has been completed in accordance with the terms and conditions of
the said permit including any general or specific conditions.
Date Authorized Work Started:
Completed:
Describe any deviations from permit (attach drawing(s) depicting the deviations):
*Note: The description of any deviations on this form does not constitute approval by the Corps.
Signature of Permittee
Date
® North Carolina Wildlife Resources Commission 9
Cameron Ingram, Executive Director
April 29, 2024
Ms. Amanda Fuemmeler
U.S. Army Corps of Engineers, Regulatory Branch
151 Patton Avenue, Room 208
Asheville, North Carolina 28801-5006
SUBJECT: Pigeonroost Pond Modification
Pigeonroost Creek, Watauga County
Dear Ms. Fuemmeler:
Biologists with the North Carolina Wildlife Resources Commission (NCWRC) reviewed an
application to dredge a pond, install a new outflow device, restore a reach of stream, and expand
a driveway, impacting at least 157 ft of Pigeonroost Creek and 0.087 acre of wetland in Watauga
County. Our comments on this application are offered for your consideration under provisions of
the Clean Water Act of 1977 (33 U.S.C. 466 et. seq.) and Fish and Wildlife Coordination Act (48
Stat. 401, as amended; 16 U.S.C. 661-667d).
There are Rainbow Trout in Pigeonroost Creek, and project activities should be avoided from
January 1 to April 15 to minimize impacts to trout reproduction. Rainbow Trout are sensitive to
excess sediment, so excellent erosion and sediment control is needed for this project.
The application proposes to dredge an existing pond, retrofit the spillway system, and install a
new riser. The riser will incorporate an adjustable coldwater release device. A reach of stream
that is braided downstream of the pond will be restored to a single channel. Flows will be
pumped around the pond during all in -pond work.
We offer the following recommendations to minimize impacts to the aquatic community:
1. Project activities should be avoided between January 1 and April 15 to minimize impacts to
trout reproduction.
2. Vigilance should be used in sediment and erosion control during site preparation,
construction, and clean up. Disturbed areas should be seeded, mulched and/or matted as
soon as possible.
3. Flows must be maintained downstream at all times, including during pond refill. We
recommend maintaining at least 50% of incoming flows in the downstream channel.
Mailing Address: Habitat Conservation • 1721 Mail Service Center • Raleigh, NC 27699-1721
Telephone: (919) 707-0220 • Fax: (919) 707-0028
Pigeonroost Pond Modification Page 2 April 29, 2024
Pigeonroost Creek, Watauga Co
4. The coldwater release structure is adjustable. It should always be in use.
Thank you for the opportunity to review and comment on this project. Please contact me at
(828) 400-4223 if you have any questions about these comments.
Sincerely,
Andrea Leslie
Mountain Region Coordinator, Habitat Conservation Program
cc: Adam Williams, Brushy Fork Environmental Consulting
Seren Homer, NC Division of Water Resources
Pigeonroost Pond Modification
Pigeonroost Dam Modification Map":,
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Feet
Streams
Roads
Watauga County, NC
SHEET INDEX
COVER 1
CONSTRUCTION NOTES and LEGEND 2
OVERALL EXISTING CONDITIONS MAP 3
OVERALL PROPOSED CONDITIONS SITE PLAN
4
OVERALL EROSION & SEDIMENT CONTROL SITE PLAN
5
PLAN & PROFILE RISER SPILLWAY
6
PLAN & PROFILE AUXILIARY SPILLWAY
7
PLAN & PROFILE PIGEONROOST CREEK
8
PIGEONROOST CROSS SECTIONS 1-3
9
PIGEONROOST CROSS SECTIONS 4-6
10
AUXILIARY PROFILE CROSS SECTIONS S1-S4
11
TYPICAL DESIGN CROSS SECTION
12
PIGEONROOST CREEK MORPHOLOGICAL TABLE
13
CONSTRUCTION DETAILS
C1-C11
GENERAL NOTES:
1. STREAM ASSESSMENT DATA (LONGITUDINAL PROFILE,
CROSS -SECTIONS, ETC.) PRESENTED HEREIN COLLECTED BY
BFEC/BFED.
2. CONTOUR DATA PRESENTED IN THIS DOCUMENT IS TAKEN FROM
USGS LIDAR DATA (2' and 10' CONTOURS).
3. HORIZONTAL AND VERTICAL GRID CONTROL TIED TO PROJECT BY
BFED. SURVEY DATA USED FOR DESIGN IS RELATIVE TO ITSELF AND
APPROXIMATELY SET TO REAL WORLD COORDINATES BASED ON
LIDAR DATA.
4. PRIOR TO CONSTRUCTION, BFEC WILL FLAG TREES APPROVED TO BE
REMOVED DURING CONSTRUCTION AS AN EFFORT TO PRESERVE THE
EXISTING RIPARIAN BUFFER.
5. PRIOR TO CONSTRUCTION, BFEC WILL ESTABLISH SURVEY CONTROL
POINTS AND WILL STAKE OUT STRUCTURES.
60 % PROGRESS DRAWINGS
DO NOT USE FOR CONSTRUCTION
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1
EROSION AND SEDIMENT CONTROL NOTES:
1. ONCE SITE CONSTRUCTION WITHIN AN AREA HAS
CEASED, ALL DISTURBED AREAS WILL BE
IMMEDIATELY SEEDED (TEMPORARY & PERMANENT
SEED), MATTED (COIR AND COCONUT FIBER
EROSION CONTROL BLANKET, NAG C700BN), AND
STABILIZED (SEE SHEET 9).
2. LIVE STAKES AND BIODEGRADABLE MATTING STAKES
WILL BE USED TO SECURE THE MATTING.
3. BROADCAST SEEDING RATES WILL BE AS SPECIFIED
ON SHEET 10.
4. PRECAUTIONS WILL BE TAKEN TO KEEP HEAVY
EQUIPMENT OUT OF THE STREAM CHANNEL EXCEPT
WHERE ABSOLUTELY NECESSARY TO INSTALL BANK
STABILIZATION/ENHANCEMENT MEASURES AND
IN -STREAM STRUCTURES.
5. NO CONSTRUCTION ACTIVITIES WILL OCCUR
OUTSIDE THE CONSTRUCTION LIMITS AS SHOWN ON
THE SITE PLAN.
60% PROGRESS DRAWINGS
DO NOT USE FOR CONSTRUCTION
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W W W W boundary
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channel, install French
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slope to existing ground
contour
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CONDITION
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5
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406
405
00
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Typical Riffle and Step
W-bkf
1 2 A-bkf
1
Typical Scour Pool
5
W-bkf
2.5
406 2 A-bkf
4058
e00
D-bkf
D-bkf
Typical Cross Section
Riffle
Scour Pool
Bankfull Area (A-bkf, sq ff)
7.4
11.5
Bankfull Width (W-bkf, ff)
10.0
10.0
Bankfull Mean Depth (ff)
0.7
1.2
Bankfull Max Depth (D-bkf, ff)
0.9
1.8
Bankfull W/D (Stream Type)
13.5
8.7
Inner Berm Width (ff)
8.2
8.2
Inner Berm Max Depth (ff)
0.45
1.35
Approx. Wetted Width (ff)
7.6
7.6
Approx. Wetted Max Depth (ff)
0.3
1.2
Channel Bottom Width (W-bottom, ff)
6.4
2.8
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Sheet
Pigeonroost Creek
Stream Assessment Parameters
Existing Condition
Proposed Condition
BOULDER REVETMENT
Restore all disturbed area
with Riparian Seeding
(see Detail)
Wooden Stake
Streambank Matting,
(see Detail) ---�
Existing Ground—, — Top of Bank (Stream Type B)
Proposed Ground
Header Rock
Streambed 1
Footer Rock
Geotextile Liner
(if needed, see Note 3)
,f
JBankfull
Elevation
Backfill with suitable
alluvial material
(see Note 7)
Section A - A View
N. T. S.
Notes:
1. Boulder Revetments shall be installed along the base of the design
streambank toe at locations and stream lengths designated in the Site Plans.
2. Footer, Header, and Sill Rock shall be min. 3.0' dia. long axis, min. 2.5' dia.
intermediate axis and min. 1.0' dia. height.
3. Geotextile Liner shall be medium weight non -woven polypropylene (Weight
7oz/sq yd; Tensile Strength 180 Ibs). Geotextile Liner shall be installed if
backfill is fine-grained, as approved by the Project Engineer. Place Liner
behind all rock layers and key in at the bottom. Trim excess or visible fabric.
4. Footer Rocks shall extend below scour depth or to bedrock, whichever is
shallower. The scour depth is estimated to be the max. pool depth near the
structure, unless otherwise specified.
5. Header Rocks must extend upwards above the bankfull elevation at least 12"
due to high shear stress of larger storm events carried in the channel. The
revetment shall have an even grade along the entire length.
6. Install two or more Header Rocks overlain and offset backwards moving up
the bank if existing substrate elevation is below that needed for Header
Rock Sill, extend
into streambank
(see Note 8)
FAO
Edge of Water
at Normal Flow
C) Q)C�
o MCA
_ N
N cLo
cLo
Q
I
c
0
Top of Bank w
(Stream Type B)
CIO
Bankfull
\ q �
i
a>
m
\ o
_ w
q
Plan View
N. T. S.
Geotextile Liner
(if needed,
see Note 3)
Rock to extend above bankfull elevation or if additional protection is
needed for exposed tree roots or other bank feature. Do not exceed the top
of bank elevation.
7. Footer Rocks and Header Rocks shall be backfilled with gravel alluvial
material, if suitable size and consistency is available. Suitable backfill shall
have a minimum median diameter of 2" and not exceed 6" dia. It shall drain
quickly and support weight without shifting or sinking. For fine sediment
substrates, outside gravel may be needed for backfill and Footer Rocks shall
be supported with a layer of stone, as approved by the Project Engineer.
8. Sill Rocks shall extend into the bank a minimum of 6', passed the top of bank
plane.
9. After Boulder Revetment has been installed, backfill any remaining vertical
streambank with clean soil fill material and compact at the proposed bank
angle (2:5:1 slope).
10. Stabilize streambank with Riparian Seeding, Streambank Matting, and
Livestaking (see Details).
Header Rock
Footer Rock
Toe of Bank
Slope
Backfill with suitable
alluvial material
(see Note 7)
N Y
� mph DU
N Q U
¢ 2
O O U
Sheet
C1
Riffle alluvial gravel layer,
Section A - A View
N. T. S.
Notes:
1. Constructed Riffle lengths and slopes are
provided in the Longitudinal Profile.
Elevation for Head of Riffle (Rock Sill) and
End of Riffle (Rock Step) are listed in
referenced Structure Tables.
2. Constructed Riffles shall be composed of
natural alluvial gravel and cobble materials
harvested from the existing channel during
installation of step -pool sequence and
excavation (see Detail).
3. The median particle size is estimated to be
small cobble (76 mm or 3" diameter).,
Avoid alluvial materials with excess fine
sediments derived from bank erosion.
CONSTRUCTED RIFFLE
D of Bank
Ensure well graded materials from the
channel is used.
4. Excavate streambed minimum 4" below
finished grade and add gravel material.
Line entire active bed to prevent scour
along the bank toe.
5. Create heterogeneity in Constructed Riffles
by embedding cobbles and woody debris
within the gravel substrate.
O
Plan View
N. T. S.
Ee
N Y
� mph DU
� ¢ 2
O O U
Sheet
C2
HEADWALLS AND EN DWALLS
SEE AUXILIARY SPILLWAY INLET AND RISER SPILLWAY OUTLET
Headwall/Endwall
Header Rocks
Geotextile Liner
Extend sill 6.0' into Bank
Top of Bank
Top of Bank
wingwail
Header Rocks
SECTION A -A VIEW
NTS
1-1.5D1.5D-7
i-li-2
_"' V��
_
Rock
1.
VEGETATED CHANNEL (DRIVEWAY
TOP OF BANK
—_� CHANNEL BOTTOM
EROSION CONTROL MATTING)
PROFILE VIEW
NTS
W
TRENCHZI D b
MATTING
6" MIN.
EROSION CONTROL MATTIN
EXISTING
GROUND OR
BEDROCK
CROSS SECTION VIEW
D
NTSN Y
a
O \ O U
7—Footer
Notes:
%Culvert
Rocks
Channel Dimensions
1.
Place Vegetated Swale along bottom of road
embankment along the Driveway Expansion (See
Headwall/Endwall
Invert
Channel Area (sq ft)
4.0
Auxiliary Spillway Cross Sections 2-4, Sheet 8)
�,�
,o
Header Rocks
(See Profiles)
Channel Width ft)
2.
Slope Vegetated Swale approx 0.8%.
-'?
N
(W,
6.0 3.
Excavate the Vegetated Swale along the
cis
SECTION A VIEW
Channel Depth (D, ft)
1.0
driveway expansion toe of slope down to the
y p p
p�
�
o
C' 2
NTS
foundation of the Erosion Control Matting +0.2',
ci
Channel Bottom Width (b, ft)
2.0 4.
Remove all stumps, roots, loose rock and other
Notes:
and key in at the bottom.
Side Slope ( X:1 )
2
debris from the channel perimeter.
°
z
1. Install a Headwall along the Auxilliary Spillway
5. Place Footer Rocks just below the culvert
5.
Seed with Permanent (Riparian) and Temporary
co
°
"
Profile at Sta 0+92 for the 30" HDPE inlet. Install
invert. Ensure the thalweg is in the center of the
Max Discharge (cfs)
11.0
Seeding (see Detail).
o
a
an Endwall along the Riser Spillway Profile at
channel.
6.
Install Erosion Control Matting (see Detail), trench
U
2
co
Sta 2+72 for the 24'' barrel pipe outlet.
6. Install Footer Rocks down to the bedrock or
Max Velocity (ft/s)
2.8
the upper, lower extent and sides of the matting a
2. All measurements for this detail are based on
erosion resistant layer in the channel bottom to
minimum of 6". Where overlap is necessary,
the culvert diameter D.
prevent scour under the structure. Ensure all
Max Shear Stress (lb/sgft)
0.5
overlap the downstream edge a minimum 6" with
3. Sill, Header, and Footer Rocks shall be min. 3' W
Header and Footer rocks are touching, with no
the upstream edge that is trenched minimum 6".
x 2' L x 1.0' H.
gaps between rocks.
7.
Extend matting minimum 18" passed the top of
4. Geotextile Liner shall be medium weight
7. Extend Headwall/Endwall min 12" above top
bank.
Sheet
non -woven polypropylene (Weight 7oz/sq yd; of culvert.
Tensile Strength 180 Ibs). Place liner on the
8. Extend wingwall a distance of 3xD into the
upstream side of both footer rock and sill rock
channel.
n3
RISER SPILLWAY BARREL EXTENSION
Notes-
i�
3.
The Barrel extensions shall be 24" corrugated
metal pipe (CMP), extending into the pond to
the riser (Sta 1 +06-1 +26, Riser Spillway Profile,
Sheet 4) and extending into the receiving
stream (Sta 2+62-2+72, Riser Spillway Profile,
Sheet 5). (ADS HDPE N-12 or similar).
Extensions will be secured to existing barrel
CMP using watertight couplers with mastic. The
barrel extension will be inserted into the bottom
riser section, and sealed using hydraulic
cement.
The interior of the CMP barrel pipe including
extensions (167') will be lined with Insituform
cured -in -place pipe to ensure structural
integrity of the entire lengh. This lining will be
installed by Federal EC, LLC, Atlanta, GA
following barrel extension.
Barrel Diameter (in)
24
Mannings n
0.012
Barrel Area (sqft) - A
3.14
Perimeter (ft)
6.28
Hydraulic Radius- R
0.50
Slope (ft/ft) - S
0.019
Capacity Discharge (cfs) - Q
33.9
DRAINAGE PIPES
DRIVEWAY FRENCH DRAIN
Notes:
l . A French Drain shall be installed along the
Driveway expansion section (190').
2. The French Drain shall consist of a 4"
corrugated HDPE perforated pipe enclosed
in filter sock surrounded by 57 stone.
3. Minimum trench size shall be 8" deep by 8"
wide extending below the groundwater
table.
4. The French Drain shall be have a minimum
1 % slope.
AUXILIARY SPILLWAY CULVERT EXTENSION
Notes:
1. HDPE pipe shall be installed at Sta 0+92 - 2+72 along
the Auxiliary Spillway Profile (see Sheet 5). HDPE
pipe shall be 30" diameter, smooth interior,
corrugated exterior (ADS HDPE N-12 or similar).
2. Pipe and connections must be soil and watertight.
Pipe shall have a flared bell and tapering spigot at
the connections, sealed with manufacturer
provided gaskets.
3. Minimum trench width required for installation is 5.0'.
Minimum cover over pipe is 12".
4. HDPE Pipe shall be bedded with 57 stone in areas
where it intercepts the water table, minimum 6"
thickness.
5. Outlet protection shall be installed at the end of the
pipe prior to entering the receiving stream. Outlet
protection shall consist of a Rock -Lined channel (see
Detail).
Barrel Diameter (in)
30
Mannings n
0.012
Barrel Area (sqft) - A
4.91
Perimeter (ft)
7.85
Hydraulic Radius - R
0.63
Slope (ft/ft) - S
0.031
Capacity Discharge (cfs) - Q
78.4
Required Discharge (cfs)
48.0
co
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GO
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OO
W
0
N Y
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� ¢ 2
O O U
Sheet
C4
RISER SPILLWAY
Top Trash Rack
Handwheel
Riser Top,
Stem Guide El: 4078.0'
Riser Access Stairs
Gate Stem (18" spacing)
Riser Section,
Square Concrete Box
3'H x 4'W x 4'L
Barrel 24" CMP with CIPP
Drainage
lining; Invert: 4069.3
Gate Valve
4„
Invert: 4071.0'
Base Section,
Square Concrete Box
4'H x 4'W x 4'L
Riser Bottom
El: 4068.0'
Concrete Footer
'
2�
, r
•
57 Stone
Bedding
10.0'
Cr]/"IAIT \/IC\A/
The Riser Spillway in combination with the
Auxiliary Spillway have been designed to
convey the 25 year 24 hour design storm. This is
the maximum flow that can be conveyed with
the existing 24" Barrel Structure.
Riser Spillway Notes
• Sheet 4 provides a complete profile of the
Riser Spillway through the dam
embankment and into the receiving stream
• Any modifications to Riser Spillway
components must be approved by the
Project Engineer.
Riser Structure:
1. The Riser Structure will be designed and
fabricated by Old Castle Infrastructure, or
similar.
2. Concrete Box Riser and Base sections shall
be square, 4'Wx4'L.
3. The Base section shall have a cut-out for the
24" Barrel pipe and the 4" Drainage Gate
Valve.
Geotextile
Liner
Drainage Gate Valve:
1. The Gate Valve shall be a 4" Asahi Gate
Valve designed and fabricated by
Asahi/America, Lawrence MA., or similar.
2. The Contractor shall coordinate with the
Riser Structure vendor to include cut-out to
accommodate the gate opening and the
bolt pattern for the gate stem guides.
Trash Rack:
1. The trash rack shall be a metal grate bolted
onto the top of the Riser
Concrete Footer: (See Detail)
Barrel Structure:
1. The Barrel will be a lined retrofit to the existing
corrugated metal pipe, with a 20' extension
into the pond interior and a 10' extension into
the receiving stream.
2. The Barrel Structure shall be inserted into the
Riser bottom section through a prefabricated
"cut-out" and sealed with hydraulic cement
(See Drainage Pipe Detail).
CONCRETE FOOTER
Riser Structure
footprint p
/ a
• 4 . • •°
• • . °
• ' •• • •• .. 4. ..
#6@12"
O.C.
2" from edg
10
3D VIEW
NTS
#6@12" O.C.
Top & Bottom Mats
Standard Hook, Both Ends
FOOTER STEEL LAYOUT
NTS
Notes:
1. Install Concrete Footer to anchor Riser Structure.
2. Concrete must have ultimate compressive strength
of 4000 psi.
3. Forms (wood or metal) shall be used on sides and
top of cradle throughout length.
co
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ro �~
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Sheet
C5
2x
Ripi
ROCK LINED CHANNEL (EMERGENCY SPILLWAY
Top of Bank
Channel Dimensions
Top of Dam
Weir
Outlet Channel
Outlet
Protection
Centerline Station
0+00-0+10
0+10-0+92
4+00-4+14
Channel Area (sq ft)
17.0
10.5
9.5
Channel Width (W, ft)
19.0
10.0
11.5
Channel Max Depth (D, ft)
1.0
1.5
1.0
Channel Bottom Width (b, ft)
15.0
4.0
7.5
Side Slope (X:1)
2
2
2
Channel Slope (ft/ft)
0.03
0.08
0.08
Max Discharge (cfs)
57.3
62.1
49.0
Required Discharge (cfs)
48.0
48.0
48.0
Velocity (ft/s)
3.1
5.5
5.2
Shear Stress (lb/sgft)
1.7
6.5
5.0
Riprap D50 (in)
18-24
18-24
18-24
PROFILE VIEW
NTS
LL
cc
Notes:
1.
Excavate the Rock -Lined Channel down to the
foundation of the Geotextile Liner +0.2', according
to the Auxiliary Spillway Profile (Sheet 5).
�
mph
2.
Remove all stumps, roots, loose rock and other
w N
DU
debris from the channel perimeter.
O
O
U
3. Install NCDOT Type 2 Geotextile (US205NW or
equivalent) and secure in place along the sides and
bottom prior to adding Riprap with heavy duty
I
W
�'
staples or rebar.
--- - - -III- -
= -III_III-III-III-''
- -1��1 4.
Trench the upper and lower extent of the channel
X I
D I
Geotextile Liner a minimum of 12". Where overlap is
0
j ��TI
b j I
necessary, overlap the downstream edge a
minimum 12" with the upstream edge that is
.N
ro
�,
Riprap Channel Lining I
5.
trenched minimum 12".°
Install riprap in outlet channel, taking care not to rip
O C/) CO o
ca
2 x D50
or tear the Geotextile Liner.
o I;' .o r
- I
III=III=III=III=III=III=III=III=III=III=III=III=III=III
6.
Riprap shall be well -graded and extend to a
z
o
minimum depth of 2 x the D50 of the rock diameter.
.c
o o
Geotextile Liner Existing ground or
7.
Key the toe of the Rock -lined channel minimum to a
CIO a�
bedrock
depth of 2 x Riprap layer thickness or down to
0 co
bedrock, which ever is shallower.
SECTION VIEW
NTS
Sheet
C6
O
ROCK SILL (STREAM)
ROCK STEP (STREAM
Bankfull Bank Toe—\
W
' W W
�/ I •Y
W W
W O
i Riffle
)otextile Liner
(see Note 3)
\I i W
1/ 1 W W
Extend Sill J/
Bank Toe (6min.)
Bankfull Width
Plan View
N. T. S.
fu
IW -A
Sill Rock Apex Step Rock
Flow �� Streambed Flow Step
- - ---
2—� Height
\
ae-------------
GC� -'-----------
Pool Riff/e Riffle __-________
Scour Rocks
Geotextile Liner ..... Pool
Geotextile Liner Bankfull Elevation (see Note 3)
Footer Rock --------------------------------- -
(see Note 3) (see Note 8) Splash Rock
1/2 Bankfull Footer Rock
_CAr�tinn d
----------------
�' �J Section C
N. T. S.
J
N.T.S.
Entire rock Sill
below proposed
Sill extends into
Bank Toe streambed
Section B elevation (Note 4)
N. T. S.
Step Rocks keyed
in at inner berm
Rock Sill and Step Notes:
1. Rock Step and Footer boulders shall be min.
3.0' dia. long axis, min. 2.0' dia. intermediate
axis, and min. 1.0' dia. height.
2. Rock Sill boulders shall be min. 2.0' dia.
3. Geotextile Liner shall be medium weight
non -woven polypropylene (Weight 7oz/sq yd;
Tensile Strength 180 Ibs). Place liner on the
upstream side of both footer rock and sill
rock/log and key in at the bottom. Geotextile
Liner shall be installed if backfill is
fine-grained, as approved by the Project
Engineer. Trim excess or visible fabric.
4. Rock Sill boulders are placed just below the
channel bottom, ensuring thalweg elevation
above the center rock.
5. Rock Step boulders are placed above the
Bankfull channel bottom, dropping the water
surface = Step Height. Step Height is the total
structure drop between the Rock Step and
next head of facet.
6. For Rock Steps, the proposed thalweg is at
the top of the center Step rock.
7. Rock Step boulders are keyed in at inner
berm elevation or higher.
8. Extend Footer rocks below the upstream
scour pool depth, as approved by the Project
Engineer.
9. For Rock Sills at the head of riffle, construct
the riffle starting at the Rock Sill and extend
the riffle length downstream. Ensure a
pavement layer of substrate covers the Rock
Sill. See Constructed Riffle Detail.
Rock Sill and Rock Step Structure Table
Centerline
Thalweg
Bankfull
Step
Structure
Station
EL (ft)
(ft)
Height
(ft)
Rock Sill
3+41
4062.6
4063.5
N/A
Rock Step
3+59
4061.85
4062.75
0.5
Rock Sill
3+81
4061.35
1 4062.25
N/A
Structures will be staked out by construction oversight staff
prior to construction
Bankfull Elevation_
Section D
N. T. S.
Step Rocks protrude
\_above proposed
streambed elevation
(Note 5-6)
N Y
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� ¢ 2
O O U
Sheet
C7
Bank Toe
Bankfull-",,,,,
I 0
r
r � s
1
Step Rock42
1
POOL
ST
STEP 2�77
�
Footer Rocks
POOL
Splash Rocks
1
STEP
i / L► I I
Bankfull
(BKF) Width
PLAN VIEW
N.T.S.
Notes:
1. The Step Pool Channel shall be placed in the
location shown on the Site Plan and Riser Spillway
Profile.
2. Step Header, Footer and Sill Rocks shall be min. 3'
dia. long axis, min., 3.0' dia. intermediate axis, and
min. 1.5height.
3. Splash Rocks in the pool shall be 6-9" median
diameter stone. A larger Splash Rock shall be
placed in front of the structure below the
maximum pool depth to protect against scour.
4. Geotextile Liner shall be NCDOT Type 2 (US205NW
or similar).
STEP -POOL CHANNEL (STREAM
le Liner
nd sill 6' min
bank toe
Armor entire pool
bottom with cobble,
extend above water
surface
FLOW
-- I�36" 12"
-- l
" 1 ` Splash Rocks Step Height
18 min
POOL
24" min
Geotextile Liner) I�
Step Rock Footer Rock
Footer
Splash
5. Extend Footer Rocks and Splash Rocks a min. 12"
below scour depth or to bedrock, whichever is
shallower. (The scour depth is assumed to be the
max. pool depth associated with the structure).
6. All Rocks must be touching and fit snug against
each other to ensure a tighter seal.
7. Step Height is the Total Structure Drop of the water
surface. The water surface drop across the Step
Rocks is measured along the stream profile. See
Section A and Structure Table.
8. The proposed thalweg is at the top of the Step
Rocks, in the center of the channel.
9. Step Structures will be keyed in at inner berm or
higher, but not above bankfull.
PROFILE VIEW (A)
N.T.S.
Bankfull
(BKF) Width �
\-Step Rock
Streambed
SECTION VIEW (B)
N.T.S.
Step -Pool Elevation Table
Step
Centerline
Station
Thalweg
(Step) EL
(ft)
Bankfull
EL (ft)
Step
Height (ft)
2+72
4066.2
4067.1
0.5
2+87
4065.7
4066.6
1.1
3+05
4064.6
4065.5
1.0
3+23
4063.6
4064.5
1.0
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SILT FENCE
6" Max. 6' Spacing without fence
Wire Fence min. Max. 8' Spacing with fence
(if applicable) Steel 6"
Geotextile Fabric Post min.
Backfill and Wire/Plastic
compact soil 24" Ties
° 24" a
Fey 8" Existing Y
Existing Q min. Ground 00
Ground — — — — E
81, I I -III-III -III-I I I I -I I p
CD
mini' 24" Bo-1 of
min. min. 24" min.
Trench Geotextile
Steel Post Fabric
PROFILE VIEW SECTION VIEW
NTS NTS
Notes:
1. Silt fence shall meet the requirements of the NC Erosion and
Sediment Control Planning and Design Manual (2013) Std
and Spec 6.62.
2. Do not install silt fence across areas of concentrated flow,
including streams, ditches, or waterways.
3. Silt fence is limited to fill heights of 10 ft or less, and shall not
exceed slope length corresponding to drainage area size
and slope (Table 6.62a).
4. Steel posts shall be 5' min. length, with 1.25 lb/linear ft steel.
Wooden stakes are not allowed.
5. Geotextile fabric shall comply with specifications in Table
6.62b. If Wire Fence reinforcement is needed, wire shall be
14 gauge min. with max. 6" mesh spacing and extend to
bottom of trench.
6. Wire or Plastic ties shall have 50 lb tensile strength min.
7. When two separate sections of geotextile fabric adjoin
each other, they shall overlap by 6" and be double folded.
8. Geotextile fabric shall be fastened with plastic or wire ties
securely to the posts at the top, vertical midpoint and
bottom of geotextile fabric.
9. The distance between the toe of the fill to the silt fence
shall be a minimum of 5'.
SLOPE MATTING
Use key trench on top edge.
min. overlap
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a
Flow Bottom Edge
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Space wood
Note: Rotate stakes 20° towards
stakes every 36" in PLAN VIEW direction of flow to prevent uplift.
diamond shape NTS
pattern.
Fill and compact
6° min. trench with topsoil
` Erosion Control Matting
min.
SECTION VIEW
NTS
Extend matting below
normal flow elevation
Notes:
1. Streambank Matting shall be applied to slopes 3:1 or greater, including
all streambanks and terrace slopes.
2. Streambank Matting shall be 700 gram coir fiber matting (20.3 oz./sq.
yd.). Rolls shall be 6' min. width.
3. Seed and mulch the ground surface before installing matting (use native
Riparian Seed mix plus a temporary cover crop).
4. Alternate fastening devices require Project Engineer's approval before
use.
5. Extend matting 18" min. past the top of bank or top of slope. Upstream
fabric overlaps downstream fabric by 6 in.
6. For streambanks, extend matting below normal flow elevation to
promote saturation in order to weigh the matting down and encourage
a biofilm seal with the underlying soil.
7. For streambanks, do not trench or stake the bottom of the matting to
avoid disturbance and instability along the toe of slope.
8. Tuck matting behind and under toe protection measures such as
revetments and rock.
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C9
PERMANENT AND TEMPORARY SEEDING
Permanent Seed Mix - Disturbed upslope areas outside of floodplain
riparian areas and streambanks
Minimum Care Lawn Total Lbs. Per Ac
Commercial or Residential 200-250
Kentucky 31 or Turf -Type Tall Fescue 90-100%
Improved Perennial Ryegrass 0-10%
Kentucky Bluegrass 0-10%
Rioarian Permanent Seed Mix — Disturbed floodDlain rioarian
areas and streambanks
NC Mountains Riparian Mix 20 lbs. per acre 2
(Ernst Conservation Seeds ERNMX-304 or similar)
Topsoil 4 inches, free from weed seeds
Fertilizer As recommended by soil test 3
Lime As recommended by soil test
Mulch 2 tons per acre (slopes < 3:1) hay,
free from weed seeds 4
Temporary Seed Mix - All areas where Permanent and Riparian
Permanent Seed Mixes are applied
Total Lbs. Per Acre
Sept 1 -Feb 15 5'
Winter wheat 100
April 15 - Sept 1
Browntop or German millet 100
Feb 15 - April 15
o mix of above species 100 6'
*Annual ryegrass shall not be applied to any areas due to
allelopathic properties with native species.
**Species may be substituted based on local availability, as 7
approved by the Project Engineer.
Mulch: 2 tons per acre (slopes < 3:1) hay or
straw, free from weed seeds
STREAMBANK LIVESTAKING
1. Following construction, all streambank areas shall be seeded with
Permanent Riparian Seeding (see Detail). Erosion Control Matting (see
Detail) shall be installed.
2. Plant livestakes in two rows with 5' spacing between rows along both
left and right streambanks of disturbed reach. Plant livestakes from
bank toe up to top of bank.
3. Livestake species include:
Corpus amomum, Physocarpus opulifolius, Salix serecia,
Sambucus canadensis.
Any substitutions must be approved by Project Engineer.
Notes:
Permanent and Temporary Seeding shall meet
the requirements of the North Carolina Erosion
and Sediment Control Planning and Design
Manual Handbook (2013) Practice Standards and
Specifications 6.11 -Permanent Seeding and 6.12
Temporary Seeding. Seed mix may be altered to
match existing land -use requirements (example
pasture needs, as suggested by the landowner).
Changes to seed mixes must be approved by the
Project Engineer.
Soil tests must be performed prior to construction
activities to determine appropriate fertilizer and
lime rates at the time of construction, in
coordination with the Project Engineer.
Permanent Seeding must be applied to all
disturbed areas within 15 working days after
reaching final grade.
Topsoil shall be applied uniformly over existing soil
to all Temporary and Permanent Seeding areas to
a depth of 4 inches. Topsoil shall be free of weed
seed, rock, and debris to the extent possible.
Apply all seed uniformly with a broadcast seeder,
drill, culti-packer seeder, or hydroseeder on a firm,
friable seedbed to a depth of a to 2 inch
according to seed rates specified above or by
the seed distributor.
Apply mulch following seeding, fertilizer, and lime
application, ensure mulch is properly tacked
down to avoid wind dispersal. For slopes >/= 3:1,
use Streambank Matting (see Detail) instead of
mulch.
The Contractor is responsible for establishing
permanent groundcover (>80% coverage)
following these details and specifications within
one year of project completion to the extent that
no erosion is occurring due to lack of permanent
groundcover, as approved by the Project
Engineer.
TEMPORARY CONSTRUCTION
A �
10'
10' min
L
Paved
Road)
ENTRANCE/EXIT
0' min.
0
Clean washed stone 2"-4" dia.,
8" depth underlain with
Geotextile Fabric
Temporary Drainage Pipe,
as needed
PLAN VIEW
NTS
Existing
— 50' min _ Ground
Paved 20% slope
Road
Clean washed stone
3" min. �� 2"-4" dia., 8" depth
Non -woven Geotextile Fabric shall
be placed under entire width/length
of stone
Temporary Drainage Pipe,
as needed
SECTION VIEW
NTS
Notes:
1. Temporary Construction Entrance specifications are
described in North Carolina Erosion and Sediment
Control Planning and Design Manual (2013) Std and
Spec 6.06.
2. Excavate 3" minimum undercut prior to placement
of stone along Entrance length.
3. Replenish stone when surface rock becomes
compressed < 8", stone becomes covered with fine
sediment, or sediment is visible on the paved road.
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C10
PUMP AROUND DETAIL
0 Pump
Hose
Sandbag Dam
Weir
"In -stream" work
location
Non -Permeable Material
Verify Hose Diameter and Pump
Size Adequate to Drain
Sand Bag Temp Dam
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Notes:
M
1. Pump around method is designed for flows of 5 cfs or less using
a maximum pump size with a 6" diameter hose.
2. Clear area of debris for temporary dam installation.
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3. Layout hose and pump along route adequate to allow for
o
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in -stream work.
4. Provide splash pad at outlet of hose to spread and slow
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CO
velocity of flow before reentering live stream flow.
5. Install Sandbags perpendicular to flow of water.
208 z
6. Allow for overflow weir --4' min width and --1.5' depth.
-6min
7. Overlay dam structure with non -permeable plastic or similar
°
z>
material.
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a
8. Begin pumping process, with regular monitoring to ensure
co
hose diameter is adequate to carry flow and check to ensure
o
filter at hose inlet does not clog and restrict flow.
"In
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0
9. If -stream" work extends beyond one day, open weir section
W
of sand bags to allow flow through work area overnight.
Sheet
C11