20160785 Ver 1_More Info Received_20160922

CMPcivil
Dif
Des.'n
ign
Concepts,PA
September 21, 2016
Mr. Zan Price, P.E. _
Assistant Regional Supervisor-Asheville Regional Office �-{Ef�[-�I -x[)
NCDEQ- Division of Water Resources Division of Water Resources
2090 US Highway 70
Swannanoa, NC 28711 SEP 2 2 2016
RE: Hawthorne South-Slope Repair
NCDWQ- Response to Comments Water Ottaiity Regional Operations
CDC Project No. 11403 A<i .F: a6ona.i office
Dear Mr. Price:
Please find the enclosed package, for your review and approval that provides revisions to the
Nationwide Permit request for the above referenced project. The previously submitted permit
package has been revised based upon comments in an email dated September 12, 2016. The
comments identified in the email are listed below along with any associated responses.
Comment No. 1:
The proposed project includes the use of rip rap armoring for up to 100-linear feet of
streambank stabilization and relocation. It is this agencies experience that rip rap
armoring is not a long term stabilization solution for streambanks. The shear stress
associated with high flows can transport rip rap downstream, which can result in
destabilization or failures. Please explore alternative methods of stabilization that would
provide for more permanent stabilization of the streambanks and provide documentation
of this evaluation. If the designer determines that rip rap armoring is the preferred
alternative, please provide justification and shear stress calculations demonstrating long
term stability. The DWR and supporting agencies involved in the permit review process
encourage the use of natural channel design and/or bioengineering with native riparian
vegetation for stream rehabilitation/restoration projects,when feasible.
Response No. 1:
Based upon the above comment and input from the project's geotechnical engineer, we
have revised the cross section for the slope repair. The revised cross section includes
slopes that are composed of engineered fill, SC250 vegetated geotextile liner, and the
placement of live stakes to provide additional vegetated slope support.
The slope itself will be structurally prepared to include engineering fill material on top of a
layer of engineered shot rock fill. This will provide for increased slope stabilization along
with a vegetative cover to allow for adequate shear protection against flood waters within
the channel.
The SC250 vegetated liner is rated to protected against the shear stress of the flood waters
during a 100 year flood event. Calculations for the channel liner have been provided as
an attachment to this correspondence.
Mailing Address: P.O. Box 5432, Asheville, NC 28813
168 Patton Avenue Asheville, NC 28801 52 Walnut Street-Suite 9, Waynesville, NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]

,y
Comment No. 2:
Please update the stream impact table on page 4 of the application to include the
temporary impacts associated with the proposed temporary stream crossings.
Response No. 2:
The stream impact table mentioned above has been updated to include the temporary
stream crossing information.
Comment No. 3:
Condition number #7 of Water Quality Certification No. 3885 states that work must be
performed in the dry. Please provide appropriate information and associated details
describing how the project will meet condition #7 of WQC 3885.
Response No. 3:
• Temporary stream crossings will be constructed in the locations indicated on the
plans. These crossings will allow access to both sides of the stream to avoid any
construction within the stream channel under normal flow conditions.
• The proposed channel will be graded to allow for normal water levels to flow within
the proposed channel section.
• During grading activities any water that seeps into the graded area will be pumped
out using a dewatering device along with a filter bag to reduce sediment transport.
• Once grading of the channel is complete it will be stabilized using alluvium fill,
vegetated SC250 geotextile liner, and other materials per the detail provided on
the plans. Once the newly graded channel has been stabilized,the water from the
existing channel will be diverted into the newly prepared channel section.
• The temporary crossings will be adjusted to allow flow to be directed into the new
channel section.
• The existing channel section will be filled and the remainder of the side slopes will
be graded and stabilized per the detail shown on the plans.
• Once all proposed activities have been stabilized the temporary crossing will be
removed.
• At no time shall construction activities take place within a channel section that
contains flowing water.
Based upon the comments and responses above, only plan sheet C202 has been revised. A
revised copy of sheet C202 has been included as an attachment to this correspondence.
If you have any questions or need any additional information please do not hesitate to contact
me.
Sincerely,
Thomas Kelley, PE r-
Civil Design Concepts, PA
CC: William Elliott, USACE-Asheville Regional Field Office
Mr. Leo Almond, Hawthorne Residential Partners
Enclosures:

C. Proposed Impacts Inventory
1. Impacts Summary .
1a. Which sections were completed below for your project(check all that apply):
❑ Wetlands Q Streams—tributaries ❑ Buffers ❑ Open Waters
❑ Pond Construction
2. Wetland Impacts
If there are wetland impacts proposed on the site,then complete this question for each wetland area impacted.
2a. 2b. 2c. 2d. 2e, 2f.
Wetland impact Type of impact Type of wetland Forested Type of jurisdiction Area of
number Corps(404,10)or impact
Permanent(P)or DWQ(401,other) (acres)
Temporary T )
W1 Choose one Choose one Yes/No -
W2 Choose one Choose one Yes/No
W3 Choose one Choose one Yes/No
W4 Choose one Choose one Yes/No
W5 Choose one Choose one Yes/No
W6 Choose one Choose one Yes/No
2g.Total Wetland Impacts:
2h.Comments:
3. Stream Impacts
If there are perennial or intermittent stream impacts(including temporary impacts)proposed on the site,then complete this
question for all stream sites impacted.
3a. 3b. 3c. 3d. 3e. 3f. 3g.
Stream impact Type of impact Stream name Perennial(PER)or Type of Average Impact
number intermittent(INT)? jurisdiction stream length
Permanent(P)or
Temporary(T) width (linear
(feet) feet)
S1 P Relocation Dingle Creek PER DWQ 6 100
S2 T Culvert Dingle Creek PER DWQ 6 24
S3 Choose one
S4 Choose one
S5 Choose one
S6 Choose one
3h.Total stream and tributary impacts
31. Comments:
S2 Above will consist of a two temporary stream crossings composed of a culvert and stone fill material. The crossing will provide dry access to
upstream and downstream portions of the stream relocation project she. Upon completion of the stream relocation project,the temporary stream
crossings will be removed and site conditions adjacent to the stream crossings will be put back to existing conditions.
Page 4 of 10
PCN Form—Version 1.4 January 2009

9/13/2016 www.ecmds.com/print/anWysis/101298/101305
NORTHTensar International Corporation
>r 5401 St. Wendel-Cynthiana Road
AMERICAN Poseyville,Indiana 47633
GREEN Tel. [phone]
Fax [phone]
www.nagreen.com
Erosion Control Materials Design Software
Version 5.0
Project Name: Hawthorne Slope Failure
Project Number: 101298
Project Location:Asheville,North Carolina
Channel Name:Dingle Creek
Discharge 1200
Peak Flow Period 24
Channel Slope 0.0173
Channel Bottom Width 6
Left Side Slope 2
Right Side Slope 2
Low Flow Liner
Retardance Class B
Vegtation Type Bunch Type
Vegetation Density Good 75-951
Soil Type Sandy Loam
SC250-Class B-Bunch Type-Good 75-95%
Phase Reach Discharg4 Velocity Normal Maniumg
Permissible Shear Calculated Shear Safety Remarks Staple
Depth N Stress Stress Factor Patterm
SC250 Unvegetated Straighl 1200 28.4 3.34 ft 0.011 2.51bs/ft2 3.61bs/ft2 0.69 UNSTABLE E
cfs ft/s
SC250 Reinforced Straigh 1200 10.67 6.15 ft 0.041 81bs/ft2 6.641bs/ft2 1.21 STABLE E
Vegetation cis ft/s
Underlying Substrate Straight 1200 10.671 6.15 ft -- 0.8 lbs/ft2 0.2381bs/ft2 3.36 STABLE --
cfs ft/s
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