20091098 Ver 1_More Info Received_20091105

S#immel
Stimmel Associates, PA
Landscape Architecture
Civil Engineering
Land Planning
November 5, 2009
Mr. Andrew Williams
US Army Corps of Engineers
Raleigh Regulatory Field Office
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Re: Action ID: SAW-2009-02025, Rockingham County
Mr. Michael Smith, Rockingham County
Dear Mr. Williams:
I am writing to address your comments regarding jurisdictional waters impacts associated with the project referenced
above. Answers to your comments are as follows:
1. Comment: (please provide) A drawing showing the proposed temporary coffer dam, for the installation of the stream
crossing, and the linear feet of associated impacts.
Answer: The stream crossing construction will incorporate a bypass channel that will divert stream flow around the
culvert construction site. The bypass channel will tie into the natural stream channel just beyond the rip rap energy
dissipaters on either end of the culvert, with a coffer dam separating the culvert construction site from the stream. The
bypass channel will be lined with woven geotextile fabric to minimize channel erosion. The dewatering effluent from
the construction site will be pumped to a sediment basin that will release flow into the overbank area adjacent to the
stream. Upon completion of the culvert and rip rap dissipaters, the coffer dams will be removed, the bypass channel
filled and the stream bank stabilized. See the attached Exhibit 1 which has been revised to show the bypass channel.
2. Comment: (please provide) An updated plan/drawing of the exhibit showing the fill within the intermittent channel.
This updated drawing/plan should clearly distinguish the portion of the stream that is proposed to be filled/impacted.
Answer: See attached Exhibit 2, which has been revised to more clearly show the impacts to the intermittent channel.
The exhibit shows this channel being filled from its origin to the 50 foot stream buffer.
3. Comment: (please provide) An updated drawing/plan of the proposed road crossing that clearly indicates the amount
of stream channel (linear feet) that will be impacted by the associated rip rap apron (upstream and/or downstream of
the culvert)
Answer: See attached Exhibit 1 which has been revised to indicate rip rap apron impacts separately from the culvert
impacts. The exhibit shows 11 linear feet and 30 linear feet of rip rap apron impact on the upstream and downstream
ends of the culvert respectively. The culvert impact has been revised to 215 linear feet. The total stream impacts
remain at 256 linear feet.
4. Comment: (please provide) Discussion regarding the design of the proposed culvert and dissipation pad. Specifically,
you must indicate if it has been designed in accordance with the current North Carolina Erosion and Sedimentation
Control Planning and Design Manual (referred to hereafter as 'State EC Manual').
Answer: The culvert was sized to convey the peak discharge resulting from a 25-year storm event (Q25) in
601 N Trade Street Suite 200
Winston Salem. NC 27101.2916
P 336 723 1067 F 336 723 1069
Rockingham County
Horse Park of the South
November 5, 2009
Page 2
accordance with NCDOT drainage design guidelines for secondary roads. Additionally, the culvert was evaluated for
the ability to pass the peak discharge resulting from a 100-year storm event (Q100). The State EC Manual requires
outlet control measures to be designed for Q10 discharge, or the design discharge of the conveyance structure. The
rip rap dissipater was designed for Q25, and then evaluated for Q100. The culvert will be operating under maximum
tailwater in both scenarios. The dissipater was sized using spreadsheets provided by the NCDENR-Land Quality
Section, and nomographs from the State EC Manual. The results indicate a dissipater length of 19 feet is sufficient for
both the Q25 and Q100, with a D50 stone size of .30 feet for Q25 and .35 for Q100.
I have chosen to lengthen the dissipater to 30 feet because the receiving channel is deflected approximately 45
degrees from the culvert axis. I feel that the additional length is needed to help control the flow through the turn. I
have also chosen to use NCDOT Class I rip rap (D50 = .83') for the dissipater in lieu of the smaller stone indicated by
the nomograph. Again, I feel the larger rip rap size is needed to remain stable under the discharge conditions at the
culvert outlet. I have attached the culvert calculations, dissipater calculations and nomograph. The dissipater
spreadsheet reflects the Q100 culvert discharge.
I trust this information adequately addresses your concerns. If you have additional questions, please feel free to contact
me at [phone].
Sincerely:

J. Neal Tucker, P.E.
Stimmel Associates, P.A.
Attachments
`,%??ttnuirti.""
??? \A CAA
a SEAL
14985
MCI
a
?l:i :a
Cc: Sue Homewood, DWQ
Michael Brame, ECS
Stimmel 601 N Trade Street date: 10-12-09 job #: 09-154
Suite 200
Winston Salem, NC project: Horse Park of the South
Landscape Architecture 27101.2916
scale: 1"=100' sheet 2 of 2
Civil Engineering p 336.723.1067
Stimmel Associates, PA Land Planning F 336123 1069 description: STREAM CROSSING
exhibit # 1 IMPACT EXHIBIT (REVISED)
20'x30' DEWATERING/
SEDIMENTATION
BASIN
` 20- LF- OF
TEMPORARY IMPACT
,/ Jlli?l?(?I?f?1?1111r? ?II?+II? j II?(IIIIIr,llli I I 1 I I 1 l
/?' ? ? f ? ! i lllli IIII I)II ?IaII?'llllljl11111111
10+0 111 Ilill??liil?ill 1 0
? Illllllll I I
II? iI?III 1?I?1111111I?lill
11
(, ?? Ill,I1i!4ffWjIJI1i?th!l!ill ?.
TEMPORARY BYPASS
CHANNEL
50'-STREW 56UFFER\
/ HORSE PARK - -- : ???
SITE -G
3 0 19?^
4R
3,375 SQ.FT.
WETLANDS IMPACT
PERENNIAL STREAM
' 215-LF- C
/`SWEAM
40-?'
?TEMP_O ?IM(ACT
t- LF RIPRAP'- - , 4 --
TREICM IMPA( '/- '? - -
JLVERrT%j?i . % _

11' 38' 11-1,
760
755
750
745
740
735
730
725
720
715
710
----- --- - ---- -

--- G
F-
5
- - - -
- - - - -
- - - -
-
71
1 i

--- --- - - NCDO 838.2 1
1 END A =

RRIPRAR
--
---
---
---
--
APRON
LE
FL-`
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-q2 - ,
-
F- INV
72 .20 727.C 0

--- RAP

IP_
- I --- --- PRON

760
755
750
745
740
735
730
725
720
715
710
10+00 10+50 11+00 11+50 12+00 12+50 13+00 13+50 14+00
J::•...,
4
SCALE: 1 60'
60 0 60
Stimmel sot N Trade street date: 10-12-09 job #: 09-154
Suite 200
Winston Salem, NC project: Horse Park of the South
Landscape Architecture 27101-2916
Civil Engineering scale: r=100' sheet 1 Of 2
336
Stimmel Associates, PA Land Planning F .723.1067
g F 336.723.1069 description: STREAM IMPACT
exhibit # 2 EXHIBIT (REVISED)
PERENNI?L STI;2EAM,. --
_
_??---_- ?:\ ? `'•_. `? ? ??. _ ? ? .` \
- -- INl):RKAfTENT ..
-? -- STREAM IMPACT
-RETAINING WALL - ? ' '
50 STREAM BU' j
5
`1 SQ. ;c
340. )
LF,
I?RMfTENT
\ \ STREA?A, IhIRAbT
89.6,
x \?? ?A Ufjq
4` 6 SS r
SCALE: 1 60'
??e? .,?, CON °a ??F-,,•
m zsae:c>° . e a
60 0 60
Culvert Report
Hydraflow Express by Intelisolve
54-Inch Culvert Scenario - Q25
Invert Elev Dn (ft) = 723.20
Pipe Length (ft) = 192.00
Slope (%) = 2.01
Invert Elev Up (ft) = 727.06
Rise (in) = 54.0
Shape = Cir
Span (in) = 54.0
No. Barrels = 1
n-Value = 0.013
Inlet Edge = Sq Edge
Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5
Embankment
Top Elevation (ft) = 760.00
Top Width (ft) = 60.00
Crest Width (ft) = 100.00
Elev (ft)
765.00
758.00
751.00
744.00
737.00
730.00
723.00
716.00
0 20 40
I Cir Culvert
Thursday, Nov 5 2009
Calculations
Qmin (cfs) = 103.22
Qmax (cfs) = 103.22
Tailwater Elev (ft) = (dc+D)/2
Highlighted
Qtotal (cfs)
Qpipe (cfs)
Qovertop (cfs)
Veloc Dn (ft/s)
Veloc Up (ft/s)
HGL Dn (ft)
HGL Up (ft)
Hw Elev (ft)
Hw/D (ft)
Flow Regime
= 103.22
= 103.22
= 0.00
= 7.29
= 9.17
= 726.95
= 730.06
= 731.78
= 1.05
= Inlet Control
54-Inch Culvert Scenario - 025
Hw Depth (ft)
37.94
30.94
23.94
16.94
9.94
2.94
-4.06
11.06
60 80 100 120 140 160 180 200 220 240 260 280
® HGL - Embank Reach (ft)
Culvert Report
Hydraflow Express by Intelisolve
54-Inch Culvert Scenario - Q100
Invert Elev Dn (ft) = 723.20
Pipe Length (ft) = 192.00
Slope (%) = 2.01
Invert Elev Up (ft) = 727.06
Rise (in) = 54.0
Shape = Cir
Span (in) = 54.0
No. Barrels = 1
n-Value = 0.013
Inlet Edge = Sq Edge
Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5
Embankment
Top Elevation (ft) = 760.00
Top Width (ft) = 60.00
Crest Width (ft) = 100.00
Elev (ft)
765.00
758.00
751.00
744.00
737.00
730.00
723.00
716.00
U Gu 4u bU
Cir Culvert
Thursday, Nov 5 2009
Calculations
Qmin (cfs) = 122.72
Qmax (cfs) = 122.72
Tailwater Elev (ft) = (dc+D)/2
Highlighted
QtotaI (cfs)
Qpipe (cfs)
Qovertop (cfs)
Veloc Dn (ft/s)
Veloc Up (ft/s)
HGL Dn (ft)
HGL Up (ft)
Hw Elev (ft)
Hw/D (ft)
Flow Regime
= 122.72
= 122.72
= 0.00
= 8.41
= 9.92
= 727.08
= 730.33
= 732.44
= 1.20
= Inlet Control
54-Inch Culvert Scenario - 0100
Hw Depth (ft)
37.94
30.94
23.94
16.94
9.94
Itrol
2.94
-4.06
11.06
00 100 120 140 160 180 200 220 240 260 280
-- HGL °-- Embank Reach (ft)
Designed By: JNT Date: 11/5/2009
Checked By: JNT Date: 11/5/2009
Company: Stimmel Associates
Project Name: Horse Park of South
Project No.: 09-154
Site Location (City/Town) Reidsville, NC
Culvert Id. Entrance Road
Total Drainage Area (acres) 61.92
titer 1. Determine the milwater depth troll/ cllalulel Characteristics below the
pipe outlet for the design capacity of the pipe. If the talh ater depth is less
than half the outlet pipe diameter. it is classified 111111111111111 tailwater colidition.
If it is greater thall half the pipe diallleter. it is classified 111aY1i1111111 conditroll.
Pipes that outlet onto wide flat areas with no defined chalmel are assulued
to lime a 1ui1lii11u111 tailwater Condition unless reliable flood stale eletiatiolls
show othem-1w.
Outlet pipe diameter, Do (in.) 54
Tailwater depth (in.) 36
Minimum/Maximum tailwater? Max TW (Fig. 8.06b)
Discharge (cfs) 122.72
Velocity (ft./s) 8.25
Step 1. Based oil the taltwater coaduions determined in step 1. enter Figure
3.06a or FigLll'e 4.06b. and determine clan riprap size and 11111111111111111)17011 lenGth
(L,). The d,., size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at tine pipe olltl:t. the apron snap:. and the
apron width at t11: outlet ;nil 11'0111 the same ti lire used in Stet? ?.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d50, (ft.) 0.83
Minimum apron length, La (ft.) 19
Apron width at pipe outlet (ft.) 13.5 13.5
Apron shape
User Input Data
Calculated Value
Reference Data
Apron width at outlet end (ft.) 4.5 12.1
titer 4. D: mrnlille the iiiaxi11111111 Stour diarueter
Minimum TW
Max Stone Diameter, dmax (ft.) 0
Step 5. Deteruline the apron thickness:
Apron thickness = 1.5 x
Apron Thickness(ft.)
Maximum TW
1.245
Minimum TW Maximum TW
0 1.8675
Step 6. Fit the riprap apron to the ,ite bti' niAin.q it level for the [lllllllillilll
len.?th. L.. from FiRture 8.06a or Figure 8.06b. Extend the apron falrther
clowin,trealn and along chaimel ba111cs until stability is assured. Deep the
apron as ?tralgllt m passible and '111 11 it with the flow of the receiving _ stream.
Make any 1lecessxa-y alignment bends near the pipe outlet so that the entrance
Into the recetk-1,119 stream is sti-algllt.
some locations iiiay require lining of the entire chatulel cross section to a,sure
stability.
It inav be 1lecessarv to increase the size of riprap where protection of the
ehalinel side slopes is 1lecessait {_?; ;?c? trr:t 8,05). Where overfills exist at
pipe outlets or flows ai-e excessive. a plun-,e pool should be considered, see
page 4.06.5.
0&*Zs PAP-je- -F TIAS sOMg
0
LA
Q 2S ? 103.22 ?s
90
1?\ 80
?PQ?o 10
r I :..
:%o
60
-t?_L

lot
z
N
N_
CL
ca
_a
1 tr
0
LO
o.1i,
50 100
Discharge (0/sec)
M,wN,uM 9111ZDM- G?+f s =
D50 = !o", .6s
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full, maximum tailwater condition J, ? 0.5 diameter).
3Do_ Outlet 1 = Do ¢ 0.41-a
pipe
diameter (Do) 1- La
Tailw P,r 5Do
5.06.4
2zc t - ?'
AbnjEj Fkg-V- of TM+z 7ounA
0
E?.rc? '?? rn C.?oss? ?I.?.
Qia7: J 22 ,'IZ cFs
3Do
Outlet = Do ¢ 0,41-a 120 --
pipe
diameter (Do) La 110 -- 1
Tai lwater a 0.5Do
100
90 i I u?, f_: l
t ll lj;
?t fl 1!1
80 r I ti' f ?, °j ' n u j'
u ? ? ft t
?QQ 70 ? +
N\ I j ti a b r. f' I?! !i
60 , n - b.L?
10 50
30
q 20
ti

w
2
a?
N_
C1
ro
n.
1 ?
0
C>
3 5 10 20 50 100 200 Wu luuu
Discharge (ft3/sec)
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full, maximum tailwater condition J,, ? 0.5 diameter).
5.06.4 e'.. 12 1,3