20070495 Ver 2_Stormwater Info_20071129

Q?- U`f~'S ~~
November 28, 2007
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Via: Federal Express
Division of Water Quality
401/Wetlands Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
Terrapin Ridge Subdivision -Stewart Mill Road culvert permit
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Enclosed are the following items for permitting the above referenced project:
• Sheets 1/2 and 2/2 of the project's Stream Impact Maps (11X17 and 24X36)
• USGS map showing the location of the project site
• Completed Pre-Construction Notification Application Form requesting
Nationwide Permit 14. We are requesting 68' (36' additional) of channel impacts
and 0 acres of wetland impacts.
• 11X17 Exhibits
• 24X36 Exhibits for USACE
• Agent Authorization form
• Project Narrative
• Supporting Calculations
• Associated Fee - $240.00
Please review the enclosed information and let me know if you have any questions or
comments. Thank you in advance for your help with this portion of our project.
Sincerely,
John A. Butler
CPT Engineering and Surveying, Inc.

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NY DOT Method The procedure presented in this section is taken from the New York Department of
8.4.4 Transportation (1971). The riprap apron dimensions and stone sizes are determined
from the charts and graphs in Figure 8-4 through 8-7. .
The sizes for the riprap aprons may be determined using Figures 8-4 and 8-5
following the steps below.
1. Estimate flow velocity V, at the culvert or paved channel outlet. V 2S ~ ~ ~ ~ ~~S
2. For pipe culverts, D, is the diameter. For arch pipe, box culverts, and
paved channel outlets, D, = A, where A, =cross sectional area of flow
at outlet.
~- For multiple culverts, use D, = 1.25 x D, of the single culvert. = .3.75
3. .For apron grades of 10% or steeper, use the recommended next higher ~,(,
zone (zones 1 through 6).
The following steps may be followed to determine stone sizes for riprap aprons
using Figures 8-6 and 8-7.
1. Use Figure 8-6 to determine maximum stone size (e.g., for 12 fps = 20"
or 550 Ibs). N,c~ S~ Z~ gyp`' ~ 5d ~ IOS,
2. Use Figure 8-7 to determine acceptable size range for stone (for 12 fps
it is 125-500 ~ lbs. for 75 % of stone, and the maximum and minimum
range in weight should be 25-500 Ibs).
8-9
x~>-. ..

-_
':
i
25
20
a 15
.,..
0 10
~ 8
5
0 3,7 S5 10
Do in
~m
Riprap Apron
Figure
t
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~-
25
.~- ~e ~'
15 20 25
feet
5 ~ _ I, ~5~~3~ e 3. ~~ ~r~u l~-- c~(,lerF.S
12 a
Design Graph
8-4
Source: 'Bank end Channel lining Procedures; New York Department
of 'hansportation, Division of Design and Construction, 1971.
8-10

Riprap Apron Design Chart
Figure 8-5

Source: "Bank and Channel Lining. Procedures;' New York Department
of Tz'ansportation, Division of Design and Construction, 1971.
8-11
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LENGTH OF APRON
Z APRON MATERIAL TO PROTECT TO PREVENT
~ CULVERT SCOUR HO1_E
L~ I.=
1 Stone Filling (Fine) 3 x D,
4 x D.
2 Stone Filling (Light) 3 x D, 6 x D
3 Stone Filling ()dedium) 4 x D, x D,
4 Stone Filling (Heavy) 4 x D, 8 x D.
~j Stone Filling (Henvy) 5 x D, 10 x D,
6 Stone Filling (Heavy) 6 x D, 12 x D,
.7 Special study required (energy dissipalors, stilling basin, or
larger size stone).

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600 ~
250 ~
100 ..,
60 ^b
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S~PGF ~
0 2 4 d 8 -10 12 14 16 18 20
X25- ~, ~ ~~ (s
Velocity in Feet/Sec
Maximum Stone Size for Riprap
Note: In determining channel velocities for stone linings and
revetments, use the following coefficients of roughness:
Diameter
(inches) ltnnning's
'n' Yin. Thickness
of Lining (inches)
Fine 3 0.031 9
Light 8 0.035 GD 0 3 ~] 12
]tedium 13 0.040 18
Heavy 23 0.044 30
Figure 8-6
Source: 'Bank and Chnnnei Lining Procedures, New York Department
of 'h~nnsportation, Division of Design and Construction, 1971.
8-12

N

~;
`'"'_ :Maximum Weight of
,~ Stone Required Minimum and Maximum Range
In Weight of Stones Weight Range of
75% of Stones
`~~ (Ibs) (Ibs) (Ibs
~~~ 150 25 - 150 50 - 150
200 25 - 200 50 - 200
250 25 - 250 50 - 250
%t
400 25 - 400 100 - 400

~~ 600 25 --600 150 - 600.
800 25 - 800 200 - 800

1, 000
~.
25 - 1, 000.
250 - 1, 000
1,300 25 - 1,300 325 - 1,300
"~`° 1,600 25 - 1,600 400 - 1,600
~~~~ 2,000 ~ 25 - 2,000 ~ 600 - 2,000
2,700 25 - 2;700. 800 - 2,700
Gradation- of Riprap
Figure 8 - 7
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~~ ~
~ ~'
~ ;~ ~ ~- >~
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Source : "Bank and Channel Lining Procedures, " New York Department
of Transportation, Division of Design and Construction, 1971.
8-13

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..~ CITY OF GREENSBORO STORM DRAINAGE DESIGN MANUAL
loon NOMOGRAPH FOR COMPUTING UIRED SIZE OF I
90o CIRCULAR CONCRETE PIPE, FLOWING FULL
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FLOW WITHIN A SYSTEM
2 Example: Given discharge Q = 4.4 cfs friction
factor rt = 0.012 slope of 0.0039 per ft.
Find: Diameter 15 inches and velocity of 3.5 it
per second, by following dashed line.
Nomograph adopted from Engineering Manual, War Department, Corps of
0.9 Engineers, Part X111, Chapter 1, June 1955.
January '07
9
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Page 62

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IY HEADWATER DEPTH FOR
HEADWATER SCALES 283 CONCRETE PIPE CULVERTS
6UREAU Of tw~Llf: troADD .,AaL tsu REVISED MAY 1964 WITH INLET CONTROL
Figure 4-1
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DcKalb County Manual ~-y

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PROJECT : ~~~r~~~~ 1t'i ,q~' C(JT PN ~Dl'(i~I' STATION ~~' ~S CULVERT DESfGN 1=4RM
S-~~(,Jarf I'` it I n~,p~t~ ~1G ~ " ~~ SHEET + I DESIGNER/OATS: ~~' / ~ . v'~`
OF
REVIEWER /DATE : I
HYDROLOGICAL DATA
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ELhd:{ (~Q
1fi)--~ ROADWAY ELEVATtON : ~~ (tt)
N ^ METH00: JCS
s
1° ^ DRAINAGE AREA:¢~_ ^ STREAM SLOPE:
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DESIGN FLOWS/TAILWATER ELi ~~' ~ I (tti FALL

R. 1. (YEARS) FLOW(cts)
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CULVERT DESCRIPTION: TOTAL
FLOW FLOW
P HEADWATER CALCULATIONS z z
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MATERIAL - SHAPE-SIZE-ENTRANCE ER
ARREL INLET CONTROL OUTLET CONTROL &; a m
COMMENTS
Q C!N HW(!D HWj FALL EL h} TW d dc`
0 hp h H EL ho ~ i ~
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TECHNICAL FOOTNOTES: (4) ELht= HWir EL((INVERT Of (6) hp=TW or (dcrD/2)(WHICHEVER IS C,R£ATER)
CI) USE OINK FOR BOX CULVERTS INLET CONTROISECTFON) (T} H=C• Nct (29 p2 L) /RL~ZV2/2q
i2) HW(/D • HW /0 OR HWt/D FROM DESIGN CHARTS (5} TW BASED ON DOWN STREAM (8I ELho= Elp ~ H • hp

I3) FALL= HWI -(ELhd- EL4f) ;FALL tS ZERO CONTROL OR FLOW DEPTH IN
CHANNEL.
FO CULVERTS ON GRAD
SUBSCRIPT DEFINITIONS : COMMENTS /DISCUSSION : CULVERT BARREL SELECTED
a. APPROXIMATE
f. CULVERT FACE
hA
DEStt-N HEADWATER
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hi. HEADWATER 1N INLET CONTROL t
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ho. HEADWATER IN OUTLET CONTROL
e. OUT ET~TROL SECTION Q ~ I G ~ ~ ~ I f , ~ e ~
I ~ ~ ~ ~~ ~ f d ~ I`
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~e SHAPE:
MATERIAL : ~~~ TM
sf. STREAMBED AT CULVERT FACE
4 WA l ~
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ENTRANCE:
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f~j
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0

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a
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TM 5-$~~D-4/AFM 88-5, Chap ~4
3
2
1
0
I
~ RANGE OF 0~ 0.40 TO 0.9 0
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~ ~ ~ ~ ~ ~ ~ ~ ~, ~ ~ I I I I I ~ l l l l
~ 10 20 30 50 RO 7o An on in

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~ISCHARGE-O-C//FS ~
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7
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6
5
F. O 100 200 300 400 500 600 700 B00 900 1000
~ DISCHARGE - Q -CFS
v
14
12
10
0
6
4
I DISCHARGE-Q-CFS
*NOTE: FOR VALUES OF d~ ABOVE
CURVE, USE a~ = D
PWEPARED By
BUREAU OF PUBLIC ROADS
Figure B-20. Circular pipe-critical depth.
B-29