20130135 Ver 1_More Info Received_20130325

1402 Cherry Drive-Wrl ingtron, NC
Stream Modification for Aerial Bridge Crossing
March 25,2013
Addendum 1-Ilistification of MpRap for Stream Armoring
From page 1, of the foregoing report, Q(100) is 448 cfs as per the NCDOTcalculatin method (which is
consistent with the Corps of EEngineers RSestimation), and is 2.15 times the estimated value for the
Q(10)value. Therefore, Q(10) is calculated to be 448 cfs/2.15, or 208 ds.
From the attached design aid, rbPO'rAmppen Channel CaNdifor the Q(10)typically through the
modified area(+/-�$� , the estimated stream velocity is on the order of 4.5 ft/sec..
From the attached design aid, 0 Zrn" Pa Sze of RpRap Required To Resist a oos s■C K-would
require a minimum D(30)stone size of J+-The proposed RpRap is a ass q w iize 4'wfo 99-,+;Vegetation
will be encouraged to re-establish within-0 voids.
Discussion: The aromoring of the stream banks with Class. �gRpRap is desirable and recommended to
provide for stabilization of the channel profile and expected to provide a high degree of dynamic
equilibrium.
Conclusion: Such placement of the proposed RpRap, along with the encouragement of volunteer
vegetation to establish itself within the interstitial voids should be of benefit, and not considered to
adversely affect the fN v �f overall dimension, pattern, profile, or performance.

Natural Open Channel Flow
version 1.08(Rev. 1/10)
Project: Q(10) RipRap Assessmt 2 1
Assisted by: @ Up Prop Line _ 1 .486 AR 3 S 2
Date: 3/24/2013 Q
n
Channel Slope (S): 0.006000 ft/ft
Manning's n: 0.040 assuming uniform stead flow
Flow Depth: 3.0 Ift
QuiE
Depth: 3.0 ftSurvey Data: ow (Q): 213.9 cfsElevation ft Distance ftelocity: 4.43 ft/sec101.3 40.0 ea (A): 48.3 sq.ft.100.2 60.0 ius (R): 1.9 ft
99.5 80.0
98.8 95.0 101.0
95.5 104.0
95.5 112.0 100.0
100.0 124.0
100.3 150.0
101.9 170.0 99.0
98.0
0
97.0
w
96.0
95.0
Distance (ft) 94.0
0.0 50.0 100.0 150.0 200.0
Notes: At UpStream Property Line of 1402 Cherry Drive
Pre Improvement to Stream; Mannings's "n" = 0.035
Q 100 =448 cfs; Q 10 =208 cfs
Note: To Convert to USGS Datum, add 525.47
TBM Top of Bridge Abutment= 100.0 Assumed= 625.47 USGS

APPROXIMATE SIZE OF RIPRAP REQUIRED TO RESIST MOVEMENT
METHOD#1 BASED ON CONDUIT OUTLET VELOCITY
KDOT 9
Standard L L
Gradationsrn w
Equivalent D
20 Diameter (ft 0.2 0.3 6.4 6.5 10.6 0.8 1.0 1.5 2.0 3.0 4.0i
I I I I I
12
I I a1 I I I
N 10 I 1 W I I
N1N� UNE
8 Example SCR
U
o
> 6
5
4
3 NOTE #5
I 1 1 I I I
I I I I I
2
Lb. 0.1 0.2 0.4 0.6 1 2 4 6 10 20 40 60 100 200 400 600 1000 2000 6000 Lb.
Weight of D. Stone
Example: A 15" pipe has an exit velocity of 7.2 fps with a tail water depth of 30" and channel slope
of 2%. Acceptable Riprap Size: D„=0.58', W =19lbs., KDOT Gradation=Light 18",
Max. Stress = (62.4)(2.5)(.02) = 3.2 psf < 5 psf O.K.
How to use this nomograph: METHOD#2 -MAX.SHEAR STRESS
Method #1 i,=yds
1. Find the exit velocity at the outlet.
2. Intersect with Turning Line. y =62.4pcf
3. Read top and bottom scales to determine approximate weight and size of stone. -
d-depth_of_tailwater_(ft)
4. Read top scale to determine KDOT gradation of stone. s=slope_at_exit_(ft1 ft)
5. Compare to see if design sizes meet or exceed the sizes
calculated by method 2 on this sheet. Allowable Shear Stress for
Method #2 KDOT Standard Gradations
1. Calculate Maximum Shear Stress (Using Table).
2. Compare Maximum Shear Stress to Allowable Shear Stress Heavy Series
from Table. Maximum shear stress must be equal or less than 4 Ton 27 psf
allowable stress or larger stone is required. 2 Ton 21 psf
General Notes: 1 Ton 16 psf
1. This nomograph allows the user to approximate the D5D stone 1/2 Ton 13 psf
size of rprop for conduit outlet protection based on the exit
velocity of the conduit. 1�4 Ton 1 0 pSf
2. This nomograph is based on Figure 2.3.12-6a, "Guide for
Estimating Stability of Channels and Large Rocks", KDOT Design Light Series
Manual, Volume III, Bridge Section. Light 24 6 psf
3. Conduit velocity as calculated by Manning's Equation. Light 18" 5 psf
4. Estimations based on this nomograph are only valid for
velocities between 5 fps and 15 fps. Outlets with higher
velocities should be investigated further. Stone for Ditch Lining
5. Riprap is not normally required for velocity below 5 f.p.s. 6" 3 psf
Consider grass lining materials. 5" 2 psf
KDOT Gradations are based on the stone specifications from the KDOT Standard Specifications for State
Road and Bridge Construction (1990) - * Table 12b Stone for Aggregate Ditch Lining, and ** Table 11
Stone for Riprap.