GRANV-004 Final Report

r
DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
LAKE ROGERS DAM
G RANV-004
GRANVILLE COUNTY, NC
PREPARED BY:
GEORGE ELLER, PE
2020

0
EXECUTIVE SUMMARY
A hydraulic capacity analysis was completed for the Lake Rogers Dam in Granville County, North
Carolina. The purpose of the study was to analyze the existing potential of the dams for
overtopping during predetermined specified rainfall events. The analyses were completed using
the United States Army Corps of Engineers developed software Hydrologic Engineering Center —
Hydrologic Modeling System (HEC-HMS) in combination with ArcGIS to develop required input
parameters. The rainfall events included in the analyses consist of 24-hour durations with return
periods of 25 years, 50 years, 100 years, 200 years, 500 years and 1000 years. Results of the
analyses indicate that this structure is not hydraulically adequate for all of the above rainfall
events. The dam was overtopped during these events by 2.2 — 4.7 feet. Data, input parameters
and final results can be found on the attached summary sheets and in the appendices of this
report as well as in the associated electronic file in which all program files are stored. The
elevation -storage calculation does not include the storage below the normal pool elevation for
this study. All elevations in this report are based on North American Vertical Datum of 1988

SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
LAKE ROGERS DAM, GRANV-004
ANALYSIS PERFORMED BY: GEORGE ELLER, PE, NC DAM SAFETY
24 HOUR - 1000 YEAR EVENT, 16.30 INCHES, MAX W.S. ELEVATION 287.8 (4.8 FT OVERTOPPED)
-------------------------------------------------
24 HOUR - 500 YEAR EVENT, 9.12 INCHES, MAX W.S. ELEVATION 287.3 (4.3 FT OVERTOPPED)
-------------------------------------------------
24 HOUR - 200 YEAR EVENT, 8.11 INCHES, MAX W.S. ELEVATION 286.6 (3.6 FT OVERTOPPED)
-------------------------------------------------
24 HOUR - 100 YEAR EVENT, 7.37 INCHES, MAX W.S. ELEVATION 286.1 (3.1 FT OVERTOPPED)
-------------------------------------------------
24 HOUR - 50 YEAR EVENT, 6.65 INCHES, MAX W.S. ELEVATION 285.7 (2.7 FT OVERTOPPED)
-------------------------------------------------
24 HOUR - 25 YEAR EVENT, 5.94 INCHES, MAX W.S. ELEVATION 285.2 (2.2 FT OVERTOPPED)
•' *F D41i FILFV4TI*U = 22RA FT ► e D::
SUMMARY OF INPUT PARAMETERS
Drainage Area (Sq. Mi.) = 17.6
Curve Number = 78.9
Lag Time (min.) = 174
Rainfall Distribution Methods = NRCS-NOAA
SPILLWAY
TYPE
Principal
Broad -crested weir
Orifices
3
(H = 2.1 ft, W=6.2, 4.7, 3.7 ft)
Emergency
Broad -crested weir
Auxiliary
Broad -crested weir
ELEVATION
STORAGE (ACRE -FT)
ELEVATION
270.0
0.0
284.0
279.0
0.5
285.0
280.0
50.6
286.0
281.0
216.5
287.0
282.0
402.8
288.0
283.0
619.5
289.0
NOT TO SCALE
ELEVATION (FT NAVD88)
279.6
279.6
280.6
283.5
STORAGE (ACRE -FT)
868.4
1,148.8
1,463.5
1,806.0
2,190.7
2,611.1
LAKE ROGERS DAM GRANV-004 May 12, 2020

APPENDIX A
Watershed Boundary

Lake Rogers Dam - GRANV-004 - Watershed Boundary
Drainage Area: 17.6 Square Miles
Flowpath Length: 48,507 Feet
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Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO,
0 0.75 1.5 3 Mlles USGS, FAO, NPS, NRCAN, GeoBase, IG_N, Kadaster NL, Ordnance
I I I I I I I I I Survey, Esri Japan, METI, Esri China (Hog Kong), (c) OpenStreetMap
contributors, and the GIs User Community

APPENDIX 6
Time of Concentration Calculation

Dam No: GRANV-004
Dam Name: Lake Rogers Dam
Maximum Potential Retention (inches): S = (1000/cn')-10
Time of Concentration (hours): Tc = 10.8*(S+1)0.7
1140*Y0-5
Basin Data:
Curve Number
Mean Basin Slope
Longest Flowpath:
Flow Length
Time of Concentration
Lag Time
Input Values in
yellow
CN = 78.9
from StreamStats
S = 2.67427 in.
Y = 6.4 %
from StreamStats
9.187 mi.
from StreamStats
I = 48507.4 ft.
Date: 11 /2/2018
Engineer: G. Eller
Tc = 4.83 Hours Tc = 290 mins
TL = 2.90 Hours TL = 174 mins

APPENDIX C
NRCS Curve Number Summary Sheet

Change CN according to TR-55 (see tables below)
HSG
Type A
Open Water
Developed, Open Space
Developed, Low Intensity
Developed, Medium Intensity
Developed, High Intensity
Barren Land
Deciduous Forest
Evergreen Forest
Mixed Forest
Shrub/Scrub
Herbaceuous
Hay/Pasture
Cultivated Crops
Woody Wetlands
Emergent Herbaceuous Wetlands
CN
0.0000 100 0
688985.8064 68 46851034.84
43281.3291 57 2467035.757
0.0000 77 0
0.0000 89 0
9958.8402 77 766830.697
1053564.012 36 37928304.45
1188682.6758 36 42792576.33
118100.5626 36 4251620.253
921774.8472 35 32262119.65
1304328.0110 50 65216400.55
1201619.841 49 58879372.19
0.0000 71 0
0.0000 80 0
0.0000 80 0
B CN C
163920.5350 100 16392053.5
3705970.5439 79 292771673
1585339.8710 72 114144470.7
266194.2757 85 22626513.43
19703.4454 92 1812716.976
0.0000 86 0
22455645.58 60 1347338735
7941189.3148 60 476471358.9
2570444.3133 60 154226658.8
1636378.3404 56 91637187.06
4743556.9880 71 336792546.1
8663431.811 69 597776795
84927.1631 80 6794173.047
256784.5463 85 21826686.44
0.0000 85 0
CN
D
CN
67170.5837
100
6717058.37
1294621.8752
100
1.29E+08
4208048.5268
86
361892173.3
23224414.9067
89
2.07E+09
1485522.6769
81
120327336.8
11132336.2889
86
9.57E+08
199962.5815
90
17996632.34
2045107.7106
92
1.88E+08
3622.7707
94
340540.4494
294261.2986
95
27954823
172448.9906
91
15692858.14
198725.9791
94
18680242
23825781.1
73
1739282020
105383039.9
79
8.33E+09
11003928.5787
73
803286786.2
61084611.5252
79
4.83E+09
3083665.6686
73
225107593.8
16299765.9731
79
1.29E+09
2493278.8401
70
174529518.8
17323841.2523
77
1.33E+09
9184133.1863
81
743914788.1
24893033.0210
89
2.22E+09
18492034.85
79
1460870753
49606236.34
84
4.17E+09
778091.1780
87
67693932.49
5728764.0411
90
5.16E+08
145873.0766
90
13128576.9
14797532.8696
95
1.41E+09
0.0000
90
0
336305.8388
95
31949055
NOTE: Curve Numbers are from SCS TR-55 with the exception of assumed HSG A (CN=60) for Herbaceous, Open Water, Woody Wetlands, and
Emergent Herbaceous Wetlands. Hydrologic Condition assumed as "Fair"
NOTE: double-check all the land types are being calculated and texts are accurate
NOTE: double-check the exported attribute table has the same table format as the "Export_Output" table
designed by dan.k
Weighted CN= 78.86

APPENDIX D
Hyetograph Results Used for Analyses

12.0
8.0
c
A
0
v
U
U
5 6.0
v
E
3
U
4.0
2.0
0.0 L
0
Hyetographs for 24-Hour Rainfall Distrubutions
2 4 6 8 10 12 14 16 18 20 22 24
Hours
25YR
50YR
100YR
200YR
500YR
1000YR

APPENDIX E
NOAA ATLAS 14 RAINFALL TABLE

Point precipitation frequency estimates (inches)
NOAA Atlas 14 Volume 2 Version 3
Data type: Precipitation depth
Time series type: Partial duration
Project area: Neuse River Basin
Location name (ESRI Maps): Creedmoor, NC, USA
Station Name: -
Latitude: 36.1300°
Longitude:-78.7050'
Elevation (USGS): 271.5 ft
PRECIPITATION FREQUENCY ESTIMATES
by duration
for ARI
(years):
1
2
5
10
25
50
100
200
500
1000
5-min:
0.406
0.474
0.542
0.606
0.671
0.721
0.765
0.804
0.847
0.885
10-min:
0.648
0.758
0.868
0.969
1.07
1.15
1.22
1.27
1.34
1.39
15-min :
0.81
0.953
1.1
1.23
1.36
1.45
1.54
1.61
1.69
1.75
30-min:
1.11
1.32
1.56
1.78
2.01
2.19
2.35
2.5
2.68
2.83
60-min:
1.38
1.65
2
2.31
2.67
2.97
3.24
3.51
3.85
4.14
2-hr:
1.64
1.96
2.4
2.8
3.28
3.69
4.09
4.49
5.02
5.48
3-hr:
1.75
2.09
2.56
3.01
3.56
4.03
4.5
4.99
5.64
6.22
6-hr:
2.09
2.51
3.08
3.62
4.3
4.91
5.51
6.14
7
7.78
12-hr:
2.47
2.95
3.64
4.32
5.17
5.94
6.72
7.56
8.72
9.78
24-hr:
2.9
3.51
4.37
5.041
5.94
6.65
7.37
8.11
9.12
9.91
2-day:
3.4
4.09
5.05
5.79
6.76
7.52
8.29
9.07
10.1
10.9
3-day:
3.59
4.31
5.31
6.08
7.1
7.91
8.73
9.56
10.7
11.6
4-day:
3.78
4.54
5.57
6.37
7.45
8.3
9.16
10
11.2
12.2
7-day:
4.37
5.2
6.31
7.18
8.35
9.27
10.2
11.2
12.5
13.5
10-day:
4.96
5.89
7.07
7.99
9.23
10.2
11.2
12.2
13.5
14.6
20-day:
6.6
7.79
9.19
10.3
11.9
13.1
14.3
15.5
17.2
18.6
30-day:
8.2
9.64
11.2
12.4
14
15.2
16.4
17.6
19.3
20.5
45-day:
10.4
12.2
14
15.3
17.1
18.5
19.9
21.2
23
24.4
60-day:
12.5
14.6
16.5
17.9
19.7
21.1
22.4
23.7
25.4
26.6
Date/time (GMT): Thu Apr 12 15:23:41 2018
pyRunTime: 0.040568113327

APPENDIX F
Outlet Works Rating Curves

Lake Rogers Dam, GRANV-004
Primary Spillway: Broad -crested Weir (279.6 ft NAVD88, 2.7 ft thick, 31.0 ft wide)
Emergency Spillway: Concrete broad -crested weir (280.6 ft NAVD88, 11.4 ft thick, 28.4 ft wide)
Auxiliary Spillway: Concrete broad -crested weir (283.4 ft NAVD88, 11.4 ft thick, 28.4 ft wide)
Orifice 1: Concrete Orifice (279.6 ft NAVD88 invert, 6.2 ft width, 2.1 ft height)
Orifice 2: Concrete Orifice (279.6 ft NAVD88 invert, 4.7 ft width, 2.1 ft height)
Orifice 3: Concrete Orifice (279.6 ft NAVD88 invert, 3.7 ft width, 2.1 ft height)
Top of Dam : 283.0 (Low Point) ft NAVD88
Normal Pool : 279.6 ft NAVD88
SPILLWAY ASSESSMENT
RWS Elevation
(ft NAVD88)
Primary
Spillway
Discharge (cfs)
Orifice Spillway Discharge (cfs)
Emergency
Spillway
Discharge (cfs)
Auxiliary
Spillway
Discharge (cfs)
Total Structure
Discharge (cfs)
1
2
3
279.6
0
0
0
0
0
0
0
279.8
9
2
1
1
0
0
13
280.0
24
5
4
3
0
0
35
280.2
45
9
7
5
0
0
65
280.4
69
13
10
8
0
0
100
280.6
96
19
14
11
0
0
140
280.8
126
24
19
15
7
0
191
281.0
159
31
23
18
20
0
252
281.2
194
38
29
22
37
0
320
281.4
232
45
34
27
57
0
395
281.6
272
53
40
31
80
0
475
281.8
314
78
59
47
105
0
603
282.0
357
85
64
51
132
0
689
282.2
403
91
69
54
161
0
778
282.4
450
97
73
58
192
0
870
282.6
499
102
77
61
225
0
965
282.8
550
107
81
64
259
0
1062
283.0
602
112
85
67
296
0
1162
283.2
656
117
89
70
333
0
1265
283.4
712
121
92
72
373
0
1370
283.6
769
126
95
75
413
2
1480
283.8
827
130
98
77
455
10
1598
284.0
887
134
101
80
499
21
1722
284.2
948
138
104
82
543
35
1850
284.4
1011
142
107
85
589
51
1984
284.6
1074
145
110
87
636
68
2121
284.8
1140
149
113
89
684
88
2263
285.0
1206
153
116
91
734
109
2408
285.2
1274
156
118
93
785
131
2557
285.4
1342
159
121
95
836
155
2709
285.6
1412
163
123
97
889
180
2865
285.8
1484
166
126
99
943
207
3024
286.0
1556
169
128
101
998
234
3186
286.2
1629
172
131
103
1054
263
3352
286.4
1704
175
133
105
1111
292
3520
286.6
1780
178
135
106
1169
323
3692
286.8
1857
181
137
108
1228
355
3866
287.0
1935
184
140
110
1287
388
4044
287.2
2013
187
142
112
1348
421
4224
287.4
2093
190
144
113
1410
456
4407
287.6
2174
193
146
115
1473
492
4593
287.8
1 2257
1 196
148
117
1536
1 528
1 4781
288.0
1 2340
1 198
150
118
1601
1 565
1 4973

289
288
287
286
00 285
a
z
284
C
O
> 283
N
w
cn
� 282
281
Primary Spillway Orifice 1
Spillway Discharge Capacity
1,500 2,000 2,500 3,000
Spillway Discharge (cfs)
Orifice 2 Orifice 3 Emergency Spillway
3,500 4,000 4,500 5,000
Auxiliary Spillway Total Structure