RANDO-003 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)
COLONIAL CTR CLUB DAM LOWER
RANDO-003
RANDOLPH COUNTY, NC
PREPARED BY:
WOOD E&I Solutions
2020
EXECUTIVE SUMMARY
A hydraulic capacity analysis was completed for the Colonial Ctr. Club Dam Lower in Randolph
County, North Carolina. The purpose of the study was to analyze the existing potential of the dam
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 Arc-GIS 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 hydraulically adequate for 25 years,
50 years, 100 years, 200 years, 500 years, and 1000 years rainfall events. 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.
Drainage Area (Sq. Mi.) =
Curve Number =
Lag Time (min.) =
Rainfall Distribution Methods =
0.39
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
COLONIAL CTR. CLUB DAM LOWER, RANDO‐003
ANALYSIS PERFORMED BY: E.OKORIE, WOOD
TOP OF DAM ELEVATION = 840
24 HOUR ‐ 1000 YEAR EVENT, 9.82 INCHES, ELEVATION 836.4 (3.6 FT FREE‐BOARD)
24 HOUR ‐ 500 YEAR EVENT, 9.03 INCHES, ELEVATION 835.8 (4.2 FT FREE‐BOARD)
24 HOUR ‐ 200 YEAR EVENT, 8.02 INCHES, ELEVATION 835.1 (4.9 FT FREE‐BOARD)
24 HOUR ‐ 100 YEAR EVENT, 7.29 INCHES, ELEVATION 834.6 (5.4 FT FREE‐BOARD)
24 HOUR ‐ 50 YEAR EVENT, 6.57 INCHES, ELEVATION 834.1 (5.9 FT FREE‐BOARD)
24 HOUR ‐ 25 YEAR EVENT, 5.86 INCHES, ELEVATION 833.6 (6.4 FT FREE‐BOARD)
SUMMARY OF INPUT PARAMETERS
74.18
39
SCS Type 2
SPILLWAY
Principal
TYPE
3x24‐inch Culvert Pipe
ELEVATION
832.0
STORAGE (ACRE‐FT)
0.0
6.6
13.4
831
NA
ELEVATION
831.0
831.5
Auxiliary NONE
832.5
833.0
833.5
834.0
834.5
59.2
835.5
836.0
836.5
837.0
835.0
20.4
27.7
35.1
42.8
50.9
67.8
76.5
85.5
94.6
104.0
843.0
843.5
ELEVATION
838.5
839.0
839.5
840.0
840.5 166.6
841.0
841.5
842.0
842.5
STORAGE (ACRE‐FT)
123.6
133.9
144.5
155.4
241.4
844.0
844.5
845.0
178.3
190.2
202.6
215.2
228.2
255.0
268.8
282.8
NOT TO SCALE
113.7
837.5
838.0
COLONIAL CTR. CLUB DAM LOWER RANDO‐003 SEPTEMBER 18, 2020

APPENDIX A
Watershed Boundary

Sources: Esri, HERE, Garmin, USGS, Intermap, INCREMENT P,
NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea,
Esri (Thailand), NGCC, (c) OpenStreetMap contributors, and the
GIS User Community
Colonial Ctr. Club Dam Lower - Watershed Boundary
Legend
LongestFlowPath
Watershed Boundary
0 0.15 0.30.075 Miles
Date: 9/9/2020
/Drainage Area: 0.390 Square Miles
Flowpath Length: 1.28 Miles

APPENDIX B
Lag Time Calculation

Dam No: RANDO-003 Date: 7/15/2020
Dam Name: Colonial Ctr. Club Dam Engineer: E.Okorie
Maximum Potential Retention (inches):S = (1000/cn')-10
Time of Concentration (hours):Tc =l0.8*(S+1)0.7
1140*Y0.5
Basin Data:Input Values in yellow
Curve Number CN = 74.18
S =3.48072 in.
Mean Basin Slope Y = 7.12 %
Longest Flowpath: 1.2758 mi.
Flow Length l =6736.22 ft.
Time of Concentration Tc =1.09 Hours Tc =65 mins
Lag Time TL =0.65 Hours TL =39 mins

APPENDIX C
NRCS Curve Number Summary Sheet

Change CN according to TR-55 (see tables below)
NLCD (2016) Landuse TR-55 Landuse HSG A (sq. ft.)CN HSG B (sq. ft.)CN HSG C (sq. ft.)CN HSG D (sq. ft.)CN
Open Water Not Available 2974 100 297378 0 100 0 1021855 100 102185497 0 100 0
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)151253 49 7411391 2142349 69 147822049 2542645 79 200868978 296249 84 24884934
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 17878 57 1019043 362966 72 26133533 524552 81 42488713 0 86 0
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 72177 85 6135043 12437 90 1119349 0 92 0
Developed, High Intensity Urban districts - Commercial and business 0 89 0 21093 92 1940576 0 94 0 9686 95 920187
Barren Land Newly graded areas 0 77 0 0 86 0 0 91 0 0 94 0
Deciduous Forest Woods - Fair 655803 36 23608907 927689 60 55661322 657050 73 47964663 196689 79 15538416
Evergreen Forest Woods - Fair 2168 36 78046 0 60 0 26891 73 1963013 0 79 0
Mixed Forest Woods - Fair 0 36 0 17440 60 1046375 0 73 0 30991 79 2448317
Shrub/Scrub Brush - Fair 0 35 0 0 56 0 0 70 0 0 77 0
Herbaceuous Herbaceuous - Fair 0 60 0 0 71 0 19372 81 1569161 0 89 0
Hay/Pasture Pasture - Fair 1334 49 65356 195811 69 13510949 110241 79 8709013 63585 84 5341152
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 547523 80 43801862 0 87 0 256270 90 23064283
Woody Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0
Emergent Herbaceuous Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0 Weighted CN=74.18
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.
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
APPENDIX D
Hyetograph Results Used for Analyses
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Cumulative Depth (in)Time (hrs)
Hyetographs for 24-Hour SCS Type II Rainfall Distributions
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: Ohio River Basin
Location name (ESRI Maps): Thomasville, North Carolina USA
Station Name: -
Latitude: 35.8784°
Longitude: -80.0383°
Elevation (USGS): None None
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.387 0.459 0.535 0.585 0.639 0.672 0.701 0.723 0.744 0.756
10-min:0.618 0.734 0.857 0.936 1.02 1.07 1.11 1.15 1.18 1.19
15-min:0.773 0.923 1.08 1.18 1.29 1.36 1.41 1.45 1.48 1.5
30-min:1.06 1.28 1.54 1.72 1.91 2.04 2.16 2.25 2.36 2.42
60-min:1.32 1.6 1.97 2.23 2.54 2.77 2.97 3.16 3.38 3.54
2-hr:1.55 1.89 2.34 2.67 3.09 3.39 3.69 3.97 4.33 4.58
3-hr:1.66 2.02 2.51 2.87 3.33 3.68 4.01 4.34 4.76 5.06
6-hr:2.02 2.44 3.04 3.49 4.09 4.55 5.01 5.47 6.09 6.56
12-hr:2.4 2.9 3.62 4.2 4.97 5.59 6.22 6.87 7.77 8.48
24-hr:2.85 3.45 4.3 4.96 5.86 6.57 7.29 8.02 9.03 9.82
2-day:3.33 4 4.95 5.67 6.64 7.39 8.15 8.93 9.98 10.8
3-day:3.53 4.23 5.22 5.97 6.99 7.79 8.6 9.42 10.5 11.4
4-day:3.72 4.46 5.48 6.27 7.34 8.18 9.04 9.92 11.1 12
7-day:4.26 5.07 6.15 7 8.15 9.06 9.98 10.9 12.2 13.2
10-day:4.84 5.74 6.89 7.79 9.01 9.96 10.9 11.9 13.2 14.3
20-day:6.5 7.66 9.05 10.2 11.7 12.9 14.1 15.3 17 18.3
30-day:8.03 9.45 11 12.1 13.7 14.9 16.1 17.3 18.9 20.1
45-day:10.1 11.8 13.5 14.9 16.6 17.9 19.2 20.6 22.3 23.6
60-day:12.1 14.1 15.9 17.3 19.1 20.4 21.7 23 24.6 25.8
Date/time (GMT): Mon Jun 22 16:04:32 2020
pyRunTime: 0.0164189338684
APPENDIX F
Outlet Works Rating Curves
Total outlet discharge from the spillway systemClient: NCEM Date: 9/3/2020Project: Overtopping Study Engineer: E.OkorieDam: Colonial Country Dam Dam No. RANDO-003Reservior Water Level (RWS) Elevation (ft)Primary spillway discharge (cfs)(from HydroCAD)Total discharge from the spillway system (cfs)831.0 0.0 0.0831.5 4.6 4.6832.0 16.6 16.6832.5 32.6 32.6833.0 46.3 46.3833.6 56.5 56.5834.1 65.1 65.1834.6 72.8 72.8835.1 79.6 79.6835.6 86.0 86.0836.1 91.9 91.9836.6 97.4 97.4837.1 102.7 102.7837.6 107.7 107.7838.1 112.5 112.5838.7 117.0 117.0839.2 121.4 121.4839.7 125.7 125.7840.2 129.8 129.8840.7 133.8 133.8841.2 137.6 137.6841.7 141.4 141.4842.2 145.1 145.1842.7 148.7 148.7843.2 152.1 152.1843.8 155.6 155.6844.3 158.9 158.9844.8 162.2 162.20.020.040.060.080.0100.0120.0140.0160.0180.0830.0 832.0 834.0 836.0 838.0 840.0 842.0 844.0 846.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)The whole spillway system rating curve (cfs)