HomeMy WebLinkAbout1.11 Existing Drainage & Flood Hazard Report
Existing Drainage and Flood Hazard Report
SPRING VALLEY RANCH PUD
December 16, 2022
Revised: November 12, 2024
Spring Valley - Drainage Exhibit December 2022
2022-22
Table of Contents
1.0 General ................................................................................................................................ 2
1.1 Preliminary Plan Drainage Report .................................................................................. 2
1.2 FEMA FIRMette ............................................................................................................. 2
2.0 Hydrology ........................................................................................................................... 3
2.1 Drainage Basin Areas ..................................................................................................... 3
2.2 Rainfall ............................................................................................................................ 3
2.3 Hydrologic Curve Numbers ............................................................................................ 3
2.4 Times of Concentration................................................................................................... 3
2.5 Peak Discharges .............................................................................................................. 3
3.0 Pre-Development Hydrologic Results ................................................................................ 3
4.0 Hopkins Dam Analysis ....................................................................................................... 4
5.0 Post Developed Water Quality and Storage ........................................................................ 5
Appendix A – Pre-Development Drainage Map ............................................................................. 7
Appendix B – Precipitation Data .................................................................................................... 8
Appendix C –Pre-Development Drainage Results ......................................................................... 9
Appendix D – Prior Studies and Dam Certifications .................................................................... 10
Appendix E – 25 Year Runoff Storage Exhibit ............................................................................ 11
Appendix F – SCS Storage Hydrographs ..................................................................................... 12
2022-22
1.0 General
The Spring Valley P.U.D site is located approximately 5 miles east of the City of Glenwood
Springs, with drainage basins covering roughly 6,245 acres. The major tributary of the property
is the Roaring Fork River basin. A small portion of the property along the northern boundary is
tributary to the Colorado River through Glenwood Canyon. The property is accessed via Garfield
County Road 114. Much of the northern boundary of the property borders the White River
National Forest, and a majority of the western boundary of the property borders Bureau of Land
Management (BLM) property. The site is bordered by private lands along the southern and
eastern boundaries. The majority of the site is currently vacant and undeveloped.
The purpose of this report is to quantify existing drainage flows of the 100-year storm event
scenario for the Spring Valley Ranch P.U.D.
1.1 Preliminary Plan Drainage Report
Gamba & Associates, Inc. (G&A) previously prepared a drainage study for this property, dated
December 21, 2000. The study was prepared for the PUD/Subdivision development plan
currently approved for the property. An updated drainage study was done by G&A, dated March
9, 2007, to reflect proposed development plan revisions.
1.2 FEMA FIRMette
A search for Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map
(FIRM) was conducted. Tiles 0802051460B and 0802051500B dated 1977 had no data and cover
most of our site. Tile 0802051470B dated 1986 shows the southern boundary of our site but
defines the zone as undetermined but possible flood hazard.
Figure 1: Vicinity Map (Spring Valley P.U.D. in yellow)
2022-22
2.0 Hydrology
The drainage basin areas were analyzed for the 100-year storm events in the predeveloped
conditions. Peak flows for all 18 predeveloped drainage basins were calculated for the 100-year
storm event using the Soil Conservation Service (SCS) TR55 tool and the Autodesk Hydraflow
Hydrographs program. Table 1 below summarizes the factors affecting peak flows for each
individual basin.
2.1 Drainage Basin Areas
For our analysis, 18 separate primary tributary drainage basins were delineated using existing
ground topography and AutoCAD flowline tools. The pre-development drainage basins
developed and analyzed are shown on the Pre-Development Drainage Map (Appendix A).
2.2 Rainfall
Rainfall intensities were derived from the NOAA Atlas 14 Point Precipitation Frequency
Estimates for the site location, included in Appendix B.
2.3 Hydrologic Curve Numbers
Curve Numbers (CN) are a measure of how easily water flows over the surface of a given
material. The higher the CN, the more easily water flows over that surface. The previous
predevelopment drainage report done for this site included detailed information on curve number
calculations – detailing surface conditions, areas, and appropriated weighting used to calculate
the CNs in their study. For the purposes of analyzing the pre-development conditions, the curve
numbers derived in this previous study were utilized.
2.4 Times of Concentration
The time of concentration for each basin is calculated based on the type of flow, and the length,
grade, roughness, and geometry of the flow path of the overland flow from the hydraulically
most distant point in the basin to the outfall point. To determine time of concentration for each
basin, first each basins’ flowline path was defined using existing ground topography and
categorizing each flow path into three types of flow – sheet flow, shallow concentrated flow, and
channel flow. Once each basins' flowlines were defined, they were input into TR55 which
calculates time of concentration. Time of concentration calculations for all basins are included in
Appendix C.
2.5 Peak Discharges
Peak flows were calculated for the 100-year storm event in the undeveloped condition of the site
by use of the SCS Runoff Curve Number method, the TR55 program and the Autodesk
Hydraflow Hydrographs program. Once times of concentration were calculated by use of TR55,
they are input to Hydraflow to calculate time to peak, and peak flow rate. Time to peak, peak
flow rates, and hydrograph reports for all basins are included in Appendix C.
3.0 Pre‐Development Hydrologic Results
The Auto CAD Civil 3D Hydraflow, Hydrograph and Hydrological tools were used along with
the SCS method to determine the peak flows. Curve Numbers and TR55 tools were used to
account for the effect on drainage from different landscaping and building materials.
2022-22
Table 1 outlines the inputs and outputs of our analyses. Additionally, a comprehensive report of
our analyses can be found in Appendix C.
Basin Area (Acres) SCS Curve
Number
TR55 Time of
Concentration (min)
Time to Peak
(hours)
Peak Flow (cfs)
A 1616.75 64 62.7 12.67 214.18
B 167.09 63 36.4 12.33 27.82
C 65.22 68 23.3 12.13 28.86
D 104.8 69 33.8 12.30 37.18
E 198.4 61 38.2 12.40 22.44
F 80 57 20.3 12.30 5.05
G 302.5 59 23.8 12.23 29.28
H 209.12 69 26.6 12.17 93.15
I 117.17 69 33.9 12.30 41.57
J-1 1648 66 105.8 13.20 194.19
J-2 678.15 67 57.2 12.53 140.70
K 87 62 38 12.37 11.69
L 193.07 68 44.2 12.40 51.69
M 292 70 64.5 12.60 73.68
N 94.09 68 31.2 12.27 32.29
O 108.07 67 48.9 12.43 24.59
P-1 228.65 62 30.3 12.30 34.83
P-2 54.57 63 16.9 12.13 13.95
Table 3: 100-year Peak Flow Calculations for each drainage basin
Existing basins peak flow were calculated for the 100-year event while all future infrastructure,
including pipes, culverts, and detention structures, will be sized to safely convey the 25-year
storm event away from the proposed homes and other structures.
4.0 Hopkins Dam Analysis
The property has a dam and reservoir that was recently improved in 2019-2020. The reservoir is
called Hopkins Reservoir. In June 2021, the Division of Water Resources performed a Dam
Safety Inspection on the Hopkins Reservoir Dam (Appendix D). They inspected a variety of
components of the dam to determine the conditions and safe storage levels. All components
2022-22
inspected were determined to be in good condition, and the overall determination of the dam’s
condition was found to be satisfactory. This reservoir overflows into Landis Creek that flow
through the property.
Wright Water Engineers, Inc. (WWE) performed a Dam Break Analysis October of 2007 for the
Hopkins Reservoir Dam (Appendix D). WWE assessed the effects of dam failure with respect to
the proposed development and its effect on drainage on the site. The potential hazard area
resulting from the failure of Hopkins Dam, WWE determined, is limited to three distinguishable
reaches between Hopkins Reservoir and Spring Valley: 1) The existing natural channel,
approximately 700 feet long between Hopkins Reservoir and its junction on the left bank of
Landis Creek. This is a steep, relatively undefined intermittent drainage channel. 2) The
approximately 3-mile-long reach of Landis Creek beginning at the terminus of Reach 1 and
ending at County Road 115. A steep, incised channel characterizes this portion of Landis Creek.
3) The area between County Road 115 and the Spring Valley bottom. This reach represents the
alluvial fan created by Landis Creek as it merges with Spring Valley.
WWE evaluated a "sunny day" scenario as the failure event of the Hopkins Dam, which assumes
a sudden breach of the dam embankment and does not add additional flows resulting from
extreme precipitation events to the dam breach hydrograph. For the purposes of their study,
WWE assumed "worst case" scenarios for the development of the dam breach hydrograph: 1)
The failure mechanism is breaching of the dam embankment. 2) The final breach height extends
downward from the crest to the toe of the dam embankment, effectively draining the entire
reservoir storage volume. 3) The reservoir stage is at full capacity at the time the breach begins
to form. The inundation areas from this report have been added to the drainage exhibit
(Appendix A).
February of 2022, Zancanella & Associates prepared a Dam Inundation Inspection Impact
Review of the previous study done by WWE (Appendix D). They found that the flood inundation
wave is not anticipated to impact current structures significantly more than current conditions,
nor get to the point of potential for loss of life with the improvements, but the emergency access
road (High Grange Pass Rd) will be impacted to the point of possible failure. No structure that is
habitable should be located within the inundation boundary unless additional review and analysis
has taken place to ensure no loss of life or significant property damage will occur during a sunny
day dam break. Additionally, the Hopkins Dam Certificate of Acceptance for the recent dam
reconstruction project is included for reference in the report (Appendix D).
5.0 Post Developed Water Quality and Storage
Post developed runoff conditions were analyzed for the Spring Valley PUD using the SCS
method and TR-55 software and AutoCAD Civil 3D hydraulic analysis tools and programs.
Existing pre-developed drainage basins were maintained for this analysis as points of
concentration for each basin is not anticipated to change. SCS curve numbers were updated for
each basin based on impervious areas. In the case of this study, proposed roadways are the only
impervious improvements in each basin, 94 acres in total for the PUD. Each proposed lot in the
PUD will be required to capture and treat stormwater to a historic rate, due to this, on property
improvements were not accounted for in this study.
2022-22
The 25-year storm was used per Garfield County storage requirements for each basin. The
proposed runoff volumes and peak flows were calculated and analyzed against pre-developed
historic runoff rates to determine the storage volume required for each basin. The results are
presented in Appendix E and Appendix F at the end of this report. Due to the size of some of the
drainage basins, the proposed impervious areas were insignificant compared to the overall size of
the basin creating no increase in the weighted curve number. In return, there is no storage
required for the basin. As design for the project is further developed, sub-basins can be
developed and analyzed that may result in more precise results and storage requirements
throughout the PUD.
Proposed treatment for impervious roadway areas will follow typical practices and temporary
and permanent best management practices for treating stormwater. Roadside swales and ditches
are proposed to be vegetated, armoring the soil and slowing the velocity of stormwater
preventing erosion. Road cross culverts will be implemented in frequencies to prevent large
volumes of stormwater from concentrating and re-introducing storm flows on the downhill side
of the roads and back to a sheet flow condition. Culvert inlets and outlets will be armored to
prevent erosion and disperse energy on the outlet side of the culvert.
2022-22
Appendix A – Pre-Development Drainage Map
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2022-22
Appendix B – Precipitation Data
NOAA Atlas 14 Data
2022-22
Appendix C –Pre-Development Drainage Results
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 1
Pre - Dev Basin A
Hydrograph type = SCS Runoff Peak discharge = 214.18 cfs
Storm frequency = 100 yrs Time to peak = 12.67 hrs
Time interval = 2 min Hyd. volume = 2,294,455 cuft
Drainage area = 1616.750 ac Curve number = 64
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 62.70 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
1
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
30.00 30.00
60.00 60.00
90.00 90.00
120.00 120.00
150.00 150.00
180.00 180.00
210.00 210.00
240.00 240.00
Q (cfs)
Time (hrs)
Pre - Dev Basin A
Hyd. No. 1 -- 100 Year
Hyd No. 1
TR55 Tc Worksheet 2
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 1
Pre - Dev Basin A
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 1.80 0.00 0.00
Travel Time (min) = 34.87 + 0.00 + 0.00 = 34.87
Shallow Concentrated Flow
Flow length (ft) = 6814.00 0.00 0.00
Watercourse slope (%) = 21.70 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.52 0.00 0.00
Travel Time (min) = 15.11 + 0.00 + 0.00 = 15.11
Channel Flow
X sectional flow area (sqft) = 4.00 0.00 0.00
Wetted perimeter (ft) = 5.66 0.00 0.00
Channel slope (%) = 7.80 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =10.99
0.00
0.00
Flow length (ft) ({0})8400.0 0.0 0.0
Travel Time (min) = 12.74 + 0.00 + 0.00 = 12.74
Total Travel Time, Tc .............................................................................. 62.70 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 2
Pre - Dev Basin B
Hydrograph type = SCS Runoff Peak discharge = 27.82 cfs
Storm frequency = 100 yrs Time to peak = 12.33 hrs
Time interval = 2 min Hyd. volume = 213,465 cuft
Drainage area = 167.090 ac Curve number = 63
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 36.40 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
3
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (hrs)
Pre - Dev Basin B
Hyd. No. 2 -- 100 Year
Hyd No. 2
TR55 Tc Worksheet 4
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 2
Pre - Dev Basin B
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 6.20 0.00 0.00
Travel Time (min) = 21.26 + 0.00 + 0.00 = 21.26
Shallow Concentrated Flow
Flow length (ft) = 2405.00 0.00 0.00
Watercourse slope (%) = 22.30 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.62 0.00 0.00
Travel Time (min) = 5.26 + 0.00 + 0.00 = 5.26
Channel Flow
X sectional flow area (sqft) = 0.25 0.00 0.00
Wetted perimeter (ft) = 1.15 0.00 0.00
Channel slope (%) = 12.50 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =6.32
0.00
0.00
Flow length (ft) ({0})3760.0 0.0 0.0
Travel Time (min) = 9.92 + 0.00 + 0.00 = 9.92
Total Travel Time, Tc .............................................................................. 36.40 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 3
Pre - Dev Basin C
Hydrograph type = SCS Runoff Peak discharge = 28.86 cfs
Storm frequency = 100 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 128,007 cuft
Drainage area = 65.220 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 23.30 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
5
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
Q (cfs)
Time (hrs)
Pre - Dev Basin C
Hyd. No. 3 -- 100 Year
Hyd No. 3
TR55 Tc Worksheet 6
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 3
Pre - Dev Basin C
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 16.00 0.00 0.00
Travel Time (min) = 14.55 + 0.00 + 0.00 = 14.55
Shallow Concentrated Flow
Flow length (ft) = 2385.00 0.00 0.00
Watercourse slope (%) = 22.20 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.60 0.00 0.00
Travel Time (min) = 5.23 + 0.00 + 0.00 = 5.23
Channel Flow
X sectional flow area (sqft) = 0.30 0.00 0.00
Wetted perimeter (ft) = 1.60 0.00 0.00
Channel slope (%) = 8.20 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =4.63
0.00
0.00
Flow length (ft) ({0})977.0 0.0 0.0
Travel Time (min) = 3.51 + 0.00 + 0.00 = 3.51
Total Travel Time, Tc .............................................................................. 23.30 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 4
Pre - Dev Basin D
Hydrograph type = SCS Runoff Peak discharge = 37.18 cfs
Storm frequency = 100 yrs Time to peak = 12.30 hrs
Time interval = 2 min Hyd. volume = 214,568 cuft
Drainage area = 104.800 ac Curve number = 69
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 33.80 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
7
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
Q (cfs)
Time (hrs)
Pre - Dev Basin D
Hyd. No. 4 -- 100 Year
Hyd No. 4
TR55 Tc Worksheet 8
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 4
Pre - Dev Basin D
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 5.10 0.00 0.00
Travel Time (min) = 22.99 + 0.00 + 0.00 = 22.99
Shallow Concentrated Flow
Flow length (ft) = 3181.00 0.00 0.00
Watercourse slope (%) = 13.10 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =5.84 0.00 0.00
Travel Time (min) = 9.08 + 0.00 + 0.00 = 9.08
Channel Flow
X sectional flow area (sqft) = 0.56 0.00 0.00
Wetted perimeter (ft) = 2.12 0.00 0.00
Channel slope (%) = 16.20 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =8.19
0.00
0.00
Flow length (ft) ({0})866.0 0.0 0.0
Travel Time (min) = 1.76 + 0.00 + 0.00 = 1.76
Total Travel Time, Tc .............................................................................. 33.80 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 5
Pre - Dev Basin E
Hydrograph type = SCS Runoff Peak discharge = 22.44 cfs
Storm frequency = 100 yrs Time to peak = 12.40 hrs
Time interval = 2 min Hyd. volume = 212,928 cuft
Drainage area = 198.400 ac Curve number = 61
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 38.20 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
9
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
Q (cfs)
Time (hrs)
Pre - Dev Basin E
Hyd. No. 5 -- 100 Year
Hyd No. 5
TR55 Tc Worksheet 10
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 5
Pre - Dev Basin E
Description A B C Totals
Sheet Flow
Manning's n-value = 0.240 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 2.00 0.00 0.00
Travel Time (min) = 22.22 + 0.00 + 0.00 = 22.22
Shallow Concentrated Flow
Flow length (ft) = 2982.00 0.00 0.00
Watercourse slope (%) = 6.00 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =3.95 0.00 0.00
Travel Time (min) = 12.58 + 0.00 + 0.00 = 12.58
Channel Flow
X sectional flow area (sqft) = 8.70 0.00 0.00
Wetted perimeter (ft) = 8.70 0.00 0.00
Channel slope (%) = 3.70 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =9.55
0.00
0.00
Flow length (ft) ({0})1963.0 0.0 0.0
Travel Time (min) = 3.42 + 0.00 + 0.00 = 3.42
Total Travel Time, Tc .............................................................................. 38.20 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 6
Pre - Dev Basin F
Hydrograph type = SCS Runoff Peak discharge = 5.046 cfs
Storm frequency = 100 yrs Time to peak = 12.30 hrs
Time interval = 2 min Hyd. volume = 56,430 cuft
Drainage area = 80.000 ac Curve number = 57
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 20.30 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
11
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
Q (cfs)
Time (hrs)
Pre - Dev Basin F
Hyd. No. 6 -- 100 Year
Hyd No. 6
TR55 Tc Worksheet 12
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 6
Pre - Dev Basin F
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 10.20 0.00 0.00
Travel Time (min) = 17.42 + 0.00 + 0.00 = 17.42
Shallow Concentrated Flow
Flow length (ft) = 1355.00 0.00 0.00
Watercourse slope (%) = 24.00 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.90 0.00 0.00
Travel Time (min) = 2.86 + 0.00 + 0.00 = 2.86
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 20.30 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 7
Pre - Dev Basin G
Hydrograph type = SCS Runoff Peak discharge = 29.28 cfs
Storm frequency = 100 yrs Time to peak = 12.23 hrs
Time interval = 2 min Hyd. volume = 259,989 cuft
Drainage area = 302.500 ac Curve number = 59
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 23.80 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
13
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
Q (cfs)
Time (hrs)
Pre - Dev Basin G
Hyd. No. 7 -- 100 Year
Hyd No. 7
TR55 Tc Worksheet 14
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 7
Pre - Dev Basin G
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 15.40 0.00 0.00
Travel Time (min) = 14.78 + 0.00 + 0.00 = 14.78
Shallow Concentrated Flow
Flow length (ft) = 2969.00 0.00 0.00
Watercourse slope (%) = 27.80 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =8.51 0.00 0.00
Travel Time (min) = 5.82 + 0.00 + 0.00 = 5.82
Channel Flow
X sectional flow area (sqft) = 11.40 0.00 0.00
Wetted perimeter (ft) = 11.70 0.00 0.00
Channel slope (%) = 12.10 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =16.98
0.00
0.00
Flow length (ft) ({0})3298.0 0.0 0.0
Travel Time (min) = 3.24 + 0.00 + 0.00 = 3.24
Total Travel Time, Tc .............................................................................. 23.80 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 8
Pre - Dev Basin H
Hydrograph type = SCS Runoff Peak discharge = 93.15 cfs
Storm frequency = 100 yrs Time to peak = 12.17 hrs
Time interval = 2 min Hyd. volume = 426,308 cuft
Drainage area = 209.120 ac Curve number = 69
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 26.60 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
15
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
60.00 60.00
70.00 70.00
80.00 80.00
90.00 90.00
100.00 100.00
Q (cfs)
Time (hrs)
Pre - Dev Basin H
Hyd. No. 8 -- 100 Year
Hyd No. 8
TR55 Tc Worksheet 16
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 8
Pre - Dev Basin H
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 25.00 0.00 0.00
Travel Time (min) = 12.17 + 0.00 + 0.00 = 12.17
Shallow Concentrated Flow
Flow length (ft) = 4754.00 0.00 0.00
Watercourse slope (%) = 15.80 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =6.41 0.00 0.00
Travel Time (min) = 12.35 + 0.00 + 0.00 = 12.35
Channel Flow
X sectional flow area (sqft) = 0.56 0.00 0.00
Wetted perimeter (ft) = 2.12 0.00 0.00
Channel slope (%) = 10.80 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =6.69
0.00
0.00
Flow length (ft) ({0})831.0 0.0 0.0
Travel Time (min) = 2.07 + 0.00 + 0.00 = 2.07
Total Travel Time, Tc .............................................................................. 26.60 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 9
Pre - Dev Basin I
Hydrograph type = SCS Runoff Peak discharge = 41.57 cfs
Storm frequency = 100 yrs Time to peak = 12.30 hrs
Time interval = 2 min Hyd. volume = 239,894 cuft
Drainage area = 117.170 ac Curve number = 69
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 33.90 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
17
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
Q (cfs)
Time (hrs)
Pre - Dev Basin I
Hyd. No. 9 -- 100 Year
Hyd No. 9
TR55 Tc Worksheet 18
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 9
Pre - Dev Basin I
Description A B C Totals
Sheet Flow
Manning's n-value = 0.240 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 0.91 0.00 0.00
Travel Time (min) = 30.44 + 0.00 + 0.00 = 30.44
Shallow Concentrated Flow
Flow length (ft) = 1567.00 0.00 0.00
Watercourse slope (%) = 22.50 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.65 0.00 0.00
Travel Time (min) = 3.41 + 0.00 + 0.00 = 3.41
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 33.90 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 10
Pre - Dev Basin J1
Hydrograph type = SCS Runoff Peak discharge = 194.19 cfs
Storm frequency = 100 yrs Time to peak = 13.20 hrs
Time interval = 2 min Hyd. volume = 2,722,290 cuft
Drainage area = 1648.000 ac Curve number = 66
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 105.80 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
19
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Q (cfs)
0.00 0.00
30.00 30.00
60.00 60.00
90.00 90.00
120.00 120.00
150.00 150.00
180.00 180.00
210.00 210.00
Q (cfs)
Time (hrs)
Pre - Dev Basin J1
Hyd. No. 10 -- 100 Year
Hyd No. 10
TR55 Tc Worksheet 20
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 10
Pre - Dev Basin J1
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 1.00 0.00 0.00
Travel Time (min) = 44.12 + 0.00 + 0.00 = 44.12
Shallow Concentrated Flow
Flow length (ft) = 3206.00 0.00 0.00
Watercourse slope (%) = 1.80 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =2.16 0.00 0.00
Travel Time (min) = 24.68 + 0.00 + 0.00 = 24.68
Channel Flow
X sectional flow area (sqft) = 4.30 0.00 0.00
Wetted perimeter (ft) = 10.00 0.00 0.00
Channel slope (%) = 10.70 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =9.23
0.00
0.00
Flow length (ft) ({0})20476.0 0.0 0.0
Travel Time (min) = 36.98 + 0.00 + 0.00 = 36.98
Total Travel Time, Tc .............................................................................. 105.80 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 11
Pre - Dev Basin J2
Hydrograph type = SCS Runoff Peak discharge = 140.70 cfs
Storm frequency = 100 yrs Time to peak = 12.53 hrs
Time interval = 2 min Hyd. volume = 1,205,520 cuft
Drainage area = 678.150 ac Curve number = 67
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 57.20 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
21
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
20.00 20.00
40.00 40.00
60.00 60.00
80.00 80.00
100.00 100.00
120.00 120.00
140.00 140.00
160.00 160.00
Q (cfs)
Time (hrs)
Pre - Dev Basin J2
Hyd. No. 11 -- 100 Year
Hyd No. 11
TR55 Tc Worksheet 22
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 11
Pre - Dev Basin J2
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 88.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 2.20 0.00 0.00
Travel Time (min) = 29.06 + 0.00 + 0.00 = 29.06
Shallow Concentrated Flow
Flow length (ft) = 3122.00 0.00 0.00
Watercourse slope (%) = 22.20 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.60 0.00 0.00
Travel Time (min) = 6.84 + 0.00 + 0.00 = 6.84
Channel Flow
X sectional flow area (sqft) = 2.00 0.00 0.00
Wetted perimeter (ft) = 6.30 0.00 0.00
Channel slope (%) = 11.20 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =7.71
0.00
0.00
Flow length (ft) ({0})9863.0 0.0 0.0
Travel Time (min) = 21.33 + 0.00 + 0.00 = 21.33
Total Travel Time, Tc .............................................................................. 57.20 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 12
Pre - Dev Basin K
Hydrograph type = SCS Runoff Peak discharge = 11.69 cfs
Storm frequency = 100 yrs Time to peak = 12.37 hrs
Time interval = 2 min Hyd. volume = 102,744 cuft
Drainage area = 87.000 ac Curve number = 62
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 38.00 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
23
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Pre - Dev Basin K
Hyd. No. 12 -- 100 Year
Hyd No. 12
TR55 Tc Worksheet 24
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 12
Pre - Dev Basin K
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 2.00 0.00 0.00
Travel Time (min) = 33.43 + 0.00 + 0.00 = 33.43
Shallow Concentrated Flow
Flow length (ft) = 2139.00 0.00 0.00
Watercourse slope (%) = 23.50 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.82 0.00 0.00
Travel Time (min) = 4.56 + 0.00 + 0.00 = 4.56
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 38.00 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 13
Pre - Dev Basin L
Hydrograph type = SCS Runoff Peak discharge = 51.69 cfs
Storm frequency = 100 yrs Time to peak = 12.40 hrs
Time interval = 2 min Hyd. volume = 368,966 cuft
Drainage area = 193.070 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 44.20 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
25
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
60.00 60.00
Q (cfs)
Time (hrs)
Pre - Dev Basin L
Hyd. No. 13 -- 100 Year
Hyd No. 13
TR55 Tc Worksheet 26
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 13
Pre - Dev Basin L
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 104.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 2.00 0.00 0.00
Travel Time (min) = 34.50 + 0.00 + 0.00 = 34.50
Shallow Concentrated Flow
Flow length (ft) = 257.00 0.00 0.00
Watercourse slope (%) = 6.10 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =3.98 0.00 0.00
Travel Time (min) = 1.07 + 0.00 + 0.00 = 1.07
Channel Flow
X sectional flow area (sqft) = 9.00 6.50 0.00
Wetted perimeter (ft) = 12.50 13.00 0.00
Channel slope (%) = 12.34 11.14 0.00
Manning's n-value = 0.030 0.030 0.015
Velocity (ft/s) =14.00
10.42
0.00
Flow length (ft) ({0})1620.0 4204.0 0.0
Travel Time (min) = 1.93 + 6.73 + 0.00 = 8.65
Total Travel Time, Tc .............................................................................. 44.20 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 14
Pre - Dev Basin M
Hydrograph type = SCS Runoff Peak discharge = 73.68 cfs
Storm frequency = 100 yrs Time to peak = 12.60 hrs
Time interval = 2 min Hyd. volume = 643,900 cuft
Drainage area = 292.000 ac Curve number = 70
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 64.50 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
27
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
60.00 60.00
70.00 70.00
80.00 80.00
Q (cfs)
Time (hrs)
Pre - Dev Basin M
Hyd. No. 14 -- 100 Year
Hyd No. 14
TR55 Tc Worksheet 28
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 14
Pre - Dev Basin M
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 94.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 1.00 0.00 0.00
Travel Time (min) = 41.99 + 0.00 + 0.00 = 41.99
Shallow Concentrated Flow
Flow length (ft) = 1062.00 0.00 0.00
Watercourse slope (%) = 8.40 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =4.68 0.00 0.00
Travel Time (min) = 3.79 + 0.00 + 0.00 = 3.79
Channel Flow
X sectional flow area (sqft) = 1.60 0.00 0.00
Wetted perimeter (ft) = 20.70 0.00 0.00
Channel slope (%) = 14.90 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =3.45
0.00
0.00
Flow length (ft) ({0})3885.0 0.0 0.0
Travel Time (min) = 18.77 + 0.00 + 0.00 = 18.77
Total Travel Time, Tc .............................................................................. 64.50 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 15
Pre - Dev Basin N
Hydrograph type = SCS Runoff Peak discharge = 32.29 cfs
Storm frequency = 100 yrs Time to peak = 12.27 hrs
Time interval = 2 min Hyd. volume = 183,698 cuft
Drainage area = 94.090 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 31.20 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
29
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
35.00 35.00
Q (cfs)
Time (hrs)
Pre - Dev Basin N
Hyd. No. 15 -- 100 Year
Hyd No. 15
TR55 Tc Worksheet 30
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 15
Pre - Dev Basin N
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 98.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 5.30 0.00 0.00
Travel Time (min) = 22.28 + 0.00 + 0.00 = 22.28
Shallow Concentrated Flow
Flow length (ft) = 1084.00 1290.00 0.00
Watercourse slope (%) = 3.00 30.00 0.00
Surface description = Unpaved Unpaved Paved
Average velocity (ft/s) =2.79 8.84 0.00
Travel Time (min) = 6.46 + 2.43 + 0.00 = 8.90
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 31.20 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 16
Pre - Dev Basin O
Hydrograph type = SCS Runoff Peak discharge = 24.59 cfs
Storm frequency = 100 yrs Time to peak = 12.43 hrs
Time interval = 2 min Hyd. volume = 193,535 cuft
Drainage area = 108.070 ac Curve number = 67
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 48.90 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
31
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (hrs)
Pre - Dev Basin O
Hyd. No. 16 -- 100 Year
Hyd No. 16
TR55 Tc Worksheet 32
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 16
Pre - Dev Basin O
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 1.36 0.00 0.00
Travel Time (min) = 39.01 + 0.00 + 0.00 = 39.01
Shallow Concentrated Flow
Flow length (ft) = 2180.00 0.00 0.00
Watercourse slope (%) = 8.34 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =4.66 0.00 0.00
Travel Time (min) = 7.80 + 0.00 + 0.00 = 7.80
Channel Flow
X sectional flow area (sqft) = 1.00 0.00 0.00
Wetted perimeter (ft) = 3.00 0.00 0.00
Channel slope (%) = 16.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =19.03
0.00
0.00
Flow length (ft) ({0})2340.0 0.0 0.0
Travel Time (min) = 2.05 + 0.00 + 0.00 = 2.05
Total Travel Time, Tc .............................................................................. 48.90 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 17
Pre - Dev Basin P1
Hydrograph type = SCS Runoff Peak discharge = 34.83 cfs
Storm frequency = 100 yrs Time to peak = 12.30 hrs
Time interval = 2 min Hyd. volume = 273,402 cuft
Drainage area = 228.650 ac Curve number = 62
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 30.30 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
33
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
35.00 35.00
Q (cfs)
Time (hrs)
Pre - Dev Basin P1
Hyd. No. 17 -- 100 Year
Hyd No. 17
TR55 Tc Worksheet 34
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 17
Pre - Dev Basin P1
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 85.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 22.20 0.00 0.00
Travel Time (min) = 11.21 + 0.00 + 0.00 = 11.21
Shallow Concentrated Flow
Flow length (ft) = 524.00 0.00 0.00
Watercourse slope (%) = 17.30 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =6.71 0.00 0.00
Travel Time (min) = 1.30 + 0.00 + 0.00 = 1.30
Channel Flow
X sectional flow area (sqft) = 1.10 0.00 0.00
Wetted perimeter (ft) = 4.70 0.00 0.00
Channel slope (%) = 8.88 0.00 0.00
Manning's n-value = 0.030 0.015 0.015
Velocity (ft/s) =5.59
0.00
0.00
Flow length (ft) ({0})5978.0 0.0 0.0
Travel Time (min) = 17.81 + 0.00 + 0.00 = 17.81
Total Travel Time, Tc .............................................................................. 30.30 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Wednesday, 12 / 14 / 2022
Hyd. No. 18
Pre - Dev Basin P2
Hydrograph type = SCS Runoff Peak discharge = 13.95 cfs
Storm frequency = 100 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 70,517 cuft
Drainage area = 54.570 ac Curve number = 63
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.90 min
Total precip. = 2.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
35
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
14.00 14.00
Q (cfs)
Time (hrs)
Pre - Dev Basin P2
Hyd. No. 18 -- 100 Year
Hyd No. 18
TR55 Tc Worksheet 36
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 18
Pre - Dev Basin P2
Description A B C Totals
Sheet Flow
Manning's n-value = 0.150 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.32 0.00 0.00
Land slope (%) = 8.70 0.00 0.00
Travel Time (min) = 8.47 + 0.00 + 0.00 = 8.47
Shallow Concentrated Flow
Flow length (ft) = 2405.00 0.00 0.00
Watercourse slope (%) = 8.70 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =4.76 0.00 0.00
Travel Time (min) = 8.42 + 0.00 + 0.00 = 8.42
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 16.90 min
2022-22
Appendix D – Prior Studies and Dam Certifications
Final Acceptance of Construction, Colorado DWR, 2022
Engineer's Inspection Report, Colorado DWR, 2021
Hopkins Dam Inundation Mapping, Zancanella & Associates, 2022
Hopkins Reservoir Dam Break Analysis, Wright Water Engineers, 2007
Dam Safety Branch
202 Center Drive, Glenwood Springs, CO 81601 P 303.518.1829 https://dwr.colorado.gov
Jared S. Polis, Governor | Dan Gibbs, DNR Executive Director | Kevin G. Rein, Director/State Engineer
June 22, 2021
SUBJECT: 2021 Engineer’s Inspection Report
Dear Mr. Van Ardenne,
On June 21, 2021, representatives from our dam safety office completed inspection of
Hopkins Dam in accordance with Section 37-87-107 of the Colorado Revised Statutes; which
assigns to the State Engineer’s Office (SEO) responsibility for determining safe storage levels
for all reservoirs in the State of Colorado. I would like to thank Mr. Matt Weisbrod of
Zancanella & Associates for taking time to participate in the 2021 inspection.
Enclosed is a copy of the Engineer’s Inspection Report (EIR) and field photographs of the
referenced dam for your files. Please sign the signature block on page 4 of the EIR to
acknowledge your receipt of the report and return a copy to our office via electronic or regular
mail. If you have any questions regarding this EIR or require assistance with dam safety related
issues, please feel free to contact me on my cell phone at (303) 518-1829.
Sincerely,
Korey J. Kadrmas, P.E.,
Division 5 Dam Safety Engineer
Enc. a/s
ec: Bill McCormick, Chief, Dam Safety Branch
Heather Ramsey, Water Commissioner
James Heath, Division Engineer, Division 5
Matt Weisbrod, Zancanella & Associates; mweisbrod@za-engineering.com
Doreen Herriott, Spring Valley Holdings; daherriott@gmail.com
Mr. Martin Van Ardenne
Seligman Group
500 Montgomery St., 40th Floor
San Francisco, California 94111
via email: mvanardenne@seligmangroup.com
When replying, please refer to:
HOPKINS DAM, DAMID 380113
Water Division 5, Water District 38
ENGINEER'S INSPECTION REPORT
OFFICE OF THE STATE ENGINEER - DIVISION OF WATER RESOURCES - DAM SAFETY BRANCH 1313 SHERMAN STREET, ROOM 818, DENVER, CO 80203, (303) 866-3581
INSPECTION PARTY :
FIELD
CONDITIONS
OBSERVED
WATER LEVEL:
GROUND MOISTURE CONDITION:
BELOW DAM CREST FT. FT. GAGE ROD READING
DRY WET SNOWCOVER OTHER
DIRECTIONS:MARK AN X FOR CONDITIONS FOUND AND UNDERLINE WORDS THAT APPLY
DAM NAME:HOPKINS
DAM ID:380113
CURRENT RESTRICTION: -- NONE --
DAM HEIGHT(FT):25.0
DAM LENGTH(FT):700.0
CRESTWIDTH(FT):15.0
CLASS:Significant hazard
EAP:11/10/2019
DATE OF INSPECTION:6/21/2021
DIV:5 WD:38
15060S0880W
Matt Weisbrod Heather Ramsey Korey Kadrmas
SPILLWAY WIDTH(FT):20.0
FREEBOARD (FT):6.0
T:
OWNER:SELIGMAN GROUP
ADDRESS:600 MONTGOMERY ST. CONTACT NAME:DOREEN HERRIOTT
CONTACT PHONE:(970) 945-6478X
YRCompl:2020
S:R: COUNTY:GARFIELD
CRESTELEV(FT):9001.0
SPILLWAY CAPACITY(CFS):700.0
DRAINAGE AREA (AC.):350.0
NORMAL STORAGE (AF):113.0
SURFACE AREA(AC):12.0
OUTLET INSPECTED:8/27/2020
2.5
SAN FRANCISCO CA 94111
REPRESENTING :Zancanella & Associates - Owner Rep Water Commissioner CO Dam Safety Branch
Below Spillway
INSPECTOR:KJK
5/28/2008PREVIOUS INSPECTION:
OWNER REP.:MARTIN VAN ARDENNE
PROBLEMS NOTED:(0)NONE (1)RIPRAP - (2) WAVE EROSION -
(3) CRACKS (4) SINKHOLE (5) APPEARS TOO STEEP (6) (7) SLIDES
(8) CONCRETE FACING - (9) OTHER
OBSERVATIONS:
The upstream slope is in good condition with uniform riprap coverage. Locally sourced riprap is well graded with larger boulders placed at toe
to key in riprap on slope. Minor areas of observed riprap bedding gravel below rock. No observed areas of surface rilling or erosion along the
groins or toe area; however, reservoir level is low and did not achieve the first hold elevation for the first fill plan.
REQUIRED ACTIONS:
None.
Refer to Photos #1 to #4
MISSING, SPARSE, DISPLACED, WEATHERED WITH SCARPS
WITH DISPLACEMENT DEPRESSIONS OR BULGES
HOLES, CRACKS, DISPLACED, UNDERMINED
UPSTREAM SLOPE
PoorAcceptableGoodXCONDITIONS OBSERVED:
PROBLEMS NOTED:(10) NONE (11 (12) EROSION (13) CRACKS - (14) SINKHOLES
(15) NOT WIDE ENOUGH (16) LOW AREA (17) MISALIGNMENT (18) IMPROPER SURFACE DRAINAGE (19) OTHER
OBSERVATIONS:
The dam crest is in good condition with even base course across the full extent to the crest. Crest has positive drainage toward the reservoir.
REQUIRED ACTIONS:
None.
Refer to Photos #5 and #6
RUTS OR PUDDLES WITH DISPLACEMENT
CREST
PoorAcceptableGoodXCONDITIONS OBSERVED:
PROBLEMS NOTED:(20) NONE (21) LIVESTOCK DAMAGE (22) (23) CRACKS - (24) SINKHOLE
(25) APPEARS TOO STEEP (26) (27) SLIDE (28) SOFT AREAS (29) OTHER
OBSERVATIONS:
The downstream slope is in good condition with uniform slope and slowly developing grass coverage. Currently, some native grasses have
established on the slope, but Engineer noted that seeding occurred in Fall 2020 and may take 1 to 2 seasons to established adequate
coverage. This item is under construction warranty and will be evaluated again in 2022. No observed areas of erosion or rilling along the
slope. Slope appears to be stable. A low lying area at the downstream toe along the spillway channel right berm was observed to have a
thicker establishment of grasses. Based on low reservoir levels, grasses in this area likely thicker since backfill had a high quantity of clay and
this area was graded as a bowl feature and likely retains water lower than other portion of the reseeded areas.
REQUIRED ACTIONS:
None.
Refer to Photos #7 to #10
EROSION OR GULLIES WITH DISPLACEMENT
DEPRESSIONS OR BULGES
DOWNSTREAM SLOPE
PoorAcceptableGoodXCONDITIONS OBSERVED:
Page 1 of 5
ENGINEER'S INSPECTION REPORT 6/21/2021DATE.
DAM NAME:HOPKINS DAM I.D.:380113
PROBLEMS NOTED:(30) NONE (31) SATURATED EMBANKMENT AREA
(39) OTHER
(32) SEEPAGE EXITS ON EMBANKMENT
(33) SEEPAGE EXITS AT POINT SOURCE (34) SEEPAGE AREA AT TOE (35) FLOW ADJACENT TO OUTLET (36) SEEPAGE
(37) FLOW (38) DRAINDRAIN OUTFALLS SEEN No Yes
Show location of drains on sketch and indicate
amount and quality of discharge.
OBSERVATION
The Engineer estimates the reservoir reached a maximum pool of about El. 8980.5 feet this season; corresponding to a stage of about 4.5 feet
(24 foot max). This pool level was below the first hold level (El. 8985) required in the Initial Fill and Monitoring Plan dated March 2021. No
seepage discharge as observed from the drain outfalls during this inspection or previous site visits by the Engineer. The initial fill and
monitoring plan should continue to be followed during the 2022 fill season. The low lying area near the right spillway berm with thicker grass
coverage noted in the DOWNSTREAM SLOPE section should be monitored during higher reservoir levels for possible seepage.
REQUIRED ACTIONS:
(1) Monitor low lying area with thicker grass coverage at the downstream toe along the spillway right berm for possible seepage.
Refer to Photo #11
INCREASED /MUDDY
INCREASED /MUDDY DRY /OBSTRUCTED
SEEPAGE
PoorAcceptableGoodXCONDITIONS OBSERVED:
PROBLEMS NOTED:(40) NONE
(49) OTHER
(41) NO OUTLET FOUND (42) POOR OPERATING ACCESS (43) INOPERABLE
(44) (45) OUTLET OPERATED DURING INSPECTION
(120) NO (121)YES (46) CONDUIT (47) JOINTS DISPLACED (48) VALVE LEAKAGEINTERIOR INSPECTED
NOYES
Riprap mounded d/s of outfall. Minor bank erosion
OBSERVATION
The outlet works consists of a concrete encased, 12-inch-diameter HDPE pipe with intake structure and outfall impact basin. The visible
portions of the outlet were generally in good condition with negligible gate leakage. The gate has been operated several times this year with no
issues. The gate was successfully exercised during this site visit. The gate operator and concrete block were in good operating condition.
Riprap downstream of the outfall structure was mounded beyond the end sill resulting in deflection of the flow at higher rates to the sides of
the riprap apron. Engineer noted that a swale (i.e., belly) will be graded in the riprap from the outfall to improve conveying of flows downstream
of the structure. There appears to be minor bank erosion within the backwater pool to the right of the outfall structure.
REQUIRED ACTIONS:
(1) Provide a swale or low flow channel within the riprap apron downstream of the outlet structure. Provide riprap along the toe of the dam in
the vicinity of the outfall structure to mitigate any bank erosion due to outlet discharge (e.g., armor bank within the backwater pool to the right
of the outlet.
Refer to Photos #12 to #18
STRUCTURE DETERIORATEDUPSTREAMORDOWNSTREAM
DETERIORATED OR COLLAPSED
OUTLET
PoorAcceptableGoodXCONDITIONS OBSERVED:
PROBLEMS NOTED:(50) NONE
(59) OTHER
(51) NO EMERGENCY SPILLWAY FOUND (52) EROSION (53) CRACK -
(54) APPEARS TO BE STRUCTURALLY INADEQUATE (55) APPEARS TOO SMALL (56) INADEQUATE FREEBOARD (57) FLOW OBSTRUCTED
(58) CONCRETE
OBSERVATIONS:
The emergency spillway consists of a riprap lined channel with buried concrete control crest, rock lined chute with a lower concrete cutoff
wall, and a small rock plunge pool. Concrete structure were in good condition with no observed cracks. Spillway has not operated.
REQUIRED ACTIONS:
None.
Refer to Photos #19 to #22
WITH BACKCUTTING WITH DISPLACEMENT
DETERIORATED /UNDERMINED
SPILLWAY
PoorAcceptableGoodXCONDITIONS OBSERVED:
Page 2 of 5
ENGINEER'S INSPECTION REPORT 6/21/2021DATE.
DAM NAME:HOPKINS DAM I.D.:380113
EXISTING INSTRUMENTATION FOUND (110) NONE (111) GAGE ROD (112) PIEZOMETERS (113) SEEPAGE
(114) SURVEY MONUMENTS (115) OTHER
(116) NOMONITORING OF INSTRUMENTATION PERIODIC INSPECTIONS BY: (118) OWNER(117) YES (119) ENGINEER
Station Markers
OBSERVATIONS:
Monitoring instruments consist of a reservoir staff gage integral to the air vent/gate stem encasement, four (4) piezometers, embankment
movement/settlement monuments, one sand blanket, outlet filter diaphragm drain, toe drains on both sides of the outlet pipe, and station
markers (every 100 feet).
The reservoir staff gage is integral to the air vent/gate stem concrete encasement along the upstream slope and consists of embedded steel
plates with elevation markings. The piezometers include three located along the dam crest and one located along the maximum section near
mid-downstream slope. The toe drain outfalls are integrated into the outlet outfall structure. The outlet filter diaphragm outfall is located to the
right of the outfall structure and daylights from the downstream toe of the dam (no headwall).
Owner/Engineer to provide an annual monitoring report with an update on the status of the initial fill per approved plans at the end of the
irrigation season for our office to review. Engineer collects monitoring data during each trip to the dam (about 2 times per month); which is in
conformance with Rule 13.4.1.1. However, due to low reservoir level and lack of water availability this season our office agreed with the
Engineer that only monthly monitoring is required for remainder of this season unless the reservoir fills from a large precipitation event.
Movement monuments are to be surveyed annually for the first 5 years after construction in accordance with Rule 13.4.2.1. Engineer plans to
schedule survey later this summer. Reservoir not likely to fill this season baring a large rainfall event due to draining in Spring for
maintenance and early runoff season. Also, reservoir max fill level under approved Initial Fill and Monitoring Plan (Plan) has been around El.
8980.5. The monitored initial fill of the reservoir will continue next Spring.
REQUIRED ACTIONS:
(1) Continue to follow monitoring and reporting requirements as documented in the Initial Fill and Monitoring Plan and agreed upon by SEO
and owner. Submit collected monitoring data in an annual monitoring report to our office at the end of the irrigation season. Include monument
survey in the annual monitoring report.
Refer to Photos #23 to #25
WEIRS FLUMES/
MONITORING
PoorAcceptableGoodXCONDITIONS OBSERVED:
PROBLEMS NOTED:
(66) DETERIORATED CONCRETE -
(68) OTHER
(60 NONE (62) LIVESTOCK DAMAGE
(63) BRUSH ON
(61) ACCESS ROAD NEEDS MAINTENANCE
(64) TREES ON
(65) RODENT ACTIVITY ON
(67) GATE AND OPERATING MECHANISM NEED MAINTENANCE
OBSERVATIONS:
Hopkins Dam was recently reconstructed (2020) and vegetated coverage is establishing in an effective manner on the downstream slope and
toe areas. The dam crest is well graded. Currently there is no need for vegetation control or animal abatement plans; however, our office
encourages the owner to start planning for woody vegetation removal via cut or spray and addressing animal burrows when present as these
are annual maintenance items are typical for most dams. The ow ner is commended on reconstructing the dam and providing the necessary
O&M and Engineering oversight.
REQUIRED ACTIONS:
None at this time; however, our office recommends to start planning for annual vegetation control (i.e., woody plant removal) and animal
abatement (i.e., filling animal burrows).
UPSTREAM SLOPE, CREST, DOWNSTREAM SLOPE, TOE UPSTREAM SLOPE, CREST, DOWNSTREAM SLOPE, TOE
UPSTREAM SLOPE, CREST, DOWNSTREAM SLOPE, TOE FACING, OUTLET SPILLWAY
MAINTENANCE AND REPAIRS
PoorAcceptableXGoodCONDITIONS OBSERVED:
Go to next page for Overall Conditions and Items Requiring Actions
Page 3 of 5
ENGINEER'S INSPECTION REPORT 6/21/2021DATE.
DAM NAME:HOPKINS DAM I.D.:380113
Based on this Safety Inspection and recent file review, the overall condition is determined to be:
(71) SATISFACTORY (72) CONDITIONALLY SATISFACTORY (73) UNSATISFACTORY
Hopkins Dam is assigned a SATISFACTORY rating on the basis that the dam has performed well under initial filling; however, requires
continued inspection and monitoring in accordance with the approved Initial Fill and Monitoring Plan until full storage is achieved to maintain
a satisfactory rating. The owner is commended for its efforts to rehabilitate the dam and continued monitoring of this dam. Monitoring data
collected by the owner/Engineer under the requirements of the Initial Fill and Monitoring Plan should be submittal as an annual report to our
office for record purposes. Perform an annual review of the EAP and updated accordingly. Our office will provide recent EAP contact updates
to the Engineer as a redline PDF. The Engineer to update the EAP document and distribute the revised EAP to all plan holders. Please note
that email distribution of the EAP is acceptable. Our office would be happy to assist with this effort so please don't hesitate to contact us.
OVERALL CONDITIONS
(101) FULL STORAGE
(102) CONDITIONAL FULL STORAGE
(103) RECOMMENDED RESTRICTION {FT. BELOW DAM CREST
FT. BELOW SPILLWAY CREST
FT. GAGE HEIGHT
NO STORAGE-MAINTAIN OUTLET FULLY OPEN
ACTIONS REQUIRED FOR CONDITIONAL FULL STORAGE OR CONTINUED STORAGE AT THE RESTRICTED LEVEL:
Engineer's
Signature INSPECTED BY
Owner's
Signature OWNER/OWNER'S REPRESENTATIVE DATE:
Continued inspection and monitoring in accordance with the approved Initial Fill and Monitoring Plan until full storage is achieved and performance
of the dam deemed to be acceptable.
(104) CONTINUE EXISTING RESTRICTION
REASON FOR RESTRICTION
ITEMS REQUIRING ACTION BY OWNER TO IMPROVE THE SAFETY OF THE DAM
SAFE STORAGE LEVEL: RECOMMENDED AS A RESULT OF THIS INSPECTION
The State Engineer, by providing this dam safety inspection report, does not assume responsibility for any unsafe condition of the subject dam. The sole
responsibility for the safety of this dam rests with the reservoir owner or operator, who should take every step necessary to prevent damages caused by
leakage or overflow of waters from the reservoir or floods resulting from a failure of the dam.
MAINTENANCE - ORDINARY REPAIR - MONITORING
EXERCISE THE OUTLET GATE THROUGH A FULL CYCLE ON AN ANNUAL BASIS.
LUBRICATE AND OPERATE OUTLET GATES THROUGH FULL CYCLE
6/21/2021 -
MONITOR FOR WOODY VEGETATION ON ALL ASPECTS OF THE DAM AND REMOVE VIA CUT, SPRAY, OR PULL
WHEN OBSERVED (LIKLEY AN ANUALLY MAINTENANCE ITEM). CURRENTLY NO SIGN OF WOODY VEGETATION.
CLEAR TREES AND/OR BRUSH FROM
6/21/2021 -
MONITOR ANIMAL BURROW ACTIVITY AND IMPLEMENT AN ABATEMENT PROGRAM IF CONDITIONS WORSEN.
CURRENTLY NO ACTIVITY WAS OBSERVED.
INITIATE RODENT CONTROL PROGRAM AND PROPERLY BACKFILL EXISTING HOLES
6/21/2021 -
MONITOR LOW LYING AREA WITH THICKER GRASS COVERAGE AT THE DOWNSTREAM TOE ALONG THE
SPILLWAY RIGHT BERM FOR POSSIBLE SEEPAGE.
MONITOR
6/21/2021 -
MONITOR EROSION RILLING ON ALL ASPECTS OF THE DAM AS GRASS COVERAGE IS ESTABLISHING. IF
CONDITIONS WORSEN, PLACE COMPACTED FILL AND SEED TO REVEGETATE THE BARE AREAS.
MONITOR
6/21/2021 -
CONTINUE TO FOLLOW MONITORING AND REPORTING REQUIREMENTS AS DOCUMENTED IN THE INITIAL FILL
AND MONITORING PLAN AND AGREED UPON BY SEO AND OWNER. SUBMIT COLLECTED MONITORING DATA IN
AN ANNUAL MONITORING REPORT TO OUR OFFICE AT THE END OF THE IRRIGATION SEASON. INCLUDE
MONUMENT SURVEY IN THE ANNUAL MONITORING REPORT.
MONITOR
6/21/2021 -
PROVIDE A SWALE OR LOW FLOW CHANNEL WITHIN THE RIPRAP APRON DOWNSTREAM OF THE OUTLET
STRUCTURE. PROVIDE RIPRAP ALONG THE TOE OF THE DAM IN THE VICINITY OF THE OUTFALL STRUCTURE TO
MITIGATE ANY BANK EROSION DUE TO OUTLET DISCHARGE (E.G., ARMOR BANK WITHIN THE BACKWATER POOL
TO THE RIGHT OF THE OUTLET.
OTHER
6/21/2021 -
EMERGENCY ACTION PLAN
ENGINEER TO PERFORM ANNUAL REVIEW AND UPDATE OF THE EAP AND DISTRIBUTE TO ALL PLAN HOLDERS.
UPDATE EXISTING EMERGENCY ACTION PLAN
6/21/2021 -
Page 4 of 5
07 07 21
ENGINEER'S INSPECTION REPORT 6/21/2021DATE.
DAM NAME:HOPKINS DAM I.D.:380113
GUIDELINES FOR DETERMINING CONDITIONS
CONDITIONS OBSERVED - APPLIES TO UPSTREAM SLOPE, CREST, DOWNSTREAM SLOPE, OUTLET, SPILLWAY
GOOD
In general, this part of the structure has a near new
appearance, and conditions observed in this area do not
appear to threaten the safety of the dam.
ACCEPTABLE
Although general cross-section is maintained, surfaces
may be irregular, eroded, rutted, spalled, or otherwise not
in new condition. Conditions in this area do not currently
appear to threaten the safety of the dam.
POOR
Conditions observed in this area appear to threaten the
safety of the dam.
CONDITIONS OBSERVED - APPLIES TO SEEPAGE
GOOD
No evidence of uncontrolled seepage. No unexplained
increase in flows from designed drains. All seepage is
clear. Seepage conditions do not appear to threaten the
safety of the dam.
ACCEPTABLE
Some seepage exists at areas other than the drain
outfalls, or other designed drains. No unexplained
increase in seepage. All seepage is clear. Seepage
conditions observed do not currently appear to threaten
the safety of the dam.
POOR
Seepage conditions observed appear to threaten the
safety of the dam. Examples:
1) Designed drain or seepage flows have increased
without increase in reservoir level.
2) Drain or seepage flows contain sediment, i.e., muddy
water or particles in jar samples.
3) Widespread seepage, concentrated seepage, or
ponding appears to threaten the safety of the dam.
CONDITIONS OBSERVED - APPLIES TO MONITORING
GOOD
Monitoring includes movement surveys and leakage
measurements for all dams, and piezometer readings for
High hazard dams. Instrumentation is in reliable, working
condition. A plan for monitoring the instrumentation and
analyzing results by the owner's engineer is in effect.
Periodic inspections by owner's engineer.
ACCEPTABLE
Monitoring includes movement surveys and leakage
measurements for High and Significant hazard dams;
leakage measurements for Low hazard dams.
Instrumentation is in serviceable condition. A plan for
monitoring instrumentation is in effect by owner. Periodic
inspections by owner or representative. OR, NO
MONITORING REQUIRED.
POOR
All instrumentation and monitoring described under
"ACCEPTABLE" here for each class of dam, are not
provided, or required periodic readings are not being
made, or unexplained changes in readings are not reacted
to by the owner.
CONDITIONS OBSERVED - APPLIES TO MAINTENANCE AND REPAIR
GOOD
Dam appears to receive effective on-going maintenance
and repair, and only a few minor items may need to be
addressed.
ACCEPTABLE
Dam appears to receive maintenance, but some
maintenance items need to be addressed. No major
repairs are requirecl
POOR
Dam does not appear to receive adequate maintenance.
One or more items needing maintenance or repair has
begun to threaten the safety of the dam.
OVERALL CONDITIONS
SATISFACTORY
The safety inspection indicates no conditions that appear
to threaten the safety of the dam, and the dam is expected
to perform satisfactorily under all design loading
conditions. Most of the required monitoring is being
performed.
UNSATISFACTORY
The safety inspection indicates definite signs of structural
distress (excessive seepage, cracks, slides, sinkholes,
severe deterioration, etc.), which could lead to the failure
of the dam if the reservoir is used to full capacity. The
dam is judged unsafe for full storage of water.
SAFE STORAGE LEVEL
FULL STORAGE
Dam may be used to full capacity with no conditions
attached.
CONDITIONAL FULL STORAGE
Dam may be used to full storage if certain monitoring,
maintenance, or operational conditions are met.
RESTRICTION
Dam may not be used to full capacity, but must be
operated at some reduced level in the interest of public
safety.
HAZARD CLASSIFICATION OF DAMS
High hazard
Loss of human life is expected in the event of failure of
the dam, while the reservoir is at the high water line.
Significant hazard
Significant damage to improved property is expected in
the event of failure of the dam while the reservoir is at the
high water line, but no loss of human life is expected.
Low hazard
Loss of human life is not expected, and damage to
improved property is expected to be small, in the event
of failure of the dam while the reservoir is at high water
fine.
NPH hazard - No loss of life or damage to improved property, or loss of downstream resource is expected in the event of failure
of the dam while the reservoir is at the high water line.
CONDITIONALLY SATISFACTORY
The safety inspection indicates symptoms of structural
distress (seepage, evidence of minor displacements, etc.),
which, if conditions worsen, could lead to the failure of the
dam. Essential monitoring, inspection, and maintenance
must be performed as a requirement for continued full
storage in the reservoir.
Page 5 of 5
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
202 Center Drive, Glenwood Springs, CO 81601 P 303.518.1829 https://dwr.colorado.gov
Jared S. Polis, Governor | Dan Gibbs, DNR Executive Director | Kevin G. Rein, Director/State Engineer
PHOTOGRAPHS
Upstream Slope
Photo 1. View from left abutment of the
upstream slope. Reservoir filled to
about stage 4.5 feet and most of the
upstream slope was exposed all season.
Upstream Slope
Photo 2. View looking right along the
upstream slope from near Sta. 3+00.
Slope is uniform with well graded riprap
rock that is angular and interlocked. No
areas of exposed riprap bedding.
Upstream Slope
Photo 3. View of shoring wall pile
installation from the spillway stilling
basin. Precast concrete shoring wall
panels to be installed from downstream
end up as the CMP is being installed.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
2 of 9
PHOTOGRAPHS
Upstream Slope
Photo 4. View from the right abutment
of the upstream slope. Large riprap and
boulders placed along the right
abutment to protect against possible
erosion.
CREST
Photo 5. View of the dam crest from
the right abutment with the Landis
Ditch diversion in the foreground.
CREST
Photo 6. Dam crest is in good condition
with positive drainage toward the
reservoir. Gravel surfacing on road is
uniform with no observed rutting.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
3 of 9
PHOTOGRAPHS
Downstream Slope
Photo 7. Looking east along the
downstream toe of the dam. Toe area
graded to avoid surface water along the
toe area.
Downstream Slope
Photo 8. Looking west (right) along the
downstream slope from about Sta. 2+00.
Slope is uniform with native grass
establishment in process. Engineer
noted that this item is under 2 year
warranty and likely will take 2 seasons
to establish native grasses.
Downstream Slope
Photo 9. A low lying area at the
downstream toe along the spillway
channel was observed to have a thicker
establishment of grasses. Based on low
reservoir levels, grasses in this area
likely thicker since fill had a high
quantity of clay and this area was
graded as a bowl feature and likely
retains water lower than other portion
of the reseeded areas.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
4 of 9
PHOTOGRAPHS
Downstream Slope
Photo 10. Looking east along the
downstream slope from the right
abutment. Slope is uniform and stable.
Seepage
Photo 11. No signs of seepage or drain
activity was observed on the dam.
Drains were dry during the inspection
and Engineer has not observed any drain
discharge to date.
Outlet
Photo 12. Intake structure on the
outlet was submerged. Trashrack
observed in place on the intake
structure.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
5 of 9
PHOTOGRAPHS
Outlet
Photo 13. View of the outlet manual
operator at the dam crest. Engineer
successfully exercised the gate.
Outlet
Photo 14. Looking downstream at the
outlet outfall structure currently in
operation.
Outlet
Photo 15. Looking upstream at the
outfall structure from the discharge
channel. Riprap downstream of the
structure was mounded at the structure
outfall resulting in deflection of the
flow with higher rates along the sides of
the riprap apron. Engineer noted that a
swale (i.e., belly) will be graded in the
riprap from the outfall to improve
conveying of flows downstream of the
structure.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
6 of 9
PHOTOGRAPHS
Outlet
Photo 16. Profile view of the outlet
discharge. Note the deflected water
spilling along the riprap apron and
backwater pool to the right side of the
outfall channel.
Outlet
Photo 17. View of the outlet outfall
pool area prior to operation of the
outlet. Minor bank erosion noted along
the right side of the backwater pool
area..
Outlet
Photo 18. Looking downstream at the
outlet discharge channel from the
riprap apron below the outfall
structure. Apron consists of gap graded
riprap with infilled rock to stabilize the
rock fill.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
7 of 9
PHOTOGRAPHS
Spillway
Photo 19. Looking west along the dam
axis with the emergency spillway
control structure in the foreground.
The concrete control sill was in good
condition with no observed cracks.
Spillway
Photo 20. Looking downstream at the
spillway discharge channel from the left
abutment area. Spillway control
structure (i.e., buried cutoff sill) in the
foreground.
Spillway
Photo 21. View along the lower spillway
cutoff wall Concrete in good condition
with no observed cracks.
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
8 of 9
PHOTOGRAPHS
Spillway
Photo 22. Looking upstream at the
spillway discharge channel from end of
riprap lining about 200 feet downstream
of the control sill.
Monitoring
Photo 23. Typical view of the reservoir
staff gauge/concrete grade beam with
1-foot elevation steel plates. Maximum
reservoir level this season appears to be
about El. 8980.5 (~stage 4.5 feet).
Monitoring
Photo 24. View of typical piezometer
with lockable steel casing. Engineer
measures piezometer levels during each
ENGINEER’S INSPECTION REPORT DATE: 06.21.2021
DAM NAME: HOPKINS DAM KJK DAMID: 380113, C-0090C
9 of 9
PHOTOGRAPHS
Monitoring
Photo 25. View of piezometer with
locking well cap (on left) and survey
monument with yellow marker lathe (on
right). Location shown near mid-
downstream slope along the maximum
section.
Diversion Structure
Photo 26. Intake end of the diversion
culvert on the Landis Ditch (location
along the dam axis just outside of the
dam embankment footprint.
Diversion Structure
Photo 27. Outfall end of the diversion
ditch culvert location about 50 feet
from the upstream toe of the dam at
the right abutment.
February 11, 2022
Martin Van Ardenne
The Seligman Group
600 Montgomery St, 40th floor
San Francisco, CA 94111
415-658-2889
RE: Review of the Hopkins Dam Inundation Mapping on Proposed Phase Development of Spring
Valley Ranch and the future development.
Dear Martin:
Garfield County has a requirement for a dam break analysis of Hopkins Dam and the impacts it
has on the proposed emergency access road and future phases of the development. This report is
intended to respond to Condition No. 8.0 of the Preliminary Plan Approval (Reception No.
747016), which states:
The dam break failure analysis for an enlarged Hopkins Reservoir must be incorporated into the
drainage plan and subdivision improvements agreement for phase 2 and incorporated into
subsequent phases as applicable in a manner adequate to prevent damage or potential loss of life
or structures within the subdivision.
Zancanella & Associates has reviewed the sunny day dam break as defined by Colorado Dam
Safety from the Dam Reconstruction Project that was recently completed including the inundation
flood boundaries from said break. This project consisted of removing the existing dam and
rebuilding it to current Dam Safety Standards.
The flood wave is confined to the Landis Creek drainage and currently does not severely impact
existing structures. It does impact the existing access road and County Road 115. With the
construction of the emergency access road (future High Grange Pass Rd) which involves
improving the existing road and raising the grades, the flood inundation wave will be affected as
will the impacts on the infrastructure.
After the flood wave impacts County Road 115, it diffuses and spreads out to have minimal
impacts on future development. The proposed improvements to the emergency access road is not
anticipated to change this. An attached map is included with this analysis that includes the flood
inundation wave boundaries, the proposed future phase lots, and other information pertinent to this
analysis.
The flood inundation wave is not anticipated to impact current structures significantly more than
current conditions, nor get to the point of potential for loss of life with the improvements, but the
emergency access road (High Grange Pass Rd) will be impacted to the point of possible failure.
Zancanella & Associates, Inc.
February 11, 2022
https://zanda5700.sharepoint.com/zdrive/28000/28604 spring valley ranch/28604.2 county permitting/innundation
mapping/inundation mapping letter.docx
Page 2
As there are alternative egress routes on the property, we do not anticipate this to be a deterrence
to the development of the property. Additionally, access to the site from Highway 82 can be
achieved by either using County Road 115 from the North or Spring Valley Road and County
Road 115 from the South.
With the construction of the emergency access road, the dam should still maintain the Significant
Hazard Classification which is defined from Colorado Dam Safety as potential for loss of property
but not loss of life.
No structure that is habitable should be located within the inundation boundary unless additional
review and analysis has taken place to ensure no loss of life or significant property damage will
occur during a sunny day dam break.
Included in this report is the full dam break and inundation study performed as part of the Hopkins
Reservoir approval documents. Additionally, the Hopkins Dam Certificate of Acceptance for the
recent dam reconstruction project is included for reference in this report.
Should you have any questions or need additional information, please feel free to contact us to
discuss the additional
Very truly yours,
Zancanella & Associates, Inc.
__________________________
Matthew V Weisbrod, PE
Attachments: Inundation Map.
Dam Break Analysis.
Hopkins Dam Reconstruction Certificate of Acceptance.
2829 27
30 26
21
19
23
22
20
17 16
18 1415
Feet
0 1200 2400
ENGINEERING CONSULTANTS1ZANCANELLA AND ASSOCIATES, INC.
Dam Safety Branch
1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 https://dwr.colorado.gov/
Jared S. Polis, Governor | Dan Gibbs, DNR Executive Director | Kevin G. Rein, Director/State Engineer
January 18, 2022
SUBJECT: Final Acceptance of Construction
Dear Mr. Van Ardenne,
Our office performed a final construction inspection of the newly constructed Hopkins Dam on October
7, 2020. Rule 8 of the Rules and Regulations for Dam Safety and Dam Construction (the Rules) requires
that your design engineer, Zancanella & Associates, prepare as-constructed plans, a completion report
documenting all aspects of construction, and their professional certification stating that the project
was completed in accordance with the approved plans and specifications. Zancanella & Associates
submitted completion documents on April 2, 2021. Our office provided final comments on April 30,
2021 which were satisfactorily addressed on January 12, 2022.
This project involved construction of a new, Significant Hazard dam at the site of a previously
breached structure. Based on observations during construction inspections, oversight and certification
by your engineer, and our review of the construction completion documents, we believe the project
has been satisfactorily completed in general accordance with the approved plans and specifications.
Therefore the project is accepted for full storage when water is physically and legally available,
and in accordance with your engineer’s monitoring plan.
The structure has a dam height of 25 feet and crest length of 700 feet. The reservoir created by the
dam covers approximately 12 acres and has full storage capacity of 113 acre-feet at the emergency
spillway crest elevation.
The State Engineer, by providing this construction acceptance does not assume responsibility for any
unsafe condition of the subject dam. The sole responsibility for the safety of this dam rests with the
reservoir owner and operator, who should take every step necessary to prevent damages caused by
leakage or overflow of waters from the reservoir or floods resulting from a failure of the dam.
Therefore, it is in the owner’s best interest to operate and maintain the facility in a manner such that
the safety of the dam and the general public are not jeopardized.
We are enclosing a copy of Rules 11 and 13 of the Rules for your reference and use. These rules
pertain to general maintenance items and the owner’s responsibilities, respectively.
We would like to recognize the efforts of Seligman Group, Zancanella & Associates, and Mueller
Construction, and all other parties who worked to complete this dam construction project. Thanks to
all for minding the safety of those who live below this dam and the resiliency of those served by it.
If you have any questions, please contact me at 719.227.5294 or Dam Safety Engineer Jackie Blumberg
at 303.505.6469.
Mr. Martin Van Ardenne
Seligman Group
600 Montgomery St.
40th Floor
San Francisco, CA 94111
via email: mvanardenne@seligmangroup.com
When replying, please refer to:
HOPKINS DAM, DAMID 380113
Water Division 5, Water District 38
Construction File No. C-0090C
Mr. Van Ardenne
Hopkins Dam – Final Project acceptance Letter
DAMID 380113, C-0090C
January 18, 2022
Page 2 of 2
Sincerely,
John Hunyadi, P.E.
Chief, Colorado Dam Safety Branch
Enc. Copy of Rules 11 and 13 of the “Rules and Regulations for Dam Safety and Dam Construction”
ec: James Heath, Division Engineer, Water Division 5
Heather Ramsey, WD 38 Water Commissioner
Jackie Blumberg, Dam Safety Engineer
Jeremy Franz, Design Review Engineer
Jason Ward, Design Review Engineer
Matt Weisbrod, Zancanella & Associates, MWeisbrod@za-engineering.com
2022-22
Appendix E – 25 Year Runoff Storage Exhibit
APPENDIX E
25 YR STORAGE EXHIBIT
N
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CHECKED BY:
#
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CONSTRUCTION
DRAWN BY:
JOB # 2022-22
NOT FOR
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9
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DCS
SP
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2022-22
Appendix F – SCS Storage Hydrographs
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin A
Hydrograph type = SCS Peak discharge (cfs) = 82.35
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 1616.700 Curve number (CN) = 65
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 63
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 1,152,131 (cuft); 26.449 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
60.00 60.00
70.00 70.00
80.00 80.00
90.00 90.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 82.35 (cfs)Outflow Hyd *Req. Stor = 151,410 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin B
Hydrograph type = SCS Peak discharge (cfs) = 7.301
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 167.090 Curve number (CN) = 63
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 36
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 94,617 (cuft); 2.172 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 7.30 (cfs)Outflow Hyd *Req. Stor = 2 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin C
Hydrograph type = SCS Peak discharge (cfs) = 10.94
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 65.220 Curve number (CN) = 68
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 23
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 63,218 (cuft); 1.451 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 10.94 (cfs)Outflow Hyd *Req. Stor = 0 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin E
Hydrograph type = SCS Peak discharge (cfs) = 4.952
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 198.400 Curve number (CN) = 61
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 38
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 84,752 (cuft); 1.946 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 4.95 (cfs)Outflow Hyd *Req. Stor = 3 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin G
Hydrograph type = SCS Peak discharge (cfs) = 6.165
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 302.500 Curve number (CN) = 60
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 24
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 111,845 (cuft); 2.568 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 6.17 (cfs)Outflow Hyd *Req. Stor = 16,644 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin K
Hydrograph type = SCS Peak discharge (cfs) = 2.873
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 87.250 Curve number (CN) = 62
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 38
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 42,851 (cuft); 0.984 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 2.87 (cfs)Outflow Hyd *Req. Stor = 1,957 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin L
Hydrograph type = SCS Peak discharge (cfs) = 24.83
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 193.000 Curve number (CN) = 69
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 44
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 206,564 (cuft); 4.742 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 24.83 (cfs)Outflow Hyd *Req. Stor = 30,329 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin M
Hydrograph type = SCS Peak discharge (cfs) = 33.40
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 292.000 Curve number (CN) = 70
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 64
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 342,920 (cuft); 7.872 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
35.00 35.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 33.40 (cfs)Outflow Hyd *Req. Stor = 16,776 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin N
Hydrograph type = SCS Peak discharge (cfs) = 12.87
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 94.680 Curve number (CN) = 68
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 31
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 93,209 (cuft); 2.140 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
14.00 14.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 12.87 (cfs)Outflow Hyd *Req. Stor = 832 (cuft) *
* Estimated
Hydrology Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Tuesday, Nov 12 2024
Basin P1
Hydrograph type = SCS Peak discharge (cfs) = 10.88
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 228.650 Curve number (CN) = 63
Basin Slope (%) = n/a Hydraulic length (ft) = n/a
Tc method = User Time of conc. (min) = 30
Total precip. (in) = 2.21 Storm Distribution = Type II
Storm duration (hrs) = 24 Shape factor = 484
Hydrograph Volume = 128,745 (cuft); 2.956 (acft)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 10.88 (cfs)Outflow Hyd *Req. Stor = 12,327 (cuft) *
* Estimated