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Home My WebLink About1.09 Existing Drainage & Flood Hazard Report Existing Drainage and Flood Hazard Report SPRING VALLEY RANCH PUD January 18, 2023 Spring Valley - Drainage Exhibit December 2022 2022-22 TableofContents 1.0General ................................................................................................................................. 2 1.1Preliminary Plan Drainage Report ................................................................................... 2 1.2FEMA FIRMette .............................................................................................................. 2 2.0Hydrology ............................................................................................................................ 3 2.1Drainage Basin Areas ....................................................................................................... 3 2.2Rainfall ............................................................................................................................. 3 2.3Hydrologic Curve Numbers ............................................................................................. 3 2.4Times of Concentration .................................................................................................... 3 2.5Peak Discharges ............................................................................................................... 3 3.0Pre-Development Hydrologic Results ................................................................................. 3 4.0Hopkins Dam Analysis ........................................................................................................ 4 Appendix A – Pre-Development Drainage Map ............................................................................. 6 Appendix B – Precipitation Data .................................................................................................... 7 Appendix C –Pre-Development Drainage Results ......................................................................... 8 Appendix D – Prior Studies and Dam Certifications ...................................................................... 9 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 PreliminaryPlanDrainageReport 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 FEMAFIRMette 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 DrainageBasinAreas 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 HydrologicCurveNumbers 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 TimesofConcentration 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 PeakDischarges 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 PreǦDevelopmentHydrologicResults 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 HopkinsDamAnalysis 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). 2022-22 AppendixA – Pre-Development Drainage Map 11 CH E C K E D B Y : #DESCRIPTIONDRAWN BY CO N S T R U C T I O N DR A W N B Y : JO B # 2 0 2 1 - 0 4 NO T F O R ROARING FORK ENGINEERING 592 HIGHWAY 133 CARBONDALE, CO 81623 PH: (970) 340-4130 DC S RV S SPRING VALLEY RANCH GARFIELD COUNTY, COLORADO 2022-22 AppendixB– Precipitation Data x NOAA Atlas 14 Data 2022-22 AppendixC –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 AppendixD – Prior Studies and Dam Certifications x Final Acceptance of Construction, Colorado DWR, 2022 x Engineer's Inspection Report, Colorado DWR, 2021 x Hopkins Dam Inundation Mapping, Zancanella & Associates, 2022 x Hopkins Reservoir Dam Break Analysis, Wright Water Engineers, 2007 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 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 Sincerely, Korey J. Kadrmas, P.E., Division 5 Dam Safety Engin (1*,1((5 6,163(&7,215(3257 2)),&(2)7+(67$7((1*,1((5',9,6,212):$7(55(6285&(6'$06$)(7<%5$1&+6+(50$1675((75220'(19(5&2 ,163(&7,213$57< FIELD CONDITIONS OBSERVED WATER LEVEL: GROUND MOISTURE CONDITION: BELOW DAM CREST FT. FT. GAGE ROD READING DRY WET SNOWCOVER OTHER ',5(&7,2160$5.$1;)25&21',7,216)281'$1'81'(5/,1(:25'67+$7$33/< DAM NAME:HOPKINS DAM ID:380113 &855(175(675,&7,21121( 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 0DWW:HLVEURG +HDWKHU5DPVH\ .RUH\.DGUPDV SPILLWAY WIDTH(FT):20.0 FREEBOARD (FT):6.0 T: OWNER:6(/,*0$1*5283 ADDRESS:0217*20(5<67CONTACT NAME:'25((1+(55,277 CONTACT PHONE:; 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 6$1)5$1&,6&2 &$ 5(35(6(17,1*=DQFDQHOOD $VVRFLDWHV2ZQHU5HS :DWHU&RPPLVVLRQHU &2'DP6DIHW\%UDQFK Below Spillway INSPECTOR:.-. 5/28/2008PREVIOUS INSPECTION: OWNER REP.:0$57,19$1$5'(11( PROBLEMS NOTED:121( 5,35$3 :$9((526,21 &5$&.6 6,1.+2/( $33($5672267((3 6/,'(6 &21&5(7()$&,1* 27+(5 2%6(59$7,216 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’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. =DQFDQHOOD $VVRFLDWHV,QF )HEUXDU\ KWWSV]DQGDVKDUHSRLQWFRP]GULYHVSULQJYDOOH\UDQFKFRXQW\SHUPLWWLQJLQQXQGDWLRQ PDSSLQJLQXQGDWLRQPDSSLQJOHWWHUGRF[ 3DJH 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. )H H W