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HomeMy WebLinkAbout4._EngineeringReportAppx_08162021Appendix A: Stormwater Drainage Basins STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST ST ST ST ST ST ST STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST B A S I N 1 0 0AREA= 0.39 ACC = 0.54B A S I N 1 0 1AREA= 0.08 ACC = 0.73BASIN 102AREA= 0.70 ACC = 0 . 5 7BASIN 103AREA= 0.68 ACC = 0 . 5 8 BASIN 104AREA= 0.90 ACC = 0.58 BASIN 105AREA= 0.98 ACC = 0.56 B A S I N 1 0 6AREA= 0.98 ACC = 0 . 5 0BASIN 107A R E A = 1 . 4 4 A C C = 0 . 5 7 4715 47104710 470547050'40'80'120'APRIL 2021PARKVIEW CROSSINGSSTORMWATER DRAINAGE BASINS Aug 05, 2021 - 8:40amCAD FILE: M:\193211\Drawings\FIGURES\Storm Basins.dwg 1OF 1 Appendix B: Basin Sizing Calculations (City of Bozeman) Existing SituationMinimum VolumeLand Use Open LandArea 10.71 AcresStorm DurationIntensity Future Runoff Rate Runoff VolumeRelease RateRelease VolumeRequired StorageSlope 2 %(Minutes) (in/hr) Q=CiA (cfs) (cf) (cfs) (cf) (cf)C= 0.2012 1.82 9.767024 0.000 0 7,024Overland Flow Distance 300 ft14 1.65 8.837414 0.000 0 7,414Time of Concentration23min16 1.51 8.097768 0.000 0 7,768Design Storm Frequency 10 year (Table I-3)18 1.40 7.508095 0.000 0 8,095Intensity at Tc 1.19 in/hr (Figure I-3)20 1.31 7.008399 0.000 0 8,399Peak Runoff Rate 2.547 cfs22 1.23 6.588684 0.000 0 8,68424 1.16 6.228953 0.000 0 8,953Proposed Situation26 1.10 5.909207 0.000 0 9,207Land Use Residential28 1.05 5.629449 0.000 0 9,449Area 10.71 Acres30 1.00 5.389680 0.000 0 9,680Slope 1.5 %32 0.96 5.169901 0.000 0 9,901 *C= 0.5034 0.93 4.9610114 2.547 306 9,808Overland Flow Distance 300 ft36 0.89 4.7810318 2.547 611 9,707Time of Concentration17min38 0.86 4.6110515 2.547 917 9,598Design Storm Frequency 10 year (Table I-3)40 0.83 4.4610706 2.547 1,222 9,48342 0.81 4.3210890 2.547 1,528 9,362Intensity at Tc 1.45 in/hr 10-yr (Figure I-3)44 0.78 4.1911069 2.547 1,834 9,2352.35 in/hr 100-yr (Figure I-3)46 0.76 4.0711242 2.547 2,139 9,10348 0.74 3.9611411 2.547 2,445 8,966Peak Runoff Rate 7.79 cfs 10-yr50 0.72 3.8611575 2.547 2,751 8,82512.60 cfs 100-yr52 0.70 3.7611735 2.547 3,056 8,67954 0.69 3.6711891 2.547 3,362 8,529Percent Impervious50%56 0.67 3.5812044 2.547 3,667 8,37658 0.65 3.5012192 2.547 3,973 8,219Runoff Treatment Volume 9719 cf60 0.64 3.4312338 2.547 4,279 8,059(RTV)62 0.63 3.3512480 2.547 4,584 7,89664 0.61 3.2912620 2.547 4,890 7,73066 0.60 3.2212756 2.547 5,196 7,56168 0.59 3.1612890 2.547 5,501 7,38970 0.58 3.1013022 2.547 5,807 7,215Weir Flowrate2.547 cfs72 0.57 3.0413151 2.547 6,112 7,038Weir Width3.5inches74 0.56 2.9913278 2.547 6,418 6,860*10-yr Detention Volume Required - 9901 cfPARKVIEW CROSSINGSDETENTION RELEASE RATEL:\193211\Computations\ON-SITE STORM.xls Appendix C: Original Stormwater Design Report July, 2018 L:\172708\Engineering Reports\Storm Report\Stormwater Report.doc Page 1 The Crossing 2 at Baxter Meadows Subdivision – Phase 4G & 4H Stormwater Report Bozeman, MT Introduction This report provides a design basis and hydraulic calculations for sizing stormwater infrastructure for The Crossing 2 at Baxter Meadows Subdivision – Phase 4G & 4H. The project in total is 5.8 acres of residential development and is located between the intersection of Vaquero Parkway and Baxter Lane to Vaquero Parkway and Davis Lane. Phases 4A through 4F of The Crossing have already been constructed. Stormwater calculations for the entire project (including phase 4G and 4H) were submitted in The Engineering Design Report for The Crossing at Baxter Meadows (March 2013). Generally the stormwater system and calculations have stayed consistent with what was originally submitted, but this report provides updated and additional information including inlet calculations, culvert capacity calculations and pond sizing. Much of this report will reference the Engineering Design Report for The Crossing at Baxter Meadows (March 2013). The City of Bozeman Design Standards and Specifications (March 2004) was used as the primary guideline for this stormwater drainage design along with The 2002 Edition of the Circular 8 of Montana Department of Environmental Quality (MDEQ). General Design Phase 4G and 4H will be a combination of roadway and residential lots. Vaquero Parkway has been designed with curb and gutter as originally designed in 2013. Stormwater runoff generated from the roadway and residential lots is designed to be collected by the curb and gutter and then directed toward the storm drain inlets. The runoff will then move through the storm sewer system pipes to the detention ponds. The detention ponds have been designed with outlet structures to limit stormwater runoff from the developed site to the pre-developed runoff rates. Inlets & Storm Sewer Using the Modified Rational Method, a contributing flow to each inlet in the system was determined. The inlet grates were designed to accommodate the 25-year storm event without overtopping a depth 0.15’ below the top of curb or spreading greater than 9 feet. Inlets at sag points were modeled using 50% clogging. Inlets and manholes will have a 9” sump for sediment collection. To avoid crossing Spring Ditch with the storm sewer, the two northern more inlets (SDI- 100 and SDI-101) were moved south from their original 2013 design location. This change created a larger drainage area that flows north to Existing Pond 7. The additional flowrate and volume was modeled to verify that Pond 7 could handle the added area without exceeding the pre-development flow rate. Storm pipes were sized to accommodate the 100-year storm event and were modeled in Storm and Sanitary Analysis. Pipes are sloped to maintain a minimum velocity of 3 ft/s when flowing full to prevent sediment deposit. The Hydraulic Grade line was plotted throughout the system and pipes were sized to keep the HGL within the pipe during the July, 2018 L:\172708\Engineering Reports\Storm Report\Stormwater Report.doc Page 2 25 yr storm and 100 yr storm. A manning’s N of 0.009 was used for the A-2000 Storm pipe within the model per the manufactures specifications. Stormwater Treatment The City of Bozeman requires infiltration, evapotranspiration or capture for reuse of the runoff generated from the first 0.5 inches of rainfall from a 24 hour storm. A common methodology for estimating the volume of direct runoff from a drainage basin is the SCS method. This method requires basic data similar to the Rational Method: drainage area, a runoff factor, time of concentration, and rainfall. However, the SCS approach is more sophisticated in that it also considers the time distribution of the rainfall and an infiltration rate that decreases during the course of a storm. The SCS method takes into account the Initial Abstraction (Ia) which is all losses before runoff begins. This includes surface depressions, water intercepted by vegetation, evapotranspiration and infiltration. Initial abstraction generally correlates with soil and cover parameters. Through studies of many small watersheds, Ia was found to be approximated by the following empirical equation: Ia = 0.2 x S [eq. 2-2 TR-55] Where S = (1000/CN) – 10 [eq. 2-4 TR-55] According to USDA’s Urban Hydrology for Small Watersheds, the Curve Number associated with soil type B and ¼ acre residential lots is 80 (Table 2-2a). Using the standard SCS method, S = (1000/80) – 10 = 2.5 inches Ia = 0.2 * 2.5 inches = 0.5 inches Using a 10-year 24-hour rain event in the City of Bozeman the total precipitation (P) is 1.88 inches of which 0.5 inches is lost due to initial abstraction according to USDA’s SCS method. Therefore this drainage plan includes provision for the first 0.5 inches of rainfall from the 24-hour storm to be retained in surface depressions, intercepted by vegetation, or evapotranspired or infiltrated Stormwater Detention Ponds Pond 5 and Pond 1A were designed in the original 2013 design report. Pond 1A will remain the same as originally designed but updated calculations are provided for clarity and it has been renamed Pond 1B. Pond 5 is similar to the original design but it has been oversized to account for future development along Vaquero Parkway. This Pond has been renamed Pond 5B and new calculations have been provided. The ponds are designed with outlet structures to limit stormwater runoff from the developed site to the pre-developed runoff rates for the 10-year storm and to not overtop during the 100-year storm. With this phase, additional drainage area will be added to the Existing Pond 7 basin. Pond 7 was originally slightly oversized allowing for this extra volume to be attenuated without exceeding the predeveloped rate. Revised pond calculations modeling the existing pond volume and existing outlet structure can be found in the appendices July, 2018 L:\172708\Engineering Reports\Storm Report\Stormwater Report.doc Page 3 Groundwater Groundwater is known to be high in this area. A geotechnical report was done in 2001 that included borings near both pond location. ST-29 near Pond 5B showed depth to groundwater at 3 feet below existing ground and ST-32 near Pond 1B showed depth to groundwater at 9 feet below existing ground. Due to the high groundwater the maximum pond excavation depth for Pond 5B is 2 feet. Culverts Both culverts under Vaquero Parkway were designed in the 2013 Design Report and modeled in the flood plain study conducted in 2007. Inverts and length changed slightly from the original design so new calculations are provided. Both culverts were modeled in HY-8 for the 25-year storm, 100-year storm, and emergency overflow events. According to the City of Bozeman standards the emergency overflow capacity shall be 100-percent of the whole culvert for the major storm. Both culverts meet this requirement by providing the entire emergency overflow capacity within the culvert and without overtopping the roadway. The headwater depth for the 25-year storm is provided in the culverts calculations and does not exceed 1.5 times the culvert depth. Maintenance Regular maintenance of stormwater facilities is necessary for proper function of the drainage system. In general, regular mowing of detention pond areas and removal of debris from the outlet structure will be required to maintain functionality of the system. Sediment removal from the ponds may be required over time to restore the detention pond volume. Additional maintenance items include removing debris from inlet grates and culverts, cleaning and flushing pipes, cleaning manhole sumps, and establishing ground cover after construction. All of the detention ponds will be maintained by the HOA (as is with the other existing ponds) after the phases have been incorporated into the HOA. Appendices L. Stormwater Drainage Basins M. Sub-Basin Runoff Calculations & Inlet Capacities N. Pipe Profiles with HGL O. Detention Pond Sizing and Outlet Structure Calculations P. Culvert Sizing Appendix D: Existing vs. Proposed Detention Pond Analyses Side by Side Comparison POND 1B (PRE-DEVELOPMENT) Basin Area (ac): 0.78 Pre-Dev C (weighted): 0.20 Overland Distance (ft): 100 Storm Event Intensity Overland Slope (%): 1.0 (yr) (in/hr)A B Gutter Flow (ft): 0.0 2 0.77 0.36 0.6 Pre-Dev. Tc (min): 16.83 5 1.17 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.46 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.76 0.78 0.64 Storm Coeff. B:0.60 0.65 0.64 0.67 50 2.13 0.92 0.66 Composite C: 0.20 0.20 0.20 0.20 100 2.37 1.01 0.67 Storm Intensity (in/hr): 0.77 1.46 1.76 2.37 Pre-Dev Qp (cfs):0.12 0.23 0.27 0.37 Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3))(FAA, USDOT, A/C 150-5320-5b, 1970) Gutter Flow V=3.28*k*(S^(1/2), where k=0.457 ( not paved) (FHWA HEC 22, EQN. 3-4) POND 5B (PRE-DEVELOPMENT) Basin Area (ac): 3.71 Pre-Dev C (weighted): 0.20 Overland Distance (ft): 300 Storm Event Intensity Overland Slope (%): 1.24 (yr) (in/hr)A B Gutter Flow (ft): 350.0 2 0.54 0.36 0.6 Pre-Dev. Tc (min): 30.63 5 0.80 0.52 0.64 Storm Event (yr): 2 10 25 100 10 0.99 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.20 0.78 0.64 Storm Coeff. B:0.60 0.65 0.64 0.67 50 1.43 0.92 0.66 Composite C: 0.20 0.20 0.20 0.20 100 1.58 1.01 0.67 Storm Intensity (in/hr): 0.54 0.99 1.20 1.58 Pre-Dev Qp (cfs):0.40 0.74 0.89 1.18 Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3))(FAA, USDOT, A/C 150-5320-5b, 1970) Gutter Flow V=3.28*k*(S^(1/2), where k=0.457 (not paved) (FHWA HEC 22, EQN. 3-4) EXISTING POND 7 (PRE-DEVELOPMENT) Basin Area (ac): 5.88 (5.66 from origional pond 7 basin +0.28 new additional area) Post-Dev C (weighted): 0.20 Overland Distance (ft): 300 Storm Event Intensity Overland Slope (%): 1.40 (yr) (in/hr)A B Gutter Flow (ft): 127.0 2 0.58 0.36 0.6 Post-Dev. Tc (min): 27.25 5 0.86 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.07 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.29 0.78 0.64 Storm Coeff. B:0.60 0.65 0.64 0.67 50 1.55 0.92 0.66 Composite C: 0.20 0.20 0.20 0.20 100 1.71 1.01 0.67 Storm Intensity (in/hr): 0.58 1.07 1.29 1.71 Post-Dev Qp (cfs):0.68 1.26 1.52 2.02 Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3))(FAA, USDOT, A/C 150-5320-5b, 1970) Gutter Flow V=3.28*k*(S^(1/2), where k=0.618 (paved) (FHWA HEC 22, EQN. 3-4) POND 5B FUTURE (PRE-DEVELOPMENT) Basin Area (ac): 9.48 Post-Dev C (weighted): 0.20 Overland Distance (ft): 300 Storm Event Intensity Overland Slope (%): 1.24 (yr) (in/hr)A B Gutter Flow (ft): 350.0 2 0.54 0.36 0.6 Post-Dev. Tc (min): 30.63 5 0.80 0.52 0.64 Storm Event (yr): 2 10 25 100 10 0.99 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.20 0.78 0.64 Storm Coeff. B:0.60 0.65 0.64 0.67 50 1.43 0.92 0.66 Composite C: 0.20 0.20 0.20 0.20 100 1.58 1.01 0.67 Storm Intensity (in/hr): 0.54 0.99 1.20 1.58 Post-Dev Qp (cfs):1.02 1.88 2.27 3.00 Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3))(FAA, USDOT, A/C 150-5320-5b, 1970) Gutter Flow V=3.28*k*(S^(1/2), where k=0.618 (paved) (FHWA HEC 22, EQN. 3-4) THE CROSSING AT BAXTER MEADOWS SUBDIVISION PHASE 4G & 4H PRE-DEVELOPMENT POND BASIN FLOWS Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) L:\172708\Computations\STORMWATER\Stormwater Calculations.xls Original Design EXISTING POND 5B (REQUIRED) Basin Area (ac): 10.71 Pre-Dev C (weighted): 0.20 Overland Distance (ft): 300 Storm Event Intensity Overland Slope (%): 2.00 (yr) (in/hr)A B Gutter Flow (ft): 0.0 2 0.64 0.36 0.6 Pre-Dev. Tc (min): 23.14 5 0.96 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.19 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.44 0.78 0.64 Storm Coeff. B:0.60 0.65 0.64 0.67 50 1.73 0.92 0.66 Composite C: 0.20 0.20 0.20 0.20 100 1.91 1.01 0.67 Storm Intensity (in/hr): 0.64 1.19 1.44 1.91 Pre-Dev Qp (cfs):1.37 2.55 3.07 4.10 Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3))(FAA, USDOT, A/C 150-5320-5b, 1970) Gutter Flow V=3.28*k*(S^(1/2), where k=0.457 ( not paved) (FHWA HEC 22, EQN. 3-4) PARKVIEW CROSSINGS MAJOR SUBDIVISION PRE-DEVELOPMENT POND BASIN FLOWS Storm Coeff. (i) L:\193211\Computations\Stormwater Calculations.xls Current Design Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Wednesday, 07 / 25 / 2018 Hyd. No. 5 POND 5B Hydrograph type = Reservoir Peak discharge = 0.472 cfs Storm frequency = 10 yrs Time to peak = 0.40 hrs Time interval = 1 min Hyd. volume = 2,364 cuft Inflow hyd. No. = 2 - POND 5B Max. Elevation = 4699.62 ft Reservoir name = POND 5B Max. Storage = 2,062 cuft Storage Indication method used. 7 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 Q (cfs) Time (hrs) POND 5B Hyd. No. 5 -- 10 Year Hyd No. 5 Hyd No. 2 Total storage used = 2,062 cuft Existing Pond Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2019.2 Thursday, 08 / 5 / 2021 Hyd. No. 5 POND 5B Hydrograph type = Reservoir Peak discharge = 1.293 cfs Storm frequency = 10 yrs Time to peak = 0.52 hrs Time interval = 1 min Hyd. volume = 7,848 cuft Inflow hyd. No. = 2 - POND 5B Max. Elevation = 4700.22 ft Reservoir name = POND 5B Max. Storage = 6,700 cuft Storage Indication method used. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 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) POND 5B Hyd. No. 5 -- 10 Year Hyd No. 5 Hyd No. 2 Total storage used = 6,700 cuft Proposed Pond Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Wednesday, 07 / 25 / 2018 Hyd. No. 5 POND 5B Hydrograph type = Reservoir Peak discharge = 0.953 cfs Storm frequency = 100 yrs Time to peak = 0.40 hrs Time interval = 1 min Hyd. volume = 3,907 cuft Inflow hyd. No. = 2 - POND 5B Max. Elevation = 4699.98 ft Reservoir name = POND 5B Max. Storage = 3,280 cuft Storage Indication method used. 14 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 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 Q (cfs) Time (hrs) POND 5B Hyd. No. 5 -- 100 Year Hyd No. 5 Hyd No. 2 Total storage used = 3,280 cuft Existing Pond Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2019.2 Thursday, 08 / 5 / 2021 Hyd. No. 5 POND 5B Hydrograph type = Reservoir Peak discharge = 3.838 cfs Storm frequency = 100 yrs Time to peak = 0.48 hrs Time interval = 1 min Hyd. volume = 12,856 cuft Inflow hyd. No. = 2 - POND 5B Max. Elevation = 4700.74 ft Reservoir name = POND 5B Max. Storage = 10,198 cuft Storage Indication method used. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 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) POND 5B Hyd. No. 5 -- 100 Year Hyd No. 5 Hyd No. 2 Total storage used = 10,198 cuft Proposed Pond Pond Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2019.2 Friday, 04 / 9 / 2021 Pond No. 2 - POND 5B Pond Data Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 4699.00 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 4699.00 2,921 0 0 1.00 4700.00 3,804 3,352 3,352 2.00 4701.00 4,787 4,286 7,638 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in)= 0.00 0.00 0.00 0.00 Span (in)= 0.00 0.00 0.00 0.00 No. Barrels = 0 0 0 0 Invert El. (ft)= 0.00 0.00 0.00 0.00 Length (ft)= 0.00 0.00 0.00 0.00 Slope (%)= 0.00 0.00 0.00 n/a N-Value = .013 .013 .013 n/a Orifice Coeff.= 0.60 0.60 0.60 0.60 Multi-Stage = n/a No No No Crest Len (ft)= 0.29 4.00 0.00 0.00 Crest El. (ft)= 4699.01 4700.50 0.00 0.00 Weir Coeff.= 3.33 3.33 3.33 3.33 Weir Type = Rect Ciplti --- --- Multi-Stage = No No No No Exfil.(in/hr)= 0.000 (by Contour) TW Elev. (ft)= 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 Stage (ft) 0.00 4699.00 0.20 4699.20 0.40 4699.40 0.60 4699.60 0.80 4699.80 1.00 4700.00 1.20 4700.20 1.40 4700.40 1.60 4700.60 1.80 4700.80 2.00 4701.00 Elev (ft) Discharge (cfs) Stage / Discharge Total Q Existing Pond Existing Pond Pond Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2019.2 Friday, 04 / 9 / 2021 Pond No. 2 - POND 5B Pond Data Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 4699.00 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 4699.00 4,542 0 0 1.00 4700.00 5,952 5,231 5,231 2.00 4701.00 7,462 6,692 11,923 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in)= 0.00 0.00 0.00 0.00 Span (in)= 0.00 0.00 0.00 0.00 No. Barrels = 0 0 0 0 Invert El. (ft)= 0.00 0.00 0.00 0.00 Length (ft)= 0.00 0.00 0.00 0.00 Slope (%)= 0.00 0.00 0.00 n/a N-Value = .013 .013 .013 n/a Orifice Coeff.= 0.60 0.60 0.60 0.60 Multi-Stage = n/a No No No Crest Len (ft)= 0.29 4.00 0.00 0.00 Crest El. (ft)= 4699.01 4700.50 0.00 0.00 Weir Coeff.= 3.33 3.33 3.33 3.33 Weir Type = Rect Ciplti --- --- Multi-Stage = No No No No Exfil.(in/hr)= 0.000 (by Contour) TW Elev. (ft)= 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 Stage (ft) 0.00 4699.00 0.20 4699.20 0.40 4699.40 0.60 4699.60 0.80 4699.80 1.00 4700.00 1.20 4700.20 1.40 4700.40 1.60 4700.60 1.80 4700.80 2.00 4701.00 Elev (ft) Discharge (cfs) Stage / Discharge Total Q Proposed Pond Proposed Pond Appendix E: Storm Drain Inlet Calculations 0.90 0.50 0.20 Note: Coefficients obtained from CoB Design Standards Table I-1 BASIN 100 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.06 0.90 0.05 Dense Residential 0.31 0.50 0.16 Open Land 0.02 0.20 0.00 Totals 0.39 0.21 Cw =0.54 BASIN 101 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.06 0.90 0.06 Open Land 0.02 0.20 0.00 Totals 0.08 0.06 Cw =0.73 BASIN 102 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.20 0.90 0.18 Dense Residential 0.40 0.50 0.20 Open Land 0.10 0.20 0.02 Totals 0.70 0.40 Cw =0.57 BASIN 103 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.17 0.90 0.15 Dense Residential 0.46 0.50 0.23 Open Land 0.05 0.20 0.01 Totals 0.68 0.39 Cw =0.58 MAJOR SUBDIVISION Weighted Runoff Coefficients PARKVIEW CROSSINGS Asphalt/Concrete Dense Residential Open Land L:\193211\Computations\Stormwater Calculations.xls BASIN 104 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.27 0.90 0.24 Dense Residential 0.51 0.50 0.26 Open Land 0.12 0.20 0.02 Totals 0.90 0.52 Cw =0.58 BASIN 105 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.24 0.90 0.22 Dense Residential 0.61 0.50 0.31 Open Land 0.13 0.20 0.03 Totals 0.98 0.55 Cw =0.56 BASIN 106 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Dense Residential 0.98 0.50 0.49 Totals 0.98 0.49 Cw =0.50 BASIN 107 Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.45 0.90 0.41 Dense Residential 0.72 0.50 0.36 Open Land 0.27 0.20 0.05 Totals 1.44 0.82 Cw =0.57 EXISTING POND 5B Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Existing (4G/4H) 3.71 0.51 1.89 Proposed 7.00 0.49 3.43 Totals 10.71 5.32 Cw =0.50 L:\193211\Computations\Stormwater Calculations.xls Storm Drain Inlet ID#Basin 10-Yr Flow (cfs) 25-Yr Flow (cfs) 100-Yr Flow (cfs) SDI-100 100 0.43 0.52 0.70 SDI-102 102 0.60 0.72 0.97 SDI-103 103 0.54 0.64 0.86 SDI-104 104 0.78 0.94 1.27 SDI-105 105 0.74 0.89 1.20 SDI-106 107 1.03 1.25 1.66 PARKVIEW CROSSINGS MAJOR SUBDIVISION SDI FLOWS Label Inlet TypeDischarge (ft³/s)Spread (ft)Gutter Width (ft)Road Slope (%)Gutter Cross Slope (%)Road Cross Slope (%)Grate Width (ft)Grate Length (ft) Grate TypeCurb Opening Length (ft)Opening Height (ft)Inlet Efficiency (%)Water Depth at Curb (in)100 - 25YR SAG 0.52 4.7 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 100 2.3100 - 100YR SAG 0.70 5.6 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 100 2.6102 - 25YR ON GRADE 0.72 4.9 1.5 0.70% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 82.4 2.4102 - 100YR ON GRADE 0.97 5.6 1.5 0.70% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 80.0 2.6103 - 25YR ON GRADE 0.64 4.7 1.5 0.70% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 84.0 2.3103- 100YR ON GRADE 0.86 5.7 1.5 0.70% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 80.2 2.6104 - 25YR ON GRADE 0.94 5.1 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 79.0 2.4104 - 100YR ON GRADE 1.27 5.8 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 73.6 2.7105 - 25YR ON GRADE 0.89 5.0 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 79.3 2.4105 - 100YR ON GRADE 1.20 5.7 1.5 1.00% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 74.5 2.6106 - 25YR SAG 1.25 7.8 1.5 0.70% 6.25% 3.00% 1.46 2.94 Curved Vaned 2.75 0.5 100 3.4106 - 100YRSAG1.669.31.50.70%6.25%3.00%1.462.94Curved Vaned2.750.51003.9PARKVIEW CROSSINGSSTORM DRAIN INLET SPREAD CALCSMAJOR SUBDIVISION Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3)) (City of Bozeman) Gutter Flow V=3.28*k*(S^(1/2), where k=0.618 (paved) (FHWA HEC 22, Eqn 3-4) BASIN 100 Basin Area (ac): 0.39 Post-Dev C (weighted): 0.54 Overland Distance (ft): 130 Storm Event Intensity Overland Slope (%): 1.8 (yr) (in/hr) A B Gutter Flow Distance (ft): 115.0 2 1.03 0.36 0.6 Gutter Flow Slope (%): 1.0 5 1.60 0.52 0.64 Post-Dev. Tc (min): 10.3 10 2.01 0.64 0.65 Storm Event (yr): 2 10 25 100 25 2.40 0.78 0.64 Storm Coeff. A: 0.36 0.64 0.78 1.01 50 2.94 0.92 0.66 Storm Coeff. B: 0.60 0.65 0.64 0.67 100 3.28 1.01 0.67 Composite C: 0.54 0.54 0.54 0.54 Storm Intensity (in/hr): 1.03 2.01 2.40 3.28 Post-Dev Qp (cfs):0.22 0.43 0.52 0.70 BASIN 101 Basin Area (ac): 0.08 Post-Dev C (weighted): 0.73 Overland Distance (ft): 30 Overland Slope (%): 2.0 Storm Event Intensity Gutter Flow Distance (ft): 115.0 (yr) (in/hr) A B Gutter Flow Slope (%): 1.0 2 1.88 0.36 0.6 Post-Dev. Tc (min): 3.8 5 3.03 0.52 0.64 Storm Event (yr): 2 10 25 100 10 3.83 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 4.54 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 5.66 0.92 0.66 Composite C: 0.73 0.73 0.73 0.73 100 6.38 1.01 0.67 Storm Intensity (in/hr): 1.88 3.83 4.54 6.38 Post-Dev Qp (cfs):0.12 0.24 0.28 0.40 BASIN 102 Basin Area (ac): 0.70 Post-Dev C (weighted): 0.57 Overland Distance (ft): 190 Overland Slope (%): 1.4 Storm Event Intensity Gutter Flow Distance (ft): 470.0 (yr) (in/hr) A B Gutter Flow Slope (%): 0.7 2 0.79 0.36 0.6 Post-Dev. Tc (min): 16.3 5 1.20 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.49 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.79 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 2.17 0.92 0.66 Composite C: 0.57 0.57 0.57 0.57 100 2.41 1.01 0.67 Storm Intensity (in/hr): 0.79 1.49 1.79 2.41 Post-Dev Qp (cfs):0.31 0.60 0.72 0.97 BASIN 103 Basin Area (ac): 0.68 Post-Dev C (weighted): 0.58 Overland Distance (ft): 280 Overland Slope (%): 1.2 Storm Event Intensity Gutter Flow Distance (ft): 405.0 (yr) (in/hr) A B Gutter Flow Slope (%): 0.7 2 0.72 0.36 0.6 Post-Dev. Tc (min): 18.8 5 1.09 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.36 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.64 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 1.98 0.92 0.66 Composite C: 0.58 0.58 0.58 0.58 100 2.20 1.01 0.67 Storm Intensity (in/hr): 0.72 1.36 1.64 2.20 Post-Dev Qp (cfs):0.28 0.54 0.64 0.86 PARKVIEW CROSSINGS POST-DEVELOPMENT SUB BASIN FLOWS MAJOR SUBDIVISION Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) L:\193211\Computations\Stormwater Calculations.xls BASIN 104 Basin Area (ac): 0.90 Post-Dev C (weighted): 0.58 Overland Distance (ft): 300 Overland Slope (%): 2.0 Storm Event Intensity Gutter Flow Distance (ft): 400.0 (yr) (in/hr) A B Gutter Flow Slope (%): 1.0 2 0.79 0.36 0.6 Post-Dev. Tc (min): 16.2 5 1.20 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.50 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.81 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 2.19 0.92 0.66 Composite C: 0.58 0.58 0.58 0.58 100 2.43 1.01 0.67 Storm Intensity (in/hr): 0.79 1.50 1.81 2.43 Post-Dev Qp (cfs):0.41 0.78 0.94 1.27 BASIN 105 Basin Area (ac): 0.98 Post-Dev C: 0.56 Overland Distance (ft): 300 Overland Slope (%): 2.0 Storm Event Intensity Gutter Flow Distance (ft): 670.0 (yr) (in/hr) A B Gutter Flow Slope (%): 1.0 2 0.72 0.36 0.6 Post-Dev. Tc (min): 18.9 5 1.09 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.36 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.63 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 1.97 0.92 0.66 Composite C: 0.56 0.56 0.56 0.56 100 2.19 1.01 0.67 Storm Intensity (in/hr): 0.72 1.36 1.63 2.19 Post-Dev Qp (cfs):0.39 0.74 0.89 1.20 BASIN 106 Basin Area (ac): 0.98 Post-Dev C: 0.50 Overland Distance (ft): 200 Overland Slope (%): 2.0 Storm Event Intensity Gutter Flow Distance (ft): 0.0 (yr) (in/hr) A B Gutter Flow Slope (%): 0.0 2 0.94 0.36 0.6 Post-Dev. Tc (min): 12.1 5 1.45 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.81 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 2.17 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 2.64 0.92 0.66 Composite C: 0.50 0.50 0.50 0.50 100 2.95 1.01 0.67 Storm Intensity (in/hr): 0.94 1.81 2.17 2.95 Post-Dev Qp (cfs):0.46 0.89 1.06 1.45 BASIN 107 Basin Area (ac): 1.44 Post-Dev C: 0.57 Overland Distance (ft): 300 Overland Slope (%): 1.0 Storm Event Intensity Gutter Flow Distance (ft): 465.0 (yr) (in/hr) A B Gutter Flow Slope (%): 0.7 2 0.67 0.36 0.6 Post-Dev. Tc (min): 21.1 5 1.01 0.52 0.64 Storm Event (yr): 2 10 25 100 10 1.26 0.64 0.65 Storm Coeff. A: 0.36 0.64 0.78 1.01 25 1.52 0.78 0.64 Storm Coeff. B: 0.60 0.65 0.64 0.67 50 1.83 0.92 0.66 Composite C: 0.57 0.57 0.57 0.57 100 2.03 1.01 0.67 Storm Intensity (in/hr): 0.67 1.26 1.52 2.03 Post-Dev Qp (cfs):0.55 1.03 1.25 1.66 Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) L:\193211\Computations\Stormwater Calculations.xls