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Home My WebLink About005 Stormwater Design ReportGallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 1 Table of Contents 1 Project Overview and Background ......................................................................................... 2 2 Hydrology ............................................................................................................................... 2 2.1 Pre-Development .............................................................................................................. 3 2.2 Post Development ............................................................................................................ 3 3 Post Development Hydraulics ................................................................................................. 4 3.1 Inlet and Gutter Capacity ................................................................................................. 4 3.2 Ponds ................................................................................................................................ 4 4 Maintenance Plan .................................................................................................................... 6 Table 1 - Pre-Development Hydrology ........................................................................................... 3 Table 2 - Post Development Drainage Basin .................................................................................. 3 Table 3 - Inlet and Gutter Summary (25-year event) ...................................................................... 4 Table 4 – Outfall Summary ............................................................................................................. 5 Table 5 - Minimum Sizing .............................................................................................................. 5 Table 6 - Pond 1 Stage-Storage ...................................................................................................... 5 Table 7 - Pond 2 Stage-Storage ...................................................................................................... 6 Attachments: Exhibit 1.1 – Vicinity Map - Topo Exhibit 1.2 – Vicinity Map - Aerial Exhibit 2.1 – Dog Park Pre-Development Drainage Exhibit 2.2 – Dinosaur Park Pre-Development Drainage Exhibit 3.1 – Dog Park Post Development Drainage Exhibit 3.2 – Dinosaur Park Post Development Drainage Appendix A – Supporting Calculations Appendix B – Storm Drainage Plans Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 2 1 Project Overview and Background The subject property is known as the Gallatin County Regional Park, located in the NE ¼ of Section 03, Township 02S, Range 5E. Vicinity maps showing the project location and extents are provided in Exhibits 1.1 and 1.2. The proposed site improvements address parking expansion for the County Regional Park’s Dog and Dinosaur Park areas. The Dog Park is located near the southeast corner of the intersection of Baxter Lane and Ferguson Avenue, the park extends south along Ferguson Ave. The proposed improvements include construction of a new asphalt parking area on the south side of the fenced dog park. Additional trails and sidewalks will be constructed as part of the improvements. A new retention pond will be provided near the northeast corner of the parking lot to meet the water quality and peak runoff rate requirements. The Dinosaur Park is located near the southwest corner of the intersection of Vaquero Parkway and Davis Lane, next to Bozeman Fire Station 3. A small gravel lot north of the playground equipment currently serves as the parking area for the Dinosaur Park. The proposed improvements include surfacing the existing gravel lot with asphalt and installing curb and gutter. Additional sidewalks will be constructed as part of the parking improvements. The existing parking lot conveys sheet flow runoff to a ditch along Vaquero Parkway. As part of the improvements, a new retention pond will be provided on the east side of the parking lot to meet the water quality and peak runoff rate requirements. The following sections describe the proposed stormwater design and its compliance with the current City of Bozeman (COB) storm drainage standards. Current regulations dictate that peak runoff rates for the post-development condition are mitigate to pre-development rates for the 10- year event. Stormwater collection and conveyance infrastructure is sized for the 25-year event. 2 Hydrology The rational method was utilized to estimate peak flow rates for conveyance sizing as outlined by the City of Bozeman Design Standards and Specifications. A weighted runoff coefficient “C” was determined based on a combination of open space (C=0.2) and pavement (C=0.95). The time to concentration was estimated using the overland flow method from the City of Bozeman Design Standards and TR-55 for shallow concentrated flow. A more detailed breakout of the data for each basin is provided in Appendix A. Basins, flow paths, and the general site layout for pre- and post-development conditions can be found on Exhibits 2.1-2.2 and 3.1-3.2, respectively. The site was divided into two basins, Basin 1 and Basin 2, which encompass the contributing drainage area for the Dog Park and Dinosaur Park improvements, respectively. An analysis of pre-development and post-development hydrologic conditions was completed with consistent basin boundaries between the pre- and post-development site conditions for the purpose of pond sizing. Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 3 2.1 Pre‐Development The pre-development condition describes the site before proposed improvements. The Dog Park parking lot site (Basin 1) is currently undeveloped, open space. Stormwater runoff sheet flows across the site and either infiltrates, or eventually enters ponds within the fenced dog park area. The Dinosaur Park parking lot site (Basin 2) currently consists of a gravel lot with a fenced storage area and shed. Stormwater runoff sheet flows across the parking lot to a drainage ditch running along Vaquero Parkway. An existing 12” storm drain conveys stormwater runoff from the adjacent fire station to the drainage ditch along Vaquero Parkway. A 15” concrete culvert runs below the existing dinosaur park drive access to convey runoff to the west. Basin 2 was conservatively assumed to have no impervious area prior to the proposed development. An overview of the pre-development drainage is provided on Exhibits 2.1 and 2.2. Table 1 provides a summary of the pre-development hydrologic conditions. Supporting calculations for time to concentration, intensity, and runoff are provided in Appendix A. Table 1 - Pre-Development Hydrology Basin Total Area (ac) Impervious (sf) Open Space (sf) Weighted C Tc (min) 10-yr Peak Runoff (cfs) 25-yr Peak Runoff (cfs) 1 0.60 0 26,208 0.20 19 0.16 0.19 2 0.33 0 14,248 0.20 19 0.09 0.11 2.2 Post Development The post development drainage basins are summarized in Table 2. An overview plan showing the drainage areas and infrastructure is provided on Exhibits 3.1 and 3.2. Basins 1.A and 1.B are areas routed though the proposed retention pond at the Dog Park site. Basin 1.C encompasses the portion of the Dog Park parking lot that will runoff to Ferguson Avenue. Basin 1.C has conservatively been included in the hydraulic capacity and pond sizing calculations. Basin 2 consists of the area routed though the proposed retention pond at the Dinosaur Park site. The supporting calculations for time to concentration, intensity, and runoff are provided in Appendix A. Table 2 - Post Development Drainage Basin Basin Total Area (ac) Impervious (sf) Open Space (sf) Weighted C Tc (min) 10-yr Peak Runoff (cfs) 25-yr Peak Runoff (cfs) 1.A 0.26 10,465 853 0.89 6 0.66 0.79 1.B 0.23 9,600 299 0.93 6 0.60 0.72 1.C 0.11 3,231 1,760 0.69 6 0.22 0.27 2 0.33 14,248 0 0.95 6 0.89 1.06 Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 4 3 Post Development Hydraulics The post development conveyance infrastructure considers the 25-year design event as outlined in the City of Bozeman Design Standards. Capacity calculations for the proposed storm drainage infrastructure are provided in Appendix A. 3.1 Inlet and Gutter Capacity The maximum allowable water surface for the 25-year event is 0.15-ft below the top back of curb. Two 3-ft wide curb cuts will be used to convey runoff from the Dog Park parking lot (Basin 1) to the proposed retention pond (Pond 1). The curb cuts (1.A and 1.B) were modeled as a 3-ft wide weir; the calculated flow depths are 0.22-ft and 0.17-ft, respectively. The gutter flow capacity is based on the HEC-22 gutter flow methodology for a composite section. Gutter capacity is 1.28-cfs for a cross slope of 1.2% and a longitudinal grade of 1.0%. The gutter flow capacity is conservatively based on an allowable spread width of 9.5-ft; flow depths will be less than allowable with a relatively low cross slope. A 3-ft wide curb cut will be used to convey runoff from the Dinosaur Park parking lot (Basin 2) to the proposed retention pond (Pond 2). The curb cut was modeled as a 3-ft wide weir; the calculated flow depth is 0.22-ft. Gutter capacity is 1.18-cfs for a cross slope of 1.1% and a longitudinal grade of 1.1%. All calculated peak flow rates are less than the typical street capacity. Sample calculations are provided in Appendix A. A summary of inlet and gutter flow is provided in Table 3. All curb cuts are located at a sag in the curb line. Table 3 - Inlet and Gutter Summary (25-year event) Inlet Cross Slope (%) Calc. Peak Flow (cfs) TBC (ft) TBC-0.15 (ft) Calculated WSE (ft) Spread (ft) Curb Cut 1.A 1.2 1.06 4736.88 4736.73 4736.65 8.42 Curb Cut 1.B 1.2 0.72 4736.88 4736.73 4736.65 7.38 Curb Cut 2 1.1 1.06 4737.93 4737.78 4737.70 9.05 3.2 Ponds The pre- and post-development peak runoff rates were previously provided in Section 2. Basins noted “1” encompass the Dog Park improvement area and drain to the proposed retention pond near the northeast corner of the parking lot (denoted as Pond 1). Basin 2 encompasses the Dinosaur Park improvement area and drains to the proposed retention pond on the east side of the parking lot (denoted as Pond 2). A summary is provided below in Table 4. Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 5 Table 4 – Outfall Summary Description Basins Area (acres) Impervious Area (sf) Weighted C Q (cfs) 10- year, 2- hour V (cf) 10- year, 2- hour Post-Dev. 1 1.A, 1.B, 1.C 0.60 23,296 0.87 0.21 1,537 Post-Dev. 2 2 0.33 14,248 0.95 0.13 912 Both retention ponds were sized for the 10-year, 2-hour storm intensity, as specified in the COB Design Standards. The water quality volume is required to be stored and infiltrated on site and is based on the first 0.5-inches of rainfall applied over the total impervious area. The retention pond sizing outputs are provided in Appendix A. A summary of the minimum pond sizing and design parameters are shown in Table 5. Table 5 - Minimum Sizing Pond Min. Required Retention Volume (cf) Water Quality Volume (cf) Actual Pond Bottom Area (sf) Actual Storage Volume (cf) 1 1,537 922 679 1,752 2 912 564 317 950 A summary of the pond stage-storage relationship is outlined in Tables 6 & 7. The pond volumes were determined based on a volume analysis in Autodesk Civil 3D. The retention ponds both satisfy the initial stormwater facility volume. The retention ponds are anticipated to tap into native gravel to provide infiltration. Tables 6 & 7 show the ponds provide adequate storage to control post development runoff rates. Overflow paths have been provided for the ponds in the case that overtopping occurs. Overflow from Pond 1 will runoff into the fenced Dog Park area and either infiltrate or enter the existing ponds within the Dog Park. Overflow from Pond 2 will enter the existing drainage ditch running along Vaquero Parkway. Table 6 - Pond 1 Stage-Storage Stage (ft) Elevation (ft) Storage (cf) 0.00 4735.00 0 0.25 4735.25 188 0.50 4735.50 415 0.75 4735.75 685 1.00 4736.00 995 1.25 4736.25 1,352 1.50 4736.50 1,752 Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 6 Table 7 - Pond 2 Stage-Storage Stage (ft) Elevation (ft) Storage (cf) 0.00 4736.25 0 0.25 4736.50 99 0.50 4736.75 243 0.75 4737.00 430 1.00 4737.25 666 1.25 4737.50 950 Geotechnical test pits were completed near the site (within the fenced dog park) on October 20, 2014 by AESI. The test pits were generally excavated to a depth of 8-ft. Groundwater was encountered between 4.00 to 4.25 ft below ground surface. Clean, sandy gravel was encountered between 1.5 to 2 ft below ground surface. Existing groundwater fed ponds within the Regional Park show water surface elevations between 4-ft to 5-ft below ground surface, which is consistent with the test pit data. The proposed dog park and dinosaur park ponds are approximately 2-ft and 1.75-ft below existing ground, respectively. Therefore, groundwater is not anticipated to be an issue. The retention ponds are anticipated to tap into native gravel to provide infiltration. 4 Maintenance Plan All proposed storm drainage features will be privately owned and maintained. Storm infrastructure generally consists of retention ponds and curb cuts. The proposed retention ponds should be mowed, and any grass clippings or other organic matter collected and removed from the pond bottom. The curb cuts located in the parking lots should be inspected in the spring and fall and cleaned of debris/sediment build-up if present. A more detailed maintenance plan for the retention pond is outlined blow. The following recommendations are from the Montana Post-Construction Storm Water BMP Design Guidance Manual. Refer to the manual for additional information and detail.  As needed Maintenance o Remove litter/debris from all components of the infiltration basin. o Repair structural components including inlets, diversion structures, and outlet structure (if applicable). o Inspect the basin for signs of erosion and repair eroded areas accordingly. Perform spot-reseeding if necessary. o Observe drain time following rainfall events to determine if the facility is clogged. If the observed drain time is longer than the local jurisdiction’s allowable maximum drain time, corrective action must be taken to return the infiltration basin to the design drain time. o Regularly manage all vegetation associated with the infiltration basin and remove all clippings.  Semiannual Maintenance Gallatin County Regional Park Improvements Jan 2022 Project: 01‐241.40 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 7 o Trim vegetation for aesthetics and to prevent the establishment of woody vegetation that may drop leaf litter, fruits, and other vegetative material that may clog the facility. o Remove all green waste and dispose of properly to prevent clogging.  Annual Maintenance o Inspect all components of the infiltration basin in accordance with an approved inspection form. Refer to the Post-Construction BMP Design Manual for additional information and example forms. o Remove sediment from inlets, in-flow paths, and overflow paths. Appendix A Supporting Calculations Drainage Basin OverviewArea Area Open (sf) paved (sf) Overland flow (ft) grade (%) C Cf (25‐yr) Tc (min) Length Grade (%) Tc (min)PRE‐DEVELOPMENT10‐yr i25‐yr I 10‐yr Q25‐yr Q1 1.35 1.63 0.16 0.20 26,2080.6026,208 00.20 190.32 138 1.16 0.2 1.1 18 69 1.45 12 1.37 1.65 0.09 0.11 14,2480.3314,248 00.20 190.31 138 1.16 0.2 1.1 18 37 4.05 0.2Area Area POST DEVELOPMENT10‐yr i25‐yr i10‐yr Q25‐yr QOpen (sf) paved (sf) Overland flow (ft) grade (%) C Cf (25‐yr) Tc (min) Length Grade (%) time1.A 2.86 3.40 0.66 0.79 11,3180.26853 10,4650.89 60.10 150 1.70 0.95 1.1 1.11.B 2.86 3.40 0.60 0.72 9,8990.23299 9,6000.93 60.10 148 1.70 0.95 1.1 1.01.C 2.86 3.40 0.22 0.27 4,9910.111,760 3,2310.69 60.10 44 3.75 0.95 1.1 0.42 2.86 3.40 0.89 1.06 14,2480.330 14,2480.95 60.10 136 1.50 0.95 1.1 1.0 25 1.1% 0.21 Combined2.86 3.40 1.49 1.78 26,2080.602,912 23,2960.87 60.10Intensity (in/hr) Peak Q (cfs)Area (sf) Area (acres)Area (acres)Area (sf)BasinOverland Tc (COB Design Standards)Tc (hr)Tc (min)C valueManual ‐ Shallow Concentrated (TR‐55)Intensity (in/hr) Peak Q (cfs)C value Tc (min) Tc (hr)Overland Tc (COB Design Standards) Manual ‐ Shallow Concentrated (TR‐55) Pre-Paved (sf) Post Paved (sf) Additional Pavement (sf) Water Quality Vol (cf) 0 23296 23296 922 Pre-Paved (sf) Post Paved (sf) Additional Pavement (sf) Water Quality Vol (cf) 0 14248 14248 564 Water Quality Volume - Dog Park Water Quality Volume - Dino Park Calculation of Required Volume for Storm Pond Pond ID Pond 1 (Dog Park) Accepts flow from basins 1 (Reference: Bozeman Stormwater Master Plan - 1982) Design Rainfall Freq. 10 year (see page III - 5 of master plan) IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 total area: 0.60 acres total area: 0.60 acres composite C: 0.20 composite C: 0.87 Total tc:19 minutes Total tc:6 minutes intensity at tc (fig 23):1.35 in/hr intensity at tc (fig 23):2.86 in/hr pre-devel peak runoff: 0.16 cfs post-devel peak runoff: 1.50 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs)Volume (cf)Volume (cf) Storage (cf) 6 2.86 1.50 539 59 480 8 2.37 1.24 596 78 518 10 2.05 1.07 644 98 547 12 1.82 0.95 687 117 570 14 1.65 0.86 725 137 588 16 1.51 0.79 759 156 603 18 1.40 0.73 791 176 616 20 1.31 0.68 821 195 626 22 1.23 0.64 849 215 634 24 1.16 0.61 875 234 641 26 1.10 0.58 900 254 646 28 1.05 0.55 924 273 650 30 1.00 0.53 946 293 653 32 0.96 0.50 968 312 656 34 0.93 0.48 989 332 657 36 0.89 0.47 1009 351 657 38 0.86 0.45 1028 371 657 40 0.83 0.44 1046 390 656 42 0.81 0.42 1064 410 655 44 0.78 0.41 1082 429 653 46 0.76 0.40 1099 449 650 48 0.74 0.39 1115 468 647 50 0.72 0.38 1131 488 644 52 0.70 0.37 1147 507 640 54 0.69 0.36 1162 527 635 56 0.67 0.35 1177 546 631 58 0.65 0.34 1192 566 626 60 0.64 0.34 1206 585 621 62 0.63 0.33 1220 605 615 64 0.61 0.32 1234 624 609 66 0.60 0.31 1247 644 603 required detention storage (ft3) =657 Detention Pond Calculations:Retention Pond Calculations: design depth of pond 1.50 feet Q = CIA max side slope 4.00 horizontal to 1.00 vertical C = 0.87 (post-development) length/width ratio 3.00 I = 0.41 in/hr (10-yr, 2-hr storm min. particle removed 40 microns (1 micron = 1 x 10-6 meters)A = 0.60 acres settling velocity of particle 0.0069 feet/second Q = 0.21 cfs min. pond to settle particle 24 square feet required retention storage (ft3) =1,537 ft3 Input Info From "Drainage Basin" Spreadsheet detention pond COB Calculation of Required Volume for Storm Pond Pond ID Pond 2 (Dino Park) Accepts flow from basins 2 (Reference: Bozeman Stormwater Master Plan - 1982) Design Rainfall Freq. 10 year (see page III - 5 of master plan) IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 total area: 0.33 acres total area: 0.33 acres composite C: 0.20 composite C: 0.95 Total tc:19 minutes Total tc:6 minutes intensity at tc (fig 23):1.35 in/hr intensity at tc (fig 23):2.86 in/hr pre-devel peak runoff: 0.09 cfs post-devel peak runoff: 0.89 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs)Volume (cf)Volume (cf) Storage (cf) 6 2.86 0.89 320 32 288 8 2.37 0.74 354 42 311 10 2.05 0.64 382 53 329 12 1.82 0.57 408 64 344 14 1.65 0.51 430 74 356 16 1.51 0.47 451 85 366 18 1.40 0.43 470 95 374 20 1.31 0.41 487 106 381 22 1.23 0.38 504 117 387 24 1.16 0.36 520 127 392 26 1.10 0.34 534 138 396 28 1.05 0.33 548 149 400 30 1.00 0.31 562 159 403 32 0.96 0.30 575 170 405 34 0.93 0.29 587 180 407 36 0.89 0.28 599 191 408 38 0.86 0.27 610 202 409 40 0.83 0.26 621 212 409 42 0.81 0.25 632 223 409 44 0.78 0.24 642 233 409 46 0.76 0.24 652 244 408 48 0.74 0.23 662 255 408 50 0.72 0.22 672 265 406 52 0.70 0.22 681 276 405 54 0.69 0.21 690 286 404 56 0.67 0.21 699 297 402 58 0.65 0.20 707 308 400 60 0.64 0.20 716 318 398 62 0.63 0.19 724 329 395 64 0.61 0.19 732 339 393 66 0.60 0.19 740 350 390 required detention storage (ft3) =409 Detention Pond Calculations:Retention Pond Calculations: design depth of pond 1.50 feet Q = CIA max side slope 4.00 horizontal to 1.00 vertical C = 0.95 (post-development) length/width ratio 3.00 I = 0.41 in/hr (10-yr, 2-hr storm min. particle removed 40 microns (1 micron = 1 x 10-6 meters)A = 0.33 acres settling velocity of particle 0.0069 feet/second Q = 0.13 cfs min. pond to settle particle 13 square feet required retention storage (ft3) =912 ft3 Input Info From "Drainage Basin" Spreadsheet detention pond COB Inlet Spread Width ‐ Composite SectionSee 4‐11 of HEC‐22 Third EditionQw Flow Rate in depressed section (gutter pan), cfsQ Total Flow Rate, cfsQs Flow rate in raised section (street section), cfsEo Ratio of flow in the gutter to the total flow (Qw/Q)Sx Street cross slope, ft/ftSL Longitudinal Slope, ft/ftSw Gutter pan cross slope, ft/ftW Gutter Width from edge of pavement to flow line, ftT Overall Spread Width ‐ measured from flow line, ftTs Spread Width on Street, ftKu 0.376 metric (0.56 English)n Manning's CoefficientStreet Spread WidthStreet Spread WidthStreet Spread WidthKu 0.56 0.376 metric (0.56 English) Ku 0.56 0.376 metric (0.56 English) Ku 0.56 0.376 metric (0.56 English)n 0.013 Manning's Coefficient n 0.013 Manning's Coefficient n 0.013 Manning's CoefficientTs 7.17 Width of Flow (spread width), ft Ts 6.13 Width of Flow (spread width), ft Ts 7.80 Width of Flow (spread width), ftSx 0.012 Street Cross Slope, ft/ft Sx 0.012 Street Cross Slope, ft/ft Sx 0.011 Street Cross Slope, ft/ftSL 0.012 Longitudinal Slope (ft/ft) SL 0.01 Longitudinal Slope (ft/ft) SL 0.011 Longitudinal Slope (ft/ft)Street Flow Qs 0.56 Based on Triangular Section Street Flow Qs 0.34 Based on Triangular Section Street Flow Qs 0.58 Based on Triangular SectionTotal Spread Width (Based on Known Q)Total Spread Width (Based on Known Q) Total Spread Width (Based on Known Q)Sw 0.0625 Gutter pan cross slope, ft/ft Sw 0.0625 Gutter pan cross slope, ft/ft Sw 0.0625 Gutter pan cross slope, ft/ftSx 0.012 Street Cross Slope, ft/ft Sx 0.012 Street Cross Slope, ft/ft Sx 0.011 Street Cross Slope, ft/ftW 1.25 Gutter Width from edge of pavement to flow line, ft W 1.25 Gutter Width from edge of pavement to flow line, ft W 1.25 Gutter Width from edge of pavement to flow line, ftQ 1.06 Total Flow Rate (cfs) Q 0.72 Total Flow Rate (cfs) Q 1.06 Total Flow Rate (cfs)Sw/Sx 5.21Sw/Sx 5.21Sw/Sx 5.68T/W 6.73T/W 5.90T/W 7.24Eo 0.47Eo 0.53Eo 0.45Ts 7.17Ts 6.13Ts 7.80T 8.42 Overall Spread Width, ftT 7.38 Overall Spread Width, ftT 9.05 Overall Spread Width, ftCurb Cut 1.ACurb Cut 1.BCurb Cut 2Note: Cells within boxes are calculation cell and shall not be edited.𝐸௢ൌ11൅𝑆௪𝑆௫1൅𝑆𝑤𝑆𝑥𝑇𝑊െ1ଶ.଺଻െ1𝑄௦ൌሺ𝐾௨𝑛ሻ𝑆௫ଵ.଺଻𝑆௅଴.ହ𝑇௦ଶ.଺଻𝑄ൌ𝑄௦1െ𝐸௢ Street/Gutter Capacity ‐ Composite SectionSee 4‐11 of HEC‐22 Third EditionQw Flow Rate in depressed section (gutter pan), cfsQTotal Flow Rate, cfsQs Flow rate in raised section (street section), cfsEo Ratio of flow in the gutter to the total flow (Qw/Q)Sx Street cross slope, ft/ftSL Longitudinal Slope, ft/ftSw Gutter pan cross slope, ft/ftW Gutter Width from edge of pavement to flow line, ftT Overall Spread Width ‐ measured from flow line, ftTs Spread Width on Street, ftKu 0.376 metric (0.56 English)n Manning's CoefficientMaximum Allowable Steet Flow RateMaximum Allowable Steet Flow RateKu 0.56 0.376 metric (0.56 English) Ku 0.56 0.376 metric (0.56 English)n 0.013 Manning's Coefficient n 0.013 Manning's CoefficientTs 8.25 Spread Width on Street, ftTs 8.25 Spread Width on Street, ftSx 0.012 Street Cross Slope, ft/ft Sx 0.011 Street Cross Slope, ft/ftSL 0.01 Longitudinal Slope (ft/ft) SL 0.011 Longitudinal Slope (ft/ft)Street Flow Qs 0.75 Based on Triangular Section Street Flow Qs 0.68 Based on Triangular SectionMaximum Allowable Total flow rateMaximum Allowable Total flow rateSw 0.0625 Gutter pan cross slope, ft/ft Sw 0.0625 Gutter pan cross slope, ft/ftSx 0.012 Street Cross Slope, ft/ft Sx 0.011 Street Cross Slope, ft/ftW 1.25 Gutter Width from edge of pavement to flow line, ftW 1.25 Gutter Width from edge of pavement to flow line, ftT 9.5 Overall Spread Width ‐ measured from flow line, ft T 9.5 Overall Spread Width ‐ measured from flow line, ftSw/Sx 5.208333Sw/Sx 5.681818T/W 7.6T/W 7.6Eo 0.4171Eo 0.4279Ts 8.25Ts 8.25Q1.282 Total Flow Rate (cfs)Q1.184 Total Flow Rate (cfs)Basin 1Basin 2Note: Cells within boxes are calculation cell and shall not be edited.𝐸௢ൌ11൅𝑆௪𝑆௫1൅𝑆𝑤𝑆𝑥𝑇𝑊െ1ଶ.଺଻െ1𝑄௦ൌሺ𝐾௨𝑛ሻ𝑆௫ଵ.଺଻𝑆௅଴.ହ𝑇௦ଶ.଺଻𝑄ൌ𝑄௦1െ𝐸௢ Appendix B Storm Drainage Plans OAK STREETBAXTER LANEFERGUSON AVE. DAVIS LANE DOG PARKDINOSAURPARKHARVEST PKWY.NCivil EngineeringGeotechnical EngineeringLand Surveying32 DISCOVERY DRIVEBOZEMAN, MT 59718PHONE (406) 582-0221FAX (406) 582-5770www.alliedengineering.comSHEETCOUNTY REGIONAL PARK IMPROVEMENTSSITE OVERVIEW PLANGALLATIN COUNTY REGIONAL PARKC1.3COUNTY REGIONAL PARKSITE OVERVIEW PLAN FERGUSON AVENUE“”“”“”“”“”SHEETCivil EngineeringGeotechnical EngineeringLand Surveying32 DISCOVERY DRIVEBOZEMAN, MT 59718PHONE (406) 582-0221FAX (406) 582-5770www.alliedengineering.comCOUNTY REGIONAL PARK IMPROVEMENTSDOG PARK SITE LAYOUTGALLATIN COUNTY REGIONAL PARKC1.4DOG PARKSITE LAYOUTN VAQUERO PKWY“”“”Civil EngineeringGeotechnical EngineeringLand Surveying32 DISCOVERY DRIVEBOZEMAN, MT 59718PHONE (406) 582-0221FAX (406) 582-5770www.alliedengineering.comSHEETCOUNTY REGIONAL PARK IMPROVEMENTSDINOSAUR PARK SITE LAYOUTGALLATIN COUNTRY REGIONAL PARKC1.5DINOSAUR PARKSITE LAYOUTN