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Home My WebLink About008 Storm Drain ReportStorm Drainage Design Report Track C Rail Extension within North Park Development Bozeman, Montana September 18, 2024 Prepared For: Bozeman TRAX Partners, LLC North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 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 ............................................................................................................ 2 2.2 Post-Development ........................................................................................................... 3 3 Post-Development Hydraulics ................................................................................................ 3 3.1 Retention Ponds .............................................................................................................. 4 3.2 Culvert............................................................................................................................. 7 4 Maintenance Plan .................................................................................................................... 8 Table of Tables Table 1 – Pre-Development Hydrology .......................................................................................... 3 Table 2 – Post-Development Drainage Basins ............................................................................... 3 Table 3 – Storage Volumes and Allowable Release Rate ............................................................... 4 Table 4 – Basin A: Northern Retention Pond ................................................................................. 5 Table 5 – Basin A: Southern Retention Pond ................................................................................. 5 Table 6 – Basin B.1 Retention Pond ............................................................................................... 5 Table 7 – Basin B.2 Tiered Retention Pond ................................................................................... 6 Table 8 – Basin C Retention Pond .................................................................................................. 6 Table 9 – Available Storage Volumes ............................................................................................ 6 Attachments: Exhibit 1.1 – Vicinity Map Exhibit 1.2 – USGS Quad Map Exhibit 1.3 – Mandeville Creek Overview Exhibit 2.1 – Pre-Development Drainage Exhibit 2.2 – Post-Development Drainage Appendix A – Supporting Calculations Appendix B – Storm Drainage Plans Appendix C – Groundwater Monitoring Data References: (copies of each included with site plan submittal) Flood Hazard Evaluation for Mandeville Creek (dated 12/9/2016) Update to 2016 Flood hazard Evaluation for Mandeville Creek (dated 8/23/2024) City of Bozeman Transfer Station Geotechnical Report (dated July of 2004) Bozeman Solvent Site Water Main Extension Geotechnical Report (dated February of 2002) North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 2 1 Project Overview and Background The Track C Rail Extension project is located on Tract 2-B of COS 2153A. This tract of land is within the North Park Development, which is located near the north end of Bozeman, MT. The overall development is bounded by the railroad to the north, Mandeville Lane to the south, North 7th Ave to the east, and Interstate 90 to the west. Most of the development area is state owned land that will be developed as lease sites. A portion of land at the north end of the project are fee simple. Tract 2-B is part of the fee simple land. The project is under jurisdiction of the City of Bozeman (COB) and is being developed under the Master Site Plan process. The terrain within and surrounding the project site is relatively flat and slopes gradually down to the northwest towards Mandeville Creek. A flood hazard evaluation dated December 9, 2016 was completed for Mandeville Creek by Allied Engineering Services, Inc. (AESI). The 2016 flood hazard evaluation was updated to account for future road and rail crossings on Mandeville Creek and future culvert replacements at the existing Railroad and Frontage Road crossings. The updated Flood Hazard report is dated August 23, 2024. Both reports have been submitted as part of the Master Site Plan for the overall development. Current improvements considered with this report are specific to the extension of Track C from the Burlington Northern Santa Fe (BNSF) right-of-way (ROW) to Tract 2-B. The extension will require crossing Mandeville Creek. Drainage improvements will provide treatment for the rail improvements until the rest of the site is developed. A future site plan for Tract 2-B will address storm drainage for the entire site and may involve reconfiguring drainage improvements outlined by this report. A temporary retention pond for the Wheat Drive Extension (a separate project) is also proposed on Tract 2-B. AESI has been coordinating with the developer for Tract 2-B and anticipate a future regional pond will be constructed to replace the temporary pond. The future pond would then accommodate runoff from the Wheat Drive Extension, Track C Rail Extension, and future site development for Tract 2-B. 2 Hydrology The rational method was utilized to estimate peak runoff 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=0.98). The time to concentration was estimated using the overland flow method from the City of Bozeman Design Standards. A more detailed breakout of the data for the basin is provided in Appendix A. 2.1 Pre‐Development An overview of the pre-development drainage is provided on Exhibit 2.1. Runoff from the site generally flows north to near the railroad right-of-way. Runoff is then directed northwest along the existing rail via natural topography and ditches associated with Red Wing Drive which has been abandoned. The pre-development basin is assumed to match the area of disturbance for the purpose of sizing treatment facilities. A small berm is proposed along the south edge of the rail improvements which will maintain the current drainage patterns. A summary of the pre- development basin characteristics is provided in Table 1. North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 3 Table 1 – Pre-Development Hydrology Basin Total Area (acres) Impervious (sf) Open Space (sf) Weighted C tc (min) 10-yr Peak Runoff (cfs) A 1.04 0 45,386 0.20 50 0.15 B.1 0.23 0 9,900 0.20 15 0.07 B.2 0.10 0 4,528 0.20 14 0.03 C 0.72 0 31,231 0.20 22 0.18 D 0.37 0 16,069 0.20 14 0.12 2.2 Post‐Development The post-development drainage basins are summarized in Table 2. An overview of the post- development drainage is provided on Exhibit 2.2. Drainage from off-site will be routed around the proposed storm ponds with a small berm on the uphill sides. This will maintain the pre- development drainage pattern with the same outfall point to the northwest at Mandeville Creek. Runoff from the temporary stilling basin from Phase 2 of North Park will also be routed around using the same berm and a shallow channel cut through slight adverse grade to convey overflow towards Mandeville Creek. Table 2 – Post-Development Drainage Basins Basin Total Area (acres) Impervious (sf) Open Space (sf) Weighted C tc (min) 10-yr Peak Runoff (cfs) A 1.04 17,354 28,032 0.50 6 1.48 B.1 0.23 3,920 5,980 0.51 9 0.45 B.2 0.10 1,773 2,755 0.51 8 0.13 C 0.72 19,247 11,984 0.68 6 1.40 D 0.37 8,076 7,993 0.59 6 0.62 3 Post‐Development Hydraulics The drainage improvements will consist of long retention ponds following along each side of the new rail line (north and south) and retention ponds in the vicinity the creek. The post- development retention ponds consider the 10-year design event as outlined in the City of Bozeman Design Standards and Specifications. During a larger event, such as a 100-year, stormwater would overtop the retention ponds and flow along the rail spur line down to Mandeville Creek, maintaining the pre-development drainage condition. A 144” equivalent CMPA (171”x110”) culvert is proposed to be installed for the railroad spur line to cross Mandeville Creek. This culvert has been designed to handle the 100-year estimated peak flow rate of 517-cfs outlined in the 2016 Mandeville Creek Flood Hazard Evaluation for the North Park Development. More information related to the proposed crossing and conveyance infrastructure for Mandeville Creek is included with the 8/23/2024 Update to the Mandeville Creek Flood Study. North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 4 3.1 Retention Ponds Retention volumes required for the proposed storm ponds was estimated using the following equations as outlined in the City of Bozeman Design Standards and Specifications. Q ൌ CIA V ൌ 7200Q Where: C ൌ Weighted C Factor I ൌ 0.41 in/hr A ൌ Area Q ൌ runoff V ൌ volume A weighted runoff coefficient “C” was determined based on a combination of open space (C=0.2) and pavement (C=0.98). Although the proposed rail spur line and gravel access road will likely have a lower runoff coefficient, a value of 0.98 was assigned to these areas to be conservative. Table 3 – Storage Volumes and Allowable Release Rate Basin Minimum Required Retention Storage Volume (cf) Water Quality Volume (cf) Minimum Required Detention Storage Volume (cf) Allowable Release Rate (Pre-Development Peak Runoff) (cfs) A 1,524 723 676 0.15 B.1 340 163 101 0.07 B.2 154 73 45 0.03 C 1,433 802 561 0.18 D 637 333 200 0.12 Current improvements do not include detention ponds. The minimum required detention storage volume and allowable release rate are provided for future sizing of a regional pond for the overall site. The future drainage improvements for full development of Tract 2-B should consider pre-and post-development drainage and facility sizing for the overall site. Values from the table should be used for future estimating only. Because the rail spur line is designed with a crowned subgrade and mostly symmetrical retention storm ponds, it is assumed that stormwater runoff will be evenly distributed between each side of the tangent section of track. Table 4 and Table 5 below show the stage-storage relationship for the two retention ponds (northern and southern sides of the rail spur line). The storage for each pond at a depth of 0.90 feet is greater than the minimum retention pond volume provided above. When adding the storage from each pond together, these tables show the retention ponds provide more than triple the minimum storage volume required for Basin A. North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 5 Table 4 – Basin A: Northern Retention Pond Stage (ft) Elevation (ft) Storage Volume (cf) 0.00 4674.60 0 0.25 4674.85 193 0.50 4675.10 774 0.75 4675.35 1741 0.90 4675.50 2506 Table 5 – Basin A: Southern Retention Pond Stage (ft) Elevation (ft) Storage Volume (cf) 0.00 4674.60 0 0.25 4674.85 193 0.50 4675.10 774 0.75 4675.35 1741 0.90 4675.50 2506 Basins B.1, B.2, and C represent areas located near the creek crossing where topography begins to fall towards the creek. It will not be feasible to include the linear retention ponds in these areas due to topography. Treatment for these drainage basins will therefore utilize small stormwater retention ponds to provide control of sediment/water quality. The stormwater retention ponds will encroach into the zone 2 watercourse setback but will not be extended into the zone 1 watercourse setback. Sheets C2.6, C2.7, and C2.8 provide plan and profile views showing the proposed elevations and detailed grading. Estimated storage volumes for the stormwater ponds are included in Table 6, Table 7, and Table 8. Basin B.2 will utilize a stormwater pond with three tiered levels of storage. The tiered stormwater pond for Basin B.2 is necessary due to space constraints. Table 6 – Basin B.1 Retention Pond Stage (ft) Elevation (ft) Storage Volume (cf) 0.00 4667.80 0 0.25 4668.05 110 0.50 4668.30 240 0.75 4668.55 393 1.00 4668.80 570 1.25 4669.05 771 1.50 4669.30 1,000 North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 6 Table 7 – Basin B.2 Tiered Retention Pond Stage (ft) Elevation (ft) Total Storage Volume (cf) 0.00 4670.55, 4671.93, 4673.07 0 0.25 4670.80, 4672.18, 4673.32 3 0.50 4671.05, 4672.43, 4673.57 23 0.75 4671.30, 4672.68, 4673.82 83 0.90, 1.0, 0.90 4671.45, 4672.83, 4673.97 165 Table 8 – Basin C Retention Pond Stage (ft) Elevation (ft) Storage Volume (cf) 0.00 4669.25 0 0.25 4669.50 401 0.50 4669.75 842 0.75 4670.00 1,324 1.00 4670.25 1,847 1.25 4670.50 2,415 1.50 4670.75 3,025 A summary of required retention volumes and provided storage for each basin is outlined in Table 9. Storage volumes for all ponds were calculated using Autodesk Civil 3D. All basins except Basin D have adequate storage volumes. Due to its proximity to the creek, the runoff from Basin D cannot be captured and conveyed to a treatment area. The runoff from Basin D is a relatively small amount and the total available storage volume has been conservatively oversized to account for this runoff that cannot be captured and treated. Table 9 – Available Storage Volumes Basin Minimum Required Retention Storage Volume (cf) Available Storage Volume (cf) Excess Storage Volume (cf) A 1,524 5,012 3,487 B.1 340 1,000 660 B.2 154 165 11 C 1,433 3,025 1,592 D 637 0 0 Total 4,061 9,202 5,141 As shown in Table 9, the total capacity of the proposed retention ponds provide storage beyond the minimum volume needed for the entire area of improvements. The relatively small area near the creek not being captured (Basin D) is not anticipated to have a significant impact on peak runoff rates. The area not captured is relatively small compared to the overall improvement area and the current retention ponds and future regional detention pond will be able to over-account and maintain overall peak runoff rates. For water quality considerations, we anticipate that the area will be well vegetated within the watercourse setback area and will provide treatment for the relatively small runoff volume. As mentioned earlier, conservative runoff coefficients were used North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 7 for the post-development runoff calculations. Actual peak runoff rates for the 10-year event are anticipated to be less than what is shown in this report. The average depth of cut for the bottom of the retention storm ponds between station 11+50 and 17+00 is anticipated to be 2.5 feet below existing ground. Although the excavation for the rail spur line is proposed to enter a region of significant “cut” during the last 80 feet (station 18+00 to 18+80) groundwater is not anticipated to be an issue. The maximum depth of cut for the storm ponds during the last 80 feet is anticipated to be 6.5 feet below existing ground. If groundwater is encountered, the overall length of the rail spur line might need to be reduced, or another solution may need to be found. Groundwater monitoring data was collected on site by Sanderson Stewart during the spring of 2023. Groundwater was measured at a depth of 7.56-ft below ground at the monitor well (#4) nearest to the end of the rail spur line. The 2023 groundwater monitoring data is included in appendix C of this report. A geotechnical test pit near the end of the proposed rail spur line was dug on January 23, 2004. This was test pit #1 for the potential City of Bozeman Transfer Station project. The test pit was dug to a depth of 8 feet and orange discoloration that may indicate high seasonal ground water was found at a depth of 7 feet. Groundwater monitoring from mid-May to early July in 2004 showed this monitor well did not encounter any groundwater. Native gravels were found at a depth of approximately 3 feet. See the referenced COB Transfer Station Geotechnical Report from July of 2004. A second geotechnical test pit in the same area was dug on June 24, 1988. This was test pit #103 (from HKM) included with the geotechnical report from February 2001 for the city of Bozeman Water Main Extension associated with the Bozeman Solvent Site. This test pit encountered gravels at a depth of 4.5 feet and groundwater at 11 feet. Test pit #104 from this report showed well-graded gravels at 3 feet and no groundwater present. Please see the attached geotechnical report for the Bozeman Solvent Site Water Main Extension. Both referenced geotechnical reports support the conclusion that groundwater is not anticipated to be an issue for the storm ponds and adequately permeable soils will likely be encountered. This is also consistent with the subsurface conditions that were encountered during the summer of 2022 while extending the existing water main and sewer main casings within the railroad ROW. 3.2 Culvert Mandeville Creek flows into the North Park development via two existing CMP culverts that cross Interstate 90. One culvert is a 48-inch equivalent, and the other is a 60-inch equivalent (see Exhibit 1.3). Existing 36-inch culverts convey flow off the development site under the main rail line and Frontage Road before Mandeville Creek outfalls to the East Gallatin River. Flood hazard evaluations have been completed for Mandeville Creek dated 12/9/2016 and an updated flood hazard evaluation dated 8/23/2024. North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 8 A culvert is necessary for the Track C rail spur line to cross Mandeville Creek. This proposed culvert has been designed to handle the estimated peak flow rate of 517-cfs from the 100-year event outlined in the 2016 Mandeville Creek Flood Hazard Evaluation for the North Park Development. A 144” equivalent CMPA (171”x110”) and embedment depth of approximately 1- foot is proposed for the Track C rail spur line crossing. This proposed culvert was modeled as part of the Updated Flood Hazard Evaluation (dated 8/23/2024) along with other proposed crossings (Wheat Drive and Cultivar Street) and existing culverts to be replaced in the future (main rail line and Frontage Road). While flowing at the design rate of 517-cfs, the headwater depth will be maintained below the crown of the culvert. The two existing culverts just downstream of this proposed box culvert are very undersized as noted by the flood hazard reports. The existing culvert at the main rail line is 36-inch diameter consisting of cast iron and heavy wall steel. The existing culvert at Frontage Road is a 36-inch diameter consisting of RCP and CMP. We have coordinated with BNSF about the existing undersized railroad culvert and they have told us we can proceed with designing a replacement culvert capable of passing the estimated peak flow from the 100-year event. We have notified MDT that BNSF is willing to allow their culvert to be upsized just upstream of Frontage Road. MDT has outlined the process for us to design a replacement culvert at the Frontage Road crossing. 4 Maintenance Plan All proposed storm ponds will be privately owned and maintained. Storm infrastructure generally consists of retention storm ponds to capture sediment. The retention ponds may collect debris and should be inspected in the spring and fall and cleaned if debris is present. The proposed retention ponds should be mowed, and any grass clippings or other organic matter collected and removed from the pond bottom. The overflow paths designed for each pond should be kept clear of debris to allow for proper conveyance. A more detailed maintenance plan is outlined below. The proposed retention ponds are relatively small and collect limited drainage areas; however, it will still be critical to monitor and maintain the ponds. 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 North Park Development – Track C Rail Extension September 18, 2024 Project: 14‐167 Bozeman Office . 32 Discovery Drive . Bozeman, Montana 59718 . Ph: (406) 582-0221 . Fax: (406) 582-5770 Page 9 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 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. P:\2014\14‐167 North Park\05 Design\H & H\Railroad Mandeville Crossing\Storm Drainage Design Report\1 Storm Drainage Report\Storm Drainage Report ‐ 2024_09_18.docx EX-Civil Engineering Geotechnical Engineering Land Surveying 32 DISCOVERY DRIVE . BOZEMAN, MT 59718 PHONE (406) 582-0221 . FAX (406) 582-5770 www.alliedengineering.com NORTH PARK DEVELOPMENT VICINITY MAP BOZEMAN, MT N N 1.1 EX-Civil Engineering Geotechnical Engineering Land Surveying 32 DISCOVERY DRIVE . BOZEMAN, MT 59718 PHONE (406) 582-0221 . FAX (406) 582-5770 www.alliedengineering.com NORTH PARK DEVELOPMENT USGS QUAD MAP BOZEMAN, MT N 1.2 EXHIBIT 1.3 MANDEVILLE CREEK OVERVIEW ƉƉĞŶĚŝǆ ^ƵƉƉŽƌƚŝŶŐĂůĐƵůĂƚŝŽŶƐ Job #: 14-167 Engineer: Eric Foss Date: 09/16/2024 Calculation of Required Volume for Storm Detention Pond Pond ID Track C Rail Extension Accepts flow from basins Basin A (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 Pre-development Calculations Post-development Calculations CC Areas (ft2):open space 45,386 0.20 Areas (ft2):open space 28,032 0.20 med. res. 0.35 med. res. 0.35 dense res. 0.50 dense res. 0.50 comm. neigh. 0.60 comm. neigh. 0.60 comm. down. 0.80 comm. down. 0.80 Pavement 0.98 Pavement 17,354 0.98 Total: 45,386 Total: 45,386 total area: 1.04 acres total area: 1.04 acres composite C: 0.20 composite C: 0.50 Overland tc Overland tcaverage slope: 0.9 percent average slope: 22.5 percent travel distance: 815 feet travel distance: 13.5 feet tc:50 minutes tc:1 minutes (calculated) tc:6 minutes (minimum) Channel tc Channel tc channel tc:minutes channel tc:minutes Total tc:50 minutes Total tc:6 minutes intensity at tc (fig 23):0.72 in/hr intensity at tc (fig 23):2.86 in/hr pre-devel peak runoff: 0.15 cfs post-devel peak runoff: 1.48 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs) Volume (cf) Volume (cf) Storage (cf) 6 2.86 1.48 534 54 480 8 2.37 1.23 591 72 519 10 2.05 1.06 639 90 548 12 1.82 0.95 681 108 573 14 1.65 0.86 719 127 592 16 1.51 0.78 753 145 609 18 1.40 0.73 785 163 622 20 1.31 0.68 814 181 634 22 1.23 0.64 842 199 643 24 1.16 0.60 868 217 651 26 1.10 0.57 893 235 658 28 1.05 0.55 916 253 663 30 1.00 0.52 938 271 667 32 0.96 0.50 960 289 671 34 0.93 0.48 980 307 673 36 0.89 0.46 1000 325 675 38 0.86 0.45 1019 343 676 40 0.83 0.43 1038 361 676 42 0.81 0.42 1056 380 676 44 0.78 0.41 1073 398 675 46 0.76 0.39 1090 416 674 48 0.74 0.38 1106 434 672 50 0.72 0.37 1122 452 670 52 0.70 0.36 1138 470 668 54 0.69 0.36 1153 488 665 56 0.67 0.35 1168 506 661 58 0.65 0.34 1182 524 658 required detention storage (ft3) =676 Detention Pond COB - Track C Rail Extension 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 = 0.50 (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 = 1.04 acres settling velocity of particle 0.0069 feet/second Q = 0.21 cfs min. pond to settle particle 22 square feet required retention storage (ft3) =1,524 ft3 pond dimentions assuming vertical side slopes (actual pond footprint will be larger) design depth 1.00 feet width 12 length/width ratio 1.00 length 37 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 39 Contour Area (ft2) Delta V (ft 3)Volume (ft3)length 39 100.0 100.5 500 125 125 101.0 1,000 375 500 101.5 1,500 625 1,125 Design storage at 1.5' depth (ft3) =1,125 Detention Pond COB - Track C Rail Extension Job #: 14-167 Engineer: Eric Foss Date: 09/16/2024 Calculation of Required Volume for Storm Detention Pond Pond ID Track C Rail Extension Accepts flow from basins Basin B.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 Pre-development Calculations Post-development Calculations CC Areas (ft2):open space 9,900 0.20 Areas (ft2):open space 5,980 0.20 med. res. 0.35 med. res. 0.35 dense res. 0.50 dense res. 0.50 comm. neigh. 0.60 comm. neigh. 0.60 comm. down. 0.80 comm. down. 0.80 Pavement 0.98 Pavement 3,920 0.98 Total: 9,900 Total: 9,900 total area: 0.23 acres total area: 0.23 acres composite C: 0.20 composite C: 0.51 Overland tc Overland tcaverage slope: 3.4 percent average slope: 5.5 percent travel distance: 190 feet travel distance: 210 feet tc:15 minutes tc:9 minutes (calculated) Channel tc Channel tc channel tc:minutes channel tc:minutes Total tc:15 minutes Total tc:9 minutes intensity at tc (fig 23):1.55 in/hr intensity at tc (fig 23):2.18 in/hr pre-devel peak runoff: 0.07 cfs post-devel peak runoff: 0.25 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs) Volume (cf) Volume (cf) Storage (cf) 9 2.18 0.25 138 38 99 11 1.92 0.22 148 47 101 13 1.72 0.20 156 55 101 15 1.57 0.18 164 64 101 17 1.45 0.17 172 72 100 19 1.35 0.16 178 80 98 21 1.26 0.15 185 89 96 23 1.19 0.14 191 97 93 25 1.13 0.13 196 106 91 27 1.07 0.12 202 114 87 29 1.02 0.12 207 123 84 31 0.98 0.11 212 131 81 33 0.94 0.11 216 140 77 35 0.91 0.10 221 148 73 37 0.88 0.10 225 156 69 39 0.85 0.10 229 165 64 41 0.82 0.09 233 173 60 43 0.79 0.09 237 182 55 45 0.77 0.09 241 190 51 47 0.75 0.09 245 199 46 49 0.73 0.08 248 207 41 51 0.71 0.08 252 216 36 53 0.69 0.08 255 224 31 55 0.68 0.08 259 232 26 57 0.66 0.08 262 241 21 59 0.65 0.07 265 249 16 61 0.63 0.07 268 258 10 required detention storage (ft3) =101 Detention Pond Calculations: Retention Pond Calculations: Detention Pond COB - Track C Rail Extension design depth of pond 1.50 feet Q = CIA max side slope 4.00 horizontal to 1.00 vertical C = 0.51 (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 = 0.23 acres settling velocity of particle 0.0069 feet/second Q = 0.05 cfs min. pond to settle particle 10 square feet required retention storage (ft3) =340 ft3 pond dimentions assuming vertical side slopes (actual pond footprint will be larger) design depth 1.50 feet width 5 length/width ratio 1.00 length 14 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 15 Contour Area (ft2) Delta V (ft 3)Volume (ft3)length 15 100.0 100.5 500 125 125 101.0 1,000 375 500 101.5 1,500 625 1,125 Design storage at 1.5' depth (ft3) =1,125 Detention Pond COB - Track C Rail Extension Job #: 14-167 Engineer: Eric Foss Date: 09/16/2024 Calculation of Required Volume for Storm Detention Pond Pond ID Track C Rail Extension Accepts flow from basins Basin B.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 Pre-development Calculations Post-development Calculations CC Areas (ft2):open space 4,528 0.20 Areas (ft2):open space 2,755 0.20 med. res. 0.35 med. res. 0.35 dense res. 0.50 dense res. 0.50 comm. neigh. 0.60 comm. neigh. 0.60 comm. down. 0.80 comm. down. 0.80 Pavement 0.98 Pavement 1,773 0.98 Total: 4,528 Total: 4,528 total area: 0.10 acres total area: 0.10 acres composite C: 0.20 composite C: 0.51 Overland tc Overland tcaverage slope: 3.2 percent average slope: 5.3 percent travel distance: 160 feet travel distance: 140 feet tc:14 minutes tc:8 minutes (calculated) Channel tc Channel tc channel tc:minutes channel tc:minutes Total tc:14 minutes Total tc:8 minutes intensity at tc (fig 23):1.61 in/hr intensity at tc (fig 23):2.46 in/hr pre-devel peak runoff: 0.03 cfs post-devel peak runoff: 0.13 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs) Volume (cf) Volume (cf) Storage (cf) 8 2.46 0.13 59 15 43 10 2.11 0.11 64 19 44 12 1.87 0.10 68 23 45 14 1.68 0.09 72 27 45 16 1.54 0.08 75 31 44 18 1.42 0.07 79 35 43 20 1.33 0.07 82 39 42 22 1.25 0.07 85 43 41 24 1.18 0.06 87 47 40 26 1.11 0.06 90 51 38 28 1.06 0.06 92 55 37 30 1.01 0.05 94 60 35 32 0.97 0.05 97 64 33 34 0.93 0.05 99 68 31 36 0.90 0.05 101 72 29 38 0.87 0.05 103 76 27 40 0.84 0.04 105 80 25 42 0.81 0.04 106 84 23 44 0.79 0.04 108 88 20 46 0.77 0.04 110 92 18 48 0.74 0.04 112 96 16 50 0.72 0.04 113 100 13 52 0.71 0.04 115 104 11 54 0.69 0.04 116 108 8 56 0.67 0.04 118 112 6 58 0.66 0.03 119 116 3 60 0.64 0.03 121 120 1 required detention storage (ft3) =45 Detention Pond Calculations: Retention Pond Calculations: Detention Pond COB - Track C Rail Extension design depth of pond 1.50 feet Q = CIA max side slope 4.00 horizontal to 1.00 vertical C = 0.51 (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 = 0.10 acres settling velocity of particle 0.0069 feet/second Q = 0.02 cfs min. pond to settle particle 5 square feet required retention storage (ft3) =154 ft3 pond dimentions assuming vertical side slopes (actual pond footprint will be larger) design depth 1.00 feet width 3 length/width ratio 1.00 length 9 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 12 Contour Area (ft2) Delta V (ft 3)Volume (ft3)length 12 100.0 100.5 500 125 125 101.0 1,000 375 500 101.5 1,500 625 1,125 Design storage at 1.5' depth (ft3) =1,125 Detention Pond COB - Track C Rail Extension Job #: 14-167 Engineer: Eric Foss Date: 09/16/2024 Calculation of Required Volume for Storm Detention Pond Pond ID Track C Rail Extension Accepts flow from basins Basin C (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 Pre-development Calculations Post-development Calculations CC Areas (ft2):open space 31,231 0.20 Areas (ft2):open space 11,984 0.20 med. res. 0.35 med. res. 0.35 dense res. 0.50 dense res. 0.50 comm. neigh. 0.60 comm. neigh. 0.60 comm. down. 0.80 comm. down. 0.80 Pavement 0.98 Pavement 19,247 0.98 Total: 31,231 Total: 31,231 total area: 0.72 acres total area: 0.72 acres composite C: 0.20 composite C: 0.68 Overland tc Overland tcaverage slope: 2 percent average slope: 22.5 percent travel distance: 260 feet travel distance: 13.5 feet tc:22 minutes tc:1 minutes (calculated) tc:6 minutes (minimum) Channel tc Channel tc channel tc:minutes channel tc:minutes Total tc:22 minutes Total tc:6 minutes intensity at tc (fig 23):1.25 in/hr intensity at tc (fig 23):2.86 in/hr pre-devel peak runoff: 0.18 cfs post-devel peak runoff: 1.40 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs) Volume (cf) Volume (cf) Storage (cf) 6 2.86 1.40 502 64 438 8 2.37 1.16 555 86 470 10 2.05 1.00 601 107 493 12 1.82 0.89 640 129 512 14 1.65 0.80 676 150 526 16 1.51 0.74 708 171 537 18 1.40 0.68 738 193 545 20 1.31 0.64 765 214 551 22 1.23 0.60 791 236 556 24 1.16 0.57 816 257 559 26 1.10 0.54 839 279 560 28 1.05 0.51 861 300 561 30 1.00 0.49 882 321 561 32 0.96 0.47 902 343 559 34 0.93 0.45 922 364 557 36 0.89 0.44 940 386 555 38 0.86 0.42 958 407 551 40 0.83 0.41 976 429 547 42 0.81 0.39 992 450 542 44 0.78 0.38 1009 472 537 46 0.76 0.37 1025 493 532 48 0.74 0.36 1040 514 526 50 0.72 0.35 1055 536 519 52 0.70 0.34 1070 557 512 54 0.69 0.33 1084 579 505 56 0.67 0.33 1098 600 497 58 0.65 0.32 1111 622 490 required detention storage (ft3) =561 Detention Pond COB - Track C Rail Extension 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 = 0.68 (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 = 0.72 acres settling velocity of particle 0.0069 feet/second Q = 0.20 cfs min. pond to settle particle 26 square feet required retention storage (ft3) =1,433 ft3 pond dimentions assuming vertical side slopes (actual pond footprint will be larger) design depth 1.50 feet width 11 length/width ratio 1.00 length 33 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 31 Contour Area (ft2) Delta V (ft 3)Volume (ft3)length 31 100.0 100.5 500 125 125 101.0 1,000 375 500 101.5 1,500 625 1,125 Design storage at 1.5' depth (ft3) =1,125 Detention Pond COB - Track C Rail Extension Job #: 14-167 Engineer: Eric Foss Date: 09/16/2024 Calculation of Required Volume for Storm Detention Pond Pond ID Track C Rail Extension Accepts flow from basins Basin D (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 Pre-development Calculations Post-development Calculations CC Areas (ft2):open space 16,069 0.20 Areas (ft2):open space 8,076 0.20 med. res. 0.35 med. res. 0.35 dense res. 0.50 dense res. 0.50 comm. neigh. 0.60 comm. neigh. 0.60 comm. down. 0.80 comm. down. 0.80 Pavement 0.98 Pavement 7,993 0.98 Total: 16,069 Total: 16,069 total area: 0.37 acres total area: 0.37 acres composite C: 0.20 composite C: 0.59 Overland tc Overland tcaverage slope: 3 percent average slope: 25.2 percent travel distance: 150 feet travel distance: 44 feet tc:14 minutes tc:2 minutes (calculated) tc:6 minutes (minimum) Channel tc Channel tc channel tc:minutes channel tc:minutes Total tc:14 minutes Total tc:6 minutes intensity at tc (fig 23):1.63 in/hr intensity at tc (fig 23):2.86 in/hr pre-devel peak runoff: 0.12 cfs post-devel peak runoff: 0.62 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes) (in/hr) Rate (cfs) Volume (cf) Volume (cf) Storage (cf) 6 2.86 0.62 223 43 180 8 2.37 0.51 247 58 189 10 2.05 0.44 267 72 195 12 1.82 0.40 285 86 198 14 1.65 0.36 300 101 200 16 1.51 0.33 315 115 199 18 1.40 0.30 328 130 198 20 1.31 0.28 340 144 196 22 1.23 0.27 352 158 193 24 1.16 0.25 363 173 190 26 1.10 0.24 373 187 186 28 1.05 0.23 383 202 181 30 1.00 0.22 392 216 176 32 0.96 0.21 401 230 171 34 0.93 0.20 410 245 165 36 0.89 0.19 418 259 159 38 0.86 0.19 426 274 152 40 0.83 0.18 434 288 146 42 0.81 0.18 441 302 139 44 0.78 0.17 448 317 132 46 0.76 0.16 455 331 124 48 0.74 0.16 462 346 117 50 0.72 0.16 469 360 109 52 0.70 0.15 475 374 101 54 0.69 0.15 482 389 93 56 0.67 0.15 488 403 85 58 0.65 0.14 494 418 76 required detention storage (ft3) =200 Detention Pond COB - Track C Rail Extension 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 = 0.59 (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 = 0.37 acres settling velocity of particle 0.0069 feet/second Q = 0.09 cfs min. pond to settle particle 17 square feet required retention storage (ft3) =637 ft3 pond dimentions assuming vertical side slopes (actual pond footprint will be larger) design depth 1.50 feet width 7 length/width ratio 1.00 length 20 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 21 Contour Area (ft2) Delta V (ft 3)Volume (ft3)length 21 100.0 100.5 500 125 125 101.0 1,000 375 500 101.5 1,500 625 1,125 Design storage at 1.5' depth (ft3) =1,125 Detention Pond COB - Track C Rail Extension Pre-Development 𝒕𝒄 Calculation for Basin A: 𝑡௖ =1.87൫1.1 −𝐶𝐶௙൯𝐷ଵ ଶ 𝑆 ଵ ଷ Where: 𝑡௖ = Time of concentration,𝑚𝑖𝑛𝑢𝑡𝑒𝑠 S = Slope of basin,% = 0.9% C = Rational Method Runoff Coefϐicient = 0.20 D = Length of Basin,𝑓𝑒𝑒𝑡= 815 𝑓𝑡 𝐶௙ = Frequency Adjustment Factor = 1.00 𝑡௖ =1.87(1.1 − (0.20)(1.00))815𝑓𝑡 ଵ ଶ 0.9%ଵ ଷ =𝟓𝟎 𝒎𝒊𝒏𝒖𝒕𝒆𝒔 Water Quality Volume Calculation for Basin A: 𝑉௤ =𝐴௜𝑃 Where: 𝑉௤ = Water Quality Volume to be Retained,𝑐𝑢𝑏𝑖𝑐 𝑓𝑒𝑒𝑡 𝐴௜ = Impervious Area,𝑠𝑞𝑢𝑎𝑟𝑒 𝑓𝑒𝑒𝑡= 17,354 𝑠𝑞 𝑓𝑡 𝑃= Precipitation from ϐirst half inch of rain,𝑖𝑛𝑐ℎ𝑒𝑠= 0.5 𝑖𝑛𝑐ℎ𝑒𝑠 𝑉௤ =(17,354 𝑠𝑞 𝑓𝑡)(0.5 𝑖𝑛𝑐ℎ𝑒𝑠)൬ 1 𝑓𝑡 12 𝑖𝑛𝑐ℎ𝑒𝑠൰ =𝟕𝟐𝟑 𝒄𝒖𝒃𝒊𝒄 𝒇𝒆𝒆𝒕 ƉƉĞŶĚŝǆ Storm Drainage Plan PROJECT LOCATION BOZEMAN TRAX - TRACK C RAIL EXTENSION BOZEMAN, MONTANABOZEMAN TRAX TRACK C RAIL EXTENSION PROJECT ENGINEER: RORY S. ROMEY, PE DESIGN ENGINEERS: RORY S. ROMEY, PE ERIC J. FOSS, PE Civil Engineering Geotechnical Engineering Land Surveying 32 DISCOVERY DRIVE BOZEMAN, MT 59718 PHONE (406) 582-0221 FAX (406) 582-5770 www.alliedengineering.com LOCATION MAP OWNER: BOZEMAN TRAX PARTNERS LLC 5148 US 89 LVINGSTON, MT 59047 DEVELOPER: BOZEMAN TRAX PARTNERS LLC 5148 US 89 LIVINGSTON, MT 59047 CIVIL ENGINEER:ALLIED ENGINEERING SERVICES, INC. 32 DISCOVERY DRIVE BOZEMAN, MT 59718 N VICINITY MAP N PARCEL & SITE COVERAGE INFORMATION: SEPTEMBER 18, 2024 BOZEMAN LEGAL DESCRIPTION:A PORTION OF THE MONTANA RAIL LINK RIGHT-OF-WAY IN SECTION 36, TOWNSHIP 01S, RANGE 05E, P.M.M., GALLATIN COUNTY, MT; SECTION 36, TOWNSHIP 01S, RANGE 05E, C.O.S. 2153A PARCEL TRACT 2-B; P.M.M., GALLATIN COUNTY, MT. PROJECT LOCATION: BOUNDED TO THE NORTH BY THE RAILROAD MAINLINE/FRONTAGE ROAD, TO THE EAST BY TRACT 4-B OF COS 2153A, TO THE SOUTH BY TRACT 3-B OF COS 2153A, AND TO THE WEST BY TRACT 1-B OF COS 2153A IN THE CITY OF BOZEMAN, MONTANA. PROJECT SURVEYOR:GREG FINK, PLS BRANDON SCHREINER, PLS SHEET INDEX PEDESTRIAN FACILITIES ARE NOT INCLUDED WITH THE PROPOSED IMPROVEMENTS ƉƉĞŶĚŝǆC Groundwater Monitoring Data January 2024 Project No. 21363.01 GROUNDWATER MONITORING MEMORANDUM FOR SIMKINS NORTH PARK BOZEMAN, MONTANA During the period of April 12, 2023, to August 16, 2023, Sanderson Stewart performed weekly manual groundwater measurements at Simkin’s proposed sites, Tracts 2-B, 3-B, and 4-B, within North Park. Ten wells were monitored to determine the peak groundwater depth at various locations, see Monitoring Well Layout Exhibit. The groundwater elevations were measured using a Dipper-T water level meter within ten semi-permeable PVC pipes inserted into the ground. Shown below is a table and graph of the manual measurements recorded relative to the ground surface during the study. GROUNDWATER DEPTH BELOW GROUND SURFACE DATE WELL #1 WELL #2 WELL #3 WELL #4 WELL #5 WELL #7 WELL #8 WELL #9 WELL #10 WELL #11 4/12/2023 #N/A 6.57 7.01 7.56 6.05 N/A N/A 9.62 8.77 5.68 4/21/2023 7.63 6.22 7.00 7.69 7.04 7.98 8.63 8.63 7.73 5.18 4/28/2023 7.63 6.89 7.64 7.60 7.63 6.84 8.75 8.42 7.77 5.16 5/5/2023 7.63 7.2 7.63 7.59 7.63 6.96 8.75 8.61 8.15 5.58 5/10/2023 7.63 7.46 7.63 7.59 7.63 7.07 8.75 8.78 8.42 5.83 5/17/2023 7.63 7.63 7.63 7.59 7.63 7.54 8.75 9.33 8.90 6.25 5/26/2023 7.63 7.63 7.63 7.59 7.63 7.62 8.75 9.33 8.86 6.23 6/1/2023 7.63 7.63 7.63 7.59 7.63 7.44 8.75 9.33 8.95 6.26 6/9/2023 7.63 7.63 7.63 7.59 7.63 7.25 8.75 9.25 8.59 5.89 6/16/2023 7.63 7.63 7.63 7.59 7.63 7.28 8.75 9.33 8.70 6.04 6/23/2023 7.63 7.63 7.63 7.59 7.63 7.12 8.75 9.15 8.47 5.83 6/30/2023 7.63 7.48 7.63 7.59 7.63 7.03 8.75 8.97 8.32 5.75 7/5/2023 7.63 7.63 7.63 7.59 7.63 7.23 8.75 9.19 8.61 6.03 7/17/2023 7.63 7.63 7.63 7.59 7.63 7.47 8.75 9.33 9.06 6.51 7/24/2023 7.63 7.63 7.63 7.59 7.63 7.59 8.75 9.33 9.28 6.72 8/16/2023 7.63 7.63 7.63 7.59 7.63 7.98 8.75 9.33 9.33 7.07 =NO GROUNDWATER PRESENT =GROUNDWATER PRESENT CONCLUSION Throughout the study three of the ten wells never contained groundwater, monitoring Wells 2 and 9 had groundwater present for a portion of the monitoring period, and monitoring Wells 7, 10, and 11 had groundwater present throughout the study. The data collected from the groundwater monitoring wells, both shown in the table and the graph, fail to provide a clear peak groundwater elevation. Wells 7, 10, and 11 did see a short peak but that is likely due to the high rainfall events which occurred in June 2023. 024681012Depth (ft)DateGroundwater DepthWELL #1WELL #2WELL #3WELL #4WELL #5WELL #7WELL #8WELL #9WELL #10WELL #11