HomeMy WebLinkAbout047_FloodHazardReport2025MEMO
To: City of Bozeman
From: Rory Romey, PE, Andrew Graham, PE, CFM, Eric Foss, PE
ProjertName: North Park Development, Phase 1 -Flood Study Update
ProjertNmnber: 14-167.10
Date: 2/14/2025
Update to 2016 Flood Hazard Evaluation for Mandeville Creek
Re: 45.705525°, -111.055547°, Bozeman, Montana
Introduction
IDA \
~~D i ENGINEERING j
SERVICES, INC. o .<;
o, \e.'-0 "erse pro
The original flood hazard evaluation for Mandeville Creek was completed in 2016 using 1-D
modeling. The model used surveyed cross sections gathered throughout the length of the study area.
Elevation data from the 2007 City of Bozeman LiDAR mapping was utilized between the surveyed
cross sections. This model focused on the North Park Development property extending from Frontage
Road upstream to Mandeville Drive. The original flood hazard evaluation discussed flood water being
directed to the northwest along the southern side of the railroad right-of-way (ROW) due to backwater
of the existing culverts under Frontage Road the main railroad track and Red Wing Drive. This
overflow path was not studied or mapped because it was beyond the Master Site Plan extents for the
development. The purpose of this Flood Study update is to discuss the proposed phases of the North
Park property development along with the required hydraulic improvements associated with each
phase and to show the corresponding effects to the 100-year inundation boundary and water surface
elevations (WSEs). Improvements impacting the flood hward boundary will include three new creek
crossing locations and grading within the flood hazard boundary. Grading within the boundary will be
related to a stormwater pond on tract 2-B and ineffective flow areas that can be filled in without
increasing WSEs. No structures exist near the flood hazard boundary. The proposed improvements
will be completed in phases, the anticipated phasing of improvements is outlined below. The final
phasing is still to be determined and may vary from what is outlined.
Project Phasing
Existing Conditions
For this study, the existing condition of the North Park Development property is considered to be the
site conditions prior to development associated with the North Park improvements. This pre-
development condition was the site condition analyzed in the 2016 Flood Study. Figure 2 shows the
existing condition topography and site features.
32 Discovery Drive ♦ Bozeman, MT 59718 ♦ (406) 582-0221 ♦ Fax (406) 582-5770
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 2
The project site conveys Mandeville Creek and the Farmers Canal from the Interstate-90 crossing to
the outfall from the property at the railroad mainline and Frontage Road. Mandeville Creek is
conveyed across I-90 via a 60-inch equivalent CMPA culvert. Farmers Canal is conveyed across I-90
via a 48-inch equivalent CMPA culvert. Mandeville Creek and Farmers Canal join into a single
channel near the south end of the project site. Prior to any improvements associated with the
development, Mandeville Creek was conveyed across Red Wing Drive via a 36-inch CMP culvert, the
railroad mainline via a 36-inch cast iron culvert, and Frontage Road via a 36-inch CMP culvert.
Additional information is provided in the original report from 2016.
As-Built Condition (as of 3/27/2023)
In 2022 a significant amount of earthwork took place within the railroad ROW to add siding tracks
and stubs for future spur lines. Some of this earthwork filled the low-laying areas that previously
provided conveyance to the northwest. The Red Wing Drive crossing was removed as part of this
work and the existing 36” cast iron railroad culvert was extended approximately 40’ upstream to
account for the additional railroad tracks. Figures 3 and 3.1 show the As-Built Condition topography
and site features.
Track C Crossing
The improvements will involve a crossing for the Track C railroad spur line that is necessary for rail
access to Tract 2-B. This crossing is anticipated to be constructed in 2025. The structure for this
crossing is modeled as a 144” equivalent CMPA culvert (171”x110”) with a 1’ embedment depth. The
design of the structure for the crossing is not yet finalized with the railroad and may require switching
to a multi-barrel crossing with equivalent hydraulic capacity. Initial modeling has indicated that the
alternative crossing configuration would have a minimal impact or no change in the WSE. Impacts to
the final WSE would need to be verified once the final configuration has been selected. Figure 4
shows the Track C crossing topography and site features.
Track C Crossing with 2-B Grading
The improvements associated with developing Tract 2-B will involve constructing a stormwater pond
falling partially within the existing 100-year flood hazard boundary. The proposed pond has been
coordinated and is planned to account for runoff associated with the site improvements and the Wheat
Drive extension. Depending on the phasing of site improvements vs. the Wheat Drive extension, a
smaller stormwater pond and swale specific to the Wheat Drive improvements may be constructed.
This smaller stormwater pond fits within the footprint of the future stormwater pond that will also
serve Tract 2-B. Only the larger stormwater pond was modeled because it results in a more
conservative flood hazard boundary. Figure 5 shows the Track C Condition with 2-B Grading
topography and site features.
Track C, Wheat Drive and Cultivar Street Crossings
Development on the west side of Mandeville Creek is anticipated to require two additional Mandeville
Creek crossings. The two crossings will be Wheat Drive and Cultivar Street. These two crossings are
anticipated to be constructed in 2025 or 2026 and are proposed as precast concrete box culverts with a
span of 18’ and rise of 6’ with embedment depths of 1’. Figure 6 shows the proposed improvements
and associated flood hazard boundary.
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 3
Final Condition
The Cultivar Street crossing Mandeville Creek results in backwater areas directly adjacent to and
upstream of Cultivar Street. Additional improvements involve grading within the 100-year flood
hazard boundary resulting from the Cultivar Street crossing. The grading/fill will maintain the
original/existing condition flood hazard boundary in this area. The proposed grading on the east side
of Mandeville Creek is necessary to connect the 10-foot-wide shared use trail to anticipated elevation
of the Cultivar Street sidewalk. The proposed grading on the west side of Mandeville Creek will
maintain the existing condition flood hazard boundary and blend with the proposed road grades. Fill
not associated with road crossing improvements will be outside of wetland areas. This grading on the
west side amounts to approximately 1,500 CY of fill. The max fill depth is approximately 2.6 feet.
Figure 7 shows the proposed topography and site features. All timelines outlined above are subject to
change. As of now, all crossing improvements outlined above are being included under a single
general permit with the Army Corps of Engineers being a primary driver due to wetland impacts.
Future Condition
Long range improvements are anticipated to involve replacing the existing undersized 36-inch culverts
at the mainline railroad track and Frontage Road. The improved crossings will provide conveyance for
the 100-year event without overflowing the northwest as is currently the case. All conveyance will be
routed under the main rail line, under Frontage Road, and to the East Gallatin River. This future
condition will be addressed by an updated Flood Hazard Evaluation with a more detailed
consideration of potential impacts to downstream properties.
Hydrology Analysis
A hydrologic analysis was performed for the 2016 Flood Study. The same flow values were adopted
for this study which are 390-cfs for Mandeville Creek and 127-cfs the Farmer’s Canal for a total of
517-cfs. The 2016 Flood Study is included by reference in this report.
Hydraulic Analysis
The updated Flood Study was performed using The Army Corps of Engineer’s Hydrologic
Engineering Center’s River Analysis System (HEC-RAS) version 6.3.1 (USACE, 2022). Mandeville
Creek and the surrounding floodplain area was modeled using a steady-state 2D model consisting of a
cell mesh, inflow and outflow boundary conditions, and 2D connections for the hydraulic structures.
Elevation data for the model was obtained from survey data provided by Allied Engineering, Inc. and
LiDAR data obtained from the 2018 City of Bozeman mapping project. The data’s vertical datum is
NAVD88.
Figure 1 shows the model extents and geometry of the existing conditions. Manning’s n values were
obtained by referencing aerial imagery and from “Open-Channel Hydraulics” (Chow 1959). A
Manning’s n value of 0.045 was appointed to the main channels describing a winding channel with
some weeds and stones. The model was extended far enough downstream so the downstream
boundary conditions did not affect the hydraulics in the development area. However, a normal depth
boundary condition with a friction slope of 0.004 was used for the East Gallatin River outflow
location. Flow hydrograph boundary conditions with constant flow values were used for the inflow
locations where Mandeville Creek and the Farmer’s Canal enter the model area. A 12-hour initial
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 4
conditions time was used to ramp up the flows to increase model stability. A model simulation time of
12 hours was used for all plans and the models were checked to ensure a steady-state condition was
met. A Courant controlled time step was selected with a maximum and minimum courant values of
1.0 and 0.4 respectively with a base time step of 1 second.
Existing Condition
The Existing Condition was modeled using the 2D methodology to compare to the 1D model from the
2016 Flood Study. Figure 2 shows a comparison of the 1D and 2D flood hazard boundaries and WSEs
for the Existing Condition. As depicted in Figure 2, the flood hazard boundary and WSEs of the 1D
and 2D model are similar. The 2D model flood hazard boundary will be used as the Existing
Condition flood hazard boundary for the remainder of this study.
Where the 1D model ended, the 2D model was extended further downstream to the confluence with
the East Gallatin River as well as further to the northwest and eventually to the East Gallatin River.
The overflow path that flows along the southern side of the railroad ROW to the northwest from the
main track railroad crossing of Mandeville Creek is shown in the 2D model. Approximately 438-cfs
of the total 517-cfs is directed along this overflow path because the culverts at Frontage Road, the
main railroad track, and Red Wing Drive are undersized.
As-Built Condition (as of 3/27/2023)
A plan was created with updated geometry and terrain to reflect the As-Built Condition and the flood
hazard boundary was remapped. The resulting flood hazard boundary was the same from the upstream
end of the model to within approximately 400-ft of the railroad ROW. In this case, the grading
associated with the railroad siding tracks results in a higher backwater elevation to overtop to the
northwest. This increased WSE causes backwater to extend further upstream and laterally in the
adjacent property. The overflow path to the northwest is maintained in this configuration with
approximately 423-cfs being directed that way. This As-Built Condition shows a 15-cfs increase in
flow rate through the Frontage Road culvert. The 15-cfs increase is measured for all following phases.
The text within the Final Condition phase provides for analysis of downstream water surface
elevations impacts. Figure 3 shows a comparison between the Existing Condition and the As-Built
Condition flood hazard boundary. Figure 3.1 shows the same comparison at a larger scale.
Track C Condition
A plan was created using the proposed Track C crossing overlaid onto the As-Built Condition terrain.
Figure 4 shows a comparison between Track C Condition and the Existing Condition flood hazard
boundary. The flood hazard boundary for the Track C Condition is nearly identical to the as-built
condition. This is because the culvert proposed for Track C is capable of passing the 517-cfs flow
from the 100-year event. The existing 36” culvert at the main rail line still causes the same backwater
scenario seen in the As-Built Condition. Figure 4.1 shows a comparison at a larger scale between the
Track C Condition and the As-Built Condition flood hazard boundary.
Track C Condition with 2-B Grading
A plan was created using the proposed Track C crossing and Tract 2-B Grading overlaid onto the As-
Built Condition terrain. Figure 5 shows a comparison between Track C with 2-B Grading and the
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 5
Existing Condition flood hazard boundary. The flood hazard boundary for the Track C Condition with
2-B Grading is nearly identical to the Track C Condition. The only measurable difference is at the
proposed storm pond area on Tract 2-B. The grading necessary for the storm pond extends the
inundation boundary to the east to match the footprint of the pond. Water surface elevation in this area
remains the same as the previous condition. Figure 5.1 shows a comparison to the Existing Condition
flood hazard boundary at a larger scale.
Track C Condition with Wheat and Cultivar Crossings
A model was created using the proposed topography from the previous condition and adding the
proposed crossings for Wheat Drive and Cultivar Street. Modeling for this phase of the project was
completed using the anticipated culvert sizing, elevations, and grading discussed in the Project
Phasing section. The two new street crossings upstream of Track C in this condition have minimal
impact to the flood hazard extents because each culvert is sized to handle the 517-cfs. However, there
is a small backwater area at the Cultivar Street crossing where the flood hazard extent expands due to
a localized increase in the WSE. This backwater area extends approximately 400’ upstream of the
proposed Cultivar Street crossing. Figure 6 shows a comparison to the Existing Condition flood
hazard boundary. Figure 6.1 shows this comparison at a larger scale.
Final Condition
The modeling for this phase of the project was completed using the anticipated culvert sizing and
grading discussed in the Project Phasing section. The area just upstream of the future Cultivar Street
crossing will be impacted by the approved (but not yet constructed) shared use trail. The grading
necessary for the shared use trail to climb up to the proposed sidewalk elevation will cut off a large
area from the 100-year floodplain. This does not result in increased WSEs. Therefore, this area on the
east side of the creek can be filled in if needed. The 10-ft-wide shared use trail is entirely outside the
Final Condition 100-year flood hazard boundary. Grading on the west side of Mandeville Creek was
modeled to show the floodplain extents can be reduced in this area without increasing the WSE.
Figure 7 shows a comparison between the Existing Condition flood hazard boundary and the Final
Condition. Figure 7.1 shows this comparison at a larger scale. Figure 7.2 displays the area just
upstream of the Cultivar crossing in detail. Similar to all other conditions listed, the Final Condition
maintains the existing overtopping path to the northwest along the railroad towards the 19th Avenue
overpass.
As mentioned previously, all phases beyond the Existing Condition result in approximately a 15-cfs
increase in flow rate through the Frontage Road culvert. The resulting increased WSEs north of
Frontage Road are under the half foot allowable rise when compared to the Existing Condition.
Exhibit 1 displays a plan and profile of the Mandeville Creek outfall to the East Gallatin River.
Exhibits 2, 3, and 4 show cross sections at corresponding stationing. These cross sections provide a
comparison between the 100-year event WSEs. Finished floor elevations of structures adjacent to the
creek are also estimated and drawn on the cross sections. The largest increase in WSE is 0.25-ft.
It should be noted that the elevation data used for this updated flood hazard study has been updated
since the original flood hazard evaluation took place in 2016. The most recent (year 2018) City of
Bozeman LiDAR was used for the current study along with finished design grading for the proposed
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 6
conditions. Table 1 shows a comparison of WSEs at key locations during the 100-year event for the
various conditions previously outlined.
Table 1. 100-year Event Water Surface Elevations Comparisons (Units = Feet, Datum = NAVD 88)
Crossing
Location*
Existing
Condition
(2016 Flood
Study)
As-Built
Condition (as
of 3/27/3023)
Track C
Condition
Track C
Condition
with 2-B
Grading
Track C
Condition
with Wheat
and Cultivar
Crossings
Final
Condition
Cultivar
Lane 4701.5 4701.5 4701.5 4701.5 4706.1 4706.1
Wheat
Drive 4674.9 4675.1 4675.2 4675.2 4676.9 4676.9
Track C 4670.6 4674.5 4674.5 4674.5 4674.5 4674.5
Railroad
Main Track 4670.6 4674.5 4674.5 4674.5 4674.5 4674.5
*These water surface elevations were measured just upstream of the indicated crossing locations.
Project Phasing and Conservative Boundary
The exact phasing outlined above is subject to change. Additionally, there are site plan applications
under review for lots adjacent to Mandeville Creek. To address unknown phasing and the current site
plan applications, a conservative flood hazard boundary is proposed. The conservative boundary is a
compilation of each condition outlined above to create somewhat of a “worst case” scenario boundary.
The widest inundation extents from each condition for all areas of Mandeville Creek will be held as
the 100-year boundary. This will eliminate the need for showing multiple flood hazard boundaries
depending on the project phasing. Figure 8 shows the conservative flood hazard boundary. This
conservative boundary is displayed on the Master Site Plan. It is our understanding that a modification
to the Master Site Plan and an updated Flood Hazard Evaluation will be required to revise this
boundary in the future.
2/14/2025
North Park Development
Allied Engineering Services, Inc. Flood Hazard Evaluation Page 7
Attachments:
1. Figure 1 – 2D Model Set Up – Existing Conditions
2. Figure 2 – Existing Conditions – 1D/2D Comparison
3. Figure 3 – As-Built/Existing Condition Comparison
4. Figure 3.1 – As-Built/ Existing Condition Comparison Overall
5. Figure 4 – Track C Condition Comparison
6. Figure 4.1 – Track C Condition Comparison Overall
7. Figure 5 – Track C Condition with 2-B Grading Comparison
8. Figure 5.1 – Track C Condition with 2-B Grading Comparison Overall
9. Figure 6 – Track C with Wheat and Cultivar Crossings Comparison
10. Figure 6.1 – Track C with Wheat and Cultivar Crossings Comparison Overall
11. Figure 7 – Final Condition Comparison
12. Figure 7.1 – Final Condition Comparison Overall
13. Figure 7.2 – Final Condition Cultivar Crossing Detail
14. Figure 8 – Conservative Boundary Comparison
15. Exhibit 1 – Mandeville Creek Plan & Profile
16. Exhibits 2, 3, and 4 – Mandeville Creek Cross Sections
REFERENCES
Allied Engineering Services Inc. (2016). Flood Hazard Evaluation for Mandeville Creek. Bozeman,
Montana.
Chow, V. T. (1959). Open-Channel Hydraulics. Caldwell: The Blackburn Press.
US Army Corps of Engineers. (2022). River Analysis System (HEC-RAS) V6.3.1. Davis, California.
Federal Emergency Management Agency (2021). Flood Insurance Study: Gallatin County, Montana
and Incorporated Areas. Volume 1 of 4.
P:\2014\14-167 North Park\05 Design\H & H\2023 Flood Study\Report Update 2025\Working Doc\North Park Flood Hazard Evaluation.docx
FIGURE: 1DRAWN BY: TWCDATE: 5/17/2023PROJECT: 14-167³0 540 1,080 1,620Feet
NORTH PARK2D MODEL SET UP - EX. CONDITIONSBOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In\Figure 1 - Model Set Up.mxd1 inch = 900 feet
Mandeville Creek
Legend
2D Model Area
Boundary Condition Lines (Inflow/Outflow Locations)
2D Connections (Hydraulic Structure Locations)
2D Existing Conditions - 1% AC Flood Hazard Boundary
East Gallatin River
46954690468047154710470046854665466047454740473547304730472546554650 47254720
47054700468046504660 46554725472047304675466546704670 467046604655473547354725473047304730471546904695
46754665 4670465547304680.44715.74709.84707.84706.24702.947004697.54694.64691.54686.74683.54675.54672.4FIGURE: 2DRAWN BY: TWCDATE: 2/12/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARKEX. CONDITIONS - 1D/2D COMPARISON
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In\Figure 2 - Existing Conditions.mxd1 inch = 400 feet
Mandeville Creek
Legend
1D Cross Sections
2016 Flood Study 1D - 1% AC Flood Hazard Boundary
2D WSE Contours (2-ft Contour Interval)
2023 Flood Study 2D - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive
36" CMP Culvert (since removed)
36" Cast Iron Culvert (since extended)
36" CMP Culvert
48" EquivalentCMPA Culvert
48" CMP Culvert
60" EquivalentCMPA Culvert
Baxter Lane
Mandeville Lane
Interstate 90
FarmersCanal
46954690470547004685467546704745474047354730472546604655467046654665466046554650
4725
4720
471547104715
46954680 47304720466546704655 47304735473547254725473047304715
4715
46904680467046604660465046554730FIGURE: 3DRAWN BY: EJFDATE: 2/5/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARKAS-BUILT/EX. COND. COMPARISON
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 3 - As-Built Conditions.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks
Existing Conditions - 1% AC Flood Hazard Boundary
As-Built (12/05/2024) - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removed and railroad culvert extended
Railroad siding and spur line stubs
FIGURE: 3.1DRAWN BY: EJFDATE: 2/3/2025PROJECT: 14-167³0 540 1,080 1,620Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 3.1 - As-Built Conditions Overall.mxd1 inch = 900 feet
Mandeville Creek
Legend
Siding Tracks
Boundary Condition Lines (Inflow/Outflow Locations)
2D Model Area
Existing Conditions - 1% AC Flood Hazard Boundary
As-Built (12/05/2024) - 1% AC Flood Hazard Boundary
East Gallatin River
AS-BUILT/EX. COND. COMPARISON OVERALL
4695469047054700468547454740473546654660466046554730472546704665 4730 472546754670
46554650
4725
4720
471547104715
46954680 4730472046704675 4665465547354735472547254730473047154690
46804670467046604660465046554730FIGURE: 4DRAWN BY: EJFDATE: 2/5/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARKTRACK C/EX. COND. COMPARISON
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 4 - Track C Condition.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks with Track C
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removed and railroad culvert extended
Railroad siding and spur line stubs
Track C crossing
FIGURE: 4.1DRAWN BY: EJFDATE: 2/3/2025PROJECT: 14-167³0 540 1,080 1,620Feet BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 4.1 - Track C Condition Overall.mxd1 inch = 900 feet
Legend
Siding Tracks with Track C
Boundary Condition Lines (Inflow/Outflow Locations)
2D Model Area
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition - 1% AC Flood Hazard Boundary Track C Crossing
Mandeville Creek
East Gallatin River
NORTH PARKTRACK C/EX. COND. COMPARISON OVERALL
4695469047204715474547354665466047304725473547304705
46854670466546554650
47254710
47054700
46804740468046604655 472047304715
46704670
4670 4735472547254725473047304715469046904675
4660465046554660FIGURE: 5DRAWN BY: EJFDATE: 2/5/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 5 - Track C Condition with 2-B Grading.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks with Track C
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition with 2-B Grading - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removedand railroad culvert extended
Railroad siding and spur line stubs
Track C crossing
TRACK C W/ 2-B GRADING/EX. COND. COMPARISON
Storm Pond for 2-Band Wheat Drive Ext.
Wheat DriveExtension
Grading within Tract 2-B
Storm pond and swale forWheat Drive Extension
FIGURE: 5.1DRAWN BY: EJFDATE: 2/3/2025PROJECT: 14-167³0 540 1,080 1,620Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 5.1 - Track C Condition with 2-B Grading Overall.mxd1 inch = 900 feet
Legend
Siding Tracks with Track C
Boundary Condition Lines (Inflow/Outflow Locations)
2D Model Area
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition with 2-B Grading - 1% AC Flood Hazard Boundary
TRACK C W/ 2-B GRADING/EX. COND. COMPARISON OVERALL
Wheat Drive Extension
Storm Pond on 2-B
Mandeville Creek
East Gallatin River
Track C crossing
4730
4720
471547104705470046954725469046654660474547404735473046704665 4685467546554650 4735468046604655 472547204730471047054670467046704665 47354725472547254730473047304715
4715
4690469546804660465046554660FIGURE: 6DRAWN BY: EJFDATE: 2/5/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 6 - Track C Condition with Wheat and Cultivar Crossings.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks with Track C
Wheat and Cultivar Crossings
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition with Wheat and Cultivar Crossings - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removed and railroad culvert extended
Railroad siding and spur line stubs
Track C crossing
TRACK C W/ WHEAT AND CULTIVARCROSSINGS/EX. COND. COMPARISON
Grading within Tract 2-B
Cultivar StreetWheat Drive
Storm Pond for 2-B and Wheat Drive Extension
FIGURE: 6.1DRAWN BY: EJFDATE: 2/3/2025PROJECT: 14-167³0 540 1,080 1,620Feet BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 6.1 - Track C Condition with Wheat and Cultivar Crossings.mxd1 inch = 900 feet
Legend
Siding Tracks with Track C
Boundary Condition Lines (Inflow/Outflow Locations)
2D Model Area
Existing Conditions - 1% AC Flood Hazard Boundary
Track C Condition with Wheat and Cultivar Crossings - 1% AC Flood Hazard Boundary
NORTH PARKTRACK C W/ WHEAT AND CULTIVARCROSSING/EX. COND. COMPARISON OVERALL
Wheat Drive
Storm Pond on 2-B
Mandeville Creek
East Gallatin River Track C crossing
CultivarStreet
4735472547154710469047204695470547004665466047304725473547304705
46854670466546554650
468046604655 4740474547204715
467046704670 467546654735472547254725473047304730471546954680
46604650465547304660FIGURE: 7DRAWN BY: EJFDATE: 2/14/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 7 - Final Condition.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks with Track C
Wheat and Cultivar Crossings
Shared Use Trail
Existing Conditions - 1% AC Flood Hazard Boundary
Final Condition - 1% AC Flood Hazard Boundary
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removed and railroad culvert extended
Railroad siding and spur line stubs
Track C crossing
FINAL CONDITION/EX CONDITION COMPARISON
Grading within Tract 2-B
Cultivar Street
Wheat Drive Shared Use Trail
Grading (fill) modeled toreduce flood hazard extents.
Storm pond for 2-B and Wheat Drive Extension
Area of ineffective flow. Can be filled in withoutincreasing water surface elevations.
Area of ineffective flow. Can be filled inwithout increasing water surface elevations.Future shared use trail embankment cutsoff area from floodplain.
FIGURE: 7.1DRAWN BY: EJFDATE: 2/3/2025PROJECT: 14-167³0 540 1,080 1,620Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 7.1 - Final Condition Overall.mxd1 inch = 900 feet
Legend
Siding Tracks with Track C
Boundary Condition Lines (Inflow/Outflow Locations)
2D Model Area
Existing Conditions - 1% AC Flood Hazard Boundary
Final Condition - 1% AC Flood Hazard Boundary
FINAL CONDITION/EX CONDITIONCOMPARISON OVERALL
Shared Use Trail
Wheat Drive
Storm Pond on 2-B
Mandeville Creek
East Gallatin River Track C crossing
CultivarStreet
47044703470247014700 47054699469846964720
4716
47114714
471047154712
471447134712471047094708471547114695469447124709470747064697 4708471347074694 4709471147074708FIGURE: 7.2DRAWN BY: EJFDATE: 2/14/2025PROJECT: 14-167³0 60 120 180Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 7.2 - Final Condition Cultivar Crossing Grading.mxd1 inch = 100 feet
Mandeville Creek
Legend
Cultivar Crossing
Shared Use Trail
Existing Conditions - 1% AC Flood Hazard Boundary
Final Condition - 1% AC Flood Hazard Boundary
FINAL CONDITION CULTIVARCROSSING DETAIL/EX CONDITION COMPARISON
Cultivar Street
Shared Use Trail
Area of ineffective flow. Can be filled in withoutincreasing water surface elevations.
Area of ineffective flow. Can be filled in withoutincreasing water surface elevations. Future shareduse trail embankment cuts off area from floodplain.
FIGURE: 8DRAWN BY: EJFDATE: 2/5/2025PROJECT: 14-167³0 240 480 720Feet
NORTH PARK
BOZEMAN, MT P:\2014\14-167 North Park\08 ArcGIS\2023 - Flood Study\Zoomed In - 2025\Figure 8 - Overall Flood Hazard Extents.mxd1 inch = 400 feet
Mandeville Creek
Legend
Siding Tracks with Track C
Wheat and Cultivar Crossings
Shared Use Trail
Existing Conditions - 1% AC Flood Hazard Boundary
Conservative Boundary - 1% AC Flood Hazard
Northwest Overflow Path
Frontage Road
Main Railroad Track
Red Wing Drive crossing removed and railroad culvert extended
Railroad siding and spur line stubs
Track C crossing
CONSERVATIVE BOUNDARYCOMPARISON TO EX CONDITION
Cultivar Street
Wheat Drive Shared Use Trail
Storm pond on 2-B for Wheat Drive Extension