HomeMy WebLinkAbout008_MasterStormDrainagePlan
Submitted: April 5, 2021
Revised: October 20, 2021
Revised: February 1, 2022
Project No. 17055
MASTER STORM DRAINAGE PLAN
FOR
GLEN LAKE ROTARY PARK
OVERVIEW NARRATIVE
The purpose of this drainage plan is to quantify storm drainage improvements required for the
proposed construction activities at the Glen Lake Rotary Park in Bozeman, Montana. The site is
located north of Griffin Drive and east of Manley Road. The park is currently a recreation area with a
beach, volleyball fields, a climbing rock, bathrooms, numerous trails, and a gravel parking lot. The
approximately 30-acre park will be improved with a new paved parking lot, an access road, and a multi-
use path.
According to the project’s Master Site Plan, the phasing sequence for all the public improvements at
the Glen Lake Rotary Park is planned in the following three phases:
Phase 1—South Section—56,000 SF
Phase 2—Middle Section—32,000 SF
Phase 3—North Section—88,000 SF
This Master Storm Drainage Plan presents a summary of calculations performed to quantify the
stormwater runoff for the improved site. A separate stormwater report will be provided for each
individual phase. All design criteria and calculations are in accordance with The City of Bozeman Design
Standards and Specifications Policy (DSSP), dated March 2004. The site stormwater improvements have
been designed with the intent to meet the current City of Bozeman drainage regulations for the entire
project to the extent feasible.
Project Information
This site is located on COS 1221, Tract GL2, T 1S R6E S 31. There is no formal physical address for
this project location.
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The entire park area is approximately 29.8 acres. However, only the area hydrologically associated with
the proposed improvements will be analyzed. The disturbed area associated with the new parking lot,
access drive, and multi-use path will be analyzed for stormwater treatment, and this area accounts for
4.24 acres. An additional 0.22 acres of unimproved area runs on to the proposed improvement area.
The final discharge point for this 4.46 acres is the northeast corner of the park to an existing vegetated
ditch that eventually discharges to the East Gallatin River. The area analyzed under pre-development
conditions, 3.44 acres, represents the area that currently drains to the existing vegetated channel. The
other improvements on the site add a negligible amount of impervious area since the improvements
are separated by pervious area. The existing impervious area outside of the parking lot, access drive,
and multi-use path will not be included in the analyzed area.
Surface
Pre-
development
acres
Post-
development
acres
Impervious 0.00 1.97
Gravel 0.54 0.20
Pervious 2.90 2.29
Total 3.44 4.46
HYDROLOGY
The Rational Method and rainfall data provided in The City of Bozeman DSSP was used to calculate
the runoff volumes for the 10-year, 2-hour storm event for the runoff storage facilities (water
quantity), and the peak flows from the 25-year storm event were used for the storm drain conveyance
facilities. Watersheds were delineated for both existing and proposed conditions, which are shown in
Exhibits A and B in Appendix A. The weighted runoff coefficient “C” was calculated for each
contributing area using 0.95 for impervious areas, 0.80 for gravel areas, and 0.30 for grassed and
adjacent pervious areas. The runoff treatment flow rate for the first 0.5-inch storm event was
calculated using the equations below. The results of the hydrologic analysis for the storm events
described above are shown in Appendix B.
The overall drainage plan includes 11 watersheds. Phase 3 includes Watersheds 1-7, Phase 2 includes
Watersheds 8 and 9, and Phase 1 includes Watersheds 10 and 11. The figures showing the watershed
delineations for pre- and post-development conditions are included in Appendix A. Detailed
calculations for both the pre- and post-development basins is provided in Table 1 and 2 of Appendix
B.
As described above, the project will be broken up into three Phases. However, each Phase is
hydrologically connected to each other. Phase 3 is the most downstream and the location of the final
discharge location. Phase 1 drains into Phase 2, which drains into Phase 3.
The time of concentration for each Phase for existing conditions was calculated to determine the
peak pre-development for rate for each phase, and detailed calculations have been provided in
Appendix B. The pre-development peak flow rate is used as the design release rate for calculating
the required storage volume.
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Hydrologic Equations
Q = Cwd x I x A
Cwd = Weighted Runoff Coefficient
A = Area (acres)
I = Rainfall Intensity (in/hr) associated with Calculated Time of Concentration
Q = Peak Runoff (cfs)
Watersheds Area
(acres)
Total Time of
Concentration
(min)
10-Year Storm
Intensity
(in/hr)
10-Year Storm
Peak Pre-
Development
Flow (ft3/s)
Existing
Phase 1 1.57 36.93 0.88 0.46
Existing
Phase 1 & 2 2.67 41.71 0.81 0.81
Existing
Phase 1, 2 & 3 3.44 46.15 0.76 0.93
Hydraulic Design
In general, the storm drain design consists of storm drainage chases that will drain the runoff from
the parking lot and into a new ditch located along the eastern edge of the new parking lot. A watershed
was delineated to each drainage chase to calculate the required capacity of the new ditch. The ditch
will direct runoff into a new basin at the northeast corner of the park. The basin will outfall into the
existing vegetated channel that runs along the east side of the park. This channel eventually outfalls
into the East Gallatin River.
The ditch cross section side slopes vary to maintain a positive longitudinal slope and tie into the
proposed gravel sidewalk along the parking lot and the existing slope to the east. The fill slope off the
edge of the proposed gravel sidewalk is 4:1 for 6.5 feet providing a 1.625 feet minimum ditch depth.
Except for the very end of the ditch, the ditch depth was increased to 1.80 feet. The back slopes range
from 4:1 to 2:1, where 2:1 side slopes are used to avoid encountering the landfill area located just east
of the new ditch. The ditch conveyance capacity was calculated using Bentley’s FlowMaster, which
applies the Manning’s Equation to determine the capacity of the ditch based off the longitudinal slope,
side slopes, Manning’s Roughness, and depth. A Manning’s Roughness coefficient of 0.03 was used
to determine the ditch capacity. The smallest ditch capacity for each watershed was compared to the
25-year, 5-minute peak flow to determine if the ditch can adequately convey the runoff. Throughout
the length of the ditch, there are gravel paths that perpendicularly cross the ditch to connect the new
gravel sidewalk along the new parking lot to the existing trails to the east of the project. Reinforced
concrete culverts will be used to convey the ditch under the gravel paths, the culverts will range
between 12 and 18 inches in diameter. The Federal Highway Association HY 8 program was used to
calculate the conveyance capacity of the culverts and the headwater depth at peak flow. The culverts
were sized to adequately convey the peak flow rates from the 25-year storm event without
overtopping, and it was confirmed the ditch depths are greater than the peak flow headwater depth.
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For calculating the total peak flow to the ditch sections and culverts, a conservative time of
concentration of 5 minutes was used. The table below compares the calculated peak flow rates to the
capacity of each hydraulic feature (ditch or culvert).
Phase Watershed Area
(sf)
Q25
Peak
Flow
(cfs)
Curb
Chase
Capacity
Downstream
Feature
Cumulative
Peak Flow
Q25 (cfs)
Ditch
Capacity
(cfs)
Culvert
Capacity
(cfs)
25-year
Headwater
Depth at
Peak Flow
(ft)
3 1 14,880 1.11 2.850 Permanent
Basin 1.11 Pond - -
3 2 16,167 1.08 - Permanent
Basin 4.14 Pond - -
3 3 12,863 1.05 2.850 WS 2 1.05 1.48 - -
3 4 7,259 0.26 2.850 WS 2 0.26 1.48 - -
3 5 8,499 0.64 - WS 2 0.64 1.48 - -
3 6 15,741 1.12 2.850 Permanent
Basin 8.81 30.74 8.92
(18-inch) 1.77
3 7 11,472 0.98 2.850 WS 6 7.68 26.49 - -
2 8 25,048 1.61 2.850 WS 7 6.70 20.93 - -
2 9 21,028 1.42 2.850 WS 8 5.09 33.43 - -
1 10 31,461 2.05 2.850
Phase 1:
Temp Basin
Phase 2: WS
9
3.68 63.45 4.17
(12-inch) 1.37
1 11 29,868 1.63 2.850 WS 10 1.63 115.11 4.10
(12-inch) 0.77
WATER QUANTITY AND QUALITY DESIGN
Water Quantity – Flood Storage
Water Quantity Volume:
Q (cfs) = Cwd x 10 – Year Intensity in/hr x Area (acre)
V (cf) = Duration (sec) x QPost (ft3) – Duration (sec) x Qpre(ft3)
V (cf) = Required Storage Volume
The required flood storage volume, referred to as the water quantity volume, was determined using
the Rational Method for the 10-year, 2-hour design storm. The pre-development peak flow rate is
used as the design release rate for calculating the required storage volume. Each storm duration for
the 10-year storm event is analyzed to determine the which storm duration produced the largest
runoff volume. The largest runoff volume is the minimum required storage volume needed for the
project. The table below summarized the required storage volume for each phase, Appendix D
provides the detailed calculations for each Phase.
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Phase 1 and Phase 2 do not have adequate area for detention basins. A temporary basin will be
constructed for Phase 1 to detain runoff to limit the peak discharge rate to the pre-development
flow rate. A circular orifice with a 4-inch diameter was designed to restrict the peak flow to 0.46 cfs.
The orifice structure has a 12-inch RCP inlet and outlet pipe, with a 1% slope and the capacity to
pass the 25-year storm event. The outlet pipe discharges into the existing vegetated channel along
the edge of the existing gravel drive.
The permanent detention basin for the entire project will be constructed at Phase 2 and will be large
enough to detain the required volume for all three Phases. The bioswale to the permanent detention
basin will also be constructed with Phase 2. The orifice structure and outfall pipe constructed in phase
1 will be moved and utilized at the permanent detention basin to limit the peak discharge rate to the
pre-development flowrate for phases 2 and 3. The inlet and outlet pipe slopes will be reset to be
oversized for phase 2 to have capacity to pass the 25-year storm for phase 3. The orifice diameter will
be adjusted between phases to adjust the allowable peak discharge rate between Phases 1, 2, and 3. At
Phase 2, the opening will be cut to 5.3-inches to reduce the discharge peak flow rate to 0.81 cfs. The
outfall pipe slope will be set to 12%, and riprap will be installed at the outlet. At phase 3, the orifice
diameter will be cut to have a 5.7-inch diameter, and the outfall pipe slope will remain.
Watersheds Area
(acres)
Provided
Storage
Location
(ft3)
10-Year
Storm
Required
Storage
(ft3)
Provided
Storage
(ft3)
Pre-
Develop.
Peak
Flow
Rate
(cfs)
Orifice
Capacity
(cfs)
25-
Year
Peak
Flow
(cfs)
Outfall
Pipe
Capacity
(cfs)
Proposed
Phase 1 1.41
Temporary
Basin at the
downstream
end of
Phase 1
683.82 2,466 0.46 0.46 3.68 4.05
Proposed
Phase 1 & 2 2.47
Permanent
Basin
within
Phase 3
1,270.39 3,200 0.81 0.81 6.7 13.37
Proposed
Phase 1, 2 &
3
4.46
Permanent
Basin
within
Phase 3
3,237.50 3,239 0.93 0.93 12.94 13.37
Water Quality
Due to high groundwater within the park, treating the runoff via infiltration is not feasible. An
exhibit of the piezometric contours is provided in Appendix E. Biofiltration swales are used to treat
the runoff from the first 0.5-inch storm event for most of the project area. Watershed 1 and 2 within
Phase 3 will utilize the proposed permanent detention basin for treatment. The calculations
provided in the DSSP were used to determine if the detention basin had adequate area to settle the
suspended solids.
Detention Basin:
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The detention basin will only need to treat the runoff from Watershed 1, 2 and 6 since the other
basins are treated via the biofiltration swales. The basin area was calculated to release the runoff at a
rate less than 145-square feet per 1-cfs for sediment control to treat the runoff. The settling velocity
of 40 micron particles is 0.0069 fps allowing sediment to settle and treat the runoff before discharge.
Based on the calculations below, the basin is adequately sized to treat the runoff by allowing
sediment to settle.
Phase 2:
Design Release Rate = 0.81 cfs
Minimum Area Required =0.81 cfs ÷ 0.0069 ft/sec = 117 sf
Provided 735 sf > 117 sf
Water Depth = 1.5 feet
Volume = 3,239.83
Phase 3:
Design Release Rate = 0.93 cfs
Minimum Area Required =0.93 cfs ÷ 0.0069 ft/sec = 134 sf
Provided 735 sf > 134 sf
Water Depth = 1.5 feet
Volume = 3,239.83
Biofiltration Swale:
The calculations outlined in the Montana Post-Construction Stormwater BMP Design Guidance
Manual from Chapter 3 were used to calculate the Runoff Treatment Flow Rate (RTF). These
calculations are provided in Appendix D. The table below summarizes the RTF, required swale
length and provided swale length for each watershed. The associated calculations for the
biofiltration swale and design assumptions are provided below.
Phase WS Area
(ft2)
%
IC
RTF
(cfs)
Long.
Slope
(ft/ft)
Bottom
Width
(ft)
Min.
Side
Slope
(z:1)
Wetted
Area
(ft2)
Velocity
(ft/sec)
Required
Ditch
Length
(ft)
Provided
Ditch
Length
(ft)
3 1 14,880 59% 0.082 0.005 0.72 4.00 0.75 0.11 Permanent Detention
Pond 3 2 16,167 47% 0.070 0.005 0.47 4.00 0.75 0.09
3 3 10,462 84% 0.080 0.005 0.69 4.00 0.75 0.11 58 59
3 4 7,259 4% 0.001 0.005 -0.99 4.00 0.75 0.00 1 N/A
3 5 8,499 60% 0.047 0.005 0.00 4.00 0.75 0.06 34 50
3 6 15,741 46% 0.066 0.006 0.26 3.00 0.69 0.10 51 107
3 7 11,472 68% 0.072 0.006 0.38 3.00 0.69 0.11 56 109
2 8 25,048 38% 0.086 0.004 1.03 2.00 0.63 0.14 75 213
2 9 21,028 44% 0.084 0.006 0.61 2.00 0.63 0.13 72 144
1 10 31,461 41% 0.117 0.015 0.92 2.00 0.63 0.19 101 223*
1 11 29,868 28% 0.071 0.008 0.69 2.00 0.63 0.11 62 138
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*At Phase 1, the new ditch/biofiltration swale will not be entirely constructed and will only provide
53 feet of length upstream of the temporary detention basin. However, runoff will outfall into the
existing vegetated channel which is 385 feet in length within the park property limits which will
adequately treat the RTF.
Bottom Width: The bottom width of the biofiltration swale was calculated using the Manning’s
Equation. The calculation to determine the bottom width of the swale result in a bottom width
of less than 2-feet. A minimum bottom width of 2-feet is required for biofiltration swales,
therefore a bottom width of 2-feet has been provided for the swale.
Bottom Width Equation
b =
n × RTF1.49
y × s − z × y
RTF = Runoff treatment design flow rate (cfs)
s = Longitudinal Slope of the swale (ft/ft)
n = Manning’s Coefficient
b = Bottom width of the swale (ft)
z = Side Slope of the swale in the form of z:1
y = Design flow depth for RTF (ft)
Longitudinal Slope: The longitudinal slope varies between 1.8% and 0.67%. to construct a
ditch that maintains positive flow and has adequate depth. The recommended longitudinal
slope is 1.5%, however, due to the high groundwater of the site and to keep import fill costs
down, a minimum longitudinal slope of 0.67% is provided.
Manning’s Coefficient: Table 5.6-1 from the Montana Post-Construction Storm Water BMP
Design Guidance Manual outlines flow resistance coefficients for various vegetation and soil
conditions. A Manning’s Coefficient of 0.22 was chosen for grass legume mix on lightly
compacted topsoil.
Side Slope: The side slope varies between 10:1 and 2:1 to tie into the new gravel path and
existing ground to the east of the ditch. It is recommended that side slopes be no steeper than
3:1, however due to the proximity to the Bozeman City Landfill, 2:1 side slopes for the
connection to the existing ground east of the park is use to avoid encountering landfill material.
Design Flow Depth: A design flow depth of 3 inches was assumed since the swale will be
seeded with primarily dryland grasses per Section 5.6.4.4
Velocity: The maximum allowable runoff treatment design flow velocity is 1 ft/section.
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V =
RTF
A
A = y (b + yz)
V = Flow velocity at RTF (ft/sec)
A = Wetted Area (sq. ft.)
RTF = Runoff treatment design flow rate (cfs)
L = Vt 60 min
sec
L = Swale length (ft)
V = Flow velocity at RTF (ft/sec)
t = Hydraulic residence time
t = The hydraulic residence time is set to a minimum allowable time of 9 minutes.
L = The minimum recommended length of a swale is 100 feet. The biofiltration swales for
Watersheds 1, 7, 8, 9, 10, and 11 all have a minimum length of 100 feet. Watersheds 2, 3, 5
and 6 do not have minimum lengths of 100 feet. However, lengths exceeding the calculated
required lengths have been provided. Watershed 4 is completely pervious and does not require
treatment.
The biofiltration swales are being used as an online best management practice and have been designed
to convey the peak flows from the 25-year storm event at depths greater than the RTF design flow
depth of 3-inches. As stated in the City of Bozeman DSSP and the Montana Post-Construction Storm
Water BMP Design Guidance Manual, 90 percent of the rainfall events are 0.5 inches or less on
average, and the General MS4 permit requires that BMPS are designed to treat the runoff generated
from the first 0.5 inches of rainfall from a 24-hour storm preceded by 48 hours of no measurable
precipitation. The biofiltration swales will have the capacity to convey the peak flows from a 0.5-inch,
24-hour storm event within the design flow depth of 3-inches. The minimum capacity of the
biofiltration swales at a 3-inch depth is 2.21 cfs, and the maximum peak flow for a 0.50 inch, 24-hour
storm event for all the watersheds is 0.22 cfs.
MAJOR STORM EVENTS
For storm events larger than the 25-year storm event, the runoff in the ditch will overtop the new
gravel trail and flow in the curb line of the parking lot to the south. Runoff will pond in the parking
lot until it can overtop at the north end of the park to the existing vegetated channel. The grading of
the new parking lot is sloped to the east/northeast. If runoff was to overtop the ditch banks and into
the parking lot, it would stay along the east side of the parking lot and would not flow west toward
the new improvements and the Glen Lake Rotary Park.
SUMMARY
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The above calculations show that the stormwater drainage system for the East Gallatin Recreation
Improvements meets the requirements of the City of Bozeman DSSP. The Drainage Master Plan is
divided into three Phases and 11 watersheds. Runoff from the access drive and parking areas flows
through storm drain chases to a ditch running along the eastern side of the project limits. The ditch
conveys and treats runoff as a biofiltration swale. The ditch flows to a permanent detention basin at
the northern portion of the project within Phase 3. A temporary basin will be installed in Phases 1 to
hold excess runoff until Phase 2 completes the ditch connection to the permanent basin at the
northern end of the park. An outfall structure will be used to discharge water from the ponds at the
pre-development flow rate into the existing vegetated channel. A maintenance plan for the stormwater
facilities has been included in the appendix.
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Appendix A
WATERSHED MAPS
PHA
S
E
1
PHA
S
E
2
PHA
S
E
2
PHA
S
E
3
EXHIBIT B
NORTH
050
SCALE:1" = 100'
10050
ASPHALT AREA
CURB AND GUTTER
EDGE OF ASPHALT
EDGE OF GRAVEL
GRAVEL AREA
CONCRETE AREA
APPROXIMATE
BOZEMAN OLD CITY
LANDFILL BOUNDARY
CONSTRUCTION
LIMITS
WATERSHED
BOUNDARY
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Appendix B
HYDROLOGY CALCULATIONS
Project: Glen Lake Rotary Park
Project #: 17055
Date: 10/14/2021
Time of Concentration=5 mins
Intensity10-Year, 2-Hr=0.41 in/hr
Water Quality=0.5 inches
WS Area
(sf)
Area
(ac.)
Area
Impervious
(sf)
Area
Gravel
(sf)
Area
Pervious
(sf)
RC % IC
Tc
(hours)
I10
(in/hr)
Q10
Peak Flow
(cfs)
Phase 1 68,235 1.57 0 4,698 63,537 0.33 0% 36.93 0.88 0.46
Phase 1 & 2 116,211 2.67 0 17,101 99,110 0.37 0% 41.71 0.81 0.81
Phase 1, 2 & 3 149,901 3.44 0 17,101 132,800 0.36 0% 46.15 0.76 0.93
PRE-DEVELOPMENT PEAK FLOW RATE CALCULATIONS
Project: Glen Lake Rotary Park
Project #: 17055
Date: 02/01/2022
Time of Concentration= 5 mins
Intensity25-Year, 5-Min= 4.76 in/hr
WS Tc
(hours)
Area
(sf)
Area
(ac.)
Area
Impervious
(sf)
Area
Gravel (sf)
Area
Pervious
(sf)
RC % IC
Q25 Peak
Flow
(cfs)
Curb Chase
Capacity
(cfs)
Downstream
Feature
Cumulative
Peak Flow Q25
(cfs)
Ditch
Capacity at
Full Depth
(cfs)
Culvert
Capacity
(cfs)
1 0.083 14,880 0.34 8,720 0 6,160 0.68 59% 1.11 2.850 WS 2 1.11 Pond -
2 0.083 16,167 0.37 7,631 193 8,343 0.61 47% 1.08 - Pond 4.14 Pond -
3 0.083 12,863 0.30 8,830 0 4,033 0.75 69% 1.05 2.850 WS 2 1.05 1.48 -
4 0.083 7,259 0.17 306 0 6,953 0.33 4% 0.26 2.850 WS 2 0.26 1.48 -
5 0.083 8,499 0.20 5,068 0 3,431 0.69 60% 0.64 - WS 2 0.64 1.48 -
6 0.083 15,741 0.36 7,195 1,751 6,795 0.65 46% 1.12 2.850 Pond 8.81 30.74 8.92
7 0.083 11,472 0.26 7,759 1,014 2,699 0.78 68% 0.98 2.850 WS 6 7.68 26.49 -
Phase 3 0.083 86,880 2.0 45,509 2,958 38,413 0.66 52% 6.24 - Pond 12.94 - -
8 0.083 25,048 0.58 9,635 1,851 13,562 0.59 38% 1.61 2.850 WS 7 6.70 20.93 -
9 0.083 21,028 0.48 9,244 1,276 10,508 0.62 44% 1.42 2.850 WS 8 5.09 33.43 -
Phase 2 0.083 46,075 1.06 18,879 3,126 24,070 0.60 41% 3.02 -Phase 3 6.70 - -
10 0.083 31,461 0.72 12,945 1,839 16,677 0.60 41% 2.05 2.850 WS 9 3.68 63.45 4.17
11 0.083 29,868 0.69 8,379 977 20,513 0.50 28% 1.63 2.850 WS 10 1.63 115.11 4.10
Phase 1 0.083 61,329 1.41 21,324 2,816 37,190 0.55 35% 3.68 -Phase 2 3.68 - -
POST-DEVELOPMENT PEAK FLOW CALCULATIONS
Project: Glen Lake Rotary ParkProject #: 17055Date: 10/14/2021TcL (ft)nP (in)s (ft/ft)Tsf (min)s (ft/ft)V (ft/s)L (ft)Tscf (min)r (ft)s (ft/ft)nV (ft/s)L (ft)Tch (min)Total(min)Existing Phase 1 229 0.150 1.280 0.0138 34.87 0.0101 1.62 201 2.0736.93Existing Phase 1 & 2 229 0.150 1.280 0.0138 34.87 0.0074 1.39 418 5.02 0.333 0.004 0.040 1.07 117 1.82 41.71Existing Phase 1, 2 & 3229 0.150 1.280 0.0138 34.87 0.0074 1.39 418 5.02 0.333 0.004 0.040 1.07 402 6.26 46.15Proposed Phase 1, 2 & 3116 0.150 1.280 0.0138 20.24 0.0200 2.87 85 0.49 0.333 0.006 0.040 1.38 798 9.63 30.36USDA Urban Hydrology for Small Watersheds TR-55 Manual.Sheet Flow Equations Shallow Concentrated Flow Equations Channel/Pipe Flow EquationsEq. 3-3TIME OF CONCENTRATIONWatershedSheet FlowShallow Concentrated FlowChannel FlowTsf0.007(nL)0.8 P20.5s0.4 L = Length of overland sheet flow (ft)n = Manning's roughnessP = 2-year, 24-hour rainfall, ins = Slope (ft/ft) V16.135s0.5for Grassed WaterwaysV6.9620.5for Short-grassed pastureV = 20.3280.5for PavementTscfL60V s = Slope (ft/ft)L = Length of overland sheet flow (ft)V1.49(r0.67s0.5) n TchL60V L = Length of overland sheet flow (ft)n = Manning's roughnesss = Slope (ft/ft) r = hydraulic radius (ft)
Project: EGRA Site Improvements
Project #: 17055
Date: 6/15/2018
Design Standards and Specifications Policy
City of Bozeman, March 2004 as Amended
RAINFALL INTENSITY-DURATION CURVES (Figures I-2, I-3)
Time 2 5 10 25 50 100
(min)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr)
1 4.20 7.15 9.16 10.72 13.72 15.69
5 1.60 2.55 3.22 3.83 4.74 5.34
10 1.05 1.64 2.05 2.46 3.00 3.35
15 0.83 1.26 1.58 1.89 2.30 2.56
20 0.70 1.05 1.31 1.58 1.90 2.11
25 0.61 0.91 1.13 1.37 1.64 1.82
30 0.55 0.81 1.00 1.22 1.45 1.61
35 0.50 0.73 0.91 1.10 1.31 1.45
40 0.46 0.67 0.83 1.01 1.20 1.33
45 0.43 0.63 0.77 0.94 1.11 1.22
50 0.40 0.58 0.72 0.88 1.04 1.14
55 0.38 0.55 0.68 0.82 0.97 1.07
60 0.36 0.52 0.64 0.78 0.92 1.01
75 0.31 0.45 0.55 0.68 0.79 0.87
90 0.28 0.40 0.49 0.60 0.70 0.77
105 0.26 0.36 0.44 0.55 0.64 0.69
120 0.24 0.33 0.41 0.50 0.58 0.63
150 0.21 0.29 0.35 0.43 0.50 0.55
180 0.19 0.26 0.31 0.39 0.45 0.48
360 0.12 0.17 0.20 0.25 0.28 0.30
720 0.08 0.11 0.13 0.16 0.18 0.19
1440 0.05 0.07 0.08 0.10 0.11 0.12
Storm Recurrence Interval
V:17055_Storm_Drainage_Plan.docx 12 (2/1/22) SH/rrr/ed
Appendix C
HYDRAULIC CALCULATIONS
Curb Chase Capacity Calculation
HY-8 Culvert Analysis Report
Culvert Data: Path Culvert 1+45
Headwater
Elevation (ft)
Total Discharge
(cfs)
Culvert 1
Discharge (cfs)
Roadway
Discharge (cfs)
Iterations
4698.85 0.50 0.50 0.00 1
4699.23 1.63 1.63 0.00 1
4699.44 2.40 2.40 0.00 1
4699.72 3.35 3.35 0.00 1
4700.02 4.30 4.14 0.13 22
4700.07 5.25 4.26 0.96 6
4700.11 6.20 4.35 1.83 5
4700.14 7.15 4.42 2.70 4
4700.17 8.10 4.48 3.60 4
4700.19 9.05 4.53 4.49 4
4700.22 10.00 4.59 5.39 4
4700.00 4.10 4.10 0.00 Overtopping
Total
Discharge
(cfs)
Headwater
Elevation
(ft)
Inlet
Control
Depth
(ft)
Outlet
Control
Depth
(ft)
Normal
Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwater
Depth
(ft)
Tailwater
Velocity
(ft/s)
0.50 cfs 4698.85 0.39 0.053 0.21 0.29 0.22 0.28 1.56
1.63 cfs 4699.23 0.77 0.400 0.40 0.54 0.42 0.44 2.10
2.40 cfs 4699.44 0.98 0.646 0.49 0.66 0.53 0.51 2.31
3.35 cfs 4699.72 1.26 1.095 0.60 0.78 0.64 0.58 2.51
4.30 cfs 4700.02 1.56 1.373 0.70 0.86 0.74 0.63 2.68
5.25 cfs 4700.07 1.61 1.419 0.72 0.87 0.76 0.68 2.81
6.20 cfs 4700.11 1.65 1.452 0.73 0.88 0.77 0.73 2.93
7.15 cfs 4700.14 1.68 1.479 0.74 0.88 0.77 0.77 3.04
8.10 cfs 4700.17 1.71 1.503 0.75 0.88 0.78 0.80 3.13
9.05 cfs 4700.19 1.73 1.526 0.75 0.89 0.79 0.84 3.22
10.00 cfs 4700.22 1.76 1.547 0.76 0.89 0.80 0.87 3.30
Culvert Data: Path Culvert 3+32
Headwater
Elevation (ft)
Total Discharge
(cfs)
Culvert 1
Discharge (cfs)
Roadway
Discharge (cfs)
Iterations
4695.42 0.50 0.50 0.00 1
4695.75 1.45 1.45 0.00 1
4696.01 2.40 2.40 0.00 1
4696.40 3.68 3.68 0.00 1
4696.61 4.30 4.20 0.07 22
4696.67 5.25 4.33 0.91 6
4696.71 6.20 4.41 1.76 4
4696.74 7.15 4.48 2.66 4
4696.77 8.10 4.54 3.53 3
4696.79 9.05 4.60 4.43 3
4696.82 10.00 4.65 5.34 3
4696.60 4.17 4.17 0.00 Overtopping
Total
Discharge
(cfs)
Headwater
Elevation
(ft)
Inlet
Control
Depth
(ft)
Outlet
Control
Depth
(ft)
Normal
Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwater
Depth
(ft)
Tailwater
Velocity
(ft/s)
0.50 cfs 4695.42 0.39 0.0* 0.21 0.29 0.21 0.30 1.38
1.45 cfs 4695.75 0.72 0.268 0.36 0.51 0.38 0.45 1.80
2.40 cfs 4696.01 0.98 0.576 0.47 0.66 0.51 0.54 2.04
3.68 cfs 4696.40 1.37 1.149 0.62 0.82 0.66 0.64 2.28
4.30 cfs 4696.61 1.58 1.344 0.68 0.86 0.72 0.67 2.37
5.25 cfs 4696.67 1.64 1.395 0.69 0.87 0.73 0.73 2.49
6.20 cfs 4696.71 1.68 1.428 0.70 0.88 0.74 0.77 2.59
7.15 cfs 4696.74 1.71 1.458 0.71 0.89 0.75 0.82 2.69
8.10 cfs 4696.77 1.74 1.483 0.72 0.89 0.76 0.85 2.77
9.05 cfs 4696.79 1.76 1.506 0.72 0.89 0.77 0.89 2.85
10.00 cfs 4696.82 1.79 1.505 0.73 0.90 0.77 0.93 2.92
* Full Flow Headwater elevation is below inlet invert.
Culvert Data: Culvert 9+34
Headwater
Elevation (ft)
Total Discharge
(cfs)
Culvert 1
Discharge (cfs)
Roadway
Discharge (cfs)
Iterations
4691.38 0.50 0.50 0.00 1
4691.65 1.45 1.45 0.00 1
4691.85 2.40 2.40 0.00 1
4692.02 3.35 3.35 0.00 1
4692.18 4.30 4.30 0.00 1
4692.33 5.25 5.25 0.00 1
4692.47 6.20 6.20 0.00 1
4692.62 7.15 7.15 0.00 1
4692.77 8.10 8.10 0.00 1
4692.88 8.81 8.81 0.00 1
4692.96 10.00 9.25 0.73 7
4692.90 8.92 8.92 0.00 Overtopping
Total
Discharge
(cfs)
Headwater
Elevation
(ft)
Inlet
Control
Depth
(ft)
Outlet
Control
Depth
(ft)
Normal
Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwater
Depth
(ft)
Tailwater
Velocity
(ft/s)
0.50 cfs 4691.38 0.35 0.380 0.28 0.26 0.40 0.40 0.79
1.45 cfs 4691.65 0.62 0.654 0.49 0.45 0.59 0.59 1.03
2.40 cfs 4691.85 0.81 0.854 0.64 0.59 0.72 0.72 1.16
3.35 cfs 4692.02 0.99 1.025 0.77 0.70 0.81 0.81 1.26
4.30 cfs 4692.18 1.14 1.182 0.90 0.79 0.89 0.89 1.35
5.25 cfs 4692.33 1.28 1.330 1.04 0.88 0.96 0.96 1.41
6.20 cfs 4692.47 1.41 1.475 1.20 0.96 1.03 1.03 1.47
7.15 cfs 4692.62 1.55 1.619 1.50 1.04 1.08 1.08 1.53
8.10 cfs 4692.77 1.70 1.767 1.50 1.10 1.13 1.13 1.58
8.81 cfs 4692.88 1.82 1.882 1.50 1.15 1.17 1.17 1.61
10.00 cfs 4692.96 1.90 1.959 1.50 1.18 1.23 1.23 1.66
Culvert Data: Culvert 9+71
Headwater
Elevation (ft)
Total Discharge
(cfs)
Culvert 1
Discharge (cfs)
Roadway
Discharge (cfs)
Iterations
4692.25 0.50 0.50 0.00 1
4692.29 1.65 1.65 0.00 1
4692.36 2.80 2.80 0.00 1
4692.43 3.95 3.95 0.00 1
4692.50 5.10 5.10 0.00 1
4692.62 6.25 6.25 0.00 1
4692.77 7.40 7.40 0.00 1
4692.99 8.81 8.81 0.00 1
4693.15 9.70 9.70 0.00 1
4693.35 10.85 10.72 0.09 16
4693.40 12.00 10.99 0.98 6
4693.33 10.64 10.64 0.00 Overtopping
Total
Discharge
(cfs)
Headwater
Elevation
(ft)
Inlet
Control
Depth
(ft)
Outlet
Control
Depth
(ft)
Normal
Depth
(ft)
Critical
Depth
(ft)
Outlet
Depth
(ft)
Tailwater
Depth
(ft)
Tailwater
Velocity
(ft/s)
0.50 cfs 4692.25 0.36 1.422 0.29 0.26 1.50 1.50 0.00
1.65 cfs 4692.29 0.66 1.456 0.53 0.48 1.50 1.50 0.00
2.80 cfs 4692.36 0.91 1.530 0.71 0.64 1.50 1.50 0.00
3.95 cfs 4692.43 1.12 1.595 0.87 0.76 1.50 1.50 0.00
5.10 cfs 4692.50 1.32 1.668 1.04 0.87 1.50 1.50 0.00
6.25 cfs 4692.62 1.51 1.792 1.24 0.97 1.50 1.50 0.00
7.40 cfs 4692.77 1.71 1.942 1.50 1.05 1.50 1.50 0.00
8.81 cfs 4692.99 1.99 2.160 1.50 1.15 1.50 1.50 0.00
9.70 cfs 4693.15 2.20 2.317 1.50 1.20 1.50 1.50 0.00
10.85 cfs 4693.35 2.45 2.515 1.50 1.26 1.50 1.50 0.00
12.00 cfs 4693.40 2.53 2.571 1.50 1.27 1.50 1.50 0.00
V:17055_Storm_Drainage_Plan.docx 13 (2/1/22) SH/rrr/ed
Appendix D
WATER QUANTITY AND QUALITY CALCULATIONS
Project: Glen Lake Rotary Park
Project #: 17055
Date: 10/14/2021
Design Storm Frequency = 10 years
Discharge Rate, d = 0.46 cfs - Phase 1 Peak Pre-Development Runoff Flow Rate
Time of Concentration = 5.00 minutes
21323.53 0.490 0.95 1 0.95
37190.18 0.854 0.3 1 0.30
2815.56 0.065 0.8 1 0.80
61329.28 1.41 0.549 1 0.549
Rainfall Rainfall Peak Flow
Duration, t Intensity, i = Cwd x A x i
(min) (in/hr)(ft3/s)
1 9.16 7.08
5 3.22 2.49
10 2.05 1.59
11 1.93 1.49
12 1.82 1.41
13 1.73 1.34
14 1.65 1.27
15 1.58 1.22
20 1.31 1.01
25 1.13 0.87
30 1.00 0.78
35 0.91 0.70
40 0.83 0.64
45 0.77 0.60
50 0.72 0.56
55 0.68 0.52
60 0.64 0.49
75 0.55 0.43
90 0.49 0.38
105 0.44 0.34
120 0.41 0.32
150 0.35 0.27
180 0.31 0.24
360 0.20 0.15
720 0.13 0.10
1440 0.08 0.06
Impervious
Landscape
Gravel
Totals
Runoff Volume Discharge Volume
RATIONAL METHOD FOR WATER QUANTITY VOLUME CALCULATIONS
PHASE 1 EXISTING ANALYSIS
Surface Type Area
A
(ft2)
Area
(acres)
Runoff
Coefficient
C
Frequency
Factor
Cf
C x Cf
424.86 27.60 397.26
746.25 138.00 608.25
Site Detention
= Cwd x A x i x t = d x t = Runoff Volume - Discharge Volume
(ft3) (ft
3) (ft
3)
1212.29 552.00 660.29
1310.76 690.00 620.76
951.14 276.00 675.14
1096.17 414.00 682.17
1013.81 331.20 682.61
1042.62 358.80 683.82
1070.01 386.40 683.61
983.40 303.60 679.80
1545.13 1104.00 441.13
1610.16 1242.00 368.16
1397.13 828.00 569.13
1474.58 966.00 508.58
1656.00 124.73
1925.38 2070.00 -----
1670.64 1380.00 290.64
1727.31 1518.00 209.31
1780.73
5415.91 39744.00 -----
2615.71 4968.00 -----
3333.88 9936.00 -----
4249.23 19872.00 -----
2269.64 3312.00 -----
2454.01 4140.00 -----
2052.24 2484.00 -----
2166.01 2898.00 -----
Project: Glen Lake Rotary Park
Project #: 17055
Date: 10/14/2021
Design Storm Frequency = 10 years
Discharge Rate, d = 0.81 cfs - Phase 1 Peak Pre-Development Runoff Flow Rate
Time of Concentration = 5.00 minutes
40202.75 0.923 0.95 1 0.95
61259.92 1.406 0.3 1 0.30
5942.05 0.136 0.8 1 0.80
107404.72 2.47 0.571 1 0.571
Rainfall Rainfall Peak Flow
Duration, t Intensity, i = Cwd x A x i
(min) (in/hr)(ft3/s)
1 9.16 12.90
5 3.22 4.53
10 2.05 2.89
11 1.93 2.71
12 1.82 2.56
13 1.73 2.43
14 1.65 2.32
15 1.58 2.22
20 1.31 1.84
25 1.13 1.59
30 1.00 1.41
35 0.91 1.28
40 0.83 1.17
45 0.77 1.09
50 0.72 1.01
55 0.68 0.95
60 0.64 0.90
75 0.55 0.78
90 0.49 0.69
105 0.44 0.63
120 0.41 0.57
150 0.35 0.50
180 0.31 0.44
360 0.20 0.28
720 0.13 0.18
1440 0.08 0.11
Impervious
Landscape
Gravel
Totals
Runoff Volume Discharge Volume
RATIONAL METHOD FOR WATER QUANTITY VOLUME CALCULATIONS
PHASE 1 & 2 EXISTING ANALYSIS
Surface Type Area
A
(ft2)
Area
(acres)
Runoff
Coefficient
C
Frequency
Factor
Cf
C x Cf
773.88 48.47 725.41
1359.29 242.37 1116.92
Site Detention
= Cwd x A x i x t = d x t = Runoff Volume - Discharge Volume
(ft3) (ft
3) (ft
3)
2208.18 969.49 1238.69
2387.55 1211.86 1175.69
1732.50 484.74 1247.76
1996.67 727.12 1269.55
1791.27
1846.66
1899.13
1949.03
533.22
581.69
630.17
678.64
1258.05
1264.97
1268.96
1270.39
2814.46 1938.98 875.48
2932.91 2181.35 751.56
2544.87 1454.23 1090.64
2685.95 1696.61 989.34
2908.47 335.13
3507.08 3635.58 -----
3043.08 2423.72 619.36
3146.30 2666.09 480.21
3243.60
9865.08 69803.18 -----
4764.52 8725.40 -----
6072.67 17450.80 -----
7739.99 34901.59 -----
4134.16 5816.93 -----
4469.98 7271.16 -----
3738.17 4362.70 -----
3945.39 5089.82 -----
Project: Glen Lake Rotary Park
Project #: 17055
Date: 10/14/2021
Design Storm Frequency = 10 years
Discharge Rate, d = 0.93 cfs - Phase 1 Peak Pre-Development Runoff Flow Rate
Time of Concentration = 5.00 minutes
85711.71 1.968 0.95 1 0.95
99673.25 2.288 0.3 1 0.30
8899.58 0.204 0.8 1 0.80
194284.53 4.46 0.610 1 0.610
Rainfall Rainfall Peak Flow
Duration, t Intensity, i = Cwd x A x i
(min) (in/hr)(ft3/s)
1 9.16 24.91
5 3.22 8.75
10 2.05 5.58
15 1.58 4.29
20 1.31 3.55
25 1.13 3.07
26 1.10 3.00
27 1.08 2.92
28 1.05 2.86
29 1.03 2.79
30 1.00 2.73
31 0.98 2.67
32 0.96 2.62
33 0.94 2.57
34 0.93 2.52
35 0.91 2.47
40 0.83 2.27
45 0.77 2.10
50 0.72 1.96
55 0.68 1.84
60 0.64 1.74
75 0.55 1.51
90 0.49 1.34
105 0.44 1.21
120 0.41 1.11
150 0.35 0.96
180 0.31 0.85
360 0.20 0.54
720 0.13 0.35
1440 0.08 0.22
4972.16
5027.72
5082.16
5135.54
1734.66
1790.61
1846.57
1902.53
3237.50
3237.10
3235.59
3233.01
RATIONAL METHOD FOR WATER QUANTITY VOLUME CALCULATIONS
PHASE 1, 2 & 3 (MASTER) EXISTING ANALYSIS
Surface Type Area
A
(ft2)
Area
(acres)
Runoff
Coefficient
C
Frequency
Factor
Cf
C x Cf
Site Detention
= Cwd x A x i x t = d x t = Runoff Volume - Discharge Volume
(ft3) (ft
3) (ft
3)
Impervious
Landscape
Gravel
Totals
Runoff Volume Discharge Volume
3346.33 559.57 2786.76
2625.48 279.78 2345.69
1494.75 55.96 1438.79
4857.44 1622.74 3234.70
4915.42 1678.70 3236.72
3856.56 839.35 3017.21
4265.10 1119.13 3145.96
3220.42
3226.63
3231.36
4611.56
4675.30
4737.46
4798.15
1398.92
1454.87
1510.83
1566.79
3212.64
5664.91 2518.05 3146.86
5877.71 2797.84 3079.87
5187.91 1958.48 3229.42
5436.13 2238.27 3197.86
6773.92 4196.75 2577.17
7220.27 5036.10 2184.17
6077.09 3077.62 2999.47
6265.01 3357.40 2907.60
8633.77 8393.51 240.26
9202.67 10072.21 -----
7620.52 5875.45 1745.07
7985.13 6714.80 1270.32
19054.40 80577.66 -----
11729.36 20144.41 -----
14949.78 40288.83 -----
Project: Glen Lake Rotary Park
Project #: 17055
Date: 02/01/2022
Time of Concentration= 5 mins
Precipitaton Depth= 0.5 in
Vi,e,c= 0 acre-feet
Mannings roughness (n)= 0.22
Design Flow Depth (y)= 3 inches
Residence Time (t)= 9 minutes
POST DEVELOPMENT BASINS
WS Area
(sf)% IC Rv
RRV
(acre-ft)
RTV
(acre-ft)
Q
(in)CN Ia Ia/P C0 C1 C2
qu Unit Peak
Discharge
(cfs/mi2/
in)
RTF
(cfs)
Long.
Slope
(ft/ft)
Bottom
Width
(ft)
Min. Side
Slope
(z:1)
A
(ft2)
V
(ft/sec)
L
(ft)
Provided
Ditch
Length
(ft)
1 14,880 59% 0.58 0.008 0.008 0.29 97.55 0.0502 0.100 2.305 -0.514 -0.117 529.024 0.082 0.005 0.72 4.00 0.75 0.11
2 16,167 47% 0.47 0.007 0.007 0.24 96.63 0.0698 0.140 2.278 -0.510 -0.106 506.307 0.070 0.005 0.47 4.00 0.75 0.09
3 10,462 84% 0.81 0.008 0.008 0.40 99.09 0.0183 0.100 2.306 -0.514 -0.118 529.259 0.080 0.005 0.69 4.00 0.75 0.11 58 59
4 7,259 4% 0.09 0.001 0.001 0.04 89.09 0.2449 0.490 1.696 -0.087 0.001 61.792 0.001 0.005 -0.99 4.00 0.75 0.00 1 N/A
5 8,499 60% 0.59 0.005 0.005 0.29 97.63 0.0486 0.100 2.306 -0.514 -0.118 529.259 0.047 0.005 0.00 4.00 0.75 0.06 34 50
6 15,741 46% 0.46 0.007 0.007 0.23 96.49 0.0728 0.146 2.274 -0.510 -0.105 502.983 0.066 0.006 0.51 3.00 0.69 0.10 51 107
7 11,472 68% 0.66 0.007 0.007 0.33 98.16 0.0374 0.100 2.306 -0.514 -0.118 529.259 0.072 0.006 0.63 3.00 0.69 0.10 56 109
8 25,048 38% 0.40 0.009 0.009 0.20 95.76 0.0886 0.177 2.251 -0.506 -0.096 485.528 0.086 0.004 1.53 2.00 0.63 0.14 75 213
9 21,028 44% 0.45 0.009 0.009 0.22 96.32 0.0764 0.153 2.269 -0.509 -0.103 498.987 0.084 0.006 1.11 2.00 0.63 0.13 72 144
10 31,461 41% 0.42 0.013 0.013 0.21 96.04 0.0824 0.165 2.260 -0.508 -0.099 492.266 0.117 0.015 0.92 2.00 0.63 0.19 101 223
11 29,868 28% 0.30 0.009 0.009 0.15 94.46 0.1172 0.234 2.199 -0.491 -0.073 439.729 0.071 0.008 0.69 2.00 0.63 0.11 62 138
RUNOFF TREATMENT FLOW RATE CALCULATIONS
Permanent
Detention Pond
[RRV] Runoff Reduction Volume
P=0.5 inches
Rv=0.332
I=31%Impervious
A=0.685678 acres
RRV= 0.009482 acre-feet 413.0 ft3
[RTV] Runoff Treatment Volume
Vi,e,c =0 acre-feet
RTV = 0.009482 acre-feet 413.0 ft3
[RTF] Runoff Treatment Flow Rate
Curve Number Determination (CN)
P =0.5 inches
Q =0.165949 inches
CN =94.9 a
Biofiltration Swale Example Calculation
See Runoff Treatment Flow Rate and Biofiltration Swale Table for Results for Each Watershed
Tc =5 minutes
Ia =0.11
Ia/P =0.21
Coefficents for Type I distribution
I/P C0 C1 C2
0.1 2.3055 -0.51429 -0.1175
0.2 2.23537 -0.50387 -0.08929
0.25 2.18219 -0.48488 -0.06589
0.3 2.10624 -0.45695 -0.02835
0.35 2.00303 -0.40769 0.01983
0.4 1.87733 -0.32274 0.05754
0.45 1.76312 -0.15644 0.00453
0.5 1.67889 -0.0693 0
C0 =2.219821
C1 =-0.49832
C2 =-0.08245
qu=458.7483 Unit Peak Discharge
RTF =0.08 cfs
Bio Swale Geometry
Flow Resistance Coefficient in Biofiltration Swales (Table 5.6-1)
0.22
Design Flow Depth (in)
3
Grass-legume mix on lightly compacted topsoil w/ 3-inch medium compost blanket
Dryland Grasses
s =0.0175 ft/ft - recommended range 1.5-5%
n =0.22
z =4
y =0.25 feet
b =-0.08 feet or 2 feet if calculated is less than 2 feet
A =0.75 ft2
V =0.11 ft/sec must be less than 1 ft/sec
t =9 minutes
L =58.72 feet
Flow Depth:3 inches
Channel Slope:1.75%
Bottom Width:2.00 feet
Side Slope:4 :1
Length:58.72 feet
Swale Geometry
V:17055_Storm_Drainage_Plan.docx 14 (2/1/22) SH/rrr/ed
Appendix E
GROUNDWATER ELEVATION EXHIBIT
!.
>
>>
>
>
>
>
>
#
#
#*
#*
#*East Gallatin River4688469746894690469246914693469546944696EGRAIrrigationWell
VW-1
VW-2
VW-5
VW-4
VW-3
1
2 - old
2
7 8
10
MW-1
MW-2MW-5
MW-4
MW-6
3
4
5
6
9
11
12
.
Legend
Active Monitoring WellProposed Monitoring Well
>Historic monitoring well
#*Proposed soil vapor probe
#Historic soil vapor probe
!.EGRA Irrigation Well
Inferred_Landfill_Boundary
Potentiometric Contours
East Gallatin Recreation Area
0 100 200 300 40050
1 inch = 100 feet
Job#: COBM02
Date: 2/26/2021 FIGURE 2
Monitoring Locations
Old Bozeman City Landfill
Path: M:\COBM03\Figure 2 - Monitoring Locations.mxd, Author: svandaele
Location of theBozeman Old City Landfill
Glen Lake
Bridger Creek Golf Course
Facilities Building
?
??
Bridger Vale Subdivision
Approximate Extent of Buried Landfill Materials Unknown
?
V:17055_Storm_Drainage_Plan.docx 15 (2/1/22) SH/rrr/ed
Appendix F
MAINTENANCE PLAN
February 1, 2021
Project No. 17055
STORM DRAINAGE FACILITY MAINTENANCE PLAN
FOR
GLEN LAKE ROTARY PARK
BOZEMAN, MONTANA
OVERVIEW NARRATIVE
The purpose of this maintenance plan is to outline the necessary details related to ownership,
responsibility and cleaning schedule for the storm drainage facilities for Glen Lake Rotary Park.
This plan has been completed in accordance with The City of Bozeman Design Standards and Specifications
Policy, dated March 2004. The site stormwater improvements have been designed with the intent to
meet the current City of Bozeman drainage regulations for the entire site to the extent feasible.
Specific site information and criteria are described below:
I. Ownership of Facilities
Glen Lake Rotary Park
The City of Bozeman will own all stormwater facilities which includes the drainage swales,
piping, structures, and detention basins within the site boundary.
II. Inspection Thresholds for Cleaning
Drainage Swale
Remove trash, debris, yard waste, accumulated sediment, and maintain grass heights as
specified during the design documents, remove all clippings. Evidence of rodent holes or
water seepage through embankments.
Surface Pond
Remove vegetation and debris at pipe inlets/outlets to pond. Fix erosion and scouring. If
piping or erosion is visible, consult engineer.
Outlet Structure
The structure is not damaged, clogged, or defective. If sediment sump exceeds 5 inches or
grate is more than 25% clogged with debris. Remove vegetation and debris from orifice.
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III. Cleaning
Drainage Swale
Remove and dispose of debris clogging the area. Reseed as needed during fall seeding to
maintain 90% turf grass cover and inspect side slopes for evidence of erosion.
Surface Pond
Remove vegetation and debris from pond inlets and outlets. Check for slumping or
sloughing of pond slopes.
Outlet Structures
Clean grate and orifice of structure by remove and dispose of debris. Use catch basin
vacuum to remove sediment and debris.
IV. Schedule
Drainage Swale
Inspection: Every 3 months and after storms
Surface Pond
Inspection: Every 6 months and after storm events
Outfall Structures
Inspection: Every 6 months and after storm events
Vacuum: Every 5 years or as needed based on inspection
V. Responsible Party
Glen Lake Rotary Park
The City of Bozeman will be responsible for the inspection and maintenance of all
stormwater facilities located within the project limits
I agree to the above operation, maintenance and replacement schedule detailed above.
Signature: ________________________________________ __
Glan Lake Rotary Park Representative