HomeMy WebLinkAboutStormwaterDrainagePlan_03-09-21Stormwater Drainage Plan
Bozeman Cohousing
Bozeman, MT
109 E. Main St. Suite B, Bozeman, MT 59715 I OFFICE 406.728.4611 I EMAIL wgm@wgmgroup.com
REPORT DATE:
March 9, 2021
AUTHOR:
Mace Mangold, PE, LEED AP
Senior Project Engineer
WGM Group, Inc.
WGM PROJECT:
20-02-03
BOZEMAN COHOUSING
Stormwater Drainage Plan
CONTENTS
1.0 LOCATION AND DESCRIPTION ........................... 1
1.1 LOCATION ....................................................................................................... 1
1.2 DESCRIPTION OF PROPERTY ............................................................... 2
1.3 GENERAL PROJECT DESCRIPTION .................................................... 2
1.4 CONSTRUCTION SCHEDULE ................................................................ 2
2.0 EXISTING DRAINAGE ............................................ 3
2.1 EXISTING DRAINAGE PATTERNS ........................................................ 3
3.0 STORMWATER DESIGN CRITERIA ................... 3
3.1 REGULATIONS............................................................................................. 3
3.2 GENERAL CRITERIA ................................................................................. 4
3.3 HYDROLOGY ............................................................................................... 4
3.4 SOILS INFORMATION .............................................................................. 5
4.0 PROPOSED DESIGN .............................................. 6
4.1 PRE-DEVELOPED RUNOFF RATES .................................................... 6
4.2 PROPOSED DRAINAGE SYSTEM ........................................................ 7
4.3 LOW IMPACT DEVELOPMENT ............................................................ 8
4.4 WATER QUALITY TREATMENT .......................................................... 11
4.5 HYDRAULIC DESIGN………………………………………………………………………11
5.0 CONCLUSIONS ....................................................... 12
5.1 HYDRAULIC DESIGN ................................................................................ 12
5.2 RELEASE RATES ....................................................................................... 12
5.3 COMPLIANCE WITH STANDARDS .................................................... 12
6.0 REFERENCES .......................................................... 13
APPENDICES
A – DRAINAGE AREA MAPS
B – NRCS SOIL INFORMATION
C – SOILS INVESTIGATION REPORT
D – STORAGE-INFILTRATION ANALYSIS
E – STORMWATER PLAN SHEETS
F – LID CONCEPT SITE PLAN RENDERING
G – HYDRAULIC CONVEYANCE ANALYSIS
H – STORMWATER SYSTEM OPERATION AND
MAINTENANCE PLAN
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Stormwater Drainage Plan
1.0 LOCATION AND DESCRIPTION
1.1 LOCATION
The Bozeman Cohousing development site is located at 3120 Wagon Wheel Road
approximately 2 miles south of downtown Bozeman. The site is located on the east side of
Wagon Wheel Road in the NW ¼ of SW ¼ of Section 19, Township 2S, Range 6E. The
development will be comprised of 10 fourplex units, 3 accessory dwelling units, a common
house, garages, storage sheds, parking areas, gardens, orchards and open space.
FIGURE 1. VICINITY MAP
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Stormwater Drainage Plan
FIGURE 2. PROJECT LOCATION
1.2 DESCRIPTION OF PROPERTY
The property is approximately 5.3-acres in total size and is comprised of two legal parcels.
The site is bounded on the west by Wagon Wheel Road. The site is bounded on the north,
east, and south sides by several private properties. Mathew Bird Creek flows through the
east edge of the property.
Existing conditions on the site are as shown in the aerial photo in Figure 2. Existing
development includes a home, storage shed, driveway, garden, corrals, and fields for
grazing.
1.3 GENERAL PROJECT DESCRIPTION
The new site development will be comprised of 10 fourplex units, 3 accessory dwelling
units, a common house, garages, storage sheds, paved parking areas, gardens, orchards,
open space, paved roadways, soft and paved woonerfs, paved and fines pedestrian paths,
water and sewer extensions, and a stormwater management system. The stormwater
management system is comprised of dispersed treatment-conveyance-infiltration features
including bioswales, rain gardens, cobble infiltration galleries, and dry streambeds, along
with standard closed storm drain conduits and inlets.
1.4 CONSTRUCTION SCHEDULE
Project construction is anticipated to begin in spring of 2021.
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Stormwater Drainage Plan
2.0 EXISTING DRAINAGE
2.1 EXISTING DRAINAGE PATTERNS
The site is located on a relatively flat terrace adjacent to Mathew Bird Creek. The majority
of the site is gently sloped toward the center of the northern property boundary. The
eastern quarter of the property is sloped toward Mathew Bird Creek. The hillside adjacent
to the stream is steep with 30-40 percent slopes. The site may receive a small amount of
offsite drainage from the Woodridge Addition to the south. Appendix A contains a pre-
development drainage area exhibit. As shown on Sheet 1 of Appendix A, there are two
major existing sub-basins for the site, and most drainage currently flows northward towards
the center of the northern property line.
3.0 STORMWATER DESIGN CRITERIA
3.1 REGULATIONS
The stormwater drainage plan for this project has been developed to exceed stormwater
drainage design criteria required by the City of Bozeman Design Standards and
Specifications Policy (City Standards), dated March 2004. Minimum design criteria per the
design standards included:
Stormwater runoff from the development site shall be limited to the pre-
development runoff rates. Adequate on-site stormwater detention shall be provided
for design storm runoff exceeding the pre-development rate.
Stormwater storage and treatment facilities shall be designed to remove pollutants.
Storm sewer facilities shall be designed to handle a 25-year storm event.
The drainage plan shall include, to the greatest extent feasible, low impact
development practices that infiltrate, evapotranspire, or capture for reuse 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 Design Standards reference a modified Rational Method to calculate detention storage
for the 10-year, 2-hour storm event and the standard Rational Method to calculate peak
runoff of the 25-year storm event.
3.2 PROJECT DESIGN CRITERIA
The Bozeman Cohousing design team has elected to implement a stormwater management
system that substantially exceeds City of Bozeman minimum design criteria. The
overarching project design goal is to fully infiltrate the 100-year, 6-hour storm event. This
translates to approximately seventy (70) percent greater rainfall depth (e.g. 0.81 inches vs.
1.35 inches) in which to base stormwater storage and infiltration design in comparison to
City Standards.
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Stormwater Drainage Plan
Stormwater conveyance infrastructure is designed based on the 25-year event as
calculated using the Rational Method per City Standards. The conveyance design
conservatively assumes that the storage and infiltration infrastructures do not attenuate
peak flow rates.
The proposed design substantially complies or exceeds the City’s objective that “the
drainage plan shall include, to the greatest extent feasible, low impact development
practices that infiltrate, evapotranspire, or capture for reuse the runoff generated from the
first 0.5 inches of rainfall from a 24-hour storm preceded by 48 hours of no measurable
precipitation.” For project design purposes and to promote infrastructure longevity, the
“0.5 inches of rainfall from a 24-hour storm” is used as a metric for pre-treatment in
advance of stormwater runoff entering cobble infiltration galleries that serve as the primary
feature for infiltrating large storm events.
3.3 HYDROLOGY
The design storms investigated for this site include the 2-year, 5-year, 10-year, 25-year, and
the 100-year recurrence intervals to document that post-development runoff rates do not
exceed that of pre-development conditions. The Soils Conservation Service (SCS)
hydrologic method is used for evaluating storage, infiltration and discharge rates as it
provides a more technically sound methodology for hydrograph generation in comparison
to the Rational Method. The Rational Method is used to evaluate peak runoff rates to
document adequate 25-year conveyance capacity.
SCS hydrologic modeling was performed in Hydraflow Hydrographs Extension Version
2020. The 6-hour duration SCS storm was used for hydrograph generation with rainfall
depths input based on precipitation data from the Montana Department of Transportation
(MDT) Hydraulics Manual, Chapter 7, Appendix B-2017 (see Table 2). The 6-hour return
interval is considered conservative relative to City Standards.
TABLE 2. MDT PRECIPITATION DEPTHS FOR BOZEMAN
PRECIPITATION DEPTHS & FREQUENCY
FREQUENCY
2-HOUR
RAINFALL
(inches)
6-HOUR
RAINFALL
(inches)
24-HOUR
RAINFALL
(inches)
Water Quality 0.5 0.5 0.5
2-YEAR .49 .71 1.18
5-YEAR .68 0.88 1.49
10-YEAR .81* 0.99 1.70**
25-YEAR .98 1.14 2.96
100-YEAR 1.22 1.35** 2.34
* Approximately equivalent to City Standard for minimum design storm
** Design objective is to fully infiltrate the 100-yr, 6-hr event and the 10-yr, 24-hr event.
The SCS method uses a combination of soil conditions and land-use to assign a runoff
factor to an area. These runoff factors, called runoff curve numbers (CN), indicate the runoff
potential. The CN is a basin parameter with a range of 0 to 100. The value of CN depends
on the hydrologic soil group, the soil cover type, the percentage of impervious areas in the
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Stormwater Drainage Plan
watershed, and the antecedent moisture conditions of the soil. Higher CN values result in
higher runoff volumes and rates.
3.4 SOILS INFORMATION
The CN values selected for the project were based upon soils information from both the
Natural Resources Conservation Service (NRCS) Web Soil Survey and review of
geotechnical test pit data. There are three NRCS soil map units on the property: 1) 350B –
Blackmore silt loam (HSG “C”), 2) 512B – Enbar-Nythar loams (HSG “C”), and 3) 542A –
Blossberg loam (HSG “B/D”). The majority of the proposed development is within the
Blackmore silt loam. The NRCS hydrologic soil group designation was taken into account
during selection of CN’s for both pre-development and post-development hydrologic
conditions. A NRCS Web Soil Survey report can be found in Appendix B. A CN value of 74
is used for pervious areas and 98 for impervious areas.
Soil test pits were dug on March 27th, 2020 by C&H Engineering as documented in the Soils
Investigation Report (see Appendix C). Groundwater was not encountered in any of the
test pits and no evidence of seasonally high groundwater was observed. Test pits generally
identified a Silty Clay Organic layer in the 0- to 2-feet below ground surface (bgs) range, a
Sandy Silt layer in the 1- to 10-feet bgs range, and a Poorly Graded Gravel with Sand and
Cobbles starting to appear around 8-feet bgs and regularly observed at depths greater
than 10-feet bgs.
Soil infiltration testing was not performed due to frozen ground conditions. Field testing will
be conducted during construction to confirm infiltration rates used for design. For design
purposes, saturated hydraulic conductivity (Ksat) values per Circular DEQ-8, Appendix C
(see Table 3) are used and anticipated to be conservative. A Ksat value 0.7 inches per hour
(in/hr) is assumed for rain gardens and cobble streambed galleries based on the “fine sandy
loam, loam” soil classification with no pretreatment. A Ksat value 3.9 in/hr is assumed for
cobble recharge galleries and drywells based on hydraulic connection provided to the
deeper gravel-sand substrate. This number is calculated based on the table classification of
“gravel, gravelly sand, or very coarse sand” and a 50 percent allowable increase based on
upgradient rain gardens and cobble streambed galleries serving as pretreatment to protect
the long-term porosity of the infiltrative footprint (i.e. 2.6 in/hr x 1.5 = 3.9 in/hr).
TABLE 3. DESIGN INFILTRATION RATES PER DEQ-8
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Stormwater Drainage Plan
4.0 PROPOSED DESIGN
4.1 PRE-DEVELOPED RUNOFF RATES
Stormwater runoff from the development site is required to be limited to the pre-
development runoff rates. Pre-development condition is assumed to be native good
standing vegetation (i.e. existing buildings and gravel road is conservatively discounted). As
shown on Sheet 1 of Appendix A, there are two existing sub-basins for the site, and most
drainage currently flows northward towards the center of the northern property line.
Smaller periphery portions of the site are not specifically assessed for pre- vs post-
developed runoff comparison as these areas remain relatively unchanged such that flow
rate alterations are negligible. Furthermore, the project’s design objective to fully infiltrate
the 100-year design storm will reliably offset any minor periphery flow increases that may
occur.
TABLE 4. PRE-DEVELOPED HYDROLOGIC SUMMARY
DRAINAGE ID STORM
FREQUENCY
PRE-DEVELOPED FLOW
(cfs)
E1
2YR 0.000
5YR 0.021
10YR 0.037
25YR 0.062
100YR 0.114
E2
2YR 0.050
5YR 0.237
10YR 0.430
25YR 0.744
100YR 1.318
4.2 PROPOSED DRAINAGE SYSTEM
The stormwater management system is comprised of dispersed treatment-conveyance-
infiltration features including bioswales, rain gardens, cobble infiltration galleries, and dry
streambeds, along with standard closed storm drain conduits and inlets. The features were
designed to fully infiltrate approximately the 25-year design storm from each individual
drainage area and the 100-year design storm when evaluated in series.
Figure 3 presents graphical illustration showing hydraulic routing of the 100-year design
storm for Drainage Area 2 (DA2). The stormwater management feature for DA2 consists of
a rain garden that infiltrates small frequent storms in the 0” to 0.5” range, while large storm
events result in the rain garden filling to a level where it directly engages the subsurface
cobble gallery. Hydraulic routing analysis results show zero discharge of the 100-year
design storm as depicted by the red line in Figure 3 and a total infiltration volume of
2500+/- cubic feet. This discharge is fully infiltrated via downgradient infiltration features.
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Stormwater Drainage Plan
FIGURE 3. DA2 STORAGE-INFILTRATION-DISCHARGE SUMMARY
The final stormwater management feature is a rain garden at the northern perimeter of the
property. This feature functions to store and infiltrate runoff from DA5 along with residual
overflow from upgradient features. Figure 4 illustrates the cumulative runoff and zero
discharge from the 100-year design storm.
FIGURE 4. FINAL RAIN GARDEN STORAGE-INFILTRATION-DISCHARGE SUMMARY
INFLOW
INFILTRATION
ZERO DISCHARGE
INFLOW
INFILTRATION
ZERO DISCHARGE
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Stormwater Drainage Plan
A plan-profile view of the “stormwater management corridor” is provided in Appendix A to
aid in visualizing downstream progression of each feature. Detailed calculations for all
drainage areas and stormwater management features are provided in Appendix D.
Stormwater design plan sheets are provided in Appendix E.
4.3 LOW IMPACT DEVELOPMENT (LID)
City Standards specify that “the drainage plan shall include, to the greatest extent feasible,
low impact development practices that infiltrate, evapotranspire, or capture for reuse 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 Cohousing design team has developed a site
plan that accommodates notable density with substantially less impervious area compared
to traditional development and provides approximately 3x the required runoff reduction
volume. The design provides greater than 60% pervious area through LID principals that
include shared parking, a woonerf style site traffic circulation model to allow narrower
streets, and Grasspave2 ™ porous pavement technology to further reduce hardscape.
To optimize stormwater infiltration and associated environmental benefits, the site grading,
drainage and landscape plan was comprehensively designed to infiltrate runoff through
features dispersed throughout the development. A summary of each feature’s design and
performance is provided below. Storage-infiltration analysis for each feature is included in
Appendix D. A conceptual illustrative rendering from early in design process is included in
Appendix F and Figure 5 below to communicate general components of the LID approach.
DA1 – Dry Streambed Infiltration Gallery
The first feature in the system is a dry channel located in drainage area (DA) #1. The dry
channel will have a 5-foot wide by 1-foot deep cobble gallery; a portion of which will be
covered by vegetated streambanks to create an aesthetic stream-like feature. Storage-
infiltration analysis indicates that the 25-year design storm will be fully infiltrated. Excess
runoff from larger storm events will be conveyed to DA2.
DA2 – Rain Garden w/ Cobble Infiltration Gallery
DA2 will have a bioswale in the parking lot island that drains to a raingarden with an 8-feet
deep cobble infiltration gallery sited directly below. This will result in the bottom of the
gallery being in- and on-top of the native gravel-sand substrate layer to maximize
infiltration. The bioswale and rain garden will function as pretreatment to protect the long-
term infiltrative capacity of the subsurface cobble gallery. Design elevations are such that
small, frequent storms will fully infiltrate through the bottom of the bioswale-rain garden
footprint. Larger events will result in the rain garden filling to approximately 1-foot and
overflow into the subsurface gallery via direct hydraulic connection through the cobble side
slope of the rain garden. Storage-infiltration analysis indicates that the 100-year design
storm will be fully infiltrated, including upgradient inflow from DA1. The above grade water
storage depth is anticipated to range from 12” to 18” during the 10- to 100-year events.
Excess runoff from larger storm events will be conveyed to DA3 through the parking lot
curb-cut and overflow to the inlet immediately to the east.
9 BOZEMAN COHOUSING Stormwater Drainage Plan FIGURE 5. CONCEPTUAL ILLUSTRATIVE RENDERING FOR LID APPROACH (SEE APPENDIX F FOR FULL-SIZE)
10
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Stormwater Drainage Plan
DA3 – Dry Stream Bed to Culvert Crossing Cobble Gallery
DA3 will utilize another dry stream bed channel that leads to a culvert crossing below the
road and connecting to a drywell. Over-excavation will be conducted during culvert and
drywell installation to expose the gravel-sand substrate located approximately 8- to 10-feet
below existing grade. The excavation will be backfilled with porous cobble to provide
additional subsurface storage capacity in which to hold runoff and increase the infiltration
period. The dry stream bed and drywell will be hydraulically connected to the cobble
storage gallery to ensure that the infiltration gallery is engaged while also providing notable
pretreatment to protect long-term infiltration capacity. Storage-infiltration analysis
indicates that the 100-year design storm will be fully infiltrated. Excess runoff from larger
storm events will be conveyed through the drywell outlet pipe to the final rain garden that
collects DA5.
DA4 – Rain Garden
DA4 is roughly 50% pervious with grades that result in broad sheet flow runoff. As such,
this area is not anticipated to contribute substantial runoff or pollutant loading. A standard
rain garden (no subsurface gallery) is proposed to treat, store and infiltrate runoff. The
discharge pipe includes a hydraulic control to provide approximately 1-foot of storage
volume prior to discharging to the DA5 rain garden. Storage-infiltration analysis indicates
that the 25-year design storm will be fully infiltrated. Excess runoff from larger storm events
will be conveyed to DA5 through an overflow inlet and buried storm drain pipe.
DA5 – Rain Garden
DA5 contains the final feature in the stormwater management system. The 1400 square feet
rain garden provides adequate storage volume to fully infiltrate runoff for DA5 along with
residual runoff from upgradient drainage areas. Storage-infiltration analysis indicates that
the 100-year design storm will be fully infiltrated. Design water surface depth during the 10-
and 100-year events is 1.6-feet and 2.7-feet, respectively.
DA6 – Depressional Areas
The eastern periphery of the project includes limited increase in impervious area such that
only marginal increase of runoff is anticipated. The grading plan results in depressional
areas at the top of the slope above Mathew Bird Creek. These areas will store and infiltrate
runoff such that post-development runoff rates are less than that of pre-development.
These features will also reduce the frequency of sheet flow runoff that is causing shallow rill
erosion on the existing slope such that vegetative cover will improve post-construction,
further decreasing runoff and reducing sediment loading to the creek.
Grasspave Pervious Road
The development design includes reduced impervious area by incorporating a porous
roadway material for a large portion of the drivable surface. This measure will reduce
runoff by promoting broad infiltration. Note that the runoff reduction provided by this
measure was not included in the hydrologic analysis such that the runoff analysis is
expected to be conservative.
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Stormwater Drainage Plan
4.4 WATER QUALITY TREATMENT
The LID design results in full infiltration of the 100-year event, equating to 1.35”. This
exceeds the required 0.5”.
4.5 HYDRAULIC DESIGN
Inlets, ditches and culverts are sized to handle the 25-year storm as calculated using the
Rational Method per City Standards. Conveyance calculations conservatively assume that
no peak flow attenuation is provided by upgradient storage-infiltration features. Hydraulic
calculations are documented in the Madison Engineering report included as Appendix G.
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Stormwater Drainage Plan
5.0 CONCLUSIONS
5.1 HYDRAULIC DESIGN
All open channel systems are adequately sized to convey the runoff from the 25-year storm
event assuming no storage or infiltration. Based on the results of the hydrograph routing
analysis described in sections 4.2 and 4.3, the stormwater management system is expected
to reliably attenuate and convey runoff up to the 100-year event.
5.2 RELEASE RATES
Runoff release rates from the project site during proposed conditions do not exceed pre-
developed rates in receiving conveyances for all design storms evaluated up to the 100-
year frequency. Table 5 provides a summary of pre-developed vs. post-developed peak
runoff rates from the site for the two primary existing condition drainage areas. Table 5
shows that the post-development peak flow rates are equal to or less than the pre-
developed rates for all three analysis point locations.
TABLE 5. SUMMARY OF PRE-DEVELOPED AND POST-DEVELOPED FLOWS AT THE
ANALYSIS POINTS
DISCHARGE
POINT
STORM
FREQUENCY
PRE-DEVELOPED
(ALLOWABLE) FLOW
(cfs)
POST-DEVELOPED
FLOW (cfs)
E1
2YR 0.0 0
5YR 0.02 0
10YR 0.04 0
25YR 0.06 0
100YR 0.11 0
E2
2YR 0.05 <0.05
5YR 0.24 <0.2
10YR 0.43 <0.4
25YR 0.74 <0.7
100YR 1.32 <1.3
5.3 COMPLIANCE WITH STANDARDS
The constructed project will improve site drainage through runoff reduction,
implementation of a designed stormwater management system, and treatment for pollutant
removal. The proposed site improvements are detailed in the construction plan sheets
developed for this site. To the best of our knowledge the Storm Drainage Plan has been
assembled per the requirements defined within the City of Bozeman Design Standards and
Specifications Policy.
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Stormwater Drainage Plan
6.0 REFERENCES
City of Bozeman, 2004. Design Standards and Specifications Policy. City Engineering Department.
March 2004. Adopted April 5, 2004, Ordinance 1611.
Montana Department of Environmental Quality, 2017. Montana Standards for Subdivision Storm Water
Drainage, Circular DEQ-8.
Montana Department of Transportation, 1995. Hydraulics Manual. Adopted from AASHTO Model
Drainage Manual.
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Stormwater Drainage Plan
APPENDIX A
DRAINAGE AREA MAPS
E13.80 ACRESE21.22 ACRESWGMGROUPWWW.WGMGROUP.COMEXISTING DRAINAGE AREAS
BOZEMAN COHOUSING
BOZEMAN, MONTANAMARCH 202101PRELIMINARYPLOTTED:SAVED:3/4/213/4/21NTc FLOW PATHSHEET FLOW = 300-FT @ 1.7%SHALLOW CONC. = 167-FT @ 1.2%CONENCTRATED = 130-FT @ 1.5%300 ft
163 ft130 ft 100-YEAR, 6-HRTc FLOW PATHSHEET FLOW = 100-FT @ 2.0%SHALLOW CONC. = 100-FT @ 25%1
0
0
f
t
100 ft100-YEAR, 6-HR
DA#1DA#2DA#3DA#4DA#5DA#6WGMGROUPWWW.WGMGROUP.COMSTORMWATER MANAGEMENT CORRIDOR
BOZEMAN COHOUSING
BOZEMAN, MONTANAMARCH 202102PRELIMINARYPLOTTED:SAVED:3/8/213/5/21N
DA#1DA#2DA#3DA#4DA#5DA#6WGMGROUPWWW.WGMGROUP.COMSTORMWATER MANAGEMENT CORRIDOR
BOZEMAN COHOUSING
BOZEMAN, MONTANAMARCH 202103PRELIMINARYPLOTTED:SAVED:3/8/213/8/21N
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX B
NRCS SOIL INFORMATION
Hydrologic Soil Group—Gallatin County Area, Montana
(Bozeman Cohousing)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/20/2021
Page 1 of 4505490050549205054940505496050549805055000505502050550405055060505490050549205054940505496050549805055000505502050550405055060496730496750496770496790496810496830496850496870496890496910496930496950496970496990
496730 496750 496770 496790 496810 496830 496850 496870 496890 496910 496930 496950 496970 496990
45° 38' 56'' N 111° 2' 31'' W45° 38' 56'' N111° 2' 18'' W45° 38' 51'' N
111° 2' 31'' W45° 38' 51'' N
111° 2' 18'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84
0 50 100 200 300Feet
0 15 30 60 90Meters
Map Scale: 1:1,210 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Gallatin County Area, Montana
Survey Area Data: Version 24, Jun 4, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 3, 2009—Sep 1,
2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—Gallatin County Area, Montana
(Bozeman Cohousing)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/20/2021
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
350B Blackmore silt loam, 0 to
4 percent slopes
C 4.2 80.4%
512B Enbar-Nythar loams, 0
to 4 percent slopes
C 0.1 1.5%
542A Blossberg loam, 0 to 2
percent slopes
B/D 1.0 18.1%
Totals for Area of Interest 5.3 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—Gallatin County Area, Montana Bozeman Cohousing
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/20/2021
Page 3 of 4
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Gallatin County
Area, Montana
Bozeman Cohousing
Natural
Resources
Conservation
Service
January 20, 2021
Preface
Soil surveys contain information that affects land use planning in survey areas.
They highlight soil limitations that affect various land uses and provide information
about the properties of the soils in the survey areas. Soil surveys are designed for
many different users, including farmers, ranchers, foresters, agronomists, urban
planners, community officials, engineers, developers, builders, and home buyers.
Also, conservationists, teachers, students, and specialists in recreation, waste
disposal, and pollution control can use the surveys to help them understand,
protect, or enhance the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil
properties that are used in making various land use or land treatment decisions.
The information is intended to help the land users identify and reduce the effects of
soil limitations on various land uses. The landowner or user is responsible for
identifying and complying with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some
cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/
portal/nrcs/main/soils/health/) and certain conservation and engineering
applications. For more detailed information, contact your local USDA Service Center
(https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as
septic tank absorption fields. A high water table makes a soil poorly suited to
basements or underground installations.
The National Cooperative Soil Survey is a joint effort of the United States
Department of Agriculture and other Federal agencies, State agencies including the
Agricultural Experiment Stations, and local agencies. The Natural Resources
Conservation Service (NRCS) has leadership for the Federal part of the National
Cooperative Soil Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its
programs and activities on the basis of race, color, national origin, age, disability,
and where applicable, sex, marital status, familial status, parental status, religion,
sexual orientation, genetic information, political beliefs, reprisal, or because all or a
part of an individual's income is derived from any public assistance program. (Not
all prohibited bases apply to all programs.) Persons with disabilities who require
2
alternative means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice
and TDD). To file a complaint of discrimination, write to USDA, Director, Office of
Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or
call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................8
Soil Map................................................................................................................9
Legend................................................................................................................10
Map Unit Legend................................................................................................11
Map Unit Descriptions.........................................................................................11
Gallatin County Area, Montana.......................................................................13
350B—Blackmore silt loam, 0 to 4 percent slopes......................................13
512B—Enbar-Nythar loams, 0 to 4 percent slopes.....................................14
542A—Blossberg loam, 0 to 2 percent slopes............................................16
Soil Information for All Uses...............................................................................18
Soil Properties and Qualities..............................................................................18
Soil Qualities and Features.............................................................................18
Hydrologic Soil Group (Bozeman Cohousing).............................................18
References............................................................................................................23
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous
areas in a specific area. They include a description of the soils and miscellaneous
areas and their location on the landscape and tables that show soil properties and
limitations affecting various uses. Soil scientists observed the steepness, length,
and shape of the slopes; the general pattern of drainage; the kinds of crops and
native plants; and the kinds of bedrock. They observed and described many soil
profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The
profile extends from the surface down into the unconsolidated material in which the
soil formed or from the surface down to bedrock. The unconsolidated material is
devoid of roots and other living organisms and has not been changed by other
biological activity.
Currently, soils are mapped according to the boundaries of major land resource
areas (MLRAs). MLRAs are geographically associated land resource units that
share common characteristics related to physiography, geology, climate, water
resources, soils, biological resources, and land uses (USDA, 2006). Soil survey
areas typically consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that
is related to the geology, landforms, relief, climate, and natural vegetation of the
area. Each kind of soil and miscellaneous area is associated with a particular kind
of landform or with a segment of the landform. By observing the soils and
miscellaneous areas in the survey area and relating their position to specific
segments of the landform, a soil scientist develops a concept, or model, of how they
were formed. Thus, during mapping, this model enables the soil scientist to predict
with a considerable degree of accuracy the kind of soil or miscellaneous area at a
specific location on the landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented
by an understanding of the soil-vegetation-landscape relationship, are sufficient to
verify predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them
to identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character
of soil properties and the arrangement of horizons within the profile. After the soil
5
scientists classified and named the soils in the survey area, they compared the
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that
have similar use and management requirements. Each map unit is defined by a
unique combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components
of the map unit. The presence of minor components in a map unit in no way
diminishes the usefulness or accuracy of the data. The delineation of such
landforms and landform segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, onsite
investigation is needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape,
and experience of the soil scientist. Observations are made to test and refine the
soil-landscape model and predictions and to verify the classification of the soils at
specific locations. Once the soil-landscape model is refined, a significantly smaller
number of measurements of individual soil properties are made and recorded.
These measurements may include field measurements, such as those for color,
depth to bedrock, and texture, and laboratory measurements, such as those for
content of sand, silt, clay, salt, and other components. Properties of each soil
typically vary from one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists
interpret the data from these analyses and tests as well as the field-observed
characteristics and the soil properties to determine the expected behavior of the
soils under different uses. Interpretations for all of the soils are field tested through
observation of the soils in different uses and under different levels of management.
Some interpretations are modified to fit local conditions, and some new
interpretations are developed to meet local needs. Data are assembled from other
sources, such as research information, production records, and field experience of
specialists. For example, data on crop yields under defined levels of management
are assembled from farm records and from field or plot experiments on the same
kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on
such variables as climate and biological activity. Soil conditions are predictable over
long periods of time, but they are not predictable from year to year. For example,
soil scientists can predict with a fairly high degree of accuracy that a given soil will
have a high water table within certain depths in most years, but they cannot predict
that a high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
Custom Soil Resource Report
6
identified each as a specific map unit. Aerial photographs show trees, buildings,
fields, roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
7
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of
soil map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
8
9
Custom Soil Resource Report
Soil Map
505490050549205054940505496050549805055000505502050550405055060505490050549205054940505496050549805055000505502050550405055060496730 496750 496770 496790 496810 496830 496850 496870 496890 496910 496930 496950 496970 496990
496730 496750 496770 496790 496810 496830 496850 496870 496890 496910 496930 496950 496970 496990
45° 38' 56'' N 111° 2' 31'' W45° 38' 56'' N111° 2' 18'' W45° 38' 51'' N
111° 2' 31'' W45° 38' 51'' N
111° 2' 18'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84
0 50 100 200 300Feet
0 15 30 60 90Meters
Map Scale: 1:1,210 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Gallatin County Area, Montana
Survey Area Data: Version 24, Jun 4, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 3, 2009—Sep 1,
2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
350B Blackmore silt loam, 0 to 4
percent slopes
4.2 80.4%
512B Enbar-Nythar loams, 0 to 4
percent slopes
0.1 1.5%
542A Blossberg loam, 0 to 2 percent
slopes
1.0 18.1%
Totals for Area of Interest 5.3 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
Custom Soil Resource Report
11
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
12
Gallatin County Area, Montana
350B—Blackmore silt loam, 0 to 4 percent slopes
Map Unit Setting
National map unit symbol: 56q7
Elevation: 4,850 to 5,550 feet
Mean annual precipitation: 18 to 22 inches
Mean annual air temperature: 37 to 43 degrees F
Frost-free period: 80 to 95 days
Farmland classification: All areas are prime farmland
Map Unit Composition
Blackmore and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Blackmore
Setting
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Calcareous loess
Typical profile
A - 0 to 10 inches: silt loam
Bt - 10 to 27 inches: silty clay loam
Bk1 - 27 to 42 inches: silt loam
Bk2 - 42 to 60 inches: silt loam
Properties and qualities
Slope:0 to 4 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Capacity of the most limiting layer to transmit water (Ksat):Moderately high (0.20
to 0.57 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:30 percent
Available water capacity:High (about 11.4 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: C
Ecological site: R043BP818MT - Upland Grassland
Hydric soil rating: No
Minor Components
Bowery
Percent of map unit:5 percent
Landform:Alluvial fans, stream terraces
Down-slope shape:Linear
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Across-slope shape:Linear
Ecological site:R044XS355MT - Silty (Si) 15-19" p.z.
Hydric soil rating: No
Blackmore
Percent of map unit:3 percent
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R043BS323MT - Silty (Si) 20"+ p.z.
Hydric soil rating: No
Brodyk
Percent of map unit:2 percent
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R044XS357MT - Limy (Ly) 15-19" p.z.
Hydric soil rating: No
512B—Enbar-Nythar loams, 0 to 4 percent slopes
Map Unit Setting
National map unit symbol: 56vw
Elevation: 4,300 to 6,100 feet
Mean annual precipitation: 15 to 19 inches
Mean annual air temperature: 37 to 45 degrees F
Frost-free period: 90 to 110 days
Farmland classification: Farmland of local importance
Map Unit Composition
Enbar and similar soils:60 percent
Nythar and similar soils:30 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Enbar
Setting
Landform:Flood plains
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Loamy alluvium
Typical profile
A - 0 to 22 inches: loam
Cg - 22 to 49 inches: sandy loam
2C - 49 to 60 inches: very gravelly loamy sand
Properties and qualities
Slope:0 to 4 percent
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Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat poorly drained
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table:About 24 to 42 inches
Frequency of flooding:RareNone
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water capacity:Moderate (about 8.8 inches)
Interpretive groups
Land capability classification (irrigated): 3w
Land capability classification (nonirrigated): 3w
Hydrologic Soil Group: C
Ecological site: R044BY181MT - Wet Meadow (WM) LRU 44B-Y
Hydric soil rating: No
Description of Nythar
Setting
Landform:Flood plains
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Loamy alluvium
Typical profile
A - 0 to 8 inches: loam
Bg - 8 to 33 inches: silt loam
Cg - 33 to 60 inches: sandy loam
Properties and qualities
Slope:0 to 4 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Very poorly drained
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table:About 0 to 12 inches
Frequency of flooding:RareNone
Frequency of ponding:None
Available water capacity:High (about 9.7 inches)
Interpretive groups
Land capability classification (irrigated): 5w
Land capability classification (nonirrigated): 5w
Hydrologic Soil Group: B/D
Ecological site: R043BP801MT - Bottomland
Hydric soil rating: Yes
Minor Components
Blossberg
Percent of map unit:5 percent
Landform:Flood plains
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R044XS365MT - Wet Meadow (WM) 15-19" p.z.
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Hydric soil rating: Yes
Straw
Percent of map unit:5 percent
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R044XS355MT - Silty (Si) 15-19" p.z.
Hydric soil rating: No
542A—Blossberg loam, 0 to 2 percent slopes
Map Unit Setting
National map unit symbol: 56wx
Elevation: 4,200 to 5,550 feet
Mean annual precipitation: 12 to 18 inches
Mean annual air temperature: 39 to 45 degrees F
Frost-free period: 90 to 110 days
Farmland classification: Farmland of local importance
Map Unit Composition
Blossberg and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Blossberg
Setting
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Alluvium
Typical profile
A - 0 to 15 inches: loam
Bg - 15 to 24 inches: sandy clay loam
2C - 24 to 60 inches: extremely gravelly loamy coarse sand
Properties and qualities
Slope:0 to 2 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Poorly drained
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.20 to 1.98 in/hr)
Depth to water table:About 12 to 24 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Nonsaline to slightly saline (0.0 to 4.0 mmhos/cm)
Available water capacity:Low (about 5.5 inches)
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Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 5w
Hydrologic Soil Group: B/D
Ecological site: R044BY181MT - Wet Meadow (WM) LRU 44B-Y
Hydric soil rating: Yes
Minor Components
Bonebasin
Percent of map unit:10 percent
Landform:Terraces
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R044XS365MT - Wet Meadow (WM) 15-19" p.z.
Hydric soil rating: Yes
Meadowcreek
Percent of map unit:5 percent
Landform:Stream terraces
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R044XS359MT - Subirrigated (Sb) 15-19" p.z.
Hydric soil rating: No
Custom Soil Resource Report
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Soil Information for All Uses
Soil Properties and Qualities
The Soil Properties and Qualities section includes various soil properties and
qualities displayed as thematic maps with a summary table for the soil map units in
the selected area of interest. A single value or rating for each map unit is generated
by aggregating the interpretive ratings of individual map unit components. This
aggregation process is defined for each property or quality.
Soil Qualities and Features
Soil qualities are behavior and performance attributes that are not directly
measured, but are inferred from observations of dynamic conditions and from soil
properties. Example soil qualities include natural drainage, and frost action. Soil
features are attributes that are not directly part of the soil. Example soil features
include slope and depth to restrictive layer. These features can greatly impact the
use and management of the soil.
Hydrologic Soil Group (Bozeman Cohousing)
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
18
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer at
or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
Custom Soil Resource Report
19
20
Custom Soil Resource Report
Map—Hydrologic Soil Group (Bozeman Cohousing)505490050549205054940505496050549805055000505502050550405055060505490050549205054940505496050549805055000505502050550405055060496730 496750 496770 496790 496810 496830 496850 496870 496890 496910 496930 496950 496970 496990
496730 496750 496770 496790 496810 496830 496850 496870 496890 496910 496930 496950 496970 496990
45° 38' 56'' N 111° 2' 31'' W45° 38' 56'' N111° 2' 18'' W45° 38' 51'' N
111° 2' 31'' W45° 38' 51'' N
111° 2' 18'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84
0 50 100 200 300Feet
0 15 30 60 90Meters
Map Scale: 1:1,210 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Gallatin County Area, Montana
Survey Area Data: Version 24, Jun 4, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 3, 2009—Sep 1,
2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
21
Table—Hydrologic Soil Group (Bozeman Cohousing)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
350B Blackmore silt loam, 0 to
4 percent slopes
C 4.2 80.4%
512B Enbar-Nythar loams, 0 to
4 percent slopes
C 0.1 1.5%
542A Blossberg loam, 0 to 2
percent slopes
B/D 1.0 18.1%
Totals for Area of Interest 5.3 100.0%
Rating Options—Hydrologic Soil Group (Bozeman Cohousing)
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
22
References
American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of sampling
and testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife
Service FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric
soils in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service.
U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for
making and interpreting soil surveys. 2nd edition. Natural Resources Conservation
Service, U.S. Department of Agriculture Handbook 436. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
23
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,
the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook
296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
24
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Gallatin County Area, Montana Bozeman Cohousing
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/20/2021
Page 4 of 4
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX C
SOILS INVESTIGATION REPORT
1091 Stoneridge Drive • Bozeman, Montana • Phone (406) 587-1115 • Fax (406) 587-9768 www.chengineers.com • E-Mail: info@chengineers.com
May 12, 2020
Bozeman Coho, LLC Attn: Mark Owkes Email: mark.owkes@gmail.com
RE: Soils Investigation Report – 3120 Wagon Wheel Road; Bozeman, Montana (200302).
Dear Mr. Owkes,
C&H Engineering and Surveying Inc., (C&H Engineering) has conducted a subsurface soils investigation for the above referenced property. The scope of services was to conduct a subsurface soils investigation and provide a soils investigation report. The report documents the site conditions, soil properties, and provides foundation design and general earthwork recommendations.
Proposed Construction
It is understood that multiple multi-family structures are planned for construction. It is understood that the structures are planned to be constructed with wither crawl space and/or basement foundations.
It has been assumed that the foundation footings will not be subjected to unusual loading
conditions such as eccentric loads. If any of the foundation footings will be eccentrically loaded please contact this office so we can appropriately revise our allowable bearing capacity and settlement estimates.
Subsurface Soil and Conditions
On March 27, 2020 a member of the staff of C&H Engineering visited the site to conduct a subsurface soils investigation. The subsurface soils investigation consisted of examining eight exploratory test pit excavations. The exploratory test pits were excavated with a backhoe provided by Val Mencas Excavation, LLC. The test pit locations were chosen based on the proposed test pit location map provided to our office via email on 3/13/2020. The soil profiles
revealed by the exploratory excavations were logged and visually classified according to ASTM D 2488, which utilizes the nomenclature of the Unified Soil Classification System (USCS).
The following paragraphs briefly summarize the subsurface soils and conditions observed in the eight exploratory test pits excavated for the field investigation. The soil horizons are described as
they were encountered in the test pit excavations, starting with the horizon nearest the surface
and proceeding with each additional horizon encountered with depth.
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 2
The first soil horizon encountered in each exploratory excavation was a Silty Clay Organic Soil of low plasticity (OL). This material was dark brown to black in color, moist, and soft. This
material was encountered to depths varying from approximately 0.5 feet below grounds surface
(bgs) to 2.0 feet bgs in each exploratory excavation. Organic soils are highly compressible and are not suitable for foundation support. This material must also be removed from beneath all interior and exterior concrete slabs as well as beneath all asphalt paving. This material may be stockpiled onsite and used for final site grading purposes.
The second soil horizon encountered in each exploratory excavation was a Sandy Silt (ML). This material was present to depths varying from 4.0 feet bgs to 10.5 feet bgs. Penetration test performed on this material indicate that it was medium stiff. This material contained approximately 55 percent fine to coarse grained sand and approximately 45 percent silty fines.
The third soil horizon encountered in all exploratory excavations except TP-2 was a Poorly Graded Gravel with Sand and Cobbles (GP). This material was present to the end of each excavation, depths varying from 10.5 feet bgs to 13.0 feet bgs. This material was medium dense to dense, and contained approximately 25 percent fine to coarse grain sand and approximately 75
percent subrounded gravels and cobbles.
TP-2: The third soil horizon encountered in this exploratory excavation was a Lean Clay (CL). This
material was present to a depth of 9 feet bgs. Penetration test performed on this material indicate
that it was medium stiff. Following the Lean Clay, Poorly Graded Gravel was encountered to a depth of 11 feet bgs. Following the Poorly Graded Gravel with Sand, Poorly Graded Sand with Gravel was encountered to 13 feet bgs. Following the Poorly Graded Sand with Gravel, Poorly Graded Gravel with Sand was encountered, this time to the end of excavation at approximately
15 feet bgs.
Based on the subsurface investigation, it is expected that the excavations for the foundations will end in varying soil types. It is likely that crawl space excavations will end within the Sandy Silt and that excavations for basements will end within Poorly Graded Gravel with Sand and
Cobbles.
If either excavation is found to end within the Sandy Silt, it is recommended that the excavation continue down to 12 inches below the desired bottom of footing elevation, or until Poorly Graded Gravel with Sand and Cobbles is encountered, whichever is shallower. This will allow
for the placement of 12 inches of structural fill beneath the foundation footings. The purpose of
the structural fill is to help mitigate any differential settlement that may occur and also to provide a buffer between the foundation footings and the moisture sensitive Silty Sand. Please note that the recommended allowable bearing capacity for foundation footings bearing on
structural fill overlying the Sandy Silt is 1,500 pounds per square foot (psf) and is 3,000 psf for
foundation footings bearing on Poorly Graded Gravel with Sand and Cobbles. Although we have proposed a general recommendation for all structures, the foundation
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 3
subgrade for each structure shall be inspected by C&H Engineering and Surveying, Inc. to verify our recommendations are consistent with the exposed subgrade conditions.
Groundwater
Groundwater was not encountered in any of the exploratory test pits, evidence of seasonally high groundwater (such as lack of calcium, mottling, high moisture was not observed within the depth of excavation). Groundwater is not expected to be encountered within the excavation for the foundations.
Please note that our subsurface investigation is not a detailed groundwater study, and groundwater conditions may change dramatically due to conditions that are out of our control. Our assessment of the groundwater conditions is based on the conditions observed within the exploratory test pits on the day of the excavation, our general experience in the project area, and
any available literature regarding groundwater conditions in the vicinity of the subject property. If more detailed knowledge of the seasonally high groundwater elevation across the subject property is desired, it is recommended that groundwater monitoring wells be installed and checked weekly from the early spring to late summer months. Foundation Recommendations
Based on the subsurface soils encountered in the eight exploratory excavations, it will be
acceptable to utilize either a crawl space or basement foundation for the proposed structures. Please find the following as general recommendations for all foundation elements:
• In order to keep the footing out of the active frost zone it is recommended that the bottom
of all footing elevations be a minimum of 48 inches below finished grade.
• Foundation footings are to bear on a minimum of 12 inches of compacted structural fill overlying the Sandy Silt. All foundation footings for this scenario shall be dimensioned
for an allowable bearing capacity of 1,500 pounds per square foot (psf).
• Foundation footings may also bear on the Poorly Graded Gravel with Sand and Cobbles or on compacted structural fill overlying this material. All foundation footings for this scenario shall be dimensioned for an allowable bearing capacity of 3,000 pounds per
square foot (psf).
• It is recommended that typical strip footings for this structure have a minimum width of 16 inches and column footings should have a minimum width of 24 inches, provided the
soils allowable bearing capacity is not exceeded. Allowable Bearing Capacity & Settlement The bearing capacity of a soil is defined as the ultimate pressure per unit area by the foundation that can be supported by the soil in excess of the pressure caused by the surrounding soil at the
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 4
footing level. Bearing capacity is determined by the physical and chemical properties of the soil located beneath the proposed structures footings.
The loads from the proposed structures that are transmitted to a 12-inch thick structural fill pad overlying the Sandy Silt, it is recommended that an allowable bearing capacity of 1,500 pounds per square foot be used to dimension all foundation footings.
The loads from the proposed structures that are transmitted to the Poorly Graded Gravel with
Sand and Cobbles or to compacted structural fill overlying this material, it is recommended that an allowable bearing capacity of 3,000 pounds per square foot be used to dimension all foundation footings.
Settlement and differential settlement were estimated using conservative soil parameters and the
assumption that the foundation footings bear on properly placed and compacted structural fill overlying Sandy Silt. Based on conservative soil parameter estimates, the bearing capacity recommended, and the assumption that all recommendations made in this report will be properly implemented, it is expected that total and differential settlement will be ¾-inch or less. Structures
of the type proposed can generally tolerate movements of this magnitude, however, this
movement should be checked by a structural engineer to determine if it is acceptable. Subgrade Preparation and Structural Fill In general, the excavation must be level and uniform and continue down to 12 inches below the desired bottom of footing elevation or to the Poorly Graded Gravel with Sand and Cobbles whichever is shallower. If any soft spots, are encountered, they will need to be removed and
backfilled with structural fill. The excavation width must extend a minimum of one footing
width from the outer edges of the footings or to a distance equal to ½ the height of the required structural fill, whichever is greater. For example, if 6 feet of structural fill is required, the excavation must extend out from the footing a minimum distance of 3 feet.
Once the excavation is completed, the native subgrade shall be proof rolled with a large
compactor to an unyielding condition, if the excavation is found to end in the Sandy Silt a layer of geotextile fabric (Mirafi 500X) must be placed, followed by placing and compacting the required structural fill. Any areas that are found to be pumping or rutting shall be sub-excavated and replaced with structural fill.
Structural fill is defined as all fill that will ultimately be subjected to structural loadings, such as those imposed by footings, floor slabs, pavements, etc. Structural fill will need to be imported for this project. Imported structural fill is recommended to be a well graded gravel with sand that contains less than 15 percent of material that will pass a No. 200 sieve and that has a maximum
particle size of 3 inches. Also, the fraction of material passing the No. 40 sieve shall have a
liquid limit not exceeding 25 and a plasticity index not exceeding 6. The gravel and sand particles also need to be made up of durable rock materials that will not degrade when compacted; no shale or mudstone fragments should be present.
Structural fill must be placed in lifts no greater than 12 inches (uncompacted thickness) and be
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 5
uniformly compacted to a minimum of 97 percent of its maximum dry density, as determined by ASTM D698. Typically, the structural fill must be moisture conditioned to within + 2 percent of
the materials optimum moisture content to achieve the required density. It is recommended that
the structural fill be compacted with a large vibrating smooth drum roller. Please note that if a moisture-density relationship test (commonly referred to as a proctor) needs to be performed for a proposed structural fill material to determine its maximum dry density and optimum moisture content in accordance with ASTM D698, a sample of the material must be delivered to this
office a minimum of three full working days prior to beginning placement of the structural fill.
At no time should surface water runoff be allowed to flow into and accumulate within the excavation for the foundation elements. If necessary, a swale or berm should be temporarily constructed to reroute all surface water runoff away from the excavation. Excavation should not
proceed during large precipitation events.
If any of the foundation footings are found to be located on a test pit, the area will need to be excavated down to the full depth of the test pit and structural fill be placed and compacted in lifts (as described in this report) to bring the area back up to the desired grade.
Foundation Wall Backfill
Approved backfill material should be placed and compacted between the foundation wall and the edge of the excavation. The soils encountered during the field investigation (except the organic soil) are suitable for use as foundation wall backfill along the exterior of the foundation, provided they are not too moist. Structural fill is recommended as foundation wall backfill in all
areas that will support concrete slabs-on-grade or other paving improvements. The backfill shall be placed in uniform lifts and be compacted to a minimum of 95 percent of the material’s maximum dry density, as determined by ASTM D698. The foundation wall backfill will need to be compacted with either walk behind compaction
equipment or hand operated compaction equipment in order to avoid damaging the foundation walls. If walk behind compaction equipment is used, lifts should not exceed 8-inches (loose thickness) and if hand operated compaction equipment is used lifts should not exceed 4-inches (loose thickness). Interior Slabs-on-Grade
In preparation for any interior slabs-on-grade, the excavation must continue down to the Sandy
Silt. Structural fill can then be placed and compacted to 6 inches below the bottom of slab elevation. For all interior concrete slabs-on-grade, preventative measures must be taken to stop moisture from migrating upwards through the slab. Moisture that migrates upwards through the concrete
slab can damage floor coverings such as carpet, hardwood and vinyl, in addition to causing musty odors and mildew growth. Moisture barriers will need to be installed to prevent water vapor migration and capillary rise through the concrete slab.
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 6
In order to prevent capillary rise through the concrete slab-on-grade it is recommended that 6 inches of ¾-inch washed rock (containing less than 10 percent fines) be placed and compacted
once the excavation for the slab is complete. The washed rock has large pore spaces between soil
particles and will act as a capillary break, preventing groundwater from migrating upwards towards the bottom of the slab. In order to prevent the upward migration of water vapor through the slab, it is recommended that
a 15-mil extruded polyolefin plastic that complies with ASTM E1745 (such as a Stego Wrap 15-
mil Vapor Barrier) be installed. The vapor barrier should be pulled up at the sides and secured to the foundation wall or footing. Care must be taken during and after the installation of the vapor barrier to avoid puncturing the material, and all joints are to be sealed per the manufacture’s recommendations.
Once the excavation for the interior slab-on-grade is completed as described in the first paragraph of this section, and the ¾ inch washed rock and moisture barriers have been properly installed, it will be acceptable to form and cast the steel reinforced concrete slab. It is recommended that interior concrete slabs-on-grade have a minimum thickness of 4 inches, unless
the slab will be supporting vehicles, then the recommended minimum thickness if 6 inches, or as
directed by a licensed structural engineer. Exterior Slabs-on-Grade For exterior areas to be paved with concrete slabs, it is recommended that, at a minimum, the topsoil be removed. The native subgrade then needs to be compacted to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. Then for non-vehicular traffic areas,
a minimum of 6 inches of ¾-inch minus rock needs to be placed, and 4 inches of 4000 pounds
per square inch (psi) concrete placed over the ¾-inch minus rock. For areas with vehicular traffic, a minimum of 9 inches of ¾-inch minus rock should be placed, followed by 6 inches of 4000 psi concrete, unless directed otherwise by a licensed structural engineer.
Exterior slabs that will be located adjacent to the foundation walls need to slope away from the
structure at a minimum grade of 2 percent and should not be physically connected to the foundation walls. If they are connected, any movement of the exterior slab will be transmitted to the foundation wall, which may result in damage to the structure. Site Grading
Surface water should not be allowed to accumulate and infiltrate the soil near the foundation.
Proper site grading will ensure surface water runoff is directed away from the foundation. If the
subgrade soils are allowed to experience a significant increase in moisture additional settlement may occur. Please find the following as general site grading recommendations:
• Finished grade must slope away from the building a minimum of 5 percent within the
first 10 feet, in order to quickly drain ground surface and roof runoff away from the foundation walls. Please note that in order to maintain this slope; it is imperative that any backfill placed against the foundation walls be compacted properly. If the backfill is not
SOILS INVESTIGATION REPORT
#200302 – 3120 WAGON WHEEL ROAD; BOZEMAN, MONTANA 7
compacted properly, it will settle and positive drainage away from the structure will not be maintained.
• Permanent sprinkler heads for lawn care should be located a sufficient distance from the structure to prevent water from draining toward the foundation or saturating the soils adjacent to the foundation.
• Rain gutter down spouts are to be placed in such a manner that surface water runoff drains away from the structure.
• All roads, walkways, and architectural land features must properly drain away from all structures. Special attention should be made during the design of these features to not create any drainage obstructions that may direct water towards or trap water near the foundation. Asphalt Paving Improvements
For areas to be paved with asphalt, it is recommended that, as a minimum, the topsoil be
removed. The native subgrade then needs to be compacted at ± 2 percent of its optimum
moisture content to 95 percent of its maximum dry density, as determined by ASTM D698. Following compaction of the native subgrade, a layer of woven geotextile (such as a Mirafi 500X) shall be installed. Next a 12-inch layer of compacted 6-inch minus gravel needs to be placed, followed by a 6-inch layer of compacted 1-inch minus road mix. Both gravel courses
must be compacted at ± 2 percent of their optimum moisture content to 95 percent of their
maximum dry density, as determined by ASTM D698. A 3-inch thick layer of asphalt pavement can then be placed and compacted over this cross-section. Construction Administration
The foundation is a vital element of a structure; it transfers all of the structures dead and live loads to the native soil. It is imperative that the recommendations made in this report are
properly adhered to. A representative from C&H Engineering should observe the construction of
any foundation or drainage elements recommended in this report. The recommendations made in this report are contingent upon our involvement. If the soils encountered during the excavation differ than those described in this report or any unusual conditions are encountered, our office should be contacted immediately to examine the conditions, re-evaluate our recommendations
and provide a written response.
If construction and site grading take place during cold weather, it is recommended that approved winter construction practices be observed. All snow and ice shall be removed from cut and fill areas prior to site grading taking place. No fill should be placed on soils that are frozen or
contain frozen material. No frozen soils can be used as fill under any circumstances.
Additionally, Concrete should not be placed on frozen soils and should meet the temperature requirements of ASTM C 94. Any concrete placed during cold weather conditions shall be protected from freezing until the necessary compressive strength has been attained. Once the footings are placed, frost shall not be permitted to extend below the foundation footings, as this
SOILS INVESTIGATION REPORT
could heave and crack the foundation footings and/or foundation walls.
It is the responsibility of the contractor to provide a safe working environment with regards to excavations on the site. All excavations should be sloped or shored in the interest of safety and in accordance with local and federal regulations, including the excavation and trench safety
standards provided by the Occupational Safety and Health Administration (OSHA).
Report Limitations
The recommendations made in this report are based on limited information obtained from the exploratory test pits excavated on the subject property. It is not uncommon for variations in the subsurface conditions to occur, the nature and extent of which do not become evident until additional exploration or construction is conducted. The variations may result in additional
construction costs, and it is suggested that a contingency be provided for this purpose.
This report is for the exclusive use of Bozeman Coho, LLC. In the absence of our written approval, we make no representation and assume no responsibility to other parties regarding the use of this report. These recommendations are applicable to the subject property only and are not
applicable to other construction sites. Under no circumstances shall a portion of this report be
removed or be used independently of the rest of the document; this report is applicable as a full document only.
Services performed by C&H Engineering and Surveying, Inc. for this project have been
conducted with the level of care and skill ordinarily exercised by members of the profession
currently practicing in this area under similar budget and time restraints. No warranty, expressed or implied, is made.
If you have any questions, or if we can assist with the future phases of your project, please contact the undersigned.
Respectfully Submitted by
Enc: Test Pit Logs
Test Pit Location Map
Reviewed by /HI lJ/'1
Michael J. Welch, P.E.
G:\c&h\20\200302\Report Documents\Soils lnvestigation(200302).doc
#200302 -3120 WAGON WHEEL ROAD; BOZEMAN, MONT ANA 8
OL
ML
GP
2.0
7.0
12.5
0 TO 2 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
2 TO 7 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff; approximately 10
percent fine to coarse grain sand; approximately 90 percent silty fines.
7 TO 12.5 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;
medium dense to dense; approximately 75 percent subrounded gravels; approximately 25
percent fine to coarse grain sand.
Bottom of test pit at 12.5 feet.
NOTES Monitoring Well Installed
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0
12.5 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP 1
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
GB
2-1
MC = 21%
Fines = 93%
OL
ML
CL
GP
SP
GP
1.5
4.0
9.0
11.0
13.0
15.0
0 TO 1.5 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
1.5 TO 4 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff;
approximately 10 percent fine to coarse grain sand; approximately 90
percent silty fines.
4 TO 9 FEET: LEAN CLAY; (CL); tan to brown; moist; medium plasticity;
medium stiff; approximately 5 percent fine to coarse grain sand;
approximately 95 percent clayey fines.
9 TO 11 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES;
(GP); moist; medium dense to dense; approximately 75 percent subrounded
gravels; approximately 25 percent fine to coarse grain sand.
11 TO 13 FEET: POORLY GRADED SAND WITH GRAVEL; (SP); brown;
moist to very moist; medium dense; approximately 35 percent subrounded
gravels; approximately 65 percent fine to coarse grain sand.
13 TO 15 FEET: POORLY GRADED GRAVEL WITH SAND AND
COBBLES; (GP); moist; medium dense to dense; approximately 75 percent
subrounded gravels; approximately 25 percent fine to coarse grain sand.
Bottom of test pit at 15.0 feet.
NOTES
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 12/18/19 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0
5
10
15 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP 2
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJTESTS
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
OL
ML
GP
1.0
9.0
13.0
0 TO 1 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
1 TO 9 FEET: SILTY SAND; (SM); brown; moist; medium stiff; approximately 55 percent
fine to coarse grain sand; approximately 45 percent silty fines.
9 TO 13 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;medium dense to dense; approximately 75 percent subrounded gravels; approximately 25
percent fine to coarse grain sand.
Bottom of test pit at 13.0 feet.
NOTES Monitoring Well Installed
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 12/18/19 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0
12.5 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP 3
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
OL
ML
GP
2.0
7.0
10.0
0 TO 2 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
2 TO 7 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff; approximately 10
percent fine to coarse grain sand; approximately 90 percent silty fines.
7 TO 10 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;
medium dense to dense; approximately 75 percent subrounded gravels; approximately 25
percent fine to coarse grain sand.
Bottom of test pit at 10.0 feet.
NOTES Monitoring Well Installed
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP-4
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
GB
5-1
MC = 22%
Fines = 93%
OL
ML
GP
0.5
8.0
10.5
0 TO 0.5 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
0.5 TO 8 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff;
approximately 10 percent fine to coarse grain sand; approximately 90
percent silty fines.
8 TO 10.5 FEET: POORLY GRADED GRAVEL WITH SAND AND
COBBLES; (GP); moist; medium dense to dense; approximately 75 percent
subrounded gravels; approximately 25 percent fine to coarse grain sand.
Bottom of test pit at 10.5 feet.
NOTES
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP-5
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJTESTS
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
OL
ML
GP
1.5
10.5
12.5
0 TO 1.5 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
1.5 TO 10.5 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff; approximately 10
percent fine to coarse grain sand; approximately 90 percent silty fines.
10.5 TO 12.5 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP);
moist; medium dense to dense; approximately 75 percent subrounded gravels;
approximately 25 percent fine to coarse grain sand.
Bottom of test pit at 12.5 feet.
NOTES Monitoring Well Installed
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0
12.5 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP-6
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
OL
ML
GP
2.0
8.0
12.0
0 TO 2 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
2 TO 8 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff; approximately 10
percent fine to coarse grain sand; approximately 90 percent silty fines.
8 TO 12 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;
medium dense to dense; approximately 75 percent subrounded gravels; approximately 25
percent fine to coarse grain sand.
Bottom of test pit at 12.0 feet.
NOTES
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP-7
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
GB
8-1
MC = 28%
Fines = 90%
OL
ML
GP
1.5
8.0
11.5
0 TO 1.5 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft.
1.5 TO 8 FEET: SANDY SILT; (ML); brown; moist; soft to medium stiff;
approximately 10 percent fine to coarse grain sand; approximately 90
percent silty fines.
8 TO 11.5 FEET: POORLY GRADED GRAVEL WITH SAND AND
COBBLES; (GP); moist; medium dense to dense; approximately 75 percent
subrounded gravels; approximately 25 percent fine to coarse grain sand.
Bottom of test pit at 11.5 feet.
NOTES
GROUND ELEVATION
LOGGED BY Noah J. Schaible, E.I.
EXCAVATION METHOD Deere 410 C Backhoe
EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS:
DATE STARTED 3/27/20 COMPLETED 3/27/20
AT TIME OF EXCAVATION ---
AFTER EXCAVATION ---
AT END OF EXCAVATION ---DEPTH(ft)0.0
2.5
5.0
7.5
10.0 SAMPLE TYPENUMBERPAGE 1 OF 1
TEST PIT NUMBER TP-8
PROJECT NUMBER 200302
CLIENT Bozeman Coho, LLC
PROJECT LOCATION 3120 Wagon Wheel Road, Bozeman, Montana
PROJECT NAME Soils Investigation
GENERAL BH / TP / WELL - GINT STD US.GDT - 5/12/20 14:37 - G:\C&H\20\200302\TP LOGS\200302.GPJTESTS
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX D
STORAGE-INFILTRATION ANALYSIS
BOZEMAN COHOUSING
Stormwater Drainage Plan
PRE-DEVELOPMENT FLOW RATES
Hydrograph Return Period Recap
1
Hyd. Hydrograph Inflow Peak Outflow (cfs)Hydrograph
No. type hyd(s)Description
(origin)1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
1 SCS Runoff ------ 0.064 0.153 ------- 0.238 0.297 0.381 ------- 0.503 DA #2
2 Reservoir 1 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#2 Infil. Gallery
3 SCS Runoff ------ 0.002 0.006 ------- 0.023 0.039 0.062 ------- 0.100 DA#1
4 Reservoir 3 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#1 to Cobble Stream
5 SCS Runoff ------ 0.007 0.047 ------- 0.105 0.149 0.216 ------- 0.325 DA#5
6 SCS Runoff ------ 0.006 0.028 ------- 0.092 0.142 0.219 ------- 0.343 DA#3
7 SCS Runoff ------ 0.002 0.009 ------- 0.030 0.046 0.070 ------- 0.110 DA#4
8 Reservoir(i) 6 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#3 to bioswale/Dry
9 Reservoir 7 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.014 DA#4 to Rain Garden
10 Combine 2, 4, 5,
8, 9
0.007 0.047 ------- 0.105 0.149 0.216 ------- 0.325 <no description>
11 Reservoir 10 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 Final Rain Garden
12 SCS Runoff ------ 0.000 0.000 ------- 0.021 0.037 0.062 ------- 0.114 EXISTING - E1
13 SCS Runoff ------ 0.000 0.050 ------- 0.237 0.430 0.744 ------- 1.318 EXISTING - E2
14 SCS Runoff ------ 0.000 0.001 ------- 0.004 0.006 0.011 ------- 0.036 DA#6
15 Reservoir 14 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#6 to Depressions
Proj. file: Cohousing_Final Calcs_03-04-21.gpw Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
TR55 Tc Worksheet 21
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
Hyd. No. 12
EXISTING - E1
Description A B C Totals
Sheet Flow
Manning's n-value = 0.050 0.011 0.011
Flow length (ft) = 300.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.29 0.00 0.00
Land slope (%) = 1.70 0.00 0.00
Travel Time (min) = 16.47 + 0.00 + 0.00 = 16.47
Shallow Concentrated Flow
Flow length (ft) = 167.00 0.00 0.00
Watercourse slope (%) = 1.20 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =1.77 0.00 0.00
Travel Time (min) = 1.57 + 0.00 + 0.00 = 1.57
Channel Flow
X sectional flow area (sqft) = 3.00 0.00 0.00
Wetted perimeter (ft) = 3.00 0.00 0.00
Channel slope (%) = 1.50 0.00 0.00
Manning's n-value = 0.035 0.015 0.015
Velocity (ft/s) =5.21
0.00
0.00
Flow length (ft) ({0})130.0 0.0 0.0
Travel Time (min) = 0.42 + 0.00 + 0.00 = 0.42
Total Travel Time, Tc .............................................................................. 18.46 min
TR55 Tc Worksheet 23
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
Hyd. No. 13
EXISTING - E2
Description A B C Totals
Sheet Flow
Manning's n-value = 0.050 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 1.29 0.00 0.00
Land slope (%) = 1.22 0.00 0.00
Travel Time (min) = 7.81 + 0.00 + 0.00 = 7.81
Shallow Concentrated Flow
Flow length (ft) = 100.00 0.00 0.00
Watercourse slope (%) = 25.00 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =8.07 0.00 0.00
Travel Time (min) = 0.21 + 0.00 + 0.00 = 0.21
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter (ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc .............................................................................. 8.00 min
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 12
EXISTING - E1
Hydrograph type = SCS Runoff Peak discharge = 0.114 cfs
Storm frequency = 100 yrs Time to peak = 216 min
Time interval = 2 min Hyd. volume = 1,388 cuft
Drainage area = 3.800 ac Curve number = 74
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 18.46 min
Total precip. = 1.35 in Distribution = SCS 6-Hr
Storm duration = 6.00 hrs Shape factor = 484
103
0 60 120 180 240 300 360 420
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
EXISTING - E1
Hyd. No. 12 -- 100 Year
Hyd No. 12
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 13
EXISTING - E2
Hydrograph type = SCS Runoff Peak discharge = 1.318 cfs
Storm frequency = 100 yrs Time to peak = 720 min
Time interval = 2 min Hyd. volume = 3,127 cuft
Drainage area = 1.220 ac Curve number = 74
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 8.00 min
Total precip. = 2.67 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
104
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (min)
EXISTING - E2
Hyd. No. 13 -- 100 Year
Hyd No. 13
BOZEMAN COHOUSING
Stormwater Drainage Plan
POST-DEVELOPMENT FLOW RATES
Hydrograph Return Period Recap
1
Hyd. Hydrograph Inflow Peak Outflow (cfs)Hydrograph
No. type hyd(s)Description
(origin)1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
1 SCS Runoff ------ 0.064 0.153 ------- 0.238 0.297 0.381 ------- 0.503 DA #2
2 Reservoir 1 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#2 Infil. Gallery
3 SCS Runoff ------ 0.002 0.006 ------- 0.023 0.039 0.062 ------- 0.100 DA#1
4 Reservoir 3 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#1 to Cobble Stream
5 SCS Runoff ------ 0.007 0.047 ------- 0.105 0.149 0.216 ------- 0.325 DA#5
6 SCS Runoff ------ 0.006 0.028 ------- 0.092 0.142 0.219 ------- 0.343 DA#3
7 SCS Runoff ------ 0.002 0.009 ------- 0.030 0.046 0.070 ------- 0.110 DA#4
8 Reservoir(i) 6 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#3 to bioswale/Dry
9 Reservoir 7 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.014 DA#4 to Rain Garden
10 Combine 2, 4, 5,
8, 9
0.007 0.047 ------- 0.105 0.149 0.216 ------- 0.325 <no description>
11 Reservoir 10 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 Final Rain Garden
12 SCS Runoff ------ 0.000 0.000 ------- 0.021 0.037 0.062 ------- 0.114 EXISTING - E1
13 SCS Runoff ------ 0.000 0.050 ------- 0.237 0.430 0.744 ------- 1.318 EXISTING - E2
14 SCS Runoff ------ 0.000 0.001 ------- 0.004 0.006 0.011 ------- 0.036 DA#6
15 Reservoir 14 0.000 0.000 ------- 0.000 0.000 0.000 ------- 0.000 DA#6 to Depressions
Proj. file: Cohousing_Final Calcs_03-04-21.gpw Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
DA2INFLOW
DISCHARGE
INFLOW DA5DA1DISCHARGE
INFLOW
DISCHARGE DA5
INFLOW DA3
DISCHARGE DA3
INFLOW DA4
DISCHARGE DA4
DA6INFLOW
DISCHARGE
RESIDUAL INFLOW DA5
PRE-DEVELOPMENT
RUNOFF
BOZEMAN COHOUSING
Stormwater Drainage Plan
STAGE-DISCHARGE PARAMETERS
Pond Report 8
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 2 - DA#1 Cobble Stream Gallery
Pond Data
Trapezoid -Bottom L x W = 200.0 x 5.0 ft, Side slope = 0.05:1, Bottom elev. = 4976.00 ft, Depth = 3.00 ft, Voids = 30.00%
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4976.00 1,000 0 00.30 4976.30 1,006 90 90
0.60 4976.60 1,012 91 181
0.90 4976.90 1,018 91 272
1.20 4977.20 1,025 92 364
1.50 4977.50 1,031 92 457
1.80 4977.80 1,037 93 550
2.10 4978.10 1,043 94 644
2.40 4978.40 1,049 94 738
2.70 4978.70 1,055 95 832
3.00 4979.00 1,062 95 928
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 12.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4976.00 0.00 0.00 0.00
Length (ft)= 10.00 0.00 0.00 0.00
Slope (%)= 0.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 5.00 0.00 0.00 0.00
Crest El. (ft)= 4977.00 0.00 0.00 0.00
Weir Coeff.= 2.60 3.33 3.33 3.33
Weir Type = Broad --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.700 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00
Stage (ft)
0.00 4976.00
1.00 4977.00
2.00 4978.00
3.00 4979.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 5
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 1 - DA#2 Rain Garden Infiltration Gallery
Pond Data
Trapezoid -Bottom L x W = 22.0 x 22.0 ft, Side slope = 0.05:1, Bottom elev. = 4970.00 ft, Depth = 10.00 ft, Voids = 50.00%
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4970.00 484 0 01.00 4971.00 488 243 243
2.00 4972.00 493 245 488
3.00 4973.00 497 248 736
4.00 4974.00 502 250 986
5.00 4975.00 506 252 1,238
6.00 4976.00 511 254 1,492
7.00 4977.00 515 257 1,748
8.00 4978.00 520 259 2,007
9.00 4979.00 524 261 2,268
10.00 4980.00 529 263 2,532
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 12.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4970.00 0.00 0.00 0.00
Length (ft)= 10.00 0.00 0.00 0.00
Slope (%)= 0.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 5.00 0.00 0.00 0.00
Crest El. (ft)= 4978.50 0.00 0.00 0.00
Weir Coeff.= 3.33 3.33 3.33 3.33
Weir Type = Rect --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 3.900 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 3.00 6.00 9.00 12.00 15.00 18.00 21.00 24.00 27.00 30.00 33.00
Stage (ft)
0.00 4970.00
2.00 4972.00
4.00 4974.00
6.00 4976.00
8.00 4978.00
10.00 4980.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 13
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 4 - DA#3 Bioswale
Pond Data
Trapezoid -Bottom L x W = 170.0 x 5.0 ft, Side slope = 0.05:1, Bottom elev. = 4972.00 ft, Depth = 4.00 ft, Voids = 30.00%
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4972.00 850 0 00.40 4972.40 857 102 102
0.80 4972.80 864 103 206
1.20 4973.20 871 104 310
1.60 4973.60 878 105 415
2.00 4974.00 885 106 521
2.40 4974.40 892 107 627
2.80 4974.80 899 107 735
3.20 4975.20 906 108 843
3.60 4975.60 913 109 952
4.00 4976.00 920 110 1,062
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 24.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4972.00 0.00 0.00 0.00
Length (ft)= 20.00 0.00 0.00 0.00
Slope (%)= 0.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 0.00 0.00 0.00 0.00
Crest El. (ft)= 4973.00 0.00 0.00 0.00
Weir Coeff.= 1.05 3.33 3.33 3.33
Weir Type = 45 degV --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.700 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00
Stage (ft)
0.00 4972.00
1.00 4973.00
2.00 4974.00
3.00 4975.00
4.00 4976.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 14
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 5 - DA#3 Dry Well w/ Pipe Trench Gallery
Pond Data
Trapezoid -Bottom L x W = 32.0 x 8.0 ft, Side slope = 0.05:1, Bottom elev. = 4967.00 ft, Depth = 10.00 ft, Voids = 32.00%
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4967.00 256 0 01.00 4968.00 260 83 83
2.00 4969.00 264 84 166
3.00 4970.00 268 85 252
4.00 4971.00 272 86 338
5.00 4972.00 276 88 426
6.00 4973.00 280 89 515
7.00 4974.00 284 90 605
8.00 4975.00 289 92 697
9.00 4976.00 293 93 790
10.00 4977.00 297 94 884
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 12.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4967.00 0.00 0.00 0.00
Length (ft)= 20.00 0.00 0.00 0.00
Slope (%)= 0.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 0.00 0.00 0.00 0.00
Crest El. (ft)= 4974.00 0.00 0.00 0.00
Weir Coeff.= 1.05 3.33 3.33 3.33
Weir Type = 45 degV --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 3.900 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00
Stage (ft)
0.00 4967.00
2.00 4969.00
4.00 4971.00
6.00 4973.00
8.00 4975.00
10.00 4977.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 16
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 6 - DA#4 Rain Garden
Pond Data
Trapezoid -Bottom L x W = 57.0 x 1.0 ft, Side slope = 2.00:1, Bottom elev. = 4975.00 ft, Depth = 2.00 ft
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4975.00 57 0 0
0.20 4975.20 104 16 16
0.40 4975.40 152 26 42
0.60 4975.60 202 35 77
0.80 4975.80 253 45 123
1.00 4976.00 305 56 178
1.20 4976.20 358 66 245
1.40 4976.40 413 77 322
1.60 4976.60 469 88 410
1.80 4976.80 526 100 510
2.00 4977.00 585 111 621
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 12.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4975.00 0.00 0.00 0.00
Length (ft)= 10.00 0.00 0.00 0.00
Slope (%)= 1.00 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 5.00 0.00 0.00 0.00
Crest El. (ft)= 4976.50 0.00 0.00 0.00
Weir Coeff.= 3.33 3.33 3.33 3.33
Weir Type = Broad --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.700 (by Wet area)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Stage (ft)
0.00 4975.00
0.20 4975.20
0.40 4975.40
0.60 4975.60
0.80 4975.80
1.00 4976.00
1.20 4976.20
1.40 4976.40
1.60 4976.60
1.80 4976.80
2.00 4977.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 19
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 7 - DA#5 Rain Garden
Pond Data
Trapezoid -Bottom L x W = 55.0 x 3.0 ft, Side slope = 2.00:1, Bottom elev. = 4972.00 ft, Depth = 4.00 ft
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 4972.00 165 0 0
0.40 4972.40 260 85 85
0.80 4972.80 361 124 209
1.20 4973.20 466 165 374
1.60 4973.60 577 209 583
2.00 4974.00 693 254 837
2.40 4974.40 814 301 1,138
2.80 4974.80 940 351 1,489
3.20 4975.20 1,071 402 1,891
3.60 4975.60 1,208 456 2,346
4.00 4976.00 1,349 511 2,857
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 24.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 4972.00 0.00 0.00 0.00
Length (ft)= 10.00 0.00 0.00 0.00
Slope (%)= 1.00 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 10.00 0.00 0.00 0.00
Crest El. (ft)= 4974.00 0.00 0.00 0.00
Weir Coeff.= 3.33 3.33 3.33 3.33
Weir Type = Rect --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.700 (by Wet area)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.000 0.003 0.006 0.009 0.012 0.015 0.018 0.021 0.024 0.027 0.030
Stage (ft)
0.00 4972.00
1.00 4973.00
2.00 4974.00
3.00 4975.00
4.00 4976.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
Pond Report 26
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Pond No. 9 - DA#6 Depressional Areas
Pond Data
Trapezoid -Bottom L x W = 10.0 x 10.0 ft, Side slope = 4.00:1, Bottom elev. = 5975.00 ft, Depth = 2.00 ft
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 5975.00 100 0 0
0.20 5975.20 135 23 23
0.40 5975.40 174 31 54
0.60 5975.60 219 39 93
0.80 5975.80 269 49 142
1.00 5976.00 324 59 201
1.20 5976.20 384 71 272
1.40 5976.40 449 83 355
1.60 5976.60 520 97 452
1.80 5976.80 595 111 564
2.00 5977.00 676 127 691
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)Inactive 0.00 0.00 0.00
Span (in)= 12.00 0.00 0.00 0.00
No. Barrels = 1 000
Invert El. (ft)= 5975.00 0.00 0.00 0.00
Length (ft)= 10.00 0.00 0.00 0.00
Slope (%)= 0.50 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a NoNoNo
Crest Len (ft)= 10.00 0.00 0.00 0.00
Crest El. (ft)= 5976.50 0.00 0.00 0.00
Weir Coeff.= 2.60 3.33 3.33 3.33
Weir Type = Broad --- --- ---
Multi-Stage = No No No No
Exfil.(in/hr)= 0.700 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
Stage (ft)
0.00 5975.00
0.20 5975.20
0.40 5975.40
0.60 5975.60
0.80 5975.80
1.00 5976.00
1.20 5976.20
1.40 5976.40
1.60 5976.60
1.80 5976.80
2.00 5977.00
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
BOZEMAN COHOUSING
Stormwater Drainage Plan
STORAGE-DISCHARGE SUMMARY
Hydrograph Summary Report
27
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 SCS Runoff 0.153 1 146 652 ------ ------------ DA #2
2 Reservoir 0.000 1 150 0 1 4970.91 222 DA#2 Infil. Gallery
3 SCS Runoff 0.006 1 239 69 ------ ------------ DA#1
4 Reservoir 0.000 1 266 0 3 4976.09 26.7 DA#1 to Cobble Stream
5 SCS Runoff 0.047 1 152 286 ------ ------------ DA#5
6 SCS Runoff 0.028 1 154 259 ------ ------------ DA#3
7 SCS Runoff 0.009 1 154 83 ------ ------------ DA#4
8 Reservoir(i) 0.000 1 n/a 0 6 4973.00 122 DA#3 to bioswale/Dry
9 Reservoir 0.000 1 185 0 7 4975.48 54.9 DA#4 to Rain Garden
10 Combine 0.047 1 152 286 2, 4, 5,
8, 9
------------ <no description>
11 Reservoir 0.000 1 171 0 10 4972.83 221 Final Rain Garden
12 SCS Runoff 0.000 2 370 0 ------ ------------ EXISTING - E1
13 SCS Runoff 0.050 2 724 371 ------ ------------ EXISTING - E2
14 SCS Runoff 0.001 2 360 6 ------ ------------ DA#6
15 Reservoir 0.000 2 n/a 0 14 5975.05 6.26 DA#6 to Depressions
Cohousing_Final Calcs_03-04-21.gpw Return Period: 2 Year Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
STORAGEELEVATION2-YEAR PEAKDISCHARGE
Hydrograph Summary Report
43
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 SCS Runoff 0.238 1 146 981 ------ ------------ DA #2
2 Reservoir 0.000 1 140 0 1 4971.72 419 DA#2 Infil. Gallery
3 SCS Runoff 0.023 1 152 147 ------ ------------ DA#1
4 Reservoir 0.000 1 234 0 3 4976.17 50.1 DA#1 to Cobble Stream
5 SCS Runoff 0.105 1 151 524 ------ ------------ DA#5
6 SCS Runoff 0.092 1 152 522 ------ ------------ DA#3
7 SCS Runoff 0.030 1 152 168 ------ ------------ DA#4
8 Reservoir(i) 0.000 1 340 0 6 4973.85 332 DA#3 to bioswale/Dry
9 Reservoir 0.000 1 219 0 7 4975.80 122 DA#4 to Rain Garden
10 Combine 0.105 1 151 524 2, 4, 5,
8, 9
------------ <no description>
11 Reservoir 0.000 1 262 0 10 4973.31 430 Final Rain Garden
12 SCS Runoff 0.021 2 360 117 ------ ------------ EXISTING - E1
13 SCS Runoff 0.237 2 722 825 ------ ------------ EXISTING - E2
14 SCS Runoff 0.004 2 360 37 ------ ------------ DA#6
15 Reservoir 0.000 2 280 0 14 5975.21 25.5 DA#6 to Depressions
Cohousing_Final Calcs_03-04-21.gpw Return Period: 5 Year Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
STORAGEELEVATION5-YEAR PEAKDISCHARGE
Hydrograph Summary Report
59
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 SCS Runoff 0.297 1 146 1,210 ------ ------------ DA #2
2 Reservoir 0.000 1 529 0 1 4972.47 604 DA#2 Infil. Gallery
3 SCS Runoff 0.039 1 152 210 ------ ------------ DA#1
4 Reservoir 0.000 1 166 0 3 4976.23 69.4 DA#1 to Cobble Stream
5 SCS Runoff 0.149 1 151 704 ------ ------------ DA#5
6 SCS Runoff 0.142 1 152 727 ------ ------------ DA#3
7 SCS Runoff 0.046 1 152 234 ------ ------------ DA#4
8 Reservoir(i) 0.000 1 262 0 6 4973.91 405 DA#3 to bioswale/Dry
9 Reservoir 0.000 1 184 0 7 4975.99 177 DA#4 to Rain Garden
10 Combine 0.149 1 151 704 2, 4, 5,
8, 9
------------ <no description>
11 Reservoir 0.000 1 203 0 10 4973.61 592 Final Rain Garden
12 SCS Runoff 0.037 2 360 300 ------ ------------ EXISTING - E1
13 SCS Runoff 0.430 2 720 1,231 ------ ------------ EXISTING - E2
14 SCS Runoff 0.006 2 360 70 ------ ------------ DA#6
15 Reservoir 0.000 2 222 0 14 5975.36 48.4 DA#6 to Depressions
Cohousing_Final Calcs_03-04-21.gpw Return Period: 10 Year Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
STORAGEELEVATION10-YEAR PEAKDISCHARGE
Hydrograph Summary Report
75
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 SCS Runoff 0.381 1 145 1,536 ------ ------------ DA #2
2 Reservoir 0.000 1 647 0 1 4973.67 904 DA#2 Infil. Gallery
3 SCS Runoff 0.062 1 151 308 ------ ------------ DA#1
4 Reservoir 0.000 1 176 0 3 4976.36 108 DA#1 to Cobble Stream
5 SCS Runoff 0.216 1 147 975 ------ ------------ DA#5
6 SCS Runoff 0.219 1 151 1,045 ------ ------------ DA#3
7 SCS Runoff 0.070 1 151 336 ------ ------------ DA#4
8 Reservoir(i) 0.000 1 188 0 6 4973.97 624 DA#3 to bioswale/Dry
9 Reservoir 0.000 1 244 0 7 4976.25 264 DA#4 to Rain Garden
10 Combine 0.216 1 147 975 2, 4, 5,
8, 9
------------ <no description>
11 Reservoir 0.000 1 363 0 10 4974.00 838 Final Rain Garden
12 SCS Runoff 0.062 2 360 668 ------ ------------ EXISTING - E1
13 SCS Runoff 0.744 2 720 1,892 ------ ------------ EXISTING - E2
14 SCS Runoff 0.011 2 154 128 ------ ------------ DA#6
15 Reservoir 0.000 2 370 0 14 5975.60 94.6 DA#6 to Depressions
Cohousing_Final Calcs_03-04-21.gpw Return Period: 25 Year Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
STORAGEELEVATION25-YEAR PEAKDISCHARGE
Hydrograph Summary Report
91
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 SCS Runoff 0.503 1 145 2,014 ------ ------------ DA #2
2 Reservoir 0.000 1 130 0 1 4975.48 1,359 DA#2 Infil. Gallery
3 SCS Runoff 0.100 1 151 465 ------ ------------ DA#1
4 Reservoir 0.000 1 531 0 3 4976.81 247 DA#1 to Cobble Stream
5 SCS Runoff 0.325 1 146 1,397 ------ ------------ DA#5
6 SCS Runoff 0.343 1 147 1,550 ------ ------------ DA#3
7 SCS Runoff 0.110 1 147 499 ------ ------------ DA#4
8 Reservoir(i) 0.000 1 770 0 6 4974.50 1,040 DA#3 to bioswale/Dry
9 Reservoir 0.014 1 329 39 7 4976.51 369 DA#4 to Rain Garden
10 Combine 0.325 1 146 1,544 2, 4, 5,
8, 9
------------ <no description>
11 Reservoir 0.000 1 240 0 10 4974.67 1,370 Final Rain Garden
12 SCS Runoff 0.114 2 216 1,388 ------ ------------ EXISTING - E1
13 SCS Runoff 1.318 2 720 3,127 ------ ------------ EXISTING - E2
14 SCS Runoff 0.036 2 152 232 ------ ------------ DA#6
15 Reservoir 0.000 2 690 0 14 5975.94 183 DA#6 to Depressions
Cohousing_Final Calcs_03-04-21.gpw Return Period: 100 Year Monday, 03 / 8 / 2021
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
STORAGEELEVATION100-YEAR PEAKDISCHARGE
BOZEMAN COHOUSING
Stormwater Drainage Plan
25-YEAR
STORAGE-INFILTRATION ANALYSIS
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 4
DA#1 to Cobble Stream
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 176 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 3 - DA#1 Max. Elevation = 4976.36 ft
Reservoir name = DA#1 Cobble Stream Gallery Max. Storage = 108 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
79
0 60 120 180 240 300 360 420 480 540 600
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
DA#1 to Cobble Stream
Hyd. No. 4 -- 25 Year
Hyd No. 4 Hyd No. 3 Total storage used = 108 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 2
DA#2 Infil. Gallery
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 647 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 1 - DA #2 Max. Elevation = 4973.67 ft
Reservoir name = DA#2 Rain Garden Infiltration GalleryMax. Storage = 904 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
77
0 60 120 180 240 300 360 420 480 540 600 660 720 780 840
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
DA#2 Infil. Gallery
Hyd. No. 2 -- 25 Year
Hyd No. 2 Hyd No. 1 Total storage used = 904 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 8
DA#3 to bioswale/Dry
Hydrograph type = Reservoir (Interconnected) Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 188 min
Time interval = 1 min Hyd. volume = 0 cuft
Upper Pond Lower PondPond name = DA#3 Bioswale Pond name = DA#3 Dry Well w/ Pipe T
Inflow hyd. = 6 - DA#3 Other Inflow hyd. = None
Max. Elevation = 4973.97 ft Max. Elevation = 4970.36 ft
Max. Storage = 341 cuft Max. Storage = 283 cuft
Interconnected Pond Routing. Storage Indication method used. Exfiltration extracted from Outflow.
83
0 60 120 180 240 300 360 420 480 540 600 660 720
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
DA#3 to bioswale/Dry
Hyd. No. 8 -- 25 Year
Hyd No. 8 Hyd No. 6 Total storage used = 624 cuft
Outflow Pond 4
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 9
DA#4 to Rain Garden
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 244 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 7 - DA#4 Max. Elevation = 4976.25 ft
Reservoir name = DA#4 Rain Garden Max. Storage = 264 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
84
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
DA#4 to Rain Garden
Hyd. No. 9 -- 25 Year
Hyd No. 9 Hyd No. 7 Total storage used = 264 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 11
Final Rain Garden
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 363 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 10 - <no description> Max. Elevation = 4974.00 ft
Reservoir name = DA#5 Rain Garden Max. Storage = 838 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
86
0 240 480 720 960 1200 1440 1680 1920 2160 2400
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
Final Rain Garden
Hyd. No. 11 -- 25 Year
Hyd No. 11 Hyd No. 10 Total storage used = 838 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 15
DA#6 to Depressions
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 25 yrs Time to peak = 370 min
Time interval = 2 min Hyd. volume = 0 cuft
Inflow hyd. No. = 14 - DA#6 Max. Elevation = 5975.60 ft
Reservoir name = DA#6 Depressional Areas Max. Storage = 95 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
90
0 120 240 360 480 600 720 840 960
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
DA#6 to Depressions
Hyd. No. 15 -- 25 Year
Hyd No. 15 Hyd No. 14 Total storage used = 95 cuft
BOZEMAN COHOUSING
Stormwater Drainage Plan
100-YEAR
STORAGE-INFILTRATION ANALYSIS
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 4
DA#1 to Cobble Stream
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 100 yrs Time to peak = 531 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 3 - DA#1 Max. Elevation = 4976.81 ft
Reservoir name = DA#1 Cobble Stream Gallery Max. Storage = 247 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
95
0 60 120 180 240 300 360 420 480 540 600 660 720 780
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
DA#1 to Cobble Stream
Hyd. No. 4 -- 100 Year
Hyd No. 4 Hyd No. 3 Total storage used = 247 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 2
DA#2 Infil. Gallery
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 100 yrs Time to peak = 130 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 1 - DA #2 Max. Elevation = 4975.48 ft
Reservoir name = DA#2 Rain Garden Infiltration GalleryMax. Storage = 1,359 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
93
0 120 240 360 480 600 720 840 960 1080
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (min)
DA#2 Infil. Gallery
Hyd. No. 2 -- 100 Year
Hyd No. 2 Hyd No. 1 Total storage used = 1,359 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 8
DA#3 to bioswale/Dry
Hydrograph type = Reservoir (Interconnected) Peak discharge = 0.000 cfs
Storm frequency = 100 yrs Time to peak = 770 min
Time interval = 1 min Hyd. volume = 0 cuft
Upper Pond Lower PondPond name = DA#3 Bioswale Pond name = DA#3 Dry Well w/ Pipe T
Inflow hyd. = 6 - DA#3 Other Inflow hyd. = None
Max. Elevation = 4974.50 ft Max. Elevation = 4973.76 ft
Max. Storage = 456 cuft Max. Storage = 584 cuft
Interconnected Pond Routing. Storage Indication method used. Exfiltration extracted from Outflow.
99
0 120 240 360 480 600 720 840 960
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
DA#3 to bioswale/Dry
Hyd. No. 8 -- 100 Year
Hyd No. 8 Hyd No. 6 Total storage used = 1,040 cuft
Outflow Pond 4
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 9
DA#4 to Rain Garden
Hydrograph type = Reservoir Peak discharge = 0.014 cfs
Storm frequency = 100 yrs Time to peak = 329 min
Time interval = 1 min Hyd. volume = 39 cuft
Inflow hyd. No. = 7 - DA#4 Max. Elevation = 4976.51 ft
Reservoir name = DA#4 Rain Garden Max. Storage = 369 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
100
0 60 120 180 240 300 360 420
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
DA#4 to Rain Garden
Hyd. No. 9 -- 100 Year
Hyd No. 9 Hyd No. 7 Total storage used = 369 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 11
Final Rain Garden
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 100 yrs Time to peak = 240 min
Time interval = 1 min Hyd. volume = 0 cuft
Inflow hyd. No. = 10 - <no description> Max. Elevation = 4974.67 ft
Reservoir name = DA#5 Rain Garden Max. Storage = 1,370 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
102
0 300 600 900 1200 1500 1800 2100 2400 2700 3000
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
Final Rain Garden
Hyd. No. 11 -- 100 Year
Hyd No. 11 Hyd No. 10 Total storage used = 1,370 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020 Monday, 03 / 8 / 2021
Hyd. No. 15
DA#6 to Depressions
Hydrograph type = Reservoir Peak discharge = 0.000 cfs
Storm frequency = 100 yrs Time to peak = 690 min
Time interval = 2 min Hyd. volume = 0 cuft
Inflow hyd. No. = 14 - DA#6 Max. Elevation = 5975.94 ft
Reservoir name = DA#6 Depressional Areas Max. Storage = 183 cuft
Storage Indication method used. Exfiltration extracted from Outflow.
106
0 120 240 360 480 600 720 840 960 1080 1200 1320
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
DA#6 to Depressions
Hyd. No. 15 -- 100 Year
Hyd No. 15 Hyd No. 14 Total storage used = 183 cuft
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX E
STORMWATER PLAN SHEETS
WAGON WHEEL RD
WGMGROUPWWW.WGMGROUP.COMSTORMWATER COVER SHEET
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021S1.0PERMIT SET
WGMGROUPWWW.WGMGROUP.COMSTORMWATER PLAN
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021S1.1PERMIT SET·····
WGMGROUPWWW.WGMGROUP.COMSTORMWATER PLAN
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021S1.2PERMIT SET·········
WGMGROUPWWW.WGMGROUP.COMCOBBLE GALLERY DETAIL
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021S1.3PERMIT SET
WGMGROUPWWW.WGMGROUP.COMSTORMWATER MANAGEMENT DETAILS
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021S1.4PERMIT SET
WGMGROUPWWW.WGMGROUP.COMPLANTING DETAILS
BOZEMAN COHOUSING
BOZEMAN, MTMarch 4, 2021L1.4PERMIT SETPLOTTED:SAVED:3/4/213/4/21
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX F
LID CONCEPT SITE PLAN RENDERING
Bozeman CohousingConceptual Landscape PlanDecember 19, 20200 15 30 45’SCALE: 1” = 30’ @ 24x36”NORTH
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX G
HYDRAULIC CONVEYANCE ANALYSIS
BOZEMAN COHOUSING
Stormwater Drainage Plan
APPENDIX H
STORMWATER SYSTEM OPERATION AND MAINTENANCE
PLAN
1 BOZEMAN COHOUSING
Stormwater System Operation and Maintenance Plan
STORMWATER OPERATION &
MAINTENANCE PLAN
PURPOSE
Stormwater runoff is a significant source of water pollution in urbanizing areas. In addition,
increasing impervious area causes increased runoff flow rates and runoff volumes
discharged to receiving drainageways. The proposed stormwater facilities help mitigate
negative effects by providing treatment for pollutant removal as well as storage and
infiltration functions to help control release rates downstream.
Properly maintained stormwater facilities are effective at removing certain pollutants and
providing necessary management of stormwater volumes during larger storm events.
Improperly maintained facilities can increase the discharge of pollutants downstream,
increase the risk of flooding downstream, increase the instability of downstream channels,
and lead to aesthetic and nuisance problems.
Studies show that poor operation and maintenance is the leading cause of facility failure.
Poor maintenance of the stormwater facilities can also create unpleasant odors, nuisance
insects, and a generally unsightly, unkempt appearance. Failure can be caused by:
poor maintenance in relation to sediment and debris removal,
clogged inlets resulting from sediment accumulation or trash and debris,
inadequate access for routine maintenance activities.
Proper maintenance and knowing the functionality of the facilities and the importance of all
the system components reduces the chance of flooding and stormwater management
deficiencies.
STORMWATER SYSTEM OVERVIEW
The stormwater features used at this site are: catch basins, stormwater conveyance pipes,
cobble bed conveyance channels (ditches), culverts, rain gardens, drywell structures, and
underground stormwater infiltration facilities, and outflow control structures. In
combination with each other, the site’s stormwater facilities have the following general
objectives:
Efficient internal conveyance of stormwater runoff to final infiltration and treatment
facilities.
Treatment and infiltration of runoff to improve water quality.
Protection of the downstream (i.e. offsite) drainage system through reduction of
runoff peak flow rates and volumes via storage and infiltration.
Properly functioning stormwater features reduce flood damage risk, protect downstream
drainageways, and enhance water quality of discharges to receiving water bodies. The
stormwater facility owner must understand the importance of the designated onsite
2 BOZEMAN COHOUSING
Stormwater System Operation and Maintenance Plan
stormwater facilities and the obligation to assure their continued proper function. This
Stormwater System Operation and Maintenance Plan will provide the information needed
to operate a fully functional stormwater treatment facility on the property.
RESPOSIBILITY TO MAINTAIN
Designation of a responsible party is important to assure proper operation of your
stormwater detention and control features. In this instance it is a responsibility of the
property owner for the correct operation and proper maintenance of the facilities. The
City of Bozeman Public Works Department is not responsible for the maintenance of these
facilities or their structural components, including the water quality devices, flow control
structures, and outlet pipes. However, the City of Bozeman Public Works Department does
have the authority to inspect and review maintenance activities to ensure the viability of
your facilities.
RECOMMENDED MAINTENANCE
Each onsite stormwater facility will have unique requirements for maintenance activities
and intervals. The facility size, type and characteristics of the tributary area, and facility
location will all influence maintenance requirements. This section outlines suggested
maintenance activities, intervals, and procedures for the stormwater system. The site’s
maintenance program should be adjusted as necessary to keep the stormwater system
functioning properly.
Regular maintenance activities should focus on the care of upstream pre-treatment
facilities (i.e. catch basins and rain gardens) to protect the viability of larger
downstream treatment features. This maintenance includes seasonal removal of
any trash, debris, and sediment that accumulates within pipes, catch basins, curb
and gutters, drywells, and rain gardens. Excessive accumulations of trash, debris,
and sediment may cause clogging in the system and result in reduced lifespan of
infiltration facilities, overflow and flooding, and damage risk to nearby structures.
Inlet grates should remain free of obstructions to flow from debris. Clogged inlets
can lead to flooding risk and damage to onsite and offsite structures. Inlet grates are
particularly prone to clogging from leaf litter in the fall and from road sanding/de-
icing material in the spring.
Keeping underground infiltration facilities and drywells clear of accumulating
sediment and debris is critical for their proper function and lifespan. If the underlying
gravel pack and soils become clogged with fine sediments, the cobble galleries and
drywells will not function as designed and may require complete replacement.
Drywells should be inspected frequently and cleaned as necessary via hydraulic
vacuum truck.
Routine Maintenance (seasonally to bi-annually):
1) Inspections: Scheduled inspections with a specified checklist should be performed
during the year. Inspections after major rainfall events are also recommended to
check for obstructions or damage and to remove debris/trash. Example inspection
checklists are included as an attachment to this plan for reference purposes that
3 BOZEMAN COHOUSING
Stormwater System Operation and Maintenance Plan
can be customized to project specific infrastructure.
DO NOT ENTER confined spaces such as manholes and underground infiltration
facilities for inspections. These facilities should be inspected from the surface.
2) Vegetation Management: When mowing, collect grass clippings and all other
clippings/trimmings and take offsite for disposal or dispose in trash on site. Do not
leave clippings in an area that will clog catch basin inlet grates and French drains.
This includes removing clippings from roadside ditches that are throughout the
development. Removing clippings, leaf litter, and sediment from the cobble drainage
channels is necessary to sustain infiltration capabilities. Channel cobble should be
open to the surface and should never be covered with mulch or sod. Limit the use of
fertilizers and pesticides around channels and rain gardens to minimize entry into
subsequent downstream waters.
3) Trash, Debris and Litter Removal: Removal of any trash, etc. causing any
obstructions to the stormwater facilities during periodic inspections and especially
after every significant runoff event. In general, pick up trash, etc. in and around the
facilities during all inspections. Inspect all catch basins and drywell structures and
clean floating debris as necessary.
4) Parking Lot Sweeping: Each parking lot is recommended to be swept on an annual
basis in the spring to reduce the winter traction sands, de-icing materials, and
sediment that would otherwise be washed into the stormwater system during runoff
events. Sweeping via vacuum broom truck is the preferred alternative so that fine
sediments are fully removed from the site.
5) Structural Component Check: Perform structural inspection of catch basins,
drywells, inlets, grates, pipes, and culverts on a regular basis for potential additions
to the Non-routine Maintenance list.
Non-Routine Maintenance includes (annually to 5 years):
1) Sediment Removal: Accumulated sediment in the bottom of catch basins, drywells,
and rain gardens may need to be removed as frequently as once annually. Sediment
removal in the drywell should be performed at frequencies of approximately once
every three to five years, or as necessary, to ensure that sediment depth or debris
accumulation in the bottom at any location does not exceed twelve inches. Sediment
removal in the rain garden bioretention areas may be required every 3 to 5 years to
ensure that vegetation is not ‘smothered’ and underlying soils are not clogged with
fine sediments.
2) Structural Repair/Replacement: Eventually structural components may need to be
repaired or replaced to ensure proper function. Monitor metal structures for excessive
rust and corrosion. Monitor concrete structures for large cracking and/or spalling.
Repair and replace as necessary.
BOZEMAN COHOUSING
Stormwater System Operation and Maintenance Plan
EXAMPLE INSPECTION CHECKLISTS
Closed Detention & Infiltration Systems Date Inspected _________
(Tanks/Vaults/Drywells)
Drainage
System
Feature
Potential
Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is
Performed Or Not Needed
Plugged Air
Vents
One‐half of the cross section of a vent is
blocked at any point or the vent is
damaged.
Vents open and functioning.
Accumulated sediment depth exceeds 10%
of the diameter of the storage area for 1/2
length of storage vault or any point depth
exceeds 15% of diameter.
Debris and
Sediment (Example: 72‐inch storage tank would
require cleaning when sediment reaches
depth of seven inches for more than 1/2
length of tank).
Remove all sediment and debris from
storage area.
Any openings or voids allowing material to
be transported into facility. Joints Between
Tank/Pipe
Section (Will require engineering analysis to
determine structural stability).
Seal all joint between tank/pipe sections.
Tank Pipe Bent
Out of Shape
Any part of tank/pipe is bent out of shape
more than 10% of its design shape. (Review
required by engineer to determine
structural stability).
Repair tank/pipe or replace to design.
Cracks wider than 1/2‐inch and any
evidence of soil particles entering the
structure through the cracks, or
maintenance/inspection personnel
determines that the vault is not structurally
sound.
Replace vault or repair to design
specifications and is structurally sound.
Storage
Area
Vault Structure
Includes Cracks
in Wall,
Bottom,
Damage to
Frame and/or
Top Slab
Cracks wider than 1/2‐inch at the joint of
any inlet/outlet pipe or any evidence of soil
particles entering the vault through the
walls.
No cracks more than 1/4 inch wide at the
joint of the inlet/outlet pipe.
Cover Not in
Place
Cover is missing or only partially in place.
Any open manhole requires maintenance. Manhole is closed.
Locking
Mechanism Not
Working
Mechanism cannot be opened by one
maintenance person with proper tools.
Bolts into frame have less than 1/2 inch of
thread (may not apply to self‐locking lids).
Mechanism opens with proper tools.
Cover Difficult
to Remove
One maintenance person cannot remove
lid after applying normal lifting pressure.
Intent is to keep cover from sealing off
access to maintenance.
Cover can be removed and reinstalled by
one maintenance person.
Manhole
Ladder Rungs
Unsafe
Ladder is unsafe due to missing rungs,
misalignment, not securely attached to
structure wall, rust, or cracks.
Ladder meets design standards. Allows
maintenance person safe access.
General Trash and
Debris
Trash or debris which is located
immediately in front of the catch basin
opening or is blocking inletting capacity of
the basin by more than 10%.
No trash or debris located immediately in
front of catch basin or on grate opening.
Drainage
System
Feature
Potential
Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is
Performed Or Not Needed
Trash or debris (in the basin) that exceeds
60% of the sump depth as measured from
the bottom of basin to invert of the lowest
pipe into or out of the basin, but in no case
less than a minimum of six inches clearance
from the debris surface to the invert of the
lowest pipe.
No trash or debris in the catch basin.
Trash or debris in any inlet or outlet pipe
blocking more than 1/3 of its height.
Inlet and outlet pipes free of trash or
debris.
Trash and
Debris
Dead animals or vegetation that could
generate odors that could cause
complaints or dangerous gases (e.g.,
methane).
No dead animals or vegetation present
within the catch basin.
Sediment
Sediment (in the basin) that exceeds 60%
of the sump depth as measured from the
bottom of basin to invert of the lowest pipe
into or out of the basin, but in no case less
than a minimum of six inches of clearance
from the sediment surface to the invert of
the lowest pipe.
No sediment in the catch basin.
Top slab has holes larger than two square
inches or cracks wider than 1/4 inch (Intent
is to make sure no material is running into
basin).
Top slab is free of holes and cracks. Structure
Damage to
Frame and/or
Top Slab
Frame not sitting flush on top slab, i.e.,
separation of more than 3/4 inch of the
frame from the top slab. Frame not
securely attached.
Frame is sitting flush on the riser rings or
top slab and firmly attached.
Maintenance person judges that structure
is unsound.
Basin replaced or repaired to design
standards.
Fractures or
Cracks in Basin
Walls/ Bottom
Grout fillet has separated or cracked wider
than 1/2 inch and longer than one foot at
the joint of any inlet/outlet pipe or any
evidence of soil particles entering catch
basin through cracks.
Pipe is regrouted and secure at basin wall.
Settlement/
Misalignment
If failure of basin has created a safety,
function, or design problem.
Basin replaced or repaired to design
standards.
Vegetation growing across and blocking
more than 10% of the basin opening. No vegetation blocking opening to basin.
Vegetation Vegetation growing in inlet/outlet pipe
joints that is more than six inches tall and
less than six inches apart.
No vegetation or root growth present.
General
Contaminants
and Pollution
Any evidence of oil, gasoline, contaminants
or other pollutants (Coordinate
removal/cleanup with local water quality
response agency).
No contaminants or pollutants present.
Catch Basins Date Inspected_________
Drainage
System
Feature
Potential
Defect
Conditions When Maintenance Is
Needed
Results Expected When Maintenance Is
Performed Or Not Needed
Trash or debris which is located immediately
in front of the catch basin opening or is
blocking inletting capacity of the basin by
more than 10%.
No trash or debris located immediately in
front of catch basin or on grate opening.
Trash or debris (in the basin) that exceeds 60%
of the sump depth as measured from the
bottom of basin to invert of the lowest pipe
into or out of the basin, but in no case less
than a minimum of six inches clearance from
the debris surface to the invert of the lowest
pipe.
No trash or debris in the catch basin.
Trash or debris in any inlet or outlet pipe
blocking more than 1/3 of its height. Inlet and outlet pipes free of trash or debris.
Trash and Debris
Dead animals or vegetation that could
generate odors that could cause complaints or
dangerous gases (e.g., methane).
No dead animals or vegetation present within
the catch basin.
Sediment
Sediment (in the basin) that exceeds 60% of
the sump depth as measured from the bottom
of basin to invert of the lowest pipe into or out
of the basin, but in no case less than a
minimum of six inches of clearance from the
sediment surface to the invert of the lowest
pipe.
No sediment in the catch basin.
Top slab has holes larger than two square
inches or cracks wider than 1/4 inch
(Intent is to make sure no material is running
into basin).
Top slab is free of holes and cracks. Structure
Damage to
Frame and/or
Top Slab Frame not sitting flush on top slab, i.e.,
separation of more than 3/4 inch of the frame
from the top slab. Frame not securely
attached.
Frame is sitting flush on the riser rings or top
slab and firmly attached.
Maintenance person judges that structure is
unsound. Replace basin or repair to design standards.
Fractures or
Cracks in Basin
Walls/ Bottom
Grout fillet has separated or cracked wider
than 1/2 inch and longer than one foot at the
joint of any inlet/outlet pipe or any evidence
of soil particles entering catch basin through
cracks.
Regrout pipe and secure at basin wall.
Settlement/
Misalignment
If failure of basin has created a safety,
function, or design problem. Replace basin or repair to design standards.
Vegetation growing across and blocking more
than 10% of the basin opening. No vegetation blocking opening to basin.
Vegetation Vegetation growing in inlet/outlet pipe joints
that is more than six inches tall and less than
six inches apart.
No vegetation or root growth present.
General
Contaminants
and Pollution
Any evidence of oil, gasoline, contaminants or
other pollutants (Coordinate removal/cleanup
with local water quality response agency).
No contaminants or pollutants present.
Drainage
System
Feature
Potential
Defect
Conditions When Maintenance Is
Needed
Results Expected When Maintenance Is
Performed Or Not Needed
Cover Not in
Place
Cover is missing or only partially in place. Any
open catch basin requires maintenance. Catch basin cover is closed.
Locking
Mechanism Not
Working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts
into frame have less than 1/2 inch of thread.
Mechanism opens with proper tools. Catch
Basin
Cover
Cover Difficult to
Remove
One maintenance person cannot remove lid
after applying normal lifting pressure (Intent is
to keep cover from sealing off access to
maintenance).
Cover can be removed by one maintenance
person.
Ladder Ladder Rungs
Unsafe
Ladder is unsafe due to missing rungs, not
securely attached to basin wall, misalignment,
rust, cracks, or sharp edges.
Ladder meets design standards and allows
maintenance person safe access.
Grate Opening
Unsafe Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and Debris Trash and debris that is blocking more than
20% of grate surface inletting capacity. Grate free of trash and debris.
Metal
Grates (If
Applicable)
Damaged or
Missing
Grate missing or broken member(s) of the
grate. Grate is in place and meets design standards.
Conveyance Storm Pipe Date Inspected_________
Drainage
System
Feature
Potential
Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is
Performed Or Not Needed
Obstructions,
Including Roots Root enters or deforms pipe, reducing flow.
Use mechanical methods to remove root.
Do not put root‐dissolving chemicals in
storm sewer pipes. If necessary, remove
the vegetation over the line.
Pipe Dented or
Broken
Inlet/outlet piping damaged or broken and
in need of repair. Pipe repaired and/or replaced.
Pipe Rusted or
Deteriorated
Any part of the piping that is crushed or
deformed more than 20% or any other
failure to the piping.
Pipe repaired and/or replaced.
Sediment &
Debris
Sediment depth is greater than 20% of pipe
diameter.
Install upstream debris traps (where
applicable) then clean pipe and remove
material.
General
Debris barrier or
Trash Rack
Missing
Stormwater pipes > than 18 inches need
debris barrier.
Debris barrier present on all stormwater
pipes 18 inches and greater.