HomeMy WebLinkAbout16 - Design Report - Sacajawea Middle School - Storm .��
S A N D E R S 0 N t�i�
Sl-E WART
June 7,2016
Project No. 15074.01
STORM DRAINAGE PLAN
FOR
SACAJAWEA MIDDLE SCHOOL
BOZEMAN, MONTANA
OVERVIEW NARRATIVE
The purpose of this drainage plan is to quantify storm drainage improvements required for the
Sacajawea Middle School additions on COS 482, Section 24, Township 2 South, Range 05 East, in
Bozeman,Montana.The property will include five additions totaling 43,258 square-feet of additional
school building. As a result of the expansions, surrounding sidewalk, parking lot, basketball courts,
and courtyard areas will be altered or replaced. The proposed drainage plan consists of existing and
proposed detention basins and dry wells to manage and mitigate stormwater on site. The proposed
stormwater system will utilize the existing discharge pipe that connects into Cambridge Drive which
ultimately outfalls to Middle Creek Ditch. This report presents a summary of calculations performed
to quantify the stormwater runoff for the improved site. All design criteria and calculations are in
accordance with The City of Bozeman Design Standards and Speccations Policy, dated March 2004. The
site stormwater improvements have been designed with the intent to meet the current City of
Bozeman drainage regulations for the entire site to the extent feasible.
Specific site information and criteria are described below:
I. Project Information
A. Address: The physical address for the site is 3525 S 3rd Ave,Bozeman,MT 59715
B. Legal Description: The site is located on COS 482, Section 24,Township 2 South,
Range 5 East.
C. Total Area: The area of the site is approximately 28.55 acres after right-of-way
dedications.
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D. Existing Impervious Area:
Impervious Area—6.18 acres
Pervious Area— 22.37 acres
E. Post-Development Impervious Area: As a result of the expanded development,
the site will exhibit the following qualities:
Impervious Area— 8.18 acres
Pervious Area— 20.37 acres
F. Type of Development: The development will be several separate additions to the
existing middle school with updates to parking areas, courtyard areas, sidewalks, and
basketball courts.
II.
A. General Design
1. The off-site discharge point will be to an existing 8-inch PVC pipe north of
the site that currently acts as the discharge point for the existing site. The
discharge pipe from the site connects into the existing stormwater
infrastructure system within Cambridge Drive. The on-site storm drain
system will utilize the new south stormwater detention pond, existing north
detention pond, and three new and three existing dry wells. The system will
limit discharge to the capacity of the existing outfall pipe rate of 0.47 cfs.
2. The stormwater storage facilities are designed to remove pollutants such as
solids, silts, oils, and greases. There is no oil/water separator required on site.
The stormwater infrastructure system will also include pretreatment
practices, such as inlet sumps and vegetated filter strips.
3. Storm Sewers:
a. Alignment between manholes is straight.
b. Storm sewer systems are designed with a slope and pipe diameter as
to ensure a velocity of 3-fps.
C. Pond inlets and outlets will be protected with riprap to prevent
erosion as shown on the Grading Plan.
d. The storm sewers are not public and will be maintained by the
school.
e. The stormwater conveyance system on site is designed to convey the
25-year storm event.
£ All inlets and manholes have a 9-inch sump for sediment collection
as shown on the Grading Plan.
4. The redevelopment project is greater than one acre and therefore will
infiltrate runoff generated from the first 0.5-inches of rainfall from a 24-hour f
i
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storm. The first 0.5-inches of rainfall from a 24-hour storm will be referred
to as the water quality storm. Table 1 below, displays the major watershed
characteristics along with the water quality volume. There are several
watersheds (4,5,8,9,10) that are untouched during this redevelopment and are
hydrologically separated from the redevelopment portion of the site.
Therefore the drainage plan for those watersheds were left as is.
B. Storm Drainage Plan
1. See the attached Figure 1 that shows the watershed delineation and area See
grading plan in attached plan set for the complete drainage plan.
2. The ultimate destination of the stormwater runoff is the Middle Creek Ditch,
west of the middle school. This is the current outfall for the stormwater
runoff from the middle school site. All runoff from the middle school site
eventually drains to the north pond where the existing outfall pipe connects
to the stormwater infrastructure system within Cambridge Drive, The
stormwater is conveyed west down Cambridge Drive and is discharged to the
Middle Creek Ditch. The proposed stormwater system on site is designed to
limit discharge to the existing discharge conditions. Since the proposed
system is designed to match existing conditions it is not expected that there
will be an increased negative impact on downstream drainage facilities or
water quality.
3. A summary of the results of the drainage calculations are provided below and
the detailed calculations are included in Appendix A.
A maintenance plan for the detention basins, dry wells, swale, and
stormwater infrastructure system has been attached in Appendix B
Table 1:Watershed Characteristics,Runoff Volumes,and Storage Volumes
i i 10-Yr,24-
j Water HR Provided Storage
Total Area !Impervious Area!Pervious Area: Quality '
Watershed! Status i (SF) (SF) i (SF) ; Detention Unit Volume i-_
Runof
Volume _---•-•------- --------- ------
C.F. Primary Secondary
;
C.F.
Storage C.F. Storage
1 New ! 319,213 i 135,523 183,690 _ Ex.North Pond 5,747 i 20,031 28,049
-- — --�-- -- ----- ----i- ---- - i South Pond --} 1,214 4,152-i-- 4,642
----?----__..__.New_ 63,504 i 28,853 34,651 _.-- .._. .................
.. . ....................i....__.___......__._.....,............._.__..._._..:...._...____._....._..__.._....,..___.._......fi.__.......____
_3..---._;.._.-New ` -34,369 i 34.369 ? _0.._.__....:Courtyard Dry Well... .._.... 3,904 ` __.... .North.Pond....
..._... . --•---
.4 i Existing ! 22,011 i 22,011 0 N Ex Dry Well ::.._. ' ....-._-.
..... .... .............. .-.........._.......... _..........._.. ......_.... ...r..
_5.._. i.......... 33,937 0 -Ex Dry Well a _ .....__ .._._ _._.._.
.... - _ ----... ....__ ....NEExisting :
6 New ! _36,042 36,042 _r.... _0 ;-SW_New Dry Well 1,427 4,094 480 North Pond
_..........................• -_.......;_
7J New i-•_•-12,868 i 12,1 0 W_New Dry Well i 509 _1,461 480 North Pond
i._.._... ........ ...................• ... _... +._ .._.. . ........._ ..... ••...............
__.....
8 Existing _60,580 i 17,723 -r...._42.857_.._..?_...NE:SheetFlow J -- --
.................i.._...._._......... ..... .................... ._....»_._..
9 -Existing- ! 74,720 _.......34,953........;_.....39,767..... SE- Dry Well... - _.. ..
._a..
Existing 1 7 ! Field Sheet Flow 1 -- i -
10 g i 587,191 0 58 ,191
4. See grading and detail plan within the plan set for details and specifications
for all storm drainage improvements.
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C. Storage/Treatment Facilities
1. The detention basins on site, one existing and two proposed, utilize locations
that make the most sense for a detention basin. The existing north detention
basin will be expanded and will have an additional detention basin connected
to it in order to utilize a manmade depression to manage the increase in
stormwater runoff. The proposed detention basin south of the school was
strategically chosen to be placed at a low point and located away from the
building and recreation areas.
2. The existing detention basin on site is proposed to be expanded in order to
manage the increase stormwater runoff from the increase of impervious area
on site. This will involve constructing a new detention basin just west of the
existing pond. The two detention ponds will be connected with a 12-inch
pipe laid flat. With the expansion and addition, the north det tion basin will
be able to detain the stormwater runoff volume from is contributing
watersheds for the 10-year, 24-hour storm event, howe er, the existing
detention portion of the pond will not be regraded o meet current
stormwater standards of providing a basin with only 2. et of basin depth
and 1.5-feet of storm water depth and will be fenced. The addition to the
north basin will be constructed to detain water up to 1.5' deep during the 10-
yr storm event. The proposed south detention basin will also be designed to
detain the runoff volume from its contributing watersheds for the 10-year,
24-hour storm event. The basin will only detain storm water up to 1.5-feet
deep during the 10-yr event. The ponds will be fenced if designed with berms
higher than 2.5'high.
The dry wells on site are designed to infiltrate water from the roof drains.
The dry wells do not have the capacity to infiltrate the water quality volume
or detain the entire 10-year, 24, hour storm event. The soils found in the
attached geotechnical report are found to be a mix of sandy gravel and clay
gravel reflecting an infiltration rate of 3.42 inches/hour. Even though this
infiltration rate does not provide adequate treatment and retainage of the
storm water therefore, the dry wells are connected to the infiltration ponds in
the event of overflow. The existing drywells on site have also performed
adequately in the past and there has been no previous issues with the existing
drywells under preforming or instigating on site flooding. All of the new dry
wells are connected to the existing north pond in the event of overflow. The
existing north pond is designed with enough capacity to manage the overflow
from the drywells.
3. Both detention basins are located on Sacajawea Middle School property.
4. Basin Characteristics
I
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l
a. The proposed detention basin lengths are not designed to be three
times the width. The existing detention basin will not be significantly
regraded and the shape will not be altered to meet current
regulations. Inlet velocities to the basins will be dissipated with
rip-rap.
b. The proposed basin side slopes are designed to have a 4:1 side slope.
The existing basin was designed with a minimum of 6:1 side slopes
and will not be regraded to anything steeper than 4:1.
C. In addition to the new storm drain piping that will be constructed
along the westerly portion of the site in order to convey storm water
to the north detention basin and into the existing discharge, a Swale is
proposed to be located west of the building and east of the sports
fields. These swales provide overflow routing to the ponds during
larger storm events without flooding the building. This channel will
help capture any wastewater contaminants before stormwater is
discharged into the Middle Creek Ditch. There are also several
locations where stormwater sheet flows over vegetation before
reaching an inlet or basin. This will aid in the removal of wastewater
contaminants.
d. The detention basins on site are not located in a floodplain.
e. Both the existing and proposed basins have an overflow path in the
event of an overflow. The overflow from the ponds will discharge
overland to the north parking lot of the facility and out to Cambridge
Drive.
5. See Table 1 above and Appendix A for detailed calculations on retention
volumes.
D. Discharge Structure
1. The discharge structure in the existing north pond will not be updated as part
of this redevelopment. The discharge structure on the proposed south pond
will be installed as a flared end section with a trash rack as displayed in The
City of Bozeman Standard Modification Storm Drain Debris Rack
No.02720-11.
2. The detention basins are designed to detain the 10-year, 24-hour design
storm with no discharge, therefore the outlet structure will not provide an
orifice or weir to control discharge to pre-development rate. The flow rate
leaving the site is controlled by the existing pond north of the site.
3. Water Surface Elevation
a. The discharge acts as an overflow for rates exceeding design storm
events. An overflow weir at the top of the pond will be utilized to
discharge excess runoff in the event of overflow.
b. The discharge pipe is a minimum of 6 inches in diameter.
V'15074.01_SacajaweabfiddleSchool_StormReport 5 (03/29/16)SN/hg
C. The bottom elevations of the existing north pond are constricted by
the downstream inverts set for the site due to the connection into
Cambridge Drive. The proposed south pond, upstream from the
existing north pond does not have the grade to allow water to fully
discharge. There is some infiltration onsite and water in the pond will
infiltrate and evaporate over time.
E. Runoff Estimation
1. The modified rational method was used to determine peak runoff rates.
a. It was assumed the rainfall is uniformly distributed over the area for
the entire duration of the storm. The rational formula provided in The
City of Bozeman Standard Specifications and Policy was used to calculate
the peak runoff rates on site. The rainfall intensity for the site was
calculated in part by using Figure I-2 and I-3.
b. The peak runoff rate occurs when the duration of the storm equals
the time of concentration. The provided time of concentration tools,
Table I-2, Table I-3 and Figure I-1, in The City of BaZeman's Design
Standard and Specifications Policy were used to calculate the time of
concentration for each of the major watersheds.
C. The runoff coefficient for a particular watershed is constant for a
similar land use. The runoff coefficients provided in Table I-1 were
used in calculating the peak runoff rates.
2. As mentioned above, runoff coefficients from Table I-1 were used to
calculate runoff rates for each of the watersheds.
3. As mentioned above, time of concentration was determined, as outlined in
The City of Bo,-pman Design Standards and Specification Policy, as a function of the
ground slope, roughness, and hydraulic radius. The time of concentration
included durations from sheet flow, shallow concentrated flow and channel
flow.
F. Conveyance Facilities
All proposed drainage facilities have been designed to accommodate the 25-yr storm
event. Please see sizing calculations included in the Appendix of this report for
additional information.
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SACAJAWEA MIDDLE SCHOOL
STORM DRAINAGE PLAN
BOZEMAN, MONTANA
CERTIFICATION
I hereby state that this Storm Drainage Plan has been prepared by xne or under my supervision and
meets the standard of care and expertise which is usual and custoinaty in this community of
professional engineers.The analysis has been prepared utilizing procedures and practices specified by
the City of Bozeman and within the standard accepted practices.
NT, N.
WAFTER R.
SN11TR '
�; No. ` y�IJ 2
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• E S��O~C
�CNA�
Walter Smith,P.E. Date
❑ -7
C11 [�-11f1C�� (Q)�'i
Sacajawea Middle School Expansion
Bozeman, Montana
February 18, 2016
Terracon Project No. AJ165001
ECG-G p a c e d fix.:
Bozeman Public Schools
Facilities Division
Bozeman, Montana
JJAMES G
PIE
U ,
/7 /
v
Terracon Consultants, Inc.
Bozeman, Montana
Employee-OwnedOffices Nationwide Established in 1965
terracon.com Irerracon I'
EnvironmentalGeoteclinical
February 18, 2016
Irerracon
Bozeman Public Schools, Facilities Division
404 West Main Street
Bozeman, Montana 59771-0520
Attn: Todd Swinehart, P.E.
Phone: 406-522-6009
Email: todd.swinehart@bsd7.org
Re: Geotechnical Engineering Report
Sacajawea Middle School Expansion
Bozeman, Montana
Terracon Project Number: AJ165001
Dear Mr. Swinehart:
Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for
the above referenced project. This study was performed in general accordance with our proposal
number PAJ150019 dated December 30, 2015. This report presents the findings of the
subsurface exploration and provides geotechnical recommendations concerning earthwork and
the design and construction of foundations and pavement for the proposed project.
We appreciate the opportunity to be of service to you on this project. If you have any questions
concerning this report, or if we may be of further service, please contact us.
Sincerely,
Terracon Consultants, Inc.
o
Jim Pierce, P.E. Brent Wilkins, P.E.
Geotechnical Engineer Department Manager/Geotechnical Engineer
Terracon Consultants, Inc. 212 Zoot Way, Suite B Bozeman, Montana 59718
P [406] 586-2687 F [406] 587 9170 terracon.com
TABLE OF CONTENTS
Page
EXECUTIVESUMMARY ............................................................................................................. i
1.0 INTRODUCTION ............................................................................................................. 1
2.0 PROJECT INFORMATION ............................................................................................. 1
2.1 Project Description ...............................................................................................1
2.2 Site Location and Description ..............................................................................2
3.0 SUBSURFACE CONDITION...........................................................................................2
3.1 Geologic Setting and Seismicity ...........................................................................2
3.2 Soil Conditions ..................................................................................................... 3
3.3 Soil Properties ..................................................................................................... 3
3.4 Groundwater ........................................................................................................ 3
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................4
4.1 Geotechnical Considerations ...............................................................................4
4.2 General Earthwork ...............................................................................................5
4.2.1 Material Requirements ............................................................................. 5
4.2.2 Compaction Requirements .......................................................................6
4.2.3 Trench Backfill .......................................................................................... 7
4.2.4 Surface Grading and Drainage .................................................................7
4.2.5 Construction Considerations.....................................................................7
4.3 New Building Addition Foundations ......................................................................8
4.3.1 Design Recommendations ....................................................................... 8
4.3.2 Foundation Drainage ................................................................................9
4.3.3 Construction Considerations — Foundation Preparation ..........................10
4.3.4 Seismic Considerations ..........................................................................11
4.4 Floor Slabs........................................................................................................... 11
4.4.1 Design Recommendations .................................................................... 11
4.4.2 Construction Considerations.................................................................. 12
4.5 Pavement ...........................................................................................................12
4.5.1 Flexible Pavement Design Recommendations .......................................12
4.5.2 Rigid Pavement Design Recommendations............................................14
4.5.3 Pavement Drainage................................................................................ 14
5.0 GENERAL COMMENTS ................................................................................................15
APPENDIX A— FIELD EXPLORATION
Exhibit A-1 Field Exploration Description
Exhibit A-2 Vicinity Map
Exhibit A-3 Boring Location Diagram
Exhibits A-4 to A-11 Boring Logs
APPENDIX B —SUPPORTING INFORMATION
Exhibit B-1 Laboratory Testing Description
Exhibit B-2 Grain Size Distribution
Exhibit B-3 Atterberg Limits
Exhibit B-4 Unconfined Compression Testing
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TABLE OF CONTENTS (CONTINUED)
Exhibit B-5 Swell/Consolidation Testing
APPENDIX C —SUPPORTING DOCUMENTS
Exhibit C-1 General Notes
Exhibit C-2 Unified Soil Classification System
Exhibit C-3 Pavement Material Specifications
Exhibit C-4 Foundation Underdrainage Detail
Exhibit C-5 Reinforced Soil Foundation (RSF) Detail
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Geotechnical Engineering ..eport Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No. AJ165001
EXECUTIVE SUMMARY
A geotechnical investigation has been performed for the proposed expansion of the Sacajawea
Middle School located at 3525 South 31 Avenue in Bozeman, Montana. Eight (8) borings,
designated B-1 through B-4, and B-6 through B-9 were drilled to depths of approximately 6.5 to 16.5
feet below the existing grades at the project site.
Based on the information obtained from our subsurface exploration, the site can be developed for
the proposed expansion project consistent with the recommendations provided in this report which
include necessary construction involvement by our engineer to ascertain foundation conditions and
preparation at the immediate foundation subgrades. The following geotechnical considerations were
identified:
® The subsurface investigation indicates that the subsoils at the site consist of lean clay
overlying clayey to poorly-graded gravel.
® The undisturbed clays underlying the site are compressible.
® For the building, conventional shallow spread and wall foundations constructed on
Structural Fill placed directly on the lean clay, or directly on native gravel are expected to
result in performance consistent with project criteria.
o The native lean clay is a fair subgrade for the proposed pavements. Proper subgrade
preparation is essential in providing the desired pavement section support. Some
movement and cracking of the new pavement section is anticipated due to the moderately
plastic clay soil subgrade.
a Earthwork on the project should be observed and evaluated by Terracon. The evaluation
of earthwork should include observation and testing of engineered fill, subgrade
preparation, foundation bearing soils, and other geotechnical elements involved with
construction of the project.
This summary should be used in conjunction with the entire report for design purposes. It should
be recognized that details were not included or fully developed in this section, and the report must
be read in its entirety for a comprehensive understanding of the items contained herein. The section
titled GENERAL COMMENTS should be read for an understanding of the report limitations.
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GEOTECHNICAL ENGINEERING REPORT
SACAJAWEA MIDDLE SCHOOL EXPANSION
BOZEMAN, MONTANA
Terracon Project No. AJ165001
February 18, 2016
1.0 INTRODUCTION
A geotechnical investigation has been performed for the proposed new classroom additions located
at the existing middle school at 3525 South 3rd Avenue in Bozeman, Montana. Eight (8) borings,
designated B-1 through B-4 and B-6 through B-9 were drilled to depths of approximately 6.5 to 16.5
feet below existing grades. Six of these were in the proposed addition areas and two in proposed
pavement areas. Logs of the borings along with a boring location diagram are included in Appendix
A of this report.
The purpose of these services is to provide information and geotechnical engineering
recommendations relative to:
® Soil and groundwater conditions
■ Site and subgrade preparation
■ Foundation type(s) and design parameters
■ Estimated performance of foundations
w Seismic site classification
■ General earthwork and drainage requirements
■ Pavement thickness design
2.0 PROJECT INFORMATION
2.1 Project Description
ITEM DESCRIPTION
Site Layout See Exhibit A-3 in Appendix A, the Boring Location Diagram
The project consists of construction of six (6) new classroom
Structures additions and a new access roadway for the south parking lot onto
3rd Avenue South.
The new classroom additions are anticipated to add approximately
Building Construction 40,000 square feet to the school. The additions are planned to be
single story, masonry construction with crawl space and spread
footing foundations.
Finished Floor Elevation (FFE)7 Assumed to be the same as the existing school
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Geotechnical Engineering .report Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 n Terracon Project No.AJ165001
ITEM DESCRIPTION
Maximum Loads (provided by Building—70 kips columns
Structural Engineer) 3.3 to 4.2 klf walls
Required grading will include matching new finish floor elevation
Grading to existing finished floor elevation and the new south parking lot
access roadway to 3rd Avenue South at the right of way.
Cut and Fill Slopes Based on observations at the site during drilling, minimal cut and
fill slopes are anticipated for the project.
Free-standing Retaining Walls None anticipated.
Below Grade Areas None anticipated.
2.2 Site Location and Description
ITEM DESCRIPTION
The project is located at 3525 3rd Avenue South in Bozeman,
Location Montana, between Cambridge and Dartmouth Drives, on the west
side of 3rd Avenue South.
Existing improvements The site is currently an existing middle school.
Current ground cover Existing building and asphalt-surfaced access roadways and
parking areas and turf-grassed areas.
Existing topography Relatively flat to gently rolling.
3.0 SUBSURFACE CONDITIONS
3.1 Geologic Setting and Seismicity
The project site is located just southeast of the MSU campus in Bozeman, Montana, an area of
Gallatin County which is on the fringe of a broad valley floor lying beneath the surrounding mountains
of the Gallatin Range. The surficial geology in the project vicinity is comprised of a veneer of
Quaternary alluvium that has been eroded from the surrounding foothills and mountains. In the near-
surface environment, these sediments typically include a shallow, fine-grained layer of clay/silt
overlying sand and gravel.
Bozeman is located in the Intermountain Seismic Belt and is considered to be a seismically active
area. The site is believed to have a deep profile (100+feet) of generally dense material.
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Geotechnical Engineering Report Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
3.2 Soil Conditions
Based on materials encountered in the borings, beneath existing topsoil, the subsurface profile
consists of very soft to very stiff lean clay overlying medium dense to very dense, clayey gravel
to poorly-graded gravel with sand and clay.
Standard Penetration Test (SPT) N-values in the clay soil ranged from 1 to 18 blows per foot
(bpf), averaging 7 bpf and becoming softer below depths of about 5 to 7 feet. The clay was brown
to black in color with some scattered gravels. Laboratory testing information for this soil is
presented below in Section 3.3.
Very loose to very dense clayey gravel and poorly graded gravel with sand and clay were
encountered in the borings in the building area. N-values in the gravel were on the order of 16 to
more than 100 bpf, averaging 42 bfp, indicating generally high shear strength. The gravel was
dark brown, sub-angular, and had maximum-sized sampled particles of 1 to 1 '/2 inches, though
cobbles and boulders at depth are typical of this formation in the Bozeman area.
Conditions encountered at each boring location are indicated on the individual logs found in
Appendix A of this report. Stratification boundaries on the logs represent the approximate location
of changes in soil materials; in situ, the transition between materials may be gradual.
3.3 Soil Properties
Atterberg Limits test results for the clay soil samples tested are shown in the following table. The
clays ranged from low to moderate plasticity with Liquid Limits ranging from 35 to 49 percent.
Location Depth, ft Material Liquid Limit (%) Plastic Limit (%) Plasticity Index(%)
Boring B-1 5.0 CL 49 25 24
Boring B-3 7.5 CL 40 19 21
Boring B-4 7.5 CL 35 20 15
Boring B-8 5.0 CL 42 19 21
Dry unit weights of the lean clay were measured and ranged from 99 to 105 pounds per cubic foot.
These test results are also shown on the boring logs.
3.4 Groundwater
The borings were observed while drilling and after completion for the presence and level of
groundwater. Groundwater was observed in 3 of the 8 borings at depths of 6.0 to 13.0 feet below
ground surface at the time of the field exploration program. Due to the low permeability of the clayey
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Geotechnical Engineering .report Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
materials encountered, a relatively long period of time may be needed for any groundwater level to
stabilize.
Groundwater level fluctuations occur due to existing drainage systems, seasonal variations in the
amount of rainfall, runoff and other factors not evident at the time the borings were performed.
Therefore, groundwater levels during construction or at other times in the life of the structure may be
higher or lower than the levels indicated on the logs. The possibility of groundwater level fluctuations
should be considered when developing the design and construction plans for the project.
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION
4.1 Geotechnical Considerations
The geotechnical issue of most concern for the classroom addition foundations is settlement.
Since this project includes the construction of several classroom additions, differential settlement
within the new construction and between the new and the original construction both are of primary
concern. Since groundwater was encountered as shallow as 6 feet below ground surface in the
borings, and the native lean clay's shear strength decreases with increase in moisture content,
groundwater is also a concern.
The school's original foundation construction detail drawings, provided us by the structural
engineer, indicate that the exterior and interior footings were originally constructed on Structural
Fill pads up to 3 feet in thickness placed on native clay or gravel soils. Recent discussions with
school district personnel indicated that there has not been any problems with the original
foundations. At a project coordination meeting on February 9,2016, the project structural engineer
indicated that the current design plan was to not impose any of the new addition loads onto any
of the existing foundations. A consensus was also reached at the meeting to include a shallow
foundation design for the classroom additions similar to what was used in the original construction.
To not impose any new loads on the existing foundations it will be necessary to not construct
above or adjacent to the existing footings or Structural Fill below the footings.
Wall Footings
The lean clay underlying the site topsoil is an acceptable foundation subgrade for the proposed
building additions provided the shallow foundations are constructed on Structural Fill bearing on
undisturbed native clay or directly on undisturbed native gravel. The lean clay is compressible,
with low shear strength, particularly below a depth of approximately 7 feet in the addition areas.
Therefore, placing Structural Fill on the foundation subgrade above this 7 foot depth is necessary
to provide acceptable bearing and mitigate both total and differential settlement. The depth below
ground surface to lean clay that is an unsuitable foundation subgrade is expected to fluctuate
throughout the year with changing groundwater levels. For this reason we recommend raising the
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Geotechnical Engineering Report Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
elevation of exterior wall footings from a conventional depth of 4 feet below ground surface, which
provides frost protection for the foundation subgrade, to 2.5 feet below ground surface, and
placing a minimum of 1.5 feet of non-frost susceptible Structural Fill below the footings to maintain
adequate frost protection for the foundation. The lean clay has low to moderate expansive
potential.
Column Footings — Reinforced Soil Foundations (RSFs)
To further mitigate settlements beneath the more heavily loaded column footings, we recommend
incorporating geogrid reinforcement into the Structural Fill layers constructed on the native lean
clay. This combination of Structural Fill and geogrids is referred to as a Reinforced Soil
Foundation, or RSF. Exhibit C-5 in Appendix C details the RSF requirements.
Gymnasium Foundations
In the area of the gymnasium, native clayey gravel was encountered at a depth of 2.0 to 2.2 feet
below ground surface in the borings. In this area, the undisturbed native gravel is an acceptable
shallow foundation subgrade that doesn't require the placement of Structural Fill prior to
foundation construction.
To reduce differential settlement, we recommend placing all footings in each addition on the same
type of subgrade soil that is either on Structural Fill placed on native lean clay or directly on native
gravel.
The above recommendations and Section 4.3 are based on the assumption that an earthwork
solution to improve the immediate subgrade for building support is desired. There are alternate
replacement/remediation techniques such as rammed aggregate piers and deep foundation
methods that could be considered.
4.2 General Earthwork
Earthwork on the project should be observed and evaluated by Terracon. Contractor methods
and equipment can make substantial differences in the success of earthwork and excavation
operations; the recommendations have been developed based on the investigation findings and
what is believed to be standard construction practices and capabilities in the area. The evaluation
of earthwork should include observation and testing of engineered fill,foundation preparation, and
other geotechnical conditions exposed during the construction of the project.
4.2.1 Material Requirements
Structural Fill will be necessary for foundation preparation, replacement of unsuitable soils and
the Reinforced Soil Foundations (RSFs) and should be specially selected to satisfy the
requirements of this section and Section 4.2.2. Gradation requirements are noted in the table
below. The material suitability should be evaluated by the geotechnical engineer prior to use.
Reliable ■ Responsive s Resourceful 5
Geotechnical Engineering .,�eport Irerracon
Sacajawea Middle School Expansion n Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
Engineered fill that is to be placed and compacted for engineering purposes should meet the
following property requirements for each material designation:
Fill Type USCS Classification Acceptable Location for Placement
Structural Fill ',z GP, GWBelow footings for foundation preparation
(and dual symbols)
On-site clay soils3 CL Trench backfill.
Structural Fill should consist of approved materials that are free of organic matter and debris, and do not
include soft, degradable, or deleterious particles. Frozen material should not be used, and fill should not
be placed on a frozen subgrade. Each proposed fill material type should be sampled and evaluated by the
geotechnical engineer prior to its delivery and/or use.
1. Structural Fill should meet the criteria outlined below:
Percent finer by weight
Gradation (ASTM C136)
3-inch............................................................................................................................................ 100
No. 4 Sieve................................................................................................................................30-75
No. 200 Sieve.......................................................................................................................10 (max)
LiquidLimit...........................................................................................................................25 (max)
PlasticityIndex.......................................................................................................................6 (max)
2. Structural Fill for non-frost susceptible (NFS) use should have a maximum percent passing the No.
200 sieve of 5 percent.
3. Significant moisture conditioning of the native clay soils will be necessary for proper compaction; this
will require mechanical reduction in clump size (disking, etc.) to a maximum 1-inch dimension to
facilitate moisture conditioning; the necessary moisture adjustment will be difficult during wet/cold
seasons.
4.2.2 Compaction Requirements
Item Description
8 inches or less in loose thickness when heavy, self-propelled compaction
Fill Lift Thickness equipment is used.
4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping
jack or plate compactor) is used.
Minimum Compaction Structural Fill
Requirement Beneath foundations: 98%
Beneath floor slabs: 95%
(ASTM D698) Trench backfill: 95%
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Geotechnical Engineering Report Irerracon
Sacajawea Middle School Expansion e Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
Miscellaneous backfill (non-structural areas): 90%
Pavement Subgrade: 95%
Moisture Content z
(ASTM D698) Generally±2% of optimum
1. We recommend that each lift of fill be observed and tested by Terracon for moisture content and
compaction prior to the placement of additional material. Should the results of the in-place density
tests indicate the specified moisture or compaction limits have not been met, the area represented
by the test should be reworked and retested until the specified moisture and compaction
requirements are achieved.
2. Significant moisture conditioning of the native clay and sand soils may be required for proper
compaction
4.2.3 Trench Backfill
All trench excavations should be made with sufficient working space to permit construction including
backfill placement and compaction. Utility/pipeline trenches are a common source of water infiltration
and migration. The clay fill should be placed to completely surround the utility/pipeline above the
bedding zone and be compacted in accordance with recommendations in this report. The bedding
zone should consist of flowable fill formed to cradle the pipe in a manner that will inhibit underflow
toward the foundation area.
4.2.4 Surface Grading and Drainage
Positive drainage should be provided during construction and maintained throughout the life of the
proposed project. Infiltration of water into utility/pipeline or foundation excavations must be
prevented during construction. All grades must provide effective drainage away from the structure
during and after construction. Water permitted to pond next to the structure can result in greater
soil movements than those discussed in this report. Estimated movements described in this report
are based on effective drainage for the life of the structure and cannot be relied upon if effective
drainage is not maintained.
4.2.5 Construction Considerations
Based on the information provided, the proposed building additions are expected to be supported
on shallow wall and column footing foundations at frost depth. The foundation excavation should
consist of removal of topsoil and any existing fill to native lean clay an adequate depth to allow
construction of the foundation options discussed above and in Section 4.3.3 below. This
preparation should be verified by our geotechnical engineer. Our observations may necessitate
sub-excavation and replacement of weak or unsuitable materials with additional Structural Fill.
Although the exposed subgrade is anticipated to be relatively stable upon initial exposure, unstable
subgrade conditions could develop during general construction operations, particularly if the clay
materials are wetted and/or subjected to construction traffic. The use of light, rubber-tracked
construction equipment would aid in reducing subgrade disturbance. Should unstable subgrade
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Geotechnical Engineering ,report Irerracon
Sacajawea Middle School Expansion a Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
conditions develop, our geotechnical engineer should review conditions and provide
recommendations for stabilization.
The site should be graded to prevent ponding of surface water on, or direction of runoff toward,
the prepared subgrades or excavations. If the subgrade should become frozen, desiccated,
saturated, or disturbed, the affected material should be removed.
As a minimum, all temporary excavations should be sloped or braced as required by Occupational
Health and Safety Administration (OSHA) regulations to provide stability and safe working
conditions. The grading contractor, by his contract, is usually responsible for designing and
constructing stable, temporary excavations and should shore, slope or bench the sides of the
excavations, as required, to maintain stability of both the excavation sides and bottom. All
excavations should comply with applicable local, state and federal safety regulations, including
the current OSHA Excavation and Trench Safety Standards.
Our geotechnical engineer should be retained during the construction phase of the project to
observe earthwork and to perform necessary tests and observations during foundation
preparation, compaction of backfill, and final preparation for construction of the tanks.
4.3 New Building Addition Foundations
In our opinion, the proposed building can be supported by shallow, continuous and spread footing
foundation systems using a Structural Fill/Reinforced Soil Foundation load distribution layer over
native, undisturbed clay or directly on native gravel. Design recommendations for shallow
foundations for the proposed structure are presented in the following paragraphs with the
assumption that column and bearing wall loads will not exceed 70,000 pounds and 3,300 to 4,200
pounds per lineal foot respectively based on current information.
4.3.1 Design Recommendations
DESCRIPTION Column Footings Wall Footings
(RSFs) (SF only, no geogrids)
Native Lean Clay Subgrade
Design allowable bearing pressure 3,000 psf 2,000 psf
Minimum footing width 3.0 feet 1.5 feet
Maximum embedment below finished grade' 2.0 feet 2.5 feet
Minimum embedment below finished floor
for interior
1.5 feet 1.5 feet
Minimum Structural Fill (SF)/RSF thickness See Exhibit C-5 1.5 feet of SF
below footings
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Geotechnical Engineering Report Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
DESCRIPTION Column Footings Wall Footings
(RSFs) (SF only, no geogrids)
Native Lean Clay Subgrade
Approximate total settlement 3 1 inch 1 inch
Approximate differential settlement 3/4 inch
DESCRIPTION Column Wall
Native Gravel Subgrade — Gymnasium Area
Design allowable bearing pressure ' 3,000 psf 3,000 psf
Minimum footing width 2.0 feet 1.5 feet
Minimum embedment below finished grade
4.0 feet 4.0 feet
for frost protection for exterior
Minimum embedment below finished floor
2.0 feet 2.0 feet
for interior
Minimum Structural Fill thickness below 0 feet 0 feet
footings
Approximate total settlements 3/4 inch 3/4 inch
Approximately differential settlement 1/2 inch
Friction
Ultimate
Material Coefficient Passive
Resistance
(Ultimate) (psf/ft depth)
Lateral Load Resistance(4)
Native Lean 0.30 200
Clay
Structural Fill 0.70 520
1. The recommended allowable bearing pressure is the pressure including surrounding overburden
pressure at the footing base elevation. Based on a minimum factor of safety of 3.0.
2. For perimeter footings and footings beneath unheated areas non-frost susceptible Structural Fill
below footings will be necessary to provide frost protection.
3. The foundation settlement will depend upon the variations within the subsurface soil profile, the
structural loading conditions, the embedment depth of the footings, and the quality of the earthwork
operations.
4. Lateral load resistance parameters are ultimate values and should be factored as appropriate for
design.
4.3.2 Foundation Drainage
To mitigate the potential for groundwater to saturate the foundation subgrade, a perimeter cutoff
drain is recommended to reduce the potential for water infiltration around the building. The
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Geotechnical Engineering .:eport Irerracon
Sacajawea Middle School Expansion n Bozeman, Montana
February 18, 2016 e Terracon Project No.AJ165001
foundation drain should be constructed in accordance with the detail provided as Exhibit C-4 in
Appendix C.
4.3.3 Construction Considerations — Foundation Preparation
The base of all foundation excavations should be free of water and loose soil prior to construction
of the Structural Fill layer or concrete placement. Prior to Structural Fill placement, the prepared
clay surface should be covered with Mirafi 140 N geotextile or an approved geotextile that extends
up the excavation sides to the surface of the Structural Fill zone. Should the soils at bearing level
become excessively dry, disturbed or saturated, or frozen, the affected soil should be removed
and replaced with Structural Fill in accordance with Section 4.2.2. It is recommended that the
geotechnical engineer be retained to observe and test the soil foundation bearing materials.
It is recommended that the footings bear on properly prepared compacted Structural Fill layers
constructed on the native clay or on properly prepared native gravel. For column footings on clay,
geogrid reinforcement should be incorporated into the Structural Fill as detailed on Exhibit C-5 in
the Appendix. For isolated footing subgrade replacement zones, over-excavation or Structural
Fill placement should extend laterally beyond all edges of the footings at least 8 inches per foot
of over-excavation depth below footing base elevation. The over-excavation should then be
backfilled up to the footing base elevation with Structural Fill material placed in lifts of 8 inches or
less in loose thickness and compacted to at least 98 percent of the material's maximum standard
effort maximum dry density (ASTM D 698). The over-excavation and backfill procedure is
described in the adjacent figure.
(s c`)It�►c�41t= t tst�c5lt�
fcc�lt�SSf tit(
1
Design Footing 2/3D > w i 2/3D
Level icy
A
tilt`_
Structural Fill
D Jl
Note: Excavation in sketch is shown vertical for convenience.
Excavations should be sloped as necessary for safety.
Reliable ■ Responsive ■ Resourceful 10
Geotechnical Engineering keport Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
4.3.4 Seismic Considerations
Code Used Site Classification
2012 International Building Code (IBC) C
1. In general accordance with the 2012 International Building Code, Table 1613.5.2.
2. Site class definitions are based on the average properties in the top 100 feet of the subsurface
profile. The current scope does not include the required 100-foot soil profile determination. Borings
extended to maximum depths of approximately 16.5 feet below grade, and this seismic site class
definition considers that very dense gravel is below the maximum depth of the subsurface
exploration.
4.4 Floor Slabs
4.4.1 Design Recommendations
ITEM DESCRIPTION
Floor slabs should bear on cushion/leveling course
Floor slab support overlying native lean clay or Structural Fill pads
placed on native clay and compacted as
recommended for building pad preparation.
Modulus of subgrade reaction 100 pounds per square inch per in (psi/in).
Aggregate base/cushion course 6 inches of densely-graded, minus%-inch crushed
gravel base course.
Additional floor slab design and construction recommendations are as follows:
1. Floor slabs should be structurally independent of any building footings or walls to reduce
the possibility of floor slab cracking caused by differential movements between the slab
and foundation.
■ Positive separations and/or isolation joints should be provided between slabs and all
foundations, columns, or utility lines to allow independent movement.
■ Control joints should be provided in slabs to control the location and extent of cracking.
■ Interior utility trench backfill placed beneath slabs should be compacted in accordance
with the recommended specifications in the earthwork section of this report.
■ Floor slabs should not be constructed on frozen subgrade.
■ Other design and construction considerations, as outlined in the ACI Design Manual,
Section 302.1 R, are recommended.
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, Geotechnical Engineering „eport Irerracon
Sacajawea Middle School Expansion o Bozeman, Montana
February 18, 2016 ® Terracon Project No.AJ165001
2. The use of a vapor retarder should be considered beneath concrete slabs on grade that
will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings,
or when the slab will support equipment sensitive to moisture. When conditions warrant
the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for
procedures and cautions regarding the use and placement of a vapor retarder.
4.4.2 Construction Considerations
The building slab subgrade will be disturbed by construction and should be prepared to repair
construction disturbance under the observation of a geotechnical engineer. On most project sites,
the site grading is generally accomplished early in the construction phase. However as construction
proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation,
rainfall, etc. As a result, the floor slab subgrade may not be suitable for placement of
cushion/leveling course material and corrective action will be required.
Particular attention should be paid to high traffic areas that may have become rutted and disturbed
earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are
located should be repaired by removing and replacing the affected material with properly compacted
fill. All floor slab subgrade areas should be moisture conditioned and properly compacted to the
recommendations in this report immediately prior to placement of the Structural Fill, cushion course
and concrete.
4.5 Pavement
4.5.1 Flexible Pavement Design Recommendations
Since final site grading plans are not yet complete, the controlling subgrade material has been
assumed to be the very soft to very stiff lean clay encountered beneath the existing topsoil. Our
design has been based on this lean clay subgrade with an assumed CBR-value of 2% based on
our experience with similar clay materials. In order to generate a pavement thickness design,
traffic loading data (typically in terms of 18-kip Equivalent Single Axle Loadings or ESAL's) is
necessary. In this case, on-site traffic data was provided by the project Civil Engineer. The primary
wheel loads are expected be imposed on the pavement by school buses in the new access
roadway and drive areas. 10 buses were estimated to make 4 trips per day each to the school
over the next 20 years. An annual growth factor of 2% was included in the ESAL estimate,
resulting in a total 20 year design life ESAL estimate of 265,000. Parking areas not used by the
buses were assumed to receive 30,000 ESALs over the 20 year design life.
Utilizing these subgrade and traffic conditions, the pavement sections listed below have been
developed generally following the procedures of the '93 AASHTO, American Association of State
Highway Transportation Officials, pavement thickness design manual. Other design parameters
used in the analysis include: Reliability= 95%, S.D. = 0.35 and Delta PSI =2.0, material structural
coefficients: a1=0.41, a2=0.14, a3=0.10; and drainage factors of 1.0. Pavement material
specifications are included in Appendix C.
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Geotechnical Engineering keport Irerracon
Sacajawea Middle School Expansion ® Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
Heavy Duty (Bus Travel Areas)
Pavement Component Thickness (inches)
Option 1
1. Asphaltic Concrete Surfacing 4
2. Crushed Aggregate Base Course 16
3. Mirafi 140 N geotextile placed on subgrade
Total Section Thickness 20
Option 2
1. Asphaltic Concrete Surfacing 4
2. Crushed Aggregate Base Course 6
3. Subbase 18
4. Mirafi 140 N geotextile placed on subgrade
Total Section Thickness 28
Light Duty (Automobile Parking Areas Only)
Option 1
1. Asphaltic Concrete Surfacing 3
2. Crushed Aggregate Base Course 12
3. Mirafi 140 N geotextile placed on subgrade
Total Section Thickness 15
Light Duty (continued)
Option 2
1. Asphaltic Concrete Surfacing 3
2. Crushed Aggregate Base Course 6
3. Subbase 9
4. Mirafi 140 N geotextile placed on subgrade
Total Section Thickness 18
If heavy, rubber-tired construction traffic is anticipated in certain areas after placement of crushed
base course and prior to placement of asphalt surfacing, increasing the base course thickness
should be anticipated since this construction traffic loading may exceed the assumed design traffic
loading. Material Specifications for the flexible pavement components are presented in the
Appendix.
Reliable ■ Responsive ■ Resourceful 13
Geotechnical Engineering ,.eport Irerracon
Sacajawea Middle School Expansion ® Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
Subgrade preparation for flexible pavements should be as described below:
• After stripping of the existing topsoil and all fill material deemed unsuitable by our
geotechnical engineer, any grade raising necessary should be conducted using
Structural Fill consisting of materials as described herein and approved by our
geotechnical engineer.
• Prior to placing any Structural Fill for grade raising, or prior to placing pavement base
course on the exposed subexcavation surface, the existing subgrade materials should
be scarified to a depth of 6 inches (or the depth of construction disturbance, whichever
is greater), and compacted in accordance with the recommendations of Section 4.2.2.
As part of the subgrade preparation process, engineering observation of the compaction process
and a subsequent proofrolling with a loaded 10 cubic yard tandem axle dump truck or other
equipment deemed appropriate by our geotechnical engineer, should be conducted to identify
soft or yielding areas. Such areas should be improved by subexcavation and replacement and/or
incorporation of an appropriate geotextile.
4.5.2 Rigid Pavement Design Recommendations
It is recommended that a Portland cement concrete, PCC, pavement be utilized in entrance and
exit driveway approaches and dumpster pads where extensive wheel turning movements and
heavy axle loads are expected. The dumpster pad should be large enough to support the wheels
of the truck which will bear the load of the dumpster. A minimum of 4 inches of minus 3/4" crushed
base course underneath a minimum 7 inch thick concrete section is recommended. The base
course should meet the requirements for flexible pavement base course provided in the Appendix
and be compacted in accordance with Section 4.2.2. Although not required for structural support,
the base layer is recommended to help improve general subgrade uniformity. It also provides a
level working surface for construction of the reinforced concrete section.
Standard saw cut control joints should be used with width, depth and spacing of 1/8", 1 '/2' and
every 250 square feet respectively will also be required to limit excessive slab curling and
shrinkage cracking.Thejoints should be cut and sealed as soon as possible to minimize infiltration
of water into the subgrade. All joints should be sealed to prevent the entry of any foreign material
and dowelled where necessary for load transfer. Adequate reinforcement should be placed in rigid
pavement in accordance with ACI requirements.
4.5.3 Pavement Drainage
Pavement surfacing and subgrade should be sloped to provide rapid drainage of surface water .
Water allowed to pond on or adjacent to the pavements could saturate the subgrade and result
in premature pavement deterioration.
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Geotechnical Engineering keport Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No.AJ165001
5.0 GENERAL COMMENTS
Terracon should be retained to review the final design plans and specifications so comments can
be made regarding interpretation and implementation of our geotechnical recommendations in the
design and specifications. Terracon also should be retained to provide observation and testing
services during grading, excavation, foundation construction and other earth-related construction
phases of the project; additional geotechnical service is particularly important for the foundation
preparation phases of this project.
The analysis and recommendations presented in this report are based upon the data obtained
from the borings performed at the indicated locations and from other information discussed in this
report. This report does not reflect variations that may occur between borings, across the site, or
due to the modifying effects of construction or weather. The nature and extent of such variations
may not become evident until during or after construction. If variations appear, we should be
immediately notified so that further evaluation and supplemental recommendations can be
provided.
The scope of services for this project does not include, either specifically or by implication, any
environmental or biological (e.g., petroleum hydrocarbons, mold, fungi, bacteria) assessment of
the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner
is concerned about the potential for such contamination or pollution, other studies should be
undertaken.
This report has been prepared for the exclusive use of our client for specific application to the
project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranties, either expressed or implied, are intended or made. Site
safety, excavation support, and dewatering requirements are the responsibility of others. In the
event that changes in the nature, design, or location of the project as outlined in this report are
planned, the conclusions and recommendations contained in this report shall not be considered
valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this
report in writing.
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APPENDIX A
FIELD EXPLORATION
Geotechnical Engineering keport Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No. AJ165001
Field Exploration Description
The boring locations were laid out on the site by Terracon personnel prior to the site investigation.
Latitude and longitude were estimated using a handheld GPS unit, and elevations determined by
engineering level and rod. The finished main floor elevation of the school was used as a benchmark
for the elevation survey. The locations and elevations of the borings should be considered accurate
only to the degree implied by the means and methods used.
The borings were drilled with a CME 55 rotary drill rig using hollow-stem augers to advance the
boreholes. Boring B-5 was not drilled as planned as it was not accessible to our drill rig due to
excessive crusted snow during the field investigation. Samples of the soils encountered in the borings
were obtained by driving split spoon samplers, pushing Shelby tube samplers and collecting auger
cuttings.
In the split-barrel sampling procedure, the number of blows required to advance a standard 2-inch
O.D. split-barrel sampler the last 12 inches of the typical total 18-inch penetration by means of a 140-
pound hammer with a free fall of 30 inches, is the standard penetration resistance value (SPT-N).
This value is used to estimate the in-situ relative density of cohesionless soils and consistency of
cohesive soils.
A CME automatic SPT hammer was used to advance the split-barrel sampler in the borings
performed on this site. A significantly greater efficiency is achieved with the automatic hammer
compared to the conventional safety hammer operated with a cathead and rope. This higher
efficiency has an appreciable effect on the SPT-N value. The effect of the automatic hammer's
efficiency has been considered in the interpretation and analysis of the subsurface information for
this report.
The samples were tagged for identification, sealed to reduce moisture loss, and taken to our
laboratory for further examination, testing, and classification. Information provided on the logs
attached to this report includes soil descriptions, consistency evaluations, boring depths, sampling
intervals, and groundwater conditions. The borings were backfilled with auger cuttings prior to the
drill crew leaving the site.
Field logs were prepared by the field engineer. The logs included visual classifications of the
materials encountered during drilling as well as the engineer's interpretation of the subsurface
conditions between samples. The final logs included with this report represent the engineer's
interpretation of the field logs and includes modifications based on laboratory observations and tests
of the samples.
Reliable ■ Responsive ■ Resourceful Exhibit A-1
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DIAGRAM IS FOR GENERAL LOCATION ONLY,AND IS AERIAL PHOTOGRAPHY PROVIDED
NOT INTENDED FOR CONSTRUCTION PURPOSES BY MICROSOFT BING MAPS
Project Manager: Project AJ165001 BORING LOCATION DIAGRAM Exhibit
JFP AJ
Irerracon
Drawn6y: JFP Scale:
t:heckedt,y: File Name: SACAJAWEA MIDDLE SCHOOL EXPANSION 212 Zoot Way,Suite B !`AA'l—3
Approved by: Date: 2/5116 Bozeman,Montana 59715 Bozeman,Montana
BORING LOG NO. B-1 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
O LOCATION See Exhibit A-3
''J ❑^LL m
~ Ar RG w w wW - LMITS
)O C w
U Latitude:45.64444° Longitude: -111.04928' WF- F W� ❑ �,=w w
LU LijZ❑ w ww w LL-PL-PI v o v' v
Surface Elev.:97.5(Ft.) O DO, a
DEPTH ELEVATION Ft. o
TOPSOIL,
dark brown to black
0.8 96.5
LEAN CLAY(CL), medium stiff to soft, brown to
black,trace sand
0.8 1-4-4 23
N=8
5
1.1 -3fi 35 49-25-24 89
N
N 0.9 2-1-1 41
z N=2
0
a
W
W
a' 10.5 87 1
2-8-13
CLAYEY GRAVEL WITH SAND(GM, medium 0.8 13
dense,dark brown,gravels to+1", wet below 15.0' N=21
0
'a
J
0
z
J
Q
15
o
0.6 11-12-12 16 N=24
cw7 116.5 81
Boring Terminated at 16.5 Feet
of
w
z
0
0
2
0
w
a
w
a Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
Q
a
w
(n Advancement Method: Notes:
LL HSA
0
J
Q
H
oz Abandonment Method:
m Borings backfilled with soil cuttings upon completion.
0
0
J WATER LEVEL OBSERVATIONS
Z Boring Started:1/26/2016 Boring Completed:1/26/2016
m No free water observed Irerracon g y
Drill Rig:CME 55 D ller:Sam Eddy
212 Zoot Way,Suite B
Bozeman,Montana Project No.:AJ165001 Exhibit: A-4
BORING LOG NO. B-2 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
(D LOCATION See Exhibit A-3 w Z a c F m p j n Q A LIMITS
RG z
Q Latitude:45.644444° Longitude: -111.04847°
a _ z FL W OO iaw X w Z -PL-PI W w
LL
oSurface Elev.:98.5(Ft.) p�coO a
DEPTH
ELEVATION Ft. m
TOPSOIL, black to brown
i 0.8 97.5 0.8 3-4-4 22
LEAN CLAY WITH SAND(CL),very stiff to medium N=8
stiff,brown to black,scattered fine gravel,silt
7-7-9
1 N=16 22
5
1.3
N
H
1.2 N36 25
0
N
Z
O
U
Q
Ld
W 1
10.5 CLAYEY GRAVEL WITH SAND(GM,dense,dark 88 1.1 2N 338 13
brown
0
o .
a
J
J
W
3
0
z
c�
0
15
0.6 12-15-18 6
0 N=33
W '16.5 82
Boring Terminated at 16.5 Feet
0
w
a
z
X
0
2
0
o_
LL
Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
a
o_
Advancement Method: Notes:
u HSA
❑
J
Q
o Abandonment Method:
z Borings backfilled with soil cuttings upon completion.
�o WATER LEVEL OBSERVATIONS
Boring Started:1/26/2016 Boring Completed:1/26/2016
mz No free water observed Irerracon
Drill Rig:CME 55 Driller:Sam Eddy
m 212 Zoot Way,Suite B
= Bozeman,Montana Project No.:AJ165001 Exhibit: A-5
BORING LOG NO. B-3 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
(D LOCATION See Exhibit A-3 J Z w _ W p w N ATL LIMITS
w
OJ v >0 } r U)U) g Z�a Z
Latitude:45.64406° Longitude: -111.047720 ~ w w w Z E W I_ W Z H
_ w > 0 7) W Z
LL-PL-PI LU
G Surface Elev.:99.0(Ft.) o ¢U) 2 o D_ o 0, 3 U
�o < of a ��� v i
DEPTH ELEVATION Ft.
' TOPSOIL,dark brown to black
i' 0.8 98 1'1 2-2-3
LEAN CLAY WITH SAND(CL),very stiff to medium N=5 23
stiff,light brown to black,silt,scattered gravel
0.8 8-8-10 23
N=18
5
0.8 3-3-4 25
N=7
N
H
z 1 N25 29 40-19-21
0
U
Q
w
W
1
a
11.0 88 0.8 3-6-12 28
N CLAYEY GRAVEL WITH SAND(GCS, medium N=18
dense to dense,dark brown,gravels to+ V,
subangular,wet below 15.0'
Q
J
3
0
z
(F)
0
J
Q
15
08 16-18-15 13 15
o . N=33
16.5 82.5
Boring Terminated at 16.5 Feet
C
w
z
0
0
0
LL
LL
W
W
a Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
af
Q
a
w
N Advancement Method: Notes:
` HSA
0
J
Q
H
o Abandonment Method:
CO Borings backfilled with soil cuttings upon completion.
0
WATER LEVEL OBSERVATIONS
z — I Boring Started:1/26/2016 Boring Completed:1/26/2016
m No free water observed rerracon g y
Drill Rig:CME 55 Driller:Sam Eddy
U) 212 Zoot Way,Suite B
Bozeman,Montana Project No.:AJ165001 Exhibit: A-6
BORING LOG NO. B-4 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
cD LOCATION See Exhibit A-3 J w _ w w y ^ A LIMITS w
U Lu �- �U) WW� n of
Z
O Latitude:45.64375' Longitude: -111.04928' w Q w z 7 W F W z ~
S W > Z U` F W Z
a n~ w Q d O of W L4 0 Z Q F LL-PL-PI W
Surface Elev.:98.5(Ft.) o ¢ < w LL z Q o O �
DEPTH ELEVATION Ft.
7777 TOPSOIL, dark brown to black
-' 1.0 97.5
LEAN CLAY WITH SAND(CL),very stiff to soft,
brown to black, siltier with depth
1.3 6-8-8 30
N=16
5 2
0.8 2-3-2 29
N=5
N
❑
T 1.4 N12 27 35-20-15 75
Z
0
LU
LU
~ 10.2 88.5 1
a CLAYEY GRAVEL WITH SAND(GCI,medium 8-11-13
dense to very dense,dark brown,subangular 0'8 N=24 24
m
b
a �
J
3
0
z
cD
15
m tO 15,50/0.3; N=
0 50/0.3'
W 16.5 82
O
Boring Terminated at 16.5 Feet
0
W
a
z
0
0
2
0
LL
❑
aStratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
X
a
a
W Advancement Method: Notes:
LL HSA
J
a
>
o Abandonment Method:
Z Borings backfilled with soil cuttings upon completion.
CO
c9
0 WATER LEVEL OBSERVATIONS
J Baring Started:1/26/2016 Boring Completed:1/26/2016
c�
Irerraccin y
Drill Rig:CME 55 Driller:Sam Eddy
m
212 Zoot Way,Suite B
= Bozeman,Montana Project No..AJ165001 Exhibit: A-7
BORING LOG NO. B-6 ' Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
o LOCATION See Exhibit A-3 ^ W z a o w ❑w ATL TERBE MITTSRG w
>o > U)U) m wig _z
O Latitude:45.64308° Longitude: -111.04881° LL w F w w F- ❑ Z cn= w— w
t
Q ❑D wfr
< w W W a O0 w i oO Z 3 z LL-PL-PI v
O Surface Elev.:99.5(Ft.) ❑ Q w w Z of o:
DEPTH ELEVATION Ft.
TOPSOIL, black
;'��•' 3-3-5
1.0 98.5 0.9 N=8 23
LEAN CLAY WITH SAND(CL),stiff, brown
2.0 97.5
CLAYEY GRAVEL WITH SAND(GC), medium
dense to very dense,dark brown,gravels to+1 1/2",
subangular to subrounded 7-17.12
1 N=29 13
5 0.8 10-20-22 9
N=42
N
N 0.6 10-8 8 11
z N=16
0
U
Q
w 9.8 89.5 0 50/0.3; N=
Boring Terminated at 9.8 Feet 50/0.3'
a
c7
vi
2
0
h
Q
>J
0
Z
J
Q
N
0
tU
0
w
Q
Z
LD
X
0
2
0
LL
w
a Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
a
a
w
N Advancement Method: Notes:
—` HSA
0
J
Q
>
H
0 Abandonment Method:
Z Borings backfilled with soil cuttings upon completion.
Ln
(9
0
WATER LEVEL OBSERVATIONS Boring Started:1/26/2016 Boring Completed:1/26/2016
measured during drilling Irerracon
m Drill Rig:CME 55 Driller:Sam Eddy
212 Zoot Way,Suite B
Bozeman,Montana Project No.:AJ165001 Exhibit: A-8
BORING LOG NO. B-7 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
CD LOCATION See Exhibit A-3 J U w of w y ^ ATL MITSRG w
wz o c m Lu>_ a o Z
Urn g Z65v LL
O Latitude:45.64272' Longitude: -111.04861° ¢ w z FL F w z F
a L w01 0 O oJUU) w Oaz Q~ LL-PLPI w
Q Lu F uJ U uiLU a Ugw 3: U
Surface Elev.:100.0(Ft.) 0 3 m LU LL a � Y OU w
DEPTH ELEVATION Ft- U U U o
' TOPSOIL, 1'of snow and ice on top of topsoil,dark
PEE
/' 0.6 brown to black topsoil 99 1 7-6-3 22
LEAN CLAY WITH SAND(CL),medium stiff, brown N=9
to black,scattered gravels,sand
2.2 98 0.9 2-6-12 24
POORLY GRADED GRAVEL WITH CLAY AND N=18
• SAND(GP-GC), medium dense to very dense,dark
® . brown,gravefis to+I",spoon bent at 7',coarse sand
lens at 11'
a
® . 0.8 10-13-11 8 11
5 N=24
0
m
m 0.4 13-30-19
o N=49
b
Z ® _
Z
O
U
• -,
8-19-31
w ® 1 0.6 N=50
a o
c�
ai
U
11.8 88 0.3 50/0.3'; N=
Boring Terminated at 11.8 Feet 1 50/0.3'
LU
>J
O
Z
Q
J
r
Q
0
0
0-
w
Q
Z
K
O
2
0
LL
Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
Q
a
N Advancement Method: Notes:
LL HSA
0
J
Q
F-
O Abandonment Method:
Z Borings backfilled with soil cuttings upon completion.
U
c7
J
OBSERVATIONS WATER LEVEL OBSERVA
U Boring Started:1/26/2016 Boring Completed:1/26l2016
U Irerracon g'
Drill Rig:CME 55 Driller:Sam Eddy
m
n 212 Zoot Way,Suite B
= Bozeman,Montana Project No.:AJ165001 Exhibit: A-9
F-
BORING LOG NO. B-8 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
(D LOCATION See Exhibit A-3 U) LU W ATTERBERG
O >L o_ } U)0 o>a o LIMITS Z
J .E U)
L) Latitude:45.64219' Longitude: -111.04861' � w� cn I- 0:F- FL
LU > ❑D w Z�(~7 2W z
Surface Elev.:106.5(Ft.) o ¢wn IL LU of o FL� a- o o m 3 o LL-PL-PI Z
�m < Q ��� U w
DEPTH ELEVATION Ft. <
TOPSOIL, dark brown to black
1.0
105.5
LEAN CLAY WITH SAND(CLI,soft to very soft,
black to brown
1.4 2-2-2 28
N=4
5
1.3 0 011 31 42-19-23 79
D 6.5 100 — X
Boring Terminated at 6.5 Feet
N
N
O
Z
O
U
D:
W
a
U
ai
0
N
O
Q
J
3
0
z
c�
0
J
Q
O
f-
0
O
W
It
Q
Z
0
O
2
O
LL
W
a Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
o:
Q
W
w
u) Advancement Method: Notes:
` HSA
J
Q
>
f-
0 Abandonment Method:
Cn Borings backfilled with soil cuttings upon completion.
0
0
zWATER LEVEL OBSERVATIONS Boring Started:1/2 612 0 1 6 Boring Completed:1/26/2016
0 No free water observed Irerracon
m Drill Rig:CME 55 Driller Sam Eddy
`° 212 Zoot Way,Suite B
Bozeman,Montana Project No.:AJ165001 Exhibit: A-10
BORING LOG NO. B-9 Page 1 of 1
PROJECT: Sacajawea Middle School Expansion CLIENT: Bozeman Public Schools, Facilities Department
Bozeman, Montana
SITE: 3525 3rd Avenue South
Bozeman, Montana
� ATTERBERG
LOCATION See Exhibit A-3 W O }� } U)U o j a o LIMITS z
v Latitude:45.64219' Longitude: -111.04756' _ of
Q W w F Z Z w P w z t-
n= a w x a >O _w w O a z ¢F LL-PL-PI W
Surface Elev.:107.0(Ft.) o m W �of ¢ Z v� w
DEPTH ELEVATION fFt.1 U)
TOPSOIL,dark brown to black
0.8 106 1.3 17-16-13 23
LEAN CLAY WITH SAND(CL),very stiff to soft, N=29
black to brown,frozen to 1.0'
0.1 3-1-1 20
N=2
5
]FO 3-2-2-2 17
N=4
r 7.0 100
F Boring Terminated at 7 Feet
❑
0
z
0
�a
a
vi
m
0
N
to
Q
J
3
0
z
(7
0
J
d'
a
0
H
0
O
W
K
Q
Z_
U`
of
O
2
O
K
LL
❑
aStratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
a
N Advancement Method: Notes:
U_ HSA
a
o Abandonment Method:
z Borings backfilled with soil cuttings upon completion.
(7
WATER LEVEL OBSERVATIONS
0
J
� Boring Started:1/26/2016 Boring Completed:1/26/2016
z No free water observed Irerracono
Drill Rig:CME 55 Driller:Sam Eddy
m
N 212 Zoo[Way,Suite B
= Bozeman,Montana Project No.:AJ165001 Exhibit: A-11
APPENDIX B
SUPPORTING INFORMATION
Geotechnical Engineering Keport Irerracon
Sacajawea Middle School Expansion ■ Bozeman, Montana
February 18, 2016 ■ Terracon Project No. AJ165001
Laboratory Testing
As a part of the laboratory testing program, the soil samples were classified in the laboratory
based on visual observation, texture, plasticity, and the laboratory testing performed as noted
below. The soil descriptions presented on the boring logs are in accordance with our enclosed
General Notes, and Unified Soil Classification System (USCS). The estimated group symbol for
the USCS is also shown on the logs, and a brief description of the Unified System is included in
this report. Results of the laboratory tests are presented on the logs and/or included herein.
Selected soil samples were tested for the following properties:
■ Water Content (ASTM D6780);
■ Atterberg Limits (ASTM D4318;)
® Grain Size Distribution (ASTM D422);
® Consolidation/Swell (ASTM D4546);
■ Unconfined Compression Test (ASTM D2166);
Reliable ■ Responsive ■ Resourceful Exhibit B-1
#\TTERBERG LIMITS RESULT'S
ASTM D4318
60
50
P
L
A / /
S 40 O
Tj oc
l '
C I
T 30 -�
Y 1
l * O
N 20
D
E ��'� MH or OH
x
10
CL-M% ML r OL
0 �
0 20 40 60 80 100
LIQUID LIMIT
Boring ID Depth LL PL PI Fines USCS Description
N
o • B-1 5-6.5 49 25 24 89 CL LEAN CLAY
o m B-3 7.5-9 40 19 21 LEAN CLAY WITH SAND
N
Z
A B-4 7.5-9 35 20 15 75 CL LEAN CLAY with SAND
W * B-8 5-6.5 42 19 23 79 CL LEAN CLAY with SAND
a
c�
ai
m
0
0
Q
F-
J
LU
w
CO
Uj
W
a
F-
O
a
w
J
a
Z
K
2i
O
w
W
F-
a
a
a
w
Cn
J
a
0
0
z
w
a PROJECT: Sacajawea Middle School Expansion PROJECT NUMBER: AJ165001
LU
> SITE: 3525 3rd Avenue South CLIENT: Bozeman Public Schools, Facilities
erracon De
o IrpartmentBozeman, MontanaBozeman,Montana
0 212 Zoot Way,Suite B
m Bozeman, Montana EXHIBIT: B-2
5
GRAIN SIZE DISTRIBUTION
ASTM D422
U.S.SIEVE OPENING IN INCHES U.S.SIEVE NUMBERS I HYDROMETER
6 4 3 2 1 5 1 3/4 1123/8 3 4 6 810 1416 20 30 40 50 60 100140200
100
95
90
85
80
75
70
65
w 60
m 55
w 50
z
LL
z
45
a w
40
a W
Lij a 35
Cn
w
30
25
a
20
0
m
N
15
a
10
°
0
5
0
`2 0
a 100 10 1 0.1 0.01 0.001
N
0 GRAIN SIZE IN MILLIMETERS
m
COBBLES �-GRAVEL SAND SILT OR CLAY
Z coarse fine coarse I medium fine
a
Boring ID Depth USCS Classification ILL PL PI Cc Cu
o • B-1 5-6.5 LEAN CLAY(CL) 49 25 24
a
m B-3 15-16.5 CLAYEY GRAVEL WITH SAND()
J
K A B-4 7.5-9 LEAN CLAY with SAND(CL) 35 20 15
o * B-7 4-5.5 POORLY-GRADED GRAVEL WITH CLAY AND SAND() 3.60 218.79
° O B-8 5-6.5 LEAN CLAY with SAND(CL) 42 19 23
° Boring ID Depth D1oa D60 D30 D16 %Gravel %Sand %Fines
• B-1 5-6.5 0.18 0.0 11.2 88.8
a
M B-3 15-16.5 25 6.756 0.633 45.4 39.3 15.3
g A B-4 7.5-9 0.18 0.0 24.9 75.1
J
F * B-7 4-5.5 37.5 13.105 1.682 58.3 30.7 11.0
O B-8 5 6.5 0.18 0.0 21.5 78.5
a PROJECT: Sacajawea Middle School
Expansion PROJECT NUMBER: AJ165001
CLIENT: Bozeman Public Schools, Facilities
SITE: 3525 3rd Avenue South Irerracon Department
o Bozeman, Montana
Bozeman, Montana
212 Zoot Way, Suite B
° Bozeman, Montana EXHIBIT: B-3
5
Unconfh Compression (Qu) of Cohesive Soil
ASTM D-2166
Project: Sacajawea Middle School Expansion Laboratory No.:
Job No.: AJ165001 Soil Class.: Lean Clay wih Sand
Diameter: 2.875
Boring No.: B-4 Depth: 4.0-6.0' Length: 6.0000
Type of Sample: STS Date Broke: 8-Feb-16 Comp. Rate: 0.70
Factor: 2.043634386
Volume (cu. ft.): 0.022540995 Wet Wt. (g): 1409.2 L/D Ratio: 2.09
Wet Unit Wt.: 119.8998064 Dry Wt. (g): 1167.2 L/D Correction: 1
Dry Unit Wt.: 96.23086676 Pan Wt. (g): 183.3 Tested By: BE
Area: 0.04508199 Moisture % 24.6 Checked By: BE
qu value: 1650.25
Time Strain% Dial Reading Proving Ring Area (ft^2) Comp Strength Corrected Strength
0.0 0.00 0.000 0.00 0.0451 0.00 0.0
0.5 0.35 0.021 3.20 0.0452 144.55 144.6
1.0 0.70 0.042 6.50 0.0454 292.59 292.6
1.5 1.05 0.063 9.20 0.0456 412.67 412.7
2.0 1.40 0.084 11.80 0.0457 527.42 527.4
2.5 1.75 0.105 15.00 0.0459 668.07 668.1
3.0 2.10 0.126 18.80 0.0460 834.34 834.3
3.5 2.45 0.147 22.50 0.0462 994.97 995.0
4.0 2.80 0.168 27.00 0.0464 1189.68 1189.7
4.5 3.15 0.189 30.20 0.0465 1325.89 1325.9
5.0 3.50 0.210 34.00 0.0467 1487.33 1487.3
5.5 3.85 0.231 36.50 0.0469 1590.90 1590.9
6.0 4.20 0.252 38.00 0.0471 1650.25 1650.2
6.5 4.55 0.273 37.80 0.0472 1635.57 1635.6
7.0 4.90 0.294 34.50 0.0474 1487.30 1487.3
7.5 5.25 0.315 20.00 0.0476 859.03 859.0
Unconfined Compression (Qu)
ASTM D-2166
1800.0
1600.0
1400.0
n.
1200.0
c
1000.0
m
800.0
m
L
E 600.0
0
U
400.0
orr c e ten h
200.0
0.0
IIEE]I#
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Strain (%)
Exhibit B-4
SWELL CONSOLIDATION TL >T
ASTM D2435
-2
-1
.173
CO
1
2
3
0
z
Q
4
J
Q
X
a 5
N
H
C7
N
N 6
Z
O
U
Uj
w
7
a
U'
0
a
m
4 8
U
U
U
Z_
9
F
U
JI
Cn
Z
0 10
100 1,000 10,000
0 Before Wet Unit Wt. = 121.1 pcf PRESSURE,psf After Wet Unit Wt. = 124.1pcf
w Before Dry UNit Wt. =97.3pcf After Dry UNit Wt. = 99.6pcf
Q Before MC%= 24.4 After MC% = 24.6
Z
a
0
w Specimen Identification Classification Yd, pcf WC,
LL
W • B-4 4 ft Lean Clay w/Sand 97 24
N NOTES:
LL
OINUNDATED
0
0
z
w
PROJECT: Sacajawea Middle School PROJECT NUMBER: AJ165001
r
SITE: 3525 3rd Avenue South Irerracon CLIENT: Bozeman Public Schools
0
1392 13th Ave. SW
m Great Falls, Montana EXHIBIT: B-5
g
APPENDIX C
SUPPORTING DOCUMENTS
GENERAL NOTES
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
Water Initially (HP) Hand Penetrometer
N N Encountered
Spoon lit Auger S S Water Level After a
9 P P �— Specified Period of Time tT) Torvane
J Water Level After (b/0 Standard Penetration
Ur LU �— a Specified Period of Time Test(blows per foot)
Z Shelby Tube Macro Core W W
� U H -i Water levels indicated on the soil boring F- (PID) Photo-Ionization Detector
a W logs are the levels measured in the
W borehole at the times indicated.
yQ Groundwater level variations will occur LL (OVA) Organic Vapor Analyzer
Ring Sampler Rock Core overtime. In low permeability soils,
e accurate determination of groundwater
levels is not possible with short term
water level observations.
Grab Sample No Recovery
DESCRIPTIVE SOIL CLASSIFICATION
Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry
weight retained on a#200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have
less than 50% of their dry weight retained on a#200 sieve;they are principally described as clays if they are plastic, and
silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be
added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined
on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.
LOCATION AND ELEVATION NOTES
Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy
of such devices is variable. Surface elevation data annotated with +/-indicates that no actual topographical survey was
conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic
maps of the area.
RELATIVE DENSITY OF COARSE-GRAINED SOILS CONSISTENCY OF FINE-GRAINED SOILS
(More than 50%retained on No.200 sieve.) (50%or more passing the No.200 sieve.)
Density determined by Standard Penetration Resistance Consistency determined by laboratory shear strength testing,field
Includes gravels,sands and silts. visual-manual procedures or standard penetration resistance
�
Standard Penetration or Standard Penetration or Descriptive Term Ring Sampler Descriptive Term Unconfined Compressive Ring Sampler
(Density) N-Value Blows/Ft. (Consistency) Strength,Qu,psf N-Value Blows/Ft.
Q' Blows/Ft. Blows/Ft.
W
F- Very Loose 0-3 0-6 Very Soft less than 500 0-1 <3
~ Loose 4-9 7-18 Soft 500 to 1,000 2-4 3-4
Z
W Medium Dense 10-29 19-58 Medium-Stiff 1,000 to 2,000 4-8 5-9
F-
Dense 30-50 59-98 Stiff 2,000 to 4,000 8-15 10-18
Very Dense >50 >99 Very Stiff 4.000 to 8,000 15-30 19-42
Hard >8,000 >30 >42
RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY
Descriptive Term(s) Percent of Major Component Particle Size
of other constituents Dry Weight of Sample
Trace < 15 Boulders Over 12 in.(300 mm)
With 15-29 Cobbles 12 in.to 3 in. (300mm to 75mm)
Modifier >30 Gravel 3 in.to#4 sieve(75mm to 4.75 mm)
Sand #4 to#200 sieve(4.75mm to 0.075mm
Silt or Clay Passing#200 sieve(0.075mm)
RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION
Descriptive Term(s) Percent of Term Plasticity Index
of other constituents Dry Weight
Non-plastic 0
Trace <5 Low 1 -10
With 5-12 Medium 11 -30
Modifier > 12 High >30
Irerracon Exhibit C-1
UNIHED SOIL CLASSIFICATION S rSTEM
Soil Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests" Group Group NameB
Symbol
Gravels: Clean Gravels: Cu>_4 and 1_<Cc:5 3 E GW Well-graded gravel F
More than 50%of Less than 5%fines G Cu<4 and/or 1 >Cc>3 E GP Poorly graded gravel F
coarse fraction retained Gravels with Fines: Fines classify as ML or MH GM Silty gravel F,G,H
Coarse Grained Soils: on No.4 sieve More than 12%fines G Fines classify as CL or CH GC Clayey gravel F,G,H
More than 50%retained
on No.200 sieve Sands: Clean Sands: Cu>_6 and 1_<Cc<3 E SW Well-graded sand'
50%or more of coarse Less than 5%fines° Cu<6 and/or 1 >Cc>3 E SP Poorly graded sand'
fraction passes No.4 Sands with Fines: Fines classify as ML or MH SM Silty sand G,"''
sieve More than 12%fines° Fines classify as CL or CH SC Clayey sand G,"''
Inorganic: PI>7 and plots on or above"A"line' CL Lean clay K,L,M
Silts and Clays: PI<4 or plots below"A"line J ML Silt K,L,M
Fine-Grained Soils:
Liquid limit less than 50 Organic: Liquid limit-oven dried 075 OIL Organic clay K,L,M,N
Liquid limit-not dried < .
Organic silt
K,L,M,O
50%or more passes the
No.200 sieve Inorganic: PI plots on or above"A"line CH Fat clay K,L,M
Silts and Clays: PI plots below"A"line MH Elastic SiltK,L,M
Liquid limit 50 or more K,L,M,P
q Organic: Liquid limit-oven dried <0.75 OH Organic clay
Liquid limit-not dried Organic silt K.L,M,a
Highly organic soils: Primarily organic matter,dark in color,and organic odor PT Peat
"Based on the material passing the 3-inch(75-mm)sieve "If fines are organic,add"with organic fines"to group name.
B If field sample contained cobbles or boulders,or both,add"with cobbles 1 If soil contains>_15%gravel,add"with gravel"to group name.
or boulders,or both"to group name. j If Atterberg limits plot in shaded area,soil is a CL-ML,silty clay.
G Gravels with 5 to 12%fines require dual symbols: GW-GM well-graded K If soil contains 15 to 29%plus No.200,add"with sand"or"with gravel,"
gravel with silt, GW-GC well-graded gravel with clay,GP-GM poorly whichever is predominant.
graded gravel with silt,GP-GC poorly graded gravel with clay. L If soil contains>_30%plus No.200 predominantly sand,add"sandy"to
°Sands with 5 to 12%fines require dual symbols: SW-SM well-graded group name.
sand with silt,SW-SC well-graded sand with clay,SP-SM poorly graded M If soil contains>_30%plus No.200,predominantly gravel,add
sand with silt,SP-SC poorly graded sand with clay "gravelly"to group name.
(D )Z "PI>_4 and plots on or above"A"line.
E Cu=D60/Di0 Cc= 30 °PI<4 or plots below"A"line.
Duo x D60 P PI plots on or above"A"line.
F If soil contains>_15%sand,add"with sand"to group name. °PI plots below"A"line.
G If fines classify as CL-ML, use dual symbol GC-GM,or SC-SM.
60 ,
For classification of fine-grained
soils and fine-grained fraction
50 of coarse-grained soils
Equation of"A"-line
CL Horizontal at PI=4 to LL=25.5.
W 40 then PI=0.73(LL-20) , ' O\
t
p Equation of"U"-line
Z Vertical at LL=16 to PI=7, G
30 then PI=0.9(LL-8) ,
0 O
� o
a 20
I
MH or OH
10 , �
0 �Z L i ML ML or OIL —
0 10 16 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT(LL)
Irerracon Exhibit C-2
RECOMMENDED SPECIFICATIONS FOR
FLEXIBLE PAVEMENT MATERIALS
1. Aggregate Base Course (MT Public Works Specification)
Screen or 3/4-Inch 1-1/2-Inch
Sieve Size Percent Passing Percent Passing
100
1" 95 - 100
3/4" 100
1/2" — 45 - 80
No. 4 40 - 70 25 - 60
No. 10 25 - 55 25 - 55
No. 200 2 - 10 0 - 8*
Mechanically Fractured Faces, one
or more on plus No. 4 aggregate,
%minimum 50* 50*
*Deviates from the MT Public Works Specification
In addition to the gradation presented above, aggregate base course quality should conform to
the MT Public Works Specification, Crushed Base Course, Section 02235, Subsection 02.
2. Asphaltic Concrete Aggregate(MT Public Works Specification 02503)
Asphalt Concrete Surfacing
Percent Passing
Screen or Sieve Size Type B Grading Requirements
3/4" 100
1/2" 80 - 100
3/8" 70 - 90
No. 4 45 - 65
No. 10 32 -45
No. 40 15 - 25
No. 200 4- 10
In addition to the grading requirements shown, the aggregate quality should conform to the
applicable portions of the MT Public Works Specifications, Section 02232, Aggregates for
Surfacing and Asphalt Plant Mixes and the requirements of MT Public Works Specification
02503, Hot Plant Mix Asphalt Concrete
Page 1 of 2
Exhibit C-3
RECOMMENDED SPECIFICATIONS FOR FLEXIBLE PAVEMENT MATERIALS
Asphalt Concrete Mix Designs
Asphalt concrete mix designs should be provided by the contractor, or materials supplier, and
should meet the following requirements, consistent with the MT Public Works Specification
Section 02503, Hot Plant Mix Asphalt Concrete:
Pro e Test Method Specifications
Stability, pounds, minimum ASTM D6927 1200 min.
Flow, 1/100 Inch Units ASTM D6927 8 - 18
Air Voids, percent ASTM D3203 3 - 5
Voids in Mineral Aggregate Asphalt Institute 14 Minimum
(VMA), Percent Minimum Manual MS-2
*50 blows each end of specimen
Minimum Density Requirements
Percent of
Material Test Method Maximum
Asphaltic Concrete Surfacing ASTM D6927 (Marshall)* 97
Crushed or Uncrushed Granular
Base/Subbase Course ASTM D698 95
Subgrade (top 12 inches)** ASTM D698 95
*50 blows each end of specimen; sampled from truck or paver at time of lay-down.
**For all pavement types, Clay subgrades should be compacted at moisture contents within f3
percent of optimum, or above as recommended specifically in the report.
Maximum compacted lift thickness should be 12 inches for granular base/subbase courses.
Also,minimum lift thickness for gravel should be twice the maximum size of the aggregate.
Page 2 of 2
Exhibit
C-3
Geocomposite Option
Provide Positive Drainage
�..
\ � 1'Soil Cover
20 mil Polyethylene Sheeting ..
..
Backfill Zone
Single-sided Drainage Composite
wrapped with non-woven
geotextile,such as Miradrain
G100N,or approved alternate.
•r.
2'layer of 3/8"to 3/4" open-graded
_____ 4"diameter slotted ADS
drainage aggregate wrapped with underdrain sloped at 0.002 ft/ft
non-woven geotextile wrap,such to positive outlet.
as Mirafi 160N,or approved
alternate. Underdrainage should follow footing
20 mil Polyethylene Sheeting grade around the full perimeter
Aggregate Option
Provide Positive Drainage
I'Soil Cover
20 mil Polyethylene Sheeting/ ,.�.
—� • E-
2'Nominal
Structural Fill —
'•ter.
..
3/8"to 3/4"open-graded drainage
aggregate with non-woven 4" diameter slotted ADS
geotextile wrap,such as Mirafi underdrain sloped at 0.002 ft/ft
MON,or approved alternate to positive outlet.
between clay and aggregate.
Underdrainage should follow footing
grade around the full perimeter
Exhibit C-4
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TABLE 1-1: Runoff Coefficients for Use in the Rational Method
LAND USE RUNOFF COEFFICIENTS, C
Open Land 0.2
Low to Medium Density Residential 0.35
Dense Residential 0.5
Commercial Neighborhood 0.6
Commercial Downtown 0.8
Industrial 0.8
Design Standards and Specifications Policy
City of Bozeman, March 2004 as Amended
RAINFALL INTENSITY-DURATION CURVES(Figures 1-2, 1-3)
Storm Recurrence Interval
Time 2 5 10 25 50 100
(min) (in/hr) (in/hr) (in/hr) (in/hr) (in/hr) (in/hr)
1 4.20 7.15 9.16 10.72 13.72 15.69
5 1.60 2.55 3.22 3.83 4.74 5.34
10 1.05 1.64 2.05 2.46 3.00 3.35
15 0.83 1.26 1.58 1.89 2.30 2.56
20 0.70 1.05 1.31 1.58 1.90 2.11
25 0.61 0.91 1.13 1.37 1.64 1.82
30 0.55 0.81 1.00 1.22 1.45 1.61
35 0.50 0.73 0.91 1.10 1.31 1.45
40 0.46 0.67 0.83 1.01 1.20 1.33
45 0.43 0.63 0.77 0.94 1.11 1.22
50 0.40 0.58 0.72 0.88 1.04 1.14
55 0.38 0.55 0.68 0.82 0.97 1.07
60 0.36 0.52 0.64 0.78 0.92 1.01
75 0.31 0.45 0.55 0.68 0.79 0.87
90 0.28 0.40 0.49 0.60 0.70 0.77
105 0.26 0.36 0.44 0.55 0.64 0.69
120 0.24 0.33 0.41 0.50 0.58 0.63
150 0.21 0.29 0.35 0.43 0.50 0.55
180 0.19 0.26 0.31 0.39 0.45 0.48
360 0.12 0.17 0.20 0.25 0.28 0.30
720 0.08 0.11 0.13 0.16 0.18 0.19
1440 0.05 0.07 0.08 0.10 0.11 0.12
STORMWATER MANAGEMENT MANUAL
TABLE 2-5 FREQUENCY FACTORS FOR THE RATIONAL FORMULA
Recurrence Interval Adjustment Factor
(Years) Cf
2 1.00
S 1.00
10 1.00
25 1.10
50 1.20
100 1.25
* C X Cfshould not exceed 1.0
Design Standards and Specifications Policy
City of Bozeman, March 2004 as Amended
Zoning District/Design Storm Requirement
Design Rainfall
Zoning Type Frequency
Open Land 2-year
Residential 10-year
Commercial 10-year
(p. 28, Table 1-3)
15074.01
6/7/16
Sacajawea Middle School; Post-Project SDI B
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.295 0.9 0.266
Landscaped Open Areas 0.748 0.2 0.150
Total 1.043 0.415
Weighted C Factor,Cwd 0.40
Calculate Developed Time of Concentration(T,:)
Channel Channel
Developed Conditions: road landscape road 6.43% 1.70%
S= 2.45% 8% 3.90% 0.2 0.2
C= 0.95 0.2 0.95 33 58
Overland Flow Distance,L= 23 76 59 V= 4.091297 V= 2.103681
From Figure I-1,TC= 4 7 2 T,= 0.134432 T,= 0.459512
Total T,= 13.59394361 mins. (overland flow)
or T.= 0.23 hrs.
Calculate Storm Intensity at T.
From Figure I-2,using the 25 year event,I=0.78*T�^(""
Intensity,I= 2.02 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 0.84 cfs
QT= SDI A+SDI B
QT= 1.66 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 12
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.005
Qom,(cfs)= 2.99
Qmax>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project SDI C
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(acres) C CYA
Impervious (roofs,parking) 0.168 0.9 0.151
Landscaped Open Areas 0.863 0.2 0.173
Total 1.031 0.324
Weighted C Factor,C«,d 0.31
Calculate Developed Time of Concentration(T J
Channel
Developed Conditions: landscape 1.60%
S = 10% 0.2
C= 0.2 209
Overland Flow Distance,L= 50 V= 2.040871
From Figure I-1,T,= 5 T,= 1.706788
Total T,= 6.706787812 mins. (overland flow)
or T,= 0.11 hrs.
Calculate Storm Intensity at Tc
From Figure I-2,using the 25 year event,I=0.78*Tc^(""'
Intensity,I= 3.17 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 1.03 cfs
QT= SDI A+ SDI B+SDI C
Qr= 2.69 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 12
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.005
Q.(cfs)= 2.99
Q .>Q•r= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project SDI D
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious(roofs,parking) 0.209 0.9 0.188
Landscaped Open Areas 0.090 0.2 0.018
Total 0.299 0.206
Weighted C Factor,CWd 0.69
Calculate Developed Time of Concentration(T.)
Channel
Developed Conditions: landscape N/A
S= N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure I-1,Tc= N/A T�= N/A
ASSUMED Total Tc= 5 mins.(overland flow)
or Tc= 0.08 hrs.
Calculate Storm Intensity at Tc
From Figure I-2,using the 25 year event,I=0.78*Tc^(_0.64)
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 0.79 cfs
QT= SDI D+SDI E+ROOF 3S+ROOF 3N
Q•r= 4.22 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 12
Mannin&Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.011
Q..(cfs)= 4.43
Q..>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project SDI E
Stormwater Runoff Calculations- 25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.183 0.9 0.165
Landscaped Open Areas 0.100 0.2 0.020
Total 0.283 0.185
Weighted C Factor,C vd 0.65
Calculate Developed Time of Concentration(T,)
Channel
Developed Conditions: landscape N/A
S= N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure I-1,Tc= N/A T,= N/A
ASSUMED Total T,= 5 mins. (overland flow)
or T.= 0.08 hrs.
Calculate Storm Intensity at Tc
From Figure I-2,using the 25 year event,I=0.78*Tc^("")
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 0.71 cfs
QT= SDI E+ROOF 3S
QT= 2.3 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 10
planning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.01
Qln,%(cfs)= 2.60
Q..>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project ROOF 3N
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious(roofs,parking) 0.327 0.9 0.294
Landscaped Open Areas 0.000 0.2 0.000
Total 0.327 0.294
Weighted C Factor,C,,,d 0.90
Calculate Developed Time of Concentration(T.)
Channel
Developed Conditions: landscape N/A
S = N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure I-1,Tc= N/A T,= N/A
ASSUMED Total T.= 5 rains. (overland flow)
or T,= 0.08 hrs.
Calculate Storm Intensity at T.
From Figure I-2,using the 25 year event,I=0.78*T,^(-0.64)
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 1.13 cfs
QT= ROOF 3N
QT= 1.13 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 8
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.0277
Q.(cfs)= 2.38
Q..>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project ROOF 3S
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.462 0.9 0.416
Landscaped Open Areas 0.000 0.2 0.000
Total 0.462 0.416
Weighted C Factor,C,,d 0.90
Calculate Developed Time of Concentration(TJ
Channel
Developed Conditions: landscape N/A
S= N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure I-1,T,= N/A T,= N/A
ASSUMED Total T.= 5 mins. (overland flow)
or Tc= 0.08 hrs.
Calculate Storm Intensity at T.
From Figure I-2,using the 25 year event,I=0.78*T�-(_"")
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 1.59 cfs
QT= ROOF 3S
QT= 1.59 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)— 8
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.02
Q..(cfs)= 2.03
Q..>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project ROOF 7
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.295 0.9 0.266
Landscaped Open Areas 0.000 0.2 0.000
Total 0.295 0.266
Weighted C Factor,Cwd 0.90
Calculate Developed Time of Concentration(T.)
Channel
Developed Conditions: landscape N/A
S= N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure I-1,T�= N/A Tc= N/A
ASSUMED Total Tc= 5 mins. (overland flow)
or T.= 0.08 hrs.
Calculate Storm Intensity at Tc
From Figure I-2,using the 25 year event,I=0.78*T�^(464)
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 1.02 cfs
QT= ROOF 7
QT= 1.02 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 8
Manning's Roughness Coefficient(n)= 0.011
Slope(F"I'/FT)= 0.0508
Q..(cfs)= 3.23
Q..>QT= TRUE
15074.01
6/7/16
Sacajawea Middle School; Post-Project 3 SIMILAR ROOF ADDITIONS
Stormwater Runoff Calculations-25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.094 0.9 0.085
Landscaped Open Areas 0.000 0.2 0.000
Total 0.094 0.085
Weighted C Factor,C,d 0.90
Calculate Developed Time of Concentration (T,)
Channel
Developed Conditions: landscape N/A
S = N/A N/A
C= N/A N/A
Overland Flow Distance,L= N/A V= N/A
From Figure 1-1,T�= N/A T,= N/A
ASSUMED Total T,= 5 mins. (overland flow)
or T.= 0.08 hrs.
Calculate Storm Intensity at T.
From Figure I-2,using the 25 year event,I=0.78*Tc^(-o.")
Intensity,I= 3.83 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 0.32 cfs
QT= INDIVIDUAL ROOF
QT= 0.32 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 6
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.02
Q..(Cfs)= 0.94
Qmas>QT= TRUE
Appendix B
Sacajawea Middle School
Stormwater Maintenance Plan
Type Maintenance Frequency
Dry Wells and Dry wells are to be cleaned and Annually or as
Stormwater Structures removed of sediment annually. Dry needed based on
wells are to be inspected after large inspection.
storm events to ensure they are still in
working order. If sediment has
accumulated in the structure after a
large storm event it should be cleaned
as soon as possible.
Detention Basin Basins are to be cleaned and removed Bi-Annually or as
of sediment bi-annually. Basins are to needed based on
be inspected after large storm events to inspection.
ensure they are still in working order.
If sediment has accumulated in the
structure after a large storm event it
should be cleaned as soon as possible.
15074.01
6/7/16
Sacajawea Middle School; Post-Project SDI A
Stormwater Runoff Calculations -25 year,24 hour Event
The following calculations were used to determine the amount of stormwater runoff based on
a 25-year,24-hour storm event.
Calculate Developed Runoff Coefficient
Area(Acres) C CxA
Impervious (roofs,parking) 0.412 0.9 0,371
Landscaped Open Areas 0.120 0.2 0.024
Total 0.532 0.395
Weighted C Factor,Cw d 0.74
Calculate Developed Time of Concentration(TJ
Developed Conditions: road landscape parking
S= 2.45% 9% 4.30%
C= 0.95 0.2 0.95
Overland Flow Distance,L= 23 77 59
From Figure I-1,TC= 4 7 2
Total T,= 13 mins. (overland flow)
or T,= 0.22 hrs.
Calculate Storm Intensity at Tc
From Figure I-2,using the 25 year event,I=0.78*T�^(0.64)
Intensity,I= 2.08 in/hr
Calculate Developed Peak Runoff Rate
Q25= CIA,using the above parameters
Q25= 0.82 cfs
QT= SDI A
QT= 0.82 cfs
Calculate Maximum Pipe Flow Rate
Pipe Diameter(in)= 10
Manning's Roughness Coefficient(n)= 0.011
Slope(FT/FT)= 0.0171
Qmax(cfs)= 3.40
Qmax"'QT= TRUE