HomeMy WebLinkAbout2012-1101 Terracon PubWksRpt
Geotechnical Engineering Report
Proposed Public Works Complex Additions
Iowa City, Iowa
November 1, 2012
Terracon Project No. 06125648.01
Prepared for:
City of Iowa City - Engineering Division
Iowa City, Iowa
Prepared by:
Terracon Consultants, Inc.
Iowa City, Iowa
November 1, 2012
City of Iowa City - Engineering Division
410 East Washington Street
Iowa City, Iowa 52240
Attn: Ms. Kumi Morris – Architectural Services Coordinator
P: 319-365-5044
F: 319-356-5077
E: kumi-morris@iowa-city.org
Re: Geotechnical Engineering Report
Proposed Public Works Complex Additions
Iowa City, Iowa
Terracon Project No. 06125648.01
Dear Ms. Morris:
Terracon Consultants, Inc. (Terracon) has completed the subsurface exploration and
geotechnical engineering services for the above referenced project. These services were
performed in general accordance with our Proposal No. P06120484 (Task 2) dated July 17,
2012. This geotechnical engineering report presents the results of the subsurface exploration
and provides geotechnical recommendations concerning earthwork and the design and
construction of foundations and floor slabs for the proposed structures, as well as the preparation
of pavement subgrades and recommended minimum pavement thicknesses.
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.
Bachan K. Sinha, P.E. Brian F. Gisi, P.E.
Project Engineer / Project Manager Iowa No. 16017
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Copies: Client (2)
Terracon Consultants, Inc. 783 Highway 1 West, Unit 5 Iowa City , Iowa 52246
P [3 19] 688 3007 F [3 19] 688 3008 terracon.com
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TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY ............................................................................................................. i
1.0 INTRODUCTION ............................................................................................................. 1
2.0 PROJECT INFORMATION ............................................................................................. 2
2.1 Project Description ........................................................................................................ 2
2.2 Site Location and Description ....................................................................................... 3
3.0 SUBSURFACE CONDITIONS ........................................................................................ 3
3.1 USDA NRCS Soil Mapping ........................................................................................... 3
3.2 Typical Subsurface Profile ............................................................................................ 3
3.3 Groundwater Conditions ............................................................................................... 4
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ...................................... 5
4.1 Geotechnical Considerations ........................................................................................ 5
4.1.1 Demolition Considerations ................................................................................ 6
4.1.2 Settlement from Site Grading ........................................................................... 6
4.1.3 Existing Fill ........................................................................................................ 6
4.1.4 Lower Strength Native Soils ............................................................................. 6
4.2 Site Preparation and Earthwork .................................................................................... 7
4.2.1 Excavation Considerations ............................................................................... 8
4.2.2 Fill Types and Compaction ............................................................................... 8
4.2.3 Compaction Requirements ............................................................................... 9
4.2.4 Grading and Drainage .................................................................................... 10
4.3 Spread Footings .......................................................................................................... 10
4.3.1 Design Recommendations ............................................................................. 10
4.3.2 Construction Considerations .......................................................................... 11
4.4 Crane Foundation (Public Works Area) ...................................................................... 12
4.4.1 Auger Cast Piles Design Parameters ............................................................. 13
4.4.2 Auger Cast Pile Construction Considerations ................................................ 14
4.4.3 Mat Foundation ............................................................................................... 14
4.4.4 Mat Foundation Design Recommendations ................................................... 15
4.5 Construction Adjacent to Existing Buildings ............................................................... 16
4.6 Seismic Considerations .............................................................................................. 16
4.7 Floor Slab .................................................................................................................... 17
4.7.1 Floor Slab Design Recommendations ............................................................ 17
4.7.2 Construction Considerations .......................................................................... 17
4.8 Subfloor Drainage (Below Grade Floors) ................................................................... 18
4.9 Lateral Earth Pressures – Below Grade Walls ........................................................... 18
4.10 Pavements .................................................................................................................. 20
4.10.1 Pavement Subgrades ................................................................................... 20
4.10.2 Pavement Design Recommendations .......................................................... 21
4.10.3 Pavement Design Considerations ................................................................ 22
4.10.4 Permeable Base & Longitudinal Subdrains .................................................. 23
4.11 Frost Considerations ................................................................................................... 23
5.0 GENERAL COMMENTS ............................................................................................... 24
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TABLE OF CONTENTS– continued
Exhibit No.
Appendix A – Field Exploration
Site Location Plan............................................................................................... A-1
Boring Location Plan .......................................................................................... A-2
Subsurface Soil Profile ....................................................................................... A-3
Boring Logs .............................................................................................. A-4 to A-9
Field Exploration Description ............................................................................ A-10
Boring Logs – Terracon Project No. 06995251 ..................................... A-11 to A-15
Appendix B – Laboratory Testing
Laboratory Test Description ................................................................................ B-1
Laboratory Compaction Test (Proctor) Result ..................................................... B-2
CBR Test Result ................................................................................................. B-3
Appendix C – Supporting Documents
General Notes .................................................................................................... C-1
General Notes – Sedimentary Rock Classification .............................................. C-2
Unified Soil Classification System ....................................................................... C-3
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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EXECUTIVE SUMMARY
A geotechnical exploration has been performed for the proposed Public Works Complex
Additions in Iowa City, Iowa. Terracon‟s geotechnical scope of work consisted of drilling and
sampling six (6) borings to depths ranging from about 10 to 70 feet below the existing site
grades.
Based on the results of this exploration, the following geotechnical issues were identified:
Special design and construction considerations will be required on this project due to
presence of existing fills and/or lower strength native soils at the site, demolition of
existing structures and utilities at various locations across the site, and additional fill
thicknesses required to achieve the planned finished grade elevations.
The proposed structures can be supported on conventional spread footing foundations
provided the bearing soils are evaluated by Terracon personnel and are prepared in
accordance with the recommendations in this report.
Due to anticipated foundation loads and in order to control total and differential
settlements in the lower strength site soils, we recommend the proposed crane structure
be supported on a either a deep foundation system of auger-cast piles or mat
foundation.
Existing fill materials were encountered in Borings B-204, 205, and 206 to depths of
about 3½ to 4½ feet and such materials should be anticipated at other locations also.
Due to the risks associated with support of the structure on the existing fill, we
recommend all foundations extend through the existing fill and bear either directly on
suitable, native deposits or new engineered fill following the overexcavation and backfill.
Lower strength native soils (loose sands) were encountered in the borings to depths
ranging from about 15 to 25 feet below the existing grades. It should be noted that
structures supported over lower strength soils would be at risk for greater than normal
settlements and the resultant distress. To reduce the potential for excessive total and
differential settlement of the foundations, designs incorporating lower bearing pressures
should be anticipated on this project.
The native sands exposed at the base of shallow foundations should be densified in
place to at least 98 percent of the material‟s standard Proctor maximum dry density or at
least 70 percent relative density using appropriate compaction equipment prior to
foundation construction.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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Based on existing grade elevations across the site, flood plain and adjacent river, and
depending on actual finished floor elevations, additional fill thicknesses on the order of 4
to 6 feet are anticipated on this project. In order to reduce the post-construction
settlements, we recommend settlements due to the weight of the new fill be allowed to
occur before proceeding with further construction. Therefore, new fill should be placed
as far in advance of construction as possible and allowed to settle as long as practical.
Based on the observed groundwater conditions and the anticipated finished grade
elevations, groundwater is not anticipated during construction of spread footing
foundations. However, it should be noted that perched water conditions may be
encountered during excavation of lower level. If encountered, groundwater should be
controlled to a depth of at least 2 feet below the excavation elevation. In addition, we
recommend that a subfloor drainage system be designed.
Construction of the foundation and 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 materials, and other
geotechnical conditions exposed during construction.
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
PROPOSED PUBLIC WORKS ADDITIONS
IOWA CITY, IOWA
Terracon Project No. 06125648.01
November 1, 2012
1.0 INTRODUCTION
This report presents the results of our subsurface exploration and geotechnical engineering
services performed for various structures for the proposed Public Works Complex Addition in
Iowa City, Iowa. The purpose of these services is to provide information and geotechnical
engineering recommendations relative to:
subsurface soil conditions groundwater conditions
foundation design and construction floor slab design and construction
site preparation and earthwork estimated seismic site classification
lateral earth pressures excavation considerations
pavement design and construction frost considerations
Terracon‟s geotechnical scope of work on this project consisted of drilling and sampling six (6)
borings across the site to depths ranging from about 15 to 70 feet below the existing site grades
where either the boring‟s designated terminations depth or practical auger/sampler refusal into
the underlying bedrock was achieved.
A Site Location Plan (Exhibit A-1), a Boring Location Plan (Exhibit A-2), a subsurface soil profile
(Exhibit A-3) and the boring logs (Exhibits A-4 through A-9) are included in Appendix A of this
report. The results of the laboratory testing performed on soil samples obtained from the site
during the field exploration are included on the boring logs of this report. Descriptions of the
field exploration and laboratory testing are included in their respective appendices.
Terracon performed subsurface exploration at this site in February 2000 for the existing Public
Works Facility (Terracon Project No. 06995251.01, Report dated February 18, 2000). The
information from this prior exploration was also considered in developing our recommendations
in this report. Selected boring logs from this previous project are included in Appendix A.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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2.0 PROJECT INFORMATION
2.1 Project Description
Item Description
Site layout Refer to the Boring Location Plan (Exhibit A-2, Appendix A)
Structures
The project will consist of construction of following structures:
Public Works Building - with parking area for city vehicles,
shops for Traffic Engineering, and Solid Waste parking and
storage
Equipment & Maintenance Division – includes a large crane to
move and service vehicles, trucks and buses
Fuel facility and canopy
Underground storage tanks
Warm Storage Building
Large Vehicle W ash area
Building construction
The project is in planning stage at this time and only limited
information was provided:
Steel frame and/or pre-cast load bearing exterior walls
Sheet metal or masonry veneer exterior panels
Slab-on-grade floors
Steel joists and metal deck roofs
Wood or steel frame pole barn (Warm Storage Building)
Finished floor elevation
Grading details and/or finished floor elevations are not finalized at
this time. We have assumed the finished floor elevations will be
within 4 feet of existing grade.
First floor: 650 to 652 feet (assumed)
Below grade areas: 635 to 640 feet (assumed)
100-year flood plain: 642.63 feet
500-year flood plan: 645.22 feet
Maximum loads
Columns: 150 kips
Columns with crane loads: 250 kips
Walls: 3 to 4 klf
Slabs: 250 psf
Site Grading
Cuts and fills thicknesses on the order of about 4 to 6 feet in
at-grade floor slab and pavement areas
Cuts on the order of 10 to 15 feet in basement and
underground storage tank areas
Below Grade Areas
Loading docks;
Underground storage tanks
Vehicle service pits (assumed)
Pavements Driveways, loading docks, truck aprons, and dumpster pads
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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2.2 Site Location and Description
Item Description
Location
The project site is surrounded by Napoleon Lane on north,
McCollister Boulevard on south, South Gilbert Street on
east, and the Iowa River on the west, in Iowa City, Iowa.
The site is located adjacent to the Iowa River.
Existing site features
Existing buildings (Public Works Office)
Salt shed, Storage buildings, and Pavements
Subsurface utilities (assumed)
Site topography
Site generally slopes downwards to the west, with surface
elevations ranging from about 636 to 666 feet
Majority of the proposed construction area has surface
elevation varying between from about 644 and 652 feet
Current ground cover Grass, trees and shrubs, pavements
3.0 SUBSURFACE CONDITIONS
3.1 USDA NRCS Soil Mapping
A review of the United States Department of Agriculture - Natural Resources Conservation Service
(USDA NRCS) Soil Survey of Johnson County, Iowa indicates that Sparta loamy fine sand,
Waukee loam, and Perks-Spillville complex soils are the primary soil types present at undisturbed
locations at or near the proposed construction area. These classifications are based on the USDA
textural soil classification system for approximately the upper 60 inches of the soil profile.
According to the Survey, the Perks-Spillville complex soils present severe limitations for building
construction activities due to shallow depths of saturated zones, flooding, and unstable excavation
walls characteristics associated with them.
3.2 Typical Subsurface Profile
Specific conditions encountered at individual boring locations are indicated on the attached boring
logs. Stratification boundaries on the boring logs represent the approximate location of changes in
material types. In-situ, the transition between native materials may be gradual. Based on the
results of this exploration, subsurface conditions on the site can be generalized as follows:
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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Description Approximate Depth to
Bottom of Stratum (feet) Material Encountered Consistency/Density
Surficial
4 to 12 inches
6 inches
Topsoil
(All except Boring B-203)
Asphalt/crushed limestone
(Boring B-203)
N/A
Stratum 1A
3½ to 4½
(Borings B-204, 205, and
206)
Existing fill materials primarily
composed of lean clay with
varying amounts of sand
NA
Stratum 1B
3 to 3½
(Borings B-201, 202, and
203)
Fine to medium sand with
varying amounts of clay
Very loose to medium
dense
(3 to 17)1
Stratum 2 8½ to 13 Silty fine to medium sand
Loose to medium
dense
(4 to 10)1
Stratum 3 152 to 26½ Fine to medium sand
Loose to medium
dense
(4 to 13)1
Stratum 3
28 to 303
(Borings B-201, 202, and
203)
Fine to coarse sand
Medium dense to very
dense
(12 to 50/3”)1
Stratum 44
25 to 69
(Borings B-201, 203, and
206)
Sandy lean clay, trace gravel
with occasional sand seams
(glacial till)
Very stiff to very stiff
Stratum 5 705
(Boring B-201)
Dolomite
(Boring B-201)
Highly weathered and
broken to sampler
refusal
1 Range of Standard Penetration Test (SPT) resistance values or “N-values”, blows per foot
2 Bottom of Boring B-204 and 205;
3 Bottom of Boring B-202;
4 Bottom of Borings B-203 and 206 at depths of about 30 and 25 feet, respectively;
5 Bottom of Boring B-201
3.3 Groundwater Conditions
The borings were observed for the presence and level of groundwater during and after drilling
operations. The borings were also left open for about one week for delayed water level
observations. After completion of the delayed groundwater measurements, the boreholes were
backfilled with on-site soils. The observed groundwater levels are presented in the following
table.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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WATER LEVEL OBSERVATIONS
Boring No. B-201 B-202 B-203 B-204 B-205 B-206
WD/WS (feet) NI 22½ 22 None None 23
DWL None None None None None None
Dry Cave-in 22½ 22 20 14 14 19
WD: While Drilling/Sampling; DWL: Delayed Groundwater Level measured on 10/22/2012;
The Soil Survey report was also reviewed for information relating to anticipated seasonally high
groundwater levels at this site. According to the Survey, the primary soil types (Sparta loamy fine
sand, Waukee loam, and Perks-Spillville complex soils) present at undisturbed locations across
the site are reported to have apparent seasonal high groundwater at depths of 6½ feet or more
below their original grades.
Fluctuations of the groundwater levels will likely occur due to seasonal variations in the amount
of rainfall, runoff, water level in adjacent river, and other factors not evident at the time the
borings were performed. Also, trapped or “perched” water could be present in the topsoil,
existing fills, sand seams, and/or higher permeability soils above lower permeability soil layers.
Significant quantities of perched water may be present in the topsoil and in the near surface
soils that have been loosened by freeze-thaw action, during wetter/cooler climatic conditions.
Therefore, groundwater levels during construction or at other times in future may be different
than the levels indicated on the boring logs. The possibility of groundwater level fluctuations
and perched water should be considered when developing the design and construction plans for
the project.
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION
4.1 Geotechnical Considerations
Based on the subsurface data and conditions encountered in our borings, it is our opinion that
the proposed structures can be supported on conventional spread footings.
Special design and construction considerations will be required on this project due to:
demolition of existing structures and utilities;
settlement from site grading;
existing fill materials;
lower strength native soils;
easily disturbed subgrade soils.
Further details are provided herein.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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4.1.1 Demolition Considerations
It is important that the demolition of the existing structure(s) and utilities at the site and other
improvements be performed with close observation and testing. Any unsuitable fill and lower
strength native materials should also be removed at this time. Grade supported slabs will likely
be supported on the new fill placed in the demolition excavations. The demolition contractor
should be aware of project requirements for backfilling so that removal of these fill materials and
replacement under controlled conditions is not necessary upon construction of the new
structure.
4.1.2 Settlement from Site Grading
Based on the limited information provided about the existing site grade elevations across the
site and anticipated finished floor elevations for the proposed structures, additional fill of
thickness on the order of 4 feet may be required at various locations at the site. Settlements
under the weight of new fill will vary across the site due to variations in the thickness of fill to be
placed, variations within the subsurface soil profile, and the quality of earthwork operations. In
order to reduce the post-construction settlements, we recommend settlements due to the weight
of the new fill be allowed to occur before proceeding with further construction. Therefore, new fill
should be placed as far in advance of construction as possible and allowed to settle as long as
practical. Settlement monuments should be placed in the deeper fill sections after the fill is
placed to monitor when primary settlements are essentially complete and foundation
construction can commence.
4.1.3 Existing Fill
Existing fill soils were encountered in Borings B-204, 205, and 206 to depths of about 3½ to 4½
feet and such materials may be encountered at other unexplored locations also. It should be
noted that structures supported over uncontrolled fills would be at risk for greater than normal
settlements and the resultant distress. Terracon recommends that all existing fill materials and
unsuitable soils be removed from below the proposed structure. All new foundations should
extend through the existing fill and bear either directly on suitable, native deposits or new
engineered fill following the overexcavation and backfill.
4.1.4 Lower Strength Native Soils
Lower strength native soils (loose sands) were encountered in all borings to depths ranging
from about 15 to 25 feet below the existing grades. It should be noted that structures supported
over lower strength soils would be at risk for greater than normal settlements and the resultant
distress. To reduce the potential for excessive total and differential settlement of the
foundations, designs incorporating lower bearing pressures should be anticipated on this
project. The native sands exposed at the base of shallow foundations should be densified in
place to at least 98 percent of the material‟s standard Proctor maximum dry density or at least
70 percent relative density using appropriate compaction equipment prior to foundation
construction.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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4.2 Site Preparation and Earthwork
Topsoil, surficial vegetation, existing fill materials, and any otherwise unsuitable materials
should be removed from the construction area. Wet or dry material should either be removed or
moisture conditioned and recompacted. Soft, dry, and/or lower strength soils should be removed
or compacted prior to placing new fill.
It is important that the demolition of the existing structure(s) and utilities at the site and other
improvements be performed with close observation and testing. We anticipate utility lines for
existing facilities at various locations at the site may be present in the proposed construction areas.
It has been our experience that poorly compacted backfill is commonly found around these utility
lines. Utility lines should be re-routed outside of the construction area whenever feasible. Whether
the utility lines are abandoned or not, any poorly compacted backfill above these lines should be
removed and replaced.
After rough grade has been established, the exposed subgrade should be proofrolled by the
contractor and test probed by Terracon. Proofrolling on clay subgrades could be accomplished
by using heavy, rubber-tired construction equipment or a tandem axle dump truck with a gross
weight in the range of about 20 to 25 tons, while in sandy soils, by using a vibratory drum roller
(gross weight of 10 tons or more). This surficial proofroll would help to provide a stable base for
the compaction of new structural fill, and delineates low density, soft, or disturbed areas that
may exist below subgrade level. Soft or loose areas should be undercut, moisture conditioned,
and recompacted or replaced with approved structural fill. Subgrade conditions should be
observed by Terracon during construction.
Corrective measures will probably be required to increase subgrade stability during subgrade
preparation, particularly if the subgrade soils are wet due to precipitation, exposed to frost
action, and/or subjected to repetitive construction traffic. The owner should budget for additional
costs to provide the required corrective measures. Based on our experience in soils of these
types, crushed stone thicknesses on the order of 1 to 2 feet could be required to stabilize
subgrade soils. A geotextile stabilization material could also be placed below the crushed stone
to help stabilize the subgrade soils. As an alternative, the unstable subgrade soils could be
undercut, scarified on-site, and compacted with moisture and density control in maximum 9-inch
loose lifts up to final subgrade elevation to provide a uniform thickness of well-compacted
material.
Based on the groundwater conditions observed in the borings, groundwater is not anticipated
within excavation depths for shallow foundations. However, it should be noted that perched water
conditions may be encountered during excavation of lower level. If encountered, groundwater
should be controlled to a depth of at least 2 feet below the excavation elevation. In addition, we
recommend that a subfloor drainage system be designed for below grade structures.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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Upon completion of grading, care should be taken to maintain the subgrade moisture content
prior to construction of grade supported floor slabs. Construction traffic over the completed
subgrade should be avoided to the extent practical. The site should also be graded to prevent
ponding of surface water on the prepared subgrades or in excavations. If the subgrade should
become frozen, desiccated, saturated, or disturbed, the affected material should be removed or
these materials should be scarified, moisture conditioned, and recompacted prior to slab
construction.
4.2.1 Excavation Considerations
All excavations should comply with the requirements of OSHA 29CFR, Part 1926, Subpart P,
"Excavations" and its appendices, as well as other applicable codes. This document states that
the excavation safety is the responsibility of the contractor. Reference to this OSHA requirement
should be included in the project specifications. Slope heights, slope inclinations and/or
excavation depths should in no case exceed those specified in local, state or federal safety
regulations, including current OHSA excavation and trench safety standards. If any excavations
extend to a depth greater than 20 feet, according to OHSA regulations, side slopes and/or
bracing must be designed by a professional engineer.
Due to presence of granular soils at the site, we recommend excavations be shored or braced
to maintain stability. The bracing or sheet piles should be designed to resist the lateral earth
pressures and would reduce the potential for caving or sloughing of these cohesionless soils.
Sloped excavations could be considered if the lateral extent would not impact adjacent utilities,
pavements or structures. Where poorly compacted variable fill materials are encountered,
flatter slopes than those required by OHSA could be required to maintain the st ability of the
excavation(s).
4.2.2 Fill Types and Compaction
New fill for the project should be low plasticity cohesive soil or approved granular material.
Granular fill should be used in overexcavations below foundation bearing elevations. Fill placed
in confined excavations such as utility trenches should consist of relatively clean and well-
graded granular material. This should provide for greater ease of placement and compaction in
confined areas where larger compaction equipment cannot be operated. The use of granular fill
in these isolated and potentially deeper excavations would reduce the potential for differential
settlement for the proposed structures‟ components.
Structural fill should meet the following material property requirements:
Fill Type 1 USCS Classification Acceptable Location for Placement
Low Plasticity
Cohesive2 CL-ML, CL General site grading fill below foundations and slabs.
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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Fill Type 1 USCS Classification Acceptable Location for Placement
Granular GW, GP, GM, GC
SW, SP, SM, SC General site grading fill below foundations and slabs.
Unsuitable MH, OL, OH, PT Green (non-structural) locations.
On-Site Soils SP, SM, SP-SC, CL
Most of the site soils consisting of inorganic sands
and lean clay soils, as encountered in the borings,
are suitable for reuse as structural fill.2,3
1. Structural fill should consist of approved materials that are free of organic matter and debris.
Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample
of each material type should be submitted to the geotechnical engineer for evaluat ion prior to use
on this site.
2. Low plasticity cohesive soils (CL, CL/ML) would have a liquid limit less than 45 and a plasticity
index of less than 23.
3. The surficial topsoil, organic matters, unsuitable materials in existing fills, and debris from removal
of existing structure and utilities should not be used as structural fill.
4.2.3 Compaction Requirements
Significant moisture conditioning of the site soils will likely be required if they are used as
structural fill. Appropriate laboratory tests, including Atterberg limits for cohesive soils and
standard Proctor (ASTM D698) tests should be performed on proposed fill materials prior to
their use as structural fill. Organic content tests should be performed on dark colored soils
and/or those that exhibit a noticeable odor. Further evaluation of any on-site soils or off-site fill
materials should be performed by Terracon prior to their use in compacted fill sections.
Recommended degree of compaction and moisture content criteria for structural fill materials
are shown in the following table:
Material Type and
Location
Per the Standard Proctor Test (ASTM D 698)
Minimum Compaction
Requirement (%)1
Range of Moisture Contents for
Compaction1
Minimum Maximum
Low Plasticity Cohesive
Beneath foundations 98 -2% +3%
Above foundations and
below floor slabs 95 -2% +3%
Granular2,3
Beneath foundations 98 -3% +3%
Above foundations and
below floor slabs 95 -3% +3%
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
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Material Type and
Location
Per the Standard Proctor Test (ASTM D 698)
Minimum Compaction
Requirement (%)1
Range of Moisture Contents for
Compaction1
Minimum Maximum
1. We recommend that structural fill be tested for moisture content and compaction during
placement. 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 as required until the specified moisture and compaction requirements are achieved.
2. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines
content, compaction comparison to relative density may be more appropriate. In this case,
granular materials should be compacted with reference to their relative density (ASTM D 4253
and D 4254).
3. Specifically, moisture levels should be maintained at levels satisfactory for compaction to be
achieved without the granular fill material bulking during placement or pumping when
proofrolled.
We recommend that fill be placed and compacted on stable subgrades in lifts of 9 inches or less
in loose thickness when heavy, self-propelled compaction equipment is used. Lift thickness
should be reduced to 4 inches in loose thickness when hand equipment (e.g., jumping jack,
vibratory plate compactor, etc.) is used. A vibrating smooth drum compactor should not be used
on clay soils. All new fill placement and compaction should be observed and tested by Terracon
personnel.
4.2.4 Grading and Drainage
Final surrounding grades should be sloped away from the structures on all sides. In addition,
roof drainage should be collected by a system of gutters and downspouts and transmitted by
pipe to the storm water drainage system or discharged a minimum of 10 feet away from the
structures. As an alternative, splash blocks may be used as long as the ground surface is
paved and slopes away from the structures.
4.3 Spread Footings
The proposed structures can be supported on conventional spread footing foundations provided
that the bearing soils are prepared in accordance with the recommendations in this report. The
new foundations should bear either on suitable native soils or compacted structural fill extending
to suitable native soils.
4.3.1 Design Recommendations
DESCRIPTION VALUE
Structure Type One to two story structures
Foundation Type Spread footings
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DESCRIPTION VALUE
Bearing Material Suitable native soils and/or properly compacted
structural fill extending to suitable native soils.
Net Allowable Bearing Pressure1 2,000 psf
Minimum Dimensions Columns: 30 inches
Load bearing walls: 16 inches
Minimum Embedment Depth Below Finished
Grade
42 inches - perimeter footings and other footings
in unheated areas
24 inches - interior footings in heated areas
Total Estimated Settlement2 1 inch
Estimated Differential Settlement ⅔ of total settlement
1. The net allowable soil bearing pressure is the pressure in excess of the minimum surrounding
overburden pressure at the design foundation base elevation.
2. The above settlement estimates also consider that adequate time is allowed for consolidation and
monitoring of the additional fill and underlying native soils prior to foundation construction.
Finished grade is defined as the lowest adjacent grade within five feet of the foundation for
perimeter (or exterior) footings and finished floor level for interior footings. The allowable
foundation bearing pressures apply to dead loads plus design live load conditions. The design
bearing pressure may be increased by one-third when considering total loads that include wind
or seismic conditions.
Footings, foundation walls, and masonry walls should be reinforced as necessary to reduce the
potential for distress caused by differential foundation movement. The use of joints at openings
or other discontinuities in masonry walls is recommended.
4.3.2 Construction Considerations
The subsurface soil conditions at and below the foundation bearing depths should be observed
and thoroughly tested by Terracon to confirm that the bearing soils are suitable for support of
the foundations. The excavations should be probed or otherwise sampled at each isolated
spread footing and at regular intervals along continuous footings.
Where existing fills, loose sands, or unsuitable materials are encountered, the excavations
should be extended deeper to suitable soils and the foundations could bear directly on these
soils at the lower level or on lean concrete backfill placed in the excavations. The foundatio ns
could also bear on properly compacted backfill extending down to the suitable soils.
Overexcavation for compacted backfill placement below foundations should extend laterally
beyond all edges of the foundations at least 8 inches per foot of overexcavat ion depth below
foundation base elevation. The overexcavation should then be backfilled up to the foundation
base elevation with well-graded granular material placed in lifts of 6 inches or less in loose
thickness and compacted to at least 98 percent of the material's maximum standard Proctor dry
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density (ASTM D698). Lateral widening is not required for overexcavations backfilled with lean
concrete. The overexcavation and backfill procedures are shown in the figures below.
Native sands exposed at the base of shallow foundations should be densified in place to at least
98 percent of the material‟s standard Proctor maximum dry density or at least 70 percent
relative density using appropriate compaction equipment prior to placement of reinforcing steel
in foundation excavations. The sands should be densified to a depth of at least 2 feet below
footing bearing elevation using hand-held dynamic compaction equipment (e.g., jumping jack).
The base of all foundation excavations should be free of water and loose or soft soils prior to
placement of reinforcing steel and concrete. If encountered, groundwater should be lowered
and controlled to a minimum depth of 2 feet below the excavation elevation. Should the soils at
the bearing level become disturbed, the affected soil should be stabilized or removed prior to
placement of concrete. Concrete should be placed as soon as possible after excavating to
minimize disturbance of bearing soils.
4.4 Crane Foundation (Public Works Area)
We recommend the heavily loaded crane structure be supported by either a deep foundation
system of auger-cast piles or reinforced concrete mat foundation with a soil improvement
method using aggregate piers that extend through lower strength sands to suitable native soils.
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4.4.1 Auger Cast Piles Design Parameters
Design parameters for auger cast-piles are provided in the following table.
DESIGN DATA SUMMARY (BASED ON BORING B-201)
Depth
(feet)
Allowable Compressive
Side Friction (psf)
Allowable Passive
Pressure (psf)***
Allowable End Bearing
Pressure (psf)
0 - 3½ * - - - - - - - - -
3½ - 8½ 150 – 400 800 – 2,000 - - -
8½ - 26 400 – 700 2,000 – 5,500 - - -
26 - 29 700 5,500 – 6,000 4,500
29 - 64 1,000 10,000 10,000
* Frost depth and groundwater depth assumed at 3½ feet;
*** If range of values is given for a specific layer, the value increases linearly with depth. Also assumes
tip of pile extends at least 1 diameter into the bearing stratum.
Highly weathered dolomite bedrock was encountered in the deeper boring (B-201) at a depth of
about 69 feet. Due to the potential for over drilling and resultant loss of ground, we recommend
the piles should not be designed to bear within 5 feet of the bedrock surface. Care should also
be taken so the piles are not “overdrilled” because this could result in loss of ground and
settlement at the surface.
Cobbles and boulders are commonly encountered in glacial deposits, and may be encountered
at this site during installation of drilled shaft foundations. Conventional drilling equipment (e.g.,
soil augers) may not be able to penetrate larger cobbles and boulders. Heavier duty rock
augers and/or core barrels will be required to penetrate larger cobbles and boulders, where
encountered.
In designing to resist uplift loading, ⅔ of the allowable side friction values provided for
compressive loading could be used along with the effective weight of the pile. Buoyant unit
weights of the soil and concrete should be used below the maximum water level in the
calculations. The auger-cast piles designed and constructed in accordance with the
recommendations of this report are anticipated to have post construction settlement on the order
of about less than 1 inch.
Group action for lateral resistance of piles should be taken into account when spacing is less
than 8 diameters (center to center), and design parameters for allowable passive resistance in
the direction of the load should be reduced in accordance with the following table.
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Pile Spacing (Diameters) Reduction Factors
8D 1.0
6D 0.7
4D 0.4
3D 0.25
It should be noted that the load capacities provided above are based on stresses induced in the
subsurface soils supporting the foundation. The structural capacity of the piles should be
checked to assure that they can safely accommodate the combined stresses that may be
induced by axial and lateral loads and overturning moments. The response of deep foundations
to lateral loads is not only dependent upon the material‟s horizontal subgrade reaction, but also
on the pile actual cross sectional features, effective length, stiffness, and fix-head or free-head
conditions. Upon request, we would be pleased to provide consultation to this regard.
4.4.2 Auger Cast Pile Construction Considerations
The auger-cast piles (12 to 18 inches in diameter) are constructed by extending continuous
hollow-stem augers to a predetermined depth and then pumping a fluid cement grout under
pressure through the center of the hollow shaft as the augers are withdrawn, leaving a
continuous concrete pile. Care should be taken during auger-cast pile installation because of
the potential water-bearing soil deposits and possibility of gravels and cobbles in the fine to
coarse sands and glacial till soils. The augers should be withdrawn slowly, and the grout
volume and grout pressure should be monitored by a geotechnical engineer on a full-time basis
during construction.
Care should also be taken so that the auger-cast piles are not “overdrilled”, as this could result in
loss of ground and settlement at the surface. We recommend a deep foundation contractor
experienced with the local site conditions be used on this project. At the time of the construction
of auger-cast piles, observation by Terracon personnel is recommended to ensure that proper
installation procedures are performed.
4.4.3 Mat Foundation
As an alternative to deep foundation system, the proposed crane structure could be supported
on reinforced concrete mat foundation with a soil improvement method such as “Geopier®,
Rammed Aggregate Piers”, “Vibro-Replacement Stone Columns®”, or other similar aggregate
pier systems that extend through lower strength sands to suitable native soils. These soil
improvement systems are proprietary systems designed by licensed contractors who could
provide further information regarding these support options. Reinforcement could be added to
the stone columns for additional uplift resistance.
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Typically, foundations supported on aggregate pier improved soils can be designed with net
allowable bearing pressures ranging from 3,000 to 6,000 psf. The design bearing pressure is
provided by the aggregate pier designer/installer. Due to the specialty of this soil improvement
procedure, we recommend that a performance specification be used for this system. We would
be pleased to provide additional information upon request.
4.4.4 Mat Foundation Design Recommendations
DESCRIPTION VALUE
Foundation type Reinforced concrete mat foundation
Foundation bearing material Site soils improved by aggregate piers
Net allowable bearing/contact pressure 3,000 to 6,000 psf - Aggregate Pier Option1
Minimum embedment depth below finished grade 48 inches
Total estimated settlement 1 inch1
Estimated differential settlement ⅔ of total settlement.
1 To be provided by the Aggregate Pier contractor
The net allowable bearing pressure could be increased by 33% for resistance to transient
loading such as that due to wind. Finished grade is defined as the lowest adjacent grade within
five feet of the foundation. The allowable foundation bearing pressures apply to dead loads plus
design live load conditions. The weight of the foundation concrete below grade may be
neglected in dead load computations.
Foundations that cannot tolerate movement from frost action should be designed with a
minimum embedment depth of at least 3½ feet from the lowest exterior grade. As an
alternative, foundations could be supported on a layer of properly compacted, non-frost
susceptible, granular materials that extend below frost depth to minimize frost action movement.
Lateral loading on the mat foundation may be resisted by the passive pressure of the soil acting
against the sides of the foundation and friction developed at base of the foundation. For
foundations placed on properly compacted backfill, the allowable passive earth pressure may be
taken as the equivalent to a fluid weight of 145 pcf above the groundwater table and 70 pcf
below the groundwater table for lean clay soils. An ultimate coefficient of friction of 0.35 could
be used for foundations placed on native soils. The ultimate coefficient of friction could be
increased to 0.5 if crushed stone is used as backfill below the mat foundation. Passive pressure
should be ignored in the upper 3½ feet due to the potential effects of frost. These values were
developed from the subsurface material encountered at the site and are, in part, based on the
assumption that the foundation can withstand minor horizontal movement.
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Uplift resistance of the foundation can be developed from the weight of the overlying soils and
from the weight of the structure itself. The soil uplift resistance may be calculated as the weight
of the soil prism defined by a diagonal line drawn from the top of the foundation to the ground
surface at an angle of 20° from vertical. The maximum allowable uplift capacity should be taken
as a sum of the weight of the soil plus the weight of the foundation divided by an appropriate
factor of safety. A total unit weight of 115 and 55 pcf could be used at this site above and below
the groundwater level, respectively. Buoyant unit weights of the soil and concrete should be
used to calculate uplift resistance below the groundwater level.
4.5 Construction Adjacent to Existing Buildings
Some of the structures/additions on the project are expected to be located close to existing
facilities. Differential settlement between the new structure/addition and the existing structures
are expected to approach the magnitude of the total settlement of the new structure/addition.
Expansion joints should be provided between the existing and proposed structures to
accommodate differential movements between the two structures. Underground piping between
the two structures should be designed with flexible couplings and utility knockouts in foundation
walls should be oversized, so minor deflections in alignment do not result in breakage or
distress. Care should be taken during any excavation adjacent to existing foundations, so as
not to disturb any existing foundation bearing soils.
New footings should bear at or near the bearing elevation of any immediately adjacent existing
foundation. Depending upon their locations and current loads on the existing footings, footings
for the new addition could cause settlements of adjacent walls. To reduce this concern and risk,
clear distances at least equal to the new footing widths should be maintained between the
addition‟s footings and footings supporting the existing building.
4.6 Seismic Considerations
DESCRIPTION VALUE
2006 International Building Code Site Classification (IBC) 1 D2
Site Latitude N 41° 37.8‟
Site Longitude W 91° 31.8‟
1 Note: In general accordance with the 2006 International Building Code, Table 1613.5.2. IBC Site Class is
based on the average characteristics of the upper 100 feet of the subsurface profile.
2 Note: The 2006 International Building Code (IBC) requires a site soil profile determination extending to a
depth of 100 feet for seismic site classification. The current scope does not include the required 100 foot soil
profile determination. The borings were extended to a maximum depth of about 70 feet, and this seismic site
class definition considers that highly weathered dolomite (bedrock) continues below the maximum depth of the
exploration. Additional exploration to deeper depths or seismic velocity testing is recommended to confirm the
conditions below the current depth of exploration.
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4.7 Floor Slab
4.7.1 Floor Slab Design Recommendations
DESCRIPTION VALUE
Interior floor system Slab-on-grade Portland cement concrete.
Floor slab support1
Minimum 6 inches of free-draining (less than 6% passing the
U.S. No. 200 sieve) crushed aggregate;
At least 18 inches of low plasticity cohesive soil or granular
soil (with at least 18% passing the U.S. No. 200 sieve) should
be present where existing fills are encountered.
Unheated areas subject to frost Minimum of 3½ feet of clean (less than 6% passing the U.S.
No. 200 sieve) material below slabs.
Modulus of subgrade reaction
100 pounds per square inch per inch (psi/in). The modulus
was obtained based on our experience with similar subgrade
conditions.
1 The 6 inch thick crushed aggregate could be used as part of the 18 inches of low plasticity soils.
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 360 for procedures and cautions regarding the
use and placement of a vapor retarder.
Any unsuitable subgrade materials observed during construction should be overexcavated and
replaced with new structural fill. Frequent control joints are recommended in the floor slabs to
help control cracking due to variable thicknesses of new fill across the site. A higher than
normal percentage of steel reinforcement should be considered in floor slabs to provide
additional strength and help control crack displacement. A high modulus geogrid (e.g. Tensar
TriAx TX 140) placed between the subgrade and base course could also be used to improve the
degree and uniformity of subgrade support.
Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other
construction objectives, our experience indicates that any differential movement between the
walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks that
occur beyond the length of the structural dowels. The structural engineer should account for
this potential differential settlement through use of sufficient control joints, appropriate
reinforcing or other means.
4.7.2 Construction Considerations
The floor slab subgrade should be prepared in accordance with Section 4.2 (Site Preparation
and Earthwork) of this report. Care should be taken to maintain the subgrade moisture content,
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Proposed Public Works Additions ■ Iowa City, Iowa
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prior to construction of the floor slabs. If the subgrade should become desiccated, the affected
material should be removed or these materials should be scarified, moistened, and
recompacted prior to floor slab placement. The new fills for floor slab support be placed as far
in advance of slab construction as possible to allow settlement of the underlying soils from the
weight of the new structural fill, and thereby, reduce post-construction total and differential
settlements.
Where practical, we recommend “early-entry” cutting of crack-control joints in floor slabs.
Cutting of the concrete in its „green” state typically reduces the potential for micro-cracking of
the slabs prior to the crack control joints being formed, compared to cutting the joints after the
concrete has fully set. Micro-cracking of slabs may lead to crack formation in locations other
than the sawed joints, and/or reduction of fatigue life of the slabs.
4.8 Subfloor Drainage (Below Grade Floors)
We recommend a subfloor drain system be constructed beneath any below grade floors. The
subfloor drain system should consist of a network of perforated, rigid plastic or metal drain lines
with a minimum diameter of 4 inches and spaced no more than 30 feet apart. The perimeter
drain discussed below in Section 4.9 (Lateral Earth Pressure – Blow Grade Walls) could be
included in this spacing. The invert of these drain lines should be at least 12 inches below the
floor slab subgrade elevation. These drain lines should be surrounded by at least a 6-inch
annulus of granular material (i.e., IDOT 4131) graded to facilitate drainage and prevent the
intrusion of fines. The drain lines should be sloped to provide positive gravity drainage to a
sump pit and pump. At least 6 inches of free-draining well-graded granular material (i.e., IDOT
4121) should be placed beneath the floor slab area and should be hydraulically connected to
the granular material surrounding the drainage pipes. We recommend that floor slab subgrades
be crowned at least 0.5 percent to promote the flow of water towards the subdrains, and to
reduce the potential for ponding of water on the subgrade.
4.9 Lateral Earth Pressures – Below Grade Walls
Reinforced concrete below-grade walls with unbalanced backfill levels on opposite sides should
be designed for earth pressures at least equal to those indicated in the following table. Earth
pressures will be influenced by structural design of the walls, conditions of wall restraint,
methods of construction and/or compaction and the strength of the materials being restrained.
Two wall restraint conditions are shown. The "at-rest" condition assumes no wall movement.
The recommended design lateral earth pressures do not include a factor of safety and do not
provide for possible hydrostatic pressure on the walls.
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EARTH PRESSURE COEFFICIENTS
Earth
Pressure
Condition
Coefficient for Backfill Type
Equivalent
Fluid Density
(pcf)
Surcharge
Pressure, p1
(psf)
Earth
Pressure, p2
(psf)
At-Rest
(Ko)
Granular - 0.50
Sandy Lean Clay - 0.53
Lean Clay - 0.60
60
64
72
(0.50)S
(0.53)S
(0.60)S
(60)H
(64)H
(72)H
Passive
(Kp)
Granular - 3.0
Sandy Lean Clay - 2.77
Lean Clay - 2.40
360
332
285
---
---
---
---
---
---
Applicable conditions to the above include:
For active earth pressure, wall must rotate about base, with top lateral movements of
about 0.002 H to 0.004 H, where H is wall height,
For passive earth pressure to develop, wall must move horizontally to mobilize
resistance,
Uniform surcharge, where S is surcharge pressure,
In-situ soil backfill weight a maximum of 120 pcf,
Horizontal backfill, compacted between 95 and 98 percent of standard Proctor maximum
dry density,
Loading from heavy compaction equipment not included,
No hydrostatic pressures acting on wall,
No dynamic loading,
No safety factor included in soil parameters,
Ignore passive pressure in frost zone.
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Backfill placed against walls should consist of granular soils or low plasticity cohesive soils. For
the granular values to be valid, the granular backfill must extend out from the base of the wall at
an angle of at least 45 and 60 degrees from vertical for the active /at-rest and passive cases,
respectively. To calculate the resistance to sliding, a value of 0.35 should be used as the
ultimate coefficient of friction between the foundation and the underlying soil.
Heavy construction equipment should not operate within a distance closer than the exposed
height of retaining walls to prevent lateral pressures greater than those provided. Backfill
placed in non-structural areas adjacent to the walls should be placed in thin lifts and compacted
using hand-operated equipment to at least 95 percent, but no more than 100 percent, of the
material‟s maximum standard Proctor dry density (ASTM D 698).
A perforated rigid drain line installed at the foundation level behind the base of walls extending
below adjacent grade is recommended to prevent hydrostatic loading on the walls. The drain
line should be sloped to provide positive gravity drainage and should be surrounded by free
draining granular material graded to prevent the intrusion of fines, or an alternative free draining
granular material encapsulated with suitable filter fabric. At least a 2 foot wide section of free
draining granular fill should be used for backfill above the drain line and adjacent to the wall and
should extend to within 2 feet of final grade. In unpaved areas, the granular backfill should be
capped with compacted cohesive fill to minimize infiltration of surface water into the drain
system. A prefabricated drainage structure may be used above a drain line as an alternative to
free draining granular fill. A prefabricated drainage structure is a plastic drainage core or mesh
which is covered with filter fabric to prevent soil intrusion, and is fastened to the wall prior to
placing backfill. The undrained earth pressure parameters should be used if provisions for
drainage are not provided.
4.10 Pavements
4.10.1 Pavement Subgrades
The subgrade for pavements should be prepared in accordance with Section 4.2 (Site
Preparation and Earthwork) of this report. In addition to the scarification and compaction
recommended, we recommend the exposed subgrade be proofrolled. This surficial proofroll would
help to provide a stable base for the compaction of new structural fill, and delineates low density,
soft, or disturbed areas that may exist below subgrade level. Unsuitable material encountered
below subgrade level should be further undercut and replaced with structural fill. Due to the
presence of existing fill on this site and in order to reduce the owner‟s risk of adverse pavement
performance, as a minimum, the upper 1 foot of subgrade material should be compacted to at least
98 percent of the material‟s maximum dry density as determined by ASTM D698.
If there is a delay between subgrade preparation and paving, the pavement subgrades should
be carefully re-evaluated as the time for pavement construction approaches. Within a few days
of the scheduled paving, we recommend the pavement areas be proofrolled again with a loaded
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tandem axle dump truck (gross weight of 20 to 25 tons) in the presence of Terracon personnel.
Particular attention should be given to the areas that were rutted and disturbed earlier during
construction operations and frequent movement of construction equipment. Areas where
unsuitable conditions exist should be repaired by removing and replacing the materials with
properly compacted fill.
4.10.2 Pavement Design Recommendations
Traffic load information was not available at the time of this report; therefore, a formal pavement
design is not provided. Some typical pavement sections are provided below. Asphaltic cement
concrete pavement thicknesses are based on the Asphalt Paving Association of Iowa (APAI)
Asphalt Paving Design Guide and local design practice. Portland cement concrete thicknesses
are from the American Concrete Institute (ACI) ACI 330R-08 – Guide for the Design and
Construction of Concrete Parking Lots. Thickness recommendations for Passenger Vehicle
Parking sections are based on light passenger vehicle (gross weight less than 4 tons) traffic
only, and only occasional truck traffic such as snow removal trucks (APAI Class II, ACI Traffic
Category A). As part of the layout design of the project we recommend the designer use signs
and preventive structures to restrict heavy truck traffic from entering these areas. The Main
Drives & Truck Access sections are based on less than assumed traffic of 25 trucks per day
(APAI Traffic Class III, ACI Traffic Category B).
As a minimum, we suggest the following typical pavement sections be considered.
Traffic Area Alternative
Recommended Pavement Section Thickness1 (inches)
Asphaltic
Cement
Concrete3
Portland
Cement
Concrete
Aggregate
Base
Course4
Total
Passenger Vehicle
Parking (Vehicles less
than 4 tons)
A --- 5 - -5 5
B 4 --- 6 10
Driveways, heavy
vehicles movement
areas, and Delivery
Truck Access2
A --- 6 - -5 6
B 6 --- 6 12
1. All materials should meet the current Iowa Department of Transportation (IDOT) Standard
Specifications for Highway and Bridge Construction.
Asphaltic Surface - IDOT Type A Asphaltic Cement Concrete: Section 2303
Asphaltic Base - IDOT Type B Asphaltic Cement Concrete, Class I: Section 2303
Concrete Pavement - IDOT Portland Cement Concrete Type C: Section 2301
2. In areas of anticipated heavy vehicles, fire trucks, delivery trucks, or concentrated loads (e.g.
dumpster pads), and areas with repeated turning or maneuvering of heavy vehicles, a minimum
concrete thickness of 7 inches is recommended but should be evaluated further when loading
conditions are known.
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3. A minimum 1.5 inch surface course should be used on ACC pavements.
4. The granular base course materials (if used) should be placed on a stable subgrade and
compacted to at least 98 percent of the materials Standard Proctor maximum dry density.
5. A 4 inch (or greater) granular base should be considered below PCC pavements to help reduce
potential for slab curl, shrinkage cracking, and subgrade “pumping” through joints, unless the
subgrades are stabilized with hydrated lime or Class C fly ash.
The estimated pavement sections provided in this report are minimums for the assumed design
criteria, and as such, periodic maintenance should be expected. Areas for parking of heavy
vehicles, concentrated turn areas, and start/stop maneuvers could require thicker pavement
sections. Edge restraints (i.e. concrete curbs or aggregate shoulders) should be planned along
curves and areas of maneuvering vehicles. A maintenance program that includes surface
sealing, joint cleaning and sealing, and timely repair of cracks and deteriorated areas will
increase the pavement‟s service life. As an option, thicker sections could be constructed to
decrease future maintenance.
All concrete for rigid pavements should have a minimum 28-day compressive strength of 4,000
psi, and be placed with a maximum slump of 4 inches. Although not required for structural
support, a minimum 4 inch thick base course layer is recommended to help reduce potential for
slab curl, shrinkage cracking, and subgrade “pumping” through joints. Proper joint spacing will
also be required to prevent excessive slab curling and shrinkage cracking. All joints should be
sealed to prevent entry of foreign material and dowelled where necessary for load transfer.
Where practical, we recommend “early-entry” cutting of crack-control joints in Portland cement
concrete pavements. Cutting of the concrete in its „green” state typically reduces the potential
for micro-cracking of the pavements prior to the crack control joints being formed, compared to
cutting the joints after the concrete has fully set. Micro-cracking of pavements may lead to
crack formation in locations other than the sawed joints, and/or reduction of fatigue life of the
pavement.
4.10.3 Pavement Design Considerations
Long term pavement performance will be dependent upon several factors, including pavement
and subgrade thicknesses, maintaining subgrade moisture levels and providing for preventive
maintenance. The following recommendations should be considered the minimum:
Site grading at a minimum 2% grade away from the pavements,
PCC joint spacing and reinforcement per ACI 330R-08,
The subgrade and the pavement surface have a minimum ¼ inch per foot slope to
promote proper surface drainage,
Consider appropriate edge drainage systems,
Install joint sealant and seal cracks immediately,
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Seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture
migration to subgrade soils,
Placing compacted, low permeability backfill against the exterior side of curb and gutter,
Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of base
course materials.
Preventive maintenance should be planned and provided for through an on-going pavement
management program. Preventive maintenance activities are intended to slow the rate of
pavement deterioration, and to preserve the pavement investment. Preventive maintenance
consists of both localized maintenance (e.g. crack and joint sealing and patching) and global
maintenance (e.g. surface sealing). Preventive maintenance is usually the first priority when
implementing a planned pavement maintenance program and provides the highest return on
investment for pavements. Prior to implementing any maintenance, additional engineering
observation is recommended to determine the type and extent of preventive maintenance.
4.10.4 Permeable Base & Longitudinal Subdrains
Due to presence of frost susceptible soils at site and in order to prolong the service of life of the
pavements, consideration could be given to installing longitudinal shoulder subdrains and
permeable base below the pavements. A permeable base will help prevent infiltrated surface
water from ponding beneath pavements and softening the pavement subgrade. Longitudinal
subdrains should drain the permeable base and help increase the overall roadbed stability and
decrease the potential for frost heave.
A permeable granular base should consist of a minimum 6 inch thickness of coarse, well-graded
free-draining granular material meeting IDOT Specifications 4121 (Gradation No. 12), 4123
(Gradation No. 14), or 4132 (Gradation No. 30). Longitudinal subdrains should be extended a
minimum of 4 feet below pavement subgrade and should be backfilled with free-draining,
granular material meeting IDOT Specification 4131 (Gradation No. 29). The subdrain lines
should be perforated and placed near the base of the excavation and surrounded with at least 6
inches of the drainage material. The drains should be hydraulically connected with the
permeable base and sloped to provide positive gravity drainage to a reliable discharge point.
The Longitudinal drains should be constructed in accordance with IDOT Standard Road Plan
RF-19C.
4.11 Frost Considerations
The soils on this site are frost susceptible, and small amounts of water can affect the
performance of the slabs on-grade, sidewalks and pavements. Exterior slabs should be
anticipated to heave during winter months. If frost action needs to be eliminated in critical
areas, we recommend the use of non-frost susceptible structural or structural slabs (e.g.,
structural stoops in front of building doors). Placement of non-frost susceptible material in large
Geotechnical Engineering Report
Proposed Public Works Additions ■ Iowa City, Iowa
November 1, 2012 ■ Terracon Project No. 06125648.01
Responsive ■ Resourceful ■ Reliable 24
areas may not be feasible; however, the following recommendations are provided to help
reduce potential frost heave:
Providing surface drainage away from the building and slabs and toward the site
storm drainage system
Installing drain tiles around the perimeter of the building, stoops, below exterior slabs
and pavements, and connect them to the storm drainage system
Grading clayey subgrades such that groundwater potentially perched in overlying
more permeable subgrades, such as sand or aggregate base, toward the site
drainage system
Placing non-frost susceptible fill as backfill beneath slabs and pavements that are
critical to the project
Placing a 3 horizontal to 1 vertical (3H: 1V) transition zone between non -frost
susceptible soils and other soils
Placing non-frost susceptible materials in critical sidewalk areas
As an alternative to extending the non-frost susceptible fill to the full frost depth, consideration
can be made to placing extruded polystyrene or cellular concrete under a buffer of at least 2 feet
of non-frost susceptible fill.
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.
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.
Support of floor slabs and pavements on or above existing fill soils is discussed in this report.
However, even with the recommended construction testing services, there is an inherent risk for
the owner that compressible fill or unsuitable material within or buried by the fill will not be
discovered. This risk of unforeseen conditions cannot be eliminated without completely
removing the existing fill, but can be reduced by performing additional testing and evaluation.
Geotechnical Engineering Report
Proposed Public Works Additions Ŷ Iowa City, Iowa
November 1, 2012 Ŷ Terracon Project No. 06125648.01
Responsive Ŷ Resourceful Ŷ Reliable 25
The scope of services for this project does not include either specifically or by implication any
environmental or biological (e.g., 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 express 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.
I hereby certify that this engineering document was prepared by me or
under my direct personal supervision and that I am a duly licensed
Professional Engineer under the laws of the State of Iowa.
_________________ ____________11/1/2012___________
Brian F. Gisi, P.E. Date
My license renewal date is December 31, 2013.
APPENDIX A
FIELD EXPLORATION
NORTHAPPROXIMATE DRAWING SCALE01600'Drawn By:Project Mngr:File Name:Layout Name:Project No.EXHIBIT #Date:SITE LOCATION PLANBKSPC0612564806125648-01.dwgOCT 2012A-1IOWA CITY PUBLIC WORKS SITE FACILITYCITY OF IOWA CITYSOUTH OF NAPOLEON LANE AND EAST OF IOWA RIVERIOWA CITY, IOWASITE LOCATIONConsulting Engineers and Scientists783 HIGHWAY 1 WESTIOWA CITY, IOWA 52246FAX. (319) 688-3008PH. (319) 688-3007THIS DRAWING IS INTENDED FOR GENERAL LOCATIONPURPOSES ONLYBASE DRAWING FROM GOOGLE MAPSPROJECT LOCATION
B-3B-13B-4B-5B-6B-2B-7B-8B-9B-10B-11B-12B-16B-15B-14B-17B-18B-19B-23B-22B-21B-20B-24B-25B-28B-29B-30B-26B-27B-31B-37B-36B-34B-35B-33B-32B-1B-101B-104B-102B-103B-201B-203B-205B-206B-204B-202EL = 648.0EL = 648.0EL = 648.0EL = 649.0EL = 651.0EL = 649.0EL = 648.0EL = 648.0EL = 647.5EL = 648.5NORTHAPPROXIMATE DRAWING SCALE0150'Drawn By:Project Mngr:File Name:Layout Name:Project No.EXHIBIT #Date:BORING LOCATION PLANBKSPC0612564806125648-01.dwgOCT 2012A-2IOWA CITY PUBLIC WORKS SITE FACILITYCITY OF IOWA CITYSOUTH OF NAPOLEON LANE AND EAST OF IOWA RIVERIOWA CITY, IOWABORING LOCATION- PROPOSED ANIMAL SHELTER BORING LOCATION- PROPOSED PUBLIC WORKS BORING LOCATION- APPROXIMATE BORING LOCATION 06995251-01- APPROXIMATE FOOTPRINT PROPOSED ANIMAL SHELTERTHIS DRAWING IS INTENDED FOR GENERAL LOCATION PURPOSES ONLYBASE DRAWING FROM PDF 'Terracon_RFP' AND 'SitePlan_2012-10-09pdf.pdf' RECEIVED FROMNEUMANN MONSON ARCHITECTSConsulting Engineers and Scientists783 HIGHWAY 1 WESTIOWA CITY, IOWA 52246FAX. (319) 688-3008PH. (319) 688-3007
570
580
590
600
610
620
630
640
650
660
570
580
590
600
610
620
630
640
650
660
5
5
6
9
13
13
20
18
13
22
11
13
12
12
13
9
27
28
BT-70
N=17
N=4
N=7
N=11
N=12
N=8
N=10
N=13
N=17
N=23
N=25
N=39
N=24
N=25
N=50/5"
N=50/5"
201
%w 5
4
5
5
6
6
17
15
BT-30
N=12
N=5
N=6
N=7
N=10
N=4
N=6
N=12
202
%w
6
6
6
11
8
8
13
11
BT-30
N=3
N=4
N=9
N=8
N=12
N=7
N=50/3"
N=33
203
%w
15
9
9
9
6
BT-15
N=8
N=8
N=8
N=7
204
%w
20
10
10
9
5
BT-15
N=7
N=10
N=8
N=10
205
%w
8
7
6
5
3
15
17 BT-25
N=7
N=10
N=8
N=6
N=13
N=14
206
%w
X
Water Level Reading
at time of drilling.
Water Level Reading
after drilling.
Soils between borings may differ.
Borehole
LithologySampling
South of Napoleon Lane
City of Iowa City
A-3
See Figure A-2 for orientation of soil profile.
GENERALIZED SOILS PROFILE
Iowa City , Iowa
ENGINEER:BKS
PROJECT:
Public Works Complex Additions
AR - Auger Refusal
BT - Boring Termination
CT - Coring TerminationElevation Distance Along Baseline
Public Works Complex Additions
Explanation
201
%wMoisture
Content LL PL Liquid and Plastic Limits
Borehole
Number
NOTES:
See Boring Legend in Appendix A for symbols and soil classifications.
Soils profile provided for illustration purposes only.
Y
AR
BT
CT
Exhibit06125648
Borehole
Termination Type
11X17 TWS FENCE 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12
3.0
8.5
26.0
29.0
4" Topsoil
FINE TO MEDIUM SAND WITH CLAY (SP-SC)
trace organics, dark brown, medium dense
SILTY FINE TO MEDIUM SAND (SM)
brown gray, loose
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown gray, loose to medium dense
cobbles @ about 24 feet
FINE TO COARSE SAND (SP)
trace clay and gravel
brown, medium dense
SANDY LEAN CLAY (CL)
trace gravel with occasional sand seams
gray, very stiff to hard
18
18
15
15
10
12
8
15
3
5
5
6
9
13
13
20
18
13
22
12-10-7
N=17
3-2-2
N=4
2-3-4
N=7
4-6-5
N=11
5-6-6
N=12
3-4-4
N=8
7-5-5
N=10
7-6-7
N=13
5-7-10
N=17
646
640.5
623
620 HP
HP
2.50
3.00
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/16/2012
Drill Rig: 83e Driller: MW
A-4
Boring Started: 10/16/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Hollow-stem auger to 10½', then
mud-rotary to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
No water observed prior to mud-rotary.
Dry cave in @ 22.3' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 2
SITE:
BORING LOG NO. 201
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 649 DEPTH (ft)5
10
15
20
25
30
35
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
69.0
70.0
SANDY LEAN CLAY (CL)(continued)
trace gravel with occasional sand seams
very stiff to hard
Sampler refusals denote possibilty of cobbles
HIGHLY WEATHERED & BROKEN DOLOMITE
gray, Practical roller-bit refusal at about 70 feet.
Boring Terminated at 70 Feet
16
3
16
17
16
11
11
13
12
12
13
9
27
28
5-9-14
N=23
7-10-15
N=25
6-10-29
N=39
5-10-14
N=24
5-9-16
N=25
N=50/5"
N=50/5"580
579
HP
HP
HP
HP
HP
3.50
3.50
4.50
4.50
4.50
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/16/2012
Drill Rig: 83e Driller: MW
A-4
Boring Started: 10/16/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Hollow-stem auger to 10½', then
mud-rotary to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
No water observed prior to mud-rotary.
Dry cave in @ 22.3' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 2 of 2
SITE:
BORING LOG NO. 201
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 649 DEPTH (ft)40
45
50
55
60
65
70
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
3.5
12.5
26.5
30.0
4" Topsoil / Root Zone over
6" Crushed Limestone
FINE TO MEDIUM SAND WITH CLAY (SP-SC), trace
organics, dark brown to medium dense
SILTY FINE TO MEDIUM SAND (SM)
brown, loose
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown, loose to medium dense
FINE TO COARSE SAND (SP)
trace clay and gravel
brown, medium dense
Boring Terminated at 30 Feet
12
13
16
16
14
16
18
18
5
4
5
5
6
6
17
15
6-6-6
N=12
3-3-2
N=5
2-3-3
N=6
2-3-4
N=7
4-5-5
N=10
2-2-2
N=4
6-4-2
N=6
4-6-6
N=12
647.5
638.5
624.5
621
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/16/2012
Drill Rig: 83e Driller: MW
A-5
Boring Started: 10/16/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Power auger to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
22½' While Drilling
Dry cave in @ 21.9' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 1
SITE:
BORING LOG NO. 202
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 651 DEPTH (ft)5
10
15
20
25
30
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
3.0
13.0
22.0
28.0
30.0
6" Crushed Asphalt and Limestone
FINE TO MEDIUM SAND WITH CLAY (SP-SC)
trace organics, dark brown, very loose
SILTY FINE TO MEDIUM SAND (SM)
brown, loose
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown, loose to medium dense
FINE TO COARSE SAND (SP)
trace clay and gravel
brown, very dense
SANDY LEAN CLAY (CL)
trace gravel, gray, hard
Boring Terminated at 30 Feet
18
16
17
18
18
13
16
14
6
6
6
11
8
8
13
11
2-1-2
N=3
2-2-2
N=4
2-4-5
N=9
4-3-5
N=8
4-6-6
N=12
3-3-4
N=7
N=50/3"
8-16-17
N=33
646
636
627
621
619 HP 4.50
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/16/2012
Drill Rig: 83e Driller: MW
A-6
Boring Started: 10/16/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Power auger to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
22' While Drilling
Dry cave in @ 19.8' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 1
SITE:
BORING LOG NO. 203
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 649 DEPTH (ft)5
10
15
20
25
30
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
4.5
12.0
15.0
6" Topsoil
FILL, LEAN CLAY, trace sand
gray brown
SILTY FINE TO MEDIUM SAND (SM)
brown to brown gray, loose
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown, loose
Boring Terminated at 15 Feet
9
12
16
16
13
17
15
9
9
9
6
111
3-4-4
N=8
2-4-4
N=8
3-4-4
N=8
3-3-4
N=7
643.5
636
633
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/17/2012
Drill Rig: 83e Driller: MW
A-7
Boring Started: 10/17/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Power auger to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
No water observed.
Dry cave in @ 14' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 1
SITE:
BORING LOG NO. 204
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 648 DEPTH (ft)5
10
15
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
3.5
11.0
15.0
4" Topsoil
FILL, LEAN CLAY, trace sand
gray brown and brown gray
SILTY FINE TO MEDIUM SAND (SM)
trace clay and gravel
brown to brown gray, loose to medium dense
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown, medium dense
Boring Terminated at 15 Feet
9
18
18
16
12
22
20
10
10
9
5
101
3-3-4
N=7
3-4-6
N=10
3-4-4
N=8
4-4-6
N=10
644.5
637
633
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/17/2012
Drill Rig: 83e Driller: MW
A-8
Boring Started: 10/17/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Power auger to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
No water observed.
Dry cave in @ 14.1' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 1
SITE:
BORING LOG NO. 205
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 648 DEPTH (ft)5
10
15
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
1.0
3.5
12.5
23.0
25.0
12" Topsoil
FILL, LEAN CLAY, with sand
brown gray
SILTY FINE TO MEDIUM SAND (SM)
brown, loose to medium dense
FINE TO MEDIUM SAND (SP)
trace clay and gravel
brown, loose to medium dense
SANDY LEAN CLAY (CL)
trace gravel, gray, stiff
Boring Terminated at 25 Feet
19
18
18
13
14
18
18
12
8
7
6
5
3
15
17
113
2-3-4
N=7
3-4-6
N=10
3-4-4
N=8
2-3-3
N=6
4-5-8
N=13
3-6-8
N=14
647
644.5
635.5
625
623
HP 2.00
LOCATION
GRAPHIC LOGDEPTH
Stratification lines are approximate. In-situ, the transition may be gradual.Hammer Type: CME 140 lb. SPT automatic hammer
See Exhibit A-2
TERRACON SMART LOG-HEADERS 06125648 IC PUBLIC WORKS.GPJ TERRACON2012.GDT 10/31/12WATER LEVEL OBSERVATIONS
Notes:
Project No.: 06125648 Exhibit
Boring Completed: 10/17/2012
Drill Rig: 83e Driller: MW
A-9
Boring Started: 10/17/2012
783 Highway 1 West, Unit 5
Iowa City, Iowa
Advancement Method:
Power auger to boring termination.
Abandonment Method:
Boring backfilled on 10/22/12.
23' While Drilling
Dry cave in @ 19' (10/22/12)
ARCHITECT/ENGINEER: Kueny Architects, L.L.C.
Pleasant Prairie, WI South of Napoleon Lane
Iowa City, Iowa
PROJECT: Public Works Complex Additions
Page 1 of 1
SITE:
BORING LOG NO. 206
See Appendix B for description of laboratory
procedures and additional data, (if any).
See Appendix C for explanation of symbols and
abbreviations.
CLIENT: City of Iowa City
See Exhibit A-15 for description of field procedures.RECOVERY(in)WATERCONTENT(%)DRY UNITWEIGHT (pcf)SAMPLE TYPEWATER LEVELOBSERVATIONSApproximate Surface Elev.: 648 DEPTH (ft)5
10
15
20
25
LL-PL-PI
ATTERBERG
LIMITS
FIELD TESTRESULTSELEVATION TESTTYPESTRAIN(%)COMPRESSIVESTRENGTH(tsf)SOIL STRENGTH
Geotechnical Engineering Report
Proposed Animal Care Center & Public Works Additions Ŷ Iowa City, Iowa
November 1, 2012 Ŷ Terracon Project No. 06125648.01
Responsive Ŷ Resourceful Ŷ Reliable Exhibit A-10
Field Exploration Description
Our field exploration consisted of performing six (6) borings at the project site. The borings
were extended to depths of about 15 to 70 feet below the existing grades. The boring locations
were selected and laid out in the field by Terracon personnel based on the supplied site plan
and/or access of the drilling equipment. The approximate boring locations are indicated on the
attached Boring Location Plan. Distances from the boring locations to the reference features
shown on the attached plan are approximate and were located using a measuring wheel and/or
cloth tape, and right angles were estimated. The ground surface elevations indicated on the
boring logs are also approximate (rounded to the nearest 1 foot), and were obtained by
Terracon personnel by interpolating between the contours of the supplied topographic contour
map. True surface elevations at the boring locations could differ due to interpolation, and other
differences could occur from superposing approximate boring locations on the topographic plan.
The locations and elevations of the borings should be considered accurate only to the degree
implied by the means and methods used to define them.
The borings were drilled with an ATV-mounted, rotary drilling rig using continuous flight, hollow-
and solid-stemmed augers and/or a mud rotary procedure to advance the boreholes. Samples
were obtained using either thin-walled tube or split-barrel sampling procedures. In the thin-
walled tube sampling procedure, a thin-walled tube or seamless steel tube with a sharp cutting
edge is pushed hydraulically into the ground to obtain relatively undisturbed samples of
cohesive or moderately cohesive soils. In the split-barrel sampling procedure, a standard 2-inch
O.D. split-barrel sampling spoon is driven into the ground with a 140-pound hammer falling a
distance of 30 inches. A CME automatic SPT hammer was used to advance the split-barrel
sampler in the borings performed for this project. The number of blows required to advance the
sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the standard
penetration resistance value. These values are indicated on the boring logs at the
corresponding depths of occurrence. The samples were sealed and returned to the laboratory
for testing and classification.
Field logs of the borings were prepared by the drill crew. Each log included visual classification
of the materials encountered during drilling as well as the driller's interpretation of the
subsurface conditions between samples. The boring logs included with this report represent an
interpretation of the field logs by a geotechnical engineer and include modifications based on
laboratory observation and tests on select samples.
PREVIOUS BORINGS
(Terracon Project No. 06995251.01)
APPENDIX B
LABORATORY TESTING
Geotechnical Engineering Report
Proposed Animal Care Center & Public Works Additions Ŷ Iowa City, Iowa
November 1, 2012 Ŷ Terracon Project No. 06125648.01
Responsive Ŷ Resourceful Ŷ Reliable Exhibit B-1
Laboratory Testing
Soil samples were tested in the laboratory to measure their natural water contents. Dry unit
weight measurements were performed on portions of intact thin-walled tube samples. The
unconfined compressive strength of some thin-walled tube samples was also measured. A
hand penetrometer was used to estimate the unconfined compressive strength of some
cohesive samples. The hand penetrometer provides a better estimate of soil consistency than
visual examination alone.
In addition, one (1) Laboratory Compaction (Standard Proctor) test, and one (1) California
Bearing Ration (CBR) test were performed to aid in classifying the soils and evaluating their
engineering properties. The results of the laboratory tests are shown on the boring logs,
adjacent to the soil profiles, at their corresponding sample depths and/or as attachments in
Appendix B.
As a part of the laboratory testing program, the soil samples were classified in the laboratory
based on visual observation, texture, plasticity, and the limited laboratory testing described
above. Additional testing could be performed to more accurately classify the samples. Portions
of the recovered samples were placed in jars, and the samples will be retained for at least 1
month in case additional testing is requested. The soil descriptions presented on the boring
logs for native soils 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 boring logs, and a brief description of the Unified System is attached to this report.
Classification of rock materials is in accordance with the enclosed General Notes –
Sedimentary Rock Classification and has been estimated from disturbed samples. Core
samples and petrographic analysis may indicate other rock types.
Laboratory Compaction Characteristics of Soil 2640 12th Street SW
Cedar Rapids, Iowa 52404
(319) 366-8321
Client Name:City of Iowa City, Iowa Project No.:06125648 Date: 10/30/2012
Project Name:Proposed Public Works Complex Additions
Location:Iowa City, Iowa
TEST RESULTS
Maximum Dry Unit Wt.:110.7 pcf
Source Material:On site Optimum Water Content:15.7 %
Sample Description: Gray Brown, Lean Clay, Trace Sand
Near Boring B-204, Depth 2 to 3 feet
Material Designation:A Sample date:Liquid Limit: NA Plastic Limit: NA
Test Method:Method A Plasticity Index:NA
Test Procedure:ASTM D-698 % passing # 200 sieve: NA
Rammer:Mechanical x Manual % moisture as received 19.5
Reviewed by:BKS
----------- Zero air voids for specific gravity of 2.68
Exhibit B-2
105
110
115
10 15 20Dry Unit Weight, pcfWater Content, %
California Bearing Ratio Test (CBR)2640 12th Street SW
Cedar Rapids, Iowa 52404
(319) 366-8321
Client Name:City of Iowa City Project No.:06125648 Date:11/1/2012
Project Name:Public Works Complex Additions
Location:Iowa City, Iowa Proctor Values: Maximum Dry Density (pcf)110.7
Optimum Moisture Content (%)15.7
Boring Number B-204 Material Designation CL
Depth 2' - 3'Test Procedure:ASTM D-1883
Sample Description:Gray Brown Lean Clay, Trace Sand
Liquid Limit:NA Plastic Limit:NA
Plasticity Index:NA
Specimen Compaction Data:
Initial Moisture Content (%)15.5 % Passing No. 200 NR
Dry Density Before Soaking (pcf)107.1
Percent Compaction (%)96.7%Specimen Swell Data:
Dry Density After Soaking (pcf)108.0 Surcharge (lb)10
Final Moisture Content (%)21.1 Compaction (%)97.6%(as tested)
CBR at 0.100 inches penetration 6.2 Swell (96 Hours) (%)-0.9%
CBR at 0.200 inches penetration 6.2
Exhibit B-3
0
20
40
60
80
100
120
140
160
0 0.1 0.2 0.3 0.4 0.5 0.6Load on Piston (psi)Piston Penetration (inches)
Raw Data
Corrected Data
APPENDIX C
SUPPORTING DOCUMENTS
PLASTICITY DESCRIPTION
Term
< 15
15 - 29
> 30
Descriptive Term(s)
of other constituents
Water Initially
Encountered
Water Level After a
Specified Period of Time
Major Component
of SamplePercent of
Dry Weight
(More than 50% retained on No. 200 sieve.)
Density determined by Standard Penetration Resistance
Includes gravels, sands and silts.
Hard
Unconfined Compressive
Strength, Qu, tsf
Very Loose 0 - 3 0 - 6 Very Soft less than 0.25
7 - 18 Soft 0.25 to 0.50
10 - 29 19 - 58 0.50 to 1.00
59 - 98 Stiff 1.00 to 2.00
> 99 2.00 to 4.00
LOCATION AND ELEVATION NOTESSAMPLING FIELD TESTS(HP)
(T)
(b/f)
(PID)
(OVA)
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
Descriptive Term
(Density)
Non-plastic
Low
Medium
High
Boulders
Cobbles
Gravel
Sand
Silt or Clay
10 - 18
> 50 15 - 30 19 - 42
> 30 > 42
_
Hand Penetrometer
Torvane
Standard Penetration
Test (blows per foot)
Photo-Ionization Detector
Organic Vapor Analyzer
Water levels indicated on the soil boring
logs are the levels measured in the
borehole at the times indicated.
Groundwater level variations will occur
over time. In low permeability soils,
accurate determination of groundwater
levels is not possible with short term
water level observations.
CONSISTENCY OF FINE-GRAINED SOILS
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing, field
visual-manual procedures or standard penetration resistance
DESCRIPTIVE SOIL CLASSIFICATION
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.
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.
Plasticity Index
0
1 - 10
11 - 30
> 30
RELATIVE PROPORTIONS OF FINES
Descriptive Term(s)
of other constituents
Percent of
Dry Weight
< 5
5 - 12
> 12
Trace
With
Modifier
Water Level After
a Specified Period of Time
GRAIN SIZE TERMINOLOGYRELATIVE PROPORTIONS OF SAND AND GRAVEL
Trace
With
Modifier
Standard Penetration or
N-Value
Blows/Ft.
Descriptive Term
(Consistency)
Loose
Very Stiff
Standard Penetration or
N-Value
Blows/Ft.
Ring Sampler
Blows/Ft.
Ring Sampler
Blows/Ft.
Medium Dense
Dense
Very Dense
0 - 1 < 3
4 - 9 2 - 4 3 - 4
Medium-Stiff
8 - 15
Exhibit C-1
5 - 9
30 - 50 WATER LEVELAuger
Shelby Tube
Ring Sampler
Grab Sample
Split Spoon
Macro Core
Rock Core
No Recovery
RELATIVE DENSITY OF COARSE-GRAINED SOILS
Particle Size
Over 12 in. (300 mm)
12 in. to 3 in. (300mm to 75mm)
3 in. to #4 sieve (75mm to 4.75 mm)
#4 to #200 sieve (4.75mm to 0.075mm
Passing #200 sieve (0.075mm)STRENGTH TERMS> 4.00
4 - 8
GENERAL NOTES
Exhibit C-2
DESCRIPTION OF ROCK PROPERTIES
WEATHERING
Fresh Rock fresh, crystals bright, few joints may show slight staining. Rock rings under hammer if crystalline.
Very slight Rock generally fresh, joints stained, some joints may show thin clay coatings, crystals in broken face show
bright. Rock rings under hammer if crystalline.
Slight Rock generally fresh, joints stained, and discoloration extends into rock up to 1 in. Joints may contain clay. In
granitoid rocks some occasional feldspar crystals are dull and discolored. Crystalline rocks ring under hammer.
Moderate Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull
and discolored; some show clayey. Rock has dull sound under hammer and shows significant loss of strength
as compared with fresh rock.
Moderately severe All rock except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority
show kaolinization. Rock shows severe loss of strength and can be excavated with geologist’s pick.
Severe All rock except quartz discolored or stained. Rock “fabric” clear and evident, but reduced in strength to strong
soil. In granitoid rocks, all feldspars kaolinized to some extent. Some fragments of strong rock usually left.
Very severe All rock except quartz discolored or stained. Rock “fabric” discernible, but mass effectively reduced to “soil” with
only fragments of strong rock remaining.
Complete Rock reduced to ”soil”. Rock “fabric” not discernible or discernible only in small, scattered locations. Quartz may
be present as dikes or stringers.
HARDNESS (for engineering description of rock – not to be confused with Moh’s scale for minerals)
Very hard Cannot be scratched with knife or sharp pick. Breaking of hand specimens requires several hard blows of
geologist’s pick.
Hard Can be scratched with knife or pick only with difficulty. Hard blow of hammer required to detach hand specimen.
Moderately hard Can be scratched with knife or pick. Gouges or grooves to ¼ in. deep can be excavated by hard blow of point of
a geologist’s pick. Hand specimens can be detached by moderate blow.
Medium Can be grooved or gouged 1/16 in. deep by firm pressure on knife or pick point. Can be excavated in small
chips to pieces about 1-in. maximum size by hard blows of the point of a geologist’s pick.
Soft Can be gouged or grooved readily with knife or pick point. Can be excavated in chips to pieces several inches in
size by moderate blows of a pick point. Small thin pieces can be broken by finger pressure.
Very soft Can be carved with knife. Can be excavated readily with point of pick. Pieces 1-in. or more in thickness can be
broken with finger pressure. Can be scratched readily by fingernail.
Joint, Bedding, and Foliation Spacing in Rock a
Spacing Joints Bedding/Foliation
Less than 2 in. Very close Very thin
2 in. – 1 ft. Close Thin
1 ft. – 3 ft. Moderately close Medium
3 ft. – 10 ft. Wide Thick
More than 10 ft. Very wide Very thick
a. Spacing refers to the distance normal to the planes, of the described feature, which are parallel to each other or nearly so.
Rock Quality Designator (RQD) a Joint Openness Descriptors
RQD, as a percentage Diagnostic description Openness Descriptor
Exceeding 90 Excellent No Visible Separation Tight
90 – 75 Good Less than 1/32 in. Slightly Open
75 – 50 Fair 1/32 to 1/8 in. Moderately Open
50 – 25 Poor 1/8 to 3/8 in. Open
Less than 25 Very poor 3/8 in. to 0.1 ft. Moderately Wide
a. RQD (given as a percentage) = length of core in pieces Greater than 0.1 ft. Wide
4 in. and longer/length of run.
References: American Society of Civil Engineers. Manuals and Reports on Engineering Practice - No. 56. Subsurface Investigation for
Design and Construction of Foundations of Buildings. New York: American Society of Civil Engineers, 1976. U.S.
Department of the Interior, Bureau of Reclamation, Engineering Geology Field Manual.
Exhibit C-3
UNIFIED SOIL CLASSIFICATION SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse Grained Soils:
More than 50% retained
on No. 200 sieve
Gravels:
More than 50% of
coarse fraction retained
on No. 4 sieve
Clean Gravels:
Less than 5% fines C
Cu 4 and 1 Cc 3 E GW Well-graded gravel F
Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F
Gravels with Fines:
More than 12% fines C
Fines classify as ML or MH GM Silty gravel F,G,H
Fines classify as CL or CH GC Clayey gravel F,G,H
Sands:
50% or more of coarse
fraction passes No. 4
sieve
Clean Sands:
Less than 5% fines D
Cu 6 and 1 Cc 3 E SW Well-graded sand I
Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I
Sands with Fines:
More than 12% fines D
Fines classify as ML or MH SM Silty sand G,H,I
Fines classify as CL or CH SC Clayey sand G,H,I
Fine-Grained Soils:
50% or more passes the
No. 200 sieve
Silts and Clays:
Liquid limit less than 50
Inorganic: PI 7 and plots on or above “A” line J CL Lean clay K,L,M
PI 4 or plots below “A” line J ML Silt K,L,M
Organic: Liquid limit - oven dried 0.75 OL Organic clay K,L,M,N
Liquid limit - not dried Organic silt K,L,M,O
Silts and Clays:
Liquid limit 50 or more
Inorganic: PI plots on or above “A” line CH Fat clay K,L,M
PI plots below “A” line MH Elastic Silt K,L,M
Organic: Liquid limit - oven dried 0.75 OH Organic clay K,L,M,P
Liquid limit - not dried Organic silt K,L,M,Q
Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-inch (75-mm) sieve
B If field sample contained cobbles or boulders, or both, add “with cobbles
or boulders, or both” to group name.
C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded
gravel with silt, GW -GC well-graded gravel with clay, GP-GM poorly
graded gravel with silt, GP-GC poorly graded gravel with clay.
D Sands with 5 to 12% fines require dual symbols: SW -SM well-graded
sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded
sand with silt, SP-SC poorly graded sand with clay
E Cu = D60/D10 Cc =
6010
2
30
DxD
)(D
F If soil contains 15% sand, add “with sand” to group name.
G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
H If fines are organic, add “with organic fines” to group name.
I If soil contains 15% gravel, add “with gravel” to group name.
J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.
K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,”
whichever is predominant.
L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to
group name.
M If soil contains 30% plus No. 200, predominantly gravel, add
“gravelly” to group name.
N PI 4 and plots on or above “A” line.
O PI 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.