Geotechnical Evaluation
Table of Contents
Description Page
A. Introduction ...................................................................................................................................... 1
A.1. Project Description .............................................................................................................. 1
A.2. Purpose ................................................................................................................................ 1
A.3. Background Information and Reference Documents .......................................................... 1
A.4. Site Conditions..................................................................................................................... 1
A.5. Scope of Services ................................................................................................................. 1
B. Results .............................................................................................................................................. 2
B.1. Exploration Logs .................................................................................................................. 2
B.1.a. Log of Boring Sheets ............................................................................................... 2
B.1.b. Geologic Origins ..................................................................................................... 2
B.2. Geologic Profile ................................................................................................................... 3
B.2.a. Geologic Materials ................................................................................................. 3
B.2.b. Groundwater .......................................................................................................... 3
B.3. Laboratory Test Results ....................................................................................................... 4
C. Basis for Recommendations ............................................................................................................. 4
C.1. Design Details ...................................................................................................................... 4
C.1.a. Building Structure Loads ........................................................................................ 4
C.1.b. Pavements and Traffic Loads ................................................................................. 4
C.1.c. Anticipated Grade Changes .................................................................................... 5
C.1.d. Precautions Regarding Changed Information ........................................................ 5
C.2. Design and Construction Considerations ............................................................................ 5
D. Recommendations ........................................................................................................................... 6
D.1. Building and Pavement Subgrade Preparation ................................................................... 6
D.1.a. Excavations ............................................................................................................. 6
D.1.b. Excavation Dewatering ........................................................................................... 7
D.1.c. Selecting Excavation Backfill and Additional Required Fill ..................................... 7
D.1.d. Placement and Compaction of Backfill and Fill ...................................................... 7
D.2. Spread Footings ................................................................................................................... 8
D.2.a. Embedment Depth ................................................................................................. 8
D.2.b. Subgrade Improvement ......................................................................................... 8
D.2.c. Net Allowable Bearing Pressure ............................................................................. 9
D.2.d. Settlement .............................................................................................................. 9
D.3. Basement Walls ................................................................................................................... 9
D.3.a. Drainage Control .................................................................................................... 9
D.3.b. Selection, Placement and Compaction of Backfill .................................................. 9
D.3.c. Configuring and Resisting Lateral Loads............................................................... 10
Table of Contents (continued)
Description Page
D.4. Interior Slabs ..................................................................................................................... 11
D.4.a. Moisture Vapor Protection .................................................................................. 11
D.4.b. Radon ................................................................................................................... 11
D.5. Exterior Slabs ..................................................................................................................... 12
D.6. Pavements ......................................................................................................................... 13
D.6.a. Subgrade Proof-Roll ............................................................................................. 13
D.6.b. Design Sections .................................................................................................... 13
D.6.c. Materials and Compaction ................................................................................... 14
D.6.d. Subgrade Drainage ............................................................................................... 14
D.7. Utilities .............................................................................................................................. 15
D.7.a. Subgrade Stabilization .......................................................................................... 15
D.7.b. Selection, Placement and Compaction of Backfill ................................................ 15
D.7.c. Corrosion Potential .............................................................................................. 15
D.8. Construction Quality Control ............................................................................................ 15
D.8.a. Excavation Observations ...................................................................................... 15
D.8.b. Materials Testing .................................................................................................. 15
D.8.c. Pavement Subgrade Proof-Roll ............................................................................ 16
D.8.d. Cold Weather Precautions ................................................................................... 16
E. Procedures...................................................................................................................................... 16
E.1. Penetration Test Borings ................................................................................................... 16
E.2. Material Classification and Testing ................................................................................... 16
E.2.a. Visual and Manual Classification .......................................................................... 16
E.2.b. Laboratory Testing ............................................................................................... 16
E.3. Groundwater Measurements ............................................................................................ 17
F. Qualifications .................................................................................................................................. 17
F.1. Variations in Subsurface Conditions .................................................................................. 17
F.1.a. Material Strata ..................................................................................................... 17
F.1.b. Groundwater Levels ............................................................................................. 17
F.2. Continuity of Professional Responsibility .......................................................................... 17
F.2.a. Plan Review .......................................................................................................... 17
F.2.b. Construction Observations and Testing ............................................................... 18
F.3. Use of Report..................................................................................................................... 18
F.4. Standard of Care ................................................................................................................ 18
Appendix
Boring Location Sketch
Log of Boring Sheets, ST-1 through ST-5
Descriptive Terminology
A. Introduction
A.1. Project Description
Hunter Emerson is planning to develop several parcels of land along the west side of Galpin Boulevard
into a new single-family housing development.
A.2. Purpose
The purpose of our evaluation was to assist you and your design team in evaluating the subsurface soil
and groundwater conditions with regard to design and construction of the new single-family housing
development.
A.3. Background Information and Reference Documents
To facilitate our evaluation, we were provided with or reviewed the following information or documents:
Available public aerial photographs showing the existing site conditions.
Geologic atlas showing the general soil types present in this area.
Preliminary site plan prepared by Sathre-Bergquist, Inc. showing the proposed development
as well as the ghost plat for an adjacent parcel of land.
A.4. Site Conditions
This site consists of 3 parcels of property with both open and wooded areas. A large wetland is present
along the west side of the properties and extends further west. Several buildings/houses are present on
these parcels.
A.5. Scope of Services
Our scope of services for this project was originally submitted July 25, 2013 as a Proposal to Mr. Scott
Carlston with Hunter Emerson. Tasks performed in accordance with our authorized scope of services
included:
The boring locations were chosen and staked in the field by Sathre-Bergquist, Inc.
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Clearing exploration locations of public underground utilities.
Performing 5 penetration test borings to nominal depths of 20 feet below grade.
Performing laboratory tests on selected penetration test samples.
Preparing this report containing a boring location sketch, exploration logs, a summary of the
geologic materials encountered, results of laboratory tests, and recommendations for
structure subgrade preparation and the design of the proposed residential development.
One of the borings, ST-2, was extended an additional 10 feet because this boring encountered
uncontrolled fill soils and very soft alluvial clays at the planned termination depth of the boring.
Our scope of services was performed under the terms of our general conditions dated June 15, 2006.
B. Results
B.1. Exploration Logs
B.1.a. Log of Boring Sheets
Log of Boring sheets for our penetration test borings are included in the Appendix. The logs identify and
describe the geologic materials that were penetrated, and present the results of penetration resistance
data, laboratory tests performed on penetration test samples retrieved from them, and groundwater
measurements.
Strata boundaries were inferred from changes in the penetration test samples and the auger cuttings.
Because sampling was not performed continuously, the strata boundary depths are only approximate.
The boundary depths likely vary away from the boring locations, and the boundaries themselves may
also occur as gradual rather than abrupt transitions.
B.1.b. Geologic Origins
Geologic origins assigned to the materials shown on the logs and referenced within this report were
based on: (1) a review of the background information and reference documents cited above, (2) visual
classification of the various geologic material samples retrieved during the course of our subsurface
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exploration, (3) penetration resistance data, (4) laboratory test results, and (5) available common
knowledge of the geologic processes and environments that have impacted the site and surrounding
area in the past.
B.2. Geologic Profile
B.2.a. Geologic Materials
Based on the current soil borings, the general geologic profile at the site consists of either fill soils or
topsoil at the surface followed by glacially deposited soil to the termination depths of the borings. The
exceptions are Borings ST-2 and ST-3 where alluvial clay or swamp deposited soils were encountered to
depths of 24 and 14 feet respectively.
A topsoil layer was encountered in Borings ST-4 and ST-5 that consisted of organic clay and was about 5
1/2 feet thick at both locations. Fill soils were encountered in Borings ST-1 through ST-3 that were up to
6 feet deep.
Below the topsoil and fill soils, borings ST-1, ST-4 and ST-5 encountered glacially deposited sandy lean
clay or lean clay to the termination depths of the borings.
Below the fill in Boring ST-2, alluvial deposits of lean clay, fat clay and sandy lean clay were encountered
to a depth of about 24 feet. Some of the deeper alluvial clay soils had trace amounts of shells in them.
Below the alluvial soils, this boring encountered glacially deposited sandy lean clay to the termination
depth of the boring.
Below the fill in Boring ST-3, swamp deposited organic clay, peat and organic silt was encountered to a
depth of about 14 feet followed by glacially deposited lean clay with sand and sandy lean clay to the
termination depth of the boring.
Penetration resistance values recorded in the fill soils ranged from 4 to 7 blows per foot (BPF) indicating
that this soil was not well compacted. The penetration resistance in the alluvial deposits of clay and fat
clay in Boring ST-2 ranged from 1 to 3 BPF, indicating consistencies of very soft to soft. The penetration
resistances in the glacial deposits of clay and sandy lean clay ranged from 2 to 17 BPF, indicating
consistencies of soft to very stiff.
B.2.b. Groundwater
While drilling, groundwater was observed in Borings ST-2 through ST-5 at depths of about 4 to 8 feet
below the surface, or at approximate elevations of about 950 1/2 to 960. Given the cohesive nature of
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the geologic materials encountered, however, it is likely that insufficient time was available for
groundwater to seep into the boreholes and rise to its hydrostatic level. Piezometers or monitoring wells
would be required to confirm if groundwater was present within the depths explored. Also,
groundwater levels will vary over time and in response to climatic conditions.
B.3. Laboratory Test Results
The moisture contents of the selected soil samples tested were determined to vary from approximately
16 to 22 percent, indicating that the material was mostly wet of its probable optimum moisture content.
Pocket penetrometer tests were taken on select soil samples in Boring ST-1 to estimate the unconfined
compressive strengths of the soil samples tested. The results of these tests ranged from 1 1/2 ton to 2
tons per square foot (tsf).
The individual test results can be found in the right hand margin of various Log of Boring sheets, opposite
the soil sample tested.
C. Basis for Recommendations
C.1. Design Details
A single-family residential development is proposed to be constructed on this site. New streets, public
underground utilities and sediment ponds will also be constructed. The preliminary garage and basement
elevations were not available at the time of this report.
C.1.a. Building Structure Loads
We have assumed that bearing wall loads associated with the proposed residential construction will
range from 3 to 4 kips (3,000 to 4,000 pounds) per linear foot (klf) and column loads, if any, will be no
greater than 75 kips per column.
C.1.b. Pavements and Traffic Loads
We have assumed that bituminous pavements, typical of residential neighborhoods, will be subjected to
normal traffic conditions over an assumed design life of 20 years.
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C.1.c. Anticipated Grade Changes
Based on the surface elevations at the borings, the existing ground surface elevations range from about
955 to 979. Based on the range of current surface grades, it is likely that the range of cuts and fills across
this site could be about 5 to 15 feet. However, any soil correction excavation depths would be added or
subtracted from these values.
C.1.d. Precautions Regarding Changed Information
We have attempted to describe our understanding of the proposed construction to the extent it was
reported to us by others. Depending on the extent of available information, assumptions may have been
made based on our experience with similar projects. If we have not correctly recorded or interpreted the
project details, we should be notified. New or changed information could require additional evaluation,
analyses and/or recommendations.
C.2. Design and Construction Considerations
The geotechnical issues influencing design of the residential development appear to be the presence of
deeper fills soils and organic soils on parts of the site. These soils are not directly suitable for support of
the proposed houses and streets.
The topsoil, fat clay and most of the alluvial lean clay soils are not suitable for use as engineered fill in the
house pads and streets.
Also, due to the possibility of deep fills of clay soils, areas of the site may require a delay between filling
and house construction to allow thick clay fills to consolidate under their own weight.
Due to the frost susceptible nature of the silt- and clay-rich soils present at anticipated exterior slab and
pavement subgrade elevations, consideration should also be given to incorporating a granular subbase
into the pavement sections. This will enhance subgrade drainage efforts and reduce the potential for
pavement subgrades to become saturated and heave upon freezing. This will also reduce subgrade
strength loss upon thawing.
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D. Recommendations
The following recommendations are based on the results of our soil borings and laboratory test results.
D.1. Building and Pavement Subgrade Preparation
D.1.a. Excavations
We recommend removing the topsoil, fill soils, organic soils and the very soft to soft alluvial soils from
beneath the proposed house pads, street subgrades and oversize areas. Based on the soil borings,
excavation depths are expected to range from approximately 7 to 24 feet, however deeper soil
correction efforts may be needed in other areas of the site not explored by our borings. Table 1 lists the
recommended excavation depths at the individual boring locations.
Table 1. Anticipated Excavation Depths for Residential Construction
Boring # Surface Elevation (ft)
Anticipated Depth of
Excavation (ft)
Approximate Bottom
Elevation (ft)
ST-1 978.7 9 969 1/2
ST-2 959.0 24 935
ST-3 955.8 21+* 934-*
ST-4 968.7 7 961 1/2
ST-5 958.1 7 951
*The depth of excavation is deeper than 21 feet for house construction, but this boring was terminated at this depth because it
is a proposed pond and planned borrow area.
Excavation depths will vary between the borings. Portions of the excavations may also be deeper than
indicated by the borings. Contractors should also be prepared to extend excavations in wet or fine-
grained soils to remove disturbed bottom soils.
Due to the wide variations in the depths of soil corrections, additional soil borings should be considered
to assist excavation contractors in estimating earthwork volumes.
To provide lateral support to replacement backfill, additional required fill and the structural loads they
will support, we recommend oversizing (widening) the excavations 1 foot horizontally beyond the outer
edges of the building perimeter footings, or pavement limits, for each foot the excavations extend below
bottom-of-footing or pavement subgrade elevations.
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D.1.b. Excavation Dewatering
Water was observed in most of the borings and will likely be encountered in most of the deeper
excavations. If encountered, we recommend removing groundwater from the excavations. Since this site
is mostly clayey soil, sumps and pumps should be adequate to control most infiltrating water situations.
D.1.c. Selecting Excavation Backfill and Additional Required Fill
If the bottoms of the excavations remain wet, we recommend the initial backfill soil consist of least 2 feet
of coarse sand having less than 50 percent of the particles by weight passing a #40 sieve, and less than 5
percent of the particles passing a #200 sieve. We anticipate that this material will need to be imported to
the site
On-site soils free of organic soil and debris can be considered for reuse as backfill and fill. However, the
topsoil, fat clay, organic soils, and most of the alluvial soils with shells should not be re-used as
engineered fill under house pads or below streets. The glacially deposited lean clay, lean clay with sand
and sandy lean clay can be used as engineered fill. The clay soils being fine-grained, will be more difficult
to compact if wet or allowed to become wet, or if spread and compacted over wet surfaces.
We recommend that granular subbase material for pavement support consist of select granular sand
having less than 12 percent of the particles by weight passing a #200 sieve. We anticipate that this
material will also need to be imported to the site
D.1.d. Placement and Compaction of Backfill and Fill
We recommend spreading backfill and fill in loose lifts of approximately 8 to 12 inches depending on the
soil type used and the size of compactor used. We recommend compacting backfill and fill in accordance
with the criteria presented in Table 2. The relative compaction of utility backfill should be evaluated
based on the structure below which it is installed, and vertical proximity to that structure.
Table 2. Compaction Recommendations Summary
Reference
Relative Compaction, percent
(ASTM D 698 – standard Proctor)
Moisture Content Variance from
Optimum, percentage points
Below foundations, less than
10 feet of fill 95 -1 to +3 for clay soils
± 3 for sandy soils
Below foundations, greater than
10 feet of fill 98 -1 to +2 for clay soils
± 3 for sandy soils
Below slabs 95 -1 to +3 for clay soils
± 3 for sandy soils
Below pavements, within 3 feet
of top of subgrade elevations 100 -1 to +2 for clay soils
± 3 for sandy soils
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Reference
Relative Compaction, percent
(ASTM D 698 – standard Proctor)
Moisture Content Variance from
Optimum, percentage points
Below pavements, more than 3 feet
below subgrade elevations 95 -1 to +3 for clay soils
± 3 for sandy soils
Below landscaped surfaces * 90 * -1 to +5 for clay soils*
± 5 for sandy soils
*Except for wall backfill. See Section D.3 of this report.
If fill depths exceed 10 feet, the minimum compaction requirement should be increased to 98 percent. As
noted above, if fill depths exceed 10 feet, a construction delay may also be necessary to allow the fill to
consolidate under its own weight. Construction delays can range from 3 to 6 months or longer,
depending on the depth and type of fill placed. We recommend placing settlement plates on lots where
a construction delay is required to allow for periodic monitoring. We recommend monitoring the
settlement plates once a week during the first month, once every other week for the second month, and
once a month thereafter until the settlement rate has declined to within tolerable ranges.
If the construction schedule is such that a construction delay cannot be tolerated, sand containing less
than 12 percent of fine-grained material, can be placed to within 10 feet of the bottom of footing
elevation. Sand soils consolidate much quicker than clay soils, and the majority of consolidation will
likely be completed during construction of the lot.
D.2. Spread Footings
D.2.a. Embedment Depth
For frost protection, we recommend embedding perimeter footings 42 inches below the lowest exterior
grade. Interior footings may be placed directly below floor slabs. We recommend embedding building
footings not heated during winter construction, and other unheated footings associated with porches,
decks or stoops 60 inches below the lowest exterior grade.
D.2.b. Subgrade Improvement
If a small amount of groundwater is present within the footing excavation, or if the footing subgrade soils
become disturbed prior to placing forms or reinforcement, we recommend subcutting the soft or wet
clay and placing a 6- to 12-inch layer of clear rock. The clear rock will provide a stable working surface,
and will allow for the flow of water to a drain tile or sump pump.
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D.2.c. Net Allowable Bearing Pressure
We recommend sizing spread footings to exert a net allowable bearing pressure of up to 2,000 pounds
per square foot (psf). This value includes a safety factor of at least 3.0 with regard to bearing capacity
failure. The net allowable bearing pressure can be increased by one-third its value for occasional
transient loads, but not for repetitive loads due to traffic, or for other live loads from snow or occupancy.
D.2.d. Settlement
We estimate that total and differential settlements among the footings will amount to less than 1 and
1/2 inch, respectively, under the assumed loads. In areas where more than 10 feet of fill are placed,
greater settlements could occur if a construction delay is not observed.
D.3. Basement Walls
The following sections address soil parameters for basement wall design. Although construction of
retaining walls has not been specified for this project to date, the following recommendations can also
be used for retaining wall design.
D.3.a. Drainage Control
We recommend installing subdrains behind the basement walls, adjacent to the wall footings, below the
slab elevation. Preferably the subdrains should consist of perforated pipes embedded in washed gravel,
which in turn is wrapped in filter fabric. Perforated pipes encased in a filter “sock” and embedded in
washed gravel, however, may also be considered.
We recommend routing the subdrains to a sump and pump capable of routing any accumulated
groundwater to a storm sewer or other suitable disposal site.
General waterproofing of basement walls surrounding occupied or potentially occupied areas is
recommended even with the use of free-draining backfill because of the potential cost impacts related to
seepage after construction is complete.
D.3.b. Selection, Placement and Compaction of Backfill
Unless a drainage composite is placed against the backs of the exterior perimeter basement walls, we
recommend that backfill placed within 2 horizontal feet of those walls consist of sand having less than 50
percent of the particles by weight passing a #40 sieve and less than 5 percent of the particles by weight
passing a #200 sieve. Sand meeting this gradation will need to be imported to the site. We recommend
that the balance of the backfill placed against exterior perimeter walls also consist of sand, though it is
our opinion that the sand may contain up to 20 percent of the particles by weight passing a #200 sieve.
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If clay or silt must be considered for use to make up the balance of the below-grade wall backfill
(assuming a drainage composite or sand is placed against the backs of the walls), post-compaction
consolidation of the clay occurring under its own weight can be expected to continue beyond the end of
construction. The magnitude of consolidation could amount to between 1 and 3 percent of the backfill
thickness, or wall height, and if not accommodated could cause slabs or pavements to settle unfavorably
or be damaged.
Should clays still be considered for use as backfill, however, we further recommend that:
The bottoms of the excavations required for basement wall construction are wide enough to
accommodate compaction equipment.
Backfill is placed at moisture contents at least equal to, but not more than three percentage
points above, its optimum moisture content.
Backfill is placed in loose lifts no thicker than 6 inches prior to compaction.
The relative compaction of the backfill is measured through density testing at intervals not
exceeding one test per 50 horizontal feet for each 2 vertical feet of backfill placed.
We recommend a walk behind compactor be used to compact the backfill placed within about 5 feet of
the basement walls. Further away than that, a self-propelled compactor can be used. Compaction
criteria for basement walls should be determined based on the compaction recommendations provided
above in Section D.1.
Exterior backfill not capped with slabs or pavement should be capped with a low-permeability soil to limit
the infiltration of surface drainage into the backfill. The finished surface should also be sloped to divert
water away from the walls.
D.3.c. Configuring and Resisting Lateral Loads
Below-grade wall design can be based on active earth pressure conditions if the walls are allowed to
rotate slightly. If rotation cannot be tolerated, then design should be based on at-rest earth pressure
conditions. Rotation up to 0.002 times the wall height is generally required to activate active earth
pressure conditions when walls are backfilled with sand*. Rotation up to 0.02 times the wall height is
required when walls are backfilled with clay.
* To design for sand backfill, excavations required for wall construction should be wide enough and flat
enough so that sand is present within a zone that (1) extends at least two horizontal feet beyond the
bottom outer edges of the wall footings (the wall heel, not the stem) and then (2) rises up and away from
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the wall at an angle no steeper than 60 degrees from horizontal. We anticipate these geometric conditions
will be met if the excavations meet OSHA requirements for the types of soils likely to be exposed in the
excavation, and the wall footings are cast against wood forms rather than any portion of the excavation.
Recommended equivalent fluid pressures for wall design based on active and at-rest earth pressure
conditions are presented below in Table 3. Assumed wet unit backfill weights, and internal friction angles
are also provided. The recommended equivalent fluid pressures in particular assume a level backfill with
no surcharge – they would need to be revised for sloping backfill or other dead or live loads that are
placed within a horizontal distance behind the walls that is equal to the height of the walls. Our design
values also assume that the walls are drained so that water cannot accumulate behind the walls.
Table 3. Recommended Below-Grade Wall Design Parameters
Backfill Soil
Wet Unit Weight
(pcf)
Friction Angle
(deg)
Equivalent Fluid
Pressure, Active Case
(pcf)
Equivalent Fluid
Pressure, At-Rest Case
(pcf)
Sand 120 33 35 50
Clay 120 26 50 70
Resistance to lateral earth pressures will be provided by passive resistance against the basement wall
footings, and by sliding resistance along the bottoms of the wall footings. We recommend assuming a
passive pressure equal to 280 pcf for clays with sliding coefficients equal to 0.30. These values are un-
factored.
D.4. Interior Slabs
D.4.a. Moisture Vapor Protection
If floor coverings or coatings less permeable than the concrete slab will be used, we recommend that a
vapor retarder or vapor barrier be placed immediately beneath the slab. Some contractors prefer to bury
the vapor retarder or barrier beneath a layer of sand to reduce curling and shrinkage, but this practice
risks trapping water between the slab and vapor retarder or barrier.
Regardless of where the vapor retarder or barrier is placed, we recommend consulting with floor
covering manufacturers regarding the appropriate type, use and installation of the vapor retarder or
barrier to preserve warranty assurances.
D.4.b. Radon
In preparation for radon mitigation systems, we recommend that slabs on grade be constructed over a
layer of gas permeable material consisting of a minimum of 4 inches of either clean aggregate, or sand
overlain with a geotextile matting suitable for venting the subgrade. The clean aggregate material should
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consist of sound rock no larger than 2 inches and no smaller than ¼ inch. Sand should have less than 50
percent of the particles by weight passing a #40 sieve and less than 5 percent of the particles by weight
passing a #200 sieve.
Above the gas permeable aggregate or sand, a polyethylene sheeting (6 mil minimum) should be placed.
The sheeting should be properly lapped and penetrations through the sheeting sealed. Penetrations
through the slab and foundation walls should also be sealed.
D.5. Exterior Slabs
All of the exterior slabs will be underlain with mostly sandy lean clays or lean clays. These soils are
considered to be moderately to highly frost susceptible. Soils of this type can retain moisture and heave
upon freezing. In general, this characteristic is not an issue unless these soils become saturated due to
surface runoff or infiltration or are excessively wet in-situ. Once frozen, unfavorable amounts of general
and isolated heaving of the soils and related surface features could also develop. This type of heaving
could impact design drainage patterns and the performance of the paved areas or exterior slabs. To
address most of the heave related issues, we recommend the general site grades and grades for surface
features be set to direct surface drainage away from buildings, across large paved areas and away from
walkways to limit the potential for saturation of the subgrade and any subsequent heaving. General
grades should also have enough “slope” shown to tolerate potential larger areas of heave which may not
fully settle when thawed.
Even small amounts of frost-related differential movement at walkway joints or cracks can create
tripping hazards. Several subgrade improvement options can be explored to address this condition. The
most conservative and potentially most costly subgrade improvement option to help limit the potential
for heaving, but not eliminate it, would be to remove any frost-susceptible soils present below the
remove space exterior slabs “footprint” down to the bottom-of-footing grades or to a maximum depth of
5 feet below subgrade elevations, whichever is less. We recommend the resulting excavation then be
refilled with sand or sandy gravel having less than 50 percent of the particles by weight passing the #40
sieve and less than 5 percent of the particles by weight passing a #200 sieve.
Another subgrade improvement option would be to build in a transition zone between those soils
considered to be frost-susceptible and those that are not to somewhat control where any differential
movement may occur. Such transitions could exist between exterior slabs and pavements, between
entry way slabs and sidewalks, and along the sidewalks themselves. For this option, the frost-susceptible
soils in critical areas would be removed to a depth of at least 4 feet below grade as discussed above. The
excavation below the footprint of the sidewalks or other slabs would then be sloped upward at a
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gradient no steeper than 3:1 (horizontal: vertical) toward the less critical areas. The bottom of the
excavation should then be sloped toward the center so that any water entering the excavation could be
quickly drained to the deepest area for removal. In the deepest areas of the excavation, a series of
perforated drainpipes will need to be installed to collect and dispose of surface water infiltration and/or
groundwater that could accumulate within the backfill. The piping would need to be connected to a
storm sewer or a sump to remove any accumulated water. If the water is not removed, it is our opinion
this option will not be effective in controlling heave.
Regardless of what is done to the walkway or pavement area subgrade, it will be critical the end-user
develop a detailed maintenance program to seal and/or fill any cracks and joints that may develop during
the useful life of the various surface features. Concrete and bituminous will experience episodes of
normal thermo-expansion and thermo-contraction during its useful life. During this time, cracks may
develop and joints may open up, which will expose the subgrade and allow any water flowing overland to
enter the subgrade and either saturate the subgrade soils or to become perched atop it. This occurrence
increases the potential for heave due to freezing conditions in the general vicinity of the crack or joint.
This type of heave has the potential to become excessive if not addressed as part of a maintenance
program. Special attention should be paid to areas where dissimilar materials abut one another, where
construction joints occur and where shrinkage cracks develop.
D.6. Pavements
D.6.a. Subgrade Proof-Roll
Prior to placing aggregate base material, we recommend proof-rolling pavement subgrades to determine
if the subgrade materials are loose, soft or weak, and in need of further stabilization, compaction or sub-
excavation and re-compaction or replacement.
D.6.b. Design Sections
Laboratory tests to determine an R-value for pavement design were not included in the scope of this
project. Based on a clay subgrade, however, it is our opinion that an R-value of 10 can be assumed for
design purposes for lean clay subgrades.
Based upon the aforementioned traffic loads and an R-value of 10, we recommend a bituminous
pavement section that includes a minimum of 3 1/2 inches of bituminous pavement (a 1 1/2-inch surface
course over a 2-inch base course) over 8 inches of aggregate base material and 18 inches of sand
subbase.
Hunter Emerson
Project BL-13-04915
August 21, 2013
Page 14
The ongoing performance of bituminous pavements is impacted by conditions under which the
pavement is asked to perform in. These conditions include the environmental conditions, the actual use
conditions and the level of ongoing maintenance performed. Because of normal thermo expansion and
contraction, it is not unusual to have cracking develop within the first few years of placement and for the
cracking to continue throughout the life of the pavement. A regular maintenance plan should be
developed for filling cracks to lessen the potential impacts for cold weather distress due to frost heave or
warm weather distress due to wetting and softening of the subgrade. It is also not unusual for the
pavement to require a seal coat within the first 5 to 10 years to increase the long-term performance of
the bituminous pavement.
D.6.c. Materials and Compaction
We recommend specifying crushed aggregate base meeting the requirements of Minnesota Department
of Transportation (MnDOT) Specification 3138 for Class 5 or similar. We recommend that the bituminous
wear and base courses meet the requirements of Specifications 2360, Type SP. We recommend the
aggregate gradations for the asphalt mixes meet Gradation B for the base course and Gradation B or A
for the surface course. Gradation A contains a smaller aggregate size than Gradation B and will provide a
surface with less visible aggregate which is desirable for some owners. We recommend the Performance
Graded Asphalt cement be a PG 58-28. (If additional resistance to rutting, scuffing and dimpling is
desired, we recommend utilizing a PG 64-28. If additional resistance to cold weather cracking is
desirable, we recommend utilizing a PG 58-34.)
We recommend that the aggregate base be compacted to a minimum of 100 percent of its maximum
standard Proctor dry density. We recommend that the bituminous pavement be compacted to at least 92
percent of the maximum theoretical Rice density.
We recommend specifying concrete for sidewalks, curb and gutter and any other concrete pavements
have a minimum 28-day compressive strength of 3,900 psi. We also recommend Type I cement meeting
the requirements of ASTM C 150. We recommend specifying 5 to 8 percent entrained air for exposed
concrete to provide resistance to freeze-thaw deterioration. We also recommend using a water/cement
ratio of 0.45 or less for concrete exposed to deicers.
D.6.d. Subgrade Drainage
We recommend installing perforated drainpipes throughout pavement areas at low points and about
catch basins. The drainpipes should be placed in small trenches extended at least 8 inches below the
granular subbase layer – or aggregate base material where no subbase is present.
Hunter Emerson
Project BL-13-04915
August 21, 2013
Page 15
D.7. Utilities
D.7.a. Subgrade Stabilization
Based on the results of the soil borings, the soils below the topsoil should be suitable for pipe support.
We anticipate that utilities can be installed per manufacturer bedding requirements. If localized soft
areas are encountered at pipe invert elevations, we recommend placing a stabilizing aggregate beneath
the pipe. The depth of the aggregate bedding will vary, however, a minimum of 6 inches and a maximum
of 2 feet is commonly used. This should be evaluated in the field at the time of installation.
D.7.b. Selection, Placement and Compaction of Backfill
We recommend selecting, placing and compacting utility backfill in accordance with the
recommendations provided above in Section D.1.
D.7.c. Corrosion Potential
The majority of the soils on this site are lean clay to sandy lean clay. These soils are potentially corrosive
to ductile iron pipe. We recommend that corrosion protection be provided for any ductile iron pipe that
may be installed on this project.
D.8. Construction Quality Control
D.8.a. Excavation Observations
We recommend having a geotechnical engineer observe all excavations related to subgrade preparation
and spread footing, slab-on-grade and pavement construction. The purpose of the observations is to
evaluate the competence of the geologic materials exposed in the excavations, and the adequacy of
required excavation oversizing.
D.8.b. Materials Testing
We recommend density tests be taken in excavation backfill and additional required fill placed below
spread footings, slab-on-grade construction, beside foundation walls behind basement walls, and below
pavements.
We recommend Gyratory tests on bituminous mixes to evaluate strength and air voids, and density tests
to evaluate compaction.
We also recommend slump, air content and strength tests of Portland cement concrete.
Hunter Emerson
Project BL-13-04915
August 21, 2013
Page 16
D.8.c. Pavement Subgrade Proof-Roll
We recommend that proof-rolling of the pavement subgrades be observed by a geotechnical engineer to
determine if the results of the procedure meet project specifications, or delineate the extent of
additional pavement subgrade preparation work.
D.8.d. Cold Weather Precautions
If site grading and construction is anticipated during cold weather, all snow and ice should be removed
from cut and fill areas prior to additional grading. No fill should be placed on frozen subgrades. No frozen
soils should be used as fill.
Concrete delivered to the site should meet the temperature requirements of ASTM C 94. Concrete
should not be placed on frozen subgrades. Concrete should be protected from freezing until the
necessary strength is attained. Frost should not be permitted to penetrate below footings.
E. Procedures
E.1. Penetration Test Borings
The most recent penetration test borings were drilled on August 15, 2013 with an off road-mounted core
and auger drill equipped with hollow-stem auger. The borings were performed in accordance with ASTM
D 1586. Penetration test samples were taken at 2 1/2- or 5-foot intervals. Actual sample intervals and
corresponding depths are shown on the boring logs.
E.2. Material Classification and Testing
E.2.a. Visual and Manual Classification
The geologic materials encountered were visually and manually classified in accordance with ASTM
Standard Practice D 2488. A chart explaining the classification system is attached. Samples were placed in
jars or bags and returned to our facility for review and storage.
E.2.b. Laboratory Testing
The results of the laboratory tests performed on geologic material samples are noted on or follow the
appropriate attached exploration logs. The tests were performed in accordance with ASTM or AASHTO
procedures.
Hunter Emerson
Project BL-13-04915
August 21, 2013
Page 17
E.3. Groundwater Measurements
The drillers checked for groundwater as the penetration test borings were advanced, and again after
auger withdrawal. The boreholes were then immediately backfilled.
F. Qualifications
F.1. Variations in Subsurface Conditions
F.1.a. Material Strata
Our evaluation, analyses and recommendations were developed from a limited amount of site and
subsurface information. It is not standard engineering practice to retrieve material samples from
exploration locations continuously with depth, and therefore strata boundaries and thicknesses must be
inferred to some extent. Strata boundaries may also be gradual transitions, and can be expected to vary
in depth, elevation and thickness away from the exploration locations.
Variations in subsurface conditions present between exploration locations may not be revealed until
additional exploration work is completed, or construction commences. If any such variations are
revealed, our recommendations should be re-evaluated. Such variations could increase construction
costs, and a contingency should be provided to accommodate them.
F.1.b. Groundwater Levels
Groundwater measurements were made under the conditions reported herein and shown on the
exploration logs, and interpreted in the text of this report. It should be noted that the observation
periods were relatively short, and groundwater can be expected to fluctuate in response to rainfall,
flooding, irrigation, seasonal freezing and thawing, surface drainage modifications and other seasonal
and annual factors.
F.2. Continuity of Professional Responsibility
F.2.a. Plan Review
This report is based on a limited amount of information, and a number of assumptions were necessary to
help us develop our recommendations. It is recommended that our firm review the geotechnical aspects
of the designs and specifications, and evaluate whether the design is as expected, if any design changes
Hunter Emerson
Project BL-13-04915
August 21, 2013
Page 18
have affected the validity of our recommendations, and if our recommendations have been correctly
interpreted and implemented in the designs and specifications.
F.2.b. Construction Observations and Testing
It is recommended that we be retained to perform observations and tests during construction. This will
allow correlation of the subsurface conditions encountered during construction with those encountered
by the borings, and provide continuity of professional responsibility.
F.3. Use of Report
This report is for the exclusive use of the parties to which it has been addressed. Without written
approval, we assume no responsibility to other parties regarding this report. Our evaluation, analyses
and recommendations may not be appropriate for other parties or projects.
F.4. Standard of Care
In performing its services, Braun Intertec used that degree of care and skill ordinarily exercised under
similar circumstances by reputable members of its profession currently practicing in the same locality. No
warranty, express or implied, is made.
Appendix
4
4
4
9
14
14
15
1 1/2
2
22
18
FILL
CL
FILL: Organic Clay, black and dark brown, moist to
wet.
with Concrete at 5 1/2 feet.
SANDY LEAN CLAY, trace Gravel, brown, moist to
wet, rather soft to stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed to cave-in depth of 17 feet
immediately after withdrawal of auger.
Boring immediately backfilled.
Benchmark:
Surface elevations
at the borings
provided by
Sathre-Bergquist,
Inc.
972.7
957.7
6.0
21.0
Braun Intertec Corporation ST-1 page 1 of 1
3 1/4" HSA, AutohammerK. Keck 8/15/13 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
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LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-1
METHOD:
BORING:
BPF
BL-13-04915LO
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Braun Project BL-13-04915
Geotechnical Evaluation
Galpin Boulevard Properties
Galpin Boulevard and W. 78th Street
Chanhassen, Minnesota
pp
tsf
MC
%Symbol
Elev.
feet
978.7
Depth
feet
0.0
5
7
3
2
2
1
2
6
8
22
FILL
CL
CH
CL
CL
CL
FILL: Lean Clay with Sand, trace organics, dark brown,
black and brown, moist to wet.
LEAN CLAY, trace organics, with seams of Silty Sand,
gray and dark brown, wet.
(Alluvium)
with layer of Fat Clay at 10 feet.
FAT CLAY, trace wood, dark gray and black, wet.
(Alluvium)
SANDY LEAN CLAY, gray, wet, very soft.
(Alluvium)
LEAN CLAY, trace shells, gray, wet, soft.
(Alluvium)
SANDY LEAN CLAY, trace Gravel, gray, wet, medium.
(Glacial Till)
END OF BORING.*
An open triangle in the
water level (WL) column
indicates the depth at
which groundwater was
observed while drilling.
Water observed at 6
feet while drilling.
Water observed at 6
feet immediately after
withdrawal of auger.
Boring immediately
backfilled.
953.0
947.0
944.0
940.0
935.0
928.0
6.0
12.0
15.0
19.0
24.0
31.0
Braun Intertec Corporation ST-2 page 1 of 1
3 1/4" HSA, AutohammerK. Keck 8/15/13 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
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LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-2
METHOD:
BORING:
BPF
BL-13-04915LO
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Braun Project BL-13-04915
Geotechnical Evaluation
Galpin Boulevard Properties
Galpin Boulevard and W. 78th Street
Chanhassen, Minnesota
MC
%Symbol
Elev.
feet
959.0
Depth
feet
0.0
8
4
2
2
2
2
3
FILL
OL
PT
OL
CL
CL
FILL: Silty Sand, fine-grained, black, moist.
ORGANIC CLAY, black, moist.
(Swamp Deposit)
PEAT, fibrous, with shells, brown and gray, wet.
(Swamp Deposit)
ORGANIC SILT, with lenses of Silty Sand, gray, wet,
very loose.
(Swamp Deposit)
LEAN CLAY with SAND, with lenses of Silty Sand,
gray, wet, soft.
(Glacial Till)
SANDY LEAN CLAY, with seams of Silty Sand, gray,
wet, soft.
(Glacial Till)
END OF BORING.
Water observed at 4 feet immediately after withdrawal
of auger.
Boring immediately backfilled.
954.8
948.8
943.8
941.8
937.8
934.8
1.0
7.0
12.0
14.0
18.0
21.0
Braun Intertec Corporation ST-3 page 1 of 1
3 1/4" HSA, AutohammerK. Keck 8/15/13 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
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LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-3
METHOD:
BORING:
BPF
BL-13-04915LO
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Braun Project BL-13-04915
Geotechnical Evaluation
Galpin Boulevard Properties
Galpin Boulevard and W. 78th Street
Chanhassen, Minnesota
Symbol
Elev.
feet
955.8
Depth
feet
0.0
2
2
7
7
7
11
17
20
20
OL
CL
CL
CL
ORGANIC CLAY, black, wet.
(Topsoil)
LEAN CLAY with SAND, grayish brown, wet, soft.
(Glacial Till)
SANDY LEAN CLAY, brown, wet, medium.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, gray, wet, medium
to very stiff.
(Glacial Till)
with seams of Silty Sand at 13 feet.
END OF BORING.
Water observed at 8 feet immediately after withdrawal
of auger.
Boring immediately backfilled.
963.2
961.7
956.7
947.7
5.5
7.0
12.0
21.0
Braun Intertec Corporation ST-4 page 1 of 1
3 1/4" HSA, AutohammerK. Keck 8/15/13 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
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LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-4
METHOD:
BORING:
BPF
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Braun Project BL-13-04915
Geotechnical Evaluation
Galpin Boulevard Properties
Galpin Boulevard and W. 78th Street
Chanhassen, Minnesota
MC
%Symbol
Elev.
feet
968.7
Depth
feet
0.0
2
2
15
12
11
9
10
21
16
OL
CL
CL
CL
ORGANIC CLAY, black, wet.
(Topsoil)
LEAN CLAY, light gray, wet, soft.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, brown, moist to
wet, stiff to rather stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, gray, wet, rather
stiff.
(Glacial Till)
with seams of Silty Sand at 19 feet.
END OF BORING.
Water observed at 8 feet immediately after withdrawal
of auger.
Boring immediately backfilled.
952.6
951.1
946.1
937.1
5.5
7.0
12.0
21.0
Braun Intertec Corporation ST-5 page 1 of 1
3 1/4" HSA, AutohammerK. Keck 8/15/13 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
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LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-5
METHOD:
BORING:
BPF
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Braun Project BL-13-04915
Geotechnical Evaluation
Galpin Boulevard Properties
Galpin Boulevard and W. 78th Street
Chanhassen, Minnesota
MC
%Symbol
Elev.
feet
958.1
Depth
feet
0.0
Descriptive Terminology of Soil
Standard D 2487 - 00
Classification of Soils for Engineering Purposes
(Unified Soil Classification System)
Rev. 7/07
DD Dry density, pcf
WD Wet density, pcf
MC Natural moisture content, %
LL Liqiuid limit, %
PL Plastic limit, %
PI Plasticity index, %
P200 % passing 200 sieve
OC Organic content, %
S Percent of saturation, %
SG Specific gravity
C Cohesion, psf
Angle of internal friction
qu Unconfined compressive strength, psf
qp Pocket penetrometer strength, tsf
Liquid Limit (LL)
Laboratory Tests
Pl
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Drilling Notes
Standard penetration test borings were advanced by 3 1/4” or 6 1/4”
ID hollow-stem augers unless noted otherwise, Jetting water was used
to clean out auger prior to sampling only where indicated on logs.
Standard penetration test borings are designated by the prefix “ST”
(Split Tube). All samples were taken with the standard 2” OD split-tube
sampler, except where noted.
Power auger borings were advanced by 4” or 6” diameter continuous-
flight, solid-stem augers. Soil classifications and strata depths were in-
ferred from disturbed samples augered to the surface and are, therefore,
somewhat approximate. Power auger borings are designated by the
prefix “B.”
Hand auger borings were advanced manually with a 1 1/2” or 3 1/4”
diameter auger and were limited to the depth from which the auger could
be manually withdrawn. Hand auger borings are indicated by the prefix
“H.”
BPF: Numbers indicate blows per foot recorded in standard penetration
test, also known as “N” value. The sampler was set 6” into undisturbed
soil below the hollow-stem auger. Driving resistances were then counted
for second and third 6” increments and added to get BPF. Where they
differed significantly, they are reported in the following form: 2/12 for the
second and third 6” increments, respectively.
WH: WH indicates the sampler penetrated soil under weight of hammer
and rods alone; driving not required.
WR: WR indicates the sampler penetrated soil under weight of rods
alone; hammer weight and driving not required.
TW indicates thin-walled (undisturbed) tube sample.
Note: All tests were run in general accordance with applicable ASTM
standards.
Particle Size Identification
Boulders ...............................over 12”
Cobbles ...............................3” to 12”
Gravel
Coarse ............................3/4” to 3”
Fine .................................No. 4 to 3/4”
Sand
Coarse ............................No. 4 to No. 10
Medium ...........................No. 10 to No. 40
Fine .................................No. 40 to No. 200
Silt ....................................... No. 200, PI 4 or
below “A” line
Clay ..................................... No. 200, PI 4 and
on or above “A” line
Relative Density of
Cohesionless Soils
Very loose ................................0 to 4 BPF
Loose .......................................5 to 10 BPF
Medium dense.........................11 to 30 BPF
Dense......................................31 to 50 BPF
Very dense...............................over 50 BPF
Consistency of Cohesive Soils
Very soft...................................0 to 1 BPF
Soft.......................................2 to 3 BPF
Rather soft...............................4 to 5 BPF
Medium....................................6 to 8 BPF
Rather stiff...............................9 to 12 BPF
Stiff.......................................13 to 16 BPF
Very stiff...................................17 to 30 BPF
Hard.......................................over 30 BPF
a.Based on the material passing the 3-in (75mm) sieve.
b.If field sample contained cobbles or boulders, or both, add “with cobbles or boulders or both” to group name.
c.Cu = D60 / D10 Cc = (D30)2
D10 x D60
d.If soil contains 15% sand, add “with sand” to group name.
e.Gravels with 5 to 12% fines require dual symbols:
GW-GMwell-graded gravel with silt
GW-GCwell-graded gravel with clay
GP-GMpoorly graded gravel with silt
GP-GCpoorly graded gravel with clay
f.If fines classify as CL-ML, use dual symbol GC-GM or SC-SM.
g.If fines are organic, add “with organic fines” to group name.
h.If soil contains 15% gravel, add “with gravel” to group name.
i.Sands with 5 to 12% fines require dual symbols:
SW-SMwell-graded sand with silt
SW-SCwell-graded sand with clay
SP-SM poorly graded sand with silt
SP-SCpoorly graded sand with clay
j.If Atterberg limits plot in hatched area, soil is a CL-ML, silty clay.
k.If soil contains 10 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.
Poorly graded sand h
Peat
Well-graded gravel d
PI plots on or above “A” line
PI 7 and plots on or above “A” line j
PI 4 or plots below “A” line j
Fi
n
e
-
g
r
a
i
n
e
d
S
o
i
l
s
50
%
o
r
m
o
r
e
p
a
s
s
e
d
t
h
e
No
.
2
0
0
s
i
e
v
e
Co
a
r
s
e
-
g
r
a
i
n
e
d
S
o
i
l
s
mo
r
e
t
h
a
n
5
0
%
r
e
t
a
i
n
e
d
o
n
No
.
2
0
0
s
i
e
v
e
Soils Classification
Gravels
More than 50% of
coarse fraction
retained on
No. 4 sieve
Sands
50% or more of
coarse fraction
passes
No. 4 sieve
Silts and Clays
Liquid limit
less than 50
Highly Organic Soils
Silts and clays
Liquid limit
50 or more
Primarily organic matter, dark in color and organic odor
Group
Symbol
Criteria for Assigning Group Symbols and
Group Names Using Laboratory Tests a
Group Name b
GW
GP
GM
GC
SW
SP
SM
CL
ML
OL
OL
SC
Poorly graded gravel d
Silty gravel d f g
Clean Gravels
5% or less fines e
Gravels with Fines
More than 12% fines e
Clean Sands
5% or less fines i
Sands with Fines
More than 12% i
Fines classify as ML or MH
Fines classify as CL or CH Clayey gravel d f g
Well-graded sand h
Fines classify as CL or CH
Fines classify as ML or MH Silty sand f g h
Clayey sand f g h
Inorganic
Organic Liquid limit - oven dried
Liquid limit - not dried 0.75
Inorganic
Organic
PI plots below “A” line
Lean clay k l m
Liquid limit - oven dried
Liquid limit - not dried 0.75
CH
MH
OH
OH
Fat clay k l m
Elastic silt k l m
Organic clay k l m n
Organic silt k l m o
Organic clay k l m p
Organic silt k l m q
Cu 6 and 1 Cc 3 C
PT
Cu 4 and 1 Cc 3 C
Cu 4 and/or 1 Cc 3 C
Cu 6 and/or 1 CC 3 C
0 10 1620 30 4050 60 7080 90 100110
7
“U”
L
i
n
e
“A”
L
i
n
e
10
20
30
40
50
60
4
0
ML or OL
MH or OHCL o
r
O
L
CH
o
r
O
H
CL - ML
Silt k l m