Geotechnical Evaluation Report 01-27-2014
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 ................................................................................................................... 2
B.2.a. Geologic Materials ................................................................................................. 2
B.2.b. Groundwater .......................................................................................................... 3
B.3. Laboratory Test Results ....................................................................................................... 3
C. Basis for Recommendations ............................................................................................................. 3
C.1. Design Details ...................................................................................................................... 3
C.1.a. Building Structure Loads ........................................................................................ 3
C.1.b. Pavements and Traffic Loads ................................................................................. 4
C.1.c. Anticipated Grade Changes .................................................................................... 4
C.1.d. Precautions Regarding Changed Information ........................................................ 4
C.2. Design and Construction Considerations ............................................................................ 4
D. Recommendations ........................................................................................................................... 4
D.1. Building and Pavement Subgrade Preparation ................................................................... 4
D.1.a. Excavations ............................................................................................................. 4
D.1.b. Excavation Dewatering ........................................................................................... 5
D.1.c. Selecting Excavation Backfill and Additional Required Fill ..................................... 5
D.1.d. Placement and Compaction of Backfill and Fill ...................................................... 6
D.2. Spread Footings ................................................................................................................... 6
D.2.a. Embedment Depth ................................................................................................. 6
D.2.b. Subgrade Improvement ......................................................................................... 6
D.2.c. Net Allowable Bearing Pressure ............................................................................. 6
D.2.d. Settlement .............................................................................................................. 6
D.3. Basement Walls ................................................................................................................... 7
D.3.a. Drainage Control .................................................................................................... 7
D.3.b. Selection, Placement and Compaction of Backfill .................................................. 7
D.3.c. Configuring and Resisting Lateral Loads................................................................. 8
D.4. Interior Slabs ....................................................................................................................... 9
Table of Contents (continued)
Description Page
D.4.a. Moisture Vapor Protection .................................................................................... 9
D.4.b. Radon ..................................................................................................................... 9
D.5. Exterior Slabs ....................................................................................................................... 9
D.6. Utilities .............................................................................................................................. 11
D.6.a. Subgrade Stabilization .......................................................................................... 11
D.6.b. Corrosion Potential .............................................................................................. 11
D.7. Construction Quality Control ............................................................................................ 11
D.7.a. Excavation Observations ...................................................................................... 11
D.7.b. Materials Testing .................................................................................................. 11
D.7.c. Cold Weather Precautions ................................................................................... 11
E. Procedures...................................................................................................................................... 12
E.1. Penetration Test Borings ................................................................................................... 12
E.2. Material Classification and Testing ................................................................................... 12
E.2.a. Visual and Manual Classification .......................................................................... 12
E.2.b. Laboratory Testing ............................................................................................... 12
E.3. Groundwater Measurements ............................................................................................ 12
F. Qualifications .................................................................................................................................. 12
F.1. Variations in Subsurface Conditions .................................................................................. 12
F.1.a. Material Strata ..................................................................................................... 12
F.1.b. Groundwater Levels ............................................................................................. 13
F.2. Continuity of Professional Responsibility .......................................................................... 13
F.2.a. Plan Review .......................................................................................................... 13
F.2.b. Construction Observations and Testing ............................................................... 13
F.3. Use of Report..................................................................................................................... 13
F.4. Standard of Care ................................................................................................................ 13
Appendix
Boring Location Sketch
Log of Boring Sheets, ST-1 through ST-5
Descriptive Terminology
A. Introduction
A.1. Project Description
Dogwood Road, LLC is planning to develop the west portion of the Westwood Church property into 5
single-family house lots. These lots will be serviced by the existing street, Dogwood Road. A new sediment
pond or infiltration basin is also planned on the north end of this site.
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 Otto Associates showing the proposed development.
A.4. Site Conditions
Most of this part of the site is heavily wooded with surface elevations at the borings ranging from about
992 at the north end to about elevation 1014 at the south end.
A.5. Scope of Services
Our scope of services for this project was originally submitted January 2, 2014 as a Proposal to Mr. Todd
Simning of Dogwood Road, LLC. The proposal was authorized by Mr. Simning on January 2, 2014. Tasks
performed in accordance with our authorized scope of services included:
Staking the proposed boring locations.
Clearing exploration locations of public underground utilities.
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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.
Our services were performed under the terms of our general conditions dated September 1, 2013.
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
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 topsoil at the surface
followed by glacially deposited soil to the termination depths of the borings.
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The topsoil layer consisted of mostly organic clay and varied from about 1/2 to 2 1/2 feet thick. Below the
topsoil, the borings encountered naturally deposited lean clay, lean clay with sand and sandy lean clay to
the termination depths of the borings.
Penetration resistance values recorded in the clay soils ranged from 11 to 20 blows per foot (BPF)
corresponding to consistencies of rather stiff to very stiff.
B.2.b. Groundwater
While drilling, groundwater was not observed in any of the borings. Based on the borings, groundwater is
likely present below the termination depths of our borings. Groundwater levels will vary over time and in
response to climatic conditions.
B.3. Laboratory Test Results
The moisture contents of the selected clay soil samples tested were determined to vary from
approximately 18 to 27 percent, indicating that these soils were mostly near or wetter than their probable
optimum moisture contents.
Pocket penetrometer tests were taken on select soil samples to estimate the unconfined compressive
strengths of the soil samples tested. The results of these tests ranged from about 1 1/2 to 3 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 the west end of the property
currently owned by Westwood Church. The development will include 5 new single-family house lots as
well as a sediment pond/infiltration basin in the north part of the site. 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.
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C.1.b. Pavements and Traffic Loads
The new house lots, including underground water and sanitary sewer, will be accessed from the existing
Dogwood Road.
C.1.c. Anticipated Grade Changes
Based on the surface elevations at the borings, the existing ground surface elevations range from about
993 to 1014. It is likely that most of these lots will only require a minimal amount of cutting or filling to
prepare the building pads. Because these lots are heavily wooded, it is likely that the grading needed to
prepare the house pads will be done on an individual, as-needed basis.
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 limited. The
geologic materials present below the topsoil generally appear suitable for support of conventional spread
footings and grade-supported slabs. The topsoil is not suitable to support fill and houses and is also not
suitable for use as engineered fill in the house pads and streets.
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 from beneath the proposed house pads and oversize areas. Based on
the soil borings, excavation depths are expected to range from approximately 1 1/2 to 2 1/2 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.
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Table 1. Anticipated Excavation Depths for Residential Construction.
Boring Surface Elevation (ft)
Anticipated Depth of
Excavation (ft)
Approximate Bottom
Elevation (ft)
ST-1 992.7 2 1/4 990 1/2
ST-2 995.5 1 1/2 994
ST-3 1007.2 2 1005
ST-4 1010.3 1 1/3 1009
ST-5 1014.0 2 1012
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.
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 subgrade elevations.
D.1.b. Excavation Dewatering
Water was not encountered in the borings, but it is possible that water could be encountered in other
parts of the site during basement excavations. If encountered, we recommend removing groundwater
from the excavations. Because the soils on this site are mostly clay, 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 should not be re-used as engineered fill under house pads. The glacially deposited soils 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. Most of the on site clay soil appears to be
suitable for use as engineered fill provided that they can be properly moisture conditioned.
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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 within the
house pads to a minimum of 95 percent of the standard Proctor dry density (ASTM D 698). If there are
areas of the building pads that require more than 10 feet of fill, the minimum compaction should be 98
percent. The clay fill should be placed and compacted at a moisture content of no less than 1 percentage
point below to no more than 3 percentage points above the soil’s optimum moisture content.
D.2. Spread Footings
D.2.a. Embedment Depth
For frost protection, we recommend embedding perimeter footings for the houses, including the attached
garages, a minimum of 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 8-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.
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.
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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 this 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.
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.
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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.
Exterior backfill not capped with slabs or pavement should be capped with a low-permeability on-site clay
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 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 excava tion.
Recommended equivalent fluid pressures for wall design based on active and at-rest earth pressure
conditions are presented below in Table 2. 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 2. 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
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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. The sliding coefficients should equal 0.30 for clay. 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
underlain with a geotextile matting suitable for venting the subgrade. The clean aggregate material should
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
Most of the exterior slabs will be underlain with mostly clay soil. These soils are considered to be
moderately to highly frost susceptible. These soils 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
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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 4 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 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.
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D.6. Utilities
D.6.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.6.b. Corrosion Potential
Most 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.7. Construction Quality Control
D.7.a. Excavation Observations
We recommend having a geotechnical engineer observe all excavations related to subgrade preparation as
well as spread footing and slab-on-grade 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.7.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 and behind basement walls.
We also recommend slump, air content and strength tests of Portland cement concrete.
D.7.c. 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.
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E. Procedures
E.1. Penetration Test Borings
The penetration test borings were drilled on January 15, 2014 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.
E.3. Groundwater Measurements
The drillers checked for groundwater as the penetration test borings were advanced, and again about 10
minutes after auger withdrawal. The boreholes were then 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.
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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 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
13
15
14
15
12
13
11
2
2 1/2
2
2
18
22
OL
CL
CL
ORGANIC CLAY, black, frozen to moist.
(Topsoil)
SANDY LEAN CLAY, trace Gravel, brown, moist to
wet, stiff to rather stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, gray, wet, stiff to
rather stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed 10 minutes after withdrawal of
auger.
Boring then backfilled.
990.5
978.7
971.7
2.2
14.0
21.0
Braun Intertec Corporation ST-1 page 1 of 1
3 1/4" HSA, AutohammerSTS 1/15/14 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
L O G O F B O R I N G
(S
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s
)
LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-1
METHOD:
BORING:
BPF
BL-14-00011LO
G
O
F
B
O
R
I
N
G
N
:
\
G
I
N
T
\
P
R
O
J
E
C
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S
\
M
I
N
N
E
A
P
O
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I
S
\
2
0
1
4
\
0
0
0
1
1
.
G
P
J
B
R
A
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N
_
V
8
_
C
U
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E
N
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.
G
D
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1
/
2
7
/
1
4
0
9
:
4
8
Braun Project BL-14-00011
GEOTECHNICAL EVALUATION
Westwood Church Site
Dogwood Road and West 78th Street
Chanhassen, Minnesota
qp
tsf
MC
%Symbol
Elev.
feet
992.7
Depth
feet
0.0
12
13
13
14
15
13
13
2
1 1/2
1 1/2
1 1/2
22
21
OL
CL
CL
CL
ORGANIC CLAY, black, frozen to wet.
(Topsoil)
LEAN CLAY with SAND, brown, wet, rather stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, brown, wet, stiff.
(Glacial Till)
Trace of fibers at 8 feet.
Seams of Silty Sand at 10 feet.
SANDY LEAN CLAY, trace Gravel, gray, wet, stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed 10 minutes after withdrawal of
auger.
Boring then backfilled.
994.0
991.5
981.5
974.5
1.5
4.0
14.0
21.0
Braun Intertec Corporation ST-2 page 1 of 1
3 1/4" HSA, AutohammerSTS 1/15/14 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
L O G O F B O R I N G
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s
)
LOCATION: See attached sketch.
(Soil-ASTM D2488 or D2487, Rock-USACE EM1110-1-2908)
Description of Materials
ST-2
METHOD:
BORING:
BPF
BL-14-00011LO
G
O
F
B
O
R
I
N
G
N
:
\
G
I
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\
P
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A
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2
0
1
4
\
0
0
0
1
1
.
G
P
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B
R
A
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_
V
8
_
C
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E
N
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G
D
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1
/
2
7
/
1
4
0
9
:
4
8
Braun Project BL-14-00011
GEOTECHNICAL EVALUATION
Westwood Church Site
Dogwood Road and West 78th Street
Chanhassen, Minnesota
qp
tsf
MC
%Symbol
Elev.
feet
995.5
Depth
feet
0.0
18
14
14
15
15
15
13
2
2 1/4
2 1/4
2
23
21
OL
CL
CL
CL
ORGANIC CLAY, black, frozen to wet.
(Topsoil)
LEAN CLAY with SAND, brown, wet, very stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, brown, wet, stiff.
(Glacial Till)
Seams of Silty Sand at 8 feet.
SANDY LEAN CLAY, trace Gravel, brown, wet, stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed 10 minutes after withdrawal of
auger.
Boring then backfilled.
1005.3
1003.2
997.2
986.2
1.9
4.0
10.0
21.0
Braun Intertec Corporation ST-3 page 1 of 1
3 1/4" HSA, AutohammerSTS 1/15/14 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
L O G O F B O R I N G
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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-14-00011LO
G
O
F
B
O
R
I
N
G
N
:
\
G
I
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\
P
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M
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N
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A
P
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2
0
1
4
\
0
0
0
1
1
.
G
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J
B
R
A
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N
_
V
8
_
C
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G
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1
/
2
7
/
1
4
0
9
:
4
8
Braun Project BL-14-00011
GEOTECHNICAL EVALUATION
Westwood Church Site
Dogwood Road and West 78th Street
Chanhassen, Minnesota
qp
tsf
MC
%Symbol
Elev.
feet
1007.2
Depth
feet
0.0
17
13
13
13
13
19
20
3
3
20
18
OL
CL
CL
ORGANIC CLAY, black, frozen to wet.
(Topsoil)
LEAN CLAY with SAND, brown, moist to wet, very stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, brown, moist to
wet, stiff to very stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed 10 minutes after withdrawal of
auger.
Boring then backfilled.
1009.0
1006.3
989.3
1.3
4.0
21.0
Braun Intertec Corporation ST-4 page 1 of 1
3 1/4" HSA, AutohammerSTS 1/15/14 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
L O G O F B O R I N G
(S
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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
BL-14-00011LO
G
O
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B
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R
I
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N
:
\
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0
1
1
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G
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0
9
:
4
8
Braun Project BL-14-00011
GEOTECHNICAL EVALUATION
Westwood Church Site
Dogwood Road and West 78th Street
Chanhassen, Minnesota
qp
tsf
MC
%Symbol
Elev.
feet
1010.3
Depth
feet
0.0
12
12
13
18
19
16
19
2 1/2
2 1/2
2 1/2
23
27
OL
CL
CL
CL
CL
ORGANIC CLAY, black, frozen to wet.
(Topsoil)
LEAN CLAY with SAND, trace roots, brown and dark
brown, rather stiff.
(Glacial Till)
LEAN CLAY, brown, moist, rather stiff.
(Glacial Till)
LEAN CLAY with SAND, trace Gravel, brown, wet,
rather stiff to stiff.
(Glacial Till)
SANDY LEAN CLAY, trace Gravel, brown, wet, stiff to
very stiff.
(Glacial Till)
END OF BORING.
Water not observed with 19 1/2 feet of hollow-stem
auger in the ground.
Water not observed 10 minutes after withdrawal of
auger.
Boring immediately backfilled.
1012.0
1010.0
1008.5
1005.0
993.0
2.0
4.0
5.5
9.0
21.0
Braun Intertec Corporation ST-5 page 1 of 1
3 1/4" HSA, AutohammerSTS 1/15/14 1" = 4'DATE:SCALE:DRILLER:
Tests or NotesWL
L O G O F B O R I N G
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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
BL-14-00011LO
G
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B
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I
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:
\
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0
9
:
4
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Braun Project BL-14-00011
GEOTECHNICAL EVALUATION
Westwood Church Site
Dogwood Road and West 78th Street
Chanhassen, Minnesota
qp
tsf
MC
%Symbol
Elev.
feet
1014.0
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
a
s
t
i
c
i
t
y
I
n
d
e
x
(
P
I
)
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