Chanhassen Specialty Grocery - Final Geotech Report
Table of Contents
Description Page
A. Introduction ...................................................................................................................................... 1
A.1. Project Description .............................................................................................................. 1
A.2. Purpose ................................................................................................................................ 1
A.3. Previous Site Experience ..................................................................................................... 1
A.4. Scope of Services ................................................................................................................. 2
A.5. Site Conditions..................................................................................................................... 2
B. Results .............................................................................................................................................. 2
B.1. Boring Locations and Elevations .......................................................................................... 2
B.2. Exploration Logs .................................................................................................................. 3
B.2.a. Log of Boring Sheets ............................................................................................... 3
B.2.b. Geologic Origins ..................................................................................................... 3
B.3. Geologic Profile ................................................................................................................... 3
B.3.a. Topsoil and Fill ........................................................................................................ 4
B.3.b. Swamp and Alluvial Deposits ................................................................................. 4
B.3.c. Glacial Deposits ...................................................................................................... 4
B.3.d. Penetration Resistance Testing .............................................................................. 4
B.3.e. Groundwater .......................................................................................................... 5
B.4. Laboratory Test Results ....................................................................................................... 5
C. Basis for Recommendations ............................................................................................................. 6
C.1. Design Details ...................................................................................................................... 6
C.1.a. Proposed Structure ................................................................................................ 6
C.1.b. Pavement Improvements ....................................................................................... 6
C.1.c. Utility Improvements ............................................................................................. 6
C.1.d. Project Schedule ..................................................................................................... 7
C.1.e. Precautions Regarding Changed Information ........................................................ 7
C.2. Considerations Impacting Design and Construction ........................................................... 7
C.2.a. Building Support ..................................................................................................... 7
C.2.b. Pavement Areas ..................................................................................................... 8
C.2.c. Reuse of Onsite Soils .............................................................................................. 8
C.2.d. Impacts of Surface and Groundwater .................................................................... 9
C.2.e. Disturbance of Onsite Soils .................................................................................... 9
D. Recommendations ........................................................................................................................... 9
D.1. Building Subgrade Preparation ........................................................................................... 9
D.1.a. Excavations ............................................................................................................. 9
D.1.b. Groundwater Control ........................................................................................... 10
D.1.c. Selecting Excavation Backfill and Additional Required Fill ................................... 11
D.1.d. Placement and Compaction of Backfill and Fill .................................................... 11
D.2. Spread Footings ................................................................................................................. 11
D.2.a. Embedment Depth and Frost Protection ............................................................. 11
D.2.b. Net Allowable Bearing Pressure ........................................................................... 12
D.2.c. Settlement ............................................................................................................ 12
D.3. Interior Slabs ..................................................................................................................... 12
D.3.a. Subgrade Modulus ............................................................................................... 12
D.3.b. Moisture Vapor Protection .................................................................................. 12
D.4. Exterior Slabs ..................................................................................................................... 13
D.4.a. Subgrade Improvement ....................................................................................... 13
Table of Contents (continued)
Description Page
D.4.b. Frost Protection .................................................................................................... 13
D.5. Pavements ......................................................................................................................... 13
D.5.a. Pavement Subgrade Preparation ......................................................................... 13
D.5.b. Construction Delay ............................................................................................... 14
D.5.c. Assumed R-value .................................................................................................. 14
D.5.d. Bituminous Design Sections ................................................................................. 14
D.5.e. Concrete Pavement Design .................................................................................. 15
D.5.f. Materials and Compaction ................................................................................... 15
D.5.g. Subgrade Drainage ............................................................................................... 15
D.5.h. Pavement Maintenance ....................................................................................... 16
D.6. Utilities .............................................................................................................................. 16
D.6.a. Subgrade Stabilization .......................................................................................... 16
D.6.b. Selection, Placement and Compaction of Backfill ................................................ 17
D.7. Construction Quality Control ............................................................................................ 17
D.7.a. Excavation Side Slopes ......................................................................................... 17
D.7.b. Observations ........................................................................................................ 17
D.7.c. Subgrade Proof-Roll ............................................................................................. 17
D.7.d. Materials Testing .................................................................................................. 18
D.7.e. Cold Weather Precautions ................................................................................... 18
D.7.f. Special Inspections of Soils ................................................................................... 18
E. Procedures...................................................................................................................................... 18
E.1. Penetration Test Borings ................................................................................................... 18
E.2. Material Classification and Testing ................................................................................... 19
E.2.a. Visual and Manual Classification .......................................................................... 19
E.2.b. Laboratory Testing ............................................................................................... 19
E.3. Groundwater Measurements ............................................................................................ 19
F. Qualifications .................................................................................................................................. 19
F.1. Variations in Subsurface Conditions .................................................................................. 19
F.1.a. Material Strata ..................................................................................................... 19
F.1.b. Groundwater Levels ............................................................................................. 20
F.2. Continuity of Professional Responsibility .......................................................................... 20
F.2.a. Plan Review .......................................................................................................... 20
F.2.b. Construction Observations and Testing ............................................................... 20
F.3. Use of Report..................................................................................................................... 20
F.4. Standard of Care ................................................................................................................ 20
Appendix
Boring Location Sketch
Log of Boring Sheets ST-100 to ST-106
Log of Boring Sheets ST-1 to ST-11 (Braun Intertec project B13-06640)
Subsurface Boring Logs 1 to 4 (AET project 01-00617)
Descriptive Terminology
A. Introduction
A.1. Project Description
This Geotechnical Evaluation Report addresses the proposed construction of a 14,000 square foot
retail/grocery facility and its associated pavements in Chanhassen, Minnesota. We understand the
proposed development will consist of a one-story 14,000 square foot commercial structure along with
supporting site improvements. There may be a potential second phase to this project which would
include construction of another retail building and pavements in the southern portion of the site. This
site is currently vacant but has been subject to past grading activities.
As part of the project, Braun Intertec has been contracted by Venture Pass Partners, LLC to perform soil
borings and a geotechnical evaluation.
A.2. Purpose
The purpose of our geotechnical evaluation was to characterize subsurface geologic conditions at
selected exploration locations and evaluate their impact on the design and construction of the proposed
retail building and its associated pavements.
A.3. Previous Site Experience
We performed a geotechnical evaluation on this site in 2013 for a project that was not constructed. The
general geologic profile encountered in our previous borings across the site consisted of a variable layer
of previously placed fill to depths of 1 to 17 feet over glacial soils associated with the Des Moines Lobe
glacial advance. Localized deposits of swamp deposited and alluvial soils were also encountered below
the fill at a few locations. The fill depths were typically greater in the southern and western portions of
the site. The available information would appear to indicate that the fill soils on this site were not placed
in an engineered fashion.
We also reviewed a Report of Subsurface Investigation performed by American Engineering Testing (AET)
under project 01-00617 that was dated December 21, 2000. The subsurface conditions encountered in
AET’s soil borings were similar to those encountered in our previous borings.
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Project B14-06766
October 8, 2014
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A.4. Scope of Services
Our scope of services for this project was originally submitted as a Proposal for Geotechnical Evaluation,
dated September 5, 2014. Geotechnical evaluation related tasks performed in accordance with our
authorized scope of services for the project included:
Reviewing previous geotechnical information for this site.
Staking soil borings and clearing exploration locations of underground utilities.
Performing 7 standard penetration test borings to nominal depths of 11 to 21 feet below
grade across the site.
Classifying soils recovered from the borings and preparing Log of Boring sheets.
Performing laboratory tests on selected penetration test samples recovered from the
borings.
Performing engineering analysis and formulating recommendations for design and
construction of foundations, interior and exterior floor slabs, utilities, and pavements.
Preparing this report containing a CAD sketch, exploration logs (new and previous), a
summary of the geologic materials encountered, results of laboratory tests, and geotechnical
recommendations.
A.5. Site Conditions
The project site is the 2.71 acre parcel bounded by Lake Drive to the south, Main Street to the east, and
Pond Promenade to the north and west. The parcel is currently vacant and lightly vegetated. A shallow
pond is present across the south side of the site. We understand the pond is not a storm water feature,
but a product of grading and water accumulation.
We understand the site has undergone significant grading operations during initial development;
however, records documenting the previous grading activities were not available.
B. Results
B.1. Boring Locations and Elevations
We performed 7 standard penetration test borings for the project, denoted as ST-100 to ST-106. The
approximate boring locations are shown on the Soil Boring Location Sketch included in the Appendix.
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Project B14-06766
October 8, 2014
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The approximate locations of our previous borings, denoted as ST-1 through ST-11, as well as those
previously performed by AET, denoted as 1 through 4, are also shown on the sketch.
The boring locations of our recent and previous borings were staked by Braun Intertec personnel.
Surface elevations and locations were acquired with GPS technology through the use of the State of
Minnesota’s permanent GPS base station network.
B.2. Exploration Logs
B.2.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
tests performed within them, 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.2.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 testing performed for the project, (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.3. Geologic Profile
The general geologic profile encountered at our recent and previous borings across the site consisted of a
variable layer of previously placed fill over glacial soils associated with the Des Moines Lobe glacial
advance. Localized deposits of swamp deposited and alluvial soils were also encountered below the fill
at a few locations. The following subsections discuss the strata in greater detail.
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Project B14-06766
October 8, 2014
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The profile encountered at our exploration locations was similar to the profile depicted within the
previous AET borings.
B.3.a. Topsoil and Fill
Where identifiable filled topsoil was encountered, the topsoil typically consisted of dark brown to black
sandy lean clay and clayey sand that was 6 to 18 inches thick. Buried topsoil was encountered in Boring
ST-105 between the 4- and 6-foot depths.
Fill was present at all exploration locations ranging in depths from less than 1 foot to approximately 17
feet below grade. Fill was also encountered to the termination of Boring ST-8 (16 feet). The fill generally
consisted with brown, dark brown, black and gray sandy lean clay and lean clay, with lesser amounts of
silty sand and clayey sand also present. The fill contained variable amounts of gravel and roots and
varied from moist (near its probable optimum moisture content) to wet (above its probable optimum
moisture content). Portions of the fill were determined to be slightly organic to organic or were mixed
with organic soils, such as topsoil or swamp deposited soils. Slightly organic to organic fill soils were
encountered within Borings ST-5 to ST-10. It is likely the organic fill soils were previously stripped from
other portions of the development.
B.3.b. Swamp and Alluvial Deposits
A layer of swamp deposited and/or alluvial soil was encountered below the fill at Borings ST-106, ST-5
and ST-10. The swamp deposited and alluvial soil consisted of black organic clay and dark gray lean clay
that were wet and ranged in thickness from about 2 to 8 feet.
B.3.c. Glacial Deposits
Glacial deposits were encountered below the fill or swamp/alluvial deposits at all boring locations,
except ST-8, which terminated in existing fill. The glacial soils predominantly consisted of brown to gray
clayey sand and sandy lean clay, with lesser amounts of silty sand . The glacial soils contained variable
amounts of gravel and have the potential to contain cobbles and boulders.
B.3.d. Penetration Resistance Testing
The results of our penetration resistance testing from the borings are summarized below in Table 1.
Comments are provided to qualify the significance of the results.
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Project B14-06766
October 8, 2014
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Table 1. Penetration Resistance Data
Geologic Material Classification
Range of Penetration
Resistances* Comments
Fill SM, SC, CL 4 to 21 BPF Variably compacted
Swamp/Alluvial OL, CL 6 to 8 BPF -
Glacial SC, CL 4 to 20 BPF
Locally rather soft and
very stiff, generally
medium to stiff
*BPF – Blows per Foot
B.3.e. Groundwater
Groundwater observations at the boring locations during drilling operations and after auger withdrawal,
prior to backfilling, are provided in the table below. Only borings where groundwater was observed are
included. Please note these observations are based on a limited observation period and should be
considered approximate.
Table 2. Approximate Observed Groundwater Levels at the Borings
Boring Surface Elevation
Shallowest Observed Depth
(feet) Observed Elevation
ST-2 950.5 9 1/2 941
ST-5 943.9 19 925
ST-9 944.0 12 932
ST-100 949.4 20 929
ST-101 945.2 20 925
ST-102 940.9 20 921
ST-103 949.0 20 929
Seasonal and annual fluctuations of groundwater levels should also be anticipated.
B.4. Laboratory Test Results
We performed moisture content, sieve analysis (percent passing the number 200 sieve tests), organic
content tests and unconfined compression (hand penetrometer) tests on samples recovered from the
soil borings in accordance with ASTM procedures. The laboratory test results are shown on the Log of
Boring Sheets included in the Appendix, across from the associated soil sample.
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Project B14-06766
October 8, 2014
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C. Basis for Recommendations
C.1. Design Details
C.1.a. Proposed Structure
We understand that the building will consist of a one-story, slab-on-grade structure encompassing an
area of 14,000 square feet. We assume that the building will be rather lightly loaded, with perimeter
loads not exceeding 4 kips per foot and column loads not exceeding 150 kips. We assume that the floor
slab load will not exceed 125 psf.
We understand the building will have a finished floor elevation of 951.5. Based on the surface
elevations of the borings, fill depths above existing surface grades will generally range from about 2 to 6
feet for most of the building, with the south central portion of the building requiring up to 10 feet of fill.
Based on our conversation with the Civil Engineer for the project, we understand that this site will
require a significant amount of soil to be imported to achieve the design grades.
C.1.b. Pavement Improvements
Based on the preliminary plans provided to us by Sambatek, the project civil engineer, there will be both
standard and heavy duty bituminous pavements, as well as heavy duty concrete pavement in the loading
dock area. Although traffic loads were not available to us, we assume that the standard duty traffic
loads will be less than 75,000 ESALs over a 20 year design life and the heavy duty traffic loads will be less
than 150,000 ESALs over a 20 year design life.
Grades changes within the new parking areas will consist of fills ranging from about 2 to 4 feet for most
of the pavement areas.
C.1.c. Utility Improvements
Standard below grade utilities, including storm sewer, sanitary sewer and watermain pipes are
anticipated for construction as part of the project. Utilities are assumed to have invert depths within
approximately 8 feet of final surface grades.
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Project B14-06766
October 8, 2014
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C.1.d. Project Schedule
We understand that the preferred project schedule would be to perform the mass grading/soil
corrections and install footings and foundation walls in November of this year and wait until March of
2015 to construct the rest of the building, install utilities and pavements. If the required approvals
cannot be obtained in time to allow earthwork to begin in November, then the mass grading/soil
correction and installation of foundations would likely begin in March of 2015.
C.1.e. 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. Considerations Impacting Design and Construction
C.2.a. Building Support
Based on the results of the soil borings and our understanding of the current building design, we
anticipate the site is suitable for support of the proposed building using typical spread footing
foundations and a ground supported slab. However, a soil correction approach will be required to
remove topsoil and previously placed fill, which are locally mixed with organic soils and do not appear to
consist of engineered fill, and underlying organic swamp deposited and soft to rather soft alluvial and
glacial clays to control settlement and improve bearing capacity. Based on the soil boring data, soil
correction depths are anticipated to range from about 1 to 7 feet below current site grades across the
north half of the building pad and from about 5 to 12 feet below site grades across the southern portion
of the building. Subsequent backfill depths to establish building grades will range from less than 1 foot
up to 16 feet.
Given the time of year that the soil correction will be done and based on the moisture contents and
occasional organic material within the existing fill, a significant amount of the excavated soil will likely
not be suitable for reuse as structural fill within the building pad and will require replacement with
imported backfill. To facilitate construction, provide a material that can be readily compacted in cool
and wet conditions, reduce the risk of frost heave, as well as reduce the risk of long term settlement in
the deeper fill areas, it is our opinion that imported select granular borrow (MnDOT Specification
3149.2B2) be utilized as replacement backfill within the proposed building pad.
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October 8, 2014
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The silty and clayey materials excavated from the building pad can be placed as fill within the existing low
area in the southwestern portion of the site.
C.2.b. Pavement Areas
Subgrade soils within the proposed pavement areas consist of poorly to moderately compacted fill soils
overlying localized organic deposits, soft alluvial soils and glacial till soils. With the planned raise in grade
of 2 to 4 feet across the pavement areas, it should be anticipated that there will be additional
consolidation and settlement of the fill, organic and alluvial soils. To reduce the risk of the additional
settlement affecting the long term performance of the pavements, we recommend delaying placement
of the curb and pavements for at least 45 days after reaching design grades.
Subgrade preparation within the pavement areas should be anticipated to primarily involve stripping of
the surface vegetation and toposoil, proofrolling the subgrade, and then scarification, moisture
conditioning and compaction of the exposed subgrade soils. Given the clayey nature of the subgrade
soils, some subcutting and replacement of soft and/or wet clayey soils may also be required, particularly
given that the schedule will have earthwork being performed in November or March/April, depending
upon the City approval process. We would anticipate that it will be difficult to obtain adequate
compaction with the majority of the on-site soils. To facilitate the ease of construction, as well as
provide a stronger, more stable subgrade, those soils would also allow a thinner pavement section to be
utilized. It is our opinion that fill placed in proposed pavement areas consist of select granular soils.
C.2.c. Reuse of Onsite Soils
The onsite glacial soils (generally clays) should be suitable for reuse as engineered fill, but most will
require moisture conditioning (drying or watering) prior to reuse and compaction. The onsite fill soils,
which will compromise a majority of the excavated soils, also generally consist of silty and clayey soils.
Based on the borings, portions of the fill appears to be slightly organic to organic. Furthermore, moisture
content test results indicate the fill soils range from near to above their estimated optimum moisture
contents and they will likely not be directly suitable for reuse unless moisture conditioned prior to reuse.
Given the planned construction schedule, moisture conditioning of the silty and clayey soils will likely not
be feasible. Without adequate moisture conditioning, the compaction level of those soils will likely be
limited. Therefore, it is our opinion the best use of the on-site soils would be to place them in the
existing low area/pond. That portion of the site potentially could be developed into a future building
pad, however, deeper fills and organic soils exist in that area. We understand that it is not planned to
correct that portion of the site during this phase of earthwork, so any future building on that site would
likely need to utilize rammed aggregate piers (or a similar ground improvement method) to support the
building so the impact of lower compaction in the fill would be minimal.
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Project B14-06766
October 8, 2014
Page 9
The contractor should attempt to obtain 95 percent compaction in that area of the site, but that level of
compaction may not be attainable, depending upon the weather, time of year and moisture condition of
the soils. If 95 percent compaction is not attainable during construction, a meeting should be held with
the Owner, contractor and design team to evaluate other acceptance criteria.
C.2.d. Impacts of Surface and Groundwater
Removal of surface water within the existing low/pond area will be required prior to excavation and
backfilling operations. Areas of perched groundwater should also be anticipated within excavations
across the site, as indicated by the soil boring results.
The contractor should assume groundwater may be present in soil correction or other onsite excavations
(including utility) and any water should be immediately removed to facilitate construction and proper
backfilling. Sump pumps may be suitable for short term dewatering within the predominant onsite
clayey soils.
C.2.e. Disturbance of Onsite Soils
The contractor should note the onsite clayey soils are susceptible to disturbance due to repeated
construction traffic. Disturbance of these soils may cause areas that were previously prepared or
suitable for pavement or structure support to become unstable and require addition moisture
conditioning, compaction, and/or subcutting. Care should be taken to avoid disturbing the soils.
D. Recommendations
D.1. Building Subgrade Preparation
D.1.a. Excavations
For building pad preparation, we recommend removing the topsoil, other organic soils, previously placed
fill, swamp deposited and alluvial soils from below the proposed building pad and oversize area. If
present, we also recommend removal of all existing utilities and associated backfill from below the
proposed building pad. Additional removal of soft to rather soft glacial soils may also be required.
After excavation of the unsuitable soils, the foundations and slabs can then be supported directly on
suitable native soils or compacted structural fill, however, prior to fill or foundation placement we
recommend the excavation bottom be observed by a geotechnical engineer.
Venture Pass Partners, LLC
Project B14-06766
October 8, 2014
Page 10
Table 5 provides the anticipated soil correction depths at the soil boring locations within or near the
proposed building.
Table 5. Anticipated Excavation Depths for Soil Correction
Boring
Ground Surface
Elevation
Anticipated Depth
of Excavation
(feet)
Approximate
Bottom Elevation
(Estimated)
Approximate
Fill Thickness to Achieve FFE
(951.5)
ST-100 949.4 7 942 9 1/2
ST-101 945.2 7 938 13 1/2
ST-102 940.9 6 934 1/2 17
ST-103 949.0 9 940 11 1/2
ST-1 950.2 1 949 1
ST-2 950.5 5 945 1/2 4 1/2
ST-3 949.2 4 945 5
ST-4 946.1 2 944 6
ST-5 943.9 12 931 1/2 20
1* 941.7 3 938 1/2 13
2* 941.6 12 929 1/2 22
*Previous AET soil boring.
Excavation depths will vary between the boring locations. Portions of the excavations may also be
deeper than indicated by the borings. Contractors should also be prepared to extend excavations if
unstable or additional fill soils are encountered.
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 (1:1 oversizing).
D.1.b. Groundwater Control
Surface water and groundwater should be anticipated and we recommend removing the groundwater
from the excavations prior to fill or backfill placement. The contractor should provide a dewatering plan
to the owner and design team for review prior to construction.
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Project B14-06766
October 8, 2014
Page 11
D.1.c. Selecting Excavation Backfill and Additional Required Fill
Due to the planned schedule for construction, the amount of fill/backfill required, potential for
groundwater, and ease of compaction in confined spaces, we recommend structural fill within the
proposed building pad and oversize areas consist of sands or sandy gravel with less than 12 percent by
weight passing the number 200 sieve (MnDOT Specification 3149.2B2). We also recommend that fill
placed for the pavement subgrade consist of sand or gravel meeting the same requirements.
The onsite glacial soils (generally clays) and fill soils can be reused as fill within the existing pond area, at
depths more than 2 feet below the top of subgrade in the pavement areas provided they contain an
organic content less than 5 percent and meet moisture and compaction specifications.
D.1.d. Placement and Compaction of Backfill and Fill
We recommend the backfill and fill be placed in lifts not exceeding 8 inches in thickness. We recommend
fill soils be compacted to the minimum densities summarized in Table 7, determined in accordance with
ASTM Test Method D 698 (standard Proctor). The fill should be within 3 percentage points of its
optimum moisture content. However, clayey fill should be placed within 3 percentage points above and
1 percent below its optimum moisture content.
Table 7. Compaction Recommendations Summary
Location
Minimum Compaction
(Standard Proctor)
Below Foundations and Interior Slabs (above
elevation 941.5)
98%
Below Foundations and Interior Slabs (below
elevation 941.5)
100%
Below Exterior Slabs 95%
Backfill Within the Existing Pond Areas 95%
Within 3 feet of Pavement Section 100%
More than 3 feet below Pavement Section 95%
D.2. Spread Footings
D.2.a. Embedment Depth and Frost Protection
For frost protection, we recommend embedding perimeter footings 42 inches below the lowest exterior
grade. Interior footings may be placed directly below floor slabs.
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Project B14-06766
October 8, 2014
Page 12
We recommend embedding building footings not heated during winter construction, and other unheated
footings, such as at canopies or stoops a minimum of 60 inches below the lowest exterior grade.
D.2.b. Net Allowable Bearing Pressure
We recommend sizing spread footings to exert a net allowable bearing pressure of 3,000 pounds per
square foot (psf), including all transient loads. This value includes a safety factor of at least 3.0 with
regard to bearing capacity failure.
D.2.c. Settlement
We estimate that total and differential settlements among the new footings will amount to less than
1 and 1/2 inch, respectively, under the reported loads.
D.3. Interior Slabs
D.3.a. Subgrade Modulus
The floor slab subgrades are anticipated to consist of compacted granular engineered fill suitable for slab
support. We recommend using a modulus of subgrade reaction, k value, of 175 pounds per square inch
per inch of deflection (pci) to design the slabs.
D.3.b. 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 place 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.
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Project B14-06766
October 8, 2014
Page 13
D.4. Exterior Slabs
D.4.a. Subgrade Improvement
Though not necessarily designed to accommodate dead and live load surcharges or vehicles, exterior
slabs can be subjected to both. Settlement of exterior slabs on poorly compacted foundation backfill,
utility backfill and other compressible/unstable soils or fills can also contribute to unfavorable surface
drainage conditions and frost-related damage to the slabs and adjacent structures, including buildings
and pavements. We recommend subgrades supporting exterior slabs should therefore be prepared in
accordance with the excavation, backfilling and compaction recommendations provided in Section D.1.
D.4.b. Frost Protection
Assuming the building pad and its oversize areas and the upper two to three feet of the pavement areas
are prepared as recommended with clean sand, the risk of frost heave will be greatly reduced. To
reduce the potential for unfavorable differential heaving between the areas of clean sand and the onsite
silty and clayey soils, we recommend tapering the sideslopes at that interface at a 3:1 (H:V) gradient, or
flatter.
Drainage of the sand fill will be critical to reducing frost heave. To help prevent surface drainage and
groundwater from accumulating within the sand backfill, we recommend installing pipe drains below slab
areas at the bottoms of the excavations and routing them to available catch basins or other suitable
disposal points.
Another option for exterior slab support, including at entrances without large slabs or sidewalks, is to
support the steps or slabs on frost-depth footings. A void space of at least 4 inches is generally required
between the bottoms of the steps/slabs and the subgrade soils to accommodate heaving without
affecting the steps/slabs.
D.5. Pavements
D.5.a. Pavement Subgrade Preparation
After stripping of surface vegetation and topsoil and prior to placement of fill, we recommend the
subgrade soils be proofrolled with a loaded tandem-axle truck and observed by a geotechnical engineer.
This will assist in identifying any soft or weak areas that will require additional soil correction work.
Areas that yield or rut more than 2 inches due to wheel traffic should be corrected or additional
subexcavation performed. If the failed areas cannot be compacted or dried to pass the proof roll, we
recommend an additional subcut equal to the rut depth and then replacment with select granular fill.
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Fill and backfill placed 3 feet or more below the pavement subgrade should be compacted to a minimum
of 95 percent of standard Proctor density, at a moisture content within 3 percentage points of optimum.
We recommend that at least the upper 2 feet of backfill material consist of MnDOT Select Granular
Borrow.
D.5.b. Construction Delay
Where compressible fill and native soils will be left in place below pavement subgrades, we recommend
a construction delay be utilized to reduce the potential for pavement settlement and its subsequent
impacts to pavement performance and surface drainage. For a construction delay, we recommend a
minimum construction delay from fill placement (up to proposed subgrade) to placement of the
pavement or curb of 45 days, however, the longer the fill is in place prior to pavement placement the
greater reduction in long term settlement will be realized.
D.5.c. Assumed R-value
After site grading, we anticipate the pavement subgrades will generally consist of at least 2 feet of select
granular borrow. Based on the soil boring results and anticipated graded, it is our opinion that an R-
value of 40 can be assumed for pavement design purposes.
D.5.d. Bituminous Design Sections
For the above subgrade and assumed traffic (Section C.1), we recommend the following minimum
section thicknesses be used for design of medium duty and heavy duty pavement sections. We
recommend medium duty pavement design sections be used in automobile parking areas and the heavy
duty design section be used in drive areas and truck parking areas. Where pavements will be subject to
static loading situations, such as the loading dock, we recommend concrete pavement be considered
Table 7. Recommended Bituminous Pavement Thicknesses
Course
Standard Duty
(inches)
Heavy Duty
(inches)
Bituminous 3 1/2 4
Gravel Base 6 8
The above pavement designs are based upon a 20-year performance life. This is the amount of time
before major reconstruction is anticipated. This performance life assumes maintenance, such as seal
coating and crack sealing, is routinely performed. However, the actual pavement life will vary depending
on variations in weather, traffic conditions and maintenance.
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D.5.e. Concrete Pavement Design
Where concrete pavements may be utilized, we recommend concrete pavements be a minimum of
7 inches thick placed over 4 inches of aggregate base. Appropriate panel sizing and jointing are critical to
performance of rigid pavements and should be reviewed after design loads are available.
Concrete design is based on a modulus of subgrade reaction (k) of 175 pci and a design life of 30 years.
D.5.f. Materials and Compaction
We recommend specifying crushed aggregate base meeting the requirements of MnDOT Specification
3138 for Class 5. We recommend that the bituminous wear and base courses comply with MnDOT
Specification 2360 and utilize the following mixes:
Standard Duty –SPWEA340E & SPNWB330E
Heavy Duty – SPWEB340E & SPNWB330E
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 an
average of at least 92 percent of the maximum theoretical Rice density, with no individual test less than
90 percent or greater than 97 percent.
We recommend specifying concrete for pavements that has a minimum 28-day compressive strength of
4,000 psi, and a modulus of rupture (Mr) of at least 650 psi. We also recommend Type V cement meeting
the requirements of ASTM C 150. We recommend specifying 5 to 7 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.5.g. Subgrade Drainage
We recommend installing perforated drainpipes throughout the pavement areas at spacing not greater
than 50 feet and along the perimeter of pavement areas where adjacent surface grades will promote
drainage towards the pavement. The drainpipes should be placed in small trenches extended at least 6
inches below the sand subbase.
If the storm sewer will not be installed during the initial phase of grading, we recommend sloping the
clayey subgrade soils below the sand section to promote drainage to a collection point and/or outside of
the pavement areas. This will prevent water snow melt and spring rains from becoming trapped in the
granular soils and destabilizing the underlying the clayey subgrade soils.
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D.5.h. Pavement Maintenance
Regardless of what is done to walkway or pavement area subgrades, 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.
The on-going performance of pavements is impacted by conditions under which the pavement is asked
to perform. These conditions include the environmental conditions, the actual use conditions and the
level of ongoing maintenance preformed. With regard to bituminous pavements in particular, 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 in bituminous pavements 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 bituminous pavements to require a seal coat within
the first 5 to 10 years to increase the long-term performance.
D.6. Utilities
D.6.a. Subgrade Stabilization
The non-organic fill and glacial soils encountered at typical invert elevations generally appear suitable for
pipe support and we anticipate utilities can be installed per manufacturer bedding requirements. If
organic or unstable soils are encountered at pipe invert elevations, they should be subcut and replaced
with engineered backfill or crushed rock. Typical subcut depths below pipe invert grades are 1 to 2 feet,
depending on the geological conditions and proposed construction. We recommend a geotechnical
engineer observe all utility trench excavations.
If present, groundwater should be removed from utility excavation to facilitate pipe installation and
backfilling.
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If utilities are planned within pavement areas where a construction delay is utilized, we recommend the
utilities be installed after the construction delay is completed.
D.6.b. Selection, Placement and Compaction of Backfill
We recommend selecting, placing and compacting utility trench backfill outside building areas to a
minimum of 95 percent of standard Proctor density. Within 3 feet of pavement subgrades, the minimum
compaction level should be increased to 100 percent of standard Proctor design. Utility trench backfill
should be within 3 percentage points of the soils optimum moisture content.
Exterior utility backfill may consist of non-organic soils that are readily compactable.
D.7. Construction Quality Control
D.7.a. Excavation Side Slopes
The onsite soils generally appear to consist of soils meeting OSHA Type B requirements. We recommend
excavation side slopes be constructed to lie back at horizontal to vertical slope of 1 to 1 or flatter.
Groundwater could cause sideslopes to lie back flatter than anticipated. An OSHA-approved competent
person or professional engineer should review the excavation conditions in the field.
All excavations must comply with the requirements of OSHA 29 CFR, Part 1926, Subpart P, “Excavations
and Trenches.” This document states that excavation safety is the responsibility of the contractor.
Reference to these OSHA requirements should be included in the project specifications.
D.7.b. 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.7.c. 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
subexcavation and recompaction or replacement. A second proof-roll should be performed after the
aggregate base material is in place, and prior to placing bituminous or concrete pavement.
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D.7.d. Materials Testing
We recommend density tests be taken in excavation backfill and additional required fill placed below
spread footings, slab-on-grade construction, behind basement walls, and below pavements.
D.7.e. 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.
D.7.f. Special Inspections of Soils
We recommend having the site grading and placement of fill, within the building pad be placed under the
direction of Special Inspections as provided in Chapter 17, Section 1704.7 of the International Building
Code. This requires observation of soil conditions below fill or footings, to evaluate if excavations extend
to the anticipate soils and if fill materials meet requirements for type of fill and compaction condition of
fill. This work should be carried out under the direction of a licensed geotechnical engineer. The purpose
of these special inspections is to evaluate whether the work is being carried out in accordance with the
approved Geotechnical Report for the project. This work should include evaluation of the subgrade, note
of preparation of the subgrade such as surface compaction or dewatering, excavation oversizing,
placement procedures and materials used for fill, and compaction testing of the fill.
E. Procedures
E.1. Penetration Test Borings
The penetration test borings were drilled with an off-road vehicle-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.
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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 Test
Method D 2488. A chart explaining the classification system is attached. Samples were sealed in jars 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 procedures.
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 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.
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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
period was 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