7.2. HRSR 08-02-2021 Request for Action
Cir•ci
Elk -
River=
To Item Number
Housing and Redevelo ment Authority 7.2
Agenda Section Meeting Date Prepared by
General Business August 2,2021 Colleen Eddy, Economic Development Specialist
Item Description Reviewed by
Main and Gates Redevelopment Update Brent O'Neil, Economic Development Director
Reviewed by
Cal Portner, City Administrator
Action Requested
Item is presented for informational purposes.
Background/Discussion
The soil borings have been completed and The Preliminary Report of Geotechnical Exploration was received.
The site continues to be mowed,property details and drone footage video are posted on the HRA/EDA website.
Staff continues to receive inquiries and is working on process to solicit development ideas for the site through a
Request for Information (RFI) per the direction of the HRA.
Financial Impact
N/A
Mission/Policy/Goal
The goal of the HRA is to improve existing housing stock by offering incentives or programs to repair and
maintain residential properties.
Attachments
• Preliminary report of Geotechnical Exploration
The Elk River Vision P O N E R E o R Y
A welcoming community avith revolutionary and spirited resourcefulness, exceptional [NAWR
service, and community engagement that encourages and inspires prosperity. Updated.August 2020
PRELIMINARY REPORT OF
GEOTECHNICAL EXPLORATION
Main & Gates Redevelopment
Main Street NW & Gates Avenue NW
Elk River, Minnesota
AET No. P-0001445
Date:
July 9, 2021
Prepared for:
City of Elk River – Housing and Redevelopment Authority
13065 Orono Parkway
Elk River, Minnesota 55330
www.amengtest.com
CONSULTANTS
ENVIRONMENTAL
GEOTECHNICAL
MATERIALS
FORENSICS Draft
July 9, 2021
City of Elk River – Housing and Redevelopment Authority
13065 Orono Parkway
Elk River, Minnesota 55330
Attn: Ms. Colleen Eddy
RE: Preliminary Geotechnical Exploration
Main & Gates Redevelopment
Main Street NW & Gates Avenue NW
Elk River, Minnesota
AET No. P-0001445
Dear Ms. Eddy:
American Engineering Testing, Inc. (AET) is pleased to present the results of our preliminary
subsurface exploration program and geotechnical engineering review for the Main & Gates
Redevelopment project in Elk River, Minnesota. These services were performed according to
our proposal to you dated April 12, 2021.
We are submitting one electronic (.pdf) copy of the report to you. Additional electronic copies
are being sent on your behalf as noted below.
Please contact me if you have any questions about the report. I can also be contacted for
arranging construction observation and testing services.
Sincerely,
American Engineering Testing, Inc.
Robert Olson, PE (MN)
Branch Manager
Phone: (763) 742-8651
rolson@amengtest.com
cc: Brandon Wisner – City of Elk River (bwisner@elkrivermn.gov)
5548 Barthel Industrial Drive, Suite 500 | Albertville, MN 55301
Phone (763) 428-5573 | (800) 972-6364 | Fax (651) 659-1379 | www.amengtest.com | AA/EEO
This document shall not be reproduced, except in full, without written approval from American Engineering Testing, Inc.
CONSULTANTS
· ENVIRONMENTAL
· GEOTECHNICAL
· MATERIALS
· FORENSICS
Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Copyright 2021 American Engineering Testing, Inc.
All Rights Reserved
Unauthorized use or copying of this document is strictly prohibited by anyone other than the client for the specific project.
Page ii
SIGNATURE PAGE
Prepared for: Prepared by:
City of Elk River American Engineering Testing, Inc.
Housing and Redevelopment Authority 5548 Barthel Industrial Drive NE, Suite 500
13065 Orono Parkway Albertville, Minnesota 55301
Elk River, Minnesota 55330 (651) 659-9001/www.amengtest.com
Attn: Colleen Eddy
Authored by: Reviewed by:
Robert J. Olson, PE (MN) Thomas P. Venema, PE (MN)
Branch Manager Principal Engineer/Vice President
I hereby certify that this plan, specification, or
report was prepared by me or under my direct
supervision and that I am a duly Licensed
Professional Engineer under Minnesota Statute
Section 326.02 to 326.15
Date: July 9, 2021 License #: 45023
Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Page iii
TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................................................................. 1
2.0 SCOPE OF SERVICES .......................................................................................................................... 1
3.0 PROJECT INFORMATION ................................................................................................................... 1
4.0 SUBSURFACE EXPLORATION AND TESTING ............................................................................... 2
4.1 Field Exploration Program .................................................................................................................. 2
4.2 Laboratory Testing .............................................................................................................................. 2
5.0 SITE CONDITIONS ............................................................................................................................... 2
5.1 Surface Observations ........................................................................................................................... 2
5.2 Subsurface Soils/Geology ................................................................................................................... 3
5.3 Groundwater ........................................................................................................................................ 4
6.0 RECOMMENDATIONS ........................................................................................................................ 4
6.1 Approach Discussion ........................................................................................................................... 4
6.2 Building Grading ................................................................................................................................. 4
6.3 Foundation Design .............................................................................................................................. 6
6.4 Floor Slab Design ................................................................................................................................ 7
6.5 Basement Backfilling/Water Control .................................................................................................. 7
6.6 Foundation and Exterior Building Backfilling .................................................................................... 8
7.0 CONSTRUCTION CONSIDERATIONS .............................................................................................. 9
7.1 Potential Difficulties ........................................................................................................................... 9
7.2 Excavation Backsloping .................................................................................................................... 10
7.3 Observation and Testing .................................................................................................................... 10
8.0 ASTM STANDARDS .......................................................................................................................... 10
9.0 LIMITATIONS ..................................................................................................................................... 10
STANDARD SHEETS
Floor Slab Moisture/Vapor Protection
Basement/Retaining Wall Backfill and Water Control
Freezing Weather Effects on Building Construction
Definitions Relating to Pavement Construction
APPENDIX A – Geotechnical Field Exploration and Testing
Boring Log Notes
Unified Soil Classification System
Figure 1 - Boring Locations
Subsurface Boring Logs
Results of Sieve Analysis Tests
APPENDIX B – Geotechnical Report Limitations and Guidelines for Use Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Page 1 of 10
1.0 INTRODUCTION
The City of Elk River – Housing and Redevelopment Authority (HRA) is proposing to redevelop
a property for mixed use development in Elk River, Minnesota. To assist planning and design,
you have authorized American Engineering Testing, Inc. (AET) to conduct a preliminary
subsurface exploration program at the site, conduct soil laboratory testing, and perform a
preliminary geotechnical engineering review for the project. This report presents the results of
the above services, and provides our engineering recommendations based on this data.
2.0 SCOPE OF SERVICES
AET's services were performed according to our proposal to you dated April 12, 2021, which the
HRA authorized on May 3, 2021. The authorized scope consists of the following.
Drilling 4 standard penetration test borings to depths of 14½ feet each.
Performing soil laboratory testing.
Performing a preliminary geotechnical engineering review based on the data and
preparing this report.
These services are intended for geotechnical purposes only. The scope is not intended to explore
for the presence or extent of environmental contamination in the soil or groundwater.
3.0 PROJECT INFORMATION
We understand that the City of Elk River HRA is planning for the redevelopment of the parcels
located in the northeast corner at the intersection of Main Street NW and Gates Avenue NW in
Elk River, Minnesota. It is likely that the proposed development will consist of a mixed-use
structure with one level below grade and multi levels (up to five) above grade. The building
design and locations have not been determined at this time. When plans are more defined, we
recommend further exploration to further evaluate the soils for foundation, slab, and pavement
support. The borings should extend to a depth of 25 to define the soil conditions below the
proposed basement level. The depth of the basement should also take into account the
groundwater level. Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
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4.0 SUBSURFACE EXPLORATION AND TESTING
4.1 Field Exploration Program
The subsurface exploration program conducted for the project consisted of four (4) standard
penetration test borings. AET in conjunction with the client determined the number of borings,
boring locations, and boring depths. The logs of the borings and details of the methods used
appear in Appendix A. The logs contain information concerning soil layering, soil classification,
geologic origins, and moisture condition. A density description or consistency is also noted for
the natural soils, which is based on the standard penetration resistance (N-value).
The boring locations are shown on Figure 1 in Appendix A. The borings were located in the field
by AET personnel by taping from nearby site features. Surface elevations were measured in the
field by AET personnel using an engineer's level. The benchmark reference was the top nut of
the hydrant located in the northeast corner of the intersection of Main Street and Gates Avenue,
with an assigned elevation of 100.0 feet.
4.2 Laboratory Testing
The laboratory test program included a sieve analysis on the sandy soil. The test results appear
in Appendix A on the individual boring logs adjacent to the samples upon which they were
performed, or on the data sheets following the logs.
5.0 SITE CONDITIONS
5.1 Surface Observations
The existing parcel is a combination of previous single family lots that consisted of homes which
have been demolished. The parcel has undergone some tree removals and grading activities
associated with demolition of the previous homes. Please provide us with records of the site
activities, if available, that shows the location and depth of removals and which residences had
basements. Records of fill placement would also be helpful.
The site has a general downward slope from southwest to northeast with elevations at the boring
locations ranging from 96.3 feet at Boring SB-1 down to 89.3 feet at Boring SB-3.
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Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
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5.2 Subsurface Soils/Geology
The site geology consists of fill or topsoil over sandy alluvial soils. Additional information on
the soil layers encountered is outlined below.
5.2.1 Fill
Fill soils were encountered at the surface of all the soil borings except Boring SB-3. The fill
extends to a depth of about 4 to 7 feet below existing grades. The fill soils are primarily silty
sands and sands with silt with trace roots and organic fines. Borings SB-2 encountered debris
consisting of wood within the fill. These soils are moderately slow draining and susceptible to
freeze-thaw movements. Due to the presence of the organic fines and low and variable N-values,
we judge that these soils were not placed and compacted for structural support.
The existing fill at Borings SB-2 contained pieces of wood. There may be other types of debris
present in the fill that were not sampled in our boring. Test pits with a backhoe could further
define the amount, type and extent of the debris with environmental sampling performed. Fill
that contains debris is considered “Regulated” by the MPCA and requires proper disposal,
usually at a designated landfill. Because cutting is anticipated at Borings SB-2 to correct the
subgrade soils, environmental pre-qualification of the fill prior to excavation would aid in
obtaining representative earthwork bids and help avoid construction delays.
5.2.2 Topsoil
Topsoil was encountered at the surface of Boring SB-3. The topsoil extends to depths of about 3
feet beneath existing grade. The topsoil consists primarily of silty sands with organics. These
soils are fairly fast draining and moderately susceptible to freeze-thaw movements. Due to the
presence of the organic fines, we judge these soils to be slightly compressible under structural
loads.
5.2.3 Alluvial Soils
Alluvial soils were encountered in all of the soil borings beneath the fill or topsoil. These soils
were classified as sands with varying amounts of gravel. These soils had N-values ranging from
2 to 18 blows per foot. The alluvial soils are judged to have moderate strength and moderately
low compressibility. They are fast draining and are low to slightly frost susceptible when they
are impacted by freezing temperatures.
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Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
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5.3 Groundwater
We encountered groundwater while drilling in Boring SB-3 at a depth of 13 feet which is an
elevation of 76 feet. Groundwater was not encountered in any of the other borings at the time
they were drilled. As these borings terminated in free draining sands, we judge the water level to
be below the depth explored by our borings.
Groundwater levels fluctuate due to varying seasonal and annual rainfall and snow melt amounts,
as well as other factors. The Twin Cities area has been in a low precipitation pattern for the last 2
years and the presently observed ground water levels may be lower than normal. Long term
monitoring of the groundwater table can be performed with piezometers, which were not part of
our work scope.
6.0 RECOMMENDATIONS
6.1 Approach Discussion
Based on the soil conditions encountered at our boring locations and on the preliminary design
information that is available, it is our opinion that the building can be supported on conventional
spread footings after removing the fill and topsoil to the underlying alluvial sands and placing
engineered fill to attain building subgrade elevation. In our opinion, the existing fill soils are
considered undocumented fill soils that were not placed with the intent to provide structural
support.
We recommend that full-time observation and testing services be provided by a Geotechnical
Engineer/Technician during stripping of the near surface soils and excavation of the previously
placed fill with observation of all exposed soils prior to placing new fill or concrete.
Details of our recommendations for site preparation are as follows.
6.2 Building Grading
6.2.1 Excavation
To prepare the building area for foundation and slab support, we recommend complete
excavation of the fill and topsoil, thereby exposing the naturally deposited alluvial sands. Any
remnants or utilities from the previous residence or structures at the site should also be Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Page 5 of 10
completely removed. This would result in excavation depths at the boring locations as shown in
Table 6.2.1.
Table 6.2.1 – Recommended Excavation Depths
Boring Location Surface Elevation (ft) Excavation Depth (ft) Approximate Excavation
Elevation (ft)*
1 96.3 4 92
2 94.4 7 87
3 89.3 3 86
4 92.9 7 86
*Rounded to the nearest ½ foot.
The depths/elevations indicated in Table 6.2.1 are based on the soil conditions at the specific
boring locations. Since conditions will vary away from the boring locations, it is recommended
that AET geotechnical personnel observe and confirm the competency of the soils in the entire
excavation bottom prior to new fill or footing placement.
Where the excavation extends below foundation grade, the excavation bottom and resultant
engineered fill system must be oversized laterally beyond the planned outside edges of the
foundations to properly support the loads exerted by that foundation. This excavation/engineered
fill lateral extension should at least be equal to the vertical depth of fill needed to attain
foundation grade at that location (i.e., 1:1 lateral oversize).
Prior to placing fill soils above the naturally deposited alluvial soils, we recommend the soils be
surface compacted to improve density and provide a more consistent subgrade condition. We
recommend the soils be compacted by a self-propelled roller having a minimum drum diameter
of 3 feet. The compactor should make at least 8 passes over the entire excavation bottom in
perpendicular directions (e.g. 4 passes east-west and 4 passes north-south) before beginning fill
placement. The base soils may need to be wetted prior and during compaction.
6.2.2 Fill Placement and Compaction
Fill placed to attain grade for foundation and floor slab support should be compacted in thin lifts
(less than 8 inches in thickness), such that the entire lift achieves a minimum compaction level of
98% of the standard maximum dry unit weight per ASTM:D698 (Standard Proctor test). Fill Draft
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placed which supports the floor slab only (outside of the 1:1 oversize zone below footings) for
cast foundation backfill or interior utilities can have a reduced minimum compaction level of
95% of the standard maximum dry unit weight. All fill should be placed at a moisture content of
+/- 2% of optimum as defined by the standard proctor test.
The excavated onsite soils can be reused as engineered fill, provided they are free of organics,
debris, and other deleterious materials. It is beyond our scope of services to determine the
volume of materials onsite that is suitable for reuse. Consideration of excavating a borrow area
in either a “green area” or possibly a parking area can also be considered to obtain naturally
deposited sand soils for the building pad fill. The borrow area can be re-filled and compacted
with on site fills placed according to MPCA Best Management Practices.
If imported soils are required, we recommend using sands with silt or sands meeting MnDOT
3149.2.B.2 Select Granular Borrow, similar to the existing site soils. The sand should be
classified as (SP) or (SP-SM). Frozen soils should not be used as fill and fill should not be
placed over frozen soils. If a different material is proposed, samples should be submitted to AET
for review.
If there are areas where fill is placed on slopes, we recommend benching the sloped surface
(benches cut parallel to the slope contour) prior to placing the fill. Benching is recommended
where slopes are steeper than 4:1 (H: V).
6.3 Foundation Design
The anticipated structure can be supported on conventional spread foundations placed on the
newly placed engineered fill or the natural alluvial soils. We recommend perimeter foundations
for heated building space is placed such that the bottom is a minimum of 48 inches below
exterior grade. We recommend foundations for unheated building space (such as canopy
foundations) be extended to a minimum of 60 inches below exterior grade.
Based on the conditions encountered, it is our opinion the building foundations can be designed
based on a net maximum allowable soil bearing pressure of 2,000 to 4,000 psf depending on the
location, depth, and building structural loads These soil bearing pressures would have a safety
factor of 3 with regard to ultimate bearing capacity. We recommend a minimum width of 30 Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Page 7 of 10
inches for column footings and a minimum width of 24 inches for strip footings to avoid
disproportionately small footing sizes. All foundation bases should be surface compacted with a
large plate compacter or vibratory roller prior to foundation placement. Some wetting of the
foundation base soils may be necessary if the sand soils are in a dry condition.
6.4 Floor Slab Design
After completion of the earthwork recommended above, it is our judgement that the floor slab
can be supported by the new compacted engineered fill soils.
For constructability purposes, we recommend placement at least 4 inches of Class 5 aggregate
base (meeting MnDOT Specification 3138) immediately below the floor. We recommend
designing the floor slab using a Modulus of Subgrade Reaction (k-value) of 175 pci if placed on
at least 4 inches of aggregate base. If at least 6 inches of aggregate base is constructed, a k-value
of 200 pci should be used for slab design.
The use of certain types of flooring may require the installation of moisture/vapor membranes
below the floor slab. Typically, if moisture sensitive floor coverings like tile or carpet will be
used, moisture/vapor membranes are recommended. Most floor covering manufacturers require
that the vapor retarder be placed directly below the concrete slab for warranty purposes. For
recommendations pertaining to moisture and vapor protection of interior floor slabs, we refer you
to the attached standard sheet entitled “Floor Slab Moisture/Vapor Protection.”
6.5 Basement Backfilling/Water Control
Our recommendations for backfilling the basement walls appear on the attached standard sheet
entitled “Basement/Retaining Wall Backfill and Water Control.” To avoid water intrusion issues
into the basement, it will be very important that these details be incorporated into the design, and
that construction monitoring be performed to assure that proper materials and construction is
implemented.
We recommend the installation of drain tiles around the perimeter of the below-grade walls, at
bottom-of-footing elevation, be included in the design. The drain tiles should be routed to sump
pits or to the sewer system (if local ordinances allow) for discharge of the collected water. If the
design elevation of the basement is within 3 feet of the groundwater level we recommend that Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
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Page 8 of 10
drain tiles be placed below the slab in a free draining sand subbase (below the Class 5 base) at a
spacing of 20 feet on center connected to the sump pump. The sand thickness should be at least
6 inches thick. These drain tiles would relieve uplift hydrostatic pressure below the slab in the
event of a significant rise in the ground water level.
We recommend that the basement wall backfill be a free draining sand, with no more than 5%
(by weight) passing the number 200 sieve and no more than 50% (by weight) passing the number
40 sieve. This type of sand would also be considered non-frost susceptible (NFS). The
basement walls should be designed for an at-rest pressure of 60 pcf (equivalent fluid density),
since they are fixed at the top and bottom. Any loads adjacent to the basement walls should be
considered surcharges with an at-rest earth pressure coefficient of 0.5 used for lateral load
application to the basement walls.
The foundations can be designed for a passive resistance of 360 pcf (equivalent fluid density) for
a compacted sand backfill against the footings. The design should include an appropriate safety
factor of at least 2 as movements on the order of 1 inch or more would be required to mobilize
the full passive resistance. The coefficient of friction for sliding resistance for concrete on
granular soil can be taken as 0.45. A safety factor of at least 1.5 should be applied to this sliding
friction value.
6.6 Foundation and Exterior Building Backfilling
All backfill placed around the foundations should be compacted to at least 95% of their
respective Standard Proctor maximum dry densities. Fill soils should be placed and compacted
at water contents within ±3% of the respective optimum water contents, based on the respective
Standard Proctor tests. The excavated sand can be used as backfill that is placed in lifts of 8
inches in thickness or less.
Some of the silty on-site fill soils are frost-susceptible and may cause some freeze-thaw
movements of exterior slabs, sidewalks, and stoops above them. Stoops placed over the
basement backfill would be supported by non-frost susceptible as described in section 6.5. If the
fill placement is not uniform below and around the surrounding pavements, there is a risk that
damage to the pavement approaches, curbs, and other exterior site features may occur. Draft
Preliminary Report of Geotechnical Exploration
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Page 9 of 10
Constructing a layer of NFS sand (beyond the basement wall NFS backfill) beneath exterior
entrances, sidewalks, and stoops will reduce heaving and associated trip hazards and other
problems. There should be tapered transition zones between the frost susceptible and non-frost
susceptible soils, and subsurface drainage will be required at the base of the NFS sand section.
Over the life of the sidewalk/entry slabs and pavements, cracks will develop and joints will open
up, which will expose the subgrade and allow water to enter from the surface and either saturate
or perch atop the subgrade soils. This water intrusion increases the potential for frost heave or
moisture related distress near the crack or joint. We recommend implementing a detailed
maintenance program to seal and/or fill any cracks and joints. The maintenance program should
give special attention to areas where dissimilar materials abut one another, where construction
joints occur, and where shrinkage cracks develop.
For further details, we refer you to the attached sheet entitled “Freezing Weather Effects on
Building Construction.”
7.0 CONSTRUCTION CONSIDERATIONS
7.1 Potential Difficulties
7.1.1 Runoff Water in Excavation
Water can be expected to collect in the excavation bottom during times of inclement weather or
snow melt. To allow observation of the excavation bottom, to reduce the potential for soil
disturbance, and to facilitate filling operations, we recommend water be removed from within the
excavation during construction. Based on the soils encountered, we anticipate the groundwater
can be handled with conventional sump pumping or be allowed to drain into the naturally
deposited sands.
7.1.2 Disturbance of Soils
The on-site soils can be disturbed under construction traffic, especially if the soils are wet. If
soils become disturbed, they should be subcut to the underlying undisturbed soils. The subcut
soils can then be dried and recompacted back into place, or they should be removed and replaced
with drier imported fill. If the sand soils used as fill become dry they should be wetted prior to
recompaction.
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7.1.3 Cobbles and Boulders, Possible Construction Debris
The soils at this site can include cobbles and boulders. There may also be remnants of the
demolished residences. This may make excavating procedures somewhat more difficult than
normal if they are encountered.
7.2 Excavation Backsloping
If excavation faces are not retained, the excavations should maintain maximum allowable slopes
in accordance with OSHA Regulations (Standards 29 CFR), Part 1926, Subpart P,
“Excavations” (can be found on www.osha.gov). Even with the required OSHA sloping, water
seepage or surface runoff can potentially induce sideslope erosion or sloughing which could
require slope maintenance.
7.3 Observation and Testing
The recommendations in this report are based on the subsurface conditions found at our test
boring locations. Since the soil conditions can be expected to vary away from the soil boring
locations, we recommend on-site observation by a geotechnical engineer/technician during
construction to evaluate these potential changes. Soil density testing should also be performed on
new fill placed in order to document that project specifications for compaction have been
satisfied.
8.0 ASTM STANDARDS
When we refer to an ASTM standard in this report, we mean that our services were performed in
general accordance with that standard. Compliance with any other standards referenced within
the specified standard is neither inferred nor implied.
9.0 LIMITATIONS
Within the limitations of scope, budget, and schedule, we have endeavored to provide our
services according to generally accepted geotechnical engineering practices at this time and
location. Other than this, no warranty, express or implied, is intended.
Important information regarding risk management and proper use of this report is given in
Appendix B entitled “Geotechnical Report Limitations and Guidelines for Use.” Draft
01REP013 (12/08) AMERICAN ENGINEERING TESTING, INC.
FLOOR SLAB MOISTURE/VAPOR PROTECTION
Floor slab design relative to moisture/vapor protection should consider the type and location of two elements, a
granular layer and a vapor membrane (vapor retarder, water resistant barrier or vapor barrier). In the following
sections, the pros and cons of the possible options regarding these elements will be presented, such that you and
your specifier can make an engineering decision based on the benefits and costs of the choices.
GRANULAR LAYER
In American Concrete Institute (ACI) 302.1R-04, a “base material” is recommended over the vapor membrane,
rather than the conventional clean “sand cushion” material. The base layer should be a minimum of 4 inches
(100 mm) thick, trimmable, compactable, granular fill (not sand), a so-called crusher-run material. Usually graded
from 1½ inches to 2 inches (38 to 50 mm) down to rock dust is suitable. Following compaction, the surface can be
choked off with a fine-grade material. We refer you to ACI 302.1R-04 for additional details regarding the
requirements for the base material.
In cases where potential static water levels or significant perched water sources appear near or above the floor slab,
an under floor drainage system may be needed wherein a draintile system is placed within a thicker clean sand or
gravel layer. Such a system should be properly engineered depending on subgrade soil types and rate/head of water
inflow.
VAPOR MEMBRANE
The need for a vapor membrane depends on whether the floor slab will have a vapor sensitive covering, will have
vapor sensitive items stored on the slab, or if the space above the slab will be a humidity controlled area. If the
project does not have this vapor sensitivity or moisture control need, placement of a vapor membrane may not be
necessary. Your decision will then relate to whether to use the ACI base material or a conventional sand cushion
layer. However, if any of the above sensitivity issues apply, placement of a vapor membrane is recommended. Some
floor covering systems (adhesives and flooring materials) require installation of a vapor membrane to limit the slab
moisture content as a condition of their warranty.
VAPOR MEMBRANE/GRANULAR LAYER PLACEMENT
A number of issues should be considered when deciding whether to place the vapor membrane above or below the
granular layer. The benefits of placing the slab on a granular layer, with the vapor membrane placed below the
granular layer, include reduction of the following:
· Slab curling during the curing and drying process.
· Time of bleeding, which allows for quicker finishing.
· Vapor membrane puncturing.
· Surface blistering or delamination caused by an extended bleeding period.
· Cracking caused by plastic or drying shrinkage.
The benefits of placing the vapor membrane over the granular layer include the following:
· A lower moisture emission rate is achieved faster.
· Eliminates a potential water reservoir within the granular layer above the membrane.
· Provides a “slip surface”, thereby reducing slab restraint and the associated random cracking.
If a membrane is to be used in conjunction with a granular layer, the approach recommended depends on slab usage
and the construction schedule. The vapor membrane should be placed above the granular layer when:
· Vapor sensitive floor covering systems are used or vapor sensitive items will be directly placed on the slab.
· The area will be humidity controlled, but the slab will be placed before the building is enclosed and sealed
from rain.
· Required by a floor covering manufacturer’s system warranty.
The vapor membrane should be placed below the granular layer when:
· Used in humidity controlled areas (without vapor sensitive coverings/stored items), with the roof
membrane in place, and the building enclosed to the point where precipitation will not intrude into the slab
area. Consideration should be given to slight sloping of the membrane to edges where draintile or other
disposal methods can alleviate potential water sources, such as pipe or roof leaks, foundation wall damp
proofing failure, fire sprinkler system activation, etc.
There may be cases where membrane placement may have a detrimental effect on the subgrade support system (e.g.,
expansive soils). In these cases, your decision will need to weigh the cost of subgrade options and the performance
risks. Draft
01REP014 (07/18) AMERICAN ENGINEERING TESTING, INC.
BASEMENT/RETAINING WALL BACKFILL AND WATER CONTROL
DRAINAGE
Below grade basements should include a perimeter backfill drainage system on the exterior side of the wall. The
exception may be where basements lie within free draining sands where water will not perch in the backfill. Drainage
systems should consist of perforated or slotted PVC drainage pipes located at the bottom of the backfill trench, lower
than the interior floor grade. The drain pipe should be surrounded by properly graded filter rock. A geosynthetic “filter
fabric” should then envelope the filter rock. The drain pipe should be connected to a suitable means of disposal, such as a
sump basket or a gravity outfall. A storm sewer gravity outfall would be preferred over exterior daylighting, as the latter
may freeze during winter. For non-building, exterior retaining walls, weep holes at the base of the wall can be substituted
for a drain pipe.
BACKFILLING
Prior to backfilling, damp/water proofing should be applied on perimeter basement walls. The backfill materials placed
against basement walls will exert lateral loadings. To reduce this loading by allowing for drainage, we recommend using
free-draining sands for backfill. The zone of sand backfill should extend outward from the wall at least 2 feet, and then
upward and outward from the wall at a 30 or greater angle from vertical. The free-draining sand backfill should contain
no more than 40% by weight passing the #40 sieve and no greater than 5% by weight passing the #200 sieve. The sand
backfill should be placed in lifts and compacted with portable compaction equipment. This compaction should be to the
specified levels if slabs or pavements are placed above. Where slab/pavements are not above, we recommend capping the
sand backfill with a layer of clayey soil to minimize surface water infiltration. Positive surface drainage away from the
building should also be maintained. If surface capping or positive surface drainage cannot be maintained, then the trench
should be filled with more permeable soils, such as the Fine Filter or Coarse Filter Aggregates defined in MnDOT
Specification 3149. You should recognize that if the backfill soils are not properly compacted, settlements may occur
which may affect surface drainage away from the building.
Backfilling with silty or clayey soil is possible but not preferred. These soils can build-up water which increases lateral
pressures and results in wet wall conditions and possible water infiltration into the basement. If you elect to place silty or
clayey soils as backfill, we recommend you place a prefabricated drainage composite against the wall which is
hydraulically connected to a drainage pipe at the base of the backfill trench. High plasticity clays should be avoided as
backfill due to their swelling potential.
LATERAL PRESSURES
Lateral earth pressures on below grade walls vary, depending on backfill soil classification, backfill compaction and
slope of the backfill surface. Static or dynamic surcharge loads near the wall will also increase lateral wall pressure. For
design, we recommend the following ultimate lateral earth pressure values (given in equivalent fluid pressure values) for
a drained soil compacted to 95% of the Standard Proctor density and a level ground surface.
Equivalent Fluid Density
Soil Type Active (pcf) At-Rest (pcf)
Sands (SP or SP-SM) 35 60
Silty Sands (SM) 45 65
Fine Grained Soils (SC, CL or ML) 70 90
Basement walls are normally restrained at the top which restricts movement. In this case, the design lateral pressures
should be the “at-rest” pressure situation. Retaining walls which are free to rotate or deflect should be designed using the
active case. Lateral earth pressures will be significantly higher than that shown if the backfill soils are not drained and
become saturated. Draft
01REP015 (07/18) AMERICAN ENGINEERING TESTING, INC.
FREEZING WEATHER EFFECTS ON BUILDING CONSTRUCTION
GENERAL
Because water expands upon freezing and soils contain water, soils which are allowed to freeze will heave and lose
density. Upon thawing, these soils will not regain their original strength and density. The extent of heave and
density/strength loss depends on the soil type and moisture condition. Heave is greater in soils with higher
percentages of fines (silts/clays). High silt content soils are most susceptible, due to their high capillary rise
potential which can create ice lenses. Fine grained soils generally heave about 1/4" to 3/8" for each foot of frost
penetration. This can translate to 1" to 2" of total frost heave. This total amount can be significantly greater if ice
lensing occurs.
DESIGN CONSIDERATIONS
Clayey and silty soils can be used as perimeter backfill, although the effect of their poor drainage and frost
properties should be considered. Basement areas will have special drainage and lateral load requirements which are
not discussed here. Frost heave may be critical in doorway areas. Stoops or sidewalks adjacent to doorways could
be designed as structural slabs supported on frost footings with void spaces below. With this design, movements
may then occur between the structural slab and the adjacent on-grade slabs. Non-frost susceptible sands (with less
than 40% by weight passing a #40 sieve and no more than 5% by weight passing a #200 sieve) can be used below
such areas. Depending on the function of surrounding areas, the sand layer may need a thickness transition away
from the area where movement is critical. With sand placement over slower draining soils, subsurface drainage
would be needed for the sand layer. High density extruded polystyrene insulation could be used within the sand to
reduce frost penetration, thereby reducing the sand thickness needed. We caution that insulation placed near the
surface can increase the potential for ice glazing of the surface.
The possible effects of adfreezing should be considered if clayey or silty soils are used as backfill. Adfreezing
occurs when backfill adheres to rough surfaced foundation walls and lifts the wall as it freezes and heaves. This
occurrence is most common with masonry block walls, unheated or poorly heated building situations and clay
backfill. The potential is also increased where backfill soils are poorly compacted and become saturated. The risk
of adfreezing can be decreased by placing a low friction separating layer between the wall and backfill.
Adfreezing can occur on exterior piers (such as deck, fence, or other similar pier footings), even if a smooth
surface is provided. This is more likely in poor drainage situations where soils become saturated. Additional
footing embedment and/or widened footings below the frost zones (which include tensile reinforcement) can be
used to resist uplift forces. Specific designs would require individual analysis.
CONSTRUCTION CONSIDERATIONS
Foundations, slabs and other improvements which may be affected by frost movements should be insulated from
frost penetration during freezing weather. If filling takes place during freezing weather, all frozen soils, snow and
ice should be stripped from areas to be filled prior to new fill placement. The new fill should not be allowed to
freeze during transit, placement or compaction. This should be considered in the project scheduling, budgeting and
quantity estimating. It is usually beneficial to perform cold weather earthwork operations in small areas where
grade can be attained quickly rather than working larger areas where a greater amount of frost stripping may be
needed. If slab subgrade areas freeze, we recommend the subgrade be thawed prior to floor slab placement. The
frost action may also require reworking and recompaction of the thawed subgrade. Draft
01REP019 (07/16) AMERICAN ENGINEERING TESTING, INC.
DEFINITIONS RELATING TO PAVEMENT CONSTRUCTION
Top of subgrade: Grade which contacts the bottom of the aggregate base layer.
Sand subbase: Uniform thickness sand layer placed as the top of subgrade which is intended to improve
the frost and drainage characteristics of the pavement system by increasing drainage of excess water in
the aggregate base and subbase, by reducing and “bridging” frost heaving, and by reducing spring thaw
weakening effects.
Critical subgrade zone: The subgrade portion beneath and within three vertical feet of the top of
subgrade. A sand subbase, if placed, would be considered the upper portion of the critical subgrade zone.
Suitable Grading Material: Mineral soil materials, typically from the project site, excluding the
following: 1) soils which have an organic content exceeding 3%, 2) cohesive soils having a Liquid Limit
exceeding 50%, 3) soils which include debris, cobbles, and/or boulders, and 4) soils which are considered
acceptable from an environmental standpoint. The soil must also be capable of attaining the specified
compaction level at its current water content or at a water content that can be reasonably scarified,
blended, and moisture conditioned to a uniform water content in order to uniformly meet compaction
requirements.
Granular Material: Soils meeting MnDOT Specification 3149.2B.1. This refers to granular soils which,
of the portion passing the 1" sieve, contain less than 20% by weight passing the #200 sieve.
Select Granular Material: Soils meeting MnDOT Specification 3149.2B.2. This refers to granular soils
which, of the portion passing the 1" sieve, contain less than 12% by weight passing the #200 sieve.
Select Granular Material (Super Sand): Soils meeting MnDOT Specification 3149.2B.3. This material
is cleaner and coarser than Select Granular Material (see specification for specific requirements).
Compaction Subcut: Construction of a uniform thickness subcut below a designated grade to provide
uniformity and compaction within the subcut zone. Replacement fill can be the materials subcut, although
the reused soils should be blended to a uniform soil condition, moisture conditioned as needed to meet
MnDOT Specification 2105.F; and re-compacted per the Specified Density Method defined in MnDOT
Specification 2105.3F.1.
Test Roll: A means of evaluating the near-surface stability of subgrade soils (usually non-granular).
Suitability is determined by the depth of rutting or deflection caused by passage of heavy rubber-tired
construction equipment, such as a loaded dump truck, over the test area. Yielding of less than 1" is
normally considered acceptable, although engineering judgment may be applied depending on the
equipment used, soil conditions present, and/or depth below final grade.
Unstable Soils: Subgrade soils which do not pass a test roll. Unstable soils typically have water content
exceeding the standard optimum water content defined in ASTM:D698 (Standard Proctor test).
Organic Soils: Soils which have sufficient organic content such that the soils engineering properties are
negatively affected (typically more than 3% organic content). These soils are usually black to dark brown
in color. Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Appendix A
Geotechnical Field Exploration and Testing
Boring Log Notes
Unified Soil Classification System
Figure 1 – Boring Locations
Subsurface Boring Logs
Sieve Analysis Tests Draft
Appendix A
Geotechnical Field Exploration and Testing
Report No. P-0001445
Appendix A - Page 1 of 2 AMERICAN ENGINEERING TESTING, INC.
A.1 FIELD EXPLORATION
The subsurface conditions at the site were explored by drilling and sampling four (4) standard penetration test borings. The
locations of the borings appear on Figure 1, preceding the Subsurface Boring Logs in this appendix.
A.2 SAMPLING METHODS
A.2.1 Split-Spoon Samples (SS) - Calibrated to N60 Values
Standard penetration (split-spoon) samples were collected in general accordance with ASTM: D1586 with one primary
modification. The ASTM test method consists of driving a 2-inch O.D. split-barrel sampler into the in-situ soil with a 140-pound
hammer dropped from a height of 30 inches. The sampler is driven a total of 18 inches into the soil. After an initial set of 6 inches,
the number of hammer blows to drive the sampler the final 12 inches is known as the standard penetration resistance or N-value.
Our method uses a modified hammer weight, which is determined by measuring the system energy using a Pile Driving Analyzer
(PDA) and an instrumented rod.
In the past, standard penetration N-value tests were performed using a rope and cathead for the lift and drop system. The energy
transferred to the split-spoon sampler was typically limited to about 60% of its potential energy due to the friction inherent in this
system. This converted energy then provides what is known as an N60 blow count.
The most recent drill rigs incorporate an automatic hammer lift and drop system, which has higher energy efficiency and
subsequently results in lower N-values than the traditional N60 values. By using the PDA energy measurement equipment, we are
able to determine actual energy generated by the drop hammer. With the various hammer systems available, we have found highly
variable energies ranging from 55% to over 100%. Therefore, the intent of AET’s hammer calibrations is to vary the hammer
weight such that hammer energies lie within about 60% to 65% of the theoretical energy of a 140-pound weight falling 30 inches.
The current ASTM procedure acknowledges the wide variation in N-values, stating that N-values of 100% or more have been
observed. Although we have not yet determined the statistical measurement uncertainty of our calibrated method to date, we can
state that the accuracy deviation of the N-values using this method is significantly better than the standard ASTM Method.
A.2.2 Disturbed Samples (DS)/Spin-up Samples (SU)
Sample types described as “DS” or “SU” on the boring logs are disturbed samples, which are taken from the flights of the auger.
Because the auger disturbs the samples, possible soil layering and contact depths should be considered approximate.
A.2.3 Sampling Limitations
Unless actually observed in a sample, contacts between soil layers are estimated based on the spacing of samples and the action of
drilling tools. Cobbles, boulders, and other large objects generally cannot be recovered from test borings, and they may be present
in the ground even if they are not noted on the boring logs.
Determining the thickness of “topsoil” layers is usually limited, due to variations in topsoil definition, sample recovery, and other
factors. Visual-manual description often relies on color for determination, and transitioning changes can account for significant
variation in thickness judgment. Accordingly, the topsoil thickness presented on the logs should not be the sole basis for
calculating topsoil stripping depths and volumes. If more accurate information is needed relating to thickness and topsoil quality
definition, alternate methods of sample retrieval and testing should be employed.
A.3 CLASSIFICATION METHODS
Soil descriptions shown on the boring logs are based on the Unified Soil Classification (USC) system. The USC system is
described in ASTM: D2487 and D2488. Where laboratory classification tests (sieve analysis or Atterberg Limits) have been
performed, accurate classifications per ASTM: D2487 are possible. Otherwise, soil descriptions shown on the boring logs are
visual-manual judgments. Charts are attached which provide information on the USC system, the descriptive terminology, and the
symbols used on the boring logs.
The boring logs include descriptions of apparent geology. The geologic depositional origin of each soil layer is interpreted
primarily by observation of the soil samples, which can be limited. Observations of the surrounding topography, vegetation, and
development can sometimes aid this judgment.
Draft
Appendix A
Geotechnical Field Exploration and Testing
Report No. P-0001445
Appendix A - Page 2 of 2 AMERICAN ENGINEERING TESTING, INC.
A.4 WATER LEVEL MEASUREMENTS
The ground water level measurements are shown at the bottom of the boring logs. The following information appears under
“Water Level Measurements” on the logs:
Date and Time of measurement
Sampled Depth: lowest depth of soil sampling at the time of measurement
Casing Depth: depth to bottom of casing or hollow-stem auger at time of measurement
Cave-in Depth: depth at which measuring tape stops in the borehole
Water Level: depth in the borehole where free water is encountered
Drilling Fluid Level: same as Water Level, except that the liquid in the borehole is drilling fluid
The true location of the water table at the boring locations may be different than the water levels measured in the boreholes. This is
possible because there are several factors that can affect the water level measurements in the borehole. Some of these factors
include: permeability of each soil layer in profile, presence of perched water, amount of time between water level readings,
presence of drilling fluid, weather conditions, and use of borehole casing.
A.5 LABORATORY TEST METHODS
A.5.1 Water Content Tests
Conducted per AET Procedure 01-LAB-010, which is performed in general accordance with ASTM: D2216 and AASHTO: T265.
A.5.2 Sieve Analysis of Soils (thru #200 Sieve)
Conducted per AET Procedure 01-LAB-040, which is performed in general conformance with ASTM: D6913, Method A.
A.6 TEST STANDARD LIMITATIONS
Field and laboratory testing is done in general conformance with the described procedures. Compliance with any other standards
referenced within the specified standard is neither inferred nor implied.
A.7 SAMPLE STORAGE
Unless notified to do otherwise, we routinely retain representative samples of the soils recovered from the borings for a period of
30 days. Draft
01REP052C (7/11) AMERICAN ENGINEERING TESTING, INC.
BORING LOG NOTES
DRILLING AND SAMPLING SYMBOLS TEST SYMBOLS
Symbol Definition Symbol Definition
AR: Sample of material obtained from cuttings blown out
the top of the borehole during air rotary procedure.
B, H, N: Size of flush-joint casing
CAS: Pipe casing, number indicates nominal diameter in
inches
COT: Clean-out tube
DC: Drive casing; number indicates diameter in inches
DM: Drilling mud or bentonite slurry
DR: Driller (initials)
DS: Disturbed sample from auger flights
DP: Direct push drilling; a 2.125 inch OD outer casing
with an inner 1½ inch ID plastic tube is driven
continuously into the ground.
FA: Flight auger; number indicates outside diameter in
inches
HA: Hand auger; number indicates outside diameter
HSA: Hollow stem auger; number indicates inside diameter
in inches
LG: Field logger (initials)
MC: Column used to describe moisture condition of
samples and for the ground water level symbols
N (BPF): Standard penetration resistance (N-value) in blows per
foot (see notes)
NQ: NQ wireline core barrel
PQ: PQ wireline core barrel
RDA: Rotary drilling with compressed air and roller or drag
bit.
RDF: Rotary drilling with drilling fluid and roller or drag bit
REC: In split-spoon (see notes), direct push and thin-walled
tube sampling, the recovered length (in inches) of
sample. In rock coring, the length of core recovered
(expressed as percent of the total core run). Zero
indicates no sample recovered.
SS: Standard split-spoon sampler (steel; 1.5" is inside
diameter; 2" outside diameter); unless indicated
otherwise
SU Spin-up sample from hollow stem auger
TW: Thin-walled tube; number indicates inside diameter in
inches
WASH: Sample of material obtained by screening returning
rotary drilling fluid or by which has collected inside
the borehole after “falling” through drilling fluid
WH: Sampler advanced by static weight of drill rod and
hammer
WR: Sampler advanced by static weight of drill rod
94mm: 94 millimeter wireline core barrel
▼: Water level directly measured in boring
: Estimated water level based solely on sample appearance
CONS: One-dimensional consolidation test
DEN: Dry density, pcf
DST: Direct shear test
E: Pressuremeter Modulus, tsf
HYD: Hydrometer analysis
LL: Liquid Limit, %
LP: Pressuremeter Limit Pressure, tsf
OC: Organic Content, %
PERM: Coefficient of permeability (K) test; F - Field;
L - Laboratory
PL: Plastic Limit, %
qp: Pocket Penetrometer strength, tsf (approximate)
qc: Static cone bearing pressure, tsf
qu: Unconfined compressive strength, psf
R: Electrical Resistivity, ohm-cms
RQD: Rock Quality Designation of Rock Core, in percent
(aggregate length of core pieces 4" or more in length
as a percent of total core run)
SA: Sieve analysis
TRX: Triaxial compression test
VSR: Vane shear strength, remolded (field), psf
VSU: Vane shear strength, undisturbed (field), psf
WC: Water content, as percent of dry weight
%-200: Percent of material finer than #200 sieve
STANDARD PENETRATION TEST NOTES
(Calibrated Hammer Weight)
The standard penetration test consists of driving a split-spoon
sampler with a drop hammer (calibrated weight varies to provide
N60 values) and counting the number of blows applied in each of
three 6" increments of penetration. If the sampler is driven less
than 18" (usually in highly resistant material), permitted in
ASTM: D1586, the blows for each complete 6" increment and for
each partial increment is on the boring log. For partial increments,
the number of blows is shown to the nearest 0.1' below the slash.
The length of sample recovered, as shown on the “REC” column,
may be greater than the distance indicated in the N column. The
disparity is because the N-value is recorded below the initial 6"
set (unless partial penetration defined in ASTM: D1586 is
encountered) whereas the length of sample recovered is for the
entire sampler drive (which may even extend more than 18"). Draft
01CLS021 (07/08) AMERICAN ENGINEERING TESTING, INC.
UNIFIED SOIL CLASSIFICATION SYSTEM
ASTM Designations: D 2487, D2488
AMERICAN
ENGINEERING
TESTING, INC.
Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA
Soil Classification Notes
ABased on the material passing the 3-in
(75-mm) sieve.
BIf field sample contained cobbles or
boulders, or both, add “with cobbles or
boulders, or both” to group name.
CGravels with 5 to 12% fines require dual
symbols:
GW-GM well-graded gravel with silt
GW-GC well-graded gravel with clay
GP-GM poorly graded gravel with silt
GP-GC poorly graded gravel with clay
DSands with 5 to 12% fines require dual
symbols:
SW-SM well-graded sand with silt
SW-SC well-graded sand with clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
(D30)2
ECu = D60 /D10, Cc =
D10 x D60
FIf soil contains >15% sand, add “with
sand” to group name.
GIf fines classify as CL-ML, use dual
symbol GC-GM, or SC-SM.
HIf fines are organic, add “with organic
fines” to group name.
IIf soil contains >15% gravel, add “with
gravel” to group name.
JIf Atterberg limits plot is hatched area,
soil is a CL-ML silty clay.
KIf soil contains 15 to 29% plus No. 200
add “with sand” or “with gravel”,
whichever is predominant.
LIf soil contains >30% plus No. 200,
predominantly sand, add “sandy” to
group name.
MIf soil contains >30% plus No. 200,
predominantly gravel, add “gravelly”
to group name.
NPl>4 and plots on or above “A” line.
OPl<4 or plots below “A” line.
PPl plots on or above “A” line.
QPl plots below “A” line.
RFiber Content description shown below.
Group
Symbol
Group NameB
Coarse-Grained
Soils More
than 50%
retained on
No. 200 sieve
Gravels More
than 50% coarse
fraction retained
on No. 4 sieve
Clean Gravels
Less than 5%
finesC
Cu>4 and 1<Cc<3E GW Well graded gravelF
Cu<4 and/or 1>Cc>3E GP Poorly graded gravelF
Gravels with
Fines more
than 12% fines C
Fines classify as ML or MH GM Silty gravelF.G.H
Fines classify as CL or CH GC Clayey gravelF.G.H
Sands 50% or
more of coarse
fraction passes
No. 4 sieve
Clean Sands
Less than 5%
finesD
Cu>6 and 1<Cc<3E SW Well-graded sandI
Cu<6 and/or 1>Cc>3E SP Poorly-graded sandI
Sands with
Fines more
than 12% fines D
Fines classify as ML or MH SM Silty sandG.H.I
Fines classify as CL or CH SC Clayey sandG.H.I
Fine-Grained
Soils 50% or
more passes
the No. 200
sieve
(see Plasticity
Chart below)
Silts and Clays
Liquid limit less
than 50
inorganic PI>7 and plots on or above
“A” lineJ
CL Lean clayK.L.M
PI<4 or plots below
“A” lineJ
ML SiltK.L.M
organic Liquid limit–oven dried <0.75
Liquid limit – not dried
OL Organic clayK.L.M.N
Organic siltK.L.M.O
Silts and Clays
Liquid limit 50
or more
inorganic PI plots on or above “A” line CH Fat clayK.L.M
PI plots below “A” line MH Elastic siltK.L.M
organic Liquid limit–oven dried <0.75
Liquid limit – not dried
OH Organic clayK.L.M.P
Organic siltK.L.M.Q
Highly organic
soil
Primarily organic matter, dark
in color, and organic in odor
PT PeatR
3 2 ½1 ¾4 10 20 40 60 140 200
100
80
60
40
20
0
0
20
40
60
80
100
81
Sieve NumberScreen Opening (in.)
50 10 5 1.0 0.10.5
PARTICLE SIZE IN MILLIMETERS
SIEVE ANALYSIS
PERCENT PASSINGPERCENT RETAINEDD60 = 15mm
D30 = 2.5mm
D10 = 0.075mm
Cu = = = 200D60
D10
15
0.075 Cc = = = 5.6(D30)
D10 x D60
2.5
0.075 x 15
2 2
CL-ML
For classification of fine-grained soils and
fine-grained fraction of coarse-grained soils.
Equation of "A"-line
Horizontal at PI = 4 to LL = 25.5.
then PI = 0.73 (LL-20)
Equation of "U"-line
Vertical at LL = 16 to PI = 7.
then PI = 0.9 (LL-8)"A" LIN
E
"U" LINECL OR OL CH OR OH
10 20 30 40 50 60 70 80 90 100 110 0 0
10
20
30
40
50
60
16
7
4PLASTICITY INDEX (PI)LIQUID LIMIT (LL) Plasticity Chart
ADDITIONAL TERMINOLOGY NOTES USED BY AET FOR SOIL IDENTIFICATION AND DESCRIPTION
Grain Size
Term Particle Size
Boulders Over 12"
Cobbles 3" to 12"
Gravel #4 sieve to 3"
Sand #200 to #4 sieve
Fines (silt & clay) Pass #200 sieve
Gravel Percentages
Term Percent
A Little Gravel 3% - 14%
With Gravel 15% - 29%
Gravelly 30% - 50%
Consistency of Plastic Soils
Term N-Value, BPF
Very Soft less than 2
Soft 2 - 4
Firm 5 - 8
Stiff 9 - 15
Very Stiff 16 - 30
Hard Greater than 30
Relative Density of Non-Plastic Soils
Term N-Value, BPF
Very Loose 0 - 4
Loose 5 - 10
Medium Dense 11 - 30
Dense 31 - 50
Very Dense Greater than 50
Moisture/Frost Condition
(MC Column)
D (Dry): Absence of moisture, dusty, dry to
touch.
M (Moist): Damp, although free water not
visible. Soil may still have a high
water content (over “optimum”).
W (Wet/ Free water visible, intended to
Waterbearing): describe non-plastic soils.
Waterbearing usually relates to
sands and sand with silt.
F (Frozen): Soil frozen
Layering Notes
Laminations: Layers less than
½" thick of
differing material
or color.
Lenses: Pockets or layers
greater than ½"
thick of differing
material or color.
Peat Description
Fiber Content
Term (Visual Estimate)
Fibric Peat: Greater than 67%
Hemic Peat: 33 – 67%
Sapric Peat: Less than 33%
Organic Description (if no lab tests)
Soils are described as organic, if soil is not peat
and is judged to have sufficient organic fines
content to influence the Liquid Limit properties.
Slightly organic used for borderline cases.
Root Inclusions
With roots: Judged to have sufficient quantity
of roots to influence the soil
properties.
Trace roots: Small roots present, but not judged
to be in sufficient quantity to
significantly affect soil properties.
ML OR OL
MH OR OH Draft
PROJECTAET PROJECTNO.P-0001445SUBJECTDATE5/25/21SCALE DRAWN BY CHECKED BY PAGEFigure 1AMERICAN ENGINEERING TESTING, INC.MAIN & GATES REDEVELOPMENTMAIN STREET NW & GATES AVENUE NWELK RIVER, MINNESOTARJO TSVnot to scaleBORING LOCATION SKETCH - BORING NOS. SB-1 to SB-4SB‐1SB‐2SB‐3SB‐4Draft
4
4
6
10
12
18
FILL
COARSE
ALLUVIUM
FILL, mixture of sand with silt and silty sand, a
little gravel, trace roots, brown and dark brown
SAND, a little gravel, fine to medium grained,
brown and light brown, moist, loose (SP)
SAND, fine to medium grained, grayish brown,
moist, medium dense (SP)
SAND. a little gravel, fine to coarse grained,
grayish brown, moist, medium dense (SP)
END OF BORING
*WD - Water level measured while drilling
*AD - Water level measured at completion of
drilling
M
M
M
M
M
M
33
SS
SS
SS
SS
SS
SS
10
8
12
12
10
12
None
None
0-13'
Rig:
*WD
*AD
6/8/21
6/8/21
Surface Elevation
DATE
BR LG:
TIME
DR:
4.0
WATERLEVEL
DEPTH:
6/8/21
NOTE: REFER TO
THE ATTACHED
SHEETS FOR AN
EXPLANATION OF
TERMINOLOGY ON
THIS LOG
CASINGDEPTHSAMPLEDDEPTH3.25" HSA
GRD751
BORINGCOMPLETED:
DR
96.3
DRILLING METHOD
CAVE-INDEPTH DRILLINGFLUID LEVEL
WATER LEVEL MEASUREMENTS
MCGEOLOGY
SB- 1 (p. 1 of 1)
Main & Gates Redevelopment; Elk River, MN
AET No:
Project:
01-DHR-060
NDEPTHINFEET
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SUBSURFACE BORING LOG
PL
FIELD & LABORATORY TESTS
03/2011
MATERIAL DESCRIPTION
RECIN.SAMPLETYPE
P-0001445
LLDENWC %-#200
Log of Boring No.
AMERICAN
ENGINEERING
TESTING, INC.AET_CORP P-0001445 MAIN & GATES.GPJ AET+CPT+WELL_20181012_JG.GDT 7/9/21Draft
5
2
3
11
4
7
FILL
COARSE
ALLUVIUM
FILL, mixture of silty sand and sand with silt, a
little gravel and clayey sand, pieces of wood,
brown
SAND, fine to medium grained, brown, moist,
medium dense (SP)
SAND, a little gravel, fine to medium grained,
grayish brown, moist, very loose, lamination of
clayey sand (SP)
SAND, fine grained, grayish brown, moist, loose
(SP)
END OF BORING
*WD - Water level measured while drilling
*AD - Water level measured at completion of
drilling
M
M
M
M
M
M
SS
SS
SS
SS
SS
SS
13
10
8
13
8
12
None
None
0-13'
Rig:
*WD
*AD
6/8/21
6/8/21
Surface Elevation
DATE
BR LG:
TIME
DR:
4.0
WATERLEVEL
DEPTH:
6/8/21
NOTE: REFER TO
THE ATTACHED
SHEETS FOR AN
EXPLANATION OF
TERMINOLOGY ON
THIS LOG
CASINGDEPTHSAMPLEDDEPTH3.25" HSA
GRD751
BORINGCOMPLETED:
DR
94.4
DRILLING METHOD
CAVE-INDEPTH DRILLINGFLUID LEVEL
WATER LEVEL MEASUREMENTS
MCGEOLOGY
SB- 2 (p. 1 of 1)
Main & Gates Redevelopment; Elk River, MN
AET No:
Project:
01-DHR-060
NDEPTHINFEET
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SUBSURFACE BORING LOG
PL
FIELD & LABORATORY TESTS
03/2011
MATERIAL DESCRIPTION
RECIN.SAMPLETYPE
P-0001445
LLDENWC %-#200
Log of Boring No.
AMERICAN
ENGINEERING
TESTING, INC.AET_CORP P-0001445 MAIN & GATES.GPJ AET+CPT+WELL_20181012_JG.GDT 7/9/21Draft
7
8
14
4
6
2
TOPSOIL
COARSE
ALLUVIUM
SILTY SAND, slightly organic, trace roots, fine
gravel, dark brown, moist, loose (SM)
SAND, a little gravel, fine to medium grained,
brown, moist, loose to medium dense (SP)
SAND, a little gravel, medium to coarse grained,
brown, moist, very loose to loose (SP)
SAND, fine to medium grained, brown,
waterbearing, very loose (SP)
END OF BORING
*WD - Water level measured while drilling
*AD - Water level measured at completion of
drilling
M
M
M
M
M
W
SS
SS
SS
SS
SS
SS
14
10
4
10
10
12
13.0
13.0
0-13'
Rig:
*WD
*AD
6/8/21
6/8/21
Surface Elevation
DATE
BR LG:
TIME
DR:
5.0
WATERLEVEL
DEPTH:
6/8/21
NOTE: REFER TO
THE ATTACHED
SHEETS FOR AN
EXPLANATION OF
TERMINOLOGY ON
THIS LOG
CASINGDEPTHSAMPLEDDEPTH3.25" HSA
GRD751
BORINGCOMPLETED:
DR
89.3
DRILLING METHOD
CAVE-INDEPTH DRILLINGFLUID LEVEL
WATER LEVEL MEASUREMENTS
MCGEOLOGY
SB- 3 (p. 1 of 1)
Main & Gates Redevelopment; Elk River, MN
AET No:
Project:
01-DHR-060
NDEPTHINFEET
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SUBSURFACE BORING LOG
PL
FIELD & LABORATORY TESTS
03/2011
MATERIAL DESCRIPTION
RECIN.SAMPLETYPE
P-0001445
LLDENWC %-#200
Log of Boring No.
AMERICAN
ENGINEERING
TESTING, INC.AET_CORP P-0001445 MAIN & GATES.GPJ AET+CPT+WELL_20181012_JG.GDT 7/9/21Draft
7
3
2
12
9
10
FILL
COARSE
ALLUVIUM
FILL, mixture of silty sand and sand with silt, a
little gravel and clayey sand, brown and dark
brown
SAND, a little gravel, fine to medium grained,
brown, moist, medium dense to loose (SP)
SAND, fine grained, grayish brown, moist, loose
(SP)
END OF BORING
*WD - Water level measured while drilling
*AD - Water level measured at completion of
drilling
M
M
M
M
M
M
SS
SS
SS
SS
SS
SS
4
10
11
12
12
4
None
None
0-13'
Rig:
*WD
*AD
6/8/21
6/8/21
Surface Elevation
DATE
BR LG:
TIME
DR:
4.0
WATERLEVEL
DEPTH:
6/8/21
NOTE: REFER TO
THE ATTACHED
SHEETS FOR AN
EXPLANATION OF
TERMINOLOGY ON
THIS LOG
CASINGDEPTHSAMPLEDDEPTH3.25" HSA
GRD751
BORINGCOMPLETED:
DR
92.9
DRILLING METHOD
CAVE-INDEPTH DRILLINGFLUID LEVEL
WATER LEVEL MEASUREMENTS
MCGEOLOGY
SB- 4 (p. 1 of 1)
Main & Gates Redevelopment; Elk River, MN
AET No:
Project:
01-DHR-060
NDEPTHINFEET
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SUBSURFACE BORING LOG
PL
FIELD & LABORATORY TESTS
03/2011
MATERIAL DESCRIPTION
RECIN.SAMPLETYPE
P-0001445
LLDENWC %-#200
Log of Boring No.
AMERICAN
ENGINEERING
TESTING, INC.AET_CORP P-0001445 MAIN & GATES.GPJ AET+CPT+WELL_20181012_JG.GDT 7/9/21Draft
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
3/4 30
medium
D10
coarse
4 14081.5 6 200100
GRAIN SIZE IN MILLIMETERS
Specimen Identification
Specimen Identification
MC% LL PL PI Cc
SILT OR CLAY
GRADATION CURVES
1.7
%Sand %Silt %Clay
95.2
%Gravel
SAND
40
fine
D30
1
D60
U.S. SIEVE NUMBERS
20161410
U.S. SIEVE OPENING IN INCHES HYDROMETER
2.80.97
23
SB- 1
5.3'
5.3'
SB- 1
1/2
3
P
E
R
C
E
N
T
F
I
N
E
R
B
Y
W
E
I
G
H
T
33/8
9.50 0.82 0.477
Classification Cu
D100
6 70504
GRAVEL
fineCOBBLES coarse
0.2866 3.1
POORLY GRADED SAND
6/8/21
Main & Gates Redevelopment; Elk River, MNPROJECT AET JOB NO.
DATE
P-0001445
AMERICAN
ENGINEERING
TESTING, INC.Draft
Preliminary Report of Geotechnical Exploration
Main & Gates Redevelopment; Elk River, Minnesota AMERICAN
July 9, 2021 ENGINEERING
Report No. P-0001445 TESTING, INC.
Appendix B
Geotechnical Report Limitations and Guidelines for Use
Draft
Appendix B
Geotechnical Report Limitations and Guidelines for Use
Report No. P-0001445
Appendix B – Page 1 of 2 AMERICAN ENGINEERING TESTING, INC
B.1 REFERENCE
This appendix provides information to help you manage your risks relating to subsurface problems which are caused by
construction delays, cost overruns, claims, and disputes. This information was developed and provided by GBA1, of which, we
are a member firm.
B.2 RISK MANAGEMENT INFORMATION
B.2.1 Geotechnical Services are Performed for Specific Purposes, Persons, and Projects
Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study
conducted for a civil engineer may not fulfill the needs of a construction contractor or even another civil engineer. Because each
geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solely for the client. No one
except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who
prepared it. And no one, not even you, should apply the report for any purpose or project except the one originally contemplated.
B.2.2 Read the Full Report
Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an
executive summary. Do not read selected elements only.
B.2.3 A Geotechnical Engineering Report is Based on A Unique Set of Project-Specific Factors
Geotechnical engineers consider a number of unique, project-specific factors when establishing the scope of a study. Typically
factors include: the client’s goals, objectives, and risk management preferences; the general nature of the structure involved, its
size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access
roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates
otherwise, do not rely on a geotechnical engineering report that was:
not prepared for you,
not prepared for your project,
not prepared for the specific site explored, or
completed before important project changes were made.
Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect:
the function of the proposed structure, as when it’s changed from a parking garage to an office building, or from a light
industrial plant to a refrigerated warehouse,
elevation, configuration, location, orientation, or weight of the proposed structure,
composition of the design team, or
project ownership.
As a general rule, always inform your geotechnical engineer of project changes, even minor ones, and request an assessment of
their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not
consider developments of which they were not informed.
B.2.4 Subsurface Conditions Can Change
A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a
geotechnical engineering report whose adequacy may have been affected by: the passage of time; by man-made events, such as
construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctuations. Always
contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional
testing or analysis could prevent major problems.
1 Geoprofessional Business Association, 1300 Piccard Drive, LL14, Rockville, MD 20850
Telephone: 301/565-2733: www.geoprofessional.org Draft
Appendix B
Geotechnical Report Limitations and Guidelines for Use
Report No. P-0001445
Appendix B – Page 2 of 2 AMERICAN ENGINEERING TESTING, INC
B.2.5 Most Geotechnical Findings Are Professional Opinions
Site exploration identified subsurface conditions only at those points where subsurface tests are conducted or samples are taken.
Geotechnical engineers review field and laboratory data and then apply their professional judgment to render an opinion about
subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated
in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most
effective method of managing the risks associated with unanticipated conditions.
B.2.6 A Report’s Recommendations Are Not Final
Do not over rely on the construction recommendations included in your report. Those recommendations are not final, because
geotechnical engineers develop them principally from judgment and opinion. Geotechnical engineers can finalize their
recommendations only by observing actual subsurface conditions revealed during construction. The geotechnical engineer who
developed your report cannot assume responsibility or liability for the report’s recommendations if that engineer does not
perform construction observation.
B.2.7 A Geotechnical Engineering Report Is Subject to Misinterpretation
Other design team members’ misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that
risk by having your geotechnical engineer confer with appropriate members of the design team after submitting the report. Also
retain your geotechnical engineer to review pertinent elements of the design team’s plans and specifications. Contractors can also
misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and
preconstruction conferences, and by providing construction observation.
B.2.8 Do Not Redraw the Engineer’s Logs
Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To
prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in
architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognizes that separating
logs from the report can elevate risk.
B.2.9 Give Contractors a Complete Report and Guidance
Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface
conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete
geotechnical engineering report, but preface it with a clearly written letter of transmittal. In the letter, advise contractors that the
report was not prepared for purposes of bid development and that the report’s accuracy is limited; encourage them to confer with
the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain
the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contractors have
sufficient time to perform additional study. Only then might you be in a position to give contractors the best information
available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated
conditions.
B.2.10 Read Responsibility Provisions Closely
Some clients, design professionals, and contractors do not recognize that geotechnical engineering is far less exact than other
engineering disciplines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims,
and disputes. To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory
provisions in their report. Sometimes labeled “limitations” many of these provisions indicate where geotechnical engineers’
responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask
questions. Your geotechnical engineer should respond fully and frankly.
B.2.11 Geoenvironmental Concerns Are Not Covered
The equipment, techniques, and personnel used to perform a geoenvironmental study differ significantly from those used to
perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenvironmental
findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated
contaminants. Unanticipated environmental problems have led to numerous project failures. If you have not yet obtained your
own geoenvironmental information, ask your geotechnical consultant for risk management guidance. Do not rely on an
environmental report prepared for someone else. Draft