Magic Toyota Building Addition Preliminary Report.pdf
8410 154 Avenue NE
th
Redmond, Washington 98052
425.861.6000
December 20, 2016
Magic Toyota
c/o Strotkamp Architects
P.O. Box 501
Burlington, Washington 98233
Attention: Tom Strotkamp and David Estes
Subject: Preliminary Geotechnical Report
Magic Toyota Building Replacement
Edmonds, Washington
File No. 11805-001-04
INTRODUCTION
GeoEngineers, Inc. (GeoEngineers) is pleased to present the results of our preliminary geotechnical
evaluation in support of the Magic Toyota Building Replacement project. The project site is located at
21300 Highway 99 in Edmonds, Washington. The location of the site is shown on the Vicinity Map, Figure 1.
The location of the building replacement relative to the existing building and features is shown on the Site
Plan, Figure 2.
The purpose of our preliminary report is to summarize the subsurface conditions and provide a preliminary
geotechnical evaluation of foundation support and infiltration feasibility for the new facility. We understand
that the new building will be about 260 feet north-south by about 150 feet east-west. The new structure
will essentially replace the footprint of the existing dealership building, with an extension on the north side.
Rooftop parking will cover a portion of the new building. Existing grades, which slope up to the north, are
such that a retaining wall about 10 feet in height will be required along the north building wall. An older
building in the northeast parcel will be demolished and the site grades revised for construction of new
parking in this area.
PREVIOUS STUDIES
Our previous experience at the site includes environmental and geotechnical studies for the site and
parking garage to the south, and geotechnical observation services during construction of the garage.
Our current exploration plan was developed based on review of our previous report and on the extend of
the new building, 1400 Highway 99,
Edmonds, 14, 2006.
Magic Toyota|December 20, 2016Page 2
FIELD EXPLORATIONS AND LABORATORY TESTING
Field Explorations
Subsurface conditions were evaluated by reviewing previous subsurface data and completing four
supplemental borings to depths of 16.5 to 41.5 feet. The approximate location of the explorations is shown
in Figure 2. A detailed description of the field exploration program and the logs of the explorations are
presented in Appendix A.
Laboratory Testing
Selected samples were tested for the determination of moisture content, fines content (material passing
the U.S. No. 200 sieve), grain size distribution (sieve analysis), and plasticity tests. The tests were
performed in general accordance with test methods of the American Society for Testing and Materials
(ASTM). A description of the laboratory testing and the test results are presented in Appendix B.
SITE CONDITIONS
Geology
The Puget Sound basin is a region of Quaternary (last 3 million years) sediments that range in thickness
between 800 and 2,400 feet. The basin area has been repeatedly overridden by Pleistocene (between
11,000 and 3 million years ago) continental glacial ice depositing till, glacial sand and gravel. As the glacial
ice retreated to the north, glaciofluvial sediment was deposited in the outwash channels. The most
recent glacial cycle of sediment deposits is referred to as the Vashon Drift, occurring between 13,500 and
15,000 years ago.
We reviewed a Unites States Geological Survey
Geological Map of the Edmonds East and Edmonds West Quadrangles, Snohomish and King Counties,
Surficial geologic deposits in the site vicinity are mapped as
recessional outwash, glacial till, and advance outwash. Recessional outwash typically consists of sand and
gravel with varying amounts of silt that was deposited by meltwater from the stagnating and receding
glacier. These soils are typically medium dense.
Glacial till is a heterogeneous mixture of sand, gravel, cobbles and occasional boulders in a silt and clay
matrix that was deposited beneath a glacier. Advance outwash typically consists of well-stratified sand with
variable amounts of gravel and cobbles. The advance outwash is usually exposed where the overlying
glacial till cap has been eroded away, typically in ravines and bluff margins. Both the glacial till and advance
outwash have been overridden by thousands of feet of ice, and are typically dense to very dense. The
Whidbey Formation underlies the advance outwash and typically consists of dense sands and gravels
overlying or interbedded with stiff to hard silts.
Surface Conditions
The project area extends about 400 feet in the north-south direction and varies from about 420 to 300 feet
east-west, including parking areas which will be reconfigured. The new building will be about 260 feet in
length north-south and 150 feet in width, east-west. Existing structures include the existing dealership and
repair shop, and a small building in the northeast corner. The remainder of the area is covered with asphalt
File No. 11805-001-04
Magic Toyota|December 20, 2016Page 3
pavement except for a small slope between the lot at the northeast corner and the surrounding dealership
parking lot. The slope is vegetated with grass and shrubs.
The original parking lot south of the dealership was constructed by placing up to 10 to 12 feet of fill. The
south parking lot now slopes gently down to the south to the new parking garage situated across the
southwest portion of the property. Existing ground surface elevations range from approximately Elevation
378 feet in the lower parking lot immediately south of the dealership building to Elevation 388 feet at the
north border of the site near 212 Street SW. Existing site features are shown in the Site Plan, Figure 2.
th
Subsurface Conditions
The borings encountered 2 to 4 inches of asphalt pavement underlain by a thin layer of crushed rock
base course or soil. Borings GEI-1 and GEI-2 encountered very dense silty sand with gravel (glacial till)
underlying the pavement section. Borings GEI-3 and 4, located on the south side of the dealership building,
encountered 8 to 10 feet of fill consisting of medium dense to dense silty sand with gravel. The fill is
underlain by glacial till. Hard silt of the Whidbey Formation was encountered beneath the till in borings
GEI-2 and GEI-3 at an elevation of approximately 356 to 360 feet (15 to 25 feet below existing ground
surface). Very dense gravel was encountered at a depth of about 14 feet in boring GEI-4. This may be a
pocket of cleaner, courser material deposited during the glaciation process.
Groundwater Conditions
Groundwater was not encountered in borings GEI-1 and GEI-2, which encountered glacial till beneath the
pavement surface. The fill was wet in boring GEI-3, which we interpret to be perched groundwater above
the relatively impermeable glacial till. The very dense gravel in boring GEI-4 was also wet. We anticipate
that the groundwater is perched on the very dense glacial deposits and will fluctuate as a function of
precipitation and other factors.
PRELIMINARY FOUNDATION RECOMMENDATIONS
We conclude that the site is suitable for construction of the proposed facility replacement. We anticipate
that subsurface soils for foundation support will vary from very dense glacial till across most of the footprint,
to medium dense fill which is likely present across the southern portion of the proposed footprint. Shallow
foundations are suitable for support of the new building. Building footings may be supported on dense
native soils or on a minimum 2-foot thickness of structural fill. Footings supported as recommended above
can be designed for an allowable soil bearing pressure of 3,000 pounds per square foot (psf) for dead plus
long-term live loads. A higher allowable soil bearing pressure of 6,000 psf may be used for the north portion
of the site where very dense glacial till is present and where the foundations will be situated at least 3 feet
below existing grades (i.e. cut into the slope).
INFILTRATION CONSIDERATIONS
At this time, in our opinion infiltration facilities are not feasible because of the presence of the very dense
glacial till across most of the site. Infiltration is also not recommended in fill soils. Glacial till is considered
as a hydraulic restriction layer per the 2012 Stormwater Management Manual resulting in conventional
infiltration not being feasible. Native glacial till soils encountered at the site are relatively impermeable,
File No. 11805-001-04
SITE
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µ
2,00002,000
Feet
Vicinity Map
Notes:
1. The locations of all features shown are approximate.
Magic Toyota Building Replacement
2. This drawing is for information purposes. It is intended to assist in
showing features discussed in an attached document. GeoEngineers, Inc.
Edmonds, Washington
cannot guarantee the accuracy and content of electronic files. The master
file is stored by GeoEngineers, Inc. and will serve as the officialrecord of
this communication.
Figure 1
Data Source: Mapbox Open Street Map, 2016
Projection: NAD 1983 UTM Zone 10N
Figure 2
Magic Toyota Building Replacement
Edmonds, Washington
Site Plan
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document. GeoEngineers, Inc. cannot guarantee the accuracy
GeoEngineers, Inc. and will serve as the official record of this
and content of electronic files. The master file is stored by
2.This drawing is for information purposes. It is intended to
1.The locations of all features shown are approximate.
Background from Strotkamp Architects dated 10/31/16.
assist in showing features discussed in an attached
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communication.
Data Source:
Notes:
P:\\11\\11805001\\CAD\\04\\GeoTech\\11805000104_F02_Site Plan.dwg TAB:F02 Date Exported: 12/19/16 - 11:48 by hmara
AA
PPENDIX
Field Explorations
Magic Toyota|December 20, 2016Page A-1
APPENDIX A
FIELD EXPLORATIONS
Subsurface conditions were explored at the site by drilling four borings (GEI-1 through GEI-4). Borings
GEI-1 through GEI-4, excluding boring GEI-2, were advanced to depths between 16½ feet below the ground
surface (bgs) and boring GEI-2 was advanced to a depth of 41½ feet bgs. The subsurface explorations were
completed by Geologic Drill, Inc. on December 12, 2016. The locations of the explorations were estimated
by taping/pacing from site features. The approximate locations of the explorations are shown on the Site
Plan, Figure 2.
Borings
Borings were completed using truck-mounted, continuous-flight, hollow-stem auger or mud-rotary drilling
equipment. The borings were continuously monitored by a representative from our firm who examined and
classified the soils encountered, obtained representative soil samples, observed groundwater conditions
and prepared a detailed log of each exploration.
We obtained disturbed soil samples from the borings using a 1.5-inch-inside-diameter split-spoon standard
penetration test (SPT) sampler driven into the soil using a 140-pound hammer free-falling a distance of
30 inches. The number of blows required to drive the sampler the last 12 inches is recorded on the logs as
the blow count. Disturbed samples were collected at 2½- to 5-foot vertical intervals. The blow counts are
shown on the boring logs at the respective sample depths.
Soils encountered in the borings were visually classified in general accordance with the classification
system described in Figure A-1. A key to the boring log symbols is also presented in Figure A-1. The logs of
the borings are presented in Figures A-2 through A-5. The boring logs are based on our interpretation of the
field and laboratory data and indicate the various types of soils observed. The logs also indicate the depths
at which these soils or their characteristics change; although, the change may actually be gradual. If the
change occurred between samples, it was interpreted. The densities noted on the boring logs are based on
the blow count data obtained in the borings and judgment based on the conditions observed. The cuttings
from the drilling were removed from the site.
Observations of groundwater conditions were made during drilling. The groundwater conditions
encountered during drilling are presented on the boring logs. Groundwater conditions observed during
drilling represent a short-term condition and may or may not be representative of the long-term groundwater
conditions at the site. Groundwater conditions observed during drilling should be considered approximate.
GeoEngineers, Inc.
File No. 11805-001-04
AB
PPENDIX
Laboratory Testing
Magic Toyota | December 20, 2016 Page B-1
APPENDIX B
LABORATORY TESTING
soil samples were selected for laboratory tests to evaluate the pertinent geotechnical engineering
characteristics of the site soils and to confirm or modify our field classifications.
Our testing program consisted of the following:
two chunk moisture density tests (MD), presented on the boring logs in Appendix A next to the
sample tested;
three percent passing the U.S. No. 200 Sieve;
one sieve (grain-size distribution) analyses; and
two Atterberg limits tests.
Tests were performed in general accordance with test methods of ASTM International (ASTM) or other
applicable procedures. The following sections provide a general description of the tests performed.
Moisture Content and Dry Density
The moisture content and/or dry density of selected samples was determined in general accordance with
ASTM D-2216 and D-2937, respectively. The test results are used to aid in determining the moisture
content of the soil, soil classification and correlation with other pertinent engineering soil properties. The
densities were estimated measuring the weight and dimensions of large intact soil samples. The test results
are presented on the exploration logs in Appendix A at the respective sample depths.
Percent Passing U.S. No. 200 Sieve (%F)
of coarse- and fine-grained particles in the soil. The percent passing value represents the percentage by
weight of the sample finer than the U.S. No. 200 sieve. These tests were conducted to verify field
descriptions and to estimate the fines content for analysis purposes. The tests were conducted in
accordance with ASTM D 1140, and the results are shown on the exploration logs in Appendix A at the
respective sample depths.
Sieve Analysis
Sieve analyses were performed on selected samples in general accordance with ASTM D 422. The wet
sieve analysis method was used to determine the percentage of soil greater than the U.S. No. 200 mesh
sieve. The results of the sieve analyses were plotted, were classified in general accordance with the Unified
Soil Classification System (USCS), and are presented in Figure B-1.
GeoEngineers, Inc.
File No. 11805-001-04
Magic Toyota | December 20, 2016 Page B-2
Atterberg Limits Testing
Atterberg limits testing was performed on selected fine-grained soil samples. The tests were used to classify
the soil as well as to evaluate index properties. The liquid limit and the plastic limit were estimated through
a procedure performed in general accordance with ASTM D 4318. The results of the Atterberg limits testing
are summarized in Figure B-2.
GeoEngineers, Inc.
File No. 11805-001-04
0.001
were
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PERCENT PASSING BY WEIGHT
: 12/16/16
Sieve Analysis Results
Date Exported
Magic Toyota Building Replacement
Edmonds, Washington
04
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Figure B-1
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Figure B
Toyota Building Replacement
Atterberg Limits Test Results
Edmonds, Washington
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OH or MH
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PLASTICITY CHART
Soil Description
LIQUID LIMIT
able
Silt (ML)
only to the specific sample on which they were performed, and should not be interpreted as representative of any other
50
lic
Note: This report may not be reproduced, except in full, without written approval of GeoEngineers, Inc. Test results are app
samples obtained at other times, depths or locations, or generated by separate operations or processes.
ML or OL
The liquid limit and plasticity index were obtained in general accordance with ASTM D 4318.
40
CL or OL
Plasticity
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(%)
16
20
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Moisture
Content
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28.6
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(feet)
Depth
6050403020100
25
PLASTICITY INDEX
Number
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2
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GEI
Symbol
XX Date Exported: 06/18/16-XXX-XXXX