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Geotechnical Engineering Report
Washington State Auto Dealers Association
621 SW Grady Way
Renton, Washington 98057
May 18, 2018
prepared for:
Sitts & Hill Engineers, Inc.
Attention: Kathy Hargrave
4815 Center Street
Tacoma, Washington 98409
prepared by:
Migizi Group, Inc.
PO Box 44840
Tacoma, Washington 98448
(253) 537-9400
MGI Project P1258-T18
i
TABLE OF CONTENTS
Page No.
1.0 SITE AND PROJECT DESCRIPTION............................................................................................... 1
2.0 EXPLORATORY METHODS ............................................................................................................. 2
2.1 Test Pit Procedures ................................................................................................................ 2
3.0 SITE CONDITIONS ............................................................................................................................ 3
3.1 Surface Conditions ................................................................................................................. 3
3.2 Soil Conditions ....................................................................................................................... 3
3.3 Groundwater Conditions ...................................................................................................... 3
3.4 Seismic Conditions ................................................................................................................. 4
3.5 Liquefaction Potential ............................................................................................................ 4
4.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................................ 4
4.1 Site Preparation ...................................................................................................................... 5
4.2 Asphalt Pavement .................................................................................................................. 7
4.3 Structural Fill .......................................................................................................................... 8
5.0 RECOMMENDED ADDITIONAL SERVICES ................................................................................ 9
6.0 CLOSURE ........................................................................................................................................... 10
List of Tables
Table 1. Approximate Locations and Depths of Explorations ............................................................................. 2
List of Figures
Figure 1. Topographic and Location Map
Figure 2. Site and Exploration Plan
APPENDIX A
Soil Classification Chart and Key to Test Data .................................................................................................. A-1
Logs of Test Pits TP-1 through TP-3 .......................................................................................................... A-2…A-4
Page 1 of 10
MIGIZI GROUP, INC.
PO Box 44840 PHONE (253) 537-9400
Tacoma, Washington 98448 FAX (253) 537-9401
May 18, 2018
Sitts & Hill Engineers, Inc.
4815 Center Street
Tacoma, Washington 98409
Attention: Kathy Hargrave
Subject: Geotechnical Engineering Report
Washington State Auto Dealers Association
621 SW Grady Way
Renton, Washington 98057
MGI Project P1258-T18
Dear Ms. Hargrave:
Migizi Group, Inc. (MGI) is pleased to submit this report describing the results of our geotechnical
engineering evaluation for a proposed asphalt parking lot expansion to be located in a vacant lot
immediately south of the existing parking lot for the Washington State Auto Dealers Association
(WSADA) building in Renton, Washington. A previous Geotechnical Letter Report was prepared for
the existing facilities by E3RA, Inc. dated April 4, 2012.
This report has been prepared for the exclusive use of Sitts & Hill Engineers, Inc., and their
consultants, for specific application to this project, in accordance with generally accepted
geotechnical engineering practice.
1.0 SITE AND PROJECT DESCRIPTION
The project site is located along the south side of SW Grady Way in a commercial area just north of
I-405 in Renton, Washington, as shown on the enclosed Topographic and Location Map (Figure 1).
The project area is rectangularly-shaped, encompassing a total area of 0.33-acres. The site is
undeveloped and lies in the ancestral floodplain of the Black and Green Rivers before the partial
draining of Lake Washington in 1916. The site is bordered by SW 12th St to the south, asphalt
parking lots to the north and east, and Bell Electronics to the west.
It is our understanding that the project area will be stripped, paved, and connected to the existing
WSADA parking area to the north. The new parking lot will be at or near existing grade.
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 2 of 10
2.0 EXPLORATORY METHODS
We explored surface and subsurface conditions at the project site on April 27, 2018. Our exploration
and evaluation program comprised the following elements:
• Surface reconnaissance of the site;
• Three test pit explorations (designated TP-1, TP-2, and TP-3) advanced on April 27, 2018;
and
• A review of published geologic and seismologic maps and literature.
Table 1 summarizes the approximate functional locations and termination depths of our subsurface
explorations, and Figure 2 depicts their approximate relative locations. The following sections
describe the procedures used for excavation of the test pits.
TABLE 1
APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS
Exploration Functional Location
Termination
Depth
(feet)
TP-1
TP-2
TP-3
Roughly central to the western third of the property
Roughly the middle-most point of the property
Roughly central to the eastern third of the property
10
3
10
The specific numbers and locations of our explorations were selected in relation to the existing site
features, under the constraints of surface access, underground utility conflicts, and budget
considerations.
It should be realized that the explorations performed and utilized for this evaluation reveal
subsurface conditions only at discrete locations across the project site and that actual conditions in
other areas could vary. Furthermore, the nature and extent of any such variations would not
become evident until additional explorations are performed or until construction activities have
begun. If significant variations are observed at that time, we may need to modify our conclusions
and recommendations contained in this report to reflect the actual site conditions.
2.1 Test Pit Procedures
Our exploratory test pits were excavated with a rubber-tracked mini-excavator operated by an
excavation contractor under subcontract to MGI. An engineering geologist from our firm observed
the test pit excavations, collected soil samples, and logged the subsurface conditions.
The enclosed test pit logs indicate the vertical sequence of soils and materials encountered in our
test pits, based on our field classifications. Where a soil contact was observed to be gradational or
undulating, our logs indicate the average contact depth. We estimated the relative density and
consistency of the in-situ soils by means of the excavation characteristics and the stability of the test
pit sidewalls. Our logs also indicate the approximate depths of any sidewall caving or groundwater
seepage observed in the test pits. The soils were classified visually in general accordance with the
system described in Figure A-1, which includes a key to the exploration logs. Summary logs of our
explorations are included as Figure A-2 through A-4.
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 3 of 10
3.0 SITE CONDITIONS
The following sections present our observations, measurements, findings, and interpretations
regarding surface, soil, groundwater, and infiltration conditions.
3.1 Surface Conditions
As previously indicated, the project site consists of a rectangularly-shaped, 0.33-acre commercial
property situated near the intersection of I-405 and WA-167 in Renton. The property lies in the
ancestral floodplain of the Black and Green Rivers before the partial draining of Lake Washington in
1916. The site is undeveloped and topographically flat, with the exception of a dry, empty pit in the
southeastern corner of the property approximately 4 feet deep and 20 feet in length.
Site vegetation is limited to sparse grass and spiky bushes lining the edges of the property, in
addition to a line of deciduous and evergreen trees on the eastern boundary near an existing
parking lot.
No hydrologic features were observed on site, such as seeps, springs, ponds and streams.
3.2 Soil Conditions
We observed subgrade conditions in three test pits across the property. These explorations revealed
structural fill and construction-related debris such as concrete, asphalt, and brick in a dense
condition down to approximately 2½ to 4½ feet below the surface. This material overlies dense
native alluvial flood plain deposits comprised of fine sand, silty sand, silt and gravel. Native soils
were all poorly consolidated and oversaturated. While excavating TP-2, a block of concrete
prevented further excavation beyond 3 feet deep and the test pit was terminated.
In the Geologic Map of the Renton Quadrangle, King County, Washington, as prepared by the
Department of the Interior United States Geological Survey (USGS) (1965), the project site is
mapped as containing Qaw, or Quaternary Alluvium associated with the flood plains of the White
and Green Rivers. The upper part of these deposits are mostly clayey silt and fine sand, locally
peaty, being 10 to 20 feet thick near Kent, thickening to 30 to 40 feet near Tukwila. The lower part of
these deposits are mostly medium and coarse sand and can reach thicknesses of up to 75 feet.
The National Cooperative Soil Survey (NCSS) for the King County Area classifies soils onsite as
Ur-Urban Land, surrounded by minor soil units of sand and silt loam. This soil series reportedly
formed along alluvial flood plains and is comprised of sandy loam, silt loam, silty clay loam and
sand. Our subsurface explorations generally correspond with the site classifications prepared by
the USGS and NCSS.
The enclosed exploration logs (Appendix A) provide a detailed description of the soil strata
encountered in our subsurface explorations.
3.3 Groundwater Conditions
We encountered groundwater seepage in two of our three subsurface explorations, at a depth of 4 to
4½ feet below existing grade. Given the fact that our explorations were performed just outside of
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 4 of 10
what is generally considered the rainy season (November 1 to March 31), we do not anticipate that
groundwater will rise much higher than that which we observed. Groundwater levels will fluctuate
with localized geology and precipitation.
3.4 Seismic Conditions
Based on our analysis of subsurface exploration logs and our review of published geologic maps,
we interpret the onsite soil conditions to generally correspond with site class E, as defined by
Table 30.2-1 in ASCE 7, per the 2015 International Building Code (IBC).
Using 2015 IBC information on the USGS Design Summary Report website, Risk Category I/II/III
seismic parameters for the site are as follows:
Ss = 1.442 g SMS = 1.298 g SDS = 0.865 g
S1 = 0.538 g SM1 = 1.292 g SD1 = 0.862 g
Using the 2015 IBC information, MCER Response Spectrum Graph on the USGS Design Summary
Report website, Risk Category I/II/III, Sa at a period of 0.2 seconds is 1.30 g and Sa at a period of
1.0 seconds is 1.30 g.
The Design Response Spectrum Graph from the same website, using the same IBC information and
Risk Category, Sa at a period of 0.2 seconds is 0.86 g and Sa at a period of 1.0 seconds is 0.86 g.
3.5 Liquefaction Potential
Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength
caused by shear strains, as could result from an earthquake. Research has shown that saturated,
loose, fine to medium sands with a fines (silt and clay) content less than about 20 percent are most
susceptible to liquefaction. Poorly consolidated soils encountered below the water table (a depth of
4 to 4½ feet) present a moderate to severe risk for soil liquefaction. Recommendations for pavement
section design and construction contained within this report helps mitigate some of this risk, but the
risk for soil liquefaction and resultant post-construction settlement should still be considered
moderate across the project area in the instance of a large-scale seismic event.
4.0 CONCLUSIONS AND RECOMMENDATIONS
It is our understanding that the project area will be stripped, paved, and connected to the existing
WSADA parking area to the north. The new parking lot will be at or near existing grade. We offer
these recommendations:
• Feasibility: Based on our field explorations, research, and evaluations, the proposed
pavements appear feasible from a geotechnical standpoint.
• Pavement Sections: We recommend a conventional pavement section comprised of
an asphalt concrete pavement over a crushed rock base course over a properly
prepared (compacted) subgrade or a granular subbase.
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 5 of 10
All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded
dump truck or heavy compactor. Any localized zones of yielding subgrade
disclosed during this proof-rolling operation should be over excavated to an
additional maximum depth of 12 inches and replaced with a suitable structural fill
material.
The following sections of this report present our specific geotechnical conclusions and
recommendations concerning site preparation, spread footings, slab-on-grade floors, asphalt
pavement, and structural fill. The Washington State Department of Transportation (WSDOT)
Standard Specifications and Standard Plans cited herein refer to WSDOT publications M41-10,
Standard Specifications for Road, Bridge, and Municipal Construction, and M21-01, Standard Plans for
Road, Bridge, and Municipal Construction, respectively.
4.1 Site Preparation
Preparation of the project site should involve erosion control, temporary drainage, clearing,
stripping, excavations, cutting, subgrade compaction, and filling.
Erosion Control: Before new construction begins, an appropriate erosion control system should be
installed. This system should collect and filter all surface water runoff through silt fencing. We
anticipate a system of berms and drainage ditches around construction areas will provide an
adequate collection system. Silt fencing fabric should meet the requirements of WSDOT Standard
Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below
existing grade. An erosion control system requires occasional observation and maintenance.
Specifically, holes in the filter and areas where the filter has shifted above ground surface should be
replaced or repaired as soon as they are identified.
Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or
near-surface water within the construction zones before stripping begins. Because the selection of
an appropriate drainage system will depend on the water quantity, season, weather conditions,
construction sequence, and contractor's methods, final decisions regarding drainage systems are
best made in the field at the time of construction. Based on our current understanding of the
construction plans, surface and subsurface conditions, we anticipate that curbs, berms, or ditches
placed around the work areas will adequately intercept surface water runoff.
Clearing and Stripping: After surface and near-surface water sources have been controlled, sod,
topsoil, and root-rich soil should be stripped from the site. The proposed work area is currently
paved and no stripping will be necessary.
Site Excavations: Based on our explorations, we expect that excavations will encounter loose/soft to
medium dense/stiff silty, sandy alluvial soils which can be easily excavated using standard
excavation equipment.
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 6 of 10
Dewatering: We encountered groundwater seepage in two of three of our explorations at a depth of
4 to 4½ feet below existing grade. Given the fact that our explorations were performed just outside
of what is generally considered the rainy season (November 1 to March 31), we do not anticipate
that groundwater will rise much higher than that which we observed. If groundwater is
encountered in shallower excavations, we anticipate that an internal system of ditches, sumpholes,
and pumps will be adequate to temporarily dewater most excavations. For deeper excavations well
below the water table, expensive dewatering equipment, such as well points, may need to be
utilized in order to adequately dewater excavations.
Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should
be adequately inclined to prevent sloughing and collapse. Temporary cut slopes in site soils should
be no steeper than 1½H:1V, and should conform to Washington Industrial Safety and Health Act
(WISHA) regulations.
Subgrade Compaction: Exposed subgrades for the foundations of the planned additions should be
compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized
zones of looser granular soils observed within a subgrade should be compacted to a density
commensurate with the surrounding soils. In contrast, any organic, soft, or pumping soils observed
within a subgrade should be overexcavated and replaced with a suitable structural fill material.
Site Filling: Our conclusions regarding the reuse of onsite soils and our comments regarding wet-
weather filling are presented subsequently. Regardless of soil type, all fill should be placed and
compacted according to our recommendations presented in the Structural Fill section of this report.
Specifically, building pad fill soil should be compacted to a uniform density of at least 95 percent
(based on ASTM:D-1557).
Onsite Soils: We offer the following evaluation of these onsite soils in relation to potential use as
structural fill:
• Fill: The fill that overlies the site contains construction debris and some organic
material, so is not reusable as structural fill. If areas of debris and organic-free fill
are encountered during the construction process and are thought to be reusable, we
recommend that MGI evaluate their potential for reuse.
• Alluvial Silt and Silty Sand: The alluvial silty sand that underlies the site is very
moisture sensitive and will be difficult or impossible to reuse during most weather
conditions. The majority of this soil type is currently above the optimum moisture
content and will not compact adequately unless extensively aerated.
• Alluvial Fine to Medium Sand with Gravel: Where encountered, and if properly
segregated from its siltier counterpart, the clean native fine sands are a possible
source of structural fill. This material type is relatively impervious to moisture
content variations and can be reused in most weather conditions.
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 7 of 10
Permanent Slopes: All permanent cut slopes and fill slopes should be adequately inclined to reduce
long-term raveling, sloughing, and erosion. We generally recommend that no permanent slopes be
steeper than 2H:1V. For all soil types, the use of flatter slopes (such as 2½H:1V) would further
reduce long-term erosion and facilitate revegetation.
Slope Protection: We recommend that a permanent berm, swale, or curb be constructed along the
top edge of all permanent slopes to intercept surface flow. Also, a hardy vegetative groundcover
should be established as soon as feasible, to further protect the slopes from runoff water erosion.
Alternatively, permanent slopes could be armored with quarry spalls or a geosynthetic erosion mat.
4.2 Asphalt Pavement
Since asphalt pavements will be used across much of the project site, we offer the following
comments and recommendations for pavement design and construction.
Subgrade Preparation: We recommend a conventional pavement section comprised of an asphalt
concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade
or a granular subbase.
All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded dump truck or
heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling
operation should be over excavated to an additional maximum depth of 12 inches and replaced
with a suitable structural fill material. All structural fill should be compacted according to our
recommendations given in the Structural Fill section. Specifically, the upper 2 feet of soils
underlying pavement section should be compacted to at least 95 percent (based on ASTM D-1557),
and all soils below 2 feet should be compacted to at least 90 percent.
Pavement Materials: For the base course, we recommend using imported crushed rock, such as
"Crushed Surfacing Top Course” per WSDOT Standard Specification 9-03.9(3). If a subbase course
is needed, we recommend using imported, clean, well-graded sand and gravel such as “Ballast” or
“Gravel Borrow” per WSDOT Standard Specifications 9-03.9(1) and 9-03.14, respectively.
Conventional Asphalt Sections: A conventional pavement section typically comprises an asphalt
concrete pavement over a crushed rock base course. We recommend using the following
conventional pavement sections:
Minimum Thickness
Section Automobile Parking Areas Driveways and Areas Subject to
Truck Traffic
Asphalt Concrete Pavement 2 inches 3 inches
Crushed Rock Base 4 inches 6 inches
Compaction and Observation: All subbase and base course material should be compacted to at least
95 percent of the Modified Proctor maximum dry density (ASTM D-1557), and all asphalt concrete
should be compacted to at least 92 percent of the Rice value (ASTM D-2041). We recommend that
an MGI representative be retained to observe the compaction of each course before any overlying
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 8 of 10
layer is placed. For the subbase and pavement course, compaction is best observed by means of
frequent density testing. For the base course, methodology observations and hand-probing are
more appropriate than density testing.
Pavement Life and Maintenance: No asphalt pavement is maintenance-free. The above described
pavement sections present our minimum recommendations for an average level of performance
during a 20-year design life, therefore, an average level of maintenance will likely be required.
Furthermore, a 20-year pavement life typically assumes that an overlay will be placed after about
10 years. Thicker asphalt and/or thicker base and subbase courses would offer better long-term
performance but would cost more initially; thinner courses would be more susceptible to “alligator”
cracking and other failure modes. As such, pavement design can be considered a compromise
between a high initial cost and low maintenance costs versus a low initial cost and higher
maintenance costs.
4.3 Structural Fill
The term "structural fill" refers to any material placed under foundations, retaining walls, slab-on-
grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and
recommendations concerning structural fill are presented in the following paragraphs.
Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock,
crushed rock, well-graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit-
run"), and miscellaneous mixtures of silt, sand, and gravel. Recycled asphalt, concrete, and glass,
which are derived from pulverizing the parent materials, are also potentially useful as structural fill
in certain applications. Soils used for structural fill should not contain any organic matter or debris,
nor any individual particles greater than about 6 inches in diameter.
Fill Placement: Clean sand, gravel, crushed rock, soil mixtures, and recycled materials should be
placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be
thoroughly compacted with a mechanical compactor.
Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we
recommend that structural fill used for various onsite applications be compacted to the following
minimum densities:
Fill Application Minimum
Compaction
Asphalt pavement base
Asphalt pavement subgrade (upper 2 feet)
Asphalt pavement subgrade (below 2 feet)
95 percent
95 percent
90 percent
Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018
Geotechnical Engineering Report P1258-T18
Migizi Group, Inc. Page 9 of 10
Subgrade Observation and Compaction Testing: Regardless of material or location, all structural fill
should be placed over firm, unyielding subgrades prepared in accordance with the Site Preparation
section of this report. The condition of all subgrades should be observed by geotechnical personnel
before filling or construction begins. Also, fill soil compaction should be verified by means of
in-place density tests performed during fill placement so that adequacy of soil compaction efforts
may be evaluated as earthwork progresses.
Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on
their grain-size distribution and moisture content when they are placed. As the "fines" content (that
soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes
in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be
consistently compacted to a firm, unyielding condition when the moisture content is more than
2 percentage points above or below optimum. For fill placement during wet-weather site work, we
recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by
weight) based on the soil fraction passing the U.S. No. 4 Sieve.
5.0 RECOMMENDED ADDITIONAL SERVICES
Because the future performance and integrity of the structural elements will depend largely on
proper site preparation, drainage, fill placement, and construction procedures, monitoring and
testing by experienced geotechnical personnel should be considered an integral part of the
construction process. Subsequently, we recommend that MGI be retained to provide the following
post-report services:
• Review all construction plans and specifications to verify that our design criteria
presented in this report have been properly integrated into the design;
• Prepare a letter summarizing all review comments (if required);
• Check all completed subgrades for footings and slab-on-grade floors before concrete
is poured, in order to verify their bearing capacity; and
• Prepare a post-construction letter summarizing all field observations, inspections,
and test results (if required).
APPROXIMATE SITE
LOCATION
P.O. Box 44840
Tacoma, WA 98448
Location Job Number Figure
DateTitle
621 SW Grady Way
Renton, Washington
Topographic and Location Map
1
05/16/18
P1258-T18
APPENDIX A
SOIL CLASSIFICATION CHART AND
KEY TO TEST DATA
LOGS OF TEST PITS
CLAYEY GRAVELS, POORLY GRADED GRAVEL-SAND-CLAY
MIXTURES
SILTS AND CLAYSCOARSE GRAINED SOILSMore than Half > #200 sieveLIQUID LIMIT LESS THAN 50
LIQUID LIMIT GREATER THAN 50
CLEAN GRAVELS
WITH LITTLE OR
NO FINES
GRAVELS WITH
OVER 15% FINES
CLEAN SANDS
WITH LITTLE
OR NO FINES
MORE THAN HALF
COARSE FRACTION
IS SMALLER THAN
NO. 4 SIEVE
MORE THAN HALF
COARSE FRACTION
IS LARGER THAN
NO. 4 SIEVE
INORGANIC SILTS, MICACEOUS OR DIATOMACIOUS FINE
SANDY OR SILTY SOILS, ELASTIC SILTS
ORGANIC CLAYS AND ORGANIC SILTY CLAYS OF LOW
PLASTICITY
OH
INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR,
SILTY OR CLAYEY FINE SANDS, OR CLAYEY SILTS WITH
SLIGHT PLASTICITY
CH
SILTY GRAVELS, POORLY GRADED GRAVEL-SAND-SILT
MIXTURES
SANDS
SILTS AND CLAYS
Figure A-1
INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY,
GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS,
LEAN CLAYS
R-Value
Sieve Analysis
Swell Test
Cyclic Triaxial
Unconsolidated Undrained Triaxial
Torvane Shear
Unconfined Compression
(Shear Strength, ksf)
Wash Analysis
(with % Passing No. 200 Sieve)
Water Level at Time of Drilling
Water Level after Drilling(with date measured)
RV
SA
SW
TC
TX
TV
UC
(1.2)
WA
(20)
Modified California
Split Spoon
Pushed Shelby Tube
Auger Cuttings
Grab Sample
Sample Attempt with No Recovery
Chemical Analysis
Consolidation
Compaction
Direct Shear
Permeability
Pocket Penetrometer
CA
CN
CP
DS
PM
PP
PtHIGHLY ORGANIC SOILS
TYPICAL NAMES
GRAVELS
ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY,
ORGANIC SILTS
WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES
MAJOR DIVISIONS
PEAT AND OTHER HIGHLY ORGANIC SOILS
WELL GRADED SANDS, GRAVELLY SANDS
POORLY GRADED SANDS, GRAVELLY SANDS
SILTY SANDS, POORLY GRADED SAND-SILT MIXTURES
CLAYEY SANDS, POORLY GRADED SAND-CLAY MIXTURES
POORLY GRADED GRAVELS, GRAVEL-SAND MIXTURES
SOIL CLASSIFICATION CHART AND KEY TO TEST DATA
GW
GP
GM
GC
SW
SP
SM
SC
ML
FINE GRAINED SOILSMore than Half < #200 sieveLGD A NNNN02 GINT US LAB.GPJ 11/4/05INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS
CL
OL
MH
SANDS WITH
OVER 15% FINES
GB
S-1
GP-
GM
SM
SP
ML
0.5
2.5
4.0
10.0
(GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill)
(SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill)
(SP) Blue/gray fine to medium sand with gravel (medium dense, moist) (Alluvium)
(ML) Blue/gray silt (very soft, wet) (Alluvium)
Moderate caving observed from 4 to 10 feet
Moderate groundwater seepage observed at 4 feet
The depths on the test pit logs are based on an average of measurements across the test pit and should be
considered accurate to 0.5 foot.
Bottom of test pit at 10.0 feet.
NOTES
LOGGED BY ZLL
EXCAVATION METHOD Rubber Tracked Mini Excavator
EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS:
CHECKED BY JEB
DATE STARTED 4/27/18 COMPLETED 4/27/18
AT TIME OF EXCAVATION 4.00 ft Moderate seepage
AT END OF EXCAVATION ---
AFTER EXCAVATION ---
TEST PIT SIZEGROUND ELEVATION
SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
10.0
PAGE 1 OF 1
Figure A-2
TEST PIT NUMBER TP-1
CLIENT Sitts & Hill Engineers, Inc.
PROJECT NUMBER P1258-T18
PROJECT NAME Washington State Auto Dealers Association
PROJECT LOCATION 621 SW Grady Way, Renton, WA
COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc.
PO Box 44840
Tacoma, WA 98448
Telephone: 253-537-9400
Fax: 253-537-9401
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
GP-
GM
SM
0.8
3.0
(GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill)
(SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill)
Refusal at a depth of 3 feet atop a large section of concrete
No caving observed
No groundwater seepage observed
The depths on the test pit logs are based on an average of measurements across the test pit and should be
considered accurate to 0.5 foot.
Bottom of test pit at 3.0 feet.
NOTES
LOGGED BY ZLL
EXCAVATION METHOD Rubber Tracked Mini Excavator
EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS:
CHECKED BY JEB
DATE STARTED 4/27/18 COMPLETED 4/27/18
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---
TEST PIT SIZEGROUND ELEVATION
SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
PAGE 1 OF 1
Figure A-3
TEST PIT NUMBER TP-2
CLIENT Sitts & Hill Engineers, Inc.
PROJECT NUMBER P1258-T18
PROJECT NAME Washington State Auto Dealers Association
PROJECT LOCATION 621 SW Grady Way, Renton, WA
COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc.
PO Box 44840
Tacoma, WA 98448
Telephone: 253-537-9400
Fax: 253-537-9401
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION
GP-
GM
SM
SM
ML
1.0
3.5
4.5
10.0
(GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill)
(SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill)
(SM) Gray silty sand with gravel, wood, glass, plastic and other detritus (loose, wet) (Fill)
(ML) Blue/gray mottled silt (very soft, wet) (Alluvium)
Moderate caving observed from 4.5 to 10 feet
Moderate groundwater seepage observed at 4.5 feet
The depths on the test pit logs are based on an average of measurements across the test pit and should be
considered accurate to 0.5 foot.
Bottom of test pit at 10.0 feet.
NOTES
LOGGED BY ZLL
EXCAVATION METHOD Rubber Tracked Mini Excavator
EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS:
CHECKED BY JEB
DATE STARTED 4/27/18 COMPLETED 4/27/18
AT TIME OF EXCAVATION 4.50 ft Moderate seepage
AT END OF EXCAVATION ---
AFTER EXCAVATION ---
TEST PIT SIZEGROUND ELEVATION
SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
10.0
PAGE 1 OF 1
Figure A-4
TEST PIT NUMBER TP-3
CLIENT Sitts & Hill Engineers, Inc.
PROJECT NUMBER P1258-T18
PROJECT NAME Washington State Auto Dealers Association
PROJECT LOCATION 621 SW Grady Way, Renton, WA
COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc.
PO Box 44840
Tacoma, WA 98448
Telephone: 253-537-9400
Fax: 253-537-9401
U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION