16-217 10000 Edmonds Way Rpt.pdfGeotechnical & Earthquake
Engineering Consultants
GEOTECHNICAL REPORT
WESTGATE VILLAGE
10000 Edmonds Way
Edmonds, Washington
PROJECT NO. 16-217
September 17, 2016
Prepared for:
Westgate Village, LLC
3213 Eastlake Avenue E Suite B, Seattle, WA 98102
T. 206.262.0370 F. 206.262.0374
________________________________________________
3213 Eastlake Avenue East, Suite B
Seattle, WA 98102-7127
Tel (206) 262-0370
Fax (206) 262-0374
Geotechnical & Earthquake
Engineering Consultants
September 17, 2016
File No. 16-217
Westgate Village, LLC
4025 Delridge Way SW #530
Seattle, WA 98106
Attention: Anthony Jansen
Subject: Geotechnical Report
Westgate Village
10000 Edmonds Way
Edmonds, WA
Dear Mr. Jansen,
Attached is our geotechnical report for the proposed four-story mixed use development with at
grade parking in the Westgate development in Edmonds. This report documents the subsurface
conditions at the site and presents geotechnical engineering recommendations for the
development.
The site is underlain by competent native advanced outwash sand at shallow depths.
Consequently, the new construction may be supported on conventional spread footing
foundations. However, the surficial loose silty, recessional outwash deposits should be over
excavated to a depth of 2 feet below the footings and replaced with compacted structural fill.
We appreciate the opportunity to work on this project. Please call if there are any questions.
Sincerely,
W. Paul Grant, P.E.
Principal Geotechnical Engineer
Encl.: Geotechnical Report
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TABLE OF CONTENTS
1.0 INTRODUCTION................................................................................................................... 2
2.0 PROJECT AND SITE DESCRIPTION ............................................................................... 2
3.0 SUBSURFACE EXPLORATIONS ....................................................................................... 3
4.0 SUBSURFACE CONDITIONS ............................................................................................. 4
4.1 SITE GEOLOGY ....................................................................................................................... 4
4.2 SOILS ..................................................................................................................................... 4
4.3 GROUNDWATER ..................................................................................................................... 5
5.0 GEOTECHNICAL RECOMMENDATIONS ...................................................................... 6
5.1 SEISMIC DESIGN PARAMETERS ............................................................................................... 6
5.2 BUILDING FOUNDATIONS ....................................................................................................... 7
5.2.1 Allowable Bearing Pressure ........................................................................................... 7
5.2.2 Lateral Resistance .......................................................................................................... 7
5.3 RETAINING WALLS ................................................................................................................ 8
5.3.1 Lateral Pressures and Resistances .................................................................................. 8
5.3.2 Wall Drainage/Damp Proofing ...................................................................................... 8
5.3.3 Wall Backfill .................................................................................................................. 8
5.4 CONCRETE SLAB-ON-GRADE ................................................................................................. 9
5.5 STORMWATER INFILTRATION ................................................................................................. 9
6.0 CONSTRUCTION CONSIDERATIONS .......................................................................... 10
6.1 DEMOLITION & SITE PREPARATION ..................................................................................... 10
6.2 EXCAVATIONS ...................................................................................................................... 10
6.3 MATERIAL REUSE ................................................................................................................ 10
6.4 STRUCTURAL FILL PLACEMENT AND COMPACTION ............................................................. 10
6.5 EROSION AND DRAINAGE CONSIDERATIONS ........................................................................ 11
6.6 WET EARTHWORK RECOMMENDATIONS .............................................................................. 11
7.0 ADDITIONAL SERVICES.................................................................................................. 12
8.0 LIMITATIONS ..................................................................................................................... 12
9.0 REFERENCES ...................................................................................................................... 15
Geotechnical Report
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September 16, 2016
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LIST OF FIGURES
Figure 1 Vicinity Map
Figure 2 Site and Exploration Plan
LIST OF APPENDIX
Appendix A Summary Boring Logs
Figure A-1 Terms and Symbols for Boring and Test Pit Logs
Figure A-2 Log of Test Boring B-1
Figure A-3 Log of Test Boring B-2
Figure A-4 Log of Test Boring B-3
GEOTECHNICAL REPORT
WESTGATE VILLAGE
10000 EDMONDS WAY
EDMONDS, WASHINGTON
________________________________________________________________________
_____
1.0 INTRODUCTION
This report presents the results of a geotechnical engineering study that was undertaken
to support the design and construction of the proposed Westgate Village mixed use
building in Edmonds, Washington (see Figure 1). Our study was performed in
accordance with our mutually agreed scope of work as outlined in our proposal letter of
August 11, 2016, which was subsequently approved by you on August 19, 2016. Our
service scope included reviewing readily available geologic and geotechnical data in the
site vicinity, conducting a site reconnaissance, advancing three test borings, and
developing the geotechnical design recommendations presented in this report.
2.0 PROJECT AND SITE DESCRIPTION
The new mixed use building at the Westgate Village development will straddle the
southwest quadrant of the existing development and extend into a recently acquired
parcel on the west as shown on Figure 2. Existing development on the Westgate Village
site includes two single story retail buildings, adjacent paved parking, and a level gravel
pad in the southwest corner of the development. Buildings on the recently acquired parcel
to the west have been demolished. However, the concrete flatwork and foundations of
the former buildings remain in place.
While the site is generally flat lying at an elevation of about 317 feet, the southwestern
edge of the development abuts the toe of a steep slope that is retained with a reinforced
concrete retaining wall on the east and a cantilever soldier pile wall on the west (see
Plates 1 and 2). The new building will be set back from the existing concrete wall.
However, the existing soldier pile wall on the west will be demolished to accommodate
the new construction and the existing reinforced concrete wall will need to extend to the
west to support the toe of the slope and allow construction of the new building.
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Plate 1 – Reinforced concrete retaining wall at
the toe of the slope and soldier pile wall at the
original west property line of the development
(view west)
Plate 2 – Low concrete retaining walls at the
toe of the slope of the newly acquired property
with soldier pile wall on the left covered in
vegetation (view south)
The proposed development will consist of a four story mixed use building as shown on
Plate 3. The development is planned to have at grade parking beneath and around the
building. The ground floor will also have 2,000 sq. ft. of retail space, as well as lobby
and storage space. The upper three stories will have 80 residential units.
Plate 3. Planned four story building, oblique view.
3.0 SUBSURFACE EXPLORATIONS
Subsurface conditions at the site were explored with three borings (B-1 through B-3)
which were drilled on August 31, 2016, at the locations shown on Figure 2. The boring
locations were determined in the field based on measurements from existing features.
Two of the borings were drilled near the ends of the proposed building to provide
information for the design of the building foundations. The third boring was drilled on
the hillside to provide data for design of the new retaining wall that will be needed on the
south side of the building.
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Borings B-1 and B-2 were drilled to a depth of 16½ feet below the ground surface. The
hillside boring (B-3) was drilled to a depth of 10 feet, which was sufficient to verify that
the slope was underlain by competent soil at a shallow depth. Boring B-2 encountered
difficult drilling conditions which may have been caused by a cobble. Consequently, the
boring was moved 5 feet to avoid the obstruction and redrilled as Boring B-2A.
All borings were drilled with hollow stem auger drilling equipment owned and operated
by BoreTec, Inc. of Valleyford, Washington. Soil samples were obtained at 2½-foot
intervals in the borings in general accordance with Standard Penetration Test (SPT)
sampling methods (ASTM test method D-1586). The SPT procedure includes driving a 2-
inch outside diameter split-spoon sampler into undisturbed soil below the tip of the auger
with a 140-pound weight falling a distance of 30 inches. The sampler is typically driven
18 inches into the ground and the number of blows required for the last 12 inches of
driving is recorded as the SPT N-value. The N-value provides an empirical measure of
the relative density of cohesionless soil or the relative consistency of fine-grained soils.
The completed borings were backfilled with drill cuttings and bentonite chips.
A geologist from PanGEO was present during drilling to assist in sampling and to
describe and document the soil samples obtained from the borings. The soil samples
were described in the field using the system outlined on Figure A-1 of Appendix A.
Summary logs of the borings are included as Figures A-2 through A-4 in Appendix A.
4.0 SUBSURFACE CONDITIONS
4.1 SITE GEOLOGY
According to the Composite Geologic Map of the Sno-King Area (Booth, et. al., 2004),
the flat portion of the site is underlain by Vashon Advanced Outwash (Qva), and the
slope area is underlain by Vashon Glacial Till (Qvt). Vashon Glacial Till (Qvt) typically
consists of a dense to very dense, heterogeneous mixture of silt, sand, and gravel which
has been laid down at the base of an advancing glacial ice sheet. Advanced outwash
(Qva) is usually comprised of dense, well sorted sand and gravel deposited in streams
issuing from the front of the advancing glacier.
4.2 SOILS
The soils observed in the site borings are generally consistent with the Composite
Geologic Map of the Sno-King Area. The borings drilled in the level area (B-1 and B-2)
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encountered medium dense to dense, sand with silt and gravel, which we interpreted
generally as Advanced Outwash. Borings B-2 and B-2A penetrated a layer of loose,
yellow brown silty sand which, based on the soil oxidation, stratigraphic position and
density, is interpreted as recessional outwash. The hillside boring (B-3) found very
dense, silty sand with gravel at a shallow depth. This material is interpreted as Vashon
till based on density and texture. The following summarizes soil conditions encountered
in the site borings:
UNIT 1: Fill – Fill was only certainly encountered in boring B-1, and it is a thin
layer of medium dense to dense, brown, fine to coarse gravel with silt and sand.
This material covers the open area of east parcel to a depth of 1 to 1½ feet.
UNIT 2: Recessional Outwash – The west parcel, outside the footprint of the
former buildings, is underlain by loose, yellow brown, very silty, fine sand to
sandy silt. The fines are slightly plastic, and the soil contains scattered gravel. As
stated above, the soil unit is interpreted as recessional outwash. The soil unit
extends to a depth of roughly 4½ feet below the surface.
UNIT 3: Advanced Outwash – Below the fill and recessional outwash, B-1, B-2
and B-2A encountered medium dense to dense, brown to brown gray, fine to
medium sand with silt and gravel. The soil unit is bedded to laminated, and
interbeds range in composition from sand with silt and gravel to sandy silt with
gravel. The outwash below the east parcel (B-1) tends to have less gravel and
lower blow counts than the material penetrated by B-2. It is likely that the blow
counts in B-2 are elevated due to the gravel. This unit extended to the full depth
of the borings.
UNIT 4: Vashon Till – B-3, located on the hillside above the main project site,
encountered very dense, brown gray, massive, silty, fine sand with gravel. The
soil texture and density confirmed the unit to be glacial till.
4.3 GROUNDWATER
Groundwater was encountered in the borings. It should be expected that the advanced
outwash will contain groundwater at depth. Also, while not observed in boring B-3,
glacial till may contain sand seams that might contain local seepage. It should be noted
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that groundwater elevations likely vary seasonally and are normally highest during the
winter and early spring.
5.0 GEOTECHNICAL RECOMMENDATIONS
The site is underlain by medium dense native outwash at shallow depths. The soils are
conducive to the use conventional spread footings to support the building. However,
because the near surface soils in the newly acquired parcel may be loose or disturbed
from prior construction, we recommend that the soil in the western half of the building be
excavated to a depth of 2 feet below the base of the new footings and replaced with
structural fill that is compacted to a dense and unyielding condition with a Ho-Pac.
Where the building footprint impinges on the toe of the slope, we recommend extending
the existing cast in place concrete wall to the west to support the toe of the slope. The
following provides details of the design recommendations.
5.1 SEISMIC DESIGN PARAMETERS
The following provides seismic design parameters for the site that are in conformance
with the 2014 and later editions of the International Building Code (IBC), which
specifies a design earthquake having a 2% probability of occurrence in 50 years (return
interval of 2,475 years), and the 2008 USGS seismic hazard maps:
Table 1 – Summary Seismic Design Parameters
Site
Class
Spectral
Acceleration
at 0.2 sec. (g)
SS
Spectral
Acceleration at
1.0 sec. (g)
S1
Site
Coefficients
Design Spectral
Response
Parameters
Fa Fv SDS SD1
D 1.26 0.49 1.00 1.51 0.84 0.50
Liquefaction Potential – Liquefaction is not a design consideration for the site because
nearby deep borings indicate that groundwater is not present within 50 feet of the ground
surface. Accordingly, special design considerations associated with soil liquefaction are
not necessary for this project.
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5.2 BUILDING FOUNDATIONS
5.2.1 Allowable Bearing Pressure
The proposed building can be supported on conventional strip and individual footing
bearing on the medium dense to dense, native outwash deposits. We recommend that,
where present, the loose, silty sand recessional outwash be over-excavated to expose the
dense, underlying advanced outwash soil and replaced with structural fill. We also
recommend that the medium dense, advanced outwash soils be over excavated to t a
depth of 2 feet below the footings. After over excavation, in both areas the exposed
subgrade should be compacted to a dense and unyielding condition using a Ho-Pac. The
over excavation should be brought back to footing grade by placing structural fill in lifts
not exceeding 8 inches of loose thickness, and compacted to a dense and unyielding
condition. The sandy and gravelly advanced outwash soil may be re-used as fill, but the
silty recessional outwash should not be used as backfill.
Footings bearing on the advanced outwash or compacted structural fill may be designed
for an allowable bearing pressure of 3 ksf with a one-third increase for seismic or
transient loads. All footings should be founded a minimum distance of 18 inches below
the finished exterior grade for perimeter footings and 12 inches below the finished floor
slab for interior footings. All strip footings should have a minimum width of 18 inches
and all individual footings should have a minimum width of 24 inches. Any footing over
excavation should extend at least 6 inches beyond the face of the footings. Footing
excavations should be observed by PanGEO to confirm that the footing subgrade has
been adequately prepared.
Footings designed in accordance with the above may experience total settlements of less
than 1 inch under static loading with differential settlement between adjacent columns
less than about ½ inch. Most settlement should occur during construction.
5.2.2 Lateral Resistance
Lateral forces from wind or seismic loading may be resisted by the combination of
passive earth pressures acting against the embedded portions of the foundations (i.e.
footings and walls) and by friction acting on the base of the foundations. Passive
resistance values may be determined using an equivalent fluid weight of 350 pounds per
cubic foot (pcf). This value includes a factor safety of at least 2 assuming that compacted
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structural fill will be placed adjacent to the sides of the footings. A coefficient friction of
0.5 may be used to determine the frictional resistance at the base of the footings. This
coefficient includes a factor safety of approximate 1.5.
5.3 RETAINING WALLS
5.3.1 Lateral Pressures and Resistances
Retaining walls may be designed for an equivalent fluid weight of 35 and 45 pcf for level
backfill and 2(H):1(V) sloping backfill, respectively. For seismic conditions, we
recommend including an incremental uniform lateral earth pressure of 6H psf (where H is
the height of the below grade portion of the wall) as an ultimate seismic load. The
recommended lateral pressures assume that the backfill behind the wall consists of a free
draining and properly compacted fill with adequate drainage provisions to prevent the
development of hydrostatic pressure.
Lateral loads on the walls may be resisted by a combination of passive earth pressures
acting against the embedded portions of the foundations and by friction acting on the base
of the foundations. Passive resistance values may be determined using an equivalent
fluid weight of 350 pounds per cubic foot (pcf). A friction coefficient of 0.5 may be used
to determine the frictional resistance at the base of the footings. Both of these values
include a safety factor of at least 1.5.
5.3.2 Wall Drainage/Damp Proofing
While groundwater is not anticipated within the planned location of the retaining wall,
the overlying soil may experience seepage from up slope runoff. Consequently, we
suggest that the design consider including prefabricated drainage mats, such as Mirafi
6000 or equivalent, at the face of the wall. Any water collected from the mats should be
directed and collected at the base of the wall and tight lined to an appropriate outlet.
5.3.3 Wall Backfill
Free draining granular soil such as City of Seattle Mineral Aggregate Type 17 (City of
Seattle Standard Specifications, 9-03.12(3)) should be used for backfill behind the
retaining walls. The wall backfill should be moisture conditioned to within about 3
percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in
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thickness, and systematically compacted to a dense and relatively unyielding condition
and to at least 95 percent of the maximum dry density, as determined using test method
ASTM D 1557. Within 5 feet of the wall, the backfill should be compacted to 90 percent
of the maximum dry density.
5.4 CONCRETE SLAB-ON-GRADE
Conventional slab-on-grade construction may be used for the at grade floor slabs. A
modulus of subgrade reaction of 150 pci may be used for the floor slab design. The
subgrade should be compacted to a dense and unyielding condition prior to slab
construction. Unsuitable materials, especially in the area underlain by recessional
outwash, should be over-excavated to a depth of 1 foot and replaced with structural fill
compacted to a dense and unyielding condition with a Ho-Pac or double drum vibratory
roller.
The concrete slab-on-grade floors should be underlain by at least 4 inches of capillary
break, consisting of free-draining, clean crushed rock or well-graded gravel compacted to
a firm and unyielding condition. The capillary break material should have no more than
20 percent passing the No. 4 sieve and less than 5 percent by weight of the material
passing the U.S. Standard No. 100 sieve. City of Seattle Type 22 material (clean crushed
5/8 inch rock) meets this gradation requirement. The capillary break should be placed
over the native, undisturbed subgrade or structural fill compacted to a dense and
unyielding condition (i.e. 95 percent of the maximum dry density, as determined using
test method ASTM D 1557). We also recommend that a minimum 10-mil polyethylene
vapor barrier be placed below the proposed basement slab.
5.5 STORMWATER INFILTRATION
Infiltration of stormwater runoff may be feasible on this site due to the granular nature of
the underlying soils. However, estimation of the potential infiltration rates is not feasible
as the configuration of the storm drain system is not established and recommendations for
infiltration are not within the present scope of work. If the owners wish an infiltration
evaluation, PanGEO will provide a separate scope of work and budget for this task.
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6.0 CONSTRUCTION CONSIDERATIONS
6.1 DEMOLITION & SITE PREPARATION
Site preparation for the proposed project includes demolishing the existing concrete
pavement and foundations from former buildings. All stripped surface materials should be
properly disposed off-site.
6.2 EXCAVATIONS
Large excavations are not expected to be required for this project. However, temporary
excavations are expected where the building footprint impinges on the toe of the steep
slope. All temporary excavations should be performed in accordance with Part N of
WAC (Washington Administrative Code) 296-155. The contractor is responsible for
maintaining safe excavation slopes and/or shoring. We believe that construction of new
retaining walls at the toe of the slope will require excavations of up to about 8 feet deep.
We believe that the lower 4 feet of the excavations will be in till soil that may be cut
vertically and that the excavation above this level may be sloped at 1(H):1(V). Steeper
cut slopes may be possible based on field inspection and approval by PanGEO. The till
soils can generally be excavated with conventional backhoes and track hoes.
6.3 MATERIAL REUSE
The sand and gravel advanced outwash soils may be re-used as an all-weather structural
fill, provided it does not contain in excess of about 7% fines. Samples of the soil should
be tested for fines content if re-using the soil is desired. Because of their fines content
the existing recessional outwash and till soils encountered may not suitable for reuse as
structural fill in the winter or during periods of rainfall. Any structural backfill for the
footings should consist of imported, Seattle Type 17 material or approved equivalent.
Recessional outwash and till may be re-used in non-structural, landscape areas.
6.4 STRUCTURAL FILL PLACEMENT AND COMPACTION
As currently envisaged, we do not anticipate the need for large quantities of fill for the
proposed development. If structural fill will be needed, City of Seattle Type 17 material
should be used. Structural fill should be moisture conditioned to within about 3 percent
of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in
thickness, and systematically compacted to a dense and relatively unyielding condition
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and to at least 95 percent of the maximum dry density, as determined using test method
ASTM D 1557.
6.5 EROSION AND DRAINAGE CONSIDERATIONS
Surface runoff can be controlled during construction by careful grading practices.
Typically, this includes the construction of shallow, upgrade perimeter ditches or low
earthen berms to collect runoff and prevent water from entering the excavation. All
collected water should be directed to a positive and permanent discharge system such as a
City of Seattle storm sewer.
It should be noted that the site soils may be prone to surficial erosion. Special care
should be taken to avoid surface water on open cut excavations. We recommend that the
exposed temporary slopes be covered with plastic sheeting.
Permanent control of surface water and roof runoff should be incorporated in the final
grading design. In addition to these sources, irrigation and rain water infiltrating into
landscape and planter areas adjacent to paved areas or building walls should also be
controlled. All collected runoff should be directed into conduits that carry the water
away from the pavement or structure and into storm drain systems or other appropriate
outlets. Adequate surface gradients should be incorporated into the grading design such
that surface runoff is directed away from structures.
6.6 WET EARTHWORK RECOMMENDATIONS
General recommendations relative to earthwork performed in wet weather or in wet
conditions are presented below:
All surface of the foundation subgrade should be protected against inclement
weather. It is the contractor’s responsibility to protect the footing subgrade
from disturbance. One option is to place a 2- to 3-inch thick layer of lean-mix
concrete on the footing subgrade as soon as the subgrade is exposed.
Earthwork should be performed in small areas to minimize subgrade exposure
to wet weather. Excavation or the removal of unsuitable soil should be
followed promptly by the placement and compaction of clean structural fill.
The size and type of construction equipment used may have to be limite d to
prevent soil disturbance.
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During wet weather, the allowable fines content of the structural fill should be
reduced to no more than 5 percent by weight based on the portion passing ¾-
inch sieve. The fines should be non-plastic.
The ground surface within the construction area should be graded to promote
run-off of surface water and to prevent the ponding of water.
Geotextile silt fences should be strategically located to control erosion and the
movement of soil. Erosion control measures should be installed along all the
property boundaries.
Excavation slopes and soils stockpiled on site should also be covered with
plastic sheets.
7.0 ADDITIONAL SERVICES
We anticipate the City of Edmonds may require a plan review and geotechnical special
inspections to confirm that our recommendations are properly incorporated into the
design and construction of the proposed development. Specifically, we anticipate that the
following construction support services may be needed:
Review final project plans and specifications;
Verify implementation of erosion control measures;
Observe the stability of open cut slopes and temporary shoring;
Verify adequacy of foundation and slab subgrades;
Confirm the adequacy of the compaction of structural backfill;
Observe installation of subsurface drainage provisions, and;
Other consultation as may be required during construction.
Modifications to our recommendations presented in this report may be necessary, based
on the actual conditions encountered during construction.
8.0 LIMITATIONS
We have prepared this report for use by Westgate Village, LLC and the project design
team. Recommendations contained in this report are based on a site reconnaissance,
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conducting a subsurface exploration program at the site, and our understanding of the
project. The study was performed using a mutually agreed-upon scope of work.
Variations in soil conditions may exist between the explorations and the actual conditions
underlying the site. The nature and extent of soil variations may not be evident until
construction occurs. If any soil conditions are encountered at the site that are different
from those described in this report, we should be notified immediately to review the
applicability of our recommendations. Additionally, we should also be notified to review
the applicability of our recommendations if there are any changes in the project scope.
The scope of our work does not include services related to construction safety
precautions. Our recommendations are not intended to direct the contractors’ methods,
techniques, sequences or procedures, except as specifically described in our report for
consideration in design. Additionally, the scope of our work specifically excludes the
assessment of environmental characteristics, particularly those involving hazardous
substances. We are not mold consultants nor are our recommendations to be interpreted
as being preventative of mold development. A mold specialist should be consulted for all
mold-related issues.
This report may be used only by the client and for the purposes stated, within a
reasonable time from its issuance. Land use, site conditions (both off and on -site), or
other factors including advances in our understanding of applied science, may change
over time and could materially affect our findings. Therefore, this report should not be
relied upon after 24 months from its issuance. PanGEO should be notified if the p roject
is delayed by more than 24 months from the date of this report so that we may review the
applicability of our conclusions considering the time lapse.
It is the client’s responsibility to see that all parties to this project, including the designer,
contractor, subcontractors, etc., are made aware of this report in its entirety. The use of
information contained in this report for bidding purposes should be done at the
contractor’s option and risk. Any party other than the client who wishes to use this report
shall notify PanGEO of such intended use and for permission to copy this report. Based
on the intended use of the report, PanGEO may require that additional work be performed
and that an updated report be reissued. Noncompliance with any of these requirements
will release PanGEO from any liability resulting from the use this report.
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Within the limitation of scope, schedule and budget, PanGEO engages in the practice of
geotechnical engineering and endeavors to perform its services in accordance with
generally accepted professional principles and practices at the time the Report or its
contents were prepared. No warranty, express or implied, is made.
We appreciate the opportunity to be of service to you on this project. Please feel free to
contact our office with any questions you have regarding our study, this report, or any
geotechnical engineering related project issues.
Sincerely,
W. Paul Grant, P.E. Stephen H. Evans, L.E.G.
Principal Geotechnical Engineer Senior Eng. Geologist
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9.0 REFERENCES
Booth, D.B., Cox, B.F., Troost, K.G. and Shimel, S.A., 2004, Draft Composite Geologic
Map of the Sno-King Area, Central Puget Lowland, Washington. University of
Washington Seattle-Area Mapping Project (SGMP) and the United States Geological
Survey (USGS), Scale 1:24,000.
City of Seattle, 2014, Standard Specifications for Road, Bridges, and Municipal
Construction.
International Building Code (IBC), 2014, International Code Council.
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APPENDIX A
SUMMARY BORING LOGS
MOISTURE CONTENT
2-inch OD Split Spoon, SPT
(140-lb. hammer, 30" drop)
3.25-inch OD Spilt Spoon
(300-lb hammer, 30" drop)
Non-standard penetration
test (see boring log for details)
Thin wall (Shelby) tube
Grab
Rock core
Vane Shear
Dusty, dry to the touch
Damp but no visible water
Visible free water
Terms and Symbols for
Boring and Test Pit Logs
Density
SILT / CLAY
GRAVEL (<5% fines)
GRAVEL (>12% fines)
SAND (<5% fines)
SAND (>12% fines)
Liquid Limit < 50
Liquid Limit > 50
Breaks along defined planes
Fracture planes that are polished or glossy
Angular soil lumps that resist breakdown
Soil that is broken and mixed
Less than one per foot
More than one per foot
Angle between bedding plane and a planenormal to core axis
Very Loose
Loose
Med. Dense
Dense
Very Dense
SPT
N-values
Approx. Undrained Shear
Strength (psf)
<4
4 to 10
10 to 30
30 to 50
>50
<2
2 to 4
4 to 8
8 to 15
15 to 30
>30
SPT
N-values
Units of material distinguished by color and/orcomposition from material units above and below
Layers of soil typically 0.05 to 1mm thick, max. 1 cm
Layer of soil that pinches out laterally
Alternating layers of differing soil material
Erratic, discontinuous deposit of limited extent
Soil with uniform color and composition throughout
Approx. Relative
Density (%)
Gravel
Layered:
Laminated:
Lens:
Interlayered:
Pocket:
Homogeneous:
Highly Organic Soils
#4 to #10 sieve (4.5 to 2.0 mm)
#10 to #40 sieve (2.0 to 0.42 mm)
#40 to #200 sieve (0.42 to 0.074 mm)
0.074 to 0.002 mm
<0.002 mm
UNIFIED SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP DESCRIPTIONS
Notes:
MONITORING WELL
<15
15 - 35
35 - 65
65 - 85
85 - 100
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
TEST SYMBOLS
50%or more passing #200 sieve
Groundwater Level at time of drilling (ATD)Static Groundwater Level
Cement / Concrete Seal
Bentonite grout / seal
Silica sand backfill
Slotted tip
Slough
<250
250 - 500
500 - 1000
1000 - 2000
2000 - 4000
>4000
RELATIVE DENSITY / CONSISTENCY
Fissured:
Slickensided:
Blocky:
Disrupted:
Scattered:
Numerous:
BCN:
COMPONENT DEFINITIONS
Dry
Moist
Wet
1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions.
2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials.
COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE
SYMBOLS
Sample/In Situ test types and intervals
Silt and Clay
Consistency
SAND / GRAVEL
Very Soft
Soft
Med. Stiff
Stiff
Very Stiff
Hard
Phone: 206.262.0370
Bottom of BoringBoulder:
Cobbles:
Gravel
Coarse Gravel:
Fine Gravel:
Sand
Coarse Sand:
Medium Sand:
Fine Sand:
Silt
Clay
> 12 inches
3 to 12 inches
3 to 3/4 inches
3/4 inches to #4 sieve
Atterberg Limit Test
Compaction Tests
Consolidation
Dry Density
Direct Shear
Fines Content
Grain Size
Permeability
Pocket Penetrometer
R-value
Specific Gravity
Torvane
Triaxial Compression
Unconfined Compression
Sand
50% or more of the coarse
fraction passing the #4 sieve.
Use dual symbols (eg. SP-SM)
for 5% to 12% fines.
for In Situ and Laboratory Testslisted in "Other Tests" column.
50% or more of the coarse
fraction retained on the #4
sieve. Use dual symbols (eg.
GP-GM) for 5% to 12% fines.
DESCRIPTIONS OF SOIL STRUCTURES
Well-graded GRAVEL
Poorly-graded GRAVEL
Silty GRAVEL
Clayey GRAVEL
Well-graded SAND
Poorly-graded SAND
Silty SAND
Clayey SAND
SILT
Lean CLAY
Organic SILT or CLAY
Elastic SILT
Fat CLAY
Organic SILT or CLAY
PEAT
ATT
Comp
Con
DD
DS
%F
GS
Perm
PP
R
SG
TV
TXC
UCC
LO
G
K
E
Y
1
3
-
1
1
3
L
O
G
.
G
P
J
P
A
N
G
E
O
.
G
D
T
9
/
1
8
/
1
3
Figure A-1
Medium dense to dense, brown, fine to coarse GRAVEL with silt and
sand: dry, massive. (Fill).
Medium dense, brown gray, fine SAND with silt: moist, occasional
gravel, homogeneous, non-plastic fines, indistinctly laminated. (Adv.
Outwash).
Medium dense, interbedded, brown, fine to coarse SAND, fine SAND
and SILT: moist with wet layers, non-plastic fines with rapid dilatancy,
laminated, trace gravel. (Adv. Outwash).
Medium dense, brown gray, fine SAND with silt: moist, occasional silt
interbed, non-plastic, some gravel, massive. Blow counts high due to
gravel. (Adv. Outwash).
Dense to medium dense, brown gray, fine to medium SAND: moist,
some non-plastic silt to with silt, occasional gravel, homogeneous,
laminated. (Adv. Outwash).
Becoming loose, occasional fine to carse SAND beds, some silt,
massive.
Bottom of Boring.
S-1
S-2
S-3
S-4
S-5
15
9
8
20
12
14
14
18
50/3
9
21
29
6
6
7
Remarks: No continuoous groundwater encountered during drilling. Thin wet soil lenses
encountered.
0
2
4
6
8
10
12
14
16
18
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-2
Ot
h
e
r
T
e
s
t
s
Sa
m
p
l
e
N
o
.
Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:
De
p
t
h
,
(
f
t
)
Proposed Development
16-217
10000 Edmonds Way, Edmonds, WA
Northing: , Easting:
16.5ft
8/31/16
8/31/16
S. Evans
BoreTec, Inc
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sy
m
b
o
l
Sa
m
p
l
e
T
y
p
e
Bl
o
w
s
/
6
i
n
.
318.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING B-1
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
Sod and silty topsoil.
Loose, yellow brown, very silty, fine SAND to sandy SILT: dry, slightly
plastic fines, scattered gravel, homogeneous, massive. (Rec.
Outwash).
Dense, brown and gray, interbedded, fine to coarse SAND with silt and
gravel, and SILT with gravel: moist, silt beds till-like, non-plastic fines,
moderate weathering, fine bedded. (Adv. Outwash).
No recovery due to pushing cobble. Blow counts high due to cobble.
Dene, brown gray, gravelly SILT with fine sand: moist with wet layers,
slightly plastic fines, till-like and massive. California sampler used to
enhance recovery. Blow counts high due to gravel. (Adv. Outwash).
Dense to very dense, brown gray, fine to medium SAND with silt:
moist with wet layers, slightly plastic fines, homogeneous, massive.
(Adv. Outwash).
California sampler used to enhance recovery. Blow counts high due
to gravel. Very moist.
Bottom of Boring.
S-1
S-2
S-3
S-4
S-5
4
1
4
17
15
20
50/6
50/6
38
50/6
Remarks: No continuous groundwater encountered during drilling. Thin wet soil lenses
encountered.
0
2
4
6
8
10
12
14
16
18
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-3
Ot
h
e
r
T
e
s
t
s
Sa
m
p
l
e
N
o
.
Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:
De
p
t
h
,
(
f
t
)
Proposed Development
16-217
10000 Edmonds Way, Edmonds, WA
Northing: , Easting:
16.8ft
8/31/16
8/31/16
S. Evans
BoreTec, Inc
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sy
m
b
o
l
Sa
m
p
l
e
T
y
p
e
Bl
o
w
s
/
6
i
n
.
316.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING B-2
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
>>
>>
Sod and topsoil.
Loose, yellow brown, silty, fine SAND: dry, some medium to coarse
sand, gravel, non-plastic, massive. (Rec. Outwash).
Dense, multi-colored brown and gray, fine to coarse SAND with fine
gravel: moist, trace to some silt, non-plastic, fine bedded. (Adv.
Outwash).
Bottom of Boring.
S-1
S-2
5
6
5
14
18
24
Remarks: No groundwater encountered during drilling. Boring drilled to confirm soil
conditions in B-2, which were unclear due to poor sample recovery and likely cobble at
auger tip.
0
2
4
6
8
10
12
14
16
18
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-4
Ot
h
e
r
T
e
s
t
s
Sa
m
p
l
e
N
o
.
Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:
De
p
t
h
,
(
f
t
)
Proposed Development
16-217
10000 Edmonds Way, Edmonds, WA
Northing: , Easting:
6.5ft
8/31/16
8/31/16
S. Evans
BoreTec, Inc
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sy
m
b
o
l
Sa
m
p
l
e
T
y
p
e
Bl
o
w
s
/
6
i
n
.
316.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING B-2A
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
Dense to very dense, brown gray, silty, fine SAND with gravel: moist,
non-plastic fines, gravel sub-rounded and blocky, homogeneous,
massive. (Till).
Gravelly intervals at 6 feet, 7.5 feet and 9 feet.
Grading to silty, fine SAND, some gravel.
Bottom of Boring.
S-1
S-2
11
38
43
50/2
Remarks: No groundwater encountered during drilling.
0
2
4
6
8
10
12
14
16
18
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-5
Ot
h
e
r
T
e
s
t
s
Sa
m
p
l
e
N
o
.
Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:
De
p
t
h
,
(
f
t
)
Proposed Development
16-217
10000 Edmonds Way, Edmonds, WA
Northing: , Easting:
10.2ft
8/31/16
8/31/16
S. Evans
BoreTec, Inc
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sy
m
b
o
l
Sa
m
p
l
e
T
y
p
e
Bl
o
w
s
/
6
i
n
.
342.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING B-3
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>