REVIEWED RESUB 1-BLD2022-1465-Geotech Report+8.28.2023_6.10.59_PM+3751784REVIEWED
CITY OF EDMONDS
GEOTECHNICAL ENGINEERING
EVALUATION
Pacquer Residence Addition
18306 Olympic View Dr., Edmonds, Washington
Prepared for: Steve Pacquer
Project No. 190276 • September 18, 2019 (Revised June 15, 2023) Final
Aspect
CONSULTING
%AsN ect
ICOLTING
GEOTECHNICAL ENGINEERING
EVAUATI O N
Pacquer Residence Addition
18306 Olympic View Dr., Edmonds, Washington
Prepared for: Steve Pacquer
Project No. 190276 • September 18, 2019 (Revised June 15, 2023) Final
Aspect Consulting, LLC
023
Eric Schellenger, PE
Project Geotechnical Engineer
eschellenger@aspectconsulting.com
Andy Holmson, PE
Associate Geotechnical Engineer
aholmson@aspectconsulting.com
Henry N. Haselton, EIT
Staff Engineer
hnhaselton@aspectconsulting.com
V:\190276 Pacquer Residence Addition\Deliverables\Pacquer Residence Addition Geotechnical Engineering
Evaluation 2023.docx
ASPECT CONSULTING
Contents
1 Introduction.................................................................................................1
1.1
Project Background and Description...........................................................1
2 Site Conditions............................................................................................ 2
2.1
Topography................................................................................................2
2.2
Existing Structures and Setback.................................................................2
2.3
Slope Conditions........................................................................................2
2.4
Subsurface Conditions...............................................................................2
2.4.1 Geology................................................................................................ 3
2.4.2 Stratigraphy..........................................................................................3
2.4.3 Groundwater.........................................................................................3
3 Geologic Hazard Evaluation.......................................................................4
3.1 Seismic Hazards.........................................................................................4
3.1.1 Code -Based Seismic Design Parameters.............................................4
3.1.2 Liquefaction..........................................................................................5
3.1.3 Surface Fault Rupture...........................................................................5
3.2 Landslide Hazards......................................................................................5
3.2.1 Rotational Landslides...........................................................................6
3.2.2 Shallow Landslides...............................................................................6
3.2.3 Toppling Failures..................................................................................7
4 Slope Stability Analysis..............................................................................8
4.1.1 Displacement Analysis..........................................................................9
5 Conclusions and Recommendations.......................................................10
5.1 Setback for Foundations...........................................................................10
5.2 Foundations..............................................................................................10
5.2.1 Vertical Foundation Support with Pin Piles.........................................10
5.2.2 Pin Pile Depths...................................................................................11
5.2.3 Settlement..........................................................................................11
5.2.4 Foundation Lateral Support................................................................11
5.3 Construction Considerations.....................................................................11
5.4 Steep Slope Management........................................................................12
5.5 Plans Review and Construction Monitoring..............................................13
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6 References.................................................................................................14
7 Limitations..................................................................................................16
List of Tables
Table 1. Code -Based Seismic Design Parameters...............................................5
Table 2. Summary of Soil Engineering Properties Used in Slope Stability
Analyses..................................................................................................8
List of Figures
1 Site Location Map
2 Site Exploration Map
List of Appendices
A Subsurface Exploration Logs
B Slope Stability Analysis
C Report Limitations and Guidelines for Use
ii FINAL PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023)
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1 Introduction
This report presents the results of a geotechnical engineering evaluation performed by
Aspect Consulting, LLC (Aspect) for the proposed addition to the existing single-family
residence (Project) at 18306 Olympic View Dr., Edmonds, Washington (Site). The Site
location is shown on Figure 1.
The purpose of this evaluation is to determine the geotechnical feasibility and
geotechnical requirements to construct an addition to the existing residence. Our
evaluation is based on our observations during a Site reconnaissance completed on July
31, 2019 and data obtained from subsurface explorations completed on August 21, 2019,
and information provided by the Owner.
1.1 Project Background and Description
Based on the most recent Project plans (Strobl Design, 2023), a new two -level addition is
proposed to the west side of the residence, which sits near the top of a steep, northwest -
facing slope above Puget Sound. The addition includes new interior living space (fitness
area, family room, and bedroom on the lower level, and a living room on the main level)
and a lower level exterior deck on the southwest corner of the residence.
The City of Edmonds (City) maps the slope in a Steep Slope and Landslide Hazard
Critical Area. (City, 2019) The existing residence was originally constructed in 1944
(Snohomish County, 2019), prior to current landslide hazard and seismic design
standards. We understand the City has indicated that they do not have any specific
setback requirements for the Project relative to the critical areas, and that they will rely
on a geotechnical engineer to provide a recommended setback from the top of the steep
slope for the addition.
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2 Site Conditions
2.1 Topography
The Site is located along Olympic View Drive, which is a relatively flat paved road that
was benched into the west -facing slope. The existing residence was also benched into this
slope on the west side of Olympic View Drive and has a 12-foot-deep, west -facing
daylight basement. The slope on the downhill/west side of the residence consists of two
topographically -distinct areas: a relatively gentle slope that comprises the backyard of the
residence that transitions to a steep slope that descends to railroad tracks along the
shoreline. The gently -sloping backyard slopes from about Elevation 160' at the downhill
side of the residence to about Elevation 155 at the top of the steep slope. The steep slope
slopes from about Elevation 155 to about Elevation 20 at the railroad tracks.
2.2 Existing Structures and Setback
The existing residence is a single -story structure with a daylight basement. We assume
the structure is typical wood frame construction supported on cast -in -place concrete
foundations. The residence has an upper and lower -level deck on the west side of the
residence that are supported with timber posts and shallow concrete pad footings.
Based on our observations and measurements, the foundations on the west side of the
residence (excluding the deck footings) are located between 45 to 55 feet (measured
laterally) from the top of the steep slope. The deck footings are located as close as 40 feet
from the top of the steep slope.
2.3 Slope Conditions
At the time of our reconnaissance on July 31, 2019, the steep slope was heavily vegetated
with a variety of ivy, brush, and trees. We also observed yard waste scattered on the
surface of the steep slope near the top. Because of the dense ground cover and the general
steepness, we were not able to complete an extensive reconnaissance of the steep slope.
In areas where we were able to observe slope features, we did not observe any signs of
past, recent, or incipient slope instability such as scarps or tension cracks. We also did not
observe any hydrophilic (water -loving) plants on the surface of the slope, which would
indicate the presence of seeps, springs, or perennial wetness.
We observed three generally straight -growing mature conifers in the gently -sloping
backyard area above the steep slope, near the location of the proposed addition. These
straight -growing trees are indicative of long-term slope stability at the top of the slope.
2.4 Subsurface Conditions
Our characterization of the subsurface conditions at the Site is based on a review of
applicable geologic literature, data obtained from four machine -drilled hollow -stem auger
borings, and our knowledge and understanding of the regional geologic setting.
1 All elevations presented were obtained using Google Earth and reference the North American
Vertical Datum of 1988 (NAVD88)
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2.4.1 Geology
The most recent geologic mapping of the Site area indicates the Site is underlain by pre -
Fraser non -glacial deposits (Qpfn; Cox, 2004). The Qpfn unit is described as an
undifferentiated geologic unit, meaning its exact age and origin was not determined for
this mapped area. Soils of pre -Fraser age were deposited prior to the most recent
glaciation between about 15,000 and 20,000 years ago and have been glacially overridden
at least once and are generally very dense.
The conditions encountered in our borings are consistent with the geologic mapping.
Locally, the borings indicate colluvium (loose soils on the surface or at the toe of slopes)
overly the pre -Fraser non -glacial deposits at the Site.
2.4.2 Stratigraphy
The subsurface conditions at the Site were explored with four hollow -stem auger borings
(designated AB-01 through AB-04) advanced to depths between 6.5 and 12 feet below the
ground surface (bgs) on August 21, 2019. The borings were advanced using a portable
Acker drill rig operated by Geologic Drill Partners under subcontract to Aspect. The
locations of the borings are shown on Figure 2. A detailed description of stratigraphy and
the drilling and sampling methods used is provided in Appendix A.
Topsoil
We encountered topsoil at the ground surface in each boring that extended to a depth of
approximately 8 inches bgs.
Colluvium
Below the topsoil in all four borings, we encountered colluvium that extended to depths
ranging from 4.5 to 6.5 feet bgs. The colluvium typically consisted of very loose to
medium dense, slightly moist, silty sand (SM) with varying amounts of gravel. The
colluvium is expected to have low shear strength and high compressibility.
Pre -Fraser Non -Glacial Deposits
Below the colluvium in all four borings, we encountered pre -Fraser non -glacial deposits
that extended to the bottom of the borings between 6.5 and 12 feet bgs. The pre -Fraser
non -glacial deposits typically consisted of dense to very dense, slightly moist, gray
brown, silty sand (SM) with varying amounts of gravel. The pre -Fraser non -glacial
deposits are expected to have high shear strength and low compressibility.
2.4.3 Groundwater
Groundwater was not encountered within the depths explored (6.5 to 12 feet bgs), and
publicly -available boring and well logs in the Site area did not encounter groundwater or
have groundwater data. Based on our experience, we expect a continuous, static
groundwater table to be at least 100 feet bgs in the Site area. Groundwater levels are
expected to fluctuate in depth as affected by seasonal conditions, Site usage, variations in
rainfall, irrigation, and other factors.
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3 Geologic Hazard Evaluation
An assessment of the geologic hazards present at the Site is presented below.
3.1 Seismic Hazards
The Site is located within a region of active tectonic forces associated with the interaction
of the offshore Juan de Fuca plate, the Pacific plate, and the onshore North American
plate. Seismic hazards include strong ground shaking from shallow crustal earthquakes
associated with the Southern Whidbey Island Fault Zone (SWIFZ), subduction zone
earthquakes associated with the Cascadia Subduction Zone (CSZ), and deep intraslab
earthquakes.
The SWIIFZ is a zone of northwest -trending faults estimated to be capable of producing
earthquakes of magnitude 7.0 or greater.
The CSZ lies along the boundary of the converging oceanic plates (Juan de Fuca and
Pacific Plates) and continental plate (North American Plate). CSZ earthquakes occur due
to rupture between the subducting oceanic plate and the overlying continental plates. The
CSZ can produce earthquakes up to magnitude 9.3, and the recurrence interval is thought
to be on the order of about 500 years (Atwater et al., 2015). The most recent subduction
zone earthquake occurred about 300 years ago.
Deep intraslab earthquakes, which occur from tensional rupture of the sinking oceanic
plate, are also associated with the CSZ. An example of this type of seismicity is the 2001
Nisqually earthquake. Deep intraslab earthquakes typically are magnitude 7.5 or less and
occur approximately every 10 to 30 years.
Inertial forces induced by strong ground shaking could destabilize the slope and trigger a
landslide at the Site. An assessment of the seismically -induced landslide hazard is
presented in Sections 3.2 and 4.0.
3.1.1 Code -Based Seismic Design Parameters
The new addition to the residence will be structurally designed for collapse prevention
for a specified earthquake ground motion. In accordance with the 2015 International
Building Code (IBC; ICC, 2015) and the American Society of Civil Engineers (ASCE) 7-
10, Minimum Design Loads for Buildings and Other Structures (ASCE, 2013), the
specified earthquake ground motion will be for a "Maximum Considered Earthquake"
(MCE) with a 2 percent probability of exceedance in 50 years, or a return period of 2,475
years.
IBC design methodologies express the effects of site -specific subsurface conditions on
the ground motion response in terms of the "site class." The site class can be correlated to
the average standard penetration resistance (N-value) or average shear wave velocity in
the upper 100 feet of the soil profile. Based on the subsurface explorations completed at
the Site, the soil profile would classify as Site Class D. Seismic design parameters for the
MCE, adjusted for Site Class D, are provided in Table 1.
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Table 1. Code -Based Seismic Design Parameters
2015 IBC Parameter
Recommended Value'
Site Class
D — "Stiff Soil'
Short Period Spectral Acceleration, SS (g)
1.287
1-Second Period Spectral Acceleration, S1 (g)
0.505
Site Coefficient (Fa)
1.00
Site Coefficient (Fv)
1.50
Design Short Period Spectral Acceleration, SDs (g)
0.858
Design 1-Second Period Spectral Acceleration, SD1 (g)
0.505
Site -Adjusted Peak Ground Acceleration (g)
0.525
Notes:
1. Based on the latitude and longitude of the Site: 47.832968°N, 122.359895°W
3.1.2 Liquefaction
The Site is not mapped in a liquefaction hazard area. Based on the presence of dense
glacially consolidated soils near the ground surface and the anticipated depth to
groundwater, we conclude liquefaction is not hazard at the Site.
3.1.3 Surface Fault Rupture
The traces of two strands of the SWIFZ are mapped near the Site --one trace is mapped
about one mile northeast of the Site and the other is mapped about 0.5 mile southwest of
the Site. The recurrence interval of earthquakes on this fault zone is believed to be on the
order of a 1,000 years or more, and the potential for surficial ground rupture at the Site is
considered low during the expected life of the structure.
3.2 Landslide Hazards
As part of our landslide hazard evaluation, we reviewed publicly available critical area
maps, slope stability maps, and LiDAR (Light Detection and Ranging) imagery. The City
of Edmonds maps the slopes on the Site and adjacent properties as a steep slope and
landslide hazard critical area (City of Edmonds, 2019). The Washington State Coastal
Atlas maps the slopes at the Site and adjacent properties as "unstable" (Ecology, 2019).
Shoreline photos available on the Washington State Coastal Atlas show bare soils and
exposures along the steep slope below nearby residences, which indicate shallow
landslides have occurred on the nearby slopes in the past. Our review of LiDAR imagery
of the slopes showed no obvious signs of past large-scale slope instability at the Site or
adjacent properties.
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Three types of landslides hazards are common for slopes in the Puget Sound region:
1. Rotational (deep-seated) landslides
2. Shallow landslides
3. Topping failures.
Landslides may be triggered by natural causes such as precipitation, freeze -thaw cycles,
or earthquakes, or by man-made events such as broken water pipes or stormwater flow.
Each of these landslide hazards is discussed in greater detail below with respect to the
Site.
3.2.1 Rotational Landslides
Rotational landslides consist of deep-seated failures that are characterized by slip along a
curved shear plane. Rotational landslides may transport larger masses of semi -intact soil
downslope, resulting in steep head scarps along the upper portion of the failure plane, and
benches and hummocks of displaced soil lower on the slope. Deep-seated landslides can
be caused by ongoing processes, such as erosion of the toe of the slope, seeps and springs
on the steep slope, and other ongoing processes. Deep-seated landslides can also be
triggered by large earthquakes.
Deep-seated landslides can be devastating when they occur because of the great volume
of soil that they can displace. However, deep-seated landslides typically don't occur
without warning signs many days in advance, such as formation of open tension cracks at
the ground surface, slow downslope creep of soils, bending and tipping trees,
displacement of infrastructure, etc.
Based on our reconnaissance and the dense, high -shear strength glacially consolidated
deposits that comprise the core of the steep slope, it is our opinion that the risk of large-
scale, deep-seated rotational landslide activity is relatively low at the Site.
3.2.2 Shallow Landslides
Shallow landslides consist of sliding of the colluvial or weathered soil layers and
overlying vegetation that typically mantle steep slopes in the Puget Sound region.
Shallow landslides are commonly triggered by a significant increase in the moisture
content within the upper soil layers of a slope combined with a slow increase in the
thickness of weathered and loose surficial soils. Increased moisture typically results from
periods of extended, heavy precipitation, groundwater seepage, or concentrated surface
water discharge onto a slope. While these landslides displace a smaller volume of soil
than deep-seated rotational landslides, they can be fast moving and can occur with little
or no warning. Shallow slides are typically less than five feet thick and several tens of
feet in width. They typically do not extensively impact the underlying denser soils or
affect overall stability of a slope beyond the area that has slid.
Based on the Site slope topography and vegetation, the thickness of the colluvial layer
that has accumulated on the face of the slope, and our experience with slopes in the Puget
Sound region, we assess the potential for shallow landslides on the slope below the
residence to be moderate to high over the anticipated life of the residence. The potential
for surficial landslides increases following extended periods of heavy precipitation.
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We assess the potential for shallow landslides that could adversely impact the proposed
addition to be low due to the proposed siting of the addition and the thickness of soils that
are susceptible to shallow landslides. The most likely impact of shallow landslides at the
Site is damage to the steep slope below the backyard, or damage to the backyard and a
reduction in useable yard area between the residence and proposed addition and the top of
the steep slope.
Shallow landslides are considered part of the natural erosion process on steep slopes in
the Puget Sound region and contribute to slope retreat and a reduction in setback of
residences at the top of slopes. The ongoing slope retreat at the Site can be conservatively
estimated at a couple inches per year. The actual rate will likely be episodic, with little
observed change over a number of years followed by sudden loss of several feet.
3.2.3 Toppling Failures
Toppling failures involve a mass of soil peeling off along naturally -occurring tension
cracks which form in soils at the crest of steep slopes and bluffs. These tension cracks
may provide conduits for surface water migration and flow, and they also promote
growth of tree roots that can extend many feet downward into the cracks. As the roots
grow and the face of the slope progresses through freeze -thaw cycles, or when the face of
the slope at the toe of the tension crack becomes oversteepened and undermined by
erosion, these cracks often become failure planes, and a slab of soil will spall or topple
off the slope face. Failures of this kind are typically not more than several feet thick and
occur only on very steep to near -vertical sections of slopes.
In our opinion, the possibility of toppling failures on the Site slope is low.
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4 Slope Stability Analysis
Using LiDAR-based topographic data, our field observations and measurements, the data
from our subsurface explorations, and our knowledge of the geologic conditions
underlying the slope, we conducted two-dimensional limit equilibrium stability analyses
using the Slide computer software program (Rocscience, 2018). We assessed slope
stability for the residence and proposed addition under static and seismic loading
conditions.
Based on the subsurface explorations and our experience, we designated the soil/material
units and assigned the engineering parameters shown in Table 2 for our slope stability
analyses. The engineering properties assigned to the glacially consolidated pre -Fraser
nonglacial deposits are within the bounds of the suggested parameters for similar
glacially consolidated granular soils discussed in Chapter 5 of the Washington State
Department of Transportation (WSDOT) Geotechnical Design Manual (GDM; WSDOT,
2019).
Table 2. Summary of Soil Engineering Properties Used in Slope Stability
Analyses
Geologic Unit
Unit Weight
(pcf)
Strength Parameters
Friction
Angle (deg)
Cohesion
(psf)
Colluvium
110
32
50
Pre -Fraser Non -Glacial Deposits (Static)
130
40
200
Pre -Fraser Non -Glacial Deposits (Seismic)
130
40
500
Notes: pcf = pounds per cubic foot; psf = pounds per square foot; and deg = degrees.
To represent structural loads exerted on the soils below the residence shallow
foundations, we modeled a surcharge load equal to 200 pounds per square foot (psf) over
the footprint of the residence. We did not include a surcharge load on the ground surface
over the footprint of the proposed addition because we assumed the addition will be
supported on a deep foundation system that will transfer structural loads to a deeper
bearing stratum. We also excluded the existing deck column loads based upon the
assumption that the existing decks will be demolished or remodeled and incorporated into
the addition that will be supported on deep foundations.
For seismic conditions, we applied a horizontal seismic coefficient of 0.2625g to
represent the horizontal inertial forces in the slope induced by ground shaking during the
MCE. This value is equal to one-half of the Site -adjusted peak ground acceleration shown
in Table 1. We also modelled the pre -Fraser non -glacial deposits with a short-term
cohesion of 500 psf during earthquake shaking. This value of cohesion is within the range
of typical values of cohesion obtained from back calculations of near -vertical exposures
of glacially consolidated granular soils with fines content similar to that of the pre -Fraser
non -glacial deposits at the Site.
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The Slide program performs slope stability computations based on the modeled slope
conditions and calculates a factor of safety against slope failure, which is defined as the
ratio of resisting forces to driving forces. A factor of safety of 1.0 indicates a "just -stable"
condition, and a factor of safety less than 1.0 would indicate unstable conditions.
Minimum factors of safety of 1.5 and 1.1 for static and seismic loading conditions,
respectively, are considered acceptable by industry standards.
The results of our slope stability analyses indicate the following:
• Potential slip surfaces with static factors of safety less than 1.5 extend about 25
feet behind the top of the steep slope.
• Potential slip surfaces with pseudo -static factors of safety less than 1.1 extend
below the entire residence and proposed addition.
The detailed results of the limit equilibrium slope stability analyses are included in
Appendix B.
4.1.1 Displacement Analysis
Since the results of our slope stability analysis indicate seismic factors of safety of less
than 1.1, we completed a displacement analysis to further investigate the potential ground
deformations near the proposed residence addition during the MCE.
In accordance with guidance from Chapter 6 of the WSDOT GDM, we used simplified
procedures available within the USGS SLAMMER program (Jibson et al., 2014) to
estimate sliding displacements along potential slip surfaces during earthquake shaking.
The simplified procedures estimate sliding displacement as a function of the slope
geometry, soil conditions, and the ground motion.
We used the Rathje and Saygili (2009) and the Saygili and Rathje (2008) simplified
empirical models within the SLAMMER program. The input parameters for these models
include yield acceleration, peak ground acceleration, and earthquake magnitude. The
yield acceleration is defined as the acceleration resulting in a slip surface with a factor of
safety of 1.0.
For the displacement analysis, we assumed the foundations for the addition will be
constructed as close as 25 feet away from the top of the steep slope (our recommended
setback based on the results of the static slope stability analysis). We considered all slip
surfaces that extended beyond this setback (i.e. the slip surfaces that could impact the
addition) and determined the yield accelerations for those slip surfaces through iteration
in our seismic stability model. We input the yield accelerations into the simplified
empirical models within SLAMMER to estimate a range of potential sliding
displacements along the slip surfaces. The models estimate sliding displacements up to 1
inch could occur for slip surfaces that extend at least 25 feet from the top of the steep
slope.
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5 Conclusions and Recommendations
Based on our subsurface explorations, up to about six feet of loose colluvium is present
below the footprint of the proposed addition. These soils are prone to compression under
new static loads and are not suitable for foundation support. To mitigate the potential for
foundation settlement, we recommend supporting new structure for the addition using
deep foundations. The deep foundations will transfer structural loads to the high shear
strength pre -Fraser nonglacial deposits that underly the compressible colluvium and
would not adversely affect slope stability.
Our limit equilibrium slope stability analyses indicate the slope below the proposed
addition is sufficiently stable under static conditions; and it is marginally unstable during
a design -level earthquake. The design -level earthquake could trigger permanent ground
deformations of one inch below the proposed addition. In our opinion, this magnitude of
ground deformation can be tolerated by a wood -framed structure without structural
collapse. Provided the addition is setback from the top of the steep slope as recommended
in Section 5.1, we conclude that a robust foundation system that is designed to resist
ground deformation during an earthquake is not necessary.
The following sections present our geotechnical engineering recommendations for the
Project. In our opinion, the Project can be constructed in a stable manner and will not
adversely effect the landslide hazards or stability of the slope, provided the
recommendations contained herein are implemented in design and construction.
5.1 Setback for Foundations
Based on our observations, the results of our slope stability analyses, and our experience
with similar steep slope residential development projects, we recommend that new
foundations for the addition be setback a minimum distance of 25 feet (laterally) from the
top of the steep slope. Portions of the addition may be designed to cantilever over the 25-
foot setback distance and encroach closer to the top of the slope, but all foundations
should be constructed beyond this minimum setback distance.
5.2 Foundations
Deep foundations are recommended to bypass the compressible colluvium and transfer
structural loads to the dense pre -Fraser non -glacial deposits (bearing stratum) that are
relatively incompressible and suitable for foundation support. Based on the anticipated
structural loads, depth to the bearing stratum, and available Site access, we consider 2-
inch diameter steel pipe pile (pin piles) to be appropriate.
5.2.1 Vertical Foundation Support with Pin Piles
Pin piles typically consist of 2- to 6-inch-diameter steel pipe piles driven to a specified
driving criterion using pneumatic or hydraulic hammers.
The 2-inch-diameter pin piles should be driven to an acceptable driving resistance within
the bearing stratum using a suitably sized hammer. For a 2-inch-diameter pin pile, we
consider an acceptable driving resistance to be less than 1 inch of penetration over 60
consecutive seconds of pile driving with a 90-pound pneumatic hammer. For a 2-inch-
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diameter pin pile driven in accordance with our recommendations, a maximum allowable
axial compressive load of 6 kips (unit of force) may be used for design. This maximum
allowable axial compressive capacity includes a factor of safety of 2.0. In our opinion,
load testing of the pin piles is not required, provided Aspect is present during
construction to observe their installation and confirm they terminate at an acceptable
driving resistance.
The pin piles should be used for axial compressive support only. Pin pile size, layout and
connections should be designed by the Project structural engineer.
5.2.2 Pin Pile Depths
For planning purposes, we estimate that the pin piles will extend approximately 10 feet
below the existing ground surface. The pin piles may achieve acceptable driving
resistance at shallower depths, and shorter piles may be acceptable based on the
judgement of the geotechnical engineer during observation of pin pile installation.
5.2.3 Settlement
Total and differential static settlement of the proposed addition, if founded on pin piles
installed in accordance with our recommendations provided above, are anticipated to be
less than 0.5 inch. Any static settlement is anticipated to occur rapidly as the structural
loads are applied during construction.
5.2.4 Foundation Lateral Support
Lateral forces will be resisted by passive and frictional resistance of below grade portions
of foundation elements between and adjacent to the pin piles (i.e., pile caps and/or grade
beams). Assuming the foundation elements are constructed within the existing colluvium
soils, we recommend using an allowable passive equivalent fluid density of 240 pounds
per cubic foot (pcf), and an allowable base friction coefficient of 0.3 for design. These
allowable values include a factor of safety of 1.5. Passive resistance within the top foot
should be neglected unless the ground surface is protected by a concrete slab.
If additional lateral resistance is required, the pin piles may be installed on a slight batter
(10 to 15 degrees from vertical) and the horizontal component of their axial capacity may
be assigned. For example, 2-inch-diameter pin piles installed at a 15-degree batter can be
assigned allowable lateral capacities of 1.5 kips each (i.e., 6 kips*sinl5°). This horizontal
capacity will be available only in the direction of batter.
5.3 Construction Considerations
We have not been provided any plans for the proposed addition, but we would anticipate
Site grading and excavation activities will be minimal and generally limited to foundation
elements (pile caps and grade beams). We expect that excavations will occur within the
loose, granular colluvium and that it can be accomplished with hand tools or small
equipment that can be mobilized on -Site, given the limited access.
PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023) FINAL 11
ASPECT CONSULTING
5.4 Steep Slope Management
Many of the factors that can cause landslides, such as site geology, topography, and deep
groundwater conditions cannot be controlled. Some factors such as vegetation and
stormwater runoff, however, can be controlled, and homeowners are advised to maintain
the Site in a manner that maximizes slope stability.
The most likely impact to the Site from a slope stability perspective would be shallow
landslides caused by saturation of the near -surface, weathered colluvium soils on the
steep slope. These surficial failures are typically limited to the soils within the outer 3 to
5 feet of the slope.
Factors that affect slope stability within the near -surface, weathered soil layer include the
following (Gray and Leiser, 1982):
Root Reinforcement
Roots mechanically reinforce a soil by transfer of shear stresses in the soil to
tensile resistance in the roots.
Soil Moisture Modification
Evapotranspiration and interception in the foliage limit buildup of soil moisture.
Buttressing and Arching
Anchored and embedded stems can act as buttress piles or arch abutments in a
slope, counteracting shear stresses.
Surcharge
Weight of vegetation on a slope exerts both a downslope (destabilizing) stress
and a stress component perpendicular to the slope, which tends to increase
resistance to sliding.
Root Wedging
Alleged tendency of roots to invade cracks, fissures, and channels in a soil or
rock mass and thereby cause local instability by a wedging or prying action.
Windthrowing
Destabilizing influences from an overturning moment exerted on a slope as a
result of strong winds blowing downslope through trees.
Root reinforcement, soil moisture modification (reduction), and buttressing and arching
will increase surficial slope stability at the Site. Surcharge, root wedging, and
windthrowing will have a destabilizing effect on surficial slope stability.
Other sources of surficial slope instability include improperly managed storm and surface
water runoff flowing near or over the top of the slope. Uncontrolled runoff or surface
water should never be allowed to flow across the slope
Care should be taken not to over -irrigate near the slope. If an irrigation system is installed
near the steep slope, we recommend you install a shutoff valve well away from the slope
and shut the valve during the wet season. This will reduce the risk of flooding of the
hillside due to pipe damage. We recommend limiting irrigation to the dry season
(between April and October).
12 DRAFT PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023)
ASPECT CONSULTING
To minimize soil erosion and reduce the risk of shallow landslides, we recommend
establishing dense native vegetative cover that is low and has deeply -penetrating roots.
We recommend consulting with a professional landscaper to determine appropriate
vegetation types and to develop a planting plan for the steep slope. Grading activities on
the slope should be minor (limited to the outer 12 inches of the slope), accomplished with
hand tools, and should only be performed to facilitate replanting and promote vegetative
growth. Grading activities should not result in a steeper inclination of the slope or the
placement of new fill at the top of the slope. Landscaping debris should not be placed on
the steep slope as this inhibits the growth of beneficial vegetation and adds mass to the
surficial soil layers.
If soils on or near the steep slope become exposed through erosion and/or surficial
landslide activity, we recommend immediately covering and aggressively revegetating
the exposed areas. This may require the temporary placement of plastic sheeting replaced
during the spring by a woven jute -mat (erosion control blanket) to provide temporary
ground cover while vegetation takes root.
For specific vegetation recommendations, the Washington State Department of Ecology
(Ecology) has several good publications on the subject including:
• Vegetation Management: A guide for Puget Sound Bluff Property Owners
(Ecology, 1993a).
• Slope Stabilization and Erosion Control Using Vegetation: A Manual of Practice
for Coastal Property Owners (Ecology, 1993b).
This information is also available from Ecology's website, along with a steep -slope
planting guide.
5.5 Plans Review and Construction Monitoring
At the time of this report, we were provided the most recent set of plans with revisions
dated 6/7/2023. Based on our review, we conclude the recommended 25-foot setback of
new foundations from the top of the steep slope, and our geotechnical engineering
recommendations for pin piles have been properly incorporated into these plans.
We recommend that we observe installation of the pin piles to document successful
compliance with our geotechnical engineering recommendations. Aspect is available to
provide geotechnical engineering and monitoring services during construction upon
request.
PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023) FINAL 13
ASPECT CONSULTING
6 References
ASTM International (ASTM), 2018, Annual Book of Standards, Vol. 4.08, West
Conshohocken, Pennsylvania.
American Society of Civil Engineers (ASCE), 2013, Minimum Design Loads for
Buildings and Other Structures, ASCE/SEI Standard 7-10.
American Society of Civil Engineers (ASCE), 2017, Minimum Design Loads for
Buildings and Other Structures, ASCE/SEI Standard 7-16.
Atwater, B.F., Musumi-Rokkaku, S., Satake, K., Tsuji, Y., Ueda, K., and
Yamaguchi,D.K., 2015, The orphan tsunami of 1700—Japanese clues to a parent
earthquake in North America, 2nd ed.: Seattle, University of Washington Press,
U.S. Geological Survey Professional Paper 1707, 135 p.
City of Edmonds (City), 2019, City of Edmonds GIS, 1
https: //maps. edmondswa. gov/Html5 V iewer/?viewer=Edmonds—S SL. HTML.
Cox, 2004, Geologic Map of the Edmonds East and Edmonds West quadrangles, WA,
USGS Pacific Northwest Mapping Project, Scale 1:24000
Gray, D.H. and Leiser, A.T., 1982, Biotechnical Slope Protection and Erosion Control,
Van Nostrand Reinhold: New York, N.Y.
International Code Council (ICC), 2015, International Building Code, January.
Jibson, R.W., E.M. Rathje, M.W. Jibson, and Y.W. Lee, 2014, SLAMMER — Seismic
Landslide Movement Modeled using Earthquake Records (ver.1.1, November
2014): U.S. Geological Survey Techniques and Methods, book 12, Chap. B1,
unpaged.
Rathje, E.M., and G. Saygili, 2009, Probabilistic assessment of earthquake -induced
sliding displacements of natural slopes: Bulletin of the New Zealand Society of
Earthquake Engineering, v. 41, p. 18-27.
Rocscience, 2018, Slide 8.08 Analysis Program. Build date October 16, 2017.
Saygili, G., and E.M. Rathje, 2008, Empirical predictive models for earthquake -induced
sliding displacements of slopes: Journal of Geotechnical and Geoenvironmental
Engineering, V. 134, p. 790-803.
Snohomish County, 2019, Snohomish County Online Property Information,
http://gis.snoco.org/maps/property/viewer.htm, Accessed September 9, 2019
Strobl Design LLC, 2023, Pacquer Residence, Sheets Al through A7, S1.0 through S3.3
(14 sheets), revisions dated 6/7/2023.
Washington State Department of Ecology (Ecology), 1979, Coastal Atlas of Washington;
Washington State Department of Ecology — Slope Stability Maps.
Washington State Department of Ecology (Ecology), 1993a, Vegetation Management: A
Guide for Puget Sound Bluff Property Owners, Publication #93-31, May 1993.
14 DRAFT PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023)
ASPECT CONSULTING
Washington State Department of Ecology (Ecology), 1993b, Slope Stabilization and
Erosion Control Using Vegetation: A Manual of Practice for Coastal Property
Owners, Publication #93-30, May 1993.
Washington State Department of Transportation, 2019, Geotechnical Design Manual,
Document M 46-03.11, Revised July, 2019.
PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023) FINAL 15
ASPECT CONSULTING
7 Limitations
Work for this project was performed for Steve Pacquer (Client), and this report was
prepared consistent with recognized standards of professionals in the same locality and
involving similar conditions, at the time the work was performed. No other warranty,
expressed or implied, is made by Aspect Consulting, LLC (Aspect).
Recommendations presented herein are based on our interpretation of site conditions,
geotechnical engineering calculations, and judgment in accordance with our mutually
agreed -upon scope of work. Our recommendations are unique and specific to the project,
site, and Client. Application of this report for any purpose other than the project should
be done only after consultation with Aspect.
Variations may exist between the soil and groundwater conditions reported and those
actually underlying the site. The nature and extent of such soil variations may change
over time and may not be evident before construction begins. If any soil conditions are
encountered at the site that are different from those described in this report, Aspect
should be notified immediately to review the applicability of our recommendations.
Risks are inherent with any site involving slopes and no recommendations, geologic
analysis, or engineering design can assure slope stability. Our observations, findings, and
opinions are a means to identify and reduce the inherent risks to the Client.
It is the Client's responsibility to see that all parties to this project, including the designer,
contractor, subcontractors, and agents, are made aware of this report in its entirety. At the
time of this report, design plans and construction methods have not been finalized, and
the recommendations presented herein are based on preliminary project information. If
project developments result in changes from the preliminary project information, Aspect
should be contacted to determine if our recommendations contained in this report should
be revised and/or expanded upon.
The scope of work does not include services related to construction safety precautions.
Site safety is typically the responsibility of the contractor, and our recommendations are
not intended to direct the contractor's site safety methods, techniques, sequences, or
procedures. The scope of our work also does not include the assessment of environmental
characteristics, particularly those involving potentially hazardous substances in soil or
groundwater.
All reports prepared by Aspect for the Client apply only to the services described in the
Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the
sole risk of that party, and without liability to Aspect. Aspect's original files/reports shall
govern in the event of any dispute regarding the content of electronic documents
furnished to others.
Please refer to Appendix C titled "Report Limitations and Guidelines for Use" for
additional information governing the use of this report.
We appreciate the opportunity to perform these services. If you have any questions please
call Eric Schellenger, Project Engineer, 206-780-7745.
16 DRAFT PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023)
FIGURES
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PROJECT NO, REVISED BY:
CONSULTING
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Sources: Esri, HERE, Garmin, Intermalp, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the
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Geotechnical Engineering Evaluation
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Edmonds, Washington
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---
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APPENDIX A
Subsurface Exploration Logs
ASPECT CONSULTING
A. Subsurface Exploration Program
Soil Borings
On August 21, 2019, Aspect Consulting, LLC (Aspect) completed four machine -drilled
borings (designated AB-01 through AB-04) at the Site. The machine -drilled borings were
advanced with hollow -stem auger drilling methods using a portable Acker drill rig
operated by Geologic Drill Partners, Inc. under subcontract to Aspect.
In the machine -drilled borings, disturbed soil samples were obtained at 2-foot intervals
using the Standard Penetration Test (SPT) in accordance with ASTM D1586, Standard
Test Method for Standard Penetration Test (SPT) and Split -Barrel Sampling of Soils
(ASTM, 2018). Typically, the Standard Penetration Test involves driving a 2-inch outside
diameter split -barrel sampler a distance of 18 inches into the soil with a 140-pound
hammer free -falling a distance of 30 inches (the drill rig employed on this project used
rope and cathead to raise and lower the hammer). For this project, the split barrel sampler
was driven an additional 6 inches for a total distance of 24 inches. The number of blows
for each 6-inch interval is recorded and the number of blows required to drive the
sampler for the middle two intervals (a total of 12 inches) is known as the Standard
Penetration Resistance ("N-value") or blow count. The N-value provides a measure of
relative density of granular soils or the relative consistency of cohesive soils.
An Aspect engineer or geologist was present throughout the exploration program to
observe the drilling procedures, assist in sampling, and to prepare descriptive logs of the
explorations. Soils were identified in general accordance with ASTM D2488, Standard
Practice for Description and Identification of Soils (Visual -Manual Procedure; ASTM,
2018). The summary exploration logs represent our interpretation of the contents of the
field logs. The stratigraphic contacts shown on the individual summary logs represent the
approximate boundaries between soil types; actual transitions may be more gradual. The
subsurface conditions depicted are only for the specific date and locations reported, and
therefore, are not necessarily representative of other locations and times.
Upon completion, the machine -drilled borings were backfilled with 3/8-inch bentonite
chips in accordance with requirements of the Washington State Department of Ecology.
PROJECT NO. 190276 • SEPTEMBER 18, 2019 (REVISED JUNE 15, 2023) FINAL A-1
00.0
o
Well -graded GRAVEL
ODOR
GW
Well -graded GRAVEL WITH SAND
N
J_
N N
In >
u-
0
O
00000
0
NI00000
Poorly -graded GRAVEL
0
0
00000
GP
Poorly -graded GRAVEL WITH SAND
0
N
6
0 Z
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Lo o
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C
M
GM
SILTY GRAVEL
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o 0"
0
SILTY GRAVEL WITH SAND
aD
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o
aNi
NI
CLAYEY GRAVEL
o
2
GC
CLAYEY GRAVEL WITH SAND
o
cs
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m
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o
Well -graded SAND
o
SW
Well -graded SAND WITH GRAVEL
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a
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o
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.
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Poorly -graded SAND
:_
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Poorly -graded SAND WITH GRAVEL
(D
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- -
m
o Z
N
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SM
SILTY SAND
co
10 (a
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SILTY SAND WITH GRAVEL
o
c
-
SAND
0
LO
�CLAYEY
SC
CLAYEY SAND WITH GRAVEL
SILT
ML
SANDY or GRAVELLY SILT
>
Lo
SILT WITH SAND
m
in
c
co
SILT WITH GRAVEL
o
s
0 w
LEAN CLAY
o
c Zn
CL
SANDY or GRAVELLY LEAN CLAY
Z
LEAN CLAY WITH SAND
On
LEAN CLAY WITH GRAVEL
U)
a
—
ORGANIC SILT
m
a
— —
IL
SANDY or GRAVELLY ORGANIC SILT
m
o
_
— —
ORGANIC SILT WITH SAND
2
�
ORGANIC SILT WITH GRAVEL
O
ELASTIC SILT
o
°'
SANDY or GRAVELLY ELASTIC SILT
Ln
o
MH
ELASTIC SILT WITH SAND
rn
T
ELASTIC SILT WITH GRAVEL
cc 0
(�
5 ,�
FAT CLAY
c oLn
CH
SANDY or GRAVELLY FAT CLAY
m =
FAT CLAY WITH SAND
E
J
FAT CLAY WITH GRAVEL
CJ=
2
�i����i
ORGANIC CLAY
U-
a
i��ii
OH
SANDY or GRAVELLY ORGANIC CLAY
ORGANIC CLAY WITH SAND
ORGANIC CLAY WITH GRAVEL
T
PEAT and other
oU)
PT
mostly organic soils
"WITH SILT" or "WITH CLAY" means 5 to 15%silt and clay, denoted by a "" in the group
name; e.g., SP-SM . "SILTY" or "CLAYEY" means >15%silt and clay. "WITH SAND" or "WITH
GRAVEL" means 15 to 30%sand and gravel.. "SANDY" or "GRAVELLY" means >30%sand and
gravel.. "Well -graded" means approximately equal amounts of fine to coarse grain sizes. "Poorly
graded" means unequal amounts of grain sizes . Group names separated by "/" means soil
contains layers of the two soil types; e.g., SM/ML.
Soils were described and identified in the field in general accordance with the methods described in
ASTM D2488. Where indicated in the log, soils were classified using ASTM D2487 or other
laboratory tests as appropriate. Refer to the report accompanying these exploration logs for details.
1. Estimated or measured percentage by dry weight
2. (SPT) Standard Penetration Test (ASTM D1586)
3. Determined by SPT, DCPT (ASTM STP399) or other field methods. See report text for details.
MC =
Natural Moisture Content GEOTECHNICAL LAB TESTS
PS =
Particle Size Distribution
FC =
Fines Content (% < 0.075 mm)
GH =
Hydrometer Test
AL =
Atterberg Limits
C =
Consolidation Test
Str =
Strength Test
OC =
Organic Content (% Loss by Ignition)
Comp =
Proctor Test
K =
Hydraulic Conductivity Test
SG =
Specific Gravity Test
Organic Chemicals CHEMICAL LAB TESTS
BTEX =
Benzene, Toluene, Ethylbenzene, Xylenes
TPH-Dx =
Diesel and Oil -Range Petroleum Hydrocarbons
TPH-G =
Gasoline -Range Petroleum Hydrocarbons
VOCs =
Volatile Organic Compounds
SVOCs =
Semi -Volatile Organic Compounds
PAHs =
Polycyclic Aromatic Hydrocarbon Compounds
PCBs =
Polychlorinated Biphenyls
Metals
RCRA8 =
As, Ba, Cd, Cr, Pb, Hg, Se, Ag, (d = dissolved, t = total)
MTCA5 =
As, Cd, Cr, Hg, Pb (d = dissolved, t = total)
PP-13 =
Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, TI, Zn (d=dissolved, t=total)
PID =
Photoionization Detector FIELD TESTS
Sheen =
Oil Sheen Test
SPT2 =
Standard Penetration Test
NSPT =
Non -Standard Penetration Test
DCPT =
Dynamic Cone Penetration Test
Descriptive Term Size Range and Sieve Number COMPONENT
Boulders
= Larger than 12 inches DEFINITIONS
Cobbles
= 3 inches to 12 inches
Coarse Gravel = 3 inches to 3/4 inches
Fine Gravel
= 3/4 inches to No. 4 (4.75 mm)
Coarse Sand
= No. 4 (4.75 mm) to No. 10 (2.00 mm)
Medium Sand
= No. 10 (2.00 mm) to No. 40 (0.425 mm)
Fine Sand
= No. 40 (0.425 mm) to No. 200 (0.075 mm)
Silt and Clay
= Smaller than No. 200 (0.075 mm)
% by Weight Modifier % by Weight Modifier ESTIMATED'
<1 =
Subtrace 15 to 25 = Little PERCENTAGE
1 to <5 =
Trace 30 to 45 = Some
5 to 10 =
Few >50 = Mostly
Dry
= Absence of moisture, dusty, dry to the touch MOISTURE
Slightly Moist
= Perceptible moisture CONTENT
Moist
= Damp but no visible water
Very Moist
= Water visible but not free draining
Wet
= Visible free water, usually from below water table
Non -Cohesive or Coarse -Grained Soils RELATIVE DENSITY
Density3
SPT2 Blows/Foot Penetration with 1/2" Diameter Rod
Very Loose
= 0 to 4 >_ 2'
Loose
= 5 to 10 1' to 2'
Medium Dense = 11 to 30 3" to 1'
Dense
= 31 to 50 1" to 3"
Very Dense
= > 50 < 1"
Cohesive or Fine -Grained Soils CONSISTENCY
Consistency3 SPT2 Blows/Foot Manual Test
Very Soft
= 0 to 1 Penetrated >1" easily by thumb. Extrudes between thumb & fingers.
Soft
= 2 to 4 Penetrated 1/4" to 1" easily by thumb. Easily molded.
Medium Stiff
= 5 to 8 Penetrated >1/4" with effort by thumb. Molded with strong pressure.
Stiff
= 9 to 15 Indented —1/4" with effort by thumb.
Very Stiff
= 16 to 30 Indented easily by thumbnail.
Hard
= > 30 Indented with difficulty by thumbnail.
GEOLOGIC CONTACTS
Observed and Distinct Observed and Gradual Inferred
Aspect
CONSULTING
Exploration Log Key
Pac user Residence-190276
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18306 Olympic View rive, Olympic, WA, West of house near proposed
addition
47.83296, 122.35999 (est)
w B
1
Contractor
Equipment
Sampling Method
Ground Surface Elev.
/' 1 _0
(GS) (NAVD88)
Geologic Drill Partners
Acker
Rope & cathead; 140 lb hammer; 30" drop
166' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
4.5" OD x2.25" ID
Jeremy Coleman
Hollow -Stem Auger
8/21/2019
NA
No Water Encountered
Depth
e
Exploration Completion
Sample
Blows/foot water Content (%)*
Blows/6
Tests
Material
Description
Depth
(feet)
(f
(feet)t)
and Notes
Type/ID
4 50
Type
(ft)
''
TOPSOIL; approximately 8 inches thick
1
COLLUVIUM
SILTY SAND (SM); very loose, slightly moist, brown with
some mottling; fine to coarse sand; trace organics and
roots.
2
164
Borehole backfilled
—
—
—
2
2
with bentonite chips
2
1
2
3
163
3
4
162
—
—
—
2
Tree root encountered.
4
2
3
6
5
161
Becomes loose.
5
6
160
—
—
—
14
PRE-FRASER NON -GLACIAL DEPOSITS
6
23
SILTY SAND (SM); dense, slightly moist, gray brown; fine
32
to coarse sand; few fine, subangular to subrounded gravel;
50/3"
1 piece woody debris.
7
159
—
—
22150/5"
7
O
Blows likely overstated due to gravel.
8
158
—
—
—
8
Boring terminated due to practical drilling refusal.
Bottom of exploration at 8 ft. bgs.
9
157
—
—
9
10
156
10
11
155
—
—
11
12
154
13
153
14
152
Legend Plastic Limit
Liquid Limit
m
E T
0No Soil Sample Recovery
Split Barrel 2" X 1.375" (SPT) @ >
No Water Encountered See Exploration Log Key for explanation
of symbols
Exploration
Log
ccc I—
Logged by: HNH
AB-01
Approved by: DHM
Sheet 1 of 1
Pac uer Residence-190276
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18306 Olympic View Drive, Olympic, WA, Top of slope (south)
47.83297, 122.36006 (est)
w B_02
Contractor
Equipment
Sampling Method
Ground Surface Elev.
/' 1
(GS) (NAVD88)
Geologic Drill Partners
Acker
Rope & cathead; 140 lb hammer; 30" drop
163' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
4.5" OD x2.25" ID
Jeremy Coleman
Hollow -Stem Auger
8/21/2019
NA
No Water Encountered
Depth
e
Exploration Completion
Sample
Blows/foot water Content (%)*
Blows/6
Tests
Material
Description
Depth
(feet)
(f
(feet)t)
and Notes
Type/ID
4 50
Type
(ft)
''
TOPSOIL; approximately 8 inches thick
1
COLLUVIUM
SILTY SAND WITH GRAVEL (SM); loose, slightly moist,
light brown; fine to coarse sand; fine to coarse, angular to
rounded gravel.
2
161
Borehole backfilled
—
—
—
2
with bentonite chips
4
4
6
6
3
160
0
—
—
3
4
159
—
—
—
s
Becomes medium dense.
4
10
12
21
5
158
0
N
5
PRE-FRASER NON -GLACIAL DEPOSITS
6
157
—
—
—
SILTY SAND (SM); dense, slightly moist, gray brown with
6
minor iron -oxide staining; fine to coarse sand; trace fine,
subangular to subrounded gravel.
16
16
7
156
—
—
22
7
24
0
�
8
155
—
—
8
15
15
9
154
—
—
16
9
0
10
153
26
10
23
26
27
11
152
N
—
—
11
0
12
151
—
—
—
12
Boring terminated due to practical drilling refusal.
Bottom of exploration at 12 ft. bgs.
13
150
14
149
Legend Plastic Limit
Liquid Limit
m
E T
0No Soil Sample Recovery
Split Barrel 2" X 1.375" (SPT) @ >
No Water Encountered See Exploration Log Key for explanation
of symbols
Exploration
Log
ccc I—
Logged by: HNH
AB-02
Approved by: DHM
Sheet 1 of 1
Pac uer Residence-190276
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18306 Olympic View Drive, Olympic, WA, Top of slope (north)
47.83294, 122.36009 (est)
w B-03
Contractor
Equipment
Sampling Method
Ground Surface Elev.
/' 1
(GS) (NAVD88)
Geologic Drill Partners
Acker
Rope & cathead; 140 lb hammer; 30" drop
163' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
4.5" OD x2.25" ID
Jeremy Coleman
Hollow -Stem Auger
8/21/2019
NA
No Water Encountered
Depth
Elev.
Exploration Completion Sample
Blows/foot
water Content (/ )*
Blows/6
Tests
Material
Description
Depth
(feet)
(feet)
and Notes Type/ID
4050
Type
(ft)
''
TOPSOIL; approximately 8 inches thick
1
COLLUVIUM
SILTY SAND (SM); medium dense, slightly moist, light
brown; fine to coarse sand; trace fine, subangular to
subrounded gravel; trace organics.
2
161
Borehole backfilled
—
—
—
2
with bentonite chips
7
8
6
8
3
160
—
—
3
O
4
159
—
—
—
6
4
10
21
31
5
158
(n
PRE-FRASER NON -GLACIAL DEPOSITS
5
O
SILTY SAND (SM); dense, slightly moist, gray brown with
minor iron -oxide staining; fine to coarse sand; few fine,
subangular to subrounded gravel subtrace organics.
13
15
7
156
—
—
17
7
M
20
V1
♦
8
155
—
—
8
0
9
154
—
—
43
9
27
33
50/4"
10
153
10
0
Gravel in sampler tip, blows likely overstated.
11
152
—
—
35
11
50/5.5"
12
151
—
—
12
Boring terminated due to practical drilling refusal.
Bottom of exploration at 11.96 ft. bgs.
13
150
14
149
Legend Plastic Limit
t--i Liquid Limit
m
E T
❑O No Soil Sample Recovery
Split Barrel 2" X 1.375" (SPT) @ >
No Water Encountered See Exploration Log Key for explanation
of symbols
Exploration
Log
ccc I—
Logged by: HNH
AB-03
Approved by: DHM
Sheet 1 of 1
Pac uer Residence-190276
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18306 Olympic View Drive, Olympic, WA, Southwest of house
47.83291, 122.36000 (est)
w B_04
Contractor
Equipment
Sampling Method
Ground Surface Elev.
/' 1
(GS) (NAVD88)
Geologic Drill Partners
Acker
Rope & cathead; 140 lb hammer; 30" drop
167' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
4.5" OD x2.25" ID
Jeremy Coleman
Hollow -Stem Auger
8/21/2019
NA
No Water Encountered
Depth
e
Exploration Completion
Sample
Blows/foot water Content (%)*
Blows/6
Tests
Material
Description
Depth
(feet)
(f
(feet)t)
and Notes
Type/ID
4 50
Type
(ft)
''
TOPSOIL; approximately 8 inches thick
1
COLLUVIUM
SILTY SAND (SM); medium dense, slightly moist, light
brown; fine to coarse sand; trace fine, subangular to
subrounded gravel; trace organics.
2
165
Borehole backfilled
—
—
—
2
with bentonite chips
5
13
14
14
3
164
—
—
3
0
13
15
4
163
—
—
—
15
4
27
19
PRE-FRASER NON -GLACIAL DEPOSITS
•
23
SILTY SAND (SM); dense, slightly moist, gray brown with
5
162
21
minor iron -oxide staining; fine to coarse sand; trace fine,
5
M
26
subangular to subrounded gravel.
V1
♦
6
161
—
—
6
0
Boring terminated due to practical drilling refusal.
7
160
—
—
Bottom of exploration at 6.5 ft. bgs.
7
8
159
—
—
—
8
9
158
—
—
9
10
157
10
11
156
—
—
11
12
155
13
154
14
153
Legend Plastic Limit
Liquid Limit
m
E T
0No Soil Sample Recovery
Split Barrel 2" X 1.375" (SPT) @ >
No Water Encountered See Exploration Log Key for explanation
of symbols
Exploration
Log
ccc I—
Logged by: HNH
AB-04
Approved by: DHM
Sheet 1 of 1
APPENDIX B
Slope Stability Analyses
N
Existing Residence
Location of Proposed Addition
200.00 Ibs/ft2
Top of Steep Slope
o
AB-01, AB-04
AB-02, AB-03
0
0
Unit Weight Cohesion Phi
Material Name
Color
Strength Type
(Ibs/ft3) (psf) (deg)
Foundation Wall
150 Infinite strength
Colluvium
110 Mohr -Coulomb 50 32
to
Pre -Fraser Non -Glacial (Static)
❑
130 Mohr -Coulomb 200 40
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0
25 50
75 100 125 150 175
i i���.l��.�l���.l��.�l
200 225 250 275 3
Legend
Seamh GrlO
S lope Stability Analysis
Model Setup
A
SearehLimits
Geotechnical Engineering Evaluation
Modeled GrountlwaterLevel
Static Analysis
Pacquer Residence Addition
1:
TTT
BOM. Location and Depth
18306 Olympic View Dr., Edmonds, WA
SCALE:1":30'
� 9 18/ 2019
HNH BV.
APPENDIX:
� spect
Q-1
Y
\\aspect.local\dfs\Projects\PacquerResidence -190276\Data\Analyses\SSA\Pacquer
PROJECT NO.
REVIEWED BY:
SLIDE
8.027
Residence SSA for export.slmd
CONSULTING
190276
ECS
0
h6s.
0 25 50 75 100 125 150 175 200 225 250 275
Legend
11 SeamhGrld Model SetuI' Slope Stability Analysis
A SearehLimits Geotechnical Engineering Evaluation
1u1: Modeled GrountlwaterLevel Static Conditions Pacquer Residence Addition
BOM. LocatiCm and Depth 18306 Olympic View Dr., Edmonds, WA
TTTT 9/18/2019 Bv. APPENDIX:
SCALE: 1":30' Aspect HNH
S:\PacquerResidence-190276\Data\Analyses\SSA\PacquerResidence SSA for PROJECT NO. REVIEWEDBV: Q-2
SLIDEINTERPRET 8.027 IC O N S U LT I N G 190276 ECS Y
Existing Residence
25 R
Top of Steep Slope
o
Results
Showing All Slip Surfaces with Factor of Safety below 1.1
Minimum Factor of Safety within Setback = 1.08
Method: Spencer
Surface Type: Circular
Search Method: Grid Search
Radius Increment: 10
Material Name Color Unit Weight Strength Type Cohesion Phi
51 (Ibs/ft3) (psf) (deg)
Foundation Wall 150 Infinite strength
Colluvium ❑ 110 Mohr -Coulomb 50 32
► 0.2625
Pre -Fraser Non -Glacial (Seismic) 130 Mohr -Coulomb 500 40
.............I....I....I....I....I...., ...�75........l
0 25 50 75 100 125 150 175 200 225 250 275 3
Legend
Seamh GrlO Model Setup Slope Stability Analysis
A SeerehLimb Geotechnical Engineering Evaluation
: Modeled GroundwAer Level Seismic Conditions Pacquer Residence Addition
1u1
BOM._Ooeion antl Depth 18306 Olympic View Dr., Edmonds, WA
9 18 2019 By
APPENDIX:
SCALE:1":30' HNH
\\aspect.local\dfs\Projects\Pacquer Residence -190276\Data\Analyses\SSA\Pacquer spect PROJECT NO. REVIEWEDBV: B-3
�SLIDEINTERPRET 8.027 1 Residence SSA for export.slmd CONSULTING 190276 ECS
APPENDIX C
Report Limitations and Guidelines
for Use
ASPECT CONSULTING
REPORT LIMITATIONS AND GUIDELINES FOR
USE
Geoscience is Not Exact
The geoscience practices (geotechnical engineering, geology, and environmental science)
are far less exact than other engineering and natural science disciplines. It is important to
recognize this limitation in evaluating the content of the report. If you are unclear how
these "Report Limitations and Guidelines for Use" apply to your project or property, you
should contact Aspect Consulting, LLC (Aspect).
This Report and Project -Specific Factors
Aspect's services are designed to meet the specific needs of our clients. Aspect has
performed the services in general accordance with our agreement (the Agreement) with
the Client (defined under the Limitations section of this project's work product). This
report has been prepared for the exclusive use of the Client. This report should not be
applied for any purpose or project except the purpose described in the Agreement.
Aspect considered many unique, project -specific factors when establishing the Scope of
Work for this project and report. You should not rely on this report if it was:
• Not prepared for you;
• Not prepared for the specific purpose identified in the Agreement;
• Not prepared for the specific subject property assessed; or
• Completed before important changes occurred concerning the subject property,
project, or governmental regulatory actions.
If changes are made to the project or subject property after the date of this report, Aspect
should be retained to assess the impact of the changes with respect to the conclusions
contained in the report.
Reliance Conditions for Third Parties
This report was prepared for the exclusive use of the Client. No other party may rely on
the product of our services unless we agree in advance to such reliance in writing. This is
to provide our firm with reasonable protection against liability claims by third parties
with whom there would otherwise be no contractual limitations. Within the limitations of
scope, schedule, and budget, our services have been executed in accordance with our
Agreement with the Client and recognized geoscience practices in the same locality and
involving similar conditions at the time this report was prepared
Property Conditions Change Over Time
This report is based on conditions that existed at the time the study was performed. The
findings and conclusions of this report may be affected by the passage of time, by events
ASPECT CONSULTING
such as a change in property use or occupancy, or by natural events, such as floods,
earthquakes, slope instability, or groundwater fluctuations. If any of the described events
may have occurred following the issuance of the report, you should contact Aspect so
that we may evaluate whether changed conditions affect the continued reliability or
applicability of our conclusions and recommendations.
Geotechnical, Geologic, and Environmental Reports Are
Not Interchangeable
The equipment, techniques, and personnel used to perform a geotechnical or geologic
study differ significantly from those used to perform an environmental study and vice
versa. For that reason, a geotechnical engineering or geologic report does not usually
address any environmental findings, conclusions, or recommendations (e.g., about the
likelihood of encountering underground storage tanks or regulated contaminants).
Similarly, environmental reports are not used to address geotechnical or geologic
concerns regarding the subject property.
We appreciate the opportunity to perform these services. If you have any questions please
contact the Aspect Project Manager for this project.