REVIEWED BLD2023-1063+Geotechnical_Report+8.30.2023_10.58.18_AM+3755509................................................
REVIEWED
BY
CITY OF EDMONDS
BUILDING DEPARTMENT'.
RECEIVED
Sep 19 2023
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
BLD2023-1063
GEOTECHNICAL REPORT
Rodriguez Residence
18418 Olympic View Drive
Edmonds, Washington
Prepared for: Raphael Rodriguez
Project No. 230007 • August 28, 2023 FINAL
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GEOTECHNICAL REPORT
Rodriguez Residence
18418 Olympic View Drive
Edmonds, Washington
Prepared for: Raphael Rodriguez
Project No. 230007 • August 28, 2023 DRAFT
Aspect Consulting, LLC
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Matthew von der Ahe, LEG
Project Geologist
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Erik O. Andersen, PE
Principal Geotechnical Engineer
eandersen@aspectconsulting.com
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ASPECT CONSULTING
Contents
ExecutiveSummary...................................................................................... ES-1
1 Introduction.................................................................................................1
1.1 Project Description.......................................................................................1
1.2 Scope of Work..............................................................................................1
2 Surface Conditions.....................................................................................2
2.1 Site Description............................................................................................2
2.2 Site Vegetation.............................................................................................3
2.3 Site Topography...........................................................................................3
2.4 Evidence of Recent Landslide Activity.........................................................4
2.5 Site Drainage...............................................................................................4
3 Subsurface Conditions............................................................................... 5
3.1 Geologic Setting...........................................................................................5
3.2 Subsurface Investigation..............................................................................5
3.3 Stratigraphy..................................................................................................6
3.3.1 Fill........................................................................................................6
3.3.2 Transitional Beds (Disturbed)................................................................6
3.3.3 Olympia Gravel (Disturbed)...................................................................6
3.4 Groundwater................................................................................................6
4 Geologic Hazards........................................................................................ 8
4.1
Seismic Hazards..........................................................................................8
4.2
Surficial Ground Rupture..............................................................................8
4.3
Liquefaction..................................................................................................9
4.4
Erosion Hazard............................................................................................9
4.5
Landslide Hazards.......................................................................................9
4.5.1 Deep -Seated Rotational Landslides.......................................................9
4.5.2 Translational Slides..............................................................................10
4.5.3 Toppling Failures.................................................................................10
4.5.4 Shallow Flow Landslides......................................................................
10
4.6
Slope Stability Analysis..............................................................................11
5 Conclusions and Recommendations......................................................12
5.1 Slope Stabilization Options........................................................................12
5.1.1 Anchored Mesh with Slope Regrading ................................................. 12
5.1.2 Soldier Pile Wall at Top of the Slope .................................................... 12
5.2 Drainage Considerations............................................................................13
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6 Additional Services...................................................................................14
7 References.................................................................................................15
8 Limitations..................................................................................................16
List of Figures
1 Site Location Map
2 Site Exploration Plan
List of Appendices
A Boring Logs
B Report Limitations and Guidelines for Use
ii FINAL PROJECT NO. 230007 • AUGUST 28, 2023
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Executive Summary
The property at 18418 Olympic View Drive in Edmonds, Washington (Site) lies at the
top of a steep, west -facing bluff above the Puget Sound. Site improvements include a
single-family residence with an attached deck and garage, a gazebo, and other associated
infrastructure. On December 27, 2022, stormwater runoff from upslope resulted in a
debris flow that impacted the Site residence and caused a landslide on the steep slope to
the west of the residence. As a result of the landslide, material was scoured from the bluff
edge, including large boulders and cyclone fence footings, and channels were incised into
the steep bluff. The foundation for the gazebo at the northwestern corner of the Site was
undermined. Unless measures are taken to stabilize the slope, future failures or erosion
will result in further damage to the gazebo and loss of yard.
Aspect Consulting, LLC (Aspect) conducted a geotechnical investigation and preliminary
geotechnical analysis to develop conceptual stabilization alternatives that will reduce the
risk for future landslide damage (Project). To evaluate the feasibility of this Project, we
performed a data review, geologic reconnaissance, subsurface exploration, and
conceptual wall design.
Based on our observations and analysis, we recommend that a soldier pile wall be
constructed across the top of the steep slope at the Site. A soldier pile wall would
stabilize the steep slope and retain the backyard more effectively than the other
stabilization methods we evaluated. The cost of construction of a soldier pile wall would
be roughly $250,000.
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1 Introduction
This report presents the results of a geotechnical engineering investigation and analysis
performed by Aspect Consulting, LLC (Aspect) regarding the slope stabilization (Project)
at 18418 Olympic View Way in Edmonds, Washington (Site; Figure 1), also known as
Snohomish County (County) parcel number 00565600200300. We performed a data
review, slope reconnaissance, subsurface exploration, and conceptual wall design in
accordance with the scope of work detailed in our proposal dated January 6, 2023, and
contract change dated February 24, 2023.
1.1 Project Description
The Site consists of a single-family residence, attached deck, and other associated
infrastructure sitting at the top of a steep, west -facing slope above Puget Sound. The
steep slope is approximately 70 feet tall. At the base of the slope, the BNSF railroad runs
parallel to the Puget Sound shoreline. On December 27, 2022, during a period of heavy
precipitation, stormwater and debris flowed around the residence and caused a landslide
on the steep slope west of the residence.
On January 23, 2023, we performed a Site reconnaissance where we observed debris flow
deposits including sand, gravel, cobbles, concrete blocks from the residence to the east,
and vegetation from upslope deposited in the yard and along the slope below the
residence. Near the top of the slope, we observed bare soil and steep erosion scarps. We
observed damage to a chain -link fence, hedge, and boulder rockery at the northwest
corner of the Site, and minor damage to the gazebo where soil had been eroded from
beneath the foundation. We did not observe any structural damage to the house.
1.2 Scope of Work
Our scope of services included a Site reconnaissance, subsurface explorations (drilled
borings), completion of qualitative geotechnical engineering and slope stability
evaluations, and evaluation of conceptual slope stability measures, and completion of a
geotechnical engineering report.
This report includes:
• Site and Project description
• Distribution and characteristics of subsurface soils and groundwater conditions
• Slope stabilization design recommendations
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2 Surface Conditions
Aspect assessed the surface conditions of the Site through a literature review and by field
observations. We conducted visits to the Site and surrounding area on December 29,
2022, January 23, 2023, February 9, 2023, and April 14, 2023.
To supplement our field observations, we performed a desktop review of County parcel
maps, geologic maps and reports, geomorphic maps, light detection and ranging (LiDAR)
studies and images, current and historical aerial photographs and topographic maps,
nearby subsurface investigations, and nearby well logs. The following sections discuss
the results of our assessment.
2.1 Site Description
The Site is a 0.41-acre residential parcel located along the east side of Puget Sound in
Edmonds, Washington (Figure 1). It is bounded by the BNSF railroad to the west and
single-family residences to the north, east, and south (Figure 2). Access to the Site is via
shared, paved driveway from Olympic View Drive. The BNSF railroad main line runs
along the shoreline at the bottom of the slope. On the seaward side of the railroad
embankment, a rock bulkhead protects the embankment from wave erosion.
The residence is a two-story, 2,858 square foot home with a basement, attached garage,
and a deck that sits on the western side of the Site facing the top of the bluff (Photograph
1).
The landslide occurred along the tall, steep, west -facing waterfront slope. Water and
debris flowed along the north and south sides of the Site and down the steep bluff face,
causing damage to the fence and gazebo foundation and eroding a gully into the bluff top
(Photographs 2 and 3).
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Photograph 1. Site on December 29, 2022, looking north. Note bare soil on slope in
foreground and damaged hedge and fence below gazebo.
2.2 Site Vegetation
The bluff face is vegetated mostly with English ivy, Himalayan blackberries, ferns, other
herbaceous ground cover, and a few immature red alder trees. A few mature conifers
stand on the slope near the north edge of the Site. No mature conifers stand on the slope
below the house.
2.3 Site Topography
The house, landscaping, parking areas, attached garage, and deck are located on a bench
that slopes gently down to the west from approximately elevation 110 feet near the
driveway to elevation 95 feet' along the bluff edge. The bluff to the southwest of the Site
forms a concave bowl -shape. The bluff face to the west of the Site, where the landslide
occurred, is very steep (near vertical in some locations) with areas of exposed soils.
From top to bottom, the bluff face has an average inclination of approximately 45 degrees
(100 percent slope), with locally oversteepened areas near vertical. At the southern edge
of the Site, the top of the slope is near vertical to overhanging. The total height of the
slope is approximately 70 feet.
1 Elevations in feet referenced to the North American Vertical Datum of 1988 (NAVD88).
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2.4 Evidence of Recent Landslide Activity
The recent landslide activity occurred on December 27, 2022, after an extended period of
high -intensity precipitation following a snow event. A concentrated surficial flow of
water and debris resulted in erosion and incision of the bluff below the Site. The erosion
scarp is located approximately 30 feet from the residence. During the landslide, the fence
at the northwestern corner of the property was damaged, several landscaping boulders
were transported down the slope, and soil erosion undermined the concrete foundation of
the gazebo (Photographs 2 and 3).
Photograph 2. Damage from the recent
landslide along the northwestern edge of the
slope below the gazebo. Note the hedge
and chain -link fence have been damaged.
Photo viewing south.
2.5 Site Drainage
Photograph 3. Erosion caused by the
recent landslide. Photo viewing east.
During our Site visit on December 29, 2022, we observed evidence that a significant flow
of stormwater had occurred on the Site and on the adjacent properties. This flow had
stopped as of our visit, and no flow was observed on follow-up visits.
We did not observe standing water or flowing water on the remainder of the Site during
any of our visits. A large catch basin at the southwestern corner of the Site was damaged
by landslide activity. It is our understanding that this catch basin has been repaired as of
April 20, 2023.
We observed a 12-inch-diameter steel drainage pipe that extended down the slope below
the Site to the railroad tracks along the water. This drainage pipe was damaged, though it
is not clear if the damage was a direct result of the landslide activity. This pipe appears to
be connected to the storm drain in the southeast corner of the Site. If so, it would convey
water from the parking around above the house. The pipe may also convey stormwater
from drain lines from around the residence (gutter downspouts, footing drains), but this
has not been confirmed.
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3 Subsurface Conditions
Subsurface conditions at the Site were inferred from our subsurface explorations
advanced at the Site on April 14, 2023, review of applicable geologic literature, our
experience with the local geology, and nearby well logs. The following sections discuss
the results of our assessment.
3.1 Geologic Setting
The Site is located within the Puget Lowland, a broad area of tectonic subsidence flanked
by two mountain ranges: the Cascades to the east and the Olympics to the west. The
sediments within the Puget Lowland are the result of repeated cycles of glacial and
nonglacial deposition and erosion. The most recent cycle, the Vashon Stade of the Fraser
Glaciation (about 13,000 to 16,000 years ago), is responsible for most of the present day
geologic and topographic conditions. During the Vashon Stade, the 3,000-foot-thick
Cordilleran Glacier advanced into the Puget Lowland. As the Cordilleran Glacier
advanced southward, lacustrine and fluvial sediments were deposited in front of the
glacier. Preglacial and proglacial sediments were overridden and consolidated by the
advancing glacier, creating dense and hard soil deposits. At the interface between the
advanced soils and the glacial ice, the Cordilleran Glacier sculpted and smoothed the
surface, and then deposited a consolidated basal till. As the glacier retreated northward
from the Puget Lowland to British Columbia, it left an unconsolidated sediment veneer
over glacially consolidated deposits.
The geologic map (Minard, 1983) indicates that the Site is underlain by Transitional Beds
(Fraser Glaciation to Pre -Fraser Glaciation; map symbol Qtb) and Olympic Gravel (Pre -
Fraser Glaciation; map symbol Qog). The Olympia Gravel unit was deposited in streams
and rivers prior to the advance of the most recent (Fraser) glaciation. The Transitional
Bed deposits overlie the Olympia Gravel at the Site and were deposited in lakes and
streams prior to and during the advance of the Fraser glaciers. Both the units were
overridden and consolidated by the weight of the 3,000-foot-thick Fraser ice sheet;
therefore, the material is generally hard, dense, and strong.
The Olympia Gravel unit consists of stratified sand and gravel. Weak cementation of the
gravel can result in vertical exposures of this unit. The Transitional Bed deposits consist
of gray clay, silt and fine sand with some layers of gravel and peaty sand. Jointing and
high water content can lead to slope instability in this unit (Minard, 1983).
At the Site, both the Olympia Gravel and the Transitional Bed deposits appeared to have
been disturbed after they were consolidated by the overriding ice sheet. Based on the
proximity of active strands of the Southern Whidbey Island Fault (SWIF), we infer that
the disturbance was caused by seismicity on the nearby fault.
3.2 Subsurface Investigation
Aspect conducted a subsurface investigation consisting of two machine -drilled borings,
AB-01 and AB-02, completed to depths of 31.5 feet below ground surface (bgs). The
borings were advanced in the lawn near the edge of the bluff at the north and south edges
of the parcel, respectively. The locations of the explorations are shown on Figure 2.
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A summary of our field explorations, including geologic soil units and groundwater
observations, are presented in the following sections. Detailed descriptions of the
subsurface conditions encountered in our explorations, as well as the depths where
characteristics of the soils changed, can be found on the boring logs in Appendix A.
3.3 Stratigraphy
The results of our subsurface investigation indicate that the Site is underlain by fill over
Disturbed Transitional Bed deposits and Disturbed Olympia Gravel. These units are
described in stratigraphic order from top to bottom below.
3.3.1 Fill
Fill refers to human -placed material. Fill was encountered at the ground surface
extending to about 3.5 feet bgs in AB-0I and 5.5 feet bgs in AB-02. The fill material
consisted of very loose to medium dense, moist, brown, silty sand with angular gravel
and fragments of organic materials. It is classified as a silty sand (SM) in the United Soil
Classification System (USCS) (ASTM, 2018).
3.3.2 Transitional Beds (Disturbed)
Transitional Bed deposits were encountered underlying the fill in AB-01 and AB-02.
Transitional Bed deposits were distinguished from the overlying unit based on color,
density, consistency, and quantity of organic matter. The deposits generally consisted of
gray -brown silty sand with gravel and trace dark organics.
The Standard Penetration Test (SPT)2 blow counts (N-values) for the Pre -Fraser to Fraser
Transitional Bed deposits ranged from 2 to 22 blows per foot (bpf), indicating that it is
very loose to medium dense. The strength of the Transitional Beds encountered was less
than would be expected if the material had not been disturbed after it was consolidated by
the overriding ice sheet. We infer the disturbance was seismic, based on the proximity of
the Site to an active strand of the SWIF.
The Transition Beds unit possesses low compressibility and moderately high strength
characteristics.
3.3.3 Olympia Gravel (Disturbed)
The Olympia Gravel unit was encountered underlying the Transitional Bed deposits in
AB-01 and AB-02 at about 18 and 15 feet bgs, respectively. Compared to the overlying
Transitional Beds, the Olympia Gravel deposits were generally more dense, sandier and
stratified or laminated.
The N-values for the Olympia Gravel ranged from 15 to 46 bpf, which translates to
medium dense to dense. These N-values were also less than would be expected with a
glacially consolidated, sandy, gravelly geologic unit, implying the unit was disturbed
after deposition and consolidation.
3.4 Groundwater
Groundwater was not encountered in the explorations. The groundwater levels and
presence of shallow perched groundwater at the Site will fluctuate seasonally with
2 SPT blow count refers to standard penetration test (SPT) N-values, in accordance with ASTM D 15 86
(ASTM, 2018).
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precipitation as well as with changes in Site and near -Site drainage and usage (such as
irrigation). Perched groundwater can occur when surface water percolates into the shallow
subsurface and collects on relatively impermeable underlying materials. At this Site, the
topsoil and fill are relatively permeable, while the Transitional Beds are less permeable;
water may perch and accumulate at the contact between them (about 4 to 6 feet below
ground surface) following periods of prolonged wet weather.
PROJECT NO. 230007 • AUGUST 28, 2023 FINAL
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4 Geologic Hazards
The following sections describe the geologic hazards at and near the Site and associated
Project design considerations for seismic design, erosion hazards, and slope stability.
4.1 Seismic Hazards
The Site is located within the Puget Lowland physiographic province, an area of active
seismicity that is subject to earthquakes on shallow crustal faults and deeper subduction
zone earthquakes.
The Site lies with a few hundred feet of a strand of the Southern Whidbey Island Fault
(SWIF) Zone. The SWIF Zone consists of shallow folds and faults that are considered
active (i.e., there is evidence for movement within the Holocene [most recent 15,000
years]) and is believed to be capable of producing earthquakes of magnitude 7.1. The
recurrence interval of earthquakes on this fault zone is believed to be on the order of
3,000 years or more. The most recent large earthquake on the SWIF occurred about 3,200
to 2,800 years ago. There are also several other shallow crustal faults in the region
capable of producing earthquakes and strong ground shaking (Sherrod et al, 2008).
The Site lies about 16 miles north of the Seattle Fault Zone (SFZ), which consists of
shallow crustal tectonic structures that are also considered active. SFZ faults are believed
to be capable of producing earthquakes of magnitude 7.3 or greater. The recurrence
interval of earthquakes on this fault zone is believed to be on the order of 1,000 years or
more. The most recent large earthquake on the Seattle fault occurred about 1,100 years
ago (Pratt et al., 2015).
The Site area also lies within the zone of strong ground shaking from earthquakes
associated with the Cascadia Subduction Zone (CSZ). 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. A recent study estimates the most recent subduction zone earthquake occurred
around 1700 (Atwater et al., 2015).
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.
The Site's seismic hazards will be considered in the design for the stabilization structures.
4.2 Surficial Ground Rupture
The strand of the SWIF mapped a few hundred feet south of the Site is capable of
producing surficial ground ruptures (Sherrod et al., 2008). Aspect reviewed the latest
publicly available LiDAR data for the Site and surrounding area (DNR, 2018) and
confirmed the likely location of the fault strand. Due to the suspected long recurrence
interval of earthquakes on the SWIF, the potential for surficial ground rupture at the Site
is considered low during the expected life of the structure and does not need to be
considered for design.
8 FINAL PROJECT NO. 230007 • AUGUST 28, 2023
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4.3 Liquefaction
Liquefaction occurs when loose, saturated, and relatively cohesionless soil deposits
temporarily lose strength from seismic shaking. The primary factors controlling the onset
of liquefaction include intensity and duration of strong ground motion, characteristics of
subsurface soil, in -situ stress conditions, and the depth to groundwater.
The liquefaction susceptibility map indicates the Site has a very low susceptibility to
liquefaction (Palmer et al., 2004). Due to the lack of a significant shallow groundwater
table and grain size distribution of the soils underlying the Site, soil liquefaction is not a
design consideration at this Site.
4.4 Erosion Hazard
The City of Edmonds' (City) Critical Areas map shows the steep slope at the Site as
having a severe erosion hazard (City, 2023).
We concur with the City's assessment. Bare soils at the Site are at risk for erosion due to
their fines content (i.e., silt and clay) and the steepness of the slope, whether the exposure
of the soil is due to slope failure, such as exists at the Site due to the December 2022
landslide, or due to construction or other causes.
The erosion hazard at the Site will be reduced significantly by implementing slope
stabilization measures. During construction, the erosion hazard should be addressed
through standard temporary erosion and sedimentation controls (TESC) and best erosion
management practices (BMPs).
4.5 Landslide Hazards
The Washington State Department of Ecology (Ecology) classifies the steep slope at the
Site as "Unstable" with regard to landslides due to the geology, groundwater, slope, or
erosion factors (Ecology, 1979). A USGS landslide survey shows that the Site is located
within a known unstable slope area (Baum et al., 2000). The City of Edmonds' Critical
Areas map classifies the steep slope at the Site as having a high landslide hazard (City,
2023). After our assessment of the Site, we concur with the USGS, state, and City
classifications. The Site, like similarly located sites around the Puget Sound, will
continue to experience landslides. Construction of slope stability measures can
substantially decrease the severity and frequency of landslides.
Four types of landslides are possible on the Site and on similar sites and slopes along the
shoreline in the Puget Sound area (Varnes, 1978): deep-seated rotational landslides,
translational landslides, topples, and shallow flows (such as occurred in December 2022).
4.5.1 Deep -Seated Rotational Landslides
Deep-seated rotational landslides consist of relatively deep (feet to tens of feet) failures
that typically involve slipping along a curved shear plane. Rotational landslides may
transport masses of semi -intact soil downslope, resulting in steep headscarps along the
upper portion of the failure plane and level or back -rotated benches in the middle and
bottom of the slope.
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At the Site, we did not observe any topographic evidence of recent or ancient rotational
landslide activity, such as bowl -shaped topography or hummocky topography, and we
consider it very unlikely such a slide will occur in the future.
4.5.2 Translational Slides
Translational landslides consist of the landslide mass moving down the slope along a
roughly planar surface with little rotation or backward tilting. Translational landslides can
transport large, more -or -less intact masses of soil downslope, resulting in steep
headscarps at the upper portion of the failure and flat "islands" or blocks of material
deposited on the bottom of the failure, often with intact vegetation and upright trees.
We did not observe evidence of recent or ancient translational slides at the Site and we
consider it very unlikely such a slide will occur in the future.
4.5.3 Toppling Failures
Toppling failures involve a mass of soil peeling off along 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 can 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 toe of the layer 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 a
few feet thick and occur only on very steep to near -vertical slope sections.
The possibility of toppling failures will eventually exist along the near -vertical scarps at
the Site if stabilization measures are not implemented. Topples pose a risk where erosion
and past landslides have caused oversteepening of slopes, such as at the southwest corner
of the yard. We did not observe evidence of any recent or incipient topple failures at the
Site. The recommended slope stabilization, where implemented, will reduce the
likelihood of toppling failures occurring at the Site.
4.5.4 Shallow Flow Landslides
The landslide that occurred at the Site in December 2022 was an example of a shallow
flow landslide.
Shallow flow landslides consist of failures that involve sliding of loose fill, colluvium,
and overlying vegetation that typically mantle steep slopes. Shallow flows are typically
triggered by a significant increase in the moisture content within the upper few feet of
soil on a slope and commonly result from periods of extended or heavy precipitation,
groundwater seepage, or concentrated surface water discharge onto a slope. Such failures
can be sudden; however, shallow flows can also occur slowly over time in a process
called "creep." Surface creep is typically evidenced by "pistol -butt" curvatures in the
lower trunks of trees on the slope. Shallow flows occur within the upper few feet of a
slope and typically do not extensively affect the deep-seated or overall stability of a
slope.
The Site and nearby areas contain steep slopes that have experienced shallow flows in the
past and are susceptible to shallow flow failures in the future. The likelihood of future
shallow flow landslide activity is dependent upon factors affecting shallow groundwater
10 FINAL PROJECT NO. 230007 • AUGUST 28, 2023
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such as precipitation, drainage, upslope development, root reinforcement from vegetation
on the slope, and seismic forces. The recommended slope stabilization will reduce the
likelihood of shallow flow landslides occurring at the Site.
4.6 Slope Stability Analysis
We performed numerical slope stability analyses for the Site using the Slide2 computer
software program (Rocscience, 2022) to model the stability of the slope in its current
condition and after the installation of slope stabilization measures. We used soil unit
engineering properties informed by our explorations and estimates of surcharge loading
from the house to evaluate the slope under seismic and static conditions.
The slope stability analysis shows that construction of stabilization measures at the top of
the slope will increase the stability of the slope. The results of the stability analysis to
support the design of the proposed stability measures are reported in the Basis of Design
report that accompanies this report.
PROJECT NO. 230007 • AUGUST 28, 2023 FINAL 11
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5 Conclusions and Recommendations
This section presents our conclusions and recommendations for design and construction
of the Project elements. These conclusions and recommendations are based on our
observations of the Site, the subsurface conditions encountered, and the results of our
preliminary geotechnical engineering analyses.
5.1 Slope Stabilization Options
Our preliminary observations and geotechnical analyses reviewed several stabilization
alternatives to reduce the risk of future landslide movement. The two options that best fit
the Site conditions and future use of the Site are:
• Installation of anchored mesh on the face of the steep slope
Construction of a soldier pile wall along the top of the slope, in the approximate
location of the hedge.
The stabilization alternatives are described further in the following subsections. After
discussions with the client and specialty contractors about stabilization effectiveness and
estimated design and construction costs, we recommend installation of a soldier pile wall
along the top of the slope at the site of the recent landslide.
5.1.1 Anchored Mesh with Slope Regrading
In this method, soil nails (I-inch-diameteror larger threaded steel bar) are drilled or
driven into the slope with a portable drilling wagon suspended over the face of the bluff.
The exposed heads of the nails at the slope surface are anchored to the slope with a steel
plate, and adjacent nails are interconnected by heavy-duty wire mesh.
This option would stabilize the exposed headscarp and reduce erosion there. It would
significantly slow recession of the headscarp toward the house. However, it would not
effectively allow retention of soft and loose fill material on the top of the slope and would
reduce the useable area to the west of the house and deck. Because the client has
expressed interest in retaining as much of the backyard area as possible, this method is
not recommended.
5.1.2 Soldier Pile Wall at Top of the Slope
A soldier pile stabilization wall constructed at the top of the slope, between the residence
and the edge of the slope landward of the existing hedge, will help reduce the likelihood
and severity of slope instability and therefore reduce risk to the house and gazebo.
This type of wall can be installed and engineered to retain and increase the stability of the
Site uplands (those areas east of the landslide headscarp) and to significantly slow future
slope retreat and landward migration of the headscarp.
Soldier pile walls typically consist of uniformly spaced drilled shafts with wide -flange
steel beams inserted into each shaft. The annular space of each shaft is filled with
concrete. Lagging is installed between each soldier pile beam to support the soil behind
the wall. Soldier piles are typically installed with horizontal spacing of 6 to 8 feet.
12 FINAL PROJECT NO. 230007 • AUGUST 28, 2023
ASPECT CONSULTING
Based on our experience with other, similar construction and on our conversation with an
experienced contractor who had seen the Site, a very rough estimate of the cost for
construction of this option (not including design and not including other preparatory and
restoration Site earthwork and landscaping costs) is $250,000.
Aspect has completed the engineering design for the wall and prepared the plan set.
When construction is underway, Aspect can provide special inspections, including
monitoring shaft drilling, pile installation, grouting of the shaft, and lagging installation.
Verification and acceptance of the completed soldier pile wall would be the responsibility
of Aspect.
5.2 Drainage Considerations
The most likely impact from slope instability to the Site is shallow flow landslides
triggered by saturation of the near -surface soils. Saturation can be caused by improperly
managed storm and surface water runoff flowing near or over the top of the slope.
Downspouts and roof drains should be connected to outfalls near the base of the slope.
Drains should include cleanouts to allow for periodic maintenance and inspection.
Uncontrolled runoff of surface water should never be allowed to flow across the Site
slopes. We understand the stormwater and drainage infrastructure at the Site has recently
been upgraded.
We recommend maintaining dense vegetative groundcover or other permanent erosion
control on the Site slope. If soils on or near the slope become exposed through erosion
and/or shallow failures, we recommend immediately covering and aggressively
revegetating the exposed area. This may require the placement of plastic sheeting
replaced by a woven jute mat to provide temporary ground cover while vegetation takes
root.
For specific vegetation recommendations, Ecology has several good publications on the
subject including:
Vegetation Management: A Guide for Puget Sound Bluff Property Owners,
Ecology Publication 93-31, at
https:Happs.ecology.wa.gov/publications/documents/933 l.pdf
• Slope Stabilization and Erosion Control Using Vegetation: A Manual of Practice
for Coastal Property Owners, Ecology Publication 93-30, at
https:Happs.ecology.wa.gov/publications/documents/9330.pdf.
PROJECT NO. 230007 • AUGUST 28, 2023 FINAL 13
ASPECT CONSULTING
6 Additional Services
Stabilization design and construction methods have been finalized. The numeric basis for
the design for the recommended stabilization measures is presented in the Basis of
Design report which accompanies this report.
We are prepared to assist with permitting, selection of a construction contractor, and
other services, as described in our proposal to the client dated March 22, 2023. Once
construction starts, we will oversee the critical phases of construction, as specified in the
plans and specifications, and as required by City of Edmonds permit documents.
14 FINAL PROJECT NO. 230007 • AUGUST 28, 2023
ASPECT CONSULTING
7 References
ASTM International (ASTM), 2018, Annual Book of ASTM Standards, West
Conshohocken, Pennsylvania.
Atwater, B.F., S. Musumi-Rokkaku, D. Satake, Y. Tsuji, K. Ueda, and D.K. Yamaguci
(Atwater et al.), 2015, The orphan tsunami of 1700Japanese clues to a parent
earthquake in North America, U.S. Geological Survey, Professional Paper 1707.
Baum, R.L., Harp, E.L., and Hultman, W.A. (Baum et al.), 2000, Map showing recent
and historic landslide activity on coastal bluffs of Puget Sound between Shilshole
Bay and Everett, Washington, USGS, Miscellaneous Field Studies Map 2346.
City of Edmonds (City) GIS Critical Areas Map, 2023, https://maps.edmondswa.gov/,
accessed March, 2023.
Minard, J.P., 1983, Geologic Map of the Edmonds East and Part of the Edmonds West
Quadrangles, Washington, USGS, Miscellaneous Field Studies Map MF-1541.
Palmer, S.P., Magsino, S.L., Bilderback, E.L., Poelstra, J.L., Folger, D.S., and
Niggemann, R.A., 2004, Liquefaction Susceptibility and Site Class Maps of
Washington State, By County, Washington Division of Geology and Earth
Resources, Open File Report 2004-20.
Pratt, T.L., K.G. Troost, J.K. Odum, and W.J. Stephenson (Pratt et al.), 2015, Kinematics
of shallow backthrusts in the Seattle fault zone, Washington State, Geosphere, v.
11, no. 6, p. 1-27, doi:10.1130/GES01179.1.
Rocscience, 2022, Slide 8.019 and 8.020 Analysis Program, accessed March 2023.
Sherrod, Brian L.; Blakely, Richard J.; Weaver, Craig S.; Kelsey, Harvey M.; Barnett,
Elizabeth; Liberty, Lee; Meagher, Karen L.; Pape, Kristin (Sherrod et al.), 2008,
Finding concealed active faults --Extending the southern Whidbey Island fault
across the Puget Lowland, Washington: Journal of Geophysical Research, v. 11.
Varnes, D.J., 1978, Slope movement types and processes, in Schuster, R.L., and Krizek,
R.J., eds., Landslides —Analysis and control: National Research Council,
Washington, D.C., Transportation Research Board, Special Report 176, p. 11-33.
Washington State Department of Ecology (Ecology), 1979, Coastal Zone Atlas of
Washington, Shoreline and Coastal Zone Management Program, Volume 10,
https:Hfortress.wa.gov/ecy/coastalatlas/tools/Map.aspx.
Washington State Department of Natural Resources (DNR), 2018, Washington LiDAR
Portal, Division of Geology and Earth Resources, https:Hlidarportal.dnr.wa.gov/,
accessed March 2023.
PROJECT NO. 230007 • AUGUST 28, 2023 FINAL 15
ASPECT CONSULTING
8 Limitations
Work for this project was performed for Raphael Rodriguez (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 B 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 Matthew von der Ahe, project manager, at 206-838-6583.
16 FINAL PROJECT NO. 230007 • AUGUST 28, 2023
FIGURES
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REVISED BY.
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Sources: Esri, HERE, Garmin, Intermap, 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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Site and Exploration Map
Geotechnical Report
Rodriguez Residence
Edmonds, Washington
eY. FIGURE NO.
PROJECCTTNNO.
%Aspect AUGMH/SCC
O. REVISED BY:
(CONSULTING 230007 MAV/SCC
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APPENDIX A
Exploration Logs
ASPECT CONSULTING
A. Subsurface Exploration Methodology
On February 9, 2023, Aspect observed two machine -drilled borings, AB-01 and AB-02,
advanced using hollow -stem auger drilling techniques. The borings were advanced by
CN Drilling, Inc., an experienced and licensed local driller, under subcontract to Aspect.
Drilling was completed with a portable Acker drill rig mounted with a rope and cathead
safety hammer. The locations of explorations are shown on Figure 2 and were collocated
in the field using a global positioning system (GPS).
The hollow -stem auger method consisted of advancing a continuous string of 5-foot-long
open -flight augers and a conical hollow -auger head with either a 2.25-inch inner diameter
and about a 6-inch outer diameter. A center plug is seated inside of the conical hollow -
auger head to ensure maximum soil removal. The augers return soil cuttings to the
surface, leaving the hollow stem free from soil.
Disturbed soil samples were obtained every 5 feet to the maximum depths explored in
both AB-01 and AB-02. The disturbed soil samples were collected using the Standard
Penetration Test (SPT) in general accordance with ASTM Method D 1586 (ASTM, 2018).
The SPT method involves driving a 2-inch-outside-diameter split -barrel sampler with a
140-pound hammer free -falling from a distance of 30 inches. The number of blows for
each 6-inch interval is recorded, and the number of blows required to drive the sampler
the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count.
The resistance, or N-value, provides a measure of the relative density of granular soils or
the relative consistency of cohesive soils. If a total of 50 blows are recorded for a single
6-inch interval, the test is terminated, and the blow count is recorded as 50 blows for the
total inches of penetration.
An Aspect geologist was present throughout the field exploration program to observe the
drilling procedure, assist in sampling, and to prepare descriptive logs of the exploration.
Samples were placed in labeled plastic jars and taken to a laboratory for further
classification. Soils were classified in general accordance with ASTM D2488 (ASTM,
2018). Detailed descriptions of the subsurface conditions encountered in our explorations,
as well as the depths where characteristics of the soils changed, are indicated on the logs
presented in this appendix.
The summary exploration log represents 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. A key to the
symbols and terms used on the logs is provided in the Exploration Log Key.
Upon completion, borings AB-01 and AB-02 were completed with bentonite chips to
within approximately 2 to 3 feet of the ground surface and topped with native material to
the ground surface elevation. Soil cuttings were spread along the vegetated portion of the
undisturbed slope.
PROJECT NO. 230007 • AUGUST 28, 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
00000
o0000
o
Lo o
00,0
C
M
GM
SILTY GRAVEL
-oo
W cc
u
o 0"
0
SILTY GRAVEL WITH SAND
aD
'm
o
aNi
NI
CLAYEY GRAVEL
o
2
GC
CLAYEY GRAVEL WITH SAND
o
cs
LID
c
m
�
o
Well -graded SAND
o
SW
Well -graded SAND WITH GRAVEL
g
U_
a
_
o
(D
iZ
.
-
U)
wl
-=. --
Poorly -graded SAND
:_
SP
Poorly -graded SAND WITH GRAVEL
(D
o
- -
m
o Z
N
o (n
SM
SILTY SAND
co
10 (a
cna
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
Rodriguez Residence - 230007
Geotechnical Exploration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18418 Olympic View Dr, Edmonds, WA, Adjacent to gazebo
47.8316,-122.3616 (est)
w B_0 1
Contractor
Equipment
Sampling Method
Ground Surface Elev
/' 1
(NAVD88)
CN Drilling, Inc.
Acker Kodiak
Rope & cathead; 140 lb hammer; 30" drop
101' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
6" OD X 2.25" ID Hollow
Mac Desranleau
Stem Auger
4/14/2023
NA
No Water Encountered
Depth
Elev.
Exploration Notes and
Completion Details
Sample
Type/ID
Blows/foot •
water Content (%)�
Blows/6
Tests
Material
Type
Description
Depth
(feet)
(feet)
0 10 0 4
(tt)
TOPSOIL
3
SANDY SILT (ML); Loose, moist, brown; grass.
1
100
—
—
4
1
FILL
`�
•
2
SILTY SAND WITH GRAVEL (SM); loose, moist, brown;
2
99
n
—
—
fine to coarse sand; fine, subrounded to subangular gravel.
2
3
98
—
—
3
TRANSITIONAL BEDS
4
97
SILTY SAND (SM); very loose, moist, gray brown; fine to
4
coarse sand; fine, subrounded to subangular gravel; trace
5
96
dark organics; disturbed fabric.
5
6
95
Backfilled with
0
N
—
—
1
6
bentonite chips.
7
94
—
—
7
8
93
—
—
—
8
SILTY SAND WITH GRAVEL (SM); very loose, moist,
9
92
—
—
gray brown to light brown; fine to coarse sand; fine to
9
coarse, subrounded to subangular gravel; few cobbles;
disturbed fabric; slight oxidation.
10
91
Drill chatter at 10 feet.
1
10
M
2
11
90
—
—
2
11
Becomes more gravelly.
12
89
—
—
—
12
13
88
—
—
13
Becomes medium dense.
14
87
14
15
86
2
15
5
16
85
0
—
13
16
17
84
Drill chatter at 17 feet.
—
—
17
18
83
—
—
—
18
OLYMPIA GRAVEL
19
82
—
—
-
SAND WITH SILT (SP-SM); medium dense, moist, gray
19
brown; fine to coarse sand; fine to trace coarse,
subrounded to subangular gravel; 0.5- to 2-inch-thick
20
81
Driller added water to
interbeds of fine silty sand and medium to coarse sand.
20
facilitate drilling.
4
5
21
80
(n
—
10
21
O
-
22
79
—
—
—
22
23
78
—
—
-
23
24
77
—
24
Legend Plastic Limit
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
Logged by: MRH
ccc I—
AB-01
Approved by: MvA
Sheet 1 of 2
Rodriguez Residence - 230007
Geotechnical Exploration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18418 Olympic View Dr, Edmonds, WA, Adjacent to gazebo
47.8316,-122.3616 (est)
w B_0 1
Contractor
Equipment
Sampling Method
Ground Surface Elev
/' 1
(NAVD88)
CN Drilling, Inc.
Acker Kodiak
Rope & cathead; 140 lb hammer; 30" drop
101' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
6" OD X 2.25" ID Hollow
Mac Desranleau
Stem Auger
4/14/2023
NA
No Water Encountered
Depth
(feet)
Elev.
(feet)
Exploration Notes and
Completion Details
Sample
Type/ID
Blows/foot •
water Content/)�
Blows/6
Tests
Material
Type
Description
Depth
(ft)
050
5
OLYMPIA GRAVEL
10
SAND WITH SILT (SP-SM); medium dense, moist, gray
26
75
0
—
12
_ _
brown; fine to coarse sand; fine to trace coarse,
26
subrounded to subangular gravel; 0.5- to 2-inch-thick
interbeds of fine silty sand and medium to coarse sand.
27
74
—
—
—
(continued)
27
28
73
—
—
-
28
SAND (SP); dense, moist, gray; fine to coarse sand;
29
72
—
—
—
green, red, dark lithics.
29
30
71
11
30
13
31
70
—
—
18
31
Bottom of exploration at 31.5 ft. bgs.
32
69
—
—
32
33
68
—
—
—
33
34
67
—
—
34
35
66
35
36
65
—
—
36
37
64
—
—
—
37
38
63
—
—
38
39
62
39
40
61
40
41
60
—
—
—
41
42
59
—
—
42
43
58
—
—
—
43
44
57
—
—
44
45
56
45
46
55
—
—
46
47
54
—
—
—
47
48
53
—
—
48
49
52
49
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
Logged by: MRH
ccc I—
AB-01
Approved by: MvA
Sheet 2 of 2
Rodriguez Residence - 230007
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18418 Olympic View Dr, Edmonds, WA, SW corner of lawn, near
catchbasin
47.8315,-122.3617 (est)
w �_02
Contractor
Equipment
Sampling Method
Ground Surface Elev VD
/' 1
(NA
CN Drilling, Inc.
Acker Kodiak
Rope & cathead; 140 lb hammer; 30" drop
100' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
6" OD X 2.25" ID Hollow
Mac Desranleau
Stem Auger
4/14/2023
NA
No Water Encountered
Depth
Elev.
Exploration Notes and
Completion Details
Sample
Type/ID
Blows/foot •
water Content (0
Blows/6
Tests
Material
Type
Description
Depth
(feet)
(feet)
0 10 0 4
(ft)
TOPSOIL
1
SANDY SILT WITH GRAVEL (ML); very loose, moist,
1
99
—
—
1
dark brown; low plasticity; fine to coarse sand; fine gravel;
1
•
3
rass; rootlets.
FILL
2
98
—
—
—
2
SAND (SP); very loose, moist, gray brown; fine to medium
sand; slight oxidation.
3
97
—
—
3
4
96
4
5
95
4
5
7
8
TRANSITIONAL BEDS
6
94
with
bentonite chips. bentoite
—
SILTY SAND WITH GRAVEL (SM); medium dense,
6
moist, gray brown; fine to coarse sand; fine to coarse,
7
93
—
—
rounded to subangular gravel.
7
$
92
Drill chatter from 7 to
—
—
—
$
9 feet.
9
10
90
8
10
12
SILTY SAND (SM); medium dense, moist, gray brown;
11
89
—
—
fine to coarse sand; few fine to coarse, rounded to
11
subrounded gravel; tan, silt rip -up clasts up to
12
88
—
—
—
1-inch-diameter.
12
13
87
—
—
13
14
86
—
14
15
85
11
OLYMPIA GRAVEL
15
16
SAND (SP); dense, moist, gray brown; fine to coarse
16
84
—
-•
20
sand; few fine to trace coarse, subrounded gravel;
16
interbedded sand and silt; trace oxidation.
17
83
—
—
17
18
82
—
—
—
18
19
81
—
—
19
20
$Q
Driller added water to
facilitate drilling.
12
20
18
21
79
(n
—
—
22
21
22
78
—
—
—
22
23
77
24
76
—
24
Legend Plastic Limit
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
Logged by: MRH
ccc I—
AB-02
Approved by: MvA
Sheet 1 of 2
Rodriguez Residence - 230007
Geotechnical Ex loration Log
%0��RFCt
Project Address & Site Specific Location
Coordinates (Lat,Lon WGS84)
Exploration Number
I N G
18418 Olympic View Dr, Edmonds, WA, SW corner of lawn, near
catchbasin
47.8315,-122.3617 (est)
w �_02
Contractor
Equipment
Sampling Method
Ground Surface Elev VD
/' 1
(NA
CN Drilling, Inc.
Acker Kodiak
Rope & cathead; 140 lb hammer; 30" drop
100' (est)
Operator
Exploration Method(s)
Work StarbCompletion Dates
Top of Casing Elev. (NAVD88)
Depth to Water (Below GS)
6" OD X 2.25" ID Hollow
Mac Desranleau
Stem Auger
4/14/2023
NA
No Water Encountered
Depth
Elev.
Exploration Notes and
mple
Sate
Blows/foot •
water Con--0
Blows/6
Tests
Material
Description
Depth
(feet)
(feet)
Completion Details
Type/ID
405
Type
(ft)
15
OLYMPIA GRAVEL
22
SAND (SP); dense, moist, gray brown; fine to coarse
26
74
—
—
24
sand; few fine to trace coarse, subrounded gravel;
26
interbedded sand and silt; trace oxidation. (continued)
27
73
—
—
—
27
28
72
—
—
28
29
71
—
29
30
70
14
30
17
31
69
—
21
31
Bottom of exploration at 31.5 ft. bgs.
32
68
—
—
32
33
67
—
—
—
33
34
66
—
—
34
35
65
35
36
64
—
—
36
37
63
—
—
—
37
38
62
—
—
38
39
61
39
40
60
40
41
59
—
—
—
41
42
58
—
—
42
43
57
—
—
—
43
44
56
—
—
44
45
55
45
46
54
—
—
46
47
53
—
—
—
47
48
52
—
—
48
49
51
49
Legend Plastic Limit
Liquid Limit
m
E T
0 No Soil Sample Recovery
Split Barrel 2" X 1.375" (SPT) @ >
No Water Encountered See Exploration Log Key for explanation
of symbols
Exploration
Log
Logged by: MRH
ccc I—
AB-02
Approved by: MvA
Sheet 2 of 2
APPENDIX 6
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 parry 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
such as a change in property use or occupancy, or by natural events, such as floods,
ASPECT CONSULTING
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.