REVIEWED PLN_RESUB2 BLD2022-0463 NEW GEO REPORTF14011
November 2, 2021
Revised June 20, 2022
Project No. 20210191EO01
Susan Stark
133 Sunset Avenue North
Edmonds, Washington 98020
a s s o c i a t e d
earth sciences
i n c o r p o r a t e d
RESUB
Jul 20 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Reviewed by
City of Edmonds
Planning Division
- - - - - - - - - - - - - -'
1 ij 1 DJ4il+0if: reD]
Subject: Limited Geotechnical Engineering Study - Settlement Mitigation
Stark Residence
133 Sunset Avenue North
Edmonds, Washington
Dear Ms. Stark:
Associated Earth Sciences, Inc. (AESI) is pleased to present this geotechnical report prepared
pursuant to Edmonds Community Development Code (ECDC) 23.80.70.0 for the above
referenced site. Our evaluation addresses geologically hazardous areas at the site, building
settlement cause and geotechnical recommendations for settlement mitigation. Our general
understanding of the project is based on discussions with you, a site visit, previous experience on
similar projects, and our knowledge of geologic conditions in the vicinity. This revised report
responds to review comments from the City of Edmonds in letters dated May 16, 2022 and June
16, 2022.
This letter -report has been prepared for the exclusive use of Ms. Susan Stark and her agents, for
specific application to this project. Within the limitations of scope and schedule, our services
have been performed in accordance with generally accepted local geotechnical engineering
practices in effect at the time our letter -report was prepared. No other warranty, express or
implied, is made. Our work was performed in general accordance with our proposal, dated July
14, 2021.
PROJECT BACKGROUND
As shown on Figure 1, "Vicinity Map," the site consists of the 0.11-acre residential parcel located
at 133 Sunset Avenue North in Edmonds, Washington (Snohomish County Parcel
00434401300500). The site contains an existing two -level building with daylight basement used
as a single-family residence and law office reportedly built in 1968. The building is constructed
on a west -facing slope toward Puget Sound. The property is bordered to the north and south
by multifamily residences, to the west by railroad tracks along the Puget Sound shoreline, and to
Kirkland I Tacoma I Mount Vernon
425-827-7701 1 www.aesgeo.com
Stark Residence Foundation Repair Limited Geotechnical Engineering Study
Edmonds, Washington Settlement Mitigation
the east by Sunset Avenue North. We understand that settlement of the building has occurred
primarily in the west -central portion and that magnitude is estimated to range from 1 to 2 inches.
Problems with closing interior doors on the west side of the building began about 7 years ago
and cracks have developed in the central brick fireplace and upper level drywall.
We understand that you would like to determine the cause of building settlement and evaluate
options for mitigation of the settlement since the long-term plans for the property include an
eventual transfer of ownership to you.
SUBSURFACE EXPLORATION
Subsurface conditions at the site are based on one exploration boring which was advanced on
August 23, 2021. The boring was completed using a limited -access, rubber -tracked, drilling rig
advancing a 6-inch outside -diameter, hollow -stem auger tool. During the drilling process,
samples were obtained at generally 5-foot intervals. The boring was continuously observed and
logged by an engineering geologist from our firm. The exploration log presented in Appendix A is
based on observed drilling action and samples collected.
Disturbed but representative samples were obtained by using the Standard Penetration Test
(SPT) procedure in accordance with ASTM International (ASTM) D-1586. This test and sampling
method consists of driving a standard, 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 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.
If a total of 50 blows are recorded at or before the end of one 6-inch interval, the blow count is
recorded as the number of blows for the corresponding number of inches of penetration. The
resistance, or N-value, provides a measure of the relative density of granular soils or the relative
consistency of cohesive soils. These values are plotted on the exploration boring log.
The samples obtained from the split -barrel sampler were classified in the field and representative
portions placed in watertight containers. The samples were then transported to our laboratory
for further visual classification and geotechnical laboratory testing, as necessary.
The various types of materials and sediments encountered in the exploration, as well as the
depths where characteristics of these materials changed, are indicated on the attached
exploration log. The depths indicated on the log where conditions changed may represent
gradational variations between sediment types. The approximate location of the exploration
boring is shown on the attached Figure 2.
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SUBSURFACE CONDITIONS
Topsoil
At the location of exploration boring E13-1, we encountered a surficial organic -rich topsoil horizon
with an approximate thickness of 8 inches. Due to its high organic content, topsoil is not suitable
for foundation support.
Fill
Underlying the surficial topsoil horizon, our exploration encountered approximately 7 feet of very
loose to loose, moist, light brown, fine sand, with variable silt and gravel content and trace
organics and trace debris present. These materials are interpreted as fill soils placed during
original site development. Fill is also expected to be found around buried utilities,
foundation/wall backfill areas, and beneath landscape improvements. Due to their very loose
condition, these fill soils are not suitable for foundation support.
Recent Beach/Marsh Deposits
Underlying the fill, exploration boring E13-1 encountered very loose, gray, fine sand interbedded
with medium stiff, fine, sandy silt with occasional peat interbeds. This material is interpreted as
recent beach and marsh sediments deposited in a low -energy environment after the most recent
glaciation of the Puget Lowlands approximately 12,500 years ago. Recent beach/marsh deposits
consist of detrital material, such as silt, sand, gravel, and organics, which have been transported
and deposited by flowing water or deposited along the shores of Puget Sound. Portions of these
sediments contained enough organic material to be classified as peat, which is indicative of a
wetland depositional environment. The thickness of the recent beach and marsh deposits was
approximately 12 feet at the location of E13-1. Due to its generally soft/loose condition and lenses
of organics, these deposits pose a high risk of settlement under foundation loads. For this reason,
the recent beach and marsh deposits are not recommended for direct structural support.
Whidbey Formation
Underlying the recent beach/marsh deposits at a depth of 20 feet below the existing ground
surface, our exploration encountered very dense, gray, massive, fine to medium sand with trace
silt content. These sediments are interpreted as belonging to the Whidbey Formation which
consists of non -glacial deposits placed prior to the most recent glaciation of the Puget Lowland
that were subsequently compacted by the weight of the overlying glacial ice during the Vashon
State of the Fraser Glaciation. Whidbey Formation sediments are suitable for foundation support.
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Pre -Whidbey Glacial Till
Underlying the Whidbey Formation sediments at a depth of approximately 23 feet below existing
ground surface and extending past the explored depth of 30.5 feet, our exploration encountered
unsorted, gray, very dense, silty, fine sand with variable gravel content. We interpret these
sediments as pre -Whidbey -age glacial till. This glacial till was deposited directly from basal,
debris -laden glacial ice during a glaciation prior to the most recent glacial advance during the
Vashon Stade of the Fraser Glaciation. The high relative density characteristic of pre -Whidbey
glacial till is due to its consolidation by the massive weight of the glacial ice from which it was
deposited and by subsequent glaciations. Pre -Whidbey glacial till is suitable for support of
structural loads.
Published Geologic Map Review
Review of the published geologic map Geologic Map of the Edmonds East and Part of the
Edmonds West Quadrangles, Washington, U.S. Geological Survey (USGS), Miscellaneous Field
Studies Map MF-1541 by J.P. Minard (1983) indicates that the subject site is underlain by
Modified Land and Whidbey Formation with Marsh Deposits mapped nearby. Our interpretation
of geologic conditions at the site is in general agreement with the referenced geologic map.
Published Soils Map Review
Review of the U.S. Department of Agriculture Soil Conservation Service, now referred to as
Natural Resources Conservation Service (NRCS), Web Soil Survey indicates that the subject site is
underlain by Urban Land. This mapped soil type consists of areas that are covered by streets,
buildings, parking lots, and other structures that obscure or alter the soils so that identification
is not possible. Due to the fill soils encountered, our interpretation of geologic conditions at the
site is in general agreement with the published soils mapping.
Hydrology
At the time of our exploration, groundwater seepage was encountered from approximately 8 to
15 feet below existing ground surface within the fill soils and upper, sandy portion of the recent
beach/marsh deposits. We interpret this groundwater as perched on top of the lower, recent
beach/marsh silt. Perched groundwater, also known as "interflow," occurs when vertical
infiltration is impeded by less -permeable soils, such as silty beach/marsh deposits, and horizontal
migration occurs. It should be noted that groundwater levels below the site fluctuate in response
to such factors as tides, changes in season, precipitation, and on- and off -site land use. Our field
exploration was conducted in mid -September when groundwater levels are typically nearing
their seasonal low.
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GEOLOGICALLY HAZARDOUS AREAS
In accordance with ECDC Section 23.80.050, we determined critical areas present at the site or
within 200 feet of the site such as landslide, erosion and seismic hazards. Based on our review of
the City of Edmond GIS mapping, the site is classified as having a seismic hazard and erosion
hazard area (15 to 40 percent slopes). Within 200 feet of the site, the City's GIS mapping indicates
that similar hazards exist along with some isolated landslide hazard areas. Since the site is
developed with a single-family residence dating back to the late 1960's and is covered by either
the house, hardscape or landscaping, our subsequent discussion focuses on seismic hazards as
required by the ECDC. The planned mitigation of observed differential static settlement is not
intended to bring up the structure to current seismic codes.
In accordance with ECDC 23.80.060.A alterations of geologically hazardous areas or associated
buffers may only occur for activities that:
1. Will not increase the threat of the geological hazard to adjacent properties beyond
predevelopment conditions;
2. Will not adversely impact other critical areas;
3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or
less than predevelopment conditions, and
4. Are certified as safe as designed and under anticipated conditions by a qualified engineer or
geologist, licensed in the state of Washington.
Per ECDC 23.40.005, "Alteration" means any human -induced action which changes the existing
condition of a critical area or its buffer including construction activities. The planned
improvements will involve installation of small diameter pipe piles around the perimeter of the
existing house. The amount of ground disturbance by construction activity for the pile installation
will be minor. In our opinion, the planned improvements will not increase the threat of the
geological hazard to adjacent properties beyond predevelopment conditions or adversely impact
other critical areas. The planned improvements are designed to mitigate soft/loose native soils
that are present underneath the existing foundations using small diameter pipe piles. Provided
the piles are designed in accordance with the recommendations contained in this report, and pile
installation is monitored by AESI, it is our opinion, that alterations of the geologically hazardous
areas will be safe.
Seismic Hazards and Mitigations
All of Western Washington is at risk of strong seismic events resulting from movement of the
tectonic plates associated with the Cascadia Subduction Zone (CSZ), where the offshore Juan de
Fuca plate subducts beneath the continental North American plate. The site lies within a zone of
strong potential shaking from subduction zone earthquakes associated with the CSZ. The CSZ can
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produce earthquakes up to magnitude 9.0, and the recurrence interval is estimated to be on the
order of 500 years. Geologists infer the most recent subduction zone earthquake occurred in
1700 (Goldfinger et al., 20121). Three main types of earthquakes are typically associated with
subduction zone environments: crustal, intraplate, and interplate earthquakes. Seismic records
in the Puget Sound region document a distinct zone of shallow crustal seismicity (e.g., the Seattle
Fault Zone). These shallow fault zones may include surficial expressions of previous seismic
events, such as fault scarps, displaced shorelines, and shallow bedrock exposures. The shallow
fault zones typically extend from the surface to depths ranging from 16 to 19 miles. A deeper
zone of seismicity is associated with the subducting Juan de Fuca plate. Subduction zone seismic
events produce intraplate earthquakes at depths ranging from 25 to 45 miles beneath the Puget
Lowland including the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001,
6.8-magnitude event) and interplate earthquakes at shallow depths near the Washington coast
including the 1700 earthquake, which had a magnitude of approximately 9.0.
The 1949 earthquake appears to have been the largest in this region during recorded history and
was centered in the Olympia area. Evaluation of earthquake return rates indicates that an
earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period.
Generally, there are four types of potential geologic hazards associated with large seismic events:
1) surficial ground rupture, 2) seismically induced landslides or lateral spreading, 3) liquefaction,
4) ground motion. The potential for each of these hazards to adversely impact the proposed
project is discussed below.
Surficial Ground Rupture
Generally, the largest earthquakes that have occurred in the Puget Sound area are sub -crustal
events with epicenters ranging from 25 to 45 miles in depth. Earthquakes that are generated at
such depths usually do not result in fault rupture at the ground surface. Based on current
knowledge, the subject property is not located near known surface faults. Therefore, based on
current information, the risk of damage to planned improvements as a result of surface rupture
due to faulting is low, in our opinion.
The site falls within the suspected traces of the southeastward extension of the Southern
Whidbey Island (SWIFZ). A recent study bythe U.S. Geological Survey (USGS) (Sherod et al, 2005 2)
indicates that "strong" evidence of prehistoric earthquake activity has been observed along two
fault strands thought to be part of the southeastward extension of the SWIFZ. The study suggests
as many as nine earthquake events along the SWIFZ may have occurred within the last
16,400 years. Understanding of this fault system is somewhat limited with studies still ongoing.
1 Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutierrez -Pastor, J., Eriksson, A.T., Gracia, E.,
Dunhill, G., Enkin, R.J, Dallimore, A., and Vallier, T.,2012, Turbidite Event History —Methods and Implications for Holocene
Paleoseismicity of the Cascadia Subduction Zone: U.S. Geological Survey Professional Paper 1661—F, 170
2 Sherrod et al., 2005, Holocene Fault Scarps and Shallow Magnetic Anomalies Along the Southern Whidbey Island Fault Zone
near Woodinville, Washington, Open -File Report 2005-1136, March 2005
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The recurrence interval of movement along this fault system is still unknown, although it is
hypothesized to be in excess of one thousand years. Due to the suspected long recurrence
interval, the potential for surficial ground rupture along the SWIFZ is considered to be low during
the expected life of the proposed structures.
Seismically Induced Lateral Spreading
Lateral spreading associated with seismic activity typically involves lateral displacement of large,
surficial blocks of non -liquefied soil when a layer of underlying soil loses strength during ground
motion. Lateral spreading usually occurs in shoreline or riverbank areas where sloping ground or
"free face" conditions (e.g., bulkheads) exist, underlain by loose or liquefiable soils. Based on the
exploration advanced for this study, review of geologic information for the site, and distance
from the shoreline it is our opinion that the risk of lateral spreading is low.
Liquefaction
Liquefaction is a process through which unconsolidated soil loses strength as a result of
vibrations, such as those which occur during a seismic event. During normal conditions, the
weight of the soil is supported by both grain -to -grain contacts and by the fluid pressure within
the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain -
to -grain contact, increase the pore pressure, and result in a temporary decrease in soil shear
strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by
pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of
overlying structures. Areas most susceptible to liquefaction include those areas underlain by very
soft to stiff, non -cohesive silt and very loose to medium dense, non -silty to silty sands with low
relative densities, accompanied by a shallow water table.
To evaluate the extent of liquefaction risk and estimated settlement potential during a
design -level seismic event, we performed a liquefaction hazard analysis utilizing data obtained
from our boring. Our liquefaction analysis was completed with the aid of LiquefyPro computer
software Version 5.9a (2015) by CivilTech Corporation. This program accepts input for SPT data,
groundwater levels, soil unit weight, and the depth and grain -size distribution of the sediments
of concern to calculate seismically induced settlement. The following parameters were used
during the analysis:
• Soil unit weights were inferred from boring data;
• Silt contents were estimated from soil samples;
• We used the Modified Robertson analysis method in the LiquefyPro computer software
to obtain the liquefaction -induced settlement values; and
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• A design event is considered a magnitude 7 earthquake with a peak horizontal ground
acceleration of 0.60g (PGAm) modified for Seismic Site Class determined from the Applied
Technology Council (ATC) Hazards by Location Tool https://hazards.atcouncil.org/ as
suggested by USGS.
The liquefaction -induced settlement calculated for the site ranges from approximately 3 to
4 inches. The results of our liquefaction analysis are presented in Appendix B.
Ground Motion
It is our opinion that earthquake damage to the existing structure will likely be caused by the
intensity and acceleration associated with the event.
SETTLEMENT EVALUATION
Based upon the conditions encountered in our exploration boring, it appears that very loose fill
and organic -rich recent beach/marsh deposits are present beneath the west side of the existing
residence. A suitable foundation bearing stratum is present at least 20 feet below existing grade.
We understand that settlement has occurred primarily in the west -central portion of the building
and that magnitude is estimated to range from 1 to 2 inches. Problems with closing interior doors
on the west side of the building began about 7 years ago, and cracks have developed in the
central brick fireplace and upper level drywall.
Review of the City of Edmonds GIS Map Portal shows permit and construction documents relating
to this property. These City of Edmonds documents show an "Application for Side Sewer Permit"
that was stamped approved on April 25, 1968. This document shows a hand -drawn site plan
describing the property, the building, and the location of the side sewer exiting at the
west -central side of the building and continuing southwest to the sewer main just outside the
west property line. Other documents describe a water meter along Sunset Avenue that was
damaged by city workers resulting in a significant leak and causing pavement subsidence and
cracking in 1984. In 1999, plans were submitted to the City to replace a portion of the east
foundation wall, with construction completed in 2000.
From discussions with you, the building is reportedly supported on piles. However, we could not
confirm the presence of piles during our review of City documents or during our site visits. If
present, the pile depth is unknown, and the building settlement suggests that the pile foundation
is not performing as designed.
It is our opinion that the settlement observed below the west -central portion of the existing
residence is likely due to the presence of fill soils and organic -rich beach/marsh sediments
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underlying the property. These sediments are in a very loose to loose condition and contain
organic material that consolidates over a long period of time as a result of the load induced from
the fill soils above. Additional consolidation within the loose fill and the organic -rich recent
beach/marsh deposits and settlement of the ground surface beneath and around the building
will likely continue. In addition, during a strong seismic event there is the potential of settlement
due to the liquefaction of these loose deposits. If a pile foundation is present, the consolidation
of the beach/marsh sediments can also induce increased loads on the piles in the form of
"downdrag" from the skin friction on the piles. It is not known whether the original design took
these additional loads into account and it is unlikely that liquefaction was considered given the
age of the building.
The site is underlain by approximately 20 feet of generally loose/medium stiff sediments that are
subject to consolidation and settlement under foundation loads and pose a risk of liquefaction
during a strong seismic event. To mitigate existing settlement and possible future settlement due
to liquefaction, we recommend underpinning the existing foundations along the west side of the
building with small -diameter pipe piles that fully penetrate the fill and recent beach/marsh
deposits and are driven to refusal in the underlying, glacially consolidated, Whidbey Formation
or pre -Whidbey glacial till sediments.
While we are confident that underpinning will mitigate future settlement along the west side of
the building, it is possible that additional settlement will occur in other parts of the structure with
time or during a strong seismic event. With installation of recommended deep foundations
embedded into very dense glacial soils along the west side of the building, there is still a risk that
differential settlement could occur between this location and other portions of the building
where foundations may be inadequate or supported on compressible/liquefiable soils. Complete
mitigation of future settlement could be accomplished if all existing foundations are underpinned
with small diameter pipe piles and if existing slab on grade floors are pile supported.
Small -Diameter Pipe Piles
Allowable axial capacities for small -diameter driven pipe piles are provided below in Table 1.
Table 1
Small -Diameter Pipe Pile Recommendations
Nominal Pipe
Diameter
Minimum Wall
Thickness
Minimum
Hammer Size
Allowable Axial
Capacity
Driving Time
(seconds/inch)
3-inch
Schedule 40
400 pounds
12 kips
30
4-inch
Schedule 40
1,100 pounds
17 kips
10
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In order for the stated pile capacities to apply, the pipe piles should be driven to refusal, which is
defined as less than 1 inch of penetration during the specified period of continuous driving. They
should also completely penetrate the fill and recent beach/marsh sediments.
No lateral capacity would be provided by vertically installed pipe piles. Lateral capacity could be
attained through the use of battered piles or passive resistance over the buried portions of the
grade beams. An allowable passive equivalent fluid of 200 pounds per cubic foot (pcf) may be
used for foundation design. For the recommended passive equivalent fluid to apply, the grade
beams must be backfilled with structural fill compacted to at least 95 percent of the modified
Proctor maximum dry density (ASTM D-1557). Piles may be battered up to 15 degrees to develop
additional lateral capacity. Lateral capacity of battered piles may be taken as the horizontal
component of the axial pile load. Battered piles inclined up to 15 degrees should be designed
with an allowable axial compressive capacity equal to that used for vertical piles. Pile spacing,
locations, splicing details, foundation connection details, grade beam design, and any other
structural design recommendations should be determined by a structural engineer.
Installation of the pipe piles should be observed by an AESI representative to verify that the
refusal and embedment criteria are met and that materials, equipment, and procedures conform
with our recommendations. This may also be required by the City of Edmonds.
For pipe piles larger than 2 inches in diameter, we recommend that load testing in accordance
with the ASTM Quick Load Test (ASTM D-1143) be conducted to 200 percent of the allowable pile
capacity on a minimum of 3 percent (1 pile minimum, 5 piles maximum) of the piles.
Existing Sewer and Drainage System Audit
Due to the proximity of the building settlement and the location of the side sewer, we
recommend that a video survey of the existing side sewer be conducted by an experienced
contractor. A broken or damaged side sewer discharging into the loose fill soils and recent
beach/marsh deposits could cause additional subsistence.
We do not have any information pertaining to the discharge locations of roof runoff and
foundation drains. We recommend an audit of the existing drainage system be performed by an
experienced contractor. The collection and discharge points of drains for existing impervious
surfaces should be identified and the "water -tightness" of these drains evaluated. If leaks are
suspected, these drains should be repaired or replaced. If the drains discharge next to the
building, these should be extended to an area downslope of the building or be connected to the
existing drainage system. Under no circumstances should stormwater be discharged on or above
the on -site slopes or next to the existing building.
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PROJECT DESIGN AND CONSTRUCTION MONITORING
We are available to provide additional geotechnical engineering upon request and monitoring
services during construction. The integrity of the earthwork and foundations depends on proper
site preparation and construction procedures. In addition, engineering decisions may have to be
made in the field in the event that variations in subsurface conditions become apparent.
Construction monitoring services are not part of this current scope of work.
CLOSURE
We appreciate the opportunity to be of service to you on this project. Should you have any
questions regarding this report or other geotechnical aspects of the project, please call us at your
earliest convenience.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
U 01
J shua S. P. Greer, G.I.T.
Senior Staff Geologist
Bruce L. Blyto , P.E.
Senior Principal Engineer
Stephen A. Siebert, P.E.
Associate Geotechnical Engineer
Attachments: Figure 1: Vicinity Map
Figure 2: Existing Site and Exploration Plan
Appendix A: Exploration Log
Appendix B
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Liquefaction Analyses
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ORIGINAL MAY REDUCE ITS
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APPENDIX A
Exploration Log
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Well -graded gravel and
Terms Describing Relative Density and Consistency
o p o o
OW
g ravel with sand, little to
2)
Density SPT blows/foot
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o
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Coarse-4 to 10
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c>
o o
- v,
o
�,o
w
Grained Soils Medium Dense 10 to 30 Test Symbols
0
0
o 0 0 0 o
and gravel with sand,
Dense 3o to 50
little to no fines
Very Dense >50 G = Grain Size
M = Moisture Content
° 0°
0
Silty gravel and silty
6
Z
C
LO o
Consistency SPT(2�blows/foot
Y A= Atterberg Limits
c a
S
GM
gravel with sand
Very Soft 0 to 2 C = Chemical
Fine -
v
~ `
.Soft
° 0
° 0
2 to 4 DID =Dry Density
Grained Soils
c
E
0
.i
Medium Stiff 4 to 8 K = Permeability
g
o
Stiff 8 to 15
Clayey gravel and
Very Stiff 15 to 30
N
NI
Gc
clayey gravel with sand
Hard >30
o
L
Component Definitions
o
Well -graded sand and
t
Descriptive Term Size Range and Sieve Number
m
SW
sand with gravel, little
Boulders Larger than 12"
o
Li
u
e
to no fines
Cobbles 3" to 12"
m
;n a�
_
eveeeveeee
Gravel 3" to No. 4 (4.75 mm)
Poorly -graded sand
con
c i °'
A
SP
and sand with gravel,
Coarse Gravel 3" to 3/4"
Fine Gravel 3/4to No. 4 75 mm
" 4 (� )
4)
c
cn
o v
N o
little to no fines
Sand No. 4 (4.75 mm) to No. 200 (0.075 mm)
0 z
Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm)
6
o y
�
SM
Silty Sand and
Medium Sand No. 10 (2.00 mm) to No. 40 (0.425 mm)
silty sand with
Fine Sand No. 40 (0.425 mm) to No. 200 (0.075 mm)
N
v
c N
o a
tp.-::'::.
gravel
Silt and Clay Smaller than No. 200 (0.075 mm)
(3) Estimated Percentage
Moisture Content
Na
sc
Clayey sand and
co
NI
clayey sand with gravel
Component Percentage by Weight
Dry - Absence of moisture,
Trace <5
dusty, dry to the touch
Slightly Moist - Perceptible
Silt, sandy silt, gravelly silt,
moisture
o
ML
silt with sand or gravel
Some 5 to <12
Moist - Damp but no visible
u7
c
T w
Modifier 12 to <30
water
Clay Of low to medium
o
`—°
(silty, sandy, gravelly)
Very Moist - Water visible but
d
CL
plasticity; silty, sandy, or
not free draining
z
•=
gravelly clay, lean clay
Very modifier 30 to <50
Wet -Visible free water, usual) Y
NE
(silty, sandy, gravelly)
from below water table
0-
a
==
Organic clay or silt of low
Symbols
2
—
OL
plasticity
Blows/6" or
0
Sampler portion of 6"
Cement grout
o
Type /
i
surface seal
Elastic silt, clayey silt, silt
2.0" OD Sampler Type
o
o
�,
MH
with micaceous or
Split Spoon p Description (4)
Bentonite
seal
�
o
or fine sand or
Sampler p 3.0" OD Split -Spoon Sampler -
:-= Filter pack with
A
o
silt
(SPT) 3.25" OD Split -Spoon Ring Sampler (4)
. -
; .
:: blank casing
::
Clay of high plasticity,
v)
U o
c �
CH
sandy or gravelly Clay, fat
_
Bulk sample 3.0" OD Thin Wall Tube Sampler
section
Screened casing
m
E
J
clay with sand or ravel
Y g
(including Shelby tube)
_ or Hydrotip
=with filter pack
U
— c
Grab Sample
- End cap
c
;%
Organic clay or silt of
o Portion not recovered
OH
medium to high
(1) (4)
Percentage by dry weight Depth of ground water
plasticity
(2) (SPT) Standard Penetration Test 1 ATD = At time of drilling
ASTM D-1586
(3) ( ) Q Static water level (date)
In General Accordance with
w
Peat, muck and other
rn
_
c
a, 0
PT
highly organic soils
Standard Practice for Description (5) Combined USCS symbols used for
and Identification of Soils (ASTM D-2488) fines between 5% and 12%
Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and
g plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification
3 methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System.
T
O!
° a s s o c i a t e d
earth sciences EXPLORATION LOG KEY FIGURE Al
N
o i n c o r p o r a t e d
a
associated
Exploration Borin
earth sciences
Project Number
Exploration Number
Sheet
i n c o rp o ra t e d
20210191EO01
EB-1
1 of
Project Name Stark Residence Foundation Repairs Ground Surface Elevation (ft) 19
Location Edmonds, WA Datum NAVD 88
Driller/Equipment Geologic Drill Partners / Mini -Bobcat HSA Date Start/Finish nc)/19/91 Q9/19/91
Hammer Weight/Drop 140# / 30" Hole Diameter (in) F
cC
Ch
E
.2 O
cL
c
.O
a)
n
�
>
J
CO
U)
3
Blows/Foot
w
d)
a
S
12 �,
0 u)
o
o
T in
DESCRIPTION
"
m
m
r
°
10 20 30 40
`
Topsoil - 8 inches
Fill
Slow gravelly drilling 0 to 3 feet.
5
Moist, light brown, fine SAND, some silt, trace debris at top; massive
2
S-1
(SP-SM).
A4
2
t
Recent Beach / Marsh Deposits
10
Wet, gray, fine SAND, some silt; layer of peat (4 inches thick) at tip of
11
S-2
sampler; organic odor; massive (SP-SM).
A3
2
15
Moist, light brown to grayish brown, SILT, some fine sand; frequently
3
S-3
bedded with fine organics; thinly bedded with peat; interbeds (1 to 2 inches
thick) near top and bottom of sampler (ML).
4
20
S 4
27
"
Whidbey Formation
Gravelly drilling at 20 feet; drill action increases; speed slows.
0/ "
50/
Very moist, gray, fine to medium SAND, trace silt, trace organics; massive
(SP).
Pre -Whidbey Glacial Till
Drill action increases; speed slows.
25
S5
Moist, gray, silty, fine SAND, trace gravel; unsorted diamict (SM).
0/„
50/
"
Adding water due to difficult removal of sample at 20 feet.
Driller notes interbedded, gravely, sandy drilling.
Very slow drill progress 27 to 30 feet.
30
S_g
Moist with wet coating from above and added water, gray, silty, fine SAND,
0/
50/
"
ace gravel; unsorted diamict (SM).
Bottom of exploration boring at 30.4 feet
Groundwater encountered 8 to 15 feet.
Sampler Type (ST):
m 2" OD Split Spoon Sampler (SPT) ❑ No Recovery M - Moisture Logged by: JG
m 3" OD Split Spoon Sampler (D & M) Ring Sample Q Water Level Q Approved by: JHS
® Grab Sample 0 Shelby Tube Sample 1 Water Level at time of drilling (ATD)
APPENDIX 6
Liquefaction Analyses
LIQUEFACTION
ANALYSIS
Stark Residence
Foundation
Repair
Hole
No.=EB-1 Water Depth=5
ft
Magnitude=7
Acceleration=0.60g
Soil Description
Shear Stress Ratio
Factor of Safety
Settlement
Raw Unit Fines
(ft)0
0 1
0 1 5
0 (in.) 10
SPO Weight
eitht115
10
�Oo
O
�Oo
O
o0
4 115 10
O
0
op�
5
O
opp
O
�Oo
O
�Oo
O
�Oo
O
10�
3 115 10
O
�Oo
O
p
7 115 60
O
�Oo
O
15oo
O
�Oo
O
0
opp
O
0
opp
O
0
20
O
100 130 NoLq
�Oo
O
�Oo
O
0
op�
O
25
O
�Oo
00
fs1=1
S = 3.76 in.
30
CRR CSR fs1
Saturated
Shaded Zone has Liquefaction Potential
Unsaturat.
35
CivilTech Corporation 20210191 E001 Plate A-1