RESUB 1-BLD2024-0064+Geotechnical_Report+9.12.2024_2.01.47_PM+4497076BLD2024-0064
DRAFT CRITICAL AREAS REPORT
Port of Edmonds
Mobile Office Building
Edmonds, Washington
HWA Project No. 2024-216-21
Port of Edmonds
August 23, 2024
0
I
RESUB
Sep 13 2024
CITY OF EDMONDS
DEVELOPMENTSERVICES
DEPARTMENT
U GEOSCIENCES INC.
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DBE/MWBE
Geotechnical Engineering
Pavement Engineering
Geoenvironmental Hydrogeology
Inspection & Testing
YLwi GEOSCIENCES INC.
DBE/MWBE
August 23, 2024
HWA Project No. 2024-216-21
Port of Edmonds
471 Admiral Way
Edmonds, WA 98020
Attention: Chris Osterman
Subject: DRAFT CRITICAL AREAS REPORT
Port of Edmonds
Mobile Office Building
Edmonds, Washington
Dear Chris:
We are pleased to submit this draft Critical Areas Report for the Port of Edmonds Mobile Office
Building project in Edmonds, Washington. This report includes the results of our geotechnical
critical areas study for the design and construction of the mobile office building at the proposed
project location. This report also provides direct responses to requirements presented in the
Edmonds Community Development Code (ECDC).
We appreciate the opportunity to provide geotechnical services on this project. Should you have
any questions, please contact us.
Sincerely,
HWA GEOSCIENCES INC.
Yen Nhi Amy Nguyen, P.E.
Geotechnical Engineer
Sean M. Gertz, P.E.
Senior Geotechnical Engineer
Enclosure: Draft Critical Areas Report, Port of Edmonds Mobile Office Building
21312 30th Dr. SE, STE.110, Bothell, WA 98021 1 425.774.0106 1 hwageo.com
TABLE OF CONTENTS
Page
1.0
INTRODUCTION..........................................................................................................1
2.0
EXISTING SITE CONDITIONS......................................................................................1
2.1 GEOLOGIC SETTING.......................................................................................1
2.2 HISTORICAL EXPLORATIONS.........................................................................1
3.0
SUBSURFACE CONDITIONS........................................................................................2
3.1 SOIL CONDITIONS..........................................................................................2
3.2 GROUNDWATER.............................................................................................2
4.0
CONCLUSIONS AND RECOMMENDATIONS..................................................................3
4.1 GENERAL.......................................................................................................3
4.2 SEISMIC DESIGN............................................................................................3
4.3 LIQUEFACTION SUSCEPTIBILITY....................................................................5
4.3.1 Liquefaction -Induced Settlement and Lateral Spreading
............5
4.4 GEOLOGIC HAzARDs.....................................................................................6
4.4.1 Landslide Hazard Area................................................................6
4.4.2 Erosion Hazard Area....................................................................6
4.4.3 Seismic Hazard Area....................................................................6
4.4.4 Responses to Requirements of ECDC 23.80.050 and
23.80.060......................................................................................7
5.0
CONDITIONS AND LIMITATIONS.................................................................................8
6.0
REFERENCES..............................................................................................................10
LIST OF FIGURES (FOLLOWING TEXT
Figure 1 Site and Vicinity Map
LIST OF TABLES (IN TEXT
Table 1. Seismic Design Parameters per the 2018 International Building Code, Site Class Fa ..... 4
APPENDICES
Appendix A: Field Explorations by Others
Appendix B: Laboratory Testing by Others
Port of Edmonds Mobile Office Building
Critical Areas Report i HWA GEOSC�ENCEs INC.
DRAFT CRITICAL AREAS REPORT
PORT OF EDMONDS
MOBILE OFFICE BUILDING
EDMONDS, WASHINGTON
1.0 INTRODUCTION
This Critical Areas Report presents the findings of our geotechnical engineering study for the site
of the proposed Mobile Office Building at the Port of Edmonds. The project site is located at the
existing Dry Storage facility at 600 Admiral Way in Edmonds, Washington. The approximate
site location is shown on the Site and Vicinity Map, Figure 1.
HWA understands that the Port proposes to construct a new mobile office at the project site to
replace an existing mobile office. The site has been identified as containing geologically
hazardous areas, and per the Edmonds Community Development Code (ECDC), a critical areas
study is required. This report includes direct responses to the criteria required by Chapter 23.80
of the ECDC.
2.0 EXISTING SITE CONDITIONS
The site is located at the southern end of the Port of Edmonds Marina, within the existing Dry
Storage Facility. The site is bounded by the Marina Beach Park to the southwest, by the Port of
Edmonds South Marina to the northwest, and by a parking lot to the north and east. The project
site is generally flat. The site ground surface is supported by an existing timber and concrete
bulkhead to the west, beyond which the mudline slopes down steeply towards the South Marina.
2.1 GEOLOGIC SETTING
General geologic information specific to the project area was obtained from the Geologic Map of
the Edmonds East and Part of the Edmonds West Quadrangles, Washington (Minard, 1983). The
map indicates the project site is underlain by modified land (fill). Due to the geographical
location of the project site, it is possible that the fill could have been derived from dredging
activities during construction of the adjacent marina. Fill deposits should be anticipated to be
highly variable and generally granular in nature. The area just upshore of the project site is
identified as being underlain by Whidbey Formation (Pre -Fraser Glaciation) deposits. This unit
is bedded, compact, commonly oxidized, medium to coarse grained sand. Peat beds or organic
rich layers are present locally in the upper part of the formation.
2.2 HISTORICAL EXPLORATIONS
HWA identified one source of existing information that was considered useful for the evaluation
of site conditions. In 1996, Landau Associates, Inc. (Landau) conducted a geotechnical study for
Peratrovich, Nottingham & Drage, Inc. to evaluate the subsurface conditions for the Dry Stack
Boat Storage facility and an adjacent bulkhead replacement. The study included the completion
of six geotechnical borings, designated B-1 through B-6. Logs of explorations from this study are
Port of Edmonds Mobile Office Building
Critical Areas Report 1 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
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provided in Appendix A. Geotechnical laboratory testing was completed on selected samples
retrieved from those explorations to characterize relevant engineering properties and index
parameters of the soils encountered. The tests included visual classification and grain size
distribution analysis. The test results are presented in Appendix B, and/or displayed on the
exploration logs in Appendix A.
3.0 SUBSURFACE CONDITIONS
3.1 SOIL CONDITIONS
Previously completed explorations at the project site (Landau, 1996) include geotechnical soil
borings to depths ranging from 21.5 to 26.5 feet below ground surface (bgs). The exploration
logs indicate variability in densities, consistencies, and elevations of soil units encountered;
however, there is a general pattern of soil types and their stratigraphic sequence. Soil conditions
at the site of the Mobile Office Building project were characterized by boring B-4, which was
completed immediately north of the proposed building location. General descriptions of the soil
units encountered in boring B-4 are presented below in order from youngest to oldest:
• Asphalt and Crushed Rock Base: Asphalt overlying a thin layer of crushed rock base
consisting of sandy gravels was encountered at the ground surface. This layer was
approximately 12 inches thick.
• Fill: Fill material was encountered below the asphalt and crushed rock base. The fill
generally appears to have been derived from dredging activities and consists of loose to
dense, sands and sandy gravels. Organics consisting of wood and shell fragments were
observed in the fill. The fill unit extended to approximately 15.5 feet bgs.
• Whidbey Formation: Below the fill material, very dense, sandy gravel with silt was
encountered. HWA has interpreted this material to be a portion of the Whidbey
Formation. This soil unit extended to the maximum depth explored (26.5 feet bgs).
3.2 GROUNDWATER
Groundwater was observed in each of Landau's 1996 explorations. The depth to groundwater
ranged from 13 to 15 feet bgs. However, these measurements were obtained during drilling and
may not represent long-term groundwater conditions. Furthermore, HWA anticipates the
groundwater table will be influenced by tidal levels in the marina and will fluctuate seasonally,
with the highest levels at times of high tide during the wet winter months; conversely, the lowest
groundwater levels can generally be expected to occur at times of low tide during the dry
summer months. Based on a review of historical explorations, the average tidal levels of the
Port of Edmonds Mobile Office Building
Critical Areas Report 2 HWA GEOSCIENCES INC.
August 23, 2024 DRAFT
HWA Project No. 2024-216-21
nearby marina, and HWA's experience within the Port of Edmonds, a depth to groundwater of 6
ft bgs was assumed for the purposes of the analyses described in this report.
4.0 CONCLUSIONS AND RECOMMENDATIONS
4.1 GENERAL
Based on a review of historical explorations near the project site and structural plans for the
mobile office, existing subgrade soil and pavement are anticipated to provide adequate support
for the proposed improvements.
Based on review of the City of Edmonds GIS map (City of Edmonds, 2024), three geologically
hazardous area designations are identified within 200 feet of the site: seismic hazards, landslide
hazards, and erosion hazards. The seismic hazard area encompasses the project site along with a
majority of the developed shoreline within the City of Edmonds. The landslide and erosion
hazard areas are identified outside of, but adjacent to the site along the revetment that borders the
South Marina. Further discussion regarding hazard area designation is provided in in Section 4.4.
HWA completed liquefaction and lateral spreading analysis to estimate the vertical settlements
and lateral displacements that can be anticipated as a result of the design level seismic event.
Based on conversations with CG Engineering (project structural engineer), it is expected that the
proposed mobile office building will be capable of tolerating the magnitude of anticipated
vertical and horizontal displacements. Further discussion regarding this analysis is provided in
Section 4.3.
4.2 SEISMIC DESIGN
It is understood that this project will be designed in accordance with the 2018 International
Building Code (IBC). The IBC requires above -grade structures to be designed for the inertial
forces induced by a "Maximum Considered Earthquake" (MCE), which corresponds to an
earthquake with a 2 percent probability of exceedance (PE) in 50 years (approximately 2,475-
year return period).
The contribution of potential earthquake -induced ground motion from known sources is included
in the probabilistic ground motion maps developed by the U.S. Geological Survey (USGS).
Design data seismic site characterization and design recommendations based on USGS mapping
and analysis are implemented in the 2018 IBC. As part of this code, the design of structures must
consider dynamic forces resulting from seismic events. These forces are dependent upon the
magnitude of the earthquake event as well as the properties of the soils that underlie the site.
Port of Edmonds Mobile Office Building
Critical Areas Report 3 HWA GEOSCIENCES INC.
August 23, 2024 DRAFT
HWA Project No. 2024-216-21
As part of the procedure to evaluate seismic forces, the 2018 IBC (which implements ASCE
7-16) requires the evaluation of the Seismic Site Class, which categorizes the site based upon the
characteristics of the subsurface profile 100 feet below the proposed foundation. Based on the
SPT blow counts noted in the boring logs by others and extrapolated to a depth of 100 feet, the
site class classifies as a site class "D;" however, because the site is underlain by potentially
liquefiable soil, the site classifies as Site Class F as defined in Table 20.3-1 of ASCE 7-16. An
exception in Section 20.3.1 of ASCE 7-16 permits the ground motion parameters to be
determined using subsurface data obtained from explorations, provided the fundamental period
of the building structure (T) is less than %2 second. Additionally, Section 11.4.8 of ASCE 7-16,
Supplement 3, states that a site -specific ground motion hazard analysis is required where values
of S1 for Site Class D are greater than or equal to 0.2.
Because the Si value calculated for this site is greater than 0.2, a site -specific ground motion
hazard analysis would be required. However, an exception in Section 11.4.8 of ASCE 7-16,
Supplement 3, allows for the determination of seismic design parameters without performing a
site -specific ground motion hazard analysis, provided the value of parameter SMi is increased by
50 percent. Seismic design parameters for this project are presented in Table 1. The
recommended value for SMi presented in Table 1 includes the required 50 percent increase.
Table 1. Seismic Design Parameters per the 2018 International Building Code, Site Class Fa
Mapped
Adjusted MCE
Design
MCE
Spectral
Spectral
Period
Spectral
Site
Response
Response
(sec)
Response
Coefficients
Acceleration
Acceleration
Acceleration
(g)
(g)
L
(g)
I
I
I I
0.0
PGA
0.545
FPGA
1.100
PGAM
0.600
-
-
0.2
SS
1.284
Fa
1.000
SMs
1.285
Sos
0.856
1.0
SI
0.452
1 Fv
1.848b
SMI
1.253
SDI
0.835
Notes:
a) 2 percent probability of exceedance in 50 years for Latitude 47.8066576' and Longitude-122.3914204°.
b) Per Section 11.4.8 of ASCE 7-16, this value of Fv should only be used for calculation of Ts, for
determination of Seismic Design Category, for linear interpolation for intermediate values of S 1, and when
taking the exceptions under Items 1 and 2 of Section 11.4.8 of ASCE 7-16 for the calculation of SDI.
Port of Edmonds Mobile Office Building
Critical Areas Report 4 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
4.3 LIQUEFACTION SUSCEPTIBILITY
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Soil liquefaction is a temporary loss of soil shear strength due to earthquake shaking. Loose,
saturated, and cohesionless soils are highly susceptible to earthquake -induced liquefaction.
Recent experience and research have shown that certain silts and low -plasticity clays are also
susceptible. Primary factors controlling the development of liquefaction include the intensity and
duration of strong ground motions, the characteristics of subsurface soils, in -situ stress
conditions and the depth to groundwater.
To evaluate the liquefaction susceptibility of the soils at the project site, the simplified procedure
originally developed by Seed and Idriss (1971), updated by Youd et al. (2001), and by Idriss and
Boulanger (2004, 2006, 2008) was used. Liquefaction was evaluated for the site modified peak
ground acceleration, designated PGAM, equal to 0.6 g.
HWA's analyses indicate that the saturated loose to medium dense sands below the groundwater
table extending to a depth of about 15.5 ft bgs will experience liquefaction during the design -
level earthquake. Soil liquefaction is likely to result in lateral displacement and vertical
settlement of the ground surface.
4.3.1 Liquefaction -Induced Settlement and Lateral Spreading
Loose sand deposits tend to densify when they are subject to earthquake shaking. For saturated
sand deposits, excess pore water pressure builds up during the earthquake excitation, leading to
loss of strength or liquefaction. After the shaking stops, excess pore water pressures dissipate and
is accompanied by a reconsolidation of the loose sand (Ishihara and Yoshimine, 1992). The
reconsolidation is manifested at the ground surface as vertical settlement, usually referred to as
liquefaction -induced settlement or seismic settlement.
The potential for liquefaction -induced settlement was evaluated based on information presented
in the summary logs for historical borings. The methodologies used to estimate the magnitude of
liquefaction -induced settlements were developed by Boulanger and Idriss (2014). As a result of
liquefaction, settlement at the site associated with the design -level earthquake is anticipated to be
up to 2 inches.
Where soil liquefaction occurs adjacent to slopes and exposed slope faces, lateral spreading can
result in slope instability and flow failures. Based on existing structural and civil drawings of the
existing marina facility provided by CG Engineering, an engineered slope with an approximate
grade of 60 percent is located adjacent to the project site. HWA evaluated lateral spreading for
the 2,475-year design seismic event using methods recommended by Youd et al. (2002). This
analysis indicates that free -field lateral spreading displacement between approximately 2 and 7
inches is possible for the slope to the northwest of the project site.
Port of Edmonds Mobile Office Building
Critical Areas Report 5 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
4.4 GEOLoGic HAZARDS
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The following sections present HWA's conclusions regarding geologic hazards at the project
site.
4.4.1 Landslide Hazard Area
Based on civil engineering drawings and site photos provided by CG Engineering, the area that
has been mapped as a landslide hazard area consists of a slope that is approximately 15 to 20 ft
in height, with grades as steep as about 60 percent. The slope was constructed as part of the
South Marina reconstruction and consists of a concrete bag revetment. This revetment is an
engineered structure that acts similarly to a rip rap slope or a rockery. Chapter 23.80.020.B.4 of
the ECDC excludes engineered rockeries from being designated as landslide hazard areas.
Additionally, HWA is not aware of any evidence of slope instability that has been reported in the
vicinity of the project site. Therefore, it is HWA's opinion that the revetment adjacent to the site
is not a landslide hazard area. It is HWA's opinion that the proposed project will not increase the
risk of landsliding on or off the site.
4.4.2 Erosion Hazard Area
Similar to the mapped landslide hazard area, the area mapped as an erosion hazard area consists
of a concrete bag revetment. While the erosion hazard designation is applicable to this revetment
due to its coastal setting, the slope is located within the marina, which is sheltered from
significant wave action that would be capable of causing erosion. Additionally, the proposed
Mobile Office Building project does not include any changes in grade or impermeable areas. The
project will not increase the surface water discharge of sedimentation to adjacent properties or
into the mapped erosion hazard area. Therefore, it is HWA's opinion that the proposed project
will not increase the extent of erosion on or off the site.
4.4.3 Seismic Hazard Area
As noted previously, the site is underlain by liquefiable soils. HWA's analyses indicate that up to
2 inches of vertical settlement and up to 7 inches of free -field lateral displacement may occur as
a result of a design -level earthquake. The proposed Mobile Office Building measures
approximately 10 feet wide by 30 feet long and will be supported by a metal chassis, similar to a
vehicular trailer. Based on conversations with CG Engineering, this type of structure should be
able to accommodate the anticipated magnitude of horizontal and vertical displacements
described herein without loss of structural integrity. Furthermore, the office will be installed on
existing pavement and will replace an existing structure of similar configuration. The
development does not include grading, excavation, or trenching. Based on the subsurface
conditions and HWA's understanding of the proposed development, it is HWA's opinion that the
seismic hazard due to soil liquefaction will be equal to or less than predevelopment conditions.
Port of Edmonds Mobile Office Building
Critical Areas Report 6 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
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An inferred fault trace of the South Whidbey Island fault zone is mapped approximately 0.25
miles to the north of the project site (USGS, 2024a); however, it is not mapped as crossing the
site. Therefore, the potential for fault rupture at the site is considered to be low.
4.4.4 Responses to Requirements of ECDC 23.80.050 and 23.80.060
Responses to bolded regulations are intended to address the project's consistency with code
requirements for geologically hazardous areas. Items 1 through 4 are intended to address the
requirements of ECDC 23.80.050 and Item 5 is intended to address the requirements of ECDC
23.80.060.
1) Include a discussion of all geologically hazardous areas on the site and any
geologically hazardous areas off site potentially impacted by the proposed project. If
the affected area extends beyond the subject property, the geology hazard
assessment may utilize existing data sources pertaining to that area.
As described in Section 4.3 of this report, the site contains potentially liquefiable soils
and is therefore considered a seismic hazard area. The site is also adjacent to mapped
landslide and erosion hazard areas.
2) Clearly state that the proposed project will not decrease slope stability or pose an
unreasonable threat to persons or property either on or off site and provide a
rationale as to those conclusions based on geologic conditions and interpretations
specific to the project.
As described in Section 3.0 of this report, geologic conditions at the project site were
interpreted based on a review of previous boring log data. Based on HWA's review of
subsurface conditions, the proposed improvements will not decrease slope stability or
pose an unreasonable threat to persons or property either on or off site, provided the
project is constructed per the Structural Plans by CG Engineering, dated January 12,
2024.
3) The hazards analysis shall include a complete discussion of the potential impacts of
seismic activity on the site (for example, forces generated and fault displacement).
Seismic design considerations are discussed in Sections 4.3 and 4.4.3 of this report. Some
of the site soils are considered liquefiable and will be subject to vertical settlement and
lateral displacement during or shortly after a design -level seismic event.
4) A geotechnical engineering report shall evaluate the physical properties of the
subsurface soils, especially the thickness of unconsolidated deposits and their
liquefaction potential. If it is determined that the site is subject to liquefaction,
Port of Edmonds Mobile Office Building
Critical Areas Report 7 HWA GEOSCIENCES INC.
August 23, 2024 DRAFT
HWA Project No. 2024-216-21
mitigation measures appropriate to the scale of the development shall be
recommended and implemented.
As described in Section 3.0 of this report, subsurface conditions at the site were
previously evaluated by Landau (1996) who advanced a series of exploratory borings in
the vicinity of the project site. As described in Section 4.3 and 4.4.3, the site is subject to
liquefaction and lateral spreading. In HWA's opinion, the use of a structure that is
capable of accommodating the anticipated displacements without loss of structural
integrity is adequate mitigation for the hazards at the site. This approach is considered to
be appropriate to the scale of the proposed development.
5) Per Chapter 23.80.060 of the ECDC, alterations of geologically hazardous areas or
associated buffers may only occur for activities that:
b) Will not increase the threat of the geological hazard to adjacent properties
beyond predevelopment conditions.
Based on a review of subsurface conditions at the site and the proposed development
plans, it is HWA's opinion that the project will not increase the threat of the
geological hazard to adjacent properties beyond predevelopment conditions.
c) Will not adversely impact other critical areas.
In HWA's opinion, the proposed improvements will not adversely impact other
critical areas at the site.
d) Are designed so that the hazard to the project is eliminated or mitigated to a
level equal to or less than predevelopment conditions.
Based on a review of subsurface conditions at the site and the proposed development
plans, it is HWA's opinion that the geological hazard to the project will be mitigated
to a level equal to or less than predevelopment conditions.
e) Are certified as safe as designed under anticipated conditions by a qualified
engineer or geologist, licensed in the state of Washington.
This report was prepared and reviewed by qualified geotechnical engineers licensed
in the state of Washington.
5.0 CONDITIONS AND LIMITATIONS
We have prepared this Critical Areas Report for the Port of Edmonds for use in design for the
Mobile Office Building project. The interpretations presented in this report should not be
Port of Edmonds Mobile Office Building
Critical Areas Report 8 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
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construed as our warranty of subsurface conditions at the site. Experience has shown that soil
and groundwater conditions can vary significantly over small distances and with time.
Inconsistent conditions can occur between explorations that may not be detected by a
geotechnical study of this scope and nature.
Within the limitations of scope, schedule, and budget, HWA attempted to execute these services
in accordance with generally accepted professional principles and practices in the fields of
geotechnical engineering and engineering geology in the area at the time the report was prepared.
No warranty, express or implied, is made.
HWA does not practice or consult in the field of safety engineering. We do not direct the
contractor's operations and cannot be responsible for the safety of personnel other than our own
on the site. As such, the safety of others is the responsibility of the contractor. The contractor
should notify the owner if any of the recommended actions presented herein are considered
unsafe.
O.O
We appreciate the opportunity to provide geotechnical services on this project. Should you have
any questions or comments, or if we may be of further service, please do not hesitate to call.
Sincerely,
HWA GEOSCIENCES INC.
Yen Nhi Amy Nguyen, P.E.
Geotechnical Engineer
Port of Edmonds Mobile Office Building
Critical Areas Report
Sean M. Gertz, P.E.
Senior Geotechnical Engineer
HWA GEOSCIENCES INC.
August 23, 2024 DRAFT
HWA Project No. 2024-216-21
6.0 REFERENCES
American Society of Civil Engineers (ASCE) 7-16, Minimum Design Loads and Associated
Criteria for Buildings and Other Structures.
Boulanger, R.W., and Idriss, L M., 2014, CPT and SPT Based Liquefaction Triggering
Procedures, Report No. UCD/CGM-14/01, Center for Geotechnical Modeling,
University of California, David.
City of Edmonds, 2024, Maps/GIS, available at:
https://www.edmondswa.gov/cros/One.aspx?portalId= 16495016&pageld=17255961
Idriss, I.M, and Boulanger, R.W., 2004, Semi -Empirical Procedures for Evaluating Liquefaction
Potential During Earthquakes, presented at the Joint 1 Ith ISCDEE & 3rd ICEGE,
January 2004.
Idriss, I.M., and Boulanger, R.W., 2006, "Semi -empirical procedures for evaluating liquefaction
potential during earthquakes", Soil Dynamics and Earthquake Engineering, 1 Ith
International Conference on Soil Dynamics and Earthquake Engineering (ICSDEE): Part
II, Volume 26, Issues 2-4, February —April 2006, Pages 115-130.
Idriss, I. M., and Boulanger, R. W., 2008, Soil Liquefaction During Earthquakes, Earthquake
Engineering Research Institute (EERI), MNO-12, 226 pp.
International Code Council (IBC), 2021 International Building Code as adopted by the State of
Washington, March 15, 2024.
Ishihara, K., and Yoshimine, M., 1992. Evaluation of settlements in sand deposits following
liquefaction during earthquakes. Soils and Foundations, JSSMFE, Vol. 32, No. 1, March,
pp. 173-188.
Landau Associates, Inc., 1996. Geotechnical Engineering Report. Proposed Port of Edmonds
Dry Stack Boat Storage, Edmonds, WA. Dated March 14, 1996.
Minard, James P., 1983. Geologic Map of the Edmonds East and Part of the Edmonds West
Quadrangles, Washington. Department of the Interior, United States Geological Survey
Miscellaneous Field Studies Map MF-1541, scale 1:24,000.
Seed, H.B. and Idriss, I.M., 1971, Simplified Procedure for Evaluating Soil Liquefaction
Potential. Journal of Soil Mechanics Foundation Division, ASCE, Vol. 97, No. SM9,
pp. 1249-1273.
Port of Edmonds Mobile Office Building
Critical Areas Report 10 HWA GEOSCIENCES INC.
August 23, 2024
HWA Project No. 2024-216-21
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U.S. Geological Survey (USGS), 2024a, Quaternary fault and fold database for the United States,
accessed July 25, 2024, at: https:llwww.usgs.goLlprograms/earthquake-hazards/faults.
U.S. Geological Survey (USGS), 2024b, Unified Hazard Tool, accessed July 25, 2024, at:
https: //earthquake. us��s.govlhazards/interactive%
Youd, T.L. et al., 2001, Liquefaction Resistance of Soils: Summary Report from the 1996
NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of
Soils, Journal of Geotechnical and Geoenvironmental Engineering, Geo-Institute of the
American Society of Civil Engineers (ASCE), Vol. 127, No. 10, October 2001.
Youd, T.L. et al, 2002, Revised Multilinear Regression Equations for Prediction of Lateral
Spread Displacement, Journal of Geotechnical and Geoenvironmental Engineering, Geo-
Institude of the American Society of Civil Engineers (ASCE), Vol 128, No 12, December
2002.
Port of Edmonds Mobile Office Building
Critical Areas Report 11 HWA GEOSCIENCES INC.
APPENDIX A
FIELD EXPLORATIONS BY OTHERS
o°
O
0
CO
v
W
uuuuu
finWnnnnn
\
\
KEY
o Approximate Boring Location
0
0
rn
v
n
�J -
I
♦ I
I
0 00400
Scale - -
Site Map Figure 2
LA ail ;l: ,`,`tit ): 1:\I E.ti. IN(
a�Z
a
MH
Inorganic silt; micoceous or diotomoceous fine sand
Uj
or silty soil
z
C 5 c
SILT AND CLAY
CH
Inorganic clay of high plasticity, fat clay
0
(Liquid Limit greater than 50)
OH
Organic
clay of medium to high plasticity, organic silt
HIGHLY ORGANIC SOIL
PT
Peat; humus; swamp soil with high organic content
OTHER
AC
Pavement; Asphalt or Concrete
Notes: 1. USCS letter symbols correspond to the symbols used by the Unified Sail Classification System and ASTM Classification methods. Dual letter
symbols (e.g., SM—SP) for a sand or gravel indicate a sail with on estimated 5-15% fines. Multiple letter symbols (e.g.,ML/CL) indicate
borderline or multiple sap classifications.
2. Sop classifications are based on the general approach presented in the Standard Practice for Description and Identification of Sm7s
/Visual -Manual Procedure). as outlined in ASTM 02488. Where laboratory index testing has been conducted, sap classifications are based
on the Standard rest Method for Classification of Sons for Engineering Purposes, as outlined in ASTM 02487.
3. Sop description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each sap type and is
defined as follows: Primary Constituent: >50% — 'GRAVEL" 'SAND,' 'SILT,' 'CLAY,' etc.
Secondary Constituents: >30% and S50% — 'very gravelly,' 'very sandy,' 'very silty,' etc.
>15% and S30x — 'gravelly,' 'sandy,' 'silty,' etc.
Additional Constituents: >5% and S15% — "with gravel," 'with sand, with silt," etc.
55% — 'trace gravel,' 'trace sand,' 'trace silt,' etc., or not noted.
Key
SAMPLE NUMBER & INTERVAL
Recovery Depth Interval
Sample
Identification — .1 Sample Depth Interval
Number 1fq-1 Portion of Sample Retained
for Archive or Analysis
TEST DATA
Code Description
GS Grain Size
SAMPLER TYPE
Code
Description
a
3.25—inch O.D., 2.42—inch I.D. Split Spoon Sampler
b
2.00—inch O.D., 1.50—inch I.D. Split Spoon Sampler
c
Shelby Tube
d
Grab Sample
e
3.00—inch I.D. Care Barrel Sampler
1
300—lb Hammer, 30—inch Drop
2
140—lb Hammer, 30—inch Drop
3
Pushed
4
350—lb. Hammer, 30—inch Drop
OTHER
Approximate Water Elevation At T'me of Drilling (AM)
AM or On Date Noted
Soil Classification System and Key
Figure A-1
I..�,:'�I)',t,:%:..It, ?, !,;ri rdr.
�ff
SAMPLE
DATA
SOIL PROFILE
u
m
S
X
!
o
E.
o
Drilling Method: Hollow Stem Auger
_E
Z m
t
>
O
LL
N
aE
N
n
3
n
N
Ground Elevation (it): _Approx. 15
E
E
w
m
U
o
in .d
to
m
(�
j
—0
ACtArSPH:ALT
pavement
GW
�„sandy,
GRAVEL (medium dense, damp
t) (crushed rock base)
1
b2
18
g
Brown, gravelly, SAND to sandy. GRAVEL
with trace wood (medium dense, moist)
(fill)
-5
2
b2
11
10
SP
Gray -brown, fine to medium SAND with
10
scattered gravel and layers of sandy
3
b2
6
gravel and with phase -separated
hydrocarbons (loose, wet)
15 .
4 b2 49
0 -n
Gray, sandy. GRAVEL with phase -separated ATD
hydrocarbons (dense, wet)
!q 0 Light bluish gray, sandy, GRAVEL (very
o
dense, wet)
.0
20 ;0
5 b2 73 0. .
I o
Boring Completed 03/04/96
o Total Depth - 21.5 ft.
25
Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. Refer to the
text for an explanation of subsurface conditions.
2. Refer to 'Soil Classification System and Key' figure for explanation of graphics and symbols.
Boring B-1 Figure A-2
B-2
SAMPLE
DATA
SOIL PROFILE
d
>
�
>
c
X
O
E
c
E.
Drilling Method: Hollow Stem Auoer
-
—
..-
2 is
i
h-•
C
U.
N
r
d
a �
Z.
;
's
V
Q
n
(n
Ground Elevation If t): Approx. 15
m
W—
m
o
a
U
N .e
N
0
Cl
—0
AC
ASPHALT pavement
O
C'W
Brown, sandy, GRAVEL (medium dense, damp
OGP
to moist) (crushed rock basal
1
b2
15
6
O
Brown, sandy, GRAVEL with trace wood bark
0. :
O.'
(medium dense, moist) (fill)
5
SP
-SM
Brown, gravelly, fine, to medium SAND with
2
b2
10
8
some coarse sand and silt (loose, moist) (fill)
oo• Brown -gray, gravelly, SAND to sandy, GRAVEL
10 Oq with trace silt and slight
0 Q
3 b2 10 .O. C hydrocarbon -like odor and sheen
)-o• (loose, wet)
10
064
Sp Brown -gray, gravelly, SAND with trace silt ATTC
(medium dense to dense, wet)
15
4 ]U b2 28 12
20
5 b2 36
0
Boring Completed 03/04/96
j� Total Depth - 21.5 ft.
Q 25
�S
go
O
g
N
O
m
30
W
O
Notes: 1. Slraligraphic contacts are based on field interpretations end are approximate. Refer to the
taxi for an explanation of subsurface conditions.
g 2. Rotor 10 -Soil Classification System and Key- ligure for explanation of prephies and symbols.
Boring B-2 Figure A-3
!_A NI )AU :\.SS0 K'IAj'j-S. INC
B-3
SAMPLE
DATA
SOIL PROFILE
d
Z
m
~
`o
X
a
a
E
E
Drilling Method: Hollow Stem Auger
io
>
O
U.
fn
>,
C
£
a
°� a
w
g
C
fn
Ground Elevation (ft): Approx. 15
m
m
m
c
g
m
in
.6 to
m
0
SJ
HALT pavement.
• O
qGP
n, sandy, GRAVEL (medium dense, damp
tB
10 0oist)
(crushed rock base)
t
b2
21
3
��
Gray -brown, sandy, GRAVEL (medium dense,
DO:
moist) [fill)
5
SO
Gray -brown, line gravelly, SAND (medium
2 f
b2
26
4
dense, moist) (fill)
P
Gray -brown, gravelly, SAND to sandy.
10
"P
GRAVEL with trace silt (medium dense to
3
b2
24
10
dense, wet)
.Q
ATD
15
4
b2
29
20
m
5
b2
44
Boring Completed
03/04/96
Total
Depth
- 21.5 It.
3�
S 25
Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. Rater to the
ctext for an explanation of subsurtace conditions.
a 2. Refer to 'Soil Classification System and Key' tigure for explanation of graphics and symbols.
n
Boring B-3
Figure A-4
B-4
SAMPLE DATA
SOIL PROFILE
d
E
�
n
a
c
r
d
o
E
0
�
Drilling Method: Hollow Stem Auger
r
Z ;
~
l0
p
N
n
d•
E S
d
E
\
3
m
U
n
N
Ground Elevation (ft): Approx. 15
co
co
C
N .a
N
Co
—0
AC
ASPHALT pavement
Gw
• O
GP
Brown, sandy, GRAVEL (medium dense, damp
0:
to moist) .(crushed rock base)
1
b2
32
3
SP
Brown and gray -brown, sandy, GRAVEL with
some wood (medium dense, moist) (fill)
_ 5
2.1
b2
35
4
Gray, gravelly, SAND (dense, moist) (fill)
-10
3
b2
8
18
SP
-SM
Gray, gravelly, fine to medium SAND with
some coarse sand, trace to some silt, and
trace shell fragments (loose to dense,
wet)
ATD
t5
4 ]U b2 75
20
5 b2 1 70
m
jo
Q 25
a
8
N
0
m
a . 30
W
0
E
0
0
n
LEI
Light brown -gray, sandy, GRAVEL with silt
(very dense, wet)
Boring Completed 03/04/96
Total Depth = 21.5 ft.
Notes: 1. Stratigraphic contacts are based on field' interpretations and are approximate. Refer to the
text for an explanation of subsurface conditions.
2. Refer to 'Soil Classification System and Key- figure for explanation of graphics and symbols.
Boring B-4
Figure A-5
!_„\*1)A 'A.. SOCiA:rla. IN(.
•
B-5
SAMPLE DATA
SOIL PROFILE
Et a1
E o.
f-
o
X
ry
c
O
E
Do
E>
Drilling Method: Hollow Stem Auper
—
_ Z m
o
w
N
9`
£ o c n
\
3
g
U
n
to
Ground Elevation (it): Approx. 15
d m— m
O N .d N
o
m
w
(y
U
j
0
kACA
ASPHALT pavement
GW
"
Brown, sandy, GRAVEL (medium dense, damp
]b226
O
GW
to moist) (crushed rock base)
SP=Brownssand�y.
1
4
GRAVEL (medium dense, damp
5
Brown -gray, gravelly, SAND (medium dense,
2 b2
25
5
moist) (lilt)
SP
Brown -gray, line to medium SAND with some
coarse sand and gravel (medium dense, damp
to moist) (fill)
10
SP
Brown -gray, gravelly, SAND with trace silt
(medium dense to very dense, wet)
3 b2
57
g
Q
ATD
15
4 b2
19
20
If b2
33
12
25
6 b2
37
c�
Boring
Completed
03/04/96
H
Total.Depth
: 26.5
It.
Notes: 1. Slratigraphic contacts are based on field interpretations and are approximate. Refer to the
utaxi for an explanation of subsurface conditions.
2. Refer to -Soil Classification System and Key- figure for explanation of graphics and symbols.
n
Boring B-5
Figure A-6
'L1'l L.S. 1:1;C.
SAMPLE
DATA
SOIL PROFILE
d
>
�
CL
>
G
X
O
E
Drilling Method: _Hollow Stem Auger
Z i
~
li
N
N
t
d Zi
Q_
m`
n
�
3
d
*,
u
C
N
Ground Elevation (ft): Approx. 15
4)CL
m—
m
o
m
U
0
N .a
N
m
ty
j
—0'
AC
ASPHALT pavement
'
GW
SP
Brown, sandy, GRAVEL (medium dense, damp
to moist) (crushed rock base)
1
b2
35
6
Brown -gray, fine to medium SAND with some
coarse sand and gravel and trace shell
fragments Idense, damp to moist) (fill)
-5
2
b2
25
4
OG Gw Brown, sandy. GRAVEL with trace silt
10
� ;;0• (loose, wet) Ifill?)
,q•
•pp
3 ]U b2
4
q ��
b. ATD
i
b• GP Brown, sandy, GRAVEL with trace sill
15
O• (vary dense, wet)
4
b2
77 O
0 Op
I
.0.
SP Gray -brown to brown, sandy. GRAVEL with
trace sill Idense, wet)
20
5
b2
43 12 ...
i
f
o
25
6
b2
50
9
Boring Completed 03/04/96
N
Total Depth 26.5 ft.
Y7
30
i
W
O
a
I
o
a
Notes: 1.
Siratigraphic contacts are based on field interpretations and are ap
proximate. pproximata. Relar to the
text for an explanation of subsurlace conditions.
a
2.
Rater to 'Soil Classification System and Key' figure for explanation of graphics and symbols.
i
Boring B-6
Figure A-7
i
LANDAU A55(K'I:' F{ . INN.
APPENDIX B
LABORATORY TESTING BY OTHERS
10 P.
100
90
80
t
on 70
60
50
i�
40
a�
U
ai 30
o-
20
10
0
10V
of Edmonds
12'
Storoge/Geotech. Report (A) 3/96
U.S. Standard Sieve Size
3' 1-1/2' 3/4' 1/2' 3/8' 1/4' 4 810 16 9n vt en Sn Fn inn un )nn
uu 10 1.0 0.1 0.01 0.001
Grain Size in Millimeters
Boulders Cobbles Grovel Sond
Coarse Fine Coorsel Medium Fine Silt or Cloy
Groin Size Curves
Figure A-8
,.e
•
10 P,N.&D/Port of
L
70
60
L
c 50
i.�
40
a)
v
a 30
rl
20
10
0
10
12. U.S.
3' 1-1/2' 3/4' 1/2*3/8* 1/4' 4 RS�tondardSie
ve A cn en
-- iv 1.0 0.1
Groin Size in Millimeters
Boulders Cobbles Grovel Sand
Course Fine Coarse Medium Fine
VQ1I Grain Size Curves
0.01
Silt or Cloy
• M
Figure A-9
0