Critical Area Notice of Decision.pdfCity of Edmonds
Critical Area Notice of Decision
Applicant: Property Owner:
#: I Permit Number: Ir I.
Site Location: Parcel Number:
Project Description:
Conditional Waiver. No critical area report is required for the project described above.
1. There will be no alteration of a Critical Area or its required buffer.
2. The proposal is an allowed activity pursuant to ECDC 23.40.220, 23.50.020, and/or
23.80.040.
3. The proposal is exempt pursuant to ECDC 23.40.230.
Erosion Hazard. Project is within erosion hazard area. Applicant must prepare an erosion and
sediment control plan in compliance with ECDC 18.30.
T Critical Area Report Required. The proposedproject is within a critical area and/or a critical area
/ buffer and a critical area report is required. A critical area report has been submitted and evaluated
for compliance with the following criteria pursuant to . C1 C'23.40�.1,60:
1. V/ The proposal initfli tines the impact on criticM areas in accordance with ECDC 23.40.120,
Mitigation sequencing;
2. ✓ The proposal does not pose an unreasonable threat to the public health, safety, or welfare
j on or off the development proposal site;
3. ✓ The, proposal is consistent with the general, purposes of this title and the public interest;
4. Any alterations permitted to the critical area are mitigated in accordance with ECDC
23.40.110, Mitigation requirements.
5. _ZThe proposal protects the critical area functions and values consistent with the best
/,available science and results in no net loss of critical functions and values; and
6. The proposal is consistent with other applicable regulations and standards.
❑ Unfavorable Critical Area Decision. The proposed project is not exempt or does not adequately
mitigate its impacts on critical areas and/or does not comply with the criteria in ECDC 23.40.160 and
the provisions of the City of Edmonds critical area regulations. See attached findings of
noncompliance.
Favorable Critical Area Decision. The proposed project as described above and as shown on the
attached site plan meets or is exempt from the criteria in ECDC 23.40.160, Review Criteria, and
complies with the applicable provisions of the City of Edmonds critical area regulations. Any
subsequent changes to the proposal shall void this decision pending re -review of the proposal.
�] Conditions. Critical Area specific condition(s) have been applied to the permit number referenced
l above. See referenced permit number for specific condition(s).
9 Notice on Title. Critical area notice on title recorded under AFN *20I105�tyOCL525.
Appeals: Any decision to approve, condition, or deny a development proposal or other activity based on the
requirements of critical area regulations maybe appealed according to, and as part of, the appeal procedure, if any,
for the permit or approval involved.
Revised 11/29/2016
April 10, 2017
Project No. 150499EO01
Mr. Mark Bailey
101512 th Avenue North
Edmonds, Washington 98020
a s s o c i e t e d
earth sciences
i r -, c o r p o r x t e d
Subject: Geotechnical Consultation
Slope Tree Removal Assessment
Bailey Residence
101512 th Avenue North
Edmonds, Washington
Dear Mr. Bailey:
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APR 13 2017
11VELIPMENT
COUNTER
As requested, this letter provides our opinion regarding proposed tree removal at your property
located at 1015 12th Avenue North in Edmonds, Washington. We have previously prepared a
"Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report — Bailey
Residence", dated May 6, 2016, for the proposed slope and settlement mitigation project at the
subject site. Based on our correspondence with Mr. Chad Wichers of Studio 342, we understand
that you wish to remove three maple trees, a cedar tree, a cherry tree, and a Japanese camellia
from the slope to the west of the residence, and that the City of Edmonds has requested a
geotechnical opinion addressing slope stability and erosion control when these specific trees are
removed.
Site Observations
The subject site is a single-family residential parcel located at 1015 12th Avenue North in
Edmonds, Washington. The ground surface at the subject site is generally moderately sloping,
with steeply -sloping ground leading downward to the west beyond the property line. The
existing residence is a one-story structure with a daylight basement that opens to the west. A
series of low retaining walls, including both rock and timber walls, facilitates a portion of the
grade change between the subject site and the property to the west.
The slope along the western portion of this property is in excess of 40 percent with greater
than 10 feet of vertical relief. As such, it is considered a Landslide Hazard Area by the City of
Edmonds. The site has been subject to past grading, including the placement of fill out over
the rear yard area likely during the original construction of the residence. One objective of the
currently proposed project is to improve rear yard stability along the top of the western slope
through the placement of a retaining wall designed to current standards.
Review of the regional geologic map titled Geologic Map of the Edmonds East and part of the
Edmonds West Quadrangles, by J.P. Minard (1983) indicates that the area of the subject site is
underlain by Vashon advance outwash deposits (Qva), with Vashon lodgement till (Qvt) mapped
Kirkland Office 1911 Fifth Avenue I Kirkland, WA 98033 P 1425.827.7701 FI 425.827.5424
Everett Office 12911 Y. Hewitt Avenue, Suite 2 1 Everett, WA 98201 P 1425.259.0522 F 1 425.827.5424
Tacoma Office 11552 Commerce Street, Suite 102 1 Tacoma, WA 98402 P 1253.722.2992 F 1253.722.2993
www.aesgeo.com
nearby. Our interpretation of the sediments encountered during the explorations completed as
part of our 2016 study was in general agreement with the Vashon lodgement till (Qvt) mapped in
the area.
Conclusions
Based on our site observations and upon review of the above-mentioned information, it is our
opinion that the proposed tree removal can be completed without a long-term decrease in the
stability of the subject slope. We recommend that the trunk and limbs be removed from the
slope in a manner to minimize ground disturbance (e.g., using a crane). Tree stumps should be
left in place to provide support to surface soils. In our 2016 report, we stated "To the extent
possible, we recommend that native vegetation be left on the slope to provide erosion control."
Therefore, the slope should be replanted as soon as possible with landscaping trees and
shrubs, as desired, and the disturbed ground surface mulched to mitigate erosion. Irrigation of
the vegetation should be limited to prevent excessive saturation of the slope and potential soil
movement.
Limitations
This letter has been prepared for, and limited to, the evaluation of the proposed tree removal.
Our conclusions and recommendations have been prepared in accordance with generally
accepted professional engineering and geologic principles and practices. We make no other
warranty, either express or implied. Our conclusions are based on the results of our
interpretation of surface conditions. If subsurface conditions are encountered that appear to be
different than those described in this report, we should be notified so that we may review and
verify or modify our recommendations.
Closure
We hope this information meets your present needs. If there are any further questions, feel free
to contact the undersigned at (425) 827-7701.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
µ
Jeffrey P. La , L.G., L.E.G.
Senior Project Engineering Geologist
J PL/pc-15499E001-3 — Projects\20150499\KE\W P
2
Bruce L. Blyton, P.E.
Senior Principal Engineer
o c i a t e
Ow"03
r t h s c i
i n c c r p o r a t e d
Subsurface Exploration, Geologic Hazard,
and Geotechnical Engineering Report
BAILEY RESIDENCE
Edmonds, Washington
Prepared For:
MR. MARK BAILEY
Project No. KE150499A
May 6, 2016
M;
a a s o o G a t e d
Ir t s c e n
May 6, 2016
Project No. KE150499A
Mr. Mark Bailey
101512 th Avenue North
Edmonds, Washington 98020
Subject: Subsurface Exploration, Geologic Hazard,
and Geotechnical Engineering Report
Bailey Residence
1015 12th Avenue North
Edmonds, Washington
Dear Mr. Bailey:
We are pleased to present the enclosed copies of the above -referenced report. This report
summarizes the results of our subsurface exploration, geologic hazard, and geotechnical
engineering studies, and offers recommendations for the design and development of the
proposed project.
We have enjoyed working with you on this study and are confident that the
recommendations presented in this report will aid in the successful completion of your
project. If you should have any questions, or if we can be of additional help to you, please do
not hesitate to call.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
Bruce 1. Blyton, P.E.
Senior Principal Engineer
BLB/Id
KE150499A2
Projects\20150499\KE\WP
Kirkland Office 1911 Fifth Avenue I Kirkland, WA 98033 P 1425.827.7701 FI 425.827.5424
Everett Office 1 2911 %: Hewitt Avenue, Suite 2 1 Everett, WA 98201 P 1425.259.0522 F 1425.827.5424
Tacoma Office 1 1552 Commerce Street, Suite 102 1 Tacoma, WA 98402 P 1253.722.2992 F 1253.722.2993
www.aesgeo.com
SUBSURFACE EXPLORATION, GEOLOGIC HAZARD,
AND GEOTECHNICAL ENGINEERING REPORT
Edmonds, Washington
Prepared for:
Mr. Mark Bailey
1015 12th Avenue North
Edmonds, Washington 98020
Prepared by:
Associated Earth Sciences, Inc.
9115th Avenue
Kirkland, Washington 98033
425-827-7701
Fax: 425-827-5424
May 6, 2016
Project No. KE150499A
Subsurface Exploration, Geologic Hazard,
Bailey Residence and Geotechnical Engineering Report
Edmonds, Washington Proiect and Site Conditions
1. PROJECT AND SITE CONDITIONS
1.0 INTRODUCTION
This report presents the results of our subsurface exploration, geologic hazard, and
geotechnical engineering study for the proposed slope and settlement mitigation project. The
location of the site is shown on the "Vicinity Map," Figure 1, and the locations of the
explorations accomplished for this study are presented on the "Site and Exploration Plan,"
Figure 2. In the event that any changes in the nature, design, or location of the structures are
planned, the conclusions and recommendations contained in this report should be reviewed
and modified, or verified, as necessary.
The purpose of this study was to provide subsurface data to be utilized in the design and
development of the subject project. Our study included a review of available geologic and past
project literature, drilling three exploration borings, and performing geologic studies to assess
the type, thickness, distribution, and physical properties of the subsurface sediments and
shallow ground water conditions. Geologic hazard evaluations and geotechnical engineering
studies were also conducted to select the type of retaining system, lateral earth pressures, and
drainage considerations. This report summarizes our current fieldwork and development
recommendations based on our present understanding of the project.
1.2 Authorization
Written authorization to proceed with this study was granted by Mr. Mark Bailey. Our study
was accomplished in general accordance with our scope of work letter dated August 26, 2015.
This report has been prepared for the exclusive use of Mr. Mark Bailey and his agents for
specific application to this project. Within the limitations of scope, schedule, and budget, our
services have been performed in accordance with generally accepted geotechnical engineering
and engineering geology practices in effect in this area at the time our report was prepared. No
other warranty, express or implied, is made. Our observations, findings, and opinions are a
means to identify and reduce the inherent risks to the owner.
The subject site is a single-family residential parcel located at 1015 12th Avenue North in
Edmonds, Washington. The ground surface at the subject site is generally moderately sloping,
with steeply -sloping ground leading downward to the west beyond the property line. The
existing residence is a one-story structure with a daylight basement that opens to the west. A
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series of low retaining walls, including both rock and timber walls, facilitates a portion of the
grade change between the subject site and the property to the west. Portions of the west side
of the main residential structure, along with paved surfacing to the west of the residence,
display signs of settlement. Also, a portion of the western foundation stemwall is bulging
outward. Surficial soil erosion is apparent along the slope west of the residence.
We understand that you wish to address the problem to mitigate future significant impacts to
the structures, and that the currently -proposed mitigations may include the underpinning of
portions of the existing residence or the construction of a retaining wall at the top of the slope
to the west of the residence.
3.0 SITE EXPLORATION
The site exploration was conducted on November 11, 2015, and consisted of three exploration
borings and a geologic and geologic hazard reconnaissance to gain information about the site.
The various types of materials and sediments encountered in the explorations, as well as the
depths where characteristics of these materials changed, are indicated on the exploration
boring logs presented in the Appendix. The depths indicated on the logs where conditions
changed may represent gradational variations between sediment types in the field. If changes
occurred between sample intervals in our borings, they were interpreted. The locations of the
exploration borings are shown on the "Site and Exploration Plan," Figure 2.
The conclusions and recommendations presented in this report are based on the exploration
borings completed for this study. The number, locations, and depths of the explorations were
completed within site and budgetary constraints. Because of the nature of exploratory work
below ground, interpolation of subsurface conditions between field explorations is necessary.
It should be noted that differing subsurface conditions may sometimes be present due to the
random nature of deposition and the alteration of topography by past grading and/or filling.
The nature and extent of any variations between the field explorations may not become fully
evident until construction. If variations are observed at that time, it may be necessary to
re-evaluate specific recommendations in this report and make appropriate changes.
,ir r �N ^�
The borings were completed on the property using a hand -portable drill rig advancing a
3.75 -inch, inside -diameter, hollow -stem auger. During the drilling process, samples were
obtained at generally 2.5- or 5 -foot intervals. The borings were continuously observed and
logged by an engineer from our firm. The exploration logs presented in the Appendix are based
on the field logs, drilling action, and inspection of the samples secured.
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Disturbed but representative samples were obtained by using the Standard Penetration Test
(SPT) procedure in accordance with American Society for Testing and Materials (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 attached boring logs.
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 soil and ground water elevations, as well as the depths where soil and
ground water characteristics changed, are indicated on the exploration boring logs presented in
the Appendix of this report. Our explorations and reconnaissance were approximately located
by measuring from known site features.
4.0 SUBSURFACE CONDITIONS
Subsurface conditions at the project site were inferred from the field explorations
accomplished for this study, visual reconnaissance of the site, and review of applicable geologic
literature. As shown on the exploration logs, the exploration borings generally encountered
consolidated, granular, glacial sediments overlain by fill. The following section presents more
detailed subsurface information organized from the youngest to the oldest sediment types.
4.1 Stratigraphy
Fill
Fill (soils not naturally placed) soils were encountered at the locations of our exploration
borings to depths ranging from approximately 5 to 7% feet below the ground surface. The fill
generally consisted of loose, fine to medium sand with varying amounts of silt and gravel.
Portions of the fill contained organic material and woody debris. Fill is also expected in
unexplored areas of the site, such as the area surrounding and under existing structure
foundations, in utility trenches, and in the existing paved and landscaped areas. Due to their
variable density and organic content, the existing fill soils are not suitable for foundation
support.
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Vashon Lodgement Till
Sediments encountered below the fill at the locations of exploration borings E13-1 through E13-3
generally consisted of medium dense silty sand with gravel. These sediments were observed to
generally become dense to very dense below depths of approximately 2 to 4 feet below the
bottom of the overlying fill. We interpret these sediments to be representative of Vashon
lodgement till. The Vashon lodgement till was deposited directly from basal, debris -laden
glacial ice during the Vashon Stade of the Fraser Glaciation approximately 12,500 to 15,000
years ago. The reduced density observed within 2 to 4 feet of the overlying fill is interpreted to
be due to weathering. The high relative density of the unweathered till is due to its
consolidation by the massive weight of the glacial ice from which it was deposited. At the
locations of exploration borings E13-1 through E13-3, the till extended beyond the maximum
depths explored.
Review of the regional geologic map titled Geologic Map of the Edmonds East and part of the
Edmonds West Quadrangles, by J.P. Minard (1983) indicates that the area of the subject site is
underlain by Vashon advance outwash deposits (Qva), with Vashon lodgement till (Qvt)
mapped nearby. Our interpretation of the sediments encountered at the subject site is in
general agreement with the Vashon lodgement till (Qvt) mapped in the area.
Ground water was not encountered in the exploration borings. We also did not observe ground
water emanating from the slope. We expect ground water seepage across much of the site to
be limited to interflow. Interflow occurs when surface water percolates down through the
surficial weathered or higher -permeability sediments and becomes perched atop underlying,
lower -permeability sediments. It should be noted that the occurrence and level of ground
water seepage at the site may vary in response to such factors as changes in season,
precipitation, and site use.
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II. GEOLOGIC HAZARDS AND MITIGATIONS
The following discussion of potential geologic hazards is based on the geologic conditions, as
observed and discussed herein.
The slope along the western portion of this property is in excess of 40 percent with greater than
10 feet of vertical relief. As such, it is considered a Landslide Hazard Area by the City of
Edmonds. The site has been subject to past grading, including the placement of fill out over the
rear yard area likely during the original construction of the residence. One objective of the
currently proposed project is to improve rear yard stability along the top of the western slope
through the placement of a retaining wall designed to current standards. The following
paragraphs discuss the stability of the slopes and recommendations to mitigate risks to the
public health, safety, or welfare. It must be understood that no recommendations or
engineering design can yield a guarantee of stable slopes. Our observations, findings, and
opinions are a means to identify and reduce the inherent risks to the owner.
5.1 Slope Stability Assessment
Associated Earth Sciences, Inc. (AESI) used GeoStudio 2007, Version 7.17, by Geo -Slope
International, Ltd. to perform the analysis of slope stability with the proposed retaining wall.
The Morgenstern -Price method was used for both static and seismic models. The 2012
International Building Code (IBC) seismic design parameter for peak ground acceleration (PGA)
was determined by the latitude and longitude of the project site using the U.S. Geological
Survey (USGS) National Seismic Hazard Mapping Project websites. The USGS website
interpolated PGA at the project site to be 0.538, with a 2 percent chance of exceedance in
50 years. Seismic stability modeling included a horizontal seismic coefficient of 0.265g.
We used the topography presented on a "Boundary and Topographic Survey," prepared by
Greene Land Surveying and dated April 3, 2016, to create a profile through the subject parcel.
A graphical representation of the cross-section we used for input is presented on Figure 3.
Surcharges used for our analysis included 500 pounds per square foot (psf) to represent the
existing residence. Data from the subsurface explorations performed for this study were used
to model the steep slope and underlying soil contacts. The soil densities and other soil
properties in the model were estimated based on SPT blow counts from our explorations, our
experience with similar soils, and correlation with published information. Soil strength
parameters used for our analysis included a 36 -degree friction angle for the native Vashon
' http://earthquake.usgs.gov/hazmaps/
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Edmonds, Washington Geologic Hazards and Mitigations
lodgement till, 32 degrees for weathered Vashon lodgement till, and 30 degrees for the fill
encountered in our explorations. Our slope stability analysis evaluated the risk of deep-seated
landslides extending through the underlying Vashon lodgement till deposits and below the
approximate location of the proposed retaining wall.
Slope stability is expressed as a factor of safety, which is a ratio between resisting and driving
forces for a given slope failure scenario. A factor of safety of 1.0 indicates that resisting and
driving forces are equal, and a failure is predicted. Factors of safety greater than 1 indicate that
resisting forces exceed driving forces, and a failure is not predicted. City of Edmonds standards
call for minimum slope stability factors of safety of 1.5 under static conditions and 1.2 under
simulated seismic conditions.
Using the above soil parameters and the geometry shown on Figure 3, the resulting factors of
safety meet or exceed the recommended minimum values of 1.2 under seismic conditions and
1.5 under static conditions. Based on our analyses, the proposed construction of a retaining
wall at the approximate location shown on Figure 2 appears feasible from a geotechnical
standpoint provided the wall is designed as a retaining wall with sufficient embedment to
provide the factors of safety predicted by our model.
The near -surface soil underlying the area along the western slope consists primarily of a zone of
loose fill overlying dense to very dense glacial deposits. Due to the loose nature of the fill soils
encountered in our explorations, it is our opinion that the improvements on the site should
include the use of a retaining wall with a deep foundation system, such as embedded soldier
piles. To the extent possible, we recommend that native vegetation be left on the slope to
provide erosion control.
As with all steep slopes, surface drainage should be properly controlled and directed away from
sloping areas. At no time should loose fill be pushed over the top of the slope or soil excavated
from the toe area without support by an engineered retaining structure. Uncontrolled fill on
slopes or toe excavation may promote landslides or debris flow activity. AESI should review
grading plans if grading is desired at the top of, on, or near the toe of the steep slope.
6.0 SEISMIC HAZARDS AND MITIGATION
Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these
events are small and are usually not felt by people. However, large earthquakes do occur, as
evidenced by the 1949, 7.2 -magnitude event; the 1965, 6.5 -magnitude event; and the 2001,
6.8 -magnitude event. The 1949 earthquake appears to have been the largest in this area during
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Edmonds, Washington Geologic Hazards and Mitigations
recorded history. Evaluation of return rates indicates that an earthquake of a magnitude
between 6.0 and 7.0 is likely within a given 25- to 40 -year period.
Generally, there are four types of potential geologic hazards associated with large seismic
events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and
4) ground motion. The potential for each of these hazards to adversely impact the proposed
project is discussed below.
6*1 Surficial Ground Rupture
The nearest known fault trace to the project site is the South Whidbey Island Fault Zone
(SWIFZ). A recent study by USGS (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) indicates that "strong" evidence of
prehistoric earthquake activity has been observed along associated fault strands thought to be
part of the SWIFZ. The study suggests as many as nine earthquake events along the SWIFZ may
have occurred within the last 16,400 years. The recognition of this fault splay is relatively new,
and data pertaining to it are limited, with the studies still ongoing. The recurrence interval of
movement along this fault system is still unknown, although it is hypothesized to be in excess of
1,000 years. Due to the suspected long recurrence interval, it is our opinion that the potential
for damage to the proposed wall and existing residence by surficial ground rupture is
considered to be low. No mitigations other than complying with 2012 IBC seismic design
recommendations are recommended.
.«lmllffllm
Our slope stability modeling has included "pseudostatic" analyses that incorporate loads
associated with an earthquake. Slope stability analyses and results are described in further
detail in the "Landslide Hazards and Mitigation" section of this report.
6.3 Liquefaction
The encountered stratigraphy has a low potential for liquefaction due to its dense state and
lack of adverse ground water conditions. No mitigation of liquefaction hazards is warranted.
6.4 Ground Motion
Design of the structures should follow 2012 IBC standards using Site Class "C" as defined in
Table 20.3-1 of American Society of Civil Engineers (ASCE) 7 — Minimum Design Loads for
Buildings and Other Structures.
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7.0 EROSION HAZARDS AND MITIGATION
A properly developed, constructed, and maintained erosion control plan consistent with City of
Edmonds standards and best management erosion control practices will be required for this
project. AESI is available to assist the project civil engineer in developing site-specific erosion
control plans. Based on past experience, it will be necessary to make adjustments and provide
additional measures to the Temporary Erosion and Sedimentation Control (TESC) plan in order
to optimize its effectiveness. Ultimately, the success of the TESC plan depends on a proactive
approach to project planning and contractor implementation and maintenance.
Due to the steep slope present within the site, we expect that grading will be restricted to the
dry season without a waiver granted by the City of Edmonds. The recommendations presented
in this section are intended to address grading activities during both the dry and wet seasons.
To mitigate the erosion hazards and potential for off-site sediment transport, we would
recommend the following:
1. The erosion hazard of the site soils is relatively low in the flat -lying areas and moderate
to high on the steep slopes. Maintaining cover measures atop disturbed ground
provides a significant reduction to the potential generation of turbid runoff and
sediment transport. During the local wet season (October 1st through March 31St),
exposed soil should not remain uncovered for more than 2 days unless it is actively
being worked. Ground -cover measures can include erosion control matting, plastic
sheeting, straw or wood mulch, crushed rock or recycled concrete, or mature
hydroseed. The contractor must implement and maintain the required measures.
2. All TESC measures for a given area to be graded or otherwise worked should be installed
prior to any construction activity.
3. Construction access points should be surfaced to mitigate sediment track -out onto
adjacent streets. Any sediment that is tracked onto adjacent streets should be promptly
swept up.
4. Silt fencing should be utilized as buffer protection and not as a flow -control measure.
Silt fencing should be placed parallel with topographic contours to prevent
sediment -laden runoff from leaving a work area or entering a sensitive area. Silt fences
that cross contour lines should have separate flow control in front of the silt fence. A
swale/berm combination should be used to provide flow control.
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5. During the wetter months of the year, or when large storm events are predicted during
the summer months, each work area should be stabilized so that if showers occur, the
work area can receive the rainfall without excessive erosion or sediment transport. The
required measures will depend on the time of year and the duration the area will be left
unworked. During the winter months, areas that are to be left unworked for more than
2 days should be mulched or covered with plastic. During the summer months,
stabilization will usually consist of seal -rolling the subgrade.
6. All disturbed areas should be revegetated as soon as possible. If it is outside of the
growing season, the disturbed areas should be covered with mulch. Straw mulch
provides an effective cover measure and can be made wind -resistant with the
application of a tackifier after it is placed.
7. Surface runoff and discharge should be controlled during and following development.
Uncontrolled discharge may promote erosion and sediment transport. Under no
circumstances should concentrated discharges be allowed to flow over the top of steep
slopes.
8. Soils that are to be reused around the site should be stored in such a manner as to
reduce erosion from the stockpile. Protective measures may include, but are not limited
to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of
straw bales/silt fences around pile perimeters. During the period between October 311t
and March 3111, these measures are required.
It is our opinion that with the proper implementation of the TESC plans and by field -adjusting
appropriate mitigation elements (best management practices) during construction, the
potential adverse impacts from erosion hazards on the project may be mitigated.
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Edmonds, Washinqton Desian Recommendations
III. DESIGN RECOMMENDATIONS
8.0 INTRODUCTION
Our exploration indicates that, from a geotechnical standpoint, the parcel is suitable for the
proposed project provided the risks discussed are accepted and the recommendations
contained herein are properly followed. It is our opinion that the proposed soldier pile
retaining wall system should provide mitigation for the risk of local shallow landsliding along
the upper portion of the western slope face, relative to the existing condition.
To mitigate the risk of future settlement for the western portion of the residence, we
recommend that the affected footings of the house be underpinned. We recommend that a
floor survey be completed to evaluate the extent and degree of settlement within the existing
structure. This information will aid the structural engineer in designing the pile layout for
underpinning of existing structures. The extent of the underpinning should include the exterior
continuous foundation and the isolated interior column pads, if present. Footings that are not
underpinned (such as the isolated piers) should be considered to be at risk of future settlement
and damage due to differential settlement. The underpinning would connect to the existing
footings and penetrate through the loose fill and into the competent, Vashon lodgement till
bearing soils at depth.
9.0 SITE PREPARATION
Site preparation of the planned wall alignment should include removal of all trees, brush,
debris, and any other deleterious materials in the immediate construction zone.
Tree/vegetation removal should be kept to the minimum required for site access and
construction with small equipment. These unsuitable materials should be properly disposed of.
Additionally, any areas of organic topsoil should be removed and the remaining roots grubbed.
Areas where loose surficial soils exist due to grubbing operations should be considered as fill to
the depth of disturbance and treated as subsequently recommended for structural fill
placement. Any buried utilities should be removed or relocated if they are under building
areas. The resulting depressions should be backfilled with structural fill, as discussed under the
"Structural Fill" section of this report.
In our opinion, stable construction slopes should be the responsibility of the contractor and
should be determined during construction based on the local conditions encountered at that
time. For planning purposes, we anticipate that temporary, unsupported cut slopes in the loose
to medium dense fill or weathered till sediments can be made at a maximum slope of 1.5H:1V
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Edmonds, Washington Design Recommendations
(Horizontal:Vertical). For temporary cut slopes within the dense to very dense, unweathered
till, up to a 1H:1V inclination may be planned. We recommend that temporary cuts be limited
to 4 feet or less in vertical height to reduce the risk posed by sloughing of surficial fill soils.
We anticipate that a minor of amount of cutting and filling will be needed to create an access
road for equipment used for retaining wall installation. We recommend that this grading be
kept to the least practical degree to allow access for small -tracked machines. Also, we
recommend that fills for the access road be comprised of "hog fuel' wood chips, which can be
incorporated as a mulch into the existing site soils subsequent to construction of the retaining
walls. This practice will promote revegetation of areas disturbed by grading activities during
access road construction. Alternatively, washed crushed rock may be used for access surfacing.
As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes
may have to be adjusted in the field. Flatter, temporary cut slopes should be anticipated in
areas of ground water seepage. In addition, WISHA/OSHA regulations should be followed at all
times.
10.0 STRUCTURAL FILL
Structural fill may be necessary to establish desired grades for hard surfaces or to backfill
around foundations and utilities, or behind the proposed wall. All references to structural fill in
this report refer to subgrade preparation, fill type, placement, and compaction of materials, as
discussed in this section. If a percentage of compaction is specified under another section of
this report, the value given in that section should be used.
After overexcavation/stripping has been performed to the satisfaction of the geotechnical
engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted
to a firm and unyielding condition. If the subgrade contains too much moisture, adequate
recompaction may be difficult or impossible to obtain and should probably not be attempted.
In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry
spalls to act as a capillary break between the new fill and the wet subgrade. Where the
exposed ground remains soft and further overexcavation is impractical, placement of an
engineering stabilization fabric may be necessary to prevent contamination of the free -draining
layer by silt migration from below.
After stripping and subgrade preparation of the exposed ground is approved, or a free -draining
rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined
as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8 -inch loose
lifts, with each lift being typically compacted to 95 percent of the modified Proctor maximum
density using ASTM D-1557 as the standard. For structural fill placed as backfill behind the
proposed wall alignments, a standard of 90 percent of the modified Proctor maximum density
using ASTM D-1557 may be used.
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Edmonds, Washington Design Recommendations
The contractor should note that any proposed fill soils must be evaluated by AESI prior to their
use in fills. This would require that we have a sample of the material 72 hours in advance to
perform a Proctor test and determine its field compaction standard. Soils in which the amount
of fine-grained material (smaller than the No. 200 sieve) is greater than approximately
5 percent (measured on the minus No. 4 sieve size) should be considered moisture -sensitive.
Use of moisture -sensitive soil in structural fills should be limited to favorable dry weather and
dry subgrade conditions. In addition, construction equipment traversing the site when the soils
are wet can cause considerable disturbance. The on-site soils contained variable amounts of
silt and are considered moisture -sensitive, and we expect that this material may be difficult to
compact to structural fill specifications, particularly during and following wet weather.
Alternatively, we recommend that a select, import material consisting of a clean, free -draining
gravel and/or sand be used. Free -draining fill consists of non-organic soil with the amount of
fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve
fraction.
A representative from our firm should inspect the stripped subgrade and be present during
placement of structural fill to observe the work and perform a representative number of
in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling
progresses and any problem areas may be corrected at that time. It is important to understand
that taking random compaction tests on a part-time basis will not assure uniformity or
acceptable performance of a fill. As such, we are available to aid the owner in developing a
suitable monitoring and testing frequency.
11.0 FOUNDATIONS
Based on the soil conditions encountered in our explorations, we recommend that the footings
along the west side of the residence which display signs of settlement, along with other
settlement -sensitive ancillary structures in the backyard area, be supported by a deep
foundation, such as small -diameter, driven pipe piles. The piles should consist of
2 -inch -diameter, Schedule 80 pipe driven to refusal in the medium dense to dense site soils.
For pipe piling driven to refusal, we recommend using an allowable bearing capacity of
4,000 pounds per pile. Refusal is defined as less than 1 inch of vertical movement after
60 seconds of sustained driving with a 90 -pound jack hammer. Resistance to lateral loads for a
pipe pile -supported foundation would be provided by a passive soil resistance against the
foundation pad (equivalent fluid equal to 200 pounds per cubic foot [pcf]) and, if necessary,
using batter piles. The upper 2 feet on the passive (downslope) side of the foundation pads
should be neglected and truncated from a triangular distribution. The lateral resistance of
batter piles would be equal to the horizontal component of the axial pile load. The maximum
batter recommended is 1H:4V. A structural engineer should determine the extent, number and
spacing of piles required and if batter piles are to be used. We recommend that a
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Bailey Residence and Geotechnical Engineering Report
Edmonds, Washington Design Recommendations
representative from our firm observe installation of the piles to verify suitable embedment and
driving resistance in the bearing soils. The City of Edmonds may require such observations.
12.0 SOLDIER PILE WALL
We anticipate that a soldier pile wall consisting of closely spaced, wide -flange beam piles
suitably embedded in the underlying, very dense lodgement till deposits will provide suitable
lateral support when designed by a qualified structural engineer. Treated timber lagging, as
specified by the structural engineer, should be used to support the soil between the piles.
The construction sequence for pile retaining systems typically involves installing each pile to the
minimum specified embedment depth below the ground surface under the observation of the
geotechnical engineer or designated field representative. Drilled and grouted piles should be
allowed to set for at least 72 hours prior to beginning excavation or filling activities. Once the
piles have been installed to the satisfaction of the geotechnical engineer, fill placement behind
the piles may proceed. Treated -timber lagging should be installed and backfilled with
permeable soils to prevent the buildup of water behind the lagging boards.
We recommend that the cantilever soldier pile retaining wall system be designed to resist an
"active" lateral earth pressure modeled as an equivalent fluid with a density of 40 pcf for a level
backslope. The active earth pressure is assumed to act over the pile spacing extending
downward to an elevation of 2 feet below the existing ground surface. An allowable "passive"
soil resistance of 250 pcf can be assumed to act over twice the pile width for the portions of the
piles beginning 10 feet below the existing ground surface. Additionally, we recommend a
minimum depth of embedment of 10 feet below the base of the existing fill for all piles. These
recommendations for lateral earth pressures are illustrated on Figure 4.
24:?
In accordance with the i,,",2012 retaining wall design should include seismic design
parameters. Based on the'—site" 01"1 and assumed wall backfill materials, we recommend a
seismic surcharge pressure in addition to the equivalent fluid pressures presented above. A
rectangular pressure distribution of 5H and 10H psf (where H is the height of the wall in feet)
should be included in design for "active" and "at -rest" loading conditions, respectively. The
resultant of the rectangular seismic surcharge should be applied at the midpoint of the walls.
If adjacent structures, heavy construction traffic, materials stockpiling, or other substantial
surcharges are to be applied during construction, these surcharges should also be included in
the design.
The drilling contractor should be prepared to use casing, drilling slurry, or other methods of
stabilizing the hole in the case of caving, ground water, or heaving soil conditions. If more than
6 inches of standing water or slough is present at the bottom of the boring prior to grout
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Edmonds, Washington Design Recommendations
placement, the contractor should be prepared to use a tremie pipe to place grout continuously
from the bottom up.
Timber lagging can be designed to resist reduced lateral earth pressures as a result of soil
arching between piles. For the site soils, the lagging can be designed to resist 50 percent of the
calculated lateral load at any given point. The lagging should extend at least 2 feet below the
existing ground surface to provide lateral resistance for the upper portion of the existing, loose
fill zone. Any void spaces behind lagging should be filled with pea gravel, controlled density fill
(CDF), or other suitable material to prevent caving and loss of support for adjacent ground.
12.1 Tiebacks
Tiebacks may be needed to provide additional lateral resistance for the retaining system, or to
mitigate the risk of future bulging of the western foundation stemwall. Grouted tieback
anchors are frequently included in the design.
For tiebacks used in the retaining system, the anchors must be located far enough behind the
soldier pile wall to develop anchorage within a stable, natural soil mass to prevent a global
failure or excessive deformation. We recommend that this anchorage be obtained behind an
assumed failure plane defined by a horizontal line extending a distance equal to H/4 behind the
retained soil at the base of the projected fill zone, which then rotates 60 degrees from the
horizontal and extends upward to the ground surface. The area between this assumed failure
plane and the wall is referred to as the "no-load zone." Depending on the wall location, anchor
inclination, and local fill depth, anchor lengths may have to be increased to reach suitable,
dense, native soil below the loose fill and behind the no-load zone. These recommendations
are presented on Figure 4. The grouted anchor loads are transmitted to the surrounding soil by
side friction or adhesion with the soil. Tieback anchors installed by hollow -stem auger
techniques may be designed for a presumptive allowable shaft friction of 2,000 psf in the dense
to very dense sediments if located greater than 20 feet below the existing ground surface.
However, it may be necessary to "score" the perimeter of the anchor drillhole and/or use post
grouting techniques to achieve this load. Presumptive anchor design loads should be confirmed
by proof -testing, as outlined subsequently for both anchors using installation techniques and
materials that match the production anchors. All grouted anchors should extend a minimum of
10 feet behind the no-load zone.
Care must be exercised when installing tiebacks to avoid existing utilities and foundations. We
recommend for this site that each anchor be sized for a design or allowable load of not more
than 50 percent of the ultimate load available through the anchor (as indicated by 200 percent
verification tests). Anchors should be tested and evaluated according to Post -Tensioning
Institute (PTI) guidelines. The test anchors should be capable of holding the ultimate load
without excessive yield or creep so that a factor of safety of at least 2.0 is available for
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Bailey Residence and Geotechnical Engineering Report
Edmonds, Washington Design Recommendations
production anchors should further stressing occur. The rods or cables should transmit the
anchor load to the soldier pile in such a manner to avoid eccentric loading.
12.2 Anchor Tests
A series of anchor tests should be performed to verify the design and ultimate skin friction or
adhesion of the tieback anchors. Because of the variation in the soil types and their densities,
we recommend that AESI monitor the anchor test program. A common anchor testing program
would consist of at least two 200 -percent verification tests of the design or allowable load in
the soil plus proof -loading every production anchor to 130 percent of the design load.
Verification test anchors are usually loaded in 25 -percent increments that are held for
5 minutes up to the final load of 200 -percent design load. The 200 -percent load is commonly
held for an hour and creep measured. The other component of the anchor test program for the
project would be proof -loading each of the production anchors to 130 percent of the design
load. Each anchor should withstand this load for at least 5 minutes. The anchor should then be
locked off at the design load.
Subsequent to locking off the tiebacks at the design load, all of the tieback holes should be
backfilled to prevent possible collapse of the holes and any related consequences. Typically,
sand is used as backfill material; however, most non -cohesive mixtures are suitable (subject to
approval by the geotechnical engineer) provided there is no bonding to the tierods.
13.0 PROJECT DESIGN AND CONSTRUCTION MONITORING
At the time of this report, site grading, structural plans, and construction methods have not
been finalized. We are available to provide additional geotechnical consultation as the project
design develops and possibly changes from that upon which this report is based. We
recommend that AESI perform a geotechnical review of the plans prior to final design
completion. In this way, our earthwork and foundation recommendations may be properly
interpreted and implemented in the design.
We are also available to provide geotechnical engineering and monitoring services during
construction. The integrity of the planned improvements depends on proper site preparation
and construction procedures. These inspections may be required by the City of Edmonds as a
part of the building permit conditions. 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. If these services
are desired, please let us know, and we will prepare a cost proposal.
May 6, 2016 ASSOCIATED EARTH SCIENCES, INC.
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Subsurface Exploration, Geologic Hazard,
Bailey Residence and Geotechnical Engineering Report
Edmonds, Washington Design Recommendations
We have enjoyed working with you on this study and are confident that these
recommendations will aid in the successful completion of your project. If you should have any
questions or require further assistance, please do not hesitate to call.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
Jeffrey P. Laub, L.G., L.E.G.
Senior Project Engineering Geologist
Bruce L. Blyton, P.E.
Senior Principal Engineer
Attachments: Figure 1: Vicinity Map
Figure 2: Site and Exploration Plan
Figure 3: Slope Stability Analysis Cross -Section A -A'
Figure 4: Soldier Pile Retaining Wall Design Criteria
Appendix: Exploration Logs
May 6, 2016 ASSOCIATED EARTH SCIENCES, INC.
JPL/Id—KE150499A2—Projects 120150499�KEJWP Page 16
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DATA SOURCES/REFERENCES:
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NOTE: BLACK
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-------------
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ACTIVE PRESSURE ACTS
OVER PILE SPACING
NOTES:
1. SOLDIER PILE EMBEDMENT DEPTH "D" SHOULD
CONSIDER NECESSARY VERTICAL CAPACITY, KICKOUT,
AND OVERTURNING RESISTANCE.
2. ALL TIEBACK ANCHORS SHALL BE PRESTRESSED TO
130 PERCENT OF DESIGN LOAD AND LOCKED OFF AT
100 PERCENT OF DESIGN LOAD. AT LEAST TWO ANCHORS
SHALL BE PRESTRESSED TO 200 PERCENT AND MONITORED
FOR CREEP. TIE -BACK ANCHOR ZONE IS TO BE LOCATED
BEHIND THE NO-LOAD ZONE.
250 (D) PSF
PASSIVE PRESSURE ACTS
OVER TWICE PILE DIAMETER
I
3, PRESUMPTIVE ALLOWABLE TIEBACK -SOIL ADHESION= 2 KIPS PER SQUARE FOOT (KSF) IN DENSE NATURAL SOIL
BENEATH FILL ZONE. SEE REPORT TEXT FOR PRESUMPTIVE DRIVEN ANCHOR RESISTANCE VALUES.
4. PASSIVE PRESSURES INCLUDE A FACTOR OF SAFETY OF 1,5,
5. ALLOWABLE SKIN FRICTION OF SOLDIER PILE - 1500 PSF OVER DEPTH "D". ALLOWABLE END BEARING = 30 KSF.
6. DIAGRAM DOES NOT INCLUDE HYDROSTATIC PRESSURES AND ASSUMES WALLS ARE SUITABLY DRAINED TO PREVENT
BUILDUP OF HYDROSTATIC PRESSURE.
7. DIAGRAM IS ILLUSTRATIVE AND NOT REFERENCED TO A PARTICULAR LOCATION.
8, DIAGRAM DOES NOT INCLUDE PRESSURES DUE TO SURFACE SURCHARGES FROM ANY ADJACENT STRUCTURES. THESE
PRESSURES MUST BE PROVIDED BY THE STRUCTURAL ENGINEER.
9. BASE OF FILL ZONE SHALL BE DEFINED AS 10 FEET BELOW THE EXISTING GROUND SURFACE.
10. ANCHOR MUST BE DEVELOPED ENTIRELY BEHIND THE NO-LOAD ZONE AND IN DENSE NATIVE SOIL BENEATH LOOSE FILL.
p 0 0 1'
Exploration Logs
Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture oonaition, grain size, and
plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification
methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System.
a s s o c 1 a t e d
e a r t h s c e n c s EXPLORATION LOG KEY FIGURE Al
I n c o r p o r a t 9 d
0Terms
Well graded gravel and
Describing Relative Density and Consistency
Q
2
I>. � 0 0
LL 0; 0
GW
gravel with sand, little to
2)
ensity SPT( blows/foot
(D
no fines
ry Loose 6 to 424)
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ose 4 to 10
Grained Soils Medium Dense 10 to 30 Test Symbols
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0
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little to no fines
Very Dense >50 G =Grain Size
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6
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Z
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Silty gravel and silty
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0
_0
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gravel with sand
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W
- .
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Grained Soils Medium Stiff 4 to 8 K =Permeability
CD
0
Stiff 8 to 15
Clayey gravel and
Very Stiff 15 to 30
GC
clayey gravel with sand
Hard >30
>
Component Definitions
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graded d and
Descriptive Term Size Ranae and Sieve Number
-S
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sand with gravel, little
Boulders Larger than 12"
0
to no fines
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LL
(D
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Poorly graded sand
Coarse Gravel 3" to 3/4"
0
Cn
0
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and sand with gravel,
Fine Gravel 3/4" to No. 4 (4.75 mm)
o
little to no fines
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12
0 Z
Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm)
q
at
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12
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silty sand with
Fine Sand No. 40 (0,425 mm) to No. 200 (0.075 mm)
M
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a- CO
gravel
Silt and Clay Smaller than No. 200 (0,075 mm)
Lo_..m-......-..
X'�'
. . . ........ . .....
Clayey sand and
(3) Estimated Percentage Moisture Content
1,
A I
sc
clayey sand with gravel
Component Percentacie bv Weiqht Dry - Absence of moisture,
U)
dusty, dry to the touch
Trace <5 Slightly Moist - Perceptible
Silt, sandy silt, gravelly silt,
moisture
LO0
ML
silt with sand or gravel
Some 5 to <12
Moist -Damp but no visible
>
4)
05
CD
F_
LO Ca
i� ;5 ,
—
Modifier 12 to <30 water
-
Very Moist Water visible but
Clay of low to medium
(silty, sandy, gravelly)
plasticity; silty, sandy, or
not free draining
6
Z
CIL
gravelly clay, lean clay
Very modifier 30 to <50 Wet -Visible free water, usually
W
CD
E
(silty, sandy, gravelly) from below water table
vj -V
Organic clay or silt of low
Symbols
a_
2?
OL
plasticity
Blows/6" or
0
2
Sampler portion of 6" Cement grout
8Type
�clayey
surface seal
j
M.._
riai�tic silt, silt, silt
2.0" OD Bentonite
H
With micaceous or
Split-Spoon sea)
to
diatomaceous fine sand or
Sampler 3.0" ODS plit-Spoon Sampler Filter pack with
N
Giltblank
. ........ .
3.25'OD Split-Spoon Ring Sampler imp casing
(SPT).._.to
Clay of high plasticity,
section
Bulk sample
aai
'a
=
sandy or gravelly clay, fat
3.011 OD Thin -Wall Tube Sampler Screened casing
m E
40
clay with sand or gravel
(including Shelby tube)
"1 or I lydratlip
V11 th pillar Pack
.5
Grab Sample
End En cap
Organic clay or silt of
0 Portion not recovered
OH
medium to high
..... . ....
. . . ........ . . . ......................µ
Percentage by dry weight (4) Depth of ground water
plasticity
(2) (SPT) Standard Penetration Test Y ATD = At time of drilling
Peat, muck and other
(ASTM D-1 586) V Static water level (date)
(3) In General Accordance with
2)9 xa'
PT
highly organic soils
Standard Practice for Description (5) Combined USCS symbols used for
0 � N
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 oonaition, grain size, and
plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification
methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System.
a s s o c 1 a t e d
e a r t h s c e n c s EXPLORATION LOG KEY FIGURE Al
I n c o r p o r a t 9 d
d
EXELi�i,6
OQ
F,
--------------Proje ct mbe .. ..
Ua n CSiaE n -Number
Sheet
-,.,.
'
,P KE 50 99
4
1
of 1
Project Name
_-----_...��_.�._.�� �� _._��._ _
Bailey II:I fElevation_.,.
_
........�
Surface
(ft)
Location
Edmond,*,, AA......................._ - - --- ------ --.-. ------ Datumd
KI/A,_
_____
__
Driller/Equipment
N,�IiOt lAht DateStart/Finish
„
11/11/15,11/11/15
Hammer Weight/Drop
O / " .. ......... Hole
Diameter
(in) F,,!nnhac..
vN
U
d
CL
a
.O
N�
a�
N
J
Blows/Foot
y
to
a)N
a S
a)rn
T
E 2T
C7
E
m
°
Co
t
�'
DESCRIPTION
"
3
10 20
30
40
°
............_...�.. ........ ........
Fill
.........
......
_
_..
S-1
1
•5
Moist, brownish gray, fine to medium SAND, some silt, some organics
4
(SP -SM).
S-2
Moist to wet, brownish gray, silty fine to medium SAND, trace gravel (SM).1
1
1
5
S-3
Moist, slightly rust -stained brownish gray, Cine to medium SAND, some silt,2
♦5
trace gravel, trace burned wood fragments (SP -SM).
g
q
Driller added water at 8 Feet
—-..-.... ---. ........._... ...... .... .... ........ .......
S 4
1Nashon Lodgement Till
4
j
Moist, slightly rust -stained brownish gray, silty fine to medium SAND, some
16
14
gravel (SM).
- 10
S-5
Moist, brownish gray, silty fine to medium SAND, some gravel (SM).
8
A4
27
- 15 .•.As
IL
I
S-6
above.
5
31
)15.
5"
16601 !,5"
Bottom of wploration boring at 16 feet
No ground water encountered.
- 20
- 25
z
Sampler
Type (ST):
❑
2" OD Split
Spoon Sampler (SPT) ❑ No Recovery M - Moisture
Logged
by:
JPL
Y OD Split
Spoon Sampler (D & M) Ring Sample Water Level()
Approved
by: JNS
®
Grab Sample
❑ Shelby Tube Sample 1 Water Level at time of drilling
(ATD)
Exploration Loa
i" Project N ..... --.�.
:Uth ie11l d :� _
Proj umber E�loration Number Sheet
fli 6 0, 0 lo I � E150499A EB -2 1 of 1
Project Name ..... _------------ -....... -- Ground Surface Elevation (ft) _
Location ..Eft s W ................................. Datum N/A..........
Driller/Equipment) ill If1C A( _ Date Start/Finish 11 /11 /15-;11 /11 /15
Hammer Weight/Drop.: .... Q Hole Diameter (in) 6..1nche%-
C d)
L -6O > f, N
=Z Blows/Foot t-
o T rn cD Cn E m° t
M
DESCRIPTION 10 20 30 40 °
Fill'
S-1
Moist, brown, silty SAND, some organics, trace gravel (SM).
2
♦g
4
S-2
As above, with woody debris.
/1
4 1
1
5
_
Weathered a il o ._ .....,
Till
1
S-3
Moist, reddish brown to brownish gray,Lodgement
silty fine to medium SAND, some gravel
2
11
SM.
9
Vashon Lodgement Till
S-4
Moist, brownish gray, silty fine to medium SAND, some gravel (SM).
23
35
A
k74
39
Driller added water at 9 feet.
10
S
Moist, brownish gray, fine to medium SAND, some silt, some gravel (SP -SM).
33
„
5ia11
Bottom of exploration boring at 11 feet
No ground water encountered.
- 15
- 20
- 25
0
+Y.
m.
E
m
'o -
Z
I
IL
c7_
Sampler
Type
...
(ST):
......................................
❑
2" OD
Split
Spoon Sampler (SPT) ❑ No Recovery M - Moisture
Logged
by:
JPL
o
3" OD
Split
Spoon Sampler (D & M) Ring Sample Q Water Level O
Approved
by: JNS
W ®
Grab
Sample
❑ Shelby Tube Sample 1 Water Level at time of drilling
(ATD)
a n 9
a, c � a a 0 d Exploration
Log
"""��
a
o :a r C qu
s c u e uu ic es Project Number Exploration Number
Sheet
f��
,
a7 r ' � ° e d KE150499A EB -3
1
of 1
Project Name
...................._..._... .........
_Ballt?v Residence _.....__
Ground
Surface
Elevation
(ft)
Location
B.NTl..n,., .. Datum
.N/A_..
Driller/Equipment
�l I%hI44..�<l -.- Date
Start/Finish
1.,.1
/11 /15.11
/1111.5 ........
Weight/Drop
A Hole
e .,40 l 30. �.. �
Diameter
in
(�)
c..lnrhPs
.
�
L
N U �
s mE
C
O>�
N
_J
N
Blows/Foot
N
0 T
O rn
EE
�
—m0
L
DESCRIPTION
10
20
30
40
Fill
S-1
Moist, slightly rust -stained brownish gray, silty fine to medium SAND, some
12
Aly
gravel (SM).
13
S-2
As above.
4
8
1
11
5
As above.
11
105
♦1
u
Cement odor at 5 1/2 to 6 feet (cement treatment?).,
Drilledd water ......... m feet.
� at 7 1 /2 feet r
..
S 4
Weathered
Weathered Vashon Lodgement Till
3
k10
sh brown to brownish gray, silty fine to medium SAND, some gravel
Moistreddish
5
(SM).
5
- 10
S-5
Moist rust -stained brownish gray, silty fine to medium SAND, some gravel
3
4
A16
14
Vashon Lodgement Till
S-6
Must, brownish a sill fine to medium SAND sorne #vel SM
. Ml ------- gray, a. :., .:
Bottom of exploration boring at 13 feet
No ground water encountered.
- 15
- 20
- 25
gra
Sampler
Type (ST):
❑
2" OD Split
Spoon Sampler (SPT) ❑ No Recovery M - Moisture
Logged
by:
JPL
3" OD Split
Spoon Sampler (D & M) !.N Ring Sample Water Level()
Approved
by: JNS
®
Grab Sample
❑ Shelby Tube Sample 1 Water Level at time of drilling
(ATD)
r
o o u a t o
ear-th scgences
May 25, 2017
Project No. 150499E001 R:F' 1 rztt
Mr. Mark Bailey MAY 2 6
101512 th Avenue North
Edmonds, Washington 98020
g
Subject: Response to City Comments
Bailey Residence
101512 th Avenue North CIPIT
Edmonds, Washington
opy
Dear Mr. Bailey:
As requested, Associated Earth Sciences, Inc. (AESI) has reviewed the comments provided in a "Plan
Review Comments for Plan Check #BLD20170496" letter, prepared by the City of Edmonds and
dated May 18, 2017. We have previously prepared a "Subsurface Exploration, Geologic Hazard, and
Geotechnical Engineering Report — Bailey Residence", dated May 6, 2016, for the proposed slope and
settlement mitigation project at the subject site, along with a "Geotechnical Consultation — Slope
Tree Removal Assessment" letter, dated April 10, 2017. Review Comment Number 4, as outlined in
the City of Edmonds letter, with AESI's response, is as follows.
Comment 4
The geotechnical letter dated April 10, 2017 by Associated Earth Sciences Inc. states the following:
"...the slope should be replanted as soon as possible with landscaping trees and shrubs, as desired..."
The geotechnical engineer, however, must review the proposed tree cutting and planting plans and
provide written documentation of how the entire project proposal is in compliance with the
applicable standards of ECDC Chapters 23.40 and 23.80, including the specific design standards in
23.80.060 and 23.80.070.
Chapter 23.40 of the Edmonds Community Development Code (ECDC) includes general
provisions for all types of environmentally critical areas (including wetlands, fish, and
wildlife habitat conservation areas, etc.), while Chapter 23.80 of the ECDC speaks
directly to "Geologically Hazardous Areas", which fall under the purview of geotechnical
study. Our responses to specific design standards outlined in ECDC 23.80.060 and
23.80.070 are presented in the following paragraphs.
ECDC 23.80.060 limits alterations of geologically hazardous areas to activities that
mitigate the hazard and will not adversely impact adjacent properties or other critical
areas. For our review in preparing this letter, we were provided with the following
plans:
Kirkland Office 1911 Fifth Avenue I Kirkland, WA 98033 P 1425.827.7701 F 1425.827.5424
Everett Office 12911 Y,. Hewitt Avenue, Suite 2 1 Everett, WA 98201 P 1425.259.0522 F 1425.827.5424
Tacoma Office 1 1552 Commerce Street, Suite 102 1 Tacoma, WA 98402 P 1253.722.2992 F 1253.722.2993
www.aesgeo.com
Studio 342 Landscape Architecture, "Bailey Silhacek Residence," Sheets L-1 through
L-4, dated May 23, 2017
SSF Structural Engineering, "Bailey Residence Shoring," Sheets S1.1, SH2.1 and
SH3.1, dated May 22, 2017
Based on our review of the provided plans, it is our opinion that: a) the proposed
project will not increase the threat of the geological hazard to adjacent properties
beyond predevelopment conditions; b) will not adversely impact other critical area; and
c) is designed so that the hazard to the project is mitigated to a level equal to less than
predevelopment conditions.
It is also our opinion that the temporary irrigation plan for the proposed plantings, as
described in Sheets L-3 and L-4, should not adversely impact slope stability. We
recommend that the temporary irrigation system be periodically checked for leaks.
ECDC 2.3,80.070 includes design standards for projects in landslide hazard areas,
including minimum factors of safety for landslide occurrences. Our May 6, 2016 report
included slope stability modeling which resulted in factors of safety meeting or
exceeding the recommended minimum values of 1.2 under seismic conditions and 1.5
under static conditions. Our report then stated that the proposed retaining wall
"appears feasible from a geotechnical standpoint provided the wall is designed as a
retaining wall with sufficient embedment to provide the factors of safety predicted by
our model." Based on our review of the above-mentioned project plans, it is our
opinion that the proposed soldier pile retaining wall is designed with sufficient
embedment to provide the predicted factors of safety.
If you should have any questions concerning this letter, please do not hesitate to call our office.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
c A-1
Jeffrey P. Laub, L. L.E.G. Bruce L. Blyton, P.E.
Senior Project Er ' ineering Geologist Senior Principal Engineer
J PL/pc—150499E001-5 — Projects\20150499\KE\W P
2