REVIEWED BLD2021-0520 APVD WWTP Remodel - GeoRepor 5.26.2021RECEIVED
BLD2021-0520
Geotechnical Engineering
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Report
Services
Project C-311 - Odor Control Improvements
Edmonds Wastewater Treatment Plant
PLAN REVIEW ACCEPTANCE
FOR COMPLIANCE WITH THE APPLICABLE
CONSTRUCTION CODES IDENTIFIED BELOW.
❑ BUILDING ® STRUCTURAL
❑ MECHANICAL ❑ PLUMBING
❑ ELECTRICAL [-]ENERGY
❑ ACCESSIBILITY ❑ FIRE
PLAN REVIEW ACCEPTANCE OF DOCUMENTS
DOES NOT AUTHORIZE CONSTRUCTION TO
PROCEED IN VIOLATION OF ANY FEDERAL,
STATE, OR LOCAL REGULATIONS.
d<-7
BY: "; F�DATE: 10/8/2021
WEST COAS CODE CONSULTANTS, INC.
Edmonds, Washington
June 23, 2009
Prepared for
City of Edmonds
200 2nd Avenue South
Edmonds, Washington 98020
LANDAU
14 A55oCIATES
130 2nd Avenue South
Edmonds, WA 98020
(425) 778-0907
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CITY OF EDMONDS
TABLE OF CONTENTS DEVELOPMENT
DE ARTMENRVICES
Page
1.0 INTRODUCTION 1-1
1.1 PROJECT BACKGROUND 1-1
1.2 SCOPE OF SERVICES 1-2
2.0 REVIEW OF AVAILABLE GEOTECHNICAL INFORMATION 2-1
3.0 SITE CONDITIONS 3-1
3.1 GENERAL GEOLOGIC CONDITIONS 3-1
3.2 SURFACE CONDITIONS 3-1
3.3 SUBSURFACE SOIL CONDITIONS 3-1
3.4 GROUNDWATER 3-2
4.0 CONCLUSIONS AND RECOMMENDATIONS
4-1
4.1
EARTHWORK
4-1
4.1.1 Temporary Excavations
4-1
4.1.2 Excavation Dewatering
4-2
4.1.3 Reuse of Site Soil
4-2
4.1.4 Structural Fill and Compaction Criteria
4-2
4.2
TEMPORARY SHORING
4-3
4.2.1 Lateral Earth Pressures
4-3
4.2.2 Shoring Installation Considerations
4-3
4.3
SEISMIC DESIGN CONSIDERATIONS
4-4
4.4
FOUNDATION SUPPORT
4-4
4.5
RETAINING WALLS
4-5
4.5.1 Lateral Earth Pressures
4-6
4.5.2 Dynamic Lateral Earth Pressures
4-6
4.5.3 Resistance to Lateral Loads
4-7
4.5.4 Retaining Wall Backfill and Drainage Considerations
4-7
4.6
CONCRETE SLABS -ON -GRADE
4-8
5.0 GEOTECHNICAL CONSULTATION AND CONSTRUCTION MONITORING 5-1
6.0 USE OF THIS REPORT 6-1
7.0 REFERENCES 7-1
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OPMENT
LIST OF FIGURES DEVE DE ARTMENRVICES
Ejgure Title
1 Vicinity Map
2 Site and Exploration Plan
3 Design Lateral Earth Pressures — Temporary Excavation Shoring
4 Surcharge Pressures
LIST OF APPENDICES
Appendix Title
A Field Explorations and Laboratory Testing
B Selected Aerial Photographs (1989 to 1991)
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OPMENT
1.0 INTRODUCTION DEVE DE ARTMENRVICES
This report summarizes the results of Landau Associates' geotechnical engineering services
conducted for the planned C-311 odor control improvements project at the Edmonds Wastewater
Treatment Plant (WWTP) located at 200 2nd Avenue South in Edmonds, Washington. The general project
location is shown on the Vicinity Map (Figure 1). The general configuration of the project area, located
between Final Clarifier No. 1 and No. 2, and some of the existing site features are shown on the Site and
Exploration Plan (Figure 2). Note that Final Clarifier No. 1 is located further south than Final Clarifier
No. 2, which has a pergola constructed on its roof and a wheel chair access ramp to the pergola located
just north of the project area.
This geotechnical report has been prepared based on the results of our previous geotechnical
studies at the site (Landau Associates 1988); project design drawings and information provided by
Brown and Caldwell; selected aerial photographs taken between 1989 and 1991 during construction of the
existing WWTP facilities; supplemental data collected during our recent field exploration program; and
our experience on similar projects. All elevations noted in this report refer to the mean lower low water
(MLLW) datum.
1.1 PROJECT BACKGROUND
The City of Edmonds (City) has retained Brown and Caldwell to provide structural and civil
engineering design services for the planned odor control improvements project. The planned
improvements will create a larger service area between Final Clarifier No. 1 and No. 2 to house a new
carbon absorption tower and fan. This will require relocating an existing retaining/screening wall farther
north and setting the slab on grade elevation of this new service area to match the existing lower pit slab
elevation of about 14.6 ft. The existing elevations in the areas to be lowered are currently at about 18.5 ft
and 21.5 ft.
Based on communications with Brown and Caldwell, we understand that the design criteria for
the four main structural elements that will require foundation support include the following:
• The carbon absorption tower will be supported on a concrete pad and spread footing founded
near elevation 12 ft and impose a load of about 800 pounds per square foot (psf)
• The slab -on -grade for the new service area will be founded near elevation 14 ft and impose a
load of about 200 psf
• The new concrete retaining/screening wall will be supported on a spread footing founded near
elevation 12 ft and impose a load of about 3,600 pounds per lineal foot of wall, or about
1,200 psf for a 3-ft wide footing. We understand that the north -south segment of the wall will
have an eccentrically loaded footing that may impose a load of about 3,300 psf.
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ENT 1E
• Two grade beams founded near elevation 12 ft will be situated in a north -south dii$Fc�.i p,,TMENRVICEs
between the new retaining/screening wall and Final Clarifier No. 1.
• The concrete stairs proposed between the existing electrical substation and the new lowered
service area will be supported by both a concrete wall with a 3-ft wide eccentrically loaded
footing founded near elevation 12 ft and a short wall segment founded on a thickened
slab -on -grade. The structure will impose a load of about 1,000 pounds per lineal foot.
1.2 SCOPE OF SERVICES
The following summarizes Landau Associates' scope tasks for the geotechnical engineering
support services for the project.
• Compiling and reviewing readily available geotechnical data for the project area, including
review of selected photographs of the project area taken during the WWTP expansion
• Advancing 2 shallow borings to a maximum depth of about 15 ft below ground surface
(BGS) at accessible locations within the vicinity of the relocated retaining wall to
characterize soil and groundwater conditions in the area
• Obtaining representative soil samples from the explorations
• Logging each exploration and recording pertinent information, including soil sample depths,
stratigraphy, soil engineering characteristics, and groundwater occurrence
• Conducting limited geotechnical laboratory testing on selected soil samples
• Evaluating data derived from the subsurface investigation and laboratory testing programs
• Developing geotechnical engineering conclusions and recommendations to support design
and construction of the planned improvements, including:
- temporary excavation slopes and excavation shoring considerations
- shallow foundation support, including allowable soil bearing pressures, and subgrade
preparation required to obtain the allowable bearing pressures
- lateral earth pressures acting on below grade walls (including seismic loads), and soil
friction and passive earth pressures to resist lateral loads
- retaining wall backfilling and drainage requirements.
• Preparing and submitting this written report summarizing our findings, conclusions, and
recommendations for the project. This report includes:
- a site plan showing pertinent site features and the approximate locations of the
explorations completed for this study, based on a site plan provided by Brown and
Caldwell
- descriptive logs of the explorations and results of geotechnical laboratory testing
- a discussion of the near -surface soil and groundwater conditions observed in the
explorations conducted for this project
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a discussion of the results of our review of readily available geotechnical informatiffiyqWMENT
PARTMENSERVICEST
the project area
geotechnical recommendations to support design of the planned improvements
recommendations for geotechnical monitoring and consultation during construction.
• Coordinating with the Brown and Caldwell design team to discuss design and construction
issues and constraints.
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2.0 REVIEW OF AVAILABLE GEOTECHNICAL INFORMATION DEVE DOPMENT
E ARTMENRVICES
As part of this project, Landau Associates reviewed the results of our previous geotechnical
studies at the site conducted as part of the design for the WWTP expansion (Landau Associates 1988), as
well as selected aerial photographs taken between 1989 and 1991 during construction of the existing
WWTP facilities that are available at the WWTP office.
The soil profile in the project area prior to the WWTP expansion generally consisted of near -
surface fill materials overlying a silty sand/sandy silt recessional deposits overlying dense glacial till. A
layer of dense sand with some hard silt and peat layers underlie the glacial till unit. The thickness and
elevation of these soil layers varies considerably, but generally the glacial till unit slopes downward in an
east -to -west direction (i.e., the till is present at a shallower depth along 2rtd Avenue South and at a much
deeper depth along SR 104). An unconfined shallow groundwater aquifer was present at a shallow depth
in the soils above the glacial till, and a confined groundwater aquifer in the sand unit below the glacial till
is under near -artesian pressure conditions. Refer to the results of our previous geotechnical studies
(Landau Associates 1988) for additional background information.
As part of the former WWTP expansion, an excavation shoring/groundwater cutoff wall was
installed around the perimeter of the WWTP; and this shoring/cutoff wall remains in place. Soil within
the shoring/cutoff wall was dewatered and soil was removed as needed to allow construction of
foundations and utilities for the existing WWTP facilities. The excavation within the shoring/cutoff wall
was backfilled around the new structures up to existing grade. We understand that drainage facilities are
present in certain structures and function in a manner that controls groundwater levels within the
shoring/cutoff wall segments that remain in place around the WWTP.
A review of certain aerial photographs taken between 1989 and 1991 during construction of the
existing WWTP facilities was conducted as part of this study. Copies of selected aerial photographs are
included in Appendix B. These photographs are useful in gaining a better understanding of the existing
subsurface conditions in the vicinity of the planned odor control improvements located between Final
Clarifier No. 1 and No. 2.
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OPMENT
3.0 SITE CONDITIONS DEVE DE ARTMENRVICES
This section briefly summarizes the general geologic setting of the project area and describes the
surface and subsurface conditions observed at the subject site at the time of our field investigations.
3.1 GENERAL GEOLOGIC CONDITIONS
General geologic information for the project area was obtained from the Composite Geologic
Map of the Sno-King Area: (Booth, et al 2004), published by the University of Washington. According to
this source, the general project area is underlain by undifferentiated pre -Fraser deposits.
3.2 SURFACE CONDITIONS
The ground surface north of the existing retaining/screening wall is covered by a narrow strip of
shrubbery and a concrete sidewalk at an elevation of about 21.5 ft, which is bounded by a wheelchair
access ramp to the north. The ground surface south of the existing retaining/screening wall is covered by
a concrete slab at an elevation of about 18.5 ft that is located adjacent to Final Clarifier No. 1, and a lower
pit slab at an elevation of about 14.6 ft located between Final Clarifier No. 1 and No. 2.
3.3 SUBSURFACE SOIL CONDITIONS
Subsurface conditions near the alignment of the new retaining/screening wall were explored by
advancing borings B-1 and B-2 through the existing concrete sidewalk at the approximate locations
shown on the Site and Exploration Plan (Figure 2). Both borings were advanced to depths of about 14 ft
below ground surface (BGS) using a limited access, hollow -stem auger drill rig. A discussion of the field
exploration and laboratory test procedures, edited logs of the exploratory borings, and the laboratory test
results are presented in Appendix A.
The near -surface soils in the project area consist of fill materials placed during construction of the
existing WWTP facilities within the perimeter shoring/cutoff wall. The subsurface conditions
encountered in borings B-1 and B-2 consisted of approximately 9 ft of loose to medium dense, fine to
medium sand (fill), overlying dense, silty, fine to medium sand with gravel (reworked glacial till fill).
The upper 5 ft of the sand fill is relatively loose, while the lower portion is in a medium dense state. The
underlying dense glacial till fill encountered in the borings is likely till material that was reworked and
recompacted as part of the former construction access ramp and/or regrading within the former WWTP
excavation. The depth to the underlying very dense, native glacial till in the project area was not
specifically determined for this study but would be expected to vary based on the proximity to deep
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excavations made for construction of the existing clarifier units. Thus, it is anticipated that the de�ft'1€I� 'TMENRVICES
fill materials, and thus the depth to the native glacial till unit, will increase to the south toward the
location of Final Clarifier No. 1.
3.4 GROUNDWATER
Groundwater was not encountered within the explored depths of the explorations advanced as
part of this study. However, some wet soil was encountered at the base of the sand fill in exploration B-2.
This wet soil is likely the result of some irrigation or storm water perched on the surface of the reworked
glacial till fill material.
As noted in Section 2.0, we understand that certain drainage facilities are present at the facility to
control groundwater levels within the shoring/cutoff wall segments that remain in place around the
perimeter of the WWTP. Thus, it has been assumed that the design groundwater elevation is below the
depth of the subject improvements.
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4.0 CONCLUSIONS AND RECOMMENDATIONS
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Based on the results of our field investigation and geotechnical evaluations, it is our opinion that
the currently planned odor control improvements at the Edmonds WWTP are feasible from a geotechnical
engineering perspective, provided that the recommendations presented in this report are implemented
during design and construction. Our conclusions and recommendations for design and construction of the
proposed improvements are provided below.
4.1 EARTHWORK
Earthwork to accommodate construction of the proposed improvements is expected to consist of
clearing and grubbing of the existing shrubbery; removal of existing concrete slabs and demolition of the
existing retaining/screening wall; and excavations and subgrade preparation for new foundations and
slabs.
4.1.1 TEMPORARY EXCAVATIONS
We understand that excavations up to about 10 to 12 ft in depth will be required to facilitate
installation of some of the proposed structures. Based on the soil conditions observed in our explorations,
we anticipate that the onsite soils can be excavated with conventional heavy duty construction equipment.
We anticipate that both temporary shored excavations and some unsupported excavations will be used
during construction.
For planning purposes relative to temporary unsupported excavations, the guidelines presented in
Safety Standards for Construction Work Part N, Washington Administrative Code (WAC) 296-155-657,
may be used. Per these guidelines, the existing on -site fill and the underlying reworked glacial till are
classified as Type C soils. Temporary unsupported excavations within Type C soils should be sloped no
steeper than 1 %2H:1 V. The recommended maximum slopes are applicable to temporary excavations
above the water table only; flatter side slopes will be required for excavations in areas where groundwater
seepage is encountered.
Actual slope configurations during construction and maintenance of safe working conditions,
including temporary excavation stability, should be the responsibility of the contractor, who is able to
monitor construction activities and has direct control over the means and methods of construction. All
applicable local, state, and federal safety codes should be followed. All open cuts should be monitored by
the contractor during and after excavation for any evidence of instability. If instability is detected, the
contractor should flatten the side slopes or install temporary shoring (see Section 4.2).
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4.1.2 EXCAVATION DEWATERING DEVELOPMENT SERVICES
DEPARTMENT
Groundwater was not encountered within the explored depths of the explorations advanced as
part of this study. However, some wet soil was encountered at the base of the fill in exploration B-2. If
any water seepage is observed within an excavation, we expect that open sump pumping should be
adequate to control seepage into the excavation.
4.1.3 REUSE OF SITE SOIL
Soil generated from planned excavations will likely consist of the sand fill and the underlying
silty sand till fill material. Both material types are considered suitable for reuse as onsite fill during dry
weather periods; however, the till fill material is likely to be moisture sensitive and may require moisture
conditioning (i.e., drying) in order to be reused as compacted fill.
We currently understand that excess soil will be generated from the project and that the need to
reuse onsite soil as fill material will be limited. Excess soil should be disposed offsite at a location
approved by the City.
4.1.4 STRUCTURAL FILL AND COMPACTION CRITERIA
Structural backfill placed beneath footings and slabs -on -grade should consist of imported crushed
rock meeting the requirements for Crushed Surfacing in Section 9-03.9(3) of the 2008 Washington State
Department of Transportation (WSDOT) Standard Specifications for Road, Bridge, and Municipal
Construction (WSDOT Standard Specifications). If imported fill is placed during periods of wet weather
or under wet conditions, the amount of fines should be limited to 5 percent by dry weight, based on the
fraction passing the 3/4-inch sieve. Structural fill placed against walls should consist of the onsite sand fill
materials or imported crushed rock.
Structural fill soils should be moisture conditioned to within about 3 percent of optimum moisture
content, placed in loose, horizontal lifts less than about 6 to 8 inches in thickness, and compacted to at
least 95 percent of the maximum dry density, as determined by the American Society for Testing and
Materials (ASTM) D 1557 test procedure (Modified Proctor).
Earthwork can be performed most economically during periods of dry weather. Compaction
should take place immediately after subgrade preparation, and the newly prepared areas should be
protected against saturation from precipitation. If protective measures are not provided, and the subgrade
soils become saturated and spongy due to rain and/or construction activities, the soft soils should be
removed, and imported crushed rock should be placed to bring the affected area to proposed grade.
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4.2 TEMPORARY SHORING
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CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
As indicated on Figure 2, temporary shoring is planned for certain excavations; however, limited
space (approximately 1-ft wide) is available for installation of shoring materials. We understand that it is
likely that temporary shoring materials will be abandoned in place due to site constraints and to limit
further disturbance to adjacent materials. We currently envision that the most feasible shoring method for
this application would be driven steel sheet piling (using a section with a limited web height); however, a
soldier pile and timber lagging system could also be potentially used.
4.2.1 LATERAL EARTH PRESSURES
Temporary shoring should be designed and constructed to resist active lateral earth pressures.
The use of active lateral earth pressures assumes that sufficient deformation of the soil behind the wall
(on the order of 0.001 to 0.002 times the height of the wall) could occur to develop an active condition.
This lateral deformation is likely to be accompanied by minor vertical settlement behind the wall.
For cantilevered shoring systems that are free to rotate at the top, the active and passive earth
pressures shown on Figure 3 are recommended for use in design. No seismic lateral earth pressures are
provided for the shoring system because it is assumed to be a temporary structure. Given site
groundwater conditions, hydrostatic pressures can be ignored for shoring design.
If the shoring system will be subjected to the influence of surcharge loading within a horizontal
distance equal to or less than the exposed height of the shoring system, the shoring system should be
designed for the additional horizontal pressure. It is typical practice to accommodate traffic and
construction equipment loading with a vertical surcharge pressure of 250 psf. Lateral loads due to
uniform surcharge are also shown on Figure 3. For non -uniform surcharge loading (such as crane
loading), refer to Figure 4.
4.2.2 SHORING INSTALLATION CONSIDERATIONS
Based on anticipated subsurface conditions, we expect that the temporary sheet pile shoring can be
installed using a vibratory hammer. While not encountered during our site explorations, cobbles within the
glacial till materials may impede sheet pile installation. Consequently, the contractor should anticipate the
presence of such obstructions and should be prepared to implement measures to facilitate sheet pile
installation where obstructions are encountered. Installation of sheet pile shoring using a vibratory
hammer will produce ground vibrations and may induce some ground settlement in the vicinity of the
shoring system.
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4.3 SEISMIC DESIGN CONSIDERATIONS
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DEPARTMENT
The Pacific Northwest is seismically active and the site could be subject to strong ground shaking
from a moderate to major earthquake. Consequently, moderate levels of earthquake shaking should be
anticipated during the design life of the proposed structures and they should be designed to resist
earthquake loading using appropriate design methodology.
We understand that the proposed improvements will be designed using the seismic design
provisions of the 2006 International Building Code (IBC 2006). For IBC 2006, an earthquake with a
2 percent probability of exceedance in 50 years (2,475-year return interval) is used for structural design.
The subject site is underlain by relatively dense glacially compacted soil, and, therefore, the site is
classified as Site Class C according to Table 1613.5.2 in IBC 2006. We obtained estimates of spectral
response accelerations for an earthquake with a 2,475-year return interval from the USGS National
Seismic Hazard Maps (USGS 2008). Based on the project location (Latitude 48.8094 and
Longitude-122.3822), the following spectral accelerations should be used to estimate the design response
spectrum:
Spectral Acceleration for short periods (Ss): 120.3% of gravity (1.203g)
Spectral Acceleration for 1-second period (Si): 42.2% of gravity (0.417g)
For Site Class C and the above spectral accelerations, a value of 1.0 should be used for site
coefficient Fa, and 1.378 for site coefficient Fv.
The density of the onsite soils and the general absence of saturated conditions effectively
preclude seismically -induced soil liquefaction within the existing WWTP shoring/cutoff wall. In
addition, it is anticipated that the project area would not be subject to seismically -induced lateral
spreading or other ground failure.
4.4 FOUNDATION SUPPORT
We recommend that footings for the proposed improvements be founded on conventional spread
footings bearing directly on dense glacial deposits, or on 2 ft of compacted structural fill placed over
properly prepared subgrade materials. Bearing soil disturbed during foundation excavation should either
be properly recompacted or removed and replaced with compacted structural fill. Soils directly below
and around footings should be compacted to at least 95 percent of its maximum dry density as determined
by ASTM D 1557prior to placement of forms and reinforcing steel.
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Where compacted structural fill is used for foundation support, the limits of the overexca4%WETMENRVICEs
should extend laterally beyond the edge of each side of the footing a distance equal to about one-half the
depth of the excavation below the base of the footing. A lean mix concrete may be used as backfill in place
of compacted structural fill. If lean concrete is used, the limits of the overexcavation do not need to extend
beyond the width of the footing.
Prior to placement of structural fill below foundation elements, the upper 1 ft of the underlying
subgrade should be prepared and compacted to at least 95 percent of its maximum dry density as
determined by ASTM D 1557 to provide proper support. The compacted subgrade should be observed
and probed by a qualified geotechnical engineer to check for the presence of soft, loose, and/or disturbed
areas. Any areas of soft, loose, and/or disturbed soil or areas exhibiting significant deflection, pumping,
or weaving that cannot be adequately reworked and/or compacted should be overexcavated and replaced
with compacted structural fill as described in Section 4.1.4 of this report.
All exterior footings should be founded at least 18 inches below the lowest adjacent finished
grade; interior footings may be founded a minimum of 12 inches below top of slab. We recommend
minimum footing widths of 18 and 24 inches for continuous strip and isolated footings, respectively.
Provided the footings are founded as described above, they may be designed for a maximum net
allowable soil bearing pressure of 3,300 ps£ The term "net allowable soil bearing pressure" refers to the
pressure that can be imposed on the soil at foundation level resulting from the total of all dead plus live
loads, exclusive of the weight of the footing or any backfill placed above the footing. The net allowable
bearing pressure may be increased by one-third for transient wind or seismic loads.
Lateral loads may be resisted by passive earth pressures on the sides of the footings and by
friction on the base of the footings and slabs. Passive and frictional resistance may be evaluated using the
design parameters presented in Section 4.5.3.
Settlement of spread foundations depends on foundation size and bearing pressure, as well as the
strength and compressibility characteristics of the underlying bearing soil. Assuming the foundation
materials are prepared as recommended herein, we estimate the total settlement of the foundations will be
less than 1 inch and differential settlement between two adjacent load -bearing components supported on
competent soil should be less than about 1/2 inch. The settlement is expected to be relatively elastic in
nature with most of the settlement occurring as loads are applied.
4.5 RETAINING WALLS
The foundation support recommendations presented in Section 4.4 above may be used to
proportion the footings for the new retaining wall segments.
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Cast -in -place retaining walls should be designed to resist lateral earth pressures presenQUWETM NT SERVICES
Sections 4.5.1 and 4.5.2 below. Sliding resistance and passive earth pressures acting on buried elements
of the wall may be used to resist lateral earth pressures, and such recommendations for resistance to
lateral loads are provided in Section 4.5.3. A discussion related to retaining wall backfill and drainage
considerations is provided in Section 4.5.4.
4.5.1 LATERAL EARTH PRESSURES
The magnitude of lateral earth pressures that develop against below -grade walls will depend upon
the inclination of any adjacent slopes, type of backfill, degree of wall restraint, method of backfill
placement, degree of backfill compaction, drainage provisions, magnitude and location of any adjacent
surcharge loads, and the degree to which the wall can yield laterally during or after placement of backfill.
When the wall is restrained against lateral movement or tilting, the soil pressure exerted is the at -rest soil
pressure. Such wall restraint may develop if a rigid structural network is constructed prior to backfilling,
or if the wall is inherently stiff or is otherwise restrained from rotation. In contrast, active soil pressure
will be exerted on a subsurface structure or wall if its top is allowed to rotate or yield a distance of
approximately 0.001 times its height or greater.
We understand that below -grade walls for this project will be designed as yielding walls with
level backfill under drained conditions. Accordingly, we recommend the below -grade walls be designed
for an equivalent fluid density of 35 lbs per cubic ft (pcf) for active soil conditions.
The above recommendation regarding active earth pressures assumes no adjacent surcharge loads.
If the subsurface walls will be subjected to the influence of surcharge loading within a horizontal distance
equal to or less than the height of the walls, the walls should be designed for the additional horizontal
pressure. For yielding walls with level backfill, a uniformly distributed lateral pressure of 0.28 times the
surcharge pressure should be included. For non -uniform surcharge loading, refer to Figure 4.
4.5.2 DYNAMIC LATERAL EARTH PRESSURES
Dynamic lateral earth pressures from a seismic event with a 10 percent probability of exceedance
in a 50-year period (1-in-475 year event) should be included in the design of the cast -in -place concrete
walls. A peak horizontal ground acceleration of O.31g was assumed in computing the dynamic lateral
earth pressures.
A uniform lateral pressure of 6H psf (H is the vertical height of the below -grade wall in feet)
should be added to the static lateral earth pressures for yielding walls with level backfill. The
recommended uniform lateral pressure should be applied over the height of the below -grade wall and the
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Geotech_rptdoc LANDAU ASSOCIATES
4-6
RECEIVED
May 26 2021
pF� /CITY OF EDMONDS
resultant should be assumed to act at a point 0.6H above the base of the wall. The recommended Id�""DEPARTMSERVICES
earth pressure assumes that the wall will be free to rotate and translate during a strong motion earthquake.
4.5.3 RESISTANCE TO LATERAL LOADS
Resistance to lateral loads may be assumed to be provided by friction acting on the base of
foundations, and by passive lateral earth pressures acting against the below -grade portion of structures.
For design purposes, the passive resistance of well -compacted fill placed against the sides of the retaining
wall may be considered equivalent to a fluid with a density of 250 pcf. The recommended value includes
a safety factor of about 1.5 and is based on the assumption that the ground surface adjacent to the
structure is level in the direction of movement for a distance equal to or greater than twice the embedment
depth. In design computations, the upper 12 inches of passive resistance should be neglected if the soil is
not covered by slabs or pavement.
We recommend that an allowable coefficient of friction between concrete and soil of 0.4 may be
used to calculate resistance to sliding at the base of foundations. This value should be applied to vertical
dead loads only. If passive and frictional resistance are considered together, one half the recommended
passive soil resistance value should be used because larger strains are required to mobilize the passive soil
resistance as compared to frictional resistance. A safety factor of about 1.5 is included in the base friction
design value. We do not recommend increasing the coefficient of friction to resist seismic or wind loads.
4.5.4 RETAINING WALL BACKFILL AND DRAINAGE CONSIDERATIONS
Free -draining sand and gravel material, meeting the requirements for Gravel Backfill for Walls in
Section 9-03.12(2) of the 2008 WSDOT Standard Specifications, should be used as retaining wall
backfill. However, in certain areas where the space between the excavation shoring and the permanent
below -grade wall is limited, a flowable fill material may need to be used as wall backfill. Within 3 ft of
the back of the wall, backfill should be compacted to about 90 to 92 percent of the maximum dry density
as determined by ASTM D 1557.
Unless the proposed retaining walls are designed to resist hydrostatic pressures, subsurface
drainage provisions should be incorporated into wall design to prevent infiltrating irrigation or storm
water from building up and exerting hydrostatic pressures behind the wall. Several types of wall drainage
materials are available; however, for this application we recommend installation of a prefabricated wall
drainage composite material that is hydraulically connected to a base drain that discharges to weep holes
in the wall or to another approved location.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Geotech_rptdoc LANDAU ASSOCIATES
4-7
RECEIVED
4.6 CONCRETE SLABS -ON -GRADE
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Conventional slab -on -grade construction is considered feasible for the planned odor control
improvements. Concrete slabs may be supported on compacted structural fill placed directly over
competent and properly prepared subgrade soils.
We recommend that concrete slabs be underlain by at least 8 inches of crushed rock meeting the
requirements for Crushed Surfacing in Section 9-03.9(3) of the WSDOT Standard Specifications. The
underslab gravel should be placed and compacted in accordance with Section 4.1.4 of this report.
Prior to placement of the underslab gravel, the upper 1 ft of the underlying subgrade should be
prepared and compacted to at least 95 percent of its maximum dry density as determined by ASTM
D 1557 to provide a smooth, unyielding surface for slab support. The compacted subgrade should be
proof -rolled in the presence of a qualified geotechnical engineer to check for the presence of soft, loose,
and/or disturbed areas. Any areas of soft, loose, and/or disturbed soil or areas exhibiting significant
deflection, pumping, or weaving that cannot be adequately reworked and/or compacted should be
overexcavated and replaced with compacted structural fill as described in Section 4.1.4 of this report.
The exterior concrete slabs may be designed based on a subgrade reaction modulus of 100 pounds
per cubic inch (pci), assuming the floor slab subgrade materials are prepared as recommended in this
report.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Geotech_rptdoc LANDAU ASSOCIATES
4-8
5.0 GEOTECHNICAL CONSULTATION AND CONSTRUCTION
MONITORING
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
We recommend that Landau Associates review the geotechnical-related portions of the project
plans and specifications to determine if they are consistent with the recommendations presented in this
report. We also recommend that monitoring, testing, and consultation be provided during construction to
confirm that the conditions encountered are consistent with those indicated by our explorations; to
provide expedient recommendations should conditions be revealed during construction that differ from
those anticipated; and to evaluate whether geotechnical-related construction activities comply with project
plans and specifications and the recommendations contained in this report. Such geotechnical-related
activities include installation of temporary shoring, subgrade preparation for concrete slabs and footings
and foundation installation for the proposed improvements.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Geotech_rptdoc LANDAU ASSOCIATES
5-1
6.0 USE OF THIS REPORT
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Landau Associates prepared this report for the exclusive use of the City of Edmonds and
Brown and Caldwell for specific application to the design of the planned C-311 Odor Control
Improvements project at the Edmonds Wastewater Treatment Plant in Edmonds, Washington. Use of this
report by others or for another project is at the user's sole risk. Within the limitations of scope, schedule,
and budget, Landau Associates' services have been conducted in accordance with generally accepted
practices of the geotechnical engineering profession; no other warranty, express or implied, is made as to
the professional advice included in this report.
The conclusions and recommendations contained in this report are based in part on the subsurface
data obtained from the explorations completed for this project. There may be some variation in
subsurface soil and groundwater conditions at the site, and the nature and extent of the variations may not
become evident until construction. Accordingly, a contingency for unanticipated conditions should be
included in the construction budget and schedule.
If variations in subsurface conditions are encountered during construction, Landau Associates
should be notified to review the recommendations of this report and make revisions, if necessary. If there
is a substantial lapse of time between submission of this report and the start of construction, or if design
requirements change, we recommend that we review this report to determine the applicability of the
conclusions and recommendations contained herein.
We appreciate the opportunity to provide geotechnical services on this project and look forward
to assisting you as needed during the final design and construction phases of the project. If you have any
questions or comments regarding the information contained in this report, or if we may be of further
service, please contact us.
LANDAU ASSOCIATES, INC.
,:� 4e Z� 46 ka",
David A. Pischer, P.E.
Senior Associate
sl-,, L4�j
Steven R. Wright, P.E.
Senior Associate
DAP/SZW/JJBIrgm
6123ro9 51F.thnlaialprojects1D74ll5a\FileRmVi4Final EWWTP Geotech Rht\Gmt tech_spt.cinc LANDAu ASSOCIATES
S-1
RECEIVED
May 26 2021
CITY OF EDMONDS
7.0 REFERENCES DEVELOPMENTDE ARTMENRVICES
Booth, D. B., Cox, B. F., Troost, K. G., and Shimel, S. A., 2004, Composite Geologic Map of the
Sno-King Area: University of Washington, Seattle -Area Geologic Mapping Project, scale 1: 24, 000.
International Code Council. 2006. 2006International Building Code. International Code Council.
Landau Associates. 1988. Geotechnical Report and Technical Memoranda, Edmonds Waste Water
Treatment Plant, Edmonds, Washington. Prepared for CWC-HDR, Inc. April 15.
USGS. 2008. Earthquake Ground Motion Parameters Software Program. Version 5.0.9. U.S.
Geological Survey.
WSDOT. 2008. Standard Specifications for Road, Bridge and Municipal Construction. M41-10.
Washington State Department of Transportation.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Geotech_rpt.doc LANDAU AssocIATES
6-1
A
0
0
N
E
1 ingstpn
Puget Sound
Q Project Location
0 0.5 1
Miles
Data Source: ESRI 2008
Snohomish
Park
C
May 26 2011
—CITY OF EDMOND
LO MENT SER C E S
SI�FMENT
Municipal Golf
Spokane*
Washington
I Edmonds Wastewater Figure
Treatment Plant Vicinity Map
LANDAU Odor Control Improvements
ASSOCIATES Edmonds, Washington
ED
9-l' W F..F
r,ON- F -'
CVI0hh
LL'2 LL'
TOP 'F V,
EL 32 CC'
TFK'PC,PA
SFJ-INV
0 10 20
Scale in Feet
May 26 20R1
CITY OF EDA
Legend DEVELOPMENT
DEPARTM
Boring Location and
&B-1 Designation
i' FiI AR JO WATCH
IS-1^ F-G
4h tS S] I::'1 f2".
L 1MLL- J'21 VN
NF
it AF " `1 F�RA.-)F
r3.13" Or, F'., 2
LtF F
Base map source: Brown and Caldwell, 2009
Edmonds Wastewater Figure
LANDAU Treatment Plant Site and Exploration Plan
Odor Control Improvements
ASSOCIATES Edmonds, Washington
M
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICE:
DEPARTMENT
S�
0.28q s
�--4101D---�
�--270+301D--�
�{
Passive Earth
Active Earth
Active
Pressure
Pressure
Surcharge
(Static)
(Static)
Earth
Pressure
Notes:
1. Active pressure diagram assumes cantilevered sheeting.
2. Solve for D by summation of moments about bottom of sheeting.
3. The passive pressure presented is an allowable value and includes a factor of safety of about 1.5.
4. Active and passive pressures are in terms of pounds per square foot, with all dimensions in feet.
5. Ignore upper 2 ft of passive pressure.
Edmonds Wastewater Figure
Treatment Plant Design Lateral Earth Pressures
14 LANDAU Odor Control Improvements Temporary Excavation Shoring
ASSOCIATES Edmonds, Washington
RECEIVED
LHNUHUH UUIHI=J,IIN U.I V:\V/4\IJo\VIVvI I\U\rlyure
A. Strip Footing
Cross Section View
Ground Surface
q a ld
1
a/2
a
ah� _ D
4 O/6/LVVU
B. Small Isolated Footing
Cross Section View
J
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPAFCf Eeontinulouls Wall Footing
Parallel to Excavation Footing
Cross Section View
Ground Surface ---,
Line Load
Pressure
(For m > 0.4)
ah=K*1.28q' mzn
D (mz+nz)z
(For m < 0.4)
a ah=K* g 0.2n
h=K*0.64q((3-sin(3cos2a) z z
Base of Excavation Base of Excavation D (0.16+n) � Base of
Excavation
Definition of Units
Q Footing Load in Pounds
D Excavation Depth below Footing in Feet
d Depth to Base of Footing in Feet
a Lateral Soil Pressure in PSF
q h Unit Loading Pressure in PSF
q' Footing Load in Pounds per Foot
a, (3 Radians
LANDAU
1A ASSOCIATES
B. Plan View
ah=K* Oh COS (1.1 a
(For m > 0.4)
ah=K*1.77Q
mznz
Dz
(m2+n2)3
(For m s 0.4)
ah=K* 0.28Q
nz
Dz
(0.16+n2) 3
Edmonds Wastewater
Treatment Plant
Odor Control Improvements
Edmonds, Washington
Notes:
1. For sheet pile walls, use k = 0.30.
2. Lateral pressures due to adjacent structures should be added to
lateral pressures shown on Figure 3.
3. Wall footings acting other than parallel to the excavation can be
treated as series of discrete point loads, using approach B.
4. Contact Landau Associates for surcharge recommendations if
necessary.
Figure
Surcharge Pressures A
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
APPENDIX A
Field Explorations and Laboratory Testing
RECEIVED
APPENDIX A
FIELD EXPLORATIONS AND LABORATORY TESTING
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Subsurface conditions at the project site were explored on May 26, 2009. The exploration
program consisted of advancing and sampling two exploratory borings (B-1 and B-2) at the approximate
locations illustrated on the Site and Exploration Plan (Figure 2). The exploratory borings were advanced
to depths of about 14 feet (ft) below ground surface (BGS) using a limited access, hollow -stem auger drill
rig. CN Drilling of Seattle, Washington advanced the borings under subcontract to Landau Associates.
The explorations were located approximately in the field by hand -taping from existing physical features
and referencing a site plan provided by Brown and Caldwell. Ground surface elevations at the
exploratory boring locations were estimated from design drawings and site layout information provided
by Brown and Caldwell.
The field exploration program was coordinated and monitored by a Landau Associates
geotechnical engineer who also obtained representative soil samples, maintained a detailed record of
observed subsurface soil and groundwater conditions, and described the soil encountered by visual and
textural examination. Each representative soil type observed in our exploratory borings was described
using the soil classification system shown on Figure A-1, in general accordance with American Society
for Testing and Materials (ASTM) D2488, Standard Recommended Practice for Description of Soils
(Visual -Manual Procedure). Logs of the exploratory borings are presented on Figures A-2 and A-3.
These logs represent Landau Associates' interpretation of subsurface conditions identified during the field
exploration program. The stratigraphic contacts shown on the summary logs represent the approximate
boundaries between soil types; actual transitions may be more gradual. The soil and groundwater
conditions depicted are only for the specific date and locations reported and, therefore, are not necessarily
representative of other locations and times. A further discussion of the soil and groundwater conditions
observed is contained in the text portion of this report.
Disturbed samples of the soil encountered in the exploratory borings were obtained at selected
intervals using a 1.5-inch inside -diameter Standard Penetration Test (SPT) split -spoon sampler. The
sampler was driven up to 18 inches into the undisturbed soil ahead of the auger with a 140-pound hammer
falling a distance of approximately 30 inches. The number of blows required to drive the sampler for the
final 12 inches of soil penetration, or part thereof, is noted on the boring logs, adjacent to the appropriate
sample notation. Samples collected in this manner were taken to our laboratory for further examination
and testing. Upon completion of drilling and sampling, the boreholes were abandoned in general
accordance with the requirements of Chapter 173-160 WAC.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPOeotechRpt\Rpt_apa.doc LANDAU ASSOCIATES
A-1
RECEIVED
May 26 2021
CITY OF EDMONDS
The laboratory testing program, which was performed in general accordance with the )kPMENT SERVICES
ARTMENT
standard test procedures described below, was limited to visual inspection to confirm our field soil
descriptions and determination of natural moisture contents and grain size distributions. The natural
moisture contents of selected soil samples obtained from our exploratory borings were determined in
general accordance with ASTM D2216 test procedures. The results from the moisture content
determinations are indicated adjacent to the corresponding samples on the summary logs. The grain size
distribution of a selected soil sample obtained from our exploratory borings was determined in general
accordance with ASTM D422 test procedures. The results are presented in the form of a grain size
distribution curve on Figure A-4.
6/23/09\\Edmdata\projects\074\158\FileRm\R\FinalEWWTPOeotechRpt\Rpt_apa.doc LANDAU ASSOCIATES
A-2
MAJOR
DIVISIONS
Soil Classification System
USCS
GRAPHIC LETTER
SYMBOL SYMBOL"'
TYPICAL
DESCRIPTIONS 12)13)
May 26 202,
CITY OF EDMONDS
DEVELOPMENT SERVIC
DEPARTMENT
GRAVEL AND
CLEAN GRAVEL
4 o a
GW
Well -graded gravel; gravel/sand mixture(s); little or no fines
o. o O o
GP
a
GRAVELLY SOIL
(Little or no fines)
Poorly graded gravel; gravel/sand mixture(s); little or no fines
_
O m'y
Q.d
GRAVEL WITH FINES
GM
o m
.N
(More than 50% of
coarse fraction
Silty gravel; gravel/sand/silt mixture(s)
w E
z w o
°
retained on No. 4
(Appreciable amount of
fines)
Clayey
GC
Q N
sieve)
gravel; gravel/sand/clay mixture(s)
0 0
w z
SAND AND
CLEAN SAND
SW
Well -graded sand; gravelly sand; little or no fines
n, com
SANDY SOIL
(Little or no fines)
Poorly graded sand; gravelly sand; little or no fines
SP
o°
SAND WITH FINES
SM
(More than 50% of
coarse fraction passed
Silty sand; sand/silt mixture(s)
SC
through No. 4 sieve)
(Appreciable amount of
fines)
Clayey sand; sand/clay mixture(s)
ML
Inorganic silt and very fine sand; rock flour; silty or clayey fine
_j o
SILT AND CLAY
sand or clayey silt with slight plasticity
CL
O lc�N
Inorganic clay of low to medium plasticity; gravelly clay; sandy
E 0
0-
(Liquid limit less than 50)
clay; silty clay; lean clay
z m .N
OL
Organic silt; organic, silty clay of low plasticity
Qo�;
T
MH
Inorganic silt; micaceous or diatomaceous fine sand
(�7 .N
76
SILT AND CLAY
z N
CH
Inorganic clay of high plasticity; fat clay
o
5—
(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
GRAPHIC LETTER
OTHER MATERIALS SYMBOL SYMBOL TYPICAL DESCRIPTIONS
PAVEMENT
AC or PC
Asphalt concrete pavement or Portland cement pavement
ROCK
RK
Rock (See Rock Classification)
WOOD
WD
Wood, lumber, wood chips
DEBRIS
O O O
DB
Construction debris, garbage
NOTES:
1. USCS letter symbols correspond to symbols used by the Unified Soil Classification System and ASTM classification methods. Dual letter symbols (e.g.,
SP-SM for sand or gravel) indicate soil with an estimated 5-15% fines. Multiple letter symbols (e.g., ML/CL) indicate borderline or multiple soil
classifications.
2. Soil descriptions are based on the general approach presented in the Standard Practice for Description and Identification of Soils (Visual -Manual
Procedure), outlined in ASTM D 2488. Where laboratory index testing has been conducted, soil classifications are based on the Standard Test
Method for Classification of Soils for Engineering Purposes, as outlined in ASTM D 2487.
3. Soil description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each soil type and is defined as
follows: Primary Constituent: > 50% - "GRAVEL," "SAND," "SILT," "CLAY," etc.
Secondary Constituents: > 30% and < 50% - "very gravelly," "very sandy," "very silty," etc.
> 15% and < 30% - "gravelly," "sandy," "silty," etc.
Additional Constituents: > 5% and < 15% - "with gravel," "with sand," "with silt," etc.
< 5% - "trace gravel," "trace sand," "trace silt," etc., or not noted.
I Edmonds Wastewater
Treatment Plant Soil Classification System and Key
LANDAU Odor Control Improvements
14 ASSOCIATES Edmonds, Washington
Figure
A-1
(1 of 2)
A
0
N
H
0
0
U
U
co
May 26 202
CITY OF EDMONDS
DEVELOPMENT SERVK
Drilling and Sampling Key Field and Lab Test Data
SAMPLER TYPE SAMPLE NUMBER & INTERVAL
Code Description
a 3.25-inch O.D., 2.42-inch I.D. Split Spoon
b 2.00-inch O.D., 1.50-inch I.D. Split Spoon
c Shelby Tube
d Grab Sample
e Single -Tube Core Barrel
f Double -Tube Core Barrel
g Other - See text if applicable
1 300-lb Hammer, 30-inch Drop
2 140-lb Hammer, 30-inch Drop
3 Pushed
4 Rotosonic
5 Air Rotary (Rock)
6 Wash Rotary (Rock)
7 Other - See text if applicable
Groundwater
Code
Description
Sample Identification Number
PP = 1.0
Pocket Penetrometer, tsf
Recovery Depth Interval
TV = 0.5
Torvane, tsf
PID = 100
Photoionization Detector VOC screening, ppm
1ju � Sample Depth Interval
W = 10
Moisture Content, %
J~
J
D = 120
Dry Density, pcf
Portion of Sample Retained
-200 = 60
Material smaller than No. 200 sieve, %
for Archive or Analysis
GS
Grain Size - See separate figure for data
AL
Atterberg Limits - See separate figure for data
VST
Vane Shear Test
GT
Other Geotechnical Testing
CA
Chemical Analysis
SZ Approximate water elevation at time of drilling (ATD).
1 Approximate water elevation at other time(s). When multiple water levels are
obtained other than ATD, only a representative range is shown. See text for additional
information.
Note: Groundwater levels can fluctuate due to precipitation, seasonal conditions, and other
factors.
I Well Loa Graphics I
Above -Ground
Monument
v v '
10 20 Sand
LLI V__1J Bentonite Chips
� J Bentonite Grout
Slough Backfill
'_Flush -Mount
Monument
PVC Blank Casing
f:
PVC Screen
(0.010-inch Slot Size)
End Cap
I Edmonds Wastewater
Treatment Plant Soil Classification System and Key
LANDAU Odor Control Improvements
14 ASSOCIATES Edmonds, Washington
Figure
A-1
(2 of 2)
REC
D
B_1 May 26 202
LAI Project No�11(�7*156aQ Cs
07
s
Moisture C,OPUT
SAMPLE DATA SOIL PROFILE
Plastic Liquid
Limit Limit
� o Hollow -Stem Auger 10 20 30 40
-0 m o Drilling Method:A SPT N-Value A
E Q E 0 Nonstandard N-Value 0
❑ _ o T E Ground Elevation (ft): 22
g n c> 3 10 20 30 40
L
m a m 0- U' � � � ❑ X Fines Content (%) X
°' m - ° `6 co Logged ed By: JJB Date: 05/26/09 °
o w cn .6 co m � (9 D C9 10 20 30 40
0 22 : ; • PC 8" Concrete Sidewalk
SP Tan to brown, fine to medium SAND with
trace silt and gravel (loose to medium
S1 b2 7 dense, moist)
(FILL)
2 20 :.......:......:.......:......
0
w
w
0
Z
S2 b2 8 A:
m
3
4 18 :.......:......:..............
2
c�
S3 b2 15 WGs 1 Xig A
6 16 7:.............:......
8 14 :.......:.............:......
= S4 b2 14
a
SM Gray, silty, fine to medium SAND with
gravel (dense, moist)
(REWORKED GLACIAL TILL FILL)
10 12....:....... :....... ....... :......
t,
z
o S5 b2 33 W = 9 • : A
on
J_
on
� 12 10
.....*....... ........ ....... .......
0
0
v
n
S6 b2 39
Cn
w (Depth to native glacial till not determined)
0 14 L 8
a Boring Completed 05/26/09
z Total Depth of Boring = 14.0 ft.
z
z
a 16
❑
w_
m
0
M
N
D Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate.
0 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
v
r`
Edmonds Wastewater Figure
Treatment Plant Log of Boring B-1
LANDAU Odor Control Improvements A-2
14 ASSOCIATES Edmonds, Washington
REC
D
B_2 May 26 202
LAI Project No;-.11(�7*156aQ Cs
07
s
Moisture C,OPUT
SAMPLE DATA SOIL PROFILE
Plastic Liquid
Limit Limit
� o Hollow -Stem Auger 10 20 30 40
-0 m o Drilling Method:A SPT N-Value A
E Q E 0 Nonstandard N-Value 0
� _ o T E Ground Elevation (ft): 22
g 0 U) 3 10 20 30 40
m U) _E � X Fines Content (%) X
°' m - ° `6 co Logged ed By: JJB Date: 05/26/09 °
o w cn .6 co m C9 D C9 10 20 30 40
0 22 : ; • PC 7" Concrete Sidewalk
SP Tan to brown, fine to medium SAND with
trace silt and gravel (loose to medium
S1 b2 6 dense, moist) o
(FILL)
2 20 :.......:.............:......
0
NA
S2 b2 NA -obstruction encountered at 2.5 ft bgs. w
Blow counts not representative of soil z
density.
a�
m
3
4 18....:....... :....... ....... :......
2
c�
S3 b2 14 A
6 16 :.......:.............:......
8 14 :.......:.............:......
= S4 b2 24 W = 15 • A
a
becomes wet, potentially perched water
c� on reworked glacial till _
SM Gray, silty, fine to medium SAND with
gravel (dense, moist)
10 12 (REWORKED GLACIAL TILL FILL) :.......:.............:......
t,
z
0 S5 b2 37 A
m
J_
0
on
� 12 10
.....*....... ........ ....... .......
0
0
W=12 V
S61 b2 37 A
Cn
w (Depth to native glacial till not determined)
0 14 8
a Boring Completed 05/26/09
z Total Depth of Boring = 14.0 ft.
Ill 16
m
0
M
N
D Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate.
0 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
v
r`
Edmonds Wastewater Figure
Treatment Plant Log of Boring B-2
LANDAU Odor Control Improvements A_3
14 ASSOCIATES Edmonds, Washington
74158.01 6/23/09 \\EDMDATA\GINT\GINT7\PROJECTS\074158.010.GPJ GRAIN SIZE FIGURE RECEIVED
100
U.S. Sieve Opening in Inches
6 4 3 2 1.5 1 3/4 1 2 3/8 3 4
May 26 2021
U.S. Sieve Numbers CITY OF EDMO I�I7 ,ter
DEVELOPMENT SE ES
DEPARTMENT
6 8 10 14 16 20 30 40 5060 100 140 200
90
80
70
(D
T
60
4
c
ii
50
c
a
40
30
20
10
H:
100 10 1 0.1 0.01 0.001
Grain Size in Millimeters
LANDAU
ASSOCIATES
Edmonds Wastewater
Treatment Plant
Odor Control Improvements
Edmonds, Washington
Grain Size Distribution
Figure
/A/�
_
`t
Cobbles
Gravel
Sand
Silt or Clay
Coarse Fine
Coarse Medium Fine
Symbol
Exploration
Sample
Depth
Naturalo
Soil Description
Unified Soil
Number
Number
(ft)
Moisture (/o)
Classification
•
B-1
S3
5.0
11
Fine to medium SAND with trace silt and gravel
SP
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
APPENDIX B
Selected Aerial Photographs (1989 to 1991)
RECEIVED
May 26 2021
CITY OF EDMONDS
APPENDIX B DEVELOPMENTDEPARTMENT
DE
SELECTED AERIAL PHOTOGRAPHS (1989 TO 1991)
Selected aerial photographs taken between 1989 and 1991 during construction of the existing
WWTP facilities are presented in this Appendix to provide a better understanding of existing subsurface
conditions in the vicinity of the planned odor control improvements located between Final Clarifier No. 1
and Final Clarifier No. 2.
6/23/09 \\Edmdata\projects\074\158\FileRm\R\FinalEWWTPGeotechRpt\Rpt_apb.doc LANDAU ASSOCIATES
B-1