REVIEWED BLD2021-0520+1987_GEO_Inv_Report+5.26.2021_11.22.37_AM+2217898RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
1
J
F
1
1
BLD2021-0520
REPORT OF GEOTECHNICAL INVESTIGATION
SECONDARY WASTE WATER ^REATMENT PLANT
DAYTON ;STREET S:!'!'E
FOR THE
CITY OF EDMONDS, WASHINGTON
I I
RECEIVED
May 26 2021
CITY OF EDMONDS
'
DEVELOPMENT SERVICES
DEPARTMENT
1
LANDAU ASSOCIATES, INC
GEOTECHNICAL ENGINEERING AND HYDROLOGY
P O BOX 694
EDMONDS, WASHINGTON 98020
(206) 778-0907
' CWC-HDR, Inc.
300 Admiral Way, Suite 204
Edmonds, WA 98020-4127
' Attention: Mr. Bud Benjes
' Report of Geotechnical Investigation
Secondary Waste Water Treatment Plant
Dayton Street Site
for the
City of Edmonds, Washington
June 16, 1987
' Gentlemen:
This letter transmits our report for the Phase I predesign
' investigation for new secondary treatment facilities at the
' existing Edmonds waste water treatment plant located at the
intersection of Dayton Street and S.R. 104. Our report of
' preliminary geotechnical investigation at the alternate Pine
Street site, dated June 10, 1987, was transmitted to you last
' week.
' The scope of this geotechnical investigation at the Dayton
Street site was developed during negotiations between Mr. Gordon
' Culp of your firm and the writer. Our services were authorized
by our Subconsultant Agreement dated April 24, 1987.
' The data in this report is intended to provide information
for preliminary design. As the specifics of design are
' developed, we are available to refine the parameters for specific
1
RECEIVED
Wn� ?Qg�s. Report addenda will be used for the supplemental
CITY OF EDMONDS
DEVELOPMENT SERVICES
ifff1dYYd9tion
.
We appreciate the opportunity to continue providing engi-
neering services for this project. Please contact Mr. Dave
Pischer or the writer if you have questions or need additional
information.
Yours very truly,
LANDAU ASSOCIATES, INC.
By:
i�
Robert G. Fulton, P.E.
Vice President
RGF/sg
No. 74-02.03
attachment
5 copies submitted
RECEIVED
May 26 2021 TABLE OF CONTENTS
' CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
' Section
INTRODUCTION
' SCOPE
PROJECT DESCRIPTION AND DESIGN CONSIDERATIONS
' SITE CONDITIONS
Surface Conditions
Subsurface Conditions
CONCLUSIONS AND RECOMMENDATIONS
' General
Dewatering
Shoring of Deep Excavations
' Site Preparation
Excavations
Fills
' Wet Weather Construction Considerations
Foundation Support
Drainage Considerations
' Buoyancy and Uplift
Lateral Earth Pressure Criteria
Lateral Soil Resistance
Floor Slab Support
Roadway Design Considerations
General Seismic Considerations
' Construction Instrumentation and Monitoring
APPENDIX A: Site Explorations
1 APPENDIX B: Laboratory Testing Program
Page
1
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3
5
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12
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RECEIVED
May26 2021 REPORT OF GEOTECHNICAL INVESTIGATION
CITY OFLOPM ETSERVI SECONDARY WASTE WATER TREATMENT PLANT
DEVELOPMENT SERVICES
DEPARTMENT DAYTON STREET SITE
FOR THE
' CITY OF EDMONDS, WASHINGTON
'
INTRODUCTION
This report presents the results of
our Phase I subsurface
exploration and geotechnical engineering
study for the planned
secondary waste water treatment plant at
the Dayton Street site
'
in Edmonds, Washington. The project site
is located on property
'
presently occupied by the existing City
of Edmonds waste water
treatment plant and adjacent storage yard.
These facilities are
'
situated south of Dayton Street between
State Route (S.R.) 104
and Second Avenue, as shown on the Vicinity
Map, Figure 1, and
'
the Site Plan, Figure 2.
SCOPE
The purpose of this geotechnical investigation is to char-
acterize the subsurface soil and ground water conditions at the
' site and provide engineering recommendations to aid in the
initial design of the planned secondary waste water treatment
' plant. Our geotechnical engineering services are scheduled to be
accomplished in three phases: Phase I - predesign investigation;
' Phase II - design consultation; and Phase III - construction
consultation.
' This report presents the results of our Phase I engineering
' services, the scope of which includes, but is not necessarily
limited to:
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Conducting a subsurface investigation to characterize
'
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
soil and ground water conditions pertinent to the
planned development;
o
Providing geotechnical parameters needed for prelim-
inary design of the permanent structures and temporary
'
facilities needed for construction, including: excava-
tion shoring; dewatering systems, shallow and deep
'
foundation support and installation requirements;
permanent subsurface walls and pavements;
'
o
Providing recommendations for earthwork operations,
including: excavations, fills and backfills, foundation
'
drainage,
subgrade preparation, site and construction
monitoring requirements;
o
Estimating settlements, evaluating potential earthquake
'
effects on the planned facilities, and construction
effects on adjacent properties;
'
Preparing summarizes our explorations,
o
a report which
'
laboratory test findings, and our preliminary geotech-
nical engineering conclusions and recommendations.
' Phase II - design consultation services will be focused on
' evaluating and providing geotechnical design parameters for final
design of specific project elements. Engineering consultation
' will be provided during:
' o Preparation and review of construction plans, specifi-
cations, and permit applications;
' o Review of value engineering results provided by others;
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RECEIVED
May26?021 Evaluation of contractor bid alternatives and
' CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT scheduling.
Phase III include
- construction consultation services will
'
a variety
of part- to full-time construction monitoring and
observation activities. Specific activities may include:
'
o
Consultation regarding alternative dewatering proce-
dures to facilitate construction below grade;
'
o
Monitoring the installation of, and evaluating perfor-
mance data for, the excavation shoring system;
o
Consultation regarding excavation and the disposal or
'
reuse of the excavated soils;
o
Observing the adequacy of foundation bearing surfaces
'
and monitoring the installation of pile foundations;
o
Monitoring the suitability and compaction of fill and
'
backfill soils;
'
o
Consultation regarding the monitoring of construction
effects on adjacent properties and facilities.
'
PROJECT DESCRIPTION AND DESIGN CONSIDERATIONS
'
Conceptual design drawings for the
proposed development
indicate that the new facilities will
be located within the
'
limits of the existing City of Edmonds
waste water treatment
plant and the adjacent storage area to the
south, as shown on the
'
Site
Plan, Figure 2. The locations and
subgrade elevations of
'
individual facility elements were not finalized at the time of
this report. We understand that most of
the below grade struc-
tures will be in the northern half of the
site. Secondary treat-
ment facilities will include, but will
not be limited to, at
1
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RECEIVED
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' DEVELOP�MF SOER11Mee clarifiers and aeration basins, a chlorine contact
DEPARTMENT
structure, numerous sludge handling and storage structures, a
' sludge dewatering/incineration building, an operations control/
' administration building, and other related facilities such as
pumping stations, flow metering and screening structures, and
' pipelines. Current plans indicate that a structural lid will be
placed over certain facilities on the north side of the site to
' permit construction of a park over the underlying treatment
' facilities.
We understand that the operations control/administration
' building may be the only major structure with lowest finish floor
elevations near existing grade. Excavation depths for the
' remaining facilities are not expected to exceed about 20 to 25
feet below existing site grades, but certain pipeline facilities
below or between some structures could be located up to about 3
feet below the base of those structures. Foundation loads have
not been finalized, but it is expected that maximum foundation
' wall loads will be about 10 kips per foot and structural slab
loads will be less than about 1500 pounds per square foot (psf).
' Apparently, the existing outfall pipeline will be utilized for
' this secondary treatment expansion project.
Construction sequencing is an important factor since waste
' water treatment must be maintained continuously during construc-
tion, disruption to traffic flow on S.R. 104 and Dayton Street
' must be minimized, and the wetland areas south of the site must
remain undisturbed. The existing clarifier units No. 4 and 5,
that have a timber pile supported roof structure and certain
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RECEIVED
Ma 36 20?f 1
irYf uen and effluent pipelines and pumps, will need to remain in
CITY OF EDMONDS
DEVELOPMENT SERVICES
oJMYWENYTon and be protected during construction. Several tempor-
ary treatment facilities will be used during the construction
period.
SITE CONDITIONS
Surface Conditions
The existing waste water treatment plant and the adjacent
storage yard is bounded to the north by Dayton Street, to the
east by 2nd Avenue, to the south by wetlands, and to the west by
the fill embankment for S.R. 104. Most of the site is fairly
level, with surface grades within the paved and landscaped area
on the northern portion of the site varying from approximately
Elevation 13 to 19 (U.S.G.S. datum) and grades within the gravel
surfaced storage yard varying from approximately Elevation 16 to
17. Variations in surface grades within the north portion of the
site are primarily related to either landscaping or fill embank-
ments supporting existing clarifiers No. 4 and 5. Concrete
retaining walls up to about 5 feet high support grade changes
between the site and the roadways near the northeast corner of
the treatment plant.
The major existing waste water treatment structures at the
site are shown on the Site Plan, Figure 2. Numerous pipelines
and utilities associated with the treatment plant are buried at
various locations and depths below both the site and the roadways
to the north and east. The area on the south side of the site is
used by the City of Edmonds for storage of a variety of equipment
and materials.
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' DE91M_tFhhd'h'. f Conditions
DEPARTMENT
General Site Geology: The geology of the study area is
' primarily a result of glacial and post -glacial deposition and
' erosion. Several advances and retreats (actually in -place
melting) of continental ice sheets have resulted in the deposi-
tion of a thick sequence of soils within the Puget Sound basin.
While several of the soil units can be traced over much of the
' Puget Lowlands, lateral discontinuities, variations in thickness,
and interfingering of adjoining soil units are common and often
result in complex geologic conditions, especially on a site
' specific basis.
Published geologic literature* indicates that the primary
natural soil units at the site are: 1) pre -glacial sediments
consisting of fine to coarse sand and silts; 2) glacial till
' (Vashon drift); 3) recessional outwash deposits consisting of
' silt, sand, and gravel mixtures; and 4) marsh deposits which
include peat and organic -rich alluvium. The local geologic map,
' Figure 3, provides a summary of this information. Fill soils are
also present throughout the site.
Site specific geologic conditions identified are more
' complex than that suggested by the literature. The various
geologic units identified during our exploration for this Phase I
' investigation, along with a brief description and general loca-
tion, are outlined below. Subsurface profiles, presented on
* Geologic Map of the Edmonds East and part of the Edmonds
West Quadrangles, Washington, U.S.G.S. Miscellaneous Field
Studies Map MF-1541, by J.P. Minard, dated 1983.
6
RECEIVED
qq���
"G�o4ogi1 unit
�OF EDMONDS
DEV LpO�f�Pip1kpwy�aF1iT§ t'
tVPVTlaCst) Soil Type General Location
-----------------------------------------------------------------
Fill Sand and silty sand Covers entire project
with gravel (medium site
dense)
Marsh Deposits Peat, organic silt Borders site to the
and silt (soft) south and west, also
present below fill in
the southwest portion
of the site
Recessional
Deposits
Glacial Till
Advance Deposits
Sand, sand and
gravel, and silt
(medium dense
to stiff)
Silt, sand, and
gravel mixtures
(very dense,
hard)
Slightly silty
sands with occa-
sional layers of
silt (very dense,
hard)
Encountered throughout
site below fill and
marsh deposits, where
present
Glacially consolidated
stratum encountered in
all borings except
in the extreme south-
west corner of the
site
Encountered below
glacial till
Figures 4 through 7, provide a visual presentation of the
relative position of each of the soil units encountered at the
site.
The fill material covering the entire site is generally a
poorly to moderately compacted sand with varying amounts of silt
and gravel. The marsh deposits are very soft and occur beneath
the fill at the southwest corner of the site and throughout an
extensive area south and west of the site. The recessional
deposits of the last glaciation which were encountered below
either fill or the marsh deposits are a poorly to moderately well
7
RECEIVED
W8figS?Qalted formation consisting primarily of silty sand and
' CITY OF EDMONDS
DEVELOPMENT SERVICES
saEmdysENsllt. The glacial till is a very dense to hard deposit
' placed and compacted by glacial ice and consists of a variable
mixture of silt, sand, and gravel. Advance deposits are found
' under the glacial till and form a dense to very dense sand unit
with occasional layers of silt. The advance deposits are the
deepest strata encountered in the explorations during this Phase
'
I investigation.
'
Available Background Information: In our evaluation of
near -surface soil conditions at and near the Dayton Street site,
'
we reviewed published literature and obtained and reviewed
exploration data for: 1) previous site developments at the waste
'
water treatment plant site; i.e. 4 soil borings drilled by
Pittsburgh Testing Laboratory and presented in their reports to
1
Reid, Middleton & Associates, Inc. dated January 23, 1967 and
'
March 31, 1969; 2) S.R. 104 facilities as available from the
Washington State Department of Transportation; and 3) selected
'
facilities at the Harbor Square Development located west of S.R.
104 as available from Puget West Corporation.
t
Site Explorations and Laboratory Tests: The subsurface soil
'
and ground water conditions at the site were explored by drilling
ten borings at the locations shown on the Site Plan, Figure 2.
'
The borings ranged in depth from about 29.5 to 64.5 feet below
' existing grades. The logs of the ten borings are presented on
Figures A-1 through A-10 in the Appendix of this report. All
' soils encountered were classified in general accordance with the
Unified Soil Classification System as described on Figure A-11.
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RECEIVED
May 26 2021
I T.Y OF EDMON S
DE JjY9Wo � Ts were installed in Borings B-1, B-3, B-5, and B-7 to
DEPARTMENT
allow monitoring of ground water levels. The boring locations
and the ground and piezometer casings elevations were surveyed by
Reid, Middleton & Associates, Inc. All elevations are based on
U.S.G.S. datum (MLLW = EL. 0.00 feet). A more detailed descrip-
tion of the field equipment and procedures used during our site
explorations is presented in Appendix A.
Laboratory tests were accomplished on representative soil
samples to evaluate their pertinent physical and engineering
characteristics relative to the planned construction. The labor-
atory program included sample inspection to confirm our site
engineer's soil classification, and determination of shear
strength, permeability, moisture -density relationships, and
grain -size distribution. A description of the laboratory equip-
ment and test procedures, in addition to the results of the
testing program, is presented in Appendix B.
Generalized Soils Description: The following descriptions
are very generalized, and both the logs of explorations and the
results of laboratory tests should be reviewed for a better
understanding of the nature of the soils encountered at specific
exploration locations. The subsurface profiles presented on
Figures 4 through 7 should also be referenced. The following
discussion of subsurface conditions is presented in order of
increasing depth below the ground surface.
Fill soils, ranging in depth from about 5 feet at Boring B-6
to about 13 feet at Boring B-1, were encountered at all boring
locations. The fill material generally consists of loose to
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RECEIVED
May 26 2021
' CITY OF EDMONDS
DEMEUTfER'd1tfihSe sand to silty sand with gravel. Occasional organic
DEPARTMENT
matter and construction debris was observed within the fill
' material.
'
Marsh
deposits consisting of soft,
compressible
peat
(Pt)
and organic
silt (OL) were encountered in
Borings B-1,
B-4,
B-9,
'
and B-10.
Ground water is often perched
in or above
the
marsh
deposits.
These deposits ranged in thickness
from about 2
feet
'
at Boring B-9 to about 5 to 6 feet at the
other boring
locations.
' The thickest and deepest peat and organic silt deposits were
encountered at Boring B-1. However, soil borings for S.R. 104
indicate that up to 10 to 15 feet of soft deposits are present at
some locations in the wetlands to the west and south of the site.
It is known that some overexcavation and replacement of these
soft soils was accomplished during previous development at the
existing the waste water treatment plant.
Recessional deposits consisting of saturated silty sand (SM)
and sandy silt (ML) with occasional lenses of clean sand were
encountered at all boring locations directly below the fill or
marsh deposits, where present. These soil deposits are quite
variable both in distribution of silt, sand, and gravel sized
material and in consistency. The silty sands are generally
medium dense and the sandy silts are generally stiff, but tend to
grade denser and stiffer with depth. This soil unit varies in
thickness from about 5 feet in Boring B-7 to nearly 14 feet in
Borings B-4 and B-8. A 6-foot thick layer of sandy gravel (GW)
to gravelly sand (SW) was encountered at the base of this unit in
Boring B-3.
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RECEIVED
May H gN l ial till was encountered in all borings except Boring
' CITY OF EDMONDS
DEVELOPMENT SERVICES
BREJAVTMEwhere it appears to have been removed by post -glacial
' erosional forces. The till is generally a very dense to hard
variable mixture of silt, sand, and gravel (SM to ML), ranging in
' thickness from about 6 feet in Boring B-2 to about 12 feet in
Boring B-4. As shown on Figures 5 and 6, the glacial till
' appears to locally dip to the west below the project site.
' Below the glacial till, a unit of dense to very dense
slightly silty fine to medium sand (SP) was encountered at all
' the boring locations. The ground water in these advance glacial
deposits was observed to have a high piezometric head. Layers of
silt (ML) with a trace of fine sand and organic matter were
observed
within this lower sand
unit at Borings B-3 and B-6.
However,
it was not determined if
the layer of silt encountered
'
in these
two deepest borings at a
depth of about 50 feet below
grade is
interconnected or exists
at other locations below the
'
project site.
'
Ground Water: Our evaluation of ground water conditions
across the site have
been based on observations made during our
'
laboratory testing
site reconnaissance,
our exploration and
'
program, as well as
by monitoring water levels in the piezo-
meters. Free water
was first observed during drilling in all
'
ten borings at depths
generally ranging from about 1 to 13 feet,
but as deep as 23 feet at one location, below existing site
'
grades, as noted on the appropriate boring logs.
Piezometers were
installed in Borings B-1, B-3, B-5, and B-7
'
to allow monitoring
of ground water levels at those boring
11
RECEIVED
4Wc�aq ?Nl . Details of the
piezometer installations are
presented
t
CITY OF EDMONDS
DEVELOPMENT SERVICES
onEPttWTappropriate boring
logs and in the discussion in
Appendix
'
A. The latest series of
water level measurements in these four
piezometeis indicate water
levels between Elevation 11.6
and 12.9
'
(see Table A-1 in Appendix
A).
Ground water within
the sands below the glacial
till was
observed to have a high piezometric
head, with the water
level in
'
Piezometer
P-3 rising up to near the existing ground
surface.
The presence of artesian water conditions in the lower
sands is
expected to
have a significant effect on site dewatering
require-
ments and
the construction of structures that extend
into or
tthrough
the
glacial till.
'
CONCLUSIONS AND RECOMMENDATIONS
GENERAL
Based on the results of our Phase I predesign investigation,
laboratory testing, and engineering analyses, we conclude that
development of the site is feasible from a geotechnical engi-
neering consideration provided that the recommendations presented
below are incorporated into the site development plans and
implemented during construction.
Significant geotechnical aspects of the project to be
addressed during site development include: 1) dewatering prior to
site excavation; 2) shoring of deep excavations due to site limi-
tations; 3) design of subsurface retaining walls; 4) buoyancy of
below grade structures; and 5) construction instrumentation and
monitoring. Recommendations regarding earthwork operations, site
preparation, foundation support, and a discussion of various
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May 26 2021
DEVEEIOPPM�NTSORV�l Egineering considerations and anticipated construction
DEPARTMENT s
difficulties, are presented in the following sections. Geotech-
nical design parameters for design of specific project elements
will be finalized and provided during our Phase II design
consultation.
DEWATERING
Ground water levels observed at the site are generally above
the anticipated elevations of the bottom of the planned facili-
ties. Also, a high piezometric head in the sand unit underlying
the till will probably result in excavation instability if the
water pressure is not significantly reduced prior to excavation.
Temporary dewatering will be required during excavation for and
construction of underground facilities, as well as during
dewatering/maintenance activities for any facilities that are not
structurally designed to resist the maximum expected buoyancy and
bottom uplift pressures.
We recommend that deep wells with submersible high capacity
pumps, and/or other appropriate means selected by the contractor,
be provided as necessary to maintain the piezometric level within
the lower sand unit at least 2 feet below the bottom of all exca-
vations. The spacing and effectiveness of the depressurizing/
dewatering system for the lower sand will depend upon the depth
of the wells below the excavation, the pumping rate, and ground
' water level to be maintained during construction. It is our
opinion that the configuration of the dewatering system should be
' designed by the contractor who can continuously monitor the
13
1 RECEIVED
N4WfZfZ_Zg2v1eness of the dewatering operations and its effect on
' CITY OF EDMONDS
DEVELOPMENT SERVICES
adElweent properties.
I
It is not possible to reasonably estimate the pumping rate
required to depressurize, and possibly dewater portions of, the
' lower sand unit until the elevation of the lowest excavation and
final facility configurations are determined, additional analyses
are performed, and possibly test pumping is accomplished.
However, for preliminary design purposes, it can be assumed that
pumping requirements for dewatering the lower sand unit may be as
'
high as about 3000 gallons per minute (gpm), with the dewatering
wells located primarily along the east side of the site. This
estimate is based on preliminary siting information with most of
'
the subsurface facilities located on the northern portion of the
site. Subsequent changes in facility locations and depths may
tchange
this estimate.
In our opinion, pumping from sumps within the excavation
'
will probably be adequate to control ground water inflows from
the soil units above the till. Higher inflows are expected when
sand layers are encountered. If more permeable soils are present
'
above the till than those encountered during our site explora-
tions, more extensive dewatering in those soils may be required.
Sufficient data does not exist at present to evaluate the sump
pumping rate required for the soils above the till. However,
'
discharge volumes are expected to be significantly lower than for
' depressurizing/dewatering the underlying sand. If needed for
preliminary design, an estimate of 500 gpm or less may be used.
' Significant water level depressions resulting from
dewatering can potentially cause adverse settlement of adjacent
' 14
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May 26 2021
DAWNCESS• This is of primary concern for areas underlain by
DEPARTMENT
soft, compressible soils, such as those located to the west of
the site. Lowering the water table will increase the effective
weight of the fill material present over the compressible soils,
thereby causing increased consolidation settlement. Mitigation
of this potential problem may require the installation of a
slurry cutoff wall between the west property boundary and S.R.
104, or injection wells on the west side of S.R. 104. Additional
field tests and monitoring of ground water levels will be
required to evaluate the need for a specific remedial action.
Due to the relatively dense nature of the soils to the north and
east of the site, dewatering induced settlement is not expected;
however, monitoring of nearby structures as described in a
following section is important.
SHORING OF DEEP EXCAVATIONS
' General Considerations: Vertical excavation sides are
expected to be necessary and/or desirable along most sides of the
' site where below grade structures are planned to be located near
the property lines. We understand that open
excavations are not
viable on the west, north, and east sides of
the site due to the
presence of roadways and pipelines, and the
need to utilize 2nd
Avenue for contractor staging and material storage purposes.
Assuming is
by
site dewatering accomplished
wells, the most
'
appropriate type of shoring for deep excavations
will be a
commonly used system of soldier piles with
tieback anchors for
'
lateral support, while shallower excavations
up to about 12 feet
in depth might be shored by a cantilever
soldier pile wall.
1
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May 26 2021
DEvJ6L01r&14 1K,q' lagging between soldier piles will be needed to retain
DEPARTMENT
the fill and native soils behind the shoring wall. Actual design
can vary depending on the actual soil and ground water condition
at various locations at the site. It should be the responsi-
bility of the shoring contractor to verify the actual conditions
and determine the construction methods and procedures needed for
installation of excavation shoring systems.
Lateral Earth Pressures: The temporary shoring system may
be designed in all areas for lateral pressures based on active
earth pressure criteria. For preliminary design purposes, we
recommend that the site be dewatered as previously discussed and
that excavation shoring systems be designed for lateral pres-
sures, expressed in pounds per square foot, of 25 (H+Hs as shown
on Figure 8. A uniform surcharge behind the wall due to adjacent
street loads may be accounted for by determining an equivalent
height of soil that will match the design surcharge load. The
design wall height (H) should then be increased by the corre-
sponding height of equivalent surcharge (Hs), which for prelim-
inary design can be assumed to be about 2 feet. If it is
determined that shoring and soil movements must be kept to a
minimum, or that a permanent tieback wall is desirable, then an
at -rest earth pressure of about 35 (H+Hs) would be appropriate.
The lateral pressure distributions presented assumes that
permanent drainage measures, as discussed in the "Drainage
Considerations" section of this report, are incorporated in the
shoring wall design so that there is no buildup of hydrostatic
pressure behind the wall. Lateral pressures due to loads from
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May 26 2021
DJL AFr ERV�Skuipment, material stockpiles, and foundations must also
DEPARTMENT
be added to the active earth pressures when the surcharge load is
' located with a horizontal distance from the excavation equal to
'
the excavation depth.
For temporary cantilever shoring walls with no tieback
anchors, the active earth pressure can be represented using an
equivalent fluid density of 35 pounds per cubic foot (pcf). This
'
active pressure should extend for the entire wall length to the
bottom of the excavation; however, below the excavation the area
'
of application of the active pressure may be reduced to two pile
'
diameters. An equivalent surcharge should also be added for
adjacent surface loads, as previously discussed.
'
Soldier Piles: The soldier piles will most likely consist
'
of steel H-sections inserted into predrilled holes backfilled
with concrete. The piles must be designed to resist the lateral
'
loads and, in the case of tied -back piles, also the vertical
loads imposed by the anchors. Pile embedment below the
'
excavation base is determined by the length needed to resist both
'
the lateral and vertical loads. For preliminary design, we
recommend a minimum embedment of 10 feet below the adjacent
'
excavation level for both tied -back and cantilever piles.
The vertical capacity of the soldier piles will be developed
by a combination of soil end bearing and frictional resistance of
'
that portion of the pile embedded below the base of the excava-
tion. For preliminary design, we recommend the use of 750 psf
allowable frictional resistance between the pile concrete and the
recessional deposits (silty sands to sandy silts); a value of
'
1
17
RECEIVED
'
M��a��jjyQQQQ[26 2021 DE�7ELACES'ay be used for the glacial till and the underlying very
DEPARTMENT
dense sands. These frictional resistance values should be
applied only over the portion of the pile embedded deeper than 2
'
feet below the base of the excavation. An allowable end bearing
value of 15 kips psf may be used in conjunction with the fric-
tional resistance for piles on the glacial till or underlying
sand soils. These allowable soil resistance values include a
factor of safety of at least 1.5. These values also assume that
'
the drilled holes for the soldier piles are dewatered and remain
open, and that all disturbed soil is removed from the bottom of
'
the holes. The shoring contractor should anticipate the need to
use casing where saturated sand layers are encountered. Water -
bearing sands under excess hydrostatic pressure should be
expected below the glacial till; consequently use of a drilling
'
mud may also be required.
'
For determining soldier pile embedment depth to provide
lateral stability, we recommend that the passive soil resistance
'
be estimated using an equivalent fluid density of 300 pcf for
competent native soils above the ground water surface, and 150
'
pcf for competent native soils below the ground water surface. A
' safety factor of at least 1.5 is included in these recommended
allowable values for passive soil resistance. The upper 2 feet
' of soil at the base of the excavation should be assumed to
provide no passive soil resistance to account for soil distur-
bance by construction traffic. For design, the lateral soil
' resistance may be computed based on the passive pressure acting
18
RECEIVED
NA4)&?6 ?Q?1e the diameter of the embedded portion of the pile or
CITY OF EDMONDS
DEVELOPMENT SERVICES
thDEPApilTe spacing, whichever is less.
Lagging: We recommend that timber lagging be installed in
' all areas. Prompt and careful installation of lagging will
reduce the potential for loss of ground between soldier piles and
' will promote safe working conditions. The requirements for
lagging should be the responsibility of the shoring contractor.
We recommend that any voids between the lagging and retained soil
be backfilled in a manner that will not allow potential hydro-
static pressure build-up behind the wall. Because of soil
I
arching between soldier piles, a reduced lateral pressure is
appropriate for lagging design. For design purposes, about 30
' percent of the lateral soil pressure uniformly distributed over
the length of the lagging should be appropriate where the free
' space between the soldier piles is three diameters or less.
' Lagging about 4 inches thick is generally sufficient to provide
the necessary support.
1 Tieback Anchors: Tieback anchors will derive all their
' capacity in the soil behind the "no load" zone. The boundary of
the no-load zone should be defined as shown on Figure 8. The
' load -carrying capacity of an anchor installed into soil may be
estimated on the basis of a soil strength of 750 psf on the
' surface area of the anchor plug behind the "no load" zone for the
first row of tiebacks. The capacity of subsequent rows of
tiebacks can be estimated using a value of 1000 psf. We recom-
mend that tieback anchors be installed at inclinations of between
20 and 30 degrees below horizontal. At most site locations, the
19
RECEIVED
May 26 2021
DEXXOMI.Anchors will extend into adjacent properties or street
DEPARTMENT
right-of-ways, thus owner permission is important. We anticipate
that the temporary tiebacks will be allowed to naturally destress
following construction of permanent subgrade walls.
The installation of any tieback anchors which penetrate
water -bearing zones of fill and native soils may be hampered by
hole caving and flow of soil into the hole. Therefore, the use
of a hollow -stem auger with grout injection under pressure for
anchor installation will probably be appropriate. This method is
generally satisfactory, if the injection pressure and grout
volumes pumped are carefully controlled. The contractor should
be prepared to drill through and install anchors in a wide
variety of soil conditions, including very dense to hard glacial
till and very dense water -bearing sands. Anchor holes should be
drilled in a manner that will minimize loss of ground and not
endanger previously installed anchors. The presence of buried
utilities adjacent to the site should be noted and avoided by the
shoring contractor.
Tieback Anchor Testing: Each anchor should be prestressed
to 130 percent of its design loads for at least 5 minutes and
then locked off at the design load. This is a means of verifying
that the anchors are properly installed and will remain stressed
without noticeable creep or excessive anchor movement. Anchor
movements in excess of about 3 inches during testing would indi-
cate deficiencies in the installation. Total movement of an
anchor in excess of about 12 inches is considered a failure
requiring anchor replacement.
20
We also recommend that at least
RECEIVED
May 26 2021
DEVE°CoPkTs�Ftvit'E of the tieback anchors be load tested to 200 percent of
DEPARTMENT
their design load to verify the adequacy of the anchor resistance
values used in design.
Design and Installation: We recommend that the shoring
system be designed by a contractor experienced in design and
installation of tieback soldier pile walls. The excavation and
installation of anchors must be sequenced such that the lateral
restraint is maintained to minimize yielding of the soil mass
behind the wall. A survey program must be accomplished during
construction to permit detection of lateral and vertical movement
of both the shoring and adjacent ground surfaces. The
contractor's proposed design, sequencing, and monitoring should
be reviewed by an experienced soils engineer and structural
engineer prior to construction. We recommend that installation
of the piles and installation/testing of the tieback anchors be
observed and monitored by an experienced soil engineer or
technician.
SITE PREPARATION
Clearing and Stripping: All deleterious material such as
grass, roots, topsoil, and any debris fill should be stripped
from areas to be occupied by structures, pavements, walkways, and
any areas that may be filled. Any topsoil removed can be stock-
piled at designated areas for later use in landscaping if the
larger roots are removed. During site preparation, any standing
water should be drained or pumped from the area and any soft
21
RECEIVED
IW13q 2�?Ih organic material should be removed and disposed off -
CITY OF EDMONDS
DEVELOPMENT SERVICES
s ffbRIMENT
1 Proof Rolling: Following clearing, stripping, and site
' excavations, but prior to placement of backfill or base course
material, the exposed subgrade under all areas to be occupied by
' pavements, earth -supported slabs, and spread foundations should
be proof -rolled with appropriate compaction equipment so that the
' native soil to a depth of at least 12 inches below the surface is
' compacted to at least 95 percent of its maximum dry density as
determined by ASTM D-1557 test procedures. The purposes of the
' proof rolling operation are to compact the soils exposed by
cutting and excavation operations and to detect possible
' localized zones of loose or soft soils. Proof rolling should be
carefully observed, and any areas exhibiting significant deflec-
tion, pumping, or weaving that cannot readily be compacted should
be overexcavated and backfilled with appropriate compacted fill
soil.
Subgrade Stabilization: The finer -grained recessional and
' glacial till deposits that may be present at the base of some
excavations will tend to become disturbed and softened when wet
' and exposed to construction traffic. Accordingly, we recommend
that the placement of a mat of lean concrete or overexcavation of
1 such soils and replacement with at least 12 inches of compacted
tgranular fill be accomplished to protect the foundation soils.
22
RECEIVED I`�(:�� �'P � U da, n 1
' "LN S
DEVELOPMENT SERVICES
DEPARTnErgcavations can be accomplished using conventional equip-
ment. Dewatering of the construction area prior to excavation is
important to reduce construction difficulty.
For dewatered conditions, the temporary excavation slopes
are expected to be stable at inclinations of 1.5H:1V in the fill
or loose native soils and 1H:1V in dense native soils. Permanent
cut slopes, if any, should be planned at no steeper than 2H:1V.
In areas of ground water seepage or in less competent soils,
flatter slopes will be required. Wherever space is not available
for stable open -cut excavations, shoring of excavations is recom-
mended to maintain the stability of adjacent ground and/or
structures.
The contractor should be responsible for maintenance of safe
' side slopes for all excavations required during construction, and
for following all applicable safety regulations regarding
ati n 1 an shoring. Excavated material or stockpiles ' excav o slopes d g ,
of construction materials or equipment, should be placed no
closer than a distance equal to the depth of the excavation from
the top edge of unshored excavations. Also, the contractor
should be responsible for the control of surface and ground water
at excavation locations and should expect that dewatering,
temporary ditching, slope protection, flattening of slopes, exca-
vation shoring, and other measures will be required at the site.
' Construction monitoring by qualified soils personnel is appro-
priate to permit timely modifications to excavation plans and
' techniques.
23
RECEIVED
*-j Z% 2021
CITY OF EDMONDS
'
DEVELOPMENT SERVICES
DEPARTNeeneral : Various
depths of fill will be required to provide
the desired width and
subgrade elevations
for roadways, parking
areas, and walkways, as
well as for backfill behind retaining
'
structures and adjacent
to foundations. We
understand that site
fill is not currently
planned to achieve
foundation subgrade
'
levels for any of the
planned structures.
Fills placed on the
site should have a final slope of no steeper than 2H:1V, or
should be supported by retaining walls. Retaining walls should
also be constructed to support any fill that might otherwise
encroach into the wetland area to the south.
Fill Placement and Compaction: Any soil placed to support
structures or other facilities must consist of competent soil
which is properly compacted as structural fill. We recommend
that structural fill consist of clean, well graded sand and
gravel containing no more than 5 percent nonplastic fines passing
the No. 200 sieve, based upon a wet sieve analysis of the
material passing the 3/4-inch sieve. All structural fill should
be placed in lifts of less than 8 inch thickness with each lift
compacted to a density of at least 95 percent of the soil's
maximum dry density as determined by ASTM D-1557 test procedures.
Subgrade material under pavement areas need be compacted to at
least 92 percent of maximum dry density; however, the upper 12
inches of fill immediately below the pavement section should be
compacted to the 95 percent criteria.
It is important that all utility trenches be properly back -
filled and compacted to minimize the possibility of localized
24
RECEIVED
�'Ws4PZQ?lfloor slab or pavement support. Backfill in trenches
CITY OF EDMONDS
DEVELOPMENT SERVICES
sff64
51M&Tmeet the above mentioned compaction criteria.
Backfill placed within the zone immediately behind retaining
walls should be compacted to only about 90 percent of its maximum
dry density. Over -compaction by vibratory equipment immediately
adjacent to walls should be avoided to minimize the possibility
of developing excessive lateral pressures against the wall.
Non-structural fill for landscaping purposes can consist of
the native granular soils, but not peat, obtained from the
excavation. To minimize settlements, we recommend that non-
structural fill be compacted to about 90 percent of its maximum
dry density as determined by ASTM D-1557 test procedures.
Use of Onsite Soils as Fill: We understand that the amount
of site excavation required to achieve design subgrade elevations
for the treatment plant facilities will result in excess soil for
disposal. Accordingly, to the degree possible, it is desirable
to reuse onsite soil as fill.
Based upon both visual and textural examination of the soils
encountered in our explorations and grain -size analyses performed
on selected soil samples, we conclude that the cleaner sands and
gravels (SP, SP/SM, SW, GW) encountered at various depths and
locations below the site will be suitable for structural fill if
properly moisture conditioned and used in earthwork operations
during relatively dry weather conditions. Dry weather earthwork
is important due to the relatively fine-grained, poorly -graded
nature and resulting moisture sensitivity during wet weather
operations of these soils. Most of the existing fill soils are
25
1 RECEIVED
NYl?'�292Ads with varying amounts of gravel that would be suitable
' CITY OF EDMONDS
DEVELOPMENT SERVICES
f®WAReral site fill, if the same use restrictions noted above
I
for structural fill are applied.
Any peat or organic silt is, of course, unsuitable for fill
' and should be disposed of. Most of the recessional and glacial
deposits consisting of silty sand (SM) and sandy silt to silt
' (ML) are not generally suitable for either structural or
' nonstructural fill at the site and should be disposed of offsite.
These soils can be evaluated during excavation to determine their
' suitability for use at other City of Edmonds' projects, if so
desired.
WET WEATHER CONSTRUCTION CONSIDERATIONS
' It is desirable that earthwork operations and foundation
construction be accomplished only during the drier periods of the
' year; however, we have incorporated in our earthwork recommenda-
tions various measures to mitigate some of the adverse effects of
unavoidable wet weather construction. These measures include:
' 1) use of structural fill that contains no more than 5 percent
nonplastic fines; 2) placement of a mat of lean concrete or
' placement and compaction of at least 12 inches of structural fill
' over the finer -grained soils that would tend to become disturbed
and softened due to both weather and construction traffic; 3)
' rolling or compacting and sloping exposed soil surfaces to limit
infiltration of water and thus reduce the potential for erosion;
' and 4) removal of unsuitable soils and replacement, as required,
with structural fill material. A soils engineer or representa-
tive should be available during earthwork operations to recommend
� 26
RECEIVED
Ma�i�6ve0ri the implementation of appropriate mitigative measures
CITY OF EDMONDS
DEVELOPMENT SERVICES
o9hPA5TMF91te-speclflc basis.
FOUNDATION SUPPORT
I! Summary: We conclude that the foundation for the proposed
III structures can be satisfactorily supported either, depending on
site location and grades, on 1) spread and/or continuous footings
and structural slabs founded on properly compacted structural
fill or on the competent native soils that underlie the site, or
2) auger -cast or driven pile foundations that penetrate a suffi-
cient distance into the supporting soils. Pile foundations are
recommended for structures where overexcavation of unsuitable
soils at a foundation location is not economical. General design
considerations for spread and pile foundations are presented
below.
General Design of Spread Foundations: Bearing soils for
footings that are disturbed during foundation excavation should
either be recompacted or removed and replaced with compacted
' structural fill consisting of clean, well graded sand and gravel
' that contains no more than 5 percent material passing the No. 200
sieve. Where removal of less competent soils and replacement
' with structural fill is required to obtain an adequate bearing
surface, the structural fill under the foundation should extend
' beyond the edges of the footings a minimum distance equal to the
' thickness of the structural fill beneath the footing. All soils
directly below and around footings and structural slabs should be
I
compacted to at least 95 percent of the maximum dry density as
27
1 RECEIVED
rd@Y4 &&?D�d by ASTM D-1557 test procedures prior to placing any
CITY OF EDMONDS
DE ELOPMENT SERVI S
(MOIF&MEa-inc7reinforcing steel.
All continuous and spread footings supported on undisturbed
native soils and properly compacted structural fill should have a
minimum width of 2 feet, and should be founded at least 1.5 feet
below the lowest adjacent finished grade or floor slab, whichever
' is lower. For preliminary design, footings and slabs supported
' on structural fill or dense native soils may be proportioned
using a net allowable bearing pressure of 2500 and 4000 psf,
' respectively. The term "net allowable bearing pressure" refers
to the pressure which is imposed on the soils at foundation level
' due to the total of all dead plus live loads, exclusive of the
' weight of the footing or any backfill placed above the footing.
These values can be increased by one-third for transient wind or
' seismic loads. If needed, higher bearing pressures can be used
for the very dense glacial till and advance outwash soils.
' Settlement of spread foundations will depend on the founda-
tion size, bearing pressure, and the strength and compressibility
' characteristics of the underlying soil. Assuming construction
' is accomplished as recommended and for the moderate to heavy
loads anticipated, we estimate that settlement of spread footings
' supported on competent native and fill soils will be less than 1
inch, with differential settlement not exceeding about 1/2 inch.
' Most of this settlement should take place rapidly during
' construction as the loads are applied.
General Design of Pile Foundations: Where competent native
' soils are not present at foundation grade, auger -cast or driven
' 28
RECEIVED
4IV1464Wulndation support may be appropriate. For preliminary
CITY OF EDMONDS
DEVELOPMENT SERVICES
deEsAPrPNJ we have considered both 12-inch diameter auger -cast piles
and 8-inch tip diameter Class B timber piles. We recommend that
piles be installed or driven into the dense glacial soils that
underlie the site. The required pile penetrations to achieve the
recommended supporting capacity will vary for each pile type.
For preliminary design purposes, pile capacities can be estimated
using the following table.
Minimum
Penetration of
Pile Tip Allowable Allowable
Into Dense Downward Lateral
Pile Diameter Supporting Pile Capa- Pile Capa-
and Type Soils (feet) city* (tons) city (tons)
-----------------------------------------------------------------
-----------------------------------------------------------------
8-inch-tip timber 6 (or refusal 25 1
in till)
12-inch auger -cast 10 40 2
* Downdrag loads due to consolidation of compressible soils
may need to be deducted from the allowable capacity.
If the need for pile foundations is identified, we will refine
the design parameters to be applicable to the specific condition.
' The allowable downward pile capacity represents the total of
all dead plus real live loads and includes a factor of safety of
' at least 1.5 for skin friction and 3 for end bearing. The allow-
able downward pile capacity may be increased by one-third for
wind and seismic load conditions. No reduction of vertical pile
' capacity as a result of group action is necessary if pile spacing
is three pile diameters or more.
'
29
1
RECEIVED
May26 �921stimate that settlement of properly installed piles will
CITY OF EDMONDS
DEVELOPMENT SERVICES
bePAJTdW_§ than about 1/2 inch. Most of this settlement should
' occur rapidly as the loads are applied. Post -construction
differential settlements are expected to be negligible.
' Timber piles should be Class B, pressure -treated timber
conforming to ASTM specification D25-37. They should have a tip
' diameter of at least 8 inches and should be driven into the
'
supporting soils or to refusal on the glacial till using a pile
driving hammer with a minimum rated energy of 15,000 foot-pounds
'
per blow. The piles should be driven either to recommended
penetrations or to a refusal blow count which should be estab-
lished subsequent to selection of the pile and hammer sizes.
'
Auger -cast piles are installed by advancing a continuous
flight hollow -stem auger to the depth required, then pumping
concrete grout under pressure (about 150 to 250 pounds per square
inch) through the hollow stem as the auger is withdrawn from the
'
hole at a rate not exceeding about 7 to 9 feet per minute. The
quality and strength of auger -cast piles are very dependent on
the installation procedure and the experience of the contractor.
' Therefore, we recommend that pile installation be accomplished
only by a contractor specializing in auger -cast piles and who has
' local experience. Since auger -cast piles are drilled and cast in
place, their length can be easily adjusted to achieve the
' required penetration into competent bearing material without
' waste of pile material. Furthermore, vibrations induced by
installation operations will be negligible and should not effect
' nearby buildings or other facilities.
30
' RECEIVED
May26 ?P?Aral forces imposed on foundation structures due to wind
' CITY OF EDMONDS
DEVELOPMENT SERVICES
aITd'AF?SNe_riTsmic loading may be resisted, in part, by a pile's lateral
' load capacity. The magnitude of allowable lateral pile capacity
is dependent on many factors, including structural characteris-
tics of the pile, soil -pile interaction, pile deflection, and
soil strength. For preliminary design purposes, an allowable
' lateral pile capacity presented in the table above may be used.
' These values assume an allowable horizontal pile deflection of
about 1/2 inch at the base of the pile cap. For final design, we
' recommend allowable lateral pile capacities be evaluated on a
case -by -case basis to reflect site -specific soil conditions and
' structural considerations. A group efficiency of 100 percent can
' be used for a center -to -center pile spacing of at least eight
pile diameters and/or if load application is normal to row align-
ment. Lateral pile capacity of pile groups should be reduced if
center -to -center pile spacing is less than eight pile diameters
' and load application parallels row alignment. The efficiency of
pile groups should be reduced by 50 percent for a center -to -
center spacing of three pile diameters. Interpolation can be
' used to estimate group efficiency reduction for other pile
spacings between three and eight pile diameters.
' Structural characteristics of the pile material and founda-
tion connections may limit pile capacities to less than the
' allowable values presented above and should be evaluated by the
' structural engineer. Recommendations for reduction in allowable
downward pile capacities due to downdrag loads caused by consoli-
dation of the peat and organic silt will be provided as required
for final design.
1
31
' RECEIVED
May 26 2021
' APcArrFSC'ONSIDERATIONS
DEPARTMENT
It is important to provide positive drainage behind
' permanent subsurface walls. Drainage systems installed behind
Permanent walls constructed flush against in -place shoring walls
should include:
' 1) A minimum one -foot -wide continuous drainage medium (such as
miradrain) attached directly to the lagging between each
' pair of soldier piles and hydraulically connected to the
underlying foundation drainage system. The drainage medium
' should be surrounded by a geotextile to reduce possible
'
siltation of the drain.
2) Polyethylene sheeting attached to cover the entire face of
'
the shored excavation and provide an impervious surface at
the back face of the concrete wall. The polyethylene
'
sheeting should be secured on each side of the drainage
'
medium with wood laths to prevent intrusion of concrete.
Drainage provisions behind below grade and retaining walls
'
foundation hydraulically to
should consist of subdrains connected
'
free -draining granular backfill. The subdrains (with cleanouts)
should consist of a minimum 6-inch diameter perforated pipe
'
placed on a bed of, and surrounded by, at least 6 inches of
clean, free -draining sand and gravel with less than 5 percent
'
nonplastic fines passing the U.S. No. 200 sieve. A minimum of
18 inches of clean free -draining sand and gravel should be placed
'
adjacent to subsurface walls that are not formed flush against
'
in -place shored walls. Approximately the upper 12 inches of
backfill behind the walls should be relatively impermeable soil
'
32
RECEIVED
May 26 2021
' &-ffdFEVhl@S pavement should be sloped away from the structures to
DEVELOPMENT SERVICE'S
DEPARTMENT
prevent surface water ponding against them.
' Subdrains should be provided behind all foundations and,
wherever needed, below earth -supported slabs, crawl space areas,
' below -grade walls, etc. We recommend all earth -supported slabs
' be underlain by at least 6 inches of clean, compacted, free -
draining angular gravel or crushed rock. This drainage layer
' should be hydraulically connected with the exterior footing
subdrain system. The thickness of this drainage layer should be
' increased to at least 18 inches if buoyancy and uplift considera-
tions require that water be pumped from the subdrain system to
locally dewater the soils below the slab, as discussed in the
following section of this report.
Pavements and sidewalks should be sloped to drain away from
above ground structures. Surface water runoff from building
roofs and paved areas should be collected and discharged into
tightline pipes to the storm drain system. A separate system
should be designed to collect and transport subsurface drainage
from behind basement and retaining walls to the storm sewer
system.
BUOYANCY AND UPLIFT
Buried tank -like structures will experience an upward buoy-
ancy force when the ground water level is higher than the fluid
level inside the structure. These upward forces may potentially
heave and crack the bottom of the structure if not properly
resisted by the structure's uplift resistance or reduced by a
dewatering system. The weight of the structure and a friction
33
1 RECEIVED
May 26 2021
DEE�OEN�TSORV�IC�ng the sides of the structure will act to resist the
DEPARTMENT
uplift forces. The uplift resistance can be increased by
extending the base of the tank outside the walls. Uplift resis-
tance is then increased by the weight of the soil above the
extended base and mobilization of the shearing resistance of the
soil above the base. Flooding the structure by use of pressure
relief valves would also reduce damage potential.
In our opinion, the structures should either be designed to
resist the maximum estimated buoyant force and bottom uplift with
an adequate factor of safety, or a dewatering system should be
constructed in conjunction with the foundation subdrain system.
We understand that it is desirable to provide temporary
dewatering around and below certain structures to limit the
design buoyancy force. This probably can be accomplished by
overexcavating the soils below the structure to allow for place-
ment of a minimum 18-inch thick blanket of free -draining angular
gravel or crushed rock that is hydraulically connected to a
minimum 6-inch diameter drain pipe system with several riser
pipes around the perimeter of the structure. High capacity
submersible pumps would be used to dewater the soils below and
around the structure to the extent required to adequately reduce
the uplift forces to an allowable level.
Structures that are founded within or slightly above the
water -bearing sands present below the glacial till must also
resist the high piezometric head associated with the ground water
in that soil unit. It may be necessary to use a ground water
cutoff in addition to the dewatering system at some locations to
34
RECEIVED
Mt1Y_Ap2P?soh sufficient drawdown of water levels with high capacity
' CITY OF EDMONDS
DEVELOPMENT SERVICES
s�� TWENSible pumps. The requirements for this type of system
' should be evaluated on a case -by -case basis when the locations
and depths of structures are finalized.
The applicability of using uplift anchorage systems
connected to the structures should also be evaluated for cost-
effectiveness. Auger -cast piles or soil anchors could poten-
tially be used to increase resistance to buoyancy and uplift
forces.
LATERAL EARTH PRESSURE CRITERIA
' General Retaining Walls: Retaining walls supporting back -
fill will be subjected to lateral earth pressures. We recommend
' that permanent drainage systems be installed and that backfill
placed directly behind retaining walls consist of free -draining
' granular material. The lateral earth pressure developed against
a retaining wall will be dependent on the method of backfill
placement and degree of compaction, the backfill slope, the type
' of backfill material, the drainage provisions, and the degree to
which the wall can yield laterally during or after placement of
' backfill.
' When a retaining wall is restrained against lateral movement
or tilting, the soil pressure exerted is the at -rest soil
pressure. Wall restraint may occur if a rigid structural network
is constructed prior to backfilling or if the wall is inherently
' stiff. We anticipate that the permanent walls of most below -
grade facilities at the treatment plant will be relatively rigid
tand, thus, will be designed for an at -rest pressure condition.
35
1 RECEIVED
May HjW21he retaining wall is freestanding, and is allowed to
' CITY OF EDMONDS
DEVELOPMENT SERVICES
r®tPaFtreNTso that the top of the wall moves an amount equal to about
' 0.001 times its height, the soil pressure exerted will be the
active soil pressure.
' We recommend that relatively flexible and nonyielding
retaining walls supporting level or moderately sloping backfill
' be designed for the equivalent fluid pressures presented in the
following table.
Equivalent Fluid
Pressures (pcf)
'
Flexible Walls
Nonyielding Walls
Backfill Slope
(active case)
(at -rest case)
'
00
35
55
50
36
57
'
100
37
59
The lateral earth pressures recommended above assume drained
' conditions behind the walls and do not include hydrostatic
forces. If drainage conditions are not included in wall design,
1 lateral earth pressures equal to the sum of hydrostatic water
' pressure and one-half the values presented above should be used
for design.
' Additional lateral pressures will be imposed by any
surcharge loads and earth -supported slabs or nearby footings
' located at a higher elevation which are adjacent to the wall.
' For uniform surcharge loads, a uniformly distributed lateral
pressure of about one-third and one-half of the surcharge load
' should be added for flexible and rigid walls, respectively. For
slabs and footings, the additional lateral pressure should be
36
RECEIVED
May 26 2021
aI&ft,FdMO*0r that portion of the wall which is below the inter -
DEVELOPMENT SERVICES
DEPARTMENT
section of a line drawn downward at 45 degrees from the base edge
of the slab or footing.
Perimeter walls: We anticipate that permanent perimeter
walls will be constructed very close to or in contact with the
temporary excavation shoring. Permanent subsurface walls
constructed flush against in -place shoring should be required to
take the full load which was carried by the temporary retention
system. As previously recommended, any voids between the lagging
and soil must be backfilled with material that will maintain
drainage conditions. Under certain circumstances, long-term
effects may increase the load on a permanent retaining wall to a
grE.ater value than that carried by the excavation shoring. This
depends mainly on whether the shoring and construction sequence
would permit any additional yielding of the surface wall. This
aspect of wall design should be reviewed after final design of
the shoring system.
LATERAL SOIL RESISTANCE
' Lateral loads transmitted to spread foundations and peri-
meter walls may be resisted by passive earth pressures developed
against the side of the buried portions of the foundations, and
' frictional resistance at the base of the foundations. For design
purposes, the passive resistance of well -drained and compacted
structural backfill placed against the sides of the foundations
may be estimated using an equivalent fluid pressure of 300 pcf.
' This value assumes drainage is provided to prevent the buildup of
�
37
1 RECEIVED
KYA26 Sic pressures in the compacted structural fill, and that
' CITY OF EDMONDS
DE�{EL�OPM�EN;SaEgVIions are embedded at least 1.5 feet below the lowest
adjacent finish grade or floor slab, whichever is
lower.
If
drained conditions do not exist, a lateral soil resistance
of
'
about 150 pcf should be used for buried portions of
walls
and
foundation elements located below water. A safety
factor
of
'
about 1.5 is included in these recommended design
values
for
' passive soil resistance. Appropriate reductions must be used if
the adjacent surface slopes downward away from the foundation
' within the zone of soil developing passive soil resistance. We
recommend that a coefficient of friction between concrete and
' soil of 0.5 be used to calculate the resistance to sliding at the
base of foundation elements bearing on well compacted granular
' fill or native soils. If passive and frictional resistance are
I
considered together, one-half the value of passive soil resis-
tance presented above should be used since larger strains are
' required to mobilize the passive soil resistance as compared to
frictional resistance.
' Lateral loads transmitted to pile -supported foundations are
' resisted by the lateral pile capacities. Allowable design values
for lateral pile capacity should be developed on a site -specific
' basis during final foundation design; however, general design
parameters are presented in the "Foundation Support" section of
' this report.
' FLOOR SLAB SUPPORT
We recommend all soil -supported slabs be underlain by a
1 minimum of 6 inches of compacted clean, free -draining angular
� 38
1 RECEIVED
NfUa��4026crushed rock to provide uniformity of support and a
' CITY OF EDMONDS
DEVELOPMENT SERVICES
capAkim1ary break. Provisions should be made so that this material
can drain freely into a foundation system connected to the storm
sewer system. If desired, a vapor barrier may be placed between
the gravel or crushed rock layer and slabs. The vapor barrier
should be covered with a thin layer of sand to protect it during
concrete placement and to improve concrete curing.
The appropriate modulus of subgrade reaction that may be
used for design of concrete slabs -on -grade or foundation mats
will not be finalized until the location, depth, and size of such
facilities are determined. However, a coefficient of vertical
subgrade reaction of at least 200 pounds per cubic inch can be
used for preliminary design of concrete slabs.
ROADWAY DESIGN CONSIDERATIONS
Recommendations for site preparation and grading, as
presented in other sections of the report, include compacting the
upper 12 inches of granular subgrade soil or structural fill
immediately below the pavement section to 95 percent of its
maximum dry density as determined by ASTM D-1557 test procedures.
The extent of overexcavation of any unsuitable fill or native
material beneath pavement subgrade level should be determined on
a site -specific basis during grading and proof -rolling opera-
tions. Adequate surface and subsurface drainage features should
be incorporated in pavement design to prevent saturation of the
subgrade soils. Assuming proper site preparation and construc-
tion procedures are used and compaction as recommended is
achieved, a California Bearing Ratio (CBR) value of 15 for the
39
RECEIVED
Mayn?6(20-28 subgrade may be used for preliminary design of asphalt
CITY OF EDMONDS
DEcL�OP60R)rKeMENT eCEpavements. This value may need to be reduced for pave-
ments located within the southwest portion of the site which are
underlain by varying thicknesses of peat and organic silt.
' GENERAL SEISMIC CONSIDERATIONS
' The Puget Sound region is a seismically active area,
classified as Zone 3 in the latest edition of the Uniform
' Building Code (UBC). All subsurface structures should be
designed to resist both static and dynamic lateral soil and
ground water pressures. Specific recommendations for dynamic
soil and ground water pressures will be provided as required
during final design, when the depth and location of specific
' structures are known. In our opinion, the probability of lique-
faction of the saturated sands encountered in our explorations is
low because of their density. There is no evidence that surface
faulting could occur at the site.
CONSTRUCTION INSTRUMENTATION AND MONITORING
Design Review and Construction Monitoring: Our Phase II
services will provide consultation during final design to evalu-
ate compliance with the intent of the recommendations presented
both in this report and in final design recommendations to be
provided by Landau Associates, Inc. at a later date. A soils
engineer or qualified representative from our firm will be avail-
able to observe earthwork procedures, foundation preparation and
construction, and installation of dewatering and drainage systems
on a full- or part-time basis, as necessary. If unanticipated
40
RECEIVED
NA@W 4 42gubsurface conditions are encountered, we will aid in the
' CITY OF EDMONDS
DEVELOPMENT SERVICES
eva,dRcHitrion of the problem and recommend additional mitigating
measures where appropriate.
' Instrumentation: An instrumentation program should be
established and maintained at the site in order to evaluate the
' performance of dewatering, earthwork operations, and drainage
measures. An appropriate observation and instrumentation program
' would include survey monitoring points on and around shored exca-
vations, survey stakes on unsupported cut slopes, observing
' ground water levels, and monitoring the effects of dewatering on
' adjacent properties. At a minimum, a condition survey of nearby
buildings prior to and after construction and establishment
' during construction of a survey monitoring system on adjacent
structures should be accomplished. It should be understood that
' modifications to the number, location, and possibly types of
' instrumentation, as well as modification in the frequency of
monitoring, may be appropriate as project construction
' progresses.
RECEIVED
May 26 ' m2,,LL0, 21 CITYOFEDng:hEjQs report has been prepared for CWC/HDR and the City of
DEVELOPMENT SERVICES
DEPARTMENT
Edmonds for evaluation of the Dayton Street site for the planned
secondary waste water treatment plant. The data and preliminary
recommendations presented in this report do not constitute a
direct or implied warranty that the soil conditions between
boring locations can be directly interpolated or extrapolated or
that subsurface conditions and soil variations different from
those disclosed by the explorations will not be revealed.
There are probable variations in subsurface conditions
between the explorations. A contingency for unanticipated condi-
tions should be included in the budget and schedule. The
construction monitoring, testing, and consultation by our firm
will provide the opportunity to confirm that the conditions
encountered are consistent with those indicated by the explora-
tions, provide recommendations for design changes should the
conditions revealed during construction differ from those antici-
pated, and evaluate whether or not earthwork and foundation
installation activities comply with contract plans and specifi-
cations. Our scope does not include services related to
construction safety precautions and our recommendations are not
intended to direct the contractor's methods, techniques,
sequences, or procedures, except as specifically described in our
report for consideration in design.
Within the limitations of scope, schedule, and budget, our
services have been executed in accordance with generally accepted
soil mechanics and foundation engineering practices in this area
at the time the report was prepared. No other warranty,
42
RECEIVED
I4xyp$Crk59Ra or implied, is made or should be understood as to the
' CITY OF EDMONDS
DEVELOP T VICES
pKE4 Jonal advice included in this report.
We appreciate the opportunity to provide this Phase I
' 9 geotechnical investigation and trust that the information
I
' provided in this report satisfies your present needs for
predesign. Please contact us if you have any questions or desire
' further information.
131 %98
�,�•'• q£G157ERF9',v��cr
' RGF/DAP:sg
No. 74-02.03
5 copies submitted
1
43
Respectfully submitted,
LANDAU ASSOCIATES, INC.
By:
a44,;L-b
Robert G. Fulton, P.E.
Vice President
and
David A. Pischer, P.E.
Senior Geotechnical Engineer
1
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L
0 1/ 2 1
Scale in Miles
Reference: Thomas Bros. Map No. 58 King -Pierce -Snohomish Counties Popular Street Atlas.
L LANDAU ASSOCIATES, INC. I vicinity Map I
r
Figure 1
RECEIVED
May 26 2021 -
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
N 10,000.00
E 10,000.00
B
B-5/P-5
Clarifier 42
Clarifier #3
Clarifier #1 Pump
Bldg.
Control g-
Bldg.
Digester
A jdB-31P-3
Effluent
Pump
Station
KEY
® B-2 Boring number and approximate location
IS B-1/P-1 Boring and corresponding Piezometer
A A' number and approximate location
Subsurface Profile designation and
approximate location
q 2nd Avenue
C' [- Siphon Drain
*4Structure
g-g B-7/P-7
r Entrance Structure
Sludge
Thickener
and
Incineration
Bldg.
Ea- Ash Pit
®B-4
Clarifier # 4
Clarifier #5
Fencing along
Property Line
- �. S.R. 104 -
9Aff
Marsh
Area
® B-9
Storage
Yard
/ A'
B-1/P-1 SSL#
B-10
0 40 80
Scale in Feet
Reference: C'NC-HDR, Inc. Drawing of Existing Facilities -
C;ty of Edmonds Wastewater Treatment Plant,
May 1987 (untitled)
Figure
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
TV Qtu
J '
Ova
Qtb
Project Site _ - -
_
-= - - - OM
Ow
Gtb
Ovt
m1— Ova
Qtb
Source: Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangle, Washington,
by James P. Minard, 1983, a U.S.G.S. Miscellaneous Field Studies map MF-1541.
Editor's Description of Map Units
Qtb TRANSITIONAL BEDS (FRASER GLACIATION TO PRE-FRASER GLACIATION)
- Glacial and nonglacial deposits occurring beneath sand of
the Vashon advance and consisting mostly of massive, thick
or thin beds and laminae of medium- to dark -gray clay, silt,
and fine to very fine sand.
Q W WHIDBEY FORMATION - The Whidbey Formation lies below glacial
sediments and the Possession Drift, where present. The
sediments mapped as the Whidbey in the quadrangle
typically are bedded, compact, commonly oxidize, medium -
to coarse -grained sand.
QM MARSH DEPOSITS - One area of marsh deposits is mapped at
Edmonds. The sediment in the marsh is mostly fine
grained, organic -rich alluvium, probably overlying tidal -
flat deposits. The marsh appears to have been an
embayment before present pier area fill was placed, partly
ponding the marsn and blocking the opening to Puget Sound.
Q vt TILL - The informally named Vashon till (Fraser Glaciation)
mostly mantles broad upland surfaces (generally higher
than 30 m altitude). The till is a non -sorted very
compact mixture of clay, silt, sand, pebbles, cobbles, and
boulders, all in variable amounts.
QVa ADVANCE OUTWASH - Advance outwash underlies the till. The
outwash typically is a thick section of mostly clean,
gray, pebbly sand with increasing amounts of gravel higher
in the section.
Figure 3
May 2A2021 Subsurface Profile A -A'
CIT 8 MONDS
EVELOPMEN F SERVICES Bori ng
DEPARTIA Lorig n Boring B-10 B- 3 B- 4
6/8/87
Fill (loose)
10 --
?Z PEAT and SILT (soft)
0
Silty SAND and sandy SILT
(medium dense/stiff, grading denser/stiffer with depth)
Sandy GRAVEL to —Z
-10 gravelly SAND ( very dense) —L
—/
c
c
0
m
w -20
-30
-40 SILT (hard)
? ? ? —
SAND (dense to very dense)
-50
KEY
6/ 8/ 87 — Ground Water Elevation and Date measured
-•— Indicates Piezometer Sand Pack Interval
Indicates Piezometer Slotted Screen Interval
Silty SAND to sandy SILT
(till) (very dense/hard)
SAND (dense to very dense)
0 30 60
Horizontal Scale in Feet
A'
Boring�20
B-1
6/8187
NOTES:
a) Subsurface profiles shown have been generalized from data obtained during the
site investigation. Variations between this profile and the actual soil conditions
may be encountered. The logs of the explorations and the discussion in the text
of this report must be referenced for a proper understanding of the nature of the
subsurface material. This profile should not be used to estimate excavation
material volumes.
b) Datum: U.S.G.S.; MLLW = El. 0.00'
10
0
-10
-20
-30
-40
-50
Figure 4
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVI(a
DEPARTMENT
20
10
N
c
0
CIS
m
w -20
-30
-40
-50
Subsurface Profile S-S'
NOTES:
a) Subsurface profiles shown have been generalized from data obtained during the
site investigation. Variations between this profile and the actual soil conditions
may be encountered. The logs of the explorations and the discussion in the text
of this report must be referenced for a proper understanding of the nature of the
subsurface material. This profile should not be used to estimate excavation
material volumes.
b) Datum: U.S.G.S.; MLLW = El. 0.00'
c) See Figure 4 for Key to symbols.
Boring
r,
0 30 60
Horizontal Scale in Feet
A
Rnrinn 20
10
C1]
-10
-20
-30
-40
-50
Figure 5
1
1
1
1
1
1
1
1
1
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Subsurface Profile C-C'
C
C'
20
Boring
20
Boring Boring
B-6
B-3 B-8
618/87 ~
10
Fill (loose)
/
10
Silty SAND and sandy SILT
0
(medium dense/stiff, grading
0
denser/stiffer with depth)
Z--1
/
m
-10
Sandy GRAVEL I
gravelly SAND(very dense) —
-10
CD
U
9
c
Silty SAND to sandy SILT
a
o
(till)(very dense)
LT (hard)
w
-20
— —
-20
SAND (dense to very dense)
-30 1-30
-40 SILT (hard) -40
SAND (dense to very dense)
-50-1 L— -50
NOTES:
a) Subsurface profiles shown have been generalized from data obtained during the
site investigation. Variations between this profile and the actual soil conditions
may be encountered. The logs of the explorations and the discussion in the text
of this report must be referenced for a proper understanding of the nature of the
subsurface material. This profile should not be used to estimate excavation
material volumes.
b) Datum: U.S.G.S.; MLLW = El. 0.00'
c) See Figure 4 for Key to symbols.
0 30 60
Horizontal Scale in Feet
Figure 6
M M M M M M M M
RECEIVED
0
c
Cr
rn
c
sv
0
cD
0
(D
v
1
0
M
m
m
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
D
20] Boring
B-10
10
CD
(D
ILL
c 0
0
as
m
w
-10
-20
Subsurface Profile D-D'
Fill (loose)
PEAT and SILT (soft)
Silty SAND and sandy SILT
(medium dense/stiff, grading
denser/stiffer with depth)
Silty SAND and sandy SILT
(till)(very dense)
D'
Boring Boring 20
B-9 B
(25' North)
[10
4J
--- i r0
SAND (dense to very dense)
NOTES:
a) Subsurface profiles shown have been generalized from data obtained during the
site investigation. Variations between this profile and the actual soil conditions
may be encountered. The logs of the explorations and the discussion In the text
of this report must be referenced for a proper understanding of the nature of the
subsurface material. This profile should not be used to estimate excavation
material volumes.
b) Datum: U.S.G.S.; MLLW = El. 0.00'
c) See Figure 4 for Key to symbols.
-10
-20
0 30 60
Horizontal Scale in Feet
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Equivalent Surcharge Load L
Hs-2'
Locate all anchors 1
behind this line L�-�\ 20-30'
No
\ Load
0.75 ksf \
Zone H
Tieback Anchors
Soldier Piles with
Lagging and
1.0 ksf Drainage System
\30�
Anchor grout -soil bond Base of
strength for anchor design Deepest Excavation
1.0 ksf Imo- H/4 (Determined by Shoring
Contractor; minimum
10 ft.) D
Passive Pressure (psf)
300 D (above GWT) or
Active Pressure (psf): 25 (H+Hs) 150 D (below GWT)
(Assumed to act over the soldier (Assumed to act over twice the width
pile spacing) of concrete filled soldier pile diameter,
or the pile spacing, whichever is less)
Soldier Pile Wall with Tieback Anchors
( Not to Scale)
LANDAU ASSOCIATES, INC. I Preliminary Shoring Design Parameters I
Figure 8
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
APPENDIX A
SITE EXPLORATIONS
Subsurface soil and ground water conditions at the Dayton
Street site for the planned City of Edmonds secondary waste water
treatment plant were explored by drilling ten borings at the
locations shown on the Site Plan, Figure 2. The borings were
drilled to depths ranging from 29.5 feet to 64.5 feet below
existing site grades with truck -mounted, power -operated, hollow -
stem auger drilling equipment. Logs of the borings drilled for
this investigation are presented on Figures A-1 through A-I0.
These logs represent our interpretation of the subsurface condi-
tions identified during this geotechnical investigation. All
soils encountered were classified generally in accordance with
the Unified Soil Classification System described on Figure A-11.
The site explorations were coordinated and monitored by an
engineer from our staff who maintained detailed records of the
subsurface soil and ground water conditions encountered, obtained
representative soil samples, classified the soils by both visual
and textural examination, and monitored installation of the
piezometers. The coordinate locations of the borings, as well as
the elevations of the ground surface and piezometer casings, were
determined by Reid, Middleton & Associates, Inc. All elevations
are based on the U.S.G.S. datum (MLLW = EL. 0.00 feet).
Relatively undisturbed samples of the soils encountered in
the borings were obtained at frequent intervals using a 2.42-inch
inside diameter (ID) split barrel sampler. The sampler was
driven into the soil with a 300-pound hammer falling a distance
A-1
1 RECEIVED
May 26 2021
t &rfOF"ON&nches. Relatively disturbed but representative samples
DEVELOPMENT SERVICES
DEPARTMENT
were also obtained in Boring B-3 with a 2.0-inch outside diameter
(OD) Standard Penetration Test split spoon sampler driven by a
300-pound hammer falling a distance of 30 inches. The number of
1 blows required to drive either sampler for the final foot of
' penetration, or part thereof, is noted on the boring logs
adjacent to the appropriate sample notation. All soil samples
' obtained from our explorations were placed in airtight containers
and transported to our soils laboratory for further visual and
' textural examination and subsequent testing. Soil cuttings from
' the borings were all deposited on the property in the southwest
corner of the'storage yard.
' The method used for backfilling the borings without piezo-
meter installations was dependent on the strata in which the
' boring was terminated. Borings that penetrated the sand unit
' with high piezometric pressure were backfilled using two
different methods. Where possible, a bentonite pellet seal was
'
installed
within
the glacial till overlying the sand
unit,
with
subsequent
backfilling using about 5 feet of Aqua 8
sand.
This
'
was followed
by
bentonite slurry backfill to within 4
feet of
the
surface.
If it
was not possible to set a bentonite
pellet
seal
'
above the
lower
sand unit, the hole was completely
backfilled
' with a cement/bentonite slurry (with less than 5 percent
bentonite). If high piezometric heads were not encountered
' during drilling, the boring was backfilled using a bentonite
slurry to within 4 feet of the surface. Backfilling of all bore -
holes was completed by placing a 4 foot or greater concrete
I
surface seal.
A-2
RECEIVED
May 26 2021
' CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMRiezometers were installed in Borings B-1, B-3, B-5, and B-7
to allow monitoring of the ground water levels. The piezometers,
consisting of 2-inch (nominal) diameter Schedule 40 PVC casing
and slotted screen, were installed through the 4-inch ID hollow -
stem auger. A 5-foot section of PVC slotted screen (0.020 inch
' horizontal slots) was installed at the depths noted on the appro-
priate boring logs. Aqua 8 silica sand was used to fill the
annular space between the boring wall and the piezometer to a
' height of 2 to 12 feet above the screen interval. A bentonite
seal was positioned above the sandpack to seal off overlying
' water -bearing zones and to prevent infiltration of the near
surface grout seal down into the sandpack. The bentonite seal
ranged in thickness from 4 to 27 feet. In some cases, the water -
bearing strata of interest was located significantly higher than
the bottom
of the boring. In
those instances, the hole was back -
filled with
Aqua 8 sand, with
a bentonite seal placed between the
aquifer of
interest and the
closest underlying low permeability
'
soil zone.
Following installation of the piezometer as noted
' above, a cement-bentonite grout seal (with less than 5 percent
bentonite) was placed from the top of the bentonite seal to
' within 2 feet of the ground surface. A flush -mounted cast iron
monument cover was then installed around the PVC casing and
' concreted in place.
A series of water level elevations have been measured in the
' four piezometers installed for this investigation. The water
I
level elevations are presented in Table A-1.
A-3
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
TABLE
A-1
DEPARTMENT
GROUND WATER
LEVELS
OBSERVED IN
PIEZOMETERS
Boring Piezometer
Casing(a)
Water Level
Elevations
Number Number
Elevation
12 May 1987
8 June 1987
B-1 P-l(b)
16.24
11.75
11.63
B-3 P-3(c)
13.27
13.30
12.90
B-5 P-5(d)
14.30
11.97
11.83
B-7 P-7(d)
17.96
14.83
11.68
(a) Elevation of top of piezometer casing as determined by Reid,
Middleton & Associates, Inc. Data refer to U.S.G.S. datum
(MLLW = EL. 0.00 feet).
(b) Piezometer screen and sandpack located in the water -bearing
sands below the peat deposits. Measurements are of the near
surface ground water conditions.
(c) Piezometer screen and sandpack located in the water -bearing
sand below the glacial till. Measurements are of the
artesian piezometric surface.
(d) Piezometer screen and sandpack located in the fill and
natural soils above the glacial till. Measurements are of
the near surface ground water conditions.
A-4
Boring B-1
May 26 2021
CITY OF EDMONDS Dr,p t I
DEVELOPMENT SERVICVJ E,,, 1
DEPARTMENT 0 _
5-
10-
15-
20-
25-
30-
35-
v
r~
o
I E
E
+Y•
7.6% 13
�
1«
12
6
Li
36 8% 2
14 O
8
e
14.2% 42
123
N 9,513.2u E 10,100.55
Elevation 16.40
Crushed rock surfacing
SM Grav silty fine to coarse
SAND with-oravel and occas-
sional construction rubble
and organic matter (loose
to medium dense) (moist to
wet) (fill)
PT Brown PEA': and organic
U1 SILT (very soft) (wet)
SM Gray silty fine to medium
SAND with occasional gravel
and lenses of sandy silt
(medium dense to dense)
(wet)
Sp Gra slightly silt fine to
41 medium SAND (denseyto very
® dense) (wet)
Boring B-1 completed at 34.5-foot
depth on 5 May 1987.
Ground water first observed at
12.5-foot depth during drilling.
65 Piezometer P-1 installed with slotted
20.4$ screen from 28- to 33-foot depth and
105 ® sandpack from 16- to 34.5-foot depth.
----- Add t l d t 1 f meter
KEY.
7.6 a — Moisture Content
122 — Dry Density in PCF
1 Blows required to drive 2 42-inch I.D. split barrel
sampler 1 loot with a hammer weight of 300
13 pounds and a stroke of 30 inches.
0 Indicates depth at which relatively undisturbed
sample was extracted.
® Indicates depth of disturbed sample.
Indicates sample attempt with no recovery.
Blows required to drive a Standard Penetration
To -it ISPTI split spoon sampler 1 foot with a
hammer weight of 300 pounds and a stroke
10 of 30 Inches.
0 Indicates sample obtained with SPT sampler.
LANDAU ASSOCIATES, INC.
i >ona a at s o piezo
construction and water level measure-
ments are presented in the text of
Appendix A.
NOTES.
1. The discussion In the text of this report is
necessary for a proper understanding of the
nature of the subsurface material
2. Boring locations were surveyed and coordinates/
elevations determined by Reid. Middleton d
Associates, Inc., Edmonds, We.
3. Elevations refer to U S.G.S. datum IMI.LW-EI.0.01.
Log of Boring
Figure A-1
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Dept]
(fee
0-
5-
10-
15-
20-
25-
30
Boring B-2
v
0
a .0
E E N 9,517.n '7 E 10,283.39
N Elevatio16.98
o,GP Crusned rock surfacing
0
e
0
22
® 00
0 o SW Grav fine to coarse SAND
,O with gravel and a trace
oa of silt (medium dense)
o.l (moist) (fill)
18.4%
109
17
10.3% 42
136
9.5% 55
135 0
58/6"
SM Gray to green silty fine
ME to medium SANd with gravel
and lenses to layers of
sandv SILT (loose/medium
stiff) (moist to wet)
(grades dense/very stiff)
SM Gray silty SAND to sandy
MT SILT with gravel (ver
dense/hard} (wet) (tily
l)
80/11 SP Gray sliRhtly silty fine to
19.3% medium SAND with occasional
gravel (very dense) (wet)
111
92/9"
Boring B-2 completed at 29.5-foot
depth on 5 May 1987.
Ground water first observed at
9-foot depth during drilling.
BoreholF: backfilled with
bentonite grout and concrete
surface s(-al.
I LANDAU ASSOCIATES, INC. I Log of Boring
Figure A-2
SM
50/4•=:•• GW
Boring B-3
N 9,9:;.75 E 10,116.40
Elevat.on 13.44
Grass and topsoil
Gray silty fine to coarse
SAND with gravel (loose)
(moist) (fill)
Gray silty fine to medium
SAND and sandy SILT with a
trace gravel and organic
matter and occasional
lenses of fine to medium
sand (medium dense/stiff)
(moist to wet)
(grades dense/hard)
Gray to black sandy GRAVEL
to gravelly SAND (very
dense) (wet)
Continued Next Page
LANDAU ASSOCIATES, INC. I Log of Boring I
Figure A
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
2 5 -
30-
35-
40-
45-
50-
55-
50/4
8 6/1 0"
18.3% �
113
76/11
50/4"
8
40
76/419
Boring B-3
rav silty SAND to sandy
ILT with'some gravel (very
L-nse'hard) (wet) (till)
ray slightly silty fine to
edium SAND (very dense) (wet)
grades with some coarse sand
nd a trace of fine gravel)
rag slightly clayey SILT
it h a trace fine sand and
rganic matter and occasional
and partings (very stiff to
ard) (wet)
SP I Gray slightly silty fine to
medium SAND with occasional
60- gravel (very dense) (wet)
Boring B-3 completed at 59.5-foot
depth on 6 May 1987.
Ground water first observed at
3-foot depth during drilling.
Piezometer P-3 installed with
slotted screen from 42- to 47-foot
depth and sandpack from 33- to
51-foot deppth. Additional details
of ptezomF4er construction and
water level measurements are
presonted in tho text of
1PP*midtx A.
LANDAU ASSOCIATES, INC. Log of Boring
Figure A- 3
ECEIVED
Boring B-4
May 26 2021
E
E
Dt�pt1)
?
N y,763.31` E 10,100.59
1
CITY OF EDMgf`j4St` t)
W
to
E e v a 1 1 O n 4. 01
1
DEVELOPMENT SERVGES
DEPARTMENT
o U
0
Grass and topsoil
0 0
-
0
_
9
0 0
SW Gray slightly silty fine
to coarse SAND with
cca ionalljravel (loose)
5-
o o
o C
-
2/18"
PT Brown PEAT (very soft) (wet)
- 2771
18
10-
15
20 SM Gray silty fine to medium
15.7% ■ Mr SANG and sandy SILT with a
- 119 trace gravel and organic
matter and occasional lenses
15- of fine to medium sand (medium
42 dense/stiff) Swet)
(grades dense, hard)
10.9% 53
126
20-
45
44
25-
11.0%50/5"
_ 134 0
50/4" SM Gray silty SAND to sandy SILT
® HE with occasional gravel (very
dense/hard) (wet) (till)
30- 52/6"
50/6"
35- 50/5"
10.8$ �
- 129
(some heaving sand)
_ 21.6$ 36
106
40-
- = SP Gra s11 htl silt fine to
g 1 y
medium SAND (dense to very
dense) (wet)
-
50
-
e
Ground
water first encountered at
45-
1-foot
depth during
drilling.
Borehole
backfilled
with cement -
Boring B-4 completed at 44.5-foot bentonite
depth 7 May
grout and
concrete
on
1987. surface seal.
LANDAU
ASSOCIATES, INC.
Log
of Boring
Figure A-4
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Dept
5-
10-
15-
20-
25-
30-
35-
Boring B-5
W
O
a
a
h m
."E,
N 1),921.011E 10,291.80
t) cn
W
Elevation 14.43
Grass and topsoil
2/18"
®
SM
Brown silty fine to medium
IC C
SAND with a trace to some
gravel and occasional organic
matter lvery loose to loose)
(wet) (fill)
(Small boulder)
(grades to dense silty fine
5.2$ 36
to coarse SAND with gravel)
134 ■
Ism
Gray silty fine to medium
E
SAND and sandy SILT with a
35
trace to some gravel and
11.3%
occasional lenses of fine to
127
medium sand (dense/very
stiff) (wet)
41
(grades very dense/hard)
50/5"'
73/11" SM Gray silty SAND to sandy SILT
11.0$ RL with gravel (very dense/hard)
136 (wet) (till)
81/10"
9.5%
134
11.8% 60
(some heaving sand)
126
SP
Gray slightly silty fine to
medium SAND (dense to very
dense) (wet)
23
(Blow count non -representative
due to heaving sand)
9 6 /9"�:
19 . 9 %
111
Boring B-5 completed at 34.5-foot
depth on 7 May 1987.
Ground water first observed near
4-foot depth during drilling.
Piezometer P-5 installed with slotted
screen from 12.3- to 17.3-foot depth
and sandpack from 10- to 22-foot depth.
Additional details of p►ezometer
construction and water level measure-
ments are presented in the text of
Appendix A.
L LANDAU ASSOCIATES, INC. I Log of Boring
Figure A-5
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Depth
(feet1
0-
5-
Boring B-6
N
O
a n
E E N 9,785.54 E 10,295.94
Elevation 15.99
w rn
Grass and topsoil
:I
SP Gray to brown slightly silty
fine SAND to silty fine to
16 coarse SAND with gravel
(medium dense) (moist) (fill)
11.7%
36
-
127
10-
9.0%
54/6
0
-
129
15-
20-
25-
30-
35-
Mr
72
®
Op
0•
0
•o
O
SW
��
16.9% 5:5
o
00°
117
o,
o p
o e
00
86/9"
°
e.
o �
op
`
ML
50�/6"
27.7%
101
Gray silty fine to medium
SAND and sandy SILT with a
trace to some gravel and
occasional small cobbles
(medium dense/very stiff
grading to dense/hard)
(moist)
Gray silty SAND to sandy
SILT with a trace to some
gravel (very dense/hard)
(wet) (till)
Gray slightly silty fine to
coarse SAND with a trace
gravel (very dense) (wet)
(grades to slightly silty
fine to medium SAND)
Gray slightly clayey SILT
with a trace organic matter
grading to silty very fine
SAND (bard/very dense)
(wet)
Continued Next Page
L LANDAU ASSOCIATES, INC. I Log of Boring I
Figure A-6
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Boring B-6
35-
SP Gray slightly silty fine to
medium SAND with a trace
41 organic matter (dense to
■ very dense) (wet)
40-
d "
- 18.81 �9 ::I (grades without organic matter)
1 33
45-
90/7"' (grades with some coarse sand
- and gravel)
50-
ML Gray SILT with a trace very
22.0% 65 fine sand and organic matter
- 102 S (hard) (wet)
55-
_ o
. o
- e
77/11"°o 'SW Gray slightly silty fine to
_ 12.4% a coarse SAND with gravel
124 o grading to slightly silty
fine to medium SAND (dense
60- o to very dense) (wet)
_ � o
o•
_ O
0
46 00
❑ o
65-
Boring B-6 completed at 64.5-foot
depth on 8 May 1987.
Ground water first observed at
L9-foot depth during drilling.
Borehole back f11led with cement-
bentonite grout and concrete
surface seal.
LANDAU ASSOCIATES, INC. Log of Boring
Figure A-6
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
2
O
Depth E
(feet) (n V1
0-
-
15.4%
15
116
5-
11.4%
12
130
10-
-
50/6
15-
50/6
8.
-
135
50/4
2H- 56/6
Boring B-7
N 9,662.60 E 10,293.48
Elevation 18.12
Grass and topsoil
SMI Brown and gray silty fine
to coarse SAND with some
gravel (medium dense)
`moist) (fill)
SM Gray mottled with reddish -
brown silty fine to medium
SAND with some coarse sand
and gravel (medium dense)
(wet)
SM Gray s=1-4tly silty SAND to
AT sandy SILT with some gravel
and a trace of clay (very
dense/hard) (wet) (till)
77/10" I"..� \
19.0% Sp Gray slightly silty fine to
111 medium SAND with a trace to
25- some coarse sand and gravel
(very dense) (wet)
50/5"'
30-
Boring B-7 completed at 29.5-foot
depth on 8 May 1987.
Ground water first observed at
8-foot depth during drilling.
Piezometer P-7 installed with
slotted screen from 7- to 12-foot
depth and sandpack from 5- to
12.5-foot depth. Additional details
of piezometer construction and
water level measurements are
presented in the text of Appendix A.
LANDAU ASSOCIATES, INC. Log of Boring
Figure A-7
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
y
DEPARTMENT
'-'
a
O
Depth
E
E
(teet)
m
n
0-
-
14.4%
2
116
5-
3
10-
-
9. 9%
40
-
135
15-
13.
-
121
20-
/11"'
_
13 . 4 %91
�
125
25-
50/6"
9.8%
136
30-
50/6"
35-
Boring B-8
N 9,869.28 E 10,204.59
Elevation 13.92
Asphalt concrete and base
course
SMI Grav silty fine to medium
SANb with -sandy silt and
occasional gravel (very
loose) (wet?
(fill)
SMGray silty fine to medium
Mr SAND and sandy SILT with a
trace to some gravel and
occasional lenses of fine
to medium sand (medium
dense/ver stiff to dense/
hard) (we�)
SMI Gray silty SAND to sandy
ML SILT with a trace to some
gravel (very dense/hard)
(wet) (till)
Gray silty fine SAND (very
dense) (wet) (transitionin
to underlying slightly sil?y
sands)
Boring B-8 completed at 34.5-foot
depth on 9 May 1987.
Ground water first observed at
8-foot depth during drilling.
Borehole backfilled with bentonite
pellet seal, Aqua 8 sand bentonite
slurry, and concrete sur{ar•r• seal .
LANDAU ASSOCIATES, INC.
Log of Boring
Figure A-8
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
N
O
a
.o
Depth
E
ea
E
IN9,508.24
E 10,209.14
16.23
(teet)
0-
cn
W
Elevation
GPI
Crushed rock surfacing
11.5% 3
SM
Brown to gray silty fine
-
109
�
to coarse SAND with gravel
gradina to slightly silty
5-
fine SAND (very loose)
(moist to wet) (fill)
2/18"
-
248%
0
PT
Brown PEAT (very soft)
20
12
(wet)
10-
-
SM
Grav to green silty fine to
medium SAND with a trace
-
22
gravel and occasional lenses
15.2$
of sandy silt and fine to
-
121
medium sand (medium dense
to dense) (wet)
15-
10.1% 32
-
133
20-
-
SM
Gray silty SAND to sandy
-FL-
SILT with occasional ravel
-
50/5"
(veri (wet)
®
)dense/hard)
(till
25-
14.8% 55
-
120
SM
Gray silty fine to medium
Sraainglttoaslightlyravl
30-
gDP silty
fine SAND (very dense)
(wet)
Boring B-9 completed at 29.5-foot
depth on 9 May 1987.
Ground water first observed at
8-foot depth during drilling.
Borehole: backfilled with cement-
bentonite grout and concrete
surface seal.
LANDAU ASSOCIATES, INC.
Log of Boring
Figure A-9
;ECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Depth
(feet)
0-
v
a
IS
m
m
a
E
>.
w
13.0% 17
5-
-
f
_
2
10-
2
_
108%
4
�
37
15-
il
_
13.5%
24
0
126
20-
33
25-
_ 10.1%87/11"
132
30-
Boring B-10
N 9,577.1- E 10,097.00
Elevation 16.16
crushoo rock surfacing
SM Gray to brown silty fine to
coarse SAND with gravel and
occasional organic matter
(medium densei (moist to
wet) (fill)
PT Brown PEAT interbedded with
7E dark gray organic SILT
(very soft to soft) (wet)
SM Gray silty fine to medium
Fir SAND and sandy SILT with a
trace to some gravel and
occasional lenses of fine
to medium sand (medium
dense/stiff) (wet)
(grades to dense/very stiff)
SM Gray silty SAND to sandy
MTSIL with occasional gravel
(ver1 dense/hard) (wet)
(till)
Boring B-10 comppleted at 29.5-foot
depth on 9 May 1987.
Ground water first observed at
8-foot depth during drilling.
Borehole backfilled with
bentonite slurry and concrete
surface seal.
L LANDAU ASSOCIATES, INC. I Log of Boring
Figure A-10
1
1
1
1
1
1
1
1
RECEIVED
fY OF EDMONDS
_OPMENT SERVICES
DEPARTMENT
Group
Major D vrsrons vmbors ITypical Names Laboratory Classrfrcarron Criteria
f
� D
„to
_
c
O
r c
d =
>
GW
Well -graded gravels gravel sand mix
fines
E C
�0
rn E
Dao
Cu — greater than 4 Cc
(030)'
---- between 1 and 3 '
n
C
lures little or no
r n
O10
Dt0 y Dao
w
GP
Poorly graded gravels grave' -sand m.x
I u s
„L.
—
fines
Lures little or nc f
m
d
Not meeting all gradation requirements for GW I
>
R N
C.
U _
c
RO
o Z
> y
r'iV
—_ [
c
Y In U
O
lO q
r
6 7
C O
O N V) N
I > h q
� :
"A"
Z
c
m
r m —
GM
Silty gravels gravel -sand silt mixtures
u
p p to inm
Atterberg limits below
Above "A" line vv.tn P I
c
t
c
_ o,
_ ;,
; c
u c
2 a u;
line or P 1 less than 4
between 4 and 7 are border
—
6 =
,[, �% m
line cases requiring use of
t
d o l
GC
Clayey gravels gravel -sand crav mix
[ E 3
Atterberg limits below "A"
dual symbols
—
m e
Lures
d C7 0 tC
line with P I greater than 7
+I
—
E E
o
o `—,
c
SW
Well -graded sands gravelly sands little
� E
C D60
u greater than 6. Cc =
(0i0)7 between 1 and 3 1
c E
c
or no fines
M
C—
D to
D Io Dao
0
-
0
0 N
[
n o
SP
Poorly graced sands, gravelly sandy
- -
c
Not meeting all gradation requirements for SW
t
s d
°v
little or no fines
=
„
N
o
I O c c —
u
O
T_� o
A [
n• O —
p
—
-a p Z
L'
_
c
7
` u d
"A"
n .
a o'
e
E.
SM
Silty sands sand -silt mixtures
c -cu —
m u c c
Atterberg limits above
P
Limits plott,n in hatched
g
r
—
`
u=_ G n
a
line or I less that'. 4
zone with P I berv.een a
r =
—
�
3 L.
SC
Clayey sands, sand cla, mr turec
_ R c p
c` [' u n r
Atterberg limits above "A"
and 7 are borderline cases
ry E
O
b u p
7 r_ N
y
E
line with P I greater than 7
requiring use of dual svm
I
c
in C
c R p
bols I
c
oe„
0
Inorganic silts and very fine sands
'
in
ML
rocF flour, silty or clayey fine sands
c
L
or clayey silts with. slrcht D'as:.c.ty
u
>
;
ti
PIustioi% Chart
`
u 4
Inorganic clays of low tc med-urn
60
00
CL
plasticity grave• ciays sand, Ja1s
graveliv
silty clays, lean C.aVs
O
Z
c
r
v
c
J
OL
Organic silts and organii- silty Clays of
low Plast'c'ty
50
I
C H
i I
I
I
„
o u
r 40
c` E
in
E
I I
I
I
I
„
Inorganic silts micaceous or d,atona
>, 3D
o.
r
MH
ceous Irne sandy or silty soils, e,a:tic
-
I
d -
„
Silts
-
•����
I I
Gli and AM
u
—
I
I
i
E
c °'
Cr
CH
Inorganic clays of high plasticity, lat
clays
`b
I
I CL
I
r
E
I
c
to =
OH
Organicclays of medium to high
r
L
�
n
plastrcy, organic silts
b1L ilia
d
0
o
J
0
i. OL
0
10 20 30 40 50 60 70 80 qD 1Of) I
>
bgwd Lmn
„
a m o
Pt
Peat and other highly organic soils
I
LANDAU ASSOCIATES, INC. UNIFIED SOIL CLASSIFICATION CHART
Figure A-11
RECEIVED
May 26 2021
CITY OF EDMONDS APPENDIX B
DEVELOPMENT SERVICES
DEPARTMENT
LABORATORY TESTING PROGRAM
Laboratory tests were performed on representative disturbed
and relatively undisturbed soil samples to evaluate pertinent
physical and engineering characteristics relative to the planned
construction. The laboratory program included sample inspection
to confirm our site engineer's soil classification, and determin-
ations of grain -size distribution, moisture -density relation-
ships, permeability, and strength of selected soil samples.
Visual Classifications
Soil samples obtained from the site explorations were
visually classified when obtained and then transported to the
laboratory where the classifications were verified. Soil classi-
fication was made in general accordance with the Unified Soil
Classification System. Visual classifications included soil
consistency or density, color, moisture content, major soil type,
and the modifying fractions of the soil samples. Classifications
of selected samples were checked by laboratory tests.
Moisture -Density Determinations
Moisture -density determinations were completed in conjunc-
tion with the strength tests and on other selected soil samples.
Moisture contents were determined in general accordance with ASTM
D-2216 test procedures. Results of the moisture -density determi-
nations are presented to the left of the appropriate sample
notation on the boring logs and on the direct shear test summary
sheet.
B-1
RECEIVED
May 26 2021
(Qradia4tNron Tests
DEVE6G+;44& ZP-6EfF',46E6
DEPARTMENT
Mechanical grain size analyses were performed on selected
' soil samples in general accordance with ASTM D-422 test proce-
dures to determine the grain size distribution of the material.
These test results were used for both classification purposes and
' to evaluate the potential use of the soils as compacted fill
material. The gradation curves are presented on Figures B-1
through B-3.
'
Wash-200
The
Wash-200 is a test method to establish the amount of
'
material
in a soil (silts
and clays) which
is finer than
the U.S.
No. 200
sieve. The tests
were performed
on selected samples
in
'
general
accordance with ASTM
D-1140 test
procedures and
involve
washing
the soil sample over a U.S. No. 200 sieve. The
results
of the tests
are presented
in Table B-1.
TABLE B-1
'
PERCENT PASSING
THE U.S. NO.
200 SIEVE
BY
WET WASH METHOD
'
Exploration
Sample
Depth Percent
Passing
U.S.
Number
Number
(feet) No.
200 Sieve (by
dry wt.)
'
-----------------------------------------------------------------
-----------------------------------------------------------------
B-2
S-2
9
17
B-2
S-5
17
33
B-3
S-2
9
52
B-4
S-4
14
36
B-4
S-9
26
44
'
B-7
S-2
9
27
B-10
S-5
16
39
B-2
'
RECEIVED
May 26 2021
' DEVFIM 22 ',ity Tests
DEPARTMENT
Constant head permeability tests were performed on selected
fsaturated soil samples to evaluate the soils vertical hydraulic
' conductivity. The permeability tests were conducted in general
accordance with ASTM D-2434 test procedures, and test results are
presented in Table B-2.
'
TABLE
B-2
LABORATORY
PERMEABILITY TEST
RESULTS
'
Vertical
Sample
Hydraulic
Boring
Sample
Depth
USCS
Conductivity
'
Number
Number
-(ft)-------
Symbol
---------(cm/sec)--_--
B-3
5-10
38.5
SP
2 x 10-3
'
B-4
5-14
39.0
SP
2 x 10-4
'
B-6
S-5
24.0
SW/SP
2 x 10-3
B-7
S-7
24.0
SP
2 x 10-3
'
B-10
S-6
18.5
SM/ML
6 x 10-6
Strength Tests
' The frictional shear strength of the granular soils that
underlie the project site were evaluated by means of direct shear
' testing. Direct shear tests were performed at a constant rate of
deflection equal to 0.025 inches per minute in accordance with
' the testing procedure described on Figure B-4. Results of the
' direct shear tests are presented on Figure B-5.
[7
1
M
RECEIVED
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
r
Z
U.S. STANDARD SIEVE SIZE
100
-
ion
C
D
90
9n
0
o
Bo
Bn
(�
In
D
70
7n n
---I
rn
m
60
6n
E
-r,
50!
50
m
n
40
40
co
7.
30
:30
20
20
10
,n
01
n
GRAIN SIZE IN MILLIMETERS
COBBLES
GRAV_E_I_
COARSE � FINE
SAND
COARSE MEDIl1M FINE
SIL1 OH
CLAti
n
c
CD
a
C
9
Symbol
Boring
Depth
USCS
Description
B-1
29'
SP
Slightly silty fine
-medium sand
•
B-4
19'
SM
Silty fine -medium
sand with a trace
of
coarse sand
and
fine
gravel
- - - -
B-5
14'
SM
Silty fine -medium
sand with a trace
of
coarse sand
and
fine
gravel
RECEIVED
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
r-
z U.S. STANDARD SIEVE SIZE
D
100 inn
D 90 9n
80 Bn
(� rn
D 70 7n n
--1 rn
m 60 6n -J
z 5n, 5n m
40 4n
3n 3n
!1z
?o zn
I ONE
10 in
G) o !11In
� � i
�- GRAIN SIZE IN MILLIMETERS
_ GRAVEL _ SANn
COBBLES - SILf OH GLAY
O COARSE FINE COARSE MEOIIIM FINE
C�
c
co
m
■I
y
�
eh
1
I
Symbol
Boring
Depth
USCS
Description
B-5
34'
SP
Slightly silty fine - medium sand
•
B-6
9'
SM
Silty fine — medium sand with a trace coarse fine
M
i.]
C
1
M
W
I
N
RECEIVED
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
r
Z U.S. STANDARD SIEVE SIZE
0 100 - 100
C
D 90 90
co
C/) 80 80
0 m
D 70 70 UJI,
•� r n
m
Cj) sn sn -+
Z 50 5n m
n Jj
40 4n CD
3n 30
20 20 {
10 1n
isINon
KI will
CL GRAIN SIZE IN MILLIMETERS
�+ GRAVEL SAN_n
COBBLES SILI OH L:I_AY
p COARS� FINE COARSE MEDIUM
0_ FINE
c
-.
co
N
i
u
d
lilt
Symbol
Boring
Depth
USCS
Description
B-8
14'
SM
Silty
fine —
medium
sand with
a trace
of
coarse sand
and fine gravel
•
B-8
28.5'
SM
Silty
fine -medium sand with a
trace of
coarse sand and
some fine gravel
— — — —
B-9
14'
SM
Silty
fine
— medium
sand with
a trace
of
coarse sand
and fine gravel
T
LZ
C
O
3
I
W
RECEIVED
May 26 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
A'ir,TIIOD OF PERFORMING DIRECT SHEAR AND FRICTION TESTS
DIRECT SHEAR TESTS ARE PERFORMED TO DETERMINE.
TILE SHEARING STRENGTIIS OF SOILS. FRICTION TESTS
ARE PERFORMED TO DETERMINE THE FRICTIONAL RE-
SISTANCES BETWEEN SOILS AND VARIOUS OTHER MATE-
RIALS SUCH AS WOOD, STEEL, OR CONCRETE. THE TESTS
ARE PERFORMED IN TILE LABORATORY TO SIMULATE
ANTICIPATED FIELD CONDITIONS.
EACH SAMPLE IS TESTED IN A SPLIT SAMPLE HOLDER,
TWO AND ONE-HALF INCITES IN DIAMETER AND ONE
INCH HIGH. UNDISTURBED SAMPLES OF IN -PLACE SOILS r
..� ....pert✓'��'O'�"_h:k,'rr:-ar--"`�.- �
ARE EXTRUDED FROM RINGS TAKEN FROM THE SAM-
PLING DEVICE IN WHICH THE SAMPLES WERE OB- DIRECT SHEAR APPARATUS WITH
ELECTRONIC RECORDER
TAINED. LOOSE SAMPLES OF SOILS TO BE USED IN CON-
STRUCTING EARTIi FILLS ARE COMPACTED IN RINGS TO PREDETERMINED CONDITIONS AND TESTED.
DIRECT SIIEAR TESTS
A ONE -INCH LENGTH OF THE SAMPLE IS TESTED IN DIRECT SINGLE SILEAR. A CONSTANT PRESSURE,
APPROPRIATE TO THE CONDITIONS OF THE PROBLEM FOR WHICH THE TEST IS BEING PERFORMED,
15 APPLIED NORMAL TO THE ENDS OF THE SAMPLE THROUGH POROUS STONES. A SHEARING FAILURE
OF THE SAMPLE IS CAUSED BY MOVING THE UPPER SAMPLE HOLDER IN A DIRECTION PERPENDICU-
LAR TO THE AXIS OF THE SAMPLE. TRANSVERSE MOVEMENT OF THE LOWER SAMPLE HOLDER IS
PREVENTED.
THE SHEARING FAILURE IS ACCOMPLISHED BY APPLYING TO TILE UPPER SAMPLE HOLDER A CON-
STANT RATE OF DEFLECTION, THE SHEARING LOAD AND THE DEFLECTIONS IN BOTH THE AXIAL AND
TRANSVERSE DIRECTIONS ARE RECORDED AND PLOTTED. THE SHEARING STRENGTH OF THE SOILS IS
DETERMINED FROM THE RESULTING LOAD -DEFLECTION CURVES.
FRICTION TESTS
IN ORDER TO DETERMINE THE FRICTIONAL RESISTANCE BETWEEN SOIL AND THE SURFACES OF VARI-
OUS MATERIALS, THE LOWER SAMPLE HOLDER IN THE DIRECT SHEAR TEST IS REPLACED BY A DISK
OF THE MATERIAL TO BE TESTED. TILE TEST IS THEN PERFORMED IN THE SAME MANNER AS THE
DIRECT SIIEAR TEST BY FORCING THE SOIL OVER THE FRICTION MATERIAL SURFACE.
Figure B-4
RECEIVED
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
r
Z
D
C
D
O
n
_
m
n
C
3
!v
0
—„
0
cD
Cn
cn
>v
--
w
r-«
BORING
DEPTH
SOIL TYPE
MOISTURE
CONTENT
%OF
DRY WEIGHT
DRY
DENSITY
LBS./ CU.FT.
NORMAL
PRESSURE
LBS./ SQ.FT.
PEAK
SHEAR
STRENGTH
LBS./SOFT.
ULTIMATE
SHEAR
STRENGTH
LBS./SOFT.
B-2
9'
Silty fine -medium sand with some
18.4
109
1000
910
840
gravel
B-3
4'
Silty fine -coarse sand with gravel
11.7
113
300
1130
420
(fill)
c�rc� i
EDMD0615W-CEIVED
EDMDo603.LOG
EDMDAPP .A May 26`�021
CITY OF EDMONDS
EDMDAPP .B DEVELOPMENT SERVICES
DEPARTMENT'
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1