GEOTECHNICAL REPORT.pdfA% Aft A% M%1
GEOSCIENCES INC.
Post Office Box 2385
Kirkldnd, WA 98083
Telephone (425) 827-1084
Facsimile (425) 828-9443
Chien Dinh Nguyen Job Number 8042
18311 — 71" Avenue West May 26, 1998
Lynnwood, WA 98037
Subject: Geotechnical Engineering Report
160XX 75 1h Place West
Edmonds, Washington
Dear Mr. Chien:
We are pleased to present the Geotechnical Engineering Report for the proposed new
residence to be constructed on the Chien Property east of the wharf at 160XX — 75,h Place
West in Edmonds, Washington. The purposes of our work were to professionally
evaluate subsurface soil and groundwater conditions, recommend general procedures for
the grading and underslab treatment in the building area, recommend a foundation
method with design parameters, and present a slope stabilization method for that portion
of the slope on the property. The City of Edmonds is responsible for ensuring stability of
their property along the roadway. The scope of our services included:
1) Logging and sampling two test borings drilled in the vicinity of the proposed
house to a maximum depth of 34.25 feet below existing grades. The test
borings were drilled with a truck -mounted drill rig and logged by the
undersigned registered engineer. Selected samnp!'w-_-, tak.-In of subsurface
soils.
2) Reviewing collected soil samples in our office, and assigning appropriate
laboratory tests consisting of moisture contents, sieve gradation, and Atterberg
Limit tests. At the conclusion of the testing program, laboratory results were
analyzed and compared with field notes and logs.
3) Preparation of this summary report in accordance with our understanding of
project requirements and generally recognized local geotechnical engineering
practices, including Nfeadowdale permit requirements. No warranty is
expressed or implied. Plate 1, attached, provides the guidelines in the use of
this report.
CHIEN RESIDENCEIED,VJONDS Job Number 8042
May 26, 1998 Page 2
ProJectLi-iderstandin s.
This office was provided with a topographic plan which documented existing conditions
including topography. Our knowledge of this project is generally limited to the
information on this site plan and information from your architect.
We anticipate the new structure will be a wood -frame and multiple storied. It will be
located near the, center of the property. We anticipate the driveway will access the site
from the roadway near the wharf,
General Site Conditions - qnrfqr-w
The proposed new residential structure will be constructed on the vacant parcel just east
of the existing wharf in the Meadowdale Area of Edmonds, Washington. The attached
Vicinity Map, Plate 2, shows the general vicinity of the site.
At the time of our fieldwork, the flat area of the site was covered primarily with long
grass and small shrubs, while the slope down from the roadway was covered with
blackberry brush and other shrubs. The proposed building site is located in the flat area
of the site. The proposed building site had a very gentle to fair slope down towards the
West.
Subsurface Exploration and Description:
Two test borings were drilled with a truck -mounted drill rig to a maximum depth of 34.25
feet below existing grades at the location shown on the Site Plan, Plate 3. The test
borings were logged and sampled by the undersigned registered engineer during drilling.
The test boring logs are attached to this report. Recovered soil samples were subjected to
moisture content, sieve gradation, and Atterberg Limit tests. Test results and field
density information are summarized on the test boring logs and attached plates. Although
there may very well be some variation in the subsurface andJor conditions may not be
readily apparent from the ground surface, we expect the following subsurface
interpretation will be essentially correct:
Our test borings revealed that the site is immediately underlain with fourteen to
more than eighteen feet of variable, soft to firm silts that are interlayered with
sand lenses, These soft soils are wet and compressible. Under these soft surficial
soils is a stiff to very hard silty clay. Groundwater was observed in our test
borings at eight to nine feet below the existing ground surface,
CHIEN RE, SIDENCEIED MONDS Job Number 8042
Alfay 26, 1998 Page 3
The final test boring logs attached to this report presents our interpretation of the field
data and laboratory tests. The stratification lines on the logs represent approximate
boundaries between soil types, at the exploration location. In actuality, the transition may
be gradual. The relative densities and moisture descriptions an the logs are interpretive
descriptions based on observed conditions during drilling. The logs should be reviewed
for specific subsurface information at each location tested.
Conclusions and Recommendations
General:
The following general geotechnical conclusions can be drawn from our field and
laboratory test data:
1) The native undisturbed stiff to very hard clay below the topsoil and soft silt
soils can provide adequate bearing to the structure,
2) A drilled pier foundation is appropriate for this site. Floor slabs should also
be pile -supported.
3,) A permanent soldier pile wall consisting of steel beams and lagging to support
the slope behind the house is required. This will provide some stability to the
slope although the City of Edmonds must stabilize the road subgrade above
the property, and they are responsible for their road.
4) We recommend footing drains around all uphill sides of footings at the
elevation of the footings. Positive drainage to an appropriate drainage
structure is recommended.
5) Soils with a high percentage of silt and/or clay (>15%) are moisture sensitive
and difficult to impossible, to utilize as structural fill is the soil is more than
two to three percent wetter or drier than the opth-nurn moisture content at the
time of compaction. Most of the soils at this site are silty and/or clayey, and
are moisture sensitive.
EoundatjanjzL]gilled Auixercast biles•
The structure can be supported on drilled augercast piers. Minimum fourteen -inch -
diameter steel -reinforced concrete augercast piles embedded a minimum of ten feet into
the underlying stiff to very hard silts are recommended. Fourteen-inc h- diameter piers
installed a minimum of ten feet into the stiff to very stiff silts will have a vertical capacity
of fifteen tons. We estimate that individual piers will experience total and differential
settlements on the order of one-half inch.
CHIE N RESIDE NCEIEDAIONDS Job Number 8042
May 26, 1998 Page 4
The augercast method of pile installation involves drilling the hole with the auger
equipment and then continuously pumping concrete grout through the center of the
hollow -stem auger during auger extraction. Steel reinforcement in then placed in the hole
through the entire depth. A head of concrete must be maintained above the auger tip to
ensure an intact column of concrete has filled the drilled hole after the auger has been
removed. Generally, this can be achieved by withdrawing the auger slowly while
maintaining a suitably high pump pressure.
As a general rule, the rate of auger extraction should not exceed about five feet a minute,
and the pressure of the concrete grout pump should be in the range of 150 to 250 pounds
per square inch (psi). The pump should be equipped with a calibrated stroke counter so
that concrete volumes may be calculated.
We can provide design criteria for different pile diameters and embedment lengths, if
desired. For transient loads, such as seismic, the allowable load may be increased by
one-third. A moderate to major seismic event may result in some shifting of the piers and
ground.
Lateral loads due to wind or seismic forces may be accommodated by the piles and by
passive pressure on the grade beams. We anticipate piles will have a lateral capacity of
1.0 ton per pile. Additional lateral capacity, if needed, can be achieved through the
installation of battered piles. Piles may be battered up, to a gradient of 1:5
(Horizontal: Vertical) without reducing the vertical toad capacity. Lateral loading is also
resisted by friction between the slab and the subgrade, and by passive earth pressure on
the sides of the grade beam. A coefficient of 0.30 may be assumed between the bottom
of the grade beam and the subgrade. Passive earth pressures on the grade beam can be
assumed to be equal to that exerted by a fluid having a density of two hundred fifty (250)
pounds per cubic foot.
As augercast piles cannot be inspected after installation, it is important that an engineer
or geologist from our office be present during installation. This will allow us: 1) To
confirm that the encountered subsurface conditions are consistent with those indicated by
our exploration; 2) To evaluate whether soldier pile construction activities comply with
the intent of contract plans and specifications; and, 3) To provide recommendations for
design changes in the event unanticipated subsurface conditions are encountered. We
would be delighted to provide these construction observation services, however it must
be understood that we will not supervise the contractor during his operations, nor are we
responsible for job and site safety during construction,
CHIEN RESIDE, NCEIL�'DA,JONDS Job Number 8042
Mqy 26, 1998 Page 5
Slove R&�inforcement-,
We recommend the slope behind the proposed house be reinforced with a permanent
soldier pile wall. This soldier pile wall shOLIld consist of minimum fourteen -inch -
diameter steel -beam -reinforced concrete augercast piles embedded a minimum of fifteen
feet into the underlying stiff to very hard clay which underlies the site. Pile embedment
may need to be deepened to a depth where pile stickup above finish excavation grade
equals embedment into the hard clay. Treated lagging should be utilized between the
(riles. The piles and lagging should stickup above finish grade to a minimum distance to
provide for a maximum 2:1 (Horizontal: Vertical) slope behind the wall, plus an
additional two feet. The wall should be backfilled with quarry spalls, and provisions
should be made to accommodate drainage which may percolate through the wall. No
structures should be constructed upslope of the soldier pile wall.
`rhe following design pressures can be used by the structural engineer for the structural
design of the wall:
1) An Active Equivalent Fluid Pressure of 65 pounds per cubic foot (pcf) for that
portion of the piles above elevation 48 feet (including the two feet of stickup),
2) An Active Equivalent Fluid Pressure of 40 pcf for that portion of the pile from
elevation 48 feet to the top of the stiff to very hard clay (elevation 36 feet),
3) A Passive Equivalent Fluid Pressure of 300 pcf acting over twice the pile
diameter starting at a depth of 36 feet.
The shoring piles will be installed in the same manner as the augercast pile method
described above. We can provide design eriteria for different shoring pile diameters, if
desired. For transient loads, such as seismic, the allowable load may be increased by
one-third. A moderate to major seismic event may result in some shifting of the piles and
ground, We should be on site during shoring pile installation also,
Seismic Design:
The site is classified as Seismic Zone 3 by the Uniform Building Code. We recommend
the designer utilize site soil coefficient SE in their analysis.
Site Drainage:
The site should be graded during, construction so that surface water is directed away from
any excavation. Water should not be allowed to pond where foundations, pavements, or
slabs are to be constructed,
CHIENRESIDENCEIP�-DIVIOlVD,3 Job Number 8042
May 26, 1998 Page 6
Final site grades adjacent to the building should be sloped away from the structure for a
minimum distance of ten feet. Roof and surface water drains should discharge to all
appropriate facility.
Footing drains are required and should consist of a slotted four -inch -diameter PVC pipe
bedded in, and covered with a minimum of six inches of drain rock. The invert of the
pipe should be placed at the elevation of the footings. A non -woven ge,otextile fabric
(Mirafi 140N, Supac 4NP, or other equivalent) should be wrapped around the outside of
the drain rock. The PVC pipe should be sloped to drain, and may be connected to the
roof and surface water discharge pipe down -gradient and away from the structures. The
pipes should discharge to an appropriate discharge facility,
Erosion Control:
Construction of this project will require excavation and grading. Erosion control
measures are required. We recommend, as a minimum, that the contractor provide a
properly installed filter fabric fence down -gradient from all construction activities.
Depending on the amount of surface runoff, hay bales and/or the placing of straw on
denuded slopes may be required. If surface runoff is channeled into a nearby storm water
system, then the gate should be protected with an approved geotextile fabric to prevent
the migration of an silt or clay particles into the storm water system.
Excavations and Slopes:
Temporary and permanent excavation and slopes for this project must meet all applicable
government safety regulations, Temporary cuts to a depth of four feet may be attempted
vertical, although they may not hold. Excavation slopes greater than four feet in depth
should be cut no steeper than 1:1 (Horizontal: Vertical). Flatter slopes may be required
depending upon location variations in soils conditions and whether there is groundwater
present. Contractors working in excavations should use caution at all times. Sudden
caving of the side slopes, is possible.
Permanent cut and fill slopes which are not otherwise reinforced should not exceed 2:1
(FIN).
CHIENRE SIDENCEIE, D MONDS
Alfay 26, 1998
General Earthwork and Structural Fill -
Job Nuinber 8042
Page 7
Site construction should begin by stripping and clearing the property of vegetation,
organic -rich topsoil, and any other deleterious material. Stripped materials may have to
be removed from the site. Groundwater seepage was noted during our fieldwork at eight
to nine feet below existing grades. The contractor should anticipate, and be prepared to
accommodate moderate seepage into even shallow excavations,
Structural fill is defined as any fill placed below structures, including slabs, where the fill
soils would need to support loads without unacceptable deflections or shearing.
Structural fill should be placed above unyielding native site soils in maximum eight -inch -
thick loose lifts and compacted to a minimum of 95% of Modified Proctor (ASTM
D1557).
Soil is typically difficult to place and compact as structural fill if more than three percent
from the optimum moisture content at the time of compaction. During wet weather or
under wet conditions, structural fill should consist of a granular soil having less than five
percent silt or clay (measured on that portion which passes the �/4-inch sieve). During dry
weather, water may have to be added to the soil to achieve the required soil density.
Wet WLather Construction.•
This project should be completed during the dry summer months. This project will be
very difficult to complete during the winter due to slickness of the silty/clayey soils and
the abundant water.
Closure:
It is absolutely imperative that we be retained to review the final development plans to
verify site specific subsurface requirements are met and our recommendations have been
accurately interpreted in the plans.
CHIEN RLSIDENCEIED,�JOIVDS
May 26,1998
Job Number 8042
Page 8
We will also need to be retained to provide professional geotechnical consultation and
observation services during design and construction, This allows us to: 1) Confirm that
design conforms to specific subsurface requirements; 2) Confirm that subsurface soils
conditions exposed during construction are consistent with those indicated by this report;
3) Evaluate, whether earthwork and foundation construction activities conform to the
intent of the contract specifications and plans; and, 4) Provide recommendations for
design changes in the event of changed conditions.While on the site during construction,
we will not direct or supervise the contractor or work, now will we be responsible for
providing oil -site safety or dimensional measurements during construction activities.
It has been a pleasure providing you with our professional services. If there are any
questions concerning this report, please contact me directly at 425-827-1084.
Thank You:
DODDS Geosciences Inc.
I
SOLES GEOSCIENCES INC.
PL"qr-� I
GUH)ELI-NF-S TN THF. USE OF THIS REPORT
This report for Job No. 8042 was prepared in accordance with local generally accepted
engineering principles and standards. No, warranty is expressed or implied.
The findings and recoinmendations contained in this report are based upon the [in-lited services
which You requested. Geotechnical engineering requires the application of professional
judgment, as no study can completely quantify subsurface conditions. The owner should
seriously consider any recommendations for additional work contained in the report, as it is then
our professional opinion that this additional work is necessary to augment and/or fulfill site
specific requirements.
This report is an inforniational document, and is not to be used for contractual purposes. Ally
interpretation of subsurface conditions in the report including the test boring logs, and/or text
discussions are based upon our testing, analysis, experience, and judgment. There is no warranty
that these subsurface interpretations represent subsurface conditions other than that which
occurred at the exact locations tested at the time the fieldwork was conducted by this firin.
Groundwater levels can be especially sensitive to seasonal changes. This firm is not responsible:
for interpretations others make using this report.
The conclusions and recominendations in this report assume that the field tests that were
conducted accurately represent subsurface conditions of the site. If, during construction,
significantly different subsurface conditions are encountered from those described in this report,
our firm should be notified at once to review these conditions and revise our recommendations as
necessary. Also, if there is a significant lapse of time between this report submittal and the start
of work at the site, our firm should be allowed to review and verify site conditions.
Unanticipated soil conditions are commonly encountered during excavation and construction,
and simply cannot be fully anticipated by periodic soil and/or rock sampling at widely spaced
testing locations. The owner should be prepared to accommodate: potential extra costs through
the development of a contingency fund.
This firm cannot be responsible for any deviation from the intent of this report including, but not
limited to the nature of the project, the construction timetable, and any construction methods
discussed in the report. The recommendations contained in the report are not intended to direct
the contractor's methods, techniques, sequences or procedures, except as may be specifically
described in the report. This finii will not be responsible for any construction activity on this
site, nor are we responsible if others attempt to apply this report to other sites.
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Job Number 8 742 Plate 3
Site Plan
Chien Residence
75th Place West
Edmonds, Washington
Hole No. 1 PROJECT: 75th PL West DATE DRILLED: 4/30/98
DRILL RIG: Truck -Mounted LOGGED BY: Mark K. Dodds P.E.
HOLE OIA: 8 inSAMPLER:SPT
INITIAL WATER DEPTH: 9.0 ft. HOLE ELEV: 1 50' MSL
FINAL WATER DEPTH: 9.0 ft. TOTAL DEPTH: 31.4 ft.
111M. �11 W
SOIL GRAPHIC BLOWS
TYC
PE LOG /Ft. REMARKS
(n
surface - Grass.
Dark Grown Silty Topsoil, Net, loose,
aJay Sandy Silt, wLt' Soft to
Sm
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Standing gro�jn(fwatfjr table,
Grey Silty Clay, wet, stiff.
CL
Mal J,
'�Cp J.0 jtu� 'JUTIng u1ming,
0
2
4
10
12
14
16
18
20
22
24
20
28
30
00010S Geosclences Inc. PAGE 1 OF I
Hole No. 2 PROJECT: 75th P1. West DATE DRILLED: 4/30/98
DRILL RIG: Truck -Mounted LOGGED BY: Mark K. Dodds P.E.
HOLE DIA: 8 in. SAMPLER: SPT
INITIAL WATER DEPTH: 8.0 ft. HOLE ELEV: 1 42' MSL
FINAL WATER DEPTH: 8.0 ft. TOTAL DEPTH: 34.25 ft.
(n
w
DESCRIPTION SOIL GRAPHIC (L . BLOWS
TYPE LOG /Ft. REMARKS
U)
uouunawater taole near m feet during drilling,
0
2
4
8
8
10
12
14
16
18
20
22
24
26
28
30
32
34
DODDS Geosclances Inc. P4GE t OF
MATERIAL: Native Soil SOURCE: B-1; 5.01- 6.51
SAMPLED BY* Mark K. Dodds, P.Ei. DATE: 4/30/98
SCREEN
SIZE
Accum-
WEIGHT
RETAINED
(Grams)
ACCUM-
PERCENT
RETAINED
PERCENT
PASSING
#10
#40
12.2
3.9
100.0
96.1
#100
35.0
11.3
88.7
#200
93.3
30.0
70.0
ASTM C136
SAMPLED BY: Mark K. Dodds, P.E.
SOURCE: B-2; 3.01- 4.5'
DATE: 4/30/98
SCREEN
SIZE
#10
ACCUM-
WEIGHT
RETAINED
(Grams)
ACCUM-
PERCENT
RETAINED
PERCENT
PASSING
100.0
#40
1.5
0.6
99.4
#100
3.2
1.2
98.8
#200
6.8
2.6
97.4
X
ASTM 0136 ASTM D1140
Job Number 8042 - Plate 7
Sieve Analyslis
Chien Residence
75th Place West
Edmonds, Washington
IE
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Plasticity
Index
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ME
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N
0 10 20 30 40 50 60 70 80 90 100
Liquid Limit
Depth (f't.
NCO
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40
Plasticity
Index
M
MCI
1E
N
U 10 20 30 40 50 60 70 80 910 100
Liquid Limit
Depth (ft.)l