HomeMy WebLinkAbout02849 - Technical Information Report - Geotechnical I
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G E O T E C H `� �� �� May zs, �sss ����
CONSULTANTS, INC. � � I
JN 99189 '
13256 NE 20th Street,Suite 16 '
Bellevue.WA 9R005 �a��.��:�==ti��':;:
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FAX(�325)747-R561
FEB 21 2000
SEB, Incorporated
240 Stadium Way South, Suite 330 BUILDING DlVISION
Tacoma, Washington 98402
Attention: Stephen M. Berg �r �"��" � ts
5 I�
Subject: Transmittal Letter- Geotechnical Engineering Study
Proposed Multi-Family Development
186xx Talbot Road South 'I
King County, Washington
Dear Mr. Berg: �'
We are pleased to present this geotechnical engineering report for the proposed multi-family '
development to be constructed in King County, Washington. The scope of our work consistect of
exploring site surface and subsurface conditions, and then developing this report to provide I
recommendations for general earthwork and design criteria for foundations, retaining walls, and
pavements. This work was authorized by your acceptance of our proposal, P-4915, dated May 4, ,
1999. '
The subsurface conditions of the project site were explored with 12 test pits that, in general,
encountered medium-dense to very dense weathered till and glacial till soils. Where the till soils
were not encountered, we found medium-dense to dense sands and silt. It is our opinion that the
proposed multi-family buildings may be constructed using conventional foundations. The primary
geotechnical concern in development of this project will be the moisture-sensitive nature of the on-
, site soils. Mass earthwork should be planned for dry weather. �
The attached report contains a discussion of the study and our recommendations. Please contact
us if there are any questions regarding this report, or if we can be of further assistance during the
design and construction phases of this project.
Respectfully submitted,
GEOTECH CONSULTANTS, INC.
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� Marc R. McGinnis, P.E.
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Associate
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GEOTECHNICAL ENGINEERING STUDY
Proposed Multi-Family Development
186xx Talbot Road South '
King County, Washington
This report presents the findings and recommendations of our geotechnical engineering study for
the site of the proposed multi-family development in King County. The Vicinity Map, Plate 1, ,
illustrates the general location of the site. ,
We were provided with a faxed site plan showing lot lines and the location of the existing house in
the northwest corner of the site. We anticipate that the property will be developed with apartment i
buildings and that the existing house will be removed or demolished. Detailed plans showing the
proposed building locations, existing topography, and final site grading were not available at the I
time of this report.
SITE CONDITIONS . _
Surface
The nearly rectangular tract covers 8.3 acres on the east side of Talbot Road South in King
County. It has approximately 375 feet of street frontage and an average depth of about 930 feet.
The ground surface slopes gently upward to the east for most of the property length. The eastern
100 to 200 feet of the property slopes steeply upward to the east property line. In addition to the
existing house located in the northwest corner of the property (18624 Talbot Road South), several
concrete structures including a barn, a bathhouse, two pump houses, and possibly a filled-in
swimming pool occupy the site. A concrete and rock basement foundation was found near the
middle of the site. Except for the area around the existing house, the property is wooded and
overgrown. �
Nearby development consists of the Summit Park Condominiums immediately south of the site,
and several houses located to the north and east.
Subsurface
The subsurface conditions were explored by excavating 12 test pits at the approximate locations
shown on the Site Exploration Plan, Plate 2. The test pits were excavated on May 14, 1999 with a
track-mounted excavator. A geotechnical engineer from our staff observed the excavation process,
logged the test pits, and obtained representative samples of the soil encountered. "Grab" samples
of selected subsurface soil were collected from the trackhoe bucket. The Test Pit Logs are
attached to this report as Plates 3 through 8.
In the southeastern portion of the site, Test Pit 4 encountered about 1 foot of topsoil, and 3.5 feet
of gravelly, silty sand overlying stiff, fractured silt. The silt is underlain by dense, slightly silty sand
extending to an explored depth of 10 feet. Elsewhere, beneath 1 to 1.5 feet of forest duff and
topsoil, the native soils consist of inedium-dense, weathered, silty sand with gravel, which became
gray and very dense with depth. The very dense silty sands have been glacially consolidated and
GEOTECH CONSULTANTS, INC.
, � �SEB, /ncorporated JN 99189
� May 25, 1999 Page 2
are referred to in this report as glacial till. In our explorations, the dense to very dense glacial till
was encountered to a maximum explored depth of 12 feet below the existing surface grade.
Based on our observations, the po�tions of the site have likely undergone grading associated with
the existing and previous structures. Therefore, some fill and demolitions debris may be
encountered. Fill will likely be found in the area of the old swimming pool.
The final logs represent our interpretations of the field logs and laboratory tests. The stratification
lines on the logs represent the approximate boundaries between soil types at the exploration
locations. The actual transition between soil types may be gradual, and subsurface conditions can
vary between exploration locations. The logs provide specific subsurface information only at the
locations tested. The relative densities and moisture descriptions indicated on the test pit logs are
interpretive descriptions based on the conditions observed during excavation.
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problem, the backfill will need to be remov�d ant!
replaced with structural fill during construction.
Groundwater
Groundwater seepage was observed at a depth of about 6 feet in Test Pits 7 and 9.
Surface water was observed flowing in several small ditches that traverse the site east to
west. Water could be heard flowing into and out of a cistern located underneath one of the
concrete pump houses. The test pits were left open for only a short time period. Therefore,
the seepage levels on the logs represent the location of transient water seepage and may
not indicate the static groundwater level. It should be noted that groundwater levels vary '
seasonally with rainfall and other factors. We anticipate that groundwater could be found ;
near the contact between the weathered upper soils and the underlying glacial till.
CONCLUSIONS AND RECOMMENDATIONS i
General I
Based on the results of the test pits and the observations made during our site visit, it is our opinion �'
that the proposed multi-family development is feasible from a geotechnical engineering standpoint.
The proposed buildings may be supported on conventional foundations bearing on the medium- ',
dense to very dense, native soils.
A significant geotechnical consideration for development of this site is the overly moist to wet
condition of some of the soils. Based on our observations, and the results of our laboratory tests,
the moisture contents of the on-site soils varied from near optimum to as much as 5 to 10 percent ,
above optimum. The fine-grained, soils are sensitive to moisture, which makes them impossible to '
adequately compact when they have moisture contents more than 2 to 3 percent above their '
optimum moisture content. The reuse of the overly-moist soils as structural fill to level the site will ',
only be successful during hot, dry weather. Aeration or chemical treatment of each loose lift of soil I
will be required to dry it before the lift is compacted. This drying will slow the earthwork process. �,
The earthwork contractor must be prepared to rework areas that do not achieve proper compaction ��
due to high moisture content. Utility trench backfill in structural areas, such as pavements, must
GEOTECH CONSULTANTS, INC.
� . �SEB, Incorporated �N 99189
May 25, 1999 Page 3
also be dried before it can be adequately compacted. Improper compaction of backfill in utility
trenches and around control structures is a common reason for pavement distress and failures.
Imported granular fill will be needed wherever it is not possible to dry the on-site soils sufficiently
before compaction, or if wet weather earthwork is attempted.
Depending on the depth of cuts necessary for site grading, seepage may be encountered. This is
most likely to occur following extended wet weather. Temporary dewatering can consist of
installing sumps or rock-lined ditches that are either pumped or that outfall by gravity. Subsurface
interceptor drains will be needed immediately upslope of permanent cuts that expose significant
seepage. These drains would consist of gravel-filled trenches excavated at least 12 inches into
dense glacial till. A non-woven filter fabric should be draped into the trench before backfilling with
gravel. A 4-inch-diameter perforated PVC pipe should be placed approximately 6 inches above the
bottom of the trench, with the pipe being sloped to a suitable discharge.
Well-constructed footing drains, free-draining wall backfill, and waterproofing are needed to prevent
seepage through below-grade walls. Underslab drains should be installed where buitding
excavations encounter heavy seepage.
Surface drainage features have been constructed on the site in the past. The grading and
drainage plan will need to include provisions for surface runoff entering the site.
The erosion control measures needed during the site development will depend heavily on the
weather conditions that are encountered. The erosion potential on the site is relatively low due to
the gentle slope of the ground, however, site clearing will expose a large area of bare soil. We
anticipate that a silt fence will be needed around the downslope side of any cleared areas. Rocked
construction access roads should be extended into the site to reduce the amount of mud carried off
the property by trucks and equipment. Following rough grading, it may be necessary to mulch or
hydroseed bare areas that will not be immediately covered with landscaping or an impervious
surface.
Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may include
revisions to our recommendations to accommodate site, development, and geotechnical
constraints that become more evident during the review process.
Conventional Foundations
The proposed structures can be supported on conventional continuous and spread footings bearing
on undisturbed, medium-dense to dense, native soil, or on structural fill placed above this
competent, soil. See the later sub-section entitled General Earthwork and Structural Fill for
recommendations regarding the placement and compaction of structural fill beneath structures
Adequate compaction of structural fill should be verified with frequent density testing during f�'
placement. We recommend that continuous and individual spread footings have minimum width
of 12 and 16 inches, respectively. They should be bottomed at least 18 inches below the lowe�
adjacent finish ground surface. The local building codes should be reviewed to determine if
different footing widths or embedment depths are required. Footing subgrades must be cleaned of
GEOTECH CONSULTANTS, INC.
. ,
. �SEB, Incorporated �N 99189
• May 25, 1999 Page 4
loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints,
this may require removing the disturbed soil by hand.
Depending on the final site grades, some overexcavation may be required below the footings to
expose competent, native soil. Unless lean concrete is used to fill an overexcavated hole, the
overexcavation must be at least as wide at the bottom as the sum of the depth of the
overexcavation and the footing width. For example, an overexcavation extending 2 feet below the
bottom of a 3-foot-wide footing must be at least 5 feet wide at the base of the excavation. If lean
concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing.
An allowable bearing pressure of 2,500 pounds per square foot (ps� is appropriate for footings
supported on competent, native soil or properly-compacted structural fill. A one-third increase in
this design bearing pressure may be used when considering short-term wind or seismic loads. For
the above design criteria, it is anticipated that the total post-construction settlement of footings
founded on competent, native soil, or on structural fill up to 5 feet in thickness, will be less than one
inch, with differential settlements on the order of one-half inch in a distance of 50 feet along a
continuous footing with a uniform load.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the
foundation. For the latter condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level structural fill. We recommend using the following
design values for the foundation's resistance to lateral loading: �
Parameter Design Value I
Coefficient of Friction 0.40 '
Passive Earth Pressure 300 pcf
Where:(i)pcf is pounds per cubic foot,and(ii)passive earth .
pressure is computed using the equivatent fluid density.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
not be appropriate. We recommend a safety factor of at least 1.5 for the foundation's resistance to
lateral loading, when using the above design values.
Seismic Considerations
The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1997 Uniform
Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the soil profile within a
depth of 100 feet is best represented by Soil Profile Type S� (very dense soil). The site soils are
not susceptible to seismic liquefaction because of their dense nature.
GEOTECH CONSULTANTS, INC.
• SEB, lncorporated JN 99189
' May 25, 1999 Page 5
Slabs-on-Grade
The building floors may be constructed as slabs-on-grade atop firm, stable, native soil or on
structural fill. The subgrade soil must be in a firm, non-yielding condition at the time of slab
construction or underslab fill placement. Any soft areas encountered should be excavated and
replaced with select, imported structural fill.
All slabs-on-grade should be underlain by a capillary break or drainage layer consisting- of a
minimum 4-inch thickness of coarse, free-draining structural fill with a gradation similar to that
discussed later in Permanent Foundation and Retaininq Walls. In areas where the passage of
moisture through the slab is undesirable, a vapor barrier, such as a 6-mil plastic membrane, should
be placed beneath the slab. Additionalfy, sand should be used in the fine-grading process to
reduce damage to the vapor barrier, to provide uniform support under the slab, and to reduce
shrinkage cracking by improving the concrete curing process.
Permanent Foundation and Retaining Walls
Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures
imposed by the soil they retain. The following recommended design parameters are for walls that
restrain level backfill:
Parameter Design Value
Active Earth Pressure ' 35 pcf
Passive Earth Pressure 300 pcf
Coefficient of Friction 0.40
Soil Unit Weight 130 pcf
Where:(i)pcf is pounds per cubic foot,and(ii)active and passive
earth pressures are computed using the equivalent fluid
pressures.
• For a restrained wall that cannot deflect at least 0.002 times its
height,a uniform lateral pressure equal to 10 psf times the height
of the wall should be added to the above active equivalent fluid
pressure.
The values given above are to be used to design permanent foundation and retaining walls only.
The passive pressure given is appropriate for the depth of level structural fill placed in front of a
retaining or foundation wall only. We recommend a safety factor of at least 1.5 for overturning and
sliding, when using the above values to design the walls. Restrained wall soil parameters should
be utilized for a distance of 1.5 times the wall height from corners in the walls
The design values given above do not include the effects of any hydrostatic pressures behind t'��
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacer'
foundations will be exerted on the walls. If these conditions exist, those pressures should be adde
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will nee
to be given the wall dimensions and the slo�e of the backfill in order to provide the appropriat
GEOTECH CONSULTANTS,INC.
, SEB, Incorporated JN 99189
• May 25, 1999 Page 6
design earth pressures. The surcharge due to tra�c loads behind a wail can typically be
accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid
density.
Heavy construction equipment should not be operated behind retaining and foundation walls within
a distance equal to the height of a wall, unless the walls are designed for the additional lateral
pressures resulting from the equipment. The wall design criteria assume that the backfill will be
well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should
be accomplished with hand-operated equipment to prevent the walls from being overloaded by the
higher soil forces that occur during compaction.
Retaining Wall Backfill
Backfill placed behind retaining or foundation walls should be coarse, free-draining,
structural fill containing no organics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of
particles passing the No. 4 sieve should be between 25 and 70 percent. The onsite soils
are not free-draining. If the excavated soils are reused as backfill, at least 12 inches of
gravel should be placed against the walls. Gravel should be used for the entire width of
backfill where seepage is encountered in the excavation.
The purpose of these backfill requirements is to ensure that the design criteria for a
retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the
wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively
impermeable soil or topsoil, or the surface should be paved. The ground surface must also
slope away from backfilled walls to reduce the potential for surface water to percolate into
the backfill. The sub-section entitled General Earthwork and Structural Fill contains
recommendations regarding the placement and compaction of structural fill behind retaining
and foundation walls.
The performance of any subsurface drainage system will degrade over time. Therefore,
moist conditions or some seepage through the walls are not acceptable, waterproofing
should be provided. This typically includes limiting cold-joints and wall penetrations, and
using bentonite panels or membranes on�the outside of the walls. Applying a thin coat of
asphalt emulsion is not considered waterproofing, but will only help to prevent moisture,
generated from water vapor or capillary action, from seeping through the concrete.
Rockeries
We anticipate that rockeries may be used in the site development. A rockery is not intended to
function as an engineered structure to resist lateral earth pressures, as a retaining wall would do.
The primary function of a rockery is to cover the exposed, excavated surface and thereby retard
the erosion process. We recommend limiting rockeries to a height of 8 feet and placing them
against only dense, competent, na`ive soil. Loose soils should be excavated and replaced �.�I?n
quarry spalls.
The construction of rockeries is, to a large extent, an art not entirely controllable by enginee� � ,..
methods and standards It is imperative that rockeries, if used are constructed with care an�+
. SEB, lncorporafed �N 99�89
• May 25, 1999 Page 7
proper manner by an experienced contractor with proven ability in rockery construction. The
rockeries should be constructed with hard, sound, durable rock in accordance with accepted loc�l
practice. Soft rock, or rock with a significant number of fractures or inclusions, should not be used, i
in order to limit the amount of maintenance and repair needed over time. Provisions for �i
maintenance, such as access to the rockery, should be considered in the design. In general, we '
recommend that rockeries have a minimum dimension of one-third the height of the slope cut I
above them. �
Excavations and Slopes
Excavation slopes should not exceed the limits specified in local, state, and national government
safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in
unsaturated soil away from property lines and existing structures, if there are no indications of
slope instability. Based upon Washington Administrative Code (WAC) 296, Part N, the soil type at
the subject site would be classified as Type B. Therefore, temporary cut slopes greater than 4 feet
in height cannot be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending
continuously between the top and the bottom of a cut. Flatter cuts, excavation sharing, and/or '
dewatering will be necessary where excavations encounter heavy seepage or caving soils. ',
The above-recommended temporary slope inclination is based on what has been successful at
other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a I
relatively short duration to allow for the construction of foundations, retaining walls, or utilities. The �
cut slopes should be backfilled or retained as soon as possible to reduce the potential for instability.
Please note that loose, wet soils can cave suddenly and without warning. Contractors should be
made especially aware of this potential danger.
All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). Fill slopes should
not be constructed with an inclination greater than 2:1 (H:V). To reduce the potential for shallow
sloughing, fill must be compacted to the face of these slopes. This could be accomplished by
overbuilding the compacted fill and then trimming it back to its final inclination. Water should not be
allowed to flow uncontrolled over the top of any temporary or permanent slope. Also, all
permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce
erosion and improve the stability of the su�cial layer of soil.
Drainage Considerations
Foundation drains should be installed around the perimeters of the buildings, at the base of all
earth-retaining walls, and behind stepped foundation walls. These drains should be surrounded by
at least 6 inches of 1-inch-minus, washed rock and then wrapped in non-woven, geotextile filter
fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert
should be at least 6 inches below the bottom of a slab floor or the level of a crawl space, and it
should be sloped for drainage. Drainage should also be provided inside the footprint of a structure,
where a crawl space will slope or be lower than the surrounding ground surface or an excavation
encounters significant seepage. We can provide recommendations for interior drains, should they
become necessary, during excavation and foundation construction.
GEOTECH CONSULTANTS,INC.
• SEB, Incorporated JN 99189
' May 25, 1999 Page 8
All roof and surface water drains must be kept separate from the foundation drain system. A
typical drain detail is attached to this report as Plate 97. For the best long-term performance,
perforated PVC pipe is recommended for all subsurface drains.
Groundwater and wet soils were observed du�ing our field work. Surface water was also observed
in shallow ditches across the site. If seepage is encountered in an excavation, it shoutd be drained
from the site by directing it through drainage ditches, perforated pipe, or French drains, or by
pumping it from sumps interconnected by shallow connector trenches at the bottom of the
excavation.
Building excavations and the site in general should be graded so that surface water is directed off
the site and away from the tops of slopes. Water should not be allowed to stand in any area where
foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to
buildings should slope away at least 2 percent, except where the area is paved.
Pavement Areas
The pavement section may be supported on competent, native soil or on structural fill compacted to
a 95 percent density. Granular structural fill or geotextile fabric may be needed to stabilize soft,
wet, or unstable a�eas. To evaluate pavement subgrade strength, we recommend that a proof roll
be completed with a loaded dump truck immediately before paving. In most instances where
unstable subgrade conditions are encountered, an additional 12 inches of granular structural fill will
stabilize the subgrade, except for very soft areas where additional fill could be required. The
subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to
grade. Recommendations for the compaction of structural fill beneath pavements are given in a
later sub-section entitled General Earthwork and Structural Fill. The performance of site
pavements is directly related to the strength and stability of the underlying subgrade.
The pavement for lightly-loaded traffic and parking areas should consist of 2 inches of asphalt
concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt-treated base (ATB).
We recommend providing heavily-loaded areas with 3 inches of AC over 6 inches of CRB or 4
inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with
truck traffic.
The pavement section recommendations and guidelines presented in this report are based on our !,
experience in the area and on what has been successful in similar situations. As with any
pavements, especially those underlain by silty soils, some maintenance and repair of limited areas
can be expected as the pavement ages. To provide for a design without the need for any repair
would be uneconomical.
General Earthwork and Structural Fill
All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and
other deleterious material. The stripped or removed materials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds.
GEOTECH CONSULTANTS,INC.
� SEB, lncorporated JN 99189
' May 25, 1999 Page 9
Structural fill is defined as any fill placed under a building, behind permanent retaining or foundation
walls, or in other areas where the underlying soil needs to support loads. All structural fill should be
placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The
optimum moisture content is that moisture content that results in the greatest compacted dry
density. The moisture content of fill is very important and must be closely controlled during the
filling and compaction process.
The allowable thickness of the fill lift will depend on the material type selected, the compaction
equipment used, and the number of passes made to compact the lift. The loose lift thickness
should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not
compacted to specifications, it can be recompacted before another lift is placed. This eliminates
the need to remove the fill to achieve the required compaction. The following table presents
recommended relative compactions for structural fill:
Location of Minimum
Fill Placement Relative Compaction
Beneath footings, slabs 95%
or walkways
Behind retaining walls 90%
95%for upper 12 inches of
Beneath pavements subgrade; 90°/a below that
level
Where: Minimum Relative Compaction Is the ratio,expressed In
percentages,of the compacted dry density to the maxlmum dry
density, as determined In accordance with ASTM Test
Designation D 1557-78(Modified Proctor).
Considerations fo� reuse of the on-site soils as structural fill are discussed in the General section.
Structural fill that will be placed in wet weather should consist of an imported, coarse, granular soil
with a silt or clay content of no more than 5 percent. The percentage of particles passing the No.
200 sieve should be measured from that portion of soil passing the three-quarter-inch sieve.
LIMITATIONS
The conclusions and recommendations contained in this report are based on site conditions as
they existed at the time of our exploration and assume that the soil and groundwater conditions
encountered in the test pits are representative of subsurface conditions on the site. If the
subsurface conditions encountered during construction are significantly different from those
observed in our explorations, we should be advised at once so that we can review these conditions
and reconsider our recommendations where necessary. Unanticipated soil conditions are
commonly encountered on construction sites and cannot be fully anticipated by merely taking soil
samples in test pits. Subsurface conditions can also vary between exploration locations. Such
unexpected conditions frequently require making additional expenditures to attain a properly
constructed project. It is recommended that the owner consider providing a contingency fund to
accommodate such potential extra costs and risks. This is a standard recommendation for all
projects.
GEOTECH CONSULTANTS, INC. _
. SEB, lncorporated JN 99189
� May 25, 1999 Page 10
This report has been prepared for the exciusive use of SEB, Incorporated, and its representatives,
for specific application to this project and site. Our recommendations and conclusions are based
on observed site materials, and selective laboratory testing and engineering analyses. Our
conclusions and recommendations are professional opinions derived in accordance with current
standards of practice within the scope of our "services and within budget and time constraints. No
warranty is expressed or implied. The scope of our services 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 repo�t for consideration in design. We recommend including this report, in its entirety, in the
project contract documents so the contractor may be aware of our findings.
ADDITIONAL SERVICES
In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide
geotechnical consultation, testing, and observation services during construction. This is to confirm
that subsurface conditions are consistent with those indicated by our exploration, to evaluate
whether earthwork and foundation construction activities comply with the general intent of the
recommendations presented in this report, and to provide suggestions for design changes in the
event subsurface conditions differ from those anticipated prior to the start of construction.
However, our work would not include the supervision or direction of the actual work of the
contractor and its employees or agents. Also, job and site safety, and dimensional measurements,
will be the responsibility of the contractor.
The following plates are attached to complete this report:
Plate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 8 Test Pit Logs
Plate 9 Footing Drain Detail
GEOTECH CONSULTANTS, INC.
. SEB, lncorporated JN 99189
• May 25, 1999 Page 11
We appreciate the opportunity to be of service on this project. If you have any questions, or if we
may be of fu�ther service, please do not hesitate to contact us.
Respectfully submitted,
GEOTECH CONSULTANTS, INC. II
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VICINITY MAP
___ GEOTECH s.E.s., �Nc.
; � CONSULTANTS . 186XX TALBOT RD. S.
� KING COUNTY, WA � -
� Jo0 No.+ Oo1�: Ploli:
�� 88189 MAY 1889 �
OTP-6 OTP-5 0 P-4
, �
� I
;
�
�
i
, OTP-7 0 P-3
� D TP-8
N
�
�
-
Z
-
0 �
OT -2
TP-10 �TP-9 I Oo
� z
� �
� v
OTP-11 �
a
a
F-
EXISTING HOUSE
. �
OTP-12 pT -� �
�
N
TALBOT RD. S.
LE(3END:
Q APPROXIMATE TEST PIT LOCATION
' SITE EXPLORATION PLAN
GEOTECH s.E.6., iNc.
�; - CONSULTANTS 186XX TALBOT RD. S.
� KING COUNTY, WA - -
� Jo0 No.+ Ob��� P/o/t�
' 99189 MAY 1989 2
� � �� `l< TEST PIT 1
,��� o��e��` a���,¢� G5
��4 �G°� ��S°'� J5 Description
TOPSOIL
I , i Red-brown, silty SAND with some gravel, fine-grained, wet, medium-dense
� (Weathered G/acial Till)
15.7% I I: I I - becomes gray-brown,_dense to very dense (Glacial Till)
5
13.9% ' �, ,
� SM
,� ,
�
�' ,
I' : �
10 I '
I: ' i
* Test Pit was terminated at 12 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
15 * No caving was observed during excavation.
�� ��,���`i�{ TEST PIT 2
��� o� �e" a���e �5
pe� �CP� ��Sd� �S5 Description
TOPSOIL
' Red-brown, silty SAND with gravel, fine-grained, moist, medium-dense
` ( : (Weafhered Glacial Till)
' . : - becomes gray-brown, dense to very dense (Glacial Till)
5 i � :
� SM ', .
i '
I' . - more gravelly and occasional cobbles within till
10 i � ' `
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
CONSULTANTS,INC. King County, Washington
�
�� _ _ _ Job No: Date: Logged by: Plate:
99189 May 1999 OBG 3
� �� `�� TEST PIT 3
24ti�'��o 0����1ad.p�� 5G5
p G �S �S Descnptton
TOPSOIL
� ' ' Red-gray, silty SAND with gravei and iron staining, fine-grained, very moist,
medium-dense (Weathered Glacial Till)
5 � Snn .
- becomes brown to gray, dense to very dense (Glacia! Ti!!)
i ' ' '.
10 � :: : : '.
" Test Pit was terminated at 10 feet on May '14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
t� ot� TEST PIT 4 '
��� �� �� ��
��, o���er�atiro�� G5 '
�p�� �G° �S°' 45 Description
TOPSOIL
I' ' :I' : ' Brown, gravelly, silty SAND with cobbles, fine-grained, moist, medium-dense
SM
5 � Brown SILT, fractured, low plasticity, moist, stiff, iron stained
�
� -
i ML
�
I
10 � SP•SM Brown, sli htl silt SAND, fine-to medium- rained, ve moist, dense
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
' TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
CONSULTANTS,INC. King County, Washington
�
� Job No: Date: Logged by: P/ate:
99189 May 1999 DBG 4
' � �����,��°�< TEST PIT 5
ti^r�o��,�,���o-'���,� �5
9�4 G° �S°' �5 Description
TOPSOIL and Forest Duff
' � � grown, gravelly, silty SAND, fine-grained, moist, medium-dense
SM
I ' �
5 I Brown, slightly silty SAND, medium-grained, moist, medium-dense
- becomes finer grained
5P-SM
- becomes gravelly
�� SM Brown with iron staining, silty, gravelly SAND, medium-to coarse-grained, wet,
,� dense
* Test Pit was terminated at 11 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
�� ��,{����� TEST PIT 6
�� o� ti��' o-�'e�,e G5
9�4 �'Go�' '�,�a�° 05 Description
TOPSOIL and Forest Duff
� �
, , ,� '; Brown, silty SAND with some gravel, moist, medium-grained, medium-dense
�
, SM : I
5
' i : ' Brown-gray, silty SAND with some gravel, fine-grained, moist, dense to very I
' � ' ' dense (Glacial Til!) '
SM i
10 �; ' ; - becomes very moist
* Test Pit was terminated at 10 feet on May 14, 1999. ;
* No groundwater seepage was observed during excavation. I,
* No caving was observed during excavation.
15 '
' TEST PIT LOG
� � GEOTECH 186xx Talbot Road South._ _
CONSULTANTS,�Nc. King County, Washington
�
���, � Job No: Date: Logged by: Plafe:
���` �l— 99189 May 1999 DBG 5
� ti� �,����,���� TEST PIT 7
�,r���,o��,�,���a�ro�,� �5
9�4 G° �C°' J5 Descripfion
TOPSOIL and Forest Duff
SM Red-brown, silty SAND with gravel, fine-grained, moist, medium-dense
18.2% Gray-brown, gravelly SAND, fine- to coarse-grained, wet, medium-dense
� - becomes dense
Z
SP
10 ��" ' Brown, silty, gravelly SAND, fine-grained, moist, very dense (Glacial Till)
* Test Pit was terminated at 10 feet on May 14, 1999.
* Moderate groundwater seepage was observed at 6 feet during excavation.
* No caving was observed during excavation.
15
�� ��� `i�� TEST PIT 8
�4���`0 ofiti��'`�aa�ti� �G5
9 G �S �S Descnption
TOPSOIL
, Gray-brown with iron staining, silty SAND, fine-grained, wet, medium-dense
' �,� i (Weathered Glacial Till)
- becomes slightly gravelly
5 '�
' SM _ becomes dense (Glacia! Til!) " �,
;
10
'' Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation. ,
* No caving was observed during excavation.
15
' TEST PIT LOG
� � GEOTECH 186xx Talbot Road South _
CONSULTANTS,INC. King County, Washington i
�
� �__ __ . Jo6 No: Date: Logged by: Plate:
99189 May 1999 DBG 6
I
� � �� `� TEST PIT 9
t,r'� o`����� a�'��,� G5
9�4 �G°� ��S°'ro �S`' Description
TOPSOIL
, , ,
5 SM Red-brown to gray with extensive iron staining, clayey SILT and fine-grained
'� i ML SAND, wet, loose to medium-dense
= i � � �
Gray, fine-grained SAND with some silt, very moist to wet, medium-dense to
I SP-SM dense
10 +
* Test Pit was terminated at 10.5 feet on May 14, 1999.
* Light groundwater seepage was observed at 6.5 feet during excavation.
* No caving was observed during excavation.
15
�� oi� TEST PIT 10
� �,� ti\ �<
ti`r�o��,ti���a�',�ti� �5
�p�4 G° �C°' 05 Description
TOPSOIL
Brown-gray with iron staining, silty SAND, fine-grained, wet, medium-dense
(Weathered Glacial Til!)
' 5 SM I
� 12.3% - becomes dense to very dense (G/acial Til!) -
* Test Pit was terminated at 8 feet on May 14, 1999. ;,
10 * No groundwater seepage was observed during excavation. '
* No caving was observed during excavation. I�
15 I!�
' TEST PIT LOG
� � GEOTECH 186xx Talbot Road South..
CONSULTAN'1'S,INC. King County, Washington
�
� _ ___ Job No: Date: Logged by: Plate:
99189 May 1999 DBG 7
- � �����`��< TEST PIT 11
�,r��o��,�,���a�ro�,� �5
p�4 G° �S°' �5 Description
TOPSOIL
' ' ' Gray-brown with iron staining, silty SAND with trace gravel, fine-grained, wet,
loose to medium-dense (Weathered G/acial TiIJ)
SM � _ becomes very dense (Glacia!Till) '
5 ; `
�I i
* Test Pit was terminated at 6 feet on May 14, 1999.
" No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
10
15
�l ��,���`i�� TEST PIT 12
e4ti� �`o o�,`'���aa,�ti� ��5
9 G �S J Description
TOPSOIL
Brown-gray with iron staining, silty SAND with trace gravel, very moist,
; , ' j : medium-dense (Weathered Glacial Till)
- becomes very dense (Glacia/ Till)
5 ' SM
; : -
�
I
,
10 * Test Pit was terminated at 9 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
' TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
CONSULTANTS,INC. King County, Washington �
�
� �_ _ _ Job No: Date: Logged by: Plafe:
99189 May 1999 DBG 8
S/ope bock/il/ owoy /�om
foundolion. �
� ` T/GHTL/NE ROOF ORA/N
� Do no/ connec/ lo toolinq droin.
BACKF/L L
See lexl /or VAPOR BARR/ER
requiremenls. SLAB �_
� ..
WASNED ROCK .o.°.'.'o'.�•• •:'�;: �•%�� `;•, 4��min.
. pp j, `/ /� �
6� O ' .' O. `� ` .�4(�
..� , FREE-ORA/N/NG
NONWOVEN GEOTEXT/LE SANO/GRAVEL
F/LTER FABR/C
4��PERFORATED NARO PVC P/PE
/nverl ol /eosl os /ow os looling ond/or
craw/ spoce. Slope fo d�oin. P/ace ,
weepho/es downword.
=� FOOTING DRAIN DETAIL
�
GEOTECH s.E.B., iNc.
' ` CONSULTANTS 186XX TALBOT RD.. S.
� KING COUNTY, WA
�y • _ JoD No.+ Oo1e: Sco/e� P/o/e�
�`'"' ��' 99189 MAY 1999 N.T.S. 9