92-101282I
SOUTH KING COUNTY MULTI —SERVICE CENTER WAREHOUSE
1200 SOUTH 336TH STREET
FEDERAL WAY, WASHINGTON
JOB NO. 9101-18G
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TABLE OF CONTENTS
Introduction Page 1
Site Description Page 2
Subsurface Conditions Page 2
Conclusions and Recommendations Page 3
I Foundation Placement Page 4
Slab -on -Grade Floor Page 4
I Grading Page 5
Pavement Design Page 6
General Page 6
Appendix A Test Pit Location Map
Appendix B Test Pit Logs
Appendix C Unified Soils Classification System
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CASCADE GEOTECHNICAL, INC.
12911 N.E. 126TH PLACE (206) 821-5080
KIRKLAND, WASHINGTON 98034 FAX: (206) 823-2203
February 14, 1991
Job No. 9101-18G
South King County Multi -Service Center
c/o Gleason and Associates
551 First Avenue South
Seattle, Washington 98104
Attention: Sharon Atkin
Reference: South King County Multi -Service Center Warehouse
1200 South 336th Street
Federal Way, Washington
Dear Ms. Atkin:
As requested By Roger Tucker of Gleason and Associates, Architects,
we have completed a soils investigation for the proposed addition
at 1200 South 336th Street in Federal Way, Washington. The
following report contains our findings, conclusions and
recommendations.
INTRODUCTION
The scope of our work was to investigate the subsurface conditions
at the site by excavating backhoe test pits and to prepare a soils
report for the site. The purpose of our study was to determine
the subsurface soil and ground water conditions at the site and to
offer conclusions and recommendations for foundation design,
drainage, grading and pavement design.
We understand that the project is to consist of a 3300 square foot,
single -story, metal framed warehouse with a slab -on -grade floor and
associated parking areas. We reviewed Sheets A-1, A-2, A-3 and C-1
of the provided plans prepared by Gleason and Associates dated
September and November 1990. We also understand that a soils
CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
Page 2
report conforming to the 1988 Uniform Building Code Chapter 29
specifications is required.
SITE DESCRIPTION
The site, approximately 900 sq. ft., is located on the north side
of South 336th in Federal Way, Washington approximately 170 feet
north of South 336th Street. At the time of our visit, the site
f was being used as a parking lot for the multi -service center
employees and was covered wOith gravel. Existing single -story
buildings were noted to the west, east and south of the site. An
asphalt paved roadway was found along the north side of the site.
The overall topography of the site was relatively flat. The site
i sloped five (5) feet down to the south at a gentle grade on the
southern side of the site. On the eastern side, the site sloped
two (2) feet down to the east also at a relatively gentle grade.
A four (4) foot cut was observed on the northern side of the
existing asphalt roadway, north of the proposed building area.
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There was no vegetation on the site at the time of our
` investigation. A deciduous tree was noted on the eastern side of
the site. Grass covered the slopes on the southern and eastern
sides of the site.
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SUBSURFACE CONDITIONS
The site subsurface conditions were investigated by excavating
four
(4) backhoe test pits on January 28, 1991. The test pit locations
determined by our geologist
and located by pacing relative to
the
property lines and existing
building are shown on the site
plan
presented in Appendix A.
Detailed test pit logs and
soil
descriptions are presented
in Appendix B. The soils
were
CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
Page 3
classified using the Unified Soils Classification System presented
in Appendix C. The depths referred to in this report are relative
to the ground surface at the time of our investigation. The test
pits were terminated at depths of between five (5) and seven and
one-half (7 1/2) feet due to very dense soils.
We observed from two and one-half (2 1/2) to six (6) feet of loose
lto dense, rusty -brown to brown, gravelly sand with minor to some
1 cobbles in Test Pits 1, 3 and 4. Below the gravelly sand in these
test pits, we found dense to very dense, gray silty sand with some
gravel (till) to the test pit termination depths.
In Test Pit 2, we noted two (2) feet of uncontrolled fill
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consisting of brown gravelly sand with some cobbles overlying a six
(6) inch layer of the old topsoil. The old topsoil consisted of
black silty sand with some gravel and roots. Three and one-half (3
1/2) feet of medium dense to dense, rusty -brown to brown gravelly
sand with some cobbles was observed beneath the old topsoil layer.
At six (6) feet below the surface, we found very dense, gray silty
i sand with some gravel (till).
There was no ground water seepage noted in any of the test pits at
the time of our investigation.
ICONCLUSIONS AND RECOMMENDATIONS
We conclude that the
site is suitable for the
proposed addition if
our recommendations
are carefully followed.
The fill and the
topsoil noted in Test Pit 2 is unsuitable for the support of a
building foundation.
If the topsoil and fill
is not removed, some
settlement
can be anticipated within
the building area. We
recommend
removing the topsoil material
from the building area and
replacing
it with compacted, structural
fill.
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CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
Page 4
Foundation Placement
The native, undisturbed medium dense to dense gravelly sand with
_1 minor to some cobbles is suitable for the placement of a spread
1 footing foundation. The fill and topsoil noted in Test Pit 2 is
unsuitable for the support of the proposed foundation and the
proposed slab -on -grade floor. We recommend replacing the
unsuitable material with structural fill meeting the
recommendations stated in the Grading Section of this report.
Spread footings placed on firm, undisturbed, horizontal surfaces of
the recommended bearing soils may be designed to a maximum safe
1 bearing value of 2000 psf if the footing excavations are free of
1 organic material, water and loose or wet soil prior to the
j placement of the concrete. We recommend that all footings be at
1 least eighteen (18) inches below the outside finished grade for
frost protection. The minimum footing widths should conform to the
local building codes.
A maximum total settlement of one (1) inch and a differential
settlement of three -fourths (3/4) inch can be anticipated over the
l site if our recommendations are followed.
] Slab -on -Grade Floor
We recommend placing the slab on structural fill placed directly on
the native gravelly sand. Fill should meet the recommendations
contained in the Grading Section of this report.
We recommend placing a minimum of four (4) inches of free draining
Jmaterial beneath the slab to act as a capillary break. The free
draining material should consist of crushed rock or clean sand with
a maximum of five (5) percent passing the #4 sieve. A vapor
CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
Page 5
barrier should be placed between the capillary break and the slab.
If desired, two (2) inches of sand may be placed on top of the
vapor barrier to aid in concrete curing.
Grading
I The on -site native gravelly sand and the fill consisting of
gravelly sand is suitable for use as a structural fill material as
long as the soil is free of organic material and the moisture is
kept at or just below the optimum value as determined by the ASTM
D-1557 moisture -density test. The topsoil noted in the test pit is
unsuitable for the use as structural fill and should be removed
from the building area.
iIf imported fill is necessary, it should meet the following
gradation:
Sieve Size Percent Passin
4 inch 100
J#4 25 - 75
#200 10 maximum
JIf a wet subg rade is encountered during fill placement, an all-
weather fill having less than five (5) percent passing the #200
sieve based on the material passing the #4 sieve, may be necessary.
We recommend using lifts not exceeding twelve (12) inches in loose
thickness and compacting to at least 95 percent of the ASTM D-1557
maximum dry density value for the foundation and slab and 90
percent of the ASTM D-1557 maximum dry density value for the
Jparking areas.
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CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
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Draina e
We recommend
placing a four (4) inch
diameter, rigid, perforated
drain pipe, backfilled with at least
twelve (12) inches of pea
gravel, along
the base of the exterior
footings and tightlining it
to the storm
system. The roof drains
should be directed into the
storm system
in a tightline separate from the footing drains.
Pavement Design
i We recommend a pavement section of four (4) inches of crushed rock
with two (2) inches of Class B asphaltic concrete. This is
suitable for the anticipated parking lot loading consisting of
passenger cars, light trucks and up to two (2) heavy trucks per
day. The subgrade should be dry and non -yielding before the
pavement is placed. Any soft, wet or yielding areas should be
removed and replaced with suitable fill as stated in the Grading
Section of this report.
General
J We recommend that we be engaged to review the final building and
grading plans for the site to confirm that our recommendations have
been properly interpreted. We also recommend that we be engaged to
confirm that suitable bearing soil has been reached, to observe
that all the topsoil and uncontrolled fill has been removed from
the building area, and to observe and test any fill that is placed.
We expect the on -site conditions to reflect our findings; however,
some variations may occur. Should soil conditions be encountered
which cause concern and/or are not mentioned herein, Cascade
Geotechnical should be contacted immediately to determine if
additional or alternate recommendations are required.
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CASCADE GEOTECHNICAL
February 14, 1991
South King County Multi -Service Center
Job No. 9101-18G
Page 7
This report has been prepared for the exclusive use of Gleason and
Associates, Architects, for specific application to the proposed
construction at 1200 South 336th Street in Federal Way, Washington,
in accordance with generally accepted soils and foundation
engineering practices. No other warranty, expressed or implied, is
made.
Thank you for this opportunity to work with you. Should you have
any questions, please feel free to contact us at any time.
Sincerely,
CASCADE EOTECHNIC.
G r g e EQEngi
Principa
Bridget Krause
Engineering Geologist
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SOUTH KING COUNTY
MULTI -SERVICE CENTER WAREHOUSE
TEST PIT LOCATION MAP
PROPOSED PARKING
PROPOSED SIDEWALK
T.P.
T,
EXISTING BLDG.
ROPOSED WAREHOUSE
EXS . OFFICE
.2.
r.p.,
0
EXST. OFFICE
FROM SITE PLAN BY GLEASON & ASSOCIATES, ARCHITECTS
Job No.
9101-18G SCALE : ' 1" = 30'
CASCADE GEOTECHNICAL, INC.
12919 N.E. 126TH PLACE (206) 821-5080 LOCATIONS ARE APPROXIMATE
�! KIRKLAND, WASHINGTON 98034 FAX: (206) 823-2203 Date 1 /28/91 Dwn. By BK jEng - G._eooll
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UNIFIED SCAS CLASSIFICATIC d"'4 SYSTEM
COARSE
GRAINED
SOILS
FINE
GRAINED
SOILS
MAJOR DIVISIONS
CLEAN
GRAVELS
GRAVEL &
GRAVELLY
SOILS
GRAVELS
WITH FINES
CLEAN
SANDS
SAND &
SANDY
SOILS
SANDS
WITH FINES
SILTS & CLAYS
Liquid Limit Less Than 50
SILTS & CLAYS
Liquid Limit Greater Than 50
HIGHLY ORGANIC SOILS
SYMBOL
LETTER
DESCRIPTION
° a
Well -graded gravels or gravel -sand mixtures.
aA Q-0oa
GW
little or no fines
Poorly graded gravels or gravel -sand mixtures,
.:�.
C' P
little or no fines
•
GM
Silty gravels or gravel -sand-silt mixtures
GC
Clayey gravels or gravel -sand -clay mixtures
Well -graded sands or gravelly sands, little or
W
no fines
Poorly graded sands or gravelly sands, little
SP
or no fines
$M
Silty sands or sand -silt mixtures
S C
Clayey sands or sand -clay mixtures
Inorganic silts & very fine sands, rock flour silty
ML
or clayey fine sands, or clayey silts with slight
plasticity
Inorganic clays of low to medium plasticity,
CL
gravelly clays, sandy clays, silty clays or lean clays
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k i l
Organic silts & organic silty clays of low
1111111
IIIIIII
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OL
plasticity
Inorganic silts, micaceous or diatomaceous fine
MH
sandy or silty soils, elastic silts
CH
Inorganic clays of high plasticity, tat clays
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Organic clays of medium to high plasticity,
',',`•'r'
OH
organic silts
r r r • �
PT
I Peat or other highly organic soils
TOPSOIL .y" Humus & duff layer
FILL Uncontrolled, with highly variable constituents
Sol
DATUM
NOTE
I2"
O.D. Split Spoon Sampler
Sample Interval
Ring or Shelby Sampler
Sample Interval
PSampler
Pushed
Sample Interval
*
Other Sample Type
Sample Interval
BO L
DATUM -7
NOTE
SzWater
Level
Date Recorded
Ts
Torvane Reading
qV
Penetrometer Reading
iWater
Observation Well
Tip Elevation
I;(C1I CASCADE GEOTECHNICAL, INC. KEY CHART