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Bradley-Noble Geotechnical Services
A Division of The Bradley Group, Inc
2401 Bristol Court SW, PO Box 10267, Olympia WA 98502
Phone 360-357-7883 FAX 360-754-4240
SOILS INVESTIGATION REPORT
FOR THE NEW TWIN COUNTY CREDIT UNION
FACILITY, YELM, WASHINGTON
presents the results of our subsurface
for the new Twin County Credit Union
be constructed at 1105 Yelm Avenue, State
in Yelm, Washington. Our purposes in
the subsurface soil conditions were to
bearing capacity of the site soils, to
recommendations for foundation design, and to
other geotechnical considerations for this
This report
investigation
facility to
Highway 510
exploring
evaluate
present
address
project.
The development of this 2.5-acre parcel is proposed in
two phases. In the first phase the western one-half
of the property will have a 2800-square foot building,
drive-up facility, and parking. The second phase is
the expansion of the building to 5825 square feet and
also expansion of the drive-up facility. Additional
parking and driveways will be constructed in the
eastern half of the property.
We expect that the new facility will be a
single-story, wood- or metal-frame building.
Conventional spread footings will be used for support
of wall loads. A concrete slab on grade is expected
to be used for the floor system. We expect that
asphaltic concrete pavement will be used for driveways
and parking areas at the site. Work was authorized on
behalf of the Twin County Credit Union by Mr. Robert
Slenes, Project Architect of the BJSS Group, the
project's designers.
SITE CONDITIONS
Surface Conditions
The project site is of low relief and nearly level
with a few large Douglas firs. The eastern half of
the property still has an occupied, single-family
residence. It is two-story, wood-frame structure
supported on a concrete block foundation system and
served by one domestic well. Outbuildings are
associated with this structure.
The western half of the site, in the area of the phase
one construction, we found surface and subsurface
96040101
Page 1 of 7
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96040101
Page 2 of 7
structures associated with a mobile home that once
occupied this area. A small, wood-frame, storage barn
is in the area of proposed construction. There is a
septic tank between Test Pits One and Two and a
drainfield in the area of Test Pit Two. We expect
that underground water lines served this residence.
There is also an abandoned gas riser in this area.
There may be an additional domestic water well in the
small storage building that served this residence, or
a water line may extend from the residence to the
east. Concrete walks are in this area. Underground
locate shows a gas line crossing the property in the
northwest corner. This line serves the Moose Lodge to
the project west.
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If the existing domestic wells on this site are not to
be used, then they will have to be abandoned according
to the Department of Ecology Water Well Division
requirements as presented in WAC 173-160-415. We are
available to work with the owner to provide the
abandonment of these wells.
Subsurface Conditions
Subsurface conditions at the site were explored by
seven test pits excavated with a tractor-mounted
backhoe. These test pits were excavated in the phase
one area of the proposed construction. We did not
extend the soil exploration to the east because of
unmarked active underground utility lines that still
serve the occupied residence and the outbuildings.
Soils under the site are typical for this area. In
the test pits, we found 1.4 to 2.0 feet of a dark
brown, silty, gravelly sand, generally referred to as
the Spanaway topsoil. Underlying the Spanaway topsoil
and extending for the full depth of the explorations,
we found the coarse sands and gravels which were
fluvially deposited as the Vashon recessional
outwash. These recessional outwash gravels contain
cobbles and boulders to 1.5 feet in diameter. The
southern area seemed to have more sand than test pits
excavated in the northern area of the site.
No ground water or indication of seasonal high ground
water was observed in the test pits. We expect that
the near surface aquifer would be encountered between
70 to 90 feet below the surface at this site.
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96040101
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DISCUSSION AND RECOMMENDATIONS
Site Work
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Based on the proposed site plan, the septic tank and
drainfield that served the former mobile home will be
under the building footprint. This tank will need to
be located and removed. The void after removal should
be filled with either a controlled structural fill
section placed and compacted in conformance with the
Earthwork Criteria section of this report or be filled
with Controlled Density Fill (CDF). The drainfield
laterals will need to be located and removed. Any
effluent-contaminated earth will also have to be
removed and disposed of in conformance with the
Thurston County Public Health Department
requirements. The septic tank and drainfield that
serve the occupied residence on this site will also
have to be abandoned after the structure is razed.
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The Spanaway topsoil unit is a silty, gravelly sand.
The silts in this soil unit are moisture sensitive and
will "mud up" rapidly if exposed to rain during site
work. The underlying coarse, sandy gravels and
gravelly sands are considered to be free draining and
non-moisture sensitive. We expect that site work on
this soil unit would not be affected by weather.
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The recessional outwash soils on this site are
considered to be suitable for use as structural fill,
gravel base material under paving sections, and trench
backfill. The oversized material, the large cobbles
and boulders, will have to be removed in order to use
this material. The Spanaway topsoil is marginal for
use as structural fill or trench backfill. It is not
considered to be suitable for use as gravel base
material under paving sections. The percentage of
fines makes this material difficult to compact as
moisture control is difficult to control in order to
achieve a uniform density of the material.
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Foundations
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All foundations are to be founded on the Vashon
outwash sands and gravels below the Spanaway topsoil
unit. We recommend that the site be stripped to
expose these soils. Clearing and grubbing and
stripping to expose the outwash soils should extend
for a minimum of 10 feet outside of building lines.
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96040101
Page 4 of 7
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For footings placed on the outwash soils after
proof-rolling, we recommend a design bearing value of
3500 pounds per square foot. A one-third increase in
this recommended bearing value is permissible for
short-term wind or seismic loadings.
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Exterior footings should be founded a m1nLmum of 18
inches below planned finish grade for frost protection
and confinement. We recommend that continuous and
strip footings have a minimum width of 16 inches.
Isolated footings supporting column loads should have
a minimum dimension of 3.0 by 3.0 feet square.
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Settlement of structures designed to the recommended
bearing values and placed on soils prepared according
to the recommendations of this report should not be
significant. Generally, we expect that both
differential and total settlements of 25 millimeters
or less will occur, mostly during construction and
immediately after the loads are imposed. There should
be little long-term settlements.
Floor Slabs
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After the site has been stripped, additional
structural fill material probably will be required to
bring the site to planned subgrade elevation. The
gradation of the material should be such that it can
also function as a capillary break material. Use of
on-site outwash soils is acceptable for structural
fill under the slab. We do not recommend that the
Spanaway topsoil be used for structural fill under the
slabs.
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Placement and compaction of the structural fill
section should be in strict conformance with the
recommendations of the Earthwork Criteria section of
this report. Placement of a thin lift of 5/B-inch
minus crushed rock is acceptable to facilitate the
fine grading operations for the slab placement.
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The native sands and gravels act as a natural
capillary break. High ground water tables are not
evident at this site, and we do not expect that
wicking of moisture will be a major concern at this
site. We do recommend that a vapor barrier be
included in the design between the capillary
break/structural fill section and the slab. The
concrete slab should be designed to the
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96040101
Page 5 of 7
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recommendations of the current
Reinforcing Steel Institutes Design
anticipated floor loads.
edition
Manual
of the
for the
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Paving Section
The paving section may be placed on the Spanaway unit
if the specified minimum paving section thicknesses
are used and the Spanaway unit is uniformly compacted
to the specified density of the paving section. This
will minimize excavation and disposal costs. This
soil will exhibit some swelling after densification
because of saturation.
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Paving sections placed on the Spanaway soil unit may
be designed to a CBR value of 25. This design value
requires that a uniform density of 95% of ASTM 0698 be
achieved on the subgrade. We recommend a minimum
paving section of 2 inches of class B asphaltic
concrete pavement, 2 inches of 5/8-inch minus crushed
rock for the leveling course, and either six inches of
ballast or eight inches of gravel base material.
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All material used in the paving section is to conform
to the current requirements of the WSDOT/APWA
specifications for quality and compaction. The
project's civil engineers should review the
recommended minimum paving sections to ensure that the
section meets the minimum design requirements based on
the project's expected traffic loads.
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Lateral Soil Pressures
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It is our understanding that
foundations walls over four
incorporated in the design.
criteria are to be built, we
design information.
no retaining walls or
feet high are to be
If walls meeting these
should be consulted for
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Lateral loads may be resisted either by passive soil
For imported structural fill, we recommend that a
clean, six-inch minus, well graded gravel or gravelly
sand (classifying as GW or SW as determined by
ANSI/ASTM test method 0-2487), conforming to APWA
specification 9-03.14 for gravel borrow, be used. We
also recommend that no more than 7% by weight pass the
number 200 screen as tested by ANSI/ASTM 0-1140 test
procedure. Other material may be used after the
review and written approval of the soils engineer or
engineering geologist.
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96040101
Page 6 of 7
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All fill should be placed in uniform horizontal lifts
of six- to eight- inch loose thickness. Each lift
should be conditioned to the optimum moisture content
and compacted to the specified minimum density before
placing the next lift. We further recommend that all
utility trench backfill be compacted as specified
above. Earthwork should be performed under the
continuous supervision and testing of Bradley-Noble
Geotechnical Services to ensure compliance with the
compaction requirements.
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Placement of fill sections on slopes greater that 4:1
(horizontal to vertical) will be benched as directed
into the native soils. Height and width of the bench
will be determined in the field by the soils engineer
or engineering geologist.
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unrestricted slopes ~hall not exceed 2:1 (horizontal
to vertical) for fill embankments and cuts that expose
native soils. All fill slopes will be rolled. The
project's civil engineer is responsible for the
protection of the constructed fill slopes from
uncollected runoff. We recommend that all
cut-and-fill slopes be seeded as soon as possible
after construction, so that vegetation can protect the
slopes from sheet washing.
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No fill is to be placed during periods of unfavorable
weather or while the fill is frozen or thawing. When
work is stopped by rain, placement of fill will not
resume until the soils engineer or engineering
geologist determines that the moisture content is
suitable for compactive effort and that the previously
placed fill has not been loosened. The contractor
will take appropriate measures during unfavorable
weather to protect the fill already placed. Measures
that may be required include limiting wheeled traffic
and grading to provide temporary drainage of the
fill. At the direction of the soils engineer or
engineering geologist, the contractor will be
responsible for the removal and reworking of fill that
has softened or has less than the required compaction.
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LIMITS OF LIABILITY
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BRADLEY-NOBLE GEOTECHNICAL SERVICES is responsible for
the opinions and conclusions contained in this
report. These are based on the data relating only to
the specific project and locations discussed herein.
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96040101
Page 7 of 7
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This report was prepared within the standard and
accepted practices of our industry. In the event
conclusions and recommendations based on these data
are made by others, such conclusions and
recommendations are not the responsibility of the
soils engineer or engineering geologist unless he has
been given an opportunity to review them and concurs
in such conclusions or recommendations in writing.
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The analysis and recommendations submitted in this
report are based upon the data obtained in the
explorations at the locations indicated on the
attached plan. This report does not reflect any
variations that may occur between these explorations.
The nature and extent of variations between
explorations may not become evident until construction
is underway.
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Bradley-Noble is to be given the opportunity to review
the final plans and specifications for soils work.
This is to verify that our geotechnical engineering
recommendations have been correctly interpreted and
implemented in the final design and specifications.
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We also recommend that we be retained to provide
geotechnical services during the foundation
construction and trenching. These services would
include review of backfill operations, excavations,
and other geotechnical considerations that may arise
during construction. We would observe compliance with
the design concept and project specifications. If the
subsurface conditions differ from those anticipated in
our explorations, we would also evaluate changes in
construction specifications.
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BRADLEY-NOBLE GEOTECHNICAL SERVICES
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Report prepared by:
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David C. trong
Engineering Geologist
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Please see attached soil's engineers review letter.
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Test Pit One:
o to -1. 7 feet
-1.7 to -6.1 feet
Test Pit Two:
o to -2.0 feet
-2.0 to -6.0 feet
Test Pit Three:
o to -2.0 feet
-2.0 to -6.0 feet
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Test Pit Four:
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TEST PIT LOGS
Dark brown silty cobbly sand,
Spanaway topsoil unit.
Dense coarse sandy gravels and
gravelly sands with cobbles
to 14 inch diameter.
Spanaway topsoil unit.
Coarse sandy gravels with
small boulders and numerous
cobbles.
Excavated soil had a musty smell
of sewage. Drain field lateral
to the west of the test pit.
Spanaway topsoil unit.
Coarse sandy gravels with
cobbles to 8 inch diameter.
Slightly sandier soils.
o to -1.7 feet Spanaway topsoil unit.
-1.7 to -6.2 feet Coarse gravelly medium sands
with cobbles to 8 inch diameter.
Test Pit Five:
o to -2.0 feet
-2.0 to -3.1 feet
-3.1 to -6.1 feet
Test Pit Six:
o to -1. 7 feet
-1.7 to -5.9 feet
Test Pit Logs
Page 1 of 2
Spanaway topsoil unit.
Coarse sandy gravel layer.
Gravelly medium gray sand.
Spanaway topsoil unit.
Yellow brown medium sandy
gravel with cobbles and
boulders.
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Page 2 of 2
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Test Pit Seven:
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o to -1. 4 feet
-1.4 to -6.3 feet
Spanaway topsoil unit.
Yellow brown sandy gravels with
cobbles and boulders.
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No seepage or ground water was observed in any test
pit. No indication of seasonal high ground water
levels were observed. The outwash deposits of sands
and gravels with cobbles and boulders is dense. The
large boulders were occasionally difficult to remove
from the test pits.
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1235 EAST 4TH AVE
SUITE 101
OLYMPIA, WA 98506
(360) 754-9339
FAX (360) 352-2044
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Me SQUARED
INCORPORATED
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April 11, 1996
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Mr David Strong
Bradley Noble Geotechnical Services
POBox 10267
Olympia, W A 98502
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RE SOILS INVESTIGATION REPORT
TWIN COUNTY CREDIT UNION
YELM, WASHINGTON
Dear David
We have reviewed the attached 7 page soils report entitled "Soils Investigation Report
for Twin County Credit Union, Yelm, Washington"
This report was prepared by you based on field work performed by you and your firm.
MC Squared, Incorporated has reviewed this report and the conclusions contained
therein It is our opinion that the report and the conclusions meet the standards of good
geotechnical practice for this place and time
MC Squared's recommendations and opinion are based on our review of the field
information and soils logs presented to us MC Squared has made recommendations to
you regarding allowing bearing stresses, lateral resistance and loads, site period, and
other items of an engineering nature These recommendations and conclusions have
been included in the attached report.
If you have any questions, or I may be of further help, please call me at
(360) 754-9339.
Sincerely yours,
MC SQUARED, INC
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Principal
STRUCTURAL. FOUNDATION · CrvIL ENGINEERS
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The
BJSS GROUP
ARCHITECTS & PLANNERS, AlA
no WEST BAY DRIVE sum 212 OLYMPIA WA 98\02 (J60) 94J.4MO
TWrlJ CIlUm)' CR6o,-:- I,)NI~ - ";6l.J\^
DATE. ~ 1& ~G.o
REVISED
COMM NO
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TAX PARCEL I 21724120300
LEGAL DESCRIPTION 24-17-IE NW4 NE4 SWLY OF OLY-YELM RD LESS 1.28A
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An Operation and Maintenance Permit has been issued on this parcel of property. This permit'is required by
Article IV of the Thurston County Sanitary Code to insure proper operation and maintenance of the on-site
sewage disposal system located on the above described property. This permit shall be obtained and kept current
by the owner of such property. '
Tnis document shall run with the land and shall be binding 0,1 all parties, their successors in intefl",st and
assigns, having or acquiring any right, title, or interest in the land described herein or any part thereof, and
shall insure to the benefit nf each owner thereof.
For information regardfng specific permit conditions, contact Thurston Coullty Environmental Health, Operation
and Maintenance p:rmit section, at 786-5455,
_ SPENCER C TRIPLETr
L2QA1. OWNU:S PIUNT1lD HAJ.CB
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FOR AUDITOR'S US~ ONLY
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OS/20/94 09:07 A~
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S.~ S. ROid, AUDITOR
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Vol: 2276 P.age: 754
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TAX PARCEL I 21724120300
LEGAL DESCRIPTION 24-17-1E NW4 NE4 SWLY OF OLY-YELM RD LESS 1.28A
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An Operation and Maintenance Permit has been issued on this parcel of property, This permit' is required by
Article IV of the Thurston County Sanitary Code to insure proper operation and maintenance of the on-site
sewage disposal system located on the above described property. This permit shall be obtained and kept current
by the owner of such property,
Tnis document shall run with the land and shall be binding 011 all parties, their successors in intert.',st and
assigns, having or acquiring any right, title, or interest in the land described herein or any part thereof, and
shall insure to the benefil of each owner thereof.
For information regarding specific permit conditions, contact Thurston COUrtty Environmental Health, Operation
and Maintenance p:rmit section, at 786-5455
_ SPENCER C TRIPLEIT
LOOA1. OWNI!P:S PIUN11lD ftUCB
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FOR AUDITOR'S USE ONLY
THURSTON COUNT\'
JLYMPIAJ WA
OS/20/94 e9:07 A~
^EQUEST OF: 217241203
Sd~ S. Ro~dt AUDITOR
BY: ILEANA,l DEPUTY
$7.e0 EHSRD
Vol: 2276 Palle: 754
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