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Report
Geotechnical Engineering Services
Sewer Line Reconstruction
' Rainier Avenue North and NW 7th Street
Renton, Washington
November 6, 1997
For
City of Renton
1
G e o E n g i n e e r s File No.0693-045-02
Geo �Engineers
Consulting Engineers
November 6, 1997 and Geoscientists
Offices in Washington,
Oregon,and Alaska
City of Renton
Utility Systems Division
200 Mill Avenue South
Renton, Washington 98055
Attention: David M. Christensen
Report
Geotechnical Engineering Services
Sewer Line Reconstruction
Rainier Avenue North and NW 7th Street
Renton, Washington
j File No. 0693-045-02, Task 2
INTRODUCTION
This report presents the results of our geotechnica. engineering services for reconstructing
a damaged sewer line located within the right of way of Northwest 7th Street, immediately west
of Rainier Avenue North in Renton, Washington. The project location is shown on the Vicinity
Map, Figure 1.
The sewer line was damaged when a landslide was reactivated during heavy rain the week
ending February 9, 1996. The sewer line was reconstructed in 1991 after a similar landslide
occurred. Our services in 1991 and 1996 were requested by David Christensen of the City of
Renton to provide an emergency evaluation of the landslide and to provide recommendations for
a permanent repair concept. The replacement sewer line will be installed by directional drilling
to locate the line below the bottom of the landslide zone. These services have been provided in
general accordance with our proposal dated November 25, 1996. Our services were authorized
by David Christensen on June 13, 1997.
The results of our previous services are described in the following documents:
GeoEngineers,Inc.
8410154th Avenue N.E.
Redmond,WA 98052
Telephone(425)861-6000
Fax(425)861-6050
www.geoengmeers.com
City of Renton
November 6, 1997
Page 2
1. "Preliminary Geotechnical Evaluation, Landslide and Broken Sewer Lines, Slope West of
Rainier Avenue North, Renton, Washington" dated May 16, 1991.
2. "Report, Supplemental Geotechnical Engineering Services, Sewer Line Construction and
Slope Stabilization, Slope West of Rainier Avenue North, Renton, Washington" dated
October 4, 1991.
We understand that the sewer line will be replaced with an 8-inch high density polyethylene
pipe using the directional drilling method. We further understand that the city of Renton has
arranged to have the west lane of Rainier Avenue North closed to provide sufficient room at the
bottom of the slope to accommodate the drilling equipment and construction of the jacking pit.
The replacement sewer line will connect to a new 48-inch diameter manhole which will replace
an existing manhole located at the top of the slope at the intersection of Northwest r and Taylor
Avenue Northwest. The pipe invert will be about 12 feet below the top of the manhole. The
pipeline will extend about 230 feet down slope to the east to connect to a new 48 inch diameter
manhole which will replace an existing manhole located in the west lane of Rainier Avenue
North. The pipe invert will be about 4 feet below the top of the manhole. An existing 16 inch
water line extends along the bottom of the slope about 20 feet west of this manhole near the toe
of the slope. The new pipeline will pass above the water line and into the manhole. We
understand that the contractor will be required to expose the water line at the toe of the slope
before beginning the directional drilling.
SCOPE
The purpose of our services is to evaluate subsurface soil and ground water conditions as
a basis for developing final design recommendations for the directional drill technique. Our
specific scope of services includes the following tasks:
1. Review previous reports and records in our files and information provided by the City of
Renton regarding site history.
2. Compare current site topography, provided by the City of Renton, with older survey data.
3. Explore subsurface soil and ground water conditions by drilling 1 boring along the
proposed alignment.
4. Evaluate the engineering characteristics of the site soils based on laboratory testing of
samples obtained from previous borings completed by GeoEngineers (see Appendix B).
5. Confirm our previous analysis and characterization of the landslide with respect to the
present landslide activity and geometry. This includes presenting a geologic cross section
of the alignment based on all available information.
s-� 6. Describe subsurface soil and ground water conditions along the proposed alignment.
7. Review the proposed horizontal and vertical alignment of the replacement sewer line and
comment on design modifications which may be necessary based on the results of our
explorations.
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 3
8. Attend a meeting with representatives of City of Renton to present our conclusions and
recommendation.
9. Provide recommendations for jacking and receiving pit construction. This includes lateral
earth pressures for design of shoring and dewatering requirements.
10. Comment on construction issues which might affect the proposed alignment.
SITE DESCRIPTION
GENERAL
Slopes west of Rainier Avenue North in the vicinity of the project site have a history of
movement that extends back several decades. Many of the older city maps show rights-of-way
on these slopes for streets that have never been constructed, primarily because of slope steepness
�l and instability. Our discussions with various City of Renton staff confirm their history of
frequent maintenance problems along Rainier Avenue, usually as a result of slopes being unstable
1 following periods of heavy rain. The heavy rains which have occurred during the past two
winters have resulted in significant slope movements at the project site and to the north of the site
along Rainier Avenue North.
REGIONAL GEOLOGY
The Renton area has been occupied by glaciers several times in the last million years. The
most recent glaciation, commonly called the Vashon Stade, occurred approximately 13,500 years
ago. The project area is located along the eastern margin of the "Skyway Uplands," a glacial
terrace underlain by Pre-Vashon glaciolacustrine and Vashon glacial and glaciofluvial deposits,
bordered on the south by a glacial valley wall underlain by late Eocene and Oligocene
sedimentary bedrock designated the Renton Formation and Tukwila Formation, respectively, and
on the east by the valley occupied by Lake Washington and underlain now by the Cedar River
delta.
SURFACE CONDITIONS
The present slope extends between Elevation 55 feet at the toe along Rainier Avenue to
approximately Elevation 125 feet at the crest along Taylor Avenue Northwest. The rise of 70
feet occurs in a horizontal distance of about 185 feet resulting in an average slope inclination of
about 40 percent. The site and adjacent areas are shown on the Site Plan, Figure 2.
The slope is generally undeveloped, except for the sewer line constructed along the
Northwest Seventh Street easement which extends from Taylor Avenue Northwest to Rainier
Avenue North. This sewer line was damaged and rerouted following the landslide which
occurred in 1996. A single family residence is located along the south side of the proposed
alignment and fronts on Taylor Avenue Northwest. The slope is vegetated with alder saplings
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 4
and dense blackberries. Individual large maple, spruce, cedar, and hemlock trees are growing
along portions of the slope to the north and south of the project site.
SUBSURFACE CONDITIONS
We explored subsurface soil and ground water conditions along the proposed alignment for
this study by drilling one boring (numbered 1) to a depth of about 36.5 feet on July 21, 1997.
A description of the field exploration program and log of the boring are presented in
Appendix A. The location of the exploration along the alignment is shown on the Site Plan,
Figure 2. Also shown in Figure 2 are the locations of explorations completed during our
previous studies. A description of the exploration program, logs of the explorations and
laboratory data from our previous study are presented in Appendix B.
Subsurface conditions encountered in Boring 1 completed for this study include about 13
feet of loose to medium dense silty sand with gravel. This upper layer appears to include fill,
slope wash and/or weathered till. We encountered dense sand below this upper layer and
extending to a depth of about 16 feet. From a depth of 16 feet to the bottom of the boring at a
depth of about 36.5 feet, we encountered hard silt. Ground water was encountered at a depth
of about 11 feet during drilling.
The subsurface conditions encountered in Boring 1 are consistent with the conditions
encountered in the nearby borings completed during our previous studies. A generalized cross
section developed during our previous studies is presented in Figure B-1. The cross section
illustrates the expected subsurface conditions along the alignment and has been revised to include
information developed during our current study.
CONCLUSIONS AND RECOMMENDATIONS
GENERAL
In our opinion, the replacement sewer line may be constructed at the site as proposed using
the directional drilling technique. The soils encountered in our borings are suitable for
directional drilling. These soils can be adequately supported by a combination of open cuts,
trench boxes and shoring during construction to create drilling and receiving pits. Dewatering
during construction will likely be limited to controlling small to moderate amounts of seepage
water which enters the drilling and receiving pits. Seepage water can be controlled by pumping
from sumps located within the excavations. It may be possible to shore the drilling and receiving
pits using conventional shoring boxes. However, we recommend that drilled soldier piles and
lagging be used for temporary excavation shoring at the toe of the slope where the water line
must be exposed to reduce the risk of creating further slope instability during construction.
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 5
SITE PREPARATION AND EARTHWORK
Site Preparation
Site preparation will consist of completing the excavations for the directional drilling
equipment and the receiving pit, placing two 48-inch diameter replacement manholes and
backfilling the excavations prior to reestablishing the paved roadways and walks. We expect that
all of the soils encountered in the excavations can be excavated with conventional equipment.
Silty soils are expected to comprise much of the material excavated from the two pits.
These soils are very moisture-sensitive, easily disturbed during construction and will be difficult,
if not impossible, to compact when wet. We therefore recommend that all backfill consist of
imported structural fill as described below.
Structural Fill
All new fill in pavement and walkway areas should be placed as structural fill. The
suitability of soil for use as structural fill will depend on its gradation and moisture content. As
the amount of fines (that portion passing U.S. No. 200 sieve)increases, soil becomes increasingly
sensitive to small changes in moisture content and adequate compaction becomes more difficult
to achieve, particularly during wet weather. Generally, soils containing more than about
5 percent fines by weight, relative to the fraction of the material passing the 3/4-inch sieve,
cannot be properly compacted when the moisture content is more than a few percent from
optimum.
During dry weather, it might be feasible to use the on-site sand and silty sand as structural
fill, provided this material is conditioned to the proper moisture content for compaction. The
on-site silt will not be suitable for structural fill where compaction to at least 95 percent of
maximum dry density (ASTM D-1557) is required.
If structural fill placement must take place during wet weather, we recommend the use of
imported sand and gravel containing less than 5 percent fines by weight relative to the fraction
of the material passing the 3/4-inch sieve. As an option, controlled density fill (CDF) should be
considered during wet weather for its ease in backfilling and uniform support for the
reconstructed roadways.
All structural fill material should be free of organics, debris and other deleterious material
with no individual particles larger than 6 inches in diameter. Structural fill should be placed in
loose lifts not exceeding 8 inches in thickness. Each lift should be conditioned to the proper
moisture content and uniformly compacted to the specified density before placing subsequent lifts.
Structural fill should be mechanically compacted to a firm, nonyielding condition. Structural fill
placed beneath pavement and walkway areas should be compacted to at least 95 percent of the
maximum dry density (MDD) per ASTM D-1557. Fill outside pavement and walkway areas
should be compacted to at least 90 percent of MDD.
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 6
We recommend that a representative from our firm be present during critical stages of site
preparation and fill placement. Our representative would evaluate the adequacy of the subgrade
soils and identify areas needing further work, perform in-place moisture-density tests in the fill
to verify compliance with the compaction specifications, and advise on any modifications to
procedures which might be appropriate for the prevailing conditions.
Temporary Open-Cut Slopes
We expect that some portion of the excavations will be made as an open cut to reduce the
need for shoring. The stability of open-cut slopes is a function of soil type, ground water level,
slope inclination, slope height and nearby surface loads. The use of inadequately designed open
cuts could impact the stability of adjacent work areas, existing utilities, and endanger personnel.
In our opinion, the contractor will be in the best position to observe subsurface conditions con-
tinuously throughout the construction process and to respond to variable soil and ground water
conditions. Therefore, we believe that the contractor should have the primary responsibility for
deciding whether or not to use an open-cut slope rather than some form of temporary excavation
support, and for establishing the safe inclination of the cut slope. All open-cut slopes and
temporary excavation support should be constructed or installed, and maintained in accordance
with the requirements of the appropriate governmental agency.
For planning purposes only, we recommend that temporary cut slopes in medium dense
native soil and fill be no steeper than 1-1/2H:1V (horizontal to vertical). We expect that this will
be appropriate for preliminary design of the excavations located at the top of the slope. We
recommend that temporary cut slopes of 1H:1V be used for preliminary design of the excavation
located at the toe of the slope where hard silt is present. These general guidelines assume that
surface loads such as equipment loads and storage loads will be kept a sufficient distance away
from the top of the cut so that the stability of the excavation is not affected. The guidelines also
assume that the excavations will be dewatered in such a way that significant seepage is not
present on the slope face. Flatter slopes and/or shoring may be necessary for those portions of
the excavations which are subjected to significant seepage.
It should be expected that the excavation face will experience some sloughing and raveling.
Berms, swales, or drainage ditches should be installed around the perimeter of the excavation to
intercept surface runoff and reduce the potential for sloughing and erosion of the cut slope.
EXCAVATION SUPPORT
Based on the planned depth of the pipeline inverts and new manhole bases, we expect that
the drilling and receiving pits will be about 14 feet deep at the top of the slope and about 6 feet
deep at the toe of the slope.
We recommend that temporary shoring for support of the pit located at the toe of the slope
consist of a combination of open cut and drilled soldier pile and lagging walls. We recommend
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 7
that the west wall of the excavation which will extend along the toe of the slope be constructed
1 as a soldier pile and lagging wall. Open cut slopes will likely form the other sides of the
excavation.
The following values may be used for design of the soldier pile and lagging shoring system:
1. AEP (active earth pressure): Equivalent fluid weight of 60 pounds per cubic foot (pcf)
based on a slope of 1.51-1:1V above the shoring wall. The AEP will act over the soldier
pile spacing above the bottom of the excavation and the grouted soldier pile width below
the bottom of the excavation. For a slope of 3H:1V or flatter above the wall an equivalent
fluid weight of 35 pcf should be used.
2. PEP (passive earth pressure): The PEP will include a uniform rectangular pressure
distribution and a triangular distribution. The rectangular distribution should be uniform
with depth and equal 1,000 pounds per square foot (psf) acting over 2 times the grouted
soldier pile width. The triangular distribution should be determined for an equivalent fluid
weight of 265 pcf acting over 2 times the grouted soldier pile width. These values include
a factor of safety of about 1.5.
3. Minimum pile embedment below dredge line: 10 feet.
4. AEP for lagging design: Equivalent fluid density of 30 pcf.
The above recommended lateral soil pressures do not include the effects of surcharges(e.g.,
equipment loads, storage loads, traffic loads, or other surface loading). Surcharge effects should
be considered as appropriate. Existing structures may be sensitive to vibrations. If shoring is
driven or vibrated as part of this project, the effect on nearby facilities should be adequately
evaluated. We recommend that the contractor submit his shoring plan to the engineer for review
prior to the start of construction.
LIMITATIONS
We have prepared this report for use by City of Renton in the design of a portion of the
project. The data and report should be provided to prospective contractors for bidding or
estimating purposes, but our report, conclusions and interpretations should not be construed as
a warranty of the subsurface conditions.
If there are any changes in the grades, location, configuration or type pipeline installation
to be constructed, the conclusions and recommendations presented in this report may not be fully
applicable. If such changes are made, we request that we be given the opportunity to review our
conclusions and recommendations and to provide a written modification or verification. When
the design has been finalized, we recommend that GeoEngineers be retained to review the final
design drawings and specifications to see that our recommendations have been interpreted and
implemented as intended.
G e o E n g i n e e r s File No.0693-045-02
City of Renton
November 6, 1997
Page 8
Our scope does not include services related to construction safety precautions and our
recommendations are not intended to direct the contractor's methods, techniques, sequences or
procedures, except as specifically described in our report for consideration in design.
There are possible variations in subsurface conditions between the locations of the
explorations and also with time. A contingency for unanticipated conditions should be included
in the project budget and schedule. Sufficient monitoring, testing and consultation should be
provided by our firm during construction to confirm that the conditions encountered are consistent
with those indicated by the explorations, to provide recommendations for design changes should
the conditions revealed during the work differ from those anticipated, and to evaluate whether
or not earthwork and foundation installation activities comply with the contract plans and
specifications.
Within the limitations of scope, schedule and budget, our services have been executed in
accordance with generally accepted practices in this area at the time the report was prepared. No
other conditions, express or implied, should be understood.
We appreciate the opportunity to be of continued service on this project. If there are any
questions concerning this report, please call.
3 McFA Respectfully submitted,
F WAShr�d
�4� `� Peones, In _
r ti — / ° %
�o
'26693GISTER ti n, P.
ALELl neer
EXPIRES `I ��
Jon W. Koloski
Principal
JJM:JWK:cdl
Document I.D. P:\0693045R.DOC
Four copies submitted
G e o E n g i n e e r s File No.0693-045-02
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o STUDY WERE LOCATED SOUTH OF THE PROJECT AREA AND ARE NOT SHOWN ON THIS SITE PLAN)
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rn HA-6 HAND AUGER FOR PREVIOUS STUDY DATED 10/04/91
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A' A LOCATION OF CROSS SECTION DEVELOPED FOR PREVIOUS STUDY DATED 10/04/91 SEE APPENDIX B FOR CROSS SECTION SCALE IN FEET"
� Note: The locations of all features shown are approximate. SITE PLAN
Geo��Engineers
> Reference: Drawing entitled "Topography, NW 7th Street Sewer Repair' by Ringel & Associates, dated 12/18/96. \� FIGURE 2
i
1
1
1
1
� APPENDIX A
1
1
1
1
1
1
1
1
i
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
FIELD EXPLORATION
The subsurface conditions at the site were explored by drilling one borings on July 21,
1997. The approximate locations of the borings are shown in the site plan, Figure 2. The boring
locations were measured from existing site features. The ground surface elevations at the boring
locations are indicated on the log. The elevations are based on topographic information presented
on a site plan titled "Topography, NW 7' Street Sewer Repair" by Ringel & Associates dated
December 18, 1996 which was provided to us by city of Renton.
The boring was drilled with a trailer/skid-mounted hollow-stem auger drill rig. The boring
was monitored continuously by a geotechnical engineer from our firm who examined and
classified the soils encountered, obtained representative soil samples, observed ground water
conditions and prepared a detailed log of each boring. The soils were classified in general
accordance with the classification system described in Figure A-1. A key to the boring log
symbols is presented in Figure A-2.
The boring log is presented in Figure A-3. The log is based on our interpretation of field
and laboratory data and indicates the various types of soils encountered. Representative samples
of the soils encountered were obtained at standard 5-foot intervals using a 1-1/2-inch-inside-
diameter split-barrel sampler. The sampler was driven with a 140-pound hammer free-falling
30 inches. The number of blows required to drive the sampler the last 12 inches or other
indicated distance is recorded on the boring logs. The logs also indicate the depths at which the
soils or their characteristics change, although the change may be gradual. If the change occurred
between samples, the depth was interpreted.
LABORATORY TESTING
All soil samples were brought to our laboratory for further examination and verification of
field classification. Detailed laboratory analyses were completed as part of our previous studies
and are presented in Appendix B.
G e o E n g i n e e r s A - 1 File No.0693-045-02
SOIL CLASSIFICATION SYSTEM
GROUP
MAJOR DIVISIONS SYMBOL GROUP NAME
GRAVEL CLEAN GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL
COARSE GRAVEL
GRAINED GP POORLY-GRADED GRAVEL
SOILS More Than 50%
of Coarse Fraction GRAVEL GM SILTY GRAVEL
Retained WITH FINES
on No. 4 Sieve GC CLAYEY GRAVEL
More Than 50%
Retained on SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND
No. 200 Sieve
SIP POORLY-GRADEDSAND
More Than 50%
of Coarse Fraction SAND SM SILTY SAND
Passes WITH FINES
No. 4 Sieve SC CLAYEY SAND
FINE SILT AND CLAY ML SILT
GRAINED INORGANIC
SOILS CL CLAY
Liquid Limit
Less Than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY
More Than 50%
SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT
Passes INORGANIC
No. 200 Sieve CH CLAY OF HIGH PLASTICITY, FAT CLAY
Liquid Limit
50 or More ORGANIC OH ORGANIC CLAY, ORGANIC SILT
HIGHLY ORGANIC SOILS PT PEAT
NOTES: SOIL MOISTURE MODIFIERS:
1. Field classification is based on visual examination of soil Dry- Absence of moisture, dusty, dry to the touch
in general accordance with ASTM D2488-90.
Moist- Damp, but no visible water
2. Soil classification using laboratory tests is based on
ASTM D2487-90. Wet- Visible free water or saturated, usually soil is
obtained from below water table
3. Descriptions of soil density or consistency are based on
interpretation of blow count data, visual appearance of
soils, and/or test data.
a
0
0? SOIL CLASSIFICATION SYSTEM
W GeoUPEngineers
FIGURE A-1
LABORATORY TESTS SOIL GRAPH:
AL Atterberg Limits
CID Compaction SM Soil Group Symbol
CS Consolidation (See Note 2)
DS Direct shear
GS Grain size Distinct Contact Between
%F Percent fines Soil Strata
HA Hydrometer Analysis
SK Permeability Gradual or Approximate
SM Moisture Content Location of Change
MD Moisture and density Between Soil Strata
SP Swelling pressure
TX Triaxial compression S7 Water Level
UC Unconfined compression
CA Chemical analysis Bottom of Boring
BLOW COUNT/SAMPLE DATA:
22 Location of relatively
Blows required to drive a 2.4-inch I.D. , undisturbed sample
split-barrel sampler 12 inches or
other indicated distances using a 12 ® Location of disturbed sample
300-pound hammer falling 30 inches.
Location of sampling attempt
with no recovery
10 Location of sample obtained
Blows required to drive a 1.5-inch I.D. in general accordance with
(SPT) split-barrel sampler 12 inches Standard Penetration Test
or other indicated distances using a (ASTM D-1586) procedures
140-pound hammer falling 30 inches.
26 m Location of SPT sampling
attempt with no recovery
® Location of grab sample
"P" indicates sampler pushed with
weight of hammer or against weight
of drill rig.
NOTES:
1. The reader must refer to the discussion in the report text, the Key to Boring Log Symbols and the
exploration logs for a proper understanding of subsurface conditions.
2. Soil classification system is summarized in Figure A-1.
����, KEY TO BORING LOG SYMBOLS
Geo �Engineers FIGURE A-2
TEST DATA BORING 1
DESCRIPTION
Moisture Dry
Content Density Blow Group Surface Elevation(ft.):
Lab Tests M (pco Count Samples Symbol
0 SOD Sod zone 0
JIT SM Brown silty fine sand with occasional gravel (medium dense,
moist)
5 5
SM Grayish brown silty fine to medium sand with fine gravel
(loose, wet)
10 10
:: SP Gray fine to medium sand(dense,wet)
15 15
38 ❑"" ML Light brown fine sandy silt(hard,wet)
H
w
w
LL
= MH Gray silt to elastic silt(hard, moist)
ow 20 i 20
52
III
III
25 I MH Gray elastic silt with occasional laminated fine sand(hard, 25
m 25 ® ( I moist)
II
� lil
30 I I 30
33
III
I �
ICI
35 I I I 35
0 27
M Boring completed at 36.5 feet on 07/21/97
_ Ground water encountered at approximately 11 feet during
N drilling
0
0
It
0 40 40
� a)
0 Note: See Figure A-2 for explanation of symbols
� LOG OF BORING
G e o�o Engineers FIGURE A-3
� APPENDIX a
APPENDIX B
PREVIOUS STUDY
FIELD EXPLORATIONS AND
LABORATORY TESTING
FIELD EXPLORATIONS
Seven borings were drilled between August 5 and 13, 1991 to evaluate subsurface
conditions along the slope located west of Rainier Avenue North. The Site Plan, Figure 2 shows
the location of the explorations completed near the proposed sanitary sewer alignment. The
explorations were located by site survey on the site plan provided by the project civil engineer
and were tied to our cross-sections using cloth tape, hand clinometer and Brunton compass.
Borings 1 and 4 were drilled with a truck mounted Acker Soilmax, using continuous flight, 4-
inch-inside-diameter hollow-stem auger. Samples were obtained from the hollow-stem auger
borings using a 3-inch-outside-diameter, split-barrel sampler driven with a 300-pound hammer
free-falling 30 inches. The number of blows required to drive the sampler the last 12 inches is
recorded on the boring logs.
The borings were continuously monitored by a representative of our firm who observed drill
action and cuttings, selected sample intervals, examined and classified the soils recovered, and
kept a log of each boring. Soils encountered were visually classified in general accordance with
the Unified Soil Classification System, briefly described in Figure B-2. A key to the boring log
symbols is presented in Figure B-3
The logs of borings B-1 and B-4 are presented in Figures B-4 and B-5, respectively.
Borings HA-6 and HA-7 were drilled with a hand auger to depths of 8.5 and 9.0 feet,
respectively. The logs of the borings are presented in Figures B-6 and B-7. Borings B-2 and
B-3 are located south of the project area and the logs are therefore not included in this appendix.
Similarly, hand auger borings completed outside the project area are not included in this
appendix.
The exploration logs are based on our interpretation of the field and laboratory data and
indicate the various types of soils encountered. They also indicate the depths at which these soils
or their characteristics change, although the change might be gradual. If the change occurred
between samples in the borings, it was interpreted from drill action or auger cuttings.
Piezometers were installed in boring B-1 to allow for future monitoring of ground water
levels at the site. Water level measurements were accomplished on the day that the boring was
completed and on August 13, 1991. Results of measurements are presented in the text section
entitled "Groundwater."
LABORATORY TESTING
All soil samples were brought to our laboratory for further examination. The samples were
examined for evidence of recent movement or disturbance. Selected samples were tested to
G e o E n g i n e e r s B - 1 File No.0693-045-02
determine moisture content, dry density, grain size and plasticity, and strength characteristics.
' A number of soil samples were evaluated to determine their gradation and Atterberg limits.
These tests were used to confirm the results of our visual-manual field testing. Results of
gradation and Atterberg limits testing for boring B-1 are summarized in Figures B-8 through 13-
10.
Numerous soil samples were tested to determine their moisture content and dry density.
These determinations were used to evaluate the unit weight and degree of saturation of various
soils, and were compared with representative Atterberg limit test results to evaluate the respective
in-place condition of the materials. The results of moisture and density determinations are
presented on the boring logs.
Strength characteristics of both fine-grained and coarse-grained samples were evaluated by
performing direct shear tests. Direct shear test results are presented in Figure B-11.
G e o E n g i n e e r s B - 2 File No.0693-045-02
130 10+00 ' I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 130
11+00 11+50 12+00 ;n
10+50 A
A (EAST) ' (WEST)
c
N.W.7th
rHouse(676 Taylor Avenue N.W.) 18.7'South) m
Azimuth �,, A52 Aye
2700 _ c M t 120
120 c°� 0 o Estimated jinEund Surface — 4
ao Subtle Crack with (9�
Discernable Offset Z y
�, rz rn A50 61
A 4a A48 m�
110 A" SU-D3 // 110
50/5'
1
J�
Fill 3 SU-D2/
A.32 50/4"
100 07/21/97 08/13/91___ 100
A40 7 SU-Di —_ ----- 50/5'
A36
Manhole for Sewer Line A38 / �_ — —
Fill Material Flowed Downslope L f/ / —� SU-C ---
Over Top of Slide Block ° A32 34 Fill / ,/ 38 Water-Bearing
Z
m A30 — SU-B2 Soil Laye
00 � r128 Fill 90
/ SU-D3 d 52 50/4"
m Broken A26
LL Sewer Pipe i I— /�� 25 SU-A5 U.
c t SU-132 /
50/6' c
C C A24 0
0 0
80- e 80
r SU-A4 '_ 33 59
W
EXPLANATION: W
27
Debris Pile r' 2
� SU-A4 m Boring Number
1 70 A22� � r/ 70 54
v
7 Sample Depth & Blow Count
(See Boring Logs for
a 1 Further Description)
1 Soil Unit Description 33
�, ap Z A20
�- 60 Fill GM Brown silty fine to coarse gravel with sand and occasional bark,plastic SU-B2 SM Brown silty fine to coarse sand with varying amounts of gravel (very Notes: 1. See Figure 2 for Cross Section location.
and concrete (medium dense, moist) dense, moist)(glaciolacustrine) 31
-60
J Rainier Averiue North 2. Subsurface conditions shown on the Cross Section
l
Sidewalk I SU-Ai ML Brown sandy silt(hard, moist)(glaciolacustrine) SU-C CL Brown to light brown clay with varying amounts of sand and occasional are based on interpolation between widely spaced
' gravel (hard, moist) (glaciolacustrine) explorations and should be considered approximate.
.. SU-A2 ML Light brown silt with layers of fine to medium sand (hard/very dense, 61
A14 moist) (glaciolacustrine) SU-D1 SM Brown sit fine sand with occasional ravel dense to very dense, 3. The round surface has changed since 1991
A10 Al2 A16 � silty 9 ( rY 9 9
d;18 moist)(till) because of continued movement of landslide.
p 50 ._ S`6 SU-A3 ML Brown silt with occasional sand (hard, moist) (glaciolacustrine) 50
11 SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense,
SLI A4 CL/CH Gray clay with occasional Interbedded silt and fine sand (hard, moist) moist)(weathered till)
finely laminated (glaciolacustrine) 0 10 20
EXISTING SU-D3 SM Brown silty fine to medium sand with fine gravel (loose,
O 16" DIAMETER 23 SU-A5 ML Gray silt with occasional interbedded clay,sand and gravel(hard,most) moist)(weathered till) SCALE IN FEET
WATER LINE massive to finely laminated (glaciolacustrine)
� 40 SU-E SM Brown to light brown silty fine sand with occasional gravel and roots FROM 10/04/91 REPORT(DRAWING REVISED 10/97) 40
O 40 SU-A6 CL Brown clay with sand and roots (soft, moist) (glaciolacustrine/topsoil) (medium dense, dry)(slope deposit) 12+00
I I I I 1 I
Q SU-Bt ML Light gray and brown sandy silt with occasional gravel and cobbles CITY OF RENTON N.W. 7TH STREET AND TAYLOR AVENUE N.W.
J (hard, moist) (glaciolacustrine) T
�� O RAINIER A liI NA TM!%-LOPE ST RIUM r Full IIATrc�1r
All
AND SEWER LINE RECONSTRUCTION CROSS SECTION A-A'
10+50 11+00 11+5Q Geo\ Engineers FIGURE B-1
30 10+� 1 1 1 I
i
SOIL CLASSIFICATION SYSTEM
GROUP
MAJOR DIVISIONS SYMBOL GROUP NAME
GRAVEL CLEAN GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL
COARSE GRAVEL
GRAINED GP POORLY-GRADED GRAVEL
SOILS More Than 50%
of Coarse Fraction GRAVEL GM SILTY GRAVEL
Retained WITH FINES
on No. 4 Sieve GC CLAYEY GRAVEL
More Than 50%
SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND
Retained on
No. 200 Sieve
SP POORLY-GRADED SAND
More Than 50%
of Coarse Fraction SAND SM SILTY SAND
Passes WITH FINES
No. 4 Sieve SC CLAYEY SAND
FINE SILT AND CLAY ML SILT
GRAINED INORGANIC
SOILS CL CLAY
Liquid Limit
Less Than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY
More Than 50% SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT
Passes INORGANIC
No. 200 Sieve CH CLAY OF HIGH PLASTICITY, FAT CLAY
Liquid Limit
50 or More ORGANIC OH ORGANIC CLAY,ORGANIC SILT
HIGHLY ORGANIC SOILS PT PEAT
NOTES: SOIL MOISTURE MODIFIERS:
1. Field classification is based on visual examination of soil Dry- Absence of moisture, dusty, dry to the touch
in general accordance with ASTM D2488-90.
Moist- Damp, but no visible water
2. Soil classification using laboratory tests is based on
ASTM D2487-90. Wet- Visible free water or saturated, usually soil is
obtained from below water table
3. Descriptions of soil density or consistency are based on
interpretation of blow count data, visual appearance of
soils, and/or test data.
0
0? SOIL CLASSIFICATION SYSTEM
W G e o��Engineers FIGURE B-2
LABORATORY TESTS SOIL GRAPH:
AL Atterberg Limits
CID Compaction SM Soil Group Symbol
CS Consolidation (See Note 2)
DS Direct shear
GS Grain size Distinct Contact Between
%F Percent fines Soil Strata
HA Hydrometer Analysis
SK Permeability Gradual or Approximate
SM Moisture Content Location of Change
MD Moisture and density Between Soil Strata
' SP Swelling pressure
TX Triaxial compression Q Water Level
UC Unconfined compression
CA Chemical analysis Bottom of Boring
BLOW COUNT/SAMPLE DATA:
22 Location of relatively
Blows required to drive a 2.4-inch I.D. • undisturbed sample
split-barrel sampler 12 inches or
other indicated distances using a 12 ® Location of disturbed sample
300-pound hammer falling 30 inches.
17 ❑ Location of sampling attempt
with no recovery
io 0 Location of sample obtained
Blows required to drive a 1.5-inch I.D. in general accordance with
(SPT) split-barrel sampler 12 inches Standard Penetration Test
or other indicated distances using a (ASTM D-1586) procedures
140-pound hammer falling 30 inches.
26 m Location of SPT sampling
attempt with no recovery
® Location of grab sample
"P" indicates sampler pushed with
weight of hammer or against weight
of drill rig.
NOTES:
1. The reader must refer to the discussion in the report text, the Key to Boring Log Symbols and the
exploration logs for a proper understanding of subsurface conditions.
2. Soil classification system is summarized in Figure B-2.
`�� KEY TO BORING LOG SYMBOLS
Geo�MpEngineers FIGURE B-3
TEST DATA BORING B-1
' DESCRIPTION
Moisture Dry
Content Density Blow Group Surface Elevation(ft.): 121.6
Lab Tests (%) (pcf) Count Samples Symbol
0 ASPHALT 3 inches asphalt concrete 0
SM SU-D3 Brown silty fine to medium sand with fine gravel
24 :. SM (loose,moist)
SU-D2 Brown silty fine to medium sand with fine gravel
(medium dense,moist)(weathered till)
5 5
:: SM SU-D1 Brown silty fine sand with occasional gravel(very
dense, moist)(till)
61
Rock fragment at 8.0 feet
10 10
11 115 5015" -
L
15 15
w 50/4"
I z
Z
2
H
Il
0 20 20
12 118 5015" 1 - : SM SU-132 Brownish gray silty fine sand(very dense, moist)
CL (glaciolacustrine)
SU-C Gray sandy clay(very dense,moist)(glaciolacustrine)
25 :: SM SU-132 Brownish gray silty fine to medium sand with gravel 25
and occasional cobble and coarse sand(very dense,wet)
(glaciolacustrine)
m
m
m
' 30 ML SU-A5 Gray silt with a trace of fine sand(hard,moist) 30
3 (glaciolacustrine)
50/4" 1
35 35
50/6" 1
N Rock fragment at 38 feet
0
c`+ L SU-A4 Gray clay with occasional fine gravel(hard, moist)
m 40 40
0
0 Note: See Figure B-2 for explanation of symbols
LOG OF BORING
G e o�o Engineers FIGURE B-4
TEST DATA BORING B-1
(Continued)
' DESCRIPTION
Moisture Dry
Content Density Blow Group
Lab Tests (%) (pco Count Samples Symbol
40 (glaciolacustrine) 4 0
59
45 45
' 26 99 2
50 50
54
55 55
~
w 33
w
Z
Z
n
p 60 CL SU-A4 Gray clay with thin lenses of sandy silt(hard, moist) 60
(laminated)(glaciolacustrine)
30 95 31
65 65
61
m Boring completed at 67.5 feet on 08/05/91
m Second hole augered to 36.0 feet depth 8.0 feet south for
piezometer installation
70 See text for water level data 70
0
I..
75 75
N
O
f
O
'm 80 80
Note: See Figure B-2 for explanation of symbols
� � LOG OF BORING
Geo\Engineers FIGURE B-4
TEST DATA BORING B-4
DESCRIPTION
Moisture Dry
Content Density Blow Group Surface Elevation(ft.): 51.6
Lab Tests (go) (pcf) Count Samples Symbol
0 CL SU-A6 Brown clay with sand and roots(soft, moist) 0
(glaciolacustrine/topsoil)
CL SU-A4 Gray clay with occasional gravel(stiff, moist)
11 (glaciolacustrine)
5 5
' 21 106 23 Grades to very stiff to hard
10 10
' 40
15 15
H
w
w
Z
Z
LL
n
a
0 20 Boring completed at 20.0 feet on 08/08/91 20
' No ground water encountered
25 25
rn
m
N 30 30
U
' 35 35
N
O
O
co a) 40— 40
co
0 Note: See Figure B-2 for explanation of symbols
��� � LOG OF BORING
Geo\0Engineers FIGURE B-5
TEST DATA HAND BORING HA-6
DESCRIPTION
Moisture Dry
Content Density Blow Group Surface Elevation(ft.): 83.0
Lab Tests (%) (pcf) Count Samples Symbol
0 GM Brown silty fine to coarse gravel with sand(loose, moist)(fill) 0
000
0
1 CL SU-A4 Gray clay(soft,moist)(glaciolacustrine, remolded by
' slope movement)
2
1 3
4
' 5-
6
W
w
w
w 7
z
t-
a
0 8
' Boring completed at 8.5 feet on 08/13/91
9 No ground water encountered
10 10
11
rn
� 12
U
13
14
15 15
N
O
O
to 16
to
O Note: See Figure B-2 for explanation of symbols
`� LOG OF HAND BORING
Geo��Engineers FIGURE B-6
TEST DATA HAND BORING HA-7
DESCRIPTION
Moisture Dry
Content Density Blow Group Surface Elevation(ft.): 68.5
Lab Tests (%) (pcf) Count Samples Symbol
0 GM Brown silty fine to coarse gravel with sand(loose, moist)(fill) 0
' 000
a
1 CL SU-A4 Light brown clay(soft, moist)(glaciolacustrine,
' remolded by slope movement)
2
3
' 4
5 5
' 6 SM SU-A4 Brown silty fine to medium sand(medium dense, moist)
(glaciolacustrine)
LU
w
w
`- 7
z
LU
a
0 8 SM/ML SU-A4 Light brown interbedded silty fine sand and silt
' (dense/very stiff,moist)(glaciolacustrine)
9
Boring completed at 9.0 feet on 08/13/91
See text for water level data
10 10
' 11
m
N� 12
U
13
14
15 15
N
7
obbbb
16 —
0 Note: See Figure B-2 for explanation of symbols
� LOG OF HAND BORING
Geos0Engineers FIGURE B-7
JJM:HLA 0693-045-02 09 22 97
U . S . STANDARD SIEVE SIZE
Fe-.7,
tim 100
� ���•���. ���. � ti� O �� �O BOO BOO
O
90
Nil }
80
3 70
m 60
z 50
LL
40
z
u 30
w
20
10
D 0
m D 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
cGRAIN SIZE IN MILLIMETERS
m z
W SA
0 COBBLES COARSE RAVEL FINE JCOARSEJ MEDIUMND FINE SILT OR CLAY
C
m
< EXPLORATION SAMPLE
m SYMBOL NUMBER DEPTH SOIL DESCRIPTION
U)
B-1 11 . 5 ' BROWN SILTY FINE TO MEDIUM SAND WITH
OCCASIONAL COARSE SAND AND FINE GRAVEL
(SM)
B-1 21 . 5 ' GRAYISH BROWN SILTY FINE TO MEDIUM SAND
WITH OCCASIONAL COARSE SAND AND FINE
GRAVEL (SM/ML)
m = = = = m = m = m m = m = m = m
JJM:HLA 0693-045-02 09 22 97
U . S . STANDARD SIEVE SIZE
F.-,7 � �• �� '�� gyp. �. �, rp. �• �p gyp.
O1 100
SRINilI90
�— 80
►—�. w 7 0
��. 3
60
cc
coo �
z 50
40
z
u 30
w }_
a_ 20
10
�
D 0
-n a 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
cO GRAIN SIZE IN MILLIMETERS
m Z GRAVEL SAND
W 0 COBBLES COARSE FINE COARSE MEDIUM FINE SILT OR CLAY
' C
cp �
< EXPLORATION SAMPLE
m SYMBOL NUMBER DEPTH SOIL DESCRIPTION
cn
B-1 31 . 5 ' GRAY COARSE SILT WITH VERY FINE SAND (t-1L )
B-1 46 . 5 ' GRAY SILT WITH OCCASIONAL FINE TO MEDIUi�i
SAND (ML)
• B-1 66 . 5 ' GRAY CLAY WITH OCCASIONAL FINE TO MEDIUi`I
SAND ( CL)
JJM:HLA 0693-045-02 09 22 97
60
PLASTICITY CHART
O
AM50cH
` 0
►�� w 4 0
in
Z
~_ 30
colD U
�.
� OH and MH
20
CL CL •
y 10
m CL-ML ML and OL
70
m 0
0 10 20 30 40 50 60 70 80 90 100
LIQUID LIMIT
c 3
m -1
m N
EXPLORATION SAMPLE MOISTURE LIQUID PLASTICITY
jo m NUMBER DEPTH CONTENT (o) LIMIT (o) INDEX (o) SOIL DESCRIPTION
o N
B-1 • 41 . 5 ' 27 . 3 51 . 0 26 . 5 GRAY , CLAY WITH OCCASIONAL
VERY FINE SAND (CH)
� B-1 • 46 . 51 26 . 3- L+3 . 8 15 . 6 GRAY SILT WITH OCCASIONAL
c FINE TO MEDIUM SAND (ML)
-i B-1 ■ 66 . 5 30 . 3'' L+4 . 5 22 . 6 GRAY CLAY WITH OCCASIONAL
N FINE TO MEDIUM SAND (CL)
M . C. S TAKE AFTER DI ECT SHEAR TE T
DIRECT SHEAR TEST RESULTS
' Sample Moisture Dry Normal Peak Shear
Boring Depth Content Density Pressure Strength
Number (feet) Sample Description M (pcf) (psf) (psf)
' 1 31.5 Gray silt with fill sand 20.1 108.5 3,100 2,870
(ML) 6,500 4,290
9,500 6,300
1 46.5 Gray clay with 26.3 98.5 4,600 3,190
interbeds of gray silt 9,500 6,320
and lens of very fine 14,000 6,300
sand (CL & ML)
1 61.5 Gray clay (CL) 31.4 93.0 6,500 4,670
' 12,000 6,180
18,000 5,920
Its
DIRECT SHEAR TEST RESULTS
Geo (Engineers FIGURE B-11