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REPORT
SUPPLEMENTAL GEOTECHNICAL
ENGINEERING SERVICES
SEWER LINE RECONSTRUCTION
AND SLOPE STABILIZATION
SLOPE WEST OF RAINIER AVENUE NORTH
RENTON, WASHINGTON
1 FOR CITY OF RENTON
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Geo Engineers
Geotechnical,
Geoenvironmental and
October 4, 1991
Geologic Services
' James M. Montgomery Consulting Engineers, Inc.
2375 - 13Oth Avenue Northeast, Suite 200
Bellevue, Washington 98005
Attention: Mr. Ed Barnhurst
' We are pleased to submit ten copies of our "Report, Supplemental
Geotechnical Engineering Services, Sewer Line Construction and Slope
Stabilization, Slope West of Rainier Avenue North, Renton, Washington."
Our services were performed in general accordance with the Subcontract
Agreement for Services between James M. Montgomery Consulting Engineers,
Inc. and GeoEngineers, Inc. , dated July 15, 1991.
' We have enjoyed working with you on this project. If you have any
questions regarding this report or if we can be of further service, please
contact us.
Yours very truly,
' GeoEngineers,
Inc.
Off,
Jon W. Koloski
Principal
JWK:wd
Enclosure
File No. 0193-027-RO2
' GeoEngineers,Inc.
8410 154th Avenue N.E.
Redmond,WA 98052
Telephone(206)861-6000
Fax(206)861-6050
Printed on awoed paper.
' Geo GEngineers
ERECUTIVE SUMMARY
' This report pertains to (1) stabilization of the slopes along Rainier
Avenue North, east of Taylor Avenue Northwest and south of Northwest Seventh
Street (extended) ; and (2) reinstallation of both a main sewer line in the
Northwest Seventh Street easement, and side sewer lines servicing homes
along the east side of Taylor Avenue Northwest. Our evaluation includes
' developing geotechnical cross sections, subsurface explorations, evaluating
stability conditions of the slopes, and discussing various design and
' construction options with engineers from James M. Montgomery Consulting
Engineers and the City of Renton Department of Public Works.
Based on our discussions with the City, our study focused on the
following three alternatives for reconstructing the side sewer lines
servicing the homes east of Taylor Avenue:
' * Alternative 1 - Construct a new sewer line along Taylor Avenue
Northwest to service all of the homes along the east side of the
street. We considered constructing the side sewer line at a
number of different elevations, depending on the amount of
subsurface drainage to be provided.
* Alternative 2 - Reconstruct the new sewer line along the existing
' easement along the top of the slope east of the houses along
Taylor Avenue Northwest.
* Alternative 3 - Construct a new sewer line northward along the
' easement from the existing cleanout east of 664 Taylor Avenue
Northwest to the next property line to the east, to service 664
and 658 Taylor Avenue Northwest, then east along the property line
' and down the steep slope to Rainier Avenue North.
We also considered a number of different alternatives for placement of the
' main sewer line between Northwest Seventh Street and Rainier Avenue North.
These alternatives are tied to the method of slope stabilization and depth
and location of side sewer lines.
Our principal conclusions and recommendations include the following:
' * The site is the outslope edge of a glacial terrace. Soils which
underlie the terrace and the slide area are glaciolacustrine clay,
silt, and silty sand, capped by glacial till and outwash silty
sand and gravel.
* Ground water within the terrace feature is perched on the
glaciolacustrine soils, at depths below ground surface ranging
' from about 30 feet at the intersection of Northwest Seventh Street
and Taylor Avenue Northwest to about 20 feet at the recent slide
headscarp.
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Geo 11�oEngineers
* Slope movement has been occurring in the subject area for decades.
The recent slope movement occurred following an intense three-day
rainstorm. We expect that previous episodes of movement are also
related to weather conditions, together with man-caused
conditions.
* In addition to destroying segments of the main and other sewer
lines, the slide zone extends under the foundation of the
residence at 676 Taylor Avenue Northwest and encroaches into the
east rear yard area of the neighboring house to the south.
* Our analysis indicates that one of the critical elements in slope
movement at this site is the position of the perched ground water
in the slope.
' * Without repair or stabilization, future movement of the slope can
be expected, especially following periods of intense inclement
weather.
* Options that we have considered for reinstalling the Northwest
Seventh Street main sewer line and stabilizing the slope in the
vicinity of the line include:
i - a variety of slope drainage procedures,
regrading the slope to remove slide debris,
' - a retaining wall at the toe of the slope along Rainier
Avenue, and
a combination of the above.
* All of the alternatives considered for reconstructing the side
sewer line serving the homes east of Taylor Avenue Northwest are
technically feasible, but have significant construction
considerations.
* Our recommendations for repairs to the Northwest Seventh Street
trunk sewer and slope stabilization in that area consist primarily
of the following elements:
- Excavate the slide-disturbed soils and bench into underlying
intact soil.
- Sub-fill drainage.
- Construct a 22-foot-high gravity buttress or retaining wall
about 100 feet long at the slide toe.
' - Reconstruct the slope using structural fill, with the
finished surface sloped approximately 1.8H:1V.
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Geo d lEngineers
T A B L E O F C O N T ENT S
Page No.
INTRODUCTION 1
SCOPE 1
SITE HISTORY 2
PRIOR SLOPE MOVEMENT ALONG RAINIER AVENUE NORTH 2
RECENT SLOPE MOVEMENT 3
SITE DESCRIPTION 3
SURFACE CONDITIONS 3
' REGIONAL GEOLOGY 5
SUBSURFACE CONDITIONS 5
Soil Units 5
Ground Water 6
CONCLUSIONS AND RECOMMENDATIONS 6
GENERAL 6
SLOPE STABILITY 6
General 6
Mechanics of Slope Movement 7
Stability Analyses 7
Stabilization Measures 9
SEWER REPLACEMENT ALTERNATIVES 9
' General 9
Evaluation of Alternatives 10
DESIGN CRITERIA FOR SLOPE REPAIR 11
General 11
Excavation 11
Drainage 11
Slope Backfill 12
Criblock Wall Design Criteria 13
General 13
Foundation Support 13
Backfill 13
Lateral Resistance 13
' Drainage 14
OTHER CONSTRUCTION CONSIDERATIONS 14
Shoring of Excavations 14
Equipment Access 14
Sewer Line Embedment 14
Erosion Control 15
Construction Monitoring 15
MAINTENANCE 15
LIMITATIONS 15
List of Figures
Figure No.
VICINITY MAP 1
CITY OF RENTON N.W. 77TH STREET TAYLOR AVENUE N.W. TO
RAINIER AVENUE NORTH SLOPE STABILITY EVALUATION AND
SEWER LINE RECONSTRUCTION CROSS SECTION A-A' 2
CITY OF RENTON TAYLOR AVENUE N.W. TO RAINIER AVENUE N.
SLOPE STABILITY EVALUATION AND SEWER LINE
RECONSTRUCTION CROSS SECTION C-C' 3
CITY OF RENTON TAYLOR AVENUE N.W. TO RAINIER AVENUE N.
SLOPE STABILITY EVALUATION AND SEWER LINE
RECONSTRUCTION CROSS SECTION D-D' 4
CITY OF RENTON TAYLOR AVENUE N.W. TO RAINIER AVENUE N.
SLOPE STABILITY EVALUATION AND SEWER LINE
RECONSTRUCTION CROSS SECTION E-E' S
CITY OF RENTON TAYLOR AVENUE N.W. TO BASE OF SLOPE
SLOPE STABILITY EVALUATION AND SEWER LINE
RECONSTRUCTION CROSS SECTION B-B' 6
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Geo 1 Engineers
Table of Contents (continued)
APPENDIX A
Page No.
' FIELD EXPLORATIONS AND LABORATORY TESTING A-1
FIELD EXPLORATIONS A-1
LABORATORY TESTING A-2
List of Appendix A Figures
Figure No.
' SOIL CLASSIFICATION SYSTEM A-1
KEY TO BORING LOG SYMBOLS A-2
' LOGS OF BORINGS A-3a through A-9
GRADATION CURVES A-10 through A-14
ATTERBERG LIMITS TESTING A-15 and A-16
DIRECT SHEAR TEST A-17
APPENDIX B
Page No.
' SOIL UNIT DESCRIPTIONS AND CLASSIFICATIONS B-1
ii
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4-AlGeopEngineers
REPORT
' SUPPLEMENTAL GEOTECHNICAL ENGINEERING SERVICES
SEWER LINE RECONSTRUCTION AND SLOPE STABILIZATION
SLOPE WEST OF RAINIER AVENUE NORTH
RENTON, WASHINGTON
FOR CITY OF RENTON
INTRODUCTION
This report presents the results of our geotechnical evaluation
regarding replacement of sewer lines and stabilization of the slope between
' Taylor Avenue Northwest and Rainier Avenue North in Renton, Washington.
The project area is located west of Rainier Avenue North (Renton
' designation) in T23N, R5E, Section 7, Willamette Meridian. The specific
study area is opposite the Renton Airport between the north end of the
' Northwest Seventh Street easement and the base of the slope east of Taylor
Avenue Northwest, as shown on the Vicinity Map, Figure 1.
We initially evaluated the site during a brief reconnaissance conducted
April 8, 1991, shortly after slope movement occurred. Our conclusions for
this preliminary evaluation are presented in our report dated May 16, 1991.
' At that time, we recommended to the City that a detailed geotechnical study
be accomplished in order to develop repair and stabilization measures.
SCOPE
The purpose of our services is to evaluate the surface and subsurface
conditions in the project area in view of the pertinent geotechnical issues,
e.g. , foundation strength characteristics, drainage, excavation shoring
related to sewer line replacement and stabilization of the slope along
' Rainier Avenue North from the Northwest Seventh Street easement south to the
end of Taylor Avenue Northwest. We are to develop design criteria for use
' by the design consultant, James M. Montgomery Consulting Engineers, Inc. ,
and recommend alternative methods of permanent sewer line installation and
stabilization of slopes above Rainier Avenue North in the study area. Our
specific scope of services for this project includes the following:
1. Develop a geotechnical cross-sections and a site plan of the slope
1 movement features along the alignment of Northeast Seventh Street
between Taylor Avenue Northwest and Rainier Avenue North, and on
' the slope south of Taylor.
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Engineers
Geo\,
2. Explore subsurface conditions b drilling five power test borings
P Y g P g
and two hand borings. Piezometers were installed in all borings
along Taylor Avenue Northwest to monitor ground water conditions.
3. Monitor the piezometers through the winter and evaluate the data
to determine the effect of water levels on slope movement.
4. Perform a limited laboratory testing program to classify soil
' samples and evaluate pertinent soil characteristics to develop
appropriate strength values for slope stability analysis and
' remediation, and sewer line design.
5. Analyze slide characteristics and the effects of excavation and
placement of soil and backfill for the repair of the sewer line
east of Taylor Avenue Northwest and the main sewer line traversing
down the Northwest Seventh Street easement.
1 6. Develop recommendations for drainage, retaining structures or
other methods to stabilize the subject slope, and sewer line
placement.
7. Summarize our conclusions and recommendations in a written report.
8. Review design specifications for sewer line installation, and
' provide design criteria for shoring of planned excavations, as
appropriate.
' 9. Summarize the results of our ground water monitoring in a written
report.
' SITE HISTORY
PRIOR SLOPE MOVEMENT ALONG RAINIER AVENUE NORTH
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 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 following periods of heavy rain.
' We discussed the local slope movement history with Mr. Wayne Dorsey,
who has resided for approximately 30 years at 658 Taylor Avenue Northwest,
the southernmost residence along the east side of Taylor. Mr. Dorsey told
us he has observed two episodes of sliding in the time he has lived at this
location. The first slide occurred on the slope at the south end of Taylor
2
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Geo Q,114Engineers
APPENDIX A
' FIELD EXPLORATIONS AND LABORATORY TESTING
FIELD EXPLORATIONS
' Subsurface conditions at the project site were explored by drilling
seven test borings at the locations shown in Plate 1. Explorations were
located by site survey on the site plan provided by JMM and tied to our
cross-sections using cloth tape, hand clinometer and Brunton compass.
' The borings were drilled between August 5 and 13, 1991. Borings 1
through 5 were drilled with a truck mounted Acker Soilmax, using continuous
' flight, 4-inch-inside-diameter hollow-stem auger, to depths ranging from 20
to 67.5 feet. 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. Borings HA-6
and HA-7 were drilled with a hand auger to depths of 8.5 and 9.0 feet,
' respectively.
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 A-1. A key to the
' boring log symbols is presented in Figure A-2. The logs of the borings are
presented in Figures A-3 through A-9.
' 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.
1 A - I
1
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Geo Engineers
Piezometers were installed in borings B-1 B-2, and B-3 to allow for
' future monitoring of ground water levels at the site. A piezometer is also
installed in Geoconsultants boring B-1. Water level measurements were
accomplished on the day that each hole 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 wre tested to determine moisture content, dry
density, grain size and plasticity, and strength characteristics.
A number of soil samples were tested to determine their gradation. In
addition, six samples received Atterberg limits testing. These tests were
used to confirm the results of our visual-manual field testing. Results
of gradation and Atterberg limits testing are summarized in Figures A-10 and
' A-16, respectively.
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 A-17.
' A - 2
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SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP GROUP NAME
' SYMBOL
GRAVEL CLEAN GRAVEL GW GRADED GRAVEL,FINE TO
COARSE
COARSE COARSE GRAVEL
' GRAINED GP POORLY-GRADED GRAVEL
SOILS MORE THAN 50% GRAVEL GM SILTY GRAVEL
OF COARSE FRACTION WITH FINES
' RETAINED
ON NO. 4 SIEVE GC CLAYEY GRAVEL
MORE THAN 50%
RETAINED ON SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO
NO. 200 SIEVE COARSE SAND
' SP POORLY-GRADED SAND
MORE THAN 50% SAND SM SILTY SAND
OF COARSE FRACTION WITH FINES
' PASSES
NO. 4 SIEVE $C CLAYEY SAND
SILT AND CLAY ML SILT
FINE INORGANIC
' GRAINED CL CLAY
SOILS LIQUID LIMIT
LESS THAN 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY
' SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT
MORE THAN 50% INORGANIC
PASSES NO. 200 OH CLAY OF HIGH PLASTICITY, FAT CLAY
SIEVE
' 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 Dry - Absence of moisture, dusty, dry
visual examination of soil in general to the touch
accordance with ASTM D2488-84.
Moist - Damp, but no visible water
2. Soil classification using laboratory
tests is based on ASTM D2487-85. Wet - Visible free water or saturated,
usually soil is obtained from
3. Descriptions of soil density or below water table
' consistency are based on
interpretation of blowcount data,
visual appearance of soils, and/or
test data.
' � SOIL CLASSIFICATION SYSTEM
co
Geo�I Eno ineers
' W \�/ b FIGURE A-1
LABORATORY TESTS: SOIL GRAPH:
AL Atterberg limits
' SM Soil Group Symbol
CP Compaction
CS Consolidation (See Note 2)
DS Direct shear
' GS Grain - size Distinct Contact Between
%F Percent fines Soil Strata
HA Hydrometer analysis
' Gradual or Approximate
SK Permeability
Location of Change
SM Moisture content
Between Soil Strata
MD Moisture and density
SP Swelling pressure Water Level
TX Triaxial compression Bottom of Boring
UC Unconfined compression
' CA Chemical analysis
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 E] Location of sampling attempt
' with no recovery
10 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 (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.
CD
m
e� to- KEY TO BORING LOG SYMBOLS
Geo p Engineers
' 1W FIGURE A-2
' TEST DATA BORING B-1
' DESCRIPTION
Moisture Dry 3 ° Group
Content Density �0 Symbol Surface Elevation(ft.) : 121.6
Lab Tests (Y6) cf)
' 0 SM— 3 inches asphalt concrete 0
SM SU-D3 Brown silty fine to medium sand with fine gravel(loose,
24 moist)
SU-132 Brown silty fine to medium sand with fine gravel(medium
' dense,moist)(weathered till)
5 SM SU-D 1 Brown silty fine sand with occasional gravel(very dense, 5
moist)(till)
61
Rock fragment at 8.0 feet
10 10
' 11 115 50/5"
15 15
LU w 50/4"
' z
n
0 20 20
12 118 50/5" - 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-B2 Brownish gray silty fine to medium sand with gravel and 25
occasional cobble and coarse sand(very dense,wet)
(glaciolacustrine)
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N
30 ML SU-A5 Gray silt with a trace of fine sand(hard,moist) 30
o (glaciolacustrine)
50/4"
' 35 35
50/6" �
mRock fragment at 38 feet
oCL SU-A4 Gray clay with occasional fine gravel(hard,moist)
40 (glaciolacustrine) 40
Note:See Figure A-2 for explanation of symbols
' /�• Logof Boring
��� 9
Geo��Engineers
Figure A-3 a
' TEST DATA BORING B-1
(Continued)
' DESCRIPTION
Moisture Dry 3 a ° Group
Content Density aj 0 �n Symbol
' 40 Lab Tests (b) (pet) 40
59
45 45
26 99 2
' 50 50
' 54
' 55 55
'
~
w 33
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' a
p 60 CL SU-A4 Gray clay with thin lenses of sandy silt(hard,moist) 60
(laminated)(glaciolacustrine)
30 95 31
' 65 65
61
N Boring completed at 67.5 feet on 08/05/91
N Second hole augered to 36.0 feet depth 8.0 feet south for
piezometer installation.
v
70 70
0
See text for water level data
' 75 75
'N
0
m
180 80
0 Note:See Figure A-2 for explanation of symbols
' Its- Log of Boring
9 9
Geo l ngineers
0
Figure A-3 b
tTEST DATA BORING B-2
DESCRIPTION
Moisture Dry 3 r" Group
Content Density .0 Symbol Surface Elevation(ft.) : 111.0
Lab Tests (%) (pcf)
0 ; SM 1 inch asphalt concrete 0
SU-D3 Brown silty fine to medium sand with gravel(loose,moist)
(weathered till)
XXX
' 7 �
5 SM SU-D 1 Brown silty fine to medium sand with gravel(very dense, 5
moist)(till)
50/6" Gravels are stained below 6 feet
1
10 10
XX
12 123 50/6"
15 CL SU-C Light brown clay with sand and occasional gravel(hard, 15
moist)(glaciolacustrine)
w
Z_ 50/4"
CL
1
p 20 : SM SU-B2 Brown silty fine to coarse sand(very dense,moist) 20
(glaciolacustrine)
50/4"
25 25
' ML SU-B1 Light gray and brown sandy silt with occasional coarse
sand and fine gravel(hard,moist)(glaciolacustrine)
N 12 117 50/4"
'0)
U
30 30
50/5" ML SU-A5 Gray silt with lenses of fine sand(hard,moist)
' (glaciolacustrine)
35 35
'N 19 112 50/5"
0
m
40 40
o Note:See Figure A-2 for explanation of symbols
' ' 1%. Logof Boring
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G e o��Engineers
Figure A-4 a
TEST DATA BORING B-2
(Continued)
DESCRIPTION
Moisture Dry o a E Group
Content Density -U rn Symbol
40 Lab Tests (%) cf) 40
50/4" ML SU-A3 Brown silt with occasional sand(hard,moist)
(glaciolacustrine)
45 45
50/4" ML SU-A2 Brown to light brown silt with fine sand interbedded with
SP layers of fine to medium sand(very dense,moist)
(glaciolacustrine)
50 50
11 100 50/5"
55 ML, SU-AI Brown sandy silt(hard,moist (glaciolacustrine) 55
w
_z 50/6" �
x
F-
0 60 60
50/6"
Boring completed at 63.0 feet on 08/06/91.
Hole backfilled with bentonite-cement-sand slurry to 36.0 feet.
65 Piezometer installed to 36.0 feet. 65
rn
N See text for water level data
U
70 70
O
75 75
N
O
m
n
N
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D
Note:See Figure A-2 for explanation of symbols
Am"' Logof Boring
GeoIM ff Engineers g
i Figure A-4 b
TEST DATA BORING B-3
qu DESCRIPTION
Moisture Dry 3 a ° Group
Content Density �°U Symbol Surface Elevation(ft.) : 116.7
Lab Tests (%) cf)
0 SM 2 inches asphalt concrete 0
SU-D3 Brown to light brown silty fine to medium sand with
occasional gravel(loose,moist)(weathered till)
10 ■
5 5
SM SU-DI Brown to light brown silty fine to medium sand with
occasional ground(dense,moist)(till)
36 ■
10 10
50/6" Grades to very dense
15 15
F-
1 w z 50/6" ■
0 20 20
ML SU-A5 Brown to light brown sandy silt(hard,moist)
(glaciolacustrinc)
50/5"
25 25
17 112 50/6" ■
N
m
N
U
30 30
3
50/6" ■
Boring completed at 33 feet on 08/07/91.
Piezometer installed to 32.5 feet.
35 35
' See text for water level data
0
9 L
1 40 40
m
0 Note:See Figure A-2 for explanation of symbols
V.Law
Log of Boring
Geo 1.Engineers
' Figure A-5
TEST DATA BORING B-4
DESCRIPTION
Moisture Dry 3 a °' Group
Content Density � Symbol Surface Elevation(ft.): 51.6
Lab Tests M (pcf)
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
w
' w
LL
Z_
2
F-
a
p 20 Boring completed at 20.0 feet on 08/08/91 20
No ground water encountered
' 25 25
rn
U
30 30
O
35 35
'N
O
ao
ri
40 40
0 Note:See Figure A-2 for explanation of symbols
Logof Boring
Geo�ft Engineers g
`po Figure A-6
TEST DATA BORING B-5
DESCRIPTION
Moisture Dry 3 a ° Group
Content Density --2 0 Symbol Surface Elevation(ft.): 51.6
Lab Tests (%) (pef) PQU
0 CL SU-A6 Brown clay with sand and roots(soft,moist)(weathered 0
glaciolacustrine)
CL SU-A4 Gray clay(very stiff to hard,moist)
20
5 5
55
10 10
46
15 15
F-
w
w
u_
Z
2
a 39
Uj
p 20 Boring completed at 20.0 feet on 08/08/91 20
No ground water encountered
' 25 25
rn
iN
U
30 30
3
0
35 35
N
O
m
n
N
40 40
0 Note:See Figure A-2 for explanation of symbols
Ge01 .. Log of Boring
� �Engineers
�/
Figure A-7
TEST DATA HAND BORING HA-6
DESCRIPTION
Moisture Dry 3 a Group
Content Density --U . Symbol Surface Elevation(ft.): 83.00
Lab Tests (96) (Oct)
0 GM Brown silty fine to coarse gravel with sand(loose,moist)(fill) 0
o � o
0
1 CL SU-A4 Gray clay(soft,moist)(glaciolacustrine,remolded by slope
movement)
2
3
' 4
5 5
6
wui
w
Z 7
2
F-
� 8
Boring completed at 8.5 feet on 08/13/91
9
' 10 No ground water encountered 10
m 11
N
U
12
O
13
' 14
15 15
0
m
N
O
16
ID
0 Note:See Figure A-2 for explanation of symbols
Lo of Hand Borin
�p•� 9 9
Geo%IN Engineers Figure A-8
1 9
TEST DATA HAND BORING HA-7
r `o DESCRIPTION
o c
Contente Density u Syrmbo1 Surface Elevation(ft.): 68.50
0 Lab Tests (%) c fi
o Qp GM Brown silty fine to coarse gravel with sand(loose,moist)(fill) 0
o
0
1 CL SU-A4 Light brown clay(soft,moist)(glaciolacustrine,remolded
by slope movement)
2
3
4
I 5 5
6 SM SU-A4 Brown silty fine to medium sand(medium dense,moist)
(glaciolacustrine)
r W
Z 7
n
uj
8 SM SU-A4 Light brown interbedded silty fine sand and silt(dense/very
ML stiff,moist)(glaciolacustrine)
9
Boring completed at 9.0 feet on 08/13/91
' 10 10
See text for water level data
m 11
N
2 12
U
3
0
13
14
15 15
0
m
N
m 16 —
0 Note:See Figure A-2 for explanation of symbols
L f
A��.. og o Hand Boring
Geo N�Engineers Figure A-9
OP 3L
U . S . STANDARD SIEVE SIZE
��• �1�,�,��, �,�� � �° �° �° �o ,�o° goo
�p 100
C
A rii 90
N11
80
• w 70
44
('t) m 60
z 50
40
z
u 30
w
20
10
Q
D 0
m D 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
O -4
C 5 GRAIN SIZE IN MILLIMETERS
m Z
m
0 COBBLES GRAVEL SAND SILT OR CLAY
n C COARSE FINE COARSE MEDIUM FINE
O m EXPLORATION SAMPLE
N SYMBOL NUMBER DEPTH SOIL DESCRIPTION
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 CSM/MLA
0693-027-R02 KGN : KKT 9/ 17 /91
U. S . STANDARD SIEVE SIZE
ti� �,��'���• ���. � do o �° �o ~oo goo
100
90
eff rii
O '
I- 80jilt w 7 0
m 60
z 50
LL 40
z
Lu
30
w
20
10
m FRTT III I I I, I .. .
D p
LH
m n 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 00 1
C GRAIN SIZE IN MILLIMETERS
m
Z
0 COBBLES GRAVEL SAND SILT OR CLAY
C COARSE FINE JCCIARSEI MEDIUM I FINE
j
-+ EXPLORATION SAMPLE
m SYMBOL NUMBER DEPTH SOIL DESCRIPTION
N
B-1 31 . 5 ' GRAY COARSE SILT WITH VERY FINE SAND (ML)
B-1 46 . 5 ' GRAY SILT WITH OCCASIONAL FINE TO MEDIUM
SAND (ML)
• B-1 66 . 5 ' GRAY CLAY WITH OCCASIONAL FINE TO MEDIUM
SAND (CL)
W 3W � = = = = m = = = = = = = m
0693-027—R02 KGN : KKT 9/ 17 /91
U . S . STANDARD SIEVE SIZE
��• �1���� ��� � �� ti� �'`� �� moo ��o
� 1 0 0 � ti' �\ �� �p. �p. �p. �p. �p• �p• �p.
O
90
\l�\=
80
w 70
3
(ID m 60
z it
S0 - -
LL
40
z
w
� 30
w
a 20
10
UFT
a 0
�t n 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
C GRAIN SIZE IN MILLIMETERS
Z
m GRAVEL SAND
C
a a COBBLES COARSE FINE COARSE MEDIUM FINE SILT OR CLAY
�
..►
►v m EXPLORATION SAMPLE
co) SYMBOL NUMBER DEPTH SOIL DESCRIPTION
B-2 12 . 5 ' LIGHT BROWN SILTY FINE TO MEDIUM SAND
WITH OCCASIONAL COARSE SAND AND FINE
GRAVEL (SM)
-- B-2 27 . 5 ' LIGHT GRAY— BROWN FINE TO MEDIUM SANDY
SILT WITH OCCASIONAL COARSE SAND AND
FINE GRAVEL (ML)
0693-017 -R02 KGN : KKT 9 / 17 /91
U . S . STANDARD SIEVE SIZE
ti� �,�c,.��c,• ��c,. �` do �o �° �o ~oo goo
100
90
\1\\= 4t-c
�- 80
w 70
3
m 60
v: A4
z 50
40
z
w
30
w
20
10
am
f7
a 0
°y 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
G) -4
C C GRAIN SIZE IN MILLIMETERS
m Z
m COBBLEs
a C COARSE
FINE COARSE MEDIUMND FINE SILT OR CLAY
G1 m EXPLORATION SAMPLE
N SYMBOL NUMBER DEPTH SOIL DESCRIPTION
B-2 37 . 5 ' GRAY SILT WITH A TRACE OF FINE SAND (ML)
B-2 52 . 5 ' LIGHT GRAY SILTY FINE SAND (SM)
3PR = = = = = m m m = m = = m r w
0693-027 -R02 KGN : KKT 9/ 17 /91
U . S . STANDARD SIEVE SIZE
~°° goo
(� 1 0 0
C
90 14111
\l\\= 80
w 7 0
m 60
z 50
40
z
w
30
w
w 20
10
G)
m I a I I:
D 0
•n D 1000 100 10 1 . 0 0 . 1 0 . 01 0 . 001
23 -1
C F) GRAIN SIZE IN MILLIMETERS
m Z
m COBBLES
a C COARSE FINE
FINE COARSE MEDIUM ND FINE SILT OR CLAY
I �
4 m EXPLORATION SAMPLE
N SYMBOL NUMBER DEPTH SOIL DESCRIPTION
B-3 27 . 5 ' GRAY SILT WITH FINE TO MEDIUM SAND AND
OCCASIONAL FINE GRAVEL (ML)
B-4 7 . 5 ' GRAY CLAY WITH OCCASIONAL FINE TO MEDIUM
SAND (CL)
• B-5 12 . 5 ' GRAY SILT WITH A TRACE OF VERY FINE
SAND (ML)
0693-027-R02 KGN : KKT 09-17 -91
60
PLASTICITY CHART
50
`1\\- CH
0 40
Z
30
U
•
�- OH and MH
20
a.
CL ZA
> 10
m CL-ML .' ML and OL
W
m 0
0 10 20 30 40 50 60 70 80 90 100
In
r LIQUID LIMIT
C ;
W -1
m N EXPLORATION SAMPLE MOISTURE LIQUID PLASTICITY
a m NUMBER DEPTH CONTENT (o) LIMIT (o) INDEX (o) SOIL DESCRIPTION
� N
B-1 • 41 . 5 ' 27 . 3 51 . 0 26 . 5 GRAY CLAY WITH OCCASIONAL
CW VERY FINE SAND (CH)
B-1 • 46 . 5t 26 . 3" 43 . 8 15 . 6 GRAY SILT WITH OCCASIONAL
FINE TO MEDIUM SAND (ML)
I B-1 ■ 66 . 5 30 . 3" 44 . 5 22 . 6 GRAY CLAY WITH OCCASIONAL
FINE TO MEDIUM SAND (CL)
"M . C. S TAKE AFTER DI ECT SHEAR TE T
0693-027-RO2 KGN : KKT 9/ 17/91
60
PLASTICITY CHART
50
CH
0 40
Z
30
u
OH and MH
20
CL ■
•
10
m CL-ML �� ML and OL
m 0
0 10 20 30 40 50 60 70 80 90 100
In r LIQUID LIMIT
C ;
m N EXPLORATION SAMPLE MOISTURE LIQUID PLASTICITY
> m NUMBER DEPTH CONTENT (off LIMIT INDEX SOIL DESCRIPTION
L N
B-3 • 27 . 5 ' 17 . 4 36 . 5 11 . 8 GRAY SILT WITH FINE TO MEDIU
m m SAND (ML)
�p B-4 ♦ 7 . 5 ' 21 . 4 33 . 0 11 . 9 GRAY CLAY WITH OCCASIONAL
r FINE TO MEDIUM SAND (CL)
N B-5 ■ 12 . 5 22 . 6 36 . 5 15 . 3 GRAY CLAY WITH OCCASIONAL
FINE TO COARSE SAND (CL)
DIRECT SHEAR TEST RESULTS
Sample Moisture Dry Normal Peak Shear
Boring Depth Content Density Pressure Strength
' Number feet Sample Description
1 31.5 Gray sift withfill sand(ml) 20.1 108.5 3,100 2,870
6,500 4,290
9,500 6,300
1 46.5 Gray clay with interbeds of 26.3 98.5 4,600 3,190
gray sift and lens of very 9,500 6,320
. fine sand (cl&ml) 14,000 6,300
1 61.5 Gray clay(cl) 31.4 93.0 6,500 4,670
12,000 6,180
' 18,000 5,920
1
Figure A-17
.�.
oq
X
H
a
r � r � � � � � � � � � � � � � � � �
' APPENDIX B
SOIL UNIT DESCRIPTIONS AND CLASSIFICATIONS
' FILL Brown Silty Fine to Coarse GRAVEL with sand and occasional bark,
plastic, and concrete (GM) . Fill material is loose to medium dense and
' moist.
SU-Al Brown Sandy SILT (ML) . This unit is a glaciolacustrine deposit
' and is hard and moist.
SU-A2 Light Brown SILT with layers of fine to medium sand (ML) . This
' unit is a glaciolacustrine deposit and is hard to very dense and moist.
SU-A3 Brown SILT with occasional sand (ML) . This unit is a
glaciolacustrine deposit and is hard and moist.
SU-A4 Cray CLAY with occasional interbedded silt and fine sand
(CL/CH) . This unit is a glaciolacustrine deposit, is hard and moist, and
' has a finely laminated structure.
SU-A5 Gray SILT with interbedded sand and gravel (ML) . This unit is
a glaciolacustrine deposit, is hard and moist, and has a massive structure.
' Where remolded by slope movement, SU-A5 is soft to medium stiff and moist.
SU-B1 Light Gray and Brown Sandy SILT with occasional gravel and
' cobbles (ML) . This unit is a glaciolacustrine deposit and is hard and
moist.
' SU-B2 Brown Silty Fine to Coarse SAND with varying amounts of gravel
(SM) . This unit is a glaciolacustrine deposit and is very dense and moist.
Where remolded by slope movement, SU-B2 is loose and moist.
' SU-C Brown to light brown CLAY with varying amounts of sand and
occasional gravel (CL) . This unit is a glaciolacustrine deposit and is hard
' and moist. SU-C is soft and moist where remolded by slope movement.
SU-D1 Brown silty fine SAND with occasional gravel (SM) . This unit is
' a glacial deposit (till) , and is dense to very dense and moist.
SU-D2 Brown silty fine to medium SAND with fine gravel (SM) . This
unit is a weathered glacial deposit (till) , and is medium dense and moist.
' SU-D3 Brown silty fine to medium SAND with fine gravel (SM) . This
unit is a weathered glacial deposit (till) , and is loose and moist) .
' SU-E Brown to light brown silty fine SAND with occasional gravel and
roots (SM) . This unit is a slope deposit and is medium dense and dry.
' B - 1
t,o;?\Engineers
Avenue several years ago, following construction of a primitive road across
the toe of the slope. The second slide is the most recent slope movement.
Mr. Dorsey reports that approximately five years ago fill was placed
downslope from the north end of Taylor for construction of the house at 676
' Taylor. Mr. Dorsey recalled that both slope movements occurred after some
type of slope modification.
RECENT SLOPE MOVEMENT
Mr. Chet Rindfuss, who owns the house at 676 Taylor Avenue Northwest,
first observed slope movement north of his property during the winter of
1989-1990, developing the scarp located closest to the end of Northwest
Seventh Street. The most recent slope movement, evaluated by our study,
occurred during the first week of April, 1991 after an intense rainstorm.
According to City of Renton maintenance personnel, movement occurred on the
' morning of Friday, April 5, 1991, several hundred feet north of the project
area. Movement occurred at the site the morning of Saturday, April 6, 1991,
' and was witnessed by Mr. Rindfuss. Mr. Rindfuss told us that soil and trees
flowed from the toe of the slope across the southbound lanes of Rainier
' Avenue North with the trees still upright. Mr. Rindfuss said that initially
there were only a few inches of vertical offset in his yard. As time
progressed, downsettling of the yard area continued. Currently, the east
' edge of his lawn is offset approximately 7 to 9 feet vertically from its
pre-April 1991 position. Movement is continuing along the upper scarp, and
' offset is developing along cracks adjacent to the headscarp. The location
of the 1991 scarps and cracks are shown on Plate 1.
SITE DESCRIPTION
SURFACE CONDITIONS
' The project slope extends between Elevation 45 feet at the toe along
Rainier Avenue to approximately Elevations 45 and 115 feet at the crest.
Overall site characteristics are shown on the attached Site Plan, Plate 1,
and on Cross-Sections A-A' through E-E' , Figures 2 through 6. Cross-
Sections A-A' , C-C' , D-D' , and E-E' , in Figures 2, 3, 4 and 5, extend from
the east portion of Rainier Avenue North to the west side of Taylor Avenue
Northwest. Cross-Section B-B' , Figure 6, extends northward from the base
' of the slope south of Taylor Avenue up to and along Taylor to the north side
3
S
Printed an rcycled paper-
1 PlEn ineers
�. g
of Northwest Seventh Street. Elevations referenced herein are based on a
benchmark located on a utility pole at the east end of Northwest Seventh
Street.
The hillside is generally undeveloped, except for the sewer line and
1 storm drain constructed along the Northwest Seventh Street easement. Back
yards of four homes are located along the top of the slope. We are
uncertain of dates of grading and home construction. Mr. Dorsey has resided
at 658 Taylor for 30 years. We do not know if he is the original owner.
Some of the debris along the top of the slope includes large pieces of
' metal, which may date back decades to the time of railroad logging, and
suggest that some grading may have occurred prior to development for homes.
' The home at 676 Taylor is the most recent construction, approximately 5
years old.
' The slope is vegetated with alder saplings and dense blackberries.
Individual large maple, spruce, cedar, and hemlock trees are growing along
the top of the slope, in yards at the top of the slope, and along Taylor
' Avenue Northwest.
There are no surface drainage features, except for springs along the
' slope and a depression and channel south of the project area. Water from
lots west of Taylor Avenue drains into the Taylor Avenue storm drain, which
' drains south along Taylor Avenue Northwest. Water from lots east of Taylor
Avenue drains overland eastward out over the slope.
The primary area of 1991 slope movement addressed in this study extends
' from slightly north of the Northwest Seventh Street right-of-way to the
south for a distance of about 100 feet. The recent slide zone is shown on
' Plate 1. The surface of the 1991 slump-earthflow feature is comprised of
a series of steps consisting of irregular benches separated by near-vertical
scarps. Bench surfaces vary from gently sloping into the hill to sloping
isteeply outward. The overall slope is generally steeper (60 percent to
nearly vertical) over the lower 50 feet and flattens to approximately 20
' percent to 40 percent in the upper 20 feet or so.
South of the 1991 slide area, slopes are somewhat more uniform.
Backyard areas, located between the top of the slope and about Elevation 100
feet, slope east at approximately 10 percent. The backyard surfaces were
levelled during home construction, with excavated materials pushed out over
' the edge of the slope as uncompacted fill. From the slope break at about
Elevation 100 feet down to Elevation 80 feet, slopes steepen to from 70
4
\OEngineers
percent to near vertical or overhanging where fill material is present, and
' are inclined at about 50 percent where no fill is present. The middle
portions of the slope, between Elevations 80 and 60 feet, flatten to about
70 percent. Between Elevation 60 feet and the elevation of the sidewalk
' along Rainier Avenue, slopes average 80 percent.
Slopes south of Taylor Avenue Northwest are similar to those found
along Rainier Avenue North, except for isolated locations where undercutting
by equipment access road construction has produced small-scale slope
' movements.
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 margins 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 rocks 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.
' SUBSURFACE CONDITIONS
Soil Units: The soils were classified using the Unified Soil
Classification System (USCS) visual-manual procedure, with confirmation of
fine-grained soils based on Atterberg Limits testing. An explanation of
USCS and a summary of laboratory test results is included in Appendix A.
Soil units (SUs) were designated based on physical characteristics
identified during measurement of the cross-sections and geologic
interpretation, and confirmed during subsurface exploration. Explorations
included five power borings using hollow stem auger, and two hand borings.
' Boring logs are included in the Appendix. We also used information from a
log provided by Geoconsultants, Inc. for their boring B-1, located about 10
' feet east of the northeast corner of the residence at 676 Taylor Avenue
Northwest.
5
Printed on recycled paper.
Geo*Engineers
' SUs were given a letter designation (for example, SU-A) for discussion
' of specific soil conditions. SUs are local in scope and are not intended
for projection beyond the immediate project area.
The SUs encountered are fine-grained glaciolacustrine deposits overlain
by glacial till and slope deposits. Glaciolacustrine deposits consist of
silt and clay with fine sand interbeds. The glacial till and slope deposits
are silty fine sand with gravel. SUs and fill material are shown on the
Site Plan, Plate l; and Geotechnical Cross-Sections, Figures 2 through 6.
' Descriptions and classifications are shown on the boring logs in Appendix A,
and are outlined in Appendix B.
Ground Water: Water was observed during our reconnaissance on April 8,
' 1991, emerging from the lower portion of the slope, approximately downslope
from the position of the broken sewer line. Slopes were drier during our
' August 1990 field work and explorations. Soils observed at that time ranged
from moist to dry. Ground water was encountered in borings B-1 and HA-7,
' perched in silty sand (SU-B1 and SU-B2) above sandy silt (SU-A4) along the
main sewer alignment. We measured ground water levels at 21.7 feet depth
(Elevation 99.9 feet) in boring B-1, 24.3 feet depth (Elevation 86.7 feet)
' in boring B-2, 35.6 feet depth (Elevation 81.1 feet) in boring B-3, and 28.3
feet depth (Elevation 81.1 feet) in Geoconsultants boring B-1 on August 13,
' 1991.
CONCLUSIONS AND RECOMMENDATIONS
' GENERAL
In our opinion, it is feasible to reinstall the sewer lines that were
broken by slope movement in April 1991 along the former sewer alignment,
provided that slopes are drained and stabilized. We also recommend
stabilizing the landslide area adjacent to the pipeline for a minimum width
' of approximately 100 feet, extending from the north end of the Northwest
Seventh Street easement to the south edge of the recent slide area.
SLOPE STABILITY
General: The stability of slopes within the project area were
' evaluated in part by site-specific examination of the distribution and
physical characteristics of soil units and ground water, and relating these
' characteristics to the existing topography. A general soil stratigraphy was
' 6
Printed on recycled paper.
Geo MOPE ngineers
developed in the field and confirmed by drilling. Soil samples were closely
' examined for strength characteristics, variations within soil units between
borings, and changes in consistency after remolding by slope movement.
We conclude that there is no evidence of past massive slope movement
south of the recent slide area, except for localized features south of
Taylor Avenue Northwest that developed after a road was excavated along the
toe of the slope. This is supported by a relatively uniform slope angle and
continuity in distribution of the soil units across this area.
' Mechanics of Slope Movement: In our opinion, the slope movement of
April 6, 1991 which severed the subject sewer pipes occurred largely as a
result of locally increased hydrostatic pressures following exceptionally
' heavy rains during the first week of April. Movement at the toe of the
slope initiated as a flow of viscous soil that carried upright trees across
the southbound lanes of Rainier Avenue North. Movement propagated upslope
as downsettling and sliding of relatively intact blocks of soil and fill
' material after loss of support occurred along the toe of the slope.
Movement migrated upslope to portions of the slope that had not been
affected by slide activity during the five years since fill was placed for
' construction of the home at 676 Taylor Avenue North. We have observed that
displacement along a northwest-trending crack near the top of the scarp has
' increased during the last two months. It is apparent, therefore, that
movement of the uppermost block is continuing at this time. Distress
' appearing in the foundation of the house at 676 Taylor Avenue North is, in
our opinion, a result of continuing slope movement.
Stability Analyses: Slopes were analyzed using an integrated slope
stability analysis program, XSTABL, Version 3.2, by Interactive Software
Designs, Inc. of Moscow, Idaho. This program facilitates analysis for a
' wide range of failure geometries, any arrangement of soil units and strength
parameters, and single or multiple ground water zones. Input parameters
' include slope topography; soil unit distribution; piezometric surfaces;
loads and other outside influences placed on the slope; and slope analysis
criteria, such as method, initiation and termination points, and numbers of
' iterations.
The relative stability of a slope is typically expressed in terms of a
' factor of safety against movement for the critical (most likely) surfaces
along which movement may occur. A factor of safety of 1.0 corresponds to
���ty
' Geo\Engineers
the condition in which the resisting and driving forces are equal; movement
would theoretically be imminent as the result of a small decrease in
resisting force or increase in driving force. A factor of safety larger
than 1.0 indicates that the resisting force is greater than the driving
' force.
The slope above Rainier Avenue was essentially at or slightly below a
factor of safety of 1.0 before movement occurred. The continuing
downsettling along the upper portion of the slope indicates that the factor
of safety in this area is still below equilibrium.
' Our slope analyses are directed to evaluate the extent to which ground
water conditions, slope configurations, or soil strength parameters need to
' be modified so that a factor of safety of 1.3 will be achieved for static
(i.e. , nonearthquake) conditions along the main sewer line alignment. We
first developed initial safety factors by using estimated values for
cohesion (C) and an angle of internal friction (0) for each soil unit based
on our experience in similar locations and then conducted preliminary back-
analyses of the slide area conditions to compare how our process model
compared with actual slope movements. We then utilized laboratory test
' values for soil density, C and 0 to refine our analyses of the recent slide
area and adjacent slopes, and evaluate design alternatives for slope
stabilization. Soil parameters used in the refined stability analysis are
summarized in Table 1.
TABLE 1
SOIL PARAMETERS
' Soil Unified Soil Unit Weight (PSF)
Units Class. Origin Moist Saturated (Degrees) C PSF
' SU-Al ML Glaciolac. 112 118 25 225
SU-A4,A5 ML,CL,CH Glaciolac. 116 125 23 1100
' ML,SM,GM Slide Debris 116 120 20 250
SU-B2 SM Glaciolac. 116 130 32 0
SU-D1 SM Till 116 120 36 0
' SU-D3 SM Wthrd. Till 116 120 35 100
GM,SM Fill 120 123 32 0
' 8
1
,n ecvcled paper
We also analyzed the slope south of the recent slide area to evaluate
the potential for movement where failure has not occurred. Our analysis
indicates that even under saturated conditions, the slope is stable. In our
opinion, this slope will likely remain stable in its current undeveloped
condition. This slope could be destabilized by removal of vegetation,
excavation, filling, or concentration of runoff.
Stabilization Measures: Possible stabilization options considered
include: 1) dewatering the slope using interceptor drains; 2) removing the
slide debris, constructing a retaining wall at the toe and rebuilding the
slope without drainage measures; and 3) the same as Option 2 with the
addition of interceptor drains to remove ground water along the base of the
tslide mass.
We recommend proceeding with Option 3. In our opinion, Options 1 and 2
' do not merit pursuit for the reasons summarized below.
Option 1 would increase the factor of safety against expanded future
t sliding to about 1.15, but would have little benefit to the existing slide-
disturbed zone. It would require very deep excavation (about 30 feet deep)
along Taylor Avenue and would be very expensive relative to the benefits
accomplished.
Option 2 would increase the factor of safety against expanded future
sliding to about 1.19 and it would improve the existing stability, but not
to the desired degree. Without excavation of the existing slide debris,
adequate stabilization of the wall and hillside would require an extra thick
wall or some form of wall tiebacks. In our opinion, the factor of safety
benefits do not merit the cost of this option.
' For Option 3, the wall would be either a structural wall constructed of
reinforced concrete or of concrete or steel soldier piles with lagging. The
' City also requested our consideration of a gravity wall such as a criblock
or a gabion structure. A gravity wall requires much more excavation to
accommodate its base width than is typical for a soldier pile structural
wall, but in this case, that excavation is recommended anyway to remove the
existing slide debris. A combination of a retaining wall with slope drains
' and slope regrading increases the factor of safety to approximately 1.45.
We understand that a 16-inch-diameter water main is located along the
' west edge of Rainier Avenue. We also understand that the City desires to
restore the backyard area of 676 Taylor Avenue as much as possible to its
9
Printed on recycled paper,
4--
e() , Engineers
pre-1991 slide configuration. The location of the water line forces the new
' wall to be located several feet west of the west sidewalk along Rainier
Avenue. Regrading of the slope to the inclination recommended below and to
restore the backyard of 676 Taylor Avenue requires the new wall to extend
' 22 feet in height above the level of the east Rainier Avenue sidewalk.
For Option 3, we recommend a gravity wall along the base of the slope
west of Rainier Avenue, excavating and removing the slide material,
constructing benches in underlying silt and clay, and rebuilding the slope
' with a compacted structural fill keyed to the native stable soils on the
benches. Example trade names of the type of gravity wall preferred by the
City include Criblock and Gabion.
We recommend construction of an interceptor drain on the highest bench,
one on a midslope bench, and one behind the heel of the retaining wall.
Specific design criteria for the slope repair are presented below in the
section entitled "DESIGN CRITERIA FOR SLOPE REPAIR. "
' SEWER REPLACEMENT ALTERNATIVES
General: Sewer replacement alternatives are closely tied to the
methods evaluated for slope stabilization. A key element considered in
sewer line placement is the benefit that could be achieved by constructing
a deep trench along Taylor Avenue Northwest that would both carry the sewer
' line and act as an interceptor drain. Initial alternatives considered for
the new sewers include:
' Alternative 1 - Construct a new sewer line along Taylor Avenue
Northwest to service all of the homes along both sides of the street.
' We considered constructing the sewer at a number of different
elevations, depending on the amount of subsurface drainage to be
intercepted. Construction of this alternative would necessitate
reconstructing a portion of the Northwest Seventh Street main sewer
line about 30 feet deep to facilitate gravity flow.
Alternative 2 - Reconstruct the new sewer line along the existing
easement along the top of the slope east of Taylor Avenue. This
' alternative would provide service to 658 and 664 Taylor Avenue. All
other service lines would remain intact. Under this alternative, the
Northwest Seventh Street main sewer line remains as is. The new sewer
' would have to be about 20 feet deep to intercept subsurface drainage
flowing toward the steep slope.
' 10
Printed on recycled paper.
Geo Engineers
Alternative 3 - Construct a new sewer line northward along the easement
from the existing cleanout east of 664 Taylor north approximately 20
feet and then directly downslope to Rainier Avenue North. This
alternative would not affect the Northwest Seventh main sewer line, and
' would provide service as outlined for Alternative 2.
Evaluation of Alternatives: Design considerations for sewer line
' alternatives are outlined in Table 2. In our opinion, either Alternative
2 or 3 are technically feasible, but both have significant considerations
' to evaluate related to construction, including equipment access, limited
working space, and considerations for protecting adjacent property and
vegetation on the slope.
Constructing a deep trench along Taylor Avenue North (Alternative 1)
sufficiently deep (30 feet) to intercept ground water is not a viable
' alternative for slope stabilization. This alternative would be very
difficult to achieve because of equipment limitations, space, access for
' homeowners, and complications related to existing buried and overhead
utilities.
Since subsurface water will be intercepted beneath the reconstructed
' slope, the Northwest Seventh Street main sewer line can be buried at normal
construction depths. We understand that a curved gravity pipe will be
' placed within the upper portion of the reconstructed slope.
DESIGN CRITERIA FOR SLOPE REPAIR
General: Slope repair will consist of constructing a 22-foot-high
gravity wall approximately 100 feet long to support the regraded slope. We
understand that Criblock or gabion baskets are the preferred alternative.
Regrading must consist of excavating all slide material within and south of
the Northwest Seventh Street easement; constructing benches in underlying
' undisturbed native soils, constructing interceptor drains along the highest
and middle benches, down the fall line of the slope beneath the fill and
' behind the retaining wall; and constructing a structural fill on the
benches. General design criteria are presented in this section.
11
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TABLE 2-DESIGN CONSIDERATIONS FOR SIDE SEWER LINE LOCATION ALTERNATIVES
NORTHWEST SEVENTH STREET AND TAYLOR AVENUE NORTHWEST TO RAINIER AVENUE
PENTON,WASHINGTON
DESIGN
SUITABIUTYAND EFFECTIVENESS LIMITING CONSTFIUCTION EXCAVATION MATERIALS
LTERNATIVE L FOUNDATION FACTORS PROBLEMS CHARACTERISTICS CONSIDERATIONS
1. Construct a side sewer line along Taylor Ave.NW to service all cf the homes
along the street
A. Drop manhole at south and north ends to EL 102.0 Minimal Improvement on Suitable Depth of ditch Requires pavement removal and Common. Sall not sultaNe for
downslope stab Itty (12 to 18 feet) reconstruction,shoring,new hookups; backlIll-haul to waste;
construct during dry weather. Import baddlil materiels.
fv
B.Drop elevation at north end of Taylor Ave to 80.0. Beneflb stability downslops Suitable Depth of excavation, Requires special trench shoring and Common Sall not suitable for baddlll-
by acting as cutoff trench specs limitations. excavation to 30 ft depth;sheet closure, Install drain In bottom,Import
for ground water flow, reinstallation of other utflitles required; materiels for bacidil.
construct during dry weather.
Construct side sewer line following existing easement along top of slope east Minimum Improvement on Suitable M founded Steep,wet,unstable slope, Requires specialtred equipment to access Common Must end-haul,waste
of houses to service SM and 864 Taylor Ave.NW. 870 and 676 Taylor Ave.NW downslope stability unless below bees of slide. narrow easement top of slope. Little room for equipment excavated edi,import
remain connected directly to the main sewer line. trench is deep enough(20feel)to to work without removing vegetation or bacMll material.
Intercept ground water,shoring yards, Spedeltred shoring needed
needed to protect property because of Instability. Construct during
upslope while trench is open. dry weather.
3. Construct side sewer line for 058 and 684 Taylor Ave.NW northward along Suitable-minimal benefit to stability; Suitable Steep slope, Requires spedellaed equipment to access Common Must end-haul,waste
easement from cleanouteast of 884 Taylor Ave.NW approximately 20 feet north, stable If construced during dry narrow easement top d slope. Spedaltred shoring needed excavated Boll,Import
and then dawn the slope drectly seat to RelnierAve.N. The two homes at the season,bacidilled with compacted for short segment along easement bacMlll material,
north end d Taylor Avenue NW(870 and B78)are connected directly to the main granular materials. Stability along
sewer line. Taylor Ave.NW Is the same as
AftematM IA.
Geo 10Engineers
Excavation: We recommend that all of the slide-disturbed soil within
1 the repair zone be excavated. The slide material averages 8 to 10 feet
thick adjacent to the Seventh Street sewer and somewhat thinner toward the
edges of the slide zone identified on Plate 1. The excavation should be
extended not less than 40 feet to the north and about 60 feet south of the
existing sanitary sewer manhole at which the Seventh Street main sewer is
' connected. This generally extends to the north and south edges of the
Northwest Seventh Street right-of-way. Benches must be excavated into the
intact native soils which underlie the slide to key the new fill into the
slope. We recommend that the benches be at least 8 feet wide, and be sloped
into the hillside at about 2 percent. Each bench must be sloped to drain
toward the center drainpipe at 1 percent. Slopes between the benches may
be excavated at 1H:1V.
1 We anticipate that most of the slide material will consist of clay and
silt soils. The excavated materials will not be suitable for use as
backfill or other construction applications, with the exception of pipe-
trench check dams, as described below, and should be hauled off-site to a
waste site.
' Drainage: We recommend that interceptor subdrainage trenches be
excavated along the inslope edge of the uppermost bench and one midslope
' bench, directly downslope along the centerline of the excavation and along
the heel of the retaining wall. We recommend that the subdrainage trenches
' be at least 18 inches deep and 18 inches wide; the centerline drainage
trench should be constructed a minimum of 18 inches below the inslope edge
of each bench.
' We recommend that backfill in the subdrainage trenches comply with the
specification for Gravel Backfill for Drains, as described in Section
9-03.12(4) of the Washington State Department of Transportation 1991
Standard Specifications for Road, Bridge and Municipal Construction (WSDOT -
1991) . Coarser screened gravel such as 7/8-inch washed or 1-1/2-inch
washed gravel is not acceptable. We recommend that a geotextile filter
fabric (Mirafi 140N or equivalent) be placed to separate the gravel backfill
from adjacent fine-grained native soils. Perforated drainpipe of 6-inch
minimum diameter should be placed in each drain trench about 6 inches above
the trench invert within the pea gravel backfill. The drainpipe can be
' 13
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G e o woEngineers
corrugated, perforated HDPE or equivalent. Lightweight corrugated plastic
"drainpipe" is not acceptable. All of the drain lines should be sloped at
not less than 1 percent (S — 0.01) . The interceptor drain should not
discharge into the perforated drain behind the gravity wall. Instead, the
slope drains should be connected to a tightline behind the criblock wall and
ultimately directed to the storm sewer in Rainier Avenue North.
We recommend that "check dams" be constructed across the downslope
drainage trench at every bench to prevent movement of water through the
backfill material and redirect water into the centerline perforated drain.
Check dams should be constructed of clay, silt, or sand with at least 40
percent fines, and should extend from the base of the trench surrounding the
' drainpipe and extend to the top of the pea gravel backfill. We expect soils
excavated from the slide area will meet this criteria. We recommend that
' the check dams be at least 18 inches wide, and be notched into the native
silt and clay at least 6 inches beyond the trench sidewalls.
Slope Backfill: We recommend that the material used to rebuild the
' slope consist of sand and gravel with less than 5 percent fines. This can
be either bank-run or processed borrow and must comply with WSDOT - 1991
LSection 9-03.14, Gravel Borrow, except that the maximum percentage passing
a No. 200 sieve must not exceed 5 percent. The backfill must be placed as
structural fill compacted to at least 92 percent of the maximum dry density
(MDD) as defined by American Society for Testing and Materials (ASTM)
D-1551, or 95 percent of MDD per WSDOT Test Method No, 609. The maximum
' loose lift thickness should be 8 inches. We recommend that the finished
slope surface be no steeper than 1.8H:1V. We recommend that the lateral
' margins of the fill slope also be constructed no steeper than 1.8H:1V. In
addition, we recommend an 8-foot-wide bench be constructed midslope to
facilitate revegetation and maintenance of the slope. The finished surface
should be track-rolled with a small dozer to compact and texture the
surface.
' We recommend that topsoil be spread on the finished embankment about
3 inches thick to facilitate revegetation. The topsoil should be spread
1 over the compacted and textured embankment surface and must also be
thoroughly track-rolled to achieve reasonable compaction and a texture
appropriate for hydroseeding.
14
Geo I Engineers
We suggest that the hydroseed mix be proposed by the earthwork
contractor and be subject to the review of the engineer. The seed mix must
consider the time of year for application, the steepness and direction of
slope, and the soil conditions. No irrigation should be planned.
Maintenance and reseeding as necessary must be anticipated until the grass
is well established.
Since the current plans are for fall construction, we recommend that a
contingency be included for alternative or supplemental slope erosion
protection such as covering the slope with plastic sheeting through the
winter months. The decision to use this alternative can be made in the
field at the discretion of the contractor, with the engineer's and/or City's
' approval.
Criblock Wall Design Criteria:
General - A retaining structure will be constructed along the toe
of the slide area. At this time, we understand that a Criblock wall is
the preferred alternative. Typically, these structures are designed by
the Criblock Company. General criteria for design and construction are
presented in this section.
' Foundation Support - The Criblock wall must be founded on
undisturbed native soils. We expect these to be hard clay. We
recommend that the base of the wall be keyed into the hard clay a depth
of at least 2 feet. We estimate that approximately 3 to 4 feet of
unsuitable material will have to be excavated to key into the hard clay
for a depth of 2 feet. Because the hard clay is susceptible to
softening, the contractor may choose to pour a lean concrete mat over
the prepared subgrade to protect it during construction if the
excavation is accomplished during wet weather or if seepage is
encountered in the excavation. Two to three inches of "lean mix"
consisting of two-sack Portland cement concrete is normally suitable
for this purpose. The criblock wall foundation bearing on hard clay as
described may be proportioned using an average bearing value of 5,000
psf for vertically-applied loads. This value may be increase to 6,000
psf when considering maximum toe or heel pressures. These values
assume a foundation width of at least 6 feet.
15
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Geo14
M Engineers
Wall Backfill - We recommend that the cribs be backfilled with
' well-graded sand and gravel or crushed rock which complies with WSDOT -
1991 Section 9-03.14 General Borrow, except that the maximum percentage
passing a U.S. No. 200 sieve must not exceed 5 percent. The backfill
must be compacted to at least 92 percent of the maximum dry density
determined in accordance with ASTM D-1557. Assuming that the cribs are
filled with the materials specified above and compacted as recommended,
an internal angle of friction of 32 degrees and a compacted fill
density of 125 pounds per cubic foot is appropriate for design of the
wall.
Lateral Resistance - Lateral loads can be resisted by friction on
the base of the foundation. We recommend using a coefficient of
friction of 0.5 between the base of the foundation and the underlying
hard clay. This value does not include a factor of safety. We
recommend that a minimum factor of safety of 1.5 be used in design of
the structure.
Drainage - Even though we anticipate that the bins will be
backfilled with free-draining material, we recommend that a drainpipe
be installed behind the back of the criblock wall. A perforated
drainpipe having a diameter of at least 6 inches should be placed along
the base of the wall for its entire length. The drain must be
backfield with free-draining backfill, as previously specified. This
drainpipe should discharge into a tightline leading to the storm sewer
' in Rainier Avenue.
OTHER CONSTRUCTION CONSIDERATIONS
Shoring of Excavations: Temporary cuts for pipeline excavations must
be sloped no steeper than 1H:1V. Where existing features preclude sloping
the excavation side walls, shoring will be necessary for safety of those
working inside the trenches, or may be necessary to minimize damage to
adjacent property. For sewer excavations, we anticipate that braced trench
boxes will probably be used. A trench box or other braced shoring should
be designed for a uniform lateral soil pressure (rectangular distribution)
of 40 H in pounds per square foot.
16
CA"�o1O�'Engineers
' In order to excavate the uppermost bench into competent native soils,
cuts will be on the order of about 10 to about 25 feet. We recommend that
' this excavation not proceed until the house at 676 Taylor Avenue is
underpinned. Options for accomplishing this cut include sloping the
' excavation, possibly excavating in intervals or segments of 20 feet or less
in length to reduce the potential for additional slope failures during
' excavation, to shore the excavation, or a combination of shoring and sloping
the cut above the shoring. We recommend that the decision to accomplish
excavation of the uppermost bench by sloping back the soils or by shoring
' be made the responsibility of the contractor. However, the excavation must
be accomplished without jeopardizing the stability of the nearby houses.
' Temporary cuts should be sloped no steeper than 1H:1V, and may need to
be flatter if soil sloughs or begins to move at this inclination. If the
' excavation is an unsupported cut, we recommend that the contractor establish
a line of stakes situated about 10 feet back from the top of the cut. It
' is important that the contractor verify alignment of the stakes on a daily
basis to confirm that additional movement is not occurring.
If shoring is used to temporarily support the cut, we anticipate that
' cantilevered sheet piles will be used. For cantilevered sheet piles or
other cantilevered shoring wall systems, the temporary shoring must be
' designed for an equivalent fluid density of at least 50 pounds per cubic
foot. This assumes that the water table will be near the base of the
' excavation. The sheet piles must be firmly embedded into dense or very
stiff to hard native sand and silt. Passive pressures may be designed using
an equivalent fluid density of 260 pounds per cubic foot which begins at a
' depth of 2 feet below the excavation level. This value assumes that the
overall slope of the competent material in front of the shoring is about
2.5H:lV. The above values do not include a factor of safety.
We recommend that our firm review the contractor's proposed excavation
and shoring plan prior to final acceptance by the City.
Equipment Access: Access to the side sewer line location and upper
parts of the slide will be difficult for standard construction equipment
' without either some kind of mechanical assistance or construction of a
pioneer road. We recommend that the contractor's proposed method be
' reviewed by the engineer.
' 17
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Geoff Engineers
Sewer Line Embedment: We recommend that bedding material for the
sewer lines complies with WSDOT - 1991 Section 9-03.12(3) , except the
portion passing a U.S. No. 200 sieve shall not exceed S percent. The
backfill over the pipe should consist of slope backfill, as described above.
' Erosion Control: We recommend use of silt fences and hay bale check
dams to retard downslope flow of sediment during wet weather. The placement
of erosion control features may be selected by the contractor, but must be
appropriate to preclude off-site sediment transport. We suggest the
contractor's plans be reviewed by the engineer.
Construction Monitoring: We recommend that a member of our firm be
present during construction as needed to observe that the slide repair
' measures and sewer pipe installation are constructed in accordance with our
recommendations and to consult with you as needed during construction.
Details of particular importance include monitoring the excavation,
evaluation of imported materials, construction of drainage and erosion
control measures, slope regrading and wall foundation conditions.
' MAINTENANCE
Sewer line facilities require periodic maintenance. We recommend that
equipment access routes constructed for this project be left in condition
to facilitate future access for maintenance. Depending on the location of
' new manholes, permanent primitive access routes for equipment may be
required as part of the design.
' LIMITATIONS
We have prepared this report for James M. Montgomery Consulting
' Engineers, Inc. and the City of Renton for their use in evaluating sewer
line reconstruction and slope remediation alternatives along the Northwest
Seventh Street main sewer line and side service line east of Taylor Avenue
Northwest in Renton, Washington. The data and report can 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.
' 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.
' 18
GeoEngineers
There are possible variations in subsurface conditions between the
locations of the explorations and that also may occur with time. A
' contingency for unanticipated conditions should be included in the project
budget and schedule. Construction monitoring and testing are important to
' confirm that the conditions encountered are consistent with those indicated
by the explorations and to evaluate whether or not the earthwork and
foundation installation activities comply with the intent of the contract
plans and specifications. For consistency in the interpretation of
subsurface conditions and the application of design recommendations,
GeoEngineers should be retained to provide construction monitoring and
consultation services during earthwork, wall, drainage and fill
' construction, and sewer line installation activities.
Within the limitations of scope and schedule, our services, consisting
of a site-specific field reconnaissance, subsurface explorations, and slope
stability and design evaluations and analyses, 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 trust this report meets your present needs. If there are questions
concerning this report or we can provide additional services, please call.
rYours very truly,
GeoEngineers, Inc.
CA
Kenneth G. Neal
Senior Engineering Geologist
-• �' Nancy L. Tochko, P.E.
1G Senior Geotechnical Engineer
emu'
Jon W. Koloski
Principal
1 KGN:NLT:JWK:wd
19
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1
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A20
60-
FYI GM Brown silty fine to coarse gravel wlth sand and occasional bark, plastic SU-62 SM Brown silty fine to coarse sand with varying amounts of gravel (very
m ✓ and concrete (medium dense, moist) dense, moist laciolacustrine 60
' Rainier Avenue North _@ I / )(9 )
3 Sidewalk SU-Al ML Brown sandy silt (hard, moist)(glaciolacustrine) SU-C CL Brown to light brown clay with varying amounts of sand and occasional
gravel (hard, moist) (glaciolacustrine)
.. /� SU-A2 ML Light brown silt with layers of fine to medium sand (hard/very dense,
All Al2 A14 A16 + moist) (glaciolacustrine) SU-Di SM Brown sit fine sand with occasional ( very to try gravel dense to ve dense,
50 ___ SU-A8 1 SU-A3 ML Brown silt with occasional sand (hard, moist) (glaciolacustrine) moist)(till) �
SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense,
' SU-A4 CL/CH Gray day with occasional Interbedded sit and fine sand (hard, moist) moist)(weathered till)
t� finely laminated (glaciolacustrine) 0 10 20
SU-03 SM Brown silty fine to medium sand wtth fine gravel 0oose,
SU-AS ML Gray skt with occasional Interbedded day,sand and gravel(hard,most) moist)(weathered till) SCALE IN FEET
' t") massive to finely laminated (glaciolacustrine)
40 SU-E SM Brown to light brown silty fine sand with occasional gravel and roots SU-A6 CL Brown day with sand and roots (soft, moist) (glaciolacustrine/topsoil)
� (medium dense, dry)(slope deposit)
12+00 40
1
U 81 ML Light gray and brown sandy silt I I
t with occasional gravel and cobbles CITY OF RENTON N.W. 7TH STREET AND TXLAR AVENUE N.W.(hard, moist) (glaciolacustrine) TO RANTER AVENUE NORTH SLOPE STAStuTV E1MLUAnON
30 10+00 10+5p 1 1+ rE'() �',�1 ;1I1eel'S AND SEWER LINE RECONSTRUCTION CROSS SECTION A-A'
11+00 50 �/ FIGURE 2
I I I I I 1 I 1 I I I I I I I I
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120
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and concrete (medium dense, moist) moist)(till)
' m 70
uJ SU-At ML Brown sandy silt (hard, moist)(glaciolacustrine) SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense,
70 moist)(weathered till)
C20 SU-A5 SU-A2 ML Light brown silt with layers of fine to medium sand (hard/very dense,
moist) (glaciolacustrine) SU-D3 SM Brown silty fine to medium sand with fine gravel goose,
N moist)(weathered till)
pj SU-A3 ML Brown silt with occasional sand (hard, moist) (glacidacustrine)
.. SU-E SM Brown to light brown silty fine sand with occasional gravel and roots
C18 SU-A4 CL/CH Gray clay with occasional Interbedded slit and fine sand (hard, moist) (medium dense, dry)(slope deposit) 60
' 60 Ralniw Avenue N.
q finely laminated (glaciolacustrine)
3 c� SU-AS ML Gray sift with occasional Interbedded day,sand anti gravel (hard,most)
CA Sidewalk massive to finely laminated (glaciolacustrine)
N id a Cie
' C10 C12 C14 m.. �_� SU-A6 CL Brown clay with sand and roots (soft, moist) (glacidacustrine/topsoA)
SU-Bi ML Light gray and brown sandy silt with occasional gravel and cobbles 50
' 50 (hard, moist) (glaciolacustrine)
0
SU-92 SM Brown silty tine to coarse sand with varying amounts of gravel (very 0 10 20 \
dense, moist)(glaciolacustrine) '\
OSU-C CL Brown to light brown clay with varying amounts of sand and occasional SCALE IN FEET
gravel (hard, moist) (glaciolacustrine) 40
40 12+00 12+50
1 1 1
CITY OF RENTON TAMOR MVENUE N.W. TO RAINIER MVENUE N.
/���s. SLOPE STASH M EWILUATION AND SEVIIER LINE
�I� RECONSTRUCTION CROSS SECTION C-C'
(le�) ��ngineers+50 FIGURE 3
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D18 Sl Unit Description
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3 Fill GM Brown slty fine to coarse gravel wlth sand and occasional bark, plastic (hard, moist) (glaciolacustrine)
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Q 01 and concrete (medium dense, moist)
SU-B2 SM Brown silty fine to coarse sand with varying amounts of gravel (very -50
SU-Al ML Brown sandy s1t (hard, moist)(glaciolacustrine) dense, moist)(glaciolacustrine)
' SU-C CL Brown to light brown day with varying amounts of sand and occasional
SU-A2 ML UgM brown sit with layers of fine to medium sand (hard/very dense,moist) (glacblacustrine) gravel (hard, moist) (glaciolacustrine)
' SU-A3 ML Brown sit with occasional sand (hard, moist) (glaciolacustrine) SU-D1 SM Brown silty fine sand with occasional gravel (dense to very dense,
moist)(tfll)
M SU-A4 CL/CH Gray day with occasional Interbedded silt and fine sand (hard, moist) 0 10 20 -40
finely laminated (glaciolacustrine) SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense,
moist)(weathered till)' SCALE IN FEET O SU-AS ML Gray at with occasional Interbedded day,sand and gravel(hard,most)
massive to finely laminated (glaciolacustrine) SU D3 SM Brown silty fine to medium sand with fine gravel (loose,
moist)(weathered till) 12+00
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SU-E SM Brown to light brown silty fine sand with occasional gravel and roots CITY OF RENTON 77MLOR AfMJE N.W.TO RAINIER A/ N.
(medium dense, dry)(slope deposit) �,is' SLOPE STABUTY MLLUATION AND SEWER LMIE
10+00 10+50 Geo 1�....Engineers
RECONSTRUCTION CROSS SECTION D-D'
' 1 , , , 11+50 �� FIGURE 4
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and concrete (medium dense, moist) (hard, moist) (glaciolacustrine)
p 1 50
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dense, moist)(placidacustrine)
SU-A2 ML Light brown silt with layers of fine to medium sand (hard/very dense,
' moist) (glaciolacustrine) SU-C CL Brown to light brown day with varying amounts of sand and occasional
gravel (hard, moist) (glaciolacustrine)
SU-A3 ML Brown silt with occasional sand (hard, moist) (glaciolacustrine)
O40 SU-D1 SM Brown silty fine sand with occasional gravel (dense to very dense, 40
' SU-A4 CL/CH Gray clay wfth occasional Interbedded silt and fine sand (hard, moist) moist)(till)
finely laminated (glaciolacustrine)
SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense,
OSU-A5 ML Gray sih with occasional Interbedded clay,sand and gravel(hard,most) moist)(weathered till) 0 10 20
massive to finely laminated (glaciolacustrine)
SU-D3 SM Brown silty fine to medium sand with fine gravel (loose, SCALE IN FEET
30 SU-A6 CL Brown clay with sand and roots (soft, moist) (glaciolacustrine/topsoil) moist)(weathered till) 12 30
SU-E SM Brown to light brown silty fine sand with occasional gravel and roots I I I I
(medium dense, dry)(slope deposit) CITY OF RENTON T W. ;VENUE N.
Afflp. [, SLOPE STAMM EMLUATION AND SEWER LINE
IO+OO � e���� 1.I��I I���r� RECONSTRUCTION CROSS SECTION E-E'
10+50 11+00 11+50 12+00 OW FIGURE 5
B o v ( < w B9
10+00 10+50 11+00 11+50 12+00 0 12+50 I2 13+00 13+50 14+00
130 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 w I I I I I I I I I I I I I I I I I I . 1 130
' rn
w I �
.2 c Profile Along Taylor Avenue I U T
End of Taylor Avenue 1 Im
Azimuth 12° Azimuth 3600' B38 B38 Asphalt
m U 120
120 Bend in Section � B34 `---
(E') m, B32 SU-D2
SU-D3 ---- ,
B30 SU-D3 _ — - --- - SU-D 1
B —�-
' 110 28 --- 1 10
SU-D3 SU-DI
100 B26 / _ -- ---- -
06/13/91 100
S U-D 1 SU-C SU-C .-
SU-C -
/ SU-B2 LL
90 B24 SU-� 08/13/91 SU-B2
SU-AS 90 O
/ - >
SU-A6
SU-B 1 ' m
W
/ SU-B1LL
-�
c0 80 B22/ _` -�
' cc> SU-A5 �— —
tD Contacts Uncertain
W SU-A5
iv 70 Old Road Cut SU-E '_
T
70
SU-A3 SU-A4 Soil Unit Description
Z B20 — 1 — ' FIN GM Brown s1ry fine to coarse gravel with sand and occasional bark, plastic SU-Bt ML Light gray and brown sandy sift with occasional gravel and cobbles
SU-A2 and concrete (medium dense, moist) (hard. moist) (giaciolacustrine)
3 / SU-A2 \ SU-Al ML Brown sand sift rd, moist acidacustrine SU-B2 SM Brown si fine to coarse sand with varying amounts of ravel (very
Y � )(gi ) Ity rY g g ( rY
Q B18 \ Contact Location Uncertain dense, moist)(glaciolacustrine)
60 SU-A2 ML Light brown silt with layers of fine to medium sand (hard/very dense, 60' moist) (glacidacustrine) SU-C CL Brown to light brown day with varying amounts of sand and occasional
O B18
/ ) SU-A3 ML Brown silt with occasional sand (hard, moist) (glacidacustrine) gravel (hard, moist) (glaciolacustrine)
I SU-A1
ti. Fil� SU-Dt SM Brown silty fine sand with occasional gravel (dense to very dense,
N fine\ SU-A4 CL/CH Gay d urinated fl ac d�ustenrbedded sM and fine sand (hard, moist) moist)(tili)
O / SU-Al SU-D2 SM Brown silty fine to medium sand with fine gravel (medium dense, 0 10 20 50
t� 50 B14 / \ SU-A5 ML Gray silt with occasional interbedded day,sand and gravel(hard,most) moist)(weathered till)
n
massive to finely laminated (glacidacustrine) SCALE IN FEET
\ SU-03 SM Brown silty fine to medium sand with fine gravel Qoose,
SU-A6 CL Brown clay with sand and roots (soft, moist) (glaciolacustrine/topsoil) moist)(weathered till)
I I I I
B12 /
810 , SU-E SM Brown to light brown silty fine sand with occasional gravel and roots CITY OF RENTON TAYLOR AVENUE N.W. TO BASE OF SLOPE
(medium dense, dry)(slope deposit)40 (�����\�EI1�llleerS SLOPE ONST U TION CROSS
ON AND
-- ��� SEWER LINE RECONSTRUCTION CROSS SECTION B-B'
1 10+50 11+00 11+50 12+00 12+50 13+00
I 1 1 1 I 1 I I I t 1 1 1 I 1 1 I I I I I
I I
0+00
13+50 14+00
1 �/ � FIGURE 6
1 I I I I