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GEOTECHNICAL ENGINEERING STUDY
SUE CHAN SHORT PLAT
405 SOUTHWEST LANGSTON ROAD AND
319 STEVENS AVENUE SOUTHWEST
RENTON, WASHINGTON
E-11997
September 6, 2005
PREPARED FOR
MS. SUE CHAN
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Eric L. Woods
Staff Geologist
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� Kristina M. Weller, PE
Manager of Geotechnica! Services
Earth Consultants, Inc.
1805 - 136th Place Northeast, Suite 201
Bellevue, Washington 98005
(425? 643-3780
Toll Free 1-888-739-6670
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September 6, 2005 E-1 1997
Ms. Sue Chan
P. O. Box 2221
Renton, Washington 98056
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Attention: Ms. Sue Chan �
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Dear Ms. Chan: I
I
Earth Consultants, Inc. (ECI) is pleased to submit our report titled "Geotechnical
Engineering Study, Sue Chan Short Plat, 405 Southwest Langston Road and 319
Stevens Avenue Southwest, Renton, Washington". This report presents the results of
our field exploration, selective laboratory tests, and engineering analyses. The purpose
and scope of our study were outlined in our proposal PR-1 1997, dated July 28, 2005.
Based on the results of our study, it is our opinion development of the site with a
residential subdivision and related infrastructure is feasible from a geotechnical
engineering standpoint. !
The proposed residences may be supported on conventional spread and continuous
footing foundation systems bearing on competent native soil, competent bedrock, or
structural fill. Slab-on-grade floors may be similarfy supported.
�ECI should review the site grading plans once completed to reevaluate the
recomrnendations provided in this report and to provide additional recommendations, as
necessary.
We appreciate this opportunity to have been of service to you. If you have any
questions, or if we can be of further assistance, please call.
Respectfully submitted,
EARTH CONSULTANTS, C.
.
Eric L. Woods
Staff Geologist
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1805 136th Place N.E., Swte 201, Bellevue,WA 98005 Other�ocations
Bellevue !�125j 643-3780 FAX (d25j 746-0860 Toll Free (883) 739-6670 Fife
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' TABLE OF CONTENTS
E-11997
PAGE
INTRODUCTION ................................................................................................ 1
General........................................................................................................ 1
ProjectDescription ........................................................................................ 2
Scopeof Services ......................................................................................... 2
SITECONDITIONS............................................................................................. 3
Surface........................................................................................................
3
Subsurface ..............................................................................................
........ 4
SoilMap Review ......................................................................................... 4
GeologicMap Review .................................................................................. 4
SubsurfaceExploration ................................................................................ 4
Groundwater ................................................................................................ 6
LaboratoryTesting ........................................................................................ 6
CRITICAL AREA CONSIDERATIONS .................................................................... 7
Review of City of Renton's Criticat Areas Regulations ....................................... :'
Geologic Hazard Review ................................................................................ .
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SteepSlopes .............................................................................................. 1 �� �,
Erosion Hazard Areas...............................................................................:... 1 �
Landslide Hazard Areas ................................................................................ 1 1
Seismic Hazard Areas .................................................................................. 12
CoalMine Hazards ...................................................................................... 12
Construction Setbacks ................................................................................. 12
DISCUSSION AND RECOMMENDATIONS............................................................. 13
General........................................................................................................ 13
Site Preparation and General Earthwork ........................................................... 13
Erosion Control and Stripping ................................................................... 13
TemporarySlopes................................................................................... 14
StructuralFill ......................................................................................... 1 5
RockFill ................................................................................................ 15
RockRippability...................................................................................... 16
Permanent Slopes................................................................................... 16
Foundations ................................................................................................ 17
Slab-on-Grade Floors .................................................................................... 18
RetainingWalls ............................................................................................. 1 8
Earth Consuliants, Irc..
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� GEOTECHNICAL ENGINEERING STUDY
SUE CHAN SHORT PLAT
405 SOUTHWEST LANGSTON ROAD AND
319 STEVENS AVENUE SOUTHWEST
RENTON, WASHINGTON
E-11997
INTRODUCTION
Generai
This report presents the results of the geotechnical engineering study completed by
Earth Consultants, Inc. (ECI) for the Sue Chan Short Plat located at 405 Southwest
Langston Road and 319 Stevens Avenue Southwest in Renton, Washington. The
general location of the site is shown on the "Vicinity Map", Plate 1 .
Project Description
We understand it is planned to short plat the approximately 1-acre, irregularly shaped
property into six, new single-family residence lots. A review of a preliminary site plan
provided by the client indicates that four lots (Lots 1 through 4) will be located along the
eastern property line, each with direct access to Stevens Avenue Southwest. A paved
access road will extend west from Stevens Avenue Southwest to provide access for tF
� two lots (Lots 5 and 6) that will be located in the western portion of the property. I,
Two, existing single-family residences and several outbuildings currently occupy the site.
The existing single-family residences will be incorporated into the proposed development
as Lots 1 and 4. The existing outbuildings will be removed.
At the time our study was performed, the proposed lot configurations and our
exploratory locations were approximately as shown on the "Test Pit Location Plan",
Plate 2.
We anticipate the proposed residences will be up to two stories in height and will be of
relatively lightly loaded, wood-frame construction with a combination of slab-on-grade
and wood joist floors. Based on our experience with similar projects, we anticipate wall
loads will be in the range of 2 to 3 kips per lineal foot, and column loads will be in the
range of 15 to 20 kips. We estimate slab-on-grade floor loads of 150 pounds per
square foot (psf).
l:�rtf� Cr�nsultarts. In�,.
- TABLE OF CONTENTS, Continued
E-11997
PAGE
DISCUSSION AND RECOMMENDATIONS, Continued
Seismic Design Considerations ....................................................................... 19
GroundRuptu�e...................................................................................... 19
Liquefaction ........................................................................................... 20
SlopeFailure ..........................................................................................20
Ground Motion Response......................................................................... 20
SiteDrainage................................................................................................21
LIMITATIONS....................................................................................................22
Additional Services ....................................................................................... 22
ILLUSTRATIONS
Plate 1 Vicinity Map
Plate 2 Test Pit Location Plan
Plate 3 Typical Footing Subdrain Detail
APPENDICES
Appendix A Field Exploration
Plate A1 Legend
Plates A2 through A6 Test Pit Logs
Appendix B Laboratory Test Results
Plate B1 Grain Size Analyses
Earth (:��n5�.i!t;_�nis. In�..
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GEOTECHNICAL ENGINEERING STUDY
v Ms. Sue Chan E-11997
September 6, 2005 pa9e 2 I
Based on the existin to o raphic relief, we estimate cuts and fills of 5 feet or less will I
9 P 9
be required to achieve proposed subgrade elevations for Lots 2 and 3, while Lots 5 and
6 will be benched into the existing slope with cuts of up to 10 feet. i
The conclusions and recommendations in this study are based on our understanding of �
ihe proposed development, which is in turn based on the project information provided �
us. If the above project description is incorrect, or the project information changes, we
should be consulted to review the recommendations contained in this study and to
make modifications, if needed.
Scope of Services
The purpose of this study was to explore the subsurface conditions at the site and,
based on the conditions encountered, to develop geotechnical engineering
recommendations for the proposed site development. Our scope of services included
excavation of five test pits across the site, laboratory testing, and preparation of this '
report that specifically addresses: '
• Surface and subsurface soil and water conditions
• Site preparation, grading and earthwork procedures, including stripping depth
recommendations and details of structural fill placement and compaction
• Suitability of existing on-site materials for use as structural fill and
recommendations for imported fill materials
� Seismic hazard analyses, including evaluation of potential flquefaction hazard
• Short-term and long-term groundwater management and erosion control
measures
• Foundation design criteria
� Estirnates of anticipated settlement magnitudes
• Temporary and permanent slope recommendations
• Visual stability assessment
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GEOTECHNICAL ENGINEERING STUDY
' Ms. Sue Chan E-11997
September 6, 2005 Page 3
SITE CONDITIONS
Surface
The property is located at 405 Southwest Langston Road and 319 Stevens Avenue
Southwest in Renton, Washington (see "Vicinity Map", Plate 1 ). The subject site is
bordered to the north by Southwest Langston Road and single-family residences, to the
west and south by single-family residences, and to the east by Stevens Avenue
Southwest.
The topography in the western portion of the site is comprised of an approximately 70
foot high, east-facing slope that descends from the western property line to a relatively
level bench area along the eastern property line. The bench in the eastern portion of the
site slopes southeast, descending approximately 15 feet from the northern property line
to a topographic low near the southeast site corner.
The slopes throughout the western portion of the site contain gradients generafly in the
range of 20 to 40 percent, with a localized area increasing to gradients of 40 to 45
percent in the north-central portion of the site near the northern property line. The 40
percent and greater slope area continues into the neighboring property to the north.
The bench area occupying the eastern porti�n of the site descends southeast from the
northern property line t_ . . _ .. _ ._�._ , . _ .� - - - . . ,. , - . -..- -;� .-
of less than 10 percent
The eastern portion of the site is primarily vegetated with grass, fruit trees, an�i
decorative plants. The slope area in the western portion of the site is vegetated with
blackberry brambles, thick mixed brush, and medium-diameter deciduous trees, with a
stand of inedium- to large-diameter pine trees occupying a portion of the steep slope
area.
Earth Consultants, Inc.
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GEOTECHNICAL ENGINEERING STUDY
` Ms. Sue Chan E-11997
September 6, 2005 Page 4
Subsurface
Subsurface conditions were evaluated by reviewing United States Department of
Agriculture (USDA) Soil Conservation Service fSCS) soil maps, reviewing geologic
maps of the area, and excavating five test pits to a maximum depth of 17 feet below
existing grade at the approximate locations shown on the "Test Pit Location Plan",
Plate 2. The following subsections of this study provide a summary of the soil and
bedrock conditions as described on the published maps and observed at our test pit
locations.
Soil Map Review
Review of the King County Area Soil Su�vey, 1973, indicated the site is underlain by
Beausite gravelly sandy loam, 6 to 15 percent slopes (Map Unit BeC). Beausite series
soils on 6 to 15 percent slopes are characterized by medium surface runoff and a
moderate erosion hazard. '
Geologic Map Review
Review of the Geologic Map of King County, Washington (Booth, Haugerud, and Sacket,
2002) indicated the site is immediately underlain by outcrops of late to middle Eocene-
aged bedrock of the Renton Formation (Map unit Epr}. The Renton Formation is described
� as fine- to coarse-grained sandstone, with interbedded siltstone, cfaystone, and coal.
The geologic units described on the geology map appear to generally be consistent with
the bedrock conditions encountered at our exploration locations, which are described
below.
Subsurface Exploration
Subsurface conditions were evaluated by excavating five test pits at the approximate
locations shown on the "Test Pit Location Plan", Plate 2. The test pits were excavated
to a maximum depth of 17 feet below existing grade. Please refer to the "Test Pit
Logs", Plates A2 through A6, for a more detailed description of the conditions
encountered at each location explored. A description of the field exploration methods is
included in Appendix A. The following is a generalized description of the subsurface
conditions encountered.
E��rth ConSUit<.�nls, tnc�.
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GEOTECHNICAL ENGINEERING STUDY II
` Ms. Sue Chan E-11997 �I
September 6, 2005 Page 5 �
At our test pit locations, we encountered a surficial layer of topsoil and sod. The I
topsoil ranged from 4 to 12 inches thick, and was characterized by its dark-brown to �
black color and organic content.
At three of our test pit locations (Test Pits TP-1 , TP-3 and TP-4), the topsoil and sod
layer was underlain by a loose, surficial layer of silty sand (Unified Soil Classification
SM). The loose surficial soil extended to depths ranging from 1 .5 to 3 feet below
existing grade. At Test Pit TP-3, the loose surficial soil was underlain by medium dense
sandy silt (ML) to a depth of 4.5 feet below existing grade.
Underlying the surficial soils at the locations of Test Pits TP-1 and TP-4, the sandy silt
at Test Pit TP-3, and the topsoil at Test Pit TP-2, weathered bedrock was encountered
that appeared to be consistent with the Renton Formation as described on the
referenced geologic map of the site. The bedrock was primarily comprised of
sandstone, with localized siltstone and coal interbeds. The bedrock was generally
medium dense to dense, weathered, and fract�red to depths of 3 to 5 feet below grade
before becoming very dense, less weathered, and less fractured. The sandstone
bedrock continued to the maximum depth explored at Test Pits TP-1 , TP-2, and TP-4. �
At Test Pit TP-3, the sandstone bedrock remained fractured to a depth of 8 feet and
was underlain by bedrock comprised of dense, fractured coal with localized siltstone
beds. The coal continued to the maximum depth of 16.5 feet below existing grade at
Test Pit TP-3.
Underlying the topsoil at Test Pit TP-5, a surficial layer of loose to medium dense silty
sand (SM) was encountered. The surficial soil extended to a depth of 6.5 feet belo�v
existing grade and was underlain by medium dense to dense deposits of silt with
varying amounts of sand (ML) and silty sand with varying amounts of gravel (SM). The
silty sand and silt deposits, characterized by the presence of interbeds of sand, silt, and
gravel, and localized coal fragments, continued to the maximum exploration depth of
1 7 feet below existing grade.
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GEOTECHNICAL ENGINEERING STUDY
V Ms. Sue Chan E-11997
September 6, 2005 Page 6
Groundwater
Groundwater seepage was encountered at two of our test pit locations at depths
ranging from 4.5 to 14 feet below existing grade. Iron oxide staining was encountered
at each of our exploratory locations at varying depths. The groundwater seepage and
iron oxide staining encountered at Test Pits TP-1 through TP-4 appear to be indicative
of seasonal groundwater collecting within the fractured bedrock encountered at our
exploratory locations. The groundwater seepage and iron oxide staining encountered at
Test Pit TP-5 appear to be indicative of seasonal perched groundwater col(ecting above
impermeable silt beds or within permeable sand and gravel lenses.
The contractor should be made aware that groundwater levels are not static and the
magnitude of flow may vary seasonally. There will be fluctuations in the level
depending on the season, amount of rainfall, surface water runoff, and other factors.
Generally, the water level is higher and seepage rate is greater in the wetter, winter
months (typically October through May).
Laboratory Testing
Laboratory tests were conducted on representative soil samples to verify or modify the
field soil classification and to evaluate the general physical properties and engineering
characteristics of the soil encountered. Visual field classifications were supplemented
by grain size analyses on representative soil samples. Moisture content tests were
performed on all samples. The results of laboratory tests performed on specific samples
are provided either at the appropriate sample depth on the individual test pit logs or on
a separate data sheet contained in Appendix B. It is important to note that these test
results may not accurately represent the overall in-situ soil conditions. Our geotechnical
recommendations are based on our interpretation of these test results and their use in
guiding our engineering judgment. ECI cannot be responsible for the interpretation of
these data by others.
In accordance with our Standard Fee Schedule and General Conditions, the soil
samples for this project will be discarded after a period of 15 days following
completion of this report, unless we are otherwise directed in writing.
F_ar�h Consultants. Inc.
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GEOTECHNICAL ENGINEERING STUDY
' Ms. Sue Chan E-11997
' September 6, 2005 Page 7
CRITICAL AREA CONSIDERATIONS
Review of City of Renton's Critical Areas Regulations
The potential geologic hazards within the subject site as defined in the Renton Municipal
Code (RMC?, Section 4-3-050 "Critical Areas Regulations", were addressed as part of our
study.
The City of Renton identifies five different types of geologic hazards: steep slopes,
erosion hazards, landslide hazards, seismic hazards, and coal mine hazards. The City's
criteria for the various hazard areas are defined as follows:
• Steep Slopes
The boundaries of a regulated steep sensitive or protected slope are determined to be
in the location identified on the City of Renton's Steep Slope Atlas. RMC 4-3-0508.4.b.
As noted in RMC 4-3-050B.1 .c, the City's steep slope types are:
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Sensitive Slopes: gradients of 25 to 40 percert
Piotected Slopes: gradients steeper than 40 percent
• Erosion Hazard Areas
The City of Renton has two classifications of erosion hazard areas.
Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource
Conservation Service (formerly U.S. Soil Conservation Service) as having slight
or moderate erosion potential, and that slope less than 15 percent. RMC 4-3-
0506.4.d.i.
Hiqh Erosion Hazard (EH): Areas with soils characterized by the Natural
Resource Conservation Service as having severe or very severe erosion potential,
and that slope more steeply than 15 percent. RMC 4-3-050B.4.d.ii.
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GEOTECI-iNICAL ENGINEERING STUDY
' Ms. Sue Chan E-11997
September 6, 2005 Page 8
• Landslide Hazard Areas
There are four classifications for landslide hazard: low, medium, high, and very high.
Low Landslide Hazard (LL): Areas with slopes less than 15 percent. RMC 4-3-
0506.4.c.i.
Medium Landslide Hazard (LMI: Areas with slopes between 15 percent and 40
percent and underlain by soils that consist largely of sand, gravel or glacial till.
RMC 4-3-050B.4.c.ii.
Hiqh Landslide Hazards (LH): A�eas with slopes greater than 40 percent, and
areas with slopes between 15 and 40 percent and .underlain by soils consisting
largely of silt and clay. RMC 4-3-050B.4.c.iii.
Very Hiqh Landslide Hazards (LV): Areas of known mappable landslide deposits.
RMC 4-3-050B.4.c.iv.
• Seismic Hazards
Seismic hazards are classified under the two following categories:
Low Seismic Hazard (SLI: Areas underlain by dense soils oc bedrock. These soils
generally have site coefficients of types S 1 or S2, as defined in the Uniform
Building Code (UBC). RMC 4-3-050B.4.e.i.
Hiqh Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils.
These soils generally have site coefficients of types S3 or S4, as defined in the
UBC. RMC 4-3-0506.4.e.ii.
Earih Consultan�s, Inc.
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GEOTECHNICAL ENGINEERING STUDY
Ms. Sue Chan E-11997
' September 6, 2005 Page 9
• Coal Mine Hazards
The City of Renton has three categories of coal mine hazards: low, medium, and high.
Low Coal Mine Hazards (CL): Areas with no known mine workings and no
predicted subsidence. While no mines are known in these areas, undocumented
mining is known to have occurred. RMC 4-3-0506.4.f.i.
Medium Coal Mine Hazaids (CM): Areas where mine workings are deeper than
two hundred (200) feet for steeply dipping seams, or deeper than fifteen (15)
times the thickness of the seam or workings for gently dipping seams. These
areas may be affected by subsidence. RMC 4-3-0506.4.f.ii.
Hiqh Coal Mine Hazards (CH): Areas with abandoned and improperly sealed
mine openings and areas underlain by mine workings shallower than two
hundred (200) feet in depth of steeply dipping seams, or shallower than fifteen
(15) times the thickness of the seam or workings for gently dipping seams.
These areas may be affected by collapse or other subsidence. RMC 4-3-
050B.4.f.iii.
Geologic Hazard Revie::
The City of Renton r�_,.�,� _� _ .�. _,�_ ,��, . .,_�, .. ,����� � _ �_ . , ,_ _�� . _ r _��� _ ;
developments containing or adjacent to sensitive and protected slopes, medium, high,
and very high landslide hazards, high erosion hazards, high seismic hazards, and
medium or high coal mine hazards. RMC 4-3-050J.2.
Based on our review, the slope in the western portion of the site appears to meet the
City of Renton's criteria for sensitive and protected slopes, and for medium and high
landslide hazards. The following sections of our study specifically address the steep
slope, erosion, landslide, seismic, and coal mine hazard areas.
Ear�h C��nsultants, Inc.
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GEOTECHNICAL ENGINEERING STUDY
Ms. Sue Chan E-11997
September 6, 2005 Page 10
Steep Slopes
The development area in the western portion of the property consists of an east-facing
slope with gradients generally in the range of 20 to 40 percent, with a localized area
increasing to gradients of 40 to 45 percent in the north-central portion of the site near the
northern property line. As noted above, the City of Renton designates two classifications
for slopes with gradients of 25 percent or more. These areas are defined as sensitive
slopes (25 to 40 percent) and protected slopes (greater than 40 percent?. Most of the
steep slope area in the western portion of the property meets the criteria of a Sensitive
Slope area. A portion of the slope in the north-central portion of the property meets the
criteria of a Protected Slope area. No development is planned within the Protected Slope
area.
Erosion Hazard Areas
The soils underlying the development area consist of Beausite gravelly sandy loam, 6 to
1 5 percent slopes (Map Unit BeC). This soil has a moderate erosion potential and meets
the City of Renton's classification of a Low Erosion Hazard (RMC 4-3-050B.4.d.i). Our
test pits indicate the surficial soils that mantle the slopes throughout the western portion
of the property consist of fine-grained silty sand. This soil is susceptible to erosion due to
sheet flow. Sheet flow is the downslope movement of shallow water flowing over a large
surface area. Due to the gradient of the slopes occupying the western portion of the site,
in our opinion, erosion in the western portion of the proposed development area wifl need
to be controlled using best management practices.
The erosion control plan should include measures for reducing concentrated surface
runoff and protecting disturbed or exposed surfaces by mulching and revegetation. The
temporary erosion and sedimentation control plan should include the following:
• Where practical, maintain vegetation buffers around cleared areas.
• Cover exposed soil stockpiles.
• Hydroseed or place straw mulch in areas where grading is complete.
• Divert water away from the top of slopes.
• Use silt fences and straw bales around the lowe� portions of the site perimeter.
• Coordinate clearing, excavation and erosion control to reduce exposed areas.
The erosion control measures should be reviewed on a regular basis to verify they are
functioning as intended.
Erirth ��onsultants, Inc.
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. GEOTECHN RING STU I
ICAL ENGINEE DY ,
, Ms. Sue Chan E-11997 i
September 6, 2005 Page 1 1
II
Landslide Hazard Areas
The slo es occu in the western ortion of the ro ert have radients enerall in I
P PY 9 P p P Y 9 9 Y �
the range of 20 to 40 percent, and meet the City of Renton's landslide hazard j
classification for a Medium Landslide Hazard (RMC 4-3-050B.4.c.ii). A localized area of I
the slope in the north-central portion of the site near the northern property line contains �'�
gradients of 40 to 45 percent and meets the City of Renton's landslide hazard �
classification for a High Landslide Hazard (RMC 4-3-0506.4.c.iii). I
�
As part of our field exploration, we traversed portions of the slope area to observe
indications of past instability and potential future instability. During our reconnaissance,
we did not observe any indications of shallow debris flow failures or signs of deep-seated
or global instability. However, based on our experience with similar projects, the loose to
medium dense granular surficial soils that underlie the site are susceptible to erosion and
shallow debris flows if surface and subsurface groundwater are not controlled during and
after construction.
Debris flow failures a�e relatively common on the steep slopes comprising the perimeters
of the glacial drift uplands in the Puget Sound Basin. When the loose, surficial soils
become saturated during periods of heavy precipitation, irrigation, or by uncontrolled
surface water, they can fail along a contact with underlying soils with a lower
permeability. These failures typically involve the upper 3 to 4 feet of the slope face and
will comprise several tens of cubic yards of soil and vegetation. The result of these
shallow failures is the slow inland migration of the top of slope and the deposition of a
fan of colluvium at the toe of the slope.
During our reconnaissance, we also observed that several of the trees growing on the
slope have curved trunks. The curvature is consistent with deformation initiated by
shallow creep of surficial soils, which is a normal slope process. The observed creep is
likely occurring within a 2- to 4-foot thick zone of loose, surficial material. The curvature
observed is not indicative of deep-seated instability. In our opinion, the observed creep
should not be affected by future development, nor should the gradual creep adversely
impact the proposed development provided site drainage is controlled and appropriate
building setbacks are established.
E,�rtY� C��nsultants. In�.
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GEOTECHNICAL ENGINEERING STUDY
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September 6, 2005 Page 1 2
Seismic Hazards
The soils encounte�ed at our test pit locations primarily consist of silty sand with varying
amounts of gravel, sandy silt, and silt with varying amounts of sand, range from loose to
dense, and do not contain an established groundwater table. In addition, the slopes
occupying the western portion of the site are underlain by dense to very dense bedrock.
In our opinion, the soils and bedrock underlying the site would not be susceptible to
liquefaction.
In accordance with the City of Renton's classification system, the site meets the criteria
for a Low Seismic Hazard (RMC 4-3-050B.4.e.i). An additional discussion of the seismic
hazards is provided in the following the "Seismic Design Considerations" section of this
study.
Coal Mine Hazards
Portions of Renton contain abandoned coal mines that can adversely impact a site. As
part of our study, we reviewed information in our library and files and reviewed
Department of Natural Resources (DNR) coal mine records for information pertaining to
historic coal mining operations in the vicinity of the site.
During our field exploration, we did not observe any surface or subsurface indications
of coal mining activity, such as mine tailing piles, abandoned mine openings, or
abandoned mining equipment, all of which are typically found near coal mine
operations.
As part of our study, we also reviewed the Washrngton State Coa/ Mine Map Collection: '
"A Catalog", "Index", and "Users Guide", Open File Report 94-7, prepared by the
Washington Division of Geology and Earth Resources, dated June 1994. Based on the
results of our file review, in our opinion, the site is not underlain by coal mine workings
and has a "Low Coal Mine Hazard" designation (RMC 4-3-050B.4.f.ii).
Construction Setbacks
The building setback should be based on physical slope characteristics (such as slope
height, slope inclination, soil type, surface water drainage, and hydrology) along �riith the
intended life of the structure. Based on the results of our reconnaissance, exploration,
and engineering analyses, a minimum building setback of 10 feet from the 40 percent or
greater slopes in the north-central portion of the site should be maintained.
E�rth C��nsult�nts, Inc.
. GEOTECHNICAL ENGINEERING STUDY
Ms. Sue Chan E-11997
September 6, 2005 Page 1 3
DISCUSSION AND RECOMMENDATIONS
Generai
Based on the results of our study, in our opinion, the proposed residences may be
supported on conventional spread and continuous footing foundation systems bearing
on competent native soils, competent bedrock, or on structural fill. Slab-on-grade floors
may be similarly supported.
The site is underlain by up to 3 feet of loose native granular soils, with a localized area
of loose to medium dense soil that extended to a depth of 6.5 feet below existing grade.
If loose native soil is encountered at construction subgrade elevation, it should either
be compacted in-place to the requirements of structural fill, or it should be
overexcavated and replaced with structural fill.
This report has been prepared for specific application to this project only, and in a manner
consistent with that level of care and skill ordinarily exercised by other members of the
profession currently practicing under similar conditions in this area, for the exclusive use
of Ms. Sue Chan and her representatives. No warranty, expressed or implied, is made.
This report, in its entirety, should be included in the project contract documents for the
information of the contractor
Site Preparation and General �a�;n Y��r n
Based on our understanding of the proposed development plan, site earthwork will likely
consist of installing erosion control measures, stripping the site, cutting and filling the site
to provide building pad grades, installing underground utilities, and constructing single-
family residences on the lots.
Erosion Control and Stripping
Prior to removal of the vegetation, the clear�ng limits should be flagged. Silt fence should
be installed downslope of the proposed grading areas and construction fence should be
installed at the top of any proposed cut slopes. We recommend that, once the site
clearing limits are flagged, ECI should be contacted to walk the site with the contractor to
provide additional geotechnical and erosion control recommendations.
E_ar[h Consul►ancs. Inc.
GEOTECHNICAL ENGINEERING STUDY
� Ms. Sue Chan E-11997
September 6, 2005 Page 14
After the site is logged and grubbed, the proposed grading areas of the site should be
stripped and cleared of surface vegetation, organic matter, and other deleterious material.
Existing utility pipes to be abandoned should be plugged or removed so they do not
provide a conduit for water and cause soil saturation and instability.
The sod and topsoil layer encountered in our test pits was generally on ihe order of 4
to 12 inches thick. The sod and topsoil should be stripped and removed from the site,
or it may be stockpiled on site to be used in landscaping areas. The stripped materials
should not be mixed with materials to be used as structural fill.
During construction, the site must be graded such that surface water is collected and
tightlined to an appropriate drainage facility. Water must not be allowed to stand in fill
areas or where buildings, slabs, or pavements are to be constructed. Loose surfaces
should be sealed by compacting the surface to reduce the potential for moisture
infiltration into the soils.
Temporary Slopes
The following information is provided solely as a service to our client. Under no
� circumstances should this information be interpreted to mean that ECI is assuming
responsibility for construction site safety or the contractor's activities; such
responsibility is not being implied and should not be inferred.
In no case should excavation sfopes be greater than the limits specified in local, stat_
(W1SHA), and federal (OSHA) safety regulations. Based on the information obtained
from our field exploration and laboratory testing, the loose to medium dense native soil
and the weathered bedrock encountered in our test pit excavations would be classified
as Type C by OSHA/WISHA. Temporary cuts greater than 4 feet in height in Type C
soils may be sloped to a maximum inclination of 1 .5H:1 V (Horizontal:Vertical). The
underlying unweathered, unfractured bedrock encountered at Test Pits TP-1 , TP-2, and
TP-4 woufd be classified as Type A by OSHA/WISHA. Temporary cuts greater than 4
feet in height in Type A soils may be sloped to a maximum inclination of 0.75H:1 V.
The actual slop� inclinations can be addressed by an ECI representative at the time of
construction.
If slopes of this inclination or flatter cannot be constructed, temporary shoring may be
necessary. If temparary shoring is required, we will be available to provide shoring
design criteria.
Earrh Consultants, lnc.
GEOTECHNICAL ENGINEERING STUDY
- Ms. Sue Chan E-11997
� September 6, 2005 Page 1 5
Structural Fill
• Structural fill is defined as compacted fill placed under buildings, roadways, floor slabs,
pavements, or othe� load-bearing areas, or on slopes. Structural fill should be placed in
horizontal lifts not exceeding 12 inches in loose thickness ar�d compacted to a
minimum of 95 percent of its laboratory maximum dry density determined in
accordance with ASTM Test Designation D-1557 (Modified Proctor). The fill materials
should be placed at or near their optimum moisture content.
Based on the results of our laboratory tests, the on-site soils at the time of our
exploration appeared to be near to above their optimum moisture content, indicating
some soils may require moisture conditioning prior to their use as structural fill. In
addition, based on laboratory testing and field observation, the site soils have between 28
to greater than 50 percent fines passing the No. 200 sieve. Soil with fines in excess of
approximately 5 percent will degrade if exposed to excessive moisture, and compaction
and grading will be difficult if the soil moisture increases significantly above its optimum
level.
' if the site soils are exposed to excessive moisture and cannot be adequately compacted,
then it may be necessary to import a soil that can be compacted. During dry weather,
any non-organic compactable soil with a maximum grain size of 4 inches can be used.
Fill for use during wet weather should consist of a fairly well-graded granular material
having a maximum grain size of 4 inches and no more than 5 percent fines passing the
No. 200 sieve based on the minus 3/4-inch fraction.
Rock Fill
As previously discussed, portions of the site are underiain by bedrock at relatively shallow
depths. Therefore, we anticipate rock may need to be used as structural fill. Where rock
is used as structural fill, it should be placed in 12-inch thick lifts that are track-walked to
a non-yielding condition.
If soil fill is placed over a rock fill, a layer of filter fabric, such as Mirafi 140N or an
approved equivalent, should be placed at the soil/rock fill contact. This will keep the fines
from migrating into voids between the rocks and resulting in settlement.
Earth Consultants. Inc:.
i
- �
GEOTECHNICAL ENGINEERING STUDY II
� Ms. Sue Chan E-11997 '
September 6, 2005 Page 16 '
Rock Rippability II�
Bedrock was encountered in Test Pits TP-1 through TP-4 at 1 to 4.5 feet below existing
grade. The bedrock was weathered and fractured to depths ranging from 2.5 to greater I
than 16.5 below grade and was excavated with a Caterpillar 31 2 excavator with little
difficulty. In Test Pits TP-1 , TP-2, and TP-4, at depths of 2.5 to 5 feet, the bedrock
became more intact, and the excavator was only able to groove the surface of the rock. �'i
Refusal on very dense bedrock was encountered at 7 to 7.5 feet at Test Pits TP-1 , TP-
2, and TP-4.
Ii
Based on our expe�ience with similar conditions, un�ippable bedrock could be
encountered in site excavations. In our opinion, if cuts of greater than 10 to 12 feet I�
below existing grade are planned for proposed Lot 6 in the western half of the site, it '
may be prudent to conduct additional subsurface exploration to further evaluate the
rippability of the bedrock. The rippability of the rock can be further assessed by li
attempting to excavate the rock with a larger excavator with ripping teeth or by I
conducting a seismic refraction survey. The additional test pits or seismic surveys can
be limited to those areas where deep cuts or utility excavations are planned. I
Permanent Slopes
Permanent cut and fill slopes should be inclined no steeper than 2H:1 V. Cut slopes
should be observed by ECI during excavation to verify that conditions are as
anticipated. Fill slope construction should also be observed under the full time
observation of an ECI representative to test structural fill soils. Supplementary
recommendations can be developed, if needed, to improve stability, including flattening
of slopes, placing erosion control fabrics, or installing of surface or subsurface drains.
Permanently exposed slopes should be hydroseeded with an appropriate species of
vegetation to reduce erosion and improve stability for the surficial layer of soil
immediately after construction. In the summer months, it may be necessary to water
the slopes to maintain the hydroseed germination.
Earth C��nsult<�r[�. In�_.
GEOTECHNICAL ENGINEERING STUDY
" Ms. Sue Chan E-11997
September 6, 2005 Page 17
Foundations
Based on the results of our study, in our opinion, the proposed residences may be
supported on conventional spread and continuous footing foundation systems bearing
on competent native soii, competent bedrock, or granular structural fill used to modify
site grades.
The site is underlain by up to 3 feet of loose native granular soils, with a localized area of
loose to medium densesoil that extends to a depth of 6.5 feet below existing grade. If
loose native soil is encountered at footing subgrade elevation, it should either be
compacted in-place to the requirements of structural fill or it should be overexcavated and
replaced with structural fill.
Exterior foundation elements should be placed at a minimum depth of 18 inches below
final exterior grade. Interior spread foundations shvuld be placed at a minimum depth of
12 inches below the top of slab, except in unheated areas, where interior foundation
elements should be founded at a minimum depth of 18 inches. Continuous and
, individual spread footings should have minimum widths in accordance with local
building codes.
With foundation support obtained as described, for design, an allowable soil bear r;
capacity of 2500 psf may be used for the competent native soil, bedrock, or structural
fill. Loading of this magnitude would be provided with a theoretical factor-of-safety in
excess of 3.0 against shear failure. For short-term dynamic loading conditions, a 1/3
increase in the above allowable bearing capacity may be used.
With structural loading as expected and provided the above design criteria is followed,
total settlement in the range of 1 inch is anticipated with differential settlement of
approximately 0.5 inch. Most of the anticipated settlements should occur during
construction as dead loads are applied.
I�:,irth �:�.r,5�ilt��n�::. !r,�..
GEOTECHNICAL ENGINEERING STUDY
- Ms. Sue Chan , E-11997
September 6, 2005 Page 18
Horizontal Ioads can be resisted by friction between the base of the foundation and the
supporting soil, and by passive soil pressure acting on the face of the buried portion of
the foundation. For the latter, the foundation must be poured "neat" against the
competent native soils or backfilled with structural fill. For frictional capacity, a
coefficient of 0.35 should be used. For passive earth pressure, the available resistance
should be computed using an equivalent fluid pressure of 250 pounds per cubic foot
(pcf). These lateral resistance values are allowable values, and a factor-of-safety of 1 .5
has been included. As movement of the foundation element is required to mobilize fu(I
passive resistance, the passive resistance should be neglected if such movement is not
acceptable.
Footing excavations should be observed by a representative of ECI prior to placing
forms or rebar to verify that conditions are as anticipated in this report.
Slab-on-G�ade Floors
Slab-on-grade floors should be supported on competent native soil, competent bedrock,
or on granular structural fill. Disturbed subgrade soil must either be recompacted or
� replaced with structural fill.
Slabs placed on structural fill or on the native soils should be provided with a capillary
break consisting of a minimum of 4 inches of free-draining sand or gravel. In areas
where slab moisture is undesirable, a vapor barrier, such as a 6-mil plastic membrane,
should be placed beneath the siab.
Retaining Walls
Based on site topography and review of the preliminary site plan provided by the client,
we anticipate the proposed structures that wiil be constructed on Lots 5 and 6 will be
benched into site slopes. The recommendations contained in this section pertain to
freestanding retaining walls and retaining walls incorporated into buildings.
Retaining walls should be designed to support the lateral loads imparted by the retained
soils and applicable surcharges. Walls that are designed to yield can be designed to resist
the lateral earth pressures irnposed by an equivalent fluid with a unit weight of 35 pcf. If
walls are to be restrained at the top from free movement, the equi��alent fluid ���eight
should be increased to 50 pcf. These values are based on horizontal backfill conditians.
�ar,h ����nsult��nts. ;n�._
GEOTECHNI�AL ENGINEERING STUDY I!
' Ms. Sue Chan E-11997 '�
September 6, 2005 Page 19 �
�i
Surcharges due to backfill slopes, hydrostatic pressures, traffic, structu�al loads, or other i
surcharge loads are assumed to not act on the wall. If such surcharges are to apply, they �i
should be added to the above design lateral pressure. The passive pressure, allowable I
bearing capacity, and friction coefficient previously provided in the "Foundations" section 'i
of this report are applicable to the retaining wall design. I
�
To reduce the potential for hydrostatic pressures to build up behind the retaining walls, �
the retaining walls and the below grade portion of the foundation walls should be
backfilled with a free-draining material, such as pea gravel or washed rock, extending at I
least 18 inches behind the wall. The remainder of the backfill should consist of structural
fill.
I
I
A rigid, schedule 40, perforated PVC or SDR 35 drainpipe should be placed at the base of
the wall and should be surrounded by a minimum of 1 cubic foot per lineal foot of pea
gravel or washed rock. The pipe should be placed with the perforations in the down
position.
i
�
Seismic Design Considerations ,
Earthquakes occur in the Puget Lowland with regularity; however, the majority of these
events are of such low magnitude they are not felt without instruments. Large
earthquakes do occur, as indicated by the 1949, 7.2 magnitude earthquake in the
Olympia area, the 1965, 6.5 magnitude earthquake in the Midway area, and the 2001 ,
6.8 magnitude earthquake in the Nisqually area.
There are four potential geologic hazards associated with a strong motion seismic
event at this site; ground rupture, liquefaction, slope failure, and ground motion
response.
Ground Rupture
The strongest earthquakes in the Puget Lovvland are widespread, subcrustal events,
ranging in depth from 30 to 55 miles. Surface faulting from these deep events has not
been documented to date. Therefore, it is our opinion that the risk of ground rupture at
this site during a strong-motion seismic event is negligible.
(:;�rih �=�,nS�:L,,rts. In�:.
_ _ _
GEOTECHNICAL ENGINEERING STUDY ;
, � Ms. Sue Chan E-11997 I
September 6, 2005 Page 20 i
Liquefaction II
Liquefaction is a phenomenon in which soils lose all shear strength for short periods of II
time during an earthquake. Groundshaking of sufficient duration results in the loss of
grain-to-grain contact and rapid increase in pore water pressure, causing the soil to
behave as a fluid. To have a potential for liquefaction, a soil must be cohesionless with
a grain size distribution of a specified range (generally sand and silt?, it must be loose, �
it must be below the groundwater table, and it must be subject to sufficient magnitude
and duration af groundshaking. The effects of liquefaction may be large total and/or �I
diffe�ential settlement for structures founded in the liquefying soils. �
�
In our opinion, based on the absence of a shallow groundwater table, the potential for I
widespread liquefaction-induced settlement of the native soil and bedrock at this site is I
low to negligible. I,
�
Slope Failu�e
, The steep slope a�eas located in the western portion of the site may be susceptible to �
surficial slope failure during a strong seismic event. However, in our opinion, the
recommended construction buffer should adequately protect the structures, provided
surface water and shallow groundwater are controlled and directed away from the
slopes, and the vegetation on the slope is maintained.
Ground Motion Response
I The 2003 Internationa! Buildin Code (IBC) Earth uake Re ulations contain a static
9 q 9
force procedure and a dynamic force procedure for design-base shear calculations.
Based on the encountered soil conditions, it is our opinion "Site Class C, Very Dense
Soil or Soft Rock" from Table 1615.1 .1 of the IBC, should be used to characterize the
site soils.
�
I
�
f_,�rrt� �:�,ns��ltants. �n�:.
I
II
GEOTECHNICAL ENGINEERING STUDY
Ms. Sue Chan E_� �gg�
September 6, 2005 Page 21
Site Drainage
Groundwater seepage was encountered at two of our test pit locations at depths
ranging from 4.5 to 14 feet below existing grade. Iron oxide staining was encountered
at each of our exploratory locations at varying depths. The groundwater seepage and
iron oxide staining encountered at Test Pits TP-1 through TP-4 appear to be indicative
of seasonal groundwater collecting within the fractured bedrock encountered at our
exploratory locations. The groundwater seepage and iron oxide staining encountered at
Test Pit TP-5 appear to be indicative of seasonal perched groundwater collecting above
impermeable silt beds or within permeable sand and gravel lenses.
If seepage is encountered, the bottom of the excavation should be sloped to one or
more shallow sump pits. The collected water can then be pumped from these pits to a
positive and permanent discharge. Depending on the magnitude of such seepage, it
may also be necessary to connect the sump pits by a system of connector trenches.
Final site grades must allow for drainage away from the residence foundations and the
descending slopes. The ground should be sloped at a gradient of 3 percent for a
distance of at least 10 feet away from the residences.
Footing drains should be installed around the perimeter of the residences, at or just
below the invert of the footing, with a gradient sufficient to initiate flow. A typical
detail is provided on the "Typical Footing Subgrade Detail", Plate 3. Under no
circumstances should roof downspout drain lines be connected to the footing drain
systern. Roof downspouts must be separately tightlined to discharge. Cleanouts should
be installed at strategic locations to allow for periodic maintenance of the footing drain
and downspout tightline systems. Outfall from roof downspouts and footing drains
should not be allowed to flow over the top of descending slopes.
I .,�r';� �: ;r� ��.�f',�nt ; Ir��:
GEOTECHNICAL ENGI�fEERING STUDY
- Ms. Sue Chan E-11997
% September 6, 2005 Page 22
LIMITATIONS
Our recommendations and conclusions are based on the site materials observed,
selective laboratory testing and engineering analyses, the design information provided
us, and our experience and engineering judgment. The conclusions and
recommendations are professional opinions derived in a manner consistent with that
level of care and skill ordinarily exercised by other members of the profession currently
practicing under similar conditions in this area. No warranty is expressed or implied.
The recommendations submitted in this report are based on the data obtained from the
test pits. Soil and groundwater conditions between test pits may vary from those
encountered. The nature and extent of variations between our explorato�y locations
may not become evident until construction. If variations do appear, ECI should be
requested to reevaluate the recommendations of this report and to modify or verify
them in writing priar to proceeding with the construction.
Additional Services
As the geotechnical engineer of record, ECI shouid be retained to perform a general
review of the final design and specifications to verify that the earthwork and
foundation recomme�dations have been properiy interpreted and implemented in the
design and in the construction specifications.
ECI should also be retained to provide geotechnical services during construction. This is
to observe compliance with the design concepts, specifications, or recommendations
and to alfow design changes in the event subsurface conditions differ from those
anticipated prior to the start of construction.
[:�:rct� �:�,nsultr�nts. Ir,�_
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+o�ar.�+oh
�
LEGEND REFEREr�CE: CRONES aASSOCia�7cs Ur�D SUP.vEfGRS,FEBRUARY�999
TP-1 I
—�— Approximate location of ECI Test Pit,
� Project No. E-11997, August 2005 Earth Consultants. Inc.
�;.�,v.,-hric,ii 5n;;in.•�rin�..•-ol�,;�y.Environmer.ia!Seences
r � I r�;nsiruc:,on irs��n�i�C9r�;'.v.•.BG Inspecnon Services
� Subject site
' �. _ TEST PIT LOCA.TION PLAN
SUE CNAN SHORT PLAT
� NORTH RENTOr�, �r�ashir��Tor� �
,
r, ao '
; APPR TE DP.'TlN. DNM PROJ. �"JO. 11997 l
;Ci,Lc I�l F=_T I
CNKD. EL'PJ f7Ai� 8/2�i�:5 P��;`= 2 I
i ,
SIOPE TO
DRAIN '� �2;"x-
' . . � �
�,
. _ _
,.. . . . . .._ . . •
... _. s,. ;
�� '�`' '�' .y-� 4 G
�. �0.LV Z
�!
� r�:' —
�� �
\ �� .}�
..+:h.�.C•
4 INCH MIN. DIAMETER V , ;�`'-'
. :���_..'�
PERFORATED PIPE ,.,,
,.�Z.-:�, �
2 INCH MIN.
2 INCH MIN.
4 INCH MAX. 12 INCH MIN.
, �
LEGcND
� Surface seal: native soil or other SCHEMATIC ONLY - NOT TO SCALE
low permeability material NOT A COfVSTRUCTION DRAWING
������j�� Washed rock or pea gravel
Earth Consult�nts, Inc.
Drain I Q; erforated or slotted ,���echrncaf Englnecnng.Geology.Envirrxvnen�al Saences
O P P P c��nsuucc�on resnng s�CBoiwneo inspeaion ser��ces
rigid Schedule 40 PVC or SDR 35
pipe laid with perforations or slots
facfng down; tight jointed;with a TYPICAL FOOTING SUBDRAIN DETAIL
positive gradient. Do not use SUE CHAN SHGRT PLAT
flexible coRugated plastic pipe. RE�ITON, �NASHINGTON
Do not tie building downspout
drains into footing lines.
DR'1VP1. DPIPA PRGJ. NO 11997
':HKD. EL'PJ I GF.`E dl291�,5 P(�'+T= ;
r APPENDIX A
FIELD EXPLORATION
E-1 1997
Our field exploration was performed on August 1 2, 2005. Subsurface conditions at the
site were explored by excavating five test pits to a maximum depth of 17 feet below
existing grade. The test pits were excavated by Northwest Excavating using a
Caterpillar 31 2 tracked excavator.
The approximate test pit locations were determined by pacing from site features depicted
on a preliminary site plan provided by the client. The elevations were estimated based on
topographic lines depicted on the site plan. The locations and elevations of the test pits
should be considered accurate only to the degree implied by the method used. These
approximate locations are shown on the "Test Pit Location Plan", Plate 2.
The field exploration was continuously monitored by a geologist from our firm who
classified the soils encountered, maintained a log of each test pit, obtained
representative samples, measured groundwater levels, and observed pertinent site
featu�es. The samples were visually classified in accordance with the Unified Soi/
Classification System, which is presented on the "Legend", Plate A1 . Representative
soil samples were placed in closed containers and returned to our laboratory for further
examination and testing.
Logs of the test pits are presented on Plates A2 through A6. The final logs represent
our interpretations of the field logs and the results of our laboratory examination and
testing. The stratification lines on the logs represent the approximate boundaries
between soil types. In actuality, the transitions may be more gradual.
L=.irtt� '. ,r'�•�;il�::n: . Ir
MA.JOR DIVISIONS GRAPH LETTER NPICAL DESCRIPTION �
Y
S MBOL SYMBOL I
. J`�J�0, p aw Well-greded gravels,gravel-sand muctures, !
Ciean gravels o 0 o g�„� Iittie or no fines i
Gravel and (little or no lines)
yravally so�ls �1��!�!� (3P Poorty•graded gravels,gravel-sand �
.� � .� /9P m�xtures, little or no fines
More than 50?6 QM ;
coarse traction Gravels+nnth fines 9m S�Iry gravels,gravel-sand-s�lt m�xtures I
retamed on No. �i
Coarse-gra�ned so�ls (appreciable amount
Sieve of lines) GC .� Ctayey gravels,grave!-sand-clay m�xtures
9� I
Syy � `Nell-graded sands, gravetly sands. little or no �
More than 50°6 Sand ard sandy Clean sand �5`N lines I
matenal larger than So�is (httle or no fines) ••- • •=•t• i , I
gp Poorly-graded sands,gravelh�sards, dtle cr no
No 2C0 sieve s�ze �w::.����� sP `ines
: • •����i�'
�.1ore;han 50 0
cearse fraction sM �� S;Iry sands, sand-s�it muctures
passing No.�l SanCs with fines gm
Sieve (appreciable amount II
of fines) SC SG Clayey sands,sand-ctay m�xtures
M� Inorganic silts and very fine sands, rock flour,
mi sitty-clayey fine sands,clayey silts with slight piasticity I�
Sifts Liquid limit CL Inorganic ctays of low to medium plasticiry,gravely I
Fine-grained soiis and cfays less than 50 cl clays,sandy clays,siliy clays,lean ciays �
' ' ' ' ' ' ' OL Organic silts and organic silty clays of low I
ii � iiii I
i i i i i i i ol plastiCity I
iiii � ii
More than 50% MH Inorganic silts,mlcaceous a diatomaceous fine
matenal smaller than mh sand or sifry soils �
No. 200 sieve size Silts � �d fimit CH I
� ch �norganic clays of high piasticiry, fat ciays �
and clays greater than 50
,' � �' ,' pH Organic clays of inedium to high plas6ciry, ��
�����,'� oh organic silts
Highly orgarnc soils '-/ � '�` PT Peat, humus, swamp scils with high crganic
_ _ pt contents
Topsoil W W � Numus and duff layer
W W
Fiil Hig�Iy vanable consutuer.ts
The discussion in the text of this report is necessary for a proper understanding of the nature of the matenal presented in the attached logs. Dual
�� symbols are used to indicate borderiine soil dassification.
C TORVANE READING, tsf ! 2"O.D. SPLIT SPOON SAMPLER
qu PENETROMETER READING, tsf �
`N MOISTURE, '/o dry weight I 2.4" I.D. RING OR SHELBY TUBE SA.1�IPL�R
P SAMPLER PUSHED "
` SAMPLE N�T RECOVERED ' `NATER OBSERVATION 'NELL
pcf DRY DE^lSITY, Ib. per cubic ft.
LL LI�UID LIMIT, % y DEPTH GF E�1COU��TERED GP.OUNDV+/ATER DURING
PI PLASTIC INGEX EXCA`✓F.TICN
� T SiJBSE1UE�T GROUND��IATER ��VEL'NITH DATE
I
�� rth ���nsult�nts, [ncJ. LEGEND - A1
,,. , �,.�� ., � ;� � ,. ,_,� .�, . �:���;.�-,� ��,��.,�.�i , .� ���� „ .
� Test Pit Log • �I
Pro�ec!Name: • ��t a� I
� • Sue Chan Short Plat � � I
Job No. Logged by: Date: Test Pit No.:
. 11997 ELW 8/12/OS TP-1
Excavatlon Contrador. Approx. Ground Surface Elevatlon: �
Northwest Excavatin 191'
Notes: '
I
� — m � Surtace Condiuons: Depth of topsoil and sod: 6"; Blackberry brambles
General W r � � . a g
Notes ���o� 1O � o °- � � a
(� cn rn �n
; � ! ! SM ' Brown silty fine SAND, loose, moist
' � � I i -contains occasional gravel i li
, � i
� �
Is�Z � � Z � -contains roots, 30.2% fines I
l � 3 i
RENTON FORMATION (Epr): Tan SANDSTONE, weathered,
medium dense, moist
�i.s 4
-iron oxide staining
9-7 5 -becomes dense, less weathered
s
-becomes very dense
! 9�� 7 � -refusal on bedrock at 7.5' 1 I'
' Test Pit terminated at 7.5 feet below existing grade. No groundwater I i
( was encountered during excavation.
- � ; Test Pits excavated by Northwest Excavating using a 312 Cat I
I I tracked excavator.
i Elevations estimated from topographic lines depicted on a
I � � preliminary site plan provided by the client.
i
�
i
� I
I ' �
I
I (
� � I
i� ; � �
i � (
I I 1 I
N I I� I
ti � �
a � � i
� I ! �
_,
w i
a !
,� �i
a
" Test Pit Log
"' �arth ConsL�lr�nts, Inc• Sue Chan Short Plat
� G�•�iir.�hnlc;il G:;S��.r�rr5.�;�••�I�n{I�;t��.f�rvlruiunr.nr.il5� V-iilt5t; Renton, V�lashington
%n
� Pro�. rio. 11997 Dwn ELW oa�P August 2005 cne�xed EL'JV Date 8/23lOS P'ate A2
�
Subsurface�Andition:�;Np�aed r�:present our obseroauons at the time and locatlon of this exploratory hole,mod�fied b� ?n�inPennq tests.analyss
�nd judqment. They:ire rOI f1BC!?;sanl`�(QP(�'.Se(lI.7UVP of other hmes�nd Iacatlons.'Ne rannot accept respon,�t�liry for rhe use ar.nterpretaticn oy
nthNrs of information pre:Pnted�n this lo��.
Test Pit Lvg -
ProJect Neme: � Shast o(
' Sue Chan Sho�t Plat � �
Job No. Logged by: Oate: Test Pit No.:
- 11997 ELW 8J12/05 TP-2
Excavatlon Contracto� Approx.Grvund Surface Elevatlon:
No�thwest Excavatin i 170'
Notes:
� „� I su�tace Condiuons: Depth of topsoil and sod: 12"; Mixed brush
Generdl I W L � $ . n; N �°
Notes I (%) U'� cn � � �n I � co �
' ' ,� .j � TPSL � Black TOPSOIL
{ �� � �
' I RENTON FORMATION (Epr) Tan SANDSTONE, weathered,
I 5.8 � , 2�; fractured, medium dense to dense, moist
i � I � I -localized iron oxide staining
3 -becomes dense, less weathered
I a
-becomes very dense
7.t
5
-contains very thin siltstone lens
s
-localized iron oxide staining,fractured in areas
$�o -iron oxide stainin alon beds, refusal on bedrock at T
�� Test Pit terminated at 7.0 feet below grade. No groundwater was �
encountered during excavation.
I '
� I
i
I
I, II,
I
� I
� (
i i I
I �
�, i i I
� I
I I II �
� ; � I
� II
� ; �
� ,
� � �
� ' I
�� � � �
w , , ,
a i I
T
" Test Pit Log
� �arth Consultants, Inc. Sue Chan Short Flat
- %�r��leCh�i��,-dP:i;�ic,�:�-:; �;�-�il���lsis.Givlr�minen�:US�:1��nUsiS Renton, Washington
n
y
� P�oi. rio. 11997 Dwn. ELV�/ Date August 2005 Checxed �L'�N Date 8l23/OS P!ate A3
9
�ubsurface�.onCi6ons 7�:picted represent our observations at the time and location of�hi:exoloratory hcle,modified by engineennq teses,analys�s
anri judqment. They are n,t necessanly representanve�f other times and locatfons.'/'/e annol�ccept responsibdih�for the u�e or interpreta0o�by
�thpr;ot informaUon prP;��nted an Ihis laq.
Test Pit Log -
� Project Neme: Sheet of
Sue Chan Short Plat � �
Job No. Lagged by: Date: Test Pit No.:
' 11997 � ELW 8/12/05 TP-3
� Excavatla�Contractor Approx.Ground Surface Elevatlon:
Northwest Excavating i 153'
Notes:
� � m N o Surtace condiuons: Depth of topsoil and sod: 9"; Blackberry brambles
General �N ;1 � �a ,,; a U �
Notes ('o) � E` p � � j E`
(� cn !n �
•. i I E`'! SM � Brown silty SAND, loose to medium dense, moist
I'E� -contains gravel
! ! ,;�;I t
, :) ��
I ;� 2
:�� �
�.s :� �I
� � '' 3 ML Mottled tan sandy SILT, medium dense, moist
' i
�9�� ; i `� 4 -Vace gravel, iron oxide staining ;
�
5 RENTON FORMATION (Epr):Tan SANDSTONE, weathered, ,
` fractured, dense, moist
i
�
� s
i '
. �
� 2�.0 -contains coal lens, becomes moist to wet
I 8 .
� RENTON FORMATION (Epr): Black COAL, fractured, dense, wet
, -contains gray, west-dipping siltstone beds
' z3.z 9 -contains moisture along fractures
I 10
i
is7.s I >> � �
12
13 �
I
� 14
-light groundwater seepage at 14'
15 ' �
; 12.0 �
16.Q ' 16
I !
I Test Pit terminated at 16.5 feet below existing grade. Light
� i I groundwater seepa5e�Nas encountered at 14.0 feet dunng
� excavation.
�
� , �
c�� � � i
U I � I I I
W IQ. �
�� I
T
�' Test Pit Lag
"' E�rth Consultants, Inc• Sue Chan Short Plat
�
1 �r��ir,�.t;iiu';,I f��{li:� �-� . �,�•��I��KIStS i F��vlrnnmrni�I�:tenU51•s Renton, 4Vashington
�
•n
y
^ P�o�. r�o. 11997 D•:�� ELW Date August 2005 Checked EL�N oate 8l23/OS P�ate A4
m
Subsurface condihon; �:Hprr,�ed represent our observatlons at the tlme and location�f this explor�rory hnle, modified by enqmeennq tesls, analygis
and judqment. Th�y ar��n�;t rn:cessanly representative of other times ard locations.'Ple�annot accept respons�bdity for the use ar�nterprelaUon by
nthers of inf�rmahon ,r.�•.��n��:�1 �n this foq.
Test Plt l.og .
' ProJect Name: � Sf�aet of
� ' Sue Chan Short Plat � �
Job No, logged by: Oate: Test Pit No.:
. 11997 ElW 8/12/OS TP-4
Excavatlon Contractor: Approx.Ground Su�face Eievatlon:
Northwest Excavatin 154'
Notes:
� — m � Surtace condiuons: Depth of topsoil and sod: 8"; Blackberry brambles,
General w L � $ . a $ mixed brush
Notes ��/a� �� � LL � � N
I � SM I Brown silty SAND, loose, moist
� � i �
I �0 2 ' i RENTON FORMATION (Epr): Tan SANDSTONE, weaihered,
� fractured, medium dense, moist
3 -iron oxide staining �
4 -becomes dense, less weathered
5
s -becomes very dense
�2.s :
14.4 . �
-refusal on bedrock at 7.5'
Test Pit terminated at 7.5 feet below existing grade. No groundwater j
was encountered during excavation. I
�
I
� I
(
I
I I
I I
!
� I
� I
a
� I I
� I
C7 � I
w I I I �
a i
m
� Test Pit Log
� Earth Consult�nts, Inc. Sue Chan Short Flat
,ee>irr;;nical F�;�lnr�rs.�;r��lo�lsis*�Gnvlronmeni,d 5�_ienilsi5 Renton, �l�/ashington
%n
W
� Proj.No. 11997 Ow�. EL`N oate August 2005 Checked EL`N oate 8/23/OS P!ate A5
�
Subsurface conditions depicied r?present aur�bservaGons at the Ume and Ioration of�his exploratory hcle,modifled by enqineennq!ests,anatys+s
and judqment. They are not necessardy representative of other times and IacaUons.`/`/e�annot accept responsibilih/for the u�.;e or�nterpre[ation by
�:thers qf informatlon presented on rhls loq.
� Test Plt Log •
� Pro�ect Name: S�eet p�
� Sue Chan Short Plat � �
Job No. logged by: Oate: Test Pit No.:
• 11997 ELW 8/12/OS TP-5
� Expvatlon Contractor� Approx. Ground Su�face ElevaUon: I�
Northwest Excavatin 136' �
Notes: �
� � o m� � o surface cond��ions: Depth of topsoil and sod: 4"; Blackberry brambles '�
Generdl W Q a a . n� V a
NOt@S (%) I � � p � � j �
� � I �i
i �I� ; � ' SM � Brown silty SAND, loose to medium dense, wet ,
I , � � I
; zo.s � i ; �;
�
Z i j -becomes tan, mottled
� �
` � i i
! 3
; -moderate caving
2s.s ; -becomes saturated '
� 4
; -28.0% fines
� 5 -light groundwater seepage at 4.5' �
I : -contains coal fragments
� s
, ML Gray SILT, medium dense, moist 1 �
7
33.6 ( -thinnly bedded, contains coal fragments
$ -contains thin sand interbeds i
� I i
9 ' � h br wn il SAND dens m i t �
' � SM Reddis o s ty e, o s
� ' -trace gravel, localized sand lenses, localized iron oxide staining
� zi.s i � �� -moisture within sand lenses
� � f
; � s : �� I SM Gray silty SAND with gravel, medium dense, wet
I E:� ;a 1 2 I -contains sand and fine gravel interbeds
, _, i
I ':� `
�l 13
21.9 , � I
� '�
;� � 14 �
� I
; F t �
' 17�3 � .� 15 ' -a ears disturbed, loses beddin , contains coa( fra ments
18�7 ' '�I i' ' ML Gra SILT with sand, dense, moist
� �s.2 I 16 SM Black silty SAND, dense, wet
I i�� »i ! � -contains coal fragments
;, ; i � Test Pit terminated at 17.0 feet below existing grade. Light
� I ! ; groundwater seepage was encountered at 4.5 feet during
� ' ' � � excavation.
�� � I I (
L , � I I I
; �
T
� Test Pit Log '
�� Earth Consult�nts, Inc�. Sue Chan Snort Plat I
- Gr��irrhn�Cal F�igli.�-�r�. ':�r�ln��l51s i F_I1VIf�111111rCIlf,�I S� ',•-i.il,;�. Renton, Washington I
n
� Proi. rio. 11997 GNn EL'N Date August 2005 Checked EL'�N Dace 8/23/05 ��ate A6
5
�ubsurface conditlons depi�ted rPpresent cur observation;�t�he hm?�nd loca[ion nf rhis?xploratory hole, modified by enqineennq�ests,analysis
;nd judGment. They arP nr,t necessardy reprPsent�tive�,(�,thPr hmn� •�nd locations. 'Ne cannot accept responsibdih/tcr Ihe use ar nterprela�on cy
;�her;of infr,rm.�ticn pr�:�;�n!�•r; �;n �hi•; Ir,;.
_ �
APPENDIX B
LABORATORY TEST RESULTS
E-1 'i 997
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GRAIN SIZE - mm
• 96 COBBLES � %GRAVEL %SANO %SILT %CLAY USCS AASHTO PL LL
C 8.5 61.3 30.2 SM
c , 5.2 66.8 28.0 SM
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SIEVE � PERCENT FiNER SIEVE PERCENT FINER SOIL DESCRIPTION
incnes � � number � G O TP-1: 2'-S�I
1 5 100.0 100.0 #4 91.5 94.8 B��silry Sand;6.2%�toisturo
3/4 100.0 100.0 #8 89.2 94.3 �TP_5:3.5'-S�t
3/8 96.7 94.9 l�16 87.2 93.4 Brown silry Sand;26.5%�toisnue
#30 85.� 91.9
#50 78.0 87.6
a 100 47.2 54.6
#200 30.2 23.0
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GRAIN SIZE REMARKS
�60 0.198 0.169 o FI'1r1LC (
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COEFriClENTS I i �
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: Source Sample Nu : TP-l Elev.iDepth: 2'
c Suurcc Sampic Nc�.: TP-� Elcv./Depch: 3.�'
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SUDIFCT:
MCCANN ENCINEERING INC.
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