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EarthSolutions
NW LLC
15365 N.E.90th Street,Suite 100 Redmond,WA 98052
(425)449-4704 Fax (425)449-4711
www.earthsolutionsnw.com
Geotechnical Engineering
Construction Observation/Testing
Environmental Services
GEOTECHNICAL ENGINEERING STUDY
SOLERA
2902 NORTHEAST SUNSET BOULEVARD
RENTON,WASHINGTON
ES-5719.03
PREPARED FOR
DEVCO, LLC
September 28, 2020
_________________________
Chase G. Halsen, L.G.
Project Geologist
_________________________
Raymond A. Coglas, P.E.
Principal Engineer
GEOTECHNICAL ENGINEERING STUDY
SOLERA
2902 NORTHEAST SUNSET BOULEVARD
RENTON, WASHINGTON
ES-5719.03
Earth Solutions NW, LLC
15365 Northeast 90th Street, Suite 100
Redmond, Washington 98052
Phone: 425-449-4704 | Fax: 425-449-4711
www.earthsolutionsnw.com
09/28/2020
09/28/2020
Geotechnical-Engineering Report
Important Information about This
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The following information is provided to help.
The Geoprofessional Business Association (GBA)
has prepared this advisory to help you – assumedly
a client representative – interpret and apply this
geotechnical-engineering report as effectively as
possible. In that way, you can benefit from a lowered
exposure to problems associated with subsurface
conditions at project sites and development of
them that, for decades, have been a principal cause
of construction delays, cost overruns, claims,
and disputes. If you have questions or want more
information about any of the issues discussed herein,
contact your GBA-member geotechnical engineer.
Active engagement in GBA exposes geotechnical
engineers to a wide array of risk-confrontation
techniques that can be of genuine benefit for
everyone involved with a construction project.
Understand the Geotechnical-Engineering Services
Provided for this Report
Geotechnical-engineering services typically include the planning,
collection, interpretation, and analysis of exploratory data from
widely spaced borings and/or test pits. Field data are combined
with results from laboratory tests of soil and rock samples obtained
from field exploration (if applicable), observations made during site
reconnaissance, and historical information to form one or more models
of the expected subsurface conditions beneath the site. Local geology
and alterations of the site surface and subsurface by previous and
proposed construction are also important considerations. Geotechnical
engineers apply their engineering training, experience, and judgment
to adapt the requirements of the prospective project to the subsurface
model(s). Estimates are made of the subsurface conditions that
will likely be exposed during construction as well as the expected
performance of foundations and other structures being planned and/or
affected by construction activities.
The culmination of these geotechnical-engineering services is typically a
geotechnical-engineering report providing the data obtained, a discussion
of the subsurface model(s), the engineering and geologic engineering
assessments and analyses made, and the recommendations developed
to satisfy the given requirements of the project. These reports may be
titled investigations, explorations, studies, assessments, or evaluations.
Regardless of the title used, the geotechnical-engineering report is an
engineering interpretation of the subsurface conditions within the context
of the project and does not represent a close examination, systematic
inquiry, or thorough investigation of all site and subsurface conditions.
Geotechnical-Engineering Services are Performed
for Specific Purposes, Persons, and Projects,
and At Specific Times
Geotechnical engineers structure their services to meet the specific
needs, goals, and risk management preferences of their clients. A
geotechnical-engineering study conducted for a given civil engineer
will not likely meet the needs of a civil-works constructor or even a
different civil engineer. Because each geotechnical-engineering study
is unique, each geotechnical-engineering report is unique, prepared
solely for the client.
Likewise, geotechnical-engineering services are performed for a specific
project and purpose. For example, it is unlikely that a geotechnical-
engineering study for a refrigerated warehouse will be the same as
one prepared for a parking garage; and a few borings drilled during
a preliminary study to evaluate site feasibility will not be adequate to
develop geotechnical design recommendations for the project.
Do not rely on this report if your geotechnical engineer prepared it:
• for a different client;
• for a different project or purpose;
• for a different site (that may or may not include all or a portion of
the original site); or
• before important events occurred at the site or adjacent to it;
e.g., man-made events like construction or environmental
remediation, or natural events like floods, droughts, earthquakes,
or groundwater fluctuations.
Note, too, the reliability of a geotechnical-engineering report can
be affected by the passage of time, because of factors like changed
subsurface conditions; new or modified codes, standards, or
regulations; or new techniques or tools. If you are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying the recommendations in it. A minor amount
of additional testing or analysis after the passage of time – if any is
required at all – could prevent major problems.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical-
engineering report did not read the report in its entirety. Do not rely on
an executive summary. Do not read selective elements only. Read and
refer to the report in full.
You Need to Inform Your Geotechnical Engineer
About Change
Your geotechnical engineer considered unique, project-specific factors
when developing the scope of study behind this report and developing
the confirmation-dependent recommendations the report conveys.
Typical changes that could erode the reliability of this report include
those that affect:
• the site’s size or shape;
• the elevation, configuration, location, orientation,
function or weight of the proposed structure and
the desired performance criteria;
• the composition of the design team; or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
or site changes – even minor ones – and request an assessment of their
impact. The geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical
engineer was not informed about developments the engineer otherwise
would have considered.
Most of the “Findings” Related in This Report
Are Professional Opinions
Before construction begins, geotechnical engineers explore a site’s
subsurface using various sampling and testing procedures. Geotechnical
engineers can observe actual subsurface conditions only at those specific
locations where sampling and testing is performed. The data derived from
that sampling and testing were reviewed by your geotechnical engineer,
who then applied professional judgement to form opinions about
subsurface conditions throughout the site. Actual sitewide-subsurface
conditions may differ – maybe significantly – from those indicated in
this report. Confront that risk by retaining your geotechnical engineer
to serve on the design team through project completion to obtain
informed guidance quickly, whenever needed.
This Report’s Recommendations Are
Confirmation-Dependent
The recommendations included in this report – including any options or
alternatives – are confirmation-dependent. In other words, they are not
final, because the geotechnical engineer who developed them relied heavily
on judgement and opinion to do so. Your geotechnical engineer can finalize
the recommendations only after observing actual subsurface conditions
exposed during construction. If through observation your geotechnical
engineer confirms that the conditions assumed to exist actually do exist,
the recommendations can be relied upon, assuming no other changes have
occurred. The geotechnical engineer who prepared this report cannot assume
responsibility or liability for confirmation-dependent recommendations if you
fail to retain that engineer to perform construction observation.
This Report Could Be Misinterpreted
Other design professionals’ misinterpretation of geotechnical-
engineering reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a continuing member of
the design team, to:
• confer with other design-team members;
• help develop specifications;
• review pertinent elements of other design professionals’ plans and
specifications; and
• be available whenever geotechnical-engineering guidance is needed.
You should also confront the risk of constructors misinterpreting this
report. Do so by retaining your geotechnical engineer to participate in
prebid and preconstruction conferences and to perform construction-
phase observations.
Give Constructors a Complete Report and Guidance
Some owners and design professionals mistakenly believe they can shift
unanticipated-subsurface-conditions liability to constructors by limiting
the information they provide for bid preparation. To help prevent
the costly, contentious problems this practice has caused, include the
complete geotechnical-engineering report, along with any attachments
or appendices, with your contract documents, but be certain to note
conspicuously that you’ve included the material for information purposes
only. To avoid misunderstanding, you may also want to note that
“informational purposes” means constructors have no right to rely on
the interpretations, opinions, conclusions, or recommendations in the
report. Be certain that constructors know they may learn about specific
project requirements, including options selected from the report, only
from the design drawings and specifications. Remind constructors
that they may perform their own studies if they want to, and be sure to
allow enough time to permit them to do so. Only then might you be in
a position to give constructors the information available to you, while
requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions. Conducting prebid and
preconstruction conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplines. This happens in part because soil and rock on
project sites are typically heterogeneous and not manufactured materials
with well-defined engineering properties like steel and concrete. That
lack of understanding has nurtured unrealistic expectations that have
resulted in disappointments, delays, cost overruns, claims, and disputes.
To confront that risk, geotechnical engineers commonly include
explanatory provisions in their reports. Sometimes labeled “limitations,”
many of these provisions indicate where geotechnical engineers’
responsibilities begin and end, to help others recognize their own
responsibilities and risks. Read these provisions closely. Ask questions.
Your geotechnical engineer should respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study – e.g., a “phase-one” or “phase-two” environmental
site assessment – differ significantly from those used to perform a
geotechnical-engineering study. For that reason, a geotechnical-engineering
report does not usually provide environmental findings, conclusions, or
recommendations; e.g., about the likelihood of encountering underground
storage tanks or regulated contaminants. Unanticipated subsurface
environmental problems have led to project failures. If you have not
obtained your own environmental information about the project site,
ask your geotechnical consultant for a recommendation on how to find
environmental risk-management guidance.
Obtain Professional Assistance to Deal with
Moisture Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, the engineer’s
services were not designed, conducted, or intended to prevent
migration of moisture – including water vapor – from the soil
through building slabs and walls and into the building interior, where
it can cause mold growth and material-performance deficiencies.
Accordingly, proper implementation of the geotechnical engineer’s
recommendations will not of itself be sufficient to prevent
moisture infiltration. Confront the risk of moisture infiltration by
including building-envelope or mold specialists on the design team.
Geotechnical engineers are not building-envelope or mold specialists.
Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly
prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of
GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind.
Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation.
Telephone: 301/565-2733
e-mail: info@geoprofessional.org www.geoprofessional.org
September 28, 2020
ES-5719.03
DevCo, LLC
10900 Northeast 8th Street, Suite 1200
Bellevue, Washington 98004
Attention: Mr. David Ratliff
Dear Mr. Ratliff:
Earth Solutions NW, LLC (ESNW) is pleased to present this report titled “Geotechnical
Engineering Study, Solera, 2902 Northeast Sunset Boulevard, Renton, Washington”. Based on
the results of our study, construction of the proposed townhome and commercial mixed-use
development is feasible from a geotechnical standpoint. Development plans include construction
of a series of townhome structures established at-grade combined with a larger multi-family
structure(s) incorporating an underground parking level, at-grade commercial space, and 5-levels
of podium supported residential units. Based on the identified subsurface conditions, soils are
comprised largely of near surface fill deposits underlain by medium dense to dense sand and
silty sand native soils. The identified fill deposits are comprised primarily of loose silty sands
extending to depths of roughly 6 to 11 feet below existing grades.
With respect to the relatively lightly loaded townhome structures constructed at-grade, building
support may be derived on conventional continuous and spread foundations bearing on at least
two-feet of structural fill. Where conditions allow, and compaction can be attained, the existing
fill present onsite may be considered for use as structural fill and compacted in-place where
feasible. Soils deemed to be unsuitable for use will require overexcavation and replacement with
a suitable structural fill material. In terms of the heavier building structure(s) incorporating a
podium and related post-tensioned slabs, column and perimeter wall foundations must derive
support within the medium dense to dense native soils encountered at-depth. Underground
garage excavation planned for the heavier building structure(s) is expected to expose the medium
dense to dense native soils suitable for foundation support. However, in the case of the heavier
building structure(s), where loose or otherwise unsuitable soils are exposed at foundation grades,
overexcavation and replacement with 2-inch clean crushed rock (or lean mix) placed directly atop
the competent native soils at-depth will be required.
Given the variability and generally dense and compact nature of the native silty sand and sand
deposits, large scale infiltration of stormwater for this project is not recommended. In this respect,
we presume that stormwater management designs will utilize limited infiltration flow control
devices such as bio-swales and rain gardens to the extent practicable. Any infiltration device
would likely serve with limited functionality and would require the incorporation of an overflow
provision into its final design.
15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
DevCo, LLC ES-5719.03
September 28, 2020 Executive Summary – Page 2
Earth Solutions NW, LLC
Geotechnical recommendations related to earthwork, temporary shoring, foundation design,
drainage, and other pertinent design aspects are provided in this study. We appreciate the
opportunity to be of service to you on this project. If you have questions regarding the content of
this geotechnical engineering study, please call
Sincerely,
EARTH SOLUTIONS NW, LLC
Chase G. Halsen, L.G.
Project Geologist
Earth Solutions NW, LLC
Table of Contents
ES-5719.03
PAGE
INTRODUCTION ................................................................................. 1
General..................................................................................... 1
Project Description ................................................................. 2
SITE CONDITIONS ............................................................................. 2
Surface ..................................................................................... 2
Subsurface .............................................................................. 3
Topsoil and Fill ............................................................. 3
Native Soil ..................................................................... 3
Geologic Setting ........................................................... 3
Groundwater ................................................................. 4
Critical Areas……………………………………………………… 4
Steep Slopes……………………………………………… 4
Wellhead Protection Areas…………………………….. . 4
DISCUSSION AND RECOMMENDATIONS ....................................... 5
General..................................................................................... 5
Site Preparation and Earthwork ............................................. 6
Site Stripping Recommendations……………………. . 6
Temporary Erosion Control ......................................... 6
Subgrade Preparation (Surface)……………………….. 7
In-situ and Imported Soils ........................................... 7
Structural Fill (General Applications)…………………. 8
Excavations and Slopes…………………………………. 8
Shoring .................................................................................... 9
Cantilever and Single-Tieback Soldier Pile Walls...... 9
Soldier Piles ................................................................. 10
Timber Lagging ........................................................... 10
Tieback Anchors .......................................................... 10
Shoring Wall Drainage ................................................. 11
Shoring Monitoring ...................................................... 11
Foundations ............................................................................ 11
Seismic Design ....................................................................... 12
Slab-on-Grade Floors ............................................................. 12
Retaining Walls ....................................................................... 13
Drainage................................................................................... 14
Preliminary Infiltration Feasibility ............................... 14
Preliminary Detention Vault Design
(Where Applicable) ....................................................... 14
Earth Solutions NW, LLC
Table of Contents
Cont’d
ES-5719.03
PAGE
Preliminary Pavement Sections…………………………… ..... 15
Utility Support and Trench Backfill ....................................... 16
LIMITATIONS ...................................................................................... 17
Additional Services ................................................................. 17
GRAPHICS
Plate 1 Vicinity Map
Plate 2 Subsurface Exploration Plan
Plate 3 Cantilever & Singe Tieback Wall
Plate 4 No Load Zone
Plate 5 Shoring Wall Drainage Detail
Plate 6 Retaining Wall Drainage Detail
Plate 7 Footing Drain Detail
APPENDICES
Appendix A Subsurface Exploration
Test Pit and Boring Logs
Appendix B Laboratory Test Results
Earth Solutions NW, LLC
GEOTECHNICAL ENGINEERING STUDY
SOLERA
2902 NORTHEAST SUNSET BOULEVARD
RENTON, WASHINGTON
ES-5719.03
INTRODUCTION
General
This geotechnical engineering study was prepared for the proposed townhome and mixed-use
development to be constructed west of Northeast Sunset Boulevard between Northeast 10 th
Street and Kirkland Avenue Northeast in Renton, Washington. The purpose of this study was to
provide geotechnical recommendations for currently proposed development plans. Our scope of
services for completing this study included the following:
Subsurface borings and test pits for the purpose of characterizing site soil and
groundwater conditions;
Laboratory testing of soil samples obtained during subsurface exploration;
Engineering analyses and recommendations for the proposed development, and;
Preparation of this report.
The following documents and resources were reviewed as part of our report preparation;
Preliminary Geologic Map of Seattle and Vicinity, Washington, by H.H. Waldron, B.A.
Liesch, D.R. Mullineaux, and D.R. Crandell;
Online Web Soil Survey (WSS) resource, maintained by the Natural Resources
Conservation Service under the United States Department of Agriculture, and;
King County Liquefaction Susceptibility, endorsed by the Washington State Department
of Natural Resources, May 2010.
DevCo, LLC ES-5719.03
September 28, 2020 Page 2
Earth Solutions NW, LLC
Project Description
Based on the current conceptual design, development activities will include construction of a
series of multi-unit townhome structures, retail space, and related infrastructure improvements.
A larger multi-family structure(s) occupying Blocks A and B will incorporate an underground
parking level, at-grade commercial space, and 5-levels of podium supported residential units
above. More traditional (lightly loaded) townhome style building structures constructed at-grade
will occupy Blocks C and D of the project site. Excavations to construct the underground parking
levels for the heavier podium style structure(s) are estimated to be on the order of 12 to 15 feet
below existing ground surface elevation. Grading plans had not been finalized at the time of this
study. However, we anticipate cuts and fills on the order of roughly 4 to 8 feet may be necessary
at some locations to establish finish (surface) grades throughout the site. Retaining walls and/or
rockeries may also be incorporated into final designs to accommodate grade transitions, where
necessary.
At the time of report submission, specific building load plans were not available for review;
however, based on our experience with similar developments foundation loading for the proposed
lightly loaded townhome structures constructed at-grade are estimated to be on the order of 3 to
4 kips per foot. The larger podium style structure(s) will incorporate post-tensioned slab
construction and will utilize relatively heavily loaded spread footing foundations. Although
foundation plans are still being developed, we estimate column loads for the larger podium
structure(s) will be on the order of 350 to 450 kips. Slab-on-grade loading for all of the structures
is anticipated to be approximately 150 pounds per square foot (psf).
If the above building design assumptions are incorrect or change, ESNW should be contacted to
review the recommendations in this report. ESNW should review the final design to verify the
geotechnical recommendations provided in this report have been incorporated into the plans.
SITE CONDITIONS
Surface
The subject site is located west of Northeast Sunset Boulevard between Northeast 10 th Street
and Kirkland Avenue Northeast in Renton, Washington. The approximate location of the subject
site is depicted on Plate 1 (Vicinity Map). The irregular-shaped property is comprised of six tax
parcels (King County Parcel Nos. 722780-1205, -1206, -1235, -1405, -1406, and -1785) totaling
approximately 11.07 acres. The site is bordered to the north by Kirkland Avenue Northeast, to
the east by Northeast Sunset Boulevard, to the south by Northeast 10 th Street and to the west by
Harrington Place. Current site development includes various commercial retail, restaurant, and
banking structures. Remaining portions of the site are largely covered with asphalt parking areas
and drive lanes. We understand these structures are to be demolished and removed during site
redevelopment. Due to the extent of current development, gradients are generally level across
the site with a minor declination from the north/central site area to the west. Approximately 20
feet of vertical elevation change occurs within the confines of the property.
DevCo, LLC ES-5719.03
September 28, 2020 Page 3
Earth Solutions NW, LLC
Subsurface
An ESNW representative observed, logged, and sampled 13 borings advanced at representative
locations within the property boundaries in December of 2017. The borings were completed with
a truck-mounted drill rig and operators retained by our firm. Subsequent to the December 2017
investigation, a series of test pits were also excavated in June of 2018. The subsurface
exploration was completed for purposes of assessment and classification of site soil and shallow
groundwater conditions. The approximate locations of the borings and test pits are depicted on
Plate 2 (Subsurface Exploration Plan). Please refer to the test pit and boring logs provided in
Appendix A for a more detailed description of subsurface conditions. Representative soil samples
collected at the test sites were analyzed in general accordance with Unified Soil Classification
System (USCS) and United States Department of Agriculture (USDA) methods and procedures.
Topsoil and Fill
Due to the extent of site development, surficial topsoil deposits are expected to be largely absent
throughout the site. However, isolated areas of topsoil may be present in current non-structural
and landscaping areas. Silty sand fill material was encountered at boring locations B-3, -4, -5, -
6, -8, and -13, extending up to an approximate depth of 11 feet below the existing ground surface
elevation (bgs). In general, the fill was encountered in a loose to medium dense and moist
condition with the exception of B-8, where the fill was encountered in a very loose condition
extending up to an approximate depth of 11 feet bgs. Shallow fill extending to a depth of
approximately 1-foot was also identified at the test pit locations. The majority of the encountered
fill was likely placed during historic construction activities for the current site development. In
addition to the fill deposits identified at the test locations, fill should be expected within, and in
proximity, to current site structures and areas of general improvements.
Native Soil
Underlying fill, native soils were encountered primarily as silty sand and sand with varying
degrees of silt (USCS: SM, SP-SM, and SP). Native soils were largely encountered in a medium
dense to dense and moist condition, extending to the maximum exploration depth of 21.5 feet
bgs.
Geologic Setting
The referenced geologic map resource identifies Vashon glacial till (Qt) deposits underlying the
site and surrounding areas. According to the geologic map resource, the till is characterized as
a concrete-like mixture of silt, sand, gravel, and clay. The referenced WSS resource identifies
Urban land and arents of Alderwood material (Map Unit Symbols: Ur and AmC, respectively).
Designation of arents indicates some reworking (earthwork and grading activities) of the native
soils. Based on our field observations, native soils are generally consistent with the geologic
map and soil survey designations. However, the compact sand deposits identified at the boring
sites may also be associated with younger sands (Qys) which are to the west of the site.
DevCo, LLC ES-5719.03
September 28, 2020 Page 4
Earth Solutions NW, LLC
Groundwater
During our December 2017 and June 2018 fieldwork, perched groundwater seepage or water
bearing conditions were not encountered at the test sites. Groundwater seepage is common
within glacial deposits and rates and elevations fluctuate depending on many factors, including
precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater
elevations and flow rates are higher during the winter, spring and early summer months. In our
opinion, the contractor should be prepared to respond to and manage areas of groundwater
seepage during construction activities. With respect to the currently proposed one-level below
grade construction for the “podium building(s)”, groundwater is not expected to significantly
impact the proposed construction based on conditions identified at the test sites. However,
potential groundwater impacts should be evaluated with respect to subsurface drainage and
possible sub-slab drainage systems for the underground garage levels during final design and
finally during construction when the excavation has been completed.
Critical Areas
As part of this report preparation, we reviewed hazard area maps maintained by the City of
Renton to identify mapped geologically hazardous areas onsite. Our review is as follows:
Steep Slopes
Based on the referenced steep slope map, infrequent and isolated areas of the site have been
preliminarily mapped as having inclinations up to approximately 25 percent. According to Renton
Municipal Code (RMC) 4-3-050G.2.5.a, these slopes are considered ‘sensitive slopes.’ However,
based on our field observations during our subsurface explorations, it appears these inclination
designations are a result of previous site construction (retaining walls, cuts/fills, etc.) rather than
a naturally occurring slope. In accordance with RMC 4-3-050.G.2, there is no required buffer of
building setback distance for development near sensitive slopes. In our opinion, no buffer or
setback need be applied to the proposed development.
Wellhead Protection Areas
Based on the referenced Wellhead Protection Area (WPA) map, the subject site is within a Zone
2 WPA designation. As defined in RMC 4-3-050.G.2.8, a Zone 2 WPA is considered the land
area situated between the three hundred sixty five (365) day groundwater travel time contour and
the boundary of the zone of potential capture for a well or well field owned or operated by the
City. In accordance with RMC 4-3-050.G.2, there is no required buffer or building setback
distance associated with WPA Zone 1 or 2. Proposed site development plans are largely limited
to construction of residential and mixed-use residential/commercial structures and associated
infrastructure improvements. In this respect, we do not anticipate that hazardous materials will
be stored on-site. As such, it is our opinion that limited infiltration of stormwater (if pursued)
combined with any applicable water quality efforts is feasible from a geotechnical standpoint.
However, development standards for WPA Zone 2, as outlined in RMC 4-3-050.G still need to be
applied to the subject project, when relevant.
DevCo, LLC ES-5719.03
September 28, 2020 Page 5
Earth Solutions NW, LLC
DISCUSSION AND RECOMMENDATIONS
General
Based on the results of our study, construction of the proposed townhome and commercial mixed-
use development is feasible from a geotechnical standpoint. The primary geotechnical
considerations associated with the proposed development include foundation subgrade
preparation, temporary excavation and shoring, subsurface drainage, and suitability of the on-
site soils for use during site mass grading activities. Development activities will include
construction of a series of multi-unit townhome structures, retail space, and related infrastructure
improvements. A larger multi-family structure(s) occupying Blocks A and B will incorporate an
underground parking level, at-grade commercial space, and 5-levels of podium supported
residential units above. More traditional (lightly loaded) townhome style building structures
constructed at-grade will occupy Blocks C and D of the project site. Based on our understanding
of preliminary design concepts, we expect temporary excavations for the underground garage
level construction to utilize open cuts (where feasible) and cantilever or single tieback soldier pile
wall shoring.
With respect to the relatively lightly loaded townhome structures constructed at-grade, building
support may be derived on conventional continuous and spread foundations bearing on at least
two-feet of structural fill. Where conditions allow, and compaction can be attained, the existing
fill present onsite may be considered for use as structural fill and compacted in-place where
feasible. Soils deemed to be unsuitable for use will require overexcavation and replacement with
a suitable structural fill material. In terms of the heavier building structure(s) incorporating a
podium and related post-tensioned slabs, column and perimeter wall foundations must derive
support within the medium dense to dense native soils encountered at-depth. Underground
garage excavation planned for the heavier building structure(s) is expected to expose the medium
dense to dense native soils suitable for foundation support. However, in the case of the heavier
building structures, where loose or otherwise unsuitable soils are exposed at foundation grades
overexcavation and replacement with 2-inch clean crushed rock (or lean mix) placed directly atop
the competent native soils at-depth will be required.
Given the variability and generally dense and compact nature of the native silty sand and sand
deposits, large scale infiltration of stormwater for this project is not recommended. In this respect,
we presume that stormwater management designs will utilize limited infiltration flow control
devices such as bio-swales and rain gardens to the extent practicable. Any infiltration device
would likely serve with limited functionality and would require the incorporation of an overflow
provision into its final design.
The following sections of this study provide geotechnical recommendations related to earthwork,
temporary shoring, foundation design, drainage, and other pertinent design aspects. This study
has been prepared for the exclusive use of DevCo, LLC and their representatives. No warranty,
expressed or implied, is made. This study has been prepared in a manner consistent with the
level of care and skill ordinarily exercised by other members of the profession currently practicing
under similar conditions in this area.
DevCo, LLC ES-5719.03
September 28, 2020 Page 6
Earth Solutions NW, LLC
Site Preparation and Earthwork
Initial site preparation activities will consist of installing temporary erosion control measures,
establishing grading limits, and performing demolition activities, clearing, and site stripping.
Subsequent earthwork activities will involve mass grading operations and related infrastructure
improvements.
Site Stripping Recommendations
In general, little if any topsoil was encountered at the test locations. Due to the general extent of
preexisting site development, it is our opinion that surficial topsoil will generally not be
encountered during general earthwork activity. However, topsoil may be present within non-
structural and landscaping areas located sporadically throughout the site. If encountered, ESNW
should be retained to observe site stripping activities at the time of construction so that the degree
of required stripping may be assessed. Over-stripping should be avoided, as it is unnecessary
and may result in increased project development costs. Topsoil and organic-rich soil is neither
suitable for foundation support nor for use as structural fill. Topsoil and organic-rich soil may be
used in non-structural areas, if desired.
Temporary Erosion Control
Prior to the installation of either initial or final pavement sections, temporary construction
entrances and drive lanes, consisting of at least six inches of quarry spalls, should be considered
to both minimize off-site soil tracking and provide a stable access entrance surface. Geotextile
fabric may also be placed beneath the quarry spalls for greater stability of the temporary
construction entrance. Utilization of the existing asphalt parking areas and drive lanes may be
considered provided that it can be maintained and soil “trackout” can be adequately managed
during construction. Erosion control measures should consist of silt fencing placed around the
site perimeter. Soil stockpiles should be covered or otherwise protected to reduce soil erosion
during extended rainfall. Temporary approaches for controlling surface water runoff should be
established prior to beginning earthwork activities. Additional Best Management Practices
(BMPs), as specified by the project civil engineer and indicated on the plans, should be
incorporated into construction activities, as necessary.
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Subgrade Preparation (Surface)
Following site stripping and removal of existing structures, cuts and/or fills will be completed to
establish proposed subgrade elevations across the site. ESNW should observe the subgrade(s)
during initial site preparation activities to confirm soil conditions are as anticipated and to provide
supplementary recommendations for subgrade preparation, as necessary. The process of
removing existing structures may produce voids where old foundations and/or crawl space areas
may have been present. Complete restoration of voids resulting from demolition activities must
be executed as part of overall subgrade and building pad preparation activities. The following
guidelines for preparing building subgrade areas should be incorporated into the final design:
Where voids and related demolition disturbances extend below planned subgrade
elevations, restoration of these areas should be completed. Structural fill should be used
to restore voids or unstable areas resulting from the removal of existing structural
elements.
Recompact, or overexcavate and replace areas of existing fill exposed at building
subgrade elevations. Overexcavations should extend into competent native soils and
structural fill should be utilized to restore subgrade elevations as necessary.
ESNW should confirm subgrade conditions, as well as the required level of recompaction
and/or overexcavation and replacement, during site preparation activities. ESNW should
also evaluate the overall suitability of prepared subgrade areas following site preparation
activities.
In-situ and Imported Soils
The on-site soils possess a generally moderate sensitivity to moisture, and successful use as
structural fill will largely be dictated by the moisture content at the time of placement and
compaction. If necessary, remedial measures, such as soil aeration and/or cement treatment
(where approved by the local jurisdiction or utility district), can be considered as part of site
grading and earthwork activities. If the on-site soils cannot be successfully compacted, the use
of an imported soil may be necessary. In our opinion, a contingency should be provided in the
project budget for export of soil that cannot be successfully compacted as structural fill if grading
activities take place during periods of extended rainfall activity. Soils with fines contents greater
than 5 percent typically degrade rapidly when exposed to periods of rainfall.
Imported soil intended for use as structural fill should consist of a well-graded, granular soil with
a moisture content that is at (or slightly above) the optimum level. During wet weather conditions,
imported soil intended for use as structural fill should consist of a well-graded, granular soil with
a fines content of 5 percent or less (where the fines content is defined as the percent passing the
Number 200 sieve, based on the minus three-quarter-inch fraction).
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Structural Fill (General Applications)
Structural fill is defined as compacted soil placed in slab-on-grade and roadway areas. Fills
placed to construct permanent slopes and throughout retaining wall and utility trench backfill
areas are also considered structural fill. Soils placed in structural areas should be placed in loose
lifts of 12 inches or less and compacted to a relative compaction of 95 percent, based on the
laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D-1557).
For soil placed in utility trenches underlying structural areas, compaction requirements are
dictated by the local city, county, or utility district, and in general are specified as 95 percent
relative compaction. The upper 12 inches of pavement subgrade should be compacted to a
relative compaction of at least 95 percent. It should be noted that the above structural fill
requirements do not apply to areas of foundation subgrade for the heavier podium style building
structure(s). Supporting subgrade for these heavily loaded foundations must consist of
competent medium dense to dense native soils exposed at-depth, or 2-inch clean crushed rock
(or lean mix) placed atop competent native soils.
Excavations and Slopes
Excavation activities are likely to expose loose to medium dense fill soils and medium dense to
dense native soils below. Provided appropriate methods of sloping and shoring (as necessary)
for the excavations are incorporated into the design and construction, overall stability of site
excavations is anticipated to be good. Based on the soil conditions observed at the boring
locations, the following allowable temporary slope inclinations, as a function of horizontal to
vertical (H:V) inclination, may be used. The applicable Federal Occupation Safety and Health
Administration (OSHA) and Washington Industrial Safety and Health Act (WISHA) soil
classifications are also provided:
Fill soils, regardless of in-situ density 1.5H:1V (Type C)
Areas containing groundwater seepage 1.5H:1V (Type C)
Medium dense to dense native sand 1H:1V (Type B)
Steeper temporary slope inclinations within undisturbed and competent native deposits may be
feasible based on the soil and groundwater conditions exposed within the excavations. Steeper
inclinations may be considered, and must be subsequently approved, by ESNW at the time of
construction.
Permanent slopes should be planted with vegetation to enhance stability and to minimize erosion,
and should maintain a gradient of 2H:1V or flatter. The presence of perched groundwater may
cause localized sloughing of temporary slopes due to excess seepage forces. ESNW must
review site plans regarding excavation placement, proposed depth of excavation, and offsets
from both on and off-site features prior to construction activities. The review will assist in
preliminarily assessing and providing adequate temporary slope inclinations or recommended
the necessity of shoring implementations to support proposed site excavations.
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During construction, an ESNW representative should observe temporary and permanent slopes
to confirm the slope inclinations are suitable for the exposed soil conditions and to provide
additional excavation and slope recommendations, as necessary. If the recommended
temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support
excavations.
Shoring
We anticipate excavations of about 12 to 15 feet bgs will be necessary to construct the below-
grade parking levels. Where open cuts utilizing temporary sloped excavations are not feasible,
the use of temporary shoring will be necessary. In our opinion, where shoring is required, the
use of a conventional cantilever or single tieback soldier pile shoring system is feasible for
temporary support of excavations. Where tiebacks are necessary with respect to the shoring
design, temporary easements will likely be required where the anchors extend beyond the
property limits.
Cantilever and Single-Tieback Soldier Pile Walls
The shoring system should be designed to resist lateral soil pressure based on an active earth
pressure condition given the proposed excavation depth. Surcharge loading from adjacent
roadways or buildings should be included in the shoring design, where applicable. The following
parameters may be used for preliminary shoring design:
Active earth pressure (level backfill) 35 pcf (fill / native soils)
At-rest earth pressure (level backfill) 50 pcf
Traffic surcharge (where applicable) 70 psf (rectangular distribution)
Preliminary building surcharge (if applicable) 150 psf (rectangular distribution) *
Passive earth pressure 350 pcf (dense glacial deposits)**
* Building surcharge values should be reevaluated based on further assessment of adjacent building foundation
levels, proximity, and loading
** Passive earth pressure value may be applied over two pile diameters
A factor of safety of 1.5 has been applied to the passive resistance values listed above. A typical
earth pressure distribution for an active earth pressure condition is provided on Plate 3 (Cantilever
& Single Tieback Wall). Allowable soldier pile deflections for walls subjected to active earth
pressures should be limited to one inch.
At-rest pressures should be used where the shoring system will support adjacent foundation
loads and where both deflection of the shoring wall and adjacent ground subsidence must be
minimized. Recommendations for allowable soldier pile deflections can be provided once the
alignment and proximity of shoring walls to adjacent structures has been established. ESNW
should review the shoring wall design in order to provide supplementary earth pressure and
building surcharge recommendations, as necessary. Where at-rest earth pressures are applied,
a triangular distribution of pressure similar to the distribution illustrated on Plate 3 should be used.
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Soldier Piles
Soldier pile installation should be observed by a representative of ESNW to verify pile depths and
soil conditions. Appropriate pile lengths and embedment depths shall be determined by the
project structural engineer or respective shoring system designer. If sloughing of the soldier pile
excavation occurs, the contractor should be prepared to case soldier pile excavations as
necessary. Where groundwater seepage is encountered in excavations, localized sloughing
should be expected. As indicated in the following Tieback Anchors section of this report, soldier
piles embedded at least 10 feet into dense native soils may be designed with an end bearing
capacity of 10,000 psf.
Timber Lagging
Lagging should be installed in four-foot maximum lifts as the excavation is advanced. A
representative of ESNW should observe the shoring excavation to assess the stability of the cut.
The lagging should be backfilled as the excavation is advanced to minimize voids between the
lagging and cut face and to reduce the potential for ground subsidence behind the shoring wall.
Where sloughing of the excavation results in the development of a void behind the lagging,
injection of lean-mix concrete into the voided area should be considered.
If the shoring wall is designed as a temporary system, a 50 percent reduction in lateral earth
pressure may be assumed. Permanent lagging should be designed with pressure equal to 100
percent of the design lateral earth pressure.
Tieback Anchors
Where necessary, tiebacks should be located as high on the wall as possible and should be
designed based on the following preliminary parameters:
Allowable anchor pullout 1.75 kips/ft. (fill / upper native)
Declination angle (from horizontal) 15 to 20 degrees
Soldier pile end bearing capacity 10,000 psf (dense native)
No load zone See Plate 4
The allowable anchor pullout value provided above applies to typical six-inch-diameter tieback
anchors that will have the capacity to be post-grouted after installation. Tieback anchors should
be verification tested and proof tested in general accordance with the most recent edition of the
Recommendations for Prestressed Rock and Soil Anchors manual, published by the Post-
Tensioning Institute. A minimum of two verification tests (200 percent of the design load) should
be performed. Verification test anchors may be used as production anchors provided anchor
testing is acceptable. Production anchors should be proof tested to 130 percent of the design
load. A representative of ESNW should observe the anchor testing and provide documentation
of the test results, which should include an evaluation of anchor creep susceptibility. Tieback
anchors should be locked off at 90 to 100 percent of the design load. The soldier pile end bearing
capacity value provided in this section is based on the soldier piles embedding at least 10 feet
into dense native soil.
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Shoring Wall Drainage
Shoring walls should be provided with adequate drainage to reduce the potential for excess
buildup of hydrostatic pressure. During construction, drainage occurring between the timber
lagging is usually sufficient to prevent the development of excessive hydrostatic pressures.
Where permanent building walls will be constructed alongside temporary shoring walls, a sheet
drain material should be installed along the face of the shoring wall. A typical detail illustrating a
sheet drain and permanent wall drainage system is provided on Plate 5 (Shoring Wall Drainage)
of this study. As appropriate, waterproofing should be specified by the project architect.
Shoring Monitoring
Due to the proximity of adjacent right-of-ways and structures, the shoring monitoring program
should consist of optical surveying during soldier pile wall installation. A video survey should be
performed prior to beginning the excavations to document the current conditions of the
surrounding features. Initial survey points should be placed at strategic locations along adjacent
right-of-way alignments that will allow for periodic measurement during and after shoring
installation. Such strategic placement will allow for efficient monitoring of the site; excessive
deflections and/or excavation-related movements can be identified and remediated, should they
occur. Prior to the start of construction, ESNW, the project owner, and the construction contractor
should review relevant project plans and develop a monitoring program for the site.
Following installation of the soldier piles, monitoring points are typically established on the tops
of the piles prior to proceeding with the excavation. Initial baseline readings of the survey points
should be acquired prior to proceeding with the excavation. Readings should be acquired twice
weekly during the excavation phase of construction and may be reduced to once weekly after
excavations have been completed. ESNW should review the optical survey data as it becomes
available during the course of construction. The monitoring program should be supplemented
with periodic observations by ESNW representatives during the excavation phase of construction.
Foundations
As previously discussed, the relatively lightly loaded townhome structures constructed at-grade
can derive foundation support on conventional continuous and spread foundations bearing on at
least two-feet of structural fill. Where conditions allow, and compaction can be attained, the
existing fill present onsite may be considered for use as structural fill and compacted in-place if
feasible. Soils deemed to be unsuitable for use will require overexcavation and replacement with
a suitable structural fill material.
With respect to the heavier building structure(s) incorporating a podium and related post-
tensioned slabs, column and perimeter wall foundations must derive support within the medium
dense to dense native soils encountered at-depth. As previously discussed, the underground
garage excavations planned for the heavier building structure(s) are expected to expose the
medium dense to dense native soils suitable for foundation support. However, in the case of the
heavier building structure(s), where loose or otherwise unsuitable soils are exposed at foundation
grades, overexcavation and replacement with 2-inch clean crushed rock (or lean mix) placed
directly atop the competent native soils at-depth will be required.
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Provided the foundations will be supported as prescribed, the following parameters may be used
for design:
Allowable soil bearing capacity 2,500 psf (lightly-loaded townhomes)
6,000 psf (podium structures) *
Passive earth pressure 350 pcf (equivalent fluid)
Coefficient of friction 0.40
* Assumes foundation support within medium dense to dense native soils exposed at-depth at the base of the
underground garage excavations. Where loose or otherwise unsuitable soils are exposed at foundation grades,
overexcavation and replacement with 2-inch clean crushed rock (or lean mix) placed directly atop the competent
native soils at-depth will be required.
A one-third increase in the allowable soil bearing capacity may be assumed for short-term wind
and seismic loading conditions. The above passive pressure and friction values include a factor-
of-safety of 1.5. Considering both the expected structural loading and foundation support as
described in this report, total settlement in the range of one inch and differential settlement of
about one-half inch (over the span of a typical column spacing) is anticipated. The majority of
the settlements should occur during construction, as dead loads are applied.
Seismic Design
The 2015 International Building Code recognizes the American Society of Civil Engineers (ASCE)
for seismic site class definitions. In accordance with Table 20.3-1 of the ASCE Minimum Design
Loads for Buildings and Other Structures manual, Site Class D should be used for design.
The referenced liquefaction susceptibility map indicates the site and surrounding areas maintain
a very low liquefaction susceptibility. Liquefaction is a phenomenon where saturated and loose
soils suddenly lose internal strength and behave as a fluid. This behavior is in response to soil
grain contraction and increased pore water pressures resulting from an earthquake or other
intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered
negligible. The dense to very dense in-situ nature of the native soils and the absence of a
uniformly established, shallow groundwater table were the primary bases for this consideration.
Slab-on-Grade Floors
Slab-on-grade floors should be supported on a firm and unyielding subgrade consisting of
competent native soil or structural fill. Unstable or yielding areas of the subgrade should be
recompacted or overexcavated and replaced with suitable structural fill prior to construction of
the slab. ESNW should observe exposed slab subgrade conditions at the time of construction
and provide supplement recommendations, as necessary.
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A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel
should be placed below the slab. The free-draining material should have a fines content of 5
percent or less defined as the percent passing the Number 200 sieve, based on the minus three-
quarters inch fraction. In areas where slab moisture is undesirable, installation of a vapor barrier
below the slab should be considered. If used, the vapor barrier should consist of a material
specifically designed to function as a vapor barrier and should be installed in accordance with the
product specifications.
As previously discussed, with respect to the currently proposed one-level below grade
construction for the “podium building(s)”, groundwater is not expected to significantly impact the
proposed construction based on conditions identified at the boring locations. However, potential
groundwater impacts should be evaluated with respect to subsurface drainage and possible sub-
slab drainage systems for the underground garage levels during final design and finally during
construction when the underground garage excavation has been completed.
Retaining Walls
Retaining walls should be designed to resist earth pressures and applicable surcharge loads.
The following parameters should be used for retaining wall design:
Active earth pressure (yielding condition) 35 pcf
At-rest earth pressure (restrained condition) 50 pcf
Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)*
Passive earth pressure 350 pcf
Coefficient of friction 0.40
Seismic surcharge 6H psf (where applicable)**
* Where applicable. Additional surcharge loading (if applicable) should be evaluated by the engineer.
** Where H equals retained height
Drainage should be provided behind retaining walls such that hydrostatic pressures do not
develop. If drainage is not provided, hydrostatic pressures should be included in the wall design.
Retaining walls should be backfilled with free-draining material that extends along the height of
the wall, and a distance of at least 18 inches behind the wall; a drainage mat can be considered
in lieu of free-draining backfill and should be evaluated by ESNW during construction. The upper
one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain
pipe should be placed along the base of the wall, and should be connected to an approved
discharge location. A typical retaining wall drainage detail is provided as Plate 6. For retaining
walls cast against shoring walls, the drainage detail provided on Plate 5 should be considered.
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Drainage
Groundwater seepage was not encountered at the test sites during our December 2017 and June
2018 fieldwork. However, it is our opinion that the contractor be prepared to respond to and
manage isolated areas of perched groundwater seepage. Where zones of groundwater seepage
are encountered, temporary measures to control groundwater seepage may be needed and
typically involve passive elements such as interceptor trenches and sumps, as necessary.
Surface grades must be designed to direct water away from buildings. The grade adjacent to
buildings should be sloped away from the buildings at a gradient of at least 2 percent for a
horizontal distance of at least ten feet (or as building and property setbacks allow). In our opinion,
perimeter footing drains should be installed at or below the invert of the building footings. A
typical (shallow) footing drain detail is provided on Plate 7 of this report.
Preliminary Infiltration Feasibility
As indicated in the Subsurface section of this study, native soils encountered during our fieldwork
were characterized primarily medium dense to dense and compact silty sand and sand deposits.
According to the results of USDA textural analyses performed on representative samples, native
soils classify primarily as gravelly loamy sand to sand. Irrespective of gravel content, the fines
contents of the native loam were about 8 to 16 percent at the tested locations. However, given
the variability and generally dense and compact nature of the native silty sand and sand deposits,
large scale infiltration of stormwater for this project is not recommended. In this respect, we
presume that stormwater management designs will utilize limited infiltration flow control devices
such as bio-swales and rain gardens to the extent practicable. Any infiltration device would likely
serve with limited functionality and would require the incorporation of an overflow provision into
its final design.
Preliminary Detention Vault Design (Where Applicable)
If applicable, grade cuts of approximately 10 feet bgs or greater would likely be necessary to
achieve subgrade elevation for vault foundations. Based on our field observations, grade cuts
for vault structures would likely expose competent native soils.
Vault foundations should be supported directly on competent native soils. Should
overexcavation(s) be necessary at the vault foundation subgrade, a suitable crushed rock
material should be used to restore grades. The final vault design must incorporate adequate
buffer space from property boundaries such that temporary excavations to construct the vault
structure may be successfully completed. ESNW should review preliminary grading plans as to
assist in determining the feasibility, and possible constraints, of utilizing temporary slopes to
facilitate construction of vault structures. Where temporary slopes cannot be successfully
achieved, temporary shoring would likely be required.
Perimeter drains should be installed around the vault and conveyed to an approved discharge
point. Perched groundwater seepage should be anticipated within the vault excavation; however,
buoyancy is not expected to influence the vault structure.
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The following preliminary design parameters may be used for the vault:
Allowable soil bearing capacity 5,000 psf (competent native soil)
Active earth pressure (unrestrained) 35 pcf
Active earth pressure (unrestrained, hydrostatic) 80 pcf
At-rest earth pressure (restrained) 50 pcf
At-rest earth pressure (restrained, hydrostatic) 95 pcf
Coefficient of friction 0.40
Passive earth pressure 350 pcf
Seismic surcharge 6H psf*
* Where H equals the retained height (in feet)
Vault retaining walls should be backfilled with free-draining material or suitable sheet drainage
that extends along the height of the walls. The upper one foot of the wall backfill may consist of
a less permeable soil, if desired. A perforated drainpipe should be placed along the base of the
wall and connected to an approved discharge location. If the elevation of the vault bottom is such
that gravity flow to an outlet is not possible, the portions of the vault below the drain should be
designed to include hydrostatic pressure.
ESNW should observe subgrade conditions prior to vault foundation concrete forming and
pouring. If the soil conditions encountered during construction differ from those anticipated,
supplementary recommendations may be provided. ESNW should be contacted to review the
final vault designs to confirm that appropriate geotechnical parameters have been incorporated.
Preliminary Pavement Sections
The performance of site pavements is largely related to the condition of the underlying subgrade.
To ensure adequate pavement performance, the subgrade should be in a firm and unyielding
condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement
areas should be compacted to the specifications previously detailed in this report. Soft, wet, or
otherwise unsuitable subgrade areas may still exist after base grading activities. Areas
containing unsuitable or yielding subgrade conditions will require remedial measures, such as
overexcavation and/or placement of thicker crushed rock or structural fill sections, prior to
pavement.
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For lightly loaded pavement areas subjected primarily to passenger vehicles, the following
preliminary pavement sections may be considered:
A minimum of two inches of hot mix asphalt (HMA) placed over four inches of crushed
rock base (CRB), or;
A minimum of two inches of HMA placed over three inches of asphalt treated base
(ATB).
Heavier traffic areas generally require thicker pavement sections depending on site usage,
pavement life expectancy, and site traffic. For preliminary design purposes, the following
pavement sections for occasional truck traffic and access roadways areas may be considered:
Three inches of HMA placed over six inches of crushed rock base (CRB), or;
Three inches of HMA placed over four-and-one-half inches of ATB.
The HMA, ATB and CRB materials should conform to WSDOT specifications. All soil base
material should be compacted to a relative compaction of 95 percent, based on the laboratory
maximum dry density as determined by ASTM D1557. Final pavement design recommendations,
including recommendations for heavy traffic areas, access roads, and frontage improvement
areas, can be provided once final traffic loading has been determined. Road standards utilized
by the City of Renton may supersede the recommendations provided in this report.
Utility Support and Trench Backfill
In our opinion, native soils will generally be suitable for support of utilities. Remedial measures,
such as overexcavation and replacement with structural fill and/or installation of geotextile fabric,
however, may be necessary in some areas to provide support for utilities. Groundwater may be
encountered within deeper utility excavations, and caving of trench walls may occur where
groundwater is encountered. Temporary construction dewatering, as well as temporary trench
shoring, may be necessary during utility excavation and installation as conditions warrant.
In general, native soils may be suitable for use as structural backfill throughout utility trench
excavations, provided the soils are at (or slightly above) the optimum moisture content at the time
of placement and compaction. Structural trench backfill should not be placed dry of the optimum
moisture content. Each section of the site utility lines must be adequately supported in
appropriate bedding material. Utility trench backfill should be placed and compacted to the
specifications of structural fill as previously detailed in this report, or to the applicable
specifications of the governing jurisdiction or other responsible jurisdiction or agency.
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LIMITATIONS
The recommendations and conclusions provided in this geotechnical engineering study are
professional opinions consistent with the level of care and skill that is typical of other members in
the profession currently practicing under similar conditions in this area. A warranty is not
expressed or implied. Variations in the soil and groundwater conditions observed at the test
locations may exist, and may not become evident until construction. ESNW should reevaluate
the conclusions in this geotechnical engineering study if variations are encountered.
Additional Services
ESNW should have an opportunity to review the final design with respect to the geotechnical
recommendations provided in this report. ESNW should also be retained to provide testing and
consultation services during construction.
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drwn.CAM
Checked CGH Date July 2020
Date 07/10/2020 Proj.No.5719.03
Plate 1
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
Vicinity Map
Solera
Renton,Washington
Reference:
King County,Washington
OpenStreetMap.org
NORTH
NOTE:This plate may contain areas of color.ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black &white reproductions of this plate.
SITE
Renton
GeotechnicalEngineering,ConstructionObservation/TestingandEnvironmentalServicesPlate
Proj.No.
Date
Checked By
Drwn.ByEarthSolutionsNWLLCEarthSolutionsNWLLCEarthSolutionsNWLLCSubsurfaceExplorationPlanSolera Renton,WashingtonCAM
CGH
07/10/2020
5719.03
2
NORTH
NOT -TO -SCALE
NOTE:This plate may contain areas of color.ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black &white reproductions of this plate.
NOTE:The graphics shown on this plate are not intended for design
purposes or precise scale measurements,but only to illustrate the
approximate test locations relative to the approximate locations of
existing and /or proposed site features.The information illustrated
is largely based on data provided by the client at the time of our
study.ESNW cannot be responsible for subsequent design changes
or interpretation of the data by others.
LEGEND
Approximate Location of
ESNW Test Pit,Proj.No.
ES-5719.02,June 2018
Approximate Location of
ESNW Boring,Proj.No.
ES-5719,Dec.2017
Subject Site
Existing Building
B-1
TP-1
KIRKLAND AVENUE N.E. N.E. SUNSET BOULEVARDN.E. 12TH STREET
HARRINGTON AVENUE N.E.N.E.10T
H
ST
R
EETApartments SUNSET LANE N.E.B-1
B-2
B-3
B-4
B-5B-6
B-7
B-8
B-9
B-10
B-11
B-12
B-13 HARRINGTON PL. N.E.TP-1
TP-4
TP-2
TP-3
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drwn.CAM
Checked CGH Date Aug.2020
Date 08/03/2020 Proj.No.5719.03
Plate 3
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
Cantilever &Single Tieback Wall
Solera
Renton,Washington
D =Pile Embedment
(per Structural Eng.)
2'
H
(Wall Height)
Active
Earth
Pressure
Passive
Earth
Pressure
EFP=350pcf
EFP=35pcf
Surcharge
(W here Applicable)
Traffic Surcharge or Building Surcharge
(W here Applicable)
Excavation Level
SCHEMATIC ONLY -NOT TO SCALE
NOT A CONSTRUCTION DRAW ING
NOTES:
Diagram for pressure distribution illustration
only,not a design drawing.
Passive Pressure includes a factor of
safety of 1.5.
For adjacent building or traffic surcharge
see text.
NOTE:
See text for recommended
Slope Backfill and At-Rest
Pressures.
Neglect Upper 2 feet
of Passive Pressure
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drwn.CAM
Checked CGH Date Aug.2020
Date 08/03/2020 Proj.No.5719.03
Plate 4
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
No Load Zone
Solera
Renton,Washington
D =Pile Embedment
(per Structural Eng.)
H
(Wall Height)
Traffic Surcharge or Building Surcharge
(W here Applicable)
Excavation Level
SCHEMATIC ONLY -NOT TO SCALE
NOT A CONSTRUCTION DRAW ING
H/4 60
Tieback No Load
Zone
Drwn.CAM
Checked CGH Date Aug.2020
Date 08/03/2020 Proj.No.5719.03
Plate 5
Earth Solutions NWLLC
Geotechnical Engineering,Construction
EarthSolutionsNWLLC
EarthSolutions
NW LLC Observation/Testing and Environmental Services
Shoring Wall Drainage Detail
Solera
Renton,Washington
W ood Lagging
Native
Soil
Excavation
PVC Tightline
Structural Fill
Foundation
(per Plan)
Drain Grate
Waterproofing and Insulation
per Architectural Plan
Continuous Sheet Drain
(Placed with Filter Fabric
Facing Shoring)
Concrete Facing
Slab-On-Grade Floor
(per Plan)
NOTE:Drain through wall should be installed at middle of lagging.
SCHEMATIC ONLY -NOT TO SCALE
NOT A CONSTRUCTION DRAW ING
Drwn.CAM
Checked CGH Date Aug.2020
Date 08/03/2020 Proj.No.5719.03
Plate 6
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC Geotechnical Engineering,Construction
Obser vation/Testing and Environmental Services
Retaining Wall Drainage Detail
Solera
Renton,Washington
NOTES:
Free-draining Backfill should consist
of soil having less than 5 percent fines.
Percent passing No.4 sieve should be
25 to 75 percent.
Sheet Drain may be feasible in lieu
of Free-draining Backfill,per ESNW
recommendations.
Drain Pipe should consist of perforated,
rigid PVC Pipe surrounded with 1-inch
Drain Rock.
LEGEND:
Free-draining Structural Backfill
1-inch Drain Rock
18"Min.
Structural
Fill
Perforated Rigid Drain Pipe
(Surround in Drain Rock)
SCHEMATIC ONLY -NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Drwn.CAM
Checked CGH Date Aug.2020
Date 08/03/2020 Proj.No.5719.03
Plate 7
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Footing Drain Detail
Solera
Renton,Washington
Slope
Perforated Rigid Drain Pipe
(Surround in Drain Rock)
18"Min.
NOTES:
Do NOT tie roof downspouts
to Footing Drain.
Surface Seal to consist of
12"of less permeable,suitable
soil.Slope away from building.
LEGEND:
Surface Seal:native soil or
other low-permeability material.
1-inch Drain Rock
SCHEMATIC ONLY -NOT TO SCALE
NOT A CONSTRUCTION DRAW ING
Earth Solutions NW, LLC
Appendix A
Subsurface Exploration
Test Pit and Boring Logs
ES-5719.03
Subsurface conditions at the subject site were explored in December of 2017 and June of 2018
by advancing 13 borings and four test pits within the boundaries of the project site. The borings
were advanced to a maximum exploration depth of 21.5 feet bgs and the test pits to a maximum
depth of six feet. The approximate locations of the borings and test pts are illustrated on Plate 2
of this study. The boring and test pit logs are provided in this Appendix.
The final logs represent the interpretations of the field logs and the results of laboratory analyses.
The stratification lines on the logs represent the approximate boundaries between soil types. In
actuality, the transitions may be more gradual.
GRAVEL
AND
GRAVELLY
SOILS
CLAYEY GRAVELS, GRAVEL - SAND -
CLAY MIXTURES
WELL-GRADED SANDS, GRAVELLY
SANDS, LITTLE OR NO FINES
POORLY-GRADED SANDS,
GRAVELLY SAND, LITTLE OR NO
FINES
SILTY SANDS, SAND - SILT
MIXTURES
CLAYEY SANDS, SAND - CLAY
MIXTURES
INORGANIC SILTS AND VERY FINE
SANDS, ROCK FLOUR, SILTY OR
CLAYEY FINE SANDS OR CLAYEY
SILTS WITH SLIGHT PLASTICITY
INORGANIC CLAYS OF LOW TO
MEDIUM PLASTICITY, GRAVELLY
CLAYS, SANDY CLAYS, SILTY CLAYS,
LEAN CLAYS
ORGANIC SILTS AND ORGANIC
SILTY CLAYS OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS OR
DIATOMACEOUS FINE SAND OR
SILTY SOILS
INORGANIC CLAYS OF HIGH
PLASTICITY
SILTS
AND
CLAYS
MORE THAN 50%
OF MATERIAL IS
LARGER THAN
NO. 200 SIEVE
SIZE
MORE THAN 50%
OF MATERIAL IS
SMALLER THAN
NO. 200 SIEVE
SIZE
MORE THAN 50%
OF COARSE
FRACTION
PASSING ON NO.
4 SIEVE
MORE THAN 50%
OF COARSE
FRACTION
RETAINED ON NO.
4 SIEVE
SOIL CLASSIFICATION CHART
(APPRECIABLE
AMOUNT OF FINES)
(APPRECIABLE
AMOUNT OF FINES)
(LITTLE OR NO FINES)
FINE
GRAINED
SOILS
SAND
AND
SANDY
SOILS
SILTS
AND
CLAYS
ORGANIC CLAYS OF MEDIUM TO
HIGH PLASTICITY, ORGANIC SILTS
PEAT, HUMUS, SWAMP SOILS WITH
HIGH ORGANIC CONTENTS
LETTERGRAPH
SYMBOLSMAJOR DIVISIONS
COARSE
GRAINED
SOILS
TYPICAL
DESCRIPTIONS
WELL-GRADED GRAVELS, GRAVEL -
SAND MIXTURES, LITTLE OR NO
FINES
POORLY-GRADED GRAVELS,
GRAVEL - SAND MIXTURES, LITTLE
OR NO FINES
SILTY GRAVELS, GRAVEL - SAND -
SILT MIXTURES
CLEAN
GRAVELS
GRAVELS WITH
FINES
CLEAN SANDS
(LITTLE OR NO FINES)
SANDS WITH
FINES
LIQUID LIMIT
LESS THAN 50
LIQUID LIMIT
GREATER THAN 50
HIGHLY ORGANIC SOILS
DUAL SYMBOLS are used to indicate borderline soil classifications.
The discussion in the text of this report is necessary for a proper understanding of the nature
of the material presented in the attached logs.
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
Earth Solutions NW LLC
351.8
351.2
351.0
348.0
347.0
MC = 7.8%
Fines = 9.2%
MC = 19.5%
SM
TPSL
SP-
SM
SM
0.2
0.8
1.0
4.0
5.0
Asphalt 1.75"
Gray silty SAND, loose, moist (Fill)
Thin relic TOPSOIL horizon ~2" thick
Brown poorly graded SAND with gravel, medium dense to dense, moist
[USDA Classification: very gravelly loamy coarse SAND]
Gray silty SAND, dense, moist
Test pit terminated at 5.0 feet below existing grade due to refusal on dense native soil. No
groundwater encountered during excavation. No caving observed.
NOTES Surface Conditions: asphalt ~1.75"
GROUND ELEVATION 352 ft
LOGGED BY CGH
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR Aero GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 6/26/18 COMPLETED 6/26/18
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-1
PROJECT NUMBER ES-5719.02 PROJECT NAME Solera
GENERAL BH / TP / WELL - 5719-2.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
349.0
347.5
345.0
344.0
MC = 3.8%
Fines = 4.7%
MC = 13.9%
Fines = 7.7%
SM
SM
SP
SP-
SM
1.0
2.5
5.0
6.0
Brown silty SAND, loose, moist (Fill)
-root intrusions to 2'
Brown silty SAND, loose to medium dense, moist
Gray poorly graded SAND, medium dense, moist
[USDA Classification: slightly gravelly SAND]
Gray poorly graded SAND with silt, medium dense, moist
[USDA Classification: slightly gravelly coarse SAND]
Test pit terminated at 6.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
NOTES Surface Conditions: gravels
GROUND ELEVATION 350 ft
LOGGED BY CGH
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR Aero GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 6/26/18 COMPLETED 6/26/18
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-2
PROJECT NUMBER ES-5719.02 PROJECT NAME Solera
GENERAL BH / TP / WELL - 5719-2.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
354.7
354.4
352.5MC = 8.5%
Fines = 20.6%
SM
0.3
0.6
2.5
Asphalt 3"
Crushed rock base coarse ~3"
Brown silty SAND, loose to medium dense, moist
[USDA Classification: slightly gravelly loamy SAND]
Test pit terminated at 2.5 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
NOTES Surface Conditions: asphalt
GROUND ELEVATION 355 ft
LOGGED BY CGH
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR Aero GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 6/27/18 COMPLETED 6/27/18
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
PAGE 1 OF 1
TEST PIT NUMBER TP-3
PROJECT NUMBER ES-5719.02 PROJECT NAME Solera
GENERAL BH / TP / WELL - 5719-2.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
359.8
359.6
354.0
MC = 10.3%
Fines = 34.0%
MC = 11.2%
SM
0.2
0.4
6.0
Asphalt ~1.75"
Crushed rock base coarse ~2" thick
Gray silty SAND, medium dense to dense, moist
-light iron oxide staining
[USDA Classification: gravelly fine sandy LOAM]
-becomes dense
Test pit terminated at 6.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
NOTES Surface Conditions: asphalt
GROUND ELEVATION 360 ft
LOGGED BY CGH
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR Aero GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 6/27/18 COMPLETED 6/27/18
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-4
PROJECT NUMBER ES-5719.02 PROJECT NAME Solera
GENERAL BH / TP / WELL - 5719-2.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
67
67
100
100
9-10-12
(22)
9-8-17
(25)
9-16-19
(35)
10-17-22
(39)
MC = 7.4%
MC = 5.5%
Fines = 8.5%
MC = 7.3%
MC = 8.1%
SP-
SM
SM
10.0
11.5
Brown poorly graded SAND with silt, medium dense, moist
-becomes gray, [USDA Classification: slightly gravelly SAND]
-silt lens ~2" thick
Gray silty SAND, dense, moist
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1.5"- 2" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-1
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
100
100
100
9-13-23
(36)
11-14-17
(31)
8-12-17
(29)
13-17-21
(38)
MC = 8.8%
MC = 8.2%
MC = 6.3%
MC = 5.3%
SM
SP-
SM
6.0
11.5
Brown silty SAND, medium dense, moist
-becomes gray, dense
Gray poorly graded SAND with silt, dense, moist
-becomes medium dense
-becomes dense
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1.5"- 2" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-2
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
100
100
100
100
100
3-4-4
(8)
2-2-3
(5)
4-6-7
(13)
7-9-14
(23)
7-12-13
(25)
MC = 9.1%
MC = 21.3%
MC = 6.7%
Fines = 7.9%
SM
SM
SP-
SM
5.5
8.5
16.5
Brown silty SAND, loose, moist (Fill)
Brown silty SAND, loose, moist
[USDA Classification: SAND]
Gray poorly graded SAND with silt, medium dense, moist
Boring terminated at 16.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
PAGE 1 OF 1
BORING NUMBER B-3
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
100
67
100
3-5-10
(15)
5-18-29
(47)
8-31-17
(48)
17-20-22
(42)
MC = 12.9%
MC = 5.8%
MC = 4.3%
MC = 4.9%
SM
SM
SP-
SM
6.0
8.0
11.5
Gray silty SAND, medium dense, moist to wet (Fill)
-trace wood debris
Gray silty SAND, dense, moist
Gray poorly graded SAND with silt, dense, moist
-possible high blow count due to rock
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-4
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
100
100
100
4-5-6
(11)
2-1-3
(4)
7-8-12
(20)
12-14-16
(30)
MC = 11.3%
MC = 12.7%
MC = 4.7%
MC = 6.1%
SM
SM
SP
6.0
7.5
11.5
Gray silty SAND, medium dense, moist (Fill)
-becomes very loose, light iron oxide staining
Brown silty SAND, very loose, moist
Gray poorly graded SAND, medium dense, moist
-becomes dense
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~2" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-5
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
67
100
100
67
100
4-3-3
(6)
8-5-7
(12)
12-11-11
(22)
12-19-24
(43)
12-17-21
(38)
MC = 10.0%
MC = 5.8%
MC = 5.6%
MC = 4.7%
MC = 8.2%
SM
SP-
SM
4.0
16.5
Gray silty SAND, loose, moist to wet (Fill)
Brown poorly graded SAND with silt, loose, moist
-becomes medium dense
-becomes gray
-becomes dense
Boring terminated at 16.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1"- 2" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
PAGE 1 OF 1
BORING NUMBER B-6
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
67
100
100
100
100
1-2-4
(6)
17-24-27
(51)
6-12-15
(27)
12-16-22
(38)
13-17-25
(42)
MC = 10.1%
MC = 10.5%
MC = 13.5%
MC = 16.7%
Fines = 15.7%
MC = 6.5%
SM
SP
11.0
Brown silty SAND, loose, moist
-becomes gray, very dense
-becomes medium dense, moist to wet
-becomes dense
[USDA Classification: slightly gravelly loamy SAND]
Gray poorly graded SAND, dense, moist
NOTES Surface Conditions: asphalt ~1"- 2" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 2
BORING NUMBER B-7
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS 100 14-19-24
(43)MC = 5.2%SP
21.5
Gray poorly graded SAND, dense, moist (continued)
Boring terminated at 21.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.SAMPLE TYPENUMBERDEPTH(ft)20
PAGE 2 OF 2
BORING NUMBER B-7
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
33
67
100
67
100
1-1-1
(2)
1-1-2
(3)
1-1-1
(2)
1-2-4
(6)
13-18-22
(40)
MC = 11.7%
MC = 9.6%
Fines = 13.2%
MC = 12.9%
MC = 16.3%
MC = 13.6%
SM
SP
11.0
20.0
Brown silty SAND, very dense, moist (Fill)
[USDA Classification: slightly gravelly loamy SAND]
-trace wood debris
-trace organic inclusions
Gray poorly graded SAND, loose, moist to wet
-becomes dense
NOTES Surface Conditions: asphalt ~2.5" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 2
BORING NUMBER B-8
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS 100 16-21-32
(53)MC = 13.5%SP
21.5
Gray poorly graded SAND, very dense, moist
Boring terminated at 21.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.SAMPLE TYPENUMBERDEPTH(ft)20
PAGE 2 OF 2
BORING NUMBER B-8
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
67
100
100
1-2-2
(4)
4-8-10
(18)
8-12-12
(24)
9-13-25
(38)
MC = 16.2%
MC = 10.9%
MC = 10.3%
MC = 11.0%
SM
11.5
Brown silty SAND, very loose, moist
-becomes gray
-becomes medium dense, moist to wet
-sand lens ~4" thick
-sand lens ~4" thick
-becomes dense
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: gravel
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-9
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
33
67
100
100
6-17-15
(32)
5-7-10
(17)
9-12-15
(27)
9-17-19
(36)
MC = 2.7%
MC = 6.1%
MC = 7.3%
MC = 3.6%
SP-
SM
SM
SP
5.0
10.0
11.5
Gray poorly graded SAND with silt, medium dense, moist
Gray silty SAND, medium dense, moist
-light iron oxide staining
Gray poorly graded SAND, dense, moist
-silty sand lens ~4" thick
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: gravel
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-10
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
100
100
100
4-7-16
(23)
6-15-24
(39)
11-24-27
(51)
11-17-20
(37)
MC = 14.6%
MC = 10.9%
MC = 9.2%
MC = 8.2%
SM
11.5
Brown silty SAND, loose, moist
-becomes gray, medium dense
-becomes dense
-becomes very dense
-becomes dense
-increased sand content
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~3" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-11
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
33
100
100
100
6-10-11
(21)
7-10-7
(17)
11-12-12
(24)
8-30-31
(61)
MC = 11.1%
MC = 10.2%
MC = 11.0%
MC = 11.6%
FILL
SM
0.3
11.5
~3" thick concrete (Fill)
Gray silty SAND, medium dense, moist
-becomes very dense
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~1", ~3" concrete
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-12
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
100
100
100
100
10-7-8
(15)
6-4-5
(9)
13-14-18
(32)
31-21-22
(43)
MC = 13.6%
MC = 8.4%
Fines = 10.9%
MC = 8.1%
MC = 9.4%
SM
SP-
SM
3.5
11.5
Gray silty SAND, medium dense, moist (Fill)
Brown poorly graded SAND with silt, loose to medium dense, moist
[USDA Classification: slightly gravelly SAND]
-becomes gray
-becomes dense
Boring terminated at 11.5 feet below existing grade. No groundwater
encountered during drilling. Boring backfilled with bentonite chips.
NOTES Surface Conditions: asphalt ~3" thick
GROUND ELEVATION
LOGGED BY CGH
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY RAC
DATE STARTED 12/4/17 COMPLETED 12/4/17
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---SAMPLE TYPENUMBERDEPTH(ft)0
5
10
PAGE 1 OF 1
BORING NUMBER B-13
PROJECT NUMBER ES-5719 PROJECT NAME Renton Highlands Townhomes
GENERAL BH / TP / WELL - 5719.GPJ - GINT STD US.GDT - 9/28/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
Earth Solutions NW, LLC
Appendix B
Laboratory Test Results
ES-5719.03
Earth Solutions NW, LLC
Report Distribution
ES-5719.03
EMAIL ONLY DevCo, LLC
10900 Northeast 8th Street, Suite 1200
Bellevue, Washington 98004
Attention: Mr. David Ratliff