23-106056-SU-Geotechnical Report-01-19-24EarthSolutionsNWLLC
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
SAGHALIE HEIGHTS
1525 SOUTHWEST 341 PLACE
FEDERAL WAY,WASHINGTON
ES-9488
ST
PREPARED FOR
PROSPECT DEVELOPMENT, LLC
December 5, 2023
_________________________
Samuel E. Suruda, L.G.
Senior Staff Geologist
_________________________
Scott S. Riegel, L.G., L.E.G.
Associate Principal Geologist
GEOTECHNICAL ENGINEERING STUDY
SAGHALIE HEIGHTS
1525 SOUTHWEST 341ST PLACE
FEDERAL WAY, WASHINGTON
ES-9488
Earth Solutions NW, LLC
15365 Northeast 90th Street, Suite 100
Redmond, Washington 98052
Phone: 425-449-4704 | Fax: 425-449-4711
www.earthsolutionsnw.com
12/05/2023
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
December 5, 2023
ES-9488
Prospect Development, LLC
2913 – 5th Avenue Northeast, Suite 201
Puyallup, Washington 98372
Attention: Justin Holland
Dear Justin:
Earth Solutions NW, LLC (ESNW) is pleased to present this report supporting the proposed
residential development to be completed in Federal Way, Washington. Based on the results of
our study, the proposed residential development is feasible from a geotechnical standpoint.
Based on the conditions observed during our fieldwork, the subject site is underlain primarily by
a highly layered sequence of Advance outwash and glacial till deposits.
In our opinion, the proposed structures can be supported on conventional spread and continuous
foundations bearing on undisturbed, competent native soil, recompacted native soil, or new
structural fill placed directly on a competent native subgrade. Where loose or unsuitable soil
conditions are encountered at foundation subgrade elevations, compaction of the soils to the
specifications of structural fill, or overexcavation and replacement with suitable structural fill will
likely be necessary. For preliminary design considerations, a long-term infiltration rate of four
inches/hour may be used for facilities releasing to Advance outwash sand/gravel deposits.
This report provides analyses and recommendations for the proposed residential development.
The opportunity to be of service to you is appreciated. If you have any questions regarding the
content of this geotechnical engineering study, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
Samuel E. Suruda, L.G.
Senior Staff Geologist
cc: Clay Loomis
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
Earth Solutions NW, LLC
Table of Contents
ES-9488
PAGE
INTRODUCTION ................................................................................. 1
General .................................................................................... 1
Project Description ................................................................. 1
SITE CONDITIONS ............................................................................. 2
Surface ..................................................................................... 2
Subsurface .............................................................................. 2
Topsoil and Fill ............................................................. 2
Native Soil ..................................................................... 3
Advance Outwash ............................................... 3
Glacial Till ............................................................ 3
Geologic Setting ........................................................... 3
Groundwater ................................................................. 3
Geologically Hazardous Areas Assessment ........................ 4
DISCUSSION AND RECOMMENDATIONS ....................................... 4
General .................................................................................... 4
Site Preparation and Earthwork ............................................. 4
Temporary Erosion Control ......................................... 5
Stripping ....................................................................... 5
In-situ and Imported Soils ........................................... 6
Wet Season Grading .................................................... 6
Structural Fill ................................................................ 7
Excavations and Slopes .............................................. 7
Foundations ............................................................................ 8
Seismic Considerations ......................................................... 9
Slab-on-Grade Floors ............................................................. 9
Retaining Walls ....................................................................... 10
Drainage................................................................................... 11
Infiltration Evaluation ................................................... 11
Stormwater Detention Pond Recommendations ....... 11
Utility Support and Trench Backfill ....................................... 12
Preliminary Pavement Sections ............................................. 12
LIMITATIONS ...................................................................................... 13
Additional Services ................................................................. 13
REFERENCES .................................................................................... 13
Earth Solutions NW, LLC
Table of Contents
Cont’d
ES-9488
GRAPHICS
Plate 1 Vicinity Map
Plate 2 Test Pit Location Plan
Plate 3 Retaining Wall Drainage Detail
Plate 4 Footing Drain Detail
APPENDICES
Appendix A Subsurface Exploration Logs
Appendix B Laboratory Test Results
Earth Solutions NW, LLC
GEOTECHNICAL ENGINEERING STUDY
SAGHALIE HEIGHTS
1525 SOUTHWEST 341ST PLACE
FEDERAL WAY, WASHINGTON
ES-9488
INTRODUCTION
General
This geotechnical engineering study (study) was prepared for the proposed residential
development to be constructed off the eastern terminus of Southwest 341st Place in Federal Way,
Washington. To complete the scope of services we performed the following:
Laboratory testing of soil samples collected at the subsurface exploration locations;
Engineering analyses and recommendations for the proposed development, and;
Preparation of this report.
Project Description
Based on the referenced preliminary plans, the site will be developed with 26 residential units,
access roadways, stormwater management facilities and associated improvements. Grading for
the project will include cuts and fills of up to about eight feet to establish site roadways and
building pads.
At the time of report submission, specific building load values were not available for review;
however, we anticipate the proposed residential structures will consist of relatively lightly loaded
wood framing supported on conventional foundations. Based on our experience with similar
developments, we estimate wall loads of about 1 to 3 kips per linear foot and slab-on-grade
loading of 150 pounds per square foot (psf) will be incorporated into the final design.
Stormwater will be conveyed to either an infiltration pond to be located within a tract to be located
in the northwestern portion of the site or a detention pond to be constructed in the south-central
area of the site. Site improvements will also include underground utility installations.
If the above design assumptions are incorrect or change, ESNW should be contacted to review
the recommendations provided in this report. ESNW should review the final design to confirm
that our geotechnical recommendations have been incorporated into the final plans.
Prospect Development, LLC ES-9488
December 5, 2023 Page 2
Earth Solutions NW, LLC
SITE CONDITIONS
Surface
The subject site is located off the eastern terminus of Southwest 341st Place in Federal Way,
Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of four adjoining tax
parcels (King County parcel numbers 192104-9026, -9024, -9018 & -9019) totaling about 10.4
acres. The parcels are currently vacant and forested, including a fairly dense understory. King
County iMap aerial photos appear to show a structure on the -9018 parcel and tax records
indicate a structure with a footprint of about 1,154 square feet; however, this improvement has
since been removed. Several wetland areas have been identified along a nearly north-south
alignment through the central area.
The site is bordered to the north, east and west by residential parcels and to the south by
Southwest 344th Street. The site topography is gently undulating, with a shallow depression
feature that roughly trends north-south through the property, which supports a seasonal wetland.
Subsurface
An ESNW representative observed, logged, and sampled three test pits excavated at accessible
locations within the proposed development area on August 2, 2023 using a mini-trackhoe and
operator retained by the client. The test pits were completed for purposes of assessing soil
conditions, classifying site soils, and characterizing near-surface groundwater conditions within
the proposed development area. A copy of a previous geotechnical report prepared by Terra
Associated (2007-2008) was provided by the client that included explorations within the current
site. This information was used to supplement the explorations completed by ESNW.
The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please
refer to the test pit logs provided in Appendix A for a more detailed description of subsurface
conditions. Representative soil samples collected at the test pit locations were analyzed in
general accordance with Unified Soil Classification System (USCS) and USDA methods and
procedures.
Topsoil and Fill
Topsoil was encountered generally within the upper six inches of existing grades at the test pit
locations. The topsoil was characterized by dark brown color, the presence of fine organic
material, and small root intrusions.
Fill was not encountered during the subsurface exploration. Based on the topography and
vegetation present on the subject site, we do not anticipate significant amounts of fill to be
encountered on the subject site. If encountered, fill soils intended for reuse as structural fill should
be free of organics and other deleterious materials, and should be evaluated by ESNW for
suitability at the time of construction.
Prospect Development, LLC ES-9488
December 5, 2023 Page 3
Earth Solutions NW, LLC
Native Soil
There appear to be two relatively distinct depositional profiles on this site; advance outwash and
glacial till. The former consists primarily of dense relatively uniform sand and/or gravel deposits,
while the later consists of dense silty sand with gravel, locally referred to as ‘hardpan’ glacial till.
Based on the conditions encountered at the test pit locations, this site is located within a transition
zone between advance outwash and glacial till, which expresses as highly layered and
Advance Outwash
Advance outwash sand and gravel deposits were encountered generally in the eastern portion of
the property and diminish to the west. The outwash soils consisted of poorly graded gravel with
varying amounts of sand (USCS: GW and GP) in a dense condition. Isolated layering of gravel
outwash within the glacial till was encountered at test pit TP-2 and TP-6.
Glacial Till
Dense silty sand with gravel (USCS: SM) glacial till deposits were encountered along the entire
profile at test pit location TP-1 and in the upper several feet at test pit locations TP-3 and TP-4
before transitioning to outwash.
Geologic Setting
Geologic mapping of the area indicates the site and surrounding area is underlain by ice contact
deposits (Qvi). As described on the referenced geologic map, ice contact deposits typically
consist of sand, gravel silt and clay and are generally in a loose condition with good permeability.
The referenced WSS identifies Alderwood gravelly sandy loam (AgC) as the primary soil unit
underlying the subject site. Based on our field observations, native soils on the subject site are
generally consistent with the Advance outwash deposits.
Groundwater
During our subsurface exploration completed on September 25, 2023, groundwater was not
observed at the test pit locations. Groundwater seepage rates and elevations fluctuate
depending on many factors, including precipitation duration and intensity, the time of year, and
soil conditions. ESNW will be installing groundwater monitoring wells within the northern
infiltration facility tract to track groundwater levels (if recorded) during the 2023/24 rainy season.
Prospect Development, LLC ES-9488
December 5, 2023 Page 4
Earth Solutions NW, LLC
Geologically Hazardous Areas Assessment
As part of our geologically hazardous areas assessment, we reviewed Chapter 19.145 –
Environmentally Critical Areas regulations of the FWMC. This Geologically Hazardous Areas
code provides designation and definition criteria for identifying specific geologically hazardous
areas and developing appropriate site development plans which will not adversely impact the site
or surrounding properties. Based on our investigation and review, no geologically hazardous
areas have been identified within or immediately adjacent to the site.
DISCUSSION AND RECOMMENDATIONS
General
In our opinion, construction of the proposed residential development is feasible from a
geotechnical standpoint. The primary geotechnical considerations associated with the proposed
project include earthwork, temporary excavations, structural fill requirements, subgrade
preparation, foundations and soil bearing capacity, utility support and trench backfill, and
drainage.
After completing earthwork activities in accordance with recommendations in this report, the
proposed structures can be supported on conventional spread and continuous foundations
bearing on undisturbed, competent native soil, recompacted native soil, or new structural fill.
Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations,
compaction of the soils to the specifications of structural fill, or overexcavation and replacement
with suitable structural fill will likely be necessary. A representative of ESNW should confirm
suitability of foundation subgrades at the time of construction.
Due to the high moisture sensitivity of the native soils on this site, foundation subgrade areas
should be protected from wet weather or areas of remediation should be anticipated; a layer of
crushed rock can be considered to protect foundation subgrade areas. If structural building pads
are disturbed during wet weather, remediation measures such as cement treatment or
overexcavation and replacement with rock may be necessary in some areas. Additionally,
perched groundwater seepage may create unsuitable soil conditions above the hardpan which
would require aeration, cement treatment, or replacement with crushed rock.
This study has been prepared for the exclusive use of Prospect Development, LLC and its
representatives. A warranty is neither expressed nor implied. 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.
Site Preparation and Earthwork
Site preparation activities should consist of installing temporary erosion control measures and
performing site stripping (as necessary) within the designated clearing limits. Subsequent
earthwork activities will involve mass grading and infrastructure and utility installations.
Prospect Development, LLC ES-9488
December 5, 2023 Page 5
Earth Solutions NW, LLC
Temporary Erosion Control
The following temporary erosion control measures should be considered:
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
stable surfaces at site entrances. Placing geotextile fabric underneath the quarry spalls
will provide greater stability if needed.
Silt fencing should be placed around the appropriate portions of the site perimeter.
When not in use, soil stockpiles should be covered or otherwise protected to reduce the
potential for soil erosion, especially during periods of wet weather.
Temporary measures for controlling surface water runoff, such as interceptor trenches,
sumps, or interceptor swales, should be installed prior to beginning earthwork activities.
Dry soils disturbed during construction should be wetted to minimize dust and airborne soil
erosion.
Additional Best Management Practices, as specified by the project civil engineer and indicated
on the plans, should be incorporated into construction activities. Temporary erosion control
measures may be modified during construction as site conditions require, as approved by the site
erosion control lead.
Stripping
Topsoil was encountered within the upper approximately 4 to 12 inches, and root intrusions
generally extended below the topsoil into the upper weathered soil. The organic-rich topsoil
should be stripped and segregated into a stockpile for later use on site or to haul off site. The
material remaining immediately below the topsoil may have some root zones and will likely be
variable in composition, density, and/or moisture content. The material exposed after initial
topsoil stripping will likely not be suitable for direct structural support as is and will likely need to
either be compacted in place or stripped and stockpiled for reuse as fill; depending on the time
of year stripping occurs, the soil exposed below the topsoil may be too wet to compact and may
need to be aerated or treated. ESNW should observe initial stripping activities to provide
recommendations regarding stripping depths and material suitability.
Prospect Development, LLC ES-9488
December 5, 2023 Page 6
Earth Solutions NW, LLC
In-situ and Imported Soils
The in-situ soils encountered at the subject site have a high sensitivity to moisture and were
generally in a damp condition at the time of exploration. Soils anticipated to be exposed on site
will degrade if exposed to wet weather and construction traffic. Compaction of the soils to the
levels necessary for use as structural fill may be difficult or impossible during wet weather
conditions. Soils encountered during site excavations that are excessively over the optimum
moisture content will likely require aeration or treatment prior to placement and compaction.
Conversely, soils that are substantially below the optimum moisture content will require moisture
conditioning through the addition of water prior to use as structural fill. Areas of existing fill may
be unsuitable for reuse as structural fill due to composition and/or deleterious material. An ESNW
representative should determine the suitability of in-situ soils for use as structural fill at the time
of construction.
Imported soil intended for use as structural fill should be evaluated by ESNW during construction.
The imported soil must be workable to the optimum moisture content, as determined by the
Modified Proctor Method (ASTM D1557), at the time of placement and compaction. 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).
Wet Season Grading
If grading takes place during the wetter, winter, spring, or early summer months, a contingency
in the project budget should be included to allow for treatment of the on-site soils or export of on-
site soils and import of structural fill as described below. Due to the high fines content of the
native soils, minimum compaction requirements will be difficult to impossible to achieve during
the rainy season.
Additional surface control and drainage measures will be necessary to control and detain runoff.
Stormwater collection tanks may be necessary to detain/treat stormwater prior to release from
the site.
Prospect Development, LLC ES-9488
December 5, 2023 Page 7
Earth Solutions NW, LLC
Structural Fill
Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway,
permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and
compacted during site grading activities should meet the following specifications and guidelines:
Structural fill material Granular soil*
Moisture content At or slightly above optimum**
Relative compaction*** 95 percent (Modified Proctor)
Loose lift thickness (maximum) 12 inches
* Existing soil may not be suitable for use as structural fill unless at (or slightly above) the optimum moisture content
at the time of placement and compaction.
** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction.
*** Relative compaction of 90 percent can be considered for mass grading activities.
With respect to underground utility installations and backfill, local jurisdictions may dictate the soil
type(s) and compaction requirements. Unsuitable material or debris must be removed from
structural areas if encountered.
Excavations and Slopes
The following allowable temporary slope inclinations, as a function of horizontal to vertical (H:V)
inclination, may be used. The following Federal Occupation Safety and Health Administration
and Washington Industrial Safety and Health Act soil classifications and maximum allowable
temporary slope inclinations may be used:
Areas exposing groundwater seepage 1.5H:1V (Type C)
Loose soil 1.5H:1V (Type C)
Medium dense soil 1H:1V (Type B)
Dense to very dense “hardpan” soil 0.75H:1V (Type A)
Permanent slopes should be planted with vegetation to both enhance stability and minimize
erosion and should maintain a gradient of 2H:1V or flatter. The presence of groundwater may
cause localized sloughing of temporary slopes. 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.
Prospect Development, LLC ES-9488
December 5, 2023 Page 8
Earth Solutions NW, LLC
Foundations
After completing earthwork activities in accordance with recommendations in this report, the
proposed structures can be supported on conventional spread and continuous foundations
bearing on undisturbed, competent native soil, recompacted native soil, or new structural fill.
Where loose or unsuitable soil conditions are encountered at foundation subgrade elevations,
compaction of the soils to the specifications of structural fill, or overexcavation and replacement
with suitable structural fill will likely be necessary. A representative of ESNW should confirm
suitability of foundation subgrades at the time of construction.
Due to the high moisture sensitivity of the site soils, foundation subgrade areas should be
protected from wet weather or areas of remediation should be anticipated; a layer of crushed rock
can be considered to protect foundation subgrade areas. If structural building pads are disturbed
during wet weather, remediation measures such as cement treatment or overexcavation and
replacement with rock may be necessary in some areas. Additionally, perched groundwater
seepage may create unsuitable soil conditions above the hardpan which would require aeration,
cement treatment, or replacement with crushed rock.
Provided the structures will be supported as described above, the following parameters may be
used for design of the new foundations:
Allowable soil bearing capacity 2,500 psf
Passive earth pressure 300 pcf
Coefficient of friction 0.40
A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind
and seismic loading conditions. The passive earth pressure and coefficient of friction values
include a safety factor of 1.5. With structural loading as expected, total settlement in the range of
one inch is anticipated, with differential settlement of about one-half inch. The majority of the
settlement should occur during construction as dead loads are applied.
Prospect Development, LLC ES-9488
December 5, 2023 Page 9
Earth Solutions NW, LLC
Seismic Considerations
The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the
Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic
design, specifically with respect to earthquake loads. Based on the soil conditions encountered
at the test pit locations, the parameters and values provided below are recommended for seismic
design per the 2018 IBC.
Parameter Value
Site Class C*
Mapped short period spectral response acceleration, SS (g) 1.335
Mapped 1-second period spectral response acceleration, S1 (g) 0.459
Short period site coefficient, Fa 1.2
Long period site coefficient, Fv 1.5
Adjusted short period spectral response acceleration, SMS (g) 1.602
Adjusted 1-second period spectral response acceleration, SM1 (g) 0.688
Design short period spectral response acceleration, SDS (g) 1.068
Design 1-second period spectral response acceleration, SD1 (g) 0.459
* Assumes very dense native soil conditions, encountered to a maximum depth of eight feet bgs during the
September 2023 field exploration, remain dense to at least 100 feet bgs.
Liquefaction is a phenomenon where saturated or loose soil suddenly loses internal strength and
behaves as a fluid. This behavior is in response to increased pore water pressures resulting from
an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction
may be considered low. The depth of the regional groundwater table and the relatively dense
characteristics of the native soil were the primary bases for this opinion.
Slab-on-Grade Floors
Slab-on-grade floors should be supported on a firm and unyielding subgrade consisting of
competent native soil or at least 12 inches of new structural fill. Unstable or yielding areas of the
subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior
to slab construction.
Prospect Development, LLC ES-9488
December 5, 2023 Page 10
Earth Solutions NW, LLC
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
manufacturer’s specifications.
Retaining Walls
Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The
following parameters can be used for retaining wall design assuming structural fill is used for
backfill:
Active earth pressure (unrestrained condition) 35 pcf
At-rest earth pressure (restrained condition) 55 pcf
Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)
Passive earth pressure 300 pcf
Coefficient of friction 0.40
Seismic surcharge 8H psf*
* Where H equals the retained height (in feet).
The passive earth pressure and coefficient of friction values include a safety factor of 1.5.
Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be
included in the retaining 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. The upper 12 inches of the wall
backfill may consist of a less permeable soil, if desired.
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.
A perforated drainpipe should be placed along the base of the wall and connected to an approved
discharge location. A typical retaining wall drainage detail is provided on Plate 3.
Prospect Development, LLC ES-9488
December 5, 2023 Page 11
Earth Solutions NW, LLC
Drainage
While no groundwater was observed during our fieldwork, in our opinion, the presence of perched
groundwater seepage should be expected in excavations, especially at the contact between the
weathered till/outwash and unweathered till soils. Where zones of groundwater seepage are
encountered, temporary measures to control groundwater seepage may be needed. Temporary
measures to control groundwater seepage and surface water runoff during construction will likely
involve passive elements such as interceptor trenches and sumps, as necessary. Surface water
should not be directed to the top or toe of slopes, modular block walls, or rockeries; wall and
rockery drainage should not be used to temporarily control surface water during construction.
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 10 feet or as setbacks allow. In our opinion, perimeter footing
drains should be installed at or below the invert of the building footings. A typical footing drain
detail is provided on Plate 4 of this report.
If buildings will incorporate crawl spaces rather than slab-on-grade, in our opinion, a crawl space
drain system can be used in lieu of perimeter footing drains. The crawl space drain must provide
positive drainage to an appropriate outlet.
Infiltration Evaluation
During the design process of this site, the feasibility of infiltration is being investigated. Current
stormwater management plans include an infiltration pond to be located in the northwestern
proposed area of the site. Final elevations have not been determined, and are pending in-situ
testing to be completed by ESNW within the pond area. ESNW was provided a geotechnical
report prepared for this site in 2008 that included two test pits excavated near the proposed pond
location. The soils within this area are highly layered; however, the test pit closest to the pond
location indicated a fairly clean gravel layer that began around 12 feet below existing grade. The
report recommended a long-term design infiltration rate of four inches/hour be used within the
outwash soils and acknowledged the high sensitivity of the Advance outwash soils to silt or fines
contamination that would significantly impact infiltration performance. This layer will be targeted
in the infiltration pond design. For preliminary design purposes, a long-term infiltration rate of
four inches/hour may be used for systems situated to release within outwash sand/gravel soils.
This will be confirmed and adjusted as necessary subsequent to in-situ testing. In any case,
ESNW recommends infiltration facilities be designed to release within the Advance outwash soils.
Stormwater Detention Pond Recommendations
We understand a stormwater pond will be constructed along the south-central portion of the site.
Test pits in this area indicate outwash sand/gravel overlying dense glacial till at depth. Therefore,
interflow groundwater seepage into the excavation should be anticipated, particularly if completed
during the wet season. A compacted till liner should be considered due to the potential presence
of outwash deposits along the side slopes of the pond. The compacted till liner should conform
to the gradation and installation guidance provided in King County SWDM Section 6.2.4.1.
Prospect Development, LLC ES-9488
December 5, 2023 Page 12
Earth Solutions NW, LLC
Utility Support and Trench Backfill
The native soil observed at the test pit locations are generally suitable for utility trench backfill.
Use of the native soil as structural backfill in the utility trench excavations will depend on the in-
situ moisture content at the time of placement and compaction. If native soil is placed below the
optimum moisture content, settlement will likely occur once wet weather impacts the trenches.
As such, backfill soils should be properly moisture conditioned, as necessary, to ensure
acceptability of the soil moisture content at the time of placement and compaction. Native soil
will be difficult or impossible to use as utility trench backfill during extended wet weather
conditions. In this respect, moisture conditioning or treatment of the soils may be necessary at
some locations prior to use as structural fill. The existing fill soil may not be suitable for utility
trench backfill and the use of imported soil should be anticipated; ESNW should evaluate
suitability of existing fill during construction. Utility trench backfill should be placed and
compacted to the specifications of structural fill provided in this report or to the applicable
requirements of the presiding jurisdiction.
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 proof rolling 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 or yielding subgrade conditions will require remedial measures, such as
overexcavation and/or placement of thick crushed rock or structural fill sections, prior to
pavement.
We anticipate new pavement sections will be subjected primarily to passenger vehicle traffic. 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 may be considered:
Three inches of HMA placed over six inches of CRB, or;
Three inches of HMA placed over four and one-half inches of ATB.
Prospect Development, LLC ES-9488
December 5, 2023 Page 13
Earth Solutions NW, LLC
A representative of ESNW should be requested to observe subgrade conditions prior to
placement of CRB or ATB. As necessary, supplemental recommendations for achieving
subgrade stability and drainage can be provided. If on-site roads will be constructed with an
inverted crown, additional drainage measures may be recommended to assist in maintaining road
subgrade and pavement stability.
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 governing jurisdiction may supersede the
recommendations provided in this report. 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.
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.
REFERENCES
The following documents and resources were reviewed as part of our report preparation:
Conceptual Site Plan, prepared by ESM Consulting Engineers, dated November 6, 2023
Lidar-revised geologic map of the Poverty Bay 7.5' quadrangle, King and Pierce Counties,
Washington, U.S. Geological Survey, Tabor, R.W., Booth, D.B., and Troost, K.G., dated
2014
Federal Way Municipal Code (FWMC)
Web Soil Survey (WSS) online resource, maintained by the Natural Resources
Conservation Service under the United States Department of Agriculture
2021 King County Surface Water Design Manual
Drawn CAM
Checked SES Date Nov.2023
Date 11/20/2023 Proj.No.9488
Plate 1
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
Vicinity Map
Saghalie Heights
Federal Way,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.
Federal Way
SITE
Tacoma
Plate
Proj.No.
Date
Checked
DrawnEarthSolutionsNWLLC GeotechnicalEngineering,ConstructionObservation/TestingandEnvironmentalServicesEarthSolutionsNWLLCEarthSolutionsNWLLCTP-1
TP-2
TP-3
TP-4
TP-5TP-6
12
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20 21
22
23
24
Storm
Storm
Tract A
Critical Area
Tract B
Critical Area
Tract C 13thplaces.w.s.w.344th street19thavenues.w.350
350
360
360 370
370 380
380
390
390
360
370370
40'Reduced
Wetland Buffer
60'Reduced
Wetland Buffer
60'Reduced
Wetland Buffer
Storm
Storm
25
26
GW
.5'
GW
4'
GW
3'
GW
4.5'
GW
2.5'-5'
0
1'-4'
SP-SM
Terra Report
2008
0 75 150 300
Sc ale in Feet1"=150'
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-9488,Sept.2023
Subject Site
Proposed Lot Number
W etland (Delineated
by Others)
Approximate Limit of
Outwash Deposit
TP-1
NORTH
22
TestPitLocationPlanSaghalieHeightsFederalWay,WashingtonCAM
SES
12/04/2023
9488
2
GW
3'
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drawn CAM
Checked SES Date Nov.2023
Date 11/20/2023 Proj.No.9488
Plate 3
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
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 DRAW ING
Retaining Wall Drainage Detail
Saghalie Heights
Federal Way,Washington
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drawn CAM
Checked SES Date Nov.2023
Date 11/20/2023 Proj.No.9488
Plate 4
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutions
NW LLC
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
Footing Drain Detail
Saghalie Heights
Federal Way,Washington
Earth Solutions NW, LLC
Appendix A
Subsurface Exploration Logs
ES-9488
Subsurface conditions at the subject site were explored on September 25, 2023 by excavating
six test pits using a trackhoe and operator retained by ESNW. The approximate locations of the
test pits are illustrated on Plate 2 of this study. The test pit logs are provided in this Appendix.
The maximum exploration depth was approximately eight feet bgs.
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.
>12%Fines<5%FinesHighlyOrganicSoilsSiltsandClaysLiquidLimit50orMoreSiltsandClaysLiquidLimitLessThan50Fine-GrainedSoils-50%orMorePassesNo.200SieveCoarse-GrainedSoils-MoreThan50%RetainedonNo.200SieveSands-50%orMoreofCoarseFractionPassesNo.4SieveGravels-MoreThan50%ofCoarseFractionRetainedonNo.4Sieve>12%Fines<5%FinesGW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
Well-graded gravel with
or without sand,little to
no fines
Poorly graded gravel with
or without sand,little to
no fines
Silty gravel with or without
sand
Clayey gravel with or
without sand
Well-graded sand with
or without gravel,little to
no fines
Poorly graded sand with
or without gravel,little to
no fines
Silty sand with or without
gravel
Clayey sand with or
without gravel
Silt with or without sand
or gravel;sandy or
gravelly silt
Clay of low to medium
plasticity;lean clay with
or without sand or gravel;
sandy or gravelly lean clay
Organic clay or silt of
low plasticity
Elastic silt with or without
sand or gravel;sandy or
gravelly elastic silt
Clay of high plasticity;
fat clay with or without
sand or gravel;sandy or
gravelly fat clay
Organic clay or silt of
medium to high plasticity
Peat,muck,and other
highly organic soils
EEaarrtthh SSoolluuttiioonnss NNWW LLC
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
EXPLORATION LOG KEYFillFILLMadeGround
Classifications of soils in this geotechnical report and as shown on the exploration logs are based on visual
field and/or laboratory observations,which include density/consistency,moisture condition,grain size,and
plasticity estimates,and should not be construed to imply field or laboratory testing unless presented herein.
Visual-manual and/or laboratory classification methods of ASTM D2487 and D2488 were used as an
identification guide for the Unified Soil Classification System.
Terms Describing Relative Density and Consistency
Coarse-Grained Soils:
Fine-Grained Soils:
SPT blows/foot
SPT blows/foot
Test Symbols &Units
Fines =Fines Content (%)
MC =Moisture Content (%)
DD =Dry Density (pcf)
Str =Shear Strength (tsf)
PID =Photoionization Detector (ppm)
OC =Organic Content (%)
CEC =Cation Exchange Capacity (meq/100 g)
LL =Liquid Limit (%)
PL =Plastic Limit (%)
PI =Plasticity Index (%)
Component Definitions
Descriptive Term Size Range and Sieve Number
Smaller than No.200 (0.075 mm)
Boulders
Modifier Definitions
Percentage by
Weight (Approx.)
<5
5 to 14
15 to 29
>30_
Modifier
Trace (sand,silt,clay,gravel)
Slightly (sandy,silty,clayey,gravelly)
Sandy,silty,clayey,gravelly
Very (sandy,silty,clayey,gravelly)
Moisture Content
Dry -Absence of moisture,dusty,dry to
the touch
Damp -Perceptible moisture,likely below
optimum MC
Moist -Damp but no visible water,likely
at/near optimum MC
Wet -Water visible but not free draining,
likely above optimum MC
Saturated/Water Bearing -Visible free
water,typically below groundwater table
Symbols
Cement grout
surface seal
Bentonite
chips
Grout
seal
Filter pack with
blank casing
section
Screened casing
or Hydrotip with
filter pack
End cap
ATD =At time
of drilling
Static water
level (date)
_>50
Density
Very Loose
Loose
Medium Dense
Dense
Very Dense
Consistency
Very Soft
Soft
Medium Stiff
Stiff
Very Stiff
Hard
<4
4 to 9
10 to 29
30 to 49
<2
2 to 3
4 to 7
8 to 14
15 to 29
_>30
LLC
EarthSolutions
NW LLC
Cobbles
Gravel
Coarse Gravel
Fine Gravel
Sand
Coarse Sand
Medium Sand
Fine Sand
Silt and Clay
Larger than 12"
3"to 12"
3"to No.4 (4.75 mm)
3"to 3/4"
3/4"to No.4 (4.75 mm)
No.4 (4.75 mm)to No.200 (0.075 mm)
No.4 (4.75 mm)to No.10 (2.00 mm)
No.10 (2.00 mm)to No.40 (0.425 mm)
No.40 (0.425 mm)to No.200 (0.075 mm)
351.5
344.0
GB
GB
MC = 6.9
Fines = 32.8
MC = 9.3
TPSL
SM
Dark brown TOPSOIL, minimal root intrusions
Brown silty SAND, very dense, damp
-weakly cemented
-becomes gray
[USDA Classification: gravelly sandy LOAM]
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
0.5
8.0SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-1
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 352 ft
LOGGED BY SES
LATITUDE 47.29490 LONGITUDE -122.35550
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
359.7
357.5
355.0
352.5
GB
GB
MC = 4.5
MC = 5.5
Fines = 28.9
TPSL
SM
GW
SM
Dark brown TOPSOIL, shallow root intrusions
Brown silty SAND with gravel, dense, damp
Brown well-graded GRAVEL with sand, dense, damp
Gray silty SAND with gravel, very dense, damp
-weakly cemented
[USDA Classification: gravelly sandy LOAM]
Test pit terminated at 7.5 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
0.3
2.5
5.0
7.5SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-2
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 360 ft
LOGGED BY SES
LATITUDE 47.29426 LONGITUDE -122.35543
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
375.5
373.0
368.0
GB
GB
MC = 2.8
Fines = 4.4
MC = 3.6
TPSL
SM
GP
Dark brown TOPSOIL, root intrusions to 2'
Brown silty SAND with gravel, dense, damp
Gray poorly graded GRAVEL with sand, very dense, damp
-weakly cemented
[USDA Classification: extremely gravelly coarse SAND]
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
0.5
3.0
8.0SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-3
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 376 ft
LOGGED BY SES
LATITUDE 47.29459 LONGITUDE -122.35320
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
359.0
356.0
352.0GBMC = 1.4
Fines = 1.4
TPSL
SM
GW
Dark brown TOPSOIL, root intrusions to 1'
Brown silty SAND with gravel, dense, damp
Gray well-graded GRAVEL with sand, dense, damp
[USDA Classification: extremely gravelly coarse SAND]
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
1.0
4.0
8.0SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-4
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 360 ft
LOGGED BY SES
LATITUDE 47.29416 LONGITUDE -122.35342
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
383.5
376.0
GB
GB
MC = 1.5
Fines = 0.9
MC = 1.8
TPSL
GW
Dark brown TOPSOIL, root intrusions to 2'
Brown well-graded GRAVEL with sand, dense, damp
[USDA Classification: extremely gravelly coarse SAND]
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
0.5
8.0SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-5
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 384 ft
LOGGED BY SES
LATITUDE 47.29375 LONGITUDE -122.35329
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
369.5
365.5
362.0
GB
GB
MC = 1.9
MC = 4.9
TPSL
GW
SM
Dark brown TOPSOIL, root intrusions to 2'
Brown well-graded GRAVEL with sand, dense, damp
Gray silty SAND with gravel, very dense, damp
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not
surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for a
complete understanding of subsurface conditions.
0.5
4.5
8.0SAMPLE TYPENUMBERDEPTH(ft)0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-6
CHECKED BY SSR
NOTES
SURFACE CONDITIONS Duff
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR Client Provided
DATE STARTED 9/25/23 COMPLETED 9/25/23
GROUND WATER LEVEL:
GROUND ELEVATION 370 ft
LOGGED BY SES
LATITUDE 47.29356 LONGITUDE -122.35389
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GENERAL BH / TP / WELL - 9488.GPJ - GINT US.GDT - 11/20/23Earth 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
Earth Solutions NW, LLC
Appendix B
Laboratory Test Results
ES-9488
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
41.65
31.67
32.03
LL
TP-01
TP-02
TP-03
TP-04
TP-05
0.315
0.398
0.414
3/4
U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
GRAVEL SAND
19
37.5
37.5
37.5
37.5
%Silt
0.79
1.52
1.06
TP-01
TP-02
TP-03
TP-04
TP-05
2 2003
Cc CuClassification
%Clay
16
PID60 D30
coarse SILT OR CLAYfinemedium
GRAIN SIZE IN MILLIMETERS
3/8 50
4.0ft.
7.5ft.
4.0ft.
8.0ft.
2.5ft.
4.00ft.
7.50ft.
4.00ft.
8.00ft.
2.50ft.
PL
3
D100
140
Specimen Identification
1
fine
6
HYDROMETER
304
32.8
28.9
4.4
1.4
0.9
101/2
COBBLES
Specimen Identification
4
coarse
20 401.5 8 14
USDA: Gray Gravelly Sandy Loam. USCS: SM.
USDA: Gray Gravelly Sandy Loam. USCS: SM with Gravel.
USDA: Gray Extremely Gravelly Coarse Sand. USCS: GP with Sand.
USDA: Gray Extremely Gravelly Coarse Sand. USCS: GW with Sand.
USDA: Brown Extremely Gravelly Coarse Sand. USCS: GW with Sand.
6 60
PERCENT FINER BY WEIGHTD10
0.082
1.807
2.764
2.411
0.393
0.583
13.119
12.606
13.273
GRAIN SIZE DISTRIBUTION
100
PROJECT NUMBER ES-9488 PROJECT NAME Saghalie Heights
GRAIN SIZE USDA ES-9488 SAGHALIE HEIGHTS.GPJ GINT US LAB.GDT 10/23/23Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711