REVIEWED RESUB 1-BLD2024-0036+Geotech Report+5.13.2024_7.44.08_PM+4254428RESUB
May 14 2024
P.O. Box 935
Ages En ineerin
Engineering
Puyallup, WA. 98371
Main (253) 845-7000
A Geotechnical Engineering Services Company
www.agesengmeermg.com
October 26, 2023
Project No. A-1674
Ozzie Lucca
2410 Dexter Aveue North
Seattle, WA 98109
Subject: Geotechnical Report
Freeman Residence
8602 Olympic View Drive
Edmonds, Washington
Parcel Number:
Dear Mr. Lucca,
As requested, we have conducted a geotechnical study for the subject project. The attached
report presents our findings and recommendations for the geotechnical aspects of project design
and construction.
Our field exploration indicates the site is generally underlain with 0.5 to 1.0 feet of topsoil
overlying silt, silty sand with gravel, and/or sand with fine gravel consistent with Advance
Outwash. In general, the soils were medium dense and moist. We did not encounter groundwater
on the site.
In our opinion, the soil and groundwater conditions at the site are suitable for the planned
development. The new retaining walls can be supported on the existing organic -free native soils
observed immediately below surface grades. Site retaining walls can consist of concrete walls or
segmental block walls. The development storm water can discharge on the subject site.
Detailed recommendations addressing these issues and other geotechnical design considerations
are presented in the attached report. We trust the information presented is sufficient for your
current needs. If you have any questions or require additional information, please call.
Respectfully Submitted,
Ages Engineering
Bernard P. Knoll, I1
Principal
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TABLE OF CONTENTS
1.0 PROJECT DESCRIPTION...................................................................I
2.0 SCOPE..........................................................................................1
3.0 SITE CONDITIONS..........................................................................2
3.1 Surface.................................................................................2
3.2 Soils....................................................................................2
3.3 Mapped Soils.........................................................................3
3.4 Groundwater..........................................................................3
4.0 GEOLOGIC HAZARDS.....................................................................4
4.1 General.................................................................................4
4.2 Landslide................................................................................4
4.3 Erosion...................................................................................5
4.4 Seismic..................................................................................6
5.0 CONCLUSIONS AND RECOMMENDATIONS.........................................7
5.1 General.................................................................................7
5.2 Site Preparation and Grading.......................................................7
5.3 Excavations...........................................................................8
5.4 Foundations.............................................................................9
5.5 Retaining Wall......................................................................10
5.6 Storm water..........................................................................12
5.7 Permanent Slopes and Embankments..............................................12
5.8 Site Drainage.............................................................................12
6.0 ADDITIONAL SERVICES...................................................................13
7.0 LIMITATIONS..................................................................................13
Figures
Site Vicinity Map............................................................................... Figure 1
Exploration Location Plan .....................................................................Figure 2
GeologicMap..................................................................................Figure 3
USDANRCS Map........................................................................... Figure 4
Appendix
Site Exploration..........................................................................Appendix A
WallDesign...............................................................................Appendix B
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Geotechnical Report
Freeman Residence
8602 Olympic View Drive
Edmonds, Washington
1.0 PROJECT DESCRIPTION
We were provided with four sheets of project plans showing the planned development. Based on
the plans provided to us, and our conversation with you, we understand the existing rockeries in
the front yard of the site will be replaced with new retaining walls. The staircase will be
reconstructed in the same location and new landscaping and plantings included. The new walls
will be constructed along the sides of the staircase to provide grade breaks between the yard and
the staircase. The walls will turn to create two planters along the north side of the staircase. We
expect the new retaining walls will consist of Murata segmental block walls with Cast -In -Place
(CIP) concrete foundations. The total height of each retaining wall will be less than 4.0 feet. Site
access is from a driveway along the north side of the site that extends east to Olympic View Drive
located along the north side of the site. The development storm water will discharge on the
subject site.
The conclusions and recommendations presented in this report are based on our understanding of
the above -stated site and the planned project design features. If actual site conditions differ, the
planned project design features are different than we expect, or if changes are made, we should
review them in order to modify or supplement our conclusions and recommendations as
necessary.
2.0 SCOPE
On September 27, 2023, we excavated three hand -augured test holes to a maximum depth of 6.0
feet below surface grades. Using the information obtained from our subsurface exploration, we
developed geotechnical design and construction recommendations for the project. Specifically,
this report addresses the following:
• Reviewing the available geologic, hydrogeologic and geotechnical data for the site area,
and conducting a geologic reconnaissance of the site area.
• Addressing the appropriate geotechnical regulatory requirements for the planned site
development, including a Geologic Hazard evaluation.
• Advancing three hand -augured test holes in the planned new development area to a
maximum depth of approximately 6.0 feet below surface grades.
• Providing geotechnical recommendations for site grading including site preparation,
subgrade preparation, fill placement criteria, suitability of on -site soils for use as
structural fill, temporary and permanent cut and fill slopes, and drainage and erosion
control measures.
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• Providing geotechnical recommendations for design and construction of new foundations,
including allowable bearing capacity and estimates of settlement.
• Providing geotechnical recommendations for new retaining walls, including backfill and
drainage requirements, lateral design loads, and lateral resistance values.
• Providing preliminary recommendations for the discharge of the development storm
water.
• Providing recommendations for site drainage.
It should be noted that our work does not include services related to environmental remediation or
design and performance issues related to moisture intrusion through walls. An appropriate design
professional or qualified contractor should be contacted to address these issues.
3.0 SITE CONDITIONS
3.1 Surface
The subject site is an irregular -shaped, 0.27-acre, residential parcel located in Edmonds,
Washington. The site is currently occupied with a single-family residence located in the
approximate center of the site. The site is bordered by residential parcels to the east, west and
south, and Olympic View Drive to the north. Access to the site is provided by Olympic View
Drive located along the north side of the site. The approximate location of the site is shown on the
Site Vicinity Map provided in Figure 1.
The front yard of the site is currently landscaped with a few scattered bushes planted along
several rockeries that appear to be overrun with eroded soil. Several areas appear to be steep
slopes as the rockery rocks are barely visible. No signs of instability were observed, just gradual
long-term erosion of the existing soils.
In general, the subject site is located in an area of undulating surface features that gradually slope
down to the west. The areas around the residence are relatively flat in all areas except the center
of the front yard where surface grades slope down to the driveway entrance to the site. The
driveway leads to the basement garage attached to the residence. The north end of the front yard
has a concrete retaining wall between the site and Olympic Drive. An aerial photograph of the
site is provided in Figure 2.
3.2 Soils
The soils we observed at the site generally consist of 0.5 to 1.0 feet of topsoil overlying native
silty sand with gravel, silt and sand with fine gravel consistent with Advance Outwash.
The soil observed in Test Hole TH-1, located along the west side of the driveway along the slope
toe, consists of 12 inches of bark and topsoil overlying tan mottled reddish orange silt with trace
amounts of clay consistent with Advance Outwash. The soil observed in Test Hole TH-2, located
along the center of the front yard along the top of the slope, consist of 6 inches of topsoil
overlying tan silty sand with gravel to a depth of 2.0 feet below surface grades. Below 2.0 feet,
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the soils became tan sand with fine gravel to a depth of 4.0 feet. Below 4.0 feet, the soils became
tan sand with fine gravel. All these soils are consistent with Advance Outwash. The soil
observed in Test Hole TH-3, located in the back yard of the site, consists of 1.0 feet of topsoil
overlying tan mottled reddish orange silt with trace amounts of clay consistent with Advance
Outwash.
Figures A -I through A-3 present more detailed descriptions of the subsurface conditions
encountered in the test holes. The approximate test hole locations are shown on the Exploration
Location Plan provided in Figure 2.
3.3 Mapped Soils
According to the Geologic Map of the Poverty Bay 7.5' Quadrangle, King and Pierce Counties,
Washington by D. B. Booth, H. H. Waldron, and K. G. Troost (2004) the soils along the site
slopes are mapped as Advance Outwash (Qva). The Advance Outwash was deposited during the
Vashon stade of the Fraser Glaciation, approximately 12,000 to 15,000 years ago. The Advance
Outwash was deposited in front of the advancing glacial ice mass during brief periods of intense
warming. Consequently, these soils were overridden by the Continental Ice Sheet. The Advance
Outwash is described as a well -graded mixture of sand, silt, and gravel. The Advance Outwash
will typically be found in a dense condition where undisturbed. The near surface soils at the site
have been disturbed by natural weathering processes that have occurred since their deposition.
No springs or groundwater seepage was observed on the surface of the site at the time of our site
visit. A copy of the Geologic Map for the subject site is provided in Figure 3.
According to the United States Department of Agriculture (USDA) Natural Resource
Conservation Service (NRCS), the soils on the north end of the site are mapped as Alderwood
gravelly sandy loam (2) soils that form on 8 to 15 percent slopes and the soils along the south end
of the site are mapped as Alderwood gravelly sandy loam (3) soils that form on 15 to 30 percent
slopes. According to the USDA NRCS, the Alderwood gravelly sandy loam (2) soils will have a
"slight" potential for erosion when exposed and the Alderwood gravelly sandy loam (3) soils will
have a "moderate" potential for erosion when exposed. Due to the USDA NRCS classification of
the site soils, the site is classified as having Erosion Hazard Areas. A copy of the USDA NRCS
Map for the subject site is provided in Figure 4.
3.4 Groundwater
We did not encounter groundwater seepage in any of the test holes excavated on the site.
However, we expect a seasonal perched water table likely develops on top of the dense glacially
consolidated soils underlying the site at times during the wet winter months. The groundwater
levels and flow rates will fluctuate seasonally and typically reach their highest levels during and
shortly following the wet winter months (October through May).
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4.0 GEOLOGIC HAZARDS
4.1 General
According to Chapter 23.80 in the City of Edmonds Municipal Code geologic hazard areas
include "areas susceptible to erosion, land sliding, earthquake, or other geological events. They
pose a threat to the health and safety of citizens when incompatible development is sited in areas
of significant hazard. Such incompatible development may not only place itself at risk, but also
may increase the hazard to surrounding development and use. Areas susceptible to one or more of
the following types of hazards shall be designated as a geologically hazardous area:
A. Erosion hazard;
B. Landslide hazard; and
C. Seismic hazard. [Ord. 4026 1 (Att. A), 2016; Ord. 3527 2, 2004]."
4.2 Landslide
According to the City of Edmonds Municipal Code 23.80.020, landslide hazard areas are defined
as: "areas potentially subject to landslides based on a combination of geologic, topographic, and
hydrologic factors. They include areas susceptible because of any combination of soil, slope
(gradient), slope aspect, structure, hydrology, or other factors. Within the city of Edmonds
potential landslide hazard areas include:
1. Areas of ancient or historic failures in Edmonds which include all areas within the
earth subsidence and landslide hazard area as identified in the 1979 report of Robert
Lowe Associates and amended by the 1985 report of GeoEngineers, Inc., and further
discussed in the 2007 report by Landau Associates;
2. Coastal areas mapped as class u (unstable), uos (unstable old slides), and urs
(unstable recent slides) in the Department of Ecology Washington coastal atlas;
3. Areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps
published by the United States Geological Survey or Washington State Department
of Natural Resources;
4. Any slope of 40 percent or steeper that exceeds a vertical height of 10 feet over a 25-
foot horizontal run. Except for rockeries that have been engineered and approved by
the engineer as having been built according to the engineered design, all other
modified slopes (including slopes where there are breaks in slopes) meeting overall
average steepness and height criteria should be considered potential landslide hazard
areas);
5. Any slope with all three of the following characteristics:
a. Slopes steeper than 15 percent;
b. Hillsides intersecting geologic contacts with a relatively permeable
sediment overlying a relatively impermeable sediment; and
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C. Springs or ground water seepage;
6. Any area potentially unstable as a result of rapid stream incision or stream bank
erosion;
7. Any area located on an alluvial fan, presently subject to, or potentially subject to,
inundation by debris flow or deposition of stream -transported sediments; and
8. Any slopes that have been modified by past development activity that still meet the
slope criteria."
Based on our document research, we found no areas on the site mapped as areas of historic slope
failures. The site is not located along a shoreline and therefore is not mapped by the Washington
State Department of Ecology Coastal Zone Atlas. The United States Geological Survey and the
Washington State Department of Natural Resources maps have not designated any areas as
quaternary slumps, earthflows, mudflows, or landslides. The site does not have a stream running
thru it, therefore no rapid stream incision or stream bank erosion. We did not observe any areas
with topographic expression of runout zones, such as fans and colluvial deposition at the toes of
hillsides. The sites' north slope area exceeds 15 percent but have no groundwater seepage or
springs, and do not have intersecting contacts with a relatively permeable sediment overlying a
relatively impermeable sediment. No site areas exceed 40 percent and have a vertical height of
over 10 feet for a 25-foot horizontal run.
The site is not classified as having landslide hazard areas. Provided surface water is controlled on
the site, and all structures are provided with proper subsurface drainage measures, the potential
for a landslide to occur at this site should be considered negligible.
4.3 Seismic
According to the City of Edmonds Municipal Code 23.80.020, the City of Edmonds defines
seismic hazard areas as, "In addition to liquefaction -prone areas described in subsection 2 above,
seismic hazard areas are the following:
a. Areas of the City subject to ground shaking from seismic hazards that are addressed by
the Building Code (SMC Title 22).
b. The Seattle Fault zone as delineated in Troost et al., 2005, The geologic map of Seattle, a
progress report, U.S. Geological Survey, Open -file report 2005-1252 or as the Director
determines is more accurately mapped by the U.S Geological Survey, as set out in a
Director's Rule."
The site is located north of the Seattle Fault zone. The site is located in an area underlain with
medium dense to dense compact glacially consolidated soils.
Liquefaction can be described as a phenomenon where there is a reduction or complete loss of
soil strength due to an increase in pore water pressure. The increase in water pressure is typically
induced by vibrations. Liquefaction mainly affects geologically recent deposits of loose, fine-
grained sands that are below the groundwater table.
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Based on the relative density and well -graded nature of the soils underlying the site, the risk for
liquefaction to occur at the site should be considered negligible.
The state of Washington has adopted the International Building Code (IBC). Based on the soil
conditions encountered and the local geology, per the (IBC) site class "D" can be used in
structural design. This is based on the inferred range of SPT (Standard Penetration Test) blow
counts for the upper 100 feet of the site relative to hand excavation progress and probing with a
'/2-inch diameter steel probe rod. The presence of glacially consolidated soil conditions were
assumed to be representative for the site conditions beyond the depths explored.
4.4 Erosion
According to the City of Edmonds Municipal Code 23.80.020, defines an Erosion Hazard Area as
"those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation
Service as having a "moderate to severe," "severe," or "very severe" rill and inter -rill erosion
hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank
erosion. Within the city of Edmonds erosion hazard areas include:
1. Those areas of the city of Edmonds containing soils that may experience severe to very
severe erosion hazard. This group of soils includes, but is not limited to, the following
when they occur on slopes of 15 percent or greater:
a. Alderwood soils (15 to 25 percent slopes);
b. Alderwood/Everett series (25 to 70 percent slopes);
C. Everett series (15 to 25 percent slopes);
2. Coastal and stream erosion areas which are subject to the impacts from lateral erosion
related to moving water such as stream channel migration and shoreline retreat;
3. Any area with slopes of 15 percent or greater and impermeable soils interbedded with
granular soils and springs or ground water seepage; and
4. Areas with significant visible evidence of ground water seepage, and which also include
existing landslide deposits regardless of slope.
The site is mapped as Alderwood gravelly sandy loam (15 to 25 percent slopes) which has a
moderate to severe potential for erosion when exposed. Based on the USDA classification of the
site, the site is classified as an erosion hazard area.
Temporary Erosion and Sediment Control (TESC) measures must be in place prior to and
maintained during construction activity at the site. In our opinion, the potential for erosion is not
a limiting factor in site development. Erosion hazards can be mitigated by applying Best
Management Practices (BMPs) outlined in the Washington State Department of Ecology's
(Ecology) Stormwater Management Manual for Western Washington. TESC measures, in
accordance with the City of Edmonds, must be in place prior to beginning construction on the
site.
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5.0 CONCLUSIONS AND RECOMMENDATIONS
5.1 General
Based on our study, in our opinion, soil and groundwater conditions at the site are suitable for the
proposed development of the site. The new retaining walls can be supported on the existing
organic -free native soils observed at depths ranging from 0.5 to 1.0 feet below surface grades, or
on structural fill placed above these soils. The development storm water can discharge on the
subject site.
The native soils encountered at the site contain a high enough percentage of fines (silt and clay -
size particles) that will make them difficult to compact as structural fill when too wet.
Accordingly, the ability to use the soils from site excavations as structural fill will depend on
their moisture content and the prevailing weather conditions at the time of construction. If
grading activities will take place during the winter season, the owner should be prepared to
import free -draining granular material for use as structural fill and backfill.
The following sections provide detailed recommendations regarding these issues and other
geotechnical design considerations. These recommendations should be incorporated into the final
design drawings and construction specifications.
5.2 Site Preparation and Grading
To prepare the site for construction, all vegetation, organic surface soils, and other deleterious
materials including any existing structures, foundations or abandoned utility lines should be
stripped and removed from the new development areas. Organic topsoil will not be suitable for
use as structural fill but may be used for limited depths in non-structural areas. The existing
topsoil and fill observed in the upper 0.5 to 1.0 feet of the site will not be suitable for support of
structural elements. Prior to construction, these organic soils should be removed from under new
foundation, floor slab, and pavement areas.
Once clearing and stripping operations are complete, cut and fill operations can be initiated to
establish desired grades. In order to achieve proper compaction of structural fill, and to provide
adequate foundation and floor slab support, the existing subgrade must be in a stable condition.
Prior to placing structural fill, and to prepare the foundation subgrade, all exposed surfaces should
be compacted with heavy vibratory compaction equipment to determine if any isolated soft and
yielding areas are present.
If excessively soft or yielding areas are present, and cannot be stabilized in place by compaction,
they should be cut to firm bearing soil and filled to grade with structural fill. If the depth to
remove the unsuitable soil is excessive, using a geotextile fabric can be considered, such as
Mirafi HP270 or an approved equivalent, in conjunction with structural fill. In general, a
minimum of 18-inches of clean, granular structural fill over the geotextile fabric should establish
a stable bearing surface.
A representative of Ages Engineering should observe the foundation subgrade compaction
operations to verify that stable subgrades are achieved for support of structural elements.
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Our study indicates the native surface soils encountered at the site contain a sufficient enough
percentage of fines (silt and clay -size particles) that will make them difficult to compact as
structural fill when too wet. Accordingly, the ability to use the soils from site excavations as
structural fill will depend on their moisture content and the prevailing weather conditions at the
time of construction. If grading activities are planned during the wet winter months, or the on -
site soils become too wet to achieve adequate compaction, the owner should be prepared to
import a wet -weather structural fill. For wet weather structural fill, we recommend importing a
granular soil that meets the following gradation requirements:
U. S. Sieve Size
Percent Passim
6 inches
100
No. 4
75 maximum
No. 200
5 maximum*
* Based on the % inch fraction
Prior to use, Ages Engineering should examine and test all materials to be imported to the site for
use as structural fill.
Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to
a minimum of 95 percent of the soils' laboratory maximum dry density as determined by
American Society for Testing and Materials (ASTM) Test Designation D-1557 (Modified
Proctor). The moisture content of the soil at the time of compaction should be within two percent
of its optimum, as determined by this same ASTM standard. In non-structural areas, the degree
of compaction can be reduced to 90 percent.
5.3 Excavations
General,
The inclination for a safe and stable excavation slope cut is determined based on two factors, the
current Washington State Safety and Health Administration (WSHA) regulations for confined
spaces and global stability of the slope cut. Most often, the WSHA regulations are more
conservative than the global stability requirements.
According to WAC 296-809-099, a confined space is defined as: "A space that is all of the
following:
(a) Large enough and arranged so an employee could fully enter the space and work.
(b) Has limited or restricted entry or exit. Examples of spaces with limited or restricted
entry are tanks, vessels, silos, storage bins, hoppers, vaults, excavations, and pits.
(c) Not primarily designed for human occupancy."
In the context of site excavation and grading, the Washington State Department of Labor and
Industries considers a confined space as a space in which a worker enters an excavation that is tall
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enough and/or narrow enough to inundate the worker and cause bodily harm if a cave-in occurs.
This does not include excavations that are less than 4.0 feet in depth.
WSHA Approved Slope Cuts,
All excavations at the site associated with confined spaces, such as utility trenches and lower
level building and retaining walls, must be completed in accordance with local, state, and/or
federal requirements. Based on current Washington State Safety and Health Administration
(WSHA) regulations, the existing near surface loose to medium dense soils and weathered glacial
soils are classified as Type C soils. The deeper unweathered glacial soils would be classified as
Type A soils.
According to WSHA, for temporary excavations of less than 20 feet in depth, the side slopes in
Type C soils should be laid back at a slope inclination of 1.5:1 (Horizontal:Vertical) or flatter
from the toe to the crest of the slope and the side slopes in Type A soils should be laid back at a
slope inclination of 0.75:1 (Horizontal:Vertical) or flatter from the toe to the crest of the slope.
All exposed slope faces should be covered with a durable reinforced plastic membrane during
construction to prevent slope raveling and rutting during periods of precipitation. These
guidelines assume that all surface loads are kept at a minimum distance of at least one half the
depth of the cut away from the top of the excavation slope and that significant seepage is not
present on the slope face. Flatter cut slopes will be necessary where significant raveling or
seepage occurs, or if construction materials will be stockpiled along the slope crest. If these safe
temporary slope inclinations cannot be achieved due to property line constraints, shoring may be
necessary.
This information is provided solely for the benefit of the owner and other design consultants and
should not be construed to imply that Ages Engineering assumes responsibility for job site safety.
It is understood that job site safety is the sole responsibility of the project contractor.
Global Stability Excavations,
Based on the composition and consistency of the site soils, stable slope cuts to provide adequate
global stability can be steeper than WSHA standards in areas that are not considered confined
spaces. Excavations into the native glacial till soils on the site that will not result in WSHA
regulated confined spaces can be cut to an inclination of 0.5:1. Some raveling of the gravel and
cobbles exposed on the slope surface may occur at an inclination of 0.5:1. Due to the potential
for raveling to occur, and to prevent erosion, the slope face should be covered with durable plastic
sheeting.
This information is provided solely for the benefit of the owner and other design consultants and
should not be construed to imply that Ages Engineering assumes responsibility for job site safety.
It is understood that job site safety is the sole responsibility of the project contractor.
5.4 Foundations
The new concrete wall foundations may be supported on conventional spread footing foundations
bearing on the existing organic -free native soils, or on new structural fill placed above the
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existing site soils. Foundation subgrades should be prepared as recommended in the "Site
Preparation and Grading" section of this report. As discussed in the "Site Preparation and
Grading" section of this report, the existing topsoil and fill observed in the upper 0.5 to 1.0 feet of
the site will not be suitable for support of structural elements. Prior to construction, these old fill
soils should be removed from under new foundation areas.
Perimeter foundations exposed to the weather should bear at a minimum depth of 1.5 feet below
final exterior grades for frost protection. Interior foundations can be constructed at any
convenient depth below the floor slab. We recommend designing new foundations for a net
allowable bearing capacity of 2,500 pounds per square foot (psf). For short-term loads, such as
wind and seismic, a one-third increase in this allowable capacity can be used. With the
anticipated loads and this bearing stress applied, building settlements should be less than one-half
inch total and one -quarter inch differential.
For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used.
Passive earth pressures acting on the sides of the footings can also be considered. We
recommend calculating this lateral resistance using an equivalent fluid weight of 300 pounds per
cubic foot (pcf). We recommend not including the upper 12 inches of soil in this computation
because it can be affected by weather or disturbed by future grading activity. This value assumes
the foundations will be constructed neat against competent soil and backfilled with structural fill,
as described in the "Site Preparation and Grading" section of this report. The values
recommended include a safety factor of 1.5.
Foundation Parameter Summary
Description
*Design Value
Net Allowable Bearing Capacity
2,500 psf
Friction Coefficient
0.35
Lateral Resistance
300 pcf
}Details regarding the use of these parameters are provided in the section above.
5.5 Site Retaining Walls
Site development will entail the construction of new retaining walls. The new retaining walls will
consist of Mechanically Stabilized Earth (MSE) Walls with Cast -In -Place (CIP) concrete
foundations.
MSE Wall with Segmental Block Facing
Based on our evaluation, it is our opinion a new segmental block retaining wall can be
constructed on the site. The Murata Anglo segmental blocks require geogrid reinforcement for
any wall that exceeds 4.0 feet (6 blocks) in total height or are surcharged by sloping backfill,
traffic loads or other structural loads. Based on our examination of the loading on the site, it
appears the walls will not have a surcharge behind them. 'Be new retaining wall system must be
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constructed according to the manufacturers' specifications and the recommendations provided in
this report. We recommended the following be incorporated into the construction of the wall:
• We recommend using the Murata Anglo segmental blocks.
• The wall batter should be in accordance with the Murata Anglo segmental blocks system.
• The walls should have maximum total heights of no more than those provided in this
report.
• If a cap block is used, it must be entirely above ground and as such will not be considered
in the total height of the wall.
• A minimum of 6 inches (0.75 full blocks) of toe embedment is necessary for erosion
protection and stability purposes.
• A 4-inch-thick layer of crushed rock can be placed along the wall subgrade to provide a
leveling course.
• The soil used in the backfill zone must consist of structural fill as described in the Site
Preparation and Grading section of this report. The native soils can be used as structural
fill in most weather conditions.
• No Geogrid will be necessary behind the walls.
• A drainage layer consisting of 7/8 to 1 '/4 inch clean crushed rock or drain rock with a
minimum horizontal thickness of 12 inches should be placed behind the blocks and up to
the top of the wall, or to within 12 inches of the top of the wall.
• A layer of separation fabric shall be placed between the drainage layer and the reinforced
fill zone and over the top of the 12-inch-wide drainage layer.
• The upper 12 inches of fill may contain organic -laced soil.
• The wall drain should outfall at the low point in the center or at the end of the wall, or
through the base of the wall at a convenient location (1 block above the base block) and
discharge onto the ground surface or into the sites' storm water system located on the
site.
Wall Design,
Based on the expected loading conditions, we performed calculations for all of the expected wall
heights and are providing calculations for the tallest wall section that can support the Murata
Anglo segmental blocks. Based on our analysis, no geogrid reinforcement is necessary behind
the walls. The wall calculations are provided in Appendix B of the report.
Wall Drainage,
To guard against hydrostatic pressure development, drainage must be installed behind the wall.
We recommend that wall drainage consist of a minimum 12 inches of clean 7/8 to 1 1/4 inch clean
crushed rock or drain rock with less than three percent fines placed against the back of the wall. In
addition, a drainage collector system consisting of 4-inch perforated PVC pipe should be placed
behind the wall to provide an outlet for any accumulated water. The drain should be provided
with a vertical cleanout at each end of the wall alignment. These cleanouts should be serviced at
least once every year. The wall drainage material can be capped at the ground surface with 1-foot
Ages Engineering Page 11
253-945-7000
of relatively impermeable soil to prevent surface intrusion into the drainage zone. The wall drain
should outfall at the low point at the end of the wall and discharge to a stabilized area on the
ground surface, or to the site storm water system. system.
5.6 Storm Water
The City of Edmonds uses the 2019 Stormwater Management Manual for Western Washington
(SWMMWW) as their stormwater code. According to the code, we expect the stormwater
collected in the wall drains will discharge on the subject site.
5.7 Permanent Slopes and Embankments
All permanent cut and fill slopes should be graded with a finished inclination of no greater than
2:1 (Horizontal: Vertical). Upon completion of grading, the slope face should be appropriately
vegetated or provided with other physical means to guard against erosion. Final grades at the top
of the slope must promote surface drainage away from the slope crest. Water must not be
allowed to flow in an uncontrolled fashion over the slope face. If it is necessary to direct surface
runoff towards the slope, it should be controlled at the top of the slope, piped in a closed conduit
installed on the slope face, and taken to an appropriate point of discharge beyond the toe.
All fill used for slope and embankment construction should meet the structural fill requirements
described in the Site Preparation and Grading section of this report. In addition, if new fills will
be placed over existing slopes of 20 percent or greater, the structural fill should be keyed and
benched into competent slope soils.
5.8 Site Drainage
Surface,
Final exterior grades should promote free and positive drainage away from the building area. All
ground surfaces, pavements, and sidewalks should be sloped away from the structures. We
recommend providing a gradient of at least three percent for a minimum distance of ten feet from
the building perimeters, except in paved locations. In paved locations, a minimum gradient of
one percent should be provided, unless provisions are included for collection and disposal of
surface water adjacent to the structures.
Subsurface,
We recommend installing a continuous drain along the lower inside edge of the wall foundations.
The foundation drains should be tightlined to an approved point of controlled discharge.
Subsurface drains must be laid with a gradient sufficient to promote positive flow to the point of
discharge. All drains should be provided with cleanouts at easily accessible locations. These
cleanouts should be serviced at least once every year.
Ages Engineering Page 12
253-845-7000
6.0 ADDITIONAL SERVICES
Ages Engineering should review the final project designs and specifications in order to verify that
earthwork and foundation recommendations have been properly interpreted and incorporated into
project design. If changes are made in the loads, grades, locations, configurations or types of
facilities to be constructed, the conclusions and recommendations presented in this report may not
be fully applicable. If such changes are made, we should be given the opportunity to review our
recommendations and provide written modifications or verifications, as necessary.
We should also provide geotechnical services during construction to observe compliance with our
design concepts, specifications, and recommendations. This will allow for expedient design
changes if subsurface conditions differ from those anticipated prior to the start of construction.
7.0 LIMITATIONS
We prepared this report in accordance with generally accepted geotechnical engineering
practices. No other warranty, expressed or implied, is made. This report is the copyrighted
property of Ages Engineering and is intended for the exclusive use of Ozzie Lucca and his
authorized representatives for use in the design, permitting, and construction portions of this
project.
The analysis and recommendations presented in this report are based on data obtained from others
and our site explorations and should not be construed as a warranty of the subsurface conditions.
Variations in subsurface conditions are possible. The nature and extent of which may not become
evident until the time of construction. If variations appear evident, Ages Engineering should be
requested to reevaluate the recommendations in this report prior to proceeding with construction.
A contingency for unanticipated subsurface conditions should be included in the budget and
schedule. Sufficient monitoring, testing and consultation should be provided by our firm during
construction to confirm that the conditions encountered are consistent with those indicated during
our exploration, to provide recommendations for design changes should the conditions revealed
during the work differ from those anticipated, and to evaluate whether earthwork and foundation
installation activities comply with contract plans and specifications.
The scope of our services does not include services related to environmental remediation and
construction safety precautions. Our recommendations are not intended to direct the contractor's
methods, techniques, sequences or procedures, except as specifically described in our report for
consideration in design.
Ages Engineering Page 13
253-845-7000
0
Approximate Site Location
Ages Engineering
P. 0. Box 935
Puyallup, WA. 98371
Main (253)845-7000
www.agesenginecring.com
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Site Vicinity Map
Freeman Residence
8602 Olympic View Drive
Edmonds, Wastiingtcm
KEY:
APPROXIMATE LOCATION OF TEST HOLE TH-1
Ages Engineering
P. O. Box 935
Puyallup, WA. 98371
Main (253) 845-7000
www.agesengineering.com
Exploration Location Plan
Freeman Residence
8602 Olympic View Drive
Edmonds, Washington
Project No.: A-1674 I October 2023 1 Figure 2
-T`
Approximate Site Location
Ages Engineering Geologic Map
P. O. Box vas
Freeman Residence
Puyallup, WA. 98371 8602 Olympic View Drive
Main (253) 845-7000 Edmonds, Washington
www.agesengineering.com
Project No.: A-1674 October 2023 Figure 3
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
Freeman Residence
Edmonds, Washington
On September 27, 2023 we explored subsurface conditions at the site by excavating three hand -augured test holes
to a maximum depth of 6.0 feet below surface grades. The approximate location of the site is shown on the Site
Vicinity map provided in Figure 1. The approximate test hole locations are shown on the Exploration Location
Plan provided in Figure 2.
A geotechnical engineering representative from our office conducted the field exploration, maintained a log of
each test hole and classified the soils encountered, collected representative soil samples, and observed pertinent
site features. All soil samples were visually classified in accordance with the Unified Soil Classification System
(USCS) described on Figure A-1. The test hole logs are presented on Figure A-2.
Representative soil samples obtained from the test holes were placed in sealed containers and taken to our
laboratory for further examination and testing. The moisture content of each sample was measured and is
reported on the test hole logs.
Project No. A-1674
UNIFIED SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS
GROUP
SYMBOL
GROUP NAME
GRAVEL
GW
Well -Graded GRAVEL
WITH
GRAVEL
< 5 % FINES
GP
Poorly -Graded GRAVEL
GRAVEL
GW-GM
Well -Graded GRAVEL with silt
GW-GC
Well -Graded GRAVEL with clay
WITH
COARSE
More than 50%
Of Coarse Fraction
Retained on
BETWEEN
5 AND 15 %
FINES
GP -GM
Poorly -Graded GRAVEL with silt
GP -GC
Poorly -Graded GRAVEL with clay
GRAINED
No. 4 Sieve
GRAVEL
GM
Silty GRAVEL
SOILS
WITH > 15 %
FINES
GC
Clayey GRAVEL
SAND
SW
Well -Graded SAND
WITH
SP
Poorly -Graded SAND
More than 50%
Retained on
SAND
< 5 % FINES
No. 200 Sieve
SAND
SW-SM
Well -Graded SAND with silt
SW -SC
Well -Graded SAND with clay
WITH
More than 5"o
Of Coarse Fraction
Passes
BETWEEN
5 AND 15 %
FINES
SP-SM
Poorly -Graded SAND with silt
SP-SC
Poorly -Graded SAND with clay
No. 4 Sieve
SAND
SM
Silty SAND
WITH > 15 %
SC
Clayey SAND
FINES
fr
GRAINED
Liquid Limit Less than 50
MI.
Inorganic SILT with low plasticity
CL
Lean inorganic CLAY with low plasticity
OL
Organic SILT with low plasticity
SOILS
SELL AND
MH
Elastic inorganic SILT with moderate to high plasticity
CLAY
More than 50%
Passm
Liquid Limit
50 or more
CH
Fat inorganic CLAY with moderate to high plasticity
Organic SILT or CLAY with moderate to high plasticity
No. 200 Sieve
HIGHLY ORGANIC SOILS
PEAT
NOTES:
(1) Soil descriptions are based on visual field and laboratory observations using the classification methods described in ASTM D-2488. Where
laboratory data are available, classifications are in accordance with ASTM D-2487.
(2) Solid lines between soil descriptions indicate a change in the interpreted geologic unit. Dashed lines indicate stratigraphic change within the unit.
(3) Fines are material passing the U.S. No. 200 Sieve.
Ages Engineering
P. O. Box 935
Puyallup, WA. 98371
Unified Soil Classification System (USCS)
Freeman Residence
8602 Olympic View Drive
Main (253) 845-7000
Edmonds, W
www.agesengineering.com
Project No.: A-1674
Wober 2023
Figure A-1
P.O. Box 935
Ages Engineering Puyallup, WA. 98371
Office (253) 845-7000
Test Hole TH-1
DATE: September 27, 2023 WICG ED BY: BPK ELEV:
t
Soil Description Notes
M% Other
0
5
12 inches TOPSOIL
Tan mottled reddish -orange SILT, trace clay, some inclusions of
wood, medium dense, moist. (ML)
Test Hole terminated at a depth of 5.0 feet below surface grades.
No groundwater seepage encountered.
Test Hole TH-2
DATE: September 27, 2023 LOGGED BY: BPK ELEV:
Depth Soil Description Notes
feet M% I Other
0 1 1C :-- "
Tan silty SAND with gravel, medium dense, moist. (SM)
Tan SAND with fine gravel, medium dense, moist. (SM)
5 Tan mottled reddish -orange SILT, trace clay, medium dense, moist.
(MI-)
Test Hole terminated at a depth of 6.0 feet below surface grades.
No groundwater seepage encountered.
Test Hole TH-3
DATE: September 27, 2023 LOGGED BY: BPK ELEV:
Depth Soil Description Notes
feet M°/n I Other
0
12 inches TOPSOIL
Tan mottled reddish -orange SILT, trace clay, some inclusions of
wood, medium dense, moist. (NE)
Test Hole terminated at a depth of 5.0 feet below surface grades.
No groundwater seepage encountered.
Figure A-2 Project No.: A-1674
APPENDIX B
RETAINING DESIGN CALCULATIONS
Freeman Residence
Edmonds, Washington
Project No. A-1674
REA Analysis
Project: Freeman Residence
Location: front yard
Designer: bpk
Date: 10/27/2023
Section: Wall 1, Section 1
CS20
Design Method: NCMA_09_3rd_Ed, Ignore Vert.
Force
CS20
Design Unit: CornerStone 200
�~ GS20
y CS20
CS20
SOIL PARAMETERS cp coh
y
CS20
Retained Soil: 33 deg Opsf
130pcf
Foundation Soil: 33 deg Opsf
130pcf
Leveling Pad: 40 deg Opsf
135pcf Crushed Stone
GEOMETRY
Design Height:
4.00ft
Live Load:
Opsf
Wall Batter/Tilt:
4.50/ 0.00 deg
Live Load Offset:
O.00ft
Embedment:
0.50ft
Live Load Width:
Oft
Leveling Pad Depth:
0.50ft
Dead Load:
Opsf
Slope Angle:
0.0 deg
Dead Load Offset:
0.Oft
Slope Length:
0.Oft
Dead Load Width:
Oft
Slope Toe Offset:
0.Oft
Leveling Pad Width:
2.83ft
Vert b on Single Dpth
FACTORS OF SAFETY
Sliding:
1.50
Overturning:
1.50
Bearing:
2.00
CornerStone Analysis and Design 5.1.21009.30 1
RESULTS
FoS Sliding:
2.55 (Ivlpd)
FoS Overturning:
2.98
Bearing.
523.52
FoS Bearing.
14.75
Name
Elev.[dpth]
ka
Pa
Paq Paqd
(PaC)
PaT
CS20
3.33[0.67]
0.264
8
0 0
0
8
CS20
2.6711.331
0.234
27
0 0
0
27
CS20
2.00[2.00]
0.234
61
0��
0
0
61
_
CS20
1.33[2.67]
0.234
. 108
0
0
0
108
_
CS20
0.67[3.331
0.234
169
0
0
_
0
�169
_
CS20
0.00[4.00]
0.234
_L243
0 —
0
0
243
Column Descriptions:
ka: active earth pressure coefficient
Pa: active earth pressure
Paq: live surcharge earth pressure
Pag2: live load 2 surcharge earth pressure
Paqd: dead surcharge earth pressure
(PaC): reduction in load due to cohesion
PaT: sum of all earth pressures
FSsl(lvl Pad): factor of safety for sliding at each layer
FSot: factor of safety of overturning about the toe.
I
FSsI
FoS OT
—
85.41
55.03
24.14
6.28
11.03
4.39
6.37
(FS sliding below the leveling pad)
CornerStone Analysis and Design 5.1.21009.30 2