GeoTech Report July 12, 2013.pdfGrEorrECH
CONSULTANTS, INC.
E. Kent Halvorson
12515 Willows Road Northeast, #20
Kirkland, Washington 98034
13256 Northeast 20th Street, Suite 16
Bellevue, Washington 98005
(425) 747-5618 FAX (425) 747-8561
July 12, 2013
JN 13245
via email: kent@halvorsonconstruction.com
Subject: Transmittal Letter — Geotechnical Engineering Study
Proposed Five -Lot Short Plat
15620 — 72nd Avenue West
Edmonds, Washington
Dear Mr. Halvorson:
We are pleased to present this geotechnical engineering report for the short -plat project in
Edmonds, Washington. The scope of our services consisted of exploring site surface and
subsurface conditions, and then developing this report to provide recommendations for general
earthwork and criteria for foundations, retaining walls and building setbacks. This work was
authorized by your acceptance of our proposal, P-8660, dated June 24, 2013.
The attached report contains a discussion of the study and our recommendations. Please contact
us if there are any questions regarding this report, or for further assistance during the design and
construction phases of this project.
ANTS, INC.
D. Rdl:fei
Principal
cc: LDC, Inc. — John Mirante
via email to:imirante@ldccorp.com
DRW: jyb
GEOTECHNICAL ENGINEERING STUDY
Proposed 5 -Lot Short Plat
15620 — 72nd Avenue West
Edmonds, Washington
This report presents the findings and recommendations of our geotechnical engineering study for
the site of the proposed short -plat project to be located at in Edmonds.
We were provided with a site plan that included topographic information. LDC Inc developed the
plan, which is dated June 10, 2013. Based on this plan, we understand that the property will be
short -platted into five lots. An existing residence that is located near the middle of the property will
remain on one of the new lots. We understand that all stormwater from impermeable surfaces
(roofs, driveways) will be directed to a designated system and not toward the western portion of the
site.
If the scope of the project changes from what we have described above, we should be provided
with revised plans in order to determine if modifications to the recommendations and conclusions of
this report are warranted.
The Vicinity Map, Plate 1, illustrates the general location of the site in the northern portion of
Edmonds. The generally square property has approximately 371 feet of frontage on its upslope,
eastern side along 72nd Avenue West. The approximate central portion of the property is
developed with an existing residence and detached garage. There is a main gravel driveway that
extends mostly westward to the garage from the street. A gravel parking area extends off the
south side of the driveway about 40 feet east of the western end of the driveway. Another driveway
that is less developed is located on the southern portion of the property. It initially extends mostly
westward from the street, but then extends northwesterly until is terminus near the southern side of
the residence.
Most of the property slopes downward to the west. With the exception of the western edge of the
property, the inclination of the property is mostly in the range of 15 to 30 percent. Some small
areas in the moderately sloped portion of the property have an inclination greater than 40 percent
and a height of 10 feet, located around the gravel parking area and east of the residence/garage; it
is very apparent that these areas were oversteepened from their original moderate inclinations
because of manmade grading. There is a very steep slope that is on the western edge of the
property and/or extends west of the property. This slope is approximately 80 to 100 feet tall.
Gentle to moderate inclined, residential property is directly west of the very steep slope.
In general, with the exception of the developed portions of the property, the site Is forested. The
southern portion of the majority, moderately -inclined property has a forest with some large trees
and native underbrush. Fewer large trees and less native underbrush are generally located on the
northern side of this moderately -inclined portion of the property. Some large trees are located near
the top of the very steep slope, but mostly it is covered with more moderately-sized trees.
An approximately 40 -foot -wide, mostly 3- to 4 -foot -deep landslide occurred on the very steep
western slope on about January 1, 1997. The landslide followed a short period of extremely high
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precipitation and a very significant amount of landslides occurred on slopes in the Puget Sound.
The landslide area was repaired by some grading at the top of the slope and installing a drainage
system to handle surface and subsurface water in the area of the residence. A Surface -mounted
stormwater pipe now extends over the slope and through a neighboring property to the west to
discharge this surface and subsurface water well west of the slope and subject property. In
addition to the drainage improvements done on the subject property, a formal stormwater system
has been constructed in the 72nd Avenue West since 1997. Apparently the water from this system
also discharges water away from the steep western slope. We did not observe indications of
recent instability of in the previous slide area and the steep western slope on and near the subject
property.
SUBSURFACE
The subsurface conditions west/southwest of the existing residence were explored with three test
borings in 1997 following the shallow landslide that occurred near the top of the steep western
slope just west of the existing residence. To supplement this information, we recently explored the
property by excavating seven test pits; the approximate locations of all the explorations are shown
on the Site Exploration Plan, Plate 2. Our recent exploration program was based on the proposed
construction, the past test borings, anticipated subsurface conditions and those encountered during
exploration, and the scope of work outlined in our proposal.
The seven test pits were excavated on July 3, 2013 with a trackhoe. A geotechnical engineer from
our staff observed the excavation process and logged the test pits. The Test Pit Logs are attached
to this report as Plates 3 through 6.
The test borings were drilled on January 18, 1997 using a truck -mounted, hollow -stem auger drill.
Samples were taken at 5 -foot intervals with a standard penetration sampler. This split -spoon
sampler, which has a 2 -inch outside diameter, is driven into the soil with a 140 -pound hammer
falling 30 inches. The number of blows required to advance the sampler a given distance is an
indication of the soil density or consistency. A geotechnical engineer from our staff observed the
drilling process, logged the test borings, and obtained representative samples of the soil
encountered. The Test Boring Logs are attached as Plates 7 through 9.
Soil Conditions
Test Borings 1 and 2, which were drilled near the top of the slope of the previous landslide
area, encountered approximately 15 to 19 feet of dense to very dense, gravelly sand at the
ground surface. This sand was underlain with stiff and dense, sandy silty and silty sand to
the maximum explored depth of 31 feet. The third boring, drilled away from the slope,
encountered dense sand near the ground surface. The sand was underlain by medium -
dense to dense, silty sand to the maximum explored depth of 26 feet. We observed a lens
of silty at about 20 feet below the crest of the slope in the landslide area.
The test pits were excavated to a maximum explored depth of 7 feet. The soil revealed in
the test pits was very similar to the upper soil in the test boring, consisting of sand with
varying degrees of gravel and silt (mostly low silt content). Some boulders were revealed in
the more gravelly sand. The upper, approximate 1 to 4 feet of the sand generally contained
organics and was loose. The sand mostly became dense below these depths.
Per the "Soil Survey of Snohomish County Area Washington" (1978), the soil on the site is
considered: 4-Alderwood-Everett gravelly sandy loam.
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July 12, 2013
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We obtained the logs of some test borings drilled at slightly higher elevations just northwest
of the property. Dense to very dense, gravelly silty sand was revealed in those test borings.
We also obtained the logs of test borings drilled at elevations near or below the base of the
steep western slope. Competent silty sand and silt were generally revealed at shallow
depths in those test borings.
Groundwater Conditions
No groundwater seepage was encountered in the test pits, but some groundwater was
observed at a depth of approximately 16 to 30 feet. The explorations were left open for only
a short time period. Therefore, the seepage levels on the logs represent the location of
transient water seepage and may not indicate the static groundwater level. Groundwater
levels encountered during drilling can be deceptive, because seepage into the boring can
be blocked or slowed by the auger itself.
It should be noted that groundwater levels vary seasonally with rainfall and other factors.
We believe that groundwater will only be found in during the normally wet winter and spring
months.
The stratification lines on the logs represent the approximate boundaries between soil types at the
exploration locations. The actual transition between soil types may be gradual, and subsurface
conditions can vary between exploration locations. The logs provide specific subsurface
information only at the locations tested. Where a transition in soil type occurred between samples
in the borings, the depth of the transition was interpreted. The relative densities and moisture
descriptions indicated on the test pit and boring logs are interpretive descriptions based on the
conditions observed during excavation and drilling.
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problem, the backfill will need to be removed and
replaced with structural fill during construction.
The City of Edmonds has mapped the western side of the subject property as being within an area
known as the North Edmonds Earth Subsidence and Landslide Hazard Area (NEESLH). The large
portion of the NEESLH is located downslope (west) and south of the property. A map of the area
has been attached in the Appendix of this report. This area has been extensively studied, and
multiple geotechnical reports have been published, with the most recent being the North Edmonds
Earth Subsidence and Landslide Hazard Area Summary Report published by Landau Associates,
dated March 14, 2007. This report describes the overall area as being a large historic/prehistoric
landslide that Includes a massive downset block of land. Large-scale landsliding of the area has.
been recorded as occurring in the 1940s and 1950s that reportedly destroyed approximately 6
homes and damaged many others. The historic Dames and Moore (1968) report indicates that the
areas of large scale sliding occurred on the lower (western) portion of the overall slide mass to the
north and south of the termination of North Meadowdele Drive. As such, the Landau report
describes the zone just beneath the steep eastern slopes as being susceptible to the following
risks: 1) reactivation of landslide debris (the slide complex) causing ground failure and movement,
2) encroaching landslide debris originating from shallow failures occurring upslope, and 3)
landsliding occurring in ground that has not previously failed. The latter risk is the one that
pertains to the subject site because the area upslope and east of the steep western slope definitely
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July 12, 2013 Page 4
has not failed or had slope movement. The 2007 Landau report indicated that the subject site
would be considered a "Zone D" area (see appendix). In 1979, Roger Lowe and Associates report
for the overall area indicates that the subject site would have a varying probability of being affected
by the various types of iandsliding described above. A follow up report by GeoEngineers (1985)
detailed the reduction slide probability associated with lowering of groundwater levels in the slide
complex following installation of subsurface drainage facilities (LID circa 1984) in the eastern
portion of the slide mass. Based on Figure 1 of the 1985 report, the western edge of the property
(the steep slope) has a 2 percent probability of sliding (due to "debris slides") in a 25 -year period.
However, as we have noted above, several surface and subsurface drainage features have been
added to the site and the adjacent street since 1997; these features reduces the probability of
sliding. Therefore, we strongly believe that, based on the analysis done for the 1985 report, the
probability of sliding in a 25 -year period is no more than 1 percent.
SLOPE STABILITY DISCUSSION AND ANALYSES
As noted above, mostly dense or denser sandy soils were revealed to the explored depth of the test
borings. However, based on our experience and on Figure 1 of the 2007 Landau report, very stiff
silt/clay soil very likely underlies the site. The depth of the sand and silt/clay interface is not exactly
known, but again based on our experience and the Landau report; it is likely in the range of halfway
down the steep western slope. We have made this assumption, and a slope/soil profile based on
this assumption for the property is given in Plate 10. The soil parameters for both the sand and
silt/clay soils are given on the profile. Also noted on the profile is the normal groundwater level,
which would very likely be perched on the silt/clay.
Using the existing slope configuration and appropriate soil parameters, stability analyses for both
static and dynamic loading conditions were performed. For the dynamic analysis, a peak
acceleration coefficient of 0.16g was used (this is based on a peak acceleration of 0.32g noted in a
later section of this report). The analyses were done to determine where the easternmost edge of
a landslide would occur having standard safety factors of at least 1.5 for static conditions, and 1.1
or 1.2 for dynamic conditions. The analyses indicated that a deep-seated slide for a static safety
factor of 1.5 and a dynamic safety factor of 1.1 could occur as far as 50 feet from the top of the
steep slope. An analysis having a dynamic safety factor of 1.2 revealed that a deep-seated slide
could occur 65 feet from the top of the steep western slope.
THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A
GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE
CONTAINED IN THE REMAINDER OF THIS REPORT. ANY PARTY RELYING ON THIS REPORT SHOULD
READ THE ENTIRE DOCUMENT.
The test pits and borings conducted for this study encountered dense to very dense, gravelly sand
soils at depths of approximately 1 to 4 feet. The dense soil is very competent for supporting the
building load, and thus conventional footings can be used for new residences and buildings. These
soils also have high shear strength against slope instability.
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Conclusions and Recommendations Regarding Edmonds Code
Based on The Edmonds Community Development Code (ECDC), Chapter 23.80 (Geologically
Hazardous Areas), the steep western slope would be classified as a Landslide Hazard Area
because it is steeper than 40 percent slope, and greater than 10 foot vertical relief. There are
some other minor slopes on the property east of the western slope that are steeper than 10
feet, but they are obviously manmade as the entire area east of the western slope on and near
the property has an average inclination of 15 to 30 percent. However, site east of the western
slope is considered an Erosion Hazard Area per Chapter 23.80. The ECDC suggests a
minimum development buffer equal to the height of the steep western slope, which is
approximately 80 to 90 feet. Per the 2007 Landau report, the steep western slope and an area
within about 80 to 90 feet of it are considered Zone D. The remainder of the property is Zone
E. The Landau report recommends that a slope buffer be established using a rate of slope
retreat or stable slope angle over a 120 year period.
Based on ECDC 23.80.070.1, the buffer may be reduced when a qualified professional
demonstrates that the reduction will adequately protect the proposed development, adjacent
developments and uses, and the subject critical area. Based on our stability analyses, for a
static and dynamic safety factor of 1.5 and 1.1, no slope movement would occur further than 50
feet east of the top of the steep western slope. Therefore, it is our professional opinion that a
buffer of 50 feet from the steep western slope is suitable for this project. We believe that this
buffer is very suitable with regards to providing a stable slope angle for at least a 120 year
period as required by the Landau report. A building setback of 15 feet is needed from the
buffer, thus residences will be located no more than 65 feet from the slope. Based on our slope
stability analysis, a dynamic safety factor of 1.2 was obtained 65 feet from the slope; thus, the
65 -foot setback for residences from the steep western slope satisfies the design standards of
ECDC 23.80.070.3. Therefore, in summary, we recommend a buffer of 50 feet be used for this
project.
Based on ECDC 23.80.060A, an alteration to a Landslide Hazard Area and associated buffer
may occur for activities that:
1. Will not increase the threat of the geologic hazard to adjacent properties beyond
predevelopment conditions;
2. Will not adversely affect other critical areas;
3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal
to or less that predevelopment conditions; and
4. Are certified as safe as designed and under anticipated conditions by a qualified
engineer licensed in the State of Washington.
In addition, ECDC 23.80.070A2 indicates that alterations of a Landslide Hazard Area and buffer
may occur for activities for which a hazards analysis is submitted and certifies that:
a) The development will not increase surface water discharge or sedimentation to adjacent
properties beyond predevelopment conditions;
b) The development will not decrease slope stability on adjacent properties; and
c) Such alterations will not adversely impact other critical areas.
Generally buffers are left undisturbed, but, as noted above, alterations can be made. We
believe that altering the buffer to that disturbance can occur to its last 25 feet is suitable for this
project provided grading will not involve adding more than 2 feet of fill in any one place and that
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no permanent sprinkler systems are installed. The 25 feet of the buffer closest to the steep
western slope should be left as -is. Although it could be argued that some additional water that
would otherwise be evapotranspirated by the native vegetation will reach the steep western
slope, we believe that the amount of surface water that will be directed away from the slope and
to a stormwater system will easily offset this additional water. We believe that the alteration is
therefore suitable because: 1) it will not increase the potential for landslide to the adjacent,
downslope properties, 2) it will not affect other critical areas, 3) the hazard is mitigated to be
equal to predevelopment standards, 4) it is safe in our professional opinion, a) the alteration will
not increase surface water discharge or sedimentation to adjacent properties, b) the alteration
will not decrease slope stability, and c) the alteration will not adversely affect adjacent critical
areas.
The erosion control measures needed during the site development will depend heavily on the
weather conditions that are encountered. While site clearing will expose a large area of bare soil,
the erosion potential on the site is relatively low due to the gentle slope of the ground. We
anticipate that a silt fence will be needed around the downslope sides of any cleared areas.
Rocked construction access roads should be extended into the site to reduce the amount of soil or
mud carried off the property by trucks and equipment. Wherever possible, these roads should
follow the alignment of planned pavements, and trucks should not be allowed to drive off of the
rock -covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet
weather. Following rough grading, it may be necessary to mulch or hydroseed bare areas that will
not be immediately covered with landscaping or an impervious surface.
The drainage and/or waterproofing recommendations presented in this report are intended only to
prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active
seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from
the surrounding soil, and can even be transmitted from slabs and foundation walls due to the
concrete curing process. Water vapor also results from occupant uses, such as cooking and
bathing. Excessive water vapor trapped within structures can result in a variety of undesirable
conditions, including, but not limited to, moisture problems with flooring systems, excessively moist
air within occupied areas, and the growth of molds, fungi, and other biological organisms that may
be harmful to the health of the occupants. The designer or architect must consider the potential
vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or
mechanical, to prevent a build up of excessive water vapor within the planned structure.
Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may include
revisions to our recommendations to accommodate site, development, and geotechnical
constraints that become more evident during the review process.
We recommend including this report, in its entirety, in the project contract documents. This report
should also be provided to any future property owners so they will be aware of our findings and
recommendations.
In accordance with the International Building Code (IBC), the site soil profile within 100 feet of the
ground surface is best represented by Site Class C (Very Dense Soil). The site soils have a low
potential for seismic liquefaction because of their dense nature and the absence of near -surface
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groundwater. This statement regarding liquefaction includes the knowledge of the determined
peak ground acceleration noted below.
As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (Ss) and
1.0 second period (Si) equals 1.2g and 0.4g, respectively. The International Building Code (IBC)
states that a site-specific seismic study need not be performed provided that the peak ground
acceleration be equal to SDs/2.5, where SDs is determined in ASCE 7. It is noted that SDs is equal
to 2/3SMs. Sms equals Fa times Ss, where Fa is determined in Table 11.4-1. For our site, Fa = 1.0.
Thus, the calculated peak ground acceleration that we utilized for the seismic -related parameters of
this report equals 0.32g.
CONVENTIONAL FOUNDATIONS
The proposed structure can be supported on conventional continuous and spread footings bearing
on undisturbed, medium -dense or denser, native sand soil, or on structural fill placed above this
competent native soil. See the section entitled General Earthwork and Structural Fill for
recommendations regarding the placement and compaction of structural fill beneath structures.
Adequate compaction of structural fill should be verified with frequent density testing during fill
placement. Prior to placing structural fill beneath foundations, the excavation should be observed
by the geotechnical engineer to document that adequate bearing soils have been exposed. We
recommend that continuous and individual spread footings have minimum widths of 12 and 16
inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest
adjacent finish ground surface for protection against frost and erosion. The local building codes
should be reviewed to determine if different footing widths or embedment depths are required.
Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending
upon site and equipment constraints, this may require removing the disturbed soil by hand.
An allowable bearing pressure of 2,500 pounds per square foot (psf) is appropriate for footings
supported on competent native soil and/or structural fill as noted above. A one-third increase in
this design bearing pressure may be used when considering short-term wind or seismic loads.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the
foundation. For the latter condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level, well -compacted fill. We recommend using the
following ultimate values for the foundation's resistance to lateral loading:
Coefficient of Friction 0.50
Passive Earth Pressure 300 pcf
Where: (i) pcf is pounds per cubic foot, and (ii) passive earth
pressure is computed using the equivalent fluid density.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's
resistance to lateral loading, when using the above ultimate values.
Halvorson
July 12, 2013
FOUNDATION AND RETAINING WALLS
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Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures
imposed by the soil they retain. The following recommended parameters are for walls that restrain
backfill:
Active Earth Pressure* 35 pcf
- backslope flatter than 3:1
H:V inclination
Active Earth Pressure *
50 pcf
- backslope inclined between
2:1 and 3:1 H:V
Passive Earth Pressure
300 pcf
Coefficient of Friction
0.50
Soil Unit Weight
135 pcf
Where: (i) pcf is pounds per cubic foot, and (ii) active and
passive earth pressures are computed using the equivalent fluid
pressures.
* For a restrained wall that cannot deflect at least 0.002 times its
height, a uniform lateral pressure equal to 10 psf times the height
of the wall should be added to the above active equivalent fluid
pressure.
The design values given above do not include the effects of any hydrostatic pressures behind the
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent
foundations will be exerted on the walls. If these conditions exist, those pressures should be added
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need
to be given the wall dimensions and the slope of the backfill in order to provide the appropriate
design earth pressures. The surcharge due to traffic loads behind a wall can typically be
accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid
density. Heavy construction equipment should not be operated behind retaining and foundation
walls within a distance equal to the height of a wall, unless the walls are designed for the additional
lateral pressures resulting from the equipment.
The values given above are to be used to design only permanent foundation and retaining walls
that are to be backfilled, such as conventional walls constructed of reinforced concrete or masonry.
It is not appropriate to use the above earth pressures and soil unit weight to back -calculate soil
strength parameters for design of other types of retaining walls, such as soldier pile, reinforced
earth, modular or soil nail walls. We can assist with design of these types of walls, if desired. The
passive pressure given is appropriate only for the depth of level, well -compacted fill placed in front
of a retaining or foundation wall. The values for friction and passive resistance are ultimate values
and do not include a safety factor. We recommend a safety factor of at least 1.5 for overturning
and sliding, when using the above values to design the walls. Restrained wall soil parameters
should be utilized for a distance of 1.5 times the wall height from corners or bends in the walls.
This is intended to reduce the amount of cracking that can occur where a wall is restrained by a
corner.
Wall Pressures Due to Seismic Forces
The surcharge wall loads that could be imposed by the design earthquake can be modeled
by adding a uniform lateral pressure to the above -recommended active pressure. The
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July 12, 2013
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recommended surcharge pressure is 8H pounds per square foot (psf), where H is the
design retention height of the wall. Using this increased pressure, the safety factor against
sliding and overturning can be reduced to 1.2 for the seismic analysis.
Retaining Wall Backfill and Waterproofing
Backfill placed behind retaining or foundation walls should be coarse, free -draining
structural fill containing no organics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of
particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand
is used as backfill, a minimum 12 -inch width of free -draining gravel or a drainage composite
similar to Miradrain 6000 should be placed against the backfilled retaining walls. The
drainage composites should be hydraulically connected to the foundation drain system. The
later section entitled Drainage Considerations should also be reviewed for
recommendations related to subsurface drainage behind foundation and retaining walls.
The purpose of these backfill requirements is to ensure that the design criteria for a
retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the
wall. Also, subsurface drainage systems are not intended to handle large volumes of water
from surface runoff. The top 12 to 18 inches of the backfill should consist of a compacted,
relatively impermeable soil or topsoil, or the surface should be paved. The ground surface
must also slope away from backfilled walls to reduce the potential for surface water to
percolate into the backfill. Water percolating through pervious surfaces (pavers, gravel,
permeable pavement, etc.) must also be prevented from flowing toward walls or into the
backfill zone. The compacted subgrade below pervious surfaces and any associated
drainage layer should therefore be sloped away. Alternatively, a membrane and subsurface
collection system could be provided below a pervious surface.
It is critical that the wall backfill be placed in lifts and be properly compacted, in order for the
above -recommended design earth pressures to be appropriate. The wall design criteria
assume that the backfill will be well -compacted in lifts no thicker than 12 inches. The
compaction of backfill near the walls should be accomplished with hand -operated
equipment to prevent the walls from being overloaded by the higher soil forces that occur
during compaction. The section entitled General Earthwork and Structural Fill contains
additional recommendations regarding the placement and compaction of structural fill
behind retaining and foundation walls.
The above recommendations are not intended to waterproof below -grade walls, or to
prevent the formation of mold, mildew or fungi in interior spaces. Over time, the
performance of subsurface drainage systems can degrade, subsurface groundwater flow
patterns can change, and utilities can break or develop leaks. Therefore, waterproofing
should be provided where future seepage through the walls is not acceptable. This typically
includes limiting cold -joints and wall penetrations, and using bentonite panels or
membranes on the outside of the walls. There are a variety of different waterproofing
materials and systems, which should be installed by an experienced contractor familiar with
the anticipated construction and subsurface conditions. Applying a thin coat of asphalt
emulsion to the outside face of a wall is not considered waterproofing, and will only help to
reduce moisture generated from water vapor or capillary action from seeping through the
concrete. As with any project, adequate ventilation of basement and crawl space areas is
important to prevent a build up of water vapor that is commonly transmitted through
concrete walls from the surrounding soil, even when seepage is not present. This is
appropriate even when waterproofing is applied to the outside of foundation and retaining
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walls. We recommend that you contact an experienced envelope consultant if detailed
recommendations or specifications related to waterproofing design, or minimizing the
potential for infestations of mold and mildew are desired.
The General, Slabs -On -Grade, and Drainage Considerations sections should be
reviewed for additional recommendations related to the control of groundwater and excess
water vapor for the anticipated construction.
The building floors can be constructed as slabs -on -grade atop firm, non-organic native sand, or on
structural fill. The subgrade soil must be in a firm, non -yielding condition at the time of slab
construction or underslab fill placement. Any soft areas encountered should be excavated and
replaced with select, imported structural fill.
Even where the exposed soils appear dry, water vapor will tend to naturally migrate upward through
the soil to the new constructed space above it. This can affect moisture -sensitive flooring, cause
imperfections or damage to the slab, or simply allow excessive water vapor into the space above
the slab. All interior slabs -on -grade should be underlain by a capillary break or drainage layer
consisting of a minimum 4 -inch thickness of gravel or crushed rock that has a fines content
(percent passing the No. 200 sieve) of less than 3 percent and a sand content (percent passing the
No. 4 sieve) of no more than 10 percent. This capillary break/drainage layer is not necessary if an
underslab drainage system is installed. As noted by the American Concrete Institute (ACI) in the
Guides for Concrete Floor and Slab Structures, proper moisture protection is desirable immediately
below any on -grade slab that will be covered by tile, wood, carpet, impermeable floor coverings, or
any moisture -sensitive equipment or products. ACI also notes that vapor retarders, such as 6 -mil
plastic sheeting, have been used in the past, but are now recommending a minimum 10 -mil
thickness. A vapor retarder is defined as a material with a permeance of less than 0.3 perms, as
determined by ASTM E 96. It is possible that concrete admixtures may meet this specification,
although the manufacturers of the admixtures should be consulted. Where vapor retarders are
used under slabs, their edges should overlap by at least 6 inches and be sealed with adhesive
tape. The sheeting should extend to the foundation walls for maximum vapor protection. If no
potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor
barrier, as defined by ACI, is a product with a water transmission rate of 0.01 perms when tested in
accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this
requirement.
In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well -graded
compactable granular material, such as a 5/8 -inch -minus crushed rock pavement base, be placed
over the vapor retarder or barrier for their protection, and as a "blotter" to aid in the curing of the
concrete slab. Sand was not recommended by ACI for this purpose. However, the use of material
over the vapor retarder is controversial as noted in current ACI literature because of the potential
that the protection/blotter material can become wet between the time of its placement and the
installation of the slab. If the material is wet prior to slab placement, which is always possible in the
Puget Sound area, it could cause vapor transmission to occur up through the slab in the future,
essentially destroying the purpose of the vapor barrier/retarder. Therefore, if there is a potential
that the protection/blotter material will become wet before the slab is installed, ACI now
recommends that no protection/blotter material be used. However, ACI then recommends that,
because there is a potential for slab curl due to the loss of the blotter material, joint spacing In the
slab be reduced, a low shrinkage concrete mixture be used, and "other measures" (steel
reinforcing, etc.) be used. ASTM E-1643-98 "Standard. Practice for Installation of Water Vapor
Halvorson JN 13245
July 12, 2013 Page 11
Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs" generally agrees with
the recent ACI literature.
We recommend that the contractor, the project materials engineer, and the owner discuss these
issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance
on the use of the protection/blotter material.
The General, Permanent Foundation and Retaining Walls, and Drainage Considerations
sections should be reviewed for additional recommendations related to the control of groundwater
and excess water vapor for the anticipated construction.
EXCAVATIONS AND SLOPES
Excavation slopes should not exceed the limits specified in local, state, and national government
safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in
unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be
made near property boundaries, or existing utilities and structures. Based upon Washington
Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as
Type B. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at
an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and
the bottom of a cut.
The above -recommended temporary slope inclination is based on the conditions exposed in our
explorations, and on what has been successful at other sites with similar soil conditions. It is
possible that variations in soil and groundwater conditions will require modifications to the
inclination at which temporary slopes can stand. Temporary cuts are those that will remain
unsupported for a relatively short duration to allow for the construction of foundations, retaining
walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet
weather. It is also important that surface water be directed away from temporary slope cuts. The
cut slopes should also be backfilled or retained as soon as possible to reduce the potential for
instability. Please note that sand can cave suddenly and without warning. Excavation, foundation,
and utility contractors should be made especially aware of this potential danger. These
recommendations may need to be modified if the area near the potential cuts has been disturbed in
the past by utility installation, or if settlement -sensitive utilities are located nearby.
All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). Compacted fill
slopes should also not be constructed with an inclination greater than 2:1 (H:V). To reduce the
potential for shallow sloughing, fill must be compacted to the face of these slopes. This can be
accomplished by overbuilding the compacted fill and then trimming it back to its final inclination.
Adequate compaction of the slope face is important for long-term stability and is necessary to
prevent excessive settlement of patios, slabs, foundations, or other improvements that may be
placed near the edge of the slope.
Water should not be allowed to flow uncontrolled over the top of any temporary or permanent
slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation
to reduce erosion and improve the stability of the surficial layer of soil. Topsoil is often placed on
regraded slopes to promote growth of vegetation. Proper preparation of the regraded surface, and
use of appropriate topsoil is necessary to prevent the topsoil from sliding off the slope. This is
most likely to occur following extended wet weather if a silty topsoil is used. On steeper slopes, it
may be necessary to "track walk" the slope or cut small grooves across the slope prior to placing
the topsoil.
Halvorson
July 12, 2013
JN 13246
Page 12
Foundation drains should be used where (1) crawl spaces or basements will be below a structure,
(2) a slab is below the outside grade, or (3) the outside grade does not slope downward from a
building. Drains should also be placed at the base of all earth -retaining walls. These drains should
be surrounded by at least 6 inches of 1 -inch -minus, washed rock and then wrapped in non -woven,
geotextile filter fabric (Mirafi 144N, Supac 4NP, or similar material). At its highest point, a
perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a
crawl space, and it should be sloped for drainage. All roof and surface water drains must be kept
separate from the foundation drain system. A typical drain detail is attached to this report as Plate
11. For the best long-term performance, perforated PVC pipe is recommended for all subsurface
drains.
As a minimum, a vapor retarder, as defined in the Slabs -On -Grade section, should be provided in
any crawl space area to limit the transmission of water vapor from the underlying soils. Also, an
outlet drain is recommended for all crawl spaces to prevent a build up of any water that may
bypass the footing drains.
Some groundwater was observed in the 1997 test borings. If seepage is encountered in an
excavation, it should be drained from the site by directing it through drainage ditches, perforated
pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches
at the bottom of the excavation.
The excavation and site should be graded so that surface water is directed off the site and away
from the tops of slopes. Water should not be allowed to stand in any area where foundations,
slabs, or pavements are to be constructed. Final site grading in areas adjacent to buildings should
slope away at least 2 percent, except where the area is paved. Surface drains should be provided
where necessary to prevent ponding of water behind foundation or retaining walls. Water from roof,
storm water, and foundation drains should not be discharged onto the steep western slope; it
should be tightlined to a suitable outfall located away from the western slope.
•- -
All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and
other deleterious material. The stripped or removed materials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds.
Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building,
behind permanent retaining or foundation walls, or in other areas where the underlying soil needs
to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or
near, the optimum moisture content. The optimum moisture content is that moisture content that
results in the greatest compacted dry density. The moisture content of fill is very important and
must be closely controlled during the filling and compaction process.
Fills placed on sloping ground should be keyed into the competent native sand soils. This is
typically accomplished by placing and compacting the structural fill on level benches that are cut
into the competent soils. The allowable thickness of the fill lift will depend on the material type
selected, the compaction equipment used, and the number of passes made to compact the lift.
Halvorson JN 13245
July 12, 2013 Page 13
The loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed.
If the fill is not sufficiently compacted, it can be recompacted before another lift is placed. This
eliminates the need to remove the fill to achieve the required compaction. The following table
presents recommended relative compactions for structural fill:
Beneath footings, slabs 95%
or walkways
Filled slopes and behind 90%
retaining walls
95% for upper 12 inches of
Beneath pavements subgrade; 90% below that
level
Where; Minimum Relative Compaction is the ratio, expressed In
percentages, of the compacted dry density to the maximum dry
density, as determined in accordance with ASTM Test
Designation D 1557-91 (Modified Proctor).
Use of On -Site Soil
Debris or organic -laden onsite soils should not be used as structural fill. The on-site soil is
somewhat silty and therefore somewhat moisture sensitive. Grading operations will be
difficult during very wet weather, or when the moisture content of this soil well exceeds the
optimum moisture content.
The moisture content of the silty, on-site soil must be at, or near, the optimum moisture
content, as the soil cannot be consistently compacted to the required density when the
moisture content is significantly greater than optimum. Moisture -sensitive soil may also be
susceptible to excessive softening and "pumping" from construction equipment, or even foot
traffic, when the moisture content is greater than the optimum moisture content. It may be
beneficial to protect subgrades with a layer of imported sand or crushed rock to limit
disturbance from traffic.
Structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or
clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve
should be measured from that portion of soil passing the three -quarter -inch sieve.
LIMITATIONS
The conclusions and recommendations contained in this report are based on site conditions as
they existed at the time of our exploration and assume that the soil and groundwater conditions
encountered in the test pits and test borings are representative of subsurface conditions on the
site. If the subsurface conditions encountered during construction are significantly different from
those observed in our explorations, we should be advised at once so that we can review these
conditions and reconsider our recommendations where necessary. Unanticipated conditions are
commonly encountered on construction sites and cannot be fully anticipated by merely taking
samples in test pits and test borings. Subsurface conditions can also vary between exploration
locations. Such unexpected conditions frequently require making additional expenditures to attain
a properly constructed project. It is recommended that the owner consider providing a contingency
Halvorson JN 13245
July 12, 2013 Page 14
fund to accommodate such potential extra costs and risks. This is a standard recommendation for
all projects.
The recommendations presented in this report are directed toward the protection of only the
proposed structure from damage due to slope movement. Predicting the future behavior of steep
slopes and the potential effects of development on their stability is an inexact and imperfect
science that is currently based mostly on the past behavior of slopes with similar characteristics.
Landslides and soil movement can occur on steep slopes before, during, or after the development
of property. However, the owner must ultimately accept the possibility that some slope movement
could occur, resulting in possible loss of ground. However, we believe that the buffer determined in
this report is suitable for at least 120 years.
This report has been prepared for the exclusive use of E. Kent Halvorson and his representatives
for specific application to this project and site. Our recommendations and conclusions are based
on observed site materials and engineering analyses. Our conclusions and recommendations are
professional opinions derived in accordance with current standards of practice within the scope of
our services and within budget and time constraints. No warranty is expressed or implied. The
scope of our services does not include services related to construction safety precautions, and our
recommendations are not intended to direct the contractor's methods, techniques, sequences, or
procedures, except as specifically described in our report for consideration in design. Our services
also do not include assessing or minimizing the potential for biological hazards, such as mold,
bacteria, mildew and fungi In either the existing or proposed site development.
ADDITIONAL SERVICES
In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide
geotechnical consultation, testing, and observation services during construction. This is to confirm
that subsurface conditions are consistent with those indicated by our exploration, to evaluate
whether earthwork and foundation construction activities comply with the general intent of the
recommendations presented in this report, and to provide suggestions for design changes in the
event subsurface conditions differ from those anticipated prior to the start of construction.
However, our work would not include the supervision or direction of the actual work of the
contractor and its employees or agents. Also, job and site safety, and dimensional measurements,
will be the responsibility of the contractor.
During the construction phase, we will provide geotechnical observation and testing services when
requested by you or your representatives. Please be aware that we can only document site work
we actually observe. It is still the responsibility of your contractor or on-site construction team to
verify that our recommendations are being followed, whether we are present at the site or not.
Halvorson JN 13245
July 12, 2013 Page 15
The following plates are attached to complete this report:
Plate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 6 Test Pit Logs
Plates 7 — 9 Test Boring Logs
Plate 10 Site Cross -Section
Plate 11 Typical Footing Drain Detail
Appendix
We appreciate the opportunity to be of service on this project. If you have any questions, or if we
may be of further service, please do not hesitate to contact us.
Respectfully submitted,
GEOTECIYCPNSULTANTS, INC.
SIQIVAL ��
D. Robert Ward, P.E.
Principal
DRW: jyb
1-7)1 v
13
GEOTECH
CONSULTANTS, INC.
(Source: The Thomas Gulde, King Cc
VICINITY MAP
a a- -0 a. -a- -a a,
m wel I Agelve &-myrnm I I I 1p wellm
Job No: Date: Plate:
13245 July 2013
F F -
.,, $
}
}
U
�
F F -
A
10
R
IE
1 ate `�l
r� ��
RA
Topsoil over;
Description
Brown, mottled, silty SAND with gravel and some organics, very dense, loose to
medium dense
-becomes cemented, no organics, medium dense to dense
-becomes gray, no gravel, more silty, wet
* Test Pit terminated at 7.0 feet on July 3, 2013.
Slight groundwater seepage was observed at 5.0 feet during excavation.
' No caving observed during excavation.
Jae
r` 00� e�ane e G5
10 =601 94M
over;
Description
Brown, slightly silty, gravelly SAND with organics, slightly moist, loose
-becomes mostly gray, no organics, less silty, moist, dense
* Test Pit terminated at 6.0 feet on July 3, 2013.
* No groundwater was observed during excavation.
* No caving observed during excavation.
GEOTECH
CONSULTANTS, INC.
ST PIT LOG
15620 72nd Avenue West
Edmonds, Washington
Job Date: Logged by: plate:
13245 July 2013 DRW 3
0
TI1
R
M
C�
oeQ�r �Go��o ���a�e JAGS
Topsoil over;
Description
Brown, slightly silty, gravelly SAND with organics, slightly moist, loose to medium dense
-becomes dense, no organics
-becomes gray, mottled, very moist to wet, medium dense to dense
* Test Pit terminated at 6.0 feet on July 3, 2013.
* No groundwater seepage was observed during excavation.
* No caving observed during excavation.
\e J�0o
Topsoil over;
Description
Brown, slightly silty, gravelly SAND with organics, slightly moist, loose
-becomes mostly gray, no organics, less silty, moist, dense
* Test Pit terminated at 6.0 feet on July 3, 2013.
* No groundwater was observed during excavation.
* No caving observed during excavation.
GEOTECH
CONSULTANTS, INC.
TEST PIT LOG
15620 72nd Avenue West
Edmonds, Washington
Job ®ate: Logged by: Plate:
13245 July 2013
)RW 4
0
Me
IF
Topsoil over;
Description
Brown, slightly silty, gravelly SAND, few organics, loose to moist
-becomes mostly gray, no organics, moist, dense
• Test Pit terminated at 4.0 feet on July 3, 2013.
* No groundwater seepage was observed during excavation.
* No caving observed during excavation.
Description
Gray, very gravelly SAND, coarse grained, medium dense
-becomes dense
* Test Pit terminated at 3.0 feet on July 3, 2013.
* No groundwater seepage was observed during excavation.
* No caving observed during excavation.
GEOTECH
CONSULTANTS, INC.
TEST PIT LOG
15620 72nd Avenue West
Edmonds, Washington
Job Date; togged by: I Plate:
13245j July 2013 )RW 5
0
M
Topsoil over;
Description
Brown, slightly silty, gravelly SAND with organics, loose to medium dense
-becomes dense, more gray, no organics
• Test Pit terminated at 4.0 feet on July 3, 2013.
* No groundwater seepage was observed during excavation.
* No caving observed during excavation.
GEOTECH
CONSULTANTS, INC.
TEST PIT LOG
15620 72nd Avenue West
Edmonds, Washington
Job ®ate: Logged by: plate:
13245 July 2013 DR W 6
,
., .......
�
�$ foo_...................._.�.....,..-...... ........... .,.....may,..~ _ _ .. .. .V ,-...,..........e...�._..�..........___.. ,.�.._.,M...............
BORING* I
uses Descr Ston
M""ll/
u- Brown; gravelly SAND with some silt, coarse-grained, mist,
very dense
5 80
!;r/srs
to ff�;�s�tt w becomes less gravelly.,
15
74 .
�becomes wet
20 1$
Brown, slightly sandy and silty SAND, low plasticity, wet, stiff
2526 :: NIL ;
,,,,
.. Mostly very fine-grained, silty SAND
33 f:; sNt i Gray, silty SANL7, moist, dense
Test boring was terminated a� 31,5 feet below grade on 1-18.9'i,
No groundwater seepage was encountered during drilling,
35
40
TECH 15620..-..76T AVENUE"WEST
CONSULTANTS, INC. EDMONDS, WA.
w-
job 3245 • I9aJAN 1997 Lp�L�RW �; Plate: 7
BORING 2
G61 usesDescrl tion
Topsoil
t!1
; X111;
1sM Brown/mottled, silty SAND With gravel,met, loose to medium -dense
1,1/11 11
111!1111
I11
5 35 I#%'
7 % Brown/mottled, gravelly SAND'with'some'silt;'very'moist; dense
SP;� .., . ..,. _
10 33 ;/ a i :..............
15
18
20
33
ao
.. 24..
Tan, very silty SAND, lenses of silt, rine-grained, very wet,
medium -dense
■ ,,, VIII
beeamesverymoist,dense
' sM
;1
"
1' becomes wet, lens of silt
.1
♦f1 1
,111111
111 ...
1111f 1
ttt 11111
11111111
111,1111
„llfl„ "becomes saturated .. .N........._.,..............•.._._....,_ _......
T :11
I1111111
,41,11
ML Gray, :sandy silt, low plasticity, wet,. very stiff-,.,-.,.
Test boring was terminated at 31,5 feet below grade on 1-1.8-97.
Groundwater seepage was encountered at 16' and 30' during drilling,
TEST BORING Lai
GEOTECH 15620 e 76TH AVENUE WEST
CONSULTANTS, INC. EDMONDS, WA
=No;®ate, Loggedbyr Plate, JAN 1,99i ®RW 8
zs
BORING
p ,
3
° °e
G
��°�,
U'SCS
Des rlatlon
...
20
To soil
Brown/mottled, silty' SAND,witf�ravel'-ve ' vet
s
-lens of silt
Brown, SAND, some silt; coarse-gitained, dens
gravelly wet,
1
5014••
A___..... _.
u£ SP
:.s
10
2
24
;;;,,;
Gray, silty SAND, very fine-grained, wet, ihedium-dense
zs
3
25
20
:.....
...
20
12)s
5
53
ao
40
®,
' -becomes less silty, moist
,,;
ISM j
becomes wet
-lens of silt
Gray SAND, medium -grained, moist, dense
Test boring was terminated at 26,5 feet below grade on 1-18-97,
Groundwater seepage was'encountered at 3r during drilling.
GEOTECH
CONSULTANTS, INC.
TEST BORING LOG
15520 m 76TH AVENUE WEST
EDMGNS, WA
glob No: gged by: Plate:
1324::=
®FfW 9
lob
(DU)
QO
cu
(N
CD cu
C\l
o
W
zT
9
Z
'BUIL
Z
Slope backfill away from
foundation. Provide surface
drains where necessary.
Tightline Roof Drain
(Do not connect to footing drain)
Backfill
(See text for
requirements)
Nonwoven Geotextile
Washed Rock Filter Fabric
Possible Slab
(7/8" min. size)
D Q p U p.A:�•p°.f�.°��.p•.A.Q�•p••�1:�°•p••f�.Q°.p°•Q
° Ow'v '� z oo.oDo•o'o opo. o' o. 'o' o. o• o. •o
°�i� 0 0
.°40° °00° Oo°qo>
odoo 000 �� ;a•oo ono.00
4" min. Vapor Retarder/Barrier and
Capillary Break/Drainage Layer
(Refer to Report text)
4" Perforated Hard PVC Pipe
(Invert at least 6 inches below
slab or crawl space. Slope to
drain to appropriate outfall.
Place holes downward.)
NOTES:
(1) In crawl spaces, provide an outlet drain to prevent buildup of water that
bypasses the perimeter footing drains.
(2) Refer to report text for additional drainage, waterproofing, and slab considerations.
GEOTECH
CONSUIXAN I'S, INC.
F®TING DRAIN DETAIL
15620 72nd Avenue West
Edmonds, Washington
Job No: Date: Plate,
13245 July 2013 11
i
GEOTECH CONSULTANTS, INC,
`Q 0, 199"
North • •
Earthf' • 1
Landslide
AreasMap
Legend
North Edmonds Earth Subsidence and
Landslide Hazard Area
(See ECDC 23,80,020 B,1 and ECDC 19,10)
(Note: Boundaries are the approximate extent
of previous landsilding; hazards are present
adjacent to the landslide boundaries)
Steep Slope Areas:
Slope of 40% or steeper and
with a vertical relief often (10) ft or more
(See ECDC 23,80.020 B,2)
Minimum buffer equal to the height
of the steep slope or 60 feet, whichever
Is greater (see ECDC 23.80.070A,1)
'I (The buffer shown is the minimum buffer
adjacent to the North Edmonds Subsidence
and Landslide Hazard Area; a similar
buffer would apply to steep slope areas,
but is not shown on this map for clarity)
V',
4
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-------------------
[itX2Z2t.t ar'413. V)&sP'iDlidlwlell A{Pusnfif9il(f 41Y(%'n I seaN proieN oryV Wa'i apuaugT 4UWycPrs�+P31^AID
Profile.out
PCSTABL6 *
by
Purdue University
modified by
Peter J. BOSScher
University of Wisconsin -Madison
--slope stability Analysis --
simplified Janbu, simplified Bishop
or Spencers Method of slices
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
4 Top Boundaries
4 Total Boundaries
Boundary
X -Left
Y -Left
No.
(ft)
(ft)
1
0.00
0.00
2
95.00
18.00
3
140.00
58.00
4
192.00
98.00
ISOTROPIC SOIL PARAMETERS
2 Type(s) of Soil
5'7ARC,,
A��ys/__y
X -Right
Y -Right
Soil Type
(ft)
(ft)
BelOW Bnd
95.00
18.00
2
140.00
58.00
2
192.00
98.00
1
510.00
168.00
1
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant surface
No. (pcf) (pcf) (Ps f) (deg) Param. (psf) No.
1 135.0 145.0 200.0 40.0 0.00 0.0 0
2 125.0 135.0 300.0 33.0 0.00 0.0 0
1 PIEZOMETRIC SURFACE(S) HAVE BEEN SPECIFIED
Page 1
Profile.out
unit Weight of Water = 62.40
Piezometric surface No
Point
X -Water
No.
(ft)
1
140.00
2
510.00
1 specified by 2 coordinate Points
Y -Water
(ft)
58.00
58.00
A critical Failure surface searching Method, Using A Random
Technique For Generating circular surfaces, Has Been specified.
225 Trial surfaces Have Been Generated.
15 surfaces initiate From Each of 15 Points Equally Spaced
Along The Ground Surface Between X = 60.00 ft.
and X = 110.00 ft.
Each surface Terminates Between X = 242.00 ft.
and X = 245.00 ft.
unless Further Limitations were Imposed, The Minimum Elevation
At which A surface Extends Is Y = 0.00 ft.
10.00 ft. Line segments Define Each Trial Failure surface.
Following Are Displayed The Ten Most critical of The Trial
Failure surfaces Examined. They Are ordered - Most critical
First.
* Safety Factors Are calculated By The Modified janbu Method * *
Failure surface specified By 19 coordinate Points
Point
x -surf
Y -surf
No.
(ft)
(ft)
1
95.71
18.64
2
105.47
20.82
3
115.14
23.40
4
124.69
26.35
5
134.12
29.68
6
143.41
33.38
7
152.55
37.44
8
161.52
41.86
9
170.31
46.63
Page 2
Failure surface specified By 19 coordinate Points
Point
x -surf
Profile.out
10
178.90
51.75
11
187.28
57.19
12
195.45
62.97
13
203.37
69.07
14
211.06
75.47
15
218.48
82.17
16
225.63
89.16
17
232.50
96.43
18
239.08
103.96
19
243.39
109.31
��Y
1.512
50.43
Failure surface specified By 19 coordinate Points
Point
x -surf
Y -surf
No.
(ft)
(ft)
1
95.71
18.64
2
105.53
20.56
3
115.25
22.91
4
124.86
25.66
5
134.35
28.81
6
143.70
32.37
7
152.89
36.31
8
161.90
40.64
9
170.72
45.35
10
179.34
50.43
11
187.73
55.87
12
195.89
61.65
13
203.79
67.78
14
211.43
74.24
15
218.78
81.01
16
225.85
88.09
17
232.61
95.46
18
239.05
103.11
19
243.93
109.43
1.518
Failure surface specified By 21 coordinate Points
Point
x -surf
Y -surf
No.
(ft)
(ft)
1
85.00
16.11
2
94.96
17.03
3
104.86
18.44
4
114.68
20.33
5
124.39
22.69
6
133.98
25.53
7
143.42
28.82
8
152.69
32.58
9
161.77
36.78
10
170.63
41.42
Page 3
Profile.out
11
179.25
46.48
12
187.62
51.96
13
195.71
57.83
14
203.50
64.10
15
210.98
70.73
16
218.13
77.73
17
224.93
85.06
18
231.37
92.72
19
237.42
100.67
20
243.08
108.92
21
243.31
109.29
202.44
1.521
209.99
Failure surface specified By 22 coordinate Points
Point
X -Surf
No.
(ft)
1
74.29
2
84.26
3
94.18
4
104.04
5
113.81
6
123.48
7
133.01
8
142.40
9
151.63
10
160.67
11
169.50
12
178.12
13
186.49
14
194.60
15
202.44
16
209.99
17
217.24
18
224.16
19
230.74
20
236.98
21
242.85
22
243.45
1.523
Y -surf
(ft)
14.08
14.85
16.08
17.75
19.88
22.45
25.45
28.89
32.75
37.02
41.71
46.79
52.26
58.10
64.31
70.87
77.76
84.98
92.50
100.32
108.41
109.33
Failure surface Specified By 22 coordinate Points
Point
X -Surf
Y -Surf
No.
(ft)
(ft)
1
67.14
12.72
2
77.14
12.87
3
87.12
13.51
4
97.06
14.63
5
106.93
16.24
6
116.71
18.32
Page 4
7
126.38
8
135.91
9
145.28
10
154.48
11
163.47
12
172.23
13
180.76
14
189.02
15
196.99
16
204.66
17
212.01
18
219.03
19
225.68
20
231.97
21
237.87
22
243.30
4r�r 1.527
Profile.out
20.88
23.90
27.38
31.32
35.70
40.51
45.74
51.38
57.41
63.82
70.60
77.73
85.20
92.97
101.05
109.29
Failure surface specified By 19 Coordinate Points
Point
x -surf
Y -surf
No.
(ft)
(ft)
1
95.71
18.64
2
105.09
22.11
3
114.38
25.81
4
123.58
29.73
5
132.69
33.86
6
141.70
38.20
7
150.60
42.75
8
159.40
47.51
9
168.08
52.47
10
176.64
57.64
11
185.08
63.01
12
193.39
68.57
13
201.57
74.33
14
209.61
80.27
15
217.50
86.40
16
225.26
92.72
17
232.86
99.22
18
240.31
105.89
19
244.12
109.47
ir4r4r
1.529
Failure surface specified By 22 Coordinate Points
Point
x -Surf
Y -Surf
No.
(ft)
(ft)
1
74.29
14.08
2
84.28
14.35
3
94.25
15.13
4
104.17
16.40
Page 5
Me
Safety Factors
1.51
1.52
1.52
1.52
1.53
1.53
1.53
1.53
1.53
1.54
Profile.out
PCSTABL6 * *
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin -Madison
--slope stability Analysis --
simplified Janbu, simplified Bishop
or spencers Method of slices
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
4 Top Boundaries
4 Total Boundaries
Boundary
x -Left
Y -Left
x -Right
Y -Right
Soil Type
No.
(ft)
(ft)
(ft)
(ft)
Below Bnd
1
0.00
0.00
95.00
18.00
2
2
95.00
18.00
148.00
58.00
2
3
148.00
58.00
192.00
98.00
1
4
192.00
98.00
510.00
168.00
1
ISOTROPIC SOIL PARAMETERS
2 Type(s) of soil
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 135.0 145.0 200.0 40.0 0.00 0.0 0
2 125.0 135.0 300.0 33.0 0.00 0.0 0
1 PIEZOMETRIC SURFACE(S) HAVE BEEN SPECIFIED
Page 1
Profile.out
Unit Weight of water = 62.40
Piezometric surface No. 1 specified by 2 coordinate Points
Point
X -Water
Y -Water
No.
(ft)
(ft)
1
148.00
58.00
2
510.00
58.00
A Horizontal Earthquake Loading coefficient
of0.160 Has Been Assigned
A vertical Earthquake Loading coefficient
of0.000 Has Been Assigned
cavitation Pressure = 0.0 psf
A critical Failure surface searching Method, using A Random
Technique For Generating circular surfaces, Has Been specified.
400 Trial surfaces Have Been Generated.
20 surfaces initiate From Each of 20 Points Equally spaced
Along The Ground surface Between X = 60.00 ft.
and X = 110.00 ft.
Each surface Terminates Between X = 242.00 ft.
and X = 245.00 ft.
unless Further Limitations Were Imposed, The Minimum Elevation
At which A surface Extends Is Y = 0.00 ft.
10.00 ft. Line segments Define Each Trial Failure surface.
Following Are Displayed The Ten Most critical of The Trial
Failure surfaces Examined. They Are ordered - Most critical
First.
* * safety Factors Are calculated By The Modified Bishop Method * *
Failure surface specified By 19 coordinate Points
Point X -surf Y -surf
No. (ft) (ft)
Page 2
1
96.84
2
106.52
3
116.09
4
125.56
5
134.90
6
144.11
7
153.17
8
162.07
9
170.80
10
179.34
11
187.69
12
195.84
13
203.77
14
211.47
15
218.94
16
226.16
17
233.12
18
239.82
19
242.11
circle center At X
Profile.out
19.39
21.92
24.80
28.02
31.59
35.49
39.73
44.29
49.17
54.36
59.86
65.66
71.76
78.13
84.78
91.70
98.88
106.30
109.03
32.0 ; Y = 287.1 and Radius, 275.4
1.120 * * *
Failure surface specified By 19 coordinate Points
Point
x -surf
Y -surf
No.
(ft)
(ft)
1
99.47
21.38
2
109.21
23.67
3
118.84
26.35
4
128.36
29.41
5
137.75
32.84
6
147.00
36.64
7
156.10
40.81
8
165.02
45.32
9
173.76
50.19
10
182.29
55.40
11
190.62
60.94
12
198.72
66.80
13
206.58
72.98
14
214.19
79.46
15
221.54
86.24
16
228.62
93.31
17
235.41
100.65
18
241.91
108.25
19
242.62
109.14
circle center At X = 46.1 ; Y = 269.0 and Radius, 253.4
Failure surface specified By 19 coordinate Points
Page 3
318
255
191
127
63.
0 63.75 127.50 191.25 255.00 318.75
We
Safety Factors
1.12
1.13
1.13
1.13
1.14
1.15
1.15
1.15
1.15
1.15
cD4
Profi 1 e . out t/0 G �
PCSTABL6
by
Purdue university
modified by
Peter J. Bosscher
university of Wisconsin-Madison
--slope stability Analysis --
simplified janbu, simplified Bishop
or spencers Method of slices
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
4 Top Boundaries
4 Total Boundaries
Boundary
x -Left
Y -Left
x -Right
Y -Right
soil Type
No.
(ft)
(ft)
(ft)
(ft)
BeloW Bnd
1
0.00
0.00
95.00
18.00
2
2
95.00
18.00
148.00
58.00
2
3
148..00
58.00
192.00
98.00
1
4
192.00
98.00
510.00
168.00
1
ISOTROPIC SOIL PARAMETERS
2 Type(s) of Soil
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type unit wt. Unit Wt. Intercept Angle Pressure constant surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 135.0 145.0 200.0 40.0 0.00 0.0 0
2 125.0 135.0 300.0 33.0 0.00 0.0 0
1 PIEZOMETRIC SURFACE(S) HAVE BEEN SPECIFIED
Page 1
Profile.out
unit weight of Water = 62.40
Piezometric surface No. 1 specified by 2 coordinate Points
Point
X -Water
Y -Water
No.
(ft)
(ft)
1
148.00
58.00
2
510.00
58.00
A Horizontal Earthquake Loading coefficient
Of0.160 Has Been Assigned
A vertical Earthquake Loading coefficient
Of0.000 Has Been Assigned
cavitation Pressure = 0.0 psf
A critical Failure surface searching Method, using A Random
Technique For Generating circular surfaces, Has Been specified.
400 Trial surfaces Have Been Generated.
20 surfaces initiate From Each of 20 Points Equally spaced
Along The Ground surface Between x = 60.00 ft.
and x = 110.00 ft.
Each Surface Terminates Between X = 257.00 ft.
and X = 300.00 ft.
Unless Further Limitations were Imposed, The Minimum Elevation
At which A surface Extends is Y = 0.00 ft.
10.00 ft. Line segments Define Each Trial Failure surface.
Following Are Displayed The Ten Most critical of The Trial
Failure surfaces Examined. They Are ordered - Most critical
First.
* safety Factors Are calculated By The Modified Bishop Method * *
Failure surface specified By 20 coordinate Points
Point X -Surf Y -Surf
No. (ft) (ft)
Page 2
1
96.84
2
106.30
3
115.69
4
125.01
5
134.24
6
143.39
7
152.45
8
161.41
9
170.28
10
179.04
11
187.70
12
196.25
13
204.68
14
213.00
15
221.19
16
229.26
17
237.20
18
245.00
19
252.67
20
259.00
Circle center At X
Profile.out
19.39
22.63
26.07
29.71
33.55
37.59
41.83
46.26
50.88
55.70
60.70
65.89
71.27
76.82
82.55
88.46
94.54
100.79
107.21
112.75
48.1 ; Y = 458.7
1.179 ***
and Radius, 462.6
Failure surface specified By 21 coordinate Points
Point
X -Surf
Y -Surf
No.
(ft)
(ft)
1
96.84
19.39
2
106.61
21.54
3
116.30
24.02
4
125.89
26.83
5
135.39
29.96
6
144.78
33.41
7
154.04
37.18
8
163.17
41.26
9
172.16
45.65
10
180.99
50.33
11
189.66
55.32
12
198.16
60.59
13
206.47
66.15
14
214.59
71.99
15
222.50
78.10
16
230.21
84.47
17
237.69
91.10
18
244.95
97.98
19
251.97
105.11
20
258.74
112.46
21
258.98
112.74
circle center At X = 38.2 ; Y = 308.7 and Radius, 295.2
1.182 ;; *
Page 3
Profile.out
Failure surface specified By 20 coordinate Points
Point
X -surf
Y -surf
No.
(ft)
(ft)
1
99.47
21.38
2
109.24
23.52
3
118.93
26.00
4
128.53
28.80
5
138.02
31.94
6
147.41
35.40
7
156.67
39.17
8
165.79
43.27
9
174.77
47.67
10
183.59
52.38
11
192.24
57.39
12
200.72
62.70
13
209.01
68.29
14
217.11
74.16
15
225.00
80.30
16
232.67
86.72
17
240.12
93.39
18
247.33
100.31
19
254.30
107.48
20
259.11
112.77
Circle Center At X =
41.9 ; Y = 307.1 and Radius, 291.5
1.193
***
Failure
surface specified
By 21 Coordinate Points
Point
X -Surf
Y -Surf
No.
(ft)
(ft)
1
96.84
19.39
2
106.75
20.78
3
116.58
22.59
4
126.33
24.82
5
135.97
27.46
6
145.50
30.50
7
154.89
33.95
8
164.12
37.80
9
173.17
42.04
10
182.05
46.65
11
190.71
51.64
12
199.16
57.00
13
207.37
62.70
14
215.33
68.76
15
223.02
75.14
16
230.44
81.85
17
237.57
88.87
18
244.39
96.18
19
250.89
103.78
20
257.06
111.64
21
257.65
112.45
Page 4
OR
255
191
127
63,
U 06.(b "12/.bU 19112b 2bb.UU 616./0 �JU.bU 44b.2b
510.00
Safety Factors
1.18
1.18
1.19
1.20
1.21
1.22
1.22
1.22
1.23
1.23