HomeMy WebLinkAboutEX04_Geotechnical_Report
13705 Bel-Red Road · Bellevue, Washington 98005
Phone 425/649-8757 · Fax 425/649-8758
October 26th, 2022 G-5204
Ms. Karen Lang
212 – S 20th Pl
Renton, Washington 98055
Phone: (208) 880-3296
Email: karenl@summitlaw.com
Subject: Critical Areas Study & Geotechnical Evaluation
Existing Backyard Deck
212 – S 20th Pl
Renton, Washington 98055
Reference: “Lang Back Yard Deck Variances, LUA22-000145, ECF, VAR-A, RUF”,
addressed to Karen Lang Crane, by Brittany Gillia, dated August 12 th, 2022.
Dear Ms. Lang,
At your request, GEO Group Northwest, Inc., conducted a critical areas study and geotechnical
engineering evaluation for the backyard deck development at the above-subject location in
Renton, Washington. The scope of our services included review of the area geologic map;
assessment of subsurface soil and groundwater conditions; assessment of geologically hazardous
areas present at the site; quantitative slope stability analysis; and preparation of this report of our
findings, conclusions, and recommendations.
SITE CONDITIONS
Site Description
The project site is located in central Renton, Washington, southeast of the I-405 and SR-167
interchange, as illustrated in Plate 1 – Site Location Map. The site is approximately rectangle-
shaped but has a wedged taper at the southern margin; the lot totals approximately 5,011 square
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
October 26th, 2022 G-5204
Ms. Karen Lang | 212 – S 20th Pl, Renton, Washington 98055 Page 2
GEO Group Northwest, Inc.
feet. An existing single-family residence lies in the central region of the property and the newly-
installed, elevated deck is located at the north face of said residence. The property generally
descends at gentle to moderate inclinations from the southern to northern site margins. The
topography descends at steep inclinations at and past the northern property line. The highest and
lowest elevations at the site are approximately 188 feet at the south property line, and 164 feet at
the north property line. The gentle to moderate slope at the site is separated from the steeply
sloping area by an approximately 4-foot-tall ecology block wall with rests along the crest of the
steep slope. Most of the residential lot space is occupied by the developed structures, however,
the site is otherwise landscaped with grass groundcover, shrubs and trees. The slope at the
northern portion of the site is well-vegetated with native trees, shrubs, ivy, and forest duff. The
site is accessed by South 20th Place to the southeast via a paved driveway extending from the
road.
Site Proximity
The site is immediately surrounded by residential developed properties to the north, east,
southwest, and west. The following sections in this report, based on the aerial photography and
contour information from the City of Renton COR Maps, describe the natural and developed
environments within 150 feet of the project site in all directions. An aerial map of the project
site vicinity can be found on Plate 2 – Site Proximity Map to this report.
North
The immediate north-adjacent parcel (#7222000410) is currently occupied with a single-story,
single-family residence, a detached garage, and a small shed. There is a concrete driveway
extending from the single-family residence to the detached garage. The detached garage and
driveway are approximately 20 feet beyond the northern project site property line. The lot
appears to otherwise be naturally forested and well-vegetated with native foliage. The parcel
moderately and steeply slopes westerly when nearing the west margin, and northerly at the
northern margin. This parcel is not within the Valley Vue Estates subdivision of the project site.
East
Three parcels are within 150 feet of the project site to the east. The parcels are a part of the
Valley Vue Estates subdivision. Each parcel (#8860500060, #8860500050, #8860500040) is
occupied with a two-story, single-family residence with a daylit basement and attached garage.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
October 26th, 2022 G-5204
Ms. Karen Lang | 212 – S 20th Pl, Renton, Washington 98055 Page 3
GEO Group Northwest, Inc.
Each parcel has a paved driveway extending south to South 20 th Place. The parcels all appear to
slope at gentle to moderate inclinations in the northeastern direction.
West
Two parcels are within 150 feet of the project site to the west. The parcels are a part of the
Valley Vue Estates subdivision. Each parcel (#8860500080, #8860500090) is occupied with a
two-story, single-family residence with a daylit basement and attached garage. They share a
paved driveway extending southeast to South 20th Place. The parcels each appear to slope at
moderate and steep inclinations in the northwestern direction. The topography continues to slope
northwesterly beyond the property lines into undeveloped land. The sloping, undeveloped land
appears to be naturally forested and well-vegetated with native foliage
Southwest
Three parcels are within 150 feet of the project site to the southwest. The parcels are a part of
the Valley Vue Estates subdivision. Each parcel (#8860500100, #8860500110, #8860500120) is
occupied with a two-story, single-family residence with a daylit basement and attached garage.
Each parcel has a paved driveway extending east to Davis Avenue South. The parcels each
appear to slope westerly at moderate and steep inclinations. The topography continues to slope
beyond the property lines into undeveloped land. The sloping, undeveloped land appears to be
naturally forested and well-vegetated with native foliage
Southeast
Five parcels are within 150 feet of the project site to the southeast. The parcels are a part of the
Valley Vue Estates subdivision. Parcels #8860500300, #8860500310, and #8860500320 are
occupied with two-story, single-family residences with daylit basements and attached garages.
These parcels have paved driveways extending north to South 20 th Place and generally appear to
slope northeasterly at moderate inclinations. Parcels #8860500290 and #8860500280 are also
occupied with two-story, single-family residences with daylit basements and attached garages.
These parcels have paved driveways extending south to South 21 st Street and generally appear to
slope northerly at gentle inclinations.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
October 26th, 2022 G-5204
Ms. Karen Lang | 212 – S 20th Pl, Renton, Washington 98055 Page 4
GEO Group Northwest, Inc.
SITE INVESTIGATION
Geologic Overview
According to published geologic mapping of the area 1, the site and adjacent vicinity is underlain
by shallow bedrock known as the Renton Formation. The formation is composed of arkosic
sandstone, mudstone, and shale, and is interpreted to be of continental origin.
Subsurface Investigation
On September 30, 2022, Garrett Dean, accompanied by Andrew Hoff, Staff Engineering
Geologists from our firm, visited the site to perform a visual reconnaissance of the site and
investigate the subsurface soil conditions. In addition to our reconnaissance, we completed two
hand auger borings at the site (HA-1 & HA-2). The boring locations are illustrated on Plate 3 -
Site Plan to this report.
Soils encountered in boring HA-1 consisted of dark brown to brown, loose, damp to moist, silty
sand to the total depth of the boring, approximately 5.8 feet below the ground surface (bgs). The
maximum depth was reached when auger refusal was met in cobble/rock material. A ½-inch
diameter, T-handled probing rod was driven approximately 18 inches into the base of the
borehole at a depth of 5.8 feet bgs, therefore, dense to very dense soils are anticipated at
approximately 7.3 feet bgs near HA-1. The loose soils encountered near HA-1 are suspected to
be of native origin, but previously disturbed during the basement construction of the residence.
Soils encountered in HA-2 consisted of grayish-brown, loose, silty sand to a depth of
approximately 6 inches bgs, underlain with a very dense soil of the same composition to the total
depth of the boring, approximately 2.0 feet bgs.
We probed other regions of the site, such as in the front, side, and backyards, and were unable to
probe deeper than 6 to 12 inches. Our findings are consistent with the local geologic mapping
(Renton Formation) in our opinion. Groundwater was not encountered in the borings during our
investigation. For information about the soils encountered, please refer to the boring logs in
Appendix A.
1 Mullineaux, D.R., 1965, Geologic map of the Renton quadrangle, King County, Washington, U.S. Geological
Survey, Geologic Quadrangle Map GQ-405, 1:24,000.
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October 26th, 2022 G-5204
Ms. Karen Lang | 212 – S 20th Pl, Renton, Washington 98055 Page 5
GEO Group Northwest, Inc.
SEISMICITY EVALUATION
In accordance with the procedures described in the 2018 International Building Code (IBC), we
conclude that the project site should be classified as Site Class C (Very Dense Soil & Soft Rock)
per ASCE 7-16. Our determination is based on the soil conditions observed in the hand auger
borings that were advanced on the site and our review of the geologic mapping literature for the
area.
Subsequently, the seismic design parameters applicable for the site (per designation as Site Class
C), per the 2018 IBC, are as follows:
Ss = 1.43g Sms = 1.716g Sds = 1.144g
S1 = 0.487g Sm1 = 0.73g Sd1 = 0.487g
The peak ground acceleration for the site, adjusted for site class effects, is 0.73g.
SLOPE STABILITY ANALYSIS
We completed an analysis of the potential slope stability impact from the backyard deck project
by using topographic information from the site survey and the City of Renton COR Maps, as
well as from the findings from our onsite soil explorations. The location of the slope profile used
for the analysis is denoted on Plate 3 – Site Plan as ‘Profile A’. Analyses were performed on
Profile A with and without the imposed loading from the deck as well as with and without
seismic loading. The analysis input parameters and results are provided in Appendix B to this
report.
The analyses were performed using the computer analysis program Slide 7.0 published by
Rocscience, Inc. This program analyzes slope stability via various methods. For this study,
Bishop’s Modified Method of Slices was used to perform the analyses.
The calculated stability is represented as a factor of safety (FS) against slope failure. The
FS value is dimensionless and is defined as the value of the resisting forces mobilized from the
soil mass divided by the driving forces toward movement of the soil. An FS value of 1.0
represents a situation where both forces are equivalent, and the potential for movement of the
soil is at or near its threshold. An FS value slightly above 1.0 indicates a slope with minimal
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October 26th, 2022 G-5204
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GEO Group Northwest, Inc.
stability. For the purposes of this study, an FS value of at least 1.5 is considered to indicate a
sufficiently stable condition for the slope under permanent, static conditions. An FS value of at
least 1.2 is considered sufficiently stable for a short-term dynamic condition such as seismic
loading during an earthquake.
Analysis Parameters
The surface and subsurface soil types encountered in our soil explorations were categorized into
discrete soil units, based on soil type classification and relative density or consistency. Analysis
parameters for these soil units (unit weight, cohesion, friction angle) were obtained from
published correlations with standard penetration test (SPT) data or other density and consistency
observations, soil grain-size properties; typical friction angle and cohesion values published in
technical literature; and our experience with past stability analyses involving similar soil types.
The soil parameters developed from this analysis are summarized in the following table.
Soil Unit Descriptions and Parameters
Unit Soil Description Unsaturated Unit
Weight (pcf)
Internal Cohesion
(psf)
Friction Angle
(deg)
I Disturbed, Loose BEDROCK 110 0 30
II Weathered BEDROCK 140 500 45
Analysis Results
Minimum failure surfaces calculated from the analyses are illustrated in the plots provided in
Appendix B to this letter. In cases where the minimum failure surface has an FS value at or
above 1.5 for the static case or 1.2 for the seismic case, only the minimum surface is illustrated.
For cases where failure surfaces having FS values below 1.5 for the static case or 1.2 for the
seismic case are calculated, each of those surfaces is illustrated.
Profile Without Deck Loads
A minimum FS value of 2.63 was calculated for potential failure surfaces along Profile A during
static site conditions without the potential additional loading from the backyard deck. A
minimum FS value of 1.84 was calculated for potential failure surfaces during seismic
conditions. The FS values for the static and seismic conditions exceed the minimum criteria of
1.5 and 1.2, respectively, for indicating acceptable stability of the slope profile.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
October 26th, 2022 G-5204
Ms. Karen Lang | 212 – S 20th Pl, Renton, Washington 98055 Page 7
GEO Group Northwest, Inc.
Profile With Deck Loads
Analysis was performed on Profile A which includes six added point loads to simulate the
loading from the backyard deck. A minimum FS value of 2.39 was calculated for the potential
failure surface for the static case, and a minimum FS value of 1.75 was calculated for the seismic
case. These FS values meet the minimum criteria for indicating acceptable stability of the slope
profile.
ENVIRONMENTALLY CRITICAL AREAS REVIEW
High Erosion Hazard
We understand that the entire project site is within a designated high erosion hazard area, per
City of Renton COR Maps. Per the City of Renton Municipal Code (RMC) 4-3-050G.5.c.ii,
Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil
Conservation Service) as having severe or very severe erosion potential, and a slope more than
fifteen percent (15%). The erosion hazard mapping for the site area is illustrated on Plate 4 to
this report.
High Landslide Hazard
We understand that the entire project site is within a designated high landslide hazard area, per
City of Renton COR Maps. Per the City of Renton Municipal Code (RMC) 4-3-050G.5.b.iii,
areas with slopes greater than forty percent (40%), and areas with slopes between fifteen percent
(15%) and forty percent (40%) and underlain by soils consisting of largely of silt and clay are
identified as high landslide hazard areas. The high landslide area mapping for the site area is
illustrated on Plate 5 to this report.
Sensitive & Protected Slopes
We also understand that slopes meeting the criteria for sensitive slope definitions are present on
the project site. Per the City of Renton Municipal Code (RMC) 4-3-050G.5.a.i the following
criteria define sensitive slopes - a hillside, or portion thereof, characterized by: (a) an average
slope of twenty five percent (25%) to less than forty percent (40%) as identified in the City of
Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of forty
percent (40%) or greater with a vertical rise of less than fifteen feet (15') as identified in the City
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
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GEO Group Northwest, Inc.
of Renton Steep Slope Atlas or in a method approved by the City; (c) abutting an average slope
of twenty five percent (25%) to forty percent (40%) as identified in the City of Renton Steep
Slope Atlas or in a method approved by the City. This definition excludes engineered retaining
walls.
Furthermore, slopes meeting the criteria for protected slope definitions are present on the project
site. Per the City of Renton Municipal Code (RMC) 4-3-050G.5.a.ii, protected slopes are
defined as a hillside, or portion thereof, characterized by an average slope of forty percent (40%)
or greater grade and having a minimum vertical rise of fifteen feet (15') as identified in the City
of Renton Steep Slope Atlas or in a method approved by the City. Sensitive and protected slopes
on and adjacent to the site are illustrated on Plate 6 to this report.
Critical Areas Evaluation
Erosion Hazard Area
We understand that Beausite gravelly sandy loam (BeC, BeD) soils have been identified on 6 to
30 percent slopes within on the project site per the USDA Web Soil Survey. The soil
identification and mapping are illustrated in Appendix C to this report.
According to the USDA NRCS Soil Map, Beausite gravelly sandy loam soils are described as till
over residuum from sandstone, with 24 to 40 inches depth to lithic bedrock. These soils have
mild to moderate erosion susceptibility ratings according to USDA classification (K Factor
Rating = 0.10). We observed that the soils at the project site are covered with native vegetation
which include trees, shrubs, grass and other groundcover. In our opinion, the existing vegetation
is a mitigating factor in regards to downslope soil erosion at the site. No additional mitigation is
necessary for the project, in our opinion. Restoration or mitigation plans, if required by the
governing municipality, should be prepared by a licensed landscaping specialist.
Landslide Hazard Area; Sensitive & Protected Slopes
Per the site survey provided by Apex Engineering and the contour mapping available on the City
of Renton COR Maps, the sloping area beneath the deck is approximately 30 to 35 percent grade
and has a vertical rise of approximately 7 to 9 feet. These conditions qualify the region as a
sensitive slope according to the City of Renton per the RMC clause referenced above. Continuing
north beyond the deck footprint, the site slopes down 18 to 19 feet at an inclination of
approximately 86 percent to the adjacent parcel below, qualifying the slope as protected per the
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
October 26th, 2022 G-5204
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GEO Group Northwest, Inc.
RMC, referenced above. The majority of this slope area, however, lies beyond the project property
boundary. Slopes on the site with inclinations 40 percent grade or higher qualify as high landslide
hazards, per the RMC. The 4-foot-tall ecoblock retaining wall at the protected slope crest is
exempted from sensitive slope designation, per RMC.
The existing deck is well supported on the dense to very dense, shallow bedrock lies on top of the
are approximately 63 or greater feet southeast from the top-of-slope, and approximately 28 or more
feet away from the toe-of-slope. During our investigation, we probed the sensitive and protected
slope areas and encountered dense soils at depths of approximately 0 to 6 inches beneath the
ground surface. A hand auger boring was performed on the protected slope, which also
encountered dense soil conditions.
We interpret that the current slope inclinations at the site were shaped through historic grading and
from earthwork necessary for the Valley Vue Estates subdivision development. The underlying
soils encountered appear to be consistent with bedrock of the Renton Formation, as identified in
the local geologic map. According to information provided by the WA DNR Geology Portal, there
is no known landslide activity immediately adjacent to the project area. We observed the slopes at
the site to be naturally forested with trees, shrubs, and native groundcover. We did not observe
indications of slope, deck, or ecoblock wall instability during our site investigation.
Conclusion
We find the existing vegetation and the dense to very dense soil and shallow bedrock conditions
present at the hazard area to be mitigating factors regarding slope stability and potential landsliding
of the hazard area at the site. Slope stability analysis results provide factors of safety greater than
2.39 for rotational landsliding in static conditions, and greater than 1.74 in seismic conditions. It
is for these considerations that, in our opinion, the mapped landslide hazard area and the sensitive
and protected slopes are stable at this time; the risk of landsliding or other adverse effects to the
site, critical areas, or adjacent properties due to the backyard deck development can be considered
negligible.
LIMITATIONS
The findings and recommendations stated herein are based on field observations, our experience
on similar projects and our professional judgment. The recommendations presented herein are
our professional opinions derived in a manner consistent with the level of care and skill
EXHIBIT 4
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October 26th, 2022 G-5204
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GEO Group Northwest, Inc.
ordinarily exercised by other members of the profession currently practicing under similar
conditions in this area and within the project schedule and budget constraints. No warranty is
expressed or implied. In the event that site conditions are found to differ from those described in
this report, we should be notified so that the relevant recommendations in this report can be
reevaluated and modified if appropriate.
CLOSING
We appreciate the opportunity to provide you with geotechnical engineering services for this
project. Please do not hesitate to contact us if you have any questions regarding this report.
Sincerely,
GEO Group Northwest, Inc.
Garrett Dean, G.I.T. William Chang, P.E.
Staff Engineering Geologist Principal Engineer
Plates and Attachment:
Plate 1 – Site Location Map
Plate 2 – Site Proximity Map
Plate 3 – Site Plan
Plate 4 – Erosion Hazard Map
Plate 5 – Landslide Hazard Map
Plate 6 – Regulated Slope Map
Appendix A – USCS Soil Classification & Hand Auger Boring Logs
Appendix B – Slope Stability Analysis Data
Appendix C – USDA Soil Mapping & Classification
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Source: King County iMap
SCALE NONE DATE 10/26/2022 MADE GD CHKD WC JOB NO.G-5204 PLATE 1
SITE LOCATION MAP
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
PROJECT SITE
N
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Source: City of Renton COR Maps
SCALE NONE DATE 10/26/2022 MADE GD CHKD WC JOB NO.G-5204 PLATE 2
SITE PROXIMITY MAP
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
N
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
This site plan adapted from Exhibit Map for Karen Lang, Prepared Apex Engineering, PLLC, Dated February 16th, 2022.
SCALE 1" = 10'DATE 10/26/2022 MADE GD CHKD WC JOB NO.G-5204 PLATE 3
SITE PLAN
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
N
Hand Auger Boring Number
& Approximate LocationHA-#
HA-1
HA-2
A
A'
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
SCALE AS SHOWN DRAWN BY GD CHECKED BY WC DATE 10/26/2022 PROJECT NO.G-5204 PLATE 4
EROSION HAZARD MAP
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
SCALE AS SHOWN DRAWN BY GD CHECKED BY WC DATE 10/26/2022 PROJECT NO.G-5204 PLATE 5
LANDSLIDE HAZARD MAP
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
SCALE AS SHOWN DRAWN BY GD CHECKED BY WC DATE 10/26/2022 PROJECT NO.G-5204 PLATE 6
REGULATED SLOPE MAP
BACKYARD DECK - RESIDENTIAL LOT
212 - S 20TH PL
RENTON, WASHINGTON 98055
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
APPENDIX A
G-5204
USCS SOIL CLASSIFICATION & SOIL BORING LOGS
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
CLEAN
GRAVELS
GW
(little or no
fines)GP
DIRTY
GRAVELS
GM
(with some
fines)GC
CLEAN
SANDS
SW
(little or no
fines)SP
DIRTY
SANDS
SM
(with some
fines)SC
Liquid Limit
< 50%ML
Liquid Limit
> 50%MH
Liquid Limit
< 50%CL
Liquid Limit
> 50%CH
Liquid Limit
< 50%OL
Liquid Limit
> 50%OH
Pt
Sieve Size
(mm)Sieve Size
(mm)
SILT / CLAY #200 0.075
SAND 0 - 4 0 -15 Very Loose < 2 < 0.25 Very soft
FINE #40 0.425 #200 0.075 4 - 10 15 - 35 26 - 30 Loose 2 - 4 0.25 - 0.50 Soft
MEDIUM #10 2.00 #40 0.425 10 - 30 35 - 65 28 - 35 Medium Dense 4 - 8 0.50 - 1.00 Medium Stiff
COARSE #4 4.75 #10 2.00 30 - 50 65 - 85 35 - 42 Dense 8 - 15 1.00 - 2.00 Stiff
GRAVEL > 50 85 - 100 38 - 46 Very Dense 15 - 30 2.00 - 4.00 Very Stiff
FINE 0.75" 19 #4 4.75 > 30 > 4.00 Hard
COARSE 3" 76 0.75" 19
COBBLES
BOULDERS
ROCK
FRAGMENTS
ROCK PLATE A1
COARSE-
GRAINED SOILS
GRAVELS
(More Than Half
Coarse Fraction is
Larger Than No. 4
Sieve)
WELL GRADED GRAVELS, GRAVEL-SAND
MIXTURE, LITTLE OR NO FINES CONTENT
OF FINES BELOW
5%
SOIL CLASSIFICATION & PENETRATION TEST DATA EXPLANATION
UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)
MAJOR DIVISION GROUP
SYMBOL TYPICAL DESCRIPTION LABORATORY CLASSIFICATION CRITERIA
Cu = (D60 / D10) greater than 4
Cc = (D30)2 / (D10 * D60) between 1 and 3
POORLY GRADED GRAVELS, AND GRAVEL-SAND
MIXTURES LITTLE OR NO FINES
CLEAN GRAVELS NOT MEETING ABOVE
REQUIREMENTS
SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES CONTENT
OF FINES EXCEEDS
12%
GM: ATTERBERG LIMITS BELOW "A" LINE.
or P.I. LESS THAN 4
CONTENT
OF FINES BELOW
5%
Cu = (D60 / D10) greater than 6
Cc = (D30)2 / (D10 * D60) between 1 and 3
(More Than Half
Coarse Fraction is
Smaller Than No.
4 Sieve)
POORLY GRADED SANDS, GRAVELLY SANDS,
LITTLE OR NO FINES
CLEAN SANDS NOT MEETING ABOVE
REQUIREMENTS
SILTY SANDS, SAND-SILT MIXTURES
CONTENT OF FINES
EXCEEDS 12%
ATTERBERG LIMITS BELOW "A" LINE
with P.I. LESS THAN 4
CLAYEY SANDS, SAND-CLAY MIXTURES ATTERBERG LIMITS ABOVE "A" LINE
with P.I. MORE THAN 7
CLAYEY GRAVELS, GRAVEL-SAND-CLAY
MIXTURES
GC: ATTERBERG LIMITS ABOVE "A" LINE.
or P.I. MORE THAN 7
INORGANIC CLAYS OF LOW PLASTICITY,
GRAVELLY, SANDY, OR SILTY CLAYS, LEAN
CLAYS
Less Than Half by
Weight Larger
Than No. 200
Sieve (i.e., fines)
INORGANIC CLAYS OF HIGH PLASTICITY, FAT
CLAYS
ORGANIC SILTS
& CLAYS
(Below A-Line on
Plasticity Chart)
ORGANIC SILTS AND ORGANIC SILTY CLAYS OF
LOW PLASTICITY
ORGANIC CLAYS OF HIGH PLASTICITY
FINE-GRAINED
SOILS
SILTS
(Below A-Line on
Plasticity Chart,
Negligible
Organics)
INORGANIC SILTS, ROCK FLOUR, SANDY SILTS
OF SLIGHT PLASTICITY
INORGANIC SILTS, MICACEOUS OR
DIATOMACEOUS, FINE SANDY OR SILTY SOIL
CLAYS
(Above A-Line on
Plasticity Chart,
Negligible
Organics)
More Than Half
by Weight Larger
Than No. 200
Sieve
SANDS WELL GRADED SANDS, GRAVELLY SANDS,
LITTLE OR NO FINES
HIGHLY ORGANIC SOILS PEAT AND OTHER HIGHLY ORGANIC SOILS
SOIL PARTICLE SIZE GENERAL GUIDANCE FOR ENGINEERING PROPERTIES OF SOILS, BASED ON STANDARD
PENETRATION TEST (SPT) DATA
FRACTION
U.S. STANDARD SIEVE
Passing Retained SANDY SOILS SILTY & CLAYEY SOILS
76 mm to 203 mm
> 203 mm
> 76 mm
13705 Bel-Red Road
>0.76 cubic meter in volume Phone (425) 649-8757 E-mail: info@geogrourpnw.com
Description
Bellevue, WA 98005
Blow Counts
N
Relative
Density, %
Friction Angle
N, degrees Description Blow Counts
N
Unconfined
Strength qu,
tsf
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100PLASTICITY INDEX (%)LIQUID LIMIT (%)
CL-ML
CL MH or OH
U-Line
PLASTICITY CHART
FOR SOIL PASSING
NO. 40 SIEVE
7
4
CH
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
ML
A-Line
ML or OL
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
LOGGED BY GD LOG DATE:9/30/2022 GROUND ELEV.181 feet +/-
DEPTH SAMPLE Water
ft. USCS SOIL DESCRIPTION No. % COMMENTS
1
2
3
4
5
6
7
LOGGED BY GD LOG DATE:9/30/2022 GROUND ELEV.169 feet +/-
DEPTH SAMPLE Water
ft. USCS SOIL DESCRIPTION No. % COMMENTS
1
2
3
4
5
6
7
JOB NO.G-5204 DATE 10/26/22 APPEND.A2
HAND-AUGER BORING: HA-1
OTHER TESTS/
HAND-AUGER BORING: HA-2
OTHER TESTS/
Total depth = 5.8 feet, auger refusal on cobbles/rocks.
No groundwater encountered.
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
Silty SAND, dark brown, loose, damp to moist;
with trace organics
(disturbed, weathered bedrock)
-cobbles/rocks encountered at approx. 5.8' of
depth.
S1
S1
-Probe 25" at 0'
BACKYARD DECK - RESIDENTIAL LOT
212 S 20TH PL
RENTON, WASHINGTON 98055
HAND AUGER BORING LOGS
SM
-Probe 1" at 0.6'
-Probe 8" at 1.5'
-Probe 48" at 0'
-Probe 30" at 2.5'
S2
Total depth = 2.5 feet
No groundwater encountered.
Patchy grass underlain with:
SM
Exposed soil surface underlain with:
-Probe 0" at 2.0'
-Probe 42" at 4.3'
-Probe 18" at 5.8'
8.5
Silty SAND, grayish brown, loose to very dense, dry to damp;
with some oxidation staining/mottling, some subrounded gravel and
trace organics at surface
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
APPENDIX B
G-5204
SLOPE STABILITY ANALYSIS DATA
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
2.6272.627
2000.00 lbs/ft2
2.6272.627
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+260240220200180160140-40 -20 0 20 40 60 80 100 120 140
Analysis Description
Company GEO Group Northwest, Inc.Scale 1:240Drawn By Garrett Dean
File NameG-5204 Lang Profile A Static [With House Loads only].slimDate10/14/2022, 2:27:14 PM
Project
Lang Slope Stability
SLIDEINTERPRET 7.038
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Slide Analysis Information
Lang Slope Stability
Project Summary
G-5204 Lang Profile A Static [With House Loads only]File Name:
7.038Last saved with Slide version:
Lang Slope StabilityProject Title:
Garrett DeanAuthor:
GEO Group Northwest, Inc.Company:
10/14/2022, 2:27:14 PMDate Created:
General Settings
Imperial UnitsUnits of Measurement:
daysTime Units:
inches/hourPermeability Units:
Left to RightFailure Direction:
StandardData Output:
20Maximum Material Properties:
20Maximum Support Properties:
Analysis Options
VerticalSlices Type:
Analysis Methods Used
Bishop simplified
Janbu simplified
50Number of slices:
0.005Tolerance:
75Maximum number of iterations:
YesCheck malpha < 0.2:
YesCreate Interslice boundaries at intersections
with water tables and piezos:
1Initial trial value of FS:
YesSteffensen Iteration:
Groundwater Analysis
Lang Slope Stability : Page 1 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House Loads only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Water SurfacesGroundwater Method :
62.4Pore Fluid Unit Weight [lbs/ft3]:
YesUse negative pore pressure cutoff:
0Maximum negative pore pressure [psf]:
NoneAdvanced Groundwater Method:
Random Numbers
10116Pseudo-random Seed:
Park and Miller v.3Random Number Generation Method:
Surface Options
CircularSurface Type:
Grid SearchSearch Method:
10Radius Increment:
DisabledComposite Surfaces:
Invalid SurfacesReverse Curvature:
Not DefinedMinimum Elevation:
3Minimum Depth [ft]:
Not DefinedMinimum Area:
Not DefinedMinimum Weight:
Seismic
NoAdvanced seismic analysis:
NoStaged pseudostatic analysis:
Loading
1 Distributed Load present
Distributed Load 1
ConstantDistribution:
2000Magnitude [psf]:
VerticalOrientation:
Material Properties
Lang Slope Stability : Page 2 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House Loads only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
ConcreteWeathered Bedrock (Very Dense )Weathered, Disturbed BedrockProperty
Color
Infinite strengthMohr-CoulombMohr-CoulombStrength Type
150140110Unit Weight [lbs/ft3]
5000Cohesion [psf]
4530Friction Angle [deg]
NoneNoneNoneWater Surface
000Ru Value
List Of Coordinates
Distributed Load
YX
17630.3
17631.7888
External Boundary
Lang Slope Stability : Page 3 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House Loads only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1400
140100
149100
14980.2
15079.1
15276.9
15474.6
15672.4
15870.3
16068.2
16266.5
16464.2
16662.1
16860.1
169.359.4
169.859
170.0558.5
170.358
17358
17356
171.356
17254.5
17449.7
17644.4
177.531.3
177.55230.8
17826.5
179.818
18017.4
1827.4
183.70
1810
1790
1780
175.7110
Material Boundary
YX
171.356
169.90656
16956
16957.2201
16958
170.358
Material Boundary
Lang Slope Stability : Page 4 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House Loads only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1810
1794.563
1777.5
172.520
175.523
17626.6
174.938.5
174.442.742
17347.488
171.751.134
17054.574
168.956
168.957.2201
168.958
168.0558.5
16860.1
Material Boundary
YX
177.55230.8
17730.8
17730.3
17630.3
17631.8
17731.8
17731.3
177.531.3
Lang Slope Stability : Page 5 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House Loads only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
2.3912.391
1600.00 lbs/ft
1600.00 lbs/ft 1600.00 lbs/ft 1600.00 lbs/ft 1600.00 lbs/ft
2000.00 lbs/ft2
2.3912.391
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+260240220200180160140-40 -20 0 20 40 60 80 100 120 140
Analysis Description
Company GEO Group Northwest, Inc.Scale 1:240Drawn By Garrett Dean
File NameG-5204 Lang Profile A Static [With House & Deck Loads].slimDate10/14/2022, 2:27:14 PM
Project
Lang Slope Stability
SLIDEINTERPRET 7.038
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Slide Analysis Information
Lang Slope Stability
Project Summary
G-5204 Lang Profile A Static [With House & Deck Loads]File Name:
7.038Last saved with Slide version:
Lang Slope StabilityProject Title:
Garrett DeanAuthor:
GEO Group Northwest, Inc.Company:
10/14/2022, 2:27:14 PMDate Created:
General Settings
Imperial UnitsUnits of Measurement:
daysTime Units:
inches/hourPermeability Units:
Left to RightFailure Direction:
StandardData Output:
20Maximum Material Properties:
20Maximum Support Properties:
Analysis Options
VerticalSlices Type:
Analysis Methods Used
Bishop simplified
Janbu simplified
50Number of slices:
0.005Tolerance:
75Maximum number of iterations:
YesCheck malpha < 0.2:
YesCreate Interslice boundaries at intersections
with water tables and piezos:
1Initial trial value of FS:
YesSteffensen Iteration:
Groundwater Analysis
Lang Slope Stability : Page 1 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Water SurfacesGroundwater Method :
62.4Pore Fluid Unit Weight [lbs/ft3]:
YesUse negative pore pressure cutoff:
0Maximum negative pore pressure [psf]:
NoneAdvanced Groundwater Method:
Random Numbers
10116Pseudo-random Seed:
Park and Miller v.3Random Number Generation Method:
Surface Options
CircularSurface Type:
Grid SearchSearch Method:
10Radius Increment:
DisabledComposite Surfaces:
Invalid SurfacesReverse Curvature:
Not DefinedMinimum Elevation:
3Minimum Depth [ft]:
Not DefinedMinimum Area:
Not DefinedMinimum Weight:
Seismic
NoAdvanced seismic analysis:
NoStaged pseudostatic analysis:
Loading
1 Distributed Load present
Distributed Load 1
ConstantDistribution:
2000Magnitude [psf]:
VerticalOrientation:
5 Line Loads present
Line Load: 1
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 2
270Angle from horizontal [deg]:
1600Magnitude:
Lang Slope Stability : Page 2 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Line Load: 3
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 4
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 5
270Angle from horizontal [deg]:
1600Magnitude:
Material Properties
Weathered,
Disturbed
Bedrock
Property
Color
Mohr-
CoulombStrength Type
110Unit Weight [lbs/ft3]
0Cohesion [psf]
30Friction Angle [deg]
NoneWater Surface
0Ru Value
List Of Coordinates
Distributed Load
YX
17630.3
17631.7888
External Boundary
Lang Slope Stability : Page 3 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1400
140100
149100
14980.2
15079.1
15276.9
15474.6
15672.4
15870.3
16068.2
16266.5
16464.2
16662.1
16860.1
169.359.4
169.859
170.0558.5
170.358
17358
17356
171.356
17254.5
17449.7
17644.4
177.531.3
177.55230.8
17826.5
179.818
18017.4
1827.4
183.70
1810
1790
1780
175.7110
Material Boundary
YX
171.356
169.90656
16956
16957.2201
16958
170.358
Material Boundary
Lang Slope Stability : Page 4 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1810
1794.563
1777.5
172.520
175.523
17626.6
174.938.5
174.442.742
17347.488
171.751.134
17054.574
168.956
168.957.2201
168.958
168.0558.5
16860.1
Material Boundary
YX
177.55230.8
17730.8
17730.3
17630.3
17631.8
17731.8
17731.3
177.531.3
Lang Slope Stability : Page 5 of 5
SLIDE 7.038
G-5204 Lang Profile A Static [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
1.8441.844
2000.00 lbs/ft2
1.8441.844
0.24
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+260240220200180160140-40 -20 0 20 40 60 80 100 120 140
Analysis Description
Company GEO Group Northwest, Inc.Scale 1:240Drawn By Garrett Dean
File NameG-5204 Lang Profile A Seismic [With House Loads Only].slimDate10/14/2022, 2:27:14 PM
Project
Lang Slope Stability
SLIDEINTERPRET 7.038
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Slide Analysis Information
Lang Slope Stability
Project Summary
G-5204 Lang Profile A Seismic [With House Loads Only]File Name:
7.038Last saved with Slide version:
Lang Slope StabilityProject Title:
Garrett DeanAuthor:
GEO Group Northwest, Inc.Company:
10/14/2022, 2:27:14 PMDate Created:
General Settings
Imperial UnitsUnits of Measurement:
daysTime Units:
inches/hourPermeability Units:
Left to RightFailure Direction:
StandardData Output:
20Maximum Material Properties:
20Maximum Support Properties:
Analysis Options
VerticalSlices Type:
Analysis Methods Used
Bishop simplified
Janbu simplified
50Number of slices:
0.005Tolerance:
75Maximum number of iterations:
YesCheck malpha < 0.2:
YesCreate Interslice boundaries at intersections
with water tables and piezos:
1Initial trial value of FS:
YesSteffensen Iteration:
Groundwater Analysis
Lang Slope Stability : Page 1 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House Loads Only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Water SurfacesGroundwater Method :
62.4Pore Fluid Unit Weight [lbs/ft3]:
YesUse negative pore pressure cutoff:
0Maximum negative pore pressure [psf]:
NoneAdvanced Groundwater Method:
Random Numbers
10116Pseudo-random Seed:
Park and Miller v.3Random Number Generation Method:
Surface Options
CircularSurface Type:
Grid SearchSearch Method:
10Radius Increment:
DisabledComposite Surfaces:
Invalid SurfacesReverse Curvature:
Not DefinedMinimum Elevation:
3Minimum Depth [ft]:
Not DefinedMinimum Area:
Not DefinedMinimum Weight:
Seismic
NoAdvanced seismic analysis:
NoStaged pseudostatic analysis:
Loading
0.24Seismic Load Coefficient (Horizontal):
1 Distributed Load present
Distributed Load 1
ConstantDistribution:
2000Magnitude [psf]:
VerticalOrientation:
Material Properties
Lang Slope Stability : Page 2 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House Loads Only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
ConcreteWeathered Bedrock (Very Dense )Weathered, Disturbed BedrockProperty
Color
Infinite strengthMohr-CoulombMohr-CoulombStrength Type
150140110Unit Weight [lbs/ft3]
5000Cohesion [psf]
4530Friction Angle [deg]
NoneNoneNoneWater Surface
000Ru Value
List Of Coordinates
Distributed Load
YX
17630.3
17631.7888
External Boundary
Lang Slope Stability : Page 3 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House Loads Only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1400
140100
149100
14980.2
15079.1
15276.9
15474.6
15672.4
15870.3
16068.2
16266.5
16464.2
16662.1
16860.1
169.359.4
169.859
170.0558.5
170.358
17358
17356
171.356
17254.5
17449.7
17644.4
177.531.3
177.55230.8
17826.5
179.818
18017.4
1827.4
183.70
1810
1790
1780
175.7110
Material Boundary
YX
171.356
169.90656
16956
16957.2201
16958
170.358
Material Boundary
Lang Slope Stability : Page 4 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House Loads Only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1810
1794.563
1777.5
172.520
175.523
17626.6
174.938.5
174.442.742
17347.488
171.751.134
17054.574
168.956
168.957.2201
168.958
168.0558.5
16860.1
Material Boundary
YX
177.55230.8
17730.8
17730.3
17630.3
17631.8
17731.8
17731.3
177.531.3
Lang Slope Stability : Page 5 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House Loads Only].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
1.7481.748
1600.00 lbs/ft
1600.00 lbs/ft 1600.00 lbs/ft 1600.00 lbs/ft 1600.00 lbs/ft
2000.00 lbs/ft2
1.7481.748
0.24
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+260240220200180160140-40 -20 0 20 40 60 80 100 120 140
Analysis Description
Company GEO Group Northwest, Inc.Scale 1:240Drawn By Garrett Dean
File NameG-5204 Lang Profile A Seismic [With House & Deck Loads].slimDate10/14/2022, 2:27:14 PM
Project
Lang Slope Stability
SLIDEINTERPRET 7.038
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Slide Analysis Information
Lang Slope Stability
Project Summary
G-5204 Lang Profile A Seismic [With House & Deck Loads]File Name:
7.038Last saved with Slide version:
Lang Slope StabilityProject Title:
Garrett DeanAuthor:
GEO Group Northwest, Inc.Company:
10/14/2022, 2:27:14 PMDate Created:
General Settings
Imperial UnitsUnits of Measurement:
daysTime Units:
inches/hourPermeability Units:
Left to RightFailure Direction:
StandardData Output:
20Maximum Material Properties:
20Maximum Support Properties:
Analysis Options
VerticalSlices Type:
Analysis Methods Used
Bishop simplified
Janbu simplified
50Number of slices:
0.005Tolerance:
75Maximum number of iterations:
YesCheck malpha < 0.2:
YesCreate Interslice boundaries at intersections
with water tables and piezos:
1Initial trial value of FS:
YesSteffensen Iteration:
Groundwater Analysis
Lang Slope Stability : Page 1 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Water SurfacesGroundwater Method :
62.4Pore Fluid Unit Weight [lbs/ft3]:
YesUse negative pore pressure cutoff:
0Maximum negative pore pressure [psf]:
NoneAdvanced Groundwater Method:
Random Numbers
10116Pseudo-random Seed:
Park and Miller v.3Random Number Generation Method:
Surface Options
CircularSurface Type:
Grid SearchSearch Method:
10Radius Increment:
DisabledComposite Surfaces:
Invalid SurfacesReverse Curvature:
Not DefinedMinimum Elevation:
3Minimum Depth [ft]:
Not DefinedMinimum Area:
Not DefinedMinimum Weight:
Seismic
NoAdvanced seismic analysis:
NoStaged pseudostatic analysis:
Loading
0.24Seismic Load Coefficient (Horizontal):
1 Distributed Load present
Distributed Load 1
ConstantDistribution:
2000Magnitude [psf]:
VerticalOrientation:
5 Line Loads present
Line Load: 1
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 2
270Angle from horizontal [deg]:
1600Magnitude:
Lang Slope Stability : Page 2 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Line Load: 3
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 4
270Angle from horizontal [deg]:
1600Magnitude:
Line Load: 5
270Angle from horizontal [deg]:
1600Magnitude:
Material Properties
Weathered,
Disturbed
Bedrock
Property
Color
Mohr-
CoulombStrength Type
110Unit Weight [lbs/ft3]
0Cohesion [psf]
30Friction Angle [deg]
NoneWater Surface
0Ru Value
List Of Coordinates
Distributed Load
YX
17630.3
17631.7888
External Boundary
Lang Slope Stability : Page 3 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1400
140100
149100
14980.2
15079.1
15276.9
15474.6
15672.4
15870.3
16068.2
16266.5
16464.2
16662.1
16860.1
169.359.4
169.859
170.0558.5
170.358
17358
17356
171.356
17254.5
17449.7
17644.4
177.531.3
177.55230.8
17826.5
179.818
18017.4
1827.4
183.70
1810
1790
1780
175.7110
Material Boundary
YX
171.356
169.90656
16956
16957.2201
16958
170.358
Material Boundary
Lang Slope Stability : Page 4 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
YX
1810
1794.563
1777.5
172.520
175.523
17626.6
174.938.5
174.442.742
17347.488
171.751.134
17054.574
168.956
168.957.2201
168.958
168.0558.5
16860.1
Material Boundary
YX
177.55230.8
17730.8
17730.3
17630.3
17631.8
17731.8
17731.3
177.531.3
Lang Slope Stability : Page 5 of 5
SLIDE 7.038
G-5204 Lang Profile A Seismic [With House & Deck Loads].slim GEO Group Northwest, Inc. 10/14/2022, 2:27:14 PM
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
APPENDIX C
G-5204
USDA SOIL MAPPING & CLASSIFICATION
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/24/2022
Page 1 of 352565005256550525660052566505256700525675052568005256850525690052569505256500525655052566005256650525670052567505256800525685052569005256950559080559130559180559230559280559330559380
559080 559130 559180 559230 559280 559330 559380
47° 27' 47'' N 122° 12' 58'' W47° 27' 47'' N122° 12' 42'' W47° 27' 33'' N
122° 12' 58'' W47° 27' 33'' N
122° 12' 42'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,210 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 18, Sep 8, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 6, 2020—Jul 20,
2020
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/24/2022
Page 2 of 3
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
BeC Beausite gravelly sandy loam,
6 to 15 percent slopes
13.0 51.4%
BeD Beausite gravelly sandy loam,
15 to 30 percent slopes
11.3 44.4%
Pu Puget silty clay loam 1.1 4.2%
Totals for Area of Interest 25.3 100.0%
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/24/2022
Page 3 of 3
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
King County Area, Washington
BeD—Beausite gravelly sandy loam, 15 to 30 percent slopes
Map Unit Setting
National map unit symbol: 1hmst
Elevation: 0 to 1,500 feet
Mean annual precipitation: 30 to 50 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 160 to 220 days
Farmland classification: Not prime farmland
Map Unit Composition
Beausite and similar soils:95 percent
Minor components:5 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Beausite
Setting
Parent material:Till over residuum from sandstone
Typical profile
H1 - 0 to 6 inches: gravelly ashy sandy loam
H2 - 6 to 19 inches: gravelly ashy sandy loam
H3 - 19 to 38 inches: very gravelly sandy loam
H4 - 38 to 42 inches: bedrock
Properties and qualities
Slope:15 to 30 percent
Depth to restrictive feature:More than 80 inches; 24 to 40 inches to
lithic bedrock
Drainage class:Well drained
Capacity of the most limiting layer to transmit water
(Ksat):Moderately high to high (0.57 to 1.98 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water capacity:Low (about 3.5 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: C
Forage suitability group: Droughty Soils (G002XF403WA)
Other vegetative classification: Droughty Soils (G002XF403WA)
Hydric soil rating: No
Minor Components
Norma
Percent of map unit:3 percent
Map Unit Description: Beausite gravelly sandy loam, 15 to 30 percent slopes---King County
Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/6/2020
Page 1 of 2
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
Landform:Depressions
Hydric soil rating: Yes
Seattle
Percent of map unit:2 percent
Landform:Depressions
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 16, Jun 4, 2020
Map Unit Description: Beausite gravelly sandy loam, 15 to 30 percent slopes---King County
Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/6/2020
Page 2 of 2
EXHIBIT 4
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2