HomeMy WebLinkAboutGEO2021-00088 BLD2021-01218, 01219 - BLD Engineering / Geo-tech Reports - 8/4/2021 2_02 I -OCxOE)E�
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earth science & geotechnical engineering
4809 Pacific Hwy. E. I Fife, Washington 98424 1 253.896.1011 1 www. georesources.rocks
November 2, 2020
Mr.Jim Williams RECEIVED
7545 East Juneau Court
Port Orchard,Washington 98366 AUG 0 4 2021
(360)509-7138
Jim75james@icloud.com 615 W. Alder Street
Geotechnical Engineering Report
Proposed Single-Family Residence
265 East Victor Road
Mason County,Washington
PN: 122213190031
Doc ID:WilliamsJ.EVictorRd.RG
PLANNING
INTRODUCTION
This geotechnical engineering report presents the results of our geotechnical assessment for
the proposed single-family residence to be constructed at 265 East Victor Road in the Victor area of
Mason County, Washington. The general location of the site is shown on the Site Location Map,
Figure 1.
Our understanding of the project is based on our discussions with you, our September 28,
2020 site visit, our review of publicly available soils data, our past experience in the area, and our
understanding of the Mason County Development Codes. The existing site configuration is shown on
the attached Site & Exploration Plan, Figure 2.
We understand that you propose to construct a new single-family and driveway at the site.
Because of the height and steepness of the slopes on and in the area of the site, Mason County is
requiring an assessment be completed to address their critical areas ordinance (MCC 8.52.140). The
code requires a geotechnical report with slope stability modeling be completed because the slopes
across the site and within the vicinity of the site are steeper than 40 percent. A copy of the Mason
County Geotechnical Report Checklist is attached at the end of this report.
SCOPE
As discussed above, because of the proximity of the proposed development to the steep
slopes on the site, Mason County is requiring a Geotechnical Report in order to address the geologic
hazards at the site. As such, our scope of work meets the performance standards as outlined in the
Mason County Development Codes and typical requirements that includes the following:
1. Reviewing the available geologic, hydrogeologic and geotechnical data for the site area;
2. Exploring surface and subsurface conditions by reconnoitering the site and monitoring
the excavation of four test pits to depths of about 6 feet below existing at select
locations at the site;
3. Describing surface and subsurface conditions, including soil type, depth to groundwater,
and estimate of seasonal high groundwater levels;
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4. Addressing the appropriate criteria for geologic hazards per the current MCC Critical
Area Ordinance Title 8.52.140, including recommended buffers and setbacks, as
appropriate;
5. Evaluating the global stability of site using the computer program SLIDE 2 by Rocscience
for the proposed site conditions to meet Mason County requirements;
6. Providing geotechnical conclusions and recommendations regarding site grading
activities including: site preparation, subgrade preparation, fill placement criteria,
suitability of on-site soils for use as structural fill, temporary and permanent cut and fill
slopes,and drainage and erosion control measures;
7. Providing recommendation for seismic design parameters, including 2015 IBC soil profile
type;
8. Providing geotechnical conclusions regarding foundations, including shallow foundation
parameters, floor slab support and design criteria, bearing capacity, and subgrade
modulus as appropriate;
9. Providing recommendation for subgrade walls, including lateral earth pressures and
applicable seismic surcharges;
10. Providing our opinion about the feasibility of on-site infiltration in accordance with the
2005 Stormwater Management Manual for Western Washington (SWMMWW), including a
preliminary design infiltration rate based on grain size data,as applicable;
11. Providing recommendations for erosion and sediment control during wet weather
grading and construction; and,
12. Preparing this written Geotechnical Engineering Report summarizing our site observations
and conclusions, addressing the Mason County Critical Areas and Stormwater
Management requirements, and providing our geotechnical recommendations and
design criteria,along with the supporting data for the proposed site development.
The above scope of work was completed in accordance with our Proposal for Engineering
Services dated August 28,2020. We received email authorization to proceed from you the same day.
SITE CONDITIONS
Surface Conditions
As stated above, the parcel is located at 265 East Victor Road in the Victor area of Mason
County, Washington. The parcel is situated within an area of existing rural residential development.
The parcel is irregular in shape and measures approximately 200 to 260 feet wide (north to south)
by approximately 450 to 540 feet long (east to west), and encompasses approximately 2.39 acres.
The parcel is bounded by an undeveloped parcel to the north, existing single-family residences to
the east and south, and by East Victor Road to the west.
According to topographic information obtained from the Mason County Public GIS website
and generally confirmed during our field observations, the ground surface at the site generally
slopes down to from east to west. The eastern half of the site is generally steeper than the western
half, and has slopes of about 35 percent. The western half of the site has slopes of about 20
percent. The site appears to encompass a large historic drainage that is oriented to flow roughly
east to west. The drainage, located in the northeastern portion of the site has side slopes of about
27 percent, with about 10 to 30 feet side slopes. Total topographic relief of the site is on the order
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of 75 feet. The site conditions and topography of the site are shown on the Site Vicinity Map, Figure
3.
Portions of the parcel were cleared prior to our site visits. The central and east-central
portions of the site were cleared of trees and stripped of vegetation. Around the perimeter of the
site, vegetation mainly consisted of a moderately dense stand of coniferous and deciduous trees
with a dense understory of native and invasive plants and shrubs.
Site Soils
The USDA Natural Resource Conservation Service (NRCS)Web Soil Survey for Mason County
maps the site as being underlain by Alderwood gravelly sandy loam (Ab) and Everett very gravelly
sandy loam (Eh)soils. The Alderwood soils underly the southeastern portion of the site, are derived
from glacial drift and/or glacial outwash over dense glaciomarine deposits, form on slopes of 8 to 15
percent, are considered to have a "moderate" erosion hazard when exposed, and are included in
hydrologic soils group B. The Everett soils are mapped in the majority of the site, are derived from
sandy and gravelly glacial outwash,form on slopes of 8 to 15 percent, is considered to have a "slight
to moderate"erosion hazard when exposed, and is included in hydrologic soils group A. An excerpt
of the NRCS soil map for the area of interest is included as Figure 4.
Site Geology
The Geologic Map of the Belfair 7.5-minute Quadrangles, Mason, Kitsap, and Pierce Counties,
Washington by Polenz et Al., (2009) indicates that the site is underlain Vashon recessional lake-
marginal outwash (Qgol). The recessional lake marginal outwash soils generally consist of gravel,
sand, and localized fines that were formed by proximal reworking of upslope units. These soils were
deposited by the recessional continental ice mass and are considered to be normally consolidated.
The outwash soils generally have moderate strength and compressibility characteristics where
undisturbed. Because of the variable nature of the soils, infiltration characteristics are also variable
depending on the composition of the soils. An excerpt of the above referenced geologic map is
attached as Figure 5.
The Washington Department of Natural Resources Landslide Inventory map does not extend
to the site vicinity. However, the site is designated by the DOE Coastal Zone Atlas as "stable." An
excerpt from the Coastal Atlas map for the site and adjacent areas is attached as Figure 6.
The Relative Slope Stability of the Southern Hood Canal Area, Washington map by Smith et Al.,
(1977) maps that the site as having areas classified as Class 1, which indicates that the area is
believed to be stable. An excerpt of the above referenced map is attached as Figure 7.
Subsurface Explorations
On September 28, 2020, we visited the site and observed the excavation of four test pits to
depths of about 6 feet below the existing ground surface, logged the subsurface conditions
encountered in each test pit, and obtained representative soil samples.
The specific number, locations, and depths of our test pit explorations were selected based
on the configuration of the proposed development and were adjusted in the field based on
consideration for underground utilities, existing site conditions, site access limitations and
encountered stratigraphy. Representative soil samples obtained from the test pits were placed in
sealed plastic bags and then taken to our laboratory for further examination and testing as deemed
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necessary. Soil densities presented on the logs are based on the difficulty of excavation and our
experience.
The subsurface explorations excavated as part of this evaluation indicate the subsurface
conditions at specific locations only, as actual subsurface conditions can vary across the site.
Furthermore, the nature and extent of such variation would not become evident until additional
explorations are performed or until construction activities have begun. The approximate locations
and numbers of our test pits are shown on the attached Site & Exploration Map, Figure 2. The
indicated locations were determined by taping or pacing from existing site features and reference
points; as such,the locations should only be considered as accurate as implied by the measurement
method. The soils encountered were visually classified in accordance with the Unified Soil
Classification System (USCS) and ASTM D2488. The USCS is included in Appendix A as Figure A-1,
while the descriptive logs of our test pits are included as Figures A-2 and A-3.
Subsurface Conditions
Our test pits encountered relatively uniform subsurface conditions that, in our opinion,
generally confirmed the mapped stratigraphy within the site vicinity. Our explorations encountered
about 0.5 to 0.75 feet of topsoil/rootzone mantling about 1 to 2 feet of bark brown silty sand with
gravel in a medium dense, moist condition. Underlying these surficial soils, we encountered tan
poorly graded sand with silt and gravel in a medium dense, moist condition for the full depth of
exploration. We interpret these soils to be weathered recessional lake-marginal outwash over
unweathered recessional lake-marginal outwash.
Laboratory Testing
Geotechnical laboratory tests were performed on two select samples retrieved from our
explorations to estimate index engineering properties of the soils encountered. Laboratory testing
included visual soil classification per ASTM D2488 and ASTM D2487, moisture content
determinations per ASTM D2216, grain size analyses per ASTM D6913, and No. 200 washes per
ASTM D1140 standard procedures. Test results are included in Appendix B.
Groundwater Conditions
No evidence of regional or perched groundwater was observed at the site at the time of our
explorations. However, we anticipate fluctuations in the local groundwater levels will occur in
response to precipitation patterns, off-site construction activities, and site utilization. Based on our
experience in the area, we anticipate the regional groundwater table is likely many tens of feet
below the existing ground surface. Analysis or modeling of anticipated groundwater levels during
construction is beyond the scope of this report.
CONCLUSIONS
Based on our site observations and data review, it is our opinion that the proposed single-
family residence is feasible from a geotechnical standpoint. While the site appears to meet the
technical criteria of a geologically hazardous area per MCC 8.52.140, based on the results of our
slope stability analysis, the site appears to meet the requirements of a "stable" site. This
Geotechnicol Report should be sufficient and suitable to address the overall stability of the slope in
the area of the proposed residence and driveway.
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Slope Stability Analysis
We analyzed the global and internal slope stability of the existing and proposed slope
geometries using subsurface profile A-A', as indicated on Figure 2. This original cross section was
selected as the most critical section given the height and steepness of the slopes, relative to the
proximity of the proposed development. The cross section and slope stability results using both
static and dynamic conditions are included in Appendix C.
We used the computer program SLIDE 2 from RocScience, 2020, to perform the slope
stability analyses. The computer program SLIDE uses a number of methods to estimate the factor of
safety (FS) of the stability of a slope by analyzing the shear and normal forces acting on a series of
vertical "slices" that comprise a failure surface. Each vertical slice is treated as a rigid body;
therefore, the forces and/or moments acting on each slice are assumed to satisfy static equilibrium
(i.e., a limit equilibrium analysis). The FS is defined as the ratio of the forces available to resist
movement to the forces of the driving mass. A FS of 1.0 means that the driving and resisting forces
are equal; a FS less than 1.0 indicates that the driving forces are greater than the resisting forces
(indicating failure).
We used the Bishop's Method of Circles, per the Mason County Code, to search for the
location of the most critical failure surfaces and their corresponding FS. The most critical surfaces
are those with the lowest FS for a given loading condition, and are therefore the most likely to move.
Our analyses included both static and dynamic loading conditions. For the seismic conditions, the
prescribed surcharge loading of 0.15g was applied in accordance with Section 8.52.140(E) of the
MCRO.
The resulting minimum FS for the existing conditions are 2.8 and 1.7 for static and seismic,
respectively. While the FS for the proposed conditions are 2.0 and 1.7 for static and seismic,
respectively. This indicates that the proposed residence will have factors of safety that meet or
exceed the required 1.5 and 1.1 for the static and seismic conditions. The proposed conditions
include shallow foundations for the building footprint. Based on the global stability analysis, the
slope does not appear to be subject to deep-seated rotational or shallow failures above or below the
residence.
Geologically Hazardous Areas per Mason County Codes of Ordinance 8.52.140
According to the Mason County Resource Ordinance 8.52.140.E,the purpose of the landslide
hazard assessment is to identify areas that present potential dangers to public health and safety, to
prevent the acceleration of natural geological hazards, to address off site environmental impacts,
and to minimize the risk to the property owner or adjacent property owners from development
activities. The County uses the following indicators to determine if a site should be considered as a
Geologically Hazardous Area.
a. Areas with any indications of earth movement such as debris slides, earthflows, slumps
and rock falls.
b.Areas with artificial oversteepened or unengineered slopes, i.e. cuts or fills.
c.Areas with slopes containing soft or potentially liquefiable soils.
d. Areas oversteepened or otherwise unstable as a result of stream incision, stream bank
erosion, and undercutting by wave action.
e. Slopes greater than 15%(8.5 degrees)and having the following:
I. Hillsides intersecting geologic contacts with a relatively permeable
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sediment overlying a relatively impermeable sediment or bedrock(e.g.
sand overlying clay);and
ii. Springs or groundwater seepage.
f. Any area with a slope of forty percent or steeper and with a vertical relief of ten or more
feet except areas composed of consolidated rock. A slope is delineated by establishing
its toe and top and measured by averaging the inclination over atleast ten feet of vertical
relief.
No evidence or indications of earth movement such as debris slides, earthflows, slumps and
rock falls were noted at the site at the time of our site visit. No areas of over-steepened slopes as a
result of wave action, stream incision, or stream bank erosion were observed at the site. No soft or
potentially liquefiable soils are mapped at the site, and the soils encountered in our test pits would
be mapped as soil site class D, and are not prone to liquefaction. There are slopes greater than 15
percent observed to be across the site, however, no adverse geologic contacts were observed and
we do not interpret springs or seepage zones to be in this area. There are no slopes steeper than 40
percent with 10 or more feet of vertical relief.
In addition, the following information may be used as a guide by the County to indicate
areas that have a higher likelihood of meeting the classification criteria above:
a.The areas identified on the Mason County Soil Survey Map as having slopes
greater than 15%.
b.The areas identified on the Coastal Zone Atlas,Volume 9, of Mason County,
Washington as:
I. Unstable- "U"
ii. Unstable Old Slides- "UOS"
iii. Unstable Recent Slides-"URS"
iv. Intermediate Slopes-"I"
v. Modified Slopes-"M"
c.The areas identified as Class 2, 3,4, or 5 of the maps: "Relative Slope Stability of the Southern
Hood Canal Area, Washington", by M. Smith and R.J. Carson, Washington State Department
of Natural Resources, Division of Earth Resources, 1977; and "The Geological Map of North
Central Mason County, Washington", by R.J. Carson, 1976, U.S. Geologic Survey OFR 76-2;
d. Areas mapped as landslide deposits(Map Unit Qls)on the: Geologic map of the Longbranch
7.5-minute quadrangle, Thurston, Pierce, and Mason Counties, Washington, by R. L. Logan, T.
J. Walsh, and Michael Polenz. 1 sheet, scale 1:24,000, 2003; Geologic map of the Squaxin
Island 7.5-minute quadrangle, Mason and Thurston Counties, Washington, by R. L. Logan,
Michael Polenz,T.J.Walsh, and H. W. Schasse. 1 sheet, scale 1:24,000, 2003; Geologic map
of the Shelton 7.5-minute quadrangle, Mason and Thurston Counties, Washington, by H. W.
Schasse, R. L. Logan, Michael Polenz, and T. J. Walsh. 1 sheet, scale 1:24,000, 2003; and
Geologic map of the Summit Lake 7.5-minute quadrangle, Thurston and Mason Counties,
Washington, by R. L. Logan and T.J.Walsh.42 x 36 in. color sheet, scale 1:24,000, 2004.
As previously stated, there are slopes steeper than 15 percent. The site is mapped by the
Coastal Atlas as being"stable." As previously stated, the "Relative Slope Stability of the Southern Hood
Canal Area,Washington"indicates that the site is in an area identified as class 1.
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It is our opinion that site does not meet the technical criteria of a geologically hazardous.
The results of our slope stability analysis also indicates that the site is stable. In our opinion, no
buffers should be required beyond the setbacks required by the IBC building code, discussed below.
Recommend Setback
The Mason County building department will require a setback from slopes steeper than 33
percent in accordance with the 2015 International Building Code (IBC). The 2015 IBC section 1808.7
requires a building setback from slopes that are steeper than 3H:1V (Horizontal:Vertical) unless
evaluated and reduced and/or a structural setback is provided by a licensed geotechnical engineer.
The setback distance is calculated based on the vertical height of the slope. The typical IBC setback
from the top of the slope equals the lesser of one third the height of the slope or 40 feet, while the
typical IBC setback from the toe of the slope equals the lesser of half the height of the slope or 15
feet,whichever is less.
We have been provided with a septic site plan for the proposed development. Based on our
review of the site plan, the septic system and proposed house location are setback in accordance
with Mason County Public Health regulations and the 2015 IBC. Based on the topographic
information obtained from the Mason County Public GIS website, slopes steeper than 3H:1V are
present in the eastern portion of the site. The vertical relief of these slopes are up to 30 feet,
thereby requiring a minimum setback of 10 feet per the IBC.
We understand the proposed residence will be constructed approximately within the central
portion of the site, exceeding the minimum setback from the toe of the slope. Where the proposed
residence is located, slopes are about 20 percent and will likely have a daylight basement
configuration. If the proposed house location changes, we should review the location and provide
revised setback recommendations if required.
Seismic Hazard Areas per Mason County Resource Ordinance 8.52.150
The purpose of the Seismic Hazard Section is to identify areas that present potential dangers
to public health and safety, and to prevent the acceleration of man-made and natural geological
hazards, and to neutralize the risk to the property owner or adjacent properties from development
activities.The following shall be classified as Seismic Hazard Areas:
1. Areas susceptible to ground failure including the following:
a. Areas with geologic faults;
b. Deep road fills and areas of poorly compacted artificial fill;
c. Areas with artificially steepened slopes(i.e. old gravel pits);
d. Postglacial stream, lake or beach sediments;
e. River deltas;
f. Areas designated as potential Landslide Hazard Areas;
g. Bluff areas; and
h. Areas underlain by potentially liquefiable soils.
In addition, the following criteria may be used as a guide by the County to indicate areas that
have a higher likelihood of meeting the classification criteria above:
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a. Areas identified on the Coastal Zone Atlas of Washington, Volume 9, Mason
County as Af,Qal, Qa2, Qvc, Qls, Qos and Qp.
b. Areas identified on the Mason County Soil Survey Map as having slopes greater
than 15 percent.
c. Faults identified on "Map Showing Known or Suspected Faults With Quaternary
Displacement in the Pacific Northwest",A.M. Rogers,T.J.Walsh,W.J. Kockelman and
G.R. Priest, US Geologic Survey, 1996; or described in "Active Faulting
Investigations on the Canyon River Fault Southern Olympic Range, Washington", T.J.
Walsh and K.G. Neal, U.S. Geologic Survey, 1997.
d. Areas underlain by potentially liquefiable soils as shown "Liquefaction
Susceptibility Map of Mason County, Washington" by Stephen P. Palmer,
Sammantha L. Magsino,James L. Poelstra, Eric L. Bilderback, Derek S. Folger, and
Rebecca A. Niggemann,September 2004.
Liquefaction is defined as a reduction or complete loss of soil strength due to an increase in
pore water pressure. The increase in pore water pressure is induced by seismic vibrations.
Liquefaction mainly affects geologically recent deposits of loose, fine-grained sands that are below
the groundwater table. The "Liquefaction Susceptibility Map of Mason County, Washington" maps
the site as a low risk for liquefaction. Based on the density and nature of the glacially consolidated
soils mapped at the site, it is our opinion that the risk for liquefaction to occur at this site during an
earthquake is negligible. An excerpt of the above referenced map is attached as Figure 8.
No faults are identified on the USGS Quarternary Fault and Fold Database. The site is about
5,200 feet north of the Tacoma Fault Zone and about 11,000 feet east of the Stansberry Lake scarp.
A copy of the map from the Department of Natural Resources Geologic Information Portal showing
the nearby faults is included as Figure 9. Given the distance to the mapped faults it is our opinion
that the site is not located in a Fault Hazard Zone.
Seismic Design
The site is located in the Puget Sound region of western Washington, which is seismically
active. Seismicity in this region is attributed primarily to the interaction between the Pacific,Juan de
Fuca and North American plates. The Juan de Fuca plate is subducting beneath the North American
plate at the Cascadia Subduction Zone (CSZ). This produces both intercrustal (between plates) and
intracrustal (within a plate)earthquakes. In the following sections we discuss the design criteria and
potential hazards associated with the regional seismicity.
Seismic Site Class
Based on our explorations and the subsurface units mapped at the site, we interpret the
structural site conditions to correspond to a seismic Site Class "Y in accordance with the 2015 IBC
documents and American Society of Civil Engineers (ASCE) standard 7-10 Chapter 20 Table 20.3-1.
This is based on anticipated SPT blow counts for the soils encountered. These conditions are
assumed to be representative for the subsurface across the site.
Design parameters
The U.S. Geological Survey (USGS) completed probabilistic seismic hazard analyses (PSHA)
for the entire country in November 1996, which were updated and republished in 2002 and 2008.
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We used the ATC Hazard by Location website to estimate seismic design parameters at the site. Table
1, below,summarizes the recommended design parameters.
TABLE 1:
20151BC Parameters for Design of Seismic Structures
Spectral Response Acceleration(SRA)and Site Short Period 1 Second Period
Coefficients
Mapped SRA SS= 1.410 g S, = 0.565 g
Site Coefficients(Site Class D) Fa= 1.000 F = 1.500
Maximum Considered Earthquake SRA SMs= 1.410 g SM, = 0.848 g
Design SRA Sos= 0.940 g So1 = 0.565 g
Peak Ground Acceleration
The mapped peak ground acceleration(PGA)for this site is 0.584. To account for site class,the
PGA is multiplied by a site amplification factor (FPGA) of 1.0. The resulting site modified peak ground
acceleration (PGAM) is 0.584. In general, estimating seismic earth pressures (kn) by the Mononobe-
Okabe method are taken as 30 to 50 percent of the PGAM, or 0.18g to 0.29g.
Seismic Hazards
Earthquake-induced geologic hazards may include liquefaction, lateral spreading, slope
instability, and ground surface fault rupture. Liquefaction is a phenomenon where there is a
reduction or complete loss of soil strength due to an increase in pore water pressure in soils. The
increase in pore water pressure is induced by seismic vibrations. Liquefaction primary affects
geologically recent deposits of loose, uniformly graded,fine-grained sands and granular silts that are
below the groundwater table. Based on the density and nature of the soils observed on the site, it is
our opinion that the risk of settlement caused by liquefaction during a subduction zone event is
minimal, and no greater than other nearby structures.
Erosion Hazard Areas per Mason County Resource Ordinance 8.52.160
The purpose of the Erosion Hazard Section is to identify areas that present potential dangers
to public health and safety, and to prevent the acceleration of natural geological hazards, and to
neutralize the risk to the property owner from development activities. The following shall be
classified as Erosion Hazard Areas:
Areas in Mason County underlain by soils which are subject to severe erosion when
disturbed. Such soils include, but are not limited to, those for which potential for erosion is
identified in the Soil Survey of Mason County, USDA Soil Conservation Service, 1960, or any
subsequent revisions or addition to this source. These soils include, but are not limited to,
any occurrence of River Wash ("Ra") or Coastal Beaches ("Cg") and the following when they
occur on slopes 15%or steeper;
a.Alderwood gravelly sandy loam ("Ac"and "Ad")
b. Cloquallum silt loam ("Cd")
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c. Harstine gravelly sandy loam ("Hb")
d. Kitsap silt loam ("Kc")
As stated, the site is mapped as being underlain by Ab and Eh soils. The Ab and Eh soils are
listed as having a "slight" and "slight to moderate" erosion hazard when exposed, respectively.
According to Mason County,these soils do not meet the technical criteria of an active erosion hazard
area. Furthermore, normal BMPs required by the 2005 SWMMWW will reduce or mitigate against
the potential for erosion.
Erosion Control
No evidence of surficial raveling or sloughing was observed at the site at the time of our
visits. To manage and reduce the potential erosion at the site, we recommend erosion protection
measures will need to be in place prior to construction activity on the site. Erosion hazards can be
mitigated by applying Best Management Practices(BMPs)outlined in the 2005 SWMMWW.
Weathering, erosion and the resulting surficial sloughing and shallow land sliding are natural
processes that affect slope areas. To manage and reduce the potential for these natural processes,
we recommend the following:
• No drainage of concentrated surface water or significant sheet flow onto or near the slope
area.
• Grading should be limited to providing surface grades that promote surface flows away from
the top of slope to an appropriate discharge location beyond the toe of the slope.
Erosion protection measures should be in place prior to the start of construction activity on
the site and should be maintained throughout construction and until final site stabilization is
established. Where native vegetation is removed, a dense vegetative groundcover, grass lawn, or
native vegetation should be reestablished as soon as feasible. Erosion control Best Management
Practices(BMPs)contained in the adopted 2005 SWMMWW,will be required by the County as part of
your building or site development permit.
Vegetation Management
Removal of trees and vegetation can adversely affect the overall slope stability, however, if
done properly,vegetation management can result in a healthy,well vegetated slope. If it is necessary
to cut or remove trees, the stumps should be left in place to the extent feasible to limit the potential
for exposed soils and erosion.
Where the vegetation or soil is disturbed during grading and construction activities, it should
be restored or mitigated with other erosion control measures until the vegetation is reestablished. It
may be necessary to reseed areas where the vegetation is completely removed or severely damaged.
We recommend obtaining a copy of the WDOE "Vegetation Management. a Guide for Puget
Sound Bluff Property Owners" (93-31) or"Slope Stabilization and Erosion Control Using Vegetation" (DOE
Publication 93-30), available online,for selecting appropriate types of deep-rooting native vegetation
to be used in the permanent revegetation and stabilization of the slope area.
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Shallow Foundation Options
If the location of the proposed development meets the recommended IBC setback distance
without the usage of a structural setback,the residence may be supported using shallow foundation
options. The following paragraphs offer options for shallow foundations for the proposed
development.
Bearing Surface Preparation
We recommend that the spread footings be founded on the medium dense poorly graded
sand with silt and gravel or on structural fill that extends to suitable native soils.
The soil at the base of the excavations should be disturbed as little as possible. All loose,
soft or unsuitable material should be removed. If material is over excavated below a footing it
should be replaced with structural fill, controlled density fill (CDF), or structural concrete. A rat slab
of CDF could be placed after excavation to prevent disturbance of the bearing surface. A
representative from our firm should observe the foundation excavations to determine if suitable
bearing surfaces have been prepared.
5pread Footing Design
We recommend a minimum width of 24 inches for isolated footings and at least 16 inches
for continuous wall footings. All footing elements should be embedded at least 18 inches below
grade for frost protection. Footings founded on the native, undisturbed normally consolidated
poorly graded sand with silt and gravel soils, or on structural fill can be designed using for an
allowable soil bearing capacity of 2,000 psf(pounds per square foot) for combined dead and long-
term live loads. The weight of the footing and any overlying backfill may be neglected. The
allowable bearing value may be increased by one-third for transient loads such as those induced by
seismic events or wind loads. For footings supported on structural fill a 1 H:1 V prism outside the
footing down to the suitable native soils should be maintained. For CDF a 0.5H:1 V prism should be
maintained.
Lateral Load Resistance
Lateral loads may be resisted by friction on the base of footings and floor slabs and as
passive pressure on the sides of footings. We recommend that an allowable coefficient of friction of
0.35 be used to calculate friction between the concrete and the underlying poorly graded sand with
silt and gravel soils. Passive pressure may be determined using an allowable equivalent fluid density
of 350 pcf(pounds per cubic foot). Factors of safety have been applied to these values.
Settlement
We estimate that settlements of footings designed and constructed as recommended will be
less than 1 inch, for the anticipated load conditions, with differential settlements between
comparably loaded footings of 0.5 inch or less over a span of 50 feet. Most of the settlements
should occur essentially as loads are being applied. However, disturbance of the foundation
subgrade during construction could result in larger settlements than predicted.
Floor Slab Support
We anticipate that the proposed single-family residence will utilize a slab-on-grade floors.
Slab-on-grade floors should be supported on the medium dense undisturbed poorly graded sand
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with silt and gravel or on structural fill prepared as described in the "Structural Fill" section of the
report. Areas of old fill material should be evaluated during grading activity for suitability for use as
structural fill, and will likely need to be removed and replaced. Areas of significant organic debris
should also be removed.
We recommend that floor slabs be directly underlain by a minimum 4-inch thick pea gravel
or washed 5/8-inch crushed rock containing less than 2 percent fines. This layer should be placed in
a single lift and compacted to an unyielding condition.
A synthetic vapor retarder is recommended to control moisture migration through the slabs.
This is of particular importance where moisture migration through the slab is an issue, such as
where adhesives are used to anchor carpet or tile to the slab, and where floor slabs bear on the
undisturbed silt soils encountered at the site.
A subgrade modulus of 200 pci (pounds per cubic inch) may be used for floor slab design.
We estimate that settlement of the floor slabs designed and constructed as recommended, will be
0.5 inch or less over a span of 50 feet.
Subgrade/Basement Walls
The lateral pressures against permanent below-grade walls are dependent upon many
factors, including groundwater conditions, method of backfill placement and degree of compaction
(if applicable), backslope, surcharges, the type of backfill soil and/or adjacent native soils, drainage
provisions, and wall flexibility. If the wall is free to yield at the top an amount equal to
approximately 0.001 times the height of the wall,then active earth pressures should be mobilized. If
movement is not allowed because of stiffness or resistance of the wall, the wall should be designed
for at-rest earth pressures. Wall restraint may occur if a rigid structural network is constructed prior
to backfilling. However, if temporary shoring is allowed to yield and the buried permanent walls are
cast against the shoring, the soil adjacent to the walls would be in an active earth pressure
condition.
Because the location of the proposed residence will be on the slope, we understand that it
will likely incorporate subgrade walls to accommodate for the grade change across the footprint of
the structure. We recommend allowable equivalent fluid pressures of 35 pcf be used for the active
condition and 60 pcf for the atrest condition. The equivalent fluid weights given are based on the
assumptions that the ground surface behind the wall is level. The pressures assume that properly
compacted structural fill is used as wall backfill.
We understand that permanent drainage is planned for the below-grade walls to prevent
build-up of hydrostatic pressures. Permanent drainage should consist of either a 1-foot-thick
(minimum) layer of clean, drainage gravel placed against the wall or a geocomposite drain mat
attached to the basement wall face. For either drainage method, the water should be collected in a
perforated, footing drain at the base of the wall. Typical wall backfill and subdrainage
recommendations are shown in Figure 10. Backfill should not be placed and compacted behind a
wall until the wall is capable of supporting lateral pressures. Compaction criteria for areas behind
walls are also presented in Figure 10.
The total active earth pressure should be analyzed for seismic loading conditions using a
dynamic load surcharge of 10R This increment should be applied as a uniform load to the wall and
is consistent with a pseudostatic analysis using the Mononobe-Okabe equation for lateral earth
pressures for a horizontal seismic coefficient of 0.25g. The horizontal seismic coefficient is not
necessarily equivalent to the design peak ground acceleration at the site. The magnitude of this
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coefficient accounts for the fact that the peak ground acceleration is experienced only a few times
within the record of earthquake shaking, and that the actual earthquake ground motion is cyclic in
nature, as opposed to a static force. Values of the horizontal seismic coefficient are typically one-
third to one-half the value of design peak ground acceleration of 0.584g that may be experienced at
the site. Those pressures assume drained conditions behind the wall and a horizontal backfill
surface.
Lateral pressures due to surcharge should be added to the recommended lateral earth
pressures when appropriate. Other lateral pressures due to surcharge loads may be determined as
required. Traffic surcharges should also be included as appropriate. For other surcharge loads,
each case should be analyzed individually;we can provide recommendations as needed.
Permanent Cut and Fill Slopes
Based on our site visits and understanding of the project, we anticipate most of the
earthwork will take place on the slope in the eastern portion of the project. Fill slopes constructed
on grades that are steeper than 5H:1V should be constructed in accordance with Appendix J of the
2015 IBC and should utilize proper keying and benching methods. The benches should be 1.5 times
the width of the equipment used for grading and be a maximum of 3 feet in height. Subsurface
drainage may be required in areas where significant seepage is encountered during grading.
Collected drainage should be directed to an appropriate discharge point. Surface drainage should
be directed away from all slope faces. An excerpt from the IBC Appendix J is included as Figure 11.
Permanent cut or fill slopes in soil should be no steeper than 2H:1V. All permanent slopes
should be protected from erosion as soon as feasible after grading is completed. Typical erosion
control methods per the 2005 SWMMWW should be sufficient for proposed site grading activities.
Additionally, permanent slopes should be planted with a hardy vegetative groundcover, mulched, or
armored with quarry spalls as soon as feasible after grading is completed.
Site Drainage
All ground surfaces, pavements and sidewalks at the site should be sloped away from the
structures. Surface water runoff should be controlled by a system of curbs, berms, drainage swales,
and or catch basins, and conveyed to an appropriate discharge point.
We recommend that footing drains are installed for the building in accordance with the 2015
IBC, Section 1805.4.2, and basement walls (if utilized) have a wall drain as describe above. The roof
drain should not be connected to the footing drain. We recommend material used for footing drains
be of approximately the same quality as "Gravel Backfill for Drains" (WSDOT Standard Specifications
Section 9-03.12(4)). A geotextile separation fabric should be placed between the drainage material and
native/structural fill soils. Recommendations for a footing or wall drain system are presented in Figure
10. For permanent drainage of below-grade walls,the groundwater level should be maintained 2 feet
below the basement finished floor.
Stormwater Infiltration Recommendations
Mason County has adopted the 2005 Stormwater Management Manual for Western
Washington (2005 SWMMWW). Based on our subsurface explorations, onsite infiltration into the tan
poorly graded sand with silt and gravel is feasible per the 2005 Stormwater Management Manual for
Western Washington(SMMWW), located on the western portion of the parcel. We do not recommend
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infiltration on the eastern half of the parcel because the slopes are too steep to be in compliance with
the 2005 SWMMWW.
Volume III, Section 3.3.6 of the 2015 SWMMWW allows for the infiltration rate to be
determined using the soil gradation based on the work done by Massmann. Per Method 2 Soil
Gradation Testing at Full Scale Infiltration Facilities,we recommend a long term design infiltration rate
of 2 inches per hour be used in the native tan poorly graded sand with silt and gravel soils.
Appropriate factors of safety have been applied to this value in accordance with the 2005 SWMMWW.
We recommend that in-situ verification tests be performed at the time of construction to verify the
provided infiltration rate. We recommend all infiltration facilities bee constructed in accordance with
the 2005 SWMMWW.
Construction Considerations
Appropriate design, construction, and maintenance measures will be required to ensure the
infiltration rate can be effectively maintained over time. It should be noted that special care is
required during the grading and construction periods to avoid fine sediment contamination of the
infiltration system. This may be accomplished by using an alternative storm water management
location during construction or leaving the bottom of the systems 1 to 2 feet high, and subsequently
excavating to the finished grade once the driveways are paved and landscaping is installed. All
contractors working on the site (builders and subcontractors) should be advised to avoid "dirty'
stormwater flowing to the site's stormwater system during construction and landscaping. No concrete
trucks should be washed or cleaned in the area around infiltration facilities.
Suspended solids could clog the underlying soil and reduce the infiltration rate. To reduce
potential clogging of the infiltration systems, the infiltration system should not be connected to the
stormwater runoff system until after construction is complete and the site area is landscaped, paved
or otherwise protected. Temporary systems may be utilized through construction. Periodic sweeping
of the paved areas will help extend the life of the infiltration system.
All proposed infiltration facilities should be designed and constructed in accordance with the
2005 SWMMWW. All minimum setback requirements and infeasibility criteria should be considered
prior to the selection, design and location of any stormwater management facility in accordance
with the 2005 SWMMWWW.
EARTHWORK RECOMMENDATIONS
Site Preparation
All areas of the site to be repaired should be stripped of organic surface soils, if present, and
other deleterious materials. We anticipate stripping depths on the order of 1 foot will be necessary
to remove the upper topsoil and organics. Where placement of fill material is required, the stripped
and exposed subgrade areas should be compacted to a firm and unyielding surface prior to
placement of any fill. Excavations for debris removal should be backfilled with structural fill
compacted to the densities described in the "Structural Fill" section of this report. Any utility lines
that are being replaced or abandoned should be removed, and/or plugged or capped, as
appropriate.
We recommend that a member of our staff evaluate the exposed subgrade conditions after
stripping is completed and prior to placement of structural fill and or base coarse material. The
exposed subgrade soil should be probed with a 'h-inch-diameter steel T-probe.
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Any soft, loose, or otherwise unsuitable areas delineated during probing should be
recompacted, if practical, or over-excavated and replaced with structural fill. The depth and extent
of overexcavation should be evaluated by our field representative at the time of construction. Any
areas of old fill material encountered should be evaluated during grading operations to determine if
they need mitigation, recompaction,or removal.
Structural Fill
All material placed as fill associated with mass grading or under building or pavement areas
should be placed as structural fill. The structural fill should be placed in horizontal lifts of
appropriate thickness to allow adequate and uniform compaction of each lift. Fill should be
compacted to at least 95 percent of the MDD.
The appropriate lift thickness will depend on the fill characteristics and the compaction
equipment used. We recommend that the appropriate lift thickness be evaluated by our field
representative during construction, and that our representative be present during site grading
activities to observe the work and perform field density tests,as appropriate.
The suitability of material for use as structural fill will depend on the gradation and moisture
content of the soil. As the amount of fines (material passing US No. 200 sieve) increases, soil
becomes increasingly sensitive to small changes in moisture content and adequate compaction
becomes more difficult to achieve. During wet weather, we recommend use of well-graded sand
and gravel with less than 5 percent(by weight) passing the US No. 200 sieve based on that fraction
passing the 3/4-inch sieve, such as"Gravel Backfill for Walls"(9-03.12(2))or"Bank Run Gravel for Trench
Backfill' (9-03.19). If prolonged dry weather prevails during the earthwork and foundation
installation phase of construction, higher fines content(up to 10 to 12 percent) may be acceptable.
Material placed for structural fill should be free of debris, organic matter,trash, and cobbles
greater than 6-inches in diameter. The moisture content of the fill material should be adjusted as
necessary for proper compaction.
Suitability of On-Site Materials as Fill
The silty sand with gravel soils encountered onsite should be suitable to use as structural fill
material, if used during periods of dry weather. The soils encountered near the location of the
proposed residence are consistent with silty sand (USCS: SM), and likely have a moderate amount
(about 20 to 35 percent) of fines. As the percentage of fines increases, soil becomes increasingly
more sensitive to small changes in moisture content and adequate compaction becomes more
difficult or impossible to achieve. The soils were generally dry to moist at the time of our
explorations. If earthwork occurs during a typical wet season, or if the soils are persistently wet and
cannot be dried due to wet weather conditions,we recommend the use of imported structural fill, as
described above.
We recommend that completed graded-areas be restricted from traffic or protected prior to
wet weather conditions. The graded areas may be protected by paving, placing asphalt-treated
base,a layer of free-draining material such as pit run sand and gravel or clean crushed rock material
containing less than 5 percent fines, or some combination of the above.
Temporary Excavations
All job site safety issues and precautions are the responsibility of the contractor providing
services/work. The following cut/fill slope guidelines are provided for planning purposes only.
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Temporary cut slopes will likely be necessary during grading operations or utility installation. All
excavations at the site associated with confined spaces, such as utility trenches and retaining walls,
must be completed in accordance with local, state, or federal requirements including Washington
Administrative Code (WAC) and Washington Industrial Safety and Health Administration (WISHA).
Excavation,trenching,and shoring is covered under WAC 296-155 Part N. #
Based on WAC 296-155-66401, it is our opinion that the medium dense sands uncovered at
the site would be classified as Type C soils. According to WAC 296-155-66403, for temporary
excavations of less than 20 feet in depth, the side slopes in Type C soils should be sloped at a
maximum inclination of 1.5H:1V or flatter from the toe to top of the slope. All exposed slope faces
should be covered with a durable reinforced plastic membrane during construction to prevent slope
raveling and rutting during periods of precipitation. These guidelines assume that all surface loads
are kept at a minimum distance of at least one half the depth of the cut away from the top of the
slope and that significant seepage is not present on the slope face. Flatter cut slopes will be
necessary where significant raveling or seepage occurs, or if construction materials will be stockpiled
along the slope crest.
Where it is not feasible to slope the site soils back at these inclinations, a retaining structure
should be considered. Retaining structures greater than 4-feet in height(bottom of footing to top of
structure) or that have slopes of greater than 15 percent above them, should be engineered per
Washington Administrative Code(WAC 51-16-080 item 5). This information is provided solely for the
benefit of the owner and other design consultants and should not be construed to imply that
GeoResources assumes responsibility for job site safety. It is understood that job site safety is the
sole responsibility of the project contractor.
LIMITATIONS
We have prepared this revised report for use by Jim Williams and members of the design team
to address code compliance requirements imposed by Mason County. The data used in preparing this
report and this report should be provided to prospective contractors for their bidding or estimating
purposes only. Our report,conclusions and interpretations are based on data from others and limited
site reconnaissance,and should not be construed as a warranty of the subsurface conditions.
Variations in subsurface conditions are possible between the explorations and may also occur
with time. A contingency for unanticipated conditions should be included in the budget and schedule.
Sufficient monitoring, testing and consultation should be provided by our firm during construction to
confirm that the conditions encountered are consistent with those indicated by the explorations, to
provide recommendations for design changes should the conditions revealed during the work differ
from those anticipated, and to evaluate whether earthwork and foundation installation activities
comply with contract plans and specifications. The scope of our services does not include services
related to environmental remediation and construction safety precautions. Our recommendations are
not intended to direct the contractor's methods, techniques, sequences or procedures, except as
specifically described in our report for consideration in design.
Within the limitations of scope, schedule and budget, our services have been executed in
accordance with generally accepted practices in this area at the time this report was prepared. No
other conditions,express or implied,should be understood.
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We appreciate the opportunity to be of service to you on this project. If you have any
questions or require additional services, please contact us.
Respectfully submitted,
GeoResources, LLC
Jon Zhdanov, EIT
Staff Engineer in Training
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Eric W. Heller, PE, LG Keith S. Schembs, LEG
Senior Geotechnical Engineer Principal
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DocID:Williamj.EVictorRd.RG
Attachments: Figure 1:Site Location Map
Figure 2:Site&Exploration Plan
Figure 3:Site Vicinity Map
Figure 4:NRCS Soils Map
Figure 5:Geologic Map
Figure 6:DOE Coastal Atlas
Figure 7:Relative Slope Stability Map
Figure 8:Liquefaction Susceptibility of Mason County
Figure 9:DNR Fault Hazard Map
Figure 10:Typical Wall Drainage and Backfilling
Figure 11:IBC Appendix)Detail
Appendix A:Subsurface Explorations
Appendix B:Laboratory Test Results
Appendix C:Slope Stability
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Site Location Map
Proposed Single-Family Residence
265 East Victor Road
G E 0 R E SOURCES Mason County, Washington
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Excerpt from the Approved Septic Plan prepared by Proposed Single-Family Residence
Thomas Weaver dated March P,2020. 265 East Victor Road
G E O R E S O U R C E S Mason County,Washington
PN:122213190031
earth science&geotechnical engineering
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Site Vicinity Map
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265 East Victor Road
G E O R E S O U R C E S Mason County, Washington
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Map created from Web Soil Survey(http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx)
Soil Type Hydrologic
T Soil Name Parent Material Slopes, % Erosion Hazard Soils Groupis
Alderwood gravelly Glacial drift and/or glacial
Ab sandy loam outwash over dense glaciomarine 8 to 15 Moderate B
deposits
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NRCS Soils Map
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earth science &geotechnital engineering, PN: 1 2221 31 90031
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Excerpt from the Geologic Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap, and Pierce Counties, Washington
by Polenz et Al., (2009)
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Geologic Map
Proposed Single-Family Residence
}' 265 East Victor Road
GE 0 R E S 0 U R C E S Mason County, Washington
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DocID:WiIIiamsj.EVictorRcI.F October 2020 Figure 5
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Slope stability i)
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DOE Coastal Atlas
Proposed Single-Family Residence
265 East Victor Road
G E O R E S O U R C E Mason County, Washington
ci7rtl scicncc &gC AQCnnlcill PN: 1 2221 31 90031
4E00 PAO;Hwy.E. I FiN.WA 98474 1 253.E:46.!011 I w*w. roik%
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Map created from Relative Slope Stability of the Southern Hood Canal Area, Washington by
Mackey Smith and R.J. Carson(1977)
Class 1:Areas believed to be stable
Class 2:Areas believed to be stable under normal conditions
Class 3:Areas inferred to be unstable
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Relative Slope Stability Map
Proposed Single-Family Residence
265 East Victor Road
V E O R E S O U R C E S Mason County, Washington
carrn s.cien,-.e &. ge;aee_chnical eng!ner_nng PN: 1 2221 31 90031
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Map created from Liquefaction Susceptibility Map of Mason County, Washington
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Liquefaction Susceptibility of Mason County
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DNR Fault Hazard Map
Proposed Single-Family Residence
265 East Victor Road
G E O R E S O U R C E S Mason County, Washington
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SLOPED TO DRAIN ELOW GRADE WALL
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(SEE NOTE 3)
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6"MIN ON SIDES OF PIPE; ?
24 BE LQW Z CD
00
� r
c WASHED PEA GRAVEL/CLEAN
a CRUSHED GRAVEL
ERIMETER 1 SUBDRAIN PIPE
Notes
1. Washed pea gravel/crushed rock beneath floor slab could be 6. The subdrain should consist of 4"diameter(minimum),
hydraulically connected to perimeter/subdrain pipe.Use of 1" slotted or perforated plastic pipe meeting the requirements
diameter weep holes as shown is one applicable method.Crushed of AASHTO M 304;1/8-inch maximum slot width;3/16-to 3/8-
gravel should consist of 3/4"minus.Washed pea gravel should inch perforated pipe holes in the lower half of pipe,with
consist of 3/8"to No.8 standard sieve. lower third segment unperforated for water flow,tight joints;
sloped at a minimum of 6"/100'to drain;cleanouts to be
2. Wall backfill should meet WSDOT Gravel Backfll for Walls provided at regular intervals.
Specification 9-03-12(2).
7. Surround subdrain pipe with 8 inches(minimum)of washed
3. Drainage sand and gravel backfill within 18"of wall should be pea gravel(2"below pipe"or 5/8"minus clean crushed gravel.
compacted with hand-operated equipment.Heavy equipment Washed pea gravel to be graded from 3/8-inch to No.8
should not be used for backfill,as such equipment operated near standard sieve.
the wall could increase lateral earth pressures and possibly
damage the wall.The table below presents the drainage sand and 8. See text for floor slab subgrade preparation.
gravel gradation.
4. All wall back fill should be placed in layers not exceeding 4"loose
thickness for light equipment and 8"for heavy equipment and Materials
should be densely compacted.Beneath paved or sidewalk areas, Drainage sand and Gravel 3/4"Nanus Crushed Gravel
compact to at least 95%Modified Proctor maximum density(ASTM: Steve Size x°a sieve sl:e %°_es'ng by
p Wei.'ah ht Wei ht
01557-70 Method Q.In landscaping areas,compact to 90% 4 10D 3 4- too
minimum. No 4 28-56 1/2" 75-100
08 20-50 1 4" 0-25
No 50 3-12 No 100 0-2
5. Drainage sand and gravel may be replaced with a geocomposite No wo o-z Jbywet slewn .— lasuc
core sheet drain placed against the wall and connected to the
subdrain pipe.The geocomposite core sheet should have a
minimum transmissivity of 3.0 gallons/minute/foot when tested
under a gradient of 1.0 according to ASTM 04716.
Not to Scale
Typical Wall Drainage and Backfilling
Proposed Single-Family Residence
265 East Victor Road
G E O f l E J O U R C E S Mason County, Washington
earrn science & geotechnlcal englnecnng PN: 1 2221 31 90031
41109 Par.Pi Hwy.E. I Firm,WA 99424 1 251.896.'011 I vw1*M.grarncrwasac.rorkc
DocID:Williamsj.EVictorRd.F October 2020 Figure 10
Property
Lure
I
or
i
WS but 2 R minimum — _ 510Fe I
and need nol exceed
10 R maximum -I
I
I
Property I
Line
I I
I I �
Cul or FIR
Slaps I Na%aal or
W5 but 2 IL miramuin I Toe of Finish Grade
and need rot excsad ' Slope
20 IL mammum
Interceptor Grain
In (if required)
I
I ~
I
I
Natural or
Finish Grade
TOP OF FILL. FILL SLOPE
•-5 FT OR GREATER
NATURAL SLOPE
i
�Y
f�i
' 2 FT MINIMUM "RFNIO'VE UNSUITABLE
KEY MATERIAL
+J1 I
5
10 FT.MINIMUM
Not to Scale
IBC Appendix J Detail
Proposed Single-Family Residence
265 East Victor Road
GE O R E S O U R C E S Mason County, Washington
earn science gt geolzeOnical englrlecring PN: 122213190031
4804 Faci t Hwy.E I File,WA 94474 1 251AW'01I I ww.w.je0f0UU(C0%.r4tkc
DocID:Wi Ilia msj.EVictorF October 2020 Figure 11
Appendix A
Subsurface Explorations
SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP GROUP NAME
SYMBOL
GRAVEL CLEAN GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL
GRAVEL
GP POORLY-GRADED GRAVEL
COARSE
GRAINED More than 50% GRAVEL GM SILTY GRAVEL
SOILS Of Coarse Fraction WITH FINES
Retained on GC CLAYEY GRAVEL
No.4 Sieve
SAND CLEAN SAND SW WELL-GRADED SAND,FINE TO COARSE SAND
More than 50% SP POORLY-GRADED SAND
Retained on
No.200 Sieve More than 50% SAND SM SILTY SAND
Of Coarse Fraction WITH FINES
Passes SC CLAYEY SAND
No.4 Sieve
SILT AND CLAY INORGANIC ML SILT
FINE CL CLAY
GRAINED
SOILS Liquid Limit ORGANIC OL ORGANIC SILT,ORGANIC CLAY
Less than 50
SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY,ELASTIC SILT
More than 50% CH CLAY OF HIGH PLASTICITY,FAT CLAY
Passes
No.200 Sieve Liquid Limit ORGANIC OH ORGANIC CLAY,ORGANIC SILT
50 or more
HIGHLY ORGANIC SOILS PT PEAT
NOTES: SOIL MOISTURE MODIFIERS:
1. Field classification is based on visual examination of soil Dry- Absence of moisture,dry to the touch
in general accordance with ASTM D2488-90.
Moist- Damp,but no visible water
2. Soil classification using laboratory tests is based on
ASTM D2487-90. Wet- Visible free water or saturated,usually soil is
obtained from below water table
3. Description of soil density or consistency are based on
interpretation of blow count data,visual appearance of
soils,and or test data.
so Unified Soils Classification System
ooe"10' _- Proposed Single-Family Residence
—.011111111111011- [] J' C 265 East Victor Road
G E O f\ E S O U R C E S Mason County, Washington
earn science & geotechnlc l engineering PN: 1 2221 31 90031
4409 Parik Hwy.E I ijfe,Wµ"474 i ]53.896,'011 I craw.apOrnw.,eeec.rorke
DocID:Wi Ilia mj.EVictorRd.F October 2020 Figure A-1
Test Pit TP-1
Location: Central portion of site; near current gravel road
Approximate Elevation: 90 feet(NAVD 88)
Depth(ft) Soil Type Soil Description
0 0.75 - Topsoil/rootzone
0.75 3 SM Dark brown silty SAND with gravel (medium dense, moist)(Weathered Qgol)
3 - 6 SM Brown silty SAND with gravel(medium dense, moist)(Qgol)
Terminated at 6.0 feet below ground surface(BGS).
No caving observed at the time of excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-2
Location: Central portion of site; downhill of proposed drainfield
Approximate Elevation: 80 feet(NAVD 88)
Depth(ft) Soil Type Soil Description
0 - 1 - Topsoil/rootzone
1 - 6 SP-SM Tan poorly graded SAND with silt and gravel (medium dense, moist)(Qgol)
Terminated at 6.0 feet BGS.
No caving observed at the time of excavation.
No groundwater seepage observed at the time of excavation.
Logged by:JZ Excavated on: September 28, 2020
Test Pit Exploration Logs
Proposed Single-Family Residence
,mwo 265 East Victor Road
V E 4 R E S O U R C E S Mason County, Washington
caret science &geotechnical cng,neering PN: 1 2221 31 90031
4R09 Pacific HMy.E. i Ph,WA U474 1 251.896.!*11 i W*W.j00r4cWar9".Igck%
DocID:WiIIiamj.EVictorRd.F October 2020 Figure A-2
Test Pit TP-3
Location: Western portion of site
Approximate Elevation: 70 feet(NAVD 88)
Depth(ft) Soil Type Soil Description
0 - 0.5 - Dark brown
0.5 - 1.5 SM Dark brown silty SAND with gravel (medium dense, moist)(Weathered Qgol)
1.5 - 6 SP-SM Tan poorly graded SAND with silt and gravel(medium dense, moist)(Qgol)
Terminated at 6.0 feet BGS.
No caving observed at the time of excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-4
Location: northeastern portion of site
Approximate Elevation: 95 feet(NAVD 88)
Depth(ft) Soil Type Soil Description
0 0.5 Dark brown
0.5 1.5 SM Dark brown silty SAND with gravel (medium dense, moist)(Weathered Qgol)
1.5 - 6 SP-SM Tan poorly graded SAND with silt and gravel(medium dense, moist)(Qgol)
Terminated at 6.0 feet BGS.
No caving observed at the time of excavation.
No groundwater seepage observed at the time of excavation.
Logged by:JZ Excavated on: September 28, 2020
Test Pit Exploration Logs
Proposed Single-Family Residence
(_ n ((�� 265 East Victor Road
('�
V E V R E S V U R C E S Mason County, Washington
earr'l science & geotechnlcal erngmeering PN: 1 2221 31 90031
4400 Pati6t Hwy.E. I iifP.WA 48424 1 251.896.1471 1 9WNN-jewt urcecrOf4a
DocID:Williamj.EVictorRd.F October 2020T Figure A-3
Appendix B
Laboratory Test Results
Particle Size Distribution Report
S o 0 0
100
I I I I I I I I I I I I I
90
I I I I I I I I I I I I I
I I I I I I I I I I I I I
80
I I I I I I I I I I I I I I
70 I I I I
I I I I I I I I I I I I I I
Z 60
I I I I I I I I I
Z 50 I I I I I I
w I I I I I I I I
W 40
a I I I I I I I I I I I I I I
I I I I I I I I I I I I I
30
I I I I I I I I I I I I
20
I I I I I I I I I I I I I I
I I I I I I I I I I I I I I
10
a?
0 I I I I I
~ y 100 10 1 0.1 0.01 0.001
GRAIN SIZE- mm.
c a %Gravel %Sand %Fines
p � �'+3 Coarse Fine Coarse Medium Fine Silt Clay
0.0 6.7 20.9 7.6 14.6 27.7 22.5
C
@ SIEVE PERCENT SPEC! PASS? Material Description
w SIZE FINER PERCENT (X=NO)
m
o 0 1 100.0 Dark brown silty SAND with gravel(Weathered Qgol)
s .75 93.3
� •� .5 86.0
Atterbera Limits
3125 80.7 PL= NP LL= NV PI= NV
C #4 72.4
w #10 64.8 Coefficients
U �
C #20 58.7 D90= 16.2024 D85= 11.7019 D60= 0.9891
w a) #40 50.2 D50= 0.4204 D30= 0.1422 D15=
f° #60 40.3 D10= Cu= Cc=
0 0
N #100 30.8 Classification
=3 o #200 22.5 USCS= SM AASHTO= A-1-b
m a3
a Remarks
U �
a)
44) — Natural Moisture: 15.9%
a> E
L COY (no specification provided)
O N
.0
o Location: TP-1,S-1
f6 " Sample Number: 100491 Depth: 9"-3' Date: 9/28/20
c
o GeoResources, LLC Client: Mr.Jim Williams
Project: WilliamJ.EVictorRd
U) to
a�
L Fife WA Project No: WilliamJ.EVictorRd Figure B-1
Tested By: JZ Checked By: KSS
Particle Size Distribution Report
000
C C C C C C V N M N
100
I I I I I I I I I I I I I
90
I I I I I I I I I I I I I
I I I I I I I I I I I I I
80
I I I I I I I I I I I I I I
7o I I I
I I I I I I I I I I I I I I
w 60
Z I I I I I I I I I I I I I
LL
Z 50 I I I I I I I I I
w I I I I I I I I I I
w ao
n I I I I I I I I I
I I I I I I I I I I I I I I
30
I I I I I I I I I I I I I
20--
10L t--t-t--t I
02
o I I I
~ M 100 10 1 0.1 0.01 0.001
.� GRAIN SIZE-mm.
c %Gravel %Sand %Fines
p %+3" Coarse Fine Coarse Medium Fine Silt Clay
E > 0.0 5.6 37.7 12.1 15.9 22.7 6.0
c
SIEVE PERCENT SPEC.` PASS? Material Description
w SIZE FINER PERCENT (X=NO)
E o 1 100.0 Tan poorly graded SAND with silt and gravel(Qgol)
s m .75 94.4
3 •2! 5 84.6
Atterber Limits
�" 3125 74.7 0 PL= NP LL= NV Pl= NP
c c #4 56.7
#10 44.6 Coefficients
v
� #20 35.9 D90= 15.8953 D85= 12.9382 D60= 5.2557
w a) #40 28.7 D50= 3.5269 D30= 0.4865 D15= 0.1602
o -0 #60 22.9 D10= 0.1126 Cu= 46.68 Cc= 0.40
y cca #100 13.9 Classification
=3 -0 #200 6.0 USCS= SP-SM AASHTO= A-1-a
a) 2
v>�, a Remarks
U
N
Natural Moisture:3.7%
E
s ca
w Cn (no specification provided)
O N
L
Location: TP-3,S-1
CO " Sample Number: 100492 Depth: 1.5'-6' Date: 9/28/20
� _
= c
GeoResources, LLC Client: Mr.Jim Williams
Project: WilliamJ.EVictorRd
� ca
a�
Fife WA Project No: WilliamJ.EVictorRd Figure B-2
Tested By: JZ Checked By: KSS
Appendix C
Slope Stability
Material Name Color Unit Weight Strength Cohesion Phi
(lbs/ft3) Type (psf) (deg)
Vashon recessional lake- 130 Mohr- 0 35
marginal outwash ® Coulomb
0
N
2.8
O
O
�r
0 100 200 300 400 500 600
Project
Williams].EVictorRd
AnalysrsOesrnpwn Proposed Single-Family Residence-Existing Static
GE O R E S O U R C E S Drawn& )Z Scale 1:800 Company GeoResources, LLC
earth science &geotechnical engineering
809 Pacific Hwy.E. I Fife.WA 98424 1 253.896.1011 1 www.georesources.rock Dafe File Name
11�2�2020 DocID:Wllliams].EVictorRd
DEINTERPRET 9.007
Material Name Color Unit Weight Strength Cohesion Phi
(lbs/ft3) Type (psf) (deg) 0.15
Vashon recessional lake- 130 Mohr- 0 35
marginal outwash Coulomb
O
N
1.7
O
J �
I �
O
0 100 200 300 400 500 600
Project
Williams].EVictorRd
;4
AW"S Oesrnpbon Proposed Single-Family Residence-Existing Dynamic
GE O R E S O U R C E S Drawn By ]Z Scale 1:800 Company GeoResources, LLC
earth science&geotechnical engineering
809 Pacific Hwy.E. i Fife.WA 98424 1 253.896.1011 1 www.georesources.rock Date 11/2/2020 File Name
IDEINTERPRET 9007 DocID:WilliamsJ.EVictorRd
Material Name Color I Unit Weight(Ibs/ft3) Strength Type Cohesion(psf) Phi(deg)
Vashon recessional lake-marginal outwash 130 Mohr-Coulomb 0 35
Wall 150 Mohr-Coulomb 10000 35
C
N
2000.00 Ibs/ft2
o
Z.0
0
0 100 200 300 400 500 600
Project
Williams].EVictorRd
-- Ana"sDescription Proposed Single-Family Residence-Proposed Static
GE O R E S O U R C E S Drawmey JZ Scale 1:800 Company Geollesources, LLC
earth science&geotechnical engineering
809 PaclBc Hwy.E. I Fife,WA 98424 1253.896.1011 I www.georesources.rock Date 11/2/2020 File Name DocID:Williams].EVictorRd
DEINTERPRET 9.007
Material Name Color Unit Weight(Ibs/ft3) Strength Type Cohesion(psf) Phi(deg)
Vashon recessional lake-marginal outwash 130 Mohr-Coulomb 0 35 0.15
Wall 150 Mohr-Coulomb 10000 35
0
N
1.7
2000.00 Ibs/ft2
0
_
0 100 200 300 400 500 600
Project
WilliamsJ.EVictorRd
AnaysisDesv/ption Proposed Single-Family Residence-Proposed Dynamic
GE 0 R E S 0 U R C E S Drawn By �Z Scale 1:800 Company GeoResources, LLC
earth science &geotechnical engineering
809 Pacific Hwy.E. I Fife,WA 99424 1 253.896.1011 1 www.georesuurces.rock Date File Name
11/2/2020 DoCID:WilliamsJ.EVictorRd
DEINTERPRET 9.007
Slide Analysis Information
WilliamJ.EVictorRd.SS
Project Summary
File Name: WilliamJ.EVictorRd.SS.slmd
Slide Modeler Version: 9.007
Project Title: WilliamsJ.EVictorRd
Analysis: Existing - Dynamic
Author: JZ
Company: GeoResources, LLC
Date Created: 11/02/2020
Currently Open Scenarios
Group Name Scenario Name Global Minimum Compute Time
Existing Bishop Simplified: None
Master Scenario 00h:00m:00.65s
Static Bishop Simplified: 00h:00m:00.475s
2.763040
Dynamic Bishop Simplified: 00h:00m:00.479s
1.683640
Proposed 0 Gle/morgenstern-price:
Master Scenario 35.219500 00h:00m:00.557s
Static Bishop Simplified: 00h:00m:00.540s
1.964260
Dynamic Bishop Simplified: 00h:00m:00.496s
1.683550
General Settings
Units of Measurement: Imperial Units
Time Units: days
Permeability Units: feet/second
Data Output: Standard
Master Static Dynamic Master Static Dynamic
Scenario Scenario
Failure Left to Right Right to Left Right to Left Left to Right Right to Left Right to Left
Direction:
Analysis Options
0 Proposed - Master Scenario
WilliamJ.EVictorRd.SS Monday, November 2, 2020
Slices Type: Vertical
Analysis Methods Used
GLE/Morgenstern-Price with interslice force
function (Half Sine)
Number of slices: 50
Tolerance: 0.005
Maximum number of iterations: 75
Check malpha < 0.2: Yes
Create Interslice boundaries at intersections with Yes
water tables and piezos:
Initial trial value of FS: 1
Steffensen Iteration: Yes
All other Scenarios
Slices Type: Vertical
Analysis Methods Used
Bishop simplified
Number of slices: 50
Tolerance: 0.005
Maximum number of iterations: 75
Check malpha < 0.2: Yes
Create Interslice boundaries at intersections with Yes
water tables and piezos:
Initial trial value of FS: 1
Steffensen Iteration: Yes
Groundwater Analysis
All Open Scenarios
Groundwater Method: Water Surfaces
Pore Fluid Unit Weight[lbs/ft3]: 62.4
Use negative pore pressure cutoff: Yes
Maximum negative pore pressure [psf]: 0
Advanced Groundwater Method: None
Random Numbers
All Open Scenarios
Pseudo-random Seed: 10116
Random Number Generation Method: Park and Miller v.3
Surface Options
® Existing - Static
2/6
WilliamJ.EVictorRd.SS Monday, November 2, 2020
Surface Type: Circular
Search Method: Auto Refine Search
Divisions along slope: 20
Circles per division: 10
Number of iterations: 10
Divisions to use in next iteration: 50%
Composite Surfaces: Disabled
Minimum Elevation: Not Defined
Minimum Depth [ft]: 3
Minimum Area: Not Defined
Minimum Weight: Not Defined
All other Scenarios
Surface Type: Circular
Search Method: Auto Refine Search
Divisions along slope: 20
Circles per division: 10
Number of iterations: 10
Divisions to use in next iteration: 50%
Composite Surfaces: Disabled
Minimum Elevation: Not Defined
Minimum Depth: Not Defined
Minimum Area: Not Defined
Minimum Weight: Not Defined
Seismic Loading
Existing - Master Scenario
Advanced seismic analysis: No
Staged pseudostatic analysis: No
® Existing - Static
Advanced seismic analysis: No
Staged pseudostatic analysis: No
® Existing - Dynamic
Advanced seismic analysis: No
Staged pseudostatic analysis: No
Seismic Load Coefficient(Horizontal): 0.15
O Proposed - Master Scenario
Advanced seismic analysis: No
Staged pseudostatic analysis: No
O Proposed - Static
Advanced seismic analysis: No
Staged pseudostatic analysis: No
O Proposed - Dynamic
3/6
William].EVictorRd.SS Monday, November 2, 2020
Advanced seismic analysis: No
Staged pseudostatic analysis: No
Seismic Load Coefficient(Horizontal): 0.15
Loading
Proposed
Distribution: Constant
Magnitude [psf]: 2000
Orientation: Normal to boundary
Materials
Vashon recessional lake-marginal outwash
Color
Strength Type Mohr-Coulomb
Unit Weight [Ibs/ft3] 130
Cohesion [psf] 0
Friction Angle [deg] 35
Water Surface Assigned per scenario
Ru Value 0
Wall
Color ■
Strength Type Mohr-Coulomb
Unit Weight [Ibs/ft3] 150
Cohesion [psf] 10000
Friction Angle [deg] 35
Water Surface Assigned per scenario
Ru Value 0
Materials In Use
Material Existing Static Dynamic Proposed Static Dynamic
Vashon ✓
recessional
lake-marginal
outwash
Wall
Global Minimums
Existing - Master Scenario
Method: bishop simplified
4/6
William].EVictorRd.SS Monday, November 2, 2020
Resisting Moment: -0 lb-ft
Driving Moment: 0 lb-ft
Total Slice Area: 0 ft2
Surface Horizontal Width: 0 ft
Surface Average Height: 0 ft
A Existing - Static
Method: bishop simplified
FS 2.763040
Center: 169.647, 142.343
Radius: 82.549
Left Slip Surface Endpoint: 168.316, 59.804
Right Slip Surface Endpoint: 210.151, 70.414
Resisting Moment: 630004 Ib-ft
Driving Moment: 228011 lb-ft
Total Slice Area: 85.9071 ft2
Surface Horizontal Width: 41.8345 ft
Surface Average Height: 2.0535 ft
Existing - Dynamic
Method: bishop simplified
FS 1.683640
Center: 169.086, 140.244
Radius: 80.503
Left Slip Surface Endpoint: 167.855, 59.751
Right Slip Surface Endpoint: 208.625, 70.120
Resisting Moment: 540033 lb-ft
Driving Moment: 320752 Ib-ft
Total Slice Area: 78.4745 ft2
Surface Horizontal Width: 40.7694 ft
Surface Average Height: 1.92484 ft
Proposed - Master Scenario
Method: g le/morgenstern-price
FS 35.219500
Center: 346.964, 96.223
Radius: 33.782
Left Slip Surface Endpoint: 317.265, 80.125
Right Slip Surface Endpoint: 380.419, 91.536
Resisting Moment: 5.77699e+06 lb-ft
Driving Moment: 164028 lb-ft
Resisting Horizontal Force: 143018 lb
Driving Horizontal Force: 4060.76 lb
Total Slice Area: 1021.98 ft2
Surface Horizontal Width: 63.1543 ft
Surface Average Height: 16.1823 ft
Proposed - Static
Method: bishop simplified
5/6
Wi Ilia mJ.EVictorRd.SS Monday, November 2, 2020
FS 1.964260
Center: 255.714, 91.888
Radius: 18.005
Left Slip Surface Endpoint: 245.693, 76.930
Right Slip Surface Endpoint: 269.246, 80.012
Resisting Moment: 259012 lb-ft
Driving Moment: 131863 lb-ft
Total Slice Area: 80.2472 ft2
Surface Horizontal Width: 23.5524 ft
Surface Average Height: 3.40718 ft
O Proposed - Dynamic
Method: bishop simplified
FS 1.683550
Center: 168.775, 140.764
Radius: 81.076
Left Slip Surface Endpoint: 167.415, 59.699
Right Slip Surface Endpoint: 208.525, 70.101
Resisting Moment: 543731 lb-ft
Driving Moment: 322967 Ib-ft
Total Slice Area: 78.4574 ft2
Surface Horizontal Width: 41.1103 ft
Surface Average Height: 1.90846 ft
6/6
PLANNING
IVMASON COUNT��IVED Submittal Checklist
COMMUNITY SE Geotechnical Report
Building,Planning,Environmental Health, Hath AUG 0 2 2021
Instructions; 615 W. Alder Street
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed
professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County
Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclusion.
Note:Unless specifically documented, this report does not provide compliance to the International Residential Code Sections
R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section 1808.7.1 of the International
Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner /"r r• `�P" �i��ia owtr Parcel# /Z Z Z 131 ?o0 3
Site Address Zt c- AtFaaf t/ii fo,, l2c a.Z
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) 3
(b) A discussion of specific soil types,
Located on page(s) 3-Y
(c) A discussion of ground water conditions,
Located on page(s) if
(d) A discussion of the upslope geomorphology,
+ Located on page(s) 3
(e) A discussion of the location of upland waterbodies and wetlands,
Located on page(s) 3
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records.
Located on page(s) 3
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) r,Z 7-, T, 4 S"
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) & A-Z 4 A-3
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall
be delineated(top, both sides, and toe)on a geologic map of the site.
Located on Map(s) Fj Z
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which
incorporates the details of proposed grade changes.
Located on Map(s) /4j3'p"��r G
(6) A description and results of slope stability analyses performed for both static and seismic loading conditions.
Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of
Circles. The minimum static safety factor is 1.5,the minimum seismic safety factor is 1.1, and the quasi-static
analysis coefficients should be a value of 0.15.
Located on page(s) `_
(7) (a) Appropriate restrictions on placement of drainage features,
Rev. February 2018
Located on page(s /3
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) /VA
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) /S
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 7
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) T
(8) Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies
vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation
removal.
Located on page(s) /0
(9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific
mitigating measures to be implemented during construction to protect the slope from erosion, landslides and
harmful construction methods.
Located on page(s) /0
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) _A02--06 r C
(11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
Located on page(s) /0 / 3
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) /-r
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of
existing and proposed development on the site.
Located on Map(s) f- Z
I, IfiH $ecr T $ZH E_Ootgl' hereby certify under penalty of perjury that I am a civil engineer licensed in the
State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering
geologist licensed in the State of Washington with special knowledge of the local conditions. I also certify that the
e o�Washy Geotechnical Report, dated ftJ&Wv,l(3C(L. 2,2vZc?and entitled
0 &UoTLTLH tq t eAt_ E y.;i G t u e f,(L(NE+ Wc;9T
V meets all the requirements of the Mason County Resource Ordinance,
Geologically Hazardous Areas Section, is complete and true,that the
gi ring eulogist assessment demonstrates conclusively that the risks posed by the
'0 925 N landslide hazard can be mitigated through the included geotechnical
eased Geo\o tt V design recommendations, and that all hazards are mitigated in such a
KEI . SCO T HEMBS manner as to prevent harm to property and public health and safety.
Page 2 of 2
Disclaimer.Mason County does not certify the quality of the work done in this Geotechnical Report.