HomeMy WebLinkAboutGEOtechnical Report - GEO General - 7/10/2024 MASON COUNTY Submittal Checklist
COMMUNITY SERVICES Geotechnical Report
Building,Planning,Environmental Health,Community Health
Instructions:
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 Dr. Young Lee Parcel# 322314100021
Site Address 4480 East State Route 106, Union, Washington
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) pages 3 -5
(b) A discussion of specific soil types,
Located on page(s) page 5
(c) A discussion of ground water conditions,
Located on page(s) page 5
(d) A discussion of the upslope geomorphology,
Located on page(s) pages 2, 7
(e) A discussion of the location of upland waterbodies and wetlands,
Located on page(s) pages 5, 7
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records.
Located on page(s) pages 3 -4, & 7
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Figure 2
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Figure 2
(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) Figure 2
(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) Appendix C
(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) pages 9 - 11
(7) (a) Appropriate restrictions on placement of drainage features,
Rev. February 2018
Located on page(s pages 13, 15-16, Appendix D
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) None proposed
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) None proposed
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) None proposed
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) None proposed
(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) page 16
(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) pages 15-16
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) slope stability analysis, pages 9-11
(11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
Located on page(s) pages 15-16, Appendix D
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) No structure proposed
(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) Figure 2
Keith S. Schembs 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
Geotechnical Report, dated July 10, 2024 , and entitled
Limited Geotechnical Engineering Report,Proposed Driveway and Trailer Pad,4480 East State Route 106,Mason County,Washington
meets all the requirements of the Mason County Resource Ordinance,
Geologically Hazardous Areas Section, is complete and true, that the
assessment demonstrates conclusively that the risks posed by the
landslide hazard can be mitigated through the included geotechnical
design recommendations, and that all hazards are mitigated in such a
(Signature and Stamp) manner as to prevent harm to property and public health and safety.
i
Page 2 of 2
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
G EO RESOU RCES
earth science & geotechnical engineering
4809 Pacific Hwy. E. Fife, Washington 98424 ( 253.896.1011 1 www. georesources.rocks
July 10, 2024
Dr.Young Lee
1879 58t" Street NE
Tacoma, Washington 98422
(252)227-4727
cceanside4444@gmail.com
Limited Geotechnical Engineering Report
Proposed Driveway and Trailer Pad
4480 East State Route 106
Mason County, Washington
PN: 322314100021
Doc ID: LeeY.EStateRoute106.RG
INTRODUCTION
This Limited Geotechnical Engineering Report summarizes our site observations, subsurface
explorations, and laboratory test results, and provides geotechnical conclusions and
recommendations for the proposed driveway and trailer pad to be constructed on the vacant parcel
at 4480 East State Route 106 in the Union area of Mason County, Washington. The general location
of the site is shown on the attached Site Location Map, Figure 1.
Our understanding of the project is based on our conversations with you,James Linsey, and
Jeremy Downs of Soundview Consultants; our April 29 and June 18, 2024 site visits and subsurface
explorations; our understanding of the Mason County (the County) development codes; and our
experience in the site area. The site is currently undeveloped except for a portion of the driveway
that provides access to the residence on the adjacent parcel to the south. The new driveway will
extend off the existing driveway where the existing paved surface crosses the property line. The new
driveway will extend to the north/northwest and will be constructed using a side-cast fill method
resulting in cuts and fills on the order of 4 to 6 feet. Near the beginning of the new driveway, a culvert
will need to be installed in the existing drainage to maintain existing surface water flows. In addition
to replacing the driveway we understand that you proposed to construct a trailer parking pad. We
were not provided with a site plan prior to the preparation of this document.
PURPOSE & SCOPE
The purpose of our services was to evaluate the surface and subsurface conditions near the
proposed driveway/trailer pad as a basis for providing geotechnical recommendations and design
criteria for the proposed development. Specifically,the scope of services for this project included 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
drilling of two borings near the proposed driveway/trailer pad;
3. Describing surface and subsurface conditions, including soil type, and depth to groundwater;
4. Addressing the Mason County Code(MCC)8.52.140.E(5)for Geologic Hazards;
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5. Providing recommendations for seismic design parameters, including 2021 International
Building Code(IBC)site class;
6. Performing a stability analysis of the slopes for the existing and proposed site conditions using
Slide 2 by Rocscience;
7. 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 slopes, and drainage and erosion
control measures;
8. Providing recommendations for retaining walls and/or rockeries that may be required on the
upslope side of the driveway to accommodate grading;
9. Preparing this written Limited Geotechnical Engineering Report summarizing our site
observations and conclusions, and our geotechnical recommendations and design criteria,
along with the supporting data; and,
10. Preparing the Mason County Geotechnica/Engineering Report Checklist.
The above scope of work was summarized in our Proposal for Geotechnica/Engineering Services
dated June l 1,2024. We received authorization to proceed on June 11,2024 from your permitting agent
James Lindsey.
SITE CONDITIONS
Surface Conditions
The site is located at 4480 East State Route 106 in the Union area of Mason County,
Washington. According to the Mason County,WA GIS website,the parcel is approximately rectangular
in shape, measures about 390 to 400 feet wide(north to south) by about 575 to 665 feet long(east to
west) and encompasses approximately 7.13 acres. The site is bounded by single-family residential
development to the north, east and south, and by East State Route 106 to the west. The Skokomish
River delta is located immediately west of East State Route 106.
The site is located at the southwest end of Hood Canal with the west-facing sloping area of
Union, Washington. Based on our review of topographic contours on the Mason County WA GIS
website and as generally confirmed in the field:the site generally slopes up steeply from East State Route
106 at 100 percent to near vertical inclinations for approximately 20 to 75 vertical feet before transitioning
to 25 to 65 percent slopes that continue through the central and eastern portion of the site and offsite to
the east. Total topographic relief across the site is on the order of 280 feet. Existing site conditions and
topography are shown on the attached Site &Exploration Map, Figure 2.
Vegetation across the site generally consists of a dense stand of coniferous and deciduous
trees with a dense to very dense understory of native and invasive shrubs, brush, and ferns. No
evidence of ponded surface water, seeps, or springs were observed in the northern portion of the
parcel at the time of our site visit. The closest upland bodies of water appear to be two wetland areas
located approximately 3,100 feet to the east of the site.These areas are located along the east side of
East McReavy Road. No evidence of soil movement or erosion was observed onsite at the time of our
site visit, however there is an over-steepened portion of the slope west of the paved driveway that
appears to be where fill was placed on the slope in order to facility the original driveway construction.
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Site Soils
The USDA Natural Resource Conservation Service(NRCS)Web Soil Survey maps the site to be
underlain by Alderwood gravelly sandy loam (Ad) soils. An excerpt of the referenced NRCS map for
the site and adjacent areas is attached as Figure 3 and a detailed description of the mapped soil unit
is included below.
• Alderwood gravelly sandy loam (Ad): The Alderwood soils are derived from glacial drift and/or
glacial outwash over dense glaciomarine deposits and form on slopes of 30 to 50 percent.
These soils have a"severe"erosion hazard when exposed and are included in hydrologic soils
group B.
Site Geology
Based on our review of the Geologic Map of the Skokomish Valley and Union 7.5-minute Quadrangles,
Mason County, Washington (Polenz et al., 2010) the site is located in an area underlain by pre-Fraser
Olympic-source glacial and nonglacial deposits (Qpuop). No landslide, alluvial fan, or mass wasting
deposits are mapped closer to the site than 1,100 feet. An excerpt of the referenced geologic map is
attached as Figure 4.
• Pre-Fraser Olympic-source glacial and nonglacial deposits (Qpu� Mapped at the site and in the
surrounding west facing sloping areas, these pre-Fraser deposits generally consist of well
graded gravel with sand, silt,clay and diamicton (sediments that are poorly sorted and contain
a wide range of clast sizes). These sediments were deposited prior to the more recent Vashon
Stade of the Fraser Glaciation. As such, these deposits are considered over-consolidated and
exhibit high strength and low compressibility characteristics where undisturbed. The infiltration
potential is generally limited.
We also reviewed the Washington State Department of Ecology (DOE) Coastal Atlas shoreline
mapping for the surrounding area. The slope stability mapping was originally published as a hard copy
map in the Coastal Zone Atlas of Washington between 1978 and 1980 and eventually digitized for
reference.The site and surrounding shoreline area are mapped by the Coastal Atlas as"intermediate"
(1). This designation is likely based on the height and steepness of the slopes across the site and
surrounding area. No areas of"unstable-old slide"(UOS)or"unstable-recent slide"(URS)are mapped
at or in the vicinity of the site. An excerpt of the Coastal Atlas for the site area is included as Figure S.
The Relative Slope Stability of the Southern Hood Canal Area, Washington by Mackey Smith and
R. J. Carson (USGS Map 1-853) maps the site as a Class 2 area. Class 2 areas are considered stable
under normal areas by may become unstable during construction if allowed to be over-steepened by
erosion and/or if subjected to seismic activity. This map does not identify any known slides or areas
of higher risk within the immediate vicinity of the site.An excerpt from the referenced Relative Slope
Stability Map is attached as Figure 6.
We also reviewed the WA Department of Natural Resources (WA DNR) 2017 Landslide
Compilation datasets for the site vicinity. The Landslide Compilation dataset consists of mapped
landslides compiled from a variety of sources including 1:24,000 and 1:100,000-scale surficial geologic
maps, landslide hazard zonation studies,watershed analyses, reconnaissance-scale landslide mapping
from winter storm landslide events and a lidar-based study of near-shore landforms. There are two
mapped landslides identified along the south shore of the Hood Canal (upslope of E State Route 106)
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but are more than 2,000 feet from the site. According to the WA DNR datasets, these deposits were
identified using reconnaissance-level mapping. An excerpt of the DNR Landslide Compilation map is
included as Figure 7.
Subsurface Explorations
On June 18, 2024 we visited the site and monitored the drilling of two borings to depths of
about 31'/2 feet below the existing ground surface. The borings were drilled with a track-mounted drill
operated by a licensed driller working for GeoResources.
The specific number, locations, and depths of our 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 our explorations were placed in sealed plastic bags and
then taken to our laboratory for further examination and testing as deemed necessary. The relative
locations and surface elevations of the explorations are presented below in Table 1.
TABLE 1:
APPROX/MATE LOCAT/ONS, ELEVATIONS,AND DEPTHS OFEXPL024TIONS
Exploration Surface Termination Termination
Number Functional Location Elevation' Depth Elevation'
(feet) (feet) (feet)
B-1 Eastern portion of proposed driveway 105 31 Y2 73Y2
--------- ----------------------------------------------------------------------------------------------- --------------------------------------------------- ------------- -
B-2 Western portion of proposed driveway 100 31 Yz 68Yz
Notes:
1=Surface elevations estimated by interpolating between contours presented on the Mason County WA GIS website.
During drilling,soil samples were obtained at 2'/z and 5-foot depth intervals in accordance with
Standard Penetration Test (SPT) as per the test method outlined by ASTM D1586. The SPT method
consists of driving a standard 2 inch-diameter split-spoon sampler 18 inches into the soil with a 140-
pound hammer. The number of blows required to drive the sampler through each 6-inch interval is
counted, and the total number of blows struck during the final 12 inches is recorded as the Standard
Penetration Resistance, or "SPT blow count'. If a total of 50 blows are recorded within any 6-inch
interval (refusal), the driving is stopped, and the blow counts are recorded as 50 blows for the actual
distance the sampler was driven. The resulting Standard Penetration Resistance values indicate the
relative density of granular soils and the relative consistency of cohesive soils. The boring was
backfilled by the drillers with bentonite chips and abandoned per Washington State Regulations.
The subsurface explorations completed 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. Based on our experience and
extent of prior explorations in the area, it is our opinion that the soils encountered in the exploration
are generally representative of the soils at the site.
The approximate locations and numbers of our borings 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
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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 borings are included as Figures A-2 and A-3.
Subsurface Conditions
At the location of our explorations, we encountered consistent subsurface conditions that, in
our opinion, generally confirmed the mapped stratigraphy. Our explorations encountered soils that
appeared to be consistent with undocumented fill and pre-Fraser sediments. These glacial soil layers
and others are described in the following paragraphs.
• Undocumented fill: Approximately 5 to 15 feet of brown silty sand with gravel in a very loose to
loose, moist condition was encountered in each boring. We interpret these soils to be consistent
with undocumented fill associated with the construction of the adjacent driveway.
• Pre-Fraser sediments: Underlying the undocumented fill soils, our borings encountered
approximately 5 to 20 feet of tan-grey silty sand with gravel in a medium dense to very dense,
moist to wet condition overlying tan sandy gravel with silt in a dense to very dense, wet
condition. These soils were encountered to the full depths explored. We interpret these soils
to be consistent with pre-Fraser deposits.
Laboratory Testing
Geotechnical laboratory tests were performed on select samples retrieved from the boring
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, and grain size analyses per ASTM D6913 standard procedures. Test results
summarized below in Table 2 and graphical output results are included in Appendix B.
TABLE 2:
LABORATORY TEST RESUL TS FOR ON-S/TE SOILS
Gravel Sand Silt/Clay D10 Ratio
Sample Soil Type Lab ID Content Content Content (mm)
(percent) (percent) (percent)
B-1, S-2, D: 5' GW-GM 105226 .3 .
-------------------------------- ---------- 61 ----------32.9 5.8------------------------------------------- -01941- ---
B-1, S-7, D: 25' SM 105227 --1.7 45.2 -
-------- ---- - ------------ -----------------------------------------------------------13----1 <0.075
-----------
B-2, S-5, D: 15' GM 105228 44.5 41.0 1 14.5 <0.075
Groundwater Conditions
Groundwater seepage and/or saturated soils were observed in both borings at about 20 feet
below the ground surface (approximately elevation 80 to 85 feet). We anticipate the encountered
groundwater seepage in our explorations is consistent with localized perched groundwater that
occurs throughout the pre-Fraser deposits. Perched groundwater typically develops when the vertical
infiltration of precipitation through a more permeable soil, is slowed at depth by a deeper, denser, less
permeable soil type. We anticipate fluctuations in the local groundwater levels will occur in response to
precipitation patterns, off-site construction activities, and site utilization. As such, water level
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observations made at the time of our field investigation may vary from those encountered during the
construction phase.
ENGINEERING CONCLUSIONS AND RECOMMENDATIONS
Based on the results of our data review,site reconnaissance,subsurface explorations,and our
experience in the area, it is our opinion that the construction of the driveway and trailer pad is feasible
from a geotechnical standpoint provided appropriate measures are taken to maintain stability at the
site during and after construction.
Our services were provided to assist in the design of a private driveway and trailer pad to be
located on a sloping property. Our recommendations are intended to improve the overall stability of
the site and to reduce the potential for future property damage related to earth movements,drainage,
or erosion. However, all development on slopes involves risk, only part of which can be mitigated
through qualified engineering and construction practices. Favorable performance of structures in the
near term does not imply a certainty of long-term performance,especially under conditions of adverse
weather or seismic activity. Detailed conclusions and geotechnical recommendations regarding the
design and construction of the proposed development are presented below.
Geologically Hazardous Areas-per MCC Chapter 8.52.140
Mason County classifies the following as geologically hazardous areas:
i) Areas with any indications of earth movement such as debris slides, earthflows, slumps,
and rock falls.
ii) Areas with artificial over steepened or un-engineered slopes, i.e., cuts or fills.
iii) Areas with slopes containing soft or potentially liquefiable soils.
iv) Areas over steepened or otherwise unstable as a result of stream incision, stream bank
erosion, and undercutting by wave action.
v) Slopes greater than fifteen percent(eighth to one-half degrees)and having the following:
a. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a
relatively impermeable sediment or bedrock(e.g., sand overlying clay); and
b. Springs or groundwater seepage.
vi) 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 at least ten feet of vertical
relief.
In addition, the County may use the following to indicate areas that have a higher likelihood
of meeting the classification criteria above:
i) Landslide hazards mapped by the Washington Department of Natural Resources, Division
of Geology and Earth Resources (Washington Geological Survey) such as"Landforms and
Hazard Ratings- Mason Watershed,"Isabelle Sarikhan and Timothy J.Walsh,August 2007.
ii) The areas identified on the Mason County Soil Survey Map as having slopes greater than
fifteen percent.
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iii) The areas identified on the Coastal Zone Atlas, Volume 9, of Mason County, Washington
as:
a. Unstable-"U";
b. Unstable Old Slides-"URS";
c. Unstable Recent Slides -"URS";
d. Intermediate Slopes-"I";
e. Modified Slopes-"M".
iv) The area 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, U.S. Geological Survey, Series
Map 1-853-F, 1977;
v) Areas described and mapped as areas of poor natural stability and historical and recent
landslides by the Washington State Department of Natural Resources, Division of Geology
and Earth Resources including "The Geological Map of North Central Mason County,
Washington,"by R.J. Carson, Washington State Department of Natural Resources, Division
of Earth Resources, 1975;
vi) Areas mapped as landslide deposits (Map Unit Qls) on the Geologic Maps of Washington
7.5-Minute Quadrangle(Longbranch, Squaxin Island, Shelton, Summit Lake,Vaughn, Lake
Wooten, Mason Lake, Belfair, Skokomish Valley and Union, Lilliwaup, Hoodsport, and
Holly).
No evidence of landslides was observed during our site visit nor are any landslide or mass-
wasting deposits mapped on or in the vicinity of the site. Our borings were completed near the
existing driveway of 4420 East State Route 106 and encountered loose undocumented fill soils in the
upper 5 to 15 feet. Additionally,we anticipate that the steeper slopes in the lower western portion of
the site are cut slopes associated with the construction of East State Route 106. No deposits of
potentially liquefiable soils are inferred by the referenced mapping, nor were any encountered in our
subsurface explorations. The site is located near a marine shoreline and river delta. We did not
observe evidence of erosion and over-steepening of the shoreline at the time of our site visit. Slopes
greater than 15 percent were observed across the site. Our borings did not encounter an adverse
contact; however, groundwater seepage was observed at approximately 20 feet below the ground
surface in our borings. Slopes of 40 percent or greater with 10 feet or more of vertical relief are
mapped and were observed across the site, particularly in the lower western portion of the site.
The Alderwood gravelly sandy loam(Ad)soils mapped at the site are listed and were observed
as having slopes greater than 30 to 50 percent. As stated, the Coastal Atlas maps the site as
"intermediate" (1). The Relative Slope Stability of the Southern Hood Canal Area, Washington (Smith and
Carson, 1977)maps the site as Class 2. Class 2 area are believed to be stable under normal conditions
but may become unstable if: disturbed by human activities, if slope is over-steepened by erosion, or
if subjected to strong seismic shaking. An excerpt of the map is included as Figure 6. Our review of
geologic maps of the site area does not indicate the presence of landslide deposits at the site.
Landform mapping by DNR(2010)presented on the Mason County WA GIS map, indicates that
the site is categorized as a "high"hazard, as shown on Figure 8. We also reviewed landslide mapping
by DNR (2009). No landslide deposits are mapped on or in the vicinity of the site (Figure 7). Our
observations and evaluation would generally concur with the Mason County mapping. However,
based on the result of our slope stability analysis, discussed later in this report, the existing site
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configuration has a minimum FS of about 1.5 and 1.1 for static and pseudo-static conditions, and
would be classified as Stable.
Erosion Hazard Areas- per MCC Chapter 8.52.160
Mason County defines erosion hazard areas as those areas underlain by soils which are
subject to severe erosion when disturbed. These soils include, but are not limited to, River Wash("Ra")
or Coastal Beaches ("Cg")and the following where they occur on slopes of fifteen percent or steeper:
(i) Alderwood gravelly sandy loam ("Ac"and "Ad")
(ii) Cloquallum silt loam ("Cd")
(iii) Harstine gravelly sandy loam("Hb")
(iv) Kitsap silt loam ("Kc")
The NRCS maps the site to be underlain by Alderwood gravelly sandy loam (Ad) soils, meeting
the County's criteria of an erosion hazard area. Weathering, erosion, and the resulting surficial
sloughing and shallow land sliding are natural processes that affect steep slope areas. It is our opinion
that if typical erosion and sediment control Best Management Practices (BMPs) are used during
clearing and replanting of vegetation as outlined in the Department of Ecology's Stormwater
Management Manual for Western Washington (SWMMWW) are followed, then the potential for
erosion resulting from the proposed development to adversely impact the project site or adjacent
areas should be minimal. Additional recommendations for erosion control are presented below in
the"Erosion Control"section of this report.
Seismic Design
The site is 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 regional seismicity.
Seismic Site Class
Based on our observations and the subsurface units mapped at the site, we interpret the
structural site conditions to correspond to a seismic Site Class "C" in accordance with the 2021 IBC
documents and American Society of Civil Engineers(ASCE)7-16,Chapter 20,Table 20.3-1. This is based
on the range of SPT blow counts of the soils encountered in our explorations. These conditions are
assumed to be representative for the subsurface across the site.
Design Parameters
We used the ASCE Hazard Tool website to estimate seismic design parameters at the site.Table
3, below, summarizes the recommended design parameters.
00-020=1—
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TABLE 3:
2021 IBC PARAMETERS FOR DES/GAt OF SEISMIC STRUCTURES
Spectral Response Acceleration(SRA)and Site Short
Coefficients Period
Mapped SRA SS= 1.555g
Site Coefficients (Site Class C) Fa = 1.200
- --— --- ----- --- ---------------------- --------------------------
Maximum Considered Earthquake SRA SMs= 1.866g
Design SRA Sos= 1.244g
Peak Ground Acceleration
The mapped peak ground acceleration(PGA)for this site is 0.670g. To account for site class,the
PGA is multiplied by a site amplification factor (FPGA) of 1.2. The resulting site modified peak ground
acceleration (PGAM) is 0.804g. In general, estimating seismic earth pressures (kh) by the Mononobe-
Okabe method or for use in slope stability analyses are taken as'/3 to Yz of the PGAM,or 0.268g to 0.402g.
Seismic Hazards
Earthquake-induced geologic hazards may include liquefaction, lateral spreading, slope
instability(as discussed above)and ground surface fault rupture
Liquefaction is a phenomenon where there is a temporary reduction or complete loss of soil
strength because of an increase in pore water pressure induced by seismic vibrations. Liquefaction
mainly affects geologically recent deposits of loose,fine-grained sands and low-plasticity silts that are
below the groundwater table. It is our opinion that the combination of steep slopes, normally
consolidated soils, and groundwater seepage in the area of the shoreline bluff indicate that there is
potential for lateral spreading during a seismic event. The site is mapped as having a "low"to "very
low" liquefaction susceptibility by the Liquefaction Susceptibility Map of Mason County, Washington
(Palmer et al., 2004) as shown on Figure 9. Based on the results of our subsurface explorations
(density and consistency of the subsurface soils) across the site, we also conclude that the potential
for liquefaction at the site is low.
The Department of Natural Resources (DNR) Geologic Hazards Map (Geologic Information
Portal) shows the site to be located about 2.4 miles southeast of the Hood Canal Fault zone and 2.4
miles northeast of the Lucky Dog fault(Figure 10). No evidence of ground fault rupture was observed
in the subsurface explorations or our site reconnaissance. Therefore, in our opinion, the proposed
structure should have no greater risk for ground fault rupture than other structures in the area.
Slope Stability Analyses
We analyzed the global slope stability of the site in the existing and proposed configuration
using subsurface profile A-A', as shown on Figure 2. The topographic information for the cross section
was based on 5-foot contour data from the Mason County WA GIS website. This cross section was
selected as the most critical section given the height and steepness of the slopes relative to the
proposed development. As stated, we were not provided with a site plan prior to the preparation of
this report. The proposed conditions were based on our understanding of the proposed
development.
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We used the computer program SLIDE2, from Rocscience, 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; and a FS
less than 1.0 indicates that the driving forces are greater than the resisting forces(indicating failure).
Soil unit weights and strength parameters were assigned based on our experience; our review
of Geotechnical Properties of Geologic Materials (Koloski, Schwarz, and Tubbs 1989), Shallow-Landslide
Hazard Map of Seattle, Washington (Harp, Michael, and Laprade 2006), and the Washington State of
Department of Transportation Geotechnical Design Manual (2022); and our subsurface explorations
completed at the site on June 16, 2024, as well as laboratory testing of representative soils for index
properties. Table 4 summarizes the values published in the two referenced reports;the reference for
the strength properties used in this analysis.
TABLE 4:
SOIL PROPERTIES FOR VARIOUS NAT/I/ESO/L TYPES ENCOUNTERED IN THE PUGETSOUND
Deposit Source Dry Unit Friction Angle Cohesion
Weight(pcfl (degrees) (Psf)
Glacial Till(SM,ML) 120-140 35-45 1,000-4,000
Glaciolacustrine(SM,ML,SP) Geotechnical Properties 100-120 15-35 0-3,000
------------------------------------------------------------------------ of Geologic Materials' ------------------ --------------------- -----------
Outwash(GW,GP,SW,SP,SM) 115-130 30-40 0-1,000
Pre-Fraser glaciation coarse-grained deposits 38 -400
-------------------------------------------------------------------------------------------
Pre-Fraser glaciation fine-grained deposits Shallow-Landslide 26 -600
---------------------- - - Hazard Map of Seattle, NA --------—----------------------------------------
Washington ------
Pre-Fraser non-glacial coarse-grained deposits 2 36 -400
------------------------------------------------------------------------------------------- -----------------------------------------------------------
Pre-Fraser non-glacial fine-grained deposits 26 -600
WSDOT
Geotechnical Design 4
Outwash Manual NA 40-45 0
(M46-03.12)
Notes:
1 Koloski,Schwarz,and Tubbs,Engineering Geology in Washington,WA Division of Geology and Earth Resources Bulletin 78 Vol 1(1989)
2 Harp,Michael,and Laprade(2006)Shallow-Landslide Hazard Map of Seattle,Washington,U.S.Geological Survey Open-File Report 2006-1139
3 Chapter 5 of the 2022 Washington State Department of Transportation(WSDOT)Geotechnical Design Manual(M46-03.12)
4 GDM does not provide range for outwash,but states"near zero cohesion for clean deposits"
NA=Not Available
GeoResources assigned soil unit weight and strength parameters based on our experience,
our subsurface explorations, as well as laboratory testing of representative soils for index properties.
Table 5 below, summarizes the estimated soil properties of on-site soils used for our slope stability
analyses.
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TABLE 5:
EMMATED SOIL PROPERT/ES OF ON-S/TESOILS USED FOR SLOPESTABILITYANAL YSES
Dry Unit Saturated Cohesion Phi �.
Soil Type Weight Unit Weight (psf) 1 (degrees)
(pcf) (pcf)
pre-Fraser, silty sand deposits 125 126 300 42
-- -----_------- ------------------------------------------------------------------------------------------------------------
pre-Fraser, sandy gravel deposits 127 128 200 4-5
— --------------------------------------------------- ----------------------------------------------------------------------
Structural fill 125 - 0 35
Based on our review,and the data shown in Tables 4 and 5 it is our opinion that the assumed
values for the various soil types appear to be within the range of tabulated values in the referenced
literature.
We used the Simplified Bishop's Method of Circles as specified by MCC 8.52.140(5)(E), which
satisfies both moment and force equilibrium, 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. Quasi-static analyses were
completed using a horizontal coefficient of 0.15g as specified by MCC 8.52.140(5)(E).
Based on our slope stability analyses, the existing site configuration has a minimum FS of
about 1.5 and 1.1 for static and quasi-static conditions, respectively. A second section was modelled
across the proposed driveway/trailer pad modelling a shallow cut and fill,as proposed. Results for the
proposed conditions did not affect the results of our analysis. Details of our slope stability analyses
are included in Appendix C.
Our analysis only examines the site under existing conditions and is based on topographic
data available on the Mason County WA GIS website. As stated,we were not provided with a proposed
site plan prior to the preparation of this document. Once a site plan has been prepared, we
recommend that additional slope stability analyses be completed.
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.
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 undocumented fill soils be classified
as Type C soils, and that the deeper pre-Fraser soils be classified as Type B soils. According to WAC
296-155-66403,for temporary excavations of less than 20 feet in depth,the side slopes in Type B soils
should be sloped at a maximum inclination of 1 H:1 V and Type C soils should be sloped at a maximum
inclination of 1 1/2H:1 V or flatter from the toe to top of 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
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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.
Permanent Cut and Fill Slopes
Permanent cut or fill slopes in soil should be no steeper than 2H:1 V. All permanent slopes
should be protected from erosion as soon as feasible after grading is completed. Typical erosion
control methods per the Stormwater Management Manual for Western Washington 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.
Fill slopes constructed on grades that are steeper than 5H:1 V(20 percent) should be "keyed" into the
undisturbed native soils by cutting a series of horizontal benches and should be constructed in
accordance with Appendix J of the 2021 IBC. The benches should be 11h 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.
Grade Separation Walls
Because a grading plan has not been established,the heights and types(supporting cuts/fills)
are unknown. If the cuts or fills need to be retained, there are several types of grade separation walls
that use pre-cast modular concrete blocks. Rockeries could also be used. These proprietary systems
can be designed as either gravity walls (without reinforcement) or as mechanically stabilized earth
(MSE) walls (with geogrid reinforcement). Below we provide a summary of gravity and MSE walls, as
well as rockeries. We can provide site specific wall design calculations once the grading plan has been
developed and the actual wall type is selected.
Mechanically Stabilized Earth (MSE) Walls
Mechanically stabilized earth (MSE)walls are constructed using compacted soil with layers of
reinforcing material, such as geosynthetics or steel strips, that extend behind the wall face to create
a reinforced soil mass. This wall system is designed to support fills taller than 4 feet in height. Other
wall systems, such as gravity walls or rockeries, are typically more cost effective for cuts of less than
12 feet and fills less than 6 feet tall. Detailed wall design should be performed by the wall designer,
including internal and global stability, sliding resistance, and required reinforcement layout and
properties. Wall backfill should consist of structural fill and should be compacted to 95 percent of the
MDD as determined by the Modified Proctor (ASTM D1557). The soil drainage zone within 12 to 18
inches of the wall should be compacted to approximately 90 percent of the MDD based on ASTM
D1557. We recommend the use of WSDOT Standard Specification 9-03.12(4) for Gravel Backfill for
Drains for the soil drainage zone aggregate.
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Typical facings for MSE walls with geogrid or geotextile reinforcement are small modular
concrete blocks (such as AIIanBlock, Keystone, and others)or large modular concrete blocks(such as
Redi-Rock and StoneTerra). Rockeries may be considered for use as a decorative facing in front of
wrapped face geosynthetic MSE walls. In our opinion, MSE wails with welded wire mesh or steel
reinforcement (or gabion style wall) such as the Hilfiker wall systems, would also be feasible from a
geotechnical perspective.
Gravity Walls
Large modular concrete block walls (such as Redi-Rock, StoneTerra, or Ultrablock) are often
designed as gravity walls(without geosynthetic reinforcement). Gravity walls depend primarily on the
weight of the concrete blocks to resist failure from overturning and sliding. Gravity walls are typically
a cost-effective option for cuts of 12 feet or less or fills 6 feet or less. Taller wall sections and walls
subject to surcharge loading(including tiered wall configurations with less than 1 H:1 V separation)will
require larger block sizes to resist the additional forces acting on the wall. Gravity walls consist of
larger, pre-cast concrete blocks and are more suited to supports cuts and fills up to about 10 feet in
height where no surcharge loads are impacting the wall.
Rockeries
Rockeries should not be used unless the retained material is stable without the rock
facing. Rockeries are considered to act principally as erosion protection, and they are not considered
to provide strength to the slope unless designed as a buttress using limit equilibrium slope stability
methods. We do not recommend rockeries be constructed in front of cuts taller than 6 feet or fills
with more than 4 feet of exposed height unless constructed as a wrapped-face MSE wall with rockery
facing.
Rockery walls should be constructed of hard, dense, sound, and durable rock, free from
seams, cracks, and other defects in accordance with WSDOT Standard Specification 9-13.7(1). Backfill
materials for rockery walls should consist of WSDOT Standard Specification 9-13.1(5)for Quarry Spalls
or shot rock of the same quality.
Rockery boulders should be placed in uniformly decreasing sizes from the bottom of the
rockery to the top,with a battered face of at least 1 H:6V from vertical towards the cut face. All rocks
should be placed in running bond construction, with no continuous joint planes in vertical or lateral
directions, and each rock should maintain at least two points of contact with adjacent rocks so that
they are keyed together. The maximum void between adjacent rocks should be less than 6 inches as
measured at the largest dimension of the void; voids larger than 6 inches should be keyed with
chinking rocks to fill the void. We recommend tiered rockeries be separated by level terraces at least
equal to the height of the lower rockery, so that the upper rockery does not place a surcharge load on
the lower rockery.
Site Drainage
All ground surfaces, pavements and sidewalks at the site should be sloped to direct surface
water away from the structures, steep slopes, and property lines. 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.
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We recommend that footing drains be installed for the residence in accordance with the 2018
IBC, Section 1805.4.2, and basement walls (if utilized) have a wall drain as described above. The roof
drain should not be connected to the footing drain.
EARTHWORK RECOMMENDATIONS
Site Preparation
All structural areas on the site to be graded should be stripped of vegetation, organic surface
soils, and other deleterious materials including existing structures, foundations or abandoned utility
lines. Organic topsoil is not suitable for use as structural fill, but may be used for limited depths in
non-structural areas. Based on our subsurface explorations, we anticipate that stripping depth will
likely range from about 6 to 12 inches for topsoil. Areas of thicker topsoil or organic debris may be
encountered in the lower pasture area, in localized depressions, or in areas of heavy vegetation.
In addition to the removal of topsoil, any undocumented fill soils across the site should also
be removed or removed and replaced from within the area of the proposed driveway or trailer pad.
As stated, our borings encountered approximately 5 to 15 feet of undocumented fill.
Recommendations regarding removal, processing and replacement of the undocumented fill is
discussed below in the"Suitability of On-Site Materials as Fill"section.
Where placement of fill material is required,the stripped/exposed subgrade areas should be
compacted to a firm and unyielding surface prior to placement of new fill. Excavations for debris
removal should be backfilled with structural fill compacted to the densities described in the
"Structural Fill"section of this report.
We recommend that a member of our staff evaluate the exposed subgrade conditions after
removal of vegetation and topsoil stripping is completed and prior to placement of structural fill. The
exposed subgrade soil should be proof-rolled with heavy rubber-tired equipment during dry weather
or probed with a Y2-inch diameter steel T-probe during wet weather conditions.
Soft, loose, or otherwise unsuitable areas delineated during proof-rolling or 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. The
areas of old fill material should be evaluated during grading operations to determine if they need
mitigation, recompaction, or removal.
Structural Fill
All material placed as fill for the proposed wall should be placed as structural fill. Material
placed as structural fill should be free of debris, organic matter, trash, and cobbles greater than 4-
inches in diameter. The moisture content of the fill material should be adjusted as necessary for
proper compaction.
Materials
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
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sieve, such as Gravel Backfill for Walls(WSDOT 9-03.12(2)). If prolonged dry weather prevails during the
wall construction, higher fines content(up to 10 to 12 percent) may be acceptable.
Placement and Compaction
The appropriate lift thickness will depend on the structural fill characteristics and compaction
equipment used, but it is typically limited to 4 to 6 inches for hand operated equipment; thicker lifts
may be appropriate for larger equipment. For larger equipment such as a hoe-pac or drum roller,we
recommend a maximum loose-lift thickness of 12 inches. Structural fill should be compacted to at
least 95 percent of the MDD as determined by the Modified Proctor(ASTM D1557), except for within
12 inches of the back of the wall, as described in the "Wall Drainage" section of this report.
Additionally, the moisture content should be maintained within 3 percent of the optimum moisture
content in accordance with ASTM D1557.
Suitability of On-Site Materials as Fill
During dry weather construction, the non-organic,granular onsite soil may be considered for
use as structural fill, provided it meets the criteria described above in the"Structural Fill"section and
can be compacted as recommended. If the soil material is over optimum moisture at the time of
excavation, it will be necessary to aerate or dry the soil prior to placement as structural fill. We
generally observed the site soils to be excessively moist (damp to wet) at the time of our subsurface
explorations.
The undocumented fill and pre-Fraser deposits encountered in our borings are generally
comparable to "Common Borrow"(WSDOT Standard Specification 9-03.14(3)). These soils should be
suitable for use as structural fill provided the moisture content is maintained within 2 percent of the
optimum moisture level.
We generally did not observe any construction material or organic material in the upper
undocumented fill soils. However, if present, screening the fill material with a 3-inch sieve to remove
organics and construction debris would be appropriate. Removal and processing of the
undocumented fill soils should include excavating down to native soils, and an appropriate level of
processing to meet the specification of"Common Borrow". GeoResources should provide sufficient
laboratory testing and monitoring to ensure the above specification is met and the material is
replaced as structural fill. Because of the higher fines content of the undocumented fill, these soils
are highly moisture sensitive and may be difficult or impossible to compact when wet.
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.
Erosion Control
Weathering, erosion and the resulting surficial sloughing and shallow land sliding are natural
processes. As noted, no evidence of surficial raveling or sloughing was observed at the site. To
manage and reduce the potential for these natural processes, we recommend erosion protection
measures be in place prior to grading activity on the site. Erosion hazards can be mitigated by applying
Best Management Practices(BMP's) outlined in the SWMMWW. To manage and reduce the potential
for these natural processes,we recommend the following:
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• No drainage of concentrated surface water or significant sheet flow onto or near steep slope
areas.
• No fill should be placed within buffer or setback areas unless retained by engineered
retaining walls or constructed as an engineered fill.
• Grading should be limited to providing surface grades that promote surface flows away from
the top of slope to an appropriate discharge location.
• The driveway and pad should be graded with a ditch constructed along the upslope side.The
ditch should have quarry spall check dams and should convey water back to the existing
drainage.
• The new culvert installed in the drainage should have a rock pad on the outfall side to
minimize potential for scour, and rock on both sides of the entrance(per guidance for cross
drains from the Washington State Department of Natural Resources Forest Practice Manual,
details of which are in Appendix D).
If the recommended erosion and sediment control BMPs are properly implemented and
maintained, it is our opinion that the planned development should not increase the potential for
erosion of the site.While a planting plan is not required,the cut and fill slopes adjacent to the driveway
and trailer pad should be stabilized with permanent erosion control including vegetation. Tree
clearing below the pad should be limited to limbing up trees to provide view corridors and selected
tree removal under the guidance of a forester or arborist.
LIMITATIONS
We have prepared this report for use by Young Lee and other members of the design team,for
use in the design of a portion of this project. 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 our subsurface explorations,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.
If there are any changes in the loads,grades, locations, configurations or type of facilities to be
constructed, the conclusions and recommendations presented in this report may not be fully
applicable. If such changes are made, we should be given the opportunity to review our
recommendations and provide written modifications or verifications, as appropriate.
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We have appreciated the opportunity to be of service to you on this project. If you have any
questions or comments, please do not hesitate to call at your earliest convenience.
Respectfully submitted,
GeoResources, LLC
?Jordan L. Kovash, LG
oject Geologist
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KBTH=TT SCHEM
Eric W. Heller, PE, LG Keith S. Schembs, LEG
Senior Geotechnical Engineer Principal
JLK:EWH:KSS/jlk
Doc ID:LeeY.EStateRoutel06.RG
Attachments: Figure 1: Site Location Map
Figure 2: Site&Exploration Map
Figure 3: NRCS Soils Map
Figure 4: Geologic Map
Figure 5: Coastal Atlas-Stability Map
Figure 6: Relative Slope Stability
Figure 7:DNR Landslide Compilation
Figure 8: Mason County Geologic Hazard Map
Figure 9: Liquefaction Susceptibility Map
Figure 10:DNR Fault Hazard Map
Appendix A-Subsurface Explorations
Appendix B-Laboratory Test Results
Appendix C-Slope Stability Analysis
Appendix D-Driveway Details
'0000
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Map created from Web Soil Survey(http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx)
Soil Slopes Erosion Hydrologic
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earth science & geotechnical engineering PN: 322314100021
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An excerpt from the Geologic Map of the S.kokomish Valley and Union 7.5-minute Quadrangles, Mason County, Washington by
Michael Polenz,Jessica L. Czajkowski, Gabrial Legorreta Paulin,Trevor A. Contreras, Brendan A. Miller, Maria E. Martin,
Timothy J.Walsh, Robert L. Logan, Robert J.Carson, Chris N.Johnson, Rian H. Skov, Shannon A. Mahan, and Cody R.
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G E O R E S O U R C E S
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks
Doc ID:LeeY.EStateRoute106.F July 2024 Figure 4
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GE 0 R E S O U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks Doc ID:LeeY.EStateRoutel O6.F July 2024 Figure 6
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f
Approximate Site Location
Map created on the Washington Geologic Information Portal
(https://geologyportal.dn r.wa.gov)
Not to Scale
�--- DNR Landslide Compilation
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks Doc ID:LeeY.EState Route 106.1' July 2024 Figure 7
Geok�ic Hazard_t,ayers
Landslides-DNR 2010
i
Landforms-DNR 2009
1-H°9h
j2-Moderate
1 -
3-Low
I
is
9pY '
P Jj
I _
t
8
3..i
4
ut.
Z ��
Approximate Site Location
Map created from Mason County WA GIS website (https://gis.masoncountywa.gov/Mason/)
w �r:
5
Not to Scale
��s■►— Mason County Geologic Hazard Map
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S a U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. ► Fife,WA 98424 1 253.896.1011 1 www.georescurces.rocks Doc ID:LeeY.EStateRoute106.F July 2024 Figure 8
EXPLANATION
Liyue6�inanrapcbtliy.HLCiH ",
® I.cpoehRioac it�tb�7ty:MODF�iAT E b H it'tl -
t
Liquetrotiov*Ac gtb0lty:MODERAn !
❑ Lyua6dim autoepif *y:LOW tvMWFAAFL
layue6cdan sU=*d Uky.LEM
L.igu.&,dm nus.oWiy:VERY LOW W WW I j-Y
Tahuya �� f
Ljac&csiansu=01a13ty,MYLOW
o l/ 8�.�nd
7b�caf nit r I�dnane turat �\
F-1
Peatdepcni per���dglrm�mWet �...w-..---.. :
re es•oi ld�Ji'
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a
m eMYs�rt ssav4s2ae0 toy lm�n>b etcaryire4 -.____,..�
Hge:tars�,;aoare c�c ra ate-.rC�pae a iW asp t"
i 106 -
-------------------------
r,
Approximate Site Location
An excerpt from the Liquefaction Susceptibility Map of Mason County, Washington by Stephen P. Palmer, Sammantha L.
Magsino, Eric L. Bilderback,James L. Poelstra, Derek S. Folger, and Rebecca A. Niggemann (2004)
Not to Scale
Liquefaction Susceptibility Map
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy,E. I Fife,WA 98424 1 253.896.1011 1 www.georesou rces.rocks
Doc ID:LeeY.EStateRoute106.F July 2024 Figure 9
Seismogenic Folds. Known or Suspected
c •
visible fold trace ` " A; `r '
-- Inferred fold trace
•- Concealed fold trace
a
fit`
Active Faults, Known or Suspected
Visible fault tr ace �0
- - Inferred fault trace
• - Concealed fault trace h' Tacoma fault
-
I ahuya .erz
2.4 miles
` Union ,
Luck Dog faultcity &` 2.4 miles?
S anticline
_oke
♦
. ` Little Hoqularn
♦ b
4
Skokom,
Mohrwefs Veltey - �
a
Oy z °
A� Luk.
a 4
x IJ<1 f�
'♦ �� lnke
ce `
~/� • t
♦ .McEwen
Approximate Site Location
Map created from the Washington Geologic Information Portal (geologyportal.dnr.wa.gov/)
NI'
S Not to Scale
DNR Fault Hazard Map
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks
Doc ID:LeeY.Estate Route 106.F 7July 2024 Figure 10
Appendix A
Subsurface Explorations
LOG OF BORING B-1
Proposed Driveway and Trailer Pad
G E O R E S O U R C E S 4480 East State Route 106
earth science &geotechnical engineering Mason County, Washington
1.Refer to log key for definition of symbols,abbreviations, and codes Drilling Company: Boretecl Logged By: DEM
2.USCS disination is based an visual manual classification Drilling Method: HSA Drilling Date: June 16,2024
and selected lab testing
3.Groundwater level, if indicated, is for the date shown and may vary Drilling Rig: EC 95 Track Drill Datum: NAVD88
4.NE = Not Encountered
5.ATD = At Time of Drilling Sampler Type: 2 inch split-spoon Elevation: 105 feet
6.HWM=Highest Groundwater Level Hammer Type- Cathead Termination Depth: 31.5 feet
Hammer Weight: 140 Ibs Latitude:
Notes: Longitude:
Test Results
ai $ Plastic Limit Liquid Limit m
Exploration n
o Soil description E E %Fines(<0.075mm) O
notes Co /Water Content ♦ 'o
w
Q. 0
Penetration- ♦ (blows per foot)
0 105 Brown silty SAND with gravel(SM)(Moist,Very Loose) a
(Undocumented Fill) 1
3 ♦ .. . ...... .. ..
1 ... ........ -. _... .....
2 .. .. . ..
. ... ......... .
5 100 Tan,gray,and brown well-graded GRAVEL with silt and sand 12 :: :
(GW GM)(Moist,Medium Dense to Very Dense)(Pre-Fraser 19 ..... .....
Olympic-source Glacial and Nonglacial Deposits) " ""......... ......... ......... ......... ......... .........
......... ......... ......... ......... ......... .........
19
16 ::::: :: ... ::
14
......... ......... ......... ......... ......... .........
. ......... ......... ......... ......... .........
1095 13 n....... .........
23 :: :
......... ......... ......... ......... ......... .........
15 90 23
......... ......... ......... ......... ......... .........
25 ... ......... ......... ......... ......... .........
......... ......... ......... ......... ......... .........
18 ...:....::... ...::...:::...:::
......... ......... ......... ......... .
......... ......... ......... ......... ......... .........
20 85 28 : ATD..... .. .. .... .. .. ...... ......... ::::::.
zs ........ ......... ......... .........
27
25 80 Gray silty SAND with gravel(SM)(Wet,Very Dense)(Pre-Fraser 28
40 .. ... .... .::
Olympic-sourced glacial and nonglacial deposits) . ., .. ,
19
....:......... ......... ......... ......... ......... ...... ..
30 75 00
5of6
(Termination Depth-June 16,2024) .... ......... ....
Silty sand Well graded GRAVEL
with silt
Sheet 1 of 1 JOB:LeeY.EStateRoute106 FIG. A-2
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% GM SILTY GRAVEL
SOILS Of Coarse Fraction GRAVEL
Retained on WITH FINES
GC CLAYEY GRAVEL
No.4 Sieve
SAND SW WELL-GRADED SAND,FINE TO COARSE SAND
CLEAN SAND
More than 50% SP POORLY-GRADED SAND
Retained on
No.200 Sieve More than 50% SM SILTY SAND
Of Coarse Fraction SAND
Passes WITH FINES
SC CLAYEY SAND
No.4 Sieve
SILT AND CLAY ML SILT
INORGANIC
FINE CL CLAY
GRAINED
SOILS Liquid Limit ORGANIC OL ORGANIC SILT,ORGANIC CLAY
Less than 50
SILT AND CLAY MH SILT OF HIGH PLASTICITY,ELASTIC SILT
INORGANIC
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.
Unified Soils Classification System
_ Proposed Driveway and Trailer Pad
4480 East State Route 106
GE O R E S O U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks
Doc ID:LeeY.Estate Route 106.F July 2024 Figure A-1
�- LOG OF BORING B-2
-"" —���■_ Proposed Driveway and Trailer Pad
G E O R E S O U R C E S 4480 East State Route 106
earth science &geotechnical engineering Mason County, Washington
1.Refer to log key for definition of symbols,abbreviations, and codes Drilling Company: Boretec1 Logged By: DEM
2.USCS disination is based on visual manual classification Drilling Method' NSA Drilling Date' June 16,2024
and selected lab testing
3.Groundwater level, if indicated, is for the date shown and may vary Drilling Rig: EC 95 Track Drill Datum: NAVD88
4.NE = Not Encountered
5.ATD =At Time of Drilling Sampler Type: 2 inch split-spoon Elevation: 100 feet
6.HWM=Highest Groundwater Level Hammer Type: Cathead Termination Depth: 31.5 feet
Hammer Weight: 140 Ibs Latitude:
Notes: Longitude:
Test Results
c y
o Plastic Limit —� Liquid Limit m
n Z- Exploration n
m Soil description E E Fines(<0.075mm) O
o" m notes iii ' %Water content • 'o
w n n
Penetration- ♦ (blows per foot)
� 100 a o 0 0 0
Brown silty SAND with gravel(SM)(Moist,Loose) """"' """"'
(Undocumented Fill) ...._. ._...... ...._... ......... _....... .........
3 ::: :::::.... ...:::::: :::::::::
3 .... .. .. .. .. .. .. .. .. .. ..
3 ...
3 .:......... ......... ......... ......... ......... .........
4 :::::......... ......... ......... ......... ......... .........
..:::......... ......... ......... ......... ......... .........
4 :::,:....._.................._.._._. ....._.._._....._....._.._...
4
7 ...
..... .. .. .. .. ... .. .. . .. .. .. .. ..
3 ...
10 90 a
..
4 ..I...... ......... ......... .........
........1 —...... ......... ......... ......... .........
3 ..... ....: .....
15 85 Tan,gray,and brown silty GRAVEL with sand(GM)(Moist, 15
Dense)(Pre-Fraser Olympic-source glacial and nonglacial 20 .... .... .... .... ....
deposits) 20
......... ......... ......... ......... ......... .........
20 80 Tan sit GRAVEL with coarse sand GW-GM 21 ... ATD
silty ( )(Wet,Dense to 17 .....
Very Dense)(Pre-Fraser Olympic-source glacial and nonglacial 23 .,,,
deposits) ::::: ::::: ::::: ::::
......... ......... ......... ......... ......... .........
. ......... ......... ......... ......... ......... .........
25 75 ..... .
.....
......... ...... .. ......... ......... ......... .... ..
30 70 50/4
......... ......... ......... ......... ......... .........
(Termination Depth-June 16,2024) _.: .....:... .......:.
Silty sand ® Well graded GRAVEL Silty gravel
with silt
sheet 1 or 1 JOB: LeeY.EStateRoute106 FIG. A-3
Appendix B
Laboratory Test Results
Particle Size Distribution Report
100
90
80 4-
70
Of
LLJ III J `
Q
Z 60-
Z 50 -
W
40
30
20
10 1 T-f
0-
100 10 1 0.1 0.01 0.001
GRAIN SIZE-mm.
%+3" %Gravel- %Sand Fines
E Coarse Fine Coarse Medium
F- to Fine Silt Clay
U) 0.0 26.0 35.3 11.1 12.4 9.4 5.8
.0
Test Results(ASTM D6913& ASTM D 1140) Material Description
Opening Percent Spec.* Pass? Well-graded GRAVEL with silt and sand(GW-GM)
a) > Size Finer (Percent) (X=Fail)
1.25 100.0
1 91.9 Atterberg Limits(ASTM D 4318)
.75 74.0 PL= NP LL= NV Pl= NP
ca .5 61.4
0 0 0.375 53.8 Classification
3:
.r- a) #4 38.7 USCS(D2487)= GW-GM AASHTO(Ml45)= A-l-a
o 2:
#10 27.6
Coefficients
i5 #20 20.4 1390= 24.6255 D85= 22.7284 D60= 12.0273
#40 15.2 D50= 7,9853 D30= 2.4155 D 1 0.4134
5
0 #60 11.4 D10= 0.1941 Cu= 61.98 Cc= 2.50
a) #100 8.6
#200 5.8 Remarks
0 -0 Natural Moisture:7.2%
a) C
U) Co
Z5 Date Received: 6/18/24 Date Tested: 6/28/24
75 0 Tested By: MAW
x
E Checked By: KSS
of Title:PM
_0 a)
(no specification provided)
Source of Sample:B-I Depth: 5 Date Sampled: 6/18/24
Sample Number:2
------- -----
0
GeoResources, LLC Client: Dr.Lee Young
Project: Proposed Driveway and Trailer Pad
Q) CU
Fife, WA Project No: LeeY.EStateRouteI06 Figure B-I
Tested By: Checked By:
Particle Size Distribution Report
100
90
80
70
Of
W
Z 60
50
LLJ
40
LLI
J:
30
20
10
0
100 10 1 0.1 0.01 0.001
vi GRAIN SIZE-mm.
%Gravel %Sand %Fines
%+3"
.r- E Coarse Fine Coarse Medium Fine
: silt Clay
0.0 18.0 23.7 15.9 18.9 10.4 13-1
Test Results(ASTIM D 6913& ASTM D 1140)
CU C Material Description
0 L:5 Opening Percent Spec.* Pass? Gray silty SAND with gravel(SM)(Wet,Very Dense)(Pre-Fraser
>
Size Finer (Percent) (X=Fail) Olympic-sourced glacial and nonglacial deposits)
Q C:
1.5 100.0
ca 1.25 94.2
a) Q Atterberg Limits(ASTM D 4318)
1 86.4 PL= NP LL= NV Pl= NP
cc
0 0 55
74.2 82.0
Classification
3: 2! 0.375 70.0 USCS(D 2487)= SM AASHTO(M 145)= A-l-a
#4 58.3
Coefficients
i6 #10 42.4
1390= 28.1340 D85= 23.1240 D60= 5.2695
#20 30.8 D50= 3.0236 D30= 0.7894 D15= 0.1194
#40 23.5 1310= Cu= CC=
W a) #60 18.9
Remarks
#100 15.9
0 -0 #200 13.1 Natural Moisture: 11.6%
0 ca
(n Date Received: 6/18/24 Date Tested: 6/28/24
75 (n Tested By:MAW
X
E Checked By: KSS
a)
Title: PM
-0 a)
(no specification provided)
Source of Sample:B-1 Depth: 25
> Date Sampled: 6/18/24
ii Sample Number: 7
0
h: Client: Dr.Lee Young
GeoResources, LLC
Q) 11 Project: Proposed Driveway and Trailer Pad
rn ICU
Fife, WA Project No: LeeY.EStateRoutel06 Figure B-21
Tested By: Checked By:
Particle Size Distribution Report
C!
'! - -E
4 iR it it 1; -:9
100
90
80
70-
LLJ
Z 60
Z 50
LLJ
LU 40-
a_
30
20-
10
0
1 00 10 1 0.1 0.01 0.001
GRAIN SIZE-mm.
Q
>1-a %Gravel %Sand %Fines%+3" i
E Coarse Fine Clay
Coarse Medium Fine Silt
co__ - i
0.0 10.6 33.9 1 13.0 16.4 11.6 14.5
49 Test Results(ASTM D 8913& ASTM D 1140) Material Description
to :2 Opening Percent Spec.* Pass? Tan,gray,and brown silty GRAVEL with sand(GM)(Moist Dense)
2 > size Finer (Percent) (X=Fail) (Pre-Fraser Olympic-source glacial and nonglacial deposits)
W C i
3: 1 1.25 100.0
89.4
Afterberg Limits AASTIA-D 4318
ram, .75 89.4
PL= NP LL-- NV Pl= NP
19 0 0.375o 71.8.5 77.0
Classification
3: ,- #4 55.5 USCS(D 2487)m GM AASHTO(Ml45)= A-l-a
0 #10 42.5
ZO
Coefficients
C C
Z #20 33.0
i D90= 25.7304 D85= 16.5093 D60= 5.7487
26.1 0.6276 D15= 0.0837
Q #40 D50= 3.2938 D30=
#60 21.0 D10= Cu= C c
#Ioo 17.6
Remarks
cc 0 #200 14.5
-0 Natural Moisture:7.5%
U)
Date Received: 6/18/24 Date Tested: 6/20/24
Tested By: MAW
X
E Chocked By: KSS
cc
Title:PM
0 4)
'G (no specification provided)
(0 Source of Sample:B-2 Depth: 15 Date Sampled: 6/18/24
-4 _-Saawle-Nu tuber;-5 -------
77,
0
GeoResources, LLC Client: Dr.LeeYoung
(D Q Project: Proposed Driveway and Trailer Pad
co
(D Co
Fife, WA Pro jectNo: LeeY.EStateRoutel06..____.___ Flaure
Tested By: Checked By: -
Appendix C
Slope Stability Analyses
o• 0 100 200 300
A
O M
ti (D
ct
t.•.
'r•d:°'
O '.;�.;�.;• '. 6) Cn U'i Cn Cn .A .A W W CO W N N N N 1--` F' O O O Ort
rc]
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n 1,r• +
O
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rtririri �r~ /r n
'•XX M ds,r tY ! A
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t 1 il4l 1 414. l
3 rrr r r
d ir•.i 1rLrtri, ••.i r J r i
it t�Nt.t.t•L.t.i.•. . i d:RfJ r
1 r1r t 1 tJ r ris l r
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1.1:ti''::r11 tirSJS`j•r•f' '.+°
1,S i
1 1•. 1 t• i t
v I
O
i
Safety Factor Unit Saturated
0 0.0 Material Strength Cohesion Phi Water Hu
o-- Color Weight U.W.(Ibs/ Hu
v 0.3 Name (Ibs/ft3) ft3) Type (psf) (°) Surface Type
0.5 � 0.15
pre-Fraser, 125 126 Mohr- 300 42 Water Custom 1
0.8 silty sand ® Coulomb Table
1.0 pre-Fraser, ■ Mohr- Water
1.3 sandy gravel 127 128 Coulomb 200 45 Table Custom 1
1.5
1.8
2.0
2.3
2.5
2.8
3.0
3.3
3.5
3.8
4.0
4.3
4.5
4.8
04 5.0
5.3
5.5 --------
5.8 1.1
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6.0+ -�
g
a2
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Project
Proposed Driveway and Trailer Pad
aExisting � n n Quasi-static (0.15g)
OcJcIenceo nBy mpay SLIDEINTERPREr 9.o28 I
Date 6/28/2024, 7:56:56 AM File Name LeeY.BtateRoute 106.SS.slmd
Unit Saturated
C� Color Weight U.W.(Ibs/ Hu
Material Strength Cohesion Phi Water Hu Ru
-
Name (Ibs/ft3) {t3) Type (pso (°i Surface Type Value
pre-
Fraser, . 125 126 Coulomb 300 42 Water Table Custom 1
silty sand
pre-
Fraser, . 127 128 Mohr- 200 45 Water Custom 1
sandy Coulomb Table
gravel
p Structural ■ 125 Mohr- 0 35 None 0
ro-s Fill Coulomb
4
o ,
o-
N
1.5
S S S. S S 5 1'L. S 1S. 1 .1 54 '•. S.
1 SL 1 S 1 ". L 4LS S L S 11 i SL S L
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0 100 200 300 400 500 600 700
v%/ert
Proposed Driveway and Trailer Pad
Group Scenario
Proposed Static
r o c s c i e n c e Drawn By Company
SLIDEINTERPRET 9.028 1 d
Date 6/28/2024 7:56:56 AM File Name LeeY.EStateRoute106.SS.slmd
CD Unit Saturated Strength Cohesion Phi Water Hu Ru
Name Cclor Weight U.b (Ibs/ Type (Psf) (°) Surface Type Hu
ft
(Ibs/ft3) ft3) Value
pre-
Fraser, ■ 125 126 Mohr 300 42 Water Custom 1
silty sand Coulomb Table
pre-
Fraser, 127 128 Mohr- 200 45 Water Custom 1
sandy ■ Coulomb Table
gravel
Structural ■ 125 Mohr- 0 35 None 0
Fill Coulomb
r
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0 100 200 300 400 500 600
project
Proposed Driveway and Trailer Pad
— i
Group Proposed Scenario Static
r o c s c i e n c e Zrawn By - -- -_-_- Company
SLIDEINTERPRET 9.028
Date 6/28/2024r 7:56:56 AM File Name LeeY.EStateRoute106.SS.slmd
Appendix D
DNR Forest Practice Details
NRCS Practice Standard 560 Access Road
Ditch Block
�.--Slo�2% lin.
1 ft min.
M04Energy Dissipator/Filter• Strip fill over pipe
CROSS SECTION
Ditch Block
Culvert {�/ t20-135 deg Road
---T T T i*- T- T
PLAN VIEW
NOTES- '
1) Minimum cover over culvert is 1 ft.
2) Spacing and size of relief culverts to be
based on local conditions
3) Disturbed areas and slopes shall be seeded
and mulched to grass upon completion.
4) Culvert outlet to be directed across a
vegetated area for filtering cut sediment
and away from wetlands and streams.
5) Use rock riprop where necessary for erosion
Protection at outlet.
&) Minimum culvert diameter 18" in Western WA
15" in Eastern, WA.
CROSS DRAIN
SCALE NTS
Typical Cross Drain Detail
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnicai engineering PN: 322314100021
4809 Pacific Hwy,E. I fife,WA 98424 1 253.896.1011 1 www.georesourcessocks
Doc ID:LeeY.Estate Route 106.f July 2024 Figure D-1
Ditch Block
c
Road Surface
F
+--5lo 2% min-
1 ft min.
till over pipe
Single Wall, Corrugated, Polyethylene Pipe
Connected to Biwall pipe culvert, snaked down slope.
CROSS SECTION
Energy Dissipater/
Filter Strip
Ditch Block
Culvert !/ Rood
120 —f135 deg
NOTES
PLAN vIEVa'
1) Minimum cover over culvert is t ft.
2) Spacing and size of relief culverts to be based on local conditions
3) Disturbed areas and slopes shall be seeded
and mulched to grass upon campletlon.
4) Culvert outlet to be directed away from
direct discharge Into wetlands and streams.
5) Use rock riprap where necessary for energy
dissipater at outlet
6) Minimum culvert diameter 18' in Western WA
15" in Eastern WA.
7) Anchor downspout where stability is necessary using rock or treated posts.
CROSS DRAIN WITH DOWNSPOUT
SCALE : NTS
Typical Cross Drain w Downspout
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesaurces.rocks
Doc ID:LeeY.EState Route 1 06.F July 2024 Figure D-1
>J.0
f
2-4" QUARRY
SPACES
3.0' (rnin)
.. Mrnr
LTER FABRIC i i=1 I►-1!1=1 I!=1
DISPERSION PAD
SCALE NT'-�
ems-- Typical Dispersion Pad
®� Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks
Doc ID:LeeY.Estate Route 1 06.F July2024 Figure D-1
ROCK MUST COMPLETELY COVER THE
BOTTOM AND SIDES OF THE DITCH
6" MIN, �
�1 24" MIN,
2:1 SLOPES
i
2"-4" ROCK
AL Et
IF, 11—
L THE DISTANCE SOCH THAT POINTS
A AND B ARE OF EQUAL ELEVATION �
CHECK DAM
SCALE NTS
Typical Check Dam
Proposed Driveway and Trailer Pad
4480 East State Route 106
GE 0 R E S 0 U R C E S Mason County, Washington
earth science & geotechnical engineering PN: 322314100021
4809 Pacific Hwy.E. I Fife,WA 98424 1 253.896.1011 1 www.georesources.rocks
Doc ID:LeeY.EState Route 1 06.F July 2024 Figure D-1