HomeMy WebLinkAboutCritical Area Report - GEO General - 7/29/2024 MASON COUNTY Submittal Checklist
COMMUNITY SERVICES Geological Assessment
Building,Planning,Ervirwmenal Health,Community Health
Instructions:
This checklist must be submitted with a Geological Assessment and completed, signed, and stamped by the licensed
professional(s)who prepared the Geological Assessment 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 Markie Smith Parcel# 419103400000
Site Address W Wivell Rd., Shelton, WA
(1) A discussion of geologic conditions in the general vicinity of the proposed development, with geologic unit
designation based on referenced maps.
Located on page(s) 2
(2) (a)A discussion of the ground water conditions at the site,
Located on page(s) 4
(b) A discussion of the estimated depth to water,
Located on page(s) 3
(c) A discussion of the quantity of surface seepage,
Located on page(s) 4
(d) A discussion of the upslope geomorphology,
Located on page(s) 4
(e) A discussion of location of upland waterbodies and wetlands.
Located on page(s) 4
(3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
Located on page(s) 2-3
(4) A discussion of any geomorphic expression of past slope instability(presence of hummocky ground or ground
cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating
downslope movement, etc.).
Located on page(s) 4
(5) A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records.
Located on page(s) 2
(6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or
setback and the potential for landslide activity at the site in light of the proposed development.
Located on page(s) 5
(7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site
conditions and the proposed development of the subject property.
Rev. February 2018
4W
Located on page(s) 5
(8) If the presence of a hazard is determined within 300 feet of the proposed development, then the following are
delineated on a geologic map/site map:
(a) the area of the proposed development,
Located on Map(s) Pg. 13, Figure 2
(b) the boundaries of the landslide hazard area(top, both sides, and toe),
Located on Map(s) Pg. 13, Figure 2
(c) the associated buffers (top, both sides, and toe),
Located on Map(s) Pg. 13, Figure 2
(d) building or other setbacks(top, both sides, and toe).
Located on Map(s) Pg. 14, Figure 3
(9) 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) Pg. 13, Figure 2
1, Luke McCann 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 Geological Assessment, dated 7/29/2024 and entitled
Smith CAO 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 manner as to prevent
harm to property and public health and safety.
e° ash
a` f
'n ast
23 /
Sed Ge
LUKE PRESTON MCCANN
Page 2 of 2
Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment.
LIALITY
z= -
EO
-NW
7/29/2024
Markie Smith
100 SE Evergreen Dr
Shelton,WA
Subject: Critical Area Ordinance(CAO)Report
Smith Slope Study-Critical Area Ordinance (CAO)Report
TPN: 419103400000; W Wivell Rd., Shelton, WA
QG Project No.: QG24-040
Dear Client:
At your request,Quality Geo NW,PLLC(QG)has completed a preliminary critical area review of
the above referenced property's existing site conditions, including site visual reconnaissance,
subsurface evaluation, slope analysis, and review of existing geologic literature for the site. The
project site consists of an undeveloped parcel comprising a portion of a regional slope. It is our
understanding that the client intends to construct within an area designated by the permitting
authority to be a potential critical slope.
QG understands that the designated permitting authority requires a geotechnical consultation to
confirm that current conditions are favorable, and to provide any additional and necessary
recommendation regarding critical slope considerations including necessary setbacks. The
following report presents the findings and conclusions of our review, addresses feasibility of
proposed site development, and provides additional geotechnical recommendations for planning
and design intended to reduce the inherent risks associated with site development within a
potentially geologically hazardous area.
A site region and vicinity map are provided in Appendix A,and a site map is presented in Appendix
B.Typical slope conditions are shown schematically on the attached site slope profile in Appendix
C. Exploration logs are included in Appendix D.
Quality Geo NW, PLLC
Serving All of Washington&Oregon I Geotechnical Investigations&Engineering Consultation
Phone: 360-878-9705 1 Web: qualitygeonw.com I Mail:4631 Whitman Lane SE,Ste D,Lacey,WA 98513
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project # QG24-040
GEOLOGIC LITERATURE REVIEW
QG reviewed available map publications to assess known geologic conditions and hazards present
at the site location. The Washington Geologic Information Portal (WGIP), maintained by the
Department of Natural Resources Division of Geology and Earth Resources, provides 1:24,000-
scale geologic mapping of the region. Due to the large size of the parcel, many geologic units are
present on the property. Narrowing down the scope to the project area to the northwest corner of
the parcel,there are three intersecting geologic units. The slope of the project site is comprised of
Tertiary volcanic rocks (Ev(c)) which is summarized as, "Mostly aphanitic basalt; pillows or
massive to columnar flows with plagioclase and pyroxene phenocrysts commonly visible in hand
sample; rare minor interbeds of sandstone or siltstone and small pockets of sandstone or siltstone
between basalt pillows". Pleistocene continental glacial drift (Qgo, Qgos, Qgas, and Qgic) has
accumulated in the lower elevation areas of the parcel.These units can be summarized as,"Cobble
and pebble gravel, sand, and occasional silt and clay; mostly quartzo-feldspathic,with high-grade
metamorphic, metasedimentary, plutonic, and basalt clasts of uncertain provenance locally
supplemented by additional basalt clasts from Crescent Formation within or near the map area;
mostly brown-gray where fresh, brown, red, and yellow where iron-stained from weathering;
mostly moderately sorted and bedded; sand and clasts are typically northern-sourced." Finally, a
stream runs through the property nearby to the project site, and covers the Pleistocene continental
glacial drift with Quaternary alluvium(Qaf)which is summarized as,"Pebbles,sand, silt,cobbles,
and boulders, in varied amounts; gray to brown; loose; moderately to poorly sorted; stratified to
poorly stratified; derived from local sources and deposited in concentric lobes where streams
emerge from confining valleys."
According to the regional-scale interactive map, there are deep-seated, undifferentiated historic
landslides mapped to have occurred along the western side of the slope in the project area, as well
as several deep-seated,undifferentiated historic landslides on the eastern side of the property away
from the project site. Available LiDAR imagery of the site does not reveal any recent
geomorphology consistent with historical mass-wasting events, and historic landslide deposits
appear to be weathered.
The United States Department of Agriculture portal(USDA)provides a soil mapping of the region.
In the project area, the slope is mapped as Delphi gravelly loam (Df), while the area below the
slope is comprised of Grove gravelly sandy loam (Gk) in the western portion and Rough
mountainous land,Tebo soil material(Rd) in the southern and eastern portion.The Df soil formed
as till plains derived from continental basal till with volcanic ash. The soils are described as
gravelly medial loam from 0 to 10 inches, very gravelly medial loam from 10 to 50 inches, and
gravelly sandy loam from 50 to 60 inches. Depth to restrictive feature is listed as 40 to 55 inches
2
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
to densic material. Capacity of most limiting layer to transmit water(ksat) is listed as very low to
moderately low(0.00 to 0.06 in/hr).Depth to water table is about 39 to 54 inches. The Gk soil unit
formed as outwash plains derived from glacial outwash. The soils are described as gravelly sandy
loam from 0 to 9 inches, very gravelly sandy loam from 9 to 24 inches, and very gravelly loamy
sand from 24 to 60 inches. Depth to restrictive feature is listed as more than 80 inches. Capacity
of most limiting layer to transmit water(ksat) is listed as high(1.98 to 5.95 in/hr). Depth to water
table is more than 80 inches.The Rd soil formed as till derived from basalt.The soils are described
as silt loam from 0 to 13 inches, and gravelly clay loam from 13 to 60 inches. Depth to restrictive
feature is listed as more than 80 inches. Capacity of most limiting layer to transmit water(ksat) is
listed as moderately high to high(0.57 to 1.98 in/hr). Depth to water table is more than 80 inches.
SITE INVESTIGATION METHODOLOGY
On 6/25/2024,a QG Staff Geologist visited the site to perform visual reconnaissance of the surface
and topographic features of the subject property and its proximal slope. While on site, we
conducted site surface explorations for a geologic hazard assessment and site feasibility
characterization. Approximate relevant property dimensions and slope topography were
documented and mapped at representative intervals as access allowed. Soil conditions were
evaluated through local exposures along the slope face. Salient slope features and existing
vegetation were documented to assess general site stability as well as observe for signs of local
instability of an erosional or subsurface nature currently or in the past.
FIELD WORK
Exploration locations were selected by a QG Staff Geologist prior to fieldwork to provide safest
access to relevant soil conditions.The geologist directed the advancement of 1 hand auger borehole
(HA).The borehole was advanced within the boundaries of the slope,to a depth of approximately
2.4 feet below present grade (BPG) in general accordance with the specified contract depth and
equipment capabilities.
During explorations QG logged and field-classified each soil horizon encountered in accordance
with the Unified Soil Classification System (USCS). Representative soil samples were collected
from each unit, identified according to boring location and depth, and placed in plastic bags to
protect against moisture loss for future reference.
QG advanced 1 Wildcat Dynamic Cone Penetrometer(DCP)test at a representative location within
the vicinity of the proposed development and as slope conditions permitted.The penetrometer test
was terminated upon reaching the equipment's maximum practical extent. During penetrometer
advancement, blow counts were recorded in 10-centimeter increments as a thirty-five-pound
3
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
weight was dropped 15 inches. Blow counts were then converted to resistance (kg/cm2), standard
penetration blow counts (N-values), and corresponding soil consistency, with complete results
shown on the attached logs.
SURFACE OBSERVATION
The parcel is a roughly square parcel that is mostly covered by a forest. Situated in the northwest
corner of the parcel is a relatively flat spot where the project site is cleared of vegetation. There is
a mild slope to the north that ascends between a 3H:1 V to 2H:1 V to a bench outside of the parcel
boundary. Flowing from east to west across the parcel is an unnamed stream with channelization
occurring in the eastern portion of the parcel along its bank. Forested land continues north and
south of the parcel and has been clearcut to the east and west. To the west the unnamed stream
merges with Gosnell Creek via a drainage channel through the neighboring agricultural parcel.
Along the northern slope, the trees were relatively straight and did not show signs of bowing or
tilting.
QG performed reconnaissance to observe and document indications of surface degradation or
large-scale slope instability. No obvious features were observed that would indicate an active or
prior deep-seated slope failure within the proposed home area, such as headscarps or significant
downslope accumulations. Topography was generally consistent across the upland site, lacking
prevalent over steepened areas, channelized runout zones, or hummocky deposits. No obvious
evidence of rotational or translational failures or major toppling hazards was observed on the slope
in the proximity of the potential building footprint.No obvious failure features were observed on
adjacent slope areas visible from the subject property during our site visit.
SUBSURFACE CONDITIONS.
Soil exposures along the slope face and stream embankments appear generally consistent
throughout the property and correspond to soils encountered in the hand auger boring. The boring
indicates the soil to be a silty sand with gravel for 29 inches.From 20 to 29 inches the SM soil had
a slightly higher fines content than the soil from 0 to 20 inches,and the soil became more cohesive.
The soil was brown, moist, medium dense to dense, and featured cobbles that were rounded to
approximately 4-inches in diameter. Organics were present in the form of roots and no mottling
was observed. Static groundwater levels are inferred to exist at approximately 81 feet below grade
based on well logs made available by the Department of Ecology.
4
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project # QG24-040
DISCUSSION& CRITICAL SLOPE RECOMMENDATIONS
The findings of QG's site reconnaissance at the subject site appear broadly consistent with
available geologic literature and do not indicate any excessively prohibitive conditions exist for
the site, assuming appropriate site management efforts are maintained. It appears that the
designation as a landslide hazard area is based on mapped topography and mapped pre-historic
mass-wasting deposits,rather than a known or existing pervasive landslide hazard.
In consideration of the available information, and our direct observations, at this time QG does
not consider the site to be within an active landslide hazard area. QG considers the potential
for landslide activity to be low and does not anticipate the proposed development of a residential
home and associated structures to cause significant adverse impacts. With this determination, our
study did not involve slope stability modeling, or deep subsurface explorations directly within the
site and at this time QG does not recommend any further exploration or analysis be conducted.
Based on the information herein, we provide the following development- and site-specific
recommendations that will minimize the inherent risks of developing in a sloped area.
Setback Recommendations:
QG reviewed existing topographic data and general site observations made during our visit to infer
general slope face and slope toe setbacks based on height and inclination of the typical slopes
present on the site in proximity to the proposed structure. Considering the inclination and
conditions of the lower slope, specific setback requirements must be followed for successful
construction at this location. The local critical area ordinance delineates minimum slope toe
setbacks for slopes inclined greater than 40% (-22°), which may be further reduced upon review
by a licensed geotechnical professional under Mason County Code section 8.52.140 (F).
Horizontal setbacks were determined based on standard International Building Code (IBC)
requirements as accepted by the State of Washington. The IBC details required setback
delineations for slopes with an overall inclination less than or equal to 45 degrees. Structures shall
maintain a minimum slope toe setback, H/2 or 15 feet from ascending slopes. These setbacks can
commonly be achieved through a combination of increasing footing embedment depths, in
combination with expanding the building fill pad,and/or partially adjusting the footprint location.
Setbacks can additionally be modified or eliminated if certain stabilization measures are taken.
QG recommends that any new foundations maintain a minimum horizontal slope toe setback
of 26 feet from all points of the slope toe on site (Appendix Q. The setback does not prohibit
lightweight surface improvements such as septic, uncovered decks,patios, walkways, driveways,
landscaping,pathways, etc(if approved by the project engineer).
5
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Foundation Recommendations:
For general foundation design considerations, QG recommends referring to guidelines and
parameters of the International Building Code (IBC, 2018; or most recent edition at the time of
construction). Footings should be placed to a minimum depth of 18 inches for freeze-thaw
protection,but not less than that required by the setback and factor of safety criteria above.
The proposed buildings may utilize either stepped continuous footings with slab-on-grade, or
daylight basement foundations, depending on the chosen development style. For these elements,
upon reaching bearing strata,we recommend benching foundation lines flat,followed by moisture
conditioning of the soil, and vibratory compaction to a firm and unyielding condition. Continuous
perimeter and strip foundations may be stepped as needed to accommodate variations in final
subgrade level. We recommend maximum vertical steps of 18 inches with horizontal spacing of at
least 5 feet be constructed unless specified otherwise by the design engineer. Structural fill may
then be placed as needed to reestablish final foundation grade.
QG recommends up to 1,500 pounds per square foot (psf) for foundations placed on compacted
native soils or approved structural fill soils placed on compacted native soils. Bearing capacities,
at or below 1,500 psf may eliminate the need for additional inspection requirements if approved
by the county. The allowable bearing capacity may be increased by 1/3 for transient loading due
to wind and seismic events.
Existing site soils may be suitable for reuse as structural fill on a case-by-case basis. Imported
material may be used as structural fill. Imported structural fill material should conform to the
WSDOT Standard Specifications, Section 9-03.14(1) Gravel Borrow, or an approved alternative.
For lateral and bearing support, structural fill placement below footings shall extend at minimum
a distance past each edge of the base of the footing equal to the depth of structural fill placed below
the footing [e.g., for a 2.0-foot wide footing, fills placed to approximately 1.5 feet below footing
grade will require a minimum backfill width of 5.0 feet (1.5 feet each side plus 2.0-foot width of
footing)]. Fill shall be placed in maximum 12" thick, horizontal lifts, compacted to a firm and
unyielding condition.
Newly Graded Permanent Slopes&Fill Embankments:
QG recommends that new areas of permanently graded slopes in native soil be inclined no greater
than 3H:IV,catching natural topography at the top and toe. We recommend that areas expected to
receive imported fill be benched, placed, and compacted in accordance with WSDOT Standard
Specifications: Embankment Construction & Hillside Terraces, sections 2-03.3(14) through 2-
03.3(14)D. Fill slopes may be inclined no greater than 2H:1 V. All site slopes should be
permanently stabilized from erosion.
6
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Drainage Controls:
QG recommends proper drainage controls for stormwater runoff during and after site development
to protect the site. The ground surface adjacent to structures should be sloped to drain away at a
5% minimum to prevent ponding of water adjacent to them. All concrete foundations should
incorporate footing drains wrapped in fabric.
Foundations shall incorporate a wraparound footing drain composed of imported clean granular
drain rock. There shall be a perforated drainpipe connected around the perimeter of the footing
drain (within the rock) graded to gravity drain to an outfall pipe,to allow any accumulated water
to be released to an approved drainage feature or location. The outfall point must be lower in
elevation than the lowest point of possible water accumulation in the mat fill, so as to allow any
captured water within the mat or crawlspace to completely drain away from the building footprint
preventing standing water from accumulating.
QG recommends all roof, footing, and wall, water sources (new or existing) be tightlined (piped)
away from the upland site to an existing catch basin, stormwater system, established channel, or
down the slope to be released beyond the base using appropriate energy-dissipating features at the
outfall to minimize point erosion.Roof and footing drains should be tightlined separately or should
be gathered in an appropriately sized catch basin structure and redistributed collectively. If storm
drains are incorporated for impervious flatworks(driveways,patios, etc.), collected waters should
also be discharged according to the above recommendations. All drainage tightlines should be
composed of appropriately sturdy material (such as rigid PVC), sized adequately according to
anticipated flow, and anchored sufficiently. QG recommends slope tightlines be inspected by the
owner periodically to look for signs of damage or displacement requiring repair.
QG does not recommend dispersion of collected stormwater directly downhill from (or adjacent
to)the house, as increased runoff or localized stormwater inundation can negatively impact long-
term erosional and global slope stability. With county/city approval, an outfall to the nearby
unnamed stream south of the project site may be considered for reasonable quantities of
stormwater, so long as appropriate energy reducing features are established at the outfall, such as
fabric and quarry spalls, or other approved methods,to prevent erosion.
Erosion Controls:
Erosion is one of the most common driving forces leading to slope instability. In addition to the
above commentary,the following general recommendations should be implemented in general to
reduce long-term erosion potential of the slope below the project site and maintain slope stability:
7
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
• Minimize the volume and velocity of water that travels toward and down the slope face (via
proper choice of site development features including stormwater controls discussed above).
• Avoid accelerating slope erosion and mass wasting due to human activity such as:
✓ Adding side-cast such as dumping landscape debris or fallen trees on or above the slopes.
✓ Using heavy construction equipment on or near steep slopes.
✓ Excavating near adjacent steep slopes toe or on slope face.
✓ Placing excavated soil near the steep slope crest.
• Prior to construction, a silt fence and/or a continuous line of straw bales should be placed on
the slopeward edge of the construction area. Heavy construction equipment, construction
materials,or native and imported soils should not be placed behind the erosion control devices.
Suitable temporary erosion and sediment control measures should be implemented at the
construction site during and immediately after ground disturbance occurs. Temporary areas
bare of vegetation should be protected from erosion via a blanket of straw or rolled erosion
control product (RECP) during prolonged breaks in site work and prior to reseeding or
revegetation.
• At the end of the project,all bare surfaces and areas of disturbed vegetation should be replanted
and maintained until fully reestablished. Concentrated surface water should not be allowed to
traverse the slope during or after the construction phase of the project. Roof downspouts and
footing drains should be routed into closed separate pipes which outfall into appropriate
drainages. Outlets for these pipes should be protected from erosion through the use of rip-rap
(quarry spalls) or some other energy dissipating device. Similarly, concentrated drainages
should be captured in closed pipe systems and routed down slope to appropriate outfalls.
• Clearing of existing vegetation outside the proposed building area on and adjacent to the
existing slopes should be avoided except as approved by a qualified professional.This provides
additional stability to the loose topsoil and minimizes the effects of down-slope water
movement.This is excepting removal of problem,dead,or dying,trees if posing a direct hazard
to site installations or adjacent roadways.
• Grading or excavation of soils during construction should be accompanied by grass reseeding
and re-vegetation as the project is completed.According to"Vegetation Management:A Guide
for Puget Sound Bluff Property Owners" (Manashe, 1993) the following types of vegetation
provide good to excellent erosion control:
8
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Common Name Botanical Name Deciduous/Evergreen Mature Height
Bi leaf Maple Acer macro h llum Deciduous 60
Douglas Fir Pseudotsu a menziesii Evergreen 200+
Evergreen Vaccinium ovatum Evergreen To 8
Oceans pray Holodiscus discolor Deciduous 10+
Oregon Grape Mahonia spp. Evergreen To 6
Pacific Madrone Arbutus menziesii Evergreen 70
Red huckleberry Vaccinium parvifolium Deciduous To 12
Rose Rose spp. Deciduous 2-10
Salal Gaultheria shallon Evergreen To 4
Salmonberry Rubus s ectabilis Deciduous To 12
Serviceberry Amelanchier alnifolia Deciduous 12+
Snowberry S m horic os albus Deciduous 3+
Vine Maple Acer cricinatum Deciduous 10+
Willow Salix spp. Deciduous 10+
9
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
CLOSING.
We trust this letter satisfies your project needs currently and thank you for the opportunity to be
of service. QG wishes you the best while completing the project.
Respectfully Submitted,
Quality Geo NW, PLLC
Prepared by: Approved by:
o{ Ias/,
e
rin e23 isc \ / 7/29/2024
Sed Ge
LUKEPRESTON MCCANN
Jason Cross Luke Preston McCann, L.E.G.
Staff Geologist Principal Licensed Engineering Geologist
Attachments: Limitations
Appendix A. Site Region and Vicinity Maps
Appendix B.Aerial Site Map
Appendix C. Site Slope Profiles
Appendix D. Exploration Logs
10
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
LIMITATIONS
Upon acceptance and use of this report,and its interpretations and recommendations,the user shall
agree to indemnify and hold harmless QG, including its owners, employees and subcontractors,
from any adverse effects resulting from development and occupation of the subject site.
Ultimately, it is the owner's choice to develop and live in such an area of possible geohazards
(which exist in perpetuity across the earth in one form or another), and therefore the future
consequences, both anticipated and unknown, are solely the responsibility of the owner. By using
this report for development of the subject property, the owner must accept and understand that it
is not possible to fully anticipate all inherent risks of development.The recommendations provided
above are intended to reduce (but may not eliminate) such risks.
This report does not represent a construction specification or engineered plan and shall not be used
or referenced as such. The information included in this report should be considered supplemental
to the requirements contained in the project plans & specifications and should be read in
conjunction with the above referenced information. The selected recommendations presented in
this report are intended to inform only the specific corresponding subjects.All other requirements
of the above-mentioned items remain valid, unless otherwise specified.
Recommendations contained in this report are based on our understanding of the proposed
development and construction activities, field observations and explorations, and laboratory test
results.It is possible that soil and groundwater conditions could vary and differ between or beyond
the points explored. If soil or groundwater conditions are encountered during construction that
differ from those described herein, or if the scope of the proposed construction changes from that
described in this report, QG should be notified immediately in order to review and provide
supplemental recommendations.
The findings of this study are limited by the level of scope applied. We have prepared this report
in substantial accordance with the generally accepted geotechnical engineering practice as it exists
in the subject region.No warranty, expressed or implied, is made.The recommendations provided
in this report assume that an adequate program of tests and observations will be conducted by a
WABO approved special inspection firm during the construction phase in order to evaluate
compliance with our recommendations.
This report may be used only by the Client and their design consultants and only for the purposes
stated within a reasonable time from its issuance, but in no event later than 18 months from the
date of the report. It is the Client's responsibility to ensure that the Designer, Contractor,
Subcontractors,etc. are made aware of this report in its entirety.Note that if another firm assumes
Geotechnical Engineer of Record responsibilities,they need to review this report and either concur
with the findings, conclusions, and recommendations or provide alternate findings, conclusions
and recommendation.
Land or facility use,on-and off-site conditions,regulations,or other factors may change over time,
and additional work may be required.Based on the intended use of the report,QG may recommend
that additional work be performed and that an updated report be issued.Non-compliance with any
of these requirements by the Client or anyone else will release QG from any liability resulting
from the use of this report. The Client, the design consultants, and any unauthorized party, agree
to defend, indemnify, and hold harmless QG from any claim or liability associated with such
unauthorized use or non-compliance. We recommend that QG be given the opportunity to review
the final project plans and specifications to evaluate if our recommendations have been properly
interpreted. We assume no responsibility for misinterpretation of our recommendations.
11
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Appendix A. Site Region & Vicinity
REGION
.4
P.f
CINITY
RY .
MIZZf
T< y�i_fY ,rns9..,f,^ [•eJ:f'iP1i1
t
f M *J
_,��1� '•` ''r. Y(�`i y, rrT.. Ri,rr ,�+y yyy{✓✓✓i,'1�ffJI
x.
Ijl,
off
r :S r s r qg: or f J f Lrk ,If
+ff Quality Geo, Site Region Source:Goople Imagery.2024
Scale&Locations are approx. Figure 1
PLLC Smith CAO Not for Construction
12
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Appendix B. Aerial Site Map
. t
J, 04
HA-1
l DCP-1
1! �,j ` •• �- fart •'� .
Legend
Mapped Landslide
Proposed Buildings
.,•;, �". Profile A
Parcel
Exploration Locations
DCP
4L Hand Auger
Slope
— Crest
Toe
SCALE . E4
Quality Geo Site Map Source:Mason Co.GIS.2024
Scale&Locations are approx. Figure 2
NW, PLLC Smith CAO Not for Construction
13
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project # QG24-040
ApPendi�µC,Sloye Profiles
Cross Section (A-A'
300
280
260
—300
U
240 Ct Proposed Home
—22o
e .
S
220
Minimum 26-foot
200 horizontal foundation
slope toe setback
1S0
0 20 40 60 80 100 120 140 160 ISO 200 220 240
Ho> zontal Distance ,feet;
Quality Geo Slope Profile A—X Source:WA DNR LiDAR&Hand Measurements Scale&Locations are approx. Fi gure 3
NW, PLLC Smith CAO Not for Construction
14
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
Appendix D. Exploration Loss
LIAL LO
G IY Hand Auger Log HA-1
t\4V
PROJECT NUMBER QG24-040 FIELD WORK DATE 6/25/24 BORING LOCATION Northwestern comer of
PROJECT NAME Smith CAO DRILLING METHOD Hand Auger Boring parcel
PROJECT LOCATION Shelton,WA SURFACE ELEVATION Existing
LOGGED BY JC
COMMENTS
F
Material Description
S W a A H
u7 n O 7
SM SILTY SAND with GRAVEL
Brown,moist,organics(roots),cobbles(up to 4 inches,rounded),no mottling,medium dense to dense
VISUAL CLASSIFICATION:
Gravel=30%;Sand=55%;Fines=15%
0.5
HA-1@7 N
inches
1
1.5
- -- -----------------------------------------
SM SILTY SAND with GRAVEL
Brown,moist,few organics(roots),cobbles(up to 4 inches,rounded),no mottling,dense
VISUAL CLASSIFICATION:
Gravel=25%;Sand=50%;Fines=25%
2
HA-1@26 N
inches
Terminated at refusal
2.5 No groundwater encountered
Quality Geo NW.PLLC-Ph:360-878-9705,qualitygeonw.com,4631 Whitman Lane SE.Ste D,Lacey,WA Page 1 of 1
produced by ESIog.ESdat.net on 25 Jun 2024
15
Smith CAO Quality Geo NW, PLLC
7/29/2024 Project# QG24-040
WILDCAT DYNAMIC CONE LOG Page 1 of 1
Quality Geo NW,PLLC
Geotechnical Consultants PROJECT NUMBER: QG24-040
Lacey,WA DATE STARTED: 06-25-2024
DATE COLLETED: 06-25-2024
HOLE It:DCP-I
CREW:JC SURFACE ELEVATION: Existing
PROJECT: Smith CAO WATER ON COMPLETION: No
ADDRESS:W Wivell Rd,Shelton,WA HAMMER WEIGHT: 35 tbs.
LOCATION:Northwestem comer of the parcel CONE AREA: 10 sq.cm
BLOWS RESISTANCE GRAPH OF CONE RESISTANCE TESTED CONSISTENCY
DEPTH PER 10 cm Kp..cm, 0 50 100 150 N NON-COHESRT COHESAT
14 62.2 17 MEDIUM DENSE VERY STIFF
22 97.7 25+ XIEDIUM DENSE VERY STIFF
I ft 50 222.0 25+ VERY DENSE HARD
2ft
3ft
- lm
- 4ft
5ft
6ft
- 2m
- 7ft
8ft
9ft
3m loft
lift
12ft
- 4m 13ft
16