HomeMy WebLinkAboutGEO2018-00070 FPA2018-00014 - FPA Permit / Conditions - 11/27/2018 Za 18 -060%
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DEC 0 5 2018
615 W. Alder SbWt
Geotechnical Report
for
Anderson and Welch Logging and Residences
Parcel No. 12220-50-60001
Parcel No. 12220-50-61004
Mason County, Washington
November 27, 2018
Project#18212
Prepared For:
Susan Welch
Kathy Anderson
4062 N E1 Sereno Circle , L ,),. , t
Mesa, AZ 85207
Prepared By: 1
Envirotech Engineering, PLLC
PO Box 984
Belfair, Washington 98528 i i/27/18
Phone: 360-275-9374
MASON COUNTY
COMMUNITY SERVICES �1
6u,[dmg,PIJnnmy.Enun comental Health Community Health Geotechnical Report
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 Anderson/Welch Parcel# 12220-50-60001 and 12220-50-60010
Site Address Allvn
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development.
Located on page(s) 5
(b) A discussion of specific soil types,
Located on page(s) 6-7
(c) A discussion of ground water conditions,
Located on page(s) 7
(d) A discussion of the upslope geomorphology,
Located on page(s) 3
(e) A discussion of the location of upland waterbodies and wetlands.
Located on page(s) 3
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records.
Located on page(s) 8
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) _ Site Plan—Appendix A
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Site Plan and Soil Logs(Appendix B)
(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) Site Plan
(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) _ Soil Profile (Appendix B)
(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) 9-10
(7) (a) Appropriate restrictions on placement of drainage features,
Rev. February 2018
Located on page(s) 15-16
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) 17
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 12-14
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 16
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 15-16
(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) 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) 10
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) 11
(11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
Located on page(s) 16- 18
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 18
(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) Site Plan
I, Michael Staten, hereby certify under penalty of perjury that I am a civil engineer licensed in the State of
Washington with specialized knowledge of geotechnicaligeological 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 November 27,2018,and entitled Anderson
„., Welch Logging& Residences, meets all the requirements of
the Mason County Resource Ordinance, Geologically Hazardous
v
Areas Section,is complete and true,that the assessment
demonstrates conclusively that the risks posed by the landslide
a 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.
Page 2 of 2
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
,
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................... 1
..............................
1.1 PROJECT INFORMATION.....................................................................................................................1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK......................................................................... 1
2.0 SURFACE CONDITIONS....................................................................................................................3
2.1 GENERAL OBSERVATIONS.........................
2.2 TOPOGRAPHY..................... 3
.... ......................................
2.2.1 Upslope Geomorphology..........................................................................
2.3 SURFACE DRAINAGE...........................................................................................................................3
..........
.3.1 Upslope Water Bodies................................................................................................ 3
2.4 SLOPE AND EROSION OBSERVATIONS................................................................................................3
3.0 SUBSURFACE INVESTIGATION.....................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5
3.2 GENERAL GEOLOGIC CONDITIONS....................................................................................................5
3.3 SPECIFIC SUBSURFACE CONDITIONS.................................................................................................7
3.3.1 Groundwater...............................................................................................................................8
4.1 SLOPE STABILITI................ ....................................................................................... 9
4.1.1 Slope Stability Analysis.......................................................................... ......................10
..................................
4.2 EROSION............................................................................................................................................ 11
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION.................................................. 11
...........................
4.3.1 Liquefaction.............................................................................................................................. 12
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS....................................................... 12
4.5 LATERAL EARTH PRESSURES......................................................................................... 12
4.6 ON-SITE AND OFF-SITE IMPACTS................................. . . .................
12
5.0 ENGINEERING RECOMMENDATIONS.......................................................................................13
5.1 BUILDING FOUNDATION RECOmMENDATIONS................................................................................ 13
S.1.1 Bearing Capach)...................................................................................................................... 13
5.1.2 Settlement.................................................................................................................................. 14
5.1.3 Concrete Slabs-on-Grade......................................................................................................... 14
5.2 EARTHWORK CONSTRUCTION RECOMNIENDATIONS........................................................ 14
5.2.1 Excavation....................................................................................................I...........................14
5.2.2 Placement and Compaction of Native Soils and Engineered Fill........................................... 14
5.2.3 Retaining Wall Backfill............................................................................................................ 15
5.2.4 Wet Weather Considerations.................................................................................................... 16
S.2.S Building Pads........................................................................................................................... 16
5.3 BUILDING A1D FOOTh�t6�ETBACKS,.. T:.. .........-.. ..:.:......... 16
5.4 SURFACE AND SUBSURFACE DRAINAGE........................................................................................... 16
5.5 VEGETATION BUFFER AND CONSIDERATIONS................................................................................. 17
5.6 TEMPORARF AND PER%I.xNENT EROSION CONTROL....................................................................... 17
5.7 SEPTIC DRAtNFIELDS........................................................................................................................ 18
5.8 STRUCTURAL MITIGATION............................................................................................................... 18
5.9 TIMBER HARVESTING RECOM%I ENDATIONS................................................................................... 18
6.0 CLOSURE............................................................................................................................................ 19
Appendix A-Site Plan
Appendix B-Soil Information
Appendix C-Slope Stability
Appendix D—Erosion Control
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned
project located in Allyn, identified as parcel numbers 12220-50-60001 and 12220-50-61004,
Mason County, Washington. See the vicinity map on die following page for a general depiction of
the site location.
An initial geotechnical evaluation of the project was conducted by Envirotech on October 10.2018.
It was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were present
within 300 feet of the planned development. Based on this site characteristic, the proposed
development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason
County Resource Ordinance (MCRO) 8.52.140. During the site visit by Envirotech, surface and
subsurface conditions were assessed. After completion of the field work and applicable project
research. Envirotech prepared this geotechnical report which, at a minimum, conforms to the
applicable MCRO.
As presented herein, this report includes infonnation pertaining to the project in this Introduction
Section: observations of the property and surrounding terrain in the Surface Conditions Section.
field methods and soil descriptions in the Subsurface Investigation Section:. supporting
documentation with relation to slope stability, erosion, seismic considerations, and lateral earth
pressures in the Engineering Analyses and Conclusions Section; and, recommendations for
foundation, settlement. earthwork construction, retaining walls, erosion control, drainage, and
vegetation in the Engineering Recommendations Section.
1.1 Project Information
Information pertaining to the planned development of the project was provided by the proponent
of the property. The properties are planned to be logged. In addition, single family residential
development is planned for the future.
1.2 Purpose of Investigation and Scope of Work
The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the
project in order to provide geotechnical recommendations that should be implemented during
development. The investigation included characterizing the general project surface and subsurface
conditions, and evaluating the suitability of the soils to support the planned site activities.
In order to fulfill the purpose of investigation,the geotechnical program completed for the proposed
improvements of the project include:
• Review project information provided by the project owner and/or owner's representative;
• Conduct a site visit to document the site conditions that may influence the construction and
performance of the proposed improvements of the project;
• Define general subsurface conditions of the site by observing subsoils within test pits and/
or cut banks, review geological maps for the general area. research published references
concerning slope stability, and review water well reports from existing wells near the
project;
• Collect bulk samples,as applicable, at various depths and locations:
Envirotech Engineering. PLLC Parcel 12220-50-61004
PO Box 981 page 1 Parcel 12220-50-60001
Belfair. %Vashincton 98528 Mason Count\. Washington
Ph. 360-275-9374 November 27.2018
• Perform soils testing to determine selected index and/or engineering properties of the site
soils; "
• Complete an engineering analysis supported by the planned site alterations,and the surface
and subsurface conditions that were identified by the field investigation, soil testing, and
applicable project research;and,
• Establish conclusions based on findings, and make recommendations for foundations,
drainage, slope stability, erosion control, earthwork construction requirements, and other
considerations.
- -- Project
C"d
Allyn
Vicinity Map from Mason County Website
Envirotech Engineering. PLLC Parcel 12220-50-61004
PO Box 984 page 2 Parcel 12220-50-60001
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 November 27.2018
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on October
10, 2018 by a representative with Envirotech. During the site visit, the type of geotechnical
investigation was assessed,site features were documented that may influence construction,and site
features were examined that may be influenced by construction. This Surface Conditions Section
provides information on general observations, vegetation, topography, drainage and observed
slope/erosion conditions for the project and surrounding areas that may impact the project.
2.1 General Observations
Currently,the property is vacant and forested. Vegetation on and near the project consists primarily
of secondary growth firs,cedars,and other trees and shrubbery. including blackberries,common to
this area of the Pacific Northwest.An aerial photo of the project and immediate vicinity is provided
on the following page.
2.2 Topography
The topographic information provided in this section was extrapolated from a public lidar source.
and incorporated observations and field measurements. Where necessary, slope verification
included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site
Plan in Appendix A in this report for an illustration of general topography with respect to the
planned development.
Critical ascending slopes,with grades exceeding 40% appear to be within 300 feet of the planned
development.The critical slopes are located to the east and south east of the project site. Descending
slopes range from critical to non-critical with a vertical relief of about 30 to 40 feet.
2.2.1 Upslope Geomorphology
The upland area of the property and beyond is generally situated on a hillside of glacial origin.
2.3 Surface Drainage
Runoff originating upslope of the development mostly sheet flows and is channelized and
controlled. Except within drainage channels, excessive scour. erosion or other indications of past
drainage problems were not observed within the immediate vicinity of the planned development.
2.3.1 Upslope Water Bodies
There are no apparent water bodies or wetlands located Upslope from the planned development that
would significantly influence the project. Although the lakes within the Lakeland development are
upslope, it is apparent that the geology and topography prevents groundwater and surface water
problems to occur on the properties directly from these lakes.
2.4 Slope and Erosion Observations
The slope gradients near the project signal a potential landslide or erosion hazard area. Some
Envirotech Engineering. PLLC Parcel 12220-50-61004
PO Box 984 page 3 Parcel 12220-i0-60001
Belfair. Washington 98-528 Mason Count\. Washington
Ph. 360-275-9 374 November 27. 2018
indicators that may suggest past slope movements include;
• Outwash of sediments near the bottom of the slope.
• Fissures, tension cracks, hummocky ground or stepped land masses on the face or top of
the slope, and parallel to the slope.
• Fine. saturated subsurface soils.
• Old landslide debris.
• Significant bowing or leaning trees, or.
• Slope sloughing or calving.
These slope instability indicators or other significant mass wasting on the property or within the
general vicinity of the project were not observed or discovered during research. Indications of past
landslides,current unstable slopes.deep-seated slope problems.or surficial slope failures were not
observed during the site visit.
♦. f
Alit
t
Aerial Photo from Google Website
Envirotech Engineering, PLLC Parcel 12220-50-61004
PO Box 984 page 4 Parcel 12220-50-60001
Belfair. Washington 98528 Mason County, Washington
Ph. 360-275-9374 November 27.2018
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on October
10. 2018 by a representative with Envirotech. Applicable information on field methods, sampling,
field testing, general geologic conditions, specific subsurface conditions, and results from soil
testing are presented in this section of the report. Appendix B of this report includes pertinent
information on subsurface conditions for the project,such as subsoil cross-section(s),test pit log(s),
and applicable water well report(s). Water well reports were utilized to estimate ground water
levels, and if sufficient, were used in identifying subsoil types. Applicable test pit locations are
depicted on the Site Plan provided in the appendix of this report.
3.1 Field Methods, Sampling and Field Testing
Information on subsurface conditions for the project was accomplished by examining soils within
test pits and/or nearby banks extending to depths of up to 3.5 feet below the natural ground surface.
Information on subsurface conditions also included reviewing geological maps representing the
general vicinity of the project, and water well reports originating from nearby properties.
Soil samples were not obtained from this project. Envirotech measured the relative density of the
near-surface in-situ soils by gauging the resistance of hand tools. Within testing locations, field
testing results generally indicated loosely dense soils in the upper 18 inches, and medium dense
soils from 18 inches to the depth of terminus.
3.2 General Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the"Geologic Map of Washington,"compiled by J. Eric Schuster,2002
indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated deposits,
and dominantly deposited from glacial drift, including alluvium deposits. This project is located
within the Puget Lowland.Typically,"lower tertiary sedimentary-rocks unconformabiy overlie the
Crescent Formation."as revealed in the Geologic Map. Initial sedimentary rocks were formed from
shales, sandstones and coal deposits from rivers. During the Quaternary period,the Puget Lowland
was covered by numerous ice sheets, with the most recent being the Fraser glacier with a peak of
approximately 14,000 years ago. Upon the glacial retreat, the landscape was formed by glacial
erosion and glacial drift deposits.
The "Geologic Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap and Pierce Counties,
Washington"by Michael Polenz.Katelin Alldritt.Nicholas J. Hehemann, Isablle Y. Sarikhan,and
Robert L. Logan.July 2009, provides the following caption(s) for the project area:
Lm irotech Eneineerin_. PLLC --- --- -- Parcel 12220-50-61004
PO Box 984 page 5 Parcel 12220-50-60001
Belfair. Washinaton 98528 Mason Count%. Washington
Ph. 360-275-9374 November 27.2018
Qgt Vashon tilt---Unsorted. unstratilicd(but locally banded) mix of clay. silt.
sand.and,raxel: typically supported by a sandy matrix: mostly gray but
locally ranging to tart. light brown.or oram,e. typically unweathered;
lodgment till compact.%%Ith%ell-developed tacics resembling concrete.
but near the surface commonly hackle and(or) looser and covered by I to
b tt of loose ablution till.deposited directly by glacial ice and commonly
includes clasts or clumps plucked front underlying units.C'lasts am
commonly striated and fitCClCd,kith angular or rounded edges. Boulders
arc gcmrally sparse"ithin the till but large(greatly)boulders of plutonic
or metamorphic rock are common on till surface-.. Some exposures include
interbands and lenses of sand and gta%cf. locally .%ith;hears and joints.
Till terms a local!-, patchy and sectttingty randomly distributed cover up to
it seycral tens of feet thick. �%ith a thickness of,;to_"o ft roost coutnxon. It
typically dominate>,but is also locally discontinuous on, flitted surfaces.
with indi,idual drumlins mcasurins,( to O.� mi wide b% tl.( to 1.3 sni
long and the Ian-axis aligned»ith the direction of ice lltm. Till typically
is in sharp.unconlurntable contact with underlying units. most commonly
advance outwash(unit Q;a and subunit). Unit Qgt lies strati,,r:sphically
below unit Q., - It may include unrccoLniicd exposures ofulder till. :
map boundary mismatch bcm cell unit Qgt on this map and unit Q,os on
the Vaughn quadrangle to the south(Lo`,an and llalsh. 2007)snav ha\c
resulted from a map-production error in the nortim cst curter of the
Vaughn map(Josh Logan.Wash. Dien.of(icology and Farth Resources.
oral commun..2INN).
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Geological Alap Department of'Aatural Resources H"ashington State
Envirotech Engineering, PLLC Parcel 12220-50-61004
PO Box 984 pay_,c 6 Parcel 12220-50-60001
Belfair. Washington 98528 Mason County. Washington
Ph. 360 275-9374 November 27.2018
3.3 Specific Subsurface Conditions
The following subsurface conditions are estimated descriptions of the project subgrade utilizing
information from the depth of penetration at all testing, sampling. observed and investigated
locations. Soils for this project were primarily described utilizing the Unified Soil Classification
System (USCS)and the Soil Conservation Service(SCS)descriptions.
The project is currently composed of native soils with some indications of fill. Within the exposed
3.5 feet of test pit, soils were generally observed to be moist, brown silty sand with gravel (SM).
These sediments extend vertically to a depth of 20 feet. This information is based on nearby well
reports, site geology. and/or knowledge of the general area. Hardpan is most likely present within
the upper 5 feet from the around surface.
The relative densities of the soil within selected test area are provided above in Section 3.1.
Expanded and specific subsurface descriptions, other than what is provided in this section, are
provided in the soil logs located in Appendix B of this report.
According to the"Soil Survey of Mason County,"by the United States Department of Agriculture,
Soil Conservation Service, the site soils are described as Sinclair shotty loam, So, with 5% - 15%
slopes,and Everett gravelly loamy sand,Ed,with 0%-5%slopes.The soil designations are depicted
in the aerial photograph below, and descriptions are provided in Appendix B of this report.
Em irotech Engineering. PLLC Parcel 1 2220-50-6 1 004
PO Box 984 page 7 Parcel 12220-50-60001
Belfair.Washington 98528 Mason County, Washington
Ph. 360-275-9374 Novernber 27.1-018
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Project
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Soil Survey From USDA Natural Resources Conservation Service
3.3.1 Groundwater
From the water well report(s)and knowledge of the general area,permanent groundwater is at least
90 feet.directly below the property at the project location. Surface seepage or perched groundwater
at shallow depths was not observed on-site,nor indicated on the well reports.
Envirotech Engineering, PLLC Parcel 12220-50-61004
PO Box 984 page 8 Parcel 12220-50-60001
Belfair. Washington 98528 Mason County, Washington
Ph. 360-275-9374 November 27.3018
4.0 ENGINEERING ANALYSES AND CONCLUSIONS
The following section includes slope stability,erosion,seismic considerations,and impacts to both
on-site and off-site properties.
4.1 Slope Stability
Landslides are natural geologic processes, and structures near slopes possess an inherent risk of
adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering
cannot eliminate these risks for any site with sloping grades because gravity,is constantly inducing
strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will exacerbate these
strains. Geotechnical engineering considers excessive wet weather and 'design' earthquakes in
order to provide an acceptable factor of safety-for developing on or near sloping terrain with relation
to current engineering protocol.These factors of safeties are based on engineering standards such
as defining engineering properties of the soil, topography, water conditions, seismic acceleration
and surcharges. Surface sloughing or other types of surficial slope movements usually do not affect
the deep-seated structural capability of the slope. However. repeated surficial slope movements, if
not repaired, may represent a threat to the structural integrity of the slope. If any slope movement
arises, the slope should be inspected by an engineer. Subsequently, maintenance may be required
in order to prevent the possibility of further surficial or deep seated slope movements that may be
damaging to life and property.
According to the Coastal Zone Atlas of Mason County, Washington,the project is within and near
terrain labeled -Stable' and 'Intermediate' regarding potential landslide activity. Descriptions of
these mapping units may be found in the aforesaid Atlas. A Stability Map from the Coastal Zone
Atlas for the general area of this project is provided below:
Project
Map from Washington State Department of Ecology Website
Envirmcch Engineering, PLLC Parcel 1 2220-50-6 1 004
PO Box 984 raec 9 Parcel 12220-50-60001
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 27.2018
According to the Resource Map from the Washington State Department of Natural Resources
(DNR), the project is not within terrain labeled 'highly unstable' relating to soils. DNR labeled
portions of this project as medium and high slope instability with relation to slopes. A Resource
Map from the DNR Forest Practices Application Review System is provided below:
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Resource Map from Washington State Department of Natural Resources Website
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4.1.1 Slope Stability Analysis
The Simplified Bishop Method, utilizing 'STABLE' software, was used to analyze the static
stability of the site slopes. Seismic conditions were estimated utilizing worst case scenario values
from the static analysis, a quasi-static analysis coefficient of at least 0.15, and applying the
applicable values to STABLE software. Various radii's and center points of the circle were
automatically selected, and produced factor of safeties in a graphical and tabular format. Worst
case scenario values were used in the slope stability analysis in regards to topography, surcharges.
water content,internal friction and cohesion of the site soils. STABLE software has been repeatedly
checked-with manual calculations.and consistently proved to be a very conservative program. The
following soil properties were used in the analysis. and are based on observed conditions, known
geology,and/or published parameters:
Envirotech Engineering, PLLC Parcel 12220-50-61004
PO Box 984 I'n'� 1 i� Parcel 12220-50-60001
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 November 27,2018
Upper layer soil depth to 3.5 feet
Soil unit weight: 132 pcf
Angle of internal friction: 30 degrees
Cohesion: 200 psf
Based on the slope stability analysis, unacceptable factors of safety could be present on and near
the critical slope, but do not reflect conditions where development is expected to occur. For this
project, at the location of the proposed development, minimum factor of safeties for static and
dynamic conditions were estimated to be over 1.5 and LI. respectively. See the slope stability-
information in Appendix C for a depiction of input parameters and example of outputs.
4.2 Erosion
Based on the USCS description of the project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,the
project is not within terrain labeled 'highly erodible.' This Project is not within an erosion hazard
area as defined by the MCRO. Erosion hazard areas are those with USDA SCS designations of
River Wash (Ra), Coastal Beaches (Cg). Alderwood Gravelly Sandy Loam on slopes 15% or
greater(Ac and Ad),Cloquallum Silt Loam on slopes 15%or greater(Cd),Harstine Gravelly Sandy
Loam on slopes 15% or greater(Hb), and Kitsap Silt Loam on slopes 15%or greater(Kc).
It is our opinion that minor erosion control recommendations provided in this report is sufficient
for the development of this project, and additional engineered erosion control plans are not
required. Temporary and permanent erosion control measures are required for site development.
Extents of temporary erosion control will mostly depend on the timeliness of construction,moisture
content of the soil, and amount of rainfall during construction. Soil erosion typical to the existing
site conditions and planned disturbance of the project include wind-borne silts during dn-weather,
and sediment transport during prolonged wet weather. Sediment transport could be from
stormwater runoff or tracking off-site with construction equipment.
The Temporary and Permanent Erosion Control Section (Section 5.6) of this report consist of
specific erosion controls to be implemented. Additional erosion control information and
specifications may be found in the latest addition of the "Stormwater Management Manual for
Western Washington." prepared by the Washington State Department of Ecology Water Quality
Program.
4.3 Seismic Considerations and Liquefaction
There are no known faults beneath this project. The nearest Class 'A' or Class 'B' fault to this
property is the Tacoma Fault Zone, in which is less than 2 miles to the south of this project. This
information is based on the USGS Quaternary Fault and Fold Database for the United States.
Potential landslides due to seismic hazards have been considered, and are addressed in the Slope
Stability Analysis Section provided earlier in this report. Soils immediately below the expected
foundation depth for this project are generally Type D, corresponding to the International Building
Code(IBC)soil profiles. According to the IBC,the regional seismic zone is 3 for this project. The
estimated peak ground acceleration ranges from 0.50g to 0.60g. This estimation is based on the
Envirotech Engineering. PLLC Parcel 12220-50-61004
PO Box 984 page I I Parcel 12220-50-60001
Belfair. N"ashinaton 98S28 Mason Counn. Washinoton
Ph. 360-275-9374 November 27.2018
United States Geological Survey (USGS) National Seismic Hazard project in which there is an
estimated 2% probability of exceedance within the next 50 years.
4.3.1 Liquefaction
The potential for liquefaction is believed to be low for this project. This is based, in part. on the
subsurface conditions such as soil characteristics and the lack of a pennanent shallow water table.
Subgrade characteristics that particularly contribute to problems caused from liquefaction include
submerged, confined, poorly-graded granular soils (i.e. gravel. sand, silt). Although gravel- and
silt-sized soil particles could be problematic,fine and medium grained sands are typically subjected
to these types of seismic hazards. No significant saturated sand stratifications are anticipated to be
within the upper 50 feet of the subsoil for this project.
4.4 Landslide,Erosion and Seismic Hazards Conclusions
DNR indicated historic landslide activity near. but away from influencing the project. Mapped
slope conditions, as delineated by the Departments of Ecology and/ or Natural Resources, were
considered in our slope stability assessment. Based on the proximity and severity of mapped
delineations with respect to the proposed development, results of the aforesaid slope stability
analysis, observed surface conditions, and other pertinent information, it is our opinion that the
proposed development may occur in accordance with the recommendations in this geotechnical
report.
4.5 Lateral Earth Pressures
Lateral earth pressures exerted through the backfill of retaining wall are dependent upon several
factors including height of retained soil behind the wall, type of soil that is retained. degree of
backfill compaction, slope of backfill,surcharges,hydrostatic pressures,earthquake pressures,and
the direction and distance that the top of the wall moves. Significant retaining structures are not
anticipated for this project. If retaining walls are later planned for this project. prescriptive
requirements from the County should be adhered to. For retaining structures with a height
exceeding County, prescriptive requirements. additional design parameters must be accounted for
in the retaining wall analysis. and recommendations should only be provided by a qualified
engineer after the type of backfill is acquired. inclination of backfill slope is estimated;and the final
wall height is determined.
4.6 On-Site and Off-Site Impacts
From a geotechnical position. it is Envirotech's opinion that the subject property and adjacent
properties to the proposed development should not be significantly impacted if all
recommendations in this report are followed. This opinion is based on the expected site
development, existing topography. existing nearby development, land cover, and adhering to the
recommendations presented in this report. Future development or land disturbing activities on
neighboring properties or properties beyond adjacent parcels that are upslope and/or downslope
from the subject property could cause problems to the subject property. For this reason, future
development or land disturbance near the subject property should be evaluated by a geotechnical
engineer.
Envirotech Engineerin;. PLLC Parcel 1 2220-50-6 1 004
PO Box 984 raL,, 1 Parcel 12220-50-60001
Belfair. % ashinuton 98528 Mason Count%. �'�ashin2ton
Ph. 360-275_9374 No%ember 27. 2018
5.0 ENGINEERING RECOMMENDATIONS
The following sections present engineering recommendations for the proposed improvements of
the project. These recommendations have been made available based on the planned improvements
as outlined in the Introduction Section of this report: general observations including drainage and
topography as recapitulated in the Surface Conditions Section: soil/geologic conditions that were
identified from the geotechnical investigation that is summarized in the Subsurface Investigation
Section:and,project research,analyses and conclusions as determined in the Engineering Analysis
and Conclusions Section. Recommendations for the project that is provided herein, includes
pertinent information for building foundations, earthwork construction, building and/ or footing
setbacks, drainage, vegetation considerations, and erosion control.
5.1 Building Foundation Recommendations
Recommendations provided in this section account for the site development of a typical one- or
two-story-, single family residential structure. The recommended allowable bearing capacities and
settlements as presented below, consider the probable type of construction as well as the field
investigation results by implementing practical engineering judgment within published engineering
standards. Evaluations include classifying site soils based on observed field conditions and soil
testing for this project. After deriving conservative relative densities, unit weights and angles of
internal friction of the in-situ soils,the Terzhagi ultimate bearing capacity equation was utilized for
determining foundation width and depth. Foundation parameters provided herein account for
typical structural pressures due to the planned type of development. A structural analysis is beyond
the scope of a geotechnical report, and a structural engineer may be required to design specific
foundations and other structural elements based on the soil investigation. Stepped foundations are
acceptable, if warranted for this project. Continuous, isolated, or stepped foundations shall be
horizontally level between the bottom of the foundation and the top of the bearing strata. The frost
penetration depth is not expected to extend beyond 12 inches below the ground surface for this
project under normal circumstances and anticipated design features.
5.1.1 Bearing Capacity
Existing in-situ soils for this project indicates that the structure can be established on shallow.
continuous or isolated footings. Foundations shall be established on relatively undisturbed native
soil that is competent and unyielding. Alternatively, foundations may be constructed on selective
re-compacted native soil or compacted engineered fill as described in the Earthwork Construction
Recommendations Section of this report.
For a bearing capacity requirement of no more than 1500 psf,a minimum continuous footing width
of 12 inches(15 inches for 2-story structures)shall be placed at a minimum of 18 inches below the
native ground surface, beneath existing fill and atop unyielding soils. For a columnar load of no
more than 3 tons, a circular or square isolated foundation diameter or width shall be at least 24
inches. Foundation recommendations are made available based on adherence to the remaining
recommendations that are provided in this report. Alterations to the aforementioned foundation
recommendations may be completed upon a site inspection by a geotechnical engineer after the
foundation excavation is completed.
Ens irotech Engineering. PLLC Parcel 12220-50-61004
PO Box 984 page 13 Parcel 12220-50-60001
Belfair. Washington 98528 Mason Count%. Washington
Ph. 360-275-9374 November 27.2018
5.1.2 Settlement
Total and differential settlement that a structure will undergo depends primarily on the subsurface
conditions, type of structure, amount and duration of pressure exerted by the structure, reduction
of pore water pressure, and in some instances. the infiltration of free moisture. Based on the
expected native soil conditions, anticipated development, and construction abides by the
recommendations in this report, the assumed foundation system may undergo a maximum of 1.0
inch total settlement, and a maximum differential settlement of 0.75 inch.
5.1.3 Concrete Slabs-on-Grade
Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted coarse.
granular material(Retained on U.S.Sieve#10 or greater)that is placed over undisturbed,competent
native subgrade or engineered fill per the Earthwork Recommendations Section below.
The recommendations for interior concrete slabs-on-grade as presented herein are only relevant for
the geotechnical application of this project.Although beyond the scope of this report,concrete slabs
should also be designed for structural integrity and environmental reliability. This includes vapor
barriers or moisture control for mitigating excessive moisture in the building.
5.2 Earthwork Construction Recommendations
Founding material for building foundations shall consist of undisturbed native soils to the specified
foundation depths. Compacted engineered fill, or selective re-compacted native soils may be used
to the extents provided in this Earthwork Construction Recommendations Section. The following
recommendations include excavations, subgrade preparation. type of fill, and placement of fill for
building foundations.
5.2.1 Excavation
Excavation is recommended to remove any excessive organic content or other deleterious material.
if present, beneath foundations and to achieve appropriate foundation depth. Additional sub-
excavation will be required for this project if the soils below the required foundation depth are
loose, saturated,not as described in this report,or otherwise incompetent due to inappropriate land
disturbing, or excessive water trapped within foundation excavations prior to foundation
construction. All soils below the bottom of the excavation shall be competent, and relatively
undisturbed or properly compacted fill. If these soils are disturbed or deemed incompetent, re-
compaction of these soils below the anticipated footing depth is necessary. Excavations shall be
completely dewatered, compacted, and suitable before placement of additional native soil.
engineered fill or structural concrete.
5.2.2 Placement and Compaction of Native Soils and Engineered Fill
For engineered fill or disturbed native soils that will be utilized as fill material directly beneath
foundations, observation and/or geotechnical testing is required prior to foundation construction.
The following placement and compaction requirements are necessary.
Envirotech Engineerin_. PLLC -- Parcel I1220-50-61004
PO Box 98.3 pa_e I4 Parcel 1� 20-;0-600u0!
Belfair. Washington 98�28
\taum Counr%. \\ashin_toll
Ph. ;60-27i-9374 \'(nemhcr 1 7. _018
For disturbed native soils or engineered fill beneath foundations, limits of compacted or re-
compacted fill shall extend laterally from the bottom edge of the foundation at a rate of one
horizontal foot for each foot of compacted or re-compacted fill depth beneath the foundation. See
the illustration below.
FOOTING
COM7ENGINEERED
D
NATOILS
OR tFIL
i 1
I l•I l 1i.�t.. _.. _ ._ T_l 1— _ _
II �
UN1ISTURBED SUBGRAI)E
Both engineered fill and native soils used as compacted fill should be free of roots and other
organics, rocks over 6 inches in size, or any other deleterious matter. Because of moisture
sensitivity, importing and compacting engineered fill may be more economical than compacting
disturbed native soils. Engineered fill shall include having the soils retained on the No. 4 sieve
crushed(angular),and should consist of the following gradation:
U.S.Standard Sieve %Finer(by weight)
6" 100
60— 100
No.4 20—60 I
No.200 0- 8 I
Table I
Particle Size Distribution of Engineered Fill
Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native soils and
engineered fill, respectively. Each lift should be uniformly compacted to at least 95% of the
modified Proctor maximum dry density (ASTM D 1557) and within 3% of optimum moisture
content. Each lift surface should be adequately maintained during construction in order to achieve
acceptable compaction and inter-lift bonding.
Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be limited to a
slope of 2:1 (horizontal:vertical). Utility trenches or other confined excavations exceeding 4 feet
should conform to OSHA safety regulations. Permanent cut and fill slopes shall be limited to a
slope of 2:1. unless otherwise approved by an engineer.
5.2.3 Retaining Wall Backfill
As previously mentioned, significant retaining structures are not anticipated for this project.
However, if used, native soils may be used as retaining wall backfill for this project. Backfill may
also consist of engineered fill or borrow materials approved by a geotechnical engineer. Placement.
compaction and extents of retaining wall backfill should also be specified by a geotechnical
engineer or qualified professional.
Envirotech Engineering.PLLC Parcel 12220-50-61004
PO Box 984 page I S Parcel 13220-50-60001
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 November 27.2018
5.2.4 Wet Weather Considerations
Due to the types of subsurface soils, additional provisions may be required during prolonged wet
weather. Every precaution should be made in order to prevent free moisture from saturating the
soils within excavations. If the bottom of excavations used for footing placement changes from a
moist and dense/hard characteristic as presented in this report to muck or soft.saturated conditions,
then these soils become unsuitable for foundation bearing material. If this situation occurs, a
geotechnical engineer should be notified, and these soils should be completely removed and
replaced with compacted engineered fill or suitable native material as presented in this section.
5.2.5 Building Pads
Building pads for this project, if utilized, shall be constructed per the fill placement and compaction
recommendations as presented above.Both engineered fill and native soils may be used for building
pads. Building pad slopes shall be no steeper than 2:1 for both compacted engineered fill and re-
compacted native soils used as fill. Building pad fill shall be"keyed" into the existing subgrade to
a depth of at least 2 feet below the existing ground surface. The term"keyed,"as used here, implies
that the interface between the building pad and subgrade is horizontally level. Alternatively,
building pads may be keyed into the subgrade to the above specified depth, and stepped. Stepped
fill should be keyed into the subgrade at a minimum width of 10 feet. All footings shall be located
at least 5 feet away from the top of the engineered fill slope.
5.3 Building and Footing Setbacks
Provided that assumptions relating to construction occur and recommendations are followed as
presented in this report, the factor of safety for slope stability is sufficient for a 50 feet footing
setback from the face of the nearby descending slopes exceeding 40%. See the figure below and
the Site Plan in Appendix A for an illustration of the setbacks.
From the illustration above. structures ma} be located closer to the top of slope by extending the
foundation deep enough to maintain the recommended setback. In addition, the required setback
may be reduced by mitigation, and subsequently would require additional geotechnical studies.
5.4 Surface and Subsurface Drainage
Positive drainage should be provided in the final design for all planned residential buildings.
Drainage shall include sloping the ground surface,driveways and sidewalks away from the project
structures. All constructed surface and subsurface drains should be adequately maintained during
Em irotech Engineering. PLLC Parcel 12220-50-61004
PO Box 984 pa,e ;G Parcel 1 2 2 20-50-6000 1
Belfair. Washington 98528 Mason Count\. Washington
Ph. 560-275-9374 November 27.2018
the life of the structure. If drainage problems occur during or after construction, additional
engineered water mitigation will be required immediately. This may include a combination of
swales, berms, drain pipes, infiltration facilities, or outlet protection in order to divert water away
from the structures to an appropriate protected discharge area. Leakage of water pipes, both
drainage and supply lines, shall be prevented at all times.
If impervious thresholds are exceeded per Mason County code, then engineered stormwater
management plans are required for this project. The drainage engineer must coordinate Nvith a
geotechnical engineer for input with relation to slope stability prior to submitting drainage plans.
If stormwater management plans are not required for this project. then the following
recommendations should be followed.
For this project, we recommend that roof infiltration or dispersion is located downslope of the
planned building pads. Drainage should conform to the Mason County Small Parcel Stormwater
Plan. For logging, we do not have any special drainage provisions.
5.5 Vegetation Buffer and Considerations
For this project,we believe that a detailed clearing and grading plan is not warranted unless Mason
County thresholds are exceeded,and basic vegetation management practices should be adhered to.
Vegetation Buffer—Vegetation shall not be removed from the face of the critical slope or within a
distance of 40 feet beyond the top of the slope. However, any tree deemed hazardous to life or
property shall be removed.If tree removal is necessary,then stumps and roots shall remain in place,
and the underbrush and soil shall remain undisturbed as much as possible. Any disturbed soil shall
be graded and re-compacted in order to restore the terrain similar to preexisting conditions and
drainage patterns. See the Site Plan in Appendix A of this report for a depiction of the vegetation
buffer.
From a geotechnical perspective,trees may be removed from the buffer. However, one tree of the
same species should be planted per each tree removed. and maintained until established.
5.6 Temporary and Permanent Erosion Control
Erosion control during construction should include minimizing the removal of vegetation to the
least extent possible. Erosion control measures during construction may include stockpiling cleared
vegetation, silt fencing, intercepting swales, berms, straw bales, plastic cover or other standard
controls. Although other controls may be used. if adequate, silt fencing is presented in this report
as the first choice for temporary erosion control. Any erosion control should be located down-slope
and beyond the limits of construction and clearing of vegetation where surface water is expected to
flow. if the loss of sediments appears to be greater than expected, or erosion control measures are
not functioning as needed, additional measures must be implemented immediately. See Appendix
D for sketches and general notes regarding selected erosion control measures. The Site Plan in
Appendix A depicts the recommended locations for erosion control facilities to be installed as
necessary.
Permanent erosion control may also be necessary if substantial vegetation has not been established
within disturbed areas upon completion of the project.Temporary erosion control should remain in
_nv�roterh Engineering. PLLC _ _ - _Parcel 12220-50-61004
PO Box 98-1 page 17 Parcel 12220-50-60001
Belfair. Washington 98528 Mason Count}. V4'ashinaton
Ph. 360-27;-9374 November 27.2018
place until permanent erosion control has been established. Permanent erosion control may include
promoting the growth of vegetation within the exposed areas by mulching,seeding or an equivalent
measure. Selected recommendations for permanent erosion control are provided in Appendix D.
Additional erosion control measures that should be performed include routine maintenance and
replacement. when necessary. of permanent erosion control. vegetation. drainage structures and/or
features.
5.7 Septic Drainfields
Drainfields may be located anytivhere on the properties. The drainfields are not expected to
adversely influence critical slopes. This is based on compliance with all recommendations in this
report.
5.8 Structural Mitigation
With respect to landslide alleviation or slope improvements, structural mitigation is not necessary
for this project. This determination is based on the anticipated improvements of the project,
engineering conclusions, and compliance with all recommendations provided in this report.
5.9 Timber Harvesting Recommendations
It is understood that timber harvesting shall be completed prior to any other site development
activities. The following information provides details on the type of recommended harvesting,
provisions for areas not to be harvested,and general logging methods.
The areas that should not be logged, extends from the top of slope exceeding 40% slope to 40 feet
beyond the top of this slope. This area shall be protected from disturbance, deforesting or site
development activities of any sort except as allowable in this report. See Section 5.5 of this report
for tree removal within the buffer. For areas with slopes of 15% or less, complete tree and stump
removal is permitted. For areas greater than 15%, stumps from harvested trees, ground and roots
shall be minimally disturbed.
Conventional equipment such as skidders and crawlers may be used for this Project. Logs shall be
elevated on one end when dragging across the Project, although dragging should be minimized as
much as possible for this site. Timber harvesting causes a disturbance of a complex interaction
between water, soil and vegetation. Recommendations in this report are provided as a cost efficient
way to alleviate problems that may arise from this disturbance. Young trees should be monitored
and protected from competing vegetation.
Permanent erosion control, drainage facilities and slopes shall be immediately maintained, if
necessary. Some conditions that may need immediate attention includes excessive erosion, scour,
sloughing, significant changes to drainage patterns, new springs. new seepages or isolated areas of
ground saturation. Maintenance may include curtain drains, swales, other drainage facilities, or
slope remediation such as reinforcement, retaining structures or surface protection.
Envirotech Engineering. PIA.0 Parcel 13_'20->0-61001
PO Box 984 � page 18 Parcel I22'0-50-60001
Belfair. Washington 985Z8 Mason Count\. w'ashin<<ton
Ph. 360-375-9374 Nm;ember 27. ?O18
6.0 CLOSURE
Based on the project information provided by the owner, the proposed development, and site
conditions as presented in this report, it is Envirotech's opinion that additional geotechnical studies
are not required to further evaluate this project.
Due to the inherent natural variations of the soil stratification and the nature of the geotechnical
subsurface exploration, there is always a possibility that soil conditions encountered during
construction are different than those described in this report. It is not recommended that a qualified
engineer performs a site inspection during earthwork construction unless fill soils will influence
the impending foundation. However, if native, undisturbed subsurface conditions found on-site are
not as presented in this report.then a geotechnical engineer should be consulted.
This report presents geotechnical design guidelines,and is intended only for the owner, or owners'
representative. and location of project described herein. This report should not be used to dictate
construction procedures or relieve the contractor of his responsibility.
Any and all content of this geotechnical report is only valid in conjunction with the compliance of
all recommendations provided in this report. Semantics throughout this report such as 'shall.'
'should' and 'recommended' imply that the correlating design and/or specifications must be
adhered to in order to potentially protect life and/ or property. Semantics such as `suggested' or
'optional' refer that the associated design or specification may or may not be performed, but is
provided for optimal performance. The recommendations provided in this report are valid for the
proposed development at the issuance date of this report.Changes to the site other than the expected
development, changes to neighboring properties. changes to ordinances or regulatory codes, or
broadening of accepted geotechnical standards may affect the long-term conclusions and
recommendations of this report.
The services described in this report were prepared under the responsible charge of Michael Staten,
a professional engineer with Envirotech. Michael Staten has appropriate education and experience
in the field of geotechnical engineering in order to assess landslide hazards, earthquake hazards,
and general soil mechanics.
Please contact Michael Staten at 360-275-9374 if you have any questions. comments, or require
additional information.
Sincerely,
Envirotech Engineering
Robert McNearny, E.I.T. Michael Staten, P.E.
Staff Engineer Geotechnical Engineer
Em irotech Engineering. PLI.0 Parcel 12220-50-61004
PO Box 984 page 19 Parcel 12220-50-60001
Belfair. \1-ashinaton 98528 'vtason Counh. W"ashin_ton
Ph. 360-275-9374 No.ember 27. ?018
SCALE, 1 INCH 100 FEET
SOILS, LOOSE AND MEDIUM DENSE SILTY SAND WITH GRAVEL 0021 100
(SM)
ARCEL
BOUNDARY
lee fT
ti
4 ,
0
!ao F
� T
i -
T�l
APPROXIMATE TOP OF
50 F T SLOPE EXCEEDING 407
CONSTRUCTION
SETBACK APPROXIMATE TOE OF
i SLOPE EXCEEDING 40%
t
40 FT
VEGETTION
SETBACK
VEGETATION MAY BE
REMOVED WITHIN BUFFER
PER GEOTECHNICAL REPORT
s
R
NOTES PROJECT/ OWNER/ LOCATIONh
1. EROSION CONTROL MAY BE REQUIRED FOR THIS SITE. GENERAL LOCATIONS SINGLE FAMILY RESIDENCE
ARE DEPICTED, AND ALTERNATIVES MAY BE UTILIZED AS EXPLAINED IN THE GEOTECHNICAL REPORT
GEOTECHNICAL REPORT.
2. CONTOURS WERE NOT PREPARED BY A LICENSED LAND SURVEYOR. ANDERSON/WELCH
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND PARCEL 12220-50-60001
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 12220-50-61004
REPORT.
3, BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR. LOCATIONS OF SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP OF SLOPES, TOE -�-EROSION CONTROL EN TEMPORARY ENGINEER-
OF SLOOPES, WATER FEATURES, ETC.., WITH RELATION TO THE PROPERTY PO BOX 984
LINES MUST BE VERIFIED BY THE OWNER. RECOMMENDATIONS IN THE --� SLOPE INDICATOR BELFAIR, VASHINGTON 98528
GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC.. WITH 360-275-9374
RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC BO EXISTING CONTOtH2
FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING SITE PLAN
PROPERTIES. TP1 TEST PIT
APPENDIX B
SOIL INFORMATION
VERTICAL AND HORIZONTAL SCALE-
1 INCH 40 FEET
EXISTING GRADE
Ipp�
�x
6p.
:x
MEDIUM DENSE SILTY SAND
WITH GRAVEL (SM)
SECTION AzA
PROJECT/ OWNER/ LOCATIM
SINGLE FAMILY RESIDENCE
GE❑TECHNICAL REPORT
ANDERSON/WELCH
PARCEL 12220-50-60001
PARCEL 12220-50-61004
NOTES, MASON COUNTY, WASHINGTON
1) MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENGINEER
POSITIVE DRAINAGE ENVIROTECH ENGINEERING
2) THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF PO BOX 984
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS, BELFAIR, WASHINGT13N 98528
LOWER DEPTHS ARE BASED ON SITE GEOLOGY, 360-275-9374
WELL LOG(S), AND/OR EXPERIENCE IN THE GENERAL AREA.
SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Anderson Welch Geotechnical Report DATE OF LOG: 10/10/2018
PROJECT NO: 18212 LOGGED BY: MCS
CLIENT: Welch et al, Susan: EXCAVATOR: N/A
Kathy Anderson DRILL RIG: None
LOCATION: Allyn ELEVATION: N/A
Mason County, Washington
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI RVE
AND TEST DATA DEPTH N1070 50
0 . . . ... .. .....
SM Medium brown, moist,loosely dense
SILTY SAND with GRAVEL. Gravel is
primarily well-graded and subrounded.
1J. Sand is mostly medium. No plasticity.
2 Medium brown, moist, medium dense
SILTY SAND with GRAVEL. Gravel is
primarily well-graded and subrounded.
Sand is mostly medium. No plasticity.
3
Excavation terminated at approximately
4 3.5 feet
5
6
7
8
9
10
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
interpreted as being indicitive of the entire site.
Map Unit Description:Everett gravelly loamy sand;0 to 5 percent slopes--Mason County,
Washington
Mason County, Washington
Ed—Everett gravelly loamy sand, 0 to 5 percent slopes
Map Unit Setting
National map unit symbol: 2hk6
Elevation: 50 to 500 feet
Mean annual precipitation. 55 to 90 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 160 to 180 days
Farmland classification., Prime farmland if irrigated
Map Unit Composition
Everett and similar soils: 100 percent
Estimates are based on observations, descriptions; and transects of
the mapunit.
Description of Everett
Setting
Landform: Terraces
Parent material: Glacial outwash
Typical profile
H1 -0 to 7 inches: gravelly ashy loamy sand
H2- 7 to 21 inches: extremely gravelly sand
H3-21 to 60 inches: very gravelly sand
Properties and qualities
Slope: 0 to 5 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Somewhat excessively drained
Capacity of the most limiting layer to transmit water(Ksat): High to
very high (5.95 to 19.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Very low(about 2.5 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonirrigated): 4s
Hydrologic Soil Group: A
Forage suitability group: Droughty Soils(G002XN402WA)
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 14, Sep 10. 2018
i_sD.� Natural Resources Web Soil Survey 11/2 012 0 1 8
a" Conservation Service National Cooperative Soil Survey Page 1 of 1
Map Unit Description:Sinclair shotty loam.5 to 15 percent slopes--Mason County,
Washington
Mason County, Washington
So—Sinclair shotty loam, 5 to 15 percent slopes
Map Unit Setting
National map unit symbol. 2hn7
Elevation: 0 to 300 feet
Mean annual precipitation: 25 to 50 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 200 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Sinclair and similar soils: 100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Sinclair
Setting
Landform: Till plains
Typical profile
H1 - 0 to 11 inches: gravelly loam
H2- 11 to 35 inches: very gravelly loam
H3-35 to 60 inches: gravelly sandy loam
Properties and qualities
Slope: 5 to 15 percent
Depth to restrictive feature: 28 to 42 inches to densic material
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat): Very
low to moderately low (0.00 to 0.06 in/hr)
Depth to water table: About 18 to 30 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low(about 3.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification (nonirrigated): 4s
Hydrologic Soil Group: B
Forage suitability group: Limited Depth Soils(G002XN302WA)
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 14. Sep 10, 2018
t,sD.,, Natural Resources Web Soil Survey 1 1 12 0/2 01 8
A� Conservation Service National Cooperative Soil Survey Page 1 of 1
APPENDIX C
SLOPE STABILITY
STABLE Slope Stability Analysis System
Jessica Legarza
Project : Anderson Welch
Datafile: Dynamic Bishop
STABLE Version 9.03.COu
Bishop
.>...x»>vrw».w*•a:a+w>..a:+aaa++:aa..aa++a.....a..a.wa*w
TITLE
Dynamic
UNITS (Metric/Imperial) = I
GEOMETRY DEFINITION
POINTS
NO. X y
1 0.000 £5.000
30.000 60.000
3 40.000 55.000
4 48.000 50.000
5 55.000 45.000
6 60.000 40.000
'1 66.000 35.000
8 74.000 30.000
9 100.000 27.000
10 10.000 63.330
11 14.210 62.630
12 18.420 61.930
13 22.633 61.230
14 26.840 60.530
15 31.050 59.470
16 35.260 57.370
17 39.470 55.260
18 43.680 52.700
19 47.890 50.070
20 52.110 47.070
21 56.320 43.680
22 60.530 39.560
23 64.740 36_050 - ----
24 68.950 33.160
25 73.160 30.530
26 77.370 29.610
27 81.580 29.130
28 85.790 28.640
29 90.000 28.150
LINES
Lo X Hi X SOIL
1 2 i
2 3 1
3 4 1
4 5 1
5 6 1
6 7 2
7 8 1
a 9 1
STABLES2002 MZ Associates Ltd Printed on: 21/11/18 @ 17:34:09 Page: 1
STABLE Slope Stability Analysis System
Jessica Legarza
Project Anderson Welch
Datatile: Dynamic Bishop
SOILS
SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT.
1 Soil_1 CONTINUOUS-BLACK 200.00 30.0 132.000
frr+frtt afar++r++awrararrar as ar++arra♦rr+atrrrwrt:trrrr rrr
PORE PRESSURE SPECIFICATION
SOIL PIE20 AU EXCESS
Y/N/P Value Value
1 N 0.000 0.000
PIE20METRIC SURFACE
POINT
POINT PORE PRESSURES
POINT PRESSURE
rrrrrrr:rrr:r}}rrrrtrrrrrrffrrrff•*}r}atwr*rrtrrrrrr}wrfrr
SLIP DIRECTION (t/- X) = +
r++rfraawaaw.wt:aaewwawwwrwwrr:•trffrxt:err**rrrrrf*ftrfr♦
SLIP-CIRCLES
AUTOMATIC
Circle Centre Grid Extremities
145.000
f.rrw.rfarrarrr
r
10.000 * 90.000
t *
t irrattrf*rit}t
65.000
X spacing -- no. of cols (max 10)= 10
Y spacing -- no. of rows (max 20)= 20
Grid 1 Circles through point 10
Grid 2 Circles through point 11
Grid 3 Circles through point 12
Grid 4 Circles through point 13
Grid 5 Circles through point 14
Grid 6 Circles through point 15
Grid 7 Circles through point 16
Grid 8 Circles through point 17
Grid 9 Circles through point 18
Grid 10 Circles through point 19
Grid 11 Circles through point 20
Grid 12 Circles through point 21
Grid 13 Circles through point 22
STABLE02002 MZ Associates Ltd Printed on: 21/11/18 @ 17:34:09 Page: 2
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APPENDIX D
EROSION CONTROL
GEOTEXTILE FABRIC
WRAP AROUND TRENCH 2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC
TO AT LEAST ENTIRE OR EQUIVALENT OR BETTER AND WIRE MESH
BOTTOM OF TRENCH 2 6 FT MAX. O,C.
BEFORE PLACING GRAVEL 0.5 FT
2'x2'x5' WOOD POST OR '�-- 6 FT --+�
12' DEEP, 8' WIDE TRENCH EQUIVALENT OR BETTER EXISTING _
FILLED WITH 3/4' TO 1 1/2' GROUND SURFACE
WASHED GRAVEL or VEGETATN 2 T
2.5 FT
DIRECTION OF ��. � t2' DEEP, 8' WIDE
WATER FLOW EXISTING TRENCH FILLED WITH t T
te" GROUND SURFACE 3/4' TO 1 1/2' <.t 2.5 FT
2.5 FT WASHED GRAVEL OR
VEGETATION
a,— BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - ILL"
SILT FENCE - CROSc SECTION N.T.S.
N,T.S. HAY OR STRAW MATTING
ENERAL NOTES
1, STRAW SHALL BE AIR DRIED, AND FREE FROM WEED SEEDS AND
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON COARSE MATERIAL.
HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR 2. APPLY AT APPROXIMATELY 75 TO 100 POUNDS PER 1000 SQUARE
HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. FEET OF GROUND.
ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE 3. MINIMUM THICKNESS SHALL HE 2 INCHES.
NSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY. 4, HAY OR STRAW IS SUBJECT TO BLOWING. KEEP MOIST OR TIED
. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN DOWN.
LACE UNTIL THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED. PERMANENT EROSION CONTROL NOTES:
EMPORARY EROSION CONTROL NOTES SEEDING FOR RAW SLOPES
OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND 1, BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL
ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES,
ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE SWALES, LEVEL SPREADERS AND SEDIMENT BASINS.
MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE,
ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR, GRASS SEEDING FOLLOWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS ACCROS
LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH OR PERPENDICULAR TO THE SLOPE.
EPTEMBER, HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF 3. SEEDING RECOMMENDATIONS, AS SHOWN BELOW, AND SHOULD BE
HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING APPLIED AT THE RATE OF 120 POUNDS PER ACRE.
R OTHER APPROVED TREATMENT, 4. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL
AND OTHER RY SEASON (MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE ROSTER ANDUIREIGATION PROTECT THE ROOT S RUCTURE.E AS NECESSARY TO
EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO 5. SEED BEDS PLANTED BETWEEN NOVEMBER 1 AND APRIL 30,
NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE ARMORING OF THE SEED BED WILL BE NECESSARY, (e.g.,
THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING).
Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR. UNLESS IMMEDIATE 6. FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS'
TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL RECOMMENDATIONS. AMOUNTS SHOULD BE MINIMIZED, ESPECIA
REAS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ADJACENT TO WATER BODIES AND WETLANDS. LLY
HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS,
REE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 OR SOONER PER THE APPROVED USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION
LAN OF ACTION. UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE.
ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE
ERFORMED DURING THE FOLLOWING PERIODS: MARCH I TO MAY 15, AND AUGUST 15 TO PROPORTIONS PURITY GERMINATIOr
CTOBER 1, SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION NAME BY WEIGHT(%,)f THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE
0 SATISFACTORY GROWTH, IN THE EVENT THAT PERANENT STABILIZATION IS NOT REDTOP (AGROSTIS ALBA) 10 92 90
OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, ANNUAL RYE (LOLIUM MULTIFLORUM) 40 98 90
LASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY NO LATER THAN CHEWING FESUE 40 97 80
EPTEMBER 30. (FESTUCA RUBRA COMMUTATA)
N THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT (JAMESTOWN, BANNER, SHADOW, KOKET)
WHITE DUTCH CLOVER 10 96 90
CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE
WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION CTRIFOLIUH REPENS)
ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT MULCHING
EAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR
HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. 1. MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000
ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED POUNDS PER ACRE.
GNSTRUCTION ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE 2, MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES
REMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED GREATER THAN 2d <HORIZONTAL:VERTICAL).
O AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 3. MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN
HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. ALL
RANSPORT OFF-SITE IS OBSERVED, AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1.
LL CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE
OVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC
HEETING, EROSION BLANKETS, FREE DRAINING MATERIAL, ETC., WITHIN 5 DAYS AFTER
AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED.
ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC., WILL NOT BE VIEWED AS
DEQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT
ING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY
TABILIZED 5 DAYS AFTER HAVING BEEN CLEARED, ALL CONSTRUCTION ACTIVITY ON
HE SITE, EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL
MMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN
PPROPRIATELY PROTECTED OR STABILIZED.
SILT FENCE
PROJECT/ OWNER/ LOCATION:
GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE
FOR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS
2. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GEOTECHNICAL REPORT
EACH BARRIER TO AVOID USE OF JOINTS, IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED gNDERSON/WELCH
TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT PARCEL N/WEL 50-60001 BOTH ENDS TO THE POST. PARCEL 12220-50-61001 3. STANDARD FILTER FABRIC SHALL BE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) e 4 IN MASON COUNTY W 61004 TON
PACING.
4. POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET, AND ENGINEER:
RIVEN SECURELY INTO THE GROUND, ENVIROTECH ENGINEERING
WIRE MESH SHALL BE 2'X2'X14 GAUGE OR EQUIVALENT. THE WIRE MESH MAY BE ELIMINATED IF PO BOX 984
XTRA-STRENGTH FILTER FABRIC (MONOFILAMENT), AND CLOSER POST SPACING IS USED, BELFAIR, WASHINGTON 98528
. A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE 360-275-9374
OSTS AND UPSLOPE FROM THE SILT FENCE.
7. SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT, EROSION CONTROL
aU'
0
MASON COUNTY G p I )
COMMUNITY SERVICES
Building,Planning,cnetrenmental Health.Community Health Geotechnical Report
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 AndersonMelch Parcel# 12220-50-60001 and 12220-50-60010
Site Address_ Allyn
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) 5
(b) A discussion of specific soil types,
Located on page(s) 6-7
(c) A discussion of ground water conditions,
Located on page(s) 7
(d) A discussion of the upslope geomorphology,
Located on page(s) 3
(e) A discussion of the location of upland waterbodies and wetlands,
Located on page(s) 3
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records.
Located on page(s) 8
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Site Plan—Appendix A
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Site Plan and Soil Logs(Appendix B)
(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) Site Plan
(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) Soil Profile (Appendix B)
(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) 9-10
(7) (a) Appropriate restrictions on placement of drainage features,
Rev. February 2018
A.-
Located on page(s) 15-16
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) 17
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 12-14
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 16
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 15-16
(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) 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) 10
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) 11
(11) Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
Located on page(s) 16- 18
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 18
(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) Site Plan
I, Michael Staten, 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 November 27,2018,and entitled Anderson
Welch Logging&Residences, 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
a _ 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.
Page 2 of 2
Disclaimer. Mason County does not certify the quality of the work done in this Geotechnical Report.
GEO I�' - -7 G
Mason County Review Checklist
for a Geotechnical Report
Instructions:
This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report is reviewed
for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the Report should
explain the basis for the conclusion. The Report is also reviewed for clarity and consistency. If the drawings,
discussion, or recommendations are not understandable, they should be clarified. If they do not appear internally
consistent or consistent with the application or observations on site, this needs to be corrected or explained. If
resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director.
Applicant's Name: AYtfih�NA C[ WekC l (�
Permit#: I 'Pa I� ) `1 Parcel#: I Z'22 G -J U -6 U C1 G d l
Date(s)of the Document(s) reviewed: 1 /9/15
1. (a) A discussion of general geologic conditions in the vicinity of the proposed development,
OK? ✓ Comment: - Z
(b) A discussion of specific soil types
OK? ✓ Comment: 3
- (c) A disc n of ground water condit ns
OK? 7 Comment: J• 3 1 i
(d) A discussion of the upslope geomorphology
OK? Comment: 'Z . Z. 1
(e) A discussion of the location of upland waterbodies and wetlands
OK? Comment: 2 . 3 _ 1
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records
OK? Comment: 41
2. A site plan that identifies the important development and geologic features.
OK? ✓ Comment: 112
3. Locations and logs of exploratory holes or probes.
OK?_o Comment: 1�
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.
OK? V Comment: k-t
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.
OK? / Comment: Py Z
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 coeffients should be a value of 0.15.
OK? ✓ Comment: `{ I . 1
7. (a) Appropriate restrictions on placement of drainage features
OK? ✓ Comment: f.`�
(b) Appropriate restrictions on placement of septic drain fields
OK? ✓ Comment: x:
(c) Appropriate restrictions on placement�f compacted fills and footings.
OK? V Comment: y
Page 1 of 2 Form Effective June 2008
(d) Recommended buffers from the landslide hazard areas horeline bluffs and the tops of other slopes.
OK? ✓ Comment: ' S
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? ✓ Comment: S . 3
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.
OK? Comment: S
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.
OK? V Comment:
10. An analysis of both on-site and off-site impacts of the proposed development.
OK? Comment: L4, 6
11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
OK? ✓ Comment: 5-
12. Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
OK? `� Comment: S
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.
OK?1z Comment:
Are the Documents signed and stamped? By whom? c �
License#: ` ?G� S License type: T7v7s 1
FIRST REVIEW 4Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by 4in I.%--) , on /12T /I S . Time spent in review:
SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info.
Reviewed by , on . Time spent in second review:
THIRD REVIEW/UPDATE ❑ Approved ❑ Need more info.
Reviewed by , on . Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
Page 2 of 2 Form Effective June 2008