HomeMy WebLinkAboutGEO2020-00018 for BLD2019-01276 - GEO Geological Review - 2/28/2020 Ge'azo --,no Olt
Geotechnical Report
Oosterveld Single Family Residence
510 E Sherwood Creek Road, Allyn
Parcel No. 12230-11-90090
Mason County, Washington
February 28, 2020
Project#2015 I ^
Prepared For: 996
Jan and Theresa Oosterveld
PO Box 1709
Port Orchard, Washington 98366
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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MASON COUNTY �',LlI'rrittal Checklist
COMMUNITY SERVICL•S Geotechnical Report
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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 Jan and Theresa Oosterveld Parcel# 1 2230-1 1-90090
Site Address 510 E Sherwood Creek Road
(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
(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 Page 1 of37
(7) (a) Appropriate restrictions on placement of drainage features,
Located on page(s) 17
(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) 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
(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
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 17
(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
CL.YDt ST Report,dated February 28,2020,and entitled Oosterveld
`,��ti,1sffr; _gar Single Family Residence, meets all the requirements of the
Mason County Resource Ordinance,Geologically Hazardous
Areas Section, is complete and true,that the assessment
43015 x demonstrates conclusively that the risks posed by the landslide
`' hazard can be mitigated through the included geotechnical
"NA'-t"�� 2/28/2020
design recommendations,and that all hazards are mitigated in
Disclaimer:Mason County does not such a manner as to prevent harm to property and public
certify the quality of the work done in health and safety.
this Geotechnical Report.
Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................................................................................I
1.1 PROJECT INFORMATION.................................................................................................................... 1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK........................................................................ 1
2.0 SURFACE CONDITIONS....................................................................................................................3
2.1 GENERAL OBSERVATIONS..................................................................................................................3
2.2 TOPOGRAPHY.....................................................................................................................................3
2.2.1 Upslope Geomorphology............................................................................................................3
2.3 SURFACE DRAINAGE..........................................................................................................................3
2.3.1 Upslope Water Bodies................................................................................................................3
2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4
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.................................................................................................6
3.3.1 Groundwater............................................................................................................................... 7
4.0 ENGINEERING ANALYSES AND CONCLUSIONS......................................................................8
4.1 SLOPE STABILITY...............................................................................................................................8
4.1.1 Slope Stability Analysis.............................................................................................................. 9
4.2 EROSION.............................................................................................................................................9
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION..............................................................................10
4.3.1 Liquefaction..............................................................................................................................10
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS........................................................10
4.5 LATERAL EARTH PRESSURES...........................................................................................................10
4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................11
5.1 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................12
5.1.1 Bearing Capacity.......................................................................................................................12
5.1.2 Settlement..................................................................................................................................13
5.1.3 Concrete Slabs-on-Grade..........................................................................................................13
5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................13
5.2.1 Excavation.................................................................................................................................13
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....................................................................................................15
5.2.5 Building Pads............................................................................................................................15
5.3 BUILDING AND FOOTING SETBACKS.................................................................................................16
5.4 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................16
5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................16
5.6 TEMPORARY AND PERMANENT EROSION CONTROL.......................................................................17
5.7 SEPTIC DRAINFIELDS........................................................................................................................17
5.8 STRUCTURAL MITIGATION...............................................................................................................17
6.0 CLOSURE.............................................................................................................................................is
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
single family residence located at 510 E Sherwood Creek Road, identified as parcel number
12230-11-90090, Mason County, Washington. See the vicinity map on the following page for a
general depiction of the site location.
An initial geotechnical evaluation of the project was conducted by Envirotech on February 12,
2020. 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) 17.01.100. 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 information 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 planned development consists of a 1-story single family residence, carport,
and other ancillary features typical of this type of development. Approximate building footprint
and other proposed features with relation to existing site conditions are illustrated on the Site Map
provided in Appendix A of this report.
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
Envirotech Engineering Geotectirkal Report
PO Box 984 page 1 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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;
• 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.
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Vicinity Map from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 2 Parcel 1 2230-1 1-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on February
12, 2020 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. Vegetation on and near the project consists primarily of
secondary growth firs, maples, and other trees and shrubbery 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 maximum critical slope is approximately 87% with a vertical relief of about
130 feet.
Descending grades are generally located to the east of the planned development.These slopes are
relatively minor within 300 feet of the project,with no apparent slope grades of at least 15%.
2.2.1 Upslope Geomorphology
The upland area of the property and beyond is generally situated on a hillside of glacial
origin.
23 Surface Drainage
Runoff originating upslope of the development is mostly diverted away from the property by
accommodating topography. 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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 3 Parcel 1 2230-1 1-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
2.4 Slope and Erosion Observations
The slope gradients near the project signal a potential landslide or erosion hazard area. Some
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.
N A �
Aerial Photo from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 4 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on
February 12, 2020 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 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 loose to medium dense soils in the upper 48 inches, and very
dense soils from 48 inches to the depth of terminous.
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 unconformably
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 glacial drift deposits.
The "Geologic Map of the Vaughn 7.5-minute Quadrangle, Pierce and Mason Counties,
Washington'by Robert L.Logan and Timothy J.Walsh,December 2007,provides the following
caption(s)for the project area:
Envirotech Engineering Geotechnical Report
PO Box 984 page 5 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
02 :Ulusium—sift,sand,and grnrel deposited in stream;may include some lacustrine deposits
and organic materials,such as peat.
Landslide deposits--Generally loose,jumbled,tan to gay,silty sandy gravel with feu to no
discernible sedimentary structures;snufaces of landslides are generally undulatory:some
landslides in the quadrangle occur as large deep-seated slides and others as shallow surface
failures or block falls.
Undifferentiated Pleistocene deposits—Vashon and pre-Vashon sedimentary deposits in
near-vertical bluff exposures not depictable at map scale or not distinguishable into glacial or
nonglacial sediments,may contain any of the above units;see breakdown of units a here
illustrated as schematic columnar sections at points along shorelines.
41
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Geological Map Department of Natural Resources Washington State
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 without indications of fill. Within test pit
locations, soils within the upper 3 feet of natural ground were generally observed to be moist,
brown silty sand with gravel(SM).
Envirotech Engineering Geotechnical Report
PO Box 984 page 6 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
The relative densities of the soil within selected test pits 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 Alderwood Gravelly Sandy
Loam, A,, with 15% - 30% 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.
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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 10 feet directly below the property at the building pad location. Surface seepage
or perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports.
Envirotech Engineering Geotechnical Report
PO Box 984 page 7 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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 present 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 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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■ Solis
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■ Hrghiy Unstable
No Data or Grave:Fits
Slope Stability•West
■ ■ ■ �■ Moderate Slope Instability
�.574'�..... ■ ■■ , ■. •u9p ■ W90 Slope Instabilrty
Resource Map from Washington State Department of Natural Resources Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 8 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
4.1.1 SlopeStability Analysis
y y
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:
Upper 3 feet soil depth
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 at least 1.5 and 1.1,
respectively. See the slope stability information in Appendix C for a depiction of
minimum factors of safety away from the project.
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 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 dry
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
Envirotech Engineering Geotechnical Report
PO Box 984 page 9 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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.
43 Seismic Considerations and Liquefaction
There are no known faults beneath this project. The nearest Class `A' or Class V fault to this
property is the Tacoma Fault Zone, which is less than .5 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 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 permanent
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 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
Retaining walls may be utilized for this project. The lateral earth pressures exerted through the
backfill of a 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. A structural or geotechnical professional should design retaining walls based
on specific conditions.
Envirotech Engineering Geotechnical Report
PO Box 984 page 10 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
Soil parameters for the structural design of retaining walls may be estimated as 134 pounds per
cubic foot (pcf) and 118 pcf for engineered fill and native soils, respectively. The angle of
internal friction may be estimated as 36 degrees and 32 degrees for engineered fill and native
soils,respectively.These soil parameters are based on soil type and placement conforming to the
Earthwork Construction Recommendations Section in this report.
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 Engineering Geotechnical Report
PO Box 984 page 11 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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 15 inches shall be placed at a minimum of 12 inches below the existing
ground surface 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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 12 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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.
5.13 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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 13 Parcel 1 2230-1 1-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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.
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 or compacted re-compacted fill depth beneath the
P P P
foundation. See the illustration below.
F❑❑TING
COMPACTED
NATIVE S❑ILS
OR ENGINEERED 1
FILLfir
1
—r� �. —
U ISTUIRBED SU
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
3" 60—100
No.4 20—60
No.200 0-8
Table 1
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
Envirotech Engineering Geotechnical Report
PO Box 984 page 14 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an
engineer.
5.2.3 Retaining Wall Backfill
Native soils may be used as retaining wall backfill for this project if the total wall height
is 4 feet or less and the recommendations below are followed. Native soils for retaining
walls exceeding 4 feet in height must be approved by the local authority or evaluated by
an engineer. Backfill may consist of engineered fill,as presented in this report,or borrow
material approved by a geotechnical engineer. Compaction of these materials shall be
achieved in compacted lifts of about 12 inches. Each lift should be uniformly compacted
to at least 85%, and no more than 90% of the modified Proctor maximum dry density
(ASTM D 1557).If pavement or building loads are planned to be located within retaining
wall backfill, then 90% compaction is required. In addition, heavy construction
equipment should be at a distance of at least '/2 the wall height. Over-compaction and
limiting heavy construction equipment should be prevented to minimize the risk of excess
lateral earth pressure on the retaining structure. Envirotech recommends that retaining
wall backfill is compacted with light equipment such as a hand-held power tamper. If
clean, coarse gravel soils are utilized as engineered fill, and surcharges will not influence
the retaining wall, compaction may be achieved by reasonably densifying granular soils
with construction equipment.
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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 15 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
5.3 Building and Footing Setbacks
Due to potential debris flow,the building location should have a minimum setback from the local
ascending slope toe equal to the slope height. The toe of the ascending slope is delineated as a
grade break in which the ascending slope is in excess of 40%. Envirotech recommends the
building setback to be at least 60 feet from the toe of the nearby ascending slope. See the Site
Plan in Appendix B for an illustration of the setbacks.
The setback for ascending slopes may be reduced by utilizing a catchment wall between the
building and ascending slope. Alternatively, the catchment wall may be incorporated into the
structure.Additional geotechnical studies may permit for a setback reduction.
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 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 the prevailing agency code, then engineered
stormwater management plans are required for this project. The drainage engineer must
coordinate with 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 any stormwater controls may be employed per County
requirements.
5.5 Vegetation Buffer and Considerations
For this project, we believe that a detailed clearing and grading plan is not warranted unless the
prevailing agency 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
10 feet from the toe of 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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 16 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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. An erosion control should be located
P P �'Y Y
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 is necessary if substantial vegetation has not been established within
disturbed areas upon completion of the project.Temporary erosion control should remain in 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
Septic drainfields are not proposed for this project, and were not considered in our geotechnical
evaluation.
5.8 Structural Mitigation
With respect to landslide alleviation or slope improvements,structural mitigation is not necessary
for this project unless setbacks are encroached. This determination is based on the anticipated
improvements of the project, engineering conclusions,and compliance with all recommendations
provided in this report.
Envirotech Engineering Geotechnical Report
PO Box 984 page 17 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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
'73!!_74 ellll� sz-aAw-
Jessica Legarza,M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
Envirotech Engineering Geotechnical Report
PO Box 984 page 18 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
APPENDIX A
SITE PLAN
SCALE, l INCH 100 FEET
0 25 50 100
APPROXIMATE TOP OF
CRITICAL SLOPE EXCEEDING
'0Z A
APPROXIMATE TOE OF CRITICAL
SLOPE EXCEEDING 40;
F FY AY,OF1'cm =l a
1 A FATE iTfOYQ71,H.fii.
ETDkEDDB 4iX
CSC / -PPOPOK3 OAST
j 3"YEY/:Y
A A¢ TP'�
'Y
60 FT CONSTRUCTION SETBACK
FROM TOE ff CRITICAL SLOPE PROPOSED SINGLE FAMILY
EXCEEDING 40% RESIDENCE
PROPERTY UPE
wtUM WAM LntAT3 w
LER% EW'W&MAY BE ra &W-V FOR THM DUE:ORAL=41100 SINGLE FAWLY RESIDENCE
ARE TK.XTIM PSG ALT--4%P•Ti PORY IC UTIL'r"CM At ZWLAT=IM TIIC U111 C:;fi:CAl.. 'FP1lRT
GEOTECIbsGM REPORT.
01.L71efT ,oft SA_7E NTT PP[ /Eli Tf'Y A LY!` _D 11 XD;,.X{tPEJgB. OOLTT7EY71T.
GONTEMS MERE EXTRAPOLATED FROM A PUOLIC LIDAR SIIURCE, )NO 510 E SFERWOOD CREEK RD
DCURPORATCD F1CLD MEASUREMENTS AS EXPa,.AIN;'D IN THE SCOTEC;fIGY. LEGEND PARCEL 12230-1t--/0M
REP:;RT, MASON C:XINTY,VASFONI'ON
3. BOJNIARIES WERE NOT PREPARED BY A LICENSED S',1RYEY3.t LOCATMONS TEMPORARY ENGINEER,
OF SITE FEATURES r4hT ARE SHOWN HERE.SUCH AS TIP OF 31-WES, TOE 'f ++IROSION CM"OL EMYIROTECH ENONEERtNG
IT SLMPCS, WATER FEATURES, Oi ETC_ WI7N RELATION TD THE PROPERTY PO BOX 404
U==7 VC YOUIM Ef i i a%ECD£k'3MH=M THE XLIPi E D=T1T2
�I'ET�I MAL REPORT PNOVFSE S O�D� ETd+6M,UFFEIM DEMIM ETIw VITA � �Il i
P L#TIM TO TDTUXL NOT MPM"LONE;THESE GM M+OX ,...W- Eip3rM CDXTMN
rriNT+ PAY>£LOCATED IN THE QW=T err IN 14=0MOM Tn TILT KT SITE PLAN
PnaNExr.�x
APPENDIX B
SOIL INFORMATION
i
VERTICAL AND NOIILONTM,SCALE,
SCALE. 1 MCN-60 META ED MET
130 30 6D
EXISTING GRADE
PROPOSED HOUSE
�13
MEDIUM DENSE SILTY SAND
WITH GRAVEL CSM> g
BP
1
SECTI41P1_8w9
PROJECT/ OWNER/ LOCATIW
SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
OOSTERvELV
PARCEL 12M-U-900'M
TES MASON COUNTY, WASHINGTON
ENGINEER
1)MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENVIROTECH ENGINEERING
POSITIVE DRAINAGE PO Box 994
0THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF BELFAIR, WASHINGTON 98529
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. 360-273-9374
LOWER DEPTHS ARE BASED ON SITE GEOLOGY,
WELL LOG(S),AND/OR ExPERIENCE IN THE GENERAL AREA, SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Oosterveld Geotechnical Report DATE OF LOG: 2t1212020
PROJECT NO: 2015 LOGGED BY: RJM
CLIENT: Jan and Theresa Oosterveld EXCAVATOR: NIA
LOCATION: 510 E Sherwood Creek Rd DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: NIA FINAL DEPTH OF WATER: NIA
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0
SM Medium brown,moist,medium dense
SILTY SAND with GRAVEL.Gravel is
primarily well-graded and subrounded..
1 Sand is mostly medium.No plasticity.
2
Excavation terminated at approximately T
3
4
5
6
7
8
9
10
No Groundwater Encountered ENVIROTECH ENGINEERING
Thes information pedarns only to Phis boring and shod nd be Geotechnical Engineering
interpreted as being indcAnre at the entire wte
Map Unit Description:Alderwood gravelly sandy loam,15 to 30 percent slopes—Mason
County,Washington
Mason County, Washington
Ac—Alderwood gravelly sandy loam, 15 to 30 percent slopes
Map Unit Setting
National map unit symbol: 2t627
Elevation: 0 to 1,000 feet
Mean annual precipitation: 25 to 60 inches
Mean annual air temperature: 46 to 52 degrees F
Frost-free period. 160 to 240 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Alderwood and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations,descriptions,and transects of
the mapunit.
Description of Aldetrwood
Setting
Landform: Ridges,hills
Landform position(two-dimensional): Backslope
Landform position(three-dimensional): Side slope,nose slope,talf
Down-slope shape: Linear,convex
Across-slope shape: Convex
Parent material: Glacial drift and/or glacial outwash over dense
giaciomarine deposits
Typical profile
A-0 to 7 inches: gravelly sandy loam
Bw1-7 to 21 inches: very gravelly sandy loam
Bw2-21 to 30 inches: very gravelly sandy loam
Bg-30 to 35 inches: very gravelly sandy loam
2Cd 1-35 to 43 inches: very gravelly sandy loam
2Cd2-43 to 59 inches: very gravelly sandy loam
Properties and qualities
Slope: 15 to 30 percent
Depth to restrictive feature: 20 to 39 inches to densie 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 inthr)
Depth to water table: About 18 to 37 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Very low(about 2.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonirrigated): 4e
Hydrologic Soil Group: B
iy5 Natural Resources Web Sal Survey 12110,12018
Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description:Alderwood gravelly sandy loam,15 to 30 percent slopes—Mason
County,Washington
Forage suitability group: Limited Depth Soils(G002XS301 WA),
Limited Depth Soils(G002XF303WA),Limited Depth Soils
(G002XN302WA)
Hydric soil rating: No
Minor Components
Everett
Percent of map unit. 5 percent
Landform: Kames,eskers,moraines
Landform position(two-dimensional): Backslope
Landform position(three-dimensional): Side slope
Down-slope shape: Convex
Across-slope shape: Convex
Hydric soil rating: No
Indianola
Percent of map unit: 5 percent
Landform: Eskers,kames,terraces
Landform position(three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Hydric soil rating: No
Shalcar
Percent of map unit: 3 percent
Landform: Depressions
Landform position(three-dimensional): Dip
Down-slope shape: Concave
Across-slope shape: Concave
Hydric soil rating: Yes
Norma
Percent of map unit: 2 percent
Landform: Depressions,drainageways
Landform position(three-dimensional): Dip
Down-slope shape: Concave,linear
Across-slope shape: Concave
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County,Washington
Survey Area Data: Version 14,Sep 10,2018
Natural Resources Web Sal Survey 12!1012018
Conservation Service National Cooperative Sal Survey Page 2 of 2
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: Pnme 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
Hf-0 to 7 arches gravely ashy loamy sand
H2-7 to 21 inches: extremely gravely sand
H3-21 to 60 inches: very gravely 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 kmrting layer to transmit water(Ksat): High to
very high(5.95 to 19.98 inlhr)
Depth to water table. More than 80 inches
Frequency or flooding. None
Frequency of pondrng: None
Available water storage in profile: Very low(about 2.5 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonirngated): 4s
Hydrologic Soil Group., A
Forage suitability group: Droughty Soils(G002XN402WA)
Hydric sail rating: No
Data Source Information
Soil Survey Area: Masan County,Washington
Survey Area Data: Version 15,Sep 16,2019
tvjA
Natural Resources Weir Sal Survey 2I242020
WO Conservation Service National Cooperative Soil Survey Page t of 1
Envirotech Engineering Geotechnical Repots
PO Box 994 page 1 Parcel 12230-11-90090
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 February 28,2020
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•e.r•aw" ow WELL CONSTRUCTOR CERTiF1CATMM:-
W A•unc.0•. _ 5.M.ww.0 Ow_..._
r.. !eon.t::c+eo and,�or x.+is++re.po�s+btl.ry�=rytn 7ia+a ma.ee..nd as
O --�Cw. cwvf. o wie+a:s Was.gw well wnatuct+on swd-d.Mates:std arM
fh.•ito*oa++on reponad aEa+.are tue rc my deal.naw�od0.Jna oaK1.
(9) WELLTESTS: o•.rmmn.i.wu�tE.,.w1 �r.c�s bwer•a Mb•'.larc MvN
d W..V v mnWa Y. N. ay.s o,wnom?__ NAME GBViS Drilling
Yr9tl _eat.rmm w*F s.a•w .R.r Ills- "''-"—TFksDI7TA1l GnYtYK�7(-7m^t 1
Aeaas.
R Bel fair IA 98528 _...._.,
— —
� R.eo,wydwa!reet.aana...'o worn pa•q t•er,dt(wn.riminwstAadaor�.s (�"� A V �Lic.rrs.Na.f.LVY
y 7smr Nr.r LM A•. wd.r ta+N Inn �'ts..l Coraaan s
� — rRio�nn UTSQ11](YlA ___D.t. N,arrh .tY92-
-.-_ (USE ADDITIONAL SHEETS IF NECESSARY)
On.d s.M
B.sr wt "Lupin..0�....a Ara.eo"da_.�—t.s Ecology 1s en FQual Opporturvly and Afinnehve Aaron er%ouyd.For stx
A~ aal.enir.asT rw w• It br _sr..
Ant.�an hr•_ 9�. OrMs ae;axommoOaGon needs.canUcl the Water Resources Ropram at I206)
407-SW The TDD nurbar is(206)407.6006.
T•TO.�ahn•o�wart__.iYaa a dn.rKM.n.ly.h end.T yY.❑ trb
ECY m.m 1sA)�--I
APPENDIX C
SLOPE STABILITY
1.00
1. 10
1 _2 0
1.30
1 .40
1.50
1 . 60
1 _70
so
1 . 9 O
92.00
0. 69
F roj�ct Ooatozv.®1d Report
D ataPila _ Dynamic Analysis
A rialysis Sishap
y § { 1 . 00
1 . 10
« 1 . 20
1 . 30
I _ 4o
so
\ 2 , 60
I . 70
z , 00
a.
\ \ �
1 . 289
- 1 - 000
�3:oa_et : oo_t_3�-.re1a Fk_1>C,
oata=IX : star±= -M-,nalysla
�aal�sia : s±a�o2
APPENDIX D
EROSION CONTROL
GEOTEXTILE FABRIC
WRAP AROUND TRENCH
TO AT LEAST ENTIRE
BOTTOM OF TRENCH
BEFORE PLACING GRAVEL 2'x2'x5, WOOD POST OR
12' DEEP, 8' WIDE TRENCH f EQUIVALENT OR BETTER
FILLED WITH 3/4' TO 1 1/2'
WASHED GRAVEL OR VECETAT N
2.5 fT
IURECTI!]M 13F -----. EX3STP45
WATER FLD'W GROUND Sl1RFACE
SLL,L�E._N.�E.�_R.17�S�EIL�N
N.T.S.
2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC
OR EQUIVALENT OR BETTER AND WIRE MESH
2 6 FT MAX, O.C.
EXISTlNti
CiRMAD S WFACE .
G T
12' DEEP, 8' WIDE
TRENCH FILLED WITH
3/4' TO 1 I/I�' RAj
WASHED GRAVEL OR VEG TI L
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - DETAIL
N.T.S.
PROVIDE FULL WIDTH
3/4 IN TO 1 i/Z N6 rr INGRESS/EGRESS
CRUSHED GRAVEL
PLACED AT 6 IN -7
MINIMUM DEPTH
WELL-DRAINED
SOILS
-0.02 IN/MIN ML LE°GIH
R=25 FT MIN
(L -
ACCESS RnAn
STABILIZED CONSTRUCTION ENTRANCE
N.T.S.
;EFEF:4.PT1TE:;E
SEEt.4l FOR 7.AV SLorn
.�17LD rH4E TE�F•ts:s,E:Y ERSI=10+A;iD sE7IyL^;r rUmTF,UL r4Ex.+.?Ls•Ail,iN ON
HC4Z MAW I'iW.'E TO BE)J4kW—^TE O,+qA—i':O47FLL'T701t.THE LIA?T►AY.7M- L T£FO.-E 4,EE f,4 W4TMLL NEV"MaYAMf W+ 0FF SJ WAOL
cl-Us TALL 4XITIO1 AL EAMIEN ARE)SEDENEXT C.u"MI. FAMIT M PEAS41MS.4A34 AS(11ARIEMT TEA5AE J IMWEMK IIKES.,
.$LL E)OTRODA ANU ZEIW TFT=KrAM FACILITIES 40 DEV'MMI ZiALA_ME r,'VA E'S•,LEVU,DP'HFAr�40 fEZD'.)IT DA•4.SrL3.
BLAILT#W DtffBUTELY RAWTADIED,m HEVEnAR'r, Z THE:FLY 7=*14ALL IE FUN WITH FAIRLY I'M X.IRFACE,
ILL ER17£M 440=WENT:M.TACL FACILITIES AHD WV=RI ALL SE LEFT DM FCL.XVDY 3t49TAPE AO.OWNJUE,FERFO"ALL O ERATlula A(ZPM '
"_E UvTIL THE CPSLOPE AMA.".HAVE DEFN TL'Y 3TAt3LINA ON TTI TTE-.LOPE.
A?.WEAN,9ET'IDKE►)XATII6'9,AR SHON'N I41OW,AWI:410111-17 J'.E
RRY MOmm(MITPUL WITEX, APvLIm i17`THE PATE IT V.-P PCIUFIIr a"Pa7HE
4.'fJX7 BEIB?1l lm LET6'EELI%ky 1 4A61 W:TU!M at VILL
ALL AMIS WHICH HA%M lTDJ'TJZr"E71 IT%TKTATmM IM MAD==L40 W7101E M CtNTIOI AMm OiH M t%PZrE0WXf AS NEET,Er w':Y TO
=rJ=ft5 PCMMrTEL MID%AEA EO FURTUM AM 3S 44TCWATE D FUR A FWITEH A0.'Ti F'rM- T=T THE I,,= k-TMR.OT.:X.
q�rZtll C TEED THE LSR:TED LI n3ZrA DELOV,ALL JJILiMZED ARENA sill AE tL=x lcm ILAI m)C-rvETDFI Iv'v E13PER I fJUQ ae "L III,
wvL4Ttl7 SKAlu-v 9 WIN HY.xcw*:N rAkv,lRL./i4T Ok MEN AIYTdNCH AM41=IF THIN 271-O A2 V:LL IE►L'+.:E$I;AT.F,trg.
MIrZTIL M.-t*"45'r LJF)r`4X-E TO THE TIME OF tiEE:-ft.VASE UxAW, cLuTD-ra ES,xTE HEAT;i3.ElAf mAzTw SSJYE uw.t ,
(E VILL INLY BE A,'X.,T.XE DLrM:1iFs THE KOITIR:OF ?ynL THIUW t,F'ET,-[LIZERN MC TO YE L%Eb AC.TD'SM TD VrAILIERZ
-TVn.--P H10:zVE7 'EMVI MAY r+WEZD-A imrv'ER i- ,;t La THE Bao=T or HE1:a4,EW:4TI0:Rim AIQ.l1Tt rx 'GNDIrm, %7: -(
e OW?PrnEwr7fL'Tr9?IIUT "T ALM I£ k.!(,F£HTED VITH NJL04141,WTTM AT.W"T To VATL4 J>OI=I AS VETL4H m
OTHER tY'rT+UvEt TLEATM 74T.
IRE 71HE FaU7 MIG AECOK-14000M"MEN MDMAK FOR EAI{5;OR.
Y SEAMY(MAY I TM) SEPTEMBER 30)-- THE CLEARTH4 OF LWD,INCLUDING THE;DnM- O A COUNTY APPROVED ALTERNATE.SEED MIXTUw-
MOVAL OF r-rSTING VEWTA71O4 OR DTHE3 rMX D COVER.MUST BE LD,rrO TD
NL'f AS MUCH LAND AS CAN RECEIVE APPRIPR:ATE PROTECTIVE COVER OR IE fTJIPORTJUNS PLRtITY GMWNA
RWISE STABILIZED,AFTER WAVING BEEN SEARED OR OTHERWISE DISTURDED . NAME BY WEIGHTIIU 42) t'L)
Y 14M LATER THAN SEPTE)WHM 30 ff A(OVEN YEAR.UNLESS IMMEDIATE �
ABILIZATION 13 SPECIFIED IN THE EROSION AID SEDIMENT ar.T.ROL PLAN, ALL REITOP(AGEOSTTS ALTA) Dt 92 90
AS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ANNUAL.RYE(LOLILIM Ml1TIFLMUM) 40 96 90
RDUCIH THE USE or MULCHING, NETTING,PLASTIC SHEETING,EROSION BLANKETS, CHEWDG FESUE 40 97 80
PEE DRAINING MATERIAL,ETC.. BY SEPTEMBER 30 OR SOO►ER PER THE APPROVED TESTUCA RUDRA COMMUTATA)
AN OF ACTION UNLESS OTHERWISE APPROVED BY THE COUNTY. SEEDING, (JAMESTOWN, BANNER,SHADOW, MET)
RT JUZING AND MULCHING [F CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE WHITE DUTCH CLOVER ID 96 90
RFORMED DURING THE FOLLOWING PERIODS.MARCH 1 TO MAY L5, AND AUGUST IS TD (TRIFULIUM REPENS)
TOBER L SEEDING AFTER OCTOBER I WILL BE DINE WHEN PHYSICAL COMPLETION
THE PROJECT IS IMMINENT AND THE ENVIRCMENTAL CONDITIONS ARE CONDUCIVE MULCHING
SATISFACTORY GROWTH IN THE EVEN THAT PERAAENT STABILIZATION IS NOT
SSIBLE,AN ALTERNATIVE METHOD OF GROUND COVER. SUCH AS MULCHING,NETTING,L MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
ASTIC SHEETING, EROSION MLAMKETS.ETC., MUST BE INSTALLED BY NO LATER THAN FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE O'LOCO
EPTE14BER 30. POUNDS PER ACRE.
.P,Hl2,CH S]HOUL4 JE APR EO IN ALL AREAS WITH LWO=SLOES
4 THE EVENT THAT risal SC'imN ACT1MMM IR mmm SITE DSy4LOPNEpT 3tEATER T444 2A CFWi,TZOMTfi_M'EKiIf:N>H.
-MTIES Alffi X=nWTAJM FOR AT LEAPT A COh=C%ITIVE DAY%THE A KA.tHOaO STB.RD._I BE USED><`G UD,ATEL►AFTER EEEMM OR_4
@ACTOR LiHLL S REYROISfILE FOR THE OrWEMEN OF ALL EROSTD4 AREAL VKMH CAMICIT DE SEEDIER IE!,NJBE OF THE SEA30K ALL
O SEMEHT C134TROL FACILI7rEA 0040MAIELY AFTER ST W r M'TSE AKk AT AKE4S REUI R91G VULCH IDW_L BE LIVERED F^ %M'ENArk L
T MU EVER?LEEK THE D4WV CUNITTMCTOR YNAL.L BE fX3001WdLE FOR
VIE q+JHTT7"ME AKL REP"OF ALL DHOSYOJ AN BEDIPUT CXKTXL FACILITIES, TTTPB:AD.m
i FEASON WL rU*ER I THTCJ APRIL 9JD— CA Mrs.HERE U)O TE7d:TEA i TQ'JATL 3HD47LD PC I=FOR 71.0 PACUECT IRA£TV HC'3LY
Ur RA*TL',CTIUR ACTIWZTT IS IN PF'.I�SS:THE CLCANNWG W M.Ul1)CC THE BE'>r�F'.4?MTD BOOlI.
AI.OF ESISTDEA', ,.' TA7J3YJ,Ni4 UTIES:I Yl]10 t 'ER.SHALLBE L14TM a IOPIOIL etil"DE PLAFED IN SLEM KII G r"CEEOP 6i
A5 AAC14 LAND AREA 4S:M 3E^MOILED W(MI13IE'B VMM P4 HOU%S IN 3 7TWIFT.Z AHD STOWIL 3[i 119-2:tTE�LZ MALL®LY IE
EVENT A X4AR 21CPA I2 PKIUTED il)7'3f OR E WINK A O SSDDffiH.T FZ4UTTEL IF TTS�l=IS F All E U OY(I_QAR,`aAAW LOte.
4T'-m IF OP7N 0tv' A 3TLT In",I:WCY CLAY LOW CLAY LOt40.
CI.FJAY7E0 OR DIgTNRGFIH NZAt%W.LL RFZEIVE APPRIPI6UE mores Irm A.WTlUgkG SHALL ME CO MU-7O THE PO4UMTE COI*TMX'TIM
OR IE OTHF$dIRE FTARIL171M. &M AR JEB nM%BETTDBR,fLAITM Aw A'7� A FO,Li 70 wx Di?4><THCT"D.K DEFT'M =F mim,DL*T
TM 0=2014 BBAH►ET&.FATE MAD-TW NATEl'CAL.ETC..VMU 3 ARM AFTER DEP7H E I OFT DES'.. L OR THE T WIALL TIE
SM.ALL
N13113 EMN iLE I)OR OTHfR'a'aE MT 40 T WT 9EDW RCrWELT WO10CL Ti!T,T',Nt.'E WLPHITT'CUiTRa R'TIi!LT_RES S1LALi lAE N PT_T.'.E 7fEFIIhC
ILr FENCING, SEUIMFhT TRAPS, SEUINENT VUMN.ETC„ WILL Nor VIE VIEWED AS nli fi�b>,
DEOUATE COVER IN AND OF THEMSELVES, IN THE EVENT THAT ANY LAND AREA NOT
NG ACTIVELY WORKED REMAINS UNPROTECTED IR HAS NOT BEEN APPROPRIATELY
TABIUZED S DAYS AFTER HAVING BEEN CLEARED,ALL CONSTRUCTION ACTIVITY ON
HE SITE,EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL
MMEDIATELY CEASE LNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN
PPROPRIATELY PROTECTED OR STABILIZED.
STOCKPILE MANACL"ENT
L STOCKPILE SHALL R SrABILUED KV1TM PLASTQ COVERING OR OTHER APPROVED DEVICE)DAILY IETW=N NOVEMIER I AND MARCH
IL
t N ANY SEASON.SEDIMENT LEACHING FILM SrOM PAM MUST DE PREVENTED.
1 TOPSOb SHALL NOT NE PLACED WHILE N A FROZEN OR MUDDY CONDITION,WHEN THE SUBGRADE IS EXCESSIVELY WET,UP WHEN
CONOTOINS EXIST THAT MAY O1IERVUE BE DMINEHTAL TO PRWER GRADING OR PKIPOSED SODDING OR SEEDING,
F%CVIW%-t3TAM.1'U WAND OD THE 4WAS TO BE TOP%MU TtW-L K"TAIF£A k7_MDBY,"s TO TWE AtWiMWLL MAY'.
KTAKLI.''EO COATTRALTION ENTI9AGHCE
L 04TH72AL SHALL EE i IMH TO R MN 21Lt3:T SPALLS f4 TD S M- H FOR REIME�STIAL MINE FAIMY LOTS(4a NAY BE
TOP-DCE$3ET VM 1 BCH 7O't DM MM 41TATE ITA7WAM Vl=xlxATTD0 ;FrTMW R-4W
$ THE ROEK?RE)SHALL BL AT LEAPT U UNDIES'THE; *40 30 FEET LOk!j;A FEET FM SI n VETH LEIa'S TWO L AGX IIF
DISTURBED SITU.VOi7HH SHALL BE FULL WIDTH OF THE LLNICLE INGIEn AND ELMIM AREA.SMALLER PADS MAY BE APPROVED
FOR SINGLE-FAMILY RESIDENTIAL AND SMALL COMMERCIAL SITES.
3.ADDITIONAL ROCK SHALL BE ADDED PERIODICALLY TO MAINTAIN PROPER FUNCTION IJF THE PAD.
4,IF THE PAD DOES NOT ADEQUATELY REMOVE THE MUD FROM THE VEHICLE WHEELS. THE WHEELS SHALL BE HOSED DIT BEFORE
THE VEHICLE ENTERS A PAVED STREET.THE WASHING SHALL BE DIME ON AN AREA COVERED WITH CRUSHED ROCK AND WASH
WATER SHALL DRAIN TO A SE13DE14T RETENTION FACILITY OR THROUCN A SILT FENCE.
ILT FENCE
GEUTID(tILE FALTER FAER'IC TT'PE 3HHALL DE HEIR SPELIF'IEC IN THE 'DTOMWATER HBAHAGE009 KVA AL
7FE MIA,GET=MLJ BAUM,•OR APPLICABLE CUM" S7A0DARDS
,GEOrMfl-E FILTER FABRIC STALL BE PM:HAM JN A(MVTMMUS NO.L CUT TO THE LENGTH Or
,H BARRJER TO AVOID USE OF,ANTS IF J )JTe ARE K CESSARY,FILTER I"=SMALL IE SPLSED
(NETHER OILY AT A SJPPORT POST VITH A-J-ONlU4 6-INCH OVE+TLA'AI49 SECLRElY FASTMED AT
I1TH ENCZ TD THE POST.
'Z"T4RD FILTER FAlkEt SHALL BE FASTENED Ja3NG 1'STAPLES OP FIE VMS(H06 RINOSS R 4 IN
ACING.
P' r5 SHALL.RE SPACED AND PLACED AT IEPTHS INIi1CAlED 7fi THE DCTAELs QI THIS SHEET,AY90
VEH SECURELY INTO THE QW-4 L
VDRL MLSH SMALL YL F'X?'X14 (AUGE UP EDUIVILLN7. IHL WIRE MESM MAY BL LLLMINATE:D It'
TRA-STRENGTH F71Ti`JR FABRIC(M�TLAMENT).AND CLIISEk POST SPACING IS USED,
.A TRENCH SHALL BE EXCAVATED ACCORDING TO THE METALS ON THIS SHEET ALONG THE LINE OF THE
TS AND UPSLDPE FROM T1E SILT FENCE.
SILT FENCES S94LL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS 13F THE PROJECT.
GEO 26
Zd_ OW IV
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: Do STEA_\f.07 9
Permit#: 8r_0 201q-012.1V Parcel#: _122.30- It -4 0010
Date(s) of the Document(s) reviewed: 3-Z^ 20 Zd
1. (a) A discussion of general geologic conditions in the vicinity of the proposed development,
OK? M Comment: 6ETw>1 3•U
(b) A discussion of specific soil types
OK? VC 5 Comment: �Ye no nJ 3.Z
(c) A discussion of ground water conditions
OK? Comment: J€CTtdN 3_3
(d) A discussion of the upslope geomorpholog
OK? Y�ST Comment: S€Tttl ?. 2. J
(e) A discussion of the location of upland waterbodies and wetlands
OK? Comment: SECT,erJ 2.3 1
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records
OK?�y7 Comment: jEc-, d oy U.
2. A site plan that identifies the important development and geologic features.
OK? f=Comment: Akt*0 t X r
3. Locations and logs of exploratory holes or probes.
OK? vL5 Comment: �rf eojol X 13
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? Comment: 6%,V- f CAN— Alf 0t
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. Q
OK? Comifient: PW7'� Lr ��p tY J
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? Yy / Comment: 4 , ( o l
7. (a) Appropriate restrictions on placement of drainage features
OK? jV5 -Comment: secyt0N -S-�f
(b) Appropriate restrictions on placemeLit of septic drain fields
OK? Comment: _ 21 AGrtO#J 5-7
(c) Appropriate restrictions on placement of compacted fills and ootings.
OK?_46 Comment: Siuc-kilk)
Page 1 of 2 Form Effective June 2008
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK?� : Z_76' ment: -SE C"0� 5.3
(e) Recommended setbac from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? Comment: jest-to.0 � .2. 5
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: CT W'y 5 .5
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. ,l
OK? Comment: 5E-CT(0'\) y• 7
10. An analysis of both on-site and off-site impacts of the proposed development.
OK? Vf5 Comment: _51tCT(0 OV
11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
OK? Comment: S�LTId"f -
12. Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
OK? VK Comment: Secx(ipN 5. 6
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? `(6 Comment:
Are the Documents signed and stamped? By whom? A I C µA(A 5 T4 ITA)
License#: 43 0 43 License type: L e
FIRST REVIEW Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by on 3 2 20 ZO 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