HomeMy WebLinkAboutGEO2018-00011 BLD2018-00077 Addendum - BLD Engineering / Geo-tech Reports - 6/16/2018 Ei v%rotech PLLC
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March 16, 2018
Thomas and Katy Cornell
PO Box 563
Port Orchard, Washington 98366
RE: Geotechnical Report Addendum #1
XXX E Cove View Drive (Parcel 12206-31-90092), Belfair, Washington
To Whom It May Concern:
Envirotech Engineering PLLC has prepared this addendum for the referenced
property. The original report was completed by Envirotech on January 28, 2018,
project#17207. This addendum was prepared in order to match our site plan with
the building site plan. See the Revised Site Plat enclosed with this addendum.
Envirotech confirms that the revised site plan does not affect our conclusions or
recommendations provided in the geotechnical report.
Please call Michael Staten at 360-275-9374 if you have any questions or need
further information.
Best Regards,
Envirotech Engineering
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3/16/18
Michael Staten
Project Director
PO BOX 984
Belfair,Washington 98528
Off: 360-275-9374
Cell: 36o-689-6045
envirotech@geotechnicalinfo.com
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PROJECT/ OWNER/ LOCATION-
NOTES'
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. CORNELL
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND E COVE VIEW DRIVE
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 12206-31-9DO92
REPORT. MASON COUNTY WASHINGTON
3. BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR, LOCATIONS TEMPORARY ENGINEER,
OF SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP OF SLOPES, TOE f++EROSION CONTROL ENVIROTECH ENGINEERING
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, WASHINGTON 98528
GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC.. WITH 36D-275-9374
RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC --BD- EXISTING CONTOUR
FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING PROPERTIES. TP1e TEST PIT REVISED SITE PLAN
RECEIVED
FS052018
eqeo 615 W. Alder Street
PL _ G
Geotechnical Report
for
Cornell Single Family Residence
31 E Cove View Drive, Belfair
Parcel No. 12206-31-90092
Mason County, Washington
January 28, 2018
Project 417207
Prepared For:
Thomas & Katy Cornell
PO Box 563 C""F s
Port Orchard, Washington 98366
Prepared By:
Envirotech Engineering, PLLC
PO Box 984
1%28i18
Belfair, Washington 98528
Phone: 360-275-9374
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............................................................................................................ 10
4.2 EROSION............................................................................................................................................ 10
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION............................................................................. 11
4.3.1 Liquefaction.............................................................................................................................. 11
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS....................................................... 11
4.5 LATERAL EARTH PRESSURES........................................................................................................... 11
4.6 ON-SITE AND OFF-SITE IMPACTS.................................................................................................... 12
5.0 ENGINEERING RECOMMENDATIONS.......................................................................................13
5.1 BUILDING FOUNDATION RECONINIENDATIONS................................................................................ 13
5.1.1 Bearing Capacity...................................................................................................................... 13
5.1.2 Settlement.................................................................................................................................. 14
5.1.3 Concrete Slabs-on-Grade......................................................................................................... 14
5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS...................................................................... 14
5.2.1 Excavation................................................................................................................................ 14
5.2.2 Placement and Compaction of Native Soils and Engineered Fill........................................... 15
5.2.3 Retaining Wall BackJill............................................................................................................ 16
5.2.4 Wet Weather Considerations.................................................................................................... 16
5.2.5 Building Pads........................................................................................................................... 16
5.3 BUILDING AND FOOTING SETBACKS................................................................................................ 16
5.4 SURFACE AND SUBSURFACE DRAINAGE........................................................................................... 17
5.5 VEGETATION,BUFFER AND CONSIDERATIONS................................................................................. 17
5.6 TF.NIPORARV AND PERMANENT EROSION CONTROL....................................................................... 18
5.7 SEPTIC DRAINFIELDS........................................................................................................................ 18
5.8 STRUCTURAL MITIGATION............................................................................................................... 18
6.0 CLOSURE............................................................................................................................................19
Appendix A-Site Plan
Appendix B-Soil Information
Appendix C-Slope Stability
Appendix D—Erosion Control
Appendix E—Drainage Details
1.0 INTRODtiCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned
single family residence located at XXX E Cove View Drive, identified as parcel number 12206-
31-90092, 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 November 8,
2017. 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 Nvalls, 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 propem'. The planned development consists of a 1-story single family residence,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:
• Reviexv 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
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page Parcel 12206-31-90092
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 January 28. 2018
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 Afap from Mason County Website
Envirotech Engineering, PLLC XXX E Cove View Drive
PO Box 984 page 2 Parcel 1 2206-3 1-90092
Belfair, Washington 98528 Mason Countv,Washington
Ph. 360-275-9374 January 28.2018
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on
November 8, 2017 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 with an existing driveway and septic drainfield. Vegetation on
and near the project consists primarily of secondary growth firs, 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 descending slopes, with grades exceeding 40% appear to be within 300 feet of the
planned development. The maximum critical slope is approximately 41% with a vertical relief of
about 30 feet.
Ascending grades are generally located to the southeast 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 crest of glacial
landslide origin.
2.3 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. PLLC XXX E Cove View Drive
PO Box 984 Parcel 12206-31-90092
Belfair. Washington 98528 Mason County Washington
Ph. 360-275-9374 January 28.2018
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.
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Aerial Photo from .Mason County Website
Envirotech Engineering, PLLC XXX E Cove View Drive
PO Box 984 page 4 Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason County, Washington
Ph. 360-275-9374 January 28.2018
3.0 SUBSURFACE LWESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on
November 8. 2017 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 18 inches, and dense
soils from 18 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, Q,. 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 tertian sedimentar\ 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 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 20091. provides the following caption(s) for the project area:
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page 5 Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason County.Washington
Ph. 360-275-9374 Januan 28. 2018
Landslide deposits—Gravel. sand, silt. clay. and boulders in slide body
and toe: due to map scale. includes exposure of underlying units in scarp
areas: angular to rounded clasts and¢rams: unsorted: generally loose.
Jumbled.and tmstratified.but miv locally retain primary,bedding:
commonly Includes liquefaction features Absence of a mapped slide does
not imph•absence of sliding or hazard as some slides are too small to
show at map scale.Although the large Alderwood landslide southwest of
Belfair mac have been triggered by seismicity about 1.1 ka (see Stricture).
review of aerial photographs also suggests historic movement for this
slide. The unit post-dates V ashon ice and is predominantly Holocene but
locally inav include some late Pleistocene deposits.
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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
Envirotech Engineering, PLLC XXX E Cove View Drive
PO Box 984 a_e 6 Parcel 12206-31-9009_'
Belfair. Washington 98528 Mason County, Washington
Ph. 360-275-9374 January 28, 2018
System(USCS)and the Soil Conservation Service(SCS)descriptions.
The project is currently composed of native soils Nvithout indications of fill. Within test pit
locations, soils within the upper 3 feet of natural ground were generally observed to be moist,
brown clayey silt with sand and gravel (CL-ML). Soils below the upper 3 feet are expected to be
a conglomerate similar to what we observed. This is based on nearby well reports, site geology,
and/or knowledge of the general area.
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 Aldenvood Gravelly Sandy
Loam. A,, with 15% - 30% 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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3.3.1 Groundwater
From the water well report(s) and knowledge of the general area. permanent groundwater
is at least 50 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,PLLC XXX E Cove View Drive
PO Box 984 page 7 Parcel 12206-31-90092
Belfair. Washington 98528 Mason County, Washington
Ph. 360-275-9374 January 28.2018
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 'Unstable' regarding potential landslide activity. Stable slopes
are generally not prone to landslides due to small grades and accommodating geology. Unstable
slopes are considered unstable because of geology, groundwater, slope and/ or erosional factors.
They include areas of landslides and talus too obscure to be individually mapped. A Stability Map
from the Coastal Zone Atlas for the general area of this Project is provided below.
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Map from Washington State Department of Ecology Website
Envirotech Engineering, PLLC XXX E Cove View Drive
PO Box 984 page 8 Parcel 1 2206-3 1-90092
Belfair, Washington 98528 Mason County, Washington
Ph. 360-275-9374 January 28,2018
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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Envirotech Engineering.PLLC _ XXX E Cove View Drive
PO Box 984 page 9 Parcel 1 2206-3 1-90092
Belfair,Washington 98528 Mason County, Washington
Ph. 360-275-9374 January 28.2018
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:
Soil unit weight: 130 pcf
Angle of internal friction: 10 degrees
Cohesion: 700 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 1.8 and 1.1. 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 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).
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
storm-water runoff or tracking off-site with construction equipment.
The Temporary and Permanent Erosion Control Section (Section 5.6) of this report contain
specific erosion control options recommended for this Project. Additional erosion control
measures than what is initially established may need to be employed if excessive erosion occurs
during construction. or required by the prevailing agency. Complete 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.
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page 10 Parcel 12206-31-90092
Beltair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 January 28,2018
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 approximately 1 mile 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 t}°pically 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 on the property. The property is mapped within an
ancient, dormant landslide. It is our opinion that this landslide will not reactivate where
development is planned to occur. Mapped slope conditions, as delineated by the Departments of
Ecology and/ or Natural Resources, were considered in our slope stabilivy 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.
) n�irotech Engineering. PLLC XXX E Core Vie%k Drive
PO Box 984 pa_r i Parcel 12206-31-90092
Belfair. Washington 98528 Mason Count%. Washington
Ph. 360-275-9374 January 28. 2018
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 10 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, PLLC XXX E Cove View Drive
PO Box 984 page 12 Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason Count}. Washington
Ph. 360-275-9374 January 28.2018
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, soiu
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
M-o-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 nonnal 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. Alternativel}, 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(18 inches for 2-story structures) shall be placed at a minimum
of 18 inches below the existing ground surface atop unyielding soils. For buildings
located on slopes exceeding 15% and not more than 25%, foundations should extend to a
minimum depth of 3 feet. 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
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page I Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 January 28. 2018
foundation recommendations may be completed upon a site inspection by a geotechnical
engineer after the foundation excavation is completed.
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 910 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 Ensineerinu. PLLC XXX E Cove View Drive
PO Box 984 page 14 Parcel 12206-31-90092
Belfair, Washington 98528 Mason County. Washington
Ph. 360-275-9374 January 28. 2018
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 compacted or re-compacted fill depth beneath the
foundation. See the illustration below.
i FOOTING
COMPACTED
NATIVE SOILS
OR ENGINEERED t
FILL
1
1—IT
II UNbl'STURBED SUBGRAD11'
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
No. 200 0 - 8
Table 1
Partical 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.
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 p:_ I Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 Jan uary 28.2018
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 '/ 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 consisting of built-up fill is not recommended for this project. However, an
engineered grading plan or details could justify building pads for this project.
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.
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 pale 16 Parcel 12206-31-90092
Belfair. Washington 98528 Mason County. Washington
Ph. 360-275-9374 January 28.2018
S-RUZ T''_RE
TCP _Y
S_' FE -
i+CL
��LT 1��i-r- - --Trl-
'
- _ SETBAZK --i F oil rlu:,
From the illustration above, structures may 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 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 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.
Both footing perimeter drains and roof drains are required for this project. Subsurface water
intercepted in the footing perimeter drains, and stormwater collected from roof drains shall be
separately tight-lined to the recommended outlet. Roof and foundation drains may share a
tightline if an above ground drainage outlet is allowable and a backflow preventer is installed
within the pipe system in order to prevent roof water from entering the foundation area.
For this project, we recommend that roof runoff dispersion is located at least 10 feet downslope
from the proposed house, and outside of geotechnical buffers or setbacks. The dispersion trench
should be at least 50 feet in length. Recommended infiltration locations are delineated on the Site
Plan in Appendix A. and drainage details are provided in Appendix E of this report.
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.
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page I, Parcel 12206-31-90092
Belfair, Washington 98528 Mason Count}, Washington
Ph. 360-275-9374 Januan 28.2018
Vegetation Buffer— Vegetation shall not be removed from the face of the critical slope or within
a distance of 35 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.
5.6 Temporary and Permanent Erosion Control
Erosion control during construction should include minimizing the removal of vegetation to the
least extent possible, and may include stockpiling cleared vegetation, silt fencing, intercepting
swales, berms, straw bales, plastic cover or other standard controls. 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 Map in Appendix A depicts the recommended locations for erosion control
facilities to be installed.
Permanent erosion control is necessan, 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
The approximate location of the existing septic drainfield is presented on the Site Plan in
Appendix A of this report. Based on the septic drainfield location with relation to the existing and
proposed topography, the drainfields are not expected to adversely influence critical slopes. This
is also 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 w ith all recommendations provided in this report.
En irotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 y page 18 Parcel 1 2206-3 1-90092
Belfair, Washington 98528 Mason Count}. Washington
Ph. 360-275-9374 January 28.3018
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 onl} 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
Envirotech Engineering. PLLC XXX E Cove View Drive
PO Box 984 page 19 Parcel 1 2206-3 1-90092
Belfair. Washington 98528 Mason Count. Washington
Ph. 360-275-9374 January 28. 2018
APPENDIX A
SITE PLAN
�FRo oRoF BUFFER
6 / Moo of aov.SLOPE
or s ova
r .`VIRS SV BLCG-SE?—FBan
/ pJ / ExEEOMc.ox SLOPE ExEEoiuG<o� �TEPOF.1so-
4�
376.39' — /[ — —
- - - 7 - - - -/- - - - - - -/
so
(SEEBET-S RE7 I i I
t`
//SILTFE-E__ PBIMR.D-11ELo °
I
Xlolls,
R'=4FIMl SF
�GMSTR.ENLB./ //
r T 394.48' o I
SITE PLAN NORTH 1010®'
SCALE:1"=40.00' T
SHEET NO. DATE: THOMAS&KATY CORNELL NEW TAM
DRAWN PARCEL# �S
TOM 91 ss Ba IAo NS k
SITE o z
TOM MaBERc MASON CO..WA HOUSE 122063190092 oRAFTNc oeslcN
REMODELS REEMEN-L
TAM GESIGNS ASBNILTE
CI AM Designs\CORNELL\SITE.dwg, 3/12/2018 5:38:13 PM, Adobe PDF
b ti`J`
APPROXIMATE TOP OF SCALE, 1 INCH = 60 FEET
SLOPE EXCEEDING 40% 0 1. 30 0
35, VEGETATION BUFFER
FROM TOP OF 40% SLOPE,
S
50' BUILDING SETBACK
FROM TOP OF 40% SLOPE.
SEE REPORT. SILT FENCE, SEE DETAILS,
EXISTING
APPR❑XIMATE T OF DRAINFIEL DAREA
SLOPE EXCEE M 40%
50' DIS ERSION TRENCH.
SEE DE AILS & REPORT.
bo +1
LL
�6•� N
TPI P POSED
❑U
0� DRIVEWAY
W
> 390 Tf
0
0 o ALL DENUDED AREAS TO BE
w .moo �o VEGETATED PER ER❑SI❑N
CONTROL NOTES,
STABILIZED CONSTRUCTION
ENTRANCE. SEE DETAILS.
NOTES PROJECT/ OWNER/ LOCATION,
L 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. CORNELL
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND E COVE VIEW DRIVE
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL I2206-31-90092
REPORT. - MASON COUNTY WASHINGTON
3. BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR. LOCATIONS 1 TEMPORARY ENGINEER-
OF SITE FEATURES THAT ARE SHOVN HERE, SUCH AS TOP OF SLOPES, TOE T+ +EROSION CONTROL ENVIROTECH ENGINEERING
OF SLOOPES, WATER FEATURES, ETC.., WITH RELATION TO THE PROPERTY PO BOX 984 BELFA[
LINES MUST BE VERIFIED BY THE OWNER. RECOMMENDATIONS IN THE SLOPE INDICATOR R, VASHINGTON 98528
GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC.. WITH DELFAI5-9374
RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC 80 EXISTING CONTOUR
FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING
PROPERTIES. TP1 TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
VERTICAL MID HMZDITAL SCALE,
I V" 40 FEET
0
PROPOSED
HOUSE
EXISTING AND
PROP❑SED GRADE
2Si+
CLAYEY SILT WITH
SAND AND GRAVEL
SECTION A-A
PROJECT/ OWNER/ LOCATION,
SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
CORNELL
PARCEL 122%-31-90092
MASON COUNTY, WASHINGTON
VDTES
ENGINEER-
[) MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENVIROTECH ENGINEERING
'DSITIVE DRAINAGE PO BOX 984
?) THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF BELFAIR, WASHINGTON 98528
IHE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. 360-275-9374
_OVER DEPTHS ARE BASED ON SITE GEOLOGY,
JELL LOG(S), AND/OR EXPERIENCE IN THE GENERAL AREA. SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Cornell Geotechnical Report DATE OF LOG: 11/8/2017
PROJECT NO: 17207 LOGGED BY: RJM
CLIENT: Thomas & Katy Cornell EXCAVATOR: N/A
LOCATION: Parcel 12206-31-90092 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 . . . . . . . . . . .
CL-ML Brown, moist, medium dense/
consistency silty clay with sand and
gravel, Gravel is primarily fine and
1 subangular. Sand is mostly medium. Low
to medium plasticity.
2
3 - -
Excavation terminated at approximately
3.0 feet
4
5
6
7
8
9
10
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
inlamrA{xl nc hoinn inrlirl5vc of fhn cn6ro rim
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 Alderwood
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
glaciomarine deposits
Typical profile
A - 0 to 7 inches: gravelly sandy loam
Bwl - 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
2Cdl -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 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 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
u= Natural Resources Web Soil Survey 1/28/2018
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
Other vegetative classification: Limited Depth Soils
(G002XN302WA), Limited Depth Soils (G002XF303WA),
Limited Depth Soils (G002XS301 WA)
Hydric soil rating: No
Minor Components
Everett
Percent of map unit: 5 percent
Landform: Karnes, 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: Karnes. terraces, eskers
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: Drainageways, depressions
Landform position (three-dimensional): Dip
Down-slope shape: Linear, concave
Across-slope shape: Concave
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 13, Sep 7, 2017
);r, Natural Resources Web Soil Survey 1/28/2018
0110 Conservation Service National Cooperative Soil Survey Page 2 of 2
APPENDIX C
SLOPE STABILITY
Project : comell
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GEOMETRY DEFINITION
POINTS
NO. X Y
1 0.000 0.000
2 50.000 -5.000
3 150.000 -30.000
4 200.000 -50.000
5 20.000 -2.000
6 28.420 -2.840
7 36.840 -3.680
8 45.260 -4.530
9 53.680 -5.920
10 62.110 -8.030
11 70.530 -10.130
12 78.950 -12.240
13 87.370 -14.340
14 95.790 -16.450
15 104.210 -18.550
16 112.630 -20.660
17 121.050 -22.760
18 129.470 -24.870
19 137.890 -26.970
20 146.320 -29.080
21 154.740 -31.890
22 163.160 -35.260
23 171.580 -38.630
24 180.000 -42.000
LINES
Lo X Hi X SOIL
1 2 1
2 3 1
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SOILS
SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT.
1 Soil—1 CONTINUOUS-BLACK 700.00 10.0 130.000
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PORE PRESSURE SPECIFICATION
Project : Comell
Datefile: dynamic Bishop
SOIL PIEZO RU EXCESS
Y/N/P Value Value
1 N 0.000 0.000
PIEZOMETRIC SURFACE
POINT
POINT PORE PRESSURES
POINT PRESSURE
SLIP DIRECTION (+/- X) - +
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SLIP-CIRCLES
AUTOMATIC
Circle Centre Grid Extremities
160.000
20.000 180.000
* fi
0.000
X spacing -- no. of cols (max 10)- 10
Y spacing -- no. of rows (max 20)= 20
Grid 1 Circles through point 5
Grid 2 Circles through point 6
Grid 3 Circles through point 7
Grid 4 Circles through point 8
Grid 5 Circles through point 9
Grid 6 Circles through point 10
Grid 7 Circles through point 11
Grid 8 Circles through point 12
Grid 9 Circles through point 13
Grid 10 Circles through point 14
Grid 11 Circles through point 15
Grid 12 Circles through point 16
Grid 13 Circles through point 17
Grid 14 Circles through point 18
Grid 15 Circles through point 19
Grid 16 Circles through point 20
Grid 17 Circles through point 21
Grid 18 Circles through point 22
L _ 00
1 _ 10
1 _ 20
L _ 30
1 _ 40
1 _ 50
1 _ 60
1 _ 70
1 _ 80
1 _ 90
2 _ 00
I
O p 0 0 O O
O � O
� � O
O O O O
O O
O O
1 _ 044
Project _ Cornell
O a-t a f i 1 e _ d y n a m i c
Analyses Bishop
S-r^Fil.S.-2002 M% nt.cn 1.t A
f I
1 . O 0
1 - 1- 0
I 1 . 2 0
I I _ 3 0
1 _1 . 4 0
1 . 50
1 . 60
1 . 70
I I
� 1 _ 80
I
1 _ 90
2 . 00
i
O 0000
• 1 _ 832
Project _ Cornell
Datafile _ static
Analyses Bishop
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 TRENCHr2.5�
EQUIVALENT OR BETTER
FILLED WITH 3/4' TO 1 1/2'
WASHED GRAVEL ❑R VEGETAT N
DIRECTION OF EXISTING
WATER FLOW GROUND SURFACE
i2•
2.5 FT
8•
SILT FENCE - CROSS SECTION
N.T.S.
2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC
OR EQUIVALENT OR BETTER AND WIRE MESH
@ 6 FT MAX. D.C.
6 FT -�{ r 0.5 FT
EXISTING I +
GROUND SURFACE
2 T
12' DEEP, 8' WIDE \ �
FT
TRENCH FILLED WITH
3/4' TO 1 1/2' 2.5 FT
WASHED GRAVEL OR VEGE TI
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - DETAIL
N.T.S.
PROVIDE FULL WIDTH
F INGRESS/EGRESS
3/4 IN TO 1 1/�IN� FT
CRUSHED GRAVEL
PLACED AT 6 IN
MINIMUM DEPTH
WELL-DRAINED
S❑ILS
-0.02 IN/MIN FULL XNGTH
R=25 FT MIN
PROJECT/ OWNER/ LOCATION,
ACCESS ROAD SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
STABILIZED CONSTRUCTI❑N ENTRANCE CORNELL
N.T.S. PARCEL 12206-31-90092
MASON COUNTY, WASHINGTON
ENGINEER,
ENVIROTECH ENGINEERING
PO BOX 984
BELFAIR, WASHINGTON 98528
360-275-9374
EROSION CONTROL P, 1
PERMANENT EROSION CONTROL NOTES,
EN£RAL NOTES-
SEEDING FOR RAW SLOPES
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON
THESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR 1. BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL
HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. MEASURES SUCH AS GRADIENT TERRACES, INTERCEPTOR DIKES,
ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE SWALES, LEVEL SPREADERS AND SEDIMENT BASINS,
NSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY. 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE,
ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE LEFT IN FOLLOWING SURFACE ROUGHENING. PERFORM ALL OPERATIONS ACCROS
LACE UNTIL THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED. OR PERPENDICULAR TO THE SLOPE.
3. SEEDING RECOMMENDATIONS, AS SHOWN BELOW, AND SHOULD BE
EMPORARY EROSION CONTROL NOTESi APPLIED AT THE RATE OF 120 POUNDS PER ACRE.
4. SEED BEDS PLANTED BETWEEN MAY 1 AND 13CTOBER 31 WILL
OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO
ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A FOSTER AND PROTECT THE ROOT STRUCTURE.
ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE 5. SEED BEDS PLANTED BETWEEN NOVEMBER 1 AND APRIL 30,
M14EDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED ARMORING OF THE SEED BED WILL BE NECESSARY, <e.g.,
ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR. GRASS SEEDING GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING).
LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH 6, FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS'
EPTEMBER, HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF RECOMMENDATIONS. AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY
HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING ADJACENT TO WATER BODIES AND WETLANDS.
R OTHER APPROVED TREATMENT.
USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION
RY SEASON (MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE CONTROL, OR A COUNTY APPROVED ALTERNATE SEED MIXTURE.
EHOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO
ONLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE PROPORTIONS PURITY GERMINATION
THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED NAME BY WEIGHT(%) (%) (7)
Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR. UNLESS IMMEDIATE
TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL REDTOP (AGROSTIS ALBA) 10 92 90
REAS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ANNUAL RYE (LOLIUM MULTIFLORUM) 40 98 90
HROUGH THE USE OF MULCHING, NETTING, PLASTIC SHEETING, EROSION BLANKETS, CHEWING FESUE 40 97 80
REE DRAINING MATERIAL, ETC,, BY SEPTEMBER 30 OR SOONER PER THE APPROVED (FESTUCA RUBRA COMMUTATA)
LAN OF ACTION. UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, (JAMESTOWN, BANNER, SHADOW, KOKET)
ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE WHITE DUTCH CLOVER 10 96 90
ERFORMED DURING THE FOLLOWING PERIODS- MARCH 1 TO MAY 15, AND AUGUST 15 TO (TRIFOLIUM REPENS)
CTOBER 1. SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION
THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE MULCHING
O SATISFACTORY GROWTH. IN THE EVENT THAT PERANENT STABILIZATION IS NOT
OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, 1, MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
LASTIC SHEETING, EROSION BLANKETS, ETC., MUST BE INSTALLED BY NO LATER THAN FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000
EPTEMBER 30. POUNDS PER ACRE.
2, MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES
N THE EVENT THAT CONSTRUCTION ACTIVITIES OR OTHER SITE DEVELOPMENT GREATER THAN 2d (HORIZONTAL!VERTICAL).
CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE 3. MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN
WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. ALL
ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1.
EAST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR
HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. TOPSOILING
ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED L TOPSOIL SHOULD BE USED FOR THIS PROJECT DUE TO HIGHLY
ONSTRUCTM ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE DENSE EXPOSED SOILS•
EMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED 2, TOPSOIL SHOULD BE PLACED ON SLOPES NOT EXCEEDING 2.1.
O AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 3. STRIPPING AND STOCKPILING ON-SITE SOILS SHALL ONLY BE
HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT PERMITTED IF TOPSOIL IS FRIABLE AND LOAMY (LOAM, SANDY LOAM,
RANSPORT OFF-SITE IS OBSERVED. SILT LOAM, SANDY CLAY LOAM, CLAY LOAM).
LL CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE 4. STRIPPING SHALL BE CONFINED TO THE IMMEDIATE CONSTRUCTION
IOVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC AREAS, A FOUR TO SIX INCH STRIPPING DEPTH IS COMMON, BUT
HEETING, EROSION BLANKETS, FREE DRAINING MATERIAL, ETC., WITHIN 5 DAYS AFTER DEPTH MAY VARY DEPENDING ON THE PARTICULAR SOIL. ALL
AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED, SURFACE RUNOFF CONTROL STRUCTURES SHALL BE IN PLACE BEFORE
ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC., WILL NOT BE VIEWED AS STRIPPING.
DEQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT
EING 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.
STOCKPILE MANAGEMENT
1. STOCKPILE SHALL BE STABILIZED (WITH PLASTIC COVERING OR OTHER APPROVED DEVICE) DAILY BETWEEN NOVEMBER 1 AND MARCH
3L
2. IN ANY SEASON, SEDIMENT LEACHING FROM STOCK PILES MUST BE PREVENTED.
3, TOPSOIL SHALL NOT BE PLACED WHILE IN A FROZEN OR MUDDY CONDITION, WHEN THE SUBGRADE IS EXCESSIVELY WET, OR WHEN
CONDITIONS EXIST THAT MAY OTHERWISE BE DETRIMENTAL TO PROPER GRADING OR PROPOSED SODDING OR SEEDING.
4, PREVIOUSLY ESTABLISHED GRADES ON THE AREAS TO BE TOPSOILED SHALL BE MAINTAINED ACCORDING TO THE APPROVED PLANS.
STABILIZED CONSTRUCTION ENTRANCE
1. MATERIAL SHALL BE 4 INCH TO 8 INCH QUARRY SPALLS (4 TO 6 INCH FOR RESIDENTIAL SINGLE FAMILY LOTS) AND MAY BE
TOP-DRESSED WITH 1 INCH TO 3 INCH ROCK. (STATE STANDARD SPECIFICATIONS, SECTION 8-15.)
2. THE ROCK PAD SHALL BE AT LEAST 12 INCHES THICK AND 50 FEET LONG (20 FEET FOR SITES WITH LESS THAN i ACRE OF
DISTURBED SOIL). WIDTH SHALL BE FULL WIDTH OF THE VEHICLE INGRESS AND EGRESS 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 OF THE PAD,
4. IF THE PAD DOES NOT ADEQUATELY REMOVE THE MUD FROM THE VEHICLE WHEELS, THE WHEELS SHALL BE HOSED OFF BEFORE
THE VEHICLE ENTERS A PAVED STREET. THE WASHING SHALL BE DONE ON AN AREA COVERED WITH CRUSHED ROCK AND WASH
WATER SHALL DRAIN TO A SEDIMENT RETENTION FACILITY OR THROUGH A SILT FENCE.
ILT FENCE
PROJECT/ OWNER/ LOCATION,
GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE
OR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS
. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GE❑TECHNICAL REPORT
ACH BARRIER TO AVOID USE OF JOINTS. IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED CORNELL
OGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT PARCEL 12206-31-90092
. S ENDS TO THE POST.STANDARD FILTER FABRIC SHALL HE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) Q 4 IN MASON COUNTY, WASHINGTON
PACING•
. 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 EQUIVILENT. 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.
SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT. EROSION CONTROL P. 2
APPENDIX E
DRAINAGE DETAILS
1'-0 MIN
1'-0 MIN END CAP OR PLUG
CLEAN OUT WYE FROM PIPE
4' OR 6' PERFORATED
PIPE LAID FLAT/LEVEL FLOW TO SECOND
DISPERSAL TRENCH
NOTCHED TYPE 30 CB W/ IF NECESSARY
GRADE BOARD SOLID COVER
2'X2' NOTCHES A A (LOCKING)
Is, ❑,C,50t a - TYPE 30 CB
W/SOLID COVER
p
CLEAN OUT WYE
FROM PIPE
a
PLAN FLOW TO OTHER
N.T.S. 18. OC BRANCHING CB'S
AS NECESSARY
�1 2•
2' GRADE BOARD NOTCHES -}
1'-0 MIN 2"
2'X12' GALVANIZE
PRESSURE BOLTS 1'-0 MIN NOTES:
TREATED
GRADE � Zp% MAX 1, THIS TRENCH SHALL BE CONSTRUCTED SO
BOARD AS TO PREVENT PINT DISCHARGE AND/OR
EROSION
4' F 6' 2, TRENCHES MAY BE PLACED NO CLOSER
N PERFORATED THAN SO FEET TO ONE ANOTHER, C100 FEET
-, M PIPE LAID ALONG FLOWLINE)
FLAT
LEAN (SS% 3, TRENCH AND GRADE BOARD MUST BE
4' X 4' SUPPORT POST FINES) LEVEL. ALIGN TO FOLLOW CONTOURS OF
Z } FILTER 1� -j WASHED SITE.
-1 FABRIC ROCK
4, SUPPORT POST SPACING AS REQUIRED BY
SOIL CONDITIONS TO ENSURE GRADE BOARD
REMAINS LEVEL,
PROJECT/ OWNER/ LOCATION-
SINGLE FAMILY RESIDENT
GEOTECHNICAL REPORT
CORNELL
PARCEL 12206-31-90092
MASON COUNTY, WASHINGTON
ENGINEER,
ENV IROTECH ENGINEERING
PO BOX 984
BELFAIR, WASHINGTON 98528
360-275-9374
DRAINAGE DETAILS
GEO
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: YM 1
Permit#: Rib L4 - 0061 Parcel#:
Date(s)of the Document(s) reviewed: �7aY) I?
1. (a) A discussion of general geologic conditions in the vicinity of the proposed development,
OK? X Comment:
(b) A discu ion of specific soil types
OK? Comment:
(c) A discussion of ground water conditions
OK?��>e Comment:
(d) A discussi of the upslope geomorphology
OK? —Comment:
(e) A discus of the location of upland waterbodies and wetlands
OK? I$r Comment:
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records
OK? _Comment:
2. A site plan that identifies the important development and geologic features.
OK? Comment:
3. Locations and logs of exploratory holes or probes.
OK? Comment:
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:
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:
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:
7. (a) Appropriat restrictions on placement of drainage features
OK? Comment:
(b) Appropriatip restrictions on placement of septic drain fields
OK?_ Comment:
(c) Appropri t restrictions on placement of compacted fills and footings.
OK? _Comment:
Page 1 of 2 Form Effective June 2008
(d) Recomrqp ed buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? Comment:
(e) Recommended setbacks from the landslideard areas shoreline bluffs and the tops of other slopes.
OK? 1 Comment: !)
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:
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?��Comment:
10. An analysis of both on-site and off-site impacts of the proposed development.
OK? Comment:
11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
OK? Comment:
12. Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
OK? Comment:
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? Comment:
Are the Documents signed and stamped? By whom? r111)Jre
License#: y 3D Li'� License type: 1" N
FIRST REVIEW Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by (�-zr�-� 1- on h Time spent in review:I L
/
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
Mason County Department of Community Development
Submittal Checklist For a 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 found to be not applicable, the report should explain
the basis for the conclusion.
Applicant/Owner Thomas & Katy Cornell Parcel# 12206-31-90092
Site Address XXX E Cove View Drive, Belfair
(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 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
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Site Plan/Soil Logs
(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
(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.
Located on page(s) 10
(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) 18
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s) 13, 14
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) 17
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
Located on page(s) 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) 17
(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) 12
(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 C 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 1/28/18 and entitled Cornell
Single Family Residence meets all the requirements of the Mason
County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment
demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the
included geotechnical design recommendations, and that all hazards are mitigated in such a manner as
to prevent harm to property and public health and safety. (Signature and Stamp)
C Ll 01.
\ �c
k, 43045 .`� � ,�
<„/;V." 4 1/28/18
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.