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PLANNING
Geotechnical Report
Colley Single Family Residence
XXX NE Klahowya Road, Belfair
Parcel No. 32223-75-00150
Mason County, Washington
December 20, 2023
Project#23242
Prepared For:
Chris Colley
7426 NE 155th Street
Kenmore, WA 98028
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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43045
12/20/2023
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MASON COUNTY
COMMUNITY SERVICES Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed
professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County
Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclusion.
Note:Unless specifically documented,this report does not provide compliance to the International Residential Code
Sections R403.1.7 for foundations on or adjacent to slopes,Section R403.1.8 for expansive soils or section 1808.7.1
of the International Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Chris Colley Parcel# 32223-75-00150
Site Address XXX NE Klahowya 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 of 38
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(7) (a) Appropriate restrictions on placement of drainage features,
Located on page(s) 16
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) 17
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 14
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 17
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
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) 11
(11) Specifications of final development conditions such as,vegetative management,drainage,erosion control, and
buffer widths.
Located on page(s) 17
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 18
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature
of existing and proposed development on the site.
Located on Map(s) Site Plan
I, Michael Staten, hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington
with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in
the State of Washington with special knowledge of the local conditions. I also certify that the Geotechnical
*`t t L)DI, S Report,dated December 20,2023 and entitled Colley Single
Family Residence, meets all the requirements of the Mason
County Resource Ordinance, Geologically Hazardous Areas
Section, is complete and true,that the assessment
43045 `� demonstrates conclusively that the risks posed by the landslide
hazard can be mitigated through the included geotechnical
12/20/2023 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
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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.....................................................................................................I I
5.0 ENGINEERING RECOMMENDATIONS........................................................................................12
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.............................................................................................................................................18
Appendix A-Site Plan
Appendix B-Soil Information
Appendix C-Slope Stability
Appendix D—Erosion Control
J �
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a planned
single family residence located at XXX NE Klahowya Road, identified as parcel number 32223-
75-00150, 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 July 19, 2023. It
was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were present
within 300 feet of the planned development. Based on this site characteristic, the proposed
development will require a geotechnical report pursuant to Landslide Hazard Areas of Mason
County Resource Ordinance (MCRO) 8.52.140. During the site visit by Envirotech, surface and
subsurface conditions were assessed. After completion of the field work and applicable project
research, Envirotech prepared this geotechnical report which, at a minimum, conforms to the
applicable MCRO.
As presented herein, this report includes 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 I- or 2-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:
• Review project information provided by the project owner and/or owner's representative;
• Conduct a site visit to document the site conditions that may influence the construction and
performance of the proposed improvements of the project;
• Define general subsurface conditions of the site by observing subsoils within test pits and/
Envirotech Engineering Geotechnical Report
PO Box 984 page 1 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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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,rt Project
Tahuya
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Union
Mason
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Vicinity Map from Mason County
Envirotech Engineering Geotechnical Report
PO Box 984 page 2 Parcel 32223-75-001.50
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on July 19,
2023 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 has a gated driveway with various mobile homes, sheds and a carport.
Vegetation on and near the project consists primarily of secondary growth maples,firs,cedars 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 85%with a vertical relief of about 200
feet.
Descending grades are generally located to the west 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.
2.3 Surface Drainage
Runoff originating upslope of the development is mostly diverted onto the property within a
confined drainage ditch.This drainage convergence empties into the Tahuya River located near the
west property line. Scour was observed within the drainage ditch. It is also apparent that much of
the property bordering the Tahuya River is within a flood plain.
2.3.1 Upslope Water Bodies
The aforesaid drainage channel originates upslope of the property, but appears to not be
influential to the development location.
Envirotech Engineering Geotechnical Report
PO Box 984 page 3 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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.
An abundant number of tees were bowing and leaning on the ascending slope indicating earth
movement. This could be slow downhill creep, or incremental shallow shifts of the land during
large seismic events.
A
145 2W 580 870
Fee
Aerial Photo from Mason County
Envirotech Engineering Geotechnical Report
PO Box 984 page 4 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on July 19,
2023 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 4 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 terminus.
3.2 General Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the"Geologic Map of Washington,"compiled by J. Eric Schuster,2002
indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated deposits,
and dominantly deposited from glacial drift, including alluvium deposits. This project is located
within the Puget Lowland.Typically,"lower tertiary sedimentary rocks 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 Lilliwaup 7.5-minute Quadrangle, Mason County, Washington" by
Trevor A. Contreras, Gabriel Legorreta Paulin,Jessica L. Czajkowski, Michael Polenz, Robert L.
Logan, Robert J. Carson, Shannon A. Mahan, Timothy J. Walsh, Chris N. Johnson, and Rian H.
Skov,June 2010,provides the following caption(s)for the project area:
Unit Description
Qaf Debris-flow diamicton and alluvial sand and gravel;gray,weathering to brownish-orange;
loose;clasts subrounded to rounded;typically poorly to moderately sorted and massive to
weakly stratified
Qpd Gravel,sand,till,and diamicton;tan to orange-brown;clasts well rounded to angular;
compact;varies from well sorted sand and gravel outwash to poorly sorted diamicton
Qa Sand to cobble gravel,locally includes clay and peat;typically gray and generally
unweathered;loose;clasts subrounded to rounded;moderately to well sorted;stratified to
massively bedded;deposited in stream valleys and estuaries
Envirotech Engineering Geotechnical Report
PO Box 984 page 5 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
N
Project
kQaf
Qa
Qaf
Vtw-
d Q pd
Qga
0 310 Feet
Geological Map Department of Noiitral 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 in places of up to 2 feet
deep. Within test pit locations, soils within the upper 4 feet of natural ground were generally
observed to be reddish brown silty gravel (GM)with sand and cobbles.
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 Everett very gravelly sandy loam, Ek and
Eg, with 0% to 30% slopes, Nuby silt loam, Nf, with 0% to 3% slopes. The soil designations are
depicted in the aerial photograph below,and descriptions are provided in Appendix B of this report.
Envirotech Engineering Geotechnical Report
PO Box 984 page 6 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
1 �1
j illill
of
0 125 250 500 750
Fee
Soil Surveh 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 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 Geotechnical Report
PO Box 984 page 7 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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 safety 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 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:
Project
t
Moderate Slope Instability
High Slope Instability
® Highly Erodible Soils
® Hydric Soils
Highly Unstable Soils
Resource Map from Washington State Department of Natural Resources
Envirotech Engineering Geotechnical Report
PO Box 984 page 8 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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 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
regard 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: 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 not within an erosion hazard
area as defined by the MCRO. Erosion hazard areas are those with USDA SCS designations of
River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on slopes 15% or
greater(Ac and Ad),Cloquallum Silt Loam on slopes 15%or greater(Cd),Harstine Gravelly Sandy
Loam on slopes 15%or greater(Hb), and Kitsap Silt Loam on slopes 15% or greater(Kc).
It is our opinion that minor erosion control recommendations provided in this report is sufficient
for the development of this project, and additional engineered erosion control plans are not
required. Temporary and permanent erosion control measures are required for site development.
Extents of temporary erosion control will mostly depend on the timeliness of construction,moisture
content of the soil, and amount of rainfall during construction. Soil erosion typical to the existing
site conditions and planned disturbance of the project include wind-borne silts during 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
specifications may be found in the latest addition of the "Stormwater Management Manual for
Envirotech Engineering Geotechnical Report
PO Box 984 page 9 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
1 .
Western Washington," prepared by the Washington State Department of Ecology Water Quality
Program.
4.3 Seismic Considerations and Liquefaction
There are no known faults beneath this project. The nearest Class `A' or Class `B' fault to this
property is the Tacoma fault,which is approximately 3 miles to the south east 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.
An equivalent fluid unit weight used for structural design may be estimated as the product of the
Envirotech Engineering Geotechnical Report
PO Box 984 page 10 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
backfill soil unit weight and the earth pressure coefficient for at-rest pressures. Retaining walls
should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of the
following:
At-Rest Active
Native Soils 49 pcf 32 pcf
Engineered Fill Soils 45 pcf 28 pcf
The values provided above shall be increased by 1 pcf for every 1 degree of backfill/natural slope
angle. These equivalent fluid unit weight values do not include lateral earth pressures induced by
earthquakes,groundwater,or surcharges from live loads. Earthquake pressures should be added to
the wall analysis,and treated as an inverted pressure triangle where the resultant pressure is located
at 2/3 of the wall height,or other method approved by a structural engineer.The following resultant
earthquake pressures as a function of the wall height(H)may be utilized:
At-Rest Active
Native Soils 15AH psf 9.8H psf
Engineered Fill Soils 13.6H psf 8.2H psf
See the Earthwork Construction Recommendations Section for details concerning the use of native
soils, engineered fill and placement of backfill.
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 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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. Foundation depth should be increased to at least 2
feet in depth from top of existing grade if the structure is located within existing fill soils
or located where flooding may occur. For a columnar load of no more than 2.5 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 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
5.1.2 Settlement
Total and differential settlement that a structure will undergo depends primarily on the
subsurface conditions, type of structure, amount and duration of pressure exerted by the
structure, reduction of pore water pressure, and in some instances, the infiltration of free
moisture. Based on the expected native soil conditions, anticipated development, and
construction abides by the recommendations in this report,the assumed foundation system
may undergo a maximum of 1.0 inch total settlement, and a maximum differential
settlement of 0.75 inch.
5.1.3 Concrete Slabs-on-Grade
Interior slabs, if utilized, should be supported on a minimum of 4 inches of compacted
coarse, granular material (Retained on U.S. Sieve #10 or greater) that is placed over
undisturbed, competent native subgrade or engineered fill per the Earthwork
Recommendations Section below.
The recommendations for interior concrete slabs-on-grade as presented herein are only
relevant for the geotechnical application of this project. Although beyond the scope of this
report, concrete slabs should also be designed for structural integrity and environmental
reliability. This includes vapor barriers or moisture control for mitigating excessive
moisture in the building.
5.2 Earthwork Construction Recommendations
Founding material for building foundations shall consist of undisturbed native soils to the specified
foundation depths. Compacted engineered fill, or selective re-compacted native soils may be used
to the extents provided in this Earthwork Construction Recommendations Section. The following
recommendations include excavations, subgrade preparation, type of fill, and placement of fill for
building foundations.
5.2.1 Excavation
Excavation is recommended to remove any excessive organic content or other deleterious
material, if present, beneath foundations and to achieve appropriate foundation depth.
Additional sub-excavation will be required for this project if the soils below the required
foundation depth are loose, saturated, not as described in this report, or otherwise
incompetent due to inappropriate land disturbing, or excessive water trapped within
foundation excavations prior to foundation construction. All soils below the bottom of the
excavation shall be competent, and relatively undisturbed or properly compacted fill. If
these soils are disturbed or deemed incompetent, re-compaction of these soils below the
anticipated footing depth is necessary. Excavations shall be completely dewatered,
compacted, and suitable before placement of additional native soil, engineered fill or
structural concrete.
Envirotech Engineering Geotechnical Report
PO Box 984 page 13 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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.
FOOTING
COMPACTED
NATIVE SOILS
OR ENGINEEREDFILL
I 4 UNDISTURBED SUBGRADE'
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 and fill slopes
shall be limited to a slope of 2:1,unless otherwise approved by an engineer.
Envirotech Engineering Geotechnical Report
PO Box 984 page 14 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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'/z 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 orderto 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. See the diagram below for a depiction of fill pads
for structural support.
Envirotech Engineering Geotechnical Report
PO Box 984 page 15 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
5.3 Building and Footing Setbacks
Due to potential debris flow, the building location should have a minimum setback from the local
ascending slope so that debris flow does not affect development if a large landslide occurs.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 50 feet from the toe of the nearby
ascending slope. See the Site Plan in Appendix A 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.
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 runoff controls for development is acceptable per Mason
County standards.
As previously mentioned,foundations located where flooding could occur should be located at least
2 feet below the existing ground surface. In addition to a residence located within a flood zone,
finish floor elevations should be at least I foot above the base flood elevation, and flood venting
should be installed within the foundation stemwalls.
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. 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
Envirotech Engineering Geotechnical Report
PO Box 984 page 16 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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.Erosion control measures during construction may include stockpiling cleared
vegetation, silt fencing, intercepting swales, berms, straw bales, plastic cover or other standard
controls. Although other controls may be used, if adequate, silt fencing is presented in this report
as the first choice for temporary erosion control.Any erosion control should be located down-slope
and beyond the limits of construction and clearing of vegetation where surface water is expected to
flow. If the loss of sediments appears to be greater than expected,or erosion control measures are
not functioning as needed, additional measures must be implemented immediately. See Appendix
D for sketches and general notes regarding selected erosion control measures. The Site Plan in
Appendix A depicts the recommended locations for erosion control facilities to be installed as
necessary.
Permanent erosion control 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 were considered in our geotechnical evaluation. This includes septic drainfields
with relation to the observed soil conditions, expected vegetation removal, and existing and
proposed topography.Based on the aforesaid parameters,the septic 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 with all recommendations provided in this report.
Envirotech Engineering Geotechnical Report
PO Box 984 page 17 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
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
szz
Jessica Smith,M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
Envirotech Engineering Geotechnical Report
PO Box 984 page 18 Parcel 32223-75-00150
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 December 20,2023
APPENDIX A
SITE PLAN
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ffE T rn_ TEXT PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
VERTICAL AND IDRIZIIiTAL SCALE-
SCALE: I INCH 60 FEET
1T•�
EXISTING GRADE� y3�j
PROPOSED HOUSE !�
1271:
SILTY GRAVEL WITH SAND AND COBBLES (GH)
SECTION A-A
PROJECT/ OWNER/ LOCATION-
SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
COLLET
XXX NE KLAHOVYA RD
PARCEL 2223-75-D8150
NOTES MASON COUNTY, WASHINGTON
ENGINEER,
1)MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENVIROTECH ENGINEERING
POSITIVE DRAINAGE PO BOX 994
2)THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF BELFAIR, WASHINGTON 98528
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. 360-275-9374
LOWER DEPTHS ARE BASED @I SITE GEOLOGY,
WELL LOGS%AND/OR EXPERIENCE IN THE GENERAL AREA, SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geological Assessment DATE OF LOG: 07/19/2023
PROJECT NO: 23242 LOGGED BY: MCS
CLIENT: Chris Colley EXCAVATOR: N/A
LOCATION: Parcel 32223-75-00140,-00150,-00160 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
STANDARD PENETRATION TEST
SOIL STRATA,
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
p _. _.. _..._ ... .
GM Reddish brown SILTY GRAVEL with
SAND and COBBLES.
1
2
Cl
4 Excavation terminated at approximately
4.0 feet
5
6
i
7
8
9
10
I
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
interpreted as being indicitive of the entire site.
Map Unit Description:Everett very gravelly sandy loam,15 to 30 percent slopes--Mason
County,Washington
Mason County, Washington
Ek—Everett very gravelly sandy loam, 15 to 30 percent
slopes
Map Unit Setting
National map unit symbol. 2t62c
Elevation: 30 to 900 feet
Mean annual precipitation: 35 to 91 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 180 to 240 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Everett and similar soils:80 percent
Minor components:20 percent
Estimates are based on observations,descriptions,and transacts of
the mapunit.
Description of Everett
Setting
Landform:Eskers,kames,moraines
Landform position(two-dimensional):Backslope
Landform position(three-dimensional):Side slope
Down-slope shape:Convex
Across-slope shape:Convex
Parent material:Sandy and gravelly glacial outwash
Typical profile
Oi-0 to 1 inches: slightly decomposed plant material
A-1 to 3 inches: very gravelly sandy loam
Bw-3 to 24 Inches: very gravelly sandy loam
Cl-24 to 35 inches: very gravelly loamy sand
C2-35 to 60 inches: extremely cobbly coarse sand
Properties and qualities
Slope:15 to 30 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat excessively drained
Capacity of the most limiting layer to transmit water(Ksat):High
(1.98 to 5.95 Whir)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply,0 to 60 inches: Low(about 3.2 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nontrrigated): 4e
Hydrologic Soil Group: A
Ecological site: F002XA004WA-Puget Lowlands Forest
t„o% Natural Resources Web Soil Survey 11/23/2021
e01111111 Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description:Everett very gravelly sandy loam,15 to 30 percent slopes---Mason
County,Washington
Forage suitability group: Droughty Soils(G002XN402WA),
Droughty Soils(G002XS401 WA)
Other vegetative classification: Droughty Soils(G002XN402WA),
Droughty Soils(G002XS401 WA)
Hydric soil rating: No
Minor Components
Alderwood
Percent of map unit:10 percent
Landform:Hills,ridges
Landform position(two-dimensional):Backslope
Landform position(three-dimensional):Nose slope,side slope,talf
Down-slope shape:Convex,linear
Across-slope shape:Convex
Hydric soil rating: No
Indianola
Percent of map unit:10 percent
Landform:Eskers,kames,terraces
Landform position(two-dimensional):Backslope
Landform position(three-dimensional):Side slope
Down-slope shape:Linear
Across-slope shape:Linear
Hydric soil rating: No
Data Source Information
Soil Survey Area: Mason County,Washington
Survey Area Data: Version 17,Aug 31,2021
USDq Natural Resources Web Soil Survey 11/2 312 0 2 1
Conservation Service National Cooperative Soil Survey Page 2 of 2
Map Unit Description:Nuby silt loam,0 to 3 percent slopes—Mason County,Washington
Mason County,Washington
Nf—Nuby silt loam,0 to 3 percent slopes
Map Unit Setting
National map unit symbol. 2hmh
Elevation: 0 to 390 feet
Mean annual precipitation: 70 to 120 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period. 180 to 200 days
Farmland classification: Prime farmland if drained
Map Unit Composition
Nuby and similar soils:100 percent
Estimates are based on observations,descriptions,and transacts of
the mapunit.
Description of Nuby
Setting
landform:Alluvial cones
Parent material.Alluvium
Typical profile
H1-0 to 10 inches: silt loam
H2-10 to 60 inches: silt loam
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Poorly drained
Capacity of the most limiting layer to transmit water
(Ksat):Moderately high to high(0.57 to 1.98 in/hr)
Depth to water table:About 0 to 6 inches
Frequency of flooding:Occasional None
Frequency of ponding:None
Available water supply,0 to 60 inches: High(about 12.0 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonirrigated): 5w
Hydrologic Soil Group: B/D
Ecological site: F004ABO07OR-Aquic Flood Plain Forest
Forage suitability group: Seasonally Wet Soils(G002XN202WA)
Other vegetative classification: Seasonally Wet Soils
(G002XN202WA)
usp-a Natural Resources Web Soil Survey V25I2023
Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description:Nuby silt loam,0 to 3 percent slopes--Mason County,Washington
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County,Washington
Survey Area Data: Version 18,Sep 8,2022
Otir1i Natural Resources Web Soil Survey 1/25/2023
+Nliiiiii Conservation Service National Cooperative Soil Survey Page 2 of 2
WATER WELL REPORT Notice o Intent Na W 163215
h E o'Crje Original&1st copy-Ecology,god copy-owner,3rd copy-driller
Unique Ecology Well ID Tag No. AGE 709
Corgid edorJDeCommtcSion("z"tncircle)
y.i Get Construction Water Right Perrmt No.
L O Deconunisswn ORIGINALCONSTRUC770N Notice
p �$ of Intent Number Property Owner Name Tnnni a Franc
PROPOSED USE: Domestic pal� (� ❑ladustnal ❑Mumci Well Strut Address PIF 490 Kl aFirwrva RA.
❑Dewater ❑Imgabon ❑Test Wcll ❑Other
vny Ta *_.F WA 911 County: Macm
: Owner's
f more
❑N£ Well 0 Reco a tinned number of well(i Method Dugs❑Bored ❑Driven Location 3`l va-va vs sK.?eL Twr R3Of_ 1aLEWM o fe
N ❑Deepened gf Cable ❑Rotary ❑Jetted W W M
��B Lai Deg Lai mwsm
DIMENSIONS: Diameter of well A inches,drilled RO ft (s,l,r suit
C Depth of completed well_�(L ft REQUIRED) Long Deg Long MtNSec
O Taa Parcel No. '4?223-75_O_O_15_0
C CONSTRUCTION DETAILS
— — -
O Casing QWeided 6 Dim hom+1A to 75A CONSTRUCTION OR DECOMMISSION PROCEDURE
+� Installed: Liner installed Dim from ft to ft Forinaboo Describe by color,character,size of material and structure,and the
t4 kind and nature of the material m each suatum penetrated,with at tent one
❑Threaded Dim hum ft to A. carry for each change of mforination Indicate all water encountered
L Perforations: []Yes @ No (USE ADDITIONAL SHEETS IF NECESSARY)
O
7ypc of perforator used MATERIAL - FROM TO
C
SIZE of perfs_m by—in and o0 of perfs from ft to—A
N
Screens:®Yes ❑No m K-Pac Location 73
Manufacturer's Name Naqa ka
` Mode No
O Tra_—etalrtl�,
5 SlotSize Dim3o from�� ft to�_fr Siltyfine brown with
c Dim slot Size-ft--ft lo ft some gravel and water 19 58
fo
Gravel/F5lierpacked: []yes [RNo ❑Stzeofgmvel/sand
ar Materials placed from R to It. Cemerited sand & gravel Wl
t0
0 Surface Seal: Q Ycs ❑No To what depth? 1 A ft water 58
G) Materials used in seal Fk-fnni t-c _
YD,d aay scat contaan uousabic water^ ❑Yes ZI No
,c>', Type of water? Deptb of strata_______.._....__......
C Method of scaling stray off
A
L PUMP: Manufacturers Name r,oyj,c�
L
u Type H P
> WATER LEVELS! Land-surface elevation above mean sea level___ft
N Static level 16 ft below top of well Date
0 Artesian pressure Ilu per square Inch Date
Z Artesian water as controlled by
1ft ca,valve,etc
gW ELL TESTS: Drawdown is amount water level a lowered below static level
"C W as a pump test made+❑yes G No If yes,by whom
>a Yield ¢anoint with _ft drawdown after his
O Yield eallmin with ft drawdowti after hrs
Yield at/nun with ft drawdown after his
0 Recovery data(tuna taken w'zero when pump turned off)(water level ineasured from
ZMD
LlJ well top to water level)
Time Water Level Time Water Level Time Water Level
1 2�0
C —
Date of test p
Baiter test 30 awjm,o with 14R drawdownaftet 1 tars W11ShI I1DD l'LZ
4.1 Air est eat/min with stem set at ft for ties •me t of Ec 400
L.
M Artesian flow - a p in Date
f1 Temperature of watef_Was a chemical analysis madcI[]yes rig No Start Date 1�8f03 Completed Date 1 f10�03
tU
(] Ns-ELL CONSTRUCTION CERTIFICATION: I constructed and/or accept responsibility for construction of tins well,and its compliance with all
y Waslungton well construction standards.Materials used and the information reported above are true to my best knowledge and belief.
'= Driller❑Engineer I-k.,anc _ _ Drilling Company navi a Dri 1 I i n
� Q ❑Trmncc Nartie�`'nt) LSa 8F}:- B P Y g
Driller/En incer/Trainee Signatitrr t a�� _ A-a
B --��—$i T Address 34(�ia—a^si�r9�'�.
Driller or Trainee License No. City,State,Zip Belfairr, Wa 98528
Contractor's
If trainee,licensed driUer's Registration NopAVI SDI 1160A Date;ar+-A3
Signature and License no
Ecology as an Equal Opportunity Employer ECY 050-1-20(Rev IlOI)
APPENDIX C
SLOPE STABILITY
ywo
0 3 �
� j
o � � cr akL � o
o c c _ o 0 0 0 0
m
77,
wq
M,.�
0 tC (4 JC, 'A Ja fi O
0 0 0 0 0 0 0 0 0 O O
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 EQUIVALENT OR BETTER
FILLED WITH 3/4' TO i 1/2'
WASHED GRAVEL OR VEGETATI\N
1i za rT
DIRECTION OF --� EXISTING
WATER FLOW - GROUND SURFACE
2.5 FT
L
SILT FENCE — CROSS SECTION
N.T.S.
2'x2' WOOD POST (TYP) GEOTEXTILE FABRIC
OR EQUIVALENT OR BETTER AND WIRE MESH
@ 6 FT MAX, O.C.
6 rT -( 0.5 FT
EXISTING
GROUND SURFACE
2 T
12' DEEP, 8' WIDE
TRENCH FILLED WITH FT
3/4' TO 1 1/2' '5 FT
WASHED GRAVEL OR VEG TI
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC - SILT FEt,W E - DETAIL
,T,S.
PROVIDE FULL WIDTH
3/4 IN TO 1 1/ N60 FT INGRESS/EGRESS
CRUSHED GRAVELI
PLACED AT 6 IN
MINIMUM DEPTH---
WELL-DRAINED
SOILS
-0.02 IN/MIN F°LL LE',GTH
R=25 FT MIN
rL —
ACCESS ROAD
STABILIZED CONSTRUCTION ENTRANCE
N.T.S.
PERMANENT EROSION CONTROL NOTES-
ENERAL NOTES-
SEEDING FOR RAW SLOPES
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON
HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR L 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,
1.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 STABILIZER OR PERPENDICULAR TO THE SLOPE,
3. SEEDING RECOMMENDATIONS, AS SHOWN BELOW, AND SHOULD BE
EMPORARY EROSION CONTRA NOTES, APPLIED AT THE RATE OF 120 POUNDS PER ACRE
4, SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 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.
MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANI'm OR OTHER APPROVED ARMORING OF THE SEED BED WILL BE NECESSARY, (e.g,,
Rasp CONTROL TREATMENT APPLICABLE TO THE TIME(IF YEAR GRASS SEEDING GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING).
ONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH 6.FERTILIZERS ARE TO BE USED ACCORDWG TO SUPPLIERS'
EPTEMBER. HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF RECOMMENDATIONS.AMOUNTS SHOUD 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.
EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER,MUST BE LIMITED TO
NLY AS MUCH LAND AS CAN RECEIVE APPROPRI4TE PROTECTIVE COVER OR BE PROPORTIONS PURITY GERMINATION
THERVISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , NAME BY WEIGH4TW (X) (X)
Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR.UNLESS IMMEDIATE
'TABILIZATICN 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 (LOLIUH MLLTIFLORUM) 40 98 90
HROUGH THE USE OF MULCNONG, NETTING.PLASTIC SHEETING,EROSION BLANKETS, CHEWING FES(E 40 97 80
REE DRAINING MATERIAL, ETC„ BY SEPTEMBER 30 OR SOONER PER THE APPROVED (FESTUCA RUBRA COMMUTATA)
LAN OF ACTION UNLESS CITHERWISE APPROVED BY THE COUNTY, SEEDING, (JAMESTOWN, BANNER, SHADOW.K'OKET)
ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE WHITE DUTCH CLOVER 30 96 90
ERFORMED DURING THE FOLLOWING PERIODS.MARCH 1 TO MAY 15, AND AUGUST 15 TO (TRIFOLIUM REPENS)
CTOBEk L SEEDING AFTER OCTOBER L WILL BE DONE WHEN PHYSICAL COMPLETION
THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE MULCHING
0 SATISFACTORY GROWTH IN THE EVENT THAT PERANENT STABILIZATION IS NOT
OSSIBLE,AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING,NETTING,L MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
ASTIC SHEETING, EROSION BLANKETS,ETC., MUST BE INSTALLED BY NO HATER THAN FIDER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1000
EPTEMBER X POUNDS PER ACRE
2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES
N THE EVENT THAT C13NSTRLICTIM ACTIVITIES OR OTHER SETE DEVELOPMENT GREATER THAN 2.1 (HORIZONTALVERTICAL).
CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS. THE 3.MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN
WNER/CONTRACTOR SMALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON,ALL
NO SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS,AND AT AREAS REQUIRING MUCH SHALL BE COVERED BY NOVEMBER 1,
AST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR
HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. TOPSOILING
T SEASON(OCTOBER 1 THRU APRIL 30)--ON SITES WHERE UNINTERUPTED 1, TOPSOIL SHOULD BE USED FOR THIS PROJECT DUE TO HIGHLY
INSTRUCTION ACTIVITY IS IN PROGRESS,THE CLEARING OF LAND, INCLUDING THE DENSE EXPOSED SOILS.
EMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SWILL BE LD4ITED 2,TOPSOIL SHOULD BE PLACED ON SLOPES NOT EXCEEDING 2-L
0 AS MUCH LAND AREA AS CAN BE COVERED OR STABIUZED WITHIN 24 HOURS IN g STRIPPING AND STOCKPILING ON-SITE SOILS SHALL ONLY BE
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).
L CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE 4, STRIPPING SHALL BE CONFINED TO THE IMMEDIATE CONSTRUCTION
AREAS, A FOUR TO SIX INCH STRIPPING DEPTH IS COMMON, BUT
OVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING. PLASTIC
NL,ALL
HEETING, EROSION BLANKETS, FREE DRAINING MATERIAL.ETC., WITHIN 5 DAYS AFTER DEPTH MAY VARY DEPENDING ON THE PARTICULAR IN PLACE BEFORE
LAVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED. SURFACE RUNOFF CONTROL STRUCTURES SHALL BE
ILT FENCING. SEDIMENT TRAPS. SEDIMENT PONDS,ETC., WILL NUT BE VIEWED AS STRIPPING.
DEOUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT
LING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY
TABD_IZED 5 DAYS AFTER HAVING BEEN CLEARED,ALL CONSTRUCTION ACTIVITY ON
HE SITE. EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL
HMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN
PPROPRIATELY PROTECTED OR STABILIZED.
STICKPLE MANAGEMENT
L STOCKPILE SHALL BE STABILIZED(WITH PLASTIC COVERING OR OTHER APPROVED DEVICE)DAILY BETWEEN NOVENER 1 AND MARCH
3L
2,IN ANY SEASON,SEDIMENT LEACHING FROM STOCJ(PILES MUST BE PREVENTEI
3,TOPSOIL SHNLL NOT BE PLACED WHOLE IN A FROZEN OR MUDDY CONDITION,WHEN THE SuNGRADE 1S EXCESSIVELY WET,OR WHEN
CD401TIONS EXNST THAT MAY OTHERWISE BE DETRIMENTAL TO PROPER GRADING OR PROPOSED SDDDING IR SEEDING.
4,PREVIOUSLY ESTABLISHED GRADES ON THE AREAS TO BE TOPSOILED SMALL 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 NAY BE
TDP-DRESSED WITH 1 INCH TO 3 INCH ROCK- (STATE STANDARD SPECIFICATIONS. SECTION 8-15.)
THE ROCK PAD SHALL BE AT LEAST 12 INCHES THICK AND 50 FEET LONG(20 FEET FOR SITES WITH LESS THAN 1 ACRE 13F
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 13F 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
GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL
THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS ROLL HE
GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS RL CUT TO T LENGTH OF
H BARRIER TO AVOID USE OL JOINTS.IF JOINTS ARE NECESSARY,FILTER FABRIC SHALL BE SPLICED
ETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT
OTH ENDS TO THE Posr,
STANDARD FILTER FABRIC SHALL BE FASTENED USING V STAPLES OR TIE WIRES (HOG RINGS) Q 4 IN
PAGING,
POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET,AND
IVEN SECURELY INTO THE GROUND.
WERE MESH SHALL BE 2'X2'X14 GAUGE OR EOUIVILENT, THE WIRE MESH MAY BE ELD41NATED IF
XTRA-STRENGTH FILTER FABRIC(0040FILAMENT). AND CLOSER POST SPACING IS USED.
A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE
OSTS AND UPSLOPE FRO(THE SILT FENCE.
SILT FENCES SHALL BE LOCATED DOVNSLOPE FROM THE CLEARING LD4ITS OF THE PROJECT.