HomeMy WebLinkAboutGEO2022-00072 BLD2022-01076 Foundation Pin Piles - BLD Engineering / Geo-tech Reports - 6/9/2022 4ED -Z022-"-'A
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RECEIVED
AUG 15 2022
615 W. Alder Street
Geotechnical Report
Lester Shoreline
481 SE Channel Point Road, Shelton
Parcel No. 32025-51-00008
Mason County, Washington
June 9, 2022
Project#22101
Prepared For:
Mike Lester
PO Box 921
Allyn, WA 98524
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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MASON COUNTY Submittal Checklist
! COMMUNITY SERVICES Geotechnical Report
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Instructions:
This checklist must be submitted with a Geotechnical Report and completed,signed,and stamped by the licensed
professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County
Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclusion.
Note: Unless specifically documented, this report does not provide compliance to the International Residential
Code Sections R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section
1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Mike Lester Parcel# 32025-51-00008
Site Address 481 SE Channel Point 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 37
(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) 15
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 18
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 17
(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) 18
(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) 18
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 19
(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
CLYp,�ST Report,dated June 9,2022 and entitled Lester Shoreline,
`L0 of WAS I meets all the requirements of the Mason County Resource
Ordinance,Geologically Hazardous Areas Section,is complete
and true,that the assessment demonstrates conclusively that
�Fc s0E55 a`� the risks posed by the landslide hazard can be mitigated
Ess�oNALE through the included geotechnical design recommendations,
6/9/2022 and that all hazards are mitigated in such a manner as to
Disclaimer.Mason County does not prevent harm to property and public health and safety.
certify the quality of the work done in
this Geotechnical Report. Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................................................................................1
1.1 PROJECT INFORMATION.................................................................................................................... 1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK........................................................................ 1
2.0 SURFACE CONDITIONS....................................................................................................................3
2.1 GENERAL OBSERVATIONS..................................................................................................................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 INVF,STIGATION.....................................................................................................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............................................................................................................................................10
4.2.1 Shoreline Recession..................................................................................................................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-SrrE IMPACTS.....................................................................................................12
5.1 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................13
5.1.1 Bearing Capacity.........................................................................Error!Bookmark not defined.
5.1.2 Settlement....................................................................................Error!Bookmark not defined
5.1.3 Concrete Slabs-on-Grade............................................................Error!Bookmark not defined.
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 Backfd]............................................................................................................15
5.2.4 Wet Weather Considerations....................................................................................................15
5.2.5 Building Pads............................................................................................................................15
5.3 BUILDING AND FOOTING SETBACKS.................................................................................................15
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
Appendix E—Drainage Details
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a recent
landslide of the shoreline bluff near the existing single family residence located at 481 SE
Channel Point Road, identified as parcel number 32025-51-00008, Mason County, Washington.
See the vicinity map on the following page for a general depiction of the site location.
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 constriction, retaining walls, erosion control, drainage, and
vegetation in the Engineering Recommendations Section.
1.1 Project Information
The planned development consists of extending the foundation of the existing single family
residence. 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/ 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,
Envirotech Engineering Geotechnical Report
PO Box 984 page 1 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
drainage, slope stability,erosion control, earthwork construction requirements, and other
considerations.
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Envirotech Engineering Geotechnical Report
PO Box 984 page 2 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on May 19,
2022 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 fully developed with an existing single family residence, septic system,
driveway and other ancillary features. Vegetation on and near the project consists primarily of
secondary growth firs, maples and other trees and shrubbery common to this area of the Pacific
Northwest. An aerial photo of the project and immediate vicinity is provided on the following
page.
2.2 Topography
The topographic information provided in this section was extrapolated from a public lidar source,
and incorporated observations and field measurements. Where necessary, slope verification
included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site
Plan in Appendix A in this report for an illustration of general topography with respect to the
planned development.
Critical descending slopes, with grades exceeding 40% are within 300 feet of the planned
development. The maximum critical slope is vertical, and averages approximately 105% with a
vertical relief of about 45 feet. Ascending grades are generally located to the southwest 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 away from the property by
accommodating topography. Excessive scour, erosion or other indications of past drainage
problems were not observed within the immediate vicinity of the planned development.
2.3.1 Upslope Water Bodies
There are no apparent water bodies or wetlands located upslope from the planned
development that would significantly influence the project.
Envirotech Engineering Geotechnical Report
PO Box 984 page 3 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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.
The shoreline bank has recently experienced a bluff peel-off landslide, and the top of the bank is
now only 8 feet from the home. A tension crack was observed approximately 2 feet from the
home.In addition,cavities were observed near the bluff toe.
1 I
0 120 Feet
Aerial Photo from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 4 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on May 19,
2022 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 20 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.
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 Squaxin Island 7.5 Minute Quadrangle,Mason and Thurston Counties,
Washington by Robert Logan et al.,2003,"provides the following caption(s)for the project area:
Q9* Pleistocene tlttsorted,wsbratitie0(but Wary bar4e0)a*of day,
0.sand.and pravd;tY KAY%*Wed M a sandy
matrix; mostly gray but ranging to tan,tght
brown,or orange;typicatty unweathered; lodgment till
compact
Envirotech Engineering Geotechnical Report
PO Box 984 page 5 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
wtr Project
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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
System(USCS)and the Soil Conservation Service(SCS)descriptions.
The project is currently composed of native soils with indications of fill.Within test pit locations,
soils within the upper 10-20 feet of natural ground were generally observed to be moist,brown
silty sand with gravel(SM). Soils below the upper 20 feet layer were observed to be mostly, low
moisture, silty sand with gravel(SM),locally known as hardpan. Pockets of grey/blue clayey silt
with fine sand were also observed. 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 Cloquallum silt loam, C.,
with 5% to 15% 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 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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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 30 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 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
4.0 ENGINEERING ANALYSES AND CONCLUSIONS
The following section includes slope stability, erosion, seismic considerations, and impacts to
both on-site and off-site properties.
4.1 Slope Stability
Landslides are natural geologic processes, and structures near slopes possess an inherent risk of
adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering
cannot eliminate these risks for any site with sloping grades because gravity is constantly
inducing strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will
exacerbate these strains. Geotechnical engineering considers excessive wet weather and `design'
earthquakes in order to provide an acceptable factor of safety for developing on or near sloping
terrain with relation to current engineering protocol. These factors of safeties are based on
engineering standards such as defining engineering properties of the soil, topography, water
conditions, seismic acceleration and surcharges. Surface sloughing or other types of surficial
slope movements usually do not affect the deep-seated structural capability of the slope.
However, repeated surficial slope movements, if not repaired, may present a threat to the
structural integrity of the slope.N 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. Descriptions of
these mapping units may be found in the aforesaid Atlas. A Stability Map from the Coastal Zone
Atlas for the general area of this project is provided below:
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Slope Stability
Intermediate slope
Stable slope
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Unstable slope
Map from Department of Ecology
Envirotech Engineering Geotechnical Report
PO Box 984 page 8 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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:
Project
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Highly Erodible Soils
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Resource Map from Washington State Department of Natural Resources Website
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:
Upper 20 feet soil depth
Soil unit weight: 132 pcf
Angle of internal friction: 30 degrees
Cohesion: 200 psf
Envirotech Engineering Geotechnical Report
PO Box 984 page 9 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
Soils below 20 feet in depth
Soil unit weight: 140 pcf
Angle of internal friction: 40 degrees
Cohesion: 400 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 by deepening the foundation. 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
Western Washington," prepared by the Washington State Department of Ecology Water Quality
Program.
4.2.1 Shoreline Recession
Due to the close proximity of a shoreline,an evaluation of the shoreline recession rate for
this project was completed. This was accomplished by interviewing property owners
within the vicinity of the project, and/ or carefully reviewing and comparing historical
aerial photographs of the project. Historical aerial photograph sources may be found in
the 1951 aerial for the Soil Survey of Mason County, aerials from the Washington State
Department of Ecology,and from the Washington State Department of Natural Resources
Envirotech Engineering Geotechnical Report
PO Box 984 page 10 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
website.Based on available information, we conclude that the past shoreline recession for
this project is less than 10 feet in 50 years.
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 Olympia Structure, which is approximately 2 miles to the south west 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
Due to the recent landslide and bluff erosion that is threatening the existing home,it is urgent that
mitigation is completed prior to the next wet season. It is our opinion that deepening the
foundation on the home nearest the slope in conjunction with modest armoring of the bluff toe
will provide an additional 75-year design life and safety for the home.Complete hard armoring of
the bluff toe,if completed before additional toe erosion occurs,will provide an adequate factor of
safety of the home for perpetuity as long as the armoring is maintained. However, based on
regulations, Washington State Fish & Wildlife are not apt to accept armoring of the bank. This
report focuses on temporary support for the home by use of pin piles.
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,
Envirotech Engineering Geotechnical Report
PO Box 984 page 11 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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
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 15AH2 psf 9.8H2 psf
Engineered Fill Soils 13.6112 psf 8.2H2 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 12 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
. 4
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
For schedule 80 steel, 2-inch vertical pipe piles driven to the specifications below, shall
have a pile capacity of no more than 2 tons. For battered piles, also driven to the
specifications below, shall have an inclination between 10 degrees and 30 degrees with
respect to the vertical plane. Minipiles, 2 inches in diameter, shall be driven with a 90
pound minimum pnuematic hammer, and terminate at or below a minimum embedment
depth when refusal is achieved. Refusal for the 2-inch pile is defined as less than 1 inch
of penetration for 60 seconds of continuous pile driving.
Based on our limited subsurface investigation and known geology of the area, each
vertical pile will have an expected embedment depth ranging from 15 feet to 25 feet.
Since geotechnical drilling has not been done on this property, these depths are an
estimate.There is always a possibility that pile refusal depth is deeper.
Non-galvanized piles may be used for this project.Couplings may be used for connecting
pipe sections.However,the succeeding pipe ends should be butted together.Each pin pile
should be a minimum of 2 inches diameter; installed within the footing excavation prior
to placing concrete; and, structurally tie into the footings with steel reinforcement. The
number of piles,material, spacing, and connections should be determined by a structural
engineer.
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
Envirotech Engineering Geotechnical Report
PO Box 984 page 13 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
foundation depth are loose, saturated, not as described in this report, or otherwise
incompetent due to inappropriate land disturbing, or excessive water trapped within
foundation excavations prior to foundation construction.All soils below the bottom of the
excavation shall be competent, and relatively undisturbed or properly compacted fill. If
these soils are disturbed or deemed incompetent, re-compaction of these soils below the
anticipated footing depth is necessary. Excavations shall be completely dewatered,
compacted, and suitable before placement of additional native soil, engineered fill or
structural concrete.
5.2.2 Placement and Compaction of Native Soils and Engineered Fill
For engineered fill or disturbed native soils that will be utilized as fill material directly
beneath foundations, observation and/ or geotechnical testing is required prior to
foundation construction. The following placement and compaction requirements are
necessary.
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 ENGINEERED t
FILL
1
I I UNDISTURBED SUBGRA)lE
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
Envirotech Engineering Geotechnical Report
PO Box 984 page 14 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
optimum moisture content. Each lift surface should be adequately maintained during
construction in order to achieve acceptable compaction and inter-lift bonding.
Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be
limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined
excavations exceeding 4 feet should conform to OSHA safety regulations. Permanent cut
and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an
engineer.
5.2.3 Retaining Wall Backfill
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 V2 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.
5.2A Wet Weather Considerations
Due to the types of subsurface soils, additional provisions may be required during
prolonged wet weather. Every precaution should be made in order to prevent free
moisture from saturating the soils within excavations. If the bottom of excavations used
for footing placement changes from a moist and dense/hard characteristic as presented in
this report to muck or soft, saturated conditions, then these soils become unsuitable for
foundation bearing material. If this situation occurs, a geotechnical engineer should be
notified, and these soils should be completely removed and replaced with compacted
engineered fill or suitable native material as presented in this section.
5.2.5 Building Pads
Building pads for this project, consisting of built up fill, shall be avoided unless designed
by an engineer.
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 15 feet footing
Envirotech Engineering Geotechnical Report
PO Box 984 page 15 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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.
STRUCTURE
TOP OF
SLOPE SLOPE
FACE _
I I—I 1 11 E-I 1
�— SETBACK —� FOOTING
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. We estimate that a foundation
depth of 9.5 feet is applicable for the portion of the home nearest the bluff.
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 infiltration is avoided in order to maintain slope stability,
and that roof downspout runoff is tightlined to beyond the toe of slope. Recommended 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 the
prevailing agency thresholds are exceeded, and basic vegetation management practices should be
adhered to.
Vegetation Buffer—Vegetation shall not be removed from the face of the critical slope or within
a distance of 10 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
Envirotech Engineering Geotechnical Report
PO Box 984 page 16 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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. 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 fast 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 necessary for
this project.We recommend deeper foundations and bluff toe armoring as presented in this report.
However,a temporary solution of using pin piles will be done at this time.
Envirotech Engineering Geotechnical Report
PO Box 984 page 17 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
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
, . j� 14_1*� SZI-
Jessica Smith,M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
Envirotech Engineering Geotechnical Report
PO Box 984 page 18 Parcel 32025-51-00008
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 June 9,2022
APPENDIX A
SITE PLAN
SCALE- I INCH = 60 FEET
0I5��0
HAMMERSLEY INLET
_ A
APPROXIMATE TOP OF APPROXIMATE TOE OF
CRITICAL SLOPE EXCEEDING CRITICAL SLOPE EXCEEDING
40% ,y 40%
25 FT C❑NSTRUCTION
SETBACK FROM TOP OF
CRITICAL SLOPE
10
20
30
EXISTING SINGLE FAMILY 10 FT VEGETATION REMOVAL
BUFFER FROM TOP OF
RESIDENCE A�? CRITICAL SLOPE
EXISTING DRIVEWAY
A PROPERTY LINE
SE CHANNEL(POINT RD
n
NOTES PROJECT/ OWNER/ LOCATION,
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. LESTER
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE,AND 481 SE CHANNEL POINT RD
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED 1N THE GEOTECHNICAL LEGEND PARCEL 0:
REPORT. MASON COUNTY, WASHINGTON
3. BOUNDARIES VERE NOT PREPARED BY A LICENSED SURVEYOR.LOCATIONS TEMPONARY ENGINEER.
[IF SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP(IF SLOPES, TOE -�- +ERUSII3N 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 360-275-9374
RELATION TO GEOLOGIC FEATURES,NO OL T PROPERTY LINES. THESE GEOGIC 80' EXISTING CONTOUR
FEATURES NAY BE LOCATED ON THE SUBJECT PROPERTY NEIGHBORING TP1 TEST PIT SITE PLAN
PROPERTIES.
APPENDIX B
SOIL INFORMATION
•O"tt uU IQ�7pTaL t"lL
C—TS��1
EXISTING HOUSE
EXISTING GRACE
Aglx��x
MEDIUM DENSE SILTY SAND WITH CIRAVEL(SM)
3
HAMPERSLEY INLET
DENSE GLACIAL TILL
moAXti Dono/L00011-
SD4CALE FAMILY RESIDENCE
GEOTECN41CAL REPQRT
LE3TDI
W u OMM[L r ars
rwrra .
W1tfK;pyMT,V.a6gtRRfla
.oTEn
OiLOa�l
u 10AX WOE CIW✓E%icxolEo a OVID •o baati£ QYL*fIRd100¢ez.�
r,TOTE t Wt 1t AM"TE Mit T.[ IVTH Or KLVAM.V DC47M ssaa7i
THE OisEPviD TE%T nTt+T THE VVrVKI L.D:ATTOrt. .t7y+fi7.
Lavo IV7W ARE WET,Eh %(TE WCL0%v.
.nL►n:AV, MO.W r.MrtNs a The CANeeAL#A'" S01L PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-4
PROJECT: SFR Geokxpeal Assessment DATE OF LOG: 0511901M
PROJECT NO: 22101 LOGGED BY: MCS
CLIENT: Lester EXCAVATOR WA
LOCATION: Parcel 32025-51-00008 DRILL RIG: None
Mason County,Washington ELEVATION: WA
INITIAL DEPTH OF WATER: WA FINAL DEPTH OF WATER: WA
DEPTH SOIL STRATA, SrntnutoINENErnATONn:sr
SAMPLERS t1SCS DESCRPTION LL PI DEPTH N CURVE
AND TEST DATA 10 30 50
B ....... ..........................................
SM Bium.mast SILTY SAND with Ravd.
medium dense Gravel is wieggraded
and subrounded.Sand is medun and
Z ooarse.Nan-plastic.
Dense.brown and gray,trace of gravel
4
Some gravel.very low moisture.
naeasng density wrth depth
-10
B
s
i'
12
K
10
18
LVM brown.bw morsture,very dense
1wdp-*
-20 Ezcavabon termnated at appro"nately
20.D feet
Noonm,d1 a6w Emoundmad ENVIROTECH ENGINEERING
lm-- - +,e?i- Geatechnocal Engr'eenng
Hil-aelIasoavillu +rGrowewesee
Uap Urd Description CIOWA n as Wn 5 b 15 peroa+s cour)•
Wasrtn4�n
Mason County, Washington
CC—Cloquailwn sift loafn,5 to 15 percent slopes
Map unit seltieq
Natiaal reap rid sp rmW 2hfh
&evafon 0 to 4W feet
Mean arruW pneciod3bon_ 50 to 75 itches
A1ean anraaal air Mnperahse: 50 degrees F
Front-bee pe►Wa 175 to 205 days
Farrriad clasmilicabow Famdand of statewide importance
rap thtit Conlposilion
Cbghulkrm and sinia salt: 100 percent
C-shawles are baxA on obaervebons,descriptions,and trantectt of
me mapunit
Description of Cioqualfum
setting
Parent material Silty iaarstnine deposes with volcanic ash
Typical profile
fff-0 to 9 inches sit barn
IV-9 io 32 indwz silt barn
tf3-32 to 60 riches silty day loam
Properties and qualities
Stile: 5 to 15 percent
DqO to retbidive feature_ More than 90 xw hes
NahM drainage lass Modvalely well draned
Capacity of the mad inhaling layer to bro—nd water(Ksat):
Moderately low to moderalely high(0.00 b 0.20 inRtr)
Deplb to water table: About 24 lo 36 inches
FrequencyoflbodiW None
Fre"encyofpordirg_ No
Available water storage in profile: ligh(about 11.3 inches)
Interpretive groups
Land capabidy dasaria bon Irrigated): None speafied
Lad capability dassilkafforh fnoninigatec9 3e
blycimiogic Sod Group: C
Forage tedabiiy group: Soils with Moderate Limitations
(G002XN902WA)
hyriic sod rating No
Data Source Information
Soil Survey Area Mason County.Washington
Survey Area Data Version 15.Sep 16.2019
i-4.. "Aft"Resources Vat Gill Hovey 1123=9
kill conowntion 1"ce Nnanat cooperave^W wrvel Page 1 of t
WATrR WELL IMPORT CTIRREKT
23
❑nczommin.tv i ORIGINAL INVAJA TIAN
P
X- Immi'vivebtf mpvtty U 40w Name ratagsanNaJ —
13 #W6�,; O llft-itV WCUSr.rvto Ail ; 4U.ki'A _6tXh*wwI Read
:3 It jitA:,,s CL�-*exwm. 13 cA-c Ci-.y-She — (r.uw.y Mmen
%%Iuwx: 4CIISS ("*a,an_ !E1:4.1.4 NC1.'•l ]CC(it Twi'ON K39 sm"13
%_,t D %&.:Aw:n ff�kvj. M_t;
t: t3 pwa 4 s,t,r Stm RI:QLJUiD) U,
r5
DAYLORE J.x L MA Lalm;'Vqcc I-STS
e..-C 0 WtAA am t-^:!�LIC 16li it TAngCkgj7_g f.migMin-'act;
�0 1 :1=311:4 ISM."a J'6x Pared No.(jI"uimd2D255.1CO!Ah
Tt..,w
0 V-S K
KI 44
%7,&JAI .0
12 17
0 -&Lwsit
S.Swab PW.-'c,a. ft—ft. stow on
76—H.
uk.0 v4s C,"s day 20"9111wrl
V::)l .sEd.—Orari 38L
13
G V.
65
SAA e! a4
KnvArI Fwe so,,.SM ill
I.rr4 IIL -6--wa -124
ID 13i,
sn't CW T74 L
-- ---- '!
SMy madkon io ces'se 76--
wd Sant uf*YIL
rM
Gray e.itlCl_*137 176'
C3 Y'f
Y.*A 4...-cl AN—2-
y tw &',A"aw -
raft.,).Jr." S.'.4
time vft— 'I" hr-1- 1- w.Z.I.twi ., A
IWA-5 Me UL' al
l
,
N"Tjb mx and dwiaffi."i0r.FlIvatc atr':L*re rug tr.M,1-03,9=19"IME--jil-14,
jrjh R� _ .4,W_djS DrM .jWk
-�Sffi" -w I
Air Mm"
*rt
APPENDIX C
SLOPE STABILITY
1 _ 00
1 _ 10
1 _ 20
1 _ 30
1 _ 40
1 _ so
1 _ 60
a. _ 70
i _ 8o
1 _ 90
_ 00
pro�sct I.esesr Report
Datafil� Dynamic Araaly�ia
Azaalyaia Bishop
i TrFtK-J YYI Ni M�«ul6�w 6aJ
3 _ 0 0
3 _ 2 O
3 _ 3 O
L _ 40
3 _ 50
3 _ 450
3 _ 70
3 _ so
1 _ 9 O
_ O 6
g 1 c
Araa.lyai.3 _ Si�l-aop
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 1 1/2'
WASHED GRAVEL OR VEGETAT N
2s rT
DIRECTION OF EXISTING
WATER FLOW GROUND SURFACE
�� zs rr
ir
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. I
6 R --+I F 0.5 rt
EXISTING
GROUND SURFACE
z
12' DEEP, 8' WIDE
TRENCH FILLED WITH ''T
3/4' TO 1 1/2' Fr
WASHED GRAVEL OR VEG TI
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - DETAIL
N.T.S.
PROVIDE FULL WIDTH
3/4 IN TO 1 1/ N60 R INGRESS/EGRESS
CRUSHED GRAVEL
PLACED AT 6 IN
MINIMUM DEPTH
WELL-DRAINED
SOILS
-0.02 IN/MIN LENM
R=25 FT MIN
(L
ACCESS ROAD
STABILIZED CONSTRUCTION ENTRANCE CONSTRUCTION ENTRANCE
N.T.S.
PERMANENT EROSION CONTROL NOTES,
ENERAI NOTES,
SEEDING FOR RAW SLOPES
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON
HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION,THE COTTRACTOR 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.
ALL CR13SI13N AND SEDIMENT CONTROL FACRITIES AND DEVICES SHALL LE 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
MPORARY EROSION CONTROL NOTES. APPLIED AT THE RATE OF 120 POUNDS PER ACRE
4. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL
R ALL AREAS WHICH HAVE BEEN STRIPPED [F VEGETATION OR EXPERIENCED LAND REQUIRE IRRIGATION AND OTTER MAINTENANCE AS NECESSARY TO
ISTURBING ACTIVITIES, AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A FOSTER AND PROTECT THE ROOT STRUCTURE
RIOD 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 PLANTING OR OTHER APPROVED ARMORING(F THE SEED RED WILL BE NECESSARY, (e.0.,
ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF 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 ACCORDING TU SUPPLIERS'
EPTEMBER. HOWEVER. SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF RECOMMENDATIONS.AMOUNTS SHOULD BE MINIMIZED,ESPECIALLY
OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING ADJACENT TO WATER BODIES AND WETLANDS.
R OTHER APPROVED TREATMENT,
USE THE F[LL13WING RECOMMENDED SEED MIXTURE FOR EROSION
RY SEASON (MAY 1 THRU SEPTEMBER 30)-- THE CLEARING(IF LAND. INCLUDING THE CONTROL,OR A COUNTY APPROVED ALTERNATE SEED MIXTURE.
MOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO
NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE PROPORTIONS PURITY GERMINA
THERWISE STABILIZED,AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , NAME BY WEIGHTW W W
Y NO LATER THAN SEPTEMBER 30[F A GIVEN YEAR.UNLESS IMMEDIATE
TABDIZATI N IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL REDTOP (AGROSTIS ALBA) 10 92 90
AS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ANNUAL RYE (LOLIUM MLLTTFLIRUM) 40 98 90
ROUGH 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)
AN IF ACTION, UNLESS QTHERWISE APPROVED BY THE COUNTY, SEEDING, (JAMESTOWN, BANNER, SWAIIM,KOKET)
RTILIZING AND MULCHING [F CLEARED OR OTHERWISE DISTURBED AREAS SHALL. BE WHITE DUTCH CLOVER 10 96 90
RFORMED DURING THE FALLOWING PERIODS.MARCH 1 TO MAY 15, AND AUGUST 15 TO (TRIFOL,IUM REPENS)
CTOBER L SEEDING AFTER OCTOBER 1 WELL BE DONE WHEN PHYSICAL COMPLETION
THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE MULCHING
SATISFACTORY GROWTH IN THE EVENT THAT PERANENT STABILIZATION IS NOT
SSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTDNG,L MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
ASTIC SHEETING, EROSION BLANKETS,ETC., MUST BE INSTALLED BY NO LATER THAN FIBER CELLULOSE, AND SHOULD BE APPLIED AT A RATE OF 1D00
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 2.1 (ORIZONTAL,VERTICAL).
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
ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER L
AST ONCE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR
HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. TOPSODING
ET SEASON (OCTOBER 1 THRU APRIL 30)—ON SITES WHERE UNINTERUPTED L T13PSUIL SHOULD BE USED FOR THIS PROJECT DUE TO HIGHLY
INSTRUCTION ACTIVITY IS IN PROGRESS,THE CLEARING OF LAND, INCLUDING THE DENSE EXPOSED SOILS.
EMIVOL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED 2. TOPSOIL SHOULD BE PLACED IN SLOPES NOT EXCEEDING al.
D AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 3, STRIPPING AND STOCKPILING 13N-SITE SOILS SHALL ONLY BE
EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT PERMITTED 7 TEPSML IS FRIABLE AND LOAMY (LOAM, SANDY LOAM,
RANSPORT OFF-SITE IS OBSERVED, SAT LOAM, SANDY CLAY LOAM, CLAY LOAM),
L CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE 4, STRIPPING SHALL BE CONFINED TD THE IMMEDIATE CONSTRUCTION
OVER OR OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC DEPTHAREAS. A FOUR TO SIX INCH STRIPPING DEPTH IS COMMON, BUT
DING, EROSION BLANKETS, FREE DRAINING MATERIAL,ETC., WITHIN 5 DAYS AFTER SURFACE MAY VARY DEPENDING ON THE S SHALL
SOIL ALL
AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED, SURFACE RUNOFF CONTR(L STRUCTURES SHALL BE IN PLACE BEFORE
STRIPPING.
ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS,ETC, WILL NOT BE VIEWED AS
DEQUATE COVER IN AND OF THEMSELVES,IN THE EVENT THAT ANY LAND AREA NOT
NG ACTIVELY W13RKCD 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
PR13PRIATELY PROTECTED OR STABILIZED.
STOCKPILE MANAGEMENT
STOCKPILE SHALL BC STABILIZED(WITH PLASTIC COVERING OR OTHER APPROVED DEVICE)DAILY BETWEEN NDVEMBER 1 AND MARCH
3L
2,IN MY SEASON,SEDIMENT LEACHING FROM STOCK PILES MUST BE PREVENTED.
3.TOPSOIL SHALL NOT BE PLACED WHOLE IN A FROZEN OR MUDDY CONDITION,WHEN THE SUBGRADE IS EXCESSIVELY WET,lA WHEN
CONDITIONS EXIST THAT MAY OTHERWISE BE DETRIMENTAL TO PROPER GRADING OR PROPOSED SODDING OR SEEDIN4
4,PREVIOUSLY ESTABLISHED GRADES ON THE AREAS TO BE TOPSOLED SHALL BE MAINTAINED ACCORDING TO THE APPROVED PLANS,
STABILIZED CONSTRUCTION ENTRANCE
L MATERIAL SMALL 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 TD 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 1 ACRE OF
DISTURBED SOIL), WIDTH S14ALL BE FULL WIDTH OF THE VEHICLE INGRESS AND EGRESS AREA.SMALLER PADS MAY BE APPROVED
FIR SINGLE-FAMILY RESIDENTIAL AND SWILL 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 OF BEFORE
THE VEHICLE ENTERS A PAVED STREET.THE WASHING SHALL BE DOE ON AN AREA COVERED WITH CRUSHED ROCK AND WASH
WATER SHALL DRAIN TO A SEDIMENT RETENTION FACILITY OR THROUGH A SILT FENCE
IL
FENCE
GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE'STTRMWATER MANAGEMENT MANUAL
THE PUGET SOUND BASIN,' IR APPLICABLE COUNTY STANDARDS
.GEDTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH 13F
H BARRIER TO AVOID USE [F JOINTS.IF .JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED
OGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT
OTH ENDS TO THE POST,
. STANDARD FILTER FABRIC SHALL BE FASTENED USING V STAPLES OR TIE WIRES (HOG RINGS) E 4 IN
PACING,
POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET,AND
RIVEN SECURELY INTO THE GROUND,
WIRE MESH SHALL BE 2*X2'X14 GAUGE OR EQUIVILENT, THE WIRE MESH MAY BE ELIMINATED IF
TRA-STRENGTH FILTER FABRIC (MONG AMENT),AND CLOSER POST SPACING IS USED.
A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE ff THE
13STS AND UPSLOPE FROM THE SILT FENCE
SILT FENCES SHALL BE LOCATED DOWNSLDPE FROM THE CLEARING LDHITS OF THE PROJECT.
APPENDIX E
DRAINAGE DETAILS
HOUSE
DRAIN,SEE
ROOF DOWNSPOUT
CONNECTION
DETAIL SOLID
LID GROUND
SURFACE
2% MIN
2X MIN
4' DI-6 MIN
SOLID PVC FINE MESH SCUD PIPE
SCREEN PER PLAN
12'CATCH BASIN ANCHOR
'YARD DRAIN) EXPOSED PIPE
PER TIGHTLI
DETAILS T
O
ROOF DRAINAGE DETAILS dlr F
N.T.S.
STEEL CLAMPS 'TYP)
CORRUGATED TIGHTLIFJE 10 R MIN SPACING 1/2 INCH DIAMETER
6-INCH MIN.DIAMETER SECURELY FASTENED TO PIPE
LEVEL SECTION
3FT DIFFUSER TEE
TWO 6-FOOT
ANCHORS CTYP), NOTES-
#4 REBAR OR 1.IT IS STRONGLY SUGGESTED TO
EQUIVALENT 3 R MDI UTILIZE A HEAT WELDED HIGH DENSITY
POLYETHYLENE CHDPE)PIPE IN LIEU OF
CORRUGATED PLASTIC PIPE
2. IF PLASTIC PIPE IS USED,FREQUENT
INSPECTION (BI-ANNUALY),AND
NECESSARY MAINTENANCE IS REQUIRED.
TIGFITLINE DETAILS 3, MILE DIAMETER SHALL BE 1 INCH FOR
N.T.S. 6-INCH TEES, AND 2 INCHES FOR 12-INCH
TEES,
4. HOLE SPACING SHALL BE EQUAL TO
'1.5 X HOLE DIAMETER).
5. DIAMETER ff TEE SHALL EQUAL
DIAMETER OF TIGHTLINE PIPE
�O
IFT
HOLES OPPOSITE
PIPE
➢RILL HOLES° IN FRONT HALF
oo°0OF TEE ONLY
'4) 6' 04 REBARS
SCREW CAP OR DENT OVER TEE AS
BOLTED FLANGE, SHOWN.ALTERNATE
EACH END ANCHORING BETWEEN
FRONT AND BACK OF
TEE
DEFFUSER TEE DETAILS
N.T.S.
ENGINEER
ENVIROTECH ENGINEERING
PO BOX 984
BELFAIR, WASHINGTON 98528
360-275-9374
DRAINAGE DETAILS