HomeMy WebLinkAboutGeoTech Report Residential Addition and Detached Garage - BLD Engineering / Geo-tech Reports - 11/26/2014 Geotechnical Report
Residential Addition and Detached Garage
40 and 50 Washington Ct, Union
Parcel No. 32234-51-00024 & -00025
Mason County, Washington
November 26, 2014
Project#14133
Prepared For:
Brian Hilgendorf
Lindsay Andreotti
PO Box 539
Union, Washington 98597
I
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.
ApplicanVOwner Brian Hilgendorf Parcel# 32234--51-00024&-00025
Site Address 40 and 50 Washington Court, Union
(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) 4
(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) 11 Page 1 of 37
(7) (a) Appropriate restrictions on placement of drainage features,
Located on page(s) 19
(b) Appropriate restrictions on placement of septic drain fields,
Located on page(s) 20
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 15 and 17
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 19
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 18
(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) 19
(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) 12
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) 14
(11) Specifications of final development conditions such as,vegetative management,drainage,erosion control, and
buffer widths.
Located on page(s) 18-20
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 20
(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
PEti C YDE Sr Report,dated November 26,2014,and entitled Residential
Its '�� Addition and Detached Garage, meets all the requirements
of the Mason County Resource Ordinance,Geologically
Hazardous Areas Section, is complete and true,that the
�+ 43045 a assessment demonstrates conclusively that the risks posed by
0i1 FC/STERN X.
�SS�ovntEaC'� ll/26 14 the landslide hazard can be mitigated through the included
/
geotechnical design recommendations,and that all hazards
Disclaimer:Mason County does not are mitigated in such a manner as to prevent harm to property
certify the quality of the work done in and public health and safety.
this Geotechnical Report.
Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION................................................................................................................................. 1
1.1 PROJECT INFORMATION...................................................................................................... ....
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................................................................................................................4
2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4
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......................................................................S
4.1 SLOPE STABELrrY...............................................................................................................................8
4.1.1 Slope Stability Analysis.............................................................................................................11
4.2 EROSION............................................................................................................................................12
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION..............................................................................13
4.3.1 Liquefaction..............................................................................................................................13
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS........................................................13
4.5 LATERAL EARTH PRESSURES...........................................................................................................13
4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................14
5.0 ENGINEERING RECOMMENDATIONS.»...»...»..—..»...»..........................................................15
5.1 BUILDING FOUNDATION RECOMMENDATIONS.................................................................................15
5.1.1 Bearing Capacity.......................................................................................................................15
5.1.2 Settlement..................................................................................................................................16
5.1.3 Concrete Slabs-on-Grade..........................................................................................................16
5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................16
5.2.1 Excavation.................................................................................................................................16
5.2.2 Placement and Compaction of Native Soils and Engineered Fill...........................................17
5.2.3 Retaining Wall Backfill.............................................................................................................18
5.2.4 Wet Weather Considerations....................................................................................................18
5.3 BUILDING AND FOOTING SETBACKS.................................................................................................18
5A SURFACE AND SUBSURFACE DRAINAGE................................ .............. ....................19
.... .....................
5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................19
5.6 TEMPORARY AND PERMANENT EROSION CONTROL.......................................................................20
5.7 SEPTIC DRAINFIELDS........................................................................................................................20
5.8 STRUCTURAL MITIGATION...............................................................................................................20
6.0 CLOSURE......».......»........»...»...».......»........»........»............»..».........»..»...».......»...........................21
Appendix A-Site Plan
Appendix B -Soil Information
Appendix C-Slope Stability
Appendix D—Erosion Control
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a home
addition and detached garage located at 40 & 50 E Mt. Washington Ct, identified as parcels
numbered 32234 510024&25, Union, Mason County,Washington. See the vicinity map on the
following page for a general depiction of the site location.
The geotechnical investigation was conducted at the request of the proponent of the property,
Brian Hilgendorf, in support of the proposed development as detailed below. The proposed
development,as provided herein,and the surrounding area that may influence the development,is
identified throughout this report as the Project.
An initial geotechnical evaluation of the Project was conducted by Envirotech on October 24,
2014. It was determined that slopes in excess of 40% with a vertical relief of at least 10 feet were
present within 300 feet of the planned development. Based on this site characteristic, the
proposed development will require a geotechnical report pursuant to Landslide Hazard Areas of
Mason County Resource Ordinance (MCRO) 17.01.100. During the site visit by Envirotech,
surface and subsurface conditions were assessed. After completion of the field work and
applicable Project research, Envirotech prepared this geotechnical report which, at a minimum,
conforms to the applicable MCRO.
As presented herein, this report includes information pertaining to the Project in this Introduction
Section; observations of the property and surrounding terrain in the Surface Conditions Section;
field methods and soil descriptions in the Subsurface Investigation Section; supporting
documentation with relation to slope stability, erosion, seismic considerations, and lateral earth
pressures in the Engineering Analyses and Conclusions Section; and, recommendations for
foundation, settlement, earthwork construction, retaining walls, erosion control, drainage, and
vegetation in the Engineering Recommendations Section.
1.1 Project Information
Information pertaining to the planned development of the Project was provided by the proponent
of the property during the geotechnical investigation. Other Project information was obtained by
Envirotech.Existing development consists of a single family residence.The planned development
consists of an addition to the east side of the existing single family residence, and a detached
garage. 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:
Envirotech Engineering Geotechnical Report
PO Box 984 page 1 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
• 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 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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Envirotech Engineering Ceotechnical Report
PO Box 984 page 2 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
10 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on October
24,2014 by Michael Staten,geotechnical engineer 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
The property is accessed from E Mt Washington Ct, an existing paved roadway. The Project is
currently developed land as previously mentioned. The access road extends near the south
property line,and E Olympic Vista Drive borders the property to the north. Beyond the property,
rural residential development exists. Vegetation on and near the Project consists primarily of
secondary growth firs, cedars, huckleberry, and other 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 located approximately 25 feet to the
north of the planned development. The maximum critical slope is approximately 83% with a
vertical relief of at least 60 feet.
Ascending grades are generally located to the south of the planned development.These slopes are
relatively minor within 300 feet of the Project, with no apparent slope grades of at least 15%.
2.2.1 Upslope Geomorphology
The upland area of the property and beyond is generally situated on a crest of glacial
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.
Envirotech Engineering Geotechnical Report
PO Box 984 page 3 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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.
2.4 Slope and Erosion Observations
The slope grades near the Project signal a potential landslide or erosion hazard area. Some
indicators that may suggest past slope movements include:
• Outwash of sediments near the bottom of the slope,
• Fissures, tension cracks,hummocky ground or stepped land masses on the face or top of
the slope, and parallel to the slope,
• Fine,saturated subsurface soils,
• Old landslide debris,
• Significant bowing or leaning trees,or,
• Slope sloughing or calving.
These slope instability indicators or other significant mass wasting on the property of the Project
were not observed. Indications of past landslides, current unstable slopes, deep-seated slope
problems, or surficial slope failures were not observed during the site visit. Visible landslides
were observed on neighboring properties, and multiple landslides were mapped by DNR on the
hillside,including one encompassing the property.
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Aerial Photo from Mason County Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 4 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the Project was primarily gathered on October
24,2014 by Michael Staten, geotechnical engineer with Envirotech. Specific 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 extending to depths of up to 8.5 feet below the existing 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 60 inches, and very
dense soils from 60 inches to the depth of terminous.
3.2 General Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the "Geologic Map of Washington," compiled by J. Eric Schuster,
2002 indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated
deposits, and dominantly deposited from glacial drift,including alluvium deposits.This project is
located within the Puget Lowland. Typically, "lower tertiary sedimentary rocks unconformably
overlie the Crescent Formation."as revealed in the Geologic Map. Initial sedimentary rocks were
formed from shales, sandstones and coal deposits from rivers. During the Quaternary period, the
Puget Lowland was covered by numerous ice sheets,with the most recent being the Fraser glacier
with a peak of approximately 14,000 years ago. Upon the glacial retreat, the landscape was
formed by glacial erosion glacial drift deposits.
The"Geologic Map of the Skokomish Valley and Union 7.5-minute Quadrangles,Mason County,
Washington" by Michael Polenz, Jessica L. Czajkowski, Gabriel Legorreta Paulin, Trevor A.
Conteras, Brendon A. Miller, Maria E. Martin, Timothy J. Walsh, Robert L. Logan, Robert J.
Carson, Chris N. Johnson, Rian H. Skov, Shannon A. Mahan, and Cody R. Cohan, June 2010,
provides the following caption(s)for the project area:
Vashon advance oatwash—Pebbles,cobbles,and sand;gray to tan;generally compact,but
commonly cohesionless;clasts well rounded,well sorted,clean;very thinly to thickly bedded.
Envirotech Engineering Geotechnical Report
PO Box 984 page 5 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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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 some indications of fill. Soils within test
pit 1, are fill within the upper 5 feet of natural ground and were observed to be moist,brown silty
sand with gravel (SM). Soils below the upper 5 feet layer to a depth of 8.5 feet below the ground
surface were native soils observed to be low moisture, silty sand with gravel (SM) over hardpan.
The hardpan may extend to depths greater than 50 feet.This is based on nearby well reports, site
Envirotech Engineering Geotechnical Report
PO Box 984 page 6 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
geology,and/or knowledge of the general area.
The relative densities of the soil within selected test pits are provided above in Section 3.1.
Expanded and specific subsurface descriptions, other than what is provided in this section, are
provided in the soil logs located in Appendix B of this report.
According to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Conservation Service,the site soils are described as Alderwood Gravelly Sandy
Loam, Ad, with 30% - 50% slopes. The soil designations are depicted in the aerial photograph
below,and descriptions are provided in Appendix B of this report.
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3.3.1 Groundwater
From the water well report(s)and knowledge of the general area, permanent groundwater
is at least 50 feet directly below the property at the building pad location. Surface seepage
or perched groundwater at shallow depths was not observed on-site, nor indicated on the
well reports. However, some groundwater is expected to flow directly above the hardpan
on occasion.
Envirotech Engineering Geotechnical Report
PO Box 984 page 7 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
4.0 ENGINEERING ANALYSES AND CONCLUSIONS
The following sections present engineering analyses and conclusions with relation to the existing
conditions and proposed improvements of the Project. This section includes slope stability,
erosion, seismic considerations, lateral earth pressures, 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, excessive and/or repeated surficial slope
movements, if not repaired, may represent a threat to the structural integrity of the slope. If this
situation does arise, the slope shall be inspected by a geotechnical engineer. Subsequently,
maintenance may be required in order to prevent the possibility of further surficial or deep seated
slope movements that may be damaging to life and property.
According to the Coastal Zone Atlas of Mason County, Washington, the Project is within and
near terrain labeled `Stable' and `Intermediate' regarding potential landslide activity. Stable
slopes are generally not prone to landslides due to small grades and accommodating geology.
Historically, intermediate terrains have no known landslides. However, this site is considered
inherently hazardous due the existing geology and/ or topography, and additional analyses and
recommendations concerning the slopes are presented herein. A Stability Map from the Coastal
Zone Atlas for the general area of this Project is provided below:
Envirotech Engineering Geotechnical Report
PO Box 984 page 8 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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Map from Washington State Department of Ecology Website
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. This
delineation is primarily dependent upon slopes and convergence. Secondly, lithology and
precipitation are modeled within this delineation. In summary, this designation is based on
mapping without field observations or knowledge of the specific site geology or soils. A
Resource Map from the DNR Forest Practices Application Review System is provided below:
Envirotech Engineering Geotechnical Report
PO Box 984 page 9 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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Resource Map from Washington State Department of Natural Resources Website
Envirotech Engineering Geotechnical Report
PO Box 984 page 10 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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Landslide Inventory Mason Watershed Isabelle Sarikhan and Timothy J.Walsh—
May 2007
4.1.1 Slope Stability Analysis
Based on site geology, a non-circular slope stability analysis should be performed.
However, the Simplified Bishop Method (circular analysis), as presented herein, was
utilized. Although the method of circles does not fit the site conditions, Envirotech
certifies that our analysis is more conservative for these project conditions than other
conforming slope stability models. For this Project and level of geotechnical
investigation, our conclusions or recommendations would not be changed by this
variation in analysis.Where applicable,our slope stability analysis utilizes the subsurface
angle of repose.
The Simplified Bishop Method, utilizing `STABLE' software, was used to analyze the
static stability of the site slopes. Seismic conditions were estimated utilizing worst case
scenario values from the static analysis,a quasi-static analysis coefficient of at least 0.15,
and applying the applicable values to STABLE software. Various radii's and center
points of the circle were automatically selected, and produced factor of safeties in a
graphical and tabular format. Worst case scenario values were used in the slope stability
analysis in regards to topography, surcharges, water content, internal friction and
Envirotech Engineering Geotechnical Report
PO Box 984 page 11 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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 5 feet soil depth
Soil unit weight: 132 pcf
Angle of internal friction: 30 degrees
Cohesion: 200 psf
Soils below 5 feet in depth
Soil unit weight: 140 pcf
Angle of internal friction: 40 degrees
Cohesion: 400 psf
Based on the slope stability analysis, minimum factors of safety were determined to be
less than 1.4 relative to static slope failures, and less than 1.0 with relation to seismic
conditions.These factors of safety were primarily limited to the face of the slope, and do
not reflect conditions where development is expected to occur. For this Project, at the
location of the proposed development, minimum factor of safeties for static and dynamic
conditions were estimated to be 1.7 and 1.2, respectively. See the slope stability
information in Appendix C for a depiction of input parameters and example of outputs.
4.2 Erosion
Based on the USCS description of the Project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,
the Project is not within terrain labeled `highly erodible.' This Project is within an erosion hazard
area as defined by the MCRO. Erosion hazard areas are those with USDA SCS designations of
River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on slopes 15% or
greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd), Harstine Gravelly
Sandy Loam on slopes 15%or greater(Hb),and Kitsap Silt Loam on slopes 15%or greater(Kc).
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 12 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
Western Washington," prepared by the Washington State Department of Ecology Water Quality
Program.
43 Seismic Considerations and Liquefaction
There are no known faults beneath this Project. The nearest Class `A' or Class `B' fault to this
property is the Tacoma Fault Zone, at approximately 10 miles to the east, and the Hood Canal
Fault Zone,at approximately 5 miles to the northwest 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.
4A Landslide,Erosion and Seismic Hazards Conclusions
DNR did indicate 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.
45 Lateral Earth Pressures
Retaining walls may be utilized for this Project. The lateral earth pressures exerted through the
backfill of a retaining wall are dependent upon several factors including height of retained soil
behind the wall, type of soil that is retained, degree of backfill compaction, slope of backfill,
surcharges,hydrostatic pressures,earthquake pressures,and the direction and distance that the top
of the wall moves. A structural or geotechnical professional should design retaining walls based
on specific conditions.
Envirotech Engineering Geotechnical Report
PO Box 984 page 13 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
Soil parameters for the structural design of retaining walls may be estimated as 134 pounds per
cubic foot (pcf) and 118 pcf for engineered fill and native soils, respectively. The angle of
internal friction may be estimated as 36 degrees and 32 degrees for engineered fill and native
soils,respectively.These soil parameters are based on soil type and placement conforming to the
Earthwork Construction Recommendations Section in this report.
4.6 On-Site and Off-Site Impacts
From a geotechnical position, it is Envirotech's opinion that the subject property and adjacent
properties to the proposed development should not be significantly impacted if all
recommendations in this report are followed. This opinion is based on the expected site
development, existing topography, existing nearby development, land cover, and adhering to the
recommendations presented in this report. Future development or land disturbing activities on
neighboring properties or properties beyond adjacent parcels that are upslope and/or downslope
from the subject property could cause problems to the subject property. For this reason, future
development or land disturbance near the subject property should be evaluated by a geotechnical
engineer.
Envirotech Engineering Geotechnical Report
PO Box 984 page 14 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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, not fill soils as found on site near the planned garage location.
Alternatively, foundations may be constructed on selective re-compacted native soil or
compacted engineered fill as described in the Earthwork Construction Recommendations
Section of this report.
For a bearing capacity requirement of no more than 1500 psf, a minimum continuous
footing width of 12 inches (1-story buildings), and 15 inches (2-story buildings) shall be
placed at a minimum of 12 inches below the existing ground surface.For a columnar load
of no more than 3 tons,a circular or square isolated foundation diameter or width shall be
at least 24 inches. Foundation recommendations are made available based on adherence
Envirotech Engineering Geotechnical Report
PO Box 984 page 15 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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.
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 (Passing U.S. Sieve #10 or greater) that is placed over
undisturbed, competent native subgrade or engineered fill. Native soils found at the
Project site may be suitable for use as material directly beneath concrete slabs if it meets
the aforesaid requirements or the soil is screened to meet these requirements. The upper
organic laden native soil should be removed prior to the placement and compaction of the
aforementioned 4-inch coarse,granular material.
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
Envirotech Engineering Geotechnical Report
PO Box 984 page 16 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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 I
FILL
1
II—Ili —I I '
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
Partical Size Distribution of Engineered Fill
Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native
soils and engineered fill,respectively.Each lift should be uniformly compacted to at least
90% 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
Envirotech Engineering Geotechnical Report
PO Box 984 page 17 40&50 E Washington Mt.Ct.
Bclfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
I
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). In addition,heavy construction equipment should be at a distance of at
least '/2 the wall height. Over-compaction and limiting heavy construction equipment
should be prevented to minimize the risk of excess lateral earth pressure on the retaining
structure. Envirotech recommends that retaining wall backfill is compacted with light
equipment such as a hand-held power tamper. If clean, coarse gravel soils are utilized as
engineered fill, and surcharges will not influence the retaining wall, compaction may be
achieved by reasonably densifying granular soils with construction equipment.
Backfill for the retaining wall should extend vertically from the top of the footing to the
proposed ground surface. The backfill should also extend horizontally from the back of
the retaining wall to at least 1- foot for every 2 feet of retaining wall height. Perforated
drain pipe for retaining walls should have a minimum diameter of 4 inches and direct
water to an appropriate infiltration or outfall as recommended in the Surface and
Subsurface Drainage Section of this report. Coarse, clean gravel (1 inch diameter) is
recommended to be placed at least 24 inches around the drain pipe in order to provide
increased drainage capabilities. Non-woven geotextile filter fabric designed to impede
fine particles should be wrapped around the aforementioned coarse gravel for reducing
the potential of silt migration and clogging of the drain pipe.
5.2.4 Wet Weather Considerations
Due to the types of subsurface soils, additional provisions may be required during
prolonged wet weather. Every precaution should be made in order to prevent free
moisture from saturating the soils within excavations. If the bottom of excavations used
for footing placement changes from a moist and dense/hard characteristic as presented in
this report to muck or soft, saturated conditions, then these soils become unsuitable for
foundation bearing material. If this situation occurs, a geotechnical engineer should be
notified, and these soils should be completely removed and replaced with compacted
engineered fill or suitable native material as presented in this section.
5.3 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 25 feet garage
Envirotech Engineering Geotechnical Report
PO Box 984 page 18 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
footing setback from the face of the nearby descending slopes exceeding 40%. See the figure
below and the Site Plan in Appendix A for an illustration of the setbacks.
STRUCTURE
TOP OF
SLOPE SLOPE
FACE
I PUT, -I I
�-- 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. In addition, the required setback
may be reduced by mitigation, and subsequently would require additional geotechnical studies.
The planned location of the house addition is acceptable as it is an ancillary room that will not
encroach the existing house footprint towards the slope.
5.4 Surface and Subsurface Drainage
Positive drainage should be provided in the final design for all planned residential buildings.
Drainage shall include sloping the ground surface, driveways and sidewalks away from the
Project structures. All constructed surface and subsurface drains should be adequately maintained
during the life of the structure.If drainage problems occur during or after construction, additional
engineered water mitigation will be required immediately. This may include a combination of
swales,berms,drain pipes,infiltration facilities,or outlet protection in order to divert water away
from the structures to an appropriate protected discharge area. Leakage of water pipes, both
drainage and supply lines, shall be prevented at all times.
If impervious thresholds are exceeded per Mason County code, then engineered stormwater
management plans are required for this project. The drainage engineer must coordinate with a
geotechnical engineer for input with relation to slope stability prior to submitting drainage plans.
If stormwater management plans are not required for this project, then the following
recommendations should be followed.
Both footing perimeter drains and roof drains are required for this Project. Subsurface water
intercepted in the footing perimeter drains, and stormwater collected from roof drains shall be a
separate tightlined system. Foundation water may exit downslope from the building, and roof
drainage shall be tied into the existing stormwater drainage system.Envirotech should be notified
if gravity feed prohibits this recommendation in order to provide different drainage mitigation.
5.5 Vegetation Buffer and Considerations
Vegetation is an excellent measure to minimize suficial slope movements and erosion on slope
faces and exposed surfaces. By removing trees, the root strength is decreased over time, thereby
lowering the `apparent' cohesion of the soil. Transpiration is decreased, which results in
additional groundwater, increased pore water pressure and less cohesion/ friction of the soil
Envirotech Engineering Geotechnical Report
PO Box 984 page 19 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Pb. 360-275-9374 November 26,2014
particles. Stormwater runoff also increases, and, fewer plants will create less absorption of the
force from raindrops,thereby creating the potential for erosion hazards.
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
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 first choice for temporary erosion control.Any erosion control should be located
down-slope and beyond the limits of construction and clearing of vegetation where surface water
is expected to flow. If the loss of sediments appears to be greater than expected, or erosion
control measures are not functioning as needed, additional measures must be implemented
immediately. See Appendix D for sketches and general notes regarding selected erosion control
measures. The Site Map in Appendix A depicts the recommended locations for erosion control
facilities to be installed,if necessary.
Permanent erosion control may also be necessary if substantial vegetation has not been
established within disturbed areas upon completion of the Project. Temporary erosion control
should remain in 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. The following Surface and Subsurface Drainage Section may
have additional recommendations with relation to permanent erosion for surface drainage
features.
5.7 Septic Drainfields
The approximate location of the septic drainfield is presented on the Site Plan in Appendix A of
this report. Based on the septic drainfield location with relation to the existing and proposed
topography, the drainfields are not expected to adversely influence critical slopes. This is also
based on compliance with all recommendations in this report.
5.8 Structural Mitigation
With respect to landslide alleviation or slope improvements,structural mitigation is not necessary
for this project. This determination is based on the anticipated improvements of the project,
engineering conclusions,and compliance with all recommendations provided in this report.
Envirotech Engineering Geotechnical Report
PO Box 984 page 20 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
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.
MCRO 17.01.100 F - The property owner may be required to acknowledge in writing the risks
inherent in developing in a geologic hazard area, to accept the responsibility of any adverse
effects which may occur to the subject property or other properties as a result of the development,
and to agree to convey the knowledge of this risk to persons purchasing the site by filing a notice
on the property title.
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
�Engiineeringg
Michael Staten,P.E.
Geotechnical Engineer
Envirotech Engineering Geotechnical Report
PO Box 984 page 21 40&50 E Washington Mt.Ct.
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 November 26,2014
APPENDIX A
SITE PLAN
SOILSI MEDIUM DENSE SILTY SAND WITH GRAVEL (SM) SCALE, 1 INCH = 60 FEET
OVERLYING VERY DENSE GLACIAL TILL 0 150 15®0
109E f ��YlyP
Tt 92FT:t VISTA DRIVE
o -H
n
w
a0 r C�
o +1 A
N
°D APPROXIMATE TOP OF
tibo SLOPE EXCEEDING 40%
ti
EXISTIN - - - - - -
0
OFT VEGETATION BUFFER.
Zo SEE REPORT.
PROPOSED ADDITION 61FTt T 2 64F 5FT BUILDING SETBACK
(APPRX) Tt
FROM TOP OF CRITICAL
E MT WASHINGTDN CT SLOPE. SEE REPORT.
A ILT FENCE
ROPOSED GARAGE
20
NOTES' PROJECT/ OWNER/ LOCATION,
L EROSION CONTROL MAY BE REQUIRED FOR THIS SITE.GENERAL LOCATIONS SINGLE FAMILY RESIDENCE
ARE DEPICTED, AND ALTERNATIVES MAY BE UTILIZED AS EXPLAINED IN THE
GEOTECHNICAL REPORT, GE❑TECHNICAL REPORT
2,CONTOURS WERE NOT PREPARED BY A LICENSED LAND SURVEYOR.
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC L1DAR SOURCE, AND HILGENDORF
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL 40 6 50 E MT WASHINGTDN CT
REPORT. LEGEND PARCELS 32234 51 00024 6 25
3. BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR.LOCATIONS MASON COUNTY. WAS N T N
If SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP OF SLOPES, TI£ TEMPORARY ENGINEER-
OF SLOOPES, WATER FEATURES,ETC., WITH RELATION TO THE PROPERTY -I'++EROSION CONTROL ENVDUMCH ENGINEERING
LINES MUST BE VERIFIED BY THE OWNER, RECOMMENDATIONS IN THE PO BOX 984
GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC., WITH SLOPE INDICATOR BELFATR, WASHINGTDN 9852E
RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC 1 360-275-9374
FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY DR NEIGHBORING --80' EXISTING CONTOUR
PROPERTIES. iLI TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
i
i
VERTICAL A WRIZONTAL SCALE-
1 INCH 40 FEET
FEET
O 10 20 40
PROPOSED GARAGE
E MT WASHINGTON CT\ C
L 5FT FILL
MEDIUM DENSE cSM)
OVER HARDPAN
GLACIAL TILL OR
ADVANCE OUTWASH
�E_OLYMPIC VISTA DR
SECTION A—A
PROJECT/ OWNER/LOCATIOW
SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
B HILGENDORF
PARCEL 32234 51 00024
MASON COUNTY, W04SKNGMN
NOTES-
1) MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENGINEER
POSITIVE DRAINAGE ENVIROT ENGINEERING
PO BOx 84
2)THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF 9B4
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS, 360FAIR, WASHINGTON 98528
LOWER DEPTHS ARE BASED ON SITE GEOLOGY,
36D-275-9374
WELL LOG(S),AND/0R EXPERIENCE IN THE GENERAL AREA. SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: Hilgendorf Geotechnical Report DATE OF LOG: 10/24/2014
PROJECT NO: 14133 LOGGED BY: MCS
CLIENT:Brian Hilgendorf EXCAVATOR: N/A
LOCATION: Parcels 32234 51 00024&25 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 . ..................................................
SM Fill.
Brown,moist,medium dense SILTY
SAND with GRAVEL.
1 Low plasticity.
2
3
4
5 Native...................................
Brown,moist,medium dense SILTY
SAND with GRAVEL.
6
7
8 Tz:
Hardpan
Excavation terminated at approximately
g 8.5 feet
110
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.
TEST PIT LOG
TEST PIT NUMBER TP-2
PROJECT:Hilgendorf Geotechnical Report DATE OF LOG: 10/24/2014
PROJECT NO: 14133 LOGGED BY: MCS
CLIENT: Brion Hilgendorf EXCAVATOR: N/A
LOCATION: Parcels 32234 51 00024&25 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 _.... .............._.....
SM Brown,moist,loose to medium dense
SILTY SAND with GRAVEL.Low
plasticity.
1 �
2
Hardpan
Excavation terminated at approximately
3 2.5 feet
4
5
6
7
8
9
I
110
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
rnterpreted as being indicitive of the entire site.
Ter O"gl:slan4"rel Copy With Application Mo.
I o f.C
WATER WELT. REPORT
STAU OF WANNIVIT" P.UVkft ..............
(1) OWNER: Nana
(2) LOCATION Or WEIJA
3"rina and dbtanoa from Nation or sub4nvW*n owner
(3) PROPOSED USE: Domebe 0 h1deatrw 0 Maklp" (10) WELL LOG:
rormilon:Donvibe b). Of"Meterla 6.4 4*6
Irrigation D Ted Wait 0 Other a w-Mazt.-d=ftaftre of the"MwM is each
swe"M larneftelisc a 40'a"A*"4M"V Tar fach cluaw of for-H-.
(1) TYPE OF WORK: owner's number of"It �9� —
1 7 then MA71ME" FIRM TO
Now W4111 M#Uwd;Due 0 Bored 0 -
Deepened 11 cable 0 Dri"M 0 ;P
I C7. 03,ra 5
Reconditioned❑ Rou"0 isaw 0 I;t uj"L Y, . 1177
(5) DIMENSIONS: Dismat"Of-all-1-1-9. fr led. /. 1 7
22 k
It, Deptb of eompktd TML.-
(s) coNmucnoN DETAILS;
QLaing histlidled: Dim.grew L to A=2j&t"t-
TMaded 0 DIMM.nap A.to R.
Welded(3 ---------�DL- from R.60 ft.
Perionflow- Yes Noo
Type at perforator MOW-
8=of p"forguous in-by---------in.
-I--.---ft.to parforations I -- — n.
ft.to --.9L
pefarstlow ftwis
Screenw. T"0 NO)o
Kanulacturft"s
Typs.
DIAM, from-------ft.'a
Gra
vel
peeked:
Yee 0 14O.K a,"of grarraj:
(;rb%*placed frown rt.I.
Surface "a]: yea-M Na T*,Rhat depthl
1 J3.41a.
Material Used In seal
Did any strats contlift UOUGM3310 wa"tt rim 0
Type of irator?.................. -Depth of
Magnaa at neling.0-4-
(7) PUMP: Merrafecturet's
'rype:
(8) WATER LEVELS: Land-Burhict QJQV8Mft
I Above WAM ft&)*Vol....
statle lent be"too of well
Artawlan grmwurg_...._._.._..__._-lea.par square incla Do"
Axted&p Water Is oneaUed by.---..
(9) WELL TESTS:- level Is Weak otarted- lot
W"a pump test M2401 Y"' N*4 U yes,by.home.....__................... WUJL DRILLER'S STATZMENT'
Yield: emlizain,wl. ..r . --
This Well was drilled under my Jurisdiction and this report Is
true to the best of my knowleep and ballet
Recovery
data (time taken as sera Wbm pump turned off) (Water level
meseured from was P N A I M....,Ptl. ........ ...............
2`19" Water XAMI Time WaW L4m@I Water Level, I Pa.,,Sm.or I pew
r
Add—./2-..
..........
Deft at"A (816ned) k., ------- (Well t I
Miller drawd"s
Artesian*DW--
Temperature Of was a themical analy"s midet Tam Q
APPENDIX C
SLOPE STABH,ITY
1 00
1 3-0
1 20
1 . 30
1 . 40
1 . 50
1 60
1 70
1 _ 80
2. . 0
. 00
r,
i
I
1 . 370
- 0000
Datafila Static
Analysis Bishop
a rwn u�:ooa rz w��eaa�..« ..ca
1 00
1 . 3-0
1 . 20
1 3 O
1 4 O
1 S 0
1 . 6 0
1 . 70
1 80
�1 . 0
2 00
1 _ O11
P r o j e
D a t a f i 1 e D y n a m i c
A n a l y s i s B i s h o p
s TApL�.-3002 MZ waao<iwG�r LGd
APPENDIX D
EROSION CONTROL
GEOTEXTILE FABRIC 2'x2' WOOD POST(TYP) GE13TEXTILE FABRIC
WRAP AROUND TRENCH OR EQUIVALENT OR BETTER AND WIRE MESH
TO AT LEAST ENTIRE
BOTTOM OF TRENCH 0 6 FT MAX.D.C. q5 FT
BEFORE PLACING GRAVEL 2'x2'x5' WOOD POST[R 6
12' DEEP, 8' WIDE TRENCH EOUIVALENT OR BETTER EXISTING
FILLED VITH 3/4' TO 1 1/2'11 GROUND SURFACE
WASHED GRAVEL or VEGETATip FA a
DIRECTION 13F—� 1 23 FT 12' DEEP, 8'WIDE
WATER FLOW EXISTING GROUND SURFACE TRENCH FILLED WITH
I T
12' 3/4' 111 1 I/2'
T� 2.3 FT WASHED GRAVEL OR
i VEGETATION
Hy BOTTOM EXTENTS OF
GE13TEXTILE FABRIC SILT FENCE-DFTATL
N.T.S.
N.T.S. HAY OR STRAW MATTING
ENERAL NOTES- 1.STRAW SHALL BE AIR DRIED, AND FREE FROM WEED SEEDS AND
COARSE MATERIAL
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN IN 2. APPLY AT APPROXIMATELY 75 TO 100 POUNDS PER 1000 SQUARE
HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR FEET OF GROUND,
HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES, 3. MINIMUM THICKNESS SHALL BE 2 INCHES.
ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE 4, HAY OR STRAW IS SUBJECT TO BLOWING,KEEP MOIST OR TIED
NSPECTED DAILY AND IMMEDIATELY MAINTAINED, IF NECESSARY. DOWN.
.ALL EROSION AND SEDIMET CONTROL FACILITIES AND DEVICES SHALL B LEFT IN
LACE UNTIL THE UPSLOPE AREAS HAVE BEEN PERMANENTLY STABILIZED. PERMANENT EROSION CONTROL NOTES.
EMPORARY EROSION CONTROL NOTES, SEEDING FOR RAW SLOPES
OR ALL AREAS WHICH HAVE BEEN STRIPPED OF VEGETATION OR EXPERIENCED LAND 1.BEFORE SEEDING,INSTALL NEEDED SURFACE RUNOFF CONTROL
1STURBING ACTIVITIES,AND WHERE NO FURTHER WORK IS ANTICIPATED FOR A MEASURES SUCH AS GRADIENT TERRACES,INTERCEPTOR DIKES,
ERIOD EXCEEDING THE LISTED CRITERIA BELOW, ALL DISTURBED AREAS MUST BE SWALES, LEVEL SPREADERS AND SEDIMENT BASINS.
MMEDIATELY STABILIZED WITH MULCHING, GRASS PLANTING OR OTHER APPROVED 2. THE SEED BED SHALL BE FIRM WITH FAIRLY FINE SURFACE,
ROSION CONTROL TREATMENT APPLICABLE TO THE TIME OF YEAR. GRASS SEEDING FOLLOWING SURFACE ROUGHENING,PERFORM ALL OPERATIONS ACCROS
LONE WILL ONLY BE ACCEPTABLE DURING THE MONTHS OF APRIL THROUGH OR PERPENDICULAR TO THE SLOPE.
EPTEMBER. HOWEVER, SEEDING MAY PROCEED WHENEVER IT IS IN THE INTEREST OF 3. SEEDING RECOMMENDATIONS,AS SHOWN BLOW,AND SHOULD BE
HE OWNER/CONTRACTOR, BUT MUST ALSO BE AUGMENTED WITH MULCHING, NETTING APPLIED AT THE RATE OF 120 POUNDS PER ACRE
R OTHER APPROVED TREATMENT, 4, SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL
REQUIRE IRRIGATION AND OTHER MAINTENANCE AS NECESSARY TO
RY SEASON(MAY 1 THRU SEPTEMBER 30) -- THE CLEARING OF LAND, INCLUDING THE FOSTER AND PROTECT THE ROOT STRUCTURE.
EMOVAL OF EXISTING VEGETATION OR OTHER GROUND COVER, MUST BE LIMITED TO 5. SEED BEDS PLANTED BETWEEN NOVEMBER 1 AND APRIL 30,
NLY AS MUCH LAND AS CAN RECEIVE APPROPRIATE PROTECTIVE COVER OR BE ARMORING OF THE SEED BED WILL BE NECESSARY, (eo,
THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR OTHERWISE DISTURBED , GEOTEXTILES. JUTE MAT.CLEAR PLASTIC COVERING).
Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR.UNLESS IMMEDIATE 6, FERTILIZERS ARE TO B USED ACCORDING TO SUPPLIERS'
TABILIZATIIIN 1S SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN,ALL RECOMMENDATIONS.AMOUNTS SHOULD BE MINIMIZED,ESPECIALLY
REAS CLEARED OR OTHERWISE DISTURBED MUST BE APPROPRIATELY STABILIZED ADJACENT TO WATER BODIES AND WETLANDS,
HROUGH THE USE OF MULCHING, NETTING,PLASTIC SHEETING, EROSION BLANKETS,
REE DRAINING MATERIAL, ETC., BY SEPTEMBER 30 13R SOONER PER THE APPROVED USE THE FOLLOWING RECOMMENDED SEED MIXTURE FOR EROSION
LAN OF ACTION. UNLESS OTHERWISE APPROVED BY THE COUNTY, SEEDING, CONTROL,OR A COUNTY APPROVED ALTERNATE SEED MIXTURE
ERT ILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE
ER FORMED DURING THE FOLLOWING PERIODS- MARCH 1 TO MAY 15, AND AUGUST 15 TO PROPORTIONS PURITY GERMINATIII
CTOBER L SEEDING AFTER OCTOBER 1 WILL BE DONE WHEN PHYSICAL COMPLETION NAME BY WEIGHT(X) (X) (X)
F THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CDNDITIONS ARE CONDUCIVE
0 SATISFACTORY GROWTH, IN THE EVENT THAT PERANENT STABILIZATION IS NOT REDTOP(AGROSTIS ALBA) 10 92 90
OSSIBLE, AN ALTERNATIVE METHOD OF GROUND COVER, SUCH AS MULCHING, NETTING, ANNUAL RYE(LOLIUM MULTIFLORUM) 40 98 90
LASTIC SHEETING, EROSION BLANKETS,ETC„ MUST B INSTALLED BY NEI LATER THAN CHEWING FESUE 40 97 80
EPTEMBER 30. (FESTUCA RUBRA COMMUTATA)
(JAMESTOWN,BANNER, SHADOW, KO(ET)
N THE EVENT THAT CONSTRUCTION ACTIVITIES IR OTHER SITE DEVELOPMENT WHITE DUTCH CLOVER 10 96 90
CTIVITIES ARE DISCONTINUED FOR AT LEAST 4 CONSECUTIVE DAYS, THE (TRIFOLIUM REPENS)
WNER/CONTRACTOR SHALL BE RESPONSIBLE FOR THE INSPECTION OF ALL EROSION
ND SEDIMENT CONTROL FACILITIES IMMEDIATELY AFTER STORM EVENTS, AND AT MULCHING
EAST OWE EVERY WEEK. THE OWNER/ CONTRACTOR SHALL BE RESPONSIBLE FOR
HE MAINTENANCE AND REPAIR OF ALL EROSION AN SEDIMENT CONTROL FACILITIES. 1,MATERIALS USED FOR MULCHING ARE RECOMMENDED TO BE WOOD
FIBER CELLULOSE,AND SHOULD B APPLIED AT A RATE OF 1000
ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED POUNDS PER ACRE.
ONSTRUCTION ACTIVITY IS IN PROGRESS,THE CLEARING OF LAND, INCLUDING THE 2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES
EMOVAL [F EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED GREATER THAN 2,1 OHOIIZONTAUVERTICAU,
0 AS MUCH LAND AREA AS CAN BE COVERED OR STABILIZED WITHIN 24 HOURS IN 3, MULCHING SHOULD BE USED IMMEDIATELY AFTER SEEDING OR IN
HE EVENT A MAJOR STORM IS PREDICTED AND/ OR EROSION AND SEDIMENT AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON, ALL
RANSPORT OFF-SITE IS OBSERVED. AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER L
LL CLEARED OR DISTURBED AREAS SHALL RECEIVE APPROPRIATE PROTECTIVE
OVER OR BE OTHERWISE STABILIZED, SUCH AS MULCHING, NETTING, PLASTIC
MEETING, EROSION BLANKETS,FREE DRAINING MATERIAL,ETC., WITHIN 5 DAYS AFTER
AVING BEEN CLEARED OR OTHERWISE DISTURBED IF NOT BEING ACTIVELY WORKED.
ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC„ WILL NOT BE VIEWED AS
DEQUATE COVER IN AND IF THEMSELVES IN THE EVENT THAT ANY LAND AREA NOT
EING ACTIVELY WORKED REMAINS UNPROTECTED OR HAS NOT BEEN APPROPRIATELY
TABILIZED 5 DAYS AFTER HAVING BEEN CLEARED, ALL CONSTRUCTION ACTIVITY ON
HE SITE, EXCEPT FOR APPROVED EROSION AND SEDIMENT CONTROL ACTIVITY, SHALL
MMEDIATELY CEASE UNTIL SUCH A TIME AS AFOREMENTIONED LAND AREA HAS BEEN
PPROPRIATELY PROTECTED OR STABILIZED,
ILT FENCE
PROJECT/ OWNER/ LOCATION
GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE
U THE T SOUND GEOTE TILEFILTER FABRICSHALL APPLICABLE:COUNTY STANDARDS
BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GEOTECHNICAL REPORT
ACM BARRIER TO AVOID USE IF JOINTS.IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED B HII.GENOORF
DGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT OTH ENDS TO THE T
PARCEL 32234 51 00024 6 25
.
. STANDARD FILTER POSFABRIC SHALL BE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) E 4 IN MASON COUNTY, WASHINGTON
PACING,
, POSTS SHALL BE SPACED AND PLACED AT DEPTHS INDICATED IN THE DETAILS ON THIS SHEET, AND ENGINEER-
RIVEN SECURELY INTO THE GROUND. ENVIROTECH ENGINEERING
. WIRE MESH SHALL BE 2'X2'X14 GAUGE OR EQUIVI ENT. THE WIRE MESH MAY BE ELIMINATED IF PO BOX 984
XTRA-STRENGTH FILTER FABRIC (MONIFILAMENT), AND CLOSER POST SPACING IS USED. BELFAIR, WASHNGTON 9e528
A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE 360-275-9374
AND
SILT FENCES ISHALL RBE LOCATED DOS!SLOPE FROM THE CLEARING LIMITS OF THE PROJECT. EROSION CONTROL