HomeMy WebLinkAboutGEO2019-00086 BLD2019-01277 - BLD Engineering / Geo-tech Reports - 11/13/2019 E v 20 I 000 8Y
RECEIVED
NOV 13 2019
Geotechnical Report 615 W. Alder Street
Oosterveld Single Family Residence
E Rasor Road Belfair PLANNING
Parcel No. 12206-13-00110
Mason County, Washington
October 2, 2019
Project #19202
Prepared For
Jan Oosterveld
PO Box 1709
Port Orchard, Washington 98366
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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0 MA50N COUNTY
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. 1:an item is found not applicable,the report should explain the basis for the conclusion.
Note: Unless specifically documented, this report does not provide compliance to the International Residential
Code Sections R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section
1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Jan Oosterveld Parcel# 12206-13-00110
Site Address XXX E Rasor Road
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located or page(s) 5-6
(b) A discussion of specific soil types,
Located or page(s) 7
(c) A discussion of ground water conditions,
Located or page(s) 7
(d) A discussion of the upslope geomorphology,
Located or page(s) 3
(e) A discussion of the location of upland waterbodies and wetlands,
Located or page(s) 3
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and
records.
Located or page(s) 8
(2) A site plan which identifies the important development and geologic features.
Located on Mal)(s) Site Plan—Appendix A
(3) Locations and I)gs of exploratory holes or probes.
Located on Mal)(s) Site Plan and Soil Logs (Appendix 8)
(4) The area of the proposed development,the boundaries of the hazard,and associated buffers and
setbacks shall he delineated(top, both sides, and toe) on a geologic map of the site.
Located on Mal)(s) Site Plan
(5) A minimum of cne cross section at a scale which adequately depicts the subsurface profile, and
which incorpora:tes 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 pace(s)__ 9 10 Page 1 0139
(7) (a) Appropriate restrictions on placement of drainage features,
Located on pace(s) 17
(b) Appropriate restrictions on placement of septic drain fields,
Located on pace(s) 18
(c) Appropriate restrictions on placement of compacted fills and footings,
Located on page(s) 13 and 15
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on pace(s) 17
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
Located on page(s) 16-17
(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) 17
(9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific
mitigating measure: to be implemented during construction to protect the slope from erosion, landslides and
harmful constructior methods.
Located on page(s) 10
(10) An analysis of both.m-site and off-site impacts of the proposed development.
Located on page(s) 11 - 12
(11) Specifications of final development conditions such as,vegetative management,drainage,erosion control,and
buffer widths.
Located on page(s) 17
(12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
Located on page(s) 18
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature
of existing and proposed development on the site.
Located on Map(E) 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
rJI* r i I r�� �t� Report,dated October 2, 2019, and entitled Oosterveld
,7 r Single Family Residence, meets all the requirements of the
Mason County Resource Ordinance, Geologically Hazardous
Areas Section, is complete and true,that the assessment
� t
demonstrates conclusively that the risks posed by the landslide
hazard can be mitigated through the included geotechnical
/ design recommendations, and that all hazards are mitigated in
9 g
Disclaimer:Mason County does not such a manner as to prevent harm to property and public
certify the quality of the work done in health and safety.
this Geotechnical Report.
Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION
1.1 PROJECT INFC-RMATION.................................................................................................................... 1
1.2 PURPOSE OF I14VESTIGATION AND SCOPE OF WORK........................................................................ 1
2.0 SURFACE CONDITIONS..................................
2.1 GENERAL OBSERVATIONS..................................................................................................................3
2.2 TOPOGRAPHY.....................................................................................................................................3
2.2.1 Upslope Geomorphology............................................................................................................ 3
2.3 SURFACE URA INAGE.......................................................................................................................... 3
2.3.1 Upslope Waler Bodies................................................................................................................ ?
2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4
3.0 SUBSURFACE 1NVESTIGATION.....................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING. _ _...................................... _ .............. 5
3.2 GENERAI.GEOLOGIC CONDITIONS.......................... .._ . ...............
.3.3 SPECIFIC SUBSURFACE CONDITIONS................................................................................................. 6
?..?.1 Groundwater............................................................................................................................... 7
4.0 ENGINEERING ANALYSES AND CONCLUSIONS......................................................................8
4.1 SLOPE STABIL ITY...............................................................................................................................8
4.1.1 Slope Stability Analysis.............................................................................................................. 9
4.2 EROSION............................................................................................................................................10
4.3 SEISMIC CONSIDERATIONS AND LIQUEFACTION..............................................................................10
4.3.1 Liquefact.'on..............................................................................................................................11
4.4 LANDSLIDE,EROSION AND SEISMIC HAZARDS CONCLUSIONS........................................................I I
4.5 LATERAL EAR 1'H PRESSURES...........................................................................................................
4.6 ON-SITE AND OFF-SITE IMPACTS.....................................................................................................I i
5.1 BUII.DIN(,FOI:NDA'I'ION RF.COMII4F.NDATIONS.................................................................................13
5.1.1 Bearing Capacity.......................................................................................................................13
.5.1.2 ,Settlemen!..................................................................................................................................14
5.1.3 Concrete Slabs-on-Grade..........................................................................................................14
5.2 EARTHWORK CONSTRUCTION RECOMMENDATIONS.......................................................................14
5.2.1 Excavation.................................................................................................................................14
5.2.2 Placemen'and Compaction of Native Soils and Engineered Fill.........................................../5
5.2.3 Retaining Wall Backfill............................................................................ ......16
...........................
5.2.4 Wet Weat,'ter Considerations....................................................................................................16
5.2.5 Building Pads............................................................................... .. ...........16
. ...............................
5.3 BUILDING AND FOOTING SETBACKS.................................................................................................17
5.4 SURFACE AND SUBSURFACE DRAINAGE...........................................................................................17
5.5 VEGETATION BUFFER AND CONSIDERATIONS.................................................................................17
5.6 TEMPORARY AND PERMANENT EROSION CONTROL.......................................................................18
5.7 SEPTIC DRAINFIELDS........................................................................................................................18
5.8 STRUCTURAL MITIGATION...............................................................................................................18
6.0 CLOSURE.............................................................................................................................................19
Appendix A-Site Plan
Appendix B-Sail 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 planned
single family residence located at XXX E Rasor Road, identified as parcel number 12206-13-
00 110, Mason Cou ity, Washington. See the vicinity map on the following page for a general
depiction of the site location.
An initial geotechnical evaluation of the project was conducted by Envirotech on September 19,
2019. it was determ ned 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 developm( nt 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 rrsearch, Envirotech prepared this geotechnical report which, at a minimum,
conforms to the app!icable MCRO.
As presented herein this report includes information pertaining to the project in this Introduction
Section; observatiors of the property and surrounding terrain in the Surface Conditions Section;
field methods and soil descriptions in the Subsurface Investigation Section; supporting
docurnentation with relation to slope stability, erosion, seismic considerations, and lateral earth
pressures in the Engineering Analyses and Conclusions Section; and, recommendations for
foundation, settlente.nt, earthwork construction, retaining walls, erosion control, drainage, and
vegetation in the Engineering Recommendations Section.
1.1 Project Information
Information pertaini-ig to the planned development of the project was provided by the proponent
of the property. The planned development consists of a I- or 2-story single family residence, new
on-site septic system, and other ancillary features typical of this type of development.
Approximate building footprint and other proposed features with relation to existing site
conditions are illustrated on the Site Map provided in Appendix A of this report.
1.2 Purpose of Investigation and Scope of Work
The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the
project in order to )rovide 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
representatiNc;
• Conduct a site visit to document the site conditions that may influence the construction
and performance of the proposed improvements of the project;
• Define general subsurface conditions of the site by observing subsoils within test pits
Envirotech F.ngineerin;; — ___--- — Geotechnical Report
PO Box 984 page I Parcel 12206-13-00110
Helfair,Washington W.528 Mason County, Washington
Ph. 360-275-9374 October 2, 2019
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 bulb. samples, as applicable, at various depths and locations;
• Perform soils testing to determine selected index and/or engineering properties of the site
soils;
• Complete an engineering analysis supported by the planned site alterations, and the
surface and subsurface conditions that were identified by the field investigation, soil
testing, and applicable project research; and,
• Establish conclusions based on findings, and make recommendations for foundations,
drainage, slope stability, erosion control, earthwork construction requirements, and other
consideraticns.
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Vicini[Y Map fran Mason County Website
1'nvirntech Fngincerin;' Gentechnical Report
N) Box 984 page 2 Parcel 12206-13-00110
fichair, Washington 9 528 Mason County, Washington
Ph. 360-275-9374 October 2. 2019
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on
September 19, 2019 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 Condition:; Section provides information on general observations, vegetation,
topography, drainage and observed slope/ erosion conditions for the project and surrounding
areas that may impa--t the project.
2.1 General Observations
Currently, the property is vacant. Vegetation on and near the project consists primarily of
secondary growth c(:dars, alders, 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 developmert.
Critical descending slopes, with grades exceeding 40% appear to be within 300 feet of the
planned developmert. The maximum critical slope is approximately 54% with a vertical relief of
about 30 feet.
Ascending grades are generally located to the south of'the project, with no apparent slope grades
exceeding 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 ►tpslope 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 omerved 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 Fngineerin;, Geotechnical Report
PO Box 984 page 3 Parcel 12206-13-00110
Belfair, Washington 9f 528 Mason County. Washington
Ph. 360-275-9374 October 2,2019
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.
Bowing and leaning trees were observed on the critical slope. Other slope instability indicators or
signs of significant mass wasting on the property near the planned development were not
observed or discovered during research. Indications of past landslides, current unstable slopes,
deep-seated slope problems, o►•surficial slope failures were not observed during the site visit.
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Aerial Photo fro►n Mason County Website
Fnvirotech Fngineering Gentechnical Report
PO Box 984 page 4 Parcel 12206-13-001 10
Helfair, Washington 9`528 Mason County, Washington
Ph. 360-275-9374 October 2,2019
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was primarily gathered on
September 19, 2019 by a representative with Envirotech. Applicable information on field
methods, sampling, field testing, general geologic conditions, specific subsurface conditions, and
results from soil to:sting are presented in this section of the report. Appendix B of this report
includes pertinent i iformation 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 2 feet below the natural ground
surface. Information on subsurface conditions also included reviewing geological maps
representing the general vicinity of the project, and water well reports originating from nearby
properties.
Soil samples were not obtained from this project. Envirotech measured the relative density of the
near-surface in-situ soils by gauging the resistance of hand tools. Within testing locations, field
testing results generally indicated loose to medium dense soils in the upper 24 inches, and very
dense soils below 24 inches.
3.2 General Geologic Conditions
In general, soils at :he 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, Qe. Quaternary sediments are generally unconsolidated
deposits. and dominantly deposited from glacial drift, including alluvium deposits. 'Phis project is
located within the I:uget 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 rivets. During the Quaternary period, the
Puget Lowland was ,overed by numerous ice sheets, with the most recent being the Fraser glacier
With a peak of app-oximately 14,000 years ago. Upon the glacial retreat, the landscape was
formed by glacial erosion glacial drift deposits.
The "Geologic Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap and Pierce Counties,
Washington" by Michael Polenz, Katelin Alldritt, Nicholas J. Heileman, Isablle Y. Sarikhan, and
Robert I., Logan,July 2009, provides the following caption(s) for the project area:
I-uvirotech F.ngincerin;z Geetechnic:al Report
PO bits y't� page� Parcel 1 2206-1 3-0(ll 1(1
liclfair. Washington 9�52{ Mason County. Washington
11h. 360-275-9374 October 2,2019
a� Landslide deposits Gravel, sand, silt, clay. and boulders in slide body
and toe; due to map scale, includes exposure of'underlying units in scarp
areas: angular to rounded clasts and grains; unsorted; generally loose,
_lurnhled, and unstratified, but may locally retain primary bedding;
cumrnunly includcs liquefaction fcatures.Absence of a mapped slide does
no+ imply absence ufsliding or hazard as sonic slides arc too small to
sho\% at map scale.Althuugh the large Alderwood landslide southwest of
t3c1f:ur rna% have hcen inggci-cd bN ,cisnlrcrty About 1.1 ka(sec Structure).
res rc\� ul"wrial photographs also su e>ts histunc nxnemcnt for this
slide. The unit past-dates Vashon tcc and is predominantly Holocene but
locally may include some late Pleistocene deposits.
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Geological Map Department of Natural Resources Washington State
3.3 Specific Subsurface Conditions
The following subsurface conditions are estimated descriptions of the project subgrade utilizing
information from the depth of penetration at all testing, sampling, observed and investigated
locations. Soils for this project were primarily described utilizing the Unified Soil Classification
System (USCS) and the Soil Conservation Service (SCS) descriptions.
The project is currently composed of native soils without indications of fill. Within test pit
F.nvirotech F.ngineerin„ Geotechnical Report
PO Box 984 page 6 Parcel 12206-13-001 10
Belfair. Washington 9t',528 Mason County, Washington
Ph. 360-275-9374 October 2.2019
locations, soils within the upper 2 feet of natural ground were generally observed to be moist,
brown silty sand wish gravel (SM). Soils below the upper 2 feet layer were observed to be mostly
grey, low moisture, silty sand with gravel (SM), locally known as hardpan. The hardpan may
extend to depths greater than 50 feet. This is based on nearby well reports, site geology, and/ or
knowledge of the general area.
The relative densities of the soil within selected test pits are provided above in Section 3.1.
Expanded and spec fic subsurface descriptions, other than what is provided in this section, are
provided in the soil ogs located in Appendix B of this report.
According, to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Ccnservation Service, the site soils are described as Alderwood Gravelly Sandy
L.uam, A, with 8% - 30% slopes. The soil designations are depicted in the aerial photograph
below, and descriptions are provided in Appendix B of this report.
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Soil Survev from USDA Namral Resources Conservation Sen r<<
3.3.1 Groundwater
From the wt ter well report(s) and knowledge of the general area, permanent groundwater
is at least 75 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.
Fnvirotech F.ngineerin,� Geotechnical Report
PO Box 984 page 7 Parcel 12206-13-001 I0
fich'air. Washington 9028 Mason County, Washington
Ph. 360-275-9374 October 2.2019
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 orde-- to provide an acceptable factor of safety for developing on or near sloping
terrain with relation to current engineering protocol. These factors of safeties are based on
engineering standards such as defining engineering properties of the soil, topography, water
conditions, seismic acceleration and surcharges. Surface sloughing or other types of surficial
slope movements usually do not affect the deep-seated structural capability of the slope.
However, repeated surficial slope movements, if not repaired, may present a threat to the
structural integrity of the slope. If any slope movement arises, the slope should be inspected by an
engineer. Subsequertly, maintenance may be required in order to prevent the possibility of further
surficial or deep seared 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 `Unstable' and `Intermediate' regarding potential landslide activity.
Descriptions of these mapping units may be found in the aforesaid Atlas. A Stability Map from
the Coastal 'Zone At as for the general area of this project is provided below:
Project
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Map from Washington State Department of Ecology Website
F.nvirotech Engineering Geotechnical Report
PO Box 984 page 8 Parcel 12206-13-00110
liell'air.Washing(oil 9028 Mason County, Washington
Ph. 360-275-9 374 October 2.2019
According to the Resource Map from the Washington State Department of Natural Resources
(DNR), the project is not within terrain labeled 'highly unstable' relating to soils. DNR labeled
portions of this project as medium and high slope instability with relation to slopes. A Resource
Map from the DNR Forest Practices Application Review System is provided below:
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1 Moderate dope InStaCruy
rrra• �:a,sta iioa.:..'moon ! 0 High swpe insta'ad+ty
Resource Map frorn 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 val;jes from the static analysis, a quasi-static analysis coefficient of at least 0.15.
and applying the applicable values to STABLE software. Various radii's and center
points of the circle were automatically selected, and produced factor of safeties in a
graphical and tabular format. Worst case scenario values were used in the slope stability
analysis in regards to topography, surcharges, water content, internal friction and
cohesion of the site soils. STABLE software has been repeatedly checked with manual
calculations and consistently proved to be a very conservative program. The following
soil properties were used in the analysis, and are based on observed conditions, known
geology,, and/or published parameters:
Upper? feet soil depth
Soil unit weight: 132 pcf
Angle of int_rnal friction: 30 degrees
Cohesion: 200 psf
F.nvirotrch F.ngincenng Geotechnical Report
PO Box 984 page 9 Parcel 1 2206-1 3-00 1 1 0
Bell'air. Washington 9:4528 Mason County, Washington
Ph. 360-275-9374 October 2.2019
Soils below 2 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. 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'
r Ili Ili III ttI'll 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. Accoirding 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 Loarn 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 :he 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 o•tracking off-site with construction equipment.
The Temporary arc Permanent Erosion Control Section (Section 5.6) of this report consist of
specific erosiojn controls to be implemented. Additional erosion control information and
specifications may be found in the latest addition of the "Stormwater Management Manual for
Western Washijngton," prepared by the Washington State Department of Ecology Water Quality
Program.
4.3 Seismic Considerations and Liquefaction
There are no known faults beneath this project. The nearest Class 'A' or Class 'B' fault to this
property is the Tacoma Fault Zone, which is approximately .5 miles to the south of this project.
This information is based on the USCS 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 Soction provided earlier in this report.
1•:nvrrotrch Engineerirg Geotechnical Report
PO Bux 984 page 10 Parcel 1 2206-1 3-00 1 1 0
Relfair, Washington 9,4528 Mason County, Washington
I'll. 360-275-9374 October 2,2019
i
I
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 potentiz.l 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 t'rom 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 mediutr 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 fDr this project.
4.4 Landslide,.EroAcin and Seismic Hazards ConeluSionS
DNR indicated historic landslide activity near the project. Mapped slope conditions, as delineated
by the Departments of Ecology and/ or Natural Resources, were considered in our slope stability
assessment. Based on the proximity and severity of mapped delineations with respect to the
proposed development, results of the aforesaid slope stability analysis, observed surface
conditions, and other pertinent information, it is our opinion that the proposed development may
occur in accordance with the recommendations in this geotechnical report.
4.5 Lateral Earth Pressures
Retaining walls] may be utilized for this project. The lateral earth pressures exerted through the
backfill of a retaining wall are dependent upon several factors including height of retained soil
behind the wall, type of soil that is retained, degree of backfill compaction, slope of backfill,
surcharges, hydrostatic pressures,earthquake pressures, and the direction and distance that the top
ol'the wall modes. A structural or geotechnical professional should design retaining walls based
on specific conditions.
Soil parameters for :he structural design of retaining walls may be estimated as 134 pounds per
cubic foot (pcl) 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 Oft'-Site Impacts
From a geotechnica. position, it is Envirotech's opinion that the subject property and adjacent
properties to Ithe proposed development should not be significantly impacted if all
recommendations irr this report are followed. This opinion is based on the expected site
development, existing topography, existing nearby development, land cover, and adhering to the
F.nvrrotech Fneinrcnii.i Geotechnical Report
PU Box 984 page I I Parcel 12206-13-001 10
Fiulfarr. Washin;tpm 9,1c522i Mason County. Washington
Ph. 360-275-9314 October 2,2019
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 o� land disturbance near the subject property should be evaluated by a geotechnical
engineer.
I
I
i
I
FnVirotech F.11ginec1.111; Geotechnical Report
PO Box 984 page 12 Parcel 12206-13-001 IU
Hc Ifair. Washington �),52 t Mason County, Washington
I'll. 360-275-9314 October 2,2019
i
I
5.0 ENGINEERING RECOMMENDATIONS
The following secti ins present engineering recommendations for the proposed improvements of
the project. "Chest 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, sing a family residential structure. The recommended allowable bearing capacities and
ments settle as resented below, consider the probable type of construction as well as the field
investigation tjesults by implementing practical engineering judgment within published
engineering st4ndards. 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 bt.aring 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.j
5.1.1 Bearing Capacity
Existin� in-situ soils for this project indicates that the structure can be established on
shallow, continuous or isolated footings. Foundations shall be established on relatively
undisturbed native soil that is competent and unyielding. Alternatively, foundations may
be constructed on selective re-compacted native soil or compacted engineered fill as
described in the Earthwork Construction Recommendations Section of this report.
For a bearing capacity requirement of no more than 1500 psf, a minimum continuous
footing widt-I of 12 inches shall be placed at a minimum of 18 inches below the existing
ground surf,,ce atop unyielding soils. For a columnar load of no more than 3 tons, a
circular or �.quare isolated foundation diameter or width shall be at least 24 inches.
Foundation recommendations are made available based on adherence to the remaining
recommendations that are provided in this report. Alterations to the aforementioned
foundation recommendations may be completed upon a site inspection by a geotechnical
engineet after the foundation excavation is completed.
Envirotech F.ngin ering Geotechnical Report
PO Boa 994 page 13 Parcel 1 2206-1 3-00 1 1 0
Relfair, VJashin�_t�m 98528 Mason County, Washington
11h. 360-275-9314 October 2,2019
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
structu�e, reduction of pore water pressure, and in some instances, the infiltration of free
moistu•e. Fused on the expected native soil conditions, anticipated development, and
constriction abides by the recommendations in this report, the assumed foundation
systems may undergo a maximum of 1.0 inch total settlement, and a maximum differential
settle"'I
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,i granular material (Retained on U.S. Sieve #10 or greater) that is placed over
Undisturbed, competent native subgrade or engineered fill per the Earthwork
Recommendations Section below.
The recommendations for interior concrete slabs-on-grade as presented herein are only
relevant for the geotechnical application of this project. Although beyond the scope of
this report, concrete slabs should also be designed for structural integrity and
environmental reliability. This includes vapor barriers or moisture control for mitigating
excessive moisture in the building.
5.2 Earthwork Construction Recommendations
i
Founding mat t rial 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 tl� the extents provided in this Earthwork Construction Recommendations Section.
The followings recommendations include excavations, subgrade preparation, type of fill, and
placement of fill for building foundations.
5.2.1 Excavation
tExcavaLlon is recommended to remove any excessive organic content or other deleterious
material, if present, beneath foundations and to achieve appropriate foundation depth.
Additional �-ub-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 ;;hall be competent, and relatively undisturbed or properly compacted fill. If
these soils t.re disturbed or deemed incompetent, re-compaction of these soils below the
anticipated footing depth is necessary. Excavations shall be completely dewatered,
compacted, and suitable before placement of additional native soil, engineered fill or
structural concrete.
Envirotech lingineenlig Geotechnical Report
PO Box 984 page 14 Parcel 1 2206-1 3-00 1 1 0
tielfair, Washingt�m 9�S2S Mason County. Washington
Ph. 360-27 -93i74 October 2,2019
5.2.2 placement and Compaction of Native Soils and Engineered Fill
i
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.
COMPACTED -SOOTING
NATIVE SOILS
OR ENGINEEREFTLL
D t
i
h
UN ISTURBED St?BLRA
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 __- °/r Finer(by weight)
_ 6" _ _ 100
3" 60— 100
No. 4 20—60
No. 200 0- 8
Table 1
Particle Size Distribution of Engineered Fill
Compaction shall be achieved in compacted lifts not to exceed 6 inches for both native
soils and engineered fill, respectively. Each lift should be uniformly compacted to at least
95% of the modified Proctor maximum dry density (ASTM D 1557) and within 3% of
optimum moisture content. Each lift surface should be adequately maintained during
construction in order to achieve acceptable compaction and inter-lift bonding.
Temporary earth cuts and temporary fill slopes exceeding 4 feet in height should be
limited to a slope of 2:1 (horizontal:vertical). Utility trenches or other confined
excavations Exceeding 4 feet should conform to OSHA safety regulations. Permanent cut
and fill slopes shall be limited to a slope of 2:1, unless otherwise approved by an
engineer.
Fnvirotech Higineerin;? Geotechnical Report
PO Box 984 page 15 Parcel 1 2206-1 3-00 1 1 0
Bc1l"air. Washington 9,528 Mason County, Washington
Ph. 360-275-931.4 October 2.2019
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 E5%, 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 t/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 Might equipment such as a hand-held power tamper. If
clean, coarse gravel soils are utilized as engineered fill, and surcharges will not influence
the retaining; wall, compaction may be achieved by reasonably densifying granular soils
with construction equipment.
5.2.4 Wet Weather Considerations
Due to the types of subsurface soils, additional provisions may be required during
prolonged wet weather. Every precaution should be made in order to prevent free
moisture from saturating the soils within excavations. If the bottom of excavations used
for footing Placement changes from a moist and dense/ hard characteristic as presented in
this report to muck or soft, saturated conditions, then these soils become unsuitable for
foundation bearing material. If this situation occurs, a geotechnical engineer should be
notified, and these soils should be completely removed and replaced with compacted
engineered fill or suitable native material as presented in this section.
5.2.5 building Pads
Building pads for this project, if utilized, shall be constructed per the fill placement and
compaction recommendations as presented above. Both engineered fill and native soils
may be used for building pads. Building pad slopes shall be no steeper than 2:1 for both
compacted engineered fill and re-compacted native soils used as fill. Building pad fill
shall be "keyed" into the existing subgrade to a depth of at least 2 feet below the existing
ground surf,.ce. The term "keyed," as used here, implies that the interface between the
building pad and subgrade is horizontally level, Alternatively, building pads may be
keyed into the subgrade to the above specified depth, and stepped. Stepped fill should be
keyed into the subgrade at a minimum width of 10 feet. All footings shall be located at
least 5 feet away from the top of the engineered fill slope.
Fnvuntech F.nginperimt Geotechnical Report
PO Box 984 page 16 Parcel 12206-13-001 10
Relfair, Washingti)n 9�528 Mason County, Washington
I'll. 360-275-9374 October 2,2019
5.3 Building and Footing Setbacks
Provided that assumptions relating to construction occur and recommendations are followed as
prevenEed in this re?ort, the factor of safety for slope stability is sufficient for a 50 feet footing
setback from the face of the nearby descending slopes exceeding 40%. See the figure below and
the Site Plan in Appendix A for an illustration of the setbacks.
STRUCTURE
TOr' Oc
Sl UPE SL7PE
i
i
-- SETBACK OC]'ING
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
i may be reduced by ritigation, and subsequently would require additional geotechnical studies.
5.4 Surface and Sttbsurface 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 ,eotechnical 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 due to shallow permeable soils. Roof downspout dispersion on splash blocks should be
employed. Driveway runoff may sheet flow over natural vegetated or re-vegetated areas.
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.
F:nvn'utrch F.ngintcrin!' Geotechnical Report
110 Box 984 page 17 Parcel 12206-13-00110
Belfair. Washington 9,�528 Mason County, Washington
Ph. 360-275-937=1 October 2,2019
Vegetation Buffer— Vegetation shall not be removed from the face of the critical slope or within
a distance of 25 feet beyond the top of the descending 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 veg-nation buffer.
5.6 Temporary and Permanent Erosion Control
F.I'OSlon 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 treasures a-e 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 recornmended locations for erosion control
facilities to be instal ed 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 n-.placement, when necessary, of permanent erosion control, vegetation,
drainage structures and/or features.
5.7 Septic DraintielAs
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 MU ation
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.
I•:nvirotech Fnginec inp; Geotechnical Report
Pt) Box 9K 4 page 18 Parcel 12206-13-001 10
Helfair, Washington 98528 Mason County,Washington
Ph. 360-27.5-9374 October 2,2019
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 di Yerent 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 recurnmendations 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 optima 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 developmc nt, 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
Jessica I_egarza,M.S. Michael Staten, P.E.
Staff Geologist Geotechnical Engineer
Fnvirotech Engineering Geotechnical Report
PO Box 984 page 19 Parcel 12206-13-001 10
Helfair, Washington 9,528 Mason County, Washington
Ph. 360-275-9374 October 2,2019
APPENDIX A
SITE PLAN
SCALE, i INCH= 150 FEET
,
SO FT COTEi'TfNA-Mk
SETBACT. ;Mh! 'FL£ EF A?PRD'.ft>k�T:
APPROXIMATE �'R"ICAL 2_.C}$
TOP OF SLOPE PRa`IjSU i1 Pp4" / LW OF UT
EXCEEDING a0'G �Dlt'_W'EkxY f APPROXIMATE
PRCPGSt2 SINGLE ( rTOE OF SLOPE
Flifs[L'f T,E SIDENCE i i' EXCEEDING AM
\ 1 T 'ER7T TINE 1 j /
4442 \ Yi^�,^_—.yam.—„• i ♦'
i
APPROXIMATE \ 44 / ; ' n �ti�` `\t$ q�• ,{p
TOE OF SLOPE 11r1lYCFD 1
EXCEEDING 4011. \ I]R::irsl-ItU MLA `
W -T ^OHSTRUCTION f \29 FT R7EGET:ITILW
L 25 F7 LEWJ--rE*I FAjX CF Eprrg:AL
REM17 i;l=F=1t FRa+. SETTeNLh. FFyM FACE C1F
FACE OF .;9ITIC.IL t-IPE MrTCCCAL SLOPE SlCli"E
NOTES, 7RMM/OWNEW LMATMN,
L EROSION CONTROL IaaT BE BE6tT.Blp R FaR IT®:S3TE:fij:ME - LanATMNS SINGLE FAWLY RESIDENCE
ARE DEPICTED, AND ALTO"ATIYEX MAY rK UTnTxn AS E)0"L4T;IW THE GEl7TECHFd=CAL REPORT
GEIITECtt,ICAL REPOR',
2.CONTMIRS WERE NOT ►401W,ED P. A LZVDZ-ZD 1-00 SIIRWEYUR, LANKM
CONTOURS WERE ExTRpFO_ATER FPJP;A FIJV-C LOIAR>eL'LI F-Vil - _ — f ice%EAST Rk"QA14
INCORPORATED FIELD t'Eh3.> +.TS AS Sa9'"VCD Dt T�f 3MTECWCAL LEGEtO I P09CEL V-ZZ 1a WOO
REPORT 74ktrN 1riWrY.VAVURQ.MN
3. BOUNDARIES WERE FE7 nEPA?0 BY A I MDAEn*URV'EYI1R.LacAIIONS TLTWLFwav k"ili<7tFTX�
OF SITE-EATURES T.V-49C OC'„'LS MZ,°AXV.RS T]F OF ILIPEX,TOE +4--r�=.y CONTROL
OF SLOOPES. WATER FEAlVj E3.ETC,WITH 1,*.T70M TO 74E PW%4)fTY E)N���EQ��NG
LINES MUST BE WERii"IED T VW WMER,WCOFX4El10AT70=IX 7ME �Sa yy,qr� INDICATOR
GEOTECK,CAL REPOR' PODYDL S£7F.K04%FFERS.B'EPTHS.FTC, VITH BELFP,RG W043,05-TN 96526
RCLATMN TD GECLOGR;F�4.TLREO,REI7 Pk7lER7 UK$. TNFX:W]LOGIC �06— EX:XTD:G CONTOUR awl{
PROPERTIES.S. Y BE =VEA M THE S11�T PROPERTY ON)&iPWI 1t>Nv TPle TEST PI7 SITE PLAN
APPENDIX B
SOIL INFORMATION
II
HE ijE:.,4SE SILT r 4A.Ib
jo;,
i �•—.� "__ _ _ JWT,.WG URArE
LINSI LLAU41- TILL
SECTION =-a
UWNM/LOrr.TMN.
&UkGf FAMILY RESIDENCE
GEUTECHNICAL REPORT
NOTES, Irk Tr, WAS14NGTON
1, MINUi( 644U LKA%,,0 WEU�]+Ell IN OWVER 10 A.HIEVE ""m TrL`4 ENEAHEERI%",,
I POSITIvE DRAINAGE PO=ft4
23 IHE SOIL
PQOFILE IS A::URA-.E FEW Ilt DEPTH OF MI.F-A)3t.VASHIICTDN 9WV.s
THE OBSERVED TEST PITS Al THE SVEZIrICr LOCATIOI.S 0
L '31 _4_
LOVER DEPTHS ARE BASED ON & CEOLMY.
WELL LOG(S). AND/OR EXFTR*,ENCE -4 THE rEmErAl AREA SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
NIR'DjEt T: Lansing Ga technir al Repott (SATE OF LOG: 9/19=19
PROJECT NO: LOGGED BY: MCS
CLIENT: Brad Lans+'ng EXCAVATOR: NIA
LOCATION: E Rasor Road DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INI*IAI nFPTI- OF dVATF-R: N/A FINAL OFPTIA OF WATT= : NJA
SOIL STFLAT.q. STANDAROPENETRATWNTEST
DEP7 N SAMPLERS U3CS DESCRIPTION LL PI CU'RVe
AND TEST DATA DEPTH N 10 30 50
0 _. .
SM Medium brown,moist,medium dense
SILTY SAND with GRAVEL.Gravel is
1 primarily well-graded and subrounded.
Sand Is mostly medium.No plasticlty.
Light brown,very dense glacial till @ 2'
2
Excavation terminated at approximately 2
feet
3
4
5
6
8
g
10
IE-
'4y sr jfvj e EN`JIROTECM ENGINEERING
TirgOpw"**'tsrrlx fm rais vbtxa r L�3nu 'w: rxw t391 h/1 vl BI 't(jIY:13fl;Ir�
vokw sa mer ut;Stir,8 ;4&x;d
Map Und n@5G11)tmn AkidlWPld gtavaily sandy loom, 15lo W pou:onl slopos..-Mastm
Counly WaShmUlon
Mason County, Washington
Ac—Alderwood gravelly sandy loam, 15 to 30 percent slopes
Map Unit Setting
National map unit symbol: 2t627
Elevation: 0 to 1,000 feet
Mean annual precipitation: 25 to 60 inches
Mean annual air temperature 46 to 52 degrees F
Frost-free period. 160 to 240 days
Farmland classification. Farmland of statewide importance
Map Unit Composition
Alderwood and similar soils 85 percent
Minor components: 15 percent
Estimates are based on observations.descriptions.and transects of
the rnapunit.
Description of Alderwood
Setting
Landform: Ridges,hills
Landform position(two-dimensional). Backslope
Landform position(three-dimensional). Side slope,nose slope,talf
Down-slope shape Linear,convex
Across-slope shape Convex
Parent material: Glacial drift and/or glacial outwash over dense
glaciomanne deposits
Typical profile
A-0 to 7 inches: gravelly sandy loam
Bw1-7 to 21 inches very gravelly sandy loam
Bw2-21 to 30 inches very gravelly sandy loam
Bg-30 to 35 inches: very gravelly sandy loam
2Cd1-35 to 43 inches. very gravelly sandy loam
2Cd2.43 to 59 inches very gravelly sandy loam
Properties and qualities
Slope 15 to 30 percent
Depth to restrictive feature: 20 to 39 inches to densic material
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat): Very
low to moderately law(0.00 to 0.06 in/hr)
Depth to water table: About 18 to 37 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile Very low(about 2.7 inches)
Interpretive groups
Land capability classification(irngated). None specified
Land capability classification(nonirngaled): 4e
Hydrologic Soil Group. B
t Jilt Natural Resources Woo s w Suivu 12;10t2018
�Oilliilll Conservation Service Natanai Cooperative Sou Sun'ey Page I of 2
hicip Unit 11)(4senplion Aldolwo,ld g1fivelly smuly kmill. 15 in:10 parcont siopt)s--fjasoll
Counly.Vinswigion
............................. ....... ........... ............-
Forage suitability group: Limited Depth Soils(G002XS301WA),
Limited Depth Soils(G002XF303WA).Limited Depth Soils
(G002XN302WA)
Hydric soil rating. No
Minor Components
Everett
Percent of map unit: 5 percent
Landform- Karries,eskers.moraines
Landform position(two-dimensional): Backsiope
Landform position(three-dimensional). Side slope
Down-slope shape: Convex
Across-slope shape: Convex
Hydric soil rating: No
Indianola
Percent of map unit: 5 percent
Landform: Eskers,kames.terraces
Landform position(three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape. Linear
Hydric soil rating. No
Shalcar
Percent of map unit: 3 percent
Landfonn: Depressions
Landform,position(three-dimensional), Dip
Down-slope shape: Concave
Across-slope shape Concave
Hydric soil rating Yes
Norma
Percent of trap unit 2 percent
Landform. Depressions.drainageways
Landform position(three-dimensional). Dip
Down-slope shape. Concave,linear
Across-slope shape: Concave
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Mason County,Washington
Survi!y Area Data: Version 14,Sep 10.2018
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APPENDIX C
SLOPE STABILITY
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APPENDIX D
EROSION CONTROL
GEo za 14- 00080
Mason County Review Checklist
for a Geotechnical Report
Instructions:
This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report is reviewed
for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the Report should
explain the basis for the conclusion. The Report is also reviewed for clarity and consistency. If the drawings,
discussion, or recommendations are not understandable, they should be clarified. If they do not appear internally
consistent or consistent with the application or observations on site, this needs to be corrected or explained. If
resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director.
Applicant's Name: VO JTE Q-V£(_ 0
Permit#: W ZO 11-0,006(1 Parcel#: 122b(0' l3 ^ 00 ! ) O
Date(s) of the Document(s) reviewed: 1—(6-ZO
1. (a) A discussion of general geologic conditions in the vicinity of the proposed development,
OK?_X Comment: .S7crld#4j 3 . 2
(b) A discussion of specific soil types
OK? c Comment: SE CT l0 Pj 3.3
(c) A discussion of ground water conditions
OK?_X Comment: 5ECT-I0N 3.3 • 1
(d) A discus ion of the upslope geomorphology
OK?_ Comment: SF C.T(0 o'V 2. 2.
(e) A discussion of the location of upland waterbodies and wetlands
OK? X Comment: .-src ct o-J Z•3. f
(f) A discussion of history of landslide activity in the vicinity, as available in the referenced maps and records
OK? ( Comment: vriff(-TtOAJ Y.
2. A site plan that identifies the important development and geologic features.
la
OK? /� Comment: St'T7 FG'0 J "A-f PFN a Y 14
3. Locations and logs of exploratory holes or probes.
OK? Comment: 61� PLAN `�- 501 L ( pG1 rj
4. The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall
be delineated (top, both sides, and toe) on a geologic map of the site.
OK? X Comment: SITS ?(-APJ
5. A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which
incorporates the details of proposed grade changes.
OK? \)( Comment: a,0 DEN iD i X
6. A description and results of slope stability analyses performed for both static and seismic loading conditions.
Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of
Circles. The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1 and the quasi-static
analysis coeffients should be a value of 0.15.OK?�X Comment: �ECTc 0'J 4. 1 1 • '
7. (a) Appropriate restrictions on placement of draingge features
OK?_ Comment: JECZ t 0"' �}
(b) Appropri to estrictions on placement of septic drain fields
OK? Comment: Jk(T IN 5.1
(c) Appropriate restrictions on placeme t of compacted fills ad footings.
OK? _Comment:
Page 1 of 2 Form Effective June 2008
(d) RecomTpnded buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? Comment: zn
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK?_ C Comment: S7•2`3
8. Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies
vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation
removal.
OK? Comment: "Se CT t0 N 13 ,5
9. Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific
mitigating measures to be implemented during construction to protect the slope from erosion, landslides and
harmful construction methods.
OK? Comment: S'EcZ tb'nJ �t•2-
10. An analysis of both on-site and off-site impacts of the proposed development.
OK? Comment: CTt 0 . • �(
11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
OK? Comment:
12. Recommendations for the preparation of structural mitigation or details of other proposed mitigation.
OK? n Comment: _'�E CT1004 '5 - 1 — k OT Al E C'E S
13. A site ma drawn to scale showing the property boundaries scale north arrow anYJ the location and nature of
P 9 P p Y
existing and proposed development on the site.
OK? Comment: Jt-t:F (cA- J
Are the Documents signed and stamped?-� By whom? At CH At L ST PrT'r"N
License#: (4 3 Q Li) License type: PE
FIRST REVIEW Approved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
11
Reviewed by on ( ''1 ^Z� Time spent in review:
SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info.
Reviewed by on . Time spent in second review:
THIRD REVIEW/ UPDATE ❑ Approved ❑ Need more info.
Reviewed by , on . Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
Page 2 of 2 Form Effective June 2008