HomeMy WebLinkAboutGEO2012-00058 for BLD2012-00887 - GEO Geological Review - 12/21/2012 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
i (360)427-9670
Geotechnical ReportReview Acceptance Letter
December 21, 2012
GREG RIVERS
3439 SACRAMENTO ST. STE. 203
SAN FRANCISCO CA 94118
Case No.: GE02012-00058
Parcel No.: 122321001030
Proiect Description: GEO REPORT FOR REPLACEMENT SFR (SEE BLD2012-00887)
The Geotechnical Report for GREG RIVERS has been received and reviewed by the Planning
Department. The report was prepared by Michael Staten dated 9/7/2012.
Based on the certification provided by the licensed engineer/geologist, the referenced
Geotechnical Report was prepared in general accordance with the requirements in the Mason
County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.5. Mason County considers
the review valid until such time as scope of project, site conditions, and/or regulations change.
Should the scope of work, site conditions, and/or regulations change after the original review, then
an addendum from the original author of the report may be required to address these changes.
The report would only be re-reviewed if a permit for development were submitted after these
changes occur. Mason County does not certify the quality of the work done in this Geotechnical
Report.
Please contact me at (360) 427-9670, ext. 365 if you have questions.
Sincerely,
Allan Borden
Land Use Planner
Mason County Planning Department
Comments:
12/21/2012 Page 1 of 1 GE02012-00058
t a ~ ow 58 RECEIVED
Nov z 8 20`12
426 W. CEDAR ST,
TO BE KU"T IN THE PLANNING
PARCEL FILE
-------------
Geotechnical Report
for
Single Family Residential Replacement
6600 E Grapeview Loop Road, Allyn
Parcel No. 12232-10-01020 & -01030
Mason County, Washington
September 7, 2012
Project#1288
Prepared For:
Greg Rivers
C
6600 E Grapeview Loop Road �GQ`PWAS
D
Allyn, Washington 98524
Prepared By:
P 43045
Envirotech Engineering OA FCISTER�
PO Box 984 SSIONALti�G
Belfair, Washington 98528
Phone: 360-275-9374
Fax: 360-275-4789
Mason County Department of Community Deyeiopment
SuiirtllKiai t,nCGKfiS?i or a Geoiiechnicat B2Rq t
instructions:
This checklist must be submitted with a Geotechnical Report and completed,signed; and stamped by the
licensed professional(s)who prepared the Geoiechnicat Report for review by Mason County pursu_nt to
th--Mason c:ou lty resource 0wd tmance- I. a3 i i+c-ya found to be not appticabie,the report should explain
the basis for the conciusion
ApplicanI10%,ner Parcel# -0t030
Site Aud�ess 66o� G��,oe✓;
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed developinneet,
Located on page(s)
(b) A discussion,of specinc soli • ppes
Located on page(s) 7
(c) A discussion of ground water conditions
Located an.page's'
(d) A discussion of the up�lope geomorphology
i_uc:aied on pages)
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s)
i Y UESC�ISSEUfi 3i f3t5Lvey or iandsude activity in the activity in the vicinity,as available in the
referenced maps and records
Loca:cd on page's, 9 /�
(2) A site plan whicb identifies the importf�' nt development and geologic features.
Located on Map(s) S,Ft' 15rGn
(3) Locations and logs of exploratory holes or probes-
�VLiGICU bltt 1Vijapi3f �il��r/yl e�- .'t _T a
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and
setbacks shall be delineated(fop; both sides,and toe)on a"geologic map of the site.
Located or Es Mapts`)
(5) A minimium of one cross section at a ale which adequately depicts the subsurface profile, and
Which incorporates the details�of proposed grade changes.
:_;ju iati uEl iviaY )0YryF, ;13
(6) A de--ription and re:uNe of slope stabliity analyses performed fir bo"m sta-tic and seismic i-oadin.g.
conditions_Analysis should examine worst case failures_The analysis should include the
�i nts :v t�.isi iu .iit3 ti3Li d's�Wkees_!he ins hka tmi static se factor
fic IS 1_5,Etta i iii3liiill313
seismic safety factor is 1-1.and the quasi-sta analysis cxeffi tents should 13'e a value of 0_15-
Located an page(s) // Ta„ " C
(7) (a)opnropriate restrictions on placement of drainage features
Located on page(s) /0
(b) Appropriate:asinctions on plaGernent of sepfic drain.fields
Located on page(s) Zo
c` Ap ra i late rash ictior its on placement or compacted fills and footings
e p p-.l.�- P 9
Located on pages) /5 /7
Page 1 of 2 Form Effec:t_!ve June 2008
DisciaiiF,er: Mason County does not certify the quality Qf the work done in this Geotochr.,-,i;
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property-
Located on page(s) /9
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other siopes on the property
Located on page(s)
(8) Recornini endaiions for the preparation of a detailed clearing and grading plan w sic:i SYec.iriveiiy
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, iandslides and harmful construction methods.
Located on page(s)
(iv) An analysis of troth on-site and off-site impacts of the proposed development.
Located on page(s) it
(i i) Specifications of final development conditions such as, vegetative management,drainage,
erosion control, and buffer widths.
Located on page(s) /g -ZO
(9 2) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s) ZQ
(13) A site map drawn to scale showing the property.boundaries,scale,-north arrow, and the location
and nature of existing anij proposed development on the site.
Lonnie d on WapCb) ,���`7t / 14n
t, c a6A �' hereby certify under penalty of
per)ury brat ii am a cM engineer Wised Ln the State of Washington wiffi spedefted knowledge of
geotechnica lgeologicai rIngineaaIng or a geolc;gist or;ra-tgi rg get ftensed En u3e S#ata of
x_ rarer"4sa:4:.:_y::ig +r �.'.3 he i' :B;C'em-'d"mis.i a-Lr'--f1p�,Y i�at�.i-3 5�����`'�';lGa'.'-
v-
Report.dated ✓-!��7� 2OJ 2- ,and entitled 4"'
SI►r��y riy,�n.`j� /C PS`��t'�� �PDIPC.er�R� fE'Fe�S �i3h2 f�il�isa"�R7t'S. f3a'u"��eLUdcSG�n
Oounty Resawce Ordinance.Landslide Hazard Section,is=npWe and true,mat the assessment
demonstrates conclusively that the risks posed by the:andslide hazard can to mitigated through the
inciuded 8gumachnicai udesi jge i r eccm u`enda�iGns,anUd That fig hazards am a'i?itfgaEaC+in such a manner as
to g33 aYer±$ �;:fto pnn r�y s;sob"e- :3e_�> D and s`'a. _i d S`aa6£t�� �7{,�A^ p
y` -, 430'r3 O �w
AL
Page 2 of 2 Form Effective June 2008
3ise!air.en kgascn County aces not cartIN,the quality of the wort:done In this GaoM'Chnical ep`!
TABLE OF CONTENTS
1.0 INTRODUCTION....................................................................................................................................................I
1.1 PROJECT INFORMATION........................................................................................................................................1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK.............................................................................................2
2.0 SURFACE CONDITIONS ......................................................».4
2.1 GENERAL OBSERVATIONS.....................................................................................................................................4
2.2 TOPOGRAPHY........................................................................................................................................................4
2.2.1 Upslope GeonatphokV.............................................................................................................................4
2.3 SURFACE DRAINAGE.............................................................................................................................................4
2.3.1 Upslope Water Bodies..................................................................................................................................5
2.4 SLOPE AND EROSION OBSERVATIONS...................................................................................................................5
3.0 SUBSURFACE INVESTIGATION...............».......................................................................................................6
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...............................................................................................6
3.2 GENERAL GEOLOGIC CONDITIONS.......................................................................................................................6
33 SPECIFIC SUBSURFACE CONDITIONS.....................................................................................................................7
311 Groundwater................................................................................................................................................8
4.0 ENGINEERING ANALYSES AND CONCLUSIONS..»»».»»»»........»...»»»....»»....»».».....»....»».».»»».».»».9
4.1 SLOPE STABILITY..................................................................................................................................................9
41.1 Slope Stability Analysis..............................................................................................................................11
4.L2 Slope Stability Assessment.........................................................................................................................12
4.2 EROSION..............................................................................................................................................................12
4 2.1 Shoreline Recession...................................................................................................................................13
43 SEISMIC CONSIDERATIONS AND LIQUEFACTION.................................................................................................13
4 3.1 Liquefaction...............................................................................................................................................13
4.4 LATERAL EARTH PRESSURES..............................................................................................................................13
4.5 ON-SITE AND OFF-SITE IMPACTS.......................................................................................................................14
5.0 ENGINEERING RECOMMENDATIONS....»...................................................................................................15
5.1 BUILDING FOUNDATION RECOMMENDATIONS....................................................................................................15
5.L1 Bearing Capacity.......................................................................................................................................15
5.1.2 Settlement...................................................................................................................................................16
5.1.3 ConcreteSlabs-on-Grnde..........................................................................................................................16
51 EARTHWORK CONSTRUCTION RECOMMENDATIONS..........................................................................................16
5.2.1 F-Wavadan.................................................................................................................................................16
5.22 Placawent and C,ompactrion of Nadve Soils and Engineefrd Fill............................................................17
5.23 Retaining Wall BadgV.............................................................................................................................18
5.Z4 Wet Weather Considerations.....................................................................................................................18
53 BUILDING AND FOOTING SETBACKS...................................................................................................................18
5.4 SURFACE AND SUBSURFACE DRAINAGE..............................................................................................................18
5.5 VEGETATION BUFFER AND CONSIDERATIONS.....................................................................................................19
5.6 TEMPORARY AND PERMANENT EROSION CONTROL...........................................................................................19
5.7 SEPTIC DRAINFIELDS..........................................................................................................................................20
5.8 STRUCTURAL MITIGATION.................................................................................................................................20
6.0 CLOSURE »........................................................................................................................................».....21
Appendix A-Site Plan
Appendix B-Soil Infonnation(Soil Profile;Soil Logs;Well Reports)
Appendix C-Slope Stability Input&Output
Appendix D-Erosion Control
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechnical investigation for a single
family residential property located at 6600 E Grapeview Loop Road, identified as parcel number
12232-10-01020 and 12232-10-01020, 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,
Greg Rivers, in support of the proposed development as detailed below. The proposed
development, as provided herein, and the surrounding area is identified in this report as the
Project.
An initial geotechnical evaluation of the Project was conducted by Envirotech on September 3,
2012. 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 abode, concrete bulkhead, driveway
and other ancillary features. The planned development consists of a 1- or 2-story single family
residence to be mostly within the existing structural footprint. Foundation construction is
expected to consist of continuous strip footings with concrete slabs-on-grade or stem walls.
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.
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 1 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax:360-2754789 September 7,2012
1.2 Purpose of Investigation and Scope of Work
g Pe
The purpose of this geotechnical investigation is to assess geological hazards, and evaluate the
Project in order to provide geotechnical recommendations that should be implemented during
development. The investigation included characterizing the general Project surface and
subsurface conditions, and evaluating the suitability of the soils to support the planned site
activities.
In order to fulfill the purpose of investigation, the geotechnical program completed for the
proposed improvements of the Project include:
• Review project information provided by the Project owner and/ or owner's
representative;
• Conduct a site visit to document the site conditions that may influence the construction
and performance of the proposed improvements of the Project;
• Define general subsurface conditions of the site by observing subsoils within test pits
and/ or cut banks, review geological maps for the general area, research published
references concerning slope stability, and review water well reports from existing wells
near the Project;
• Collect bulk samples 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.
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 2 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax:360-275-4789 September 7,2012
21
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Vicinity Map from Mason County Website
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 3 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax:360-2754789 September 7,2012
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on
September 6, 2012 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 Grapeview Loop Road, an existing paved roadway. The Project is
currently developed land as previously mentioned. The access road extends along the western
boundary of the property, and Case Inlet borders the parcel to the east. Beyond the property,rural
residential development exists. Vegetation on and near the Project consists primarily of secondary
growth firs, cedars, huckleberry,and other trees and shrubbery common to this area of the Pacific
Northwest. An aerial photo of the Project and immediate vicinity is provided on the following
page.
2.2 Topography
The topographic information provided in this section was extrapolated from a public lidar source,
and incorporated observations and field measurements. Where necessary, slope verification
included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site
Plan in Appendix A in this report for an illustration of general topography with respect to the
planned development.
Critical descending slopes, with grades exceeding 40%, are located adjacent to the existing deck.
The maximum critical slope is approximately 70% with a vertical relief of approximately 16 feet.
This descending slope is followed by a level bench of over 10 feet, and an approximate 5 feet
high bulkhead.
Ascending grades are generally located to the southeast of the planned development. These slopes
are relatively minor within 300 feet of the Project,with no apparent slope grades of at least 15%.
2.2.1 Upslope Geomorphology
The upland area of the property is situated on a gentle sloping hillside of glacial origin.
23 Surface Drainage
Stormwater runoff originating upslope from the anticipated development appears to primarily
sheet flow, and is expected to be minimal to moderate. Runoff originating upslope of the property
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 Rivers Geotechnical Report
PO Box 984 page 4 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-275-4789 September 7,2012
2.3.1 Upslope Water Bodies
There is an apparent water body located upslope from the property, and at least 1000 feet
away from the house.This water body does not appear to affect the planned development.
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.
Both leaning and bowing trees were observed along the shoreline. Other significant slope
instability indicators were not observed. Indications of deep-seated slope problems were not
observed during the site visit.
"r r
E NELSON RD
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4
Aerial Photo from Mason County Website
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 5 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax: 360-275-4789 September 7,2012
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the Project was primarily gathered on
September 3, 2012 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 water well report(s). Water well reports were
utilized to estimate ground water levels, and if sufficient,were used in identifying subsoil types.
Additional well reports than what is provided in this report may be available from Envirotech
upon request.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 3.5 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 24 inches, and very
dense soils from 42 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 Vaughn 7.5-minute Quadrangle, Pierce and Mason Counties,
Washington"by Robert L. Logan and Timothy J. Walsh,December 2007, provides the following
caption(s)for the project area:
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 6 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax:360-275-4789 September 7,2012
Q9t V:ashon till--Unstratified to moderately stratified.compact_unsorted mixture of clay. silt. sand.
and gravel deposited directly by glacial ice: gray to tan: nearly evenzrhere in sharp contact with
underlying units:does not drain n•ell as permeability and porosity are low-: sand and finer grains
in matrix are very angular.pebble-to boulder-size clasts are commonly striated and faceted,
having angular and(or)rounded edges:boulders are generally disseminated and relatively rare:
may contain interbeds of sand and gravel. The surface of this unit is characterized by streimlined
drunthns. striations.and flutes that are generalh•hundreds to thousands of feet long Angular to
subrounded glacial erratic boulders. consisting mostly of plutonic or metamorphic rock-.are
connmon but disseminated on the surface of this unit.Unit may be capped by a few feet of
unsorted and stained ablation sand and gravel or by unit Qgos. Vashon till locally crosscuts older
sediments. forming angular unconformities Drag folding and horizontal shearing may occur at
the base of the till or internally between layers of till_especially in thick deposits Unit Qgt
ranges in thickness from 0 to at least 50 ft.
Beach deposits—Niud. sand. and gravel deposited in the intertidal zone. or residual
Ob
pebble-cobble gravel and isolated boulders on a wave-cut platform.
33 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 borrowed fill. Within test
pit locations, soils within the upper 3.5 feet of natural ground were observed to be moist, brown
silty sand with gravel (SM). Soils below the upper 3.5 feet layer were observed to be low
moisture, silty sand with gravel (SM), locally known as hardpan. The hardpan may extend to
depths greater than 30 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 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 lowland site soils where development is expected to
occur are described as Alderwood Gravelly Sandy Loam, Ab,with 5% - 15% slopes. The upland
site soils are delineated as Sinclair Shotty Loam. The soil designations are depicted in the aerial
photograph below,and descriptions are provided in Appendix B of this report.
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 7 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-275-4789 September 7,2012
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Soil Survey From USDA Natural Resources Conservation Service
3.3.1 Groundwater
From the water well report(s)and knowledge of the general area, permanent groundwater
is at least 40 feet directly below the property at the building pad location. 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
during some or all wet seasons.
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 8 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax: 360-2754789 September 7,2012
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' regarding potential landslide activity. Stable slopes are generally not
prone to landslides due to small grades and accommodating geology. 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 Rivers Geotechnical Report
PO Box 984 page 9 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax:360-275-4789 September 7,2012
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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 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 Rivers Geotechnical Report
PO Box 984 page 10 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax: 360-2754789 September 7,2012
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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
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
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 11 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-275-4789 September 7,2012
soil properties were used in the analysis, and are based on observed conditions, known
geology,and/or published parameters:
Upper 4 feet soil depth
Soil unit weight: 134 pcf
Angle of internal friction: 33 degrees
Cohesion: 0 psf
Soils below 4 feet in depth
Soil unit weight: 140 pcf
Angle of internal friction: 40 degrees
Cohesion: 400 psf
Based on the slope stability analysis, a minimum factor of safety was determined to be
1.0 relative to static slope failures, and 0.7 with relation to seismic conditions. These
factor of safeties 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 over 1.5 and 1.1, respectively. See the slope stability information in
Appendix C for a depiction of input parameters and example of outputs.
4.1.2 Slope Stability Assessment
DNR did not indicate previous landslide activity near the Project. Mapped slope
conditions, as delineated by the Departments of Ecology and 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 an evaluation of the shoreline
recession rate, it is our opinion that the proposed development should occur in
accordance with this geotechnical report.
4.2 Erosion
Based on the USCS description of the Project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,
the Project is not within terrain labeled `highly erodible.' This Project is not within an erosion
hazard area as defined by the MCRO. Erosion hazard areas are those with USDA SCS
designations of River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on
slopes 15% or greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd),
Harstine Gravelly Sandy Loam on slopes 15% or greater (Hb), and Kitsap Silt Loam on slopes
15%or greater(Kc).
It is our opinion that minor erosion control recommendations provided in this report is sufficient
for the development of this Project, and additional 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
Envirotech Engineering Rivers Geotechnical Report
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Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax:360-275-4789 September 7, 2012
of the soil, and amount of rainfall during construction. Soil erosion typical to the existing site
conditions and planned disturbance of the Project include wind-borne silts during dry weather,
and sediment transport during prolonged wet weather. Sediment transport could be from
stormwater runoff or tracking off-site with construction equipment.
The Temporary and Permanent Erosion Control Section (Section 5.6) of this report consist of
specific erosion controls to be implemented. Additional erosion control information and
specifications may be found in the latest addition of the "Stormwater Management Manual for
Western Washington," prepared by the Washington State Department of Ecology Water Quality
Program.
4.2.1 Shoreline Recession
Due to the close proximity of a shoreline, an evaluation of the shoreline recession rate for
this Project was completed. The future shoreline regression will be zero on the subject
property with ordinary care and maintenance of the existing bulkhead.
43 Seismic Considerations and Liquefaction
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.
There are no known faults beneath this Project, however,the property is near a mapped fault line.
The nearest Class `A' or Class `B' fault to this property is the Tacoma Fault Zone, in which is
approximately 200 feet to the north of this Project. This information is based on the USGS
Quaternary Fault and Fold Database for the United States.
43.1 Liquefaction
The potential for liquefaction is believed to be low for this Project. This is based, in part,
on the subsurface conditions such as soil characteristics and the lack of a permanent
shallow water table. Subgrade characteristics that particularly contribute to problems
caused from liquefaction include submerged, confined, poorly-graded granular soils (i.e.
gravel, sand, silt). Although gravel-and silt-sized soil particles could be problematic, fine
and medium grained sands are typically subjected to these types of seismic hazards. No
significant saturated sand stratifications are anticipated to be within the upper 50 feet of
the subsoil for this Project.
4.4 Lateral Earth Pressures
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. Significant retaining structures are
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 13 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
not anticipated for this Project. If retaining walls are later planned for this Project, prescriptive
requirements from the County should be adhered to. For retaining structures with a height
exceeding County prescriptive requirements, additional design parameters must be accounted for
in the retaining wall analysis, and recommendations should only be provided by a qualified
engineer after the type of backfill is acquired, inclination of backfill slope is estimated, and the
final wall height is determined.
4.5 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 Rivers Geotechnical Report
PO Box 984 page 14 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
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. 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 16 inches shall be placed at a minimum of 18 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. For lightly loaded decks with
foundations on or within 5 feet from the steep slope, foundations may be 12 inches
circular or square, and founded at a minimum of 2.5 feet below the ground surface as
measured on the downslope side. Foundation recommendations are made available based
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 15 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-275-4789 September 7,2012
on adherence to the remaining recommendations that are provided in this report.
Alterations to the aforementioned foundation recommendations may be completed upon a
site inspection by a geotechnical engineer after the foundation excavation is completed.
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 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
geotechnical engineering, concrete slabs should also be designed for structural integrity
and environmental reliability. This may include some type of vapor barrier 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 Rivers Geotechnical Report
PO Box 984 page 16 6600 E Grapeview Loop Road
Belfair,Washington 98528 Parcel 12232-10-01020&-0 103 0
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
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.
FD❑TING
COMPACTED
NATIVE SOILS
OR ENGINEERED t
FILL
1
I I—I I � II II I
UNDISTURBED SUBGRAI)E
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 Rivers Geotechnical Report
PO Box 984 page 17 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax:360-275-4789 September 7,2012
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
As previously mentioned, significant retaining structures are not anticipated for this
Project. However, if used, native soils may be used as retaining wall backfill for this
Project. Backfill may also consist of engineered fill or borrow materials approved by a
geotechnical engineer. Placement, compaction and extents of retaining wall backfill
should also be specified by a geotechnical engineer or qualified professional.
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.
53 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 10 feet house
footing setback from the face of the nearby descending slope exceeding 40%. See the Site Plan in
Appendix A for an illustration of these setbacks. For lightly loaded decks, the setback may be
reduced to zero if deck foundations are founded at an appropriate depth per the Building
Foundation Recommendations Section in this report.
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.
Both footing perimeter drains and roof drains are required for this Project. Subsurface water
intercepted in the footing perimeter drains, and stormwater collected from roof drains shall be
separately tight-lined to an appropriate infiltration location or an above ground energy dissipater.
If infiltration is utilized, the drainage facility should be located to the west of the planned
Envirotech Engineering Rivers Geotechnical Report
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Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
residence, but not directly upstream, and at least 15 feet from foundations. Drainage may also be
tightlined to the beach using an Ecology pipe tee outlet for energy dissipation.
5.5 Vegetation Buffer and Considerations
Vegetation is an excellent measure to minimize surficial 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
particles. Stormwater runoff also increases, and, fewer plants will create less absorption of the
force from raindrops,thereby creating the potential for erosion hazards.
For this project, we believe that a detailed clearing and grading plan is not warranted, and basic
vegetation management practices should be adhered to. Vegetation shall not be removed from the
face of the critical slope. However, any tree deemed hazardous to life or property shall be
removed. If tree removal is necessary, then stumps and roots shall remain in place, and the
underbrush and soil shall remain undisturbed as much as possible. Any disturbed soil shall be
graded and re-compacted in order to restore the terrain similar to preexisting conditions and
drainage patterns.
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.
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.
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 19 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
5.7 Septic Drainfields
The approximate location of the proposed 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 Rivers Geotechnical Report
PO Box 984 page 20 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County, Washington
Fax: 360-2754789 September 7,2012
6.0 CLOSURE
Based on the project information provided by the owner, the proposed development, and site
conditions as resented in this re o it is Envirotech's opinion that additional geotechnical
P P � P
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.
By developing the property and following the recommendations provided in this report, the
property owner(s) shall 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,
Envirotecp Engineering
If
P�
Michael Staten, P.E.
Geotechnical Engineer
Envirotech Engineering Rivers Geotechnical Report
PO Box 984 page 21 6600 E Grapeview Loop Road
Belfair, Washington 98528 Parcel 12232-10-01020&-01030
Ph. 360-275-9374 Mason County,Washington
Fax: 360-2754789 September 7,2012
APPENDIX A
SITE PLAN
S❑ILSi VERY DENSE N
GLACIAL TILL WITH EXISTING HOUSE AND SCALE, 1 INCH a 50 FEE
A SILTY SAND AND DECK TO BE
GRAVEL (SM) REPLACED WITHIN ° 25 °
OVERBURDEN AND ❑UTSIDE THE
EXISTING F❑OTPRINT APPROXIMATE TOP OF
LOPE EXCEEDING 40%
A
EXISTING
DRIVEWAY 77 AVG '�� � rno =
EROSION CONTROL i�
PER//REPORT A
—DRAINFIELD AREA L❑C/ATED
AT LEAST 100 'FEET FROM EXISTING
+ -5' HIGH
\-
CONCRETE
PROPERTY LINE lOFT RESIDENCE SETBACK BULKHEAD
FROM TOP OF SL❑PE, DECK
MAY ENCROACH PER APPRX, HIGH
GE❑TECHNICAL REPORT, WATER
APPR❑XIMATE TOE OF ELEVATION
SLOPE EXCEEDING 40% VEGETATION TO
REMAIN
UNDISTURBED ON
FACE OF SLOPE
NOTES, PROJECT/ OWNER/ LOCATION
1. EROSION CONTROL MAY BE REQUIRED FOR THIS SITE. GENERAL LOCATIONS SINGLE FAMILY RESIDENCE
ARE DEPICTED, AND ALTERNATIVES MAY BE UTILIZED AS EXPLAINED IN THE GEOTECHNICAL REPORT
GEOTECHNICAL REPORT,
2. CONTOURS WERE NOT PREPARED BY A LICENSED LAND SURVEYOR. SFR REPLACEMENT
CONTOURS WERE EXTRAPOLATED FROM A PUBLIC LIDAR SOURCE, AND 6600 E GRAPEVIEW LOOP RD
INCORPORATED FIELD MEASUREMENTS AS EXPLAINED IN THE GEOTECHNICAL LEGEND PARCEL 12232-10-01020, -01030
REPORT. MASON COUNTY WASHINGTON
3. BOUNDARIES WERE NOT PREPARED BY A LICENSED SURVEYOR. LOCATIONS TEMPORARY ENGINEER]
OF SITE FEATURES THAT ARE SHOWN HERE, SUCH AS TOP OF SLOPES, TOE yL +EROSION CONTROL ENVIROTECH ENGINEERING
OF SLOOPES, WATER FEATURES, ETC.., WITH RELATION TO THE PROPERTY PO BOX 984
LINES MUST BE VERIFIED BY THE OWNER, RECOMMENDATIONS IN THE SLOPE INDICATOR BELFAIR, WASHINGTON 98528
GEOTECHNICAL REPORT PROVIDE SETBACKS, BUFFERS, DEPTHS, ETC.. WITH 360-275-9374
RELATION TO GEOLOGIC FEATURES, NOT PROPERTY LINES. THESE GEOLOGIC -80- EXISTING CONTOUR
FEATURES MAY BE LOCATED ON THE SUBJECT PROPERTY OR NEIGHBORING PROPERTIES, I TPj@ TEST PIT SITE PLAN
APPENDIX B
SOIL INFORMATION
VERTICAL AND HORIZONTAL SCALE-
I INCH = 40 FEET
0 to 20 40
PROPOSED HOUSE
PROPOSED DECK LOOSE TO MEDIUM
DENSE OVERBURDEN
EXISTING BULKHEAD (SM)
CASE
INLET
DENSE GLACIAL TILL
SECTION A-A
PROJECT/ OWNER/ LOCATION,
SINGLE FAMILY RESIDENCE
GEOTECHNICAL REPORT
SFR REPLACEMENT
PARCEL 12232-10-01020
MASON COUNTY, WASHINGTON
NOTES,
ENGINEER'
1) MINOR GRADE CHANGES REQUIRED IN ORDER TO ACHIEVE ENV IROTECH ENGINEERING
POSITIVE DRAINAGE P❑ BOX 984
2) THE SOIL PROFILE IS ACCURATE FOR THE DEPTH OF BELFAIR, WASHINGTON 98528
THE OBSERVED TEST PITS AT THE SPECIFIED LOCATIONS. 360-275-9374
LOWER DEPTHS ARE BASED ON SITE GEOLOGY,
WELL LOG(S), AND/OR EXPERIENCE IN THE GENERAL AREA, SOIL PROFILE
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geotechnical Report DATE OF LOG: 9/3/2012
PROJECT NO: 1288 LOGGED BY: MCS
CLIENT: Greg Rivers EXCAVATOR: N/A
LOCATION: Parcel 12232-10-01020 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. Gravel is
_ primarily well-graded and subangular.
1 Sand is mostly medium and coarse. Low
plasticity.
2
3
Very dense, low moisture
Excavation terminated at approximately
4 3.5 feet
5
6
7
8
9
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.
Map Unit Description:Alderwood gravelly sandy loam,5 to 15 percent slopes—
Mason County,Washington
Mason County, Washington
Ab—Alderwood gravelly sandy loam, 5 to 15 percent slopes
Map Unit Setting
Elevation: 50 to 800 feet
Mean annual precipitation:25 to 60 inches
Mean annual air temperature:48 to 52 degrees F
Frost-free period: 180 to 220 days
Map Unit Composition
Alderwood and similar soils: 100 percent
Description of Alderwood
Setting
Landform: Moraines
Parent material: Basal till with a component of volcanic ash
Properties and qualities
Slope: 5 to 15 percent
Depth to restrictive feature:24 to 32 inches to densic material
Drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat):Very low
to moderately low (0.00 to 0.06 in/hr)
Depth to water table:About 18 to 36 inches
Frequency of flooding: None
Frequency of ponding: None
Available water capacity: Low(about 3.4 inches)
Interpretive groups
Land capability(nonirrigated):4s
Typical profile
0 to 10 inches: Gravelly ashy loam
10 to 28 inches: Very gravelly loam
28 to 60 inches: Gravelly sandy loam
Data Source Information
Soil Survey Area: Mason County, Washington
Survey Area Data: Version 7, Jun 29, 2012
Natural Resources Web Soil Survey 9/5/2012
Conservation Service National Cooperative Soil Survey Page 1 of 1
700 01`111-1 and Mot Copy with
Department of Ecology
Second Copy—Owrjii*g Copy WATER WELL REpORT Application jq0. ..........
Third Copy—DrUj&es Copy VrATX OF WAMNC"N permit No. ....... ...............
(1) OWNER: xam.......M-r_.-....jR......kms..................................... Addrion........................................
(2) LOCATioN OF WELL: County_............
......................— V�_% Sec_::..?1.
CL 0 Bearing and distance from auction or subdivision corner
(3) PROPOSED USE: 1301111*111d, 8 1-dU.W.1 0 Municipal 0 (10) WELL LOG:
irrigation 0 Test Well [] Other ❑ Formation,Describe by color,character size of materfal and structure,and
- - show thtelentfli Of aquifers and the kind and nature
(4) TYPE OF WORM Owner's number of well stfugumt Penetrated, with at least am entry for#Qcho'cth:,Wt#rW's each
(if mor Meth
.... .. . .................... ot formation.
New well 19 a Method: DIA9 Cl Bored [I MATJ3LTAL FROM To
Deepened Cl Cable O Driven(3
Reconditioned 0 Rotary 0 U
Brown
0 (5) DIKEN NS Diameter of wen 6 Inch".
r_ Drilleti. 199 M_... — 5a ri Wa t R r-
0 ......ft. Depth of completed well............... __4a., 54 ,
(6) CONSTRUCTION DETAILS: 3and GravLat
E -
Casing installed:_6........... Dism. from ft.to .....58._ ft.
Threaded 0 .............. plain. from .............. ft.to ft.
Welded 19 ................ Main.from ft. to ft
4) Perforations: Yes 13 19091
Type Of Perforator used_.................................................
S= of perforations in. by in.
0 ................. Perforations from ..................... ft. to ............. ft. -
partorations from ft. to ................... ft.
..................... Perforations from ..........._ ft. to ....................... ft.
cc
co Scremic Yen 0 No V
Manufacturers Nome..........................
Model No.__..------...___..
Dram................ Slat site................!torn ft.to............ft.
Diarn................Slot*I" from ............... fl,to ft.
Gravel P"ked: Yes(i NO 0J Site of gravel:..__...._.
Gravel placed from.......................... ft.to.................
Sarfaee sail: Yeses( No(3 To what depth7 fL 11%6
Material used In seal....8.9.111on'10.............L.................... 9A; V r. Lop
Did any strata contain unusable water? Yes C) max]
Type Of water?...-._.._._.........._._....._Depth of strata..........__--..._-... A77
0 Method of sealing strata off.............................................................. LG
z
(ft (7) PUMP. Manufft-tum'. memo.......................................... —
& Type: .................................. H.P..............
0 Zt,-T"Eff RETMAL
(8) WATER LEVELS: Land-.di:.elevation,
.3�. obov sea lord........................
Static level below top Of well Date.....
Artesian pressure ---------------------------Jbs.per square inch Date............ ........
6 Artesian water is controlled by
Uj (9) WELL, TESTS:
O=31:1121a"unt water level Is
0 static level
46 Was a pump test model Yes[3 No If yet,by who ? .L L......... ........... Work started__ ------- 1111-4.4. Completed.....7,/4-1.............. 19 7_7
in
Yield: gal./rain. with ft. drawdoWn after
bra. WELL DRHLE]9'S STATEMENT-
This well was drilled under my jurisdiction and this report is
E true to the best of my knowledge and belief.
4.0
Recovery data (time taken As rLero when pump turned off) (water level
measured from wall top to water level)
Q. Time Water Lftwi Time Water Level Time Water Uvel NAME........................T yipjp....Uell Drilling. Co. Inc.
---------------
(Person. Arm. Q,'rcOrPOrMtJOn-)-- (Type.or print!
............................ d �
10 -------*1---------- ............... 'AddrM......................P.O . ox 3 0 Allyn,..............................................................jaSh.................
... --a f-..................... ........................------------ ...............................
Dace e ...-
.........................
..................... ........L [Signed]_-
Boiler test.... ......4911I./Mill.with...................A. drawdown
(well De1Ler)
Artesian ............__..........II.Pm. Date.............................
0
Temperature Of water_........_...Was a chemical analysis made?Yes(3 no 0 Lkvnn No..............._.._131 ..... 7._.......... ......bate...........VIA......... 19-17.
ECY 050-1-20 (USE ADDITIONAL SMIXTS IF NECESSARY) .0jW
J
WATER WEL L R E P 0 R T ,v Start Card No. D94816
STATE OF WASNINGTON _ Water Right Permit No.
iaaas.................a.ssz.ms====
L (1) OWNER: Name CLAYTON, WALTER Address 2819 26TH AVE. SEATTLf, WA., WA 98199-
Q. za-.aasseiasssa"uiru.a................azisss"sissa...saaau"asaia......a...=...=.sTfeu as=as.coazas.+sisasasasssw uissssasaazr:
(2) LOCATION OF WELL: County MASON - MW 1/4 ME 1/4 Sec 32 T 22M M_, R 1W WM
(2s) STREET ADDRESS OF WELL (or nearest address) 5758 GRAPEVIEW LOOP
asssaaaazza.sasss.z=sssa=Co=s=a__________________________c==r_s=ac=z=========zaz......s=====____�=====s===nz====:aa:z..czz====-
7@ (3) PROPOSED USE: DOMESTIC (10) WELL LOG
-------------------------------- ------------.-------------
(4) TYPE OF WORK: Dwner's Mumber of well Formation- Describe by color, character, size of material
V) (If more then one) and structure, and show thickness of aquifers and the kind
t NEW WELL Method: ROTARY and nature of the material in each stratus penetrated, with
++ ====a...= ...mass at least one entry for each change in formation.
C (5) DIMENSIONS: Diameter of well 6 inches ---------------------------------------------------------------
O Drilled 57 ft. Depth of completed watt 57 ft. MATERIAL FROM TO
C Z=aai...n.n.aZ=aaai.a.=ZZZZZZZ3 =zz=man.. BROWM TOP SOIL 0 1
O (6) CONSTRUCTION DETAILS: BROWII CLAY i GRAVEL 1 6
R Casing installed: 6 " Dia. from 1 ft- to 57 ft. COURSE BROWN SAND 6 30
WELDED " Die. from ft. to ft. COURSE SAND CLAY i GRAVEL 30 46
E " Dim. from ft. to ft. SAND L GRAVEL WATER CLAY i GRAVEL 46 57
tr' ----------------------------------------------------------
wPerforations: MO
C Type of perforator used
SIZE of perforations in. by in.
perforations from ft. to ft.
�.+ perforations from ft. to ft.
s_ perforations from ft. to It.
O --------------------------------------------------------
Screens: YES
C Manufacturer's Name COOKS
f0 Type SLOTTED Model No.
Diam. 5 slot size 20 from 52 ft. to 57 ft.
}' Diam. slot size from ft. to ft.
R ------
Gravel packed: MO Size of gravel
a Gravel placed from ft. to ft.
----------------------------------------------------------
Surface seat: YES To what depth? 20 ft.
Material used in seal BENTONITE
C Did any strata contain unusable water? NO
Type of water? Depth of strata ft.
/i_ Method of sealing strata off CASED OFF
♦y --3...ia.aia.i laaaa.i.iia.iz....-c_L__=Z.........a.Ci =7=_1=aa9
(7) PUMP: Manufacturer's Name
Type SUBMERSIBLE M.P.
Oseizoiasissziasissisusli.ia.suz............s=ss.=naszuiie.ai
Z (8) WATER LEVELS: tand-surface elevation above mean sea level . ft.
V) Static level 36 ft. below top of well Date 05/19/92
4) Artesian Pressure lbs. per square inch Date
O Artesian water controlled by CAP
'd Work started 05/19/92 Completed 05/19/92
•z==========0=====___^_______________ssx"====___________=====caaszz==O=O='=0===�_____=====saz=====____=__=___======s==2°====___
IM (9) WELL TESTS: Drawdown is amount water level is lowered below WELL COMSTRUCTOR CERTIFICATION:
_O static level. 1 constructed and/or accept responsibility for con-
6 Was a pump test mode? NO If yes, by whom? struction of this welt, and its comptiance with ell
Q Yield: gal./min with ft. drawdown after hrs. Washington welt construction standards. Materials used
L1.1 and the information reported above are true to my best
4, knowledge and belief.
O Recovery data
+�+ Time Water Level Time water Level Time Water Level NAME ARCADIA WELL DRILLING INC
C (Person, firm, or corporation) (Type or print)
d
ADDRESS SE PWZ,PAZ.A
Date of test '
QBailer teat gal/min. ft. drawdown after hrs. ISIGNEO License No. 0950
C Air test 10 gal/min. w/ stem set at 37 ft. for 1 hrs.
Q Artesian flow g.p.m. Date Contractor's
Temperature of water Was a chemical analysis made? NO Registration No. ARCADD1098KI Date 05/20/92
APPENDIX C
SLOPE STABILITY
STABLE Slope Stability Analysis System
New User
Project Rivers
Datafile: Dynamic ; Bishop
STABLE Version 9.03.00u
Bishop
TITLE
Dynamic
UNITS (Metric/Imperial) = I
GEOMETRY DEFINITION
POINTS
NO. X Y
1 0.000 0.000
2 16.000 0.000
3 41.000 16.000
4 91.000 17.000
5 9.100 0.000
6 12.930 0.000
7 16.760 0.490
8 20.590 2.940
9 24.430 5.390
10 28.260 7.850
11 32.090 10.300
12 35.920 12.750
13 39.750 15.200
14 43.580 16.050
15 47.420 16.130
16 51.250 16.200
17 55.080 16.280
18 58.910 16.360
19 62.740 16.430
20 66.570 16.510
21 70.410 16.590
22 74.240 16.660
23 78.070 16.740
24 81.900 16.820
LINES
Lo X Hi X SOIL
1 2 1
2 3 1
3 4 1
SOILS
SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT.
1 Soil-1 CONTINUOUS-BLACK 0.00 33.0 134.000
PORE PRESSURE SPECIFICATION
SOIL PIEZO RU EXCESS
Y/N/P Value Value
STABLEBM2 MZAssociates Ltd Printed on: 06MO/12 @ 13:34:29 page; 1
r
1 . C-)F)
1 1 0
. 035
project Rivers
Datafile Stable
Analysis Bisl-iop
STABLE.2002 MZ ASSOCiotes Ltd
1 . 00
1 . 1 0
1 . 20
1 . 30
1 . 40
1 . 50
1 . 60
1 . 70
1 . 80
1 . 90
2 . 00
. 691
Project Rivers
Dctcfile Dynamic
Anclysis Bishop
STABLE.2002 MZ Associates Ltd
APPENDIX D
EROSION CONTROL
GEOTEXTILE FABRIC GEOTEXTILE FABRIC
WRAP AROUND TRENCH 2'x2' WOOD POST (TYP) AND WIRE MESH
TO AT LEAST ENTIRE OR EQUIVALENT OR BETTER
2 6 FT MAX. O.C.
BOTTOM OF TRENCH 0.5 FT
BEFORE PLACING GRAVEL 2'x2'x5' WOOD POST OR �+-- 6 FT
12' DEEP, 8' WIDE TRENCH EQUIVALENT DR BETTER EXISTING
FILLED WITH 3/4' TO 1 1/2) GROUND SURFACE
WASHED GRAVEL 2 T
DIRECTION OF ---�
2.5 F7 12' DEEP, 8' VIDE
WATER FLOW EXISTING TRENCH FILLED WITH I T
12, GROUND SURFACE 3/4' TO 1 1/2' lm u 2.5 FT
2.5 FT WASHED GRAVEL
4 :7
BOTTOM EXTENTS OF
GEOTEXTILE FABRIC SILT FENCE - DETAIL
SILT FENCE - CROSS SECTION N.T.S.
N.T.S. HAY OR STRAW MATTING
ENERAL NOTES 1. STRAW SHALL BE AIR DRIED, AND FREE FROM WEED SEEDS AND
SHOULD THE TEMPORARY EROSION AND SEDIMENT CONTROL MEASURES SHOWN ON COARSE MATERIAL.
HESE PLANS PROVE TO BE INADEQUATE DURING CONSTRUCTION, THE CONTRACTOR 2. APPLY AT APPROXIMATELY 75 TO 100 POUNDS PER 1000 SQUARE
FEET OF GROUND.
HALL INSTALL ADDITIONAL EROSION AND SEDIMENT CONTROL FACILITIES. 3. MINIMUM THICKNESS SHALL BE 2 INCHES.
2. 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.
3. ALL EROSION AND SEDIMENT CONTROL FACILITIES AND DEVICES SHALL BE 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
ISTURBING 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 BELOW, 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 I 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, (e.g.,
THERWISE STABILIZED, AFTER HAVING BEEN CLEARED OR ❑THERWISE DISTURBED , GEOTEXTILES, JUTE MAT, CLEAR PLASTIC COVERING).
Y NO LATER THAN SEPTEMBER 30 OF A GIVEN YEAR. UNLESS IMMEDIATE 6. FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS'
TABILIZATION IS SPECIFIED IN THE EROSION AND SEDIMENT CONTROL PLAN, ALL RECOMMENDATIONS. AMOUNTS SHOULD BE MINIMIZED, ESPECIALLY
REAS CLEARED OR ❑THERWISE 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 OR 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.
ERTILIZING AND MULCHING OF CLEARED OR OTHERWISE DISTURBED AREAS SHALL BE
ERFORMED DURING THE FOLLOWING PERIODS MARCH 1 TO MAY 15, AND AUGUST 15 TO PROPORTIONS PURITY GERMINATIO
CTOBER 1. SEEDING AFTER OCTOBER I WILL BE DONE WHEN PHYSICAL COMPLETION NAME BY WEIGHT(%) (7) (%)
THE PROJECT IS IMMINENT AND THE ENVIROMENTAL CONDITIONS ARE CONDUCIVE
❑ 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 BE INSTALLED BY NO LATER THAN CHEWING FESUE 40 97 80
EPTEMBER 30. (FESTUCA RUBRA COMMUTATA)
(JAMESTOWN, BANNER, SHADOW, KOKET)
N THE EVENT THAT CONSTRUCTION ACTIVITIES OR 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 ONCE 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 BE APPLIED AT A RATE OF 1000
ET SEASON (OCTOBER 1 THRU APRIL 30) -- ON SITES WHERE UNINTERUPTED POUNDS PER ACRE.
❑NSTRUCTION ACTIVITY IS IN PROGRESS, THE CLEARING OF LAND, INCLUDING THE 2. MULCH SHOULD BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES
REMOVAL OF EXISTING VEGETATION AND OTHER GROUND COVER, SHALL BE LIMITED GREATER THAN 2-1 (HORIZONTAL-VERTICAL).
TO 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
TRANSPORT OFF-SITE IS OBSERVED. AREAS REQUIRING MULCH SHALL BE COVERED BY NOVEMBER 1.
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 ❑THERWISE DISTURBED IF NOT BEING ACTIVELY WORKED.
ILT FENCING, SEDIMENT TRAPS, SEDIMENT PONDS, ETC., WILL NOT BE VIEWED AS
DEQUATE COVER IN AND OF THEMSELVES. IN THE EVENT THAT ANY LAND AREA NOT
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.
SILT FENCE
PROJECT/ OWNER/ LOCATION,
1. GEOTEXTILE FILTER FABRIC TYPE SHALL BE PER SPECIFIED IN THE 'STORMWATER MANAGEMENT MANUAL SINGLE FAMILY RESIDENCE
OR THE PUGET SOUND BASIN,' OR APPLICABLE COUNTY STANDARDS
2. GEOTEXTILE FILTER FABRIC SHALL BE PURCHASED IN A CONTINUOUS ROLL CUT TO THE LENGTH OF GE❑TECHNICAL REPORT
EACH BARRIER TO AVOID USE OF JOINTS. IF JOINTS ARE NECESSARY, FILTER FABRIC SHALL BE SPLICED ENT
TOGETHER ONLY AT A SUPPORT POST WITH A MINIMUM 6-INCH OVERLAP AND SECURELY FASTENED AT PARCEL SFR REPLACEMENT
10-01020
BOTH ENDS TO THE POST. MASON COUNTY, WASHINGTON
3. STANDARD FILTER FABRIC SHALL BE FASTENED USING 1' STAPLES OR TIE WIRES (HOG RINGS) e 4 IN
SPACING.
4. 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'Xl4 GAUGE OR EQUIVALENT. THE WIRE MESH MAY BE ELIMINATED IF PO BOX 984
EXTRA-STRENGTH FILTER FABRIC (MONOFILAMENT), AND CLOSER POST SPACING IS USED. BELFAIR, WASHINGTON 98528
6. A TRENCH SHALL BE EXCAVATED ACCORDING TO THE DETAILS ON THIS SHEET ALONG THE LINE OF THE 360-275-9374
POSTS AND UPSLOPE FROM THE SILT FENCE,
7. SILT FENCES SHALL BE LOCATED DOWNSLOPE FROM THE CLEARING LIMITS OF THE PROJECT. EROSION CONTROL
c
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: V"5
Permit# 24 l y 00907 Parcel #
Date(s)of theDocument(s) reoao e �i Z�
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed development,
OK? V Comment:
(b) A dis ssion of specific soil types
OK? V Comment:
(c) A dis ssion of ground water conditions
OK? Comment:
(d) A disc psion of the upslope geomorphology
OK? r/ Comment:
(e) A discu lion of the location of upland waterbodies and wetlands
OK?Comment:
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
refer ced maps and records _OK? Comment: lid
(2) A site plan rich identifies the im ort nt deve opment and geologic features.
OK? Comment:
(3) LocationspDo logs of exploratory hole prob .
OK? Comment:
(4) The area of the proposed development,169 boundaries of the hazard, and associated buffers and
setbacks sh9H be delineated (top, bot s es,qqd toe)on a geologic map of the site.
OK. Comment:
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorpprates the details of sed ra ng
OK? pro Comment: ,6
(6) A description and results of slope stability aAalyseg performed for th 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 sai ty factor is 1.1. and the quasi-staticanalysis coeffients should be a value of 0.15.
OK? V Comment: 0 ejo C
(7) (a)Appropria restrictio A placeme t of drainage features
OK? Comment:
(b) Appropr ate restrictions on placement of septic drain fields
OK?Comment:
(c) Appro,r to restrictions on placement of compacted fills and footings
OK? Comment:
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Page 1 of 2 Form Effective June 2008
A
OK?Comment:
(e) Recommended setbac s from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.-
OK? 1/Comment: l C
(8) Recommendations for the ep ration of a detailed clearing and grading plan which specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method ofyegetation removal.
OK? v,' Comment:
(9) Recommendations for the preparation of a detailed temporary erosion control plan which
identifies the specific mitigating measures to be implemented during construction to protect the
slope from eLqi�ion, lands sI'd and harmful construction methods.
OK? VComment: '7/
(10) An a analysis of both on-site n off-site impacts of the proposed development.
OK? Comment:
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer w'dths.
OK? Comment:
(12) Recommendations for the l5reparation of structural mitigation or details of other proposed
mitigation.
OK? LComment:
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location
and natur f existing and prod d lopment on the site.
OK?Comment:
Are the Documents signed and stamped?—41 ✓ aA I U
Type and #of License: L+
6qY4
If not approved, what is the next action/recommendation for further action? IA
Y
Reviewed by on
Time spent in review:
SECOND REVIEW/ UPDATE:
Reviewed by on
Time spent in second review:
THIRD REVIEW/UPDATE:
Reviewed by on
Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment
Page 2 of 2 Form Effective June 2008