HomeMy WebLinkAboutGEO2008-00001 - GEO Geological Review - 12/2/2008 Mason County Department of Community Development
Submittal Checklist For a Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance. If an item found to be not applicable,the report should explain
the basis for the conclusion.
Applicant/Owner &4\r S¢uire' Parcel# �2332 50 00977
Site Address O _ !Sz �,tz I aka P1 r C/✓� 9 S2g
(1) (a)A discussion of gener I geologic conditions in the vicinity of the proposed development,
Located on page(s) TO BE KEPT IN THE
(b) A discussion of speT
c soil types
Located on page(s) PARCEL FILE
(c) A discussion of ground water conditions
Located on page(s) 7
(d) A discussion of the ugslope geomorphology
Located on page(s) qF
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s)_4:
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps and4ecords
Located on page(s)
(2) A site plan which identifies the import nt develo ment and geologic features.
Located on Map(s) ✓r" I . .
(3) Locations and logs of exgl ratol'y hole r probes.
Located on Map(s)y js Nlan � k
(4) The area of the proposed development,the boundaries of the hazard, and associated buffers and
setbacks shall be delineated(top,both side ,andtoe)on a geologic map of the site.
Located on Maps) geo g
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details of Oro
osed grade anges.
Located on Map(s)
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditft.Analysis should examine worst case failures.The analysis should include the
Simpliffe-gSishop'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.
Located on page(s) /O
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) f Z-
(b) Appropriate restrictions on placement of septic drain fields
Locatedoop,page(s) l2 z
(c) Ap `priate restrictions on placement of compacted fills and footings
Located on page(s)
l
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
I
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) / �
(e) Recommended setb cks frbm the landslide hazard areas shoreline bluffs and the tops of
other slopes on the prope '
Located on page(s)�T al" Q
(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) 13
(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`t from erosion, lands ides and harmful construction methods.
Loa"ToWila��� '`t O-T
(10) An ayis$f pdp# Qrl`, ' N4 off-site impacts of the proposed development.
(11) Specifications of final development conditions such as, vegetative management,drainage,
erosion control, and buffer widths.
Located on page(s)- f 3
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s)1T/�
(13) A site map drawn to scale showing the property boundaries,scale, north arrow, and the location
and nature of existin a d oposed develo merit on the site.
Located on M��a^^p(s) an1I ou.
1, v ` T hereby certify under penalty of
perjury that I am a civil a gineer 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 Geotechnicat
Report, dated LO g , and entitled 'oc���
rY itiT Fcxwvl ge5rk"ce-- meets all the requirements of the Mason
County Resource O dinan e, Landslide Hazard Section, is complete and true, that the assessment
demonstrates conclusively that the risks posed by the landslide hazard can be mitigated throu h the
Included geotechnical design recommendations, and that all hazards are mitigated i as
to prevent harm to property and public health and safety. (Signature and Stamp)
P
APPROVED
MASON COUNTY DCD PL.ANNI'IC
SUBJECT TO APPi?OVAL
CHANGES j�
By — to (V?n.S//
a
EXPIRES-TA !,0 700
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
s
r
(d) Recommended buffers from the-landslide hazard are shorellhe bluffs and the tops of other
slopes on the property.
Located on page(s) f 3 v' 13
(e) Recommended sett cks frbm the landslide hazard areas shoreline bluffs and the tops of
other slopes on the prop
Located on pages) �/ �`lDv. Q
(8) Recommendations for the preparation of a`detailed clearing and grading plan which spectfltratly
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method of vegetation removal.
Located on page(s) /3
(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.
(10) An at, >ysisbftot. pn §i �nc�off-site impacts of the proposed development.
nrafed nn naa (c) /3
(11) Specifications of final development conditions such as, vegetative management,drainage,
erosion control, and buff r widths. r
Located on page(s). 13
(12) Recommendations for the preparation of structural mitigation br detalls of other proposed
mitigation.
Located on page(s)
i
(13) A site map drawn to scale showing the property.boundaries,scale, north arrow, and the location
and nature of existla d oposed deveto meat on the site.
Located on Ma s a,^ ,
��-1(-
T
12 u� C" 544 hereby certify under penalty of
perjury that I dim a civil erigineer licensed In the State of Washington with specialized knowledge of
geotechnicat/geologfical englneering or a geologist or engineert60" genj6glst 1( ensed in the.State of
Washington with special knowledge of the local coiitlitions. balsa certify Ith' the Geotechnicat
Report,dated 2 2 0 g , and entitled Gey7 Al M l —y tri f
Sguke— iS41 5,44LFO(M'k lLt21944111Ce, meets alfi the.requirements of the Mason
County Resource O dinance, Landslide Hazard Section, is complete and true, that the assessment
demonstrates conclusively that the risks posed by the landslide hazard can be.mitigated throu ,the
Included geotechnical design recommendatto' ns, and that alt firazi rds gre mil ated = as
to prevent harm to property and pubtic`heaith and`safety. (Sfigr�ature arrd Starf7p)
CES°`St�B�I
DCPfiI���� !p�2oa
Page 9 Form Effective June 200$
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
Ly
E
rt
Mason County Deaartmen, t of Community.Qeveloament
Submittal Checklist For a Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed,signed,,and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance. If an item found to be not applicable,,the report should explain
the basis for the conclusion.
Applicant/Owner &4V aulve- Parcel# 12- q Z 50 0097 7
. -{ter 9
Site Address
(1) (a)A discussion of gener 1 geologic conditions in the vicinity of the.,proposed development;.
Located on page(s) TO BE KEPT IN THE
(b) A discussion of specific soil types PAR.0 E L FILE
Located on page(s) fo
(c) A discussion of ground water conditions
Located on page(s) 7
(d) A discussion of the ugslope geomorphology
Located on page(s)
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) k
(f) A discussion of history of landslide activity in the activity in thevicinity, as-available in the
referenced maps an cords
Located on page(s) y
(2) A site plan which identifies the i port nt develo ment and 9eologic. 4eatures.
Located on Map(s) ✓�" ��n���
(3) Locations and logs of ex Prato hole Qr probes:
Located on Map,(s) Rctn t A P,l
(4) The area of the proposed development,the boundariesof file hazard, and associated buffers-and
setbacks shall;be"delineated top,both side , and oe).on,a geologyrr ap of the_site.
Located on Maps) v
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile,and
which incorporates the details o p osed grade anges.
Located on Maps)
(6) A d lion�gd-results of slope stability analyses pe00mei b_bath.s#atic and,seismic laae4ing.
cd „� Analysis should examine worst case failures the analysis should Include the.
�'in P . ishop's-Method of Circles.The minimum static safetyfactor is 1.5, the minimum
seismic salary factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
Located>or) page(s) /4 &a, y
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) /2
(b) Apopriate tions on placement of septic drain fields
Loc restric
ateertage(s) l Z
(c) riatiy restrictions on placement of compacted fills andffootings
Located on page(s)
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) 13 pa,
(e) Recommended setb cks frbm the landslide hazard areas shoreline bluffs and the tops of
other slopes on the properly.
Located on page(s)
(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) 13
(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, lands ides and harmful construction methods.
Loci&oh pag€(s) 5' �'."�'
(10) An adal,�sis'bf bett p'-13 anc off-site impacts of the proposed development.
(11) Specifications of final development conditions such as,vegetative management, drainage,
erosion control, and buff r widths.
Located on page(s). /�, (3
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s)IA
(13) A site map drawn to scale showing the property.boundaries,scale, north arrow, and the location
and nature of existing a d op(
develo,ment on the site.
Located on Ma s a,„ ,
C, ✓W'e*1 hereby certify under penalty of
penury 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. 1 also certify that the Geotechnical
Report,dated l c,/ 2 0 S ,and entitled 6e0t. dma I Dor�Q f
uiY iST�q � 9L F mJ1 /�e'S ce, meets all the requirements of the Mason
County Resource O dinan e, Landslide Hazard Section, is complete and true, that the assessment
demonstrates conclusively that the risks posed by the landslide hazard can be mitigated throw h the
Included geotechnical design recommendations, and that all hazards are mitigated i as
to prevent harm to property and public health and safety. (Signature and Starnp) �+
MA n
.,.
��
9NANGES SUBJECT TO APP_R j �'r0 CS
By 1119
tc �t t
DtPIREST}1 l� 200
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report,
E
..r
Mason County Department of Community Development
Submittal Checklist For a Geotechnical.Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed,signed, and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance, if an item found to be not applicable,the report should explain
the basis for the conclusion.
Applicant/Owner
1ya' Parcel# 12M_- 50 0097 7
-&H)L4
Site Address r'e- 4 iY11 14 g
(1) (a)A discussion of gener I geologic conditions in the vicinity of the proposed development,
Located on page(s) TO BE KEPT 1N THE
(b) A discussion of
Located on page(s)speci c soil types PARCEL FILE
(c) A discussion of ground water conditions
Located on page(s)
(d) A discussion of the ulplope geomorphology
Located on page(s) q'
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s)
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps anc).,('ecords
Located on page(s) y
(2) A site plan which identifies the import'Elntt develo ment and geologic features.
Located on Map(s) Ana,ft
(3) Locations and logs of ex t ratoXy hole r probes.
Located on Map(s) a OD
(4) The area of the proposed.development,the boundaries of the hazard, and associated buffers and
setbacks shall be delineated top,both side , and oe)on a geologic map of the site.
Located on Map(s) roge
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile,and
which incorporates the details o p osed grade angel.
Located on Map(s) Gyd
(6) A descrptipn and results of slope stability analyses performed far both static and seismic loading
`I co641t,,(6$.Analysis should examine worst case failures.The analysis,should include the
'j Sim,ptifi %ishop's Method of Circles.The minimum static safety factor is 1.5,the minimum
j seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
j Located on page(s) /0 _
I (7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) 12,
(b) AQpriate restrictions on placement of septic drain fields
( Locatedwn pages) 1Z
(c) App,riate restrictions on placement of compacted fills and footings
Located on page(s)
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
C)w I Z
evwvLroteoh 5In,OLmerLK,0
ceotecl�wioal.� 6wv%roww�.ewtal�Draiwage �tzoadwa�
RECED VED
DEC 0 4 2008
December 4, 2008
BELFAIR OFFICE
Mindi Brock
Mason County Department of Community Development
PO Box 279
Shelton, Washington 98584
RE: Geotechnical Report for Betty Squire Property Located at 80 NE Squire Lane,
Parcel 12332 50 0977,Belfair, Washington
Dear Ms. Brock,
Envirotech Engineering has completed a geotechnical report for the referenced property.
Two copies of the report and a submittal checklist are enclosed.
I�
Please contact Michael Staten at 360-275-9374 if you have any questions or require
additional information.
i
Yours Truly,
Envirotec Engineering
Michael Staten,P.E.
' Project Director
�4 N6 Hurd x.oad
geLfair,washiwgtow98s2g
Off: 360-2�5-93¢4
ceidL: 3oo-6g9-c o45
Fax: 360-275-47?9
mv%rCrter'k@O'keoteak Kica U. fo.cowL
Coo a ova cw v i
1
1
1
1
Geotechnical Report
for
Squire Existing Single Family Residence
80 NE Squire Lane, Belfair
Parcel 12332 50 00977
' Mason County,Washington
December 2, 2008
tProject#08119
' Prgmvd For
' Betty Squire ti CLYAP
80 NE Squire Lane sT
Belfair, Washington 98528 of wAs� 09��
Pf epwcd W.
' Envirotech Engineering '0� 43045
74 NE Hard Road o� RAcr �
Belfair, Washington 98528 �SSjONAL� G
' Phone: 360-275-9374
Fax: 360-275-4789
1 �
TABLE OF CONTENTS
1.0 INTRODUCTION...........................................................................................................................2
1.1 PROJECT INFORMATION...............................................................................................................2
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK.....................................................................2
2.0 SURFACE CONDITIONS..............................................................................................................4
2.1 GENERAL OBSERVATIONS............................................................................................................4
' 2.2 TOPOGRAPHY...............................................................................................................................4
2.21 Upslope Gemnorphology.......................................................................................................4
2.22 DownslopeConditions..........................................................................................................4
2.3 SURFACE DRAINAGE.....................................................................................................................4
' 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
3.3 SPECIFIC SUBSURFACE CONDITIONS.............................................................................................6
3.3.1 Groundwater......................................................................................................................... 7
3.4 SOILS TESTING.............................................................................................................................7
3.4.1 Visual ClaWficadon............................................................................................................. 7
4.0 ENGINEERING ANALYSIS,CONCLUSIONS AND RECOMMENDATIONS..........................8
4.1 BUILDING FOUNDATION RECOMMENDATIONS..............................................................................8
4.LI Bearing Capacity..................................................................................................................8
4.L2 Settkwkwt.............................................................................................................................8
4.2 LATERAL EARTH PRESSURES........................................................................................................8
4.3 EARTHWORK CONSTRUCTION RECOMMENDATIONS....................................................................8
4.4 SLOPE STABILITY.........................................................................................................................9
4.4.1 Slope Stability Analysis....................................................................................................... 10
4.4.2 Building and Footing Setbacks........................................................................................... 11
4.4.3 Slope Assessnwnt................................................................................................................ 11
4.5 EROSION CONTROL.................................................................................................................... 12
4.6 SURFACE AND SUBSURFACE DRAINAGE...................................................................................... 12
4.6.I Septic Drainfield Impacts................................................................................................... 12
4.7 VEGETATION BUFFER AND CONSIDERATIONS............................................................................. 13
4.8 ON-SITE AND OFF-SITE IMPACTS............................................................................................... 13
4.9 SEISMIC CONSIDERATIONS AND LIQUEFACTION......................................................................... 13
4.9.1 Liquefaction........................................................................................................................ 13
5.0 CLOSURE.....................................................................................................................................14
' Appendix A-Site Plan
Appendix B-Geologic Map
Appendix C Soil Information(Soil Profile; Soil Logs;Well Reports)
Appendix D-Slope Stability Input&Output
Appendix E—Geotechnical Testing Laboratory Geotechnical Report
I
I
1.0 INTRODUCTION
Envirotech Engineering (Envirotech) has completed a geotechmcal investigation for a property
located at 80 NE Squire Lane, identified as parcel number 12332 50 00977, Mason County,
Washington (Project). 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; and, recommendations for foundation, settlement, earthwork construction, lateral earth
pressures, slope stability, erosion control, drainage, vegetation, and seismic considerations in the
Engineering Analysis and Recommendations Section.
An initial geotechnical evaluation of the Project was conducted by Envirotech on December 17,
2007, with subsequent site visits on November 21, and November 28, 2008. It was previously
determined by Mason County that landslide activity downslope from the residence requires a
geotechnical report per the Landslide Hazard Areas of Mason County Resource Ordinance
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 in order to fulfill the MCRO.
1.1 Project Information
Information pertaining to the Project was provided by the property owner's representative during
the preparation of this report. A previous geotechnical report was prepared after earth movement
activity at the Project by Geotechnical Testing Laboratory (GTL). The most recent landslide is
apparently within the same limits as the previous earth movement that was addressed by GTL.
' The aforementioned geotechnical report is provided at the end of the appendices in this report.
The landslide was reported to be within the limits of unclassified fill soils. The landslide occurred
during or immediately after a period of extremely wet weather and rapid snowmelt. This wet
period occurred in December 2007, and reportedly consisted of more than 6 inches of snowmelt
coupled with high intensity rainfall exceeding a 100yr-24hr event. In addition, a broken water
pipe during this time induced an added point load of water that is approximated to be 238 cubic
feet of volume per day. The top of the slide is located within a few feet,and downslope from the
existing garage. Most of the sidewalk nearest the north comer of the garage consisted of a 6-to
12-inch gap between the bottom of the concrete and the top of the landslide. The toe of the slide
is visible on the south side of NE Squire Lane where the edge of pavement has heaved about 1
foot.Approximate site features are illustrated in the Site Map in Appendix A of this report.
1.2 Purpose of Investigation and Scope of Work
The purpose of this geotechnical investigation was to evaluate the Project in order to provide
geotechnical conclusions/ recommendations relating to the existing structures on the property,
and potential off-site impacts. The investigation included characterizing the general Project
surface and subsurface conditions, and evaluating the suitability of the soils to support the
planned site activities.
In order to fulfill the purpose of investigation, the geotechnical program completed for the
proposed improvements of the Project include:
' Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 2 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
December 2,2008
• Review project information provided by the Project owner and/ or owner's
representative. This information included a geotechnical report prepared for the previous
' landslide by GTL.
• Conduct a site visit to document and verify site conditions that may influence the stability
of the slope;
• Define the general subsurface conditions of the site by utilizing the information from
' GTL,a test pit and probing to a depth of approximately 11.5 feet, review geological maps
for the general area,and research published references concerning slope stability;
• Collect bulk samples at various depths and locations;
• Perform soils testing to determine selected index and engineering properties of the soils
that include 3 visual classifications;
• Complete an engineering analysis supported by the existing conditions, and the surface
' and subsurface conditions that were identified by field investigations, soil testing, and
applicable project research;and,
• Establish conclusions based on findings, and make recommendations for foundations,
drainage, slope stability, erosion control, earthwork construction requirements, and other
considerations.
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Vicinity Map from Mason County Website
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 3 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County, Washington
December 2,2008
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the Project was gathered on
December 17, 2007 and November 21, 2008 by Michael Staten, geotechnical engineer with
Envirotech. During the site visits, the type of geotechnical investigation was assessed, and site
features were documented that may influence construction and slope stability. This Surface
Conditions Section provides information on general observations, vegetation, topography,
drainage and slope/ erosion conditions for the Project and surrounding areas that may impact the
Project.
2.1 General Observations
The Project is currently developed land as previously mentioned. Squire Lane runs along the
North property line. Beyond the property lines, residential and commercial development exists.
Envirotech observed pin piles beneath the sidewalk that were constructed in conjunction with the
mitigation measures implemented after the initial earth movement in 2001. An approximate 6 feet
in height ecology block retaining wall is located at the slope toe beyond Squire Lane. Visible
movement of the gravity wall due the recent slide was not observed during the site visits.
Vegetation on and near the Project consists primarily of firs, hemlocks, maples, and other trees
and shrubbery common to this area of the Pacific Northwest. An aerial photo of the Project and
immediate vicinity is provided on the following page.
2.2 Topography
The Project is situated within and near moderate sloping terrain. The existing building is mostly
t on a knoll. 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 Map in Appendix A and the Geological Map in Appendix B in this report for an
illustration of general topography with respect to the planned development.
' 2.2.1 Upslope Geomorphology
Ascending grades are generally located at least 300 feet to the southeast of the Project,
' and are not considered to influence the residence. A stream is located upslope from the
residence. However, the stream channel directs the surface water beyond the limits of the
property.
2.2.2 Downslope Conditions
Descending grades ranging from approximately 30%to 59% exist to the north and west
of the development with a maximum vertical relief of approximately 32 feet. 'Be area of
the landslide exhibited average grades of 29%with a local vertical relief of up to 25 feet.
2.3 Surface Drainage
Stormwater runoff originating upslope from the residence and landslide area is expected to be
very minimal due to existing topography. Excessive scour, erosion or other indications of past
surface drainage problems were not observed within the immediate vicinity of the landslide and
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 4 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County, Washington
December 2,2008
residence.
2.4 Slope and Erosion Observations
The slope in which the recent landslide occurred appears to be moderately unstable with respect
to deep seated slippage. For this Project, significant erosion was not observed. The most recent
landslide is easily delineated from observations of the ground surface, leaning trees, and leaning
utility poles. Although the crown or head of the landslide was easily delineated in December
2007, recent landscaping has made the top of the slide not as readily noticeable. See the Slope
Stability Section of this report for additional information concerning the landslide and slope.
f
NE SQUIRE LN
C' 1
4 T
1
' Aerial Photo from Mason County Website
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1
1
1
Envirotech Engineering Squire Geotechnical Investigation
Ph 360-275-9374 page 5 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
' December 2,2008
A
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the Project was gathered on November 28,
2008 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 C 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).Applicable test pit locations are depicted on the
Site Plan and Geologic Map 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
a test pit extending to depths of 6 feet below the existing ground surface,probing to an additional
depth of 5.5 feet at the bottom of the test pit, and collecting data from both the aforementioned
GTL Geotechnical Report and the contractor associated with the first slope mitigation.
Information on subsurface conditions also included reviewing geological maps representing the
general vicinity of the project, and water well reports originating from nearby properties.
One bulk sample was collected at the Project site at approximately 8 feet below the existing
ground surface within the landslide location. The soil sample collected was secured and
transported for possible laboratory testing.
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 11.5 feet, and very dense soils from 11.5 feet to the depth of
terminus.
3.2 General Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the "Geologic Map of Washington," compiled by J. Eric Schuster,
2002 indicates Quaternary sediments, Q8. 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.
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 described utilizing the Unified Soil Classification System
(USCS). Using the USCS in conjunction with estimated relative densities and other anticipated
engineering properties of the soil, susceptibility for potential landslides, erosion and seismic
hazards may be assessed.
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 6 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County, Washington
December 2.2008
The Project is composed of native soils with indications of fill within the landslide area. For
engineering purposes,these native soils consist of distinguishable layers, as presented below.
Soils within the upper 6 feet were observed to be moist,brown silty sand with gravel (SM). Soils
between 6 feet and 11.5 feet from the ground surface were observed to be mostly brown, very
moist, sandy clay(SC)and clay with sand(CL)soils.
Soils below the upper 6 to 12 feet layer are believe to be a hardpan conglomerate of sand, silt,
gravel and clay. This is based on subsurface observations and reports from the contractor who
constructed pin piles at the top of the slope.
The relative densities of the soil 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 C of this report.
3.3.1 Groundwater
From the water well report(s)and knowledge of the general area,permanent groundwater
is over 50 feet directly below the property at the building pad location. Perched
groundwater at shallow depths was observed directly above the hardpan. The
groundwater appears to be constant,with additional water during the wetter months of the
year.
3.4 Soils Testing
The soil samples obtained at the Project site during the field investigation were preserved and
transported for possible laboratory testing. Visual classification of soils was performed in the
field. The following soil tests were performed in accordance with the American Standards for
Testing and Materials(ASTM):
3 Visual Classifications (ASTM D2488)
3.4.1 Visual Classification
The general results from the visual classification are presented above in the Subsurface
Conditions Section. Specifically, soils within the upper 6 feet in the testing location
consisted of approximately 25%gravel, 55%sand-sized soils, and 20%silt with medium
plasticity. Soils from 6 feet to 11.5 feet below the ground surface consisted mainly of 0%
gravel, 50% sand, and 50% medium plastic clay. Minor variations observed during the
visual classification of particle size content (i.e. gravel, sand, fines), or isolated pockets
within the soil stratification were insignificant in relation to the overall engineering
properties of the soil.
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 7 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
December 2,2008
4.0 ENGINEERING ANALYSIS,CONCLUSIONS AND RECOMMENDATIONS
The following sections present engineering analysis and 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; and, soil
conditions that were identified from the geotechnical investigation that is summarized in the
Subsurface Investigation Section. Engineering analysis and recommendations for the Project that
is provided herein, includes pertinent information for building foundations, earthwork
construction, slope stability, erosion control, drainage,vegetation and seismic considerations.
4.1 Building Foundation Recommendations
Conclusions provided in this section account for the existing site development of a single family
residential structure. Below the upper 12 inches of Project soils, there are apparently two
distinguishable layers of soil that will influence the bearing capacity and settlement of the
structure. The frost penetration depth is not expected to extend beyond 12 inches below the
ground surface for this Project under normal circumstances.
4.1.1 Bearing Capacity
For the existing foundations at the unknown depth, bearing capacity appears to be
adequate. This is based on the length of time the structure has been in place, and the lack
of visible bearing failures.
4.1.2 Settlement
Due to the soil types and length of structural pressures, any significant settlements due to
bearing pressures have already occurred for this Project. Additional settlements due to
structural loads are not anticipated for this Project.
4.2 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
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.
4.3 Earthwork Construction Recommendations
Earthwork construction has been completed during development, and is not anticipated for this
- Project.
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 8 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
December 2,2008
4.4 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 for the current conditions. 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. A Stability Map from the
Coastal Zone Atlas for the general area of this Project is provided below:
p
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1 `..
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' or `highly erodible' relating to
soils. In addition, DNR did not indicated previous landslide activity near the Project. A Resource
' Map from the DNR Forest Practices Application Review System is provided below:
' Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 9 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County, Washington
December 2,2008
1
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4.4.1 Slope Stability Analysis
The Simplified Bishop Method, utilizing `STABLE' software, was used to analyze the
static stability of the site slopes. Seismic conditions were estimated utilizing worst case
scenario values from the static analysis,a quasi-static analysis coefficient of at least 0.15,
and applying the applicable values to STABLE software. Various radii'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:
Top 6 feet of soils
• Soil unit weight: 135 pcf
• Angle of internal friction: 32 degrees
• Cohesion: 50 psf
Intermediate soils
• Soil unit weight: 124 pcf
• Angle of internal friction: 0 degrees
' • Cohesion: 230 psf
1 Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 10 Parcel 12332 50 00977
Fax:360-275-4789 Mason County,Washington
December 2,2008
1
Hardpan
• Soil unit weight: 140 pcf
• Angle of internal friction: 40 degrees
' • Cohesion: 400 psf
Other parameters utilized in the slope stability analysis included a tension crack near the
' top of the slope, piezometric surface in the lower strata of the intermediate soils that
extends to the top of the hardpan,and toe reinforcement due to the existing retaining wall
on the neighboring property.
' Based on the slope stability analysis, a minimum factor of safety was determined to be
1.3 relative to static slope failures. In addition, a minimum factor of safety of 0.8 was
calculated for seismic conditions. These factor of safeties were primarily limited to the
face of the slope on the south side of Squire Lane, and do not reflect conditions at the
location of the existing residence or downslope structures. For this Project,at the location
of the existing residence, minimum factor of safeties for static and dynamic conditions
were estimated to exceed 1.5 and 1.1, respectively. See the slope stability information in
Appendix D for a depiction of input parameters and example of outputs.
4.4.2 Building and Footing Setbacks
Provided that GTL, client and contractor information is correct regarding past slope
mitigation, a footing setback from the top of descending slopes is not deemed necessary
1 for this Project.
Due to the prevailing surface and subsurface conditions (moderate slope grades and deep
hardpan surface), potential debris flow is extremely unlikely for this Project. In addition,
separate earth movement activities, one during a large seismic event and one after
excessive wet conditions, induced a relatively minor amount of earth movement.
Conservative development, with relation to existing Project conditions, should have a
minimum setback from the ascending slope toe equal to '/2 the slope height.The toe of the
ascending slope is delineated as a grade break between the problem slope and Squire
Lane. This setback would be 13 feet from the slope toe. The building on the adjacent
downslope property is currently much further from the ascending slope toe than the
generally accepted 13 feet building setback.
' 4.4.3 Slope Assessment
The original slope movement on this property was reported to be a result of unclassified
' fill materials, and the 2001 Nisqually earthquake. Due to this episode, a geotechnical
report was prepared(see GTL geotechnical report in Appendix E of this report), and pin
piles were constructed. Envirotech assumes that the pin pile remedy, as presented in
' the aforesaid GTL geotechnical report,was adhered to.
The first slope movement in 2001 was apparently a slumping/ lateral spreading
' mechanism as a result of loose fill soils achieving a denser configuration during ground
movement (earthquake). The most recent slope movement is most likely a deep-seated
' Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 11 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
December 2,2008
I
rotational landslide directly related to a combination of natural subsurface groundwater
and leaking pipes. Although we are not certain, the slip surface appears to be partially
' within the deep sand and clayey soils, and on the hardpan located within 6 to 12 feet
below the existing ground surface.
It is our opinion that the recent landslide is currently moderately unstable with a very low
probability of detrimental consequences. Earth movement appears to be restricted to the
fill material placed on this property during initial construction. Envirotech believes that
future earth movement is probable, but not life threatening. The pin pile mitigation
appears to be functioning as intended, and upslope dwelling units are adequately
mitigated from this hazard. It is possible that underground utilities, utility poles,
pavement, and large trees may be compromised in the future. Tree cutting, and utility/
street repair may or may not be required in the future. Downslope properties are
sufficiently away from landslide hazards, and potential debris flow as presented in the
Building and Footing Setback Section above.
It is our opinion that additional mitigation measures are not required for this Project. Due
to the possibility of additional earth movement and the possible nuisance of re-
landscaping, road repairs, etc.., Envirotech is providing the following optional
remediation strategies for slope improvement that may be implemented at the owner's
discretion:
• Drainage. Because water was the primary cause of the recent landslide, drainage
enhancements are viable for this situation. Finger drains,which run parallel to the
slope face,are best suited for existing condition.
t • Buttressing. Retaining walls and/ or fill near the slope toe are common for
resisting upslope sliding pressures.
• wo k. Removing the existing fill and replacing with engineered fill could
alleviate potential slope movement.
4.5 Erosion Control
Based on the USCS description of the Project soils,the surface soils are considered moderately
to highly erodible. Currently,the Project appears to be sufficiently stabilized,and erosion control
! ' is not necessary. However, temporary and/ or permanent erosion control measures may be
required if future site alterations or earth moving activities are performed.
4.6 Surface and Subsurface Drainage
Based on the Project information, surface conditions,and subsurface investigation as presented in
this report, surface and subsurface drainage requirements are not needed for this Project.
However, drainage enhancements are optional as presented in the Slope Assessment Section of
this report. Envirotech will provide general details and additional guidance if the aforesaid
enhancements are performed.
4.6.1 Septic Drainfield Impacts
The approximate location of the existing septic drainfield is presented on the Site Plan in
' Appendix A of this report. Based on the septic drainfield location with relation to the
Envirotech Engineering Squire Geotechnical hwestigation
Ph. 360-275-9374 page 12 Parcel 12332 50 00977
Fax: 360-275-4789 Mason County,Washington
December 2,2008
' existing topography,the drainfields are not expected to adversely influence the structure
or critical slopes.
4.7 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/ fiction 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.
Vegetation shall not be removed from the face of the problem slopes or any slope with grades
exceeding 40%. However, any tree deemed hazardous to life or property shall be removed.
Leaning trees due to earth movement may have compromised root structures, and are frequently
unsafe. Problem trees have been removed since the initial site visit in December 2007. Other
unsafe trees could be present, and an arborist would be qualified professional to ascertain the
safety of trees.
4.8 On-Site and Off-Site Impacts
From a geotechnical position, it is Envirotech's opinion that the subject property and adjacent
properties should not be detrimentally impacted due to the critical slope. This is based on the
existing site development, existing topography, land cover, and the conclusions presented in this
report. See the Slope Assessment Section of this report for additional information pertaining to
on-site and off-site impacts.
4.9 Seismic Considerations and Liquefaction
Soils within the exploration areas for this Project are generally Type E, corresponding to the
International Building Code (IBC) soil profiles. Soils below the hardpan surface may be
considered Type C. 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. The nearest Class `A' or Class `B' fault to this
property is the Tacoma Fault Zone, in which is approximately 4 miles to the south of this Project.
' This information is based on the USGS Quaternary Fault and Fold Database for the United States.
4.9.1 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 propIgms
caused from liquefaction include submerged, confined, poorly-graded granular soil(}.e.
gravel, sand,silt).No significant saturated sand stratifications are anticipated to be within
the upper 50 feet of the subsoil for this Project.
Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 13 Parcel 12332 50 00977
Fax:360-275-4789 Mason County,Washington
December 2,2008
'I
1 5.0 CLOSURE
Based on the project information 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.
This report presents geotechnical design guidelines, and is intended only for the owner, or
owners' representative,and location of project described herein.
The conclusions and recommendations provided in this report are valid for the existing
development and proposed design features at the issuance date of this report. Changes to the site
other than the expected improvements, changes to ordinances or regulatory codes, or broadening
of accepted geotechnical standards may affect the 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
Michael Staten,P.E.
Geotechnical Engineer
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' Envirotech Engineering Squire Geotechnical Investigation
Ph. 360-275-9374 page 14 Parcel 12332 50 00977
l Fax:360-275-4789 Mason County,Washington
December 2,2008
`t
I
APPENDIX A
SITE PLAN
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1 GEOLOGIC MAP
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APPENDIX C
SOIL INFORMATION
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1
TEST PIT LOG
TEST PIT NUMBER TP-1
PROJECT: SFR Geotechnical Report DATE OF LOG: 11/28/2008
PROJECT NO: 08119 LOGGED BY: MCS
CLIENT: Squire EXCAVATOR: N/A
LOCATION: Parcel 12332 50 00977 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: 10.5' FINAL DEPTH OF WATER: 9'
SOIL STRATA, STANDARD PENETRATION TEST
DEPTH SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 ....... ..........................................
r SM Brown, moist, loose SILTY SAND with
GRAVEL.Gravel is primarily well-graded
and subangular. Sand is mostly medium
1 and coarse. Medium plasticity.
2
3
4
6 _'' SC Brown, moist, medium to stiff consistency
CLAYEY SAND with traces of gravel.
_ Sand is mostly fine and medium. Medium
Plasticity.
8
' _.,_::• Increasing moisture
,;•-: Pockets of Sandy Lean Clay
9
Y '
10
i
' Wet soils
Very dense hardpan
Excavation terminated at 11.5 feet
Groundwater Encountered ENVIROTECH ENGINEERING
This Mfo► odw Pertains ontytoMbodno and mmw not be Geotechnical Engineering
Inle►pmW as being AKXddw of the enft sNe.
III/I+IIII�II�I ��IM
PIN PILE LOG
t TEST PIT NUMBER TP-2
PROJECT: SFR Geotechnical Report DATE OF LOG: 11/28/2008
' PROJECT NO: 08119 LOGGED BY: Jesfield
CLIENT: Squire EXCAVATOR: N/A
LOCATION: Parcel 12332 50 00977 DRILL RIG: None
Mason County, Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: N/A FINAL DEPTH OF WATER: N/A
STANDARD PENETRATION TEST
' DEPTH SOIL STRATA,
SAMPLERS USCS DESCRIPTION LL PI CURVE
AND TEST DATA DEPTH N 10 30 50
0 ..................................................
Unknown
1
d
2 n.
n.L
3
t
4
5
I
Very dense hardpan
6 Pin pile terminated at 6.0 feet
7
8
9
10
11
I
No Groundwater Encountered ENVIROTECH ENGINEERING
Tm#fogan permns owytoMbwft8W MMM ndbe Geotechnical Engineering
ln*pmW as beip#xVoWw of Me enft aft.
I,
RESOURCE PROTECTION WELL REPORT
i �
Washington State Department of Ecology
i :5 Original and In copy-Ecology,a Copy-o,mow,Yd copy-dtNlw
� fdfR-l o t3
PROPOSED USE: /
iM Construction CwTent Notice of Intent No. 6
=i a Decommission ORIGINAL INS7ALL4T10NNotxc
Type of WeRA(Resource Protection
of Intent Number 0 Geotoch Sal Bar'
,y
Consulting Firm A.Irrn i L Unkue Ecology Weil ID Tag No.,(�a-
DRILLING METHOD WELL TION
XHollow Stem Auger 0 Air Rotary Project Name yr fie
0 Mud Rotary 0 Dual Rotary Owner
` 0 Core 0 Other Wen
Borehole Diameter D Cm' County
Location I/ 1/4 S Twu M E or
V MONUMENT Tax Parcel llio.
1{1 0 Above Ground Riser 0 6"x S' 0 V x S' Stickup height 8 C ' Start Date O
Flush Mount )ir8" 012" 0 Other Corti ssion Completed Date !
Amount of Concrete used_; Sk s Static Level
CASING INSTALLED CONSTROCTION OR DECOMMISSION PROCEDURE
PVC )d Sch 40 0 Sch 80 0 Inelinometer ❑Other MatwW or Formation From To
0 Threaded "Diameter fro¢t ft to ft
X Glued _� "Diameter frotp_ b ft to-;0
0 Welded "Diameter frotp ft to ft MIMI
r
SCREEN Izad
PVC * Sch 40 0 Sch 80 0 Other
H Diameter_L Slot 3iu 6on, Q_ft to D ft
0 Pre Pack TYPO PVC Sch 40 0 Sch 80 0 Other
: ';:
Z Diameter of inner,acen� - "x Diameter of suer screen
Slot Size InsW�from ft to ft
i0 Stain less Steel "Diameter from ft to ft
V 0 Other "Diameter from ft to ft
SEAL
Type of material used)(Bentonite Chips Amount L3=V<
❑Bentonite Grout Amount
LU -_ •- __ _ .0 PorU*d Cement Amount
❑Q&qd Amount
® Placed from J ft to
SAND/GRAVEL PACK
Type of material used Silica Sand Size/Q.V ❑Pea Gravel
o oq�w as in to fate
Placed froau ft to 49%wrL _ L
Amount of material used es yz-S
i WELL CONSTRUCTION CERTIFICATION: I constructed and/or accept responsibility,for construction of this well.and its compliance with all
Washington well construction standards. Materials used and the infomnation reported above,are true to my best knowledge and belief.
Driller 0 Tminee Name 0, A Drilling Company Gregory Drilling.Inc.
tiller/Trainee Signatur If TrOnce,licensed driller's
D jAy or Trainee License No. Signature and License No.
1
' APPENDIX D
SLOPE STABILITY
III
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�f
STABLE Slope Stability Analysis System
Envirotech Engineering
Project : squire
Datariie: Dynamic Bishop
STABLE Version 9.03*00u
Bishop
TITLE
Dynamic
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' UNITS (Metric/Imperial) e I
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GEOMETRY DEFINITION
POINTS
NO. X Y
1 0.000 0.000
2 40.000 -0.100
3 126.000 -25.000
4 150.000 -25.000
' 5 150.000 -31.000
6 200.000 -31.000
7 0.000 -6.000
8 40.000 -6.000
' 9 126.000 -31.000
10 150.000 -37.000
11 200.000 -37.000
' 12 0.000 -7.000
13 40.000 -7.000
14 126.000 -37.000
15 150.000 -39.000
16 200.000 -39.000
17 20.000 -0.050
18 28.420 -0.070
19 36.840 -0.090
20 45.260 -1.620
21 53.680 -4.060
22 62.110 -6.500
23 70.530 -8.940
24 78.950 -11.380
25 87.370 -13.810
26 95.790 -16.250
27 104.210 -18.690
' 28 112.630 -21.130
29 121.050 -23.570
30 129.470 -25.000
' 31 137.890 -25.000
32 146.320 -25.000
33 154,740 -31.000
34 163.160 -31.000
¢ 35 171.580 -31.000
36 180.000 -31.000
LINES
Lo X Hi X SOIL
1 2 1
2 3 1
3 4 1 -- - -
sTi48LE®2002 MZ Assocleles Ltd Prinisd on: o4N2= 010:06:27 pme: 1
STABLE Slope Stability Analysis System
Envirotech Engineering
Project : Squire
DataBle: Dynamic Bishop
4 5 1
5 6 1
7 8 2
8 9 2
9 10 2
10 11 2
12 13 3
13 14 3
14 15 3
15 16 3
SOILS
SOIL NAME LINETYPE-PEN COHESION FRICTION UNIT WT.
1 Soil-1 CONTINUOUS-BLACK 50.00 32.0 135.000
2 Soil-2 CONTINUOUS-BLUE 230.00 0.0 124.000
3 Soil-3 CONTINUOUS-BROWN 400.00 40.0 140.000
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PORE PRESSURE SPECIFICATION
SOIL PIEZO RU EXCESS
Y/N/P Value Value
1 N 0.000 0.000
2 Y 0.500 0.000
3 N 0.000 0.000
' PIEZOMETRIC SURFACE
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POINT
g 8
9
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9 POINT PORE PRESSURES
' POINT PRESSURE
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f SLIP DIRECTION (+/- X) _ +
SLIP-CIRCLES
AUTOMATIC
' Circle Centre Grid Extremities
' 160.000
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20.000 * # 180.000
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APPENDIX E
' GEOTECHNICAL TESTING LABORATORY GEOTECHNICAL REPORT
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GEOTECHNICAL TESTING LABORATORY
1BETriv SQUIRE
80 Nt SQUIRE(LANE
BELFIAIR,9 WA 98528
I Rr:: GUOTECHNICAI.REPORT
PARCEL 123325000977
80 NE$QtI1RE LANE
' BEL AIR,WA 98528
N47,,26.083'W1.22^50.256'
�5O
Dcarl Betty:
The above referenced site, the driveway, sidewalk, and adjacent slope
was inspected for damage resulting from the 2001 Nisqually y:p
earthquake. Several cracks were observed in the asphalt driveway, an
area of fill material. Tlae cracked sidewalk surrounding the comer of f.
the rage illustrates slumping of the underlying material. Portions of
the s dewalk and driveway have dropped approximately four inches-
The top of the hillside parallel to the driveway demonstrated slumping
by pull-apart lateral spreading, The garage has no visible cracks or
' unusual spaces and does not appear damaged above the ground
surface.
Adjacent to the garage, trees tilt toward the slope. Although the fill
material is now in a denser configuration, the material may still spreading
compact (settle) further. Since the material has slumped and pulled
' away from the garage, lateral support of the garage footing is non-
existent. The reduction. of the lateral support will allow the garage
footing to fail outward. We are not certain the garage will survive the
next earthquake event without damage. Without further exploration
of the subsurface material, we cannot determine if the garage is
founded on fill material or native soil.
10011 Blomberz Strcet SW,51 pia.WA 98512 1
Phone 0:(360)754-4612 Fax 4:(360)754-4848
GEOTECHNIcAL TESTING LABo ATORY
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To remedy the situation, we propose the following. Excavate the soil, vegetation, asphalt, avid concrete
surrounding the garage corner to a depth below the footing. Notice the amount of organic material in
the excavated material. inspect the garage footing for. damage. Below the excavated area, the soil must
r be compacted. Either drive pin piles to refusal near the footing and surround with concrete or place
ecology blocks next to the footing to provide lateral support. Fill material shall be imported and
compacted in 12-inch lifts. Sidewalks and asphalt are then replaced.
Or, since pin piles are founded deep in native material, we suggest using the pin pile remedy. Over the
past several years, we have implemented a system for underpinning or supporting relatively light
structures such as residences and/or one to two-story apartment or office bui.l.dings where access is
restricted and a competent bearing layer is located at relatively shallow depth. This system consists of
installing 2-inch diameter pipe piles with a jackhammer to transfer building loads to the bearing stratum.
Structures that have been underpinned or supported with this system are currently performing
satisfactorily. The 2-inch diameter pipe pile support system is particularly adaptable to conditions
where access is restricted but it requires that structure loads are such that the load per pile does not
exceed about 2 tons and that a suitable bearing layer exists at relatively shallow depth(about 30 ft.)
Installation of the 2-inch pipes requires a jackhammer, air hose, and air compressor. This equipment is
compact and mobile, allowing economic installation of the pile. For example, the air compressor can.be
parked ua a driveway or on the street and a length of air hose selected so that a.jackhammer can be used
where required for installing.footing underpinning for support.
n design load of tons per pile may be used for designing footing underpinning for support. Load tests
performed during past installations demonstrate that this design load is achieved when the pipes are
driven to a resistance of one inch or less of penetration for one minute of continuous driving.
The pipe underpinning piles are generally considered as end bearing since they normally penetrate soft
' or loose soils overlying the bearing stratum.
The pipe piles should be driven with an 80 to 90 pound jackbanuner to a depth of 10 feet or to reach the
' specified driving resistance (one inch or less of penetration for one minute of continuous driving).
Standard threaded couplings are used to connect pipe sections.
1.0011 Biomberg Street SW,Olympia,WA 98512 2
Phone#: (360)754-4612 Fax#: (360)754-4848
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GEOTECHNIGAL TESTING LAB®RA,TORX
The pipe sections should be butted together about the center of the coupling to avoid stripping the
threads during driving. If hard driving is anticipated, the ends of the pipe sections can be machined
square to provide more surface area for stress transfer during driving.
In the areas to be underpinned, the piles arc driven in the excavation exposing the bottom of footings.
The piles are installed as close to the footing as possible. The protrusion of the footing is normally
removed to allow as near a vertical orientation as possible. The spacing between piles generally ranges
from about 2 to 3 .feet center to center beneath typical structure walls to about 1.5 feet center to ceater
for supporting heavier elements such as fireplaces or brick trimmed walls.
following driving, the piles are cut to Length to allow for clearance for the leveling system- There are
two methods that are used for leveling and transferring footing loads to the piles. One system consists
of attaching a screw jack assembly in the pipes and then laterally Jacking and shimmi_og the pipes
beneath the footing. Screw jacks and/or shuns as well as the tops of piles are protected in a backii.11 of
cement mortar.
The piles should be installed as close to the center of the footing as possible. The spacing between piles
should be six feet center to center maxinium beneath typical structure walls. The pile need only be
placed along the side nearest the slope in order to meet the setback requirement, as measured from the
bottom of the.footing(end bearing of the pile)perpendicular to the intercept of the face of the slope. We
suggest two pin piles for the garage corner.
The piles after being installed vertically as required should then have a pile cap constructed over them..
:A plan is enclosed.
' If you have any questions. please call us at(360) 754-4612.
' Respectfully Submitted,
GFOTECHNTCAL TESTING LABORATORY
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' Harold Parks, L.G., L.E.G.
Senior Engineering Geologist
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1001 l Blomberg Street SW,Olympia, WA 98512 3
Phone ff-. (360)754A612 Fax#t:(360)754-4848
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GEOTECHNICAL TESTIlNG LABORATORY
Typical Pin Pile Drawing
#3 Rebar
Footing laootinLy Form
2 in.
1 � _
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Pine Pin Pil � P ? deep
I P
Profile View(End)
Not to scale
#3 Rebar
Pipe Pin PiI.
' 2 in.
Plan View
' Nnt to cralF
' 10011 Blomberg Sftm SW,Olympia WA 98512 4
Phone#:(360)754-4612 Fax#: (360)754-4848
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