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OF EDMONDS
CITY
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121 Sill AVI:NUF NOR)'11 - 1?UMONUS.W A 98021I
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PI IONS: (425) 771-0220 - FAX: (425) 771.0221
STATUS: ISSUED
Permit #: BLD206WU 6.
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Expiration Datee:7/6/2007
Project Address: 16105 75TH PL, W,'EDMONDS
Parcel No, 00-i 13105800600
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"I'UNG& III:\N)' ISUI
4D ARCIIH ECTS S211 AA1LINI� HOMES
18811 1�. 1.1 \V
1414 NIARK17r 51' 18811 ISI1'l. W
BO'I'111.11 ,1 \ ISO 1'-
KIRKLAND, WA 98033 BO'r111:1.1., WA 93012
•125-34, --
425-576-1414
LICENSE ft 51'Rl-A111,944JC EXIT 4/3/200R
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ISLr1A S1 R
LOWER I I ()( )it 427 SI' WITH $40
SF GARAQ AND 581 SF UNI IF7 TE) STORAGE
i 2532 SI' WITH 456 SF (GARAGE- 492 SF ROOF UHCK. COVI?RED'I'ERRACH 248 SF AND 79 SF COVERED PORCI 1.
MAIN 1 I .R)11
UPPER I.I S R )It 1970 SF W IT1I 198 SF DECK.
VALUATION: S529,892
PERN41'I I \'PI.. Itesidenlial
PERMIT GROUP: 64-Si!ielo Family Residence Nmc
GRADING. Y CVDS: 3240
TYPE OFCONSr RUCTION: VB
RETAININO \VAI.1. ROCKERY: Y
OCCUPANT OROUI': R3
OCCUPANT LOAD:
PENCI. t 0 X 0 IT.)
CODE: 2003
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O'I'l1Elt a. -..- O'1' im msc:
ZONE KS-20
NUNllfl..lc III M'ORIES:3 -
VESYED DAT 1::
NUNIBI:1< OF DW EI.LINGUNI'I'S. I
BASRNII'N"I O I SI' r1.00R: I) ?NO 1:I.00W 0
BASEMEN'(': 427 151' 17I.00R: 2532 4ND rI.00R: 0
3RD 1:11' It 11 GARAGE (I DE —K: 0 OTHER
3RD FI.00R: 1970 GARAGE 1296 DECK. 1017 O'LIIER'
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Itl?I)l Rltl'D PROPOIED'29 RI-QDIRI:D: 1("13 I'ROI'OSI:D: 37 i-QUIRI:D' I'I<I )I'lltil�D _'
I IISItll l'I \1.I OWL*.D:25 IIROIIOSFD:24. 125 REQUIRL'D: 10/35 PRorosliu: l8
SI'1'IIA( ). Nul Fs RpUu Per Landscape ('Ian Prier 10 0ns1.
APPROVALPERIMIT
I Al 4tl.l.. 10 CONII'I.Y WI'rll CITY AND SPATE I.AWSREGUI.A'I' INGC'ONSI"RUCTION AND IN DOING THE WORK ALI'I'I IORI%I-O
'I'III:RI M. NO PERSON WILL. BE EMPIA) ED IN VIOI.A'I'ION OF) "III: LABOR CODE OF'I'lll: Sr ATE OF WASIIINGI"ON RI.I.ATINGTO
WORKNIEN'SC'OMPENSAI' ION INSURANCE AND I(C\\' 1827.
THIS AITI R: ATION ISNOT A PERMIT UNT11. SIGNED BY THE BUIUANOOPPIC'IAI. OR IIISIIII:R OEPU'I'Y AND AU. IT SARI: PAID.
4 a
ff Ih re n irll le Released By le
ATTENTION
I'1' IINIAMTIn.10L'tit:OR(1(VITY:\01!II.UI\t)ON 51A1!CII(RIi ONI: Ill. rINA1.IN81'1'IIONlIASRI:I:N NIADV AND APPROVAL ORA('I!Rl'll'ICA11: tll
OfY'l!I':\NCl' I IA8111IFN (iN.\N'lli U.1'R(•I119 IRVI III- IRCI I II
,11N'I IIVI'. APPLICANT ASS F5SOR O O'1'IIm
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• REQUIRLn SPECIAL INSI'1•.CI'IONS FORTIRS PROJECT:
1)STARTOP WORK Idi1'1'1`R FROM CTol'I)CHNICALf•NCANI:iI512OP RECORD
2)f1NERAL SI1 E MONrrORING BY (Td)TECIi OR RECORD DURING W Er W EATHPR CONSTRUC110N
3) SOIL BEARING VIRIFICATION
4) STRUCT-URAL PILL PLACFAIENr AND COMPACr1ON
5) ROCKERY/RETAINING WALLCONSTRUCrION INCLUDING DRAINAGE
6)17001•ING DRAINS AND SUBSURFACE DRAINAGE
7) I-INA L GEOTECII CONSTRUCTION REPORT
• REPLANTPERI.ANDSCAI'EPI:ANPRIOR'1'O1'INAI.
• Site Restoration Bond 550,000 posted 6127/06.
• Lot line stakes must be in place at the time of foundation/setback inspection.
• All new. wdended. m-built or relocated electrical utility and/or service shall be placed underground.
• Approval ofthis foundation design is conditional subject to inspection ofexisting site soil conditions.
Retaining Walls must be designed and constructed to resist the lateral pressure of the retained arterial.
y Provisions must be erode forthe control and drainage ofsurl'ace tinter around buildings.
Installer shall provide the ns ralf scmrces installation, operating instructions, and a whole house ventilation system operation
• description. A label shall be alTsrrd to the whole house,timer control that reads "Whole House Ventilation" (see operating
n inslctlons).
Maxingrm Ileight 25 feet. Measured from average elevation ofundisunbed soil at comers ofexiended building rectangle.
Subject to field check by his ilding departn—L
• Special inspections have been called fnron this project and arc noted on the approved construction plans and building permit.
It is the owner and/or contractors responsibility to assure that reports are provided to the City on a weekly basis. Be advised—
ifspecial inspection reports am not Ibrthconsing. the Building Official mty issue a "Stop Work" and no City inspections will be
provided until such tine as the reporting agency has complied and reports arc reviewed and approved by the City.
Hose Bibbs (exterior lauccis) arc required to have a penronently affixed anti -siphon device installed.
• In addition to the required pressure/mlicfvalve, an approved listed c4ransion tank shall be installed on all hot water tanks. Per.
UPC 608.
• Type B or vent connectors required tin firel-burning appliances passing through unheated spaces: per IMC 803.2
Obtain Electrical Pens it Irons State Dupannrcro ofLabor & I uslustries. 425-290-13(P)
• Pursuant to UPC 605.2a timer service sit utoff shall be installed on the water line as it enters the building.
Cos pipe test must be observed by City Building Inspector. allidavils shall not be accepted.
I• City approved plastic piping may be used in waterservice piping provided that where metal water service piping is used fix
1 electrical grounding purposes, replacement piping shall be of like ncncrials (UPC 604.8). A slate electrical permit and
S inspection is required ifelectrical grounding is altered. rerawed,unproved. or added Contact Slate Dept - of Labor&
Industries Electrical Division at 425-ZW21(). -
} Subunit all special inspection reports to the City Building Inspectoron a weekly basis.
M1. As required by Ordinance #2661. the geotechnical engfneerofrecord shall monitorthis site during construction I'oreompliunce
with the recortunendations in the geotechnical report including: site exuavation, shoring, soil support for foundation including
piles. soil bearing capacity. subdrainage installation. soil cornmetions, and other geotechnical aspects of the construction.
x: Specific recommendations contained in the approved geotechnical report must he implemented by the owner.11m
geotechnical engineer shall nuke written.datedreports on the progress oftbc construction and submit the report to the
Building Official on a weekly basis until all site grading, drainage, lbundation and associated ground work is complete.
Omissions or deviations friwmthe approved geolechinical rcpon and/orapproved plans or specifications shall be highlighted
and immediately submitted in a seperatc letter to the City 1•orrevicw.'I'he City shall be advised in writing of\auk stoppages of
rnore than one week. In addition to the geotechnical mc;ihoring.special inspections based on the provisions ol'IBCSectiou
1704 arc required when specified on the nppmved plans. Olherspecial inspections nay also be required by the geotechnical
engineer, architect. or structural engineer of record (refer to approved plan set). At the corn letion offinal inal site grading and all
pernsitled structures, a final geotechnical report, prepared by the geotechnical enginecrshall be subnrittcd to the Building
Official. Ibis report shall contain a statement that. based upon his/herprofessional opinion. site observations. and testing
during the nxnsiutring ollhe construdkrn. the completed devclnpnxint substantially complies with the recorintendalions in the
geotechnical reportand with all geotechnical related perm requirenKnls. Any deviations oromissions in the rcpon. plans. or
specifications that occured during construction shall be addressed separately. Oceupancr. find approval. orrcicase of the
bond for the project shall not be granted until the rcpon has been reviewed and accepted by the Building Official.
• Any request for the tindification.w ariance or other adninistmlive devimiun lhereinaller"vnrkmee")rust be sprs;ificalh called
out and ident ifued. Approral ofany plat or plan con(uining provisions which do not conyrh' with City code and fix which a
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variance has not been specifically identified, request and considered by the appropriate City official in accordance w9lh the
appropriate provision of CIy code or Slate lacy does not approve any items nut to code specification.
• Pursuant to Ul'C608a pressure regulator valve(I'RV) shall be installed near the avater shutoff
• Sound/Noise originating from temporary construction sites as a exult ofconslmCiion activity arc cycnpt from the noise limits
of r(CC C7rnpter 5.30 only during the hours of7:ODnm to G:(X)pnl on weekdays and 10:(X),im and G:(X)pmod Saturdays. cu:luding
Sundays and Federal Holidays. At all other liras the noise originating liumconstmctiou sites/activites Trust Comply with the
noise limits ol'Chapter 530. unless a variance has been granted pursuant to ("CC 5.30.120. -
• Applicant, on behait-ofhis or hcrspouse. heirs, assigns, and successors in interests. agrees Io indemnify defend and hold
hamdess the City of FdHrlonds, Washington, its officials, employees. and agents Innnany and all claims I'urdarnrges of
whatever nature, arising directly or indirectly rrom the issuance Ib this pewit. Issuance of this pemlit shall not be decried to
nudity, waive or reduce any requirements of any City ordinance not flout in any wry the Cny's ability to enforce any ordinance
provision.
• 48 hours notice is required vvhcn requesting your FINAL Engineering Inspection. 425-771-0220. eN.1320.
THIS PERMT AUTHORIZES ONLY THE WORK NOTED. THIS PERMIT COVERS WORK TO BE DONE ON PRIVATE PROPERTY ONLY. ANY CONSTRUCTION ON 111E
PUBLIC DOMAIN (CURBS, SIDEWALKS, DRIVEWAYS, MARQUEES. ETC.) WILL REQUIRE SEPARATE PERM SSION.
PERMIT TIME LIMIT'. SEE ECDC 10.00.005(A)16)
e•
BUILDING (425) 7710 20 LXT 1333 FNCINEERING (425)771-0220 EXL 1326 1 FIRE(425)77"21
PUBLIC WORKS(425) 771-0235 1'R&TREA'ITIIENT025) 672-5735 RECYCLING 1425) 2754801
&Emsion ControllMubiliration
• &Traf is Control
&Stoml Tightline
• - EStom Connect to Stub
• &Storm Detention System
E-Foolin_g Drain Connection
&Water Sur ice Unc
• E-Driveway Foml&Slope V&.
• &Engineering Final
B-Setbacks
B-Footings
B-Foundation Wall
B-Isolated Footings/Piers
• B-Retaining Wall
• B-Slab Insulation
• B-Plumb Cmund Work
• B-First Floor Framing -
B-Plumb Rough In
B-Cas'rest/Pipe
LLEquipment-Mesh
• B-Evterior Sheathing
• B-Shear Nailing -
• B-Ilcight Verification -
B-I'mming - -
B-W all Insulation/Caulk
B-Floor Insulation/Caulk
• B-Ceiling Insulation/Caulk
• B-ShcetmckNail
• L4-Building Final
• B-I,alh Inspection -
• EMMA SPI-CIALINSI'f•: rIONS SELAIPROVO) PLr1NS
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GARY HAAKENSON
CITY OF EDMONDS MAYOR
+Y` %(•r fa 121 5TH AVENUE NORTH • EDMONDS. WA 9BO20 • (425) 771-02M • FAX (425) 771-0221
Website: www.ci.etlmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
1" c. 18gZ Planning • Building • Engineering
August 12, 2005
Tung Bui
18811 Ist Place West
Bothell, Washington 98012
RE: 16105 75th Place West, Request for Waivers
Dear Mr. Bui,
The City is in receipt of your letter dated July 21, 2005. As you were informed I was out of the office
until August 9th and could not respond earlier.
The development ordinance regulating the Earth Subsidence and Landslide Hazard area of North
Edmonds (City Ordinance 92661) was enacted to provide both substantive and procedural provisions
relating to the issuance of building permits. The City requires peer review to ascertain whether the
submittals were prepared in accordance with generally accepted engineering practice or the practice of
a particular specialty; primarily because the City lacks a team of professional engineers on staff to
perform such review. Peer review also provides objective technical assistance to both the City and the
applicant into the various engineering aspects of the project. Although your design professionals have
impressive backgrounds, it is noted that none have extensive design or review experience in our
landslide hazard area. Accordingly I am denying your request for a peer review waiver.
Regarding the surety bond requirement, the reason the City requires a surety bond is to facilitate clean-
up or repair if failure occurs during construction and causes damage to City -owned infrastructure. The
surety bond is an expeditious way for the City to be assured that immediate action (within 72 hours)
will be taken (rather than waiting for insurance claims, etc.). For homeowners who desire to post the
bond (instead of their contractor), most choose to establish a frozen fund account with their lender (in
this way there is no out-of-pocket expense as a portion of the loan is simply held in a separate
account). Although the City has not yet experienced a failure during construction, most development
projects exceed one year (through the wet season) and it is reasonable and prudent for a surety bond to
be posted to protect public improvements; therefore your request for waiver denied.
df you hove any further questions please feel free to contact my office at 425-771-0220.
Sincerel�, r
Duane V. Bowman
Development Services Director
• Incorporated August 11, 1890
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RECEIVED
JUL 2
Mr. Duane B: Bowman July 21, 2005
Director of Development Services DEVELOPMENT SERVICE:
121 5th Ave No.
Edmonds, WA 98020
Tung Bui
18811 1" Place West
Bothell, WA 98012
Dear Mr. Bowman,
I am in the process of designing my home to be built at 16105 75th Place West in the
Meadowdale area. By this letter, I request your waiver of two building permit conditions set forth
in Ordinance Number 2661, Chapter 19.10 defined to be under your discretion. I believe my site -
specific situation warrants such waivers as noted by the facts below:
I. RMucst to Waive 19 05 060 Review to Determine Compliance with Engineering Practice.
The same code section states that, at the discretion of the Director, he may require or waive
the need for a peer review of applications by a City -retained engineer, gcotechnical engineer,
i geologist, architect, or structural engineer to determine whether the submittals were prepared
in accordance with generally accepted engineering practice or the practice of the particular
i specialty. I think it is in both mine and the City's interest to hold my retained professionals to
be responsible and accountable for their professional expertise without the "safety net" of a
city -retained professional(s) that may give my professionals a reason for denying liability
because their work was reviewed and approved by City -retained professionals. In fact, I am
so confident in my hand-picked highly qualified professionals in their respective Fields that I
find duplicating their work would both be an economic waste and time consuming. I am
concerned that an unintended consequence of a peer review may provide my professionals
with a possible legal argument that they should not be liable for any faults because their work
were approved by City -retained professionals. I am willing to put forth the extensive
experience of my professionals, including architects, structural engineers, geotechnical
engineers, and foundation and excavation experts as among the best in their fields um the
Puget Sound area. In my profession as commercial builder of cellular sites in the past 10
years in the Pacific Northwest, the last six years in the Puget Sound area, I have built the
most complex and challenging structures 150 feet high, 40 feet deep in the ground, steep
mountainous slopes, using various footing techniques to assure soil and foundation stability.
My affiliation with the construction professionals has afforded me an opportunity to select the
top people in their profession to be on my home design team. rhey are as follow:
❑ Barbara Pickens of 4D Architects is one of the founding principals of 4D Architects for
the past 20 years. Most of Barbara's projects involve complex sites: steep slopes,
waterfronts, and other environmentally critical areas. Starting in the schematic design
state, Barbara involves structural engineers and geotechnical professionals experienced at
working on the steepest and most geologically challenging sites in the Puget Sound area.
From design to permitting, Barbara has developed an approach and an experienced team
capable of working on the most difficult lots. Barbara's diverse background includes
homes from 900 square feet to 33,000 square feet as well as commercial architectural
projects such as schools, hospitals, and Olympic villages.
❑ Khew Lew, P.E of LSl Adapt, is the Principle Engineer functioning as Geoeechnical and
Environmental Consultant with specialized skills in slope stability and slides assessment
on many Pacific Northwest and international projects. In the past years, Khew has been
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credited with 41 significant local and international geotechnical and environmental
projects such as his investigative and restoration efforts at large landslide within
glaciolacustrinc silt and clay along side of SR-2 above the Skykonrish River, SR-27014
bridge replacement in Pullman, Washington as part of an embankment construction over
alluvial soils, organic silt, and loess fill. Khew was also responsible for the subsurface
exploration for the City of Centralia to establish conditions for the siting of a 4.5 million
gallon water tank on an existing landslide at Seminary Hill, many significant riverbank
subdividision projects and nuclear facility siting geotechnical subsurface studies and
various other significant geotechnical projects in Winnipeg, Manitoba, Pinawa, including
Malaysia and Antarctica. Khew also authored or co-authored 8 international papers on
various soils engineering topics such as Riverbank Stabilization to Yield States and
Stress -Strain Relationship in A Natural Plastic Clay. Khew's expertise is brought to my
home project to assure that the best geotechnical engineering talent is applied to the
conditions presented in Meadowdale.
3 Rolf Hyllseth, P.E., L.G. of LSI Adapt, is the Senior Gcotechnical Engineer, received his
B.S. in Geological Engineering in 1988 and is a registered Civil Engineer and Licensed
Geologist in the state of Washington with over 16 years of experience as a geotechnical
engineer and project manager. He specializes in the areas of slope stability,
landslide analysis, liquefaction and seismic analyses, and stone column ground
improvement. He has been involved in major civil engineering projects such as port
facilities, storm water handling facilities, railroad yards, pipelines, schools, and
transportation facilities.
❑ Cheryl Girad of American Engineering Corporation has 22 years of land development
experience with field survey, drawing preparation, development feasibility research and
analysis, subdivision planning, erosion control design, site grading, storm drainage,
roadway and utility design for commercial and residential projects. Recently, Cheryl
works on private and public municipal water and sanitary sewer systems comprehensive
planning, hydraulic analysis, and systems design.
Accordingly, I request that we not dilute their professional liability by having another entity
(City -retained) effectively certifying their work. I realize that the City -retained professional
may challenge certain aspects of my team's work as any design has a certain acceptable range
that may be interpreted differently by different engineers. However, having City -retained
engineers modify my team's work could give rise to arguments by my professionals (1) that it
was the City -retained engineers who altered the design, or (2) that they are absolved of
liability because their work was independently supported by City -retained professionals.
Neither of the situations would be in my, nor the City's, best interest should there be
questions of liability be raised with my professionals in the future.
In the same Code section, it states that "the Building OJjicial shall not be required to inquire
further into the adequacy of the report, but rather may rely upon the submittals as warranted
by the owner." Relying on this language, 1 request that the City not inquire further into the
adequacy of the report, but rather, rely upon my professional design team that the design
work is done in a mariner consistent with current engineering practices with care and
precaution to the landslide concerns in the Meadowdale area.
Due to the fact that my design team is extremely experienced in working on complex sloped
projects, deep earth design experience, and the fact that having City -retained engineers may
dilute my ability to hold my professionals liable for their work products, I respectfully request
that you waive the peer review requirement.
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2. Rccluest to Waive 19 05 O50 (A) Surety Bond requirement by Owner. The Code states that
"whenever the Director determines that the public interest would not be served by the
issuance of a permit in a potential slide area without assurance of a means of providing for
restoration of areas disturbed" he may require a surety bond to be posted by the
applicant/owner. In terms of a sloped project, my property is relatively simple. The existing
home is on nearly half an acre with gentle 18 degree slope. I am attaching a site plan for your
review. The risk of damage as to the public interest may be that there would be some dirt on
the public street, which could be easily removed back to my property as the first 45 feet in my
property from the street is essentially Bat. Because the risk of harm is small (we have an
extensive water retention plan, civil engineering plan, water erosion plan, and construction
staging plan) and the gravity of harm is also small, I request that the Surety Bond requirement
be waived for this project. Alternatively, I request that a posting of $5,000 instrument of
credit be on file with the Director's office similarly conditioned as a surety bond to assure
restoration due to any damages resulting the construction.
If you need any clarifications as to my requests, please feel free to contact me by phone, email, or
home address listed. I respectfully await your decision.
Sincerely,
c--
Tuug"�ui�
Email: tunes bui d.ccmon.aet
Phone: (425)345-8864
Address: 18811 1" Place West, Bothell, WA 98012
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LSI Adapt, Inc.
® 615 _ eh Avenue South
Seattle, Washington 98104
Tel (206)654-7045
Fox (206) 654-7048
Adapt-'ymvl.IsiadaPt.com
May 23, 2005
WA05-12239-GEO
Tung Bui
18811 — I' Place West
Bothell, Washington 98012
Subject: Geotechnical Engineering Report
Proposed Residence.
16105 — 75ih Place West
Edmonds, Washington
Dear Mr. Bud:
LSI Adapt, Inc. (Adapt) is pleased to submit this report summarizing our geotechnical engineering evaluation
for the above -referenced project. The purpose of our evaluation was to derive design conclusions and
recommendations concerning site stability, site preparation, excavations, foundations, floors, drainage, and
structural fill.
As outlined in our proposal letter dated December 22, 2004, and subsequent discussions, our scope of work
comprised field exploration, geotechnical research, geotechnical analyses, and report preparation. We received
your written authorization for our evaluation on January 6, 2005. This report has been prepared for the
exclusive use of Mr. Tung Bui, 4D Architects, and their agents, in accordance with generally accepted
geotechnical engineering practice and for the specific application to this project. Use or reliance upon this
report by a third party is at thew own risk. Adapt does not make any representation or warranty, express or
implied, to such other parties as to the accuracy or completeness of this report or the suitability of its use by
such other parties for any purpose, whether known or unknown to Adapt.
We appreciate the opportunity to be of service on this project Should you have any questions concerning this
report or need further assistance, please contact us at (206) 654-7045.
Respectfully Submitted,
LSI Adapt, Inc.
Rolf B. H llset4P.-//tp
Senior Geotechnical Engineer
Distribution: Tung Bui(1)
4D Architects (3) Attn: Ms. Barbara Pickens, ALA
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TABLE OF CONTENTS
WA05-12239-GEO
I
1.0 SUMMARY...............................................................................................................
2.0 SITE AND PROJECT DESCRIPTION...........................................................................................3
3.0 REVIEW OF PREVIOUS DOCUMENTS........................................................
.............................. 3
4.0 EXPLORATORY METHODS..............................................................................................
4
5
5.0 SITE CONDITIONS.......................................................................................................................
5.1 Surface Conditions..............................................................................................................5
5.2 Soil Conditions.................................................................................:..................................5
6
5.3 Groundwater Conditions ..................................... :..........................:............................
........
5.4 Seismic Conditions.......................................................:.....................................................7
:7
5.5 Environmentally Critical Area Conditions...............................................................
..........
6.0 CONCLUSIONS AND RECOMMENDATIONS ..........:..............................................................8
6.1 Site Liquefaction Risk Evaluation......................................................................................9
10
6.2 Slope Stability Considerations and Landslide Risk..........................................................
6.3 Site Preparation...................................................................................
12
14
6.4 Spread Footings.............................................................
6.5 Slab -on -Grade Floors.......................................................................................................15
16
6.6 Backfilled Walls .................................................... :...........................................................
t 8
6.7 Drainage Systems..............................................................................................................
6.8 Structural Fill....................................................................................................................20
22
7.0 RECOMMENDED ADDITIONAL SERVICES ................................................................
. ..........
24
8.0 CLOSURE...................................................................................................................
Figure l Location/ropographic Map
Figure 2 Site & Exploration Plan
Figure 3 Geological Cross Section A -A'
Figure 4 Geological Profile B-B'
Figure 5 Drainage Plan
Appendix A Field Exploration Procedures and Logs
Appendix B Laboratory Testing Procedures and Results
Appendix C Slope Stability Analyses and Results
May 23. 2005
Tung Bui Table of Contents
Adapt Project No. WA05-12239-GEO
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1.0 SUMMARY
Based on our field explorations, research and analyses, the proposed construction appears feasible from a
geotechnical standpoint,. contingent on the implementation of the recommendations presented in this
report. The following summary of project geotechnical considerations is presented for introductory
purposes and, as such, should be used only in conjunction with the full text of this report.
Project Description: Development plans call for construction of a private residence with
basement and associated driveways within the central portion of the site.
Environmentally Critical Area: Because of the site -specific geologic (landslide area) and
topographic (steep slopes) conditions, the site is classified as a Earth Subsidence and
Landslide Hazard Area based on the Edmonds City Critical Area Regulations. Provided
that the recommendations of this report are implemented, the project is considered
feasible and is not anticipated to adversely affect the stability of the subject site or
adjacent properties.
Exploratory Methods: We explored subsurface conditions by means of three borings and
four CPT probings, advanced at strategic locations across the house footprint area and the
site slopes, to depths ranging from about 17 feet to 47 feet below ground surface (bgs).
Soil Conditions: soil conditions within the central portion of the subject site consist of
varying thickness of landslide debris (interlayered clay, clayey silt, and silty sand/sandy
silt), underlain by a 5 to 8-feet thick layer of intermixed, loose to medium dense, clayey
silt and silty sand, with inclusions of hard clayey silt fragments, roots, and peat lenses
(landslide shear zone). Our explorations disclosed this landslide shear zone to be very
thin or non-existent within the western margins of the site (lower portion of site slopes
along 75 h Place W). The underlying, native soils below the slide shear zone consist of
stiff to very stiff, interlayered clay and silty clay.
Groundwater Conditions: At the time of exploration (January through April, 2005),
groundwater seepage was encountered below a depth of about 13.0-feet bgs in our
explorations within the central portion of the site. These observed zones of seepage are
interpreted to be perched atop underlying layers of relatively impermeable, native, stiff to
very stiff clays and silty clay below the slide shear zone.
Foundations: In our opinion, the house may be supported by conventional spread
footings that bear on the medium stiff clay/clayey silt or medium dense sandy silt/silty
sand, provided that the slight risk of potential post -liquefaction settlement is acceptable
and the structural design incorporates provisions to minimize the adverse effects of such
potential settlement. For properly prepared footing subgrades, these spread footings may
be designed for an allowable, static bearing pressure of 2,500 psf and a seismic bearing
pressure of 3,300 psf.
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• Floors: Typical soil -supported, slab -on -grade floors are feasible at this site, contingent
on proper subgrade preparation and provided that the slight risk of potential post -
liquefaction settlement is acceptable and the structural design incorporates provisions to
minimize the adverse effects of such potential settlement.
• Subsurface Walls: In our opinion, conventional backfilled, cast -in -place concrete walls
will adequately support the proposed basement and site perimeter retaining wall system,
provided that the slight risk of potential post -liquefaction settlement is acceptable and the
structural design incorporates provisions to minimize the adverse effects of such potential
settlement. These walls should be designed to withstand appropriate lateral pressures, as
discussed in this report.
• Seismic Considerations: Based on our literature review and subsurface interpretations,
we recommend that the project structural engineer use the following seismic parameters
for design of buildings, retaining walls, and other site structures, as appropriate.
Design Parameter Value
Acceleration Coefficient (10 % probability) 0.30
Acceleration Coefficient (2 % probability) 0.55
Site Class (2003 IBC) D
• Temporary Excavation Considerations: All temporary soil cuts associated with site
regrading or excavations should be adequately sloped back to prevent sloughing and
collapse. For the soft to medium stiff clay/clayey silt and loose to medium dense sandy
silt/silty sand (landslide debris), we tentatively recommend a maximum temporary cut
slope inclination of LSH:IV.
• Trench Drain Dewaterine System: In order to mitigate the potential adverse affect of the
proposed house basement cuts on site stability and to improve the overall stability of the
subject site, we recommend that a permanent, subsurface, trench drain dewatering system
be installed to a depth of about 5.0-feet below the finished floor elevation of the basement
portion of the proposed house. This dewatering will also aid in limiting the extent of
potential liquefaction and minimize the potential for liquefaction -induced settlements
below the house.
Tung Bui
Adapt Project No. WA05-12239-GEO
May 23, 2005
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2.0 SITE AND PROJECT DESCRIPTION
The proposed building site is located at I6105 — 75" Place West in Edmonds, Washington, as shown on
the enclosed Location/Topographic Map (Figure 1). The subject site comprises three previous residential
West approximately 200 feet north of 1.62nd
building parcels, located along the east side of 75' Place and
The is shaped as a parallelogram and is bounded by 75" Place West on the west side,
Street SW. property
and adjacent residential house lots on the north, east, and south sides.
Development plans indicate that the new residence will be situated within the central portion of the site.
the with the lowest floor level
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The house will comprise three floor levels stair -stepping up slope,
daylight basement with a planned finished floor level at about 66.8-feet elevation.
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consisting of a
Conventional, shallow spread foundation support, combined with subsurface, cantilever concrete walls,
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are proposed to provide support for the house. It is anticipated that temporary, open -cut excavatiuns will
The to the west and the east of the
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be feasible during construction, within the given site constraints. areas
to accommodate driveways, car parking, and patio areas. Limited site grading will
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house will be regraded
also take place within yard areas north and east of the proposed house. The enclosed Site &Exploration
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Plan (Figure 2) illustrates the site boundaries, the existing and proposed topographic contours, the
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locations of the proposed house and other planned structures, as well as adjacent existing features.
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The subject site is located within a documented, recent landslide area designated as the Meadowdale
by Adapt a
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Landslide Hazard Area by the City of Edmonds. This current geotechnical report provides
the subject site and makes specific
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comprehensive evaluation of the subsurface conditions at
site development, in accordance with the City of Edmonds Development
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recommendations concerning
Services Department (DSD) guidelines for geotechnical reports.
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The conclusions and recommendations contained in this report are based on our understanding of the
from layout drawings, written information,
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currently proposed utilization of the project site, as derived
Consequently, if any changes are made in the currently proposed
and verbal information supplied to us.
to modify our conclusions and recommendations contained herein to reflect those
project, we may need
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3.0 REVIEW OF PREVIOUS DOCUMENTS
the following previous documents pertaining to the subject property
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As a part of our study, we reviewed
and vicinity (on file with the City of Edmonds DSD):
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s Terra Associates, Inc.; Geotechnical Report — Derry Residence; January 1992.
• Terra Associates, Inc.; Geotechnical Report — Meadowdale Beach / Anderson Subdivision
(Lorian Estates); June 6, 1989.
• GeoEngineers; Geotechnical Consultation Report — Proposed Short Plat, Block 59 of
Meadowdale Beach; November 22, 1989.
Inc.; Geotechnical Engineering Report — Proposed Residence, 7P Place
• DODDS Geosciences
West (75`" Place W & Meadowdale Road); November 12, 1996.
May 23, 2005
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• Neil H. Twelker and Associates, Inc.; Proposed Construction at 16008 — 75`h Place W; October
7, 1996.
• Geolingineers; Geotechnical Consultation — Proposed Residential Construction, Meadowdale
Beach Area (Lot 2ofShort plat No. S-13-90) ; March 29, 1994.
If any of these documents were not available for review through public record, we obtained permission to
use the document from its rightful owner, as indicated above. Our conclusions and recommendations are
based in part or wholly on the information contained in these documents. Our geotechnical
recommendations are only as good as the accuracy of these previous documents; Adapt assumes no
responsibility for errors or omissions resulting from possible inaccuracies on documents prepared by
others. We recommend that Adapt be retained to perform supplementary engineering evaluations and
field observations during construction, in order to address any deviations that may become evident during
the construction phase of this project.
4.0 EXPLORATORY METHODS
We explored surface and subsurface conditions at the project site during a series of site visits during
January through April, 2005. Our exploration and testing program included the following elements:
• A visual surface reconnaissance of the site;
• Three borings (designated 13-1 through B-3) with Standard Penetration Tests, advanced at
strategic locations across the proposed residence footprint and slope areas;
• Four Cone Penetrometer Test (CPT) probings (designated CPT-1 through CPT-4),
advanced at strategic locations across the proposed residence footprint and slope areas;
• Two Monitoring Wells (designated MW-I through MW-2), installed at two of the boring
locations and monitored for three consecutive months during the wet season (January
through April).
• Seven No. 200 wash tests (materials finer than U.S. No. 200 Sieve), performed on
representative soil samples obtained from the site soils;
• Seven Atterberg limits tests, performed on representative soil samples obtained from the
site soils;
• Nineteen moisture content determinations, performed on representative soil samples
obtained from the site soils;
• A review of published geologic and seismologic maps and literature.
The specific number, locations, and depths of our explorations were selected in relation to the existing
and proposed site features, under the constraints of surface access, underground utility conflicts, and
budget considerations. The elevation and relative location of the borings were surveyed and plotted on
the site survey plan by others. The locations of the CPT probes were obtained by measuring from
existing features and scaling these measurements onto a layout plan supplied to us. We then estimated
their elevations by referencing the surveyed boring locations and by interpolating between contour lines
shown on this same plan. Figure 2 depicts the elevations and relative locations of the field explorations.
May 23. 2005
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The exploration locations depicted on Figure 2 should be considered accurate only to the degree permitted
by our data sources, the surveying methods by others, and implied by our measuring methods. Appendix
A of this report describe our field exploration procedures and Appendix B describes our laboratory testing
procedures.
It should be realized that the explorations performed for this evaluation reveal subsurface conditions only
at discrete locations across the project site and that actual conditions in other areas could vary.
Furthermore, the nature and extent of any such variations would not become evident until additional
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explorations are performed or until construction activities have commenced. If significant variations are
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observed at that time, we may need to modify our conclusions and recommendations contained in this
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5.0 SM CONDMONS
The following sections of text present our observations, measurements, findings, and interpretations
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regarding surface, soil, groundwater, seismic conditions, and environmentally critical area conditions at
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5_1 Surface Conditions
According to the site survey and our reconnaissance field observations, the site slopes in an undulating
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fashion downward towards the west at an overall inclination ranging from roughly 3H:IV
(Horizontal:Vertical, 33 percent) within the east -central portion to about 21-1:IV (50 percent) within the
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western portion of the site, with an overall topographical relief of about 35 feet from the northeast to the
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southwest property corner. The site is vegetated with grass, brush, and scattered trees. Hydrophilic
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vegetation was observed at various locations along the site slope areas, indicating wet to saturated near-
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surface soil conditions, although we did not observe any surface seepage conditions or standing surface
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water across the site at the time of our site work. Nor did we observe any apparent evidence of recent
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surftcial soil movement or sloughing. The older trees observed at the site appeared to be relatively
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straight and ranging up to approximately 36 to 48-inches in diameter.
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5_2 Soil Conditionsin
The site is located within the documented Meadowdale Landslide Hazard Area, which extends
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approximately 3,200-feet in a north -south direction along the shoreline and about 650-feet in an easterly
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direction from the Burlington Northern railroad right-of-way at the base of the landslide area. The
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topographical relief of the landslide mass is on the order of 150-feet, while the landslide scarp extends up
to 300-feet elevation. Earlier reports describe this landslide mass to consist of blocks of sandy and silty
material, along with more deformed material. The initial failure of the landslide complex is believed to
have occurred a few thousand years ago as a result of rising sea levels due to the recession of glaciers and
resulting increase in shoreline wave erosion. Recent movements of the landslide complex has been
observed to occur at various times from the 1940's through the 1970's. A risk assessment was then
performed by Roger Lowe & Associates (1979) and a landslide risk map was developed showing the
probability of landsliding within the Meadowdale landslide area. In the early 1980's, the City of
Edmonds implemented construction measures that contributed to lowering the general groundwater levels
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within portions of the Meadowdale landslide area, which resulted in a reduction of the probability of
landsliding reported on the Meadowdale landslide risk map (GeoEngineers, 1985).
Our on -site explorations generally confirmed the presence of landslide material (landslide debris)
overlying a basal, stiff to very stiff clay/silty clay layer, which is interpreted to be undisturbed native soil
below the shear zone at the base of the Meadowdale landslide. Specifically, our site explorations within
the upper and middle portions of the site slopes (central and eastern portions of property) generally
revealed the near -surface portion of the landslide material to consist of loose, silty sand overlying up to
15-feet of soft to medium stiff, interlayered clay and clayey silt. These surficial soils are underlain by a
roughly 5-feet thick layer of medium dense silty sand/sandy silt, which in turn is underlain by a roughly 5
to 8-feet thick layer of intermixed, loose to medium dense, clayey silt and silty sand, with inclusions of
hard clayey silt fragments, roots, and peat lenses (landslide shear zone). Our explorations disclosed this
landslide shear zone to be very thin or non-existent within the western margins of the site (lower portion
of site slopes along 75" Place V). The underlying, native soils below the slide shear zone consist of stiff
ions ating and
to very stiff, interlayered clay and silty clay, which was found in rexprrou to 2e0ante tl elevation
ranging from about 56 to 60-feet elevation within the southern portiontoghly
e enclosed Geologic Cross Section (Figure 3) and
(deeper) within the northern portion of the site. Th
'i Geologic Profile (Figure 4) depicts the general site soil conditions described.
g_3 Groundwater Conditions
At the time of exploration (January and March, 2005), static groundwater levels were observed at a depth
of about 13.0-feet bgs (below ground surface) in borings B-1 and B-2 within the central and upper
in boring B-3 at
portions of the site, while groundwater seepage was indicated at a de th f bout 8. groundwaterist interpreted to be
the base of the site slopes (lower portion of site along 75 ° Place W)• The Br
perched atop the underlying, native, stiff to very stiff clays. These ware levels
rmonit was found
tored in the
installed monitoring wells over the next 4 months (see Table t below); groundwater
to be relatively stable, with recorded fluctuations on the order of 1.0-foot, or less. Because our
explorations and groundwater well readings were performed during an extended period of wet weather,
these observed groundwater conditions may represent the yearly high levels; somewhat lower levels may
occur during the drier summer and early fall months. Throughout the year, groundwater levels would
likely fluctuate in response to changing precipitation patterns, off -site construction activities, and changes
in site utilization.
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TABLE 1
SUMMARY OF GROUNDWATER WELL READINGS
Top of Casing
Date of
Groundwater
Groundwater
Well No.
Boring No.
Elevation (ft)
Reading
Depth (ft)
Elevation (ft)
MW-1
B-1
83.5
14-Jan-05
13.2
70.3
24-Jan-05
13.2
70.3
15-Feb-05
13.4
70.1
I1-Mar-05
13.8
69.7
13-Apr-05
13.2
70.3
06-May-05
13.8
69.7
MW-2
B-2
84.0
14-Jan-05
13.6
70.4
24-Jan-05
13.5
70.5
15-Feb-05
13.8
70.2
II-Mar-05
14.2
69.8
13-Apr-05
13.5
70.5
06-May-05
14.1
69.9
5_4 Seismic Conditions
Based on our analysis of subsurface exploration logs and a review of published geologic maps, we
interpret the on -site soil conditions to correspond to Site Class D, as defined by Table 1615.1.1 of the
2003 International Building Code. The soil profile type for this site classification is characterized by stiff
soils with an average blowcount ranging from 15 to 50 within the upper 100 feet bgs. Current (2003)
National Seismic Hazard Maps prepared by the U.S. Geological Survey indicate that peak bedrock site
acceleration coefficients of about 0.30 and 0.55 are appropriate for earthquakes having a 10-percent and
2-percent probability of exceedance in 50 years (corresponding to return intervals of 475 and 2,475
years), respectively. For purposes of seismic site characterization, the observed soil conditions were
extrapolated below the exploration termination depth, based on a review of geologic maps and our
knowledge of regional geology.
5_5 Environmentally Critical Area Conditions
The subject site is located within a documented, recent landslide area designated as the Meadowdale
Landslide Hazard Area by the City of Edmonds. The extent and nature of this landslide area is described
in the Landslide Hazards Investigation — Meadowdole Area by Roger Lowe & Associates (1979,
amended by GeoEngineers in 1985). This investigation report included a risk assessment which
identified zones with different risk factors (percent risk of landsliding) within the entire landslide complex
area. Based on this landslide risk map, the northern two-thirds of the subject site is situated within a 10-
percent risk zone, while the southwest comer of the site is located within a 30-percent risk zone.
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Because of the site location (within the Meadowdale Landslide Hazard Area), along with the site -specific
geologic and topographic conditions, the subject site is classified as an Earth Subsidence and Landslide
Hazard Area based on the Edmonds Community Development Code (ECDC). This designation generally
applies when a site is located within mapped areas of historic landslides or areas with slopes steeper than
15 percent, in combination with certain adverse geologic and groundwater seepage conditions. For sites
with this designation, the City of Edmonds DSD requires a site -specific geotechnical evaluation
addressing the risk associated with the landslide hazard area and providing specific recommendations
concerning development of the site, in accordance with the specific City of Edmonds geotechnical report
guidelines. The recommendations and conclusions of this geotechnical engineering report address the
concerns related to the landslide hazard designation, in general accordance with City of Edmonds
Ordinance No. 2661 (Title 23 — Critical Areas Regulations).
Provided that the recommendations of this report are implemented, the proposed development is
considered feasible and is not anticipated to adversely affect the stability of the site, the adjacent
properties, or the surrounding areas. It is our opinion that the subject site will remain stable following
development, as defined in Ordinance No. 2661, which defines stable to mean "...that the risk of damage
to the proposed development, or to adjacent properties, from soil instability shall be minimal ... and the
proposed development will not increase the potential for soil movement."
6.0 CONCLUSIONS AND RECOMMENDATIONS
Development plans call for the construction of a private residence and associated access driveways within
the central portion of the site. Shallow spread foundations, along with concrete cantilever basement walls
are proposed to support the house. Some excavation along the lower portion of the existing site slopes is
planned for the construction of the lower (daylight basement) and middle floor levels of the proposed
residence. In order to assess the potential effect of these proposed, permanent cuts, we performed a site -
specific slope stability evaluation, along with a liquefaction risk evaluation (limited to isolated, saturated
layers of loose to medium dense sandy and silty soils at depth. Based on the results of our analyses, we
recommend that a permanent, subsurface, trench drain dewatering system be installed to a depth of about
5.0-feet below the finished floor elevation of the basement portion of the proposed house, to mitigate the
potential adverse affect of the proposed cuts on site stability and to improve the overall stability of the
subject site. This dewatering will also aid in limiting the extent of potential liquefaction and minimize the
potential for liquefaction -induced settlements below the house. Based on our conversations with
representatives of the City of Edmonds, dewatering undertaken as part of site development within the
Meadowdale landslide area is encouraged. Our initial review of site topography and elevations of nearby
City storm drainage systems indicate that our proposed dewatering system is feasible.
Based on our findings and the results of our analyses, the project is considered feasible from a
geotechnical standpoint, provided that the recommendations of this report are implemented. The
following text sections of this report present our specific geotechnical conclusions and recommendations
concerning site liquefaction risk evaluation, slope stability considerations, site preparation, slope
regrading and erosion control considerations, spread footings, slab -on grade floors, backfilled walls,
drainage systems, trench drain dewatering system, and structural fill. WSDOT Standard Specifications
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and Standard Plans cited herein refer to WSDOT publications M41-10, 2004 Standard Specifications for
Road, Bridge, and Municipal Construction, and M21-01, 2004 Standard Plans for Road. Bridge, and
Municipal Construction, respectively.
6_i Site Liquefaction Risk Evaluation
Given the presence of potentially liquefiable site soils at depth, we performed an engineering evaluation
to assess the site -specific liquefaction risk. The following sections describe the procedures and the results
of this engineering evaluation:
Liquefaction is the sudden loss of soil shear strength and sudden increase in pore water pressure caused
by shear strains, as could result from an earthquake of sufficient magnitude and duration to induce cyclic
mobility. Research has shown that saturated, loose to medium -dense sands with a silt content less than
about 35 percent are most susceptible to liquefaction. In certain cases, non -plastic silts and low -plasticity,
fine-grained soils are also susceptible to liquefaction. Our explorations at this site encountered layers of
loose to medium dense sands, silts, and silty sands below the groundwater table. Some of these site soils
are generally considered potentially susceptible to soil liquefaction.
Given the observed soil conditions and the results of our laboratory testing on the site soils, we have
performed a site -specific liquefaction risk evaluation using the empirical SPT and CPT analysis
procedures established by Seed et al. (1983) and updated by the 1998 NCEER/NSF Workshop (published
March 2001 — ASCE Journal of Geotechnical and Geoenvironmental Engineering). Based on the results
of this engineering evaluation, we conclude that there is a relatively high risk that soil liquefaction will
occur within the lower portion of the medium dense silty sand/sandy silt layer and the underlying,
intermixed, loose to medium dense, clayey silt and silty sand, with inclusions of hard clayey silt
fragments, roots, and peat lenses (landslide shear zone). These potentially liquefiable soils were
encountered within our explorations directly above the native base clay layer, which appears to be
undulating between elevations ranging from about 52.0 to 60.0-feet, as described in the soil conditions
section of this report. The potentially liquefiable landslide shear zone was observed in our explorations to
be very thin or non-existent within the western margins of the site (lower portion of site slopes along 75a
Place W). Based on the varying depth of these potentially liquefiable layers within our site explorations,
even within short distances, we conclude that the potential liquefaction is likely to occur within somewhat
discontinuous pockets and lenses of these soil layers at depth. The remaining soil layers within the
landslide mass above the shear zone are either deemed to exhibit a low risk of soil liquefaction due to
relatively high soil density (granular soils) or to be non -liquefiable due to their high clay content (fine-
grained soils). For purposes of evaluating liquefaction potential, we selected a design earthquake with a
Magnitude of 7.5 and a peak bedrock acceleration of 0.30g, which corresponds to a large earthquake
event in the Puget Sound region with a return period of about 500 years (as promulgated by the 2003
UBC, see Seismic Conditions section above).
Sites where soil liquefaction occurs may experience liquefaction -induced ground damage, such as sand
boils or surface fissures, and/or general total and differential surface settlement. The magnitude of such
disturbance or settlement depends on the thickness of the liquefiable layer and the thickness of the non -
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liquefiable surface soils overlying the liquefiable soil layers. Given the presence of potentially liquefiable
site soils, we have performed a site -specific, surface damage risk evaluation using the empirical analysis
procedure established by /shihara et al. (1985). Based on this analysis, we conclude that liquefaction -
induced ground damage is not likely to result from the potential liquefaction of isolated soil layers at
depth, due to the relative thickness of the non -liquefiable surface layers (below the planned basement
floor footprint area). However, because post -liquefaction soils tend to consolidate after the seismic event,
the site will likely experience some general, liquefaction -induced, surface settlements on the order of I to
3 inches over extended areas of the subject site and surrounding areas, even if the liquefiable soil layers
are relatively deep below the ground surface. We anticipate that such settlement will be greatly reduced
due to the lowering of the groundwater level (6 to 8-feet below existing static water levels) resulting from
the proposed dewatering system below the planned house basement footprint area. If the slight risk of
potential liquefaction -induced settlement is acceptable to the owner, we recommend that the structural
engineer make provisions in the foundation design to minimize the adverse effects of a potential
differential settlement on the order of 1 to 2 inches. If the risk of settlement is found to be unacceptable,
we recommend that the house be supported on piles; Adapt could provide further design
recommendations should this alternative be required.
6_2 Slope Stability Considerations and Landslide Risk
Given the location of the subject site within the documented Meadowdale landslide area, we perforated an
engineering evaluation to assess the site -specific landslide risk. The following sections describe the
procedures and the results of this engineering evaluation:
In order to evaluate the stability of the project site, we developed two representative Geologic Cross
Sections A -A' and C-C' (Figure 3 and Slope/W computer printouts) based on available topographic
information and the subsurface conditions encountered in our explorations. We then used a computer
program (Slope/W) to perform slope stability analyses of the existing (native) slope conditions and the
proposed regraded site configuration, including the proposed permanent cuts for the planned daylight
basement We evaluated the daylight basement configuration (excavated) for various groundwater
drawdown depths (following dewatering) in order to estimate the minimum drawdown requirement to
obtain an acceptable seismic safety factor (most critical, including potential liquefaction parameters
within susceptible soil layers); printouts are provided only for the final groundwater drawdown
configuration used in design. Appendix C of this report describe our slope stability analysis procedures
and presents the results of the stability analyses performed for this project.
The soil strength parameters used in our slope stability analyses were based on the results of laboratory
testing performed on representative samples of the site soils from our borings, on the direct measurement
of in -situ soil properties from our CPT probings, and on generally accepted correlations reported in the
geotechnical literature. The cohesive soils within the landslide shear zone were modeled in the static case
using fully deformed and remolded soil strength values, based on correlations between residual friction
angles and the clay fraction/plasticity index. The soils within the potentially liquefiable soil layers were
modeled in the seismic case as a liquefied mass with a residual shear strength estimated based on
correlations between mobilized critical strength (liquefied) and equivalent SPT blowcounts (pre-
Tung Bui May 23. 2005
Adapt Proiect No. WA05-12239-GEO Page 10
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liquefaction) reported by Seed et al. (1990) and updated in the 2003 Earthquake Engineering Research
Center (EERC) publication Recent advances in soil liquefaction engineering: A unified and consistent
to dense silty/sandy soils were modeled with
framework (EERC 2003-06). The overlying medium dense
any apparent cohesion, while the stiff to very stiff clay/silty
an appropriate friction angle without
silt was modeled using lower -bound undrained shear strength. The groundwater level was
clay/clayey
modeled based on the observed groundwater levels within our borings, measurements of static
measurements within the CPT
groundwater levels within the monitoring wells, and on pore pressure
probings.
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Based on our slope stability analyses the most critical slope configuration (see Geologic Cross Section
a minimum, global, static safety
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A -A - Native Slope Configuration printouts in Appendix C), we estimate
failure, with the potential failure plane extending through the lower
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factor on the order of 2.75 against
portion of the site slopes (western portion of site). For the seismic case, our analyses indicate an existing
through the potentially
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safety factor on the order of 1.28, with the potential failure plane extending
liquefiable soils within the landslide shear zone at depth.
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To assess the effect on the site slope stability of the proposed, permanent cuts for the planned daylight
slope stability
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basement near the base of the site slopes, we evaluated both the static and seismic global,
(excavated) slope configuration (see Geologic Cross Section A -A -Basement Cut
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of the regraded
Configuration printouts in Appendix Q. In the static case, we estimate a minimum, global, static safety
failure extending throughplane
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factor on the order of 2.53 against failure, with the potential plane
(central portion of site). In the seismic case, we evaluated two potential failure p locations.
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the cut
static safety factor for the regraded site condition was estimated by the
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Initially, the minimum, global,
computer program to be on the order of 1.05, with the potential failure plane being about 140-feet long
line on the uphill side of the site.
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and extending through the base of the cut and 40-feet past the property
landslide mass dimensions for deep-seated landslides and the nature of the observed
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Based on typical
slide configurations within the Meadowdale landslide area, we estimate that this potential failure plane
140-feet in order to fail. Since the
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in the north -south direction is only about 70- eat we
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horizontal extent of the proposed basement cut
failure plane extending through the base of the cut and about 7 -
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analyzed a more representative potential
side of the cut; the global, seismic safety factor for this potential failure plane was
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feet on the uphill
estimated by the computer program to be on the order of 1.26, which is comparable to the pre -excavation
static and seismic safety
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safety factors computed for the native slope conditions. Both the computed
and seismic safety factors of
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factors for this cross section exceed the generally accepted, minimum static
1.5 and 1.1, respectively.
In reviewing the results of these slope stability analyses, it is important to realize that the computer
soil strength or surface
program analysis method is two-dimensional, and does not consider changed
horizontal extent of the slide mass (parallel to the slope contour
configuration conditions along the entire
does it consider the resisting frictional forces acting to restrain the outer limits of the slide
lines), nor dune plane analyzed by the
mass, as would be the case for the above -referenced, most critical potential
tions at the south and
computer. Given the observed, varying subsurface and surface topographic
May 23, 2005
Page 11
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ar ornin t No. WA05-12239-GEO
LSI Adapt, Inc.
the north ends of the planned house footprint, we also evaluated the seismic global, slope stability of the
regraded (excavated) slope configuration (see Geologic Cross Section C-C - Basement Cut Configuration
printouts in Appendix Q. For the same reasons discussed above, we evaluated two potential failure plane
locations for this cross section, as well. The minimum, global, static safety factor for the regraded site
condition was computed by the computer program to be on the order of 1.16, with the potential failure
plane being about I I0-feet long and extending through the base of the cut and up to the property line on
the uphill side of the site. However, the global, seismic safety factor for a more representative potential
failure plane extending through the base of the cut and about 70-feet on the uphill side of the cut was
estimated by the computer program to be on the order of 1.63. We attribute the higher safety factor
computed for Section C-C to the increased depth of the liquefiable soils below the planned basement cut
elevation, as compared with cross section A -A. The average, seismic, global, slope stability safety factor
for representative potential slide plane configurations through cross sections A -A and C-C is therefore
estimated to be on the order of 1.4 for the entire basement cut proposed. Both the computed static and
seismic safety factors for this cross section exceed the generally accepted, minimum static and seismic
safety factors of 1.5 and 1.1, respectively.
Based on our site explorations and site -specific slope stability evaluation, we concur with the statistical
probability (risk) of earth movement indicated on the landslide hazard map for the Meadowdale landslide
area (Roger Lowe & Ass/GeoEngineers, 1985), which maps the northern two-thirds of the subject site
within a 10-percent or less risk zone, while the southwest corner of the site is located within a 30-percent
or less risk zone. .
63 Site Preparation
Preparation of the project site should involve temporary drainage, demolition, clearing, stripping, cutting,
filling, excavations, dewatering, and subgrade compaction. The paragraphs below discuss our
geotechnical comments and recommendations concerning site preparation.
Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or
near -surface water within the construction zones before stripping begins. Because the selection of an
appropriate drainage system will depend on the water quantity, season, weather conditions, construction
sequence, and contractor's methods, final decisions regarding drainage systems are best made in the field
at the time of construction. Nonetheless, we anticipate that curbs, berms, or ditches placed along the
uphill side of the work areas will adequately intercept surface water runoff.
Demolition: As a part of the initial site preparation, any existing structures present within the
construction areas should be demolished. Any associated underground structural elements or utilities,
such as old footings, stemwalls, and drainpipes, should be exhumed as part of this demolition operation.
Clearing and Stripping: After surface and near -surface water sources have been controlled, the
construction areas should be cleared and stripped of all trees, bushes, sod, topsoil, debris, asphalt, and
concrete. Our explorations indicate that an average thickness of about 6 to 12 inches of sod and topsoil
will be encountered across the proposed development areas. The native soils underlying the surficial
May 23. 2005
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organics consist of clays and clayey silts, which are considered highly moisture -sensitive. Therefore, it
should be realized that if the stripping operation proceeds during wet weather, a generally greater
stripping depth might be necessary to remove disturbed, surficial, moisture -sensitive soils; therefore,
stripping is best performed during a period of dry weather.
Excavations: Site excavations ranging up to about 10-feet deep will be required to accommodate
basement floor of the proposed house. Based on our explorations, we anticipate that these excavations
dense sandy silt/silty sand.
will encounter soft to medium stiff clay/clayey silt and loose to medium
equipment such as small dozers and
These soils can likely be cut with conventional earth working
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adequately sloped back to prevent sloughing and collapse. For the soft to medium stiff clay/clayey
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seepage encountered
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seepage conditions exposed in the cuts at the time of construction. It is the responsibility of the contractor
for in accordance with
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to ensure that the excavation is properly sloped or braced worker protection,
should be draped with plastic
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OSHA guidelines. In addition to proper sloping, the excavation cuts
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sheeting for the duration of the excavation to minimize surface erosion and ravelling
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Dewaterine: Our explorations revealed the groundwater table near the base of the planned excavation
to mitigate the potentially
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cuts at the time of exploration. As a part of the recommended measures
site regrading, we are recommending that a permanent subsurface
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adverse effect of the proposed
dewatering trench drain system be installed below the planned daylight basement (as discussed in the
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groundwater levels prior to permit the installation of such a permanent system. Depending upon the
a temporary system may consist of
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well points, sump pumps, etc. Adapt should be allowed to evaluate the temporary dewatering system
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Subgrade Preparation: Exposed subgrades for footings, floors, pavements, and other structures should be
density and warranted by soil
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within a subgrade should be
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moisture conditions. Any localized zones of loose granular soils observed
with the surrounding soils. In contrast, any uncontrolled fill
compacted to a density commensurate
or organic, soft, or pumping soils observed within a subgrade should be overexcavated and
material
replaced with a suitable structural fill material. It should be noted that some of the bearing soils at this
loose to medium dense, silty
site are anticipated to consist of soft to medium stiff, clay/clayey silt and
To minimize disturbance
sand/sandy silt, which are generally considered to be highly moisture sensitive.
that all bearing subgrade areas be excavated with
and subsequent need for recompaction, we recommend
a smooth -edged bucket.
May 23, 2005
Page 13
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Adaot Proiect No. WA05.12239-GEO
LSI Adapt, Inc.
Permanent Slopes: All permanent cut and fill slopes should be adequately inclined and revegetated to
minimize long-term ravelling, sloughing, and erosion. A hardy vegetative groundcover should be
established as soon as possible following grading, to further protect the slope from runoff water erosion.
We generally recommend that permanent slopes not be steeper than 2HAV, to minimize long-term
erosion and to facilitate revegetation.
Slope Protection: We recommend that a permanent berm, swale, or curb be constructed along the top edge
of all permanent slopes to intercept surface Flow. Also, a hardy vegetative groundcover should be
established as soon as feasible, to further protect the slopes from runoff water erosion. Alternatively,
permanent slopes could be armored with quarry spalls or a geosynthetic erosion mat.
6_4 Spread Footings
In our opinion, conventional spread footings will provide adequate support for the proposed house,
provided the subgrades are properly prepared and the slight risk of potential post -liquefaction settlement
is acceptable. We offer the following comments and recommendations for purposes of footing design and
construction.
Footing Depths and Widths: For frost and erosion protection, the bottoms of all exterior footings should
penetrate at least 18 inches below adjacent outside grades, whereas the bottoms of interior footings need
penetrate only 12 inches below the surrounding slab surface level. All footings should bear within the
native, medium stiff clay/clayey silt or medium dense sandy sildsilty sand. Continuous (wall) and
isolated (column) footings should be at least 18 and 24 inches wide, respectively, to act as a true footing
element providing the specified bearing capacity.
Bearing Subgrades: The underlying the proposed house footprint appear well -suited for supporting the
proposed shallow spread footing system. Before concrete is placed, any localized zones of loose soils
encountered in the footing subgrades should be compacted to a firm, unyielding condition.
Subarade Verification: All footing subgrades should consist of firm, unyielding, dense, undisturbed,
native soils. Footings should never be cast atop loose, soft, or frozen soil, slough, debris, existing
uncontrolled fill, or surfaces covered by standing water. We recommend that the condition of all
subgrades be verified by an Adapt representative before any concrete is placed.
Bearing Capacities: Based on the bearing subgrade conditions described above, we recommend that all
footings be designed for the following allowable bearing capacities for static and seismic loadings:
Design Parameter
Static Bearing Capacity
Seismic Bearing Capacity
Tung Bui
Adapt Project No. WA05.12239-GEO
Allowable Value
2,500 psf
3,300 psf
may w
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LSI Adapt, Inc.
Footing Settlements: We estimate that total post -construction settlements of properly designed footings
bearing on properly prepared subgrades will not exceed 1-inch. Differential settlements between isolated
footings and/or adjacent pile caps/groups could approach one-half of the actual total settlement. As
previously discussed in the Site Liquefaction Risk Evaluation section of this report, shallow footings may
be subjected to general, liquefaction -induced, surface settlements on the order of 1 to 3 inches over
extended areas of the subject site. We therefore recommend that the structural engineer make provisions
in the foundation design to minimize the adverse effects of a potential differential settlement on the order
of l to 2 inches.
Footing and Stemwall Backfill: To provide erosion protection and lateral load resistance, we recommend
that all footing excavations be backfilled on both sides of the footings and stemwalls after the concrete
has cured. Either imported structural fill or non -organic on -site soils can be used for this purpose,
contingent on a suitable moisture content at the time of placement. Regardless of soil type, all footing
backfill soil should be compacted to a density of at least 90 percent (based on ASTM:D-1557).
Lateral Resistance: Footings and stemwalls that have been properly backfilled as described above will
resist lateral movements by means of passive earth pressure and base friction. Passive pressure acts over
the embedded front of the footing (neglecting the upper l foot for soil foreslopes) and varies with the
foreslope inclination. For site -specific design purposes, we are providing recommended allowable
passive pressure values for level foreslopes. The level foreslope condition may be assumed if the ground
surface is level within a horizontal distance equal to two times the footing depth. We recommend using
the following design values, which incorporate a static safety factor of at least 1.5:
Design Parameter
Static Passive Pressure
Seismic Passive Pressure
Base Friction Coefficient (native soil subgrade)
Base Friction Coefficient (crushed rock subgrade)
Allowable Design Values
300 pcf
400 pcf
0.35
0.45
It should be noted that the higher base friction coefficient value may be assumed for design purposes if a
minimum 6-inch thick layer of compacted crushed rock is placed below the poured footing.
6_5 Slab -on -Grade Floors
In our opinion, soil -supported slab -on -grade floors can be used for the proposed house, provided the
subgrades are properly prepared and the slight risk of potential post -liquefaction settlement is acceptable.
We offer the following comments and recommendations concerning slab -on -grade floors. As previously
discussed in the Site Liquefaction Risk Evaluation section of this report, slab -on -grade floors may be
subjected to general, liquefaction -induced, surface settlements on the order of I to 3 inches over extended
May 23, 2005
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areas of the subject site. We therefore recommend that the structural engineer make provisions in the
floor design to minimize the adverse effects of a potential differential settlement on the order of I to 2
inches.
Capillary Break: To retard the upward wicking of groundwater beneath the floor slab, we recommend
that a capillary break be placed over the subgrade. Ideally, this capillary break would consist of a 4-inch-
thick layer of pea gravel or other clean, uniform, well-rounded gravel, such as "Gravel Backfill for
Drains" per WSDOT Standard Specification 9-03.12(4), but clean angular gravel can be used if it
adequately prevents capillary wicking.
Vapor Barrier. We recommend that a layer of plastic sheeting (such as Crosstuff, Visqueen or Moistop)
be placed directly between the capillary break and the floor slab to prevent ground moisture vapors from
migrating upward through the slab. During subsequent casting of the concrete slab, the contractor should
exercise care to avoid puncturing this vapor barrier.
Vertical D Deflections Soil -supported slab -on -grade floors can deflect downward when vertical loads are
applied, due to elastic compression of the subgrade. In our opinion, a subgrade reaction modulus of 200
pounds per cubic inch (pci) can be used to estimate such deflections within the site soils.
Suberade Verification: All slab -on -grade floors should bear on firm, unyielding native soils or on
suitable structural fill soils. We recommend that the conditions of all subgrades and overlying layers be
verified by an Adapt representative before any concrete is placed.
6_6 Backfd►ed Wads
In our opinion, backfilled concrete retaining walls can be used around the below -grade portions and to
support interior shear walls of the house, provided the subgrades are properly prepared and the slight risk
of potential post -liquefaction settlement is acceptable. Our wall design recommendations and comments
are presented below.
Footing Depths: For frost and erosion protection, all perimeter and basement retaining wall footings
should penetrate at least IS inches below the adjacent ground surface, whereas the bottoms of interior
wall footings need only penetrate 12 inches below the surrounding slab surface level. All footings should
bear within the medium stiff clay/clayey silt or medium dense sandy silt/silty sand.
Curtain Drains: To preclude hydrostatic pressure development behind the perimeter retaining walls, we
recommend that a curtain drain be placed behind the entire wall along the perimeter of the house. Ideally,
this curtain drain should consist of pea gravel, washed rock, or some other clean, uniform, well-rounded
gravel, extending outward a minimum of 2 feet from the wall and extending from the footing drain
upward to within about 12 inches of the ground surface. We also recommend that a 4-inch-diameter
perforated drain pipe be installed behind the heel of the wall, as described for Perimeter Drains in the
Drainage Systems section of this report.
May 23. 2005
Tung Bui Page 16
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Backfill Soil: The on -site granular soils could be used as backfill placed behind the curtain drain, if they
are near the optimum moisture content. Alternatively, the wall backfill would consist of clean, free -
draining, granular material, such as "Gravel Backfill for Walls" per WSDOT Standard Specification
9-03.12(2).
Backfill Compaction: Because soil compactors may induce significant lateral pressures on retaining
walls, we recommend that only small, hand -operated compaction equipment be used within 3 feet of a
completed wall. Also, all backfill should be compacted to approximately 90 percent of the maximum dry
density (based on ASTM:D-1557); a greater degree of compaction closely behind the wall would increase
the lateral earth pressure, whereas a lesser degree of compaction might lead to excessive post -construction
settlements.
Grading and Capping: To retard the infiltration of surface water into the backfill soils, the backfill
surface of exterior walls should be adequately sloped to drain away from the wall. We also recommend
that the backfill surface directly behind the wall be capped with asphalt, concrete, or 12 inches of low -
permeability (silty) soils.
Applied Loads: Overturning and sliding loads applied to retaining walls can be classified as static
pressures, surcharge pressures, seismic pressures, and hydrostatic pressures. We offer the following
specific values for design purposes.
• Static Pressures: Yielding (cantilever) retaining walls should be designed to withstand
an appropriate active lateral earth pressure, whereas non -yielding (restrained) walls
should be designed to withstand an appropriate at -rest lateral earth pressure. The criteria
for yielding walls may be applied where the top of the wall is allowed to translate or
rotate a distance equal to 0.001 to 0.002 times the wall height. These pressures act over
the entire back of the wall and vary with the backslope inclination. For various backslope
angles, we recommend using the following active and at -rest pressures (given as
equivalent fluid unit weights):
Backslope Active At -Rest
Angle Pressure Pressure
Level 35 pcf 55 pcf
3H:iV 44pcf 62pcf
Surcharge Pressures: Static lateral earth pressures acting on a retaining wall should be
increased to account for any surcharge loadings from traffic, construction equipment,
material stockpiles, or structures. For simplicity, traffic loads can be modeled as a
uniform horizontal pressure of 70 psf over the upper 6 feet of the wall.
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Adaot Project No. WA05-12239-GEO
LSI Adapt Inc.
• Seismic Pressures: Static lateral earth pressures acting on a retaining wall should be
increased to account for seismic loadings. These pressures act over the entire back of the
wall and vary with the backslope inclination, the seismic acceleration, and the wall
height. Based on a design acceleration coefficient of 0.25 to 0.30 and a wall height of
"H" feet, we recommend that these seismic loadings be modeled as the following uniform
horizontal pressures for various backslope angles:
Backslope
Active
At -Rest
Angle
Pressure
Pressure
Level
4H psf
12H psf
3H:1 V
6H psf
18H psf
• Hydrostatic Pressures: If groundwater is allowed to saturate the backfill soils,
hydrostatic pressures will act against a retaining wall. If an adequate drainage and
discharge system is installed behind the retaining wall, we do not expect that hydrostatic
pressures will develop.
Resisting Forces: Static pressures, surcharge pressures, seismic pressures, and hydrostatic pressures are
resisted by a combination of passive lateral earth pressure, base friction, and subgrade bearing capacity.
Passive pressure acts over the embedded front of the footing (neglecting the upper I foot for soil
foreslopes) and varies with the foreslope inclination, whereas the base friction and bearing capacity act
along the bottom of the footings. For site -specific design purposes, we are providing recommended
allowable passive pressure values for level foreslopes. The level foreslope condition may be assumed if
the ground surface is level within a horizontal distance equal to two times the footing depth. We
recommend using the following design values, which incorporate a static safety factor of at least 1.5:
Allowable Design
Design Parameter
Values
300 pcf
Static Passive Pressure
400 pcf
Seismic Passive Pressure
Base Friction Coefficient (native soil subgrade)
0.35
Base Friction Coefficient (crushed rock subgrade)
0.45
2,500 psf
Static Bearing Capacity
3,300 psf
Seismic Bearing Capacity
May 23, 2005
Tung Bui Page 13
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LSI Adapt, Inc.
It should be noted that the higher base friction coefficient value may be assumed for design purposes if a
minimum 6-inch thick layer of compacted crushed rock is placed below the poured footing.
6_7 Drainage Systems
In our opinion, the proposed residence and the perimeter retaining walls should be provided with
permanent drainage systems to minimize the risk of future moisture problems. In addition, we
recommend that a permanent, subsurface, trench drain dewatering system be installed to a depth of about
5.0-feet below the finished floor elevation of the basement portion of the proposed house, to mitigate the
potential adverse affect of the proposed cuts on site stability and to improve the overall stability of the
subject site. We offer the following recommendations and comments for drainage design and
construction purposes.
Perimeter Drains: We recommend that the house be encircled with a perimeter drain system to collect
seepage water. This drain should consist of a 4-inch, perforated pipe within an envelope of pea gravel or
washed rock, extending at least 6 inches on all sides of the pipe, and the gravel envelope should be
wrapped with filter fabric to reduce the migration of fines from the surrounding soils. The drain invert
should be installed no more than 8 inches above the base of the perimeter footings. All perimeter drains
should discharge to a municipal stone drain, sewer system, or other suitable location by gravity flow.
Over bank discharge of storm water should be prohibited.
Runoff Water: Roof -runoff and surface -runoff water should not discharge into the perimeter drain
system. Instead, these sources should discharge into separate tight line pipes and be routed away from the
building to a storm drain or other appropriate location.
Grading and Caooine: Final site grades should slope downward away from the building so that runoff
water will flow by gravity to suitable collection points, rather than ponding near the building. Ideally, the
area surrounding the building would be capped with concrete, asphalt, or low -permeability (silty) soils to
reduce surface -water infiltration. We further recommend that the general surface grades across the upper
plateau be sloped away (eastward) from the top -of -slope along the west edge of the plateau. The lower
yard area should be sloped to drain into the yard collector drains.
Dewatering System Design: As discussed above, we recommend that a permanent, subsurface, trench
drain dewatering system be installed to a depth of about 5.0-feet below the finished floor elevation of the
basement portion of the proposed house. This will draw down the groundwater level within the house
footprint area to approximately elevation 62.0-feet, resulting in a drawdown of the groundwater levels on
the order of 6 to 9 feet along the east perimeter of the house. Our proposed trench drain system is
illustrated on the enclosed Drainage Plan (Figure 5). The proposed spacing of the trench drains is based
on the seepage flow analysis method established by Hutchinson (1977), and modifled to reflect the site
specific, slope and groundwater conditions. For the silty fine sand and sandy silt revealed within the
groundwater seepage zone, we estimate a coefficient of permeability ranging from about 1.0 (104) to 1.0
(to-) cm/sec, based on site -specific measurements of seepage rates into our groundwater monitoring
wells (Bouwer & Rice Slug Test method, 1989) and generally accepted correlations between grain size
May 23, 2005
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distribution and permeability rate reported in the geotechnical literature. Based on this estimated range of
permeability rates, and using the analysis method for seepage flow and drawdown to drainage slots
provided in the ArAVFAC Dewatering Manual (1983), we anticipate steady state, seepage rates into the
trench drain system on the order of 0.05 to 0.15 gallons per minute (gpm) per linear foot of trench line.
The proposed trench drain pipe has been conservatively sized to take more than 2 or 3 times this expected
groundwater seepage volume. To better assess the most appropriate temporary dewatering system, we
recommend that this seepage rate be verified during the initial phase of construction, following
excavation to slab subgrade level when the actual soil conditions within the slab subgrade area can be
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more accurately assessed (prior to excavation to install the permanent trench drain system). We
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furthermore recommend that the two monitoring wells installed as a part of this study be retained and
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used during construction to monitor the actual drawdown levels and verify that adequate drawdown levels
have been achieved within the installed permanent trench drain system; additional monitoring well points
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Trench Drain System Installation: In general, the trench drains should consist of a 6-inch diameter,
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sides of the pipe and upwards to the slab -on -grade subgrade elevation or to connect with the basement
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retaining walls, as illustrated on Figure 5. The gravel drain rock should be wrapped with filter fabric
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(same as footing drains) to reduce the migration of fines from the surrounding soils. Clean -outs should be
provided for the drain pipe at convenient locations at the ends of all straight trench line sections. It
lines should
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should be noted that the installation of the trench drains parallel to the topographic contour
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be installed in maximum 20-feet long sections, to limit the risk of causing slippage within the landslide
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mass on the uphill side of the excavated trench line.
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6_8 Structural Fill
The term "structural fill" refers to any placed under foundations, retaining walls, slab -on -grade floors,
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sidewalks, pavements, and other such features. Our comments, conclusions, and recommendations
concerning structural fill are presented in the following paragraphs.
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Materials: Typical structural fill materials include clean sand, granuhthic gravel, pea gravel, washed
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rock, crushed rock, quarry spalls, controlled -density fill (CDF), lean -mix concrete, well -graded mixtures
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of sand and gravel (commonly called "gravel borrow" or "pit -run"), and miscellaneous mixtures of silt,
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sand, and gravel. Recycled asphal4 concrete, and glass, which are derived from pulverizing the parent
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materials, are also potentially useful as structural fill in certain applications. Soils used for structural fill
should not contain any organic matter or debris, nor any individual particles greater than about 6 inches in
diameter.
Fill Placement: Generally, pea gravel, washed rock, quarry spalls, CDF, and lean -mix concrete do not
require special placement and compaction procedures. In contrast clean sand, granulithic gravel, crushed
rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in
i
loose thickness, and each lift should be thoroughly compacted with a mechanical compactor.
May 23, 2005
Tung Bui Page 20
Adapt Project No. WA05-12239-GEO -
LSI Adapt, Inc.
on -Site Soils: Because relatively large cuts are planned for the project, we expect that large quantities of
on -site soils will be generated during earthwork activities. We anticipate that fill will be needed to
backfill footings and retaining walls at the site. As such, we offer the following evaluation of these on -
site soils in relation to potential use as structural fill.
• Surricial Organic Soils: The topsoil or organic -rich silts mantling the site, or organic
soils disclosed elsewhere during construction, are not suitable for use as structural fill due
to their high organic content. Consequently, these materials can be used only for non-
structural purposes, such as in landscaping areas.
Clays and Clayey Silts (Landslide Debris): The near -surface clays and clayey silt do not
• appear to be suitable for reuse as structural fill at their present moisture contents.
However, these soils may become suitable for reuse during a period of dry weather if
they can be aerated to reduce their moisture content, and provided that they are free of
wood chips and other organic/deleterious material. It should be noted that these fine-
grained soils are extremely moisture -sensitive and are not likely to be suitable for use as
structural fill during wet site conditions.
Silty Sand and Sandv Silts Landslide Debris): The underlying silty Sand/sandy silts
appear to contain a significant amount of fines and are significantly above their optimum
moisture condition. We anticipate that these silty sandy soils may be reworked and
recompacted, given favorable weather conditions when they can be aerated to reduce
their moisture content, and provided that they are free of wood chips and other
organic/deleterious material. However, these soils would be difficult or impossible to
reuse during wet weather, due to their relatively high silt content and in -place moisture
condition.
Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we recommend
that structural fill used for various on -site applications be compacted to the following minimum densities:
Minimum
Fill Application
Compaction
Footing subgrade or bearing pad
95 percent
Footing and retaining wail backfill
90 percent
Slab -on -grade floor subgrade and subbase
90 percent
Roadway embankment (upper 2 feet)
95 percent
Roadway embankment (below 2 feet)
90 percent
Concrete sidewalk subgrade
90 percent
It should be noted that the municipal compaction standard for construction work within right-of-way areas
may require 95 percent density, based on the Standard Proctor test (ASTM:D-698). This requirement is
May 23, 2005
Tung Bui Page 21
Adapt Project No. WA05-12239-GEO
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generally equivalent to about 90 percent compaction using the more stringent Modified Proctor criteria
(ASTM:D-1557).
Subgrade Verification and Compaction Testing: Regardless of material or location, all structural fill
should be placed over firm, unyielding subgrades prepared in accordance with the Site Preparation
section of this report. The condition of all subgrades should be verified by an Adapt representative
before filling or construction begins. Also, fill soil compaction should be verified by means of in -place
density tests performed during fill placement so that adequacy of soil compaction efforts may be
evaluated as earthwork progresses.
Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their
grain -size distribution and moisture content when they are placed. As the "fines" content (that soil
fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in
moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently
compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points
above or below optimum. The majority of the near -surface site soils contain a significant amount of fines
and should be considered moisture sensitive. For fill placement during wet -weather site work, we
recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by
weight) based on the soil fraction passing the U.S. No. 4 Sieve.
CDF Strength Considerations: CDF is normally specified in terms of its compressive strength, which
typically ranges from 50 to 200 psi. CDF having a strength of 50 psi (7200 psf) provides adequate
support for most structural applications and can be readily excavated with hand shovels. A strength of
l00 psi (14,400 psf) provides additional support for special applications but greatly increases the
difficulty of hand -excavation. In general, CDF having a strength greater than about too psi requires
power equipment to excavate and, as such, should not be used where future hand -excavation might be
needed.
7.0 RECOMMENDED ADDITIONAL SERVICES
Because the future performance and integrity of the structural elements will depend largely on proper site
preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced
geotechnical personnel should be considered an integral part of the construction process. Consequently,
we recommend that Adapt be retained to provide the following post -report services:
Review all construction plans and specifications to verify that our design criteria
presented in this report have been properly integrated into the design;
Prepare a letter summarizing all review comments (if required by City of Edmonds);
Attend a pre -construction conference with the design team and contractor to discuss
important geotechnically related construction issues;
May 23, 2005
Tung Bui Page 22
Adaot Project No. WA05-12239-GEO
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8.0 CLOSURE
The conclusions and recommendations presented in this report are based, in pal, on the explorations that
we performed for this study; therefore, if variations in the subgrade conditions are observed at a later
we may need to modify this report to reflect those changes. Also, because the future performance
time,
and integrity of the project elements depend largely on proper initial site preparation, drainage, and
.construction procedures, monitoring and testing by experienced geotechnical personnel should be
considered an integral part of the construction process.
We appreciate the opportunity to be of service on this project. If you have any questions regarding this
report or any aspects of the project, please feel free to contact our office.
Respectfully submitted,
LSI Adapt Inc.
v v�
Rolf B. Hyllseth, P.E., L.G.
Senior Geotechnical Engineer
4LeP.Engineer
Senior Reviewer
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May 23, 2005
Tung But Page 24
Adapt Project No. WA05.12239-GEO
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Project : Bui Residence
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20 LEGEND:
B-5 - BORING NUMBER
(25' N) - OFFSET FROM ACTUAL EXPLORATION LOCATION TO SECTION LINE
5 - GROUNDWATER ETRATION LEVEL AT TIME OF DRILLINGESISTANCE IN OWS PER FOOT
CPT-04 - CONE PENETROMETER TEST NUMBER
CONE TIP RESISTANCE (TSF) VS. DEPTH (FT)
GROUND WATER LEVEL AT TIME OF PROBING
40.5' - TOTAL DEPTH OF DRILLING/PROBING
NOTES:
1) THE STRATA ARE BASED UPON INTERPOLATION BETWEEN EXPLORATIONS AND MAY NOT REPRESENT
ACTUAL SUBSURFACE CONDITIONS.
2) SIMPLIFIED NAMES ARE SHOWN FOR SOIL DEPOSITS. BASED ON GENERALIZATIONS OF SOIL
DESCRIPTIONS. SEE EXPLORATION LOGS AND REPORT TEXT FOR COMPLETE SOIL DESCRIPTIONS.
0 20 40
APPROXIMATE SCALE IN FEET
FIGURE 4 - Geologic Profile B-B'
LSI A®APT
Project :Bui Residence
615 8th Avenue South Location :16105 75th Ploce West
Seattle, Washington 98104 Edmonds, Woshington 98026
Went : Tung Bui
Ph 206.654.7045 Fax 206.654.7048 Dace : 05/15/05
Jobs : S—WA-05-12239—GEO
FREE -DRAINING
BACKFILL
L. 72.0' (MIN)' x+ t k xt t x t
STRUCTURAL—
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PVC PIPE (MIN. SCH. 20)
\L. 62.0' (MAX)
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CONCRETE
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LEGEND: WASHED ROCK
TRENCH DRAIN 6-INCH DIA. MIN; MIRAFI 180N FILTER
(min 2 % SLOPE TO DRAIN) —� FABRIC (OR EQUAL)
-SOLID PVC PIPE (6-INCH DIA.) i
NOTE: 6-INCH DIA. PERFORATED
SITE DRAWING BASED ON "SITE PLAN" 1 PVC PIPE (MIN. SCH. 40)
DATED 05/17/2005. — EL. 62.0' (MAX)
I TRENCH DRAIN SECTION
l URE 5 Drainage Plan
jaet : Bui Residence
J )atlae : 16105 75th Place West
Edmonds, Washington 98026
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APPENDIX &
FIELD EXPLORATION PROCEgrRESAND LOGS
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Adapt m-No. WA0wm O
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The following paragraphs describe our procedures associated with the field explorations and field tests
that we conducted for this project. Descriptive logs of our borings (B-1 through B-3), monitoring wells
(MW-I and MW-2), and CPT probings (CPT-01 through CPT-04) are enclosed in this appendix.
Auger Boring Procedures
Our exploratory borings were advanced with a hollow -stem auger, using a track -mounted drill rig
operated by an independent drilling firm working under subcontract to Adapt. A geotechnical engineer or
specialist from our firm continuously observed the borings, logged the subsurface conditions, and
collected representative soil samples. All samples were stored in watertight containers and later
transported to our laboratory for further visual examination and testing. After each boring was
completed, the borehole was backftlled with a mixture of bentonite chips and soil cuttings, and the surface
was patched with asphalt or concrete (where appropriate).
Throughout the drilling operation, soil samples were obtained at 2%- or 5-foot depth intervals by means
of the Standard Penetration Test (SPT) per ASTM:D-1586. This testing and sampling procedure consists
of driving a standard 2-inch-diameter steel split -spoon sampler 18 inches into the soil with a 140-pound
6-inch
hammer free -falling 30 inches. The number of blows required to drive the sampler through each
interval is counted, and the total number of blows struck during the final 12 inches is recorded as the
Standard Penetration Resistance, or "SPT blow count." If a total of 50 blows is struck within any 6-inch
interval, the driving is stopped and the blow count is recorded as 50 blows for the actual penetration
The resulting Standard Penetration Resistance values indicate the relative density of granular
distance.
soils and the relative consistency of cohesive soils. Where soft soils were encountered, these split -spoon
samples may have been supplemented with Shelby tube samples. A Shelby tube consists of a 3-inch-
diameter thin -wall steel tube that is pushed into the soil by means of hydraulic rams. Where gravelly soils
were encountered, a larger -diameter split -spoon sampler may have been utilized to improve the sample
recovery, and the resulting blow counts would subsequently be converted to SPT blow counts by means
of energy correlations.
The enclosed Boring Logs describe the vertical sequence of soils and materials encountered in each
boring, based primarily on our field classifications and supported by our subsequent laboratory
examination and testing. Where a soil contact was observed to be gradational, our logs indicate the
average contact depth. Where a soil type changed between sample intervals, we inferred the contact
depth. Our logs also graphically indicate the blow count, sample type, sample number, and approximate
depth of each soil sample obtained from the borings, as well as any laboratory tests performed on these
soil samples. If any groundwater was encountered in a borehole, the approximate groundwater depth is
depicted on the boring log. Groundwater depth estimates are typically based on the moisture content of
soil samples, the wetted height on the drilling rods, and the water level measured in the borehole after the
auger has been extracted.
May 23, 2005
Tung But Appendix A — Page 2
Adaot Project No. WA05-12239-GEO
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Monitorine Well Procedures
The groundwater monitoring wells were installed by the independent drilling firm working under
subcontract to Adapt. A geotechnical engineer or specialist from our firm continuously observed the
installation of the monitoring wells. The wells were installed in general accordance with Washington
State Department of Ecology (DOE) requirements.
Typically, a 2-inch diameter PVC pipe is used when groundwater sampling is required for environmental
site characterization is required, while a 1-inch diameter PVC pipe may be used when only the
(slotted PVC) portion of the
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groundwater levels are required to be monitored. Generally, the screened
is observed during drilling
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well is carefully placed within the depth interval where groundwater seepage
The screened section of the well is
or anticipated based on soil stratification or groundwater fluctuations.
backfrlled with select #10-420 sand backfrll. The remainder of the well pipe (solid PVC) is backftlled
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with bentonite to seal off the screened zone of the well from underlying and overlying groundwater
is maintained at the surface
17 in
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infiltration. A minimum 5-feet of solid PVC with bentonite backfrll always
a cast iron well monument with a bolted lid is
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above any screened well section. At the ground surface,
then installed with a concrete seal to protect the monitoring well from tampering.
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Cone Penetrometer Procedures
test (CPT) soundings consisted of advancing an electric penetrometerUi
r
The exploratory cone penetrometer
piezocone, using a truck -mounted probe rig operated by an independent firm working under subcontract
the
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to Adapt. The electronic monitoring equipment in the probe rig automatically logged subsurface
with a mixture of sand and
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conditions. After each sounding was completed, the probehole was backfilled
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bentonite chips.
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During probing, the piezocone tests were performed in general accordance with ASTM D-3441 standards
located the shoulder behind the cone tip. Thet
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using a 5-ton electric piezocone with a porous element at
consisted of a standard tip design having a 60° apex, 10 cm2 projected area at the tip, 150 cmZ sleeve,
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cone
and was advanced at a rate of approximately 2.0 cm/sec. The cone tip resistance (q,), sleeve friction (f,),
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and penetration pore water pressure (uz) were recorded continuously during the tests.
_
The enclosed Cone Penetrometer Test Logs (CPTu graphs) depict vertical plots of the cone tip resistance
was recorded during the
rn
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1
(q,), sleeve friction ratio (f�/q,), and penetration pore water pressure (uz) which
the sequence of soil types
m
CPT sounding. The logs also include a general soil profile depicting vertical
Resistance (SPT-Nw) values
based on the recorded data, along with estimated Standard Penetration
corresponding to each test interval based on published conversion charts.
i
I
May 23, 2005
Tung Bui Appendix A —Page 3
Adapt Proiect No. WA05.12239-GEO
LSI ADAPT
615
BORING/MONITORING WELL LOG Se Avenue ttle,BWasFngton South 99104
TEL: 206.654.7045 FAX: 206654.
Job Number: WA05-12239-GEO Boring No.: B-1
PROJECT : Bui Residence
LOCATION : 16105 75th Place West
Monitoring Well No.: MW-1
Edmonds WA 98026
age
Elevation Retere'Site Plan by 40 Amhileas dated 0121/05 01 0l 2
nce: '
Ground Surface Elevation B0.5 h Casing Elevation : 80.5It
:
WELL
LABORATORY TESTING
=SOIL DESCRIPTION
w
3-inches grass, sod and topsoil
__ _ __ _' _ ;--------------------------j
f
Loose, moist to wet, rustytannish gray, fine to
�.
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medium SAND and silty fine SAND with some
rootlets and wood debris (Landslide Debris)-
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with rusty stains, silty
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Soft, moist to wet, gray
CLAY, thinly laminated and microfractured
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(Landslide Debris)
i
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Medium stiff to stiff, moist to wet, gray with10
blue -gray inclusions and trace rusty stains,
sa s
clayey SILT with thin lenses of fine sandy SILT
y _._=___�_J_�_!_
4 - - - r
(Landslide Debris)
---------------------------------
Medium dense, wet to saturated, gray with rusty
--1-�-
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banding, silty fine to medium SAND interlayered
with lenses of blue -gray, fine sandy SILT
15 (Landslide Debris)
sd B
5 -----.----.-.- --
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Loose to medium dense, wet to saturated, bluish
_ _ •, _ _ _ _ _;_ �_ _ ; _ _ _
gray, intermixed clayey SILT and silty fine to
hard, dark gray,
r I
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medium SAND with inclusions of
S5
20
fragments of clayey SILT and root fragments
s _ _ l
(Landslide Debris)
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25
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MOISTURE CONTENT
LEGEND
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i rlEWnim, ePi eanwwa5Mwn1 �_ SmXcwaiu tw
iaw •=u,m si
P^^",ama° qmi mrnPy h�� o.. -^ � zoo w,m,
Ie.N Sam aadma ®Iy, rynacama lx aa.. �1
d Tf SnaW T—Sample E
• J1 �_ PeMue a,vunMmr
O.O.iN W mm. exNin
uc�„M•p, ®e }orvana nwm,g pT � NaMN MI
i�/ s,mPw.a e.Pm.ma =
/�
c.Mlua s.m Loaaed Bv: F
nvonms
z
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m
1 T
rn �
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MID
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OC
_ M
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to
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m
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ON
r
CCA
m(D
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zb
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rn
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0
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LSI ADAPT
1615
pp�� /'� q�p, �up�/�
z
O
O
m
iT
[n '--1
cm
mo
�o
o�
c
mm
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r=
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77-22
oN
r
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A
z
z
z
m
I
Start Date : 01/13lob Gamolehon Date . 01/13/05
t✓®����I/�®�e��®�'�� WELL LOG Seatlte.eWashington South
TEL: 206.654,7045 FA%: 206.654.7046
PROJECT: Bui Residence Job Number: wn05-12239-GEo Boring No.: a-1
LOCATION : 16105 75 Place west Monitoring Well No.: Mw-1
Edmonds, Washington 98026
Ground Surface Elevaton : 00.5 It Casing Elevation: 87.51t Elevation Relerenw 'Site Plan' by 40 Architects tlated Oa2t/05 age'
02 of 02
ws
-
SOIL DESCRIPTIONof
a
ns
�
a
�s
WELL
LABORATORY TESTING
30 Stiff, dam to moist, blue- ra CLAY Massive M
7
Becomes very stiff
35
m
Hard, damp blue -gray, CLAY with fine silt
laminations
40 s�lo e
29
---------------------------------
Very stiff, moist, blue -gray,. CLAY (Massive)
Boring terminated at 46.5 feet bgs.
Groundwater encountered at -13.0 feet bgs.
3
LEGEND
= xn.„o. o. souso�senwe � d we iruv nn. ® cnoseewels�c�noel f�(� �eeemw•e,wec
� 1r a �e. non. Demua won svnpe � te�no,m.a���iory e� ���
�L. filEpiv�Nm sfltBbcum 5Mwn1 � Fy.� o- �o-.Mr$O�Bn
m � �_ enec Wvv Lwd fla+Nq Ms
sneroy Tua Smpe e.o.i.�� oW
fl _ ennea (;n11ntM'YY Ca'nveSW � ® eweo
X �„o rva,m _
,I
� I
--'r-r---- i---i-;-
I i
-----:-------.-----
- - - - - -- _I-' "4- - -
MOISTURE CONTENT
w1s
r =2.a
T =te
PP=4.0
ew,p
R.B.H.
aia r �I n �at u4�m um
®Gicin S're.voryme �Wiee
M1 fines vwnl ® M1 snee
none Ffl pu'
Huang Ml eMgPl�l
Loacetl Bv:
615
z
O
A
m
—I T
to =
Cm
mo
8O O
c
mZ
O1
DZ
Om� (,
S�
mm
O�
r
�m
it
2
Z
-i
2
co
z
0
n
m
,ar, oo. oamw,arwo:.swrow Tro•tlaar•a r.P:mJ �io-mu, ae"Prcwn�\.
5 ]I a t3PT B,w,caua 5m+m1 f'l Snec Walw Lwtl Pua,N Pwlamtl F'* �eSO $and BatltllS� o-su.. ® 200 waN 1
y ® lxfina , (n fines Mwn
D
T�T �
I I Sn.Oy TUM Oar°la . W Pouw Pantwmnaw
JJ- S_ PercnvECmunlwa,w M w;,w, vl' ® Bw,onn OaNlo ry Tave:ro Rutlnp Odl PP Pu Pq
a
Lcaaed fiv : R.6.H
45tart Data: Ot/10/OS Completion Date 01/73/05
LSI ADAPT
BORING/MONITORING WELL LOG Saaale,6Washington o9610a
TEL 206.654.7045 FAX: 206.654.7048
PROJECT : eui Residence JOb NUfnber : WA05-12239-GEO Boring No.: s-2
LOCATION : 16105 75Ih Place Wes[ Monitoring Well No.: Mw-z
Edmonds WA98026 ase:
64.D fl Elevadon Reference : "Site Plan by 40 Architects dated 0921/OS O7 0l 2
Grcund Surtace Elevation : 84.0 fl Casing Elevation :
a
DESCRIPTION
WELL
LABORATORY TESTING
�
SOIL
3-inches, grass sad and topsoil
2
Medium stiff, moist to we[, gray with some rusty
_ - _' _ _ _ _ _ _ _ _ _ _ _ _
mottling, clayey SILT with some medium rootlets
_
rnottlin-
SUff, moist to wet, tan -gray with rusty 9.
_ __ j _ ! _
'!
clayey SILT interlayered with silty fine sand
IensesandVacerootlets(LandslideDebris)
L--r-;--;-"'�- �-"-'�-
------------------
5
s2
4
N=0.6
Becomes medium stiff, thinly laminated
_ _�_ _ _w _ , _
_D 4
PP=1.6
10
(at 30° inclination to horizontal)
sa
2
1
A
sa
a
e
15
rv=o.6
interlayered
PP=3.0
Stiff, moist to wet, gray, silty CLAY
with gray to rusty tan -gray, fine sandy SILT with-1-
thin lenses of brown -black, organic -rich
inclusions (Landslide Debris)
_ - _ _ _ _
i �.
-'-
Loose, wet to saturated, gray, fine to medium
SAND (Landslide Debris)
-------
'-
_ : _
� o;
20
S5
z
I
/
1
Medium dense, saturated gray, fine to sandy
SILT with trace brown -black, peat inclusions,
non -plastic (Landslide Debris)
s-7
lu
a
L
-`-�
---i - --- ®
25
�
tLoose, gray, saturated silty fine SAND-
'intermixed with soft, wet, gray and tannish gray
with rusty mottling, SILT with some fine sand and
t
�
to
--
-�-------�---=-'
trace clay and [race peat inclusions (Landslide
i
i 3
Debris
D MOISTURE CONTENT
LEGEND
� Static Wa,wlmtlw nme ®rase
SwnOe
lSW cwempl
j��
�I.o.3w°u.+aPm
In
Bwawela
BadRv
a aum�
PWSCc limit NaN21 Wi
O. O,SytSpoan Sz:ya
° onPP]
LSI ADAPT
BORING/MONITORING WELL LOG
615
Seante.6W sh gtonouth 981104
TEL 206.654.7045 FAX: 206.654.7048
PROJECT: Bui Residence Job Number: WA05-12239-GEO Boring No.: B-2
LOCATION : 16105 75 Place West
Monitoring Well No.: MW-2
Edmonds, Washin ton 98026
casing Elovauon: 84.0 tt Elevation Rut--:
Ground Surface Elevaton : 64.0 ft 9
'Site Plan' by 40 Architects dated o021/05 pZ o1 02
�s
SOIL DESCRIPTION ai € aw as
WELL LABORATORY TESTING
30
Loose, gray, saturated, silty fine SAND
.8 2
0
!�.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
intermixed with soft, wet, gray and tannish gray
4
with rusty mottling, SILT with some fine sand and
- - - - - - -- -
r
trace clay and trace peat inclusions (Landslide i
sy
_ _ _ _ _- _ _,_ _ _ _` _ _ _
TV—
r
IDEbPIS) _________________�
Stiff, moist, blue -gray, CLAY ("varved")
4
9
j _ _ i5_3 PP=2.0
-'
35
-�---�--- ^-
.i
-----------------
Becomes very stiff---
3-10 5
Tv=2.1
__ _____,___��_-_ PP=4.1
•
12
Boring terminated at 39.0 feet bgs.
I t 7
40
Groundwater encountered at -13.5 feet bgs.
I
---7---I----1-------
45
----------------
50
_
55
-----
- ----.- - ---
's
o is 20 as ao so
MOISTURE CONTENT
LEGEND
aP
R M
T o. o. sun sw..sww. �, avnm. ® c,m samoi. tsuivans.l p0D0 .nn ea,nwue axtfiec
Plastic Lmt Nawrdl Liwialm
x.ncn
O.D. o.m..sxoo,.s mpw Tn.ap y 1T.a �, sa• xoo w•n,
z tea, n<•>n 1� n^.. mQ„t Ix au« eo.m
T a (1--eu�a.es 1 mu<wm«�«.�P..4�^9 P. onn 11b oxo s,m a,amu
—
m o.o rNww« w
ZTs�nY sNw• �— P. 000, maw ®a.mai.awc
1a. Tuoe a
n,VI MI PP nm6„91M m
mn• m
Xs>ma•^°. n•d..•neLoaned
By : F
z
O
n
On
Z�
om
PH O
__1O
On
C
mZ
A
-H_
DZ
r—1
_
�2;
O-n
m
_M
mm_
oCl)
r
C Cl)m
KV)
1m�
D
zZ
2
_z
O
n
In
LSI ADAPT
BORING LOG
Saafi158th Avenuo South
nle. Washington 98104
TEL. 206.654.7045 FAX. 206.654.7048
PROJECT: Bui Residence Job Number: WA05-12239-GEO Boring No.: B-3
LOCATION : 16105 75th Place West
Edmonds, Washin ton 98026
0321I05 of
Ground Surface Elevation: 70.0 8
Elevation Reference :
'Site Plan' by 40 Architects dated
01 01
SOIL DESCRIPTION
a!
€ 4
m
a s
LABORATORY TESTING
-0
6-inches, grass sod and topsoil
1-------------------------------J
Medium stiff, moist, gray to tan -gray with some
rusty mottling, SILT with trace fine sand
_ansLs9taeJslelzG�lstgll.�ns idf ge_rt� -----
Soft, moist to wet, tannish gray with some rusty
to blue -gray stains, clayey SILT with some fine
-5 rootlets and trace brown -black topsoil/peat
inclusions (Landslide Debris)
st 2
2
3
S2 2
1
2
---- --- - --
----------------------
-------- - -- -
= - - - - -'- - - - iT
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -;
-
- - - -
_ - _ _
TV=0.6
PP=0.7
N=0.3
-----------------
Interlayered with loose, saturated,
-------------------------
_ - _ - _ - - - - _ - _ - _ _ _ _ _ _ _ _
.. _ _ -
gray, silty fine SAND
10- - - - - - - - - - - - - - - - -
sa 3
2
- ---- -- ---- --- -- -
- - --
Tv=as
2
----
N=0.5
PP=1.6
----
Medium stiff, moist to wet, blue -gray, silty CLAY
(Massive)
sa 2
2
---------------
- - - -- _ - -
--
--
- - - - - -
N=1.3
- - - - - - - - - - - -
15 Stiff, moist, blue -gray, CLAY (rrvarved")
s.5 4
- - - - -
(g41
PP=3.5
fi
SE 3
5
7
----i-------------�------
_-__
N=1.4
7P=3.0
zo
----------------------
Becoming damp
l - -'- --
- - -
&7 3
___-_- -----
N=1.a
s------
Boring terminated at -24.0 feet bgs. Perched
25 groundwater encountered at -8.0 feet bgs.
_ _ _ _ _ _ ._ _ _ _
-------------
_ _ _ _ _
---------------------- -----------
30
---------------------
0 0 20 w
MOISTURE CONTENT
w
w
LEGEND® x.1 = ReW Npm
Pq1
O. e. SPT SPe.Spaon Samph Gne samP�a l$oluM�al TV roman. Ples(k limn NdW2l
(erm+wrelrcn�m�.m�c+^^.'^I warp N
ava �Ircfi O O. atmY4 Moan SampY � YaR i,ma � ry •n>Incai iotirg P.fiarme4
(Ewi,MwraPT Obwrow. Sndml yUniw„ram
51WyTub SMnpM aMuc er Laa map ® Gren Sloe N,aW.
sarE M1fim.Nanl
i V SunV�e nq RI-w �_ ParcriaC erounMwr'_..__n.,., _ _- nulnm5
L 'quid limit
BOO
� Rfin.,
L00aetl 8v:
WaM
tlonl
R.e.H
Z
O
n
m
-I T
fn 2
C: m
IT, a
On
c
mZ
O 't
DZ
r1
x
n
mm
ON
r
Cco
m�
,-Z-I m
�1
2
Z
1
2
N
O
mm
LSI Adapt Engineering
Operator: Broom CPT Date/Time: 4/13/2005 2:55:23 PM
Sounding: CPT-01 Location: But Residence West Side
Cone Used: DSG0708 - Job Number: WA05-12239-GEO
i Tip Resistance Friction Ratio Pore Pressure - Soil Behavior Type' SPT N'
Ot TSF Fs/Ot (%) PW PSI Zone: UBC-1983 60% Hammer
- 0 200 0 8 -10 10 0 12 0 40
0
i
t
I
1
d
I 5
gg{{(
3
sz
10
`
15
I
20
- Depth
V
25
30
I I
35
1.
f
f
40
Maximum Depth = 17.22 feel Depth Increment = 0.164 feet -
■ 1 sensitive fine grained ■ 4 siltyclay to clay 07 silty sand to sandy silt 010 gravelly sand to sand
■ 2 organic material ■ 5 clayey silt to silly day 0 8 sand to silty sand ■ 11 very stiff fine grained (')
■ 3 day ■ 6 sandy silt to clayey silt ■ 9 sand 012 sand to clayey sand (')
"Soil behavior type and SPT Eased an data from UBC-1983 Northwest Cone Exploration
O
-I
0
m
I
r
-i T F
om
C
�O0
C
mm
� f
C Z ti
ca
n b
S� pp
mm E
ON'
r
CN
� N
�m
X
2
z
z I
z
0
-4
0
rn
M,
LSI Adapt Engineering
Operator: Brown CPT Dale/Time: 4/13/2005 3:31:50 PM
jSounding: CPT-02 Location: But Residence North Side
Cone Used: DSGO708 Job Number: WA05-12239-GEO
t
t
- Tip Resistance Friction Ratio Pore Pressure Soil Behavior Type' SPT N•
at TSF Fs/Ol (%) Pw PSI Zone: UBC-1983 60%Hammer
0 200 -0 8 .10 10 0 12 0 40
i
I
0
5
j'
i
10
i
16
20
Depth
(ftl
- -
- 25
30
i
f
35
1
40
Maximum Depth = 38.39 feet Depth Increment = 0.164 feel
Y 1 sensitive fine grained 04 silly clay to clay ■ 7 silty sand to sandy silt 010
gravelly sand to sand
■ 2 organic material ■ 5 clayey sill to silty clay ® 8 sand to silty sand ■ 11 very sfi8 fine grained V)
3 clay 06 sandy sill to clayey sill 09 sand ■ 12 sand to clayey sand (')
Northwest Cone Exploration
'Soil behavior type and SPT based on date from UBC-1983
x
LSI Adapt Engineering
Operator: Brown CPT Date/Time: 4I73120054:59:07 PM
Sounding: CPT-03 Location: Sul Residence Northwest Side
Cone Used: DSG0708 Job Number: WA05-12239-GEO
Tip Resistance Friction Ratio Pare Pressure Soil Behavior Type' SPT N'
Qt TSF FSIQt (%) PW PSI Zone: UBC-1983 60% Hammer
0 200 0 8 -10 10 0 12 0 40
0
. �. 5
i
1
j10 - 7
15 - - -- - - - - -- - --
Depth 20 __ __.__ __ _ __ _ __ __
(ft)
25
30
40
Maximum Depth = 30.35 feet Depth Increment = 0.164 feel
.1 sensitive fine grained E 4 sllty clay to clay ■ 7 silty sand to sandy silt ■ 10 gravelly sand to sand
■ 2 organic material IN5 clayey silt to silty Gay IN 8 sand to silty sand ■ 11 very still fine grained (')
R 3 Gay ® 6 sandy silt to clayey sill 09 sand ■ 12 sand to clayey sand f)
Northwest Cone Exploration
-Soil behavior type and SPT based on data from UBC-1983
Z
Oj.
--I
m
=a -n k'
o M €'
m0
0
ti
mz
0 1 .0
CZ
_ �_ )
�m
n
T
mm
00
r
C fmA
K fn
Zmr
D
A
5
Z
Z
O
Q
m
LSI Adapt Engineering
Operator: Brown CPT DateTme: 4/1312005 6:03:58 PM
Sounding: CPT-04 Location: Bui Residence South Side
Cone Used: DSG0708 Job Number: WA05-12239-GEO
Tip Resistance Friction Ratio Pore Pressure Soil Behavior Type' SPT N'
Ql TSF Fs1Qt (%) PW PSI Zone: USC-1983 60% Hammer
p 200 0 8 -10 10 0 12 0 40
O
i
I
5
i
10
16
t
Depth 20
(fU
25
30
i
i 35
+{I
f
40
2
O
m
Maximum Depth = 30.51 feel Depth Increment = 0.164 feel
■ 1 sensitive fine grained ■ 4 silty clay to clay ■ 7 silty sand to sandy silt E10 gravelly sand to sand
■ 2 organic material i 5 clayey silt to silty clay ■ 8 sand to slily sand ■ 11 very sfiff One grained (')
3 clay ■ 6 sandy sill to clayey silt ■ 9 sand 12 sand to clayey sand (')
Northwest Cone Exploration
•Sail behavior type and SPT based on data horn UBC-1983
a®
APPENDIX 8
LABORATORY TESTING PROCEDURES AND RESULTS
.May 2005
_,_ . . Appendix wPage 1
{ Adapt pmle .No._m»_EO
LSI Adapt, Inc.
The following paragraphs describe our procedures associated with the laboratory tests that we conducted
for this project. Graphical results of certain laboratory tests are enclosed in this appendix.
Visual Classification Procedures
Visual soil classifications were conducted on all samples in the field and on selected samples in our
laboratory. All soils were classified in general accordance with the United Soil Classification System,
which includes color, relative moisture content, primary soil type (based on grain size), and any accessory
the exploration logs contained in
soil types. The resulting soil classifications are presented on
Appendix A.
z
O
Moisture Content Determination Procedures
samples to aid in identification and
1
o
RI
Moisture content determinations were performed on representative
All determinations were made in general accordance with ASTM:D-2216. The
n
correlation of soil types.
results of these tests are shown on the exploration logs contained in Appendix A.
N1
c inm0
Atterbe I Limit Determination Procedures
used for classifying and indexing cohesive soils. The liquid and plastic
On
c
C
Atterberg limits are primarily
limits, which are defined as the moisture contents of a cohesive soil at arbitrarily established limits for
O 1
liquid and plastic behavior, were determined for selected samples in general accordance with ASTM:D-
Atterberg Limits Test Reports (2 pages) and
�z
4318. The results of these tests are presented on the enclosed
N
on the exploration logs contained in Appendix A.
O -n
Grain Size Analvsis Procedures
A size analysis indicates the range of soil particle diameters included in a particular sample. A
_M
in m_
N
O
grain
general grain size analysis indicates the range of soil particle diameters included in a particular sample,
how much fines (silt and clay) is
C CO
while a 200 wash (Materials finer than U.S. No. 200 Sieve test) indicates
samples in general
z 0
contained in a sample. Grain size analyses were performed on representative
in general accordance with
>o
accordance with ASTM:D-422. 200 Wash tests were performed
on the enclosed Grain Size
zb
ASTM:D-422 and ASTM:C-117. The results of these tests are presented
Analysis Reports (2 pages) and on the exploration logs contained in Appendix A.
z
CO
z
O
1
n
m
May 23, 2005
Tung Bui Appendix B — Page 2
Adapt Project No. WA05-12239-GEO
Grain Size Analysis Report
100
31n. 1--m. ]IO La wA a1e 120 aw0 160 pIDa w200
I: I. :1 V I' 1:.. 1 1 i 1 :.
90
g
BO
w 70.
i
Z
a 50
0
.I.
I
I
m
S 50
—0-4
1 =1
cc
0. 40
c m
30
A.
:
I
a
l
I
0
20
I
Y~—
_ M
mZ
10
•...
1
I
I
1
C z
0 I
11,
r 1
0 .
loo0 1ao
10 111'
0.1
0.01
0.001
=
� w
Grain Size (mm)
n
Cobbles
Gravel Sand
Coene Fine Coarse Medfum Ffne
Silt or Clay
mm
(.-
O N
i s
C m
m
m
1�
1
D
Z
1
x
Z
O
1
0
m
r
Project Name:
Bui Residence
NOTES:
p Single er (no size
wrveJ indicates'Mate al
Project No:
WA05-12239-GEO
200 Si.e'
Finer than No. 2GG Sieve' test
than N .
Client Name:
Tung Bui
Test Standard:
ASTM:D-422 / C-117
�.
Date:
w •1'1T I..w
2/11/2005
12239- Bui Residence• Grain S-2.wls
Rev.3
—102
Source
Native
Silt/
or
Boring/
Sample
Moisture
Gravel
Sand
Clay
Test
Test Pit
Sample
Depth
Content
Content
Content
Content
No.
No.
No.
ft
Soil Description
1
B-2
S-7
25.0
F. Sandy SILT
30.0
0
25
75
2
B-2
S-8
30.0
Silty F. SAND
33.1
0
52
48
3
4
5
Grain Sin - For
s
Atterberg Limits Test Report
60
50 - ---
v 40
30 - - - - — -
- -- — or
to 20 - --- - - -- - -
10
r -- -_ -- -
4 -_-- _-.-
0 10 20 30 40 50 60 70 80 90 100
Liquid Limit
NatureSample
WaterPlastic
Liquid
Plaeticlty
ple
Depth
Content
Limit
Limit
Index
.
ft
Soil Descri tion
%
%
%
%
USCS
k
5
150
CLAY
35.6
29
64
35
CH
7
22.5
CLAY
32.933
82
49
CH
5
Project Name:
Bui Residence
Project No:
WA05-12239-GEO
Client Name:
Tung Bui
Test Standard:
ASTM:D-4318
Date:
3/3/2005
1 Q1 AnArrT 1--
12239 - 8u1 Residence - All.-19 2A.
LSI Adapt, Inc.
APPENDIX C
SLOPE STABILITY ANALYSES AND RESULTS
May 23. 2005
Tung Bul Appendix C—Page 1
Adapt Project No. WA05A 2239-GEO
z
0
Q
m
1�
Om
Cm
O.
mz
c z ';
O -n C
n �t
M
m_
oN
r
Zr w
Mnrm
D
W
z
S
N
z
O
..t
n
m
IN
LSI Adapt, Inc.
In order to evaluate the global stability of the existing native slope and the proposed daylight basement
excavation configuration, we used Slope/W to perform slope stability analyses along Geologic Cross
Sections A -A' and C-C'. Graphical printouts of representative slope stability sections (10 pages) are
enclosed in this appendix, as follows:
e Geologic Cross Section A -A (Native Slope Configuration): Definition w/assumed soil
parameters, Most Critical Potential Failure Locations for both Static and Seismic Case;
e Geologic Cross Section A -A (Basement Cut Configuration): Definition w/assumed soil
Z
parameters, Most Critical Potential Failure Locations for Static Case, 2 Potential Failure
n
for Seismic Case;
e Geologic Cross Section C-C (Basement Cut Configuration): Definition w/assumed soil
RILocations
=i
parameters, 2 Potential Failure Locations for Seismic Case;
—I
c m
m0
�O
Slone Stability Analysis Procedures
Slope/W analyzes a series of pre -selected failure circles with varying inclination and radius within certain
C
zones of the cross section. The resulting range of radius centers and associated factors of safety are then
critical portions of the slope
in Z
--Iconfiguration.
shown with a set of safety factor contour lines indicating the most
as a factor of safety, which is computed
D
r.
The results of the stability analyses are expressed
slope failure to the gravitational forces tending to cause a slope failure.
_
O V
as the ratio of the forces resisting
The most critical failure circle (minimum safety factor) for each slope condition is shown. Additional
failure circles and associated factors of safety are also shown when specific site construction or
factor of safety against slope failure
rn in
developmental conditions require additional review. [f the computed
and 1.1 or greater in the seismic case, the safety margin against slope
n m
is 1.5 or greater in the static case
instability is generally considered to be adequate by the geotechnical engineering community.
C CD
K in
Geotechnical strength parameters for the site soils were assigned based on the results of the field and
of slope stability analyses, non -plastic soils are generally modeled
laboratory test results. For the purpose
(combination of friction angle and intercept cohesion), while cohesive soils
Z
using effective stress analysis
normally modeled using undrained shear strength (cohesion). Soils that have been previously
are
subjected to significant strain or displacement, such as along pre-existing slide surfaces, are typically
friction and residual cohesion).
Z
p
modeled with residual effective stress parameters (residual angle
or more pizometric lines. Each piezometric line e
m
Groundwater conditions are usually applied as one
buoyant soil density conditions to selected soil layers below the line, to model either
apply saturated,
static groundwater level or perched groundwater conditions:
Each analysis section, is typically analyzed for both static and seismic conditions. A pseudo -static
assuming an average horizontal ground
analysis is performed to evaluate a potential seismic loading case,
horizontal ground acceleration for the site, in accordance
acceleration of about half of the anticipated peak
with generally accepted local practice.
May 23, 2005
Tung Bull Appendix C — Page 2
Adapt P-Oct No. WA05-i 2239-GEO
REPORT NO.
EERC 2003.06
EARTHQUAKE ENGINEERING RESEARCH CENTER
RECENT ADVANCES IN SOIL LIQUEFACTION
ENGINEERING: A UNIFIED AND CONSISTENT
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-- --- ... .......... ...,-ram_. ..._.—
Fig. 40: Post-Fallure Configuration of Centrifuge
Model Dam with Sand "Core" and Clay Shells
Showing Shear Localization Along Top of Sand
(Arulanandan at at., 1993)
Owing to the very sensitive relationship between post -
liquefaction strength (S..,) and void ratio (a) for loose to
medium density soils, even apparently minor amounts of
increase in void space (reduction in dry density) at the top of a
sub -layer can result in large reductions in %,,• In extreme
cases, water attempting to escape from the sublayer can be
temporarily trapped by the overlying, less pervious layer, and
can form a "film" or water -filled "blister" at the interface
between the two layers (in which case the shear strength, S,,,"
is reduced fully to zero along this interface.)
An interesting early example of this behavior was produced in
a centrifuge test performed by Arulanandan et at. (1993), as
illustrated in Figure 40. In this experiment, an embankment
was constructed with a sand "core" and a surrounding clay
"shell" to prevent drainage during cyclic loading. The sand
core was marked with layers of black sand so that localized
changes in volume (and density) could be tracked during
globally undmined shearing. When subjected to a model
earthquake, cyclic pore pressure generation within the sand
occurred, and the embankment suffered a stability failure.
During the "undrained" eanhquakc loading, the overall
volume of the saturated sand "core" remained constant,
satisfying the definition of globally undrained loading.
Localy, however, the lower portions of the sand "core"
became denser, and the upper portions suffered corollary
Loosening. The top of the sand layer suffered the greatest
loosening, and it was along the top of this zone of significantly
reduced strength that the slope failure occurred.
Given the propensity for occurrence of localized void
redistribution during seismic loading, and the ability of Nature
to selectively push failure surfaces preferentially through the
resulting weakened zones at the tops of localized sub -strata
(and water blisters in worst -cases), the overall post -
liquefaction strength available is a complex function of not
only initial (pre -earthquake) soil conditions (e.g. density, etc.),
but also the scale of localized sub -layering, and the relative
Seed ct al. (2003)
orientations and permeabilities of sub -strata. The
qualities that can be reliably characterized, at this ti
laboratory testing of soil samples (or "elements") of
dimensions.
Accordingly, at this time, the best basis for evaluation of post- "ll
liquefaction strengths is by development of correlations
between in -situ index tests vs. post -liquefaction strengths
back -calculated from field case histories. These failure case
histories necessarily embody the global issues of localized
void redistribution, and so provide the beat indication
available at this time regarding post -liquefaction strength for
engineering projects.
Figure 41 presents a plot of post -liquefaction resit)uefst`rength
(S,,,) vs. equivalent clean sand SPT blow count (lft,bo,u). This
was developed by careful back analyses of a suite of
liquefaction failures, and it should be noted that these types of
back analyses require considerable judgement as they arc
sensitive to assumptions required for treatment of momentum
and inertia effects. The difficulties in dealing with these
momentum/inertia effects (which are not an issue in
conventional "static" stability analyses) are an important
distinction between the efforts of various investigators to
perform back -analyses of these types of failures. In this
figure, the original correction for fines used to develop N1.6a..a
is sufficiently close to that of Equations 6 and 7, that
Equations 6 and 7 can be used for this purpose.
Stark and Mesri (1992), noting the influence of initial
effective stress on S _„ proposed an alternate formulation and
proposed a correlation between the ratio of S.,,/P and N1,6o,a„
as shown in Figure 42, where P is the initial major principal
effective stress (d1j). This proposed relationship overstates
the dependence of s,,r on dt,i, and so is overconservalive at
shallow depths (di,; < 1 ("mosphere) and is somewhat
unconservative at very high 4 tial effective stresses (di,t > 3
atmospheres).
it is also true, however, that the relationship of Figure 41
understates the influence of dt,t on S, Figure 43 shows an
excellent example of this. Figure 43(a) shows the stress paths
for a suite of four iC-U triaxiat tests performed on samples of
Monterey 630 sand, all at precisely the same density, but
initially consolidated to different effective stresses prior to
undrained shearing. (The sample void ratios shown are post -
consolidation void ratios.) As shown in this figure, the
samples initially consolidated to higher effective stresses
exhibited higher undrained residual strengths (Sv 0. The ratio
between %,, and P was far from constant, however, as shown
in Figure 43(b).
The influence of dt,t on S",, (and on the ratio of %.R) is a
function of both density and soil character, Very loose soils,
and soils with higher fines contents, exhibit Su., behavior that
is more significantly influenced by di.t than soils at higher
densities and/or with tower fines content. At this time, the
authors recommend that the relationship of Figure 41 (Seed &
Harder, 1990) be used as the principal basis for evaluation of
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Fig. 41: Recommended Relationship Between S_ and
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([ . MC.SMafe 5Pr ADD UfIMNIRp CIaR., 51AEN•.M DATA
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Fig, 42! Relationship Between Sa /P vs. NI,60,cs as
Proposed by Stark and Mesri (1992)
in -situ S,,r for "lively clean" sandy soils (Fines Content <
12%). For these sods it Is recommended that both
relationships of Figures 41 and 42 be used, but that a 5:1
weighting be employed in favor of the values from Figure 41.
_ _
Simarly, ila more nearly intei—maiaie basts (averaging t Tl—e
results of each method, with 3:1 weighting between the
relationships of Figures 41 and 42) is recommended for v
silly soils (Fines Content > 30%). For fines contents between
12%end 3A, a linear vars-11 in weighting between the two
proposed relationships can be used.
It must be noted that engineering judgement is still required in
selection of appropriate post -liquefaction strengths for specific
project cases. Consideration of layering and sub -layering,
permeability/drainage, and potential void redistribution, and
the potential for confluence of alignment of layering interfaces
with shear surfaces must ell be considered. For most "typical"
cases, use of S,,r values in the lower halves of the ranges
shown in Figures 41 and 42 (with due consideration for
weighting of these) appears to represent a suitably prudent
range for most engineering purposes at this time, but lower
overall average post -liquefaction strengths can be realized
when layering and void redistribution combine unusually
adversely with potentially critical failure modes.
Finally, a common question is "what happens at Nt,6q„ values
greater than about 15 blows/ft.?" The answer is that the
relationships of Figures 41 and 42 should be concave upwards
(to the right), so that extrapolation at constant slope to the
right of N,boe=15 blows/tt should provide a conservative
basis for assessment of S,,,r in this range. As these projected
values represent relatively good strength behavior, this linear
extrapolation tends to be sufficient for most projects. It should
be noted, however, that values of S,,,T should generally not be
taken as higher than the maximum drainedshear strength.
Values of Ft, higher than the fully -drained shear strength
would suggest significant dilation. Dilation of this sort tends
to rapidly localize the shear zone (or shear band), and so
reduces the drain path length across which water must be
drawn to satisfy the dilational "suction". As these distances
can be small, rapid satisfaction of this dilational demand is
possible, and "undraincd" (dilational) shear strengths higher
than the drained strength can persist only briefly.
Accordingly, for most engineering analyses the use of the
fully drained shear strength as a maximum or limiting value is
prudent. Similarly, the maximum shear strength cannot
exceed the shear strength which would be mobilized at the
effective stress corresponding to "civitation" of the pore water
(as it reaches a pore pressure of —1 atmosphere). The above
limit (to not more than the fully -drained strength) is a stronger
or more limiting constraint, however, and so usually handles
this problem as well.
5.0 EVALUATION OF ANr FATED
LIQUEFACTION-RNDI CED DEFORMATIONS
AND DISPLACEMENTS
S. I Introduction:
Engineering assessment of the deformations and
displacements likely to occur as a result of liquefaction or
pore -pressure -induced ground softening is a difficult and very
challenging step in most projects, and this is an area where
further advances are needed.
5.2 Assessmcntof"Large"Liquefaction-Induced
Displacements:
For donations in which the post -liquefaction strengths are
judged to be less than the "static" driving shear stresses,
deformations and displacements can be expected to be "large'
generally greater than about Im., and sometimes much greater -
Figure 44 shows examples of global site instability
corresponding to situations wherein post -liquefaction strengths
are less than gravity -induced driving sheer stresses. These arc
schematic illustrations only, and are not to scale.
Seed ct al. (2003) 42
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370 Seed and Harder ( w o)
yC EVALUATION OF UNDRAINED RESIDUAL STRENGTH
As early as 1936, Casagrande (341 postulated that soils sheared under
undraned conditions would achieve a residual condition at which further
shearing would cause no additional change in strength or volume or pore
press re, This principle is the underlying basis of "critical state" soil
mechan cs [35] as well as recently proposed "steady state" analysis
techniques for evaluation of "post -triggering' stability of liquefiable soils.
Poulos and Castro [36] recently proposed a methodology for evaluation of
in situ undrained residual "steady state' strengths (S.), based on obtaining
hieh quality soil samples with minimal disturbance, testing these in the
laboratory, and then usin specially developed techniques to correct the
resulting laboratory S values for the effects of void ratio changes due to
sampling, handling ant`Ftest set-up in order to develop estimates of the field
(in situ) S_ This represents a major contribution to geotechnical practice,
as it has spurred considerable interest and research into the use of residual
undrained strengths for post -liquefaction stability assessment
Unfortunately, due to the 'very high sensitivity of Soy to even small changes
in void ratio, these techniques for laboratory -based evaluation of S. do not
presently appear to represent a reliable basis for engineering analyses,
�employed conservative the iucefactors f32j are
to account for assumptions
onsdeble ratiwold [6,
Dr. Seed recommended an alternate technique for evaluation of in situ
undrained residual strength (Sr) based on Standard Penetration testing 137].
He presented the results of back -analyses of a number of liquefaction
failures from which values of the residual undrained strength could be
calculated for soil zones in which SPT data was available and proposed a
correlation between Sr and (Nio a (NI) is a "corrected" penetration
resistance, as discussed previously, but with an additional coueetion for
fines content to generate an equivalent "clean sand" blowcount as
(NO60-a = (NI)60 + Ncorr
where Nrorr is a function of percent fines, as shown in Table 4. It should be
noted that this is not the same "fines" correction as is used in the
"triggering" analyses (e.g. Figure 3).
Table 4: Recommended Fines Correction for Sr Evaluation Using SPTData
Percent Fines N. (blows/ft)
10% 1
25% Z
50TO 4
75%a. 5
Cyclic Pore Pressure 371
Figure 11 presents an updated correlation between Sr and (Nil60-u, based
on values back -calculated from an increased number of case studies, as
listed in Table 5. Many of the S values presented are slightly different
from those originally presented [37J as: (a) improved techniques have been
used to account for dynamic effects (e.. momentum) in developing
estimates of S from the field failures, and ($b) additional data has recently
become available regarding several of these case studies. It is
recommended that' the lower -bound, or near lower -bound relationship
between Sr and (Nil in Figure 11 be used for residual uudrained
strength analyses at In time owing to scatter and uncertainty, and the
limited number of case studies back -analyzed to date.
i
Assigning "post -triggering' analysis strengths to the various soil elements of
Figure 9, based on FSl and Figures 10 and 11, the resulting Post -earthquake
static factor of safety for the most critical failure surface in the upstream
portion of the dam is considerably less than 1.0, indicating the onset of
major slide movements, in good agreement with the actual observed
Performance. It is interesting to note that the actual residual undrained
i strength of the lower zone of the upstream hydraulic fill (with (Nt)60 = 11.5,
and (NrI�,, = 13.5 blows/ft) was judged to have been on the order of
I. S, = 300 to 500 psf, as shown in Table 5 and Figure 11. Assigning
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(NI)6o-a and Undrahed Residual. Strength (Sr) from Case Studies
i
..i
�y Seed and Harder
j/* Table 5: UndrResistance (NI)sae, Based oed Residual Strength
Analysof Case Histories
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reasonable strength values to the upstream toe and overlying soil canes (1,
61, an average residual undrained strength of S, a SOD to 900 psf in the
upstream hydraulic fill zone would have been required to provide an overall
factor of safety equal to one.
Ass going strength values to the various elements in the downstream
hydraulic fill zones, using the same procedures, the resulting static factor of
safety is well above one (FS = 13 to 1.4). A lying Newmark -type seismic
displacement analyses [48], as modified by Seed and Makdisi 49, SO], and
usingg these assigned strength values, results in calculation of lilcely seismic
dispplacements for the downstream section of the dam of on the order of 4
to 30 inches, again in reasonably good agreement with the observed field
performance.
SUMMARY AND CONCLUSIONS
Ile methods presented herein are successfully able to reproduce the
observed behavior of the Lower San Fernando Dam during the 1971 San
Fernando Earthquake, Predicting large slide movements of the upstream
section and limited displacements of the downstream section. These
analytical methods, coupled with appropriate engineering judgments,
appear to provide a sound basis for evaluation of the seismic stability of
Cyclic Pore Pressure 373
dams and slopes comprised of, or founded on, potentially liquefiable sandy,
and silty soils. This is a tremendous achievement, and the authors applaud
Dr. Seed and the many others who have contributed to the development of
these procedures over the last 20 years.
This does not mean that further advances would not be highly desirable.
There is a need for additional study of the transition from conditions in
which cyclic pore pressure generation or cyclic strain accumulation control
behavior to conditions in which residual or large -strain strength and
deformation characteristics control behavior. Closely related to this issue is
the need to further investigate the influence of static "driving" shear
stresses, as currently incorporated in the analyses usingg a and K., especially
at relatively high initial effective confining stresses. In addition, there is a
need to extend these methods to permit similar, reliable analysis of gravelly
soils (e.g. recent research involving the use of Becker Hammer large-scale
penetration res stance). Finally, additional investigation of the liquefaction
resistance of moderately plastic soils, and the influence of clayey fines on
liquefaction resistance would also be useful.
All of this would please Harry Seed, who so enjoyed the challenges
ppresented by his own geotechnical career and who devoted so much of
himself to preparing the next generation for challenges such as these.
{ REFERENCES
[1] Seed, H. B, Lee, K L, Idriss, 1. M. and Makdisi, F. (1973). "Analysis
of the Slides in the San Fernando Dams During the Earthquake of
Feb. 9, 1971', Rept. No. UCS/EERC-73/2, Univ. of Calif., Berkeley. `
(2) Seed H. B. and Idriss, I. M. (1971). A Simplified Procedure for
i Evaluating Soil liquefaction Potential", JSMFD, ASCE, Vol. 97, No.
SM 9, pppp. 1249-1274.
[31 Seed, H B, Lee, K L., Idriss, I. M. and Makdisi, F. (1975). " Ibe
Slides in the San Fernando Dams During the Earthquake of February
9, 1971", J. of Gent. Engin, ASCE, Vol. 101, No. =, pppp 651.688.
! [4) Seed, H. B., Lee, K L, ldriss, I. M. and Makdisi, F. (1975). "Dynamic
Analyses of the Slide in the Lower San Fernando -am During the
Earthquake of February 9, 1971", J. of Geot. Engin., ASCE, Vol. 101,
No. GT9, ppp. 889-911.
151 Lee, K L, Seed, H B, Idriss L M. and Makdisi, F. ()975).
"Properties of Soil in the San Fernando Hydraulic Fill Dams", J. of
Geot. End ASCE, VOL 101, No. GT8, pp. 801-821.
i [6] Seed, H- B•, Seed, R. B, Harder, L F. and Jong, H. L (1989). 'Re -
Evaluation of the Slide in the Lower San Fernando Dam in the 1971
San Fernando Earthquake", Rept. No. UCB/F,ERC-88/04, University
of California, Berkeley.
[7) Castro, G, Keller, T. O. and Boynton, S. S. (1989). "Re -Evaluation of
1 the Lower San Fernando Dam. Report 1: An Investigation of the
February 9, 1971 Slide", Rept. No. G1,89-2, U.S. Army Corps of
Engineers, WES, .
M�
Table 4.5
RELATIVE VALUES OF EFFECTIVE STRESS FRICTION ANGLE
FOR NORMALLY CONSOLIDATED COHESIVE SOILS
Test Typo Friction Angle (degrees)
Triaxial compression' (TC) 1.0 dtc
Triaxial extension (TE) 1.22 Oct
Plane strain compression (PSC) 1.10 etc
Plane strain extension (PSE) 1.10 (for PSC/TC) x 1.22 (for TE/TC)
— 1.34 ;te
Direct shear2 (DS) tan-1 (tan dpsc cos �cvj
or tan-1 jtan(1.10 etc) cos ¢Ovj
1 - CIUC, CKoUC, or CAUL
2- Speculative, based on results from sand
it is understood that the strains necessary to accomplish this remolding may exceed
100 percent. Earlier studies of this subject may not have subjected the soil to
the necessary strains, and therefore residual angles quoted in earlier sources may
be somewhat on the high side.
Extensive research (e.g., 27, 2g) has shown that the clay fraction (percent finer
than two microns) and mineralogy perhaps are most important in evaluating Or. If
the soil clay fraction is leas than about 15 percent, the soil behaves much like
cohosionless soil, with Or typically greater than 256 and not much different from
If the clay fraction is greater than 50 pexcenc,O
r to appreciably lower than
rev and is governed entirely by sliding of the clay minerals. For the most common
clay minerals, Or ranges approximately from 15' for koolinite, to 10" for illite,
and then to 5' for montmorillonite. Soils with clay fractions between 15 and 50
percent exhibit transitional behavior, as shown 'in Figure 4-24.
The value of �r also is stress -dependent because of curvature of the failure enve-
lope (22, 27, 29). Values given in Figure 4.24 are appropriate for an effective
normal Stress equal to about one atmosphere. Figure 4.25a illustrates the typical
changes in 4r which occur with changes in effective normal stress and plasticity
4-25
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with PI/CF -0.5 to 0.9
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Sands \ p\\
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`08` CO�p c00 ._ O —
a Values of, O
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° p 20
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Cloy Fraction, CF (%)
Figure 4-24. ilr.from Ring Shear Tests and Field Studies
Source: Skempton (28), p. 14.
30°
Q 201 2
a
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.Vi (a)
rr
0
0 10 20 30 40 50
Plasticity Index, PI (%)
g
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4 Eflective Normal Stress, o/po
Figure 4-25. 4 for Amuay Soils
Source: Based on Lambe (29), P. 144.
4-26
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parallel, indicating that the change in 4r as a function of stress change is inde-
pendent of the plasticity index. Re -plotting these changes in friction angle (A00
results Figure 4-25b. Other data (e.g., 27) are consistent with these 47or values.
The final values of Or therefore should be evaluated from Figure 4-24, modified for
effective normal stress level as given in Figure 4-25b.
UNDRAINED SHEAR STRENGTH OF COHESIVE SOILS - GENERAL EVALUATION BASIS .
The undrained shear strength (su) may very well be the most widely used parameter
for describing the consistency of cohesive soils. However, su is not a fundamental
material property. Instead, it is a measured response of soil during undrained
loading which assumes zero volume change. As such, su is affected by the mode of
testing, boundary conditions, rate of loading, confining stress level, initial
stress state, and other variables. Consequently, although not fully appreciated by
many users, su is and should be different for different test types (See Figure 1-1
for test types.).
As described earlier in this section, it is appropriate to use a standard "test of
reference", which is the isotropically consolidated, triaxial compression test for
undrained loading (CIUC), With the CIUC test as a standard reference, the results
of all other tests can be compared simply and conveniently. It should be noted
that simpler forms o£_triaxial test are available, such as the unconsolidated,
undrained (UU) triaxial and unconfined (U) compression tests. With the UU test, a
total confining stress is applied, but no soil consolidation is allowed under this
confining stress. With the U test, the soil is unconfined with a zero confining
stress.
Many detailed studies (e.g., 11. 23) have shown that the UU and U tests often are
in gross error because of sampling disturbance effects and omission of a reconsoli-
dation phase. Based on studies such as these, the CIUC test also is considered to
be the minimum quality laboratory test for evaluating the undrained shear strength
of cohesive soils. Other simple tests such as the torvane and pocket penetrometer
have an error potential that is comparable to that of the UU and U tests. There-
fore, these tests should only be considered general indicators of relative beha-
vior. They should never be used directly for design.
Since su is stress -dependent, its value commonly Is normalized by the vertical
effective overburden stress (ovo) at the depth where su is measured. This
4-27
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Rolf Hyllseth
From: Rolf Hyllseth
Sent: Thursday, May 04, 2006 12:20 PM
To: 'Hauck, Kristopher T'
Cc: Tung Bui (E-mail); Nega Weyesa (E-mail), Khew Lew
Subject: RE: Bui Residence Review
Seed - Residual EPRI - Residual
strength of it... strength of fl
Kristopher,
We did use residual soil strength values for the lower soils within the estimated shear
zone directly above the base clays, as stated in our report pg. 10 6 11;
..The cohesive soils within the landslide shear zone were modeled in the static case
using fully deformed and remolded soil strength.values, based on correlations between
residual friction angles and the clay fraction/plasticity index. The soils within the
potentially liquefiable soil layers were modeled in the seismic case as a liquefied mass
with a residual shear strength estimated based on correlations between mobilized critical
strength (liquefied) and equivalent SPT blowcounts (pre -liquefaction) reported by Seed at
al. (1990) and updated in the 2003 Earthquake Engineering Research Center (EERC)
f publication Recent advances in soil liquefaction engineering: A unified and consistent
( framework (EERC 2003-06)..."
I Please see attached pdf scan files of the referenced literature used to obtain the
residual soil strength values used in our analysis.
If any other questions, please call.
I
Thanks,
Rolf Hyllseth, P.E., L.G.
LSI Adapt, Inc.
615 Eighth Avenue South
Seattle, WA 98104
ph# (206) 654-7045
mob# (206) 786-1619
fax# (206) 654-7048
--Original Message -----
From: Hauck, Kristopher T(mailto:kris.hauck@zipperzeman.com)
Sent: Thursday, April 27, 2006 3:49 PM
To: Rolf Hyllseth
Subject: Bui Residence Review
Rolf,
John Zipper and I spoke with K.V. yesterday on the phone regarding the
slope stability analyses. For the most part, our question was what soil
strength parameters were used for the stability analyses? If residual
strengths were used, could you provide summary of conclusions/analysis
for the values? If you have any question, please do not hesitate to
call. We feel this is the quickest way t6 complete this process, as.
opposed to going through an entire round again. This way, with the
additional information, we should be able to move ahead. Thanks.,
Kristopher T. Hauck, P.E.
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i Broject Engineer
Zipper Zeman Associates, Inc - A Terracon Company
18905 33 Avenue West, Suite 117
Lynnwood, Washington 98036
P 425.771.3304 / F 425.771.3549
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JAN -9 2005 1 ii FP OflCROO 71-LE 425 255 6279 31c256405830 P.02,04
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OCT IS JW
CITYCOPY TOTAL P-02
FUA
RE I i*URN ADDRESS:
..
-E J7,tV-of dmonds, City Clerk
1� k5th Avenue North
`Edlnorid�. WA 98020
............ .
Y, 5 " WHI
jims,116 5 PG
SH C101 I%GTON
COd?ENANT OF NOTIFICATION
ANDANbEMNIFICATION/11OLD HARMLESS
Reference #:
Grantor(s): (I
(2)— 1 Additional on pg.
Legal Description (abbreviatpd)F See': . �)--Tvvu 6ET RngU,.t tjir �w
OR Ubt Block Plat
Assessor's Tax Parcel EDN(s): (2)
—Asseq,s(;Ps TaifParclkl FDN not yet assigned
CITY 0ftD?40'ND.$
APPROVED FOR RECORDING i
By--,,j DATE:
...... ......
Under the review procedures established pursuant to,-tbe S6te`lauilding Code,
incorporating amendments promulgated by the City '-.4 Etlyntindi,'%and as a
prerequisite to the issuance of a building permit for the consliuclion.of-A residential
Mdential
structure and attendant facilities, the undersigned OWNERS ot-J)"r.operty-tto 4reby
covenant, stipulate and promise as follows:
.. ..... ... ;
address), Edmfigds
0
APPROVED FOR RE CO DING
BY _&_ DATE
PAGE _7 OF
iubiect Property. This covenant of notification and
triless relaters to a tract of land at the street address of
�IpfF 1nti fInuA�I,(L=(insert street
orNsh County, Washington and legally described as:
Tz'1�1—rsl-
2. Notification and Covenant of Nolificati66. : ,'The., above referenced site
(hereinafter "subject site") lies within an area which"has,been identirted by the City
of Edmonds as having a potential for earth subsidenee,or'-Mgdslide hazard. The
risks associated with development of the site have been`evatiiateq by technical
consultants and engineers engaged by the applicant as apart oYtbe.process to
obtain a building permit for the subject site. The results of the .co5isujwaiies. reports
and evaluations of the risks associated with development are eonfained in'
building
permit rile number (IMP' (insert number) on file wifbthe City of
Edmonds Building Department. Conditions, limitations, or prohitiitions...on-..
development may have been imposed in accordance with the recommeudatieu5 of
AP
- APPRO ED FOR RECO G
,
DATE
PAGE OF —�
the :consultants in the %course of permit issuance. The conditions, limitations, or
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prohabitieiis may reggile,6ngoing maintenance on the part of any owner or lessee or
=�
0
may requfi-e,mudifrc�tions to the structures and earth stabilization matters in order
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to address future or.-aatiaipated changes in soil or other site conditions. The
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statements and. conditions by the OWNERS' geotechnical engineer,
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...Prop.osed
geologist, architect'anl/or struetural engineer are hereby incorporated by reference
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from the contents ofYh6:Fle-as folly as if herein set forth. Any future purchaser,
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lessee, lender or any other person acquirfng;or seeking to acquire an interest in the
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property is put on notice of the'exisfenice'of the content of the file and the City urges
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review of its contents. The file may be reviewed 'during normal business hours or
-
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copies obtained at the Building Departrtient,.•Gty of Edmonds, 121 5th Avenue
=
North, Edmonds, Washington 98029,,
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3. Indemnification and (fold Harmless. Tlie: undersigned OWNERS
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hereby waive any and all liability associated With development, stating that they
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have fully informed themselves of all risks associated''"with: development of the
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property and do therefore waive and relinquish ady and all causes, of action against
the City of Edmonds, its officers, agents and empleyees aridiug.from spd out of such
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development. In addition, the OWNERS on behalf of themselves, their..successors in
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interest, heirs and assignees, do hereby promise to indemnify.agd-6old.liarmless the
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City of Edmonds, its officers, agents and employees from any fgss cla'im,.liatility or
damage of any kind or nature to persons or property either 'ou-'or.flff the site
resulting from or out of earth subsidence or landslide hazard, arising:,frohYor o,.ut.of,
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the issuance of any permit(s) authorizing development of the site, or of curi'iu9 or
....
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... ....... ....
APP!l��,,O,,V 13 FOR RECO G
" = jGl= _ .DATE
PAGE _r OF
arising.qut ofany_Aalsr, misleading, or inaccurate information provided by the
OWNERS; theiremplgy0s, or professional consultants in the course of issuance of
the building permit
4. InsurhodeRedni>ement jn addition to any bonding which may be
t
required during'the•`eo6se---6f development, the Community Services Director
has/has not (strike oue)-spoei[iea ly iequired the maintenance of an insurance policy
for public liability coveragE i iAhe ainoun't aqd for the time set forth below in order
to provide for the financial resppnsibilities established through the indemnification
and hold harmless agreemenf'abave:
5. Covenant to Touch and Concern the Ladd.: ;'this, covenant of
notification and indemnification/hold harmless touches•'and'concerns the subject
tract and shall run with the land, binding, obligating dadlormilriog to the benefit of
future owners, heirs, successors and interests or''ariy: other' .person or entity
acquiring an interest in property, as their interest may dp 0 ...-Tgfs:pr@yision shall
not be interpreted to require a mortgagor or lender to indemnifythe.Ciiy'cxcept to
the extent of their loss nor to obligate such persons to maintaiu,th'e insurarice'above
required.
STATE OF WASHINGTON
COUNTY OF
. ..... ......
I certify that I know or have satisfiii6r .,y evidence -that Sow gum_
j_L.sig6edihis instrument and
... ............ ..
acknowledged it to h-(j"er) free and volun'&ry-u#1ar,the purposes mentioned in
this instrument.
DATED this 16:,— day of
e C OLDAf,
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1, WEMMBUILDINQMEAPOVACOVENANT
W
Height Calculation/Grading Verification Worksheet
Address: /ip%�,5— -7 ' � — T J Ll) Permit #: -zwL, o s S 6
Date: 1 �/
A. Datum Point:
B. Datum Point Elevation: (orj, 2T
C. Average Grade: $d
(For. Grading Verifieatioii Onlyj .
1 Lowest Footing Elevafiom(shown on grading plan):
,2.1 Actual Footing Elevation:
3. Maximum Elevation Allowed: �O average grade) + 25' _ )
4. Reference Point Elevation Shot to House:
(datum elevation) + if (grade to transit level line shot to house) _D 3
6. Measurements from line shot onto house to roof ridge:.
t
Total:
7. Actual Elevation: 71'D3 (reference point elevation) + 3 VOmeasurements from
#6) =
Conclusion:
1O�i. <'-7 (actual) is greater ess tha JCG, (allowed); therefore the house is/
s no over the height requirement per ECDC 16.20.30 requirements �
LATENIMBUILDINGNISCUleight CalculationGrading Verification Workshect.doc r /
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1116 -B-Retaining Wall
Complete?
Y
05/23/2007 Snook
25 CORRECTION NOTICE WRITTEN
N
05124/2007 Bullis
45 Front stair retaining wall footings approved subject to Geotech Special
Inspection. Correction
N
notice written for rear driveway retaining wall.
06/20/2007 Bullis
45 Front retaining wall at entry stair approved for pour. See correction notice regarding rear
N
retaining wall and new rockery, on north side.
10/03/2007 TEMP-
20 FRONT STAIR FORMS INSPECTED AND APPROVED
Y
NATOLA
Total Time:
135
1118 - BSiab Insulation
-
Complete?
Y
03/13/2007 Snook
25 APPROVED
Y
Total Time:
25
1120--B-Plumb Ground Work
-
Complete? -
Y
12/27/2006 Snook
20 APPROVED
Y
Total Time:
20
1122.-'.B-First Floor Framing
Complete?
Y
02127/2007 Snook
25 APPROVED
Y
Total Time:
25
1126 - B-PlumbRough In <.
-
..Complete?
Y
03/13/2007 Snook
25 HYDRONIC HEAT AIR TEST APPROVED
N
05/03/2007 Snook
30 CORRECTION NOTICE WRITTEN
N
06/29/2007 Bullis
30 See correction — anti -hammer devices by insulation inspection.
N
j 07/1012007 Bullis
30 Approved. RPBA at boiler to be inspected at final.
Y
Total Time:
115
1128-.B-Gas.Test/Pipe
-
Complete?
Y
O6/29/2007 Bullis
20 Approved
Y
Total Time:
20
1131.'e'8-Equipment-Mech-
_ .Complete?
- - Y
06/.29/2007 Bullis
30 Mechanical ductwork only approved -- no equipment
N
08113/2007 Bullis
40 Pressure test on in -floor hydronic system approved.
N
08/13/2007 Bullis
40 Correction notice issued for geotech monitoring reports.
N
01/26/2009 steinike
15
Y
Total Time:
125
1132-:B-Exterior Sheathing
Complete?
Y
06/20/2007 Bullis
30 Signed off
Y
Total Time:
30
1136 - 6-Shear Nailing
Complete?
Y
0612,91N07 Bullis
30 Interior shearwall nailing approved
Y
Total Time:
30
1140 - B;Height Verification
Complete?
- . Y
07/10/2007 Bullis
30
Y
Total Time:
30
1142 - B-Framing
- -
Complete?
Y
06/29/2007 Bullis
90 See corrections
N
07/10/2007 Bullis
60
Y
Total Time:
150
1144 - B•Wall Insulation/Caulk -
complete?
Y
j 07/10/2007 Bullis
30
Y
Total Time:
30
1146 - B-Floor Insulation/Caulk
Complete?
Y
07/1012007 Bullis
30 Floor insulation in crawl space areas and at garage ceiling approved.
Y
Total Time:
30
1148 - B-Ceiling Insulation/Caulk
Complete?
Y
2/2/2009 10:18:44 AM
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