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DATE RECEIVED
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CITY OF EDMONDS USE
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CONSTRUCTION PERMIT APPLICATION
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SEPARATE PERMISSION.
PERMIT APPLICATI N; 18D DAYS
PERMIT LIMIT I YEAR , PROVIDED W RK IS STARTED WITHIN 180 DAYS
SEE BACK OF PINK PERMIT FOR MORE INFORMATION
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'A PUCANT. ON BEHALF OF HIS OR HER SPOUSE, HEIRS. ASSIGNS AND SUCCESORS
ENG, INSPECTION �EE
IN INTEREST, AGREES TO INDEMNIFY, DEFEND AND HOLD HARMLESS T14E CITY OF
ANIICIIING
21 EDIVONDS, WASHINGTON, ITS OFFICIALS, EMPLOYEES, AND AGENTS IF ANY AND
ALL CLAIMS FOR DAMAGES OF WHATEVER N URE. ARISING DIRECTLY INDIRECTLY
OR
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DEEMEDTO MODIFY, WAIVEOR REDUCEANY REQUIREMENT OF ANYCTY CE
PLAN CHECK DEPOSIT
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NOR LIMITIN ANYWAYTHE CITY'SABILITY TO ENFORCE ANYORDINANCE PROVISION �
TOTAL AMOUNT DUE
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I HERE Y ACKNOWLEDGE THAT I HAVE READ THIS APPLICATION THAT THE INFORMATION
GIVEN IS CORRECT. AND THAT I AM THE OWNER. OR THE DULY AUTHORIZED AGENT OF
APPLICATION APPROVAL
THE OWNER. I AGREE TO COMPLY WITH CITY AND STATE LAWS REGULATING CONSTRUC
TION. AND IN DOING
CALL
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THE WORK AUTHOR ED THEREBY, NO PERSON WILL BE EMPLOYED
IN VIOLATION OF THE LABOR CODE
Bllfl-g Olh—I X hIll- D,p.ty -d I ... ... ,o. Ild
OF THE STATE OF WASHINGTON RELATING TO
WORKMEN $�ZP,4NSATIO INSURANCE AND RCW 181T
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771-0220
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IT IS UNLAWFUL TO USE OR OCCUPY A BUILDING OR STRUCTURE UNTIL
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A FINAL INSPECTION HAS BEEN MADE AND APPROVAL
771-0221
OR A CERTIFI-
OF OCCUPANCY HAS BEEN GRANTED. UBC SECTION 109
ORtGINAL FILED -. YELI OW. INSPECTOR
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OF'CEDMONDS
121 GTH AVENUE NO. CONFORMED COPY
EDMONDS, WA 08020 200211210005
11/21/2002 09:16 AM Snohomish
P-0001 RECORDED
County
ACCESSIDAY DWELLING UNIT COVENANT
Property Address: -2-or "r- --w—s- P=A
Edmonds, Washington
Assessoes Pare el Ni imber: c5c>�s i& A - c�oo - o15 5 -S) 2-
Legal Description: V�o�Cj I �kC�=O_ -r t4 LOT
ADU File Number:
1, the undersigned, have.affained approval for an accessory dwelling unit (ADU) at the
property address above, in accordance with the provisions of Section 17.40.025.
(Nonconforming Accessory Dwelling Units) of the Edmonds Community Development Code.
I agree and understand that it is ray responsibility to notify all future property owners or long
term lessor-, of the existence of the ADU and that its existence is prgdicated upon the
occupancy of either the ADU or primary dwelling unit by. the, owncr-of the'property.
maintenance of
Additionally, I will notify all prospective buyers of the limitations on use and
-Edmonds
the ADU as stipulated in Chapter 20.21 (Accessory Dwelling Units) of the
Community Development Code. An example* of the limitations of the ADU per Chapter
unit for
20.21 is the property owner is required to reside in the primary or accessory dwelling
6 months out of every year. No changes to the Accessory Dwelling Unit. can make it more
nonconforming than itwas at the time of registration.
Finally, this covenant shall be recorded in order to notify all current and. futu ' re property
owners that if any conditions of the ADU approval are violated, the property owner will be
required to remove all improvements which were added to convert the primary dwelling unit
into an ADU and restore the site to a single-family dwell' g unit.
Property Owner Signature:
Print Name:
Date -
STATE OF WASHINGTON
COUNTY OF SNOHOMISH)
certify that I know or have satisfactory evidence that
I �ce and v(ffuntary act for me uses and
signed this instrument and acknowledge it to be his/her'fi
purposes mentioned in this instrument.
Notary' pstbe smudgedi Dated: 1-2
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Signature of 7
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— my Public:
.%AOTARY �0 - Notary Public:
PUBUC
Residing at:
My Appointment
OPW,
Expires:
THIS DOCUMENT MUST BE RECORDED WITH THE SNOHOMISH COUNTY AUDITOP-
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ACCESSORY DWELLING UNff AFFIDAVrr
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On iatwh, I cart* that I reside at Edmonds, Washington, in
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the pin' ary or� accessory unit tor more than six months of every year.
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SubsccAo o before me this day of
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Hardson, Marie
From: Gruweil, Meg
Sent: Monday, August 30, 2004 5: 10 PM
To: Harrison, Marie
Subject: Jennifer Mantooth's Frozen Fund Account
Based on legal advice, Duane Bowman is recommending that we accept Ms. Mantooth's offer to plant 15 vine maple trees
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in the area south of her house during the fall planting season and continue to remove the small alders, as stated in her
July 28, 2004 letter. Her frozen fund account with the $5,000 balance can now be released. If you have any questions,
please let me know. Ms. Mantooth would like to have the $5,000 released by August 31, 2004, (per her letter of August
17, 2004), so I would appreciate your doing whatever you need to do and letting her know the funds are now available.
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Thank you.
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MICROFILM
6 GARY HAAKENSON
CITY OF EDMONDS MAYOR
121 STH AVENUE NORTH - EDMONDS. WA 98020 - (425) 771-0220 FAX 1425) 771-0221
WebSfte: �.Med=ndS us
DEVELOPMENT SERVICES DEPARTMENT
Planning - Building Engineering
August 31, 2004
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First Horizon Bank
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Attn: Steven Carmody
5808 Lake Washington Blvd, #400
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Kirkland, WA 98033
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RE: Maintenance Frozen Fund Account #0027563162 for Jennifer Mantooth
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Single Family Residence at 7220 North Meadowdale Road, Edmonds, WA
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Dear Sir or Madam:
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The City of Edmonds hereby authorizes the release of $5,000.00 from the above
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referenced account. All interested City departments have approved release of this
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Maintenance bond amount.
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Sincerely,
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Permit Coordinator
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Cc: Applicant
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File
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MICROFILM
Incorporated August 11, 1890
Sister City - Hekinan, Japan
720OZ-090]
RETURN ADDRESS:
City of Edmonds, City Clerk
121 5th Avenue North
Edmonds, WA 98020 CONFORMED COPY
200211210004
D9-16 AM Snohomish
11121/2002 1 - County
p.0005 RECORDED
COVENANT OF NOTMCATION
AND INDEMNMCATION/HOLD HARMLESS
Reference ao L C)6�
Grantor(� �Lr(2)L— Additional on pg—
Grantee(s): City of Edmonds
Legal Description (abbreviated): See--5—Twn-=-L-j-6L_Ru2 Qtr-5-%L—.
OR Lot--±----331oc lat.
Assessor's Tax Parcel MN(s): (1) aesc I-V I -wo- I)SI? 2)
----�-�ssessorls Tax Parcel M# not yet assigned
CITY OF EDMONDS
APPROVED FOR RECORDING
BY.
DATE-144.1tPAGid_ OF
Under the review procedures established pursuant to the State Building Code,
Incorporating amendments promulgated,by the City of Edmonds, and as a
prere4ulsite to the issuance of a building permit for the construction of a residential
structure and attendant facilities, the undersigned OVMRS of property do hereby
covenant, stipulate and promise as follows:
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12�scription ofSubject Prol2glU This covenant of notification and
of land at the street addre
indemnification/bold harmless relates to a tract ssof—
9i
ert street
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address) Edmonds Snohomish Cbunty, Washington, and legally des cribid as: —
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2. Notification and Covenant of Notification. The. above referenced site
(hereinafter "subject sitell lies within an area which has been identified by the.City
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of Edmonds as having a potential for earth subsidence or landslide hazard. The
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risks associated with development of.the site have been evaluated by technical
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consultants and engineers engaged by the applicant as a part of the process to
obtain a building Permit for the subject site. - The results of the consultant's reports
and evaluations of the risks associated with development are contained in building
permit file number qm*,Ok 0 \ (insert no mber) .'o'n Me with the City of
Edmonds Building Department. Conditions, limitations, or prohibitions on
development may have been Imposed in accordance with the recommendations of
A P OR REC! IN
DATE..0
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By
PA OF
the consultants in the Course Of Permit Issuance. , E M
The conditions, limitations, or
prohibitions may require
ongoing Maintenance on*the part ofe
11Y owner or lessee or
may require modificiitio,
as to the structures and earth stabilization matters in order
to address future or anjicip'
ated changes In soil or other site conditions.
The
statements and conditions proposed by the
geOteebuical. engineer,
geologist, architect and/or structural engineer' are hereby Incorporated by reference
from the contents Of the file as fully as if herein set io
rth- Any future purchaser,
lessee, lender or any oiher person acquiring or seeking to acquire an'interest in the
property is put on no
tice of the existence of th * c
review of Its contents. e Ontent Of the Ale and the City urges.
The file may be reviewed during normal business hours or
copies obtained at the Building Department,. City of Edmonds, 12i 5th Avenue
North, Edmonds, Washington §SO20.
3. The undersigned OVrNERS
hereby waive any and all liability associated With developme
nt, stating that, they
have fully informed themselves 0'
f all risks associated with
development of the
property and do therefore ive and relinquish any and all causes
wa
of action against
the City ofEdmondsp its officers, agents and employees arising from -and out orsuch
development. In addition, the-0
VVMRS on behalf of themselves, theirsuccessors In
lnteres4 heirs and assignees, doiereby Promise to indemnify and hold harmless the
City ofEdmonds, Its officers, agents and employees from any I . Oss, claim, liability or
damage of any kind. or'nature to persons or Property either on or off the site
resulting from or oift of earth subsidence or landslide hazard, arising from or out of
the -issuance of any permit(s) autb6ridng development of the site,* or occurring or
APPRW FOR RECO ING:
BY: DkM tL Ft Ot
PAGE _GF
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of
arlsiti out of any false, misleading, or Inaccu
9 rate information Provided by th-
OWNERS, their employees, or professional consultants In the course of issuance of
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the building permit
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4. Insurance Requirement In addition to any bonding wbjch� may be
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required during the course of development, the Community Services Director
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Jj)(Aas not (strike one) specifically required the maintenance of an insurance policy
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for public liability coverage In the amount and for the time set forth below in order
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to provide for the f
mancial responsibilities establishe d through the Indemnification
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and hold harmless agreement above:
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�5. Covenan This covenant of
notification and Indemnification/hold harmless touches and concerns the s ubject
tract andsliall run with the land, binding, obligating and/or Inuring to the benerit of
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future owners, heirs, successors and Interests or an' other person ii' entity
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acquiring an interest In property, as their interest may appear. This provision shall
not be interpreted to require a mortgagor or lender to ludentinify the City except to
the extent of their loss nor to obligate such persons to maintain the Insurance above
required.
J PPRI RECO�RDINII.,:
AWROVED FOR �CO�
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BY. �)ATM
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PAdE op
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DONE this3o day
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OWNER(S)
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By:
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STATE OF WASMNGToN
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COUNTYOF
I certify that I know or h2ve satisfactory gvidence that-u�-�-'n 74r-.
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signed this instrument and
acknowledged it to be (hislber) free and vOlulitary act for the. purposes mentioned in
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this instrument.
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DATED this day of
bep-
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NOTARYPUBLIC,
My commission expires;
LATEMMMMINGMADOVACO VEMANT
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GEOTE CHNICAL ENGINEERING STUDY
SEQUOIA RIDGE SHORT SUBDIVISION
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EDMONDS, WASHINGTON
G-1061-1
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-G-roupNorthwest, Inc.
GeoloChnlcal Engi-ers, Geologists & EnAronmental Scientists
GEOTECHNICAL ENGINE ERING STUDY
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SEQUOIA RIDGE SHORT SUBDIVISION
EDMONDS, WASHINGTON
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Prepared for
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Mr. John Thoresen
Sequoia Ridge Partners
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15621 - 481h Place West
Edmonds, Washington 98026
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February 29, 2000
GEO GROUP NORTHWEST, INC.
13240 NE 2& Street, Suite 12
Bellevue, Washington 98005
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Phone: (425) 649-8757
February 29, 2000 G-1061-1
Mr. John Thoresen
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Sequoia Ridge Partners
15621 - 48' Place West
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Edmonds, Washington 98026
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Subject: Geotechnical Engineering Study
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Sequoia Ridge Short Subdivision
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Edmonds, Washington
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Dear Mi. Thoresen:
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Geo Group Northwest, Inc., is pleased to present our Ge otechnical Engineering Study report for
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the Sequoia Ridge Short Subdivision in Edmonds, Washington. This report was prepared in
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accordance with our proposal dated September 22, 1999, and the City of Edmonds guidelines for
geotechnical reports.
It is the opinion of Geo Group Northwest, Inc that the site is geotechnically suitable for the
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proposed development� provided the recommendations in our report are followed. Although
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there is some inherent risk in any proposed development located in or near to areas of steep
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slopes or geological hazards, it is our opinion that the proposed development will not increase the
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potential for soil movement at the site. Please refer our report for a detailed discussion of our
conclusions and recommendations.
We appreciate this opportunity to provide you with geotechnical engineering services for this
project. Please feel free to cal I us ifyou have any questions.
February 29, 2000
G4061-1
Mr. John Thoresen - Sequoia Ridge Partners
Page ii
Sincerely,
Geo Group Northwest, Inc.
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William Chang, P.E.
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TABLE OF CONTENTS
G-1061-1
Page
INTRODUCTION ...................................................... 1
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1.1
Project Description .................................. I., ........ 1
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1.2
Scope of Work ................................................... I
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2 SITE CONDITIONS .................................................... 2
2.1
Site Description . .................... .............................. 2
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2.2
Geologic Conditions ............................................... 3
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2.2.1 Regional Geology ................................... 3
2.2.2 Soil Survey ........................... .................... 5
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12.3 Site Geology . ......................................... 5
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2.2.4 Groundwater ............................. ................. 6
2.3
Wetlands ..... ................ .................................. 7
2.4
Geologic Hazards ................................................. 8
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2.4.1 Erosion Hazard ............ ....................... 8
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2.4.2 Steep Slope and Landslide Hazards ............... ............ �. 9
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2.4.3 Seismic Hazard ............................................ 10
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2.5
Geologic Hazard Area Buffers and Setbacks ........................... I I
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3 CONCLUSIONS AND RECOMMENDATIONS ............................ 12
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3.1
General ........................................................ 12
3.2
Site Stability Evaluation ............................................ 13
3.3
Site Preparation and Earthwork ..................................... 14
3.3.1 Temporary Slopes and Excavations ............................ 15
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3.3.2 Subgrade Stabilization ....................................... 15
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3.3.3 Structural Fill ............................................. 17
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3.3.4 Pipe Bedding . .................................... ........ 1.8
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3.3.5 Trench Backfill ............................................ 19
3.4
Erosion and Sedimentation Control .................................. 20
3.4.1 General Development Standards ............................... 20
3.4.2 Erosion and Sedimentation Control Plan ........................ 21
3.5
Foundations ...................................... .............. 22
3.5.1 Deep Foundation Systems . ................................... 22
3.5.2 Shallow Foundation Systems ................................. 23
3.6
Building Floors .................................................. 25
3.7
Permanent Basement and Conventional Retaining Walls .................. 25
3.8 Modular Block Walls ...................... ........... ......
27
3.9 Rockeries ......... ................... .........................
28
3.10 Site Drainage .......................................... .........
30
3.10.1 SurfaceDrainage ......................... ..30
3.10.2 Footing and Wall Drains .................. .... ...............
30
3.11 Pavements ......................................................
3.11.1 Driveway Support ........................................ —31
31
3.11.2 Driveway Stream Crossing ...................................
32
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3.12 Post -Construction Soil Stabilization and Re -vegetation .............. ....
33
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4 CONSTRUCTION MONITORING AND ADDITIONAL SERVICES ..........
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5 Lrmrmion .......................................................
34
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REFERENCES
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ILLUSTRATIONS
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Plate I Site Vicinity Map
Plate 2 Site Plan
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Plate 3 Development Plan
Plate 3A Vicinity Drainage Map
Plate 4 Geologic Map
Plate 5 Subsurface Profile A -A'
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Plate 6 Subsurface Profile B-B'
Plate 6A Subsurface Profile C-C'
Plate 7 Landslide Hazard Map
Plate 8 Basement Wall Backfill Details
Plate 9 Typical Footing Drain
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APPENDIX A
Soil Boring Logs (Geo Group Northwest, 1999)
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Hand Auger Boring Logs (Nelson-Couvrette & Associates, 1995)
APPENDIX B
Rockery Construction Guidelines
GEOTECHNICAL ENGINEERING STUDY
SEQUOIA RIDGE SHORT SUBDIVISION
EDMONDS, WASHINGTON
G-1061-1
I INTRODUCTION
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1.1 Project Background
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Sequoia Ridge Partners proposes to subdivide and develop the subject site located in the
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Meadowdale neighborhood of Edmonds, Washington, into four single family residential lots.
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The proposed short subdivision would be named Sequoia Ridge. The four proposed rcsidenccs
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would be built on the western part of the site, near the top of a steep west -facing slope that offers
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views of Puget Sound and the Olympic Mountains. The site location is illustrated in Plate I -
Plate 2 Site Plan.
Vicinity Map. The proposed lots, labeled Lots I through 4, are indicated on -
Access to Lots 1 through 3 would via a proposed driveway that would extend from the northern
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terminus of 72,d Avenue West. The driveway for the proposed residence in the northwest part of
the site (Lot 4) would be via a driveway from North Meadowdale Road. The north driveway
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would cross a small stream on the north side of the site.
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1.2 Scope of Work
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The scope of work performed for this study was consistent with generally accepted geotechnical
engineering practices and with that presented in our proposal dated September 22, 1999, The
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scope of work included the following tasks:
Use the results ftorn the on -site subsurface investigation work previously performed d uring
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the Limited Scope Environmental Impact Study completed by Geo Group Northwest, Inc., in
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1999 (Geo Group Northwest, 1999), and the results from a preliminary geotechnical
inve stigation of the site reported by Nelson-Couvrette & Associates (NCA) in 1995 (NCA,
1995), to assess soil and groundwater conditions at the site.
Perform engineering analysis for foundation support, grading considerations, pavement
section design, utility trench backfilling, and earthwork criteria for on -site soils and
imported soils.
Gen Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 2
Prepare a report that summarizes our activities, findings, and conclusions regarding the
proposed development of the site. The report will contain recommendations for the
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geotechnical aspects of the proposed development at the site, including;
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Pile -supported foundations and floor slab support,
Subgrade preparation,
Concrete and asphalt pavement section design,
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Soil parameters for rockery and retaining walls,
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Rockery construction guidelines,
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General gradin g and earthwork criteria,
Site drainage,
Gcotechnical recommendations for the driveway stream crossing, and
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Suitability of on -site soils as structural fill.
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Detailed construction plans for each of the four proposed residences were not available at the
time this study was conducted. Geo Group Northwest did receive and review construction plans
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for Lot 2 at the site, but not for Lots 1, 3, and 4. A geotechnical review of the construction plans
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fof the other three lots can be performed when the plans are available.
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2 SITE CONDITIONS
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2.1 Site Description
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The site is an 3.66-acre parcel of undeveloped land located in the Meadowd e n ighborhood of
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Vic Map The site is
Edmonds, Washington. The site vicinity is illustrated on Plate I inity
bordered by North Meadowdale Road on the north, by undeveloped land on the east, by
residential property on the south, and by a residential development at the bottom of the slope to
the west. A small stream (Mcadowdale Creek) runs across the north part of the site, adjacent to
North Meadowdale Road. Utility improvements in the site vicinity include a municipal sanitary
sewer system and a system of interceptors drains and trenches that capture drainage and convey it
the local storm drain system, Site conditions and proposed storm drain and sanitary sewer
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Tboresen - Sequoia Ridge Partners Page 3
systems are illustrated on Plate 2 - Site Plan, and the currently proposed residence locations are
shown on Plate 3 - Development Plan. The drainage system installed by the City ofEdmonds in
the Meadowdale area to mitigate potential landslide activity in the vicinity of the site is
illustrated in Plate 3A - Vicinity Drainage Map.
The site is characterized by moderate to steep slope topography. A narrow ridge with moderate
to steeply sloping sides runs roughly north -south along the western part ofthe property, and
broadens eastward along the south margin of the property. The slope on the western side of the
ridge consists of a steep slope (portions of which consist of near -vertical bluffs) and is thickly
vegetated. The upper part of this slope on site has an overall inclination of about 45 to 60
degrees (equivalent to 100 to 173 percent), but tends to flatten out somewhat further downslope.
The east side of the ridge is moderately steep in its upper portion, having slopes of about 24 to 30
gr wnslope.
degrees (45 to 58 percent) and also becomes flatter to about 16 de ees (30 percent) do
The height of the steep west -facing slope ranges from about 40 feet at the north end of the site on
Lot 4, to about 110 feet below Lot 3, to approximately 130 feet at the south end ofthe site on Lot
2, based on topographic data for the site (shown on Plate 2), and available topographic data for
the adjacent property to the west presented in a geotechnical engineering report prepared in 1989
aries in steepness, with the
by Terra Associates, Inc. (Terra, 1989). As noted above, the slope v
uppermost portions typically being steepest (up to vertical in places). Below the steeper, upper
part ofthe slope, groundwater seepage and silty soils are present. Most ofthe slope is thickly
vegetated with shrubs, vines, grasses, and deciduous trees.
2.2 Geologic Conditions
2.2.1 &dQnaLQJO1QU
�m .4 qj t sife is loc-cd in the Pu et Lowland nhvsiooTanhic province a north -south
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trending topographic and structural basin. Geologic processes including tectonic uplift and
subsidence, glaciation, and erosion by streams have acted to shape the physiography of the area.
The site vicinity is underlain with Quaternary -age sediments associated with past glaciation of
the Puget Sound region, as illustrated on Plate 4 - Geologic Map. Limited areas are underlain
with younger alluvium deposited by streams, and some of the sloped areas may have a surficial
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February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 4
layer ofcolluvium. The majority of the glacial sediments are from the Vashon Stade of the
Fraser Glaciation, which occurred approximately 13,000 to 11,000 years ago. Some pre-Vashon
age, non -glacial to transitional environment sediments also are found below the Vasbon
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sediments in the proposed project area (Minard, 1983).
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The Vashon-age glacial sediments present in the site vicinity consists of (in downward
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succession) compact till (composed of unsorted mixtures of silt, sand, and gravel); moderately to
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very dense, fine-grained advance outwash sand and silty sand; and dense silt with lenses ofsilty
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sand. At the site, the pre-Vashon age deposits consist of silts with some interbedded fine sand
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interpreted to be the Whidbey Formation. The geologic contact between the Whidbey Formation
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silts and the overlying outwash sand often is an area of groundwater springs and seeps.
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Meadowdale Landslide Complex,
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The site is located immediately east of the which was mapped
and characterized by Roger Lowe and Associates (RLA, 1979) and GeoEngincers
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(GeoEngineers, 1985). The Meadowdale Landslide Complex is a large area oftistorical
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landsliding (slumps and debris flows) extending about 3,200 feet north -to -south and up to 650
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feet east -to -west. The steep west -facing slope on the site forms the eastern margin of the
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landslide complex, and is the head wall of the landslide zone. The initial movement of the
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landslide is believed to have occurred about 7,000 years ago. Active landsliding in the area has
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primarily occurred within a 400 feet wide zone immediately east ofthe Burlington Northern
railroad tracks (the zone would be located about 100 to 200 feet west ofthe proposed project
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site). The most recent movements in the landslide complex (in 1946-47,1955-56, and 1970-71)
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have occurred in the middle and western portions of the complex, away from the site.
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The previous studies determined the primary cause of ground failure in the Meadowdale
Landslide Complex has been a combination of shoreline processes at the bottom of the slide area
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and erosion caused by groundwater flowing from springs and seeps on slopes at the contact
between the outwash sand unit and the underlying silt deposits. Erosion ofthe base oftbe
affected area was the primary cause of the initial large-scale landsliding and of subsequent
smaller slumps and movements in the middle to western parts ofthe slide complex. Sloughing
and small slumps in the eastern portion of the complex (including the west side of the site) that
occurred after the initial large-scale landslide event have been caused primarily by erosion by
springs and seeps in the steep west -facing slope
Geo Group Northwest, Inc.
February 25,2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 5
2.2.2 Soil Surve
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Surficial soils at the proposed project site consist ofAlderwood gravelly sand loam on 8 to 15
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percent slopes and Aiderwood-Everett gravelly sand loarn on 25 to 70 percent slopes, according
to the U.S. Department of Agriculture Soil Conservation Service (SCS) soil survey for
Snohomish County (SCS, 1983). Alderwood-type soils are typically moderately well drained,
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have a depth to the hardpan (glacial till substratum) of about 3 5 inches, and are developed on till
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plains. Alderwood-Everett soils are typically moderately well to excessively drained, have a
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depth ofup to about 60 inches over hardpan and glacial outwash, and are found on nearly level to
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very steep slopes on till plains, terraces, and outwash plains. Permeability ofthe Alderwood
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soils is relatively rapid above the hardpan and very slow through it, while permeability of the
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Everett soils is rapid.
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2.2.3 Site Geology
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Based on the findings from site exploration performed by NCA in 1995 and by Geo Group
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Northwest in 1999, surficial soils on Lots I and 3 consist of glacial outwash sand to at least 30
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feet bgs. We encountered a surficial veneer of gravelly, fine to medium grained sand in the soil
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boring drilled at the proposed building location on Lot 1. This surficial soil corresponds to the
uppermost part of the outwash sand unit where it was directly overlain by glacial till. A cap of
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glacial till may have been cut from this part of the site when the residence immediately to the
south was constructed.
Surficial soils at the proposed building location on Lot 2 consisted of at least 12 feet of very
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dense glacial till soils composed of silty fine to medium grained sand with gravel. Shallow hand
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auger borings completed further east on Lot 2 encountered outwash sand and not glacial till soils.
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Based on this information, the extent of glacial till soils on the site is anticipated to be limited to
the western part of Lot 2.
Silt and silty sand deposits identified as transitional between the outwash sand and the pre-
Vashon age Whidbey Formation deposits were found at the ground surface on Lot 4.
Encountered soils consisted of a surficial layer of fine sand and silty sand (similar to glacial
outwash sand) about 4 feet thick, underlain by interbedded silty sand and silt to 30 feet bgs.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 6
A soil classification legend and logs for the soil borings drilled by Geo Group Northwest in May
1999 are provided in Appendix A. Soil logs from hand -auger borings performed by NCA in
1995 also are included in Appendix A. A south -to -north subsurface profile of Lots I through 3
on the site is presented in Plate 5 - Subsurface Profile A-A'.A west -to -east profile across Lot 2 is
presented in Plate 6 - Subsurface Profile 13-13'. A south to north subsurface profile of Lots 3 and
4 is presented in Plate 6A - Subsurface Profile C-C'. It should be understood that the proposed
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locations and configurations of the homes and driveways on Lots 1, 3, and 4 are schematic at thi
time. Final locations and elevations of these features will be determined at a later time.
During our site investigation, we observed small slumps and areas of relatively recent sloughing
on the steep slope in the west part of Lots 2 and 3. A silver -colored tarpaulin was observed to be
covering one such area of sloughing along the steep slope near the boundary between Lots 2 and
3. We observed no evidence of significant soil movement on the north and east -facing slopes on
site, and NCA reported that they did not observe any indications of deep-seated soil instability on
the site, but did notice some evidence of surface soil creep.
2.2.4 Grouri
During our subsurface exploration of the site, we encountered groundwater at a depth of
approximately 30 feet in the soil boring drilled on Lot 3. Groundwater was not encountered in
the borings drilled on Lots I and 2, but is suspected to be present at a greater depth (the borings
on Lots I and 2 were located at much higher elevations than the boring on Lot 3). A very thin
zone of wet soil (about I foot thick) was noted in the surficial weathered soils on top of the very
dense glacial till in the boring on Lot 2. These findings are consistent with the geologic literature
for the area, which describe the presence of groundwater in the glacial advance outwash deposits
on top of the underlying silt deposits.
Groundwater was present within the silty sand lenses in the silt soils encountered in the soil
boring drilled on Lot 4. These observations are consistent with similar findings reported in the
literature.
We observed that the steep west -facing slope on Lots 2 and 3 of the site has a distinct zone of
seepage and springs located at the boundary between the overlying fine sand layer and underlying
silt layer. This zone is located at elevations of approximately 220 to 230 feet. Water from these
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February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 7
springs flows downslope off site and infiltrates into the soils on the Lorian Woods property, or is
diverted into catch basins connected to the local storm drain system. Seepage from the west-
facing slope on Lot 4 was not observed during May or June 1999, but was observed further
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downslope on the adjacent residential development property.
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The elevation ofthe stream as it passes through the site, according to the topographic survey data
on the site plan, ranges from approximately 215 or 219 feet at the northeast comer of the site to
55
less than 180 feet in the northwest part ofthe site, A comparison ofthe stream elevation to the
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seepage and springs elevations indicates that the seepage elevation is not lower than the elevation
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ofthe stream. Thus, the stream does not appear to provide recharge to the seepage and springs at
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elevations of`220 to 230 feet on the west -facing slope. The source of these springs and seeps
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appears to be local precipitation and recharge from higher areas to the south and southeast.
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2.3 Wetlands
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One wetland and one stream are located on the site. The wetland edges and the stream were
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delineated by Pacific International Engineering, P.L.L.C. (PIE), in May 1998 (PIE, 1998). The
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wetland and stream areas delineated by PIE were surveyed and plotted by David Evans &
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Associates, Inc. (DEA), and appear in Plate 2 - Site Plan and Plate 3 Development Plan.
Wetlands on the site total 1. 12 acres. The wetland is channelized near the northwest comer of
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the site and is more accurately described as a stream. Off -site to the west the water resource
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continues as a stream. Off -site to the northeast, the wetland edge is disturbed and bounded by a
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storm drainage line and fill from residential yards. Thus, the majority of the wetlandis located
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within the Sequoia Ridge site.
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The majority ofthe wetland consist ofmixed palustrine, forested, scrub -shrub wetland. Within
the stream corridor and flood zone, the wetland meets the definition of a riverine, forested, scrub -
shrub classification. Small areas of uplands are located within some parts of the wetland. These
upland areas appear to be both natural knolls and remnants of site manipulation (road fill, side
cast, and fill piles) and are included within the wetland boundaries.
Under ECDC regulations, the wetland meets the criteria to be classified as a Category 2 wetland
due to its size (greater than one acre) and presence of two or more wetland classes. Under this
Geo Group Northwest, Inc.
February25,2000 G-1061-1
Mr, John Thoresen - Sequoia Ridge Partners Page 8
classification, a 50-foot wide buffer is required adjacent to the wetland edge and a 15-foot
building setback area is required beyond the wetland buffer area.
A small stream (Meadowdale Creek) enters the site at the northeast side of the site. This stream
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appears to be supported by sto rm water from the unopened right-of-way for 72" Avenue West
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and from groundwater seeps in the wetland areas on site, This stre am appears to have been
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ditched through the wetland. The stream channel terminates at a catch basin under North
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Mead.wdale Road. The stream flow eventually discharges to Brown's Bay in Puget Sound.
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No evidence of fish presence has been observed in the stream on site. This stream is not
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identified in the Washington Department of Fish and Wildlife "Catalog of Washington Stream
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and Utilization -Puget Sound". The stream is not likely to be an anadromous fisheries stream due
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to the presence of downstream barriers.
Parts of this riparian area also include the wetland areas identified as riverine, forested, scrub -
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shrub habitat. The stream channel shows evidence of carrying "flashy" flows due in large part to
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the storm water discharge from off site to the east. The stream channel is vertical sided, incised
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in several locations, and lacking vegetation along the steepest sidewalls of the ditch. The stream
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appears to be perennial, carrying water from groundwater discharge and flow from the wetlard.
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Under ECDC regulations, this stream meets the criteria for classification as a Category 2 Stream.
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ECDC regulations require a 25 foot b er adjacent to a Category
setback area beyond the stream buffer area.
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2.4 Geologic Hazards
2.4.1 Erosion -Hazard
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The soil types present on the proposed project site have moderate to high erosion potential,
according to the SCS soil survey (SCS, 1983). The Alderwood soils at the site have medium
erosion potential and are susceptible to sheet wash and rill erosion, if exposed. The Everett soils
at the site have high erosion potential and are susceptible to sheet wash, rill, and gully erosion.
Geo Group Northwest, Inc.
February 25, 2000 G-1 661-1
Mr. John Thoresen - Sequoia Ridge Partners Page 9
Based on site observations during geotechnical studies in May 1999 and historical experience in
the Puget Sound region, Gen Group Northwest, considers the advance outwash sand (Everett)
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soils at the site to have a high erosion potentiaL The sil (Alderwood) soils associated wi e
on -site areas underlain by glacial till are considered to have a low to moderate erosion potential,
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when exposed. Geo Group Northwest, Inc. anticipates that the soils in the wetlands area on site
have relatively lower susceptibility to erosion due to the relatively lesser slopes and the thick
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cover of vegetation.
The City of Edmonds Community Development Code (ECDC) identifies areas with Alderwood
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or Everett Series soils on slopes of 15 percent or greater as erosion hazard areas (ECDC Section
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20.1 5B.060(A)(3)(a)). Based on this criterion, the sloped portions of the project site underlain
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with glacial till and advance outwash soils (Lots 1, 2, and 31 and the proposed building location
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on Lot 4) are erosion hazard areas. The flat area on the southwest comer of the site is not an
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erosion hazard area by this criterion.
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2.4.2 S"e Slope and Landslide Hazards
The site has moderate to steep slopes across its west, north, and east -central parts. The steepest
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slopes are found in the western part of the site on Lots 2, 3, and 4. The slopes in this part of the
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site tend to be irregular in steepness, and much of the slope is obscured by thick vegetation. The
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steepest slopes on the site reach near-verfical inclinations of about 60 degrees.
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According to the geotechnical reports by RLA (RLA, 1979) and GeoEngineers (GeoEngineers,
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1985), the steep slopes along the southwest part of the proposed project site have a 5 percent
probability of failure within 25 years, and the slopes in the north and northe ast part of the site
have a 2 percent probability of failing within 25 years. The reports characterize the landslide risk
in the west part of the site as involving slumps of material that has not previously failed. The
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landslide risk in the north and northeast parts of the site are characterized as debris slides 'in
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material that has not previously failed. The criteria used in these reports for determini g e
landslide risk included steepness of slope, height of slope, soil types, presence and character of
evidence of previous landsliding, and presence of groundwater seepage or springs. Landslide
hazard areas are shown on Plate 7 - Landslide Hazard Map.
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February 25, 2000
Mr. John Thoresen - Sequoia Ridge Partners
G-1061-1
Page 10
The ECDC incorporates by reference the landslide hazard findings in the GeoEngineers and RLA
reports (ECDC Section 20. 1 5B.060(A)(3)(b)). The ECDC also defines landslide hazard areas as
those areas that have interbedded permeable and impermeable soils, groundwater springs or
seepage, and slopes of 15 percent or greater. Based on these criteria, the steep west -facing slope
on the site is a landslide hazard area.
2.4.3 Seismic Hazard
The project site is located within the Puget Sound Lowland, The greater Puget Sound area has
experienced a number of small to moderate earthquakes and occasional strong shocks during the
brief 155-year historical record in the Pacific Northwest. The major earthquakes in the region are
believed to be associated with deep-seated plate tectonic activity. Major faults within the region
have not been active in the Holocene Age (geologic period dating since the last glacial retreat
14,000 years ago), consequently, none are known to be associated with historical seismicity.
Historical records for the region indicate that the Olympia earthquake of April 13, 1949, with a.
Richter magnitude of 7. 1, produced ground -shaking of intensity VIR near its epicenter; and the
Seattle -Tacoma earthquake of April 29, 1965, with a Richter magnitude of 6.5, produced a
ground -shaking of intensity IV to VIH on the Modified Mercalli Scale near its epicenter. This
level of ground -shaking is estimated to be the maximum that has occurred in the region during
the 155 years ofbistoric record.
The ECDC identifies seismic hazard areas as those area which are subject to severe risk of
earthquake damage as a result of seismically induced landslides, earth adjustments (such as
displacement by faulting), settlement, or liquefaction (ECDC Section 20. 1 5B.060(A)(3)(d)).
Liquefaction is a phenomenon where loose granular materials below the water table temporarily
behave as a liquid due to strong shaking or vibrations, such as earthquakes. Clean, loose and
saturated granular materials are the soils susceptible to liquefaction phenomena.
During our site investigation, subsurface soils consisted of medium dense to dense, fine grained
sand (advance outwash) and silty sand with gravel (glacial till) on Lots 1, 2, and 3. Groundwater
was encountered at approximately 30 feet bgs in boring B-3 on Lot 3. Light seepage was
observed at depths of2 to 3 feet bgs on top of dense glacial till soils in boring B-2 on Lot 2. No
groundwater was encountered in boring B- I on Lot 1. Subsurface soils encountered in boring B-
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4 on Lot 4 consisted of medium dense to dense silt, silty sand, and fine grained sand. Wet soils
were encountered at approximately. 6 feet bgs in boring B-4, but the predominant silt and silty
sand are not soil types susceptible to liquefaction. Thus, subsurface soils at the proposed
building locations on site are not susceptible to liquefaction, based on the observed soil types,
densities, and'moisture contents.
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The saturated soils in the northeast part ofthe site (where wetlands have been identified) may be
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susceptible to liquefaction because of the presence of shallow groundwater conditions and the
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possible presence of fine sandy soils below the surficial layer of organic soils. The potential
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hazard is not considered to be a significant concern for the proposed development, however,
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because this part ofthe site will not be developed. Based on these criteria, the areas ofthe site
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proposed for development are not considered to contain seismic hazard areas.
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2.5 Geologic Hazard Area Buffers and Setbacks
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The ECDC requires a 50 feet wide buffer for geologically hazardous areas, including erosion,
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landslide, and steep slope hazard areas (ECDC Section 20.15B. 11 O(A)). The width of the buffer
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can be reduced to as low as 10 feet if it can be demonstrated that the proposed buffer alteration
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will have no adverse impact on the site, City, or any private party. The ECDC also requires that
a 15 feet wide building setback be established from the edge of any buffer, including buffers for
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geologic hazards, to prevent construction intrusion into the buffer (ECDC Section 20.15B.080
(Q. Thus, the minimum total distance between the proposed buildings and geologic hazard
areas is 25 feet.
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Alterations within erosion hazard areas require City approval of an erosion control plan that
mindmizes disruption of soils to the minimum degree necessary to provide reasonable use of the
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site (ECDC Section 20.15B.110(B)). Alterations in steep slope hazard areas require an
exemption or exception pursuant to ECDC Section 20.15B.040, or a variance pursuant to ECDC
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Section 20.15B.170. Categories for exemption or exception include situations where critical
areas studies had previously been prepared for the type ofproposed development, and reasonable
use exceptions where application of the critical areas regulations would deny all reasonable use
ofthe property. Categories for variance also include situations where cri tical areas regulations
would deny the reasonable use of the subject property.
Gee Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 12
The ECDC Chapter 20.15B specifies that a 50 feet wide buffer and a 15 feet building setback be
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established for geologically hazardous areas (such as steep slope and landslide areas). The buffer
can be reduced to 10 feet if it can be demonstrated that the proposed buffer reduction will have
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no adverse impact on the site, public, or any private party.
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3 CONCLUSIONS AND RECOMMENDATIONS
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3.1 General
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Based on a review of the available information for the proposed development, Geo Group
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Northwest concludes that the site is geotechnically suitable for development into a four -lot
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residential subdivision as proposed, provided that the development is designed and constructed
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a manner that minimizes impacts to the site that could adversely affect site stability. Issues of
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primary geotechnical concern include establishing appropriate building setback distances from
tile steep west -facing slope on the site, controlling soil erosion during and following site
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development, using deep foundation systems for the proposed residences to mitigate impacts
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from future sloughing along the steep slope on site, and constructing a driveway across the
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stream at the north end of the site. Asa result, we recommend the following measures be
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incorporated into the design and construction of the proposed development:
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. support the homes on Lots 2, 3, and 4 entirely on deep pile foundation systems;
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. configure residences on slopes to minimizing grading, where feasible;
29
supp ort fills below the driveways with modular block walls and geogrid reinforcement and
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support cut slopes with rockeries or concrete retaining walls; and
perform daily, on -site, geotechnical quality control monitoring of erosion and sedimentation
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control measures, earffiwork activities, pile installation, driveway and roadway construction
activities, underground utilities installation and backfilling, site stability, and other aspects
as required by the City ofEdmonds.
These items and other geotechnical issues involved in the proposed development are discussed in
detail in the following sections of this report.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Seq uoin Ridge Partners page 13
3.2 Site Stability Evaluation
in their preliminary geotechnical study, NCA recommended that a 15 feet wide setback be
established between the top of the steep west -facing slope and any buildings. It is the opinion of
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Geo Group Northwest, however, that a 15 feet wide setback will be suitable for Lots 3 and 4, but
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that a setback of 25 feet should be established for Lot 2, where the steep west -facing slope is
higher. These recommended setbacks for Lots 2, 3, and 4, should be conditioned on the
reqiurement that the residences on these lots be supported on deep-seated pile foundation
systems. Our rationale for these proposed buffer/setbacks is as follows:
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Based on the findings from the site investigation work performed by Geo Group Northwest,
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Inc. in May 1999, dense soils are present at depths of approximately 5 feet bgs at each of the
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proposed building locations. The depth to groundwater at the proposed building loca o
ranges from approximately 6 feet on Lot 4 to 30 feet bgs at Lot 3, to depths greater than 30
feet bgs on Lots 1 and 2.
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The geotechnical reports by Roger Lowe Associates (1979) and by GeoEngineers, Inc.
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(1985), have described a lack of recorded, historical large-scale landsliding on the steep
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west -facing slope at the site, but have also noted that historical records of past landslide
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events are incomplete. The owner of the adjacent property south of the site, Mr. John
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Johnson, has reported that no landslides have occurred on the slope during his residence in
the area (approximately 40 years).
Geo Group Northwest believes it is possible for the proposed buildings to be located at
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minimum distances of 15 to 25 feet from the top of the steep west -facing slope (15 feet on
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Lots 3 and 4, 25 feet on Lot 2), if the buildings are supported on deep fo undation systems
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that are embedded in soils that less susceptible to future sloughing along the nearby steep
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slope. The proposed residence on Lot 1, however, can be supported on shallow
conv entional spread footing foundation systems, provided that the residence is located at
least 50 feet from the top of the steep slope.
As discussed in the Limited S cope Environmental Impact Study prepared by Geo Group
Northwest in 1999 (Geo Group Northwest, 1999), steep slope and landslide hazard areas on Lots
2, 3, and 4 at the site can be protected from potential impacts by establishing 15 to 25 feet wide
Geo Group Northwest, Inc.
February 25, 2000
Mr. John Thoresen - Sequoia Ridge Partners
G- 1061 -1
Page 14
building setbacks zone from the top of the steep west -facing slope on the site. The recommended
setbacks have been approved by the City of Edmonds through a review of the EIS by the City
Hearing Examiner. The proposed development incorporates such setbacks for these lots.
It is the opinion of Gen Group Northwest that the proposed development, utilizirig the proposed
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15 and 25 feet setbacks from the top of the steep slope, will not affect the site stability during or
following construction, provided the recommendations provided in this report are followed.
3.3 Site Preparation and Earthwork
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To minimize the amount of site grading for construction of the proposed residences, the building
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pads should be step -graded to where dense native soils are exposed. Split-level building floors
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could be incorporated into the construction plans and design to accommodate the topographic
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relief across the proposed building locations. This would require the removal of minimal
amounts of loose soils on Lots I and 2, and removal of about 5 feet of loose soils on Lots 3 and
4. The areas between the residences should be graded to permanent slopes no steeper than
2Horizontal:lVertical (2H:IV); alternatively, rockeries and modular block retaining walls can be
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used to accommodate changes in grades, where available space would require steeperslopes.
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The building, driveway, and sidewalk areas should be stripped and cleared of surface vegetation.
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Disturbance to the site should be kept to a minimum. Silt fences should be installed around areas
disturbed by construction activity to prevent sediment -laden surface runoff from being
discharged off -site. Exposed soils that are subject to erosion should be compacted or covered
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with plastic sheeting, or both.
The surficial topsoil and loose sand soils below the proposed building foundation areas should be
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excavated down to dense, native soil. Based on the findings from our soil investigation at the
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site, we anticipate that the medium dense to dense soil under the building area is present at
approximately 3 feet bgs. Based on these findings, some over -excavation and replacement of the
loose to medium dense silty sand soils with structural fill may be required.
After the loose soils are excavated, we recommend that the bottom of the excavation be
compacted and proof -rolled with a piece of heavy construction equipment. Any soft spots or
disturbed areas thus detected should be re -compacted or excavated and replaced with compacted
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 15
structural fill. To protect underground utilities from settlement, we recommend that the bottom
of utility trenches be compacted using a backhoe-mounted "hoe -pack".
City of Edmonds regulations (ECDC 20.15B.080(A)(1)) prohibit site clearing activities in critical
areas (including geologically hazardous areas, erosion hazard areas, steep slope areas, and
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sensitive habitat areas) between October I and April 30. An appeal process exists for requesting
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a variance from this regulation (FCDC 20.15B.040). The City of Edmonds does allow for
weekly consultation from the project geotechnical engineer on whether earthwork can continue
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past September 30. We recommend that Geo Group Northwest be retained to monitor site
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earthwork and consult with Sequoia Ridge Partners and the City of Edmonds, in the event at a
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vananc e to continue earthwork past September 30 is requested.
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3.3.1 Tempor= Slopes and Excavations
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Under no circumstances should temporary excavation slopes be greater than the limits specified
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in local, state and national government safety regulations. Temporary cuts greater than four feet
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in height should be sloped atan inclination no steeperthan IH:IV (Horizontal:Vertical) in the
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weathered glacial till and no steeper than I H:2V in the dense glacial till soils. Permanent fill
slopes at the site should be inclined no steeper than 2H: IV.
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Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the
excavated area. During wet weather exposed cut slopes should be covered with plastic sheeting
during construction to minimize erosion. If groundwater seepage is encountered during
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construction, excavation of cut slopes should be halted and the cut slopes should be re-evaluated
by Geo Group Northwest, Inc.
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3.3.2 Subprade Stabilization
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The silty sand soils encountered in the borings on Lots 2 and 4 are moi sture sensitive and may
prove to be unsatisfactory as a subgrade base for the pavements, slabs, and structures if
earthwork takes place during wet weather condition s. We recommend using either or both of the
two following methods for subgrade stabilization: 1) bridging the soft sub grade soils; or 2)
cement treating the soils.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 16
3.3.2.1 Bridging
Soft subgrade conditions can be stabilized by bridging with an 18-inch minimum thickness of 2-
inch minus crushed rock, or a 24-inch thickness of class A pit run. A woven geotextile fabric,
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such as Mrafi 50OX or equivalent, should be laid below the bridging soils to provide base
reinforcement, separation and stabilization. Areas of additional rock/pit run thickness may be
needed depending on the subgrade conditions at the time of construction. Standing water should
be puraped or drained prior to placement ofthe geotextile and bridging soils.
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It should be noted that bridging may require over -excavation and export of the over -excavated
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spoils, depending on the planned final site grades. The cost of over -excavation and export and
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disposal ofthe over -excavated soils should be considered in the decision to over -excavate and
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bridge or to cement treat unsuitable subgrades. Over -excavation and export can be minimized by
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raising the finished site grades or by cement treating the subgrade.
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3.3.2.2 Cement Treatment
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Unsuitable subgrade soils at the site can be cement treated, instead ofe�cavated and replaced. In
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general, cement treatment should provide a minimum 12-inch thickness of cement treated base
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(CTB) or extend down to firm soils, whichever is encountered first. The site should be pre -
graded prior to treatment to prevent cutting or removing the minimum thickness ofCTB during
the final grading process. The final, post -grading CTI3 thickness should be at least 12 inches.
The rate of application of the cement is dependent on the soils moisture content and may vary
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from about 4 percent to 8 percent ( 43 lbs to 86 lbs per square yard by I -foot deep). We
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anticipate that a 5 percent cement content or an application rate of 6 pounds per square foot (54
lbs per square yard) would be used at the site.
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It should be noted that site traffic of equipment, trucks, backhoes and forklifts can soften areas
treated with cement. Yielding subgrade areas should be evaluated by the geotechnical engineer
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and if necessary we recommend applying additional cement treatment or over-excava ng d
replacing with imported structural fill, underlain by geotextile fabric. It should also be realized
that the cement treatment base can harden to the point of having an impact on later site utility
work, especially ifhigher cement application rates are used. We recommend that the CTB be
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 17
protected from site traffic by covering with a minimum of 4-inches of 5/8 inch minus crushed
surfacing top coarse or other imported soil approved by the geotechnical engineer.
3.3.3 Structural Fill
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All structural fill material used to achieve design, site elevations below the building,area and
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below non -structurally supported sidewalks, driveways, and patios, should meet the requirements
for structural fill. During wet weather conditions, material to be used as structural fill should
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have the following specifications:
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1. Be free draining, granular material containing no more than five (5) percent fines (silt and
clay -size particles passing the No. 200 mesh sieve);
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2. Be free of organic material and other deleterious substances;
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3. Have a maximum size of three (3) inches in diameter.
All fill material should be placed at or near the optimum moisture content. The optimum
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moisture content is the water content in soil that enables the soil to be compacted to the highest
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dry density fourt given compaction effort.
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We anticipate that the on -site silty sand soils will be moisture -sensitive and will be unsuitable for
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use as structural fill if they become wet. These soils should be suitable for use as structural fill as
long as they are placed at or near their optimum moisture content. Alternatively, an imported
granular fill material may provide more uniformity and be easier to compact to tile specifications
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for structural fill. The fine to medium grained sand soils without silt should be suitable for use as
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structural fill under anticipated site conditions.
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If the on -site soils are to be used as engineered structural fill, it will be necessary to segregate the
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topsoil and any other organic- or debris -containing soil, because such soils would be unsuitable
for use as structural fill. Excavated on -site material that is stockpiled for later use as structural
fill should be protected from moisture or contamination with unsuitable materials by covering it
with plastic sheeting until it is used.
Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness.
Structural fill under building areas (including foundation and slab areas), should be compacted to
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 18
at least 95 percent maximum density, as determined by ASTM Test Designation D-1557-91
(Modified Proctor). Structural fill under driveway areas should be compacted to at least 90
percent of maximum density, with the exception of the upper twelve (12) inches. The top twelve
(12) inches should be compacted to at least 95 percent maximum density, as determined by
ASTM Test Designation D-1557-91.
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Poor quality subgrade conditions are anticipated in the location of the existing sewer line trench.
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For this reason, we recommend that the fill section over the trench area consist of 18 inches of
clean, 2-inch sized, crushed rock wrapped with a geotextile filter fabric such as Mirafl 140NL or
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equivalent. We also recommend that the driveway fill consist of a free -draining pit run sand and
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gravel or a clean crushed rock material.
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We recommend that Geo Group Northwest be retained to evaluate the suitability of structural fill
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material and to monitor the compaction work during construction for quality assurance of the
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earthwork.
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3.3.4 Pipe Bedding
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The pipe and pipe bedding interact to form a soil stru cture system, therefore, the bedding support
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requirements differ for flexible and rigid pipes. Our recommendations for pipe bedding materials
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follow the 1996 Standard Specifications for Road, Bridge and Municipal Construction, published
by Washington State Department of Transportation and American Public Works Association
(APWA) Specifications Sections 9-03.15 and 9-03.16. Any changes to these material
specifications must be approved by the geotechnical engineer.
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Bedding material should be placed between at least 6 inches below the base of the pipe and at
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least 6 inches above the top of the pipe. Bedding material shall have a maximum dimension of
1.5-inches in diameter and shall be a clean sand and gravel mixture free of organic matter and
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fines (material passing a #200 sieve), conforming to the following gradations:
Geo Group Northwest, Inc.
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No. 4
55- 100
No. 10
35-95
No. 20
20-80
No. 40
10-55
No. 100
0-10
No. 200
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All pipe bedding materials should be compacted to provide the lateral support needed for the M
pipe. However, caution should be exercised when compacting the soils in the vicinity ofnon-
reinforced pipe to prevent damage to the pipe.
3.3.5 Trench Backfill
Trench backfill (above the pipe bedding materials) beneath concrete slabs and pavement areas
may consist of native soils, provided the backfill can be compacted to the specified compaction
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partne rs Page 20
criteria. The backfill should be placed in lifts of approximately 8 inches in un-compacted
thickness. If the native soils cannot be compacted to the specified compaction standard, we
recommend that a suitable imported structural fill material be used. During wet weather, we
recommend using a pit -run sand and gravel material with 100 percent smaller than 3-inches in
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diameter and less than 5 percent passing a #200 sieve.
Trench backfill beneath pavement areas and sidewalks should be placed and compacted
according to the recommendations for structural fill. Trench backfill should be compacted to a
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minimum of 90 percent of maximurn density according to ASTM D1557-91 (Modified Proctor)
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and to 95 percent of the maximum dry density for the top 12-inches.
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3.4 Erosion and Sedimentation Control
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The west and center parts of the site are the most susceptible to erosion impacts, since the- —as
have the steepest slopes on the site, are underlain generally with Alderwood and Everett soils,
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and are the areas proposed for development. Uncontrolled runoff during construction could
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impact surrounding areas in the form of erosion, sloughing, and sedimentation. Sloughing or
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erosion along the steep slopes on the west side of the site could result in sediment or slough
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debris traveling onto the adjacent property west of the site. Sediments eroded from cleared land
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on Lot 4 could reach the nearby stream if not controlled.
Measures to control erosion and sedimentation impacts can be implemented during construction.
Typical measures would include application of General Development Standards as outlined in
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ECDC Chapter 18.30, and implementation of an Erosion and Sedimentation Control Plan
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(ESCP) per ECDC requirements.
3.4.1 General Develop—ment Standar d
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Anticipated impacts to soil during construction can be mitigated by application of General
Development Standards pursuant to ECDC Chapter 18.30. These standards include:
Clearing shall occur only during the dry season of May I through September 30, unless
authorized by the project geotechnical engineer and agreed to by the City. Extensions of
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 21
clearing activities beyond September 30 can be recommended by the project geotechnical
engineer, where appropriate, and approved by the City on a weekly basis.
No clearing shall be allowed within protected critical areas, including buffers, as approved
by the City and identified by survey on the Final Short Plat map.
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Prior to sdkt of construction, the approved, protected critical areas and buffer areas shall be
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protected with temporary fencing.
All utilities, including grading for utilities shall be located outside the approved protected
critical areas and buffer areas.
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All structures, including grading for structures, shall be located outside the steep slope
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setback line approved by the city during the short plat review process.
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A site specific management plan for both ternpor* sediment and erosion control and
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permanent storm water management shall be prepared and approved by the city for
protection of the wetland, stream, and buffers in accordance with the ECDC Storm Water
Management standards.
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3.4.2 Erosion and Sedimentation Contio-I Plan
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The ECDC requires the preparation and implementation of an Erosion and Sedimentation
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Control Plan (ESCP) for construction projects located in critical areas (including steep slope
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hazard, erosion hazard, and wetland areas). The ESCP shall be approved by the City of
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Edmonds, and implemented pursuant to ECDC Chapter 18.30. Mi in requirements for an
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ESCP include, but are not limited to, the following:
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Construction vehicle access shall be limited to one route, whenever practical (for the
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proposed development, two routes would be most practical —one route from North
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Meadowdale Road for Lot 4, and one ro ute from 72 n' Avenue West for the remaining lots).
The route(s) shall be stabilized with quarry spalls or crushed rock.
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Adjacent properties shall be protected from sediment deposition by appropriate use of
vepetative buffer strips, sediment barriers or filters, dikes or mulching, or combination of
these measures and other appropriate BMPs.
Cover exposed soils that will be left unworked either overnight or over longer periods of
time during rainy periods; at a minimum, no soils should be exposed for more than two
days from October 1 to April 30.
Regular inspection and maintenance of BMPs.
Geo Group Northwest, Inc.
N
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 22
Delineate clearing and easement limits including setbacks, critical areas and buffers, and
trees.
Limit construction traffic to access roads and designated traffic areas and provide
designated areas for staging equipment, to minimiz the area of soil disturbance.
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Re -vegetate disturbed areas as soon as practical following grading, and stabilize newly
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vegetated areas with mulch, straw, or jute netting until vegetation is established; do not
remove BMPs until disturbed areas are stabilized.
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Drainage off impervious areas (building roofs and pavements) would be directed to catch basins
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and tightlined to discharge to the storm drainage line below North Meadowdale Road. Drainage
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off the roadway and driveways also would be treated by being passed through an oil/water
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separator before being discharged. Water associated with drainage behind retaining structures
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(such as walls that support proposed driveways and cut slopes, and rockeries greater than 4 feet
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in height) also can be tightlined into the storm drain system, instead of being discharged to site
soils. A decrease of the infiltration rate into site soils could result in a marginal decrease in the
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groundwater elevations at the site and thereby slightly increase the stability of the slopes on site,
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3.5 Foundations
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3.5.1 Deep FQu ndation Systems
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The proposed buildings can be supported on a pile foundation system such as angered concrete
piles. The piles would be embedded deeply into the dense soils so that they transfer the building
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loads to deeper soils which are less susceptible to sloughing along the nearby slope. Placing the
buildings on a deep pile foundation system will significantly help to protect the buildings from
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potential damage from possible future sloughing along the top of the steep slope (which co dbe
anticipated to occur over the long term even if no development occurred on the site).
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We recommend that the piles be installed to a minimum depth of 25 feet into the dense, native
soils. However, specific geotechnical recommendations for pile lengths at each proposed
building location should be further studied during the design ofthe residences and after the
topography of the steep west -facing slope is better defined. We recommend that the piles have a
minimum diameter of 14 inches. The piles should have a minimum allowable bearing capacity
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 23
s
of 25 tons, as calculated based on the encountered soil conditions in the oil borings drilled on
site.
Lateral loads can also be resisted by using battered piles or by the passive earth pressures acting
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on grade beams. To fully mobilize the passive pressure resistance, the grade beams must be
poured "neat" against compacted fill. Our recommended allowable passive soil pressure for
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lateral resistance is 300 pcf equivalent fluid weight, with a f ction factor of 0.3.
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The performance of piles depends on how and to what bearing stratum the piles are installed.
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Since a completed pile in the ground cannot be observed, it is critical that judgement and
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experience be used as a basis for determining the embedment length and acceptability of a pile.
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Therefore, we recommend that the project geotechnical engineer be retained to monitor the pile
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ta and ve s table be gs a
installation operation, collect and interpret installation da rify ui arin tr turn
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We also suggest that the getechnical engineer review the contractor's equipment and installation
hi gress.
procedure prior to pile installation to help mitigate problems w ch may delay work pro
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3.5.2 Shallow Foundation Systems
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An alternative to constructing deep foundations for the proposed buildings is to create building
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pad areas on which the buildings could be constructed with shallow, conventional spread footing
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foundation systems. The existing soils below the proposed building locations have adequate
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bearing strength to support typical shallow conventional spread footing foundations, after the
surficial loose soils are removed. However, the springs, seepage, and visual evidence of previous
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small slumps and sloughing on the steep west -facing slope indicate a potential exists for future
sloughing or slumps to occur along the slope. Future sloughing or slumps could adversely affect
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structures placed on shallow foundations. The use of shallow foundation systems, such as
conventional spread footings, should be limited to buildings whichwill be located at least 50 feet
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from the top of the steep west -facing slope (such as the proposed residence on Lot 1).
Loose or soft soils below the foundation footings should be excavated down to dense soil and the
over -excavated areas should be replaced with compacted structural fill. Based on the findings
from our soil investigation at the site, we anticipate that medium dense to dense native soil under
the building area is present at approximately 3 feet bgs.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Tho resen - Sequoia Ridge Partners Page 24
Individual spread footings may be used for supporting columns and strip footings for bearing
walls. Our recommended design criteria for foundations are as follows:
Allowable bearing pressure, including all dead and live loads
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Dense native soil (glacial till) = 2,000 psf
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Compacted structural fill = 2,000 psf
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Minimum depth to bottom of perimeter footing below adjacent final exterior grade 18
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inches
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Mnimurn depth to bottom of interior footings below top of floor slab 12 inches
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Minimum width of wall footings 16 inches
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Minimmn lateral dimension of column footings 24 inches
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Estimated post -construction settlement = 1/4 inch
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Estimated post -construction differential settlement; across building width 1/4 inch
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A one-third increase in the above allowable bearing pressures can be used when considering
short-term transitory wind or seismic loads.
Lateral loads can also be resisted by friction between the foundation and the supporting
compacted fill subgrade or by passive earth pressure acting on the buried portions of the
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foundations. For the latter, the foundations must be poured "neat" ag ainst the existing
undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural
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fill. Our recommended parameters are as follows:
Passive Pressure (Lateral Resistance)
300 pcf equivalent fluid weight for compacted structura f
350 pef equivalent fluid weight for native dense soil.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 25
Coefficient of Friction (Friction Factor)
0,30 for compacted structural fill
0.35 for native dense soil
We recommend that footing drains be placed around all perimeter footings. More specific details
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of perimeter foundation drain are provided below in Section 3.10: Drainage.
3.6 Building Floors
The building floors can be supported on either the dense native soils at the site (where
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conventional footing foundations are used), or can be structurally supported on a pile foundation
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system. In preparing the subgrade for slab -on -grade floors, any areas of the building pad
disturbed by construction activity should be either re -compacted or excavated and replaced with
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compacted structural fill material, We recommend the building pad area be proof-mlled with a
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piece of heavy construction equipment prior to placing the capillary break material. Anysoftor
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low areas thus detected should be filled to grade and re -compacted or excavated, and replaced
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and compacted with crushed rock as described in S ection 3.3: Site Preparation and General
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To avoid moisture build-up on the subgrade, slab -on -grade floors should be placed on a capillary
break, which is in turn placed on the prepared subgrade. The capillary break should consist ofa
no more
minimum of a six (6) inch thick layer of free -draining crushed rock or gravel containing
than five (5) percent finer than No. 4 sieve. A vapor barrier, such as a 6-mil plastic membrane, is
recommended to be placed over the capillary break beneath the slab to reduce water vapor
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transmission through the slab. Two to four inches of sand may be placed over the barrier
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membrane for protection during construction.
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3.7 Permanent Basement and Conventional Retaining Walls
Permanent basement walls restrained horizontally on top are considered unyielding and sbou Id be
designed for a lateral soil pressure under the at -rest condition; while conventional reinforced
concrete walls free to rotate on top should be designed for an active lateral soil pressure.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 26
Active Earth Pressure
Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002
times the wall height� should be designed to resist the lateral earth pressure imposed by an
equivalent fluid with a unit weight of.
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35 pef for level backfill behind yielding retaining walls;
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At -Rest Earth Pressure
65
Walls supported horizontally by floor slabs are considered unyielding and should be
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designed for lateral soil pressure under the at -rest condition. The design lateral soil
pressure should have an equivalent fluid pressure of-
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45 pef for level ground behind permanent unyielding retaining walls;
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Passive Earth Pressure
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300 pef equivalent fluid weight for structural fill
350 pcf equivalent fluid weight for native soil
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Base Coefficient of Friction
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0.30 for structural fill
0.35 for native soil
We recommend that a vertical drain mat, Miradmin 6000 or equivalent, be used to facilitate
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drainage behind permanent concrete basement walls. The drain mat core is placed against the
basement wall with the filter fabric side facing the backfill. The drain mat extends from the
55
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finished surface grade, down to the footing drain pipe. A minimum of 18 inches of clean, free-
draining, washed rock, crushed rock, or pea gravel should be placed in the bottom of the footing
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trench. With the above exceptions, perimeter foundation drainage recommendations and
installation procedures should be followed in Section 3.10.2: Footing and Wall Drains. Please
also refer to Plate 9 - Typical Basement Wall Backfill and Drainage Details.
To prevent buildup of hydrostatic pressure behind permanent concrete basement or conventional
retaining walls, a granular, free draining structural backfill material should be placed within a
horizontal distance of 18 inches of the wall, in place of vertical drain mats. We recommend
Gee Group Northwest, Inc.
February 25, 2000 0-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 27
using a clean, granular, free -draining, structural fill material. The free-drairfing granular material
should surround the wall subdrain system as described in the footing drain section of this report.
The top twelve (12) inches of the fill should consist of compacted and relatively impermeable
soil. This cap material can be separated from the underlying more granu lar drainage material by
a geotextile fabric. The surface should be sloped to drain away from the building wall.
Alternatively, the surface can be sealed with asphalt or concrete paving.
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Backfill material behind permanent concrete basement or conventional retaining walls should be
compacted to 90 percent of the maximum dry density determined by ASTM D 1557-91
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(Modified Proctor Method) as specified in Section 3.3.3: Structural Fill. The top 12-inches
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should be compacted to 95 percent of the maximum dry density.
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The backfill in areas adjacent to basement or conventional ret ng walls should be compacted
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with hand held equipment or a hoe -pack. Heavy compacting machines should not be allowed
height, the are
within a horizontal distance to the wall equivalent to one half the wall unless walls
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designed with the added surcharge.
3.8 Modular Block Walls
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We understand that a retaining wall will be required along the south side of the driveway for
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support. The proposed wall is anticipated to be approximately 125 feet long and up to
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approximately 8 feet high. This wall may consist of either a conventional concrete retaining wall
ogrid reinforcement
founded on the dense glacial till soils, or a modular block wall with ge set on
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the dense glacial till soils. Design parameters for a conventional retaining wall are presented in
Section 4.7.* Permanent Basern ent and Conventional Retaining Walls.
The modular cement block wall can consist of keystone walls or ecology block walls and should
In
include reinforcement by geogrid layers embedded in compacted structural fill. The wall base
pad should be prepared by excavating a trench into dense, bearing soil The cement blocks
I
should then be stacked on a 6-inch thick layer of free -draining crushed rock. Steps shout d be
excavated on the existing slope behind the wall to allow the backfill to interlock with the existing
soils. The wall should be designed using the following parameters:
A-
Gen Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 28
Friction Angle (phi): 35 degrees
Unit Weight (gamma): 130 pef
A wall drain should be installed behind the wall. The drain should consist of a 4-inch diameter
0,
perforated PVC pipe placed at the inside base of the wall. The pipe should be surrounded by a
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free -draining crushed rock and geotextile fabric as illustrated in Plate 8 Typical Basement Wall
Backfill and Drainage Details, and tightlined to a suitable discharge location away from the wall
(such as the local storm drain system). The drain should extend the entire length of the wall and
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be installed at a grade sufficient to maintain flow to the tightline.
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The geogrid layers should be attached to the cement blocks and embedded within a compacted
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structural fill material. Backfill behind the wall shall consist of free -draining structural fill
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material that meets the compaction requirements in Section 3.3.3: Structural Fill.
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3.9 Rockeries
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It should be understood that a rockery is not intended to function as an engineered structure to
resist lateral earth pressures, as a retaining wall would be. The primary function of a rockery is
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to cover the exposed excavated surface and thereby retard the erosion process. However, some
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lateral support is provided by virtue of the weight of the rock. Therefore, the larger the rock the
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greater the mass and the more lateral load resistance available. However, since this support
depends on the contact areas and characteristics between individual rocks, it is virtually
impossible to predict or provide for a specific lateral resistance.
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Also, rockery construction is to a large extent a skilled craft not entirely controllable by
55
engineering methods. Because of this, it is imperative that rockeries be constructed in a proper
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manner by contractors experienced in, and with a proven capability in, rockery construction, and
E5
in accordance with the guidelines specified by the Association of Rockery Contractors, presented
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in Appendix B to this report.
Rock Specifications
Where cut slopes less than six feet high, or fill slopes less than four feet high exist, rockeries may
be constructed entirely of four -man rock. Rockeries placed in front of six to eight feet high cut
slopes should have one basal course of six -man rock. Rockeries with a height of eight to ten feet
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 29
should have at least two basal courses of six -man rock. For rookeries with a height of 10 to 12
feet, there should be at least three basal courses of six -man rock. The remaining courses may be
four -man rock. The rock should be hard, sound, durable, free of seams and cracks, and broken in
generally tabular to cubical shapes, Preferably, the rock density should be at least 165 pounds
0
per cubic foot (pcf), but you should recognize rock densities will vary from source to source.
Fills Behind.Rockeries
Any fills behind a rookery should consist of structural fill compacted to at least 95 percent
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relative compaction as determined by ASTM Test Designation D1557-91 (Modified Proctor).
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We do not recommend using rookeries in front of fills more than four feet high unless the fills
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have been reinforced with geogrids.
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Construction Procedure
The initial step in rookery construction involves the excavation and preparation of a "keyway".
65
This should be about six to eight feet wide, about 18 inches deep, and slightly inclined back in
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towards the face to be protected. The keyway should be excavated into dense, compacted soil
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capable of bearing the rookery. We recommend a shallow ditch, about 12 inches wide and deep,
then be dug along the rear edge of the keyway. A four -inch minimum diameter perforated or
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slotted plastic drain pipe should be placed on and surrounded by a free -draining ballast or
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crushed rock. The pipe should be directed to a positive and permanent discharge.
Once the exposed keyway subgrade has been prepared, the first basal layer of rock should be
carefully "slammed" into place. These rocks should be placed in as close contact with each other
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as possible. Each row of rock should be well seated and thoroughly tamped and driven into place
having as few voids as possible.
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Since the rookery derives its support partially from friction between individual rocks, point
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contact of rocks should be avoided wherever possible. Succeeding layers of rock should be
placed so that rocks overlap each other. The face of the rookery wall should be inclined at a
slope of approximately IH:6V.
The filter rock behind the rookery should be installed concurrently with the rookery. It should
consist of a well -graded crushed angular rock with a three-inch maximum size. The filter layer
should not be less than 12 inches in thickness.
Gen Group Northwest, Inc.
February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 30
Geotechnical Observation
We recommend that the construction of the rockery (including placement of the rocks) be
performed under our periodic observation. We will be available to meet with you and your
rockery contractor to discuss these matters in more detail.
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3.10 SiteDrainzge
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3.10.1 SurfaceDraina
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The finished ground at the site should be graded such that surface water is directed off the site.
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Water should not be allowed to stand mi any area where footings, slabs or pavements are to be
constructed. During construction, loose surfaces should be scaled at night by compacting the
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surface to reduce the potential for moisture infiltration into the soils. Final site grades should
allow drainage away from the building. We suggest that the. ground be sloped at a gradient of
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three (3) percent for a distance of at least ten feet away from the building except in areas that are
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to be paved.
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3.10.2 Footina and Wall Drains
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We recommend that drains be installed around the perimeter of the foundation footings. The
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drains should consist of a four (4) inch minimum diameter, perforated or slo tted, rigid drain pipe
laid at or near the bottom of the footings with a gradient sufficient to ge nerate flow, as
schematically illustrated in Plate 9 - Typical Footing Drain. The drain line should be bedded on,
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surrounded by, and covered with a free -draining rock, pea gravel, or other free -draining granular
material. Once the drains are installed, the excavation should be backfilled with a compacted
structural fill material. The surface can be sealed with asphalt or concrete paving.
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Under no circumstances shoul d roof downspout drain lines be connected to the footing drainage
system, Al I roof downspouts must be separately tightlined to discharge into the storm water
collection system. We recommend that sufficient cleanouts be installed at strategic locations to
allow for periodic maintenance of the footing drains and downspout tightline systems.
Gen Group Northwest, Inc.
February25,2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 31
3.11 Pavements
We recommend the driveway subgrades be prepared as described in Section 3-3: Site
Preparation and General Earthwork. Areas of soft, wet or unstable subgrade may still exist
after this process. If so, over -excavation of the unsuitable material and replacement with
compacted structural fill or crushed rock may be required.
The overlying pavement section should consist ofat least 3 inches ofasphalt. The asphalt may
be placed either directly over the crushed rock layer above the sewer line trench, or over a
crushed rock base ofat least 6 inches above other driveway areas. Alternatively, the pavement
section can consist of a 2-inch thickness of asphalt concrete over a 3-inch thickness of asphalt
treated base (ATB).
3,11.1 Drivewav—SWDP—Ort
To minimize the width of the area that would be covered by the roadway, the roadway can be
designed to include gravity retaining walls and rockeries to stabilize cuts and fills. The
downslope (east) side of the roadway can be supported by a modular block wall reinforced with
Geogrid layers placed in the underlying fills. Such a wall can be located adjacent to the east side
of the roadway pavement (or about two feet out from the pavement edge to accommodate a guard
rail) and can be constructed to be vertical or nearly vertical, as desired. Rockeries, Ecology
block, or cast -in -place concrete retaining walls can be constructed along the west side of the
roadway to retain cut slopes. The use of concrete retaining walls (instead of rookeries or block
walls) may be more favorable where cuts exceed 10 feet in height and where surcharge loads
vity typ as
from buildings, driveways, or traffic, may affect cut slopes. Non gra e walls (such
CMU walls) will not be adequate to retain the cuts along the roadway and are not recommended.
Drainage associated with the cut slope retaining structures and with water on pavements can be
directed to catch basins that are installed in the roadway and connected to the local storm drain
system. Drainage associated with the fill slope walls on the east side of the roadway should also
be tightlined to a storm drain system.
Geo Group Northwest, Inc.
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February 25, 2000 G-1061-1
Mr. John Thoresen - Sequoia Ridge Partners Page 32
3.11.2 Driygw--a_y Strearnfrossin
Based on the available information; earthwork for the driveway on Lot 4 is anticipated to require
more filling than cutting in order to meet the ECDC requirements for driveway slopes (driveway
slopes should not exceed 14 percent except under certain -conditions, where slopes of up to 20
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percent may be allowed). The proposed driveway is approximately 80 feet long over an elevation
gain of approximately 15 feet. In this scenario, Geogrid-reinforced fills and modular block walls
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can be used to support the roadway in a minimum amount of space and can easily be
incorporated into the design for the stream crossing that involves either a box culvert or a
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backfilled corrugated metal pipe.
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Another option that could be implemented in construction of the driveway and stream crossing
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consists of designing a pile-supportcd structural driveway deck that spans the stream and the
portion of the stream buffer that is lower than the design driveway grade. Storm drain and side
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sewer lines could be attached to the underside of the driveway deck. Post -construction impacts
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to the stream and stream buffer areas would be significantly reduced, as there would be minim—
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loss of habitat area.
Poor quality subgrade conditions are anticipated in the location of the sewer line trench in the
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driveway areas. For this reason, we recommend that the pavement section over the trench area
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consist of a layer of crushed rock at least 18 inches in thickness wrapped with a layer of
geotextile fabric (such as Mirafi 140NL or equivalent). The crushed rock and geotextile can be
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subsequently covered with structural fill where needed to achieve the design driveway subgrade
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elevation. No upper layer of geotextile fabric is needed if asphalt pavement is placed directly on
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the crushed rock base.
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A drainage pipe should be installed at the lowest part of the crushed rock layer. The drain pipe
should consist of a 4-inch diameter perforated PVC pipe. The pipe should have a slope sufficient
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to generate flow and should be connected to a tight line for discharge to an appropriate location
(such as a storm drain system). This line should not be tightlined into the wall drain system.
Geo Group Northwest, Inc.
February 25, 2000 G- 1061 -1
W John Thoresen - Sequoia Ridge Partners Page 32
3.11.2 DrivgmLay Strearn Crossing
Based on the available information; earthwork for the driveway on Lot 4 is anticipated to require
more filling than cutting in order to meet the ECDC requirements for driveway slopes (driveway
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slopes should not exceed 14 percent except under certainconditions, where slopes of up to 20
0
percent may be allowed). The proposed driveway is approximately 80 feet long over an elevation
in
gain of approximately 15 feet. In this scenario, Geogrid-reinforced fills and modular block walls
can be used to support the roadway in a minimum amount of space and can easily be
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incorporated into the design for the stream crossing that involves either a box culvert or a
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backfilled corrugated metal pipe.
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Another option that could be implemented in construction of the driveway and stream crossing
10 " 1'�
consists of designing a pile -supported structural driveway deck that spans the stream and the
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portion of the stream buffer that is lower than the design driveway grade. Storm drain and side
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sewer lines could be attached to the underside of the driveway deck. Post -construction impacts
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to the stream and stream buffer areas would be significantly reduced, as there would be minimal
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loss of habitat area.
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Poor quality subgrade conditions are anticipated in the location of the sewer line trench in the
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driveway areas. For this reason, we recommend that the pavement section over the trench area
consist of a layer of crushed rock at least 18 inches in thickness wrapped with a layer of
geotextile fabric (such as Mirafi 140NL or equivalent). The crushed rock and geotextile can be
subsequently covered with structural fill where needed to achieve the design driveway subgrade
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elevation. No upper layer of geotextile fabric is needed if asphalt pavement is placed directly on
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the crushed rock base.
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A drainage pipe should be installed at the lowest part of the crushed rock layer. The drain pipe
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should consist of a 4-inch diameter perforated PVC pipe. e pipe should have a slope sufficient
to generate flow and should be connected to a tight fine for discharge to an appropriate location
(such as a storm drain system). This line should not be tightlined into the wall drain system.
Geo Group Northwest, Inc.
February 25, 2000 G-1061-1
P� '
Mr. John Thoresen - Sequoia Ridge Partners Page 33
3.12 Post -Construction Soil Stabilization and Re -vegetation
Areas where soils were exposed during construction should be replanted with appropriate native
plant species to stabilize the soils. Selected plants should not require significant watering by
homeowners. The vegetation should be monitored as it becomes established, arfd areas where
vegetation does not take hold should be evaluated for repeated re -planting or for other methods to
0
stabilize the surficial soils. Mulching andjute netting can be used to help stabilize the surficial
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soil during the re -vegetation process.
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The utility easement should also be monitored by the homeowners to ensure that re -vegetation
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and soil stabilization measures instituted after construction are adequately preventing erosion or
sedimentation impacts to downslope areas. The easement should not be re -vegetated with trees,
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to avoid possible damage to the utilities and to allow access along the length of the easement if
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repairs are needed.
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4 CONSTRUCTION MONITORING AND ADDITIONAL SERVICES
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We recommend that Gen Group Northwest be retained to perform a geote chnical review of the
final completed construction plans for each lot of the proposed development, per ECDC Section
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19.05.040. We also recommend that we be retained to conduct geotechnical construction
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monitoring and observation of the following:
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earthwork quality control,
subgrade preparation,
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pile installation,
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site drainage,
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temporary erosion and sedimentation control,
pavement subgrade preparation,
utility trenching and backfilling, and
rockery and retaining wall construction.
We also recommend periodic monitoring of the steep west -facing slope during construction for
indications of soil movement or other signs of potential instability.
Gen Group Northwest, Inc.
February 25, 2000
N4r. John Thoresen - Sequoia Ridge Partners
5 LINUTATIONS
This project has been prepared for the specific application to this site for the ex(
Sequoia Ridge Partners, and its authorized representatives. Reliance on this rep
parties is solely at their own risk. We recormnend that this report be included ir
the project contract documents for reference during construction.
Our findings and recommendations stated herein are based on field observation:
and judgement. The recommendations are our professional opinion derived in i
consistent with the level of care and skill ordinarily exercised by other member!
currently practicing under similar conditions in this area and within the budget
constraints. No warranty is expressed or implied. In the event that soil conditi(
vary from those anticipated, Gen Group Northwest, Inc. should be notified and
recommendation should be re-evaluated.
We appreciate the opportunity to provide Sequoia Ridge Partners with geotechr
Please feel free to contact us if you have any questions regarding this report.
Sincerely,
Geo Group Northwest, Inc.
WAS
0
Keith Johnson William Chang, P.E.
20114
Geologist Principal
AL
Geo Group Northwest, Inc.
G-1061-1
Page 34
REFERENCES
(7,
City of Edmonds, 1999, Determination of Significance and Request for Comments on Scue
FIS, February 26, 1999.
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0
City of Edmonds, 1998, City of Edmonds Environmental Checkli Sequoia Ridge Short
3
Subdivision, June 12,1998.
A:H
DEA, 1998, Drainage RMort & Calculations, Sequoia Ridge- Subdivision. City of Edmonds,
am
WashingLon, David Evans & Associates, Inc., September 25,1998.
C
to
0
GeoEngineers, 1985, &e port of Geotechnical Consultation. P=gM Value AMraisals.and
m;
mz
Assessments, Meadowdale Landsli& Area, Edmonds. Washinglon Geo Engineers, Inc., for City
j0-4
C-
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of Edmonds, February 28, 1985.
C4
f
Geo Group Northwest, 1999, Final.Limited ScQpe Environmental !=act SULdy, P=osed
0 -n
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Sequoia Ridme Short Subdivision. Edmonds. Washing-tga, Geo Group Northwest, Inc., and 13-
mm
twelve Associates, Inc., August 31, 1999.
DO
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CA
Minard, 1983, Geologic Map of the Edmonds East and Part of the Edmonds West Quadranpjes.
co
M 0:
—
WashinZon, Minard, James P., U.S. Geological Survey Miscellaneous Field Studies Map MF-
1541,1983.
NCA, 1995, Prelimmga Geotechnical Engineering R-eport. Residential Developtnent_Edmonds.
Washing —ton Nelson-Couvrette & Associates, Inc., for Mr. John Johnson, March 28, 1995.
65,
Z'
PIE, 1998, Critical Area Study, Sgquoia Ridge, Edmonds. Washington Pacific International
0
Engineering, P.L.L.C., for David Evans and Associates, Inc., Everett, Washington, July 1998.
m
RLA, 1979, Final Report. Landslide Hazards Investigation. Meadowdale Area, Edmonds.
Washimftn Roger Lowe Associates, Inc., for the City of Edmonds, October 16, 1979.
Terra, 1989, Geotechnical Report. Meadowdale Beach, Lots 54 to 57, Edmonds, Washington
Terra Associates, Inc., June 6, 1989.
Geo Group Northwest, Inc.
0
SCS, 1983, Soil SgmLey -of Sn a. Washin o
Qhomish Comly Are gLn, U.S. Department of
Agdculture Soil Conservation Service, 1983.
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VICINITY MAP
'Group Northwest, Inc. SEQUOIA RIDGE SHORT SUBDIVISION
I Gwech 1�1 Engineem, GmlogisM, & 160XX - 72ND AVENUE WEST
Znvironmental Scienfists EDMONDS, WASHINGTON
SCA LF: I" = 2000' 1 DATE: 6/14/99 MADF.' KJ CHKD: Wc I 1..N.-. G-1067�PLATE I
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LEGEND
Exploratory Soil Boring Drilled by Geo Group
Northwest, Inc. (Approximate Location)
Hand -Auger Soil Boring by Nelson-Couvrette
Assoicates, Inc. (Approximate Location)
NC-1
L
WATER MANHOLE
(FRV) SS MANHOLE
BUFFER / - —
IE 192.09-8"N
IE 192.04-8'E
IE 191.9+-8'W
CATCH BASIN
A,� �OP 202.08
/V, � EXIS71NG HYDRANT
C-1
C8 if If
DP 2QX
4 CATCH BA
00 —TOP215.4
DP 6
I< SF/
C6. TYPE.,!.
STREAM AN 2!
WETLAND BOU Y
52 248 SF
21,
SEME RT FOR
RAI,,
ID R
'51,222 SF
UP 61
j
C8
v TER 'rQR
'FE 260
B, 6SMt
NC.4 ,
4fh891 SF
;ED
ISE
2 'N8 '47f%.
ON
10 ?.Uu
SE 'I > 2.,/
NC-3 �.z _EA
#,X
130 04
iz
1'38 4"
1� 1p"PT
122.07'
4
\\'�'—TOP IF
BANK
"G
JOHN L JOHNSON
EDGE OF
GUE-A-122,91811SIF"o'
OCCOO
ROCKERY ASPHALT
ILIFFER IDIIIIIN/COUPCNSATI(X4
AREA-5750 SF
FENCE
0
SANITARY SEWER MANHOLE
POTENTIAL STIIE� & BUFFER
LOSS MITIGATION AREA-1283 SF
)0.
FIRE HYDRANT
TOP OF
*
CATCH BASIN
_ss—
SANITARY SEWER LINE
BANK
*
WATER VALVE
--OP—
OVERHEAD POWER LINE
GAS VALVE
—I.—
ITOR. BRAIN LINE
UTILITY POLE wl Guy WRC
—W—
WATER LINE
TELEPHONE CLOSURE
— --
EDGE OF ASPHALT
-,,,-25' STREAM BUFFER
ist—
R
4 DP 26X
DP 26'l
222 SV
27.
'10
A'5
AND
$TREAM oj
WETLAND SPU<ARY
�Z 2lF8 SF
2
51,222 SF
__DF
A'
_25
'21
. .... ....
4:6.891 SF
9.2
IT,
NC-5 NC4 6P 41—
d. �00
34,052 �F
NC4 3! 40'
LEGEND
EXPLORATORY SOIL BORING BY GEO, GROUP
NORTHWEST (APPROXIMATE LOCATION)
*13-1 EXPLORATORY HAND AUGER BORING BY NELSON-
COUVRETTE & ASSOC. (APPROXIMATE LOCATION)
SUBSURFACE PROFILE LINE
A 5'0 1�0
SCALE: I inch 50 feet
mom
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80
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SOUTH NORTH
PROPOSED RESIDENCE
LOT I LOT 2 LOT 2 LOT 3
1401 PROPOSED ROCKERY
PROPOSED RESIDENCE
[131
300 --P2t:m�_ NC-51�-.
. P91
-1641
PROPOSED DRIVEWAY
B-2
280
WIGRAVE�,,'�,, ,[61-
PROPOSED RESIDENCE
N,
p ", � [50+1
? TO BE DETERMINED
260
Z,
PSI
S'mw (SP) ?
FA 240
220
LEGEND
LXPLORATORY SOIL BORING WITH
1321
SAWLING LOCATIONS AND
200
SOIL PENETRATION TEST RESULT
NC-5
HAND AUGER BORING
APPROXMIATE OR MIKERRED
GEOLOGIC CONTACT
GROUNDWATEP TABLE
26 4 ='Group Nori.
Gwtechmcal
SCALE; I inch 20 feet 14W Envimmeat
SCALE' 2/1'
?
260
240
220
200
WEST EAST
BUILDING SETBACK
300 AREA PROPOSED RESIDENCE
TOP OF BANK I
LEGEND
B-1
. .... .. B-2 EXPLORATORY SOIL BOMG WITH
1,321 SAMPLING LOCATIONS AND
280 SILTY SAND f6jr SOIL PENETRATION TEST RESULT
WIGRAVEL (SM) — [401 PROPOSED ROCKERY
APPROXIMATE OR WERRED
PROPOSED DRIVEWAY GEOLOGIC CONTACT
260
z SAND (SP)
SAND (SP)
240 240
SEEPAGE ELEVATION
(APPROXIMATE) 7-
220 220
SILT, SILTY SAND,
AND SAND (MIJSM(SP)
200 200
180 180
Group Northwest, Inc. SUBSURFACE PROFILE I
0 �0 Geotedmital eng�, Geologists, & SEQUOIA RIDGE SHORT SUBDIVISIO
SCALE. I inch 20 feet Environmentaillcierdists EDMONDS, WASHINGTON
SCALE: V=20' 1 DATE: 2117/00 1 MADE: KJ CIM: G-1061-1 I PLA
SOUTH
C
PROPOSED RESIDENCE
260 B-3 [21 ELEVATION
TO BE DETERMINED
its]-
- [251
240
- 1601 SAND (SP)
1791
1 ISO+]
220 =?
200
180
1 160
EXPLORATORY SOIL BORING WITR SOIL
1281 PENETRATION TEST RESULTS (BLOWS
PER 12 INCHES OF PENETRATION)
APPROX]MATE OR INFERRED
GEOLOGIC CONTACT 0 20 40
SCALE: I inch 20 feet Group Is
GROUNDWATER ELEVATION OBSERVED
DURING DRILLING (MAY 1999) Er
SCALE. V=2W EDAM-
NORTH
ct
Sl
PROPERTY LINE
'WALLWITH - 220
MENT
NAY
- 200
STREAM
160
Basement
Wall
Slope to
drain
Pertical Drain mat
(Miradrain 6000
Pelative Impermeable or equivalent)
CotnoactedBac4ful
COMPAMD
ONSITE BACKF7LL
Free draining material AMTERUL (IF USABLE)
(Wwhed rack or Cwhed rock)
Geotextile
Xafll 140 NL4 or
equivaleno
x
4 or 6 inch diameter slatted A00
orperfarated PVCpipe
NOT, TO SCALE
NOTES:
1.) Do not replace rigid PVC pipe with flexible corrugated plastic pipe.
2.) Perforated or slotted PVC pipe should be tight jointed and laid with
perforations or siots down, with positive gradient to discharge.
3.) Do not connect roof downspout drains into the footing drain lines.
4.) Backfill should be compacted to 90% of maximum dry density based on
Modified Proctor. The top one foot should be compacted to 95% of
maximum dry density if backfill is to support sidewalks, driveway, etc.
Ad TYPICAL BASEMENT WALL
Group Northwest, Inc. BACKFILL AND DRAINAGE
(;eotecnnicw Enoneem, c;eoiogists, & SEQUOIA RIDGE SHORT SUBDIVISION
Envi—mental Sdenfists EDMONDS, WASHINGTON
DATE _.2/23/00. MADE KJ OHNO. G-1061-1 PLATE 8
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LEGEND OF SOIL CLASSIFICATIUN ANU Ft:Nt: I KA I IUN I L51
UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)
MAJOR DIVISION
GROUP
TYPICAL DESCRIPTION
LABORATORY CLASSIFICATION CRITERIA
WELL GRADED GRAVELS. GRAVEL�SANO
Cu = (C60 1 010),Tdatvr�4
CLEAN
GW
MMMRF UTTLE OR NO FINES
DETERMINE
G_ LOW) INA0 - 06M la�n I and 3
GRAVELS
PERCENTAGES OF
Gp
POORLY GRADED GRAVELS. AND GRAVEL -SAND
NOTMEETINGAEOVE LRENIENTS
GRAVELS
ottil. n,
GRAVELMOSAND
(Men, The, H.Lf
fl—)
A, D(TURGS UMEOR NO FINES
FROM AIM SIZE
C
COARSE.
G.BC,LB
C—enGal�.
DISTRIBUTION
GINTY
Gm
SILTY GRAVELS, GRAVEL.AnIMSILT MIX'FURES
ATTEROER BELOW
A�UNFF
L.G. Tlea. No. 4
CURVE
SI—)
GRAVELS
CONTENT
. RLLSSS THAN 4
�S
OF FINES
EXCEEDS - 12�
ATTERBERG UNITS A13OVE
GO
CLAYEY GRAVELS, GRAVEL -SAND -CLAY
COARSEGRAINED
VUNE
An.)
MMMFEG
SOILS ARE
e, ILL.R... I
CJSSIFIED AS
FOLLOWS
WELL GRADED SANDS, GRAVELLY SANDS.
C. = mm I D10) greater ft. a
SANDS
CLEAN
SANDS
sw
LITFUE OR No FINES
C, PW) 1 (010 - OR ludwaen I and 3
(M.. Th.. HALF
C— G.I.
vottle ar n.
� 5% sn, Gmi,ed:
SP
POORLY GRADED SANDS. GRAVELLY SANDS.
NOT MEETING ABOVE REKILIN194ENTS
S,n.11.'Than N.,
N—)
UTTLEORNOFINES
GW, GP, M. Ste
A78ERG LIMITS BELOW
4SI—)
DIRTY
SNI
SILTY SANDS, $ANDSLT MIXTURES
T2% Ft. tLlI;d:
SANDS
Gm, GO, S _
S W 12% R-
GO = OF
EXCEEDS 12%
W. P.L LEW THAN 4
G LIMITS ABOVE
SO
CLAYEY SANDS, SAND.CLAY MDDURES
wth
G.Ined: .. deal
-fir UNE
fin.)
I
mw.
with PlMORSTHAN 7
SILTS
Uqld U.4
INORGAMOMLTSROCKFLOUR,SA OYSILTS
Load- ALIn. -
�W%
IAL
OF SLIGHT PLASTICITY
No
Ptaat�ay Chem
—
—
RNE4RAINED
N"1191M.
Liquid Limit
MH
INORGANIC SILTA M[CACMUS OR
So
SOILS
Oqpane)
CHATOMACEOUS. FINE SANDY OR SILTY SOIL
—
9
'NO ANIC CLAYS OF LOW PLASTICITY.
Ao
CLAYS
Ud Lnnft
CL
GRAVELLY, SANDY. OR SILTY CLAYS. CLEAN
(Ab— A�Une
30%
CLAYS
Plasocilychart
---
U�Wd Urnft
INORGANIC CLAYS OF HIGH PLASTICITY, FAT
N.90911da
50%
CH
CLAYS
20
Then it.—
'Th'a"Ne—
L�`d U' a
-
OL
ORGANIC SILTS AND ORGANIC SILTY CLAYS OF
A.
.2m
ORGANICSLTS&
CLAYS
So,
LOW PLASTIC"
Llquldu.ft
� Both
ON
(Bal—ALl-
PlealkityCh.ftl
—
o I . . . 40 So SO 70 No So I- I'LL
HIGHLYORGANIC ILS
Pt
PEATAND OTHER HIGHLY ORGANIC SOILS
LIQUID LIMIT (%)
SOL PARTICLE SIZE
GENERAL GUIDANCE OF SOIL ENGINEERING
PROPERTIES FROM STANDARD PENETRATION TEST ISPT)
U.S. STANDARD SIEVE
FRACTION
PassIng
Retained
SANDY SOILS
SILTY & CLAYEY SOILS
Steve
size
III-
R.4.6"
Frictien
III—
U—Sual
(Fron)
C—%
N
Denalty
%
Mgt
4. dN—
D,.dpd..
Dean.
SN--p
q., hi
0.,4.Pd.A
SILTICLAY
N20WD
0.0
SAND
Fleve
0.4
0.15
Vrf Looen
�2
NILS
Vaq anN
FINE
m
0.425
W40
0.075
4.10
IS-35
0.30
2-4
0.25-0.50
Sao
MEGRIM
010
200
040
0.426
10-30
M-65
28-�
Medin. D—
4.8
O.M. 1.00
Medim SO
COARSE
N4
4.75
emo
2.00
W-50
� 50
65-85
85-100
35-42
w-`6
D.—
VmDenee
8-15
16-30
140-zoo
ZOO - 4.00
SUN
Vety S'"
GRAVEL
—
FINE
19
#4
4.76
I
4.OD
Hand
Group Northwest, Inc
COARSE
76
19
COBBLES
76 "'f"
13OULDERS
RCCX
FRAGMENTS
132Q RE 2ft SVaet Bede 12 Self —WA 98005
Phene (4�) 84"757 Fee (425) UM755
PLATE
-0.70.bk-11nW.—
ROCK
BORING NO. B-1
Page I of I
Logged By: —KJ DateDrilled:- 5/18/99 Surface Elev. 310 feet +/-
Semple
Blow
Water
Depth
USCS
Description
I
Count per
Content
Other Tam &
ft.
Code
6-inches
%
Comments
a
—T;;�
No.
Lavrn surf=
SI
9�20,20
2.2
Blow wants afte, led
SP-
(N=40)
by tree root near
SM
SAND to SILTY SAND, damp, medium dense, fine grained sand
9.0
surfitee.
10- 15% fines, little subrounded gravel, dark brown (becarnes
S2
SP-
at 2 fiec�).
(N=22)
SM
iLK ;;n;,-m-e de-nae,-& gm-in-c -d -=- - - - -
-gr-ay
S3
7.3
S P
d i-m- on d-, i a h b to wn.
SP
As above, dcnsc� fine to medium grained sand, tram gravel,
S4
10,14,18
8.0
occasional leases ofwell graded silty sand,
(N=32)
10
Sp
As above, brownish gmY, trace coarse sand and gravel.
SS
13,19,20
(N=39)
7�8
sp
As above, very dense, line grained sand.
S6
21,30,34
8.7
20
Sp
As above.
S7
29,50/3"
7.4
25
Sp
As above.
-T
32
62
8
(n-,50
_50+)
30
SP
As above, very fine to fine grained, V thick silty sand lens in
sample.
23,28,50
Sq
(N=78)
6.4
Bottom ofboring: 31.5 ficeL
35
Drilling Method: Hollow-stemauger (Portable).
Sampling Method: 2-inch-O.D. standard penetration sampler
driven using a 140 lb. hammer with a 30-inch drop.
No groundwater encountered during drilling.
LEGEND: T 2* O.D. Splft-Speon Sampler GROUNDWATER a
T 3- O.D. Shelby -Tub. Sampler OBSERVAT70N WELL: water level
F.e'll
3- O.D. California Sampler up
BORING LOG
00 Group Northwest, Inc.
PROPOSED RESIDENTIAL DEVELOPMENT
1449VI
SEQUOIA RIDGE SHORT SUBDIVISION
Geotmfuleal Edgla� G010915% &
Environmental Sctudists
EDMONDS, WASHINGTON
6—
__g-_10611 DATE 120/99
JOB NO. __L_ I PLATE:�:j
z
n
M
C
M
0
-4 C)
C
M
0-4
P4
4 FE
MM
0
0 Fn
C V)
M C)�
z
M
z
z
M,
BORIING NO. B-2 Page I of I
Logged By: Ki Date Drilled: 5/18/99 Surface Elev. 285 feet
Depth
USCS
Description
Sarnpl.
Blow
Count per
Water
Content
Other Tests &
It.
Code
6-inches
%
Commeras
T
No.
SM
Ivy landscaping, SILTY SAND, bmwiL damp, loose, 10-15%
§1
3.2�2
13.6
Wet endings
gravel.
(N-4)
encountered at about
SM
SILTY SAND, damp, medimn do -me, fine grained sand, 10-15%
S2
3.1's
11.7
3 lbet during drilling
(apeeted perched
fines, little subrouraded gravel, gray.
(N=6)
water zone
5
SM
SILTY SAND with gravel, damp, dense, fine grained sand,
S3
14,15,25
9.5
encountered).
olNc gray (GLACLAL TILL).
(N�40)
SM
As above, very dense,
S4
39,26,35
(N�61)
9.1
to
SM
As above, poor sarnpler penetration due to mck.
S5
3250
(N=�61)
Drilling refusal at 13 fact.
Bottom ofboring: 13 feet
Drilling Method: Hollow-sternauger (portable).
Sampling Metho& 2-inch-O.D. standard petuaraction sampler
driven wing a 140 lb. harmater with a 3D-inch drop.
Minor groundwater seepage noted around 2 feet during chilling.
30
35
III III I I
LEGEND: T 2" O.D. Split -Spoon Sampler GROUNDWATER
3- O,D. Shelby -Tub. Sampler OBSERVATION WELL:
3- OM. California S—pia
BORING LOG
Group Northwest, Inc.. pROpOSED RESIDENTIAL DEVELOPMENT
SEQUOIA HEDGE SHORT SUBDIVISION
Gonecketcal Eugta� Geolughb, & EDMONDS, WASHINGTON
fro,koomeeftl Scicutis" JOB NO. -1 61 DATE 5120/99 PLATE A3
Z'
0
0
M
"n
M
a
M
0
M,
M z
C
>Z
0 -n
.n
mm,
0 Fn
C (A
ma
Z'
0
M
BORING NO. B-3
Page I of I
Logged By: KI DateDrilled: 5/18/99 Surface Elev. 255 feet
Depth
USCS
Description
I
S—ple
Blow
Countper
Wrarr
Content
Ono,rTests&
&
Code
6-moh.
%
C—ts
1�
—
No.
Sp
Ivy surfk= SAND, dark yellowish brown, damp, fave grained
Sl
1,1,1
16,6
i 0 C.
n - - - - - - - - - - - - -
(N-2)
SM
- - - - - - - - - - - - - -
SILTY SAND, moisL medium dense, fine grained sand with
5,87
11.2
gravel, brown.
S2
(N=i5)
- - -
- - - - - - - - - - - - - - - - - - - - - - - - - -
-;;
S3
27,12,13
9.3
Sample at 5 feet
Sp
I';. p'-M
� lum dense, fine grained sand, brown.
(N=25)
affected by water
added to hot..
SP
As above, very dense, fine to medium grained sand, grayish
S4
15,25,26
6.6
brown.
(N=5 1)
10
Sp
As above, maist, medium dense, silty sand lease at bottom of
9,12,17
11.5
sample, brownish gray.
(N=29)
Sp
As abovc� downp, dense, free grained sand, gray.
Sri
12,17,29
(N-t6)
12.9
SP
As above, very dense, moist.
S7
1927,33
8.0
(N=60)
25
Sip
As above, damp.
25,34,4S
S&
(N-79)
6.3
30
SP
As above, well, very fine to fine grained sand, 5% fines.
28150
Groundwater
S9
(N-50+)
24.5
emuntered at 29 to
30 feet during
Bottom ofboring: 31 fed,
drilling.
35
Drilling Method: Hollow -stem auger (portable),
Sampling Method: 2-inch-O.D. standard penetration sampler
driven using a 140 lb. hommer with a 30-inch drop.
Groundwater encountered at approximately 29 to 30 feet during
drilling.
LEGEND: 2* OD, Splft�Spoan Smplrr GROUNDWATER seat
3"O.D. Shalby-Tube S—plar OBSERVA71ON WELL: -��Maaauredvtirterkvrl
3- O.D. California Sampler wrll tip (s..n)
BORING LOG
ro*1 Group Northwest, Inc.
PROPOSED RESIDENTIAL DEVELOPMENT
SEQUOIA RIDGE SHORT SUBDIVISION
Gwtedwiml Englatem Geologirn, &
Sdentins
EDMONDS, WASHINGTON
JOBNO. G-1061 DATE 5/20/99
P"
A"
z
M
0
0
M
C4
0 -n
3:
M M
a 6V
0
0 Fn
Co
Q 0
z
z
W
z
0
0
M
r,
BORING NO. B-4 Page I of I
Logged By: KJ Date Drilled: 5/19199 Surface Elev. 215 feet
Depth
USCS
Description
Sampt.
Blow
Count per
W.I.,
Content
OtherTests&
C.—ems
T
No.
I,
Code
6-in6hes
%
Sp
Forest duff surface. SILTY SAND, damp, loose, fine grained
I
Sl
1,1,3
32.1
..............................
(N=d)
- - - -
SP/
SAND and SILTY SAND, moist, loosc� finegraincil sand,
S2
5,4,4
14A
SM
mottled brown and gray.
5
---------------------------------------
SM/
SILTY SAND and SILT, moist to wet, medium dense, gray and
S3
3,4,7'
(N=11)
33.3
Possible thin perched
water zone at about 6
brown with reddish oxide staining, silty sand is micaceous,
feet based on
ML
occasional fine sand layers (without fines).
ML
SILT, damp to moist� stiff, reddish oxide staining, olive gray.
S4
8,7,9
(N=16)
31.6
obs"Med Wet
cutting$.
to
ML
As above, damp, very stiff, no oxide staining, some very thin
S 5
7,12,16
(N=28)
34.3
vertical fine sand laminae and occasional powdery horizontal
laminae, occasional wet fine sand lenses I to 2" thicL
Is
- - -
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
S6
15,17,22
(N=39)
217
SP-
dump, dense, 10-15% lines, very fine to fine grained
Sm
20
---------------------------------------
SrvV
SILTY SAND and SILT, dense, very fine sand is wet "ce mica
S7
1417,27
32.5
ML
and lines, silt is dump and laminated to thinly bedded, gmy.
25
----------------------------------------
SM
SILTY SAND, we4 dense, very fine grained sand, occasional silt
SS
17�23,25
25.6
----------------------------------------
lenses. gray,
(N--48)
30
SW
SILTY SAND and SILT, very dense, sand is very fine to fine
ML
grained and wet; silt is damp, gray, gravel clast in sand lcrus.
S9
35,50/5'
33.9
(N--,50+)
Bottom ofboring: 31 feet
Drilling Method: Hollow -stem auger (portable).
35
Sampling Method: 2-inch-O.D. standard penetration sampler
driven using a 140 lb. hammer with a 30-inch drop.
Suspected thin perched groundwater zone encountered at
proximately 6 feet during drilling; most send layers observed
to be wet, but no flowing water.
LEGEND: T 2'O.D. Split -Spoon Sampler GROUNDWATER Isew
T 3'O.D. Shelb�,T.b. Sionpler OBSERVATION WELL: 4--Kz- measured water level
JE YOO. C.lifomi. Seenple, well up onneen)
BORING LOG
PROPOSED RESIDENTIAL DEVELOPMENT
SEQUOIA RIDGE SHORT SUBDIVISION
EDMONDS, WASHINGTON
Group Northwest, Inc.
G I.W.1 fte—, G.I.&M
F—i—tal Sdenfla,
JOB NO. G-1061 A 1, 5/20199
M
C M
,a
0
-10
0 C
M M
C
0
In M
0
0 Fn:
C 0)
C U)
.1�
rr 0
Z
M
Z�
Z
0
DI
j
N Cc
UNITC
to
UNITR
UNI;T �A,,
to t
yj
to jt
It
ZIApkiTr
to to to
of,
Nr
I /
to to I I I,
NUMBER AND APPRO)OMATS
to 1 v LOCATION OF HAND AUGERS
a ft
UNirA LETTE ING SYSTEM BY 14CA
R
FOR DESCRIPTIVE PURPOSES
PROPOSED 72nd AVENUE WEST
a too 'JOHNSON -Til- URI 2
PLAN CREATED FROM UNTffLED AND UNDATED PLAN Lj H LE
VIDEDTO US BYLOVELL-SAUERLAND 16 ASSOCIATES, INC. to, I)ATE
MARCH 1998
----------
SOIL CLASSIFICATION SYSTEM
MAJOR DMSIONS
GROUP
SYMS& GROUP NAME
�ARSE
GRAVEL IT��WIAVEL
GW WELL4MED WvFL, FINE TO COARSE
GRAVEL
GRAINED
GRAVEL
16001AVEL
GP POORLY -GRADED
SOILS
WITH FINES
GM SILTY
GC MAYEY GRAVEL
SAND CLEAN SAND
SW WELL-GRAGEO SMO. FINE TO COARSE $AND
SP POORLY -WADED SAND
FMACTM PAS=
SM S1L`rY SAND
SAND
VATH FINES
sc CLAYFEY SAND
FINE
SILT AND CLAY INORGANIC
ML SILT
GRAINED
LIOWLW
CL CLAY
ORGANIC
OL ORGANIC SILT. ORGANIC CLAY
SOILS
MH SILT OF IjIQIj PLA=C�RY. ELAS= SILT
SILT AND CLAY INORGANIC
MY"'T
UMMIAWSSORNAM
CH CLAY OF HM PLAsmorTY, FAT c4AY
ORGANIC
_y7w SILT
Ott ORGANIC CLAY. OR—= $LT
HIGHLY ORGANIC SOILS
PT PEAT
NarES:
SOIL m61sTuRE moatFiERs
1)
Field dasWffcNon Is based an
Dry - AbsenOe.of moisture. dusty. dry
visual exambuvion of son In geneml
to the touch
accordance with ASTM D 2488-83.
MOW . Damp, but no visIble water
2)
Soil classification using laboratory
tests is based an ASTM D 2487-83.
Wet - Visible fte water or saturated.
: usually soil is obtained from
3)
DcscdpUonS of soil density or
below water table
consitency are based an
Interpretation of blowcourd date.
v1su., ance of —'I. andlor
test date.
NELSON-COUVR IIE&ASSOCIATESAC. SOIL CLASSIFICATION S-EYSTEJM�
CWW-WM GEON� EN 9= &Sr
FIGURE 3
z
In
rn
-40
0 C
m m
0 -n
mm
0
00]
C
9 co
rn 0
z
co
z
0
m
06/30/1998 09:29 4254812510
NELSON-COLIVE= PAGE 17
LOG OF EXPLORAMON
OEM use
SM DESCRIPTION
HAM JMIGM ONE
"-&4
BRANCNES, STICM AMC DUFF (VERY 1,0091� MMTJ
OA - 1.7 SP4M
13RMN FINE TO MEDIUM SAND WITH SILT. TRACE ROOTS AWL) QRAVM
"OSE TO MEDIUM DENSE. MOIST)
V-22 SP
'DIUM! SAND WITH SUVEL. SCATTERED COBBLES AND TRACE
BROWN ME
SILT (LOOSE TO MEDIUM DENSE, MOIST) Po)
SAMPLES WERE COLLECTED AT 12 -IJANO 1.9- 23 FEET
GROUND WATER SEEPAGE WAS NOT ENCOUNTERED
HAND AUGER WAS COMPLETED AT Z3 FEET ON 3161116
NANDAUQERTA0
CLO - 2A SP
UGNT BROWN MEDIUM SAND WM TRACE SILT AND ROOTS (LOOSE TO
MEDIUM DENSE, MOWn
U-33 SP
TAN -GRAY MEDIUM SAND WITH TRACE SILT PEDIUM DENM MCIST) (Q&)
SAMPLES WERE COLLECTED AT 1 -1 - 1.0 AND 2.8 - a2 FEET
GROUND WATER SEEPAGE WAS NOT Ew=wrERFD
HAND THMM
HAND AUGER WAS COMPLETED AT 35 FEET ON SAW
AUGM
OA-10 Sp
LOU BROWN MEDIUM SAND WfM TRACE GRAVEL AND MT (LOOSE,
DAMPTOMOwr)
20-3.0 SIP
TM -GRAY MEDIIUM SAND " TRACE GRAVEL AND SILT &OOSE TO
MEDIUM OEM GRADES TO MEDIUM OENSF- MOIST) (Qv)
SAMPLES WERE COLLECTED AT 1.5 - 20 AND 25 - 2.9 FEET
GROUND WATER SEEPAGE WAS NOT ENCOUNTERED
NANO AUGER WAS COMPLETED AT 3A FEET ON 31SW
HANDAUGERFOUR
MO-0.2
DUFF
62-CLS Sp
LIMIT BROWN MEDIUM SANO WITH TRACE SILT IVERY LOOSF— Imy To
MOIST) (SLOPE WASH)
f OA-12 ML
tiARx BROWN To wAcK opi4wc sAwDy SILT (sm, DAMP TO Mown
"IEDTOPsOu.)
12-45 SP
LIMIT BROWN MEDIUM SAND WrTN TRACE GRAVEL AND SILT (LOOSE TO
MEDIUM DENSE GRADES TO MEDIUM DENSE. MO" (Q.)
SAMPLES WERE COLLECTED AT ILG - I A AND 413 - 46 FEET
GROUND WATER SEEPA09 WAS NOT ENCOUNTERED
HMO AUGER WAS COMPLETED AT 45 FEET ON MW
DUFF
SM
uGw Gmy RusT BROWN *mnEo siLTY mE To mFoium SAND WITH
GRAVELAND SCATTERED COBBLES (MEDIUM OgNSE, Man MR)
SAMPLES WERE COLLECTED AT 1.3- 1.3 AND 2.0-74 FEET
GROUND WATER WAS NOT ENCOUNTERED.
HAND AUGER WAS COMPLETED AT 2.5 FEET ON 310M
RIELSON-COUVRIETTE ASSOCATES,
RLE NO. '145M
FIGURE4
z
0
=4
a M
I I
c I
.
0
oc�
M
10-4
03
M M
0
o Fn
M C)
Z�
;U
z
co
z
0
M
ARCO,
Association of Rockery Contractors
ASSOCIATION OF ROCKERY CONTRACTORS
STANDARD ROCIIMRY CONSTRUCTION GUIDELINES
25
0
i.oi introduction
1.01.1 Historical Backaround, These standard rocIzery
construction guidelines have been developed in an effort
1
-4
to provide a more stringent degree of control on rock-ry
materials and construction methodology in the Pa=ific
C
MO
Northwest. They have been assembled from numerous other
0
-40
standards presently in use in the area, from expertise
0 c:
E Ell
provided by local gectechnical engineers, and from the,
i
Fn
wide experience of the members of the Rssociation of
M
Rockery Contractors (ARC).
1.03-2 Goal: The primary goals of this document are to
standardize the methods of construction, and to provide a
0 -n t'�,
warranty for the materials used in construction and the
n La
workmanship employed in construction. This standard has
-4-
alsc�, been developed in a manner that makes it, to the best
MM
of ARC's knowledge, more stringent than the other stan-
0
dards presently in use by local municipalities.
0 Fn
C
W
K
2.01 Materials:
M
2.01.1 Rock Ouality: All rock shall be sound, un-
weathered, weathering resistant, angular ledge rock. The
longest- dimension of any individual rock should not -exceed
three times its shortest dimension. Acceptability of rock
Z
will be determined by laboratory tests as hereinafter
specified, geologic examination and historical usage
records.
Z
All rock delivered to and incorporated in the project
M
shall meet tho following minimum specifications:
a. Absorption
(Corps of Engineers CRD-C-107) Not more than 3.0%
b. Accelerated Expansion (15 days)
(CRD-C-148) Not more than 15%
breakdown
P.O. a Ox 1794, Woodinville. Washington 9807� (206)481-3456. or (206)481-7222
Association of Rookery Contractors Page 2
Standard Rookery Construction Guidelines
The test sample will be prepared and tested in accordance
with corps of Engineers Test ing procedure CRD-C-148,
k
"Method of Testing Stone for Expansive Breakdown on
Z
0
Soaking in Ethylene Glycol." Test requirements of not
more than 15 per cent breakdown will be computed by
0
M
dividing the number of individual pieces of initial sample
suffering breakdown (that is, separating into two o;: more
pieces) by the total number of initial pieces in the
sample.
M
C
MO
c. Soundness
(MgSO4 at 5 cycles) Not greater than 5%
(CRD-C-137) loss
3:,
M M
2.01.2 Frecruency of Testing. Quarry sources for rockery
either becoming a
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ID
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rock shall begin a testing program when
supplier or when a new area of the sourc e pit is opened.
The tests described in Section 2.ol.1 shall be perf,.)rmed
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for every four thousand (4000) tons for the first twelve
thousand (12000) tons of material blasted and removed to
The' tests shall then
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establish that specific -rock source.
at an appar ent change in
be performed once a year or
material. If problems with a specific area in a pit or
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with a particular material are encountered, the initial
testing cycle shall be restarted.
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Recognizing that numerous sources
vary not
of rock exist, and th at the nature of rock will
the
only between sources but also within each source,
hundred fifty-
Z;
density of the rock shall range between one
hundred sixty five (165) pcf. Typical -
five (155) and one
ly, rocks used for rookery construction s hall be sized
Z
appro ximately as follows:
Rock Size Rock WeIg
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Small One Man 58
Large One Man 210
Small Two Man 265
Large Two Man 580
Small Three Man 760
Large Three Man 1830
Small Four Man 3000
Large Four Man 4000
Five Man >5000
Six Man >7000
I
Association of Rockery Contractors Page 3
standard RockerY Construction Guidelines
rock, and sometimes smaller, are of�_en used to fill
Two and one-man Om rookery to create an
the c
surface gaps along the top of pleted
surface. This is an acceptable practice
pleasing
aesthetically section 3.01.5 occur, and
the events described in
Z,
provided none of
r prevents people from climbing or walking on the
that the owne
completed rookery.
M
In rookeries over eight feet in height, it should not be possible to
with a prybar. If
move the large sized roc ks (four to six -man size)
the rookery should not be considered
Fo
CIM
s can be moved,
these rock an ignificant lateral load. However, it is
y
capable of restraining s particularly
rocks,
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even desirable. that smaller
both practica2 and th a prybar to
be moved wi
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those used for "chinking" purposest can
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achieve the "best fit"-
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2.0j.4 _Submittals: The rock source shall present current
testin� r described in
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or most recent, test data for the
2.01.1 on request by either the rockery contrac-
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section
tor, the client or the applicable municipality-
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3.01 Roo v Construction
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struction is a craft and
3.01.1 General: Rookery con ience of the
and eXPer
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depends largely on the skill
I tective system which helps to
is a
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A rookery pro
builder. an an exposed
�ring and erosion process
weathe
retard the
cut or fill soil face. Whil e by its nature (the mass,
some degree
t will,provide
size and shape of the rocks) i aered system in
it is not a designed or engini
X
retention,
of wall would be
concrete retaining'.
sense a reinforced
the de ree of reten
con idered designed or engineered. The
s r�)ck used; that
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tion achieved is dependent on the size Of
the height of the wall being
is, the mass or weight, and
The larger the rock, the mor a competent the
of four
Z
9
constructed.
wall. To accomplish this, all rockeries in excess
"mass" basis.
0
feet in height should be built on a
M
constructed in front of cuts and fill$ in
All rockeries in
be constructed
excess of eight feet in height should
this standard and the
accordance with cgeotechnical
supplemental recomm endations whi h should be
The
neers
engi nstruction.
provided before bidding or the start of cc
to monitor
geotechnical engineer should be retained
same the
in writing, that
rookery construction and to verify,
tructed in general accordance with this
in
rockery was* cons mmendations,
ARC standard and with his supplemental reco
suitable mater-
a professional manner and of competent- and
ials.
Association of Rockery Contractors Page 4
Standard Rockery Constru ;tion Guidelines
Geotechnical Encrineer- The geatechnical engineer
3.01.2 . supplemental rockery
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to provide necessary
retained be a practicing geotech-
guidelines shall
construction
licensed as a professional civil
nical/civil engineer least four
has at
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engineer in the State of Washington who
employment as a geotechnical
=1
years of professional
engineer in responsible charge, including experience with
55
a
fill construction and stability and rockery constructicn.
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Tile geotechnical engineer should be hired either by the
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rookery contractor or the client.
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Responsibility: The ultimate responsibility for
the
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rookery "design" and construction should remain with
protecting moderate
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builder. However, rookeries
rockery h steep sloping surfaces above or helow
thick fills, wit
to
them, with multiple steps, with foundation or other loads
0 r soils subject
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affecting them, protecting sandy gravelly
wet conditio ns, or that are
to ravelling, with seepage or
-ant special
in height, all repres
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than eight feet
more Itation and/or advice from
conditions and require consu
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qualified experts.
a co
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3.01.4 Workmanship: All workmanship is guaranteed by the
by
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rockery contractor and all materials are guaranteed
for a period of six years from the date
5
supplying quarry
of completion of erection, prov-iding no modification or
changes to the condi tions existing at the tim a of comple-
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tion are made.
to I Product: Such changes
3.01.5 Changes _.!I, n �is h a d�q 1�3� of
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ot n,7-essarily limited to, excavation
include, but are n less than 1. 5
a distance of
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ditches or trenches within
times the rockery height measured from t he toe of the
subgrade in
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removal of any material from the
rookery, removal of
and/or
excavation
front of the rockery, a
from any location behind the rockery within
material Is height, the
distance at least equal to the rockery
loads within a similaz
addition of any surcharge or other
"kery, or surface or subsur-
distance of the top of the roc flow
face water forced directed, or otherwise caused to
behind the rockery in any quantity.
Association of Rockery Contractors Page 5
Standard Rockery construction Guidelines
slopes above rockeries should be kept as
3.01.6 SloPe :
flat as possible, but should not exceed 2:1 (Horizon-
tal:Vertical) unless the rookery -is. designed specifically
to the load imp6sed by the
to provide some restraint
leted rookery
slope. Any slope existing above a comp
cover by the owner to
should be provided with a vegetative
tential for surface water flow induced
help. reduce the po
0 deep rooted, rapid growth
erosi n. It should consist of a
vegetative mat and typically will be placed by hydroseed-
ing and covered with a.mulch.
It is often useful t6 overlay the. seed. and mulch with
either pegged in -place jute matting, or so . me other form of
to help maintain the seed
approved geotechnical fabric,
in -place until the root mat has an opportunity to ger-
minate and take hold.
3.01.7 Monitori All rookeries constructed against
cuts or fills in excess of* eight feet in�haight shall. be
periodically monitored during construction by the geotech-
nical engineer to verify the nature and quality of the
materials being used are appropriate,. that the construc-
tion procedures are appropriate, and that the wall is
being constructed in a generally professional manner and
in accordance with this ARC standards and any supplemental
recommendations.
the geotiechnical engineer
on completion of the rookery, ractor, and to
shall -submit to the client, the rockery cont his rockery
the appropriate mun�.,tipality, copies 'of
rt summarizing
examination reports aY6ng with a final repo
rockery construction.
3.01.8 Fill compaction: Where rockeries are constructed
in front of a fill,, it is imperative that the owner ensure
fill be placed and compacted in a manner that will
the To achieve this goal,, all
provide a competent fill mass.
clean, organic and
fills should consist of relatively Of
debris free, granular materials with a maximum size
articularly if pdacement and
four.inches. Ideally, but P u
compaction is to take. place d ring the wet season, they
ld contain no mar'-d' than five percent fines (silt and
shou
passing the number 200 mesh sieve) -
clay size particles
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Association of Rockery contractors Page 6
Standard Rookery Construction Guidelines
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01
All fills should be placed in thin lifts not exceeding ten
0
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inches in loose thickness. Each lift should ' be compacted
to at least 90 percent of the maximum dry density, as
%
determined by ASTM Test Method D-1557 -78 (Modified
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Proctor), before any additional fill is placed and
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compac ted. In -place density tests should be- performed at
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random locations within each lift of the f ill to verify
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this degree of comp action is being achieved-
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3.01.9 Fill Construction a Reinforcement: There are
A
10
two methods of constructing a fill. aSainst which to build
c: —Z
a rookery. The first, which typically applies to rock-
eries of less than eight feet in height, is to overbuild
and then cut back the fill. The second, which applies to
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all rookeries in excess of eight feet in j�eight, is to
echnical fabric
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4
construct ths fill using a geogrid or geot
reinforcement.
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overbuilding the fill allows for satisfactory compaction
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of the fill mass out beyond the location of the �fill face
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to be protected. overbuilding also allows the earthwork
contractor to use larger and more effective compaction
equipm ent in his compactive efforts, thereby typically
achieving a more competent fill mass. Cutting back into
the well compacted fill also typically results in con-
face against
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struc tion of a competent near vertical fill
-4
which to build the rockery.
For the higher rockeries the use of a geogrid or geotech
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nical fabric to help reinforce the fill results in
0
construction of a more stable fill face against which to
M
construct the rockery. This form of constru ction leads to
a longer lasting and more stable rookery and helps reduce
the risk of signifi�ant long term maintenance.
This latter form of construction requires a design by the
The
geotechnical engineer for each specific case.
the specific type
vertical spacing of the reinforcement,
of reinforcement, and the distance to which it must extend
back into the fill, and the amount of lapping must be
determined on a rockery -by -rockery basis.
Association of Rockery Contractors
Standard Rockery Construction Guidelines
Page 7
3.01.10 Rockery KeyXav: The first step in rockery
construction, after general site clearing and/or general
ekcavation, is to construct a keyway in which to build the
rockery. The keyway shall comprise a shallow trench of
between twelve (12) and eighteen (18) inches in depth,
extending for the full length of the rockery, and inclined
back slightly towards the face being protected. It is
typically dug as wide as the rockery (including the width
of the rock filter layer).
If the condition of the protected face is of concern, the
keyway should be constructed in sections of manageable
length, that is of a length that can be constructed in one
shift or one days work.
The competency of the keyway subgrade to support the
rockery shall be verified by probing with a small diameter
steel - rod. The rod shall leave a diameter of between
three -eights and one-half inch, and shall be pushed into
the subgrade in a smooth unaided manner under the body
weight of the prober only.
Penetration of , up to six inches, with some difficulty,
shall indicate a "competent" keyway subgrade unless other
factors in the geotechnical engineer's opinion shall
indicate otherwise. Penetration in excess of six inches,
or of that depth with ease, shall indicate a "soft"
subgrade and one that could require treatment. Soft areas
of the- subgrade can be "firmed up" by tamping a layer of
coarse quarry spalls into the subgrade-
3.01.11 Kejn�av a d Rockery-Drainacie: On completion of
keyway excavation, a shallow ditch or trench, approxi-
mately twelve (12) inches wide and deep, should be dug
along the rear edge of the keyway. A minimum four -inch
diameter perforated or slotted ADS drain pipe, or equiv-
a;ent approved by an engineer, should be placed in this
shallow trench and should be bedded on and surrounded by a
free -draining crushed rock. Burial of the drain pipe in.
this shallow trench provides protection to the pipe and
helps prevent it from being inadvertently crushed by
pieces of the rockery rock. This drain pipe should be in
stalled with sufficient gradient to initiate flow, and
should be connected to a positive and permanent discharge.
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am
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Association of Rookery Contractors Page 8
Standard Rockery Construction Guidelines
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Positive and permanent drainage should be considered to
mean an existing, or to be installed, storm drain system,
a swale, ditch or other form of surface water flow
collection system, a detention or retention pond, or other
stable native site feature or previously installed
collection system.
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3.01.12 Rockery Thickness:. The individual -�rockery
M 0
-4
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thickness, including the rock filter layer, should be at
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least 40 percent of the rocker height. Unless otherwise
specified in writing, the individual rocks should be
arranged in a single course which, when measured to
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include the filter layer, is equal to the required rookery
:�
thickness.
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3.01.13 Rock Selection: The contractor should have
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sufficient space available so that he can select from
ME
mm
among a number of stockpiled rocks for each space in the
j,
rockery to be filled. ' Rocks which have shapes which do
not match the spaces offered by the previous course of
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rack should be placed elsewhere to obtain a better fit.
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Rock should be of a generally cubical, tabular or semi-
Z
rectangular shape. Any rocks of basically rounded or
X
tetrahedral form should be rejected or used for filling
large void spaces.
Smaller rocks (one to two -man size, or smaller) are Often
used to create an aesthetically pleasing ,top edge" to a
rookery. This is acceptable provided none of the events
Z
J�
described in Section 3.01.5 occur, and that people are
prevented from cl imbing or walking on the finished
rookery. This is the owner's responsibility.
M
3.01.14 Rock P�acement* The first course of rock should
be placed on firm unyielding soil. There should be full
contact between the rock and soil, which may require
shaping of the ground surface or slamming or dropping the
rocks into place so that the soil foundation conforms to
the rock face bearing on it. As an alternative, it is
satisfactory to pl ace and tamp crushed rock into the
subgrade to tighten it up. The bottom of the first course
of rock should be a minimum of twelve (12) inches below
the lowest adjacent site grade.
Association of Rookery Contractors Page. 9
standard Rockery Construction Guidelines
As the rockery is constructe(4, the rocks should be placed
so that there are no continuous�joint planes in either the
vertical or lateral direction. Each rock s hould bear on
0
at least two rocks below it. Rocks should be placed so
-1
that there is scme bearing between flat rock faces rather
M
than on joints. Joints between courses should slope
downwa rd towards the material being protected (away from
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the face of the rookery).
3.01.15 Face Inclination: The face of the rocYery should
M
CO
MO
be inclined at a gradient of about 1:6 'Hori-zontal:-
0
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back towards the face being pr otected. The
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Yertical)
incli nation should not constructed flatter than 1H:4V.
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3.01.16 Voids: Because of the nature of the product used
'0-4
to construct a rockery, it is virtually impossible to
>
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avoid creating void spaces between individual rocks.
it should be re that voids do not
However, cognized
in construdtion.
O-n
necessarily constitute a problem rockery
Where voids of greater than six inches in dimension exist
M M
in the face of a rookery they should be vi sually examined
a 6
0
to determine if contact between the rocks exists within
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the thickness of the rookery. If contact does exist, no
(D
- there is no rock
further action is required. However, if
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contact within the rockery thickness the void should be
"chinked" with a smaller piece of rock. If a. void of
greater than six inches exist s in the rear face of the
rockery, it should be "chinked" with a smaller rock.
3.01.17 Filter LayeM! In order to provide some degree of
drainage control behind the rookery, and as a means of
helping to preven t loss of soil through the face of the
rockery, a drainage filter shall be i nstalled layer
between the rear face of the rockery and the soil face
M
being protected. This filter layer shou id be at- least
twelve inche s thick; and for walls in excess of eight
(12) (18), inches
feet in height, it should be at least eighteen
four inch minus 'crushed
thick. It should be composed of
approved by th e geotechnical
rock, or other material
engineer.
If one of the rockery rocks extends back to the exposed
soil face, it is not necessary that the filter rock layer
exten d between it and the soil face.
Association of Rockery Contractors Page 10
Standard Rookery Construction Guidelines
In the event seepage is encountered emanating from a
protected face, we recommend the use of a well -graded
Z�
filter layer. We do not recommend the use of* a geotech-
0"
-4,
nical fabric for other than coverage of relatively small
and isolated seepage areas because it has been the
industry's experience that the filter fabric tends to clog
rapidly. This quickly leads to a buildup of hydrostatic
1
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pressure which can subsequently cause failure and collapse
of the rookery and is to be avoided.
M
0
This clogging is apparently due to the virtual- impos-
-40
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sibility of achieving full contact between the soil face,
fabric and rock filter material. If full surface contact
M
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cannot be achieved, there is often a tendency for the soil
0-4
materials to flush from the protected f ace into the
a _��
Z
"pockets" in the fabric which leads. to the a forementioned
clogging,
M.
3.01-18 Surface Ora nage: it is the owner's respon-
.4
sibility to intercept surface drainage from above the
X e,
M M"
rookery and direct it away from the rookery to a positive
ana permanent discharge- well below and beyond the toe of
0
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the wall. Use of other drainage control measures should
be determined on a case -by -case basis by the geotechnical
M,
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engineer prior to bidding on the project.
M
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4/20/88
J.
Fig. A. ROCKERY SECTION
Fig. S. ROCKERY ELEVATION
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
NOTES.
Roc kery construction Is a craft and depends largely
Pocks should be placed to avoid concinuou
on the skill and experience of the builder.
Joint planes in vertical or lateral diretsions.,
A rackety is a protective system which helTis retard
Each rock shou*.d be r on t� or more rocks
the weachering and erosion process on an exposed
be low it, with gold flat -to -fiat contact.
sail face. While by its nature (mass, size and
All rookeries over 4 feet in height Should be
shape of the rocks) it will provide some degree of
constructed on basis of wall mass, not square
retention, it is not a designed or engineered sys-
footage of face.
Eel in the sense a reinforced concrete retaining
Approximate Approximate
.11 would be considered dedigned or engineered.
Weight - lbs. Volume (h3)
The degree of retention achieved is dependent on
the size of the rock used; that is, the mass or
1 Man 58,210 0.9 - 4.0
weight, and the height of the —11 being construc-
2 Man 265�580 4.1— 8.25
ted. The larger the rock, the more competent the
3 Man 760 - 1830 12.3 - 27.1
wall.
4 Man 3000 - 7000 49.0 - 76.0
5 Man 5000 76
R keries should be considered maincenance item
" S
6 Man 7000 100
t hat will require periodic inspection and repair.
0
They sh uld be located so that they Can be reached
I fe
a er.r;e,','; 1,1of9u.ryy weight stud, using
no ess t an six tocks f
y a C
b ontractor if repairs become necessary.
_,&�Ea
each man size conducted in January, 1988.
Maximum inclination of slopes behind rock walls
is 2:1 (Horizontal:Vertical)
LECEND:
Minimum embedment D - 12 inches undisturbed native
sail or compacted fill placed in accordance with
Drainage materials to consist of
report recommendations.
clean angular well -graded quarry
SP-11s, with 3-inch maximum size, or
Maximum rock wall height H feet.
other matertal approved by the
Rockeries greater than 8 feet in height to be
geotechntcal engineer
in. tal led under periodic observation of the
geotechnical engineer.
Surface seal; may consist of imper-
Pat ks placed in the lower two-thirds of the wa 11
vious soil or asphalt
'should be 5 to 6 man rock, 5000 lbs. or larger.
jljla�lltz� Undisturbed firm Native Soil
Pocks p laced above this level should gradually
T_
decrease in size with incre" ing wall height using
'Int Drain pipe; 4-inch. minimum diameter,
3 to 5 .. rock_760 to 5000 lbs.
per forated or slotted rigid plastic
The long dimension of the rocks should extend into
0 ADS pipe laid with a positive
the earth to provide maximum stability.
gradient to discharge onder control
.ell away from the wall.
TYPICAL ROCKERY DETAILS
AR
,y C.nua.icw.
Prol. No. Date Plate
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0
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jo-4
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mm
0
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9
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DO
Associated Earth Sciences, Inc.
July 31, 2002
Project No. KE01760A
City of Edmonds
Community Services Department DI)IISION
tiEFRING
1215' Avenue North
z
Edmonds, Washington 98020
Attention: Lara Palmatier
Subject: Mantooth Residence Geotechnical Review
Vj
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Lot 4 Sequoia Ridge
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Edmonds, Washington
00"
Dear Ms. Palmatier:
m
As requested, Associated Earth Sciences, Inc. (AESI) is pleased to present our geotechnical,
C:
>
review for the above -referenced project. This review was requested by you in your transmittal
55
dated June 24, 2002. This review has been performed pursuant to Section 19.05.060 of the
0 _n
Edmonds Community Development Code and,is a follow-up to our initial geotechnical plan
-4
review letter for the project dated December 14, 2001. This letter is based on our review of
m
the following documents provided the City of Edmonds:
C) Vi
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I . WJA & Associates, Plan Check No. 01-407, Proposed Mantooth Residence, dated
C (a
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March 25, 2002, prepared by Codispoti Company Consulting
2. Associated Earth Sciences, Inc., Project No. KE01 760A, Proposed Mantooth Residence
Geotechnical Review, dated April 1, 2002, prepared by Codispoti Company Consulting
z
3. City of Edmonds: Plan Review Corrections, Plan Check No. 01-407, Proposed Mantooth
0
Residence, dated April 1, 2002, prepared by Codispoti Company Consulting
z
4. Response to Geotechnical Review, Proposed Jennii�r Mantooth Residence, dated April
0
m
16, 2002, prepared by Geo Group Northwest, Inc.
5. Sharing Recommendations, Proposed Mantooth Residence, dated February 20, 2002,
prepared by Gen Group Northwest, Inc,
6. Building Plans. for A New Residence for Jennifer Mantooth, Sheets I through 9 and
Sheet S I through S4, dated November 1, 2001 and April 1, 2002 (Sheet 3. 1 of 4),
prepared by Codispoti Company Consulting
911 fifth&,,S.d� 100 - KAMM, WA98033 Ph125 827X01 F,1xJ25 827�5424
Based on our review of the above -referenced documents, the following comments are
C2
presented:
1. Codispoti and Comp��Plans, Sheet 2 of 4: Details 3, 6, and 13 for the retaining
walls should indicate thafthe vertical drain mat is tied into the footing drain to provide
for proper drainage.
2. The geotechnical engineering report for the project (Gen Group Northwest, Inc., dated
February 29, 2000) recommends a special pavement section for the diiv'eway where
the driveway crosses the sewer line. The plans reviewed refer to Sheet CI for
Z'
driveway details. Sheet C I is not included in the plans provided for review.
0
3. Response to Geotechnical Review, Proposed Jennifer Mantooth Residence, dated April
16, 2002, prepared by Geo Group Northwest, Inc. The information for the slope
stability� analysis completed for the steep slope to the west appears to be for the static
case; no seismic accelerations have been applied. The factor of safety presented for
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to
the deep-seated failure under static conditions are above the FS--' 1.5 corpmonly
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considered acceptable, The factor of safety for the shallow failure is below what is
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generally considered acceptable, but this case luis been mitigated by founding the house
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on P iling. However, the stability analyses should also be run for dynamic (seismic)
conditions because, even though the acceptable factor of safety for the dynamic case is
lower (FS = 1. 1), addition of a ground acceleration to the stability analysis can also
I
greatly increase the chances of slope failure or increase the size.of the failure circle.
We appreciate the opportunity to be of service to you on this project. Should you have any
m M
questions regarding this letter or other geotechnical aspects of the project, please call us at
0
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your earliest convenience,
C bj�
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Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
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Virldand, Washington
Me
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7/3//�wz
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2
Of
JURRES
J J N Sonde gaad, P.G.,' P.E.G. G. Aaron McMichael, P.E.
tNS/JdKEU1760A2
te G I is
og t
i.te logist 'Senior Geotechnical Engineer
PTojecUX2001760WMWP - W2K
2
August 6, 2002 Project No. G- 106 1 -1)
Ms. Jeannine Gr4 Building Official
Development Services Department
R E'C I V
CITY OF EDMONDS
1215" Avenue North
9
M02
Z
0
k,
Edmonds, WA 98020
0
Subject: Response to Geotechnical Review - July 31, 2002
4 5i
Proposed Jennifer Mantooth Residence
0 M
K,
Lot 4 - Sequoia Ridge Short Subdivision
C: a
m
Edmonds, WA
0
80,
Ref: L "Mantooth Residence Geotechnical Review, Lot 4, Sequoia Ridge, Edmonds,
to
Washington", Associated Earth Sciences, Inc., July 31, 2002.
10
C;l
2. "Response to Geotechnical Review, Proposed Jennifer Mantooth Residence, Lot 4 -
V;
Sequoia Ridge Short Subdivision, Edmonds, WA!', Geo Group Northwest, Inc., April
0 -n
16,2002.
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3. "Geotechnical Declaration and Statement of Risk, Proposed Jennifer Mantooth
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Residence, Lot 4 Sequoia Ridge Short Subdivision, Edmonds, Washington", Geo
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Group Northwest, Inc., November 7, 2001.
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4. "Geotechnical Engineering Study, Sequoia Ridge Short Subdivision, Edmonds,
Washington", Geo Group Northwest, Inc., February 29, 2000.
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S�:
Dear Ms. Graf
Geo Group Northwest, Inc. has reviewed the geotechnical review letter dated July 31, 2002 by
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Associated Earth Sciences, Inc. for the proposed Jennifer Mantooth residence, In response to
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item 3 of the referenced review we have performed slope stability analysis with regards to seismic
accelerations on the steep west facing slope at the project development.
We analyzed the slope stability for the Sequoia Ridge development with regard to seismic
accelerations due to the 100-year earthquake event. We assumed a pseudostatic horizontal
coefficient of acceleration equal to 0. 1 and applied the acceleration an the same shallow and deep
slope configurations included in our referenced response dated April 16, 2002. The slope stability
13240 NE 20th Street, Suite 12 neiievuo, washington 98005
Phone 425/649-8757 FAX 425/649-8758
August 6, 2002 G-1061-D
Ms. Jeannine Graf - City of Edmonds Page 2
analysis was performed using the XSTABL computer program developed by Surtil Sharma.,
version 3.2.
The results of our analysis indicate that under the assumed seismic condition the factor of safety
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with regard to a deep slope failure is 1.4. Similarly the factor of safety for shallow sloughing
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under seismic loading is less than 1 (0.96).
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Accordingly, we conclude that the site slopes with regard to deep failure are relatively stable in
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the seismic condition. We anticipate that under the design earthquake some sloughing and small
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surficial sliding may occur on the steep west facing slopes. The possiblity ofdamage to the
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proposed house due to the surficial sliding has been mitigated by supporting the house on pilings.
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We have attached copies of our XSTABL analysis input and output to this letter.
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Respectively Submitted,
GEO GROUP NORTHWEST, INC. .,NM C
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W illiam Chang, RE,
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Principal
LEXPIRES! 2/191W
attachment: XSTABL Analysis input and Critical Surfaces
cc: Ms. Jennifer Mantooth, Owner of Lot 4
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Mr. Mark Codispoti, P.E., Codispoti Company Consulting
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Geo Group Northwest, Inc.
G1061-DE
8-06-** 10:18
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10 most critical surfaces, MINIMUM JANBU FOS
1.392
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25 50 75 100 125 150
175 200
X—AXIS (feet)
PROF I L
FILE: C1061-DE 8-06--- 10:18 f t
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11.0
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11.0 216.0
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24.5 240.0
34.0
260.0 2
34.0 260.0
40.0
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40.0 277.5
45.5
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45.5 288.0
116.0
280.0 1
116.0 280.0
125.0
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167.0
260.0 2
40.0 277.5
125.0
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100.0 30.00
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8-66-** 10:24
Mantooth shallow w/seismic
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< 240
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175 200
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PROFIL
FILE: G1061-SE 8-06--- 10:24 ft
Mantooth shattow W/selsmic
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10
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212.0
11.0
216.0 2
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216.0
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225.0 2
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240.0 2
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260.0 2
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40.0
277.5 2
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277.5
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125.0
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Height Calculation Worksheet
Address:
Date:
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Inspector(s):
1. Datum Point:
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2.. Datum Point Elevation:
3. Average Grade:
mm
4. Maximum Elevation Allowed: '�2)Lk �k buU (average grade)'+ 25'
5. Reference Point Elevation Shot to House:
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(dtu- -levti. I (grade to transit level line shot to house) I
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6. Measurements from line shot onto house to mof ridge:
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to
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Total:
7. Actual Elevation: (reference point elevation) +12 - (measurements
from #6) = -7-f --qz
Conclusion:
SS f1Z (actual) is greater<Q� �Itli� a 5426 (allowed); therefore the house isl
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is not over the height requirement per ECDC 16.20.30 requirements
FM PROJECT APPROVAL F RM
TO:
DATE:
MEMO TO: PERMIT COORDINATOR, BUILDING DIVISION
FROM: FIRE DEPARTMENT DATE
ENGINEERING DIVISION DATE
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PROJECT -
SITE ADDRESS
PERMIT# INSPECTED
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DESCRIPTION OF WORK TO BE INSPECTED
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A field inspection was conducted to determine final compliance with approved plans. Final approval
denotes that there are no object ions from the above signed Department to the release of
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PERFORMANCE BONDS and the granting of:
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GRANT FINAL PROJECT APPROVAL
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DESCRIPTION OF WORK TO BE INSPECTED
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RE INSPECTED OUTSTANDING ISSUES - GRANT FINAL PROJECT APPROVAL
Date. sign -------
ocaprvl.doc.l:mW:bldW.fomisIO/OI
U-NAL PROJECT APPROVAL FORM
TO:
DATE:
MEMO TO: PERMrr COORDINATOR, BUILDING DIVISION
FROM: FIRE DEPARTMENT' DATI�
ENGINEERING DIVISIONDATE
P DIVISION DATE
PROJECT ��7f-rA,
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2.
3.
RE -INSPECTED OUTSTANDING ISSUES - GRANT FINAL PROJECT APPROVAL
Date Sign_
ocapryl.doc.l:temp.*bldg!formsIO/OI
RECORD OF INSPECTIONS
INSPECTOR
DATE APPROVED
S ETBACKS .....................
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FOUNDATION:
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Footing....................
Wall.....................
Pier/Porch .................
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Retaining Wall
Stab Insulation
PLUMBING:
Underground .............
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Rough -in ...............
Commercial Final
HEATING�
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GasTest ................
GasPiping
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.................
Equipment .................
Commercial Final
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EWrERIOR SHEATHING
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NAILING . . .............
FRAMING ...................
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FIRST FLOOR FRAMING
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INSULATION ...................
Floor Insulation
Wall Insulation ...........
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Ceiling Insulation
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SHEETROCK NAILING
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SPECIAL INSPECTION
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MISCELLANEOUS
FINAL APPROVAL FOR
OCCUPANCY ..........
S66 13L,06
Amoutftld $
Datebsued.,
VaterM�Ur 'size
Am ountrwalILLiecel"t 41,
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