S-06-144 Staff Report.pdfCITY OF EDMONDS
121 - 5TH AVENUE NORTH, EDMONDS, WA 98020
PLANNING DIVISION
FINDINGS, CONCLUSIONS, AND DECISION
To: File No. S-2006-144
From:
ennifer Mac , Planner
Date: January 17, 2008
File: S-2006-144
Owner(s): Greg Hinkel and Steve Miles
Applicant: Fred Brown
TABLE OF CONTENTS
Section Page
I.
INTRODUCTION............................................................................................................... 2
A. Application.......................................................................................................................................2
B. Decision on Subdivision................................................................................................................... 2
II,
FINDINGS OF FACT AND CONCLUSIONS...................................................................4
A. Compliance with the Subdivision Ordinance.................................................................................... 4
B. Compliance with the Comprehensive Plan........................................................................................6
C. Compliance with the Zoning Code.................................................................................................... 6
D. Compliance with the Flood Plain Management Provisions...............................................................6
E. Environmental Assessment............................................................................................................... 6
F. Critical Areas Review....................................................................................................................... 7
G. Comments......................................................................................................................................... 8
III.
RECONSIDERATIONS AND APPEALS.. ...... ................................................................. 8
A. Request for Reconsideration............................................................................................................. 8
B. Appeals............................................................................................................................................. 8
C. Time Limits for Reconsideration and Appeals.................................................................................. 8
IV.
LAPSE OF APPROVAL.....................................................................................................8
V.
NOTICE TO COUNTY ASSESSOR, ................................................................................. 9
VI.
ATTACHMENTS...............................................................................................................9
VII.
PARTIES OF RECORD......................................................................................................9
Hinkel/Miles
File No, S-2006-144
Page 2 of 9
I. INTRODUCTION
The applicant is proposing to subdivide two existing lots addressed as 7005 and 7027 174th Street Southwest
into a total of four lots (Attachment 1). See the Zoning and Vicinity Map for reference (Attachment 2). The
subject site is located in a Single -Family Residential (RS -20) zone that allows lots with a minimum area of
20,000 square feet. The proposed lot layout is shown on the subdivision map and the preliminary
development plan (Attachments 3A and 313). The existing residences are proposed to be retained on Lots 2
and 4.
A. Application
I. Applicant: Fred Brown for Greg Hinkel and Steve Miles
2. Site Location: 7005 and 7027 170 Street Southwest (see Attachment 2)
3. Request: To divide the subject site with a total area of approximately 2.15 acres into four lots
in a Single -Family Residential (RS -20) zone (see Attachment 3A).
4. Review Process: Following the comment period, Planning staff makes an administrative
decision.
5. Major Issues:
a. Compliance with Edmonds Community Development Code (ECDC) Section 16.20.030,
site development standards for the RS -20 zone.
b. Compliance with Edmonds Community Development Code (ECDC) Title 18, public
works requirements.
c. Compliance with Edmonds Community Development Code (ECDC) Section 20.75,
subdivision requirements.
d. Compliance with Edmonds Community Development Code (ECDC) Section 20.95,
staff review requirements.
e. Compliance with Edmonds Community Development Code (ECDC) Sections 23.40 and
23.80, critical areas requirements.
f. Compliance with Edmonds Community Development Code (ECDC) Section 23.90.040.C,
native vegetation retention requirements.
Note: All code sections referenced in this report can be viewed via the City's website at
www.ci.edmonds.wa.us.
B. Decision on Subdivision
Based upon the Findings of Fact and Conclusions, and Attachments submitted with the application
and during the comment period, the following is the decision of the City of Edmonds Planning
Division:
The subdivision as proposed is APPROVED with the following conditions:
1. Prior to recording, the applicant must complete the following requirements:
a) Civil plans must be approved prior to recording. In completing the civil plans, you
must address the following:
(1) Pursuant to ECDC 23.90.040.C, a vegetation management plan must be
submitted. The plan must be created by a qualified professional and must
identify areas of existing native and nonnative vegetation within the Native
Growth Protection Area, indicating which portions of the Native Growth
Protection Area are proposed to be retained and which portions will be
removed and replanted with native species. The management plan must also
describe how the Native Growth Protection Area will be maintained and
must include a proposal for construction fencing as well as permanent
signage and fencing installed to delineate the boundary of the Native
Hinkel/Miles
File No, S-2006-144
Page 3 of 9
Growth Protection Area. For further direction, see section ILF of this
report.
(2) Complete the Engineering Division conditions listed "Required prior to
Recording" on Attachment 4.
b) Follow Fire Department requirements provided in Attachment 12.
c) Remove the portion of the existing shed that encroaches onto the northeast comer of
Lot 1, as indicated on the preliminary plans.
d) Make the following revisions to the plat:
(1) The vegetation that is to be retained in order for the project to comply with
ECDC 23.90.040.0 must be shown on the plat as part of a Native Growth
Protection Area. Language approved by the Planning Division for
maintenance and protection of the Native Growth Protection Area must also
be provided on the plat.
(2) Delineate the slopes that are steep enough to be considered Landslide
Hazard Areas on the documents to be recorded.
(3) If setbacks are to be included on the plat, add the following statement to the
face of the plat: "Setbacks shown are for reference only and vest no right."
(4) Add to the face of the plat: "Conditions of approval must be met and can be
found in the final approval for the short subdivision located in File No. 5-
2006-144 in the City of Edmonds Planning Division."
(5) Include on the plat all required information, including owner's certification,
hold harmless agreement, and Planning Division and Engineering Division
staff's approval blocks.
e) Make sure all documents to be recorded meet the Snohomish County Auditor's
requirements for recording, including all signatures in black ink.
f) Submit an updated copy of the title report (short plat certificate) with the documents
proposed to be recorded. Note that the updated title report must be prepared within
30 days of submittal.
g) Submit copies of the documents to be recorded for the Planning Division's and
Engineering Division's approval. Once approved, the applicant must record the
documents with Snohomish County Auditor's office,
2. After recording the plat, the applicant must complete the following:
a) Provide the City Planning Division with three copies of the recorded plat, with the
recording number written on them. The City will not consider the subdivision to
have been completed until this is done.
b) Complete the Engineering Division conditions listed "Required with Building
Permit" on Attachment 4.
c) Development of the site is subject to the requirements of ECDC 19.10,
3. Any tree removal must meet the requirements of ECDC 18.45 and 2390.040.C.
4. Follow the recommendations of the geotechnical reports by Soil and Environmental
Engineers, Inc. dated March 14, 2007, August 3, 2007, September 28, 2007, and
December 17, 2007 (Attachments 5, 6, 7, 8, and 10) as well as all future geotechnical
reports for the subject site.
5. Follow the recommendations of the technical memorandum by Landau. Associates dated
October 19, 2007 (Attachment 9).
Hinkel/Miles
File No. S-2006-144
Page 4 of 9
II. FINDINGS OF FACT AND CONCLUSIONS
A. Compliance with the Subdivision Ordinance
1. Introduction
a. Setting:
The subject site at 7005 and 7027 174" Street Southwest is located in the Single -Family
Residential (RS -20) zone (Attachment 2). Refer to the Zoning and Vicinity Map (Attachment
2) for the zoning of adjacent properties, which are zoned a range of RS -20, RS -12, and RS -8.
All surrounding properties appear to be developed with single family residences.
b. Topography and Vegetation:
The subject site slopes downwards generally to the north, with some slopes that are steep
enough to be considered Landslide Hazard Areas. The site contains typical residential
landscaping surrounding the two existing residences, including grass, shrubs, and trees. The
majority of the site, particularly the northern portion of the site contains more natural
vegetation, including numerous large trees.
C. Lot Layout
The proposed lot layout is shown on the preliminary subdivision map (Attachment 3A). Lot
1 will be created on the northwestern portion, Lot 2 will be created on the southwestern
portion, Lot 3 will be created on the northeastern portion, and Lot 4 will be created on the
southeastern portion of the subject site. The existing residences are proposed to be retained
on Lots 2 and 4. Lots 1 and 2 will be accessed via a shared easement along the existing
access drive to the property addressed 7027 174`h Street Southwest, which also currently
provides access to the adjacent property addressed 7107 174`h Street Southwest. Lots 3 and 4
will be accessed via a shared easement along the existing access drive to the property
addressed 7005 174"' Street Southwest.
2. Environmental Resources
a. The subdivision chapter, ECDC 20.75.085, states that a proposed subdivision should be
designed to minimize significant adverse impacts where environmental resources exist (such
as trees, streams, ravines, or wildlife habitats). The existing trees are an environmental
resource on the subject site. The majority of the trees on the subject site are located on the
northern portion of the site. ECDC 23.90.040.0 requires the retention of a minimum of 30%
of native vegetation on subdividable properties that are zoned RS -12 and RS -20. Since the
subject property is zoned RS -20, the applicant will need to show how the proposal complies
with ECDC 23.90.040.0 prior to final approval. A condition. of approval has been added
requiring the applicant to provide a Native Growth Protection Area (NGPA) and to submit a
vegetation management plan indicating which portions of the NGPA are proposed to be
retained and which portions will be removed and replanted with native species. The plan
must also describe how the NGPA will be maintained. Additionally, construction fencing
and permanent fencing should be utilized to further protect this vegetation. See Section 11.17
of this report for further discussion on this topic.
b. The proposal minimizes grading because Lots 1 and 2 and Lots 3 and 4 will share access,
portions of which is currently paved. Additionally, no grading will be permitted within the
required Native Growth Protection Area.
C. A drainage plan must be submitted to the Engineering Division when a building permit is
applied for on this site. Any proposed development on the site must be designed to code in
order to minimize off-site impacts on drainage. All new impervious surfaces must be
connected to a detention system.
Hinkel/Miles
File No. S-2006-144
Page 5 of 9
3. Lot and Street Layout
a. This criteria requires staff to find that the proposed subdivision is consistent with the
dimensional requirements of the zoning ordinance and that the lots would ultimately be
buildable. Based on a review of the project and the analysis in this section, staff agrees that a
four -lot short plat is a reasonable use of the property.
Lot sizes and dimensions:
Lot Area:
Lot Width: The required lot width in the RS -20 zone is 100 feet. All proposed lots meet this
requirement.
4. Setbacks and Lot Coverage
a. In order to approve a subdivision, the proposal must meet all requirements of the zoning
ordinance, or a modification must be approved. Based on the development standards for the
RS -20 zone, setbacks for the lots should be as follows:
Since all of the proposed lots are considered to be flag lots, required setbacks are side
setbacks from all property lines. The RS -20 zone requires a minimum side setback of 10 feet,
and all side setbacks for each lot must add up to a minimum total of 35 feet.
Note: No structures are allowed to be located within the Native Growth Protection Area.
Therefore, the setbacks stated above are superseded by the boundaries of the Native Growth
Protection Area.
Existing Structures I Encroachments: The existing residences are proposed to be retained on
Lots 2 and 4. The proposal will not reduce the setbacks of the existing residences below the
minimum required for the RS -20 zone. The portion of the existing shed shown overlapping
the property line onto the northeast corner of proposed Lot I must be removed prior to
recording in order to clear the potential title issue of the shed overlapping the property line.
b. Corner Lots: None of the proposed lots are considered corner lots.
C. Flag or Interior lot determination: All of the proposed lots are considered to be flag lots.
d. Lot Coverage of Existing Buildings on Proposed Lots:
35% maximum lot coverage is allowed in the RS -20 zone
2) According to Snohomish County Assessor's records, the existing residence addressed
7005 174s' Street Southwest covers 1,416 square feet and the attached garage covers
594 square feet, which would result in a lot coverage for Lot 4 of approximately 10%.
Also according to Snohomish County Assessor's records, the existing residence
addressed 7027 174a' Street Southwest covers 1,879 square feet and the attached garage
covers 928 square feet, which would result in a lot coverage for Lot 2 of approximately
10.6%. Lots 1 and 3 will not contain any structures and will, therefore, have a zero
percent lot coverage. Pursuant to ECDC 16.20, any future buildings or structures on
any of the proposed lots will be permitted to cover no more than 35% of each lot.
5. Dedications
a. None required, per City Engineer's Requirements (Attachment 5).
Required
Lot Area
Proposed
Gross sq. ft
Proposed
Nets . ft
Lot 1
20,000
20,569
20,569
Lot 2
20,000
29,320
26,438
Lot 3
20,000
20,002
20,002
Lot 4
20,000
23,880
20,017
Lot Width: The required lot width in the RS -20 zone is 100 feet. All proposed lots meet this
requirement.
4. Setbacks and Lot Coverage
a. In order to approve a subdivision, the proposal must meet all requirements of the zoning
ordinance, or a modification must be approved. Based on the development standards for the
RS -20 zone, setbacks for the lots should be as follows:
Since all of the proposed lots are considered to be flag lots, required setbacks are side
setbacks from all property lines. The RS -20 zone requires a minimum side setback of 10 feet,
and all side setbacks for each lot must add up to a minimum total of 35 feet.
Note: No structures are allowed to be located within the Native Growth Protection Area.
Therefore, the setbacks stated above are superseded by the boundaries of the Native Growth
Protection Area.
Existing Structures I Encroachments: The existing residences are proposed to be retained on
Lots 2 and 4. The proposal will not reduce the setbacks of the existing residences below the
minimum required for the RS -20 zone. The portion of the existing shed shown overlapping
the property line onto the northeast corner of proposed Lot I must be removed prior to
recording in order to clear the potential title issue of the shed overlapping the property line.
b. Corner Lots: None of the proposed lots are considered corner lots.
C. Flag or Interior lot determination: All of the proposed lots are considered to be flag lots.
d. Lot Coverage of Existing Buildings on Proposed Lots:
35% maximum lot coverage is allowed in the RS -20 zone
2) According to Snohomish County Assessor's records, the existing residence addressed
7005 174s' Street Southwest covers 1,416 square feet and the attached garage covers
594 square feet, which would result in a lot coverage for Lot 4 of approximately 10%.
Also according to Snohomish County Assessor's records, the existing residence
addressed 7027 174a' Street Southwest covers 1,879 square feet and the attached garage
covers 928 square feet, which would result in a lot coverage for Lot 2 of approximately
10.6%. Lots 1 and 3 will not contain any structures and will, therefore, have a zero
percent lot coverage. Pursuant to ECDC 16.20, any future buildings or structures on
any of the proposed lots will be permitted to cover no more than 35% of each lot.
5. Dedications
a. None required, per City Engineer's Requirements (Attachment 5).
Hinkel/Miles
File No. S-2006-144
Page 6 of 9
6. Improvements
a. See Engineering Requirements (Attachment 5).
7. Flood Plain Management
a. This project is not in a FEMA designated Flood Plain.
S. Compliance with the Comprehensive Plan
1. Comprehensive Plan Goals and Policies:
The Comprehensive Plan has the following stated goals and policies for Residential Development
that apply to this project.
Residential Development
B. Goal. High quality residential development which is appropriate to the diverse
lifestyle of Edmonds residents should be maintained and promoted. The options
available to the City to influence the quality of housing for all citizens should be
approached realistically in balancing economic and aesthetic consideration, in
accordance with the following policies:
B.1. Encourage those building custom homes to design and construct homes
with architectural lines which enable them to harmonize with the
surroundings, adding to the community identity and desirability.
6.3. Minimize encroachment on view of existing homes by new construction or
additions to existing structures.
6.4. Support retention and rehabilitation of older housing within Edmonds
whenever it is economically feasible.
6.5. Protect residential areas from incompatible land uses through the careful
control of other types of development and expansion based upon the
following principles:
B.5.d. Private property must be protected from adverse environmental
impacts of development including noise, drainage, traffic, slides,
etc.
B.6. Require that new residential development be compatible with the natural
constraints of slopes, soils, geology, vegetation and drainage.
2. Compliance with the Residential Development goals and policies: The proposal will retain the
existing residences that were constructed in 1952 and 1984 according to Snohomish County
Assessor's records and would allow for construction of two new residences.
C. Compliance with the Zoning Code
1. The proposed subdivision complies with the provisions of the Zoning Code. See sections II.A.3
and ILAA of this document.
D. Compliance with the Flood Plain Management Provisions
1. The proposed project is not located in a Flood Plain.
E. Environmental Assessment
1. Is this site within a shoreline area (within 200 feet of the ordinary high water mark of the Puget
Sound)? No.
Hinkel/Miles
File No, S-2006-144
Page 7 of 9
2. Is an Environmental Checklist Required for this application? No. If more than 500 cubic yards
of grading will be required for the subdivision improvements, an Environmental Checklist is
required. At this point in time, the applicant has indicated that the total amount of grading for the
subdivision improvements is not anticipated to exceed 500 cubic yards. If through the review of
the civil plans, it is determined that more than 500 cubic yards of grading will be required, the
City will require an Environmental Checklist to be submitted and will issue an Environmental
Determination.
F. Critical Areas Review
1. Critical Areas Review number: Critical areas reconnaissance was conducted under File No.
CRA -1999-0298 for the property addressed 7005 174`h Street Southwest and File No. CRA -2000-
0020 for the property addressed 7027 174a' Street Southwest.
Results of Critical Areas Reviews: During initial critical areas review of the subject properties,
staff issued a waiver from the requirement to complete a study. However, after reviewing the
survey submitted with the short plat application and a subsequent site visit, it was noted that the
site contains slopes that are steep enough to be considered Landslide Hazard Areas as defined by
ECDC 23.40 and ECDC 23.80. As a result, the critical areas determinations were changed, and
the requirement to complete a study was issued. The applicant submitted a memo from Soil and
Environmental Engineers, Inc. dated March 14, 2007, which stated that the proposed subdivision is
feasible, subject to a future geotechnical report providing findings and recommendations for the
development (Attachment 5). These future findings and recommendations were provided in two
separate geotechnical reports by Soil and Environmental Engineers, Inc. dated August 3, 2007.
The report for the property addressed 7005 1741s Street Southwest is provided as Attachment 6 and
the report for the property addressed 7027 174"' Street Southwest is provided as Attachment 7.
Staff requested additional geotechnical information from the applicant, which is provided as
Attachment 8. Pursuant to ECDC 23.40.090.8, the geotechnical reports listed above were
provided to the City's consultant, Landau Associates, for peer review (Attachment 9). The
applicant's geotechnical engineer submitted a response to the peer review (Attachment 10). These
reports concluded that as long as the recommendations set forth in the reports are followed, the
proposed subdivision will result in four buildable lots. A condition of approval has been added
requiring the applicant to follow the recommendations of these and any future geotechnical reports
related to the subject site.
2. ECDC 23.90 Fish and Wildlife Habitat Conservation Areas: ECDC 23.90.040.0 requires all
subdividable properties in the RS -12 and RS -20 zones to retain or create an area of native
vegetation equal to 30% of the total area of the site. This is meant to provide additional protection
for fish and wildlife habitat throughout Edmonds. As a condition of approval, the applicant must
submit a vegetation management plan showing how the requirements of ECDC 23.90.040.0 will
be met.
To make sure that the vegetation that is to be retained will survive, a Native Growth Protection
Area (NGPA) is required. This area will protect the vegetation from excavation, grading,
impervious surfaces and other construction activities. It will also establish ongoing maintenance
activities that are allowed and prohibited (i.e. tree toping is prohibited, pruning to eliminate
hazardous branches is permitted). A construction fence around the NGPA is required throughout
both subdivision and home construction. After construction is complete, the construction fencing
may be removed from around the NGPA, but it must be replaced with a permanent split -rail or
equivalent fence providing protection of the NGPA into the future. No impervious surfaces should
be allowed in this same area without having the plan reviewed by a certified or consulting arborist
to ensure that the trees and other vegetation are being protected to the greatest extent possible.
Prior to recording of the subdivision, a qualified professional must identify areas within the NGPA
as areas of existing native and existing nonnative vegetation. The nonnative vegetation must be
removed and replanted with native vegetation. Pursuant to ECDC 23.90.040.C, a vegetation
management plan must be submitted. The plan must be created by a qualified professional and
must identify areas of existing native and nonnative vegetation within the NGPA, indicating which
portions of the NGPA are proposed to be retained and which portions will be removed and
Hinkel/Miles
File No. S-2006-144
Page 8 of 9
replanted with native species. The management plan must also describe how the NGPA will be
maintained and must include a proposal for construction fencing as well as permanent fencing to
protect the vegetation both during construction and into the future.
G. Comments
One public comment letter was received during review of the proposal and is included as
Attachment 6. Penelope Jones commented that she does not want the proposed subdivision to be
approved. Ms. Jones is concerned that the subdivision will increase traffic and that 174`x' Street
Southwest is not wide enough to support increased traffic.
City's Response: The proposed four lot subdivision is allowed as long as it meets all requirements
set forth in the Edmonds Community Development Code. These requirements are discussed in
further detail throughout this staff report. The Engineering Division has reviewed the proposed
subdivision for compliance with the City's engineering and traffic standards. A traffic impact fee
is required for the two new lots as mitigation for any potential traffic impacts from the future
homes.
III. RECONSIDERATIONS AND APPEALS
The following is a summary of the deadlines and procedures for filing reconsiderations and appeals. Any
person wishing to file or respond to a recommendation or appeal should contact the Planning Department
for further procedural information.
A. Request for Reconsideration
Section 20,100.010.G allows for City staff to reconsider their decision if a written request is filed
within ten (10) working days of the posting of the notice required by this section. The
reconsideration request must cite specific references to the findings and/or the criteria contained in
the ordinances governing the type of application being reviewed.
B. Appeals
Section 20.105.040 and 20.105.020 describes how appeals of a staff decision shall be made. The
appeal shall be made in writing, and shall include the decision being appealed along with the name
of the project and the date of the decision, the name of the individual or group appealing the
decision, their interest in the matter, and reasons why the appellant believes the decision to be
wrong. The appeal must be filed with the Community Development Director within fourteen (14)
calendar days after the date of the decision being appealed.
C. Time Limits for Reconsideration and Appeals
The time limits for reconsiderations and appeals run concurrently. If a request for a
reconsideration is filed before the time limit for filing an appeal has expired, the time "clock" for
filing an appeal is stopped until a decision on the reconsideration request is completed. Once the
staff has issued his/her decision on the reconsideration request, the time clock for filing an appeal
continues from the point it was stopped. For example, if a request is filed on day 5 of the appeal
period, an individual would have 9 more days in which to file an appeal after the staff issues their
decision on the reconsideration request.
IV. LAPSE OF APPROVAL
Section 20.075.100 states, "Approval of a preliminary plat or preliminary short plat shall expire and have
no further validity at the end of five years, unless the applicant has acquired final plat or final short plat
approval within the five-year period."
HinkellMiles
File No. S-2006-144
Page 9 of 9
V. NOTICE TO COUNTY ASSESSOR
The property owner may, as a result of the decision rendered by the staff, request a change in the valuation
of the property by the Snohomish County Assessor's Office.
VI. ATTACHMENTS
1. Application
2. Vicinity / Zoning Map
3A, Preliminary Subdivision Map
3B. Preliminary Development Plan (for reference only)
4. Engineering Requirements
5. Memo from Soil and Environmental Engineers, Inc. dated March 14, 2007
6. Geotechnical Report by Soil and Environmental Engineers, Inc. dated August 3, 2007 for the property
addressed 7005 174t' Street Southwest
7. Geotechnical Report by Soil and Environmental Engineers, Inc. dated August 3, 2007 for the property
addressed 7027 170 Street Southwest
8. Geotechnical Report by Soil and Environmental Engineers, Inc. dated September 28, 2007
9. Peer Review Technical Memorandum by Landau Associates dated October 24, 2007
10, Geotechnical Report by Soil and Environmental Engineers, Inc. dated December 17, 2007
11. Comment letter from Penelope Jones received June 12, 2007
12. Fire Department Requirements from Fire Marshal John Westfall
VII. PARTIES OF RECORD
Engineering Division
Planning Division
Fred Brown
1013 --- 140`h Street Ct. NW
Gig Harbor, WA 98352
Greg Hinkel
7517-172 n1 Street SW
Edmonds, WA 98026
Steve Miles
7005 — 174'h Street SW
Edmonds, WA 98026
Penelope Jones
7210 — 173rd Street SW
Edmonds, WA 98026
city of edmonds
land use application
❑ ARCHITECTURAL DESIGN REVIEW
❑ COMPREHENSIVE PLAN AMENDMENT
Cd CONDITIONAL USE PER RECEIVED
❑ HOME OCCUPATION
❑ FORMAL SUBDIVISION NOV 13 2006
�. SHORT SUBDIVISION
❑ LOT LINE ADJUSTMENT PERMIT COli.1NT1=R
❑ PLANNED RESIDENTIALI)EVELOPMEN
❑ OFFICIAL STREET MAP AMENDMENT
❑ STREET VACATION
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The undersigned applicant, and his/her/its heirs, and assigns, in consideration on the processing of the application
agrees to release, indemnify, defend and hold the City of Edmonds harmless from any and all damages, including
reasonable attorney's fees, arising from any action or infraction based in whole or part upon false, misleading,
inaccurate or incomplete information furnished by the applicant, his/her/its agents or employees,
By my signature, I certify that the info ion and its herewith submitted are true and correct to the best of my
knowledge and that I am authori to f. is app 'c�tio on the behalf of the owner as listed below.
SIGNATURE OF APPLICANT/AGENT J�.DATE
Property Owner's Authorization
By my signature, I certify that I have authorized the above Applicant/Agent to apply for the subject land use
application, and grant my permission for the public officials and the staff of the City of Edmonds to enter the subject
property for the purposes o inspecti and stin ttendant to this application,
SIGNATURE OF OWNER DATE
This application for4was revised on 1127100. To verify whether it is still current, call (425) 771-0220,
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CITY 0f �t?MONJ5
MINETO% k WUII�Y-MM5 FM 5HOkf PLA5
Name: HINKLE/MILES File No.: PLN -2006-144
Reviewed by: JAIME HAWKINS Vicinity: 700517027174TH ST SW
Rnq,ineerinu Division date
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keci' d prior to
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Complete
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Permit
for uHlc 5treet5,
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No dedication required per official street map _
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€ a5emelTt5tC1 utllltle5, prlvat,-aCCe55,otherutlhtie5)
Provide all easements as needed.
-. ---TT T-_ --
X W
------------------------------
All lots shall share.a-private access road
X
- -- ----- -
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- - - - - --
_ w_
Private access easements shall be 15 feet in width-
- ._ -.
_ _ X
-- -- -- - -- -
- - - - -- ----
- - -
-----------.............................._ .-.
- - ----—.-...-------------------------------------------------
for
for 2 lots, 20 -ft for 3 lots.
5. Street lm (ACP
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ovementh with curb and utter) ;
No street improvements required on 174 _ ST SWX
-------------------------------------------------------------..-.-.-.-.-.-.-.-.-.-.-......-....-.-.-.-.-.-.-.-.-.
Private access road shall be paved a minimum of 12 -ft wide for
X
-----
X
2 -lots, and 16 -ft wide for 3 -lots plus 18" asphalt thickened
---- edge. 6" concrete extruded curb may be used:-.-.-. - - -- .-....-..
- - --------- - --
---- --- --
_ Slope of private access road/driveway shall not exceed 14%.
X
— X— _
_ _
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4, SF,reet turnaround;
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Provide
----- on-site turn around to City.standards........................................_...............-.---.---...---...----------
--- ---X----- --
---- -- -.........--------------
5€ Sidewalks
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and/ or walkwa s; €t
- -- Insufficien# pro-perty frontage, no sidewalks are required. ....... .............
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6 , 5treet li Fts,
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B. Water system ImprovemeC pipelines, fire hydrant, pump
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Fire sprinkler system required by FD, Backflow required at
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meter __-_ . _.-.._-.-.-_.-.-. - -- ----
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Provide water service to each lot.
__ _ ._.-.-_-.-.-..--._...........................
X
... - - ------ ... --
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----Connect to public water systems - _.-. .......
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9, 5anita�I sewers Stem ImProvemen&C lpenes, pump
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Provide new sanitary sewer service -to each lot
.-.-_.-.-.-.-X -.-._ --------------
..........------X
. -.-.- .-.....-.............-.........................._......
Connect to public sewer system
X
X
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Attachment 4
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req' d prior to
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recordincl
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10. Storm sewer 5q{,nts tem improvemeC pipelines, pump
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Provide storm sewer service to all proposed lots.
- - _
X
Construct storm detention system sized to provide adequate
X
capacity for proposed single family dwellings and access
improvements in accordance with ECDC 18.30.
__.
Connect to Public Storms stem .. _. ...-._-.-.-.-..-
.--_-------------- - ----------------- --- y
---------------_- -
-_. ----.-X_._
----- _.-
-------------
11, On-site drainage ( Ian per Ord, 5015):
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Connect all new impervious surfaces to detention stem.
X
12. Underground (per Ord. 1307}
wlrin
- Required -for all new services
X
X
13. �xcavation (per IC3C, 02003
and gradirg a pendix] edition)
Submit a grading plan as part of engineered site plan. Grading
X
for foundations to be included with the building permit only__-.-._..
-------------------------------------
..............-.._.__
_____-.-.-.-.-.-._--.-.-.-.-------.-.---------.-._--_--
_.--
14, 51 n e Cper G �n Ineer) ;
All signs shall be vinyl letters and to City Stds. No silk screen
X
............. will be permitted - -_--_-_-.-_.-.-.-.-.------------------------
----- ------------------ --------
ProvideFire and aid address sigh- ------------
--
?.... .-..._..y........._........................._.--............................-.-.....-_.
Provide " Private Access Ends"
X
15 5urve Monumentation (per Ord, 5ection 12.10.120):
,
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fib, As -built drawln 5 C erG Ineer) ;
-T MIMI�� i �a ��l.='
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- --Required for all utility construction _.-.-_------------------- --------------
17, Other
re ulrement5,
�.
a) Plat showing lots, easements, legais, survey information-
X.._..__—__
--
b) Leal documents for each lot _-_- ......................
---------X
X -.-_.-.-.- .-.-.-.
_...-__-_-__--_.-__-
c)-µ Fxeld stake lot comers�byprofessional surveoz)w _
X
--.—..__.... ----.
......................_.-.-.-.-.-.-_.-.-.-.-..
_.-.-.----.-.--.--_.._ -...
d) Field stake utility stubs at property lines.
X
e) Clustered mailbox location per Postmaster-----------------------------
X
I
Maintenance
X
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revised: 11/15/05
ya, t & re" &M a, W 12-11-2006
ENGINEERING PROGRAM MANAGER, CITY OF EDMONDS DATE
The Engineering requirements have been completed and the subdivision can be recorded.
Authorized for recording
http:llcdmondspmtwcblpermittraxiPe,rmitTraxMainlAttachmentsILivelPERMITIPMT-56579112112006131639906-doc
revised: 11115105
recj'd prior to kcq' J W/ bljq.
recording Perm it
Pond ported
Complete
Storm §y access
.......
........
N/A
---------------_
Storm System �T ).
-------------- ------- - .............___-.-._-.___X.-.-.-_._-.-.-_-.
-_---- - ----------- -------- -
-- ----- ------------- -------------
-D-----e-v---e--l--o--pm-----e--n---t----c---h--- _(............$428/1ot
Sewer LID fees to be paid in full
- -
- - ------------ --------------------------------------------- --- --------- ----- - - - - - - - - - -
Sewer Connection fee �y $730/lot
----------------------------------------
e) Water meter fee (based on -114")
--xm
------------------------------- - ----
x
--------
$550/meter
Water Connection fee new lots y $908/10t
.. ................. I-.-.-.---.----.---��'.) ----------
---------- - --------- --- ----- -- ------ x
............... ..................
__-
___.-.-.-._-_Trafficj!pp!ct $840.72/lot $_-----__--_.. - ------
---------------- - -
Plan Review fee$860
--- ----------- ----- ---------------------------------------------------
x
- - - - -
i) Plat inspection fee (2.2% of improvement costs)NIA
ya, t & re" &M a, W 12-11-2006
ENGINEERING PROGRAM MANAGER, CITY OF EDMONDS DATE
The Engineering requirements have been completed and the subdivision can be recorded.
Authorized for recording
http:llcdmondspmtwcblpermittraxiPe,rmitTraxMainlAttachmentsILivelPERMITIPMT-56579112112006131639906-doc
revised: 11115105
s�EE
SOIL & ENVIRONMENTAL ENGINEERS, INC.
16625 Redmond Way, Suite M 124, Redmond, Washington 98052, (42 5) 868-5868 FAX (425) 868-7427
March 14, 2007
Mr. Fred Brown
F.F. Brown Design Y
CC: Mr. Steve Miles
CC: Mr. Greg Hinkel
Geotechnical Engineering Services
Proposed Short Subdivision
7005 and 7027, 17401 Street SW
Edmonds, Washington
Dear Fred:
Per your request, I have reviewed your site plan dated July 1, 2006. The pian shows that the project
involves sub -dividing each of the above referenced two properties into two residential lots. The existing
houses on the south side of each property will remain and a new lot will be created in the northern portion of
the properties. Prior to the preparation of this letter, I have reviewed Edmonds Community Development
Code ECDC 23.80. 1 have also visited the site on July 20, 2007.
Based on my review and site observation, I am of the opinion that the proposed development is feasible
from a geotechnical standpoint. We intend to perform a test pit exploration program after the current wet
season. We will then produce a geotechnical report documenting our findings and detailed
recommendations regarding foundation support and earthwork.
If you have any questions, please feel free to contact the undersigned.
Sincerely,
SOIL & ENVIRONMENTAL ENGINEERS, INC.
Miles and Hinkel Short Plats
C.J. Shin, PhD_, P.E.
President
3- 1'�4 - 0�1
Attachment 5
REPORT OF GEOTECHNICAL INVESTIGATION
PROPOSED MILES SHORT PLAT
EDMONDS, WASHINGTON
S&EE JOB NO. 622
AUGUST 3, 2007
622Ept
Attachment 6
S&EE
SOIL & ENVIRONMENTAL ENGINEERS, INC.
16625 Redmond Way, Suite M 124. Redmond. Washington 98052. (425) 868-5868 FAX (425) 868-7427
August 3, 2007
Mr. Steve Miles
7005 174"' Street SW
Edmonds, WA 98026
Report
Geotechnical Investigation
Proposed Miles Short Plat
Edmonds, Washington
Dear Steve:
We are pleased to present herewith our Report of Geotechnical Investigation for the referenced project. Our
services were authorized by you on July 20, 2006, and have been provided in accordance with our proposal
dated the same.
We appreciate the opportunity to provide our services. Should you have any question regarding the contents
of this report or require additional information, please call.
EXPIRES: r/6'/. ZDor
Very truly yours,
SOIL & ENVIRONMENTAL ENGINEERS, INC.
C. J. Shin, Ph.D., P.E.
President
622rpt S&EE
TABLE OF CONTENTS
Section
1.0 INTRODUCTION .........................................
.................... 1
2.0 SCOPE OF SERVICES....................................................................................................................................... I
3.0 SITE CONDITIONS............................................................................................................................................ 2
3.1 SURFACE CONDITIONS................................................................................................................................. 2
3.2 SUBSURFACE CONDITIONS......................................................................................................................... 2
4.0 ENGINEERING EVALUATION OF SLOPE STABILTY.............................................................................. 3
5.0 CONCLUSIONS AND RECOMMENDATIONS.............................................................................................. 4
5.1 GENERAL.........................................................................................................................................................4
5.2 SLOPE PROTECTION......................................................................................................................................
4
5.2.1 EROSION CONTROL AND DRAINAGE.....................................................................................................
4
5.2.2 LEAKAGE CONTROL....................................................................................................I—-......__...............:
5
5.2.3 FOOTING NEAR SLOPE...............................................................................................................................
5
5.3 SITE PREPARATION AND STRUCTURAL FILL..........................................................................................
5
5.4 FOUNDATION SUPPORT...............................................................................................................................
6
5.5 SLAB SUPPORT. ..................................................................................................................... —.— ..................
7
5.6 LATERAL EARTH PRESSURES.....................................................................................................................
8
5.7 ROCKERY WALLS........................................................................................................................................
10
5.8 FLEXIBLE PAVEMENT......................................................................... ......................
5.9 SEISMIC CONSIDERATIONS........................................................................................................................
12
5.10 ADDITIONAL SERVICES............................................................... ..
12
6.0 LIMITATIONS................................................................................................................................................... 13
FIGURE 1: SITE VICINITY MAP
FIGURE 2: SITE AND EXPLORATION PLAN
FIGURE 3: SURCHARGE LOADS ON SUBSURFACE WALLS
FIGURE 4: GEO-GRID REINFORCED ROCKERY WALLS
APPENDIX A: FIELD EXPLORATION LOGS AND KEY
622rpt i S&EE
REPORT OF GEOTECHNICAL INVESTIGATION
PROPOSED MILES SHORT PLAT
EDMONDS, WASHINGTON
for
Mr. Steve Miles
1.0 INTRODUCTION
We present in this report the results of our geotechnical investigation for the proposed residential
development. The site is located to the north of 174'h Street S.W., in Edmonds, Washington. A site vicinity
map is included in Figure 1 and a site plan is shown in Figure 2; both are included at the end of this report.
We understand that the project will involve subdividing the property into two lots. The existing house in the
southern portion of the property will remain and a new lot in the northern portion will be created. An
access road for the new house is proposed in the southeastern portion of the new lot. The construction of
this road will require about 10 feet of maximum fill. The existing road for the existing house will be
widened. About 10 feet of maximum cut will be required for widening the road. We understand from your
architect, Mr. hied Brown, that about 20 feet of excavation at the new house will be required to reach the
proposed building subgrade. A new storm water retention structure is proposed on both the new and
existing lots.
2.0 SCOPE OF SERVICES
The purpose of our geotechnical investigation is to develop geotechnical recommendations regarding site
preparation and foundation support. Specifically, our services included:
1. Site reconnaissance to observe surface conditions including obvious signs of slope instability and
wet and unstable soils.
2. Exploration of the soil and groundwater conditions underlying the site through the excavation of S
test pits, TP -1 through TP -5. The approximated exploration locations are shown on Figure 2.
Details of the exploration program and the logs of explorations are presented in Appendix A of this
report.
622rpt S&EE
3. Recommendations regarding foundation support.
4. Recommendations regarding the construction of the new access road.
5. Recommendations regarding seismic design.
6. Evaluation of the stability of the onsite slopes, recommendation regarding mitigations, if needed.
7. Recommendations regarding active and at -rest earth pressures to be used for the design of any
retaining structures.
8. Recommendations regarding site preparation, including removal of unsuitable soils, suitability of
onsite soils for use as fill, fill placement techniques, and compaction criteria.
9. Five copies of ibis written geotechnical report containing a site plan, exploration logs, a description
of subsurface conditions, and our findings and recommendations.
3.0 SITE CONDITIONS
3.1 SURFACE CONDITIONS
The site (the new lot) is located on slopes with inclination varying from about 20% to 40%. The
maximum relief across the site is about 36 feet. At the time of our field exploration, the site surface is
covered with dense trees and thick undergrowths. We did not observed any signs of obvious slope
instability which typically include slumps, cracks or fissures in the ground, wet and unstable soils, and
springs.
3.2 SUBSURFACE CONDITIONS
PUBLISHED SOIL SURVEY INFORMATION
Published SCS map of the Snohomish County area indicates that the surficial soil at site consists of
Alderwood-Everett gravelly sandy foams. According to SCS the erosion hazard for these soils are high.
622rpt 2 S&EE
TEST PIT FINDINGS
The soil conditions underlying the site were explored by the excavation of 5 test pits on July 3, 2007. Test
pits TP -1 through TP -4 were excavated in the new lot. TP -5 was excavated near the north end of the
proposed widened road. The onsite test pits indicate that the site is covered by approximately 12 inches of
topsoil. Under the topsoil, the test pits encountered a brown silty sand of about 2.5 to 3 feet in thickness.
This material was mostly dry and medium dense to dense. Under this layer, a brownish gray, silty sand with
various amounts of gravel and cobbles was encountered. The material was very dense and cemented.
Based on their appearances and densities, we believe that these onsite soils were glacially deposited and
consolidated (till). TP -5 encountered about 4 feet of possible fill at the ground surface. This material was
loose to medium dense silty sand and was underlain by about 4 feet of medium dense silty sand. The latter
was in turn underlain by very dense till. Groundwater was not encountered in any test pit.
4.0 ENGINEERING EVALUATION OF SLOPE STABILTY
Based on our understanding of the subsurface conditions underlying the site and slope, and our estimate of
the soil parameters, we have evaluated the stability of the slope using the computer program STABLSM.
The analyses consider both steady state and dynamic loading conditions. The latter included an earthquake
producing a ground acceleration of 0.1 Sg which would represent an earthquake magnitude (M) of about 6.0
to 7.0.
The information obtained from the slope stability analyses includes safety factors against deep-seated slope
movement. The standard engineering practice considers a slope to be acceptably stable if it demonstrates
factors of safety of at least 1.5 and 1.1 for static and dynamic loading conditions, respectively. A factor of
safety is defined as the summation of resisting forces divided by the summation of driving forces.
The following table presents the results of our slope stability analyses for the project.
Factor of Safety
Type of Slope Movement Steady -State Dynamic (Earthquake)
Deep -Seated 1.8 1.2
These results indicate that the potential of a deep-seated movement of the steep slope is low.
62.2ipt 3 S&EE
5.0 CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL
Our explorations indicate that the site area is underlain by competent native soils. Based on our
evaluation, the onsite slopes are currently stable and should remain stable provided that the
recommendations presented in this report are followed.
Please be aware that there is always an inherent risk of slope movement for any development near slopes. In
addition to natural factors (soil, groundwater, heavy rainfall), other factors that may affect stability include
excavations, fills, leaking or broken utility, improper drainage, lack of maintenance of drainage facilities or
vegetation cover, unwise actions by adjacent property owners, or similar events or unknown conditions that
may cause instability. Therefore, future property owners must be alert of any adverse impacts on the slope
and take corrective actions as needed.
5.2 SLOPE PROTECTION
5.2.1 EROSION CONTROL AND DRAINAGE
The surficial soils at the site are highly erosion prone. During construction, any exposed area should be
covered by visqueen before inclement rain storms or when the area is un -worked for 48 hours during
October I through April 30, or un -worked for 7 days during May 1 through September 30. The site surface
should be graded so that surface water is directed away from the structural areas. Standing water over site
surface and runoff over any slope face should not be allowed.
Vegetation on slopes is the key to long-term slope stability. Lack of vegetation cover can result in the
development of erosion channels which can in turn cause slope instability. Hence, all permanent slopes
should be planed with appropriate species of vegetation and the vegetation should be adequately
maintained. Any surface becomes bare should be re -planted immediately.
Site surface and permanent slopes should be graded so that no runoff will concentrate and flow over any
part of the slope face. Footing and roof drains should be separated and both tie -lined to the storm
drainage system.
622rpt 4 S&EE
5.2.2 LEAKAGE CONTROL
Based on the current plan, storm water retention structures are proposed for both the existing and the new
lots. Since these structures will be located on a continuous slope, leakage control measures should be
installed to handle any possible future leakage and to avoid uncontrolled flow over slope. Typical control
measures include the installation of a perforated drainpipe at the downhill side of the structure, and
connecting the drainpipe to the storm drain.
5.2.3 FOOTING NEAR SLOPE
To avoid loading of slopes by building foundations, footings near any slope should be deepened so that the
horizontal distance from the outside footing edge to the slope face is at least 10 feet.
5.3 SITE PREPARATION AND STRUCTURAL FILL
Site preparation should begin with stripping vegetation and topsoil of the structural areas including
driveway, building and stabs. The subgrade should be thoroughly proof -rolled using heavy construction
equipment. if proof rolling is not feasible due to wet condition, the area should be probed using a steel bar
so as to avoid disturbance and rutting of the subgrade soils. Areas which are found to be loose or soft, or
which contain organic soils should be over -excavated.
A qualified geotechnical engineer should conduct the proof -rolling and/or probing to assist in identifying
loose soils and evaluating the over -excavation requirements.
After stripping, over -excavation and excavation to the design grade, the top 12 inches of the native soils
should be re -compacted to at least 92% of their maximum dry density as determined using ASTM D-1557
test procedures (Modified Proctor test). Structural fill can then be placed in the over -excavation and fill
areas.
The structural fill materials should meet both the material and compaction requirements presented below.
Material Requirements: Structural fill should be free of organic and frozen material and should
consist of hard durable. particles, such as sand, gravel, or quarry -processed stone. The on-site soils
622rpt 5 S&EE
are suitable for use as structural fill. However, most of these soils are moisture sensitive and should
be moisture -conditioned to within ± 2% of their optimum moisture content prior to use. Suitable
imported structural fill materials include sand and gravel (pitrun), and crushed rock.
Placement and Compaction Requirements: Structural fill should be placed in loose horizontal lifts
not exceeding a thickness of 6 to 12 inches, depending on the material type, compaction equipment,
and number of passes made by the equipment. Structural fill should be compacted to at least 95%
of the maximum dry density as determined using the ASTM D-1557 test procedures.
Care must be taken when structural fill is placed on slopes. The procedure requires that the
existing slope be benched so that the new rill can be keyed into the slope. Proper placement
and compaction are critical to long-term slope stability. It is strongly recommended that the
earthwork be monitored by a qualified geotechnical engineer.
5.4 FOUNDATION SUPPORT
The proposed house and all retaining walls can be supported by conventional spread footings which should
penetrate topsoil, and be founded on at least medium dense, native soils. Details of our recommendations
regarding the foundation design are presented in the following sections.
Bearing Capacity: We recommend an allowable bearing pressure of 2,000 pounds per square feet (psf) for
the design of the footings. This value includes a safety factor of at least 3, and can be increased by one-third
for wind and seismic loads.
Footing? Construction: The footing bearing surfaces should be protected from weather and disturbance, and
all organic, softened and loosened soils must be removed by over -excavation. Any over -excavation at the
footing subgrade should be backfilled with concrete, lean concrete or structural fill.
Please note that our test pits were backfilled with the excavated soils, which were placed in 2 -foot thick lifts
and compacted with the trackhoe bucket. If these test pits are located at the future footings, the upper 3 feet
of the fill below the footing subgrade should be over -excavated. The over -excavation should be backfilled
with structural fill.
All footing subgrade should be inspected by a qualified geotechnical engineer prior to re -bar and concrete
622rpt 6 S&EE
placements.
All exterior footings should be founded at least 18 inches below the adjacent finished grade to provide
protection against frost action, and should be at least 18 inches in width to facilitate construction.
Settlement: Interior column footings designed in accordance with the above recommendations are expected
to experience approximately 1/2 inch of settlement. Continuous wall footings should experience about 114
to 1/2 inch. Differential settlement between adjacent footings is expected to be 114 to 1/2 of an inch.
Lateral Resistance: Lateral resistance can be obtained from the passive earth pressure against the footing
sides and the friction at the contact of the footing bottom and bearing soil. The former can be obtained
using an equivalent fluid density of 250 pounds per cubic foot (pcf), and the latter using a coefficient of
friction of 0.5. These values include a safety factor of 1.5.
FootingD_ rain: Rigid, perforated drainpipes should be installed around all perimeter footings. Drainpipes
should be at least 4 inches in diameter, covered by a layer of uniform size drain gravel of at least 12 inches
in thickness, and be connected to a suitable discharge location. An adequate number of cleanouts should be
installed along the drain line for future maintenance. Footing drains should be separated from roof
drains.
5.5 SLAB SUPPORT
All slabs -on -grade can be supported on structural fill or at least medium dense native soils. We envision
that the soil at the slab subgrade will be disturbed and loosened by construction activities at the time of slab
construction. We therefore recommend that the slab subgrade be proof -rolled or probed. Any wet and loose
areas should be over -excavated and backfilled with structural fill.
In order to promote uniform support and provide a capillary break, we recommend that slabs be underlain
by a 6 mil. vapor barrier over a 4 -inch thick layer of free draining gravel.
622rpt 7 S&EE
5.6 LATERAL EARTH PRESSURES
Lateral earth pressures on retaining walls or permanent subsurface walls, and resistance to lateral loads may
be estimated using the following recommended soil parameters:
Note: Hydrostatic pressures are not included in the above lateral earth pressures.
The active case applies to walls that are permitted to rotate ortranslate away from the retained soil by
approximately 0.002H, where H is the height of the wall. This would be appropriate for a cantilever
retaining wall. The at -rest case applies to unyielding walls, and would be appropriate for walls that are
structurally restrained from lateral deflection such as basement walls, utility trenches and pits.
SURCHARGE INDUCED LATERAL LOADS
1) Additional lateral earth pressures will result from surcharge loads from floor slabs or pavements for
parking that are located immediately adjacent to the walls. The surcharge -induced lateral earth
pressures are uniform over the depth of the wall. Surcharge -induced lateral pressures for the
"active" case may be calculated by multiplying the applied vertical pressure (in psf) by the active
earth pressure coefficient (Ka). The value of Ka may be taken as 0.3. The surcharge -induced lateral
pressures for the "at -rest" case are similarly calculated using an at -rest earth pressure coefficient
(Ko) of 0.5. For surcharge loads that are not adjacent to the wall, the induced lateral earth pressure
will depend on the magnitude of the surcharge and the distance from the wall. Such induced lateral
load can be estimated using the equations shown on Figure 3.
2) The traffic -induced lateral earth pressure can be accounted for by increasing the effective wall
height by 2 feet.
622rpt S S&EE
Equivalent Fluid Unit Weight (PCF)
Coefficient
of
Friction
Active
At -rest
Passive
Flat Backfill
30
50
300
0.5
QH:1 V) Slope Backfill
45
75
300
0.5
Note: Hydrostatic pressures are not included in the above lateral earth pressures.
The active case applies to walls that are permitted to rotate ortranslate away from the retained soil by
approximately 0.002H, where H is the height of the wall. This would be appropriate for a cantilever
retaining wall. The at -rest case applies to unyielding walls, and would be appropriate for walls that are
structurally restrained from lateral deflection such as basement walls, utility trenches and pits.
SURCHARGE INDUCED LATERAL LOADS
1) Additional lateral earth pressures will result from surcharge loads from floor slabs or pavements for
parking that are located immediately adjacent to the walls. The surcharge -induced lateral earth
pressures are uniform over the depth of the wall. Surcharge -induced lateral pressures for the
"active" case may be calculated by multiplying the applied vertical pressure (in psf) by the active
earth pressure coefficient (Ka). The value of Ka may be taken as 0.3. The surcharge -induced lateral
pressures for the "at -rest" case are similarly calculated using an at -rest earth pressure coefficient
(Ko) of 0.5. For surcharge loads that are not adjacent to the wall, the induced lateral earth pressure
will depend on the magnitude of the surcharge and the distance from the wall. Such induced lateral
load can be estimated using the equations shown on Figure 3.
2) The traffic -induced lateral earth pressure can be accounted for by increasing the effective wall
height by 2 feet.
622rpt S S&EE
SEISMIC INDUCED LATERAL LOADS
For seismic induced lateral loads, the dynamic force can be assumed to act at 0.6 H above the wall base
and the magnitude can be calculated using the following equation:
Pe = 318*7*H2*a
Where Pe = seismic -induced lateral load
7 = soil density = 130 pcf
H = wall height
a = horizontal acceleration, 0.15g
BACKFILL IN FRONT OF RETAINING WALLS
Backfill in front of the wall should be structural fill. The material and compaction requirements are
presented in Section 53 of this report. The density of the structural fill can be assumed to be 130 pounds
per cubic feet.
BACKFILL BEHIND RETAINING WALLS
Backfill behind the wall should be free -draining materials which are typically granular soils containing less
than 5% fines (silt and clay particles) and no particles greater than 4 inches in diameter.
The backfill material should be placed in 6 to 8 -inch thick horizontal lifts and compacted to at least 90
percent of the maximum density in accordance with ASTM D-1557 test procedures. In the areas where the
fill will support pavement, sidewalk or slabs, the top two feet of the backfill should be compacted to at least
95 percent of the maximum density_ Care must be taken when compacting backfil I adjacent to retaining
wal Is, to avoid creating excessive pressure on the wall.
DRAINAGE BEHIND RETAINING WALLS
Rigid, perforated drainpipes should be installed behind retaining walls. Drainpipes should be at least 4
inches in diameter, covered by a layer of uniform size drain gravel of at least 12 inches in thickness, and be
connected to a suitable discharge location. An adequate number of cleanouts should be installed along the
drain line for future maintenance.
62Zrpt 9 S&EE
5.7 ROCKERY WALLS
In addition to concrete retaining walls, reinforced or non -reinforced rockery walls can be considered for
grading purposes. Reinforcement should be used when:
1. The wall will be used to retain Ell embankment that is over 4 feet in height.
2. The wall will retain a cut embankment greater than 6 feet in height.
A typical reinforced rockery wall details are shown in Figure 4 and the general notes for reinforced rockery
walls are presented below. Please note that the figure and notes are for planning purposes. A detailed
designed by a qualified geotechnical engineer should be performed based on the final grading plan.
GENERAL NOTES FOR GEO-GRED REINFORCED ROCKERY WALL
ROCK SIZE
THE LOWER HALF SHALL BE CONSTRUCTED OF FOUR -MAN OR LARGER ROCKS
(DEFINED BELOW). FOR THE UPPER HALF, PROGRESSIVELY SMALLER ROCKS MAY BE
USED, WITH A MINIMUM SIZE OF TWO-MAN FOR THE UPPERMOST COURSE.
APPROXIMATE ROCK SIZES
SIZE
WEIGHT (LBS_)
1 -MAN
58-210
2 -MAN
265-580
3 -MAN
760-1,830
4 -MAN
3,000 - 4,000
5 -MAN
5,000
6 -MAN
7,000
ROCK PLACEMENT
VOLUME (CUBIC FT_)
0.4-1.3
1.6-3.6
4.7-11.2
18.4-24.5
30.7
42.9
THE BASE COURSE OF ROCKS MUST BE EMBEDDED INTO FIRM UNDISTURBED EARTH
TO A MINIMUM DEPTH OF 12 INCHES TO PROVIDE A SECURE FOOTING FOR THE
ROCKERY. THE LONG DIMENSION OF THE ROCKS MUST EXTEND INTO THE SLOPE
BEHIND THE ROCKERY TO PROVIDE MAXIMUM STABILITY. SUBSEQUENT COURSES OF
ROCKS MUST BE PLACED TO LOCK INTO THE ROCKS IN THE LOWER COURSE OR TIER.
622tpi - 10 S&EE
GEO-GRID
1. GEO-GRID SHALL CONSIST OF MIRAFI MIRAGRID 5XT OR ITS EQUIVALENT HAVING THE
FOLLOWING PROPERTIES:
PHYSICAL PROPERTY TEST METHOD MINIMUM VALUE (LB/FT)
LONG TERM ALLOWABLE DESIGN LOAD GRI GG -4 2327
TENSIL STRENGTH (AT 5% STRAIN) ASTM D 6637 1740
CREEP REDUCED STRENGTH ASTM 5262 2688
2, FIELD ADJUSTMENT OF THE GEO-GRID INTERVAL MAY BE REQUIRED. NO GEO-GRID IS
REQUIRED FOR WALL HEIGHTS EQUAL TO OR LESS THAN 4'- 0".
3. GEO-GRID REINFORCEMENT SHALL BE PLACED TAUT (NO WRINKLE) WITH ADJACENT
REINFORCEMENT OVERLAP AT LEAST 12 INCHES_
STRUCTUAL FILL
STRUCTURAL FILL MATERIAL SHALL BE APPROVED BY PROJECT GEOTECHNICAL
ENGINEER PRIOR TO USE. THE MATERIAL SHALL BE COMPACTED TO AT LEAST 95% OF
MAXIMUM DENSITY AS DETERMINED USING ASTM D1557 (MODIFIED PROCTOR) TEST
METHOD.
DRAINAGE
DRAIN PIPE SHALL BE 4" DIAMETER PERFORATED, PVC, PIPE. INSTALL ONE CLEANOUT
AT BEGINNING AND EVERY 150 FEET OF LINE.
622rpt S&EE
5.8 FLEXIBLE PAVEMENT
We recommend that the subgrade for flexible pavement be prepared in accordance with the
recommendations presented in Section 5.3 SITE PREPARATION AND STRUCTURAL FILL.
Based on the subsoil conditions, we believe that the prepared subgrade will have a California Bearing
Ratio (CBR) of at least 12.
For the proposed access road, we recommend a pavement section consisting of 2 inches asphaltic
concrete over 4 inches base course. The base course should be compacted to at least 95 percent of the
maximum dry density as determined by ASTM D-1557 test method. The material should meet WSDOT
aggregate specification 9-03.9(3) and have the following gradation:
Sieve Size
Percent Passing
I F/4 -inch
100
518 -inch
50-80
114 -inch
30-50
US No. 40
3-18
US No. 200
7.5 max.
% Fracture
75 min.
5.9 SEISMIC CONSIDERATIONS
We recommend that Site Class C as defined in the 2003 IBC be considered for the building design. The
site is underlain by dense soils. As such, the liquefaction potential is negligible.
5.10 ADDITIONAL SERVICES
Additional services may be required during the design and construction of the project. We envision that
these additional services may include the following:
1. Review of design plans and responses to city's comments.
622rpt 12 S&EE
2. Provision of construction monitoring services. The tasks of our monitoring service typically include
the followings:
2.1 Monitoring of temporary excavations.
2.2 Monitoring of spread footing subgrade preparation. Our representative will confirm the bearing
capacity of the subgrade soils, and will assist the contractor in evaluating the over -excavation
requirements, if any.
2-3 Monitoring the placement and compaction of structural fill. Our representative will confirm the
suitability of the fill materials, perform field density tests, and assist the contractor in meeting
the compaction requirements.
2.4 Monitoring the installation of subsurface drains. Our representative will confirm that these
drains are installed in accordance with our recommendations.
3. Other geotechnical issues deemed necessary.
6.0 LIMITATIONS
The recommendations presented in this report are provided for design purposes and are based on soil
conditions disclosed by field observations and subsurface explorations. Subsurface information presented
herein does not constitute a direct or implied warranty that the soil conditions between exploration locations
can be directly interpolated or extrapolated or that subsurface conditions and soil variations different from
those disclosed by the explorations will not be revealed. The recommendations outlined in this report are
based on the assumption that the development plan is consistent with the description provided in this report.
If the development plan is changed or subsurface conditions different from those disclosed by the
exploration are observed during construction, we should be advised at once so that we can review these
conditions, and if necessary, reconsider our design recommendations.
622rpt 13 S&EE
REPORT OF GEOTECHNICAL INVESTIGATION
PROPOSED HINKEL SHORT PLAT
EDMONDS, WASHINGTON
S&EE JOB NO. 623
AUGUST 3, 2007
623rpt
Cil'4S
m
Attachment 7
S&EE
SOIL & ENVIRONMENTAL ENGINEERS, INC.
16625 Redmond Way Suite M 124 Redmond, Washington 99052__(425) 868-5868 FAX (425)..868-7427
August 3, 2007
Mr. Greg Hinkel
7027 174'[' Street SW
Edmonds, WA 98026
Report
Geotechnical Investigation
Proposed Hinkel Short Plat
Edmonds, Washington
Dear Greg:
We are pleased to present herewith our Report of Geotechnical Investigation for the referenced project. Our
services were authorized by you on September 2, 2006, and have leen provided in accordance with our
proposal dated July 20, 2006.
We appreciate the opportunity to provide our services. Should you have any question regarding the contents
of this report or require additional information, please call.
Very truly yours,
ENS SOIL & ENVIRONMENTAL ENGINEERS, INC.
was\�S'�.
2e166 4 w4
rONAL'� C. J. Shin, Ph.D., P.E.
President
�t�: iV tiv. ZUo
623rpt S&EE
TABLE OF CONTENTS
Section
1.0 INTRODUCTION....................................................................................
2.0 SCOPE OF SERVICES
........................................... I
................ I
3.0 SITE CONDITIONS............................................................................................................................................ 2
3.1 SURFACE CONDITIONS.... ................ .................... ........... ......... -- ....................__.........._................ 2
3.2 SUBSURFACE CONDITIONS.........................................................................................................................2
4.0 ENGINEERING EVALUATION OF SLOPE STABILTY.............................................................................. 3
5.0 CONCLUSIONS AND RECOMMENDATIONS.............................................................................................. 4
5.1 GENERAL. .............................. — ........... ....... ........................................................ ........................... 4
5.2 SLOPE PROTECTION .......... .............................. .............................................................................................. 4
5.2.1 EROSION CONTROL AND DRAINAGE..................................................................................................... 4
5.2.2 LEAKAGE CONTROL .... ............. ......._............._._...._..._................................................................................ 5
5.2.3 FOOTING NEAR SLOPE............................................................................................................................... 5
5.3 SITE PREPARATION AND STRUCTURAL FILL.......................................................................................... 5
5.4 FOUNDATION SUPPORT............................................................................................................................... 6
5.5 SLAB SUPPORT.................................................................................................... ... 7
5.6 LATERAL EARTH PRESSURES..................................................................................................................... 8
5.7 ROCKERY WALLS........................................................................................................................................ 10
5.8 FLEXIBLE PAVEMENT................................................................................................................................ 12
5.9 SEISMIC CONSIDERATIONS............................................................._......................................................... 12
5.10 ADDITIONAL SERVICES........................................................................................................................... 12
6.0 LIMITATIONS................................................................................................................................................... 13
FIGURE 1: SITE VICINITY MAP
FIGURE 2: SITE AND EXPLORATION PLAN
FIGURE 3: SURCHARGE LOADS ON SUBSURFACE WALLS
FIGURE 4: GEO-GRID REINFORCED ROCKERY WALLS
APPENDIX A: FIELD EXPLORATION LOGS AND KEY
623rpt i S&EE
REPORT OF GEOTECHNICAL INVESTIGATION
PROPOSED HINKEL SHORT PLAT
EDMONDS, WASHINGTON
for
Mr. Greg Hinkel
1.0 INTRODUCTION
We present in this report the results of our geotechnical investigation for the proposed residential
development. The site is located to the north of 170 Street S.W., in Edmonds, Washington. A site vicinity
map is included in Figure I and a site plan is shown in Figure 2; both are included at the end of this report.
We understand that the project will involve subdividing the property into two lots. The existing house at the
southeastern portion of the property will remain and a new lot in the northwestern portion will be created.
An access road for the new lot will be constructed in the southwestern portion of the property. A maximum
cut of about 5 to 6 feet will be required for the road. We understand from your architect, Mr. Fred Brown,
that about 13 feet of excavation at the new building will be required. A new storm water retention structure
is proposed on both the new and existing lots.
2.0 SCOPE OF SERVICES
The purpose of our geotechnical investigation is to develop geotechnical recommendations regarding site
preparation and foundation support. Specifically, our services included:
1. Site reconnaissance to observe surface conditions including obvious signs of slope instability and
wet and unstable soils.
2. Exploration of the soil and groundwater conditions underlying the site through the excavation of 4
test pits, TP -1 through TP -4. The approximated exploration locations are shown on Figure 2.
Details of the exploration program and the logs of explorations are presented in Appendix A of this
report.
3. Recommendations regarding foundation support.
4. Recommendations regarding the construction of the new access road.
623rpt S&EE
5. Recommendations regarding seismic design.
6. Evaluation of the stability of the onsite slopes, recommendation regarding mitigations, if needed.
7_ Recommendations regarding active and at -rest earth pressures to be used for the design of any
retaining structures.
8. Recommendations regarding site preparation, including removal of unsuitable soils, suitability of
onsite soils for use as fill, fill placement techniques, and compaction criteria.
9. Five copies of this written geotechnical report containing a site plan, exploration logs, a description
of subsurface conditions, and our findings and recommendations.
3.0 SITE CONDITIONS
3.1 SURFACE CONDITIONS
The site (the new lot) is located on a north-east facing slope with inclination varying from about 15% to
ala%. The maximum relief across the site is about 34 feet. At the time of our field exploration, the site
surface is covered with dense trees and thick undergrowths. We did not observed any obvious signs of
slope instability which typically include slumps, cracks or fissures in the ground, wet and unstable soils, and
springs.
3.2 SUBSURFACE CONDITIONS
PUBLISHED SOIL SURVEY INFORMATION
Published SCS map of the Snohomish County area indicates that the surficial soil at site consists of
Alderwood-Everett gravelly sandy foams. According to SCS the erosion hazard for these soils are high.
623rpt 2 S&EE
TEST PIT FINDINGS
The soil conditions underlying the site were explored by the excavation of test pits on July 3, 2007.
These explorations indicate that the site is covered by approximately 12 inches of topsoil. Under the
topsoil, the test pits encountered about 2 to 4 feet of silty sand. This material was mostly dry and medium
dense. Under this silty sand, dense sand with various amounts of gravel and cobbles was encountered. The
material was moist and slightly cemented at places. Based on their appearances and densities, we believe
that these onsite soils were native materials deposited by last glaciations. The upper 2 to 4 feet of the
material might be deposited by recessing glacier (recessional outwash), and the material below was likely
consolidated by the advancing glacier. Groundwater was not encountered in any test pit.
4.0 ENGINEERING EVALUATION OF SLOPE STABILTY
Based on our understanding of the subsurface conditions underlying the site and slope, and our estimate of
the soil parameters, we have evaluated the stability of the slope using the computer program STABL5M.
The analyses consider both steady state and dynamic loading conditions. The latter included an earthquake
producing a ground acceleration of 0.158 which would represent an earthquake magnitude (M) of about 6.0
to 7.0.
The information obtained from the slope stability analyses includes safety factors against deep-seated slope
movement. The standard engineering practice considers a slope to be acceptably stable if it demonstrates
factors of safety of at least 1.5 and 1.1 for static and dynamic loading conditions, respectively. A factor of
safety is defined as the summation of resisting forces divided by the summation of driving forces.
The following table presents the results of our slope stability analyses for the project.
Factor of Safety
Type of Sloe Movement Steady -State Dynamic (Earthquake)
Deep -Seated 2.9 1.6
These results indicate that the potential of a deep-seated movement of the steep slope is very low.
623rpt 3 S&EE
5.0 CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL
Our explorations indicate that the site area is underlain by competent native soils. Based on our
evaluation, the onsite slopes are currently stable and should remain stable provided that the
recommendations presented in this report are followed_
Please be aware that there is always an inherent risk of slope movement for any development near slopes. In
addition to natural factors (soil, groundwater, heavy rainfall), other factors that may affect stability include
excavations, fills, leaking or broken utility, improper drainage, lack of maintenance of drainage facilities or
vegetation cover, unwise actions by adjacent property owners, or similar events or unknown conditions that
may cause instability. Therefore, future property owners must be alert of any adverse impacts on the slope
and take corrective actions as needed.
5.2 SLOPE PROTECTION
5.2.1 EROSION CONTROL AND DRAINAGE
The surfcial soils at the site are highly erosion prone. During construction, any exposed area should be
covered by visaueen before inclement rain storms or when the area is un -worked for 48 hours during
October l through April 30, or un -worked for 7 days during May I through September 30. The site surface
should be graded so that surface water is directed away from the structural areas. Standing water over site
surface and un -controlled runoff over any slope face should not be allowed.
Vegetation on slopes is the key to long-term slope stability. Lack of vegetation cover can result in the
development of erosion channels which can in turn cause slope instability. Hence, all permanent slopes
should be planed with appropriate species of vegetation and the vegetation should be adequately
maintained. Any surface becomes bare should be re -planted immediately.
Site surface and permanent slopes should be graded so that no runoff will concentrate and flow over any
part of the slope face. Footing and roof drains should be separated and both tie -lined to the storm
drainage system.
623rpt 4 S&EE
5.2.2 LEAKAGE CONTROL
Based on the current plan, storm water retention structures are proposed for both the existing and the new
lots_ Since these structures will be located on a continuous slope, leakage control measures should be
installed to handle any possible future leakage and to avoid uncontrolled flow over slope. Typical control
measures include the installation of a perforated drainpipe at the downhill side of the structure, and
connecting the drainpipe to the storm drain.
5.2.3 FOOTING NEAR SLOPE
To avoid loading of slopes by building foundations, footings near any slope should be deepened so that the
horizontal distance from the outside footing edge to the slope face is at least 10 feet.
5.3 SITE PREPARATION AND STRUCTURAL FILL
Site preparation should begin with stripping vegetation and topsoil of the structural areas including
driveway, building and slabs. The subgrade should be thoroughly proof -rolled using heavy construction
equipment. If proof rolling is not feasible due to wet condition, the area should be probed using a steel bar
so as to avoid disturbance and rutting of the subgrade soils. Areas which are found to be loose or soft, or
which contain organic soils should be over -excavated.
A qualified geotechnical engineer should conduct the proof -rolling and/or probing to assist in identifying
loose soils and evaluating the over -excavation requirements.
After stripping, over -excavation and excavation to the design grade, the top 12 inches of the native soils
should be re -compacted to at least 92% of their maximum dry density as determined using ASTM D-1557
test procedures (Modified Proctor test). Structural fill can then be placed in the over -excavation and fill
areas.
The structural fill materials should meet both the material and compaction requirements presented below.
Material Requirements: Structural fill should be free of organic and frozen material and should
consist of hard durable particles, such as sand, gravel, or quarry -processed stone. The on-site soils
623rpt . 5 S&EE
are suitable for use as structural fill. However, most of these soils are moisture sensitive and should
be moisture -conditioned to within ± 2% of their optimum moisture content prior to use. Suitable
imported structural fill materials include sand and gravel (pitrun), and crushed rock.
Placement and Compaction Requirements: Structural fill should be placed in loose horizontal lifts
not exceeding a thickness of 6 to 12 inches, depending on the material type, compaction equipment,
and number of passes made by the equipment. Structural fill should be compacted to at least 95%
of the maximum dry density as determined using the ASTM D-1557 test procedures.
Care must be taken when structural fill is placed on slopes. The procedure requires that the
existing slope be benched so that the new fill can be keyed into the slope. Proper placement
and compaction are critical to long-term slope stability. It is strongly recommended that the
earthwork be monitored by a qualified geotechnical engineer.
5.4 FOUNDATION SUPPORT
The proposed house and all retaining walls can be supported by conventional spread footings which should
penetrate topsoil, and be Founded on at least medium dense, native soils. Details of our recommendations
regarding the foundation design are presented in the following sections.
Bearing Capacity: We recommend an allowable bearing pressure of 2,000 pounds per square feet (psf) for
the design of the footings. This value includes a safety factor of at least 3, and can be increased by one-third
for wind and seismic loads.
Footing Construction: The footing bearing surfaces should be protected from weather and disturbance, and
all organic, softened and loosened soils must be removed by over -excavation. Any over -excavation at the
footing subgrade should be backfilled with concrete, lean concrete or structural fill.
Please note that our test pits were backfilled with the excavated soils, which were placed in 2 -foot thick lifts
and compacted with the trackhoe bucket. If these test pits are located at the future footings, the upper 3 feet
of the fill below the footing subgrade should be over -excavated. The over -excavation should be backfilled
with structural fill.
All footing subgrade should be inspected by a qualified geotechnical engineer prior to re -bar and concrete
623 rpt 6 S& EE
placements.
All exterior footings should be founded at least 18 inches below the adjacent finished grade to provide
protection against frost action, and should be at least 18 inches in width to facilitate construction.
Settlement: Interior column footings designed in accordance with the above recommendations are expected
to experience approximately 112 inch of settlement. Continuous wall footings should experience about 114
to 112 inch. Differential settlement between adjacent footings is expected to be 114 to 112 of an inch.
Lateral Resistance: Lateral resistance can be obtained from the passive earth pressure against the footing
sides and the friction at the contact of the footing bottom and bearing soil. The former can be obtained
using an equivalent fluid density of 250 pounds per cubic foot (pef), and the latter using a coefficient of
friction of 0.5. These values include a safety factor of 1.5.
Footing Drain: Rigid, perforated drainpipes should be installed around all perimeter footings. Drainpipes
should be at least 4 inches in diameter, covered by a layer of uniform size drain gravel of at least 12 inches
in thickness, and be connected to a suitable discharge location. An adequate number of cleanouts should be
installed along the drain line for future maintenance. Footing drains should be separated from roof
drains.
5.5 SLAB SUPPORT
All slabs -on -grade can be supported on structural fill or at least medium dense native soils. We envision
that the soil at the slab subgrade will be disturbed and loosened by construction activities at the time of slab
construction. We therefore recommend that the slab subgrade be proof -rolled or probed. Any wet and loose
areas should be over -excavated and backfilled with structural fill.
In order to promote uniform support and provide a capillary break, we recommend that slabs be underlain
by a 6 mil. vapor barrier over a 4 -inch thick layer of free draining gravel.
623rpt 7 S&.EE
5.6 LATERAL EARTH PRESSURES
Lateral earth pressures on retaining walls or permanent subsurface walls, and resistance to lateral loads may
be estimated using the following recommended soil parameters:
Note. Hydrostatic pressures are not included in the above lateral earth pressures.
The active case applies to walls that are permitted to rotate or translate away from the retained soil by
approximately 0.002H, where H is the height of the wall. This would be appropriate for a cantilever
retaining wall. The at -rest case applies to unyielding walls, and would be appropriate for walls that are
structurally restrained from lateral deflection such as basement walls, utility trenches and pits.
SURCHARGE INDUCED LATERAL LOADS
3) Additional lateral earth pressures will result from surcharge loads from floor slabs or pavements for
parking that are located immediately adjacent to the walls. The surcharge -induced lateral earth
pressures are uniform over the depth of the wall. Surcharge -induced lateral pressures for the
"active" case may be calculated by multiplying the applied vertical pressure (in psf) by the active
earth pressure coefficient (Ka). The value of Ka may be taken as 0.3. The surcharge -induced lateral
pressures for the "at -rest" case arc similarly calculated using an at -rest earth pressure coefficient
(Ko) of 0.5. For surcharge loads that are not adjacent to the wall, the induced lateral earth pressure
will depend on the magnitude of the surcharge and the distance from the wall. Such induced lateral
load can be estimated using the equations shown on Figure 3.
2) The traffic -induced lateral earth pressure can be accounted for by increasing the effective wall
height by 2 feet.
623rpt 8 S& EE
Equivalent Fluid Unit Weight (PCF)
Coefficient
of
Friction
Active
At -rest
Passive
Flat Backfill
30
50
300
0.5
(211: IV) Slope Backfill
45
75
300
0.5
Note. Hydrostatic pressures are not included in the above lateral earth pressures.
The active case applies to walls that are permitted to rotate or translate away from the retained soil by
approximately 0.002H, where H is the height of the wall. This would be appropriate for a cantilever
retaining wall. The at -rest case applies to unyielding walls, and would be appropriate for walls that are
structurally restrained from lateral deflection such as basement walls, utility trenches and pits.
SURCHARGE INDUCED LATERAL LOADS
3) Additional lateral earth pressures will result from surcharge loads from floor slabs or pavements for
parking that are located immediately adjacent to the walls. The surcharge -induced lateral earth
pressures are uniform over the depth of the wall. Surcharge -induced lateral pressures for the
"active" case may be calculated by multiplying the applied vertical pressure (in psf) by the active
earth pressure coefficient (Ka). The value of Ka may be taken as 0.3. The surcharge -induced lateral
pressures for the "at -rest" case arc similarly calculated using an at -rest earth pressure coefficient
(Ko) of 0.5. For surcharge loads that are not adjacent to the wall, the induced lateral earth pressure
will depend on the magnitude of the surcharge and the distance from the wall. Such induced lateral
load can be estimated using the equations shown on Figure 3.
2) The traffic -induced lateral earth pressure can be accounted for by increasing the effective wall
height by 2 feet.
623rpt 8 S& EE
SEISMIC INDUCED LATERAL LOADS
For seismic induced lateral loads, the dynamic force can be assumed to act at 0.6 H above the wall base
and the magnitude can be calculated using the following equation:
Pe = 318*7*H'*a
Where Pe = seismic -induced lateral load
7 = soil density = 130 pcf
H = wail height
a = horizontal acceleration, 0.15g
BACKFILL iN FRONT OF RETAINING WALLS
Backfill in front of the wall should be structural fill. The material and compaction requirements are
presented in Section 5.3 of this report. The density of the structural fill can be assumed to be 130 pounds
per cubic feet.
BACKFILL BEHIND RETAINING WALLS
Backfill behind the wall should be free -draining materials which are typically granular soils containing less
than 5% fines (silt and clay particles) and no particles greater than 4 inches in diameter.
The backfill material should be placed in 6 to 8 -inch thick horizontal lifts and compacted to at least 90
percent of the maximum density in accordance with ASTM D-1557 test procedures. In the areas where the
fill will support pavement, sidewalk or slabs, the top two feet of the backfill should be compacted to at least
95 percent of the maximum density. Care must be taken when compacting backfill adjacent to retaining
walls, to avoid creating excessive pressure on the wall.
DRAINAGE BEHIND RETAINING WALLS
Rigid, perforated drainpipes should be installed behind retaining walls. Drainpipes should be at least 4
inches in diameter, covered by a layer of uniform size drain gravel of at least 12 inches in thickness, and be
connected to a suitable discharge location. An adequate number of cleanouts should be installed along the
drain line for future maintenance.
623rpt 9 S&EE
5.7 ROCKERY WALLS
In addition to concrete retaining walls, reinforced or non -reinforced rockery walls can be considered for
grading purposes. Reinforcement should be used when:
1. The wall will be used to retain fill embankment that is over 4 feet in height.
2. The wall will retain a cut embankment greater than 6 feet in height.
A typical reinforced rockery wall details are shown in Figure 4 and the general notes for reinforced rockery
wails are presented below. Please note that the figure and notes are for planning purposes. A detailed
designed by a qualified geotechnical engineer should be performed based on the final grading plan.
GENERAL NOTES FOR GEO-GRID REINFORCED ROCKERY WALL
ROCK SIZE
THE LOWER HALF SHALL BE CONSTRUCTED OF FOUR -MAN OR LARGER ROCKS
(DEFINED BELOW). FOR THE UPPER HALF, PROGRESSIVELY SMALLER ROCKS MAY BE
USED, WITH A MINIMUM SIZE OF TWO-MAN FOR THE UPPERMOST COURSE.
APPROXIMATE ROCK SIZES
SIZE
WEIGHT (LBS.)
1 -MAN
58-210
2 -MAN
265-580
3 -MAN
760-1,830
4 -MAN
3,000 - 4,000
5 -MAN
5,000
6 -MAN
7,000
ROCK PLACEMENT
VOLUME (CUBIC FT.)
0.4-1,3
1.6 - 3.6
4.7-11-2
18.4-24.5
30.7
42.9
THE BASE COURSE OF ROCKS MUST BE EMBEDDED INTO FIRM UNDISTURBED EARTH
TO A MINIMUM DEPTH OF 12 INCHES TO PROVIDE A SECURE FOOTING FOR THE
ROCKERY. THE LONG DIMENSION OF THE ROCKS MUST EXTEND INTO THE SLOPE
BEHIND THE ROCKERY TO PROVIDE MAXIMUM STABILITY. SUBSEQUENT COURSES OF
ROCKS MUST BE PLACED TO LOCK INTO THE ROCKS IN THE LOWER COURSE OR TIER_
623rpt 10 S& EE
GEO-GRID
1. GEO-GRID SHALL CONSIST OF MIRAFI MIRAGRID 5XT OR ITS EQUIVALENT HAVING THE
FOLLOWING PROPERTIES:
PHYSICAL PROPERTY TEST METHOD MINIMUM VALUE LB/FT
LONG TERM ALLOWABLE DESIGN LOAD GRI GG -4 2327
TENSII_ STRENGTH (AT 5% STRAIN) ASTM D 6637 1740
CREEP REDUCED STRENGTH ASTM 5262 2688
2. FIELD ADJUSTMENT OF THE GEO-GRID INTERVAL MAY BE REQUIRED. NO GEO-GRID IS
REQUIRED FOR WALL HEIGHTS EQUAL TO OR LESS THAN 4'- 0".
3. GEO-GRID REINFORCEMENT SHALL BE PLACED TAUT (NO WRINKLE) WITH ADJACENT
REINFORCEMENT OVERLAP AT LEAST 12 INCHES.
STRUCTUAL FILL
STRUCTURAL FILL MATERIAL SHALL BE APPROVED BY PROJECT GEOTECHNICAL
ENGINEER PRIOR TO USE. THE MATERIAL SHALL BE COMPACTED TO AT LEAST 95% OF
MAXIMUM DENSITY AS DETERMINED USING ASTM D1557 (MODIFIED PROCTOR) TEST
METHOD.
DRAINAGE
DRAIN PIPE SHALL BE 4" DIAMETER PERFORATED, PVC, PIPE. INSTALL ONE CLEANOUT
AT BEGINNING AND EVERY 150 FEET OF LINE.
623rpt 1 I S&EE
5.8 FLEXIBLE PAVEMENT
We recommend that the subgrade for flexible pavement be prepared in accordance with the
recommendations presented in Section 5.3 SITE PREPARATION AND STRUCTURAL FILL.
Based on the subsoil conditions, we believe that the prepared subgrade will have a California Bearing
Ratio (CBR) of at least 12.
For the proposed access road, we recommend a pavement section consisting of 2 inches asphaltic
concrete over 4 inches base course. The base course should be compacted to at least 95 percent of the
maximum dry density as determined by ASTM D-1557 test method. The material should meet WSDOT
aggregate specification 9-03.9(3) and have the following gradation:
Sieve Size
Percent Passim
I '/4 -inch
100
518 -inch
50-80
1/4 -inch
30-50
US No. 40
3-18
US No. 200
7.5 max.
% Fracture
75 min.
5.9 SEISMIC CONSIDERATIONS
We recommend that Site Class C as defined in the 2003 IBC be considered for the building design. The
site is underlain by dense soils. As such, the liquefaction potential is negligible.
5.10 ADDITIONAL SERVICES
Additional services may be required during the design and construction of the project. We envision that
these additional services may include the following:
1. Review of design plans and responses to city's comments.
623rpt 12 S&EE
2. Provision of construction monitoring services. The tasks of our monitoring service typically include
the followings:
2.1 Monitoring of temporary excavations.
2.2 Monitoring of spread footing subgrade preparation. Our representative will confirm the bearing
capacity of the subgrade soils, and will assist the contractor in evaluating the over -excavation
requirements, if any.
23 Monitoring the placement and compaction of structural fill. Our representative will confirm the
suitability of the fill materials, perform field density tests, and assist the contractor in meeting
the compaction requirements_
2.4 Monitoring the installation of subsurface drains. Our representative will confirm that these
drains are installed in accordance with our recommendations.
3. Other geotechnical issues deemed necessary.
6.0 LIMITATIONS
The recommendations presented in this report are provided for design purposes and are based on soil
conditions disclosed by field observations and subsurface explorations. Subsurface information presented
herein does not constitute a direct or implied warranty that the soil conditions between exploration locations
can be directly interpolated or extrapolated or that subsurface conditions and soil variations different from
those disclosed by the explorations will not be revealed. The recommendations outlined in this report are
based on the assumption that the development plan is consistent with the description provided in this report.
If the development plan is changed or subsurface conditions different from those disclosed by the
exploration are observed during construction, we should be advised at once so that we can review these
conditions, and if necessary, reconsider our design recommendations.
623rpt 13 S&EE
5&EE
SOIL & ENVIRONMENTAL ENGINEERS, INC.
16625 Redmond WE, Suite M 124, Redmond, Washington 98052,(425).868-5868 FAX (425) 868-7427
September 28, 2007
Mr. Fred Brown
1013 140`s Street Ct. NW RECmV ED
Gig Harbor, WA 98352 1 2007
CC: Mr. Steve Miles BUILDING UEP!.
Mr_ Greg Hinkel
Report of Critical Area Study
Proposed four -Lot Subdivision
7005 and 7027 —174` Street SW
Edmonds, Washington
File No 5-2006-144
Dear Fred:
Per your request, I have prepared this report for the above referenced project. This report is prepared in
accordance with guidelines stated in Chapters 23.40 and 23.80 of the Edmonds Community Development
Code. A copy of my resume is included at the end of this report.
Our company has performed a geotechnical investigation for the project at Miles (7005) and Hinkel (7027)
properties. The scope of the investigation includes site reconnaissance, test pit explorations; engineering
evaluation regarding foundation support, slope stability, and site development. We have prepared one
geotechnical report for Miles and one for Hinkel properties. Both reports were dated August 3, 2007 and
have been submitted previously.
Erosion Hazard
Based on our site exploration and Soil Conservation Survey (SCS), we believe that both sites are covered by
Alderwood-Everett gravelly sandy loams, 25 to 70 percent slopes. According to SCS the erosion hazard for
this soil is high (see Attached Figures 1 and 2).
Landslide Hazard
Based on our site exploration and topographic information, portions of the sites are located in areas of
landslide hazard as the slopes in these areas are steeper than 40% and their heights are greater than 10 feet.
These areas are shown on the attached Figures 1 and 2-
6221623 -Critical Area Report
Attachment 8
Mr. Fred Brown
September 28, 2007
Page 2 of 3
Seismic Hazard
Based on seismic hazard maps published by USGS, no active fault is located within 200 feet of the sites.
Also, the maps indicate a peak ground acceleration (PGA) of 0.4g with 10% probability of exceedance in
50 years.
Storm Water Management
I understand that the post -construction storm water will be collected and discharged to existing public storm
drain. Such arrangement will reduce the potential of saturating the soil on the steep slopes and thus enhance
their stability.
MITIGATION RECOMMENDATIONS
Erosion Hazard
1. We recommend that any exposed area should be covered by visqueen before inclement rain storms
or when the area is un -worked for 48 hours during October 1 through April 30, or un -worked for 7
days during May I through September 30.
2. Any slope face becomes bare for any reason should be re -vegetated immediately. During
construction, site surface should be graded so that surface water is directed away from the structural
areas. Standing water and runoff over any slope face should not be allowed.
Landslide Hazard
1. All temporary excavation during construction should be 1.5H:1V or flatter. All permanent
slopes should be no steeper than 2H:1 V. Water should not be allowed to flow uncontrolled over
the top of any slope. Also, all permanent slopes should be seeded with the appropriate species
of vegetation to reduce erosion and maintain the slope stability.
2. To avoid loading of slopes by building foundations, footings near any slope should be deepened so
that the horizontal distance from the outside footing edge to the slope face is at least 10 feet.
3. Care must be taken when structural fill is placed on slopes. The procedure requires that the
existing slope be benched so that the new fill can be keyed into the slope. Proper placement and
compaction are critical to long-term slope stability. It is strongly recommended that the
earthwork be monitored by a qualified geotechnical engineer.
6221623 -Critical Area Report
S&EE
Mr. Fred Brown
September 28, 2007
Page 3 of 4
Seismic Hazard
We have evaluated the stability of the onsite slopes using STABL5M program. Both building and
seismic loads are considered. The standard engineering practice considers a slope to be acceptably stable
if it demonstrates factors of safety of at least 1.5 and 1.1 for static and seismic loading conditions,
respectively. A factor of safety is defined as the summation of resisting forces divided by the summation
of driving forces. The results show that onsite slopes are stable for both loading conditions -
We recommend that Site Class C as defined in the 2003 IBC be considered for the building design. The
sites are underlain by dense soils. As such, the liquefaction potential is negligible.
Storm Water Management
Since the storm water detention vault will be located on slopes, leakage control measures should be installed
to handle any possible future leakage and to avoid uncontrolled flow over slope. The measures should
include the installation of a perforated drainpipe at the downhill side of the structure, and connecting the
drainpipe to the storm drain.
622/623 -Critical Area Report S&EE
r
Mr. Fred Brown
September 28, 2007
Page 4 of 4
CONCLUSIONS
The subject sites are located in an area of erosion hazards. Portions of the sites are located in areas of
landslide hazard. Based on our knowledge of the soil and groundwater conditions at the site, it is our
opinion that the above mitigations are sufficient to avoid additional potential risk associated with the
development.
As we stated in our August 3, 2007 reports, there is always an inherent risk of slope movement for any
development near steep slopes. In addition to natural factors (soil, groundwater, heavy rainfall), other
factors that may affect stability include excavations, fills, leaking or broken utility, improper drainage, lack
of maintenance of drainage facilities or vegetation cover, unwise actions by adjacent property owners, or
similar events or unknown conditions that may cause instability. Therefore, future property owners must be
alert of any adverse impacts on the slope and take appropriate actions as needed.
We appreciate the opportunity to provide our continuous services for the project. Should you have any
questions or require additional information, please call.
y� �Oak
28,66 e2
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Very truly yours,
SOIL & ENVIRONMENTAL ENGINEERS, INC.
'-7',T — � w IP_ o�
C. J. Shin, Ph.D., P.E.
President
Attachments: Qualification Statement (CJ. Shin's Resume)
Figure 1: Site Plan ---- Miles Property
Figure 2: Site Plan — Hinkel Property
8221823 -Critical Area Report
S&EE
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RESUME
Firm Name S&EE, Inc.
Name C.J. Shin, PhD, PE Title President/Principal EngineerlOwner
Years employed by firm 12 Total professional experience 20 years
Education (college/degreelyear):
• University of Missouri/ MSI 1983
• University of Colorado/ PhD/ 1987
Registrations and licenses:
• Professional Engineer/WA/1991-Current
Awards, publications, etc.:
• "Using Recovered Glass as Construction Aggregates Feedstock," C.J. Shin and Vicki
Sonntag, Transportation Research Record No. 1437, September 1994, pp. 8-18.
• "Blast Loading of Buried Structures," C.J. Shin, H.Y. Ko and Stein Sture, the 3rd International
Conference on Numerical Models in Geomechanics, Niagara Falls, Canada, May, 1989.
• "Subsurface Conditions in And Foundation Construction on Pinnacled Carbonate Bedrock," JJ
Belgeri and C.J. Shin, 20th Ohio River Valley Soils Seminar, Louisville, Kentucky, October,
1989.
• "Modeling of Dynamic Soil -Structure Interaction Phenomena in Buried Conduits," C.J. Shin,
J.P. Whittaker and H.Y. Ko, Geotechnical Centrifuge Conference, Boulder Colorado, June
1991.
Previous employment (firm/location/title/dates):
• University of Colorado, Boulder Colorado, Research Associate/ 1987-1988
• S&ME, Inc./Nashville, TN/Engineer Dept. Manager/1988-1990
• Dames & Moore/ Seattle, WA/ Project Engineer/1990-1995
Brief summary of relevant experience:
Over 20 years of experience in the management and performance of geotechnical investigations,
analyses, consultations, design recommendations and construction monitoring for government,
municipal, industrial, commercial and residential projects. Experience included projects for U.S.
Navy, U.S. Coast Guard, WSDOT, Washington State's Clean Washington Center, Port of Seattle,
Port of Tacoma, King County, METRO, Snohomish County PUD, City of Seattle, City of Renton,
Town of Hunts Point, City of Bellevue, The Boeing Company, Weyerhaeuser, Scott Paper
Company, NUCOR Steel Corporation, and the A&E industry and developers overall. Some
specialties are listed below:
Resume -CJS S&EE
r
• Landfill investigation, design and construction monitoring
• Investigation, design recommendations and construction monitoring of deep foundations
including drilled shafts, augercast pile, H -piles, pipe -pile, concrete pile, and pin pile
• Assessment of liquefaction, lateral spread and remediation
• Evaluation of lateral loads on piles or caissons
• Landslide investigation and remediation
• Design recommendations and construction monitoring of soil nail wall, soldier pile walls
with tiebacks, and sheet pile walls
• Geotechnical investigation, construction monitoring and material testing
• Recycled materials in construction applications
Recent key projects:
• Mixed used building at 1811 Eastlake Avenue, Seattle. Owner: Low Income Housing Institute.
Contact: Ms_ Sharon Lee 206-443-9935. S&EE provided geotechnical services for the 4 -
story building. Scope of work includes exploration, laboratory testing, engineering analyses
for excavation shoring, building support, and recommendation for general site work. Project
completed in 2005.
• Mixed used building at 2245 Eastlake Avenue East, Seattle. Owner: Val Thomas Inc..
Contact: Mr. Joe Borden 206-621-1221. S&EE provided geotechnical services for the 4 -story
building. Scope of work includes exploration, laboratory testing, engineering analyses for
excavation shoring, building support, and recommendation for general site work. Project will
be completed in 2007.
• Cedar Hills Regional Landfill. Owner: King County Solid Waste Division. Owner's project
manager: Mr. Victor Okereke (206) 296-4422. S&EE has been providing design and
construction services for Cedar Hills Regional Landfill from 1997 to current. Work include
Area 4 cover system (100 acres); Area 5 development and closure (40 acres), and Area 6
development and closure (50 acres). Design included slope stability evaluation and
mitigation, roadway development, interface shear for liner system; alternative lining system
(GCL) equivalency demonstration, settlement evaluations. Construction services included
review of CQA plans and documents, observation of materials, conformance with drawings
and specifications, observation of field conditions and confirmation of design parameters.
Project will be completed in 2007.
• East Cap Extension, Tacoma Landfill, Tacoma, Washington. Owner: City of Tacoma. Client:
Parametrix, Inc. Project manager: Mr. Steve Emge (425) 458-6371. S&EE performed
geotechnical studies including evaluation of foundation stability and settlement, assessment of
interface strengths, engineering evaluations of global and veneer slope stability, reinforced
rockery wall design. Project will begin in 2007.
Resume -CJS S&EE
• Landslide Evaluation and Repair at Four & Five Newport, Bellevue Washington. Owner:
Bentall Capital. Owner's project manager: Ms. Kam Boulle. (425) 562-3320. S&EE conducted
geotechnical investigation for two large landslides in a commercial development. The slides
were about 100 feet by 100 feet each. Slide debris caused relatively severe property damage.
S&EE evaluated the cause of the slides, developed repair options, produced construction
plans, and monitored the repair. Project completed in 2006.
• Firwood Pit Reclamation, Edgewood, Washington. Client: Scarsella Brothers, Inc. Project
manager: Ms. Tamarah Hancock (253) 872-7173. Project involves filling of a gravel pit. Fill
thickness will be about 50 feet; volume will be about 700,000 cubic yards. S&EE performed
geotechnical studies including evaluation of foundation stability, settlement potential,
surcharge preloading, earthwork, drainage and slope stability. Project will be completed in
2010-2012.
• Phase I Development (about 20 acres), Ephrata Landfill, Grant County, Washington. Owner:
Grant County. Client: Parametrix, Inc. Project manager: Mr. Steve Emge (425) 458-6371.
S&EE performed geotechnical studies including evaluation of foundation stability and
settlement, assessment of interface strengths, engineering evaluations of global and veneer
slope stability, recommendation regarding benching requirement, evaluations of drainage
requirement and material drainage capacity. Project will be completed in 2007.
• Project: The Boeing Company, 13-03 Building, Boeing Military Flight Center, Seattle,
Washington. Owner's project manager: Mr. Kevin Rambaldini (206) 544-1479. S&EE
conducted geotechnical and environmental investigations for the multi -story concrete structure.
Project involved about 250 18 -inch diameter augercast piles, sheet pile walls, dewatering, and
the use of recycled concrete for structural fill. Project completed in 2000.
• Capital Improvement Projects since 1995. NUCOR Steel Corporation, Seattle, Washington.
Owner: NUCOR Steel, Owner's project manager: Mr. Craig Anderson, (206) 933-2211.
S&EE provided geotechnical investigation, design and construction monitoring services for
various projects for the steel manufacturing plant from 1995 to current. Projects included: new
oxygen plant, craneway support at billet yard, new shot pit, new scrap yard roof (1997) and its
extension (2005); post -earthquake evaluation and repair, Terminal 105 improvements: pile
foundations for light pole and scale supports, roadway subgrade support (use geo-foam to
reduce surcharge loads on compressible soils). This is an on-going project.
Resume -CJS S&EE
LANDAU
TECHNICAL MEMORANDUM 14 ASSOCIATES
wumftswfm
TO: Rob Chave and Jen Machuga, Planning Division
City of Edmonds, Development Services Department
Cc: Jeannine Graf, Building Division
FROM: Dennis R. Stettler, P.E. (Dn VE
DATE. October 24, 20.07 4 2007
RE: GEOTECHNICAL, REVIEW PLANNING DEP-
HtNKEL / MILES SHORT PIAT SUBMITTAL
7005 AND 7027174T" STREET SW
EDMONDS, WASHINGTON
This technical memorandum provides the results of our geotechnical review of documents for a
permit application related to a proposed short plat at the referenced properties. We understand that the
property owners at 7005 and 7027 174`x' Street SW have applied to subdivide their properties to create a 4 -
lot short plat. Landau Associates has been requested to review the submittal materials and to provide
comments related to compliance with Edmonds Community Development Code (ECDC) 23.80 and
whether the development should be subject to the provisions of ECDC 19-10. Landau Associates services
have been provided in. accordance with our On -Call Geotechnical and Environmental Engineering
Services agreement with the City of Edmonds and Task Order No. 07-05.
We have received the following information forwarded by the City of Edmonds for review:
• Preliminary Short Plat drawing prepared by Western Engineers, Inc. dated March 20, 2007
• Proposed Short Plats and Boundary Litre Adjustments drawing prepared by F. F. Brown
Design dated March 20, 2007 (Based on Survey and Topo by Lovell Sauerland and
Associates, Inc.)
• Geotechnical Engineering Services, Proposed Short Subdivision, 7005 and 7027174`x' Street
Sly, Edmonds, Washington letter prepared by Soil & Environmental Engineers, Inc., dated
March 14, 2007
• Report of Critical Area Study, Proposed Eoui-Lot Subdivision, 7005 and 7027174`' Street
Sff ; Edmonds, Washington, File No. S-2006--144 prepared by Soil & Environmental
Engineers, Inc., dated September 28, 2007
• Report of Geotechnical Investigation, Proposed Miles Short Plat, Edmonds, Washington,
S & EE Job No. 622 prepared by Soil & Environmental Engineers, Inc., dated August 3, 2007
• Report of Geotechnical Investigation, Proposed Hinkel Short Plat, Edmonds, Washington,
S & EE Job No. 62.3 prepared by Soil & Environmental Engineers, Inc., dated
August 3, 2007.
130 2nd Avenue South • Edmonds, WA 98020 . (425) 778-0907 . fax (425) 778-6499 • www.iandauinc.:
Attachment 9
GEOLOGICALLY HAZARDOUS AREAS
The submitted materials were reviewed for compliance with the requirements for Geologically
Hazardous Areas in accordance with ECDC 23.80. Geologically hazardous areas were addressed in the
Critical Areas Study report prepared by Soils & Environmental Engineers, Inc. (S & EE). In addition,
geotechnical investigation reports were prepared for each of the two proposed lots that included the
results of test pit excavations, geotechnical engineering analyses, and preparation of geotechnical
recommendations for design and construction of houses on each of the two proposed lots.
Critical areas reports for geologically hazardous areas must be prepared by a qualified
professional as defined in ECDC 23.80.050.A. The Critical Area Study prepared by S & EE includes a
resume of the report author that demonstrates appropriate education, licensing, and experience to prepare
such reports.
The following comments address each of the identified geologically hazardous conditions on the
proposed lots.
Erosion Hazard
The Critical Areas Study report by S & EE identifies the site soils as composed of Alderwood-
Everett gravelly sandy loam on slopes of 25 percent or more. These soils are classified as Erosion Hazard
Areas in accordance with the designations in ECDC 23.80.020.A. The Soil Conservation Service also
considers such soils to have a high erosion hazard.
Erosion mitigation recommendations are contained in the Critical Area Study Report and the
geotechnical investigation reports prepared for the proposed Lots 1 and 3. The reports also address the
importance of surface water control. We agree with the geotechnical engineer's recommendations and
recommend that their recommendations be appropriately incorporated into the project plans and
specifications for construction on each of the lots. In addition, an erosion and sediment control pian
should be prepared for the project in compliance with the requirements in ECDC 18.30.
Landslide Hazard Areas
Landslide Hazard Areas are identified in the Critical Areas Study on each of the two proposed
lots. The designation of Landslide Hazard Areas are based on the criteria contained in ECDC
23.80.020.B.2, which designates any slope of 40 percent or steeper and with a vertical relief of 10 R or
more. Proposed Lot 1 has two steep areas classified as Landslide Hazard Areas and proposed Lot 3 has
three steep areas classified as Landslide Hazard Areas based on this criteria. Each of the identified
Landslide Hazard Areas is of limited horizontal extent, typically on the order of about 15 ft by 30 fl in
16124107 N%drndataVroject.IG74114DnleRmlRXHlnkel-w&es_SubottalReview_tm.doc LANDAU AsSOCIAT@S
plan dimensions or less, and is typically on the order of 10 to 12 ft in vertical relief. The identified areas
appear to be slightly steeper than 40 percent, based on the topographic information available.
Soil conditions disclosed in test pits excavated by S & EE on the proposed lots disclosed
relatively competent soils including recessional outwash, glacial till, and advance outwasb. No areas of
existing or historic landslide activity such as slumps, cracks, fissures, wet and unstable soils, or springs
were identified by S & EE in their reports. Slope stability analyses were completed for the existing slope
conditions on each of the two lots and the results presented in the geotechnical investigation reports for
each of the proposed lots. The computed factors of safety against slope instability appear to be
satisfactory based on comparison to conventional geotechnical practice and the criteria of ECDC
23.80.070.A,3.a.
Steep slopes are mapped in the vicinity and to the north of the proposed lots based on city-wide
LiDAR mapping completed for the City of Edmonds. ECDC 23.80 requires that if the toe or top of a
slope is located off of the subject property, then the location of the toe or top shall be delineated 200
horizontal feet from the property boundary or at its natural location, whichever is closer to the subject
parcel. The Critical Areas report for a geologically hazardous area must address all geologically
hazardous areas within 200 ft of the project area. From the topography and critical areas report submitted
for the proposed short -plat, it is not possible to assess the extent of steep slopes adjacent to the proposed
lots and whether these slopes, if present, could be affected by, or could impact, conditions on other
properties. We recommend that the offsite conditions be addressed in accordance with the ECDC 23.80
requirements.
ECDC 23.80 requires that a minimum no disturbance buffer and minimum building setback be
established from the edge of all landslide hazard areas_ Buffers and setbacks were not specifically
addressed in the geotechnical reports, although a requirement is provided that foundations must be
setback or deepened so that the base of the footing is located at least 10 ft horizontally from the face of
the slope_ We recommend that the recommended minimum no disturbance buffer and minimum building
setback be specifically addressed by the geotechnical engineer for the proposed development. For
alterations of an erosion or landslide hazard area or development within an erosion or landslide hazard
area and/or buffer, the requirements of ECDC 23.80.060.A, sections 2 and 3 must also be addressed by
the geotechnical engineer and the design team.
It is not clear from the submittal what efforts in terms of structure siting, no disturbance buffers,
or other means are being taken to avoid or minimize impacts to critical areas as a part of the development.
In accordance with ECDC 23.44.120, the applicant "shall demonstrate that all reasonable efforts have
been examined with the intent to avoid and minimize impacts to critical areas." This issue needs to be
addressed by the applicant and the design team.
1W24M7 6EdmtlalalpraJects19T441a01FiteRmlRtiHinke]-N61es SubmittalReview tmAae LANDAU AssoclATEs
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The geoteclmical reports prepared for each of the proposed lots appear to be relatively complete
and address the standard geotechnical design criteria for typical grading, foundations, and retaining
structures. However, the current submittal is for a proposed short plat. The documents submitted indicate
the location of proposed houses on the proposed lots and proposed grading. We assume that at this stage
of the permit process, the location of the proposed house and the proposed grading is conceptual for
purposes of illustrating the nature of the proposed development. However, the short plat application
package does not represent a complete site development and building permit application package. As
such, the actual configuration of the house, elevation, and site grading could change from the conceptual
design presented -
It appears that the existing geotechnical reports addressed the existing slope stability at the two
proposed lots. According to the. geotechnical report, excavation depths of 13 to 20 ft are planned at the
location of the proposed structures. The slope stability associated with the proposed excavations,
retaining walls, and regrading on the property needs to be addressed in the geotechnical report.
If the proposed short plat is approved and site development and building plans are prepared, we
recommend that the geotechnical engineer provide additional consultation during the design of the
proposed building, grading, and site development plans for the proposed construction, and confirm or
modify the geotechnical report recommendations as appropriate for the specific details of the proposed
construction. In addition, we recommend that the geotechnical engineer review the design plans for the
building and site development in order to confirm that the geotechnical recommendations have been
properly interpreted and implemented in the project design. The City of Edmonds Development Services
Department may desire to have a geotechnical peer review of the final development plans prior to
issuance of a building permit to confirm that the geotechnical issues on the site have been appropriately
addressed in the final design.
Seismic Hazards
The Critical Area Study report and the individual geotechnical reports prepared for each of the
proposed lots appropriately address seismic hazards.
EARTI3 SUBSIDENCE AND LANDSLIDE HAZARD AREAS (ECDC 19.10)
The proposed lots are outside of the designated North Edmonds Earth Subsidence and Landslide
Hazard Area as defined in ECDC 19.10. However, portions of each of the two proposed. lots have slopes
that are 40 percent or more for a vertical height of 10 iI or more. As such, they meet the definition of
Landslide Hazard. Area as defined in ECDC 23.80. In accordance with the definition of Earth Subsidence
and Landslide Hazard Area contained in ECDC 19.10, such areas meeting the definition of Landslide
10124197 11Edmdalalpriij"tsNO74t1401FIeRm�RUnkel-Mies SubmlltalReview lm.doc LANDAu AssociATEs
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Hazard Area in ECDC 23.80 shall also be considered to be an Earth Subsidence and Landslide Hazard
Area. Consequently, applicants for permits in such areas shall submit a geoteclinical report and complete
plan set as required by ECDC 19.10 to the Building Official for review.
SUMMARY
Landslide Hazard Areas as defined by ECDC 23.80 are present on both of the proposed lots. The
Landslide Hazard Areas are of limited extent on each of the lots, and evidence of current or previous
slope' instability on the proposed lots were not observed by the applicant's geotechnical consultant. The
present information does not suggest significant problems with development of these lots with respect to
Landslide Hazard Areas. However, development of any property with an identified Landslide Hazard
Area presents some degree of risk and highlights the importance of careful consideration of design and
construction practices in order to properly identify and reduce that risk.
For purposes of considering the short plat application, we recommend the following issues be
addressed.
* The topography within 200 ft of the proposed lots should be examined by the geotechnical
engineer to assess the toe and top of adjacent slopes, whether these nearby slopes meet the
definition of a landslide hazard area, and whether the proposed lots could be affected by
adjacent offsite conditions or whether development of the proposed lots could affect offsite
conditions.
• The provisions of ECDC 23.40.120 regarding avoiding or minimizing impacts to identified
critical areas should be addressed.
The geotechnical engineer should specifically address buffers and setbacks from the landslide
hazard areas identified on the site, and if alterations or development within an erosion or
landslide hazard area are planned, then the development standards contained in ECDC
23.80.070 sections 2 and 3 should be addressed by the geotechnical engineer and the design
team.
If the City of Edmonds decides to approve the short plat application, the following points provide
a brief summary of Landau Associates' recommendations for additional considerations resulting from this
review_
• An erosion and sediment control pian should be prepared in accordance with ECDC 18.30
and the recommendations of S & EE related to erosion control protection and handling of
surface water should be incorporated into the plans.
The geotechnical engineer should provide additional consultation during the development of
site grading and building plans by the design team, and the geotechnical engineer should
review the completed design plans and specifications to confirm that the geotechnical
recommendations have been properly interpreted and implemented in the design. The
additional consultation should include an assessment of the slope stability associated with the
specifically proposed arrangement of building, retaining walls, and site grading. The City of
1412007 11Ed�ndatalprajeclsl07417405FdcRmSRh}iinkcl-lu�les_SubmilgiReview im.tloc LANDAU AssociA7r=s
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Edmonds may desire to have a geotechnical peer review conducted to confirm that the
geotechnical recommendations have been appropriately incorporated into the design plans.
• ECDC 19.10 appears to apply to this project and the permit submittal requirements of ECDC
19.10 should be addressed as a part of the project permit applications.
This technical memorandum has been prepared for use by the City of Edmonds in evaluating the
adequacy of permit submittal documents related to the proposed 4 -Lot Short Plat at 7005 and 7027 1740'
Street SW. The focus of this review was the geotechnical aspects of the application. The purpose of the
review was to assess whether the geologically hazardous areas provisions of ECDC 23.80 have .been
appropriately addressed and whether ECDC 19.10 should apply to the proposed development, and to
assess the adequacy of the application documents for compliance with City requirements and
conformance with conventionally accepted geotechnical engineering -practices. This geotechnical peer
review by Landau Associates does not lessen the requirements for the applicant's geotechnical consultant
and other design professionals to prepare an appropriate design for the site conditions.
We appreciate this opportunity to be of service to the City. PIease contact us if you have any
questions or if we may be of further service.
DRS/kes
40124/07 1lEdmdatatprolecl5l074514OT7leRmMiHnke3-NMlas_SubmlttalReview tm.doc LANDAti AsSOCiATes
6
s�EE
SOIL & ENVIRONMENTAL ENGINEERS, INC.
16625 Redmond Way, Suite M 124, Redmond, Washington 98052 (425) 868-5868 FAX (425) 868-7427
December 17, 2007
Mr, Steve Miles
7005 174`' Street SW 1*
Edmonds, Washington �1�
741-160f�Mr. Greg Hinkel �� ��
7027 174`' Street SW N�40�
Edmonds, Washington �j a
Letter Report
Proposed four -Lot Subdivision
7005 and 7027 --174" Street SW
Edmonds, Washington
File No S-2006-144
Dear Steve and Greg:
Per your request, I have reviewed the October 24, 2007 Technical Memorandum prepared by Landau
Associates and prepared this letter in response to the geotechnical related comments. On page 5 of the
memorandum, it indicates that "For purposes of considering the short plat application, we recommend the
following issues be address." I restate these issues and provide corresponding responses below.
Item 1 : The topography within 200 feet of the proposed lots should be examined by the geotechnical
engineer to assess the toe and top of adjacent slopes, whether these nearby slopes meet the definition of a
landslide hazard area, and whether the proposed lots could be affected by adjacent offsite conditions or
whether development of the proposed lots could affect offsite conditions.
Response:
I visited the site on November 11, 2007 to observe the offsite topography conditions. I noted that the
slope at the north side of Miles property continues northward for about 35 horizontal feet and meets the
neighbor's level backyard. The offsite slope is about 3H: I V with a 2 -foot high retaining wall present at
the toe of the slope. I did not observe any sign of slope instability. Using a 3 -inch diameter hand auger I
drilled a 4 -foot deep boring, HA -1, and found about one foot of topsoil underlain by a native soil
(medium dense to dense, fine to medium sand with gravel). This offsite slope and boring location are
shown on the attached Figure 1. The top of onsite slope extends southward to the existing Miles
residence that is adjacent to the proposed lot.
622!623 -Letter Report
Attachment 10
Messer. Steve Miles and Greg Hinkel
December 17, 2007
Page 2 of 5
The offsite slope conditions adjacent to the Hinkel property are shown on the attached Figure 2. 1
observed that the north slope continues northward for about 50 horizontal feet and meets the neighbor's
level backyard. A small steep slope at the northeast corner of the lot continues northward for a short
distance and meets a level yard. Using a 3 -inch diameter hand auger I drilled a 4 -foot deep boring, HA -2,
near the toe of the slope. Like HA -1 to the north of Miles property, HA -2 encountered about one foot of
topsoil underlain by a competent native soil (medium dense to dense, fine to medium sand with gravel).
The slope to the northwest of the property continues for about 100 horizontal feet and meets the
neighbor's level yard at the top of the slope. The topography to the west of the property consists of a few
horizontal benches where neighbor's yards and houses are present. I did not observe any sign of
instability of these offsite slopes.
Based on my observation, it is my'opinion that the offsite slopes do not meet the definition of a landslide
hazard area. Provided that our recommendations presented in our August 3, 2007 geotechnical report,
September 28, 2007 critical area study report, and this letter report are followed, I believe the proposed
lots will not be affected by adjacent offsite conditions and the development of the proposed lots will not
affect the offsite conditions.
Item 2: The provisions of ECDC 23.40.120 regarding avoiding or minimizing impacts to identified
critical areas should be addressed.
Response:
In regards to mitigation sequencing stated in ECDC 23.40.120, 1 am of the opinion that the code
requirements would be satisfied provided that the following recommendations are incorporated in the
grading and drainage plans.
1. The grading activities should avoid the onsite steep slopes whenever possible. The locations of
these slopes are identified in Figures I and 2.
2. When grading activities must encroach upon the steep slope areas, a few criteria should be
followed:
a) Permanent slope must be 2H:1 V or flatter. For fill over steep slopes, subgrade
preparation and fill placement should follow stringent requirements so that slope
stability can be ensured. These include removal of vegetation and topsoil; benching the
slope so that the new fill can be keyed into the slope; use of structural fill materials;
6221623 -Letter Report S&EE
Messer. Steve Miles and Greg Hinkel
December 17, 2007
Page 3 of 5
erosion control by the establishment of vegetation cover; and activities monitored by a
qualified geotechnical engineer. The criteria of structural fill materials are stated in our
August 3, 2007 geotechnical reports.
b) If permanent slope cannot be 2H:1 V or flatter, retaining structures including cast -in-
place concrete or reinforced or non -reinforced rockery or block wall should be used to
retain cut banks. The structures should be designed based on the geotechnical
parameters presented in our geotechnical reports.
Item 3: The geotechnical engineer should specifically address buffers and setbacks from the landslide
hazard areas identified on the site, and if alterations or development within an erosion or landslide hazard
area are planned, then the development standards contained in ECDC 23.80.070 sections 2 and 3 should
be addressed by the geotechnical engineer and the design team.
Response:
In regards to development standards in ECDC 23.80.070 and related standards in ECDC 23.80.060, 1 am
of the opinion that the code requirements would be satisfied provided that the following
recommendations be incorporated in the project plans.
Buffer and Alteration
The onsite steep slopes are relatively small in plan dimensions and elevation relief. Provided that
all recommendations in our geotechnical reports, critical area study and this letter report are
followed, we believe that no buffer is necessary.
Some alterations to the steep slopes may be incorporated in the design. The alterations may
include fill over steep slopes, or excavation to remove parts of the steep slopes. It is our opinion
that the alteration will not: a) Increase surface water discharge or sedimentation to adjacent
properties beyond pre -development conditions; b) The development will not decrease slope
stability on adjacent properties; and c) Such alternations will not adversely impact other critical
areas. We recommend that grading and drainage plans be reviewed by us to confirm that the
above requirements are incorporated in the design.
In regards to item (a) above, some yard/french drains may be need near the property boundaries to
control surface runoff. The need and location of this drain should be determined during the
development of the grading plan.
6221623 -Letter Report S&EE
Messer. Steve Miles and Greg Hinkel
December 17, 2007
Page 4of5
Design Standards
a) Slope Stability
I have performed slope stability analyses using profiles that include the offsite slopes. The
results of the computer (STABL5M) runs are included at the end of this report. The analyses
assume the maximum loading conditions, that is, no excavation at the proposed building sites
and full building loads are included. The results of our analyses are shown below:
Factor of Safety
Location Steady -State Dynamic (Earthquake)
Miles Property 1.7 1.2
Hinkel Property
1.7
1.2
These results indicate that the proposed development will not decrease the slope stability to the
acceptable limits (1.5 for static and 1.2 for dynamic conditions).
The analyses also assume a_5 feet building setback from the top of any fill or natural_ slope.
Please note that for footings near any slope, the bottom of the footings should be deepened so
that the horizontal distance from the outside footing edge to the slope face should be at least 10
feet. This requirement should be incorporated in the building and grading designs.
I recommend that the following design standards as stated in ECDC 23.80.070 — Section 3 be
followed during the development of the final design.
b) Structures and improvements shall be clustered to avoid geologically hazardous areas and
other critical areas;
c) Structures and improvements shall minimize alterations to the natural contour of the slope,
and foundations shall be tiered where possible to conform to existing topography;
d) Structures and improvements shall be located to preserve the most critical portion of the site
and its natural landforms and vegetation;
e) The proposed development shall not result in greater risk or a need for increased buffers on
622!823 -Letter Report S&EE
Messer. Steve Miles and Greg Hinkel
December 17, 2007
Page 5 of 5
neighboring properties;
f) The use of retaining walls that allow the maintenance of existing natural slope area is
preferred over graded artificial slopes; and
g) Development shall be designed to minimize impervious lot coverage;
Finally, as stated in Landau Associates' October 24, 2047 Technical Memorandum, S&EE should provide
additional consultation during the development of site grading and building plans. In addition, we should
review the completed design plans and specifications to confirm that the geotechnical recommendations
have been properly interpreted and implemented in the design. The additional consultation should include
an assessment of the slope stability associated with the specifically proposed arrangement of building,
retaining walls and site grading.
I appreciate the opportunity to provide our continuous services for the project. Should you have any
questions or require additional information, please call.
28168_.p
NAL
EX' 4V. 2008
Attachments: Figure is Site Plan — Miles Property
Figure 2: Site Plan — Hinkel Property
STABL5M Results
Very truly yours,
SOIL & ENVIRONMENTAL ENGINEERS, INC.
C. J. Shin, Ph.D., P.E. /
President
6221623 -Letter Report S&EE
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. Attachment 11
%ice %�����'` ��.��,
MEMORANDUM
Date: November 16, 2006
To: Planner Jen Machuga
From: Fire Marshal John J. Westfall 425.771.0213
Subject: PLN20060144 4 -lot Subdivision 7027 174"n St SW
The following project has been evaluated under the 2003 International Codes and current
Edmonds Community Development Code.
1) Existing fire hydrant spacing meets ECDC .
2) Complete design submittal showing profile/slope of access from public way made to
proposed lot(s) (email request Fred Brown 7117106).
a) Grades in excess of 12% may require the installation of an automatic fire sprinkler
system for dwellings in accordance with NFPA 13D standard.
b) Dwelling architectural submittals will require a fireflow analysis. Fireflows in excess
of IFC Tables B105.1 and C105.1 and restricted paved driveway widths for
emergency response may require installation of an automatic fire sprinkler system
for dwellings in accordance with NFPA 13D.
3) Post address for property access visible from 174th St SW. Signage shall conform to
local standard for emergency response signage.
Cc: Mr. Fred Brown
Engineering Technician Lyle Chrisman
Residential Plans Examiner Jenny Readwin
City of Edmonds Sb Fire Marshal Attachment 12