20080725155821.pdfOV SDO City of Edmonds
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PLAN REVIEW COMMENTS
w. rr ry BUILDING DIVISION
Esc 18go (425) 771-0220
DATE: July 25, 2008
TO: Brian and Cindy Isaacson (contact for Lot 2)
FAX: 425-778-4499
Amy Ross (contact for Lorian Wood HOA common area)
1611973 d Place West
Edmonds, WA 98026
FROM: Ann Bullis, Building Official
RE: Plan Check: 2007-0833 and 2007-0834
Project: Grading and Drainage
Project Address: 16007 73`d Place W and adjacent common area
During review of the permit applications for the above noted project, it was found that the following
information, clarifications or changes are needed. Please provide written responses to each
comment as to how it has been addressed, and where changes can be found on the plans. Please
submit revised plans/documents to Theresa Umbaugh, Senior Permit Coordinator.
1. The City is still not clear specifically what work is proposed under the subject permit
applications. On the coversheet of the plans, provide a detailed written scope of work for the
subject permit applications. Distinguish between work to be done on Lot 2 vs. the common
area.
2. Revise plans to o.?1X show the proposed work to be done under the scope of these permits (as
noted in 91 above). The City will only review the work to be done under the subject permit
applications. You may provide general plans for information only as a design concept, such as
the house location, retaining wall, other drainage improvements, etc., but such plan sheets must
note in large letters: THIS PLAN FOR CONCEPT INFORMATION ONLY, NOT FOR
CONSTRUCTION.
3. The scope of work reviewed for the subject permit applications was based on the 3`d paragraph
of Terra Associates Geotechnical Consultation letter to you dated 5122108: Installation of the
upper seepage collection drains and the lower tight line storm drains along the northern and
southern property lines, removal of log and soils behind the log currently acting as a soil
catchment facility, installation of vegetation replacement as approved under Conditional Use
Permit PLN2006-0104.
See attached comments from Landau Associates.
TECHNICAL LA LANDAU
ASSOCIATES
RAN
:MEMORANDUM
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M E M O D UM ermorrwmg I GE0rfC ,Cnr. f rwz= mo=Fs
TO: Ann Bullis, Building Official RECEIVED
City of Edmonds Development. Services Department, Building; Division
JILL 2 3 1908
FROM: Dennis R. Stettler, P.E. (9
BUILDING
DA'T'E; July 22, 2008
RE.. GEonCHNICAL PEER REVIEW FOR ICI ARTH SLBSIDENCI AND LANDSLIDE HAZARD
AREA SUBMITTAL PACKAGE — PLAN REVIEW NO: BLD2007-0833
ISAACSON GRADING AND DRAINAGE'
LOT 2 AND ADJACENT COMMON AREA - LORIAN WOODS.
EDMONDS, WASHINGTON
This technical memorandum provides our geotechnical peer review of portions of the permit
package submitted to the City of Edmonds (City) for the proposed referenced development within the
Earth Subsidence and Landslide HazardArea (BSLHA) of North. Edmonds: The purpose of this
geotechnical' peer review was to review portions of the submittal package and assess its compliance with
City development and, permit requirements as contained in Edmonds Community Development Code
(ECDC) Chapters 19.10 and 23::80: This;geotechncal peer review was accomplishedin accordance with
Task Order No. 08-11 of Landau Associates' On -Call Geotechnical Engineering Services Agreement with
the City.
We have received. the following information forwarded: by the City for review:
Geotechnical Report, Lorian Woods Lot 2, London Woods, Ednionds; Washington, report
prepared for Brian & Cindy Isaacson by Terra Associates, Inc., dated March 3.1, 2008.
• Geotechnical Consultation, Drainage Plait Review, Lot 2, Plat of Lorian Woods, Edmonds,
Washington, letter prepared for Brian and Cindy Isaacson by Terra Associates, Inc., dated
May 22, 2008:.
o. Supplemental Geotechnical Consultation, Drainage Plait Review, Lot 2, Plat of Lorian
Woods, Edmonds, Washington, letter .prepared for Brian and Cindy Isaacson by Terra
Associates, Inc., dated April 25, 2007.
o
Geotechnical Report, ;Lorian Woods Lot 2; :Lorian Woods, Edmonds, Washington, report
prepared for Mr. Brian Isaacson by Terra.. Associates, .Inc., dated September 14, 2005.
• Plein Sheets (including Sheet I - Existing Conditions, Plan, Sheet 2 — Grading & TESC Plan,
Sheet 3 - Grading & TESC Notes & Details; Sheet: 4 --Road & Drainage Plana, Sheet 5 -
Road & Drainage Plan, and Sheet U Utilities Plait, prepared for Brian & Cindy Isaacson
by Western Engineers,. Inc., dated June 4, 2008.
® Cit), Review Connnnents, Letter of Release of Liability, letter addressed to the City of
Edmonds, prepared by Western.Engineers, Inc., dated May 2, 2008.
130 2nd Avenue South • Edmonds, WA 98020..(425) 77870907 • fax. (425) 778-6.409 : ww.w.1andauinc.aom
• Isaacson Drainage Plan, Lorian Woods, Edmonds, letter addressed to the City of Edmonds,
prepared by Western Engineers, Inc., dated March 12, 2007.
In addition to the materials forwarded by the City, we also referred to two documents prepared by
Landau Associates for earlier geotechnical peer review aspects of this project:
+ Completeness Review for Earth Subsidence and Landslide Hazard Area Submittal Package —
Plan Review Nos. BLD 2007-0833, BLD 2007-0834, Isaacson Grading and Drainage —
16007 73d Place West, Edmonds, Washington, Technical Memorandum addressed to the City
of Edmonds, prepared by Landau Associates, dated August 20, 2007.
• Peer Review Summary, Lorian Woods Tree Cutting, 73rd Place West, South of North
Meadowdale Road — Tract A, Edmonds, Washington, letter addressed to the City of Edmonds,
prepared by Landau Associates, dated December 28, 2006.
The permit submittal package provided to us for review contains only elements related to grading
and drainage. The May 22, 2008 letter from Terra Associates identifies the scope of the currently planned
work as installation of the upper seepage collection drains and lower tight line storm drains along the
northern and southern property lines, along with the vegetation replacement plan on the slope above Lot
2. Although the planned location of the house, catchment wall, and other proposed site improvements are
shown on the plans, no specific design plans were provided for the proposed house, catchment wall, or
related structural elements of the proposed project. Therefore, we have assumed that these other project
elements are provided for background information only and our geotechnical peer review is limited to the
grading and drainage elements of the project as noted in the aforementioned scope of work outlined in the
Terra Associates May 22, 2008 letter. We assume that a separate geotechnical peer review will be
required at the time the house and retaining wall plans are submitted for a permit to confirm the
appropriateness of the foundation and retaining wall design elements of the project. The following
sections provide our review comments on the grading and drainage elements.
GEOTECHNICAL REPORTS
The geotechnical report prepared by Terra Associates dated March 31, 2008 provides a
reasonably comprehensive evaluation and discussion of site conditions and risks, and provides
geotechnical recommendations for grading, drainage, and other design elements of the project.
Conceptually, the approach of intercepting seepage on the slope and incorporating a landslide debris
catchment wall east of the proposed house are prudent measures.
The report identifies the risk of a landslide upslope from the building lot at 5 percent in 25 years.
The report mentions that "only one significant episode of movement" has been documented to have
occurred on or -adjacent to the site over the past 20 years. A slope failure on the slope above the lot "in
the winter of 2005/2006" is mentioned. Our records indicate that ground cracking was observed at the top
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of the slope at this location in September 2003. A landslide occurred on February 13, 2005 and another
landslide occurred at approximately the same location on January 30, 2006. In addition to this specific
landslide activity that is directly above the Isaacson building lot, we have observed several other
landslides on this slope in the vicinity of this lot in the last 12 years located both to the north and south of
this location (but not directly above the Iot). Given the history of landsliding along this slope, it is our
opinion that the upslope landslide risk is significantly greater than the stated risk in the Terra Associates
report of 5 percent over 25 years. We recommend that the property owner be advised of this landslide
history and the related risk.
The City's Geotechnical Report Guidelines requires that the Geotechnical Consultant provide at
least one cross section extending across the site drawn perpendicular to the contours showing soil and
groundwater conditions in relation to the proposed site grading and structures. The Terra Associates
report does not include a cross section. Although not necessary for the drainage improvements and
limited grading that is the subject of the current permit application, a cross section will be required
associated with the later review of the catchment wall and building structure. We recommend that a
cross section be provided at the time of the submittal for permit review of the catchment wall and
residential structure.
CIVIL PLANS
Trees were cleared from the slope last year under a separate permit. As a part of that permit
application, specific replanting plans were developed and submitted as a part of that permit application in
order to replant and help stabilize the slope. The Grading & Drainage plans provided for review do not
contain or reference the replanting plans that were a part of the previous permit. However, it is necessary
to implement the approved replanting plan in conjunction with the grading and drainage improvements
that are proposed as a part of the current permit submittal. We recommend that the slope replanting and
related landscapingplans for the property he incorporated into the currentpermit application package.
Both the letter from Western Engineers dated May 2, 2008 and the letter from Terra Associates
dated May 22, 2008 point out the need for maintenance of the drainage system by the property owner.
We concur that the drainage system on the slope above Lot 2 will require regular and long-term
maintenance by the property owner in order to be effective and we consider this maintenance requirement
to be a critical issue that needs to be recognized by the property owner.
Geotechnical monitoring and inspection of carthwork, including grading, drainage, and erosion
control measures, by the Geotechnical Engineer of Record is required. The plans should note this
requirement.
7122106 11Pdmdatalpmje=ko744136TileRoomVR%Ce iPeerReviewGrading_tmdoc 3 t.ANDAu AssocIATES
Terra Associates has noted that a downed log that has acted as a soil catchment for landslide
debris remains on the slope above the house. Terra Associates has recommended that this log and
accumulated landslide debris above the log be removed, and we concur. We recommend that the
requirement for removing this log and the accumulated landslide debris be specifically included on the
grading plans.
The Terra Associates March 31, 2008 report recommends that "no fills should be placed on-site
that result in raising existing site grades." We note on the Grading & TESC Plan prepared by Western
Engineers that 270 cubic yards of fill are planned that result in raising site grades by as much as about 4 ft
in locations such as the proposed catchment wall maintenance path. We recommend that this discrepancy
between the geotechnical report recommendations and the plans be addressed by the design team.
The Terra Associates March 31, 2008 report states that "soils excavated from the site that are not
needed for foundation backfill must be exported from the site." The Grading & TESC Plan contains the
statement that "Excess cut may be spread on site." We recommend that the Grading & TESC Plan be
revised to reflect the geotechnical report recommendations.
A temporary stockpile area is shown on Plan Sheet 2. Temporary or permanent stockpile of fill
on the top or bottom of slopes is a prohibited action under the requirements of the ESLHA. We
recommend that the plans be revised to reflect this requirement.
The conceptual locations of a catchment wall and the building structure are shown on the plans.
We note that landslide debris flow could potentially pass by the south end of the catchment wall and
impact the building structure. Although conceptual, we recommend that the civil engineer and
geotechnical review the catchment wall location at this time and consider lengthening the wall to the
south to increase the protection to the conceptual location of the proposed structure, as this may affect
the location of the drainage improvements under the scope of this permit application.
Inspection, maintenance, and regular reporting of TESC measures by the Geotechnical Engineer
of Record are required [see the City of Edmonds Earth Subsidence and Landslide Hazard Area
Temporary Erosion and Sediment Control (TESC) Requirements]. A pre -construction meeting is
required and needs to include the Geotechnical Engineer of Record [see City of Edmonds Earth
Subsidence and Landslide Hazard Area Temporary Erosion and Sediment Control (TESC)
Requirements]. These requirements should be noted on the Grading and TESC sheet and the owner or
lead design professional should arrange for these services with the Geotechnical Engineer of Record.
The City requires that earthwork during the winter season between October l and April 30 be
restricted. We recommend that the TESC and Grading plans specifically indicate that earthwork is
restricted between October I and April 30 and any earthwork in this time period requires approval from
both the Geotechnical Engineer of Record and the City Building Oficial.
7122106 NWAmd& 4 mjects4074kl3b4FileRwm\k\GeolPe &eviewGcading_hitdoc 4 t.ANDAu ASSOCIATES
This technical memorandum has been prepared for the exclusive use by the City of Edmonds in
evaluating the adequacy of permit submittal documents related to the proposed Issacson grading permit
for property at Lot 2 and adjacent common area of the Plat of Lorian Woods on 73`d Place West in
Edmonds, Washington. The focus of this review was the geotechnical aspects of the application. The
purpose of the review was to assess the adequacy of the application documents for compliance with City
requirements contained in ECDC 23.80 and ECDC 19.10 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. Please contact us if you have any
questions or if we may be of further service.
DRS/rgm
7122108 15EdmdataVTojem\074113UileRoom\RlGeotPe rReviewGradng hn.doe 5 LANDAU ASSOCIATES