20080815123251.pdfLANDAU
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TO Ann Bullis, .Building Official
City of Edmonds Development Services Department, Building Division
FROM: Dennis R. Stettler, PX. (Dw
DATE: August 14, 2008
RE: GEoTE, cmIIGAL PEER REVIEW FOR .EARTH SUBSIDE, NCE AND LANDSLIDE- HAZARD
AREA SUBMITTAL PACKAGE — Bull mNG PERMIT leo. BLD20080593
JoHNSoN SFR —16117 74T PLACE WEST
111+ DMONDSa 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 Hazard Area (ESLHA) of North Edmonds. The purpose of this
geotechnical peer review was .to review portions of the submittal package and assess its compliance with
City developmentand building permit requirements as contained in Edmonds Community Development
Code (ECDC) Chapters 19.10 and 23.811. This geotechnical peer review was accomplished in accordance
with Task Order No, 08-14 of Landau Associates' On -Call. Geotechnical Engineering Services Agreement
with the City. Landau Associates had previously conducted two completeness reviews of the submittal
package, and the results of those completeness. reviews are contained in Technical Memoranda dated
.April 11, 2008 and July 11, 2008.
We have received the following information forwarded by the City for review;
o Report. of Geotechnical Say'Vices, Proposed Single-Fand4y Residence, .Lorican Woods Plat Lot
9, Edmonds, Washington report prepared for Mr. Sieve Johnson by Zipper Zeman Associates,
Inc., dated May 30, 200&
® Geotechnical Plan Review, Proposed Single F'an ly Residence, 16117 7e Place Vest,
.Lor•ian Moods Plat, Loi 9, Edmonds, Washington letter prepared for Steve Johnson by
ZZA: Terracon,, dated May 30,'2008.
o. Ternporwy Ecologt! Block Gravity Shoring Wall Figures r& Calculations prepared for Mr.
Steve Johnson by ZZA:-Terracon; dated May 30, 2008.
Vicinit}f Map- Johnson 16117 74"' PI West, author unknown, undated (stamped received by
Building Dept July 1; .2009).
• Etccaivation Playa for.dohnson, 15117 70' Place best, Edmonds 98026, prepared by Ken
Davis, Ken Dads Backhoe, undated (stamped received by Building Dept. July 1, 2008).
w Memo — Response. to Completeness Review lvfemo of April 11, 2008, prepared by Kristin
Hanson, dated July 1, 2008.
130.2nd Avenue ,South a Edmonds, WA 980320 e (425) 778-0907 m fax (425) 778-6409 a. www.landauinc.00rn
• Site Plan Johnson 16117 74'" Place West, revised July 15, 2008.
• Drawings —Johnson 16117 74h Place West, Sheets 2 through 14, dated July 15, 2008.
• Structural Drawings for Johnson Residence, Sheet SI through S6, prepared by Baker
Engineers, Inc., P.S., dated June 12, 2008.
• Calculation Sheets 35 through 40, L8, L9, and L13, prepared for Johnson Residence by Baker
Engineers, Inc., P.S., various dates (stamped resub July 15, 2008 by Building Dept.).
• Grading & TESC (Sheet 1) and Road & Drainage Plan (Sheet 2) for Steve and Joan Johnson,
prepared by Donna L. Breske, P.E., dated March 13, 2008.
• Map of Lorian Woods Planned Residential Development, page 1 of 2 (with Lot 9 marked),
prepared by Dowl Engineers, undated.
• North Edmonds Earth Subsidence and Landslide Hazard Areas Map (with property location
noted) and signed certification as to property location, by Kristin Hanson, dated March 27,
2008.
The following sections provide our review comments.
GEOTECHNICAL, REPORT
The geotechnical report prepared by Zipper Zeman Associates, Inc. (ZZA), dated May 30, 2008
provides a reasonably comprehensive evaluation and discussion of site conditions and risks, and provides
geotechnical recommendations for design. In our opinion, the geotechnical report adequately addresses
the requirements contained in ECDC 19.10 and 23.80 related to projects in the North Edmonds ESLHA.
A significant temporary cut is planned in landslide debris. ft will be critical that the stability of
this cut be monitored by the contractor and the geotechnical engineer, and the work be accomplished in
consideration of site conditions disclosed during construction, weather, duration the cut is open, and other
factors to limit the risk to upslope property.
Geotechnical monitoring and inspection of earthwork by the Geotechnical Engineer of Record is
required, including placement and compaction of structural fill, foundation bearing, temporary shoring,
retaining walls, and retaining wall backfill and drainage. The plans should note this requirement.
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TEMPORARY ECOLOGY BLOCK GRAVITY SHORING WALL
ZZA-Terracon has prepared two figures with supporting calculations for temporary ecology block
gravity shoring walls. We recommend that these figures and the accompanying notes on Figures 1 and 2
be incorporated into the construction drawings.
In accordance with the ZZA-Terracon review letter dated May 30, 2008, we assume that the
ecology block walls surrounding the lower level will not be removed, but will be left in place and
backfilled. We recommend that a note be added to the Figures to reflect that condition.
Temporary excavations and ecology block walls are shown extending beyond the Lot 9 property
boundaries into adjacent "Common Areas." We recommend temporary construction easements or other
documentation be obtained that grants approval to extend temporary excavations and ecology block walls
into the adjacent Common Area.
ZZA-Terracon recommends in their May 30, 2008 review letter that the plan set include an
excavation plan that includes the excavation sequence and layout of cut slopes and temporary shoring
walls. Davis Backhoe has submitted an undated, written "Excavation flan" that outlines a general
sequence of construction. We are concerned that project information and requirements regarding this
critical temporary cut is scattered between the ZZA-Terracon temporary wall design figures, the
ZZA-Terracon review letter, the Davis Backhoe Excavation Plan, and other plans and documents. We
recommend that the ZZA-Terracon temporary shoring wall design, the Excavation Plan, and all related
requirements regarding the temporary cut and shoring be integrated and combined into one plan sheet
document for purposes of construction.
ARCHITECTURAL AND STRUCTURAL PLANS
ZZA-Terracon has reviewed the project architectural and structural plans and has concluded in a
May 30, 2008 review letter that they appear to be in accordance with the geotechnical recommendations
in their updated May 30, 2008 report, with some specific exceptions noted. The May 30, 2008
ZZA-Terracon review letter presents I1 bulleted items that need to be addressed. We have reviewed
these items and concur with ZZA-Terracon's recommendations. The 10th bulleted item in the
ZZA-Terracon review letter relates to uplift forces on the stormwater detention system and appears to
have been addressed in calculations provided by Donna Breske. However, none of the other listed items
appear to have been addressed in the architectural or structural plans that were submitted for our review.
We recommend that the recommended revisions or additions to the plans as contained in the bulleted list
of the ZZ4-Terracon letter be addressed by the design team and incorporated into thefinal drawings.
The structure will be built on three levels stepped up the slope with retaining walls. It appears
that the upper retaining wall is in relatively close proximity to the lower wall. City of Edmonds Retaining
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Wall Requirements (Handout 1362), as well as conventional engineering practice, requires that if the
horizontal distance between the upper and lower walls is less than the height of the lower wail, then the
lower wall will be required to support a surcharge load from the upper wall. It is not clear from the
information available to us whether the lower wall has been designed for this additional surcharge
requirement. We recommend that the structural engineer confirm that the lower wall has been designed
to accommodate surcharge loading from the upper retaining wall.
CIVIL PLANS
The civil plans show a rockery wall or block wall on each side of the driveway. Rockery walls
are not permitted in the North Edmonds ESLHA and the callout and detail for a rockery wall should be
removed. The civil plans show a detail for a block wall ranging from 2 to 4 ft in height. However, the
wall on the north side of the driveway appears to be as high as 5 ft. A written response to the
Geotechnical Completeness Review Tech Memo of April 11, 2008 from Kristin Hanson, dated July 1,
2008, states that the rockery(s) shown on the civil plan will be concrete walls per the structural engineer.
The civil plans should be revised to show the concrete retaining walls now planned for the area adjacent
to the driveway.
A retaining wall is also shown adjacent to the asphalt -paved driveway adjacent to the entrance
porch near the southeast corner of the house. A note on the plans states that this will be an "Engineered
Retaining Wall (By Geotec)." No plans for this wall are included in the materials provided for our
review. The type of retaining wall and the details need to be addressed in either the civil or structural
plans.
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 (TESL) Requirements]. The pre -construction meeting needs to
include the Geotechnical Engineer of Record [see City of Edmonds Earth Subsidence and Landslide
Hazard Area Temporary Erosion and Sediment Control (TESL) 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 1 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 Official.
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REQUIRED STATEMENTS AND DECLARATIONS
We reviewed the submittal package to confirm that the statements and declarations as required by
the City for development within the Earth Subsidence and Landslide Hazard Area have been addressed
and our findings are summarized below:
• ZZA-Terracon has provided a Geotechnical Hazard Identification/Declaration and Mitigation
Statement of Risk in their letter dated May 30, 2008, as required by the City.
• Statements from other design professionals were not included in the package that we were
provided to review. We assume that the City is confirming that the other required statements
and declarations have been submitted and are in order.
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 Johnson single family
residence at 16117 701 Place West. 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.
DRSlrgim
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