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NELSON GEOTECHNIC¡rL
Assocu\TEs, INc.
GEOTECHNTC14.L Erq<¡tNgrng & GeOlOelsTs
Main Office
l73l I -. t35rh Ave ND,4.500
Woodinville, WA 980?2
(425) 486- r 669 . FÀX (425) 48 r -25 r 0
Engineering-Geology Branch
5526 Industry Lane,#2
East Wenatchee, WA 98802
(509) 665-7696' FAX (50e) 66s-'t692
TO:
MEMORANDUM
DATE:August 14,2018
Ms. Darlene Stern
FROM:Khaled M. Shawish, PE
Carston T. Curd, GIT
RE:Minimum Risk Statement
Stern Deck Addition
Edmonds, Washington
NGA File No. 8800D18
This memorandum documents our response to Cþ of Edmonds review comments regarding the Stern
Residence Deck Addition, located at 17019 - 73d Place West in Edmonds, Washington.
The site meets the criteria for landslide hazañ areas and erosion hazard ¿ìreas, as outlined in the Edmonds
Municipal code (ECDC 23.80.020). Pursuant to ECDC 23.80.070(4), the planned project meets the
requirements of design standards for development within Erosion and Landslide Hazard Areas.
. The proposed development shall not decrease the factor of safety þr landslide occurrences below
the limíts of 1.5 þr static conditions and 1.2 þr dynamic condìtions
The planned deck will include deep foundations into the native glacial soils within the core of the steep
slopes. It is our opinion that ifthe project is constructed according to plans and specifications, the factor
of safety for landslide occurrences should not decrease below 1.5 for static conditions and 1.2 for
dynamic conditions.
. Structures and improvements shall be clustered to avoid geologically hazardous areas and other
critical areas
Proposed structures are located within the upper portion of the site adjacent to the existing residence to
avoid disturbing slopes to the east of the property.
. Structures and improvements shall mìnirnize alîerations to the natural contour of the slope, and
foundations shall be tieredwhere possible to conþrm to existing topography
No cuts or fills are proposed to the existing topography. Pin pile foundations were explicitly
recommended to reduce alterations to the contour of the existing slopes.
Memorandum - Minimum Risk Statement
Stern Deck Addition
Edmonds, Washinglon
NGA FileNo. 8800D18
August 14,2018
PageZ
. Structures and improvements shall be located to preserve the most crítical portion of the site and
its natural landforms and vegetation
The most gentle slopes in the properly will be occupied by the proposed deck in order to preserve the
critical areas within the vicinþ of the site and reduce impact on geological and other critical areas in the
vicinity.
o The proposed development shall not result in greater risk or a need for increased buffers on
n e i ghb orin g pr op erti e s
lncreased buffers are unnecessary for adjacent property due to proposed development as part of this
project
t The use of retaining walls that allow the maintenance of existing natural slope area is preferred
over graded artificial slopes
No grading is proposed to be completed for the proposed deck addition.
c Development shall be designed ta minimize impervious lot coverage
We understand that the proposed deck does not contribute to impervious lot coverage. Project
construction drawings show the areas beneath the deck to remain as present soil and covered with mulch
andlor plantings. No ba¡e soil areas are to remain after construction is complete.
MINIMUM RISK STATEMENT
Pursuant to ECDC 23.80.060, it is our opinion that construction will not increase the threat of erosion or
landsliding to adjacent properties beyond predevelopment conditions, will not adversely impact other
critical areas, is designed so that thehazardto the project is eliminated or mitigated to a level equal or less
than predevelopment conditions, and is safe as designed under anticipated conditions.
'We trust that this memorandum should satisfy your needs at this time. Please do not hesitate to contact us
should you require anything further.
o-o-o
NELSON GEOTECHNICAL AETOCIATES, INC.