REV1- RFI BLD2023-1060+Geotechnical_Report+4.11.2024_8.50.39_AM+4189758As ect
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A Geosyntec Company
April 2, 2024
Sean Niesel
18500 Olympic View Drive
Edmonds WA 98020
Re: Response to Correction Notice
Project No. AS220625
Dear Mr. Niesel:
On 14 March 2024, City of Edmonds Engineering Department issued a Correction Notice for
Permit Number BLD2023-1060 for the project at 18500 Olympic View Drive. A note in the
correction notice reads as follows:
"The bank on the north side of the new wall has visible erosion, cracking in the soil and has not
been permanently stabilized. Please reach out to the project geotechnical engineer on what
measures need to be taken to permanently stabilize the slope. Please see photos below from the
inspection on 3/14/2024."
In response to this, Aspect notes that the soldier pile wall that the City of Edmonds approved was
never intended to stabilize the slope on the downhill side of the wall. Rather, as was explicitly
stated in documents that were submitted for the permitting of the project (Geotechnical Report:
August 28,2023 and Basis of Design Report: August 29, 2023), the wall was intended to retain the
soil supporting the existing yard, deck, and other features on the uphill side of the wall. The basis
of design for the wall, which was approved and permitted by the City, did account for continued
erosion and shallow sliding on the downslope side of the wall.
We further note that before the landslide that precipitated this project, this area of the slope was
obscured by a thick blanket of invasive non-native English ivy. The ivy was not rooted on the slope
but at the top, and the curtain of vines blanketed and hid the soil on the slope from view. Erosion
and instability were certainly present on that slope under the ivy, as is evidenced by the fact that the
slope was oversteepened and no mature trees were growing on there. However, because of the thick
blanket of ivy, no sign of the erosion and instability was visible.
Having said that, erosion control measures do need to be implemented at the site, as at any
construction site. We recommend that the bare soil be completely covered with jute mat or similar
erosion -control fabric, then planted with low -growing, native vegetation that is adapted to sunny,
steep slopes. We recommend referring to Washington Department of Ecology guides for stabilizing
steep slopes with vegetation, such as the following.
• Vegetation Management: A Guide for Puget Sound Bluff Property Owners, Ecology
Publication 93-31, at https://apps.ecology.wa.gov/publications/documents/933 Lpdf
• Slope Stabilization and Erosion Control Using Vegetation: A Manual of Practice for
Coastal Property Owners, Ecology Publication 93-30, at
https:Happs.ecology.wa.gov/publications/documents/9330.pdf
Sean Niesel
April 2, 2024 Project No. AS220625
Snohomish County Extension office Master Gardeners (425-357-6010) will also be able to provide
planting guidance for the site. Finally, many local landscaping firms have extensive experience
with the challenges of plantings on steep bluffs in the Puget Lowland.
Please contact us with questions or comments.
Limitations
Work for this project was performed for Sean Niesel (Client), and this letter was prepared in
accordance with generally accepted professional practices for the nature and conditions of work
completed in the same or similar localities, at the time the work was performed. This letter does not
represent a legal opinion. No other warranty, expressed or implied, is made.
All reports prepared by Aspect Consulting for the Client apply only to the services described in the
Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk
of that party, and without liability to Aspect Consulting. Aspect Consulting's original files/reports
shall govern in the event of any dispute regarding the content of electronic documents furnished to
others.
Sincerely,
Aspect consulting
Matthew von der Ahe, L.E.G.
Project Geologist
matthew.vonderahe@aspectconsulting.com
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