HomeMy WebLinkAbout2041.01 McCarthy Impacts Ltr 10-18-19
19019 36th Avenue West, Suite E Lynnwood, Washington 98036 (425) 582-9928
Zipper Geo Associates, LLC
Geotechnical and Environmental Consulting
Project No. 2041.01
October 18, 2019
Mary McCarthy
3403 Burnett Avenue North
Renton, WA 98105
Subject: Short and Long Term Impacts
McCarthy Slope Stabilization
3403 Burnett Avenue North
Renton, WA
Dear Ms. McCarthy:
Zipper Geo Associates, LLC prepared retaining wall construction plans and stability calculations for the
proposed slope stabilization project located on your property dated August 8th , 2019. The City of
Renton granted an emergency exemption to begin the work prior to obtaining all of the necessary
permits due to the emergency nature of the project. As a condition to granting the exemption, the
City will not finalize the permit until a Shoreline Permit, Critical Areas Permit, and a Wall Modification
have been approved. In order to further process the required additional permits/approvals, the City
has requested a narrative describing the short and long term impacts the project may have on adjacent
properties. The purpose of this letter is to provide that narrative.
Short Term Impacts
The project involves earth work on a steep slope with areas of relatively unstable soils. The work will
expose soils highly susceptible to erosion. Additionally, the work could result in shallow landslides in
the unstable soils. The potential impacts of erosion are deposition and transport of sediment off-site.
The potential impacts of landslides include safety concerns for the traveling public along Lake
Washington Boulevard below and potentially destabilizing areas along the sides and tops of the slope.
The project plans were developed to mitigate the potential short term impacts through the use of
temporary erosion and sediment control measures and observatio n of construction by a geotechnical
engineer from Zipper Geo Associates. The work is currently proceeding and the mitigation measures
outlined in the plans are proving successful at mitigating the potential short term impacts.
Long Term Impacts
The long term impacts of the project are, in our opinion, beneficial to neighboring properties.
Specifically, prior to construction, the slope was over-steepened, covered with invasive plant species,
and contained areas of unstable soils. The project will stabilize an otherwise unstable slope, which if
failed, would have negative impacts on adjacent properties. The project will remove invasive species
and replace them with non-invasive species therefore increasing the potential for biodiversity in the
area. As such, we do not foresee negative long term impacts associated with the work.
Zipper Geo Associates, LLC
McCarthy Slope Stabilization
Project No. 2041.01
October 18, 2019
19023 36th Avenue West, Suite D Lynnwood, Washington 98036 (425) 582-9928
Page 2
We trust this information meets the City’s current request. If we can be of further assistance, please
contact us.
Respectfully submitted,
Zipper Geo Associates, LLC
Robert A. Ross, P.E.
Principal
Copies:
Vanessa Dolbee (City of Renton) – 1 electronic copy, Jason Laskelle (May Creek Landscaping) – 1
electronic copy
10/18/19