HomeMy WebLinkAbout2018_0522_Memo_MayCreek Bridge SW Access.docxMay 22nd, 2018
TO: City of Renton - DRAFT
FROM: Brian Elrod
SUBJECT: I-405 Renton to Bellevue, May Creek Bridge SW Access Restoration
The objective of this memorandum is to provide City of Renton with additional information on the potential tree impact and subsequent restoration actions for a construction access route
proposed in the SW corner of the I-405 bridge crossing over May Creek,
May Creek is located in the City of Renton, Washington. It is expected that the proposed construction access route at May Creek bridge would impact approximately 6,000 square feet of
area in City’s jurisdiction. Within the impacted area, WSDOT identified trees for removal as shown in the attached Exhibit A. The city needs to be advised that the location of trees
was not surveyed, but visually observed and documented during a site visit by WSDOT, I-405 personnel.
The table below summarizes field observations including species, quantity, and average DBH of trees anticipated for removal.
Table #1 – Summary of Trees for Removal
Species
Quantity
Avg. DBH
Notes
Alnus rubra
(red alder)
23
2-8"
4 alders covered in ivy; dying
Populus trichocarpa
(black cottonwood)
1
36"
dead
Salix spp
(willow)
3
15"
leaning
Thuja plicata
(Western red cedar)
6
4-7”
Following the completion of the construction, restoration will be accomplished through performing weed control, soil preparation and amendments, restoration with native tree and shrub
species, including plant establishment on the site for 5 years. During the plant establishment period, the site will be furnished with a temporary, above ground, piped irrigation system
connected to the existing water line. Please see the attached Exhibit B for the location and type of proposed planting species.
Additional observations on the existing site include:
Access from the shoulder of Interstate 405 Southbound on-ramp.
Steep slope, up to 2:1 (H:V)
Contains undesirable vegetation that can reasonably be removed
Based on surrounding reference plants, will likely support western red cedar and Douglas fir.
Will likely support vine maple, salal, mock orange, and snowberry in the shrub layer.
Attachments:
Exhibit A – May Creek Bridge SW Access - Existing Trees for Removal
Exhibit B – May Creek Bridge SW Access – Restoration Planting