4.18.18 - Geo Report on Rockery.pdfNELSON EOT C ICAL
AssoCIATES, INC.
GEOTECHNICAL ENGINEERS & GEOLOGISTS
Main Office
17311 — 135" Ave NE, A-500
Woodinville, WA 98072
(425) 486-1669 • FAX (425) 481-2510
MEMORANDUM
DATE: April 18, 2018
TO: Mr. Derek Abbott
CC: Mr. Ron Johnson
FROM:, Khaled M. Shawish, PE
Lee S. Bellah, LG
RE.: Reinforced Rockery Design Change
Abbott Residence Rockeries
16404 — 751 Place West
Edmonds, Washington
NGA File No. 9175B 16
Engineering -Geology Branch
5526 Industry Lane, #2
East Wenatchee, WA 98802
(509) 665-7696 • FAX (509) 665-7692
This memo presents our updated geotechnical recommendations and opinions regarding reinforced rockery
construction for the residence project located at 16404 — 75" Place West in Edmonds, Washington.
INTRODUCTION
We have previously prepared a geotechnical engineering evaluation for the project titled "Preliminary
Geotechnical Engineering Evaluation — Abbott Residence — 16404 - 75" Place West — Edmonds,
Washington," dated March 27, 2015. We also performed part-time construction monitoring for the
residence construction.
Recent Observations and Recommendations
We met on -site on April 16, 2018 for a preconstruction meeting to discuss project plans prior to building
the rockeries throughout the site. The earthwork contractor brought to our attention that the wall drains for
the two lower western rockeries will not be able to tie into the existing storm system as the elevation of the
rockery drains will be several feet higher than the existing storm system. The two rockeries are each
approximately 4-feet high and are separated by an approximately 7-foot bench. We discussed options with
the contractors and concluded that omitting the drain should not adversely impact the wall as there are
free -draining layers of crushed rock and quarry spalls behind and beneath both walls, which will allow
water to migrate through and mitigate ponding of water.
Reinforced Rockery Design Change
Abbott Residence Rockeries
Edmonds, Washington
NGA Project No. 9175B 16
April 18, 2018
Page 2
It is our opinion that omitting the wall drains for the two tiered rockeries on the western edge of the site
should not affect stability or performance of the rockery walls, provided that the specifications detailed in
our previous report and rockery design memos are strictly followed.
We should be retained to review final rockery locations and plans, provide construction monitoring
services during rockery construction, and to evaluate subgrade conditions, cut conditions, fill compaction,
geogrid installation, and drainage installation.
We trust this memorandum should satisfy your needs at this time. Please contact us if you have any
questions or require additional services.
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NELSON GEOTECHNICAL ASSOCIATES, INC.