18345 Essential Nature of Pouring and Backfilling Foundations Thuesen 514 8th AVE N--� GEOTECH
CONSULTANTS, INC
2401-10" Avenue East
Seattle, WA 98102
(425) 747-5618 FAX 747-8561
Memorandum
To:
Company:
Date:
RE:
Eric Thuesen
JN: 18345
Fron James H. Strange, Jr.
April 10, 2020 Pages: 1 of 1
Essential Nature of Pouring and Backfilling Foundations
514 8th AVE N, Edmonds
You have asked us to render an opinion if it is essential from a geotechnical perspective to complete pouring and backfilling of the foundations
for the new house, which is in the early stages of construction. We visited the site on April 3, 2020 to observe the existing conditions. The
tall free standing retaining wall along the upslope bench of the foundation is in place a backfilled, and the excavation below that bench is on
the order of 10 feet tall and inclined at about a 1:1 (H:V) with some small pipe pile shoring at the very toe to assist with the raveling sands.
The pipe piles have been driven for foundation support, and the grade beams in the pile areas are tied. The excavation was generally
complete when the Stay Home -Stay Healthy Proclamation (20-25) was issued.
The pin pile slough protection along the toe of the cut was put in by the contractor as an additional effort to prevent sloughing of the toe of
the sandy cut soils to keep from causing undermining of the retaining foundation wall constructed on the upper bench at the site. This
shoring is intended only for temporary conditions, not a potentially extended delay in construction. This particular project is frozen at its least
stable phase and all of the steps forward though backfilling of the foundation will improve the stability of the site which is a critical area due
to the steep slope above the site. A delay in the construction could cause the stability of the site to degrade and become costly to mitigate
(could result in spoilage). Preventing this environmental risk over the construction shut -down will require that the concrete for the foundations
is poured and the spaces within the foundation be backfilled with free -draining granular fill. Based on conversations with the contractor, we
understand that the proposed activities through backfill of the foundation and stabilization of the site would be as follows:
1. Foundation contractor mobilization; Obtain supplies site preparation
2. Set forms and steel - inspection; Pour footings, cure time and strip footings
3. Lay -out walls, tie steel, form walls - inspection; Pour walls and strip walls;
4. Water -proof foundation; Install drainage - inspection
5. Rough in plumbing basement — inspection; Backfill interior and pour slab
6. Walls cured; Frame basement floor and second floor to plywood only (for structural wall support)
7. Backfill basement walls to grade
Following completion of the backfill (from a geotechnical standpoint), the project could then be put on hold for the remaining duration of the
Stay Home -Stay Healthy Proclamation.
Considering the above, it is our professional opinion that it is essential from a geotechnical perspective to complete pouring and backfilling
of the foundations. This is necessary to prevent spoilage (degradation and environmental harm) of the property and potentially the adjacent
critical slope. Given that the fill to be placed against the foundations is necessary to provide lateral support for the future building, we expect
that a representative of Geotech Consultants, Inc. would need to make at least one site visit during the placement and compaction of the fill,
once the concrete for the foundations has been poured.
This opinion relates only to the geotechnical necessity of completing the above -described work. Site safety (including COVID-19
precautions) is the responsibility of the project's general and subcontractors.
Please contact us if you have any questions regarding this letter.
Sincerely,
'EOTECH CONSULTANTS INC.
James H. Strange, Jr., P.E.
Associate