REVIEWED BLD2021-1362+Geotechnical_Report+2.10.2022_2.08.14_PM+2674295REVIEWED
Earth Solutions NW«C BY
CITY OF EDMONDS
s
15365 NE 90" Street, Suite 100
Redmond, WA 98052
Main (425) 449-4704 1 Fax (425) 449-4711
www.esnw.com
REVISION
Feb 10 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
FIELD REPORT
Project No.
8394 Page 1 of 2 ReportID 8394.00 G 01172022
Date
Mon 1/17/2022 Weather Overcast, 46°F
Arrival/Departure Time(s)
2:00 1 2:45 Travel Time (hr) 1.0
Project Name
Tollefson ADU
Location
633 Walnut Street, Edmonds
ESNW Rep. & Phone
Henry Wright 1 206-793-4193
Client Info/Contact
L. Tollefson 1 425-773-9302
General Contractor Info/Contact
Leif Helleren Construction, Inc. 425-770-1970
Contractor #2 1 nfo/Contact
Permit No(s).
Reviewed By
LAC HTW
Field Supervisor Initials/Date Project Manager Initials/Date
Limitations: The presence of ourfield representative at the site is to provide our clientwith a source of professional advice, opinions, and recommendations based upon the field representative's
observations and testing of the contractor's work. Our services do not include supervision or direction of the contractor, their employees, or agents. Geotechnical recommendations for
obtaining project objectives may be made by our representatives; however, direction of the actual work should come from the owner or contractor, as appropriate. The contractor is responsible
for complying with the contract documents at all times, regardless of the presence of our field representative. Jobsite safety, including compliance with all applicable state or federal regulations,
is the sole responsibility of the contractor. The observations, recommendations, and conclusions provided in this field report are preliminary until reviewed by the ESNW project manager.
ESNW rep. was on site to observe a test pit excavation within the proposed ADU building pad.
ESNW rep. observed dark brown, loose, wet, organic -rich material exposed along the proposed ADU
building pad subgrade. ESNW rep. observed the contractor excavate a test pit approximately 10.5 feet
deep below the current building pad subgrade. The upper 4.5 feet was observed to consist of loose, wet,
topsoil/peat material which may have been old fill or reworked native material; an approximate 6-inch
layer of washed rock was observed at about 4 feet deep and heavy seepage was emerging from the
rock. Native dark brown peat was observed from about 4.5 feet to about 10 feet deep. The native peat
was underlain by loose to medium dense, wet gray silty sand. Moderate caving was observed
throughout the depth of the test pit.
The peat material is not suitable for support of the proposed structure. The peat should be removed and
replaced with suitable structural fill, or the structure should be supported on pipe piles. Removal of the
material may prove to be impractical due to the depth of the peat. It is our opinion that supporting the
structure on pipe piles is a suitable option. Based on the local geologic mapping (advance outwash) and
the depth of the peat, we anticipate pipe piles would be driven to depths of approximately 20 to 25 feet;
however, we recommend driving a test pile or advancing a test boring to better delineate anticipated
depth to refusal. If the proposed structure is supported on pipe piles, assuming the pipe piles are driven
to refusal, the allowable axial load capacities listed below can be used for design:
Pile Diameter
Load Capacity*
Refusal Criteria
seconds/inch
Hydraulic Hammer
2-inch
6 kips
8
400 lbs.
3-inch
12 kips
10
850 lbs.
4-inch
20 kips
16
850 lbs.
* Assumes a factor -of -safety of at least 2.0
Report ID 8394.00 G 01172022
Page 2 of 2
With structural loading as expected, total settlement in the range of one inch is anticipated, with
differential settlement of approximately three quarters of an inch. The majority of the settlements should
occur during construction, as dead loads are applied.
Due to the groundwater conditions, we recommend the piles include corrosion protection.
We recommend supporting the slab on grade beams if pipe piles are utilized.
An ESNW representative should observe and document the pipe pile installation to confirm the refusal
criteria during the pile driving operation.
ESNW can provide additional testing and information upon request.
IT�W
TONAL V
01 /24/2022
Henry T. Wright, P.E.
Associate Principal Engineer
Earth Solutions NW. LLC