16-217 Westgate Village_Final Letter.pdf________________________________________________
3213 Eastlake Avenue East, Suite B
Seattle, WA 98102
Tel: (206) 262-0370
Geotechnical & Earthquake
Engineering Consultants
July 1 , 2019
File No. 16-217
Mr. Anthony Jansen
Westgate Village, LLC
4025 Delridge Way SW #530
Seattle WA 98104
Subject: Final Letter - Geotechnical Construction Observations
Westgate Village, Edmonds, WA
Permit No. BLD2018-0034 (Shoring)
Permit No. BLD2016-1538 (Building)
Dear Mr. Jansen,
PanGEO, Inc. has completed geotechnical construction support services for the above property as
required by the City of Edmonds Building and Engineering and Fire Department. This final report
summarizes our observations.
The scope of construction support services performed was in general accordance with the
geotechnical inspection items discussed in pre-construction meetings with the City and project
team on February 6 and 9, 2017, as summarized below.
Geotechnical inspection items for Permit No. BLD2018-0034 (Shoring):
• Soldier pile and lagging installation
• Tieback installation
• Tieback stressing/testing
• Performance monitoring
Geotechnical inspection items for Permit BLD2016-1538 (Building):
• Footing/slab subgrade
• Monitoring of Excavation
• Fill placement and compaction
Final Letter – Westgate Village, Edmonds, WA
Permit No. BLD2016-1538 (Building)
Permit No. BLD2018-0034 (Shoring)
July 1 , 2019
16-217 Westgate Village_Final Letter Page 2 of 4 PanGEO, Inc.
• Subsurface drainage installation
• Permeable pavement subgrade
We performed geotechnical construction monitoring between February 6, 2017 and May 9, 2019.
Our observations were documented in 15 field reports, which were e-mailed to the City, you, and
other members of the project team. Based on our observations, the geotechnical elements of the
project were constructed in general accordance with our recommendations and the design plans as
discussed in this letter.
OBSERVATIONS AND CONCLUSIONS
Details of our observations are contained in our field reports. The following summarizes our
observations:
1. Shoring Installation and Performance Monitoring – PanGEO provided monitoring
during installation of permeant soldier pile walls with tiebacks that extended from existing
soldier pile walls in the west portion of the site (see Field Reports #2, #3, and #4). Tiebacks
and walers were also installed on portions of the existing soldier piles walls per plans.
Based on our observations, it is our opinion that the permeant soldier pile walls with
tiebacks was installed in general accordance with the project plans.
Additional Notes: The installed permeant soldier pile walls consist of timber lagging
without concrete facing. Based on the information provided to PanGEO, the use of the
timber lagging as the permanent soldier pile wall facing is acceptable to the shoring
designer (i.e. Ground Support), provided the inspection and maintenance are conducted in
future years. In our opinion, we concurred with the shoring designer. It is also our opinion
that permanent soldier pile wall could allow water (if present behind the wall) to drain
through the face of the exposed timber lagging.
2. Shoring Wall Performance Monitoring – PanGEO visually monitored the performance
of the soldier pile walls, and evaluated survey monitoring data made from the targets
installed on the top of the soldier piles. In summary, the monitoring survey data showed
total wall movements during the excavation were less than half an inch, indicating the walls
performed adequately.
3. Tieback Anchor Installation & Testing – PanGEO provided full-time monitoring for the
installation of all tiebacks. Based on our observations, it is our opinion that the tiebacks
were installed in general accordance with the project plans. Verification tests (i.e. 200%
Final Letter – Westgate Village, Edmonds, WA
Permit No. BLD2016-1538 (Building)
Permit No. BLD2018-0034 (Shoring)
July 1 , 2019
16-217 Westgate Village_Final Letter Page 3 of 4 PanGEO, Inc.
design load) were performed on three production tiebacks, and the reminder of the
production tiebacks were proof tested to at least 130% design load per plans. Based on
the test data, it is our opinion that the tested tiebacks appeared to be satisfactory and were
in accordance with the project specifications.
4. Soil Bearing Verification – PanGEO observed the exposed subgrades for all footings prior
to concrete placement. In general, the exposed soils were consistent with what was assumed
for design, and consisted of medium dense to very dense, sand with gravel (native outwash
sand). In our opinion, based on our observations, the footing subgrades were properly
prepared and adequate to support the design bearing pressure of 3,000 psf (6,000 psf for
interior footings in basement).
5. Monitor Excavation – During our site visits, we observed the condition of the excavation.
The excavation was made in general accordance with the approved shoring and excavation
plans, and no signs of unstable conditions were observed. At this time, the site excavation
has been completely backfilled to the design finished grades.
6. Structural Fill and Compaction – As described in our field reports #12 and #13, structural
fill included backfill below and around footings, and behind the retaining walls. On-site
soils (outwash sand with gravel) were used for structural fill. Based on our observations
of the backfill material and compaction procedure, as well as the results of probing the
surface of the fill, in our opinion the structural fill was adequately compacted per the project
specifications and our recommendations.
7. Subsurface Drainage Installation – During our site visits, we observed the installation of
footing drains along the perimeter of the basement wall footings (see Field Report #7). The
footing drains consisted of 4-inch diameter perforated PVC pipe, bedded in clean crushed
rock and surrounded with a geotextile fabric. Based on our observations, the drainage
provisions were installed in general accordance with the project plans.
8. Permeable Pavement Subgrade – During our site visits, we observed the subgrade below
the permeable pavement subgrade (see Field Reports #14 and #15). The subgrade
generally consisted of silty, medium sand (native outwash sand with silt and gravel). After
the subgrade was exposed, it was backfilled with ¾ - 2” and 1” clean crushed rock, per
plans. Based on our observations, it is our opinion that the prepared subgrade observed
was consistent with the approved plans.
Final Letter – Westgate Village, Edmonds, WA
Permit No. BLD2016-1538 (Building)
Permit No. BLD2018-0034 (Shoring)
July 1 , 2019
16-217 Westgate Village_Final Letter Page 4 of 4 PanGEO, Inc.
In summary, the above-discussed geotechnical elements of the project have been accomplished in
general accordance with the project design plans and specifications for the project, and our
recommendations.
LIMITATIONS
The geotechnical observation services were performed in accordance with generally accepted
standards of the profession in this geographic area. PanGEO personnel were on site on an as-
needed basis. The conclusions contained herein apply only to our observations at the time of our
site visits. Our conclusions and opinions as to whether the work essentially complies with the
project requirements are based on our observations and experience. We cannot provide advice,
opinions, or conclusions relative to site work that we have not observed.
We appreciate the opportunity to be of service.
Sincerely,
Yi-Hsun William Chao, P.E. W. Paul Grant, P.E.
Senior Project Geotechnical Engineer Principal Geotechnical Engineer