20101001073941135.pdfN
Main Office
17311 — 135'" Avenue NE, A-500
Woodinville, WA 98072
(425) 486-1669 • FAX (425) 481-2510
(425) 337-1669 Snohomish County
August 12, 2010
Mr, Phil Tiegs
16911 Talbot Road
Edmonds, Washington 98026
NELSON GEOTECHNICAL,
AssocIATEs, INC.
GEOTECHNICAL. ENGINEERS & GEOLOGISTS
Geotechnical Special Inspection Summary Letter
Tiegs Residence
16911 Talbot Road
Edmonds, Washington
NGA File No. 78711309
Engineering -Geology Branch
112 Olds Station Road, Suite C
Wenatchee, WA 98801
(509)665-7696 (Phone/Fax)
Dear Mr. Tiegs:
This letter summarizes our geotechnical consultation and construction monitoring services for the new
residence located at 16911 Talbot Road in Edmonds, Washington. The project generally consisted of
constructing a two-story residence and a raingarden stormwater system. We previously issued a
geotechnical engineering evaluation for this project dated May 12, 2008. We also issued an infiltration
letter for this project, dated July 31, 2009.
The City of Edmonds required geotechnical inspections for earthwork construction at this project site as
indicated in a Ietter dated June 23, 2009. The geotechnical inspections included soil bearing verification,
subsurface drainage installation, temporary and permanent erosion control inspections and stormwater
infiltration system installation, We were retained by you to provide geotechnical engineering inspection
and consultation services for the project.
We monitored geotechnical related construction activities at the project site on a part-time basis from
November 9, 2009 to August 10, 2010. Our observations, opinions, and recommendations regarding
earthwork activities at this project site were included in Field Reports I through 5, which have been
submitted to you.
Special Inspections Summary Letter
Tiegs Residence
16911 Talbot Road
Edmonds, Washington
August 12, 2010
NGA Pile No. 7871B09
Page 2
We evaluated the residence and garage foundation subgrade by observing the material exposed in the
excavation and by probing with a V2 -inch diameter probe rod under moderate pressure. The soils exposed
at the foundation subgrade consisted of native brown -gray, fine to medium sand with silt and gravel; and
gray sandy silt that we interpreted as native glacial soils. In general the footing subgrade probed
approximately one to three inches and was interpreted to be medium dense to dense and should
adequately support the planned loads.
We observed the footing drains around the residence consisted of 4- inch PVC perforated pipes embedded
in 718 -inch drainage rock, and covered in filter fabric, extending around the perimeter of the structure per
the project plans. We did not observe the installation of the footing drains around the garage. However,
the contractor provided us with pictures showing a 4 -inch perforated PVC pipe around the garage
foundation that was covered with 1.5 -inch drain rock and filter fabric similar to the footing drains around
the residence. The footing drains were then directed to the raingarden stormwater system.
Stormwater for the site including roof drains, footing drains and driveway drains have been directed to the
raingarden system along the western portion of the property. We observed that an approximately 3 to 6
foot deep trench was excavated for the raingarden exposing fill materials in the excavation walls and
brown -gray fine to medium sand with silt at the base of the excavation. The trench was then filled with
two feet of washed rock and covered with filter fabric. An organic -rich soil mixture was then placed on
the filter fabric to form the raingarden bottom. An overflow pipe system was placed along the western
portion of the raingarden and connected to the existing stormwater system within Talbot Road. A sample
of the organic -rich soils within the raingarden was evaluated for the organic content in accordance with
ASTM D2974. Test results indicated that the raingarden soils contained approximately 10 percent
organic content.
Erosion control measures were utilized at the project site. Temporary erosion control measures generally
included a silt fence and straw bales around the excavation. We did not observe stormwater flowing
uncontrolled off-site during our visits. Based on our observations while on site, materials were not
tracked into public right of way or onto neighboring properties during earthwork construction. It is our
opinion that temporary erosion control measures were adequate.
NELSON GEOTECHNICAL ASSOCIATES, INC,
Special Inspections Summary Letter
Tiegs Residence
16911 Talbot Road
Edmonds, Washington
August 12, 2010
NGA File No. 78711309
Page 3
Permanent erosion control measures were observed on August 10, 2010 at the site and generally included
mulch, grass, bark and low vegetation. We did not observe any exposed areas or areas that we would
consider at risk of significant soil erosion. It is our opinion that the long-term erosion control measures
that have been implemented at the site are adequate.
Based on our part-time construction monitoring, it is our opinion that the geotechnical special inspection
items for this project that we observed were completed in general accordance with the plans and our
recommendations.
NELSON GEOTECHNICAL ASSOCIATES, INC,
Special Inspections Sunnnary Letter
Tiegs Residence
16911 Talbot Road
Edmonds, Washington
August 12, 20 10
NGA File No. 7871BO9
Page 4
We appreciate: the opportunity to be of service to you on this project. Please contact us if you have any
questions regarding this letter or require further information.
Sincerely,
07,11 m 1� li��l ill ljrllipi;
Le S. Bellah, GIT
Staff Geologist
c,P
Khaled M. Shawisb
Principal
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Three Copies Submitted