Report Carlson Geotec _111Cal Mafn Box Salem Office
Bend Office
P.O.BoX 23814 4060 Hudson Ave., NE P.O. Box 7918
A Division of Carlson Testing, Inc. Tigard, Oregon 97281 Salem, OR 97301 Bend, OR 97708
Phone (503) 684 -3460 Phone (503) 589.1252 Phone 541
GeOtechnical Consulting ( ) ( ) 330 -9155
Construction Inspection and Related Tests FAX (503) 870.9147 FAX (503) 589 -1309 FAX (541) 330-9163
CGT No: G0602953.A 8 -, 0000 ( + �
7 —) I 'i
FIELD REPORT
DATE COVERED: April 28, 2008
PROJECT: TVFR Fire Station 50 "Walnut"
ADDRESS: / 2 ( /',� .1258b -3W Walnut Street, Tigard, Oregon:. ~ `
BY: M. David Irish ()Ai
WEATHER: Cloudy, -60 °F
PURPOSE OF VISIT: Subgrade & Proof -Roll Observation
Carlson Geotechnical (CGT) staff, David Irish, arrived on site at about 10:55 a.m. at the request
of Matt with DBEC Excavation & Construction (DBEC). The purpose of my visit was to observe
the exposed subgrade soils on a portion of the site. I met with Rick, with DBEC, at the site.
Proof -roll Observation:
Today I observed a proof -roll of the parking area at the north end of the proposed fire station.
The approximate area proof - rolled today is marked out on the attached site plan (elevations
were provided by DBEC). Rick informed me that there was approximately 2.5 feet of fill (1 -
minus crushed rock from Cobb Rock Products) to be placed within the area proof - rolled to reach
finished elevations.
The proof -roll test was performed using a fully loaded, dual axle, dump truck and revealed areas
of minor pumping and rutting as the tires of the dump truck passed over the fill. I informed Rick
of my observations and that I observed the fill to be below optimum moisture for compaction. I
recommended that the fill be watered down and recompacted. I informed Rick that no more fill
should be placed within the area indicated until another proof -roll test could be observed by
CGT personnel. Rick indicated that he understood and agreed with my recommendations.
Based on my observations the area proof - rolled today has not been prepared in general
conditions with CGT recommendations and additional proof -roll testing will be necessary.
Subgrade Observation:
I observed the DBEC crew excavate the southwest corner for the proposed fire station building.
The area observed measured approximately 28 feet (east -west) by 38 feet (north- south). Most
of the area was over - excavated 4- inches to allow for a minimum 16 -inch rock section. The only
exception was the northwest corner of the area, which was over - excavated approximately 2 feet
to remove large tree roots. The area that was over - excavated approximately 2 feet measured
approximately 10 feet by 10 feet.
The exposed subgrade soils consisted mainly of native, brown, moist, silt. Probing the exposed
subgrade soils with a 1/2-inch-diameter soil probe and using moderate effort, I was generally able
to penetrate the exposed subgrade soils 8 to 10 inches, indicating soft soil conditions.
While on -site, Rick brought to my attention that the basement of the previously existing
residential structure located on the site had been backfilled prior to the DBEC crew's arrival on-
site. I observed that the basement excavation was located within the southwest corner of the
proposed parking area and measured approximately 20 feet (east -west) by 40 feet (north -
south). Pot - holing through the center of the backfilled excavation revealed that the excavation
TVFR Fire Station 50 'Walnut'
Tigard, Oregon
CG Project No. G0602953.A
April 28. 2008
was approximately 4 feet in depth and had been backfilled with crushed rock and sand and that
construction debris (concrete and brick) was still present at the bottom of the excavation.
I recommended to Rick that the undocumented fill be removed from the excavation and that the
excavation be backfilled with structural fill. Rick indicated that he understood and agreed with
my recommendations.
Based on my observations the subgrade soils observed within the southwest corner of the
proposed building have been prepared in general conditions with CGT recommendations.
I left the site at about 12:15 p.m.
Should you have any questions regarding this report, please contact us at (503) 601 -8250.
Respectfully submitted;
Carlson Geotechnical
M. David Irish yan T. Houser, CEG
Senior Engineering Assistant Senior Engineering Geologist
Note: Our reports pertain to the locations observed at the time of our visit only. Information
contained herein is not to be reproduced, except in full, without prior authorization from this
office.
ATTACHMENTS: Site Plan (1 page)
DISTRIBUTION: Mr. Gary Wells, TVFR, FAX: 503.642.9655
Daniel Watkins, City of Tigard Building Department, FAX: 503.624.3681
Lance Cerny, Lewis & Van Vleet, FAX: 503.885.1206
Jeff Bringenberg, Peck Smiley Ettlin Architects, FAX: 503.248.0223
Michael Krecklow, First Cascade Corporation, FAX:
Kendra Laminack, PBS Environmental, FAX 360.696.9064
Matt, DBEC Excavation & Construction, FAX: 503.513.6254
WALNUT STREET FIRE STATION - TIGARD, OREGON
SITE PLAN •
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r NOTES: LEGEND
Drawing based on approved construction CGT Job No.
drawings. G0602953.A
, Approximate Scale i inch = 40 feet
Gp►R 0p Carlson Geotechnical INMEINEMIE Construction
P.O. Box 23814 UMMENIMENNEMII. Observation
° 503.60i4250 ` Tigard, Oregon 97281 0 40 80 • Plan