Report S 1 02005 -0378" No 0766 P. 2
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Real World Geotechnlcal Solutions
Investigation 6 Design • ConstrUCtlon Support
September 8, 2005
GeoPacific Project No. 04 -8608
Terry Kinney / Jim Cavanaugh
West Hills Development
15500 SW Jay Street
Beaverton, Oregon 97006
f ax No (503 6141 -7661
Copy: ' :.n : o d LDC Desi s emu • l c. a . t -645-55
e A i ! a ..c G Constructio t • _ .. 50. ; •
Subject Summary Report of Geotechnical Observation and Testing
Arbor Summit
Tigard, Oregon
References: 1. Preliminary Geotechnical Engineering Washington o County, Oregon,
Property, 12780 SW Bull Mountain Road,
GeoPacific Engineering, Inc. report dated February 17, 2004.
2. Preliminary Geotechnical Engineering Report, Arbor S tf u ic E Inc lsll
Mountain Road, Washington County, Oregon,
report dated May 24, 2004.
3. Rockery Wall Analysis and "Lock +Load" Wall Design Parameters, Arbor
Summit, Tigard, Oregon, GeoPacific Engineering, Inc. letter report dated
August 13, 2004
4. Wet Subgrade Pavement Section, Arbor umt 8, 2 Tigard, Oregon, GeoPacif c
Engineering, Inc. letter report dated November
5. Geotechnical Engineering Report, Bull Mountain Road Improvements at Arbor
Summit, Arbor Summit Subdivision, c. letter Road,
report dated 12 2064
Oregon, GeoPacific Engineering,
GeoPacific Engineering, Inc. (GeoPacific) conducted testing ro improvements S�.eation
services for Arbor Summit Phases 1 and 2. The project site and proposed The
shown on the attached reduced grading plan sheet prepared by LDC Design Group, I I c The ted
evelopment consists of grading 42 lots (Lots 1 -42) for single-family
improvements that include new streets and driveways, and d an d 9 fr in utilities. T project Load
also included construction of several rockery walls up
type wall up to about 11 feet high, in the southeast corner of the property.
Tel (503) 598-8445
7312 SW Durham Road Fax (503) 598 -8445
Portland, Oregon 97224
ro5 1051AM No. 0766 P. 3
September 8, 2005
GeoPacific Project No. 04 - 8608
GeoPacific performed geotechnical engineering studies for the site (References 1 and 2), which
include geotechnical recommendations for the project, Reference 3 includes recommendations
for rockery retaining wall design and construction, and soil parameters for use by others in design
of the Lock +Load retaining wall.
Results of field monitoring and density testing for the Arbor Summit development are attached to
this report. In addition to providing a summary of geotechnical observation and testing
performed to date, this letter report provides recommendations for residential structure
construction.
SITE PREPARATION AND FILL PLACEMENT
Prior to fill placement, areas to receive fill were stripped and proof-rolled. Stripped materials
were removed from the site. Based on the grading plan and our field observations, engineered
fill was placed on the following lots:
• Lot 6
• Lots 14 — 25
• Lots 35 — 37
• Lot 41
The remaining lots were planned as either cut lots or near previously existing grade.
Engineered fill consisted of on -site native silt, moisture conditioned to facilitate compaction.
During placement of the engineered fill, we performed periodic density testing to verify the
relative compaction of fill materials. The compaction specification for engineered fill was a
minimum of 95 percent of maximum dry density based on Standard Proctor (ASTM D 698).
Density test results are attached. Due to wet soil conditions, some of the engineered fill was
cement treated to facilitate compaction. From our observations and test results, fill soils were
adequately compacted and are suitable for spread foundation support under dry weather
conditions (see Structural Foundations section below).
RETAINING WALLS
GeoPacific performed wall stability analysis and provided construction recommendations for
rockery walls on the project (Reference 3). During construction, we monitored rockery walls for
keyway soil suitability, rock size and placement, wall batter and subsurface drainage. Based on
our observations, the rockery walls on site were constructed in general accordance with the
geotechnical recommendations.
Lock +Load walls on the project were designed by others, with soil parameters for design .
provided by GeoPacific (Reference 3). The wall extends southeast of Lots 14 and 15, above the
new cul -de -sac for SW Terravicw Drive in the southeast corner of the site.
04- 8605 -Artror Summit Final 2 GEOPACIFIC ENGINEERING, INC.