HomeMy WebLinkAboutBuilding Miscellaneous 2014-5-2 g//-- Sck'owy - cn -' ® anch
May2, 2014 ENGINEERING=
Mr. Derrick Westover • SLnm 1977
Bruce Wiechert Custom Homes, Inc. civil• tratisportatlon
3073 Skyview Lane structui.51., geotechnical
Eugene, Oregon 97401
RE: SUBGRADE EVALUATION
6143 GRAYSTONE Loop
SPRNGFIEID,OREGON
BRANCH ENGINEERING INC.PROJECT NO.14-058
BRANCH ENGINEERING FIELD REPRESENTATIVE MATT RENNER PE
•
April 21, 2014: A Branch Engineering Inc. (BEI) geotechnical representative visited the above
referenced site to observe the building pad excavation, assess the shrink/swell potential of the
subgrade soil and the placement of compacted crushed rock aggregate fill for the construction of
a level building pad. The site is situated on a hillside generally sloping to the southwest. At the
time of the visit the northern half of the building pad subgrade had been excavated into native
basalt while the southern half of the building pad had been excavated through topsoil and clay fill
into hard rock fill consisting of fractured basalt with silty clay from 6- inches in diameter up to
1.5- foot diameter boulders. The building pad sits approximately 6 to 8-feet below the lot to the
north with a boulder wall along the northern boundary of the building pad. Cuts transitioned
along the eastern cut of the excavation from 4-feet in height at the northern side to daylight
grades at the southern side.
Crushed rock aggregate fill 12 to 18- inches in thickness was in the process of being placed and
compacted with a 15- ton smooth drum roller. A density test with a nuclear densometer(ASflI D-
6938) was performed during the visit. The crushed rock aggregate consisted of 3/4" -(0) material
from the Knife River Springfield Quarry. A modified Proctor (AASHTO 1'-180) curve for the
material dated 7-29-2013 was used to evaluate percent relative compaction. 90% relative
compaction is required for a passing test. Results are listed below.
•
Moisture
Dry Density Content Relative
Location (pcf) (%) Compaction(%)
Northern portion of building pad--"` 124.2 7.0 96
The building pad is suitable for a conventional perimeter-style foundation, and an allowable soil
bearing capacity of 1,500 psf. We recommend that the foundation perimeter be backfilled and
graded to slope away from the structure as soon as concrete curing allows. Differential
settlements are expected to be less than 1/2-inch over a span of 20 feet. Footing drains are
recommended as the subject lot lies below the adjacent lots north and east of the pad. Surface
drainage shall be established to convey water to a suitable disposal area, and final perimeter
landscape grades shall slope away from t • 'oundation and surface water not be allowed to pond
adjacent to the foundation. tcLO PROFF
Sincerely, N GIN ",
Branch Engineering Inc, . - rt16.17 rr•
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OREG•
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Ronaldy..Derrick (24/(24/ FP% 15. t9°• (\��
Principal Geotechnical Engineer 44p J
EUGENE-SPRINGFIELD SALEM-
310 DECEMBER 31, 2015
310 5U Street,Springfield,OR 97477 1 p: 541.746.0637 1 wvnv.branchengineering.com