HomeMy WebLinkAboutEngineer's Foundation Recommendations - 08.03.2015Engineering, Inc.
August 3, 2015
CIVIL/GEOTECHNICAL
Clinton Omang
262 Wooden Deer Rd.
Carbondale, CO, 81623
email: el intandsue(a?gmail.com
Dear Clint:
RE: Foundation Recommendations
Garage Addition
Lot 20, Wooden Deer Subdivision
262 Wooden Deer Road
Garfield County, Colorado
Project No. 15-3039
At your request, on July 31, 2015, we met on your property, Lot 20, Wooden Deer
Subdivision, 262 Wooden Deer Road, Garfield County, Colorado. The purpose of our site visit
was to observe the soils exposed in the foundation excavation for your proposed garage and
provide additional recommendations for the foundation support. Prior to our site visit we
received your email with the Open Hole observation report by HP Geotech, dated May 31, 2015,
and the structural drawings S-1 through 3, by James Jackson Romeo, PE, Structural Design
Consultant, LLC, dated June 4, 2015. In addition, after the site visit you emailed us the report by
HP Geotech dated May 31, 2012, prepared for the construction of your main residence.
We reviewed the information submitted and agreed that the subgrade soils have high
potential for hydro consolidation. We also agree with their recommendations for the foundation
support of your proposed garage.
During our site visit, we observed the foundation excavation for the garage. The
excavation was located adjacent to the east side of your existing residence. The trenches were
about three feet deep, except in the area of the southwest and northwest corners, where they will
be attached to the main residence. In these areas the trenches were excavated down to the bottom
of the existing foundation, which was about eight feet below the existing grade.
We recommend an additional alternative for the support of your proposed garage.
The proposed garage can be supported on a structural fill improved with Tensor Triaxial
Geogrid with conventional type spread footings, designed for a maximum allowable soil bearing
pressure of 2000 psf.
The existing soil will be overexcavated four feet below the proposed bottom of footing
elevation and backfilled with improved, compacted, structural fill. The width of the
overexcavation should be according to the attached, overexcavation and compaction detail,
Figure No.1. The structural fill will be minus 3 -inch road base. The first layer of geogrid should
P.O. Box 724, Eagle, CO 81631 Tel (970) 926-9088 www.lkpengineering.co.m
Omang Garage Addition
Page 2 of 2
August 3, 2015
be placed 6 inches above the subgrade. The next two layers should be placed at 1.5 feet apart
with a 6 -inches, and up to half of the footing width, backfill material above the last geogrid layer.
We recommend minimum width of 20 inches for the continuous footings and 2 feet for
the isolated footing pads. Continuous foundation walls should be reinforced top and bottom to
span an unsupported length of at least 12 feet. Proof rolling of the minus 3 -inch road base will
be scheduled with the undersigned engineer. Any substitutions must be reviewed for approval
prior to implementation.
We also recommend overexcavation of the subgrade under the slab on grade area. For the
slab grade overexcavation, three feet of the unsuitable on-site native soil will be removed and
replaced with three feet of minus 3 -inch road base, improved with three layers of Triaxial
Geogrid, TriAx-140.
The geogrid installation will be done according to the manufacturer's recommendations.
This report has been prepared according to locally accepted professional Geotechnical
engineering standards for similar methods of testing and soil conditions at this time. Geologic
Hazard Studies are outside of our scope of services.
There is no other warranty either expressed or implied.
Sincerely,
LKP Engineering, Inc.
Luiza Petrovska, PE
29 =c
�+ s e.c,
Attachments: Figures 1 and 2, OEX Detail, Perimeter Drain
Cc: j im{ir j jrstructural.com
J:\ WP X4-LKP\ 2015\15-3039oex-geogrid.wpd
P.O. Box 724, Eagle, CO 81631 Tel (970) 926-9088 www.lkpengineering.com