HomeMy WebLinkAboutObservation of Excavationrcn tunur&Igchbe,lrc.c
C'eotochnlcaland Materials Engineen 5020 County Road 1S4
and EnvironmentalSclentiets Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employcl orrntd Conpony wwwkumaruga.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
December 27,2023
Timbedine Construction
Attn: Eric Fisher
204ParkAvenue
Basalt, Colorado 8162t
eri c@timberl ineconstruct. com
Project No. 23-7-584
Subject Observation of Excavation, Proposed Addition to Existing Residence, 2368
County Road I12, Garfield County, Colorado
Dear Eric:'
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on December 20,2023 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation support are presented in this report. The
services were performed in accordance with our agre€ment forprofessional engineering services
to Timberline Constnrction dated October 4,2023.
Theproposed addition will be located on the west side of the existing house.
At the time of our visit to the site, the foundation excavation had been further exoavated in four
levels from 2 to 7 feet below the adjacent ground surface. The excavation had recently been
deepened. The soils exposed in the bottom of the excavation consisted of firm, silty to clayey
sand with scattered gravel and cobbles. No free water was encountered in the excavation and
the soils were slightly moist. The excavation was blanketed to protect the subgrade from
freezing.
Considering the conditions exposed in the excavation and the nature of the proposed
constructionn spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psf can be used for support of the proposed addition. The exposed
soils te'lrd to compress and there could be some post-construc'tion settlement of the foundation.
Footings should be a minimum width of 18 inches for continuous walls and2 feet for columns.
Loose and disturbed soils and existing fill in footing areas should be rernoved and the bearing
level extended down to the undisturbed natural soils. The bearing soils should be protected
against frost and concrete should not be placed on frozen soils. Exterior footings should be
provided with adequate soil cover above their bearing elevations for frost protection. Continuous
foundation walls should be reinforced top and bottom to span local anomalies such as by
assuming an unsupported length of at least l0 feet. Foundation walls acting as retaining
structures should also be designed to resist a lateral earth pressure based on an equivalent fluid
unit weight of at least 50 pcf for on-site soil as backfill. A perimeter foundation drain should be
provided as needed to prevent ternporary buildup of hydrostatic pressure behind the below grade
Timbedine Construction
December 27,2023
Page2
walls and prevent wetting of the lower level. Structural fill placed within floor slab areas can
consist of the on-site soils or a suitable imported material compacted to at least 95% of standard
proctor density at a moisture content near optimum. Backfill placed around the structure should
be compacted and the surface graded to prevent ponding within at least 10 feet of the building.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and do not include subsurface exploration to evaluate the
subsurface conditions within the loaded depth of foundation influence. This study is based on
the assumption that soils beneath the footings have equal or better support than those exposed.
The risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. In order to reveal the nature and extent of variations in
the subsurface conditions below the excavation, drilling would be required. It is possible the
data obtained by subsurface exploration could change the recommendations contained in this
letter. Our services do not include determining the prese,nce, prevention or possibility of mold or
other biological contaminants (MOBC) developing in the futrne. If the client is concemed about
MOBC, then a professional in this special field of practice should be consulted.
If you have any questions or need further assistance, please call our office.
Sincerely,
Kunrar & Associatcs, In
q__.
Daniel E. Hardin, P.E.
DEH/kac
Cc: MartinMata@)
Kumar & Associates, lnc. @ Project No. 23-7-584