HomeMy WebLinkAboutObservation of Excavation 05.26.2022K+AGeotechnipl and Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
�— email: kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
May 26, 2022
Edgar Cuc
1853 County Road 109
Glenwood Springs, Colorado 81601
valenzcuc(a gmail.com
Project No. 21-7-392.A
Subject: Observation of Excavation, Proposed Residence, 893 County Road 102, Missouri
Heights, Garfield County, Colorado
Dear Edgar:
As requested, the undersigned representative of Kumar & Associates observed the excavation at
the subject site on May 25, 2022, 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 agreement for professional
engineering services to you dated May 25, 2022. We previously performed a subsoil study at the
site, dated June 7, 2021, our Project No. 21-7-392
The proposed residence will be about 6,000 square feet, mostly one level over a crawlspace.
There will be a second level over the garage at the northeast corner of the house.
At the time of our visit to the site, the foundation excavation had been cut in one level from %2 to
7 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of stiff sandy silty clay in the shallower cut areas to stiff sandy silt in the deeper cut
areas. No free water was encountered in the excavation and the soils were slightly moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 2,000 psf can be used for support of the proposed residence. The
exposed soils tend to compress when wetted and there could be some post -construction
settlement of the foundation if the bearing soils become wet. Footings should be a minimum
width of 18 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in
footing areas should be removed and the bearing level extended down to the undisturbed natural
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 12 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 55 pcf for on -site soil as backfill. A
perimeter foundation drain should be provided to prevent temporary buildup of hydrostatic
pressure behind the crawlspace walls and prevent wetting of the crawlspace. An impervious
membrane, such as 20 mil PVC should be provided below the drain gravel in a trough shape and
Edgar Cuc
May 26, 2022
Page 2
attached to the foundation wall with mastic to prevent wetting of the bearing soils. Structural fill
placed within floor slab areas can consist of the on -site soils 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. Landscape that requires regular heavy irrigation, such as sod, and sprinkler
heads should not be located within 10 feet of the foundation.
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 presence, prevention or possibility of mold or
other biological contaminants (MOBC) developing in the future. If the client is concerned 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,
Kumar & Associates. In.
Daniel E. Hardin, P.E.
Rev. by: SLP
DEH/kac
Kumar & Associates, Inc. 0 Project No. 21-7-392A