HomeMy WebLinkAboutObservation of Excavation 10.05.2022€'#
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October 5,2A22
Marcelino Holguin
274 Lariat Road
Silt, Colorado 81652
Subject:
Prnject No, 21-7-330
Observation of Excavation, Proposed Residence, 928 County Road 2lB, Silt,
Colorado
I)ear Marcelino:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on September 30. 2Q22 ta evaluate the soils exposed for foundation support. The findings of our
obseft'ations and recommendations for the foundation support are presented in this report. We
previously observed the site as described in our report dated April 15, 2A21. The services were
performed in accordance with our agreement for professional engineering services to you dated
April 8, 2A21.
The proposed residence will be a one-story wood fi'ame structure with a slab-on-grade floor and
attached garage. Fcundations were designed based on an assumed allowable soil bearing
pressure of 1,500 psf^
At the titne of our visit to the site, the foundation excavation had been cut in one level from 3 to
15 feet below the original ground surface. The soils exposed in the bottom of the excavation
consisted of medium dense silty sand rryith scattered cobbles.
Cr¡nsidering the conditions exposcd in the excavation and the nature of the proposed
cr¡¡rstruction, spread tbotings placed on the undisfurbed natural soil designed for an allowable
soil bearing pïessure af 1,500 psf can be used for support ofthe proposed residence. Footings
slroulcl be a mininrum width of 18 inches for continuous walls and 2 feet for columns. Loose and
disturbed soils in footing areas should be moistened and compacted or removed and the bearing
level extended down to the undisturbed natural gravel soils. Exterior footings should be
provided r,r,'ith adequate soil cûver above their bearing elevations for fi"ost protection. Continucus
foundation walls should be reinforced top and bottom to span local anomalies such as by
assuming an unsupported length af at least 15 feet. Founclation 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. Structural filI 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 neat optimum. Backfill placed around the structure should be compacted ancl
the surface graded to prevent ponding within at least l0 feet of the building. Landscape that
Marcelino Hoiguin
Octc¡ber 5,'2422
P*ge 2
requires reguiar heavy irrigation, such as sod, and sprinkler heads should not be located within
l0 feet of the firundation.
"fhe recomrnendations submitted in this letter are based on our observafion 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 thc footings have equal or better support than those exposed,
Tl"re risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. In order ta 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 explorrtion could change the recommendations contained in this
letter. Our services do not include dctermining the presence, prevention or possibility of rnold or
other biological contaminants (MOBC) developing in the future. if the client is concerned about
MOBC, then a professional in this special field of practicc shoulcl be consulted"
If you have any questions or need further assistance, please call our office.
Sincerely,
!tfi
Daniêl E. Hardin, P
Rev" by: SLP
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