HomeMy WebLinkAboutObservation of Excavation 12.10.18Y{"-WwW\Jf\ñhW 5020 County Road 154
Glenwood Springs, C0 8160rf
Phone: (970) 945-7988
Far {970) 945{454
Email: hpkglenwood@kumarusa.com
Office Locations: Ðenver {HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Sumrnit County, Colorado
December 10,2018
Divide C.reek Builders
Attn: Kevin Wakefield
1531 Cor¡ntry Road 342
Silt, Colorado 81652
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Project No.l8-7-721
Subject:Observation of Excavation, Proposed Cabin Additions, Inyanga Ranch, 398
County koad 136, Garfield County, Colorado
Gentlemen:
As requested, â representative of H-PlKumar observed the excavation at the subject site on
December 5 and 7, 2018 to evaluate the soils exposed for foundation support. The findings of
our observations and recommendafions for the foundation design are presented in this report.
The scrvices were perfcrrmed in accordanse with our agreement for professional engineering
services to Divide Creek Builders, dated November 30, 2018.
Additions are proposed to 2 of the existing cabins. Spread footings placed on natur¿l granular
soils nnd sized for an allowable bearing pressure of 2,000 psf were assumed for the foundation
support.
,4.t the tirne of our initial visit to thç site, the foundatian excavation for thc southern cabin
addition had been cut in one level &om 3 to 3Yz feet below the adjacent ground surface. The
soils exposed in the bottom of the excavation consisted of nafural, silty sand end gravel with
cobbles. The soils exposed in the bottom of the northern cabin addition area consisted of organic
silty clay with gravel fill which was reconÌmended to be removed down to the nafural gravel
soils. When observed on Decemb er 7 , the excavation was cut 8Y2 to 9 feet deep and into the
natural såndy gravel and cobbles with scattered boulders. No free water was encountered in the
excavations and the soils were stightly moist to moist.
Considering the conditions exposed in the excavations and the nature of the proposed
construction, spread footings placed on thb undisturbed natural gravel soil designed for an
allowable soil bearing prsssure of 2,000 psf should be adequate for support of the proposed cabin
additions. Footings should be a minimum width of l6 inches for continuous walls and 2 feet for
columns. Loose disturbed soils and existing fill in footing areas shauld be removed and the
bearing level extended down to the undisturbed natural pavel 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.
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Divide Creek Builders
Decernber 10,2018
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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 50 pcf for on-site soil as backfill excluding organics and rock larger than 6
inches. A perimeter foundation drain should be provided to prevent temporary buildup of
hydrostatic pressure behind the basement walls and prevent wetting of the lower level. Structural
fill placed within floor slab areas can consist of the on-site gravel soils compacted to at least 95%
of standard Proctor density at a moisture content near optimum. Backfill placed around the
sfructure 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 5 feet of the foundation.
The recommendations submitted in this lett€r are based on our observation of the soils exposed
within the foundation excavations 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 movsment 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.
Sincerel¡
H-P+KUMAR
Steven L. Pawlak,
SLP/kac
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