HomeMy WebLinkAboutSoils Report 08.04.2016P
-AR
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax (970) 945-8454
Email: hpkglenwood@kumarusa.com
August 4, 2016
Dave Cardiff Construction, Inc.
Attn: Dave Cardiff
506 Mesa Verde
Carbondale, Colorado 81623
Subject:
Dear Dave:
Office Locations: Parker, Glenwood Springs, and Siiverthome, Colorado
Project No. 16-7-283
Observation of Pit Excavation, Proposed Residence, Nieslanik Ranch, 979 County
Road 101, Garfield County, Colorado
As requested, the undersigned representative of H-P/Kumar observed the pit excavation at the
subject site on August 2, 2016 to evaluate the soils exposed for foundation support. The findings
of our observations and recommendations for the foundation design are presented in this report.
The services were performed in accordance with our agreement for professional engineering
services to you, dated August 2, 2016.
The proposed residence will be a one and two story wood frame structure over a crawlspace.
The house site is located on a low ridge and slopes gently down to the south. Vegetation at the
site consists of grass and weeds with scattered juniper and pinon trees.
Pit Observation: At the time of our visit to the site, the pit excavation had been dug in the
southern part of the house site to a depth of 71/2 feet below the adjacent ground surface. The soils
exposed in the pit consisted of z foot of topsoil and 3 feet of gravelly sand and silt overlying 31/2
feet of slightly silty sand and gravel with cobbles. The results of a gradation analysis performed
on a sample of the sand and gravel (minus 5 -inch fraction) obtained from the pit are presented on
Figure 1. No free water was encountered in the excavation and the soils were slightly moist. A
nearby profile pit in the leach field area showed a similar soil profile to a depth of 10 feet.
Recommendations: Considering the conditions exposed in the pit excavation and the nature of
the proposed construction, spread footings placed on the undisturbed natural gravel soil designed
for an allowable soil bearing pressure of 2,000 psf should be adequate for support of the
proposed residence. Footings should be a minimum width of 16 inches for continuous walls and
2 feet for columns. Loose and disturbed soils (and the upper layer of sand and silt) in footing
areas should be removed and the bearing level extended down to the undisturbed natural gravel
soils. We should observe the completed foundation excavation prior to placing footing forms.
Exterior footings should be provided with adequate soil cover above their bearing elevations for
frost protection which is typically 36 inches in this area. Continuous foundation walls should be
Dave Cardiff Construction, Inc.
August 4, 2016
Page 2
reinforced top and bottom to span local anomalies such as by assuming an unsupported length of
at least 10 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 sand
and silt soil as backfill. 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 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 pit 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,
H -Pt KJ MAI
Daniel E. Hardin, P.E.
Rev. by: SLP
DEH/ksw
attachment Figure 1 Gradation Test Results
IHYDROMETER ANALYSIS 1 SIE
ANALYSIS 1
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12 5 127
DIAMETER OF PARTICLES IN MIWMETERS
SA141
SNM
COBBLES 18 % GRAVEL 39 %
MOISTURE CONTENT 3 8%
SAMPLE OF Silty Sand and Gravel with Cobbles FROM Pit 1 at 6 to 7 Feet
rhinal
caarasE
C1145
SAND 34 % SILT AND CLAY 9 %
4
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0
N PASSI e
16-7-283
H
GRADATION TEST RESULTS
Figure 1