HomeMy WebLinkAboutSubsoil Study for Foundation design 01.15.2021lGrtiiçl[#:ifß$n''lËü**'
An Employcc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Ofüce Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit Comty, Colorado
January 75,2021
Cyr Construction
Attn: Barrett Cyr
P.O. Box 9064
Aspen, Colorado 81612
barrett@cyrandcompany. com
Project No.20-7-757
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 1, St. Finnbar
Farm Subdivision, 3 St. Finnbar Farm Road, Garfield County, Colorado
Dear Barrett:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was conducted in accordance with our agreement for geotechnical
engineering services to you dated December 9, 2020. The data obtained and our
recommendations based on the proposed construction and subsurface conditions encountered are
presented in this report.
Proposed Construction: The proposed residence will be one story wood frame construction
with attache d garage located in the area of the backhoe pits on the site as shown on Figure l.
Ground floor will be slab-on-grade. Cut depths are expected to range between about2 to 4 feet.
Foundation loadings for this type of construction are assumed to be relatively light and typical of
the proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The site is relatively flat with about2 feet of elevation difference in the
building area. Vegetation is mostly grass and weeds with scattered trees and brush. Blue Creek
is located north of the building area along the north side of the lot.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about I foot of topsoil, consist of about
% foot of slightly silty sand with gravel overlying medium dense, slightly silty sand with gravel,
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cobbles and scattered small boulders down to the maximum depth explored. 7%feet. Free water
was observed in Pit I af 6% feet deep at the time of excavation and the upper soils were ntoist to
very moist.
Foundation Recommend¿tions: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread footings
placed on the undisturbed natural soil designed for an allowable soil bearing pressure of
2,000 psf for support of the proposed residence. The sandy soils tend to compress under load
and there could be some post-construction foundation settlement. Footings should be a
minimum width of 18 inches for continuous walls and2 feet for columns. Loosc and disturbcd
soils and existing fill encountered at the foundation bearing level within the excavation should be
removed and the footing bearing level extended down to the undisturbed natural soils. We
should observe the completed foundation excavation prior to forming footings. Exterior footings
should be provided with adequate cover above their bearing elevations for frost protection.
Placement of footings at least 36 inches below the exterior grade is typically used in this area.
Continuous foundation walls should be 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 (ifany) should be designed to resist alateral earth pressure based on an equivalent
fluid unit weight of at least 45 pcf for the on-site soil as backfill excluding organics and rock
larger than 6 inches.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab-on-grade construction. To reduce the effects of some differential movement, floor slabs
should be separated from all bearing walls and columns with expansion joints which allow
unrestrained vertical movement. Floor slab control joints should be used to reduce damage due
to shrinkage cracking, The requirements fbr joint spacing and slab rçinfbrccmcnt should be
established by the designer based on experience and the intended slab use. A minimum 4 inch
layer of free-draining gravel should be placed beneath slabs to act as a break for capillary
moisture rise and drainage. This material should consist of minus 1-inch aggregate with less
than 50Yo passing the No. 4 sieve and less than2Yo passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximnm
standard Proctor density at a moisture content near optimum. Requircd fill can consist of thc on-
site soils devoid of vegetation, topsoil and oversized rock.
Kumar & Associates, lnc. @ Project I'lo. 20.7'757
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Underdrain System: An underdrain should not be needed for the proposed slab-on-grade floor
levels.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
l) Inundation ofthe foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95Yo of the maximum standard Proctor density in pavement and slab areas
and to at least 90o/o of the maximum standard Proctor density in landscape areas.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first l0 feet in pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. 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. Our
findings include interpolation and extrapolation of the subsurface conditions identified at the
exploratory pits and variations in the subsurface conditions may not become evident until
excavation is performed. If conditions encountered during construction appear different from
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
Kumar & Associates, lnc. o Project No. 20-7-757
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should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verifii that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
Kurnlr & Associntes, Inc.
Daniel E. Hardin, P.
Rcv. by: SLP
DEHlkac
attachments Figure 1 - Location of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
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Kumar & Associates, lnc. €'Project No. 20-7-757
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LEGEND
TOPSOIL; ORGANIC SILTY SAND, LOOSE, MOIST, DARK BROWN
SAND (SM-SP); SL|GHTLY StLTy, W|TH GRAVEL, LOOSE, MO|ST, BROWN
SAND AND GRAVEL (GM-GP)
DENSE, MOIST TO WET WITH
; WITH COBBLES AND SCATTERED SMALL BOULDERS, MEDIUM
DEPTH, LIGHT BROWN.
INDICATES 4" DIA PERFORATED PVC PIPE INSTALLED IN PIT TO DEPTH SHOWN.
I orprn To wATER LEVEL ENcouNTERED AT THE TIME oF DrccrNG
--+ DEPTH AT WHICH PIT CAVED. BOTH PITS WERE BACKFILLED ON DECEMBER gth, 2O2O
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON DECEMBER 9, 2020,
2. THE EXPLORATORY PITS WERE LOCATED BY THE CLIENT.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY
TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER
CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 4''
DIAMETER PVC PIPE WITH PERFORATIONS IN BOTTOM 4 FEET WAS PLACED AT A DEPTH OF 7
FEET IN PIT 1.
20-7 -757 Kumar & Associates LOGS OF EXPLORATORY PITS lis, 2
NN JNoÚt6l2r
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ùlject No.
20128
JN RY05,2021
.o. Box
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Rifle, Co 81650
Phonc (970) 625-19s4
FINNBAR FARM, LLC,
CÀRFIELD COUNTY, COLORADO
EXISTING CONDITIONS SURVEY
LOT 1 ST. FINNBAR FARM
OO3 ST FINNBAR FARM ROAD 10F 1
20t28
EXISTING CONDITIONS SURVEY
LOT I, ST. FINNBARFARM
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PRELIl,lIl'lARY
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