HomeMy WebLinkAboutObservation of Excavation 03.27.2019Kj-tf
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lknar & û*sf ulåtr$, lnc,
tìsr:tech¡icalând Mâtarla¡s fnçineers 6020, Counly Road 154
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,",'o'o Glenwood Springs, CO 91601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwcod @kumåru$a.c0mån Fmployca Owngd tømpony såMûrhufiätlsê!çem
Offìce Locaiions: Aenvêr (HQ), Parkel Colorado $prings, Fort Collins, Çlenwood Springr, ancJ $ummit County, Colorado
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March 27,2019
Ernie Kollar
746 Wooden Deer
Carbondale, Colorado 81623
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Subject;observation of Excavation, Proposed New Garage, 'west of Existing Garage,746
wooden Deer Road,Lot 6, wooden Deer subdivision, Garfield county, Colorado
Dear Ernie:
As requested, the undersigned representative of Kumar & Associates observed the excavation at the
subject site on March 26,2019 to evaluate the soils exposed for foundation support. The fïndings of
our observations and recomrnendations for the foundation design are presented in this report
The proposed garage will be a two-story frame strucfure with a slab-on-grade floor similar to the
adjacent existing gardge to the east. Foundations were designed for an assumed allowable soil bearing
pressure of 2,000 psf and a lateral earth loading based on an assumed equivalent fluid pressure of 45
pcf
At the time of ow visit to the site, the foundation excavation had been cut in 3 levels from 3 to l5 Íbet
below the adjacent gtound surface. The soils exposed in the bottom of the excavation consisted of
basalt rocks in ¿ gravelly sandy silt matrix. There was a small area of siltstone bedrock near the
bottom of the excavation in the northeast corner adjacent to the back of the existing garage. The
bedding of the siltstone appeared to be down to the north into the hillside. No free water was
encountered in the excavation and the soils were stightly moist. There was no ice or snow in the
excavation and the subgrade soils were free of frost.
Considering the conditions exposed in the excavation and the nature of the proposed construction,
spread footings placed on the undisturbed naturai soil designed for an allowable soil bearing pressure
of 2,000 psf can be used for support of the proposed garage. The exposed matrix 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 16 inches for continuous walls and
2 feet for columns' Loose and disturbed soils in footing areas should be compacted or removed and
the bearing level extended down to the undisturbed natural soils. The beari¡g soils should be
protected against frost and concrete should not be placed on frozen soils. Exterior footings should beprovided with adequate soil cover above their bearing elevations for frost protection. continuousfoundation walls should be reinforced top and bottom to span local anomalies such as by assuming anunsupported length of at least 10 feet. Foundation walls acting as retaining structures should also bedesigned to resist a latcral earth pressure based on an equivalent fluid unit weight of at least 45 pcf foron-site soil as backfill' A perimeter foundation drain should be provided to prevent temporary buildupof hydrostatic pressure behind the rear retaining walls. structural fill placed within floor slab areascan consist of the on-site soils compacted to at least 95%o or stundard proctor density at a moisturecontent neal optimum. Backfill placed around the structure should be compacted and the surfacegraded to prevent ponding within at reast 10 feet of the building.
The recommendations submitted in this letter are based on our observation of the soils exposed withinthe foundation excavation and do not include subsurface exploration to evaluate the subsurfaceconditions within the loaded depth of foundation influence. This study is based on the assumption thatsoils beneath the footings have equal or better support than those exposed. The risk of foundationmovement may be greater than indicated in this report because of possible variations in the subsurfaceconditions' In order to reveal the nafure and extent of variations in the subsurface conditions belowthe excavation, drilling would be required. It is possible the data obtained by subsurface explorationcould change the recomrnendations contained in this letter. our services do not include determiningthe presence, prevention or possibility of mold or other biological contaminants (M6BC) developingin the future' If the client is concemed about MOBC, then a professional in this special field ofpractice should be consulted.
If you have any questions or need further assistance, please call our office.
Sincerely,
Kumar & Associates, fnc.
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Daniel E. Hardin, p.E."... r â 2 444 3
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