HomeMy WebLinkAboutObservation of Excavation Letter 08.25.2017H.PVKUMAR
Geolechnlcal Enginccrlng I Englneering Geology
Materials Testlng I Envlronmcntal
5020 County Road 154
Glenwood Springs, C0 81601
Phone: (970) 945-7988
Fax (970) 945-8454
Email: hpkglenwood@kumarusa.com
Ofüce Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
August 25,2017
Starkworks,Inc.
Attn: Whit Dean
1136 County Road 129
Glenwood Springs, Colorado 81601
gi¡1'[r1glk s in_c G lio t miti l. cçrUl
Subject:
Project No. 17-7-645
observation of Excavation, Proposed Garage Addition, 1068 county Road 129,
No Name, Garfield County, Colorado
Dear Whit:
As rcquested, a representative of H-P/Kumar observed the excavation at the subject site on
August 24,2017 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 Starkworks, dated August 23,2A17.
The proposed garage will be a one story wood frame structure with a slab-on-grade floor
attached to the north side of the existing house. Foundations were designed for an allowable soil
bearing pressure of 1,500 psf.
At the time of our visit to the site, the foundation excavation was complete on the north and east
sides and had been cut in one level from 4 to 6 feet below the adjacent ground surface. The west
side excavation had not been completed. The soils exposed in the bottom of the excavation
consisted of relatively dense, silty sand and gravel with cobbles. No free water was encountered
in the excavation and the soils were slightly moist.
Considering the conditions exposed in the excavation and the natuÍe of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psf can be used for support of the proposed garage. Footings
should be a minimum width of 16 inches for continuous walls and2 feet for columns. Loose and
disturbed soils and existing fill in footing areas should be removed and the bearing level
Starkworks,Inc.
August 25.2017
PageZ
extended down to the undisturbed natural soils. Exterior footings should be provided with
adequate soil cover above their bearing elevations for frost protection. Continuous foundation
walls should be reinforced top and bottom to span local anomalies such as by assuming an
unsupported length of at least l0 feet, Foundation walls acting as retaining structures (if any)
should also be designed to resist a lateral earth pressure based on an equivalent fluid unit weight
of at least 45 pcf for on-site soil as backfill. A perimeter foundation drain should not be needed
for the proposed slab-on -grade structure. Structural fill placed within floor slab areas can
consist of the on-site gravel soils devoid of topsoil, organics and oversized rock compacted to at
least 957o 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 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 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 fîeld of practice should be consulted.
Ifyou have any questions or need further assistance, please call our office.
Sincerely,
1)0t tç
Daniel E. Hardin, P.E.24443 zi
( l>{lrt ,
Reviewed by: SLP
DEH/kac
L
H-P+KUfVIAR
AL
Project No 17-7-645