HomeMy WebLinkAboutObservation of Excavation 10.09.2017H-PKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
October 9, 2017
Josh Ellis
44289 U.S. Highway 6
Glenwood Springs, Colorado 81601
Josh.ellis@citvolaspcli.com
Project No. 17-7-735
Subject: Observation of Excavation, Proposed Barn, 1518 County Road 241 (East Elk
Creek Road), Garfield County, Colorado
Dear Josh:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on
October 4 and 7, 2017 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations are presented in this report. The services are supplemental to
Hepworth-Pawlak Geotechnical's (now H-P/Kumar) agreement for geotechnical services to you
dated April 7, 2015.
Hepworth-Pawlak Geotechnical previously conducted a subsoil study for design of foundations
at the site and presented the findings in a report dated June 26, 2015, Job No. 115 136A. The
proposed construction is slightly different than that discussed in the previous report and will
consist of a two story pole barn type structure with a slab -on -grade ground floor. Spread
footings designed for an allowable soil bearing pressure were recommended for foundation
support with some risk of settlement.
At the time of our October 4 site visit, the foundation excavation had been cut in one level from
about 3 to 4 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavation consisted of generally loose, silty to slightly silty sand. While attempting to compact
the footing areas, the subgrade along the eastern side of the excavation reportedly became
unstable. At this time, we recommended the subgrade in the unstable area be sub -excavated
2 feet and replaced with coarse granular soils. We understand groundwater seepage was
encountered at the bottom of the 2 feet deep sub -excavation when the minus 11/2 inch crushed
Josh Ellis
October 9, 2017
Page 2
screened rock was placed.
footing subgrade appeared
inches of disturbed natural
recommended be removed.
moist to very moist.
When we observed the excavation on October 7, the eastern end
adequately stabilized with the minus 1I inch rock. There were a few
sand soils in other areas of the excavation subgrade that we
No free water was encountered in the excavation and the soils were
The soil conditions exposed in the excavation are generally consistent with those previously
encountered on the site and the eastern end subgrade adequately stabilized, and suitable for
support of spread footings designed for the recommended allowable bearing pressure of 1,200
psf. There is some with some risk of differential settlement due to the variable bearing
conditions. Prior to the footing construction, all disturbed soils should be removed in the footing
areas to expose the undisturbed natural soils in the sand subgrade areas. The bearing soils should
be protected from frost and concrete should not be placed on frozen soils. Other
recommendations presented in our previous report which are applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and the previous subsurface exploration at the site. Variations
in the subsurface conditions below the excavation could increase the risk of foundation
movement. We should be advised of any variations encountered in the excavation conditions for
possible changes to recommendations contained in this letter.
If you have any questions or need further assistance, please call our office.
Sincerely,
H -P KUMAR
David A. Young, P.t;r:,Fit%/mit„
DAY/kac 4r•y
cc: Garfield County Building Dept. - Jim^Wilson(jwilkoni.garfield-ootiiny.coin)
H-P%KUMAR
Project No. 17-7-735