HomeMy WebLinkAboutSoils Report 11.18.2016H-P�KUMAR
Geotechnical Engineering j Engineering Geology
Materials Testing I Environrnental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
November 18, 2016
Glenwood Caverns
Attn: Steve Beckley
51000 Two Rivers Plaza Road
Glenwood Springs, Colorado 81601
steve@glenwoodcaverns.com
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
IECEIV ;
MAR 2 9 7017
Project No. 16-7-524
Subject: Observation of Partial Excavation, Proposed Mine Drop Building, Glenwood
Caverns, North of Glenwood Springs, Garfield County, Colorado
Gentlemen:
As requested, the undersigned representative of H-P/Kumar observed the partial building
excavation at the subject site on October 13, 2016 to evaluate the ground conditions 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 Glenwood Caverns, dated October 12, 2016.
The proposed building is located just west of the path to the lower cave entrance on a moderately
steep (about 30%), south facing slope at about elevation 7035 feet. The mineshaft excavation
located in roughly the center of proposed building site was in progress and reportedly about 80
feet deep at the time of our site visit. A concrete wall had been constructed on the downhill side
of the shaft with the bottom of wall close to the original ground surface. The mineshaft was not
entered but thickly bedded to massive limestone was exposed in the upper part of the excavation.
Mineshaft excavation spoil covered part of the building area but in relatively natural or cut areas,
the top of rock appeared to be below about 1 to 2 feet of loose soil. Previous laboratory testing
of the limestone for the giant swing and carousel structures gave unconfined compressive
strengths between about 7,000 to 12,000 psi in a perpendicular direction to the bedding joint of
the sound rock like that observed at this site. Observation of the limestone in exposed
excavations at the mine drop building site indicated a bedding thickness of at least 5 feet at the
top of the rock.
Considering the rock conditions exposed in the partial excavation and the proposed construction,
spread footings placed on the undisturbed limestone at a distance of at least 5 feet from the
mineshaft designed for an allowable bearing pressure of 10,000 psf can be used for support of
the proposed building. Footings should be a minimum width of 18 inches for continuous walls
and 2 feet for columns. We should observe the footing excavations for limestone rock bearing
conditions prior to forming footings. Foundations should be designed to span the section closer
than 5 feet from the mineshaft.
Glenwood Caverns
November 18, 2016
Page 2
The recommendations submitted in this letter are based on our observations of the rock exposed
within the limited excavation of the building area and the upper part of the mineshaft excavation
and are suitable for preliminary building foundation design. We have assumed the rock beneath
the site has equal or better support than that exposed. Variations in the bedrock condition could
increase the risk of foundation movement. Further study of the bearing conditions should be
performed when the building excavation has been completed.
If you have any questions or need further assistance, please call our office.
Sincerely,
Steven L. Pawlak, P.
Rev. by: DEH
SLP/ksw
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