HomeMy WebLinkAboutObservation of Pit Excavations 11.02.2020Kumar & Associates, Mc.
Geotechnical and Materials Engineers
and Environmental Scientists
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
November 2, 2020
Thad Eshelman
7380 County Road 100
Carbondale, Colorado 81623
thad@tebuilders.net
Project No. 20-7-494
Subject: Observation of Pit Excavations, Proposed Barn/Shop Building, 178 Blue Heron
Lane, Garfield County, East of Carbondale, Colorado
Dear Thad:
As requested, the undersigned representative of Kumar & Associates observed the pit
excavations at the subject site on October 13, 2020, 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 you, dated September 2, 2020.
The proposed barn/shop building will be 60 feet square and will be post and beam construction
with a slab -on -grade floor. The shop will be located west of the existing house and parking area.
The proposed shop area is in a relatively flat, traditionally irrigated pasture. There are active
irrigation ditches in the vicinity and groundwater is expected to be very shallow.
At the time of our visit to the site, about 8 pits were excavated in the proposed building area with
a large trackhoe. The soils exposed in the pits consisted of 1/2 to 11/2 feet of soft organic topsoil
overlying relatively dense, sand and gravel with cobbles. Free water was encountered in the
shallow pit excavations between 1/2 to 1'/2 feet deep and the soils were very moist to wet. Based
on the soils and water conditions encountered, the proposed building location was moved to the
east about 20 feet, where the gravel soils were slightly higher in elevation relative to the water
level.
Considering the conditions exposed in the pit excavations and the nature of the proposed
construction, a thickened edge slab foundation placed on the undisturbed natural gravel soil or
compacted on-site sandy gravel with cobbles designed for an allowable soil bearing pressure of
2,500 psf can be used for support of the proposed shop/barn. Thickened portions of the slab
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. Exterior footings should be provided with
adequate insulation to provide for frost protection. Structural fill placed below floor slab areas
should be non frost -susceptible material such as roads base or the on-site granular soils excluding
organics and rock larger than 6 inches compacted to at least 95% of standard Proctor density at a
moisture content near optimum.
Thad Eshelman
November 2, 2020
Page 2
The recommendations submitted in this letter are based on our observation of the soils exposed
within the shallow pit excavations 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 with depth 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. 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.
If you have any questions or need further assistance, please call our office.
Sincerely,
Kumar & Associates, Inc.
Daniel E. Hardin, .
Rev. by: SLP
DEH/kac
Kumar & Associates, Inc. ® Project No. 20-7-494