HomeMy WebLinkAboutObservation of Excavation 05.05.20231(+AandI�.Geotechnical and Materials Engineers 5020 County Road 154
Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
1� fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employ" Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
May 5, 2023
SCIB, LLC
Attn: Luke Gosda
0115 Boomerang Road, Suite 5201 B
Aspen, Colorado 81611
Luke. og sda(&sunriseco.com
Project No. 21-7-684.A
Subject: Observation of Excavation, Proposed Residence, Lot 20, Ironbridge Phase 3,
1820 River Bend Way, Garfield County, Colorado
Dear Luke:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on April 11 and 13, 2023 to evaluate the soils exposed for foundation support. The
findings of our observations and recommendations for the foundation design are presented in this
report. We previously conducted a subsoil study for design of foundations at the site and
presented our findings in a report dated September 29, 2021, Project No. 21-7-684.
The proposed residence will be a two-story residence with an attached garage. Ground floor will
be structural over crawlspace for the living areas and slab -on -grade for the garage. The
residence has been designed to be supported on spread footings sized for an allowable bearing
pressure of 3,000 psf.
At the time of our April 11, 2023 visit to the site, the foundation excavation had been cut in one
level from 11/2 to 41/2 feet below the adjacent ground surface. The soils exposed in the bottom of
the excavation consisted primarily of sandy clay with localized areas of gravel in the garage
footing areas. We recommended the clay soils be removed from below footings to exposed the
gravel soils and the sub -excavated depth backfilled with imported granular material as structural
fill.
At the time of our April 13, 2023 visit to the site, the foundation excavation had been cut in
generally 1 level from 4 to 5%2 feet below the adjacent ground surface. The soils exposed in the
bottom of the excavation consisted of silty clayey sandy gravel and cobbles. The exposed soils
were compacted at the time of our visit. No free water was encountered in the excavation and
the soils were slightly moist to moist.
The sub -excavated depth was backfilled with imported CDOT Class 6 base course compacted to
at least 98 percent standard Proctor density at a moisture content near optimum. A representative
of Kumar & Associates tested the structural fill for compaction. The results of these test will be
presented under separate cover.
SCIB, LLC
May 5, 2023
Page 2
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site and once sub -excavated and backfilled with structural fill are suitable for support of
spread footings designed for the recommended allowable bearing pressure of 3,000 psf. Loose
disturbed soils should be removed in the footing areas to expose the undisturbed natural 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. 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, I
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James H. Parsons,y5/9/23
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Kumar & Associates, Inc. " Project No. 21-7-684.A