HomeMy WebLinkAboutObservation of Excavation 01.03.20231(+AGeatechnical and Materials Engineers 5020 County Road 154
and En*onmental Scientists 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
January 3, 2023
SCIB, LLC
Attn: Luke Gosda
0115 Boomerang Road, Suite 5201B
Aspen, Colorado 81611
Luke. og sda(a,sunriseco.com
Project No. 21-7-686.A
Subject: Observation of Excavation, Proposed Residence, Lot 28, Ironbridge, 1486 River
Bend Way, Garfield County, Colorado
Gentlemen:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on December 9, 2022 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 October 18, 2021, Project No. 21-7-686.
The proposed residence will have a basement level below most of the living area with partial
crawlspace and slab -on -grade garage at the main level. Spread footings placed on the natural
soils were designed for the foundation support and sized for an allowable bearing pressure of
1,500 psf. Because the footings will bear at different levels and will bear on different soils, it
was recommended in our email date August 12, 2022 to Luke Gosda that the shallow footings be
placed on at least 3 feet of structural fill to help mitigate potential differential settlement mainly
with respect to the basement level foundation placed on dense gravel.
At the time of our visit to the site, the foundation excavation had been cut in 2 levels from about
8 to 10 feet deep in the basement area and about 2%2 to 3%2 feet below the adjacent ground
surface in crawlspace and garage areas. The soils exposed in the bottom of the basement
excavation consisted of relatively dense, sandy gravel and cobbles. The soils exposed in the
crawlspace and garage areas consisted of sandy silt and clay. No free water was encountered in
the excavation and the soils were slightly moist and not frozen.
The soils exposed in the excavation are consistent with those previously encountered on the site
and the silt and clay soil areas should be sub -excavated and replaced with structural fill to at least
3 feet below bearing level. The in -place density testing was taken during the placement of road
base structural fill on December 21 and 22, 2022 in the garage area with acceptable compaction.
We understand that the structural fill in the garage and crawlspace footing areas was placed in
similar manor to the tested areas. Based on these findings, the natural gravel soils and properly
placed and compacted structural fill are suitable for support of spread footings designed for the
recommended allowable bearing pressure of 1,500 psf with a low settlement potential. Loose
disturbed soils in the footing areas should be removed or compacted prior to placing concrete.
SCIB, LLC
January 3, 2023
Page 2
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. 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 &
Steven L. F
SLP/kac
Kumar & Associates, Inc.Project No. 21-7-686.A