HomeMy WebLinkAboutObservation of Excavation
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
February 21, 2024
SCIB, LLC
Attn: Luke Gosda
0115 Boomerang Road, Suite 5201B
Aspen, Colorado 81611
luke.gosda@sunriseco.com
Project No. 21-7-436
Subject: Observation of Excavation, Proposed Residence, Lot 41, Phase 3, Ironbridge,
354 Blue Heron Drive, Garfield County, Colorado
Gentlemen:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on February 15 and 20, 2024 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 July 19, 2021, Project No. 21-7-436.
The proposed residence is similar to that described in our previous report except that a walkout
lower level will be provided below the main level of the living area. Spread footings placed on
the existing soils and designed for the recommended allowable bearing pressure of 1,500 psf
were sized for the foundation support.
At the time of our initial visit to the site, the building excavation had been cut in 2 levels from
about 5 to 6 feet below the adjacent uphill ground surface. When observed on February 20, the
downhill side of the lower level had been stepped down through the topsoil at about 2 to 2½ feet
below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted
of existing silty sand with gravel fill in the upper level and natural sandy silt and clay in the
lower level. No free water was encountered in the excavation and the soils were slightly moist to
moist. We understand the upper level garage area was cut 5 feet too deep and will be backfilled
with compacted structural fill.
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site and suitable for support of spread footings designed for the recommended allowable
bearing pressure of 1,500 psf with a settlement risk mainly if the bearing soils are wetted. Loose
disturbed soils should be removed in the footing areas to expose the existing soils. The bearing
soils should continue to be protected from frost and concrete should not be placed on frozen
soils. We recommend the basement area be protected from wetting and hydrostatic pressure
buildup by an underdrain system placed in a “U” shape along the uphill sides of the foundation
walls but not the walkout side. The drains should consist of drainpipe placed in the bottom of
the wall backfill surrounded above the invert level with free-draining granular material. The
drain should be placed at least 1 foot below the adjacent floor slab and sloped at a minimum 1%