HomeMy WebLinkAboutObservation of Excavation 08.06.191(+AKumar ni Assocfa#e
Geotechnical and Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
t fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employe Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
August 6, 2019
Giard Homes
Attn: Roger Giard
1431 Airport Road
Rifle, Colorado 81650
giardhomes(cr�,gmail. com
Project No. 17-7-624.A
Subject: Observation of Excavation, Proposed Residence, Lot B-8, Aspen Equestrian
Estates, 156 Equestrian Way, Garfield County, Colorado
Dear Roger:
As requested, the undersigned representative of Kumar & Associates, Inc. observed the
excavation at the subject site on July 30 and 31, 2019 to evaluate the soils exposed for
foundation support. The findings of our observations and recommendations for the foundation
design are presented in this report. H -P Kumar (now Kumar & Associates) previously conducted
a subsoil study for design of foundations at the site and presented our findings in a report dated
August 22, 2017, Project No. 17-7-624.
The proposed house will have a slab -on -grade floor. Footings were designed to bear on the
natural gravel soils and for an allowable soil bearing pressure of 2,500 psf.
At the time of our initial visit to the site, the foundation excavation had been cut in one level
from 2 to 3 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavation consisted of mostly slightly silty sandy gravel with cobble and small boulders. Clay
soils were observed at footing grade in the central part of the north side, most of the east side and
a small part near the southwest corner of the building excavation. Probing of the clay with a
metal rod indicated the rocky soils underlay the clay at depths of %2 foot to over 2 feet. No free
water was encountered in the excavation and the soils were moist. We recommended to Roger
Giard at the site that the clay should be excavated down to the underlying gravels and that
footing grade could be re-established with CDOT Class 6 road base compacted to at least 98% of
the maximum standard Proctor density.
We visited the site the following day and observed that the three sub -excavated areas were down
to the gravel soils and had varying amounts of ground water in them. The northern portion had
been sub -excavated about 1 to 11/2 feet and had about 6 inches of water. The eastern portion had
been sub -excavated 1 to 2 feet and only had water in a small area on the north end of the trench.
Giard Homes
August 6, 2019
Page 2
The southwest corner had been sub -excavated about 2'/ feet and had about Moot of water in it.
We recommended to Luis Murillo of E & L Trucking that the water should be pumped out and
the sub -excavations mucked out as much as practical. A layer of 3/ inch screened rock should be
placed and compacted to above the current water level and then the remainder of the trench
should be backfilled as needed with 3/ inch road base compacted to at least 98% of the maximum
standard Proctor density or the footing bearing level lowered to the screened rock.
The soil conditions exposed in the excavation are generally consistent with those previously
encountered on the site and suitable for support of spread footings designed for the
recommended allowable bearing pressure of 2,500 psf. The areas that were sub -excavated and
backfilled should also be suitable for footings as designed. 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 limited 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, Inc.
llaniel L. riaTtTin, ;
Rev. by: SLP
DEH/kac
Kumar & Associates, Inc. z, Project No. 17-7-624.A