HomeMy WebLinkAboutObservation of Excavation 11.09.2023lGrtffir'ffiffiil-'rrü*
5020 CountY Road 154
Glenwood SPrings, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
-
email:
¡ln ãnPloYcr Otrncd ComgnY
Office Locations: Denver (HQ), Parker' Colorado Springs, Fort Collins,Glenwood Springs, and Summil County, Colorado
November 9,2023
Scott VanDeursen
I132 Westbank Road
Glenwood SPrings, Colorado 81601
scott@brikor.com Project No.23'7-637
Subject:observation of Excavation, Proposed Addition, 1132 rwestbank Road,
Garfield CountY, Colorado
Scott:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on Novemb er 6,2023to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation support are presented in this report' The
scrviccs wcre perrformed in accordance with our agreement for professional engineering services
to you dated Novembet 1,2023,
The proposed addition will be attached to the west side of the residence (garage) and be
supported by spread footings sized for an assumed allowable bearing pressure of 1,500 psf'
At the time of our visit to the site, the foundation excavation had been cut in two levels from
about I to 3 feet below the adjacent ground surface. The grade along the existing garage side
was about one foot higher than the remaining excavation. The terrain suggests that the upper'
northern part of the ud¿ition area was filled io the garage slab elevation. The soils exposed in the
bottom of the excavation were variable and consisted of very stiff clay in the north part and
shallow cut depth, southwest comer' existing sand and gravel fill near the garage and natural'
relatively dense gravel in the rønaining areas. The clay area on the north side was probed by
hand with a metal rod and resistance was met at a depth up to about lYz feetindicating the depth
of clay above the gravel. Laboratory testing performed on a sample of clay resulted in a
moisture content of ll.}Yoand dry density of 108 pcf. No free water was encountered in the
excavation and the soils were slightly moist to moist'
considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings ptacea on the exposed soil designed for an allowable bearing
pressufe of 1,500 psf can be used for foundation support. The exposed soils tend to compress
when wetted and there could be some post-construction differential settlement of the foundation
mainly if the bearing soils are wetted. Footings should be a minimum width of 16 inches for
continuous walls and 2 feetfor columns. Loose disturbed soils in footing areas should be
moistened and compacted. Exterior footings should be provided with adequate soil cover above
their bearing elevations for frost protection. continuous foundation walls should be reinforced
top and bottom to span local anomalies such as by assuming an unsupported length of at least
12 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral
kaglenwood@kumarusa'com
www.kumarusa.com
Scott Van Deursen
November 9,2023
Page2
earth pressure based on an equivalent fluid unit weight of at least 50 pcf for on-site granular soil
as backfill. A perimeter foundation drain should not be needed for the shallow cut depths with
proper surface grading. Backfill placed around the structure should be compacted and the
surface graded to prevent ponding within at least 10 feet of the building. Landscape that requires
regular heavy irrigation, such as sod, and sprinkler heads should not be located within 5 feet of
the foundation.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation 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 beneath the footings 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. In order to reveal the nature and extent of variations in
the subsurface conditions below the excavation, drilling would be fequired. It is possible the
data obtained by subsurface exploration could change the recommendations contained in this
lotter. Our services do not include cle,termining 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, ln
Steven L Pawlak,
SLPlkac
u,
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Kumar & Associates, lnc. o Project No. 23-7-637