HomeMy WebLinkAboutObservation of Excavation 06.14.2017H-P=KUMAR
Geotechnical Engineering ; Engineering Geology
Materials Testing I Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
June 14, 2017
AML Construction
Attn: Luis Hernandez
P.O. Box 806
Glenwood Springs, Colorado 81601
amlconstruction@hotmail.com
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
LA' zip
MAY 1 6 2017
Project No. 17-7-445
Subject: Observation of Excavation, Proposed Residence, Lot 13, Blue Creek Ranch, 142
Ponderosa Pass, Garfield County, Colorado
Gentlemen:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on June
6, 2017 to evaluate the soils exposed for foundation support. The findings of our observations
and recommendations for the foundation design are presented in this report. Hepworth-Pawlak
Geotechnical (now H-P/Kumar) previously conducted a subsoil study for design of foundations
at the site and presented the findings in a report dated March 24, 2015, Job No. 115 060A.
The proposed residence is essentially the same as described in the previous report. Spread
footings placed on the gravel soils and sized for an allowable bearing pressure of 2,500 psf were
designed for the foundation support.
At the time of our visit to the site, the foundation excavation had been cut in one level from
about 1 to 21/2 feet below the adjacent ground surface. The downhill, north part of the excavation
in the garage area had the minor cut depth. The soils exposed in the bottom of the excavation
mainly consisted of silty, sandy gravel in the residence area and very sandy silty clay in the
garage area. The clay soil area was probed by hand with between about 1/ to 11/2 probe depths
likely onto the underlying gravel soil. Results of swell -consolidation testing performed on a
sample of the clay taken from the garage area, shown on Figure 1, indicate the soils are
moderately compressible under loading after wetting. No free water was encountered in the
excavation and the soils were slightly moist to moist.
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site and the gravel soils are suitable for support of spread footings designed for the
recommended allowable bearing pressure of 2,500 psf. As an alternative to digging the clay
AML Construction
June 14, 2017
Page 2
soils out down to the gravel soils, the footings in the garage area can be sized for an allowable
bearing pressure of 1,500 psf which we understand is the selected foundation support in the
garage area. Loose disturbed soils in the footing areas should be removed or compacted. 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,
H-PKU MAR
Steven L. Pawlak, P.E y ,j 1 2 2 w
.,1..,
SLP/kac ;G� 7 14.74-::::•,'
Attachment:Figure 1 — Sw6lt tiii: # ation Test Results
Project No. 17-7-445
1
Compression %
Cn -P CJ N — O
Moisture Content = 9.8 percent
Dry Density = 100 pcf
Sample of: Sandy Silty Clay
From: Bottom of Excavation
/
/]
�
Compression
_upon
— wetting
\:>
0.1 1.0 10 100
APPLIED PRESSURE - ksf
17-7-445
H -P = KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Figure 1