HomeMy WebLinkAbout4872 Meadow Ln Open Hole Inspection 16-7-596.01 (08-23-18) Ex. Ob. signed.pdf H-p-- KU mAR5020 County Road 154
Glenwood Springs, CO 81601
Geotechnical Engineering I Engineering Geology Phone:(970)945-7988
Materials Testing I Environmental Fax: (970)945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Parker,Glenwood Springs,and Silverthorne,Colorado
August 23, 2018
Paragon Homes
Attn: Ed Venerable
6460 S. Quebec St. #400
Centennial, Colorado 80111
ed@paragonhomesdenver.com
Project No. 16-7-596.01
Subject: Observation of Excavation, Proposed Residence, Lots 14A and 14B,Bighorn
Fifth Addition,4872 Meadow Lane, Vail, Colorado
Dear Ed:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on
August 22, 2018 to evaluate the materials exposed for foundation support. The findings of our
observations and recommendations for are presented in this report. The services are being
performed in accordance with our agreement for professional services to Paragon Homes dated
August 21, 2018. Only a portion of the excavation is complete for footings at this time.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated February 7, 2017, Project No. 17-7-596. The proposed construction is
similar to that discussed in our previous report. The building has been designed to be supported
on spread footings using an allowable bearing pressure of 2,000 psf based on recommendations
provided in the previous report.
At the time of our site visit, the foundation excavation which was essentially complete to design
footing bearing elevation had been cut in multiple levels from about 3 to 20 feet below the
adjacent ground surface. The materials exposed in the bottom of the excavation consisted of
hard sandstone/siltstone bedrock in the upper level deeper cut area to the northeast, relatively
dense silty sand and gravel with cobbles in the middle and southern portions, and clayey silty
sand in the shallower cut areas for garage on the western side. Results of swell-consolidation
testing performed on samples taken from the site, shown on Figure 1, indicate the clayey silty
sand soils are moderately compressible under conditions of loading and wetting. The results of a
gradation analysis performed on a sample of the silty sand and gravel with cobble soils (minus 3-
inch fraction) obtained from the site are presented on Figure 2. Free water was encountered in
the excavation in the southeastern and southern parts and water being partly controlled by a
sump and pump system. The soils were moist to wet and the bedrock was slightly moist.
The conditions exposed in the excavation are somewhat different than those previously
encountered on the site. The upper level (northeastern portion with bedrock exposed at
subgrade) at approximate excavation subgrade elevation 8567.5' and the adjacent step down wall
Paragon Homes
August 23, 2018
Page 2
area to the south at approximate subgrade elevation 8563' are suitable for support of spread
footings designed for the design allowable bearing pressure of 2,000 psf. There is some risk of
differential settlement due to the variable bearing conditions. Loose and disturbed material
should be removed as needed in the footing areas prior to concrete placement.
The remaining southern, central and western portions of the excavation have water seepage and
compressible sand soils that need additional work before footings can be constructed. The
garage area to the west, that has the compressible clayey silty sand soils at excavation subgrade,
should be deepened to the coarse granular soils or a minimum 3 feet of the sand soils in this area
removed and replaced with suitable coarse granular compacted structural fill as per the
recommendations in the previous report. The on-site coarse granular soils may be feasible for
use as the structural fill and should be further evaluated for that purpose, or a suitable material
such as CDOT Class 2 aggregate base course (minus 3-inch material) can be imported. The
excavation should be dewatered for the structural fill construction and permanently to prevent
wetting of below grade construction. Other recommendations presented in our previous report
which are applicable should also be observed.
We should observe the subexcavation and dewatering conditions in the remaining portion of the
excavation as it progresses and perform compaction testing on the structural fill placement on a
regular basis.
The recommendations submitted in this letter are based on our observation of the materials
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,
otoi
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David A. Young, P.E. -2.214 I,,
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attachments Figure 1, Sw 1 q action Test Results
Figure 2, Gradation Test Results
cc: Mountain Home Concrete—Jim Meehan (jmeehan-mhc@comcast.net)
H-PKUMAR Project No. 16-7-596.01