HomeMy WebLinkAbout18-7-361.A (09-21-18) Revised Exc Obs signed.pdf 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: Denver(HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs,Summit County, Colorado
September 19, 2018
Revised September 21, 2018
Solaris Redevelopment Corporation
Attn: Brian Redinger
141 East Meadow Drive, Suite 211
Vail, Colorado 81657
brian@solarisvail.com
Project No. 18-7-361.A
Subject: Observation of Excavation, Proposed Residence, Lots 14 and 17, Block 7, Vail
Village Filing 1, 307 Rockledge Road, Vail, Colorado
Dear Brian:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on
September 11 and 14, 2018 to evaluate the soils exposed for foundation support. The findings of
our observations and recommendations are presented in this report. The services are
supplemental to our agreement for professional services to Solaris Redevelopment Corporation
dated May 15, 2018. The revision addresses minimum footing widths for bearing on bedrock.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated September 10, 2018, Project No. 18-7-361. The proposed construction
is similar to that discussed in our previous report. The building has been designed to be
supported spread footings using in allowable soil bearing pressure of 3,000 psf as recommended
in our subsoil study. The uphill (southern) side of the foundation excavation has been shored
with a soil nail wall and the east and west sides of the excavation shored with vertical micro-pile
walls.
On September 11, the excavation was well underway with mostly hard shale bedrock exposed at
subgrade in the deeper cut areas. There was some minor seepage from below the soil nail wall
that was planned to be controlled with drain-pipe and gravel at the base of the wall to gravity
outlet. In the northwest portion of the excavation was relatively deep fill and fine-grained soils
that we recommended be removed.
At the time of our September 14 site visit, the foundation excavation was essentially complete
and had been cut in multiple levels from about 3 to 23 feet below the adjacent ground surface.
The deeper cuts were on the south side of the excavation at the soil nail wall. Steps in grade
between the excavation levels ranged from about 1 to 7 feet. The materials exposed in the
bottom of the excavation consisted of hard claystone to claystone/siltstone shale bedrock. The
bedrock was too hard to obtain undisturbed hand driven liner samples for swell-consolidation
testing. Based on the shale's hardness, we believe it has a nil to minor swell potential when
wetted similar to that reported in our subsoil study. The groundwater encountered at the soil nail
wall portion of the excavation was observed being controlled by a drain to gravity outlet. The
exposed shale bedrock materials were generally slightly moist.
Solaris Redevelopment Corporation
September 19, 2018
Revised September 21, 2018
Page 2
The shale bedrock exposed in the excavation is generally consistent with that previously
encountered on the site and suitable for support of spread footings designed for the
recommended allowable bearing pressure of 3,000 psf. Minimum footing widths for bearing on
the shale bedrock can be 16 inches for continuous walls and 2 feet for isolated pads. Loose and
disturbed materials should be removed in the footing areas to expose the undisturbed bedrock.
The water seepage into the excavation should continue to be collected and diverted away from
the footing areas and any softened subgrade and mud removed before concrete placement. 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 materials
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.
If you have any questions or need further assistance, please call our office.
Sincerely,
1.1-p KU AR e`` 411
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cc: Suman Architects —Michael Suman (michael@sumanarchitects.com)
KRM Consultants—Nicholas Ripp (nicholas@krmconsultants.com)
H-P�KUMAR Project No. 18-7-361.A