HomeMy WebLinkAboutEngineer's Excavation Observation Report 11.30.2016HPI<UMAR
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5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
November 30, 2016
Eastbank, LLC
Attn: Robert MacGregor
710 East Durant Avenue
Aspen, Colorado 81611
rmac@n'dunrene.Caml
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
Project No. 16-7-583
Subject: Observation of Two Pit Excavations, Proposed Diesel Repair Shop, 3929 County
Road 154, Garfield County, Colorado
Dear Mr. MacGregor:
As requested by Bruce Upton, the undersigned representative of H-P/Kumar observed the
excavation at the subject site on November 10, 2016 to evaluate the soils exposed for foundation
support. The findings of our observations and recommendations for the foundation design are
presented in this report. The services were performed in accordance with our agreement for
professional engineering services to Eastbank, LLC, dated November 10, 2016.
The diesel repair shop is proposed to be built on the existing slab and footing pads remaining
from a previous steel frame shop building at this site. The new shop will also be a one-story
steel frame/metal skin building with a slab -on -grade floor.
At the time of our visit to the site, two pits had been excavated, one about 30 feet north of the
southwest corner of the existing slab -on -grade (Pit 1) and one at the northwest corner of the
existing slab -on -grade (Pit 2). Pit 1 was 4 feet deep and consisted of about 2 feet of on-site clay
fill overlying natural sandy silty clay soils. Pit 2 was 9 feet deep and consisted of about 3 feet of
on-site clay fill overlying natural sandy silty clay. The existing northwest footing pad was
partially exposed on the south side of Pit 2 and the bottom of the pad appeared to be Tess than 2
feet below the top of the concrete slab. The corner pad appeared to extend 2 feet north and 1
foot east of the northwest corner column, indicating that the pad is probably on the order of 2 by
4 feet in size. Results of swell -consolidation testing performed on samples of the natural clay
soils taken from the site, shown on Figure 1, indicate the soils have low compressibility under
light loading and have a low to moderate collapse potential when wetted under light load. The
samples were moderately to highly compressible under increased loading after wetting. No free
water was encountered in the pit excavations and the soils were moist.
Considering the conditions exposed in the pit excavations and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psf can be used for support of the proposed shop. The exposed
Eastbank, LLC
November 30, 2016
Page 2
soils tend to compress when wetted and there could be some post -construction settlement of the
foundation if the bearing soils become wet. New footings should be a minimum width of 18
inches for continuous walls and 2 feet for columns. Exterior footings should be provided with
adequate soil cover above their bearing elevations for frost protection or should be insulated.
Structural fill placed within floor slab areas can consist of the on-site soils compacted to at least
95% of standard Proctor density at a moisture content near optimum. 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 10 feet of the foundation.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the pit excavations 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 required. It is possible the
data obtained by subsurface exploration could change the 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 -P: KUMAR
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Daniel E. Hardin, P.E. '-.1,...?/5-4, ' .
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attachment Figure 1 — Swell -Consolidation Test Results
cc: Kaup Engineering — Dale Kaup (katrperw0Prof.net)
Bruce Upton (bruce.Ihcarcreck reomcast.net)
H -P1 KUMAR
Project No 16-7-583
Compression %
Compression %
0
2
4
6
8
10
12
14
0
2
4
6
8
Moisture Content = 12.2 percent
Dry Density = 91 pcf
Sample of: Sandy Silty Clay
From: Pit 1 at 2 iz Feet
Compression
upon
wetting
0.1
1.0 10
APPLIED PRESSURE - ksf
100
Moisture Content = 18.4 percent
Dry Density = 98 pcf
Sample of: Sandy Silty Clay
From: Pit 2 at 4 Feet
-0
Compression
upon
wetting
0.1
16-7-583
1.0 10
APPLIED PRESSURE - ksf
H -P- I<UMAR
SWELL -CONSOLIDATION TEST RESULTS
100
Figure 1