HomeMy WebLinkAboutObservation of Excavation 05.13.20201(4-A
Kumar & itaseetatse,, LS8. •
Geotechnical and Materials Engineers
and Environmental Scientists
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.cam
An Employes Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
May 13, 2020
James Gornick Building Specialists
Attn: Jim Gomick
1005 Cooper Avenue
Glenwood Springs, Colorado 81601
jgornick 1988tar7,gmaii.com
Subject:
Dear Jim:
Project No. 20-7-264
Observation of Excavation, Proposed Garage, 278 Rippy Lane, Garfield County,
Colorado
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on May 7, 2020 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 James Gornick Building Specialists, dated May 6, 2020.
The proposed garage will be a single story structure with a footprint of approximately 55 feet by
44 feet. Two overhanging awning areas will be built off of the garage on the south and east sides
and supported on isolated pads. Ground floor will be slab on grade. Spread footings placed on
the natural soils and sized for an assumed 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 1 level from 2 to
3 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of very stiff clay. Results of swell -consolidation testing performed on samples taken
from the site, shown on Figure 1, indicate the soils are slightly compressible under existing
moisture conditions and light loading and possess a low expansion potential when wetted. The
laboratory testing is summarized in Table 1. 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 placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 2,500 psf can be used for support of the proposed garage. The exposed
soils tend to expand when wetted and there could be some post -construction movement of the
foundation if the bearing soils become wet. Footings should be a minimum width of 16 inches
for continuous walls and 2 feet for columns. Loose disturbed soils in footing areas should be
removed and the bearing level extended down to the undisturbed natural soils. 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
James Gornick Building Specialists
May 13, 2020
Page 2
structures (if any) should also be designed to resist a lateral earth pressure based on an equivalent
fluid unit weight of at least 55 pcf for on-site soil as backfill. A perimeter foundation drain
should not be needed for the proposed shallow footing and slab -on -grade construction. The
onsite soils, exclusive of topsoil, can be used to support lightly loaded slab -on -grade construction
with movement risk mainly if the bearing soils are wetted. 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. Surface grading to encourage drainage and prevent ponding is
necessary to prevent wetting of the bearing soils and decrease the risk and magnitude of
foundation movement. 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 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 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,
K.uniar,& Associates. Inc„
James H. Parsons
Reviewed by:
Steven L. Pawl
JHP/kac
attachments Fig
Table 1
solidation Test Results
iry of Laboratory Test Results
Kumar & Associates,
Lon, :catj\0.cn n0,2a724
Tg
SAMPLE OF: Clay
FROM: Southwest Corner
WC = 18.4 %, DD = 103 pcf
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
— 3 1
— 4
1
0
— 2
— 3
4
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
1.0 APPLIED PRESSURE — KSF 10
TMw Iwel n..ul4 appy nN/ to 11..
epnpiee 'Looted. The I.nklop Maar!
erwe nol be rupn,duceo, s.ofpl N
foe. without the approval of
*Una], ontl nOMOIclos, Inc. Swell
Gpneailaailen I0AY.p performed In
accordance with ASTM 12-4548.
10
SAMPLE OF: Clay
FROM: Southeast Corner
WC = 18.8 %, DD = 99 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
1.0 APPLIED PRESSURE — KSF 10 100
20-7-264
Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS
Fig. 1
1(±A
Kumar & Associates, Inc..®
Geotechnical and Materials Engineers
and Environmental Scientists
SAMPLE LOCATION
BOTTOM OF EXCAVATION
Northwest Corner
NATURAL
MOISTURE
CONTENT
()
25.5
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
GRADATION
SAND
(%)
NATURAL
DRY GRAVEL
DENSITY
(pct)
93
PERCENT
PASSING NO.
200 SIEVE
96
ATTERBE
RG LIMITS
LIQUID LIMIT
PLASTIC
INDEX
(%)
UNCONFINED
COMPRESSIVE
STRENGTH
(PSF)
4,100
Clay
Project No. 20-7-264
SOIL OR
BEDROCK TYPE
1
Southwest Comer
18.4
103
Clay
Southeast Comer
18.8
99
Clay