HomeMy WebLinkAboutObservation of Excavation 07.05.2018H-PKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
July 5, 2018
Mike Rainey
3177 West 315( Court
Rifle, Colorado
444reload @ small .com
Subject:
Dear Mike:
Project No. 18-7-231.01
Observation of Excavation, Proposed Steel Building, Lot 5, Rifle Creek
Highlands, County Road 317, Garfield County, Colorado
As requested, a representative of H-P/Kumar observed the excavation at the subject site on June
25, 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 you dated March 27, 2018.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated April 25, 2018, Project No. 18-7-231. The proposed construction is
similar to that discussed in the previous report. Spread footings bearing on the natural soils
designed for an allowable soil bearing pressure of 2,000 psf were recommended for foundation
support with some risk of movement.
At the time of our site visit, the foundation excavation was essentially complete and had been cut
in two levels from about 1 to 4 feet below the adjacent ground surface. The shallower cuts were
for the interior floor slab area. The soils exposed in the bottom of the excavation consisted of
stiff, sandy clay with scattered basalt gravel and cobbles with boulders. Results of swell -
consolidation testing performed on samples taken from the site, shown on Figure 1, indicate the
soils are slightly to moderately compressible under conditions of loading and wetting with a low
to moderate expansion potential when wetted under a constant light surcharge. No free water
was encountered in the excavation and the soils were slightly moist to moist. The moderate
expansion potential was in the shallow cut for the floor slab area where the soils were slightly
moist.
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site and suitable for support of spread footings designed for the recommended allowable
bearing pressure of 2,000 psf. The risk of movement is due to the clay nature of the subsoils and
especially if the bearing soils were to become wetted, and precautions should be taken to prevent
Mike Rainey
July 5, 2018
Page 2
wetting. Prior to the footing construction, all loose disturbed soils should be removed to expose
the undisturbed natural soils and the subgrade compacted. We understand a 6 -inch depth of
compacted road base is planned on the clay subgrade below footing areas which is acceptable.
Other recommendations presented in our previous report which are applicable, including those
relating to providing a depth of road base below the floor slab to reduce potential movement and
distress, 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.
If you have any questions or need further assistance, please call our office,
Sincerely,
H -P -t KU
• .1 iry & 6_,
E r r.
David A. Young, Ft folk 2-216 r
DAY/kac ., ''=OJAL ,
attachment Figure 1, Swell -Consolidation Test Results
H -P _KUMAR Project No. 18-7-231.01
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
1
0
— 1
— 2
— 3
— 4
1
0
—2
— 3
APPLIED PR SSURE — KSF
SAMPLE OF: Sandy Clay with Gravel
FROM: Bottom of NE Portion of Excavation
WC = 13.5 %, DD = 109 pcf
I
I
—
11
EXPANSION UNDER
PRESSURE UPON
CONSTANT
WETTING
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
I
I
1
t
.
These test recalls appIY anlY to the
samples tested 7 c lasting report
shall not be reproduced. elcepl in
lull, without the written approval of
Kumor and Nsoei les Inc Swell
Consol,dot,on lestIng performed in
cordance w,lh ASTM 0-4546
— ..
_
APPLIED PR SSURE — KSF
10 APPLIED PRESSURE - KSF
10
0
100
18-7-231.01
H-PvK1JMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 1
SAMPLE OF: Sandy Clay with Grovel
FROM: Bottom of Middle Portion of
Excavation
WC = 9.3 %, DD = 113 pcf
—
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
I
I
1
t
.
These test recalls appIY anlY to the
samples tested 7 c lasting report
shall not be reproduced. elcepl in
lull, without the written approval of
Kumor and Nsoei les Inc Swell
Consol,dot,on lestIng performed in
cordance w,lh ASTM 0-4546
— ..
_
10 APPLIED PRESSURE - KSF
10
0
100
18-7-231.01
H-PvK1JMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 1