HomeMy WebLinkAbout18-7-252.A (10-24-18) Ex. Ob. signed_1.pdf H-P 1 ICIJ 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
October 24, 2018
Stan Jeranko
11367 Ranch Reserve Parkway
Denver, Colorado 80234-2529
pwdrhnd @aol.com
Project No. 18-7-252.A
Subject: Observation of Excavation, Proposed Duplex Residence, Parcels A and B,
Resubdivision of Lot 8,Block 1,Gore Creek Subdivision, 5128 Grouse Lane,
Vail, Colorado
Dear Stan:
As requested by Scott Hoffman, a representative of H-P/Kumar observed the excavation at the
subject site on October 17, 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 proposal services to you dated April 3, 2018.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated June 6, 2018, Project No. 18-7-252. The proposed construction is
similar to that discussed in our previous report. The building has been designed to be supported
on spread footings designed for an allowable soil bearing pressure of 2,000 psf, as
recommended.
At the time of our October 17 site visit, the foundation excavation was nearly complete and had
been cut in multiple levels from about 3 to 17 feet below the adjacent ground surface. The soils
exposed in the bottom of the excavation consisted primarily of medium dense to dense, clayey
silty sand and gravel with cobbles. The soils were rockier and less clayey in the deeper cut areas.
There was some organic topsoil in the northeastern portion of the excavation over the granular
soils that we recommended be removed, which based on pictures provided to us, was done. The
results of a gradation analysis performed on a disturbed bulk sample of the natural granular soils
(minus 11/inch fraction) obtained from the deeper cut area of the excavation are presented on
Figure 1. No free water was encountered in the excavation and the soils were slightly moist to
moist.
The soil conditions exposed in the excavation are generally 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 with some risk of settlement. The risk of
settlement is primarily due to the somewhat variable bearing conditions and especially if the
bearing soils were to become wetted, and precautions should be taken to prevent wetting. Prior
to the footing construction, any topsoil and all loose and disturbed soils should be removed in the
Stan Jeranko
October 24, 2018
Page 2
footing areas to expose the undisturbed natural granular soils and the subgrade compacted. The
bearing soils should be protected from frost and concrete should not be placed on frozen soils.
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 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�KUM + - ti467, 41.ft I �
G
4 J,i4 -A .Y
!Q' �/ •
David A. Young, P.E. 32.216
DAY/ksw *10;47/01, NAL' `���
attachment Figure 1, Gradation Test Results
cc: Crestone Building Company - Scott Hoffman (scott@crestonebuilding.com)
H-P%-KUMAR
Project No. 18-7-252.A
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S.STANDARD SERIES CLEAR SQUARE OPENINGS
24 HRS 7 NRS
100 45 MIN 15 MIN 604114 19MIN MAIN 1MIN 1200 100 50/40 30 .16 #1• 6 4 4' 1 1 S^_•
T 111121 Warj
90 -- -_�����_ _- ■ 10
inommonmsom
60 iiiia iiiii■ 20
70 MN iiRU 1..1.111111.111111111.1 30
60 IIIMINIMIIIMINIIIIMINIMIENIMIIIMININIVIr 50 ■-■ ■■■■ ■�■■ _-�■40
1�1.. ■■■1111,50
W 40 _-___-.1.11' MINI_.1.11-__--M■ fi0
1.1111.11MITIMITIMIIMPW M.1.1.11.1.111.111111.1.11.11.11.1MIEMMIn
30 I
t 70
I
20
60
1
10
I 90
I
0
100
.001 .002 .005 .009 .019 .037 .075 .150 .300 I .600 1.18 12.36 4.75 9.5 19 38.1 76.2 127 200
.425 2.0
DIAMETER OF PARTICLES IN MILLIMETERS 152
CLAY TO SILT SAND GRAVEL
FINE MEDIUM COARSE FINE COARSE COBBLES
GRAVEL 15 % SAND 56 % SILT AND CLAY 29
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Silty Sand with Gravel FROM: Bottom of Southwest Portion of Excavation
is
a
B
s
A
bThese test results apply only to the
samples which were tested. The
E testing report shall not be reproduced,
except in full, without the written
approval of Kumar & Associates, Inc.
Sieve analysis testing is performed In
accordance with ASTM 0422, ASTM C136
and/or ASTM D1140.
$g 18-7--252AFig.
H-P=�KUIVIAR GRADATION TEST RESULTS 1