HomeMy WebLinkAboutSoils Report 12.16.2016H-PvKUMAR
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
December 16, 2016
Aspen Built Homes
Attn: Eric Fisher
P.O. Box 3551
Basalt, Colorado 81621
(Ericfisher5050@msn.com)
Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado
NOV 077017
Project No.16-7-505
Subject: Subsoil Study for Foundation Design, Proposed Residence and Barn, Lot 22,
Stirling Ranch, Garfield County, Colorado
Dear Mr. Fisher:
As requested, H-P/Kumar performed a subsoil study for design of foundations at the subject site.
The study was conducted in accordance with our agreement for geotechnical engineering
services to Aspen Built Homes dated October 7, 2016. The data obtained and our
recommendations based on the proposed construction and subsurface conditions encountered are
presented in this report.
Proposed Construction: The proposed residence will be one story wood frame construction
above a walkout basement and with an attached garage. Basement and garage floors will be slab -
on -grade. The barn will be a one or story wood frame structure with slab -on -grade floor. The
buildings will be located on the site as shown on Figure 1. Cut depths for the residence are
expected to range between about 3 to 10 feet and 3 to 4 feet for the barn. Foundation loadings
for this type of construction are assumed to be relatively light and typical of the proposed type of
construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The vacant property was covered with about 4 inches of snow at the time of
our exploration. The upper part of the property in the building areas is vegetated with scattered
juniper trees, sage brush, grass and weeds. The lower portion, below the irrigation ditch, is a
grass pasture. The ground surface is moderately sloping down to the north at the house site and
down to the east at barn site and becoming relatively flat below the irrigation ditch. The
irrigation ditch location is shown on Figure 1.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits at the residence site and two exploratory pits at the barn site. The locations are
-2 -
shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered,
below about 6 inches of topsoil at the house site and one foot of topsoil at the barn site, consist of
sandy silty clay overlying basalt cobbles and boulders in a sandy silt matrix. Basalt rock was not
encountered in Pit 2 to the bottom depth of 7'/2 feet. Sand and silt with basalt gravel was
encountered in Pit 4 below the clay soils. Results of swell -consolidation testing performed on
relatively undisturbed samples of the sandy silty clay, presented on Figures 3, 4, 5, 6 and 7
indicate low compressibility under existing moisture conditions and light loading. Results of a
gradation analysis performed on a sample of slightly sandy silty gravel with cobbles (minus 5
inch fraction) obtained from the site are presented on Figure 8. No free water was observed in
the pits at the time of excavation and the soils were slightly moist to moist.
Foundation Bearing Conditions: The upper sandy silty clay is of varying thickness and the
underlying calcareous basalt gravel varies in cobble and boulder content. We expect the
foundation excavations will expose the sandy silty clay in shallow cut areas and basalt gravel in
deeper cut areas. There is a low risk of differential settlement if the bearing soils become wetted.
Care should be taken in the surface and subsurface drainage around the house and barn to
prevent the soils from becoming wet. It will be critical to the long term performance of the
structures that the recommendations for surface drainage and subsurface drainage contained in
this report be followed.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread footings
placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 1,500
psf for support of the proposed residence and barn. The soils tend to compress after wetting and
there could be some post -construction foundation settlement. Footings should be a minimum
width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils and
existing fill encountered at the foundation bearing level within the excavation should be removed
and the footing bearing level extended down to the undisturbed natural soils. Exterior footings
should be provided with adequate cover above their bearing elevations for frost protection.
Placement of footings at least 36 inches below the exterior grade is typically used in this area.
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
structures should be designed to resist a lateral earth pressure based on an equivalent fluid unit
weight of at least 50 pcf for the on-site soil as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab -on -grade construction. To reduce the effects of some differential movement, floor slabs
should be separated from all bearing walls and columns with expansion joints which allow
unrestrained vertical movement. Floor slab control joints should be used to reduce damage due
to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be
established by the designer based on experience and the intended slab use. A minimum 4 inch
layer of free -draining gravel should be placed beneath basement level slabs to facilitate drainage.
This material should consist of minus 2 inch aggregate with less than 50% passing the No. 4
sieve and Tess than 2% passing the No. 200 sieve.
H -Pt KUMAR
Project No. 16-7-505
-3 -
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site soils devoid of vegetation, topsoil and oversized rock.
Underdrain System: Although free water was not encountered during our exploration, it has
been our experience in the area that local perched groundwater can develop during times of
heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched
condition. We recommend below -grade construction, such as retaining walls and basement
areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The
barn, with slab -on -grade floor, should not need an underdrain.
The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above
the invert level with free -draining granular material. The drain should be placed at each level of
excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to
a suitable gravity outlet. Free -draining granular material used in the underdrain system should
contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a
maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence and barn have been completed:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
Free -draining wall backfill should be capped with about 2 feet of the on-site, finer
graded soils to reduce surface water infiltration.
3) The ground surface surrounding the exterior of the buildings should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3
inches in the first 10 feet in pavement and walkway areas. A swale may be
needed uphill to direct surface runoff around the residence and barn.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping which requires regular heavy irrigation should be located at least 10
feet from the building. Consideration should be given to the use of xeriscape to
limit potential wetting of soils below the foundation caused by irrigation.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. 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. Our
H -P = KUMAR
Project No, 16-7-505
-4 -
findings include interpolation and extrapolation of the subsurface conditions identified at the
exploratory pits and variations in the subsurface conditions may not become evident until
excavation is performed. If conditions encountered during construction appear different from
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
H-P-K1Jl< AR
Louis Eller
Reviewed by:
Daniel E. Hardin, P.E.
LEE/kac
attachments
H -P le KUMAR
Figure 1 Loc''''' xploratory Pits
Figure 2 — Logs of Exploratory Pits
Figures 3 thru 7 — Swell -Consolidation Test Results
Figure 8 - Gradation Test Results
Table 1 — Summary of Laboratory Test Results
Project No. 16-7-505
11
11
P9.
.1
ors
wog
•
✓ 1
�.r
.I 4 rJ'
PIT 2 .S
•
PR 1 HOUSE
Of!
610,01
• /
Vie
/
fib . SPIT 4
Car r�sxS
/
16-7-505
H -P KUMAR
50 0 50 100
APPROXIMATE SCALE—FEET
LOCATION OF EXPLORATORY PITS
Fig. 1
w
Li
- 0
--- 5
10
PIT 1 PIT 2
/
WC=5.9
D0=94
9 WC=6.7
0D=79
-; WC=5.1
-[+4=60
-200=33
HOUSE SITE
WC=5,5
0D-100
WC=8.1
DD=80
PIT 3
PIT 4
WC=6.7
DD=105
WC=8.5
DD=80
-200=86
BARN SITE
LEGEND
�1.
f
TOPSOIL; ORGANIC SANDY SILTY CLAY, FIRM, MOIST, DARK BROWN.
CLAY (CL); SANDY, SILTY, STIFF, SLIGHTLY MOIST TO MOIST, RED, POROUS, BLOCKY.
GRAVEL AND SILT (GM -ML); SANDY, SCATTERED COBBLES, MEDIUM DENSE, SLIGHTLY MOIST,
LIGHT BROWN, CALCAREOUS.
BASALT COBBLES AND BOULDERS (GM); WITH A SANDY SILT MATRIX, DENSE, SLIGHTLY MOIST,
LIGHT BROWN, CALCAREOUS.
1 HAND DRIVEN LINER SAMPLE.
DISTURBED BULK SAMPLE.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A DEERE 600 MINI -EXCAVATOR ON DECEMBER
8, 2016.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE
EXPLORATORY PITS ARE PLOTTED TO DEPTH.
4. THE EXPLORATORY PIT LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE
IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
0--
5
10
W
1-
w
0
16-7-505
H-P46KUMAR
LOGS OF EXPLORATORY PITS
Fig. 2
X
CONSOLIDATION - SWELL
2
0
- 2
- 4
- 6
-8
-10
.1
16-7-505
I.0
APPLIED PRESSURE — KSF
H -P- KUMAR
10
SWELL -CONSOLIDATION TEST RESULT
100
Fig . 3
SAMPLE OF: Sandy Silty Clay
FROM: Pit 1 0 3'
WC = 5.9 X, DD = 94 pcf
1
I_
1UNDER
ADDITIONAL COMPRESSION
CONSTANT PRESSURE
DUE TO WETTING
r-----.-'1
._4
nd. 1 uiy h r*
.. S .tatnbI
�r0. nd .4 rs+1tr.�1..,�+p� �+
V. M
RJ..1Yw1 M...Sow
CMw61W1 t1V� M
WwMT4L
scant ,IN1N q7Y p-�gaR
.1
16-7-505
I.0
APPLIED PRESSURE — KSF
H -P- KUMAR
10
SWELL -CONSOLIDATION TEST RESULT
100
Fig . 3
CONSOLIDATION - SWELL
1
0
— 1
— 2
— 3
—4
— 5
100
16-7-505
H-P-KUMAR
SWELL -CONSOLIDATION TEST RESULT
Fig. 4
SAMPLE OF: Sandy Silty Clay
FROM: Pit 2 0 2'
WC = 5.5 X, DD = 100 pct
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1
_.r._
.
..
_
--.�.-.-.___._.
�._�
_
h..,. LIP nN1..psy mg M n
Vr0104n
M''';144 M rgre�w.i, w... M
0,! •.64 C. whin
Iwil ✓7
Krw W 4Mcikw, k f.w
_._.1..�.
_
s
C`.n.d.lfw� M
o1n.100'if i�h ASHD O��ii
100
16-7-505
H-P-KUMAR
SWELL -CONSOLIDATION TEST RESULT
Fig. 4
2
0
x - —2
w
—4
—6
z
0
a
0 -8
J
O
N
z
O
U 10
—12
—14
—16
16-7--505
H-PkIKUMAR
10
SWELL -CONSOLIDATION TEST RESULT
I00
Fig. 5
SAMPLE OF: Sandy Silty Clay
FROM: Pit 2 0 6'
WC = 8.1 X. OD = 80 pcf
P
ADDITIONAL
UNDER
DUE
COMPRESSION
CONSTANT PRESSURE
TO WETTING
i
-
..
.
1:—.. un ..w .moy we a m.
Mt( s. 4 a n.. •— . r.y$d
M
rn r..a.r�
n+. .0 1m r+,mm swami1.0w
ww w waxes... fa w.
c....N.U.n Y .m..e 1
ee.arean. rv.
16-7--505
H-PkIKUMAR
10
SWELL -CONSOLIDATION TEST RESULT
I00
Fig. 5
7
11
m
z
0
O
TP4.• ews r—.t. yey 10/ ss re
iondooswrr. n..4 . repel
awl mt w .w wins' $.01 w
SAMPLE OF: Sandy Silty Clay
FROM: Pit 3 ID 1'
WC = 10.0 X. DD = 98 pcf
ADDITIONAL COMPRESSION
-0-- UNDER CONSTANT PRESSURE
DUE TO WETTING
4-
16-7-505
fA APPLIED PitentigE - K r 1
H-P--11KUMAR
SWELL—CONSOLIDATION TEST RESULT
Fig. 6
1
0
J —1
3
— 2
z
U —4
— 5
—6
16-7-505
H-P1KUMAR
SWELL -CONSOLIDATION TEST RESULT
i00
Fig. 7
SAMPLE OF: Sandy Silty Clay
FROM: Pit 4 0 2'
WC=6.7X,00= 105 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANTPRESSURE
DUE TO WETTING
____
Pi
• _.
____.__
...
,,
_,
,„
_
—_....__.
_
____,.
�.
_--_
-....
.._
_____
T
.
..d
TM
=11�,
Mei
W6
M/ M f'v wriin , —wwl M
IL. 4 W4 &W .R[Lb -nw.4 et
.4+.w MfH *j pMc i.N
Sa—�Mwn r
O-�.7�C
laoesy/ru� rtl1
16-7-505
H-P1KUMAR
SWELL -CONSOLIDATION TEST RESULT
i00
Fig. 7
'S
4S
.,a
100
90
90
70
00
30
40
70
20
10
0
.0
HYDROMETER ANALYSIS
SIEVE ANALYSIS
TimC *CAW=V
149-145104 11971 7 41
■sr1 111114 195111114 1101194 +2,914
Ram 4'0a
S. S7A 10. 90 SCn1CS
Asn eau 020 me■10 19
et
0/1•
CLEFS?
y!.•
5.11C 0P0121901
W
4 I.1^ s'
.
`e 9
I
,
I
i
_Olga
1
,
1
,
__J.
1
it S
_..._
...�.
111
_.
—_-__.__.
..
-
....
5.
......--
.io,
1
t
1 I ..nn1
1
I
f
+j'i
1 1 1 1
1 1 1 1 1
... -_ -
ki
1
'_-
I
.RO�
1 I .002
I
1 l
1
1 1 1 . .
1
.
i I
[.. L1 !
. ..
1 1
.00
! As7Filk: .20,71
r1
.p 19
DIAMETER OF PARTICLES IN MILLIMETERS
152
CLAY TO SILT
SAND
GRAVEL
FINE 1 MEDIUM 'COARSE
FINE COARSE
J
COBBLES
16-7-505
GRAVEL 60 X
SAND 7 X
SAMPLE OF: Slightly Sandy Silty Gravel with Cobbles
H- -.-1 UMAR
SILT AND CLAY 33 Y.
FROM: Plt 1 0 6.-7'
t0
20
30
110
0s
00
70
00
90
100
Thole 1.11 mulls apply only lo 1h■
samples which were lolled. The
listing sport shall nal be reproduced,
step! In full, without the within
approval of Kumar p Assoe2cle... Inc.
Sieve onaly+le Inlln9y h performed In
accordance IFh ASTM 0400, ASTM C136
and%ar AST1. DPI O.
SWELL-CONSOLIDAT10N TEST RESULTS
Fig. 8
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 16-7-505
SAMPLE LOCATION
PIT
DEPTH
(h)
NATURAL
MOISTURE
CONTENT
NATURAL
DRY DENSITY
(pci)
GRADATION
GRAVEL
(90
SAND
(%)
PERCENT
PASSING NO.
200 SIEVE
ATTERGERG LIMITS
LIQUID LIMIT
I%)
PLASTIC
INDEX
1%)
UNCONFINED
COMPRESSIVE
STRENGTH
[P50
SOIL TYPE
1
3
4
5.9
6.7
94
79
88
Sandy Silty Clay
Sandy Silty CIay
6 to 7
5.1
60
7
33
2
2
6
5.5
8.1
3
4
1
2
41/
10.0
6.7
8.5
100
80
98
105
80
86
Slightly Sandy Silty Gravel
with Cobbles
Sandy Silty Clay
Sandy Silty CIay
Sandy Silty Clay
Sandy Silty CIay
Sandy Silty Clay