HomeMy WebLinkAboutSoils Report 07.16.2020K+A
Kumar & Associates, Inc.
Geotechnical and Materials Engineers
and Environmental Scientists
An Employee Owned Company
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
July 16, 2020
Liz Coplon
1121 Spring Park Road
Carbondale, Colorado 81623
1 izard. coplanna,gmail. con
Project No. 20-7-370
Subject: Subsoil Study for Foundation Design, Proposed Swimming Pool, 1121 Spring
Park Road, Missouri Heights, Garfield County, Colorado
Dear Liz:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was conducted in accordance with our proposal for geotechnical
engineering services to you dated June 26, 2020. The data obtained and our recommendations
based on the proposed construction and subsurface conditions encountered are presented in this
report.
Proposed Construction: The proposed pool will be about 5 feet deep and about 15 feet by
40 feet in plan area. We understand the pool will be located in the area of our pits, located on the
site as shown on Figure 1. The pool will be a shotcrete structure with a pool deck elevation close
to the elevation of Pit 1. Cut depths are expected to range between about 4 to 8 feet. Foundation
loadings for this type of construction are assumed to be relatively light and typical of the
proposed type of construction.
If structure 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 site is currently developed with a two-story residence and garage. The
proposed pool area is vacant hillside sloping down to the south at grades of 15 to 25 percent.
Vegetation consisted of field grass, weeds and sagebrush, with scrub oak northeast of the
proposed pool area.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about 1 to 11/2 feet of topsoil, consist of
4 to 5 feet of medium dense, clayey silty sand overlying relatively dense, gravelly sandy silty
clay to clayey sandy gravel with scattered cobbles. Results of gradation analyses performed on
samples of clayey gravel and gravelly clay (minus 3 -inch fraction) obtained from the site are
presented on Figure 3. No free water was observed in the pits at the time of excavation and the
soils were slightly moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend the shotcrete pool
-2
bottom slab or spread footings (if any) placed on the undisturbed natural soil or compacted
structural fill be designed for an allowable soil bearing pressure of 1,200 psf for support of the
proposed pool. The soils tend to compress after wetting and there could be some post -
construction foundation settlement. Footings (if any) should be a minimum width of 18 inches
for continuous walls. Loose and disturbed soils encountered at the foundation bearing level
within the pool excavation should be moistened and compacted or removed and the bearing level
extended down to the undisturbed natural soils. We should observe the completed excavation for
bearing conditions. Footings (if any) should be insulated or 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. The pool walls should be reinforced top and bottom
to span local anomalies such as by assuming an unsupported length of at least 12 feet. The pool
walls acting as retaining structures should be designed to resist a lateral earth pressure based on
an equivalent fluid unit \•eight of at least 60 pcf for the on-site soils or similar materials used as
backfill.
Pool Deck 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, deck
slabs should be separated from the pool walls with expansion joints which allow unrestrained
vertical movement. Deck 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 the deck slabs to facilitate drainage. This material
should consist of minus 1 -inch aggregate with less than 50% passing the No. 4 sieve and less
than 2% passing the No. 200 sieve.
All fill materials for support of deck 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 predominantly granular soils or a suitable imported gravel such as 3/4 -inch road base devoid
of vegetation, topsoil and oversized rock.
Underdraiu System: The pool should be provided with an underdrain system consisting of a
gravel or sand bed under the entire pool sloped to drain downhill at a minimum 1% grade to a
suitable gravity outlet. Free -draining granular material used in the underdrain system can be a
medium to coarse grained sand or gravel containing less than 2% passing the No. 200 sieve, less
than 50% passing the No. 4 sieve and have a maximum size of 1 inch. The drain gravel backfill
should be at least foot deep. An impervious membrane such as 20 mil PVC should be placed
beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to
prevent wetting of the bearing soils.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the pool has been completed:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
Kumar & Associates, Inc. ® Project No. 20-7-370
3
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density under deck slab areas and
to at least 90% of the maximum standard Proctor density in landscape areas.
3) The ground surface surrounding the exterior of the pool should be sloped to drain
away from the pool in all directions. We recommend a minimum slope of 6
inches in the first 10 feet in landscape areas and a minimum slope of 2 inches in
10 feet in deck and walkway areas. A swale may be needed uphill to direct
surface runoff around the pool deck area.
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 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 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,
Kumar & Associates, Inc.
Daniel E. Hardin, P. ! .
24443
Rev. by: SLP + % j 6
DEH/kacSSIi •••••.
attachments Figure 1 —`�ti �.,ti. :-* xploratory Pits
Figure 2 — Logs of Exploratory Pits
Figure 3 —Gradation Test Results
Table 1 — Summary of Laboratory Test Results
Kumar & Associates, Inc.
Project No. 20-7-370 •
Y
1
tit
1121 SPRING PARK ROAD
CARBONDALE, COLORADO
i
-
30 0 30 60
APPROXIMATE SCALE -FEET
20-7-370
Kumar & Associates
LOCATION OF EXPLORATORY PITS
Fig. 1
LEGEND
;Z.
1-
w
w
I
1-
a
w
0
5
10
PIT 1
EL. 100'
1 WC=8.9
J +4=23
-200=54
LL=34
PI=16
PIT 2
EL. 105'
0 -
5 -
1 WC=9.8
+4=42
-200=31
LL=38
PI=16 10-
TOPSOIL, ORGANIC, SANDY CLAYEY SILT, FIRM, SLIGHTLY MOIST, DARK BROWN.
SAND (SM -SC): SILTY, GRAVELLY, SCATTERED COBBLES, LOOSE TO MEDIUM DENSE,
SLIGHTLY MOIST, REDDISH BROWN, SLIGHTLY CALCAREOUS.
GRAVEL (GC): SANDY, CLAYEY TO GRAVELLY, SANDY SILTY CLAY, DENSE, SLIGHTLY MOIST,
REDDISH BROWN.
HAND DRIVE SAMPLE.
DISTURBED BULK SAMPLE.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON JULY 1, 2020.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY TAPING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO
THE GROUND ELEVATION AT PIT 1 AS ELEV. 100'.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS 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 DIGGING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140);
LL = LIQUID LIMIT (ASTM D 4318);
PI = PLASTICITY INDEX (ASTM D 4318).
20-7-3701 Kumar & Associates
LOGS OF EXPLORATORY TEST PITS
Fig. 2
HYDROMETER ANALYSIS SIEVE ANALYSIS
100
TIME READINGS
24 NRS 7 NRS
45 15 M!N 49MIN 10M9i lMIN lMlti ono
U.S. STANDARD SERIES
f199 159.049 439 11.10 116 to.
3LC—__J11,4"
CLEAR SOUAR'L OPENIROS
i Ira * W..-.....0
so
_MIN
.
,o
I
r
..
---
-j—
1
•i
=
i
.
BO-
_
—.1
f
-
-
—
-.1
—._!6
_
f
•
—
—
i
—
I
•
.10
70
I
1
40
30
I
I
I
1
i
70
20
�
I
_ 1
_ t
M
10
o
.002
_l_.:1
.005
1...1.1-
.00e
1..
m19
I I
.057
1 1.1.1111
.078
DIAMETER
.180
I I
.500
OF PARTICLES
1
11 I
1 .000
.425
I I. 1.1
1.6
IN
1 .]I
12.31
2.0
MILLIMETERS
I.
4.78
I 1.1.:1111
1.A
19
1 __I_—I-11_LL7J—f
7e.1
7e.2 117
152
200
106.001
CLAY TO SILT
SAND
GRAVEL
COBBLES
FINE MEDIUM COARSE
FINE I COARSE
GRAVEL 23 X
LIQUID LIMIT 34
SAMPLE OF: Gravelly Sandy Silty
SAND 23 X SILT
PLASTICITY INDEX 16
Clay FROM:
AND CLAY 54 X
Psi 1 0 6'-7'
HYDROMETER ANALYSIS
SIEVE ANALYSIS
24 HRS
45 MIN
TIME 5LR0UI
7 HRS
15 MIN
U.S. STANDARD SERIES
CLEAR SQUARE OPENINGS
109
eo70
IIIH1i't
30
eo
_i_
---1
IT
ea
I
I
I'
20
..
1.. _
f
1
eo
_..-.�.
!
_..
_..
00
10
0 11.
.Gal .00x .69e
I. t 1 1.1
.I. I.I. 1 . MO .019
f .Off .677 .078
DIAMETER
11 I I 1. I
.150 .200 .900
4x5
OF PARTICLES
1111 i 1 1 t i 1.11
1.15 2.35 4.02 5 e 1st
2.0
IN MILLIMETERS
1. I....1-_1 1...L1.1.1.
7611 71.2
too
127 200
152 1
SAND
GRAVEL
COBBLES
CLAY TO SILT
FINE I MEDIUM
MEDIUM COARSE
FINE
1
GRAVEL 42 X SAND 27 X SILT AND CLAY 31 X
LIQUID LIMIT 38 PLASTICITY INDEX 16
Thaw test results apply only to the
SAMPLE OF: Clayey Sandy Gravel FROM: Pit 2 0 7'-7.5' samples which were tested. The
testing report shall not be reproduced,
exoepl In full, without the written
approval of Kumar & Assoalotes, Ino.
Steve analysis tasting la performed In
accordance with ASTM D0913, ASTM D7928,
ASTM C130 and/or ASTM D1140.
20-7-370
Kumar & Associates
GRADATION TEST RESULTS
Fig. 3
K±A
Kumar & Associates, Inc.°
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITY(%)
(Pci)
GRADATION
PERCENT
PASS GE VE NO.
ATTERBERG LIMITS
UNCONFINED
COMPRESSIVE
STRENGTH
(psf)
SOIL TYPE
PIT
DEPTH
(ft)
GRAVEL
SAND
(%)
LIQUID LIMIT
(%)
PLASTIC
INDEX
(%)
1
6 to 7
8.9
23
23
54
34
16
Gravelly Sandy Silty Clay
2
7 to 7'/2
9.8
42
27
31
38
16
Clayey Sandy Gravel
1: