HomeMy WebLinkAboutSoils Report for Foundation Design 04.16.2018ti
Geotechnlcal 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,
April 16, 2018
Chris Janusz
3644 Highway 82
Glenwood Springs, Colorado
Crujanusz123@gmail.com
Subject:
Fort Collins, Glenwood Springs, Summit County, Colorado
RECEIVED
Subsoil Study for Foundation Design
JUN 0 4 2018
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
Project No. 18-7-240
, Proposed Residence, Lot 2, Janusz
Exemption Plat, 3644 Highway 82, Garfield County, Colorado
Dear Mr. Janusz:
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 Chris Janusz dated April 3, 2018. The data obtained and our recommendations based
on the proposed construction and subsurface conditions encountered are presented in this report.
A geologic hazards assessment of the subject site is beyond the scope of this report.
Proposed Construction: An existing mobile home on the lot will be removed and a new
residence constructed. The proposed residence will be a modular home over a garden level
basement located on the site as shown on Figure 1. Ground floors will be slab -on -grade. Cut
depths are expected to range between about 4 to 6 feet. 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: There are currently multiple sheds and a mobile home on the lot. The building
site is relatively flat with the terrain sharply steepening further to the east down to the driveway.
There is minor grading including cut and fill leveling of the proposed building site. Vegetation
consists of grass, sagebrush, scrub oak, and scattered conifers with landscape.
used for support of the proposed residence with a risk of settlement.
-2 -
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits at the approximate locations shown on Figure 1. The pits were dug by the client
prior to our arrival on the site. The logs of the pits are presented on Figure 2. The subsoils
encountered, below about 1 foot of topsoil, consist of silty sand and gravel with cobbles and
boulders that extended down to the pit depths of 71/2 and 51/2 feet. Around 1 foot of older man -
placed fill was encountered in Pit 2 below the topsoil. Results of gradation analyses performed
on samples of silty sand and gravel (minus 3 -inch fraction) obtained from the site are presented
on Figure 3. The laboratory testing is summarized in Table 1. 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 believe
spread footings placed
on the undisturbed natural soil designed for an allowable bearing pressure of 1,500 psf can be
The risk of settlement is if
the bearing soils were to become wetted and precautions should be taken to prevent wetting.
Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns.
All topsoil, existing fill, and all loose disturbed soils encountered at the foundation bearing level
within the excavation should be removed and the footing bearing level extended down to the
undisturbed natural soils. The subgrade should then be moistened and compacted. 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 well 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 also 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, excluding debris, topsoil and
oversized (plus 6 inch) rocks, as backfill.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded
slab -on -grade construction. There could be some slab settlement if the subgrade becomes
wetted. To reduce the effects of some differential movement, floor slabs should be separated
H -P KUMAR
Project No. 18-7-240
-3 -
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.
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 debris, topsoil and oversized rocks (plus 6 -inch size).
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 also 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 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. If rigid PVC drain pipe is used, which we recommend, a pipe slope of
'h% can be used. 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 1'/2 feet deep and be
covered by filter fabric. An impervious membrane such as 20 or 30 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:
Positive surface drainage is a very important aspect of the project to prevent
wetting of the bearing soils.
The following drainage precautions should be observed during
construction and maintained at all times after the residence/ADU have been completed:
H-PiKUMAR
Project No. 18-7-240
-4-
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 filter fabric and about 2 feet of
the on-site, finer graded soils to reduce surface water infiltration.
3) The ground surface surrounding the exterior of the building 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 will likely be
needed uphill to direct surface runoff around the residence and ADU.
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
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.
H -P rKUMAR
Project No. 18-7-240
-5 -
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,
I -1-P KU MAIC
Robert L. Duran, E. I.
Reviewed by:
David A. Young, P.E.
RLD/kac
attachments Figure 1
Figure 2
Figure 3
Table 1 —
— Location of Exploratory Pits
— Logs of Exploratory Pits
— Gradation Test Results
Summary of Laboratory Test Results
cc: Kurtz & Associates
— Brian Kurtz (kurtzengineer@yahoo.com)
H-P%KUMAR
Project No. 18-7-240
18-7-240
H -P: KUMAR
LOCATION OF EXPLORATORY PITS
Figure 1
0
H
w
w
5
PIT 1
EL 5866'
0
o '
o '
"I +4=26
-200=36
PIT 2
EL. 5862'
o '
_1 +4=29
-200=32
0
5
10 10
LEGEND
'L. TOPSOIL; SAND AND SILT, SCATTERED GRAVEL, SLIGHTLY MOIST, DARK REDDISH BROWN,
SLIGHTLY ORGANIC.
[_i
-s
FILL; SAND AND GRAVEL, SILTY, SLIGHTLY MOIST, REDDISH -BROWN.
SAND AND GRAVEL (GM -SM); SILTY, SCATTERED COBBLES AND BOULDERS, MEDIUM DENSE,
SLIGHTLY MOIST, REDDISH -BROWN.
DISTURBED BULK SAMPLE.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON APRIL 2, 2018.
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 DRILLING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140).
18-7-240
H-P-MJMAR
LOGS OF EXPLORATORY PITS
Fig. 2
100
90
6o
70
60
F �o
40
30
20
10
HYDROMETER ANALYSIS
SIEVE ANALYSIS
24 HRS 7 HRS
45 MIN 40 .MIN_J494RI._1.1
TIME 4ENS1No3
iIlt 4 U+ .J, 4,20S
U 5. STANDAR° SERIES
11 p .
C LEAK S°UARE OPEDiR103
-
.
w
.. .
—_--
.
..
-....--.....
_..�
_....F ..
�_.._.
--- ..
_
1
l"
..�.
..
_ ..
...,.......
._..... _.
_
J.....
1 .
1.:.II
. ....._._..
- -
--
._
-
`_.-.
-__.r--`
--.._.__.__
..•-_--__
�.
r
.11---
II
. _.
-
1
1
I
_
3
I
-1-
1
.-
_....
-1
E.__
•
W
1-
1
M-
-_1-
.....__1-
......__
-_
I-
r T'—.Z
1..1.
1
1"'•-T
1 1 r UST
1
ItT
T1 1
1
1 1
i -T TTr
--1
i
r-r-K-T•r
j7
r 1 1--
r-'-
""01
.002 .005 .090 .010 .037 .01716
DIAMETER
.153 .300 r .600 1.
OF PARTICLES IN MILLIMETERS
8 1 2.38 A.75
9
5 19
3
.1 744.2 122
rat
20!
SAND
CLAY TO SILT
GRAVEL
COBBLES
FINE I MEDIUM 1COARSE
FINE COARSE
GRAVEL 26 X
LIQUID LIMIT
SAMPLE OF: Silty Sand with Gravel
SAND 38 X
HYDROMETER ANALYSIS
24 HRS 7 HRS
5
TIME READINGS
PLASTICITY INDEX
SILT AND CLAY 36 X
FROM: Pit 1 0 6.5'-7.5
SIEVE ANALYSIS
U.S. STANDARD SERIES
CLEAR SQUARE OPENINGS
10
20
30
40
50
00
70
00
90
100
rI
.019 .3 7 .973 .730 .300 I .500
.425
DIAMETER OF PARTICLES IN
I L36 4.75
2.0
MILLIMETERS
CLAY TO SILT
SAND
GRAVEL
FINE
MEDIUM 'COARSE
FINE COARSE
COBBLES
18-7-240
GRAVEL 29 X
LIQUID LIMIT
SAMPLE OF: Silty Sand with Gravel
SAND 39 X
H - P- KU MAR
PLASTICITY INDEX
SILT AND CLAY 32 %
FROM: Pit 2 0 4.5'-5.5'
Moto layl ?atolls apply only to lila
a0mp146 whlth wort haled. Tho
haling rsparl 111011 nal he rsproduc.d,
allcapl in lull, venom, 1110 wrill.n
opprnval of Kumar & Ameoc101d1, Inc.
SW* onoly,la 1661419 I1 porfor nad 1n
accardonoa wllh ASTM 0422. ASTM C136
and/or AST17 01140.
GRADATION TEST RESULTS
Fig. 3
1
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 18-7-240
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITY
cP�
GRADATION 1.
PERCENT 1
PASSING ;
NO. 200
SIEVE
ATTERBERG LIMITS 1
UNCONFINED
COMPRESSIVE
STRENGTH
(Psf)
SOIL TYPE
PIT
DEPTH
(ft)
GRAVEL
(%)
SAND
(%)
LIQUID
LIMIT
(%) 1
PLASTIC
INDEX
(%)
1
61/2-7 1/2
26
38
36
Silty Sand with Gravel
2
41 -51/2
29
39
32
Silty Sand with Gravel