HomeMy WebLinkAboutSoils Report 10.19.2017H-PKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
RECEIVEP
DEC 202017
GARFIELD COUNTY
)MMUNITY DEVELOPMENT
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Parker, Glenwood Springs, and Summit County, Colorado
October 19, 2017
Uriel Mellin
144 Cliffrose Way
Glenwood Springs, Colorado 81601
uriel.mellin@hotmail.com
Project No.17-7-695
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 2, Callicotte
Ranch, 62 Meadow Point, Garfield County, Colorado
Dear Uriel:
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 proposal for geotechnical engineering services
to you dated September 14, 2017. 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 about 5,000 square feet, one story
wood frame structure over a crawlspace located on the site as shown on Figure 1. Ground floor
in the attached garage will be slab -on -grade. Cut depths are expected to range between about 3
to 9 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: The site is currently vacant, gently rolling pastureland with pinon/juniper
forest on the south side of the lot and sagebrush on the northern fence line. The lot slopes
moderately down to the east at grades of 5 to 10 percent. An active irrigation ditch crosses the
site above and west of the building area. A rough graded driveway accesses the lower part of the
lot.
-2 -
Subsurface Conditions: The subsurface conditions in the building area were evaluated by
excavating three 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 6 to 8 inches of
topsoil, consist of 3 to 7 feet of stiff, sandy silty clay overlying basalt rocks in a sandy clayey silt
matrix at 31/2 to 7 feet deep. Refusal to digging with the backhoe was encountered in all three
pits at depths of 5 to 81 feet. Results of swell -consolidation testing performed on relatively
undisturbed samples of the sandy silty clay, presented on Figures 4 & 5, indicate low to moderate
compressibility under existing moisture conditions and light loading and a low collapse potential
(settlement under constant load) when wetted. The clays were moderately compressible under
increased loading after wetting. 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 spread footings
placed on the undisturbed natural clay soils designed for an allowable soil bearing pressure of
1,200 psf and footings placed on the basalt rock soils designed for an allowable soil bearing
pressure pf 2,000 psf for support of the proposed residence. The clay soils tend to compress after
wetting and there could be 1/2 to 11/2 inches of post -construction foundation settlement. Footings
should be a minimum width of 18 inches for continuous walls and 2 feet for columns. Loose and
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
exposed soils 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 heavily 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
55 pcf for the on-site soil as backfill, excluding rock larger than 6 inches.
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
H-P�KUMAR
Project No. 17-7-695
-3 -
layer of free -draining gravel should be placed beneath slabs to facilitate drainage. This material
should consist of minus 2 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 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 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 crawlspace
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 Ievel 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. 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 residence has 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 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
H-P45KUMAR
Project No. 17-7-695
-4 -
inches in the first 10 feet in pavement and walkway areas. A swale may be
needed uphill to direct surface runoff and possible irrigation ditch overflow away
and around the residence.
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.
Percolation Testing: Percolation tests were conducted on September 16, 2017 to evaluate the
feasibility of an infiltration septic disposal system at the site. Two profile pits and three
percolation holes were dug at the locations shown on Figure 1. The test holes (nominal 12 inch
diameter by 12 inch deep) were hand dug at the bottom of shallow backhoe pits and were soaked
with water one day prior to testing. The soils exposed in the percolation holes are similar to
those exposed in the Profile Pits shown on Figure 2 and consist of silt loam. USDA gradation
test results are shown on Figure 6. The percolation test results are presented in Table 2. Based
on the subsurface conditions encountered and the percolation test results, the tested area should
be suitable for a conventional infiltration septic disposal system. A civil engineer should design
the infiltration septic disposal system.
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.
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
H-P%KUMAR
Project No. 17-7-695
-5 -
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; KUMAR
Daniel E. Hardin, P.. 24443/obo`
Reviewed by:
Steven L. Pawlak, P.E.
DEH/kac
attachments
Figure 1 — Location of Exploratory Pits
Figure 2 — Logs of Exploratory Pits
Figures 3 — Legend and Notes
Figures 4 and 5 — Swell -Consolidation Test Results
Figure 6 — USDA Gradation Test Results
Table 1 — Summary of Laboratory Test Results
Table 2 — Percolation Test Results
cc: Patrick Stuckey Architect stuarchC comcast.net
H-PitKUMAR
ProJect No. 17-7-695
FUME
OLD
Dara,
'ENrERLINE
-"k7s OrT
ON
0.
'59313 No
N84°40'35"E 289.32'
(N84°40'12"E 289,30') N83653'29"E 255.72'
ilialriNS INNIaswerir► .1azussai
(N83°52'16"E 255.651
�•� •
. 111//�><llltl�
1� y1lvolllcatRurriOlbiave ° riffr
7L grailb
1 0410M-11-4 it
(L-;,-�. �►�r,:fit .�r�r ifirionkgs;ifr.-,;..-7.1,--lag it itAi Illitifrifr /
10' .�. : Edi:. -____,nt 'ittv.inrd$ii1IJ r�' LIQ
'47�:>fil'i�''' g ON"Ftilil 4 '';;'iii ; —
r� i=;, �pii .its �' r
►,,41,,+4,.griw ! pY Pyr 3 jfr��jj'
‘ ,,e,r 'Far P-*IP'w
Nilifir
111
i l
arrrMrielirrirrwnmis
� � srttr�
AF�� r3OMa
30 0 30 60
APPROXIMATE SCALE -FEET
LOT
17-7-695
H-PvKUMAR
LOCATION OF EXPLORATORY PITS
Fig. 1
4
3
-.2 A
e9
ELEVATION -FEET
1-
LJ
w
z
0
>
J
H
PIT 1
EL. 6837'
PIT 2
EL. 6835'
PIT 3
EL. 6823'
6840 6840 —
6835
6830
- 6825
WC=5.5
DD=100
WC=7.1
-200=91
WC=9.1
DD=96
-200=91
6835
6830 ----'
6825 —
6820 6820 -- -
6820
— 6815
6810
PROFILE PIT 1
EL. 6820'
f
PROFILE PIT 2
EL. 6816'
H GRAVEL=4
_-1 SAND=21
SILT=63
CLAY=12
6820
6815
6810-
- 6805 6805
17-7-695
H-PWUMAR
LOGS OF EXPLORATORY PITS
Fig. 2
LEGEND
TOPSOIL; ORGANIC SANDY SILTY CLAY, FIRM, MOIST, DARK BROWN.
CLAY (CL); SILTY, SANDY, STIFF, SLIGHTLY MOIST, BROWN. POROUS.
BASALT ROCKS; FROM GRAVEL TO SMALL BOULDER SIZE, IN A SANDY CLAYEY SILT MATRIX,
SLIGHTLY MOIST, WHITISH BROWN, CALCAREOUS.
Sl HAND DRIVEN LINER SAMPLE.
DISTURBED BULK SAMPLE.
_1
t PRACTICAL DIGGING REFUSAL.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON SEPTEMBER 15, 2017.
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 OBTAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
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);
DD = DRY DENSITY (pcf) (ASTM D 2216);
—200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140);
GRAVEL = PERCENT RETAINED ON NO. 10 SIEVE
SAND = PERCENT PASSING NO. 10 SIEVE AND RETAINED ON NO. 325 SIEVE
SILT = PERCENT PASSING NO. 325 SIEVE TO PARTICLE SIZE .002mm
CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002mm
17-7-695
H-PtiKUMAR
LEGEND AND NOTES
Fig. 3
J
J —
W
tnz
0
0
o
J
0
(/)
z
O
U
SAMPLE OF: Sandy Silty Clay
FROM: Pit 1 0 4'
WC = 5.5 %. DD = 100 pcf
Thar falx ran . op* mei to lM
OM*. lu 4 f1 l I'. fapaal
ahpa nal he r,pmduma0. Osaka!
fa, rIlneut ths rrglaa ayDroval wi
Kumar men nrx7Msit Ina- 5.11
�nadrdalIen Ivenpp paHmewd
wdm.as with A fl O'4 IL
NO MOVEMENT UPON
WETTING
17-7-695
1.6 APPLIED PRESSURE - KSF 1Q i
H-P"-t-KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 4
CONSOLIDATION - SWELL
— 2
— 3
— 4
Muss toot mole a w// to thm
motet". lata/ IIu tioilroa nowt
.fiw tint t. .p e/yc./, ..c.pt In
!W, nNpyl YI. .011.1 epprcrpr ar
K.rnt, aro Awoc:ofati 1nF $..11
Come•follan tooling. Wormy/ In
accarde.c..ith ASU 0.046
SAMPLE OF: Slightly Sandy Silty Clay
FROM: Pit 3 ® 3'
WC = 9.1 %, DD = 96 pcf
—200 = 91 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1.0 APPLIED PRESSURE - }(SF 10
100
17-7-695
H-P45KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 5
HYDROMETER ANALYSIS
1 SIEVE ANALYSIS
f
24F1.
n45MIN.
TIME READINGS
il-H 1MM1
15 W1. OW 1Sr@i IW1 #325
U.5. STANDARD SERIES 1 CLEAR SQUARE
#140 #60 #35 # 8 # 0 OA 318' 3/4 1
OPENINGS
/2' 3' S'$' 6'
.__
PERCENT RETAINED
3 $ o o g S o' 8 8 o
I V . A Cn 0) v m �p
O O O O E S
PERCENT PASSING
1
.
_x2
i
V.001 .002 .005 .009 ,019 045 106 .025 .500 1.00 2.00 4.75 95 ?9.0 3.5 762 152 203 6
DIAMETER OF PARTICLES IN MILLIMETERS
CLAY SIL'
COBBLES
51_'_,/,T FF1/WE6'.ii,.' OARSI; .Lf WA:ft ME01WS
GRAVEL 4 % SAND 21 % SILT 63 % CLAY 12 %
USDA SOIL TYPE: Silt Loam FROM: Profile Pit 2 @ 3-4'
17-7-695
H-P--KLJMAR
USDA GRADATION TEST RESULTS
Fig, 6
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 17-7-695
SAMPLE LOCATION NATURAL
NATURAL GRADATION PERCENT
USDA SOIL TEXTURE
PIT
MOISTURE
DEPTH CONTENT
(n) (%)
DRY
DENSITY
(PO
i PASSING
GRAVEL SAND NO. 200
SIEVE
1 (%) (%)
GRAVEL SAND
(%) (%)
SILT CLAY
(%) (%)
SOIL TYPE
1 4
5.5
100
Sandy Silty Clay
2 3
7.1
91
Slightly Sandy Silty
I Clay
3
3
9.1
96
91
Slightly Sandy Silty
1 Clay
F
Profile
Pit 2
3_4
4
21
63
12
Silt Loam
HOLE
DEPTH
(INCHES)
43
44
40
H-PKUMAR
TABLE 2
PERCOLATION TEST RESULTS
LENGTH OF
INTERVAL
(MIN)
Water Added
WATER WATER
DEPTH AT DEPTH AT
START OF END OF
INTERVAL INTERVAL
(INCHES) (INCHES)
53/4 43/4
43/4 41/4
PROJECT NO, 17-7-695
DROP IN
WATER
LEVEL
(INCHES)
1
1/2
4'/4 4
1/4
4 33/4
1/4
61/2
51/2
1
51/2 5
1/2
AVERAGE
PERCOLATION
RATE
(MIN./INCH)
5 4'/2
1/2
41/2 4
1/2
4 33/4
1/4
Water Added
Water Added
5% 43/4
1
43/4 4'/4
2
4'/4 41/4
4'/4 4
t/4
61/2 6
1/2
6 5%
1/4
53/4 5'/2
1/4
51/2 5
1/2
5 41/2
1/2
24
24
51/2 5
1/2
5 41/2
1/2
41/2 4
4 31/2
1/2
1/2
5% 53/4
5'/4 4%
43/4 41/4
4'/4
—4
1/2
1/2
4
1/4
31/2
1/2
24
Note: Percolation test holes were hand dug in the bottom of backhoe pits and soaked
on September 15, 2017. Percolation tests were conducted on September 16,
2017. The average percolation rates were based on the last three readings of
each test.