HomeMy WebLinkAboutSoils Report for Foundation Design & Perc Testing 10.12.2018PKUMAR
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
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
October 12, 2018
Tito Montes
c/o Palomino Design Build
Attn: Jack Palomino
919 Palmer Avenue
Glenwood Springs, Colorado 81601
jackpalomino55@gmail.com
Subject:
RECEIVED
NAR ;12 2019
CIVGARFIELD
cOMMlJNITY DEVELOPMENT
Project No.18-7-532
Subsoil Study for Foundation Design and Percolation Testing, Proposed
Residence, TBD Highway 6, Canyon Creek, Garfield County, Colorado
Dear Mr. Montes:
As requested, H-P/Kumar performed a subsoil study and percolation testing for foundation and
septic disposal designs at the subject site. The study was conducted in accordance with our
agreement for geotechnical engineering services to you dated August 15, 2018. The data
obtained and our recommendations based on the proposed construction and subsurface
conditions encountered are presented in this report. We previously reviewed potential geologic
hazard impacts on this site as described in our letter report dated August 27, 2018, Project No.
18-7-532.
Proposed Construction: The proposed 1,900 square foot residence will be located on the site in
the area of Pits 1 and 2, shown on Figure 1. There will be an attached 500 square foot garage.
Ground floors are proposed to be slab -on -grade. Cut depths are expected to range between about
2 to 5 feet. Foundation loadings for this type of construction are assumed to be relatively light
and typical of the proposed type of construction. The septic disposal system is proposed to be
located in the eastern part of the site.
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 mostly open grass field with apple trees along the northern property
line. There are reeds and cattails along the ditch at the south property line. The lot is moderately
sloping at about 10 percent down to the southwest. A drainage ditch is located along the western
-2 -
property line. There is an existing water well in the northwest corner of the lot. There is an
existing shed in the northeast corner of the property.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two
exploratory pits in the building area and two profile pits in the septic disposal area at the
approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The
subsoils encountered, below about 1/2 to 1 foot of topsoil, consist of mostly medium dense, silty
sand with gravel and cobbles down to the maximum depth explored, 8 feet. Dense, sandy gravel
with cobbles was encountered at 3 feet in Profile Pit 2 on the east side of the site. Refusal to
backhoe digging was encountered in the dense gravel at 5 feet. Results of swell -consolidation
testing performed on relatively undisturbed samples of the silty sand, presented on Figures 3 and
4, indicate low compressibility under existing moisture conditions and light loading and a
moderate collapse potential (settlement under constant load) when wetted. The samples were
moderately compressible under increased loading after wetting. Results of a gradation analysis
performed on a sample of silty gravelly sand (minus 3 -inch fraction) obtained from the house site
are presented on Figure 5. The laboratory test results are summarized in Table 1. No free water
was observed in the pits at the time of excavation and the soils were slightly moist to moist.
Foundation Recommendations: A low settlement risk foundation would be to extend the
bearing level down to dense river gravel which is expected to underlie the alluvial fan soils at
this site. If a deep foundation is desired, additional subsurface exploration will be needed to
develop design recommendations. Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, spread footings placed on the
undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psf can be used
for support of the proposed residence with a risk of settlement.
The soils tend to compress after
wetting and there could be post -construction foundation settlement of around 1 to 2 inches
depending on the depth and extent of wetting. Care should be taken to prevent wetting of the
subgrade soils as described in the Surface Drainage section of this report. Footings should be a
minimum width of 20 inches for continuous walls and 2 feet for columns. The topsoil and loose
disturbed soils encountered at the foundation bearing level within the excavation should be
removed. The exposed undisturbed natural 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
H-Pk4KUMAR
Project No. 18-7-532
-3 -
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, can be used to support lightly loaded
slab -on -grade construction with a risk of settlement if the bearing soils are wetted. 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 relatively well graded sand and gravel such as
road base 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 12% 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 in this 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,
crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by
an underdrain system.
underdrain system.
The proposed slab -on -grade main floor level should not require an
If installed, 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. 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.
H -P: KUMAR
Project No. 18-7-532
-4 -
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 (if any) 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 inches in the first 10 feet in pavement and walkway areas. A swale may be
needed uphill to direct surface runoff 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 building caused by irrigation.
Percolation Testing: Percolation tests were conducted on September 4, 2018, 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 prior to testing. The soils exposed in the percolation holes are similar to those
exposed in the Profile Pits and the USDA gradation test results shown on Figures 6 and 7 and
consist of gravelly loamy sand. 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
expressed 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,
H-P�KUMAR
Project No. 18-7-532
5 -
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
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 KUMAI
11411111,_
Danie E. ardin,
Reviewed by:
Steven L. Pawlak
DEH/kac
attachments
24
•
Figure 1 — Location of Exploratory Pits
Figure 2 — Logs of Exploratory Pits
Figures 3 and 4 - Swell -Consolidation Test Results
Figure 5 — Gradation Test Results
Figures 6 and 7 — USDA Gradation Test Results
Table 1 — Summary of Laboratory Test Results
Table 2 — Percolation Test Results
H -P: KUMAR
Project No. 18-7-532
± 500' TO __
LEWIS LOOP
co I
z
GRAVEL DRIVEWAY
PIT 2
PROPOSED
RESIDENCE AREA
1
BENCHMARK ELEVATION TOP
i OF WELL CASING = 100'
i I
PIT 1
1
e PRCIFII F Pr
I
L-1
PERC 1
PERC 2 ' PERC 3
I ,
PROFILE PIT 2
20 0 20 40
APPROXIMATE SCALE—FEET
EXISTING
SHED
18-7-532
HH-P-v5KUMAR
LOCATION OF EXPLORATORY PITS
Fig. 1
1-
w
LJ
L_
d
LJ
0
0
5
10
LEGEND
PIT 1
EL. 99'
WC=3.2
DD=98
WC=6.9
DD=89
-200=18
PIT 2
EL. 93.5'
WC=6.6
DD=97
1 WC=9.5
I +4=18
-200=33
PROFILE PIT 1
EL. 95'
PROFILE PIT 2
EL. 97'
GRAVEL=23
--1 SAND=48
SILT=19
CLAY=10
GRAVEL=51
-I SAND=38
SILT=8
CLAY=3
TOPSOIL; ORGANIC SAND, SILTY, CLAYEY, LOOSE, SLIGHTLY MOIST, DARK BROWN.
SAND (SM): SILTY WITH GRAVEL AND COBBLES, MEDIUM DENSE, SLIGHTLY MOIST TO MOIST,
REDDISH BROWN, SUBANGULAR ROCK.
GRAVEL (GM): SANDY, SILTY, WITH COBBLES, DENSE, SLIGHTLY MOIST, RED.
HAND DRIVEN 2 -INCH DIAMETER LINER SAMPLE.
DISTURBED BULK SAMPLE.
t PRACTICAL REFUSAL TO DIGGING WITH BACKHOE.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON SEPTEMBER 4, 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 MEASURED BY HAND LEVEL AND REFER TO
THE BENCHMARK ON FIG. 1.
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);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-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
0
5
10 -
18-7-532
H -P- I<UMAR
LOGS OF EXPLORATORY PITS
Fig. 2
—12
—14
Puma left results appy. only to Me
Ipmpfe> tested. The teltioq ,oilerl
Ince not Ce repedJCed, e.Cepl �n
lull, .ilhoul I. written opprorol of
Kutner old Hseeieles, SIC. Sr.N
Calselidafen tell;nQ pefforrned in
oecadtnce Lin ASTM D-4546
1
SAMPLE OF: Silty Sand
FROM: Pit 1 0 2'
WC = 3.2 %, DD = 98 pcf
1.0 APPLIED PRESSURE - KSF 10
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
100
18-7-532
H-PtiKUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 3
—6
z
0
1-
a
J —8
0
V)
z
0
—10
—12
—14
trete teat results copy PAII, CO Vitt
samaras tested The lest0h report
'holt not he reproduced, ss -sal m
fall. without the written approval of
Sumo. and Associates, Inc. Swell
Caneoydoilee ternTpe worried m
accardence we[h ASAH 0-4546.
SAMPLE OF: Silty Sand
FROM: Pit 2 0 2.5'
WC = 6.6 %, DD = 97 pcf
1.0 APPLIED PRESSURE - 10
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
100
18-7-532
H-PtiKUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 4
GRAVEL
FINE 1 COARSj
GRADATION TEST RESULTS
H -P- KUMAR
HYDROMETER ANALYSIS
SIEVE ANALYSIS
TINE READINGS
24 HRS 7 HRS /.� 40
100 i5 MIN 15 PAIN SOWN 19NIN 1PAIN IINN /200 1100 i „IR ___j. �._/,1,�lIZ.._�4——..?/01-.3�(
II fP
U.S. STANDARD SERIES CLEAR SQUARE QPSNINGS
90
T"
80
70
i 60
P. 50
8
IC
40
30
20
10
I
0 1 I 111 t 1 1 1 .1...1 111.L— 1_._L.A. 1111 —_J.. 1�._1j..u.iJ I._..1 t I .1.I.t11 1 too
.001 .002 .005 ,004 .019 .037 .075 .155 .300 i1 .600 1.16 212 .36 4.78 9 4 19 36.1 76.2 727 204,
152
DIAMETER OF PARTICLES IN MILLIMETERS
ii707.0.0
10
20
30
ro
30 S`
8
60
70
90
1
CLAY TO SILT
SAND
FINE
MEDIUM
COARSE
GRAVEL 18 %
LIQUID LIMIT
SAMPLE OF: Silty Gravelly Sand
SAND
49 %
PLASTICITY INDEX
SILT AND CLAY 33 %
FROM: Plt 2 0 4-5'
COBBLES
These 1651 results apply only to the
samples which were tested. The
Inslln5 report shall not be reproduced,
except In full, without the written
approval of Kumar & Associates, Inc.
Slave analysis texIing Is perfarmnd In
accordance with ASWM D422, ASTM C136
and/or ASTM D1140.
18-7-532
Fig. 5
PERCENT RETAINED
10
20
30
4U
50
60
70
60
90
100
.001
.002
.005 .009
.019
.045
.106 .025 .500 1.00 2.00
4.75 9.5 19.0 37.5 76.2 152 203
DIAMETER OF PARTICLES IN MILLIMETERS
CLAY I SILT
SWJ0
V. FINE FINE J ME[IRiM 1 COARSE 1V. COARSE
GRAVEL 23 % SAND 48 %
GRAVEL I
SMALL 1 MEDIUM 1 LARGE iE COBBLES
SILT 19 % CLAY 10 %
USDA SOIL TYPE: Gravelly Loamy Sand FROM: Profile Pit 1 @ 2-3'
100
90
80
70
GO
50
40
30
20
10
0
PERCENT PASSING
18-7-532
H-P%-KUMAR
USDA GRADATION TEST RESULTS
Fig. 6
'
HYDROMETER ANALYSIS J
SIEVE ANALYSIS1
TIME READINGS U.S. STANDARD SERIES CLEAR SOUAAE OPENINGS
14 HR. 7 H 1MIN.
5 MIN. 15 MIN. 56MIi1. MIN. 4 MK 4200 4100 #50 #30 416 #8 #4 3/8' 3/4' 1 l/2' 3' 5' 6' 8
/".............1
.
I
.002
.005 .009
.019
.045
.106 .025 .500 1.00 2.00
4.75 9.5 19.0 37.5 76.2 152 203
DIAMETER OF PARTICLES IN MILLIMETERS
CLAY I SILT
SWJ0
V. FINE FINE J ME[IRiM 1 COARSE 1V. COARSE
GRAVEL 23 % SAND 48 %
GRAVEL I
SMALL 1 MEDIUM 1 LARGE iE COBBLES
SILT 19 % CLAY 10 %
USDA SOIL TYPE: Gravelly Loamy Sand FROM: Profile Pit 1 @ 2-3'
100
90
80
70
GO
50
40
30
20
10
0
PERCENT PASSING
18-7-532
H-P%-KUMAR
USDA GRADATION TEST RESULTS
Fig. 6
PERCENT RETAINED
f
24H0.
045 AWL
10
20
30
40
50
60
70
80
90
HYDROMETER ANALYSIS
SIEVE ANALYSIS
TIME READINGS
7 HR
15 MN1. 61MN. f91AIN. 4 MIN.
U.S, STANDARD SERIES 1 CLEAR SQUARE OPENINGS
1 MIN.
#325 #140 #60 #35 #18
#10 #4 318' 3/4' 1 1 ? 3' 5' 6'
8" 100
100
.001
.002 .005 .009 .019 .045
CLAY SILT
.106 .025 .500 1.00 2.00 4.75 9.5 19.0 37.5 76.2 152 203
DIAMETER OF PARTICLES IN MILLIMETERS
SAND GRAVEL
V. FIRE FRJE M€OLIM i COARSE IV. COARSE SMALL MEDIUM LARGE
COBBLES
GRAVEL 51 % SAND 38 %
SILT 8 % CLAY 3 %
USDA SOIL TYPE: Very Gravelly Sand FROM: Profile Pit 2 @ 3-4'
90
60
70
60
50
40
30
20
10
0
PERCENT PASSING
18-7-532
H-PMKIJMAR
USDA GRADATION TEST RESULTS
Fig. 7
H-P�KUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
SAMPLE LOCATION
PIT
1
2
Profile
Pit 1
DEPTH
(ft)
2
6
2'/2
4-5
2-3
NATURAL
MOISTURE
CONTENT
(%)
3.2
6.9
6.6
9.5
NATURAL
DRY
DENSITY
(pcf)
98
89
97
Project No.18-7-532
GRADATION
GRAVEL
(%)
18
SAND
(%)
49
PERCENT
PASSING
NO. 200
SIEVE
18
33
Profile
Pit 2
3-4
USDA SOIL TEXTURE
GRAVEL
(%)
SAND
(%)
SILT
(%)
CLAY
(%)
23
48
19
10
51
38
8
3
SOIL TYPE
Silty Sand
Silty Sand
Silty Sand
Silty Gravelly Sand
Gravelly Loamy Sand
Very Gravelly Sand
JI1,7d/....IN
TABLE 2
PERCOLATION TEST RESULTS
PROJECT Nn 11:1_7_5R9
HOLE NO.
Perc 1
HOLE
DEPTH
(INCHES)
Perc 2
Perc 3
32
311/2
28
LENGTH OF
INTERVAL
(MIN)
10
10
10
WATER WATER DROP IN
DEPTH AT DEPTH AT WATER
START OF END OF LEVEL
INTERVAL INTERVAL (INCHES)
(INCHES) (INCHES)
5
AVERAGE
PERCOLATION
RATE
(MIN./INCH)
41/2
1/2
41/2
41/8
41/
33/4
3%
31/2
1/4
31/2
31/4
31/4
3
1/4
1/4
Water added
5
41/2
1/2
41/2
41/
41/
3'/8
1/4
3'/3
35/
1/4
35/
31/4
3
31/4
5
3
41/4
1/4
3/4
41/4
35/
5/5
3%
3%3
1/2
53/4
53/8
'
5'
43/4
43/4
5/8
41/4
1/2
40
34
20
Note: Percolation test holes were hand dug in the bottom of backhoe pits. Percolation
tests were conducted on September 4, 2018. The average percolation rates
were based on the last three readings of each test.