HomeMy WebLinkAboutSoils Report for Foundation Design & Perc Test 02.13.2017H-PKUMAR
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
February 13, 2017
Heidi Beattie
109 Valley Court
Basalt, Colorado 81621-7303
(lhcidi.beattic@ 2111ilil.rnin)
Office Locations: Parker, Glenwood Springs, and Summit County, Colorado
ECE!V:
JUL 17 2017
GARFIEL.D COUNTY
)MMUNtfY DEVELOPMENT
Project No.17-7-147
Subject: Subsoil Study for Foundation Design and Percolation Test, Proposed Residence,
Lot 22, Callicotte Ranch, Garfield County, Colorado
Dear Ms. Beattie:
As requested, H-P/Kumar performed a subsoil study and percolation test for foundation and
septic disposal designs at the subject site. The study was conducted in accordance with our
proposal for geotechnical engineering services to you dated January 25, 2017. The data obtained
and our recommendations based on the proposed construction and subsurface conditions
encountered are presented in this report. Hepworth-Pawlak Geotechnical, Inc. (now H-P/Kumar)
previously performed a preliminary geotechnical study for Callicotte Ranch and reported their
findings April 19, 2002, Job No. 101 821.
Proposed Construction: The proposed residence will be one and two story wood frame
construction above a crawlspace or basement and with an attached garage. The house will be
located on the site as shown on Figure 1. Garage and basement floors will be slab -on -grade. Cut
depths are expected to range between about 3 to 6 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 downhill and southeast of the house.
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 property was vacant and snow cover was about 18 inches at the time of
our field exploration. Vegetation consists of pinion and juniper forest in the western portion of
the lot and scattered sage brush, grass and weeds in the eastern and southern part of the lot. The
ground surface slopes down to the southeast at a grade of 15 to 20 percent in the building area
-2 -
and becomes less steep below. A natural drainage swale is located below the septic disposal
area.
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 one foot of topsoil, consist of one to three feet of sandy silty
clay overlying basalt cobbles and boulders in sand, silt and clay matrix. Results of swell -
consolidation testing performed on a relatively undisturbed sample of the matrix soils, presented
on Figure 3, indicate low compressibility under existing moisture conditions and light loading
and a low collapse potential (settlement under constant load) when wetted. The sample was
moderately compressible under increased Ioading after wetting. Results of a gradation analysis
performed on a sample of silty sandy gravel with cobbles (minus 5 inch fraction) obtained from
the site are presented on Figure 4. The laboratory test results are summarized in Table I. No free
water was observed in the pits at the time of excavation and the soils were slightly moist to
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 granular basalt rock soil designed for an allowable soil bearing
pressure of 2,000 psf for support of the proposed residence. The matrix 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 sandy silty clay encountered at the foundation bearing level within the
excavation should be removed and the footing bearing level extended down to the undisturbed
natural granular basalt soils. It is our experience in the basalt rock soils that a conventional large
excavator can dig about 2 feet deeper in a house excavation than the refusal depths encountered
in our pits. Deeper excavations and narrow utility trench excavations may require rock
excavation techniques such as chipping or blasting. Exterior footings should be provided with
adequate cover above their bearing elevations for frost protection. Placement of footings at least
Continuous foundation walls
should be reinforced top and bottom to span local anomalies such as by assuming an unsupported
length of at least 10 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.
42 inches below the exterior grade is typically used in this area.
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
H-PKUMAR
Project No 17.7-147
-3 -
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 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 in mountainous areas 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,
basements 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 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 I'/z feet deep.
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
inches in the first 10 feet in pavement and walkway areas. A swale may be
needed uphill to direct surface runoff around the residence.
Surface Drainage:
H-P'KUMAR Project No 17-7-147
-4-
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 5
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: The soil texture and structure conditions in the proposed septic disposal
area were evaluated by excavating two profile pits at the approximate locations shown on Figure
1 and performing percolation testing. The logs of the profile pits are presented on Figure 2. The
subsoils encountered consist of topsoil and sandy silty clay overlying basalt cobbles and boulders
in a sand, silt and clay matrix. The upper two feet of the granular soil contained less cobbles and
boulders. Results of a USDA gradation analysis performed on a sample of gravelly loamy sand
with cobbles (minus 5 inch fraction) obtained from the site are presented on Figure 5. The soil
type based on gradation analysis is 0 due to the rock content. No free water or evidence of
seasonal perched water was observed in the pits at the time of excavation and the soils were
slightly moist to moist.
Percolation tests were conducted on February 1, 2017 to further evaluate the feasibility of an
infiltration septic disposal system at the site. Three percolation holes were dug at the locations
shown on Figure 1. Test holes 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. The tests were conducted in the granular soils below the
topsoil and sandy silty clay soils. The percolation test results are presented in Table 2. Based on
the subsurface conditions encountered in the profile pits and the percolation test results, the
tested area and subsoils should be suitable for a 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,
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-PkKUMAR Protect No 17-7-147
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,
H -P; KUMAR
Louis Eller
Reviewed by:
L2—
Daniel
E. Hardin, P.E.
LEE/ksw
attachments Figure 1 — Location of Exploratory Pits and Percolation Test Holes
Figure 2 — Logs of Exploratory Pits
Figure 3 - Swell -Consolidation Test Results
Figure 4 — Gradation Test Results
Figure 5 — USDA Gradation Test Results
Table 1— Summary of Laboratory Test Results
Table 2 — Summary of Percolation Test Results
cc: DGP Structural - Don Pettygrove brL' .l1dn.nel)
H-PkKUMAR Project No. 17-7-147
r
�," BUILDING SETBACK LINE
0c)
•' ra
-%%
r
11
111� PROPOSED RESIDENCE
PIT 1 i I •
PIT 2
25 Q 25 50
APPROXIMATE SCALE -FEET
17-7-147
4
It
P 1 ;
PROFILE • 0 P 2
PIT 1 A Q 3ti
PROFILE r`I
ei
PIT 2
1
H -P K JMAR
�o
co
LOCATION OF EXPLORATORY PITS
1I
Fig. 1
X
0
— O
— 5
— 10
PIT 1
EL. 6688'
PIT 2
EL. 6684'
PROFILE PIT 1 PROFILE PIT 2
EL. 6679' EL. 6676'
z, WC=1 Q.4
D0=77
—200=29
+4=55 GRAVEL=53
—200=24 SAND=32
SILT=13
CLAY=2
0--
5 —
10 --
LEGEND
EJ TOPSOIL; ORGANIC SANDY SILT AND CLAY, WITH COBBLES AND BOULDERS IN BUILDING AREA,
..1 FIRM, MOIST, DARK BROW.
(CL); SANDY, SILTY, STIFF, SLIGHTLY MOIST, REDDISH BROWN.
f771CLAY
BASALT COBBLES AND BOULDERS (GM); IN A SAND, SILT AND CLAY MATRIX, DENSE,
SLIGHTLY MOIST, LIGHT BROWN, CALCAREOUS. UPPER 1' TO 2' LESS ROCKY IN PROFILE PITS.
HAND DRIVEN LINER SAMPLE.
DISTURBED BULK SAMPLE.
t PRACTICAL DIGGING REFUSAL.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON FEBRUARY 1, 2017.
2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SHOWN ON THE SITE PLAN PROVIDED AND GPS.
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 EXCAVATING. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (X) (ASTM D 2216);
DD = DRY DENSITY (pcf) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM
—200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM
Gravel = Percent retained on No. 10 Sieve
Sand = Percent passing No. 10 sieve and retained
Silt = Percent passing No. 325 sieve to particle
Cloy = Percent smaller than particle size .002mm
D 422);
D 1140);
on No. 325 sieve
size .002mm
17-7-147
H -P KUMAR
LOGS OF EXPLORATORY PITS
Fig. 2
CONSOLIDATION - SWELL
1
0
— 2
— 3
—4
— 5
— 6
twig ZTS I cn7 w IN
wv1,f 1..1M. SM S..1M1 atrI
*WI rgrl 1. .,.d. WW1 h
R4 MlTM L 41414 , .1py.p
dvrq W 4«.44w 6, 3.611
W.*ds 1 .mri h
s 1. rM ASSY 9-Wi.
SAMPLE OF: Calcareous Silty Clayey Sand
(matrix)
FROM: Boring 2 0 2'
WC = 10.4X, DD = 77 pcf
—200 = 29%
COMPRESSION UNDER
CONSTANT PRESSURE UPON
WETTING
17-7-147
10 APPLIED PRESSURE - I<SF
H -P- KUMAR
10
SWELL -CONSOLIDATION TEST RESULT
X00
Fig. 3
A
50
100
O 0
60
70
B O
.0
30
20
t0
a
17-7-147
GRAVEL 55 7:
LIQUID LIMIT
SAMPLE OF: SI►iy Sandy Gravel with Cobbles
SAND 21 %
H -P I(UMAR
PLASTICITY INDEX
SILT AND CLAY 24 %
FROM; Baring 2 0 3-3.5'
10
20
20
'0
30
e0
70
60
ID
100
Masa Nil results apply only to inn
4nmplft which wort 14114d. the
14,04,0 .4p60 14011 nal 66 r.produe•d,
e.71 In lull, wilhoul Ihs wrlll.n
appr0rol 01 Numor i Assoclabs, Int
Slsn nnory10 1.111100 11 puler/n.1.1 In
ac20rdcn r• with AS711 D022, 4574 0136
and/or ASTM 01140.
GRADATION TEST RESULTS
Fig. 4
HYDROMETER ANALYSIS
SrCVE ANALYSIS
14 HAS 7 Hoy
23 u10 H 074
74.0 0E,0011003
1041/ 14010 412!0
1011
/100
►100
0.3- 50203000 1[111[5
en* e00 /30 ale ■+tl et 20
3/j'
C0101 300091 oritimo5
3/.' 1 1/7' 3"
1 1 LI 1 1 1
1
I I/
1- t 1
r 1 I IIS t 1
1
1 !_l 1
l' 1 11
I 1 1 t
01 .1107
.1100 .000 .01*
.037
.010 .120
DIAMETER OF
.700 .000 1.10 2.30 a 72
.213 2.3
PARTICLES IN MILLIMETERS
0.3
19 32.1
76.7 171 20
152
CLAY TO SILT
SAND
GRAVEL
FINE
L MEDIUM 1COAFISE
FINE
I COARSE
COBBLES
17-7-147
GRAVEL 55 7:
LIQUID LIMIT
SAMPLE OF: SI►iy Sandy Gravel with Cobbles
SAND 21 %
H -P I(UMAR
PLASTICITY INDEX
SILT AND CLAY 24 %
FROM; Baring 2 0 3-3.5'
10
20
20
'0
30
e0
70
60
ID
100
Masa Nil results apply only to inn
4nmplft which wort 14114d. the
14,04,0 .4p60 14011 nal 66 r.produe•d,
e.71 In lull, wilhoul Ihs wrlll.n
appr0rol 01 Numor i Assoclabs, Int
Slsn nnory10 1.111100 11 puler/n.1.1 In
ac20rdcn r• with AS711 D022, 4574 0136
and/or ASTM 01140.
GRADATION TEST RESULTS
Fig. 4
414:014ZliziakflillA
HYDROMETER ANALYSIS J
2pqq��{{RR� m TIME READINGS {
0 45 MIM.15 MIN, 60MIN19MEN.4 MIN.1 MI#.
-
10
20
30
40
50
60
70
80
100
-
lllllllllllllll�-�
SIEVE ANALYSIS
U.S. STANDARD SERIES 1 CLEAR SQUARE OPENINGS
325 #140 #60 #35 018 #10 _ #4 3/e. 3f4' 1 1/T 3' 5R6' 6. 100
IrME
I�Wan
MEI
IM
NNW
INi!
up=1111/17m M.=
INEWMMim
ISI riffiat�s
■"Z'%"'a �Tis�"
r i
R �
wife
1111.011M1•11
1..M.--
S�
-;
-
I�r
.001 -002 .005 .009 .019 :045
90
80
70
60
50
4o
30
2D
10
.106 .025 500 1.00 200 4,75 9 5 190 37 5 _ 76.2 152 203
DIAMETER OF PARTICLES IN MIWMETERS
air J SL=
17-7-147
SAM
V FTlF I Fu.=. 1 KERN. ICnwcse 1' Cour .
S�fALt 1 !Ji -n 'PGF.
COBBLES 33 % GRAVEL 34 %
SILT 13 %
USDA SOIL TYPE: Gravelly Loamy Sand with Cobbles
H-P---k4KUMAR
ocaus
SAND 18 %
CLAY 2 %
FROM: Profile Pit 1 @ 3-4'
USDA GRADATION TEST RESULTS
Fig. 5
H-PKUMAR
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 17-7-147
SAMPLE LOCATION
NATURAL
MOISTURE
CONTENT
(%)J
NATURAL
DRY
DENSITY
(pcf)
GRADATION
PERCENT
PASSING
NO. 200
SIEVE
USDA SOIL TEXTURE
SOIL TYPE
PIT
DEPTH
(ft)
GRAVEL
(%)
SAND
(%)
GRAVEL.
And
COBBLES
(%)
SAND
(1)
SILT
(%)
CLAY
(%)
2
2
10.4
77
29
Calcareous Silty Clayey
Sand (matrix)
3 to 31/2
55
21
24
Silty Sandy Gravel with
Cobbles
Profile
Pit 1
3 to 4
4
67
18
13
2
Gravelly Loamy Sand with
Cobbles
HOLE
NO.
P1
HOLE
DEPTH
(INCHES)
57
P2
P3
52
40
LENGTI
INTER
(MIN
15
Water A
Water A
15
Water A
15
Water A
Water A
Water A
H-P�INMAR
TABLE 2
PERCOLATION TEST RESULTS
PROJECT NO. 17-7-147
t OF
IAL i
WATER
DEPTH AT
START OF
INTERVAL
(INCHES)
WATER
DEPTH AT
END OF
INTERVAL
(INCHES)
DROP IN
WATER
LEVEL
(INCHES)
AVERAGE
PERCOLATION
RATE
(MIN./INCH)
1511
ided
ided
61/2
53/4
'/4
714
53/4
112
8
6'/4
11/4
6'/4
534
1
53/4
43/4
1
4%
3%
1
ided
5'/a
5
1/x
3011
5
412
1/2
412
4
12
5%
5
'/4
5
4%
1/4
4%
4
'4
ided
ided
ided
6
5
1
30/1
7
51/2
1%
71/2
51/2
2
61/2
5'/4
'/4
5%
514
12
5%
43/4
1/2
Note: Percolation test holes were hand dug in the bottom of backhoe pits and soaked
on January 31, 2017. Percolation tests were conducted on February 1, 2017.
The average percolation rates were based on the last two readings of each test.