HomeMy WebLinkAboutSoils Report for Foundation and OWTS Design 01.05.2018H-P�KUMAR
Geotechnical Engineering I 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
January 5, 2018
Deanna Spracher & Ryan Beringer
2607 Woodberry Drive
Glenwood Springs, Colorado 81601
doanna@ dofianccgym,co
tyan.bcringg__.@yahrso.com
r@Yahrso.cnm
Project No.17-7-826
Subject: Subsoil Study for Foundation Design and Septic Disposal Area Profile Pits,
Proposed Residence, Parcel C, Homestead Estates, Stoner Valley Road, Garfield
County, Colorado
Dear Deanna and Ryan:
As requested, H-P/Kumar performed a subsoil study for foundation design at the subject site.
The study was conducted in accordance with nnr agreement for geotechnical engineering
services to you dated November 13, 2017. The data obtained and our findings and
recommendations based on the proposed construction and subsurface conditions encountered arc
presented in this report. Evaluation of potential geologic hazard impacts on the site are beyond
the scope of this study.
Proposed Construction: The proposed residence will be a 1 and 2 -story structure with a
walkout lower level and attached garage located on the site as shown on Figure 1. Ground floors
are proposed to be slab -on -grade. Cut depths are expected to range between about 3 to 8 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
to the west of the residence.
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 building site was vacant and accessed with a rough cut driveway at the
time of our field exploration. The ground surface is moderately sloping down to the west with
about 10 feet of elevation difference across the building site. Vegetation consists of scrub oak,
-2 -
sage brash, grass and weeds. Basalt boulders are exposed on the ground surface in the southwest
part of the building area.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating 2
exploratory pits in the building area and 2 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 typically 2 to 4 feet of topsoil, consist of slightly sandy to sandy,
blocky clay at Pit 1 and basalt gravel, cobbles and boulders in a sandy clay matrix at the other
pits. Below about one foot of gravel and cobble soils at Profile Pit 2, the blocky clay was
encountred to the pit depth of 8 feet. Results of swell -consolidation testing performed on
relatively undisturbed samples of the clay soils, presented on Figures 4 and 5, indicate low
compressibility under existing low moisture conditions and light loading and a low to moderate
expansion potential when wetted. Results of gradation analyses performed on samples of the
gravel soils (minus 5 -inch fraction) obtained from the pits are presented on Figures 6 and 7. The
laboratory test results are sununarized 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:
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 basalt gravel, cobble and boulder soil designed for an
allowable soil bearing pressure of 2,000 psf for support of the proposed residence. The clay soils
tend to expand after wetting which could result in excessive post -construction foundation
movement and should be removed from beneath footing and floor slab areas. Footings should be
a minimum width of 16 inches for continuous walls and 2 feet for columns. The topsoil, clay
soils and 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 basalt
rock soils. The exposed soils should be observed by us prior to footing construction for bearing
conditions. Structural fill placed to reestablish design bearing level (such as in the garage area)
should consist of imported granular soil such as road base compacted to at least 98% of standard
Proctor density at near optimum moisture content. 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 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 50 pcf for the
-3 -
on -site granular soil or imported road base as backfill. A sliding coefficient of 0.45 and
equivalent fluid unit weight, passive earth pressure of 350 pcf can be used to resist lateral
loading on foundation walls.
Floor Slabs: The natural on-site basalt rock soils are suitable to support lightly loaded slab -on -
grade construction.
The topsoil and blocky clay soils should be removed from beneath floor slab
areas due to potential for excessive slab movement. We should evaluate the exposed subgrade
conditions for expansive clay soils and needed areas of sub -excavation. 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 he 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
onsite basalt rock soils devoid of vegetation, topsoil and oversized rock or imported granular
soils such as road base.
Underdrain System:
Although free water was not encountered during our exploration, it has
been our experience in mountainous areas and where there are clay soils that local perched
groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground
during spring runoff can 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.
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.
-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 should be covered with filter fabric and 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.
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.
Profile Pits: Two profile pits were dug in the general proposed septic disposal area at the
locations shown on Figure 1. The subsurface profiles encountered in the pits, as shown on
Figure 2, were variable and below the topsoil consist of mainly basalt gravel, cobbles and
boulders in Profile Pit 1 and blocky, slightly sand clay in Profile Pit 2. Based on the subsurface
conditions encountered, we expect the area of Profile Pit 1 and the basalt rock soils will 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
H-PvKUMAR
Prnio,t Nn 17_7_fl')
-5 -
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 hearing 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 KU MAR
Steven L. Pawlak, 1'E.' tl
SLP/kac
h
1 222 14 frh
Attachments: Figure 1 — ty ":a���` �, xi�rator p y
Pits
Figure 2 — Logs of Exploratory Pits
Figure 3 — Legend and Notes
Figures 4 and 5 — Swell -Consolidation Test Results
Figures 6 and 7 — Gradation Test Results
Table 1 — Summary of Laboratory Test Results
1
H-P1KUMAR
Prniprt Nn 17-7-R9e
PARCEL C
HOMESTEAD ESTATES
'confirm easement in
fitlework (and with county)
to determine if it can be
relocated?
1
1
1
1
PROFILE PIT 2
■ 1
soil test
!matan #3
(septic
loction)
proposed septic
roc lion, to be
conti ed by dollar
PROFILE PIT 1
20 0 20 40
APPROXIMATE SCALE -FEET
17-7-826
70'-5"
H-P%KUMAR
_ buildino envelope
rough driveway
alignment shown
(to be designed /
graded by civil)
entry porch
f
df
% ^ I
eutocourl
'` (lobe designed 1
;y by civil)
I
turn
around
1
arch elev 100'0" = attached FIT 1— _ 52'11"-
civil elev -7550'0" 2 -car
10 be adjusted w/civil garagey, sails test 1
!n of jlocation #1 :�
1 deck
!
Et:
building envelope / property line
115'-"
f
I
J
1
12
LOCATION OF EXPLORATORY PITS
p1
cc
p1
a
Fig. 1
1-
L.1.1
w
o_
w
0
-5
PIT 1
EL. 7551'
WC=10.7
DD=98
WC=11.9
DD=107
PIT 2
EL. 7540'
WC=12.9
DD=103
+4=67
-200=13
PROFILE PIT 1
EL. 7525'
PROFILE PIT 2
EL. 7522'
- GRAVEL=63
- I SAND=16
SILT=14
CLAY=7
WC=22.3
-200=98
0-
5--
10 10
17-7-826
H-PtiKUMAR
LOGS OF EXPLORATORY PITS
DEPTH -FEET
Fig. 2
LEGEND
TOPSOIL; ORGANIC SANDY SILT AND CLAY, SCATTERED GRAVEL, FIRM, MOIST, DARK BROWN_
CLAY (CL); SLIGHTLY SANDY TO SANDY, SCATTERED GRAVEL, VERY STIFF, SLIGHTLY MOIST TO
MOIST, BROWN, MEDIUM PLASTICITY, CLAY LOAM, BLOCKY.
�, GRAVEL AND COBBLES (GC); SANDY CLAY MATRIX, BOULDERS, MEDIUM DENSE/VERY STIFF,
SLIGHTLY MOIST, MIXED BROWN, GRAVELLY SANDY LOAM.
v _ _
SI HAND DRIVEN 2—INCH DIAMETER LINER SAMPLE.
DISTURBED BULK SAMPLE.
t PRACTICAL DIGGING REFUSAL ON BOULDERS.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON DECEMBER 7, 2017.
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 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);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
—200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM 0 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
17-7-826
H-PtiKUMAR
LEGEND AND NOTES
Fig. 3
1.1/+a:ew1 .—
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
2
—1
— 2
—3
— 4
SAMPLE OF: Sandy Silty Clay
FROM: Pit 1 ® 4'
WC = 10.7 %, DD = 98 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
1.0 APPLIED PRESSURE — KSF
1I.,. 1ni f1Wt. Op* �n17 I tm
.0luq. rl0lhI w1.l110
tin mNA. .I*nv,,e.u,lylc.mt
.0nr...1 .I
umar .n0 K+x M.f, Inc, S.rn
CKaNd.lan M°1- bmxd in
uea.00 • i+n .SrS.
10 100
SAMPLE OF: Sandy Clay
FROM: Pit 1 @ 5.5'
WC = 11.9 %, DD = 107 pcf
1.0 APPLIED PRESSURE — KSF 10
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
100
17-7-826
H-PtiKUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 4
4
1
ae
SAMPLE OF: Sandy Clay Matrix
FROM: Pit 2 ® 1.5'
WC = 12.99 %, DD = 103 pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
—2
J
O
Z
O
U
n..HH usl a.. dI lamp, *67 to I d
.cmma. trend. D.. Iral:ri
11a0 nal IN r.p o&arAd, .cyI In
V/. vd.eul lav .nl4n 'aym..prpl 01
Nwner pip A..ocel.o. Po S..11
Cer006 0Gen taal+qq prleran.d in
eCCerpenc..Oh ASTM O -♦y.6.
17-7-826
1.0 APPLIED PRESSURE - KSF
H-PtiKiJMAR
5
SWELL—CONSOLIDATION TEST RESULTS
100
Fig. 5
HYDROMETER
24 NRS 7 NRS
at_rli.14l_14wN
•
ANALYSIS
TIME READINGS
tYIN \NL_ 14131_,300
- [— _ _
U.S.
1 WO I
_ _
STANDARD
o /top fp
_
SERIES
ILS
— .
SIEVE ANALYSIS
IT Ie 1
CLEAR SQUARE OPENINGS
3 " 4" J 1/3" �• d•0
100
00
- -
- - ---
-T
ii
:
t•
t.
eo
-
-
-
—
I
T
I
--7-"-•
L
10
70
_•
f
3 :
..t �..
l
1
L
..
._
�
--
zD
60
-
1
t'
1
I
!
1
y30
SG
1
-1
----r-r
I
- -
1
i
I
40
----
.:I--
1�
—
-
..k
30
-
-
_r
i
1
E.
t
-.
-
1
E
}
-
70
-
-
- --
-
T.
eD
lo
o
.001
202
..!- :[_-,_!.i I
.003 .006
1' ,1
,010
'1',1'
.037
1 11.111
.075
DIAMETER
.100
1
.300.475.000
OF PARTICLES
-1
TIT LI,
Tr
1,
IN MILLIMETERS
1'
I
e Z G
r I _1•. -TTI TT
,30 4.75 0
rt
5 10
1
3e.T
1, T 1 1.71.1...L:-_-
70.2
.1.._
--1-
177
152
200
BO
100
CLAY TO SILT
SAND
GRAVEL
FINE MEDIUM COARSE
FINE
COBBLES
i
...1::)A.1
GRAVEL 67 M SAND 20 % SILT AND CLAY 13 %
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Clayey Sandy Gravel with Cobbles FROM: Pit 2 0 2-3'
These test results apply only to the
samples which were tested. The
healing report shall not be reproduced,
except In full, without the written
approval of Kumar & Associates, Inc.
Store anolysle testing Is performed In
occordancs with ASTM 0422, ASTM C136
and/or ASTu 01140.
17-7-826
H-PtiKUMAR
GRADATION TEST RESULTS
Fig. 6
HYDROMETER ANALYSIS
SIEVE ANALYSIS
21
TIME READINGS
HR 7HA
EMT,- E31,11' MY 4765—"—
srul
*325
U.S. STANDARD SERIES I CLEAR SQUARE UPENINUS
e1 0 f60 035 010 0ID k4 3,R' 3144 11x6' 3 5'6' 6'
OESL00I
400
10
90
PERCENT RETAINED
o p O V O 0 v� 0
0
Q NJ Lr.
O C 0 O C @ 0 U
PERCENT PASSING
��
—
— f
—_
"'
--
_-4-
—
_y
-
—
—
— —
—4
I loll
001 002
005 .009 019 045 106 025 500 1 00 200
DIAMETER OF PARTICLES IN MILLIMETERS
4.75
9
5 19.0
37
5 76
2
152 203
CLAY
Dia
51L 1
_ V. FIY:£ T f•IM1 fA�L11EIM C07ASE I7- co r -t R...41. 1 11EAllMRi f LAME
cone is
GRAVEL 63 % SAND 16 % SILT 14 % CLAY 7 %
USDA SOIL TYPE: Gravelly Sandy Loam FROM: Profile Pit 1 @ 3-4'
17-7-826
H-P%KUMAR
USDA GRADATION TEST RESULTS
Fig. 7
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 17-7-826
SAMPLE LOCATION
j NATURAL NATURAL
1 MOISTURE DRY
I CONTENT DENSITY
I
(%) (pet)
GRADATION
PERCENT
PASSING
NO. 200
SIEVE
USDA SOIL TEXTURE
SOIL TYPE
PIT DEPTH
I
(ft)
GRAVEL SAND
(%) (%)
GRAVEL SAND
(%) 1 (%)
SILT CLAY
(%) (%)
1
4
10.17
98
Sandy Silty Clay
5'/2
11.9
107
Sandy Clay
I
2
11/2
12.9
103
Sandy Clay Matrix
2-3
67
20
13
Clayey Sandy Gravel
with Cobbles
Profile
Pit 1
3-4
63
16
14
7
Gravelly Sandy Loam
Profile 5-5'h
Pit 2
22.3
98
Clay
1