HomeMy WebLinkAboutSubsoils Report for Foundation DesignI(tA$#r;lflffi:ruHi'ifd-*
An Employoc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kunarusa.com
Olfice Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Sumrnit County, Colorado
March 14,2A25
Danae Morris
6601 214 Road
New Castle, Colorado 81647
danaemorris@ gmail. com
Project No. 25-7- 169
Subject: Subsoil Study for Foundation Design, Proposed Residence,0083 County Road
105, Garfield County, Colorado
Dear Danae:
As requested, Kumar & Associates, Inc. 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 you revised March 4"2A25. 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 wilt be single-story manufactured home
located on the site roughly as shown on Figure l. Ground floor will be structural over
crawlspace. Cut depths are expected to range between about 1 to 5 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 fbundation loadings are significantly different frorn those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The subject site was developed with two existing modular residences and a
third modular residence that was removed from the site before our field exploration. Utilities
and a septic system were present on the site but had been disconnected. The ground surface was
moderately sloping down to the south/southwest at grades estimated at between 5 to l0 percent.
Vegetation consists of pinon and juniper trees, sagebrush and grass. Basalt boulders and cobbles
were observed on the surface of the site.
Subsnrfnce Conditions: The subsurfbce conditions at the site were evaluated by excavating two
exploratory pits at the approxirnate locations shown on Figlrre 1. The logs of'the pits are
presented on Figure 2. The subsoils encountered, below about i foot of topsoil, consist of
medium dense to dense" silty sandy gravel with cobbles down to the maximum explored depth of
9 feet. Results of'swell-consolidatron testing perfbrmed on a relatively undisturbeci sampie of
the siiry sanci rnatnx, presented ori i;igure 3, rnclicate ir:w ccrnpressibiiity under light loading and
-2-
moderate compressibility under increased conditions of loading and wetting. Results of
gradation analyses performed on a sample of the coarse granular soils (minus 3-inch fraction)
obtained from the site are presented on Figures 4 and 5. 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 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 l6 inches for continuous walls and2 feet fbr columns. Loose disturbed soils and
existing fill encountered at the foundation bearing level within the excavation should be removed
and the footing bearing level extended down to the undisturbed natural soils. 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 shor"rld 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, 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 controljoints 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 rnaterial 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 tbr support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture ccntent 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 the area that [oca[ perched groundwater can develop during times of
heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched
ccndition. We recommend below-grade construction, such as retaining walls, crawlspace areas
deeper than about 4 feet and basement areas, be protected from wetting and hydrostatic pressure
buildup by an underdrain system. The assumed slab-on-grade or shallow crawlspace foundation
should not require a foundation drain.
Kumar & Associates, lnc. o Proiect No. 25-7,169
-3-
If installed, the drains should consist of rigid perforated PVC drainpipe placed in the bottom of
the wall backfitl surrounded above the invert level with free-draining granular material. The
drain should be placed at each level of excavation and at least I foot below lowest adjacent finish
grade and sloped at a minirnum'/ra/a to a suitable gravity outlet, drywell or sump and pump
system. 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 lYzfeetdeep and covered with filter
fabric such as Mirafi l40N or 160N.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
I ) 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 6 inches in the first l0 feet in unpaved areas and a minimum slope of 3
inches in the first l0 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 inigation 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 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 tirne. 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 I
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
Kumar & Associates, lnc. @ Project No. 2$7-169
-4-
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are
not responsible for technical interpretations by others of our information. As the project evolves,
we should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verifu that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural frll by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfu lly Submitted,
Kumar & Associates, lnc.
James H. Parsons, P
Reviewed by:
b
Daniel E. Hardin, P.E.
JHP/kac
attachments Figure 1 - Location of Exploratory Pits
Figure 2 - Logs of Exploratory Pits
Figure 3 - Swell-Consolidation Test Results
Figure 4 and 5 - Gradation Test Results
Table I - Summary of Laboratory Test Results
Cc: David Mahovsky (pe:ad;liltev.$l{y(a}ql.Iyt_o_nlyrqtrs,c )
Kumar & Associates, lnc, @ Proiect No. 25-7-169
Parcel 2
2.63 Acres +
44.28'
PIT 2 qq;-o9q*\q
*\I
\
\'F 8,
,ob'
I \zi
-ro'lo
,
to?.
a
Septic
Tank uds
22.25',
G@ 0,
p-p*^}\ t
Tqk /
Wat€t
Spigot hop6{tu Tek
665$
$
Fen@
6649
\
\
""a
6ong
""",
tD
t
6647
ta" cMP
6646 Itrv.d644.75'&
66,{s
6644 R=212.21
18" cMP
Inv.-6642.5'
=198.00
&CH=190.90
APPROXIMATE SCALE-FEET
25-7- 1 69 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
E
Y]
ri
?
PIT 1
EL" 6654'
PIT 2
EL. 6652'
0 0
Flrjlrll+
I3Fo-
trJo
WC=9.4
+4=33*200=45 WC=.l0.5
DD=85
FLJ
tIJt!
I:cFo-
t4JA
5 5
WC=1 1.3
+4=1 1
-200=59
WC= 10.6
*4=4
-2AO=74
10 10
TOPSOIL; SAND, SILTY, SCATTERED GRAVEL, ORGANICS, BROWN' SLIGHTLY MOIST
GRAVEL WITH COBBLES (CM): SANDY, SILTY, SCATTERED SMALL BOULDERS, MEDIUM DENSE
TO DENSE, SLGIHTLY MOIST, LIGHT BROWN.
F
HAND DRIVE SAMPLE
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON MARCH 3, 2025.
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 OBIAINED BY INTERPOLATION BETWEEN
CONTOURS ON THE SITE PLAN PROVIDED.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY
TO THE DEGREE IMPLITD 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 EXCAVATION. PITS WERE
BACKFILLED SUBSEQUENT TO SAMPLING.
7. LABORATORY TEST RESULTS:
wc = WATER C0NTENT (%) (ASTM a 2216)z
DD = DRY DENSITY (PCt) (ASTU D 2216);
+4 = PERCENTAGE RETATNED ON NO. 4 SIEVE (ASTM D A22);
-200= PERCENTAGE PASSING No. 200 SIEVE (ASTM D 1140).
25-7- 1 69 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2
f
I
SAMPLE 0F: Grovelly Sondy Silt
FROM:Pit2@4'
WC = 10.5 %, DD = 83 pcf
of
|rc.
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1
A0N
j-1
lrJ
=tn
t_2
zotr
o
Jo
an
oc)-4
-5
-6
100t.0
25-7- 1 69 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 3
SIEVE ANALYSISHYDROMETER ANALYSIS
RSdXOS U.S. SI XOARD SEfrES CL€AR SQU^RE OPElrIilOs
100
90
ao
70
60
!o
iao
50
20
flRS
ulN
7 HRSt5 xrN ,t00 lqo a.c *so ,'t&tro t6 3/E"t/.:| /2'
Ig
a
IE
E
H
tO l
o:
.ool
I I rtt
.oos
t,l I r r I lr,l lJ-om .orc .oJ7 .o75
i
I.150
i
I l, I irlt.500 .e00
.124
PARTICLES IN
tt.l
M
IE 2.t5
2.0
{LLIMETERS
r.lrrlll1.73 9,5
,ft9 I .tta,I
t
ttl
76.2
oo
.oo2
D ETER OF
CLAY TO SILT COBBLES
ERAVEL 55 X SAND
LIQUID LIMIT
SAMPLE OFr Sondy Grovelly Sllt
22 t6
PLASTICITY INOEX
SILT ANO CLAY 15 %
FROM:PltlO2'-5'
N*E REAITNGS CLEAR SqUARE
HRS 7xrx ts
HRSrltN 60M!N lgraN IMIN flgq a{o fJo fto
Ia2
P
fr
E
Px
o, . r I I , I tl,l :l I it I I l'tll.oo1 .o02 .oo5 ,oot .olt .017 .o?5
ir
.600
lll r
t. tt ,I I,t rtrlt2.5G 1.75 9,5
2.O
LLIMETERS
:l I ,l I I I I I tt9 Jt.r 76,2 121
t00
200
.42!
PARTICLES
132
ETER OF IN MI
CLAY TO SILT COBBLES
GRAVEL 1I X SAND
LIQUID LIMIT
SAMPLE 0F: Grovally Sondy Silt
50 X SILT AND CLAY
PLASTICITY INDEX
FROM: Pit2O5.5'*6.5'
59X
Thr!. hll rcsull! Epply only lo fh.
sompl.r whlch wor. t.!hd. lha
b8llng r.porl lholl nol ba ruproduccd,
sxcapl ln full, wllhoul th. wrltl.tr
opprovol ol Kumor & Astoclobr, lnc.
SlGv! qnslyrh hlllng It porlomld ln
occordonc. rlth ASIM 06913, ASTM 0792E,
ASTM Ct56 ondlor ASTM 0llao.
GRAVELSAND
FINE COARSEFINEMEDTUM lCOanSe
HYDROMETER ANALYSIS SIEVE ANALYSIS
GRAVELSAND
COARSEFINEMEDTUM lCOanSr FINE
25-7- 1 69 Kumar & Associates GRADATION TEST RISULTS Fig. 4
€
I
E
E
too
ao
ao
70
co
!o
,.o
to
at
to
o
to
20
!o
art
50
ao
,o
to
90
too
fr
E
.a2!
OF
CLAY IO SILT COBBLES
CRAVEL 1
'(
LIQUID LIMIT
SAMPLE OF: Sondy Slll
SAND 22 X
PLASTICITY INDEX
SILT AND CU\Y 71 X
FROM:Pll 2O8'-9'
lhaa lilt rerullt opply only lo lh.
romplor rhloh w.ru l.rtrd. lhr
l.tllng r.porl rholl not b. nprcducrd.
.xaaDl ln lull, {llhoul lh. wrlll.n
opprovol ol Kumor ll Atroclolca' lnc,
Slav. onolyrb Ldlng lt p.rfom.d ln
mcordonc. trllh ASTII 06913. A.Sru 0792E,
ASil C136 ondlor ASt[a Dlt40.
HYDNOIiEIER ANALYSIS SIEVE ANALYSIS
u.s.
-t -
I
.-t.-
i
!
I
It'--'- -- -f
I I tlr I
SAND GRAVEL
FINE MEDTI M ICOARSE FINE COARSE
25-7- 1 69 Kumar & Associates GRADATION TEST RESULTS Fig. 5
t c't *ffi ifffif#n1r'{n;"'*
::
TABLE I
SUMMARY OF LABORATORY TEST RESULTS
Project llo,25.7.169
SAUPL LOCATION
NATURAL
MOISTURE
col{IENT
{%}
NAIURAL
DRY
DENSITY
{dll
GRAD toN
FERCEI{T
PASS||G NO.
200 stEvE
IT LIMTTS
UNCOI{RI{ED
C0iIFRESSIVE
SIRENGTH
lGfl
SOII IYPEPITDEPTH
aftt
GRAVEL
(%)
sAl'rD
{%t
LIOU|O Lllilll
t%t
PLASIIC
INDEX
pt"l
I 2-3 9.4 JJ 22 45 Sandy Gravelly Silt
2 4 r0.5 83
5%-6Y2 I 1.3 il 30 59 Gravelly Sandy Silt
8-9 r0.6 4 22 74 Sandy Silt