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IIEiPWo17IH-PAWLAK GEOTECHNICAL
November 29, 2006
Must: Architects
Attn: Dan Muse
46 Weant Boulevard
Carbondale, Colorado 81623
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Job No.106 0943
Subject: Subsoil Study for Foundation Design and Percolation 'Test, Proposed
I lewitt Guest House and Detached Garage, Lot 7. Roaring Fork Preserve,
Garfield County, Colorado.
Dear Mr. Muse:
As requested, 1•iepwortlt-Pawlak Geoteclhnicul, lac, 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 agreement far geotechnical engineering services to
Muse Architects dated November 1, 2006. The data obtained and our recommendations
based an the pmposcd construction and subsurface conditions encountered are presented
in ibis report. llepworih-Pawlak Geotechnical, inc. previously conducted a preliminary
gem -clinical study for the development and presentee] aur findings in a report dated
November 30, 2000, Job No. 100 627.
Proposed Construction: The proposed guest house and detached garage will be single
story wood frame stmentres located on the site as shown on Figure 1. Ground floors will
be structural over a crawlspace for the guest pause and stub-on•gradc in the garage. Cut
depths Are expected to be about 3 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 southwest of the structures.
if building conditions or foundation loadings arc significantly different from those
described above, we should be notified to re-evaluate the recommendations presented in
this report.
Site Condllione The site was vacant at the time of our field exploration. There are
shallow irrigation ditches across the site. Two deeper irrigation ditches are located to the
north of the guest house. The ground surface is relatively flat with a gentle slope down to
the northwest. Vegetation consists of grass and weals with cottonwood irces olnng the
larger ditches. Tim area of standing water shown on the site plan was not observed at the
time of our site visit an November 20, 2006.
Subsurface Conditions: The subsurface conditions at the site were evaluated by
excavating two exploratory pits in the building area and one profile pit in the septic
disposal arra at the approximate locations sltovn► on Figure 1. The logs of the pias fire
presented on Figure 2. Tlic subsoils encountered, below abaut 1 to I'A feet of topsoil,
Parker 303.841.7119 • Colorado Sennas 719.633.5562 • Silvcrthnme 970168 l 9b9
-2 -
generally consist or relatively dense, slightly silty sandy gravel with cobbles and small
boulders. About 1 h feet of medium dense, silty to very silty sand was encountered
between the topsoil area gravels in Pit 2. Po:sults or swell -consolidation testing performed
on a relatively undisturbed -tempts of the silt and sand soils, presented on Figure 3,
indicate low compressibility under existing moisture conditions and light loading and a
low to nwderatc collapse potential (settlement under constant load) when wetted. The
sample showed high comprossibility upon increased knitting after wetting. RcsuI1S of a
gradation analysis performed on a sample of the gravels (minus 5 inch fraction) obtained
from the site arc presented on Figure 4. The laboratory test results ore summarized in
Table 1. No free water was observed in the pits at the time of excavation and the soils
ware slightly moist to moist. A pit excavated on Lot 7 as part of the preliminary study
encountered similar soils to cite excavated depth of 6 fent and groundwater at a depth of
5V2 feet in August 2000.
Fouadatlan Bearing Conditions: Constructs on of the guest house and garage at the site
should be feasible based on gentecttnical considerations. The natural gravel alluvium sail
possesses moderate bearing capacity with a low risk of settlement and should be adequate
for support of the proposed building foundation.
Groundwater was observed in n pit excavated on lot as pari of the preliminary study at a
depth of S`'h feet below the existing ground surface- It has been our experience in the arca
that groundwater levels can rise during periods of seasonal runoff and heavy
precipitation. Cue to the relatively shallow groundwater conditions encountered in the
arca, crawlspacc arras should be relatively shallow and kept well ventilated. As an
alternative, a slab -on -grade floor could be considered to reduce the risk of having a wet
crawlspacc.
Foundation Recommenrlatiosun Considering the subsoil conditions encountered in the
exploratory pits and the mature of the prcnoscd construction, we recommend spread
footings placed on the undisturbed natural gravel soil designed for an allowable soil
caring pressure of 33 OO f for support of the proposrc�gucsl house an rEl ge. -The
upper silt and sated soils tend to compress after wetting and there could be some post-
construction foundation settlement. Footings should be a minimum width uf i 6 inches
for continuous walls and 2 feet for co(uxrtns. Silty sand and loose disturbed soils
cncauntc cJ ut the i'aundution fxas rig eve within the excavation should be removed and
the footing tearing level extended down to the undisturbed natural gravel soils. Voids
created by the removal of large rocks should be backfilled with compacted sand and
gravel or with concrete. 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 arca. Continuous foundation walls
should be reinforced top and bottom to span local anomalies such as by assuming an
unsupported length of at least ID feet. Foundation walls acting as retaining structures
should be designed to resist a lateral earth pressure based on an equivalent fluid unit
weights of at least 45 pef for the on-site soil, excluding vegetation, topsoil or oversized
rock, as backfill.
lob No.It)b owl
-3 -
door Stabs: 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 of ow 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 an experience and die intended
slab use. A layer of -1/4-inch screen rock could be placed below slabs -on -grade as a
leveling course.
All fill materials for support of floor slabs should be compacted to at least 95% of
maximum standard Proctor density ata moisture content near optimum, Required fill can
consist of the on-site gravel soils devoid of vegetation, topsoil and oversized rock.
Surface Drainage: The following drainage precautions should be observed during
construction and maintained nt all times idler the buildings have been completed
1) Inundation of the foundation excavations and understab 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.
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 10 feet in unpaved
areas and a minimum slope of 3 im.bes in the first 10 feet in pavement and
walkway omas.
4) Roof downspouts and drains should discharge well beyond the limits of all
bacltft11.
Percolation Testing: Percolation tests were conducted on November 21.2006 to
evaluate the fcnsibility of an infihrinion at septic
r ti locations shown l system
at Figuretasite The test fide it
and three percolation holes were dug
(nominal 12 inch diameter by 12 inch deep) were hand dug et 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 Pit drown on Figure 2 and
consist of about 11/2 feet of topsoil overlying slightly silty sandy gravel with cobbles and
small boulders to the pit depth of 8 feet. The percolation test results are presented in
Table 2. The percolation test results indicate infiltration rates between 3 and 5 minutes
per inch with an average of4 minutes per inch. Based on the subsurface conditions
encountered and the percolation test results, we recommend that a professional engineer
be engaged to design the infiltration septic disposal system.
Limitations: This study has been conducted in accordance with generally accepted
gcuteclmical engineering principles and practices in this arca at this time. We make no
wamutty 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 oI conSlrttCtion and our experience in
Job No.106 0943 G+ "
-4 -
the arca. Our services do not include determining the presence, prevention or possibility
❑fmold or other biological contaminants (MOI3C) developing in the future. if the client
is concerned about MODC, 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 mrd variations in the subsurface conditions
may not become evident until excavation is performed. If conditions encountered during
curistructIan appear different fmtn those described in this report, we should be notilcd al
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
or not responsible for technical interpretations by others of our information. M the
project evoive.s, we should provide continued consultation and field services during
construction to review and monitor the implementation of our recommendations, and to
verify that the recommendntians 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 n representative of the geotechnical
engineer.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
HEPWORTh - PAWLAK G_ .`��, t j :'' ; NC.
Reviewed by:
Daniel E. Hardin, P.E.
JZ.Nksw
atlnehMeniS 1Figute 1
Figure 2
Figure 3
Figure 4
Table l -
Tablc 2
- Location of Exploratory lits and 1'ercoluttvn fest I toles
Logs of Exploratory Pits
- Swell -Consolidation Test Results
Gradation Test Results
Summary of Laboratory Test Results
Percolation Test Results
cc: Ernest Kollar Engineers, Inc. - Attn: Ernie Kollar
Joh 14o.1O6494
106 0943
Gig:Reel f LOCATION OF EXPLORATORY PRS AND
PERCOLATION TEST HOLES
ilavpgnrrMlt.rrt C1
FIGURE 1
PO t
EL.EV.w 998'
—5
PIT 2
ELEV s 909'
WC'52
0093
2Mr50
PROFILE P17
ELEV 1001'
— 10
LEGEND:
TOPSOIL: sand! sot and day, arui roots, f m. moist, dark brown.
ElSAND ISM); silty to very silly, medium dense. slightly moist. Yght brawn.
i 44.411
J 200,2
5-
10
I3RAVELMD COBBLES (GP -GM): sandy, slightly silty, with small bauldere. dense. moist. Ohl brawn,
subnxrnded to rounded rocks.
2' Diameter hand drum finer sample.
_
Disturbed UUL sample.
a
NOTES:
1. Exploratory pits were excavated on November 20. 2006 with a Yanrnar kom was drawn on rhe site plan
2. Locations of meplora2o Y pts were measured eppreowrntaly by pacing
pro aide
5. Elevations d exploratory pits were obtained by interpolation between contours shown an the site plan provided.
Logs are drawn lo depth.
4. The ex ploraloly pit locations and elevations should be cnnsklefa d accurate only to the degree impieed by the method
used
5. The lire between eletf fWs shwa e]n Ute explareiery pit logs represent the approximate brafrrdnries between
- malarial types and eansibans may be gradual.
O. No tee water was encountered in Ora pts at the time of excavating. Fluctuation in Wier levet may occ rwilh lime.
T. Laboratory Tasting Reed
WC 01 Water Content (%
DO I- tory Density
+4 - Percent xotainnd cn the No. 4 gave
-200 M. t'eiC.enl passing No. 200 sieve
1060943 1---GettSWL.
n.
LOGS OF EXPLORATORY PITS 1 immure 2
ac 2
4
5
6
T
8
11
10
Moisture Content -1 5.2
Dry Renally In. 93
Sample 01: MI and Sand
Front Pi1 2 at 2ji Feat
GoolPress ur1
14P01'1
welling
l
{
1.0
APPUED PRESSURE -Id
10
i
T
1 1
100
106 0943 I
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IrrlMdl.+li w,wcao,,.cvil SWELL -CONSOLIDATION ZEST RESULTS
Figure 3
i6
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10
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ill %NC U 51AF1 W1 SF3i[':s 1 GttN MARE as
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is
OD
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- - errs 276 a.76 y$ 199 5r- 7112 1152 2172
.001 .007 g5 .077 1l9 1737 Z74 ,750 .263
OSMETEFI OF PAROCLEs 04 MILIJACIU07Gamma ,1:3=21=12=L
mrn
12,8
GRAVEL 76 %
UODUD LIMIT %
SAMPLE OF' Sandy Gravel wilts Cobbles
SAND 22 %
SILT AND CLAY 2 %
PLASTLCfY INDEX %
FROM: PLl 3 at d Feet
GRADATION TEST RESULTS
20
10
0
iFigur°
HEPWORTH-PAWLAK GEOTECHNICAL., INC.
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
300 No. 105 0943
S.MPLE LOCAflNATURAE. NATURAL ` . ON maga
MCIS9URE CRY GRAVEL SAND1N 5 C
PIT CUMCOMMIT 4B15i11r CV(%) LIMIT INCE(
STM
1 l%1 PS
R % I Silt and Sand
1 1 21 I 5.2 93 1.1111MEMMIIII
Profile 3 to 4 M
11.1111MMEMili°11111111111.111111
IM
MIIIIIMIIIIIIIIIIIIII
MIIIIININIMMINIIIIMMINIIII
1111•Mimumil......M.1.11.11.....iiiiiimilimm111111MIMIA
UNCONFINED
COMPRESSIVE
sori OR
NORCO:TYPE
Sandy Gravel with Cobbles