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March 18,2016
Clearwater Construction Management
Attn: Jason furthony
P.O. Box 6236
Snowmass Villagc, Colorado 81615
{ifl nthony @ ccr¡r{ssÊn.coml
Iob No.l 16 0664
Subject:Subsoil Study for Fbundation Desþ, Proposed Butter Residence, Lot 5,
Roaring Fork Prcservc, 6 Silver Spruce Drive, Garf¡eld Count5 Colorado
DearMr. Anthon¡
As requested, Hepworth-Pawlak Geotechnical,Inc, performed a subsoil study fordesign
of foundations at the subject site. The study was conducted in ¡ccordancc with our
agreement for geoæchnical cngincering serviccs to Clea¡watsr Construction Mamgement
date.d March 11,2016. The data obtained and our rocommcndations based on thc
proposed constn¡ctioû and subsurfacc conditions encountercd are presentÊd in this ¡eport,
Hepworth-Pawlak Gcotechnical, Inc. previously conducted a preliminary geotcchnical
study for the development and presentcd our findings in a rcport dated November 30,
2(X)0, Job No. Læ 627.
kopoæd Co¡utructlon: The propos€d residence will be one and two story wood frame
constrructiotr witb slab-on-grade floor and located on thc sitc as sbown on Fþre l. The
attached gar¡ge will also have a slab-on-gradc floor. Cut depths are expectcd to range
betwecn about 2ro3 feet. Foundation loadings for this typc of construction are assumed
to be rclatívcly light and tlpical of the proposed t¡rpe of consüuction.
If building conditions or foundation loadings are sígnificantly diffcrent from tbose
described abovo, we should be notiñed to re+valuate the recommcndations presentod in
this rcport
Site Conditlons¡ The lot is vacant and acccssed by an existing gravel drive. Thcrc was
about two inches of frcsh snow cover at the time of our field cxploratíon. Vcgetation
consi¡ts of grass and weeds. Prcvious trees $rere destroyed in a wildfirc in Apríl 2008.
Thc ground surface is relatively flat with a sligbt slopc down to thc soutt¡ and west. A¡r
abandoned inigation ditch is locaæd just north of the building site. An existing dry pond
is locatcd on thc south side of the building arca. Eagte Vallcy Evaporíte Formation is
exposed on thc hillside south of County Road 100.
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Subsurface Conditions¡ The subsurface conditions at the site werc evaluated by
excavating threc exploratory pits at the approxímatc locations shown on Figure l. The
logs of thc pits are presented on Figure 2. The subsoils cncountered, below about one
foot of topsoil, consist of siltysandy gravel with cobbles and small boulders. A thin silty
sand layer was cncountercd in Pits 2 and 3 betwcen the topsoil and gravel. Resuls of a
gradation analyses performed on a sample of silty sand and sandy gravel (minus 3-inch
fraction) obtained from the site are presentcd on Figures 2 and 3. No frec water was
observed in the pits at the timc of cxcavatíon and the soils were slightly moist to moist.
An exploratory pit dug on [¡t 5 in August, 2000 encountcred groundwater at a depth of 7
feet and groundwater level is generally known to bc seasonally shallow.
$ubsldentrPotentiak Bedrock of the Pcnnsylvanian age Eaglc VallcyEvaporite
underlies thc Roaring Fork Preservo Subdivision. These rocks arË a sequence of
glrysiferous shale, fine-grained sandstonc and siltstone wíth some massive beds of
glpsum and limestonc. Thcre is a possibility that massive gypsum deposits associaæd
with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum
undcr certain conditions can cause sinkholes to develop and can produce arcas of
localiz¡d subsidence. During previous work in the area, several sinkholes were observed
scattered th,roughout the lower RoarÍng Fork River vatley. These sinkholes appcar similar
to others associated with thc Eagle Vallcy Evaporiæ in arcas of thE Eagle Vallcy,
Sinkhole.s were not observed in the immediatc arca of tbe subject lot or within the
subdivision. No evidencc of cavities $ras encountered in ths subsurface materials;
howevcr, the exploratory pits were relatively shallow, for foundation design only. Based
on our present kaowledge of thc subsurfsce conditions at the site, it canûot bc said for
certain that sinkholes will not develop. The rÍsk of future ground subsidcncc on Lot 5
throughout the scrvice life of the proposed rcsidcncc, in our opinion, is low; bowevcr, the
owncr should bc rnadc awa¡E of the potential for sinküole development. If ñ¡rthcr
investigation of possible cavities in thc bcdrock below thc sitc ís desired, we should be
contacted.
Found¡tlon Recornmendalions: Considering the subsoil conditions cncountc¡cd in the
exploratory pits and the nature of tho proposed constn¡ctíon, we rccommend sprcad
footíngs placed on the undistuúcd natural gravcl soil desþed for an allowable soil
bcaring pressurÊ of 2,500 psf for support of thc proposcd residsnce. Ttre upper sand soils
tcnd to comprcss under loading and should bc rcmovcd to limit foundation settlement.
Footings should be a minimurn width of 16 inches forcontinuous walls and 2 feet for
cotumns, I¡osc and disturbed soils encountcrcd at tbe foundation bcaring level within
thc excavation sbould bc rcmovcd and the footing bcadng level extendcd down to the
undisturbcd natural gravel soils. Erærior footings should be provided with adequatc
cover abovs their bearing elevatíons for frost protection. Placcmcnt of footings at lcast
36 inchcs bclow the exterior gradc is typically uscd ín this arca Continuous foundation
walls should bc reinforccd top and bottom to span local anomalíes such as by assuming
an unsupporæd lcngth of at least l0 fe¡f Foundation walls acting as retaining structurcs
(if any) should be dcsþed to rcsist a latcral errth pressure based oD an cquivalcnt fluid
unit wcight of at least 45 pcf for thc on-site soil as backfill. A rcpresentative of tho
geotcchnical enginccr should observe all footing excavations prior to concrete placement
Job No, t 16 fl66À
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to evaluatc bearing conditions and adequate removal of the upper topsoÍl and silty sand
soils.
Floor Slsbs¡ Thc natural on-sitc soils, exclusive of topsoíl, arc suitablc to support lightly
loaded slab-on-grade construction. To reduce the effccts of some differcntial movemenq
floor slabs should be separated from all bearing walls and columns with expansion joints
which allow umestrainÊd vertical movement. Floor slab control joints should be used to
rcducc damage duc to shrinkage cracking. The rcguirerncnts forjoint spacing and slab
reinforcement should be established by tbe designerbased on experience and the intended
slab use. A minimum ¿þinch layer of frecdraining gravel should be placed bcncath
interior slabs to facilitate drainage. This material should consist of minus 2-inch
aggrcgate withlcss than 50% passing theNo,4 sicvc and less ttwz% passing the No.
200 sieve.
All f¡ll materials for support of floor slabs should be compacted to at least 95?o of
manimum standad Proctor density at a moisture content near optimum. Required fill can
consist of the on-site soils devoid of vcgctation, topsoil and ovcrsizpd rock.
Underdrain Systeml It is our understanding the finisbcd floor elcvation at the lowest
level will be at or above the surrounding grade. Thcrcfore, a foundation drain system is
not rcquired. It has been our expcrience in the area that local perched groundwatcr can
devcþ during times of heavy precipÍtation or seasonal n¡noff. Frozen ground during
spring runoffcan create a percbed condition.
If the finished floor elevation of the proposod strr¡cturc has a floor level below the
surrounding grade, we should be contactcd to provide rccommendations for an undcrdrain
systcm ormakíng thc foundation and floorslab watcrtíght All carthretaining süucturss
should be properly dr¡ined.
SurfsceDminage; TTte following drainage precautions should be obscrved during
consün¡ction and maintained at all times aftor the residonce has be¿n complctcd:1) lnundarion of the foundation cxcavatíons and underslab areas should be
avoided during constn¡ction.2, Ertcrior backfill shoutd be adjusted to near optimum moisture and
compacted to at least 95?å oî the maximum standard P¡octor density in
pavsment and slab areas and to at least 90% of the ma¡dmum standard
Proctor density in landscape arcas.3) Tbe ground surfacc surrounding thc exteriorof the building should be
slopcd to drain au'ay from the foundation in all directions. lVe
recomncnd a minimum slope of 6 inches in the first t0 fect in unpaved
arcas and a minimum slope of 3 Íncbcs iu thc first l0 fcet in pavemÊtrt and
wallnray arsas.4, Roof downspouts and drains should discharge well beyond thc limits of all
backfill.5) Ialrdscaping which requires regular heavy inigation should be locatcd at
lcast 5 fcct from thc building.
Job No.l 160664
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4
Limlt¡üons: This study has bcen conducted in accordancÊ wíth gcncrally acceptcd
geotechnical enginæring principles and practices in this arpa at this time. Yfe make no
warranty cither er(prcss or implied. ïhe conclusions and rcconrmêndations submitted in
this rcport are based upon thc data obt¡incd from thc exploratory pits Êxcavated at the
locations indicated on Figurc I and to the depths shown on Figure 2, the proposed type of
construction, and our experience in the area. Our services do not includc dctermíning the
presence, prevention or possibility of mold or other biological contaminants (MOBC)
developing in the firture. If the client is concerned about MOBC, then aprofessional in
this special field of practice should be consulted. Our findings includc intcrpolation and
extrapolation of the subsurface conditions identified at the cxploratory pits and variations
in the subsurface conditions may not become evident until cxcavation is performcd. ff
conditions encountcrcd during construction appear different from those describcd in thís
rÊport" wo should be notified at oncc so re-evaluation of the rccommendations may be
made.
firis report has bsen prepared forthe çxclusive use by ourclicnt fordesìgn purposes. lVe
arc not rcsponsible for tcchnical intcrprctations by others of ourinformation. As the
project evolves, we should provide continued consultation and field serviccs during
construction to review and monitor the implementãtion of our rccornmendations, and to
verify that the rccommcnd¡tions have becn appropriatcly intcrpreted. Significant dcsign
changes rnny rcquire additional analysis or modifications to the rccorn¡nendations
presentcd hcrcin. lVc rccom¡ncnd on-sitc obscrvation of cxcavations and foundation
bearing strata and tcsting of stn¡ctural fill by a repranentative of the geotcchnical
engineer.
If you have any questions or if we may be of ft¡rthcr assistance, pleasc let us know.
Respecffirlly Submitted,
TIEPTI¡ORTH . PAWI.AK GEOTECHNICAL INC.
L¡uis Eller
Revicwed by:
Steven L Pawlalç P.E.
LEBlcsw
attachmcnts Figure I - Location of Ëxploratory Pits
Figure 2-Lngs of Exploratory Pits
FigurÊ 3 - Gradation Test Rcsults
Job No.l 16 0664
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LOT4
//
Ø4
\
/
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LOT6
APPHOXIh,IATE SCATE
1'* 80'
POND
1 16 066A LOCATION OF EXPLORATORY PITS Figure 1
1 PrÍ 2
ELB/.* 662CI
PIT 3
ELFy'.= 6619.5'ELFf.= 6620
0
wc-15,r
DD,*100
-200*38- ì +4*69
- r -2oo*1
5 5
10
LEGEND:
TOPSOIL; organic sand, sllt ând clay, Íirm, moist, black, upper 6 inctres disturbed.
SAND (SM); silty to very silty, medium dense, mo¡sl, reddish bro¡vn.
GRAVEL (GP€M); with coþHes and smdl boulders, sandy to very Eandy, deñse, rncr¡st, light brorun,
rounded rock.
2' Diameter hand ddven liner samplo.
Disturbed bulk sample.
NOTES: :
1. Exploratory pils were excavated on March 15, 2016 with a Deere 50c míni-excavator.
2. Locallons of o<ploratory prts were msasured approximately by pacirq from features shown on the site plan
provided.
3. Elevations of exploratory pilswere obtained by intøpolation between contours shown on ttn sitè plan provided.
4, The exploratory pit locat¡ons and elevations should be considered accurate onþ to the degree implied by the method
used.
5. The lines beh¡/een materials shown on the exploratory pit logs represent tte approximate boundar¡es between
materialtypes and transitions rnay bs gradual.
6. No free water was encounlered ¡n lhê pits at the tinre of excavâting. Fluctualion in wâter lwel may occur with tinp.
7. Laboratory Testirg Results:
WC = Water Content (oá)
DD = Dry Density (pcf)
+4 = Peßent retained on the No.4 sieve l
-?00 = Percent passing No. 200 sieve
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1 16 0664 LOGS OF EXPLORATORY PITS Figure 2
TIME REAOINGS U 8 STAT.¡DAFDSERIES CLEAR SOUAÊE OPENINGS
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DÍA¡ì,IEfER OF Ë¡RTiüIEg tÑ MITIJMTTEF$
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GRAVEL 69 %SAND 30 9å SILT AND CLAY 1 YO
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F,AMPLE OF: Sandy Gravel
1 16 066A GNADATION TEST RESULTS Figure 3