HomeMy WebLinkAboutGeotechnical Investigation Report 04.20.19AMERICAN
GEOSERYICES
Geotechnical Evaluaiion RePort
294 Red Cliff Gir, Glenwood Spríngs, CO 816û1
Date: April2ü, 2019
Project Na: û199-WS19
AMERICAN
CFCSERVICES
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April 20, 2019
PRÕJECT Nû: 01$$-WS19
CLIENTS: Ms. \Mritney Grûss
Reference: Soil Testing I Lot-specific Geotechnical Evaluation, ?94 Red cliff Circle, Glenwood
Springs, CO
At your request, we have completed the geotechnical evaÍuation for the referenced project in
accordance with the American Geoservices, LLC (AGS) Proposal. Results of our evaluation and
design recommendations are summarized belaw.
PROJECT ¡hIFORMAT¡ON
The site is located as shown in Figure 1 and Figure 2. The proposed development will consist of
residential construct¡on. We do not anticipate significant site grading forthis prcject. We anticipate
proposed structure will be constructed with light to moderate foundation loads.
scoPE oF i ftRK
Our scope of services included the geologic literature feview, soil explorations, geologic hazards
evaluation, geotechnical evaluation, and the preparation sf this report. Evaluation of any kind of
existing structures on and adjacent to ihe site was beyond our scope of services.
ln April2019, rive performed sailexplorations {81) at approximate locatian shown in Figure 2 and
collected soil/rock samples. Our soil explonation included logging of soils from goil boring. Our
explorations extended to a maximum depth of f 5 feet below existing ground surface (BGS). All
soillrock samples were identified in the field and were placed in sealed containers and transported
to the laboratory for further testing and classification. Logs of all soil explorations showing details
of subsurface soil conditions encountered at the site are included in an appendix. The Legend
and Notes necessary to interpret our Exploration Logs are also included in an appendix.
1338 Grand Avenue #3û6
Glenwood Springs, CO 81601
Ph; (303) 325 3869
www.ãmedcangeoservlces. cÕm
sma @america ngeoservices.ctm
Ph: (888) 276 4C?7
Fx: {87Ð 471 0369
Mailing: 191 Unlversity Blvd, *375
Denver, CO 802S6
Ph; (303) 325 3869
Data obtained from site observations, subsurface exploration, laboratory evaluation, and previous
experience in the area was used to perform engineering analyses. Results of engineering
analyses were then used to reach eonclusions and recommendatians presented in this repart.
$URFACE CCND¡?IGNS
The site is roughly a rectangularly-shaped parcel of land as shown in Figure 2. Cun"ently the site
topography is gently sloping downwards to the east-northeast. At the time of our síte visit, there
was no visual indication of active slope instabilig or active landslides in the site vícinity. CIur
review of avaiiable geology maps and geologic hazards information did nat reveal the presence
of active geologic hazards at or immediately adjacent to the site.
SUBSURFACE CûNÐITIÛNS
Subsurface conditions encountered in our explorations and noted in our literature research are
descriþed in detail in the Exploration Logs provided in an Appendix and in the following
paragraphs. Soil ctassification and identification is based on commonly accepted methads
employed in the practice of geotechnicalengineerlng. ln some cases, the stratigraphic boundaries
shown on Exploration Logs represent transitions between soiltypes ratherthan distinct litholcgical
boundaries. ft should be recognized that subsurface conditions often vary both with depth and
iaterally betlr¡een individual exploratlon locations. The following is a sumrnary of the subsurface
conditions encountered at the site.
Surface Conditions: Approximately 8-1û inches of topsoil, lcam, sand, and root mass is present
at the surface.
$andy Silty Clay: Site is primarily underlain by generally medium stiff to hard sandy silty clays
extending to a maxirnum depth of about 15 feet. These soils exhibited low to medium plasiicity
in the field. These soils may consist of old debris flow deposit or ancient landslide deposit'
Gomptetely Weathered Bedrock: Below about 14 feet, the site is generally underlain by
completely weathered local shale or sedimentary bedrock fonnation.
Groundwater: Graundwater was not enccuntered during exploraticn or at the lime of completion
of our soil explorations. This observation may nct be indicative of othertimes or at locations ather
than the site. Some variations in the groundwater level may be experienced in the future- The
magnitude of the variation will largely depend upon the duration and intensity of precipitation,
temperature and ihe surface and subsurface drainage characterisiics of the surrounding area-
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April 20, 2019
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ÇEüLÛGIC I.IÅãARÊS EVALUATITN
Expansive Soils and Bedrock: The site is not underlain by highly expansive clayey soils or
clayey sedimentary bedrock materials. The site location is not near known swell hazard zones
that pose a significant geotechnical concem. However, local pockets of expansive clayey
materials can occur through the site and may cause heave in the flatwork around the site. This is
typical of many areas in Colorado.
Flooding: Our review of available flood hazards map and literature did nat indicate that the site
is susceptible to flooding due to rive¡ and perennial and intermittent tributaries across the project
area. Notwithstanding, a detailed flood hazard evaluation was beyond our scope of services. We .
recommend hiring an experienced hydrologist to evaluate the flcod hazards for the siie.
Debris Flow: Site is not located within alluvial fans or flood channels. Debris flow hazard at the
site is minimal under normal site, topographic, geologic, and weather conditions. However, the
site and vicinity area may consist of ancient debris flow or ancient landslide deposit, which is
cunently inactive.
Roekfall: Site is not located within rockfall hazard zone. Rockfall haza¡d at the site is minipnal
under normal síte, topographie, geologic, and weather conditions.
Landslides: Our review of available geologic maps and landslide hazard maps did not indicate
that recent landslides or recent debris frow had occurred at the site or in the irnrnediate proposed
building area. During our site reconnaissance, we did not notice scarps, crevices, depressions,
tensíon cracks in the ground surface, irregular slope toes, exposed surfaces of ruptures without
vegetation, pre$ence of distinct fast-growing vegetation, undrained depressions, €úc., that are
generally indicative of local active andlor inactive landslides or slope instability that would
adversely impact the on-site structure at this time, however, a detaild landslide evaluation of any
kind or slope stability evaluation under seismic conditions was beyond our scope sf services.
Ïhe site is located within or extrernely close to the mapped landslide hazard areas surrounding
the site {Figure 5). There are potentially mapped landslides andor ancient landslide deposits very
close to the site boundaries, within 250-500 feet. There is also moderate to high potentialfor the
pre$ence of darmant and/or unknown histaric landslides, deepseated ancient landslides, or
geologically-recently developed dormant landslides in the site vicinity close to the site.
The site itself is not mapped as being situated within the existing active or ancient active landslide
mass or an ancient active global landslide. However, the site vicinity area is mapped as having
landslide hazard (Figure 5). Considering these findings, the site topography, and site geologic
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April 20,2019
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rondit¡ons, it is our opinion that the immediate site and the vicinity area have 'site-specific
landslide hazards' and has some 'inherent' risk associated with slope Ínstability and structural
impact from the movernent of any globallancient landslide and local slope movemenls. Moreover,
historically, with construction in such areas, there is ahi,rrays an inherent risk associated with
ground movement andlor settlements and related structural damage. The or¡mer should
understand these inherent risks. Since this report and preliminary recommendations contained
herein have been prepared to maintain a low degree of risk for future structural damage, all our
recommendations should be strictly followed. lf the owner wants to better understand the risks
and to eliminate the site-specific landslide hazard risks, then a detailed and comprehensive
geotechnical evaluation including deep drilling, detailed slope stability modeling, and a detailed
geologic hazards assessment (including global landslide hazards evaluatíon) should be
performed to quantifo the abovementioned risks and to provide detailed geotechnical design
recommendations for comprehensive mitigation measures. Unless these recommended studies
are performed, the owrìer is completely responsible for taking all risks associated with any future
potential for instabili$ at the site or in the site vicinity.
lnitial Slope Stability Evaluatlon: Based on the results of our initial analyses (as discussed in
foltowing paragraphs), in our opinion, at present there are no slope instability hazards at the site
provided site drainage is properly maintained during the design life of the structure,
Using the results of geologic and soils literature review (as attached in the appendix) and site
reconnaÍssance data, we analyzed on-síte slopes by performing preliminary slope stability
analysis. We used the software SLOPE/W to model on-site slopes, suþsurface soil conditions,
and the Ímpact of existing construction on the stabili$ of the site. We used several methods
(Bishop, Janbu, Spencer, etc.) in order to obtain the lowest factor of safety against slope failures.
The SLûPEAff computer soffuyare calculates the most likely failure plane based on topography,
subsurface conditions (ineluding soil parameters), and groundwater conditions. The stability of
this most likely failure plane is calculated as the factor of safety {FOSi, which is a ratia of the
resisting farces or shear strength to the driving forces or shear stress required for equilibrium of
the slope. A FOS of 1.û indicates the resistive forces and driving forces are equal. A FOS below
1.0 indicates the driving forces are greater and the landslide is active. A FOS above 1.0 indicates
the resisting forces are greater and the slope is stable. Based on the engineering community and
our experience, a fac{or of safety in the range of 1.3-2.0 is generally acceptable to assure slope
stability in residential applications.
Slope stability analysis was performed using various input soil parameters derived from the results
of our subsurface exploration and laboratory evaluation, in order to properly evaluate the stability
of a slope. Of particular irnportance were surface and subsurface profiles (slape geometry), soil
strength parameters, and groundwater conditions. Based on our experience with past slope
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atability evaluations in similar geologic conditions, soil strength parameters can vary considorably.
Notwithstanding, we used soil strength values typical of on*site soils and native soilslbedrock
based on our experience with soil strength testing, as well as back-calculation of soil strength
parameiers for failed slopes in similar geologic conditions.
For sur .design" slope stabili$ analysis, which was used as a basis for obtaining our
recommended geotechnical parameters for initial site design, we assigned optimal range of soil
parameters- We assumed the presence of perched groundwater and soil saturation in orde¡'to
model possible broken drainage pipes in future. During slope stabili$ analyses, both translational
and circular failure surfaces were considered. A sensitiviff analysis was also performed using
various soil strength values, groundwater configurations and slip surface profiles. We analyzed
a typical cross section using post-construction conditions in order to determine the FtS of the
slope. Based on the results of our initial analyses (as discussed in following paragraphs), in our
opinion, at present there are no slope instabilig hazards at the site providd site drainage is
properly maintained during the design life of the structure.
lnherent Slope lnstability Risks; Historically, with construction in hilly or mountainous areas,
there is an inherent risk associated with slope failures. Although there was no actíve slope
instability observed within the proposed building envelope or adjacent to the site boundaries, and
the potential for future active slope failure is low the owner ís stíll responsible for taking any risks
associated with any existing or future potential for instability at the site or in the site vicinity. Since
this report and recommendations continued herein have been prepared iñ order to maintain a low
degree of risk for future slope instability, all of our recommendations should be strictly followed.
Earthquakes: Based on site geology, topography, and our prelirninary evaluation, in our opinion,
the site is generally not considered to be located within highly active seismic area. Therefore,
anticipated ground motions in the region due to seismic activity are relativeþ low and do not pose
a significant hazard. Ground accelerations in excess of 0.19 ta -0.29 are not anticipated to occur
at the site.
Based on ihe results of our subsurf,ace explorations and review of available literature i2009
lnternational Building Code), in our opinion, a site classification "C" may be used for this project.
However, this site classification måy be revised by performing a site-specific shear wave velocity
study.
Subsurface soil conditions atthe site are not susæptible to liquefaction. Seisrnically induced slope
instabili$ may occur on a global scale impacting not just the site but also the surrcunding area,
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April 20, 2019
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however, such an evaluatian was beyond our scope of services. A detailed seismic hazards
evaluation of the site was beyand our scûpe of services.
CTT{CLU$¡TSIS AN* RTC*$& ilÆENüAT¡ÕN*
Based on the results of our geotechnical evaluation, in our opinion, the site is suitable for the
proposed construction provided following recommendations are strictly followed. lt should be
noted that our conclusions and recommendatíons are intended as design guidance. They are
based on our interyretation of the geotechnicaf data obtained during our evaluation and following
assumpticns:
e ProposedlFinal site grades witl not differ significantly from the current síte grades,
r Proposed foundations will be constructed on level ground; and
. Structural laads will be staiíc in nature.
Construction recommendations are provided to highlight aspects of construction that could affect
the design of the project. Entíties requiring information on various aspects of construction must
make their own ínterpretation of the subsurface conditions to determine construction methods,
cost, equiprnent, and work schedule.
SHÂLLSW F*Uå\¡ÐAT¡*NS
We recommend that the proposed structure be supported on shallow spread footings designed
and constructed in accordance with following criteria:
. Over-excavate any boulders or large clasts or híghly expansive soils frorn within the
foundation areas, then surficial compact the excavated surface, and then backfill (if
necessaryi with granular free-draining structural fill {ar onsiie sandy scils) cempacted tc at
least 95clo of ASTM D698 maximum dry density in order ta acf:ieve ã "uniform {non-rocky)
subgrade" and to facilitate the placement of foundation drain. Over-exeavation can be
minimized or eliminated based on the results of open-hole inspection cr foundaticn subgrade
inspection performed by AGS. Gnsite materials may be used as structuralfill provided, they
are apprûved by AGS,
r Fcundations bearing upon properly prepared and approved subgrade should be designed for
a maximum allowable bearing pressure of 2,000 pounds per square foot {psfi.
r Estimated final stn¡ctural loads will dictate the final form and size of foundations to be
constructed. However, as a minimum, we recommend bearing walls be supported by
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tontinuous footings of at lcast 18 inches in width. lsolsted columns should bc supportcd on
pads with minímum dimensions of 24 inches square.
Exteriar footings and footings in unheated areas should extend below designlpreferred frost
depth of 36 inches.
Continueus foundation walls should þe reinforced in the top and bottom to span an
unsupported length of at least I feet to fudher aid in resisting differential movement. As a
minimum, additionatreinforcement as shown in Figure 6 should be placed.
Foundation/stem walls should be adequately desígned as retaining walls and adequaie
drainage measures should be implemented as shown in Figure 7.
a
We estimate total settlement for foundations designed and constructed as discussed in this
section will be one inch or less, with differential settlements on the order of one-half to three-
fourths of the totaf settlement-
$TRT.¡GTURAL FLÜÛR & CRAWL SFACE
We understand a etruciurallframed floorwith crawl space may be used forthis project. The gmde
beams (if used) and floor system should be physically isolated from the underlying soil materials
with crawl-space type construction. The vsid or crawl space of minimum of 6 inches or whatever
minimum cunent Uniform Building Code {UBC} requirement is.
For crawl-space construction, various items should be considered in the design and construction
that are beyond the scope of geotechnical scope of work for this project and require specialized
expertise. Some of these include design considerations associated with clearance, ventilation,
insulation, standard construction practice, and local building codes. lf not properly drained and
constructed, there is the potentialfor moisture to develop in crawl-spaces through transpiration af
the moisture/groundwater within native soils underlying the structure, water intrusion from
snowmelt and precipitation, and surface n¡noff or infiltration of r¡¡ater ihrough inigation of lawns
and landscaping, ln craw{ space, excessive moisture or sustained elevated humidity can increase
the potentialfor mold to develop on organic building materials. A qualified professional engineer
in building systems should address moisture and humidity issl¡es.
CRATÂ'L SPACE PERIMETËRJUNDERÛRAIN SYSTEM
ln order for the craud space to remain free of moisture, it is important that drainage
recomrnendations are properþ implemented, and adequate inspections are performed priorto the
placement of concrete.
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As a minimum, subgrade beneath a structural floor system should be graded so that water
does not pond. Perimeterdrains and under-slab drains should be installed in conjunction with
a sump pump system to eliminate the potential fcr ponding and any subsequent damage to
foundation and sfab elements. The lot-specific perimeterdewatering, and ¡¡nderdrain systems
should be properly designed and conneeted to the area underdrain system ar a sump-pump
system for suitable discharge from the lot,
Drainage recommendations illustrated in Figure 7 should be implemented. The subsurface
drainage system should consist typically of 4-inch minimum diameter perforated rigid PVC or
flexible pipe {rigid prefened due to depth of placement) surrounded by at least one pipe
diameter of free draining gravel. The pipe should be wrapped in a geosynthetic to prevent fine
soils f¡om clogging the system in the future. The pipe should drain by gravlty to a suitable all-
weather outlet or a sump-pit. Surface cleancuts of the perimeter drain should þe installed at
minimum serviceability distances around the structure. A properly constructed drain system
can result in a reduction of moisture infiltration cf the subsurface soils. Ðrains which are
improperly installed can intrcduce settlement or heave of the subsurface soils and could result
in improper surface grading only compounding the potential issues.
a The underdrain system should cansist of adequate lateral drains and a main drain, regular
clean out and inspection locatians, and proper csnnections to the sump-pump system for
discharge into suitable receptacles located away from the site.
a The eniire design and canstruction team should evaluate, within their respective field of
expertise, the cunent and potential gources of water throughout the life of the structure and
provide any designiconsiruction criteria to alleviate the potential for moisture changes. lf
recommended drain systems alÊ used, the actual designllayout, outlets, locations, and
construction means, and methods shauld be observed by a representative of AGS.
SLÂB-ÛN.GRAÐE AND PE RI ÉJI ËTERJUN TERDRA¡T\I $YSTEM
Groundwater is not expected to be at depths below the proposed foundation levels if excavation
is performed during dry seasons. ln order to assure proper slab-on-grade construclion {if used},
following recommendations should be strictly followed:
r A perimeter dewatering system should be installed io reduce the potential for groundwater
entering slab-on-grade areas. The lot-specific perimeter dewatering should be properly
designed and connected to the area underdrain system or a sump-pump system for suitable
discharge fiom the lot.
As a minimum, drainage rccomÍlendations illustrated in Figure 7 shculd be implemented. The
subsurface drainage system should consist typically of 4-inch minimum diameter perforated
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April 2O, 2019
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rigid PVG or flcxiblc pipc (rigid preferred due to depth of placement) eunounded by at least
one pipe diameter of free draining gravel. The pipe should be wrapped in a geosynthetic to
prevent fine soils from clogging the system in the future. The pipe shoufd drain by gravity to
a suitable all-weather outlet or a sump-pit. Surface cleanouts of the perirneter drain should
be installed at minimum serviceability distances around the structure. A properly construcied
drain system can result in a reduction of moisture infiltration af the subsurface soils. Drains
which are improperly installed can introduce settlement or heave of the subsurface sails and
could result in improper surface grading only compounding the potential issues.
The entire design and construction team should evaluate, within their respective field of
expertise, the cunent and potential sources of water throughout the life of the structure and
provide any designlconstruction criteria ta alleviate the potential for moisture changes. lf
recommended drain systems are used, the actual design/layout, outlets, locations, and
construction means, and methods should be observed by a representative of AGS.
The "Slab Performance Risk" associated with native soils is "Low". Therefore, the slab can be
constructed as a slab-on-grade provided the owner is aware that there is stilt potential risk of
some slab movement. Properwetting of the subgrade to obtain soil moisture content in the range
al 20-22'lc ancllor moisture-conditioning and recompaction of onsite mater¡als for upper 2 feet
should reduce the risk of rnovement. lf the owner is not willing to assume any risk, then a
structuralfloor slab system option should be considered.
The aetual slab movements that will occur on a particular project site are very difficult, if not
impossible, to predict accurately because these mcvements depend on loads, evapCI-
transpiration cycles, surface and subsurface drainage, consolidation characteristics, swell índex,
swell pressures and soil suction väluÊr. The actual time of year during which the slab-on-grade
is constructed has been found to have a large influence on future slab-on-grade movements.
SIab heaves or settlements are normally defined in terms of "total" and "differential" movement.
"Tetal" movement refers to the maximum amount of heave or settlement that the slab may
experience as a wlrole. "Differcntial" movement refers to unequal heave or settlement that
different points of the sâme slab may experience, sometimes over relatively short horizontaf
distances- Differential movements are arbitrarily determined to be one-half of the total msvement
in soils exhibiting Low Slab Perfonnance Risk. Greater differential movements can occur in areas
where expansive soils have been encountered and vchere the natural soils abruptþ transition to
fill material.
For design of floor slabs, a modulus of subgrade reaction of 200 pounds per cubic inch (pci) may
be used. Based on the results of our analyses, we believe that interior floor slabe designed as
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April 2O, 2019
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recomrnended above and constructed as recommended in following paragraphs could result in
"total" movement of approximately up to 1-inch with "differential' movement on the order of half
the totalmovement.
We recommend that the construction measures outlined in the following paragraphs be followed
to reduce potential damage to floor slabs, should excessive wetting of the subsurface soils occur:
e Design and construct the floor slab to move independently cf bearing rnembers (floating slab
construction). Prcvlde slip joints around exterior walls and interior columns to allow free
vertical movement of the slaþs.
Frequent controljcints should be provided at aþout 1û feet spacing in the floor slab ta reduce
problems with shrinkage and cnacking according to ACI specifications. Controljoint spacing
is a function of slab thickness, aggregate size, slump and curing conditions. The requirements
for concrete slab thickness, joint spacing, and reinforcement should be established by the
designer, based on experience, recognized design guidelines and the intended slaþ use.
Placement and curing conditions will have a strong impact on the final concrete slab integrity.
Floor slabs should be adequately reinfcrced with welded wire mesh and steel rebar- Structural
engineer should include steel rebar in addition to vrrclded wire mesh in order to reduce the risk
of differential rncvement due to bending over I feet cf unsupported tengith.
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The need for a vapor barrier will depend on the sensitivity of fioor coverings to moisture. lf
moisture sensitive floor coverings are proposed for portions sf the proposed struçture, a
capillary break rnaterial, typicalþ consisting of a "clean" gravel, should be considered. We can
prcvide additional recornmendations if this is the case.
Provided gravel is desired þelcw the slab, a layer of 4 to 6 inches can be used. Plumbing
passing through slabs should be isolated from the slabs and providedwith flexible connections
to allow for movement. Under slab plumbing should be avoided if possible and should be
braught above the slab as soon as possible.
lf slab-bearing partitions are used, they should be designed and constructed ta allow for
movement. A minimum of 2 inches of void space {as illustrated Ín Figure 3} should be
maintained below or above partitions. lf the void is pravided at the top of partitions, the
connectians between the interior, slab-supported partitions and exterior foundation supported
walls should allow for differential movement.
l/Ulrere mechanical equipment and HVAC equipment are supported on slabs, we recommend
provision of a flexible connecfion between the furnace and ductwork w¡th a minimum af 2
inches of vertical movement.
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RËTAININË WALL
Retaining walls for at*rest ccnditions can be designed to resist an equivaleni fluid density of 55
pcf for on-site fill materials if needed only ímported granular backfill meeting CDOT Class 1
structural backfill should be used. Retaining walls for unrestrained conditions ffree lateral
movement) can be designed to resist an equivalent fluíd density of 35 pcf for cn-site fill materials
and 35 pcf for imported granular backfill or CDOT Class 1 structural backfill. For passive
resistance of unrestrained walls, we recommend passive resistance of 300 psf per foot of wall
height. A coefficient af friction value of 0.35 may be used for contact between the prepared soil
surface and concrete base.
The above recommended values do not include a factor ef safety cr allowances for surcharge
loads such as adjacent foundations, sloping backfill, vehicle traffìc, cr hydrostatic pressure. We
should be contacted to provide additional reccmmendat¡ûns for any specific site retainÍng
conditions.
Retaining wallbackfiltshould be placed in strict accordance with aur earthwork recommendations
given below and as illustrated in Figure 7. Backfill should not be ûver-compacted in order to
minimize excessive lateral pressures on the walls" As a precautionary measure, a drainage
collection system {drains or geosynthetic drains) should be included in the wall design in order to
minimize hydrostatic pressures. A prefabricated draínage composite or drain board such as the
MiraDrain 2û00 or an engineer-appraved equivalent may be installed afcng the backfilled side af
the basement foundation wall.
EARTI-IWTRK CÕNSTRUCTIûN
Site grading should be carefully planned sa that positive drainage away from all structures is
achieved. Following earthwork recommÊndations should be followed forallaspects of the project.
Fill material should be placed in uniform horizontal layers (tiÊs) nct exceeding I inches þefore
compacting to the required density and before successive layers are placed. lf the contractor's
equipment is not capable of properly moisture conditioning and compacting 8-inch lifts, then the
lift thickness shall be reduced until satisfactory results are achieved.
Clays or weathered sandstone/claystone bedrock (if encountered) should not be re-used onsite
except in landscaped areas. lmport soils should be apprcved by AGS prior to placement. Fill
ptaæment oþservations and fíll compaction fesfs should be perfarmed by,4GS Engrneering in
order to minimize the potantial far futurc prablems. Fílf material should not be placed on frozen
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April 2O, 2019
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ground. Vegetaiion, roots, topsoil, the existing fill materials, and other deleterious material ta
depth of approximately 6 inches should be removed before new fill material ís placed.
On-site fillto be placed should be moisture treated to within 2 percent of optimum moisture content
{OMC) for sand fill and from OMC to 3-4 percent above OMC for clay and weathered bedrock.
Fillto þe placed in wall backfillarëas and driveway areas and allother structuralâreas should be
compacted to 95% of Standard Proctor iASTM D 69e) dry density or greater. Compactíon in
landscape areas should be 85% or greater.
lmported structural fill should consist of sand or gravef material with a maximum particle size of 3
inches or less. ln addition, this material shall have a liquid limit less than 30 and a plasticity index
of 15 or less. Structurat fill should also have a percent fine between 15 to 30 perceni passing the
No. 200 sieve. Structural fill should be moisture conditianed to within 2 percent of OMC and
compacted to at least 95 percent of Standard Proctor {ASTM D69S}'dry density.
ln cur opinion, the materials enccuntered at this site may be excavated with conventional
mechanícal excavating eguipment. For deeper excavations, heavier equipment with toothed
bucket may be required. Although our soilexplorations did not reveal "buried" foundation elements
or other structures or debris within the buifding footprint, these materials may be encountered
during excavation activitíes. Debris materials such as brick, wood, concrete, and abandoned
utility lines, íf enccuntered, should be removed from structural areas wt¡en encountered in
excavations and either wasted from the site or placed in landscaped areas.
Temporary excavations should comply with OSHA and other applicable federal, state, and local
safety regulations. ln our opinion, OSHA Type B sails should be encountered at this site during
excavation. OSHA recommends rnaximum allowable unbraced temporary excavation slopes of
I .25:1iH:V) for Type B soils for excavations up to 10 feet deep. Pennanent cut and fill slopes are
anticipated to be stable at slope ratios as steep as 2H:1V {horizontal to vertical) under dry
conditions. New slopes should be revegetated as soon as possible affer completion to minimize
erosion.
We recommend a minimum of 12 feet of clearance beh¡¡een the top of excavation slopes and soil
stockpiles or heavy equipment or adjacent structures. This setback recornmendation may be
revised by AGS once the project plans are available for rcview. lf braced excavations or shoring
systems are to be used or needed, they should be reviewed and designed by AGS. lt should be
noted that near-surface soíls encountered at the sÍte wilt be susceptible to sûme sloughing and
excavations sho¡.¡ld be periodically monitored by AGS's representative.
Prc¡jec't No: fie9-WSlS
April 2O,2019
Page No: 12ol 16
The proposecl excavatiali should nol adversely irnpact arry existing structurus. Prapcr shoring
and/or underpinning should be used to maintain the stability of existing structure as well as the
excavated faces of the new construction area.
It should be noied that ihe above excavation recommendations are comflnonfy provided by local
consultants. The evaluation of site safety during construction, stability of excavated slopes and
cuts, and overall stabílity of the adjacent areas during and afrer construction is beyond our scope
of seruices. At your request, uúê can provide these services at an additional cost.
Ðuring construction in wet or cold weather, grade the síie such that surface water can drain readily
away from the building areas. Promptly pump out or otherwise remove any water that may
accumulate in excavations or on subgrade surfaces and allow these aneas to dry before resuming
construction. Berms, ditches and similar means may be used ta prevent storm water from
entering the work area and to convey any water off-site efficiently.
lf earthwork is performed during the winter manths when freezing is a factcr, no grading fill,
structunal fill or other fill should be placed on frosted or frozen ground, nor should frozen material
be placed as fill. Frczen ground should be allowed to thaw or be completely removed prior to
placement of fill. A good practice is to covêr the compacted fill with a "blanket" of loose fill to help
prevent the compacted fill from feezing overnight. The "blanket" of loose fill shsuld be removed
the next morning priar to resuming fill placement.
During eold weather. foundaiicns, crncrete slabs-an-grade, or other concrete elements should
not be constructed on frazen soil. Frozen soil should be completely rernoved from beneath the
concrete elements, or thawed, scarified and re-compacted. The amount of iime passing between
excavalion or subgrade preparaticn and placing csncrete should be minimized during freezing
conditions to prevent the prepared soils from freezing. Blankets, soil cover or heating as required
may be utilized to prevent the subgrade from freezing.
CENERAL TR&I$¡AGE
Proper drainage is critical for achieving long-term stability and overall success. ln general, where
interior floor elevations are situatad at an elevation below proposed exterior grades, we
recommend installation of a perimeter drains arcund the exterior grade beam and foundations as
illustrated in Figurc 7. ln addition, drain laterals that span the crawl space are recommended ta
prevent ponding of water within the cnawlspace (if used). lf necessary, AGS can provide further
recommendations forthe exteriordrain system and a typicaldrain detail.
Prô]êct Nô:0199-WS19
April 2C, 2O1g
Page Nc: 1 3 of 16
Groundwater was not encountered at the time of our explorations. However, based on the
weather and surface water run-off conditions in the site vicinity area during construction, site may
require pumping and other dewatering methods during construction.
proper surface drainage should be maintained at this site during and after completion of
construction operations. The ground surface adjacenl tc buildings should be slcped to prcmote
rapid run-off of surface water. We recommend a minimum slope of six inches in the first five
horizontal feet for landscaped or graveled areâs. These slopes shauld be maintained during the
sen¡ice life of buildings. lf necessary, adequate interceptor drains should be installed on uphilt
sides to intercept any surface water run-off towards the siie-
Landscaping should be limited around building areas ta either xeri-scaping, landscaping gravel,
or plants with low mcisture requirements. No trees should be planted or present within 15 feet of
the foundations. lrrigation should þe minimal and limited to maintain plants. Roof downspouts
should discharge on splash-blocks or ather impervious surfaces and directed away from the
building. Ponding of water should not be allowed immediately adjacent to the buitding.
It is important to follow these reecmrnendations to minimize wetting or drying af the foundation
elements throughout the life of the facility. Construction rneans and methods should afsa be
utilized which minimize improper increases/decreases in the moisture contents of the soils during
construction.
Again, pcsitive drainage away ffom the new structures is essentialto the successfulperformance
of foundations and flatworlc and should be provided during the life of the structure. Paved areas
and landscape ¿lreas within 10 feet of structures should slope at a minimum grade of 10H:1V
away from foundations. Ðownspouts from all roof drains, if any, should cross all backfilled areas
such that they discharge all water away from the backfilf Ecnes and structures. Drainage should
be created such that water is diverted away fram building sites and away -from backfill areas of
adjacent buildings.
csf\¡sRFTË tÕFr* sTRtçcH eru
Concrete sidewalks and any ather exterior concrete flatwork around the proposed structure may
experience some differential movement and cracking. While it is nat likely that the exterior
flatworks can be economically protected from distress, we recommend following techniques to
reduce the potential long-term mcvement.
. Scarify and re*compact at least 12 inches of subgrade material located immediately beneath
structures.
Project No: 0199-WS19
April 2t, 2019
Pâge No: 14oi 16
. Avoid landscape inigation and moisture halding plants adjacent to structures. No trees should
be planted cr preseni within 15 feet af the foundations.
r Thicken or structurally reinforce the structures.
We recommend Type l-ll cement for all concrete in contact with the soil on this site. Calcium
chloride should not be added. Concrete should not be placed on frost or frozen soil. Concrete
must be protected from low temperatures and properly cured.
L¡TÞT¡TATIONS
Recammendatisns contained in this report are þased on our fiefd oþservations and sr¡bsurfaee
explorations, limited laboratory evaluation, and our present knowledge of the proposed
construction. lt is possible that soil conditions could vary between or beycnd the points explored.
lf soil conditions are encountered during construction that differ from those described herein, we
should be noiified so that we can review and make any supplemental recommendations
necessary. lf the scope of the propcsed construction, including the proposed loads or structural
locations, changes fram that described in this report, our recommendations should also be
reviewed and revised by AGS.
Our Scope of Work for this project did not include research, testing, or assÊssment relative to past
or present contamínation of the site by any source. lf such coniamination were present, it is very
likely that the exploration and testing conducted for this report wauld nct reveal its existence. lf
the Owner is concemed aþout the potential for such confamination, additional studies should be
undertaken. We are available to discues the scope of such studies wíth you. No tests were
performed to detect the existence of mold or other environmental hazards as it was beyond Scope
of Work.
Local regulations regarding land or facility use, on and off-site conditions, or other factors may
change over time, and additional work may be required wlth the passãge of tirne. Based on the
intended use of the report within one year from the date of report preparation, AGS may
recommend additionalwork and repert updates. Non-compliance with any of these requirements
by the client or anyorle else w¡ll release AGS fronr any liability resulting frorn the use of this report
by any unauthorized party. Client agrees to defend, indemnify, and hold harmless AGS from any
claim or liability associated with such unauthorized use or Ron-compliance.
ln ihis report, we have presented judgments based partly on rur understanding of the proposed
construction and partly on the data we have obtained. This report meets professional standards
expected for reports of this type in this a¡ea" Our ccmpany is not responsible for the conclusions,
Prujeut Nr:. 019$WS19
April 20, 2û19
Page No: 15 of 'f 6
op¡nions or recommendations made by others based on the data we have presented. Refer to
American Society of Foundation Engineers iASFE) general conditions included in an appendix'
This report has been prepared exclusively for the client, its' engineers and subcontractors for the
purpose of design and construction of the proposed structure. No other engineer, consultant, or
contractor shall be entifled to rely on information, conclusions cr recommendations presented in
this docr.¡ment without the prior written approval cf AGS-
We appreciate the opportunity to be of service to you on this project. lf we can provide additional
assistance or obseruation and testing services during design and construction phases, please call
us at 1 888 276 4427.
Sincerely
Sam,Adettiwar, MS, PE, GE, P.Ëng, ftif.ASCE
Senior Engineer
Attachments
Project No:019S-WS19
April 20, 2019
Page No: 16of 16
B1
294 Red Cliff Cir, Glerwaod Springs, CO 81681Pr{ect Address
Drill Rig: CME55 Solid Stem Auger, 4" Diameter0199-WSlgNumber
Ground Elevation See FiguresGeologneer SMA
Total Depth of Borehsle 7.5 Feetû+09-2019Date Drilled
Not Encounteredto WaterBorehole Biameter 4 OÞ lnches
s
Jo.
s
JJ
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Description I LithologY
ct¡0J
.g
ÉL
tú
CI
CU
CH 29,18
1û
8-1 1-1S
15^17-1
TOPSûIL: 8.0" thick, silt, sand. clay
SANDY SILTY ÛLAY, brcwn to pale brown,
medium stiff to very stiff, dry to rnoist, low to
medium plasticity
End of Borehole.
Groundwater was not encounlered during
or at the completion of drilling.
At completion, borehole was backfilled
with soilcuttings.
,organics
AMËRICAN CLOSIRVI{-LS Page IÈ*r.f,i6.{Êr rúrlil¿r¡¡1x$icrluov
B2
Project Address 294 Red Cliff Cir, Glenwood Springs, CO 816Û1
Prnjecl Ntrnher 0199-WS19 DrillRig: CME55 Solid Stem Auger, 4" Diameter
GeologisUEngineer SMA Ground Elevation See Figures
Total Depth of Borehole 15 FeetDate Drilled 04-09-2019
Borehole Ðiameter 4 OD lnches Depth to Water Not Encountered
CDo
.9
o.ñ
(9
Description J Lithology
$o
CLoo
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E
tú
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ML
TOPSOIL: 1û.t" thick, sand, clay,organics
SANDY CLAYEY SILT,
lnedium stiff, moíst, low
\
brown to dark brown,
to medium
SANDY SILTY ÛLAY, brown lo pale
brown, medium stiff to hard, dry to moisi,
low to medium plastici$, trace to some
gravel
Hard drilling below l4 feet. Possibly
completely weathered shale below 14 feet
5
10
1
5-10-14
7-',t2-18
15-50+
10û
I
10
102
108
24,14
JJ, ¿J
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CH
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(
End of Borehole.
Groundwater was not encountered during
or at the completion of drilling.
At completion, borehole was backfilled
with soilcuttings.
f/ *Y"t"llcAN ctosrRvrcts Page 1
FIGURE 1: SITE LCICAT'¡ON MAP
AMERICÅN CEOSERVICES
38F 2?la J{t2l - å*ríecÂtu*n i**s¡¡¡?
rjÐ 'ì' l i-ri:: '
t :-,:,:; r--:.'¡: .,.r:-¡:':i ., llr,h f_:f,:*:r lf,Criii. trj
T,{a\/
;,rart¡ ¡i*rr!.
i;:åi,,,,,ilJr-j i¡;;r r ,.¡5-
116
m
163 i:r
J1
Çroo rìÊrr t--irir l:JrctÊ
I
L_ srr. LocAroN
@ 'fg'
t¡
_Ðã-*
$ t),ríli r, 1.1 ;:ìriiiliirirt¡
...r- ¡r+_ -.jirî !!-4
..-" . ,; .,-.1i ;i,,,
.'t
\
\
T'
1
*,';
SITE LOPAT}ON
.' ,l:
t'',',. t**".-"
, 1. l-!
1ît'.;i" . g' "';:'.'¡r
11¡tde
:. çre€*
REFERENÇE:
GOOGLE MAPS N
1t5
USGS TOPOGRAPHIC MAPS
LEGEND
Rifle Àrea, Colorado, Pãrts of Grfield änd lilesã
Cöunt¡es {CÞOE3}
Rifle Area, Colorado, Parls of Garfield Ö
and þ{eaa Counties (CO6Ê3}
LlapUnit ldap Unit ilarn*
Symbol
2 Arle-Ansari-Rock
outcrCIp comp¡ex,
12 to 55 percent
stopes
6 Ascalon fine sandy
loam, 6 Èo 12
percent slopes
I Atencio-Azeltine
complex, 1to 3
pêrcent slopee
34 lldefonso stony
loarn. 25 to 45
p€fcent slopes
73 lfater
Totals for Area of
InterÊst
åcrcs
in
ACII
7.7
P€rceßt
of ÂOI
16.4%
18.2 38.99o
2,5 5,5%
12.6 77.Aa/s
5.7 12.3%
46,7 AA$.Oolo
N
REFERENCE:
WEB SCIIL SURVEY
AMERICAN GËOSERVICES
i98::ú,S¡ . ¡msricût*{*nìcc¡..oftv FIGURE 4: SOIL SURVEY MAP
FIGURE 5: LANDSLIDE HAZARD MAPAMERICAN CËCSERVICES
3s¡::(:,+j?:' t#iàrlfcrcñ ;(sorrïr
r
Colorado-landsl ide-i nv€ntory-new
co m pi led-la n d sl i des-from-24K-m aps
ccmpiled-la ndslides-from-H B 1 04 1 -maps
N
REFERENCE:
COLÛRADO LANDSLIÐE
¡NVENTORY
i\À4ERICÂN CEÜSERVICM
t88.2:ó.$J2" - ¡úÈ.iü¡¡Lesñjc6crñv FIGURE 6: TYPICAL DETAILS
NOTE$:
A. ADDITIONAL REINFORCEMENT, #4 æNTINUOUS BAR,
BOTTOM OF FOOTING.
B. ADDITIONAL REINFORCEMENT, #4 AT ¿18" C/C. TOP OF
FCIOTING.RETAINING WALL DIMENSIONS AND
REINFORCËMENT TO BE DONE BY
PROJECT STRUCTURAL ENGINEER BASED
ON GEOTECHN ICAL RECOMMENDATIONS.
G. REINFORCEMENTAS PER STRUCTURAL ENGINEER'S
DESIGN. AS A MINIMUM, USE #4 AT 48" C/C.
CONCRETE FOOTING TO BE
DIMENSIONED BY PROJECT
STRI.'CTURAL ENGINEER BASEB ON
GEOTECHNICAL RECOMMENDATIONS.
ADDITIONAL FOOTING REINFORCEMENT NETAIL
NEW INTFRIOR
WALL
NüTES:
B.4Od NAILS EVERY 24'THROUGH BOTTOM PLATE
INTO PRE-DRILLEÐ HOLES OF THE FLOOR PLATE.
WALL FINISH
RL4L
WALL SASE BOARD
NAILED ONLY TO BASE
PRESSURE TREATEÐ 2'X4" BASE
PLATE SECURED WÍTH 3"
CONCRETE NAILS OR FQUIVALENT
PLATE;TOP IS FREE
3'lvllN VOID SPACË
SPACER-SAME TH ICKNESS AS
WALL FINISH MATERIAL
CONCRETE BASEMENT SLAB
"FLOAT' TFLOAïNG WALL DETAIL)
Ð
."
Þi
Þ
ö'
"P
FIGURE 7: DRAINAGE DETAILSAMERICAN CEOSERVICES
ì882î{riûli - æc¡ic¡B¡ænn-':¡mV
FLEXIBLE ADHESIVE EQUIVALENT'
4-ABOVE GROUND;
MAINTAIN LEAK-FRËE
LEAK-FREE AND ADËOUATE
CAPFTCITY ÐOWNSPOUTS
- EXTEND DOWNSPOUT
BEYOND
DECORATIVE LAYËR,
10H:1V GRADE;
WITHOUT CAUSING
ADVERSE IMPACT
ON AÐJACENT
PROPERTIES; DISTHARGEi o¡¡ra sPL-AsH BLocKs.
MINIMUM 3" THICK
DETORATIVE GRAVEL.
ROCK OR BARK LAYER
AT LEAST 4 FT LONG
4"
ô"MIN L_
20 MILTHICK POLY
SHEET LINER AT LEAST
4FT LONG; EXTEND 4'
ABTVE GROUNÐ & 36"
BELOW GROUND
OFFSET FOR ANY
SPRINKLER
HEADS; PART CIRCLE
SPRAYING
AWAY FRCIM BUILDING
DOWNSPOUT & MOISTURE BARRIER DETAIL
CTMPACTED EARTH BACKFILUSOIL CAP
(DCI NCIT USE IF STEM WALL IS
DESIGNED AS A RETAINING WALL. IN
CASE OF RETAINING WALL, USE
FREE-DRAINING CRUSHED ROCK FILL TO
AVOI D HYSRûSTATIC PRESSURE.
SLûPE TO DRAIN AWAY
FROM STRUCTURE, 1ûH:1V
{sEE DOWNsPour DETAIL}
FOUNDATION/STEM WALL
MIRAFIl4O N FILTER
FABRIC OR EQUIVALENT
POLYETHYLENË FILM GLUED TO
FOUNDATION WALL ANB ËXTENDËD
BELOW THE DRAIN AS SHOWN f
12'MtNI
I:SLAB-ON-GRADE WITH
ËXPANSION JOINTS OR CRAWLSPACE-ì
6" MIN
OVER-EXCAVATION
(SEE NOTE B)FXCAVATED TRËNCH,
NEAR VERTICAL TO
0.5H:1VFREE-ÐRA¡NING
CLEAN CRUSHED
ROCI{iGRAVEL
TES:A.4-!NCH DIAMETER
I*-SUBGRAÐE, IN-SITU SOITì
(sEE NOTE C)
PERIMETER OR FOUNDATION DRAIN DETAIL
PERFORATED PIPE PLACED 2" ABOVE DRAIN SUBGRADE ËMBEDDED IN FREE -DRAI NING GRAVEL ORNT
DISC HARGEÐ TO A SUITABLE REçEPTACLE S UCH THA T TN-SITE
CRU SHED ROCK ENVE LOPE WITH 40t GRA DE TO SUMP PIT OR
WELL AS OFF-S ITE STAB¡LITY IS NOT ADVERSELY MPACTED B.DEPTH BASED ON TFEN HOLE INSP ECTITN FOR SHALLOW
FOUNDATION OPTION c.ALL FOUNDATION OR OVER.EXCAVA TED S UBGRADES MUST B E NS PECTEÐ AND APP ROVE D BY A
GEÐTECHNICAL ENGINEER-
AS