HomeMy WebLinkAboutSubsoils Report for Foundation DesignAMERICAN
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COMMUNITY DEVEL0PM'rrHTGeotechnical Evaluation Report
Lot 43 Grass Mesa Ranch
Near 311 Rodeo Drive Rifle CO
Date: November 03, 2023;Project No: 0285-WS23
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8882:76-402:7
November 06,2023
PROJECT NO: 0285-D23
CLIENTS: Mr. Mario
Reference: Lot-specific Geotechnical Evaluation, Lot 43 Grass Mesa Ranch, Near 311 Rodeo
Drive, Rifle, CO
At your request, we have completed the geotechnical evaluation for the referenced project in
accordance with the American GeoServices, LLC (AGS) Proposal. Results of our evaluation and
design recommendations are summarized below.
PROJECT INFORMAT¡ON
The site is located as shown in Figure 1 and Figure 2. The proposed development will consist of
residential construction. We do not anticipate significant site grading for this project. We anticipate
proposed structure will be constructed with light to moderate foundation loads.
SCOPE OF WORK
Our scope of services included the geologic literature review, soil explorations, preliminary
geologic hazards evaluation, geotechnical evaluation, and the preparation of this report.
Evaluation of any kind of existing structures on and adjacent to the site was beyond our scope of
services.
ln October 2023, we performed soil exploration (81) at approximate location shown in Figure 2
and collected soil/rock samples. Our soil exploration included logging of soils from an excavated
test pit, Our exploration extended to a maximum depth of I feet below existing ground surface
(BGS). All soil/rock 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.
www,americangeoservices.com
sma @a merica ngeoservices.com
Ph: (BBB) 276 4027
Fx: (877\ 47L 0369
The Legend and Notes necessary to interpret our Exploration Logs are also included in an
appendix. Data obtained fróm 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 conclusions and recommendations presented in
this report.
SURFACE CONDITIONS
The site is roughly an irregular-shaped parcel of land as shown in Figure 2. Currently the site
topography is moderately to steeply sloping. At the time of our site visit, there was no visual
indication of active slope instability or active landslides in the site vicinity. However, our review
of available geology maps and geologic hazards information did reveal the presence of possibly
active geologic hazards in the immediately vicinity of the site. lt should be noted that a detailed
geologic hazards evaluation was beyond our scope of services.
SUBSURFACE CONDITIONS
Subsurface conditions encountered in our explorations and noted in our literature research are
described in detail in the Exploration Logs provided in an Appendix and in the following
paragraphs. Soil classification and identification is based on commonly accepted methods
employed in the practice of geotechnical engineering. ln some cases, the stratigraphic boundaries
shown on Exploration Logs represent transitions between soil types rather than distinct lithological
boundaries. lt should be recognized that subsurface conditions often vary both with depth and
laterally between individual exploration locations. The following is a summary of the subsurface
conditions encountered at the site.
Surface Gonditions: Approximately 8-10 inches of topsoil, loam, sand, silt, clay and root mass
is present at the surface.
Sand-Silt-Glay-Rock Reworked Alluvium: Site is primarily underlain by stiff mixtures of sand-
silt-clay-rock (CL/ML, SC, GC) extending to a depth of about I feet. These soils exhibited low
plasticity in the field and in the laboratory. Below a depth of about 4-6 feet, cobbles and small
boulders are present.
Groundwater: Groundwater was not encountered during exploration or at the time of completion
of our soil explorations. This observation may not be indicative of other times or at locations other
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 the surface and subsurface drainage characteristics of the surrounding area.
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PRELIMINARY GEOLOGIC HAZARDS EVALUATION
Expansive/Collapsible Soils: The site is possibly underlain by low expansive clayey soils or
clayey sedimentary bedrock materials. The site location is not located within or near known swell
hazard soil zones that pose a significant geotechnical concern. Moreover, local pockets of
'collapsible' soils/materials can occur through the site and may cause settlement in the
foundations or flatwork around the site.
Flooding: Proposed construction area is not located within 1O0-year flood hazard zone, however,
a flood hazard evaluation was beyond our scope of services. We recommend hiring an
experienced hydrologist to evaluate the flood hazards for the site, or an in-depth evaluation of
published flood hazard maps, considering the proximity of the site to the river.
Debris Flow: Site may be located within alluvial fans or flood channels. Debris flow hazard at the
site is minimal under normal site, topographic, geologic, and weather conditions.
Rockfall: At the time of our site visit, rockfall hazards were not noted in the proposed construction
area. ln our opinion, rockfall hazard at the site are minimal under normal site, topographic,
geologic, and weather conditions. lf the owner is not willing to assume any and all risks associated
with rockfall hazards, then we recommend performing a detailed rockfall hazard evaluation.
Landslides: Our review of available geologic maps and landslide hazard maps did not indicate
that recent landslides or recent debris flow had occurred at the site or in the immediate proposed
building area. During our site reconnaissance, we did not notice scarps, crevices, depressions,
tension cracks in the ground surface, irregular slope toes, exposed surfaces of ruptures without
vegetation, presence of distinct fast-growing vegetation, undrained depressions, etc., that are
generally indicative of local active and/or inactive landslides or slope instability that would
adversely impact the on-site structure at this time, however, a detailed landslide evaluation of any
kind or detailed slope stability evaluation was beyond our scope of services.
Notwithstanding, the site vicinity area is located within the mapped landslide hazard areas
surrounding the site (Figure 6). There are potentially mapped landslides and/or ancient landslide
deposits close to the site boundaries. There is also moderate to high potential for the presence
of dormant and/or unknown historic landslides, deep-seated ancient landslides, or geologically-
recently developed dormant landslides in the site vicinity close to the site.
The proposed construction area itself is not mapped as being situated within the existing active
or ancient active landslide mass or an ancient active global landslide. Howêvêr, the site vicinity
area to the east is mapped as having landslide hazards (Figure 6). Considering these findings,
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the site topography, and site geologic conditions, it is our opinion that the immediate site vicinity
area have 'site-specific landslide hazards' and has some 'inherent' risk associated with slope
instability and structural impact from the movement of any global/ancient landslide and local slope
movements. Moreover, historically, with construction in such areas, there is always an inherent
risk associated with ground movement and/or settlements and related structural damage. The
owner should understand these inherent risks related to site vicinity. 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 evaluation)
should be performed in the site vicinity area to quantify the abovementioned risks and to provide
detailed geotechnical design recommendations for comprehensive mitigation measures. Unless
these recommended studies are performed, the owner is completely responsible for taking all
risks associated with any future potential for instability at the site occurring due to landslide
hazards in the site vicinity.
Earthquakes: Based on site geology, topography, and our preliminary 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 relatively low and do not pose
a significanthazard. Ground accelerations in excess of 0.19 to -0.29 are not anticipated to occur
at the site.
Based on the results of our subsurface explorations and review of available literature (2009
lnternational Building Code), in our opinion, a site classification "C" may be used for this project.
However, this site classification may be revised by performing a site-specific shear wave velocity
study.
Subsurface soil conditions at the site are not susceptible to liquefaction. Seismically induced slope
instability may occur on a global scale impacting not just the site but also the surrounding area,
however, such an evaluation was beyond our scope of services. A detailed seismic hazards
evaluation of the site was beyond our scope of services.
CONCLUSIONS AND RECOMMENDATIONS
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, and provided the
owner is willing to assume any and all risks associated with geologic hazards described earlier in
this report. lt should be noted that our conclusions and recommendations are intended as design
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guidance. They are based on our interpretation of the geotechnical data obtained during our
evaluation and following assumptions:
. Proposed/Final site grades will not differ significantly from the current site grades;
. Proposed foundations will be constructed on level ground; and
¡ Structural loads will be static in nature.
Construction recommendations are provided to highlight aspects of construction that could affect
the design of the project. Entities requiring information on various aspects of construction must
make their own interpretation of the subsurface conditions to determine construction methods,
cost, equipment, and work schedule.
SHALLOW FOUNDATIONS
We recommend that the proposed structure be supported on shallow spread footings designed
and constructed in accordance with following criteria:
Due to the presence of potential collapsible soils, over-excavate soils from within the
foundation areas to a depth of 24 inches below the bottom of footings, then surficial compact
the excavated area with a vibratory roller, and then call AGS for an open hole
inspection.
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Foundations bearing upon properly prepared and approved subgrade should be designed for
a maximum allowable bearing pressure of 2,000 pounds per square foot (psf).
Estimated final structural loads will dictate the final form and size of foundations to be
constructed. However, as a minimum, we recommend bearing walls be supported by
continuous footings of at least 18 inches in width. lsolated columns should be supported on
pads with minimum dimensions of 24 inches square.
Exterior footings and footings in unheated areas should extend below design/preferred frost
depth of 42 inches.
Continuous foundation walls should be reinforced in the top and bottom to span an
unsupported length of at least 8 feet to further aid in resisting differential movement. As a
minimum, additional reinforcement as shown in Figure 7 should be placed.
Foundation/stem walls should be adequately designed as retaining walls and adequate
drainage measures should be implemented as shown in Figure 8.
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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 total settlement.
STRUCTURAL FLOOR & CRAWL SPACE
We understand a structural/framed floor with crawl space may be used for this project. The grade
beams (if used) and floor system should be physically isolated from the underlying soil materials
with crawl-space type construction. The void or crawl space of minimum of 6 inches or whatever
minimum current 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 of
the moisture/groundwater within native soils underlying the structure, water intrusion from
snowmelt and precipitation, and surface runoff or infiltration of water through irrigation of lawns
and landscaping. ln crawl space, excessive moisture or sustained elevated humidity can increase
the potential for mold to develop on organic building materials. A qualified professional engineer
in building systems should address moisture and humidity issues.
CRAWL SPACE PERIMETER/U NDERDRAIN SYSTEM
ln order for the crawl space to remain free of moisture, it is important that drainage
recommendations are properly implemented, and adequate inspections are performed prior to the
placement of concrete.
As a minimum, subgrade beneath a structural floor system should be graded so that water
does not pond. Perimeter drains and under-slab drains should be installed in conjunction with
a sump pump'system to eliminate the potential for ponding and any subsequent damage to
foundation and slab elements. The lot-specific perimeter dewatering, and underdrain systems
should be properly designed and connected to the area underdrain system or a sump-pump
system for suitable discharge from the lot.
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Drainage recommendations illustrated in Figure I should be implemented. The subsurface
drainage system should consist typically of 4-inch minimum diameter perforated rigid PVC or
flexible pipe (rigid preferred 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
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soils from clogging the system in the future. The pipe should drain by gravity to a suitable all-
weather outlet or a sump-pit. Surface cleanouts of the perimeter drain should be installed at
minimum serviceability distances around the structure. A properly constructed drain system
can result in a reduction of moisture infiltration of the subsurface soils. Drains which are
improperly installed can introduce settlement or heave of the subsurface soils and could result
in improper surface grading only compounding the potential issues.
a The underdrain system should consist of adequate lateral drains and a main drain, regular
clean out and inspection locations, and proper connections to the sump-pump system for
discharge into suitable receptacles located away from the site.
a The entire design and construction team should evaluate, within their respective field of
expertise, the current and potential sources of water throughout the life of the structure and
provide any design/construction criteria to 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.
S LAB.ON.G RADE AN D PERI M ETERYU N DERDRAI N SYSTEM
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 construction (if used),
following recommendations should be strictly followed:
A perimeter dewatering system should be installed to 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 from the lot.
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a As a minimum, drainage recommendations illustrated in Figure 8 should be implemented. The
subsurface drainage system should consist typically of 4-inch minimum diameter perforated
rigid PVC or flexible pipe (rigid preferred 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 from clogging the system in the future. The pipe should drain by gravity to
a suitable all-weather outlet or a sump-pit. Surface cleanouts of the perimeter drain should
be installed at minimum serviceability distances around the structure. A properly constructed
drain system can result in a reduction of moisture infiltration of the subsurface soils. Drains
which are improperly installed can introduce settlement or heave of the subsurface soils 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 current and potential sources of water throughout the life of the structure and
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provide any design/construction criteria to 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 to moderate". Therefore, the
slab can be constructed as a slab-on-grade provided the owner is aware that there is still potential
risk of some slab movement due to presence of possibly expansive soils. ln order to reduce this
potential, recommendations given for the over-excavation and backfilling of the foundation areas
should be used for the slab areas as well.
The actual slab movements that will occur on a particular project site are very difficult, if not
impossible, to predict accurately because these movements depend on loads, evapo-
transpiration cycles, surface and subsurface drainage, consolidation characteristics, swell index,
swell pressures and soil suction values. 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.
RETAINING WALL
Retaining walls for at-rest conditions can be designed to resist an equivalent fluid density of 55
pcf for on-site fill materials if needed only imported granular backfill meeting CDOT Class 1
structural backfill should be used. Retaining walls for unrestrained conditions (free lateral
movement) can be designed to resist an equivalent fluid density of 35 pcf for on-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 of 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 of safety or allowances for surcharge
loads such as adjacent foundations, sloping backfill, vehicle traffic, or hydrostatic pressure. We
should be contacted to provide additional recommendations for any specific site retaining
conditions.
Retaining wall backfill should be placed in strict accordance with our earthwork recommendations
given below and as illustrated in Figure 8. Backfill should not be over-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 drainage composite or drain board such as the
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MiraDrain 2000 or an engineer-approved equivalent may be installed along the backfilled side of
the basement foundation wall.
EARTHWORK CONSTRUCTION
Site grading should be carefully planned so that positive drainage away from all structures is
achieved. Following earthwork recommendations should be followed for all aspects of the project.
Fill material should be placed in uniform horizontal layers (lifts) not exceeding 8 inches before
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 f-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 approved by AGS prior to placement. Fill
placement obseruations and fill compacfion fesfs should be performed by AGS Engineering in
order to minimize the potential for future problems. Fill material should not be placed on frozen
ground. Vegetation, roots, topsoil, the existing fill materials, and other deleterious material to
depth of approximately 6 inches should be removed before new fill material is placed.
On-site fill to 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.
Fill to be placed in wall backfill areas and driveway areas and all other structural areas should be
compacted to 95% of Standard Proctor (ASTM D 698) dry density or greater. Compaction in
landscape areas should be 85% or greater.
lmported structural fill should consist of sand or gravel 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, Structural fill should also have a percent fine between 15 to 30 percent passing the
No. 200 sieve. Structural fill should be moisture conditioned to within 2 percent of OMC and
compacted to at least 95 percent of Standard Proctor (ASTM D698) dry density.
ln our opinion, the materials encountered at this site may be excavated with conventional
mechanical excavating equipment. 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 building footprint, these materials may be encountered
during excavation activities. Debris materials such as brick, wood, concrete, and abandoned
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utility lines, if encountered, should be removed from structural areas when 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 soils should be encountered at this site during
excavation. OSHA recommends maximum allowable unbraced temporary excavation slopes of
1.25:1(H:V) for Type B soils for excavations up to 10 feet deep. Permanent 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 after completion to minimize
erosion.
We recommend a minimum of 12feet of clearance between the top of excavation slopes and soil
stockpiles or heavy equipment or adjacent structures. This setback recommendation may be
revised by AGS once the project plans are available for review. 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 soils encountered at the site will be susceptible to some sloughing and
excavations should be periodically monitored by AGS's representative.
It should be noted that the above excavation recommendations are commonly provided by local
consultants. The evaluation of site safety during construction, stability of excavated slopes and
cuts, and overall stability of the adjacent areas during and after construction is beyond our scope
of services. At your request, we can provide these services at an additional cost.
During construction in wet or cold weather, grade the site 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 areas to dry before resuming
construction. Berms, ditches and similar means may be used to prevent storm water from
entering the work area and to convey any water off-site efficiently.
lf earthwork is performed during the winter months when freezing is a factor, no grading fill,
structural fill or other fill should be placed on frosted or frozen ground, nor should frozen material
be placed as fill. Frozen ground should be allowed to thaw or be completely removed prior to
placement of fill. A good practice is to cover the compacted fill with a "blanket" of loose fill to help
prevent the compacted fill from freezing overnight. The "blanket" of loose fill should be removed
the next morning prior to resuming fill placement.
During cold weather, foundations, concrete slabs-on-grade, or other concrete elements should
not be constructed on frozen soil. Frozen soil should be completely removed from beneath the
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concrete elements, or thawed, scarified and re-compacted. The amount of time passing between
excavation or subgrade preparation and placing concrete 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.
GENERAL DRAINAGE
Proper surface drainage should be maintained at this site during and after completion of
construction operations. The ground surface adjacent to buildings should be sloped to promote
rapid run-off of surface water. We recommend a minimum slope of six inches in the first five
horizontal feet for landscaped or graveled areas. These slopes should be maintained during the
service life of buildings. lf necessary, adequate interceptor drains should be installed on uphill
sides to intercept any surface water run-off towards the site.
Landscaping should be limited around building areas to either xeri-scaping, landscaping gravel,
or plants with low moisture requirements. No trees should be planted or present within 15 feet of
the foundations. lrrigation should be minimal and limited to maintain plants. Roof downspouts
should discharge on splash-blocks or other impervious surfaces and directed away from the
building. Ponding of water should not be allowed immediately adjacent to the building.
It is important to follow these recommendations to minimize wetting or drying of the foundation
elements throughout the life of the facility. Construction means and methods should also be
utilized which minimize improper increases/decreases in the moisture contents of the soils during
construction.
Again, positive drainage away from the new structures is essential to the successful performance
of foundations and flatwork and should be provided during the life of the structure. Paved areas
and landscape areas within 10 feet of structures should slope at a minimum grade of 10H:1V
away from foundations. Downspouts from all roof drains, if any, should cross all backfilled areas
such that they discharge all water away from the backfill zones and structures. Drainage should
be created such that water is diverted away from building sites and away from backfill areas of
adjacent buildings.
CONCRETE CONSTRUCTION
Concrete sidewalks and any other exterior concrete flatwork around the proposed structure may
experience some differential movement and cracking. While it is not likely that the exterior
flatworks can be economically protected from distress, we recommend following techniques to
reduce the potential longterm movement:
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Scarify and re-compact at least 12 inches of subgrade material located immediately beneath
structures.
Avoid landscape irrigation and moisture holding plants adjacent to structures. No trees should
be planted or present within 15 feet of the foundations.
. 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.
LIMITATIONS
Recommendations contained in this report are based on our field observations and subsurface
explorations, limited laboratory evaluation, and our present knowledge of the proposed
construction. lt is possible that soil conditions could vary between or beyond the points explored.
lf soil conditions are encountered during construction that differ from those described herein, we
should be notified so that we can review and make any supplemental recommendations
necessary. lf the scope of the proposed construction, including the proposed loads or structural
locations, changes from 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 a detailed geologic hazards evaluation of the
site. Therefore, any and all risks associated with geologic hazards are assumed by the owner.
Otherwise, a detailed geologic hazards evaluation should be performed by AGS. Our Scope of
Work for this project did not include research, testing, or assessment relative to past or present
contamination of the site by any source. lf such contamination were present, it is very likely that
the exploration and testing conducted for this report would not reveal its existence. lf the Owner
is concerned about the potentialfor such contamination, additional studies should be undertaken.
We are available to discuss the scope of such studies with 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 with the passage of time. Based on the intended
use of the report within one year from the date of report preparation, AGS may recommend
additional work and report updates. Non-compliance with any of these requirements by the client
or anyone else will release AGS from any liability resulting from 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 non-compliance.
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ln this report, we have presented judgments based partly on our 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 area. Our company is not responsible for the conclusions,
opinions or recommendations made by others based on the data we have presented. Refer to
American Society of Foundation Engineers (ASFE) 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 entitled to rely on information, conclusions or recommendations presented in
this document without the prior written approval of AGS.
We appreciate the opportunity to be of service to you on this project. lf we can provide additional
assistance or observation and testing services during design and construction phases, please call
us at 1 8882764Q27.
Sincerely,
I
Sam Adettiwar, MS, PE, GE
Senior Engineer
Attachments
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Project No: 0285-D23
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DESIGNATES SUBSURFACE EXPLORATION LOCATION, BY AMERICAN GEOSERVICES, LLC. ,NOVEMBER 2023 SEE
RATION LOG IN APPENDIX FOR FURTHER DETAILS.
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' C€Þ ô 5 aI e Ê ¿EæaÐQ 'oÈoÉa ËsleàE\t€¡dI É O ø¡ E Co¿ c4 0 ÍÞ cd --GO! EECç¡OCOc t ðô > h ¡o o ¡ I ol ci ¡ ð E ¡!¡t¡ e d o% oa þ g¡ b¡! €¡ övÞ E Od.-¡O a O ^Ð 6h ÉÊ .-OH .o
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't óaÉv!*r É E¡ aÉa -< a ! Ê U¡!q g !o o 6Ég t -gO.¡¡d'o r lo É-a !úd^þ ¡¡ c - Eo o t Ed À,! u o 0æI Íid! ¡.ño c s É5 ód!)ÊCo9 -o r¡ o¡ 5¡O¡r O a êvT
aø
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-;
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'16r
. O ÀËâdvi t Xãt âEuEIÊ0ôlJr¡{ıù:Ë- - Õ,Ë .oÀ gEÈuu @!o d- C Þ Êliþ o I ¡ca 5 q
I!68 Ed¡¡ o!É¿9Ét 3É¿ óld cüo o e > tr t Éf¡ o 5 u* ta å G þ itlt-O'. ÉûG¡Cti ! ! c É te c aa¡a o o I. > ô al t| €a É:!èÉtl.¡.¡oas!dÉoop! it* .É&ÐL\da Hd oÉ od¡â0 ¡ tÉ !ftÉ€ !e¡! O ö a a cad5 ! t !i¡t t ¡. ! o ¡oo I 6.6 C Êdlld a Êd a ca aÊ!û3elrD! a oha çl a É -É 6 !¡ 4.ê o o Ed!o¡ lÉ! rôr -!EO a5otCOO! -oaU'.1 > O 6 r. i{ r|Õ¡d A3t¡! 3l¡ ! ¡ó É > f..é o{ o a kád a øaEqıóêd6ùâa
C.
+
If'li
lr
I
I
I
s s'Þ s
å
î
ê"0g
-".
í
¿r.
I
)
I
. elì
_ Ì'.fils;f*a_.¡
z
LEGEND
Rifle Area, Colorado, Parts of Garfield and Mesa
Counties (CO683)
Rifle Area, Colorado, Parts of Garfield e
and Mesa Counties (CO583)
Map
Unit
Symbol
Map Unit Name
Totals for Area of
fnterest
29.O lOO.Oo/o
¡\tul F-Rlf ,{.N C EL}SERV ICES
Acres Percent of
in AOI AOI
N
REFERENCE:
WEB SOIL SURVEY
44 Morval loam, 3 to
12 percent slopes
4.9 16.90/0
45 Morval-Tridell
complexn 5 to 25
percent slopes
Torriorthents-
Rock outcrop
complex, steep
11.3 38.Bo/o
67 12.8 44,34/o
.4v ùtêl:ia{r:ll: - ¡D.rirÐßrY,\*'irr(rm FIGURE 4: SOIL SURVEY MAP
(j
s
ca
a\
C4ç
JÙq
t6fr
Leg en d
Co I la pså b I e-So i ls-with Mee ke r
EG-1 4 Eolian (wind-blown) deposits
EG-l4 Dune and sheet sand depnsits
r¡s"lÉ::ì.rlt
EG-14 Cretaceous and Tertiary Fo¡-metions
ffi
EG- 1 4 Eva porite Forr¡atlons
:'.'jì ]
¡\,\'trER ICAN C ËL)SERV ICES
,itttflf! +,Éì . ,turir¡nÈ.,tsrf |iÂ-.$fr
N
IEFERENCE:
}OLORADO GEOLOGICAL
iURVEY 4V FIGURE 5: COLLAPSIBLE SOILS MAP
.-,ll I
í,.
RiflË
Å,\,1Llt lt.-¡\ N Ct,ùSf.lt\¡lt-[ 5
Colorado-landslide-inventory-new
com pi led-le ndsl id es-from-Li DAR-and-otlrer-me ps
T
compi led-la ndslld es_from_24K_rns ps
compiled-l;ndslides-from-48-1 û0K-mapsI
compiìed-landslides-from-H B 1 041 -maps
Fcd
oo-p¡t.¡-l "nerl
ìd *s-frcnr-250K-nrapst
GeolocicQu adsln dex
SITE LOCATION
FIGURE 6: COLORADO LANDSLIDES
INVENTORY
¡J fj I tr {.r ¡r _ct
(ij,¿;,'.4
:ra
i-l
,.¡5 li.tll.iÅ
il
;.ri
{
ta
ír- ; : ., ,,'; '\'
.s\ ;!lf, + i,r,.- { :i,: rft¡¡i]\((1{.r -ú,r
*î'ù-.',----
\
\\
/
t
Nürlh
IEFERENCE:
)OLORADO LANDSLIDES
{VENTORY
l r
N
V
NOTES:
A. ADDITIONAL REINFORCEMENT, #4 CONTINUOUS BAR,
BOTTOM OF FOOTING.
B. ADDITIONAL REINFORCEMENT, H AT 48" C/C, TOP OF
FOOTING.
C. REINFORCEMENTAS PER STRUCTURAL ENGINEER'S
DESIGN. AS A MINIMUM, USE #4 AT 48" CIC.
NOTES:
D. 4Od NAILS EVERY 24' THROUGH BOTTOM PLATE
INTO PRE-DRILLED HOLES OF THE FLOOR PLATE.
WALL BASE BOARD
NAILED ONLY TO BASE
PLATE;TOP IS FREE
3" MIN VOID SPACE
ADDITIONAL FOOTING REINFORCEMENT DETAIL
NEW INTERIOR
WALL
RETAINING WALL DIMENSIONS AND
REINFORCEMENT TO BE DONE BY
PROJECT STRUCTURAL ENGINEER BASED
ON GEOTECHN ICAL RECOMMENDATIONS.
CONCRETE FOOTING TO BE
DIMENSIONED BY PROJECT
STRUCTURAL ENGINEER BASED ON
GEOTECHNICAL RECOMMENDATIONS.
WALL FINISH
MATERIAL
PRESSURE TREATED 2-X4" BASE
PLATE SECURED WITH 3'
CONCRETE NAILS OR EQUIVALENT
SPACER-SAME TH ICKN ESS AS
WALL FINISH MATERIAL
CONCRETE BASEMENT SLAB
"FLOAT' (FLOATING WALL DETAIL)
AMERICAN CEOSERVICES
888.27ó.40?? â¡¡ericangeoservices.conr_,iv FIGURE 7: TYPICAL DETAILS
FLEXIBLE ADH ESIVE EQU IVALENT,
4" ABOVE GROUND;
MAINTAIN LEAK-FREE
COMPACTED EARTH BACKFILUSOIL CAP
(DO NOT USE tF STEM WALL rS
DESIGNED AS A RETAINING WALL. IN
CASE OF RETAINING WALL, USE
FREE-DRAINING CRUSHED ROCK FILL TO
AVOI D HYSROSTATIC PRESSURE.
LEAK.FREE AND ADEQUATE
CAPACITY DOWNSPOUTS
4"
MINIMUM 3'THICK
DECORATIVE GRAVEL,
ROCK OR BARK LAYER
AT LEAST 4 FT LONG
20 MIL THICK POLY
SHEET LINER AT LEAST
4FT LONG; EXTEND 4'
ABOVE GROUND & 36'
BELOW GROUND
DOWNSPOUT & MOISTURE BARRIER DETAIL
EXTEND DOWNSPOUT
BEYOND
DECORATIVE LAYER,
10H:1V GRADE;
WITHOUT CAUSING
ADVERSE IMPACT
ON ADJACENT
PROPERTIES; DISCHARGE
ONTO SPLASH BLOCKS.
t
6'MlN l-_
OFFSET FOR ANY
SPRINKLER
HEADS;PART CIRCLE
SPRAYING
AWAY FROM BUILDING
SLOPE TO DRAIN AWAY
FROM STRUCTURE, 10H:1V
(sEE DOWNSPOUT DETAIL)
FOUNDATION/STEM WALL
POLYETHYLENE FILM GLUED TO
FOUNDATION WALL AND EXTENDED
BELOW THE DRAIN AS SHOWN
MIRAFI 140 N FILTER
FABRIC OR EQUIVALENT
f-
l2'MlN
I
TzSLAB-ON-GRADE WITH
EXPANSION JOINTS OR CRAWL-S
6" MIN
OVER-EXCAVATION
(sEE NOTE B)EXCAVATED TRENCH.
NEAR VERTICAL TO
0.5H:1VFREE-DRAINING
CLEAN CRUSHED
ROCIIGRAVEL
\-,SUBGRADE, IN-SITU SOITI
(sEE NOTE C)
PERIMETER OR FOUNDATION DRAIN DETAIL
NOTES:A.4-INCH DIAMETER PERFORATED PIPE PLACED 2'ABOVE DRAIN SUBGRADE EMBEDDED lN FREE-DRAINING GRAVEL OR
CRUSHED ROCK ENVELOPE WIÏH 2% GRADE TO SUMP PIT OR DISCHARGED TO A SUITABLE RECEPTACLE SUCH THAT ON-SITE AS
WELL AS OFF-SITE STABILITY IS NOT ADVERSELY IMPACTED, B. DEPTH BASED ON OPEN HOLE INSPECTION, FOR SHALLOW
FOUNDATION OPTION. C. ALL FOUNDATION OR OVER-EXCAVATED SUBGRADES MUST BE INSPECTED AND APPROVED BYA
AMERICAN CEOSERVICES
888.271'.4027 - rft cnc¡ogeosen iccs.cornl-FIGURE 8: DRAINAGE DETAILS
GEOTECHNICAL ENGINEER,
APPENDIX
B1
Project Number 0285-D23 Test pit excavation using an excavator
GeologisVEngineer SMA Ground Elevation See Figures
Date Explored 10-30-2023 Total Depth of Borehole I Feet
Borehole Diameter Not Applicable Depth to Water Not Encountered
cttoJ
.9
o.
(Et-o
Description / Lithology
*aoo
.C
CLoo
o
çL
E
fú
U'
oJ
troÀ
Jo(toÀ
s
Ðo
ooo
É.
s
o
+a
,9o
=
o
CL
oo
s
JÈ
s
JJ
s
oìØ
tro
-9
CL
Eoo
cLt
ML
cLt
sc/
GC
TOPSOIL: S" thick
Mixture of SILT, CLAY, and ROCK
fragments, light brown to pale tan, low
plasticity, stiff, damp
Mixture of SILT, CLAY, SAND, ROCK
fragments, COBBLES, small
BOULDERS, light brown to pale tan, low
plasticity, damp
Ã
-10-
-15-
-20-
3
I
End of Exploration.
Groundwater was not encountered during
or at the completion of drilling.
At completion, exploration was backfilled
with soilcuttings.
AMERICAN CEOSERVICES,)/888.27ó.4027 - âñcdmgosenìc€scoñ Page 1
Map Unit Description: Morval loam, 3 to l2 percent slopes--Rifle Area, Colorado, Parts of
Garfield and Mesa Counties
Rifle Area, Golorado, Parts of Garfield and Mesa
Counties
44-Morval loam, 3to 12 percent slopes
Map Unit Setting
National map unit symbol: jnyc
Elevation: 6,500 to 8,000 feet
Farmland classification; Not prime farmland
Map Unit Composition
Morval and similar so/s; 85 percent
Estimates are based on obseruations, descriptions, and transects of
the mapunit.
Description of Morval
Setting
Landform: Valley sides, mesas
Down-slope shape: Convex, linear
Across-s/op e shape : Convex, linear
Parent material: Reworked alluvium derived from sandstone and/or
reworked alluvium derived from basalt
Typical profile
H1 -0 foSrnchesr loam
H2 - 5 to 17 inches; clay loam
H3 - 17 to 27 inches: stony clay loam
H4 - 27 to 60 inches; stony loam
Properties and qualities
S/ope; 3 to 12 percent
Depth to restrictive feature: More than B0 inches
Drai n age c/ass: Well d rained
Runoff class; High
Capacity of the most limiting layer to transmit water
(Ksat): Moderately high (0.20 to 0.60 in/hr)
Depth to water table: More than B0 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 25 percent
Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water supply, 0 to 60 inches: Moderate (about 8.4
inches)
lnterpretive groups
Land capability classification (irrigated): 4e
Land capabi I ity cl assification (noni rrig ated) : 4e
Hydrologic Soil Group: C
EcologicalsÍe; R04BAY292CO - Deep Loam
USDA
-
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11t3t2023
Page 1 of 2
Map Unit Description: Morval loam, 3 to 12 percent slopes--Rifle Area, Colorado, Parts of
Garfield and Mesa Counties
Hydric soi/ rafing: No
Data Source lnformation
Soil Survey Area:
Survey Area Data
Rifle Area, Colorado, Parts of Garfield and Mesa Counties
Version 16, Aug 22,2023
USDA7-Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11t3t2023
Page 2 of 2
Map Unit Description: Morval-Tridell complex, 6 to 25 percent slopes--Rifle Area, Colorado,
Parts of Garfield and Mesa Counties
Rifle Area, Colorado, Parts of Garfield and Mesa
Counties
45-Morval-Tridell complex, 6 to 25 percent slopes
Map Unit Setting
National map unit symbol: jnyd
Elevation: 6,500 to 8,000 feet
Farmland classification; Not prime farmland
Map Unit Gomposition
Morual and similar so/s: 55 percent
Tridell and similar so/s: 30 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Morval
Setting
Landform: Mesas, alluvial fans
Down-slope shape: Convex, linear
Across-s/op e sh ape : Convex, linear
Parent material: Reworked alluvium derived from sandstone and/or
reworked alluvium derived from basalt
Typical profile
H1 -0toSinches: loam
H2 - 5 to 17 inches; clay loam
H3 - 17 to 27 inches: stony clay loam
H4 - 27 to 60 inches; stony loam
Properties and qualities
S/ope; 6 to 12 percent
Depth to restrictive feature: More than B0 inches
Drainage c/ass; Well drained
Runoff class: High
Capacity of the most limiting layer to transmit water
(Ksat): Moderately high (0.20 to 0.60 in/hr)
Depth to water table; More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 25 percent
Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water supply, 0 to 60 inches: Moderate (about 8.4
inches)
lnterpretive groups
Land capabil ity cl assification (i rrigated); None specified
Land capab i I ity cl assification (non i rrigated) : 4e
Hydrologic Soil Group: C
Ecologicalsde; R048AY292CO - Deep Loam
USDA:-Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
't1t3t2023
Page 1 ol 2
Map Unit Description: Morval-Tridell complex, 6 to 25 percent slopes--Rifle Area, Colorado,
Parts of Garfield and Mesa Counties
Hydric soil rating: No
Description of Tridell
Setting
Landform: Alluvial fans, mesas
Down-slope shape : Convex
Across-s/op e sh ape : Convex
Parent material: Reworked alluvium derived from sandstone and/or
reworked alluvium derived from basalt
Typicalprofile
H1 - 0 to 10 inches; stony loam
H2 - 10 to 60 inches,: very stony loam
Properties and qualities
S/ope;6 to 25 percent
Depth to restrictive feature: More than 80 inches
Drainage c/ass: Well drained
Runoff class.' Low
Capacity of the most limiting layer to transmit water
(Ksat): Moderately high to high (0.60 to 6.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum content: 30 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water supply, 0 to 60 inches: Low (about 5.2 inches)
lnterpretive groups
Land capabil ity cl assification (i rrig ated); None specified
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: A
Ecologicalsfe: R048AY287CO - Stony Foothills
Hydric so/ rafing; No
Data Source lnformation
Soil Survey Area:
Survey Area Data
Rifle Area, Colorado, Parts of Garfield and Mesa Counties
Version 16, Aug 22,2023
USDA
-
Natural Resources
Gonservation Service
Web Soil Survey
National Cooperative Soil Survey
1'U3t2023
Page 2 of 2
Map Unit Description: Torriorthents-Rock outcrop complex, steep--Rifle Area, Colorado, Parts
of Garfield and Mesa Counties
Rifle Area, Golorado, Parts of Garfield and Mesa
Counties
G7-Torriorthents-Rock outcrop complex, steep
Map Unit Setting
National map unit symbol: jnz1
Elevation: 5,800 to 8,500 feet
Mean annual precipitation; 10 to 15 inches
Mean annual air temperature: 39 to 46 degrees F
Frost-free period: B0 to 105 days
Farmland classification; Not prime farmland
Map Unit Gomposition
Torriorthents, steep, and similar so/s; 60 percent
Rock outcrop, steep:25 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Torriorthents, Steep
Setting
Landform : Mountainsides
Landform position (two-dimensional) : Footslope
Landform position (three-dimensional): Mountainflank, base slope
Down-slope shape: Convex, concave
Across-s/ope shape : Convex, concave
Parent material: Stony, basaltic alluvium derived from sandstone
and shale
Typical profile
H1 - 0 to 4 inches: variable
H2 - 4 to 30 inches: fine sandy loam
H3 - 30 to 34 inches.' unweathered bedrock
Properties and qualities
S/ope; l5 to 70 percent
Depth to restrictive feature:4 to 30 inches to lithic bedrock
Drainage c/ass; Well drained
Runoff class: High
Capacity of the most limiting layer to transmit water
(Ksat): Moderately low to moderately high (0.06 to 0.20 in/hr)
Depth to water table; More than B0 inches
Frequency of f/oodrng: None
Frequency of ponding: None
Calcium carbonate, maximum content:5 percent
Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water supply, 0 to 60 inches: Very low (about 2.4 inches)
lnterpretive groups
Land capability cl assification (i rrigated); None specified
USDA
-
Natural Resources
Conseruation Service
Web Soil Survey
National Cooperative Soil Survey
11t3t2023
Page 1 ol 2
Map Unit Description: Torriorthents-Rock outcrop complex, steep--Rifle Area, Colorado, Parts
of Garfield and Mesa Counties
Land capability classification (nonirrigated): 7e
Hydrologic Soil Group: D
Hydric so,7 rafmg.' No
Description of Rock Outcrop, Steep
Setting
Landform : Mountainsides
Landform position (th ree-di mensional) : Free face
Down-slope shape : Convex
Across-s/op e sh ape : Convex
Typicalprofile
Hl - 0 to 60 inches.' unweathered bedrock
Properties and qualities
S/ope: 15 to 70 percent
Depth to restrictive feature:0 inches to paralithic bedrock
Runoff class; Very high
Capacity of the most limiting layer to transmit water (Ksat); Very low
to moderately high (0.00 to 0.20 in/hr)
Available water supply, 0 to 60 inches: Very low (about 0.0 inches)
lnterpretive groups
Land capabil ity cl assification (i rrigatedl: None specified
Land capability classification (nonirrigated): 8s
Hydric so/ rafing; No
Data Source lnformation
Soil Survey Area:
Survey Area Data
Rifle Area, Colorado, Parts of Garfield and Mesa Counties
Version 16, Aug 22,2023
USDA
-
Natural Resources
Gonservation Service
Web Soil Survey
National Cooperative Soil Survey
11t3t2023
Page 2 ot 2
,r'jv AMERICAN
CEOSERVICES
DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION
UNIFIED SOIL CLASSIFICATION SYSTEM
UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART LABORATORY CLASSIFICATION CRITERIA
COARSE-GRAINED SOILS
(more than 50% of material is larger than No. 200 sieve size.)
Clean Gravels (Less than 57o fines)
", = +
greater than 4;c" =--r, -_
between 1 and 3GWWell-graded gravels, gravel-sand
mixtures, little or no fines GW
GRAVELS
More than 50%
of coarse
fraction larger
than No. 4
sieve size
GP Poorly-g raded gravels, gravel-sand
mixtures. little or no fines GP Not meeting all gradation requirements for GW
Gravels with fines than 12o/o
GM Silty gravels, gravel-sand-silt mixtures GM Atterberg limits below'4"
line or P.l. less than 4 Above "4" line with P.l. between
4 and 7 are borderline cases
requiring use of dual symbolsGCClayey gravels, gravel-sand-clay
mixtures (,t-Atterberg limits above "4"
line with P.l. greater than 7
Clean Sands than 5%
c,, = ?uo greater than 4:C^ =
D¡o
between 1 and 3" D1o ' DrnxDeo---''--"SW Well-graded sands, gravelly sands,
little or no fines SW
SANDS
50% or more
of coarse
fraction smaller
than No. 4
sieve size
SP Poorly graded sands, gravelly sands,
little or no fines Sp Not meeting all gradation requirements for GW
SM Silty sands, sand-silt mixtures SM Atterberg
line or P.l.
limits below "A"
less than 4
Limits plotting in shaded zone
with P.l. between 4 and 7 are
borderline cases requiring use
of dual symbols.sc Clayey sands, sand-clay mixtures sc Atterberg limits above "A"
line with Pl. greater than 7
FINE-GRAINED SOILS
(5O% or more of material is smaller than No. 200 sieve size.)Determine percentages of sand and gravel from grain-size curve. Depending
on percentage of fines (fraction smaller than No. 200 sieve size),
coarse-grained soils are classified as follows:
SILTS
AND
CLAYS
Liquid limit
less than
50%
ML
lnorganic silts and very fine sands, rock
flour, silty of clayey fine sands or clayey
silts with slight plasticity
Less than 5 percent
More than 12 percent
S to l 2 percent . . . . . ,
.GWGESWSP
. GM, GC, SM, SC
Borderline cases requiring dual symbols
CL
lnorganic clays of low to medium
plasticity, gravelly clays, sandy clays,
silty clays, lean clays PLASTICITY CHART
OL Organic silts and organic silty clays of
low plasticity
60
3Ìso
E-
x40
l¡¡o
=30F
ø, 20
t-.nf10
0.
SILTS
AND
CLAYS
Liquid limit
50%
or greater
MH
lnorganic silts, micaceous or
diatomaceous fine sandy or silty soils,
elastic silts
CH lnorganic clays of h¡gh plasticity, fat
clays
OH Organic clays of medium to high
plasticity, organic silts
\,\ l/0 10 20 30 40 50 60 70 80 90 100
L|QUTD LrMtT (LL) (o/o)
HIGHLY
ORGANIC
SOILS lJ¿
CH
N
=0
CL
I
MH&OH
I
ML&OL
I
PT Peat and other highly organic soils
DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION
LABORATORY/FIELD TESTING
EXPLORATION LOGS
DRY DENSTTY (PCF)
wET DENSTTY (PCF)
MOTSTURE CONTENT (%)
PT.ASTTC LrMrT (%)
LIQUID LIMIT (o/o)
PLASTICITY INDEX
oRGAN|C CONTENT (%)
SATURATTON PERCENT (%)
SPECIFIC GRAVITY
coHEstoN
ANGLE OF INTERNAL FRICTION
UNCONFINED COMPRESSION
STRENGTH
PERCENT PASSING THE #2OO SIEVE
CALIFORNIA BEARING RATIO
VANE SHEAR
POCKET PENETROMETER
DRIVE PROBE
STANDARD PENETRATION TEST
BLOWS PER FOOT (N VALUE)
SHELBY TUBE SAMPLE
GROUND WATER
ROCK QUALIry DESI DNATION
TEST PIT
BORING
HAND AUGER
NCY OF COHESIVE SOILS
CONSISTENCY sTP (BPF)
0-1
2-4
MEDIUM STIFF 5-8
STIFF 9-15
VERY STIFF 16-30
HARD 30+
RELATIVE DENSITY OF COHESIONLESS SOILS
DENSITY
DD
WD
MC
PL
LL
PI
oc
S
SG
c
o
QU
#200
CBR
VS
PP
DP
SPT
BPF
SH
GW
RQD
TP
B
HA
PP (TSF)
0.25 - 0.5
0.5 - 1.0
1.0 - 2.0
2.O - 4.O
OVER 4.0
VERY LOOSE
sPT (BPF)
ó-4
LOOSE 5-10
MEDIUM DENSE 11-30
DENSE 31-50
VERY DENSE 50+
PARTICLE SIZE IDENTIFICATION
ñn¡¡e
ROCK BLOCK
BÓÙiDÈR
DIAMETER
(rNcHES)
SIEVE NO.
>120
12-120
COBBLE 3-12
GRAVEL
COURSE 3t4-3
FINE
SAND- coÀRSÈ
1t4 - 3t4 NO.4
4.75 MM NO. 10
l
I
l
j
1
-1
j
¡
t.
j
I
l
!
I
l
i
I
l
l
l
i
)
i
I
I
i
I
MEDIUM 2.OMM NO.40
FINE
Sir-i
.425MM NO.200
.075 MM
CLAY <0.005 MM
GRAIN SIZE
FINE
GRAINED
<0.04 tNcH FEW GMINS ARE
DISTINGUISHABLE IN THE
FIELD OR WITH HAND LENS
GRAINS ARE
DISTINGUISHABLE WITH THE
AID OF A HAND LENS.
V
-
GR9UNDWATERLEVEUSEEPAGE
ENCOUNTERED DURING EXPLORATION
V.-
STATIC GROUNDWATER LEVEL WITH
DATE MEASURED
MEDIUM
GRAINED
côÀRSÈ
GRAINED
0.04-0.2 tNcH
0.04-0.2 tNcH MOST GRAINS ARE
DISTINGUISHABLE WITH THE
NAKED EYE.
-.1.,...._._.) .-.
VERY SOFT
SOFT
LESS THAN 0.25
-l
l
DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION
SPT EXPLORATIONS
STANDARD PENETRATION TESTING IS
PERFORMED BY DRIVING A 2 - INCH O,D. SPLIT-
SPOON INTO THE UNDISTURBED FORMATION AT
THE BOTTOM OF THE BORING WITH REPEATED
BLOWS OF A 140 - POUND PIN GUIDED HAMMER
FALLTNG 30 |NCHES. NUMBER OF BLOWS (N
VALUE) REQUIRED TO DRIVE THE SAMPLER A
GIVEN DISTANCE WAS CONSIDERED A MEASURE
OF SOIL CONSISTENCY.
SH SAMPLING:
SHELBY TUBE SAMPLING IS PERFORMED WITH A
THIN WALLED SAMPLER PUSHED INTO THE
UNDISTURBED SOIL TO SAMPLE 2.0 FEET OF
solL.
AIR TRACK EXPLORATION
TESTING IS PERFORMED BY MEASURING RATE
OF ADVANCEMENT AND SAMPLES ARE
RETRIEVED FROM CUTTI NGS.
HAND AUGUR EXPLORATION:
TESTING IS PREFORMED USING A 3.25'
DIAMETER AUGUR TO ADVANCE INTO THE EARTH
AND RETRIEVE SAMPLES.
DRIVE PROBE EXPLORATIONS:
THIS "RELATIVE DENSITY' EXPLORATION DEVICE
IS USED TO DETERMINE THE DISTRIBUTION AND
ESTIMATE STRENGTH OF THE SUBSURFACE SOIL
AND DECOMPRESSED ROCK UNITS. THE
RESISTANCE TO PENETRATION IS MEASURED IN
BLOWS-PER-112FOOT OF AN 11-POUND HAMMER
WHICH FREE FALLS ROUGHLY 3,5 FEET DRIVING
THE 0.5 INCH DIAMETER PIPE INTO THE GROUND.
FOR A MORE DETAILED DESCRIPTION OF THIS
GEOTECHNICAL EXPLORATION METHOD, THE
SLOPE STABILITY REFERENCE GUIDE FOR
NATIONAL FORESTS IN THE UNITED STATES,
VOLUME I, UNITED STATES DEPARÏMENT OF
AGRICULTURE, EM-7170-I3, AUGUST 1994, P. 3'17-
321.
CPT EXPLORATION
CONE PENETROMETER EXPLORATIONS CONSIST
, OF PUSHING A PROBE CONE INTO ÏHE EARTH
USING THE REACTION OF A 2O-TON TRUCK. THE
CONE RESISTANCE (OC) AND SLEEVE FRICTION
(FS) ARE MEASURED AS ïHE PROBE WAS
PUSHED INTO THE EARTH. THE VALUES OF QC
AND FS (tN TSF) ARE NOTED AS THE LOCALTZED
INDEX OF SOIL STRENGTH.
ANGULAR
ANGULARITY OF GRAVEL & COBBLES
SUBANGUI.AR
SUBROUNDED
ROUNDED
SOIL MOISTURE MODIFIER
WEATHERED STATE
SLIGHTLY
WEATHERED
MODERATELY
WEATHERED
HIGHLY
WEATHERED
COMPLETELY
WEATHERED
RESIDUAL SOIL
COARSE PARTICLES HAVE SHARP
EDGES AND REI.ATIVELY PLANE SIDES
WITH UNPOLISHED SURFACES.
COARSE GRAINED PARTICLES ARE
SIMILAR TO ANGULAR BUT HAVE
ROUNDED EDGES.
COARSE GRAINED PARTICLES HAVE
NEARLY PLANE SIDES BUT HAVE WELL
ROUNDED CORNERS AND EDGES.
COARSE GRAINED PARTICLES HAVE
SMOOTHLY CURVED SIDES AND NO
EDGES.
l
ABSENCE OF MOISTURE; DUSTY, DRY
TO TOUCH
DAMP BUT NO VISIBLE WATER
VISIBLE FREE WATER
NO VISIBLE SIGN OF ROCK MATERIAL
: WEATHERING; PERHAPS SLIGHT
' DISCOLORATION IN MAJOR
DISCONTINUIry SURFACES.
: DISCOLORATION INDICATES
WEATHERING OF ROCK MATERIAL AND
DISCONTINUITY SURFACES. ALL THE
: ROCK MATERIAL MAY BE DISCOLORED
BY WEATHERING AND MAY BE
SOMEWHAT WEAKER EXTERNALLY
THAN ITS FRESH CONDITION.
LESS THAN HALF OF THE ROCK
MATERIAL IS DECOMPOSED AND/OR
DISINTEGRATED TO SOIL. FRESH OR
DISCOLORED ROCK IS PRESENT EITHER
AS A CONTINUOUS FRAMEWORK OR AS
CORE STONES.
MORE THAN HALF OF THE ROCK
MATERIAL lS DECOMPOSED AND/OR
DISINTEGRATED TO SOIL. FRESH OR
DISCOLORED ROCK IS PRESENT EITHER
AS DISCONTINUOUS FRAMEWORK OR
AS CORE STONE.
ALL ROCK MATERIAL IS DECOMPOSED
AND/OR DISINTEGRATED TO SOIL. THE
' ORIGINAL MASS STRUCTURE lS STILL
LARGELY INTACT.
ALL ROCK MATERIAL IS CONVERTED TO
SOIL. THE MASS STRUCTURE AND
MAÏERIAL FABRIC IS DESTROYED.
THERE IS A LARGE CHANGE IN VOLUME,
BUT THE SOIL HAS NOT BEEN
SIGNIFICANTLY TRANSPORTED.
FRESH
IMPORTANT INFORMATION ABOUT YOUR
GEOTECHNICAL ENGI NEERING REPORT
As the client of a consulting geotechnical
engineer, you should know that site subsurface
conditions cause more construction problems than
any other factor. ASFE/the Association of
Engineering Firms Practicing in the Geosciences
offers the following suggestions and observations
to help you manage your risks.
A GEOTECHNICAL ENG.NEERING REPORT IS
BASED ON A UNIQUE SET OF PROJECT.
SPECIF¡C FACTORS Your geotechnical
engineering report is based on a subsurface
exploration plan designed to consider a unique set
of project-specific factors. These factors typically
include: the general nature of the structure
involved, its size, and configuration; the location of
the structure on the site; other improvements, such
as access roads, parking lots, and underground
utilities; and the additional risk created by scope-
of-servíce limitations imposed by the ct¡eirt. tó
help avoid costly problems, ask your geotechnical
engineer to evaluate how factors that change
subsequent to the date of the report may affect the
report's recommendations.
Unless your geotechnical engineer indicates
otherwise, do not use your geotechnical
engineering report:
MOST GEOTECHNICAL FINDINGS ARE
PROFESSIONAL J UDGMENTS
Site exploration identifies actual subsurface
conditions only at those points where samples are
taken. The data were extrapolated by your
geotechnical engineer who then applied judgment
to render an opinion about overall subsurface
conditions. The actual interface between materials
may be far more gradual or abrupt than your
report indicates, Actual conditions in areas not
sampled may differ from those predicted in your
report. While nothing can be done to prevent such
situations. you and your geotechnical engineer
can work together to help minimize their impact.
Retaining your geotechnical engineer to observe
construction can be particularly beneficial in this
respect.
. when the nature of the proposed structure is
changed. for example, if an office building will
be erected instead of a parking garage, or a
refrigerated warehouse will be built instead of
an unrefrigerated one;¡ when the size, elevation. or configuration of the
proposed structure is altered;
o when the location or orientation of the proposed
structure is modified;¡ when there is a change of ownership; or .for
application to an adjacent site.
A REPORT'S RECOMMENDATIONS CAN ONLY
BE PRELIMINARY
The construction recommendations included in
your geotechnical engineer's report are
preliminary, because they must be based on the
assumption that conditions revealed through
selective exploratory sampling are indicative of
actual conditions throughout a site.
Because actual subsurface conditions can be
discerned only during earthwork, you should retain
your geo- technical engineer to observe actual
conditions and to finalize recommendations. Only
the geotechnical engineer who prepared the report
is fully familiar with the background information
needed to determine whether or not the report's
recommendations are valid and whether or not the
contractor is abiding by applicable
recommendations. The geotechnical engineer who
developed your report cannot assume
responsibility or liability for the adequacy of the
report's recommendations if another party is
retained to observe construction.
SUBSURFACE CONDIT¡ONS CAN CHANGE A
geotechnical engineering report is based on condi-
tions that existed at the time of subsurface
exploration. Do not base construction decisions on
a geotechnical engineering report whose
adequacy may have been affected by time. Speak
with your geotechnical consult- ant to learn if
additional tests are advisable before construction
starts. Note, too, that additional tests may be
required when subsurface conditions arsaffected
by construction operations at or adjacent to the
site, or by natural events such as floods,
earthquakes, or ground water fluctuations. Keep
your geotechnical consultant apprised of any such
events.
GEOTECHNICAL SERVICES ARE PERFORMED
FOR SPECIFIC PURPOSES AND PERSONS
Consu lti n g geotech n ical en gineers prepare reports
to meet the specific needs of specific individuals. A
report prepared for a civil engineer may not be
adequate for a construction contractor or even
another civil engineer. Unless indicated othenvise,
your geotechnical engineer prepared your report
expressly for you and expressly for purposes you
indicated. No one other than you should apply this
report for its intended purpose without first
conferring with the geotechnical engineer. No
party should apply this report for any purpose
other than that originally contemplated without first
conferring with the geotechnical engineer.
GEOENVIRONMENTAL CONCERNS ARE NOT
AT ISSUE
Your geotechnical engineering report is not likely
to relate any findings, conclusions, or
recommendations
Geotechnical engineers cannot accept
responsibility for problems that may occur if they
are not consulted after factors considered in their
report's development have changed.
about the potential for hazardous materials
existing at the site. The equipment, techniques,
and personnel used to perform a
geoenvironmental exploration differ substantially
from those applied in geotechnical engineering.
Contamination can create major risks. lf you have
no information about the potential for your site
being contaminated. you are advised to speak with
your geotechnical consultant for information
relating to geoenvironmental issues.
A GEOTECHNICAL ENGINEERING REPORT IS
SUBJECT TO MISINTERPRETATION Costly
problems can occur when other design profes-
sionals develop their plans based on
misinterpretations of a geotechnical engineering
report. To help avoid misinterpretations, retain
your geotechnical engineer to work with other
project design professionals who are affected by
the geotechnical report. Have your geotechnical
engineer explain report implications to design
professionals affected by them. and then review
those design professionals' plans and
specifications to see how they have incorporated
geotechnical factors. Although certain other design
professionals may be fam- iliar with geotechnical
concerns, none knows 'as much about them as a
competent geotechnical engineer.
BORING LOGS SHOULD NOT BE SEPARATED
FROM THE REPORT Geotechnical engineers
develop final boring logs based upon their
interpretation of the field logs
(assembled by site personnel) and laboratory
evaluation of field samples. Geotechnical
engineers customarily include only final boring
logs in their reports. Final boring logs should not
under any circumstances be redrawn for inclusion
in architectural or other design drawings. because
drafters may commit errors or omissions in the
transfer process. Although photographic
reproduction eliminates this problem, it does
nothing to minimize the possibility of contractors
misinterpreting the logs during bid preparation.
When this occurs. delays. disputes. and
unanticipated costs ara the all-too-frequent result.
To minimize the likelihood of boring log
misinterpretation, give contractors ready access to
the complete geotechnical engineering report
prepared or authorized for their use. (lf access is
provided only to the report prepared for you, you
should advise contractors of the report's
limitations. assuming that a contractor was not one
of the specific persons for whom the report was
prepared and that developing
construction cost estimates was not one of the
specific purposes for which it was prepared. ln
other words. while a contractor may gain important
knowledge from a report prepared for another
party, the contractor would be well-advised to
discuss the report with your geotechnical engineer
and to perform the additional or alternative work
that the contractor believes may be needed to
obtain the data specifícally appropriate for
construction cost estimating purposes.) Some
clients believe that it is unwise or unnecessary to
give contractors access to their geo- technical
engineering reports because they hold the
mistaken impression that simply disclaiming
responsibility for the accuracy of subsurface
information always insulates them from attendant
liability. Providing the best available information to
contractors helps prevent costly construction
problems. lt also helps reduce the adversarial
attitudes that can aggravate problems to
d isproportionate scale.
READ RESPONSIBILITY CLAUSES CLOSELY
Because geotechnical engineering is based
extensively on judgment and opinion, it is far less
exact than other design disciplines. This situation
has resulted in wholly unwarranted claims being
lodged against geotechnical engineers. To help
prevent this problem, geotechnical engineers have
developed a number of clauses for use in their
contracts, reports, and other documents.
Responsibilíty clauses are not exculpatory clauses
designed to transfer geotechnical engineers'
liabilities to other parties. lnstead, they are
definitive clauses that identify where geotechnical
engineers' responsibilities begin and end. Their
use helps all parties involved recognize their
individual responsibilities and take appropriate
action. Some of these definitive clauses are likely
to appear in your geotechnical engineering report.
Read them closely. Your geotechnical engineer
will be pleased to give full and frank answers to
any questions.
RELY ON THE GEOTECHNICAL ENGINEER
FOR ADDITIONAL ASSISTANCE
Most ASFE-member consulting geotechnical
engineering firms are familiar with a variety of
techniques and approaches that can be used to
help reduce risks for all parties to a construction
project, from design through construction. Speak
with your geotechnical engineer not only about
geotechnical issues, but others as well, to learn
about approaches that may be of genuine benefit.
You may also wish to obtain certain ASFE
publications. Contact a member of ASFE of ASFE
for a complimentary directory of ASFE
publications.
ASFE
881 I Colesville Road/Suite G106/Silver Spring, MD 20910
Telephone: 301 1565-2733 Facsimile: 301/589-2017
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