HomeMy WebLinkAboutHARMONY 23 - PDP - PDP160031 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTKumar & Associates, Inc.
TABLE OF CONTENTS
SUMMARY .................................................................................................................................... 1
PURPOSE AND SCOPE OF STUDY ........................................................................................... 3
PROPOSED CONSTRUCTION .................................................................................................... 3
SITE CONDITIONS ...................................................................................................................... 4
SUBSURFACE CONDITIONS ...................................................................................................... 4
LABORATORY TESTING ............................................................................................................. 6
GEOTECHNICAL ENGINEERING CONSIDERATIONS .............................................................. 7
SITE GRADING AND EARTHWORK ........................................................................................... 8
SPREAD FOOTINGS FOUNDATIONS ...................................................................................... 12
DRILLED PIER FOUNDATIONS ................................................................................................ 13
SEISMIC DESIGN CRITERIA ..................................................................................................... 18
FLOOR SLABS ........................................................................................................................... 18
LATERAL EARTH PRESSURES ................................................................................................ 22
UNDERDRAIN SYSTEM ............................................................................................................ 24
SURFACE DRAINAGE ............................................................................................................... 25
WATER SOLUBLE SULFATES .................................................................................................. 26
PAVEMENT THICKNESS DESIGN ............................................................................................ 27
DESIGN AND CONSTRUCTION SUPPORT SERVICES .......................................................... 30
LIMITATIONS ............................................................................................................................. 31
FIG. 1 – LOCATION OF EXPLORATORY BORINGS
FIG. 2 – LOGS OF EXPLORATORY BORINGS
FIG. 3 – LEGEND AND NOTES
FIGS 4 TO 8 - SWELL-CONSOLIDATION TEST RESULTS
FIG. 9 & 10 – GRADATION TEST RESULTS
FIG. 11 – CONCEPTUAL DESIGN - UNDERDRAIN SYSTEM FOR SUBSLAB FILL ZONES
TABLE I – SUMMARY OF LABORATORY TEST RESULTS
APPENDIX A -- DARWIN™ PAVEMENT DESIGN CALCULATIONS
APPENDIX B – EARTH ENGINEERING CONSULTANTS GEOTECHNICAL REPORT
Kumar & Associates, Inc.
SUMMARY
1. The field exploration program for the project was performed on September 19, 2016. Six
(6) exploratory borings were drilled at the general locations shown on Fig.1 to explore
subsurface conditions and to obtain samples for laboratory testing. Logs of the
exploratory borings are presented on Fig. 2 and a legend and explanatory notes is
presented on Fig. 3.
Subsurface conditions encountered in the exploratory borings generally consisted of a
few inches of topsoil containing rooted matter underlain at four boring locations and by
existing fill and from the ground surface at two locations by native cohesive and granular
soils extending to the full depths explored of approximately 25, feet or to bedrock at
depths ranging from about 6.5 to 19.5 feet.
Where encountered the existing fill extended to depths ranging from approximately 0.5
feet to 4 feet below the ground surface. The existing fill generally consisted of slightly
moist to moist, brown lean clay with sand to sandy lean clay with a fine to coarse sand
fraction. The horizontal and vertical limits along with the consistency of the fill were not
determined during this study. Based on sampler penetration resistance blow counts the
consistency of the fill appeared to be highly variable, suggesting the fill was not placed
under controlled conditions.
Native cohesive soils extending to depths ranging from about 4.5 feet to 24 feet were
encountered beneath the existing fill or from the ground surface. The native cohesive
soils generally consisted of slightly moist to moist, brown, lean clay to lean clay with
sand to isolated fat clay. Native granular soils consisted of wet, tan, fine to coarse
grained silty sand to poorly-graded sand with gravel were encountered beneath the
cohesive soils in Boring 2 through 5 and extended to the full depths explored of about 25
feet in Borings 3 and 4 and to bedrock of depths of about 19 feet and 19.5 feet in
Borings 2 and 5. The native granular soils contained isolated to occasional coarse gravel
and cobbles. Based on sampler penetration resistance, the native cohesive soils ranged
from medium to stiff to occasionally soft or very stiff, and the native granular soils were
generally medium dense to occasionally very loose to loose.
The claystone bedrock was, moist to wet and gray to brown. Based on sampler
penetration resistance values, the claystone bedrock ranged from firm to very hard.
Groundwater was encountered in Borings 2 through 5 during drilling at depths ranging
from about 3 feet to 23 feet below ground surface; groundwater was not encountered in
Borings 1 and 6. Stabilized groundwater levels were measured in all borings seven days
after drilling at depths ranging from about 1.5 feet to 20.5 feet. Generally, stabilized
groundwater depths were shallowest near the Box Elder ditch, ranging from about 1.5
feet to 12 feet in Borings 2, 3 and 5, and deepest along the east side of the Fossil Creek
Inlet Ditch, ranging from about 14.5 feet to 20.5 feet.
2. Based on the data obtained during the field and laboratory studies, we recommend
straight-shaft piers drilled into the bedrock be used to support the proposed twins 5-story
buildings. Piers should be designed for an allowable end bearing pressure of 30,000 psf
and an allowable skin friction of 3,000 psf for the portion of pier penetration into bedrock.
Piers should also be designed for a minimum dead load pressure of 15,000 psf
calculated as the unfactored dead load applied to the pier cross sectional area. Piers
should be drilled to a minimum of 10 feet of penetration of the underlying competent
bedrock.
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We recommend that the 12-plex, 25-plex, garages, and recreation center buildings be
founded on spread footings placed on undisturbed and/or properly compacted structural
fill. Footings placed on the undisturbed natural soils or compacted structural fill
extending to natural soils should be designed for an allowable soil bearing pressure of
2,000 psf
3. Slab-on-grade floors may be feasible provided the slabs are underlain by a minimum 8-
foot-thick zone of non- to low-swelling compacted structural fill and the increased risk of
distress resulting from slab movement is accepted by the owner. Placing a zone of non-
expansive to low-swelling material beneath slab-on-grade floors will require sub-
excavation and backfilling the upper portion of the excavation with imported structural fill.
A perimeter underdrain system should extend below the base of the subslab fill zone.
4. Based on this procedure, flexible pavements for light-duty pavement areas should
consist of 6.0 inches of full-depth asphalt, or, alternatively, a composite pavement
section consisting of 4.5 inches of asphalt over 6.0 inches of compacted aggregate base
course material. Flexible pavements for heavy-duty pavement areas should consist of
7.5 inches of full-depth asphalt, or, alternatively, a composite pavement section
consisting of 8.0 inches of asphalt over 8.5 inches of compacted aggregate base course
material.
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PURPOSE AND SCOPE OF STUDY
This report presents the results of a geotechnical engineering study performed by Kumar &
Associates for the proposed Harmony 23 Development to be constructed at the intersection of
Harmony Road and Strauss Cabin Road in Fort Collins, Colorado. The project site is shown on
Fig 1. The study was conducted in accordance with the scope of work in our Proposal No. P-
16-657 to Terra Development Group dated September 14, 2016.
A field exploration program consisting of 6 exploratory borings was conducted to obtain
information on subsurface conditions. Samples of the soils and bedrock materials obtained
during the field exploration program were tested in the laboratory to determine their
classification and engineering characteristics. The results of the field exploration and laboratory
testing program were analyzed to develop recommendations for use in design and construction
of the proposed facility. The results of the field exploration and laboratory testing are presented
herein.
A previous geotechnical subsurface exploration program was performed for the project by Earth
Engineering Consultants (EEC). The results of that program were presented under their Job
Number: 1152123 in a report dated January 14, 2016. Data from that study is included in
Appendix B.
This report has been prepared to summarize the data obtained during this study and to present
our conclusions and recommendations based on the proposed construction and the subsurface
conditions encountered. Design parameters and a discussion of geotechnical engineering
considerations related to construction of the proposed facility are included herein.
PROPOSED CONSTRUCTION
We understand the project will include twelve 3-story multi-unit buildings, nine 5-car garages,
two 2-story apartment buildings with several additional garage units, two 5-story twin office
buildings, a single–story community clubhouse, and paved driveways and parking areas. We
understand that the maximum wall and column loads will range from light to moderately heavy.
The project will include detention/water quality ponds near the eastern limits of the project.
If the proposed construction varies significantly from that described above or depicted in this
report, we should be notified to reevaluate the recommendations provided in this report.
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SITE CONDITIONS
The project site is a roughly triangular property located at the northwest corner of the
intersection of Harmony Road and Strauss Cabin Road (South County Road 7) and east of the
Fossil Creek Inlet Ditch. The site is bounded on the north by Harmony Road, on the east by
Strauss Cabin Road, on the west by Fossil Creek Inlet Ditch and on the south by residential
buildings. The site is vegetated with native grasses and is bisected by the Box Elder drainage
ditch, which flows from south to north across the site. The site is essentially flat with an overall
relief of approximately 5 feet. The Fossil Creek Inlet Ditch was observed to be flowing during the
field exploration program.
SUBSURFACE CONDITIONS
The field exploration program for the project was performed on September 19, 2016. Six
exploratory borings were drilled to depths of approximately 25 feet below ground surface at the
approximate locations shown on Fig.1 to explore subsurface conditions and to obtain samples
for laboratory testing. Logs of the exploratory borings are presented on Fig. 2 along with a
legend and explanatory notes.
The borings were advanced through the overburden soils and into the underlying bedrock,
where encountered, with 4-inch diameter continuous flight augers. The borings were logged by
a representative of Kumar & Associates, Inc. Samples of the soils and bedrock materials were
obtained with a 2-inch I.D. California liner sampler. The sampler was driven into the various
strata with blows from a 140-pound hammer falling 30 inches. This sampling procedure is
similar to the standard penetration test described by ASTM Method D1586. Penetration
resistance values, when properly evaluated, indicate the relative density or consistency of the
soils. Depths at which the samples were obtained and the penetration resistance values are
shown adjacent to the boring logs on Fig. 2.
Subsurface Soil and Bedrock Conditions: Subsurface conditions encountered in the exploratory
borings generally consisted of a few inches of topsoil containing rooted matter underlain at four
boring locations and by existing fill and from the ground surface at two locations by native
cohesive and granular soils extending to the full depths explored of approximately 25, feet or to
bedrock at depths ranging from about 6.5 to 19.5 feet.
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Where encountered the existing fill extended to depths ranging from approximately 0.5 feet to 5
feet below the ground surface. The existing fill generally consisted of slightly moist to moist,
brown lean clay with sand to sandy lean clay with a fine to coarse sand fraction. The horizontal
and vertical limits along with the consistency of the fill were not determined during this study.
Based on sampler penetration resistance blow counts the consistency of the fill appeared to be
highly variable, suggesting the fill was not placed under controlled conditions.
Native cohesive soils extending to depths ranging from about 4.5 feet to 24 feet were
encountered beneath the existing fill or from the ground surface. The native cohesive soils
generally consisted of slightly moist to moist, brown, lean clay to lean clay with sand to isolated
fat clay. Native granular soils consisted of wet, tan, fine to coarse grained silty sand to poorly-
graded sand with gravel were encountered beneath the cohesive soils in Boring 2 through 5 and
extended to the full depths explored of about 25 feet in Borings 3 and 4 and to bedrock of
depths of about 19 feet and 19.5 feet in Borings 2 and 5. The native granular soils contained
isolated to occasional coarse gravel and cobbles. Based on sampler penetration resistance, the
native cohesive soils ranged from medium to stiff to occasionally soft or very stiff, and the native
granular soils were generally medium dense to occasionally very loose to loose.
The claystone bedrock was, moist to wet and gray to brown. Based on sampler penetration
resistance values, the claystone bedrock ranged from firm to very hard.
Groundwater Conditions: Groundwater was encountered in Borings 2 through 5 during drilling at
depths ranging from about 3 feet to 23 feet below ground surface; groundwater was not
encountered in Borings 1 and 6. Stabilized groundwater levels were measured in all borings
seven days after drilling at depths ranging from about 1.5 feet to 20.5 feet. Generally, stabilized
groundwater depths were shallowest near the Box Elder ditch, ranging from about 1.5 feet to 12
feet in Borings 2, 3 and 5, and deepest along the east side of the Fossil Creek Inlet Ditch,
ranging from about 14.5 feet to 20.5 feet.
Fluctuation in groundwater levels are likely dependent on water levels in the Fossil Creek Inlet
Ditch and the Box Else Ditch, although the depth to groundwater near the Fossil Creek Inlet
Ditch, which was flowing at the time of our measurements, suggest a limited contribution from
that source to site groundwater.
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LABORATORY TESTING
Samples obtained from the exploratory borings were visually classified in the laboratory by the
project engineer and samples were selected for laboratory testing. Laboratory testing included
index property tests, such as moisture content (ASTM D2216), dry unit weight, grain size
analysis (ASTM D422) and liquid and plastic limits (ASTM D4318). Swell-consolidation tests
(ASTM D4546, Method B) were conducted on several samples to determine the compressibility
or swell characteristics under loading and when submerged in water. The percentage of water
soluble sulfates was determined in general accordance with Colorado Department of
Transportation (CDOT) CP-L 2103. The results of laboratory tests performed on selected
samples obtained from the borings are shown to the right of the logs on Fig. 2, plotted
graphically on Figs. 4 to 10, and are summarized in Table 1.
Swell-Consolidation: Swell-consolidation tests were conducted on samples of the natural lean
clay soils and bedrock in order to determine their compressibility and swell characteristics under
loading and when submerged in water. Each sample was prepared and placed in a confining
ring between porous discs, subjected to a surcharge pressure of 1,000 psf, and allowed to
consolidate before being submerged. The sample height was monitored until deformation
practically ceased under each load increment.
Results of the swell-consolidation tests are presented on Figs. 4 through 8 as plots of the curve
of the final strain at each increment of pressure against the log of the pressure. Based on the
results of the laboratory swell-consolidation testing, the natural lean clay and claystone bedrock
soil samples exhibited low to moderate swell potential when wetted under surcharge pressures
of 1,000 psf.
EEC tested similar samples of the natural cohesive soils and bedrock. Based on the results of
the laboratory tested swell-consolidation testing performed by EEC, the natural lean clay and
claystone bedrock soil samples exhibited low to moderate swell potential when wetted under
surcharge pressures of 150 psf and 200 psf.
Index Properties: Samples were classified into categories of similar engineering properties in
general accordance with the Unified Soil Classification System. This system is based on index
properties, including liquid limit and plasticity index and grain size distribution. Values for
moisture content, dry density, liquid limit and plasticity index, and the percent of soil passing the
U.S. No. 4 and No. 200 sieves are presented in Table I and adjacent to the corresponding
sample on the boring logs. Results of gradation tests area presented on Figs. 9 and 10.
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GEOTECHNICAL ENGINEERING CONSIDERATIONS
Based on the data from the field exploration and laboratory testing programs, the primary site
considerations are the presence of variable depths of undocumented fill, near-surface moisture-
sensitive native soils, isolated to occasional soft or loose native soils, and very shallow to
shallow groundwater conditions over portions of the site. Shallow spread footing foundations
and slab-on-grade construction should be feasible with proper subgrade preparation and raising
site grades for building pads to an appropriate height above design groundwater levels, where
necessary. Raising grades in pavement areas may also be necessary in places to avoid loss of
pavement support due to saturated subgrade conditions.
In absence of placement records, the existing fill should be considered unsuitable for support of
foundations, floor slabs, and settlement- or heave-sensitive flatwork and pavements. Subgrade
preparation in areas of existing fill should include complete removal of the existing fills in those
situations and replacement with structural fill. For areas of flatwork and pavement that may be
able to tolerate some settlement- or heave-related movement, a partial removal and
replacement option may be considered provided the owner understands and accepts the risk of
potentially unacceptable post-construction movement.
The near-surface native cohesive soils exhibited generally low swell potential or additional
compression upon wetting, although one sample of sandy lean clay exhibited a moderate to
high potential for collapse. Shallow foundations and soil-supported slabs underlain by these
moisture-sensitive soils will be at risk of variable heave-related total and differential movement
should these soils experience post-construction increases in moisture content. This is
particularly true of lightly loaded floor slabs. Mitigation of the risk of post-construction
movement can be accomplished by replacing the native soils to a specific depth below the
bottom of footings and floor slabs with a zone of structural fill consisting moisture-conditioned,
non- to low-swelling on-site native soils or imported fill.
Shallow groundwater will affect excavations, site grading activities, foundation and slab support,
and pavement subgrade support. Excavations extending to or below groundwater will require
temporary dewatering to facilitate excavation, subgrade preparation and placement of
compacted fill, and permanent dewatering would be necessary where the subgrade level of floor
slabs, exterior flatwork and pavements is within 2 feet of the design groundwater level, which
could be higher than the stabilized groundwater levels shown on the boring logs on Fig. 2.
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Permanent dewatering would require permitting by the Water Quality Control Division of the
Colorado Department of Public Health and Environment, which may require treatment of
collected groundwater prior to discharge.
Areas of loose to very loose soils are present across the site. Proposed buildings with 4-stories
or more should be supported on drilled piers in order to prevent unacceptable settlements.
SITE GRADING AND EARTHWORK
Ideally, existing fills should be completely removed and overexcavated areas backfilled with
compacted fill meeting the material and compaction criteria presented in this section. As
discussed in specific sections of this report, the owner may elect to partially remove and replace
existing fills in areas such as hardscape and pavements that can tolerate movement possibly in
excess of normal tolerances.
Temporary Excavations: We assume that the temporary excavations will be constructed by
over-excavating the slopes to a stable configuration where enough space is available. All
excavations should be constructed in accordance with OSHA requirements, as well as state,
local and other applicable requirements. Site excavations will encounter existing fill native lean
clays, native granular soils and claystone to siltstone to sandstone bedrock. The existing fill and
native granular soils will classify as OSHA Type C soils. The native lean clay soil and the
bedrock will generally classify as Type A soil, although fractured or weakly-cemented bedrock
may classify as Type B and, in some cases, Type C soils depending on the degree of fracturing
and cementation and on presence of groundwater seepage. Excavations encountering
groundwater could require much flatter side slopes than those allowed by OSHA or temporary
shoring. Areas where insufficient lateral space exists may also require temporary shoring.
Surface water runoff into the excavations can act to erode and potentially destabilize the
excavation side slopes and result in soft or excessively loose ground conditions at the base of
the excavation, and should not be allowed. Diversion berms and other measures should be
used to prevent surface water runoff into the excavations from occurring. If significant runoff
into the excavations does occur, further excavation to remove and replace the soft or loose
subgrade materials or stabilize the slopes may be required.
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Excavation Dewatering: Excavations extending below groundwater should be properly
dewatered prior to and during the excavation process to help maintain the stability of the
excavation side slopes and stable subgrade conditions for foundation and slab construction.
Selection of a dewatering system should be the responsibility of the contractor. Dewatering
quantities will depend on excavation size, water table drawdown, and soil permeability. Based
on gradation test results, the natural soils are anticipated to be of moderately permeable for the
native cohesive soils and highly permeable for the native granular soils. Accordingly, relatively
large dewatering quantities should be anticipated at the site. We are available to provide
estimates of ranges of dewatering quantities for given excavation configurations based on soil
gradation characteristics. Dewatering systems should also be properly designed to prevent
piping and removal of soil particles which could have damaging effects.
The construction dewatering systems should be capable of intercepting groundwater before it
can reach the face of excavation side slopes, and to maintain a groundwater level at least 2 feet
below the bottom of the excavation. Dewatering should continue until construction and
associated backfilling extends above the ground water table.
Fill Material: Unless specifically modified in the preceding sections of this report, the following
recommended material and compaction requirements are presented for fill materials on the
project site. A representative of the geotechnical engineer should evaluate the suitability of all
proposed fill materials for the project prior to placement.
1. Moisture-Stabilized Fill: Fill used for site grading and beneath exterior flatwork and
pavements that are not movement sensitive may consist of properly compacted, moisture
conditioned, on-site materials provided the swell potential of those materials when
remolded to 95% of the standard Proctor (ASTM D698) maximum dry density at optimum
moisture content and wetted under a 200 psf surcharge pressure does not exceed 2%.
2. Structural Fill: Structural fill placed beneath spread footings, floor slabs and movement
sensitive exterior flatwork and pavement should consist of on-site moisture- conditions
native soils or an imported, low permeability, non- to low-swelling material meeting the
following requirements:
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Percent Passing No. 200 Sieve Maximum 70
Liquid Limit Maximum 35
Plasticity Index Maximum 15
Imported fill source materials for structural fill not meeting the above liquid limit and
plasticity index criteria may be acceptable (provided the minimum percentage passing
the No. 200 sieve is satisfied) provided they meet the swell criteria in Item 4 below.
Evaluation of potential structural fill sources, particularly those not meeting the above
liquid limit and plasticity index criteria for imported fill materials, should include
determination of laboratory moisture-density relationships and swell-consolidation tests
on remolded samples prior to acceptance.
3. Utility Trench Backfill: Materials other than claystone excavated from the utility trenches
may be used for trench backfill above the pipe zone fill provided they do not contain
unsuitable material or particles larger than 4 inches and can be placed and compacted as
recommended herein.
4. Material Suitability: Unless otherwise defined herein, all fill material should be a non- to
low-swelling, free of claystone, vegetation, brush, sod, trash and debris, and other
deleterious substances, and should not contain rocks or lumps having a diameter of more
than 6 inches. Unless otherwise defined herein, a structural fill material generally should
be considered non- to low-swelling if the swell potential under a 200 psf surcharge
pressure does not exceed 0.5% when a sample remolded to 95% of the standard Proctor
(ASTM D698) maximum dry density at optimum moisture content is wetted.
Compaction Requirements: We recommend the following compaction criteria be used on the
project:
1. Moisture Content: Fill materials should be compacted at moisture contents within 2
percentage points of the optimum moisture content for predominantly granular materials
and between optimum and 3 percentage points above optimum for predominantly
cohesive materials. The contractor should be aware that the clay materials, including
on-site and imported materials, may become somewhat unstable and deform under
wheel loads if placed near the upper end of the moisture range.
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2. Placement and Degree of Compaction: Site grading fill and structural fill should be
placed in maximum 8-inch-thick lifts. The following compaction criteria should be
followed during construction:
Percentage of Maximum
Standard Proctor Density
Fill Location (ASTM D698)
Adjacent to Foundations .................................................................................. 95%
Beneath Spread Footing Foundations ............................................................. 95%
Beneath Retaining Wall Foundations ............................................................... 95%
Wall Backfill
Upper 8 Feet of Backfill .............................................................................. 95%
Backfill Deeper than 8 Feet ....................................................................... 98%1
Beneath Floor Slabs, Exterior Flatwork and Pavements
Fill less than 8 Feet thick ........................................................................... 95%
Fill more than 8 Feet Thick ....................................................................... 98%
Utility Trenches ............................................................................................... 95%
Landscape and Other Areas ............................................................................ 95%
1 Some difficulty could be encountered achieving adequate
compaction with small equipment to avoid exerting excessive
compaction stresses on walls.
3. Subgrade Preparation: Prior to placing site grading fill and structural fill, the upper 12
inches of the subgrade soils at the base of the fill zone should be scarified, moisture
conditioned, and recompacted to at least 95% of the standard Proctor (ASTM D698)
maximum dry density at moisture contents between optimum and 3 percentage points
above optimum moisture content. All other areas to receive new fill not specifically
addressed herein should be scarified to a depth of at least 8 inches and recompacted to
at least 95% of the standard Proctor (ASTM D698) maximum dry density at moisture
contents recommended above.
Excessive wetting and drying of excavations and prepared subgrade areas should be
avoided during construction.
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SPREAD FOOTINGS FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory borings and the nature of
the proposed construction, we recommend that the buildings less than 4-stoyies in height be
founded on spread footings placed on suitable undisturbed native soils or structural fill
extending to undisturbed native soils.
The design and construction criteria presented below should be observed for a spread footing
foundation system. The construction details should be considered when preparing project
documents.
1. Footings should bear on suitable undisturbed native soils or structural fill extending to
undisturbed native soils. Existing fills or areas of loose, soft, or disturbed material
encountered within the foundation excavation should be removed and replaced with
structural fill meeting the material and placement criteria in the “Site Grading and
Earthwork” section of this report.
2. Footings supported as recommended herein should be designed for an allowable soil
bearing pressure of 2,000 psf. The allowable bearing pressure may be increased by
one-third for transient loads. Footings should also be designed for a minimum soil
bearing pressure of 800 psf.
3. Spread footings placed on native soils or compacted structural fil should have a
minimum footing width of 16 inches for continuous footings, and 24 inches for isolated
pads.
4. Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement of
foundations at least 30 inches below the exterior grade is typically used in this area.
5. Based on experience we estimate total settlement for footings designed and
constructed as discussed in this section will be 1 inches or less.
6. The lateral resistance of a spread footing will be a combination of the sliding resistance
of the footing on the foundation materials and passive earth pressure against the side of
the footing. Resistance to sliding at the bottoms of the footings can be calculated based
on an allowable coefficient of friction of 0.30. Passive pressure against the sides of the
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footings can be calculated using equivalent fluid density of 185 pcf. The above values
are working values.
7. Continuous foundation walls should be reinforced top and bottom to span an
unsupported length of at least 10 feet.
8. Fill placed against the sides of the footings to resist lateral loads should consist of
material meeting the material and placement criteria for structural fill procedures in the
“Site Grading and Earthwork” section of this report.
9. Granular foundation soils should be densified with a smooth vibratory compactor prior to
placement of concrete.
10. The native fine-grained soils may pump or deform excessively under heavy construction
traffic due to the high moisture content of the soils and close proximity of the
groundwater table in portions of the site. The use of track-mounted construction
equipment and other equipment that exert lower contact pressures than pneumatic tires
should be used, and the movement of vehicles over proposed foundation areas should
be restricted to help reduce this difficulty.
11. A representative of the project geotechnical engineer should observe all footing
excavations prior to concrete placement.
DRILLED PIER FOUNDATIONS
As previously discussed in the “Geotechnical Engineering Considerations” section of this report,
we recommend that building with 4 or more stories be founded on straight shaft drilled piers
extending into the undying bedrock.
The design and construction criteria presented below should be observed for a straight-shaft
drilled pier foundation system. The construction details should be considered when preparing
project documents.
1. Piers should penetrate at least 10 feet into the bedrock and have a minimum pier length
of 20 feet.
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2. Piers with a minimum bedrock penetration of 10 feet should be designed for an
allowable end-bearing pressure of 30,000 psf and a skin friction of 1,500 psf for the
portion of the pier embedded less than 10 feet into bedrock and 3.000 psf for the portion
of the pier embedded more than 10 feet into bedrock. Uplift due to structural loadings on
the piers can be resisted by using 75% of the allowable skin friction value plus an
allowance for pier weight.
3. Piers should also be designed for a minimum dead load pressure of 10,000 psf based on
pier end area only. Application of dead load pressure is the most effective way to resist
foundation movement due to swelling soils and bedrock. However, if the minimum dead
load requirement cannot be achieved and the piers are spaced as far apart as practical,
the pier length should be extended beyond the minimum bedrock penetration and
minimum length to mitigate the dead load deficit. This can be accomplished by
assuming one-half of the skin friction value given above acts in the direction to resist
uplift caused by swelling soil or bedrock near the top of the pier. The owner should be
aware of an increased potential for foundation movement if the recommended minimum
dead load pressure is not met.
4. The lateral capacity of the piers may be analyzed using the LPILE computer program
and the parameters provided in the following table. The strength criteria provided in the
table are for use with that software application only and may not be appropriate for other
usages.
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Material
c
(psf)
ø γT ks kc ε50
Soil
Type
Granular structural fill/ Native
Granular Soils Above
Groundwater
0 34 125 90 90 ---- 1
Granular structural fill/ Native
Granular Soils Below
Groundwater
0 34 63* 60 60 ---- 1
Clay Structural Fill / Native
Soils Above Groundwater
1,000 0 110 1,000 400 0.005 2
Clay Structural Fill / Native
Soils Below Groundwater
1,000 0 53* 100 ---- 0.010 2
Bedrock 4,000 0 130 1,000 400 0.005 2
*Submerged unit weight
c Cohesion intercept (pounds per square foot)
Φ Angle of internal friction (degrees)
γT Total unit weight (pounds per cubic foot)
ks Initial static modulus of horizontal subgrade reaction (pounds per cubic inch)
kc Initial cyclic modulus of horizontal subgrade reaction (pounds per cubic inch)
ε 50 Strain at 50 percent of peak shear strength
Soil Types:
1. Sand (Reese)
2. Stiff clay without free water
5. Closely spaced piers may require appropriate reductions of the lateral and axial
capacities. Reduction in lateral load capacity may be avoided by spacing the piers at
least 5 pier diameters (center to center). For axial loading, the piers should be spaced a
minimum of 3 pier diameters center to center. Piers placed closer than that indicated
above should be studied on an individual basis to determine the appropriate reduction in
axial and lateral load design parameters.
If the recommended minimum center-to-center pier spacings for lateral loading cannot
be achieved, we recommend the load-displacement curve (p-y curve) for an isolated pier
be modified for closely-spaced piers using p-multipliers to reduce all the p values on the
curve. With this approach, the computed load carrying capacity of the pier in a group is
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reduced relative to the isolated pier capacity. The modified p-y curve should then be
reentered into the LPILE software to calculate the pier deflection. The reduction in
capacity for the leading pier, the pier leading the direction of movement of the group, is
less than that for the trailing piers.
For center-to-center spacing of piers in the group in the direction of loading expressed in
multiples of the pier diameter, we recommend p-multipliers of 0.8 and 1.0 for pier
spacing of 3 and 5 diameters, respectively, for the leading row of piers, 0.4 and 0.85 for
spacings of 3 and 5 diameters, respectively, for the second row of piers, and 0.3 and 0.7
for spacings of 3 and 5 diameters, respectively, for row 3 and higher. For loading in a
direction perpendicular to the row of piers, the p-multipliers are 1.0 for a spacing of 5
diameters, 0.8 for a spacing of 3 diameters, and 0.5 for a spacing of 1 diameter. P-
multiplier values for other pier spacing values should be determined by interpolation. It
will be necessary to determine the load distribution between the piers that attains
deflection compatibility because the leading pier carries a higher proportion of the group
load and the pier cap prevents differential movement between the piers.
6. Based on the results of our field exploration, laboratory testing, and our experience with
similar, properly constructed drilled pier foundations, we estimate pier settlement will be
low. Generally, we estimate the settlement of drilled piers will be less than 1 inch when
designed according to the criteria presented herein. The settlement of closely spaced
piers will be larger and should be studied on an individual basis.
7. Piers should be designed with additional reinforcement over their full length to resist an
un-factored net tensile force from swelling soil pressure of least 45,000 pounds. The net
tensile force is for a 1.5-foot diameter pier. For larger pier diameters, this force should
be increased in proportion to the pier diameter. If the minimum dead load requirement is
not met, the tensile force should be increased by the deficit between the required
minimum dead load and the applied dead load. Similarly, the tensile force may be
reduced if the design dead load exceeds the recommended minimum dead load.
8. A minimum 4-inch void should be provided beneath the grade beams to concentrate pier
loadings. Absence of a void space will result in a reduction in dead load pressure, which
could result in upward movement of the foundation system. A similar void should also
be provided beneath necessary pier caps.
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9. A minimum pier diameter of 18 inches is recommended to facilitate proper cleaning and
observation of the pier hole. The pier length-to-diameter ratio should not exceed 30.
10. The bottom 10 feet of bedrock penetration in all pier holes should be roughened
artificially to assist in the development of peripheral shear stress between the pier and
the bedrock. Roughening should be accomplished installed with a grooving tool in a
pattern considered appropriate by the geotechnical engineer. Horizontal grooves at 1 to
2-foot centers or helical grooves with a 1 to 2-foot pitch are acceptable patterns. Care
should be taken that only the bottom 10 feet of bedrock penetration portion of the pier is
roughened; roughening in the upper portion of the pier above the bottom 10 feet of the
pier could increase uplift forces on the pier resulting from swelling bedrock. The
specifications should allow the geotechnical engineer to eliminate the requirements for
pier roughening if it appears that roughening is not beneficial. This could occur if a
rough surface is provided by the drilling process or if the presence of water and/or
weakly cemented materials results in a degradation of the pier hole during roughening.
11. Difficult drilling conditions may be experienced in hard to very hard bedrock. The drilled
shaft contractor should mobilize equipment of sufficient size and operating condition to
achieve the required bedrock penetration. A small diameter pilot hole may be required
to advance auger drilling.
12. The presence of water in the exploratory borings indicates the use of temporary casing
and/or dewatering equipment in the pier holes will be required to be excavate through
saturated granular soils and to reduce water infiltration. Where excavation encounters
cohesive soils and bedrock the requirements for casing and dewatering equipment can
sometimes be reduced by placing concrete immediately upon cleaning and observing
the pier hole. In no case should concrete be placed in more than 3 inches of water
unless an approved tremie method is used. If water cannot be removed or prevented
with the use of temporary casing and/or dewatering equipment prior to placement of
concrete, the tremie method should be used after the hole has been cleaned.
13. Care should be taken that the pier shafts are not oversized at the top. Mushroomed pier
tops can reduce the effective dead load pressure on the piers. Sono-Tubes or similar
forming should be used at the top of the piers, as necessary, to prevent mushrooming of
the top of the piers.
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14. Pier holes should be properly cleaned prior to the placement of concrete.
15. Concrete used in the piers should be a fluid mix with sufficient slump so it will fill the void
between reinforcing steel and the pier hole. We recommend a concrete slump in the
range of 5 to 8 inches be used.
16. Concrete should be placed in piers the same day they are drilled. If water is present,
concrete should be placed immediately after the pier hole is completed. Failure to place
concrete the day of drilling will normally result in a requirement for additional bedrock
penetration.
17. A representative of the geotechnical engineer should observe pier drilling operations on
a full-time basis to assist in identification of adequate bedrock strata and monitor pier
construction procedures.
SEISMIC DESIGN CRITERIA
The soil profile is anticipated to consist of about 25 feet or less of overburden soils underlain by
relatively hard bedrock. The bedrock is considered to extend to a depth of at least 100 feet
below ground surface. Overburden consisting of new structural fills and nativel soils will
generally classify as International Building Code (IBC) Site Class D. The underlying bedrock
generally classifies as IBC Site Class C. Based on our experience with similar profiles,
including the presences of occasional soft and loose zones we recommend a design soil profile
of IBC Site Class D. Based on the subsurface profile, site seismicity, and the anticipated depth
of ground water, liquefaction is not a design consideration.
FLOOR SLABS
Floor slabs present a difficult problem where expansive materials are present near floor slab
elevation because sufficient dead load cannot be imposed on them to resist the uplift pressure
generated when the materials are wetted and expand. The most positive method to avoid
damage as a result of floor slab movement is to construct a structural floor above a well-vented
crawl space. The floor would be supported on grade beams and piers the same as the main
structure. Based on the moisture-volume change characteristics of the native soils
encountered, we believe slab-on-ground construction may be used, provided the risk of distress
resulting from slab movement is accepted by the owner. The following discussion presents
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estimates of slab heave for different wetting depth scenarios to aid in the floor system decision
making process.
In accordance with the practice in this area, the following discussion presents estimates of
ground heave for different wetting depth scenarios to aid in the decision making process for
floor support systems. The risk of ground heave beneath soil-supported floor slabs can be
reduced to a certain degree by providing a zone of non- to low-swelling, relatively impervious,
compacted fill directly beneath the slabs. Heave estimate calculations can be useful in
evaluating the relative effectiveness of varying the thickness of this prepared fill zone. However,
such calculations cannot address the uncertainty in the potential depth and degree of wetting
that may occur under beneath the building or the variability of swell potential across the site,
which is erratic at the site.
We have performed calculations to demonstrate the potential for ground heave if the native soils
and bedrock beneath the building should be thoroughly wetted to significant depth, including
below the depth of the compacted fill zone. The following table presents estimates of potential
slab heave based on the results of swell-consolidation tests using test and analysis methods
generally accepted in the Colorado Front Range. Both depth of wetting and depth of the
prepared fill zone were considered as variables in the analysis.
Alternative
Ground Heave in Inches
5 feet of
wetting
10 feet of
wetting
15 feet of
wetting
No moisture treatment 2.44 3.69 4.75
8 feet of non- to low-swelling structural fill 0.88 1.33 1.71
The heave estimate calculations demonstrate that moderate slab heave should be expected if
thorough wetting of the native cohesive soils and bedrock beneath the building occurs to
significant depth below the bottom of the prepared fill zone. However, our experience indicates
that the large majority of similar structures underlain by similar materials do not experience
extreme moisture increases in the underlying materials to significant depth provided that good
surface and subsurface drainage is designed, constructed, and maintained, and that good
irrigation practices are followed. Wetting can also occur as a result of unforeseeable influences
such as plumbing leaks or breaks, or, in some cases, even due to off-site influences depending
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on geologic conditions. Heave may also be mitigated to some extent by the presence of non- to
low swelling siltstone or sandstone bedrock.
Considering the above discussion, we believe soil-supported floor slabs may be considered for
the project, provided that the potential for floor slab movement due to ground heave and
associated possible distress is recognized by the owner. The intent of our recommendations for
soil-supported floor slabs is to provide for conditions where there is a good chance slab heave
will not exceed amounts acceptable to the owner. The recommendations should result in heave
movements that do not exceed 1 inch and are unlikely to significantly exceed 2 inches unless
extreme wetting is allowed. Barring unforeseen events, we do not believe extreme wetting is
likely to occur if the surface drainage and irrigation recommendations presented in this report
are followed.
If a slab-on-grade approach is selected, the following measures should be taken to mitigate or
reduce slab movements, and reduce the potential for damage which could result from
movement should the underslab materials be subjected to moisture changes.
1. Floor slabs should be placed on a subslab fill zone consisting of minimum of 4 feet of
properly compacted non- to low-swelling structural fill meeting the material requirements
provided in the “Site Grading and Earthwork” section of this report.
2. Floor slabs should be separated from all bearing walls and columns with expansion
joints which allow unrestrained vertical movement.
3. Non-bearing partitions resting on floor slabs should be provided with slip joints so that, if
the slabs move, the movement cannot be transmitted to the upper structure. This detail
is also important for wallboards and door frames. Slip joints that will allow at least 2
inches of vertical movement are recommended.
If wood or metal stud partition walls are used, the slip joints should preferably be placed
at the bottoms of the walls so differential slab movement won’t damage the partition wall.
If slab-bearing masonry block partitions are constructed, the slip joints will have to be
placed at the tops of the walls. If slip joints are provided at the tops of walls and the
floors move, it is likely the partition walls will show signs of distress, such as cracking.
An alternative, if masonry block walls or other walls without slip joints at the bottoms are
required, is to found them on grade beams and piers and to construct the slabs
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independently of the foundation. If slab-bearing partition walls are required, distress
may be reduced by connecting the partition walls to the exterior walls using slip
channels.
Floor slabs should not extend beneath exterior doors or over foundation grade beams,
unless saw cut at the beam after construction.
4. Floor slab control joints should be used to reduce damage due to shrinkage cracking.
Joint spacing is dependent on slab thickness, concrete aggregate size, and slump, and
should be consistent with recognized guidelines such as those of the Portland Cement
Association (PCA) or American Concrete Institute (ACI). The joint spacing and slab
reinforcement should be established by the designer based on experience and the
intended slab use.
5 If moisture-sensitive floor coverings will be used, additional mitigation of moisture
penetration into the slabs, such as by use of a vapor barrier may be required. If an
impervious vapor barrier membrane is used, special precautions will be required to
prevent differential curing problems which could cause the slabs to warp. American
Concrete Institute (ACI) 302.1R addresses this topic.
6. All plumbing lines should be tested before operation. Where plumbing lines enter
through the floor, a positive bond break should be provided. Flexible connections should
be provided for slab-bearing mechanical equipment.
7. The geotechnical engineer should evaluate the suitability of proposed underslab fill
material. Evaluation of potential replacement fill sources will require determination of
laboratory moisture-density relationships and swell consolidation tests on remolded
samples.
We recommend that an underdrain system be constructed at the base of the subslab fill zone to
prevent development of perched water in the fill. Inclusion of a properly designed and
constructed underdrain system will be a critical component in reducing potential slab heave.
This underdrain system should be designed in accordance with recommendations in the
“Underdrain System” section of this report.
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The precautions and recommendations itemized above will not prevent the movement of floor
slabs if the underlying materials are subjected to alternate wetting and drying cycles. However,
the precautions should reduce the damage if such movement occurs.
LATERAL EARTH PRESSURES
Below-grade walls and other retaining structures should be designed for the lateral earth
pressure generated by the backfill materials, which is a function of the degree of rigidity of the
retaining structure and the type of backfill material used. Retaining structures that are laterally
supported and can be expected to undergo only a moderate amount of deflection should be
designed for a lateral earth pressure based on the following equivalent fluid densities:
On-site of imported free-draining granular backfill (< 5% passing No. 200 sieve)45 pcf
On-site or imported, silty sand ..................................................................... 55 pcf
On-site or imported, moisture-conditioned clay backfill* .............................. 65 pcf
* Swell potential less than ½%
Cantilevered retaining structures that can be expected to deflect sufficiently to mobilize the full
active earth pressure condition should be designed for the following equivalent fluid densiteis:
On-site or imported free-draining granular backfill (< 5% passing No. 200 sieve)...35 pcf
On-site or Imported, non-expansive, silty or clayey sand ........... ……………45 pcf
On-site or imported, moisture-conditioned clay backfill* .............................. 55 pcf
* Swell potential less than ½%
The equivalent fluid densites recommended above assume drained conditions behind the
retaining structures and a horizontal backfill surface. The buildup of water behind a retaining
structure or an upward sloping backfill surface will increase the lateral pressure imposed on the
retaining structure. All retaining structures should also be designed for appropriate surcharge
pressures such as traffic, construction materials and equipment.
The zone of backfill placed behind retaining structures to within 2 feet of the ground surface
should be sloped upward from the base of the structure at an angle no steeper than 45 degrees
measured from horizontal. To reduce surface water infiltration into the backfill, the upper 2 feet of
the backfill should consist of a relatively impervious imported soil containing at least 30% passing
the No. 200 sieve, or the backfill zone should be covered by a slab or pavement structure.
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If mechanically stabilized earth (MSE) retaining walls are used, the reinforced zone should
generally be backfilled with CDOT Class 1 Structure Backfill material. Backfill within the
reinforced zone should be compacted to at least 95% of the standard Proctor (ASTM D698)
maximum dry density. Care should be taken not to over compact the backfill since this could
cause excessive lateral pressure on the structure. Hand compaction procedures, if necessary,
should be used to prevent lateral pressures from exceeding the design values.
An internal angle of friction of 34 degrees and a moist unit weight of 120 pcf may be used for
properly compacted granular Structure Backfill. Higher friction angles may be used for crushed
aggregate products such as Class 6 aggregate base course or crusher fines. An internal friction
angle of 24 degrees and a moist unit weight of 120 pcf should be used for the on-site soils in the
retained fill zone behind the reinforced zone. Use of claystone in the retained fill should be
avoided.
Free-standing retaining structures that can tolerate some differential movement should be
designed in accordance with the recommendations provided in the “Spread Footings” section of
this report.
Adequate surface drainage should be provided, and retaining structures should include
subsurface drainage provisions to reduce the potential for saturation of the backfill and the
development of hydrostatic pressures on the structure. The buildup of water behind a retaining
structure will increase the lateral earth pressure imposed on the wall.
The drainage system should consist of a drainage zone behind conventional retaining structures
and behind the facing of an MSE wall, and a perimeter underdrain system at the heel of the
backfill zone, including reinforced fill zone of MSE walls. Drainage systems for conventional
retaining structures may consist of a free-draining granular zone or manufactured drain boards
placed adjacent to the back of the retaining structures. The drainage system could connect
hydraulically to a collection system that discharges the water away from the wall. If collection and
discharge is not ideal, the wall drainage system could discharge to the exposed face of the wall
via weep holes. Perimeter underdrain systems should be designed in general accordance with
the recommendations provided in the “Underdrain System” section of this report.
We are available to design MSE walls or to perform a design review if such retaining structures
are provided by a design-build contractor. Low-height walls no more than 3 or 4 feet high may
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require only minimal design, whereas steep multi-tiered systems or high walls may require global
stability analysis as well as formal design of the wall itself. At a minimum, we should review
foundation preparation and drainage provisions. We should also observe and test wall backfill
placement and compaction.
Free-draining backfill, if used, should extend down to the top of the perimeter underdrain system.
For other backfill materials, drainage should be provided by geocomposite drainage boards
affixed to the exterior walls. The geocomposite drainage board should be hydraulically connected
to the perimeter underdrain.
UNDERDRAIN SYSTEM
It is our experience that perched groundwater conditions typically will occur post-construction
where the excavation for a fill zone beneath slab-on-grade construction extends into relatively
hard and essentially impermeable soils and bedrock. At the site, this perched water would likely
be due to infiltration of natural precipitation and water used for irrigation, and, in some cases,
accidents such as broken utility and irrigation lines. In portions of the site where groundwater is
close to the existing ground surface the site grades may be raised accordingly, a subdrain
system is not considered necessary.
To prevent development of perched water in the subslab fill zone beneath slab-on-grade
construction, an underdrain system should be constructed at the base of the subslab fill zone.
This recommendation should also be considered for flatwork areas immediately adjacent to the
buildings. The underdrain system should consist of drain lines extending along the perimeter of
the overexcavated zone. Where feasible, the alignment of the underdrain system should
preferably be just outside of the structure perimeter, but far enough away that the drain doesn’t
interfere with construction of drilled pier foundations.
The drain lines should consist of minimum 4-inch-diameter, rigid, perforated PVC drain pipe
placed in the bottom of a trench excavated to a depth of at least 1 foot below the base of the
overexcavated zone. The drain pipe should be surrounded above the invert level by drainage
aggregate. Drainage aggregate used in the perimeter subdrain systems should conform to the
requirements of CDOT Class B or Class C Filter Material, and the drain pipe should be factory
slotted or otherwise perforated in accordance with graded filter criteria. Alternatively, if a filter
geotextile is used in subdrain trenches to wrap the drainage aggregate, the pipes may be
covered by free-draining gravel not meeting graded filter criteria, such as AASHTO No. 57 or
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No. 67 Aggregate. During design, alternative drain aggregates and filtration methods can be
considered. The perforated drain pipes themselves should not be directly wrapped in geotextile
due to the potential for clogging of the geotextile at the perforations or slots.
The base of the overexcavation should be graded to slope towards the drain lines with a
minimum slope of ½%. The overall underdrain pipe system should be sloped at a minimum
slope of ½% to an overall site subdrain collection system or to a sump or sumps where water
can be removed by pumping or gravity drainage. Sumps should be provided with alarms and/or
redundant pumps in the event the pumping equipment malfunctions. In addition, the drain lines
should be provided with appropriately spaced cleanouts for maintenance and inspection, which
we recommend be performed on a routine basis. An over-designed sump and pump capacity is
desirable in the event that groundwater or other subsurface conditions change. We also believe
that standby pump capacity and standby generators should be provided in the event of pump or
energy failure.
A conceptual detail of the type of underdrain system recommended above is shown on Fig. 11.
We are available to assist in design of the underdrain system.
SURFACE DRAINAGE
Proper surface drainage is very important for acceptable performance of structures during
construction and after the construction has been completed. Drainage recommendations
provided by local, state and national entities should be followed based on the intended use of
the structure. The following recommendations should be used as guidelines and changes
should be made only after consultation with the geotechnical engineer.
1. Excessive wetting or drying of slab subgrades should be avoided during construction.
2. Exterior backfill should be adjusted to near optimum moisture content (generally ±2% of
optimum unless indicated otherwise in the report) and compacted to at least 95% of the
standard Proctor (ASTM D698) maximum dry density.
3. The ground surface surrounding the exterior of the building and movement sensitive
exterior flatwork areas should be sloped to drain away from the structure and flatwork in
all directions. We recommend a minimum slope of 12 inches in the first 10 feet in
unpaved areas. Site drainage beyond the 10-foot zone should be designed to promote
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runoff and reduce infiltration. A minimum slope of 3 inches in the first 10 feet is
recommended in paved or flatwork areas. These slopes may be changed as required
for handicap access points in accordance with the Americans with Disabilities Act.
4. To promote runoff, the upper 1 to 2 feet of the backfill adjacent to the building should be
a relatively impervious on-site soil or be covered by flatwork or a pavement structure.
5. Ponding of water should not be allowed in foundation backfill material or in a zone within
10 feet of the building or areas of movement sensitive flatwork.
6. Roof downspouts and drains should discharge well beyond the limits of all backfill or be
tight-lined to planned storm water facilities.
7. Landscaping adjacent to the building and movement sensitive flatwork areas should be
designed to avoid irrigation requirements that would significantly increase soil moisture
and potential infiltration of water within at least ten feet of the building or flatwork areas.
Landscaping located within 10 feet of the building and movement sensitive flatwork
areas should be designed for irrigation rates that do not significantly exceed
evapotranspiration rates. Use of vegetation with low water demand and/or drip irrigation
systems are frequently used methods for limiting irrigation quantities.
Lawn sprinkler heads and landscape vegetation that requires relatively heavy irrigation
should be located at least 10 feet from the building and movement sensitive flatwork
areas. Even in other areas away from the building, it is important to provide good
drainage to promote runoff and reduce infiltration. Main pressurized zone supply lines,
including those supplying drip systems, should be located more than 10 feet from the
building an movement sensitive flatwork areas in the event leaks occur. All irrigation
systems, including zone supply lines, drip lines, and sprinkler heads should be routinely
inspected for leaks, damage, and improper operation.
WATER SOLUBLE SULFATES
The concentrations of water soluble sulfates measured in samples of the on-site soils obtained
from the borings ranged from 0.00% to 0.06%. These concentrations of water soluble sulfates
represent a Class 0 severity exposure to sulfate attack on concrete exposed to these materials.
The degree of attack is based on a range of Class 0, Class 1, Class 2, and Class 3 severity
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exposure as presented in ACI 201. Based on the laboratory data and our experience, we
believe special sulfate resistant cement will generally not be required for concrete exposed to
the natural on-site soils.
PAVEMENT THICKNESS DESIGN
A pavement section is a layered system designed to distribute concentrated traffic loads to the
subgrade. Performance of the pavement structure is directly related to the physical properties
of the subgrade soils and traffic loadings. Soils are represented for pavement design purposes
by means of a soil support value for flexible pavements and a modulus of subgrade reaction for
rigid pavements.
Pavement design procedures are based on strength properties of the subgrade and pavement
materials assuming stable, uniform conditions. Certain soils, such as those encountered on this
site, are potentially expansive and require additional precautions be taken to provide for
adequate pavement performance. Expansive soils are problematic only if a source of water is
present. If those soils are wetted, the resulting movements can be large and erratic. Therefore,
pavement design procedures address expansive soils only by assuming they will not become
wetted. Proper surface and subsurface drainage is essential for adequate performance of
pavement on these soils.
Subgrade Materials: Based on the results of the field exploration and laboratory testing
programs, the pavement subgrade materials at the site are anticipated to generally classify as
A-6 and A-7-6 with group indices between 7 and 36 in accordance with the American
Association of State Highway and Transportation Officials (AASHTO) soil classification system.
Soils classifying as A-6 and A-7-6 would generally be considered to provide poor subgrade
support.
A Hveem stabilometer (R-Value) was performed by EEC resulting in an R-Value of 10. Using
the CDOT correlation between R-Value and MR, R-value of 10 is considered equivalent to a
resilient modulus of 3562. We believe these values are not conservative for the soil types
encountered on the project site. Considering this, a resilient modulus value of 3,025 psi was
selected for design of flexible pavements and a modulus of subgrade reaction of 34 pci was
selected for rigid pavements.
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Design Traffic: Since anticipated traffic loading information was not available at the time of
report preparation, an equivalent 18-kip daily load application (EDLA) of 5 was assumed for
automobile and light truck traffic areas (light-duty pavement), an EDLA of 15 was assumed for
combined automobile and heavier truck traffic areas, including fire lanes (heavy-duty
pavement). The designer should verify which traffic loads are valid for the project. If higher
EDLA values are anticipated, the pavement sections presented in this report will have to be
reevaluated.
Pavement Sections: The pavement thicknesses were determined in accordance with the 1993
AASHTO pavement design procedures. For flexible pavement design, initial and terminal
serviceability indices of 4.5 and 2.0, respectively, were selected, with a reliability of 85 percent
for light-duty pavement areas and 85 percent for medium-duty and heavy-duty pavement areas.
If other design parameters are preferred, we should be contacted in order to reevaluate the
recommendations presented herein.
Based on this procedure, flexible pavements for light-duty pavement areas should consist of 6
inches of full-depth asphalt, or, alternatively, a composite pavement section consisting of 4.5
inches of asphalt over 6 inches of compacted aggregate base course. Flexible pavements for
heavy-duty pavement areas should consist of 7.5 inches of full-depth asphalt, or, alternatively, a
composite pavement section consisting of 5.0 inches of asphalt over 8 inches of compacted
aggregate base course material.
Our experience indicates full-depth asphalt sections generally perform better on expansive
subgrades than combined asphalt/aggregate base course sections. The reasons for the better
performance of full-depth asphalt are not fully understood. However, the use of aggregate base
course provides a pervious layer above a relatively impervious subgrade. The base course can
transmit water causing changes in moisture content within the potentially expansive subgrade
materials. Variations in the subgrade moisture content can be erratic and result in erratic
volume changes which cause premature deterioration of the pavement. In addition, the thinner
asphalt surface of a combined section can more easily allow water to penetrate through cracks
and migrate through the aggregate base course. High moisture contents in the subgrade or
base course will also result in loss of strength.
In lieu of an asphalt pavement section, 6 inches of Portland cement concrete may be used, in
light-duty and heavy-duty areas. Concrete pavement should contain sawed or formed joints to
¼ of the depth of the slab at a maximum distance of 12 to 14 feet on center. Because of its
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rigidity concrete pavement will be more sensitive to settlement or heave-related movements
than asphalt pavement, and prone to associated cracking and distress.
Pavement Materials: Asphalt and Portland cement concrete pavement should meet the latest
applicable requirements, including the CDOT Standard Specifications for Road and Bridge
Construction. We recommend that the asphalt placed for the project is designed in accordance
with the SuperPave gyratory mix design method. The mix should generally meet Grading S or
SX requirements with a SuperPave gyratory design revolution (NDESIGN) of 75. Asphalt mixes
should have a PG 58-22 asphalt binder. Concrete pavement should meet CDOT Class P
specifications and requirements, including matching the coarse aggregate size to the presence
of dowels, if used.
The concrete sections presented above are assumed to be un-reinforced. Providing dowels at
construction joints would help reduce the risk of differential movements between panel sections.
Providing a grid mat of deformed rebar within the concrete pavement section would assist in
mitigating corner breaks and differential panel movements. If a rebar mat is installed, we
recommend that the bars be placed in the lower half of the pavement section. On projects that
elect to install rebar mats, we have commonly seen No. 4 rebar placed at 24 inch centers in
each direction, however we recommend that a structural engineer evaluate the placement and
spacing of rebar if needed.
Aggregate base course materials should meet CDOT requirements for Class 6 aggregate base
course.
Subgrade Preparation: Pavement subgrade conditions are projected to generally consist of
existing non-engineered fill and/or low to moderately expansive native clay soils. These
subgrade conditions are a problem where present beneath pavements. When subjected to
increases in moisture, non-engineered fill could result in unacceptable post-construction
settlement, and expansive soils could result in potentially excessive heave.
Ideally, existing fill should be completely removed and replaced with moisture conditioned fill. If
the risk of potentially excessive post-construction settlement is acceptable to the owner, a
partial removal and replacement option may be considered. For a partial removal option, we
recommend overexcavating the existing fill encountered at planned subgrade elevation to a
depth of at least one foot below planned subgrade elevation and backfilling with moisture-
conditioned fill meeting the criteria in the “Site Grading and Earthwork” section of this report.
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The native clay soils exhibited low to moderate swell potential. In areas where the native clay
soils are exposed at pavement subgrade, the subgrade soils should be over-excavated to a
depth of at least 2 feet and replaced with moisture conditioned fill. Care should be taken to
place the top 1 foot of subgrade backfill at moisture contents that are not too moist, which could
result in an unstable subgrade.
Prior to placement of compacted fill or the pavement section, the exposed subgrade should be
thoroughly scarified and well-mixed to a depth of 12 inches, adjusted to a moisture content
between optimum to 3 percentage points above optimum, and compacted to 95% of the
standard Proctor (ASTM D698) maximum dry density. The pavement subgrade should also be
proofrolled with a heavily loaded pneumatic-tired vehicle. Pavement design procedures assume
a stable subgrade. Areas that deform excessively under heavy wheel loads are not stable and
should be removed and replaced to achieve a stable subgrade prior to paving.
The owner should be aware that subexcavation and replacement will reduce but not eliminate
potential movement of pavements should moisture levels increase within the expansive soils
beneath the replacement fill.
Drainage: The collection and diversion of surface drainage away from paved areas is extremely
important to the satisfactory performance of pavement. Drainage design should provide for the
removal of water from paved areas and prevent the wetting of the subgrade soils.
DESIGN AND CONSTRUCTION SUPPORT SERVICES
Kumar & Associates, Inc. should be retained to review the project plans and specifications for
conformance with the recommendations provided in our report. We are also available to assist
the design team in preparing specifications for geotechnical aspects of the project, and
performing additional studies if necessary to accommodate possible changes in the proposed
construction.
We recommend that Kumar & Associates, Inc. be retained to provide construction observation
and testing services to document that the intent of this report and the requirements of the plans
and specifications are being followed during construction. This will allow us to identify possible
variations in subsurface conditions from those encountered during this study and to allow us to
31
Kumar & Associates, Inc.
re-evaluate our recommendations, if needed. We will not be responsible for implementation of
the recommendations presented in this report by others, if we are not retained to provide
construction observation and testing services.
LIMITATIONS
This study has been conducted in accordance with generally accepted geotechnical engineering
practices in this area for exclusive use by the client for design purposes. The conclusions and
recommendations submitted in this report are based upon the data obtained from the
exploratory borings at the location indicated on Fig. 1, and the proposed type of construction.
This report may not reflect subsurface variations that occur, and the nature and extent of
variations across the site may not become evident until site grading and excavations are
performed. If during construction, fill, soil, bedrock or groundwater conditions appear to be
different from those described herein, Kumar & Associates, Inc. should be advised at once so
that a re-evaluation of the recommendations presented in this report can be made. Kumar &
Associates, Inc. is not responsible for liability associated with interpretation of subsurface data
by others.
Swelling soils and bedrock occur on this site. Such soils and bedrock materials are stable at
their natural moisture content but will undergo high volume changes with changes in moisture
content. The extent and amount of perched water beneath the building site as a result of area
irrigation and inadequate surface drainage is difficult, if not impossible, to foresee.
The recommendations presented in this report are based on current theories and experience of
our engineers on the behavior of swelling soil and bedrock materials in this area. The owner
should be aware that there is a risk in constructing a building in an expansive soil and bedrock
area. Following the recommendations given by a geotechnical engineer, careful construction
practice and prudent maintenance by the owner can, however, decrease the risk of foundation
movement due to expansive soils and bedrock.
JDC/jw
cc: Book, File
Kumar & Associates
TABLE I
SUMMARY OF LABORATORY TEST RESULTS
PROJECT NO.: 16-1-578
PROJECT NAME: Harmony 23 Development
DATE SAMPLED: 9-19-16
DATE RECEIVED: 9-20-16
SAMPLE
LOCATION DATE
TESTED
NATURAL
MOISTURE
CONTENT
(%)
NATURAL
DRY
DENSITY
(pcf)
GRADATION PERCENT
PASSING
NO. 200
SIEVE
ATTERBERG LIMITS WATER
SOLUBLE
SULFATES
(%)
AASHTO
CLASSIFICATION
(group index)
SOIL OR BEDROCK TYPE
BORING DEPTH
(feet)
GRAVEL
(%)
SAND
(%)
LIQUID
LIMIT
(%)
PLASTICITY
INDEX
(%)
1 5 9-20-16 6.3 99.2 Sandy Lean Clay (CL)
1 10 9-19-16 20.2 99.2 0 21 79 Lean Clay with Sand (CL)
1 12.5 9-20-16 18.9 106.5 Claystone Bedrock
2 1 9-20-16 25.9 97.7 Lean Clay with Sand (CL)
2 9 9-20-16 8.0 124.8 43 54 3 Poorly-Graded Sand with Gravel (SP)
3 1 9-20-16 32.5 88.4 91 57 36 A-7-6 (36) Fat Clay (CH)
4 5 9-20-16 7.2 98.4 76 27 13 A-6 (7) Fill: Lean Clay with Sand (CL)
4 10 9-20-16 12.1 113.4 Lean Clay (CL)
4 14 9-20-16 18.4 98.2 97 36 17 Lean Clay (CL)
4 19 9-19-16 27.6 91.8 74 NV NP 0.06 Silt with Sand (ML)
4 24 9-20-16 12.0 123.7 37 59 4 Poorly-Graded Sand with Gravel (SP)
5 4 9-20-16 6.8 101.7 68 30 15 A-6 (8) Fill: Sandy Lean Clay (CL)
5 9 9-20-16 10.5 93.6 62 29 14 Sandy Lean Clay (CL)
6 2.5 9-20-16 6.7 103.6 Sandy Lean Clay (CL)
6 5 9-20-16 15.5 105.8 74 32 18 A-6 (11) Lean Clay with Sand (CL)
6 7.5 9-20-16 15.8 106.6 77 38 21 0.00 Claystone Bedrock
6 12.5 9-20-16 12.6 119.1 Claystone Bedrock
APPENDIX A
DARWINTM PAVEMENT DESIGN CALCULATIONS
APPENDIX B
EARTH ENGINEERING CONSULTANTS
GEOTECHNICAL REPORT
GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED HARMONY 23 DEVELOPMENT
SOUTH OF HARMONY ROAD AND WEST OF STRAUS CABIN ROAD
FORT COLLINS, COLORADO
EEC PROJECT NO. 1152123
Prepared for:
AMGI USA
1855 Quarley Place
Henderson, Nevada 89014
Attn: Mr. Greg Arnold (greg.arnold@amgiusa.com)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
January 14, 2016
AMGI USA
1855 Quarley Place
Henderson, Nevada 89014
Attn: Mr. Greg Arnold (greg.arnold@amgiusa.com)
Re: Subsurface Exploration Report
Proposed Harmony 23 Development
Fort Collins, Colorado
EEC Project No. 1152123
Mr. Arnold:
Enclosed, herewith, are the results of the geotechnical subsurface exploration for the proposed
eleven (11) 24-plex 3-story buildings, one (1) 12-plex 3-story building, nine (9) 5-car garage
with two dwelling 2-story apartment complexes along with several other garage units, two
(2)/twin 5-story in height office buildings having approximately 70,000 square feet each in plan
dimensions, a single-story community clubhouse/recreation center having approximately 11,500
sf in plan dimensions, as well as the associated on-site pavement improvements planned for
construction within the proposed Harmony 23 development property in Fort Collins, Colorado.
The site is located on the south side of Harmony Road, and west of Straus Cabin Road in Fort
Collins. This study was completed in general accordance with our proposal dated December 3,
2015.
In summary, the subsurface materials encountered within the eighteen (18) soil borings
completed for this project consisted of a thin layer of topsoil and vegetation. Underlying the
surficial topsoil/vegetation layer was generally cohesive subsoils, classified as lean clay with
sand grading to clayey sand, which extended to depths of approximately 4 to 22 feet below
existing site grades. Underlying the cohesive lean clay to clayey sand subsoils, in general, was
essentially granular silty sand grading to poorly graded sand and gravel to the depths explored in
borings B-2, B-6, B-11, B-13, and B-16 through B-18 or to underlying
claystone/siltstone/sandstone bedrock in the remaining borings encountered at approximate
depths of 16 to 28 feet below existing site grades, which extended to the depths explored,
approximately 20 to 30 feet.
Earth Engineering Consultants, LLC
Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 2
In review of the field and laboratory test results, we observed the upper portion of the cohesive
subsoils were generally stiff to very stiff in consistency (along the southern portion of the project
site), exhibited drier in-situ moisture contents and slightly higher in-place dry density results, and
revealed low to moderate swell potential characteristics while we observed cohesive subsoils that
were soft to medium stiff in consistency (along the bisecting irrigation ditch and the northeast
corner of the project site), exhibited saturated/wet in-situ moisture contents, slightly lower in-
place dry density results, and revealed low swell potential characteristics. With the anticipated
maximum wall and column loads for the proposed various building types, and the necessity to
ground modify the on-site subsoils as described in the text portion of this report, the proposed
apartment, garage, and community rec center buildings could be supported on a post-tension-slab
(PTS)-on-grade foundation/floor system or on conventional type spread footings bearing on
native materials or a zone of engineered fill material placed and compacted as described within
this report. With the soft/loose zones observed in the subgrade soils in the vicinity of the
proposed two (2)/twin 5-story office buildings, we recommend a deep foundation system
consisting of a straight shaft drilled pier/caisson system be used for support of the new buildings.
Groundwater was encountered across the site within the borings at approximate depths of 2 to 19
feet below existing site grades, except for boring B-13, which did not encounter groundwater. If
below grade construction is being considered for the site, we would suggest that the lower level
subgrade(s) be placed a minimum of 4 feet above the maximum anticipated rise in groundwater
levels, or a combination exterior and interior perimeter drainage system(s) be installed. Also,
consideration could be given to 1) either designing and installing an area-wide underdrain system
to lower the groundwater levels provided a gravity discharge point can be established. If a
gravity outlet/system cannot be designed another consideration would be to design and install a
mechanical sump pump system to discharge the collected groundwater within the underdrain
system, or 2) elevate/raise the site grades to establish the minimum required 4-foot separation to
the maximum anticipated rise in groundwater. Additional drainage system recommendations are
provided within the text portion of this report.
The interior floor slabs, exterior flatwork, and pavements could be supported on recondition on-
site soils or ground modified subsoils, understanding that some movement may occur. Fly ash
stabilization of the pavement subgrades should be expected to mitigate for the expansive
characteristics and to increase the subgrade integrity. Geotechnical recommendations
GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED HARMONY 23 DEVELOPMENT
SOUTH OF HARMONY ROAD AND WEST OF STRAUS CABIN ROAD
FORT COLLINS, COLORADO
EEC PROJECT NO. 1152123
January 14, 2016
INTRODUCTION
The subsurface exploration for the proposed Harmony 23 development planned for construction
at the southwest corner of Harmony Road and Straus Cabin Road in Fort Collins, Colorado has
been completed. For this study a total of eighteen (18) soil borings were completed within the
development area to obtain information on existing subsurface conditions. The borings were
extended to depths of approximately 10 to 30-feet below present site grades. Individual boring
logs and a site diagram indicating the approximate boring locations are provided with this report.
We understand this project includes the planned construction of eleven (11) 24-plex 3-story
buildings, one (1) 12-plex 3-story building, and nine (9) 5-car garage with two dwelling 2-story
building apartment complexes, two (2)/twin 5-story in height office buildings having
approximately 70,000 square feet each in plan dimensions, one (1) single-story community
clubhouse/recreation center, as well as on-site parking improvements and regional detention
ponds/water quality areas. We anticipate maximum wall and column loads will be on the order of
1 to 4 klf and 25 to 150 kips, respectively, for the apartment and garage/apartment buildings and
possibly up to 6 klf and 350 kips, respectively, for the two (2) 5-story twin office buildings. We
would expect some grade changes are required to develop final site grades. As shown on the
enclosed site development improvement diagram, on-site pavement improvements along with
detention ponds/water quality ponds are also planned and will be coordinated and designed in
general accordance with the City of Fort Collins’ and/or LCUASS pavement design criteria.
The purpose of this report is to describe the subsurface conditions encountered in the completed
borings, analyze and evaluate the test data, and provide geotechnical recommendations
concerning design and construction of the foundations, support of floor slabs and pavements.
EXPLORATION AND TESTING PROCEDURES
The boring locations were established in the field by a representative of Earth Engineering
Consultants, LLC (EEC) by pacing and estimating angles from identifiable site features. The
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 2
locations of the borings should be considered accurate only to the degree implied by the methods
used. Photographs of the site, taken at the time of drilling, are also provided with this report.
The borings were performed using a truck mounted, CME-55 drill rig equipped with a hydraulic
head employed in drilling and sampling operations. The boreholes were advanced using 4-inch
nominal diameter continuous flight augers and 4¼-inch hollow stem augers. Samples of the
subsurface materials encountered were obtained using split-barrel and California barrel sampling
techniques in general accordance with ASTM Specifications D1587 and D3550, respectively.
In the split-barrel and California barrel sampling procedures, standard sampling spoons are driven
into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of
blows required to advance the samplers is recorded and is used to estimate the in-situ relative
density of cohesionless materials and, to a lesser degree of accuracy, the consistency of cohesive
soils and hardness of weathered bedrock. Relatively undisturbed samples are obtained in the
California sampler. All samples obtained in the field were sealed and returned to the laboratory
for further examination, classification, and testing.
Laboratory moisture content tests were performed on each of the recovered samples. In addition,
the unconfined strength of appropriate samples was estimated using a calibrated hand
penetrometer device. Washed sieve analysis and Atterberg limits tests were completed on
selected samples to evaluate the quantity and plasticity of the fines in the subgrade soils.
Swell/consolidation tests were completed on selected samples to evaluate the tendency of the soil
to change volume with variation in moisture content and load. Selected samples of near surface
soils were also tested to determine quantities of water soluble sulfates to evaluate the potential for
sulfate attack on site concrete. Results of the outlined tests are indicated on the attached boring
logs and summary sheets.
As a part of the testing program, all samples were examined in the laboratory and classified in
general accordance with the attached General Notes and the Unified Soil Classification System
based on the texture and plasticity of the soil. The estimated group symbol for the Unified Soil
Classification System is indicated on the boring logs. A brief description of the Unified Soil
Classification System is included with this report. Classification of the bedrock was based on
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 3
visual and tactual observation of disturbed samples and auger cuttings. Coring and/or
petrographic analysis may reveal other rock types.
SITE AND SUBSURFACE CONDITIONS
The proposed project site, located south of Harmony Road, west of Straus Cabin Road (AKA
South County Road 7) and east of the Fossil Creek Inlet Ditch as presented on the enclosed site
diagram, is currently a vacant, undeveloped tract of land with sparse vegetation, is relatively flat,
is bisected by an irrigation ditch which was flowing during the site investigation (please note the
alignment traverses in the vicinity of borings B-4, B-7, B-10 and B-18), and exhibits positive
surface drainage generally in the north and east direction on the west side of the bisecting
irrigation ditch, with an approximate 5 feet (+/-) of relief across the site. Evidence of prior
building construction was not observed on the referenced property by EEC personnel.
An EEC field engineer was on site during the drilling operations to evaluate the subsurface
conditions encountered and supervise the drilling activities. Field logs prepared by EEC site
personnel were based on visual and tactual observation of disturbed samples and auger cuttings.
The final boring logs included with this report may contain modifications to the field logs based
on the results of laboratory testing and evaluation. Based on the results of the field borings and
laboratory evaluation, subsurface conditions can be generalized as follows.
In summary, encountered at the surface of each boring was a thin layer of topsoil and vegetation.
Underlying the surficial topsoil/vegetation layer was generally cohesive subsoils, classified as
lean clay with sand grading to clayey sand, which extended to depths of approximately 4 to 22
feet below existing site grades. Underlying the cohesive lean clay to clayey sand subsoils, in
general, was essentially granular silty sand grading to poorly graded sand and gravel to the depths
explored in borings B-2, B-6, B-11, B-13, and B-16 through B-18 or to underlying
claystone/siltstone/sandstone bedrock in the remaining borings at approximate depths of 16 to 28
feet below existing site grades which extended to the depths explored, approximately 20 to 30
feet.
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 4
The near surface cohesive subsoils encountered beneath the surface topsoil/vegetation layer, in
the southern portion of the project site, were generally relatively dry, medium stiff to very stiff in
consistency and exhibited low to moderate swell potential at current moisture and density
conditions. The cohesive soils generally became stiff to medium stiff with depth, exhibited
higher moisture contents and exhibited low to moderate swell potential. The near surface
cohesive subsoils in the northeast portion of the project site and along the bisecting irrigation
ditch, were generally relatively moist/wet, soft to medium stiff in consistency and exhibited a
tendency to consolidate at current moisture and density conditions. Soft/compressible and/or
loose zones were observed approaching and in the apparent groundwater table. Swell potential of
these soils is illustrated on the enclosed swell-consolidation curves, (i.e., swell-index values of
ranging from approximately (-) 0.4% to (+) 9.2%), presented in the Appendix of this report. The
claystone/siltstone/sandstone layer was moderately hard to hard and exhibited low swell potential
characteristics (i.e., swell-index values from approximately (+) 2.1% to (+) 2.7%). With depth
the claystone/siltstone/sandstone layer was hard exhibiting moderate to high bearing
characteristics.
The stratification boundaries indicated on the boring logs represent the approximate locations of
changes in soil and rock types. In-situ, the transition of materials may be gradual and indistinct.
GROUNDWATER CONDITIONS
Observations were made while drilling and after the completion of drilling to detect the presence
and level of free water. Subsequent groundwater measurements were also performed
approximately 6 hours and 2-weeks after the completion of the drilling operations in borings B-
17 and B-18, which had piezometers installed. Groundwater was generally observed at depths
ranging from approximately 2 to 19 feet below ground surface as indicated on the enclosed
boring logs, except for borings B-13 which did not encounter groundwater.
Field slotted temporary PVC piezometers were placed in two (2) of the open boreholes drilled on
December 28, 2015 prior to backfilling to allow for future water level measurements. The
groundwater measurements approximately 6 hours and 2 weeks after drilling and placement of
piezometers in borings B-17 and B-18 were 1.5 and 4.5 feet below existing site grades,
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 5
respectively. The piezometers were backfilled following the two week measurements and all
other borings were backfilled the same day they were drilled; therefore subsequent groundwater
measurements are not available for those locations.
Shallowest groundwater levels were noted near the bisecting irrigation ditch and towards the
northeast corner of the property. The measured depths to groundwater are recorded near the
upper right hand corner of each boring log included with this report. Groundwater measurements
provided with this report are indicative of groundwater levels at the locations and at the time the
borings/groundwater measurements were completed.
Fluctuations in groundwater levels can occur over time depending on variations in hydrologic
conditions, water levels in the Fossil Creek Inlet Ditch and the bisecting irrigation ditch, and other
conditions not apparent at the time of this report. Longer term monitoring of water levels in cased
wells, which are sealed from the influence of surface water would be required to more accurately
evaluate fluctuations in groundwater levels at the site. We have typically noted deepest
groundwater levels in late winter and shallowest groundwater levels in mid to late summer. Zones
of perched and/or trapped water can be encountered at times throughout the year in more permeable
zones in the subgrade soils and perched water is commonly observed in subgrade soils immediately
above lower permeability bedrock.
ANALYSIS AND RECOMMENDATIONS
Evaluation of “Soft/Compressible” Overburden Soils based on SPT Results
The following table identifies the soil classification/characterization of the overburden subsoils
based on the recorded Standard Penetration Test (SPT) results as presented on the boring logs
included in Appendix A of this report.
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 6
STRENGTH TERMS
Table I – Soil Description
RELATIVE DENSITY OF COARSE GRAINED
SOILS CONSISTENCY OF FINE-GRAINED SOILS
(More than 50% retained on No. 200 sieve.) (50% or more passing the No. 200 sieve.)
Density determined by Standard Penetration
Resistance Includes Gravels, sands and silts.
Consistency determined by laboratory shear strength testing, field visual-
manual procedures or standard penetration resistance
Descriptive
Term (Density)
Standard
Penetration
or
N-Value
Blows/Ft.
Ring Sampler
Blows/Ft.
Descriptive
Term
(Consistency)
Unconfined
Compressive
Strength, Qu, psf
Standard
Penetration or
N-Value
Blows/Ft.
Ring
Sampler
Blows/Ft.
Very Loose 0 - 3 0 - 6 Very Soft less than 500 0 - 1 < 3
Loose 4 - 9 7 - 18 Soft 500 to 1,000 2 - 4 3 - 4
Medium Dense 10 - 29 19 - 58 Medium-Stiff 1,000 to 2,000 4 - 8 5 - 9
Dense 30 - 50 59 - 98 Stiff 2,000 to 4,000 8 - 15 10 - 18
Very Dense > 50 ≥ 99 Very Stiff 4,000 to 8,000 15 - 30 19 - 42
Hard > 8,000 > 30 > 42
The boring logs and the soil descriptions identified as “soft and/or very loose” subsoils, in
essence are those in which we recorded Standard Penetration Tests – N-Blows/Ft. less than 4 per
12-inch intervals. We have plotted the SPT results with increased depth for each test boring with
graphical presentations included in the Appendix of this report. Please note those borings and
respective depths which plot in the less than 4-blows/ft. range for soft and/or loose soils. In
general the majority of the overburden subsoils were within the medium stiff/medium dense to
very stiff/dense soil descriptions; however intermittent soft and/or loose zones were encountered
and special precaution will be required to address these conditions during the construction phase.
Swell – Consolidation Test Results
The swell-consolidation test is commonly performed to evaluate the swell or consolidation potential
of soils or bedrock to assist in determining foundation, floor slab and pavement design criteria. In
this test, relatively undisturbed samples obtained directly from the California barrel sampler are
placed in a laboratory apparatus and inundated with water under a predetermined load. The swell-
index is the resulting amount of swell or collapse as a percent of the sample’s thickness after the
inundation period. Samples obtained at approximate depths of 1 to 2-feet are generally pre-loaded
at 150-psf to simulate the floor and pavement loading conditions, samples obtained at the 3 to 4-foot
intervals are generally pre-loaded at 500 psf to simulate the overburden soil pressure, and samples
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Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 7
obtained at greater depths are generally pre-loaded at 1000 psf to simulate deep foundation system
loading conditions. All samples are inundated with water and monitored for swell and
consolidation. After the inundation period, additional incremental loads are applied to evaluate the
swell pressure and consolidation characteristics.
For this assessment, we conducted twelve (12) swell-consolidation tests on relatively undisturbed
soil and bedrock samples obtained at various intervals/depths on the site. The swell index values
for the in-situ soil samples analyzed revealed low to moderate swell characteristics as indicated
on the attached swell test summaries. The (+) test results indicate the material’s swell potential
characteristics while the (-) test results indicate the material’s collapse/consolidation potential
characteristics when inundated with water. The following tables summarize the swell-
consolidation laboratory test results for samples obtained during our field explorations for the
subject site.
TABLE II - Swell Consolidation Test Results
Boring
No.
Depth,
ft.
Material Type
In-Situ
Moisture
Content, %
Dry
Density,
PCF
Inundation
Pressure,
psf
Swell
Index,
(+/-) %
B-1 4 Lean Clay with Sand 16.1 108.8 500 (+) 0.3
B-1 24 Claystone / Siltstone / Sandstone 16.0 114.5 500 (+) 2.7
B-2 2 Silty Clayey Sand 6.9 121.5 150 (+) 4.0
B-5 2 Lean Clay with Sand 32.3 91.4 150 (-) 0.4
B-6 2 Sandy Lean Clay / Silt 16.2 115.5 150 (+/-) 0.0
B-9 2 Sandy Lean Clay / Clayey Sand 12.4 100.1 150 (+) 2.7
B-12 4 Lean Clay with Sand 13.2 117.0 500 (+) 3.9
B-12 24 Claystone / Siltstone / Sandstone 16.3 111.0 500 (+) 2.1
B-13 2 Sandy Lean Clay 7.1 99.5 150 (+) 2.9
B-14 4 Sandy Lean Clay 10.1 114.5 150 (+) 9.2
B-15 4 Sandy Lean Clay 10.2 121.8 500 (+) 4.4
B-16 2 Silty Clayey Sand 27.8 100.8 150 (-) 0.3
Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide
uniformity in terminology between geotechnical engineers to provide a relative correlation of slab
performance risk to measured swell. “The representative percent swell values are not necessarily
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Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 8
measured values; rather, they are a judgment of the swell of the soil and/or bedrock profile likely to
influence slab performance.” Geotechnical engineers use this information to also evaluate the swell
potential risks for foundation performance based on the risk categories.
Table III - Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Slab Performance Risk Category Representative Percent Swell
(500 psf Surcharge)
Representative Percent Swell
(1000 psf Surcharge)
Low 0 to < 3 0 < 2
Moderate 3 to < 5 2 to < 4
High 5 to < 8 4 to < 6
Very High > 8 > 6
Based on the laboratory test results, the in-situ samples analyzed for this project were within the low
to moderate range. The moderate swell-index values were of relatively undisturbed subgrade
samples which appeared to be relatively dry, stiff to very stiff in-situ. In our opinion, these subsoils
when over-excavated, moisture conditioned and properly placed and compacted as
engineered/controlled fill material would most likely reveal low swell potential characteristics.
General Considerations and Site Preparation
As presented on the enclosed boring logs and laboratory test results, low to moderate swelling
cohesive soils are present on this site. This report provides recommendations to help mitigate the
effects of soil expansion and/or consolidation. Even if these procedures are followed, some
movement and at least minor cracking in the structures should be anticipated. The severity of
cracking and other cosmetic damage such as uneven floor slabs will probably increase if any
modification of the site results in excessive wetting or drying of the site’s subsoils. Eliminating
the risk of movement and cosmetic distress may not be feasible, but it may be possible to further
reduce the risk of movement if significantly more extensive/expensive measures are used during
construction. To reduce the potential movement of foundations, floor slabs, flatwork and
pavements, included herein are recommendations for an over-excavation and replacement
concept. This approach will significantly reduce but not eliminate post construction movement.
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 9
All existing topsoil/vegetation should be removed from the site improvement areas. To reduce
the potential for post-construction movement caused by expansion of the dry, in-situ soils
(primarily in the southern portion of the project site in the areas of borings B-12 through B-15),
we recommend the entire building footprints be over-excavated and replaced as moisture
conditioned/compacted engineered controlled fill. The over-excavation should extent to a depth
to allow for at least 3-feet of processed/engineered controlled fill material below all foundation
bearing elements or to a depth of at least 4-feet below existing site grades, whichever provides
the greatest over-excavation depth. Since movement of pavements is generally more tolerable, in
our opinion, the over-excavation depth in the pavement areas could be reduced to 2 feet below
existing site grades or final grades, whichever provides the greatest over-excavation depth. The
over-excavated areas should extend laterally in all directions beyond the edges of the
foundations/pavements a minimum 8 inches for every 12 inches of over-excavated depth.
After removal of all topsoil/vegetation within the planned development areas, as well as removal
of unacceptable or unsuitable subsoils, removal of over-excavation materials, and prior to
placement of fill and/or site improvements, the exposed soils should be scarified to a minimum
depth of 9 inches, adjusted in moisture content to within (+/-) 2% of standard Proctor optimum
moisture content and compacted to at least 95% of the material's standard Proctor maximum dry
density as determined in accordance with ASTM Specification D698.
Fill materials used to replace the over-excavated zone and establish grades in the building areas
and pavement/flatwork areas, after the initial zone has been prepared as recommended above,
should consist of approved on-site lean clay with sand to clayey sand subsoils or approved
structural fill material which is free from organic matter and debris. If on-site cohesive subsoils
are used as engineered fill, they should be placed in maximum 9-inch loose lifts, and be moisture
conditioned and compacted as recommended for the scarified soils. If structural fill materials are
used they should be graded similarly to a CDOT Class 5, 6 or 7 aggregate base with sufficient
fines to prevent ponding of water within the fill. Structural fill material should be placed in loose
lifts not to exceed 9 inches thick, adjusted to a workable moisture content and compacted to at
least 95% of standard Proctor maximum dry density as determined by ASTM Specification D698.
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Areas of soft/compressible cohesive subsoils across the site (particularly near the bisecting
irrigation ditch and/or the northeast corner of the project site with relatively shallow
groundwater) may require ground stabilization procedures to create a working platform for
construction equipment prior to placement of any additional fill. If necessary, consideration
could be given to placement of a granular material, such as a 3-inch minus pit run and/or recycled
concrete or equivalent material, embedded into the soft soils, prior to placement of additional fill
material or operating heavy earth-moving equipment. Supplemental recommendations can be
provided upon request.
Prior to placement of fill materials and/or overlying improvements, consideration could also be
given to a subgrade stabilization approach within the improvement areas utilizing an over-
excavation and replacement by incorporating either reinforced geo-grid and/or a geo-synthetic
product as follows.
Use of a Tensar BX1100 or BX1200 Geogrid reinforcement product or equivalent installed over
the subgrade soils, then placement of an approximate 18 to 24 inch layer of an interlocking coarse
granular, fractured face 3 to 1-1/2 inch minus aggregate material, such as recycled concrete or
equivalent be placed over the top of the geogrid and incorporated into the unstable subgrade soils
could be considered as a subgrade stabilization method. Placement and installation of the geogrid
product should be completed in general accordance with the manufacturer’s specifications.
In the roadway and possibly even within the interior floor slab areas, consideration could also be
given to the use of a geo-synthetic to reduce the overexcavation depth. If a geo-synthetic product
is used, (such as a Mirafi HP570, Mirafi RS380i or RS580i of equivalent), we recommend over-
excavating a minimum of 2 feet of the subgrade soil from beneath the roadways and interior floor
slab areas. Once the overexcavation is complete, the exposed subgrades should be proof rolled to
identify significantly soft and unstable soils. Proof rolling would commonly be accomplished by
observation of the subgrades immediately behind a tire supporting the axle of a loaded water
truck. Significant instability may require additional overexcavation depths. To redevelop the
pavement subgrade and/or possibly the interior floor slab subgrade elevations, prior to placement
of backfill materials, we recommend installing the approved/selected geo-synthetic product above
the exposed subgrades. The geo-synthetic should be installed according to the manufacture’s
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recommendations. Once installed the backfill materials could be placed to redevelop the
pavement and floor slab subgrade elevations.
Fill materials placed to develop the subgrades should consist of approved structural fill material
which is free from organic matter and debris. Structural fill should be graded similarly to a
CDOT Class 5, 6 or 7 aggregate base with sufficient fines to prevent ponding of water within the
fill. Recycled concrete graded to the outlined CDOT Specifications would be acceptable fill
material. Structural fill material should be placed in loose lifts not to exceed 9 inches thick,
adjusted to a workable moisture content and compacted to at least 95% of standard Proctor
maximum dry density as determined by ASTM Specification D698.
After the backfill materials are placed to grade, we recommend a supplemental proof roll be
conducted to verify stability of the subgrades prior to placement of floor slabs, the recommended
pavement sections and/or gravel surfacing materials. Unstable subgrades may require further
reworking in place or additional stabilization. The ground modification procedures
recommended herein for the referenced site will help reduce the amount of anticipated movement
of the floor slabs and pavements/parking, but some movement should be expected.
Close observation of each buildings subgrade in the form of an “open-hole” or foundation
excavation observations should be conducted at the start of construction to determine which
recommendation above should be followed.
After preparation of the subgrades, care should be taken to avoid disturbing the prepared
materials. In-place soils which are loosened or disturbed by construction activity should be
removed and replaced or reworked in-place prior to placement of the overlying improvements.
Care should be exercised after preparation of the subgrades to avoid disturbing the subgrade
materials. Positive drainage should be developed away from the structures and pavements to
avoid wetting of subgrade materials. Subgrade materials becoming wet subsequent to
construction of the site improvements can result in unacceptable performance.
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In areas where excavations will extend below existing groundwater table or the perched water
surface level, such as utility excavation, placement of cleaner granular fill material would be
desirable. Those materials should be placed in lifts and compacted to at least 70% relative
density.
If below grade and/or lower level construction is considered for the site, we would suggest that
the lower level subgrade(s) be placed a minimum of 4 feet above the maximum anticipated rise in
groundwater levels, or a combination exterior and interior perimeter drainage system(s) be
installed. Also, consideration could be given to 1) either designing and installing an area
underdrain system to lower the groundwater levels provided a gravity discharge point can be
established. If a gravity outlet/system cannot be designed another consideration would be to
design and install a mechanical sump pump system to discharge the collected groundwater within
the underdrain system, or 2) elevate/raise the site grades to establish the minimum required 4-foot
separation to the maximum anticipated rise in groundwater.
Areas of deeper fills may experience settlement from within the placed fill materials. Settlement
on the order of 1 to 1.5% of the fill depth would be estimated. The rate of settlement will be
dependent on the type of fill material placed and construction methods. Granular soils will
consolidate essentially immediately upon placement of overlying loads. Cohesive soils will
consolidate at a slower rate.
In addition, the existing bisecting lateral ditch currently appears to run through one office
building, one 24-plex building, and the community rec center building (i.e. in the vicinity of
borings B-4, B-7, and B-10). Upon request, and depending on the plan for the bisecting lateral
ditch, additional recommendations can be provided in regards to overexcavation depths, backfill
procedures and other recommendations to reduce the potential impact on future foundations
and/or site improvements
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Foundation Systems – General Considerations
The site appears suitable for the proposed construction based on the results of our field exploration
and review of the proposed development plans. The following foundation systems were evaluated
for use on the site with the understanding of slab-on-grade structures.
Conventional spread footings
Post-Tensioned Slab Foundation System
Straight shaft drilled piers bearing into the underlying bedrock formation.
Close attention will be required during the supplemental site observations, such as “open-hole” or
foundation excavation observations to further assess the soil conditions, recommendations and
foundation design bearing strata for each of the various buildings.
Conventional Spread Footing Foundations
The native undisturbed lean clay to clayey sand generally exhibited low to moderate swell
potential and low bearing characteristics with the moderate swell potential appearing to be
primarily in the southern portion of the project site in the general vicinity of borings B-12
through B-15. To reduce to potential for post-construction heaving of the footings subsequent to
construction, we recommend the existing site subgrades and proposed fill materials be worked
and placed as recommended in the General Considerations and Site Preparation section of this
report.
Conventional type spread footings could be used to support the proposed lightly to moderately
loaded slab-on-grade 12-plex, 24-plex, garage, and recreation center buildings provided the
footings are placed on approved native subgrade material or moisture/density controlled fill
material and the maximum anticipated wall and column loads do not exceed those presented
herein. If actual design loads exceed the assumed values as previously presented, we should be
consulted to provide supplemental design criteria, possibly including alternative foundations,
such as drilled piers as further discussed herein.
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Footings bearing on approved native subsoils or moisture/density conditioned soils could be
designed for a maximum net allowable total load bearing pressure of 2,000 psf. Footing
foundations should maintain separation above maximum anticipated rise in groundwater
elevation of at least 4 feet indicated earlier. The net bearing pressure refers to the pressure at
foundation bearing level in excess of the minimum surrounding overburden pressure. Total load
should include full dead and live loads.
Footings should be proportioned to reduce differential foundation movement. We estimate the total
long term settlement of footings designed as outlined above would be less than one-inch.
The backfill soils adjacent to the foundations should be placed in loose lifts not to exceed 9
inches thick, moisture conditioned to ± 2% of the material’s standard Proctor optimum moisture
content, and mechanically compacted to be at least 95% of standard Proctor maximum dry
density, ASTM D698.
After placement of the fill materials, for foundation support, care should be taken to avoid
wetting or drying of those materials. Bearing materials, which are loosened or disturbed by the
construction activities, or materials which become dry and desiccated or wet and softened, should
be removed and replaced or reworked in place prior to construction of the overlying
improvements.
Exterior foundations and foundations in unheated areas should be located at least 30 inches below
adjacent exterior grade to provide frost protection. We recommend formed continuous footings
have a minimum width of 12 inches and isolated column foundations have a minimum width of
24 inches.
Post-Tensioned Slab Foundation Systems
The results of our field exploration and laboratory testing completed for this study indicate the
upper cohesive clay subsoils exhibited low to moderate swell potential and low to moderate
bearing capabilities. Based on the subsurface conditions encountered we expect the proposed slab-
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on-grade 12-plex, 24-plex, garage, and recreation center structures could be supported by PT slab-
on-grade foundations that are supported/bear on a zone of engineered/controlled fill materials
placed and compacted as outlined in the General Conditions and Site Preparation section of this
report or on acceptable underlying native soils. The design parameters provided below assume
subgrade materials outlined under General Conditions and Site Preparation.
Outlined below are the post tensioned slab (PTS) design criteria based on the subsurface
conditions and information provided in the 3rd Edition of the Post-Tensioning Institutes design
manual. Post-tensioned slabs, thickened or turn-down edges, and/or interior beams should be
designed and constructed in accordance with the appropriate design criteria.
Table IV – Post-Tension Slab (PTS) Design Criteria
Post-Tensioned Slab (PTS) – 3rd Edition Design Parameters
Maximum Allowable Bearing Pressure, psf 2,000
Edge Moisture Variation Distance, em
Center Lift Condition, ft. 8.6
Edge Lift Condition, ft. 4.3
Differential Soil Movement, ym
Center Lift Condition, Inches 0.4
Edge Lift Condition, Inches 0.8
Slab-Subgrade friction coefficient,
on polyethylene sheeting 0.75
on cohesionless soils – (sands) 1.0
on cohesive soils – (clays) 2.0
Drilled Piers/Caissons Foundations
Based on the subgrade conditions observed in the test borings and on the anticipated foundation
loads, we recommend supporting the proposed twin 5-story in height office buildings on a grade
beam and straight shaft drilled pier/caisson foundation system extending into the underlying
bedrock formation. Particular attention will be required in the construction of drilled piers due to
the presence of soft/wet clays, loose/wet sands and gravels and shallow groundwater.
For axial compression loads, the drilled piers could be designed using a maximum end bearing
pressure of 30,000 pounds per square foot (psf), along with a skin-friction of 3,000 psf for the
portion of the pier extended into the underlying firm and/or harder bedrock formation. Straight
shaft piers should be drilled a minimum of 10-feet into competent or harder bedrock. Lower values
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may be appropriate for pier “groupings” depending on the pier diameters and spacing. Pile groups
should be evaluated individually.
To satisfy forces in the horizontal direction, piers may be designed for lateral loads using a modulus
of 50 tons per cubic foot (tcf) for the portion of the pier in native cohesive soils, 75 tcf for native
granular materials or engineered fill, and 400 tcf in bedrock for a pier diameter of 12 inches. The
coefficient of subgrade reaction for varying pier diameters is provided in the table below:
TABLE V - Coefficient of Subgrade Reaction for Varying Pier Diameters
Pier Diameter (inches)
Coefficient of Subgrade Reaction (tons/ft3)
Cohesive Soils
Engineered Fill or
Granular Soils
Bedrock
18 33 50 267
24 25 38 200
30 20 30 160
36 17 25 133
When the lateral capacity of drilled piers is evaluated by the L-Pile (COM 624) computer program,
we recommend that internally generated load-deformation (P-Y) curves be used. The parameters in
Table V below may be used for the design of laterally loaded piers, using the L-Pile (COM 624)
computer program:
TABLE VI – L-Pile Design Parameters
Parameters Native Granular Soils
or Structural Fill
On-Site Overburden
Cohesive Soils Bedrock
Unit Weight of Soil (pcf) 125(1)
100(1)
125(1)
Cohesion (psf) 0 70 5000
Angle of Internal Friction () (degrees) 35 25 20
Strain Corresponding to ½ Max. Principal
Stress Difference 50
--- 0.02 0.015
*Notes: 1) Reduce by 64 PCF below the water table
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Drilling caissons to design depth should be possible with conventional heavy-duty single flight
power augers equipped with rock teeth on the majority of the site. However, areas of well-
cemented sandstone bedrock lenses may be encountered at various depths where specialized drilling
equipment and/or rock excavating equipment may be required. Varying zones of cobbles may also
be encountered in the granular soils above the bedrock. Excavation penetrating the well-cemented
sandstone bedrock may require the use of specialized heavy-duty equipment, together with rock
augers and/or core barrels. Consideration should be given to obtaining a unit price for difficult
caisson excavation in the contract documents for the project.
Due to the presence of soft to very soft cohesive soil, loose to very loose granular soil and shallow
groundwater at approximate depths of 2 to 3 feet below site grades in the proposed office building
areas, maintaining open shafts for the caissons may be difficult without stabilizing measures. We
expect temporary casing will be required to adequately/properly drill and clean piers prior to
concrete placement. Groundwater should be removed from each pier hole prior to concrete
placement. Pier concrete should be placed immediately after completion of drilling and cleaning.
A maximum 3-inch depth of groundwater is acceptable in each pier prior to concrete placement. If
pier concrete cannot be placed in dry conditions, a tremie should be used for concrete placement.
Due to potential sloughing and raveling, foundation concrete quantities may exceed calculated
geometric volumes. Pier concrete with slump in the range of 6 to 8 inches is recommended. Casing
used for pier construction should be withdrawn in a slow continuous manner maintaining a
sufficient head of concrete to prevent infiltration of soil/water or the creation of voids in pier
concrete.
Foundation excavations should be observed by the geotechnical engineer. A representative of the
geotechnical engineer should inspect the bearing surface and pier configuration. If the soil
conditions encountered differ from those presented in this report, supplemental recommendations
may be required.
We estimate the long-term settlement of drilled pier foundations designed and constructed as
outlined above would be less than 1-inch.
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Interior/Exterior Perimeter Drainage Systems
Groundwater was encountered across the site within the soil borings at approximate depths of 2
to 19 feet below existing site grades. If lower level construction is being considered for the site,
we would suggest that the lower level subgrade(s) be placed a minimum of 4-feet above
maximum anticipated rise in groundwater levels, or a combination exterior and interior perimeter
drainage system(s) be installed.
Consideration could be given to 1) either designing and installing an area underdrain system to
lower the groundwater levels provided a gravity discharge point can be established. If a gravity
outlet/system cannot be designed another consideration would be to design and install a
mechanical sump pump system to discharge the collected groundwater within the underdrain
system, or 2) elevate/raise the site grades to establish the minimum required four (4) foot
separation to the maximum anticipated rise in groundwater. EEC is available to assist in the
underdrain design if requested.
The following information should also be considered, which as previously mentioned, would be
to install an interior and exterior perimeter drainage system for each individual building. To
reduce the potential for groundwater to enter the lower level/basement area of the structure(s),
installation of a dewatering system is recommended. The dewatering system should, at a
minimum, include an underslab gravel drainage layer sloped to an interior perimeter drainage
system. The following provide preliminary design recommendations for interior and exterior
perimeter drainage systems.
The underslab drainage system should consist of a properly sized perforated pipe, embedded in
free-draining gravel, placed in a trench at least 12 inches in width. The trench should be inset
from the interior edge of the nearest foundation a minimum of 12 inches. In addition, the trench
should be located such that an imaginary line extending downward at a 45-degree angle from the
foundation does not intersect the nearest edge of the trench. Gravel should extend a minimum of
3 inches beneath the bottom of the pipe. The underslab drainage system should be sloped at a
minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system.
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The underslab drainage layer should consist of a minimum 6-inch thickness of free-draining
gravel meeting the specifications of ASTM C33, Size No. 57 or 67 or equivalent. Cross-
connecting drainage pipes should be provided beneath the slab at minimum 15-foot intervals, and
should discharge to the perimeter drainage system.
Sizing of drainage pipe will be dependent upon groundwater flow into the dewatering system.
Groundwater flow rates will fluctuate with permeability of the soils to be dewatered and the
depth to which groundwater may rise in the future. Pump tests to determine groundwater flow
rates are recommended in order to properly design the system. For preliminary design purposes,
the drainage pipe, sump and pump system should be sized for a projected flow of 0.5 x 10-3 cubic
feet per second (cfs) per lineal foot of drainage pipe. Additional recommendations can be
provided upon request.
To reduce the potential for surface water infiltration from impacting foundation bearing soils
and/or entering any planned below grade portion of any residential structure, installation of an
exterior perimeter drainage system is recommended. This drainage system should be constructed
around the exterior perimeter of the lower level/below grade foundation system, and sloped at a
minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system.
The exterior drainage system should consist of a properly sized perforated pipe, embedded in
free-draining gravel, placed in a trench at least 12 inches in width. Gravel should extend a
minimum of 3 inches beneath the bottom of the pipe, and at least 2 feet above the bottom of the
foundation wall. The system should be underlain with a polyethylene moisture barrier, sealed to
the foundation walls, and extended at least to the edge of the backfill zone. The gravel should be
covered with drainage fabric prior to placement of foundation backfill.
Seismic Conditions
The site soil conditions consist of approximately 16 to 23 feet of overburden soils or greater
overlying moderately hard to hard bedrock. For those site conditions, the 2012 International
Building Code indicates a Seismic Site Classification of D.
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Lateral Earth Pressures
For any portion of the proposed various structures constructed below grade, those portions will be
subject to lateral earth pressures. Passive lateral earth pressures may help resist the driving forces
for retaining wall or other similar site structures. Active lateral earth pressures could be used for
design of structures where some movement of the structure is anticipated, such as retaining walls.
The total deflection of structures for design with active earth pressure is estimated to be on the
order of one half of one percent of the height of the down slope side of the structure. We
recommend at-rest pressures be used for design of structures where rotation of the walls is
restrained. Passive pressures and friction between the footing and bearing soils could be used for
design of resistance to movement of retaining walls.
Coefficient values for backfill with anticipated types of soils for calculation of active, at rest and
passive earth pressures are provided in the table below. Equivalent fluid pressure is equal to the
coefficient times the appropriate soil unit weight. Those coefficient values are based on
horizontal backfill with backfill soils consisting of essentially granular materials with a friction
angle of 35 degrees or low volume change cohesive soils. For the at-rest and active earth
pressures, slopes down and away from the structure would result in reduced driving forces with
slopes up and away from the structures resulting in greater forces on the walls. The passive
resistance would be reduced with slopes away from the wall. The top 30-inches of soil on the
passive resistance side of walls could be used as a surcharge load; however, should not be used as
a part of the passive resistance value. Frictional resistance is equal to the tangent of the friction
angle times the normal force.
Table VII – Lateral Earth Pressure Coefficients
Soil Type On-Site Cohesive Soils Import Structural Fill
Wet Unit Weight 115 135
Saturated Unit Weight 135 140
Friction Angle () – (assumed) 25° 35°
Active Pressure Coefficient 0.40 0.27
At-rest Pressure Coefficient 0.58 0.43
Passive Pressure Coefficient 2.46 3.70
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Surcharge loads or point loads placed in the backfill can also create additional loads on below
grade walls. Those situations should be designed on an individual basis.
The outlined values do not include factors of safety nor allowances for hydrostatic loads and are
based on assumed friction angles, which should be verified after potential material sources have
been identified. Care should be taken to develop appropriate drainage systems behind below
grade walls to eliminate potential for hydrostatic loads developing on the walls. Those systems
would likely include perimeter drain systems extending to sump areas or free outfall where
reverse flow cannot occur into the system. Where necessary, appropriate hydrostatic load values
should be used for design.
Floor Slabs
In our opinion, floor slabs could be supported on a zone of engineered fill material and/or
approved structural fill material following the protocol outlined in the section titled General
Conditions and Site Preparation to allow for at least 4-feet of processed/engineered controlled
fill material beneath interior floor slabs in the southern portion of the site or at least 2 feet of
structural fill material near the bisecting irrigation ditch and/or the northeast corner of the project
site. Close observation of subgrade materials during construction should be conducted to
determine the appropriate recommendations. Floor slabs supported on reconditioned engineered
fill could be designed using a modulus of subgrade support (k-value) of 100 pci. We estimate the
long term movement of slab-on-grade floors with properly prepared subgrade subsoils as outlined
above would be on the order of 1-inch.
Care should be taken after preparation of the subgrades to avoid disturbing the subgrade
materials. Materials which are loosened or materials which become dry and desiccated or wet
and softened should be removed and replaced prior to placement of the overlying floor slabs.
Care should be taken to maintain proper moisture contents in the subgrade soils prior to
placement of any overlying improvements. An underslab gravel layer or thin leveling course
could be used underneath the concrete floor slabs to provide a capillary break mechanism, a load
distribution layer, and as a leveling course for the concrete placement.
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Additional floor slab design and construction recommendations are as follows:
Positive separations and/or isolation joints should be provided between slabs and
all foundations, columns or utility lines to allow independent movement.
Control joints should be provided in slabs to control the location and extent of
cracking.
Interior trench backfill placed beneath slabs should be compacted in a similar
manner as previously described for footing and floor slab fill.
In areas subjected to normal loading, a 4 to 6-inch layer of clean-graded gravel or
aggregate base course should be placed beneath interior floor slabs.
Floor slabs should not be constructed on frozen subgrade.
Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1R are recommended.
Pavement Subgrades/Pavement Design Sections
Subgrades for site pavements should be prepared as outlined in the section titled General
Considerations and Site Preparation. It will be imperative to maintain the moisture content of
the prepared subgrade up to and immediately prior to surfacing. Subgrade soils allowed to
become dry and dense would be prone to swelling, potentially causing additional post-
construction heaving of the site pavements. Densification of subgrade soils can occur with
construction traffic. Prior to surfacing the roadway subgrades with aggregate base, we
recommend the subgrades be proof rolled to help identify any soft or yielding areas. Soft or
yielding areas delineated by the proof rolling operations should be undercut or stabilized in-place
to achieve the appropriate subgrade support.
If unstable subgrades exist due to pumping conditions after subgrade preparation stage,
consideration should be given to stabilizing the top 12 inches of pavement subgrades with the use
of an ASTM C618 Class C fly ash. We estimate stabilization of the site lean clay with sand
clayey sand soils could be accomplished by incorporating at least 12%, by dry weight of Class C
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fly ash into the upper 12 inches of subgrade. To take full advantage of the increased stiffness of a
stabilized subgrade for a reduction in pavement thickness, a mix design utilizing the fly ash with
the site soils would be required prior to surfacing.
We expect the site pavements will include areas designated primarily for light-duty automobile
parking/traffic use and areas for heavy-duty truck traffic. For design purposes, an assumed
equivalent daily load axle (EDLA) rating of 7 is used in the light-duty areas and an EDLA rating
of 15 in the heavy-duty areas. A Hveem stabilometer R-value of 10 was assumed and used in
design.
Hot mix asphalt (HMA) underlain by aggregate base course with a fly ash treated subgrade, or a
non-reinforced concrete pavement may be feasible options for the proposed on-site paved
sections. HMA pavements may show rutting and distress in areas of heavy truck traffic (trash
truck routes) or in truck loading and turning areas. Concrete pavements should be considered in
those areas. Suggested pavement sections are provided in the table below. The outlined
pavement sections are minimums and thus, periodic maintenance should be expected.
TABLE VIII: RECOMMENDED MINIMUM PAVEMENT SECTIONS
Automobile Parking Heavy Duty Areas
18-kip EDLA
18-kip ESAL
Reliability
Resilient Modulus
PSI Loss
7
51,100
75%
3562
2.5
15
109,500
85%
3562
2.2
Design Structure Number 2.47 2.96
Composite Section – Option A (assume Stable Subgrade)
Hot Mix Asphalt
Aggregate Base Course
Structure Number
4"
7"
(2.53)
5"
8"
(3.08)
Composite Section with Fly Ash Treated Subgrade
Hot Mix Asphalt
Aggregate Base Course
Fly Ash Treated Subgrade (assume half-credit)
Structure Number
4"
6"
12"
(3.02)
5"
7"
12"
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We recommend aggregate base be graded to meet a Class 5 or Class 6 aggregate base. Aggregate
base should be adjusted in moisture content and compacted to achieve a minimum of 95% of
standard Proctor maximum dry density.
HMA should be graded to meet a SX (75) or S (75) with PG 58-28 binder. The HMA should be
designed in accordance with LCUASS design criteria. HMA should be compacted to achieve 92 to
96% of the mix's theoretical maximum specific gravity (Rice Value).
Portland cement concrete should be an acceptable exterior pavement mix with a minimum 28-day
compressive strength of 4,200 psi and should be air entrained.
The recommended pavement sections are minimums, thus, periodic maintenance should be
expected. Longitudinal and transverse joints should be provided as needed in concrete pavements
for expansion/contraction and isolation. The location and extent of joints should be based upon the
final pavement geometry. Sawed joints should be cut in accordance with ACI recommendations.
All joints should be sealed to prevent entry of foreign material and dowelled where necessary for
load transfer.
Since the cohesive soils on the site have some shrink/swell potential, pavements could crack in the
future primarily because of the volume change of the soils when subjected to changes in moisture
content of the subgrades. The cracking, while not desirable, does not necessarily constitute
structural failure of the pavement. Stabilization of the subgrades will reduce the potential for
cracking of the pavements.
The collection and diversion of surface drainage away from paved areas is critical to the
satisfactory performance of the pavement. Drainage design should provide for the removal of
water from paved areas in order to reduce the potential for wetting of the subgrade soils.
Long-term pavement performance will be dependent upon several factors, including maintaining
subgrade moisture levels and providing for preventive maintenance. The following
recommendations should be considered the minimum:
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EEC Project No. 1152123
January 14, 2016
Page 25
The subgrade and the pavement surface should be adequately sloped to promote proper
surface drainage.
Install pavement drainage surrounding areas anticipated for frequent wetting (e.g. garden
centers, wash racks)
Install joint sealant and seal cracks immediately.
Seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture
migration to subgrade soils.
Place and compact low permeability backfill against the exterior side of curb and gutter.
Preventive maintenance should be planned and provided for through an on-going pavement
management program. Preventive maintenance activities are intended to slow the rate of pavement
deterioration, and to preserve the pavement investment. Preventive maintenance consists of both
localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g.
surface sealing). Preventive maintenance is usually the first priority when implementing a planned
pavement maintenance program and provides the highest return on investment for pavements. Prior
to implementing any maintenance, additional engineering observation is recommended to determine
the type and extent of preventive maintenance.
Site grading is generally accomplished early in the construction phase. However as construction
proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation,
or rainfall. As a result, the pavement subgrade may not be suitable for pavement construction and
corrective action will be required. The subgrade should be carefully evaluated at the time of
pavement construction for signs of disturbance, rutting, or excessive drying. If disturbance has
occurred, pavement subgrade areas should be reworked, moisture conditioned, and properly
compacted to the recommendations in this report immediately prior to paving.
If during or after placement of the stabilization or initial lift of pavement, the area is observed to be
yielding under vehicle traffic or construction equipment, it is recommended that EEC be contacted
for additional alternative methods of stabilization, or a change in the pavement section.
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 26
Water Soluble Sulfates – (SO4)
The water soluble sulfate (SO4) testing of the on-site subgrade materials taken during our
subsurface exploration are provided in the following table below. Based on the reported sulfate
contents test results, this report includes a recommendation for the CLASS or TYPE of cement
for use for contact in association with the on-site subsoils.
TABLE IX - Water Soluble Sulfate Test Results
Sample Location Description
Soluble Sulfate
Content (mg/kg)
Soluble Sulfate
Content (%)
B-3, S-1 at 4’ Sandy Lean Clay (CL) 170 0.02
B-4, S-2 at 9’ Sand and Gravel (SP/GP) 140 0.01
B-7, S-5 at 9’ Claystone / Siltstone / Sandstone 100 0.01
B-13, S-2 at 4’ Sandy Lean Clay (CL) 260 .03
Based on the results as presented above, ACI 318, Section 4.2 indicates the site overburden soils
and underlying bedrock have a low risk of sulfate attack on Portland cement concrete. Therefore
Class 0 and/or Type I/II cement with or without the use of fly ash could be used for concrete on
and below site grades within the overburden soils. Foundation concrete should be designed in
accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. These results
are being compared to the following table.
TABLE X - Requirements to Protect Against Damage to Concrete by Sulfate Attack from External Sources of Sulfate
Severity of Sulfate
exposure
Water-soluble sulfate (SO4)
in dry soil, percent
Water-cement ratio,
maximum
Cementitious material
Requirements
Class 0 0.00 to 0.10% 0.45 Class 0
Class 1 0.11 to 0.20% 0.45 Class 1
Class 2 0.21 to 2.00% 0.45 Class 2
Class 3 2.01 of greater 0.45 Class 3
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 27
Utilities
Near surface, the cohesive soils were relatively dry and medium dense, generally becoming more
moist and soft with depth approaching groundwater. Cuts extending into the near surface soils
would be expected to stand on relatively steep temporary slopes. However, cuts extending to
greater depths or in the northeast corner of the property could expose soft, wet, pumping soils and
groundwater. The soft, wet cohesive soils may be unstable in the trench excavations.
Stabilization of the sides and bottoms of some of the trenches and at least some dewatering
should be anticipated for utilities. Although the excavated soils could be used for backfilling the
utility excavations, moisture conditioning of those soils will be necessary before the excavated
material can be used for backfilling. Backfill material should be placed and compacted as
recommended in the section General Considerations and Site Preparation.
The individual contractor(s) should be made responsible for designing and constructing stable,
temporary excavations as required to maintain stability of both the excavation sides and bottom.
All excavations should be sloped or shored in the interest of safety following local and federal
regulations, including current OSHA excavation and trench safety standards.
Other Considerations
Positive drainage should be developed away from the structure and pavement areas with a
minimum slope of 1-inch per foot for the first 10-feet away from the improvements in landscape
areas. Care should be taken in planning of landscaping adjacent to the building and parking and
drive areas to avoid features which would pond water adjacent to the pavement, foundations or
stemwalls.
Placement of plants which require irrigation systems or could result in fluctuations of the
moisture content of the subgrade material should be avoided adjacent to site improvements.
Lawn watering systems should not be placed within 5 feet of the perimeter of the building and
parking areas. Spray heads should be designed not to spray water on or immediately adjacent to
Earth Engineering Consultants, LLC
Geotechnical Subsurface Exploration Report
Proposed Harmony 23 Development
EEC Project No. 1152123
January 14, 2016
Page 28
the structure or site pavements. Roof drains should be designed to discharge at least 5 feet away
from the structure and away from the pavement areas.
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data obtained from
the soil borings performed at the indicated locations and from any other information discussed in
this report. This report does not reflect any variations, which may occur between borings or
across the site. The nature and extent of such variations may not become evident until
construction. If variations appear evident, it will be necessary to re-evaluate the
recommendations of this report.
It is recommended that the geotechnical engineer be retained to review the plans and
specifications so comments can be made regarding the interpretation and implementation of our
geotechnical recommendations in the design and specifications. It is further recommended that
the geotechnical engineer be retained for testing and observations during earthwork and
foundation construction phases to help determine that the design requirements are fulfilled.
This report has been prepared for the exclusive use of AMGI USA, for specific application to the
project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranty, express or implied, is made. In the event that any changes in
the nature, design, or location of the project as outlined in this report are planned, the conclusions
and recommendations contained in this report shall not be considered valid unless the changes are
reviewed and the conclusions of this report are modified or verified in writing by the geotechnical
engineer.
Earth Engineering Consultants, LLC
DRILLING AND EXPLORATION
DRILLING & SAMPLING SYMBOLS:
SS: Split Spoon ‐ 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample
ST: Thin‐Walled Tube ‐ 2" O.D., unless otherwise noted WS: Wash Sample
R: Ring Barrel Sampler ‐ 2.42" I.D., 3" O.D. unless otherwise noted
PA: Power Auger FT: Fish Tail Bit
HA: Hand Auger RB: Rock Bit
DB: Diamond Bit = 4", N, B BS: Bulk Sample
AS: Auger Sample PM: Pressure Meter
HS: Hollow Stem Auger WB: Wash Bore
Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2‐inch O.D. split spoon, except where noted.
WATER LEVEL MEASUREMENT SYMBOLS:
WL : Water Level WS : While Sampling
WCI: Wet Cave in WD : While Drilling
DCI: Dry Cave in BCR: Before Casing Removal
AB : After Boring ACR: After Casting Removal
Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated
levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D‐2488. Coarse Grained
Soils have move than 50% of their dry weight retained on a
#200 sieve; they are described as: boulders, cobbles, gravel or
sand. Fine Grained Soils have less than 50% of their dry weight
retained on a #200 sieve; they are described as : clays, if they
are plastic, and silts if they are slightly plastic or non‐plastic.
Major constituents may be added as modifiers and minor
constituents may be added according to the relative
proportions based on grain size. In addition to gradation,
coarse grained soils are defined on the basis of their relative in‐
place density and fine grained soils on the basis of their
consistency. Example: Lean clay with sand, trace gravel, stiff
(CL); silty sand, trace gravel, medium dense (SM).
CONSISTENCY OF FINE‐GRAINED SOILS
Unconfined Compressive
Strength, Qu, psf Consistency
< 500 Very Soft
500 ‐ 1,000 Soft
1,001 ‐ 2,000 Medium
2,001 ‐ 4,000 Stiff
4,001 ‐ 8,000 Very Stiff
8,001 ‐ 16,000 Very Hard
RELATIVE DENSITY OF COARSE‐GRAINED SOILS:
N‐Blows/ft Relative Density
0‐3 Very Loose
4‐9 Loose
10‐29 Medium Dense
30‐49 Dense
50‐80 Very Dense
80 + Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
joints. May be color change.
Moderate Some decomposition and color change
throughout.
High Rock highly decomposed, may be extremely
broken.
Group
Symbol
Group Name
Cu≥4 and 1<Cc≤3
E
GW Well-graded gravel
F
Cu<4 and/or 1>Cc>3
E
GP Poorly-graded gravel
F
Fines classify as ML or MH GM Silty gravel
G,H
Fines Classify as CL or CH GC Clayey Gravel
F,G,H
Cu≥6 and 1<Cc≤3
E
SW Well-graded sand
I
Cu<6 and/or 1>Cc>3
E
SP Poorly-graded sand
I
Fines classify as ML or MH SM Silty sand
G,H,I
Fines classify as CL or CH SC Clayey sand
G,H,I
inorganic PI>7 and plots on or above "A" Line CL Lean clay
K,L,M
PI<4 or plots below "A" Line ML Silt
K,L,M
organic Liquid Limit - oven dried Organic clay
K,L,M,N
Liquid Limit - not dried Organic silt
K,L,M,O
inorganic PI plots on or above "A" Line CH Fat clay
K,L,M
PI plots below "A" Line MH Elastic Silt
K,L,M
organic Liquid Limit - oven dried Organic clay
K,L,M,P
Liquid Limit - not dried Organic silt
K,L,M,O
Highly organic soils PT Peat
(D30)2
D10 x D60
GW-GM well graded gravel with silt NPI≥4 and plots on or above "A" line.
GW-GC well-graded gravel with clay OPI≤4 or plots below "A" line.
GP-GM poorly-graded gravel with silt PPI plots on or above "A" line.
GP-GC poorly-graded gravel with clay QPI plots below "A" line.
SW-SM well-graded sand with silt
SW-SC well-graded sand with clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
Earth Engineering Consultants, LLC
IIf soil contains >15% gravel, add "with gravel" to
group name
JIf Atterberg limits plots shaded area, soil is a CL-
ML, Silty clay
Unified Soil Classification System
1
2
B-11
B-14
B-12
B-13
B-9
B-10
B-7 B-16
B-1
B-2
B-3
B-4
B-5
B-6
B-8
B-17
B-15 B-18
Boring Location Diagram
Harmony 23 Development
Fort Collins, Colorado
EEC Project Number: 1152123 Date: December 2015
EARTH ENGINEERING CONSULTANTS, LLC
B-1 thru B-15: Foundation
Borings Drilled 15-30'
Legend
B-16: Pavement Boring
Drilled 10'
B-17 & B-18: Detention /
Water Quality Borings with
Piezometers Drilled 15'
1 Site Photos
(Photos taken in approximate location, in
direction of arrow)
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
EEC PROJECT NO. 1152123
DECEMBER 2015
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
stiff _ _
3
_ _
4
_ _
CS 5 8 4000 16.1 95.5 34 17 72.4 700 psf 0.3%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
sand & gravel seams SS 10 4 -- 23.1
_ _
11
_ _
12
_ _
13
_ _
14
sand & gravel seams _ _
CS 15 13 1000 35.6 89.3
_ _
SAND & GRAVEL (SP/GP) 16
brown / red _ _
dense 17
_ _
18
_ _
19
_ _
SS 20 43 -- 10.3
_ _
21
_ _
22
_ _
23
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 24
grey _ _
moderately hard to hard CS 25 38 9000+ 16.0 110.9 43 24 57.7 5200 psf 2.7%
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
grey _ _
moderately hard to hard 28
_ _
29
_ _
SS 30 50/3" 9000+ 10.7
_ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SILTY CLAYEY SAND (SM/SC) _ _
dark brown / brown 2
medium dense _ _ % @ 150 PSF
with traces of gravel CS 3 13 9000+ 6.9 102.8 24 7 41.4 3000 psf 4.0%
_ _
4
_ _
brown SS 5 9 8000 14.0
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 6 2000 13.1
brown _ _
loose 11
_ _
12
_ _
13
SILTY SAND (SM) _ _
brown 14
medium dense _ _
with gravel SS 15 14 -- 22.0
_ _
16
_ _
17
_ _
18
_ _
19
SAND & GRAVEL (SP/GP) _ _
brown; medium dense CS 20 20
BOTTOM OF BORING DEPTH 20.0' _ _
21
_ _
22
_ _
23
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24
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25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
stiff _ _
with traces of gravel 3
_ _
4
_ _
CS 5 7 3000 14.0 103.9
_ _
6
_ _
7
_ _
SILTY CLAYEY SAND (SM/SC) 8
brown _ _
medium dense 9
_ _
SS 10 23 -- 24.0
_ _
SAND & GRAVEL (SP/GP) 11
brown / red _ _
medium dense 12
_ _
13
_ _
14
_ _
CS 15 27 -- 8.6 136.8
_ _
16
_ _
17
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18
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19
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SS 20 16 -- 17.0
_ _
21
_ _
22
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23
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 24
grey _ _
hard CS 25 50/3"
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
grey _ _
hard 28
_ _
29
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SS 30 -- 1000 20.9
_ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SILTY SANDY LEAN CLAY (CL) _ _
brown 2
soft to medium stiff _ _
3
_ _
4
_ _
CS 5 4 2000 26.7 96.6 33 8 64.5
_ _
6
_ _
SAND & GRAVEL (SP/GP) 7
brown / red _ _
dense to very dense 8
_ _
9
_ _
SS 10 33 -- 11.6
_ _
11
with cobbles _ _
12
_ _
13
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14
_ _
SS 15 50/6" -- 11.1
_ _
16
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17
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18
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19
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SS 20 45 8000 20.8
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 21
brown / grey / rust _ _
moderately hard to hard 22
_ _
23
_ _
24
grey _ _
CS 25 50/5" 9000+ 13.8 115.7
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
A-LIMITS SWELL
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
grey _ _
hard 28
_ _
29
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SS 30 50/6" 9000+ 17.9
_ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
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33
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34
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
soft to stiff _ _ % @ 150 PSF
CS 3 2 -- 32.3 90.9 40 21 72.7 <150 psf None
_ _
4
_ _
brown / dark brown SS 5 7 1000 31.3
_ _
6
_ _
SANDY LEAN CLAY / CLAYEY SAND (CL/SC) 7
brown _ _
8
_ _
9
_ _
CS 10 34 -- 23.9
SAND & GRAVEL (SP/GP) _ _
brown / red 11
dense _ _
12
_ _
13
_ _
14
_ _
SS 15 50 -- 11.0 4.5
_ _
16
_ _
17
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 18
grey _ _
moderately hard to hard 19
_ _
CS 20 50/5.5" 9000+ 16.4 121.5
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 50/6" 9000+ 15.9
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
grey _ _
hard 28
_ _
29
_ _
CS 30 50/4" 9000+ 13.9 121.1
BOTTOM OF BORING DEPTH 30.0' _ _
31
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY / SILT (CL/SM) _ _
brown 2
stiff _ _ % @ 150 PSF
CS 3 7 5000 16.2 108.8 23 4 64.5 <150 psf None
_ _
4
_ _
medium-stiff to stiff SS 5 5 1000 22.4
_ _
6
_ _
7
_ _
8
_ _
9
SILTY CLAYEY SAND (SM/SC) _ _
dark brown / brown / rust CS 10 6 -- 35.4 81.3
loose _ _
11
_ _
SAND & GRAVEL (SP/GP) 12
brown / red _ _
very dense to medium dense 13
_ _
14
_ _
SS 15 51 -- 10.2
_ _
16
_ _
17
_ _
18
_ _
19
_ _
CS 20 29 -- 11.3 126.9
BOTTOM OF BORING DEPTH 20.0' _ _
21
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22
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23
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24
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25
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
medium stiff to stiff _ _
CS 3 3 1000 26.0 98.2
_ _
4
_ _
SS 5 6 2000 34.0
_ _
6
_ _
7
_ _
SAND & GRAVEL (SP/GP) 8
brown / red _ _
dense 9
_ _
SS 10 33 -- 15.4
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 42 -- 11.3
_ _
16
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 17
brown / grey / rust _ _
moderately hard to hard 18
_ _
19
_ _
SS 20 50/8" 9000+ 18.3
_ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
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23
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24
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25
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Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY / CLAYEY SAND (CL/SC) _ _
brown 2
stiff _ _
3
_ _
4
_ _
CS 5 6 7000 8.2 111.7
_ _
6
_ _
7
_ _
8
_ _
9
_ _
medium stiff SS 10 4 -- 25.8
_ _
11
_ _
12
_ _
SAND & GRAVEL (SP/GP) 13
brown / red _ _
dense to medium dense 14
_ _
CS 15 30 -- 17.5 126.4
_ _
16
_ _
17
_ _
18
_ _
19
_ _
SS 20 34 -- 9.8
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 18 -- 14.7
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
SAND & GRAVEL (SP/GP) 27
brown / red _ _
dense to medium dense 28
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 29
grey _ _
moderately hard to hard SS 30 50/3" -- 22.6
_ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
_ _
33
_ _
34
_ _
35
_ _
36
_ _
37
_ _
38
_ _
39
_ _
40
_ _
41
_ _
42
_ _
43
_ _
44
_ _
45
_ _
46
_ _
47
_ _
48
_ _
49
_ _
50
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
SANDY LEAN CLAY / CLAYEY SAND (CL/SC) 1
brown _ _
very stiff to stiff 2
_ _ % @ 150 PSF
CS 3 18 9000+ 12.4 104.7 -- -- -- 1520 psf 2.7%
_ _
4
_ _
with calcareous deposits SS 5 10 9000+ 11.2
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 5 7000 17.2 102.5
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 2 -- 29.8
brown _ _
soft 16
_ _
17
_ _
SAND & GRAVEL (SP/GP) 18
brown / red _ _
dense 19
_ _
CS 20 40 -- 7.3 123.8
BOTTOM OF BORING DEPTH 20.0' _ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
stiff _ _
3
_ _
4
_ _
CS 5 8 5000 17.1 111.5
_ _
6
_ _
7
_ _
8
_ _
9
with traces of gravel _ _
SS 10 9 1000 23.7
_ _
SAND & GRAVEL (SP/GP) 11
brown / red _ _
dense 12
_ _
13
_ _
14
_ _
CS 15 35 -- 10.5 131.7
_ _
16
_ _
17
_ _
18
_ _
19
_ _
SS 20 35 -- 14.8
_ _
21
_ _
22
_ _
23
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 24
grey / rust _ _
moderately hard to hard SS 25 50/6" 9000+ 16.5
BOTTOM OF BORING DEPTH 25.5' _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits CS 3 16 9000+ 10.1 93.7 33 20 62.5
_ _
4
_ _
SS 5 5 9000+ 15.8
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 4 3000 22.8 102.4
_ _
11
_ _
12
_ _
13
_ _
SILTY / CLAYEY SAND (SM/SC) 14
dark brown / brown _ _
medium dense SS 15 14 -- 29.4
_ _
16
SAND & GRAVEL (SP/GP) _ _
brown / red 17
dense _ _
18
_ _
19
_ _
SS 20 30 -- 9.2
_ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
3
_ _
4
_ _
CS 5 14 9000 13.2 115.1 35 20 72.4 6800 psf 3.9%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 4 1000 34.1
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SILTY SAND (SM) CS 15 5 1000 30.4 91.9
brown / rust _ _
loose to dense 16
_ _
17
_ _
18
_ _
19
_ _
SS 20 42 -- 16.8
_ _
21
CLAYSTONE / SILTSTONE / SANDSTONE _ _
brown / rust / grey 22
moderately hard to hard _ _
23
_ _
24
_ _
CS 25 50/6" 9000+ 16.3 111.0 38 18 88.2 3800 psf 2.1%
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
brown / rust / grey _ _
hard 28
_ _
29
_ _
grey SS 30 50/6" 8000 18.1
with calcareous deposits _ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
_ _
33
_ _
34
_ _
35
_ _
36
_ _
37
_ _
38
_ _
39
_ _
40
_ _
41
_ _
42
_ _
43
_ _
44
_ _
45
_ _
46
_ _
47
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48
_ _
49
_ _
50
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _ % @ 150 PSF
with calcareous deposits CS 3 23 9000+ 7.1 108.5 30 15 57.5 1020 psf 2.9%
_ _
4
_ _
SS 5 17 9000+ 9.2
_ _
6
_ _
7
_ _
8
_ _
9
_ _
CS 10 8 7000 10.9 111.5
_ _
11
_ _
12
_ _
13
_ _
14
_ _
brown / red SS 15 7 3000 24.8
_ _
16
_ _
17
_ _
18
_ _
19
SILTY SAND (SM) _ _
brown, loose CS 20 3 -- 30.1
BOTTOM OF BORING DEPTH 20.0' _ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits 3
_ _
4
_ _ % @ 150 PSF
CS 5 18 9000+ 10.1 102.7 -- -- -- 4800 psf 9.2%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 7 3000 22.0
_ _
11
_ _
12
_ _
13
_ _
14
_ _
CS 15 5 -- 24.8
_ _
16
_ _
17
SAND & GRAVEL (SP/GP) _ _
brown / red 18
dense _ _
19
_ _
SS 20 56 6000 16.7
CLAYSTONE / SILTSTONE / SANDSTONE; grey _ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff _ _
with calcareous deposits 3
_ _
4
_ _
CS 5 17 9000+ 10.2 104.4 34 19 60.8 3500 psf 4.4%
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 12 9000+ 10.0
_ _
11
_ _
12
_ _
13
_ _
14
brown / rust _ _
with traces of gravel CS 15 8 5000 12.6 112.7
stiff _ _
16
_ _
17
_ _
18
_ _
19
_ _
SILTY SAND / CLAYEY SAND (SM/SC) SS 20 17 -- 21.5
brown / rust _ _
medium dense 21
with traces of gravel _ _
22
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 23
grey _ _
moderately hard to hard 24
_ _
CS 25 50/4" 9000+ 14.8 118.5
Continued on Sheet 2 of 2 _ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
Continued from Sheet 1 of 2 26
_ _
CLAYSTONE / SILTSTONE / SANDSTONE 27
grey _ _
hard 28
_ _
29
_ _
SS 30 50/6" 6000 17.7
_ _
BOTTOM OF BORING DEPTH 30.5' 31
_ _
32
_ _
33
_ _
34
_ _
35
_ _
36
_ _
37
_ _
38
_ _
39
_ _
40
_ _
41
_ _
42
_ _
43
_ _
44
_ _
45
_ _
46
_ _
47
_ _
48
_ _
49
_ _
50
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SILTY / CLAYEY SAND (SM/SC) _ _
brown 2
soft to medium stiff _ _ % @ 150 PSF
CS 3 2 1000 27.8 95.8 31 17 42.4 <150 None
_ _
4
_ _
SILTY SAND (SM) SS 5 5 -- 26.3 27.5
dark brown / brown _ _
loose 6
_ _
7
with gravel _ _
8
_ _
9
SAND & GRAVEL (SP/GP) _ _
brown / red SS 10 32 -- 14.4
dense _ _
BOTTOM OF BORING DEPTH 10.5' 11
_ _
12
_ _
13
_ _
14
_ _
15
_ _
16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY / CLAYEY SAND (CL/SC) _ _
brown 2
stiff to medium stiff _ _
3
_ _
4
_ _
CS 5 4 -- 25.5
_ _
SAND & GRAVEL (SP/GP) 6
brown / red _ _
medium dense 7
_ _
8
_ _
9
_ _
SS 10 25 -- 16.5 6.3
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 22 -- 9.8
_ _
BOTTOM OF BORING DEPTH 15.5' 16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
_ _
SANDY LEAN CLAY (CL) 1
brown _ _
medium stiff 2
_ _
3
_ _
4
_ _
CS 5 3 1000 28.0
_ _
6
_ _
7
_ _
8
SAND & GRAVEL (SP/GP) _ _
brown / red 9
dense _ _
SS 10 30 -- 10.4
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 33 -- 12.1 10.6
_ _
BOTTOM OF BORING DEPTH 15.5' 16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
HARMONY 23 DEVELOPMENT
Standard Penetration Test (SPT) N-Blows/Ft. with Increased Depth
EEC's Test Boring Nos. 1 through 9 - Drilled December 2015
CLIENT: AMGI USA PROJECT NO. 1152123
PROJECT: Proposed Harmony 23 Development DATE: 1/12/2016
LOCATION: Sothwest Corner of Harmony Road and Strau Cabin
Fort Collins, Colorado
Note:
(1)
SPT denotes Standard Penetration Test using a 140 LB. Hammer Falling 30-Inches
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30
Increased Depth below existing site grades, ft.
Standard Penetration Test (SPT) Results N-BLOWS PER FOOT
SPT N-Blows/Ft. with Increased Depth - Boring B-1 SPT N-Blows/Ft. with Increased Depth - Boring B-2
SPT N-Blows/Ft. with Increased Depth - Boring B-3 SPT N-Blows/Ft. with Increased Depth - Boring B-4
SPT N-Blows/Ft. with Increased Depth - Boring B-5 SPT N-Blows/Ft. with Increased Depth - Boring B-6
SPT N-Blows/Ft. with Increased Depth - Boring B-7 SPT N-Blows/Ft. with Increased Depth - Boring B-8
SPT N-Blows/Ft. with Increased Depth - Boring B-9 "SOFT SOILS" SPT N-Values between 1 to 4
"MEDIUM STIFF" SPT N-Values between 4 to 8 "STIFF" SPT N-Values between 8 to 15
Note: Relatively low SPT test results, (i.e. SOFT
characteristics N‐Blows/FT less 4) were recorded at
various intervals within a few borings as illustrated
herein. Predominantly the majority of the subsoils
were medium stiff to very stiff.
SOFT SOILS < 4 Blows/Ft.
MEDIUM STIFF 4 to 8
STIFF SOILS ‐ 8 to 15 Blows/FT.
VERY STIFF ‐ 15 to 30
Blows/FT.
HARD Blows/FT. > 30
Standard Penetration Test (SPT) N-Blows/Ft. with Increased Depth
EEC's Preliminary Boring Nos. 10 through 18 - Drilled December 2015
CLIENT: AMGI USA PROJECT NO. 1152123
PROJECT: Proposed Harmony 23 Development DATE: 1/12/2016
LOCATION: Sothwest Corner of Harmony Road and Strau Cabin
Fort Collins, Colorado
Note:
(1)
SPT denotes Standard Penetration Test using a 140 LB. Hammer Falling 30-Inches
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30
Increased Depth below existing site grades, ft.
Standard Penetration Test (SPT) Results N-BLOWS PER FOOT
SPT N-Blows/Ft. with Increased Depth - Boring B-10 SPT N-Blows/Ft. with Increased Depth - Boring B-11
SPT N-Blows/Ft. with Increased Depth - Boring B-12 SPT N-Blows/Ft. with Increased Depth - Boring B-13
SPT N-Blows/Ft. with Increased Depth - Boring B-14 SPT N-Blows/Ft. with Increased Depth - Boring B-15
SPT N-Blows/Ft. with Increased Depth - Boring B-16 SPT N-Blows/Ft. with Increased Depth - Boring B-17
SPT N-Blows/Ft. with Increased Depth - Boring B-18 "SOFT SOILS" SPT N-Values between 1 to 4
"MEDIUM STIFF" SPT N-Values between 4 to 8 "STIFF" SPT N-Values between 8 to 15
Note: Relatively low SPT test results, (i.e.
SOFT characteristics N‐Blows/FT less 4) were
recorded at various intervals within a few
borings as illustrated herein. Predominantly
the majority of the subsoils were medium
stiff to very stiff.
SOFT SOILS < 4 Blows/Ft.
MEDIUM STIFF 4 to 8
STIFF SOILS ‐ 8 to 15 Blows/FT.
VERY STIFF ‐ 15 to 30
Blows/FT.
HARD Blows/FT. > 30
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
Sample Location: Boring 1, Sample 1, Depth 4'
Liquid Limit: 34 Plasticity Index: 17 % Passing #200: 72.4%
Beginning Moisture: 16.1% Dry Density: 108.8 pcf Ending Moisture: 21.1%
Swell Pressure: 700 psf % Swell @ 500: 0.3%
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
Beginning Moisture: 16.0% Dry Density: 114.5 pcf Ending Moisture: 18.8%
Swell Pressure: 5200 psf % Swell @ 500: 2.7%
Sample Location: Boring 1, Sample 5, Depth 24'
Liquid Limit: 43 Plasticity Index: 24 % Passing #200: 57.7%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Grey Claystone/Siltstone/Sandstone
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
Beginning Moisture: 6.9% Dry Density: 121.5 pcf Ending Moisture: 16.8%
Swell Pressure: 3000 psf % Swell @ 150: 4.0%
Sample Location: Boring 2, Sample 1, Depth 2'
Liquid Limit: 24 Plasticity Index: 7 % Passing #200: 41.4%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Dark Brown, Brown Silty/Clayey Sand with Trace Gravel (SM/SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
Sample Location: Boring 5, Sample 1, Depth 2'
Liquid Limit: 40 Plasticity Index: 21 % Passing #200: 72.7%
Beginning Moisture: 32.3% Dry Density: 91.4 pcf Ending Moisture: 28.4%
Swell Pressure: <150 psf % Swell @ 150: None
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
Beginning Moisture: 16.2% Dry Density: 115.5 pcf Ending Moisture: 18.3%
Swell Pressure: < 150 psf % Swell @ 150: None
Sample Location: Boring 6, Sample 1, Depth 2'
Liquid Limit: 23 Plasticity Index: 4 % Passing #200: 64.5%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay / Silt (CL-SM)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
Beginning Moisture: 12.4% Dry Density: 100.1 pcf Ending Moisture: 19.6%
Swell Pressure: 1520 psf % Swell @ 150: 2.7%
Sample Location: Boring 9, Sample 1, Depth 2'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay / Clayey Sand (CL/SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
Sample Location: Boring 12, Sample 1, Depth 4'
Liquid Limit: 35 Plasticity Index: 20 % Passing #200: 72.4%
Beginning Moisture: 13.2% Dry Density: 117 pcf Ending Moisture: 14.8%
Swell Pressure: 6800 psf % Swell @ 500: 3.9%
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown, Rust, Grey Claystone / Siltstone / Sandstone
Sample Location: Boring 12, Sample 5, Depth 24'
Liquid Limit: 38 Plasticity Index: 18 % Passing #200: 88.2%
Beginning Moisture: 16.3% Dry Density: 111.7 pcf Ending Moisture: 19.8%
Swell Pressure: 3800 psf % Swell @ 500: 2.1%
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
Beginning Moisture: 7.1% Dry Density: 99.5 pcf Ending Moisture: 21.5%
Swell Pressure: 1020 psf % Swell @ 150: 2.9%
Sample Location: Boring 13, Sample 1, Depth 2'
Liquid Limit: 30 Plasticity Index: 15 % Passing #200: 57.5%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay (CL)
Sample Location: Boring 14, Sample 1, Depth 4'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
Beginning Moisture: 10.1% Dry Density: 114.5 pcf Ending Moisture: 16.6%
Swell Pressure: 4800 psf % Swell @ 150: 9.2%
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay (CL)
Sample Location: Boring 15, Sample 1, Depth 4'
Liquid Limit: 34 Plasticity Index: 19 % Passing #200: 60.8%
Beginning Moisture: 10.2% Dry Density: 121.8 pcf Ending Moisture: 18.3%
Swell Pressure: 3500 psf % Swell @ 500: 4.4%
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Clayey Sand (SC)
Sample Location: Boring 16, Sample 1, Depth 2'
Liquid Limit: 31 Plasticity Index: 17 % Passing #200: 42.4%
Beginning Moisture: 27.8% Dry Density: 100.8 pcf Ending Moisture: 21.6%
Swell Pressure: <150 psf % Swell @ 150: None
Harmony 23 Development
Fort Collins, Colorado
1152123
December 2015
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Harmony 23 Development
Location: Fort Collins, Colorado
Project No: 1152123
Sample ID: B5, S4, 14'
Sample Desc.: Sand & Gravel
Date: December 2015
20
13
10
7
4.5
68
64
58
56
45
100
100
94
78
70
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
Gravel
Coarse Fine
Sand
Coarse Medium Fine
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
B5, S4, 14'
Sand & Gravel
December 2015
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Harmony 23 Development
Location: Fort Collins, Colorado
Project No: 1152123
Sample ID: B16, S2, 4'
Sample Desc.: Sand / Silty Sand
Date: December 2015
84
72
60
44
27.5
97
97
96
96
95
100
100
100
100
98
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
Gravel
Coarse Fine
Sand
Coarse Medium Fine
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
B16, S2, 4'
Sand / Silty Sand
December 2015
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Harmony 23 Development
Location: Fort Collins, Colorado
Project No: 1152123
Sample ID: B17, S2, 9'
Sample Desc.: Sand / Silty Sand
Date: December 2015
54
49
39
14
6.3
76
69
63
62
58
100
100
100
90
78
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
Gravel
Coarse Fine
Sand
Coarse Medium Fine
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
B17, S2, 9'
Sand / Silty Sand
December 2015
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
2" (50 mm)
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Harmony 23 Development
Location: Fort Collins, Colorado
Project No: 1152123
Sample ID: B18, S3, 14'
Sample Desc.: Sand & Gravel
Date: December 2015
35
29
24
16
10.6
88
77
63
60
49
100
100
100
95
91
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
Gravel
Coarse Fine
Sand
Coarse Medium Fine
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Harmony 23 Development
Fort Collins, Colorado
1152123
B18, S3, 14'
Sand & Gravel
December 2015
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-18 (PIEZOMETER) DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 5'
SURFACE ELEV N/A 6 HOUR 4.5'
FINISH DATE 12/28/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-17 (PIEZOMETER) DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 4'
SURFACE ELEV N/A 6 HOUR 1.5'
FINISH DATE 12/28/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-16 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 4'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/28/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-15 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 19'
12/22/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-15 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 19'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-14 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 15'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-13 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING None
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-12 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 11'
12/22/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-12 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 11'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-11 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 9'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-10 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 5'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-9 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 14'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-8 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 11'
12/22/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-8 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 11'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-7 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 5.5'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/28/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-6 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 7'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-5 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 3'
12/28/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-5 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 3'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/28/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-4 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 2'
12/28/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/28/2015 AFTER DRILLING N/A
SHEET 1 OF 2 WATER DEPTH
START DATE 12/28/2015 WHILE DRILLING 2'
HARMONY 23 DEVELOPMENT
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-4 DECEMBER 2015
PROJECT NO: 1152123 LOG OF BORING B-3 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 6.5'
12/22/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-3 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 6.5'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-2 DECEMBER 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 10'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
PROJECT NO: 1152123 LOG OF BORING B-1 DECEMBER 2015
SHEET 2 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 9'
12/22/2015 AFTER DRILLING N/A
SURFACE ELEV 24 HOUR N/A
FINISH DATE
A-LIMITS SWELL
N/A
FORT COLLINS, COLORADO
PROJECT NO: 1152123 LOG OF BORING B-1 DECEMBER 2015
SHEET 1 OF 2 WATER DEPTH
START DATE 12/22/2015 WHILE DRILLING 9'
SURFACE ELEV N/A 24 HOUR N/A
FINISH DATE 12/22/2015 AFTER DRILLING N/A
A-LIMITS SWELL
Soil Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests
Sands 50% or more
coarse fraction
passes No. 4 sieve
Fine-Grained Soils
50% or more passes
the No. 200 sieve
<0.75 OL
Gravels with Fines
more than 12%
fines
Clean Sands Less
than 5% fines
Sands with Fines
more than 12%
fines
Clean Gravels Less
than 5% fines
Gravels more than
50% of coarse
fraction retained on
No. 4 sieve
Coarse - Grained Soils
more than 50%
retained on No. 200
sieve
CGravels with 5 to 12% fines required dual symbols:
Kif soil contains 15 to 29% plus No. 200, add "with sand"
or "with gravel", whichever is predominant.
<0.75 OH
Primarily organic matter, dark in color, and organic odor
ABased on the material passing the 3-in. (75-mm)
sieve
ECu=D60/D10 Cc=
HIf fines are organic, add "with organic fines" to
group name
LIf soil contains ≥ 30% plus No. 200 predominantly sand,
add "sandy" to group name.
MIf soil contains ≥30% plus No. 200 predominantly gravel,
add "gravelly" to group name.
DSands with 5 to 12% fines require dual symbols:
BIf field sample contained cobbles or boulders, or
both, add "with cobbles or boulders, or both" to
group name. FIf soil contains ≥15% sand, add "with sand" to
GIf fines classify as CL-ML, use dual symbol GC-
CM, or SC-SM.
Silts and Clays
Liquid Limit less
than 50
Silts and Clays
Liquid Limit 50 or
more
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
PLASTICITY INDEX (PI)
LIQUID LIMIT (LL)
ML OR OL
MH OR OH
For Classification of fine-grained soils and
fine-grained fraction of coarse-grained
soils.
Equation of "A"-line
Horizontal at PI=4 to LL=25.5
then PI-0.73 (LL-20)
Equation of "U"-line
Vertical at LL=16 to PI-7,
then PI=0.9 (LL-8)
CL-ML
HARDNESS AND DEGREE OF CEMENTATION:
Limestone and Dolomite:
Hard Difficult to scratch with knife.
Moderately Can be scratched easily with knife.
Hard Cannot be scratched with fingernail.
Soft Can be scratched with fingernail.
Shale, Siltstone and Claystone:
Hard Can be scratched easily with knife, cannot be
scratched with fingernail.
Moderately Can be scratched with fingernail.
Hard
Soft Can be easily dented but not molded with
fingers.
Sandstone and Conglomerate:
Well Capable of scratching a knife blade.
Cemented
Cemented Can be scratched with knife.
Poorly Can be broken apart easily with fingers.
Cemented
(3.57)
PCC (Non-reinforced) – placed on a stable subgrade 5-1/2" 7"