HomeMy WebLinkAboutINNOVATION ISLAND, FIRST FILING - PDP - 40-05A - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT/m �T,
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T.B. Nos. 1 — 7 FOUNDATION RELATED BORINGS DRILLED 15' TO 20'. llV
T.B. Nos. 8 & 9 PAVEMENT RELATED BORINGS DRILLED 10'.
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Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracon
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 Terracon reviews the
changes and either verifies or modifies the conclusions of this report in writing.
21
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
Surface Drainage
1rerracon
Positive drainage should be provided during construction and maintained throughout the life of
each structure on the site. Infiltration of water into utility or foundation excavations must be
prevented during construction. Planters and other surface features, which could retain water in
areas adjacent to the building or pavements, should be sealed or eliminated. In areas where
sidewalks or paving do not immediately adjoin the structure, we recommend that protective
slopes be provided with a minimum grade of approximately 10-percent for at least 10 feet from
perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches
should be well compacted and free of all construction debris to reduce the possibility of moisture
infiltration.
1 Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when
J the ground surface beneath such features is not protected by exterior slabs or paving. Sprinkler
systems should not be installed within 10-feet of foundation walls. Landscaped irrigation
1 adjacent to the foundation system should be minimized or eliminated.
GENERAL COMMENTS
Terracon should be retained to review the final design plans and specifications so comments can be
made regarding interpretation and implementation of our geotechnical recommendations in the design
and specifications. Terracon also should be retained to provide testing and observation during
excavation, grading, foundation and construction phases of the project.
The analysis and recommendations presented in this report are based upon the data obtained from the
borings performed at the indicated locations and from other information discussed in this report. This
report does not reflect variations that may occur between borings, across the site, or due to the
modifying effects of weather. The nature and extent of such variations may not become evident until
during or after construction. If variations appear, we should be immediately notified so that further
evaluation and supplemental recommendations can be provided.
The scope of services for this project does not include either specifically or by implication any
environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or
prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the
potential for such contamination or pollution, other studies should be undertaken.
This report has been prepared for the exclusive use of our client for specific application to the project
discussed and has been prepared in accordance with generally accepted geotechnical engineering
practices. No warranties, either express or implied, are intended or made. Site safety, excavation
support, and dewatering requirements are the responsibility of others. In the event that changes in the
1 20
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracon
As a safety measure, it is recommended that all vehicles and soil piles be kept to a minimum
lateral distance from the crest of the slope equal to no less than the slope height. The exposed
slope face should be protected against the elements.
Additional Design and Construction Considerations
Exterior Slab Design and Construction
Compacted subgrade or existing clay soils will expand with increasing moisture content;
therefore, exterior concrete grade slabs may heave, resulting in cracking or vertical offsets. The
potential for damage would be greatest where exterior slabs are constructed adjacent to the
building or other structural elements. To reduce the potential for damage, we recommend:
• exterior slabs be supported on fill with no, or very low expansion potential
• strict moisture -density control during placement of subgrade fills
• placement of effective control joints on relatively close centers and isolation
joints between slabs and other structural elements
• provision for adequate drainage in areas adjoining the slabs
• use of designs which allow vertical movement between the exterior slabs and
adjoining structural elements
In those locations where movement of exterior slabs cannot be tolerated or must be reduced,
consideration should be given to:
• Constructing slabs with a stem or key -edge, a minimum of 6 inches in width
and at least 12 inches below grade;
• supporting keys or stems on drilled piers; or
• providing structural exterior slabs supported on foundations similar to the
building.
Underground Utility Systems
All piping should be adequately bedded for proper load distribution. It is suggested that clean,
graded gravel compacted to 75 percent of Relative Density ASTM D4253 be used as bedding.
jUtility trenches should be excavated on safe and stable slopes in accordance with OSHA
regulations as discussed above. Backfill should consist of the on -site soils or imported material
approved by the geotechnical engineer. The pipe backfill should be compacted to a minimum of
95 percent of Standard Proctor Density ASTM D698.
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Geotechnical Engineering Report lrerracon
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
Imported soils (if required) should conform to the following:
Percent finer by weight
Gradation (ASTM C136)
3"..........................................................................................................100
No. 4 Sieve......................................................................................50-100
No. 200 Sieve...............................................................................35
(max)
• Liquid Limit...................................................................................30
(max)
Plasticity Index.............................................................................15
(max)
• Group Index.................................................................................10
(max)
Engineered fill should be placed and compacted in horizontal lifts, using equipment and
procedures that will produce recommended moisture contents and densities throughout the lift. It
is recommended all fill material to placed on the site be compacted to at least 95 percent of
Standard Proctor Density ASTM D698.
On -site clay soils should be compacted within a moisture content range of 1 percent below, to 3
percent above optimum. Imported granular soils should be compacted within a moisture range
of 3 percent below to 3 percent above optimum unless modified by the project geotechnical
engineer.
Excavation and Trench Construction
Excavations into the on -site soils will encounter a variety of conditions. Excavations into the
clays can be expected to stand on relatively steep temporary slopes during construction.
However, caving soils and groundwater may also be encountered. 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.
The soils to be penetrated by the proposed excavations may vary significantly across the site.
The preliminary soil classifications are based solely on the materials encountered in widely
spaced exploratory test borings. The contractor should verify that similar conditions exist
throughout the proposed area of excavation. If different subsurface conditions are encountered
at the time of construction, the actual conditions should be evaluated to determine any
excavation modifications necessary to maintain safe conditions.
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Geotechnical Engineering Report lferracan
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
1 Fort Collins, Colorado
Project No. 20055152
mounds and depressions that could prevent uniform compaction. After the required
overexcavation is performed, the site should be initially graded to create a relatively level surface
to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed building
addition.
Exposed areas, which will receive fill, once properly cleared where necessary, should be
scarified to a minimum depth of 12-inches, conditioned to near optimum moisture content, and
j compacted.
It is anticipated that excavations for the proposed construction can be accomplished with
conventional earthmoving equipment.
Based upon the subsurface conditions determined from the geotechnical exploration, the
majority of the underlying subgrade soils exposed during construction are anticipated to be
relatively stable; however unstable areas may be encountered depending upon seasonal
conditions or where the cohesive soils have a high moisture content. The stability of the
subgrade may be affected by precipitation, repetitive construction traffic or other factors. If
unstable conditions develop, workability may be improved by scarifying and drying.
Overexcavation of wet zones and replacement with granular materials may be necessary. Use
of lime, fly ash, kiln dust, cement or geotextiles could also be considered as a stabilization
technique. Laboratory evaluation is recommended to determine the effect of chemical
stabilization on subgrade soils prior to construction. Lightweight excavation equipment may be
required to reduce subgrade pumping.
Subgrade Preparation
iSubgrade soils beneath interior and exterior slabs, should be scarified; moisture conditioned and
compacted to a minimum depth of 12-inches below proposed controlled fill material. The
moisture content and compaction of subgrade soils should be maintained until slab or pavement
I construction.
Fill Materials and Placement
Properly moisture -conditioned on -site material or approved imported materials may be used as
fill material and are suitable for use as compacted fill beneath interior or exterior floor slabs.
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Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lrerracon
• Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of base course
materials.
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 or excessive rutting. 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.
Please' note that 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 Terracon
be contacted for additional alternative methods of stabilization, or a change in the pavement section.
Earthwork
General Considerations
The following presents recommendations for site preparation, excavation, subgrade preparation
and placement of engineered fills on the project.
All earthwork on the project should be observed and evaluated by Terracon. The evaluation of
earthwork should include observation and testing of engineered fill, subgrade preparation,
foundation bearing soils, and other geotechnical conditions exposed during the construction of
the project.
Site Preparation
Strip and remove any topsoil, existing debris, unreliable existing fill material, or other deleterious
materials from proposed building and pavement areas. All exposed surfaces should be free of
16
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracan
with fly ash. Terracon is available to provide the required laboratory soil and fly ash mix design as
well as placement recommendations upon request.
(3) Alternative A assumes a minimum of 2-feet of approved moisture conditioned/non-expansive fill
material is positioned beneath the planned paved sections, after an approved proof -roll has been
completed.
Due to the properties of the existing cohesive on -site soils, full depth HMA pavement is not
recommended.
Each alternative should be investigated with respect to current material availability and economic
conditions. Aggregate base course (if used on the site) should consist of a blend of sand and gravel,
which meets strict specifications for quality and gradation. Use of materials meeting Colorado
Department of Transportation (CDOT) Class 5 or 6 specifications is recommended for base course.
Aggregate base course should be placed in lifts not exceeding six inches and should be compacted to a
minimum of 95% Standard Proctor Density (ASTM D698).
HMA pavement should be composed of a mixture of aggregate, filler, binders, and additives, if required,
and approved bituminous material in accordance with the LCUASS Pavement Design Criteria. The
HMA should conform to an approved mix design stating the Hveem and/or Superpave properties,
optimum asphalt content, job mix formula and recommended mixing and placing temperatures.
Aggregate used in the HMA should meet particular gradations, such as the Colorado Department of
Transportation Grading S, SX or SG specifications. Mix designs should be submitted prior to
construction to verify their adequacy. Asphalt material should be placed in maximum 3-inch lifts and
should be compacted to a within a range of 92 to 96 % of Maximum Theoretical Density.
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:
• Site grading at a minimum 2% grade away from the pavements;
• The subgrade and the pavement surface have a minimum % inch per foot slope to promote proper
surface drainage.
• Consider appropriate edge drainage and pavement under drain systems,
• 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;
• Placing compacted, low permeability backfill against the exterior side of curb and gutter; and,
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Geotechnical Engineering Report
Habitat for Humanity - Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lrerramn
saturated subgrade conditions, result in a design drainage coefficient of 1.0 when applying the AASHTO
criteria for design.
For flexible pavement design, a terminal serviceability index of 2.0 was utilized along with an inherent
reliability of 70%, and a design life of 20 years. Using an estimated design R-value estimated at 7
based on the laboratory test results, appropriate ESAUday, environmental criteria and other factors, the
structural numbers (SN) of the pavement sections were determined on the basis of the 1993 AASHTO
design equation.
In addition to the flexible pavement design analyses, a rigid pavement design analysis was completed,
based upon AASHTO design procedures. Rigid pavement design is based on an evaluation of the
Modulus of Subgrade Reaction of the soils (K-value), the Modulus of Rupture of the concrete, and other
factors previously outlined. The design K-value of 100 for the subgrade soil was determined by
correlation to the laboratory tests results. A modulus of rupture of 650 psi (working stress 488 psi) was
used for pavement concrete. The rigid pavement thicknesses for each traffic category were determined
on the basis of the AASHTO design equation.
Recommended alternatives for flexible and rigid pavements, summarized for each traffic area, are as
follows:
Recommended Miriimum Pavemer£ Thickness - inches
Traffic Area
Alternatives
` f'l HMA Surface
HMA Surface
Aggregate Base
Course - Ctass 5
(2) Fly Ash Treated
Portland
Cement Total
Grading S or SX
Grading SG
or
Sub Base
Concretew
A
1.5
2.5
6.0
10.0
Automobile
B
3.5
6.0
12.0
21.5
Parking Areas
C -1
6.0
6.0
C - 2
12.0
5.5
17.5
(3) A
2.0
3.0
7.0
12.0
Heavy
B
1.5
2.5
6.0
12.0
22.0
Duty/Truck
Traffic Areas
C -1
7.0
7.0
C-2
12.0
6.0
18.0
(1) If the HMA surface course is to consist of Grading S, then the required minimum lift/thickness
placed should be 2-inches. If the HMA surface course is to consist of Grading SX, the required
minimum lift/thickness placed should be 1-1/2-inches.
(2) If fly ash is utilized for the on -site pavement improvement areas to mitigate the soft subgrade
materials, it is recommended that at least the upper 12-inches of the prepared subgrade be treated
14
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
11erracon
pavement operations due to swelling soils. We provide herein, site -specific recommendations for
subgrade stabilization if necessary after proofrolling the subgrade section.
Stabilization may include incorporation of a chemical treatment such as kiln dust, and/or fly ash to
mitigate swell potential soils. An alternate would be to over -excavate and replace with approved
materials or provide 2-feet of non -expansive granular soils.
Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the
aggregate road base section. Soft or weak areas delineated by the proofrolling operations should be
undercut or stabilized in -place to achieve the appropriate subgrade support.
If the fly ash section is selected, Terracon recommends incorporating approximately 12 percent by
weight, Class C fly ash, into the upper 12-inches of subgrade. Hot Mix Asphalt (HMA) underlain by
crushed aggregate base course with or without a fly ash treated subgrade, and non -reinforced concrete
pavement are feasible alternatives for the proposed on -site paved sections. Based on the subsurface
conditions encountered at the site, and the laboratory test results, it is recommended the on -site private
drives and parking areas be designed using a minimum R-value of 7.
Pavement design methods are intended to provide structural sections with adequate thickness over a
particular subgrade such that wheel loads are reduced to a level the subgrade can support. The
support characteristics of the subgrade for pavement design do not account for shrink/swell movements
of an expansive clay subgrade such as the soils encountered on this project. Thus, the pavement may
be adequate from a structural standpoint, yet still experience cracking and deformation due to
shrink/swell related movement of the subgrade. It is, therefore, important to minimize moisture changes
in the subgrade to reduce shrink/swell movements.
Design of pavements for the project has been based on the procedures outlined in the 1993 Guideline
for Design of Pavement Structures by the American Association of State Highway and Transportation
Officials (AASHTO). Areas within proposed pavements on the site will be divided into two categories
based upon anticipated traffic and usage.
Because traffic data is not available, Terracon assumes 18-kip equivalent single axle loads (ESAL's) of
51,100 for automobile parking, and 146,000 for heavy volume and/or truck access areas. When traffic
data becomes available, Terracon should be notified so our assumptions can be verified.
Local drainage characteristics of proposed pavement areas are considered to vary from fair to good
depending upon location on the site. For purposes of this design analysis, fair drainage characteristics
are considered to control the design. These characteristics, coupled with the approximate duration of
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Geotechnical Engineering Report
Habitat for Humanity - Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracon
• 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 accordance with
recommended specifications outlined below.
• In areas subjected to normal loading, a minimum 4-inch layer of clean -graded gravel or
aggregate base course should be placed beneath upper level interior slabs.
• Floor slabs should not be constructed on frozen subgrade.
• Other design and construction considerations, as outlined in the ACI Design Manual,
Section 302.1 R are recommended.
Pavement Design and Construction
Based on the subsurface conditions encountered during the site exploration, it is our opinion the
proposed on -site pavement areas are feasible provided the following recommendations are
implemented. The subsoils encountered throughout the site are generally plastic/cohesive soils
exhibiting low subgrade strength characteristics and low swell/expansive potential. This report provides
recommendations to help mitigate the effects of soil shrinkage and expansion. Even if these
recommendations are followed some pavement distress and exterior slab movement should be
anticipated.
To evaluate the existing on -site soils for use as subgrade material beneath on -site pavement sections,
we elected to use the design criteria established in the Larimer County Urban Area Street Standards
(LCUASS) Pavement Design document as a guideline. In the LCUASS guidelines, undisturbed
samples usually obtained directly from a ring barrel sampler, California Barrel or a cylindrical Shelby
Tube device are placed in a laboratory one-dimensional consolidometer apparatus and inundated after
a predetermined load, (approximately 150 psf to simulate the actual loading conditions experienced
within an asphalt paved section underlain by an aggregate base course), is placed. The swell index is
the resulting amount of swell as a percent of the sample's thickness after the inundation period.
The swell potential for the subgrade soils, (i.e. subsoil samples collected approximately 1-foot below
existing site grades in Test Boring Nos. 8 and 9), based on the LCUASS Pavement Design laboratory
testing procedures, resulted in a swell index value (+) 2.0% to (+) 3.2%. These values exceed the
maximum 2 percent criteria established for determining if swell -mitigation procedures in the pavement
sections are required. Therefore, it will be necessary to mitigate the cohesive subgrade soils prior to
12
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
1(erracon
Fill' against grade beams and retaining walls should be compacted to densities specified in Earthwork.
Medium to high plasticity clay soils or claystone shale should not be used as backfill against retaining
walls. Compaction of each lift adjacent to walls should be accomplished with hand -operated tampers
or other lightweight compactors. Overcompaction may cause excessive lateral earth pressures,
which could result in wall movement.
Seismic Considerations
The project site is located in Seismic Risk Zone I of the Seismic Zone Map of the United States as
indicated by the 1997 Uniform Building Code. Based upon the nature of the subsurface materials, Soil
Profile Type "Sc" should be used for the design of structures for the proposed project (1997 Uniform
Building Code, Table No. 16-J). A site classification "C" should be used for the design of structures for
the proposed project (2000 International Building Code, Table No. 1615.1.1).
Floor Slab Design and Consideration
For interior concrete slabs used in conjunction with spread footings or for exterior slabs constructed
directly on the low expansive clays, differential movement on the order of 1 to 2 inches should be
expected if the clay soils become elevated in moisture content. Therefore positive drainage away
from the foundation system and floor slabs during and after construction should be implemented to
reduce and minimize the potential for the underlying subosoils to become elevated in moisture
content.
This report provides recommendations to help mitigate the effects of soil movement. However, even if
these procedures are followed, some movement and at least minor cracking in the structure's
foundation and slabs 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 compressible materials. 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 expensive
measures are used during construction. Some of these options, such as the use of structural floors or
mechanically stabilizing the underlying subsoils are discussed in this report. We would be pleased to
discuss other construction alternatives with you upon request.
Additional floor slab design and construction recommendations for upper and lower level slabs 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.
11
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferacon
where lower level construction is planned. The exterior drainage system should be constructed around
the exterior perimeter of the basement foundation, 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, and 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 1-foot above the bottom of the foundation wall. The
gravel should be covered with drainage fabric prior to placement of foundation backfill.
Lateral Earth Pressures
For soils above any free water surface, recommended equivalent fluid pressures for unrestrained
foundation elements are:
• Active:
Cohesive soil backfill (on -site clay soils).................................45 psf/ft
Cohesionless soil backfill (granular imported soils) ................ 35 psf/ft
On -site bedrock materials .......................... not recommended for use
• Passive:
Cohesive soil backfill (on -site clay soils)...............................250 psf/ft
Cohesionless soil backfill (granular imported soils) .............. 350 psf/ft
Drilled Piers.........:................................................................500 psf/ft
• Adhesion at base of footing ..................................................... 500 psf
Where the design includes restrained elements, the following equivalent fluid pressures are
recommended:
• At rest:
Cohesive soil backfill (on -site clay soils).................................60 psf/ft
Cohesionless soil backfill (granular imported soils) ................ 50 psf/ft
On -site bedrock materials .......................... not recommended for use
The lateral earth pressures herein do not include any factor of safety and are not applicable for
submerged soils/hydrostatic loading. Additional recommendations may be necessary if submerged
conditions are to be included in the design.
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Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lreffacon
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 significantly from those presented in this report, supplemental recommendations will
be required.
Basement Construction
Groundwater was not encountered in any of the test borings to maximum depths of exploration during
the initial field exploration. However, when checked 5 days after the drilling operations, a dry cave in
(DCI) was recorded at approximate depths of 13-1/2 to 22-feet below existing site grades within
Boring Nos. 2 through 4, and groundwater was measured at approximate depths of 9 to 21-feet below
site in Boring Nos. 6 through 8. Test Boring Nos. 1 and 9 remained dry to the maximum depths
explored. Therefore, full -depth basement construction is considered acceptable on the site provided the
lower level foundations bear a minimum of 3-feet above the maximum anticipated groundwater level,
and/or an interior and exterior perimeter dewatering systems are installed.
Perched groundwater may occur at times since the subsurface soils are relatively impermeable and
tend to trap water. Completion of site development, including installation of landscaping and irrigation
systems, may lead to perched groundwater development.
To reduce the potential for groundwater fluctuation to impact foundation bearing soils and/or enter the
basement of the structure, installation of an interior dewatering system is recommended where
groundwater fluctuations are anticipated to be within 4-feet of the lower level floor slabs. The interior
dewatering system should, at a minimum, include an underslab gravel drainage layer sloped to an
interior perimeter drainage system. The interior drainage system should consist of a properly sized
perforated pipe, embedded in free -draining gravel, and 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 drainage system should be sloped at a
minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system.
The underslab drainage layer should consist of a minimum 8-inch thickness of free -draining gravel
meeting the specifications of ASTM C33, Size No. 57 or 67. Cross -connecting drainage pipes should
be provided beneath the slab at 15 to 20-foot intervals, and should discharge to the perimeter drainage
system.
To intercept the potential for surface water infiltration from impacting the foundation bearing stratum and
entering the lower levels of any structure, an exterior perimeter drain is recommended for all buildings
9
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lrerraran
For axial compression loads, piers may be design for a net allowable end -bearing pressure of 20,000
pounds per square foot (psf), and skin friction of 2,000 psf for the portion of the pier in firm or harder
bedrock.
All piers require sufficient dead load and/or additional penetration into the bearing strata to resist the
potential uplift of the expansive materials. All piers should be designed for a minimum dead -load
pressure of 5,000 psf, based upon pier end area.
All piers should be reinforced full depth for the applied axial, lateral and uplift stresses imposed. The
tensile force created by the uplift force on each pier, with allowance for dead load, should determine the
amount of reinforcing steel for expansion.
To reduce potential uplift forces on piers, use of long grade beam spans to increase individual pier
loading, and small diameter piers are recommended. For this project, use of a minimum pier diameter
of 10 to 12-inches is recommended. A minimum 6-inch void space should be provided beneath grade
beams between piers. The void material should be of suitable strength to support the weight of fresh
concrete used in grade beam construction, and to avoid collapse when foundation backfill is placed.
Drilling to design depths should be possible with conventional single flight power augers on the majority
of the site. Interbedded cemented sandstone lenses may be encountered during caisson drilling
activities; therefore, use of specialized heavy-duty equipment may be required.
Shafts will probably remain open without stabilizing measures. However, pier concrete should be placed
soon after completion of drilling and cleaning. Groundwater was not encountered to maximum depths
of exploration during the initial field exploration. However, when checked 5 days after the drilling
operations, a dry cave in (DCI) was recorded at approximate depths of 13-1/2 to 22-feet below
existing site grades within Boring Nos. 2 through 4, and groundwater was measured at approximate
depths of 9 to 21-feet below site in Boring Nos. 6 through 8. Therefore it appears temporary casing
may be required to adequately/properly drill and clean piers prior to concrete placement. If
encountered, 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. If casing is used for
pier construction, it should be withdrawn in a slow continuous manner maintaining a sufficient head of
concrete to prevent infiltration of water or the creation of voids in pier concrete.
e
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracon
Final recommendations during 'open -hole" or foundation excavation observations may vary depending
upon conditions at that time, additional overlot grading procedures or design elevations. Foundation
excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ
significantly from those presented in this report, supplemental recommendations will be required.
Foundation and walls should be reinforced as necessary to reduce the potential for distress caused by
differential foundation movement. The use of joints at openings or other discontinuities in walls is
recommended.
Foundation Systems — Conventional Type Spread Footings
Conventional type spread footings may be used to support the proposed townhome structures and the
commercial/retail building provided the footings are placed a minimum of 3-feet above the underlying
bedrock formation. The majority of the overburden native subsoils exhibited low expansive
characteristics. The granular subsoils exhibited moderate bearing characteristics. Conventional -type
spread footings bearing on the existing native cohesive type soils (i.e. the sandy lean clay or clayey
sand soils) should be designed for a net allowable bearing pressure of 1,500 psf. In addition, these
footings should also be sized to maintain a minimum dead load pressure of 500 psf. Footings founded
on approved engineered fill material or extended to the underlying coarse granular subsoils should be
designed for a net allowable bearing pressure of 2,000 psf.
Footings should be proportioned to reduce differential foundation movement. Proportioning on the basis
of equal total movement is recommended; however, proportioning to relative constant dead -load
pressure will also reduce differential settlement between adjacent footings. Total movement resulting
from the assumed structural loads is estimated to be on the order of 1-inch. Additional foundation
movements could occur if water from any source infiltrates the foundation soils; therefore, it is
imperative proper drainage should be provided in the final design and during construction for each
structure. If the subsoils become wetted below the proposed structures, movement exceeding 1-inch is
likely. If movement less than 1-inch is desired, then use of a drilled pier foundation system is
recommended.
Foundation Systems — Drilled Piers/Caissons
If the 3-foot separation between the bottom of the foundation system and the underlying bedrock
formation cannot be achieved due to design elevations, then an alternative foundation system for
supporting the proposed structures would be a grade beam and drilled pier/caisson foundation
system. Straight shaft piers, drilled a minimum of 10-feet into competent or harder bedrock, with
minimum shaft lengths of 20-feet are recommended.
7
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
Groundwater Conditions
lrerracon
Groundwater was not encountered in any of the test borings to maximum depths of exploration during
the initial field exploration. However, when checked 5 days after the drilling operations, a dry cave in
(DCI) was recorded at approximate depths of 13-1/2 to 22-feet below existing site grades within
Boring Nos. 2 through 4, and groundwater was measured at approximate depths of 9 to 21-feet below
site in Boring Nos. 6 through 8. Test Boring Nos. 1 and 9 remained dry to the maximum depths
explored. These observations represent groundwater conditions at the time of the field exploration, and
may not be indicative of other times, or at other locations. Groundwater levels can be expected to
fluctuate with varying seasonal and weather conditions.
Zones of perched and/or trapped groundwater may occur at times in the subsurface soils overlying
bedrock, on top of the bedrock surface or within permeable fractures in the bedrock materials. The
location and amount of perched water is dependent upon several factors, including hydrologic
conditions, type of site development, irrigation demands on or adjacent to the site, fluctuations in water
features, seasonal and weather conditions.
ENGINEERING ANALYSES AND RECOMMENDATIONS
Geotechnical Considerations
The site appears suitable for the proposed construction from a geotechnical engineering point of view.
Potentially expansive siltstone/claystone bedrock lenses were encountered at various depths throughout
the site, (i.e. approximately 11 to 12-feet below site grades), which will require particular attention in the
design and construction depending upon the final design elevations for the lower level/basement floor
slab grades. It is important to establish and maintain good/positive surface drainage, especially in the
immediate area of the proposed residential footprints during and after construction.
The following foundation systems were evaluated for use on the site:
• Conventional type spreads footings bearing on the native subsoils or approved
engineered fill material a minimum of 3-feet above the underlying bedrock formation, or
• If the 3-foot separation cannot be maintained; a grade beam and straight shaft drilled
piers/caisson foundation system extending into the underlying bedrock formation.
Basement construction is considered feasible for the site provided a complete dewatering system is
placed around the basement area and construction recommendations presented herein are followed.
C^
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferracon
pre -loaded and inundated with water at approximately 500 pounds per square foot (psf), while samples
obtained at the 7 to 9-foot intervals are pre -loaded and inundated with water at approximately 1,000 psf.
For this assessment, we conducted 8 swell -consolidation tests at various intervals/depths throughout
the site. The swell index values for the soil samples tested at the 150 psf inundation loading scheme
revealed a low to moderate swell potential of approximately (+) 2.0 to (+) 3.2 percent. Additional
discussion will be presented in the "Pavement Design and Construction" section of this report for a
swell -mitigation plan. The samples tested at the 500-psf-inundation pressure, varied between
approximately (-) 0.4 % to (+) 0.1 %, while the only sample test at the 1000-psf inundation loading
pressure revealed a swell -index of (-) 2.0%. This typically indicates a slight tendency of hydro-
compactable soils; however this generally coincides with a granular soil, (i.e. a silty sand with gravel
material).
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
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.
Recommended Representative Swell Potential Descriptions and Corresponding
Slab Performance Risk Categories
Low 0 < 3 0 < 2
Moderate 3 to < 5 2 to < 4
High 5to<8 4to<6
Very High > 8 > 6
Based on the laboratory test results, the subsurface soils at the depths analyzed revealed low to
moderate expansive potential. Intermittent siltstone and/or claystone lenses are prone to exist within the
Pierre Shale formation, which may exhibit a moderate to high expansive potential, therefore depending
upon final design elevations, certain precautions will be required if foundations are to be in closed
proximity to the underlying bedrock formation. Terracon has experienced moderate to high expansive
conditions for the underlying bedrock in close proximity to the subject site.
5
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
1rerracan
below site grades and extended to the depths explored. The upper 2 to 2-1/2-feet of the bedrock was
weathered, however the underlying siltstone/claystone was hard with increased depths.
The stratification boundaries shown on the enclosed boring logs represent the approximate locations of
changes in soil types; in -situ, the transition of materials may be gradual. The subsurface soil and
groundwater conditions are presented on the Logs of Borings included in Appendix A of this report.
Field and Laboratory Test Results
Approximately 2 to 3-feet of overlot grading fill material was encountered in the majority of the test
borings drilled for this study. At this point, we do not have any documentation or records that indicate or
verify the construction methods used during the placement of this surface layer. Field density test
results were not made available to us prior to the submittal of this report. Field tests indicate the fill
material is generally stiff to very stiff in consistency and exhibits low swell potential. Based upon the
field penetration resistance values, in -situ dry densities, and the laboratory consolidation test data, it
appears the existing fill could be used for support of foundations, and floor slabs -on -grade without the
need for removal or re -compaction. However, the consistency and relative density of the existing fill
material must be verified per building footprint prior to foundation, and slab -on -grade construction
activities to assess that similar conditions exist across each footprint with those encountered in the test
borings.
The native cohesive sandy lean clay stratum is medium stiff to very stiff in consistency and exhibits low
swell potential, a slight tendency to compress under increased loading conditions, and low to moderate
load bearing capabilities. The granular stratum is medium dense to dense in relative density and
exhibits moderate load bearing characteristics. The underlying weathered bedrock formation is soft to
moderately hard and the siltstone/claystone is hard with increased depths and exhibits low to moderate
swell potential and moderate bearing capacity characteristics.
Swell — Consolidation Test Results
The swell -consolidation test is commonly performed to evaluate the swell or collapse potential of soils or
bedrock for determining foundation, floor slab and pavement design criteria. In this test, relatively
undisturbed samples obtained directly from the ring barrel sampler or Shelby Tube sampling devices are
placed in a laboratory apparatus and inundated 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 the 0.5 to 1-foot intervals for pavement analyses are typically pre -loaded and
inundated with water at approximately 150 pounds per square foot (psf) to simulate actual pavement
loading conditions in general accordance with the Larimer County Urban Area Street Standards
(LCUASS) Pavement Design guidelines. Samples obtained at the 3 to 4-foot intervals are generally
4
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lferramn
System described in Appendix C. Samples of bedrock were classified in accordance with general notes
for Bedrock Classification. At that time, the field descriptions were confirmed or modified as necessary
and an applicable laboratory testing program was formulated to determine engineering properties of the
subsurface materials. Boring logs were prepared and are presented in Appendix A.
Laboratory tests were conducted on selected soil and bedrock samples. The test results were used for
the geotechnical engineering analyses, and the development of foundation and earthwork
recommendations. All laboratory tests were performed in general accordance with the applicable
ASTM, local or other accepted standards.
Selected soil samples were tested for the following engineering properties:
• Water Content
• Dry Density
• Swell -Consolidation
SITE CONDITIONS
• Plasticity Index
• Grain -Size Distribution
The site for the proposed townhome and commercial/retail development is situated near the southeast
corner of Harmony Road and Taft Hill Road in southwest Fort Collins, Colorado. Directly at the
southeast corner of the intersection along the northwestern portion of the site is an existing Fort Collins -
Loveland Water District pump station, with a chain fence enclosure. This property is not included within
the Innovation Island Parcel. The proposed development site is sparsely vegetated with grass and
weeds, is relatively flat, exhibiting positive surface drainage in the south to east directions and exhibits
an approximate 8 to 10-feet of relief across the site from the northwest portion to the southeast portion.
Harmony Road meanders along the northern and eastern boundaries, Taft Hill Road borders along the
west, and the existing Overlook Residential Development is located to the south.
SUBSURFACE CONDITIONS
Soil and Bedrock Conditions
The subsurface soil conditions encountered on the site consisted of an approximate 2 to 3-foot layer
of overlot grading sandy lean clay fill material underlain by the native cohesive soils. The native
sandy lean clay and clayey sand strata was encountered beneath the surface fill material and
extended to the coarse granular soils or weathered bedrock stratum below. Silty sand with gravel
was encountered in eight (8) of the nine (9) test borings at approximate depths of 4 to 12-feet below
site grades and extended to the depths explored or to the underlying bedrock. Siltstone/claystone
bedrock was encountered in Test Boring Nos. 4 through 8 at approximate depths of 11 to 12-feet
3
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
lrerracon
and 18,200 square foot commercial/retail property. We assume the townhome structures and the
commercial/retail building will be single to 3-story structures having either slab on grade or full -
basement construction with assumed maximum wall and column loads on the order of 1 to 4 kips per
linear foot and 10 to 75 kips respectively. Also included will be associated parking and driveways
areas which we assume will be asphalt paved.
SITE EXPLORATION
The scope of the services performed for this project included a site reconnaissance by an engineering
geologist and/or a geotechnical engineer, a subsurface exploration program, laboratory testing and
engineering analyses.
Field Exploration
A total of 9 test borings were drilled on for this project on September 7, 2005, at the locations shown on
the Test Boring Location Plan, Figure No. 1, to an approximate depth of 10 to 25-feet below existing site
grades. The test borings were drilled within the proposed footprints of the townhome structures and the
commercial/retail building and were located in the field using a hand held global positioning system
(GPS) unit prior to our drilling operations. All of the borings were advanced with a truck -mounted drilling
rig, utilizing 4-inch diameter solid stem augers.
Ground surface elevations at each boring location were obtained by measurements with an engineers
level and referenced to a temporary benchmark (TBM) consisting of a surveyor's control point as shown
on the Site Plan, Figure No. 1 and using an assumed elevation of 100.00. The accuracy of boring
locations and elevations should only be assumed to the level implied by the methods used.
Lithologic logs of each boring were recorded by the engineering geologist during the drilling operations.
At selected intervals, samples of the subsurface materials were taken by driving a split -spoon (SS)
and/or a Dames and Moore ring barrel (RS) sampling device.
Penetration resistance measurements were obtained by driving the split -spoon and/or ring barrel into
the subsurface materials with a 140-pound hammer falling 30 inches. The penetration resistance value
is a useful index in estimating the consistency, relative density or hardness of the materials
encountered. Groundwater conditions were evaluated in each boring at the time of site exploration and
follow-up measurements were obtained on September 13, 2005.
Laboratory Testing
All samples retrieved during the field exploration were returned to the laboratory for observation by the
project geotechnical engineer and were classified in accordance with the Unified Soil Classification
E
GEOTECHNICAL ENGINEERING REPORT
PROPOSED INNOVATION ISLAND — HABITAT FOR HUMANITY
28 TOWNHOMES AND 18,200 SF OF COMMERCIAL/RETAIL
APPROXIMATELY 4.4-ACRE SITE
SOUTHEAST CORNER OF HARMONY ROAD AND TAFT HILL ROAD
FORT COLLINS, LARIMER COUNTY, COLORADO
TERRACON PROJECT NO.20055152
SEPTEMBER 20, 2005
INTRODUCTION
This report contains the results of our geotechnical engineering exploration for the proposed Habitat for
Humanity's Innovation Island project which is to consist of approximately 28 townhome units, an
approximate 18,200 square foot commercial/retail building, along with associated pavement area for
parking and drive lanes. The project is to be located on an approximate 4.4-acre parcel of land situated
at the southeast comer of Harmony Road and Taft Hill Road in southwest Fort Collins, Colorado. The
site is located in the Southwest Y4 of Section 34, Township 7 North, Range 69 West of the 6"' P.M.,
Larimer County, Colorado.
The purpose of these services is to provide information and geotechnical engineering recommendations
relative to:
• subsurface soil and bedrock conditions
• groundwater conditions
• foundation design and construction
• basement construction
• floor slab design and construction
• lateral earth pressures
• pavement design and construction
• earthwork
• drainage
The recommendations contained in this report are based upon the results of field and laboratory testing,
engineering analyses, and experience with similar soil conditions, structures and our understanding of
the proposed project.
PROJECT DESCRIPTION
The project as we understand it is to develop an approximate 4.4-acre vacant parcel of land situated
at the southeast corner of Taft Hill Road and Harmony Road into an approximate 28 townhome units
TABLE OF CONTENTS
Letter of Transmittal ----------------------------- —------------------------------------------------------------- — --- i
INTRODUCTION............................................................................................................................. 1
PROJECT DESCRIPTION............................................................................................................. 1
SITEEXPLORATION..................................................................................................................... 2
FieldExploration...................................................................................................................
2
LaboratoryTesting................................................................................................................
2
SITECONDITIONS.........................................................................................................................
3
SUBSURFACECONDITIONS.......................................................................................................
3
Soil and Bedrock Conditions.................................................................................................
3
Field and Laboratory Test Results........................................................................................
4
Swell -Consolidation Test Results.........................................................................................
4
Groundwater Conditions.......................................................................................................
6
ENGINEERING RECOMMENDATIONS........................................................................................ 6
Geotechnical Considerations................................................................................................
6
Foundation Systems — Conventional Type Spread Footings ...............................................
7
Foundation Systems — Drilled Piers/Caissons.....................................................................
7
BasementConstruction.........................................................................................................
9
Lateral Earth Pressures......................................................................................................
10
Seismic Considerations......................................................................................................
11
Floor Slab Design and Consideration.................................................................................
11
Pavement Design and Construction...................................................................................
12
Earthwork............................................................................................................................
16
General Considerations............................................................................................
16
SitePreparation........................................................................................................
16
Subgrade Preparation...............................................................................................
17
Fill Materials and Placement.....................................................................................
17
Excavation and Trench Construction........................................................................
18
Additional Design and Construction Considerations..........................................................
19
Exterior Slab Design and Construction.....................................................................
19
Underground Utility Systems....................................................................................
19
SurfaceDrainage......................................................................................................
20
GENERALCOMMENTS.............................................................................................................. 20
APPENDIX A
Test Boring Location Plan - Figure No
Log of Boring Nos. 1 through 9
APPENDIX B
Laboratory Test Results
APPENDIX C
General Notes
Geotechnical Engineering Report
Habitat for Humanity — Innovation Island
S/E/C of Harmony Road and Taft Hill Road
Fort Collins, Colorado
Project No. 20055152
1rerracon
Based on the geotechnical engineering analyses, subsurface exploration and laboratory test results,
Terracon recommends the townhome structures and the commercial/retail building within the
proposed Innovation Island project be supported by conventional type spread footings bearing upon
the existing native overburden soils, or on approved engineered fill material a minimum of 3-feet
above the underlying bedrock formation. An alternative foundation system to be considered, if the a-
foot separation cannot be achieved, would be a drilled pier/caisson system extending to the bedrock
below.
Slab -on -grade construction is feasible provided the recommendations set forth in this report are
followed. Other design and construction recommendations for basement construction, utilities, and
pavements based upon geotechnical conditions, are presented in the report.
We appreciate being of service to you in the geotechnical engineering phase of this project, and are
prepared to assist you during the construction phases as well. If you have any questions concerning
this report or any of our testing, inspection, design and consulting services, please do not hesitate to
contact us.
Sincerely,
TERRACON
David A. Richer
NAP* rrrrrrrr v
Geotechnical Enginry)w-p nt Manager
,.
Reviewed by: Doug J. Jobe, P.E.
Geotechnical Engineer/Department Manager
Copies to: Addressee (5)
September 20, 2005
Interwest Consulting Group
C/o Habitat for Humanity
1218 West Ash — Suite C
Windsor, Colorado 80550
Attn: Mr. Bob Almirall, P.E.
Irerracon
Consulting Engineers & Scientists
Terracon Consultants, Inc.
301 North Howes
Fort Collins, Colorado 80521
Phone 970.484.0359
Fax 970.484.0454
www.terracon.com
Re: Geotechnical Engineering Report
Innovation Island — Habitat for Humanity
Proposed 28 Townhomes and 18,200 square Feet of Commercial/Retail
Approximately 4.4-Acre Parcel — Southeast Corner of Harmony Road and Taft Hill Road
Fort Collins, Larimer County, Colorado
Terracon Project No. 20055152
Terracon has completed a geotechnical engineering exploration for the proposed Habitat for Humanity's
Innovation Island project, which is to consist of approximately 28 townhome units, approximately 18,200
square feet of commercial/retail space along with associated pavement areas for parking and drive
lanes. The project is to be located on an approximate 4.4-acre parcel of land situated at the southeast
corner of Harmony Road and Taft Hill Road in southwest Fort Collins, Colorado. This study was
performed in general accordance with our Proposal No. D2005305 dated August 17, 2005.
The results of our engineering study, including the boring location diagram, laboratory test results, test
boring records, and the geotechnical recommendations needed to aid in the design and construction of
foundations, floor slabs, basements, pavements and other earth connected phases for this project are
attached.
The subsurface soil conditions encountered on the site consisted of an approximate 2 to 3-foot layer
of overlot grading sandy lean clay fill material underlain by the native cohesive soils. The native
sandy lean clay and clayey sand strata was encountered beneath the surface fill material and
extended to the coarse granular soils or weathered bedrock stratum below. Silty sand with gravel
was encountered in eight (8) of the nine (9) test borings at approximate depths of 4 to 12-feet below
site grades and extended to the depths explored or to the underlying bedrock. Siltstone/claystone
bedrock was encountered in Test Boring Nos. 4 through 8 at approximate depths of 11 to 12-feet
below site grades and extended to the depths explored. The upper 2 to 2-1/2-feet of the bedrock was
weathered, however the underlying siltstone/claystone was hard with increased depths. Groundwater
was not encountered in any of the test borings to maximum depths _of exploration during the initial
field exploration. However, when checked 5 days after the drilling operations, a dry cave in (DCI) was
recorded at approximate depths of 13-1/2 to 22-feet below existing site grades within Boring Nos. 2.
through 4, and groundwater was measured at approximate depths of 9 to 21-feet below site in Boring
Nos. 6 through 8. Test Boring Nos. 1 and 9 remained dry to the maximum depths explored. The
subsurface soil, bedrock and groundwater conditions are presented on the Logs of Borings included
in Appendix A of this report.
Delivering Success for Clients and Employees Since 1965
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GEOTECHNICAL ENGINEERING REPORT
PROPOSED INNOVATION ISLAND — HABITAT FOR HUMANITY
28 TOWNHOMES AND 18,200 SF OF COMMERCIAL/RETAIL
APPROXIMATELY 4.4-ACRE SITE
SOUTHEAST CORNER OF HARMONY ROAD AND TAFT HILL ROAD
FORT COLLINS, LARIMER COUNTY, COLORADO
TERRACON PROJECT NO.20055152
SEPTEMBER 20, 2005
Prepared for.
INTERWEST CONSULTING GROUP
C/O HABITAT FOR HUMANITY
1218 WEST ASH — SUITE C
WINDSOR, COLORADO 80550
ATTN: MR. BOB ALMIRALL, P.E.
Prepared by.
Terracon
301 North Howes Street
Fort Collins, Colorado 80521
Irerracon