HomeMy WebLinkAboutReports - Soils - 10/31/2024
CTL|Thompson, Inc.
Denver, Fort Collins, Colorado Springs, Glenwood Springs, Pueblo, Summit County – Colorado
Cheyenne, Wyoming and Bozeman, Montana
VOA Mason Place II
3800 South Mason Street
Fort Collins, Colorado
Prepared for:
Volunteers of America
1660 Duke Street
Alexandria, Virginia
Attention:
Doug Snyder
Project No. FC11376.000-120
October 31, 2024
GEOTECHNICAL INVESTIGATION
Table of Contents
Scope 1
Summary Of Conclusions 1
Site Conditions 2
Proposed Construction 2
Investigation 2
Subsurface Conditions 3
Groundwater 3
Geologic Hazards 4
Expansive Soils 4
Seismicity 4
Site Development 5
Fill Placement 5
Excavations 6
Lateral Earth Pressures 6
Foundations 8
Footings 8
Below Grade Areas 9
Floor Systems 9
Structurally Supported Floors 11
Exterior Flatwork 12
Pavements 12
Pavement Selection 14
Subgrade and Pavement Materials and Construction 14
Pavement Maintenance 14
Water-Soluble Sulfates 15
Surface Drainage 16
Construction Observations / Additional Services 16
Geotechnical Risk 17
Limitations 17
FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS
APPENDIX A – SUMMARY LOGS OF EXPLORATORY BORINGS
APPENDIX B – RESULTS OF LABORATORY TESTING
APPENDIX C – SAMPLE SITE GRADING SPECIFICATIONS
APPENDIX D – PAVEMENT CONSTRUCTION RECOMMENDATIONS
APPENDIX E – PAVEMENT MAINTENANCE PROGRAM
APPENCIX F – PAVEMENT DESIGN CALCULATIONS
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
1
Scope
This report presents the results of our Geotechnical Investigation for the VOA Mason Place
II project in Fort Collins, Colorado (Figure 1). The purpose of the investigation was to evaluate
the subsurface conditions and provide geotechnical design and construction criteria for the
project. The scope was described in our Service Agreement (CTL|T Proposal No. FC-24-0301
Revision 3) dated August 23, 2024. Evaluation of the property for the presence of potentially
hazardous materials was not included in our work scope.
The report was prepared from data developed during field exploration, field and laboratory
testing, engineering analysis, and our experience. The report includes a description of subsurface
conditions found in our exploratory borings and discussions of site development as influenced by
geotechnical considerations. Our opinions and recommendations regarding design criteria and
construction details for foundations, floor systems, slabs-on-grade, lateral earth loads,
pavements, and drainage are provided. The report was prepared for the exclusive use of
Volunteers of America and your team in design and construction of the proposed improvements.
If the proposed construction differs from descriptions herein, we should be requested to review
our recommendations. Our conclusions are summarized in the following paragraphs.
Summary Of Conclusions
1. Strata encountered in our borings generally consisted of gravelly sands and sandy
clays over sandstone bedrock. Sandstone bedrock was encountered at
approximately 12 feet in three borings and extended to the maximum depths
explored. Testing indicates the clays are slightly expansive.
2. Groundwater was measured at approximate depths ranging from 8 to 10 feet in
three borings during drilling. Groundwater levels may fluctuate seasonally and rise
in response to precipitation, irrigation, and changes in land-use. Existing
groundwater levels are not expected to significantly affect site development. We
recommend a minimum 3-foot separation between foundation elements and
groundwater.
3. We judge there is low risk of heave on this site upon post-construction wetting. The
presence of expansive soils and bedrock constitutes a geologic hazard. There is
risk that slabs-on-grade and foundations will experience heave or settlement and
be damaged. We believe the recommendations presented in this report will help
to control risk of damage; they will not eliminate that risk. Slabs-on-grade and, in
some instances, foundations may be damaged.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
2
4. Footing foundations placed on natural, undisturbed soil and/or properly compacted
fill are recommended for the proposed construction. Design and construction
criteria for foundations are presented in the report.
5. Some movement of slab-on-grade floors should be anticipated. If movement
cannot be tolerated, structural floors should be considered. Based on the
measured swell, we estimate potential heave of 1-inch or less.
6. Surface drainage should be designed, constructed, and maintained to provide
rapid removal of surface runoff away from the proposed structure. Conservative
irrigation practices should be followed to avoid excessive wetting.
7. Samples of the subgrade soils generally classified as AASHTO A-1-a and A-7-6
soils, with a group index of 13.1 for the A-7-6 (clay) soils. For the parking lot, we
recommend 4 inches of asphaltic concrete over 6 inches of aggregate base course
or a full depth asphaltic concrete pavement with a thickness of 6 inches. Thicker
sections are recommended for areas with heavier traffic.
Site Conditions
The site is located at 3800 South Mason Street in Fort Collins, Colorado (Figure 1). The
lot is currently a parking lot, with the existing VOA Mason Place to the north. The New Mercer
Canal is 500 feet west of the site. The existing parking lot is of unknown age and is in fair condition.
There is little to no evidence of maintenance.
Proposed Construction
The provided plans indicate the project will include the construction of a four-story, wood
and steel-framed structure. No below grade construction is planned. Paved parking lots and
access roads are planned and buried utilities will be constructed.
Investigation
The field investigation included drilling and sampling five exploratory borings at the
approximate locations presented on Figure 1. The borings were drilled to depths of approximately
10 to 25 feet using 4-inch diameter continuous-flight augers, and a truck-mounted drill rig. Drilling
was observed by our field representative who logged the soils and bedrock and obtained samples
for laboratory tests. Summary logs of the exploratory borings, including results of field penetration
resistance tests and a portion of laboratory test data, are presented in Appendix A.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
3
Soil and bedrock samples obtained during drilling were returned to our laboratory and
visually examined by our geotechnical engineer. Laboratory testing was assigned and included
moisture content, dry density, swell-consolidation, particle-size analysis, Atterberg limits, and
water-soluble sulfate concentration. Swell-consolidation test samples were wetted at a confining
pressure which approximated the pressure exerted by the overburden soils (overburden
pressures). Results of the laboratory tests are presented in Appendix B and summarized in Table
B-I.
Subsurface Conditions
Strata encountered in our exploratory borings generally consisted of 10 to 12 feet of
gravelly sand and sandy clay over sandstone bedrock. Sandstone bedrock was encountered in
three borings at 12 feet and extended to the maximum depths explored. Select pertinent
engineering characteristics of the soils encountered are presented in the following
paragraphs/sections. Further descriptions of the subsurface conditions are presented on our
boring logs and in our laboratory test results.
Overburden soils consisted of gravelly sand, sandy gravel, and sandy clay. The clay was
medium stiff to stiff based on results of field penetration resistance tests. Four clay samples
swelled up to 0.5 percent when wetted under applied approximately overburden pressures. Two
samples we wetted under a pressure of 150 psf, in accordance with Larimer County Urban Street
Standards (LCUASS) for pavement samples. Those samples exhibited swells of 0.3 and 1.2
percent. One sample of the clay contained 59 percent silt and clay-sized particles. Two samples
of the sand and gravel contained 7 to 12 percent silt and clay-sized particles.
Groundwater
Groundwater was estimated at depths ranging from 8 to 10 feet in three borings during
drilling. Groundwater may develop on or near the bedrock surface or other low permeable soil or
bedrock when a source of water not presently contributing becomes available. Groundwater levels
may fluctuate seasonally and rise in response to precipitation, landscape irrigation, and changes
in land-use. Groundwater is not expected to affect below-grade construction at the site. We
recommend a minimum separation of 3 feet from groundwater to foundations and floor systems.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
4
Geologic Hazards
Our investigation addressed potential geologic hazards, including expansive soils and
seismicity that should be considered during planning and construction. None of these hazards
considered will preclude proposed construction. The following sections discuss each of these
geologic hazards and associated development concerns.
Expansive Soils
Expansive soils and bedrock are present at the site which constitutes a geologic hazard.
There is a risk that ground heave will damage slabs-on-grade and foundations. The risks
associated with swelling soils can be mitigated, but not eliminated, by careful design, construction,
and maintenance procedures. We believe the recommendations in this report will help control risk
of foundations and/or slab damage; they will not eliminate that risk.
Seismicity
According to the USGS, Colorado’s Front Range and eastern plains are considered low
seismic hazard zones. The earthquake hazard exhibits higher risk in western Colorado compared
to other parts of the state. The Colorado Front Range area has experienced earthquakes within
the past 100 years, shown to be related to deep drilling, liquid injection, and oil/gas extraction.
Naturally occurring earthquakes along faults due to tectonic shifts are rare in this area.
The soil and bedrock at this site are not expected to respond unusually to seismic activity.
The 2021 International Building Code (Section 16.13.2.2) defers the estimation of Seismic Site
Classification to ASCE7-22, a structural engineering publication. The table below summarizes
ASCE7-22 Site Classification Criteria.
ASCE7-22 SITE CLASSIFICATION CRITERIA
Seismic Site Class 𝑣̅𝑠, Calculated Using Measured or Estimated
Shear Wave Velocity Profile (ft/s)
A. Hard Rock >5,000
B. Medium Hard Rock >3,000 to 5,000
BC. Soft Rock >2,100 to 3,000
C. Very Dense Sand or Hard Clay >1,450 to 2,100
CD. Dense Sand or Very Stiff Clay >1,000 to 1,450
D. Medium Dense Sand or Stiff Clay >700 to 1,000
DE. Loose Sand or Medium Stiff Clay >500 to 700
E. Very Loose Sand or Soft Clay ≥500
F. Soils requiring Site Response Analysis See Section 20.2.1
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
5
Based on the results of our investigation, the reduced, empirically estimated average shear
wave velocity values for the upper 100 feet range between 1,250 and 1,330 feet per second. We
judge a Seismic Site Classification of CD. The field penetration test results along with the empirical
estimates imply that shear-wave velocity seismic tests to directly measure 𝒗̅𝒔 could result in a
better Seismic Site Classification. The subsurface conditions indicate low susceptibility to
liquefaction from a materials and groundwater perspective.
Site Development
Fill Placement
The existing onsite soils are generally suitable for re-use as new fill from a geotechnical
standpoint, provided debris or deleterious organic materials are removed. Clay soils found in
foundation excavations should be removed and replaced with properly compacted fill. In general,
import fill should meet or exceed the engineering qualities of the onsite soils. In addition, particles
larger than 3 inches should be broken down or removed. If import material is used, it should be
tested and evaluated for approval by CTL|Thompson.
Prior to fill placement, debris, organics/vegetation, and deleterious materials should be
substantially removed from areas to receive fill. The surface should be scarified to a depth of at
least 8 inches, moisture conditioned and compacted to the criteria below. Subsequent fill should
be placed in thin (8 inches or less) loose lifts, moisture conditioned and compacted. Fill should be
compacted to a dry density of at least 95 percent of standard Proctor maximum dry density (ASTM
D 698, AASHTO T 99). Fill depths greater than 15 feet should be evaluated by CTL|T to
recommend appropriate compaction specifications. Sand soils used as fill should be moistened
to within 2 percent of optimum moisture content. Clay soils should be moistened between
optimum and 3 percent above optimum moisture content. The fill should be moisture-conditioned,
placed in thin, loose lifts (8 inches or less) and compacted as described above. We should
observe placement and compaction of fill during construction. Fill placement and compaction
should not be conducted when fill material is frozen. CTL|Thompson should observe placement
and compaction of fill during construction.
Site grading in areas of landscaping where no future improvements are planned can be
placed at a dry density of at least 90 percent of standard Proctor maximum dry density (ASTM D
698, AASHTO T 99). Example site grading specifications are presented in Appendix C.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
6
Water and sewer lines are often constructed beneath areas where improvements are
planned. Compaction of trench backfill can have a significant effect on the life and serviceability
overlying structures. We recommend trench backfill be moisture conditioned and compacted as
described above. Placement and compaction of backfill should be observed and tested by a
representative of our firm during construction.
Excavations
We believe the soil and bedrock penetrated in our exploratory borings can generally be
excavated with conventional, heavy-duty excavation equipment. Excavations at this site
exceeding 12 feet may encounter very hard bedrock. Difficult excavation should be expected
where N values (blow counts) are less than 50 blows per 5 inches (50/5) as indicated in our boring
logs. Excavations of 8 feet or more may encounter groundwater.
Excavations should be sloped or shored to meet local, state, and federal safety
regulations. Excavation slopes specified by OSHA are dependent upon types of soil and
groundwater conditions encountered. The contractor’s “competent person” is responsible to
identify the soils and/or rock encountered in excavations and refer to OSHA standards to
determine appropriate slopes and safety measures. Based on our investigation and OSHA
standards, we believe the soils at this site may classify as Type C soils.
Type C soils require a maximum slope inclination of 1.5:1 in dry conditions. Stockpiles of
soils, rock, equipment, or other items should not be placed within a horizontal distance equal to
one-half the excavation depth, from the edge of excavation. Excavations deeper than 20 feet
should be braced, or a professional engineer should design the slopes.
Wind and water erosion is more likely with disturbed conditions expected during
construction and may need to be addressed due to municipal regulation. The erosion potential
will decrease after construction if proper grading practices, surface drainage design and re-
vegetation efforts are implemented.
Lateral Earth Pressures
All below grade walls and/or retaining walls should be designed to resist lateral earth
pressures that act upon the wall. The appropriate load distribution to apply for design depends
not only on the soil type, but also on the wall type and restraint. For retaining walls that are integral
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
7
to adjacent structures and restrained from rotation, the walls should be designed to resist the “at
rest” earth pressure. For walls, which are free to rotate to develop the shear strength of the
retained soils, such as walls not integral to the structure, the walls should be designed to resist
the “active” earth pressure. Resistance to lateral loads can be provided by friction between
concrete and soil, and/or by “passive” earth pressure. Passive earth pressure should be ignored
for the top one foot of soils against the structure since it can be removed easily with time. The
proper application of these loading conditions is the responsibility of the wall designer. Wall
backfill should be placed according to the Fill Placement section.
The following table provides the necessary equivalent fluid pressure values for the backfill
comprised of native soils anticipated at this site. The pressures given do not include allowances
for surcharge loads such as sloping backfill, vehicle traffic, or hydrostatic pressure. These values
also do not include a factor of safety. Normally, a factor of safety of 1.5 is used for sliding and 1.6
for lateral earth pressure. For design purposes, compacted fill can be considered at 120 pcf.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
8
Loading Condition Equivalent Hydrostatic
Fluid Pressure
Active (A) pcf 35
At-Rest (o) pcf 50
Passive (p) pcf 425
Horizontal Friction Coefficient (μ) 0.54
Foundations
Our investigation indicates sandy clay and gravelly sand soils are present at the
anticipated foundation levels and are likely to influence the performance of foundations. Based
on the planned site development, we anticipate foundations will be placed at, or near, frost depths.
Footing foundations can be considered for the proposed construction provided the potential
movement can be tolerated. Clay soils found in foundation excavations should be removed and
replaced with properly compacted granular fill.
If foundations will be deeper than 5 feet below existing grade, or if some foundation
movement cannot be tolerated, we recommend supporting the structure on drilled shafts or helical
piers extending to the bedrock surface. In that case, our office should be contacted to provide
deep foundation recommendations.
Design criteria for footing foundations developed from analysis of field and laboratory data
and our experience are presented below.
Footings
1. Footings should be constructed on natural, undisturbed soils or properly
compacted fill (see Fill Placement). All existing, uncontrolled fill should be
removed from under footings and within one footing width around footings and
replaced with properly compacted fill. If any soft, loose, or poorly compacted fill is
present in footing excavations, or is the result of the excavation/forming process,
then it should be removed and recompacted or stabilized
2. Footings should be designed for a net allowable soil pressure of 3,000 psf. The
soil pressure can be increased 33 percent for transient loads such as wind or
seismic loads. We recommend a minimum 3-feet of separation between foundation
elements and groundwater.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
9
3. We anticipate footings designed using the soil pressure recommended above
could experience 1-inch of movement. Differential movement of ½- inch should be
considered in the design.
4. Footings should have a minimum width of at least 12 inches. Foundations for
isolated columns should have minimum dimensions of 16 inches by 16
inches. Larger sizes may be required depending on loads and the structural
system used.
5. The soils beneath footing pads can be assigned an ultimate coefficient of friction
of 0.5 to resist lateral loads. The ability of grade beam or footing backfill to resist
lateral loads can be calculated using a passive equivalent fluid pressure of 425
pcf. This assumes the backfill is densely compacted and will not be removed.
Deflection of grade beams is necessary to mobilize passive earth pressure; we
recommend a factor of safety of 2 for this condition. Backfill should be placed and
compacted to the criteria in Fill Placement.
6. Exterior footings should be protected from frost action. We believe 30 inches of
frost cover is appropriate for this site.
7. Foundation walls and grade beams should be well reinforced both top and bottom.
We recommend reinforcement sufficient to span an unsupported distance of 10
feet. The reinforcement should be designed by a structural engineer.
8. The completed foundation excavations should be observed by a representative of
our firm to confirm subsurface conditions are as anticipated. Our representative
should observe and test moisture and compaction of the fill and backfill.
9. Excessive wetting of foundation soils during and after construction can cause
heave, or softening and consolidation, of foundation soils and result in footing
movements. Proper surface drainage around the buildings is critical to control
wetting.
Below Grade Areas
No below grade areas are planned for the buildings. For this condition, perimeter drains
are not usually constructed. If any portion of a floor will be below exterior grade, or a crawl space
is planned, we should be contacted to provide recommendations for foundation drains. If below
grade structures are to be included, guidance for soil pressures can be found in the Lateral Earth
Pressures section of this report.
Floor Systems
Some movement of slab-on-grade floors should be anticipated. If movement cannot be
tolerated, structurally supported floors should be used. Structural floors should also be considered
for specific areas that are particularly sensitive to movement or where equipment on the floor is
sensitive to movement.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
10
Based on measured swell, we estimate potential heave of 1-inch or less. Conventional
slab-on-grade floors can be used provided the risk of heave and distress is acceptable to the
owner. There will likely be distress to sensitive finishes on the main level. We recommend
structurally supported floors if movements cannot be tolerated.
Slabs may be subject to heavy point loads. The structural engineer should design floor
slab reinforcement. For design of slabs-on-grade, we recommend a modulus of subgrade
reaction of 175 pci for onsite soils.
Where structurally supported floors are selected, we recommend a minimum void between
the ground surface and the underside of the floor system of 8 inches. The minimum void should
be constructed below beams and utilities that penetrate the floor. The floor may be cast over void
form. Void form should be chosen to break down quickly after the slab is placed. We recommend
against the use of wax or plastic-coated void boxes.
If the owner elects to use slab-on-grade construction and accepts the risk of movement
and associated damage, we recommend the following precautions for slab-on-grade construction
at this site. These precautions can help reduce, but not eliminate, damage or distress due to slab
movement.
1. Slabs should be separated from exterior walls and interior bearing members with
a slip joint that allows free vertical movement of the slabs. This can reduce cracking
if some movement of the slab occurs.
2. Slabs should be placed directly on properly moisture conditioned, well-compacted
fill. The 2021 International Building Code (IBC) requires a vapor retarder between
the base course or subgrade soils and the concrete slab-on-grade floor, including
PTS. The merits of installation of a vapor retarder below floor slabs depend on the
sensitivity of floor coverings and building use to moisture. A properly installed
vapor retarder (10 mil minimum) is more beneficial below concrete slab-on-grade
floors where floor coverings, painted floor surfaces or products stored on the floor
will be sensitive to moisture. The vapor retarder is most effective when concrete is
placed directly on top of it, rather than placing a sand or gravel leveling course
between the vapor retarder and the floor slab. The placement of concrete on the
vapor retarder may increase the risk of shrinkage cracking and curling. Use of
concrete with reduced shrinkage characteristics including minimized water
content, maximized coarse aggregate content, and reasonably low slump will
reduce the risk of shrinkage cracking and curling. Considerations and
recommendations for the installation of vapor retarders below concrete slabs are
outlined in Section 5.2.3.2 of the 2018 report of American Concrete Institute (ACI)
Committee 302, “Guide for Concrete Floor and Slab Construction (ACI 302.1R-
15)”.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
11
3. Use of slab-bearing partitions should be minimized. If used, they should be
designed and constructed with a minimum 1.5-inch space to allow for slab
movement. Differential slab movements may cause cracking of partition walls. If
the void is provided at the top of partitions, the connection between the slab-
supported partition and foundation-supported walls should be detailed to allow
differential movement. Doorways, in-wall utility connections, wall partitions
perpendicular to the exterior wall, or walls supported by foundations should be
detailed to allow for vertical movement. Interior perimeter framing and finishing
should not extend onto slabs-on-grade, or if necessary, should be detailed to allow
for movement.
4. Underslab plumbing should be eliminated where feasible. Where such plumbing is
unavoidable, it should be thoroughly pressure tested for leaks prior to slab
construction and be provided with flexible couplings. Pressurized water supply
lines should be brought above the floors as quickly as possible.
5. Plumbing and utilities that pass through the slabs should be isolated from the slabs
and constructed with flexible couplings. Utilities, as well as electrical and
mechanical equipment should be constructed with sufficient flexibility to allow for
movement.
6. HVAC or other mechanical systems supported by the slabs (if any) should be
provided with flexible connections capable of withstanding at least 3 inches of
movement.
7. The American Concrete Institute (ACI) recommends frequent control joints in slabs
to reduce problems associated with shrinkage cracking and curling. To reduce
curling, the concrete mix should have a high aggregate content and a low slump.
If desired, a shrinkage compensating admixture could be added to the concrete to
reduce the risk of shrinkage cracking. We can perform a mix design or assist the
design team in selecting a pre-existing mix.
Structurally Supported Floors
To our knowledge, there are no soil treatments combined with slab-on-grade floors that
will result in the same reduction in risk of floor movement (relative to the risk inherent for a floor
slab placed directly on the natural soils), as would be provided by a structural floor. If floor
movement cannot be tolerated, then a structurally supported floor should be used.
A structural floor is supported by the foundation system. Design and construction issues
associated with structural floors include ventilation and lateral loads. Where structurally supported
floors are installed over a crawl space, the required air space depends on the materials used to
construct the floor and the potential expansion of the underlying soils. Building codes require a
clear space of 18 inches between exposed earth and untreated wood floor components. For non-
organic floor systems, we recommend a minimum clear space of 4 inches. This minimum clear
space should be maintained between any point on the underside of the floor system (including
beams and floor drain traps) and the soils.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
12
A slab-on-void system may also be considered. Void form should be chosen to break down
quickly after the slab is placed. A sand or gravel leveling base below the void form should not be
used. We recommend against the use of wax or plastic-coated boxes unless provisions are made
to allow softening.
Where structurally supported floors are used, utility connections including water, gas, air
duct, and exhaust stack connections to floor supported appliances should be capable of absorbing
some deflection of the floor. Plumbing that passes through the floor should ideally be hung from
the underside of the structural floor and not lain on the bottom of the excavation. It is prudent to
maintain the minimum clear space below all plumbing lines; this configuration may not be
achievable for some parts of the installation.
Control of humidity in crawl spaces is important for indoor air quality and performance of
wood floor systems. We believe the best current practices to control humidity involve the use of
a vapor retarder or vapor barrier (6 mil) placed on the soils below accessible subfloor areas. The
vapor retarder/barrier should be sealed at joints and attached to concrete foundation elements.
Exterior Flatwork
We recommend exterior flatwork and sidewalks be isolated from foundations to reduce
the risk of transferring heave, settlement, or freeze-thaw movement to the structure. One
alternative would be to construct the inner edges of the flatwork on haunches or steel angles
bolted to the foundation walls and detailing the connections such that movement will cause less
distress to the building, rather than tying the slabs directly into the building foundation.
Construction on haunches or steel angles and reinforcing the sidewalks and other exterior flatwork
will reduce the potential for differential settlement and better allow them to span across wall
backfill. Frequent control joints should be provided to reduce problems associated with shrinkage.
Panels that are approximately square perform better than rectangular areas.
Pavements
The project will include a paved parking lot and access drives. The performance of
pavements is dependent upon the characteristics of the subgrade soil, traffic loading and
frequency, climatic conditions, drainage, and pavement materials. We drilled two exploratory
borings and conducted laboratory tests to characterize the subgrade soils, which consisted of
sandy gravel and sandy clay.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
13
The subgrade soils classified as A-1-a for gravel and A-7-6 with a group index of 13.1 for
clays in accordance with AASHTO procedures. The subgrade soil will likely provide good to poor
support for new pavement. If fill is needed, we have assumed it will be soils with similar or better
characteristics. A Hveem stabilometer test of a composite sample of the subgrade soil resulted in
an R-value of 49, which we converted to a resilient modulus of 10,039 psi based on CDOT criteria
(Eq. 4-1). For rigid pavement design, we estimated a modulus of subgrade reaction (k-value) of
175 psi/in based on soil classification. Swell tests indicate the subgrade soils have a low to
medium expansion potential based on Table 10-3 of LCUASS. LCUASS requires swell mitigation
where swell is 2 percent or greater. Based on the results of laboratory testing and LCUASS, we
believe that mitigation for swell will not be required.
Traffic loading of a parking lot can be estimated based on type of usage and number of
parking spaces. We understand there will be approximately 47 parking spaces, and traffic will
primarily consist of lightly loaded passenger vehicles. Delivery and garbage truck traffic is
anticipated to be minor and possibly isolated to certain areas of the parking lot. Pavement
thicknesses were calculated based on AASHTO methods for flexible pavement and CDOT
methods for rigid pavement with inputs from LCUASS. Recommended pavement thicknesses are
presented in the table below. Our calculations for rigid pavement indicate that 5 inches of PCC
are sufficient, however LCUASS requires a minimum PCC pavement thickness of 6 inches. Our
calculations for pavement thickness can be found in Appendix F.
Flexible hot mix asphalt (HMA) over aggregate base course (ABC) is likely planned for
pavement areas. Rigid Portland cement concrete (PCC) pavement should be used for trash
enclosure areas and where the pavement will be subjected to frequent turning of heavy vehicles.
Our designs are based on the AASHTO design method and our experience. Using the criteria
discussed above we recommend the minimum pavement sections provided in the following table.
RECOMMENDED PAVEMENT SECTIONS
Classification
Hot Mix Asphalt (HMA) +
Aggregate Base Course
(ABC)
Portland Cement
Concrete (PCC)
Parking Area 4" HMA +
6" ABC 6" PCC
Access Drives /
Heavy Traffic
Areas
4" HMA +
6" ABC 7" PCC
Trash Enclosures - 7" PCC
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
14
Pavement Selection
Composite HMA/ABC pavement over a stable subgrade is expected to perform well at this
site based on the recommendations provided. HMA provides a stiff, stable pavement to withstand
heavy loading and will provide a good fatigue resistant pavement. However, HMA does not
perform well when subjected to point loads in areas where heavy trucks turn and maneuver at
slow speeds. PCC pavement is expected to perform well in this area; PCC pavement has better
performance in freeze-thaw conditions and should require less long-term maintenance than HMA
pavement. The PCC pavement for trash enclosures should extend out to areas where trash trucks
park to lift and empty dumpsters.
Subgrade and Pavement Materials and Construction
The design of a pavement system is as much a function of the quality of the paving
materials and construction as the support characteristics of the subgrade. The construction
materials are assumed to possess sufficient quality as reflected by the strength factors used in
our design calculations. Moisture treatment criteria and additional criteria for materials and
construction requirements are presented in Appendix D.
Pavement Maintenance
Routine maintenance, such as sealing and repair of cracks, is necessary to achieve the
long-term life of a pavement system. We recommend a preventive maintenance program be
developed and followed for all pavement systems to assure the design life can be realized.
Choosing to defer maintenance usually results in accelerated deterioration leading to higher
future maintenance costs, and/or repair. A recommended maintenance program is outlined in
Appendix E.
Excavation of completed pavement for utility construction or repair can destroy the
integrity of the pavement and result in a severe decrease in serviceability. To restore the
pavement top original serviceability, careful backfill compaction before repaving is necessary. We
recommend installing all underground utilities prior to paving.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
15
Water-Soluble Sulfates
Concrete in contact with soil can be subject to sulfate attack. We measured water-soluble
sulfate concentrations of 0.01 percent in one sample in the building footprint and a concentration
of <0.01 to 0.70 percent in two samples for the parking lot. As indicated in our tests and ACI 318-
19, the sulfate exposure class is S2 for building foundations.
SULFATE EXPOSURE CLASSES PER ACI 318-19
Exposure Classes
Water-Soluble Sulfate (SO4)
in Soil A
(%)
Not Applicable S0 < 0.10
Moderate S1 0.10 to 0.20
Severe S2 0.20 to 2.00
Very Severe S3 > 2.00
A) Percent sulfate by mass in soil determined by ASTM C1580
For a S2 level of sulfate concentration, ACI 318-19 Code Requirements indicates there
are cement type requirements for sulfate resistance as indicated in the table below. This type of
cement should be used for building foundations only. The sulfate concentration of 0.70 in the
parking lot will prohibit the use of reclaimed concrete pavement (RCP) in the aggregate base
course (ABC), per LCUASS. PCC pavement would need to be constructed using Type V, or High
Sulfate designated concrete.
CONCRETE DESIGN REQUIREMENTS FOR SULFATE EXPOSURE PER ACI 318-19
Exposure
Class
Maximum
Water/
Cement
Ratio
Minimum
Compressive
Strength
(psi)
Cementitious Material Types A
Calcium
Chloride
Admixtures
ASTM
C150/
C150M
ASTM
C595/
C595M
ASTM
C1157/
C1157M
S0 N/A 2500 No Type
Restrictions
No Type
Restrictions
No
Type
Restrictions
No
Restrictions
S1 0.50 4000 IIB
Type with
(MS)
Designation
MS No
Restrictions
S2 0.45 4500 V B Type with (HS)
Designation HS Not
Permitted
S3 Option 1 0.45 4500
V + Pozzolan
or Slag
Cement C
Type with (HS)
Designation
plus Pozzolan
or Slag
Cement C
HS +
Pozzolan or
Slag
Cement C
Not
Permitted
S3 Option 2 0.4 5000 V D Type with (HS)
Designation HS Not
Permitted
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
16
A) Alternate combinations of cementitious materials shall be permitted when tested for sulfate resistance meeting
the criteria in section 26.4.2.2(c).
B) Other available types of cement such as Type III or Type I are permitted in Exposure Classes S1 or S2 if the
C3A contents are less than 8 or 5 percent, respectively.
C) The amount of the specific source of pozzolan or slag to be used shall not be less than the amount that has
been determined by service record to improve sulfate resistance when used in concrete containing Type V
cement. Alternatively, the amount of the specific source of the pozzolan or slab to be used shall not be less
than the amount tested in accordance with ASTM C1012 and meeting the criteria in section 26.4.2.2(c) of ACI
318.
D) If Type V cement is used as the sole cementitious material, the optional sulfate resistance requirement of
0.040 percent maximum expansion in ASTM C150 shall be specified.
Superficial damage may occur to the exposed surfaces of highly permeable concrete,
even though sulfate levels are relatively low. To control this risk and to resist freeze-thaw
deterioration, the water-to-cementitious materials ratio should not exceed 0.50 for concrete in
contact with soils that are likely to stay moist due to surface drainage or high-water tables.
Concrete should have a total air content of 6 percent ± 1.5 percent. We advocate damp-proofing
of all foundation walls and grade beams in contact with the subsoils.
Surface Drainage
Performance of foundations, flatwork, and pavements is influenced by changes in
subgrade moisture conditions. Carefully planned and maintained surface grading can reduce the
risk of wetting of the foundation soils and pavement subgrade. We recommend a minimum slope
of 5 percent in the first 10 feet outside foundations in landscaped areas. Backfill around
foundations should be moisture treated and compacted as described in Fill Placement. Roof
drains should be directed away from buildings. Downspout extensions and splash blocks should
be provided at discharge points, or roof drains should be connected to solid pipe discharge
systems. We do not recommend directing roof drains under buildings.
Construction Observations / Additional Services
This project will involve many activities that should be monitored during the construction
phase by a geotechnical engineering firm. To provide continuity between design and construction,
CTL|Thompson, Inc. should provide these services. Other observations are recommended to
review general conformance with design plans. If another firm is selected to provide these
services, they must accept responsibility to evaluate whether conditions exposed during
construction are consistent with findings in this report and whether design recommendations
remain appropriate. When construction schedules and quantities are defined, we can develop an
appropriate scope of services and budget for construction observation and materials testing.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
17
Geotechnical Risk
The concept of risk is an important aspect with any geotechnical evaluation, primarily
because the methods used to develop geotechnical recommendations do not comprise an exact
science. We never have complete knowledge of subsurface conditions. Our analysis must be
tempered with engineering judgment and experience. Therefore, the recommendations presented
in any geotechnical evaluation should not be considered risk-free. Our recommendations
represent our judgment of those measures that are necessary to increase the chances that the
structures and improvements will perform satisfactorily. It is critical that all recommendations in
this report are followed during construction. Owners or property managers must assume
responsibility for maintaining the structures and use appropriate practices regarding drainage and
landscaping. Improvements after construction, such as construction of additions, retaining walls,
landscaping, and exterior flatwork, should be completed in accordance with recommendations
provided in this report and may require additional soil investigation and consultation.
Limitations
This report has been prepared for the exclusive use of Volunteers of America and the
design team for the project, to provide geotechnical design and construction criteria for the
proposed project. The information, conclusions, and recommendations presented herein are
based upon consideration of many factors including, but not limited to, the type of construction
proposed, the geologic setting, and the subsurface conditions encountered. The conclusions and
recommendations contained in the report are not valid for use by others. Standards of practice
evolve in the area of geotechnical engineering. The recommendations provided are appropriate
for about three years. If the proposed construction is not constructed within about three years, we
should be contacted to determine if we should update this report.
Our borings were spaced to obtain a reasonably accurate picture of subsurface conditions
at this site. The borings are representative of conditions encountered only at the location drilled.
Subsurface variations not indicated by our borings are possible. We believe this investigation was
conducted with that level of skill and care ordinarily used by geotechnical engineers practicing
under similar conditions. No warranty, express or implied, is made.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
18
If we can be of further service in discussing the contents of this report, or in the analysis
of the influence of subsurface conditions on design of the structures or any other aspect of the
proposed construction, please call.
CTLTHOMPSON, INC.
James Pettus, E.I.T. R.B. “Chip” Leadbetter, III, PE
Staff Geotechnical Engineer Senior Engineer
10.31.2024
TH-2 TH-1
TH-3
TH-4
TH-5Ma
s
o
n
S
t
r
e
e
t
MA
N
H
A
T
T
A
N
A
V
E
HW
Y
2
8
7
HARMONY RD.
HORSETOOTH RD
MA
S
O
N
S
T
COLBOARD DR
CREGER DR
SITELEGEND:
INDICATES APPROXIMATE
LOCATION OF EXPLORATORY
BORING
TH-1
FIGURE 1
Locations of
Exploratory Borings
VICINITY MAP
(FORT COLLINS, COLORADO)
NOT TO SCALE
100'50'
APPROXIMATE
SCALE: 1" = 100'
0'
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL I T PROJECT NO. FC11376.000-120
APPENDIX A
SUMMARY LOGS OF EXPLORATORY BORINGS
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
35
40
27/12
7/12
50/4
50/2
50/2
WC=20.1DD=112SW=0.0
WC=20.1DD=112SW=0.0
TH-1
9/12
8/12
50/3
50/2
WC=18.1DD=115SW=0.3SS=0.01
WC=21.0DD=109SW=0.2
WC=18.1DD=115SW=0.3SS=0.01
WC=21.0DD=109SW=0.2
TH-2
24/12
7/12
50/4
50/2
50/1
WC=5.0-200=7
WC=23.6DD=106SW=0.5
WC=5.0-200=7
WC=23.6DD=106SW=0.5
TH-3
24/12
8/12
13/12
WC=5.7-200=12
WC=17.7DD=104SW=1.2SS=0.70
WC=5.7-200=12
WC=17.7DD=104SW=1.2SS=0.70
TH-4
14/12
9/12
7/12
WC=13.8DD=112SW=0.3SS=<0.01
WC=23.4DD=102LL=43 PI=28-200=59
WC=13.8DD=112SW=0.3SS=<0.01
WC=23.4DD=102LL=43 PI=28-200=59
TH-5 LEGEND:
CLAY, SANDY, MOIST, MEDIUM STIFF TO STIFF, GREY, BROWN (CL)
SAND, GRAVELLY, MOIST, MEDIUM DENSE, GREY, BROWN (SP)
SANDSTONE, MOIST, VERY HARD, BROWN, TAN
PRACTICAL DRILL REFUSAL.
DRIVE SAMPLE. THE SYMBOL 27/12 INDICATES 27 BLOWS OF A 140-POUND HAMMER
FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES.
ASPHALT
1.
NOTES:
3.
GRAVEL, SANDY, CLAYEY, MOIST, MEDIUM DENSE, BROWN, GREY (GP)
DE
P
T
H
-
F
E
E
T
WATER LEVEL MEASURED AT TIME OF DRILLING.
Summary Logs of
Exploratory Borings
THE BORINGS WERE DRILLED ON OCTOBER 3, 2024 USING 4-INCH DIAMETER
CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG.
FIGURE A- 1
WC
DD
SW
-200
LL
PI
SS
-
-
-
-
-
-
-
THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN
THIS REPORT.
ROADBASE
INDICATES MOISTURE CONTENT (%).
INDICATES DRY DENSITY (PCF).
INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%).
INDICATES PASSING NO. 200 SIEVE (%).
INDICATES LIQUID LIMIT.
INDICATES PLASTICITY INDEX.
INDICATES SOLUBLE SULFATE CONTENT (%).
2.
DE
P
T
H
-
F
E
E
T
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
APPENDIX B
RESULTS OF LABORATORY TESTING
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=112 PCF
From TH - 1 AT 9 FEET MOISTURE CONTENT=20.1 %
APPLIED PRESSURE -KSF
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
Swell Consolidation
Test Results FIGURE B-1
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
GTTINO WET DUE TNEMEVOMON
0.1 1.0 10 100
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=115 PCF
From TH - 2 AT 2 FEET MOISTURE CONTENT=18.1 %
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=109 PCF
From TH - 2 AT 9 FEET MOISTURE CONTENT=21.0 %
APPLIED PRESSURE -KSF
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
Swell Consolidation
FIGURE B-2
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
-4
-3
-2
-1
0
1
2
3
TNTAONSER CION UNDSNAPXE
GINETTTO WRE DUESSUERP
0.1 10 1001.0
0.1 1.0 10 100APPLIED PRESSURE -KSF
-4
-3
-2
-1
0
1
2
3
TNSTAONER CION UNDANSPXE
GINTETWTORE DUESSUERP
Test ResultsVOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=106 PCF
From TH - 3 AT 9 FEET MOISTURE CONTENT=23.6 %
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=104 PCF
From TH - 4 AT 4 FEET MOISTURE CONTENT=17.7 %
APPLIED PRESSURE -KSF
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
Swell Consolidation
FIGURE B-3
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
-4
-3
-2
-1
0
1
2
3
TNTAONSER CION UNDSNAPXE
GINETTTO WRE DUESSUERP
0.1 10 1001.0
0.1 1.0 10 100APPLIED PRESSURE -KSF
-4
-3
-2
-1
0
1
2
3
TNSTAONER CION UNDANSPXE
GINTETWTORE DUESSUERP
Test ResultsVOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=112 PCF
From TH - 5 AT 2 FEET MOISTURE CONTENT=13.8 %
APPLIED PRESSURE -KSF
CO
M
P
R
E
S
S
I
O
N
%
E
X
P
A
N
S
I
O
N
Swell Consolidation
Test Results FIGURE B-4
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
TNSTANDER CONUNIOSNPAEX
TINGE TO WETUDERUSESPR
0.1 1.0 10 100
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
Sample of SAND, GRAVELLY (SP)GRAVEL 43 %SAND 50 %
From TH - 3 AT 4 FEET SILT & CLAY 7 %LIQUID LIMIT %
PLASTICITY INDEX %
Sample of GRAVEL, SANDY (GP)GRAVEL 54 %SAND 34 %
From TH - 4 AT 2 FEET SILT & CLAY 12 %LIQUID LIMIT %
PLASTICITY INDEX %
FIGURE B-5
Gradation
Test Results
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR.7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PE
R
C
E
N
T
P
A
S
S
I
N
G
0
10
20
30
50
60
70
80
90
100
PE
R
C
E
N
T
R
E
T
A
I
N
E
D
40
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR.7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PE
R
C
E
N
T
P
A
S
S
I
N
G
PERCEN
T
RETAINED
0
10
20
30
40
50
60
70
80
90
100
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL | T PROJECT NO. FC11376.000-120
PASSING WATER-
MOISTURE DRY LIQUID PLASTICITY APPLIED NO. 200 SOLUBLE
DEPTH CONTENT DENSITY LIMIT INDEX SWELL*PRESSURE SIEVE SULFATES
LOT BLOCK (FEET)(%)(PCF)(%)(PSF)(%)(%)DESCRIPTION
S 1 0-5 31 16 CLAY, SANDY (CL)
TH 1 9 20.1 112 0.0 1,100 CLAY, SANDY (CL)
TH 2 2 18.1 115 0.3 500 0.01 CLAY, SANDY (CL)
TH 2 9 21.0 109 0.2 1,100 CLAY, SANDY (CL)
TH 3 4 5.0 7 SAND, GRAVELLY (SP)
TH 3 9 23.6 106 0.5 1,100 CLAY, SANDY (CL)
TH 4 2 5.7 12 GRAVEL, SANDY (GP)
TH 4 4 17.7 104 1.2 150 0.70 CLAY, SANDY (CL)
TH 5 2 13.8 112 0.3 150 <0.01 CLAY, SANDY (CL)
TH 5 4 23.4 102 43 28 59 CLAY, SANDY (CL)
SWELL TEST RESULTS*
TABLE B-I
SUMMARY OF LABORATORY TESTING
ATTERBERG LIMITS
Page 1 of 1
* NEGATIVE VALUE INDICATES COMPRESSION.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL|T PROJECT NO. FC11376.000-120
Specification Title:Onsite/Native (Clay or Silt)
ASTM D75 / AASHTO T2 / CDOT CP30
Material Description:
Sample Location:
Brown, sandy CLAY
FC11376, S-1
R-Value (ASTM D2844)
66
49
31
0100200300400500600700
Exudation Pressure (psi)
0
20
40
60
80
100
R-
V
a
l
u
e
Test
Point
Moisture
(%)
Exudation
Pressure
(psi)
R-Value
1 8.3 445 66
2 10.1 300 49
3 12.2 162 31
R- Value at 300 psi
Exudation Pressure
49
Remarks:
8.3 10.1 12.2
0100200300400500600700
Exudation Pressure (psi)
0
10
20
30
40
50
Mo
i
s
t
u
r
e
C
o
n
t
e
n
t
(
%
)
Sampling Method:
CTL Thompson
400 North Link Lane
Fort Collins, CO 80524
Craig Ellis
2023-2024 Miscellaneous Services (CTL Thompson)
Client:
Report Date:
Soil/Aggregate Laboratory Summary
23-0695.SoilSampling.0014; ver: 2Oct 24, 2024 Work Order No.:
Work Order Date:Oct 16, 2024 Reviewed by:Aaron Klingsmith
Results apply only to the specific items and locations referenced and at the time of testing, observations or special inspections. Unless noted otherwise, samples were received in adequate condition.
This report should not be reproduced, except in full, without the written permission of GROUND Engineering Consultants, Inc.
41 Inverness Drive East, Englewood, Colorado www.groundeng.com 303-289-1989
Englewood | Commerce City | Loveland | Granby | Gypsum | Colorado Springs
APPENDIX C
SAMPLE SITE GRADING SPECIFICATIONS
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
C-1
SAMPLE SITE GRADING SPECIFICATIONS
1. DESCRIPTION
This item shall consist of the excavation, transportation, placement, and compaction of
materials from locations indicated on the plans, or staked by the Engineer, as necessary
to achieve building site elevations.
2. GENERAL
The Geotechnical Engineer shall be the Owner's representative. The Geotechnical
Engineer shall approve fill materials, method of placement, moisture contents and percent
compaction, and shall give written approval of the completed fill.
3. CLEARING JOB SITE
The Contractor shall remove all trees, brush and rubbish before excavation or fill
placement is begun. The Contractor shall dispose of the cleared material to provide the
Owner with a clean, neat appearing job site. Cleared material shall not be placed in areas
to receive fill or where the material will support structures of any kind.
4. SCARIFYING AREA TO BE FILLED
All topsoil and vegetable matter shall be removed from the ground surface upon which fill
is to be placed. The surface shall then be plowed or scarified to a depth of 8 inches until
the surface is free from ruts, hummocks, or other uneven features, which would prevent
uniform compaction by the equipment to be used.
5. COMPACTING AREA TO BE FILLED
After the foundation for the fill has been cleared and scarified, it shall be disked or bladed
until it is free from large clods, brought to the proper moisture content and compacted to
not less than 95 percent of maximum dry density as determined in accordance with ASTM
D 698 or AASHTO T 99.
6. FILL MATERIALS
On-site materials classifying as CL, SC, SM, SW, SP, GP, GC, and GM are acceptable.
Fill soils shall be free from organic matter, debris, or other deleterious substances, and
shall not contain rocks or lumps having a diameter greater than three (3) inches. Fill
materials shall be obtained from the existing fill and other approved sources.
7. MOISTURE CONTENT
Fill materials shall be moisture treated. Clay soils placed below the building envelope
should be moisture-treated to between optimum and 3 percent above optimum moisture
content as determined from Standard Proctor compaction tests. Clay soil placed exterior
to the building should be moisture treated between optimum and 3 percent above optimum
moisture content. Sand soils can be moistened to within 2 percent of optimum moisture
content. Sufficient laboratory compaction tests shall be performed to determine the
optimum moisture content for the various soils encountered in borrow areas.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
C-2
The Contractor may be required to add moisture to the excavation materials in the borrow
area if, in the opinion of the Geotechnical Engineer, it is not possible to obtain uniform
moisture content by adding water on the fill surface. The Contractor may be required to
rake or disk the fill soils to provide uniform moisture content through the soils.
The application of water to embankment materials shall be made with any type of watering
equipment approved by the Geotechnical Engineer, which will give the desired results.
Water jets from the spreader shall not be directed at the embankment with such force that
fill materials are washed out.
Should too much water be added to any part of the fill, such that the material is too wet to
permit the desired compaction from being obtained, rolling and all work on that section of
the fill shall be delayed until the material has been allowed to dry to the required moisture
content. The Contractor will be permitted to rework wet material in an approved manner
to hasten its drying.
8. COMPACTION OF FILL AREAS
Selected fill material shall be placed and mixed in evenly spread layers. After each fill
layer has been placed, it shall be uniformly compacted to not less than the specified
percentage of maximum dry density. Fill materials shall be placed such that the thickness
of loose material does not exceed 8 inches and the compacted lift thickness does not
exceed 6 inches. Fill placed under foundations, exterior flatwork and pavements should
be compacted to a minimum of 95 percent of maximum standard Proctor dry density
(ASTM D698).
Compaction, as specified above, shall be obtained by the use of sheepsfoot rollers,
multiple-wheel pneumatic-tired rollers, or other equipment approved by the Engineer.
Compaction shall be accomplished while the fill material is at the specified moisture
content. Compaction of each layer shall be continuous over the entire area. Compaction
equipment shall make sufficient trips to ensure that the required dry density is obtained.
9. COMPACTION OF SLOPES
Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment.
Compaction operations shall be continued until slopes are stable, but not too dense for
planting, and there is no appreciable amount of loose soil on the slopes. Compaction of
slopes may be done progressively in increments of three to five feet (3' to 5') in height or
after the fill is brought to its total height. Permanent fill slopes shall not exceed 3:1
(horizontal to vertical).
10. DENSITY TESTS
Field density tests shall be made by the Geotechnical Engineer at locations and depths of
his choosing. Where sheepsfoot rollers are used, the soil may be disturbed to a depth of
several inches. Density tests shall be taken in compacted material below the disturbed
surface. When density tests indicate that the dry density or moisture content of any layer
of fill or portion thereof is below that required, the particular layer or portion shall be
reworked until the required dry density or moisture content has been achieved.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
C-3
11. SEASONAL LIMITS
No fill material shall be placed, spread, or rolled while it is frozen, thawing, or during
unfavorable weather conditions. When work is interrupted by heavy precipitation, fill
operations shall not be resumed until the Geotechnical Engineer indicates that the
moisture content and dry density of previously placed materials are as specified.
12. NOTICE REGARDING START OF GRADING
The contractor shall submit notification to the Geotechnical Engineer and Owner advising
them of the start of grading operations at least three (3) days in advance of the starting
date. Notification shall also be submitted at least 3 days in advance of any resumption
dates when grading operations have been stopped for any reason other than adverse
weather conditions.
13. REPORTING OF FIELD DENSITY TESTS
Density tests performed by the Geotechnical Engineer, as specified under "Density Tests"
above, shall be submitted progressively to the Owner. Dry density, moisture content and
percent compaction shall be reported for each test taken.
APPENDIX D
PAVEMENT CONSTRUCTION RECOMMENDATIONS
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
D-1
SUBGRADE PREPARATION
Moisture Treated Subgrade (MTS)
1. The subgrade should be stripped of organic matter, scarified, moisture
treated and compacted to the specifications stated below in Item 2. The
compacted subgrade should extend at least 3 feet beyond the edge of the
pavement where no edge support, such as curb and gutter, are to be
constructed.
2. Sandy and gravelly soils (A-1-a, A-1-b, A-3, A-2-4, A-2-5, A-2-6, A-2-7)
should be moisture conditioned near optimum moisture content and
compacted to at least 95 percent of standard Proctor maximum dry density
(ASTM D 698, AASHTO T 99). Clayey soils (A-6, A-7-5, A-7-6) should be
moisture conditioned between optimum and 3 percent above optimum
moisture content and compacted to at least 95 percent of standard Proctor
maximum dry density (ASTM D 698, AASHTO T 99).
3. Utility trenches and all subsequently placed fill should be properly
compacted and tested prior to paving. As a minimum, fill should be
compacted to 95 percent of standard Proctor maximum dry density.
4. Final grading of the subgrade should be carefully controlled so the design
cross-slope is maintained and low spots in the subgrade that could trap
water are eliminated.
5. Once final subgrade elevation has been compacted and tested to
compliance and shaped to the required cross-section, the area should be
proof-rolled using a minimum axle load of 18 kips per axle. The proof-roll
should be performed while moisture contents of the subgrade are still within
the recommended limits. Drying of the subgrade prior to proof-roll or paving
should be avoided.
6. Areas that are observed by the Engineer that have soft spots in the
subgrade, or where deflection is not uniform of soft or wet subgrade shall
be ripped, scarified, dried, or wetted as necessary and recompacted to the
requirements for the density and moisture. As an alternative, those areas
may be over-excavated and replaced with properly compacted structural
backfill. Where extensively soft, yielding subgrade is encountered; we
recommend a representative of our office observe the excavation.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
D-2
PAVEMENT MATERIALS AND CONSTRUCTION
Aggregate Base Course (ABC)
1. A Class 5 or 6 Colorado Department of Transportation (CDOT) specified
ABC should be used. A reclaimed concrete pavement (RCP) alternative
will not be acceptable, due to high sulfate contents in the subgrade soils.
2. Bases should have a minimum Hveem stabilometer value of 72, or greater.
ABC, RAP, or blended materials must be moisture stable. The change in
R-value from 300-psi to 100-psi exudation pressure should be 12 points or
less.
3. ABC base should be placed in thin lifts not to exceed 6 inches and moisture
treated to near optimum moisture content. Bases should be moisture
treated to near optimum moisture content and compacted to at least 95
percent of standard Proctor maximum dry density (ASTM D 698, AASHTO
T 99).
4. Placement and compaction of ABC should be observed and tested by a
representative of our firm. Placement should not commence until the
underlying subgrade is properly prepared and tested.
Hot Mix Asphalt (HMA)
1. HMA should be composed of a mixture of aggregate, filler, hydrated lime,
and asphalt cement. Some mixes may require polymer modified asphalt
cement or make use of up to 20 percent reclaimed asphalt pavement
(RAP). A job mix design is recommended and periodic checks on the job
site should be made to verify compliance with specifications.
2. HMA should be relatively impermeable to moisture and should be designed
with crushed aggregates that have a minimum of 80 percent of the
aggregate retained on the No. 4 sieve with two mechanically fractured
faces.
3. Gradations that approach the maximum density line (within 5 percent
between the No. 4 and 50 sieves) should be avoided. A gradation with a
nominal maximum size of 1 or 2 inches developed on the fine side of the
maximum density line should be used.
4. Total void content, voids in the mineral aggregate (VMA) and voids filled
should be considered in the selection of the optimum asphalt cement
content. The optimum asphalt content should be selected at a total air void
content of approximately 4 percent. The mixture should have a minimum
VMA of 14 percent and between 65 percent and 80 percent of voids filled.
5. Asphalt cement should meet the requirements of the Superpave
Performance Graded (PG) Binders. The minimum performing asphalt
cement should conform to the requirements of the governing agency.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
D-3
6. Hydrated lime should be added at the rate of 1 percent by dry weight of the
aggregate and should be included in the amount passing the No. 200 sieve.
Hydrated lime for aggregate pretreatment should conform to the
requirements of ASTM C 207, Type N.
7. Paving should be performed on properly prepared, unfrozen surfaces that
are free of water, snow, and ice. Paving should only be performed when
both air and surface temperatures equal, or exceed, the temperatures
specified in Table 401-3 of the 2006 Colorado Department of
Transportation Standard Specifications for Road and Bridge Construction.
8. HMA should not be placed at a temperature lower than 245oF for mixes
containing PG 64-22 asphalt, and 290oF for mixes containing polymer-
modified asphalt. The breakdown compaction should be completed before
the HMA temperature drops 20oF.
9. Wearing surface course shall be Grading S or SX for residential roadway
classifications and Grading S for collector, arterial, industrial, and
commercial roadway classifications.
10. The minimum/maximum lift thicknesses for Grade SX shall be 1½
inches/2½ inches. The minimum/maximum lift thicknesses for Grade S
shall be 2 inches/3½ inches. The minimum/maximum lift thicknesses for
Grade SG shall be 3 inches/5 inches.
11. Joints should be staggered. No joints should be placed within wheel paths.
12. HMA should be compacted to between 92 and 96 percent of Maximum
Theoretical Density. The surface shall be sealed with a finish roller prior to
the mix cooling to 185oF.
13. Placement and compaction of HMA should be observed and tested by a
representative of our firm. Placement should not commence until approval
of the proof rolling as discussed in the Subgrade Preparation section of this
report. Subbase, base course or initial pavement course shall be placed
within 48 hours of approval of the proof rolling. If the Contractor fails to
place the subbase, base course or initial pavement course within 48 hours
or the condition of the subgrade changes due to weather or other
conditions, proof rolling and correction shall be performed again.
Portland Cement Concrete (PCC)
1. Portland cement concrete should consist of Class P of the 2021 CDOT -
Standard Specifications for Road and Bridge Construction specifications
for normal placement. PCC should have a minimum compressive strength
of 4,500 psi at 28 days and a minimum modulus of rupture (flexural
strength) of 600 psi. Job mix designs are recommended and periodic
checks on the job site should be made to verify compliance with
specifications.
2. Portland cement should be Type V “high sulfate” and should conform to
ASTM C150/C150M.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
D-4
3. Portland cement concrete should not be placed when the subgrade or air
temperature is below 40°F.
4. Concrete should not be placed during warm weather if the mixed concrete
has a temperature of 90°F, or higher.
5. Mixed concrete temperature placed during cold weather should have a
temperature between 50°F and 90°F.
6. Free water should not be finished into the concrete surface. Atomizing
nozzle pressure sprayers for applying finishing compounds are
recommended whenever the concrete surface becomes difficult to finish.
7. Curing of the Portland cement concrete should be accomplished by the use
of a curing compound. The curing compound should be applied in
accordance with manufacturer recommendations.
8. Curing procedures should be implemented, as necessary, to protect the
pavement against moisture loss, rapid temperature change, freezing, and
mechanical injury.
9. Construction joints, including longitudinal joints and transverse joints,
should be formed during construction, or sawed after the concrete has
begun to set, but prior to uncontrolled cracking.
10. All joints should be properly sealed using a rod back-up and approved
epoxy sealant.
11. Traffic should not be allowed on the pavement until it has properly cured
and achieved at least 80 percent of the design strength, with saw joints
already cut.
12. Placement of Portland cement concrete should be observed and tested by
a representative of our firm. Placement should not commence until the
subgrade is properly prepared and tested.
APPENDIX E
PAVEMENT MAINTENANCE PROGRAM
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
E-1
MAINTENANCE RECOMMENDATIONS FOR FLEXIBLE PAVEMENTS
A primary cause for deterioration of pavements is oxidative aging resulting in brittle
pavements. Tire loads from traffic are necessary to "work" or knead the asphalt concrete to keep
it flexible and rejuvenated. Preventive maintenance treatments will typically preserve the original
or existing pavement by providing a protective seal or rejuvenating the asphalt binder to extend
pavement life.
1. Annual Preventive Maintenance
a. Visual pavement evaluations should be performed each spring or fall.
b. Reports documenting the progress of distress should be kept current to provide
information on effective times to apply preventive maintenance treatments.
c. Crack sealing should be performed annually as new cracks appear.
2. 3 to 5 Year Preventive Maintenance
a. The owner should budget for a preventive treatment at approximate intervals
of 3 to 5 years to reduce oxidative embrittlement problems.
b. Typical preventive maintenance treatments include chip seals, fog seals, slurry
seals and crack sealing.
3. 5 to 10 Year Corrective Maintenance
a. Corrective maintenance may be necessary, as dictated by the pavement
condition, to correct rutting, cracking, and structurally failed areas.
b. Corrective maintenance may include full depth patching, milling and overlays.
c. In order for the pavement to provide a 20-year service life, at least one major
corrective overlay should be expected.
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTLT PROJECT NO. FC11376.000-120
E-2
MAINTENANCE RECOMMENDATIONS FOR RIGID PAVEMENTS
High traffic volumes create pavement rutting and smooth polished surfaces. Preventive
maintenance treatments will typically preserve the original or existing pavement by providing a
protective seal and improving skid resistance through a new wearing course.
1. Annual Preventive Maintenance
a. Visual pavement evaluations should be performed each spring or fall.
b. Reports documenting the progress of distress should be kept current to provide
information of effective times to apply preventive maintenance.
c. Crack sealing should be performed annually as new cracks appear.
2. 4 to 8 Year Preventive Maintenance
a. The owner should budget for a preventive treatment at approximate intervals
of 4 to 8 years to reduce joint deterioration.
b. Typical preventive maintenance for rigid pavements includes patching, crack
sealing and joint cleaning and sealing.
c. Where joint sealants are missing or distressed, resealing is mandatory.
3. 15 to 20 Year Corrective Maintenance
a. Corrective maintenance for rigid pavements includes patching and slab
replacement to correct subgrade failures, edge damage, and material failure.
b. Asphalt concrete overlays may be required at 15 to 20 year intervals to improve
the structural capacity of the pavement.
APPENDIX F
PAVEMENT DESIGN CALCULATIONS
Roadway(s):
Reliability 75 %
Standard Deviation 0.44
Initial Serviceability 4.5
Terminal Serviceability 2
Resilient Modulus 10,039 psi
Design ESALs 36,500
Layers
Structural
Coefficient Drainage Thickness SN
HMA 0.44 1 4 1.76
ABC 0.11 1.05 6 0.69
CSS 0.1 1 0 0.00
SUM 2.45
FIGURE F-1
Design Structural Number
1.58
Parking Lot
Flexible Structural Design
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL|T PROJECT NO. FC11376.000-120
Roadway(s):
Reliability 75 %
Standard Deviation 0.44
Initial Serviceability 4.5
Terminal Serviceability 2
Resilient Modulus 10,039 psi
Design ESALs 365,000
Layers
Structural
Coefficient Drainage Thickness SN
HMA 0.44 1 4 1.76
ABC 0.11 1.05 6 0.69
CSS 0.1 1 0 0.00
SUM 2.45
FIGURE F-2
Design Structural Number
2.30
Access Drives
Flexible Structural Design
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL|T PROJECT NO. FC11376.000-120
CDOT (MODIFIED AASHTO) RIGID PAVEMENT DESIGN
Project:VOA MASON PLACE II
What is the Design ESAL ?36,500
What is the Reliability ?90
What is the Serviceability Loss ?2.5
What is the Concrete Elastic Modulus ?3,400,000 psi
What is the Concrete Modulus of Rupture ?600 psi
What is the Drainage Factor ?1.0
What is the Standard Deviation ?0.34
What is the Load Transfer Coefficient ?4.2
What is the R-value ?49
Computed Resilient Modulus =10,039 psi
psiIf R is not available, Input Resilient Modulus =
DESIGN RESILIENT MODULUS = 10,039 psi
5Design Concrete Slab Thickness is inches
FIGURE F-3
PARKING LOT
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL|T PROJECT NO. FC11376.000-120
CDOT (MODIFIED AASHTO) RIGID PAVEMENT DESIGN
Project:VOA MASON PLACE II
What is the Design ESAL ?365,000
What is the Reliability ?90
What is the Serviceability Loss ?2.5
What is the Concrete Elastic Modulus ?3,400,000 psi
What is the Concrete Modulus of Rupture ?600 psi
What is the Drainage Factor ?1.0
What is the Standard Deviation ?0.34
What is the Load Transfer Coefficient ?4.2
What is the R-value ?49
Computed Resilient Modulus =10,039 psi
psiIf R is not available, Input Resilient Modulus =
DESIGN RESILIENT MODULUS = 10,039 psi
7Design Concrete Slab Thickness is inches
FIGURE F-4
ACCESS DRIVES
VOLUNTEERS OF AMERICA
VOA MASON PLACE II, FORT COLLINS
CTL|T PROJECT NO. FC11376.000-120