HomeMy WebLinkAboutReports - Soils - 10/31/2024
Report Cover Page
Prepared for:
Touchmark Development and Construction
5150 Southwest Griffith Drive
Beaverton, Oregon 97005
Touchmark Development
Retirement Homes
Preliminary Geotechnical Engineering Report
Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
1901 Sharp Point Drive, Suite C
Fort Collins, Colorado 80525
P (970) 484-0359
Terracon.com
Facilities | Environmental | Geotechnical | Materials
Report Cover Letter to Sign
October 31, 2024
Touchmark Development and Construction
5150 Southwest Griffith Drive
Beaverton, Oregon 97005
Attn: Ryan Benson
P: (503) 646-5186
E: ryan.benson@touchmark.com
Re: Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes
4710 Cinquefoil Lane
Fort Collins, Colorado
Terracon Project No. 20245032
Dear Mr. Benson:
We have completed the scope of Preliminary Geotechnical Engineering Report services
for the project referenced above in general accordance with Terracon Proposal No.
P20245032 (revised) dated July 23, 2024. This report presents the findings of the
preliminary subsurface exploration and provides preliminary geotechnical
recommendations concerning earthwork and the design and construction of foundations,
floor systems and pavements for the proposed project.
We appreciate the opportunity to be of service to you on this project. Materials testing
and construction observation services are provided by Terracon as well. We would be
pleased to discuss these services with you. If you have any questions concerning this
report or if we may be of further service, please contact us.
Sincerely,
Terracon
Andrea L. Wahls Eric D. Bernhardt, P.E.
Field Engineer Regional Geotechnical Manager
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials i
Table of Contents
Report Summary .............................................................................................. i
Introduction .................................................................................................... 1
Project Description .......................................................................................... 1
Site Conditions ................................................................................................ 4
Geotechnical Characterization ......................................................................... 4
Groundwater Conditions ............................................................................. 5
Seismic Site Class ............................................................................................ 5
Corrosivity ...................................................................................................... 6
Geotechnical Overview .................................................................................... 7
Expansive Soils and Bedrock....................................................................... 7
Low Relative Density Soils .......................................................................... 7
Preliminary Foundation and Floor System Recommendations ........................... 8
Earthwork ....................................................................................................... 8
Site Preparation........................................................................................ 9
Excavation ............................................................................................... 9
Subgrade Preparation ............................................................................... 10
Subgrade Stabilization .............................................................................. 10
Fill Material Types .................................................................................... 12
Fill Placement and Compaction Requirements ............................................... 12
Utility Trench Backfill ............................................................................... 13
Grading and Drainage ............................................................................... 14
Exterior Slab Design and Construction ......................................................... 15
Earthwork Construction Considerations ....................................................... 15
Construction Observation and Testing ......................................................... 16
Foundations .................................................................................................. 16
Shallow Foundations – Preliminary Design Recommendations ......................... 16
Drilled Piers - Preliminary Design Recommendations ...................................... 17
Floor Slabs .................................................................................................... 18
Floor Slab Preliminary Design Recommendations .......................................... 18
Floor Slab Construction Considerations ........................................................ 19
Below-Grade Structures................................................................................. 20
Lateral Earth Pressures ................................................................................. 20
Preliminary Design Parameters .................................................................. 20
Pavements .................................................................................................... 22
General Pavement Comments .................................................................... 22
Pavement Subgrade Preparation ................................................................ 22
Pavement Preliminary Design Recommendations ........................................... 23
Pavement Construction Considerations ........................................................ 26
Pavement Maintenance ............................................................................. 26
General Comments ........................................................................................ 26
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials ii
Figures
GeoModel
Attachments
Exploration and Testing Procedures
Site Location and Exploration Plans
Exploration and Laboratory Test Results
Supporting Information
Note: This report was originally delivered in a web-based format. Blue Bold text in the
report indicates a referenced section heading. The PDF version also includes hyperlinks
which direct the reader to that section and clicking on the logo will bring you
back to this page. For more interactive features, please view your project online at
client.terracon.com.
Refer to each individual Attachment for a listing of contents.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials i
Report Summary
Topic 1 Overview Statement 2
Project
Description
A preliminary geotechnical exploration has been performed for the
proposed retirement community to be constructed at 4710
Cinquefoil Lane in Fort Collins, Colorado. Five borings were
performed to depths of approximately 24.3 to 49.3 feet below
existing grades.
Geotechnical
Characterization
Subsurface conditions encountered in our exploratory borings
generally consisted of about 19 to 24 feet of clay with varying
amounts of sand and clayey sand over about 5 feet of poorly
graded sand with varying amounts of clay and gravel. Claystone
bedrock and/or clayey sandstone bedrock were encountered below
the overburden soils in most of the borings at depths of
approximately 19 to 34 feet below existing site grades.
Groundwater was observed during our exploration at depths of
about 22 to 28 feet below existing site grades.
Earthwork
On-site soils typically appear suitable for use as general
engineered fill and backfill on the site provided they are placed
and compacted as described in this report. Import materials (if
needed) should be evaluated and approved by Terracon prior to
delivery to the site.
Foundations
The final building site locations and site grading will likely dictate
the ultimate selection of the foundation system for the proposed
project. Based on our understanding of the proposed project, we
believe the proposed lightly to moderately loaded structures can
be constructed on a spread footing foundation system, provided
the soils are over-excavated to a depth of 1 to 3 feet below the
bottom of footings and replaced with moisture conditioned,
properly compacted fill to reduce the risk for settlement as well as
reduce swell potential.
For heavily-loaded structures, we recommend supporting these
buildings on deep foundations consisting of drilled piers. The
drilled piers should be bottomed into the hard to very hard
bedrock encountered below the site to develop the capacity of
each pier.
Below-Grade
Structures
We understand a below-grade parking structure is planned as part
of the new development. We anticipate the below-grade
parking structure will be constructed of reinforced concrete.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials ii
Topic 1 Overview Statement 2
Pavements
With subgrade prepared as noted in Earthwork.
Recommended pavement thickness includes 4 inches of asphalt
over 6 inches of aggregate base course in light-duty parking
areas, and 6 inches of asphalt over 6 inches of aggregate base
course in main drive lanes and loading areas. Thicker pavement
sections may be needed for these sites if comparatively heavy
traffic loads are anticipated.
General
Comments
This section contains important information about the limitations
of this geotechnical engineering report.
1. If the reader is reviewing this report as a pdf, the topics above can be used to
access the appropriate section of the report by simply clicking on the topic
itself.
2. This summary is for convenience only. It should be used in conjunction with the
entire report for design purposes.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 1
Introduction
This report presents the results of our preliminary subsurface exploration and
geotechnical engineering services performed for the proposed retirement community to
be located at 4710 Cinquefoil Lane in Fort Collins, Colorado. The purpose of these
services was to provide information and preliminary geotechnical engineering
recommendations relative to:
■ Subsurface soil and rock conditions
■ Groundwater conditions
■ Preliminary seismic site classification per IBC
■ Preliminary site preparation and earthwork
■ Preliminary foundation design and construction
■ Preliminary floor system design and construction
■ Preliminary lateral earth pressures
■ Preliminary pavement design and construction
The preliminary geotechnical engineering Scope of Services for this project included the
advancement of test borings, laboratory testing, engineering analysis, and preparation
of this report.
Drawings showing the site and boring locations are shown in the Site Location and
Exploration Plan section of this report. The results of the laboratory testing performed
on soil and bedrock samples obtained from the site during our field exploration are
included on the boring logs and as separate graphs in the Exploration Results section.
Project Description
Our initial understanding of the project was provided in our proposal and was discussed
during project planning. A period of collaboration has transpired since the project was
initiated, and our final understanding of the project conditions is as follows:
Item Description
Information
Provided
The project information described below is based on the
following:
■ Email and phone correspondence with Ryan Benson
■ Tract K_Grading Plan_Detention Pond prepared by
Boulder Associates Architects dated August 25, 2016
■ TFCO Geotech Boring Map prepared by Ripley Design
dated July 10, 2024
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 2
Item Description
Project
Description
We understand Touchmark seeks to identify preliminary
subsurface conditions and foundation requirements to construct
a proposed retirement community. The approximately 14-acre
site will include an apartment building (4-story or 5-story) with
an underground parking structure, a secondary apartment
building (2-story or 3-story), single-family units and duplexes
around the main buildings and a common area/amenity building
(1-story or 2-story).
The apartment building (4-story or 5-story) is estimated to be
approximately 60,000 square feet and will include around 100
units. The underground parking structure is estimated to be
approximately 40,000 square feet.
The secondary apartment building (2-story or 3-story) is
estimated to be approximately 20,000 square feet and will
include around 50 to 80 units.
The single-family cottages and duplexes will be approximately
2,000 to 3,000 square feet each. There are 40 to 50 units
planned.
Proposed
Construction
Terracon’s proposed scope of services presented in this report
has been provided under the belief that this site will be used as
apartments. As such, Terracon would like to inform the Client
that if this apartment project is converted at any time to
another purpose such as condominiums, the Client understands
the services Terracon is proposing are not applicable for a
condominium project and that a separate consultant will need to
be retained for such services. Terracon will have no liability for
any such unintended use of our services and Client agrees to
defend, indemnify, and hold harmless Terracon for any such
unintended usage.
Finished Floor
Elevation
Plans were not provided at the time of this report. We anticipate
the finished floor elevation for the proposed buildings is not
more than 5 feet from existing grade. Impacts of proposed site
grading should be evaluated during a design-level geotechnical
study to be complete once project details are better understood.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 3
Item Description
Maximum Loads
(assumed)
Anticipated structural loads were not provided. In the absence
of information provided by the design team, we used the
following loads in our engineering analysis based on our
experience with similar projects.
Main building (4-story or 5-story):
■ Columns: 600 to 700 kips
■ Walls: 9 to 10 kips per linear foot (klf)
Secondary building (2-story or 3-story):
■ Columns: 200 to 500 kips
■ Walls: 4 to 9 kips per linear foot (klf)
Single family cottages and duplexes:
■ Columns: 20 to 100 kips
■ Walls: 1 to 5 kips per linear foot
Grading/Slopes
Grading plans were not provided to Terracon at the time of this
proposal. We anticipate minor cuts and fills on the order of 5
feet or less will be required to achieve proposed grades. We also
anticipate deeper cuts and fills will be required for utility
construction.
Below-Grade
Structures
A below-grade parking level is planned for the proposed
development. We anticipate elevator pits will be incorporated
into the design of all muti-story buildings.
Pavements
New pavements are planned as part of this project and will
likely consist of flexible asphalt and rigid concrete pavement.
Traffic loads were not available at the time of this proposal. We
will assume traffic loads consistent with that of similar use. Unless
information is provided prior to the report, we assume the traffic
classification will consist of:
■ Automobile Parking: Parking stalls for passenger vehicles
and pickup trucks
■ Main Traffic Corridors: Traffic consisting of passenger
vehicles, single-unit delivery trucks and garbage trucks
■ The pavement design period is 20 years.
Building Code 2021 International Building Code (IBC)
Terracon should be notified if any of the above information is inconsistent with the
planned construction, especially the grading limits, as modifications to our
recommendations may be necessary.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 4
Site Conditions
The following description of site conditions is derived from our site visit in association
with the field exploration and our review of publicly available geologic and topographic
maps.
Item Description
Parcel
Information
The approximately 14-acre project is located at 4710 Cinquefoil
Lane in Fort Collins, Colorado.
Latitude/Longitude of center of property (approximate):
(40.52063, -105.00598) (See Exhibit D)
See Site Location
Existing
Improvements The project site is on a vacant lot.
Current Ground
Cover The site is covered in native grasses and vegetation.
Existing
Topography
Based on our site visit and interpolation from a publicly
available USGS topographic map, approximate ground surface
elevations at the boring locations range from about El. ±4,900
feet to El. ±4,907 feet AMSL (above mean sea level).
Geotechnical Characterization
We have developed a general characterization of the subsurface conditions based upon
our review of the subsurface exploration, laboratory data, geologic setting and our
understanding of the project. This characterization, termed GeoModel, forms the basis of
our geotechnical calculations and evaluation of the site. Conditions observed at each
exploration point are indicated on the individual logs. The individual logs can be found in
the Exploration Results and the GeoModel can be found in the Figures attachment of
this report.
As part of our analyses, we identified the following model layers within the subsurface
profile. For a more detailed view of the model layer depths at each boring location, refer
to the GeoModel.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 5
Model
Layer Layer Name General Description
1 Lean Clay
Lean clay with varying amounts of sand and gravel;
medium stiff to very stiff, light brown to brown, tan,
red brown, light gray, gray brown
2 Sand
Poorly graded sand with varying amounts of clay and
gravel, loose to very dense, light brown to brown, red
brown, gray
3 Claystone
Bedrock
Claystone bedrock; hard to very hard, gray brown to
dark gray with orange brown and red orange
4 Sandstone
Bedrock
Clayey sandstone bedrock; very hard, brown, gray,
orange brown to dark gray
Groundwater Conditions
The boreholes were observed while drilling and shortly after completion for the presence
and level of groundwater. The water levels observed in the boreholes are noted on the
attached boring logs, and are summarized below:
Boring
Number
Depth to
Groundwater While
Drilling, ft.
Depth to
Groundwater After
Drilling, ft.
Elevation of
Groundwater After
Drilling, ft.1
B-1 28 22 4,882.0
B-2 27 23.6 4,881.4
B-3 Not encountered Backfilled after drilling
B-4 Not encountered Backfilled after drilling
B-5 Not encountered Backfilled after drilling
1. Elevation of groundwater is based on the ground surface elevations, interpolated from the
USGS National Viewer.
Groundwater conditions may change because of seasonal variations in rainfall, runoff,
and other conditions not apparent at the time of drilling. Long-term groundwater
monitoring was outside the scope of services for this project.
Seismic Site Class
The seismic design requirements for buildings and other structures are based on Seismic
Design Category. Site Classification is required to determine the Seismic Design
Category for a structure. The Site Classification is based on the upper 100 feet of the
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 6
site profile defined by a weighted average value of either shear wave velocity, standard
penetration resistance, or undrained shear strength in accordance with Section 20.4 of
ASCE 7 and the International Building Code (IBC). Based on the soil and bedrock
properties observed at the site as described on the exploration logs and laboratory test
results, our professional opinion is that a preliminary Seismic Site Classification of C
be considered for the project. Subsurface explorations at this site were extended to a
maximum depth of 49.3 feet. The site properties below the boring depth to 100 feet
were estimated based on our experience and knowledge of geologic conditions of the
general area. Additional deeper borings or geophysical testing may be performed to
confirm the conditions below the current boring depth.
Corrosivity
The table below lists the results of laboratory soluble sulfate, soluble chloride, sulfides,
electrical resistivity, Redox, and pH testing. The values may be used to estimate
potential corrosive characteristics of the on-site soils with respect to contact with the
various underground materials which will be used for project construction.
Corrosivity Test Results Summary
Boring
(Sample
Depth)
Soluble
Sulfate
(mg/kg)
Soluble
Chloride
(mg/kg)
Sulfides
(mg/kg)
Total
Salts
(mg/kg)
Electrical
Resistivity
(Ω-cm)1
Redox
(mV) pH
B-3 at
0.5 to
5.0 feet
2 20 Nil 358 2,100 +219 8.1
1. Laboratory electrical resistivity testing was performed on a saturated sample.
Results of water-soluble sulfate testing indicate Exposure Class S0 according to ACI 318.
ASTM Type I, IL or II portland cement should be specified for all project concrete on and
below grade. Foundation concrete should be designed for low sulfate exposure in
accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4.
Numerous sources are available to characterize corrosion potential to buried metals
using the parameters above. ANSI/AWWA is commonly used for ductile iron, while
threshold values for evaluating the effect on steel can be specific to the buried feature
(e.g., piling, culverts, welded wire reinforcement, etc.) or agency for which the work is
performed. Imported fill materials may have significantly different properties than the
site materials noted above and should be evaluated if expected to be in contact with
metals used for construction. Consultation with a NACE certified corrosion professional is
recommended for buried metals on the site.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 7
Geotechnical Overview
Based on subsurface conditions encountered in the borings, the site appears suitable for
the proposed construction from a geotechnical point of view provided certain precautions
and preliminary design and construction recommendations described in this report are
followed and the owner understands the inherent risks associated with construction on
sites underlain by expansive soils and bedrock. We have identified several geotechnical
conditions that could impact design, construction and performance of the proposed
structures, pavements, and other site improvements. These included expansive soils and
bedrock, and potentially loose, low relative density sand soils. These conditions will
require particular attention in project planning, design and during construction and are
discussed in greater detail in the following sections.
Expansive Soils and Bedrock
Expansive soils and claystone bedrock are present on this site. Swell test results on
samples obtained during this preliminary geotechnical study were low to moderate
swelling to moderately compressible. This report provides preliminary recommendations
to help mitigate the effects of soil shrinkage and expansion. However, even if these
procedures are followed, some movement and cracking in the structures, pavements,
and flatwork is possible. The severity of cracking and other damage such as uneven
floor slabs and flatwork will probably increase if modification of the site results in
excessive wetting or drying of the expansive clays and/or claystone bedrock. Eliminating
the risk of movement and cosmetic distress is generally not feasible, but it may be
possible to further reduce the risk of movement if significantly more expensive measures
are used during construction. It is imperative the recommendations described in section
Grading and Drainage section of the Earthwork section of this report be followed to
reduce potential movement.
Low Relative Density Soils
Comparatively loose, low relative density sand soils were encountered at depths of
approximately 7 feet of the Boring No. B-1 completed at this site. These materials
present a risk for potential settlement of shallow foundations, floor slabs, pavements
and other surficial improvements. These materials can also be susceptible to disturbance
and loss of strength under repeated construction traffic loads and unstable conditions
could develop. Stabilization of loose and/or soft soils may be required at some locations
to provide adequate support for construction equipment and proposed structures.
Terracon should be contacted if these conditions are encountered to observe the
conditions exposed and to provide guidance regarding stabilization (if needed).
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 8
Preliminary Foundation and Floor System Recommendations
Based on the results of the preliminary field exploration, new lightly- to moderately-
loaded structures constructed at the project site can likely be supported on a shallow
foundation system consisting of spread footings, reinforced concrete mats, post-
tensioned slabs, or monolithic slab foundations. On-site soils can be used as engineered
fill below foundations.
For more heavily-loaded structures, we recommend supporting these buildings on deep
foundations consisting of drilled piers. The drilled piers should be socketed into the hard
to very hard claystone or sandstone bedrock encountered below the site.
Other foundation alternatives to those presented above could also be considered for the
site. Terracon can be contacted to discuss other foundation alternatives as needed.
Preliminary design recommendations for foundations for proposed structures and related
structural elements are presented in the Foundations section of this report.
We believe a concrete slab-on-grade floor system can be used for proposed buildings/
structures planned at the site. On-site soils are suitable for use as engineered fill below
floor slabs. The upper 6 to 12 inches of the engineered fill zone could consist of Colorado
Department of Transportation (CDOT) Class 1 structure backfill for improved slab
support and reduction of risk for potential movement. If the owner cannot accept the
risk of floor slab movement associated with a slab-on-grade floor system, the use of a
structural floor system can be considered. Terracon can be contacted to provide
additional recommendations if a structural floor system is desired for buildings.
Preliminary design recommendations for floor systems for proposed structures and
related structural elements are presented in the Floor Slabs section of this report.
The preliminary recommendations contained in this report are based upon the results of
field and laboratory testing (presented in the Exploration Results), engineering
analyses, and our current understanding of the proposed project. The General
Comments section provides an understanding of the report limitations.
Earthwork
Earthwork is anticipated to include site preparation, excavations, subgrade preparation,
soil stabilization (if needed), and engineered fill placement. The following sections
provide recommendations for use in the preparation of specifications for the project.
Recommendations include critical quality criteria, as necessary, to render the site in the
state considered in our geotechnical engineering evaluation for foundations, floor slabs,
and pavements.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 9
Site Preparation
Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.
Complete stripping of the topsoil should be performed in the proposed building and
parking/driveway areas. Stripped organic materials should be wasted from the site or used
to re-vegetate landscaped areas or exposed slopes after completion of grading operations.
Prior to the placement of fills, the site should be graded to create a relatively level surface to
receive fill, and to provide for a relatively uniform thickness of fill beneath proposed
structures.
Where fill is placed on existing slopes steeper than 5H:1V, benches should be cut into
the existing slopes prior to fill placement. The benches should have a minimum vertical
face height of 1 foot and a maximum vertical face height of 3 feet and should be cut
wide enough to accommodate the compaction equipment. This benching will help provide
a positive bond between the fill and natural soils and reduce the possibility of failure
along the fill/natural soil interface.
Although no evidence of fill or underground facilities (such as septic tanks, cesspools,
basements, and utilities) was observed during the exploration and site reconnaissance,
such features could be encountered during construction. If unexpected fills or
underground facilities are encountered, such features should be removed, and the
excavation thoroughly cleaned prior to backfill placement and/or construction.
Excavation
We anticipate excavations for the proposed construction can be accomplished with
conventional earthmoving equipment. Excavations into the on-site soils will encounter
weak and/or saturated soil conditions with possible caving conditions. The bottom of
excavations should be thoroughly cleaned of loose/disturbed materials prior to backfill
placement and/or construction.
Any over-excavation that extends below the bottom of foundation elevation should
extend laterally beyond all edges of the foundations at least 8 inches per foot of over-
excavation depth below the foundation base elevation. The over-excavation should be
backfilled to the foundation base elevation in accordance with the recommendations
presented in this report.
Depending upon depth of excavation and seasonal conditions, surface water infiltration
and/or groundwater may be encountered in excavations on the site. We anticipate
pumping from sumps may be utilized to control water within excavations. Well points
may be required for significant groundwater flow, or where excavations penetrate
groundwater to a significant depth. Groundwater seepage should be anticipated for
excavations approaching the level of bedrock.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 10
The subgrade soil conditions should be evaluated during the excavation process and the
stability of the soils determined at that time by the contractors’ Competent Person as
defined by OSHA. Slope inclinations flatter than the OSHA maximum values may have to
be used. 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. If any excavation, including a utility trench, is extended to a
depth of more than 20 feet, it will be necessary to have the side slopes and/or shoring
system designed by a professional engineer.
As a safety measure, we recommend all vehicles and soil piles be kept a minimum
lateral distance from the crest of the slope equal to the slope height. The exposed slope
face should be protected against the elements.
Subgrade Preparation
After site preparation, and completion of any required undercuts or recommended over-
excavations, the top 10 inches of the exposed ground surface should be scarified,
moisture conditioned, and compacted to at least 95 percent of the maximum dry unit
weight as determined by ASTM D698 before any new fill, foundations, slabs, pavements,
and other site improvements are placed or constructed.
Large areas of prepared subgrade should be proof rolled prior to new construction. Proof
rolling is not required in areas which are inaccessible to proof rolling equipment.
Subgrades should be proof rolled with an adequately loaded vehicle such as a fully-
loaded tandem-axle dump truck. Proof rolling should be performed under the
observation of the Geotechnical Engineer or representative. Areas excessively deflecting
under the proof roll should be delineated and subsequently addressed by the
Geotechnical Engineer. Excessively wet or dry material should either be removed or
moisture conditioned and compacted.
After the bottom of the excavation has been prepared as recommended above,
engineered fill can be placed to bring the building pad and pavement subgrade to the
desired grade. Engineered fill should be placed in accordance with the recommendations
presented in subsequent sections of this report.
Subgrade Stabilization
Methods of subgrade stabilization/improvement, as described below, could include
scarification, moisture conditioning and compaction, removal of unstable materials and
replacement with granular fill (with or without geosynthetics), and chemical treatment.
The appropriate method of improvement, if required, would be dependent on factors
such as schedule, weather, the size of area to be stabilized, and the nature of the
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 11
instability. More detailed recommendations can be provided during construction as the
need for subgrade stabilization occurs. Performing site grading operations during warm
seasons and dry periods would help reduce the amount of subgrade stabilization
required.
If the exposed subgrade is unstable during proof rolling operations, it could be stabilized
using one of the methods described below.
■ Scarification and Compaction - It may be feasible to scarify, dry, and compact
the exposed soils. The success of this procedure would depend primarily upon
favorable weather and sufficient time to dry the soils. Stable subgrades likely
would not be achievable if the thickness of the unstable soil is greater than about
1 foot, if the unstable soil is at or near groundwater levels, or if construction is
performed during a period of wet or cool weather when drying is difficult.
■ Crushed Stone - The use of crushed stone or crushed concrete is a common
procedure to improve subgrade stability. Typical undercut depths would be
expected to range from about 6 to24 inches below finished subgrade elevation.
Crushed stone and/or concrete can be tracked or “crowded” into the unstable
subgrade until a stable working surface is attained. The use of high modulus
geosynthetics (i.e., geotextile or geogrid) could also be considered after
underground work such as utility construction is completed. Prior to placing the
geosynthetic, we recommend all below-grade construction, such as utility line
installation, be completed to avoid damaging the geosynthetic. Equipment should
not be operated above the geosynthetic until one full lift of crushed stone fill is
placed above it.
■ Chemical Treatment - Improvement of subgrades with portland cement, lime or
fly ash could be considered for improving unstable soils. Chemical treatment
should be performed by a pre-qualified contractor having experience with
successfully treating subgrades in the project area on similar sized projects with
similar soil conditions. Results of chemical analysis of the chemical treatment
materials should be provided to the Geotechnical Engineer for review prior to use.
The hazards of chemicals blowing across the site or onto adjacent properties
should also be considered. Additional testing would be needed to develop specific
recommendations to improve subgrade stability by blending chemicals with the
site soils. Additional testing could include, but not be limited to, determining the
most suitable chemical treating agent, the optimum amounts required, the
presence of sulfates in the soil, and freeze-thaw durability of the subgrade.
Further evaluation of the need and recommendations for subgrade stabilization can be
provided during construction as the geotechnical conditions are exposed.
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Fill Material Types
Fill for this project should consist of engineered fill. Engineered fill is fill that meets the
criteria presented in this report and has been properly documented. On-site soils free of
deleterious materials or approved granular and low plasticity cohesive imported
materials may be used as fill material. Bedrock excavated during site development and
construction can be reused as fill provided the material is broken down and thoroughly
processed to a “soil-like” consistency, with no particles greater than 2 inches in size. The
earthwork contractor should expect significant mechanical processing and moisture
conditioning of the site soils and/or bedrock will be needed to achieve proper
compaction.
Imported fill materials (if required) should meet the following material property
requirements. Regardless of its source, compacted fill should consist of approved
materials that are free of organic matter and debris. Frozen material should not be used,
and fill should not be placed on a frozen subgrade.
Gradation Percent Finer by Weight (ASTM C136)
3” 100
1” 70-100
No. 4 Sieve 30-100
No. 200 Sieve 15-65
Soil Properties Values
Liquid Limit 35 (max.)
Plasticity Index 15 (max.)
Aggregate base course used below new pavements should meet CDOT requirements for
Class 5 or 6 aggregate base course materials.
Other import fill material types may be suitable for use on the site depending upon
proposed application and location on the site and could be tested and approved for use
on a case-by-case basis.
Fill Placement and Compaction Requirements
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.
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Item Description
Maximum Lift
Thickness
9 inches or less in loose thickness when heavy, self-propelled
compaction equipment is used
4 to 6 inches in loose thickness when hand-guided equipment
(i.e., jumping jack or plate compactor) is used
Minimum
Compaction
Requirements 1
Engineered Fill: At least 95% of the maximum dry unit weight
as determined by ASTM D698.
Engineered Fill 8 Feet or Greater: At least 98% of the maximum
dry unit weight as determined by ASTM D698 for the entire
depth of fill in areas receiving 8 feet of fill or greater.
Aggregate Base Course: At least 95% of maximum dry unit
weight as determined by ASTM D1557 (or AASHTO T180) in
pavement areas.
Water Content
Range 2,3
Cohesive (clay): -1% to +3% of optimum moisture content
Granular (sand): -3% to +3% of optimum moisture content
1. We recommend engineered fill be tested for moisture content and compaction during
placement. If the results of the in-place density tests indicate the specified moisture or
compaction limits have not been met, the area represented by the test should be
reworked and retested as required until the specified moisture and compaction
requirements are achieved.
2. Moisture conditioned clay materials should not be allowed to dry out. A loss of moisture
within these materials could result in an increase in the material’s expansive potential.
Subsequent wetting of these materials could result in undesirable movement.
3. Specifically, moisture levels should be maintained low enough to allow for satisfactory
compaction to be achieved without the fill material pumping when proof rolled.
Utility Trench Backfill
Any loose, soft, or unsuitable materials encountered at the bottom of utility trench
excavations should be removed and replaced with engineered fill or bedding material in
accordance with public works specifications for the utility to be supported. This
recommendation is particularly applicable to utility work where settlement control of the
utility is critical. Utility trench excavation should not be conducted below a downward
1:1 projection from existing foundations without engineering review of shoring
requirements and geotechnical observation during construction.
On-site materials are considered suitable for backfill of utility and pipe trenches provided
the material is free of organic matter and deleterious substances.
Utility trench backfill should be placed and compacted as discussed earlier in this report.
Compaction of initial lifts should be accomplished with hand-operated tampers or other
lightweight compactors. Flooding or jetting for placement and compaction of backfill is
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not recommended. If utility trenches are backfilled with relatively clean granular material,
they should be capped with at least 18 inches of cohesive fill in non-pavement areas to reduce
the infiltration and conveyance of surface water through the trench backfill.
For low permeability subgrades, utility trenches are a common source of water
infiltration and migration. Utility trenches penetrating beneath the building should be
effectively sealed to restrict water intrusion and flow through the trenches, which could
migrate below the building. The trench should provide an effective trench plug that
extends at least 5 feet from the face of the building exterior. The plug material should
consist of cementitious flowable fill or low permeability clay. The trench plug material
should be placed to surround the utility line. If used, the trench plug material should be
placed and compacted to comply with the water content and compaction
recommendations for engineered fill stated previously in this report.
All underground piping within or near the proposed structures should be designed with
flexible couplings, so minor deviations in alignment do not result in breakage or distress.
Utility knockouts in foundation walls should be oversized to accommodate differential
movements.
We recommend a representative of the Geotechnical Engineer provide full-time
observation and compaction testing of trench backfill within building and pavement
areas.
Grading and Drainage
All grades must provide effective drainage away from the buildings during and after
construction and should be maintained throughout the life of the buildings. Water
retained next to the buildings can result in soil movements greater than those discussed
in this report. Greater movements can result in unacceptable differential floor slab
and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should
have gutters/drains with downspouts that discharge onto splash blocks at a distance of
at least 10 feet from the buildings.
Exposed ground should be sloped and maintained at a minimum 5% away from the
buildings for at least 10 feet beyond the perimeter of the buildings. Locally, flatter
grades may be necessary to transition ADA access requirements for flatwork. After
building construction and landscaping have been completed, final grades should be
verified to document effective drainage has been achieved. Grades around the structures
should also be periodically inspected and adjusted, as necessary, as part of the
structure’s maintenance program.
Flatwork and pavements will be subject to post-construction movement. Maximum
grades practical should be used for paving and flatwork to prevent areas where water
can pond. In addition, allowances in final grades should take into consideration post-
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construction movement of flatwork, particularly if such movement would be critical.
Where paving or flatwork abuts the structures, care should be taken that joints are
properly sealed and maintained to prevent the infiltration of surface water.
Planters located adjacent to structures should preferably be self-contained. Sprinkler
mains and spray heads should be located a minimum of 5 feet away from the buildings
line(s). Low-volume, drip style landscaped irrigation should be used sparingly near the
building.
Exterior Slab Design and Construction
Exterior slabs-on-grade, exterior architectural features, and utilities founded on, or in
backfill or the site soils will likely experience some movement due to the volume change
of the material. Subgrade soils below new fill should be scarified to a depth of at least
10 inches, moisture conditioned, and compacted prior to placement/construction of new
engineered fill, aggregate base course, or pavement/flatwork materials. Potential
movement could be reduced by:
■ Minimizing moisture increases in subgrade soils and new fill;
■ Controlling moisture-density during subgrade preparation and new fill placement;
■ Using designs which allow vertical movement between the exterior features and
adjoining structural elements; and
■ Placing control joints on relatively close centers.
Earthwork Construction Considerations
Upon completion of filling and grading, care should be taken to maintain the subgrade
water content prior to construction of grade-supported improvements such as floor slabs
and pavements. Construction traffic over the completed subgrades should be avoided.
The site should also be graded to prevent ponding of surface water on the prepared
subgrades or in excavations. Water collecting over or adjacent to construction areas
should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the
affected material should be removed, or the materials should be scarified, moisture
conditioned, and recompacted prior to floor slab construction.
Construction site safety is the sole responsibility of the contractor who controls the
means, methods, and sequencing of construction operations. Under no circumstances
shall the information provided herein be interpreted to mean Terracon is assuming
responsibility for construction site safety or the contractor's activities; such
responsibility shall neither be implied nor inferred.
Excavations or other activities resulting in ground disturbance have the potential to
affect adjoining properties and structures. Our scope of services does not include review
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of available final grading information or consider potential temporary grading performed
by the contractor for potential effects such as ground movement beyond the project
limits. A preconstruction/ precondition survey should be conducted to document nearby
property/infrastructure prior to any site development activity. Excavation or ground
disturbance activities adjacent or near property lines should be monitored or
instrumented for potential ground movements that could negatively affect adjoining
property and/or structures.
Construction Observation and Testing
The earthwork efforts should be observed by the Geotechnical Engineer (or others under
their direction). Observation should include documentation of adequate removal of
surficial materials (vegetation and topsoil), subgrade stabilization, as well as proof
rolling and mitigation of unsuitable areas delineated by the proof roll. Each lift of
compacted fill should be tested, evaluated, and reworked, as necessary, as
recommended by the Geotechnical Engineer prior to placement of additional lifts.
In areas of foundation excavations, the bearing subgrade and exposed conditions at the
base of the recommended over-excavation should be evaluated by the Geotechnical
Engineer. If unanticipated conditions are observed, the Geotechnical Engineer should
prescribe mitigation options.
In addition to the documentation of the essential parameters necessary for construction,
the continuation of the Geotechnical Engineer into the construction phase of the project
provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface
conditions, including assessing variations and associated design changes.
Foundations
If the site has been prepared in accordance with the requirements noted in Earthwork,
the following preliminary design parameters are applicable for conceptual planning of
shallow foundations and deep foundations. These recommendations are subject to
change once a design-level geotechnical study has been completed for the project.
Shallow Foundations – Preliminary Design Recommendations
Based on the results of the preliminary field exploration, new lightly- to moderately-
loaded structures constructed at the project site can likely be supported on a shallow
foundation system consisting of spread footings, reinforced concrete mats, or monolithic
slab foundations. Also, we recommend over-excavating the materials to a minimum
depth of 1 to 3 feet below the foundation elevation and replacing the excavated material
with new engineered fill. This over-excavation will help reduce the potential for post-
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construction movement of foundations due to the presence of expansive soils and
bedrock at the site. On-site soils can be used as engineered fill below foundations.
If shallow foundations bear on a zone of engineered fill as presented above, a maximum
net allowable bearing pressure of 2,000 to 3,000 pounds per square foot (psf) can be
used for preliminary design of spread footing foundations and 1,000 to 2,000 psf can be
used for preliminary design of reinforced concrete mat foundations. Ranges of bearing
pressures are provided as design-level information for new structures is not known at
the time of this report. We recommend shallow foundations bear at a minimum depth of
30 inches below lowest adjacent grade for frost protection. We estimate total
movements of shallow foundations to be up to about 1 inch and differential movements
to be about ½ to ¾ of the total movement.
Any excavation extending below the bottom of foundation elevation should extend
laterally beyond all edges of the foundations at least 8 inches per foot of excavation
depth below the foundation base elevation. The excavation should be backfilled to the
foundation base elevation in accordance with the recommendations presented in this
report.
Drilled Piers - Preliminary Design Recommendations
For heavily-loaded structures, we recommend supporting these buildings on deep
foundations consisting of drilled piers. The drilled piers should be bottomed into the hard
to very hard claystone or sandstone bedrock encountered at the site to develop the
capacity of each pier. If the drilled piers bear in very hard claystone bedrock, a
maximum allowable end-bearing pressure of 20,000 to 35,000 pounds per square foot
(psf) with an allowable skin friction for the portion of the piers embedded into bedrock
only of 1,500 to 2,500 psf can be used for preliminary design of drilled pier foundations.
These values for allowable side friction and end bearing include a factor of safety. Drilled
piers should not bear in soft/loose soils. We recommend piers have a minimum diameter
of 18 inches and a length to diameter (L/D) ratio of 30 or less. We estimate total
movements of drilled pier foundations to be up to about ½ to ¾ inch and differential
movements to be about ½ to ¾ of the total movement. Due to the presence of
expansive soils and bedrock, uplift forces on the piers will need to be considered and
accounted for in the pier capacity estimates.
Drilled piers should have a minimum (center-to-center) spacing of three diameters, and
adjacent piers should bear at the same elevation. Closer spacing may require a
reduction in axial load capacity.
Drilled piers should also be designed to resist lateral loads. Design parameters for use in
LPILE analyses for lateral loading can be provided once the design-level geotechnical
study has been completed.
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A full-depth temporary steel casing will likely be required to shore the sides of the pier
excavations in the overburden soils. Difficult drilling conditions should be expected
within the bedrock, and the potential for hard bedrock drilling conditions should also be
anticipated. Water or loose materials should be removed from the bottom of the drilled
pier excavations prior to placement of the concrete.
The drilled pier installation process should be performed under the observation of the
Geotechnical Engineer. The Geotechnical Engineer should document the pier installation
process including soil/rock and groundwater conditions observed, consistency with
expected conditions, and details of the installed pier.
Floor Slabs
Preliminary design parameters for floor slabs assume the requirements for Earthwork
have been followed. Specific attention should be given to positive drainage away from
the structures and positive drainage of the aggregate base beneath the floor slabs.
The subgrade soils are comprised of moderately plasticity clays exhibiting the potential
to swell with increased water content. Construction of the floor slab, and revising site
drainage creates the potential for gradual increased water contents within the clays.
Increases in water content will cause the clays to swell and damage the floor slab.
Depending on proposed construction, anticipated floor loads, planned site grading and
results of design-level geotechnical study, we anticipate an over-excavation of about 1
to 3 feet may be needed to reduce risk of potential floor slab movement. Some of these
preliminary geotechnical recommendations may change as a result of a design-level
study.
Due to the potential for significant moisture fluctuations of subgrade material beneath
floor slabs supported at-grade, the Geotechnical Engineer should evaluate the material
at the base of the recommended over-excavation immediately prior to placement of
additional fill or floor slabs. Soils below the specified water contents within this zone
should be moisture conditioned or replaced with structural fill as stated in our
Earthwork section.
Floor Slab Preliminary Design Recommendations
Even when bearing on properly prepared soils, movement of the slab-on-grade floor
system is possible should the subgrade soils undergo an increase in moisture content.
We estimate movement of about 1 inch is possible. If the owner cannot accept the risk
of slab movement, a structural floor should be used. If conventional slab-on-grade is
utilized, over-excavation of the subgrade soils should be performed as presented above
and in the Earthwork section of this report.
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For structural design of concrete slabs-on-grade subjected to point loadings, a modulus
of subgrade reaction of 175 pounds per cubic inch (pci) may be used as part of
preliminary planning for floors supported on native clay soils at the site or engineered
fill.
The use of a vapor retarder should be considered beneath concrete slabs on grade
covered with wood, tile, carpet, or other moisture sensitive or impervious coverings,
when the project includes humidity-controlled areas, or when the slab will support
equipment sensitive to moisture. When conditions warrant the use of a vapor retarder,
the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions
regarding the use and placement of a vapor retarder.
Additional floor slab design and construction recommendations are as follows:
■ Positive separations and/or isolation joints should be provided between slabs and
all foundations, columns, or utility lines to allow independent movement.
■ Control joints should be saw-cut in slabs in accordance with ACI Design Manual,
Section 302.1R-37 8.3.12 (tooled control joints are not recommended) to control
the location and extent of cracking.
■ Interior utility trench backfill placed beneath slabs should be compacted in
accordance with the recommendations presented in the Earthwork section of this
report.
■ Floor slabs should not be constructed on frozen subgrade.
■ Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1R are recommended.
Floor Slab Construction Considerations
Movements of slabs-on-grade using the recommendations discussed in previous sections
of this report will likely be reduced and tend to be more uniform. The estimates
discussed above assume that the other recommendations in this report are followed.
Additional movement could occur should the subsurface soils become wetted to
significant depths, which could result in potential excessive movement causing uneven
floor slabs and severe cracking. This could be due to over watering of landscaping, poor
drainage, improperly functioning drain systems, and/or broken utility lines. Therefore, it
is imperative that the recommendations presented in this report be followed.
Finished subgrade, within and for at least 10 feet beyond the floor slab, should be
protected from traffic, rutting, or other disturbance and maintained in a relatively moist
condition until floor slabs are constructed. If the subgrade should become damaged or
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desiccated prior to construction of floor slabs, the affected material should be removed,
and structural fill should be added to replace the resulting excavation. Final conditioning
of the finished subgrade should be performed immediately prior to placement of the floor
slab support course.
The Geotechnical Engineer should observe the condition of the floor slab subgrades
immediately prior to placement of the floor slab support course, reinforcing steel, and
concrete. Attention should be paid to high traffic areas that were rutted and disturbed
earlier, and to areas where backfilled trenches are located.
Below-Grade Structures
We understand a below-grade parking structure is planned as part of the new
development. Maximum excavations for the below-grade parking are anticipated to be
on the order of 15 to 18 feet below existing grades. We anticipate the below-grade
parking structure will be constructed of reinforced concrete. The structure will need to
be designed for to resist lateral earth pressures as presented in the following section. If
a permanent dewatering system is not installed to keep water levels below the bottom
floor elevation of the parking structure, then the structure will also need to resist
hydrostatic pressures if lower levels extend below groundwater.
Lateral Earth Pressures
The following preliminary lateral earth pressure recommendations are for conceptual
planning only and subject to change once a design-level geotechnical study has been
completed for the project.
Preliminary Design Parameters
Structures with unbalanced backfill levels on opposite sides should be designed for earth
pressures at least equal to values indicated in the following table. Earth pressures will be
influenced by structural design of the walls, conditions of wall restraint, methods of
construction, and/or compaction and the strength of the materials being restrained. Two
wall restraint conditions are shown in the diagram below. Active earth pressure is
commonly used for design of free-standing cantilever retaining walls and assumes wall
movement. The “at-rest” condition assumes no wall movement and is commonly used
for basement walls, loading dock walls, or other walls restrained at the top. The
recommended design lateral earth pressures do not include a factor of safety and do not
provide for possible hydrostatic pressure on the walls (unless stated).
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Lateral Earth Pressure Design Parameters
Earth
Pressure
Condition 1
Coefficient for
Backfill Type 2
Surcharge
Pressure 3
p1 (psf)
Equivalent Fluid Pressures
(psf) 2,4
Unsaturated 5 Submerged 5
Active (Ka) Granular - 0.27
Fine Grained - 0.33
(0.27)S
(0.33)S
(30)H
(40)H
(80)H
(80)H
At-Rest (Ko) Granular - 0.43
Fine Grained - 0.50
(0.43)S
(0.50)S
(50)H
(60)H
(90)H
(90)H
Passive (Kp) Granular – 3.69
Fine Grained – 3.00
---
---
---
---
---
---
1. For active earth pressure, wall must rotate about base, with top lateral
movements 0.002 H to 0.004 H, where H is wall height. For passive earth
pressure, wall must move horizontally to mobilize resistance. Fat clay or other
expansive soils should not be used as backfill behind the wall.
2. Uniform, horizontal backfill, with a maximum unit weight of 120 pcf for cohesive
soils and 120 pcf for granular soils.
3. Uniform surcharge, where S is surcharge pressure.
4. Loading from heavy compaction equipment is not included.
5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage
for Below-Grade Walls below. “Submerged” conditions are recommended
when drainage behind walls is not incorporated into the design.
Backfill placed against structures should consist of granular soils or low plasticity
cohesive soils. For the granular values to be valid, the granular backfill must extend out
and up from the base of the wall at an angle of at least 45 degrees from vertical for the
active case.
Footings, floor slabs or other loads bearing on backfill behind walls may have a
significant influence on the lateral earth pressure. Placing footings within wall backfill
and in the zone of active soil influence on the wall should be avoided unless structural
analyses indicate the wall can safely withstand the increased pressure.
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The preliminary lateral earth pressure recommendations given in this section are
applicable to the design of rigid retaining walls subject to slight rotation, such as
cantilever, or gravity type concrete walls. These preliminary recommendations are not
applicable to the design of modular block - geogrid reinforced backfill walls (also termed
MSE walls). Recommendations covering these types of wall systems are beyond the
scope of services for this assignment. However, we would be pleased to develop a
proposal for evaluation and design of such wall systems upon request.
Pavements
General Pavement Comments
Preliminary pavement designs are provided for the traffic conditions and pavement life
conditions as noted in Project Description and in the following sections of this report.
A critical aspect of pavement performance is site preparation. Pavement designs noted
in this section must be applied to the site which has been prepared as recommended in
the Earthwork section.
Support characteristics of subgrade for pavement design do not account for shrink/swell
movements of an expansive to moderately collapsable clay subgrade, such as soils
observed 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. For preliminary planning purposes, swell mitigation of
subgrade soils below proposed pavements may consist of scarification to a depth of 10
to 12 inches, moisture conditioning, and compacting or up to about 2 feet of over-
excavation and replacement with low swell, engineered fill.
Pavement Subgrade Preparation
On most project sites, the site grading is accomplished relatively early in the
construction phase. Fills are typically placed and compacted in a uniform manner.
However, as construction proceeds, the subgrade may be disturbed due to utility
excavations, construction traffic, desiccation, or rainfall/snow melt. 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 instability. We recommend the pavement
subgrade be thoroughly proof rolled with a loaded tandem-axle dump truck prior to final
grading and paving. All pavement areas should be moisture conditioned and properly
compacted to the recommendations in this report immediately prior to paving.
Prior to pavement construction and after the pavement areas have been stripped, and
the recommended over-excavation (if any determined by a design-level study) has been
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completed within the planned pavement areas, the top 10 inches of the exposed ground
surface should be scarified, moisture conditioned, and compacted as described in this
report before any new fill is placed or constructed. After the subgrade has been scarified
and compacted and before placement of new fill and pavement, we recommend the
subgrade be proof rolled as described above.
Pavement Preliminary Design Recommendations
Design of new privately-maintained pavements for the project has been based on the
procedures described by the National Asphalt Pavement Associations (NAPA) and the
American Concrete Institute (ACI). We assumed the following design parameters for
NAPA flexible pavement thickness design:
■ Automobile Parking Areas
o Class I - Parking stalls and parking lots for cars and pick-up trucks, with
Equivalent Single Axle Load (ESAL) up to 7,000 over 20 years
■ Main Traffic Corridors
o Class II – Parking lots with a maximum of 10 trucks per day with
Equivalent Single Axle Load (ESAL) up to 27,000 over 20 years (including
trash trucks)
■ Subgrade Soil Characteristics
o USCS Classification – CL, classified by NAPA as poor
We assumed the following design parameters for ACI rigid pavement thickness design
based upon the average daily truck traffic (ADTT):
■ Automobile Parking Areas
o ACI Category A: Automobile parking with an ADTT of 1 over 20 years
■ Main Traffic Corridors
o ACI Category B: Entrance and truck service lanes with an ADTT of up to 10
over 20 years
■ Subgrade Soil Characteristics
o USCS Classification – CL
■ Concrete modulus of rupture value of 600 psi
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We should be contacted to confirm and/or modify the recommendations contained herein
if actual traffic volumes differ from the assumed values shown above.
Recommended alternatives for flexible and rigid pavements (preliminary) are
summarized for each traffic area as follows:
Traffic Area Alternative
Preliminary Recommended Pavement
Thickness (inches)
Asphaltic
Concrete
Surface
Portland
Cement
Concrete
Aggregate
Base
Course
Total
Automobile
Parking
(NAPA Class 1
and ACI
Category A)
A 4 -- 6 10
B -- 5 4 1 9
Main Traffic
Corridors
(NAPA Class II
and ACI
Category B)
A 6 -- 6 12
B -- 6 4 1 10
1. Although not required for structural support, a minimum 4-inch thick aggregate base
course layer is suggested for the portland cement concrete (PCC) pavements to help
reduce the potential for slab curl, shrinkage cracking, and subgrade “pumping” through
joints.
Aggregate base course 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 aggregate base
course. Aggregate base course should be placed in lifts not exceeding 6 inches and
compacted to a minimum of 95 percent of the maximum dry unit weight as determined
by ASTM D1557 (or AASHTO T180).
Asphaltic concrete should be composed of a mixture of aggregate, filler and additives (if
required) and approved bituminous material. The asphalt concrete should conform to
approved mix designs stating the Superpave properties, optimum asphalt content, job
mix formula and recommended mixing and placing temperatures. Aggregate used in
asphalt concrete should meet particular gradations. Material meeting CDOT Grading S or
SX specifications or equivalent is recommended for asphalt concrete. Mix designs should
be submitted prior to construction to verify their adequacy. Asphalt material should be
placed in maximum 3-inch lifts and compacted within a range of 92 to 96 percent of the
theoretical maximum (Rice) density (ASTM D2041).
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Where rigid pavements are used, the concrete should be produced from an approved mix
design with the following minimum properties:
Properties Value
Compressive strength 4,500 psi
Cement type Type I, IL or II portland cement
Entrained air content (%) 5 to 8
Concrete aggregate ASTM C33 and CDOT section 703
Concrete should be deposited by truck mixers or agitators and placed a maximum of 90
minutes from the time the water is added to the mix. Longitudinal and transverse joints
should be provided as needed in concrete pavements for expansion/contraction and
isolation per ACI 330 and ACI 325. The location and extent of joints should be based
upon the final pavement geometry.
Proper joint spacing will also be required for portland cement concrete (PCC) pavements
to prevent excessive slab curling and shrinkage cracking. All joints should be sealed to
prevent entry of foreign material and dowelled where necessary for load transfer.
For areas subject to concentrated and repetitive loading conditions, such as dumpster
pads, truck delivery docks and ingress/egress aprons, we recommend using a PCC
pavement with a thickness of at least 7 inches underlain by at least 4 inches of granular
base. Prior to placement of the granular base, the areas should be thoroughly proof
rolled. For dumpster pads, the concrete pavement area should be large enough to
support the container and tipping axle of the refuse truck.
Pavement performance is affected by its surroundings. In addition to providing
preventive maintenance, the civil engineer should consider the following
recommendations in the design and layout of pavements:
■ Site grades should slope a minimum of 2 percent away from the pavements;
■ The subgrade and the pavement surface have a minimum 2 percent slope to promote
proper surface drainage;
■ Consider appropriate edge drainage and pavement under drain systems;
■ Install pavement drainage surrounding areas anticipated for frequent wetting;
■ Install joint sealant and seal cracks immediately;
■ Seal all landscaped areas in, or adjacent to pavements to reduce moisture
migration to subgrade soils; and
■ Placing compacted, low permeability backfill against the exterior side of curb and
gutter.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 26
Pavement Construction Considerations
Openings in pavement, such as landscape islands, are sources for water infiltration into
surrounding pavements. Water collects in the islands and migrates into the surrounding
subgrade soils thereby degrading support of the pavement. This is especially applicable
for islands with raised concrete curbs, irrigated foliage, and low permeability near-
surface soils. The civil design for the pavements with these conditions should include
features to restrict or to collect and discharge excess water from the islands. Examples
of features are edge drains connected to the storm water collection system or other
suitable outlet and impermeable barriers preventing lateral migration of water such as a
cutoff wall installed to a depth below the pavement structure.
Pavement Maintenance
The preliminary pavement sections represent minimum recommended thicknesses and,
as such, periodic upkeep should be anticipated. Preventive maintenance should be
planned and provided for through an on-going pavement management program.
Maintenance activities are intended to slow the rate of pavement deterioration and to
preserve the pavement investment. Pavement care consists of both localized (e.g., crack
and joint sealing and patching) and global maintenance (e.g., surface sealing).
Additional engineering consultation is recommended to determine the type and extent of
a cost-effective program. Even with periodic maintenance, some movements and related
cracking may still occur, and repairs may be required.
General Comments
Our analysis and opinions are based upon our understanding of the project, the
geotechnical conditions in the area, and the data obtained from our site exploration.
Variations will occur between exploration point locations or due to the modifying effects
of construction or weather. The nature and extent of such variations may not become
evident until during or after construction. Terracon should be retained as the
Geotechnical Engineer, where noted in this report, to provide observation and testing
services during pertinent construction phases. If variations appear, we can provide
further evaluation and supplemental recommendations. If variations are noted in the
absence of our observation and testing services on-site, we should be immediately
notified so that we can provide evaluation and supplemental recommendations.
Our Scope of Services 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.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials 27
Our services and any correspondence are intended for the sole benefit and exclusive use
of our client for specific application to the project discussed and are accomplished in
accordance with generally accepted geotechnical engineering practices with no third-
party beneficiaries intended. Any third-party access to services or correspondence is
solely for information purposes to support the services provided by Terracon to our
client. Reliance upon the services and any work product is limited to our client and is not
intended for third parties. Any use or reliance of the provided information by third
parties is done solely at their own risk. No warranties, either express or implied, are
intended or made.
Site characteristics as provided are for design purposes and not to estimate excavation
cost. Any use of our report in that regard is done at the sole risk of the excavating cost
estimator as there may be variations on the site that are not apparent in the data that
could significantly effect excavation cost. Any parties charged with estimating excavation
costs should seek their own site characterization for specific purposes to obtain the
specific level of detail necessary for costing. Site safety and cost estimating including
excavation support and dewatering requirements/design are the responsibility of others.
Construction and site development have the potential to affect adjacent properties. Such
impacts can include damages due to vibration, modification of groundwater/surface
water flow during construction, foundation movement due to undermining or subsidence
from excavation, as well as noise or air quality concerns. Evaluation of these items on
nearby properties are commonly associated with contractor means and methods and are
not addressed in this report. The owner and contractor should consider a
preconstruction/precondition survey of surrounding development. If changes in the
nature, design, or location of the project are planned, our conclusions and
recommendations shall not be considered valid unless we review the changes and either
verify or modify our conclusions in writing.
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Figures
Contents:
GeoModel
4,850
4,855
4,860
4,865
4,870
4,875
4,880
4,885
4,890
4,895
4,900
4,905
4,910
EL
E
V
A
T
I
O
N
(
M
S
L
)
(
f
e
e
t
)
Layering shown on this figure has been developed by the
geotechnical engineer for purposes of modeling the subsurface
conditions as required for the subsequent geotechnical engineering
for this project.
Numbers adjacent to soil column indicate depth below ground
surface.
NOTES:
B-1 B-2
B-3
B-4
B-5
Legend
This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.
GeoModel
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032
Touchmark Development Retirement Homes
1901 Sharp Point Dr Ste C
Fort Collins, CO
Second Water Observation
First Water Observation
Groundwater levels are temporal. The levels shown are representative
of the date and time of our exploration. Significant changes are
possible over time.
Water levels shown are as measured during and/or after drilling. In
some cases, boring advancement methods mask the presence/absence
of groundwater. See individual logs for details.
Vegetative Layer Clayey Sand
Lean Clay with Sand Poorly-graded Sand
with Clay
Lean Clay
Sandy Lean Clay Poorly-graded Sand
with Clay and Gravel
Poorly-graded Sand
with GravelSandy Lean Clay
with Gravel
Model Layer Layer Name General Description
1
Lean clay with varying amounts of sand and gravel;
medium stiff to very stiff, light brown to brown, tan, red
brown, light gray, gray brown
3 Claystone bedrock; hard to very hard, gray brown to dark
gray with orange brown and red orange
4 Clayey sandstone bedrock; very hard, brown, gray, orange
brown to dark gray
2
Poorly graded sand with varying amounts of clay and
gravel, loose to very dense, light brown to brown, red
brown, gray
Lean Clay
Claystone Bedrock
Sandstone Bedrock
Sand
2
1
2
3
22
28
14
19
29
49.3
1
2
4
23.6
27
24
34
49.3
1
2
19
25
1
3 24
24.3
1
3
19
25.4
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Attachments
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Exploration and Testing Procedures
Field Exploration
Number of Borings Approximate Boring
Depth (feet) Location
2
(Boring Nos. B-1 and B-2) 49.3 Apartment building area
3
(Boring Nos. B-3 through
B-5)
24.3 to 25.4 Spread throughout the site
Boring Layout and Elevations: Terracon personnel provided the boring layout using
handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) and
referencing existing site features. Approximate ground surface elevations were obtained
by interpolation from a publicly available USGS topographic map. If surface elevations
and a more precise boring layout are desired, we recommend the borings be surveyed.
Subsurface Exploration Procedures: We advanced the borings with a truck-mounted,
rotary drill rig using solid-stem, continuous-flight augers. Sampling was performed using
standard split-barrel and modified California barrel sampling procedures. In the
split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling
spoon was driven into the ground by a 140-pound automatic hammer falling a distance
of 30 inches. The number of blows required to advance the sampling spoon the last 12
inches of a normal 18-inch penetration is recorded as the Standard Penetration Test
(SPT) resistance value. The SPT resistance values, also referred to as N-values, are
indicated on the boring logs at the test depths. In the modified California barrel
sampling procedure, a 2½-inch outer diameter split-barrel sampling spoon is used for
sampling. Modified California barrel sampling procedures are similar to standard split
spoon sampling procedure; however, blow counts are typically recorded for 6-inch
intervals for a total of 12 inches of penetration. Modified California barrel sampler blow
counts are not considered N-values. The samples were placed in appropriate containers
and taken to our soil laboratory for testing and classification by a Geotechnical Engineer.
We also observed the boreholes while drilling and at the completion of drilling for the
presence of groundwater. The groundwater levels are shown on the attached boring
logs.
Our exploration team prepared field boring logs as part of the drilling operations. The
sampling depths, penetration distances, and other sampling information were recorded
on the field boring logs. These field logs included visual classifications of the materials
observed during drilling and our interpretation of the subsurface conditions between
Preliminary Geotechnical Engineering Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
samples. Final boring logs were prepared from the field logs. The final boring logs
represent the Geotechnical Engineer's interpretation of the subsurface conditions at the
boring locations based on field data, observation of samples, and laboratory test results.
We backfilled the borings with auger cuttings after completion of drilling. Our services
did not include repair of the site beyond backfilling the boreholes. Excess auger cuttings
were dispersed in the general vicinity of the boreholes. Because backfill material often
settles below the surface after a period, we recommend checking boreholes periodically
and backfilling, if necessary.
Laboratory Testing
The project engineer reviewed the field data and assigned laboratory tests. The
laboratory testing program included the following types of tests:
■ Moisture Content
■ Dry Unit Weight
■ Unconfined Compressive Strength
■ Atterberg Limits
■ Grain-size Analysis
■ One-dimensional Swell
■ Corrosive Properties
The laboratory testing program often included examination of soil samples by an
engineer and/or geologist. Based on the results of our field and laboratory programs, we
described and classified the soil samples in accordance with the Unified Soil
Classification System. A brief description of this classification system as well as the
General Notes can be found in the Supporting Information section.
Laboratory test results are indicated on the boring logs and are presented in depth in
the Exploration Results section. Laboratory tests are performed in general accordance
with applicable local standards or other acceptable standards. In some cases, variations
to methods are applied as a result of local practice or professional judgement.
Rock classification was conducted using locally accepted practices for engineering
purposes; petrographic analysis may reveal other rock types. Rock core samples
typically provide an improved specimen for this classification. Boring log rock
classification was determined using the Description of Rock Properties.
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Site Location and Exploration Plans
Contents:
Site Location Plan
Exploration Plan
Note: All attachments are one page unless noted above.
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above
and outside the table – please leave that alone. Limit editing to inside the table.
Site Location
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Note to Preparer: This is a large table with outside borders. Just click inside the table
above this text box, then paste your GIS Toolbox image.
When paragraph markers are turned on you may notice a line of hidden text above
and outside the table – please leave that alone. Limit editing to inside the table.
Exploration Plan
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Exploration and Laboratory Results
Contents:
Boring Logs (B-1 through B-5)
Atterberg Limits
Grain Size Distribution
Unconfined Compressive Strength (3 pages)
Corrosivity
Note: All attachments are one page unless noted above.
4903.5
4890
4885
4880
4875
4854.7
VEGETATIVE LAYER, about 6 inches thick
CLAYEY SAND (SC), brown to red brown,
loose to medium dense
LEAN CLAY WITH SAND, brown, very stiff
CLAYEY SAND, brown to red brown, very
dense, with trace gravel
POORLY GRADED SAND WITH CLAY, light
brown, very dense
CLAYSTONE BEDROCK, brown gray to dark
gray with orange brown and red orange, hard
to very hard
Boring Terminated at 49.3 Feet
Boring Log No. B-1
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40
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6160
8.5
6.6
7.1
9.7
9.7
13.5
5.1
21.0
18.7
21.8
17.1
19.1
83
111
108
27-18-9
0.5
14.0
19.0
24.0
29.0
49.3
+2.3/2004-5
9/12"
3-4-5
N=9
10-10
20/12"
5-6-5
N=11
10-12
22/12"
7-10-50/6"
50/5"
18-30-37
N=67
50/6"
50/6"
50/3"
50/3"
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032 Fort Collins, CO
1901 Sharp Point Dr Ste C
Drill Rig
CME-75
Hammer Type
Automatic, Hammer
Efficiency = 77%
Driller
Terracon Consultants
Logged by
PA
Boring Started
10-01-2024
Boring Completed
10-01-2024
Abandonment Method
Boring backfilled with auger cuttings upon completion.
Advancement Method
4-inch outside diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
22 feet at completion of drilling
28 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory procedures used and
additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevations were interpolated from a publicly available USGS map
Touchmark Development Retirement Homes
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Elevation.: 4904 (Ft.)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5215° Longitude: -105.0064°
Depth (Ft.)
Sw
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s
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1
2
3
4904.5
4901
4898
4881
4871
4855.7
VEGETATIVE LAYER, about 6 inches thick
LEAN CLAY, brown, stiff
SANDY LEAN CLAY, tan, medium stiff
LEAN CLAY WITH SAND, red brown to tan
with light gray, stiff to very stiff
POORLY GRADED SAND WITH CLAY AND
GRAVEL, brown with red and gray, very
dense
no recovery at about 29 feet, cobbles present
CLAYEY SANDSTONE BEDROCK (SC), brown
with gray and orange brown to dark gray, very
hard
Boring Terminated at 49.3 Feet
Boring Log No. B-2
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7.8
8.9
6.9
9.4
9.7
17.7
22.3
18.7
17.8
27.4
20.3
84
105
37-21-16
0.5
4.0
7.0
24.0
34.0
49.3
-4.3/1000
6-8-7
N=15
3-4
7/12"
7-7-7
N=14
11-10
21/12"
10-11-12
N=23
9-11
20/12"
13-30-40
N=70
50/1"
35-50/5"
50/3"
50/1"
50/4"
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032 Fort Collins, CO
1901 Sharp Point Dr Ste C
Drill Rig
CME-75
Hammer Type
Automatic, Hammer
Efficiency = 77%
Driller
Terracon Consultants
Logged by
PA
Boring Started
10-01-2024
Boring Completed
10-01-2024
Abandonment Method
Boring backfilled with auger cuttings upon completion.
Advancement Method
4-inch outside diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
23.6 feet at completion of drilling
27 feet while drilling
See Exploration and Testing Procedures for a description of field and laboratory procedures used and
additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevations were interpolated from a publicly available USGS map
Touchmark Development Retirement Homes
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Elevation.: 4905 (Ft.)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5202° Longitude: -105.0060°
Depth (Ft.)
Sw
e
l
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s
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2
4
4899.5
4893
4886
4881
4875
VEGETATIVE LAYER, about 6 inches thick
LEAN CLAY, brown, stiff to very stiff
SANDY LEAN CLAY (CL), tan to light brown,
stiff
LEAN CLAY WITH SAND, gray brown, very
stiff
POORLY GRADED SAND WITH GRAVEL, tan
to reddish brown with brown, dense to very
dense
trace clay at about 24 feet
Boring Terminated at 25 Feet
Boring Log No. B-3
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Facilities | Environmental |Geotechnical | Materials
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8.7
11.4
9.1
15.6
5.9
94
29-16-13
0.5
7.0
14.0
19.0
25.0
+0.6/500
7-9-9
N=18
10-8
18/12"
5-6-9
N=15
9-9
18/12"
6-8-12
N=20
37-38
75/12"
46-50/6"
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032 Fort Collins, CO
1901 Sharp Point Dr Ste C
Drill Rig
CME-75
Hammer Type
Automatic, Hammer
Efficiency = 77%
Driller
Terracon Consultants
Logged by
PA
Boring Started
10-01-2024
Boring Completed
10-01-2024
Abandonment Method
Boring backfilled with auger cuttings upon completion.
Advancement Method
4-inch outside diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
No free water observed
See Exploration and Testing Procedures for a description of field and laboratory procedures used and
additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevations were interpolated from a publicly available USGS map
Touchmark Development Retirement Homes
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Elevation.: 4900 (Ft.)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5211° Longitude: -105.0052°
Depth (Ft.)
Sw
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4902.5
4899
4879
4878.7
VEGETATIVE LAYER, about 6 inches thick
SANDY LEAN CLAY, light brown, stiff
LEAN CLAY WITH SAND (CL), light brown to
brown and tan, medium stiff to very stiff
CLAYSTONE BEDROCK, brown, very hard
Boring Terminated at 24.3 Feet
Boring Log No. B-4
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7.1
6.2
5.6
8.1
7.5
7.6
81
27-19-8
0.5
4.0
24.0
24.3
+0.6/2005-5
10/12"
5-5-7
N=12
4-5
9/12"
5-8-12
N=20
15-12
27/12"
13-14-12
N=26
50/3"
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032 Fort Collins, CO
1901 Sharp Point Dr Ste C
Drill Rig
CME-75
Hammer Type
Automatic, Hammer
Efficiency = 77%
Driller
Terracon Consultants
Logged by
PA
Boring Started
10-01-2024
Boring Completed
10-01-2024
Abandonment Method
Boring backfilled with auger cuttings upon completion.
Advancement Method
4-inch outside diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
No free water observed
See Exploration and Testing Procedures for a description of field and laboratory procedures used and
additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevations were interpolated from a publicly available USGS map
Touchmark Development Retirement Homes
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Un
c
o
n
f
i
n
e
d
Co
m
p
r
e
s
s
i
v
e
St
r
e
n
g
t
h
(
p
s
f
)
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Elevation.: 4903 (Ft.)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5201° Longitude: -105.0049°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
1
3
4906.5
4903
4893
4888
4881.6
VEGETATIVE LAYER, about 6 inches thick
LEAN CLAY, brown, stiff
LEAN CLAY WITH SAND (CL), light brown to
brown with tan, medium stiff to stiff
SANDY LEAN CLAY WITH GRAVEL, brown
with red and gray, very stiff
CLAYSTONE BEDROCK, olive brown with
gray, orange and orange brown, medium hard
to very hard
Boring Terminated at 25.4 Feet
Boring Log No. B-5
Wa
t
e
r
L
e
v
e
l
Ob
s
e
r
v
a
t
i
o
n
s
De
p
t
h
(
F
t
.
)
5
10
15
20
25
Facilities | Environmental |Geotechnical | Materials
Gr
a
p
h
i
c
L
o
g
Mo
d
e
l
L
a
y
e
r
71
4430
11.0
9.6
9.2
10.9
7.8
17.4
18.4
107
30-20-10
0.5
4.0
14.0
19.0
25.4
3-4-4
N=8
4-5
9/12"
3-4-5
N=9
5-8
13/12"
10-10-10
N=20
19-31
50/12"
22-40-50/5"
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032 Fort Collins, CO
1901 Sharp Point Dr Ste C
Drill Rig
CME-75
Hammer Type
Automatic, Hammer
Efficiency = 77%
Driller
Terracon Consultants
Logged by
PA
Boring Started
10-01-2024
Boring Completed
10-01-2024
Abandonment Method
Boring backfilled with auger cuttings upon completion.
Advancement Method
4-inch outside diameter, continuous-flight, solid-stem
augers
Notes
Water Level Observations
No free water observed
See Exploration and Testing Procedures for a description of field and laboratory procedures used and
additional data (If any).
See Supporting Information for explanation of symbols and abbreviations.
Elevation Reference: Elevations were interpolated from a publicly available USGS map
Touchmark Development Retirement Homes
Sa
m
p
l
e
T
y
p
e
Pe
r
c
e
n
t
Fi
n
e
s
Un
c
o
n
f
i
n
e
d
Co
m
p
r
e
s
s
i
v
e
St
r
e
n
g
t
h
(
p
s
f
)
Wa
t
e
r
Co
n
t
e
n
t
(
%
)
Dr
y
U
n
i
t
We
i
g
h
t
(
p
c
f
)
Elevation.: 4907 (Ft.)
Atterberg
Limits
LL-PL-PI
See Exploration PlanLocation:
Latitude: 40.5208° Longitude: -105.0069°
Depth (Ft.)
Sw
e
l
l
-
C
o
n
s
o
l
/
Lo
a
d
(
%
/
p
s
f
)
Fi
e
l
d
T
e
s
t
Re
s
u
l
t
s
1
3
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
"A" Line
ASTM D4318
CH or OH
CL or OL
ML or OL
MH or OH
9
16
13
8
10
37.3
39.7
54.8
76.3
71.0
SC
SC
CL
CL
CL
18
21
16
19
20
9
16
13
8
10
37.3
39.7
54.8
76.3
71.0
SC
SC
CL
CL
CL
18
21
16
19
20
27
37
29
27
30
K
SANDY LEAN CLAY
LEAN CLAY with SAND
LEAN CLAY with SAND
Atterberg Limit Results
"U" Line
Liquid Limit
LL PL PI Fines USCS DescriptionFines
Pl
a
s
t
i
c
i
t
y
I
n
d
e
x
CL - ML
16
4
7
Facilities | Environmental |Geotechnical | Materials
7 - 8
34 - 34.9
9 - 10
4 - 5.5
4 - 5
B-1
B-2
B-3
B-4
B-5
Boring ID Depth (Ft)
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
140
HydrometerU.S. Sieve Opening in Inches
Grain Size Distribution
ASTM D422 / ASTM C136
SandGravel
2 10 14 506 2001.5 83/4 1/23/8 30 403 601
U.S. Sieve Numbers
16 2044 10063
Grain Size (mm)
coarse fine coarse finemedium Silt or ClayCobbles
Pe
r
c
e
n
t
C
o
a
r
s
e
r
b
y
W
e
i
g
h
t
Pe
r
c
e
n
t
F
i
n
e
r
b
y
W
e
i
g
h
t
100
90
80
70
60
50
40
30
20
10
0
AASHTOUSCSUSCS Classification
A-4 (0)
A-6 (2)
A-6 (4)
A-4 (4)
A-4 (5)
SC
SC
CL
CL
CL
CLAYEY SAND
K
SANDY LEAN CLAY
LEAN CLAY with SAND
LEAN CLAY with SAND
Facilities | Environmental |Geotechnical | Materials
27
37
29
27
30
9
16
13
8
10
18
21
16
19
20
%CobblesD60
0.145
0.115
0.084
D100 %Clay%Sand%Gravel
1.0
0.0
0.0
0.0
0.0
61.7
60.3
45.2
23.7
29.0
37.3
39.7
54.8
76.3
71.0
LL PL PI Cc Cu
0.0
0.0
0.0
0.0
0.0
D10D30
9.5
4.75
4.75
4.75
4.75
%Fines %Silt
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
Boring ID
7 - 8
34 - 34.9
9 - 10
4 - 5.5
4 - 5
B-1
B-2
B-3
B-4
B-5
7 - 8
34 - 34.9
9 - 10
4 - 5.5
4 - 5
Depth (Ft)Boring ID
B-1
B-2
B-3
B-4
B-5
Depth (Ft)
-12
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
ASTM D4546
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: Sample exhibited 2.3 percent swell upon wetting under an applied pressure of 200 psf.
8.588
(pcf) WC (%)Description USCS
CLAYEY SAND
Boring ID Depth (Ft)
2 - 3B-1
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
-12
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
ASTM D4546
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: Sample exhibited 4.3 percent compression upon wetting under an applied pressure of 1,000 psf.
9.484
(pcf) WC (%)Description USCS
LEAN CLAY with SAND
Boring ID Depth (Ft)
9 - 10B-2
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
-12
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
ASTM D4546
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: Sample exhibited 0.6 percent swell upon wetting under an applied pressure of 500 psf.
8.795
(pcf) WC (%)Description USCS
LEAN CLAY
Boring ID Depth (Ft)
4 - 5B-3
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
-12
-10
-8
-6
-4
-2
0
2
4
100 1,000 10,000
Ax
i
a
l
S
t
r
a
i
n
(
%
)
Pressure (psf)
ASTM D4546
One-Dimensional Swell or Collapse
Facilities | Environmental |Geotechnical | Materials
Notes: Sample exhibited 0.6 percent swell upon wetting under an applied pressure of 200 psf.
7.182
(pcf) WC (%)Description USCS
SANDY LEAN CLAY
Boring ID Depth (Ft)
2 - 3B-4
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
5,500
6,000
6,500
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Facilities | Environmental |Geotechnical | Materials
3081
0.0800
2.64
2.09
2.7
6163
4.00
1.91
0.56
89.84
108
18.7
Remarks:
Assumed Specific Gravity:
CARS
Calculated Void Ratio:
Undrained Shear Strength (psf):
Height / Diameter Ratio:
Calculated Saturation (%):
Depth (Ft)
34 - 34.5
ASTM D2166
Unconfined Compression Test
Specimen Test DataSpecimen Failure Mode
Axial Strain - %
Moisture Content (%):
Dry Density (pcf):
Diameter (in.):
Height (in.):
Failure Strain (%):
Co
m
p
r
e
s
s
i
v
e
S
t
r
e
s
s
-
p
s
f
Sample type LL PL PI
Strain Rate (in/min):
Boring ID Description
CLAYSTONE BEDROCK
Unconfined Compressive Strength (psf):
B-1
Fines (%)
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
2,200
2,400
0 1 2 3 4 5 6 7 8 9
Facilities | Environmental |Geotechnical | Materials
1180
0.0800
5.07
2.09
2.7
2361
4.01
1.92
0.60
79.34
105
17.7
Remarks:
Assumed Specific Gravity:
CARS
Calculated Void Ratio:
Undrained Shear Strength (psf):
Height / Diameter Ratio:
Calculated Saturation (%):
Depth (Ft)
19 - 20
ASTM D2166
Unconfined Compression Test
Specimen Test DataSpecimen Failure Mode
Axial Strain - %
Moisture Content (%):
Dry Density (pcf):
Diameter (in.):
Height (in.):
Failure Strain (%):
Co
m
p
r
e
s
s
i
v
e
S
t
r
e
s
s
-
p
s
f
Sample type LL PL PI
Strain Rate (in/min):
Boring ID Description
LEAN CLAY with SAND
Unconfined Compressive Strength (psf):
B-2
Fines (%)
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Facilities | Environmental |Geotechnical | Materials
2214
0.0800
1.93
2.11
2.7
4429
4.03
1.91
0.58
81.52
107
17.4
Remarks:
Assumed Specific Gravity:
CARS
Calculated Void Ratio:
Undrained Shear Strength (psf):
Height / Diameter Ratio:
Calculated Saturation (%):
Depth (Ft)
19 - 20
ASTM D2166
Unconfined Compression Test
Specimen Test DataSpecimen Failure Mode
Axial Strain - %
Moisture Content (%):
Dry Density (pcf):
Diameter (in.):
Height (in.):
Failure Strain (%):
Co
m
p
r
e
s
s
i
v
e
S
t
r
e
s
s
-
p
s
f
Sample type LL PL PI
Strain Rate (in/min):
Boring ID Description
CLAYSTONE BEDROCK
Unconfined Compressive Strength (psf):
B-5
Fines (%)
1901 Sharp Point Dr Ste C
Fort Collins, COTerracon Project No. 20245032
4710 Cinquefoil Lane | Fort Collins, CO
Touchmark Development Retirement Homes
Client
B-3
0.5'-5.0'
8.06
5 2 5
Nil
4 20 5
+219
358
2100
Analyzed By:
The tests were performed in general accordance with applicable ASTM and AWWA test methods. This report is exclusively for the use of the client
indicated above and shall not be reproduced except in full without the written consent of our company. Test results transmitted herein are only applicable to
the actual samples tested at the location(s) referenced and are not necessarily indicative of the properties of other apparently similar or identical materials.
10/23/2024Date Received:
Results from Corrosion Testing
Water Soluble Sulfate, ASTM C1580, (mg/kg)
20245032
Project
Beaverton, OR
Sample Location
Sample Depth (ft.)
Staff Geologist
pH Analysis, AASHTO T289
Sulfides, AWWA 4500-S D, (mg/kg)
Chloride, ASTM D512, (mg/kg)
Red-Ox, ASTM G200, (mV)
Total Salts, AWWA 2520 B, (mg/kg)
Resistivity (Saturated), ASTM G57, (ohm-cm)
Touchmark Development & Construction Co Touchmark Development Retirement Homes
ChrisAnne Ross
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Supporting Information
Contents:
General Notes
Unified Soil Classification System
Description of Rock Properties
Note: All attachments are one page unless noted above.
Auger
Cuttings
Modified
California
Ring
Sampler
Standard
Penetration
Test
Facilities | Environmental |Geotechnical | Materials
Unconfined
Compressive
Strength
Qu (psf)
less than 500
500 to 1,000
1,000 to 2,000
2,000 to 4,000
4,000 to 8,000
> 8,000
Touchmark Development Retirement Homes
4710 Cinquefoil Lane | Fort Collins, CO
Terracon Project No. 20245032
1901 Sharp Point Dr Ste C
Fort Collins, CO
N
(HP)
(T)
(DCP)
UC
(PID)
(OVA)
Standard Penetration Test
Resistance (Blows/Ft.)
Hand Penetrometer
Torvane
Dynamic Cone Penetrometer
Unconfined Compressive
Strength
Photo-Ionization Detector
Organic Vapor Analyzer
Water Level After a
Specified Period of Time
Water Level After
a Specified Period of Time
Cave In
Encountered
Water Level Field Tests
Water Initially
Encountered
Sampling
Water levels indicated on the soil boring logs are the
levels measured in the borehole at the times
indicated. Groundwater level variations will occur over
time. In low permeability soils, accurate
determination of groundwater levels is not possible
with short term water level observations.
General Notes
Location And Elevation Notes
Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude and Longitude are
approximate. See Exploration and Testing Procedures in the report for the methods used to locate the exploration points for this project. Surface
elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface
elevation was approximately determined from topographic maps of the area.
Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory data exist to classify the
soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this procedure is used. ASTM D2488 "Description and
Identification of Soils (Visual-Manual Procedure)" is also used to classify the soils, particularly where insufficient laboratory data exist to classify the
soils in accordance with ASTM D2487. In addition to USCS classification, coarse grained soils are classified on the basis of their in-place relative
density, and fine-grained soils are classified on the basis of their consistency. See "Strength Terms" table below for details. The ASTM standards
noted above are for reference to methodology in general. In some cases, variations to methods are applied as a result of local practice or
professional judgment.
Exploration/field results and/or laboratory test data contained within this document are intended for application to the project as described in this
document. Use of such exploration/field results and/or laboratory test data should not be used independently of this document.
Relevance of Exploration and Laboratory Test Results
Descriptive Soil Classification
> 30
15 - 30
8 - 15
4 - 8
2 - 4
0 - 1
Very Stiff
Consistency of Fine-Grained Soils Bedrock
(More than 50% retained on No. 200 sieve.)
Density determined by Standard Penetration
Resistance
Relative Density of Coarse-Grained Soils
< 3
Consistency
Stiff
Medium Stiff
Soft
Very Soft
(50% or more passing the No. 200 sieve.)
Consistency determined by laboratory shear strength testing, field
visual-manual procedures or standard penetration resistance
Strength Terms
6- 10
11 - 18
19 - 36
> 36
Standard
Penetration
or N-Value
(Blows/Ft.)
Ring
Sampler
(Blows/Ft.)
Relative Density
Very Loose
Loose
Standard
Penetration
or N-Value
(Blows/Ft.)
> 50
30 - 50
10 - 29
4 - 9
Ring
Sampler
(Blows/Ft.)
Hard
Medium Dense
Dense
Very Dense
15 - 46
0 - 3
3 - 5
Consistency
Standard
Penetration or
N-Value
(Blows/Ft.)
< 20
20 - 29
30 - 49
50 - 79
> 96
0 - 5
6 - 14
> 80
Weathered
Firm
_
47 - 79
Medium Hard
Hard
Very Hard
Ring
Sampler
(Blows/Ft.)
< 24
24 - 35
36 - 60
61 - 96
>79
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Unified Soil Classification System
Criteria for Assigning Group Symbols and Group Names Using
Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse-Grained Soils:
More than 50% retained
on No. 200 sieve
Gravels:
More than 50% of
coarse fraction
retained on No. 4
sieve
Clean Gravels:
Less than 5% fines C
Cu≥4 and 1≤Cc≤3 E GW Well-graded gravel F
Cu<4 and/or [Cc<1 or Cc>3.0] E GP Poorly graded gravel F
Gravels with Fines:
More than 12% fines C
Fines classify as ML or MH GM Silty gravel F, G, H
Fines classify as CL or CH GC Clayey gravel F, G, H
Sands:
50% or more of
coarse fraction
passes No. 4 sieve
Clean Sands:
Less than 5% fines D
Cu≥6 and 1≤Cc≤3 E SW Well-graded sand I
Cu<6 and/or [Cc<1 or Cc>3.0] E SP Poorly graded sand I
Sands with Fines:
More than 12% fines D
Fines classify as ML or MH SM Silty sand G, H, I
Fines classify as CL or CH SC Clayey sand G, H, I
Fine-Grained Soils:
50% or more passes the
No. 200 sieve
Silts and Clays:
Liquid limit less than
50
Inorganic: PI > 7 and plots above “A” line J CL Lean clay K, L, M
PI < 4 or plots below “A” line J ML Silt K, L, M
Organic: 𝐿𝐿 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑
𝐿𝐿 𝑛𝑜𝑡 𝑑𝑟𝑖𝑒𝑑<0.75 OL Organic clay K, L, M, N
Organic silt K, L, M, O
Silts and Clays:
Liquid limit 50 or
more
Inorganic: PI plots on or above “A” line CH Fat clay K, L, M
PI plots below “A” line MH Elastic silt K, L, M
Organic: 𝐿𝐿 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑
𝐿𝐿 𝑛𝑜𝑡 𝑑𝑟𝑖𝑒𝑑<0.75 OH Organic clay K, L, M, P
Organic silt K, L, M, Q
Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-inch (75-mm) sieve.
B If field sample contained cobbles or boulders, or both, add “with
cobbles or boulders, or both” to group name.
C Gravels with 5 to 12% fines require dual symbols: GW-GM well-
graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM
poorly graded gravel with silt, GP-GC poorly graded gravel with clay.
D Sands with 5 to 12% fines require dual symbols: SW-SM well-
graded sand with silt, SW-SC well-graded sand with clay, SP-SM
poorly graded sand with silt, SP-SC poorly graded sand with clay.
E Cu = D60/D10 Cc =
F If soil contains ≥ 15% sand, add “with sand” to group name.
G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
H If fines are organic, add “with organic fines” to group name.
I If soil contains ≥ 15% gravel, add “with gravel” to group name.
J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.
K If soil contains 15 to 29% plus No. 200, add “with sand” or
“with gravel,” whichever is predominant.
L If soil contains ≥ 30% plus No. 200 predominantly sand, add
“sandy” to group name.
M If soil contains ≥ 30% plus No. 200, predominantly gravel, add
“gravelly” to group name.
N PI ≥ 4 and plots on or above “A” line.
O PI < 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.
6010
2
30
DxD
)(D
Preliminary Geotechnical Engineering Report Report
Touchmark Development Retirement Homes | Fort Collins, Colorado
October 31, 2024 | Terracon Project No. 20245032
Facilities | Environmental | Geotechnical | Materials
Rock Classification Notes
WEATHERING
Term Description
Fresh Mineral crystals appear bright; show no discoloration. Features show little or now staining on surfaces. Discoloration
does not extend into intact rock.
Slightly
weathered
Rock generally fresh except along fractures. Some fractures stained and discoloration may extend <0.5 inches into
rock.
Moderately
weathered
Significant portions of rock are dull and discolored. Rock may be significantly weaker than in fresh state near
fractures. Soil zones of limited extent may occur along some fractures.
Highly weathered Rock dull and discolored throughout. Majority of rock mass is significantly weaker and has decomposed and/or
disintegrated; isolated zones of stronger rock and/or soil may occur throughout.
Completely
weathered
All rock material is decomposed and/or disintegrated to soil. The rock mass or fabric is still evident and largely intact.
Isolated zones of stronger rock may occur locally.
STRENGTH OR HARDNESS
Description Field Identification Uniaxial Compressive
Strength, psi
Extremely strong Can only be chipped with geological hammer. Rock rings on hammer blows. Cannot be
scratched with a sharp pick. Hand specimens require several hard hammer blows to break. >36,000
Very strong Several blows of a geological hammer to fracture. Cannot be scratched with a 20d
common steel nail. Can be scratched with a geologist’s pick only with difficulty. 15,000-36,000
Strong
More than one blow of a geological hammer needed to fracture. Can be scratched with a
20d nail or geologist’s pick. Gouges or grooves to ¼ inch deep can be excavated by a
hard blow of a geologist’s pick. Hand specimens can be detached by a moderate blow.
7,500-15,000
Medium strong
One blow of geological hammer needed to fracture. Can be distinctly scratched with 20d
nail. Can be grooved or gouged 1/16 in. deep by firm pressure with a geologist's pick
point. Can be fractured with single firm blow of geological hammer. Can be excavated in
small chips (about 1-in. maximum size) by hard blows of the point of a geologist’s pick;
3,500-7,500
Weak
Shallow indent by firm blow with geological hammer point. Can be gouged or grooved
readily with geologist's pick point. Can be excavated in pieces several inches in size by
moderate blows of a pick point. Small thin pieces can be broken by finger pressure.
700-3,500
Very weak
Crumbles under firm blow with geological hammer point. Can be excavated readily with
the point of a geologist's pick. Pieces 1-in. or more in thickness can be broken with finger
pressure. Can be scratched readily by fingernail.
150-700
DISCONTINUITY DESCRIPTION
Fracture Spacing
(Joints, Faults, Other Fractures)
Bedding Spacing
(May Include Foliation or Banding)
Description Spacing Description Spacing
Intensely fractured < 2.5 inches Laminated < ½-inch
Highly fractured 2.5 – 8 inches Very thin ½ – 2 inches
Moderately fractured 8 inches to 2 feet Thin 2 inches – 1 foot
Slightly fractured 2 to 6.5 feet Medium 1 – 3 feet
Very slightly fractured > 6.5 feet Thick 3 – 10 feet
Massive > 10 feet
ROCK QUALITY DESIGNATION (RQD) 1
Description RQD Value (%)
Very Poor 0 - 25
Poor 25 – 50
Fair 50 – 75
Good 75 – 90
Excellent 90 - 100
1. The combined length of all sound and intact core segments equal to or greater than 4 inches in length, expressed as a percentage
of the total core run length.