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SUBSURFACE EXPLORATION REPORT
HEARTIHFIRE PAVEMENTS
FORT COLLINS, COLORADO
EEC PROJECT NO. 1034124P
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EARTH ENGINEERING
CONSULTANTS, INC.
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January 31, 2005 EARTH ENGINEERING
CONSULTANTS, INc.
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Schmidt Earth Builders, Inc.is
111 7250 Greenridge Road
Windsor, Colorado 80550
1 Attn: Mr. Darrell Bragg
III
Re: Geotechnical Exploration and Pavement Design
Hearthfire 2nd
Larimer County, Colorado
ll
EEC Project No. 1034124P
Mr. Bragg:
ll Enclosed, herewith, are the results of the geotechnical subsurface exploration completed
by Earth Engineering Consultants, Inc. personnel for Bateleur Lane, Buteos Court and a
Iportion of Buntwing Lane and Town Center Drive in the Hearthfire development in Fort
Collins. The structural pavement design for the roadways is included with this report
based on traffic numbers provided by the City of Fort Collins Engineering Department.
We appreciate the opportunityopportunity to be of service to you on this project. If you have any
questions concerning the enclosed report, or if we can be of further service to you in any111otherway,please do not hesitate to contact us.
Very truly yours,
1111 Earth Engineering Consultants,Inc.
Reviewed by:
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Wolf von Carlowi ,P.E. Lester L. Litton,P.E.
4 Senior Project Engineer Principal Engineer
cc: Rick Richter- City of Fort Collins(4)
111 4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
NI 970) 224-1522 FAX (970) 663-0282
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ME SUBSURFACE EXPLORATION REPORT
HEARTHFIRE PAVEMENTS
FORT COLLINS, COLORADO
EEC PROJECT NO. 1034124P
January 31, 2005
INTRODUCTION
The subsurface exploration for Bateleur Lane,Buteos Court and portions of Buntwing Lane
and Town Center Drive in the Hearthfire development in Fort Collins, Colorado has been
completed. Thirteen(13)soil borings were advanced in the right-of-way of the new streets to
develop information on existing subsurface conditions. At the time of our exploration,the
1 sanitary sewer and water lines had been installed in the roadway rights-of-way. Individual
boring logs and a diagram indicating the approximate boring locations are included with this
111
report.
The Hearthfire development is located south of Douglas Road and west of Larimer County
Road 11 in northeast Fort Collins. The locations of referenced roadways are indicated on the
attached location diagram. At the time of our exploration, the street subgrades were at
approximate final grade and the sanitary sewer and water utilities had been installed in the
street rights-of-way. The purpose of our exploration was to define the existing subsurface
11 conditions in the referenced streets and provide recommended pavement sections for the
roadways.
EXPLORATION AND TESTING PROCEDURES
The boring locations were selected and established in the field by Earth Engineering
Consultants, Inc. (EEC) personnel. In accordance with current City of Fort Collins,
requirements, two (2) soil borings were advanced at each of six (6) test areas where deep
utilities had been installed. In roadway areas where deep utilities were installed,one of the
borings at each test location was advanced in the utility trench backfill area to a depth of
approximately 5 feet below present grade. A second boring was advanced to a depth of
I
111 Earth Engineering Consultants,Inc.
EEC Project No. 1034124P
January 31,2005
Page 2
approximately 10 feet below surface grade at each test location outside the utility backfill
area. The boring locations were selected and established in the field by Earth Engineering
111 Consultants, Inc. (EEC)personnel. The field locations were established by approximating
locations relative to identifiable site features. The locations of the field borings should be
considered accurate only to the degree implied by the methods used to make the field
measurements.
The borings were performed with a CME-45 drill rig using 4-inch nominal diameter
continuous flight augers. Samples of the subgrade materials were obtained in general
accordance with split-barrel and California barrel sampling procedures(ASTM Specification
D-1586) and from the auger cuttings. Subsurface samples were also obtained by pushing
thin-walled "Shelby" tubes in general accordance with ASTM Specification D-1587. All
samples were sealed and returned to our Fort Collins laboratory for further examination,
classification and testing.
Moisture content tests were completed in the laboratory on each of the recovered samples.
Washed sieve analysis and Atterberg limits tests were performed on selected samples to help
evaluate the quantity and plasticity of fines in the subgrade soils. Swell/consolidation tests
were performed on selected samples to help evaluate subgrade volume change
characteristics.
I
As a part of the testing program,all samples were examined in the laboratory by an engineer
U and classified in accordance with the attached General Notes and the Unified Soil'
Classification System,based on the soil's texture and plasticity. The estimated group symbol.
for the Unified Soil Classification System is shown on the boring logs and a brief description
of that classification system is included with this report.
111 SITE AND SUBSURFACE CONDITIONS
The roadways evaluated include Bateleur Lane,Buteos Court and portions of Buntwing Lane
and Town Center Drive. The configuration of the roadways evaluated is indicated on the
N
1
Earth Engineering Consultants,,Inc.
EEC Project No. 1034124P
January 31,2005
Page 3
attached boring location diagram. At this time,utility installations have been completed in
the referenced roadways. Field density tests have been completed on the utility backf ll.
Based on the results of our subsurface exploration and laboratory testing, subsurface
conditions can be generalized as follows. The subgrade soils encountered in the test borings
generally consisted of light to dark brown lean clay with varying amounts of silt and sand
sized particles. A portion of material encountered in the test borings was site fill and/or
utility backfill. Clayey sand was encountered underlying the lean clay at depths of
approximately 7 to 8 feet below present grade in borings B-4b,B-5b,B-6b and B-7b. The
site materials are slightly to moderately plastic as indicated from the Atterberg limits tests. A
portion of the near surface lean clay was relatively dry at the time of drilling and showed low
to moderate swell potential in their in-situ moisture and density conditions. The subsurface
soils have low to moderate remolded.strength. Bedrock was not encountered in any of the
completed borings. The site borings were terminated at depths of approximately 5 and 10
feet below ground surface in the lean clay and clayey sand.
The stratification boundaries indicated on the boring logs represent the approximate locations
of changes in soil types; in-situ,the transition of materials may be gradual and indistinct.
Observations were made while drilling and after completion of the borings to detect the
presence and depth to free water. Free water was not observed in any of the completed
borings at the time of drilling. Fluctuations in groundwater levels can occur over time
depending on variations in hydrologic conditions and other conditions not apparent at the
time of this report. Zones of perched and/or trapped water may be encountered at times
throughout the year in more permeable zones in the subgrade materials.
ANALYSIS AND RECOMMENDATIONS
The subgrades for the roadways have been prepared in general accordance with City of Fort
Collins criteria. The sewer and water utilities have been installed within the roadway rights-
of-way in accordance with City requirements. Field density tests have been completed on the
Earth Engineering Consultants,Inc.
EEC Project No. 1034124P
January 31,2005
Page 4
utility backfill materials within the roadway areas. The test results indicate the site fill and
backfill materials were compacted to at least 95%of standard Proctor maximum dry density.
SWELL.MITIGATION
The subgrade soils in the roadway areas generally consist of lean clay with low to moderate
swell potential. At current moisture and density conditions, some movement of lightly
loaded pavements placed directly on dry near surface soils would be expected. To develop a
low expansion potential pavement subgrade and reduce the potential for total and differential
movement subsequent to construction, we recommend stabilization of the pavement
subgrades with Class C fly ash.
We recommend the roadway subgrades be stabilized to a minimum depth of 12 inches.
Based on previous experience with similar materials and subgrade conditions, it is our
opinion that the addition of Class C fly ash to the subgrades would result in higher stability
and lower expansion potential. We estimate 12%Class C fly ash based on the dry weight of
the materials could be used for the subgrade stabilization. The Class C fly ash should be
thoroughly blended with the subgrade soils with the blended mixture adjusted in moisture
content and compacted to at least 95%of the material's maximum dry density as determined
in accordance with ASTM Specification D-698, the standard Proctor procedure. The
moisture content of the blended materials should be adjusted to be within the range of f2%
of standard Proctor optimum moisture. A slightly dry blend would result in higher
compressive strengths of the fly ash/soil blend. Those materials should be compacted and
finished within 2 hours of the initial fly ash addition.
We expect the stabilized subgrades could be used for direct support of composite asphalt
concrete pavement sections as required by the City of Fort Collins. Because the fly ash
stabilization will be used as'a swell mitigation procedure, credit for the stabilized zone
cannot be included\in the pavement design under current City of Fort Collins guidelines.
Care will be needed to insure pavement subgrades are not disturbed prior to paving.
Earth Engineering Consultants,Inc.
EEC Project No. 1034124P
January 31,2005
Page 5
I
PAVEMENT DESIGN
Pavement section recommendations are provided in this report based on the traffic loading
provided by the City of Fort Collins Engineering Department and remolded subgrade
strength characteristics. An R-value less than 5 was estimated for the rough graded
pavement subgrades. Using the American Association of State Highway and Transportation
Officials (AASHTO) correlation,that R-value corresponds to a resilient modulus value of
3775. The resilient modulus value of 3775 was used in the pavement evaluation.
The AASHTO design guidelines for pavement design were used to evaluate a recommended
pavement section for this project..Recomniended pavement sections based on that evaluation
is provided below in Table 1. Other sections could be considered; however, City of Fort
Collins standards require the use of a composite section.
TABLE 1
EARTH ENGINEERING CONSULTANTS,INC.
RECOMMENDED PAVEMENT SECTIONS
Roadway Buntwing Lane Bateleur Lane Bateleur Lane
Town Center West) East),Buteos
Drive Court
Traffic Load
18=Kip EDLA 25 15 5
Classification Collector Connector Local
Design Structural Number 2.97 2.74 2.29
Section A—Composite
Asphalt Surface(S or SX) 2 in. 4 in. 4 in.
Asphalt Base(SG) 3 in.
Aggregate Base 7 in. 9 in. 6 in.
Section Structural Number 2.97) 2.75) 2.42)
Minimum section required by current City of Fort Collins design standards
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Earth Engineering Consultants,Inc.
EEC Project No. 1034124P
January 31,2005
Page 6
The asphaltic concrete used as the surface course in the pavement area should be consistent
with City of Fort Collins classification for Grading S or SX for the local drives; Grading S
should be used for collector roadways. Grading SG asphaltic concrete will be required for
the bottom lift in asphalt sections greater than 4 inches. The aggregate base should be
consistent with Colorado Department of Transportation requirements for Class 5 or Class 6
base.
GENERAL COMMENTS
The preliminary analysis and recommendations presented in this report are based upon the
data obtained from the soil borings performed at the indicated locations and from any other
information discussed in this report. This report does not reflect any variations which may
occur between borings or across the site. The nature and extent of such variations may not
become evident until further exploration or construction. If variations appear evident,it will
be necessary to re-evaluate the recommendations of this report.
It is recommended that the geotechnical engineer be retained to review the plans and
specifications so that comments can be made regarding the interpretation and implementation
of our geotechnical recommendations in the design and specifications. It is further
recommended that the geotechnical engineer be retained for testing and observations during
earthwork and foundation construction phases to help determine that the design requirements
are fulfilled.
This report has been prepared for the exclusive use of Schmidt Earth Builders Inc-. for
specific application to the project discussed and has been prepared in accordance with
generally accepted geotechnical engineering practices. No warranty,express or implied,is
made. In the event that any changes in the nature, design or location of the project as
outlined in this report are planned,the conclusions and recommendations contained in this
report shall not be considered valid unless the changes are reviewed and the conclusions of
this report modified or verified in writing by the geotechnical engineer.
III DRILLING AND EXPLORATION
III
DRILLING&SAMPLING SYMBOLS:
SS: Split.Spoon- 13/8"I.D.,2"O.D.,unless otherwise noted PS: Piston Sample
ST: Thin-Walled Tube-2"O.D.,unless otherwise noted WS: Wash Sample
R: Ring Barrel Sampler-2.42"I.D.,3"O.D.unless otherwise noted
U PA: Power Auger FT: Fish Tail Bit
HA; Hand Auger RB: Rock Bit
DB: Diamond Bit=4",N,B BS: Bulk Sample
AS: Auger Sample PM: Pressure Meter
HS: Hollow Stem Auger WB: Wash Bore
Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2-inch O.D. split spoon, except where
noted.
WATER LEVEL MEASUREMENT SYMBOLS: r
WL : Water Level WS : While Sampling
WCI: Wet Cave in WD While Drilling
DCI: Dry Cave in BCR Before Casing Removal
AB : After Boring ACR: After Casting Removal
Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils,the indicated
levels may reflect the location of ground water. In low permeability soils,the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
Soil Classification is based on the Unified Soil Classification joints. May be color change.
system and the ASTM Designations D-2488. Coarse Grained Moderate Some decomposition and color change
Soils have move than 50% of their dry weight retained on a throughout.
200 sieve; they are described as: boulders, cobbles, gravel High Rock highly decomposed, may be
or sand. Fine Grained Soils have less than 50% of their dry" extremely broken.
weight retained on a#200 sieve;they are described as : clays, HARDNESS AND DEGREE OF CEMENTATION:
if they are plastic, and silts if they are slightly plastic or non- Limestone and Dolomite:
plastic. Major constituents may be added as modifiers and Hard Difficult to scratch with knife.
minor constituents may be added according to the relative
Moderately Can be scratched easily with knife.
proportions based on gram size. In addition to gradation,
coarse grained soils are defined on the basis of their relative Hard Cannot be scratched with fingernail.
in-place density and fine grained soils on the basis of their Soft Can be scratched with fingernail.
consistency. Example: Lean clay with sand, trace gravel,
stiff(CL);silty sand,trace gravel,medium dense(SM). Shale,Siltstone and Claystone:
Hard Can be scratched easily with knife, cannot
CONSISTENCY OF FINE-GRAINED SOILS
be scratched with fingernail.
Moderately Can be scratched with fingernail.
Unconfined Compressive Hard
Strength,Qu,psf Consistency Soft Can be easily dented but not molded with
fingers.
500 Very Soft Sandstone and Conglomerate:
500- 1,000 Soft Well Capable of scratching a knife blade.
1,001 - 2,000 Medium Cemented
2,001 - 4,000 Stiff Cemented Can be scratched with knife.
4,001 - 8,000 Very Stiff
8,001. 16,000 Very Hard Poorly Can be broken apart easily with fingers.
Cemented
RELATIVE DENSITY OF COARSE-GRAINED SOILS:
N-Blows/ft Relative Density
0-3 Very Loose
4-9 Loose
10-29 Medium Dense EC."'30-49 Dense
50-80 Very Dense S '
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80+Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
UNIFIED SOIL CLASSIFICATION SYSTEM
Soil Classification
Group Group Name
Criteria for Assigning Croup Symbols and Croup names Using Laboratory Tests Symbol
Coarse-Grained Gravels more than Clean Gravels Lees
Soils more than 50%of coarse than 5% fines Cu4-and r 3° GW Well-graded gravel'
50% retained on fraction retained
No. 200 sieve on No. 4 sieve Cu<4 and/or 1)Cc>31 GP Poorly-graded graver
Gravels with Fines Fines dossify as ML or NH GM Silty,gravel, G,H
more than 12% - -
finesfines Fines classify as CL or CH_ GC Clayey Gravel 1A1
Sands 50% or dean Sands Less Cut$and l<c 3`SW Well-graded sand'
il
more coarse than 5% fines
fraction posses Cu<6 and/or 1>Cc>3` SP Poorly-graded sand'
No. 4 sieve
Sands with Fines Fines classify as ML or MH SM Silty sand mu
more than 12%
fines Fines classify as CL or CH SC Clayey sand
Fine-Gained Silts and Cloys inorganic PI>7 and plots on or above'Kline' CL Lean clay"".
Soils 50%or Liquid Limit less•
more.:passes the than 50 PI<4 or plots below•A•Line'Mi. Sllt'4'
No. 200 sieve
organic Liquid Unlit - oven dried Organic clay
D.75 OL
Liquid Limit - not dried Organic silt'd"1O
Silts and Clays inorganic PI plots on or above*Kline CH Fat cloy"°
LiquidinLimit50orw,
more PI plots below.A•Line MH Elastic Silt
organic Liquid Lidnit - oven dried • Organic clay"'
0.75 OH
Liquid Limit- not dried. Organic silte""
Highly organic soils Primarily organic matter,dark in color, and organic odor PT Peat
I,;-,
Based on the motarid passing the 3-tn.(75-of soil ountaen 15 to 2pp 1i No 200.add
CY[?b/D,Ces with°
nabnadr
or*with greed-.'Mahood is
9f ileld,sonpls contained cobbles or boulders. f4eW.wn tdm 2 3C'plus Na 2a0
or both.odd"wadi oobblos or tuonddare.or both" predominantly sand add d°iidr to group
to coup rrdme. If soil contains 245%mod adroit!'sane'to
0 c ravels ulth S to 12%fines required dud 9ra'names of sage oant°Im:3a-pin No 10D
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OP-0c poorly-gredsd.g ewl id%day iifnie-oantaem>1 word.*dd'witl,grmwr plots on or Shires'A• m
Sands-with 5 to 12%firm require dud to q"rop.names. gel pats below A•Ono.
If nursers limits plots°haled grog soil is o.
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BORING LOCATION DIAGRAMPt1HEARTHFIRE2ND - LARIMER COUNTY, COLORADO
EEC PROJECT NUMBER: 1034124P
JANUARY 2005
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EARTH ENGINEERING CONSULTANTS