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SUBSURFACE EXPLORATION REPORT
HOMESTEAD II PAVEMENTS
HEARTHSTONE AND CORNERSTONE DRIVES)
FORT COLLINS, COLORADO
p EEC PROJECT NO. 1034086P
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EEC ;
EARTH ENGINEERING
CONSULTANTS, INc.
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E EC
II April 15, 2004 EARTH ENGINEERING
CONSULTANTS, INC.
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Splittgerber Professional Builders
U P.O. Box 271307
Fort Collins, Colorado 80527-1307
1111 Attn: Mr. Rick Splittgerber
Re: Pavement Design
II Homestead II(Cornerstone and Hearthstone Drives)
Fort Collins, Colorado
EEC Project No. 1034086P
IIMr. Splittgerber:1
111 Enclosed,herewith,are the results of the geotechnical subsurface exploration completed by
Earth Engineering Consultants,Inc.personnel for Cornerstone and Hearthstone Drives in the
II Homestead II 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.
IIWe appreciate the opportunity 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 any
Uother way,please do not hesitate to contact us.
Very truly yours,
U Earth Engineering Consultants,Inc.
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IIWolf von arl itz, P.E. Lester . Litton, P.E.
Senior Project ngineer Principal Engineer
II cc: Rick Richter- City of Fort Collins (4)
111 CENTRE FOR ADVANCED TECHNOLOGY
2301 RESEARCH BOULEVARD, SUITE 104
FORT COLLINS, COLORADO 80526
111 970) 224-1 522 (FAX) 224-4564
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SUBSURFACE EXPLORATION REPORT
HOMESTEAD II PAVEMENTS
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HEARTHSTONE AND CORNERSTONE DRIVES)
FORT COLLINS, COLORADO
EEC PROJECT NO. 1034086P
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April 15, 2004
INTRODUCTION
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The subsurface exploration for Hearthstone and Cornerstone Drives in the Homestead II
111 development in Fort Collins, Colorado has been completed. Four(4) hand auger 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 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 report. .
The Homestead development is located south of Kechter Road and west of Ziegler Road in
southeast Fort Collins. The locations of referenced roadways are indicated on the attached
location diagram. At this time, the referenced streets have been in service as gravel
surfaced roadways since the fall of 2003. We understand the existing aggregate base
surfacing will need to be undercut to allow for the incorporation of the new pavement
111 structure. We understand the water main was installed prior to the fall of 2003. The
sanitary sewer and water services were installed in the street rights-of-way in the fall of
2003. The purpose of our exploration was to define the existing subsurface conditions in
the referenced streets and provide recommended pavement sections for the roadways.
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EXPLORATION AND TESTING PROCEDURES
The boring locations were selected and established in the field by Earth Engineering
Consultants, Inc. (EEC) personnel. The hand auger borings were extended to a depth of
approximately 4 to 41/2 feet below subgrade level. The field locations were established by
approximating locations relative to identifiable site features. The locations of the test
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111 Earth Engineering Consultants,Inc.
EEC Project No. 1034086P
April 15, 2004
Page 2
111 borings should be considered accurate only to the degree implied by the methods used to
make the field measurements.
The borings were completed with a hand augering device. Samples of the subgrade
materials were obtained by pushing thin-walled tubes and from the excavated materials.
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.
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As a part of the testing program, all samples were examined in the laboratory by an
engineer 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.
SITE AND SUBSURFACE CONDITIONS
The roadways evaluated include Cornerstone and Hearthstone Drives in the Homestead II
development. The configuration of the roadways evaluated is indicated on the attached
111 boring location diagram. The water utility mainline was installed prior to the fall of 2003.
In the fall of 2003, the sewer and water services were installed. Field density tests have
been completed on the utility backfill.
1111 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
11 borings generally consisted of approximately 10 to 12 inches of aggregate base underlain
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Earth Engineering Consultants,Inc.
EEC Project No. 1034086P
April 15, 2004
Page 3
by reddish brown to dark brown sandy lean clay. A portion of material encountered in the
test borings was utility backfill. The site materials are moderately plastic as indicated from
the Atterberg limits tests. The lean clay subgrade soils showed low swell potential at
current moisture and density conditions. The subsurface soils have low remolded strength.
111 Bedrock was not encountered in any of the completed borings. The lean clay soils
encountered extended to the depth explored of approximately 4 to 4 t/2 feet below ground
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surface.
The stratification boundaries indicated on the boring logs represent the approximate
locations of changes in soil typesi in-situ, the transition of materials may be gradual and
indistinct.
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Observations were made while drilling and after completion of the borings to detect the
111 presence and depth to free water. Free water was not observed in any of the completed
borings at the time of augering. 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
A majority of the aggregate base surfacing for the roadways will need to be stripped to
allow for placement of a composite asphaltic concrete/aggregate base pavement section.
We understand a portion of the aggregate base materials and lean clay subgrades will be
111 blended, reconditioned and compacted to develop a stable roadway subgrade. Proofrolling
of the subgrades will be required prior to paving to insure a stable paving platform is in
place. At this time, field density tests have been completed on the utility service backfill
materials within the roadway areas. The test results indicate the site backfill materials
were compacted to at least 95% of standard Proctor maximum dry density.
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EEC Project No. 1034086P
April 15, 2004
Page 4
PAVEMENT DESIGN
Earth Engineering Consultants,Inc.
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 lean clay pavement
subgrades anticipated after stripping the aggregate base materials. 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
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111 3775 was used in the pavement evaluation.
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The AASHTO design guidelines for pavement design were used to evaluate a
recommended pavement section for this project. Recommended pavement sections based
on that evaluation is provided below in Table 1. Other sections could be considered;
ilhowever, City of Fort Collins standards require the use of a composite section.
II TABLE 1
EARTH ENGINEERING CONSULTANTS, INC.
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RECOMMENDED PAVEMENT SECTIONS
Roadway Cornerstone Drive Hearthstone Drive
U Traffic Load
18-Kip EDLA 15 10
Classification Local Connector Local
IIDesign Structural Number 2.71 2.55
Section A - Composite
Asphalt Surface (S or SX)4 in. 4 in.
IllAggregate Base 9 in. 7 in.
Section Structural Number, 2.75) 2.53)
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The asphaltic concrete used as the surface course in the pavement area should be consistent
Uwith City of Fort Collins classification for Grading S or SX for the local drives; Grading S
should be used for collector roadways. The aggregate base should be consistent with
IIColorado Department of Transportation requirements for Class 6 base.
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Earth Engineering Consultants,Inc.
EEC Project No. 1034086P
I April 15, 2004
Page 5
GENERAL COMMENTS
The analysis and recommendations presented in this report are based upon the data
obtained from the soil borings performed at the indicated locations and from any other
information discussed in this report. This report does not reflect any variations which may
occur between borings or across the site. The nature and extent of such variations may not
become evident until 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
111 observations during earthwork and foundation construction phases to help determine that
the design requirements are fulfilled.
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This report has been prepared for the exclusive use of Splitgerber Professional Builders 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
U 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.
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