HomeMy WebLinkAboutCT 02-19; BRESSI RANCH PA 11; PAVEMENT SECTION DESIGN RECOMMENDATIONS FOR KEENELAND DRIVE; 2004-09-21Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
September 21, 2004
CITY OF CARLSBAD
APPROVED
Q WITH ADDITIONS
mo~ BY DATE
Project No. 971009-023
To: Lennar Communities
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Attention: Mr. John Slatton
Subject Pavement Section Design Recommendations for Keeneland Drive, Station No. 1+00
to 11+10, Planning Area PA- 11, Bressi Ranch, Carlsbad, California
References: Carlsbad, City of, 1996, Standards for Design and Construction of Public Works
Improvements in the City of Carlsbad, California, Project No. 05332-12-01, dated
April 20, 1993, revised December 10, 1996
Project Design Consultants (PDC), 2004, Plans for the Improvement of Bressi
Ranch, Planning Area 11, Carlsbad, California, Drawing No. 418-8, 11 Sheets,
dated June 30, 2004
Introduction
In accordance with the requirements of the City of Carlsbad, this letter presents our pavement
design recommendations for Keeneland Drive (between Station No. 1+00 and 11+10), in Carlsbad,
California. Two representative subgrade soil samples were obtained along the roadway alignment.
The samples were transported to our laboratory and R-value testing (in accordance with Caltrans
Test Method 301) was performed. The test results indicated the subgrade soils have R-values
ranging from 14 to 17. The approximate sample locations and results of the laboratory testing are
presented in Appendix A.
Based on the project Improvement Plans (Project Design Consultants, 2004), we understand that
Keeneland Drive have a Traffic Index (TI) of 6.0. According to the city requirements (Carlsbad,
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongeo.com
9711090-023
1996), the minimum pavement section for streets having a TI of 6.0 is 4 inches of Asphalt Concrete
(AC) over 6 inches of Aggregate Base (AB) regardless of the R-Value.
Pavement Section Utilizing Class 2 Aggregate Base Material
Based on the above information, the recommended Class 2 Aggregate Base pavement section
was calculated using the Caltrans Highway Design Manual Method and compared with the City
of Carlsbad's minimum section thickness requirements. The recommended pavement sections are
presented on Table 1.
Table 1
Recommended Pavement Section Utilizing Class 2 Aggregate Base
Asphalt Concrete Class 2
Location Traffic Design Thickness Aggregate Base
Index R-Value (inches) Thickness
(inches)
Keeneland Drive, 6.0 17 4.0 11.0 Station No. 1+00 to 6+00
Keeneland Drive, 6.0 14 4.0 12.0 Station No. 6+00 to 11+10
Prior to placement of the street aggregate base material, the upper 12 inches of subgrade soils in the
street (including beneath the curb and gutter and 6-inches behind the curb and gutter) shall be
scarified, moisture-conditioned (or dried back) as necessary to at least optimum moisture content
and compacted to a minimum 95 percent relative compaction based on American Standard of
Testing and Materials (ASTM) Test Method D1557.
Class 2 Aggregate Base shall then be placed and compacted at a minimum 95 percent relative
compaction in accordance with ASTM Test Method D1557. The aggregate base material shall be a
maximum of 6 inches thick below the curb and gutter and extend a minimum of 6 inches behind the
back of the curb. The Class 2 Aggregate Base shall conform to and be placed in accordance with
the latest revision of the California Department of Transportation Standard Specifications (Section
26), the Greenbook specifications, and/or the City of Carlsbad requirements. Asphalt Concrete shall
conform to and be placed in accordance with the "Greenbook" Standard Specifications for Public
Works Construction and the City of Carlsbad requirements.
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971009-023
If pavement is planned adjacent to landscaped areas, we recommend that appropriate measures be
taken (such as keeping the amount of landscape irrigation to a minimum, installing area drams or
other devices, etc.) to reduce the possible adverse effects of water on the pavement subgrade.
If you have any questions regarding our letter, please contact this office. We appreciate this
opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
AK
neZT6i2 Randall K. wag
Senior Associate P
Attachments: Appendix A - Laboratory Testing Procedures and Test Results
Distribution: (2) Addressee
(2) Lennar Communities, Attention: Mr. Jim Urbina
(2) City of Carlsbad, Public Works Department, Attention: Mr. Casey Arndt
Leighton
971009-023
APPENDIX A
Laboratory Testing Procedures and Test Results
"R"-Value: The resistance "R"-value was determined by the California Materials Method No. 301
for subgrade soils. Three samples were prepared and exudation pressure and "R"-valiie determined
on each one. The graphically determined "R"-value exudation pressure of 300 psi is summarized in
the table below:
Sample Number Sample Location Sample Description R-Value
R-133 Keeneland Drive, Station No. 4+30 Yellow-Brown clay clayey 17 SAND
R-134 Keeneland Drive, Station No. 9+75 Yellow-Brown clayey, 14 SAND
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