HomeMy WebLinkAboutCT 03-03; BRESSI RANCH AFFORDABLE HOUSING; PAVEMENT SECTION DESIGN RECOMMENDATIONS; 2004-09-30C77'3 7;
/ APPROVED
I WITH ADDlTIONS
/Z/Z8/04
BY DATE
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
September 30, 2004
Project No. 971009-025
To: Greystone Homes
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Attention: Mr. Keith Randhahn
Subject: Pavement Section Design Recommendations for Liberty Place, Affordable Housing
Site, Planning Area PA- 15, 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, Bressi Ranch Affordable Housing
Improvement Plans, CT 03-03, Carlsbad, California, Drawing No. 415-3, 8 Sheets,
dated April 12, 2004
Introduction
In accordance with the requirements of the City of Carlsbad, this letter presents our pavement
design for Liberty Place between Buildings 3 and 4 for the Affordable Housing within Planning
Area PA-is of the Bressi Ranch project located in Carlsbad, California. One representative
subgrade soil sample was obtained along the subject street alignment. The sample was transported
to our laboratory and R-value testing (in accordance with Caltrans Test Method 301) was
performed. The test result indicates the subgrade soils have an R-value of 14. The approximate
sample location and results of the laboratory testing are presented in Appendix A.
Based on the project Improvement Plans (Project Design Consultants, 2004), we understand that
Liberty Place has a Traffic Index (TI) of 5.0. According to the city requirements (Carlsbad, 1996),
the minimum pavement section for streets having a TI of 5.0 is 4 inches of Asphalt Concrete (AC)
over 4 inches of Aggregate Base (AB) regardless of the R-Value.
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongeo.com
971009-025
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 (in inches) Thickness
(in inches)
Liberty Place [ 5.0 [ 14 4.0 6.0
Prior to placement of the street aggregate base material, the upper 12 inches of subgrade soils in the
street (including 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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Leighton
971009-025
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 drains 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.
ENGINEE
( No. 161-2
* CERTIFIEJ
Randall K. Wagner, EG 1612
Senior Associate
Attachments: Appendix A - Laboratory Testing Procedures and Test Results
Distribution: (4) Addressee
(2) City of Carlsbad, Public Works Department, Attention: Mr. Casey Arndt
-3- Leighton
971009-025
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"-value 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-136 E~ _ ] Liberty Place Pale olive-brown sandy lean CLAY 14
A-i
Leighton