HomeMy WebLinkAboutCT 00-06; BRESSI RANCH; CONCRETE BUS PAS DESIGN RECOMMENDATIONS; 2004-04-05croO-oc
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
April 5, 2004
Project No. 971009-015
To: Lennar Communities
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Attention: Ms. Kristine Zortman
Subject: Concrete Bus Turnout Pad Design Recommendations for the South Side of Palomar
Airport Road (Station Nos. 104+30 to 106+00 and 144+30 to 146+00) and the East
Side of El Camino Real (Station No. 303+93 to 305+53), Bressi Ranch, Carlsbad,
California
References: North County Transit District (NCTD), 2004, Bus Stop Development Handbook,
dated February, 2004
Project Design Consultants (PDC), 2003a, Plans for the Improvement of Palomar
Airport Road, Carlsbad, California, Project No. CT 00-06, Drawing No. 400-8H, 31
Sheets, dated May 22, 2003
2003b, Improvement Plans for El Camino Real, Carlsbad, California,
Project No. CT 00-06, Drawing No. 400-8G, 16 Sheets, dated June 24, 2003
Introduction
This letter presents our preliminary concrete pad design recommendations for the bus stop turnouts
on Palomar Airport Road and El Camino Real along the perimeter of the Bressi Ranch project,
located in Carlsbad, California. The bus stops are proposed along the south side of Palomar Airport
Road between Station No. 104+30 to 106+00 and 144+30 to 146+00 and along the east side El
Camino Real between Station No. 303+93 to 305+53.
Three representative subgrade soil samples were obtained within the general vicinity of the
proposed bus stops. 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 5 to 47. The approximate sample locations and results of the
laboratory testing are presented in Appendix A.
3934 Murphy Canyon Road, Suite B205 w San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongeo.com
971009-015
Based on the North County Transit District requirements (NCTD, 2004), we recommend that the
concrete pavement design for the Bressi Ranch bus stops consist of a minimum of 9 inches of
Portland Cement Concrete (PCC) over 6 inches of Cement Treated Base (CTB). As an
alternative, the concrete pavement design may consist of 8 inches of PCC with reinforcement
rebar over 6 inches of CTB. The PCC should have a minimum modulus of rupture of at least
600 psi and a minimum strength of 3,000 psi. If the 8-inch thick concrete with reinforcement
section is used, the rebars should be placed at mid-height and consist of No. 4 rebars at 18 inches
on center (each way) at a minimum. Instead of the placement of cement treated base beneath the
PCC, a minimum of 9 inches of Class 2 Aggregate Base (AB) may be utilized as an additional
alternative.
Prior to placement of the PCC and base material (CTB or AB), the upper 12 inches of subgrade
soils 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. The CTB or AB shall then be
placed and compacted at a minimum 95 percent relative compaction in accordance with ASTM
Test Method D1557. The PCC, CTB or AB shall conform to and be placed in accordance with the
latest revision of the California Department of Transportation Standard Specifications, the
Greenbook specifications, and/or the City of Carlsbad and NCTB requirements.
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.
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William D. Olson, RCE 45283
Senior Project Engineer CI
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CEG 161 Randall K.
Senior Associate
Attachments: Appendix A - Laboratory Test Results
Distribution: (2) Addressee
Lennar Communities, Attention: Mr. Jim Urbina
City of Carlsbad, Public Works Department, Attention: Mr. Casey Arndt
(1) J. T. Kruer, Attention: Mr. Chuck Knight
(1) Hazard Construction Company, Attention: Mr. Lino Cruz
-2-
Leighton
971009-015
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
1
R-Value
R-2 El Camino Real, Station No. Light brown clayey 23 305+00 SAND
R-23 Palomar Airport Road, Station No. Light brown silty CLAY 5 105+00
R-24 Palomar Airport Road, Station No. Light brown silty SAND 47 145+00
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