CASE

STUDY

S49BALLAST REINFORCEMENT

Using Tensar BX Geogrid allowed the reduction of ballast thickness while

improving the line’s long-term, load-carrying capacity.

ST. CHARLES AVENUESTREETCAR LINENEW ORLEANS, LOUISIANA

Application: The New Orleans Regional Transit

Authority relied on the Spectra® Rail System

to reinforce a 14-mile section of the historic

St. Charles Avenue streetcar line.

The Challenge: The St. Charles Avenue trackbed

had not been renovated in nearly 80 years.

The project was part of a $47 million effort that

included installing new tracks, ties and ballast.

The challenge was to reduce the ballast thickness

while limiting vertical stress on the subgrade

to 20 psi as recommended by the American

Railway Engineering and Maintenance of Way

Association (AREMA).

Site Conditions: The existing light-rail bed

included more than two feet of ballast placed

on top of a cypress plank foundation. Soft

conditions were a challenge due to a high water

table throughout the rail corridor.

Alternative Solutions: Tensar® Biaxial (BX)

Geogrids were the only solution considered for

this project. The Spectra Rail System was

recommended as a lower cost alternative to

traditional strategies of increasing ballast

thickness. Reinforcing the new ballast with Tensar

BX1300 Geogrid would produce a strong

construction platform with less need for the

excavation of the existing subgrade or importing

of new aggregate material.

The Solution: Design calculations indicated that

using a single layer of Tensar BX Geogrid along

the main line segments and two layers at each

road crossing would decrease the effective stress

at the bottom of the trackbed by up to 65 percent

thus offering longer life and less maintenance

relative to an unreinforced section. The geogrid

would also reduce the total ballast profile from

PROJECT HIGHLIGHTS

Project:

St. Charles Avenue Streetcar Line

Location:

New Orleans, Louisiana

Installation:

1994

Product/System:

BX1300 Geogrid/Spectra Rail System

Quantity:

80,000 sq yds

Owners:

New Orleans Transit Authority

Design Engineer:

Daniel, Mann, Johnson, Mendenhall Inc.,

New Orleans, Louisiana

General Contractor:

Comtrak Inc., Atlanta, Georgia

Materials Supplier:

CONTECH Construction Products, Inc.

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Tensar International Corporation

5883 Glenridge Drive, Suite 200

Atlanta, GA 30328

800-TENSAR-1

www.tensar-international.com

For more information on the Spectra Rail® System or other Tensar Systems,

call 800-TENSAR-1, e-mail info@tensarcorp.com or visit www.tensar-international.com.

©2007, Tensar International Corporation, Limited LLC, Inc. Certain products and/or applications described or illustrated herein are protected under one or more

U.S. patents. Other U.S. patents are pending, and certain foreign patents and patent applications may also exist. Trademark rights also apply as indicated herein.

Final determination of the suitability of any information or material for the use contemplated, and its manner of use, is the sole responsibility of the user.

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Authorized Representative:

BALLAST REINFORCEMENT

26 inches to 12 inches while improving the line's

long-term, load-carrying capacity.

The St. Charles Avenue trackbed was prepared

by removing the old rails and ties and then

excavating the existing ballast to the top of the

cypress plank foundation or to a maximum depth

of 26 inches. In areas where the cypress planks

were exposed, a one inch thick layer of sand was

placed and compacted.

Next, a layer of filter fabric was installed to help

maintain free drainage. The filter fabric was

covered with four inches of rock ballast followed

by Tensar BX1300 Geogrid. The larger aperture

size of BX1300 allowed the ballast rock to strike-

through the reinforcement. The end seams of

each roll were overlapped by 12 inches before

covering with an additional 8 inches of

compacted railroad ballast.

The Spectra Rail System Advantage:

The New Orleans Transit Authority benefited from

the Spectra Rail System by substantially reducing

the construction time and costs associated with

renovating the track. It was able to improve

subgrade performance and durability by reducing

and more evenly distributing the load imposed

on the subgrade. The authority gained these

advantages even while reducing the required

ballast thickness. Overall, the project required

less excavation and the installation was simpler,

faster and less expensive than traditional

solutions. Work was able to continue even when

the installers encountered difficult working

conditions such as inclement weather.

Additional Information and Services:

Tensar International Corporation, the leader in

geosynthetic soil reinforcement, offers systems for

improving structures such as roadways, railyards,

construction platforms and parking lots. Our

products and technologies, backed by the most

thorough quality assurance practices, are at the

forefront of the industry. Highly adaptable, cost-

effective and installation-friendly, they provide

exceptional, long-term performance under the

most demanding conditions. Our support services

include site evaluation, design consulting and

site construction assistance.

For innovative solutions to your engineering

challenges, rely on the experience, resources and

expertise that have set the industry standard for

more than two decades.

The Spectra Rail System was used to get the historic

St. Charles Avenue streetcar line back on track.

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