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FOUNDATION IMPROVEMENT D09

WEST HYNES TANK FARMLONG BEACH, CALIFORNIA

Application: Plains All American Pipeline neededa foundation improvement solution for a new 205-

foot diameter, fuel-storage tank. GeoPentech, the

project engineers, suggested using a mechanically

stabilized earth (MSE) raft as an affordable solution.

The Challenge: Schedule, performance and costwere significant project drivers, but the overriding

concern was the potential effects of total and

differential settlement caused by subsurface

conditions or seismic events. Any foundation

approach would have to be capable of minimizing

differential settlement while supporting a maximum

applied bearing pressure of 3,500 psf.

Site Conditions: A subsurface soil investigation

revealed silty sand and clay soft soils to 10 feet

below grade with other weak soils continuing to

a depth of 50 feet. Soil borings also indicated

groundwater from 7 to 12 feet below grade.

These conditions increased the potential for soil

liquefaction during a seismic event.

Alternative Solutions: A traditional deepfoundation with stone columns proved to be more

expensive in terms of labor cost and materials.

The Solution: GeoPentech developed a rigidfoundation design using biaxial geogrid from

Tensar International Corporation (TIC). The design

consisted of a 265-foot diameter circle by 10-foot

deep MSE raft constructed with one layer of

geotextile fabric and seven equally spaced layers

of Tensar® BX Geogrid.

A crew began the installation by undercutting the

foundation to a maximum depth of 10 feet. Then,

they leveled and rolled the subgrade and covered

it with geotextile fabric followed by a one-foot lift

of 3/4-inch crushed rock. Next, they covered the

stone lift with overlapping layers of Tensar BX

Geogrid followed by a one-foot lift of crushed

aggregate base compacted to the specified density.

The crew repeated the layering process seven

times to create the MSE raft. As they neared theThe foundation had to be undercut prior to the installation of the MSE rafts.

PROJECT HIGHLIGHTS

Project:

West Hynes Tank Farm

Location:

Long Beach, California

Installation:

August 2007

Product/System:

Tensar® BX Geogrid

Dimension®Foundation Improvement System

Quantity:

50,000+ square yards

Owner/Developer:

Plains All American Pipeline, L.P.

Engineers:

GeoPentech, Inc.

Materials Supplier:

CONTECH Construction Products, Inc.

CASE

STUDY

DIM_CS_WHYNES_12.07

Tensar International Corporation5883 Glenridge Drive, Suite 200

Atlanta, GA 30328

800-TENSAR-1

www.tensar-international.com

For more information on the Dimension Foundation Improvement 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 moreU.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.Printed in the U.S.A.

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FOUNDATION IMPROVEMENT

finished grade, they began installing unreinforced

lifts of compacted fill. This unreinforced layer was

3-feet thick at the foundation's perimeter and

gradually tapered to 4-feet thick at the foundation's

center point.

"The tank farm owner was looking for an equivalent

solution that would be less time consuming and

less costly to install," says TIC Pacific South

Regional Manager Lars Nelson. "The MSE raft

design developed by GeoPentech satisfied those

requirements despite challenging soil conditions."

The Dimension System Advantage: An alternativesolution to deep overexcavation, chemical

stabilization, concrete slabs, grouting and deep

foundations, the Dimension System:

• Increases the effective bearing capacity of soils

beneath shallow spread footings.

• Reduces total and differential settlement

by forming a stiffened mat beneath

concrete footings.

• Improves the margin of safety against

unforseen soil conditions.

• Provides a Load Transfer Platform (LTP) System

when usedwith deep foundation systems such

as piles or vibro-concrete columns (VCCs).

• Provides an efficient load transfer mechanism

for intermediate foundation systems such as

Geopier® Rammed Aggregate Piers™.

Additional Information and Services:Tensar International Corporation, the leader in

geosynthetic soil reinforcement, offers different

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.Tensar® Geogrid provided the solution needed for a MSE raft foundation.