The Plains All American Pipeline needed to improve the foundation for a new 205-foot diameter fuel storage tank due to soft soils and groundwater at the site. An MSE raft foundation using Tensar BX Geogrid was selected as it would be more affordable and reduce differential settlement compared to deep foundations. Crews installed the 265-foot diameter MSE raft by excavating 10 feet, placing layers of geotextile and geogrid, and compacting aggregate between the layers. The MSE raft foundation satisfied the project needs of supporting the tank weight while minimizing settlement risks from subsurface conditions.

1. CASESTUDY
FOUNDATION IMPROVEMENT D09
WEST HYNES TANK FARM
LONG BEACH, CALIFORNIA
Application: Plains All American Pipeline needed
a 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 cost
were 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 deep
foundation with stone columns proved to be more
expensive in terms of labor cost and materials.
The Solution: GeoPentech developed a rigid
foundation 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®FoundationImprovementSystem
Quantity:
50,000+ square yards
Owner/Developer:
Plains All American Pipeline, L.P.
Engineers:
GeoPentech, Inc.
Materials Supplier:
CONTECH Construction Products, Inc.

2. CASESTUDY
DIM_CS_WHYNES_12.07
Tensar International Corporation
5883 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 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.
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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 alternative
solution 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 used with 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.