Environmental Science & Engineering - www.esemag.com - November 2004
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Innovative secondary containment design in Northern British Columbia
By Dave Martin, P.Eng.
In the winter of 2002 a major international
oil and gas producer faced
the challenge of providing secondary
containment for a series of tank
farms at three remote sites in
Northeastern B.C. Adding to the challenge
was the need for winter installation
as the sites were accessible only
by a winter road which would be
decommissioned in late March.
The three sites were located on very
soft soils and a significant amount of
settlement was anticipated in the
regions directly under the tanks.
Layfield Environmental Systems Ltd.
was contacted early in 2002 to provide
a containment design for this project.
This project was completed on an
extremely fast track, with the design
and fabrication completed within
weeks of the project initiation; this was necessary to allow the construction
phase to be completed before site
access was lost.
The final approved design involved
an innovative combination of a modular,
steel containment system, HAZGARD
® 1000 geomembrane, and a
spray applied polyurea coating. The
owner determined that the project
required an Underwriter’s Laboratories
of Canada (ULC) registered
geomembrane liner in order to meet
the requirements of the National Fire
Code of Canada. HAZGARD® 1000
was selected as it meets the requirements
of ULC ORD C58.9 (1997)
Secondary Containment Liners for
Underground and Aboveground
Flammable and Combustible Liquid
Storage Tanks.
It was also a natural choice for a
winter project, as it remains flexible
enough to withstand the rigors of installation
down to temperatures of –20 C.
The containment berms around the
perimeter of the tank farms were constructed
from a modular steel system.
The steel panels were bolted together
on site to provide a continuous impermeable
barrier. The steel berm was
welded onto mounting piles to prevent
them from sinking into the soft
muskeg. The heavy, durable steel containment
panels were ideal for on-site
modifications. Some panels were cut
and welded on site to meet the complex
containment requirements.
A foundation ring was placed
around the tank piles and a spray
applied polyurea lining was applied to
the area within the ring. This method
was chosen because, with the tanks
and piles in place, it would have been
impossible to use a standard geomembrane
and get a leak tight seal against
the existing piling, due to the space
limitations. It was also felt that the
spray applied lining would elongate in
the case of localized settlement of the
piles under the tanks, and, if it
stretched to the breaking point, it could
be easily repaired.
The geomembrane was attached to
the perimeter dike walls and to the
outer surface of the foundation rings
using a steel batten bar. Sufficient
slack was allowed for in the geomembrane
to maintain its attachment to the
perimeter wall if the area inside the
containment sank up to 18 inches.
Dave Martin is Research &
Technology Manager at
Layfield
Geosynthetics and Industrial Fabrics Ltd.
Contact e-mail: dmartin@layfieldplastics.com.
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