Environmental Science & Engineering - www.esemag.com - May 2005
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Secondary containment dilemma

Gone are the days when one could buy an inexpensive storage tank, set it up or bury it, then forget about it.

Now, seemingly endless new guidelines regarding liquid containment require some serious decisions concerning the selection, operation and maintenance of suitable “environmentally responsible” storage methods.

Companies need to be prudent in considering initial capital expense vs. long-term operational cost in deciding on the type of tank installation: above or below-grade; heated or unheated; metal or non-metal; and secondary containment (such as earthen dykes, enclosure rings, or double wall vs. dual-containment). Choosing the right combination will translate into substantial cost savings and reduced corporate liability exposure.

Traditionally, except for buried tank installations, earthen dykes or enclosure rings (steel or concrete), in combination with plastic liners covered by a layer of sand, were common choices for secondary containment of abovegrade single wall tanks.

Spill containment for below-grade tanks usually involved the installation of buried plastic liners, complete with liquid collection monitoring devices, or double wall designs with either vacuum or pressure sensing units monitoring the interstitial wall space.

However, associated with these traditional installation methods are certain inherent secondary containment problems. To combat these problems, TankSafe Inc. (Calgary, AB) developed the concept of an “environmentally responsible” above-grade, dualcontainment tank (heated or unheated).

This novel design, for which TankSafe obtained both Canadian and U.S. patent rights, safeguards against overflow and leakage problems; prevents soil, groundwater and product contamination; reduces liability exposure and reclamation costs; saves on heating requirements; and allows for unhindered year-round tank installation and relocation at minimal expense. Also, fabricated as a split tank, the design can easily incorporate multiple product storage, such as new and used lube oil at compressor stations.

TankSafe’s dual-containment design, however, provides a minimum 110% secondary containment capacity (compared to primary tank volume) and may be fitted with an internal overflow device on the primary tank. This extra spare volume not only allows for considerable accidental spillage and overflow containment, but also primary tank mechanical protection, additional insulating value and greater uniform heat distribution (for heated tanks).

Contact: www.tanksafe.com.

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