Tank Storage and Secondary Containment on a Lease

Storage is where fluid waits, and waiting is when things leak. Most reportable releases on producing properties do not come from dramatic failures; they come from a corroded tank bottom, a valve left cracked open, a flowline connection that has been weeping for weeks, or a containment berm that quietly stopped being able to hold anything.

This guide covers the storage side of the operation and, more importantly, the containment around it.

Tank Types You Will See

Steel bolted or welded tanks are the traditional production tank: robust, repairable, and vulnerable to internal corrosion where they hold brine. Internal coating extends life considerably and its condition is worth knowing.

Fibreglass tanks resist corrosion very well, which makes them attractive for produced water service. They are less tolerant of impact and of UV over long periods, and repairs are a more specialised job.

Poly tanks and totes serve smaller volumes and chemical storage. They are cheap and easy to place, which is exactly why they end up sitting on bare gravel without containment.

Above-ground storage in a tank farm for larger facilities, with the containment sized for the whole battery rather than per tank.

What Secondary Containment Is For

Primary containment is the tank. Secondary containment is what catches the contents when the tank fails, and it exists because tanks do fail.

The standard approach in this region is an earthen berm around the tank area with an impermeable liner, sized to hold a meaningful proportion of the stored volume plus an allowance for precipitation. The specifics of sizing and construction are set by the applicable requirements and by the fluid stored, so check the current directive rather than working from a rule of thumb someone told you.

The two things that quietly defeat containment are both mundane. The first is accumulated water: a berm half full of rainwater and snowmelt has half the capacity it was designed for. The second is berm and liner degradation: erosion after heavy rain, frost heave, rodent burrows, vehicle tracks cut through the berm for convenience, and liner damage at the anchor trench.

The Walk-Around

Most of what matters is visible to someone who walks the site properly. A useful routine:

• Berm integrity. Walk the whole perimeter, not just the side you park on. Look for erosion channels, low spots, animal burrows and vehicle crossings.
• Liner condition where visible, particularly at the anchor trench and at any penetration.
• Standing water inside containment. How much, and is there a managed way of dealing with it? Water removed from containment may itself require handling depending on what it has been in contact with.
• Tank exterior. Corrosion at the base, where water sits, is the usual failure point on steel. Check seams and any external coating.
• Staining. Discoloured gravel or soil under a valve or fitting is a leak that has been running long enough to leave a mark.
• Valves and fittings. Weeping packing, open drain valves, missing plugs.
• Level indication and overfill protection. Does the level device actually work? Overfills are a common and entirely preventable release.
• Vents. Blocked or frozen vents cause tanks to deform on filling or emptying.
• Access and signage. Gates, fencing, and whatever identification is required.

Write it down each time, with the date. A contemporaneous record showing a regular inspection routine is worth a great deal if something does go wrong, and the trend across inspections is what tells you a problem is developing rather than static.

Winter

Southern Alberta winters create their own failure modes. Frost heave moves berms and cracks liners. Snow accumulation inside containment melts into capacity you were counting on. Frozen valves and vents cause problems on the first warm day. Ice in a containment area hides what is underneath it, so a walk-around in February tells you less than one in June, and inspection frequency should account for that rather than pretending otherwise.

Common Questions