Features Structures & Equipment Water and irrigation
Safety is key to managing water tanks

Unleashed water can be dangerous stuff

May 3, 2018 By Gary Jones

When we talk about ‘water management’ in greenhouses, our thoughts typically consider irrigation scheduling, control equipment or maybe simply having enough. At this year’s Lower Mainland Horticulture Improvement Association (LMHIA) Growers Short Course (held simultaneously with the Pacific Agriculture Show in Abbotsford, B.C.), Olaf van Marrewijk of Hagelunie (Leiden, N.L.) gave a different ‘take’.

For those not familiar, ‘Hagelunie is a Dutch insurance company, which supplies its products to (greenhouse) horticultural businesses in Europe’.¹ ‘It offers a range of products to greenhouse businesses and works in close cooperation with local construction companies and suppliers. It is closely involved in innovations and developments in greenhouse horticulture’.² So, you may ask, what would Olaf have to say on the topic of water management?

Well (no pun intended), the size of water storage tanks in greenhouse horticulture has been increasing over the last decade or so. With larger greenhouses in particular, irrigation water tanks (“cold water silos”) and heat dump tanks (“hot water tanks”) have increased dramatically in size. If you’ve ever climbed to the top of one of those monster hot water tanks, you’ll know it looks like a very long way down.

A few years ago, I saw firsthand the aftermath of what happens when one of those cold water (irrigation) silos bursts. Like the majority of such tanks, it was located inside the greenhouse, near the fertilizers, mixing tanks and control systems. In turn, these are often located fairly close to the office for the grower and his/her team. The force of the water escaping the failed tank, pushed a full pallet of fertilizer across the irrigation room floor, through the greenhouse wall and about 20 ft. further into the crop. I was shocked at just how much energy was released so quickly. Fortunately, the tank failure happened at night, so no one was around to get injured. It could have been a much different story had this occurred during lunch with people near the office areas.

Back to Olaf. As an insurance guy, he reminded his audience that “Risk = Probability x Effect”. For cold water silos, the risk stems from the facts that they are (typically) made of thin panels, are often built by the growers themselves, are sometimes constructed on ground that may subside, may contain acidic liquid and corrode from the inside – in other words where the damage is not easily visible. These large volumes of water are often near occupied spaces and near fertilizers, as noted in my example above.

For hot water tanks, the risk is lessened in that they are made of thick steel plates, are constructed by expert contractors and typically corrode from the outside. They may however leak and corrode near the roof line. The consequences of failure are still severe since they contain massive volumes of water and are also often close to high occupancy areas.

In either case, failure is not an option. Or at least not preferred. Growers should therefore pay attention to regular prevention. This may include visual inspections (of areas that can be seen), checks of ground for signs of subsidence and examinations of concrete bases for any signs of corrosion or potential failure. Olaf suggested having tanks overhang the base, so that water does not run down the outside and pool on the concrete base – but talk to your engineers and/or insurers first. If possible, try to also check the insides, which may mean periodic drain downs.

Olaf is of the mindset that cold-water irrigation storage tanks pose more of a risk than do the huge hot-water buffer tanks, and gives some valid reasons why this may be so. Either way, if any of these tanks fail, the effects can be catastrophic. It would be wise for us all to pay attention to ensuring they remain safe. Give it some thought the next time you walk past that tank in the fertilizer room.

Gary Jones is Co-Chair of Horticulture at Kwantlen Polytechnic University, Langley, B.C. He sits on several industry committees and welcomes comments at
Gary.Jones@kpu.ca.

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