If you’re used to only ordering fertilizer for short-term storage in totes or mobile tanks, you may not know much about the different levels of protection needed for long-term holding. Primary and secondary containment are easy to misunderstand due to many technical explanations using scientific jargon. On the most basic level, primary containment is the container you use to hold the fertilizer in the first place. This ranges from pre-formed tanks to custom concrete bunkers or short-term pads made from a few layers of geomembrane. Secondary containment measures can be built into the primary container or added on separately. Make sure you’re combining primary and secondary containment measures the right way with these tips.
Immediate vs Potential Risks
Primary containment measures are designed to protect the environment and workers from the immediate risks of a material. For fertilizer, this is still true because loose piles of dry fertilizer can collapse, cause potentially dangerous dust clouds, and pose fire hazards. Wet fertilizers are often unsafe or impractical to store in anything but a tightly closed or covered primary container.
In contrast, secondary containment is aimed to handle potential risks instead. Dikes, curbs, and impermeable liners aren’t used every day, but they’re built in case of a potential leak or spill. This makes it easier to overlook the importance of secondary containment until an emergency occurs.
Double Walled Designs
Most tanks, and other primary storage containers, only feature single wall design for affordability and easier transport to the site. These containers will require you to build some kind of separate, secondary containment method to protect the area in case of a spill. Double walled containers are designed to circumvent the need for dikes and other secondary fertilizer containment. The second wall creates an open space around the primary container that can hold a limited amount of liquid or dry powder when it leaks out. However, you’ll find that double walled tanks and containers are often highly limited in the amounts they can hold during a leak. Since many states require you to have secondary containment with a volume well over 100% of the volume of the container, a double walled design may not be feasible for fertilizer storage on the farm.
Types of Secondary Containment for Fertilizer
While regulations vary based on the state and the material being stored, the Environmental Protection Agency has set a federal level of secondary containment requirements. These rules apply to tanks holding 660 gallons or more; if they can leak into the waters of the United States. If the tank can’t leak into a public body of water, it’ll still need secondary containment if you’ll storing 1,100 gallons or more at once. Some of the EPA approved secondary containment methods include:
- Secondary impoundments lined with impermeable geomembranes, concrete, or a combination of the two
- Clay-lined holding ponds shaped out of the ground below the tanks
- Liners applied along the floor of a building or shed used to hold fertilizer
- Dikes and curbs built around the edges of a containment area to keep liquids and powders from spilling out the control area.
Impermeable Barriers
No matter the specific design or method of secondary containment you choose for your fertilizer system, you’ll need to include impermeable barriers to protect the soil below the surface. Even concrete floors and walls can let chemicals leech through over time and then find their way into sensitive waters under the ground or nearby. Impermeable barriers must also withstand chemical contact without reacting in order to remain waterproof over time. Choosing the wrong geomembrane or flexible liner can result in leaks that begin within the first few years of use. Don’t shorten the lifespan of your secondary containment system for fertilizer since they require a lot of labor and money to repair and renovate on a regular basis.
Reusing Runoff and Rinsate
Secondary containment around mixing and cleaning areas is particularly important. Not only will liners and curbs prevent environmental damage and runoff, it also provides the opportunity to redirect the runoff to drains for collection. Rinse water, from fertilizer tanks and trucks, is known as rinsate. It’s a valuable fertilizer product of its own. Applying rinsate is often a good way to finish out a season when crops only need a diluted application and you’d otherwise need to order more materials. If you don’t need the rinsate, you may be able to sell it to another operation and recoup some of your fertilizer expenses. Liners help ensure that every drop of valuable rinse water is directed to where it’s needed, rather than wasting it. The same containment method can work for areas where field runoff gathers, so it can’t enter local creeks or streams.
By now you should have an idea of how primary and secondary containment work together to keep fertilizer under control. Tanks and silos form your primary containment efforts, while it’s the liners and curbs that keep occasional spills and leaks controlled with secondary containment. The impermeable geomembranes we provide at BTL Liners can be put to good use in both stages of containment; thanks to their reinforced construction and chemical resistance.
