• Position the bunker above flood levels.
• The pad must be above the surrounding ground level to ensure natural drainage.
• Choose a site with all-weather access and sufficient truck access to the pad.
• Consider the orientation of your pad. It is best to have the closed end of your bunker facing into the prevailing wind.
• Ensure your bunker pad is well compacted to sustain loaded trucks and machinery.
• Prepare your pad with a slight camber either side with a small rise in the centre. This allows for any moisture to naturally drain to the sides.
• Maintain a gradient of at least 0.8% towards the open bunker end so rainfall drains away from the grain face.
• A drainage area around the base of the pad can help to divert water run-off from the tarps.
• Consider using a bunker shape with round ends to suit an augers natural loading shape.
• Evaluate different wall options such as no walls, concrete, steel, or earth walls.

Determine your desired capacity based on your grain storage requirements.
Two factors will determine how wide you can build your bunker; the angle of repose for the grain you want to store, and your auger size.

Minimum auger size for Wheat, Barley, Sorghum, Chickpeas, Rye and Soya Beans

• 15m Wide Bunker – 45ft auger
• 20m Wide Bunker – 50ft auger
• 25m Wide Bunker – 60ft auger
• 30m Wide Bunker – 70ft auger
• 35m Wide Bunker – 80ft auger
• 40m Wide Bunker – 90ft auger

Minimum auger size for Rice and Oats

• 15m Wide Bunker – 50ft auger
• 20m Wide Bunker – 60ft auger
• 25m Wide Bunker – 70ft auger
• 30m Wide Bunker – 75ft auger
• 35m Wide Bunker – 85ft auger
• 40m Wide Bunker – 95ft auger

Here are a few points to help select the right covers for your grain bunker.

1. Choose an appropriate tarp fabric option – Polyethylene, Polypropylene, or PVC.
   • PVC is a heavier fabric (610gsm) and will sit flatter on your grain pile.
   • Polypropylene (370gsm) The strength-to-weight ratio is considerably better compared to PVC which means it is a lot lighter for the same given strength.
   • Polyethylene (180gsm or 250gsm) is often used for ground sheets, being a lighter fabric.
2. Determine the size of the tarp based on the bunker dimensions and ease of handling.
3. Understand the typical lifespan of a tarp. This will vary depending on how it is cared for but typically you should get around three years for a top tarp and 1-2 years for a ground sheet.

In order to kill grain pests at all stages of their life cycle, fumigants need to reach, and be maintained at, a concentration possible only in a gas-tight storage. That is why it is important to get a good seal all around your bunker to provide suitable conditions for fumigation to be
effective.

For best results with fumigation it is recommended to talk to a licensed fumigator who will know the most current and effective fumigation methods. Licenced/commercial fumigators will have monitoring equipment to measure gas concentration throughout the fumigation and venting process.

Polytex can weld fumigation zips into your top tarp for easy access and proper ventilation during the fumigation process. Our fumigation zips are waterproof, gas tight and air tight providing a secure seal. They can also be used for extracting grain samples for testing.

• Line the bunker with a ground sheet to prevent moisture entering from below and contamination with the soil.
• When filling the bunker, ensure the grain pile angles down to the top of your earth or concrete wall for the rain to flow off the tarp.
• If your bunker is a flat pad, it is a good idea to mark out a line at your desired width with chalk so the auger operator knows when to move the auger along.
• Move your auger in small increments to get a smooth ridge on the top of your grain pile.
• The bunker does not have to be completely full before starting to cover the grain. Cover the grain as filling progresses to avoid possible damage by sudden storms.
• The most efficient method to pull your tarp over is to have two telehandlers (or a JCB, tractor, loader etc.) on either side pulling the tarp with webbing, and one person walking over the centre of the pile with a tarp puller to keep the centre of the tarp up.
• Do not attempt to handle large tarps in windy conditions as they will quickly become unmanageable.
• If you require more than one tarp you will need to sew them together. Consider borrowing a sewing machine if you don’t have one, or Polytex can supply these.
• Your grain bunker covers should be secured down tight to prevent damage from billowing and flapping in the wind. They also should be sealed to protect from insects, rodents and water and allow for effective fumigation. There are a number of methods to secure and seal your tarps:
  • Concrete tyres
  • Earth trench
  • Concrete walls

The first and most essential method to maintain grain quality is to practice good farm hygiene to reduce overall numbers of insects and pests on your property.

• Vermin control: Mostly, vermin control comes down to site hygiene. If there is spilled grain around, that will attract mice and birds, then foxes and other pests. Keep the area around the bunkers clean and free of spilled grain to avoid attracting vermin.
• Insect pest control: Fumigation is the only way to control an infestation. Polytex can weld fumigation zips into your tarps to avoid the need for fumigators to slit and repair your tarp when fumigating. For more information on fumigating your grain, we can provide fumigator contacts near your area.

Common methods of outloading include a mobile auger with a cross sweep or bulk-handling buckets on front end loaders or telehandlers to fill direct into trucks.

1. During outloading, progressively remove the top cover back and fold in the reverse manner to which it was applied (concertinaing). Neck the corners of the tarp with a strap or use tarp pullers and pull tarp back with a telehandler or similar machinery.
2. Ensure that covers still on the bunker during outloading are held down against the wind. The grain stack can be recovered after partial outloading.

• Address tarp damages promptly using products like Glomastic and Repair Tape.
• Covers should be swept or cleaned of any dirt or grain. Utilize equipment like the Bunker Broom to clean ground sheets.
• Roll tarps manually or utilize a tarp roller for efficient storage.
• Store in a shed away from the sunlight to avoid exposure to UV rays. An enclosed shed is preferred to reduce rodent damage.

For more detail on the above points, download a FREE copy of our Grain Bunker Construction & Storage Guide. It provides insights into best practices and expert advice from Australian Farmers for successful bunker storage.