Grain Bunker Storage Part 2: Site Dimensions and Capacity

Welcome back to our second edition of Grain Storage Feature. After covering the basics with Site Selection and Positioning last month, this month it is time to jump into the all-important Site Dimensions and Capacity!

You might be asking yourself...

“I have an area in mind and it is X by X – how much barley could I store here?”

OR

“I am needing to store 800 tonnes of wheat, how big an area will I need?”

Well, we're here to answer all those questions plus many more. But, before we dive in, here are a couple of quick grain storage options to get you started:

If you are in a rush (say it is in the height of the season and you have a 1000 tonnes of grain that you need to store within the next week), you may choose to put your grain straight into the ground without pushing up a wall
If you have plenty of time up your sleeve and are preparing prior to harvest you can prepare an earthen wall or even invest in a concrete or tin wall (more about walls in a coming edition – stay tuned!)

Whichever option you choose will affect the capacity of grain you can store, as a walled bunker will store more than a than a bunker without walls.

Let’s dive in...

Determining Height and Width

The best point to start at, when determining dimensions, is by looking at your grain handling equipment. The height to which your auger can form a stack of grain, together with the side retaining wall (if you have one) determines the distance between each side of the bunker and subsequently the length you will need to store your required quantity of grain.

Remember, when assessing your stack height that different types of grain will form a heap relevant to its angle of repose:

23° for wheat
26° for barley or sorghum
30° degrees for oats

❓ What you need to do
	Wind your auger up to full height
	Tie a string or rope to the tip of the auger and let the string drop to the ground directly below
	Measure from this point on the ground back to the wheels of the auger
	Take this measurement and multiply it by 2 and this will be the maximum width of your bunker (Formula: Measurement from ground directly below auger outlet to the wheels x 2 = Max width of bunker)

This will mean that your auger will be positioned far enough back to prevent the wheels been buried by the grain during filling of the bunker.

Determining Length

Now that we have determined the height and the maximum width, the length of the of bunker can be calculated from the tables below.

These tables refer to bunkers with a wall height of either 0.5m or 1m and are for wheat, barley, sorghum or oats. For anything outside these parameters, please contact us and we are more than happy to calculate this for you.

**A note here: Some growers prefer to spread their total storage requirements over a couple of smaller bunkers rather than one larger bunker to keep the tarps a more manageable size, which also allows for segregation of different grades of grains. Others find that one larger dump is more suited to their requirements; it is entirely a matter of preference.

So this sums of this month’s newsletter on Site Dimensions and Capacity. Stay tuned for next step in the bunker building process in November.

Got a bunker cover question? Click here!