Fanatic Dig! – Dang! – Dug! – Done!!! WHEW!!!


Woe be the person whom has to dig a hole in the Arizona desert!!!

I say this to start off my topic, because if you have ever wondered why nearly 98% of the homes built in Phoenix DO NOT have a basement, you will understand why shortly after you’ve laid your shovel into the Phoenician soil. This stuff is nasty!!! It can be summed up by one simple word… Caliche.

Caliche occurs in the subsoil, the layer beneath the surface soil. Caliche is common throughout Arizona. It is a layer of soil that can be up to six feet deep and the soil particles are essentially cemented together with calcium carbonate. Hand-digging a hole in caliche soil is next to impossible and any serious digging requires a jackhammer (of which I did not have on hand). The means by which I was able to excavate my hole was made possible by running the hose on the area overnight and letting the ground soak a good 12 hours before putting shovel to dirt.

All in all the final dimensions came to 8 feet, 7 inches long by 4 feet, 5 inches wide by 3 1/2 feet deep and took all of 4 full days of shoveling, or about 32 hours total.

Now, the million dollar question you may have for me, is why go to all this trouble?
Well, the reason is very simple… water temperature regulation. Using the thermal mass properties of the soil, the goal is to keep the tanks water at a steady 75-85 degrees year round. This is also helped by the fact that the tank will hold 112 cubic feet of water or the equivalence of 837 gallons. The more water you have in a system, the more energy that is required to change the overall temperature of that body of water.

I did this because as most people may know, our summers here are friggin HOT!
Our summer seasonal average puts us around 92 days that are over 100 degrees and at 110 degrees, our average has been over 19 days each year, during the past 30 years. This was one the main reason for all the effort to dig the hole. Our only other option to cool the water would’ve involved misters, but that technique loses a LOT of water through evaporation.

Thankfully, this endeavor also serves us well in the cooler months. We’ve found that if we did need to warm the water, its easier and less costly to do with a large aquarium heater, than if we tried to cool the water.

Talapia, like any fish, need a good place to stretch their fins. So keeping the temps as close to 80 degrees is going to be our main goal. Any lower and they start to eat less food and become lethargic, thereby decreasing their growth. Any hotter and they will do fine up to say around 95 degrees, but then the plants will suffer. So our goal is to hit that sweet spot between 75-85 degrees year round. In that way we keep both animals and plants happy.

Following the initial dig, I then had to put down some paver stones and work with a level to make sure the base for the tank will be as level as possible. Took a bit more time than I expected, but in the end it worked out fine.

The next step is moving the pieces of the tank over to the hole and starting assembly. With that I’m doing a bit of overkill by adding in foam insulation on the sides (but not the bottom, as that would negate the purpose of the thermal mass of the hole). I’ll then wrap the entire exterior with a vapor barrier to add a further layer of protection from the bugs and elements.

As always, check back in regularly as I will be continuing with more updates as I progress with the overall build 😉

Posted on May 28, 2012, in Aquaponics, Garden, Greenhouse, Inspiration and tagged , , , , , . Bookmark the permalink. Leave a comment.

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