Monthly Archives: May 2012
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.
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 😉
Even had a quick rain storm kick through and the new paint worked like a champ. I’ll be getting the framing put together upon completion of the new task at hand, which is digging a very large hole using only sweat equity on my part. I had thought about renting a jackhammer to get through the unusually hard ground one finds here in Phoenix. But luckily, I took the advice of my best friend and also my wife and ran the hose at a slow trickle the night before I was to dig.
Sure enough it did the trick! The ground softened up nicely and I’m currently about half way through the dig. Granted I’m exhausted. The bod is sore. But it was a good days work and progress went much better than day one.
Once I’ve got the hole dug, the question that is pondering my mind is should I piece together the framing in the hole, or just assemble topside, then get a few grunts to help me lower the whole thing. I had recently helped a friend do the same with his own tank burial, and that was not an experience I wish to repeat. Especially since my tank is about 1/4 larger (and most likely heavier) than his. I would definitely say a minimum of 4 people with rope to help lower this beast into the ground.
Which is also why I pondered doing the assembly in ground. Problem with that idea is that the hole then needs to be dug considerably wider and longer to accommodate a human being. After my recent two digs, I’m a bit put off by that requirement. So most likely I’ll be lowering this beastie with some buddies in the near future.
As always, you’ll see it here first!
Essentially the framing for the tank is now complete. Per a fellow AP’er on a local forum’s suggestion, I decided to beef up the base of the tank with some additional cross members spaced roughly a foot apart to give it additional strength. I decided to go this route rather than deviate from using my reclaimed lumber and buying a large piece of thick plywood (that stuff’s expeeeensiiiiive!). The real test came when I decided to take this tubby body and jump up and down all over the base to see if I would cause any bowing between members. Figure at 200+ pounds and hitting a square foot area with all I could muster, its gonna hold!
I also got the rest of the sides adjoined to the OSB boards. This was the most time consuming since I was adamant about putting in enough screws in this beast to effectively turn in into a bunker when complete 😉
Lastly I did decide to deviate a bit from the use of regular deck screws and go with large 4″ lag bolts to secure the sides and base together. These will DEFINITELY be able to hold up to the shear forces involved with holding 7000 pounds of water.
At this stage it now goes to paint. I was able to get a commercial grade outdoor paint at Home Depot on the cheap. Simply go and ask for their ‘reject’ pile. Came across a nice 5 gallon bucket of tan paint which I will apply liberally come tomorrow. The fact that it was 80% off… BONUS!
This little number is not so little. As mentioned in my previous post, the tank will be quite large.. close to 840 gallons! Jacuzzi anyone?… I’m sure the fish won’t mind 😉
So with all the reclaimed lumber, I’ve had a busy day of selecting pieces that were not warped. Surprisingly there was little termite damage, but warping seems to be the most prevalent issue with reusing this wood. So took my time, found lengths that had minimal issues and got to cutting!
All in all, not a bad Friday’s work! There’s still a bit more work to do. I must get the OSB fitted to each frame piece. Then comes some outdoor paint to help give the wood some extra protection from the elements (it is after all going to buried in the ground.. more on that later). Then some foam insulation on the inset areas to help keep the water as well insulated as possible. I’m trying to minimize temperature fluctuations as much as possible, which of course might be a little overkill on my part. But that’s how I roll!
Much of the framing is pretty straight forward. I had to offset the additional support sections so that I could properly screw them to the rest of the framing. I got this nifty little idea from my friend John who has already got his AP system setup and growing food. But for the size of the tank.. the idea was to do as little cutting of the OSB board material as possible. I’ll only have to cut one section in half, then add to each end piece. The rest of the tanks sides can be fitted with the OSB without cuts since those sides are the same dimensions as the 4×8 boards.
I plan on following up with more later on the tank build, but got all excited about getting it going, that I just had to post something!