# Underground Cache



## norseman (Dec 8, 2018)

Hello
I was able to pick up a 500 Gal underground septic tank that was being used for ground water to use as a cache on my 25 acres property. it is roughly 5' by 5' by 5' with 24" access cover in the top. There is an extension available for the access cover so I can get it below the surface. My questions is: do I need to vent the tank to fresh air or keep it air tight?
Thank you


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## Slippy (Nov 14, 2013)

Excellent question norseman,

However, we will need more info on exactly what it is you plan on storing in this underground cache? For example;

If it is a couple of midgets that you kidnapped and plan on taking to the local bar for Midget Bowling Nite and want to keep them alive, YES, please vent the tank to fresh air. However, understand that any vent will also allow for their screams for help to be heard so that brings up a whole 'nother issue!

Your friend,

Slippy!:vs_wave:



norseman said:


> Hello
> I was able to pick up a 500 Gal underground septic tank that was being used for ground water to use as a cache on my 25 acres property. it is roughly 5' by 5' by 5' with 24" access cover in the top. There is an extension available for the access cover so I can get it below the surface. My questions is: do I need to vent the tank to fresh air or keep it air tight?
> Thank you


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## norseman (Dec 8, 2018)

Well
I had not planned on storing midgets but that is always an option. I was thinking more of tent, sleeping bag, dehydrated food, and ammo. Just where can I sign up for Midget bowling?


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## Camel923 (Aug 13, 2014)

I wood keep it sealed. If air gets in so will moisture and possibly critters. Do not burry too far under because w/o water in the container the weight of the earth may cave in on the tank.


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## bigwheel (Sep 22, 2014)

If a preson cant find any screaming midget bowlers to kidnap and hold hostage...Sounds like the making of a good storm/rootcellar to me. Yes..it needs venting for that most likely. A floor drain would also be nice. 


__ https://www.pinterest.com/pin/238268636508613137/


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## Smitty901 (Nov 16, 2012)

Most underground tanks I have seen are meant to be filled. If not they will not stand up to being buried.


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## MikeTango (Apr 13, 2018)

Or if it’s really wet and the ground is soft the tank my float up during a big rain. 


Sent from my iPhone using Tapatalk Pro


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## Illini Warrior (Jan 24, 2015)

I'd prepare it for a shelter - not just a cache - so you need all the utilities run and pipe in a fluid drain into a sump ....

already mentioned is the tendancy of those tanks to float and come popping up like a cork >>>> if there's lugs incorporated into the tank think about cables to a ground anchor - otherwise use an arresting cable around the tank ends ....


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## Slippy (Nov 14, 2013)

norseman said:


> Well
> I had not planned on storing midgets but that is always an option. I was thinking more of tent, sleeping bag, dehydrated food, and ammo. Just where can I sign up for Midget bowling?


For World Class Midget Bowling, try The Buffalo Chip, Sturgis, SD https://www.buffalochip.com/EVENTS/Famous-Events/Midget-Bowling

My buddy Zac tried it back a few years and while he enjoyed it, he has not lived it down with the libtards...


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## Kauboy (May 12, 2014)

Some things to think about...
If you sealed it, under what condition would it be sealed? Would you vacuum out the air that was left in when you closed it up? Or, would it be full of air?
If vac-sealed, and not reinforced, it will likely collapse under the side pressure of the earth.
If air-filled, temperature changes will become a problem. As air warms, two things happen that you don't want. First, the volume that the air takes up expands. Second, moisture in the air condenses onto surfaces that are cooler than the air. Now you have a warm and moist environment just perfect for bacterial and fungal growth. As air cools, the volume of that air contracts, and potentially causes the original problem with weakened sides.
If the temperature swings regularly, you get a "breathing" effect that will eventually compact the soil around the tank, causing gaps to form between the earth and the tank walls. Rain will become a problem at that point.

If you vent it, *most* of these concerns go away, but others are introduced.
You still have the problems with temperature swings affecting the contents, but now you have a potential method for drying out the condensed moisture. If you intend to visit this tank regularly, you can look into using large desiccant packages that will handle the moisture between visits. Once saturated, they will need to be swapped out and recharged. Being open to the environment, this will saturate quickly in humid climates.
With an open air passage to the outside, you have to deal with filtering out all the things you don't want entering the tank. This includes water, debris, bugs, and UV. Most bunkers handle this with an upside-down "u" piped vent. This keeps out the rain and most debris. A physical barrier would be necessary for small particulates and bugs. It should also prevent direct sunlight from entering the tank.

In either scenario, moisture and temperature changers in the soil outside the tank walls will still have an effect on the tank, and should be considered.
Reinforcement is recommended.


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## Mad Trapper (Feb 12, 2014)

If you want to eliminate collapse concerns build a framework around, and on top of it, using used railroad ties. Sort of log cabin style w/jointed corners, or drill and use rebar.

Even if you seal it, what happens if it leaks?

If you have a hillside to locate it at, you can make a discrete drain downhill, and the drain exit will be below the tank and not require any sort of sump or pump. Sort of like a line in a septic leach field.

Make any vents rodent/worm/insect proof.

We could help more if besides midgets what else might it contain?

Anything moisture sensitive will have to sealed in it's own container.


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## Back Pack Hack (Sep 15, 2016)

Get a section of concrete culvert. Bury it inside of that. The culvert will easily bear the weight.


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## Slippy (Nov 14, 2013)

norseman said:


> Well
> I had not planned on storing midgets but that is always an option. I was thinking more of tent, sleeping bag, dehydrated food, and ammo. Just where can I sign up for Midget bowling?


norsey,

You are one sick puppy wanting to kidnap midgets and all. :devil:

Good times you rascal!?!


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## Mad Trapper (Feb 12, 2014)

Slippy said:


> norsey,
> 
> You are one sick puppy wanting to kidnap midgets and all. :devil:
> 
> Good times you rascal!?!


Slippy, we've heard about the parties at the Slippy ranch :tango_face_grin:


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## bigwheel (Sep 22, 2014)

Good show Slippy .


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## azrancher (Dec 14, 2014)

norseman said:


> I was able to pick up a 500 Gal underground septic tank that was being used for ground water


Septic tanks in my area are concrete so there is no (little) chance of then collapsing.

*Rancher *


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## Chipper (Dec 22, 2012)

It's an UNDERGROUND septic tank. Wouldn't it be designed to be buried?? Don't worry about it collapsing.


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## Illini Warrior (Jan 24, 2015)

Chipper said:


> It's an UNDERGROUND septic tank. Wouldn't it be designed to be buried?? Don't worry about it collapsing.


the one's I'm familar with are - a septic tank by design would never be filled totally and made to be buried >>>> great way to disguise a buried cache - a stinky septic tank


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## Elvis (Jun 22, 2018)

I agree that a concrete septic tank would not be crushed, Unless a septic tank is too full they never are filled all the way up with grey water.

My concern would be getting stuff out for periodic inspection. A 24"x24" hole would be hard to reach into to get stuff out of, especially if it's below ground level.

Assuming the ground is firm and stable for in-ground storage I'd consider a 20-30 gallon plastic or steel barrel with a water tight lid. Bury it so the top is about 2 inches above grade in a woody area with lots of trees and leaves on the ground. Bury it in leaves with some desiccant packs in it. A 55 gallon drum is too deep to easily reach into.

I've seen 18 gallon double walled plastic containers with heavy screw on lids used to import bulk packed meds from over overseas that can hold a partially disassembled AR in. The lid was easily strong enough to walk on. I've also seen 30 gallon blue plastic barrels that held hot sauce with a waterproof lid that used a metal band to secure the top. Either would work well.


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## norseman (Dec 8, 2018)

This is the tank. The manufacture says it does not need to be filled.


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## StratMaster (Dec 26, 2017)

Mad Trapper said:


> Slippy, we've heard about the parties at the Slippy ranch :tango_face_grin:


Ahhh.... I remember those heady days long ago when I was a cornerman at one of these.


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## Smitty901 (Nov 16, 2012)

StratMaster said:


> Ahhh.... I remember those heady days long ago when I was a cornerman at one of these.


 That is just not right, not ever.


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