What If we were to take some 3 or 4 foot sections of concrete culvert, sink them upright in the ground on small
concrete pads? These can then be filled with supplies and a manhole cover or concrete lid fitted on top and
buried. The tensile strength of culvert is very good as are the chances of the supplies inside. As far as fastening
goes how about drilling 4 holes in a cross pattern into the base of the pipe, then inserting rebar through the holes.
Then, pour a pad, wait about 10 minutes and plunk the pipe down followed by pouring another 3 inches or so of
concrete inside and covering the rebar cross bracing.
As far as water I plan to coat the entire pipe with a rubber waterproofing compound most commonly used on foundations. The lid itself is probably the most crucial of the issues facing this idea. I know that these sections of culvert are commonly held together by rubber gaskets and I am still working on the problem of fitting a practical lid to it. The lid must be light enough for 1 person to lift but strong enough to resist the forces of nature. The items inside must also be protected from water in case the integrity of the pipes is compromised, possibly by wrapping them in a thick layer of plastic and filling any spaces with an expandable foam product such as Great Stuff.
Offered by Linda.
This sounds like an excellent Idea to me. I have a couple of additional thoughts. The culverts should be attached to the concrete pads, possibly while the pad is still wet. Or maybe it would be easier to seal one end of the culvert with concrete and steel mesh before lowering it into the ground. I think that your manhole cover should also be sealed so that it is water tight, possibly with foam or a rubber compound. Great Stuff is an excellent foam sealer. I've used it myself. But I'm not sure how it stands up under water pressure or even seepage. Your fastening with rebar idea seems feasible also. No matter what sealers you use, best to play it safe and individually wrap your stored items in plastic, and then I would group wrap everything. When they bury a time capsule for 20 or 30 years, what type of seals do they use on those cement cylinders? Might be worth looking into.
Offered by Brent.
To enhance the viability of this storage method, I would think one should bury the culvert using the concrete/steel mesh for sealing the bottom. Additionally, it should be buried in a gradually sloped hill with drainage rock and a 3 inch drain pipe in the bottom as well as up the sides of the hole to prevent a seepage problem that could destroy the contents. The 3 inch drain pipe should be ditched out and the ditch refill with drain rock to prevent surface contamination. Do not do this in the lowlands.
Offered by Michael.