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Aug 092014
It is essential to skillfully conceal your tunnel exit.

It is essential to skillfully conceal your tunnel exit.

We’ve seen very little written about adding an escape tunnel to your retreat, and what has been written has not necessarily been practical or prudent.

First, of course, do you need an escape tunnel for your retreat?  That’s something you have to decide for yourself, and probably also something you have to do a cost/benefit calculation on.  Most of us have our retreat designs limited first and foremost by our budget, and we have to compromise between the ideal retreat and the achievable retreat.  You need to make a list of all the features you’d like to have, approximately cost out each feature, and then based on the importance and value and need of each feature, balanced against its cost, decide what you will spend your money on and what you won’t.

It would be ridiculous, for example, spending money on a deluxe tunnel while overlooking the need for a good solar cell array.  But we suggest there will come a point, somewhere on your priority list, where an escape tunnel becomes a prudent consideration, and of course the first part of that evaluation is understanding what form an escape tunnel would take, and what its approximate cost might be.

In considering the need and value of an escape tunnel, there are several issues to look at.  The first of course is your evaluation for how likely the circumstances of needing an escape tunnel, the second is the practicality of building such a tunnel, and the third would be the cost involved.

Let’s quickly look at all three points.

The Need for an Escape Tunnel

Is it possible that your retreat might at some future point be attacked by a lawless group of marauders?  In a Level 3, and possibly even a Level 2 situation (defined here) – at a time when society has broken down and there is no longer any ‘rule of law’ – it is definitely foreseeable that you’ll be visited by outlaw bandits of some form or another.

What do you think might happen when such people do come ‘visiting’?  They’re unlikely to limit their visit to a polite knock on the door, an even politer request for some free food and supplies, and a most polite of all acceptance of your refusal and a peaceable departure!  Sure, it is likely that individual beggars might adopt this approach, but it is also likely that some organized gangs – either new gangs that will spring up from the ruins of our society, or extensions of the current ever-increasing number of gangs in our society – will come and be prepared to use any amount of deadly force to secure whatever they wish from you.

So, what do you think will happen when an armed battle-hardened gang attempts to shoot their way into your retreat?  Assume, for the sake of this discussion, there are 20 of them, and they’ve surprised you, unawares, either at 2am when you’re sleeping, or, if you prefer, at 2pm when some of you are out in the fields working and others of you are attending to chores inside.

There are several outcomes from such a surprise attack.  The first outcome is sadly quite likely, and that is that you’ll be immediately and totally overrun.  If that happens, there’s of course no need for an escape tunnel!

The second outcome is that you quickly rally around, you have a quick response force who immediately returns fire, and after a harrowing time, you win and they retreat.  Again, no need for an escape tunnel.

The third outcome is that as many of you as can make it back to your retreat, you secure the retreat, but the marauders continue to press their attack, rather than giving up and going away.  They either set siege to your retreat, or they manage to break into the retreat and overrun it.

This is the scenario where an escape tunnel might come in very handy.  A secure retreat is all very well and good, but it is also a ‘prison’ that confines you in one place, while your attacker is free to come and go, to resupply, and generally do as they wish.

Opinions differ as to if marauders would be ‘casual’ in attitude – ie, if they would selectively pick off only the easy targets, and leave harder targets well alone.  Or maybe, particularly after all the easy targets had been plundered, then they might become more fixated on taking anything they come across, even if it requires some time and patience to do so.

So, how likely do you feel these different scenarios could be?  Should you be considering an escape tunnel?

The Practicality of an Escape Tunnel

There are several things to consider when looking at the practicality of building an escape tunnel.  Clearly, if your retreat is built on bedrock, it will be close to impossible to tunnel through solid rock.  (Note that, in the other extreme, it is actually quite easy to build a tunnel through sand or marshy ground.)

So the first part of considering the practicality of a tunnel is to understand what you’d be tunneling through.

The next consideration is how long the tunnel would need to be, and where it would finish?  The tunnel exit needs to be out of the field of view of your main retreat structure.

If you are using the tunnel exit, it seems reasonable to assume that your retreat has been overrun, and there are bad guys all around, in a moderate state of alert.  If they look behind themselves, or through a window of your retreat and see you climbing out of a manhole just 20 ft from the front door, well, you can guess what will happen next.

This obscured visibility also needs to extend to a continued above ground escape route on away from the retreat.  The problem with this is that if you’ve designed your retreat well, you’ve made sure that you have excellent views for all the approaches around your retreat, so people can’t sneak up close to it and surprise you, and so people have no cover if attacking you.

If you have nothing but open ground, enlivened only by lawn, concrete, and vegetable gardening, for 100 ft or more all around your retreat, then you might have to consider a scenario where you will hide in an obscured basement safe room until nightfall and then make your retreat at that point.

That’s a far from desirable scenario, but so too is running across open ground in broad daylight!

The other consideration is just how long a tunnel you can afford to build – generally, the longer the better.  Which leads to our third point.

The Cost of an Escape Tunnel

The cost of your tunnel of course depends on the method of tunnel construction you adopt, and if you do some/most of the work yourself or not.

We’ll look at those issues subsequently in this article.  For now, let’s just assume an all up cost is $200 per foot of tunnel, which of course means that even a ‘short’ 100 ft length costs you $20,000.  Obviously, the longer the tunnel length you can put in place, the more secure your eventual exit and escape (or regroup and return) will be.  But this cost has to be balanced against all the other needs to spend money on hardening your retreat and ensuring your survival (not just in this quasi-military sense, but also in things like energy independence, food supply, and everything else).

Clearly, the longer the tunnel needs to be, the more expensive it becomes, and the lower the cost/benefit becomes compared to other risks that might be equally life threatening and probable and which require less investment to optimize and solve.

Let’s now move on and consider some of the issues associated with constructing a tunnel.

Another Tunnel Purpose/Benefit

So far, we’ve been considering tunnels for one purpose only – as an escape tunnel for you to abandon your retreat and hightail it away.

That’s a sad but essential purpose, but there’s another more positive use for a tunnel as well.  Depending on where it exits, maybe a tunnel can be used to move part of your defensive team to a second unexpected location, and to suddenly engage the enemy from its rear or flank, in addition to your continued defense from the retreat itself.

If this thought appeals, its practicality is somewhat terrain dependent.  You don’t want to be at a point where you are yourself caught in the own cross-fire between your in-retreat team and the bad guys.  You need to be able to guess at likely locations where attackers would base their attacks from, and then work out suitable points to have a defensive team appear.

If doable, the benefits of this tactical resource could be enormous.  Indeed, don’t just trust to chance with this.  As part of your total retreat design, you might even choose to skew the odds in your favor with some judicious landscaping and creating of some apparently better and worse locations for attackers to base themselves.

Tunnel Design and Construction

Your tunnel doesn’t need to be particularly deep, and neither does it need to be large enough for people to stand up and comfortably walk along.  You’ve probably seen pictures of the Gaza Strip tunnels, or even our own tunnels leading in to the US from Mexico – enormous things and put to terrible misuse in both cases.  You don’t need anything like that.

A relatively small tunnel is all you need, and here’s the trick.  You don’t need to worry about claustrophobically crawling through it.  There’s a much better way to travel through a small tunnel.

Our recommended tunnel would be a pipeline with a circular or oval profile, and rather than walking or crawling through the tunnel, you’d have creeper/trolleys –  boards you lie on with wheels on the sides, like mechanics use when going underneath cars.  You’d then propel yourself through the tunnel by using your hands and legs on the sides of the tunnel, or possibly you’d have a rope along the top of the tunnel that you could haul yourself along.  In both cases, you’d lie on your back on the board.

One of the benefits of using these boards is that you’d never be on the very bottom of the tunnel, so if there was an inch or two of water on the bottom of the tunnel, it would not be an issue.

Depending on the size of the people in your retreat, you might find a 24″ inside diameter sufficient, you’d probably find 27″ more than sufficient, and 30″ would be starting to become expensively spacious.  Yes, it sounds very small, and if you were crawling through it, you’d hate it.  But scooting along on a wheeled creeper board would be easy, quick, and not nearly as unpleasant.

Needless to say, this type of tunnel could not have any sharp corners or kinks in it, because the boards wouldn’t be able to turn around tight corners.  But also, needless to say, you’d not want your tunnel to be anything other than the straightest shortest distance needed.  It shouldn’t have corners in it.

As long as the tunnel is deep enough to be undetectable from the surface, and as long as there is no danger of what is happening on the surface harming the tunnel or causing a cave-in, then your tunnel is clearly deep enough.

You need to consider, when digging a tunnel, drainage issues and also the potential for tree roots impacting on the tunnel over time.  It is easy enough to make sure there are no large trees close to the tunnel (although keep in mind that any tree which is currently small may potentially grow to become big in time).  As for water, if that is likely to become a challenge, it is entirely possibly to make your tunnel tubing waterproof, and we’d also suggest provision for some sumps and pumps just in case water subsequently starts to leak in.

Probably the easiest way to dig a tunnel is to use a ‘cut and cover’ approach.  You’d use a backhoe/excavator/JCB to dig a trench, put in preformed piping, then fill up the trench over the tunnel structure.

Most dedicated backhoes can easily dig a trench 10′ – 14′ in depth.  Smaller machines that are a combination loader/backhoe and built on a glorified tractor frame can usually go down 7′ or so.  If you consider a 12′ depth, that would give you say 2.5′ for your tunnel tube, and 9.5′ of cover over it – an enormous amount of cover and almost certainly much more than is really needed.  Better to have less depth – it will be easier and quicker and less expensive to dig/construct, and there would be less weight of soil on top.  A 7′ deep trench would still have 4.5′ of cover over a 30″ pipe.  That’s way more than enough so that no-one would accidentally dig into your tunnel from above, and to keep vegetable and small plant roots away from it.

If you are worried about having a third-party contractor come in and construct your tunnel for you, you could buy a backhoe second-hand, use it as needed yourself, and then sell it when you’d finished for probably close to the same price you paid for it.  If you are doing this, you’d probably want a combo backhoe/loader unit.

Concrete pipe is much heavier and thicker than polyethylene (plastic) pipe, but also more robust and long-lived.  It can weigh in the order of 400 – 500 lbs per foot, and have side walls of 4″ in thickness or more (depending on pipe diameter of course – here’s a useful table).  Figure on a cost of about $100 per foot of concrete pipe, and you’ll be close to right.  Plus an unknown amount extra to lay the pipe – depending on the land and soil conditions, etc.

We mentioned in a preceding section using a rule of thumb of about $200/foot all up for tunnel construction.  We hope that’s on the high side, particularly if you are running a reasonably long tunnel over easy ground and doing much of the work yourself, but best to start off with a high guess and then improve on the real cost as you progress through the exercise.

On the other hand, modern high density polyethylene (HDPE) or polyvinyl chloride (PVC) plastic pipe is about 20 times lighter than concrete, has much thinner side walls (which makes for easier trenching and allows for smaller outside diameters), and is claimed to be about as reliable in use as concrete.  Price-wise, there doesn’t seem to be a huge difference, although the plastic piping is less expensive.

Some people argue that plastic piping requires greater care while being laid than concrete pipe, due to its innate lower strength and greater reliance on optimized ground loadings.  But its lighter weight makes it very much easier for you to work with it yourselves, without needing trained crews of men and specialized machinery to move multi-ton pieces of concrete piping exactly into position.

Overall, there seems to be no clear consensus on concrete vs plastic, and we suspect the price advantages of one over the other will vary depending on where you are and how close you are to sources of either, and what the associated trucking and installing costs and considerations may be.

There are also various types of metal pipe material as well.  Black iron and steel are the most expensive materials.

We don’t know enough to recommend one type of material over another, but we do note that most ‘general purpose’ tunnels and pipes are made of either concrete or HDPE.

Permits and Approvals For Your Tunnel

If you are in a jurisdiction that requires formal permits, plans, inspections and approvals for building construction, and if those requirements extend to tunnels as well, you have to make a difficult decision as to whether you get all the necessary paperwork or not.  If you don’t, there’s a measurable danger that your tunnel may be discovered, in which case the best case scenario is you are up for major fines, and the worst case scenario is that you could have your entire retreat structure condemned, temporarily or permanently.

You might think that what you do on your retreat, perhaps in the middle of a pristine wilderness and miles from any road and totally out of sight of any public land would be a secure safe secret.  But look up.  See that plane flying overhead?  Maybe it is mapping the landscape for Google Maps, or directly for the county (we understand that it is not uncommon for counties to use aerial mapping to confirm the accuracy and completeness of their records about what structures exist on the land they tax).  Look even further up – see the satellite in the sky?  No, of course you don’t, but it can probably see you, and it too may be transmitting pictures of your construction project to all sorts of interested agencies.

Update – here’s another interesting article on the capabilities of observation (ie spy) satellites – they have such fine sensors they can detect shotshell cases on the ground, and evidence of recent digging, and are being launched in ever greater numbers.

Another update – here is information that Google plans to launch its own constellation of 24 satellites operated by Skybox.  The satellites will, between them, take three pictures, every day, of every place on the planet.  They will also have video capability.

Final update :  We became fascinated by the topic of aerial observation, and so rather than continuing to add to this article, we’ve now added a separate standalone article about aerial imagery.

The other interesting thing to note from these articles is that the current 10″ resolution capability of the satellites does not represent the highest quality resolution the satellites are capable of.  Instead, it is an artificial limit that the satellites are restricted to by US law.

On the other hand, it is surely unappealing to have your super-duper secret emergency escape tunnel on the permanent public record, available for anyone to scrutinize at the county office, and even online too.  It is true that such facilities may disappear entirely in a Level 2/3 situation, but who knows how many people have found out about your tunnel already.  Even if marauding strangers don’t know about your tunnel, you can be sure the locals would, and sometimes you might have as much to fear from locals as from strangers.  Suffice it to say that building a tunnel clearly labels you, your property and your retreat as being ‘out of the ordinary’ and ‘interesting’.

Perhaps one possible approach is telling half the truth.  Have a septic line running above your tunnel, and get that permitted.

Another possible approach would be not doing a ‘cut and cover’ approach (which is obviously very visible and obvious) but instead doing a true below ground tunneling exercise, like prisoners do to get out of jail.  However, we’d urge you not to do this unless you have an enormous amount of manpower and time, and also a highly detailed knowledge of the soil conditions that you’re tunneling through.

Creating a tunnel that way would require tens of manhours per foot, plus a lot of resource for removing/secreting the dirt from the tunneling, and all the necessary wood and other materials for shoring up the tunnel from the inside, along with an ever-present risk of cave-ins if you made any mistakes in your calculations.  You’d also need to make it larger than a pipe type tunnel, because you need a work area at the tunnel face as you dig your way forward.

Hand digging a tunnel is not impossible, but it is definitely a very undesirable approach to tunneling.

Choosing and Obscuring Tunnel Exits

One of the most difficult aspects of designing a tunnel is choosing where its exit will be.  As already mentioned, you don’t want it to be in the middle of an open field, with you emerging out of the tunnel being in plain view of everyone.  Not only this would be in plain view, but so too would be your continued escape across the open ground.

Ideally your tunnel exit needs to be out of sight of both the retreat structure and also out of sight of likely locations where attackers might situate themselves.

The specific topography of your location will determine the what/where/how of this, and obviously, the longer your tunnel and the further away from your retreat, the safer your exit will be.  Note also that you might do some landscaping or plant some particular types of bushes or whatever,  to create some visual obstructions or other features to make it easier to make your escape unseen.

The other consideration is concealing the exit so it is not obvious to people, prior to your using it, that it is a tunnel exit.  Remember that tunnels work both ways – you don’t want your attacker to use it as a means of safe passage right into the heart of your retreat, and neither do you want, when emerging from the tunnel, to find a ‘welcoming party’ assembled to surprise you.

It is common to attempt to locate tunnel exits inside some sort of building or other structure.  There are obvious advantages in doing this, and if you have a barn or shed or pumphouse or any other sort of structure that could be used for this purpose, so much the better.

Another possibility would be to disguise the tunnel exit in some junk.  If you saw the movie RED, then you’d have noticed how Marvin used the trunk of a junked car as an obscured entrance to his underground hideaway.  Something similar might also work well for you, and it is far from unusual for rural lots to have some old vehicles rusting away somewhere.

If you have a large tree that you could cut down some distance off the ground (ie above eye level) and then use the tree stump, hollowed out, for egress, that’s another approach to look at.

There are any number of other ways that a tunnel could terminate.  For example, maybe you have a short storm water drain/waterway running under a road.  Anyone can look from one side of it through to the other, and can see it to be a normal simple water drain.  But your tunnel terminates on the side in the middle of this and you can simply move a panel of the drain’s side material and step into it.

Another method is to have your tunnel’s exit shaft end a short distance below the ground surface, and when you need to exit, you simply remove the reinforcing at the top of the shaft and dig through the remaining dirt or whatever.

Maybe you have a shallow pool somewhere and your tunnel actually terminates underneath the pool.  The benefit of this is that normally, the water obscures the tunnel exit.  The downside – do we need to tell you this – is that when you open up the exit hatch, you’re going to get wet.  And there’s a risk that the exit hatch might develop a leak, potentially flooding out the tunnel and making it unusable.

Keep in mind there are two types of tunnel exits, with different considerations.  There are ‘single use’ exits that you will only need to use once, and once you’ve used it, you’ll not have any need to reconceal it for future reuse.  There are also multi-use exits that you will want to be able to use on a repeated basis.

Instinctively, the thought of multi-use exits appeals.  But think carefully – how often are you likely to need to use this?  Using your emergency exit presupposes that you’ve been not only attacked, but defeated and your retreat has been overrun.  Hopefully you’ll never need to resort to this, possibly you might use it once, probably never twice.

On the other hand, you will want to occasionally do drills to practice using the tunnel, and ideally these drills should go all the way through to having your group exit at the far end, which would require opening up the exit and being able to subsequently obscure the signs of people exiting and moving around.  So, if possible, it is better to have a multi-use exit.

Checking the Security of Your Tunnel Exit

Think about this.  You’ve constructed a tunnel, with a secure exit out of view of the retreat.  You’ve been attacked and unfortunately find yourself unable to defend your retreat and so need to escape.

But, you can’t see the far end of your tunnel.  You don’t know if by chance some of your attackers are camped right on top of the exit, or maybe they have discovered it and have a couple of people guarding it, just waiting for you to emerge.

It would obviously be highly desirable to be able to monitor the situation around the tunnel exit before emerging.  We recommend you should have some type of facility to allow you to do this.

There are several ways you could check what was immediately outside the tunnel exit before emerging.  Again, the method you select will probably depend on the nature of the terrain around the tunnel.  If it is in an open field, you’ll do something very different to if it is in a building or in a forest.

The lowest tech approach would be to have a thin tube periscope that you can poke up through the ground and then survey around the area.  If the periscope also had a microphone that passed down to a set of headphones, you could listen as well as look.

A more complicated approach would be to have a hidden video camera somewhere that is pointing at the general area where the exit is located.  The downside to this is that if the camera is discovered, it begs the question ‘what is this camera doing here and what is it looking at’, so you might choose to have several cameras or to have the viewing angle set so that it is apparently looking at an obvious different place to look at, as well as less obviously at the tunnel exit.

The other issue with video cameras is how you get power to the camera and then the video signal back to a monitoring point.  We suggest this should all be done by wire rather than wirelessly, and we also suggest the wire go, buried below ground, back to your retreat rather than directly to your tunnel exit.  That way, if the camera is discovered, the wire can’t be traced to the tunnel, but instead, to your retreat, which is what a person would expect.

The chances are you will be setting up some video (and audio) surveillance around your retreat anyway, so including at least one camera to monitor the state of your tunnel exit is just part of the total picture.

Note that it would be best to have a periscope at the tunnel exit as well.  If something happens to disable the video feed, or even just so you can get an updated evaluation between when you left the retreat and were ready to exit the tunnel, this would be useful.


You’re building your retreat as a haven and safety to protect you against as many eventualities and circumstances as possible.  This means you’ll make your retreat as robust and secure as possible, of course.

But one eventuality is the possibility that, your best efforts notwithstanding, you might be forced to abandon your retreat.  A secure secret exit tunnel would increase your chances of doing so and living to fight or at least to survive beyond that.  Without such a feature, your retreat has changed from being your safe haven to instead being your prison and potentially your coffin.

We feel that adding a tunnel is an important and necessary feature of a complete retreat design.  Using a cut and fill method of tunneling and preformed concrete or plastic tubing makes it a relatively quick and straightforward process.


David Spero[suffusion-the-author display='description']

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