Cover Image
close this book Wells construction: hand dug and hand drilled
close this folder Appendices
View the document Appendix I: Conversion factors and tables
View the document Appendix II: Vegetation as an index of ground water
View the document Appendix III: Uses of dynamite in hand dug wells
View the document Appendix IV: Cement
View the document Appendix V: Leveling and plumbing the mold
View the document Appendix VI: Pipe
View the document Appendix VII: Pumps
View the document Appendix VIII: Water treatment in wells
View the document Appendix IX: Rope strength

Appendix III: Uses of dynamite in hand dug wells

This article by Christopher Henney was written as an overview of the uses of dynamite in the Peace Corp/Togo wells construction program.

It is reprinted from the Action/Peace Corps P&T Program and Training Journal (Special Issue: Wells Manual) published by the Peace Corps in 1974.

PART I: Obtaining ft

When to use dynamite

When and if you encounter a hard rock layer and there is NO OTHER WAY to break it in order to attain the aquifer, then dynamite Is in order. Of course, you could move the well site, but in some regions this probably would not make much difference. Never use dynamite before It is absolutely necessary as villagers will immediately start to rely on it as soon as the going gets rough. It is very difficult to stop using ft once you have started. Dynamite in an old well or using dig-a-meter-pour-a-meter method Start with small charges and deep blast holes and try to leave 50 cm between caissons and rock.

How to get ft

Because it is an extremely dangerous substance and can be used for sabotage or other crimes, most governments are very caution about whom they give permission to use dynamite; thus one's procedure for obtaining it should always be through all necessary officials channels. In Togo this generally means:

1) Chef-Cir

2) Travaux Publics or Assainissement

3) Interior Ministry

4) An authorized dealer

First you get your Chef-Cir to address a "demande de permission d'achat" permission to buy request to the Minister of Interior. This will state quantity and type of dynamite plus quantity and type of detonators. What purpose it is to be used for and where' where it will be kept, and by whom. Attached to this should be an agreement of your local boss; in my case the Engineer of Assainissement Sokode. This letter will then be transmitted to Lome (the capital) and will be returned as a letter of permission to the bureau of the Chef-Cir. He will give it to you. Remember this permission expires after six months, so use it immediately. With this letter you then go to Lome and order the dynamite and detonators from Brossette et Valor (an authorized dealer). This could take time as it must come from France. So plan 6 months ahead.

Another option is to have Travaux Publics-Service Hydraulique order it for you when they order theirs. Especially if you only want one or two cases. This is because Broesette requires a minimum order of three cases unless you want to wait until it can be attached to someone else's order. This also has the advantage of free transport up-country. It is not always easy to get a transporter to carry high explosives.

WHAT TO ORDER:

The Dynamite

There are a number of kinds of dynamite or explosives adaptable to wells. And the choice is probably bost made with expert help. Service Hydraulique is your best bet or Service des Mines. after wing three different types and talking to a number of people, I decided on the type known as "Comme A. Tolamite. This is a red gelatinous substance rolled into 50 grms. packages by means of wax paper. It is waterproof and maleable. The gases it releases upon ignition are non-toxic {although they may frritate lungs, but I will get to that later) and the stuff won't go off if bumped, smashed, dropped, etc. The maleability is important as sometime you want to squeeze it into a crack like toothpaste. I generally figure quantities on this scale:

1 charge - 50 or 100 grms. dynamite

Meters depth of rock

Diameter of well

Quantities

Number of blast holes

1 METER

1 meter ø

12 charges

3

1 METER

1 meter 25 ø

10 charges

5

1 METER

1 meter 40 ø

24 charges

6

1 METER

1 meter 80 ø

28 charges

7

This should be more than adequate; usually it takes two rounds of explosions to do a meter although this depends on the depth of the blast holes and the hardness of the rock. Normally your local water bureau or Travaux Publics will be able to tell you how deep you will have to blast. One case of dynamite weighs about 25-30 kg.

The Detonators

For each three charges, you will need two detonators. This will insure an adequate supply. Make sure they are electrical firing detonators. Fuses are dangerous and should not be used. The best kinds are type B66 low intensity, total resistance 1.5-3 ohms, medium 2 ohms. Make sure the wires are 2 m long.

In general both dynamite and detonators have an expiration date. So make sure you don't get an old batch, because it may be unstable and therefore DANGEROUS.

Where to Store and Now

The storage of dynamite is most important for your own health and that of others. Don't keen it at home as you may have kids or ocher curious people around. Personally, I prefer to keep ft at the local gendarmerie, police or travaux publics. This has a number of advantages:

a) You cannot be accused of sabotage for political reasons

b) If you work on weekends, you can get it at the first two places

c) If there is an accident, you are not around or responsible

Keep detonators away from dynamite,if possible at the other side of a locked room and in a case. Never let dynamite and detonators come into contact until you are ready to use them. Remember a good shock can set off the detonators, and detonators can blow your hand off. Keep tabs on how much you have and how much has been used. If you cannot keep it at the above mentioned locations, make sure you have a good store room with lock and the only key in your possesion.

How to Carry to your Site (If You Must)

If you don't want to keep it at the side because there is no adequate store room or you have many sites and prefer to bring it in when needed from a central store, then you must decide how it will be carried. I personally don't like this as there is a small amount of risk involved; but I did it for over six months. Anyway, if you follow certain simple rules, you should be all right.

1) Keep detonators and dynamite in separate waterproof sealed cans - The detonators preferably in a plastic one.

2) Keep the batteries or exploder somewhere else in your pack and separate from the detonators. This will insure you except if you get hit by lightning or squashed by a true*, both of which are very real dangers.

A normal crash because of sand, etc., should cause you no problems. (I had two).

PART II: Row to Use

Rules for Use in a Well

The use of dynamite follows a couple of rules of thumb:

a) Use common sense

b) Don't use more than needed to get the Job done

c) Make sure the site is cleared of people

d) Keep children away from site at all times

e) Get someone else to trigger ft

f) Don't let anyone else handle dynamite or detonators

g) Keep the batteries in your pocket or pack until you are out of the well and the site is cleared

h) Check whether all charges went off (see Part III)

i) Never send someone else to get dynamite or detonator. from the store room

j) Never go down in a well containing unfired charges unless you have secured the batteries

k) Place the charges yourself.

Rules a, b, c, d, g, j are constants, but e, f, i, k are changeable if you have trained a competent person to do the job. But no matter what happens, you will always be held responsible.

Tools You Need

Assuming you are working on a village level and you don't have a jack hammer (compressor), you will need:

1) Mining bar

2) 75 meters of extension cord flex

3) 1 roll of insulation tape

4) 1 flat file (to sharpen mining bar)

5) 5 flash light 1.5 volt cell batteries, size D

6) Dynamite and detonators

7) One 2-meter spoon

How to Place Charges

As I have said before, the number of charges is In proportion to the depth of the blast holes and the diameter or the well. A good rule of thumb is two charges per hole (blast hole) and:

3 holes for 1 m ø

5 holes for 1 m 25 cm ø

6 holes for 1 m 40 cm ø

7 holes for 1 m 80 cm ø

but depending on the rock, you may have three charges per hole (or one). Never blast if your holes are not deep enough. It is a waste of dynamite. The blast holes should be at least the length of a man's arm, 80 cm and preferably more. The deeper the better. Blast holes should always be in the most protruding places.


Figure A.


Here is a good diagram of where to place them in general

The charges toward the outside walls of the well should slope out as In Figure A and In the case of 4 - 1 charges.

How to Make up Charges

There are two methods thee I use: placing side by side, or one on top of the other.


Figure B.

I prefer the side by side method where the hole is large enough. This is done by unwrapping the wax paper around the dynamite and sticking the two charges together, then rewrapping. The detonator is then inserted until completely inside the dynamite. This method has the advantage of never having only one charge go off because the other got covered by mud and separated from the first charge as in the one on top of the other method. But in really hard rock it is sometimes not always possible to make the blast hole wide enough. The one on top method is also better for really deep holes as you can put 3-4 charges in with no difficulty. I might also mention that the tighter the fit of the dynamite, the better blast you are going to get. once the dynamite is in the hole with the detonator securely in the dynamite, pack the hole with damp sand. And pack the sand with a stick so it is well in and well packed.


Well packed hole

Don't pussy-foot but don't pound as if you were driving railroad spikes. This insures that the dynamite has some thing to push off on and that the gas does not escape out the open hole. Never till your hole up to the top with dynamite. This just is a noisy waste.

If you have more than one charge as you will most of the tame, you most hook them up in series. Each detonator has two wires, on one will be a flag.


Figure C. (a)

Now in order to hook up a series, you must hook flag to non flag of another charge:

This leaves you with one flag and one non flag which is than attached to the extension cord that goes above ground. Next collect your ends and tie them to the extension cord:


Figure C. (b)

If you have four detonators, there should be five joints left out of the *not, and so on. Make sure those are separated so as not to cause a short circuit.


Figure C. (c)

Also make sure that this knot is above the water level- -Preferably as high as possible without pulling the detonators out - and that is easier than imagined even when the charges are packed in sand. Than get out of your well, being careful not to pull on the extension cord.

How to Dig the Blast Roles

Using the blade end of the mining bar, pound the rock. This must be done while continually rotating the blade so as to make a nice neat round hole. At intervals, add water to make a slurry - this is messy but necessary. After a bit, use the 2 mater long spoon to get out the dust and dirt made from pulverized rock; or if the hole is wide enough, use your hand. Never make holes wider than your hand (fist) as this is Just wasteful of dynamite.

The sand will be blown out and little rock will be blasted. This is hard work and can take several days.

Ignition

To set off the dynamite, place the four or five batteries end to end and touch the two ends with the two ends of the cord. Make sure you do this firmly and keep the cord touching until you have counted five (oven though the explosions will happen spontaneously). This could save you many hours of looking for live charges that did not go off. For 1-3 charges, four batteries. Add one battery for every additional charge; i.e.

for 5 charges, 6 batteries; for 6 charges, 7 batteries, and

for 7 charges, 8 batteries.


Figure D.

Before you fire, clear the site. Let no one stand nearer than 50 meters to the well. Let a Togolese do the firing. There are two reasons for this. If someone gets hurt you did not pull the trigger, and Togolese-American relations will not be upset. Also, you are needed to keep a sharp look out for

falling rocks, impulsive children, or new arrivals. But if anything does happen, you will still be responsible for the sit. and though not legally, you will be held responsible in the eyes of. the people you are working with.

Once the explosion has gone off waft a minute. You will often be surprised how long ft takes rock to fall back to earth. Then pull up the extension cord and count the number of detonator wires. If all have gone off great, but if one is severed half way up, there is a chance it is still alive. Also, if there is anything holding the cord don't yank ft up. This could well be the wire that did not fiew, and by following it you will easily find the unfired charge instead of digging all over to find ft. Now waft 15 minutes half an hour until the smoke clears. You can choke to death by smoke inhalation even if the smoke is not toxio per se.

What to Do if a Charge does not go off

First, climb down and check your detonator wires. If one stays stuck, dig around it reasonably carefully. (If an explosion could not sat the charge off, you would really have to try). There is not too much danger if you are careful. When you reach sand, pull the detonator out slowly, then dig out the charge. The charge is now harmless. Or you can also rewire the detonator, climb out, and fire ft. If this does not work and you cannot extract the charge, put a net one In on top of it and fire that. This way your well is clean. Then sand workers down but Nor until you have at least extracted the detonator(s).

The causes of unfired charges are:

1) A short circuit

2) A sot of old batteries (no power)

3) Old detonators

After each explosion, chock out your cable and patch or cut. Then place batteries at one end and the two wires on your tongue at the other end' if ft tingles, all is well. Coil and put away. If not, find the short. Always do this after each explosion. It saves embarassmant when nothing goes off. You can work in up to 1 meter of water.

Recap of Procedure Rules

1) Only use dynamite where nothing else works.

2) Never use before it is absolutely needed, even when the work is hard.

3) Follow all official procedures in obtaining it.

4) Make sure It is not outdated stuff.

5) Never we fuses, always electric detonators.

6) Don't keep it at home, store safely.

7) Never send an inexperienced person to got it out of storage. Go yourself.

8) Keep dynamite separate from detonators and detonators separate from batteries.

9) Use commonsense (take all the risks that need taking yourself).

10) Don't use more than you have to.

11) Make sure the site is cleared of people.

12) Keep children away from site.

13) Get someone else to fire it while you watch.

14) Don't lot others handle dynamite or detonators or batteries.

15) When you are in well, keep batteries in your pocket. This is your only insurance.

16) After explosion, chock for unfired charges.

17) Never go after unfired charges unless you hero secured the batteries

18) Place all charges yourself.

19) Always pack some sand on top of a charge.

20) Make sure your detonators are wired properly and that the jointed ends don't touch.

21) Tie the wires to the cord.

22) Make sure knot is above water.

23) Don't pull on cord. You might extract detonators by accident.

24) Lot no one stand clover than 50 m when you blast.

25) Touch batteries firmly. Count to five.

26) Chock for dead charges yourself.

27) Wait for smoke to clear.

28) Check extension cable after each explosion.

29) Keep tools in good repair.

30) Remember you are responsible for your life and other lives.

PLEASE NOTE: Under no circumstance should dynamite be used unless an exhaustive study concernong its use has been conducted by experts who are knowledgeable In the use of dynamite.

GOOD LUCK AND TAKE CARE.