Blasting stumps

[Anonymous Poster]

I want to remove some 6"-12" stumps from my wooded area. Someone suggested blasting them with a stick of dynamite. Now to do that you need a license. My brother suggested I just use a Timothy McVey bomb--- Ammonium Nitrate fertilizer mixed with diesel fuel, a long run of wire and a battery. Anyone ever hear of doing that?

 

[DrDan]

You need an explosion to set it off. Check out what it takes to get a license. It shouldn't be too bad. Didn't used to be.

Dr Dan

 

[HalseyGreen]

Here in Virginia, you can purchase explosives for instate personal use, only one source in southwestern part of the state. Have a friend that has gotten some and opened up some sink holes on his farm. Find a local road contractor and find out where he gets his.

 

[RPM]

Believe me - you're doing yourself a favor if you take a short course and get the right paperwork. Keep it legitimate - especially since people are so paranoid about using explosives these days. Explosives are not inherently bad - it's the bad apples that occasionally get hold of them.

ANFO (Ammonium Nitrate - Fuel Oil) as they call it is really too messy and cumbersome for stump removal. For effective blasting you need at least a 4 inch diameter core (critical diameter depending on grain size in the slurry) - and you have to also prepare and contain the slurry. You also need to initiate a detonation - this is fundamentally different from burning or 'deflagration'. Much better off with the old fashioned dynamite - and less likely to cause yourself a serious injury. ANFO is really only used in road blasting and quarrying anymore.

Be careful!! It is very easy to hurt / kill yourself doing this. It is also easy to run afoul of the local law enforcement agencies. If it's done right then everyone is happy!

 

[dmccarty]

MarkH,

I looked into this last year. Using something that goes BOOM! to remove stumps is problematic.

In NC you did not need a license to buy the dynamite but there were very few places that would sell to the general public because of liability reasons. I talked to a contractor who was "cracking" rock on the road side and later talked to the owner of his company. They did not want to blow stumps for me either. They could not sell to me either. They did tell me a company that would sell but I did not pursue the matter.

One is cost, ease of use and storage. ATF has a web site that will tell you the law/regulations on storing and transportation of explosives. PITA. I have enough land that I could store the stuff if I had to but then you run the risk of some kid getting into something they should not. So you would have to buy just enough to use in one day. PITA.

The other problem is you apparently have to dig under the stump to blow it out. PITA. Then you are supposed to tamp in material into the hole you dug to get the explosion from blowing out and not up.
PITA. How do you dig a hole under a pine tree with a long tap root?

Cost I think it was going to work out to 2-3 dollars per stick of dynamite plus cord plus detonators. My father in law has blown stumps before and said it used to be much, much cheaper than it is now. I figured it was going to cost around 5-10 dollars per stump if I was lucky. I counted my stumps. I have about 100 per acre and 5-6 acres. Sooo, that is 500 to 1,000 dollars per acre or 2,500/3,000 to 5,000/6,000 dollars total. I figured I can do it easier and cheaper with my own equipment, rental equipment or just paying someone.

There is a web site for explosive engineers. They have a book for farmers/contractors/etc who need to use explosives. It was $100. I would love to read the book but not for $100. If I was going to use boom boom stuff $100 is pretty cheap but it was one more nail in the coffin holding my idea of using explosives to remove stumps.

6-12 inch stumps are little. You can rent a backhoe for a day that an remove the stumps easily. I have a JD 4700 tractor with a JD 48 backhoe that I have dug up oak stumps 36 inches in diameter. 6-12 inch stumps are pretty easy. An industrial back hoe would make this an easy job.

Buy or rent the equipment to pull the stumps. Much easier, far safer, and cheaper than using explosives. I think explosives on 12 inch stumps is over kill...

My two cents...

Hope this helps...
Dan McCarty

 

[DrDan]

I used to have an auger about 6" long with a "T" handle on one end. You just made a hole about 1 1/2" in diameter under the stump, attached some fuse cord to a cap and fused the stick of dynamite. The fused stick was pushed into the hole and ya lite the fuse and ran like he#! After you do a few ya get used to how much it is going to take. The sticks can be cut into 1/4's of 1/2 depending on how big a stump.

Yes by all means, take a short course. You need a special fiber pliers to crimp the caps and you never do it around your store of dynamite. Dynamite by itself is fairly safe. It's the caps that are dangerous. Everything has to be fiber or wood. Don't want any sparks.

The thing is... It does an exceptionally nice job of lifting the stump. If you are willing to invest the time to learn how to handle the stuff right it's a fast, effective way to remove any stump <unless it's next to your house or barn>.

 

[RPM]

Here's the full set of regs on the ATF site.

Search for '55.201 General' and read from there on - it'll tell you about storage requirements etc.

There's also a good list of general questions (like a FAQ) at the site - search for 'General Questions' on the page.

If you're just an individual, best to find a local contractor who will store for you - or just buy enough to use/dispose of that day.

Here's another interesting part ...

<font color=blue>16. I want to buy a small quantity of dynamite from my local dealer to use on my property. Do I need a Federal user's permit?

No, provided it is purchased in your State of residence and not transported across State lines. A Federal user's permit is required when a nonlicensee acquires or transports explosives in interstate or foreign commerce. It allows transactions for personal use, only. [See Question 17.]

</font color=blue>

 

[RPM]

We used to use a set of brass tools when handling ... also spark-free.

 

[DrDan]

Yup brass is good. "Sparks are a bad thing" I always used fuse cord and timing cord. Never trusted electric caps. Dang static electricity can set em off and that makes me nervous. Fused caps are a little more stable IMHO, but it still always made me cringe a little when you crimp the cap on the fuse.

I was working downtown Washington, DC when they were building the subway and blasting everyday. It was amazing what an experienced blaster can do. Had heavy steel mats made up of links that they laid over the area to keep anything from flying around.

It's unfortunate <as with guns> that such a tool is misused because it really takes the work out of lots of projects. We removed about 50 big stumps in just a couple of days. The dynamite would just lift them about 6 or 8" into the air and you could go hook onto them with a FEL and away you went.

Thanks for the link. I used to buy supplies from a gravel quarry that had lots of different charges for different work. As I remember it we used either 50% or 60% for stumps. Don't want to much blast - just a slow push.

Dr Dan

 

[RPM]

I have to admit - I've never used fuse. Always used electric detonators. Always felt that the risk was lower and better defined. The main challenges were capacitance in the firing cable due to damage / natural capacitance and induced currents due to electromagnetic interference.

The capacitance is fairly easy to get around - just touch the cable to ground and twist the ends together at the command/firing end while you are at the business end with the det.

Electromagnetic interference can be harder - that long firing cable serves as a great antenna. We used to confiscate cell-phones and 2 way radios. Just had too many incidents where people flat out lied to me that they had turned theirs off. Some people just don't seem to realize that this can cost a person their life in the wrong set of conditions. You also had to watch out for thunderheads - all blasting stopped at that point.

You also ended up with some really good buddies who you could trust - and vice versa - who would watch the opposite end of the cable for you. Had great fun for a few years doing this, then along comes the wife and kids and all of a sudden it's not so appealing anymore. At least I got the urge to make big explosions out of my system - I just see it as a practical challenge anymore, not quite so exciting as it used to be.

 

[RPM]

Whoops - missed one point. The old electric dets or 'hot wire' dets did have a fair reputation for being unreliable. They used very dodgy primary explosives like azides and styphnates that go off with exposure to heat or percussion.

If anyone does go this route you want to use the more modern, much safer, exploding bridge-wire (EBW) type. These use a much safer secondary explosive like PETN. The vaporizing bridge-wire initiates the shock that causes detonation in the PETN.

You can also get them with a little toroid core that means they can only be fired at a specific frequency of current - lowers risk due to electrical noise (but not capacitive discharge). I think the brand name is Magnadet or something like that.

Always have an experience explosives engineer on hand when tackling anything like this etc. etc. etc.

 

[DrDan]

RPM

Yes, I'm also one of those who like anything that goes "bang"! As soon as I turned 21 I went and got a blasters licence in IL. Now since I'm in a wheelchair I can't get back as fast so I've mellowed out a little. I have a friend that teaches blasting for the coal miners. Real "milktoast" guy. You'd never place his face with that of an expert explosives person. I do have a lot of respect for those who really know how to use explosives to get a job done. My expertise was limited to stumps, however when we finished we had about a half case of 2 X 16 sticks and proceded to hollow out a 30' crater in the bottom of a gravel pit. Great fun!!!

Regarding the dangers, I guess I've always looked at it like I'd rather go via a quick accident then living to 90 in a nursing home with some nurse wiping my rear. I am pretty careful though.

Refresh my memory on what the percentages of dynamite mean. I think the higher percentage the faster the explosive burn. Right?

Boom!

Dr Dan

 

[RPM]

We always joked about that too. Since the blast wave would be traveling supersonically, you wouldn't know anything about it. It would be just like turning the lights off.

As far as the percentage - my hands on experience is all plastic explosives work. If I remember rightly though, it is the proportion of nitroglycerin to total mass of the charge.

Alfred Nobel made all his money by discovering kieselguhr - which acts as a stabilizer for nitroglycerin - and his combination of the two as dynamite. I believe that kieselguhr was long ago replaced by other inert ingredients, but couldn't tell you their names.

There's a good reference at the US Army Corps of Engineers site - it's a sizable Adobe Acrobat document. All public domain stuff although pretty dated.

By the way, some more detail on modern detonators such as I was referring to can be found here.

 

[skent]

My Uncle worked as a welder for the Army, one of his jobs was to modify/weld Japanese/German bombs to be used by the Allies. He was wounded in action and sent home early. His 'buddies' packed his footlocker and included some souvenirs, several (40mm I think) anti-aircraft rounds. . They didn't have powder in them, but had live primers. When he unpacked his footlocker in the states, he was afraid of getting into trouble so he stashed them upstairs in the hog pen.

Fast Forward 40 years. . . .

When we moved out to the farm, my kids were quick to locate the three anti-aircraft rounds and told me
about them. State Police advised me to contact the State Fire Marshal who in turn contacted the Ft
Indiantown Gap Bomb Squad who showed up the next day. They determined that two of the rounds were
tracers and asked if they could 'detonate' them in an open field. I asked if I could videotape the process and they said sure.

They coordinated with the fire marshal and he in turn contacted the State Police, 911 operator, Fire
Departments and county governments to notify them of the boom. They took the rounds to the middle of an open field about 500 yards from my house and mixed a 'quantity' of plastic explosive. I didn't realize that the plastic explosive came in two parts and had to be mixed just prior to use, and was safe for several minutes after mixing. They then used a radio controlled detonator (had a 4 digit code that was set) and the receiver was 10' from the rounds with a twin lead going to the cap.

My 5 year old was home from school that day and when the Lt. yelled "fire in the hole" three times, let Paula
push the button. All of us jumped when it went off. Got it all on videotape, including the Sargent saying "I
think I used a little too much"

There wasn't much left of the rounds, just some scrap metal and a hole in the field 4 feet round and 18 inches deep.

Seems the Army has had quite a problem with this very thing over the years. The in flux of souvenirs from
soldiers have caused quite a problem and many people are afraid of charges from the Army. According to the two men from Ft Indiantown Gap, the Army has adopted a policy of "No Questions Asked" for those people who have this very situation. Seems many munitions were ending up buried in back yards or discarded in landfills. Quite a problem.

All this occurred months after we moved in and just after the Oklahoma City Bombing, and neighbors seeing
the State Fire Marshal going in and out of out driveway several times, and the Bomb Squad show up, and the explosion. . . . . what would you think????? We still enjoy the videotape from time to time. . . . .




Steve

 

[RPM]

Skent,

You don't have to mix plastic explosives - what you saw was probably a binary explosive. These usually have a couple of liquid components which are mixed prior to use. I'm very surprised they used this approach - it's primitive and I would argue less safe than plastic explosives. A plastic explosive is normally a powdered high explosive mixed with a plasticizer in bulk or sheet form. No further preparation required.

You can burn several pounds of plastic explosives and even discharge a rifle into them and they won't detonate. You have to initiate the detonation with a shockwave - it's fundamentally different physics from burning (deflagration).

You were right to be careful around the primers on those old shells though. They become very unstable over time - stay well away and let the guys in the padded suits deal with them!

 

[dmccarty]

Dr. Dan,

When you used the auger on stumps, did the stumps have tap roots like some pine trees or where they wide stumps like oaks? Did you have to tamp material into the auger hole after placing in the BoomBoom stuff?

Most of the stumps I have to remove are pines and from the trees that have been blown down they have 2-3 feet long tap roots. I could never figure out how I was going to get under the stump to blow it out of the ground. Oaks would be easy but the pines with tap roots I could not see doing. Now there are some pines without tap roots and I have some on the property. I just can't tell which has a tap root from looking at the cut stump.

This problem and the money side pushed the idea of blowing the stumps out of the ground.

Later...
Dan McCarty