Help Us Construct the Perfect Berm

[OF]

Howdy,


Looks like we're going to build some practical pistol ranges at the local club to accomodate IDPA at first and then other practical pistol sports later on.

We will most likely be carving the ranges out of a hillside. What I'm looking for right now is tips and advice on how to build a great berm - both rear impact and side berms.

My understanding is that the base of the berm will end up twice the height if it's just dirt piled up, or more. What are some ways to increase the height without increasing the base width? Or decrease the base width at the same height? What have people seen that they were impressed with? It has to look professional, clean and, if at all possible, attractive. I can't stand the 'garbage dump' look that seems to be so pervasive in these sports, and the range location is very visible here.

We're talking about a hillside ~200ft wide, ~50ft deep and ~8ft high before the big trees start. The hillside fills about 1/2 of that total area. So we have lots of material to work with, but it's going to be tight fitting (4) 30' wide bays in that space, but we're shooting for 4 at a minimum. If you figure 16ft of side berm base width for an 8ft berm, it just fits. I'd like more room and higher berms.

Any advice is greatly appreciated as we try to make this bird fly.


Thanks folks,

- Gabe

 

[hps1]

Have seen berm height extended by using "eyebrow catchers". These were constructed using old power poles and covering both sides with planks or plywood, then filled the void with gravel. Any bullet striking the eyebrow passes thru the wooden surface and self destructs in the gravel. Needless to say, these should be some distance from firing line in event a bullet should turn 180*. While not likely, suppose it could happen. (We have a railroad rail at our range for setting silhouettes and there was some concern of bullets hitting side of rail just right and turning 180*. We placed a 2x6 "friendly surface" in front of the rail and, while this surface must be replaced fairly regularly due to very frequent hits, have seen no evidence of anything exiting the friendly surface in the direction of the firing line which is 200 meters away.)

Check with NRA range development office. They publish a range construction manual, IIRC the cost is about $75.00, but will save your club/group more than the cost and result in a better range.

Regards,
hps

 

[OF]

I'll have to check into that NRA manual - sounds like a good idea. Re: the eyebrow thing, I'm having a hard time envisioning what you're talking about...

Also I should mention that the side berms will have to be impact-friendly of course, as we'll be shooting at 'em.

- Gabe

 

[hps1]

GRD:
Please see my original post......I edited it regarding "friendly surface" as used on our range.

Re: Eyebrow, picture an interior wall in your house and the power poles are the studs, the plywood or planks are the sheetrock; then the void between the "sheetrock" is poured full of gravel. The surface of this resulting wall toward the firing line is your "friendly surface".

I'm not too sure how this would work for partitions between ranges as the bullets would be most likely to strike the wall at an angle, as opposed to 90*. It would prevent a bullet getting to the next range, but might let it ricochet downrange and, depending upon backstop could possibly escape the range??????

Give NRA a call @ 800-336-7402, then 6 and then ext. 1278. These ext. numbers are quite old, probably 15 years or so but the 800 number is still good and you can wait for operator to place your call if you prefer.

Regards,
hps

 

[hps1]

Gabe:

After reading your reply again, I realized you will be shooting directly at the berm separating firing lines.....missed that the first time.

Probably not a good idea to try to use the eyebrow for a primary backstop, but work well to extend the height of the berm and allow for a narrower berm footprint due to lower height of dirt bank. Your impact area would be the dirt bank but the eyebrow gives added safety margin. Considreable maintenace would be reauired to keep up the friendly surface, especially if hits are concentrated in a small area as they would be directly behind a target.

Regards,
hps

 

[OF]

Thanks hps.

Anyone else have any thoughts? The more ideas I can exposed to the better...

- Gabe

 

[JJohnston015]

Tip #1: Hire a properly licensed civil (or better yet geotechnical) engineer to do the engineering. Post notices around the club; you may have one among the membership.

Tip #2: Anything you do beyond piling soil up by hand is going to get expensive.

The right kind of soil, properly compacted (this is where the engineer earns his fee) can easily stay up at 1.5:1, meaning that the base of the berm will be 1.5 times the height. Your 8’ high berm will be 12’ wide at the bottom. A 16’ base width will give you almost 11’ height. That’s assuming zero width at the top. Do you want some flat on the tops? You’ll need some if you plan to get a roller up there.

If I read the description right, you’ll have about 750 cubic yards of material to work with. Ignoring changes in density/volume due to compaction, that’s enough to build 5 berms 12’ wide and 8’ high and about 80’ long. 16’ x 11’ berms will be about 45’ long.

Earth moving and compaction on that scale REQUIRES heavy equipment. You can rent or hire a loader and roller, but you must balance the size/rental cost with capacity/time on the job (bigger will be faster, but will cost more per hour/day). Also keep in mind that proper compaction requires the roller to be there the entire time, compacting every lift (every foot or two). You can’t just pile up 8’ and roll the top.

If you want to go steeper, you’ll probably have to go to some kind of reinforced or stabilized earth. That’s basically a “layer cake†of 1’ to 2’ layers of compacted soil with thin layers of some kind of fiber/matting/fabric in between. Some approaches just mix fibers right into the soil like the straw in mud bricks. There are commercial products (“geofabricsâ€) you can get, or you can improvise – sometimes the matting is made of tire sidewalls (cut away from the tread to make flat rings) held together with steel cables. Berms made this way are usually capped off with unreinforced earth for looks. Must be engineered. FWIW, the oldest sections of the Great Wall, in the Gobi desert, were built this way, by hand, 2000 years ago, and are still standing.

Another approach is some kind of retaining structure, but that would probably be an eyesore. Briefly: build a long, narrow box from railroad ties, one layer high, with steel cables or rods across the short dimension connecting the opposite sides. Fill it in, compact, build another layer with cables/rods on top of that, fill it in, etc. My local range built their high-power target pit that way, with a conventional sloped berm on the range side, but with reinforcement built into it, and connected to the ties on the backside, to make a vertical wall.

As for the rear berm, you’ll have to cut back farther than where you want it to end up, then replace and recompact the material (after sifting the bigger rocks out). The cut should also be engineered, so the hillside doesn’t slide.

 

[OF]

Thanks DJJ. Great post. Exactly the kind of thing I'm looking for.

We do have an engineer at the club who is going to help out, real nice guy too, although I don't have a handle on just what exactly he does...I know it has something to do with earthmoving, however. I haven't spoken extensively with him yet but I'd like to have some kind of an idea of what is going on before I/we meet with him. The construction is in the early early planning stage at this point..obviously. I'm also fairly new at this club but am heavily involved in getting the practical shooting started.

I have a math question: why wouldn't there be 1500 cu yards of material available in the hillside? 200*50*8 = 80,000 cu ft. divided by 27 = ~3000 cu yards divided by 2 (the hillside takes up half the total area) = ~1500 cu yards. I've never done any of this kind of thing before, so please be patient with me if if I'm being a retard.

Our goal is to fit 4 bays in the 200 available feet of width (and we'll have to build out one side a bit to reach that 200, there's only 185 in the existing hillside). The depth is going to be whatever we can get away with, but any less than 4 bays may not be worth bothering with.

Again, thanks everyone for the posts so far - great stuff. Please feel free to continue with either education or tips

- Gabe

 

[JJohnston015]

why wouldn't there be 1500 cu yards of material available in the hillside?

Because I didn't read the description right. It goes without saying that a rectangular wedge takes up half the volume of a rectangle of the same LxWxH. When you said it takes up half the area, I took that to mean something else. So yeah, you will have about 1500 cy to work with - more when it's loose, less after it's compacted. How much more & less, you'll only be able to say for sure after running some tests (not complicated or difficult).

Edit - since there now seems to be plenty of material to build berms, how about using any excess to build one between the range and the public (parallel to the backstop?) Plant some grass on the public side, and some shrubs on the top, etc.

 

[OF]

Volume is right, not area - my bad.

how about using any excess to build one between the range and the public (parallel to the backstop?)

Problem there is that there isn't that much depth available. At the proposed firing line, we'll have our backs to the dirt road that runs through the club as it is. This road runs parallel to the treeline and ~60' away, the treeline is the proposed backstop location. Between the trees and the road is the hillside that we'll be digging out. Moving forward in a line perpendicular from the firing line/road downrange through the backstop/treeline, the hillside rises smoothly to it's ~8' apex at the treeline (~60' from the firing line/road) then is level for another 25 to 30' then drops into a valley at a very steep pitch.

How deep the bays are depends on how far back into the woods we can cut from the edge of the road/firing line. We could dig into the treeline for any part of that extra 25 or 30' but it would mean losing a bunch of the large trees. It would be nice to have as many left there as possible, it looks great and provides a little shade later in the day.

The ability to get 4 bays in there looks like it hinges on the construction of each bay's side berms. If they're too wide, we're not going to make it in the 200' of width we have available. The depth of the bays will depend on how vertical we can get the backstop and how far into the treeline we go.

There will be plenty of material left over, so we have alot to play with in terms of dirt, we're just short on room.

- Gabe

 

[hps1]

Gabe:
Don't know anything about your club's finaces, but , don't know any gun clubs that cannot use a hand, and as DJJ mentioned, moving that much dirt costs money to do right. We spent over $35,000 pushing up and compacting a 60 ' wide by 35' high backstop on our range using dirt from our (flat) property and we have no rocks to deal with.

You should look around your area and see if there is a Friends of NRA committee nearby. FONRA groups hold fundraisers to support the shooting sports and range building grants are a distinct possibility. Our club applied for and received anearly $10,000 grant from FONRA. These are grants and do not have to be repaid.

Edited: If intersted be glad to give you a few tips on how to apply for a grant.

Regards,
hps

 

[grassy knoll]

we had to haul in the material for our new berms last year, we built 2x 25 yd ranges and a 50 yard beside an existing 100 yard so we had 4 dump trucks, 2 excavaters and a loader to pile up the material for 6 days and then we had to top dress with topsoil, for another day with 3 trucks

the bases do get wide as you go higher

we tried burying trees and wood to bulk up the berm but it was hard to handle and not worth it,

when we hauled the material over it was very dry and settled over the winter but the faster you get grass cover on it the better

we were lucky that most of the equipment was donated and all we paid for was fuel and operator time, (we have a pitbull for a fundraiser)

some of the ranges around also were built with landfill material from a pulp and paper mill, but watchout, they don't give this stuff away for no reason, one range was closed for a year while the ministry of environment did an study of runoff and ground water

www.grenvillefishandgame.com

 

[Steve Smith]

Lime pit?

Always need limes, because there's always cervezas to drik.

Oops. Wrong topic.

FYI, a lot of ranges will have a 4'x4' lyme pit in front of the berm as a "seive" for nasty particles during runoff.

 

[Grump]

The eyebrow catcher is essential for keeping berm ricochets from leaving the range. There are a LOT of berm ricochets.