Efficient Level 2 Surveys Using Mechanical Detonators:
Returning More Land, Creating More Wealth, Saving More Lives
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In a recent article4, Daniel Wolf and Steven Barmazel
discussed a public health approach to demining. Here, they
clarify and expand on some of the major points in that article.
by Daniel H. Wolf and
Steven Barmazel, Terra Segura International
Effective Mine Clearance Involves Triage
The biggest problem
facing demining enterprises is this: productivity of individual deminers
is so low that total labor costs per unit of land cleared remain
exorbitant—despite minuscule wages in mine-affected countries.
Clearing agricultural land in developing countries typically costs many
times the land’s expected mine-free annual revenues. Most remediation
is uneconomic for public and private parties alike, and funding is never
Some demining agencies have responded
with a triage system—classifying mine clearance operations into three
levels of intensity and corresponding expense and limiting expensive
clearance to critical areas.
In Level 1 (general location) Surveys,
civilian employees gather anecdotal evidence to identify danger zones. They
do not enter suspect areas. Though relatively cheap, they may be
costly to local residents. According to Col. Alastair McAslan, former
United Nations Demining Technology Assessment Officer, 100 suspect acres
typically include only five acres with mines, but all 100 are put off
limits because no one is sure exactly where the mines are. Worse,
foragers learn to disregard danger postings because the odds favor them—even
though losing the gamble means losing big.
Level 3 (complete clearance)1 is at the
opposite end of the scale from Level 1 Survey: it reduces risk as much
as humanly possible, but is correspondingly expensive.
Level 2 (area reduction) Surveys in
theory fill the gap between general location and complete clearance.
Demining personnel enter suspect areas to delineate actual mine field
perimeters, then mark or fence off the smaller mined areas, declaring
areas outside to be not mine fields and releasing them for
use. By greatly reducing quarantined land, Level 2 surveys slash
economic burdens and lessen the need of foraging residents and livestock
to enter suspect areas.
Most demining authorities would gladly
fence off lower-priority mine fields, if they only knew their locations.
But can they find the locations at a price they can afford?
Unfortunately, the answer is usually no. Funding shortfalls have forced
demining agencies to leave thousands of people exposed to unmarked mine
fields while they devote themselves to clearing just a few. Faster,
cheaper and more reliable Level 2 Surveys would allow officials to
escape this dilemma. Mechanical substitutes for slow and vulnerable
deminers can make this possible.
Good-Enough Statistics and Perfect Knowledge
Unless reliable maps
or warning signs still exist, a mine field surveyor has to choose
between two options: 1. clearing an entire suspect area, finding the
mine field but wasting considerable resources on unmined land; or 2.
taking samples, which is cheaper but inevitably runs the risk of missing
mines. Not surprisingly, the latter is the usual choice. This transforms
the Survey manager, like it or not, into a statistician, and the survey
into a statistical problem.
The statistician’s greatest concerns
are randomness and sample size. All samples produce only approximations
of the truth of the universe being sampled; the laws of probability
dictate that larger, more random samples are more reliable than smaller,
more selective samples; and very small samples run the risk of being
Great surveyors are familiar with
local military tactics that help them focus on likely mine field
locations. Traditional sampling involves cutting paths through suspect
areas.2 The pace is very slow because their tools are slow and they are
trying to locate every mine in their way. Because the paths are narrow
and not numerous, they sample only a tiny proportion of the surveyed
To increase their odds of finding the
mine field, surveyors cut multiple sample paths, eventually finding a
mine field or satisfying themselves that none exist. As paths multiply,
however, costs approach those of Level 3 clearance—reducing or even
eliminating the cost advantage of Level 2 Surveys.
Can Increase Sample Sizes Inexpensively
detonators detect a lower proportion of
mines than do skilled deminers, locating a mine field requires finding
only some mines, not all
mines. The critical question is: Are the lower detection rates
nevertheless sufficiently reliable for Level 2 Surveys?
The key to reliability is to increase
area coverage to compensate for decreased detection rates. By design,
detonators withstand blasts from anti-personnel mines, so in the same
amount of time that deminers can sample only small strips (at
significant risk), detonators can sample nearly all open areas and
substantial amounts of vegetated areas (in safety). In fact, under many
conditions mechanical detonators will find mine fields faster than
manual probing or detection.
Some mine clearance officials agree.
Col. McAslan, commenting on Terra Segura’s ArmadilloTM
landmine detonator system, said "I could just run this back and
forth until it encountered mines. I could map the blasts and thereby the
mine field. I could do with a half-dozen men in two days what it
presently takes me three platoons [about 100 deminers] and three weeks
That’s 96 person-hours versus 14,400—only 1/150 as much
How Reliable is
What detection rate is sufficient for
Level 2 Surveys, given the larger areas sampled? In general, an
effectiveness rate (the proportion of mines detonated in one pass) of
40-60 percent should be adequate to inspire confidence. To illustrate,
assume a detonator with 50 percent effectiveness, i.e., coin-flipping
odds. On a single pass, it will cover a high proportion of the suspect
area and cause every other mine (on average) to betray its position by
exploding. Detonating half the mines on a field’s perimeter is
sufficient to delineate approximate mine field boundaries. Numerous
overlapping samples, meaning multiple passes, will further increase the
probability that the sample findings approximate the "ground
truth" (which, of course, cannot be known).
Every additional pass will detonate
more mines, although detonation rates will fall with each pass as the
"easy" mines disappear. But even a one-pass rate of 40 percent
would reveal more mines—approximately 40 percent of mines encountered—and
greater pattern detail, than completely cleared test paths cut across
four percent of the same land.
Empirical research will improve
understanding of what is required to assure adequate confidence in
mechanical detonation sample findings, taking into account variables
such as expected mine type (and other ordnance), soil composition,
moisture content, vegetation, terrain, climate, infrastructure and the
economics of the project. Just as the U.S. Navy develops algorithms that
help marine minesweepers decide how many passes is enough to protect the
fleet, so algorithms will be developed to help land operators choose the
right equipment to use, the right way to use it, and where not to trust
it, given local conditions.
To reiterate, where local knowledge
and tactical speculation are unreliable, the larger sample sizes from
detonators will produce information that is more dependable. At the
other extreme, where mines have been emplaced according to accepted
military doctrines and knowledge of location is good, traditional trench
(path) samples can find mine fields effectively.
Let us be clear, mechanical detonators
will not always be the best technique to apply in all situations.
Operators will have to account for conditions when deciding where and
how to use detonators. Once it is determined that terrain,
infrastructure or other local variables do not contraindicate sampling
by mechanical detonation, however, the large samples permitted by
imperfect detonators will be superior to the small samples obtained by
"perfect" human detectors.
Conducting Detonation Surveys
Most mines are planted
where people tend to walk. When emplaced according to military doctrine
(as opposed to random sowing to induce terror), the logic of their
placement helps the surveyors. Because belts of mines tend to be laid at
set distances, about three feet apart, with a line behind and offset, a
detonator likely would hit a mine with one side of its detonator array
and a few feet along might hit another mine with the other side. When
used only for finding a belt perimeter, the machine would be advanced
until a detonation occurs, then withdrawn and advanced in another
direction, as many times as necessary to confidently demarcate the
Perimeter delineation will be all that
is required in areas where human incursions are infrequent and the best
use of demining resources dictates marking or fencing but not clearance.
It is also the least expensive, because it is faster and causes the
least wear on the equipment.
In more populous areas it may be
desirable to reduce potential risk still further by detonating as many
mines as possible. We call this density reduction, in contrast to
the area reduction of a normal Level 2 Survey—a Level 2.5
Survey, if you will. One would never declare such mine fields
"cleared," and they would still require marking or fencing, as
well as local education about the remaining danger. But if most exposed
mines have been detonated (which is not possible using traditional
survey methods), and most remaining mines are relatively inaccessible or
insensitive, children, foragers and livestock ignoring mine field
markings will be much more likely to walk out alive.
Increases Wealth and Well-Being
by cutting Level 2 Survey costs ($1,250-2,500 (U.S.) per hectare is
quite plausible) for a given national budget, could allow geometric
improvement in effectiveness as measured by the number of casualties
avoided and hectares of land returned to use, even if many mine fields
are left marked and not cleared. A simplified example will serve to
The Cambodian Mine Action Center in its heyday cleared
10 square kilometers a year,
spending on average almost $7,000/hectare. Let’s assume, using high
numbers, that Level 2 Surveying with mechanical detonators costs
$2,500/hectare, and that 10 percent of a Level 1 surveyed parcel
actually contains mines. For the same $7,000 that CMAC spent clearing a
single hectare, mechanical detonators could locate mine field perimeters
in 2.8 hectares. They would find mines in 0.28 hectare, which would be
marked or fenced. So, for the cost of clearing one hectare, the Level 2
Survey would free for productive use more than 2.5 hectares.
If we use lower survey costs and a
smaller proportion of suspect land actually mined, the result is even
more remarkable. At $1,250 per hectare and only five percent of suspect
land actually mined, that $7,000 frees up 5.32 hectares (5.6 hectares
surveyed less .28 hectare that remains quarantined). So, simply by using
mechanical detonators to conduct Level 2 surveys, mine clearance
projects could return to use three to five times more land for the same
Mine-afflicted countries need to lower
unemployment and provide work to ex-combatants. Won’t labor-saving
technology put local people out of work and delay economic recovery?
Though superficially compelling, this objection does not withstand close
examination because high productivity in mined area reduction would more
quickly induce more employment than it displaces. A comparison of three
scenarios (shown in the table below) shows how.
Scenario 1, the CMAC scenario,
maximizes employment in Year 1, using demining jobs. During Years 2-5,
normal economic forces produce normal employment. In this example, 3,000
workers clear 10 square kilometers of land each year. Employment impact
in Year 1 is 3,000. In Year 2, the 10 square kilometers of land released
for agriculture employs 2,000 farmers (100 hectares/km2
x 10km2 x 2
farmers/hectare). With an economic multiplier effect of 1.5, the 2,000
farmers induce another 1,000 jobs elsewhere, for 3,000 jobs in Years
3-5. The total five-year impact is 14,000 job-years, assuming nothing
else is happening to change the employment picture.
Scenario 2 maximizes the number of
hectares freed, even at the cost of minimum Year 1 employment. In this
case, 500 workers with mechanical detonators free 30 unmined square
kilometers. Employment in Year 1 is only 500, but in Year 2 the
newly-released land employs 6,000 farmers. With the economic multiplier
effect, the employment impact in Years 3—5 is 9,000 jobs. The total
five-year impact is 33,500 job-years. This is, in fact, the program that
maximizes employment for the five years.
Scenario 3 balances Year 1 postwar
employment—1,500 in demining and 1,500 in paid apprenticeships to be
farmers and artisans--after which they go to fulltime jobs. In this
case, we assign 300 workers to Level 2 surveying because a substantial
part of the budget is going instead to employment generation and
training. Deminers will release and clear more land than in Scenario 1
but less than in Scenario 2. If 300 workers with mechanical detonators
free up 18 square kilometers, and the other 1,200 clear four square
kilometers (straight proportions of prior figures), then employment in
Year 1 will be 3,000 (including trainees), Year 2 employment will be
4,400, and Years 3-5 employment will be 6,600 per year. The total
five-year impact will be 27,200 job-years. Not surprisingly, this result
falls between the other two scenarios.
Obviously, a hundred variables could
affect actual results. But as the example illustrates, conducting Level
2 surveys with mechanical detonators could create great employment
Objections to Surveying with Mechanical Detonators
has many adherents, but the arguments of opponents persevere. One
objection is that all technologies must achieve 100 percent in a single
pass because there are personnel in the mine field. Another is that even
during surveys all mines must be eliminated; leaving any number is
irresponsible. A third is that flails can damage mines, or rollers can
push them deeper into wet soil, creating serious problems for the
deminers who encounter them later, or even miss mines altogether if the
ground is uneven. An objection occasionally heard is that spreading
additional metal around mine fields makes subsequent detection more
difficult and expensive. Finally, some deminers fear that local people
who see mines cleared during a survey may conclude that the land has
been made safe when it has not.
Valid concerns underlie these
objections, but defining and conducting the surveys properly can
alleviate them. Unmanned mine-resistant devices, for instance, keep
personnel out of harm’s way. If a survey’s objective is to
quarantine the land for an indefinite period of time, then the obvious
risk of leaving mines behind must be counterpoised not against the low
consequent safety risks to surveyors, but against the high risks to the
local population if the survey is not done because cheap methods are
Concern about breakage, displacement and misses can be
met by using the right machine:
avoid flails if breakage is unacceptable; use heavy rollers only when
the ground is fairly firm and flat; use ground-conforming disks or
flails if the ground is very uneven. There is not one mechanical
technology but many, each with its own particular virtues and flaws.
Spreading shrapnel around is a concern
only when shrapnel-loaded mines are prevalent and metal detectors are
the primary detection tool. Many mine fields have mainly blast-effect
(low metal content) AP mines, however. If blow-in-place neutralization
is acceptable, mechanical detonation usually will also be acceptable.
Finally, the responsible way to
address the fear of local misunderstanding of the level of clearance is
not to abandon cheap Level 2 Surveys, but to make local populations
strongly aware that only some mines have been neutralized and
that the mine fields remain extremely dangerous, albeit less so than
before. The savings realized by the fast surveys will more than
compensate for the additional costs to the local mine-awareness program.
Complete elimination of found
mines and UXO is a valid requirement for surveys in two cases only: One,
the survey is being combined with the creation of safe paths through the
mine field, in which case of course all mines must be removed
from the paths (but only the paths); and/or two, the site is scheduled
for complete clearance in the near future, so any found mines may as
well be neutralized.
reduction is maximized when resources are used optimally across the
entire national demining enterprise. Complete clearance would always be
preferred over surveying and density reduction if it were as cheap and
fast. But clearance is so costly that clearing a few mine
fields completely may actually endanger more people because scarce
resources are diverted from lessening the risk in all mine fields.
We argued this point at length in the last issue of this journal.
No technology by itself has
demonstrated 100 percent effectiveness, yet deminers continue to use
their favored technologies, with which they are familiar and which they
know how to use safely, shortcomings notwithstanding. Mechanical
detonators likewise will produce a body of expertise governing the safe
and effective use.
Level 2 Surveys are expensive now, but
judicious use of mechanical detonators will make them more reliable and
cheaper. In particular, they can slash labor costs—drastically. We’d
like to see demining become so cheap that even poor landowners in
developing countries can afford to have the job done. We may never see
that. But each step demining takes toward such economic viability means
that we can free more land, create more wealth and save more lives. And
that’s worth some fireworks.
1 Clearance of miscellaneous unexploded ordnance
conceptually occurs at Level 4, but as a practical matter is commonly
included in Level 3 mine clearance.
2 We used the term "sample path" instead of
"sample trench" to avoid giving non-deminers the impression
that the surveyor is actually digging a trench through the ground.
3 Conversation with Daniel Wolf at demining policy
conference, Sanford School of Public Policy, Duke University, Raleigh,
North Carolina, USA, May 1, 1998.
4 See The Necessity of Adopting a Public Health
Approach to Demining, Journal of Mine Action, Summer 2001.
Daniel H. Wolf is President and Steven Barmazel is
Publications Director of both Terra Segura International and Ploughshare
Technologies. This article is based on a paper Mr. Wolf presented to the
UXO/Countermine Forum, New Orleans, April 9-12, 2001.
Daniel H. Wolf
Terra Segura International
1846 Granada Avenue
San Diego, CA 92102 USA
Terra Segura International
1846 Granada Avenue
San Diego, CA 92102 USA