Helen Gray remembers a field of 30,000 mines that ran straight through a village in Mozambique in south east Africa. Some of the homes were on one side, the local school was on the other.
Parents and children had to carefully walk the safe path through, but every so often someone would stumble and fall, losing a leg, or worse.
The dense, deadly minefield was laid around the Cahora Bassa hydroelectric dam in Mozambique's Tete Province in the 1970s. The Portuguese colonial government was trying keep independence fighters at bay. But over 30 years after that war ended, the mines were still killing and maiming people.
Helen, a program director at the HALO Trust, led the team that went through the minefield, clearing the explosives inch by inch. Last year, the UK's Prince Harry famously visited the village after the field was cleared.
But like many other countries affected by land mines, Mozambique is dotted with dozens of other minefields that have terrified residents for decades, said Helen, 31. "Mothers are always very frightened, they say 'we know it's there, we've told our children not to go there, but you know what little boys are like,'" she added.
And the dangers vary. The teams clearing mines come across everything from antipersonnel mines filled with less than an ounce of explosive powder, to anti-tank mines filled with 15 lbs of explosives. They also find other kinds of wartime trash: mortar bombs, grenades and even rockets. To get rid of the explosive devices they blow them up, eliciting everything from tiny puffs of smoke to mini-mushroom clouds.
In these places, many local residents still vividly recollect the conflict that led to the problem, and even the military positions the minefields were laid around. Tapping this local knowledge, the HALO Trust hires and trains locals to help clear the minefields, which also helps people feel safer about the newly cleared fields, Helen said. "It gives the local population a lot more confidence in the work that they've done," she added. And it means most of the money the HALO Trust spends stays in the affected communities. HALO's biggest donor is currently the U.S. State Department, followed by the governments of the UK and Japan.
Trained as an ecologist, Helen was working in the Peruvian rainforest when she realized she wanted to work directly with people, and and help make a difference that she could see. She started clearing mines in 2004. The HALO Trust, along with other organizations, are working towards helping to make sure Mozambique is landmine free by 2014.
Helen says this is the most exciting thing about her work. Unlike most of the problems affecting former war zones, the problem of land mines can be decisively fixed. "It can be made to go away, it's not an endless issue," said Helen. "It's a problem you can solve."