Since the early 1980s, more and more of the land mines used have been made of plastic. Cheap ($3-7 each) and hard to detect, these mines rendered current mine clearing operations much less effective. Soldier trained in detecting metal mines were missing 70-96 percent of plastic mines. But some Army officers noted that private mine clearing operations, contracted to clear mines in areas where wars had recently ended, had somehow developed techniques to clear plastic mines using the same equipment available to American troops. The civilian mine clearing teams (often composed of army veterans) were carefully observed and it turned out that they had adapted to the more difficult-to-detect plastic mines. For example, the civilians found that if you kept the mine detection sensor (similar to metal detectors sold to civilians) closer than the usual two inches from the ground, and swept the ground more slowly (one foot a second, instead of three feet), you were likely to get some signal. There were also a lot of different signs to look for that revealed the presence of a plastic mine. The researchers developed a 15 hour training program for soldiers, and when it was applied, the troops could suddenly detect 90 percent of plastic mines. The civilian mine clearing specialists had gotten their detection rate close to a hundred percent. Indeed, it was the fact that these civilians had been clearing plastic mines for years, and were still in one piece, that attracted the attention of the army in the first place. Starting in 2002, the mine clearing training was changed to incorporate the new ideas. In addition, new detection equipment, which includes a short range ground penetrating radar, makes it easier to find plastic mines. But the big break through was simply going to those were doing it successfully in the field. There's nothing better than experience.