Berlin , our days. The earth shakes briefly in Mittelheide city park, and a cloud of rain-soaked earth rises over the ferns in the woods. A football-sized anti-tank grenade from World War II has been just detonated by police.
More than 60 years after the war's end, removing unexploded bombs, grenades and artillery shells remains a full-time task for police and private companies all over Germany.
It's an occurrence so common that police explosives experts Thomas Mehlhorn and Joerg Neumann can joke about their delicate job as they sift still-warm pieces of shrapnel from wet dirt reeking of sulfur.
"When the weather isn't as bad as it is today, of course this job is fun," Mehlhorn said.
"It beats writing traffic tickets," said Neumann.
In Berlin alone, an average of 900 explosive clean-up operations take place each year. Of these, about 100 unexploded bombs are deemed too dangerous for removal - a job for "sprengmeister," explosives experts like Mehlhorn and Neumann, who blow them up on site.
On a soggy Tuesday in August, workers from the Heinrich Heides GmbH company uncovered the anti-tank weapon during a typical day at the government-funded project to ensure the safety of public land in Berlin's Friedrichshagen district. Often, it is construction or road workers who find them.
"There are weapons of all kinds lying hidden everywhere in the ground," said Fritjof Luetzen, who heads hazardous waste and military ordnance disposal for the city. "Everyone who works in construction knows that if they spot something cylindrical or suspicious in the ground to drop everything and call the police."
British and American bombers dropped almost 2.7 million tons of bombs on Germany during WWII. Many went wide of their targets and did not go off, a buried legacy that affects construction, forestry, farming and fisheries.
Berlin, which was bombed heavily throughout the war and then captured by the Soviet army in a bloody battle in April and May 1945, has the most hidden bombs. The entire city is categorized as potentially dangerous.
The problem gets trickier with time as bombs corrode and destabilize. In an ongoing effort to find and remove the unpredictable relics, Luetzen's office pays private firms EUR2.1 million (US$2.87 million) each year. The companies uncover an average of 87 tons of weaponry each year in public and private clean-up projects. In 2004 alone, workers found 160 bombs, 2,400 grenades, 1,500 explosive devices, and 2,700 guns and other weapons.
It's not uncommon for entire neighborhoods and thousands of residents to be evacuated so workers can remove an old bomb. Most discoveries, like the 2,200-pound (one-ton) Soviet bomb found at a construction site in Berlin's Lichterfeld suburb in July, are defused without incident.
While construction companies are not required to have their sites surveyed for bombs, most prefer to avoid grisly accidents like one that killed three construction workers, injured eight bystanders, and tore through nearby buildings and cars in 1994.
At a company's request, the Senate Department for Urban Development hires a private firm to survey a site, a standard practice that experts estimate will keep weapons removal companies in business into the 22nd century.
Once they're hired, companies like Heinrich Hirdes consult the city's archive of historical documents and wartime aerial photos to determine which parts of a site are at risk.
The archive has two full-time employees who study the photos, taken by Allied planes during their bombing campaigns and acquired from the Americans at EUR60 (US$82) apiece. Researchers can tell whether certain bombs exploded by examining the smoke patterns in the photos, giving workers an idea of where to start looking.
Company employees know from their research that the woods they're surveying were in the path of Russian soldiers as they approached Berlin from the east and began combing the area with powerful metal detectors. Small holes pock the ground where workers have unearthed rusty helmets, combat knives, artillery shells and bombs. Their findings and actions will be entered into a computer system that records all bomb disposal work in the city.
Weapons removal projects go on across the city year round, but Berliners aren't likely to know about them, even if they're