This wrecked city's nickname now mocks emergency workers as they comb its flooded streets. Nothing here is easy, not even for some of the nation's most experienced first responders.

Collectively, they have seen it all: car wrecks, chemical spills and the truly devastating -- California wildfires, hurricanes Andrew and Camille, and, of course, the terrorist attacks of Sept. 11, 2001, when many pulled comrades from the rubble of the World Trade Center.

Yet Hurricane Katrina has presented even the most seasoned search and rescue workers with logistical, medical and safety challenges that far surpass those of any U.S. disaster the veterans here can recall. The sheer geographic extent of the calamity, covering 90,000 square miles of Gulf Coast, with floodwaters containing gasoline, chemicals and human and animal waste, and a complete meltdown of the region's communications networks are only the most obvious difficulties in a search and rescue effort now nearing two weeks.

"I don't think I've ever had a more surreal experience in my life," said Michael Enright, first deputy mayor of Baltimore, who led a contingent of 150 responders to the devastated St. Bernard Parish, east of New Orleans. "It's just post-apocalyptic."

The toxic stew surrounding New Orleans has made decontamination a top priority and a major hurdle in the rescue and recovery operation, Enright said. The water is so polluted that the team decided not to use its inflatable Zodiac boats for fear "it would corrode the rubber," he said. And after he learned that four search and rescue dogs had died, Enright kept his out of the field.

There has not been enough equipment -- boats, helicopters, satellite phones -- to locate, retrieve and evacuate hundreds of people holed up in attics, bars and other dry urban islands.

Members of Colorado's search and rescue team desperately hunted for hip waders, which were in short supply and critical for the murky waters.

A pair of National Guardsmen from bone-dry Arizona said they were flummoxed by three people with snakebites they feared might have come from deadly water moccasins.

If the rescuers manage to navigate those roadblocks, they must still find a way to persuade people to leave where they have been staying.

"I tell them, 'You're welcome in New Mexico,' " said Paul Holcombe, a Farmington, N.M., firefighter who has been plucking out survivors since Aug. 31. On Wednesday, under Mayor Paul Nagin's orders to add muscle to the evacuation, Holcombe's message became more ominous: "No more water, no more MREs," or meals ready to eat.

The Federal Emergency Management Agency has deployed 7,500 people to the Gulf Coast to perform rescue missions, triage and treat patients, and help victims begin to rebuild their lives. With fewer than 2,500 permanent FEMA employees nationwide, most of the response corps is a phalanx of highly trained emergency workers such as Holcombe, who spend their careers surrounded by injury and suffering. The contingent, known as FEMA reservists, includes Baltimore paramedics, Colorado firefighters, emergency room doctors from Illinois and swift-water rescue teams from California.

For more than 10 days, officials in Baton Rouge and Washington have derided FEMA's seemingly slow and spotty response to Katrina. But on the ground here, in the blistering heat, with no water, power or hospital for perhaps 35 miles, rescue workers describe an overwhelming variety of unusual, even unique, conditions.

"This is one of the more complex incidents we have ever responded to," said Jim Strickland, a retired Fairfax County firefighter overseeing FEMA's search and rescue efforts. Comparing Katrina with the Oklahoma City bombing and the Sept. 11, 2001, attack on the Pentagon, Strickland said the hurricane has required coordination among many more federal and state agencies and installation of a sophisticated communications system from the ground up.

In a matter of days, he said, he built a tent city in the parking lots of Zephyr Field, home to the local AAA baseball team, importing food, portable showers and toilets, cots and fuel to support 1,500 emergency workers. The 560 search and rescue workers directly under Strickland's command have been sleeping on the turf of the adjacent New Orleans Saints indoor practice field. On the walls of the command center, Strickland studies geologic maps, status reports and a map titled "Known Hazard Areas" that uses yellow marker to highlight oil spills. Until recently, he also kept his personnel out of neighborhoods marked "No Go Gunfire."

Every day at 6 a.m., Strickland dispatches search and rescue teams in four-wheel-drive vehicles, military helicopters and boats borrowed from the Coast Guard, Environmental Protection Agency and the U.S. Fish and Wildlife Service. His personnel have rescued more than 5,500 people.

On Wednesday, the New Mexico and Nevada task forces took over the helipad -- essentially a debris-strewn parking lot -- on the corner of Wilson Avenue and Chef Menteur Highway in New Orleans East. One search team, hitching a ride in a sand-colored National Guard truck, dropped off seven evacuees who had been living in their apartment building in the Gentilly neighborhood.

A 61-year-old man, hobbling and barefoot, was escorted to a white tent, where two physicians patched him up. A moment later, an elderly woman arrived by ambulance, her legs covered in red scars. They signified staph infections, contracted from wading in water, said Diane Rimple, an emergency room worker at the University of New Mexico hospital.

"The challenge is doing the medicine outside in a tent," said Rimple, who has seen numerous cases of dehydration, infected cuts, mental illness and unmanaged diabetes. Normally, Rimple treats first responders, but in the chaos that is New Orleans, she has been stabilizing sick and injured residents before they are airlifted out of the destruction zone to a field hospital at the airport outside the city.

Using borrowed boats, members of Colorado's FEMA team searched door-to-door, marking each house they inspected with the date, their initials and the number of bodies -- dead or alive -- found inside. Corpses are secured and their locations recorded with GPS coordinates, which will allow private contractors to retrieve them. Every rescuer reported seeing bodies, many blackened and swollen by decomposition.

In St. Bernard Parish, where up to 10 feet of water surged into homes and at least one oil refinery suffered a major spill, emergency teams from out of state found themselves worrying about immunizations. Fred Paavola, a retired pharmacist who arrived a week ago, said the Arizona team he was leading had given nearly 2,000 vaccinations against hepatitis A and B, and tetanus.

Now with Hurricane Ophelia hovering off the Carolina coast, Enright, the Baltimore official, has one more worry: His 50-truck unit might have to race home.

National Guard Spec. Stephen Kirk of Arlington, Tex., rides in search of survivors west of downtown New Orleans.