DISPENSING WITH NARVAEZ, the Frente's mobile horde now reassembled at the Guanta oil-processing station, about 20 minutes outside Lago Agrio. The size of several city blocks, Guanta is set amid a wheezing jungle that should be placed on an environmental respirator.

We pulled up in a drizzle at about 11 in the morning, but Petroecuador guards wouldn't let the group through the main gate. Because a security fence encloses only half the station, and because the guards seemed to care only about the gate, everyone simply slogged a few hundred yards through the waterlogged earth to an area that wasn't fenced.

To our right was a pit the size of several Olympic pools, filled with an oozy mix of oil and water. Smart people placed handkerchiefs over their mouths and noses. Red and yellow flames leaped into the air from a set of elevated natural-gas flares; I stood about 50 yards away but was blasted by the heat as fumes stung my throat.

"If you don't have a headache yet, you will soon," Donziger warned. Ten minutes later, I did.

The pit didn't have a liner, which meant the gunk could seep, drop by drop and second by second, into the water table below. This is the technology, or lack of it, that Texaco had used decades before; although plastic liners were employed in many parts of the world, Texaco didn't spend the money to do it that way, and Petroecuador wasn't modernizing, either. There was a smaller pit across a dirt road and, a few dozen yards from it, a pond-size swamp. The swamp was black, filled with oil.

"Do we need to come here and look at this and have a debate?" Donziger asked. "I mean, honestly, why are we taking samples? In the United States, the EPA would say, 'Visible standing petroleum. You are obligated to clean it up immediately.'"

This was just one allegedly toxic site among more than 350—including as many as 1,500 pits, the Frente alleges—spread around the Oriente. So far, the samples have yielded a bonanza of data that has been interpreted in opposite ways by experts on both sides. Of the 35 site results reported to the judge so far, Amazon Watch said last September, 100 percent have revealed "shocking" levels of pollution containing "life-threatening carcinogens." At a site called Lago 2, the group states, the plaintiffs' experts measured total petroleum hydrocarbons at 325,000 parts per million—3,250 times the legal limit in California and 325 times the limit in Ecuador.

Chevron counters that the Frente is cooking up phony science and testing samples at a substandard lab. "Many of their reports," Gidez wrote me, "are so scientifically unsound they would never be allowed in a U.S. court."

To get a better look, I met up with 33-year-old Donald Moncayo, secretary general of the Frente. Moncayo, whose father was a settler, remembers swimming in a local river that had veins of oil running through it. As a young man, he worked briefly in the oil industry as a roughneck but soon left for the ranks of environmental activists. He lives in a wood shack without running water or electricity; when I stopped by one afternoon, a very large pig was napping by the front door.

We bounced in my rented 4x4 over the red dirt roads that crisscross the feeble jungle around Lago Agrio and trundled past rickety homesteads made of salvaged wood slats. Our first stop was a dirt field the size of a soccer pitch that had, at its center, a rusted wellhead. Moncayo said the well was shut by Texaco in the early 1990s, and he led me to a grassy pond 50 yards away that was filled with brackish water in which I could see globs of oil. Oil that leaked into the ground long ago was resurfacing or being revealed as the ground cover eroded.

"Every so often, more oil comes out, and they put more dirt on it," Moncayo said, referring to Petroecuador.

We drove another 15 minutes, parked at the end of a road, and walked through the jungle until we reached what looked like a swamp. This was another waste pit, filled with sludge. The remarkable thing was that there was no oil facility nearby; whatever well this oil came from had been closed long ago.

"What would happen in Texas if there was a spill like that?" Moncayo asked.

I said it would be cleaned up, quickly.

"We've been waiting 17 years," he replied.