The project was originally scheduled to be completed this December, but the government still needs one final permit from the Army Corps of Engineers to begin construction. And while the Puerto Rican government has held hearings and completed an impact study on the sensitive project, activists have asked federal agencies to take a more deliberative look at the fast-moving plan. Officials for the Corps say they are still working on a draft environmental assessment of the project. The Corps may then choose to hold public hearings or start a more rigorous impact study.

“All I can say is that it’s extremely complex,” said Nancy Sticht, a Corps of Engineers spokeswoman.

Critics of the project see the delay as a sign that their concerns are resonating.

“It’s like building a gas pipeline in Illinois, and there have been no hearings and the governor has declared an energy emergency,” said Representative Luis V. Gutierrez, a Democrat from Illinois and a forceful critic of the project. “It appears that our constant questioning and our constant demanding that they follow all of the rules have had the impact we wanted. That is, stop, hold on a minute, let’s be a little more careful.”

Opponents of the pipeline, led by Casa Pueblo, an environmental group that once blocked mining projects in this area, say a pipeline cutting across mountains and running almost the full length of the tremor- and hurricane-prone tropical island is dangerous.

And they say it would be ecologically unsound, requiring the felling of 270,000 trees across 1,500 acres and potentially threatening 32 species of endangered plants and animals, as well as part of the country’s water supply. To make way for the pipeline, the government also would have to buy out at least 90 property owners, including Mr. Rodriguez’s son, who lives next door to him.