In an earlier life, David Daniel jumped through fire and performed a motorcycle stunt called the Wheel of Death. For his second act, he picked a fight with a $7bn oil pipeline set to run through Texas.

He is not doing badly for a man taking on big oil in the home of black gold. Growing opposition to a Canadian project to pump crude from tar sands in Alberta across six American states to the Gulf coast could force the Obama administration to reconsider – and possibly delay – the project.

The grassroots rebellion will come to Washington on 9 March, just as the state department is due to decide whether to grant final approval to the 1,700-mile Keystone XL pipeline. If it orders additional environmental or safety reviews it would force a delay in the construction start date, now set for the end of the year.

But a delay could also be forced by activists along the proposed pipeline route through Nebraska, Oklahoma and Texas. About 750 landowners have refused to allow the company, TransCanada Corp, on their land, setting the stage for court battles over compulsory purchase.

It's more than Daniel expected when he began posting "stop the pipeline" signs on roads near his rural east Texas home. "Normally people are so used to pipelines that they don't think twice about it," said Daniel, a carpenter who gave up his life as a stuntman six years ago when he settled on 20 acres near Winnsboro. "Everybody has a pipeline running through their yard, or will have one eventually, so it is kind of the accepted standard," he said. "There is a mindset of apathy."

But last year Americans began to pay more attention to the potential for oil and gas disasters. In addition to the BP blowout in the Gulf of Mexico, a natural gas explosion killed six people and destroyed 35 homes in California, and a pipeline leak spewed 1m gallons of oil into the Kalamazoo river in Michigan. That pipeline was owned by another Alberta firm.

Then there were the environmental consequences associated with tar sands crude, which has a far higher carbon footprint than other sources. Its exploitation has turned Canada into the villain of international climate change negotiations.

National environmental organisations said the project jeopardised Obama's commitment to a clean energy future.

Activists are worried about the dangers of pumping gritty, thick crude at high temperature and pressure through a pipeline with walls less than half an inch thick across vital sources of groundwater.

A report by a coalition of environmental organisations said piping oil from the tar sands was inherently more risky than other pipelines. The pipeline crosses one of the world's largest aquifers in Nebraska, which provides drinking water to eight states and irrigates about a third of the farmland in the midwest. Daniel's stretch of Texas, meanwhile, is rich in lakes that locals fear could be contaminated if there is a leak.

But environmental concerns alone did not turn Daniel's neighbours against the pipeline. They claim that bullying did.

Locals in east Texas accuse TransCanada's agents of threatening them with compulsory purchase and of dismissing their concerns about safety in case of a leak.

"They just laid some papers down on the table and said: 'Read these papers. We have eminent domain.' That scared me nearly to death," said Susan Scott, who blames her heart attack on the stress.

Daniel said the company did not bother to notify him when it sent the first survey team to his property in 2008. A neighbour told him outsiders had been on his land. He found surveyors' stakes with flags reading PL. "My heart was just falling," he said. "I knew that meant pipeline."

The anger spread to Tea Party conservatives, the local chapter of Hawks – which stands for Handguns Are Worth Keeping Sacred – and even those who owed their fortunes to oil. "I had nothing against it at first," said Eleanor Fairchild. Her late husband headed international exploration for Hunt oil, and she has an abandoned pipeline on her 300 acres of land, which is wooded with oak, pine and sweetgum trees and fed by its own springs.

"It was later I found out about the pollution and I got involved with this environmental stuff. They don't tell you it is not a regular pipeline, or that the pipeline is so thin, or that the grit going down there is going to wear out the pipeline."

Fairchild said she got angry when TransCanada's lawyers told her she had no choice but to agree on their terms.

TransCanada says it has reached agreements for nearly 90% of the route. "Whenever you build a project, especially a project of this size, you know not everybody will agree with you," said a spokesman, Shawn Howard. He said the pipeline would be the safest ever built, with 16,000 sensors to detect the first sign of a leak.

But opposition may be gaining momentum. "Nobody likes it when somebody comes and says you are going to sell to us, like it or not," said Harlan Hentges, an Oklahoma lawyer representing families suing TransCanada. "The Canadian executives have been a little bit tone deaf."

He said he knows of about a dozen landowners in Oklahoma who are challenging TransCanada's claim, as a foreign corporation, to be expropriating land in the national interest. In Nebraska, 21 members of Congress have signed a petition calling on the Obama administration to re-route the pipeline away from its aquifer. In South Dakota, the state legislature is considering a bill that would compel corporations to obtain all the necessary permits before they start trying to obtain rights to privately held land.

Activists like Daniel hope the secretary of state, Hillary Clinton, will be forced to rethink her support for the project.

The Environmental Protection Agency rejected TransCanada's draft environmental study of the project last July. Daniel and other activists now hope the state department will order further studies on the safety of transporting gritty crude, the potential damage to groundwater from a leak, and emergency response plans.

He doesn't yet dare to hope that the pipeline will be halted. But he is ready to use skills he picked up as a stuntman.

If the state department signs off the pipeline, Daniel says, he will build a platform in an elm on his land and live on it. "If I am in it, they can't cut the tree down."