CALGARY -- TransCanada Corp. (TSX:TRP) has filed an amended application for the Energy East pipeline project that raises the projected cost by nearly $4 billion.

The Calgary-based company says the filing with the National Energy Board makes nearly 700 changes to the route in response to concerns about environmentally sensitive areas.

TransCanada already signalled last month that it was prepared to make changes to the Energy East proposal when it announced there would be no export terminal built in Quebec due to opposition over the environmental risks.

At the time, the project was estimated to cost $12 billion but TransCanada now estimates the pricetag at $15.7 billion -- not counting the value of existing pipeline assets that will be used for part of Energy East.

The proposed pipeline would take Alberta crude as far east as an Irving Oil refinery in Saint John, N.B. It would include existing TransCanada pipeline as far east as Montreal, plus new pipeline through Quebec.

TransCanada says the amended proposal includes details of an agreement it made with local natural gas distribution companies. Those side deals will provide sufficient capacity for natural gas consumers, the company says.

The main purpose of Energy East is to build a system capable of carrying 1.1 million barrels per day from west to east. The company has emphasized the benefit of providing a domestic supply to Canadian refineries, but critics say the real purpose is to ship oil to foreign markets from eastern ports.

Environmental groups were quick to dismiss TransCanada's updated plans, saying the pipeline that would transport carbon-intensive oilsands crude could not be built now that the Trudeau government has committed to a climate plan that combats global warming.

"The climate math for building Energy East doesn't add up," said Andrea Harden-Donahue of the Council of Canadians. The group is one of 100 that has asked the federal government to halt pipeline reviews until it assesses the review process.

The Conservation Council of New Brunswick expressed concern that the revised plan would mean increased tanker traffic through the Bay of Fundy and along the East Coast and would increase the risk of oil spills along the route.

Quebec's government has also challenged TransCanada's estimates for job gains and other economic benefits.

Russ Girling, TransCanada's president and CEO, said in a statement that thousands of people understand the importance of the project for Canada's energy security and economic prosperity.

"This amended filing has been shaped by direct, on-the-ground input from Canadians across the country," Girling says.

"However, Canadians also want assurances this project does not come at the expense of safety and the environment -- and this application shows we can do that. We are listening and acting on what we have heard."