CHEYENNE, Wyo. - A proposed project would potentially double the number of gas wells that have been drilled to date in western Wyoming's biggest gas fields.

Encana Oil & Gas, USA proposes to drill as many as 3,500 gas wells on 220 square miles of as-yet undrilled land in the Upper Green River Basin. The drilling would take place over 10 years.

Heavy drilling since the 1990s has resulted in 1,500 wells in the Jonah Field and 1,400 in the neighboring Pinedale Anticline field, which are among the most productive U.S. gas fields.

Thousands more wells could yet be drilled in the Jonah and Anticline, but over time Encana's proposed Normally Pressured Lance project could rival either for well numbers.

"It's a big deal for the benefits that will come back to Wyoming," Encana spokesman Randy Teeuwen said Friday.

The new drilling south and west of Jonah would create more than 700 drilling jobs and 175 production jobs while bringing in an estimated $8.75 billion in taxes and royalties over 30 years, he said.

An environmentalist said she wants to see how Encana limits air pollution, which became a serious issue with high ozone levels in the basin this past winter, and protects wildlife such as antelope and sage grouse.

"It's an area of intense interest for a lot of reasons. What it will do is it will add a lot of surface disturbance to previously undisturbed habitat," said Linda Baker, director of the Upper Green River Alliance.

Encana has invited Baker to serve on an advisory committee for the development, she said, and she's accepted.

"It looks like Encana's trying to address the concerns of the community," Baker said.

The U.S. Bureau of Land Management on Tuesday opened a monthlong period for the public to comment on the project, the start of what will likely be a long environmental review process.

"What we're looking for is input from the public on what their concerns are and what the issues are," said Kellie Roadifer, planning and environmental coordinator in the BLM's Pinedale Field Office.

The BLM's next step will be to draft an environmental impact statement for the project.

The Normally Pressured Lance project will target a different portion of the Lance Formation than the Jonah Field. The gas is under less pressure than in the Jonah Field, hence the project's name, Teeuwen said.

Gas to be recovered would total about 5 trillion cubic feet, compared to about 13 trillion for the Jonah Field, which the U.S. Energy Information Administration ranks seventh in the U.S. for gas reserves.

Encana plans to use the most up-to-date drilling techniques to keep environmental damage to a minimum, Teeuwen said. That would include drilling up to 16 wells per well pad, with no more than four pads per square mile.

Pipelines would be installed from the start to collect gas condensate and produced water - gas production byproducts that otherwise would require lots of truck traffic to haul out, he said.

"There's not been development out there previously, so we are able to design this in a way that is most efficient and environmentally sound," Teeuwen said.

Encana expects to begin drilling in the Normally Produced Lance in a few years and will ramp up operations as drilling in the Jonah tapers off.