The U.S. Army Corps of Engineers is preparing an Environmental Impact Statement for the proposed Pebble mine, and the Walker administration is asking for more time to comment on it.

The proposed gold and copper mine would sit upstream from Bristol Bay. Gov. Bill Walker has said he doesn’t support the mine and believes the priority should be on the region’s salmon.

The corps announced a “scoping” period that would last the month of April. During those 30 days, the corps plans to identify the areas and concerns it will focus on in its environmental study.

Alaska Natural Resources Commissioner Andy Mack is asking that the scoping period be three or four months.

In a letter to the Alaska commander of the Corps of Engineers, Mack said a 30-day scoping period isn’t adequate for the scale of the project. Mack described it as “an open-pit mine, a mile across, near the headwaters of the most prolific salmon fishery in the world.”

The Pebble Limited Partnership said it’s committed to minimal impact and that its latest design incorporates new environmental safeguards.