The planned expansion of a major gold mine in northeast Nevada could cause big problems for Nevada's largest herd of mule deer, a sportsmen and conservationist group contends.

The Coalition for Nevada's Wildlife is urging people to weigh in on Barrick Gold Corp.'s proposed expansion of its Bald Mountain Mine, a project the group insists could disrupt a key migration route used by deer in the winter.

"This is their principal migration route," said Larry Johnson, coalition president. "In bad weather, this could be devastating to this herd."

Later this month, the U.S. Bureau of Land Management is expected to release a draft environmental impact statement on Barrick's plan to expand the Bald Mountain Mine, located about 70 miles northwest of Ely on the south end of the Ruby Mountains.

Barrick proposes to expand "surface disturbance" at Bald Mountain's north operations area from 9,292 acres to 13,640 acres, adding four new heap leach pads and to expand disturbance in the mine's south operations area from 943 acres to 3,499 acres. The project would also install an electric transmission line and build a road linking the two mining areas.

Bald Mountain, already one of the nation's largest mining sites, produced 94,000 ounces of gold in 2013 with proven and probable mineral reserves put at 2.5 million ounces of gold, according to Barrick's website.

In a statement issued in late December, Johnson said the project will create a "convoluted pathway" for migrating mule deer that would wind between deep open pits, ore and waste rock stockpiles and haul routes.

Potentially affected, Johnson said, would be the Ruby Mountain deer herd, "the largest and most important deer resource in the state," that comprises 22 to 24 percent of Nevada's entire deer population.

While impacts to migrating deer might not be significant during mild winters, the situation could be much different during harsh winters when deer sometimes migrate more than 100 miles south past U.S. 50 in search of suitable winter habitat.

"They are effectively going to cut it off," Johnson said. "When you put a barrier in their path that stops their migration route, (deer) burn energy and a certain percentage don't make it."

In its statement, the coalition alleges among other things that Barrick is "refusing to pay for impacts of loss of winter range in areas to be destroyed by mining activity," is refusing to include recent collaring data collected by the Nevada Department of Wildlife in environmental analysis of the project and is refusing to consider operational changes in the event future data indicates serious impacts are occurring.

Barrick officials refuted the coalition's contentions.

"Mr. Johnson's accusations are misinformed and ignore Barrick's good-faith efforts to work with NDOW and BLM to protect mule deer habitat over many years," Barrick spokesman Louis Schack said in a statement.

"The Bald Mountain Mine has operated continuously since the 1980s and we have established a long record of successful habitat protection and enhancement in and around our operations," Schack said. "Many of these projects were completed in support of NDOW and other agencies' habitat improvement and land management goals."

Once the draft environmental study is released, Schack said, "we will work with the BLM to address specific concerns that may arise."

Preserving the integrity of the mule deep migration corridor in question is a high priority, said Chris Healy, spokesman for the Nevada Department of Wildlife. Latest estimates put the size of the Ruby Mountain mule deer herd at about 24,000 animals.

"This is a very important mule deer herd. You're talking literally about a quarter of the herd in the state," Healy said. "We have been heavily involved in this process, in trying to maintain the migration corridors. We're hoping as this process goes along we're going to be able to use the best available science and try to maintain these migration corridors. We know these corridors are indeed necessary."

Johnson said his group issued its statement as a way to notify Nevada sportsmen that the Bald Mountain project's environmental study will soon be released and to urge them to make any concerns clear before key decisions are made.

"More than anything else it's a notification that this is coming," Johnson said. "Everyone needs to weigh in on this very important issue."