Federal officials are reviewing drilling plans for a potential silver mine near Patagonia on public land that the mining company says contains one of the world's 10 largest known, undeveloped silver deposits.

A Canadian company wants federal permission to drill 46 exploratory holes in the Patagonia Mountains about 50 miles southeast of Tucson.

Wildcat Silver Inc. would drill on about 9.2 acres of U.S. Forest Service land in Santa Cruz County, about six miles southeast of Patagonia.

The project will require a Forest Service environmental analysis, although the analysis's scope remains unsettled. The Forest Service expects to do a relatively routine environmental assessment. An environmental group is pushing for a full-fledged environmental impact statement.

The drilling plans have caused controversy over water use and quality as well as habitat disturbance, with debate expected to continue through a protracted process.

The silver mine might not begin operations until 2018.

The mining company has promised numerous environmental mitigation measures for the drilling, and has said it will create at least 150 jobs once mining begins.

Known as the Hermosa Drilling Project, the drilling program would be run by Arizona Minerals Inc., a Nevada corporation and a subsidiary of Wildcat Silver, a publicly traded company headquartered in Vancouver, B.C.

Last year, Wildcat Silver increased its estimates of "measured and indicated" silver resources in the area to 271 million ounces, from 123 million ounces previously. In mining parlance, measured and indicated resources are a cut below mineral reserves, known to be economically recoverable. Usually, it takes additional analysis to determine the level of mineral reserves.

Wildcat Silver has dramatically increased its mining claims in the area in recent years to more than 14,000 acres.

The company says the site may also be the only one in the country for potential manganese production. Manganese is used in steel production and is considered a strategic metal by the U.S. government, Wildcat Silver Vice President Letitia Cornacchia said via email.

The drilling "helps us understand and address geotechnical and hydrologic uncertainties," said Cornacchia, who said she was speaking for Donald Taylor, the company's president and chief operating officer.

Details of the drilling plans:

• Ten boreholes to try to pin down the extent of silver.

• Twelve drill holes to study groundwater supplies, quality and flow direction.

• Twenty-four geotechnical drill holes to determine soil and rock conditions.

• Sixteen soil test pits, dug up to 20 feet deep, 20 feet long and three feet wide.

• Much of the work could be done using existing forest roads for access, although about .2 mile of existing roadway would require reconstruction. Also required would be construction of five temporary access roads covering .8 of a mile, 10 vehicle paths covering about four miles and footpaths covering 1.2 miles.

This work would last about two years, including all reclamation except at eight monitoring well sites that would be reclaimed in 15 years.

Drilling could be conducted for up to seven days a week, 24 hours a day.

Typically in mineral exploration projects, the Forest Service conducts an environmental assessment, which doesn't take as long and isn't as detailed as an environmental impact statement, the service said.

Currently, the service is taking written public comments on the drilling project, to gauge public concerns and determine what kind of analysis to do. While it hasn't decided on only an environmental assessment, "this is an exploration project, not a mining project like Rosemont," Coronado National Forest Supervisor Jim Upchurch said.

"An exploration project has much less potential effect," Upchurch said.

Last year, Wildcat Silver and the Forest Service agreed to abandon an earlier drilling plan by the company for 15 holes after three environmental and community groups sued to block the drilling.

Michael Stabile, president of the environmentalist Patagonia Area Resource Alliance, said his group favors an environmental impact statement because in total, "it's going to be an awful lot of disturbance to a really beautiful place. That whole space will be shredded with roads and drill pads. It's never going to look the same.

"The major concern for us is the watershed - this project lies at the headwaters of the watershed for the town of Patagonia. It would be disturbance in a really pristine area."

Wildcat Silver's Cornacchia agreed with the Forest Service that an environmental assessment is suitable. The company hasn't decided whether to build the mine, and is proposing this drilling program to help it with a feasibility study to further determine the mine's economic viability, Cornacchia said.

She noted that the company has reduced its planned drill hole count from 176 a year ago.

Public meeting and comments

• Coronado National Forest will host a meeting on the proposed Hermosa drilling projects on Aug. 20 from 6 to 8 p.m. in the Patagonia High School Cafeteria, 200 Naugle Ave., Patagonia.

• Fax comments to 520-388-8305, attention Margie DeRose.

• Snail mail comments to Coronado National Forest, attention: Margie DeRose, 300 W. Congress St., Tucson, AZ 85701.

• Written comments must be submitted by Sept. 6.

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746.