Big Springs showcase for Nevada mining

The Big Springs gold mine 60 miles north of this thriving community isn’t the newest or the largest mining operation in the state. It does, however, have the unique distinction of being the first hard rock mine in the United States to be officially dedicated by the U.S. Forest Service as a national mining “showcase.” Located in the northern Independence Mountains on land administered by the Forest Service, the 40,000-ton-per-day mining operation is 60%-owned by Independence Mining (NYSE), with the remaining interest held by Bull Run Mines (NASDAQ).

Independence (known formerly as Freeport-McMoRan) is the mine operator and it also wholly owns and operates the 1,150-ton-per-day mill associated with the mine which was built on private land. This year, Big Springs is expected to turn out about 70,000 oz. gold: 60,000 oz. from milled sulphide ore with a head grade of about 0.17 oz. gold and the remainder from heap leaching of lower grade oxide reserves.

The dedication ceremony took place Aug. 30 when mining industry executives and operators, politicians, Forest Service officials and others gathered at Big Springs to recognize the joint venture’s efforts in demonstrating that minerals can be extracted from the earth in an environmentally sound manner, and in a way that integrates other resource values and uses of the land.

“Since the mine’s construction in 1987, Independence Mining has been outstanding in its attention to operating in a very environmentally conscientious manner,” said John Inman, Humboldt National Forest supervisor. “The Big Springs mine is an example for other mining companies of what can be accomplished.”

Joseph Murray, president of Independence, said the company was “honored” to represent not only Nevada, but also the mining industry through the important tribute paid to it by the Forest Service.

“We will strive to maintain our outstanding environmental record and continue to demonstrate that mining can take place in harmony with the environment,” he said.

Although Big Springs began life as a heap leach operation, oxide ore milling began in 1988. Last year, Independence began processing refractory sulphide reserves after adding its patented roasting technology ahead of the standard carbon-in-leach circuit. The oxygen fluid-bed roaster is the first in the U.S. for processing whole-rock gold ore, and emissions from the mill are substantially below permitted levels.

The designation of Big Springs as a public showcase is viewed as a positive development by Nevada’s mining industry because of a growing public perception that the impact of mining on public lands is unacceptable. As in many parts of Canada, organized groups are seeking to remove areas from any resource development by advocating the creation of huge wilderness preserves.

Besides providing an opportunity for the public to see and understand mineral operations and observe successful partnerships between industry and government agencies, a mineral showcase is meant to demonstrate multiple use and how mineral activities can be co-ordinated with other uses and values.

In the case of Big Springs — one of the most picturesque mine sites in Nevada — it has meant extensive reclamation to reduce the visual impact of mining activities, efforts to preserve and enhance fish and wildlife habitat, rangelands for ranchers and traditional recreational areas.

Company officials estimate $10- 20 million will be spent during the mine life for mitigation to preserve the habitat of the Lahontan cutthroat trout (a threatened species) in the North Fork of the Humboldt River. According to the latest count, fish levels are the highest ever since 1955.

In addition, a $300,000 campsite was constructed to offset recreation displacement and access to traditional camping areas was enhanced. Although cattle and sheep grazing has been halted in the immediate mine area, it will resume at various locations when mining is complete.

During a tour of operations, mine superintendent Jim Collard pointed out several re-vegetated areas where backhoe recontouring of exploration roads was carried out. In addition, Big Springs was the first mine in the area to replace topsoil and seed a waste rock dump.

Other reclamation efforts have involved partial backfilling and the re-vegetation of a mined-out pit, while interim reclamation has included the hydro-mulching and seeding of the canyon haul-public access road to minimize erosion (and thereby protect fish habitat) and to improve aesthetics.

The mine is viewed as a community asset, and it has already been visited by boy scouts, school children, the Sierra Club and other wildlife organizations, university groups, a Congressional fact-finding group, local ranchers, and other agencies and residents.

Because of the high elevation (7,400-8,400 ft.), mining at Big Springs is carried out on a seasonal basis (9-11 months per year) by Gibbons & Reed, a Salt Lake-based contractor. The average daily production is 40,000 tons, and about 10 tons of waste rock is mined for every ton of ore.

Currently, ore comes from the North Sammy Creek pit which is best described as a side hill cut. The ore is found in a series of steeply dipping zones (veins), and mining takes place on 15-ft. benches, with the pit walls averaging about 45 degrees .

After first-stage crushing, ore feed to the roaster is prepared by dry ball mill grinding. The finely ground dried ore is then fed into the top of the roaster, where it moves through two roasting stages before being quenched and moved into carbon-in-leach tanks for final processing. Recoveries are in the 90-95% range.

Independence continues to explore at its mine property and nearby land holdings in an effort to expand reserves and extend the remaining four years of mine life.