Proposed Expansion of the Continental Mine in Grant County, New Mexico

DEPARTMENT OF THE INTERIOR

Bureau of Land Management

[NM-030-7122-03-8546]

Proposed Expansion of the Continental Mine in Grant County, New

Mexico

AGENCY: Bureau of Land Management (BLM), Interior.

ACTION: Notice of Intent to Prepare an Environmental Impact Statement

(EIS) and Notice of Scoping Meeting.

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SUMMARY: Pursuant to Section 102(2)(C) of the National Environmental

Policy Act (NEPA) of 1969, as amended, the BLM, Las Cruces District

Office, will be directing the preparation of an EIS to be prepared by a

third party contractor. The EIS will describe the potential impacts of

Cobre Mining Company's proposed Continental Expansion Project at its

Continental Mine located approximately 3 miles north of the town of

Hanover in Grant County, New Mexico. The proposed development would

occur partially on patented Cobre land and partially on Federal land

administered by the BLM and the U.S. Forest Service (USFS).

The public is invited to participate in the planning process. A

public scoping meeting will be held at the following time and location:

TIME/DATE/LOCATION: 7:00 p.m., November 15, 1995, Grant County

Courthouse Bldg., Third Floor Conference Room, 201 North Cooper Street,

Silver City, New Mexico.

DATES: Written comments on the scoping process will be accepted through

November 27, 1995.

ADDRESSES: Comments should be sent to Chuck O'Donnell, BLM, Las Cruces

District, 1800 Marquess, Las Cruces, New Mexico 88005.

FOR FURTHER INFORMATION CONTACT: Chuck O'Donnell, BLM Las Cruces

District Office, at (505) 525-4373.

SUPPLEMENTARY INFORMATION: On April 12, 1995, Cobre Mining Company

submitted a Plan of Operations (POO) to expand mining activities at the

Continental Mine. It was determined by the BLM that the preparation of

an EIS would be required for these operations. A Memorandum of

Agreement (MOA) between Cobre Mining Company, the BLM, and the USFS

outlining the responsibilities of each party has been executed.

Cobre is currently engaged in mining ore using open pit and

underground mining methods. The primary production metal is copper,

with the potential for zinc, silver, gold and magnetite recovery as a

by-product. Ore is crushed and processed via milling on-site. Tailings

material generated in the milling process is discharged to an on-site

tailings pond.

The copper mineralization within the Hanover Mountain deposit is

predominantly chalcocite, and is economically recoverable by acid heap

leaching techniques, followed by solvent extraction (SX) and

electrowinning (EW) to produce cathode copper.

Development of Hanover Mountain will take place on land owned by

Cobre, and will eventually extend onto BLM land. Expansion of the

Continental pit and underground working will occur on or beneath

property owned by Cobre, and on or beneath land administered by BLM and

the USFS.

Proposed activities and facilities for the Continental Expansion

Project include: open pit mining at Hanover Mountain, expansion of the

Continental open pit, development of additional underground mining

operations, ore crushing and conveying, waste rock disposal, heap

leaching, solvent extraction, electrowinning, ancillary facilities,

including a truck stop, change rooms, water supply, electrical

substation and power distribution.

The Hanover Mountain ore body will be mined using conventional open

pit mining techniques and equipment. The planned rate of ore mining of

Hanover Mountain is 10 million tons per year. The primary waste rock

disposal area for the Continental Expansion Project is located west of

Hanover Mountain. Waste rock disposal for current mining operations

occurs on two waste rock dumps located south and east of the current

Continental Pit. Placement of approximately 88 million tons of waste

rock is planned on 233 acres, of which 179 acres are administered by

the BLM. Additional waste rock capacity of a combined 82 million tons

is planned on Cobre patented land. Waste rock will also be used to

stabilize leach pad sites, for haul roads and process facilities, and

to shape and stabilize existing mine waste rock dumps. Ore from the

proposed Hanover Pit will be delivered to a primary crusher. Crushed

ore will be stockpiled and reclaimed to a secondary crushing plant.

Crushing facilities will be located north of the existing office

facilities on Cobre patented land.

Ore crushed to nominal one-inch size will be conveyed and stacked

onto a lined leach pad. A drip emitter or spray irrigation system will

be placed over the ore pile, and acidic solution will be percolated

through the ore for 90 to 120 days. A pad liner and drainage pipes will

collect and drain the solution to a pregnant leach solution (PLS) pond.

The PLS will be pumped to a SX/EW facility for copper recovery.

The primary area for leaching will be the Fierro area, with a

design capacity of approximately 92 million tons. The Fierro leach pad

will be developed in phases, with the initial phase taking place on

Cobre property. Later phases of development will expand the 177-acre

leach pad to include 50 acres of land administered by the BLM.

Additional leaching capacity of up to 89 million tons may be developed

south of the existing Continental Pit, which encompasses 67 acres of

BLM land.

The SX/EW plant will be located entirely on Cobre patented land on

the east side of County Road 3-5, north of the Fierro town site.

As the Hanover Pit expands toward its design limit, it will become

necessary to re-route drainage from the upper portion of Hanover Creek

around mining

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operations. This may be accomplished through either gravity flow or

pumping through either a pipeline or a relocated stream channel.

In order to ensure continued access to lands north of the

Continental Mine, the expansion of the Hanover Pit will also require

the relocation of County Road 3-5 around mining operations. Surface

mining operations currently conducted at the Continental Mine produce

approximately 10,000 tons of ore per day from the Continental Pit.

Exploratory drilling has indicated that economic ore reserves

recoverable by open pit mining techniques occur around the perimeter of

the existing Continental Pit. Based on these results, the existing pit

is proposed to be expanded. Expansion of the pit will include

additional land owned by Cobre, and BLM land, and may also include

approximately 7 acres of USFS land.

Cobre also currently conducts underground mining activities at the

Continental Mine site. Between 2,000 and 5,000 tons per day of ore are

crushed in an underground crushing facility. The crushed ore is

transported to the surface and is sent to either the #1 Mill by

conveyor or to the #2 Mill stockpile by truck for processing.

Due to the nature and depth of mining activities and the rock

stability in the mining area, no subsidence has occurred, and none is

expected to occur.

Reclamation of the site will comply with BLM provisions of an

approved reclamation plan and plan of operations. It is anticipated

that the New Mexico Mining Act regulations will also be instrumental

for ultimate closure requirements. The BLM and the USFS will determine

``post mining land use'' for the portions of the pit areas, the waste

rock dumps, and the leach pads located on Federal land.

The objective of the reclamation plan will be to minimize public

safety hazards, and to provide for long-term protection of the

environment and restoration of the site to a condition consistent with

planned long-term land use. Major components of the reclamation plan

are anticipated to include: rinsing the leach heaps to remove residual

copper-bearing solution; recontouring the top surfaces of the leach

heaps and the waste rock dumps; removal of buildings, equipment and

foundations; recontouring roads, building sites and other disturbed

areas; protection of natural stream channels and permanent diversion

ditches at strategic points to ensure long-term stability; and blocking

access to the open pits. An evaluation of the stability of proposed

slopes of the reclaimed open pit, waste rock dump slopes, and heap

leach slopes will be performed. After initial dewatering and drying,

the tailings will be re-contoured and capped.

The EIS will address the resources of geology and minerals, soils,

water resources, vegetation, wildlife, range management, air quality,

visual resources, reclamation, land use, access, recreation,

wilderness, cultural resources, social and economic values,

transportation and noise. The BLM has identified the following

potentially significant impacts as requiring additional analysis:

quality of post-mining surface and ground water generated by the

Continental and Hanover open pits; potential impacts to surface and

ground water from acid mine drainage from the mine's waste rock dumps;

potential impacts to ground water from the mine's tailings impoundment;

potential impacts of the diversion of Hanover Creek; potential impacts

of the re-routing of County Road 3-5.

Because these issues were determined to require special

investigation, it is anticipated that the majority of work for other

resources will be limited to summarizing and incorporating by reference

data and analyses from existing environmental studies as prescribed in

40 CFR Sec. 1500.4 and Sec. 1500.5. Additional investigation may be

indicated for other resources after review of existing data and

comments received during the scoping process.

BLM's scoping process for the EIS will include: (1) identification

of issues to be addressed; (2) identification of viable alternatives;

and (3) notifying interested groups, individuals, and agencies so that

additional information concerning these issues can be obtained. The

scoping will consist of a news release announcing the start of the EIS

process; letters of invitation to participate in the scoping process;

and a scoping document which further clarifies the proposed action and

significant issues being considered to be distributed to those on the

mailing list and available upon request.

Dated: October 18, 1995.

Linda S. C. Rundell,

District Manager, Las Cruces.

[FR Doc. 95-26295 Filed 10-23-95; 8:45 am]

BILLING CODE 4310-FB-P