Santa Cruz In Situ Copper Mining Research Project; Draft Environmental Assessment; Public Meeting

DEPARTMENT OF THE INTERIOR

Bureau of Mines

Santa Cruz In Situ Copper Mining Research Project; Draft

Environmental Assessment; Public Meeting

AGENCY: Bureau of Mines, Interior.

ACTION: Notice of availability of draft environmental assessment (EA)

prepared for the Santa Cruz In Situ Copper Mining Research Project and

notice of public meeting.

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SUMMARY: In accordance with section 102 (2) (C) of the National

Environmental Policy Act (NEPA), a draft EA has been prepared for the

Santa Cruz In Situ Copper Mining Research Project and is currently

available for public review and comment. The proposed action is the in

situ mining of copper from a copper oxide zone using a pattern of

injection and recovery test wells, and fabrication and operation of a

pilot-scale solvent extraction-electrowinning (SX-EW) facility to

remove dissolved copper from solution. The project site is located

approximately 7 miles west of the city of Casa Grande, Arizona. A

public meeting to receive comments on the draft EA is scheduled.

Individual copies of the draft EA may be requested directly from the

Bureau or viewed at the Casa Grande city library.

DATES: The public meeting will be held on September 14, 1994, beginning

at 7 p.m. MST. The meeting room will be open at 6:30 p.m. for review of

displays and informal discussions with project personnel. Comments on

the draft EA must be received no later than September 26, 1994.

ADDRESSES: The public meeting will be held at the Holiday Inn, 777

North Pinal Avenue, Casa Grande, AZ.

Comments on the draft EA should be sent to: Daniel J. Millenacker,

U.S. Bureau of Mines, Twin Cities Research Center, 5629 Minnehaha

Avenue South, Minneapolis, Minnesota 55417-3099.

FOR FURTHER INFORMATION CONTACT: For information or to obtain a copy of

the draft EA, contact Daniel J. Millenacker at the address identified

above or by phone at (612) 725-4588.

SUPPLEMENTARY INFORMATION: In situ copper mining involves the injection

of a dilute sulfuric acid solution through a well or wells completed

into an otherwise undisturbed ore zone; selective dissolution of copper

as the solution moves through and contacts copper oxide mineralization

located along natural fractures; collection of copper-bearing solution

by recovery wells; removal of the dissolved copper from collected

solution using a conventional SX-EW plant located on the surface;

rejuvenation of solution to its original strength; and solution

reinjection back into the ore zone to repeat the cycle. The project

well field will consist of one injection test well in the center of a

square measuring 127 ft to a side, and a recovery test well located at

each of the four corners of the square. This arrangement is referred to

as a ``five-spot'' well pattern. Injection of solution will occur at a

rate of about 10 to 50 gal/min. The total area to be occupied by the

various components of the project (including injection and recovery

test wells, ground water monitor wells, and SX-EW facility) is 8 1/2-

acres.

The research project is a cooperative effort of the Bureau of Mines

and the Santa Cruz Joint Venture (a joint venture formed between ASARCO

Santa Cruz, Inc., and Freeport Copper Company). The goal of the

research project is to determine the technical, economic, and

environmental feasibility of in situ mining of copper oxide minerals.

The research plan calls for in situ mining to continue until sufficient

data are collected to evaluate the mining technique. This time period

is presently estimated to require 18 months to complete, but it may

extend for up to 4 years. In addition to an environmental review

performed under NEPA, this project is subject to Federal, State, and

local environmental permitting requirements.

Dated: August 18, 1994.

Lewis V. Wade,

Research Director, Twin Cities Research Center.

[FR Doc. 94-20858 Filed 8-24-94; 8:45 am]

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