2013-20733. Notice of Intent To Prepare A Draft Environment Impact Statement for the Proposed Ray Mine Tailings Storage Facility in Pinal County, Arizona

AGENCY:

U.S. Army Corps of Engineers, DoD.

ACTION:

Notice of Intent.

SUMMARY:

The U.S. Army Corps of Engineers, Los Angeles District (Corps) is examining the environmental consequences associated with the proposed construction, operation, and closure of a new tailings storage facility in eastern Pinal County, Arizona, in connection with Asarco LLC's application for a Department of the Army permit under Section 404 of the Clean Water Act. The proposed tailings storage facility and associated facilities would discharge fill materials into approximately 138 acres of waters of the U.S. and indirectly impact an additional 17 acres through dewatering. The primary federal environmental concerns are the proposed discharges of fill material into waters of the U.S. and the potential for significant adverse environmental effects resulting from such activities. Therefore, to address these concerns in accordance with the National Environmental Policy Act (NEPA), the Corps is requiring preparation of an Environmental Impact Statement (EIS) prior to consideration of any permit action. The action must comply with the Section 404(b)(1) Guidelines (40 CFR Part 230) and not be contrary to the public interest to be granted a Corps permit. The Corps may ultimately make a determination to permit or deny the above project, or permit or deny modified versions of the above project.

FOR FURTHER INFORMATION CONTACT:

Questions about the proposed action or the scoping of the Draft EIS can be answered by Michael Langley, Corps Senior Project Manager, at [phone]. Comments regarding scoping of the Draft EIS shall be addressed to: U.S. Army Corps of Engineers, Los Angeles District, Arizona Regulatory Branch, ATTN: SPL-2011-01005-MWL, 3636 North Central Avenue, Suite 900, Phoenix, Arizona 85012-1939, or [e-mail]. Comments letters sent via electronic mail shall include the commenter's physical address and the project title “Ray Mine Tailings Storage Facility Project” shall be included in the subject line.

SUPPLEMENTARY INFORMATION:

1. Project Site and Background Information: The 2,350-acre project site is located in eastern Pinal County, Arizona approximately four miles south of the Ray Mine Complex, south of the Gila River, on lands owned by Asarco, on lands owned and managed by the Bureau of Land Management, and on lands currently owned and managed by the Arizona State Land Department that Asarco is seeking to acquire. The project pipelines would run along the Florence-Kelvin Highway from the thickeners at the Ray Mine to the proposed TSF.

Asarco is the owner and operator of the Ray Mine Complex in Pinal County, Arizona, an open-pit copper mine with an on-site concentrator and leaching facilities. Asarco also owns associated concentrating and smelting facilities located in Hayden, Arizona, approximately 17 miles southeast of the mine. The Ray Mine was originally founded in 1882 as a silver mine with the mining of copper beginning somewhat later.

A Clean Water Act Section 404 permit was issued for construction of the Elder Gulch tailings impoundment at Ray Mine in 1991; modifications to that permit were issued in 1996, 1997, and 1998 for ongoing mining and mitigation activities. In May 2011, a new Section 404 permit was obtained that authorizes continued operation and expansion of the Elder Gulch tailings facility, construction of a stormwater diversion system upgradient of the tailings facility, and continued placement of rock into rock deposition areas previously authorized in the 1991 Section 404 permit (as modified by the subsequent amendments). Prior to the May 2011 Section 404 permit that authorized expansion of the Elder Gulch impoundment, that facility was expected to reach capacity in approximately 2013. Raising the crest elevation of the impoundment to the 2,590 ft level as authorized by the May 2011 Section 404 permit, will allow the existing Elder Gulch tailings impoundment to be used for an anticipated five to seven additional years. The Ray Mine has proven ore reserves that will allow mining to continue well past that timeframe, and additional expansions of the Elder Gulch facility are not technically and environmentally feasible.

2. Proposed Action: Asarco is proposing to construct, operate, and close a tailings storage facility to support continuing copper mining activities at the Ray Mine Complex. The facility would accommodate tailings that would be collected at the mine, transported via a tailings delivery pipeline, and deposited in slurry form at a discharge point east of Ripsey Wash, an ephemeral wash that is a tributary to the Gila River. The facility footprint is estimated at 2,129 acres and currently has an elevational range of approximately 1,800 to 2,400 feet above mean sea level. The facility is designed for an overall storage capacity of 751.3 million tons of tailings and embankment materials with a final crest elevation of 2,440 feet. The proposed facility would be built with centerline and upstream construction methods.

A diversion embankment, stormwater detention pond, and channel would be constructed at the upgradient end of the facility to divert flows around the facility to the west to Zelleweger Wash. The diversion embankment and stormwater detention pond are designed to handle the 500-year, 24-hour storm event. Water from this impoundment would be pumped and piped to the western diversion channel for conveyance to Zelleweger Wash. A second diversion channel would be constructed along the east side of the facility to drain stormwater runoff from upgradient of the facility to an unnamed tributary wash to the Gila River.

The starter tailings embankment would be constructed at the downgradient end of the facility with a 50-foot-wide berm. Cyclone sands would be used to construct the phased embankments. The ultimate embankment would be constructed to an elevation of 2,440 feet above mean sea level with a tailings deposition elevation just below this elevation.

Some seepage from the tailings impoundment is expected and would infiltrate the alluvial deposits located within Ripsey Wash and its tributaries. Therefore, a seepage collection trench would be constructed within Ripsey Wash downstream of the impoundment to contain the seepage, and a second seepage collection trench will be constructed in a drainage on the east side of the facility. The seepage collection trench will be constructed with a geomembrane liner anchored to bedrock and granular drain rock along the upstream face of the trench to intercept seepage from the tailings facility. A series of riser pipes will be installed within the trench and fitted with submersible pumps to pump collected seepage to the associated reclaimed water ponds.

Asarco is proposing to construct and operate tailings delivery and reclaimed water pipelines as part of the project. The tailings generated from the mill at the Ray Mine would be pumped in slurry form through the tailings delivery pipeline to the proposed facility impoundment area for deposition and a reclaimed water pipeline would be used to pipe reclaimed water back to the Ray Mine for reuse. The pipelines would be constructed along the Florence-Kelvin Highway and connect to the proposed tailings deposition point and reclaimed water ponds located at the proposed facility. The pipelines would be constructed along the existing alignment of the Florence-Kelvin Highway. To address the unlikely event of a pipeline failure, a drain down pond is planned along the pipeline route north of the Gila River for containment of tailings and/or reclaimed water. A pipeline bridge would be constructed at the point where the pipeline route crosses the Gila River.

A 2.2-mile segment of the Florence-Kelvin Highway, a Pinal County-maintained roadway, would require realignment as a result of constructing the facility. A 2.1-mile section of the road would be relocated north of its current alignment.

The proposed facility would require the relocation of the San Carlos Irrigation Project power line which currently passes though the northern portion of the facility footprint. An approximately 2.3-mile segment of the power line will be moved north of the TSF and rerouted around the western portion of the project area, approximately following the proposed and existing alignment of the Florence-Kelvin Highway. The planned rerouted power line corridor is approximately 3.2 miles in length.

3. Issues: There are several potential environmental issues that will be addressed in the Draft EIS. Additional issues may be identified during the scoping process. Issues initially identified for evaluation in the Draft EIS include:

1. Visual/aesthetics impacts from landform alterations,

2. air quality impacts from construction and operation of the facility,

3. cultural resources (prehistoric and historic resources),

4. surface water hydrology and quality,

5. groundwater hydrology and quality,

6. potential land use incompatibility,

7. noise impacts from construction and operation,

8. Impacts to recreation resources,

9. socioeconomic effects,

10. soils and geotechnical stability issues,

11. transportation network impacts, and

12. biological impacts (vegetation, wildlife, waters of the U.S.).

4. Alternatives: Several alternatives to the proposed action are being considered in the Draft EIS. The Draft EIS will include a co-equal level of analysis of the No-Action and project alternatives considered. Currently, there are five potential off-site project alternatives being considered along with the proposed action and two variations of the proposed action. These alternatives will be further formulated and developed during the scoping process. Additional alternatives may be developed during scoping that will also be considered in the Draft EIS.

5. Scoping: The Corps will conduct two public scoping meetings for the proposed Ray Mine Tailings Storage Facility Project Draft EIS to receive public comment and to assess public concerns regarding the appropriate scope and preparation of the Draft EIS. Participation in the public meetings by federal, state, local, and tribal agencies and other interested organizations is encouraged. The first meeting will be held on September 24, 2013 beginning at 6:00 p.m. (Arizona Time Zone) at Kearny Junior-Senior High School, 701 Arizona 177, Kearny, Arizona 85137. The second meeting will be held on September 25, 2013 beginning at 6:00 p.m. (Arizona Time Zone) at Apache Junction High School, 2525 South Ironwood Drive, Apache Junction, Arizona 85120. Comments on the proposed action, alternatives, or any additional concerns should be submitted in writing. Written and electronic comment letters will be accepted through October 28, 2013.

The Corps also anticipates formally consulting with the U.S. Fish and Wildlife Service under Section 7 of the Endangered Species Act and with the State Historic Preservation Officer and appropriate Tribal Historic Preservation Officers under Section 106 of the National Historic Preservation Act.

6. Availability of the Draft EIS: The Draft EIS is expected to be published and circulated in the fourth quarter of 2014, and a public meeting will be held after its publication.

Dated: August 12, 2013.

David J. Castanon,

Division Chief, Los Angeles District, U.S. Army Corps of Engineers.