US Army Corps of Engineers
Albuquerque District

Albuquerque District, Regulatory Division, Approved Jurisdictional Determination for Little Rock Mine

NM/TX Branch Chief, Regulatory Division, Albuquerque District
Published Feb. 15, 2019

ALBUQUERQUE, N.M. -- The U.S. Army Corps of Engineers, Regulatory Program, routinely conducts determinations of geographic jurisdiction under Section 404 of the Clean Water Act (CWA). Section 404 geographic jurisdiction is referred to as “waters of the U.S.”; the regulatory definition of this includes tributaries down to the smallest of streams. Based on U.S. Supreme Court decisions in Rapanos v. United States and Carabell v. United States, in December 2008, the USACE issued guidance on making determinations of how some aquatic resources, such as ephemeral streams, meet the definition of “waters of the U.S.” in order to be regulated by Section 404. This guidance quickly became known as the Rapanos Guidance, and required USACE regulatory staff to: collect data on the chemical, physical and biological connection (i.e., tributary) to the integrity of traditionally navigable waters; document determinations using a form developed by USACE HQ; and provide rationale for decisions regarding geographic jurisdiction in light of the U.S. Supreme Court decision. These decisions are referred to as approved jurisdictional determinations (AJD). 

 

Anyone can request that USACE conduct AJDs within a given parcel. Frequently, members of the public seek AJDs from USACE in order to inform project planning and potential for Section 404 requirements of a particular project.

 

The Albuquerque District received such a request from a private mining organization, Freeport-McMoRan Tyrone, Inc. (FMTI), in 2017, for the Little Rock Mine, located in Grant County, New Mexico. The Little Rock Mine includes a project area of approximately 682 acres, and is bordered by the Tyrone Mine to the north, and the Gila National Forest to the south and west. The Little Rock Mine is located approximately 10 miles southwest of Silver City, New Mexico, near the Continental Divide in the Gila River basin. Turquoise, copper, and fluorspar were mined in the area, from the late 1870s through the early 1900s. Open-pit copper mining began in 1967. 

 

The principal features at the Little Rock Mine include an open pit, the North and West Canyon overburden stockpiles, the historic Ohio Mine and Dam, the reclaimed Copper Leach Stockpile and the Precipitation Plant. The closed, and reclaimed, leach stockpile contains about 1.7 million tons of primarily copper oxide ore that was leached with sulfuric acid solutions during the early 1970s. 

 

An ephemeral stream, called Deadman Canyon, runs through Little Rock Mine. The natural flowpath of Deadman Canyon has been altered, through Little Rock Mine, by historic mining operations, and for the purpose of preventing transport of sediment, and water, to downstream receiving waters, which include the Mangas Creek and the Gila River. 

 

Based on a large amount of information, USACE determined that Deadman has a significant chemical nexus to the Gila River and, therefore, meets the definition of “waters of the U.S,” based on Rapanos Guidance. USACE provided its determination to FMTI on Oct. 31, 2017. Since then, FMTI has submitted three separate requests for reconsideration of the AJD on Deadman Canyon, each with new information. USACE has evaluated each request, and has continued to assert jurisdiction over Deadman Canyon; the most recent AJD was made on Dec. 14, 2018.