Nevada Regulations Regarding Mining Pit Lakes
There are no specific numerical water quality standards for the water in pit lakes. However, pit lake water falls within “Waters of the State,” defined in the NRS as:
NRS 445A.415. “Waters of the State” means all waters situated wholly or partly within or bordering upon this State, including but not limited to:
1. All streams, lakes, ponds, impounding reservoirs, marshes, water courses, waterways, wells, springs, irrigation systems and drainage systems; and
2. All bodies or accumulations of water, surface and underground, natural or artificial. (Added to NRS by 1973, 1709)—(Substituted in revision for NRS 445.191)
Waters of the State are protected and it is illegal, in general, to degrade these waters. Degradation is defined by:
NAC 445A.357. “Degrade” means to alter the physical or chemical properties of or to cause a change in the concentration of any substance in the waters of the State in violation of the standards established pursuant to NAC 445A.424.
Pit lakes only exist after mining is concluded, so there is no existing surface water during mining. The pit lake is a new surface water, which although Waters of the State, does not have a designated beneficial use for which specific numerical standards exist. Control of water quality in pit lakes is found in the Nevada Administrative Code:
NAC 445A.429 Procedures required to prevent release of contaminants; requirements concerning impoundments. (NRS 445A.425, 445A.465)
1. The holder of the permit must institute appropriate procedures to ensure that all mined areas do not release contaminants that have the potential to degrade the waters of the State.
2. Open pit mines must, to the extent practicable, be free-draining or left in a manner which minimizes the impoundment of surface drainage and the potential for contaminants to be transported and degrade the waters of the State.
3. Bodies of water which are a result of mine pits penetrating the water table must not create an impoundment which:
(a) Has the potential to degrade the groundwaters of the State; or
(b) Has the potential to affect adversely the health of human, terrestrial or avian life.
4. The holder of a permit may apply to the Commission to establish a beneficial use with a level of protection less than that required by paragraph (b) of subsection 3 for water impounded in a specific mine pit.
This regulation is essentially the “standard” used. Although not numerical it does qualify under NRS 445A.420 as a “descriptive” water quality standard, which states, “Water quality standard” means the degree of pollution of water or the physical, chemical or biological condition of water, as expressed numerically or descriptively, used for controlling the quality of water in each segment of a stream and each other body of surface water in this State. To date there has no “beneficial use” established for any hard rock pit lakes, although NDEP does have the authority to do so. Ultimately, the Bureau of Water Quality Planning would be responsible for designating a beneficial use and developing the appropriate administrative code including numerical standards.
Thus, action should be taken by NDEP if the pit lake is causing groundwater to become degraded, or if the water in the pit lake is of such poor quality that it “has potential to affect adversely the health of human, terrestrial or avian life.” This was the case for the Sleeper pit lake and has been the case for the Lone Tree pit lake. Unlike a numerical standard, NAC 445A.429 allows for an ecological risk assessment (ERA) to determine compliance. ERA’s hinge on a numerical modeling process that uses input data and calculates “hazard quotients” for wildlife. All of which is based on the known understanding and assumptions of how the ecosystem absorbs and transports contaminants and the sensitivity of wildlife to these contaminants. Thus, ERA assessments can vary considerably depending upon the input parameters, and conceptual basis of the calculations.
Nevada reclamation requirements also do not specify a post mining use for pit lakes. NAC 519A.275 specifies requirements for productive postmining use of the land:
“1. A productive postmining use of the land required to be submitted with a plan for reclamation need not provide a use of the land and degree of productivity which is identical with the use of the land before the mining began or the use of the adjacent land or the degree of use.
2. Land which is returned to its pre-mining use or reclaimed after mining or exploration to a level of productivity which is generally consistent with the pre-mining level of productivity or the level of productivity of the surrounding land shall be deemed to be a productive postmining use.”
The Nevada Revised Statutes does allow for an exception to reclaim open pits and rock faces, NRS 519A.230(2) – “The operator may request the Division to grant an exception for open pits and rock faces which may not be feasible to reclaim. If an exception is granted, the Division shall require the operator to take sufficient measures to ensure public safety.” This legislative intend is codified in NAC 519A.250:
“1. An operator may request in writing that the Division grant an exception to the requirements for reclamation for open pits and rock faces which may not be feasible to reclaim.
2. If the operator proves to the satisfaction of the Division that reclamation is not feasible, the Division shall exempt an open pit or rock face from the requirements for reclamation of NAC 519A.010 to 519A.415, inclusive.
3. The Division shall base its determination of the feasibility of reclaiming open pits and rock faces on the technological and economic practicability of achieving a safe and stable condition suitable for a productive postmining land use. The Division shall consider, without limitation, the:
(a) Topography of the site;
(b) Geology and stability of the site;
(c) Time required to complete reclamation;
(d) Consumption of resources required to complete reclamation;
(e) Potential adverse environmental impacts to the quality of the air and water associated with the activities for reclamation; and
(f) Future access to mineral resources.
4. Upon request by the applicant, the return of material to the open pit from which it was extracted shall be considered to be not feasible for the purposes of reclamation.
5. If an open pit or rock face is exempted from reclamation, public safety must be provided for by means other than reclamation, including, but not limited to, restrictions on access to the site or restrictions on the deed to the property.”
In most cases in accordance with section 5 above reclamation of pit lakes involves some stabilization of pit walls and fencing off the pit lake to prevent human intrusion. NDEP does according to NAC 519A.345b have authority “if appropriate” to require certain reclamation as stipulated in subsection 9:
“9. Open pit mines by:
(a) Performing activities that will provide for public safety;
(b) Stabilizing pit walls or rock faces where required for public safety;
(c) Constructing and maintaining berms, fences or other means of restricting access;
(d) Creating a lake for recreational use, wildlife or other uses; and
(f) Reclamation of open pits or rock faces does not require backfilling although backfilling in whole or in part with waste rock from an adjacent mining operation may be encouraged if backfilling is feasible and does not create additional negative environmental impacts.”
Thus, a use could be established for a pit lake, but just as with the water quality regulations it is not required by law and conditional within the discretion of the agency.
If the mine is on public (federal) land or both private and public land then it is the federal land management agency (often the Bureau of Land Management or Forest Service) that determines post-mining land use. The State of Nevada retains its authority through NDEP to designate beneficial use of the water. In accordance NAC 519A.150 and NAC 519A.155 the Nevada reclamation permit is incorporated into the Plan of Operations the mining company submits to the federal agency, and is reviewed to the same level of detail for public and private land. Generally, the federal agency holds the surety only for projects where the majority of the disturbance will be on public land; NDEP holds the bond for projects where the majority of the disturbance will be on private property. The federal agencies and NDEP work cooperatively through MOU’s to ensure the reclamation of lands disturbed by mining and exploration.