Oregon Administrative Rules
Chapter 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
Division 43 - CHEMICAL MINING
Section 340-043-0120 - Guidelines for the Design, Construction, Operation and Closure of Chemical Mining Operations: Guidelines for Design, Construction, and Operation of Heap-Leach Facilities
Current through Register Vol. 63, No. 3, March 1, 2024
(1) This section applies to heap-leach facilities using dedicated, or expanding, pads. Heap-leach facilities using on-off, reusable pads may require variations from these rules; they shall be approved on a case-by-case basis by the Department.
(2) The heap-leach facility (pad and associated ponds, pipes and tanks) shall be sized to prevent flooding of any of its components.
(3) Table 1 of this Division establishes minimum capacity-sizing criteria for the leach-pad and ponds. The pad and ponds may be designed to act separately or in conjunction with each other to obtain the required storage volumes. Other design criteria may be used, with Department approval, if local conditions warrant. The best available climatic data shall be used to confirm the critical design storm event and estimate the liquid levels in the system over a full seasonal cycle. The liquid mass balance may include provision for evaporation.
(4) The heap leach pad liner system shall be designed, constructed, and operated to meet the following criteria:
(5) The processing chemical pond liner system shall be designed, constructed, and operated to meet the following criteria:
(6) Emergency ponds may be constructed as an alternative to larger pregnant and barren ponds. The emergency pond may be constructed to a lesser standard, with the limitation that it is to be used only infrequently and for short periods of time. The Department will specify reporting and use limitations for the ponds in the permit. A between-liner leak detection system is not required for the emergency pond.
(7) The emergency pond liner shall be of composite construction consisting of:
(8) The heap-leach pad shall be provided with a process chemical collection system above the upper-most liner that will prevent an accumulation of process chemical within the heap greater than 24 inches in depth.
(9) The permittee shall prepare a written operating plan for safe temporary shutdown of the heap-leach facility and train employees in its implementation.
(10) The permittee shall respond to leakage collected by the heap-leach and processing-chemical storage pond leak-collection systems according to the process defined in Table 2.
(11) The permittee shall determine the acid-generating potential of the spent ore by acid/base accounting and other appropriate static and dynamic laboratory tests. If the spent ore is shown to be potentially acid generating under the conditions expected in the heap at closure, the permittee shall submit a plan for acid correction for Department approval prior to loading the heap.
To view tables referenced in rule text, click here to view rule.
Statutory/Other Authority: ORS 468.020
Statutes/Other Implemented: ORS 468.020 & 468B.160