Or. Admin. Code § 340-043-0150 - Guidelines for the Design, Construction, Operation and Closure of Chemical Mining Operations: Guidelines for Heap-Leach and Tailings Disposal Facility Closure
(1) The waste
disposal facilities shall be closed under these rules in conjunction with the
reclamation requirements of DOGAMI (Oregon Department of Geology and Mineral
Industries).
(2) An updated closure
plan and post-closure monitoring and maintenance plan shall be submitted to the
Department by the permittee at least 180 days prior to beginning closure
operations or making any substantial changes to the operation. The closure plan
must be compatible with DOGAMI's reclamation plan and may be part of
it.
(3) Chemical conveyances
(ditches, troughs, pipes, etc.) not necessary for post-closure monitoring shall
be removed. The secondary containment systems shall be checked before closure
for process-chemical contamination, and contaminated soil or other materials,
if any, shall be removed to an acceptable disposal facility.
(4) Closure of the heap-leach facility:
(a) The heap shall be detoxified over a
suitable period of time prior to closure, using rinse/rest cycles of rinsing
and chemical oxidation, if necessary. The WAD cyanide concentration in the
rinsate shall be no greater than 0.2 ppm;
(b) Following detoxification as defined in
subsection (a) of this section, the heap shall be closed in place on the pad by
covering the heap with a cover designed to prevent water and air infiltration.
The cover should consist, at a minimum, of a low-permeability layer and
suitable drainage and soil layers to prevent erosion and damage by animals and
to sustain vegetation growth, in accordance with DOGAMI's reclamation
rules;
(c) The ponds associated
with the heap shall be closed by folding in the synthetic liners and filling
and contouring the pits with inert material. Residual sludge may be disposed of
in one of the on-site waste disposal facilities, provided it meets the criteria
for such wastes in these guidelines. The process chemical collection system of
the heap shall be maintained in operative condition so that it can be used to
monitor the amount and quality of infiltrated water, if any, draining from the
heap.
(5) The tailings
disposal facility shall be closed by covering with a composite cover designed
to prevent water and air infiltration and be environmentally stable for an
indefinite period of time. Maximum effort shall be made to isolate the tailings
from the environment. Construction of the cover shall generally follow the
principles and practices contained in EPA/530-SW-89-047. Technical Guidance
Document - Final Covers on Hazardous Waste Landfills and Surface Impoundments.
[NOTE: View a PDF of EPA Guidance Document by clicking on "Tables" link below.]
Notes
To view tables referenced in rule text, click here to view rule.
Statutory/Other Authority: ORS 468.020
Statutes/Other Implemented: ORS 468.020 & 517.770
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