Or. Admin. Code § 340-043-0180 - Guidelines for Open-Pit Closure

(1) Open pits that will be left as a result of the mining operation shall be assessed prior to, and following, mining operations for the potential to contaminate water to the extent that it might not meet water-quality standards due to buildup of acid or toxic metals.

(2) If the Department finds that the potential for water accumulation in the pit(s) exists, the permit applicant shall submit a closure plan for the pit that will address contamination prevention and possible remedial treatment of the water. The closure plan shall, at a minimum, examine the following alternatives:

(a) Avoidance, during mining, of acid-generating materials that can be left in place, rather than being exposed to oxidation and weathering;

(b) Removal from the pit and disposal, during or after the mining operation, of residual acid-generating materials that would otherwise be left exposed to oxidation and weathering;

(c) Protective capping in-situ of residual acid-generating materials;

(d) Treatment methods for correcting acidity and toxicity of accumulated water;

(e) Installation of an impermeable liner under ponded water to prevent groundwater contamination;

(f) Backfilling of the pit(s) to the level necessary to, in conjunction with other appropriate control measures, prevent oxidation of residual acid-generating materials.

Notes

Or. Admin. Code § 340-043-0180

DEQ 23-1992, f. & cert. ef. 9-8-92

Stat. Auth.:ORS 468.020

Stats. Implemented:ORS 468.020,ORS 468B.030 &ORS 468B.160