Section 406.110  Alternate Effluent Standards for Coal Mine Discharges During Precipitation Events

a)         Discharges from mountaintop removal areas, steep slope areas, and coal preparation plants and plant associated areas, and discharges of alkaline mine drainage are eligible for alternate effluent limitations during precipitation events.  Discharges ineligible for alternate effluent limitations during precipitation events include drainage from coal refuse piles and discharges of alkaline mine drainage from underground mines that are not commingled with other eligible discharges.  Any discharge or increase in discharge volume  caused by precipitation within any 24-hour period less than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply with the following limitations instead of those in Section 406.106(b):

b)         Discharges of acid or ferruginous mine discharge from coal refuse disposal piles are eligible for alternate effluent limitations during precipitation events.  Any discharge or increase in discharge volume caused by precipitation within any 24-hour period greater than the 1-year, 24-hour precipitation event and less than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply with the following limitations instead of those in Section 406.106(b):

c)         Discharges of acid or ferruginous mine drainage (excluding discharges in subsection (b), mountaintop removal area discharges, steep slope area discharges, controlled surface mines discharges, and discharges from underground workings) caused by precipitation:

1)         Within any 24-hour period less than or equal to the 2-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply with the following limitations instead of those in Section 406.109(b):

2)         Within any 24-hour period greater than the 2-year, 24-hour precipitation event but less than or equal to the 10-year, 24-hour precipitation event must comply with subsection (c)(1), except for the total iron effluent standard.

d)         All discharges mentioned in subsections (a), (b), and (c), discharges of acid or ferruginous mine drainage from underground workings that are commingled with other discharges, and controlled acid or ferruginous surface mine discharges caused by precipitation within any 24-hour period greater than the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) are subject only to a pH limitation range of 6-9.

(Source:  Amended at 43 Ill. Reg. 11620, effective September 25, 2019)