Section 620.440  Groundwater Quality Standards for Class IV:  Other Groundwater

a)         Except as provided in subsection (b), (c), (d), or (e) Class IV:  Other Groundwater standards are equal to the existing concentrations of constituents in groundwater.

b)         For groundwater within a zone of attenuation as defined in 35 Ill. Adm. Code 810.103 and determined in compliance with 35 Ill. Adm. Code 811.320(c), the standards specified in Section 620.420 must not be exceeded.  This prohibition does not apply to any concentrations of contaminants within leachate released from a permitted unit.

c)         For groundwater within a previously mined area, the standards specified in Section 620.420 must not be exceeded, except the standards are the existing concentrations for TDS, chloride, iron, manganese, sulfates, pH, 1,3-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), nitrobenzene, RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine royal), 1,3,5-trinitrobenzene, and TNT (2,4,6-trinitrotoluene). 

d)         For groundwater regulated under Part 845, the groundwater protection standard (GWPS) under Section 845.600 must not be exceeded for any constituent with a GWPS under Section 845.600. For any constituent that does not have a GWPS under Section 845.600, the groundwater quality standards (GWQS) of Sections 620.410, 620.420, 620.430 or 620.440(b) and (c) apply.

e)         Nothing in this Section limits underground injection in compliance with an underground injection control program administered by the Agency under the Act, by the Department of Natural Resources, Office of Oil and Gas Resource Management under the Illinois Oil and Gas Act [225 ILCS 725], or by USEPA under the federal UIC regulations [40 CFR 144].

(Source:  Amended at 49 Ill. Reg. 4488, effective March 28, 2025)