620.240 - Class IV: Other Groundwater

Except as provided in Section 620.250, Other Groundwater is as described in subsection (a), (b), (c), (d), (e), (f), (g), or (h).

a) Groundwater within a zone of attenuation under 35 Ill. Adm. Code 811 and 814.

b) Groundwater within a point of compliance under 35 Ill. Adm. Code 724, but not to exceed a lateral distance of 200 feet from the edge of a potential primary or secondary source.

c) Groundwater that naturally contains more than 10,000 mg/L of total dissolved solids.

d) Groundwater that has been designated by the Board as an exempt aquifer under 35 Ill. Adm. Code 730.104.

e) Groundwater that underlies a potential primary or secondary source, in which contaminants may be present from a release, if the owner or operator of the source notifies the Agency in writing and the following conditions are met:

1) The outermost edge of what would be considered the Class IV groundwater is the closest practicable distance from the source, but does not exceed:

A) A lateral distance of 25 feet from the edge of the potential source or the property boundary, whichever is less, and

B) A depth of 15 feet from the bottom of the potential source or the land surface, whichever is greater;

2) The source of any release of contaminants to groundwater has been controlled;

3) Migration of contaminants within the site resulting from a release to groundwater has been minimized;

4) Any on-site release of contaminants to groundwater has been managed to prevent migration off-site; and

5) No potable water well exists within the outermost edge as specified in subsection (e)(1).

f) Groundwater that underlies a coal mine refuse disposal area not contained within an area from which overburden has been removed, a coal combustion waste disposal area at a surface coal mine authorized under Section 21(s) of the Act, or an impoundment that contains sludge, slurry, or precipitated process material at a coal preparation plant, in which contaminants may be present, if the area or impoundment began operating after February 1, 1983, the owner and operator notifies the Agency in writing, and the following conditions are met:

1) The outermost edge of what would be considered the Class IV groundwater is the closest practicable distance from the area or impoundment, but does not exceed:

A) A lateral distance of 25 feet from the edge of the area or impoundment, or the property boundary, whichever is less; and

B) A depth of 15 feet from the bottom of the area or impoundment, or the land surface, whichever is greater;

2) The source of any release of contaminants to groundwater has been controlled;

3) Migration of contaminants within the site resulting from a release to groundwater has been minimized;

4) Any on-site release of contaminants to groundwater has been managed to prevent migration off-site; and

5) No potable water well exists within the outermost edge as specified in subsection (f)(1).

g) Groundwater within a previously mined area, unless monitoring demonstrates that the groundwater is capable of consistently meeting the standards of specified in Section 620.410 or 620.420. If that capability is determined, groundwater within the previously mined area must not be considered Class IV.

h) Groundwater regulated under 35 Ill. Adm. Code 845.

Notes

620.240

Amended at 49 Ill. Reg. 4488, effective 3/28/2025