Section 620.505  Compliance Determination

a)         Except as this Part provides otherwise, compliance with the standards of this Part at a site is to be determined as follows:

1)         For a structure (e.g., buildings), at the closest practicable distance beyond the outermost edge of the structure.

2)         For groundwater that underlies a potential primary or secondary source, the outermost edge as specified in Section 620.240(e)(1).

3)         For groundwater that underlies a coal mine refuse disposal area, a coal combustion waste disposal area, or an impoundment that contains sludge, slurry, or precipitated process material at a coal preparation plant, the outermost edge as specified in Section 620.240(f)(1) or the location of monitoring wells in existence as of November 25, 1991, on a permitted site.

4)         For a groundwater management zone, as specified in a corrective action process.

5)         For groundwater, any point where monitoring is conducted using a water well or a monitoring well that meets one of the following conditions:

A)        For a potable water supply well if:

i)          Geologic logs exist for this well;

ii)         Geologic logs in the immediate 1,000-foot area of this well are representative of the hydrogeologic materials encountered by this well as determined by a licensed professional geologist or a licensed professional engineer; or

iii)        A WHPA has been delineated in compliance with the "Guidance Document for Groundwater Protection Needs Assessments" and "The Illinois Wellhead Protection Program", incorporated by reference in Section 620.125.

B)        For a potable water supply well other than a community water supply well, a construction report has been filed with the Department of Public Health for the potable well, or the well has been located and constructed (or reconstructed) to meet the Illinois Water Well Construction Code [415 ILCS 30] and 77 Ill. Adm. Code 920.

C)        For a potable water supply well that was constructed before August 20, 1965, the well meets the following criteria:

i)          Construction must be done in a manner that will enable the collection of groundwater samples that represent in situ groundwater conditions;

ii)         Casings and screens must be made from durable material resistant to expected chemical or physical degradation that do not interfere with the quality of groundwater samples being collected; and

iii)        The annular space opposite the screened section of the well (i.e., the space between the bore hole and well screen) must be filled with gravel or sand if necessary to collect groundwater samples.  The annular space above and below the well screen must be sealed to prevent migration of water from adjacent formations and the surface to the sampled depth.

D)        For a community water supply well, the well has been permitted by the Agency or constructed in compliance with 35 Ill. Adm. Code 602.115.

E)        For a water well other than a potable water supply well (e.g., a livestock watering well or an irrigation well), a construction report has been filed with the Department of Public Health or the Office of Mines and Minerals in the Department of Natural Resources for the well, or the well has been located and constructed (or reconstructed) to meet the Illinois Water Well Construction Code [415 ILCS 30] and 35 Ill. Adm. Code 920.

F)         For a monitoring well, the well meets the following requirements:

i)          Construction must be done in a manner that will enable the collection of groundwater samples;

ii)         Casings and screens must be made from durable material resistant to expected chemical or physical degradation that do not interfere with the quality of groundwater samples being collected; and

iii)        The annular space opposite the screened section of the well (i.e., the space between the bore hole and well screen) must be filled with gravel or sand if necessary to collect groundwater samples.  The annular space above and below the well screen must be sealed to prevent migration of water from adjacent formations and the surface to the sampled depth.

6)         Monitoring must not be conducted for compliance determinations under subsection (a):

A)        Using a water well that is:

i)          Less than 15 feet in total depth from the land surface,

ii)         bored or dug,

iii)        constructed of permeable materials (e.g., cement, tile, stone, or brick), and

iv)        36 inches or more in diameter.

B)        Using a water well with water quality problems due to damaged well-construction materials or poorly designed well construction;

C)        Using a water well in a basement or pit; or

D)        Using water-well water from a holding tank.

b)         For a spring, compliance with this Subpart must be determined at the point of emergence.

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