35 Ill. Adm. Code 616.204
Groundwater Monitoring System
Section 616
Section 616.204 Groundwater
Monitoring System
a) The groundwater monitoring system must consist of a sufficient
number of wells, installed at appropriate locations and depths to yield
groundwater samples that:
1) Represent the quality of background water that has not been
affected by contamination from the facility or unit; and
2) Represent the quality of groundwater at the compliance point
or points.
b) If a facility contains more than one unit, separate
groundwater monitoring systems are not required for each unit, provided that
provisions for sampling the groundwater will enable detection and measurement
of contaminants that have entered the groundwater from all units.
c) Monitoring wells must meet the following requirements:
1) Construction must be done in a manner that will enable the
collection of groundwater samples;
2) Casings and screens must be made from durable material that is
resistant to expected chemical or physical degradation and that does not
interfere with the quality of groundwater samples being collected; and
3) 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 overlying adjacent formations and the surface to the sampled depth.