Current through Register Vol. 48, No. 38, September 20, 2024
The impacts of the seepage of leachate from the unit shall be
assessed in a systematic fashion using the techniques described in this
Section.
a) Procedures for Performing
the Groundwater Impact Assessment
1) The
operator shall estimate the amount of seepage from the unit during operations
which assume:
A) That the minimum design
standards for slope configuration, cover, liner, leachate drainage and
collection system apply; and
B)
That the actual design standards planned for the unit apply. Other designs for
the unit may be used if determined by the operator to be appropriate to
demonstrate the impacts to groundwater, pursuant to subsection (b).
2) The concentration of
constituents in the leachate shall be determined from actual leachate samples
from the waste or similar waste, or laboratory derived extracts.
3) A contaminant transport model meeting the
standards of subsection (c) shall be utilized to estimate the concentrations of
the leachate constituents over time and space. The Agency must review a
groundwater contaminant transport model for acceptance in accordance with 35
Ill. Adm. Code
813.111.
b) Acceptable Groundwater Impact
Assessment
The groundwater contaminant transport (GCT) model results
shall be used in the assessment of the groundwater impact. The groundwater
impact shall be considered acceptable if the GCT model predicts that the
concentrations of all constituents of the leachate outside the zone of
attenuation are less than the applicable groundwater quality standards of
Section
811.320,
within 100 years of closure of the unit.
c) Standards for the Contaminant Transport
Model
1) The model shall have supporting
documentation that establishes its ability to represent groundwater flow and
contaminant transport and any history of its previous applications.
2) The set of equations representing
groundwater movement and contaminant transort must be theoretically sound and
well documented.
3) The numerical
solution methods must be based upon sound mathematical principles and be
supported by verification and checking techniques.
4) The model must be calibrated against site
specific field data developed pursuant to this Part.
5) A sensitivity analysis shall be conducted
to measure the model's response to changes in the values assigned to major
parameters, specified error tolerances, and numerically assigned space and time
discretizations.
6) Mass balance
calculations on selected elements in the model shall be performed to verify
physical validity. Where the model does not prescribe the amount of mass
entering the system as a boundary condition, this step may be
ignored.
7) The values of the
model's parameters requiring site specific data shall be based upon actual
field or laboratory measurements.
8) The values of the model's parameters which
do not require site specific data shall be supported by laboratory test results
or equivalent methods documenting the validity of the chosen parametric
values.
