Current through Register Vol. 48, No. 38, September 20, 2024
a) An existing CCR
surface impoundment is considered to be an existing lined surface impoundment
if it has been constructed with either a composite liner that meets the
requirements of subsection (b) or an alternative composite liner that meets the
requirements of subsection (c).
b)
Composite Liner
1) A composite liner must
consist of two components: the upper component consisting of, at a minimum, a
30-mil geomembrane liner, and the lower component consisting of at least a
two-foot layer of compacted soil with a hydraulic conductivity of no more than
1 x 10-7 centimeters per second (cm/sec). The
geomembrane liner components consisting of high-density polyethylene (HDPE)
must be at least 60 mil. The geomembrane liner or upper liner component must be
installed in direct and uniform contact with the compacted soil or lower liner
component.
2) The composite liner
must be:
A) Constructed of materials that have
appropriate chemical properties and sufficient strength and thickness to
prevent failure due to pressure gradients (including static head and external
hydrogeologic forces), physical contact with the CCR or leachate to which they
are exposed, climatic conditions, the stress of installation, and the stress of
daily operation;
B) Constructed of
materials that provide appropriate shear resistance of the upper and lower
component interface to prevent sliding of the upper component, including on
slopes;
C) Placed upon a foundation
or base capable of providing support to the liner and resistance to pressure
gradients above and below the liner to prevent failure of the liner due to
settlement, compression, or uplift; and
D) Installed to cover all surrounding earth
likely to be in contact with the CCR or leachate.
c) Alternative Composite Liner
1) An alternative composite liner must
consist of two components: the upper component consisting of, at a minimum, a
30-mil geomembrane liner, and a lower component, that is not a geomembrane,
with a liquid flow rate no greater than the liquid flow rate of two feet of
compacted soil with a hydraulic conductivity of no more than 1 x
10-7 cm/sec. The geomembrane liner components
consisting of high-density polyethylene (HDPE) must be at least 60 mil. If the
lower component of the alternative liner is compacted soil, the geomembrane
liner must be installed in direct and uniform contact with the compacted
soil.
2) The liquid flow rate
through the lower component of the alternative composite liner must be no
greater than the liquid flow rate through two feet of compacted soil with a
hydraulic conductivity of 1 x 10-7 cm/sec. The
hydraulic conductivity for the two feet of compacted soil used in the
comparison must be no greater than 1 x 10-7 cm/sec.
The hydraulic conductivity of any alternative to the two feet of compacted soil
must be determined using recognized and generally accepted methods.
3) The liquid flow rate comparison must be
made using the following equation, which is derived from Darcy's Law for
gravity flow through porous media.
Q/A = q = k ((h/t)+1)
Where:
Q = flow rate (cubic centimeters/second)
A = Surface area of the liner (squared centimeters)
q = flow rate per unit area (cubic centimeters/
second/squared centimeter)
k = hydraulic conductivity of the liner (centimeters
/second)
h = hydraulic head above the liner (centimeters); and
t = thickness of the liner (centimeters)
4) The alternative composite liner must meet
the requirements specified in subsection (b).
d) The hydraulic conductivity of the
compacted soil must be determined using recognized and generally accepted
methods.
e) The owner or operator
of an existing CCR surface impoundment that has not completed an Agency
approved closure before July 30, 2021 must submit an initial operating permit
application under Section
845.230
that demonstrates whether the CCR surface impoundment was constructed with
either of the following:
1) A composite liner
that meets the requirements of subsection (b); or
2) An alternative composite liner that meets
the requirements of subsection (c).
f) A CCR surface impoundment is considered to
be an unlined CCR surface impoundment if either:
1) The owner or operator of the CCR surface
impoundment determines that the CCR surface impoundment is not constructed with
a liner that meets the requirements of subsection (b) or (c); or
2) The owner or operator of the CCR surface
impoundment fails to document whether the CCR surface impoundment was
constructed with a liner that meets the requirements of subsection (b) or
(c).
g) All unlined CCR
surface impoundments are subject to the requirements of Section
845.700.
h) The owner or operator
of the CCR surface impoundment must obtain a certification from a qualified
professional engineer attesting that the CCR surface impoundment meets the
requirements of subsection (a) and submit the certification to the Agency in
the facility's initial operating permit application.
