35 Ill. Adm. Code 730.106
Area of Review
Section 730
Section 730.106 Area of
Review
The area of review for each
injection well or each field, project, or area in Illinois must be determined
according to either subsection (a) or (b). The Agency may solicit input from
the owners or operators of injection wells within Illinois as to which method
is most appropriate for each geographic area or field.
a) Zone of Endangering Influence.
1) The zone of endangering influence must be the applicable of
the following:
A) In the case of an application for a well permit pursuant to 35
Ill. Adm. Code 704.161, that area the radius of which is the lateral distance
in which the pressures in the injection zone may cause the migration of the
injection or formation fluid into an underground source of drinking water; or
B) In the case of an application for an area permit pursuant to 35
Ill. Adm. Code 704.162, the project area plus a circumscribing area the width
of which is the lateral distance from the perimeter of the project area, in
which the pressures in the injection zone may cause the migration of the
injection or formation fluid into an underground source of drinking water.
2) Computation of the zone of endangering influence may be based
upon the parameters listed below and should be calculated for an injection time
period equal to the expected life of the injection well or pattern. The
following modified This equation illustrates one form that the mathematical
model may take.
r
=
√
2.25 kHt
S
x 10
x
where:
x
=
4 π KH (h
w
-
h
bo
x
S
b
G
b
)
2.3
Q
r
=
Radius of endangering
influence from injection well (length)
k
=
Hydraulic conductivity of the
injection zone (length/time)
H
=
Thickness of the injection
zone (length)
t
=
Time of injection (time)
S
=
Storage coefficient
(dimensionless)
Q
=
Injection rate (volume/time)
h
bo
=
Observed original hydrostatic
head of injection zone (length) measured from the base of the lowermost
underground source of drinking water
h
w
=
Hydrostatic head of
underground source of drinking water (length) measured from the base of the
lowest underground source of drinking water
S
p
G
b
=
Specific
gravity of fluid in the injection zone (dimensionless)
π
=
3.14159 (dimensionless)
3) The above equation is based on the following assumptions:
A) The injection zone is homogenous and isotropic;
B) The injection zone has infinite area extent;
C) The injection well penetrates the entire thickness of the
injection zone;
D) The well diameter is infinitesimal compared to "r"
when injection time is longer than a few minutes; and
E) The emplacement of fluid into the injection zone creates
instantaneous increase in pressure.
b) Fixed Radius
1) In the case of an application for a well permit pursuant to 35
Ill. Adm. Code 704.161, a fixed radius around the well of not less than 402
meters (one-quarter mile) may be used.
2) In the case of an application for an area permit pursuant to
35 Ill. Adm. Code 704.162, a fixed width of not less than 402 meters (one-quarter
mile) for the circumscribing area may be used.
3) In determining the fixed radius, the following factors must be
taken into consideration: the chemistry of injected and formation fluids; the
hydrogeology; the population and groundwater use and dependence; and historical
practices in the area.
c) If the area of review is determined by a mathematical model
pursuant to subsection (a), the permissible radius is the result of such
calculation even if it is less than 402 meters (one-quarter mile).