5.1. The Director
shall select the methods by which the area of review shall be established for
each injection well or each field, project, or area of the State.
5.2. The area of review may be defined as
either:
5.2.1. The zone of endangering
influence as determined in accordance with subdivision 5.3.1; or
5.2.2. An area within a fixed radius around
each injection well as determined in accordance with subdivision
5.3.3.
5.3. Zone of
endangering influence. The zone of endangering influence shall be:
5.3.1. In case of application(s) for well
permit(s) under subsection 14.3, that area the radius of which is the
horizontal distance from the injection well in which the pressures in the
injection zone may cause the migration of the injection and/or formation fluid
into an underground source of drinking water; or
5.3.2. In the case of an application for an
area permit under subsection 14.4, the area of the project plus a
circumscribing area, the width of which is the horizontal distance for the
perimeter of the project, in which the pressures in the injection zone may
cause the migration of the injection and/or formation fluid into an underground
source of drinking water. Computation of the zone of endangering influence
should be based upon but not limited to, the parameters listed below and should
be calculated for an injection time period equal to the expected life of the
facility. The Theis equation is an example of one possible objective method:
5.3.2.a. Where "r" is equal to the radius of
endangering influence from injection well (length):
Where "r" is equal to the square root of a quantity which
consists of a numerator divided by the denominator where the numerator is equal
to 2.25 multiplied by "K" multiplied by "H" multiplied by "t"; and, the
denominator is equal to "S" multiplied by 10 to the "x" power. And, where "x"
is equal to a numerator divided by a denominator, where the numerator is equal
to four multiplied by "pi" multiplied by "K" multiplied by "H" multiplied [by
the quantity equal to the product of ("h(subscript w)" minus "h(subscript
bo)")] multiplied by "S(subscript p)G(subscript b)"; and, the denominator is
equal to 2.3 multiplied by "Q". (See Figure 47-13-5 at the end of this rule)
5.3.2.a. Where "r" is equal to the radius of endangering influence from
injection well (length):
5.3.2.a.1.
"K" is equal to hydraulic conductivity of the injection zone
(length/time);
5.3.2.a.2. "H" is
equal to thickness of the injection zone (length);
5.3.2.a.3. "t" is equal to time of injection
(time);
5.3.2.a.4. "S" is equal to
storage coefficient (dimensionless);
5.3.2.a.5. "Q" is equal to injection rate
(volume/time);
5.3.2.a.6.
"h(subscript bo)" is equal to observed original hydrostatic head of injection
zone (length) measured from the base of the lowermost underground source of
drinking water;
5.3.2.a.7.
"h(subscript w)" is equal to hydrostatic head of underground source of drinking
water (length) measured from the base of the lowest underground source of
drinking water;
5.3.2.a.8.
"S(subscript p)G(sub-script b)" is equal to specific gravity of fluid in the
injection zone (dimensionless);
5.3.2.a.9. "pi" is equal to 3.142
(dimensionless)
5.3.2.b.
The above equation is based on the following assumptions:
5.3.2.b.1. The injection zone is homogenous
and isotropic;
5.3.2.b.2. The
injection zone has infinite area extent;
5.3.2.b.3. The injection well penetrates the
entire thickness of the injection zone;
5.3.2.b.4. The well diameter is infinitesimal
compared to "r" when injection time is longer than a few minutes; and
5.3.2.b.5. The emplacement of fluid into the
injection zone creates instantaneous increase in pressure.
5.3.3. Fixed radius:
5.3.3.a. In the case of application(s) for
well permit(s), a fixed radius around the well may be used but not less than
1/4 mile, except for:
5.3.3.a.1. For Class1
hazardous waste wells, the area of review is a 2 mile radius.
5.3.3.b. In the case of an
application for an area permit, a fixed width may be used but not less than 1/4
mile for the circumscribing area.
5.3.3.c. In determining the fixed radius, the
following factors shall be taken into consideration: the chemistry of the
injected and formation fluids; geology; hydrogeology; population and
groundwater use and dependence; and historical practices in the area.
5.4. For Class 6 wells,
the area of review is the region surrounding the geologic sequestration project
where USDWs may be endangered by the injection activity. The area of review is
delineated using computational modeling that accounts for the physical and
chemical properties of all phases of the injected carbon dioxide stream and is
based on available site characterization, monitoring, and operational
data.
