Code of Federal Regulations Title 40. Protection of Environment § 40.146.6 Area of review

(1) The zone of endangering influence shall be:

(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 Theis equation illustrates one form which the mathematical model may take.

r=	((2.25KHt)/(S10x))
where:
X=	(4piKH(hw-hboxSpGb)/(2.3Q)

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=Hydrostratic head of underground source of drinking water (length) measured from the base of the lowest underground source of drinking water

S_pG_b=Specific gravity of fluid in the injection zone (dimensionless)

π=3.142 (dimensionless)

The above equation is based on the following assumptions:

(1) In the case of application(s) for well permit(s) under § 122.38 a fixed radius around the well of not less than one-fourth ( 1/4 ) mile may be used.

(2) In the case of an application for an area permit under § 122.39 a fixed width of not less than one-fourth ( 1/4 ) mile for the circumscribing area may be used.