The area of review shall be defined as follows:

(a) Class II wells. The area of review for Class II permits and area permits shall be defined by a fixed radius as described in § 146.6(b) (1) and (2) of this chapter except that the radius shall be one-half mile.

(b) Class I and III wells. The area of review for Class I and III wells are well fields which may be either:

(1) An area defined by a radius two and one-half miles from the well or well field; or

(2) An area one-quarter mile from the well or well field where the well field production at the times exceeds injection to produce a net withdrawal; or

(3) A suitable distance, not less than one-quarter mile, proposed by the owner or operator and approved by the Director based upon a mathematical calculation such as that found in § 146.6(a)(2) of this chapter.