(a) Conditions exist that are beyond the control of the persons granted such variance; or

(b) Special circumstances render strict compliance unreasonable, burdensome or impractical due to special physical conditions or cause; or

(c) Strict compliance would result in substantial curtailment or closing down of a business, plant or operation; or

(d) No other alternative facility or method of handling is yet available.

(2) The commission may delegate the power to grant variances to legislative bodies of local units of government or regional air quality control authorities in any area of the state on such general conditions as it may find appropriate. However, if the commission delegates authority to grant variances to a regional authority, the commission shall not grant similar authority to any city or county within the territory of the regional authority.

(3) A copy of each variance granted, renewed or extended by a local governmental body or regional authority shall be filed with the commission within 15 days after it is granted. The commission shall review the variance and the reasons therefor within 60 days of receipt of the copy and may approve, deny or modify the variance terms. Failure of the commission to act on the variance within the 60-day period shall be considered a determination that the variance granted by the local governmental body or regional authority is approved by the commission.

(4) In determining whether or not a variance shall be granted, the commission or the local governmental body or regional authority shall consider the equities involved and the advantages and disadvantages to residents and to the person conducting the activity for which the variance is sought.

(5) A variance may be revoked or modified by the grantor thereof after a public hearing held upon not less than 10 days’ notice. Such notice shall be served upon all persons who the grantor knows will be subjected to greater restrictions if such variance is revoked or modified, or are likely to be affected or who have filed with such grantor a written request for such notification. [Formerly 449.810 and then 468.345]