Okla. Admin. Code § 785:25-1-4
Applicants who request a variance or waiver to rules specified in this chapter must demonstrate, and shall bear the burden of demonstrating that operations under the variance will equal or exceed the protections accorded by the particular rule for which the variance is sought. The variance may also be granted if the Board finds that the cost of compliance with the rule without a variance would impose significant expense without providing for additional safety of the construction for which the variance or waiver is sought, and integrity of the dam will not be adversely affected. The Board may require that a registered professional engineer certify that the variance or waiver being requested will not adversely affect the integrity of the dam.
Okla. Admin. Code § 785:25-1-4