dissenting.
I must respectfully dissent to the majority’s affirmance of the superior court’s reversal of the administrative decision made by the DMA Commissioner. Although I certainly sympathize with appellee and understand its reluctance to repay a substantial amount of money that it thought it was entitled to receive, the procedural and substantive law applicable to this case mandates a reversal of the superior court’s ruling. While there is no doubt that appellee accepted and received the payments “in good faith,” it was beyond the superior court’s power and authority to find and determine that appellee’s acceptance of such payments constituted a good faith reliance.
The contract between appellant and appellee specified that “the [appellant] shall make no reimbursement for any claim, or portion thereof, for which federal financial participation is not available. ...” However, I must respectfully disagree with any restrictive *889construction of this contractual provision so as to hold that it did not apply in the event that federal financial participation was disallowed retroactively. Such a conclusion is contrary to the plain meaning and obvious intent and spirit of the parties’ contract. It is uncontroverted that based upon the ruling of the federal government, which appellant vigorously opposed on behalf of appellee, there simply was no federal financial participation available.
“The court shall not substitute its judgment for that of the agency as to the weight of the evidence on questions of fact. . . . The court may reverse or modify the decision if substantial rights of the appellant have been prejudiced because the administrative findings, inferences, conclusions, or decisions are . . . [a]ffected by [an] error of law. . . .” OCGA § 50-13-19 (h) (4). In the instant case, the superior court concluded that the “failure to apply [a certain legal] principle was an error of law” which mandated reversal pursuant to OCGA § 50-13-19 (h) (4). That legal principle was the following: “ ‘ “[T]he equitable right to restitution from one unjustly enriched at another’s expense is terminated or diminished if circumstances have so changed that it would be inequitable to require full restitution.” [Cit.]’ [Cit.]” State of Ga. Dept. of Admin. Svcs. v. Pritchett, 160 Ga. App. 294, 295 (287 SE2d 290) (1981).
There has been no affirmative showing that any evidence adduced concerning DMA’s estoppel to obtain a refund was not fully considered during the administrative hearing process. See Francis Egg Farm v. Durrance, 169 Ga. App. 879 (315 SE2d 436) (1984) (construing OCGA § 34-9-105). Compare Rowell v. Transport Ins. Co., 153 Ga. App. 456 (265 SE2d 364) (1980) (construing OCGA § 34-9-105); Miller v. Travelers Ins. Co., 111 Ga. App. 245, 248 (1) (141 SE2d 223) (1965) (construing OCGA § 34-9-105). Estoppel is a question for the trior of fact unless it can be unequivocally established. Smithloff v. Benson, 173 Ga. App. 870, 874 (3) (328 SE2d 759) (1985).The evidence did not demand a finding in appellee’s favor as to the estoppel issue. See Graham v. Hogan, 185 Ga. App. 842 (366 SE2d 219) (1988). There is absolutely no evidence that appellee would be prejudiced by being required to make full restitution other than that it “had spent the money of the [state] which had been mistakenly advanced (which generally does not constitute ‘prejudice.’ [Cit.]).” (Emphasis supplied.) Gulf Life Ins. Co. v. Folsom, 256 Ga. 400, 406 (349 SE2d 368) (1986).
Accordingly, the superior court erred in basing its reversal of DMA’s decision on the purported administrative “failure” to have applied the legal principle of estoppel. There was no reversible administrative “failure” to apply that legal principle, but there was, instead, a controlling administrative factual determination as to the applicability of that legal principle based upon sufficient evidence. The superior *890court was without authority to substitute its judgment for that of the administrative agency. Georgia Real Estate Comm. v. Burnette, 243 Ga. 516 (2) (255 SE2d 38) (1979). Because I believe that the superior court had no authority to reverse the administrative determination, I must respectfully dissent.
Decided July 31, 1991 Reconsideration denied September 3, 1991 Michael J. Bowers, Attorney General, William C. Joy, Kathryn L. Allen, Senior Assistant Attorneys General, for appellant. Walter H. New, for appellee.I am authorized to state that Chief Judge Sognier, Judge Cooper and Judge Andrews join in this dissent.