KAUGER, J.:

¶ 1 This is the second appeal resulting from the Grand River Dam Authority's (GRDA) termination of the appellant, Chester Rouse (Rouse/employee). The first case, Rouse v. Grand River Dam Authority, 2014 OK 39, 326 P.3d 1139, involved the issues of whether the employee: 1) was barred by sovereign immunity from bringing a federal claim under the Fair Labor Standards Act, 29 U.S.C. §§ 201 et seq.; and 2) could assert a tort claim under Oklahoma law. The unanimous Court affirmed the trial court's dismissal of the employee's lawsuit because we determined that legislatively authorized administrative remedies were available through an appeal to the Oklahoma Merit Protection Commission (OMPC). The employee appealed to the OMPC, and then to the district court. This cause concerns the employee's appeal of the district court's order upholding the GRDA's termination of Rouse.

¶ 2 The employee raises 16 issues in his petition in error, some of which are either redundant, repetitive, related,1 or were not briefed on appeal.2 We consolidate the allegations of error into four succinct, broader encompassing issues. The four determinative issues are whether the trial court erred in: 1) its statutory interpretation and application of 74 O.S.2011 § 840-6.5;3 2) determining that the reasons for termination were not pretextual, or post hoc rationalizations; 3) determining that the employee was estopped from challenging the level of discipline imposed (termination); and 4) its review of the OMPC's ruling and the introduction of evidence. After consideration of all of the dispositive issues, we affirm the trial court.

FACTS

¶ 3 The appellee, the GRDA terminated the employment of the appellant, Chester Rouse (Rouse/employee) on February 17, 2012. The GRDA had employed Rouse at its electricity generating, coal fired plant in Chouteau, Oklahoma, since May of 1982. Rouse started as an auxiliary equipment operator, and in 1984 he was promoted to the position of control room operator where he remained until 2005. In November of 2005 he was made operations shift supervisor, a position in which he remained until he was terminated. Nothing in the record indicates specific performance issues during his tenure at GRDA prior to 2005. However, it appears that after he was placed in the position as of shift supervisor in November of 2005, his performance became a reoccurring issue.

¶ 4 In 2006 and 2007, his evaluations noted he was taking a lot of extra time on smoke breaks. In 2008, he was told that he was wasting excessive time smoking and reading fictional books while on duty. Apparently, Rouse spent so much time in the designated smoking room, the room became referred to as "Jay's Office" by other employees. Rouse's 2008 performance reviews rated him as needing improvement, inefficient, guilty of misconduct, and needing to set a better example for his crew. His 2009 evaluations again noted the need to set a better example for his crew.

¶ 5 Rouse was suspended without pay for seven working days on July 19, 2010. The reasons given for the suspension included: wasting time smoking and reading fictional books at work, having evaluations rated as needing improvement because of inefficiency and misconduct, lack of setting a good example for employees, negative and unprofessional behavior, and using bitter language. The GRDA initially considered a ten day suspension, but reduced it to only seven days after Rouse expressed remorse and commitment to improve in behavior and leadership.

¶ 6 At the time of his discharge, Rouse was a classified employee. The GRDA provided Rouse with notice of proposed disciplinary action of termination on January 11, 2012, and a pre-termination hearing was conducted on January 20, and February 6, 2012, giving Rouse an opportunity to respond. By letter dated February 17, 2012, Rouse was officially terminated based on Merit Rule 530:10-11-914 and 74 O.S.2011 § 840-6.5.5

¶ 7 The letter stated that Rouse was being terminated for inefficiency, misconduct, insubordination, inability to perform the duties of the position, and violations of the Oklahoma Personnel Act. Additionally, it referenced specific instances such as Rouse's: 1) incomplete work task assignment from August of 2011; 2) incompetence in handling an alarm event occurring on December 13, 2011; and 3) inattentiveness to a costly tube leak/overflow event on December 14, 2011. It also referenced the fact that staff members reported that Rouse was regularly unable to identify key problems and take the necessary actions appropriate for his position and it referenced the prior suspension without pay in 2010.

¶ 8 Just prior to the termination, on December 1, 2011, the GRDA got a new CEO and Director of Investments, Dan Sullivan (CEO). On December 15, 2011, the day after a significant flooding event had occurred and two days after a significant boiler chemistry event had occurred, Sullivan met with Rouse at Rouse's request. Apparently, Rouse requested to switch to an unclassified position, a switch which he previously had been denied. In an otherwise cordial meeting, Sullivan testified at the very end of their meeting Rouse made veiled threats about taking further action on a wage claim, but he really did not recall exactly what was said or explain what he meant by "veiled threats."

¶ 9 After receiving the February 17, 2012, termination letter, Rouse contacted the GRDA's human resources department about retiring in lieu of termination. Even though he was terminated, the GRDA's CEO, Sullivan, in deference to his years of service, accommodated Rouse by halting the termination and permitting him to retire instead, and even waiving the sixty day notice period. As a result, Rouse secured thousands more than he would have had he been terminated including his full salary and longevity pay until his retirement date of March 1, 2012, in addition to other retirement benefits such as an insurance subsidy of $200.00 that is not available to terminated employees.

¶ 10 The employee appealed his termination to the OMPC on March 9, 2012, alleging that he was fired as retaliation for cooperating with a Department of Labor (DOL) investigation which had resulted in the GRDA having to pay some employees back wages in May of 2010, for asking employees to show up 10-15 minutes before their shifts started so that they would start their shifts on time. The time frame for the back wages was January of 2008 to January of 2010. Rouse received a total of $506.10 before taxes as a result of the investigation.6

¶ 11 On appeal, Rouse sought reinstatement, as well as back pay and a promotion to an unclassified position. An administrative law judge (ALJ) held a two day trial on June 13-14, 2013, and issued a final order on August 16, 2013, finding that the GRDA had proven, by a preponderance of the evidence, just cause to discipline the employee for insubordination, inefficiency, and inability to perform his duties and that the discipline imposed was just.

¶ 12 During the proceeding, the GRDA argued that Rouse had agreed to waive an appeal to the OMPC in exchange for being allowed to retire rather than be terminated. However, the judge determined there was insufficient evidence of a "meeting of the minds" to such an agreement which would bar an appeal, but that Rouse accepted the benefits of retirement without taking any steps to clarify any misunderstanding even after the GRDA took steps to advice Rouse and his attorney of its understanding that an appeal right was waived. Accordingly, the judge determined the Rouse should be estopped from challenging the level of dicipline imposed (termination) but that even if such estoppel were inapplicable, the cumulative effect of his misconduct, the serious nature of the incidents concerned, and Rouse's refusal to acknowledge his misconduct or take any responsibility thereof justified termination.

¶ 13 On October 1, 2013, the OMPC issued its final order upholding the ALJ's decision and denying reconsideration. On October 7, 2013, the employee filed a petition for judicial review in the District Court of Mayes County, Oklahoma.7

¶ 14 On February 20, 2014, the trial court affirmed the ALJ and OMPC. On March 11, 2014, the employee filed an appeal and on June 5, 2014, filed a motion for this Court to retain the cause. We granted the motion to retain on June 19, 2014, and the cause was assigned to this office on November 13, 2014. This Court has long been committed to the rule that an administrative decision will be affirmed on appeal if it is supported by substantial evidence8 and it is not arbitrary or capricious.9

PURSUANT TO 74 O.S.2011 § 840-6.5, WILLFULNESS OR CULPABLE NEGLIGENCE IS NOT REQUIRED TO JUSTIFY TERMINATION FOR JUST CAUSE.

¶ 15 The employee argues that: 1) pursuant to 74 O.S.2011 § 840-6.5,10 the GRDA must prove that the employee acted with an element of willfulness or culpable negligence to justify any cause for termination of a classified employee; and 2) because the GRDA offered no specific evidence of Rouse's willful conduct or culpable negligence, the termination must be reversed. The GRDA contends that such intent or culpability is not required.

¶ 16 The pertinent language of 74 O.S.2011 § 840-6.5 provides that:

The purpose of the OMPC is to encourage prompt and equitable resolutions of grievances at the lowest possible level and encourage resolution of disputes quickly and informally.11 It also provides a system for the prompt, fair, and equitable disposition of appeals by employees.12

¶ 17 The statute is plain and unambiguous. When a statute is plain and unambiguous, there is no need to resort to statutory construction13 nor does any justification exist for the use of interpretive devices to fabricate a different meaning.14 The class of employees affected by the statute is clearly classified employees. Such employees can be discharged for any of a litany of things. The only conduct requiring willful behavior under the clear terms of the statute is "willful violation of the Oklahoma Personnel Act, the Merit Rules for Employment or of the rules prescribed by the Oklahoma Merit Protection Commission." Nothing in the terms of the act or its stated purposes or any previous decision by this Court requires that an employee terminated for "just cause" must, as Rouse argues, have been proved to have acted with an element of willfulness or culpable negligence. Accordingly, neither the OMPC nor the district court erred in refusing to infuse such a requirement into this cause.

THE RECORD REFLECTS THAT THE GRDA'S REASONS FOR TERMINATION WERE NEITHER PRETEXTUAL NOR POST HOC RATIONALIZATIONS.

¶ 18 The OMPC found that, despite the employee's valiant efforts to establish that the termination was pretextual to cover the CEO's alleged real motivation for firing Rouse as retaliation for filing a wage claim, there was "simply no evidence to support this." The trial court determined that he failed to establish any pretext because Rouse admitted to: 1) not completing the assignment given to him in August of 2011; 2) neglecting to check the equipment during his shift on December 14, 2011 and; 3) he did not specifically instruct his crew to check the equipment. Additionally, the trial court found that because of these same admissions by Rouse, he failed to demonstrate that the offered reasons for termination were post hoc rationalizations.

¶ 19 Rouse argues that the evidence is clear that his supervisors had knowledge that he complained to the DOL for not getting paid to show up for shifts 10-15 minutes early, and that it was not until he did complain, that, for the first time during his thirty year tenure, he faced discipline. He also insists that he was targeted to be discharged. GRDA argues that it had multiple, valid reasons for discharge unrelated to any DOL complaint and that the reasons for supporting discharge have been consistent with his poor evaluations.

¶ 20 Pretextual reasons for an employer's termination of an employee come into question when an employee is alleged to have been terminated in retaliation for things such as filing a workers compensation claim,15 or, in retaliation for reporting an employer's violation of the law and/or public policy.16 An employer can rebut an employee's claim by showing that the discharge was for a legitimate non-retaliatory reasons which obviously includes the inability to perform the assigned duties.17 This is precisely what the GRDA did in this cause.

¶ 21 The only evidence in the record supporting Rouse's claim that supervisors and the CEO knew that he filed a complaint with the DOL and that he was fired in retaliation for doing so, was Rouse's own "because I said so" testimony.18 This evidence is countered with substantial evidence of years of inefficiency, insubordination, and inability to perform the duties of his position, all of which were admitted to by Rouse. The wage claim was resolved by 2010, nearly two years before Rouse was terminated, and no one knew who actually called the DOL to complain about not getting paid for showing up 15 minutes early.

¶ 22 Additionally, the cited reasons for termination were supported by testimony and documentation because Rouse: 1) failed to complete a work assignment that every other supervisor managed to complete on time; 2) was inattentive and failed to react to a severe water chemistry condition on December 13, 2011; and 3) failed to take action during a water leak on December 14, 2011, that destroyed and damaged equipment.19 The GRDA was entitled to terminate Rouse for just cause and it appears that it did so and the employee has made no showing otherwise. Even if the three reasons as stated above had not occurred, the employee's inefficiency of the repetitive behavior of wasting time smoking and reading year after year while at work would have been more than adequate just cause for termination. Accordingly both the trial court and the OMPC are affirmed on this issue.

THE APPLICATION OF ESTOPPEL IS IMMATERIAL.

¶ 23 The employee was allowed to appeal his termination, despite accepting retirement benefits in lieu of termination. However, he argues that he should not have been estopped from challenging the level of discipline imposed — termination. He also contends that applying estoppel would be unfair and contrary to public policy in this cause. The GRDA argues that whether estoppel was appropriately applied to this cause is immaterial. We agree.

¶ 24 Estoppel is an equitable doctrine used to prevent one party from taking a position which is inconsistent with an earlier action that places the other party at a disadvantage.20 The employee was not estopped from appealing his termination and the GRDA's decision to terminate was supported by the evidence and was not arbitrary or capricious. Had Rouse's conduct, insubordination, inefficiency and inability to perform his duties not justified termination, then the application of estoppel may have been material to determining what level of discipline, if any, was appropriate. Nevertheless, the ALJ additionally determined that regardless of the applicability of estoppel, termination was appropriate.

¶ 25 Even if estoppel were incorrectly applied to this cause, because the GRDA's decision to terminate was supported by sufficient evidence, the application of estoppel was immaterial. Furthermore, the employee, while being represented by his attorney, accepted all the benefits of retirement and the financial effects of the termination were abandoned by the GRDA. If estoppel were applicable to this cause, it is the GRDA who should have been able to rely on it. However, the doctrine of estoppel is not ordinarily applicable to state agencies operating under statutory authority.21

THE TRIAL COURT DID NOT ERR IN ADMITTING EVIDENCE OF PRIOR DISCIPLINE.

¶ 26 The employee argues that he was denied due process because he was not provided with a specific written statement that his prior evaluations of spending too much time smoking, reading fictional books, and other incompetence would be used against him as a reason for termination after the events in December of 2011. He also then incongruously argues that he should have been given some type of progressive discipline without termination.22 The GRDA contends that his notice was adequate and that he was given progressive discipline leading to termination.23 Rouse's arguments regarding notice are unconvincing.

¶ 27 The facts demonstrate that since 2005, Rouse was progressively disciplined culminating in termination in 2012. In 2006, 2007, 2008, and 2009, his evaluations reflected his inefficiency, and insubordination. By 2010, the cumulative effect of these evaluations led to suspension without pay. By 2012, the cumulative effect of the suspension without pay, coupled with inability to perform assigned tasks and other significant incidents led to termination.24 To argue that there was no progressive discipline imposed ignores the facts altogether. Nevertheless, progressive discipline is not mandated in all causes, nor are public employers required to prove that some less severe disciplinary act would be ineffective before the imposition of a more stringent penalty.25 The system is designed to be conformable to a variety of circumstances and it is not a rigid program.26

¶ 28 The minimal statutory notice required by the employer is found in 74 O.S.2011 § 840-6.4 and it provides in pertinent part:

In the pretermination letter issued to Rouse on January 11, 2012, and attached to this opinion as an exhibit, Rouse was expressly notified that he had been disciplined in July of 2010 for a suspension without pay for inefficiency, misconduct, insubordination and inability to perform his job duties. He knew exactly why he was suspended in 2010 without pay because he actually had a pre-suspension hearing at that time, which he participated in and he was actually suspended without pay. He was expressly notified that this suspension was one of the reasons he was being terminated in 2012, in addition to the other enumerated events outlined in the notice. The employee has made no convincing showing that the statute was not followed nor does he argue that the statutory directives are on their face inadequate. Accordingly, we must determine that the trial court did not err in admitting evidence of prior discipline to support its decision to terminate.

CONCLUSION

¶ 29 An administrative decision will be affirmed on appeal if it is supported by substantial evidence27 and is not arbitrary or capricious.28 Pursuant to 74 O.S.2011 § 840-6.5,29 the GRDA was not required to prove that the employee acted with an element of willfulness or culpable negligence to justify the termination of its classified employee. The GRDA's reasons for termination were neither pretexual nor post hoc rationalizations, but were, instead, supported by substantial evidence. Estoppel was immaterial to this cause. Because the trial court did not err in admitting evidence of prior discipline, and the employee was given adequate notice of the reasons for termination, we affirm the OMPC and the trial court.

OKLAHOMA MERIT PROTECTION COMMISSION AFFIRMED: TRIAL COURT AFFIRMED.

ALL JUSTICES CONCUR.