dissents and votes to reverse the order and judgment, deny the petition, and dismiss the proceeding, with the following memorandum: Franklin Woodruff was an employee of the petitioner New York City Transit Authority (hereinafter the NYCTA) for 22 years. He was employed as a stock handler, a nonsafety sensitive employee. Woodruff sustained injuries in an on-the-job accident which caused him to be absent from work for over 21 days. Pursuant to section 5.3 of Appendix E-l of the collective bargaining agreement between the NYCTA and the appellant Transport Workers’ Union of America, Local 100, AFL-CIO (hereinafter the TWU), of which Woodruff was a member, he was required to undergo a drug test before returning to work. This test, administered pursuant to the rules and regulations of the United States Department of Transportation, required Woodruff to supply a urine sample of a specified quantity within a three-hour period (see 49 CFR 40.193 [b] [4]). After failing to provide this specimen, Woodruff was examined by a medical doctor who found no medical condition limiting his ability to urinate (see 49 CFR 40.193 [d] [2]). His failure to produce a urine specimen within the allotted time was deemed a “refusal” to undergo the drug test. He was dismissed from service as mandated by the Drug and Controlled Substances Policy incorporated in Appendix E-l of the collective bargaining agreement.
After filing a grievance, the TWU ultimately brought Woodruffs dismissal to arbitration. The collective bargaining agreement gives the arbitrator “authority to decide all grievances and complaints but he/she shall not have the authority to . . . amend, modify or change [the] Agreement or any of its terms.” The arbitrator rendered an award that failed to make a finding that Woodruffs behavior was or was not a refusal to take the drug test. Instead, the arbitrator found that Woodruffs failure to supply the urine specimen was caused by his own actions in *545urinating beforehand. Thus, the arbitrator determined that Woodruff “constructively failed to comply with the legitimate request by the Authority for a urine test” and “violated a legitimate rule and regulation with regard to the testing.” The arbitrator found that termination was inappropriate for this failure and penalized Woodruff with loss of back pay upon his reinstatement.
The petitioners brought this proceeding pursuant to CPLR 7511 (b) (1) (iii) to vacate the award, limited to the ground that it was made in excess of the arbitrator’s power. The petitioners never invoked that branch of CPLR 7511 (b) (1) (iii) that provides for vacatur for the arbitrator’s imperfect execution of the award such that “a final and definite award upon the subject matter submitted was not made.” The Supreme Court granted the petition and vacated the award, recognizing that the arbitrator had not ruled on whether Woodruffs failure to provide the required specimen constituted a refusal to undergo the drug test. Nevertheless, the Supreme Court found that the arbitrator created a new category of infraction, namely, a constructive failure to comply, which modifies the collective bargaining agreement and creates a lesser penalty than dismissal. The Supreme Court held that such a determination was in excess of the arbitrator’s power.
Because the arbitrator never ruled on the central question presented to him, and therefore, never found that Woodruff was guilty of a “refusal,” it was sheer speculation by the Supreme Court to conclude that the award embodied an excess of power to the prejudice of the petitioners. Therefore, I disagree with an affirmance. At best, the arbitrator imperfectly executed the award. But, the petitioners did not invoke this ground for vacating it. Consequently, I would deny the petition resting on the sole ground of excess of authority.
In order to vacate an award on the ground that the arbitrator exceeded his or her power, the award must represent a completely irrational construction of the agreement, in effect making a new agreement for the parties (see Matter of National Cash Register Co. [Wilson], 8 NY2d 377, 383 [I960]; Weinstein-Korn-Miller, NY Civ Prac ¶ 7511.17b). On a motion to vacate an award a “court cannot examine the merits of an arbitration award and substitute its judgment for that of the arbitrator simply because it believes its interpretation would be the better one. Indeed, even in circumstances where an arbitrator makes errors of law or fact, courts will not assume the role of overseers to conform the award to their sense of justice” (Matter of New York State Correctional Officers & Police Benevolent Assn. v *546State of New York, 94 NY2d 321, 326 [1999]; see Weinstein-Korn-Miller, NY Civ Prac ¶ 7511.17a).
The award here was not irrational, and the petitioners never alleged that it was. The petitioners failed to challenge the arbitrability of the issue presented to the arbitrator (see CPLR 7503). They “may not revive what is, in actuality, a challenge to arbitrability in another guise. By submitting to arbitration, the [petitioners] ran the risk that the arbitrator would find [that Woodruffs failure to pass sufficient urine was not a refusal]” (Matter of United Fedn. of Teachers, Local 2, AFT, AFL-CIO v Board of Educ. of City School Dist. of City of N.Y., 1 NY3d 72, 83 [2003]). Once the arbitrator was free to make such a determination, he was also licensed to fashion an appropriate remedy (see Matter of United Fedn. of Teachers, Local 2, AFT, AFL-CIO v Board of Educ. of City School Dist. of City of N. Y., supra), despite the enumerated contractual limitation on his power (see Matter of Town of Callicoon [Civil Serv. Empls. Assn., Town of Callicoon Unit], 70 NY2d 907, 909 [1987]; Matter of National Coverage Corp. [Kulesh], 202 AD2d 368 [1994]).
If anything, the arbitrator, if he actually found that Woodruff did not refuse a drug test, exceeded his power by imposing punishment on him nonetheless, namely the loss of back pay upon reinstatement. Yet, the TWIT does not complain, and the TWU is the only party that can be said to have been prejudiced by the arbitrator exceeding his power in this way (see CPLR 7511 [b] [1] [iii]; Weinstein-Korn-Miller, NY Civ Prac ¶ 7511.12).
Finally, by eschewing the only viable ground for vacating this award—that it was so imperfectly executed that a final and definite award on the subject matter was not made—the petitioners discarded the opportunity for a new hearing and determination by the arbitrator (see CPLR 7511 [d]). Consequently, since the petitioners did not sustain the sole ground on which their petition was founded—that the arbitrator exceeded his powers—the petition should have been denied and the proceeding dismissed.