CONCURRING OPINION BY
Judge LEAVITT.I join in the concurring opinion of Judge Leadbetter. I write separately because I do not agree with the majority opinion analysis for additional reasons. Specifically, unlike the majority, I do not believe the arbitrator’s award bears any rational relation to the language of the collective bargaining agreement. Unfortunately, as this Court has previously observed, there is “not much” that can be done about an arbitrator’s disregard of the CBA under the narrow certiorari standard of review. Bensalem Township v. Police Benevolent Association, 803 A.2d 239, 240 (Pa. Cmwlth.2002).
In September 2002, walk-through metal detectors and x-ray machines were installed in five different locations, two in the Capitol and three in adjacent government buildings, for the first time anywhere in the Capitol Complex. The Commonwealth assigned security officers the task of operating the x-ray machines and walk-through metal detectors. In addition, the Commonwealth assigned an armed capitol police officer to each location as back-up, in the event a threat to security should develop that required the exercise of police powers.1 In response, Fraternal Order of Police, Lodge 85 (Union), which represents the capitol police, filed a grievance, claiming that the operation of these devices was work that could only be done by capitol police, not by security officers. The arbitrator found in favor of the Union, and the Commonwealth now seeks to have the award vacated.
Article 44, Section 2 of the CBA states as follows:
Effective July 1, 2000, any and all new posts or assignments which could be staffed by Capitol Police or the Commonwealth of Pennsylvania Security Officers shall not be staffed in a manner that would reduce the current complement of Capitol Police Officers.
R.R. at 42a. This provision prevents the Commonwealth from assigning a security officer to a new post if it would have the effect of reducing the complement of capitol police officers. Here, because capitol police officers have been assigned to each of the five new security stations, the complement of capitol police officers has increased, not decreased. In spite of this fact, the arbitrator concluded that the operation of security devices was a post that could be assigned only to capitol police officers.
*92The arbitrator agreed that Article 44, Section 2 of the CBA was implicated, and he acknowledged, at numerous points in his award, that the five new stations in the Capitol Complex were “new posts.” However, the arbitrator reasoned that because the “Terry-type” stop and frisk search of a suspect had historically been the work of capitol police, it followed that the operation of x-ray machines and metal detectors was bargaining unit work “that should remain with the police officers.” Award at 12. It is impossible to join the words “new post” and “remain” in a single sentence. If a post is new, how then can it “remain?”2
The absence of logic is not a basis for setting aside an arbitration award given our limited scope of review. The Act of June 24, 1968, P.L. 237, No. 111, 43 P.S. §§ 217.1-217.10, commonly known as Act 111, governs labor relations between police and fire employees and their public employers. Act 111 is elliptical, and the word “grievance” appears but once.3 Our Supreme Court found that single appearance sufficient to support the conclusion that grievances must be resolved by binding interest arbitration.4 Pennsylvania State Police v. Pennsylvania State Troopers’ Association (Betancourt), 540 Pa. 66, 656 A.2d 83 (1995). Further, the Supreme Court has established that grievances arbitrated pursuant to Act 111 are subject to the narrow certiorari scope of review, not the essence test. Id. at 78, 656 A.2d at 89. It did so for two reasons. First, the only type of arbitration specified in Act 111 is interest arbitration, an extension of collective bargaining. Second, the Supreme Court believed that it was the legislature’s intent that labor disputes under Act 111 be resolved swiftly. Under this standard of review, courts are not free to set aside an award merely because it is against public policy. See City of Philadelphia v. Fraternal Order of Police, Lodge No. 5, 711 A.2d 1060 (Pa.Cmwlth.1998) (wherein this Court upheld an arbitration award reinstating an officer who had crashed a police cruiser under the influence of alcohol and cocaine because public policy was not a consideration). In sum, erroneous arbitration decisions that do not pass the essence test can, and do, survive narrow certiorari review.
Nevertheless, Betancourt did caution that an arbitrator may not exceed his authority under the narrow certiorari standard of review. Betancourt, 540 Pa. at 79, 656 A.2d at 90. The Commonwealth argues that the arbitrator here exceeded his authority by adding language to the CBA. Specifically, it contends that the arbitrator added to the terms of the CBA, and he was not permitted to do so. Indeed, the CBA states that,
[t]he arbitrator shall neither add to, subtract from, nor modify the provisions of this Agreement.
*93Article 27, Section 2, R.R. 39a. This Court has also stated that an arbitrator cannot add “previously non-existent provisions to a collective bargaining agreement.” Township of Ridley v. Fraternal Order of Police Lodge No. 27, 718 A.2d 872, 875 (Pa.Cmwlth.1998).
The arbitrator added a new provision to Article 44, Section 2 of the CBA, to reach the conclusion that the operation of an x-ray machine and a walk-through metal detector required, exclusively, the hands of a capítol police officer.5 The arbitrator adopted a “similarity principle” to reason that machine searches of purses are like a pat-down search of a suspect.6 This similarity principle is not very workable because it can just as easily support the conclusion that security officers should check members of the public entering buildings. Further, this principle is nowhere stated in the CBA. In applying his new rule, the arbitrator also disregarded the Commonwealth’s managerial prerogative to “plan, direct and control the operation of all equipment and other property of the Employer.” CBA, Article 2, Section 1; R.R. 37a. It is a small wonder that in two other arbitrations, also raising Article 44, Section 2 of the CBA, the Union was unsuccessful in pursuing its grievance.7
The controlling question here is whether the arbitrator exceeded his authority. In Ridley, we held out the possibility that an award that does violence to the language of the CBA can be set aside; however, we have never set aside an award for this reason. The most extreme example is Bensalem Township where this Court found that an arbitrator did not exceed his authority in awarding 21 months backpay even though the CBA expressly limited backpay to 12 months. Unless the arbitrator orders an illegal act or an act that the Commonwealth cannot do voluntarily, the arbitrator does not exceed his authority. Bensalem, 803 A.2d at 242. Thus, even where an arbitrator’s award does violence to the words of the agreement, “we cannot say, unfortunately, that [the arbitrator] exceeded his authority.” Id. at 242.
Because the arbitrator ordered the Commonwealth to do that which it could have done voluntarily, the award must be *94affirmed. However, the award cannot be supported by the language of the CBA. The Union has agreed in Article 44, Section 2 to allow the Commonwealth managerial discretion to decide whether to assign a new post to a capítol police officer or to a security officer. Whenever the Commonwealth exercises that discretion, the Union responds with a grievance. This disregard of the CBA erodes the value of collective bargaining under Act 111, but until Be-tancourt is revisited or Act 111 amended, no other result is possible.8
Judge LEADBETTER and Judge COHN JUBELIRER join in this concurring opinion.
. According to evidence presented to the arbitrator, security officers perform "routine security or introductory police work.” Commonwealth Ex 1, Reproduced Record at 16a (R.R-). They patrol assigned areas in the Capitol Complex "to protect and guard property or persons from fire, theft, trespass or other hazards.” Id. Their work can involve regulating “the activities of ... the general public, and may include performing limited police duties.” Id.
By contrast, capitol police officers do "general duty police work in protecting Commonwealth employees, public officials, the general public, property and facilities, and enforcing the Pennsylvania Crimes Code and the Motor Vehicle Code." Commonwealth Ex. 2, R.R. 16a.
The "work” of each overlaps. Capitol police "protect” property and enforce criminal laws. Security officers regulate "activities of the general public” by, inter alia, doing "routine security work.” Operating security machines seems work more appropriate for security officers.
.It is true that work cannot be shifted away from the bargaining unit without negotiation. American Federation of State, County, Municipal Employees, Council 13, AFL-CIO v. Pennsylvania Labor Relations Board, 150 Pa. Cmwlth. 642, 616 A.2d 135 (1992). The arbitrator tried to draw on this principle, reasoning that because a stop and frisk “Terry-type” search was bargaining unit work, mechanical "searches” could only be done by capitol police. A pat down search bears no relationship to putting a purse through an x-ray scanner, and it is sheer sophistry to argue otherwise.
. Act 111 states, simply, that "[pjolicemen and firemen ... have the right to an adjustment of settlement of their grievances or disputes in accordance with the terms of this act.” Section 1 of Act 111, 43 P.S. § 217.1.
. See Kurt H. Decker, Assessing Pennsylvania’s Police and Fire Collective Bargaining as Its Silver Anniversary Approaches, 29 Duquesne Law Review 695, 695-718 (Summer, 1991). Decker recommends, inter alia, a comprehensive legislative revision to give the Pennsylvania Labor Relations Board jurisdiction and in other ways fill the ellipses in the current statutory scheme.
. Notably, the Union’s chief witness acknowledged he had never before operated these machines.
. The Union, citing to County of Allegheny v. Allegheny County Prison Employees Independent Union, 476 Pa. 27, 381 A.2d 849 (1977) argues that past practice supports the arbitrator’s decision. Its reliance on this holding is misplaced. First, in Allegheny, the Supreme Court declined to use past practice as a tool for interpreting the CBA at issue. Second, the Supreme Court’s past practice discussion was based entirely upon the observations of a commentator, R. Mittenthal, Past Practice and the Administration of Collective Bargaining Agreements, Proceedings Of The 14th Annual Meeting Of The National Academy Of Arbitrators 30 (1961). Mittenthal makes clear that the only basis for using a past practice is its "clarity and consistency. A course of conduct which is vague and ambiguous or which has been contradicted as often as it has been followed can hardly qualify as a practice.” Id. at 32, 381 A.2d 849.
It is impossible to use past practice here. The metal detectors and x-ray machines in question were brand new. There simply was no past practice, let alone a clear and consistent practice.
.On February 8, 2005, Arbitrator Scott F. Bucheit held that the Commonwealth did not violate Article 44, Section 2 of the CBA by assigning a receptionist, not a capítol police officer, to the new post of providing security and reception services at a state building in Harrisburg. R.R. 76a-90a. On March 5, 2005, Arbitrator Martha R. Cooper, found that the Commonwealth did not violate Article 44, Section 2 of the CBA when it assigned to the new post of providing security in the office lobby to security officers because it did not reduce the complement of capítol police. R.R. 51a.-75a.
. See John P. McLaughlin and Patrick J. Harvey, Betancourt and the Narrow Certiorari Scope of Review of Appeals from Act 111 Grievance Arbitration Awards, 5 University of Pennsylvania Labor of Journal & Employment 427, 427-439 (Spring, 2003), for a strong criticism of the current state of the law in this area.