The Port Authority of New York and New Jersey voted Thursday to require a construction company overseeing La Guardia Airport’s redevelopment to pay for an outside “integrity monitor” after it admitted to overbilling at the World Trade Center site. The board of the company, Tishman Construction Corp., is headed by Dan Tishman, who led a panel appointed by New York Gov. Andrew Cuomo to reassess the airport’s design. The company is a subsidiary of AECOM, a major consulting firm. The Port Authority’s board approved on Thursday the monitoring requirement in light of Tishman’s deferred prosecution agreement in December with federal prosecutors in Brooklyn. According to that agreement, Tishman admitted to fraudulently overbilling clients and agreed to pay more than $20 million in restitution and penalties. The company agreed to reimburse the Port Authority more than $400,000 as part of the agreement, according to the agency. MORE ON THE PORT AUTHORITY Port Authority Advances Major Projects March 24, 2016 Port Authority Grapples With Competing Transit Projects March 23, 2016 New York Subway System Can’t Keep Pace With Growing Number of Riders March 23, 2016 Leaks at Hudson Yards Station Rile MTA Officials March 21, 2016 A Tishman spokesman said the company thinks “the monitor is unnecessary because of robust protocols already in place, but will comply with whatever is required by our client.” “There has never been an assertion of billing problems at LGA,” said the spokesman, referring to La Guardia. In a joint venture, Tishman and STV Construction Inc. are managing construction related to La Guardia’s redevelopment. Port Authority Executive Director Patrick Foye said the integrity-monitoring firm would report to the agency’s inspector general, and he described the arrangement as a routine step. “We believe that’s a useful—and ought to be an effective—prophylactic device,” he said. The design panel that Mr. Tishman headed recommended changes to La Guardia’s configuration, including a new, $310 million central hall as part of a replacement of Terminal B. A Cuomo spokeswoman said the Port Authority’s inspector general would hire “independent, outside staff to ensure the integrity of all the work done at La Guardia.” She noted the Tishman-STV joint venture was chosen through a competitive bidding process in 2013, before the airport design panel was created. WE WANT TO HEAR FROM YOU Have something to say about an article in Greater New York? Email us, along with your contact information, at email@example.com. Letters will be edited for brevity and clarity. Please include your city and state. The monitoring resolution noted that Tishman Construction has “substantial ongoing contracts” with the Port Authority. The agency’s decision to subject Tishman to an outside watchdog comes as Port Authority Chairman John Degnan, the top New Jersey appointee on the agency’s board, has questioned the growing estimates related to overhauling La Guardia. The agency’s official tally of costs for La Guardia’s redevelopment stands at $5.3 billion, exceeding some previous estimates by more than $1 billion. Top New York officials at the agency have disputed the $5.3 billion figure, saying it is misleading because it includes work going back to 2004 and other costs.