The new $450,000 light installation around the restored Washington Sq. Arch will go on for the first time at 5:30 p.m. Wed., Dec. 29, in a celebration that includes caroling by the Bond St. Euterpean Singing Society of the Merchant’s House Museum and refreshments from the Sullivan St. Bakery. Parks and Recreation Commissioner Adrian Benepe will turn on the new lighting system, the final element in the complete restoration of the arch. Domingo Gonzalez Associates designed the lighting that includes multiple elements to emphasize various restored features of the Washington Sq. Arch.