500 4th Avenue is a new 12-story concrete residential building with 220,000 sq. ft. of space in Park Slope Brooklyn, NY. This project consists of a cast-in-place concrete structure supported on a mat foundation. Lower columns utilize 6000 psi concrete, while upper columns utilize 4000 psi concrete. The building is located approximately 22 feet away from NYC Subway Tunnel.In order to address NY Transit Authority requirements, we added a retaining structure using steel walers and timber lagging. This design was approved by the TA and construction was successfully completed.