The Cincinnati and Whitewater Canal Tunnel is a historic yet abandoned canal tunnel in the southwestern corner of the U.S. state of Ohio. Located within the village of Cleves near Cincinnati, it was constructed in 1837 as part of the Whitewater Canal system. Since the canal's closure, it has largely been forgotten, but it has been designated a historic site.
The historic site of the canal is open to the public and being used now.
The site is historic, but abandoned, so it is isn't currently being used. However, since the sentence stated it was historic and open to the public and being used, the agent found it confusing.