The 110-meter long gas tanker Schloss Mainau collided with the empty barge pushed by the Herkules IV at Barendrecht.    Both vessels were in a dense fog before they met in the head-to-head collision.   Luckily, the damage was limited to the bow as the Schloss Mainau.  It was carrying 1800 tons of propylene oxide, a highly flammable liquid, but the cargo holds remained intact.  Reports state no one was injured, but the Schloss Mainau was towed to dry dock at Heinenoord   The cause of collision is not known as both vessels had AIS onboard.