In circumstances where it is not practical to lock all external openings of tanks, for example wineries with extensive external storage tank farms, alternative security arrangements will be accepted. Security arrangements shall be based on documented risk assessment including specific reference to the area where tanks/silos or external opening intake pipes are located. As a guide this may include additional security fencing with a locked gate around the tank farm, a security controlled perimeter and or use of surveillance cameras and lighting. The controls must minimise the risk of access for malicious contamination and ensure that any deliberate contamination is detected.