1. A system for continuously monitoring the intake of a fresh water system to detect and contain a hazard, the system having an intake pipe, the apparatus comprising: (a) at least one hazard-detector within the intake pipe sensing the presence of a hazard in the water in the intake pipe; (b) a sampling unit associated with the at least one hazard-detector, the sampling unit further comprising a gate and gate valve in proximity to the at least one hazard-detector, the gate and gate valve diverting a sample of water to a collection unit when a hazard is detected; and (c) a shut-off valve for simultaneously with diverting the sample shutting off further water intake in the intake pipe when a hazard is detected.