I really have two responses to this, first, yes of course I can claim that, because a small handful of VC incidents over 30 years of course doesn't contradict my point that we don't currently have any VC in the harbor or bay. Anyway, second more in depth response:

Yes, there have been a few incidents where vinyl chloride has been detected in small areas in the watershed. These are brief points in time and not a consistent presence of VC. This is quite different I would think than dumping a huge amount of effluent that still has significant amounts of it into, effectively, the bay. And to be clear, one of your links doesn't show a vinyl chloride leak, it lists VC as a chemical of concern. Another shows that it was detected at just over 1 ppb in a very small area. The Frog Martin link says that was an area of concern because, in part, vinyl chloride was found in the area (at a concentration of 0.7 ppb). The sum of all of this is that the detection of virtually any vinyl chloride in any area in the Chesapeake watershed has been a Big Deal. So how is your conclusion that discharging effluent at 4 ppm into the sewers is totally cool?