4 million tons of sediment, hundreds of millions of gallons of sewage, and enough freshwater to completely refill it
flowed into the Bay after the most recent storm. Algae feeding on the nutrients found in sewage and other pollutants produced probably the largest Bay dead zone since scientists have been keeping track, and to have all of this new organic matter on top of this summer's damage is, as the Japanese would say, "Oni ni Kanabou"- overkill. (Literally, not just a monster, but a monster with a huge club.) Here's another (short, clearer)
description of the process.