One of the ways that Mission Bay was filled was that it was used as a pretty major garbage dump from the 1870's up until after the 1906 earthquake. The area South of Channel street was known as "Dumpville" and by 1895 it covered as much as 20 acres and received almost 400 cartloads of garbage a day from the densely populated and rapidly growing South of Market area. This image is from a Sanborn map from the SF Public Library and it calls to mind the society of "ragpickers" that grew up around the disposal of garbage. Anything and everything that could be put to use was gleaned from the trash by whole families that lived in the area and made their living from the dump. Notice the piles of tin cans duly noted in the drawings. it's a pretty big building for just burning trash. Perhaps it was a facility for sorting garbage as well. The dredged cut along Channel Street still exsited throughout this time and it collected all manner of toxic effluvia to the point that instead of being called Mission Creek, it was commonly referred to as "Shit Creek".
Its rather ironic to note that Mission Bay served for many years as an informal "dump" area during its post industrial decline. Only a few years ago it was possible to wander about the open lots of Mission Bay and to stumble upon bedframes, old tossed out baby carriages, toilets, teddy bears, abandonded shoes, stoves, refrigerators, tires, whole vehicles and all other forms of detritus that people didn't wish to pay to offload at the city dump.