Back when I was in the USN I was Oil King on a LPD. We carried about 750,000 of fuel oil (later, JP-5) for the boilers and about 20K of Avgas for helicopters. We went to the yards in Philly for drydock and a whole bunch of systems improvements including conversion to JP-5 from fuel oil. So I had to strip the tanks of all oil. First we were dang near empty when we arrived. Then we off-loaded something like 40,000 gallons. Then I had to use a stripping pump to completely evacuate all of the fuel tanks with the waste going into a 20k contaminated oil storage onboard. There wasn't 20k, more like a thousand gallons, mostly water. So they brought a special kind of barge alongside called a donut. I pumped the stripping waste into the donut. theoretically the lighter fluids (oil, avgas, etc) would float to the top of the donut and the waste water would descend down to the bottom of the bottomless collar of the donut. The shipyard would then pump the contaminated oil into some containment system of their own.

Even though I had just fallen off the turnip truck before joining the Navy, I had a bad feeling about what we were doing. But this was before Nixon's environmental legislation so it was okay. I guess the Navy probably sent 1-3 ships per month to the yards for major repairs resulting in probably 1k-3k gallons of contaminated water pumped into the river. Multiply that by 40 years of naval usage and you have an idea of the contamination from one well-run facility that contaminated the Chesapeake. How many shipyards are in the Chesapeake? Now the suburban population is expanding exponentially into the farmed areas. Everybody on a neighborhood or a 4 acre ranchette thinks they have to have a dark green lawn and no bugs. All of that run-off, largely uncontrolled, enters the estuaries of the Chesapeake.

It's going to take millennia to completely decontaminate that whole estuary of the shipyard and industrial waste alone. The problem of suburban waste is probably even more intractable. I guess a reasonable question to ask would be when will the contamination reach an inconsequential level?