I have missed something here....I thought the problem was HC (hydrocarbons), which equates to unburned fuel, last I checked. I used to be a mechanic and know a little something about HC/CO/NO emissions

I'm a little stumped by this aspect; Is the report saying that 600 gals of fuel are essentially "dumped" into the river as in "unburned fuel" (which would be extremely difficult to calculate), or that 600 gallons of fuel are burned in outboard motors daily (which would be relatively easy to estimate)? Because even if the engines only burned 50% of the fuel they process (I would suspect the percentage is higher) then is the report talking about the 300 gallons of unburned fuel, or are the motors using 1200 (600x2) gallons of fuel daily of which 50% (600 gals) is released as unburned fuel?

Now THAT'S about as clear as mud. Anybody understand what I'm saying here?