Here's a simple guide to turbidity measurement:
The Baywatch folks take samples back to a lab instrument that is much more accurate, but the measurement is still "how much light penetrates the sample". It does not discriminate silt vs organics but repetitive historic samples correlate with rainfall events, seasons, etc. These spikes into 200+ NTU have only occurred since airport construction.
DEP is now ordering NTU measurements at some outfalls daily or even every 8 hours - these are locations at the project boundary so there is no confusion about the source. All measurements cited by DEP in the Consent Orders were taken at these locations.
here's a key map to the locations:
Monday, March 1, 2010