In 2009, EPA set forth to create new rules that would hold all construction sites responsible for the quality of water they were discharging directly from their projects.  The Effluent Limit Guideline (ELG) was created in hopes that water quality would improve nationwide.

Turbidity, or the clarity of water, is measured by the amount of small soil particles that are suspended in a given body of water.  The muddier the water, the more turbid it is.  We express this in NTUs or nephelometric turbidity units.