EPA issued a notice on November 1, 2010 indicating that it will be proposing a rule in December that would revise the numeric limit for turbidity in effluent limitations guidelines for stormwater runoff from construction and development because of an error in the way the agency calculated the limit. The correction rule will be available for public comment with final action on a revised limit taken by May 30, 2011. EPA also signed a direct final rule on November 1 to formally stay the numeric limit of 280 nephelometric turbidity units (NTUs) while it makes the correction. The construction and development effluent limits were issued on December 1, 2009, at 40 C.F.R. Part 450 and became effective February 1, 2010. Under the rule, discharges to the nation's waters associated with construction activity at certain sites may not exceed an average turbidity for any day of 280 NTUs.
An EPA fact sheet indicates that the agency must incorporate the new construction and development rule requirements, including the numeric limit, in its construction general permit by June 30, 2011. States are also required to incorporate the new rule requirements into any reissued National Pollutant Discharge Elimination System construction stormwater permits. EPA said it estimates that 16 states will need to incorporate the new effluent limitations guidelines in their general permits.