In March, EPA published a new Final Rule that revised a 2009 Final Rule addressing stormwater discharges from its Construction and Development (C&D) point source category.  The March revision withdrew the numeric turbidity effluent limitation and monitoring requirement and made certain other changes and clarifications.  (Federal Register: March 6, 2014 Federal Register)  The revised rule results from litigation filed by a number of entities, Wisconsin Builders Association, et al. v. EPA, Case Nos. 09-4113, 10-1247, and 10-1876 (7^th Cir.), and specifically from a settlement agreement entered between the parties on December 10, 2012.  (Settlement Agreement).

While several parts of the original 2009 Final Rule raised concerns, attention focused substantially on the numeric limit for turbidity.  For the first time in C&D regulation, EPA imposed a standard or limit of 280 nephelometric turbidity units (NTU) for  discharges from a C&D site.  Historically, turbidity impacts from a construction site have been evaluated on a comparative basis using in-stream turbidity measured upstream and compared with a similar measurement downstream from the construction activity.  Ordinarily any increase of 50 NTU or less would be considered to comply with the development’s construction stormwater permit or regulatory obligations.  The Associated General Contractors of America estimated that the numeric limit for turbidity would have imposed a cost of around $10 billion dollars a year.  Thus, the industry focused on this number in the challenge to the final rule, raising specific questions about the scientific basis EPA relied on in developing the numeric limit.  (Stormwaterone   Article).  The concerns raised specifically about the numeric limits were prompted EPA to stay that portion of the rule, and neither EPA nor the various authorized States were required to implement the limit while the court challenges proceeded leading to the Settlement Agreement.

Despite withdrawing the numeric turbidity limit, EPA indicated in its Summary of the revised Rule that it has reserved the section for potential revision if it decides to “. . . promulgate additional effluent limitations guidelines and monitoring requirements in a future rulemaking.”  (Subsection II. B. 8., 79 FR 44, p. 12665).  Thus, the idea of numeric turbidity limits may reappear as the Agency continues to evaluate the issue.