|Federal Effluent Guidelines|
The new ELGs reflecting Best Practicable Technology Currently Available (BPT) are narrative in nature, for the most part requiring various measures to minimize impacts. The new ELGs reflecting Best Available Technology Economically Achievable (BAT), including a numerical limit for turbidity of 280 NTU, will be phased in over the next four years applicable to all construction sites that disturb 10 or more contiguous acres. If you are unfamiliar with EPA jargon and acronyms, BPT and BAT represent effluent limits based on minimum technology-based determinations required under the Clean Water Act. In other words, even if water quality standards in the receiving stream would not be adversely affected by the discharge of stormwater from your site, you are still required to install a certain minimum level of treatment technology.
EPA estimates that compliance with the new rules will cost the construction and development industries $8 million in 2010, $63 million in 2011 and $204 million in 2012, and once fully implemented, will cost the industry approximately $953 million a year nationwide.
The North Carolina Division of Water Quality will be required to implement the new ELGs in permits no later than is allowable in the federal implementation schedule. The overwhelming majority of construction sites are permitted under NCG010000 (which was reissued on January 1, 2010). You might not realize that you have sites which are covered under this general permit, because you are covered without need of an additional application once you receive approval of your erosion and sedimentation control plan.
For existing, ongoing projects (those on which land has been disturbed and which are discharging stormwater prior to February 1, 2010), compliance with BAT limits will be required as of August 2, 2011, for construction activity that disturbs 20 or more acres of land at one time, including non-contiguous land disturbances that take place at the same time and are part of a larger common plan of development or sale, and as of February 2, 2014, for construction activity that disturbs 10 or more acres of land at one time, including non-contiguous land disturbances that take place at the same time and are part of a larger common plan of development or sale. The BAT limit applies to the turbidity of the stormwater discharged from the project. The BAT limitation is a daily maximum of 280 NTU, or nephelometric turbidity units. This limitation represents an enormous improvement (from the developer’s or builder’s point of view) from the proposed limit of 13 NTU as instantaneous maximum. If you cannot picture 13 NTU, think of the water you draw from your tap. It is not far off. The water in most coastal rivers and streams is nowhere close to 13 NTU. The water quality standard for trout streams is 10 NTU. For all other streams, the standard is 50 NTU. In rainfall events (which is when you would be discharging stormwater), the turbidity in many streams may go well above 50 NTU.
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