As a result of a California case against the EPA by the Natural Resources Defense Council, EPA published its proposed changes to the construction stormwater permitting rules on November 28, 2008. The rule, when finally implemented, has been projected to have an estimated $1.9 billion cost to the construction industry. EPA will accept public comments on the proposed rule through February 26, 2009.
Preempting less stringent state and local rules, the new stormwater rule proposes major revisions to the construction National Pollutant Discharge Elimination System ("NPDES") permit program administered under the federal Clean Water Act. It will establish technology-based Effluent Limitations Guidelines and New Source Performance Standards for the "Construction & Development" point source category.
The most significant impacts of this rule would be that all construction and development point sources would be required to implement tighter erosion and sediment controls, proposed by EPA as non-numeric effluent limitations. Compliance with the effluent limitations will require the use of specific minimum "best management practices." In addition, the proposed rule incorporates mandatory pollution prevention measures at all construction sites.
As examples of the new requirements, for common drainage locations serving 10 or more acres disturbed at one time, the rule requires the construction of sediment basins to control and treat stormwater runoff. The sediment basin must be designed according to regulatory specifications, unless the permitting authority allows the use of alternative controls capable of achieving the same or better level of pollutant reduction.
An example of the detailed hydrologic and soils analysis to be required under the rule, which will be new to the industry, if construction will take place at a site with 10% or greater by mass of soils less than 2 microns in diameter and with an annual rainfall erosivity factor of 50 or higher, maximum turbidity for discharges from construction activities of 30 or more acres is 13 NTU (Nephelometric turbidity units).
In conjunction with the proposed rule, EPA is soliciting comments and data on a number of the technical details underlying the rule. Some of the multitude of topics for which EPA is soliciting comments and data include: (1) whether effluent limitations should be developed for pH; (2) whether the annual R-factor used to determine whether construction activity must comply with turbidity limits is appropriate; (3) whether porous baffles in sediment basins should be adopted as a nationwide requirement; (4) whether dischargers will be able to meet a numeric turbidity limit using passive rather than active treatment; (5) whether EPA should set a turbidity limit in the range of 50-150 NTUs based on passive treatment rather than active treatment systems; and (6) feasibility and ease of implementation of the proposed 10% clay content applicability criteria.