Recently, the Environmental Protection Agency (EPA) proposed a rule under the Clean Water Act entitled "Effluent Limitations Guidelines and Standards for the Construction and Development Point Source Category."

The proposed non-numeric effluent limitations guidelines (ELGs) would require contractors, developers, and others conducting land-disturbing activities to implement specific minimum best management practices (BMPs) for erosion control, sediment control, and pollution prevention. Certain sites could be required to implement stormwater treatment processes in addition to BMPs in order to meet the new standards, and other large sites may have to meet numeric turbidity limits. Treatment and numeric limits would be a significant change from existing standards, which focus chiefly on BMPs.

The proposed ELGs are intended to work in concert with state and local programs, establishing minimum requirements or a "floor" that would be applicable nationally. The ELGs, if promulgated, will be applied to construction and development sites as EPA, states, and tribes incorporate the new requirements into general and individual stormwater discharge permits. EPA has requested public comment on the proposed rule, and the comment period will remain open until Feb. 26, 2009.

In 2004, EPA decided not to issue ELGs for stormwater discharges from construction and development sites. The Natural Resources Defense Council and other plaintiffs filed suit, however, alleging that EPA's decision not to promulgate ELGs for the construction industry violated a mandatory duty under the Clean Water Act. The U.S. District Court and the Ninth Circuit agreed with the plaintiffs and established a timetable for EPA to promulgate the ELGs. In response, EPA designed the proposed rule to achieve cleaner streams and greener neighborhoods through implementation of erosion and sediment control measures and pollution prevention practices. According to EPA, sediment is one of the leading causes of water quality impairment nationwide. Construction activities such as clearing, excavating, and grading disturb the land, and the disturbed soil, if not managed properly, can wash off construction sites and enter streams and other bodies of water. Stormwater discharge from construction sites can cause a variety of physical, chemical, and biological impacts to water bodies.

In addition to requiring BMPs, the proposed ELGs mandate that construction sites disturbing ten or more acres at a time also would be required to install sediment basins or approved alternatives to treat stormwater discharge. Also, certain large sites of 30 acres or more located in areas with high rainfall and with high clay content soils would have to comply with a numeric limit on the allowable level of turbidity. The turbidity limit would be set to remove fine-grained and slow-settling or non-settleable particles contained in stormwater, since particles such as clays and fine silts contained in stormwater discharges typically cannot be effectively removed by conventional stormwater best management practices. To achieve this numeric limit of turbidity, many developers may have to treat and filter the stormwater discharge at their construction sites.

Industry officials have voiced concern over the proposed numeric discharge limit that potentially requires installation of expensive control technologies at large construction sites. In addition, some industry and trade groups oppose numeric standards generally in the context of stormwater regulation, preferring BMPs as more flexible and as adding less to the bottom line on construction projects compared to complying with numeric standards. On the other hand, EPA did not include any post-construction runoff controls in its proposal, as environmentalists had urged. Post-construction stormwater is regulated indirectly, through the requirements imposed on municipal stormwater systems. Environmentalists had argued that post-construction standards should be imposed directly on developers.

EPA estimates that the proposed rule will reduce the amount of sediment discharged from construction sites by up to 27 billion pounds each year, at a projected annual cost of $1.9 billion. EPA says that the benefits from the proposed rule include better protection of drinking water supplies, improvements in aquatic environments, and reduced need for dredging of navigation channels.