EPA Introduces New Stormwater

EPA Introduces New Stormwater Guidelines and Standards

EPA has finalized national effluent limitations guidelines (ELG) and new source performance standards (NSPS) for construction and development sites to help address improvement of water quality throughout the nation. While the standards focus on discharges occurring during stormwater events, these new guidelines affect all discharges of pollutants from construction activities into waterways, including dewatering and concrete washout.

Non-numeric ELGs: All construction and development sites will be required to meet a series of non-numeric ELGs beginning in February 2010. These are intended to minimize any discharge from a construction site to a water body, and may include:

• Strict stormwater runoff control from sites
• Minimization of steep slope disturbances, amounts of exposed soil, and soil compacting
• Stabilization of soils
• Provision and maintenance of natural buffer zones
• Discharge control from non-stormwater activities like dewatering, truck and tire washing, concrete washouts, etc.

Numeric Limits: Construction and development sites must sample stormwater discharges and comply with the numeric limitation for turbidity of 280 NTU (nephelometric turbidity units). EPA is phasing in the numeric effluent limitations over four years to allow permitting authorities adequate time to develop monitoring requirements and to allow the regulated community time to prepare for compliance with the numeric effluent limitation. These phases consist of:

• Sites that disturb 20 or more acres at one time will be required to conduct monitoring of discharges from the site and comply with the numeric effluent limitation beginning 18 months after the effective date of the final rule (August 1, 2011).
• Sites that disturb 10 or more acres at one time will be required to conduct monitoring of discharges from the site and comply with the numeric effluent limitation beginning four years after the effective date of the final rule (February 2, 2014).

Although streams and rivers naturally carry sediment loads, discharges associated with construction activity can elevate these loads to levels above those in undisturbed watersheds. Discharges from such sites may also increase the proportion of silt, clay and colloidal particles, along with other pollutants in receiving streams because these fine-grained particles may not be effectively managed by conventional erosion and sediment.

EPA stated the proposed rule is designed to achieve cleaner streams and waterways 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. Activities such as clearing, excavating, and grading can lead to soil erosion into streams and other bodies of water. This discharge can cause a variety of physical, chemical, and biological impacts to water bodies.