Regulatory & Policy Background
In 1972, under the authority of Public Law 92-500, the Federal Water Pollution Control Act, Environmental Protection Agency (EPA) created the National Pollutant Discharge Elimination System (NPDES). This was intended to control discharges to the Nation's waters from industrial, commercial, and municipal point sources; these discharges presented a threat to water quality and public health. Initial efforts focused on traditional pollutant discharges from industrial manufacturing processes and municipal Wastewater Treatment Plants (WWTP).
Clean Water Act
Later amended to become the Clean Water Act (CWA), this law provides broad authority for EPA or States (authorized by EPA) to issue NPDES permits. Specific reporting requirements are established in the permits to require monitoring and reporting of discharges. The CWA establishes two types of standards for conditions in NPDES permits: technology-based standards and water quality-based standards. These standards are used to develop effluent limitations and special conditions in NPDES permits.
Numeric effluent limitations establish pollutant concentration limits for effluents at the point of discharge. Section 402(a)(1) authorizes the inclusion of other types of conditions that are determined to be necessary, known as special conditions, in NPDES permits. Special conditions can include requirements for best management practices (BMPs) to control Wet Weather Flows (WWF).
Wet Weather Flows
Pollutants in WWF discharges from many sources remain largely uncontrolled. The EPA in both its 1992 National Water Quality Inventory (EPA, 1994a) and its 1995 Report to Congress (EPA, 1995a) cited pollution from WWF as the leading cause of water-quality impairment. WWF from both point and non-point sources is one of the largest remaining threats to water quality, aquatic life, and human health that exists today. The National Research Council (1992) concluded that correction of NPS pollution problems is a major priority to surface water protection and should be implemented as part of a large-scale aquatic ecosystem program.
Meeting Clean Water Standards
The treated wastewater (effluent) that our Treatment Plant discharges into the Ocean is subject to stringent water quality standards specified in our discharge permit. This permit-part of a program called the National Pollutant Discharge Elimination System, or NPDES-is issued by the San Francisco Regional Water Quality Control Board. Permits are usually renewed every five years. Specific discharge standards are determined by the Regional Board on a case-by-case basis and often differ from one wastewater treatment plant to another. For example, a treatment plant that discharges into the Bay or river will have more stringent standards than North San Mateo County Sanitation District (NSMCSD), which discharges into the ocean.
NPDES permits specify maximum permissible levels for various technical measurements, including the quantity of effluent discharged in wet and dry weather (flow rates), plus:
- Acute Toxicity
- Carbonaceous Biochemical Oxygen Demand
- Grease and Oil
- Settleable Solids
- Suspended Solids
Although no specific discharge limitations have been set, NSMCSD's discharge permit also requires regular monitoring of eighty-three other water quality standards. In addition the discharge permit requires monitoring at the point of discharge into the Ocean. Separate permits address disposal of the solids removed from wastewater and the quality of stormwater runoff.