POINT LOMA WASTEWATER TREATMENT PLANT
Opened in 1963, the Point Loma Wastewater Treatment Plant (PLWTP) treats approximately 175 million gallons of wastewater per day generated in a 450-square-mile area by more than 2.2 million residents. Located on a 40-acre site on the bluffs of Point Loma, the plant has a treatment capacity of 240 million gallons per day (mgd).
The PLWTP Operations Building & Visitors Center houses the Control Center, which monitors and controls every phase of the treatment process. The facility is staffed 24 hours a day, 365 days a year. Plant operations can also be monitored from Metropolitan Wastewater's Communications Center in Kearny Mesa. The PLWTP Operations Building also houses Process Control Laboratories where samples of wastewater from every stage of treatment are analyzed.
The plant uses an advanced primary treatment process under a waiver granted by the U.S. Environmental Protection Agency. Although scientists maintain that advanced primary is more than adequate to protect the ocean environment, it is possible that secondary treatment may be required when the current waiver expires.
The Point Loma Ocean Outfall was built in 1963 to discharge treated wastewater into the ocean. It was extended from a length of 2 miles to 4.5 miles in 1993. The outfall is 12 feet in diameter and operates by gravity feed. It ends 320 feet below the surface with a Y-shaped diffuser to ensure wide dispersal of treated effluent into the ocean.
SECONDARY TREATMENT WAIVER APPLICATION
The Point Loma Wastewater Treatment Plant (Point Loma WTP) is a terminal treatment facility of the San Diego Metropolitan Sewerage System (Metro System). The discharge of treated wastewater from the Point Loma WTP to the Pacific Ocean is regulated by a joint National Pollutant Discharge Elimination System (NPDES) permit issued by the California Regional Water Quality Control Board, San Diego Region (Regional Board) and the U.S. Environmental Protection Agency (EPA). In accordance with provisions of Section 301(h) of the Clean Water Act, the existing five-year Point Loma NPDES permit establishes the following modified secondary treatment standards:
• A monthly average percent removal of total suspended solids (TSS) of 80 percent,
• An annual average biochemical oxygen demand (BOD) percent removal of 58 percent, and
• A TSS monthly average effluent limit of 75 milligrams per liter (mg/l).
The City of San Diego, as operator of the Metro System, requests renewal of the Point Loma NPDES permit and renewal of existing modified secondary treatment standards for BOD and TSS. During the prior five-year NPDES permit period, the City complied with these BOD and TSS requirements by a significant margin. During 2006, for example, the Point Loma WTP effluent averaged a TSS concentration of 35 mg/l. Additionally, during 2006 the City achieved an average TSS percent removal of 88 percent and an average BOD percent removal of 65 percent. In seeking renewal of NPDES requirements, the City does not request any increase in allowable flow rates, effluent concentration limits, or effluent mass emission limits established in the current Point Loma WTP NPDES permit.
INTERNATIONAL BOUNDARY & WATER COMMISSION
The International Boundary & Water Commission (IBWC) is the agency charged with finding solutions to the problem of untreated wastewater flowing into San Diego's South Bay area from Mexico. Organized in 1889, the IBWC has responsibility for establishing the boundary and water treaties between the United States and Mexico and settling differences that may arise out of these treaties. The IBWC is a binational body with a U.S. Section and a Mexican Section, each headed by an engineer-commissioner appointed by their respective Presidents. The U.S. Section is headquartered in El Paso, TX. For more information, go to: http://www.ibwc.state.gov/