Institute
for Regional Studies of the CaliforniasInstitute
for Regional Studies of the CaliforniasSewage collection, treatment, and disposal are critical elements of the infrastructure of the International Border Planning Area. The San Diego region has adequate collector and treatment infrastructure, although the system is aging and subject to frequent failures in the collector system. San Diego will be challenged to finance and implement upgrades to the current system and provide new capacity to accommodate projected population growth in the future. Tijuana's collector and treatment system has grown rapidly in recent years, but many areas in canyons and new informal settlements are unsewered and rely on pit privies, septic systems, or discharge of wastewater into canyons. Approximately 85 percent of Tijuana's population is covered by sewerage service. The rapid population growth rate of Tijuana, combined with its difficult topography and the higher cost of retrofitting neighborhoods that have resulted from land invasions, have made it very difficult for Baja California authorities to meet the full demand for these services. Tijuana also faces the issue of retrofitting the aging conveyance infrastructure.
Currently, all wastewater generated in San Diego's portion of the International Border Planning Area is pumped north through the South Metro Interceptor Sewer to the Point Loma Wastewater Treatment Plant for treatment and disposal through the ocean outfall. In order to accommodate future urban expansion and to provide a source of reclaimed water in the South Bay, the City of San Diego is building new sewer treatment and water reclamation facilities to serve this area. The Grove Avenue Pump Station (GAPS), reclamation sewer, and sludge pipelines are three components of an integrated wastewater treatment plan for the South Bay, including the San Diego portion of the border planning area. The GAPS and reclamation sewers will divert reclaimable quality wastewater to the South Bay Water Reclamation Plant (SBWRP) for treatment. Since there will be no sludge processing facilities at the SBWRP, a 10-inch (25.4-centimeter) diameter sludge pipeline will convey raw (undigested) sludge to the South Metro Interceptor Sewer. Ultimately, the sludge will be processed at the Point Loma Wastewater Treatment facility. Construction of these facilities is under way and will be completed by mid-2001 to serve the SBWRP. The Otay River Pump Station is a proposed facility that would convey an additional eight million gallons per day (350 liters per second) of wastewater effluent to the South Bay Water Reclamation Plant.
The South Bay Water Reclamation Plant, located on Dairy Mart Road adjacent to the International Wastewater Treatment Plant, will treat raw sewage and produce reclaimed water. It will treat 15 million gallons per day (657 liters per second) of average flow and up to 18 million gallons per day (789 liters per second) during wet weather flow. All flows through the reclamation plant will receive a minimum of secondary treatment, with up to 15 million gallons per day (657 liters per second) of flow receiving tertiary treatment for reuse. Any effluent not being reused will receive secondary treatment and will be discharged to the Pacific Ocean through the South Bay Ocean Outfall.
The South Bay Outfall (SBO) is jointly owned by the City of San Diego and the federal government. The SBO conveys treated wastewater effluent from the International Boundary and Water Commission's International Wastewater Treatment Plant and the City of San Diego's South Bay Water Reclamation Plant, currently under construction, to the Pacific Ocean for final disposal. The current design flow rates are 174 million gallons per day (7,623 liters per second) (average dry-weather flow) and 333 million gallons per day (14,588 liters per second) (peak flow). The 174 million gallons per day (7,623 liters per second) flow is allocated as 100 million gallons per day (4,381 liters per second) for the IBWC for Mexican effluent and 74 million gallons per day (3,242 liters per second) for the City of San Diego.
Originally constructed in the mid-1960s, the 30-inch (76.2-centimeter) diameter Emergency Connection provides relief to the Tijuana sewerage system by diverting up to 13 million gallons per day (570 liters per second) of sewage to the City of San Diego's sewerage system on an emergency, as-needed basis. In October 1991, a diversion connection was built in Tijuana to divert flows from the Tijuana River low flow channel to the emergency connection to prevent sewage from flowing into the Tijuana River. Ultimately, this connection will be discontinued when the International Wastewater Treatment Plant is expanded and capable of regularly treating these flows.
The Mesa de Otay and Zona Centro portions of the International Border Planning Area are served by a system of collectors that transports sewage by gravity from the hills and mesas to main collectors in the Tijuana River Valley. From there, the sewage is transported to Pump Station 1, located at the low spot in Tijuana's collector system, which is adjacent to the International Wastewater Treatment Plant. There is also an interceptor located in the channelized Tijuana River that diverts renegade sewage to the pump station and collector system. Most of the Zona Centro of the planning area is served fully by sewage service, but coverage on Mesa de Otay is incomplete, particularly in the growing spontaneous settlements on the eastern portion of this area.
From Pump Station 1, the sewage is pumped up over a series of hills to the ridge above Playas de Tijuana where it enters an open canal and is transported some 3.1 miles (5 kilometers) south to the treatment plant at San Antonio de los Buenos. Another pump station lifts sewage from the area of Playas de Tijuana adjacent to the ocean to the conveyance canal to San Antonio de los Buenos. In the past, the system from Pump Station 1 to the treatment plant has been plagued by pump failures and breaks in the main conveyance pipe, resulting in diversion of sewage flows to the Tijuana River channel, to the emergency connector, or down the canyons that drain into the Tijuana River Valley in San Diego. In order to address these problems, the Parallel Conveyance System project will soon be completed. It was approved by the Border Environment Cooperation Commission and financed by Mexican government resources as well as loans and grants from the North American Development Bank. This project will upgrade the pumps and provide redundancy in the conveyance system to facilitate system upkeep without having to divert sewage flows from San Antonio de los Buenos. This project will also upgrade the treatment plant at San Antonio de los Buenos so that it can operate effectively at approximately 25 million gallons of sewage per day (1,095 liters per second).
As unsewered areas of Tijuana are hooked up to the system and as services are provided to newly urbanizing areas, the sewage treatment capacity of Tijuana will have to be expanded beyond that currently provided by the International Wastewater Treatment Plant and the San Antonio de los Buenos Treatment Plant. A number of alternatives are now under consideration, including building four new sewage treatment/water reclamation plants at different sites in urban Tijuana.
 Photo |
| International Wastewater Treatment Plant with internationla border, Zona Centro, Zona Río, and Mesa Otay delegation in the background. 2000. |
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