Most of the wastewater collection in San Diego relies on gravity for the flow of wastewater through sewers to a treatment plant. In some instances, it is necessary to pump this wastewater uphill before it can return to a gravity flow. There are nine major pump stations in the Metropolitan Sewerage System and 75 smaller pump stations throughout the Municipal Sewerage System.
The largest Pump Stations are Pump Stations #1 and #2. Pump Station #1, located on East Harbor Drive, collects all of South San Diego's wastewater and has an average daily flow of 75 million gallons. It sends the wastewater flow north via the 8-mile South Metro Interceptor to Pump Station #2 which is located on North Harbor Drive. The average daily flow into Pump Station #2 is approximately 180 million gallons. This station pumps the wastewater to the Point Loma Wastewater Treatment Plant through two 87-inch diameter force mains. The two pump stations have 24-hour staffing.