Sewer Service Charges are collected through the annual property tax bills issued by the County. A sample property tax bill can be seen here. The fee shown for residential properties is an annual rate (monthly rate multiplied by 12). The line item STEGE SEWER CHG are the fees assessed to your property by Stege Sanitary District. Note that this is only for the collection of sanitary sewer flows and that EBMUD charges separately for wastewater treatment.
You may look up your property tax bill here: Contra Coats County Treasurer & Tax Collector.