Customers in the Central Service Area or within the satellite areas of Meadowglade and Hockinson, all Tier 1 and Tier 2 areas, are charged a flat base rate per month for one (1) ERU. Customers within the City of Ridgefield, Tier 3, are also charged a System Integration Charge and City Operating Fee in addition to the base rate. An ERU is a sewer term for an “Equivalent Residential Unit” and represents the average flow for a residential household. Please note that Residential customers are billed bi-monthly, every other month, for two months of service. Commercial and industrial customers are billed monthly based on the corresponding usage of the system. Depending on your location, additional sewer service charges or fees may apply. For more information visit our Rates and Charges page or contact the District via email or phone at 360-750-5876.