19F - RECEIVE AND FILE SEWER SYSTEM

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FOG Control Program Manual Based on the process flow chart, the majority of existing FSEs that do not have grease interceptors installed have been issued a "Conditional Waiver" from the requirement to install a grease interceptor. However, if the FSE has continued program violations or if the FSE is identified as a significant contributor of FOG (i.e., causes or contributes to blockage or SSO) to the sewer system, the "Conditional Waiver" may be revoked requiring the installation of a grease interceptor. An example Conditional Waiver Approval is available as Appendix I. 4.3.2.2 Other Requirements or Modifications There are other situations where specific requirements may be required by the FOG Control Program Manager. For example: • Authorization for the utilization of an additive • Requirement for increased maintenance frequency of the grease interceptor • Authorization for decreased maintenance frequency of the grease interceptor • Requirement to submit records (grease interceptor maintenance log and waste hauling manifests and other logs) to the City on a semi-annual basis 4.4 Grease Interceptors 4.4.1 OVERVIEW Grease interceptors are grease collection devices that separate FOG (or grease), solids, and water based on the principle of Stoke's Law. Stoke's Law describes the rising or settling of a particle in a fluid (water in this case). Simply put, under non -turbulent conditions in an interceptor, given enough time, particles that are lighter than water (e.g., grease) will rise to the surface and particles that are heavier than water (e.g., solids) will settle to the bottom. The facility's grease waste lines must be separated from the sanitary waste lines (Appendix J, Plumbing Segregation Example, provides an example of the plumbing that is required to be segregated from a grease interceptor. Facilities receiving conditional waivers must separate their grease waste lines from the sanitary waste lines in -case a grease interceptor is required to be installed at a future date. The different types of grease interceptors are discussed below. 4.4.2 GRAVITY GREASE INTERCEPTORS Gravity grease interceptors (GGI) are larger, volume -based grease -control devices that are typically installed outside and underground. GGIs can range in volume from 300 to 15,000 gallons. The flow of water through the GGI is controlled by the baffle tubes; therefore, it is critical that the baffle tubes are installed properly and kept in good condition for the GGI to function properly. A conceptual view or a typical GGI configuration is illustrated in Figure 4-2, Typical Conceptual Gravity Grease Interceptor Design — Side View, and in Appendix K, Grease Interceptor Standard Plan. 19F-193 12