Because of their size, in-ground interceptors are installed underground, outside the facility. NBC Rules and Regulations require that in-ground grease interceptors have a minimum depth of four feet, a minimum capacity of 500 gallons, and sufficient capacity to provide at least 24 hour detention for process flow. The sizing shall be based on fifteen gallons of wastewater per seat or chair per day, or based upon actual water usage where available.
All wastewater from food preparation operations and/or washing and clean‐up operations, including but not limited to pot sinks, pre‐rinse stations, wok stations, soup kettles, braising pans, mop sinks and wastewater generated from exhaust fan hood cleaning operations must discharge to the grease removal device. All automatic dishwasher wastewater, excluding pre‐rinse stations must bypass the grease removal device and be discharged directly into the sewer system downstream of the GRU. Garbage disposal units may be installed in facilities with properly sized and operational in‐ground passive type grease interceptors provided the interceptor has been properly designed for retention of settleable solids.
No wastewater, other than from kitchen fixtures or food processing equipment, shall discharge into the grease interceptor unless approved by the NBC in writing. Wastewater from sanitary sources such as toilets and bathroom sinks is prohibited from being discharged to the grease interceptor.
Inground Grease Interceptor Maintenance
The in-ground grease interceptor must be maintained according to manufacturer’s specifications. Weekly inspections of the in-ground grease interceptor must be conducted to determine the amount of grease collected in the unit. The grease interceptor must be pumped out before grease accumulates to the point where it could discharge to the NBCs sewer system and must be pumped out immediately when grease is observed in the effluent sampling tee. In addition, solids that accumulate within the interceptor must be monitored and pumped out as needed. The in-ground grease interceptor must be pumped out a minimum once each year by a licensed hauler.
Wastewater Discharge Permits require maintenance activities such as inspections, monitoring of solids accumulation and monitoring of grease layer thickness to be documented in a logbook. The logbook must be available to NBC personnel for their review. Physical receipts such as waste manifests for each pump-out are to be kept with the logbook.