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The responses below apply to businesses and institutions that prepare or serve food.

Why is the issue of overflowing sanitary sewers important?

Overflowing sewers release disease-causing bacteria, viruses and other pathogens to the natural waters of the state. Public health, safety and welfare can be jeopardized by sewage in waterways.

Is there a law against overflowing sanitary sewers?

Yes. The federal Clean Water Act and comparable state water quality regulations prohibit wastewater discharges into the waters of the state without a permit. An overflowing manhole is an example of a prohibited discharge.

Is there a difference between grease traps and grease interceptors?

Both devices do the same thing - separate and retain free-floating oils and grease. The two terms can be used interchangeably. Grease traps are most often referred to as the small, in-floor units. Grease interceptors are the larger devices located outside in the ground that offer much longer hydraulic retention times. Both small and large devices are marketed as grease interceptors.

What does FOG stand for?

Animal and vegetable Fats, Oils and Greases washed off of cookware, bake ware and serving ware.

I plan to purchase or lease an existing building for a food service establishment. It does not have a grease interceptor or the grease interceptor is inadequate. What will the Town of Cary require?

In cases where there is a physical hardship in place for installing a properly-sized grease interceptor, the Town of Cary may require multiple point source grease interceptors for the control of fats, oils and grease inside the facility.

How do buildings with retail flex spaces provide adequate grease interceptors for tenants within the building?

For new construction, a good approach is installation of a common grease waste lateral that is plumbed to a community grease interceptor. This method ensures that each facility within the flex space can provide for sufficient grease interception without having to install separate interceptors.

What formulas, other than the Town of Cary formula, are available for sizing grease interceptors?

Sizing of grease interceptors is based on wastewater flow and can be calculated from the number and kind of sinks and fixtures discharging to the interceptor. In addition, a grease interceptor should be rated on its grease retention capacity, which is the amount of grease that the device can hold before its average efficiency drops below acceptable levels.

The Environmental Protection Agency created a formula that relies on varying factors; e.g., type of highway, varying storage capacity factors, number of seats in the dining area, and gallons of wastewater generated per meal. The EPA recommended minimum size interceptor is 750 gallons. The Unified Plumbing Code also details a formula that relies on the number of meals served per maximum serving hour, waste flow rates from facilities with and without dishwashers and garbage grinders, and various retention times and grease storage factors. Both of these methods are somewhat subjective to individual interpretation.

The Plumbing and Drainage Institute, a consortium representing prefabricated grease interceptors, developed a marketing-driven sizing formula based on a non-required one-minute or two-minute sink drain time. That method purports nondescript benefits of making sinks drain in one or two minutes, although no such requirement exists in state health regulations. Grease interceptor choice is then made on size of sinks and drain time.

What is Cary's grease interceptor sizing formula?

Cary's grease interceptor sizing formula relies on calculated peak hydraulic wastewater flow rates from all drainage units plumbed to the grease interceptor. Cary's procedure relies on a laboratory-derived hydraulic retention time of 24 minutes at peak hydraulic rate for effective oil-water separation.

What is the difference in grease interceptor sizing formulas?

EPA and Unified Plumbing Code sizing methods result in grease interceptors with much larger volumes than does the method used for small, prefabricated under-the-sink devices promoted by Plumbing and Drainage Institute. The Town of Cary hydraulic retention time formula results in interceptor sizes that closely match those of the EPA and Unified Plumbing Code.

Can I clean the grease interceptor at my food service establishment?

The N.C. Division of Waste Management requires a permit for anyone or any firm that pumps, transports, stores, treats or disposes of grease septage.

I have a large grease interceptor and I do not generate a lot of grease and food solids. Do I still have to clean my grease interceptor every 60 days?

Food service establishments that have Town approved grease interceptors and believe that they are not generating sufficient grease and food solids to warrant a 60 day cleaning frequency can apply for a Grease Interceptor Service Variance in order for the Town to conduct a review of your grease interceptor over time to determine if cleaning frequencies can be adjusted.

Do I have to keep a copy of grease interceptor service records on file or can my grease interceptor cleaning company keep records for me?

Food Service Establishments are required to keep a copy of all grease interceptor cleaning records for three years. Food Service Establishments are also responsible for obtaining all the required cleaning information from their grease interceptor cleaning company.

I am going to have my exhaust hood system cleaned. Where should the wash water and cleaners be disposed of?

Grease, cleaners, and wash waters from hood cleaning should be discharged into an adequately sized grease interceptor. Large volumes of grease can be removed from exhaust hood cleaning operations. Exhaust hood cleaning companies should be directed to dispose of cleaning wastewaters in a floor drain or can wash that connects to a large grease interceptor. If you do not have a large grease interceptor, consult with your exhaust hood cleaning company to determine alternative disposal options.

I plan on opening a food service establishment in the Town of Cary (or Town of Morrisville). Do I need to contact the Town about grease interception before submitting my application for building permits?

It is highly recommended that a prospective food service establishment contact the Town in order to better understand grease control requirements prior to submitting construction plans for review. Knowing what information should be included for grease interception will help in expediting grease control plan review and approval.

I have a food service business in the Town of Morrisville, why is the Town of Cary inspecting my grease interceptor?

The Town of Cary provides water and sewer service in the Town of Morrisville. The Town of Cary Fats, Oils and Grease Control Ordinance applies to all commercial food service establishments that discharge into the Town of Cary’s sewer system.

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