15A NCAC 02T .0114 – Wastewater Design Flow Rates

(a) This Rule shall be used to determine wastewater flow rates for all systems governed by this Subchapter unless
alternate criteria are provided by a program-specific rule or for flow used for the purposes of 15A NCAC 02H .0105. Higher flow rates shall be required where usage and occupancy are atypical, including those in Paragraph (e) of this Rule. Wastewater flow calculations shall take hours of operation and anticipated maximum occupancies and usage into account when calculating peak flows for design.
(b) In determining the volume of sewage from dwelling units for a wastewater system:
1. (1) A permittee may calculate its wastewater flows for new dwelling units discharging to wastewater systems serving two or more dwelling units that have yet to be connected and for which the permittee has allocated capacity, at 75 gallons per day per bedroom, or at a lower rate approved by the Department pursuant to the requirements in Paragraph (f) of this Rule. Unless adjusted pursuant to Paragraph (f) of this Rule, the minimum volume of sewage from each dwelling unit is 75 gallons per day and each additional bedroom above one bedroom increases the volume by 75 gallons per day.
2. (2) An applicant, or permittee modifying their existing permit, shall calculate its wastewater flows for new dwelling units discharging to wastewater systems serving two or more dwelling units that have yet to be connected and for which the applicant or permittee has not allocated capacity at 75 gallons per day per bedroom, or at a lower rate approved by the Department pursuant to the requirements in Paragraph (f) of this Rule. Unless adjusted pursuant to Paragraph (f) of this Rule, the minimum volume of sewage from each dwelling unit is 75 gallons per day and each additional bedroom above one bedroom increases the volume by 75 gallons per day.
3. (3) For wastewater systems serving one dwelling unit, the flow rate shall be 120 gallons per day per bedroom. The minimum volume of sewage from each dwelling unit shall be 240 gallons per day and each additional bedroom above two bedrooms shall increase the volume by 120 gallons per day. Each bedroom or any other room or addition that can function as a bedroom shall be considered a bedroom for design purposes. When the occupancy of a dwelling unit exceeds two persons per bedroom, the volume of sewage shall be determined by the maximum occupancy at a rate of 60 gallons per person per day.
(c) The following table shall be used to determine the minimum allowable design daily flow of wastewater facilities. Design flow rates for establishments not identified below shall be determined using available flow data, water‑using fixtures, occupancy or operation patterns, and other measured data.
Type of Establishments Daily Flow For Design
Barber and beauty shops
Barber Shops 50 gal/chair
Beauty Shops 125 gal/booth or bowl
Businesses, offices and factories
General business and office facilities 25 gal/employee/shift
Factories, excluding industrial waste 25 gal/employee/shift
Factories or businesses with showers or food preparation 35 gal/employee/shift
Warehouse 100 gal/loading bay
Warehouse – self storage (not including caretaker residence) 1 gal/unit
Churches
Churches without kitchens, day care or camps 3 gal/seat
Churches with kitchen 5 gal/seat
Churches providing day care or camps 25 gal/person (child & employee)
Fire, rescue and emergency response facilities
Fire or rescue stations without on site staff 25 gal/person
Fire or rescue stations with on-site staff 50 gal/person/shift
Food and drink facilities
Banquet, dining hall 30 gal/seat
Bars, cocktail lounges 20 gal/seat
Caterers 50 gal/100 sq ft floor space
Restaurant, full Service 40 gal/seat
Restaurant, single service articles 20 gal/seat
Restaurant, drive-in 50 gal/car space
Restaurant, carry out only 50 gal/100 sq ft floor space
Institutions, dining halls 5 gal/meal
Deli 40 gal/100 sq ft floor space
Bakery 10 gal/100 sq ft floor space
Meat department, butcher shop or fish market 75 gal/100 sq ft floor space
Specialty food stand or kiosk 50 gal/100 sq ft floor space
Hotels and Motels
Hotels, motels and bed & breakfast facilities,
without in-room cooking facilities 120 gal/room
Hotels and motels, with in-room cooking facilities 175 gal/room
Resort hotels 200 gal/room
Cottages, cabins 200 gal/unit
Self service laundry facilities 500 gal/machine
Medical, dental, veterinary facilities
Medical or dental offices 250 gal/practitioner/shift
Veterinary offices (not including boarding) 250 gal/practitioner/shift
Veterinary hospitals, kennels, animal boarding facilities 20 gal/pen, cage, kennel or stall
Hospitals, medical 300 gal/bed
Hospitals, mental 150 gal/bed
Convalescent, nursing, rest homes without laundry facilities 60 gal/bed
Convalescent, nursing, rest homes with laundry facilities 120 gal/bed
Residential care facilities 60 gal/person
Parks, recreation, camp grounds, R-V parks and other outdoor activity facilities
Campgrounds with comfort station, without
water or sewer hookups 75 gal/campsite
Campgrounds with water and sewer hookups 100 gal/campsite
Campground dump station facility 50 gal/space
Construction, hunting or work camps with flush toilets 60 gal/person
Construction, hunting or work camps with chemical or
portable toilets 40 gal/person
Parks with restroom facilities 250 gal/plumbing fixture
Summer camps without food preparation or laundry facilities 30 gal/person
Summer camps with food preparation and laundry facilities 60 gal/person
Swimming pools, bathhouses and spas 10 gal/person
Public access restrooms 325 gal/plumbing fixture
Schools, preschools and day care
Day care and preschool facilities 25 gal/person (child & employee)
Schools with cafeteria, gym and showers 15 gal/student
Schools with cafeteria 12 gal/student
Schools without cafeteria, gym or showers 10 gal/student
Boarding schools 60 gal/person (student & employee)
Service stations, car wash facilities
Service stations, gas stations 250 gal/plumbing fixture
Car wash facilities 1200 gal/bay
Sports centers
Bowling center 50 gal/lane
Fitness, exercise, karate or dance center 50 gal/100 sq ft
Tennis, racquet ball 50 gal/court
Gymnasium 50 gal/100 sq ft
Golf course with only minimal food service 250 gal/plumbing fixture
Country clubs 60 gal/member or patron
Mini golf, putt-putt 250 gal/plumbing fixture
Go-kart, motocross 250 gal/plumbing fixture
Batting cages, driving ranges 250 gal/plumbing fixture
Marinas without bathhouse 10 gal/slip
Marinas with bathhouse 30 gal/slip
Video game arcades, pool halls 250 gal/plumbing fixture
Stadiums, auditoriums, theaters, community centers 5 gal/seat
Stores, shopping centers, malls and flea markets
Auto, boat, recreational vehicle dealerships/showrooms
with restrooms 125 gal/plumbing fixture
Convenience stores, with food preparation 60 gal/100 sq ft
Convenience stores, without food preparation 250 gal/plumbing fixture
Flea markets 30 gal/stall
Shopping centers and malls with food service 130 gal/1000 sq ft
Stores and shopping centers without food service 100 gal/1000 sq ft
Transportation terminals – air, bus, train, ferry, port and dock 5 gal/passenger
(d) Design daily flow rates for proposed non-residential developments where the types of use and occupancy are not known shall be designed for a minimum of 880 gallons per acre, or the applicant shall specify an anticipated flow based upon anticipated or potential uses.
(e) Design daily flow rates for residential property serving two or more dwelling units on barrier islands and similar communities located south or east of the Atlantic Intracoastal Waterway and used as vacation rental as defined in G.S. 42A-4 shall be 75 gallons per day per habitable room. Habitable room shall mean a room or enclosed floor space used or intended to be used for living or sleeping, excluding kitchens and dining areas, bathrooms, shower rooms, water closet compartments, laundries, pantries, foyers, connecting corridors, closets, and storage spaces.
(f) An adjusted daily sewage flow design rate shall be granted for permitted but not yet tributary connections and future connections tributary to the system upon showing that the capacity of a sewage system is adequate to meet actual daily wastewater flows from a facility included in Paragraph (b) or (c) of this Rule without causing flow violations at the receiving wastewater treatment plant or capacity-related sanitary sewer overflows within the collection system as follows:
1. (1) Documented, representative data from that facility or a comparable facility shall be submitted by an authorized signing official in accordance with Rule .0106 of this Section to the Division for all flow reduction requests, as follows:
  1. (A) dates of flow meter calibrations during the time frame evaluated and indication if any adjustments were necessary;
  2. (B) a breakdown of the type of connections (e.g. two bedroom units, three bedroom units) and number of customers for each month of submitted data as applicable. Identification of any non-residential connections including subdivision clubhouses and pools, restaurants, schools, churches and businesses. For each non-residential connection, information identified in Paragraph (c) of this Rule (e.g. 200 seat church, 40 seat restaurant, 35 person pool bathhouse);
  3. (C) a letter of agreement from the owner or an official, meeting the criteria of Rule .0106 of this Section, of the receiving collection system or treatment works accepting the wastewater and agreeing with the adjusted design rate;
  4. (D) age of the collection system;
  5. (E) analysis of inflow and infiltration within the collection system or receiving treatment plant, as applicable;
  6. (F) if a dedicated wastewater treatment plant serves the specific area and is representative of the residential wastewater usage, at least the 12 most recent consecutive monthly average wastewater flow readings and the daily total wastewater flow readings for the highest average wastewater flow month per customers, as reported to the Division;
  7. (G) if daily data from a wastewater treatment plant cannot be used or is not representative of the project area: 12 months worth of monthly average wastewater flows from the receiving treatment plant shall be evaluated to determine the peak sewage month. Daily wastewater flows shall then be taken from a flow meter installed at the most downstream point of the collection area for the peak month selected that is representative of the project area. Justification for the selected placement of the flow meter shall also be provided; and
  8. (H) an estimated design daily sewage flow rate shall be determined by calculating the numerical average of the top three daily readings for the highest average flow month. The calculations shall also account for seasonal variations, excessive inflow and infiltration, age and suspected meter reading and recording errors.
2. (2) The Division shall evaluate all data submitted but shall also consider other factors in granting, with or without adjustment, or denying a flow reduction request including: applicable weather conditions during the data period (i.e. rainy or drought), other historical monitoring data for the particular facility or other similar facilities available to the Division, the general accuracy of monitoring reports and flow meter readings, and facility usage, such as whether the facility is in a resort area.
3. (3) Flow increases shall be required if the calculations required by Subparagraph (f)(1) of this Rule yield design flows higher than that specified in Paragraphs (b) or (c) of this Rule.
4. (4) The permittee shall retain the letter of any approved adjusted daily design flow rate for the life of the facility and shall transfer such letter to a future permittee.

History Note: Authority G.S. 143‑215.1; 143‑215.3(a)(1);
Eff. September 1, 2006;
Readopted Eff. September 1, 2018;
Amended Eff. Pending Legislative Review.