WAC 246-272B-06150. Design flows

(1) The design engineer shall use the following minimum design flows, which include the appropriate peaking factors, for developments or portions of developments serving residential facilities such as single-family residences, multi-family dwellings, and mobile home parks with total LOSS design flows of 14,500 gpd or less: (a) Modifications of existing developments: (i) 120 gpd per bedroom; or (ii) 240 gpd per existing dwelling unit, residence or mobile home lot or space, whichever is greater. (b) New residential developments and new mobile home parks: (i) 120 gpd per bedroom; or (ii) 360 gpd per lot or space, whichever is greater. (2) The design engineer shall use 270 gpd minimum design flow per dwelling unit, residence or mobile home lot or space for residential developments or portions of developments serving residential facilities, with total LOSS design flow greater than 14,500 gpd. (3) For commercial and nonresidential developments or portions of developments that serve commercial and nonresidential facilities, the department may accept the following: (a) Design flows listed in Table 4 in this section; or (b) Design flows from other generally recognized sources, on a case-by-case basis. Table 4: Typical Design Flows for Nonresidential Facilities Type of Facility Design Unit 1 Design Flow (gpd) Schools with showers and cafeteria 2 per student 16 Schools without showers and with cafeteria 2 per person 12.6 Schools without showers and without cafeteria per person 10 Boarding schools 2 per person 75 Temporary farm worker housing 2 per person 50 Hotels, motels, and B&Bs per room 130 Restaurants 2 per seat 50 Truck stops and Interstate restaurants 2 per seat 180 Offices, with showers per person, per 8-hr shift 25 Offices, without showers per person, per 8-hr shift 15 Nursing homes 2 per bed 200 Elder care facilities, retirement homes 2 per bed 100 Laundromats 2 per machine 500 Churches, without kitchen per seat 3 Churches, with kitchen 2 per seat 5 Day care centers per person 20 Picnic areas per person 5 Campgrounds, RV parks with flush toilets only, no laundry or wet sewer hookup per camp site 50 Campgrounds, RV parks with flush toilets, showers, laundry, no wet sewer hookup per camp site 75 Campgrounds, RV parks with flush toilets, showers, and wet sewer hookup, with or without laundry 2 per RV space 120 Trailer dump stations 2 per dump 40 Resort cabin per person 40 Bar, cocktail lounge 2 per seat 20 Type of Facility Design Unit 1 Design Flow (gpd) Schools with showers and cafeteria 2 per student 16 Schools without showers and with cafeteria 2 per person 12.6 Schools without showers and without cafeteria per person 10 Boarding schools 2 per person 75 Temporary farm worker housing 2 per person 50 Hotels, motels, and B&Bs per room 130 Restaurants 2 per seat 50 Truck stops and Interstate restaurants 2 per seat 180 Offices, with showers per person, per 8-hr shift 25 Offices, without showers per person, per 8-hr shift 15 Nursing homes 2 per bed 200 Elder care facilities, retirement homes 2 per bed 100 Laundromats 2 per machine 500 Churches, without kitchen per seat 3 Churches, with kitchen 2 per seat 5 Day care centers per person 20 Picnic areas per person 5 Campgrounds, RV parks with flush toilets only, no laundry or wet sewer hookup per camp site 50 Campgrounds, RV parks with flush toilets, showers, laundry, no wet sewer hookup per camp site 75 Campgrounds, RV parks with flush toilets, showers, and wet sewer hookup, with or without laundry 2 per RV space 120 Trailer dump stations 2 per dump 40 Resort cabin per person 40 Bar, cocktail lounge 2 per seat 20 1. Does not include employees and staff, unless indicated. 2. Indicates potential for waste strength to exceed that of residential strength sewage, requiring Treatment Level E or higher. 1. Does not include employees and staff, unless indicated. 2. Indicates potential for waste strength to exceed that of residential strength sewage, requiring Treatment Level E or higher. (4) For the department to evaluate alternate design flows, a written request and the following information must be submitted: (a) The preceding year's actual metered flow data read at intervals acceptable to the department to capture seasonal and peak usage; or (b) Comparable flow data from similar existing facilities, including: (i) From a minimum of three similar developments; and (ii) Using a peaking factor if average flows are recorded.