1991, 01-16 Health District Sewage System MemoSPOKANE COUNTY HEALTH DISTRICT
•'Interoffice Memorandum
'DATE: January 16, 1991
TO: Environmental ealth Staff
FROM: Daryl E. Way, R.Si, Acting Director, Environmental Health
SUBJECT: Commercial Sizing for On -Site Sewage Systems (Revised 1/25/93)
These sizing figures and/or actual water use data are to be utilized first
before referring to the EPA Manual. Any sizing questions, check with the
program coordinator.
Restaurants:
Multiple Food Menus/Lounges, etc 50 gals./seat
Drive-ins/Small Fast Food Facilities 35 gals./seat
Sandwich Shops/Taverns 20 gals./seat
Specialty Food Facilities:
Deli's/Meat Markets/Bakeries 150 gals./day
(Retail take-out - no dining)
Groceries (convenience stores only)
Store/Office/Industry (not including production which will be determined by
water usage figures) 15 gals./employee/shift
(waterless equipment) 15 gals./patient visit
Doctor's/Dentist Office
Church
•
3 gals./member
Theatre 3 gals./seat or car stall
+15 gal./employee/shift
Hotel/Motel (without kitchen) 100 gals./unit
Laundry Rate based on machine type
yp (gal. per wash
cycle x number of turns/day/machine).
Resthome/Nursing Home 93 gals./resident
+15 gal./employee/shift
Day Schools:
With Cafeteria, Gym, Showers
With Cafeteria Only
Without Cafeteria, Gym, Showers
Boarding School .
Apartments
Mobile Home
Beauty Shops
21 gals./student
16 gals./student
11 gals./student
+15 gal./employee/shift
74 gals./student
+15 gal./employee/shift
120 gals./bedroom
Parks
360 gals./lot space
(full 200 gals./chair
processing shops only — otherwise address on individual basis)
dmercial Sizing for On —Site Sewage Systems
,,;age 2
Barber Shops. 82 gals./chair
Campgrounds/R.V. Park:
Limited Plumbing (no central restroom & shower) . . 3.Q gals./campsite
Central Restroom and Shower 100 gals./campsite
Note: The sponsor may provide water usage figures of similar operations in
lieu of these numbers for sizing:.
Grease Traps
Any commercial food facility which generates grease must have grease traps.
They are to be sized as follows:
Without Garbage Disposal 0 5 x projected flow = trap size
With Garbage Disposal 0.75 x projected flow = trap size
Water Use Figures
Monthly water use figures are to be provided for one complete year when water
use data is used to size the sewage system. Select the peak water month meter
figure and use the following mathematical formulas to determine daily sewage
flow:
# of units/mo..x # of cu. ft./unit x 7.5 gallons/cu. ft. = Total # of gal./mo.
Total # of gallons/month 4-# of operating days/mo. = # of gallons/day
If the development being •considered generates cyclic daily flows (i.e., food
facilities, motels, etc::), the "# of gallons/day is to be multiplied by 1.5 to
determine the peak daily:flow of the project.
If the peak water month is in the irrigation season, select the highest peak
month outside of the season and determine the daily water usage flow. Then
compare the business/sales figures of the two months, and if the sales are
greater in the irrigation month, prorate the water flow according to the
amount of sales increase and add to daily flow (i.e., # of gallons/day of
non —irrigation month x % of sales increase = # of gallons/day increase + # of
gallons/day of non —irrigation month = # of gallons/day of irrigation month).
If the meter is read every six months rather than monthly, the average monthly
figure must be multiplied by 1.5 to obtain a peak water usage figure.
If the sizing figures for the project are not covered under the previously
stated sizing criteria, and the applicant does not have representative water
usage figures, here is another method of determining sewage flows (i.e., golf
course restrooms, wilderness restrooms, etc.):
Plumbing #of X GPM X Cycle X Use/Hr. X # of Operating = Total
Fixtures Fixtures Time Hours Flow
(Minutes)
Showers 3 6 1.5
Water
Closets 3 1.25 3
Urinals 2 .167 6
Sinks 2 .167 6
0318E/bls
Table 1-B.
Discharge Facility
Schools with showers and
cafeteria
Schools without showers
and with cafeteria
Schools without showers
and without cafeteria
Boarding schools
Motels at 65 gal/person
(rooms only)
Restaurants*
Interstate or through
highway restaurants*
Interstate rest areas
Service stations
Factories(showers)
Factories(no showers)
Shopping centers*
Hospitals*
Nursing homes*
Homes for the aged*
Doctoi s office in medical
cenie,*
Laundromats
Community colleges
Swimming pools
Theaters, drive-in type
Theaters, auditorium type
Churches (no kitchen)
Churches (with kitchens)
Day Care Centers
Picnic areas
Campgrounds, with
limited comfort stations
No laundry, no wet sewer hookup
Campgrounds/RV parks, with
flush toilets
showerslaundry, no wet sewer hookup
Campgrounds/RV Parks, with
flush toilets, showers,
with or without laundry facilities
and wet sewer hookup
Campgrounds/RV Parks with
wet sewer hookup only, no
comfort station
Trailer Dump Stations*
Design Flows for Facilities Other than Residential Development
(Reference 8)
Design Units
per person 16
per person 12.6
per.person 10
per person
per room
per seat
per seat
per person
per vehicle served
per person per 8-hr shift
per person per 8-hr shift
per 1,000 sq ft.of
ultimate floor space
per bed
per bed
per bed
per 1,000 ft
per machine
per student axid faculty
per swimmer
per car
per seat
per seat
per seat
per person
per person
per camp site
per camp site
per camp site
per camp site
per dump
Indicates potential high waste strengths facilities requiring pre-treatment
Includes normal infiltration
75
130
50
180
Flow** Flow Duration
(gpd) (1rr)
8
8
16
24
16
16
5 24
10 16
25 Operating Period
15
200-300 12
300
200
100
500
500
15
10
5
5
3
5
20
5
50
75
100
50
20
24
24
24
12
16
12
12
4
12
4
4
12
12
24
24
24
24
24
18