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1950-51 Theatre Catalog, 9th Edition, Page 191 (171)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 191
Page 191

1950-51 Theatre Catalog, 9th Edition, Page 191

Table I: Toilet Usage

septic tanks for more than 150 drive-in operations.

area is reduced and the cesspool often overflows. Thus, a cesspool is not recommended as a substitute for a septic tank

Cl" U595 Average U898 Mainsenance under any circumstances.

Capacity Per Day Per Day However, inasmuch as waste water 500 200-260 230 Maintenance 0f any septic tank Will other than sewage should not be per600 280-325 302 depend largely on the daily How of mitted to enter a septic tank, a cesspool 700 300-370 335 sewage and the number of persons may often be provided to take care of 800 320-410 365 served. With ordinary use and care, this type of waste from refreshment 900 350-440 385 cleaning of the average septic tank stand sinks, fioors of buildings, etc., if

1,000 375.455 415 should be necessary only every two to regulations permit.

1,100 400-520 450 three years, provided the tank has been . ' .

1,200 450-580 515 properly designed with adequate sludge Dls'h'lbu'l'lon BOX

The method commonly used to determine the capacity of septic tanks for schools, factories, residences, etc., is to allow four cubic feet of tank capacity per personebased upon 18 hours of use and 6 hours of rest per day with multiple use by each person. Drive-in theatres, however, usually operate only three hours per day and are idle for 21 hours. There is also practically no multiple use, so we may assume that the capacities for septic tanks shown in Table II should be adequate.

storage space. However, the tank should be inspected every 12 to 18 months, and the depth of accumulated sludge checked. When the scum accumulations and the sludge deposits reach a combined depth of 18 to 20 inches, the tank should be cleaned. Sludge should be removed in the spring rather than in the fall to avoid loading the tank with undigested solids during the cold weather months. As the sludge may contain diseasebearing bacteria, its disposal should be accomplished by burial or other methods satisfactory to the state health department. Excessive amounts of foreign substances should not be permitted to enter the tank. Rain 'water, surface drainage,

Table II: Tank Capacity and Relative Dimensions

Tank Capacity

A distribution box ('see Fig. 5) is a box or chamber into which the septic tank efHuent may be discharged to enter subsurface field lines. As far as drive-in theatres go, it is generally applicable only in cheap installations and is not recommended. It is merely designed to regulate and equalize the flow in all lines, Serve as an inspection manhole for checking the quality of efiiuent, and determine whether or not sludge particlesare being carried out into the disposal area. It is connected to the septic tank by a short tight sewer line and is located at the upper end of the distribution field. Under ordinary circumstances, however, an efncient septic tank, in combination with a well-constructed filter bed, should obviate the need for a distribution box.

Distribution boxes get attention here only for the benefit of the reader who

No.0] Cars gal, Length Width Depth may hear of them and want the added 610/! 2760 4/0" information. 300 400 7'0" 3'6" 4'0" 400 500 8'0" 4'0" 4'0" 500 760 9'0" 4'6" 4'3" , I , 700 800 9'6" 4'8" 4'6" Table III: Filter Bed Dlmenslons 900 932 1040" 5'0" 4'8" Car Capacity Length Width 1,200 1,064 101;" 5'3" 4'9" 500 40, 25, 600 45' 27' 700 50' 29' 800 55' 31' Although the above tables and those into the ground. Furthermore, since the 900 60: 33: following cannot ' be positively guar- raw sewage discharged into the cesspool

anteed by the writer, they have been applied satisfactorily to the design of and foundation drainage also should be prevented from entering the tank.

It is recommended that a chart be provided for all installations and placed at a suitable location to show the loca-. tion of the tank and the field system. This chart also should contain brief instructions as to the inspection and maintenance required. Such a chart should assist in acquainting drive-in operators with the necessary maintenance which septic tanks require and forestall many of the failures by assuring satisfactory operation.

Advantages Over Cesspool

A cesspool (see Fig. 4) is a covered pit with open-jointed lining into which raw sewage is discharged. The liquid portion is disposed of by seepage or leaching into the surrounding porous soil, while the solids are retained in the pit and create a stench that would not be permitted within a drive-in theatre area. A cesspool is also likely to contaminate a water supply within a range of 300 feet.

A septic tank, on the other hand, holds the solid matter until it is converted into a liquid, and the efliuence is then conducted into a filter bed; here the liquid is further purified and absorbed


tends to seal the openings in the lining of the porous formation, the leaching

FIGURE 4 Sectional drawing at a cesspool that has certain drive-in disadvantages.

1950-51 Theatre Catalog, 9th Edition, Page 191