A Comparative Study of Imhoff Tanks 
361 
Placing reinforcement in floor. The conical bottom would re- 
quire much more careful placing^ more cutting, and this difference 
will be taken care of by estimating the cost as 5 cents a pound 
for the rectangular tank and 6 cents for the circular. 
Concreting floors. There will probably be little difference here, 
as there will be no forms in either tank and small difference in 
finishing. 
Forms for walls. Owing to the extreme variability in cost of 
lumber, the dearth of adequate or satisfactory cost data, this 
item will not be considered separately but will be included in 
the cost of concrete in the two instances as noted below. 
Reinforcement for walls. Variations in prices for this will be 
taken care of in the same proportion as in placing reinforcement 
for the floor; that is, 5 cents a pound for the rectangular walls 
and 6 cents a pound for circular. 
Concrete for walls. After investigation of cost data covering 
all available sources, it seems within the limit of accuracy to 
assume a difference in price for the concrete in circular walls 
over that in the rectangular walls and to include in that difference 
all items involved that would be affected. The items involved 
are erecting forms, placing reinforcement and placing concrete. 
The price for the rectangular tank will be taken as $12 a cubic 
yard and that for the circular tank at $14 a cubic yard. 
All other items common to both tanks will be assumed at the 
same unit costs. 
QUANTITIES FOR RECTANGULAR TANK 
Concrete: cubic yards 
Sides 28.5 
Ends 16.9 
Bottoms. 13.2 
Buttresses 0.9 
Channels 6.2 
Partition 9.3 
75.0 
Timber: feet 
57 feet — 2x6 inch cypress plank 57 
12 feet — 2 X 4 inch cypress plank 8 
28 feet — 6x8 white oak plank 112 
32 feet — 2x6 inch cypress plank. 32 
