CONSTRUCTION NOTES 249 



which a backfill of natural subsoil is made. The installation of tile drainage 

 in heavy clay soils without a backfill of cinders or light sandy loam accom- 

 plishes little, and many times a backfill of clay will practically destroy the 

 entire value of the drain. 



Catch basins. Inlets and catch basins are of various types, as shown 

 on Plate 107. They may also be of varying depth depending upon the 

 depths of the pipes entering and leaving from these basins. The various 

 types of sand traps are shown in figures 2, 3 and 5 on Plate 107. A detailed 

 discussion of catch basins is omitted in this paper because of lack of space. 



Drainage of pools. There are two important problems in the drainage 

 of pools. The first is the problem of the overflow, and the second is the 

 problem of completely draining the bottom of the pool. On Plate 109 the 

 writer has shown various common methods for draining pools. It is very 

 important in the overflow drainage of a pool that the drainage outlet should 

 earn* the water from the surface of the pool, thus constantly removing a 

 certain amount of dust and other foreign materials that may rest upon the 

 surface of the water. The methods of controlling the height of the water 

 in the pool are shown in the figures on Plate 109. 



Cost Data Notes. 



All cost data figures include no charge for teaming or carting of materials 

 to or from site of the trench. The excavated material is thrown immediately 

 along the sides of the trench, from which location it is shoveled into the 

 trench as backfill. Cinders are delivered in piles along the side of the trench. 

 No allowance is included for cost of materials, superintendence, or contin- 

 gencies, nor for cleaning up after the work is completed. All excavations 

 made in average clay loam during dry weather. 



Shallow trenches. The cost per cubic yard to excavate trenches for 

 drain pipes will vary according to the soil and the depth of the trenches. 

 The following tables showing man hours required to excavate trenches to 

 various depths in different soils have been compiled from the cost records 

 of a number of operations over a period of several years, when trenching 

 has been done under varying conditions of soil, labor and weather. 



Man Hours per cubic yard of excavation 



Depth of Average width Easy Average Tough Hard- 



trench of trench earth earth earth pan 



1 foot 12 inches I 1.25 1.75 2.5 



2 feet 15 inches I 1.25 1.75 2.5 



3 feet 1 8 inches 1.25 1.5 2 3 



4 feet 18 inches 1.5 1.75 2.25 3.5 



5 feet 21 inches 2.25 4 



6 feet 24 inches 2.75 



