INLAND DRAINAGE 



133 



was then filled with coarse stone and cinders. A main ditch was then 

 dug in the center of the pond its entire length, with occasional laterals. 

 This main ditch and the lateral led to the four effective drains described 

 above. 



"The cost of this work, labor at 30 cents per hour, was S173.42. This 

 included 1,500 feet of ditching and the work on the four rejected drains, 

 which were filled in." 



Bishop 1 describes a vertical drainage project, in which it was 

 necessary to pierce 40 to 50 feet of clay before the limestone was 

 reached. The holes were dug with an ordinary post-hole auger 

 with sectional pipe extensions at a cost of 2 cents per foot. It 

 has been found, however, that the post-hole auger will not work 

 in certain soils. 



VERTICAL DRAINAGE FOR LARGE AREAS 



Sometimes, when the area to be drained is extensive, it is 

 necessary to make the hole of considerable size. This, of course, 



^ Drain- head 



m >>>>;wvv>>»w»»>>)>>,MMWW>M»mww* ^^ 



/ 



^P opt 



Shaft 



Fig. 93. — Profile of pool, drain-head and shaft. 



greatly increases the cost of the operation. Stromquist 2 describes 

 such a hole, which drained a pond covering more than 40 acres 

 in extent. 



A shaft, 7 feet square, was sunk to a depth of about 41 feet, 

 at which point a fissure, about 4K feet high by \ l A feet wide 

 was found in a vertical wall of limestone. The shaft was curbed 

 with 2 by 6 material, double braced, at intervals of 3 feet, and 



1 Transactions of the First Annual Conference of Sanitary Engineers, 

 IT. S. Public Health Service, 1919. 



2 Transactions of the First Annual Conference of Sanitary Engineers, U. S. 

 Public Health Sendee, 1919. 



