92 



LAND DRAINAGE 



basins and noting the flow of the water into and out from 

 them. 



121. How the silt-basin performs its work. The 

 bottom of the silt-basin should stand at least a foot 

 below the lower edge of the tile running from the basin. 



FIG. 35. Silt-basin built of concrete. 



The basin should be at least 12 inches in diameter or 18 

 to 24 inches for large tile. As the water enters the silt- 

 basin from the tile, its velocity is suddenly decreased and 

 its capacity to carry silt is thus reduced. Therefore 

 most of the silt settles to the bottom of the silt basin as 

 the water passes through and into the out-leading tile. 

 When the silt has accumulated sufficiently in the bottom 

 of the silt basin, it may be removed with a shovel or hoe. 



