GRADING, DRAINAGE AND LAWNS 



13 



lowest level and there remain until it evaporates or soaks up. The 

 existence of such conditions requires the installation of a storm drainage 

 system. A suitable number of drain inlets, catchbasins and tile lines 

 should be installed to carry off the maximum amount of excess water 

 that would accumulate at any one time. This is a case where the tile 

 lines may run full and with pressure at times, so vitrified tile, usually laid 

 with closed joints, are used. The outlets of tile lines laid for sub- 

 surface drainage may be provided in the storm drainage system if the 

 proper joining is made. 



Drain inlets where the water enters the tile must be placed at the 

 low points of the grade level. The drain inlet should be large or small 

 according to the work it will have to do. There are many specially 

 constructed types, but in all cases there is a perforated opening so 

 designed as to let in the water and exclude as much as possible of the 

 refuse which the water would otherwise wash in. A simple drain inlet 

 may be constructed as shown in the drawing. (Fig. 4). 



IS/1 H HODS Of" DRAINING WALL5 



&ETAlP>lirN6 WALL- 



Fig. 6 



