GRADING 51 



to it, thus making a combined sewer. This means an 

 enlargement of size. Difficulty is often experienced in 

 maintaining in dry weather a proper depth of flow without 

 flushing. The flow from these sewers should not be dis- 

 charged into lakes and water courses unless there is a pro- 

 vision for removing the dry-weather flow to another outlet. 



GRADING 



The grading plan is prepared after a careful examination 

 of the topographical map and a personal examination of 

 the site. This is the function of the landscape architect. 

 Some of the features in the design directly affect the drain- 

 age and other plans and will thus be explained. 



Grass Gutters. Instead of allowing the sides of drives 

 and paths to act as channels or gutters for the collection and 

 removal of water, it is customary in modern practice to 

 provide grass gutters wherever possible. These consist 

 of depressions 4 to 6 inches deep and 6 to 12 feet wide on 

 the sides of drives and paths, running parallel with them. 

 (See Fig. 15, on page 47.) In vertical cross-section the 

 traces of these gutters should be curves which are con- 

 tinuous with the lines cut from the adjacent slope. These 

 gutters possess marked advantages. They intercept storm- 

 water and prevent it from washing away the surfaces of 

 drives and paths. Since the flow of water through them is 

 gentle by reason of obstruction by blades of grass, there is 

 practically no erosion and very little solid matter is deposited 

 in the catch-basins. In fact in designing the drainage 

 system some engineers dispense with basins altogether and 

 merely use inlets. On the lower sides of driveways and 

 paths, the gutters of course are unnecessary. There are 

 times, however, when by reason of the steepness of the 

 slope and its close proximity to the drive or path, grass 



