CONSTRUCTION NOTES 271 



II. Types of Curbs, Gutters and Combined Curbs and Gutters. The fol- 

 lowing tabulation shows the various kinds of materials most frequently 

 used for the construction of curbs, gutters and combined curbs and gutters: 



(a) Curbs, i. Concrete (usually cast in place, Plate 114, figure 2, 

 page 274); 2. Stone (Plate 113, figure 4, page 272). 



(b) Gutters, i. Turf (Plate 113, figure i); 2. Brick (Plate 114, 

 figure i); 3. Concrete (Plate 113, figure 3); 4. Cobblestone (Plate 114, 

 figure 3). 



(c) Combined curbs and gutters, i. Concrete (Plate 114, figure 4<a); 

 2. Stone curbs and concrete gutters (Plate 113, figure 4). 



III. Subsoil Drainage under Curbs and Gutters. The cross section of 

 any gutter should be so designed that the gutter will readily remove during 

 storms all the surface water coming to it. This is a fundamental require- 

 ment. It is also very necessary that the subsoil under the gutter should 

 be thoroughly drained. The different methods of draining this subsoil are 

 shown in the following figures: Plate 113, figure i; Plate 113, figure 4; 

 Plate 114, figure 4. 



In the subsoil drainage for turf gutters (Plate 113, figure i) the drain 

 may be installed as shown under Type A or as under Type B. When the 

 tile drains are installed as shown in Type A there is great danger that these 

 tiles will be broken by the steam roller unless placed at an adequate depth. 

 A safe depth should approximate 18 inches below the subgrade. In many 

 instances the top of the tile is laid approximately eight inches below the 

 subgrade, but this is not a safe general practice. If the tile is installed as 

 shown in Type B the only reason for the added depth is to provide com- 

 plete drainage for the subsoil under the full width of the sod gutter. Some- 

 times a tile may be installed under the middle line of the sod gutter. This 

 is not a recommended practice, particularly if the drain is laid only eight 

 inches deep, because tile thus located will not provide so good drainage 

 for the subsoil under the traveled roadbed. The usual method for draining 

 the subsoil under concrete, brick and cobblestone gutters is shown in Plate 



113, figure 3. The tile drain is installed at the required depth under the 

 middle line of the gutter, and the drainage of the subsoil under the traveled 

 roadbed is accomplished as shown in Plate 113, figure 3, and Plate 114, 

 figure i. The usual method for installing drainage to remove ground water 

 under combination curbs and gutters is shown in Plate 113, figure 4; Plate 



114, figure 2, and Plate 114, figure 4. The tile drain thus installed accom- 

 plishes three purposes as follows: (a) Drainage of the road subgrade; (b] 

 Drainage of the subsoil under the gutter; (c) Drainage of the subsoil under 

 the curb. 



Wherever curbs or gutters are installed on a sandy soil, from which 



