EOAD MODELS. 9 



gravel, macadam, or other road of crushed stone. These drains are 

 generally a little deeper than the subgrade and slope toward the side 

 ditches, to which they carry the water. They are filled with crushed 

 stone to a depth of 6 or 8 inches and are covered over with earth. The 

 shoulder drains are required in clay soils and are placed at the low 

 points in the grade as well as at frequent intervals on flat grades. 



The telford base is extensively used in locations on swampv or 

 marshy ground. 



The guard rail shown in the model is desirable along steep slopes to 

 protect travelers. The fence is painted to prolong its life. The 

 white color enables the public to discern it at night. The posts are 

 about 6 inches in diameter and about 7 feet long, and are set in the 

 ground to a depth of 3| feet. About 18 inches from the ground a 

 plank, 2 by 6 inches, is notched into the posts. The top rail is then 

 placed about 18 inches above the top edge of this plank. It may be 

 either 4 by 4 inch timber, notched into the top of the post, or a plank, 

 2 by 6 inches, spiked to the top of the post, which has been sawed off 

 to a slope of 3 inches. 



Section B shows a V drain base with a side outlet. 



The V drain base, when used in through cuts, is cheaper than the 

 telf ord method with two side drains, especially in a section of country 

 where field stone abounds. It, like the telf ord, is often used in wet 

 and spongy ground. The water flows to and along the point of the 

 V drain (0 until a suitable outlet can be secured. The center is 

 usually excavated 2 feet and the sides about 16 inches below the 

 finished grade. The material excavated is thrown to the sides, 

 forming the shoulders. In swamp sections it is sometimes necessary 

 to haul material for the shoulders. The V drain is then filled with 

 stone to a depth of 18 inches at the center and 10 inches at the sides. 

 These stones grade from 8 inches in thickness down to a few inches. 

 The large-sized stones are placed at the bottom, while the small stones 

 are used at the top. The surface should then .be rolled and the 

 surfacing material spread and rolled. V drains are sometimes built 

 of brickbats, slag, or even sand, or any material that will permit the 

 water to seep rapidly to the point of the V. This type of construction 

 permits the use of field stone of an inferior type and assists hi clearing 

 many farm lands of an otherwise waste product. 



Section C shows a center drain with laterals and cobble gutters. 



The center drain with laterals, sometimes called a blind or French 

 drain, furnishes another mode of draining the foundation of a road. 

 As with the V drain, the water is brought to the center of the road 

 and conducted to some suitable outlet. The model shows these 

 drains about 2 feet deep, about 12 inches wide at the bottom, and 

 about 18 inches wide at the top. ■ A drain tile is placed at the bottom 

 87538°— Bull. 220—15 2 



