ROADS 



177 



The area of waterway in square feet should equal 



C X "I / (drainage area in acres) 3 



in which C is a coefficient and will vary from Y§ to 1, the larger 

 value being used where the slopes are steep and the ground is 

 broken. The 4th root of the quantity under the radical may 

 be obtained by extracting the square root of the square root. 



Foundation. Many bridges fall because they are not 

 placed upon a proper foundation. Great care should be used 

 to see that solid earth which will not be undermined by water 

 is available for the smaller bridges. For larger bridges the 

 foundation should be placed on solid rock, if possible; and 

 where this can not be done, piling and other methods of 

 providing large surface for the foundation should be used. 



Concrete Culverts and Bridges. Perhaps there is no 

 purpose to which concrete made of Portland cement can be 

 put to better use than in the construction of culverts and 



LO/IDirlO 



ull -lOOiei pcriffr 



C LI • ZOtom ffo/ier 

 O I SOO lei pv-iq ft 



Conertre fhr Toe t-^-4 

 111 Other Concrete t-i^S 



2-rm-rz ooj< cm. vcar 



QEiriFO QCED CON CBZTC 



IOWA morlwAy COMMISSION 

 July. 1906 Scalt^.l-0 



Fig. 96, Plans and table of materials for reinforced concrete culvert. 



