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(d) Use a culvert size of at least 40 to 50 cm, depending on 

 expected debris problems. 



(e) Install culverts at the gradient of the original fill slope 

 if possible: otherwise provide anchored downspouts to carry 

 the water safely across the fill slope. Skew culverts 20o to 

 30O toward the inflow to provide better inlet efficiency and 

 flow characteristics. Provide rock or other splash basins at 

 the downstream end of culverts to reduce the erosion energy 

 of the emerging water. 



(f) Protect the upstream end of culverts from plugging with sediment 

 by using sediment catch basins, drop inlets, changes in road 

 grades, headwalls, and recessed cut slopes. 



(g) Install the culvert deep enough to assure that it will not 

 be crushed by traffic leads. This requires a depth of about 

 1.2 m for metal culverts subjected to loads from large, loaded 

 logging trucks. 



21. In some areas, alternating inslope and outslope sections can be 

 built into the road, especially if road grades are "rolled" (provide 

 alternating adverse and favorable grades). In such instances, install 

 dips or cross drains on the surface of the road to control erosion of 

 the roadway. 



22. It is usually necessary to construct cross drains in the road surface 

 on either insloped or outsloped roads to help prevent erosion caused 

 by water concentrations in ruts. Various types of cross drains 



are used, including open-top culverts and intercepting dips. Some 

 points to consider when installing cross drains are: 



