30 BULLETIN 181^ U. S. DEPARTMENT OF AGEICULTUEE. 



The ground should be carefully inspected to secure the best loca- 

 tion. The locations as shown on the map may be varied from when- 

 ever by so doing advantage can be taken of higher or firmer ground. 

 In no case should a levee be located less than 200 feet from the bank 

 of the river, and care should be taken to protect the levees against 

 washing or midermining at the sharp bends of the stream. Changes 

 in direction should be made by easy curves rather than by sharp 

 angles. 



The base should be cleared of all vegetation and stumps, and the 

 large roots removed. For levees more than 10 feet high a muck 

 ditch about 3 feet deep and 6 feet wide should be dug along the 

 center line of the embankment. This ditch may be filled as is any 

 other portion of the levee. The surface of the ground on which the 

 levee is to be built should be broken with a plow, so that a bond wiU 

 be formed which wiU prevent seepage from following the surface 

 between the old and the new material. 



The soil of which the levees are to be built is a heavy river silt or 

 clay and wiU form a strong and fairly impervious embankment. The 

 durations of the extreme high-water stages wiU be short, so that the 

 levees will not ordinarily be saturated for more than a few feet from 

 the ground surface. The estimates for the levees have therefore 

 been based on a top width of 4 feet, side slopes of 2^ to 1 on water 

 side and 1^ to 1 on land side for river floodway levees, and 3 to 1 on 

 water side and 2 to 1 on land side for the creek floodway levees. 

 This difference in slopes is recommended because of the fact that 

 the creek floodway levees wiU be subjected to a current of greater 

 velocity than will those of the river floodway. 



The levees should be built of clean earth that is free from vegeta- 

 ble matter taken from the side of the levee next to the waterway. 

 The pits from which the earth is taken should have side slopes at 

 least as flat as 1 to 1 ; and if practicable should not be more than 6 

 feet deep. Along the river levees a berm or strip of land at least 

 10 feet wide, from which no earth has been taken, should be left 

 between the pit and the toe of the levee. For the creek floodway 

 levees the berm should be 50 feet wide and the borrow pit of the 

 shape specified. The widths of right of way for levees were com- 

 puted by adding to the width of base and berm, the width of borrow 

 pit, based upon a depth of 6 feet and side slopes 1 to 1 . 



The material can be most economically handled by a dry-land 

 excavator of some type that will take the material from the pit and 

 place it in the levee at one operation. When the required amount of 

 material is in place, the top and sides of the embanlanent should be 

 smoothed to an even surface and the whole planted in any grass 

 adapted to the soil and climate. 



