13 



Earth from somewhere within the pond area can be 

 used to provide dirt for constructing the dam. Most of 

 the soil for the dam should be obtained in the vicinity 

 in order to save labor. The whole bottom area of the 

 pond should be deepened and graded to drain properly, 

 and soil should be removed from all the pond edges so 

 that the water has a minimum depth of approximately 2 

 feet. Earth taken from the edges and not used in the 

 dam may be used for sloping the bottom of the pond so 

 it will drain properly (fig. 3). 



Earth can be properly placed on the fill by keeping 

 the fill higher on the edges than in the middle. If 

 this is done, there will be no tendency for equipment 

 to spill over and earth can be dumped the proper dis- 

 tance from the edge. Dirt should first be dumped about 

 2 feet from the upstream or inside toe stakes and about 

 18 inches from the lower or downstream stakes. This 

 procedure will save labor by making a natural slope. 

 Conversely, all cuts with the scraper should be made 

 deeper at the edges than at the center. Thi"s prevents 

 the equipment from sliding away from the banks, a 

 possibility which might result in a ragged slope. 



Fill placed on the dam should be properly compacted. 

 Maximum compaction is effected by putting earth in place 

 in thin layers and traveling the full length of the 

 fill each time. On high dams special compacting equip- 

 ment, such as a sheepsfoot roller, is needed and the 

 required density is obtained by the control of moisture 

 content. Although compacting reduces the amount of 

 settling, allowance should always be made for it. 



The actual process of constructing a series of 

 hatchery ponds is somewhat different from building a 

 dam, but the method of placing and compacting the 

 material is the same. The slope on the dikes bet'ween 

 the ponds may be uniformly 2 to 1. Where there is a 

 series of ponds, it will be necessary to make only the 

 dams or levee on the outside of the series water-tight 

 through use of a clay core or other method of close 

 binding with the clay subsoil. However, all levee bases 

 should be properly prepared by clearing off organic 

 debris and plowing the entire area. 



The design of a hatchery is dependent, on the size, 

 shape, and topography of the land on which it is 

 located. If the plot of land is properly sloped, ponds 

 may be planned in such a way that sufficient earth can 

 be removed from the pond site for the embankments. 

 Ideally, the ponds should be from 1/4 to 1 acre in 



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