15 



area, but the topography of the land will dictate to 

 some extent the size of pond that is constructed most 

 economically. Under no circumstances should there be 

 any large number of ponds of an acre or more in size. 

 Small ponds are handled more easily and are generally 

 more productive (fig. 4). 



Plans for excavation and for the placement of 

 drains and water lines should be made by a competent 

 engineer. All elevations, all stakes for drain and 

 water lines and for the dikes, should be placed before 

 excavation starts. The drainage lines are generally 

 placed in or through the levees so that it is essential 

 to have these lines in place before pond construction 

 starts. The drainage lines always lead from the deepest 

 part of the pond to a convenient watercourse that will 

 carry off the drainage water. 



Ponds should be so constructed that the minimum 

 depth at the shallow end is about 2 feet. Ponds to be 

 used for propagation purposes should be sloped so that 

 they are at least 5 to 6 feet deep at the outlet. Ponds 

 used for holding fish through the winter must be at 

 least 10 to 12 feet,' deep in the northern States. How- 

 ever, the size of the pond will to some extent determine 

 the depth at the outlet. 



The pond bottom should be sloped from the sides and 

 ends toward the center and the center sloped from the 

 shallow end to the outlet. The grade through the center 

 of the pond should be not less than 1 foot for each 100 

 feet of pond length. Where a series of hatchery ponds 

 is being constructed, the ponds are partly above and 

 partly below natural ground level. 



The type of equipment most economical to use for 

 excavating a series of ponds depends upon the size of 

 the job and the distance that earth must be moved. 

 Horse-drawn equipment is economical only for small jobs 

 and short hauls but may be used for larger jobs if it 

 is the equipment available. With horses, a slip scraper 

 may be used economically for moving as much as 50 feet 

 but for more than 150 feet the cost is so great that 

 some other type of equipment should be considered. If 

 horses are used at longer distances, a four-horse- 

 loaded, two-horse-transport wheeler should be used. 



Maximum efficiency may be obtained with perhaps a 

 35-dhp (D-4) tractor bulldozer at distances from 100 to 

 150 feet and where the grade is not more than 5 percent. 

 As th« grade increases, the efficiency of a bulldozer 

 decreases rapidly. A self-loading, carrying-type 

 scraper should be used at distances greater than these. 



