17 



On larger jobs, or where hauls are more than 500 feet, 

 a 113-dhp track-type tractor is more economical. Of 

 course, availability of equipment may be the decisive 

 factor in most cases. 



STRUCTURES 



Types of structure to be used in conjunction with 

 hatchery layouts are largely a matter of opinion, but 

 experience has shown that general designs are more 

 advantageous. Likewise, experience has demonstrated 

 that adequate construction is more economical than 

 skimping on sizes and materials. Thus, pipelines of 

 sufficient size are more economical than .pipelines that 

 are too small. In the past, tile drain lines, caulked 

 with cement, have been used extensively because the 

 original construction cost is lower. Unfortunately, 

 there have been many failures with these lines on 

 account of loose caulking, the entrance of tree roots, 

 pressure from the fill, and for other reasons. 



Great advances have been made in the last few 

 years in pipeline fabrication. Among those types 

 recently developed, the most suitable for use as outlets 

 and the most easily installed are spiral-welded steel 

 pipe and asbestos-cement cast pipe. Spiral-welded pipe 

 is light inweight, long-lasting .if properly installed, 

 and comes in long lengths. Asbestos-cement pipe comes 

 in shorter lengths but can be cut with a saw, and the 

 joints have considerable flexibility. It is not subject 

 to corrosion, so its utility is almost indefinite. 

 Standard fittings can be used with both kinds of pipe, 

 and they can be utilized for both drainage and water 

 lines. 



In ponds 1/4 acre or less in area, the drainline 

 should be not less than 6 inches in diameter; and in 

 ponds 1/4 to 1-1/2 acres, the line should be not less 

 than 8 inches. Use of large drainlines has a number of 

 advantages, including savings in time and labor and 

 frequently a saving in fish (which may be lost otherwise 

 through high temperature, suffocation, muddy water, 

 etc., in the draining process). 



Every pond should be equipped with an outlet 

 structure of some type. This outlet or kettle serves 

 a number of purp.oses. It acts as an overflow where 

 rain or other inflow of water raises the pond level 

 above normal, and in the process of draining the pond 

 the outlet holds back the fish so that they can be 



