20I2 



The Cornell Reading Courses 



Fig. 170. — Diagram showing relation of dam 

 and intake box. A, apron; B, intake box; 

 C, core; D, drainpipes; E, bulkheads; F, 

 screen; G. coarse grating; H, stream bed; I, 

 spillway 



The form and the arrangement of a structure for regulating the volume 

 of water flowing into a fishpond is shown diagrammatically in figure 170. 



The dam need not necessarily be 

 high ; from two and one-half 

 to three feet of water in the 

 deepest part of the pond formed 

 by it will usually suffice. The in-' 

 take box (B) is built in the side 

 of the embankment so that it 

 may be away from the swiftest 

 part of the stream and therefore 

 out of the path of ice and debris coming down during the early spring 

 freshets. At G there should be a coarse grating in order to prevent any 

 large masses, particularly ice, logs, and brush, from entering the intake 

 box. F is a screen, loosely inserted so that it may be withdrawn and 

 cleaned. It keeps leaves and other suspended material from passing into 

 the intake pipe, which enters the box at J. The size of this pipe will 

 depend on the size and the number of ponds to be supplied, but from 

 four to six inches in diameter will be large enough to supply a pond of 

 from four to six acres in extent. For a one-acre pond, the pipe must 

 De at least two inches in diameter. At E on each side of the dam are 

 the bulkheads, which are designed to protect the stream banks and should 

 be as high as are the latter. The spillway (I), where the dam overflows, 

 must be wide enough to allow free passage of ice and other debris during 

 high water. The height must not be so great as to cause the bulkheads 

 and the banks of the stream to overflow, yet it must be great enough to 

 permit a gravity flow from dam to fishpond. 



A dam of any sort should be provided with some means for draining 

 the pond above it. A simple way 

 of accomplishing this in small 

 streams is to insert one or more 

 elbows of sewer pipe (Fig. 171, D) 

 in the bottom of the dam in such 

 a place that they may be opened or 

 closed by a person standing on one 

 of the bulkheads. A circular disk 

 made from two-inch planking and 

 just small enough to fit loosely into 

 the flange of each pipe, will serve 

 as a plug. By means of a wire loop, 



wmf/m^^m^m^^i'A^^^m, 



Fig. 171. — Cross section of a dam showing 

 drain made of sewer pipe. A, apron; 

 B, dam; C, wooden plug; D, sewer pipe 



inserted as in figure 171, the disk can be pulled out with a rake or a 

 hook. Each disk should be weighted down with iron or lead and should 



