PIPE UNION 



WATER DISCHARGE 

 PUMP 



PIPE UNION 

 WATER INTAKE 



WINCH 

 ASSEMBLY VACUUM SLED 



~^s^ 



\/ 



RAFT-MOUNTED WATER DREDGE 



Figure 1. — Schematic drawing of the suction sampler. 



WINCH LINE 



BRIDLE - 



FLEXIBLE VINYL HOSE 



SUCTION HEAD 



SUCTION INTAKE 



■INNER RUNNERS 



FRONT VIEW 



SCALE 



I- 



15.2 cm. 



H 



SIDE VIEW 



Figure 2. — Schematic drawings (front and side view) of the vacuum sled. 

 Note that the inner runners penetrate substrate. 



into the substrate and thus control the depth 

 sampled. The two inner runners are spaced 

 8.0 cm. apart down the center of the sled 

 frame and form the sides of a trough. These 

 runners project 3.8 cm. below the skis, pene- 

 trate the substrate, and effectively limit the 

 width of the swath sampled. 



The suction head is constructed of two 

 15.2-cm. sections of 7.6-cm. outside diameter 

 aluminum irrigation pipe, welded to form a 

 100° elbow. The suction head is inserted 

 through a 7.6-cm. diameter circular hole in 

 the after transverse plate of the sled frame 

 and through a 7.6-cm. access hole in the roof 

 of the trough. The opening on the suction head 

 is 5.7 cm. above the substrate which it faces. 

 An adjustable brass clamp serves to hold a 

 hard rubber flap, 0.3 cm. thick by 7.6 cm. 

 wide, in place around the after portion of the 

 suction head. The flap spans the width and 



depth of the trough behind the suction head. 

 Because the opening on the suction head is in 

 the afterpart of the trough, most organisms 

 are enclosed before being subjected to suction. 

 In addition to preventing the escape of or- 

 ganisms, the enclosing effect of the trough and 

 flap serves to concentrate and increase suction 

 directly under the suction head intake. 



A bridle and ballast complete the sled as- 

 sembly. The wishbone-shaped bridle, con- 

 structed from 1.0-cm. stainless steel rod, is 

 affixed rigidly to the outer sled frame. The 

 ballast, a 9.1-kg. lead block is supported by a 

 pair of 2.5- by 2.5-cm. aluminum angle pieces 

 welded to the inner runners. The angle pieces 

 extend 25.4 cm. behind the sled body. The 

 ballast causes the two inner runners to cut 

 into the substrate when the sled is pulled. The 

 sled, including ballast, weighs 16.3 kg. and is 

 84 cm. long, 45.7 cm. wide, and 30.5 cm. high. 



