CRANBERRY GROWING 



13 



Dams^ 



The reservoir and bog dams (Fig. 7C) usually have a wide core of sand walled 

 on both sides with turf. Sometimes the turf is necessary on only one side. The 

 turf walls are built layer on layer with some sand between the layers for ballast, 

 the pieces of adjoining layers overlapping. The turf is often taken from the 

 upland near the bog; but when the swamp itself is scalped, the turf obtained may 

 be used partly in facing the dams. 



A trench deep enough to reach below all tree roots should be dug along the 

 middle of the dam location and filled with sand to make a good connection with 

 the soil for holding water. If the dam is to cross very soft land, it must be sheet- 

 piled lengthwise in the middle with matched boards or planks. It should have 

 sloping sides and be widest at the bottom, with dimensions according to the head 

 of water. The wider it is the better it will resist muskrats. It should be a foot 

 higher than high water to keep waves from wearing a hole through the top. It 

 may also serve as a roadway. It is well to ditch the bog a few feet from the dam, 

 making a berm. 



Fig. 10. A Covered or Trunk Gate. 



A gate^ for the passage of the water must be built in the dam — a job which 

 requires an experienced gate builder, for it must be made properly and carefully. 

 It often pays to make the gate of reinforced concrete, but redwood or kyanized 

 cedar lumber is better on soft land. A continuous cross sheet of matched piling 

 under the middle of the gate and extending out into the dam on each side of it is 

 necessary, and two or three sheets may be needed if the water held is to be deep 

 and the soil under the gate is soft or disturbed by springs. A stream of water 

 from the hose of a power sprayer, delivered under high pressure through a piece 

 of iron pipe with its tip compressed to a very narrow slit, helps greatly in driving 

 the piling by loosening the soil. 



The most experienced growers prefer the covered or trunk gate (Fig. 10). It 

 is much stronger than the open gate (Fig. IIB) and rots less when made of wood. 

 A concrete bulkhead opening into piping (Fig. 11 A) is advisable in some places. 



The outlet gate must be large enough to carry off the water of the heaviest 

 rains and of flowages quickly. 



' R. B. Wilcox (Proceedings of the 78th .\nnual Meeting of the American Cranberry Growers' 

 Association, 1948, pp. 2.S, 28, and 32). 



° Commonly called a "flume" by the growers. 



