. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. 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
. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. 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 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 m
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