90 DAMS AND HEADWORKS 



top should be slightly convexed and of a minimum width of 8 feet 

 plus 1 foot in width for every 5 feet over 15 feet in height. The 

 slopes should be two horizontal to one vertical, except if stone is 

 used on the downstream half it may be one and one-half horizontal 

 tc one vertical. If the upstream part is of very fine material, the 

 slope must be less. A berm, or horizontal surface, which shall 

 be not less than 4 feet wide, shall be constructed on the slopes at 

 every 20 feet horizontally from the top. On the downstream 

 face these berms shall be provided with paved gutters. The up- 

 stream face shall have an 18-inch stone pavement laid in broken 

 stone or gravel from the top to the upper berm, and below shall 

 have a pavement of rip-rap. The downstream face is to be sodded 

 or covered with 12 inches of gravel or rip-rap. 



" Every earth dam must be provided with a masonry spillway 

 of sufficient unobstructed area to take the high flow, and built 

 with the same requirements as for masonry dams. The height 

 of the dam shall be at least 3 feet above high flow, plus 3 feet for 

 a reach, or expanse of water upstream, of one mile, plus 8 feet for 

 a reach of two miles, and proportional for an intermediate reach. 

 " Earth dams of over 10 feet in height shall be provided with 

 a masonry core in the middle, the top to be not more than 2 feet 

 below the top of the dam, and a top width of not less than 2 feet 

 with a batter of 1 horizontal to 24 vertical on each side. Or, the 

 core may be placed on the upstream side, in which case the width 

 of the core at any point must be equal to half of the depth. Or, 

 the core may be omitted and the dam made 5 feet wider and 3 feet 

 higher than above specified; in this case the hydraulic process of 

 construction may be employed. 



" Masonry Dams: The least width of masonry dams shall be 

 one-tenth of the height, with a minimum of 4 feet. The mini- 

 mum width at any depth shall be two-thirds the depth below the 

 highest water level. 



" The masonry must be built up in horizontal sections with 

 center grooves in the top and sides for bonding, formed by em- 

 bedding beveled timbers in the concrete. Concrete masonry 

 shall have vertical cast-iron bars in the upstream face, placed at 

 least 2 feet apart and of sufficient length to protect the masonry 

 against ice and floating bodies. 



"Reinforced Buttressed Dams: The buttresses shall not be 

 over 20 feet apart for dams over 100 feet high on rock foundations, 



