U6 



lERIGATION INVESTIGATION'S IN CALIFORNIA. 



rubblestone of large size. The downstream face wall is 15 to 18 feet thick at the 

 bottom, diminishing to 6 or 8 feet at the top. Many of the stones weigh from 0.75 

 of a ton to 4.5 tons. The lower portion of the wall is 17.5 feet high, with a batter of 

 15 per cent. It is built of heavy stone in horizontal beds. The backing is tied to 

 the stone hj long iron rods. The upper portion is built with a slope of 45 degrees. 

 A plank skin is firml}' spiked on the upper face of the dam. This planking is of 

 heart sugar pine, 3 by 8 inches, dressed. At the bottom the plank is fitted to bed 

 rock and calked with pine wedges. There are three thicknesses on the lower 25 feet, 

 two thicknesses on the next 35 feet, and one thickness on the upper 36 feet. A cul- 

 vert, with foundation and avails built of heavy dry rubble covered with heavy granite 

 slabs 16 to 18 inches thick, extends through the dam. Three wrought-iron pipes of 

 No. 12 iron, 18 inches in diameter, pass thi-ough the water face of the dam. Their 

 intakes are protected by a strainer. A valve is placed at the lower end of each pipe. 

 The aggregate discharge of these pipes is 280 cubic feet per second. The dam is 

 built V-shaped, with the angle, of 165 degrees, pointing up stream. The cost was 

 $151,521. The wasteweir is over a crib of round cedar timbers, from 12 to 30 inches 

 in diameter, firmly bolted together, with the foundation logs securely fastened to the 

 bed rock with li-inch bolts. The cribs are solidly filled with granite blocks of 

 various sizes. A plank fencing of 3-inch heart sugar pine is spiked on the water 

 face. The crest of the original dam is 92.5 feet above datum line, being 4 feet longer 

 than the crest of the main dam. A light superstructure of 4 feet allows the water 

 to be raised to the height of the main dam. The wasteweir is provided with twenty- 

 eight escapes, each 4 feet wide and 11 feet deep. These wasteways are closed when 

 all danger from freshets is passed. 



It is believed that the structure is sufficiently stable to allow a flood of 16,000 

 cubic feet per second to pass with safety through the wastes and over its crest. The 

 water passing over the dam falls on bare granite bed rock, and thence down a steep 



gorge. 



Besides Bowmans Reservoir the companj^ has the following reservoirs: 



Reservoirs of the North BloomfiM Gravel and Mining Company. 



Name. 



Capacity. 



Sawmill . 

 Shotgun . 

 Island ... 

 Middle .. 

 Round . . . 

 Crooked . 



Cubic feet. 

 2,000,000 

 3, 423, 816 



23,027,558 

 2,395,800 

 2,907,630 



16,000,000 



The combined storage capacity of these reservoirs is 961,754,804 cubic feet, or 

 445,257 24-hour miner's inches. 



The main canal is the Bloomfield Ditch, which commences at Bowmans Lake 

 and follows along the main ridge, between the South and Middle forks of Yuba 



'The above description of the Bowmans dams is essentially the same as written for Bowie by 

 Hamilton Smith, jr., who )>lanned and constructed the dams. 



