128 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
Yukon-Tanana field. Mr. J. P. Hutchins a states that during the sum- 
mer of 1904 a reservoir was built in the Klondike which has a 
capacity of 26,000,000 gallons and requires a dam 40 feet in height. 
Many small reservoirs (see -PI. XXI, B) are used in the North, 
affording from 50 to 100 inches of water for a run of a few hours. 
Reservoirs for the providing of sluicing water for winter dumps have 
been built on Anvil Creek for catching snow water. In some cases 
even snow fences have been erected behind the dams to increase the 
size of the snowdrifts. 
The Alaskan miner has at hand the vegetable sod or peat, a material 
which has proved efficient under Alaska conditions for the building of 
small dams. The construction of dams is discussed on pages 56-57. 
In building small storage reservoirs for hydraulicking, it is as necessary 
in Alaska as elsewhere to determine the proper elevation, to select as 
large a catchment area as possible, and to take into consideration 
absorption, evaporation, and the character of the ground and underly- 
ing bed rock. The angle of slope for a peat dam, as given by J. T. 
Fanning, 6 is 2.75 horizontal to 1 vertical. Experience has shown that 
in Alaska, owing to the permanent frost, such dams will stand at a 
smaller angle, especially if brush is laid alternately with sod. The 
cost of storage dams in the interior may be reckoned at $1.75 per cubic 
yard of earthwork, and in Seward Peninsula at $1 per cubic yard. 
The expedient of building settling ponds must be resorted to in 
places where a small amount of sluice water is used over and over 
for successive operations, as on Anvil Creek, in Seward Peninsula. 
Two such dams for retaining sediment, one of which is shown in 
PI. XXII, A, are in. use on Anvil Creek. The water is drawn off 
from these as often as possible. In the second case it is drawn off at 
intervals of ten hours to the supply Hume. 
PIPE LINES. 
In hydraulic mining the water is distributed from the pressure box 
to the monitors and elevators by means of wrought-iron or, more gen- 
erally, steel-riveted pipe, usually made up in sections 17 to 19 feet 
in length. Sheet steel is used, from 8 to 16 U. S. standard gauge, 
bent, each plate, 30 or 36 inches in length, being riveted in double 
rwws lengthwise and single on the ends. The sizes used in Alaska 
vary from 8 to 36 inches. The pipe is shipped by the manufacturers 
either made up and riveted, as above, ready to be laid with slip joints, 
or the material is supplied in short plate sections, bent, punched, and 
furnished with necessary rivets, baled and nested for transportation, 
ready to be cold riveted on the ground. Fig. 22 shows a form of ship- 
«Eng. and Min. Jour., Jan. 5, 1905. 
^Treatise on Water Supply and Engineering, p. 345. 
