118 GRAVEL AND PLACER MLN1NG IN ALASKA. [bull. 263^ 
Ditches and flumes for conveying- water must, as hitherto, be of 
small size. They will deliver a small amount of water at a low head. 
J 00 miner's inches of water at 75-foot head being about what may be 
obtained under favorable conditions. 
Special difficulties encountered in the interior of Alaska and the 
North generally have been found to be as follows: 
At Atlin the action of frost causes the ditch to enlarge after con- 
struction. The opinion was expressed that steel-pipe conduits do not 
freeze as quickly as flumes. In a 19- by 40-inch flume of L,960 feet in 
length it was found that the frost heaved the flume and put it out of 
grade each season, but even then it was regarded as more economical 
than a ditch. The flumes on McKee Creek have to be gone over every 
spring to restore the grade. Sills are set in 4 inches of blocking on 
the stringers so that the grade can be regulated. It was also said that 
the native Atlin lumber is preferred for the flumes and sluices, as 
imported Pacific coast lumber warped badly. If native lumber is 
used, 8 inches is the greatest width available. Notwithstanding the 
cost of maintenance, ditches are much used at Atlin, one company 
operating 10 miles of ditch. 
In the Klondike district, where nearly all ground is solidly and per- 
manently frozen, it is said that three years after construction must be 
allowed to get a ditch into condition to stand. Various estimates have 
been made and projects formulated in this field for bringing in water 
from a distance for the purpose of working the remaining gravels of 
the benches (the so-called ''White Channel") which lie at an average 
elevation of 270 feet above the rich bottoms of Bonanza, Eldorado, 
and Hunker creeks. The building and maintenance of a ditch having 
its source in some of the higher tributaries of Klondike River and 
affording water at a sufficient head is not regarded as an impossible 
engineering feat, but up to the present the cost has been considered 
prohibitive. Dry seasons alternate with wet ones, and in consequence 
the amount of water available during a given season might vary 
from, say, 1,000 inches to 5,000 inches. No calculations based on the 
full capacity of the ditch could be made in advance, therefore, 
regarding the season's product. 
Recent information concerning the Acklen ditch, led along the north 
side of Klondike River near Dawson for the purpose of hydrauliek- 
ing high benches bordering that stream, has been embodied in the 
table. It is stated that the cost of the earth excavation of this ditch, 
7 by 4 by 2i feet deep and 41,500 feet in length, was $34,000. 
Small storage reservoirs are used by many of the Klondike operators 
to impound the small and variable amount of water available for 
working the benches of the White Channel. On Hunker Creek a 
small ditch 3 by 2 feet and 4 miles long is in excellent condition after 
