1 - Alaska Energy Data Inventory

Where:Q = Flow of air at atmospheric pressure (ft 3 /min)K = Permeability coefficient (ft/min)A = Air surface area of tank interior (ft2)H l= Tank internal air pressure (gage - ft of water)H 2= External groundwater head (gage - ft of water)L = Linear distance from tank interior to face of mountain (ft).,Air leakage, adjusted to a gage pressure of 850 ft of water, was calculatedto be 3,895 ft 3 /mo.The Jukla tank, having a total volume of 219,000 ft 3 , was found toleak no air when the internal air pressure was below the externalgroundwater pressure of 558 ft of water, and 1 eaked between 20 and 200normal litres (at atmospheric pressure) per minute when the internal airpressure exceeded 558 ft of water.Assuming that air leakage is directlyproportional to total tank volume, and using the maximum air leakage rateof 200 normal litres per minute from Jukla, the Crater Lake tank with avolume of 65,508 ft 3 would leak air at 3,509 ft 3 /mo when adjusted to agage pressure of 850 ft of water. The largest anticipated tank of88,628 ft 3 , corresponding to the 12.2 ft diameter power tunnel, wouldleak at 4,747 ft 3 /mo on this same basis.The air chamber at the Driva project, which operates with 177,000 ft3of air and is excavated from very sound rock with over 3,000 ft of rockoverburden, showed no air 1 eak age dur -j ng air and water pressure tests andno leakage during its first two years of operation. The compressors hadnot been used except to fill the tank initially.Regarding possible air loss through entrapment in the air chamberwater, studies have been performed at the Jukla project which give anindication of possible air loss. Although laboratory studies prior toconstruction at Jukla indicated that air could be lost at a rate of0.6 ft 3 up to 1.6 ft 3 of air per thousand ft 3 of the water volumeB4-20