1 - Alaska Energy Data Inventory

In anticipation of additional materials being introduced, the rock trapwas designed to handle at least 60 yd 3 of additional sediment beforeconstriction becomes a concern.A smaller rock trap was considered in which "self cleansing" wouldoccur i.e., if a severe constriction occurred, higher velocities would becreated which would simply move rubble out of the way and create more flowarea. This approach was abandoned because of the variety of intangiblesthat exist in sediment transport and tractive force analysis.(3 ) Tractive Forces in Rock Trap Tractive force theory(references 19 and 20) indicates that under normal conditions the maximumexpected velocity in the power tunnel of 5.04 ft/s will move particlesranging in size from 0.5 inches to 2.2 inches. Reference 1 shows thathighly turbulent flows can produce tractive forces considerably greaterthan those predicted by tractive force theory and considering the highlyturbulent conditions at the rock trap and for some distance downstream, itis possible that stones much larger than 2.2 inches in diameter can bemoved toward the gate structure. The bulk of these larger stones will cometo rest downstream from the rock trap in the unlined tunnel, but if any arecarried further, the secondary rock trap at sta 11+40 assures that no largestones will reach the gate structure.E. Final Lake Tap Blast. When tunnel excavation is completed,preparations will begin for the lake piercing blast. Instrumentation,piping and blast ignition wires will be installed in the tap area as shownon Plates 11 and 12. The instrumentation will consist of:(1) A water level monitoring device in the rock trap that willtransmit to a readout panel near the gate structure access adit portal. A2-inch pipeline will be installed to supply compressed air to the lake taparea from a compressor at the gate structure access adit portal.(2) Devices to measure blast pressures at three locations in therock trap and tunnel. The locations will be immediately under the tapBl-44