long and in diameter and runs under McKinley Mountain. It begins at the Strawberry Portal in Strawberry Canyon near California State Route 18 and continues east to the City Creek Portal near California State Route 330. The East tunnel was also constructed at a slight downhill grade to allow water to flow by gravity; from the time the water enters the Strawberry Portal until it exits the City Creek Portal, the tunnel will have dropped about 55 feet in elevation. The tunnel was constructed in two segments. Original construction commenced in early 1997 at the City Creek Portal, and mining progressed along an uphill gradient from east to west. After two years of mining effort, and more than 8,000 feet into the tunnel alignment, groundwater flows into the excavated tunnel began to steadily increase. Following extensive consultation with the United States Forest Service, MWD decided to halt mining on the east tunnel and install the final 12-foot diameter pipe liner in the excavated portion of the tunnel. MWD and the Forest Service worked to determine how best to complete the remaining 22,458 feet of the tunnel. This collaboration resulted in significant revisions to the original design, revisions that would ultimately allow the tunneling effort to meet the strict groundwater inflow requirements of the Forest Service Special Use Permit. The tunnel was redesigned to use bolted and gasketed precast concrete tunnel segments. Not only were these segments designed to provide structural support to the mined tunnel, but they also were capable of delivering a nearly watertight environment inside the tunnel to dramatically limit the amount of groundwater inflow during the mining operations. Construction resumed from the Strawberry portal, working toward the original City Creek Portal construction. The tunnel was constructed using a TBM, originating from the Strawberry Portal and mining at a slight downhill gradient of approximately 18 feet per 100 linear feet (0.25%). Much like the West Tunnel, the TBM in the east tunnel encountered water-bearing strata of metamorphic and granitic rock. The presence of water, coupled with the depth of the tunnel below the surface, up to 2,100 feet underground, forced the tunneling team to deal with water pressures in the tunnel heading in excess of 200 pounds per square inch. Also, much like the West tunnel mining efforts, the TBM had to traverse branches of the San Andreas fault, and on one occasion in late 2006, the TBM