To look down from the center narrow high walkway of the overhead frame bridge into the Grand Bypass Channel was to look directly into the throat of an impending deep-rock disaster.
Ninety feet below, the channel was a sheer, upright trench blasted through the dark stone of the western mountain. It was ninety feet wide, its walls jagged and unmortared. He dropped down to a boulder-strewn floor where forty years of flood debris had piled up into massive dams of dead hemlock trunks, gravel bars, and shattered rock.
At the upstream head of the trench, forty yards to the north, sat the temporary earth-and-timber coffer-dam. The crumbling dike of clay loam and hemlock piling that had held back the Inland Sea for four decades.
The coffer-dam was dying.
The lake level had risen so high that brown, muddy water was already spilling over the center crest of the earth embankment in a dozen ragged notches. The water was not merely overflowing. It was scouring the downstream face, cutting deep erosion gullies into the clay with every passing minute.
Tomas watched from the narrow high walkway rail. Then, a twenty-foot section of hemlock timber stacked timber frame gave way under high-pressure suction, washing down into the rock trench with a bone-shaking roar that sent mud geysers twenty feet into the air.
