| Summary: | Here the river has been blocked off by the downstream arm of the cross river cofferdam, forcing it to flow thru the new channel on the west side of block 40. The upstream arm of the cofferdam is about to be closed, after which the enclosed area will be pumped dry and excavated. Note the frozen earth dam across the narrow gorge in the foreground. It is believed that drainage from the second ice sheet, flowing in the opposite direction to the present channel, exposed the east side bedrock possibly a million years longer than the west side, causing it to be much more weathered and deeply eroded. All granite proved remarkably sound and strong; many other dams having to accept 15,000 pounds per square inch as good.
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