It is the construction project that local residents prayed for, that cannot come soon enough, based on the whims of a winding, crumbling, Highway 1.
"If you maintain it properly, it will last forever," said Dan Zerga who helped to design the Devil's Slide tunnel with two single-lane parallel bores, each 4,400 feet long and now at a symbolic milestone because the digging and excavating have finished.
Crews removed 314,000 cubic yards of soil, enough to build a mountain above the project. Inside is a cool, dark, hardhat environment.
Crews have covered and sealed every square-inch inside the bores with thick layers of waterproofing plastic that fits like a glove. But most of us will never see it, not after more crews come along to cover the details with thick layers of concrete.
The byproduct of all that fresh concrete, the tunnel floors are always wet from continuous rivers of water and mud. In some sections the puddles are so big and deep, that crews refer to them as lakes.
Meantime, giant trucks move men and equipment in and out, and even though some of them take up most of the width of a bore, they rarely get in each other's way.
The speed limit? Five miles an hour.
And if you ever make the assumption that building a tunnel is just a matter of digging, you will change your mind after walking through the construction from one end to the other.