It seems even state-of-the-art construction projects like the Calaveras Dam Replacement Project aren’t without their ghostly places.

While moving the rock and soil to make space for the New Calaveras Dam, workers uncovered what looked like holes dug into the area surrounding the existing dam.

The holes are actually adits excavated by the builders of the first Calaveras Dam (built 1913 to 1925).  

Technically, an adit is an entrance or tunnel into a mine. Back in the early 1900’s the best way engineers had to explore the rock and soil for a dam site was to excavate adits to look at the underground geology. There are 16 total adits that were uncovered at the site.

The SFPUC knew about the presence of these adits before we started to dig for the new dam foundation. However, it didn’t ease the creepy feeling workers had when they uncovered them. And some even claim equipment broke down and didn’t work properly while they were working around the adits, as if they were haunted. Some workers avoided working around the adits altogether.

Crews carefully mapped and filled each adit with concrete or rock to stabilize the ground prior to the construction of the the new dam on top. And this also sealed in any ghosts that might be still be there.