Built in 1921, the San Clemente Dam near Carmel Valley, California was once an important source of water for towns on the Monterey Peninsula on the Carmel River.
But now, the 106-foot-tall structure is just a liability. It hasn’t been used as a water source since 2002 and in 1991 it was declared at risk of failure during an earthquake.
According to MercuryNews.com, construction crews began the three-year, $84 million process of tearing down the San Clemente Dam last week. It is the largest dam-removal project in the state’s history.
In addition to removing the risk of wiping out hundreds of home downstream in the event of an earthquake, the removal will open up 25 miles of upstream tributaries and creeks, allowing endangered steelhead trout to return to their historical spawning grounds, the site reports.
The removal will be an intricate process for Granite Construction of Watsonville, California. Simply blowing up the dam would release roughly 2.5 million cubic yards of sediment that has accumulated behind the dam and kill just about everything in the river—not to mention flooding 1,500 homes downstream.
Instead, Granite Construction will build a dike and dig a permanent 450-foot channel to reroute the river into the San Cemente Creek. The dike will block off the huge sediment pile which will be covered with plants.
Meanwhile, the dam itself will be “broken down, chipped in pieces” by excavators, project manager Jeff Szytel told MercuryNews.