In total, the Central Pacific had eleven tunnel projects (Nos. 3 through 13) under construction in the Sierra from 1865-68, with seven tunnels located in a stretch on the east side of Donner Summit. The tunnels were usually built by drilling a series of holes in the tunnel face, filling them with black powder and detonating it to break the rock free. The black powder was provided by the California Powder Works near [[Santa Cruz, California]]. These works had started production in 1864 after the [[U.S. Civil War]] had cut off shipments of black powder from the East to the mining and railroad industry of California and Nevada. The Central Pacific was a prolific user of black powder, often using up to 500 kegs of each per day.