The Hastings Mine is a mineral extraction site approximately 4.5 miles (7.2 km) northeast of the city of Vallejo, Solano County, California. The Hastings site on Sulfur Springs Mountain was used for extraction of cinnabar until the year 1930. The Hastings Mine is classified as a medium priority mine from the standpoint of environmental oversight. In the last inspection of the Hastings Mine in 1997, sediments in a drainage below the mine were found to contain ten parts per million of mercury; furthermore, spring water below the mine exhibited a water concentration of .31 micrograms per liter (a violation of the State of California standard for receiving waters of .05 micrograms per liter). Miles of underground shafts were driven in the course of working the quicksilver deposits in the area.