From the late 1800s to about 1920, gas for lighting and heating was produced from coal and oil at manufactured gas plants (MGPs). These plants generated residues such as coal tars and "lampblack," a powdery material similar to soot that contain toxic chemicals. The residues were often buried on-site.
When SCE was a young company, it acquired a number of Southern California's manufactured gas plants. Although most of the manufactured gas plants were sold around 1916 when natural gas became available, SCE is still legally responsible for the residues associated with the long-closed plants under terms of the federal Superfund law enacted in 1980.
SCE has Superfund liability at 20 former manufactured gas plants in Southern California. Under supervision of state regulators, Edison is investigating and cleaning up the former MGP sites. One innovative technique being used to clean sites includes injecting oxidizing agents-such as ozone gas or liquid peroxide-into soil in order to break down contaminants into harmless component chemicals in-place. This technique minimizes the impact to communities by eliminating the need for excavation, transportation and offsite disposal of contaminated soil.
Of the 20 MGP sites, six have been cleaned and closed with approval of state environmental regulators; the remaining 15 are currently being investigated or are actively being remediated.
