A California refinery has been fined $1 million for threatening groundwater supplies by dumping oil refinery waste into its wells, U.S. officials said.

Santa Maria Refining Co., a subsidiary of Greka Energy Corp., was sentenced to three years probation and ordered to pay a $1 million penalty for violating the federal Safe Drinking Water Act. Half of the fine is to be applied to the Los Padres National Forest Restoration Project.

Santa Maria Refining pleaded guilty in U.S. District Court and was sentenced last week, the U.S. Environmental Protection Agency said Friday.

Federal investigators determined that Santa Maria Refining dumped wastewater containing benzene into injection wells that could have seeped into groundwater supplies. Benzene can cause anemia, excessive bleeding and cancer, as well as damage the immune system.

The three Santa Maria Refining officials who pleaded guilty in the case each face up to five years in federal prison.

Copyright 2007 by United Press International