The EPA has signed a rule finalizing its approval of California’s ban on all sewage discharges from large cruise ships and most other ocean-going ships in state marine waters along the 1,624 mile long coast from Mexico to Oregon and surrounding major islands.

A press release from the EPA said that “several dozen large cruise s hips make multiple California port calls each year while nearly 2,000 cargo vessels made over 9,000 California port calls in 2010 alone.” The EPA said it estimates that the rule will prohibit the discharge of more than 22 million of the 25 million gallons of treated vessel sewage generated in California waters each year, “which would greatly reduce the contribution of pollutants still found in treated vessel sewage.”

Under the Clean Water Act, states may request the EPA to establish vessel sewage no-discharge zones if necessary to protect and restore water quality.