EPA is promulgating water quality standards that establish methods to implement Puerto Rico's existing antidegradation policy for waters in the Commonwealth of Puerto Rico. EPA was required to propose antidegradation implementation methods under court order. The Clean Water Act requires that all States, Territories, and authorized Tribes develop water quality standards that include the designated use or uses of the water, water quality criteria to protect those uses, and an antidegradation policy and implementation methods. Through this promulgation, the federal antidegradation implementation methods are added to Puerto Rico's water quality standards.