Congress amended the Clean Water Act in 1996 to create a new section, section 312(n), captioned "Uniform National Discharge Standards (UNDS) for Vessels of the Armed Forces." Section 312(n) directs the EPA and DoD to establish national discharge standards for discharges incidental to the normal operation of a vessel of the Armed Forces in three phases of rulemaking. After the final phase is complete, these national standards will preempt State discharge standards for these vessels though States may enforce the uniform national standards. The EPA and DoD jointly promulgated Phase I of these regulations, 40 CFR part 1700, on May 10, 1999 (64 FR 25126). Phase I concluded that 25 out of 39 discharges from vessels of the Armed Forces would require the EPA and DoD to jointly establish discharge performance standards by regulation (Phase II). During Phase III of the rulemaking process, DoD will establish implementing regulations. The discharges have the potential to introduce oil or other organics into receiving waters (such as bilge water); some have the potential to introduce copper or other metals (such as hull coating leachate); and some have the potential to introduce aquatic nuisance species (such as ballast water). Phase II of the regulations establishes discharge performance standards for each of the 25 discharges identified in Phase I. The development of the Phase II discharge performance standards is being done in three separate "batches" of rulemaking. The EPA and DoD proposed the UNDS Phase II - Batch One Rule on February 3, 2014, and published the UNDS Phase II - Batch One Final Rule on January 11, 2017. Batch One included the following 11 discharges: aqueous film forming foam; chain locker effluent; distillation and reverse osmosis brine; elevator pit effluent; gas turbine water wash; non-oily machinery wastewater; photographic laboratory drains; seawater cooling overboard discharge; seawater piping biofouling prevention; small boat engine wet exhaust; and well deck discharges. Current Action: The EPA and DoD proposed the UNDS Phase II - Batch Two Rulemaking on October 7, 2016. The EPA and DoD are working on the UNDS Phase II - Batch Two Final Rule and anticipate publication in the Fall of 2018. Batch Two includes the following 11 discharges: catapult water brake tank & post-launch retraction exhaust; controllable pitch propeller hydraulic fluid; deck runoff; firemain systems; graywater; hull coating leachate; motor gasoline compensating discharge; sonar dome discharge; submarine bilgewater; surface vessel bilgewater/oil-water separator; and underwater ship husbandry. Future Action: UNDS Phase II - Batch Three will include discharge performance standards for the three ballast water related discharges. The agencies have not yet identified a target date for proposal of the Batch Three standards.