On June 30, 2004, the U.S. Environmental Protection Agency (EPA) completed regulations under the Clean Water Act (CWA) establishing Effluent Limitations Guidelines (ELGs) and New Source Performance Standards for the Concentrated Aquatic Animal Production (CAAP) Point Source Category. The regulations contain requirements for wastewater discharges that must be met by new and existing CAAP facilities discharging directly to U.S. waters. The CWA establishes a comprehensive program for protecting the Nation's waters. Among its core provisions, the CWA generally prohibits the discharge of pollutants from a point source to waters except as authorized by a National Pollutant Discharge Elimination (NPDES) permit. Direct dischargers must comply with effluent limits in NPDES permits. EPA's NPDES regulations define a hatchery, fish farm, or other facility as a CAAP and therefore subject to the NPDES permit program. The regulation defines a CAAP by, among other things, the size of the operation and frequency of discharge. Those CAAP facilities subject to the ELGs must develop and maintain a best management practice (BMP) plan describing how they will achieve the ELG requirements. The CAAP must certify in writing to the permitting authority that a BMP plan has been developed and make the plan available to the permitting authority upon request. EPA did not revise the National Pollutant Discharge Elimination System (NPDES) regulation, as it applies to CAAPs. EPA has produced this document to help CAAP facility owners/operators and NPDES permit writers to understand and comply with the NPDES and ELGs regulations.