Clean Water Affordability Act of 2015

This bill amends the Federal Water Pollution Control Act (commonly known as the Clean Water Act) to require the Environmental Protection Agency (EPA) to establish a comprehensive and integrated planning approach to the permit obligations under the National Pollutant Discharge Elimination System (NPDES) program of a publicly owned treatment works (POTW) or a municipal separate storm sewer system.

A state may extend the term of a NPDES permit to up to 25 years under a state-administered NPDES program, if the permittee has an approved integrated plan.

The EPA must update the guidance entitled "Combined Sewer Overflows--Guidance for Financial Capability Assessment and Schedule Development," to ensure that the evaluations by the EPA of financial capability assessment and schedule development meet specified criteria.

States must set aside 15% of the amount of each capitalization grant they receive for water pollution control revolving funds to provide assistance to municipalities of fewer than 10,000 individuals that meet specified affordability criteria for activities on the state's priority list of POTW construction projects.

Effluent limitations must be applied at the final point of discharge from a POTW treatment facility and not to flows within the facility.

The EPA may issue NPDES permits with modified effluent limits for discharges of pollutants from a collection system servicing a POTW during periods of peak wet weather if a state concurs and the permit applicant has an approved peak wet weather management plan. States may adopt peak wet weather-related water quality standards for receiving waters during periods of peak wet weather events. The EPA must develop and publish guidance with respect to peak wet weather-related water quality standards and waste water management practices.