This study is based on using available published data on nutrient enrichment of U.S. surface waters, EPA and state nutrient control guidance, policy, and water quality standards, prior analysis performed for API by a third-party consultant, petroleum refinery effluent quality data from the EPA Integrated Compliance Information System/National Pollutant Discharge Elimination System (ICIS-NPDES), and permit data collected from the files of the Texas Commission on Environmental Quality (TCEQ).