Due to enforcement complexities and other problems, an approach based solely on water quality standards was deemed insufficiently effective. In the Federal Water Pollution Control Act Amendments of 1972 (Pub. L. 92500, Clean Water Act or CWA), Congress established the National Pollutant Discharge Elimination System (NPDES) whereby each point source discharger to waters of the U.S. is required to obtain a discharge permit. The 1972 Amendments require EPA to establish technology based effluent limitations that are to be incorporated into NPDES permits. In addition, the amendments extended the water quality standards program to intrastate waters and required NPDES permits to be consistent with applicable state water quality standards. Thus, the CWA established complementary technology-based and water quality-based approaches to water pollution control.