Even though more U.S. cities are trying to come up with more efficient ways to control storm-water runoff, some developers and regulators are still not up to speed with technology and methods, according to Thomas Ballestero, a civil engineering professor at the University of New Hampshire. Some systems in cities such as New York and Chicago treat sewage and storm water that have been carried in the same pipe and have problems with overflow when there is too much rain. Green roofs and permeable pavement could help mitigate the problem.