As cities grow and impervious area increases, it becomes extremely difficult to control the flow and quality of storm water. In urban areas, the water is exposed to oils, toxic chemicals, dirt, trash, and other pollutants before it is captured by drains and catchment systems. Such pollutants contaminate the drinking and recreational waters. Municipalities are working on this issue through local regulations, policies and comprehensive plans. Ultra Urban Best Management Practices, known as BMP's, are only one method to increase the quality of storm water runoff. Experts are currently testing the most reliable BMP's and integrating them into common use.