Heal the Bay claims that "storm water runoff is a serious problem in Southern California because it is one of the major sources of pollution that impacts the health of our beaches and ocean life. The health and economic impacts are still being studied. The rapid population growth in Southern California coupled with the high cost of large scale containment and treatment have resulted in years of inaction."
To give the reader an idea of the magnitude of the problem a 2003 study estimated that in an average rainfall year approximately 300 Billion gallons of storm water runoff empties into our local ocean together with 120,000 metric tons of suspended solids, 2000 metric tons of fertilizers (nitrates), 100 plus metric tons of zinc and substantial amounts of pesticides and weed killers. The zinc comes primarily from roof guttering and down spout piping.
The Environmental Protection Agency (EPA) has recognized this problem and the problems inherent with the high cost of large scale infrastructure developments. The EPA’s phase II regulation acknowledges the need to tackle the problem at the local level (upstream) with smaller Low Impact Development (LID) projects. The EPA is investigating the use of Best Management Practices (BMP) for storm water containment to minimize runoff and to mitigate the First Flush Effect (FFE).
A number of articles have been written that address Low Impact Development which incorporates a new philosophy to keep the storm water on-site. The storm water can drain through permeable paving or open pavers or drain into a landscaped catchment area. While these are acceptable solutions they are not viable for high traffic volume areas or even high foot traffic areas. In addition landscaped catchment and treatment areas are not a practical solution in heavily built up metropolitan and urban areas. The lack of availability of land and the high cost in these areas prohibit large scale development. There is also a need to remove chemical hydrocarbons and other biological contaminants through active filtration which further limits the effectiveness of open pavers and pervious concrete. Active filtration can be as simple as a screen to capture suspended solids and polypropylene pellets or activated charcoal to absorb hydrocarbons.