Storm Water TreatmentMenu:
Chesapeake Bay Foundation's Philip Merrill Environmental Center- three cisterns collect rainwater from roof for use in building
Photo by Robb Williamson, NREL PIX #10291
Storm water is becoming a more critical issue every day. As urban sprawl continues to replace natural areas with impervious surfaces, we compromise the hydrologic cycle's natural ability to filter water and recharge aquifers. Instead of rain drops irrigating the areas on which they fall, storm water runs off pavement, accumulates in the streets, and enters the storm sewer. The water is often carrying a myriad of pollutants picked up along the way, like motor oil, antifreeze, heavy metals and even pathogens. In most cities, storm sewers empty their contents into nearby waterways. Other cities still have combined sewers and storm water overwhelms the capacity of their wastewater treatment facilities. During heavy rains, release valves in the sanitary sewer open, discharging raw sewage and liquid industrial waste into nearby systems. In either scenario, the ever increasing storm water runoff poses major problems for cities and its citizens, and causes major damage to riparian habitats.
Storm water is not only a hazard and an expense for cities, but businesses as well. Storm water mitigation methods must be employed for most newly constructed buildings, leading to the addition of impervious surfaces like parking lots and rooftops. Retention ponds, and in some cases large underground storage tanks, must be installed and maintained at the expense of the building or business owner.
On the other hand, there are ways to be proactive about storm water mitigation as a business owner, such as capturing rainwater and using it for irrigation or hand washing. A common and very simple method of rainwater harvesting is the placement of rain barrels under gutters. The landscape around buildings can also be designed to allow storm water to infiltrate the ground rather than run off into the storm sewer or the sanitary sewer. Creating a rain garden, for example, can be a very effective method that will allow water to recharge aquifers. In addition, rain gardens reduce the otherwise added expense of the retainment and treatment of runoff posed upon business owners, local treatment facilities and area water bodies. Another very effective way to reduce storm water runoff is to landscape the rooftops of buildings. Green roofs are beneficial in many ways besides capturing rain water, such as extending the life of the roof, keeping the building cool in summer and warm in winter, providing wildlife habitat, reducing the urban heat island effect, absorbing carbon dioxide and creating aesthetically pleasing green space amidst the surrounding concrete.
Our rate of growth and consumption of green space is allowing storm water to overwhelm our waterways and city infrastructure. The most important thing to realize as business owners and home owners is that we must begin to employ storm water reduction methods if we want to protect our vital water resources.
CDM is a consulting, engineering, construction, and operations firm providing service to public and private clients worldwide. The CDM site offers case studies on various water management strategies.