The summer of 2001 brought with it torrential downpours, dumping heavy rains across many parts of the country. From the Midwest to the Southwest, communities across the U.S. coped with excessive water conditions for a second consecutive year.

In Washington D.C., flood conditions brought concern over the proper treatment and release of excess storm water. As storm pipes overflow, officials continue to seek a viable solution to prevent contaminated water from damaging the region during future storms. A draft plan currently being considered in the nation's capital is the construction of miles of tunnels in which millions of gallons of excess water could be held until it can be treated.

While flooding is debilitating for a number of obvious reasons, including power outages and drowned streets, what is not as clear are the other detrimental effects uncontrolled flood conditions bring. Bacteria, pathogens and other harmful toxins are easily spread as untreated water rises and courses through flooded streets and homes. Overflow also feeds into nearby bodies of water, breaching water quality standards and potentially harming the people and wildlife that depend on them. When the floodwaters recede, one fact remains: Many cities are ill prepared for the aftereffects of heavy rains.

Storm water discharges from many sources are inadequately controlled
Combined sewer overflow (CSOS) is discharge from a sewer system that is designed to carry wastewater and storm water in the same pipe to a sewage treatment plant. In periods of heavy rainfall - such as the conditions experienced in the D.C. area this summer - a combined sewer system can become overburdened and spill over. According to the U.S. Environmental Protection Agency (EPA), about 950 jurisdictions serving 40 million people have systems in which sewage and storm runoff share pipes. Because many water treatment facilities cannot adequately handle the extra flow, they often are left to discharge excess raw wastewater directly to rivers, lakes and estuaries without being properly treated, causing numerous health and environmental hazards.

Chlorine curbs contamination
Chlorination is by far the most common method of wastewater disinfection and is used worldwide for disinfecting pathogens before water is discharged into receiving streams, rivers or oceans. Indeed, the EPA and the U.S. Centers for Disease Control and Prevention (CDC) both advise chlorine should be used to treat water in flood situations to prevent the spread of disease by killing harmful substances.

Underground tunnels bring viable solution
It is estimated that nearly three billion gallons of unprocessed wastewater and storm water spew into area waterways across the nation. Lawmakers continue to actively seek an effective and long-term solution.

Washington D.C. is joining other metropolitan areas, including Atlanta, Milwaukee and Chicago, to investigate the use of underground tunnels to help control and prevent harmful flood conditions. The Washington D.C. Water and Sewer Authority proposed a plan that, if realized, would divert excess water to such tunnels. Once the flooding conditions eased, the tunnel contents would be released back into the main system for thorough treatment.

A deterring factor in the development of these tunnels is cost. In Washington, D.C., officials have put a $1 billion price tag on their plan, and estimate that the project could increase residential sewer bills by 20 percent over time. Supporters of the plan argue that the cost is offset by the benefit - in Washington, the tunnels are estimated to reduce emergency discharges of excess water by 92 percent.

Controlling storm releases "is necessarily priority number one," says Jim Colier, chief of the bureau of environmental quality in Washington, D.C.'s Department of Health. The development of underground tunnels to handle water overflow is an increasingly attractive solution in certain locales. As more communities experience the effects of flooding, they may continue to seek tunnel designs as a potential option to some of the problems flooding can bring.

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