There’s More Than You Think Beneath the Surface

March 1, 2002
The Clean Water Act turns 30 this year. Along with more recent regulations, such as the Water Resources Development Act and the much-debated total maximum daily load (TMDL) program, the CWA has increasingly focused attention and resources on protecting and achieving water quality. Despite great progress, ongoing monitoring efforts are pointing out some new dilemmas, as well as some decades-old ones, the extent of which are only now coming to light. Of all nonpoint-source pollutants, sediment tops the list of those that impair surface waters. This should be no surprise to those working in the erosion and sediment control field. Add point-source pollutants to the mix, however, and the problem starts to look worse than you might have imagined. Last December, USEPA released a new draft report on the National Sediment Quality Survey, a detailed account of the location and severity of contaminated sediments in US surface waters ( Of nearly 20,000 sites where sediments have been sampled, contamination at 71% of them is “probably” or “possibly” associated with harmful effects on human health or aquatic life. Only 29% of the sampling sites received a clean bill of health. People involved with ESC understand the damage sedimentation-let alone the contaminants that adhere to sediment particles-can cause an ecosystem. Contaminants found at the survey’s sampling sites include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), mercury and other metals, nutrients, and pesticides including chlordane and DDT, which was banned in the US about the same time as the birth of the Clean Water Act. The main concerns with regard to contaminated sediments are bioaccumulation, as bottom-dwelling critters ingest them, and biomagnification, as fish, shellfish, birds, and mammals feed on the contaminated organisms and the toxins move up the food chain. Current regulations are designed to prevent the release into the environment of additional contaminants-or at least to limit the amounts released to match what the receiving waters can handle, which is the point of the TMDL program. But the fact remains that tons of contaminants are already out there. Cleanup is expensive and logistically difficult, and in some cases it’s questionable whether we should try. For example, although EPA has now decided to dredge the more than 2 _ million yd.3 of PCB-contaminated sediment from the Hudson River, some argued that stirring up and thus resuspending the sediment would be riskier for the environment than simply leaving it where it was. (One proponent of this view, of course, was General Electric, whose plants had dumped the chemical over a 35-year span and who will pay hundreds of millions of dollars for the cleanup.)One goal of this massive monitoring effort is identifying point sources of contamination, notably industrial sites and combined sewer overflows but also such places as mines and landfills. Erosion control practitioners have been involved in efforts at many of these types of sites and in many different capacities, some of them covered in the magazine. Nonpoint-source pollution from urban runoff is also a significant source of contaminants. EPA itself encourages a watershed approach to protect, restore, and maintain water quality, and this type of approach necessarily involves a multidisciplinary effort. EPA’s report calls for, among other things, developing better monitoring and assessment tools and devising methods to more accurately assess just what effects existing contamination has on the ecosystem-that is, figuring out what’s actually toxic. Erosion control as a discipline, with its particular sets of tools and techniques and its ongoing research into, for example, the mechanics of sediment transport, plays a central role in water-quality efforts, one that necessarily comes before many of these other efforts. Keeping the sediments in place is the first line of defense.