Bacteria and beaches. These are topics we keep revisiting in the stormwater community, because they’re a bad combination and a costly one. The implications are significant—for human health as well as for the economies of the communities that experience frequent beach closures.

Even if your area isn’t faced with a total maximum daily load (TMDL) for bacteria, your program could still be under the gun to confront the issue, not only from the health and economic standpoints but also because of recent lawsuits that have the potential to set a wide precedent. Two groups, the Natural Resources Defense Council (www.nrdc.org) and the Santa Monica Baykeeper (www.smbaykeeper.org), are suing Los Angeles County and the City of Malibu, CA, for exceeding water-quality standards in a number of areas. One of these areas is violating a bacteria TMDL that requires zero dry-weather exceedance days.

As anyone knows who has tried to track down the sources of bacteria in surface waters, figuring out where the contamination is coming from can be fiendishly difficult, and treating it can be just as tough. Great advances have been made in source identification, however, including molecular and DNA testing to identify the source species and the probable origin, such as wildlife, agricultural operations, or leaking sewers or septic systems.

The article on page xx of this issue offers some good news on the treatment side, as well, focusing on the International Stormwater BMP Database project and what it has revealed so far about the effectiveness of various BMPs against bacteria. As the authors point out, a substantial data set now exists—paired data from more than 70 sites in 10 states and provinces—and they suggest how it might affect the design of selection of BMPs to help meet TMDLs. Not surprisingly, BMPs that are effective at removing other pollutants such as total suspended solids and metals are not necessarily effective against bacteria, although simply by reducing runoff volumes they can reduce bacteria loading.

Bacterial contamination continues to be a complicated issue, and questions arise even with regard to what we’re measuring. For example, there is some evidence that the indicator bacteria we use to determine beach closures aren’t very reliable: just because bacteria levels are high on a given day doesn’t necessarily mean swimmers are more likely to get sick, and vice versa. But when these are the most reliable indicators we have, we usually have to go with them rather than take chances with public health and public confidence. The so-called Annapolis protocol is still being researched to see if we can’t establish more definite relationships between fecal coliform, enterococci bacteria, and risks to human health.

Evidence has also emerged in the last few years showing that bacteria, rather than just being carried to the beaches in dry-weather runoff or with every fresh storm, actually persist in sediment and debris on the beaches. Under the right conditions, a beach might become its own source of contamination.

The BMP database doesn’t yet provide definitive answers to every problem, but those working on the project have been steadily compiling data, and it offers the most comprehensive, reliable, and useful source of information on treatment methods that we have available. The research presented here, and the suggestions for further investigation, are  a welcome addition to this ongoing exploration of the puzzle.

SW May 2008