Solving the Mystery of
Nonpoint Source Pollution

© 1999 Streamline Publications
A winter downpour engorges storm drains with torrents of runoff. Soon, signs appear on coastal beaches warning swimmers and surfers that elevated levels of coliform bacteria pollute the ocean's waters. Another sewage spill from broken pipes or an overburdened treatment plant—an all-too-common occurrence. But sewage system failures are only part of the overall coastal water pollution problem, as is becoming increasingly apparent.

Since implementation of the federal Coastal Zone Act Reauthorization Amendments of 1990, a heightened awareness has begun to develop over the effects of nonpoint source (NPS) pollution of coastal waters.

As the term implies, the very nature of NPS makes its control and elimination difficult in many cases, presenting scientists with seemingly unsolvable mysteries. Yet, there are some stunning successes in the battle to first identify, then eliminate, NPS pollution.

One promising technique for revealing a pollution source involves DNA fingerprint matching of Escherichia coli (E. coli) bacteria.

San Diego Seals

Harbor seals in San Diego came under suspicion as a possible source of pollution at one beach. After feeding in the ocean the seals would haul out on the protected beach and laze about in the sun digesting their dinners and fouling the beach with fecal matter—as seals will do. By collecting polluted water samples and seal excrement samples, scientists were able to draw an 80 percent DNA similarity in 72 out of 83 water samples.

The possible comparisons for other than harbor seal E. coli were done using a DNA library at Virginia Tech in Blacksburg, Virginia. Matches were made revealing high similarity, as well, to a number of other animals. In addition to humans, the polluted water DNA samples pointed to raccoons, beavers and ducks.

But the evidence clearly pointed to the seals being the major culprits.

How can such a thing happen in the natural world, you might ask. Weren't the seals here before man?

Yes! And they were around before a breakwater was built to protect the sand, where they snoozed in the sun, from the erosive effects of ocean waves. The beach had thus become enlarged over the years, providing accommodation for an increasing number of seals. The result was a high concentration of seal feces and pollution of the beach and water.

San Diego's proposed solution is to remove sand, returning the beach to the size it was in 1940, thereby restricting hotel accommodations for the harbor seals.

Green Farms

Agriculture tends to contribute disproportionately to NPS pollution because of the acreage devoted to growing food and the incidence of chemical use. The characteristics of irrigation and storm runoff, and the effects of animal waste, present further problems. Fields are subject to topsoil erosion because of large areas of unprotected soil, necessary for row crops. Farm runoff can be a vile mixture of soil, pesticides, fumigants, manure, and hydrocarbons such as gas or diesel fuel.

The December 1998 issue of Nonpoint Source News-Notes, reveals that farm runoff controls are not only possible, but have been demonstrated by farmers to have positive economic effects. One success is the Barrett Farm, in Pennsylvania near Chesapeake Bay, where both water quality and profitability have been improved through use of enlightened methods. The Barrett Farm is small, with a dairy comprising fewer than 100 cows, but it serves as an example for larger scale operations. Techniques include:

• Manure and milk house waste water are stored in an earthen pond most of the year to prevent runoff. In the spring, the manure is plowed under on cornfields and pastures.
• A nutrient management plan is used to control and balance use of the manure on crops. Chemical fertilizers and their attendant expense are avoided.
• Cover crops are planted in the fall to reduce susceptibility to winter erosion.
• Eroded streambanks are stabilized and repaired and cows are prevented from fouling the streams and damaging the embankments.
• When pesticides are used, the application rates are carefully specified by target area to prevent overuse or misdirection—saving money and reducing contamination of surface water.

Some Early Results

Though the problem of nonpoint source pollution—by its very nature—can be stubborn, progress is apparent in a number of locales.

In Puget Sound, several shellfish beds have recently been reopened for harvest after being closed for years. Sewage and farm runoff were responsible for toxic contaminants. The problem was worst near urban concentrations. A county survey of the Eld Inlet revealed that 16.5 percent of on-site sewage systems—septic tanks—were failing. The septic systems were repaired with county assistance. Two towns installed community sewage systems. The residents, who for 17 years have had restricted access to the shellfish beds, acted in their own economic self interest and are now reaping the rewards of a cleaner environment.

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