The net, stretched across a concrete storm-drain channel here, is clogged with cellophane chip bags, plastic bottles, and Styrofoam cups. The idea is to filter out visible trash before it empties into the sea and washes up on beaches.
But it's the unseen contaminants - microbes that scientists say can threaten human health - that in recent months have caused the greatest angst among America's environmentalists and water-pollution cops.
From e coli bacteria on Milwaukee lakefronts to the mysterious presence of human-originated viruses in the waters off southern California's sandy playgrounds, the discovery of such invisible threats is forcing the US to rethink how to deploy public funds to clean up rivers, lakes, and beaches.
"In general, the  Clean Water Act has been successful in dramatically reducing the amount of pollutants in the nation's waters," says Ted Morton, California policy director for America Oceans Campaign, a national environmental group. "Ironically, it is the perception of success in eradicating the most visible pollution that threatens to let our guard down for what we can't see."
Chief among the findings is that the microbe problem is not one solved solely by better sewage-treatment facilities. What recent months have shown is that, despite billions of dollars sunk into massive wastewater-treatment plants (Los Angeles just opened the country's costliest), water-borne pathogens are persisting as contaminants.
As a result, scientists are looking elsewhere to find the source of such pollution. Their likely culprit: urban runoff.
New studies show that potentially dangerous concentrations of microbes are present in the nasty soup of oil, grease, pesticides, and animal waste that washes off the nation's streets during storms, flowing into storm drains and emptying eventually into nearby rivers and bays.
"We are realizing the new frontier in water-pollution control includes some elusive and significant challenges [in the form of] pathogens and viruses," says Alexis Strauss, director of the US Environment Protection Agency's (EPA) Western Region in San Francisco. "Developing the standards as well as the technologies to clean them up is our primary focus now."
That is requiring an unusual degree of sleuthing. When world-famous Huntington Beach was closed this summer because of unsafe bacteria levels, authorities assumed the problem was a leaky sewer system. But officials never found such a source - and new studies are finding human viruses in areas where no sewer discharge is located. As a result, their Sherlock Holmes microscope is leading them to urban runoff.
A new study by the Natural Resources Defense Council (NRDC) shows about 63 percent of US beach closings and health advisories in 1998 were because of bacteria levels that exceeded water-quality standards (as opposed to 27 percent resulting from a specific sewage spill or treatment-plant overflow).
Moreover, new tests show the presence of viruses in storm-water runoff from urban, suburban, and rural areas. Such runoff includes fecal matter of farm animals and pets, fertilizers and pesticides, leaky septic tanks, and drained pools and hot tubs.
These findings surprised many in the environmental community, says David Beckman, who heads the water-quality program for the NRDC in Los Angeles. He and other scientists say swimmers' and surfers' risk of exposure to such organisms is high, because some microbes can survive in marine surf for months.
The findings are also forcing researchers to reexamine fundamental assumptions about pollutants in the ocean.
"We used to think the ocean could just handle all this stuff by mixing it in and whisking it away," says Anthony Michaels, director of the Wrigley Institute for Environmental Studies at the University of California, where genetic tests for detecting viruses in sea water have been developed. "What we are now learning about viruses in ocean water is transforming our whole world view on how the ocean works [in assimilating pollutants]."
The fight against the problem includes a large arsenal of tactics: the first-ever caps on allowable levels of key contaminants, more funding, citizen-generated lawsuits, court-assisted crackdowns, better monitoring and advisory programs, and public education.
Since 1972, about 60 percent of US waterways have been made "fishable" or "swimmable;" 40 percent are too polluted for such activities. Congress recently doubled (to $1.7 billion) the money it gives to states each year for infrastructure projects, but the US EPA estimates $140 billion is needed over the next 20 years.
Last year, the Clinton administration unveiled a "clean water action plan," and last month it signed off on regulations to chip away at remaining pollution. Officials claim progress on more than 100 action items of the plan, including a strategy for reducing water pollution from animal feeding operations; improved beach monitoring with public notification; and a draft plan to eliminate 12 toxins, from PCBs to dioxin and mercury.
The US EPA is also finishing regulations for control of storm-water runoff from municipalities, which it will release this fall.
Recent lawsuits have added momentum by forcing states to specify allowable limits for each of a long list of pollutants - depending on whether the body of water is used for drinking, swimming, or fishing.
"What is happening on the beaches of southern California is the same for every metropolitan region in America," says Roger Gorke at the EPA in Washington. "That's why there are increasing moves to zero in on what we can't see but know is there."
(c) Copyright 1999. The Christian Science Publishing Society