John M. Mudre and Bobby Lewis are wading across Rock Creek on a perfect October morning. The temperature is in the 70s; the sky is cerulean and framed by leaves that are just beginning to show fall colors.

Although Lewis carries a rod and Mudre juggles a dip net and a bucket, these are no ordinary anglers. The rod is connected to a power pack on Lewis's back. Soon the fish they are after will be caught in a different kind of current, stunned by electricity so that they can be scooped into the bucket.

Mudre and Lewis are employees of International Science & Technology Inc., a Washington environmental company trying to help identify and restore Rock Creek's indigenous fish population. Part of the two scientists' work will involve tracking the herring that swim up the creek to spawn each spring. Mudre and Lewis are looking for a fish large enough to carry a radio transmitter for a test run of the equipment that will help them monitor the herring's activity in the spring.

International Science & Technology, whose business also includes restoring lakes in Florida and figuring out how to neutralize acid runoff from coal mines in Maryland, is one of dozens of small environmental firms that have sprung up in the last 10 years in the Washington area.

Like larger, publicly traded firms such as American Capital and Research Corp. and Versar Inc., these entrepreneurs have launched themselves on what they hope will be a rising tide of environmental concerns.

The Washington area probably has more environment-oriented businesses per capita than any other area of the country, said James Easterly, senior economist with Management Information Services Inc., a consulting firm with a large environmental practice.

This new breed of entrepreneurs is as remarkably diverse as the concerns about the environment, as low tech as manufacturing canvas bags for grocery shopping and as high tech as building "miniaturized gas chromatograph/mass spectrometers" to trace toxins contaminating an area.

It ranks among its members Pam Hamilton and her husband, Michael Bruen, two Takoma Park residents who started Eco-Concerns Inc. in February to sell such items as recycled bulk paper, reusable coffee filters and string bags for shoppers. And it includes Al C. Rich, whose patented design for solar hot-water heating systems is struggling to turn a profit after a difficult start.

Though starting a business is never easy, in a time when other areas of the economy are stagnant, scaling back or closing up altogether, these businesses are in an area that anticipates growth.

"Environmental issues are a growth sector for the 1990s," said Kaye Sloan Burke, marketing manager for the Virginia Department of Economic Development, whose office helps recyclers locate in Virginia, where they can qualify for tax credits.

Lyman Clark, president of Environmental Economics Associates of Traverse City, Mich., has done a study of environmental business opportunities for the Environmental Protection Agency. "We estimate it's about a $100 billion-a-year industry, and that should grow," he said.

The passage of the federal Clean Air Act alone could produce approximately 20 percent growth, according to Clark. More prospects lie abroad as foreign countries turn to their environmental problems.

That makes the environmental industry a bright spot in a somewhat gloomy economy.

"It's a hard time for start-up corporations, but we're very fortunate, because we're in an area where people have problems that they feel like they have to solve," said Mark Weinstein, chief operating officer of Ecological Systems Inc., an environmental entrepreneurial firm. "It's not a luxury."

Fishing for Contracts

Like many of Washington's environmental start-ups, Douglas L. Britt started International Science & Technology in a on a shoestring budget in his basement.

That was in 1984. This year, the privately owned company anticipates revenue of about $1.5 million. "The problems we are dealing with won't go away during a recession," Britt said.

A native of Indiana whose background is in freshwater ecology, Britt launched his own business after working for several firms around the Capital Beltway.

"Within four months we had a contract base large enough to hire four people, and before the year was out we were able to establish a small office in Reston," he said. The company suffered a setback in 1987, when a large contract ended before anticipated. Since then, it has been rebuilding through contracts like the one it has with the National Park Service to track fish in Rock Creek.

Last year the company moved to Sterling, where it now employs 24 workers. It also has a small office in Indiana.

"A lot of people look at the environmental problems and think first of the Superfund," the federal fund for cleaning up toxic waste, Britt said. "Of course, the Superfund contracts tend to be very large, and the large companies tend to be in that field. We're looking at some of the more conventional water problems and water resource issues. It is a very good market."

Converting Trash to Cash

Richard W. Tynes, president of Eagle Maintenance Services Inc., left his job as a government lawyer 10 years ago to start a janitorial firm. The company cleaned up after concerts, sporting events and other big trash-generating outings, which meant it often found itself in possession of large amounts of recyclables -- for instance, 72,000 cases of beer cans from RFK Stadium.

"We were bringing the trash to the door," Tynes said. "I started to follow the trash out of the door, to find out what was happening to it -- where it was going and how it was being handled. I began to learn a little bit about recycling."

Tynes read, researched and traveled to the West Coast to study some more about the business of recycling. His company already had acquired a warehouse in Capitol Heights, which Tynes began to view as a potential materials-recovery site -- a facility that processes paper, cans, bottles and plastic for recycling. Prince George's County was soliciting bids from companies that could pick up and process recyclables on an interim basis while the county builds a large materials-recovery facility.

This year Tynes joined forces with Waste Management Inc., the nation's largest solid-waste collection company, to successfully bid on the nearly $1 million contract. An investment of about $500,000 and some equipment supplied by the county allowed him to open the facility.

"We've been dealing with the same bank since we've been in business," Tynes said, referring to Sovran Bank of D.C. "They've been most aggressive in making loans, as we have become aggressive. Of course, they have my firstborn."

The recycling operations are still small compared with his maintenance business and "we don't make money, money money, money," he said. "I went into it with a purpose of learning the business."

Eagle Management Systems, as Tynes's recycling subsidiary is called, is "just what we needed as an interim facility," said Jesse Buggs, manager of residential recycling programs for Prince George's County. According to Buggs, Eagle's facility is the only minority-owned, licensed material-recycling facility in the nation.

The company employs about 600 people, according to Tynes. It has 16 workers who separate the recyclables that Waste Management collects from the bright yellow-and-green bins the county has provided to residents who participate in the curb-side collection program.

Approximately 1,000 tons of newspaper and 200,000 pounds of glass get processed each month at the facility, where a visitor can pick up a faint whiff of stale beer from the cans and bottles. Workers rotate from job to job in the warehouse to increase their skills and to cut down on tedium, Tynes said.

By the time the Prince George's County contract runs out, Tynes said he hopes to have lined up some commercial accounts and to be able to move into other jurisdictions, possibly including the District, to take care of their needs. "We're building this thing with one purpose in mind -- expansion."

Recycling Printer Cartridges Marcus Webster, a University of Michigan computer and engineering graduate, was a computer consultant at Georgetown University before starting Laser Recharge Inc. about a year ago. Among other duties, Webster's job required him to keep an eye on Georgetown's laser printers, used to make clear printouts of documents generated by computers.

Each printer contains a toner cartridge that must be changed occasionally, just like a typewriter ribbon.

"We were having our toner cartridges at Georgetown recycled, but the quality wasn't that good," he recalled. "I said -- Hey, I can do this."

And through trial and error, he did.

Webster devised his own process for taking apart old cartridges, refilling and rebuilding them.

Customers not only have the satisfaction of knowing their used cartridges are not going to the landfill, they also recognize substantial savings from using the recycled product.

Webster said his cartridges sell for $39 to $49, compared with about $100 for new cartridges.

With Georgetown University as one of his first customers, Webster now serves a growing clientele in downtown Washington from his shop on Georgia Avenue, competing with other entrepreneurs who have started similar businesses.

"The total cartridge market is expected to grow 33 percent from 1989 to 1993," said the 27-year-old entrepreneur.

And Webster seems to be getting his fair share of that: From his initial start of one or two cartridges a month, he now averages about 500 monthly.

"We have about 30 printers that use laser jet toner," said Sandra Valderrama, systems coordinator for the Health Insurance Association of America, one of Webster's customers.

Initially the association ordered a single recycled cartridge to check the quality, she said.

Finding that it matched the quality of a new cartridge, the association became a steady customer.

While most of the incentive for the business is economic, it also provides large environmental benefits, Webster said. "Cannon sold about 15 million {new cartridges} last year, and the majority of them go into landfills."

"It does everything I wanted to do with a business," he said. "One, I make money doing it; two, I'm doing something for the environment and the community."

Firm's Fortunes in the Bag

The environmental business is a part-time occupation for David Ferry of Leesburg, Va. Inspired by Earth Day, he said, he began looking for a canvas bag in which to carry home groceries. When he couldn't find one, Ferry created Earth Bags Ltd. in April, and contracted with Maryland Industries for the Blind to manufacture them.

Magazines and membership organizations have bought the bags with their logo printed on them to use as subscription or fund-raising premiums, he said. They are also sold by direct mail.

Ferry, who works in direct mail, said that he started the company with $5,000 borrowed on a credit card. He expects the first year's sales of the $5.98 bags to total less than $100,000. But the business is already in the black, and "next year, who knows?" he said.

Ecological Systems Inc. of Bethesda has the rights to a patented technology developed by Walter Adey, director of the Smithsonian's Marine Systems Lab. Called the Algal Turf Scrubber, it is a nonchemical way to treat water by recreating natural systems. The system is used to maintain the water in the living coral reef exhibit at the Smithsonian Museum of Natural History and at the world's largest coral reef aquarium at the Great Barrier Reef Wonderland in Townsville, Australia.

The company was set up in part by Calvert Social Venture Partners, a venture capital firm that focuses on firms addressing environmental and other social issues. It hopes to market its systems to fish farms and to firms that need a system that cleans water and reuses it rather than releasing effluent. It also plans to market a version of the product for home fish tanks.

Russell C. Drew and Thomas J. Kuehn started Viking Instruments Corp. in 1983, but only introduced their first product last year. Their product is a field portable gas chromatograph/mass spectrometer developed for the National Aeronautics and Space Administration's Viking Mars Lander missions.

The portable version of the spectrometer allows technicians on the trail of toxics to more quickly analyze air, soil and water samples, creating an electronic fingerprint that can be compared with a library of such fingerprints for different contaminants to speed identification.

Drew, a former White House deputy science adviser, and Kuehn, who helped establish the energy research advisory board at the Department of Energy, have the Environmental Protection Agency as their first firm customer, and several potential industrial clients are testing the product.