Tim and Yvonne Treadwell were tanking up their 34 foot Formula on an October weekend, getting ready for one last trip before pulling the boat for the winter. Over the summer, they’d gone to Fells Point, Chestertown and Rock Hall for swimming and concerts.

"We just play all up and down the bay," Yvonne Treadwell said. "It’s a lot of fun."

But they want things clean. Clean water, clean facilities. That’s why they were using a cup to catch any potential fuel spills.

Frank Bean, the office manager at the Chesapeake Yachting Center in Middle River, where the Treadwells gassed up, says that’s a big change from when he was a kid growing up on the Patuxent River.

"You know you had an oily rag, you threw it over board and it sank and everybody was happy," Bean said. "Change your oil, if it leaked in the water, nobody paid any attention to it."

Boating fuels a two billion dollar economic engine in Maryland. And all those boats in the water can lead to pollutants winding up in streams, rivers and Chesapeake Bay.

Now, pollution in the bay from boats is minuscule when compared with, say, runoff from farm fields, lawns and golf courses. But it’s not small fry. There are around 200,000 registered boats and 600 marinas in Maryland.

Still, a combination of changing times and government programs are making boating less of a threat to the health of the bay. Over the last few decades, government regulations required boaters to clean things up. For instance, no more dumping sew-age overboard, please.

And in 1998, Maryland became the first state to start a voluntary clean marina program.

Take the Chesapeake Yachting Center, for example. This time of year, the lion’s share of the marina’s business is storing boats for the winter.

A crew pulls a boat from the water and power washes the hull before putting the craft up for the winter. But the runoff from that doesn’t end up in the creek. It goes down a drain into the sewage system where any gunk from the clean-ing is captured and properly disposed of.

Donna Morrow, who coordinates the clean marina program for the Department of Natural Resources, says facilities qualify if they do things above and beyond what the law requires. “Most of the things that we ask you to do don’t cost money,” she explained. “They take time.”

Things like training staff how to prevent accidental spills and picking up trash every day.

About a quarter of the state’s marinas have qualified as "clean."

The state promotes them and offers them technical assistance. Morrow said some marinas don’t want to participate because they don’t want the government poking around their business.

"If we run into that resistance, we usually have them talk to other folks that have done the program," she said. "I don’t have any environmental or enforcement authority. I can’t get you into any trouble unless I see something unconscionable."

In Baltimore County, clean marinas get a tax break on their storm water management fee. But the County Council decided to phase out the so-called rain tax next year. Morrow admits losing that tax break hurts her pitch to marinas to sign up. But she adds that’s not why a marina should participate.

"You really have to want to protect the water and the bay and everything to do this for the right reasons," Morrow said. "Otherwise you’re not going to do it well and it’s not going to stick."

There are also clean marina programs in Virginia, The District of Columbia and Delaware.