If your idea of managing rainwater is to simply put guttering on your house, you might want to reconsider.

People are re-thinking the old idea that if they divert water away from buildings and parking lots to get it away as quickly as possible they've washed their hands of it.

But capturing some of the rainwater can be more beneficial to the land and local bodies of water. The Oregon State University Extension Service can tell you how.

Robert Emanuel, an OSU water resources and community development specialist, and Dave Ambrose, a district technician with the Clatsop Soil and Water Conservation District, will conduct a class to teach homeowners and professional landscapers how to construct rain gardens. The class will be held from 2 to 5 p.m. Friday, at the Seaside Library, 989 Broadway, in the Community Room. Reservations are not necessary, and there will be no admission fee.

The class will instruct people about how to plan, design, and build the water feature that will collect and filter storm runoff before it reaches the watershed.

The Clean Water Act of 1972 targeted "point-source" pollution - pollution typically discharged in one location.

The act greatly reduced the effects those sources - such as factories - have had on United States waters.

But a realization of the need to deal with runoff from building roofs, parking lots and streets has been slower to materialize.

Rainwater accumulates, then runs off hard surfaces, picking up speed, which prevents it from soaking into the soil. If it can't soak in when it hits the ground, or there are no plants to slow it down when it flows, it begins to pick up more speed and volume.

As its velocity increases, it also picks up all sorts of pollutants - fertilizers, pesticides, motor oil, gasoline, grease, chemicals and metals.

"The first rain comes, and all this stuff moves into the surface water," said Ambrose, with the Clatsop Soil and Water Conservation District. "The cumulative effect is there."

"Big housing developments use stormwater retention ponds," Emanuel said.

"Most metropolitan areas regulate how people deal with that water," Ambrose said.

Ambrose said he and Emanuel want to appeal to people who want to "wake up a little bit."

"Every person who installs one of these is taking responsibility. We're not building fountains or ponds that hold water for a long time," Emanuel said. "If you've got rain, it might be there for a day."

Emanuel said it is an opportunity for individuals to help recharge the aquifer. And he explained that the feature slowly absorbs water into the ground, rather than diverting it to some other place on the surface. If there is a very hard rain, the feature would have a channel to allow excess water to drain out.

In addition to slowing runoff, some plants act as bioaccumulators - absorbers of toxic materials.

"Cattails leap to mind," said Carla Cole, a natural resources manager and botanist at Lewis and Clark National Historical Park. "Cattail is a tasty wild edible, but you've got to be careful where you harvest them."

She explained that the plant accumulates toxins. Anything with a substantial root mass like sedges, she said, is going to stop some heavy materials from passing into the water table.

She added that recent research has shown that certain species of fungi absorb toxins.

Emanuel and Ambrose are telling people who live on slopes greater than 10 percent, they shouldn't install a rain garden, because oils and other pollutants that might already be in the ground will lubricate the soil and could lead to small landslides when water is added.

But for other homeowners it can be cheap to build, and can be retrofitted to the homeowners' needs.

"It's the cost of digging a pit, adding soil, adding plants and adding mulch," Emanuel said.

Some plants absorb pollutants out of the water.

"One of the key features of rain gardens - we encourage people to go native with their plants. The plants are going to get wet and then dry out," Emanuel said. "You will get some more birds."

He said using native plants will increase the area's biodiversity.

Emanuel said the Oregon Sea Grant Extension is going to publish a rain gardens guide, which Ambrose will have available in his office. Emanuel can be reached at (503) 842-5708 Ext. 210. Ambrose can be reached at the Soil and Water Conservation District office at (503) 325-4751.