Brian Zimmerman pushed a shovel into the muddy dirt, pressed his foot on top of the blade and tossed a big chunk of soil over his shoulder.
He stood in a large hole nearly 3 feet deep that by next month will be a 434-square-foot rain garden at the Malcolm House in Jericho, the historic 18th-century home that is the headquarters of the Nassau County Soil & Water Conservation District.
"We wanted to do this because it's a good demonstration for people," said Zimmerman, the district's manager. "It's kind of a learning experience for them, so they can do rain gardens on their properties."
Rain gardens are dugout gardens that absorb stormwater runoff and filter the water through sandy soil. The garden can be planted with any kind of noninvasive vegetation.
A rain garden's size is determined by the amount of water expected to flow into it, said Zimmerman, adding that a typical homeowner's garden would be much smaller than the district's demonstration garden, which will collect as much as 4 1/2 inches of rain in a 24-hour period.
"They're generally digging no more than 12 inches, if that," he said of homeowners.
Residents should first determine which direction water flows on their property by checking for a low spot in the yard. A simple equation, posted on the district's website, can be used to determine the garden's square footage.
The conservation district used native plants, such as little bluestem and switch grass, to draw insects, bird life and butterflies that once populated the area, Zimmerman said.
One recent morning, a small, brownish-green frog hopped out of a crevice in the dirt.
"Look at him!" he said. "They're coming in already. That's habitat we're creating!"
Meanwhile, intern Gabrielle Rovegno used a hand saw to cut off the roots of an old tree protruding from the soil.
Before the garden's construction, "you could see where the water was cutting through . . . washing away all the dirt and sediment onto the street and into the storm drain," said Rovegno, 20, of Glen Head. One benefit is that "pollutants and oil will be trapped in the rain garden, so it won't go into the Sound and hurt the fish," she said.
Megan Bové, one of the nearly 20 local Green Building Council members who volunteered, said the garden is something anyone can do because "it almost maintains itself, if done correctly.""It takes planning in the beginning, but the payback keeps giving," she said.
"It's a natural filtering system. Once you build it, it's there, and you can watch the beauty that nature has to rebuild itself."