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Palmer 'rain garden' is scenic sponge for polluted runoff

  • Author: Zaz Hollander
  • Updated: September 28, 2016
  • Published June 12, 2014

PALMER -- A new garden unveiled this week near downtown Palmer makes pollution cleanup look pretty.

The freshly planted ferns and delicate purple irises in a "rain garden" next to the Mat-Su Senior Services building serve as a natural sponge and filter for dirty water running off the center's paved parking lot and straight toward the Matanuska River.

Representatives of the Alaska Department of Environmental Quality, the Matanuska-Susitna Borough and others gave the media a look at the garden on Wednesday. A crew of volunteers planted it Tuesday and Wednesday.

Rain gardens generally include water-loving plants -- dogwood, aspen, shooting stars, tufted hair grass -- with rocks to slow the flow of runoff and guard against erosion, according to a borough guide.

The demonstration garden is part of a movement to treat pollutant-carrying stormwater runoff and keep it out of rivers or lakes to safeguard water quality, project coordinators say. They hope the gardens serve as examples for municipalities, businesses and residents to do the same.

Runoff flowing over hard surfaces like asphalt can gather oil and grease, sediment, fertilizers and herbicides from roads, parking lots and yards. Polluted runoff can harm or kill fish and other wildlife.

"A lot of people think runoff gets treated. It doesn't," said Laura Eldred, an environmental program specialist with the state Department of Environmental Conservation. "A lot of this runoff is going to end up in our creeks and our lakes."

The Valley's continued growth is a driving force behind the local rain garden movement, Eldred said.

The Mat-Su population is pushing 100,000 -- it's more than 95,000 now -- and that's led to more roads, driveways and other paved surfaces, borough planner Frankie Barker said. The borough is "on the cusp" of new stormwater discharge regulations that are triggered when population hits 100,000 or when an area reaches certain population densities, Barker said.

Relatively low-cost preventive methods like rain gardens could help municipalities get ahead of future regulations by reducing storm water runoff, Eldred said.

The Palmer garden is designed to soak up more than 11,000 cubic feet of water, she said.

"We're actually kind of a cutting-edge community," said Catherine Inman, who served as project coordinator on the Palmer rain garden through her company, Mat-Su Conservation Services.

The gardens are part of a larger stormwater management strategy paid for with $800,000 in U.S. Environmental Protection Agency and borough funds for water quality protection. That money helped pay for rain gardens as well as a stormwater management plan and conservation easements through the Greatland Trust, according to Barker.

There are already more than a dozen rain gardens in the Valley, from the Sutton Public Library to Big Lake Elementary School. The first was installed in 2009 at Cottonwood Creek Elementary School near Wasilla.

The latest garden at the senior center is a great example of how rain gardens work, said Barker, who wore a "Mat-Su Rain Gardens" T-shirt Wednesday. Barker helped more than 100 volunteers install the garden, including girls from a nearby church camp and members of the Colony High School baseball team.

Rainwater will flow off the parking lot into the newly planted ditch along South Chugach Street, Barker said. Before the garden was installed, that water flowed untreated into the river. Now it will soak into the ground while the plants filter some pollutants and others break down in the soil.

This rain garden cost about $70,000: $38,000 from the Alaska Department of Environmental Conservation, about $20,000 from the U.S. Environmental Protection Agency and $10,000 from the borough, officials say. But homeowners can do their own rain gardens for much less, Barker and Inman said.

Someone might shell out a few hundred dollars for plants or choose to take advantage of native vegetation growing nearby or a friend who's dividing perennials, they say. A homeowner might have to spend a few thousand dollars for an excavator or hand-dig a smaller garden.

The borough will pay half the cost of installing a rain garden, up to $500. How-to guides are available to homeowners and contractors. For more information, go to

Reach Zaz Hollander at or 257-4317.