CRWA in the News

Runoff remedies

Communities tap new technologies to keep pollution out of waterways

By Globe Staff

Boston Globe, Sunday, April 6, 2008

For nearly a century, water was one of the last things that urban and suburban planners thought about when they were designing town squares, subdivisions, commercial zones, and shopping areas.

Install a few pipes to bring fresh water in and out. Situate a few well-placed catch basins connected to a pipe leading to a river or a stream to deal with storm water. Job done.

Yet, as the region along the Charles River and other waterways has been built up, impermeable surfaces such as parking lots, roadways, sidewalks, and roofs have increased the amount of rainwater and snow melt that flows directly into storm drains, bypassing the natural filtering effect of the local water table. Industries and municipalities were long ago forced to clean up their waste water, but storm-water pollution, including petroleum products and fecal-coliform bacteria, continues to spill into local waterways, frustrating efforts by regulators and environmental groups to keep them truly clean.

"Water was a minor element when we designed our cities and towns," said Kate Bowditch, chief of the Green Streets program for the Charles River Watershed Association. "Yet now it is turning out to be one of the most important and problematic issues we face."

Pushed by an increasingly green-conscious citizenry and anxious to avoid federal Environmental Protection Agency fines, many communities are embracing a host of new technologies to capture storm and snow runoff so that any pollution they carry does not wash into rivers, streams, ponds, and lakes.

Measures being considered and tested by local communities include:

• Tree and bush planters that act both as water-retention tanks and natural pollution filters.
• Permeable asphalt and sidewalk construction materials that allow water to seep through into the ground rather than channeling it into gutters and storm drains.
• So-called "bio-swales" and other engineered wetlands that trap water and use specially selected soil mixes and plant species to remove pollutants and return storm water into the local water table.

"Before, the thinking was just to get the water off the road for safety reasons, and there wasn't much thought given to pollution," said Denise Zambrowski, storm-water manager for the town of Franklin. "But we have 48 miles of streams and 266 acres of ponds, and 95 percent of our watershed ends up in the Charles River. We are now giving storm water a serious look."

Zambrowski said the town recently received a $131,000 federal matching grant to pay for several projects, including installing a man-made wetland area or other technology to capture runoff from a large condominium development near Route 140. Storm water from the complex, which has approximately 200 units, flows through overflow pipes directly into Mine Brook, a tributary of the Charles.

Franklin, like a number of other area communities, is also considering redeveloping its town center to make it more pedestrian and retail-friendly, and officials are considering measures such as storm-water planters as part of the redesign, she said.

At least above the surface, storm-water planters look like typical urban landscaping, with a tree or large shrub set into the sidewalk and surrounded by a metal grate.

Underneath, however, they are radically different. Storm water is directed into the base of the planter through a cut in the curb, where it first enters a layer of specially developed mulch that traps trash and large debris on the surface, so that it can be collected by town workers. The mulch also traps smaller particles of debris and pollution.

After passing through the mulch, the water then flows into an engineered mix of soil and microbes, which work with the plant's root system to remove bacteria and heavy metals. Filterra, a company that recently exhibited storm-water-planter technology at a Charles River Watershed Association forum for area communities, stated that its products remove as much as 85 percent of oil, grease, and suspended solids, as much as 82 percent of heavy metals, and as much as 76 percent of fecal-coliform bacteria from runoff.

Maria Rose, Newton's environmental engineer, said crews there have installed five storm-water planters in a portion of the parking lot of the Chestnut Hill Mall that formerly drained directly into Hammond Pond through a series of asphalt trenches. Other than the fact that local waterfowl have developed an unfortunate taste for the sweet pepper bush, irises, and other vegetation in the planters, the system is working well, she said.

"The geese are eating a bunch of the plants and grasses," she said. "But the situation is much better. It used to just be uncontrolled runoff."

Thanks to a two-year-old dedicated user fee - $25 annually for residents, $150 for businesses - Newton has an annual budget of $700,000 for storm-water projects, Rose said.

The city also installed at the mall storm-water settlement basins that use sand as a filtering agent, and is working on plans to uncover and restore a nearby brook that for decades has been buried underground in a culvert, Rose said.

Other technologies being promoted by the watershed association include "rain gardens" (basically larger versions of the storm-water-planter concept) and permeable sidewalk and asphalt products, Bowditch said.

A number of officials from area communities have already made visits to the University of New Hampshire's Stormwater Center in Durham, where Aggregate Industries, one of the country's largest suppliers of concrete, asphalt, and other road-building materials, has a demonstration parking lot made of permeable asphalt.

The lot's surface allows moisture to seep through into the ground below. In addition to helping recharge the local ground water, the material also limits water pooling and and refreezing during the winter, Bowditch said, making the surface less prone to developing potholes and allowing it to get by with 50 percent to 75 percent less salt.

The permeable material does have limitations in its help to the environment, officials said.
In addition to water, permeable asphalt would also allow hazardous waste such as a gasoline spill to seep through into the underlying soil and the local water table. That makes it impractical for streets, where traffic accidents involving gasoline or oil spills are most likely to occur. There is also a question about whether the street sweepers in use by most municipalities can pick up enough dirt and grit to keep the permeable asphalt from clogging.

Limitations aside, however, Bowditch said, the new generation of green, storm-water technologies offer a much better solution than the alternative - trying to fix the existing storm-drainage systems.
"There is a huge infrastructure investment down there and it is not working that well anymore.
"We can either take the approach that we are going to fix it, which would be enormously expensive, or we can put a green skin over it."