Grate Mates put drains on a silt-free diet

Published 2:00 pm Friday, November 19, 2004

A lot goes down a street drain.

Try 20 plastic bags worth of oil-soaked sediment.

That’s what Bainbridge High School’s Earth Service Corps volunteers dug out of one drain, while installing a “silt sack” to catch sediment and pollutants in storm water run-off.

The Grate Mates program could make that the exception.

“(Installing a silt sack) doesn’t take that long and it is something that really makes an impact on the filtration of the water,” said BHS sophomore Jonathan Hallet of the Earth Service Corps.

Pollutants in storm water – mainly from cars – of oil, lead, arsenic and other toxins, account for a third of all contamination in Washington waters, according to King County’s Water and Land Resources Division. Pollutants may go directly into streams, creeks and the sound.

The Earth Service Corps is tackling and publicizing the problem by installing special silt sacks, whose telltale black hem rings drains. The project is part of Grate Mates, a program of nonprofit, Seattle-based PlanetCPR.

This year the corps expanded its coverage of island drains through a city grant and a new program asking area businesses to “adopt a grate.”

The silt sacks need annual replacement and cost nearly $100 each.

“We hope to increase knowledge of the system and storm drain protection leading to a more permanent solution for storm water, Hallet said.

Grate Mates is one project of the student-run corps that gets students involved in the environment; the group has provided recycling at events like the Blackberry Festival, done beach clean-ups, and lobbied school officials to replace disposable lunch trays with reusable ones.

Natural Landscapes Project contacted the corps as part of a city-funded educational outreach for “non-point source” pollution, urging students to apply for a grant and expand the program.

Non-point pollution is tough to solve, since by definition contaiminants come from thousands of small sources: oil from cars, fertilizers and pesticides washed off lawns, car wash soap.

But a study by the National Fish and Wildlife Foundation found that the cloth filters on drains can capture 80 percent of pollutants, and absorb a half-quart of oil every six months.

A corps team of 14 students went out in October to replace old filters downtown.

Money for filters in drains in the rights-of-way came from a $1,717 grant from the city’s storm and surface water management program.

The Department of Public Works lent the corps traffic cones and staff, and directed them to old drains that needed silt sacks the most.

In modern drainage systems, quantity controls like bioswales – vegetated channels, in the ground – prevent water from rushing out and give water time to soak back into the ground. Separators can do the job of silt sacks, allowing sediment to sink to the bottom instead of running off with the water.

Most pollutants – such as oil – are attached to sediment, said the city’s senior engineering technician Melva Hill, who works with storm water issues.

“The number one best practice is sweeping, which is why we sweep constantly,” Hill said. “What doesn’t get cleaned up gets picked up by water and ends up in our creeks.”

In addition to replacing old filters and putting in new ones, the corps also called on 35 businesses near high-traffic areas to sponsor grates for needed filters.

Sponsors receive a certificate of Earth stewardship.

Responses were mixed; only five businesses signed up immediately.

“We invited them to see us put it in, and they were excited to see a community action like that,” said co-president and junior Cynthia Foley.

Others said they would think about it, and still others said they thought this was a problem that should be taken care of by the city.

The city grant does pay for silt sacks in an additional 20 drains in rights-of-way, but funding for replacements is not clear, which is why the corps has approached businesses to sponsor a drain, Foley said.

The corps doesn’t have a goal of how many drains to cover, but wants “to expand the program as much as funds allow,” Foley said.

“In the long term, we need LID (low impact development) fixes,” NLP’s Cara Cruickshank said.

“There are hundreds of drains around the island and we can only put filters on so many.”