What's in that Storm Drain?

What's in that Storm Drain?

The view down under

Herb Stern (photo, above) reached into the cab to operate the controls of the clamshell truck parked beside the storm drain at the corner of Pearl and Allston. The special feature of this Cambridge Department of Public Works vehicle is the clamshell, which appears to be an industrial-strength version of a post hole digger (below).

Stern had moved the grate away from the storm drain. Now he guided the steel-jawed apparatus down through the opening into the catch basin below, raised it back up with its dripping burden, and swung it over to unload in the bed of the truck.

IMG_0354It was August 3, the first Friday of the month, so a city crew was busy sweeping the upper surface on the odd-numbered side of the street. Stern was dealing with what lay below.

“We pick a street sweeping day to work on the storm drains – people park on the other side then, so there aren’t any cars in the way,” he said.

The catch basin, a barrel-like container that sits below street level under a grating, is part of the storm water management system designed to protect the city from flooding and pollution of the Charles River, Alewife Brook and other local bodies of water. The system criss-crosses the two Cambridge watershed areas, with storm water going from the east side of the city into the Charles River watershed and from the west side into Alewife Brook, which is part of the Mystic River watershed.

Run-off from rain and snow, often loaded with solid or dissolved débris, flows down into the catch basin through the grating or a slit above it in the curb. Heavy materials and sediment sink to the bottom of the basin, and the water travels on into the storm water management system via connecting pipes.

What was Stern clearing from the catch basin at Pearl and Allston?

“Layers of things,” he said. “Floating on top there’ll be leaves and sticks. There's stuff that people drop in the street – newspapers, food wrappers, plastic bags that they use to clean up after their pets. At the bottom you often find those little glass bottles from individual servings of liquor. People who can’t afford a whole bottle will buy one of those and toss the empty into the street.”

baby ducks rescued from storm drain, Cambridge MA
Photo, left: Surprising things show up in the catch basins. In May, 2010, this family of ducklings tumbled into one a few blocks further uptown on Pearl Street. Passers-by called the Animal Commission for help, and the babies were rescued.

How do we keep our storm drains from getting clogged up and sending polluted overflow into the rivers and flooding streets and basements?

“Well, how do you want your tax money to be spent?” Stern asked. “What I'm doing here is probably the most expensive way to keep a drain clear. When you leave something on the street and it gets washed down there, you’re paying for a special truck and a driver to clean it out, plus a lot of other city services -- and then on top of that, the things we fish out end up in the landfill. Composting the leaves, recycling the paper and bottles, putting regular trash in a trash can – that’s a much better deal.”

IMG_0363The Department of Public Works picks up yard waste, materials for recycling, and trash on a regular schedule.