‘Living Lab’ explores managing runaway rainfall

The lab at Stevens Institute mitigates contaminated storm water overflow damage.

“This area is probably considered the bottom of the bathtub in the City of Hoboken,” said Hoboken councilman David Mello.

When rain comes down in buckets, like during Hurricane Irene, the councilman said, it swamps parts of Hoboken where drainage just can’t keep up with the downpour.

Storm water overflow mixes with sewage and runs into the Hudson. Pumps the city installed have helped, but the problem’s not fixed.

“We still haven’t gotten to the point where if the rain falls very quickly, it’s kind of like if you took a lobster pot full of water and poured it into your sink, there’s only so quickly it can dissipate,” described councilman Mello.

“The thought of untreated sewage in our receiving environment, in our water environment, is pretty horrifying,” said Stevens Institute of Technology professor Elizabeth Fassman-Beck.

And it’s one reason researchers are looking for ways to handle runaway rainfall at Stevens. Professor Fassman-Beck set up three different experiments to seek solutions that would work in a city so squeezed for open space even parking’s a problem.

“You can’t take up ground space for something like a rain garden or some other big system that’s going to trap water, like our traditional detention pond,” said Fassman-Beck.

The first experiment put narrow concrete planters flush against the back of a building. They contain two different media mixtures and sensors to measure how fast rainwater falls down the drainage pipes, and how long it takes to flow through each mixture, before it finally exits the planter.

Here’s the challenge, according to Fassman-Beck.

“Can we design a really confined space system that effectively reduces peak flow and maybe shaves a little bit of that volume off in an effective manner. Can we design it to be effective? It’s a really big question mark!” she exclaimed.

To see the second experiment, NJTV News climbed onto the roof where shallow trays of lightweight, porous media mixtures and special moisture-absorbing plants will catch rainfall. It’s called a ‘living roof’.

The question is, out of 19 different mixture-and-plant combos, which one best contains runoff? Fassman-Beck explains that plants are crucial.

“Just after it rains and the system is really wet with the maximum amount of water, these plants just pump out the water. Dry out the system. They’re little workhorses,” she says.

Basically, each tray becomes a sponge and each one will also get an extra layer of material to strain out pollutants.

The third experiment’s a so-called rain garden, one of three. Sunken to catch heavy downpours they also filter out pollutants and meter drainage. These will be designed for maximum efficiency, but with tight cityscapes in mind.

“Because of underground utilities, because of proximity to the buildings, there were a lot of factors in play,” explained Fassman-Beck. “So, what you have in our first rain garden at Stevens is an extremely atypical design.”

“We can have in our construction, even construction that already exists, we can make modifications to buildings that already exist that can help alleviate the flooding,” said councilman Mello. “That’s why I’m excited about working with people like Stevens Institute.”

It’ll take time for these experiments to yield results. After all, they depend on rainfall. But the researchers are eager to share their findings with Hoboken and other urban communities to help keep the flow clean and slow.

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