Yesterday I went to a workshop hosted by Expedition Gowanus an “underground” group looking at local and alternative ways (vs. Superfund ways) to remediate our waterways.

Expedition Gowanus hosts a series of workshops on DIY sustainability techniques that will culminate in the final design of an off grid, regenerative, floating structure on the Gowanus Canal this fall. For future events, or to be added to the email list, email expeditiongowanus at

This particular workshop was on making low tech, floating water remediation gardens out of trash, which is a form of Phytoremediation.

Phytoremediation is the use of plants to pull pollutants from the environment and render them harmless. In polluted bodies of water, gardens of water plants can be attached to buoyant structures, thus creating ‘floating restoration devices’. The plants provide habitats for other organisms to live. First it starts small with amoeba and small plankton. Then you get slightly larger things like bugs and snails that feed off the smaller ones. Then comes mollusks and small fish. Then larger fish and birds. Eventually you get huge whales! Well maybe not but you get the idea.

Scott Kellog, co-founder of Albany’s Radix Ecological Sustainability Center and co-author of the book Toolbox for Sustainable City Living: A Do-it-Ourselves Guide, lead the workshop. He introduced basic concepts in phytoremediation and some of the techniques for applying these concepts to the remediation of polluted water (living machines, constructed wetlands, etc).

After an introduction, we built a mini ‘floating trash island’. Made out of construction debris and old soda bottles gathered from trash, the island was planted with local wetland plants, and then given the ultimate challenge; an inaugural float on the infamous Lavender Lake (aka Gowanus Canal).

The whole thing went swimmingly.

As a Brooklyn green builder and contractor my daily focus when we do green brownstone renovations is to keep the water on site in the first place. We us techniques that reduce rain water runoff. These are things like permeable surfaces – green roofs, no concrete etc. We divert the rain water to dry wells or water holding tanks. The rainwater capture barrels then water the garden, green roof or provide water to the toilets.

We also focus on reducing the water produced. Low flush toilets, low flow fixtures  and appliances all lend to this. A gray water system takes all the water from showers, baths, sinks and washing machines and reuses it for toilets, green roofs, living walls and the garden.

This web of techniques play into the Zero Brownstone goal of eliminating the need for off site water and eliminating the water run off from the site.

But what if water does leave the site? It enters the sewer system and when it rains the water goes into and polutes the waterways. The is where groups like Expedition Gowanus come in. They deal with this problem of too much sewage and water polluting the waterways.

Their goal is to clean the waterways using low impact natural systems. Phytoremediation is one such system.

Here are some pics from the workshop:


One minor issue I saw was the concept of using trash. Eco Brooklyn constantly uses trash to build brownstones, the definition of trash being stuff that is on its way to the dump. But the quality of the trash is important. We try to salvage everything but even Eco Brooklyn regards some things as not fit for use.

I have some concerns that using trash islands to cultivate bio communities still does not address the issue of toxins leaching out of the trash.

In the case of a floating island we use old plastic bottles. Plastic lasts forever, which is its mixed blessing, but that does not mean it is inert. Over time and especially when exposed to uv light, oils, chemicals and heat it breaks down. Over many years plastic eventually does break down into fine dust. During the breakdown process it releases toxins.

Here is a quote about plastic and food, but it relates just as well to floating trash islands. The Smart Plastics Guide says that

“a myriad of petroleum-based chemicals go into the manufacture of plastics. Some can leach into food and drinks and possibly impact human health. Leaching increases when plastic comes in contact with oily or fatty foods, during heating and from old or scratched plastic. Types of plastics shown to leach toxic chemicals are polycarbonate, PVC and styrene. This does not imply that other plastics are entirely safe. These plastics have just been studied more.

Polycarbonate, the one with bisphenol-A, used in most plastic baby bottles, 5-gallon water bottles, “sport” water bottles, metal food can liners, clear plastic “sippy” cups and some clear plastic cutlery. PVC or Polyvinyl chloride, used for cling wrap, some plastic squeeze bottles, cooking oil and peanut butter jars, detergent and windown cleaner bottles. Polystyrene, used in Styrofoam products.

With a floating plastic bottle island you are creating micro bio environments and right from the beginning exposing the food chain to toxins. Not good.

A floating island made out of plastic bottles in the polluted Gowanus Canal probably has more benefits from the added life than the leaching plastic causes. But it is not an ideal solution. I think a better solution is to be more stringent of the definition of a natural  environment – a natural environment should not have plastic bottles no matter what good they are causing.

Just like in our construction we try to use as much salvaged material as possible there are certain things we remove from the home and let pass on to the dump – formaldehyde cabinets, linoleum, carpeting, and anything else that has toxins – we should probably get the plastic out of the waterways.

The goal of cleaning out waterways is to remove as much toxins as possible, including all plastic bottles.

In the case a floating plastic bottle island we would need to replace the plastic with something more natural. The first thing that comes to mind as a plastic bottle alternative for a floating island are wood logs like the image below:


Keeping the logs from sinking would be more of a challenge than with plastic bottles but that is a minor issue compared to the huge benefits an organic element like wood adds the the island habitat. And when the log does sink it simply adds to the organic process of cleaning the bottom of the canal.