My arm was up to the elbow in water classified as unfit for human contact. I was staring down a double-barreled shotgun of pipes that release some 90 million gallons of untreated sewage and storm water annually into the very water I was canoeing in. This is the Gowanus Canal, in Brooklyn, N.Y. I was there as a participant in a hackathon created to develop tools to better understand the nature of urban water pollution.

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DIY water quality monitoring by Public Laboratory and DontFlush.Me. Photo credit: Eymund Diegel

The Water Hackathon, held March 23-25, brought together a diverse group of people all interested in better understanding the complex issues affecting water in urban environments. Public Laboratory co-sponsored the event together with Pachube, Ushahidi, Citizen Sensor, and DontFlush.Me, and the event was hosted by the Geospatial Design Lab at Parsons the New School for Design.

Ignite-style talks kicked off the event Friday night, with presentations by activists, engineers, boaters and technologists. These presentations led to the formation of groups which worked together to develop working prototypes by the end of Saturday.

The problems tackled during the event included: understanding the diverse impacts affecting urban water quality; enabling recreational boaters to collect real-time water quality information using a smartphone connected to a sensor kit; creating a sensor-based reporting system for Ushahidi crowdmaps; and providing New York City building owners a direct way to share and better understand water usage in buildings.

Detecting Sewer Overflow

On Sunday we all headed out to the Gowanus canal to test the water quality sensor we built together. Naturally, we canoed right up next to a set of pipes called “Combined Sewer Outfalls” (CSO) since these pipes dump overflowing sewage into the canal almost every time it rains.

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Water Hackers in Gowanus Dredgers’ canoes.

The idea behind our design for this particular sensor was to create a device that could be installed outside of a CSO, in a publicly accessible place, and would use a variety of different sensing techniques to detect when a sewer overflow happened. The group decided that the first sensor should be water temperature. Even when mixed with storm runoff, overflows should be measurably warmer than the receiving waterbody. The temperature probe that we used is a waterproof digital sensor from Adafruit, a woman-owned business based in NYC.

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Adafruit’s waterproof digital temperature sensor.

For the second sensor, we decided to create our own electrical conductivity (EC) probe. The Environmental Protection Agency has a some great details about EC and how it is an indicator of water quality. Basically, the purer the water, the lower the conductivity. Conversely, the more stuff (in our case, sewage), that is in the water, the higher the conductivity will be.

Environmental Monitoring with Arduino“ is a great recently published book which includes plans for a DIY EC sensor. Using parts from Radio Shack, the team created our EC sensor and calibrated it with a solution from Atlas Scientific and some other concoctions.

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Calibrating the sensor. Photo Credit: Dan Seldon

These two sensors were connected to a custom arduino shield which was milled on the awesome PCB (Printed Circuit Board) machine at Parsons the New School for Design.

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Printed circuit board layout for Arduino shield.

Everything was connected to an Arduino including a big battery, a charging circuit and a solar panel all from Adafruit, and a GPRS Shield from SeeedStudio. This all was put into a small Pelican case so that it could be installed in the Gowanus Canal.

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Water quality sensor before installation in the Gowanus Canal.

Water Hack can be seen as a high energy moment in Public Laboratory’s multi-year, ongoing engagement with Gowanus Canal activists and designers. Many Gowanus-based community groups came together around this event. The Gowanus Dredgers provided canoes; the Gowanus Canal Conservancy shared their knowledge and experience with urban water quality issues; and innumerable other individuals and organizations either participated for the weekend or contributed perspective on issues during the planning stages.

The social media feed for the event can be found here. The full description of the tool is posted on Public Lab. Related work with sensors and sewers can be found on DontFlush.Me. You can read more about our work with the Gowanus Canal here.

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The solar-powered water sensor installed in the canal in front of combined sewer overflow pipes.