Quill Analyzes Sensor Data From Chicago Public Beaches

August 19, 2014 Matt Bramson

The City of Chicago has over 15 miles of bathing beaches and receives tens of thousands of daily visitors during its peak summer months. One of the most popular beaches, and where I frequently swim, is the facility at Ohio Street Beach (OSB), pictured above. It’s proximity to downtown Chicago and relatively calm waters make it an ideal training ground for triathletes and open-water swimmers.

Although there have been fewer OSB closures this year due to lower overall bacteria levels, Chicago Public Beach closures are quite common. Summer storms bring rain, causing run-off from the city to occur and beaches to get really dirty really fast.

The City of Chicago ‘Open Data Portal‘ contains a treasure trove of information on everything from potholes patched to crime statistics. It also contains time-stamped sensor data on Chicago Public Beaches that display water temperature, wave height, wave period and, most important to swimmers, turbidity; turbidity being a fancy word for the ‘haziness’ of water. Meaning, the higher the turbidity the nastier the water.

After recently swimming in a noticeably cloudy OSB, I solicited Quill to help me answer the following 3 questions:

  1. How dirty is OSB compared to other Chicago Public Beaches?
  2. What drove its haziness?
  3. Where else should I consider swimming if I want to avoid swimming in these conditions?

For the week ending July 16th, 2014 Quill generated the following report:

Chicago Beach Recap – Week Ending July 16, 2014

Best Beach

For the week ending July 16, 2014, 63rd Street Beach was the cleanest beach in Chicago, as measured by the hourly turbidity of the water by our sensors (average NTU 0.64). Not only did the beach have the cleanest water throughout the week, but also measured the cleanest out of all beach waters at any time (NTU 0.13), which was achieved on Wednesday around 9 PM. Calumet Beach was the calmest throughout the entire week, with an average wave height of 0.12 meters. This beach also happened to be the warmest, with an average temperature of 19.1º C.

Worst Beach

Ohio Street Beach was the dirtiest beach in Chicago, as measured by the hourly turbidity of the water by our sensors (average NTU 1.22). Ohio Street Beach did not record the highest turbidity rating of the week, however. Rainbow Beach saw a reading of 6.57 NTU, which was recorded Wednesday around 1 PM. In fact, it has recorded the highest turbidity each week for the last four weeks. In terms of other measures of poor conditions (i.e. waviness and temperature), Montrose Beach was the choppiest, with an average hourly wave height of 0.19 meters. It was also the coldest of all the beaches, with an average hourly temperature of 16.0º C.

Beach with Poorest Quality After Rain

Stay away from Osterman Beach on rainy days, as of late. Rainy days have raised the beach’s turbidity as high as 2.13 NTU. For example, throughout the day and the rain on June 30, 2014, the turbidity rose 1.76 NTU, with a large hourly increase around 7 PM

So what does all this mean? Of particular note, weather is a key factor in this analysis. With severe storms earlier in the week, I am not surprised OSB was ranked the dirtiest beach. The facility is also wedged awkwardly between Michigan Avenue and the outer entrance of Navy Pier. There is long standing concern that this beach, which faces north, limits water movement and is a cause of concern for public health. In other words, should I still be swimming here?

Quill could potentially generate these reports for me on a weekly basis, providing better insight into where to  swim – a much better solution to finding consistently cleaner beaches than chancing the potential grime of OSB.

By Matt Bramson. Matt Bramson works on the Business Development team at Narrative Science. Connect with Matt on Google + and Twitter.

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