2015 Gantry Plaza State Park Water Quality

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2015 Citizen Water Quality Testing Program Report

by Josue Silvestre, Engineer in Training
HarborLAB Water Quality Sampling Coordinator

HarborLAB takes part in the Citizen Water Quality Testing Program (CWQTP), an initiative of the New York City Water Trail Association that coordinates weekly grassroots monitoring of metropolitan area waterways for a 20-week period from May through October. I had the opportunity to lead HarborLAB’s participation in 2015. Our focus was again Gantry Plaza State Park, where we serve cumulatively thousands of children, teens, and adults through public paddling programs and special partnerships with organizations serving disadvantaged youth.

We received training from The River Project and a research team at Columbia University’s Earth Institute on water sampling at docks and shorelines. The sampling season launched on May 28 with 38 sites from Yonkers to Jamaica Bay. We measured nitrate and phosphate with in-situ testing kits and brought chilled samples rapidly to five labs to test for Enterococcus, a gut bacterium indicative of sewage. While nitrate and phosphate levels are immediately registered, bacteria must be incubated for more than 24 hours.

Gantry Plaza State Park is on the East River, a tidal strait within the Hudson River Estuary. The CWQTP concerns itself with wastewater contamination of the East River due to past and recurring contamination from combined sewer outfalls (CSO) and malfunctioning of wastewater treatment facilities. Paddling groups and nonprofit littoral ecology experts assert that because NYC Department of Environmental Protection surveys sample in deeper water, official statistics don’t account for bacterial colonies near shore, where human contact and wildlife activity is greatest. NYC Department of Health water testing focuses on swimming beaches, not kayak and canoe launches.

HarborLAB cancels programming at Gantry Plaza State Park on days following significant rain as a precaution against CSO contamination.

Enterococcus levels are presented as a Most Probable Number (MPN), or the number of colonies per 100 ml of water counted after incubation. These numbers set thresholds for recommending public notifications or temporary closures. New York City Department of Health Enterococcus standards for swimming are as follows:

MPN <35 = acceptable for swimming

MPN between 35 and 104 = unacceptable if level persist

MPN >104 = unacceptable for swimming

Throughout the 2015 CWQTP season (see figure 1) lab results showed that the presence of Enterococcus at Gantry Plaza State Park usually measured within acceptable conditions for swimming. It was observed that on three occasions Enterococcus levels at the site were unacceptable for swimming. Similar results were obtained in the previous 2014 CWQTP season (see figure 2) with one measurement exceeding the limit acceptable for swimming.

These spikes might correlate to rainfall prior to measurement (with one of the three a possibly anomalous result), as seen in figure 3, provided by the Riverkeeper organization through the citizen testing data web tool hosted on its website. That is, a wetter season in 2015 may be the cause for having have three peaks in Enterococcus counts compared to one peak in 2014. The amount of rainfall in the 2014 season, from May 22 to October 02, was 14.76 inches, according to the National Weather Service Forecast Office. That was 1.59 inches less than the 2015 season’s 16.35 inches for a same period (May 21-October 01).

Nitrate (NO3) and Phosphate (PO4) in-situ testing was new to the 2015 season. Nitrates and phosphates from urban runoff can cause eutrophication, a process that depletes lakes, streams, and rivers of oxygen. The procedure for in-situ testing was straight forward. The test kit consisted of two small tubes with nitrate and phosphate reactors and a small cube (see figure 4). Each tube would absorb water from a small cube of the sampled water. The tubes would change color after a few minutes indicating the level of NO3 or PO4 respectively. Throughout the season, low concentrations of Nitrate and Phosphate testing were recorded and these remained constant.

For me, as an international student with an engineering background in water resources, and an advocate of sustainable water management, constant monitoring of water bodies is of utmost relevance. It informs environmental regulators whether the water body supports a healthy aquatic ecosystem. While participating with HarborLAB collecting water samples, I came to appreciate the importance of keeping New York City’s waterways pollutant free. It helps revitalize shores once plentiful with aquatic life and maintain a balance in the ecosystem. In addition to revitalizing shores, effectively protecting our water bodies from pollutants creates an increased public interest in recreational water activities.

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Fig. 1 2015 CWQT Season Enterococcus test results

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Fig. 2 2014 CWQT Season Enterococcus test results

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Fig.3 Enterococcus count and rainfall correlation. (Extracted from Riverkeeper.org/water-quality/citizen-data.)

 

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Fig. 4 Nitrates and Phosphates in-situ testing kit

 

One thought on “2015 Gantry Plaza State Park Water Quality

  1. Pingback: Sewage Nixes Manhattanhenge Paddle | HarborLAB

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