Water Quality Monitoring Charts

One of the most common questions we receive at NCA: ‘Is the Creek getting cleaner?’ In many regards Newtown Creek is absolutely cleaner than it has been in the past 100+ years. We have less oil spills, less illegal dumping of hazardous material, better environmental protection laws/enforcement, and improved sewage infrastructure as compared to recent decades. But on a smaller time scale what kind of improvements are we seeing to the surface waters of Newtown Creek and how does water quality actually measure up to federal standards prescribed by the Clean Water Act?

In analyzing our Newtown Creek SAMPLES data (monitoring of 10 Creek locations from 2016 to 2020) as well NYC DEP’s Harbor Survey Data (four fixed Creek locations from 2003 to 2020) we focussed on two standard parameters to see what kind of gains have or have not been accomplished in recent years. Included below are five water quality graphs and a brief analysis to explain the graphs and give background information for potential trends. The column to the right explains the two parameters, their importance for ecological health and human exposure, and why they so largely influenced by rain events and resulting Combined Sewer Overflow (CSO).

Enterococcus is a sewage-indicating bacteria used by federal, state and city agencies in determining water quality. Because the bacteria provides a high correlation with human pathogens often found in sewage, it is a good indicator for how safe a body of water may be for human contact, as well as determining baseline health of the waterbody. It is measured as Most Probable Number (MPN) of colonies per 100 mL. The Clean Water Act uses a Geometric Mean, or weighted average, guideline of ≤ 30 (MPN/100 mL) over a 30-day period for determining if water is clean or not. 

Dissolved oxygen (DO), the amount of oxygen present in the water, is a key factor in determining the health of a waterway and ability for fish, crabs and other marine wildlife to survive. DO can be influenced by multiple factors including water temperature, nutrient pollution, depth of sampling and the flow of water. Warmer water, for instance, holds less oxygen. Typically, DO levels are most impacted during summer months in areas of the Creek that are more stagnant and located near CSO outfalls. New York State requires that DO in the most impaired waterways, including Newtown Creek, not fall below 3 mg/L.

The vertical axis indicates the percentage of samples in a given year that were above the 3 mg/L threshold (with 100% being the goal in maintaining a minimally healthy waterway). Levels have varied year to year with no significant improvements aside from East Branch and Plank Road, which is where an aeration line was installed and began operating in 2018. English Kills however, has declined over 4 years despite proximity to an aeration line. The four sites in Dutch Kills have progressively worse DO levels further upstream where water is more stangant and larger CSO outfalls exist.

The vertical axis indicates the percentage of samples in a given year that were above the 3 mg/L threshold (with 100% being the goal in maintaining a minimally healthy waterway). As seen there were two large increases in DO levels occurring after 2008 and after 2013. We believe this is in large part because of the upgrade to the Newtown Creek Wastewater Treatment plant in 2009 which raised the quality of water being discharged from the plant, and activation of the Lower English Kills aeration system in 2014 which artificially infuses air into the water for the explicit reason of raising DO. As may be expected, the locations closest to the East River and furthest from large CSO outfalls (Nature Walk and Penny Bridge) have the highest percentages of DO above 3 mg/L.

With the exception of a few outlier years (2005 and 2020) there have not been any significant gains in reducing enterococcus levels in Newtown Creek. As would be expected areas furthest from the East River and closer to large CSO pipes (English Kills and the Turning Basin) are the most impaired. The sampling site near the Dutch Kills Mouth (less than a mile from the East River) is the only site that has met Clean Water Act standards more than once since 2003.

Unfortunately, the majority of Newtown Creek is far from meeting Clean Water Act standards (red line), including the highest number being 57 times higher than the federal threshold (East Branch, 2019). One explanation for the differences year to year may relate to when those samples were taken, and if it had rained in the proceeding days thus creating Combined Sewer Overflow and resulting enterococcus levels. The blue dotted line indicates this by showing the percentage of wet weather sampling days each year (defined as .3” or more of rain occurring 72 hours prior to sampling).

This logarithmic graph breaks down the specific days over 5 years to gauge how rainfall impacts enterococcus levels. Heavy Rain signifies when .3” or more of rainfall occurred 24 hours prior to sampling, and Moderate Rain signifies when .3” or more of rainfall occurred 72 hours prior to sampling. Clearly, both Rain Day designations were well above the Clean Water Act (CWA) standard (red line), with many individual sample levels actually being beyond the limit of detection (24,196 MPN/100mL). In addition to the horrific results seen from samples taken after rain events, we also see that some sites still failed to meet the CWA during dry sampling days (East Branch, English Kills and Dutch Kills Head).