Read our 2025 Water Quality Data Report

If you look at our timeline, you’ll notice just how iterative, complicated, and incremental the process of building first-of-a-kind infrastructure can be (especially if it’s designed to swim in!). 

You may also notice how our water testing operations have evolved over time.

We’ve been testing East River water quality samples since 2011. We tested a floating filtration system in 2014. We reported on samples from 4 separate locations in 2015. We built a real-time water floating quality monitor in the River in 2019. We joined the Community Water Testing Program and started publishing annual water quality reports in 2021, and in 2024 we piloted a scaled version of our advanced filtration system on a barge to demonstrate its ability to treat East River water to meet swimming standards.

From citizen scientists to sondes, Secchi disks to certified labs, we’ve been out here.

Water Quality (and Quantity)

But 2025 was above and beyond. Our years of baseline monitoring culminated in an intensive, multi-parameter water characterization program designed to meet the New York City Department of Health (DOH)’s protocols for novel bathing facilities and satisfy DOH requests for a full health risk assessment.

We may be building a pool of filtered river water, but we’re also building a pool of public water quality data. And we think that data helps tell a New York story. Why isn’t the East River “swimmable”? How do CSOs and nutrient runoff affect our harbor estuary? Based on the trends, what’s the future of New York’s waterfront look like?

We’ve collected a lot of data so far, but there’s a lot more to track (both in and out of the pool) as we hope to contribute to that New York water story.

But let’s back up a bit. What exactly did we test? Why? And what did (or didn’t we find)?

Basically, to permit a floating water-filtering pool that does not rely on chlorination for disinfection, we need a waiver from the New York City Department of Health. No waiver, no pool. 

Now there are a lot of things we need to demonstrate, questions we need to answer, and approvals from other agencies we need to get that waiver. But one of the requirements is a complete and thorough characterization of the East River, specifically at our proposed site location. 

From that extensive dataset, we can conclude that our system could predictably meet recreational water quality criteria.

So that’s the “why.” Sounds pretty straightforward, right?

But what makes 2025 special is the “what”?

What’s in the report?

To do provide a satisfactory characterization to the Departments of Health, we need to provide the following things for our proposed location:

• Existing water quality data for the most recent 15 year period
• A map
• Collection and review of  water quality data from the most recent 3-year period for the proposed location
• Research of historic and current site use such that it identifies and characterizes the presence of physical, chemical, or biological contaminants or substances that may potentially present a public health risk.
• Accurately summarized the environmental studies, site history, and water quality data to identify and evaluate the pattern and frequency of contaminants of concern at the proposed location.
• Raw data in spreadsheet format (parameter, concentration, analytical method)
• Trend analysis between fecal indicator bacteria concentrations and rainfall intensity and duration
• Raw data by categories, including physical, chemical, biological contaminants or substances that may potentially present a public health risk
• Independent certification of all the above from a third-party subject matter expert (credentials and qualifications to be approved by NYC DOHMH)
• Independent certification that the project location can feasibly and predictably meet recreational water quality criteria or meet design influent parameters for source water that can be treated for use in a contained project, under both dry and wet weather conditions.

And with regard to the parameters of water quality to be tested, that includes bacteria, viral pathogens, minerals, metals, oil and grease, and emerging contaminants such as PFAS and dioxins.

The full menu, really.

The process included weekly mid-river sampling, volunteer-led monitoring along the Pier 35 esplanade, and intensive chemical screenings analyzed by certified independent laboratories. We worked with our partners at the IEC (Interstate Environmental Commission) to primarily analyze bacterial parameters, most notably enterococci, and IEC coordinated with the Eurofins Group to analyze a host of other industrial, organic, and emerging contaminants.

Then we had a 3rd party expert firm review it all and confirm that we’d complied with DOH’s reporting requirements.

No sweat… 

So.. what did (or didn’t) we find?

Testing for a broad range of substances, including pesticides, PCBs, and industrial chemicals (VOCs and SVOCs), resulted in almost entirely non-detects. This suggests that these man-made pollutants (industrial and organic contaminants) are either absent or present at levels too low to measure.

While some metals and PFAS compounds were detected, they were found at low, often approximate levels. These detections are identified as “approximate” (or ‘J’ qualified) because the concentrations were so low they fell between the laboratory’s most sensitive detection limit and its reliable reporting limit.

We did find increases in bacteria levels following heavy rainfall, which was to be expected (it’s our raison d’etre, as it were). We also found elevated concentrations of Sodium and Magnesium, which are natural to brackish (saline) river water and don’t pose a public health risk for swimming.

So while the East River’s raw water is subject to temporary changes during storms, the 2025 data shows that chemical contaminants have not revealed any concerns to date. 

And the pool’s filtration system is engineered to take care of the bacteria and pathogens that get tracked and regulated by the departments of health. With a >4-log reduction (99.99%) of bacteria, our Ultra-filtration system reduces even the highest recorded river bacterial concentrations to safe levels. And that’s not even factoring in the UV disinfection zapping any viral DNA after that!

More updates to come as we demonstrate this Summer!

More Information

2025 Water Quality Data Report

Appendices and Raw Data

Disclosure: We’ve attached the full report here in the spirit of transparency. As of publishing, the report is still currently undergoing regulatory review by the NYC Health Department. If you would like to view any of the supplemental documents, please contact us at info@pluspool.com.