Sewage from the plant disabled at Riverbank State Park is being re-routed to several sites on the Hudson and Harlem Rivers. Here is one sewage source into the Hudson River, 10am on July 22nd, located a few blocks north of Christopher Street, Manhattan.

Linked below is today’s updated sewage plume hindcast/forecast video based on the Stevens Institute of Technology NYHOPS ocean model and created using NOAA’s GNOME particle tracking tool.  The simulation runs from 5:15 PM, Wednesday July 20th to 12:00 AM, Saturday July 23rd, 2011 (tonight at midnight).  This forecast information is being utilized by the NYC’s Department of Environmental Protection (DEP) and the New Jersey State DEP.

Note that the simulation simply shows where water “parcels” (black dots) travel from the six (reportedly) primary spill sites, and does not directly simulate the sewage or pathogens, which would be significantly more complicated.  The dangerous bacteria in the sewage are thought to survive less than one day, and this is an area where the physics can only tell you so much.  Based on continuing visual observation, the sites in Harlem are sourced with five times the outflow of the sources in lower Manhattan.

The New York City DEP is in charge of making decisions on public safety, and is taking observations and running detailed microbiological models in place that should be more useful for determining where beach closures are necessary.  So one should consult the DEP website for questions of water safety.

Plume simulation movie -- click to watch. Black dots simulate discrete parcels of water moving through the system. The material in the plume model does not decay or biodegrade, so the dispersion of black dots gives a conservative estimate of where pathogens may be present. Also note the caveats below about whether the plume reaches Long Island Sound.

We have moderately high confidence in a few conclusions about the plume transport.  These relate to the forecast model results in the Hudson, New York Harbor and out to the ocean, and these are also based on our assessment of the extensive observations that are also available in NYHOPS.  Tides are dominating the plume movement, and cause it to pulse back and forth up the Hudson.  The plume gets spread mostly through the lower Hudson along Manhattan, The Bronx, and New Jersey, but also in smaller amounts to near the ocean beaches of Brooklyn and Staten Island.  (See below about Long Island Sound).  The results also suggest that transport northward up the Hudson (e.g. upstate New York, Westchester County) may be small, compared to transport out toward the ocean beaches, though caution should still be exercised and measurements made to check water quality.  They suggest that transport across the Hudson to New Jersey takes less than one day, so contamination could occur there – incidentally, Hoboken has put out a warning.

We do not have confidence in the results for the sewage outfall(s) apparently occurring in Harlem River, and whether or not it is transported to the upper East River – the results there don’t seem to match the physics we know exist, and we cannot comment on the impact to Western Long Island Sound beaches with confidence.  However, based on our previous experience, the western sound should be monitored carefully too, and may be dangerous for swimming.  The problem is presumably due to having water currents flowing through narrow tidal channels with only a few model grid cells fed into the NOAA GNOME tool we use to simulate the plume.

Yesterday’s post demonstrated how a spill site can be identified, including smooth water surfaces, bad smells, and seagulls feeding on the small fish that are attracted to the plume.

Additional credit for producing the plume simulations goes out to Dr. Alan Blumberg, Dr. Julie Pullen, Liang Kuang, and the Center for Secure and Resilient Maritime Commerce (CSR) Summer Institute students: Fernando Arroyo, Chris Filosa, Chris Francis, Drew Orvieto, Brian Paul, Greg Sciarretta.