Drones with Infrared Cameras Can Help Us Find Illicit Discharges

By Eric Swenson, Executive Director

One important aspect of keeping our harbors clean is to stop “illicit discharges”.  But first you need to find them.  One promising technology that is coming into its own is the use of drones with infrared “thermal imaging” cameras that can identify such discharges by detecting slight increases in temperature.  Since municipalities are required under their NYS stormwater permits (“MS4 permits”) to have a program to identify and eliminate illicit discharges, this technology may offer a valuable tool in their toolboxes.

Earlier this month, the Nassau County Soil and Water Conservation District awarded funds to Friends of the Bay in Oyster Bay to undertake such a project in Oyster Bay, Cold Spring Harbor, and Mill Neck Creek. Partners in the project are the Oyster Bay / Cold Spring Harbor Protection Committee, Walden Associates, and Harkin Aerial. 

Since illicit discharges from manmade sources typically emit more thermal energy (heat) than the surrounding water or soil they are discharged into, and since heat rises, modern day infrared cameras can detect these relative changes in surface temperature with a sensitivity up to 0.1 degrees F.  When mounted to a drone, a set of thermal images can be taken covering about 50 acres in under an hour.  Experience shows that the best time of day to do this is early to mid-morning when the temperature difference is greatest (before the sun heats up the land and water).

The drones also have a “regular” camera that can take simultaneous photos so that any “hot spots” found can be more easily located. The drone also logs GPS data. Particularly important to the process is the use of people trained and experienced in interpreting the photos as there can be false positives.

Walden Associates and Harkin Aerial, both based in Oyster Bay, have been pioneers in this technology.  In 2018, they conducted a study in the Village of New Paltz. Their work identified illicit discharges from residential sump pumps, leaking sewer main valves, discharges into fields and farmland, and outfalls into the Wallkill River.  

Locally, they will focus on the area around the Village of Laurel Hollow’s beach which has been frequently closed due to high bacterial levels; the Mill Neck Creek subwatershed area in the vicinity of Bayville’s “Stands” area where illicit discharges are suspected, and the subwatershed area around the Town of Oyster Bay’s Beekman Beach which also has experienced high bacteria levels.

This project is believed to be the first of its kind on Long Island.  If successful, this may also help us in Hempstead Harbor.

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