NORTH SALEM, N.Y. - Stench. Stink. Reek.
Whatever you call it, the foul odor that’s making folks gag and their eyes water in and around the North Salem hamlet of Purdys has a fairly simple explanation: hydrogen sulfide, a colorless gas that smells like rotten eggs.
So where is it coming from?
The Titicus Reservoir. It’s one of 12 reservoirs in New York City’s Croton Watershed. There are also three lakes.
Altogether the city has 19 reservoirs. (People have reported a similar funk emanating from the East Branch Reservoir in the Town of Southeast.)
What’s to blame for the pungent situation?
There are a number of factors.
Number One. The New York City Department of Environmental Protection is required by the state Department of Environmental Protection to release 5 million gallons of water each day from the Titicus Reservoir into the stream below the dam for fish.
The water then flows into the nearby Muscoot Reservoir.
Because of the lack of rain, water is not flowing over the top of the dam and the city has had to release water from the Titicus via pipes at the bottom of the structure.
Hydrogen Sulfide is held in water under pressure. When that’s reduced, such as when it comes out of the pipe at the base of a dam, it outgases.
According to the state Health Department, much of the hydrogen sulfide in the air comes from natural sources and is produced when bacteria break down plant and animal material. The hot weather hasn’t helped things either.
Secondly, the DEP last month launched the final phase of its $2 billion Delaware Aqueduct Repair Project, which had been planned and prepared for more than 20 years and is the largest.
The 85-mile-long aqueduct carries about half of the city’s drinking water supply. It draws from four reservoirs (Rondout, Cannonsville, Neversink, and Pepacton) in the Catskill Region to three (West Branch, Kensico, and Hillview) on the east side of the Hudson.
Built between 1939 and 1945, it’s considered to be the world’s longest tunnel.
In 1988, the city discovered that the aqueduct was losing 36 million gallons of water a day.
The DEP ultimately decided to build a 2.5-mile-long Rondout-West Branch Bypass Tunnel beneath the Hudson, parallel to the existing aqueduct. This will permanently convey water around the leak. Construction began in 2013.
Now in its final phase, the project required the temporary shutting down of the Delaware system while things are drained, plugged, and reconnected. That started in October and is expected to last for eight months.
This means that capacity for the complementary Catskill system on the west side of the Hudson has been increased.
Also, more drinking water has to be drawn from suburban reservoirs such as the Titicus in the Croton Watershed, which has a 24-square-mile drainage basin that includes parts of Lewisboro and North Salem in Westchester County, Southeast in Putnam County, and Ridgefield in Fairfield County, Conn.
With the Croton system being used more heavily, most of the reservoirs will be lowered “substantially,” North Salem Supervisor Warren Lucas explained.
Officials pointed out that could affect the taste and aroma of the city’s drinking water because of the higher presence of algae and minerals in the Croton system.
According to the DEC, when bacteria in the lower level of a reservoir “respirate” they use up all the oxygen and the water goes “anoxic” meaning it has no oxygen.
Some of the bacteria will continue to respirate by using sulfur and phosphorus instead. This creates hydrogen sulfide gas.
Lucas had asked the DEP to draw from the reservoir’s higher intake levels.
This is the response he got from David Warne, assistant commissioner of the NYCDEP.
“Warren, I reviewed this with our operations staff. We are already at our top-level intake, so there is no further adjustment we can make on the elevation. The state mandates a minimum release of 5 million gallons per day. Our current release is above that due (to) the aqueduct shutdown project and the resulting change in reservoir operations. The persistent hot, dry weather is also a factor. We’ll need some cold weather to get past this.”
For More Info
For more information on how hydrogen sulfide reacts in the environment, what impacts on human health it may have, and ways to reduce exposure, visit https://www.health.ny.gov/environmental/chemicals/hydrogen_sulfide/.
Heath effects information: Call New York State Department of Health, Bureau of Toxic Substance Assessment at 1-800-458-1158 or BTSA@health.ny.gov.
To report hydrogen sulfide odor issues: Call New York State Department of Environmental Conservation at 1-800-457-7362, a toll-free 24-hour hotline.
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