Project Profile: Keeping Public Water Clean Naturally

Sept. 19, 2016

When we see news stories about lead-contaminated water flowing out of faucets in Flint, MI, and see the troubles the city is having as a result, many of us become concerned about our own city’s drinking water supply that we use every day to brush our teeth, take a shower, and fill our dog’s water bowl.

The US Army Corps of Engineers has an interagency program in place that helps keep New York City’s drinking water clean and safe.

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Recently one of the program’s projects was successfully completed in the Town of Walton, NY. The project is protecting drinking water and also sustaining this rural community.

The program is called the New York City Watershed Environmental Assistance Program, and it assists in the creation of projects that protect the water quality of New York State’s watersheds that provide drinking water to millions of New York City residents and businesses.

Many people ask, “Isn’t the water treated before it reaches our faucets?” Yes, but minimally.

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“New York City prides itself on its minimal filtration of its drinking water,” explains Rifat Salim, project manager with the Army Corps of Engineers. “In 1996, all of the municipalities in the New York City watershed region came to an agreement. They wanted to avoid the creation of a huge filtration plant. Instead of a plant, they agreed to have small projects throughout the region to provide the public with clean water with minimal filtration. This is how our program came about.”

The New York City watershed region encompasses approximately 2,000 square miles and includes three watershed systems: the Catskill, Delaware, and Croton systems. They are all located north of New York City in the counties of Greene, Schoharie, Ulster, Sullivan, Westchester, Putnam, Dutchess, and Delaware.

The rural Town of Walton is in Delaware County. A while back, the town was devastated by a major flood that damaged many homes and businesses, resulting in approximately $30 million in losses for the community.

Trees along streams got uprooted and fell into the streams, were carried down the waterways, and clogged several bridges. The fast-moving water had nowhere to flow but out onto the streets, flooding businesses and homes.

When streambanks start failing, all of the materials that used to be on the bank become potential contaminates to the water that eventually becomes New York City’s drinking water. This flood didn’t cause water contamination, but many could.

Salim says, “These slope failures can do a lot of damage to the water. When the slopes or embankments get eroded, a lot of sediment and soil enters the stream. These sediments cause turbidity in the water. It then flows into the reservoir and eventually adversely affects New York City drinking water.”

One of the streams that was severely eroded during this flood was Third Brook. Third Brook flows into the West Branch Delaware River, which in turn flows into the Cannonsville ­Reservoir. This reservoir provides 97 ­billion gallons of water to New York City’s drinking water supply.

To keep this water safe, steps were taken to stabilize Third Brook. The agencies that worked together included the Army Corps’ New York District, the New York State Department of Environmental Conservation, Delaware County Soil and Watershed Conservation District, the New York City Department of Environmental Protection, the Village of Walton, and the Town of Walton.

According to Graydon Dutcher, project manager and administrator of the Delaware County Soil and Water Conservation District, workers stabilized the toe of the failing streambanks with stacked rock walls or rock riprap and provided protection to the streambed with the placement of in-stream structures such as boulder riffles.

“We had to use large rock to stabilize the toe of the banks and the streambed itself, because the stream has no floodplains,” explains Dutcher. “All of the floods, large and small, are contained within the limited channel. This produces very rapid stream flow. Wherever it was possible, we buried the rocks and planted around them with native vegetation. This combination creates a more diverse and flood resilient stream corridor.”

He adds, “We also hydroseeded all of the bare slopes and planted willow stakes and native trees along the floodplain, which provides for habitat and increases the stream’s long-term stability.”

Credit: Delaware County Soil and Water Conservation District
Third Brook was highly susceptible to failure after a major flood.

Salim says, “This vegetation helps stabilize the slopes. The roots stabilize the soil and they can also absorb contaminants before they reach the stream, providing us cleaner water.”

Clean water is also beneficial to fish and aquatic life. Sediments that get into the water may carry phosphorus and pathogens, or parasites. Algae in the water may feed off these nutrients and deplete the water’s oxygen, adversely affecting water quality.

An added benefit to stabilizing the slopes is that it helps to protect from flooding and returns the stream corridor to more aesthetically pleasing and natural-appearing embankments, some of which are in the backyards of homes.

Credit: JoAnne Castagna, Public Affairs, USACE
Third Brook today is now stabilized and vegetated.

The project is already showing success. “The landowners have expressed gratitude for completing the project,” says Dutcher. “This project has already seen a few high-water events just after installation, and the stream’s response has been very favorable.”

Salim adds, “Communities benefit from having a nice embankment and added safety to their property, and New York City residents benefit by having clean drinking water. It’s a win-win situation.”