DEP Eyes Expansion of P’ville Water Purification Chemical Facility
The planned temporary closure of a massive watershed pipeline will force additional chemical treatment of drinking water at the Pleasantville plant and an expansion of the facility.
New York City Department of Environmental Protection (DEP) officials told village planning commission members last week that the Delaware Aqueduct, which provides half of the city’s drinking water, will be closed in 2022 for five to eight months to repair leaks. To compensate, water flow from the Catskill Aqueduct that runs from Ashokan in Ulster County will be increased.
The DEP plan is to build an auxiliary 31-foot by 31-foot building just north of the existing plant off of Broadway in advance of the closure to store the de-chlorination chemical to reduce turbidity. The new building, planned to open in November 2018, will have three truck bays.
“The way we currently deal with the turbidity at Catskill is we turn down the flow and we turn up the dry alum,” explained DEP Project Manager Vasyl Krauchyk. “During the shutdown we cannot turn down the flow, so there is not enough capacity for dry alum to handle the turbidity. So we need to bring in liquid alum on site to make sure we make sure we are delivering high-quality water.”
The Catskill Aqueduct has more turbidity than the Delaware water supply, so during the shutdown the DEP needs to treat with additional alum, a chemical used for water purification, during high turbidity events, explained DEP Assistant Program Manager Emily Pereira.
The DEP will also be treating water to remove residual chlorine dioxide upstate before it enters the Kensico Dam. Liquid sodium bisulphate will be used before and during the Delaware shutdown.
The Pleasantville DEP facility was built in 1916 along with the aqueduct, and has been using dry alum to regulate turbidity during those 100 years. Liquid alum will be added to the water system at the facility during the Delaware closure. The liquid alum delivery will be intense during that eight-month closure, with trucks continuously unloading into the system.
The planned building will store 1,300 gallons of sodium bisulphate, which could trigger up to nine delivery trucks per week at the site, depending on how much chlorine is being added upstate. However, it is more likely there will be only one or two deliveries a week, Krauchyk said. The addition of sodium bisulphate will end when the project is completed, he added.
There will be as many as 24 liquid alum deliveries per week. Each truck takes about six hours to unload into the system, and there will be three or four deliveries per day, seven days a week. The deliveries will occur during normal work hours, Krauchyk said.
The more potent liquid alum will be permanently added at the site, and stored as a backup when needed, Krauchyk said. When asked by board members if they could switch to using liquid alum in the future, he said it was a possibility.
“It’s getting harder and harder to get dry alum, and the bureau of water supply would like to have that flexibility just in case they don’t have dry alum,” Krauchyk said.
Neither chemical is hazardous to the public, Krauchyk stressed.
The alum, which has no odor, solidifies and ends up at the bottom of the Kensico Reservoir as sediment, which will eventually have to be dredged out, he said. The DEP has avoided using alum when possible for that reason, he said.
Noise will not be an issue, Krauchyk said. Once the trucks pull into the bays to unload they will be turned off and will not idle. Commission member David Keller asked if the plant had an area for the drivers so they would not be tempted to keep their truck cabs running.
“If there are three trucks there at a time, where will the drivers go in February when it’s five degrees?” Keller asked.
Krauchyk said there was a restroom and a small desk area at the site already, but would look into an additional rest area.
“The New York (City) DEP does not allow trucks to idle because we get fined,” he added.
There is a spill containment tank beneath the current facility and there will also be one under the new structure. If a spill did occur, a clean-up crew would be sent to pump the spilled liquids.
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