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Ashokan Reservoir

Ashokan Reservoir

Ashokan Reservoir

Final Scope for the Modification of the CATALUM SPDES Permit Environmental Impact Statement

The New York State Department of Environmental Conservation (NYSDEC), as lead agency, has issued a Final Scoping Document for the Draft Environmental Impact Statement to be prepared for the proposed modification to the NYSDEC State Pollutant Discharge Elimination System (SPDES) Permit for the Catskill Influent Chamber (Catalum SPDES Permit No. 026 4652), to incorporate measures to control turbidity in water diverted from Ashokan Reservoir and to postpone dredging of alum floc at Kensico Reservoir until completion of certain infrastructure projects. NYSDEC has also issued a companion Response to Comments on the Draft Scope. The Final Scoping Document and Response to Comments are available for public review at the NYSDEC and New York City Department of Environmental Protection (NYCDEP) offices listed below, and are also available below and at the NYCDEP's website:

It is also available for review locally at:

NYSDEC Central Office - Division of Environmental Permits
ATTN: Kristen Cady-Poulin, Project Manager
625 Broadway, 4th Floor
Albany, New York 12233-1750/ Tel: (518) 402-9167

NYSDEC Region 3
New Paltz Headquarters
ATTN: John Petronella, Regional Permit Administrator
21 South Putt Corners
New Paltz, NY 12561
(845) 256-3000

NYSDEC Region 3
White Plains Sub-Office
ATTN: Shohreh Karimipour, Regional Water Engineer
100 Hillside Avenue, Suite 1W
White Plains, NY 10603-2860
(914) 428-2505

NYCDEP - Kingston Office
ATTN: Ira Stern
71 Smith Ave
Kingston, NY 12410
NYCDEP - Valhalla Office
ATTN: David Warne
465 Columbus Avenue
Valhalla, NY 10595

NYCDEP - Lefrak Office
ATTN: Susan Darling
59-17 Junction Blvd. 11th Floor
Flushing, NY 11373

The Environmental Impact Statement (EIS) will evaluate the potential for significant adverse environmental impacts to occur from implementation of the turbidity control measures proposed to be incorporated into the Catalum SPDES Permit (Turbidity Control Measures), as well as from the postponement of dredging in the Kensico Reservoir. Implementation of the turbidity control measures analyzed in this EIS would allow NYCDEP to continue to provide reliable, clean, and safe drinking water while reducing reliance on chemical treatment of the water supply, specifically the use of alum, during episodic turbidity events.

Contact: Kristen Cady-Poulin, NYS DEC, Division of Environmental Permits, 625 Broadway, 4th Floor, Albany, NY 12233-1750, Phone: (518) 402-9167, E-mail:


Final Scope for the Modification of the Catalum SPDES Permit, Environmental Impact Statement (PDF, 6.97 MB)

Agreement to Manage Turbidity

Construction for Ashokan Reservoir. View of Olive Bridge dam showing down-stream face of masonry section. Stone crusher and concrete mixing plant in left background. June 21, 1910.
Construction for Ashokan Reservoir. View of Olive Bridge dam
showing down-stream face of masonry section. Stone crusher
and concrete mixing plant in left background. June 21, 1910.

DEC and the New York City Department of Environmental Protection (NYCDEP) have agreed on an to manage turbidity and manage reservoir releases. This will improve water supply, water quality and habitat, and provide flood mitigation in the New York City watershed. The terms of the consent order also decrease the need for aluminum sulfate to be used in the Catskill Water Supply System.


CATALUM ENB - Notice of Positive Declaration/Notice of Public Meetings (PDF)

CATALUM SPDES Permit Modification Draft Scoping Preamble (PDF)

CATALUM SPDES Permit Modification EIS Draft Scope Document (PDF)

Environmental Assessment Forms Part 1 (PDF)

Environmental Assessment Forms Part 2 (PDF)

Environmental Assessment Forms Part 3 (PDF)

Coastal Assessment Form (PDF)

Final Consent Order (PDF) - October 2013

Response to Comments - Ashokan Order on Consent (PDF) - October 2013

Frequently Asked Questions - Lower Esopus Consent Order (PDF) - October 2013

Order on Consent, Environmental Review and Application to Modify Permit (PDF) - January 2018

Information About the Ashokan Reservoir

From New York City's Department of Environmental Protection: Located in Ulster County, about 13 miles west of Kingston and 73 miles north of New York City. Formed by the damming of the Esopus Creek. Consisting of two basins separated by a concrete dividing weir and roadway, it holds 122.9 billion gallons at full capacity and was placed into service in 1915. It is over 190 feet deep at its deepest point.

The Ashokan is one of two reservoirs in the City's Catskill Water Supply System. The other is the Schoharie, located 27 miles to the north, whose water flows into the Ashokan via the Shandaken Tunnel and the Esopus Creek. Including the water it receives from the Schoharie Reservoir, the Ashokan supplies about 40% of New York City's daily drinking water needs in non-drought periods. Water enters the Ashokan's West Basin and, after a settling period, is withdrawn from its East Basin. It is carried southeast under the Hudson River via the 92-mile Catskill Aqueduct, which has a maximum depth of 1,114 feet. It ordinarily enters the Kensico Reservoir in Westchester for further settling, where it mixes with Delaware system water and then travels south in two aqueducts before entering New York City's water supply distribution at the Hillview Reservoir in Yonkers, just north of the City line.

The Ashokan watershed's drainage basin is 255 miles and includes parts of 11 towns: Denning, Hardenburgh, Hurley, Kingston, Marbletown, Olive, Shandaken and Woodstock in Ulster County; Hunter and Lexington in Greene County and Middletown in Delaware County.