DEP Environmental Protection Invoices, 1999-2001

NYC 9/11 Public Portal Document ?1/09/2001 16:12 518-402-7659. BPWSP PAGE 02/05

STATE OF NEW YORK D011 DEPARTMENT OF HEALTH Flanigan Square, 547 River Street. Troy, New York 12180.2216 itonia C. Novella. M.D., M.P.H., Dr.P.H. Dennis P. Whalen Commissioner Executive Deputy Commissioner

January 9, 2001

Mr. Mark D. Hoffer, Esq. General Counsel Bureau of Legal Affairs New York City Department of Environmental Protection 59-17 Junction Boulevard Corona, NY 11368-5107

RE: Alum and sodium bydroxide treatment of Catskill System

Dear Mr. Hoffer:

We have received and reviewed your January 8, 2001 request for approval to add alum and sodium hydroxide to Catskill system water at the Pleasantville Alum Facility prior to it entering Kensico Reservoir. The purpose of the addition of alum and sodium hydroxide is to reduce the level of turbidity in water currently being delivered from the Ashokan Reservoir and thereby prevent a violation of the State and Federal raw water turbidity requirements for an unfiltered surface water source as set forth in the federal Surface Water Treatment Rule (SWTR) (See 40 CFR 141.7]) and the New York State Sanitary Code in 10 NYCRR Section 5-1.30 (c) (2). Such a violation could result in an imminent condition which can be responsible for causing illness and thus could constitute a public health hazard as defined in 10 NYCRR Section 5-1.1 (ar).

Both the SWTR and the State Sanitary Code specify for a filtration avoidance system, such as the Catskill system, that raw water turbidity immediately prior to the first or only point of disinfection cannot exceed 5 nephelometric units (NTU). The fast point of disinfection for New York City's Catskill System is the Lower Effluent Chamber at Kensico Reservoir. An exceedance of this turbidity value is a violation under the State Sanitary Code and could result in the loss of a system's filtration avoidance if there are more than two turbidity "events" during the previous twelve month period or five events during the previous 120 month period. In addition, disinfection must also be sufficient to ensure at least 99.9 percent inactivation of Giardia lamblia cysts and 99.99 percent inactivation of viruses.

NYC-WTC 000137776 It