Operating the New York City Water Supply System Thomas Murphy, P.E. - - PowerPoint PPT Presentation

Operating the New York City Water Supply System

Thomas Murphy, P.E.

Chief, Reservoir Releases Policy Development Bureau of Water Supply June, 6 2013

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Agenda

 Water Supply History  Consumption  Operations  Integration of the OST  New Infrastructure Questions

Cross River Spillway

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Water Supply History

 On July 4th 1842 Croton Aqueduct placed in service.  City realized a need for more water and began to look elsewhere.

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Water Supply History

Adirondacks Lake George Berkshires Wallkill/ Ramapo & Moodna Upper Catskills Lower Catskills Long Island

NY VT MA CT PA NJ

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Burr, Herring, Freeman Report (1903)

 General Problem  Provide greater New York area with an abundant quantity of water with satisfactory quality  Requisite Qualities of Public Water Supply  Free of organisms  Agreeable appearance  Odorless and tasteless  Not too hard  Not contain substances that are liable to corrode pipes  Should have cool and equable temperature

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Water Supply Act of 1905

 Board of Water Supply created to develop system  NYC required to allow municipal connections to system in counties with water supply infrastructure  Dutchess County Excepted  Fishing & Boating to be permitted

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 Primarily a surface water supply  19 reservoirs & 3 controlled lakes  System Capacity: 580 billion gallons  Serves 9 million people (1/2 of population of New York State)  Delivers approx. 1.1 billion gallons per day  Source of water is a 2,000 square mile watershed in parts

• f 8 upstate counties

 Operated and maintained by NYCDEP

System Overview

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Water Demand and Dry Weather Wastewater Flows

Historic Flows and Future Projections 2012

Demand has declined approximately 30% since the early 1990s – despite increasing population Since 2009, water usage is below the 1960s drought-of-record

S c hoha rie Cre ek

West Branch Sub-System 1 West Branch Reservoir

Bureau of Water Supply Operations

 Essential Tasks  Meet the supply needs of New York City  Meet all reservoir release & diversion requirements  Maintain system to ensure a dependable supply  Objectives  Divert the best quality water available  Maintain balanced system  Provide downstream habitat and flood mitigation benefits w/o water supply impact

Operational Framework-Delaware System

 1954 Supreme Court Decree  1982 Good Faith Agreement  NYS-DEC - 6 NYCRR Part 671  NYS-DEC - 6 NYCRR Part 672  Flexible Flow Management Plan (FFMP)

Operational Framework-Catskill System

 NYS-DEC - 6 NYCRR Part 670  Shandaken Tunnel SPDES Permit  Catskill Alum SPDES Permit  Interim Operating Protocol  Schoharie Snowpack Void Program

Sc hoha r i e C r e ek

Operational Framework-Croton System

 NYS-DEC - 6 NYCRR Part 672

West Branch Sub-System 1 West Branch Reservoir

Reservoir Operations

 Goal to delay start of system drawdown to as late as possible in the hydrologic year  All reservoirs full on or around June 1  Avoid spilling any reservoir after start of system drawdown  Preserve storage for use during times of drought conditions  Limited reliability of short and long term forecasting necessitates conservative system operation

Reservoir Operations

All NYC systems are not created equal.

Rondout Ashokan Croton

Operational Decision Making

 Operational decisions are made based on the following: Water Quality Demand Modeling NWS Forecasting Maintenance Hydrological conditions

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Water Quality Considerations

 Turbidity  Coliform bacteria  Phytoplankton  DBP precursors  Heavy flow events  High wind events  Drought Drivers Parameters

Water Quality and Operational Decisions

 Water delivered is selected or mixed based on available quantity and quality  Operational Strategies Selective Withdrawal Selective Diversion Blending Operations Treatment Operations

Selective Withdrawal

DEP monitors water quality at different elevations within reservoirs to determine the optimal level of withdrawal

Rondout Effluent Chamber

Selective Diversion

DEP can prevent negative impacts to downstream reservoirs by maximizing the flow from reservoirs with the best water quality and minimizing the flow from reservoirs with inferior water quality.

Terminal Reservoir Operation

 Rondout, West Branch, & Kensico Reservoirs conditions have target elevations - dependent upon season  Critical to keep as much water as possible closest to the City consumers  Limiting bank exposure of terminal reservoir reduces wind induced turbidity  High storage in terminal reservoirs increases detention time promoting better quality  Diversion capacities are elevation dependent

Rondout Kensico West Branch

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 Reservoir mode Cat/Del flow through the reservoir  Del bypass mode Del flow bypasses reservoir  Float mode Del flow bypasses but some flow from reservoir also

Kensico Reservoir Operations

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Disinfection

Chlorine Target: ≈0.2 mg/L Cl @ Hillview

Fluoride

Hydrofluorosilicic acid Target: 0.8 mg F/L

Delaware Aqueduct Shaft 18 Treatment

Balanced System

 Maintain similar chance of refill for subsystems  Balanced with water quality  Especially important during dry periods

As of April 2, 2013.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 88% 90% 92% 94% 96% 98% 100% 102% 104% 106%

Probability Storage (Percent of Usable)

Probability of Refill-Delaware System

May 15 – June 15

Operations Support Tool

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 Probabilistic foundation for water supply reliability More accurate assessment of likely future inflows, release requirements, storage levels–better drought warning triggers  Better defines system capacity to meet water quality & environmental objectives Maximize benefits while maintaining water supply reliability More water quality based operations

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New Treatment Facilities

Catskill/Delaware Ultraviolet Disinfection Facility Croton Filtration Plant

UV Plant

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 Treatment required under LT2  Improve disinfection by providing Cryptosporidium inactivation  Capacity to treat 2,020mgd  Facility in service August 2012  Includes 56, 40-mgd UV disinfection units  Approximate Construction Cost - $1.5 Billion

Shaft 4 Connection

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 Delaware Aqueduct Shaft 4 was built with riser valve adjacent to Catskill Aqueduct  Connection provides:

 Transfer of up to 365 MGD to Catskill Aqueduct  Increases Delaware Aqueduct capacity to 1000 MGD

 Approximate Cost $31.8 million Shaft 4

Rondout-West Branch Tunnel

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Questions

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