Operating the New York City Water Supply System

Transcription

1 Operating the New York City Water Supply System Thomas Murphy, P.E. Chief, Reservoir Releases Policy Development Bureau of Water Supply June,

2 Agenda Water Supply History Cross River Spillway Consumption Operations Integration of the OST New Infrastructure Questions 2

3 Water Supply History On July 4 th 1842 Croton Aqueduct placed in service. City realized a need for more water and began to look elsewhere. 3

4 Water Supply History Adirondacks VT Lake George Upper Catskills Lower Catskills Wallkill/ Ramapo & Moodna NY PA NJ MA CT Berkshires Long Island 4

5 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 5

6 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 6

7 System Overview 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 of 8 upstate counties Operated and maintained by NYCDEP 7

8 Water Demand and Dry Weather Wastewater Flows Demand has declined approximately 30% since the early 1990s despite increasing population Since 2009, water usage is below the 1960s drought-of-record Historic Flows and Future Projections

9 Essential Tasks Bureau of Water Supply Operations Meet the supply needs of New York City Meet all reservoir release & diversion requirements Schoharie Creek 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 West Branch Sub-System 1 West Branch Reservoir

10 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)

11 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 Schoharie Creek

12 Operational Framework-Croton System NYS-DEC - 6 NYCRR Part 672 West Branch Sub-System 1 West Branch Reservoir

13 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

14 Reservoir Operations All NYC systems are not created equal. Ashokan Rondout Croton

15 Operational Decision Making Operational decisions are made based on the following: Water Quality Demand Modeling NWS Forecasting Maintenance Hydrological conditions 15

16 Water Quality Considerations Parameters Turbidity Coliform bacteria Phytoplankton DBP precursors Drivers Heavy flow events High wind events Drought

17 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

18 Selective Withdrawal DEP monitors water quality at different elevations within reservoirs to determine the optimal level of withdrawal Rondout Effluent Chamber

19 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. Selective Diversion

20 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 West Branch Kensico

21 Kensico Reservoir Operations 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 21

22 Delaware Aqueduct Shaft 18 Treatment Disinfection Chlorine Target: 0.2 mg/l Hillview Fluoride Hydrofluorosilicic acid Target: 0.8 mg F/L 22

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

24 Probability 100% Probability of Refill-Delaware System May 15 June 15 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 88% 90% 92% 94% 96% 98% 100% 102% 104% 106% Storage (Percent of Usable) As of April 2, 2013.

25 Operations Support Tool 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 25

26 New Treatment Facilities Catskill/Delaware Ultraviolet Disinfection Facility Croton Filtration Plant 26

27 UV Plant 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 27

28 Shaft 4 Connection 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 Shaft 4 Approximate Cost $31.8 million 28

29 Rondout-West Branch Tunnel 29

30 Questions 30