Review of the New York City Department of Environmental Protection Operations Support Tool for Water Supply (2018) / Chapter Skim
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3 Metrics for the Catskill Turbidity Control Program
3 Metrics for the Catskill Turbidity Control Program
Pages 97-114
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From page 97... ...
operational changes, some of which are facilitated by the Operations Support Tool (OST) , the development of which was a major product of the Catskill Turbidity Control Study.
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From page 98... ...
Alum can be added to the Catskill Aqueduct just prior to Kensico Reservoir, where precipitated aluminum hydroxide and aggregated clay particles then settle. This was the state of affairs prior to and during the course of the Catskill Turbidity Control Study.
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From page 100... ...
Profiling monitors collect a complete vertical profile at 1-ft resolution every three to six hours, while fixed-depth monitors record data at a higher frequency, from one to 15 minutes. For Ashokan and Kensico reservoirs, the existing monitoring infrastructure allows complete input–output monitoring of turbidity TABLE 3-1 Real-Time Turbidity Monitors Within the Catskill System Monitor Location Type Schoharie Schoharie Reservoir at Shandaken Tunnel intake Profiler Shandaken Tunnel diversion Fixed Shandaken Tunnel diversion at discharge to Esopus Fixed Ashokan Esopus Creek at Allaben above the Shandaken Tunnel discharge Fixed Esopus Creek at Coldbrook below the Shandaken Tunnel discharge Fixed West Ashokan Reservoir significantly upstream of Catskill Aqueduct headworks Profiler West Ashokan Reservoir near Catskill Aqueduct headworks Profiler East Ashokan Reservoir near Catskill Aqueduct headworks Profiler Catskill Aqueduct diversion Fixed Kensico Catskill Aqueduct diversion at Catalum Fixed Delaware Aqueduct diversion at Shaft 17 Fixed Above West Branch Reservoir at Shaft 9 Fixed Between outlet works and Catskill Aqueduct inflow Profiler Between outlet works and Delaware Aqueduct inflow Profiler Near outlet works (5-m depth)
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From page 101... ...
NYC DEP's response to this requirement became known as the Catskill Turbidity Control Study. The primary goal of the Catskill Turbidity Control Study was to identify feasible, effective, and cost-effective interim and longterm measures for reducing peak turbidity levels entering Kensico Reservoir from the Catskill Aqueduct, thereby reducing the need for treatment of the Catskill Aqueduct water with alum.
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From page 102... ...
. Subsequent studies followed on the heels of the Catskill Turbidity Control Study, including a Turbidity Control Alternatives Analysis (NYC DEP, 2011)
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From page 103... ...
development of OST. C ATSKILL TURBIDITY CONTROL PROGRAM Since completion of the Catskill Turbidity Control Study, the NYC DEP has continued its emphasis on controlling turbidity in the Catskill System through a variety of actions collectively called the Catskill Turbidity Control Program.
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From page 104... ...
It should be noted that the NYC DEP runs a Stream Management Program to help reduce turbidity loadings to the tributaries of the Esopus Creek and hence to Ashokan Reservoir. However, because this program is going to be evaluated during a subsequent National Academies review of the entire Watershed Protection Program, this report does not discuss evaluation of this aspect of the Catskill Turbidity Control Program.
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From page 105... ...
For the purposes of this report, and with the concurrence of the NYC DEP, the Committee considered the following activities to be part of the Catskill Turbidity Control Program: (1) infrastructure improvements such as the Shaft 4 interconnection, the rehabilitation of the Schoharie intake, and the Catskill Aqueduct stop shutters; and (2)
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From page 106... ...
OST would be used to produce modeled turbidity values under the no-action scenario. In other words, NYC DEP proposed that actual turbidity following implementation of the various components of the Catskill Turbidity Control Program could be compared to OST-modeled turbidity levels projected to occur if the program had not been implemented.
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From page 107... ...
Doing so would allow the model validation process to support not only the no-action scenario but also the ongoing evolution of OST and its e mbedded process models. Data-Based Approaches Beyond the performance measure suggested in the 2011 NYC DEP l etter, one can glean additional possible performance measures from the Phase I, II, and III Catskill Turbidity Control Study reports and associated analyses.
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From page 108... ...
First, one would need a clear basis for defining two periods of time -- before the Catskill Turbidity Control Program and after its implementation. In practice, this is not a simple matter because the program is the combination of many actions that may have gone into effect at different times.
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From page 109... ...
In Figure 3-2, the cross symbols are for events prior to the start of the Catskill Turbidity Control Program, and the solid circles are for events after the completion of the program. The horizontal axis is a measure of the mass of input to the reservoir system (measured as incoming water turbidity multiplied by discharge for each day in each turbidity event period)
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From page 110... ...
For example, one might formulate the appropriate dependent variable differently, such as using the alum addition for an event. This would be a very direct way to evaluate the benefits of the control program.
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From page 111... ...
CONCLUSIONS AND RECOMMENDATIONS The Catskill Turbidity Control Study, and now the Catskill Turbidity Control Program, have been crucial to the improvement of the New York City water supply to handle high turbidity events in the Catskill Systems. The Study led to the creation of OST and the Program has led to the building of critical infrastructure that has greatly increased the flexibility of the NYC DEP to operate the system under a wider range of conditions than in the past.
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From page 112... ...
In particular, analysis of covariance is a useful statistical tool that can help quantify and test for differences between the period prior to the Catskill Turbidity Control Program and the period after the program was put in place. Such techniques are ideal for detecting step changes when the variable of interest (turbidity)
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From page 113... ...
2004. Phase 1 Final Report on the Catskill Turbidity Control Program.
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