Review of the New York City Department of Environmental Protection Operations Support Tool for Water Supply (2018) / Chapter Skim
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4 Use of OST Within the Environmental Impact Statement for Modifications to the Catalum SPDES Permit
4 Use of OST Within the Environmental Impact Statement for Modifications to the Catalum SPDES Permit
Pages 115-130
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From page 115... ...
has proposed modifications to its SPDES permit for adding alum to the Catskill Aqueduct just prior to Kensico Reservoir for the purpose of controlling high turbidity. These modifications, including operation of the Ashokan Release Channel, the dredging of alum floc from Kensico Reservoir, and the addition of alum to the Catskill Aqueduct, will undergo a review to determine their environmental impacts.
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From page 116... ...
and sodium hydroxide to the Catskill Aqueduct and essentially in turn to the Kensico Reservoir. The purpose of alum addition is to decrease the impact of Catskill Aqueduct high turbidity loading on Kensico Reservoir diversion turbidity, primarily to protect public health but also to avoid the need for filtration.
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From page 117... ...
They also were authorized to release highly turbid Ashokan Reservoir waters to the Lower Esopus Creek. Following the expiration of the emergency authorization, NYC DEP applied for and was granted a SPDES permit in 2007 (herein referred to as the Catalum SPDES permit)
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From page 118... ...
Also, the proposed structural alternatives at Ashokan and Kensico reservoirs already have had environmental reviews completed (NYC DEP, 2017)
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From page 119... ...
Ashokan Release Channel operation IRP No IRP No IRP IRP IRP Alum additionb If needed If needed If needed If needed If needed Dredging alum flocc Not yet Not yet Not yet Not yet Completed completed completed completed completed Catskill and Delaware interconnection Not complete Online Online Online Online at Shaft 4 Improvements to Catskill Aqueduct stop Not complete Online Online Online Online shutters Repaired Rondout-West Branch Tunnel Not complete Not complete Complete Not complete Complete aAll scenarios assume use of OST and administration of NYC DEP's Watershed Protection Programs. bIn all scenarios, alum addition would be considered, if needed, to comply with New York State Department of Health drinking water quality standards.
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From page 120... ...
The first area is the Ashokan Reservoir and the 30-mile extent of the Lower Esopus Creek (shown in Figure 5 of NYC DEP, 2017) , extending to the Lower Esopus Estuary where the river merges with the Hudson River.
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From page 121... ...
For example, for the Lower Esopus Creek study area, the major focus will be on how much water may be introduced to the system from the Ashokan Release Channel and its quality (focusing mainly on turbidity)
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From page 122... ...
The charge for this Committee is much narrower, to "review the City's plan for use of OST in evaluating proposed modifications to the Catalum State Pollutant Discharge Elimination System permit, as well as alternatives to be considered in the associated environmental review." Hence this chapter focuses only on those elements of the EIS that relate to the City's plan to use OST. The primary functions of OST with regard to the Catalum EIS are to simulate reservoir operations and conditions consistent with the framework and scenarios outlined in Table 4-1 and to provide simulated reservoir volumes, water quality information, spills, releases, and diversions for the EIS analysis, some of which will feed into other models and analyses.
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From page 123... ...
These relate to: • Reducing the frequency of alum treatment, • Reducing the depth and extent of alum floc deposition in Kensico Reservoir, • Achieving Ashokan Reservoir storage objectives, • Maintaining downstream Lower Esopus flow objectives as stated in the IRP (e.g., sufficient community release and flood mitigation)
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From page 124... ...
. Their approach for the Ashokan Reservoir and Lower Esopus Creek area is illustrated with examples as follows: • Land use, zoning, and public policy (1)
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From page 125... ...
In this fashion, the OST modeling output combined with other analyses will be used to calculate impacts and performance metrics to compare the various alternatives. For the Kensico Reservoir study area, OST will be used to estimate the quantity of turbid water entering Kensico Reservoir, water quality in the reservoir, and depositional amounts and patterns in CATIC cove.
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From page 126... ...
Other Methods and Models Used. In the Lower Esopus Creek, detail is needed on the methods that will be used for examining how changes in water quality and flow impact aesthetics, fish, habitat, and erosion, among others.
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From page 127... ...
. In addition to using the historical streamflow record as input, the EIS team should consider creating simulated streamflow inputs to OST that might reflect climate change.
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From page 128... ...
However, development of the TMDL has been deferred because the Lower Esopus is under category 3c for TMDL development where a "waterbody is awaiting the development/evaluation of other restorative measures." To be conservative, the EIS team may want to assume that the TMDL will be developed in the near future, in which case the EIS analysis should take into consideration whether each alternative will meet the water quality standard and the TMDL. The narrative standards include many prohibitions such as not causing "visible contrasts to natural conditions" (Title 6 Section 703.2, New York Codes, Rules and Regulations)
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From page 129... ...
2017. Final Scope for the Modification of the Catalum SPDES Permit Envi ronmental Impact Statement.
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From page 130... ...
130 NYC DEP OPERATIONS SUPPORT TOOL FOR WATER SUPPLY USACE (U.S. Army Corps of Engineers)
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