Public Participation Plan for Catskill Aqueduct SPDES Permit Modification
October 4, 2022 — SPDES No. NY 028 1042
DEC No. 3-9903-00102/00002
Project Overview
The New York City’s Department of Environmental Protection (DEP) developed the Water for the Future (WFF) Program to address significant leakage in one of its most critical pieces of water supply infrastructure, the Delaware Aqueduct. WFF involves construction of a bypass tunnel around a leaking section of DEP’s Rondout-West Branch Tunnel (RWBT), the upper portion of the City’s Delaware Aqueduct.
To support connection of the bypass tunnel to the RWBT, DEP has advanced several components of WFF which collectively comprise the Upstate Water Supply Resiliency (UWSR) Project. Catskill Aqueduct Repair and Rehabilitation (CAT-RR) is one component which will restore the capacity of the Catskill Aqueduct.
A key goal of the overall CAT-RR project would be to restore and/or increase the capacity of the aqueduct to supply water, thereby augmenting water supply during the RWBT shutdown. This would be accomplished by fixing leaks, removing biofilm, and controlling biofilm regrowth. Construction associated with fixing leaks and the removal of biofilm has been completed.
Permit Modification
As part of the CAT-RR project, DEP received a State Pollutant Discharge Elimination System (SPDES) permit from the New York State Department of Environmental Conservation (NYSDEC) for discharges associated with the CAT-RR project on September 1, 2019. The permit allows for discharges to surface or ground waters associated with chlorinated aqueduct waters at numerous locations along the Catskill Aqueduct. These discharges result from the addition of chlorine dioxide to the aqueduct, an oxidizing agent used to control the regrowth of biofilm. The permit also allows discharges associated with construction wastewaters and biofilm wash washwaters, however, internal construction and biofilm removal has been completed, and discharges from those two sources no longer occur.
DEP has requested a modification if its current permit for the following reasons:
- Add a new representative sampling point to facilitate safer and more efficient discharge monitoring.
- Change the discharge monitoring and reporting to methods that are better aligned for detecting amounts of chlorine dioxide, the primary biofilm control chemical used in the aqueduct. This means that the discharges will need to meet concentration-based action levels for chlorine dioxide and chloride.
- Chlorine dioxide has been selected as the primary biofilm control chemical because, in addition to controlling biofilm, it decays into byproducts that are suitable for discharge at the protective action levels proposed in the permit modification.
- The current effluent limit, total residual chlorine, would still be in place should sodium hypochlorite, an alternative to chlorine dioxide, ever be used to control biofilm in the aqueduct.
Site Descriptions
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Outfall 013
Outfall 013 is located in a forested area along the Rondout Pressure Tunnel segment of the Catskill Aqueduct, which lies approximately 300 to 500 feet below grade at this location. Outfall 013 is located approximately 0.3 miles northwest of Lucas Turnpike and 0.5 miles southwest of State Route 213, and is located within a delineated freshwater wetland west of the aqueduct. Outfall 013 forms a small pool impounded by an existing wooden weir. Outfall 013 flows over the weir and into a shallow channel, which flows to the southeast, then continues to travel southward towards Outfall 014.
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Outfall 014
Outfall 014 is located in a forested area, near Shaft 4 of the Rondout Pressure Tunnel segment of the Catskill Aqueduct, which lies approximately 300 to 500 feet below grade at this location. Outfall 014 bubbles into a ponded area at the surface, which is impounded by an existing wooden weir. Outfall 014 is located approximately 0.15 miles northwest of Lucas Turnpike and 0.5 miles southwest of State Route 213, and is located adjacent to a delineated freshwater wetland west of the aqueduct. After joining the flow from Outfall 013, the flow passes through a culvert under the existing Marbletown Ontario & Western Rail Trail, where they join an unnamed tributary to Rondout Creek. The unnamed tributary then continues south through a second culvert under Lucas Turnpike and ultimately discharges to Rondout Creek.
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Outfall 015
Outfall 015 is located at the bottom of the drainage shaft of the Rondout Drainage Chamber in the Town of Marbletown. Outfall 015 is located approximately 0.03 miles southeast of Canal Road, south of Rondout Creek, and immediately adjacent to an unnamed tributary to Rondout Creek. An existing subsurface blow-off conduit connects the Rondout Drainage Chamber to a headwall along the southern bank of Rondout Creek where aqueduct water can be discharged. Outfall 015 has been created by an inoperable valve in the Rondout Drainage Chamber that diverts a small portion of aqueduct water to the blow-off conduit. This flow is then conveyed underground through the conduit before it daylights at an existing concrete headwall at Rondout Creek.
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Outfall 096
Outfall 096 is located approximately 1,000 feet east of St. Andrews Road along the western side of the Catskill Aqueduct in the Town of Montgomery, Orange County, NY. Along cut-and-cover segments of the Catskill Aqueduct, the original design included drains at certain locations where culverts were constructed beneath the aqueduct. Culvert drain sluice gates, when opened, would allow aqueduct water to drain into the culvert and into streams or drainage channels.
The existing sluice gate at this site has one discharge point that historically allowed for the release of raw aqueduct water to the culvert and Tin Brook when DEP required unwatering of the aqueduct for maintenance, repair, and/or inspection.
Permit Modification Documents
Public Information Meetings
Virtual Public Information Meetings will be held as shown below:
Montgomery
High Falls
Project-Related Questions
Phil Simmons
NYCDEP
59-17 Junction Boulevard
Flushing, New York 11373
718-595-4471