Catskill Aqueduct Repair and Rehabilitation (CAT-RR) — New York City, NY

Built between 1907 and 1916, New York City’s Catskill water supply system consists of two reservoirs and 92 miles of a 19-foot-diameter horseshoe-shaped aqueduct consisting of a mixture of rock tunnels, at-grade concrete reinforced cut-and-cover tunnels, and steel siphons, supplying up to 50 percent of New York City’s water supply.

The Need For Rehabilitation

The Catskill Aqueduct normally carries approximately 40 percent of New York City’s water supply (490 mgd) and requires coordinated shutdowns to allow work to proceed within the aqueduct. The Catskill Aqueduct Repair and Rehabilitation restored the capacity of the Catskill Aqueduct, which had been lost over time due primarily to the accumulation of biofilm (a naturally occurring layer of microorganisms) along the Aqueduct’s interior surface, and repaired leaks from cracks in the unreinforced concrete lining/structure. 

Key Project Elements And Services

Parsons provided comprehensive construction management and inspection services associated with the project; project elements included: 

• Performing a complete visual inspection of the aqueduct 
• Repairing leaks within the aqueduct 
• Replacing valves, gates, and other mechanical equipment 
• Adding air vents to facilitate water flow 
• Repairing multiple deteriorated aqueduct bridge crossings 
• Reconstructing the Catskill Influent Weir (CIW) located at the Kensico Reservoir 
• Constructing a new chlorination facility at the upstream end of the aqueduct 
• Constructing a new dechlorination facility at the downstream end of the aqueduct 

“This complex project to rehabilitate the Catskill Aqueduct has required more coordination and flexible planning than perhaps any in the history of our water supply,” NYCDEP Commissioner Vincent Sapienza

Logistical And Regulatory Challenges

This challenging logistical project required entering the at-grade sections of the aqueduct in a multitude of locations located all along the 74-mile length of the aqueduct being repaired under this contract. Careful planning and coordination were necessary to: 

• Ensure compliance with more than 1,800 permit/regulatory requirements associated with 17 municipalities and numerous New York City, State, and Federal government agencies 
• Maintain water quality in the overall watershed system to enable coordinated shutdowns of the aqueduct to perform construction activities 
• Provide adequate ventilation and safe access at all times across the entire 74 miles of aqueduct length during the Covid pandemic 
• Ensure water quality in the downstream Kensico Reservoir was maintained while adjacent construction activities (associated with the CIW) took place 
• Ensure construction activities did not impact water quality following shutdowns by testing and treating water passing through the aqueduct immediately following shutdown activities