1944 New York Delaware Aqueduct Water Supply has an 85-mile tunnel, world's longest

Inlet Portal: (Satellite)

Outlet Portal: (Satellite)

The Delaware Aqueduct goes from Rondout Reservoir to Yonkers, NY. [wrrv_project]

"The massive tunnel can be as wide as 19 feet [5.8m] and as deep as 2,500 feet [762m] underground, and supplies nearly half of New York City's water."  [wrrv_longest] This source claims that the tunnel is 105 miles long. I think that is the length of the total aqueduct. The tunnel is 85 miles long.

This is one of the sources that provides the tunnel length of 85 miles.

Facebook Reel

11:00 video @ 3:51 (source)

Better resolution:

NewYorkAlmanack

Technically, the tunnel is a siphon. The water is under significant pressure when it goes under the Hudson River under Newburgh, NY.

@ 4:18
[39 cubic meter/sec is 1,377cfs.]

Another segment of the Delaware Aqueduct moves the water from the Kensico Reservoir to the Hillview Reservoir, which is the official termination of the Delaware Aqueduct in Yonkers, NY.

@ 5:06

They have also built bypass tunnels under each of the reservoirs so there is a continuous tunnel from the Rondout Reservoir to the Hillview Reservoir.

@ 5:23

@ 6:44
By 2012, it was estimated that the aqueduct was leaking about 35mgd. And it had been leaking that much for at least 25 years. The video was made in 2020, and the bypass tunnels around the leaky sections were supposed to be done in 2023 and cost $1.5b.

I'm writing this in 2026, and the bypass "is not expected to be completed until after 2027." And they are now talking $2b. [nyc_new_contract]

parsons
Nora is the name of the Tunnel Boring Machine that is being used to dig the bypass tunnel.

The tunnel north of the West Branch Reservoir is 13.5' (4m) in diameter. [parsons]

The tunnel south of the Kensico Reservoir is 19.5' (6m) in diameter. [britannica]

wrrv_project
When they are ready to connect the bypass tunnel to the original tunnel, they will have to shut down the aqueduct so that they can dewater it. They will shut it down between October and June because Winter has the lowest water usage. 

The October shutdown was supposed to happen in 2022, and then in 2023, and then in 2024. 2024 was skipped because of draught conditions. [drbc]

Because of the delays, the contract expired. Since a new procurement process is needed, some more Winters are going to be skipped. [dep_contract]

3:10 video @ 0:15
Delaware Aqueduct Bypass Tunnel Steel liners

1:43 video @ 0:26
[In the video, they show the Croton Dam instead of the Rondout Dam.]