Stories from DEP is a collection of feature articles
published in DEP's internal newsletter, Weekly Pipeline.
This article was originally published June 5, 2012.
Design of Rondout-West Branch Tunnel Shaft Sites 'Draws' on In-House Expertise
As the centerpiece of the Water for the Future program, repair of the Rondout-West Branch Tunnel of the Delaware Aqueduct represents a critical infrastructure investment for New York City. The 85-mile Delaware Aqueduct has a capacity to convey more than 840 million gallons of water per day from Cannonsville, Pepacton, Neversink and Rondout Reservoirs. It transports approximately half of the drinking water supply for more than eight million New York City residents and one million residents of Orange, Putnam, Ulster and Westchester Counties. Additionally, residents of the Towns of Newburgh and Marlboro are supplied directly by the Rondout-West Branch Tunnel. Leaks in the tunnel are causing the loss of up to 35 million gallons of water per day, and the necessary design that will allow for repair work is complex and has a multitude of moving parts.
What’s remarkable about this undertaking is that its design is being spearheaded almost entirely by DEP staff. Housed in the Bureau of Engineering, Design and Construction, the Tunnel Structural Design team comprises 30 staff and includes a mix of project managers, engineers, designers, and computer-aided design technicians. The design process involved structural, mechanical and electrical components, all under the leadership of Chief Tunnel Engineer Burjor Kharivala. Construction includes two new shafts for launch and retrieval of the tunnel boring machine in the towns of Newburgh and Wappinger — on opposite sides of the Hudson River. When completed, the shaft in the Town of Newburgh will reach 900 feet below the surface, while its counterpart across the river will be 700 feet underground. The taking of geotechnical borings required for shaft design necessitated extensive site work, with DEP purchasing land, securing permits from local municipalities and regulators, and clearing space for construction. The site work brought external partners from the private sector to the table in a fruitful partnership for the design team.
“It was a great venture to bring public and private sectors together on the site work,” said Floren Ansley, Environmental Engineer II. “Working together with the contractors brought a nice sense of collaboration to the project, with private businesses coming onboard with a big public infrastructure project.”
Drill rigs are set up at each site to allow for boring, and one of the primary responsibilities of the design team is to keep logs of the boring process. These log entries are analyzed by Waterworks Design project managers, and interpreted to determine the appropriate linings for the shafts once they’re built. This study of the logs brings an understanding of geological specifications to bear, as the shaft lining must support the structure and protect the safety of the workers below.
The work thus far has entailed a substantial permitting process in addition to the design itself. The BEDC Permit Resources Division has played a crucial role in coordinating the various regulations from the towns of Newburgh and Wappinger. An Environmental Impact Statement was also produced before any construction could begin; upon completion of the design contract, procurement began on the shaft construction itself. Bidding is currently underway, and boring is expected to begin early next year.
According to Design Manager Ted Dowey, “There are a lot of moving parts to this project. It really was a very big undertaking.” Considering that the critical repair of the Delaware Aqueduct was designed almost entirely in-house, it’s easy to conclude that there’s very little that would be considered impossible for DEP staff to achieve.