A pump service proposes to design & supply a dewatering system
In September 2013, Pump Service and Supply of Troy in Troy, N.Y., presented a proposal to design and supply a dewatering system to Schiavone Construction Co. LLC of Secaucus, N.J. Schiavone had been awarded a $101.6-million contract to construct shafts for the Delaware Aqueduct Bypass Tunnel in New York state and was in need of dewatering pumps.
Pump Service and Supply of Troy is a full-service facility with pickup and delivery service in eastern New York, Vermont, Massachusetts and Connecticut. The facility offers sales, service and rentals, and can assist with pump sizing and system design.
Schiavone has extensive tunneling and excavation experience, particularly in the congested New York metro area. The construction company has earned a reputation for on-time performance with the major mass transportation and rail systems in the Northeast. This expertise was instrumental in Schiavone’s selection to perform the first successful tunnel boring machine (TBM) tunnel work in New York City.
At 85 miles long, the Delaware Aqueduct is the longest tunnel in the world. It is responsible for supplying approximately 500 to 600 million gal of clean drinking water to New York City every day. The project to repair a major leak in the tunnel included the construction of two shafts, 30 and 33 ft in diameter. The west shaft in the town of Newburgh was built to a depth of 837 ft, and the east shaft in the town of Wappinger was excavated to a depth of 673 ft.
The shafts acted as the starting points for a 2.5-mile-long tunnel that New York City currently is constructing 600 ft under the Hudson River. The bypass tunnel will be connected to structurally sound portions of the existing Delaware Aqueduct, allowing water to be conveyed around the leaking section. The leaking stretch of the original tunnel, which was activated in 1944, will be plugged and abandoned in place. During typical operations, the tunnel leaks approximately 20 million gal each day into the Hudson River.
The dewatering system that Pump Service and Supply designed consisted of three Tsurumi LH430W 40-hp two-state dewatering pumps. These pumps are three-phase dewatering pumps used for extra high head pumping. Tsurumi Pump was chosen for a multitude of reasons, including its high chrome impellers and wear plates, which stood up to the harsh conditions of rock fines and grout.
Another reason to use these pumps was their inclusion of pressure relief ports, which allow for higher heads, and a small 143/8-in. footprint, which is always critical in tight-space tunneling. An LH430W pump was added every 250 to 300 ft as the shafts were constructed. Custom tandem connections were designed to connect each unit. The flow design was for 300 gal per minute at 900 ft total dynamic head. It also included a redundant system.
Pump Service and Supply also designed and supplied custom triplex control systems at each site. The panels included time delay start-ups from bottom to top and shutdowns from top to bottom of the system to alleviate water hammer. This also allowed for the installation of a much smaller standby generator by not having all pumps start at once.
The second phase of the project has been awarded and is now under construction. Excavation of the tunnel is approximately 60% finished. The system is still in place and is now being used by the present contractor. The equipment is maintained and all repairs are done in-house by Pump Service and Supply.