The existing Rondout West Branch Tunnel (RWBT) is part of the Delaware Aqueduct which has been in service since 1944 and accounts for more than 50 percent of New York City’s water supply. In early 2015, the New York City Department of Environmental Protection contracted Kiewit-Shea Constructors, AJV (KSC) to construct the Rondout West Branch Bypass Tunnel project (Rondout) in order to mitigate the leakage of 132 million L/ day (35 million gpd) of water from two areas of the existing tunnel; the Roseton and Wawarsing areas.
The scope of the Bypass Tunnel 2 project is separated into two distinct phases. Phase 1 consists of completing the shaft sinking to a depth of approximately 274 m (900 ft) at shaft 5B, 213 m (700 ft) at shaft 6B and the excavation of approximately 3,850 m (12,500 linear ft) of tunnel at a diameter of 6.6 m (21 ft 7 in). This phase also includes the installation of 2,804 m (9,200 linear ft) of 4.8 m (16 ft) diameter steel interliner pipe through the new bypass tunnel with cast-in–place concrete liner for a finished diameter of 4.2 m (14 ft). Access chambers at the top of shafts 5B and 6B will be constructed for access and housing of the mechanical and electrical equipment for supporting pumps and valves.
Included in phase 2 is the additional excavation from shafts 5B and 6B to the RWBT, and the drainage tunnel to remove ground water infiltration from RWBT. This work will be completed during a scheduled shutdown of the RWBT and will include approximately 31 m (100 ft) of excavation of the two connection tunnels. Additionally, construction of the permanent plugs within the RWBT will be undertaken. Figure 2 shows the layout of the work.
Access to the work through the deep shaft at site 5B was critical to the success of the project. The hoisting system needed to be multi-functional to handle the different types of construction from drill and shoot of the shaft, starter and tail tunnel, the assembly of the tunnel boring machine (TBM), the excavation of the TBM tunnel including the supply of the precast segmental liner, the grouting operations, the installation of the steel interliner pipe and the cast-in-place concrete as well as ingress and egress of personnel. The production of the TBM operations was critical to the schedule of the project. This required a quick cycle for muck haulage and supply of the precast segmental liner in order to keep pace with the excavation time of the TBM. For TBM assembly, components were limited to a maximum weight of 104 t (115 st) for a single lift. Various cranes were analyzed for hoisting, however, none would meet all of the citeria. Therefore, the project team selected a specialized hoisting system designed in house in conjunction with Timberland Equipment Ltd. that consisted of a total of 14 separate hoists and winches with a total of more than 2,833 kW (3,800 hp).
Structural and mechanical design
The structural portion of the high capacity hoisting system at the Rondout project consisted of eight separate designed and fabricated major structural components weighing more than 567 t (625 st). These components were designed and supplied to access the 10-m (30-ft) diameter shaft to accommodate all of the previously mentioned operations throughout phase 1 of the project. The main components consisted of:
- A movable heavy-duty shaft cover.
- Shaft runner beams with Hilman rollers.
- The collar mounted base frame structure.
- Muck head frame, dump scroll, chute and back wall.
- Supply head frame.
- Muck and supply back legs with erection frame.
- Twenty-eight person personnel cage and access platform.
- Muck car bails and muck cars.
Movable heavy-duty shaft cover. The movable shaft cover measures approximately 19 x 26 m (63 x 26 ft) and rolls on Hilman rollers in an east west direction powered by a 7-kW (10- hp), electric, Stanspec dual directional car puller. The dual directional puller utilizes 2.2 cm (0.875-in.) diameter wire rope with a 18,000-kg (40,000-lb) line pull at approximately 5 m/min (15 ftpm).
The overall length of the shaft cover is necessary because there are two 9-cm (36-in.) gage rail tracks installed on the cover to accommodate the roll-on of various TBM components that, along with carrier supports, will weigh approximately 127,000 kg (280,000 lbs). The cover is made up of three separate compartments, each with a very specific purpose.
The most eastern compartment is fixed and measures 10 m (30 ft) in length and only serves the purpose of supporting the dual rail tracks. The northwestern section measures 11 x 5.4 m (33 x 18 ft) and consists of five removable panels that will be removed during a mucking operation so that this section of the shaft will be opened for the raising and lowering of the muck bail and boxes.
The remaining area of the cover is designated as the supply door and measures 11 x 2.4 m (33 x 8 ft) in size. This section of the cover is supported by a series of four offset hinges so that the supply door may be rotated and moved to the north in such a way to completely open the supply area for the transport of tunnel rail, tunnel supplies and precast segmental liner. An electric Thern winch and an overhead sheave deck mounted on the north side of the shaft cover and base frame is used to open and close the hinged supply door as required.
A 2.4-m (8-ft) high safety fence is installed between the muck deck and the supply door so that hoisting of these two functions may take place simultaneously.
Shaft runner beams with Hilman Rollers. The shaft runner beams consist of two beams spliced together to form a continuous section, 30 m (100 ft) in length. Each 30-m (100-ft) long section is supported on four concrete footings founded on base rock foundations. There is a total of 10 Hilman rollers, each complete with Accu-Roll guides and a capacity of 50 t (55 st), that run on top of the two runner beams and, in turn, support the movable shaft cover as previously described. The 50 t (55 st) capacity of each Hilman roller is required to support the shaft cover and the point loading from the various TBM components during installation.
The collar-mounted base frame structure. The base frame structure is a large fabrication that measures 12 m (42 ft) wide by 12 m (39 ft) deep with a height of approximately 16 m (54 ft). The entire base frame is supported on four wide flange legs resting on concrete foundations on a solid rock base surrounding the shaft collar.
The required function of the base frame is to support the main muck and supply head frames, the personnel access platform, the muck dump scrolls and chute as well as provide an east and west opening that will allow the entrance of all tunnel supplies, all TBM components and the entrance of truck loaded interliner pipe that will measure 5 m (16 ft) in diameter by 12 m (40 ft) in length.
The east and west side openings in the base frame measure 9-m (30-ft) wide by 7-m (24-ft) high. The western portion of this 7-m (24-ft) high opening allows a rail mounted carrier to enter the interior of the base frame while supporting a 7-m (22-ft) diameter TBM cutter head. The same opening is used to allow the interliner pipe to enter as well. After the truck loaded interliner pipe has entered the interior of the base frame, the hoist blocks are attached to the east end of the interliner pipe and the pipe is rotated and hoisted to a vertical position so that it may be lowered down the shaft to the invert and its final destination within the driven tunnel.
The same opening is used to allow the interliner pipe to enter as well. After the truck loaded interliner pipe has entered the interior of the base frame, the hoist blocks are attached to the east end of the interliner pipe and the pipe is rotated and hoisted to a vertical position so that it may be lowered down the shaft to the invert and its final destination within the driven tunnel.
The second floor of the base frame structure supports the hoist house control room. From here all hoisting functions and shaft cover movement is controlled. A stair tower and walkway allow access to the control room and to the muck and supply head frames.
Muck head frame, dump scroll, chute and back wall. The muck head frame is a prefabricated structure that measures 4 x 6 m (12 x 21 ft) with an overall height of 28 m (94 ft). The entire muck frame complex which includes the dump scroll, chute and sheave deck is supported on heavy beams that are a part of the upper portion of the previously described base frame.
To allow the rotation and the dumping sequence of the 15 m3 (20 cu yd) muck boxes, a portion of the north face of the muck head frame is completely open and designated as the dump slot. Because of the complete lack of bracing in this portion of the frame, an external frame work truss is attached to the two legs of the muck head frame to reinforce the legs of the frame in this area.
The dump scroll consists of two heavy plates attached to the north-east and north-west legs of the muck head frame. This heavy plate structure supports two tracks that allow the bail supported muck cars to rotate and automatically dump 15 m3 (20 cu yd) of tunnel muck onto the chute which is also supported from the northern legs of the muck head frame. This dumping method is a mining technique, well known as a “Kimberly” dump.
The dumped material from the 15 m3 (20 cu yd) box is slowly displaced and falls onto the dump chute which measures approximately 8 m (27 ft) in length on an angle of 42° to the horizontal. A portion of the dump chute is supported on the top deck of the base frame in addition to the muck head frame support. The upper surface of the muck chute and the impact area is lined with two layers of steel plate and a layer of antiabrasive material designed to protect the chute, provide a low coefficient of sliding friction and lower the sound of material being dispersed.
The top section of the muck head frame consists of a series of heavy beams that support the sheave deck and three wire rope sheaves. The main sheave that is attached to the muck bail has a pitch diameter of 118 cm (46.5 in.) and supports a 3.8-cm (1.5-in.) diameter Briden Endurance Dyform 34LR Max wire rope with a breaking strength of 151 t (166 st). This wire rope is two parted around a 145-cm (57-in.) diameter Crosby block and returns to the sheave deck where it is anchored in a fixed support frame.
The two remaining sheaves are designated as guide rope sheaves and have a pitch diameter of 71.4 cm (28.125 in.) and support a 2.8-cm (1.125-in.) diameter Briden Dyform 6 wire rope with a breaking strength of 78 t (82.5 st). The two guide ropes are used to guide the muck bail while running in the shaft and are anchored at the foot of shaft by way of a hydraulically operated cylinder designed to measure the required tension in the rope guides.
Supply head frame. The supply head frame is a prefabricated structure that measures 3 x 7 m (9 x 22 ft) with an over-all height of 14 m (46 ft). The supply frame, like the muck head frame, is supported on heavy beams that are a part of the upper portion of the previously described base frame. The supply sheave deck is of similar design and configuration as the muck sheave deck with identical sheaves and wire ropes for ease of design and functionality with the double drum hoist for synchronized loads.
The supply head frame is used to support the required services of the underground works for the transport of tunnel rail, tunnel supplies and precast segmental liner. The two guide ropes are used to guide the precast segment handling device and other supplies while running in the shaft which are also anchored at the foot of shaft.
Muck and supply back leg with erection frame. Both the muck and supply head frames have inclined back legs designed to support the loading from the two 3.8- cm (1.5-in.) diameter main ropes as well as the four 2.8-cm (1.125-in.) diameter guide ropes. The loading from these wire ropes can impose a force of up to 49,270 kg (102,000 lbs) of compression into the back-leg structure. The lengths of the muck and supply back legs are 48 and 32 m (159 ft and 105 ft), respectively, and they are horizontally supported laterally at mid and one-third points along their lengths.
It is virtually impossible to erect these long back legs in one piece so a back leg erection frame is designed and fabricated to allow reasonable sections of the back legs to be erected as units including the attached lateral support struts. The erection frame is outfitted with varying length wire rope slings so that dual sections of the back legs may be raised from a horizontal position on the ground to a predetermined and accurate inclined position in the air to accommodate connections to the two head frames and the foundation anchors on the ground.
Twenty-eight person personnel cage and access platform. Personnel ingress and egress to and from the shaft invert is undertaken with the use of a specially designed two-level personnel cage capable of transporting 28 people. The lower section of each level is enclosed with solid plate, whereas the upper half of each level has a fine mesh enclosure. The entrance to the cage is by way of three sliding doors, two on the lower level and one sliding door on the upper level.
The personnel cage is raised and lowered with a single wire rope that is supported from a personnel sheave located on the top deck of the base frame structure. The base frame structure supports a sheave deck and three wire rope sheaves. The main sheave that is attached to the personnel cage has a pitch diameter of 98 cm (38.75 in.) and supports a 3.1-cm (1.25- in.) diameter Briden Endurance Dyform 34LR wire rope with a breaking strength of 110 t (122 st). The two remaining sheaves are designated as guide rope sheaves and have a pitch diameter of 71.7 cm (28.25 in.) and support a 2.85-cm (1.125-in.) diameter Briden Dyform 6 wire rope with a breaking strength of 75 t (82.5 st). The two guide ropes are used to guide the personnel cage while running in the shaft and are anchored at the foot of the shaft.
Access to either level of the cage at the collar level is by way of a personnel access platform with an internal stairway that is prefabricated and located inside the south end of the base frame structure. This access platform also allows for a method of traversing from the west side to the east side of the shaft area. Access at the foot of shaft is by way of a 10-m (30-ft) high stair tower.
The personnel cage is equipped with a broken rope safety device installed on each end of the upper framework of the cage. The safety device utilizes a linkage system and a heavy coil spring to activate a pair of high strength serrated wedges that, when activated, grip the 2.85-cm (1.125-in.) diameter rope guides. The cage is guided throughout the shaft area with a total of four bronze thimbles located on the four corners of the cage.
Muck car bails and muck cars. The excavation of the tail and starter tunnels is with the use of the drill and shoot method. The excavation of the main tunnel drive is with the use of a 6.7-m (22-ft) diameter Robbins TBM. The TBM deposits muck into a series of 15-m3 (20-cu yd) lift off box muck cars from a trailing conveyor belt system and is transported with a diesel powered locomotive.
When the train reaches the area at the foot of the shaft, each successive car enters into a bail structure that is designed to raise the lift-off box only to the surface dump area. The bail system consists of an inner and outer bail. The inner bail is pinned at one corner to the outer bail so that it can rotate and dump the contents of the 15 m3 (20-cu yd) box while traversing through the dump scroll on the north face of the muck head frame. The combination of bail, box and tunnel muck weighs approximately 48,000 kg (106,000 lbs) and travels to the surface at a maximum velocity of 167 m/min (550 ft/m).
Hoist requirements and specification
The main mucking and material hoist is a double drum electrical variable frequency drive (VFD) hoist that has two drums capable of running simultaneously locked together or independently. The hoist consists of three separate modules; the main drive module, the drum hoist module and the HPU module. The main drive module has two 970-kW (1,300-hp) electric drive motors directly coupled to a two-speed gear reducer with two high speed input shafts and one low speed output shaft. The primary feed for these drives is 4160V. The drum module has a 480V 372 kW (500 hp) drive motor that transmits torque through a gear reducer with a final bullgear reduction acting directly on the supply drum. Depending on the mode of operation, the two 970-kW (1,300-hp) drives can drive one or both drums through the single shaft at various speeds and capacities. Similarly depending on the mode of operation, the 372-kW (500- hp) drive can drive one or both of the drums through the bullgear with slower speeds and less capacity. With that said, when the hoist is configured correctly, the muck drum can be driven at high speeds from the two 970-kW (1,300-hp) motors at the same time the supply drum can be driven by the 372-kW (500-hp) motor.
The HPU module provides hydraulic pressure for the brake system, the clutch system and the shifting for the two-speed gear reducer as well as cooling the gear oil. Each drum and driveline has an independent brake system spring applied, hydraulically released that is capable of stopping and holding 150 percent of the linepull. The clutches are engaged and disengaged from each drum independently using hydraulic cylinders allowing the hoist to be operated in various modes.
The electrical setup for the main hoist is extensive. The incoming feed to the electrical hoist pad is 13,200 V, which then steps down to 4,160 V for the two 970 kW (1,300 hp) or medium voltage drives and steps down again to 480 volts for the 372-kW (500- hp) or low voltage drive. Each of the three motors is driven with a VFD. The two 970-kW (1,300-hp) drives are regenerative drives that reduce the harmonics to less than 5 percent distortion so that the power generated by the drives can be put back into the grid as reusable power. The low voltage 372 kW (500 hp) drive dissipates the energy produced through a separate brake resistor. A requirement of the hoist manufacturer was to provide an electrical switchgear building to house all of the drives, control equipment and communication systems with plug and play connections for the main hoist feeds. This allowed the manufacturer to permanently install all of the major electrical components, test the equipment and ship the building as a single unit to avoid tear down, packaging and resetting up of the equipment.This was a significant time and cost savings on the job and simplified the site commissioning.
The double drum hoist has six modes of operation;
- Mode 1: The muck/supply mode is set up to have the two drums run independently. The muck drum primarily for high-speed mucking cycles while being able to hoist materials on the supply drum. The muck drum has a line speed of 5.5 m/sec (1,100 ft/m) with a linepull of 28,210 kg (62,210 lbs) and the supply drum has a line speed of 2.5 m/sec (500 ft/m) with a linepull up to 14,890 kg (32,650 lbs).
- Mode 2: The double-drum heavy lift mode operates with both drums clutched in together utilizing the two 970-kW (1,300-hp) drives providing a total lifting capacity of 113 t (124.4 st) at 0.25 m/sec (50 ft/m).
- Mode 3: Also utilizing the two 970 kW (1,300 hp) drives, the double-drum, high-speed mode operates with both drums clutched in together providing a total lifting capacity of 56.4 t (62.2 st) at 1.27 m/sec (250 ft/m).
- Mode 4: The muck drum heavy-lift mode runs the muck drum in low speed at 0.25 m/s (50 ft/m) and a capacity of 56 t (62.2 st), utilizing the two 970- kW (1,300-hp) drives.
- Mode 5: The supply drum heavy-lift moderuns the supply drum in low speed at 0.25 m/s (50 ft/m) and a capacity of 56 t (62.2 st), utilizing the two 970 kW (1,300-hp).
- Mode 6: Emergency mode runs both drums from the 372-kW (500-hp) drives if the two 970-kW (1,300-hp) drives or gearbox were to fail.
Personnel ingress and egress is achieved with Timberland’s model PH250 and a 28-man, two-level cage. The hoist will lower personnel the 274 m (900 ft) at a rate of about 1.2 m/sec (240 ft/m). The hoist is a single drum, electric over hydraulic hoist system that incorporates a hydrostatic drive and two independent braking systems similar to the brakes on the main hoist. The system is powered utilizing two independent 186 kW (250 hp) electric motors direct coupled to the hydraulic pumps providing a spare pump drive all the time. The control for this hoist is fed back to the operator’s cab in the headframe using a single joystick and HMI screens. For emergency purposes, the 480 V power for the personnel hoist system is feed from the essential services switchgear on site that includes backup generator power. For this reason the PLC for the personnel hoist is independent of the remainder of the hoist system and is located at the HPU with a local operator’s station for setup and operator control during a power outage.
The hoist system includes six guide-rope winches, two for each of the three main drums; muck, supply and personnel. These winches were primarily used during the sinking of the shaft as the depth continued to increase. Once the bottom was established the guide ropes are fixed and the drums locked. Each winch is a single drum electrically powered with a 15-kW (20-hp) motor and a gear reducer between the motor and drum with a linepull of 3,175 kg (7,000 lbs). The winch has a single spring brake within the motor and a locking dog that is engaged once the guides are set.
Four stage hoists were utilized in the system as well to raise and lower a full diameter shaft work deck for the installation of all the utilities and have a linepull capacity of 16,700 kg (36,980 lbs) each. Each hoist is controlled with a single 15-kW (20-hp) electric motor through a gear reducer and a set of open gears. The brake system consists of a fast acting motor brake and an air controlled band brake. The control for these four hoists are also in the operator’s cab within the headframe.
The controls for all of the hoists were set up in a 2.4- x 2.4-m (8 x 8-ft) cab to be operated with one operator utilizing three joysticks for the main hoists, two HMI display touchscreens and a series of control panels. Traditionally, the operator’s station is positioned in the hoist house overlooking the hoists. However, it was decided to place the cab inside the headframe structure over the shaft cover. This allowed the operator an unobstructed view of the cover and rigging operations as well as providing the safest viewpoint for personnel. The main PLC cabinet for the hoist system was located in the cab along with the load cell control cabinet and CCTV equipment. Additionally, there were controls designed and installed by KSC that were tied into the hoist control system for the anti-two block systems, the load cell system, personnel cage proximity switch and door locks and muck dumping proximity switch.
Set up and erection
The assembly of the hoist and head frame consisted of three phases of work; foundations, preassembly and erection over the shaft. The foundations were poured for the runner beams, base frame, back legs and the hoists, which included 35,000 kg (77,000 lbs) of rebar and 920 m3 (1,200 cu yd) of concrete. The most challenging piece of the foundations was assuring the embedded bolts for the double-drum hoist were accurately laid out, as the two skids weighed 91 t (100 st) combined and needed to be placed so that the drive output shaft and the drum shaft were perfectly aligned. Preassembly of the structure included the shaft cover, the muck and supply towers, the sheave decks, the base frame and the back legs, all of which took place on site yard while the site utility, shaft utility and foundation work were being performed. Once shaft utilities were completed, the assembly over the shaft began with the base frame. The base-frame stair tower was installed prior to installing the supply tower and lower muck tower for easy access from the deck to all of the tower mounting base plates. Similarly, the upper stair tower was installed prior to the upper muck tower eliminating the need to work out of a 57-m (185-ft) man lift. Lastly the back legs were pinned to the towers and secured to the foundation slab.
Once all of the structural steel was in place, rope up of all the hoists was completed along with the electrical and mechanical installations throughout the hoist and head frame assembly. The technical hook ups and commissioning took an additional few weeks to complete. The crews used throughout the setup were made up of ironworkers, laborers, mechanics and electricians along with assistance from the hoist manufacturer.
Commissioning and testing
There were three phases to the commisioning of the hoists; at the factory, on site and finally the tuning of the medium voltage drives. Timberland performed a factory acceptance test in their plant prior to the equipment being shipped to site. All systems and fuctions were tested to ensure minimal troubleshooting on site. Similarly, thorough site acceptance tests were completed once all of the components were installed and functional, which included KSC’s control system. The final step was the testing and tuning of the drives for each mode of operation. Tests were performed at different load capacities and speeds as well as floating the load, changing the load simulating loading a muck box, and emergency stopping. These trial runs for each mode were to fine tune the parameters for each drive to adjust for the drift during floating of the load, the inertia settings, and meshing of the low speed and high speed.
By code, the hoist needed to be load tested to a minimum of 110 percent, which was accomplished using a water bag system consisting of two water bags per load block. The water bags were used to calibrate the load cells as well.
Operation and challenges
The job faced many operational challenges that a multiple hoist system had to accommodate. The initial challenge was coming up with a system designed to accommodate all of the operations for the various aspects of the project from high-speed to high-capacity to size constraints with equipment and 12 m (40 ft) lengths of steel pipe lowered within a 9-m (30-ft) diameter shaft. The logistics of keeping up with supplies to match the performance of the TBM excavation as well as quickly changing over to a grouting operation had to be well planned to be well executed. There was also the difficulty of having a fixed hoist system along with a smaller shaft that needed to accommodate many utilities with the conveyance of the 13 various hoists. The most time consuming challenge of the fixed hoist was getting the material and equipment under the hooks and the rigging required to properly place these items down the shaft.
The Rondout West Branch Bypass Tunnel is a complicated and challenging project and the hoisting at shaft 5B was no exception. But with a bit of ingenuity and the right technical expertise the challenges were overcome. At the time this paper was written, the project had successfully completed the drill-and-shoot operation, hoisted various pieces of equipment in and out of the shaft, lowered the heaviest components of the TBM and completed more than 60 percent of the TBM tunnel excavation.
JA Underground: Professional Corporation, dba Jacobs Associates. 2014. Rondout-West Branch Bypass Tunnel Construction and Wawarsing Repairs Project; Geotechnical Baseline Report.
Timberland Equipment Limited. 2015. Timberland Proposal. Owner’s Manual for Model 620X2-2-2X1300EVFD, PH250-1-2X250EH and GP70-1-20E.