services are activated, the old ones can be decommissioned and demolished. However, in this case, due to the logistics and limited space for utility relocation, workers had to carefully demolish and shift these many active communications duct banks while the service inside remained “live.” They also had to carefully install excavation support around this relocation and perform the utility relocation work with painstaking care to ensure service was not accidentally disrupted. Electric services varied from 2 to 6 ft Relocating utilities adjacent to building protect those structures. Ground improve- ment technologies included jet grouting, compaction grouting, compensation grout- ing and permeation grouting, plus under- pinning of structures. These technologies were implemented on a case-by-case basis to minimize settlement of existing foundations. The utility relocation phase of the project involved maintenance and relocation of over 3.5 mi (5.6 km) of Manhattans’ utility services over a 0.2 mi (0.32 km) long stretch of Second Avenue. Within approximately 14 months, the contractor relocated all sewer, water, high and low pressure gas mains, and electric and communication utilities. These utilities ranged from 6 ft (1.8 m) wide by 5 ft (1.5 m) high duct bank constructed to depths of 19 ft (5.8 m) below grade to 3 in (76 mm) diameter electric conduits installed only 2 ft (0.6 m) deep below existing grade. Relocat ion work began wi th constructing the deepest utilities first and progressed to the shallow services. Typically, the relocation sequence proceeded from sewer to water and gas lines followed by electrical and communication conduits. However, on this project, one communication duct bank was 19 ft (5.8 m) deep and needed to be relocated prior to all other utility work in the vicinity. Sewer services ranged from 5 ft (1.5 m) to 8 ft (2.4 m) diameter pipes and were typically the most challenging to install due to their depths ranging from 9 to 15 ft (2.7 to 4.6 m) below grade. Installing these deep utilities was challenging due to the high 42 • DEEP FOUNDATIONS • JAN/FEB 2013 groundwater table and the required con- struction methods. Since sewer services could not be temporarily shutdown, the contractor had to constantly maintain the sewer flow through the work trench by means of temporary bypasses. This always posed a construction challenge and involved altered procedures for each and every sewer. High and low pressure gas services ranged from 12 to 30 in (305 to 762 mm) diameter pipes and were typically installed within depths of 3 to 6 ft (0.9 to 1.8 m). For system redundancy, we typically installed gas services in the new alignment and a temporary service shutdown was allowed for activating new gas mains. Water utilities ranged from 42 to 12 in (1,067 to 305 mm) diameter pipes and were also typically installed within depths of 3 to 6 ft (0.9 to 1.8 m). Similar to gas line installation procedures, the new alignment was installed and a temporary service shutdown was allowed for commissioning the new water mains. Communication utilities also known as Empire City Subway (ECS) ducts, ranged from duct banks, which included over sixty-five, 4 in (102 mm) diameter con- duits to only two, 3 in (76 mm) diameter conduits and varied from 2 to 19 ft (0.6 to 5.8 m) deep. The largest duct bank on this project was approximately 8 ft (2.4 m) wide and 5 ft (1.5 m) high. Ideally, conduits are installed in their new alignment locations and new communication services then pulled through the conduits. Once the new (0.6 to 1.8 m) deep and ranged from banks of sixteen, 4 in (102 mm) conduits to two, 4 in (102 mm) conduits. This relocation work progressed in similar sequences as the communication utility relocation des- cribed previously. Once we completed this utility relocation work and temporary decking, many existing utility crossings needed to be supported from the decking structure. We coordinated custom supports with the utility owner and designed them for all sewer, water, gas, electric and ECS crossings. As excavation for the station box pro- gressed, several hundreds of feet of utility support were installed to support utilities from the temporary decking system. Decking the Street Second Avenue is a major southbound, one-way thoroughfare, and even closing a section of the avenue is unthinkable. Nevertheless, the project’s construction limits consume most of the roadway’s width, including sidewalks. The slurry walls that support the roadway decking at each end were constructed on each side of the avenue, approximately 15 ft (4.6 m) from property lines. To add complexity to the situation, the contract documents required three vehicular lanes, a bus lane and two pedestrian walkways to be accessible at all times throughout the construction phase of the project. These constraints required maximum utilization of Second Avenue’s right-of-way limits to divide the roadway into construction and traffic zones. With this arrangement, we placed a temporary Jersey barrier, delineating the construction area from the traffic corridors, approximately at the roadway center. Within this zone,
