It looks like they'll be building faster on Block 1129 than in any of the three scenarios presented--which are supposed to illustrate the potential impacts of delay-- but it's not clear whether and when open space--beyond courtyards for the two towers--will be available.
For now, some version of Construction Phasing Plan 1 or Plan 3 seems plausible, since they both start with construction (other than arena block construction) on that southeast block. However, documents indicate a plan to build a school in Phase 2, likely Building 15, which is east of Sixth Avenue between Dean and Pacific Streets.
That might come before Block 1129 is finished, but who knows. B15 requires the acquisition and demolition of existing, active residential buildings, as well as an industrial building.
From the document
According to Chapter 3A: Construction Overview:
This chapter frames the analyses that will assess whether the construction of Phase II of the Project under the Extended Build-Out Scenario and changed background conditions since the 2006 FEIS would result in any significant adverse impacts not previously disclosed, and whether any additional mitigation measures beyond those identified in the 2006 FEIS and the Amended Memorandum of Environmental Commitments (MEC) would be warranted and are practicable.(Emphasis added)
As discussed in more detail below, there are three illustrative construction phasing plans that are analyzed: Construction Phasing Plan 1—continuous sequential phasing with Block 1129 first; Construction Phasing Plan 2—continuous sequential phasing with Building 15 on Block 1128 first; and Construction Phasing Plan 3—start and stop sequential phasing with periods of more intense construction activities. These illustrative phasing plans are not intended to serve as a prediction of the exact schedule and sequence of the Phase II construction, but rather have been developed to illustrate how the timing of the construction of certain project components may vary and to provide for a reasonably conservative analysis of the range of environmental effects associated with a delayed build-out of Phase II. The three illustrative construction phasing plans serve as the basis of analysis in this chapter because they provide a range of potential impacts within the envelope of the reasonable worst-case construction schedule under the Extended Build-Out Scenario.
Plan 1 Early Stage
Plan 1: Intermediate Stage
Plan 1: Late Stage
Plan 2: Early Stage
Plan 2: Intermediate Stage
Plan 2: Late Stage
Plan 3: Early Stage
Plan 3: Intermediate Stage
Plan 3: Late Stage
Average number of workers/trucks
Forget Phase 1
Note that the projections regarding workers and trucks are for Phase 2 only, and ignore any simultaneous work on the Phase 1 site, including Building 1 (replacing the temporary arena plaza) and Site 5 (currently occupied by P.C. Richard and Modell's). The document states:
For Construction Phasing Plan 1, the average number of workers throughout the entire period would be approximately 347 per day. The peak number of workers would be 793 per day, and would occur in the 3rd quarter of 2030 when construction of Building 10 and the platform over Block 1120 would be simultaneously occurring. For truck trips, the average number of trucks throughout the entire construction period would be 99 per day, and the peak would occur in the 3rd quarter of 2032 when construction of Buildings 5 and 6 and the platform over Building 7 would be simultaneously occurring, with 207 truck trips per day.These of course are scenarios, not plans.
For Construction Phasing Plan 2, the average number of workers throughout the entire period would be approximately 347 per day. The peak number of workers would be 932 per day, and would occur in the 4th quarter of 2028 when construction of Buildings 8 and 9 and the platform over Block 1121 would be simultaneously occurring. For truck trips, the average number of trucks throughout the entire construction period would be 100 per day, and the peak would occur in the1st quarter of 2028 when construction of Buildings 7, 8, and 9 would be simultaneously occurring, with 210 truck trips per day.
For Construction Phasing Plan 3, the average number of workers throughout the entire period would be approximately 442 per day for the period when construction activities are occurring. The peak number of workers would be 1,356 per day, and would occur in the 1st quarter of 2032 when construction of Buildings 5, 9, and 10 and the platform over Block 1120 would be simultaneously occurring. For truck trips, the average number of trucks throughout the entire construction period would be 127 per day, and the peak would also occur in the 1st quarter of 2032, with 327 truck trips per day.
Regarding the platform
The document describes construction techniques, which differ whether construction is on terra firma or over the railyard:
Platforms would be built over the open, below-grade portions of the newly relocated Vanderbilt Yard. One platform would span over the below-grade portion of Block 1120 and a second platform would span over Block 1121. The platform would provide a base for the Phase II buildings on Blocks 1120 and 1121 (Buildings 5, 6, and 7 on Block 1120 and Buildings 8, 9, and 10 on Block 1121). The construction techniques and sequencing for both platforms would be basically the same. Columns and shear walls would be constructed on the mat foundations for future buildings. Large steel trusses, running north to south, would be supported by the columns and the shear walls. Concrete would be poured upon decking, which would have been placed on the steel trusses to form and finish the platform. Equipment that would be used during platform construction would include cranes, lift trucks, concrete pumps, compressors, and generators.
Buildings 11 through 15 would require excavation and foundation activities. Excavators and front end loaders would be used for the tasks of soil excavation. The soils would be loaded onto dump trucks for transport to a licensed disposal facility or for reuse on a construction site that needs fill. The dump trucks would be loaded in the excavation area itself, and a ramp may be built to the street level. Next, the concrete footings and walls would be erected and subsequently the cellar floor would be installed. A spread footing foundations system is expected to be used for the project buildings. In this type of foundation system, concrete column footings would be used to accommodate the concentrated load placed on them and to support the structure above. These concrete footings would be reinforced with rebar as they are traditionally done. Equipment that would also be used during excavation and foundation would also include the use of cranes, backhoes, drill rigs, bulldozers, concrete pumps, compressors, and generators.