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    Continued Construction Work For The WTC Transportation Hub 

MAY 17, 2006 POSTING

 

Pursuant to section I.B of the Memorandum of Agreement (MOA), the following comprises the pre-final plans at the 75% design completion level for foundations and other miscellaneous infrastructure in the southern portion of the WTC West Bathtub for the WTC Transportation Hub project (refer to Figure 1).

Foundations would also be installed for the Central Chiller Plant and other shared infrastructure and equipment rooms located in the West Bathtub, that are expected to serve the WTC Transportation Hub and other WTC facilities, including the WTC Memorial and Memorial Museum. This posting depicts foundations at the bottom level (approximately elevation 242) of the WTC West Bathtub (in the southern portion, inside and outside of the PATH right of way) that would support future structural elements including walls, columns, and slabs that will be part of the WTC Transportation Hub, Central Chiller Plant, and WTC Memorial and Memorial Museum projects. This represents most of the work described in the posting of March 27, 2006, at the 35% level of design completion.

Other structural elements at the 242 level that are the exclusive responsibility of the WTC Memorial and Memorial Museum or other projects are not the subject of this posting. The WTC Transportation Hub work covered in this posting does not further impact on the WTC Tower Footprint areas, beyond the impacts already discussed in previous Section 106 consultations and described in the MOA.

The Central Chiller Plant and associated distribution system are expected to provide chilled water for air conditioning of the WTC Transportation Hub, and other WTC facilities, including the WTC Memorial and Memorial Museum. The Central Chiller Plant is planned for an area outside of the Tower footprints, in the same location as the pre-9/11 Chiller Plant facility. The scope of work depicted in this posting includes construction of the following shared structures in the southern portion of the WTC West Bathtub: Foundations for walls and columns, liner walls, structural slabs, elevator pits, sump pits, underslab drainage and plumbing systems (refer to Figure 1 and Figure 4).

The foundation work is based on design progress through April, 2006, for the WTC Transportation Hub project (by the Port Authority), and the WTC Memorial and Memorial Museum project (by the Lower Manhattan Development Corporation), including shared infrastructure. The Port Authority has determined that the following elements of the WTC Site Historic Resource may be impacted. Mitigation measures are planned consistent with the Resource Protection Plan (RPP).

* South Tower Footprint – inside the PATH right of way: The proposed work requires excavation and construction of column foundations at the South Tower Footprint within the PATH right of way. This work is consistent with the MOA with regard to limits on the effect of construction to the South Tower perimeter column base remnants and footprint area. It should be noted that the perimeter column bases inside the PATH right of way may have been permanently impacted or removed during the WTC site recovery and construction of the Temporary WTC PATH station (refer to Figure 2).

Along the east face of the footprint, structural design concerns dictate that the location of columns within the PATH Right of Way coincide with the location of the perimeter strip footing of the former WTC South Tower. These columns, required for support of both the Memorial and WTC Transportation Hub projects, have been placed to make use of the existing strip footing, thereby reducing the need for additional footing construction, while avoiding the location of potentially remaining perimeter column bases (refer to Figure 2).

One column foundation (along the south face) will be connected to the existing strip foundation that supports the perimeter column remnants through the use of dowels to create a composite structural element. Additionally, a shear wall foundation will be interrupted at the location where it would cross the line of perimeter column remnants on the east face of the footprint. The opening in the shear wall will span over the line of perimeter column remnants, and the space between the remnant and the shear wall will be filled with rigid insulation material (refer to Figure 2).

* WTC Site (outside of South Tower Footprint) – inside the PATH right of way: The proposed work requires excavation and construction of foundations, slabs and drainage in the southeast and southwest quadrants of the WTC West Bathtub. It is likely that remnant subgrade features, such as drainage lines and pits within the work area may be partially or entirely removed (refer to Figure 2 and Figure 3).

* WTC Site (outside of South Tower Footprint) – outside the PATH right of way: The proposed work will require additional excavation and construction of column foundations, slabs and drainage in the southwest quadrant of the WTC West Bathtub. Existing slabs, manholes, walls and utility chambers, drainage lines and pits, within the work area are expected to be partially or entirely removed during construction. A portion of the west slurry wall buttress slab will be removed for the construction of an elevator pit. The existing drainage system trenches are incorporated into the new drainage system to the maximum extent possible, reducing the need to construct additional trenches (refer to Figure 3 and Figure 4).

* West Slurry Wall: A new concrete liner wall, two to three feet thick, will be constructed along the face of the existing west slurry wall of the WTC West Bathtub. The liner wall will protect and reinforce the existing slurry wall. The liner wall will extend north from the southwest corner of the Bathtub continuing along and west of the Central Chiller Plant (refer to Figure 3).

* Other WTC Site Remnants

o West Bathtub Subsurface remnants: It is anticipated that some miscellaneous subgrade remnants, such as drainage lines and pits, within the work area may have been permanently impacted or removed as noted above. Although pre-9/11 plans may indicate these features, their current status is uncertain due to disturbances during the WTC site recovery and construction of the Temporary WTC PATH Station. Any unanticipated features encountered will be evaluated to determine whether removal is necessary and if the Project Historic Architect (PHA) should be notified. If removal is necessary, the feature will be documented in consultation with the PHA and the Engineer will make a determination as to whether it should be salvaged or demolished.

o Temporary WTC PATH Station: The construction described in this posting will occur adjacent to the Temporary WTC PATH Station and related facilities (refer to Figure 2). The work will result in modifications to the infrastructure supporting the Temporary WTC PATH.

This preliminary scope of work reflects review and comment by the Project Historic Architect (PHA), as stipulated by the Resource Protection Plan (RPP; Section 2.2 Design Phase Responsibilities).

This construction work is expected to begin in the second quarter of 2006 and would be completed in the second quarter of 2007.

http://www.panynj.gov/drp/wtcth/initwtcprep.php?sprep=wbathtubexc75Prcnt

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