Sublevels B1–B6: source review
All rendered subgrade systems were reviewed: level datums, slabs, railway, wall references, columns, foundations, anchors and circulation. Unsupported geometry has been removed. This is a partial reconstruction, with remaining gaps identified below.
The architectural floor names are offset from the B-level numbers. These are Tower A title elevations; the station and other local areas can have different elevations.
| Level | Tower A architectural name | Absolute elevation | Below concourse | Drawing |
|---|---|---|---|---|
| B1 | Service level | 294 ft | -16 ft | A-A-16 |
| B2 | Sublevel 1 | 284 ft | -26 ft | A-A-14 |
| B3 | Sublevel 2 | 274 ft | -36 ft | A-A-12 |
| B4 | Sublevel 3 | 264 ft | -46 ft | A-A-10 |
| B5 | Sublevel 4 / Upper mechanical equipment room | 253 ft | -57 ft | A-A-9 |
| B6 | Sublevel 5 / Lower mechanical equipment room | 242 ft | -68 ft | A-A-8 |
SUB-01 · confirmed
Level names and datums
Architectural Service Level is B1; Sublevels 1–5 are B2–B6. Title elevations are 294, 284, 274, 264, 253 and 242 ft.
Applied: Use the same six records in both bathtub views and foundation inspections.
Source: A-A-16, 14, 12, 10, 9, 8 title blocks
SUB-02 · unresolved geometry
Continuous basement slabs and wall bracing
A level elevation does not define a site-wide diaphragm, a slab outline, its openings, thickness or connection to the slurry wall. B5 has extensive open upper fan-room space.
Applied: No complete slab, full-perimeter diaphragm ring or inferred core hole is rendered. Level ticks are annotation only.
Source: All six Tower A plans; SKA10/84–SKA12/84
SUB-03 · confirmed local section
Station and mechanical floor elevations
R-65 Section X-X labels platform top EL250, top of rail EL246′6″ and local excavation EL243′4″. Tower A B5 is EL253; B6 is EL242.
Applied: Platform references have no invented thickness. Station rails use the local section datum. Approach grades remain unresolved.
Source: R-65 Section X-X; A-A-9; A-A-8
SUB-04 · approximate plan trace
Railway geometry and switches
SKA12/84 resolves the five-track/three-platform arrangement. Hand-traced curves and synthetic joined rail offsets do not establish switch blades, frogs, exact radii, clearances or setting-out coordinates.
Applied: The SKA12 rereading corrects station/approach curves and Platform A. Keep the trace explicitly approximate. Rail lines alone clear the current steel, but a 9 × 12 ft diagnostic corridor still flags the scheduled South Tower column 301 section. This is not a sourced vehicle gauge; approach grades remain unresolved. The old tube on R-74 was removed, as required by 3-B3-8; it is distinct from the later terminal alignment.
Source: SKA12/84; R-65 Section X-X
SUB-05 · qualified both tower supports
Basement columns, framing and connections
R-72 gives 47 named North Tower core workpoints, independently checked against B6. NIST Fig. 2–3 establishes the exterior column spacing and bracing pattern. NIST 1-2A §3.2.4 distinguishes B5 brace-column junctions from floor framing: its floor did not frame into the perimeter spandrels. R-74 independently locates 43 ordinary South Tower core workpoints and 12 N/S support references. The original SB-125–SB-128 elevations establish four different South Tower exterior frames and eight localized openings. Book 3 distinguishes permanent PT507/PT707/PT806/PT1007 from temporary TT607/TT907. Complete member and joint sections, floor openings and the surrounding plaza structure remain unresolved.
Applied: Render 47 traced core columns, 84 perimeter columns and a representative perimeter frame for the North Tower, clipped between B6 and concourse. Steel sections are qualified display envelopes; gold junction markers identify connections without inventing their hardware. Omit the unsupported repeated B5 horizontal ring; retain its EL253 datum and mark only brace-column intersections of the qualified pattern. Preserve independent foundation components. Continue 43 South Tower ordinary core envelopes to the EL242 schedule cut. Add four permanent core trusses, eight split supports, two upper stems and four dimensioned apex bearing plates from Book 3. Remove the four temporary N/S607 and N/S907 markers; straight permanent columns remain there. Reconstruct all four South perimeter elevations from SB-125–SB-128: 84 column axes, with 88 vertical segments, diagonal braces, transfer trusses and eight localized openings. Hanging columns connect to the tower above and interrupted columns resume below openings where shown. B3 and B5 have diagonal chamfer links at three corners, with none at the northeast corner. Eight terminal columns use Book 1 plate schedules and splice elevations through EL363; 26 chamfer links replace the former square-corner arms. Permanent transfer geometry uses written longitudinal dimensions and elevations, sixteen scheduled four-plate diagonal/support box sections and qualified bottom chords. The box interiors and web setbacks are modeled; eight support-joint weld schedules are recorded. Transverse registration, joint-end cuts, weld geometry, stiffeners, footing connections and floor framing remain incomplete. Opening locations come from the elevations, not clearance edits to the approximate railway. The rail lines clear the modeled tower steel; the separate diagnostic corridor still flags column 301. The later Book 1 corner correction changes eight column sections and the chamfer topology without moving the railway. Exact track setting-out, vehicle clearances and approach grades remain unresolved.
Source: Book 3: 3-B1-49, 3-B3-2–16; SB-125–SB-128; 1-B2-18; R-72; R-74; A-A-8; NIST NCSTAR 1-1 pp. 9–11, Fig. 2–3 p. 19; NCSTAR 1-2A §3.2.4 p. 35, Fig. 3–5 p. 36
SUB-06 · corrected
Tower B anchors
R-73 schedules 26 bore paths at 13 named Tower A columns only. Rotating them to Tower B falsely assigns Tower A details to a different tower.
Applied: Render 26 Tower A drilled envelopes, zero inferred Tower B anchors, and independent Tower B R-74 contours.
Source: R-73; R-74
SUB-07 · removed unsupported
Bedrock and footing elevations
General excavation varies across the plans. R-72/R-74 parenthesized values are highest permitted footing bottoms, not concrete tops or a uniform bedrock elevation.
Applied: Remove the flat EL240 bedrock mesh. Retain 46 selected reference contours and four explicitly bounded minimum concrete envelopes.
Source: R-61; R-65; R-72; R-73; R-74
SUB-08 · qualified system restoration
Wall panels, tiebacks and buttresses
Tamaro documents a 3-ft cast-in-place wall, 158 panels, four to six original tieback tiers and 30–35 ft drilled into bedrock. Those dimensions do not locate individual joints, anchors or the wall toe. Original ties were decommissioned after the permanent floors braced the wall.
Applied: Restore nominal wall thickness with explicit EL310/242 display cuts and PATH inspection windows. Show original tiebacks directly on the bathtub in a default-visible construction layer. Its 10-ft display spacing provides representative overall density; the five tiers, individual head elevations and inclination remain illustrative. Keep the unlocated section as a supplemental detail. Do not present the generated layout as an installed anchor schedule or restore unsupported buttresses or a flat rock surface. The R-61 reference to R-77 concerns internal buffer-wall anchors; it is not a verified perimeter tieback schedule.
Source: LERA R-60–R-71; Tamaro, The Bridge 32(1), 2002 pp. 12–13; FEMA 403 Chapter 2
SUB-09 · unresolved geometry
Ramps, stairs, pits, shafts and transfer framing
Their footprints and terminations vary by level. A generic spiral ramp to B6, repeated shaft holes or a guessed transfer truss cannot be derived from one site plan.
Applied: Keep original level-specific drawings inspectable. No invented 3D circulation or repeated shaft volumes.
Source: A-A-8–A-A-16; SKA10/84–SKA12/84
SUB-10 · partial source coverage
Scope and drawing dates
Tower A architectural sheets with revisions, 1968 foundation drawings and 1984 space surveys are different evidence sets. A complete Tower B architectural B1–B6 set and full-site B6 plan were not located.
Applied: Retain sheet identity, TIFF hash and separate coverage for each source. Do not certify a complete final as-built reconstruction or mirror Tower A rooms to Tower B.
Source: Local LERA drawing inventory
SUB-11 · corrected from survey witnesses
Site coordinates and Tower B orientation
R-69 and R-74 independently give Tower B center N4465.50 W9848.50, not W9842.50. In the established N4634/W9954 frame the tower centers are (−111.5,−168.5)/(105.5,168.5). R-74 is north-up: its wall 200 is Tower B north. The former east-up interpretation rotated the footing contours by 90 degrees.
Applied: Correct Tower B registration and move its survey center six feet west. Preserve source pixels, footprint dimensions and elevations. Use these same survey centers in the above-grade towers, floor-block view, plaza openings and sublevels. Remove the old context similarity fit so no scale, rotation or translation separates the supports from the towers.
Source: R-64; R-69 center; R-74 center, north line N4569.08, south line N4361.92 and west line W9952.08