# Slurry wall and original tiebacks — restoration, 2026-09-10

The wall is back as a nominal three-foot-thick 3D envelope. Original tiebacks now appear directly on the bathtub as a default-visible construction overlay, with an independent toggle in both views. Placement is illustrative: no individual anchor coordinates have been recovered from the reviewed drawings. The separate unlocated section remains available for closer study.

## Evidence and geometry

| Item | Evidence | Applied representation |
|---|---|---|
| Plan perimeter | LERA R-60–R-71 survey working points; registered SKA12/84 bends | Existing survey-controlled perimeter retained; no changes to the approximate railway trace. |
| Wall thickness / construction | Tamaro 2002 pp. 12–13: 3-ft cast-in-place slurry wall, 158 panels approximately 22 ft long | Continuous nominal-thickness envelope; no artificial seams at the earlier equal subdivisions. The reference line is treated as mid-thickness for display; exact face offset remains unresolved. |
| Top / toe | Tamaro describes variable rock depth and a wall extending from local grade into bedrock | Visible wall is cropped to EL310/242. These display bounds do not establish local grade, wall toe or socket profile. No flat bedrock mesh is restored. |
| PATH penetrations | Tamaro 2002 pp. 12–14 describes concrete sealing around existing tubes and socketing into rock alongside them; LERA locates the west projections | Explicit full-height inspection windows, 24 ft wide along the first 45 ft of each approximate approach trace. These are presentation cutaways, not reconstructed physical opening dimensions. Both rendered rails remain clear of wall concrete. |
| Original tieback tiers | Tamaro 2002 p. 13: four to six | Five illustrative tiers along the perimeter, with an independent construction-layer toggle. Display count is not an installed count. |
| Rock embedment | Tamaro 2002 p. 13: drilling 30–35 ft into bedrock | Cyan segment is 32.5 ft; the free tendon continues separately to the wall. This corrects the old interpretation of short total anchors. |
| Construction sequence | Tamaro 2002 p. 13; FEMA 403 pp. 2-10–2-11 | Original excavation ties are labeled as a construction overlay on the later basement references. The original anchors were decommissioned after permanent floor diaphragms took over support. Those floors are not yet fully reconstructed. |
| Recovery work | Tamaro 2002 pp. 16–17; Tamaro 2004 case history | New post-2001 anchors are excluded from the original construction section. |

## Explicit assumptions in the construction section

The five heads are shown at depths of 10, 22, 34, 46 and 58 ft below the section's display top. Each anchor slopes 45° down and outward and enters a hypothetical rock interface at 80 ft depth. None of these locations, slopes or the rock interface is surveyed. The 32.5-ft bond is a midpoint example within the documented range. The free lengths follow these illustrative inputs; they are not extracted schedules. Head blocks and bond-cylinder radii are enlarged symbols, not hardware sizes. The wall strip is 22 ft wide and vertically clipped to 68 ft; it is not an identified installed panel. No rock plane is drawn.

The integrated overlay adds illustrative stations at 10-ft spacing, chosen to represent the overall density reported in the case histories, independent of the approximate panel subdivisions. Banks are omitted within 9 ft of sharp corners, beside the PATH display windows (with a 4-ft margin), and wherever an outward tendon would re-enter the enclosure. These omissions are display-clearance rules, not historical anchor-free zones. The current overlay contains 1,425 illustrative anchors in 285 banks; this is not an as-built inventory. The former 645-anchor display was too sparse. This density adjustment retains the five-tier example and the same corner/PATH clearance rules; it does not establish individual anchor coordinates. The assumptions and construction stage are visible in the main description, layer control, legend and component records. The supplemental section retains its own unlocated coordinates.

## Source discrepancies and missing information

Tamaro's 2002 account gives approximately 1,500 original anchors and 3,500 ft of wall; the 2004 account gives 1,400 and 3,300 ft. The local reconstructed plan measures approximately 3,318 ft. Neither aggregate figure supplies an anchor layout, and the model therefore labels its generated display count separately and leaves the installed site anchor count unresolved. Both accounts agree on the nominal thickness, panel count, tier range and 30–35-ft rock drilling length.

The R-61 callout to R-77 examined during the previous audit concerns internal buffer-wall rock anchors. It is not evidence that R-77 contains the perimeter slurry-wall tieback schedule. The inventory does not include R-77, and its exact additional contents remain unknown. R-73 separately schedules Tower A foundation bore paths; those are not slurry-wall tiebacks.

Still needed for an as-built reconstruction: installed anchor setting-out and inclination schedules, actual panel joints, wall face offsets, local grade and wall-top profiles, rock sockets, PATH tube interface sections and permanent basement-to-wall bracing details.

## Sources

- George J. Tamaro, [World Trade Center “Bathtub”: From Genesis to Armageddon](https://www.les-crises.fr/wp-content/uploads/2016/09/Bridge-v32n1.pdf), *The Bridge* 32(1), Spring 2002, pp. 11–17. Author supervised original slurry-wall construction. Local PDF: `sources/NAE-Bridge-2002-v32n1.pdf`; content hash is in the generated dataset.
- George J. Tamaro, [The World Trade Center “Bathtub”, a Case History](https://scholarsmine.mst.edu/icchge/5icchge/session00f/6/), 2004. Primary publication record; the publicly indexed text was also consulted to distinguish original and recovery work.
- FEMA 403 Chapter 2, pp. 2-10–2-11, local `sources/fema403/fema403_ch2.pdf`.
- Local LERA foundation and sublevel drawings recorded and hashed in the existing source datasets.

## Verification

`tools/check_slurry_wall.mjs` checks actual Three.js wall meshes for three-foot thickness, vertical cut limits, clear passages along every rendered rail segment, unchanged independent foundation geometry, and identical wall geometry in both views. It also checks every integrated anchor head against the actual rendered wall, tendon/bond endpoints, outward direction, PATH rail clearances, and layer toggling in both renderers. The supplemental section remains independent. Numerical consistency is not proof of as-built accuracy.