Construction of an 87 foot diameter x 120 foot deep shaft wall and invert slab. The invert slab is 14 foot thick and the 3200 cubic yards of concrete was poured monolithically over the course of a 12 hour period. Once the invert slab was construction a steel skinned climbing wall forming system was used to pour the walls in 14 foot tall lifts. The reinforcing mats were installed ahead of the forming system and anchored back to the slurry wall. The construction of each lift averaged about 7 days. A steel divider plate ring with flat shoulders was installed at the location where a tunnel boring machine would be fit up and begin its drive. Unreinforced CDF was placed inside of the divider plate as to allow the climbing wall forming system a surface to bear on as the adjacent reinforced concrete was placed.

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