Construction of the second pass walls continues at the Front of Plant receiving lift station (RLS). Shea-Parsons Joint Venture constructed the vertical shaft by installing support of excavation (SoE) as a method to support the surrounding soil, facilitating a safe and efficient work space for construction of the shaft. Second pass wall is an interior wall constructed immediately inside the SoE wall and is a part of the structural support for the shaft. The second pass wall will be the visible wall surface within the RLS shaft.
The rebar was bowed to fit the curvature of the shaft’s interior walls. Formwork will be placed against the rebar as a temporary structure to allow concrete to be placed between the panels and the SoE walls in 20-foot vertical sections, or lifts. A total of four lifts will constitute the entire length of the second pass walls, which span 80-90 feet.
In the photo below, near the fence, is the form work that will be placed within the receiving lift station (RLS) in advance of concrete pour. The forms will be moved in and out between the RLS concrete pours; this area is used as the staging area and storage only. It is not a permanent feature of the project; however, the forms will be visible in that location over the next 3-4 months until the entire second pass wall is placed.
In preparation for the arrival of Salus, the Tunnel Boring Machine, the surge and flow splitter (SFS) shaft will be backfilled with about 6 feet of compacted gravel. When Salus breaks through at the end of its second drive, it will be through a specially prepared section of the SFS shaft wall.