Construction of Water Tight Shafts in a Restricted Access Environment-Video

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Video Summary

A sewer serving Manhattan’s 207th Street train yard had to be rerouted as part of flood-protection work following Hurricane Sandy. Because the route ran beside and beneath a century-old elevated railway, through congested streets with high groundwater and numerous utilities, conventional excavation support was unsuitable.<br /><br />The team redesigned the owner’s proposed secant-pile system as a flexible, watertight support system using micropile soldier piles and jet-grouted lagging, with tailored bottom seals or deeper cutoffs where needed. A test program in variable sandy fill and layered silts optimized grout parameters and confirmed low permeability and strong columns, eliminating the need for further test sections.<br /><br />Construction required low-headroom equipment, reinforced work platforms, adjustments for obstructions and soil variability, and careful coordination around both known and unmarked utilities. Pre-trenching helped identify unexpected services, while field teams adjusted column layouts to maintain coverage and avoid damage. Seven of 11 shafts have been completed, four successfully excavated, and tunnel-boring work has progressed safely.

Keywords

sewer rerouting

flood protection

micropile soldier piles

jet-grouted lagging

utility coordination