Upon successfully correcting the below grade water intrusion that was entering through the SC level OIL Tank and Boiler Room of the North Tower, Silverstein Management requested that the elevator pits of the South Tower be investigated. The C level freight elevator pit and 2 passenger elevator pits were exhibiting excessive groundwater infiltration. Previous attempts of ceasing the groundwater intrusion by implementing chemical grout injection with steel ports had failed. As this Tower was relatively new in construction, the steel dunnage of the elevator pits was beginning to corrode and management needed to prevent further corrosion promptly.

The freight service elevator pit floor slab was about 7 ft. below the cellar level floor slab. In this pit, there was a sump pit that was chopped out about 2 ft. in depth lower in elevation than the elevator pit floor slab. The maintenance created this make shift sump pit in order to install a sump pump to discharge the groundwater into a nearby sewer ejection pit. The sump pump(s) could not handle the tremendous rate that the groundwater was entering and would eventually burn out. This pit was completely filled with water and ponded water was seen through the floor slab of this pit. The sump pit and the bottom of the floor slab to foundation walls interface locations were comprehensively injected and the ground water was eliminated.

The passenger elevator pits’ floor slabs were about 16 ft. deep below the C level floor slab and therefore were within the exterior groundwater table. There were concrete wall horizontal cold joints, vertical cracks, and the perimeter walls to floor slab interface locations that were exhibiting groundwater infiltration that needed to be rectified. In order to reach the higher elevations of these wall cold joints and cracks above the pits’ floor slab, single and two stage height pipe scaffolding and planking was erected for the mechanics to safely access same.

The old steel ports from the previous chemical foam injections were grinded out and the resulting holes were filled with hydraulic cement. The old residual yellow foam itself was scraped off the walls. The CGI waterproofing procedure was then implemented within all of the groundwater crack and cold joint entry points. The groundwater infiltration was completely rectified.