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Norwalk Water Pollution Control Facility Upgrade

Norwalk, Connecticut

Services: Site Development, Underground Utilities
Clients Served: Government

Loureiro was selected as the trade contractor for both the site improvements and utilities package, and the excavation and piles package for the construction of the Norwalk Water Pollution Control Facility Upgrade; Phase 1-CSO/Wet Weather Preliminary Treatment System. The scope of the work included a new pile supported building and pile supported utilities to provide preliminary treatment for wastewater flows up to 35 MGD. The existing wastewater treatment plant is located on the east side of the Norwalk River and within the footprint of a large municipal complex that also includes other existing city facilities (DPW, Fire Department Training Tower, Material Transfer Area and Animal Control Building). The scope of work included construction of a cofferdam in conjunction with excavation and dewatering to a depth of approximately 40 ft. to accommodate a cast-in-place concrete tank; backfilling of the tank (which is also the foundation for the building); installation of 450 precast concrete friction piles (up to 95 ft. long) for the building foundation and site utilities; and construction of a variety of site amenities.

Highlights

  • Excavation of an approximately 80 ft. wide by 150 ft. long by 40 ft. deep hole. This excavation was completed with the use of a steel sheet piling cofferdam which included 3 levels of perimeter whales, cross lot braces and corner braces.
  • Excavation dewatering consisting of 8 deep (85 ft.) wells each with 300 GPM electric pumps connected to a discharge header pipe. The system was capable of pumping nearly 3.5 MGD. The pumps were powered off of the grid and were backed up by a 100 KW diesel standby generator.
  • Installation of 450 precast concrete friction piles (up to 95 ft. long) for both the building and a number of utility lines. These included a 72” diameter reinforced concrete pipe raw influent line, a 36” diameter ductile iron primary influent line, a 36” diameter HDPE storm overflow line and a 16” diameter ductile iron storm flow line. Loureiro also installed pile supported concrete pads for a 2500 KW emergency generator, switch gear and manholes.
  • By-pass pumping of up to 35 MGD of raw wastewater in order to make the final connection to the new plant.