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Norwalk Water Pollution Control Facility Upgrade

Norwalk Water Pollution Control Facility Upgrade

Norwalk Water Pollution Control Facility Upgrade

Location: Norwalk, CT

Services: , , , ,

Markets: Government

Highlights

  • Excavation of an 80 ft. wide by 150 ft. long by 40 ft. deep hole for sheet piling cofferdam
  • 3-year project completion while maintaining constant sewage flow through the plant

Overview

Loureiro Contractors, Inc. was the trade contractor for the site excavation, utilities, and piles package for the construction of the Norwalk Water Pollution Control Facility/Wet Weather Preliminary Treatment System. The existing plant is located on the east side of the Norwalk River, and within a large municipal complex. Scope of work included construction of a deep cofferdam; dewatering; excavation; installation of precast concrete friction piles; and construction of site amenities.

Approach

Loureiro Contractors, Inc. provided excavation of an approximately 80 ft. wide by 150 ft. long by 40 ft. deep hole. Excavation was completed with the use of a steel sheet piling cofferdam. The contaminated excavated material was transported and disposed of at a facility in New Jersey. Excavation dewatering consisted of 8 deep (85ft) wells with 300 GPM electric pumps connected to a discharge header pipe. The system was capable of pumping nearly 3.5 MGD. The pumps, powered off of the grid, were backed up by a 100 KW diesel standby generator. Loureiro was responsible for the 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 fused HDPE storm overflow line, and a 16” diameter ductile iron storm flow line. Loureiro also installed a pile-supported concrete pad for a 2500 KW emergency generator, switch gear, and manholes. The team was responsible for the design and installation of a by-pass pumping system for up to 35 MGD of raw wastewater, in order to make the final connection to the new plant. Site improvements included an underground electric duct bank, a new storm drainage system, new pavement, concrete sidewalks and stairs, miscellaneous concrete equipment pads and turf restoration.

Results

Through Loureiro’s management, the project was successfully completed while maintaining constant sewage flow through the treatment plant for nearly 3 years. Of particular note was the dewatering system for the deep excavation and the by-pass pumping system for the final connection to the new plant. The dewatering system was designed and installed in a couple of months and operated 24/7 for nearly 2 years. The by-pass pumping system was many months in planning, design, construction and testing and needed to operate for only a few hours to make the final 36” diameter connection.

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