IAI provided geotextile tube dewatering and water treatment operations services for the Mill River Remediation Project (Fairfield, CT), and was additionally responsible for odor control during dredging operations. Work was performed over a three year period, from 2014 – 2016, with operations scheduled in dredging windows, to accommodate shellfish spawning and fish migration periods. The project involved removing about 36,000 cubic yards of lead-impacted sediment from the river, processing the dredged sediment and contact water, and final disposal of the dewatered sediment.

Overview of water treatment plant, with river in background

Active dewatering of stacked geotextile tubes, during second year of operations

Dewatering pad and water treatment plant during construction

Overview of landside operations; stacked geotextile tubes in foreground, beyond that, the water collection sump and in the background, the water treatment plant

Dewatering pad after several months of dredging operations

Active geotextile tube dewatering

Inclined plate clarifier (lamella)

Deploying geotextile tubes over stacked tubes, during second year of operations

Geotextile tube header construction

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Project Statistics

4,875 lineal feet of geotextile tubes utilized
36,000 cubic yards of lead-impacted, dredged sediment dewatered
101.5 million gallons of water treated
Four layers of geotextile tubes stacked over the dewatering pad

Dewatering & Water Treatment Systems: Design-Build-Operate

IAI designed, constructed and operated the geotextile tube dewatering and water treatment systems used to process the dredged material, as well as separate chemical feed systems for controlling dredge slurry odors and flocculating the dredge slurry prior to dewatering. The geotextile tube dewatering system received dredge flow of up to 1,600 gallons per minute, or gpm, (averaging 1,200 gpm), and the water treatment plant (WTP) was capable of processing up to 1,500 gpm of water.

The WTP consisted of inclined plate separators, multimedia pressure filters and bag filters, and incorporated a pH adjustment process to remove dissolved metals such as lead. Plant instrumentation included real-time pH, turbidity and temperature monitoring. Treated water was discharged to the river under an NPDES permit issued by Connecticut Department of Energy and Environment (CT DEEP).