The Ashtabula River Remediation is the largest Great Lakes Legacy Act funded project to date. The project was performed in two phases by numerous contractors, working over three dredging seasons. At project close, approximately 640,000 cubic yards of contaminated soft sediments had been removed from the lower Ashtabula River.
The contaminated sediment was removed from the river by the dredging contractor, using a 12 inch diameter cutter head dredge. The sediment slurry was pumped over three miles at a rate of about 5,000 gallons per minute to the 12.5 acre sediment consolidation facility (CF). The CF was a TSCA permitted landfill, designed to provide both a dewatering facility and permanent disposal site for geotextile tubes filled with dewatered sediment. At the CF, the dredged slurry was conditioned with polymers, and then dewatered in geotextile tubes, which ranged in circumference from 75 to 90 feet and in length from 80 to 275 feet. The geotextile tubes used in the project were stacked in 10 layers inside the CF.
Water released from the geotextile tubes was collected in a sump at the bottom of the CF and transferred to an on-site water treatment plant, where it was treated prior to discharge into the Ashtabula River under an NPDES permit.
All of IAI’s on site project personnel were 40-hour HAZWOPER certified and also received Radiation Worker II training for the project.
IAI was contracted by the general contractors of both Phases I & II of the project to design, construct, operate and maintain the sediment dewatering system and was additionally responsible for operation of chemical addition and water treatment processes during Phase II of the project. IAI performed this work with an on-site staff of approximately 55 personnel during Phase II, operating 24 hours, 7 days a week for both phases of the project. IAI also provided engineering support to the project after the conclusion of active dredging and water treatment operations.
Sediment Dewatering & Water Treatment Equipment Utilized
- 12 inch and 10 inch diameter HDPE geotextile tube header systems
- Flow- and density-paced automated chemical feed systems for dredge slurry conditioning
- Chemical delivery header system
- 91,500 lineal feet of geotextile tubes, 75 – 90 feet in circumference
- Telehandlers and 6-wheel ATVs
- Water treatment system consisting of lamella clarifiers, pressurized sand filters and granular activated carbon adsorption units
- Sediment Consolidation Facility, 09-08-2006 The sediment consolidation facility before dredging began. Rolled up geotextile tubes are staged along the haul road.
- Sediment Consolidation Facility, 09-15-2006 First layer of geotextile tubes being filled in the consolidation facility.
- Geotextile tube header system, 09-15-2006 The header system, designed and installed by Infrastructure Alternatives, conveyed dredge flow to the geotextile tubes in the consolidation facility.
- Sediment Consolidation Facility, 06-15-2007 Geotextile tubes, stacked in the consolidation facility.
- Sediment Consolidation Facility, 07-04-2007 Geotextile tubes, stacked in the consolidation facility.
- Sediment Consolidation Facility, 05-20-2008 Geotextile tubes, stacked up to the 10th and final layer, in the consolidation facility.
- On-site wastewater treatment plant, Lamella clarifiers, 05-29-2008 These clarifiers were used to remove suspended solids from the flow of water produced by geotextile tube dewatering operations.
- On-site wastewater treatment plant, filters, 05-29-2008 These pressurized multi-media filters were used to remove suspended and colloidal solids from the flow of water produced by geotextile tube dewatering operations.
- On-site wastewater treatment plant, GAC vessels, 05-29-2008 These Granular Activated Carbon (GAC) adsorption vessels were used to remove dissolved organic contaminants from the flow of water produced by geotextile tube dewatering operations.
- Polymer make down system, 05-29-2008 The make down system was used to prepare dilute polymer solution, which was injected into the flow of dredge slurry to enhance dewatering in the geotextile tubes.
- Capping the Sediment Consoliation Facility, 07-17-2008 At the conclusion of the project, the Sediment Consolidation Facility (a TSCA permitted landfill) was capped and closed. The dewatered sediment will remain there permanently.