DuPage River Sediment Remediation

Significant Project Features

• Design/build residential remediation project requires careful planning and execution. Ongoing community relations was a key to project’s success
• Constructability review was incorporated into remedial design and the project planning process. Included the analysis of multiple remediation methodologies, impacts and costs
• Partnered with Arcadis/BBL to create an integrated team
• Project is broken into smaller, more manageable segments or “phases”. Best value analysis determines whether phases are executed sequentially or simultaneously
• Excavation, characterization, transportation and disposal of 130,000 CY of LLRW sediments
• Sediments were mechanically excavated, chemically stabilized, transferred to a Railcar Loading Facility (RLF), and shipped, via rail, to the approved disposal facility
• Sediment removal technique selected was “excavation in the dry.” Utilized both a bypass pumping system capable of handling 25,000 GPM and individual sheet pile pods
• Designed and installed a structural sheet pile wall (utilizing a cantilever wall system) to EJ&E Railroad specifications to maintain the integrity of the tracks during earth removal work within the railroad right-of-way

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History & Location Details

Project Description

PRE-WORK ACTIVITIES

This project was awarded to ARCADIS and Sevenson on a design/build basis. During RD Sevenson participated in regularly scheduled constructibility review sessions. The purpose of the constructibility review sessions were to evaluate and price a variety of remediation alternatives including bypass pumping, sheet pile diversion, subaqueous capping, and hydraulic dredging; identify the most appropriate approach to meet the regulatory requirements surrounding the project; and establish the means and methods to implement the selected remedy in a safe and cost-effective manner under “Best Value.”

DESCRIPTION OF WORK

Sevenson mobilized to the site and initiated pre-construction activities. This included removal and disposal of vegetation; establishment of site controls and access; securing permits; identification and protection of utilities; implementation of erosion and sedimentation controls; survey and site layout; establishment of health and safety protocols; environmental monitoring; and verification of removal limits. Since this project was executed on a “phased approach” temporary site controls and staging areas were constructed and demobilized at each of the eight (8) “Reach” locations.

Sevenson excavated and restored Reaches 1, 2, 3, and 4 in and adjacent to Kress Creek and Reaches 5, 6, 7, and 8 in and adjacent to the West Branch DuPage River. A total of 130,000 cubic yards of sediment and bank/floodplain soils (target material) was removed from all remediation areas. Materials targeted for disposal were transported to a rail loading facility, staged and loaded onto rail cars for off-site disposal.

Upon mobilization to each Reach Sevenson prepared the work areas for remediation. This included clearing and grubbing obstructing vegetation. All trees scheduled for removal were catalogued so similar specimens could be planted during restoration. As clearing proceeded, Sevenson established a staging area that included the construction of target material and overburden holding cells, and material and equipment staging locations. Haul roads were constructed to provide equipment access and egress to each removal area. Installation of site controls and erosion control measures were the final item included in the site setup. Temporary fencing was utilized to prevent unwanted traffic onsite and erosion control measures are implemented to minimize the migration of soils from stormwater runoff. Measures included the installation of construction fence, silt fence, hay bales, silt curtains, turbidity barriers, earthen berms and/or steel sheet pile to reduce contaminant migration.

Sevenson installed pumping systems to bypass the river/creek flow during the remedial activities when necessary. The bypass pumping systems included large circuited pumps ranging from 6 inch to 20 inch with capacities ranging from 2,000 to 25,000 GPM through 10 inch to 48 inch fusion welded HDPE pipe. Other components of the bypass system included upstream and downstream earthen or steel sheet pile berms to serve as dams and water dissipation measures built at the downstream discharge point to prevent streambed erosion. Water within the excavation areas generated from groundwater, surface drainage, and decontamination activities is treated onsite. The WWT system included pumps, holding tanks, and bag filters to remove solids from the water before it was discharged downstream.

Once the excavation areas were dewatered, remediation work was performed quickly and efficiently, and in a manner which minimized the release of impacted material into the environment. Overburden material (radiation levels less than or equal to 7.2 pCi/g) was removed to the design elevation (predetermined during the investigative sampling) and segregated in a holding area. The overburden was scanned for radiation levels to determine whether the material could be used as backfill. Any material over the 7.2 pCi/g limit was rejected and treated as target material. Contaminated river sediments and bank soils (radiation levels greater than 7.2 pCi/g) was removed to the design elevations and placed in a temporary staging area. There the target material was solidified using quicklime prior to transportation for off-site disposal to meet the moisture percentage restrictions.

Sevenson worked closely with subcontracted surveyors to maintain the small allowable deviations from the design depths when excavating both the overburden and the target material. The surveyors used GPS capable equipment to measure the elevations. From the recorded elevation readings, Sevenson and ARCADIS generated overburden and target material verification reports within 24 hours that were immediately submitted to the regulators for approval. This quick turnaround allowed Sevenson to continue excavation and backfill operations without sampling delays.

Offsite disposal of the contaminated material included a two-stage process. After material was stabilized, it was loaded into tarped trucks for transport to the Railcar Loading Facility (RLF). At the RLF the material was stockpiled under a protective canopy for additional analysis and radiological testing before loading it into 100-ton railcars. Railcar loading was a stringent process complicated by exacting weight requirements, decontamination procedures, railcar shipment regulations, and maintenance and repair of the railcars. Sevenson had dedicated a trained and supervised crew to perform this operation and ensure that loading operations were executed safely and in compliance with established plan guidelines and regulations.

Upon completion of the excavation activities, Sevenson restored each reach. Restoration required coordination and input from ARCADIS, the townships, and the Dupage County Forest Preserve. Restoration included bank and streambed fortification, installation of wildlife habitats and riffles in the streambed, and wetland reconstruction.

In addition to maintaining communication with local utility, regulatory and emergency response agencies, Sevenson and ARCADIS secured approvals for permits and approvals from USACE, Illinois Department of Nuclear Safety, USEPA, Illinois EPA, DuPage County and local municipalities, and Forest Preserve District.