By Cassandra Fracassi
At the 1,455-acre DuPont Chambers Works in Deepwater, N.J., a complex cleanup of radiological contaminants has been underway since September 2014 as part of the Formerly Utilized Sites Remedial Action Program (FUSRAP). More than 44,000-yd³ of radiologically contaminated soil and debris has been excavated. Additionally, the environmental remediation project has installed 1,444-linear-ft of sheet pile; operated an on-site radiological lab; and upgraded and operated an on-site wastewater treatment plant to year-round operations.
Through the rapid integration of on-site test results with geospatial information system capabilities, the contractor was able to streamline the identification of new areas of contamination and expedite overall project execution.
A five-year, $75 million contract was awarded to remediate Areas of Concern 1, 2, and 6 at the FUSRAP site, consisting of excavating 27,000-yd³ of material. Through the use of advanced tools and technology and expert management, crews remediated these three areas of concern in just under three years, about 44 percent ahead of schedule, for a cost savings of over $40 million. Time and costs were saved through the setup, furnishing, staffing, operation, and maintenance of the on-site radiological laboratory, which was approved by the U.S. Army Corps of Engineers (USACE) to perform sample analyses and waste screening sampling activities in support of remediation activities. The facility is staffed by a manager who oversees all laboratory personnel.
A minimum laboratory turnaround time for gamma spectroscopy is seven days; for gas-flow proportional counting it is three days. By leveraging the on-site radiological laboratory, turnaround times for these two analyses were able to be reduced to approximately 24 hours and two hours, respectively. With more than 14,000 gamma spectroscopies and over 10,000 gas-flow proportional countings conducted, the time savings are notable. The expedited turnaround from the on-site laboratory facilitated excavation and remediation productivity—allowing for near-immediate decision-making regarding excavation and backfill requests.
Throughout the excavation, crews encountered radiological contaminated debris consisting of concrete, wood piling, asphalt, process equipment, and steel ranging in size from 1-in to 20-ft. Addressing this varied debris required a number of processes to ensure expeditious removal. Crews used an excavator with bucket for contaminated debris at 0-ft to 16-ft below ground surface and utilized a hydraulic ram attachment when required to break up concrete. For extremely large debris, it was scanned in place with a scaler/rate meter coupled with a scintillation type detector to determine if the debris was radiologically impacted and check the underlying soil. A water truck also was used during debris removal for dust control as needed.
Meeting Cleanup Criteria. Over 44,000-yd³ of radiologically contaminated soil and debris was excavated to achieve multi-agency radiation survey and site investigation manual radiological closure, meeting the 65-pCi/g cleanup criteria of total uranium. Gamma radiation scans and samples were performed in completed excavations and in active excavation areas to verify waste profiles and determine whether further excavation was required. Soils were directly loaded into haulers and transported to a temporary holding area for dewatering purposes while awaiting off-site transport. Material was dewatered by gravity and through evaporation, with excess water collected and treated in the wastewater treatment plant. Portland cement was utilized as necessary if additional drying was required for transport.
Additionally, 1,444-linear-ft of sheet pile was installed at depths of 51.5-ft below ground surface for excavation support. Within the sheeted excavation areas, 11,622-yd³ of radiologically contaminated soils and debris were excavated between 2-ft and 16-ft below ground surface. Vibration monitoring took place to ensure that sheet-driving operations did not disturb nearby structures.
All excavations that did not require sheeting were adequately sloped/benched to allow safe access and work inside the excavation areas.
Once all radiological soil and debris was excavated, personnel prepared and reviewed shipping papers in accordance with local and state guidelines and both Federal Railroad Administration and Department of Transportation regulations. Gondola car loading operations and manifest preparation were coordinated so railcars were not idle due to transportation and disposal schedule challenges.
Transporting Waste Material. After soil was sufficiently dewatered, field crews used loaders to transport material to the waste transfer facility, where it was loaded into individual 110-T lined gondola railcars. After each railcar reached holding capacity, waste loading personnel sealed the railcar liners with zip ties, a bungie cord, and “stitched” down the center of the flap. The Radiation Controls Group then conducted a full surface scan of each railcar prior to being released to ensure that there was no surface contamination on the railcar, that it was ready for public rails, and that the crews had met the requirements of the disposal facility.
All waste loading operations conducted at the DuPont site, including the lining, loading, surveying, and manifesting of each railcar, needed to be conducted in a 14-day period. This included the time from receipt of the cars at the gate to final exit for off-site disposal. Under the initial contract, the average operation length was 10 days, which was shortened even further under a subsequent task order to just eight days. To date, over 50-T of radiological contaminated steel and 1,400-T of concrete have been sent off-site for disposal along with the contaminated soils by way of railcar to disposal facilities in Utah, Michigan, and Texas.
While much remediation work remains at the site, significant progress has been made toward reaching the ultimate clean-up goal due to the cooperative actions of all the stakeholders involved with the project. By combining on-site capabilities and advanced technology, crews have been able to overcome the complex challenges at DuPont and accomplish their mission safely and expeditiously.
The project is truly a testament to the outstanding support and collaborative efforts of those involved. Not only has the work resulted in great progress toward achieving USACE’s overall project goals for remediating the radiological contamination, it is helping create new and better processes for the FUSRAP Program.
Cassandra Fracassi is Government Proposal Writer, Sevenson Environmental Services Inc.; firstname.lastname@example.org.
[This article first published in the May-June 2022 issue of The Military Engineer.]