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Dennis G. Grubb

Dr. Grubb will present the results of an Innovative Reuse of Dredged Material Demonstration Project recently completed at the Cox Creek Dredged Material Containment Facility (DMCF) in Curtis Bay, Maryland, USA, sponsored by the Maryland Port Administration (MPA). MPA is challenged with having to recycle approximately 500,000 CY of dredged material (DM) from the inner harbor by 2023 due to limited DMCF storage capacity. This project received numerous awards including the 2104 Samuel Arnold Greeley Award (best industry paper) from the Environmental and Water Resources Institute of the American Society of Civil Engineers. The Innovative Reuse Project consisted of three main phases.

Phase I documented the environmental quality of DM and regional amendments to provide simultaneous geotechnical and environmental enhancements to the DM. Significant emphasis was placed on understanding the fate and transport of the arsenic associated with the DM, due to its potential health concerns and its relative importance over other elements. It was determined that the environmental quality of the steel slag fines (SSF ; USCS SP soil) was superior to the DM and that the compacted DM-SSF blends (in the lab) did not exhibit adverse arsenic leaching, settlement or swell behavior.

Phase II involved an extensive laboratory evaluation of the DM, SSF and five DM-SSF blends to characterize the mineralogical, environmental and geotechnical attributes of the materials and possible aging (time dependent) effects. Phase III involved a field demonstration project at the Cox Creek DMCF to construct five trial, single lane highway embankments : 100% DM, 100% SSF and 80/20, 50/50 and 20/80 DM-SSF blends, where the DM content is reported first (dry basis). The feasibility of blending the DM and SSF media in targeted ratios using conventional soil pugmill was successfully demonstrated at high throughputs. The construction of the DM-SSF blends as geotechnical fill using conventional equipment was successfully demonstrated to against structural fill, highway embankment and general fill standards. The environmental and geotechnical aging of the embankments was measured 365 days after construction.

Based on the multiple lines of research and analysis performed as part of this project, the leaching of As from the 100% DM, 100% SSF and the DM-SSF Blends was extremely low to negligible. The laboratory aging study showed aged DM-SSF Blends containing up to 45 mg/kg As were below detection limit (DL) on SPLP-As leaching (<0.056 mg/L) at 360 days. This field aging study showed that the 95% upper confidence limit (UCL) on the average leached As concentration to be less than the SPLP DL (0.028 mg/L), and almost matching the TCLP DL of (0.02 mg/L) for DM containing approximately 26 mg/kg As.

As little as 20% SSF blending promoted significant geotechnical improvement (φ’=52°) while maximizing the DM content such that the resulting 80/20 DM-SSF blend it could be used for large scale highway and port facility construction and similar geotechnical uses. These geotechnical improvements were immediate and increase with aging, and perhaps more significantly, appear to exclude the formation of crystalline cementitious end-products. Dr. Grubb holds a M. Eng. and Ph.D. in geotechnical engineering from the University of California at Berkeley, a MSCE in environmental engineering and science from Stanford University and a BSCE in civil engineering from Drexel University. Dr. Grubb is a former Assistant Professor (Georgia Tech ; 1996-2000),NSF-NATO Postdoctoral Fellow (Katowice, Poland) and Fulbright Fellow (Lima, Peru). Phoenix provides a broad range of expertise in the removal, handling and processing of slag, a byproduct of iron and steel manufacturing, as well as metal recovery services. Locally, Phoenix supports Arcelor-Mittal at Fos-sur-Mer and other steel mill locations in Europe. For more information please see www.phxslag.com.



Fluides & Matériaux Complexes