- Processing Facility Site Remediation
Burns & McDonnell began investigating the site of a former ore processing facility in Tennessee in 2007, for a confidential client. In operation from the mid-1950s to 1982, the facility processed ore into ferroalloys for the production of stainless steel. Waste byproducts included ferrochromium, ferromanganese, ferrosilicon slag and baghouse dust. The site was decommissioned by 1992 and was placed in the Tennessee Department of Environment & Conservation (TDEC) Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) program. A number of environmental investigations and remedial activities were conducted by other firms for a 15-year period, which later proved to have been unsuccessful.
Burns & McDonnell's work included optimizing the existing remedial design and implementing remedial activities. Burns & McDonnell successfully identified and mitigated these environmental impacts related to the presence of slag materials:
- Manganese and arsenic contamination in surface soil
- Increased concentrations of chromium and elevated pH in surface water
- A dissolved metals groundwater plume which impacted adjacent properties
- Site characterization
- Engineering design
- Groundwater monitoring and assessment
- Optimized remedial approach
- Regulatory negotiations
- Cost estimating
- Construction management
Upon joining the project, Burns & McDonnell performed supplemental investigations to refine the site's conceptual site model (CSM), which featured a complex hydrogeological setting. This CSM was used to optimize the existing remedial design when addressing a number of slag piles that were contributing to the environmental impacts. Site data was reviewed using criteria outlined in U.S. Environmental Protection Agency guidance documents and maintained by Burns & McDonnell in an Access-based environmental database.
Burns & McDonnell's remedial solution included the construction of multiple landfill caps including an innovative 60-acre, evapotranspirative (ET) landfill cap with an integrated capillary barrier. The ET landfill cap's design reduced remediation costs by more than 40 percent and allowed for beneficial reuse of the site as a hay farm. The project also involved the rerouting, lining and environmental restoration of two surface water streams. Streams were rerouted and lined to prevent the infiltration of surface water through slag, reducing the amount of leachate generated at the site. Site restoration included native grasses, wildflowers, bushes and trees to improve wildlife habitat.
Before remediation, existing buildings were decommissioned, which involved the identification and disposal of lead- and asbestos-containing materials. Decommissioning followed local, state and federal standards. After decommissioning, the buildings were demolished. Building materials were disposed off-site or reused as fill where possible.
Burns & McDonnell performed routine groundwater and surface water sampling throughout the project. This included the collection of groundwater and surface water samples for the analysis of total and dissolved metals, hexavalent chromium and pH. Data was validated and reported to the TDEC in quarterly groundwater reports. Trend analysis was used to assess the data, establish baseline conditions before remediation, and assess the effectiveness of the remedial design. After remedial activities were complete, Burns & McDonnell finalized the monitoring well network to assess the potential for off-site migration of hexavalent chromium to adjacent properties.
Remedial activities were completed in March 2012, when a final site walk was conducted by representatives from Burns & McDonnell, the client and the TDEC. No further action was granted by TDEC in 2013, and the site remains in use as a hay farm.