Floodplain

LimnoTech and BASF worked closely with EPA and other stakeholders to gain approval of the remedy design, and post-remedial monitoring has confirmed the project's effectiveness.

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Success Story

Support for Contaminated Sediments and Groundwater at BASF McIntosh, Alabama

DDT and several other organic chemicals were produced on this site from the 1950s to 1960s, resulting in contamination on the property. There are also freshwater wetlands in the floodplain of the Tombigbee River, not far from plant buildings and former disposal areas. This area is subject to periodic flooding, which historically resulted in further contamination of the floodplain/wetland area.

Problem

BASF needed a remediation approach that could be implemented rapidly, reduce ecological exposures to DDT, and maintain the integrity of the site’s bottomland hardwood forest.

Approach

BASF (formerly Ciba Specialty Chemical Corporation [Ciba]) turned to LimnoTech for development of a remediation approach. LimnoTech developed and refined a conceptual site model (CSM) through sediment coring and analyses, complemented by sediment fate and transport studies using clay sedimentation pads and turf mats. Because the CSM and supporting studies demonstrated the stability of impacted floodplain sediments, a sand cover with organic amendments was selected as the appropriate remedy. Geostatistical modeling of contaminant distribution and a simple cap diffusion model were used to determine the necessary extent and thickness of the cover. LimnoTech and BASF worked closely with EPA and other stakeholders to gain approval of the remedy design. Post-remedial monitoring has confirmed the cover’s effectiveness.

Result

Work on the site continues. For the floodplain area that was remediated with a sand cover, work consists mostly of annual monitoring. LimnoTech is also working on the groundwater of the site that is also contaminated with DDT and other organic and inorganic compounds. This work includes streamlining Operation and Maintenance of an Alluvial Aquifer extraction system; characterizing the extent and distribution of impacts to two aquifers; developing cost-effective groundwater monitoring and reporting programs in accordance with RCRA Permit requirements; and developing a Corrective Action Plan to address offsite migration of groundwater impacts. In 2011 this project was awarded an Environmental Stewardship award from the Partners for Environmental Progress, a group promoting business growth and enhancing the environment in the greater Mobile, Alabama area.