Chromium-Contaminated Site Remediation for POTW Expansion

The long standing contamination of the Baltimore sewage works site by chromium ore residue was first fully appreciated in the 1980s when extensions were being planned. Soil chromium levels exceeded U.S. EPA standards and maximal unfiltered groundwaters showed total chromium concentrations of 180 and chromium(VI) of 6.2 mg per litre. The solution was to line existing lagoons with 2 mm thick high density polyethylene sheet, store 19,000 m3 of contaminated soil and cover it with a 1 mm thick sheet of the same material. Old concrete structures were uncontaminated so were safely removed from site after demolition. The chromium content of groundwater and other process waters was generally sufficiently low to permit discharge to the works inlet. The public were kept fully informed and airborne dust was prevented by ensuring exposed soil remained moist at all times.