From the early 1800s to the mid-1900s, over 50,000 manufactured gas plants (MGPs) across the U.S. supplied homes and industry with fuel for heating, cooking, and lighting. The process to create that fuel at industrial plants resulted in the release of residues, including tar, sludge, oils and other wastes. Although many of the by-products were recycled, residual coal tar remains in surface water sediment adjacent to thousands of MGP sites today.
Managing the environmental legacy of MGP contamination is a significant issue for many utilities and communities nationwide.
Current experience shows that dredging is only partially successful, and conventional sediment caps only delay eventual contaminant releases. Gas that bubbles up from degrading organic matter on MGP sites causes the migration of contaminants and leads to the failure of conventional caps. TRC has developed a better capping design that stops contaminant migration.
MGP sediment sites in Ann Arbor, Michigan and Bangor, Maine have been capped with a newly-patented design that prevents releases of coal tar, petroleum and other non-aqueous phase liquids (NAPL) into the overlying water. The innovative design is a permanent solution, stopping NAPL migration and safely venting the gas to the atmosphere. Both of these sites are part of urban redevelopment.
Almost all MGP sites are on or close to a waterfront in an urban area. These sites can represent valuable properties for urban redevelopment.
Are you or your client facing challenges in redeveloping a MGP site? Do you need a permanent solution to environmental contamination in an adjacent water body via a rate payer-funded remediation? Please share your ideas and questions in the comments section below.