U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Environmental Occurrence

Multi-Component Waste

Coal tars, coal tar creosotes, and heavy oil are three types of DNAPL mixtures commonly found in the environment. Coal tars are generally produced during the fractional distillation of coal to make coke for the steel industry and through a different distillation process to make gas. Their environmental occurrence is tied to improper disposal practices, mainly within the coking and manufactured gas industries. The most widespread environmental problems posed by coal tars occur at closed manufactured gas plants, and EPA estimates there may be 36,000 to 55,000 of these plants nationwide (U.S. EPA 2004).

Coal tar creosotes are made from the fractional distillation of coal tar. Ninety-seven percent of the creosote produced is used as a wood preservative. Exposure to creosotes occurs mainly from the mishandling of creosote at wood treatment sites and from the leaching of creosote chemicals from treated wood. Chemicals associated with creosote can be found in the soil around treated wood, including home decking, and in the sediment near piers made of treated wood. EPA's Superfund National Priorities List contains a number of closed wood treatment sites.

Heavy oils for the purposes of this section are defined as those used in industrial boilers and marine diesels (e.g., bunker C and fuel oil no. 6). These oils are extremely viscous. Their environmental occurrence is generally associated with the accidental release by ships at sea and leakage from storage tanks at industrial facilities. Depending upon their individual composition, which varies widely, heavy oils can float on surface water, be neutrally buoyant, or sink. They are very toxic to wildlife.

For Further Information

Adobe PDF LogoCleaning Up the Nation's Waste Sites: Markets and Technology Trends, Chapter 10
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency (U.S. EPA), EPA 542-R-04-015, 9 pp, 2004.

This EPA market study examines the occurrence of hazardous waste problems and costs to clean them up. Chapter 10 evaluates manufactured gas plants.

Manufactured Gas Plant Remediation: A Case Study
Hatheway, A.W. and T.B. Speight.
CRC Press, Boca Raton, FL. eBook ISBN 9781498796866, 1084 pp, 2017

The history of the manufactured gas industry in Massachusetts (the largest in the United States) is discussed, as well as the toxicity of gasworks waste products such as coal tar. The book then addresses the technical challenges in the MGP cleanup process, from site assessment, to remediation, to redevelopment. See a brief PDF preview.

Remediation of Former Manufactured Gas Plants and Other Coal-Tar Sites
Hatheway, A.W.
CRC Press, Boca Raton, FL. ISBN: 9780824791063, 1,398 pp, 2011

This massive compendium combines historic information about MGP processes and residues with modern data and technology in an exploration of the bases for selecting remedial alternatives to address sites contaminated with coal tar. Table of ContentsAdobe PDF Logo