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Manufactured Gas Plants/Coal Tar Sites


This Industry Profile Fact Sheet is presented by the Environmental Protection Agency, Region III (EPA) to assist state, local, and municipal agencies, and private groups in the initial planning and evaluation of sites being considered for remediation, redevelopment or reuse. It is intended to provide a general description of site conditions and contaminants which may be encountered at specific industrial facilities. This fact sheet is presented for informational purposes only, and should not be construed as a federal policy or directive.


Manufactured gas has been produced since the early 1800s as a fuel source for residential and industrial locations. Coal, or to a lesser extent oil, was burned to volatilize the desired gas fuel. The primary gas product from this reaction was purified, while the wastes were consolidated in a tar-like matrix known as coal tar.


The heating of the coal volatilizes the impurities into oven or furnace gas which is transferred to a by-products recovery plant. The oven gas usually goes through distillation processes to remove the waste products as coal tar. Depending on the complexity of the facility, various by-products including natural gas, benzene, toluene, xylenes, phenol, creosols, pyride, anthracene, naphthalene, sulfuric acid, light oils, paraffin and ammonia sulfate may be recovered. This by-products recovery is more common with large coking operations. Numerous waste products may be generated including hydrogen sulfide gas, coal tar, complex cyanide salts, coal fines, wastewater and process still bottoms.


Due to the immense amounts of coal which could be handled per year, manufactured gas plant sites often have very large wastewater lagoons and coal tar pits. Common waste products encountered at Superfund assessment and remediation projects include high concentrations of polynuclear aromatic hydrocarbons (PAHs), sulfur compounds, complex cyanide compounds and lower concentrations of volatile and phenolic compounds. These wastes are concentrated in a dense, aromatic coal tar and associated waste waters. This coal tar waste is typically found in large on-site pits, many of which are over 20 feet deep. The metals concentration accumulated in the ash collection system is dependent on the content of the original fuel. The most common metals include aluminum, iron, lead, nickel, and chromium. The ash may be encountered on site mixed with the coal tar or as a separate waste pile. Other inorganic compounds are not typically encountered at significant levels.

Groundwater may be contaminated as a result of leaching or percolation of surface and subsurface contaminants, surface impoundments and leaking process lines and tanks.

Additionally, contaminated buildings and the associated demolition debris may be encountered at abandoned or inactive sites. Associated heat transmission equipment may contain significant amounts of asbestos. Decontamination, asbestos remediation, and wipe testing of this material may be required prior to off-site landfill disposal or scrapping of process equipment.


All waste materials encountered on site should be visually identified and confirmed using immuno-assay, qualitative indicators, or wet chemistry field screening techniques. It should be noted that many of the waste materials may represent a significant direct contact and/or inhalation hazard to assessment personnel. Visually identified contaminated areas, waste piles and lagoons should be characterized by collecting several samples for laboratory analysis. Surface and subsurface soil sampling should be performed to confirm the extent of the contamination. Once the contaminated areas are established, grid or random sampling may be performed to confirm the suspected clean areas. The application of non-intrusive subsurface geophysics should be evaluated to detect subsurface tar pits, process lines and chemical storage tanks.

On-site and local wells may be sampled if groundwater is an environmental concern. Installation of monitoring wells or other groundwater sampling techniques should be evaluated if it is necessary to fill data gaps.


Benzene, Toluene, Ethylbenzene, Xylene (BTEX) Analysis

Cyanide (total/available) Analysis

Heavy Metals Analysis:

Phenol Analysis

Sulfate/Sulfide Analysis

pH Analysis

Region 3 | Mid-Atlantic Cleanup | Mid-Atlantic Brownfields & Land Revitalization

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