Remediation of Former Manufactured Gas Plants and Other Coal-Tar Sites

Geologists working on hazardous waste sites often think of them as relics of history, albeit recent, human-scale history. We can often find people who worked at the plant in question or who have good second-hand knowledge of past operational practic-es. Failing that, we can reason by analogy with similar operations that we have seen. However, there is a large group of heavily affected sites that are truly historic, contaminated by an industry that has been gone for so long that minimal information about plant operations remains. These sites are manufactured gas plants (MGPs), which supplied combustible gas for home lighting, cooking, and heating before construction of the natural gas pipeline network. Here in New York, nearly every town with a population of 5,000 (per the 1900 census) had at least one MGP. By 1950, nearly all of the facilities were gone, with the last one closing in 1973. While they operated, MGPs were notoriously bad neighbors, fouling the air and water of their immediate surroundings. Most of the problems related to the handling of coal tar emulsions: the near-neutral density of this smelly, non-aqueous phase liquid allowed it to either float or sink in water and to remain emulsified indefinitely. Many plants made little effort to recover this nuisance material, discharging it instead into nearby water bodies or allowing it to escape into the subsurface. Complaints ranging from taste and odor problems in nearby drinking water to paint damage on boat hulls hundreds of feet away are well documented. But memory fades with time. Despite their history, most of these sites have been totally forgotten, and man