Former manufactured gas plants (FMGPs) generically are the most difficult of uncontrolled hazardous waste sites for characterization as the basis for threat assessment and remedial action. In fact, partial or flawed site and waste information may magnify actual risks to humans, earth resources and the environment.

Gas works served North America (1810-1993) to produce a form of energy, from various organic feedstocks. A sizeable percentage of the original feedstock was converted to residuals, some of which could be converted to useful by-products, but this was not always done. Treatment of raw gas was required to serve consumers. Residues of treatment generally were toxic. Process-water liquors both from feedstocks and generated by the plants, always contained toxic wastes.

Plant solid and liquid wastes came to be associated with existing site geologic conditions in the course of their historic management. The wastes have lives measured geologic time and are virtually nondegradable and non attenuable when dumped, leaked or spilled into the environment. No gas works site can be considered environmentally innocuous.

A protocol for full-disclosure of gas plant geologic and waste conditions is proposed. Without full disclosure attempts to manage real gas works environmental risks are meaningless and, as such, dangerous to society.