According to the US EPA, every day, the United States generates about 4.5 pounds of trash per person. Most is paper, cardboard, yard waste, metal, and plastic. However, approximately 1.6 tons per year is household hazardous waste.  In addition, approximately 20,000 industries generate both hazardous and non-hazardous wastes.  Before the Resource Conservation and Recovery Act (RCRA) of 1976, waste (even hazardous waste) could be - and was - disposed of in pits, trenches, and unregulated landfills. Even today, illegal disposal in unregulated landfills, trenches, and pits continues.  As a result, in almost every municipality in the country, there are disposal sites ranging from nuisances to National Priority List (NPL) or “Superfund” sites.

Old or recent disposal sites may include a wide variety of materials - cloth, paper, glass, appliances, auto parts, construction debris, tires, hazardous or radioactive materials, medical waste, drums or other containers, unexploded ordnance (UXO)… the list goes on endlessly.  However, the common feature of nearly all disposal sites is the presence of either metallic debris, or moisture with high levels of dissolved solids (i.e. leachate).  Either or both of these (metal and leachate) render the waste electrically conductive relative to adjacent natural soil or rock.  For this reason, the footprints of landfills, trenches, and pits can often be readily detected and delineated using electrical or electromagnetic (EM) geophysical methods. Disposal sites that contain ferromagnetic (e.g. scrap iron or steel drums), or thermoremnantly magnetized (e.g. incinerated) materials can also be detected/delineated using magnetic mapping methods.  The depth/thickness of disposal sites can usually be determined using electrical imaging.



Since most materials dumped in unregulated or illicit pits are not compacted (i.e. the waste is low density), the thickness of waste material can often be determined using seismic or microgravity methods.  Seismic, microgravity, and ground penetrating radar (GPR) can also be used to delineate the footprint (as well as the depth) of disposal sites containing no metal, or with no leachate production. Radioactive wastes can often be directly detected using radiometric (RAD) mapping methods.

The type of waste in an unregulated or undocumented disposal site is often difficult to predict. Therefore, Enviroscan usually recommends a two-or-more technique geophysical survey to ensure that the full extent and thickness of waste materials is determined, and to provide characterization of the potential types of buried waste.  For characterization in particular, selection of which techniques to use requires great care since, for instance, a landfill with a clay cap will be largely impenetrable to GPR; surficial steel could readily conceal buried drum caches from a magnetic survey; the presence of a conductive leachate plume infiltrating downward from a trench could cause a large overestimate of the waste thickness on an electrical image; etc. Enviroscan’s careful choice of methods minimizes these potential difficulties.