Landfill
During the past 25 years, geophysical methods have proven to be an efficient and effective means for characterizing the subsurface geology and hydrogeology associated with landfills. As a result, geophysical characterization of landfills is now a routine practice. Even so, due to the inherent uniqueness of each site, it is necessary to carefully select the method and appropriately design the survey parameters in order to derive adequate benefit. In many cases, particularly when multiple objectives are desired, it is best to use complimentary geophysical methods.
Landfill characterization survey
A variety of techniques can be applied to define landfill properties, leachate circulation, or regional contamination from offsite seepage. HGI offers a suite of services designed to investigate landfills from every angle. Depending on the project’s objective and desired resolution, methods for characterization include electrical resistivity, electromagnetic induction, magnetic gradiometry, and seismic refraction. The table below offers some guidance in choosing a method that may be suitable for your particular needs.
| Method | Purpose | Depth-of Investigation (ft) | Resolution | Acquisition-rate (lineal coverage) | Cost |
| Magnetic Gradiometry | Define boundary / find iron | 30 | Low | 1-10 miles/day | Low |
| Electrical Resistivity | Define moisture characteristics | 1000 | High | >1 mile/day | Moderate |
| Induced Polarization | Define clay or organic material | 1000 | High | >1 mile/day | High |
| Electromagnetic Induction | Define boundary / find metal | 15 | Low | 1-10 miles/day | Low |
| Transient Electromagnetics | Define moisture characteristics | 1000 | Low | >1 mile/day | High |
| Seismic Refraction | Define strength characteristics | 100 | Moderate | >1 mile/day | Moderate |
| MASW | Define strength characteristics | 100 | High | >1 mile/day | High |
HGI has completed landfill investigation services for City of Tucson, City of Phoenix, US Army Corps of Engineers, Davis Monthan Air Force Base, as well as multiple private consulting firms.
Example: Resistivity Imaging of a Municipal Landfill
Below is an example of a landfill characterization using High Resolution Resistivity (HRR), one of HGI’s signature methods. The two transects are approximately 700 ft long and separated by 100ft. The data show, as interpreted from the contrasts in high and low electrical resistivity values, the edges of the landfill as well as the bottom edge. Smaller structural features are also seen, such as faults and underlying basement basalt.
Landfill characterization using High Resolution Resistivity (HRR).
The figure below shows results for the same site using Total Field Magnetics.
Landfill characterization using Magnetics.