Ground water monitoring regulations of Subtitle D, Part 258, Subpart E of the Resource Conservation and Recovery Act (RCRA) require a substantial investment by owners/operators. A poor understanding of hydrogeological settings can lead to erroneous interpretations of geochemical data and mistaken sources of indicator parameters; these are costly in terms of time and money. Improper well construction, drilling and development methods, and sampling methodology can also lead to variability of geochemical data. In addition, some hydrogeological settings have parameters in the ground water from either natural or other anthropogenic sources. Attempting to differentiate other sources using the sixty-two constituents listed in Subtitle D is not a practical solution in many cases. Owners/operators can establish alternative indicator parameters in lieu of some of the Subtitle D indicator parameters. This paper offers several alternative methods for innovative ground water monitoring that are specific to municipal solid waste landfills (MSWLFs) that provide more definitive data for interpretation of sources that are also cost-effective. These methods include free carbon dioxide determination, thermal surveys, stable isotope analyses, and tritium analyses. Such methods can help delineate whether the source is landfill gas, leachate, or unrelated to the landfill and reduce the need for labor intensive assessments. Case studies demonstrate the variability of geochemical data and innovative methods to fingerprint actual sources of parameters found in ground water.