In 1980, the Tahoe Regional Planning Agency (TRPA) was charged with developing and attaining environmental threshold carrying capacities referred to as Thresholds. Nine categories of Thresholds were adopted in 1982: 

Each Threshold category contains a number of specific indicators and standards that are used to track, evaluate, and report the status of each Threshold over time. Beginning in 1991, the nine Thresholds are evaluated every 5 years through assessment of the 36 Threshold indicators. Currently, an extensive Threshold Update is underway (with anticipated completion date in 2004), the results of which will set TRPA´s direction and lay the groundwork for the adoption of the next 20-year Regional Plan in 2007.