Guest Opinion: Using Threshold Standards to Measure Environmental Quality |

Guest Opinion: Using Threshold Standards to Measure Environmental Quality

Juan Palma

In our last column, we talked about the document that created the Tahoe Regional Planning Agency in 1969. The document, called the Tahoe Regional Planning Compact, directed TRPA to adopt standards called environmental threshold carrying capacities. In this column, we’ll look at what those are, how they are used to measure environmental quality, and what out latest progress report is telling us.

This is a lot to try to cover in one column, so we encourage you to check our Web site at for more information.

The Compact defines environmental threshold carrying capacities as “standards necessary to maintain a significant scenic, recreational, educational, scientific, or natural value” of the region. In 1982, TRPA adopted a number of standards in nine areas; water quality, air quality, soil conservation, wildlife habitat, fish habitat, vegetation, scenic quality, recreation and noise.

Some of the standards are expressed in very specific terms. For example, the standard for algae growth says that “annual mean phytoplankton primary productivity shall not exceed 52 gC/sq.m/yr. Other standards are more qualitative in nature, like the recreation standard that says the policy shall be to “preserve and enhance the high quality recreational experience, including preservation of high quality undeveloped shorezone and other natural areas”.

Whether specific or descriptive in nature, different standards are expected to be attained or show positive trends at different times. When they were adopted 20 years ago, some standards were already in attainment or anticipated to reach attainment in a few years. Others were not expected to reach attainment for years to come. For example, we’ve known for years that the ambitious lake clarity threshold standard would probably not be reached for decades.

Every five years, TRPA conducts a comprehensive evaluation of where the region is in terms of achieving threshold standards. It should be pointed out that no one agency, including TRPA, could ever single-handedly achieve and maintain the threshold standards. That’s why the Compact says that the responsibility for preserving the unique values of the Lake Tahoe region is shared among federal, state, regional, and local governments.

The most recent evaluation, finished just a few months ago, generally says that we’re not doing as well as we would like in many areas, but fairly well in a few others. As easy to understand as it would be, we aren’t able to give simple “pass/fail” grades to our threshold standards. For example, despite three straight years of overall improvement, the lake clarity data continues to show a long term downward trend. And despite having made scenic quality improvements in our urban areas through redevelopment, we have seen a loss of natural scenic quality in the shoreline due to increases in the size and scale of new structures.

In short, of the 36 indicators TRPA measures to determine attainment, non-attainment, and trends, eight are in attainment and 25 are in non-attainment, although seven of those are close. We cannot determine the status of the remaining three indicators because we just don’t have enough reliable data.

As a result, TRPA staff is recommending a three-pronged strategy as we look forward to the next several years.

First, we are recommending a new package of corrective actions that range from new development restrictions and higher mitigation fees to further study in many areas where unanswered questions remain.

We are also urging a more intense effort to implement the Environmental Improvement Program, the cornerstone of which is a long list of environmental projects such as soil erosion control and sensitive streamzone restoration.

And, we are asking for regional cooperation as we look forward to 2007 when a new 20-year regional plan must be adopted. There is much collaborative work to do as we review all of our underlying threshold standards and build the foundation for the next generation of preservation efforts.

The TRPA Governing Board will conduct a public hearing in May before adopting the recommended strategy.

In our next column, we will talk about development provisions at Lake Tahoe, including the TRPA permitting process.

— Juan Palma is executive director of the Tahoe Regional Planning Agency.

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