Watershed, Summer 2000
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What are TMDLs and How Will They
Affect the Santa Clara River?
by Ron Bottorff

A relatively unfamiliar term is getting more attention these days - the Total Maximum Daily Load, or TMDL. No, this is not the amount of daily stress in your job or in dealing with your teenagers. For our waters, however, TMDLs will come to play an increasingly important role over time. A TMDL defines how much of any given pollutant can be tolerated by a water body and still meet water quality standards. A TMDL is typically an allowable discharge expressed in pounds per day of the targeted pollutant, such as copper, ammonia or nitrates.

Congress enacted the Clean Water Act in 1972. In the Act, Congress created two overlapping approaches to regulating water quality. One, familiar to all who follow water quality issues, regulates discharges from sewers, factory pipes, and other "point sources". The other, which lay quiescent for almost 12 years, requires states to establish quality standards for their lakes, rivers, and other water bodies, and to do whatever is required to meet those standards. Since pollution from point sources has been largely (though not completely) cleaned up, this requirement leads in the direction that states regulate and clean up water pollution from all other sources. This may include runoff and irrigation return flows from farms, runoff from forestry operations, and runoff from urban areas.

This "new" approach to water quality stems from Section 303(d) of the Clean Water Act. Section 303(d) requires states to identify all the water bodies that do not meet applicable water quality standards, and for those "impaired" water bodies, states must establish TMDLs. All of the sources of the pollutant in the watershed combined, including nonpoint sources, are limited to discharging no more than the specified limit. The TMDL is intended as an objective, quantitative standard against which water quality can be measured.

This section of the Clean Water Act was essentially ignored for years. The EPA and the states were fully occupied with developing the standards and permit program for point sources, known as the National Pollutant Discharge Elimination System, or NPDES. However, beginning in 1984, numerous environmental lawsuits had the result of placing the EPA under court order to produce TMDLs in accordance with the Clean Water Act.

Portions of the Santa Clara River watershed were involved in the above-mentioned litigation. Over the next few years, TMDLs will be established for various reaches of the river and the estuary. Pollutants to be covered include coliform, ammonia, nitrates, nitrites and various organics.

FSCR Board of Directors members Ron Bottorff and Richard Sweet attended an all-day symposium "Achieving Success in the TMDL Program" at the University of Southern California on September 29, 1999. Panels of various experts discussed the TMDL regulatory framework, the problem of implementing pollutant load reductions, and the TMDL program in the Los Angeles Region. Dr. Mark Gold of Heal the Bay provided an overall view of the water quality problem from the standpoint of environmental groups. He stated that point sources of pollution (e.g. sewage treatment plant outflow) have been pretty well controlled but that efforts to control nonpoint sources, such as stormwater runoff, have been much less successful. He further stated that extensive water quality data analyses are needed to identify data gaps, and that the TMDL implementation plans and completion schedules are critically important. Dr. James Karr of the University of Washington Zoology Department presented an outstanding closing address, in which he covered the limitations of chemical monitoring in assessing the health of water bodies. He stressed that the real key is what is happening relative to biological organisms; clean water is not enough - major focus must be placed on ensuring that biotic interactions in our streams and lakes are restored and maintained. This will require a strong program of biological monitoring.

In the future, an Index of Biological Indicators (IBI) may become a TMDL parameter, with the potential of active participation by FSCR. We plan to keep in close touch with the Los Angeles Regional Water Quality Control Board on all of these issues.


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