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A group of stakeholders comprised of two refineries, a municipality, and a wastewater district in Denver, Colorado are currently working together with State and Federal agencies to develop appropriate site-specific stream standards for selenium, lessening the likelihood that a Total Maximum Daily Load (TMDL) would be required for the stream segment in the future.

In year 2000, Colorado commenced movement toward lowered chronic standards for selenium, moving from 12 μg/L total selenium to 4.6 μg/L dissolved selenium. This action led to the formation of the Stakeholder group – with the intent of rationally evaluating these lower limits in light of impact to dischargers while still supporting the receiving water beneficial uses. The Stakeholders successfully negotiated a Temporary Modification of the proposed lower standard for a period of three years, in which the group can study selenium and alternative criteria on both Sand Creek and Segment 15 of the South Platte River while maintaining existing discharge limits for each entity affected. Additionally, in a move favorable both to the State and dischargers, 303(d) listing of the receiving waters was deferred, allowing greater time to fully characterize the stream systems both biologically and physically. A better understanding of stream attributes will benefit both the environment and needs of the dischargers – benefits that might not be fully realized under a strict TMDL approach.

A National Research Council technical committee reviewed the TMDL regulation at Congress' request in a report entitled “Assessing the TMDL Approach to Water Quality Management,” (National Research Council 2001) which in many ways validated this stakeholder effort. The technical work group suggested that before a waterbody is placed on the 303(d) list, the water quality standards should be reviewed to see if they are appropriate and if site-specific conditions preclude standards from being met. If stream standards and discharge limits can be developed for a stream segment on a site-specific basis without having to place the stream on the 303(d) list, there may be no need for a TMDL. By working outside of the regulatory framework of the TMDL, it is possible to gain more flexibility and streamline the permitting process, and from the State's perspective, will aid in avoiding further burden to the TMDL backlog.

The Stakeholders put together a plan of study and action to develop the appropriate water quality standard for Sand Creek and South Platte River Segment 15. The plan also includes examining the upstream sources of selenium in Sand Creek, which average 11 μg/L (based on current data), exceeding the proposed standard of 4.6 μg/L. Because upstream site-specific conditions are above current and proposed standards, the stakeholders will likely define and propose an ambient criterion. As required in setting an ambient criterion, the study will determine if the sources of selenium are natural or man-made, and if the man-made sources are irreversible.

The study plan developed to implement the overall effort was reviewed by the agencies involved with the project: the Colorado Department of Public Health and Environment - Water Quality Control Division, Colorado Division of Wildlife, U.S. Fish and Wildlife Service, and U.S. EPA Region 8. The plan, which has been underway for the past year, includes collecting and analyzing water quality, physical habitat, sediment, and biological data. In particular, the biological data include concentrations from both fish and macroinvertebrate tissue, and fish egg/ovary tissue. Data and information collected during the study along with existing data from previous studies will be used to determine the appropriate effect concentration for selenium and set separate site-specific criteria for the South Platte River Segment 15 and its tributary, Sand Creek. These criteria will be protective of indigenous populations of fish and macroinvertebrates in these streams.

The benefits of being proactive and working outside of the traditional TMDL framework in this case has provided each of the stakeholders with the additional time necessary to thoroughly study and understand the issue, to develop economically viable means to reduce selenium loading, and provide a scientifically sound analysis of standards that are truly necessary to support a healthy biological population and meet beneficial uses.
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Document Type: Research Article

Publication date: 01 January 2002

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