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2007 Release of Causal Analysis/Diagnosis Decision Information System (CADDIS)

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Environmental Protection Agency.


Notice of public release.


The U.S. Environmental Protection Agency (EPA) announces the availability of the EPA Web site, “Causal Analysis/Diagnosis Decision Information System (CADDIS)”—2007. EPA's National Center for Environmental Assessment (NCEA) in the Office of Research and Development (ORD) led the development of the CADDIS Web site in response to strong demand within the EPA (e.g., the Office of Water) and from stakeholders and citizens across the United States seeking a defensible method for determining causes of ecological impairment. CADDIS guides users through EPA's Stressor Identification process, with interactive tools and methods, worksheets, and examples to help scientists and engineers evaluate causes of biological impairment observed in aquatic systems such as streams, lakes, and estuaries.

Access: The CADDIS 2007 Web site can be accessed via the Internet at​caddis/​.

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For further information about CADDIS, contact Rick Ziegler, NCEA, via phone: 202-564-2257, or e-mail:

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Thousands of water bodies in the United States have been reported to have an “unknown” cause of impairment. To formulate appropriate management actions for impaired water bodies, it is critical to identify the causes of biological impairment (e.g., excess fine sediments, nutrients, or toxic substances). Effective causal analyses call for knowledge of the mechanisms, symptoms, and stressor-response relationships for various stressors, as well as the ability to use that knowledge to draw appropriate, defensible conclusions. NCEA developed CADDIS, a Web-based decision support system, to help regional, state, and tribal scientists perform causal analyses. With this release, CADDIS will also help scientists find, access, organize, and share information useful for causal evaluations of impairment in aquatic systems. It is based on EPA's Stressor Identification process, which is an EPA-recommended method for identifying causes of impairments in aquatic environments. EPA released the first version of CADDIS in 2006, after addressing comments from the public and independently selected, external peer reviewers. The first release of CADDIS included a step-by-step guide to conducting causal analysis, downloadable worksheets and examples, a library of conceptual models, and links to useful information sources.

CADDIS 2007 adds considerable power and usability to the first release. Namely, CADDIS ecologists and Web specialists made the following changes:

  • Added eight modules, each describing a common stressor or candidate cause of biological impairment; the stressor modules include metals, sediments, nutrients, dissolved oxygen, temperature, ionic strength, flow alteration, and unspecified toxic chemicals.
  • Added material on data analysis including:

○ Information on how nine analytical methods (e.g., scatter plots, linear regression, predicting environmental Start Printed Page 56756conditions from biological observations, quantile regression and species sensitivity distributions) can be used to analyze causal relationships.

○ CADStat, a downloadable software package for analyzing data using a variety of exploratory and statistical approaches.

○ SSD Generator, a tool for deriving species sensitivity distributions.

○ Databases of stressor-response information including chronic exposure-response relationships and species sensitivity distributions for metals from laboratory tests; and stressor-response associations from field observational data for metals and sediments.

  • Greatly expanded the conceptual model library by adding generic conceptual models for common causes of biological impairment.
  • Developed an interactive Flash-based conceptual model diagram for one common stressor (phosphorus), which provides source citations for cause-and-effect linkages shown in the diagram. (The CADDIS team anticipates this part of the site will expand to include other common stressors and—at some point in the future—harness information collaboratively from the greater scientific community.)
  • Updated CADDIS's underlying code, which adheres to EPA's latest Web guidelines, and—similar to the first release—continues to maintain accessibility and 508 compliance.

The CADDIS 2007 release provides users with state-of-the-art causal assessment information and tools for determining why aquatic systems are biologically impaired. Ultimately, use of the CADDIS Web site translates to healthier ecosystems within the United States, while serving as an example stressor identification tool for our global environment.

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Dated: September 27, 2007.

Rebecca Clark,

Acting Director, National Center for Environmental Assessment.

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[FR Doc. E7-19624 Filed 10-3-07; 8:45 am]