Publication Summary

Public and regulatory concerns regarding the conditions of communities within mixing zones have been increasing in recent years. As a result of this increased concern, Washington State is reevaluating existing guidance for monitoring conditions within mixing zones. This project constitutes a preliminary effort to determine the manner in which biological conditions within mixing zones are monitored in states throughout the U.S.

Ecology is reviewing its mixing zone policies and guidance. The objective of this project was to inform this process by collecting available information on how other states evaluate the biological condition within mixing zones. Further, available data and reports from such studies were assembled so that the impacts of mixing zones on biological communities within those zones might be evaluated.

Task 1: Contact EPA and States and Collect Data and Other Relevant Information

In this task available biological monitoring data from evaluations of mixing zones conducted throughout the U.S. were located and gathered. In addition to the actual monitoring data, we collected additional information, including supporting information on the methods used, study design (e.g., replication and site selection), thresholds for determining impairment (and whether a state has a set protocol for making such a determination), and other such information that may be useful in selecting appropriate biological methods for use in such mixing zone evaluations.

Task 2: Compile and Summarize Collected Data and Relevant Information

In this task, the monitoring information collected in Task 1 was compiled and summarized in an Access database. In summarizing these data it was critical to include the methods used in collecting the biological data. A key aspect of this task was to identify the criteria used (if any) to decide whether an authorized mixing zone is protective of the biological community.

Task 3: Compile Stratified List of Biological Assessment Methods

The goal of Task 3 was to use the gathered data and available scientific information to develop recommendations as to the biological monitoring required upon or prior to authorization of a mixing zone. As discussed below, these recommendations are presented in the form of recommendations for development of such guidance using Washington State′s existing Biological Monitoring Program. These recommendations are based upon the results of Task 1 and 2 of this study, and upon the expertise of this project team and applicable scientific literature.