Publication Summary

This report is a TMDL for fecal coliform bacteria and covers 41 miles of mainstem Willapa River. Target reductions (load allocations) for fecal coliform bacteria were established at seven mainstem and four tributary locations.

The target reductions were calculated based on a statistical difference between existing water quality conditions and the water quality standards, following the standard roll-back-method.

The report includes an Implementation Strategy that describes a conceptual approach to improving water quality, and the framework through which improvement can be accomplished. Appendix I describes how the local community was involved in helping to complete the report and the action plan.

Segments of the Willapa River have been placed on the federal Clean Water Act section 303(d) list for failing to meet Washington State′s water quality standard for fecal coliform bacteria. A previous draft Total Maximum Daily Load (TMDL) was based on data that were almost ten years old. During 2006, new data were collected by the Department of Ecology at various locations in the Willapa River watershed.

This report provides an evaluation of the 2006 data. It establishes target reductions, or numeric cleanup goals called load allocations, for nonpoint (diffuse) sources of bacteria pollution. This report also describes what it will take for the present and future permitted facilities to help the Willapa River meet state water quality standards. The target reductions were determined using the statistical roll-back method and are considered to be load allocations at the various river segments. The roll-back method compares monitoring data to standards, and the difference is the percent change needed to meet the standards. We found that the current permitted discharge limits for point sources will be adequate to help achieve this TMDL.

Load allocations are provided for all the river segments sampled. In some places, the river met standards, so the load allocation reflects that no reduction is needed. But target reductions are shown for 11 of the 24 stations sampled that did not meet standards.

Bacteria reductions are needed in six places of the upper watershed, and in three areas of the lower watershed. Data were too sparse to calculate statistically meaningful load allocations for four tributaries in the cities of Raymond and South Bend because these areas were only sampled during rain events in 2006. The cities and the Pacific Conservation District should continue to investigate and reduce pollution sources to manageable levels in these tributaries. Additional data from other studies were included in an analysis to calculate load allocations for two of the tributaries which are on the 303(d) list.

Ongoing tracking of cleanup activities as well as monitoring for water quality conditions in the impaired areas will be important. Monitoring will help focus ongoing cleanup into the highest priority locations and will help account for improvements.

Link to EIM data for User Study ID OGEO0001