Publication Summary

Dungeness Bay in Clallam County does not meet Class AA marine water quality standards. Fecal coliform bacteria reductions of from 41-65% are required in the inner bay during the November - February period to meet water quality standards. Irrigation ditches to the inner bay do not meet Class AA freshwater standards. Ditches need a 33-97% reduction in bacteria to meet standards. A year-round 60% reduction in bacteria levels is required for the Dungeness Bay near the mouth of the Dungeness River. The Dungeness River does not meet total maximum daily load targets set in 2002.

A variety of management activities are necessary to meet the bacterial standards in the bay, ditches, and river.

The Washington State Department of Ecology prepared a total maximum daily load (TMDL) study for fecal coliform bacteria in Dungeness Bay and ditches to inner Dungeness Bay. The study summarizes information from a technical study of the bay conducted by Rensel Associates Aquatic Sciences Consultants.

From October 2001 through September 2002, Rensel sampled numerous sites in the inner and outer Dungeness Bay, the Dungeness River, and six ditches (irrigation and stormwater) to the inner bay. Sites were sampled for fecal coliform, salinity, and temperature. Surface and sub-surface samples were obtained under a variety of environmental conditions. Rensel also conducted circulation and reflux studies.

In order to meet the Class AA marine water quality standard of 14 fecal coliform (fc)/100 mL geometric mean and 43 fc/100 mL 90th percentile, fecal coliform reductions of 41% for west inner Dungeness Bay and 65% for the convergence zone are required during the November - February critical period. A year-round 60% reduction in bacteria is required for Dungeness Bay near the mouth of the Dungeness River. Rensel′s data confirm the TMDL bacteria target value set for the Dungeness River of 13 fc/100 mL geometric mean and 43 fc/100 mL 90th percentile. Bacteria reductions needed in the ditches vary from 33 - 97% during the November – February critical period.

TMDL recommendations for Dungeness Bay include (1) practices to control pollution to irrigation and stormwater ditches and (2) monitoring during the non-irrigation season to determine the extent and location of fecal coliform pollution. For the Dungeness River, actions for reducing bacteria inputs include continuing to implement recommendations in the Water Cleanup Plan for Bacteria in the Lower Dungeness Watershed (Hempleman and Sargeant, 2002).