Publication Summary

This report presents a comprehensive assessment by the Washington State Department of Ecology of fecal coliform bacteria sources to Grays Harbor. This study includes quantification of sources of fecal coliform, levels of contamination, pollutant transport mechanisms, and die-off within Grays Harbor. Shellfish growers in the outer harbor are experiencing repeated temporary closures, due to violations of fecal coliform discharge limits in existing point source and nonpoint sources of fecal coliform.

This report presents a comprehensive assessment by the Washington State Department of Ecology (Ecology) of fecal coliform bacteria sources to Grays Harbor. This study includes quantification of sources of fecal coliform, levels of contamination, pollutant transport mechanisms, and die-off within Grays Harbor. Shellfish growers in the outer harbor are experiencing repeated temporary closures, due to violations of fecal coliform discharge limits in existing point source and nonpoint sources of fecal coliform.

A numerical model of fate and transport of fecal coliform in Grays Harbor was developed. The model shows the effect of nonpoint loading events due to high runoff, as well as the potential impact of point source discharges of fecal coliform. Results of the model confirm the appropriateness of conditional closure actions taken by the state Department of Health to protect against potential contamination of shellfish that are harvested from Grays Harbor. Model results suggest that expansion of conditional closures to other areas or for longer periods may be justified.

During the study year, May 1, 1997 through April 30, 1998, most of the fecal coliform loading to Grays Harbor came from the Chehalis River. Most of the load from the Chehalis River originates in the upper watershed above the town of Porter. Loading of fecal coliform from tributaries would need to be reduced by approximately 65 percent for Grays Harbor to meet water quality standards. The Chehalis River is the most important single loading source that requires reduction, followed by the Humptulips, Wishkah, and Hoquiam rivers. Collectively these tributaries account for approximately 80 percent of the required reduction in loading for Grays Harbor to meet water quality standards.

The Weyerhaeuser Cosmopolis Outfall 1 (Weyco 1) at times exceeded the combined loading from all other sources, and on average accounted for almost 4 percent of the total load for the study year. During the times when the Weyco 1 discharge was in compliance with its permit, it represented a relatively minor contribution of loading compared with other sources. The highest loading event from Weyco 1 occurred on July 24 and 25, 1997, during which the loading from Weyco 1 accounted for more than 95 percent of the total load from all sources. For Weyco 1, the current permit limit of 20,000 colonies per 100 ml was found to be inadequate to protect water quality in inner Grays Harbor. A daily maximum limit of 14,000 colonies per 100 ml was found to satisfy the requirement of exceeding the 90th percentile standard no greater than 10 percent of the time during a 24-hour period.

Link to EIM data for User Study ID GPEL0007