Projects & Programs
Cumulative Plume Modeling Study, Washington
The Cherry Point industries, consisting of ARCO Products Company (ARCO), TOSCO Refining Company (TOSCO) and Alcoa–Intalco Works (Alcoa) are located near Ferndale, Washington. Approximately nine miles of the Strait of Georgia shoreline from Point Whitehorne and Birch Bay bound it on the north, and Sandy Point and Lummi Bay to the south, is used by the Pacific herring for spawning. In the last 20 years, this stock has been slowly declining, causing various state and federal regulatory agencies to be concerned over its future viability. Cherry Point industries are participating in a number of studies aimed at identifying the cause of this decline.
One PNNL study funded by the Cherry Point industries was The Cumulative Plume Modeling Study. As a part of this study, a three-dimensional hydrodynamic model (EFDC) was set up and calibrated for the study area. The calibrated hydrodynamic model then was used to generate a velocity field to drive the effluent transport model. The effluent plume transport model was set up using the same grid as the hydrodynamic model. The effluent plume transport model was calibrated using dye study data from the site. The models were used to evaluate potential accumulation of effluent. The models were also used to evaluate if cumulative effects of multiple plumes would result in exceedance of water quality standards.
At Alcoa's request, the model was used to evaluate net circulation and transport of effluent/water released from the facilities. This was accomplished by tracking the movement of numerical drogues released from the outfalls. The study showed that the majority of the drogues travel along the coastline with net transport to the south.
Project Highlights:
- EFDC, calibrated using dye study data, was used to conduct the cumulative plume modeling study
- The model showed conclusively that long-term accumulation of effluent does not occur and that adequate flushing is available
- The model showed that individual discharges are separated sufficiently such that cumulative effects are negligible.