Wastewater effluent dispersal in Southern California Bays

Uchiyama, Yusuke; Idica, Eileen Y.; McWilliams, James C.; Stolzenbach, Keith D.

Wastewater effluent dispersal in Southern California Bays

Type

Article

Authors

Uchiyama, Yusuke
Idica, Eileen Y.
McWilliams, James C.
Stolzenbach, Keith D.

Date

2014-03

Abstract

The dispersal and dilution of urban wastewater effluents from offshore, subsurface outfalls is simulated with a comprehensive circulation model with downscaling in nested grid configurations for San Pedro and Santa Monica Bays in Southern California during Fall of 2006. The circulation is comprised of mean persistent currents, mesoscale and submesoscale eddies, and tides. Effluent volume inflow rates at Huntington Beach and Hyperion are specified, and both their present outfall locations and alternative nearshore diversion sites are assessed. The effluent tracer concentration fields are highly intermittent mainly due to eddy currents, and their probability distribution functions have long tails of high concentration. The dilution rate is controlled by submesoscale stirring and straining in tracer filaments. The dominant dispersal pattern is alongshore in both directions, approximately along isobaths, over distances of more than 10. km before dilution takes over. The current outfall locations mostly keep the effluent below the surface and away from the shore, as intended, but the nearshore diversions do not. © 2014 Elsevier Ltd.

Citation

Uchiyama Y, Idica EY, McWilliams JC, Stolzenbach KD (2014) Wastewater effluent dispersal in Southern California Bays. Continental Shelf Research 76: 36–52. Available: http://dx.doi.org/10.1016/j.csr.2014.01.002.

Acknowledgements

We thank our colleagues Florian Lemarie, Jeroen Molemaker, and Alexander Shchepetkin for their help in preparing the meteorological fields and developing the modeling capabilities. We also thank Burt Jones (USC, KAUST) and George Robertson (OCSD) for guidance on effluent plumes. We appreciate support from the Office of Naval Research (N00014-12-1-0939), the Orange County Sanitation District, the National Oceanic and Atmospheric Administration (A11NOS0120029) through the Southern California Coastal Ocean Observing System, and the Grant-in-Aid for Scientific Research (24560622).