Conclusions

Noble, Xu, Rosenfeld, Largier, Hamilton, Jones, and Robertson, 2003, Huntington Beach Shoreline Contamination Investigation, Phase III: U.S. Geological Survey Open-file Report 03-62, version 1.0

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7. Conclusions

Although the study identifies several possible coastal ocean pathways by which diluted wastewater may be transported to the beach, including internal tide, sea breeze, subtidal flow features and anthropogenic features such as the AES cooling system, there were no direct observations of either the high bacteria concentrations seen in the OCSD plume at the shelf break reaching the shoreline in significant levels or of an association between the existence of a coastal ocean process and beach contamination at or above AB411 levels. The only physical variables clearly identified as being related to surfzone contamination were phase of the lunar cycle, with high values of all three fecal indicator bacteria found preferentially at spring tides; time of day, with high values found at night š particularly for Enterococci; and phase of the tide, with high values found near low tide š particularly for total and fecal coliform bacteria. It is concluded that the OCSD plume is not a major cause of beach contamination; no causal links could be demonstrated. This conclusion is based on the absence of direct observation of links between bacteria in the outfall plume and beach contamination, on analysis of spatial and temporal patterns of shoreline contamination and coastal ocean processes, and on the observation of higher levels of contamination at the beach than in the plume.

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