U.S. Geological Survey
Open-file Report 03-62
Version 1.0

Huntington Beach Shoreline Contamination Investigation, Phase III

Coastal Circulation and Transport Patterns: The Likelihood of OCSD's Plume Impacting Huntington Beach Shoreline

By
Marlene Noble, Jingping Xu, Leslie Rosenfeld, John Largier, Peter Hamilton, Burt Jones, and George Robertson

Note: this report is an executive summary. You can also see the full version: USGS Open-File Report 2004-1019.

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Abstract

A consortium of agencies have conducted an extensive investigation of the coastal ocean circulation and transport pathways off Huntington Beach, with the aim of identifying any causal links that may exist between the offshore discharge of wastewater by OCSD and the significant bacterial contamination observed along the Huntington Beach shoreline. This is the third study supported by OCSD to determine possible land-based and coa

Although the study identifies several possible coastal ocean pathways by which diluted wastewater may be transported to the beach, including internal tide, sea-breeze and subtidal flow features, 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. 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 plume-beach links, on analysis of the 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.

1. Background

The beaches off Huntington Beach ( Figure 1a - 2.41MB PDF file ) were closed or posted for several months in the summers of 1999 and 2000 because bacteria levels in the swash zone exceeded beach sanitation standards contained in California Health and Safety Code ¤115880 (Assembly Bill 411, Statutes of 1997, Chapter 765; AB411) for extended periods. Because these closures and postings occurred during the peak of summer seasons, they had a major impact on the local, recreational and business communities. There were a wide variety of studies conducted during Phase I (OCSD, 1999) and Phase II (Grant et al., 2000) of the Huntington Beach Shoreline Contamination Investigations, but specific sources for many of the contamination events that caused beach closures and postings could not be determined. However, possible contamination pathways from upland sources, adjacent estuaries and the coastal ocean were identified. In particular, it was suggested that bacteria-rich effluent from the Orange County Sanitation District‰s (OCSD) outfall plume might be brought to shore through several coastal ocean pathways. Bacteria from this effluent plume might then account for the contamination events observed along the Huntington Beach shoreline. To identify and evaluate potential coastal-ocean pathways, OCSD formed a Technical Advisory Committee (TAC) to help design and oversee a Phase III study for the summer of 2001. The TAC formed an ad-hoc committee consisting of regulators, research scientists, environmental groups and interested citizens. It was responsible for considering historical contamination patterns, evaluating known coastal ocean processes and obtaining public comments to determine processes that were most likely to contaminate the beach in summer.

Download the entire 35-page paper of03-62.pdf as a single large PDF file (9.4 MB)

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