Offshore Winds May Be Cause of Bacteria Surge

Re “Bacteria Spike a Wind Effect?,” Jan. 9:

There is a another explanation for the bacteria spike along the beaches that was seen recently during the Santa Ana wind condition that was not addressed in the article. The sewage plume from the Orange County Sanitation District outfall pipe could be the culprit. In February 2002, the sewage plume was seen higher up in the water column and closer to shore than usual in the Newport submarine canyon offshore from the Newport Pier.

It was this observation that led to the policy decision of the sanitation district in March 2002 to disinfect its sewage before release into the ocean. This observation of the sewage plume coming closer to shore was during a Santa Ana wind condition, similar to the current circumstance.

Santa Ana winds bring the sewage plume closer to shore because the wind is blowing the surface of the ocean water out to sea. The deeper ocean waters then are drawn to the shore to replace the surface water that is being blown out. The sewage plume exists in the deeper water and is thus drawn toward the shore. The disinfection of the sewage before release will disrupt the normal readings of the different types of indicator bacteria. Enterococci, being more resistant to disinfection, thus may be seen without the other indicators being present.

This all goes to show that it was a good decision of the sanitation district to give up its waiver from the full secondary treatment requirements of the Clean Water Act. We will all feel more comfortable with a higher degree of treatment of the sewage. Then we might not have periodic surfacing of the pathogens from the sewage making their way to the beaches during certain weather conditions.

Jan D. Vandersloot, M.D.

Director, Ocean Outfall Group

Newport Beach