Heal the Bay staff member uses a hand auger to collect sand samples at various depths in the sewage spill zone. Photo: Heal the Bay
Heal the Bay staff members prepare a sand core sample for transport to UCLA for testing. Photo: Heal the Bay

On Tuesday, February 7th, Heal the Bay staff members went to the closed stretch of Manhattan Beach at 21st and the Strand to collect samples for E. coli and enterococcus analysis. We were inspired to proceed with the sample collection and analysis to have an independent look at the contamination at the beach that resulted from the sewage spill on January 15-16, 2006.

A hand auger was used to collect sand samples at one foot, three feet and five feet depths. This was performed at five locations in the closed area and at a reference location at El Porto. The samples (some of which did not smell too pleasant) were placed in sterile 100 ml bottles and transferred on ice to Professor Jenny Jay in the Civil and Environmental Engineering Department at UCLA. Professor Jay and her students completed the analysis of the sand.

Test Results
The results confirmed what the Los Angeles County Sanitation Districts had found: the sand is still highly contaminated in many places. However, an interesting trend was found in the results. We speculated that the one foot samples would have been the cleanest because supposedly clean sand was used to cap the spill site four weeks ago. Also, we thought that samples at 5 feet would be the most contaminated because the Sanitation Districts’ chlorination efforts did not target depths of five feet.

The actual results were surprising:

• The most contaminated depth was at one foot. One sample had an E. coli density of nearly one million bacteria per 100 grams of sand!!! Three of the four samples analyzed had densities of over 100,000 E. coli per 100 grams.

• Almost as surprising was the result that only one of the three feet samples had any E. coli and that was at 5,000 per 100 gms. The Sanitation Districts did not have similar results at three feet, but most of their samples were collected further away from the manhole cover that discharged the sewage during the spill.

• The five feet samples ranged from non-detect to over 50,000 E. coli per 100 gms.

• Perhaps the most critical result, no E. coli were found at the El Porto reference site at any of the three depths so we know that all of the fecal bacteria probably came from the sewage spill.

These were unexpected results. One explanation is that the capping material clearly wasn’t clean. It was made of the sand that was used to contain the sewage spill. The rationale for three feet being so clean was that the area tested must have been dosed pretty highly with chlorine before capping on the day of the sewage spill. At that time, 3 feet deep may have been near the surface. Finally, the five feet numbers may have been lower because of chlorine or bacteria die-off.

Now What? — Cleaning the Sand
Heal the Bay has been pushing for using mechanical mixing and sunlight for disinfection rather than chlorinating the whole beach. The rationale is that the chlorine reacts with all of the organic material and bacteria left in the sand from the spill.  The reaction can lead to the formation of a wide variety of toxic chlorination byproducts that can remain in the sand or migrate to underlying groundwater.  In essence, the chlorine disinfection trades an imminent public health problem for an environmental problem (potential detrimental impacts to animals like sandcrabs and grunion eggs) and a potentially longer term public health concern. Having those toxins contaminate groundwater and remain in the sand doesn’t make sense. Allowing sunlight to disinfect the fecal bacteria and viruses would take more time, but in the long run, is better for the environment and for protecting public health.

In response to the concerns we’ve voiced, the Sanitation Districts will test the effectiveness of mechanical mixing and sunlight on reducing fecal bacteria densities. The only problem is that they started to chlorinate the sand on February 13th. The results of the special study on the effectiveness of sunlight as a disinfectant only will be useful for research purposes elsewhere.

If there is one thing we’ve all learned, containing sewage spills on the beach is a bad idea because it poses a public health threat for weeks to months after the spill. Of course, preventing future sewage spills by insuring that sewer infrastructure is properly maintained and upgraded, back-up power and generators function well when needed, and there is storage capacity at pump stations in the event of a spill, will prevent a Manhattan Beach type spill from ever occurring again.

You can help by visiting our Action Alert to urge the city councilmembers of Manhattan Beach and Hermosa Beach and other affected beach cities to make sure that your right to public health is protected now and in the future.