New data reveals that LA Sanitation (LASAN) may be underestimating the severity of El Segundo residents’ exposure to hydrogen sulfide in the months following the Hyperion Sewage Spill.

As mentioned in the last update, the South Coast Air Quality Management District (AQMD) is monitoring hydrogen sulfide levels in El Segundo. However, AQMD’s site at St. Anthony Church is more than a mile from Hyperion. Many residents live closer to the plant, and thus AQMD’s air quality data does not fully capture what those residents experienced during the spill.

Despite this, AQMD’s data is useful for calculating how the noxious odors spread throughout El Segundo.  For example, LASAN reports the presence of hydrogen sulfide at 321.5 ppb on August 3, 2021. AQMD data recorded at St. Anthony showed hydrogen sulfide of .33 ppb five minutes later.  The hydrogen sulfide levels recorded at the Hyperion fenceline appear to have dropped to 974 times lower before reaching AQMD’s test equipment. 

When we compared AQMD’s data to LASAN’s data through the end of August, we discovered that hydrogen sulfide levels at the Hyperion fenceline are, on average, 89.55 times higher than the levels recorded at St. Anthony Church.

Using this average dilution rate, we can approximate hydrogen sulfide levels closer to Hyperion on the days and at the times when LA Sanitation failed to test for hydrogen sulfide.  The hydrogen sulfide levels at the Hyperion fence line appear consistently very high—well over the World Health Organization’s standard of 5 ppb in thirty minutes, and over California’s 30 ppb standard for one hour of exposure.  

We gathered this information to calculate the dilution rate because LASAN failed to properly test and reveal the extent of the public’s exposure to hydrogen sulfide for almost the entire month of July.

In addition, LASAN is not testing hydrogen sulfide data at night, when El Segundo residents are most likely to be home. The inversion layer that covers El Segundo most nights causes higher concentrations of air pollutants. AQMD’s data recorded at St. Anthony confirms this—the most significant spikes in El Segundo’s hydrogen sulfide levels usually happen at night.

LASAN also failed to disclose what other pollutants may have escaped into the community in the months following the sewage spill.

PARRIS founding attorney R. Rex Parris sent a letter to AQMD detailing this information and requesting AQMD’s help. The experts at AQMD can calculate the dilution rates and extent of El Segundo residents’ exposure to hydrogen sulfide.  AQMD can also require the disclosure of the other emissions.  This information is crucial to the ongoing investigation into LASAN’s conduct and its effect on hundreds of innocent families.

You can read our letter to AQMD here.

Your attorneys at PARRIS are committed to fighting for El Segundo. If you have not yet joined the lawsuit against LASAN, you have about two months left to protect your rights before the initial six-month deadline on January 11, 2022.

Call PARRIS Law Firm today at 310-362-3921 to speak with our legal team.