How to test soil toxins after LA fire

During the three days in late March, four Los Angeles Times environmental reporters and an editor dispersed in Eaton and Palisades stabbing, collecting 40 soil samples from residential properties: 10 in each combustion zone, each of which was completed by the Army Corps of Engineers, and each Corps of Engineers completed by 10 in each combustion zone, and in each of the combustion zones, there were 10 in each yard of burning zones.

At each site, the team wore vinyl gloves and boot covers to prevent the spread of contamination and collected five evenly spaced samples using a handheld 4-inch soil core handheld tool. At the residence, we sampled throughout the yard. In the destroyed property, we sampled the footprint of the former structure, where federal cleaners cleared the debris and scraped 6 inches of soil.

Times reporters mixed the five samples in lined buckets to create a “composite” sample tested in the lab. This sample pattern is designed to take into account the various soil conditions for each characteristic and as an average level, since part of a given characteristic may be completely free of metal contamination, while the other may be severely contaminated. Composite sampling is a common practice in wildfire recovery.

Between each property, the team sanitized all soil collection equipment with distilled water and wipes and replaced gloves and boot covers, so there was no potential toxin that could accidentally track from one location to another.

We store the samples in a lab-supplied jar and keep the samples at 38-40 degrees refrigerated. At the end of the collection week, our editor drove the samples to BSK Associates, an economically certified environmental testing lab that tested the soil on behalf of the government after the 2018 camp fire and the 2024 mountain, park and Borel fires.

BSK tested 17 metals that are often studied in post-fire recovery using an environmental protection agency approved method. To this end, BSK uses an instrument that classifies different elements in the soil by mass and calculates atoms. Since each of these 17 elements has a unique atomic mass (for example, only lead has an atomic mass of 334 billion, BSK can determine the concentration of the metal.

At each step of the process, our team and BSK carefully record the guardianship chain of samples, creating records at every moment, and individuals are responsible for the safe preservation of each sample.

Times’ approach strictly follows the soil testing practices of previous official wildfire efforts. Our team reviewed documents outlining the responses to the camp and Wolsey fires and spoke with soil testing experts familiar with the standard methods of California wildfires.

To find participants, we identified conventional properties using damage inspection data from the California Forestry and Fire Protection Agency and damage inspection data and characteristics of debris removal using Army Corps dashboards. All participants agreed to test their attributes and their exact address has been anonymous.

The testing method used in the times is conservative reading. By using composite samples, high levels of contaminants can be diluted through relatively uncontaminated parts elsewhere in the property.

Furthermore, Times’ methodology differs from typical postfire soil testing practices due to cost considerations: In previous fires, soil testers would collect multiple composite samples for larger properties, about one sample per 500 square feet. Regardless of size, our team takes only one composite sample for each attribute.

This means that Times results have greater potential to miss smaller pollution hotspots.

The Times found that the Army’s two properties cleaned up in Altadena are still above the state’s typical health-based cleaning targets: one arsenic and one leading. Altadena’s residences In three of the 10 homes tested by our team, the arsenic, lead and mercury content was higher than the typical cleanup target. The Times has only one typical cleanup target in Palisades: a high level of arsenic residence.