Over the three days in late March, four Los Angeles Times environmental reporters and editors were fan-outed from the housing estate. 10 From properties where debris has been removed by the Army Corps of Engineers, 10 from the gardens of houses with 10 standing in each combustion area.
At each stop, the teams wore vinyl gloves and boot covers and collected five evenly spaced samples with a handheld tool using a 4-inch soil core. In the standing house, sampled it throughout the garden. In the destroyed properties, federal cleanup crews cleaned up the debris and sampled them in footprints of the previous structure, which had shattered up to six inches of soil.
The Times journalist mixed these five samples into a lined bucket to create one “composite” sample to be tested in the lab. This sample pattern is designed to describe the broad soil conditions for each property, as some of the specific properties may be completely lacking metal contamination, and other parts may be heavily contaminated. Combined sampling is a common practice in wildfire recovery.
Between all properties, the team sanitized all soil collection equipment with distilled water and wipes, and changed gloves and boot covers.
Samples were stored in laboratory-provided jars and samples were left refrigerated to 38-40 degrees. At the end of Collection Week, the editor drove the samples to BSK Associates. BSK Associates is a nationally accredited environmental testing laboratory that tested soil on behalf of the government following the 2018 camp fire and the 2024 mountain, park and borell fire.
BSK has tested 17 metals that are most studied in post-fire recovery using methods approved by the Environmental Protection Agency. To do this, BSK used equipment to organize different elements from within the soil by mass and count atoms. Each of these 17 elements has a unique atomic mass, so BSK can determine the concentration of metals, for example, as lead only has an atomic mass of 1.34 trillion grams.
At each stage of the process, our team and BSK meticulously documented the custody of the samples and at each moment, we created a record of our responsibility to store individual samples.
We followed strict soil testing practices. Our team reviewed documents outlining camp and Woolsey fire responses and spoke with soil testing experts who are familiar with standard methodologies for California wildfires.
To locate participants, we used the California Department of Forestry and Fire Prevention damage inspection data and properties that completed debris removal using the Army dashboard to identify standing properties. All participants agree to test their properties and the exact addresses have been anonymized.
The testing methods used by Times are conservative readings. By using composite samples, high levels of contamination from some of the properties may be diluted by relatively uncontaminated sections elsewhere in the property.
Furthermore, cost considerations have led to the Times methodology being different in one important way from typical post-fire soil testing practices. In previous fires, soil testers collected multiple composite samples for larger properties, about one sample per 500 square feet. Our team collected only one composite sample per property, regardless of size.
This means that Times results are likely to miss smaller contamination hotspots for the property.
The Times discovered that two properties cleared by the Army Corps of Altadena are still more contaminated than the state’s typical health-based cleanup goals. One is arsenic, one lead. Altadena’s standing home had arsenic, lead and mercury levels exceeding typical cleanup targets at three of the 10 homes the team tested. The Times found only one read beyond the typical cleanup goal of Pallisard. This is a standing home with a high level of arsenic.
