Altadenans are finding common ground when it comes to returning to their gardens after the Eaton fire, and a trio of experts have banded together to help.

For those who still have gardens standing along with their homes, the question of contaminated soil supercedes any thoughts of what to plant or whether or not to eat that orange from their tree. Local groups, from Eaton Fire Survivors Network, Eaton Fire Residents United and UC Master Garden Los Angeles are working with nonprofits to answer such questions as what levels of lead or other metals are safe for children, adults and pets and what long-term health risks are people facing post-Eaton fire.

But it does start with soil. UCLA, Tree People and Mount St. Mary’s University in Los Angeles have teamed up with Master Garden Los Angeles to offer free soil testing and resources and solutions for affected residents. A pop-up they held at the Altadena Grocery Outlet on May 10.

About 120 people registered to have their soil samples tested, with many submitting two to three different samples from their property, according to Kristy Brauch with UC Master Gardeners.

Rep. Judy Chu, D-Pasadena; Victoria Knapp, chair of the Altadena Town Council; and Vannia De La Cuba, deputy mayor of Pasadena also attended.

Valerie Borel, coordinator for the UC Master Gardener Program, said master gardeners have been at farmers markets, festivals, fairs and other events adjacent or near the burn areas in the week after the fires. They’ve taught workshops on the impacts of ash and smoke on backyard produce and soil, as well as post-fire tree assessments. Borel said they will also help run workshops on creating fire-resilient gardens and landscapes in the next few months.

UC Master Gardeners know the local landscape well, having partnered with Altadena Community Garden for more than 25 years.

Borel said gardeners should first find out what is in their soil, including the distance from burned areas, fuel types burned, fire intensity, duration, and wind direction, which affect the composition and amount of deposited particulate matter.

A curated primer on minimizing risks, safe exposure levels and food contamination is available through the group’s fire recovery resources online, “After the Fire: Home Garden and Fruit Tree Safety.”

The Master Gardener resource guide also includes information on produce safety, backyard chicken and eggs post-fire, and resources and how-to’s on soil testing.

Soil test results will include how much lead, arsenic, cobalt and copper, as well as nickel, mercury, and chromium are found in the samples.

Igor Bronz, research senior coordinator with Tree People, advised residents at the Grocery Outlet event on their contamination level results, and what steps to take next, since these depend on personal risk tolerance and costs.

“We’re looking for heavy metals in soil,” Bronz said. “These are stable in the soil, so if you don’t do anything to remediate them, they stay there.”

So while these “forever chemicals” don’t dissolve into the surface, groundwater or into plants, removing just a few inches of contaminated soil is usually sufficient.

“If, for lead, you’re finding 1,000 mg/kg, definitely remove,” said Scott Fendorf, professor of earth sciences at Stanford University. “If you’re finding 100-200 mg/kg, then there’s no need, just top cap and do a thicker top cap to be extra safe.”

Fendorf discussed soil safety and remediation options at an online meeting sponsored by the Eaton Fire Survivors Network on April 24. The Discord network is made up of more than 2,000 displaced Eaton Fire survivors.

Fendorf, who has tested and will continue to monitor Altadena’s soil post-fire, said no matter what landscape you want, “mostly what you want is cover,” top capping, or covering contaminated soil with a barrier such as clean compost, topsoil or mulch.

“Top cap takes care of a lot, and if you remove soil, you don’t need to remove very much, just a surface layer,” he said. “Recap if you see erosion.”

Worries of children touching the soil and putting it in their mouths or pets tracking in contaminated soil is mitigated by this top layer, which works as a barrier from whatever particles are in the soil. This concern comes weeks before the Pasadena Unified School District released soil testing results for its schools, with some showing elevated levels of certain substances.

“Wash your hands really well with soap and water after digging in yard, and wear an N-95 mask if you see dust in the air,” Fendorf said.

To that point, he doesn’t recommend using leaf blowers in town.

The good news for thrifty gardeners is that top capping doesn’t have to be expensive or complicated. Some cities give away mulch for free, although recipients are sometimes limited to its residents. Store-bought redwood mulch works well too.

The UCLA/Tree People/Mount St. Mary’s team said they have more than 500 people sign up with them to stay updated on soil collection and testing dates as well as workshop and webinars on other topics, including choosing fire-resilient, native plants.

“Compost and mulch is a suggested solution to improving soil health by researchers and promoted by the Master Gardener team,” Brauch said.

Amending marginally contaminated soil with compost will break down chemicals.

Other tips to get your garden growing after the fires:

Use low-impact irrigation methods. Drip irrigation or soft sprayers to stop soil particles from splashing onto vegetables.

Consider raised garden beds. Numerous studies have found raised garden beds have significantly lower levels of arsenic, cadmium and lead than in-ground gardens.

Explore mycoremediation. The soil in the Altadena Community Garden will be laid out with oyster mushroom mycelium after soil scraping, and installation of new soil. The mycelium spread will then be covered with straw and left to sit for about two months. This treatment breaks up toxic substances that may still be in the soil.

Fruits and leafy vegetables should be safe to eat after rinsing. And while master gardeners say disasters happen, they remind people that the wildfire damage to the gardens of the burn scar is not permanent.