Redding / Chico area — Researchers and regional waterboard staff described multi‑year post‑fire sampling in Northern California that links metal export and certain organic contaminants to the intensity of burning and the presence of burned structures.

The Central Valley and Regional Water Boards and university teams have sampled runoff after the Carr Fire (2018), the Camp Fire (2018), the North Complex (2020) and more recent fires including the Dixie and Park fires. Presenters said the strongest, most persistent chemical signals appeared where fires destroyed large numbers of structures.

Why it matters: regional sampling and campus research indicate that destructive urban fires can create a different contaminant mix than wildland fires alone. That has implications for debris removal, public‑health outreach and which analytes managers prioritize for rapid sampling after an event.

What the monitoring and research found: Central Valley Water Board and collaborating researchers reported consistent patterns across several fires:
- Metals: Many post‑storm samples showed elevated metals compared with pre‑fire baselines when available. Central Valley staff and CSU Chico researchers reported repeated increases in iron, manganese and aluminum; the Camp Fire and other heavily structural fires were also associated with zinc, lead and chromium spikes. As Sandrine Matayzek of CSU Chico summarized, in storm runoff after the Camp Fire the team “documented an increase in metal concentrations after burning with increases in concentrations 1 to 3 orders of magnitude for zinc especially, lead, and chromium.”
- Ash sources and fingerprints: CSU Chico researchers and Central Valley staff found that different ashes have distinct signatures. Vehicle and structure ash commonly contained far higher total metal concentrations (for example, titanium, zinc and copper) than burned vegetation or soils, suggesting that vehicles and buildings are important metal sources in urban fire runoff.
- Organics and emerging contaminants: The CSU Chico team detected pentachlorophenol (PCP) in most early runoff samples from the Camp Fire — the researchers reported PCP in roughly 90% of first‑flush samples — and flagged it as a compound of concern because it can be a precursor to dioxins. High‑resolution screening also found early pulses of PFAS in runoff that tapered over time in the Camp Fire case. Researchers emphasized the value of non‑targeted screening to reveal contaminants not anticipated in standard lists.
- PAHs and structural loss: Central Valley monitoring showed PAHs at multiple locations during the Camp Fire where structure loss was dense; those detections were less common after fires with lower structure loss.

Sampling design and timing: Teams emphasized the importance of fast, storm‑event sampling. Many chemical signals — PFAS pulses, PCP and other urban organics — were largest in the first flushes immediately after initial storms and then decreased over subsequent sampling rounds. CS UC Chico and Central Valley Water Board teams said continuous turbidity monitoring and coordinated stream gauges helped target sampling times and catch peaks.

Practical takeaways for managers: Researchers suggested the following actions for future post‑fire response:
- Prioritize rapid first‑flush sampling in watersheds with concentrated structure loss; these areas are most likely to show elevated metals and urban organics.
- Use ash characterization (structure ash, vehicle ash, vegetation ash) to prioritize analytes in nearby waterways. Vehicle and structure ash tended to carry higher metal burdens.
- Include both targeted analyte lists (metals, PAHs, PCBs) and non‑targeted high‑resolution screening to detect unexpected contaminants such as PCP or PFAS.
- Pair grab samples with continuous sensors (turbidity) and existing stream gauges so sampling can capture rising limbs and peak flows that transport the highest contaminant loads.

Researchers noted remaining questions: how long elevated concentrations persist in receiving waters, whether specific contaminants are bioavailable and bioaccumulate in local food webs, and how best to integrate non‑targeted results into regulatory decision frameworks. Presenters urged more pre‑fire baseline sampling in high‑risk watersheds so post‑fire changes can be compared to local background.

Ending note: Northern California experience shows urban fires can shift runoff chemistry in ways that differ from wildland fires alone. Local managers and scientists said investments in near‑term event sampling, ash characterization and paired continuous monitoring will make post‑fire assessments more useful for public‑health and recovery decisions.