Effects of Wildfires on Contaminant Runoff and Emissions


Stormwater Contaminant Loading Following Southern California Wildfires


This goal of this project was to investigate the fate of water quality constituents resulting from southern California wildfires in order to quantify the effects of post-fire runoff on downstream metals and organic constituent concentrations and loads.  Contaminant loading and effects on instream biota were investigated as part of this project.

A regional post-fire monitoring strategy was completed in 2009 that describes an agreed-upon approach for post-fire sampling. This plan was implemented for the first time following the 2010 Station Fire, which burned portions of the Los Angeles and San Gabriel River watersheds.  Two sites were sampled for solids, metals, and PAHs over six storms following the 2010 fires; Tujunga Wash and Arroyo Seco.  Results showed dramatic increases in concentrations and loads of all constituents sampled following storms, but returned to near pre-fire levels by the end of the storm season. The results of this analysis along with additional analysis of post-fire pollutant concentration data for storms dating back to 2003 was accepted for publication in the journal Environmental Toxicology and Chemistry. In addition, post-fire bioassessment data from both the 2003 San Diego county fires and the 2009 Los Angeles County Station fire have been compiled and analyzed to assess fire effects on benthic indices typically used as part of regional bioassessment monitoring.

Future implementation of the regional monitoring plan will be at the discretion of the stormwater agencies and regional and state water boards.