Responding to Post-Wildfire Water System VOCs and SVOCs

Abstract

The 2021 Marshall Fire burned 593 properties within the City of Louisville, CO, and over 1,000 properties total. Responding to fire impacts on the drinking water system, Louisville developed a sampling and flushing recovery plan to address volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs). Of the 882 samples collected and 94,469 individual VOC and SVOC analyses conducted, 528 (0.56%) analyses were above the method reporting limit, and 31 of those (0.03%) exceeded an MCL. VOC analysis alone captured 85% of all detections and captured 100% of all MCL exceedances. Benzene was not a comprehensive surrogate for the presence of all VOCs detected in Louisville. Flushing reduced fire-related contamination below health limits in Louisville's distribution system. After one flush, > 95% of samples were below the MCL; all samples were below the MCL after a second flush. Key findings are summarized for water systems preparing for and responding to wildfires.