Posted March 5, 2021
Written by Ignacio Dayrit
Since the turn of the 21st century, California cities and developers have successfully and safely reused urban sites for housing. For sites potentially compromised by vapor intrusion (VI) - where contaminants in the subsurface can volatilize and enter buildings through cracks on the floor, joints, walls and pipes - California regulatory agencies typically applied a 0.001 attenuation factor (AF) to estimate the concentration of vapors entering proposed residential sites. In 2015, the U.S. EPA proposed a guidance AF of 0.03. There has been little discussion on the cost impact of the 0.03 AF to VI response costs, which currently are the responsibilities of cities and developers, though it is expected that they will increase substantially. State agencies should resolve their differences expeditiously, look beyond their silos, and realize the unintended impacts of this new policy.