Vapor Intrusion through Sewer Systems: Migration Pathways of Chlorinated Solvents from Groundwater to Indoor Air

摘要

The presentation will focus on gas phase migration by advection and diffusion of chlorinated solvents into houses through the sewer system. The findings indicate that migration through the sewer system can be a very significant and maybe overlooked pathway for vapor intrusion. If overlooked the result may be unnoticed indoor air problems in houses located outside areas with soil and groundwater contamination. In Skuldelev, Denmark, a plume of chlorinated ethenes (300 m in length) has been detected and delineated in a shallow aquifer. Chlorinated ethenes (primarily PCE) have been detected in the indoor air in 29 houses through repeated monitoring over a 5-year period. The affected houses are located both above the plume and outside the periphery of the plume. The PCE concentrations in soil gas, soil and groundwater have been investigated in detail at the locations of all the affected houses. Comprehensive investigations have been undertaken to map the migration pathways of the contaminants to the indoor air. The following methods have been applied for this purpose: Perfluorcarbon gas tracer test, Formier gas tracer test, thermography, continuous radon measurements, continuous differential pressure measurements, video inspection of sewer line, water and air sampling in sewer catch pits, and repeated sampling from vertical soil gas nests.