Sewer Gas: An Indoor Air Source of PCE to Consider During Vapor Intrusion Investigations.
The United States Environmental Protection Agency (USEPA) is finalizing its vapor intrusion guidelines. One of the important issues related to vapor intrusion is background concentrations of volatile organic chemicals (VOCs) in indoor air, typically attributed to consumer products and building materials. Background concentrations can exist even in the absence of vapor intrusion and are an important consideration when conducting site assessments. In addition, the development of accurate conceptual models that depict pathways for vapor entry into buildings is important during vapor intrusion site assessments. Sewer gas, either as a contributor to background concentrations or as part of the site conceptual model, is not routinely evaluated during vapor intrusion site assessments. The research described herein identifies an instance where vapors emanating directly from a sanitary sewer pipe within a residence were determined to be a source of tetrachloroethylene (PCE) detected in indoor air. Concentrations of PCE in the bathroom range from 2.1 to 190 ug/m3and exceed typical indoor air concentrations by orders of magnitude resulting in human health risk classified as an "Imminent Hazard" condition. The results suggest that infiltration of sewer gas resulted in PCE concentrations in indoor air that were nearly two-orders of magnitude higher as compared to when infiltration of sewer gas was not known to be occurring. This previously understudied pathway whereby sewers serve as sources of PCE (and potentially other VOC) vapors is highlighted. Implications for vapor intrusion investigations are also discussed.
University of Massachusetts-Dartmouth, Civil and Environmental Engineering Department, North Dartmouth MA 02747.
Kelly G
KG
Pennell
Madeleine Kangsen
MK
Scammell
Michael D
MD
McClean
Jennifer
J
Ames
Brittany
B
Weldon
Leigh
L
Friguglietti
Eric M
EM
Suuberg
Rui
R
Shen
Paul A
PA
Indeglia
Wendy J
WJ
Heiger-Bernays
Vapor Intrusion; groundwater; indoor air; sewer gas