Author(s)

B.M. Ghadiali, J.B. Putnam, C.W. Stark & D.J. Sperry

Abstract

Methane gas has frequently been encountered during tunneling for the new Metro Red Line in Los Angeles. Field explorations during final design of the Mid-City Segment identified high concentrations of hydrogen sulfide (^S). Like methane, H^S is flammable. Unlike methane, I^S is highly toxic at relatively low concentrations and has a noxious odor at extremely low concentrations (2ppb). Additional studies included gas extraction testing; gas reservoir modeling; a data search for other known soil gas occurrences in the future tunnel development area; and a hazard evaluation was performed to analyze the feasibility of tunnel and station construction and operation

Keywords