Problems Encountered on the Upper Reach of the Northeast Interceptor Sewer Project
Abstract
The Upper Reach segment of the Northeast Interceptor Sewer (NEIS) is a 3.2-km-long tunnel excavated in interbedded marine sedimentary deposits with approximately 40 m of cover. The tunnel was initially classified by Cal/OSHA as “potentially gassy.” During excavation, high levels of hydrogen sulfide and methane were encountered, prompting Cal/OSHA to reclassify the tunnel as “gassy.” In addition, the tunnel excavation encountered an abandoned, 100-year-old water tunnel known as the “Narrows Gallery.” This existing tunnel was completely full of water and under 30 m of hydrostatic head. This paper will discuss the unanticipated difficulties and design solutions implemented to construct a gassy tunnel exposed to high volumes of water.
2005
Steve Dubnewych
Jacobs Associates
Michael McKenna
Jacobs Associates
John McDonald
Traylor Bros., Inc.
Rajni Patel
City of Los Angeles, Bureau of Engineering