INTRODUCTION

The Los Angeles County Metropolitan Transportation Authority began construction on the modern day subway in 1987. The Metro Red Line contains three segments.

Segment 1 became operational in January-1993. This route runs from Union Station to MacArthur Park and is comprised of five stations. The stations are Union, Civic Center, Pershing Square, 7th Street/Metro Center, and Westlake/MacArthur Park. The length of Segment 1 is 4.4 miles.

Segment 2A became operational in July-1996. This includes three additional stations and the route runs under Wilshire Boulevard. The stations are Wilshire/Vermont, Wilshire/Normandie, and Wilshire/Western.

Segment 2B is scheduled to open in June-1999. This route turns north at the Wilshire/Vermont station, runs under Vermont Avenue and includes three stations. The stations are Vermont/Beverly, Vermont/Santa Monica, and Vermont/Sunset. Segment 2B turns west at Hollywood Boulevard, continues west past the Hollywood/Highland station, and includes two stations. The stations are Hollywood/Western and Hollywood/Vine. The total length of Segments 2A and 2B is 6.7 miles.

Segment 3 is scheduled to open in May-2000. This route runs west past Hollywood/Highland, turns north towards North Hollywood, and consists of three stations. The stations are Hollywood/Highland, Universal City, and North Hollywood. The length of Segment 3 is 6.3 miles.

I am going to discuss the construction of the twin tunnels of Segment 2B, which began in 1992 and will open in June-1999.

TUNNEL CLASSIFICATION

The first order of business prior to the bidding of the tunnel contracts is to obtain a tunnel classification from CAL/OSHA (Division). CAL/OSHA has the following tunnel classifications as defined below: Extrahazardous, Gassy, Potentially Gassy, and Nongassy.

  • Extrahazardous - classification shall be applied to tunnels when the Division finds that there is a serious danger to the safety of employees and:

    1. flammable gas or petroleum vapors emanating from the strata has been ignited in the tunnel; or

    2. a concentration of 20 percent of LEL* petroleum vapors has been detected not less than three inches from the roof, face, floor and walls in any open workings with normal ventilation.

  • Gassy - classification shall be applied to tunnels where it is likely gas will be encountered or if a concentration of 0.25 percent by volume (5% of LEL*) or more of flammable gas has been detected not less than 12 inches from the roof, face, floor and walls in any open workings with normal ventilation.

  • Potentially gassy - classification shall be applied to tunnels where there is a possibility flammable gas or hydrocarbons will be encountered.

  • Nongassy - classification shall be applied to tunnels where there is little likelihood of encountering gas during the construction of the tunnel.

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