Red Line Subway Tunnel Safety
* On Aug. 29, The Times ran an article questioning the safety of the Metro Red Line subway. Since that article was based on a draft report written before all the facts were obtained, and after reading some of the letters to the editor, I feel that clarification is necessary.
Your article and the resultant concerns about concrete thickness were based on an independent consultant’s draft ground-penetrating radar report. Unfortunately, the report is incomplete without required core drillings to confirm the radar data. Once the report was completed, the area needing reinforcement steel plating consisted of 40 feet out of the 10,000 feet inspected.
Public safety is the most important concern of the Parsons-Dillingham team. We are building the system knowing our families will use the subway, and are confident that the subway tunnels are safe. The subway sustained no damage during the Sierra Madre quake in 1991 or the Landers quake in 1992.
The tunnels are really a “tunnel within a tunnel.” The first tunnel holds back the earth while the final, inner concrete tunnel is constructed. To further strengthen the inner tunnel, reinforcing steel is added. Additionally, the concrete used in constructing the subway is 43% stronger than required.
Now for some common sense. Even The Times calls this one of the largest, most complicated public works projects in the nation’s history. For example, the drilling machine weighs 200 tons (equal to the weight of 50 full-sized elephants). Because of the enormity of the equipment, variations in the earth’s density and the closeness of the working quarters, the thickness of any concrete tunnel wall will vary throughout its length. This is normal in tunnel construction. When these variations exceed allowable tolerances, the thin portions are strengthened by adding extra steel reinforcement or as otherwise approved by the designer.
Parsons-Dillingham looks forward to having an impartial group of tunnel experts review this subway. We believe that they will find it is constructed properly and is both safe and structurally sound.
GEORGE B. MORSCHAUSER
Construction Manager
Parsons-Dillingham, Los Angeles
* The current brouhaha over the construction of the Metro Rail Red Line tunnels and the cost overrun contractor scandals present us with an incredible opportunity. The opportunity to re-evaluate and reassess the entire mass transit system now administered by the MTA.
Every line is being engineered for a different technology, different trains, with no ability for cars from one line to be used on another.
Many important places that are well traveled and can be expected to generate a great deal of transit traffic in the region are not now scheduled to be served.
Now that we have a new MTA general manager, the time is ripe to totally reassess this most expensive of all public works projects. It is up to the public to demand a complete and thorough re-evaluation.
DOROTHY GREEN
Los Angeles
