Thursday, February 2, 2012

Airplane in Flight

Rebuilding our water system has often been compared to repairing an airplane in flight. With 2.5 million people relying on safe, high quality water- the Hetch Hetchy Regional Water System must continue to operate even as it is systemically upgraded to meet seismic standards. The work currently taking place at the New Irvington Tunnel Project is an excellent example of the balancing act that takes place.

The major water transmission pipelines that connect into the New Irvington Tunnel can only be taken out of service individually, and for short periods of time in winter, when demand is typically low. This allows for other waterlines to continue to operate while individual ones are under construction. This also means the construction team only has a limited window of time to complete their work before waterlines must come back into service.

This winter workers have the challenge of replacing three waterlines between October 2011 and May 2012. Each line must be completely drained before workers can demolish and remove the 70 year old concrete and steel pipes. Workers then install new welded steel pipe connections as large as 102” in diameter. The waterlines are then buried until the new tunnel can be connected to them. A fourth waterline will be taken out of service next winter when water demand is again low.

Crews are working hard and are on track to meet the tight schedule this year As we move forward with the New Irvington Tunnel’s critical seismic safety upgrades, we will continue to provide the same high quality water to our customers at the same time.

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