Cloudy Water Dissipates as Coast Range Tunnel Returns to Service
February 16, 2010
For the last 41 days, the San Francisco Public Utilities Commission (SFPUC) has been without the use of its system's longest tunnel - the Coast Range Tunnel.
The tunnel is used to convey Hetch Hetchy water supply which is 85% of the SFPUC water source, and was put back into service on Sunday--a full week ahead of schedule. It also means that the cloudy water will begin to dissipate as it works its way through the system over the next several days. The SFPUC will resume delivering Sierra snowfall by gravity flow instead of local source water which requires our water treatment plants to increase their flows. This increased flow sometimes results in air bubbles or cloudiness in our drinking water.
The tunnel was put back into service on Sunday--just in time for Valentines Day --a full week ahead of schedule.
One of the many things that happen when you take the water out, naturally occurring methane gas comes in. In 1930, 12 miners died during the construction of the tunnel due to a methane explosion. Therefore, not only did crews have to work 24/7 to complete their tasks on time in horrible weather and changing conditions, this shutdown required taking extra precautions including huge ventilation fans and careful control of ignition sources.
The task of providing water to our customers without the Coast Range Tunnel fell to SFPUC's Water Supply and Treatment division. "When Hetch Hetchy supplies are unavailable, the Harry Tracy Water Treatment Plant and the Sunol Valley Water Treatment Plant must work double time to provide sufficient water to our customers from local reservoirs only," said David Briggs, Water Supply and Treatment Division Manager. "We also employed the first ever simultaneous use of our two major interties with East Bay Municipal Utility District and Santa Clara Valley Water District," he added.
Mother Nature did not help matters. Crews from Steve P. Rados, Inc., PCL Civil Constructors (PCL), and Mountain Cascade Inc. had to work around the clock on a tight schedule during heavy rains and muddy conditions. The Calaveras Fault in the Sunol Valley decided to throw off two small earthquakes during this period.
Just when the end of the shutdown was in sight, Harry Tracy Water Treatment Plant was struck by lightning that burned out some of its electrical boards. Water Supply and Treatment crews worked feverishly to bring the plant back online within several hours.
For more on this story please see the full article at SFWater.org
