The Los Angeles Aqueduct conveys water from the Owens River in the Eastern Sierra Nevada mountains to the city of Los Angeles. The system provides 80% of the water to Los Angeles. Part of the aqueduct system travels through the 5.5 mile (9 km) Elizabeth Tunnel. The San Andreas fault cuts across the tunnel and a major earthquake at this location has the potential to cut off this water supply to the city for over a year.
Ray Hamilton of AMEC made a fascinating presentation of his work using AFT Fathom on the Elizabeth Tunnel at the AFT Denver User Group meeting earlier this month. He went so far as to compare AFT Fathom predictions to those made a century ago by water engineers using slide rules, pencil and paper. Even more fascinating is that his presentation coincided with the 100th anniversary of the first tunnel operation almost to the day.
AMEC was contracted to look at the viability of inserting HDPE pipe into the tunnel to allow for continued flow should the tunnel fracture due to slippage of the San Andreas fault during a major seismic event. Estimates were that the fault could slip by about 11 feet (3.5 meters) and this could potentially cut off all water flow through the tunnel. It was believed an HDPE insert could be used to maintain water flow due to its ability to deform.
Mr. Hamilton compared AFT Fathom predictions of the full tunnel capacity to those made by engineers 100 years ago. The predictions were within 3%.
Mr. Hamilton then looked at different sizes of HDPE pipe and settled on a size that should allow the tunnel to continue to operate after a major earthquake - but at a reduced capacity until the tunnel can be repaired.
We at Applied Flow Technology continue to be impressed with what engineers do with our software. The modeling of the Elizabeth Tunnel certainly held the interest of all the engineers who attended the User Group meeting this month.