Credit: Photos: Psomas
An asbestos cement pipeline was sheared due to a 5-foot horizontal offset at the fault line during the Landers, Calif., earthquake.
Above: This shows how easy it is to bypass a damaged tank when the inlet/outlet pipes are above grade. Right: Sloshing water caused a lateral force on the effluent launders for this clarifier, shearing the support connections at the perimeter.
Earthquakes are not predictable, and they certainly are not preventable. So how can engineers responsible for lifeline facilities prepare for these often devastating natural disasters?
In late January, the American Society of Civil Engineers (ASCE) sent three teams of engineers to the tsunami disaster zone in Southern Asia to help answer that question. They visited Thailand, Sri Lanka, and India to collect firsthand information on the massive damage wreaked by the December 2004 magnitude 9.0 earthquake and tsunami that left nearly 400,000 people missing or dead in hundreds of coastal communities.
This journey is just one of several overseas trips taken over the past two decades by members of ASCE's Technical Council on Lifeline Earthquake Engineering (TCLEE). Lifelines are the critical systems and facilities that provide water and wastewater, communication, electric power, liquid fuel, natural gas, and transportation services to our communities. TCLEE was formed to give engineers the opportunity to document quake damage and incorporate this information into facility design.Documenting Quake Damage
Members of the TCLEE committee have traveled the world to investigate earthquake damage to vital facilities. Reports were prepared from trips to Algeria, Turkey, Peru, India, Mexico, El Salvador, Taiwan, and Japan, and from the sites of domestic earthquakes as well. These reports are used to encourage engineering professionals to consider the impacts of earthquakes in the planning, design, and operation of lifelines.
During the trip to the tsunami disaster zone, the Thailand team visited the Patong wastewater treatment and pumping station, where the tsunami waters flooded the sewage system. Salt water flooded coastal pumping stations and was pumped to the activated sludge treatment plant, causing the system to fail. In addition, six of 13 pump stations were flooded and remained out of service, causing raw sewage to flow into the bay. The tsunami also destroyed coastal roads, damaged water mains, and damaged power/communication facilities. The team also toured the severely flooded navy base near Khao Lak, where power poles were knocked over, the main water treatment plant was flooded, and power generation severely damaged.
The traveling teams, made up of geotechnical, structural, power systems, and water/wastewater engineers were looking in particular for lifeline system vulnerabilities. The teams also examined how breakdowns in lifelines can affect each other. A water main break can cause a road washout; a road or bridge closure can increase response times and even cause some damaged lifelines to go unrepaired. A tank failure can leave firefighters with no water to fight fires.
TCLEE members, who come from the United States, Canada, Europe, and Asia, look for success stories and lessons learned, what worked, and what didn't. They gather performance data—both good and bad—in order to provide information for practitioners to improve lifeline systems performance.Speeding Earthquake Repairs
Earthquake damage cannot be entirely prevented, and as a result, must be as easily repairable as possible. Systems should be designed accordingly. For instance it is easier to repair above-grade than below-grade utilities. TCLEE recommends that public works departments provide for system redundancy and isolation, consider bypass and detour routes, and conduct earthquake vulnerability assessments. Here are some success stories of municipalities that used these recommendations.
On June 28, 1992, a magnitude 7.5 earthquake struck the high desert area around Landers, Calif. This caused a surface rupture with up to 20 feet of horizontal displacement and 6 feet of vertical displacement. In the town of Landers, there were horizontal displacements of 12 feet and vertical displacements of 2 feet.
There were numerous pipeline breaks in the Landers area, mostly to small-diameter asbestos cement pipe that was easily sheared by the fault offsets. Pipeline repairs were complicated by the fact that the displacements created a condition where the ends of the break no longer lined up. Repair crews had to realign up to 100 feet of the undamaged pipeline, significantly lengthening repair times.