Preparing for disasters: lifeline vulnerabilities in earthquake-prone areas.
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 Pa-tong 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.
Storage tanks in the Landers area also sustained damage. One was a 210,000 gallon bolted steel tank built in 1979. It received water from two onsite wells and provided water to a booster pumping station. Tank damage included a horizontal bulge, commonly known as elephant's foot, around the base. This caused a failure of a number of the bolts and a tear at the inspection access hatch. However, since this tank had above-grade inlet/outlet piping, it was easily bypassed by connecting the onsite wells directly to the booster pump. This remedy restored water service to the system within a few hours.
On Jan. 17, 1994, the heavily populated urban area in and around Northridge, Calif., was struck by a magnitude 6.7 earthquake, resulting in more than $20 billion dollars in damage. This event caused significant damage to the infrastructure, including the water system.
One unique aspect of the recovery effort was the speedy repair of damage to an 85-inch-diameter influent pipe entering the Metropolitan Water District's Jensen Filtration plant. The earthquake caused a welded joint to crack and start to leak. Fortunately, the water district has its own pipe fabrication plant and was able to quickly manufacture two 5-foot sections of pipe. The new pipe was installed within 48 hours after the earthquake, quickly returning the plant to service.
On Oct. 17, 1989, a magnitude 7.1 earthquake occurred in the mountains 20 miles south of San Jose, Calif. This event caused significant infrastructure damage throughout the San Francisco Bay Area and the Santa Cruz region. At the Palo Alto wastewater treatment plant, wave action in a clarifier broke connections of troughs, causing them to fall into the water, rendering the clarifier useless. However, adjacent to the damaged clarifier, there was an identical unit that was out of service. Because it was dry, it remained undamaged. As a result, the agency was able to divert sewage to the empty clarifier and immediately restore service.
In the San Francisco Bay Area, earthquake preparedness recommendations that have come out of the TCLEE international investigations (along with those of other earthquake organizations) currently are being implemented in the form of a major water system retrofit program. The East Bay Municipal Utility District is nearing completion of a 10-year, $189 million seismic improvement program to protect the district's ability to transport, treat, and deliver water throughout its 325-mile service area. Where pipelines cross fault zones and a break cannot be avoided, the district is constructing a bypass system in order to circumvent a break after it happens. The Claremont Corridor Seismic Improvement Project is a two-year effort to construct a permanent bypass tunnel (known as the Short Bypass Tunnel) where the Claremont Tunnel crosses the Hayward Fault.
As members of the TCLEE continue their travels around the world, the lessons learned from the disaster sites they visit will continue to translate into improved lifeline system performance to help communities quickly recover from earthquake devastation.
--Edwards is the vice president of Psomas, based in their San Diego office. As the national chairman of the Earthquake Investigation Committee of TCLEE, he organized the engineering teams sent to investigate the tsunami disaster and led the team sent to Thailand.
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|Title Annotation:||Pipeline construction & maintenance|
|Date:||Jun 1, 2005|
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