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.
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.