Southern California will spend hundreds of millions of dollars to repair water treatment and wastewater treatment infrastructure damaged in the April 4 Baja Earthquake, which was registered at 7.2 magnitude, state and city officials say.
In the city of El Centro, Director of Public Works/City Engineer Terry Hagen estimated that local public and private interests sustained $25 million in damage, although that estimate could grow. As many as 24 condominium units were evacuated when four of six 2-inch-dia anchor bolts sheared off an empty landmark, a 1924-era water tank. The city awarded an emergency $77,000 contract to remove the tank so that residents could return to their homes. An operating 5-million-gal tank ruptured. “It opened like a can of beans,” Hagen said.
It did not spill water, but was drained anyway, leaving the city to rely on three other intact tanks with a combined capacity of 10 million gal.
At the 8-million-gal-per-day capacity wastewater treatment plant, four of six clarifiers were damaged, concrete cracked and a baffle shook loose. The plant will run at half capacity until repairs are made.
The city’s aging 16-mgd water treatment plant went off-line when sediment plugged the ferric-sulfate pipe system. That prompted the certification and immediate use of a 21-mgd water treatment plant that was recently constructed, but still in commissioning. After a day of sustained aftershocks, a rack drive failed and the rotating center structure was damaged. The plant is now operating at half capacity.
At the El Centro Regional Medical Center, damage to the external wall of the central plant could speed a planned $10-million seismic retrofit. Although the walls were designed for some expansion, the wall joints separated so much that concrete chips fell off the top, according to Mark Obeso, construction supervisor for the hospital.
Farther south, in the border city of Calexico, the damage was even worse. Much of the historic downtown is still off limits as building integrity is being tested after a roof caved in during an aftershock. A broken sewer line is dumping sewage into the river.
The city is using a back-up 5-mgd water treatment plant as the toppling of a clarifier in the 10 mgd plant put it out of commission. Repairs could take as long as three months and $17 million.
Hundreds of aftershocks as large as 5.5 magnitude continue to rock the area and could continue for a month, according to seismic experts.