While the delays pushed the project completion date to December 2015, DWP still needed the East Reservoir and associated tunnel piping system finished by Nov. 21, to fulfill the EPA requirement that water departments cover all open reservoirs by the end of the year or face an $11,000-per-day fine.

To meet the rushed schedule, Quinones says WOL used things like "good old-fashioned overtime" and an extra work shift. That combined with an on-site batch plant, built by concrete supplier Catalina Pacific, helped avoid the pitfalls of transporting the concrete mix. "To avoid trucks getting caught in traffic and us missing concrete when we need it here, it was decided that a concrete plant would be the best thing," Quinones says.

Seven trucks mixed the basin's 75,000 cu yd of concrete. The plant also helped keep concrete temperatures low, so they could deliver it to the project at around 60˚F, says Steve Lode, senior operations manager for Catalina Pacific.

"We kept the temperature down through the utilization of chilled water and shaved ice," adds Lode. Water was cooled to a temperature of about 35˚F while a wood-chipper-like device crushed ice and blew it into the batch. Everything went together "like a giant snow cone machine," Lode says.

Once the concrete mix arrived from across the jobsite, it had to be kept cool to avoid fractures during curing.

"One of the biggest challenges has been thermal control [against] the cracking of concrete slabs," says Robert Brouses, WOL's senior project manager. "Sometimes there are patterns, but for the most part, [cracks] are random."

With a water-bearing structure, shrinkage crack control is critical, says WOL's Quinones. Though cracks cannot be eliminated, they can be minimized and managed by controlling the heat of hydration given off during curing. This is accomplished by lowering the temperature of the concrete as it sets.

SSC's crews strategically placed cooling tubes circulating 35˚F to 40˚F chilled water throughout the reservoir. A team of four workers also mapped each crack by hand, using tape measures and gauges. They scoured the reservoir's walls and slabs, looking for any crack larger than .004 in. across, or about the thickness of a human hair. Crews injected nearly 76,000 of these cracks with an epoxy filling.

Sinkhole-prone Alluvium

Construction workers numbered 180 per day, on average, both for the reservoir and the tunnel. Crews from Michels Corp., Brownsville, Wis., have been digging the 2,900-ft-long tunnel and laying the 8-ft-dia pipe that will deliver water from DWP's North Hollywood Pump Station to the new reservoir.