New $78-Million Water Treatment Plant Takes the High Ground
As Hurricane Irene rumbled toward the Northeast last August, crews at the Canoe Brook Water Treatment Plant in Millburn, N.J., scrambled to defend two potential casualties—the existing 90-year-old treatment plant and the construction site of its 47,000-sq-ft replacement. The crews knew that in the aftermath of major storms like Irene, which turned out to be one of worst in New Jersey's recent history, the potential for damage was high.
The old facility near the banks of Canoe Brook, by its confluence with the Passaic River, wound up taking a direct hit. Waterways crested well above flood stage and swamped the plant's pump and switch equipment, shutting down its filtration operation temporarily and impairing the water supply for seven nearby municipalities. But the new project, which was then focused on the foundation, only saw stormwater collect in open excavation areas and made it through the storm intact.
"We had a lot of cleanup and a lot of pump-out to do, but thankfully the new construction did not get flooded," says Bob Biehler, engineering project manager for the plant's operator, New Jersey American Water, Voorhees, N.J.
That was one of the results that the planning team had aimed for when they chose to site the facility on higher ground, outside of the 100-year-old floodplain. The biggest push for the $78-million project came not from Mother Nature, but from Uncle Sam and the need to meet stricter federal water quality standards that go into effect this year.
Over the years, regulators have been "ratcheting down permissible levels of disinfectant by-products in our water," including chlorine, says Dave Pringle, campaign director for advocacy group New Jersey Environmental Federation, based in Belmar and Montclair, N.J. While chlorine is effective at killing waterborne bacteria, it also reacts with other naturally occurring organic matter, creating acids and substances—some of which are carcinogenic, he says.
In some cases, the new regulations halve from past levels the allowable amounts of such by-products in drinking water. These changes particularly affect New Jersey, the most densely inhabited state and one whose population, "more than any other state, literally lives on top of and right next to our drinking water," Pringle says. This often forces extensive disinfecting efforts.
The new regulations called for a "gut check" at Canoe Brook, says Suzanne Chiavari, vice president of engineering for New Jersey American Water. "We knew the existing plant from the [1920s], even though it was upgraded over the years, just wasn't robust enough to be able to deliver that water quality day in and day out because of fluctuations in raw water quality," she says.
The utility considered renovating and flood-proofing the existing plant or closing it outright. "Through a thorough engineering analysis, we determined that building a new plant on the same property at a higher elevation was our least costly alternative to delivering the quality of water to meet the regulation," Chiavari says.
New treatment equipment was also needed to curb the "brown water" problem that occurred last summer after a major algae bloom developed in a feeder reservoir.
The project team of CDM Smith, Cambridge, Mass., as design-builder and Hatch Mott MacDonald, Milburn, N.J., as design and permitting sub consultant, broke ground on the new facility in January 2011. An earlier phase involving construction of a new 2-million-gallon, clear well water tank on the site took place in late 2010.
Excavation and foundation work on the main facility progressed through the summer, followed by erection of structural steel, reinforced concrete and masonry block, along with the installation of one pre-engineered metal structure, Biehler says. The team passed the halfway mark of construction earlier this year. When completed this summer, the new facility will be able to pump nearly 14 million gallons of water daily to local customers.
The project features a 24,000-sq-ft treatment building, an 11,000-sq-ft facility with pumping equipment and water basins and several smaller structures in addition to upgrades for another pumping station on site.
The facility is aiming for LEED certification through natural lighting, materials recycling, power monitoring and other energy and water-efficiency measures, says Bill Getting, principal at CDM Smith. "The architectural design of the facility also has some curb appeal," he adds.
Construction has gone smoothly, in part because the project team met a primary challenge early on by maximizing the use of only five acres of available land. Much of the 500-acre property contains reservoirs, wetlands and wildlife, which narrowed the choice for a staging and storage area used by the utility's infrastructure repair crews. The site that was chosen was deemed the best choice partly because it is elevated, Getting says.
The team also had to work around the existing plant, which remains in use, Biehler says. "There are a lot of very old structures here, and that really makes the site the biggest challenge," he says.
Another hurdle was replacing the plant's clear-well tank, which holds treated water for distribution. Demolition of the old tank and building the new one on site began months earlier to take advantage of lower customer water usage during late fall and winter, Getting says.
The prestressed concrete structure ended up being one of the most innovative project features because of its "tank-in-tank" design, he adds.
The site constraints forced the alternative design, Chiavari says. "We didn't really have room to put in two tanks," she says.
The design has an inner 1-million-gallon capacity tank encircled by a second outer tank with equal volume, each with its own piping and flow systems. This enables them to operate together or independently, Biehler says. "They're piped in such a way that we could take one of those tanks out of service for inspection or maintenance" and not interfere with normal water delivery, he says. "If that's your only tank, and you have to take it offline, then you're out of business." The team hooked up the new tank to the existing plant in early 2011.
Crews are also installing new technology to help the plant meet tighter federal standards. It includes "pre-ozone" treatment equipment in the pump building that first oxidizes biological materials in the water, helping to improve taste and odor, and lightening the load for later filtering treatments. "The pre-ozone filtration system in the new facility is cutting edge for surface drinking water plants," Getting says.
The next stage of the project carries water to the larger treatment building for mixing in debris-removing chemicals and a dissolved air flotation process that extracts algae and other materials, Biehler says. The water then flows through a carbon filtering process and finally a lighter chlorine-disinfecting treatment.
Use of the new facility will be phased, with the existing plant set for demolition later this year. Some of the old structure's materials will be recycled. The final step will switch the Canoe Brook facility fully over to the newer, more efficient plant—one that should stand on much sounder footing for the long haul.