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Waste Reduction

Greenville, S.C., precast/prestressed producer Metromont Corp. has logged the first North American installation of a European-modeled recycling system

Don Marsh

Greenville, S.C., precast/prestressed producer Metromont Corp. has logged the first North American installation of a European-modeled recycling system for mixer and yard-vehicle washout, banking on payback over a reasonable window when measured against smaller, but perpetual waste handling and hauling expenses. The system is part of a major batch plant and material-handling overhaul at the company's 59-acre, Hiram, Ga., structural and architectural operation.

Upon its 1986 opening, the plant had no neighbors and presumably room to grow as future volume dictated. Twenty years later, as tract housing developments and big box and specialty retail properties have stretched the Atlanta periphery to Hiram and beyond, limited yard expansion options challenged Metromont to rethink production methods that pre-date self consolidating concrete and widely adopted, automated mix delivery.

Dubbed Water Wash, the recycling system combines technology proven in overseas concrete operations with proprietary wastewater treatment processes from the U.S. textile industry. Metromont's prototype 1,320-gal./hour recycling system comprises a 1) conventional concrete reclaimer for capturing and cleaning fine and coarse aggregate from mixer and yard vehicle washout; 2) 32,000-gal. slurry collection pit with twin four-blade agitators; and, 3) clarifier structure whose five tanks separate cement fines from water, treating each before transfer to disposal sacks and main reclaimed water storage vessel, respectively.

Investment in this level of concrete batching, reclaiming and water washing innovation shows our commitment to being an eco-effective company, striving for Îcradle to cradleÌ in production, says Metromont Director of Business Development and Marketing Jay Cariveau. From a sustainability standpoint, we are promoting the features and benefits of precast concrete methods Û from thermally efficient wall systems and lower waste volume to use of recycled-content materials and less site impact.

Our plant is land-locked, and we needed to create more storage area by making better use of existing space, adds Metromont/Hiram General Manager John Wenkel. Our old method of stockpiling hardened washout was consuming valuable yard area and in some months costing thousands of dollars in hauling and disposal. By investing in the slurry containment structure and processing equipment, he notes, the plant is able to reuse previously landfill-bound fine and coarse aggregate; fully recycle water through automatic pH adjustment; and, package cement fines in a clay cake-like form that a landfill operator can readily use for layering or capping.

The Water Wash installation coincides with construction of a low-profile batch plant to serve Hiram's 1,400-ft.-long production bay, plus a separate 1,700-sq.-ft. admixture tank building enclosure. The 200-plus yd./hour batch plant is specifically geared to self consolidating mixes and incorporates a 6-yd. twin shaft mixer. The latter is the fourth such unit for Metromont, following installations at its flagship and Charlotte, N.C., plants.

The Hiram batch plant work has included construction of a 13-ft.-square, drive-over aggregate bunker and four-compartment, 510-ton aggregate bin to easily pace the mixer's output capability. The batch plant's low profile Û partly a nod to the operation's neighbors Û enabled Metromont to save yard space by incorporating separate bin-loading and mixer-charging conveyors, each at 20-deg. angles. Charged by a reversible belt conveyor, the bins feed a weigh belt. The latter transfers aggregate to the charge conveyor, running parallel to the bin structure and its lateral main belt.

The charge conveyor has a 30-in. belt, sufficient to deliver aggregate for more than 250 yd. of concrete in an hour. The batch plant's twin shaft mixer, cement weigh batcher and 7-yd. aggregate holding hopper rest on one of two robust, precast structures. Built side-by-side and shaped like parsons tables, the structures offer an elevated platform for one 100-ton and twin 200-ton cement silos. On the ground level underneath, Metromont has enclosed one quadrant as a quality control lab Û enabling rapid, efficient sampling and test specimen handling Û and devoted much of the open area to transfer of concrete from the double-gate twin shaft mixer.

FIRM COMMITMENT

Hiram's main production bay is served by Tuckerbilt and front discharge mixer trucks. Over the next year, Metromont plans to install a monorail down the center of the bay, allowing a 6-yd. bucket to travel from the mixer to a form-feeding shuttle hopper. The monorail installation will follow the upgrade of Hiram's second batch plant, which loads conventional front discharge mixer trucks supplying an architectural line.

The Georgia ramp up coincides with strong market conditions for Metromont, which for the past four years has operated under members of the founding family, the Pennells. They regained full ownership of the four-plant precast/prestressed franchise in a 2003 transaction with (pre-Cemex) RMC Industries Inc., which had held a controlling stake. Since the early 1990s, the Pennells had maintained a 25 percent stake in the precast/prestressed business, and Metromont Materials' extensive ready mixed and manufactured-concrete operations in the Carolinas. (After the prestressed division deal, RMC kept the Carolinas businesses, which have since been integrated with other former RMC properties into Cemex USA.)

Private ownership and timely decisions on large capital outlays have Metromont solidifying its role as a leading Southeast precast/prestressed producer. On top of the Hiram investment, the company plans a mid-2007 groundbreaking on a fifth structural plant. The facility will be located on an 83-acre plot in Haines City, Fla., and have a projected payroll of 100. In a formal announcement at the site earlier this year, Metromont President and CEO Rick Pennell noted, We have been serving Florida for a number of years from our Atlanta plant, and believe the time is right to build a state-of-the-art facility in central Florida. Initially, we will target the parking structures market and, in the future, schools, office buildings, medical office buildings and manufacturing facilities.

Haines City will become part of a Southeast network spanning Metromont's Carolinas, Hiram, and LaVergne, Tenn., plants.